ES2773332B2 - ABOUT ABSORBENT - Google Patents

Description

DESCRIPTION

ABOUT ABSORBENT

FIELD OF THE INVENTION

The present invention belongs to the field of preservation of perishable products, such as vegetable or animal products. More specifically, the invention relates to an absorbent device for ethylene and other harmful gases, such as ethanol, acetaldehyde, hydrogen sulfide, among others, produced by vegetable products or other perishable products. The device of the invention is designed to be placed in or attached to containers or packaging that contain perishable products during their transport, distribution and / or marketing, to absorb the emissions of said products, which induce their maturation and deterioration.

BACKGROUND OF THE INVENTION

When a perishable product, such as fruits, vegetables, vegetables, flowers, etc., is packed in packaging, such as boxes, bags, etc., a more or less confined atmosphere is created in which various gases, typically emitted by the gases themselves Products packed or produced due to emissions from such products induce maturation, spoilage, rotting and fungal development of packaged products. Examples of these gases that induce maturation, deterioration, decay and fungal development are ethylene, ethanol, acetaldehyde, among others.

To prevent or slow down spoilage, maturation, etc. of these perishable products, during their packaging in various packages, such as boxes, bags, etc., it is customary to take various measures. On the one hand, harmful gas absorption filters are used. These filters are usually located inside the confined spaces, often refrigerated, in which perishable products are transported. And on the other hand, harmful gas absorption envelopes are used, which are inserted into the packaging (bags, boxes, etc.) in which the products have been packed. For example, it is very common to use bags made of Tyvek® (synthetic material made of polyethylene fibers), filled with silicon gel, used to alleviate the effects of humidity, or filled with clays or aluminas impregnated with permanganate. for the absorption of ethylene. Although in principle the Tyvek® used by this type of bags is impermeable to water in a liquid state and permeable to harmful gases, this material is also permeable to water vapor, as stated by the manufacturer of the product itself at http: // www. dupont.com/products-and-services/constructionmaterials/building-envelope-systems/articles/understanding-vapor-permeability.html), last accessed January 7, 2019. This causes a double problem: On the one hand, when the Filler (typically clays or aluminas impregnated with permanganate) becomes saturated with water when condensations occur, it is no longer effective. For this reason, the manufacturers of these sachets are forced to overdose the filler (for example, salts impregnated with permanganate), with the consequent waste of resources and the potential increase of dangerous spills. On the other hand, condensed water, mixed with permanganate, migrates out of the Tyvek® envelope over time, causing a serious food safety risk if the permanganate comes into contact with product, such as fruit.

The international patent application WO2015110682A1 discloses an envelope for the absorption of gases that accelerate the ripening and deterioration of vegetable products, to be applied in the packaging boxes and bags of said products. The envelope disclosed in this document is formed by a support sheet of plastic material, such as low-density polyethylene (LDPE, in its acronym in English), waterproof, and by a sheet, superimposed on the previous one, resistant of permeable material , such as cellulose, which provides strength. The thickness of the plastic sheet for envelopes as described in WO2015110682A1 and currently on the market is about 35 microns. Inside the envelope a filter granulate is housed.

In view of the known proposals, it is desirable to optimize the effectiveness of the envelopes, so as to optimize the permeability to harmful gases and impermeability to water, while reducing the amount of materials used in their manufacture, especially plastics and / or active or filter material.

DESCRIPTION OF THE INVENTION

The present disclosure provides a gas absorbing envelope, intended to be placed in packages - such as bags, boxes or packaging - of products. perishables, such as vegetables, to remove gases, such as ethylene, which accelerate the ripening and spoilage of packaged perishable goods.

In a first aspect of the present disclosure, a gas absorbing envelope is provided comprising a receptacle inside which is housed a filter material for absorbing gases. The receptacle is formed of a stiffening sheet, which is made of a gas-permeable material, and attached to or integrated with a plastic material that is impermeable to water and permeable to harmful or unwanted gases. Non-limiting examples of harmful or unwanted gases to which said plastic material is permeable are: ethylene, ethanol, acetaldehyde and hydrogen sulfide. The grammage of the plastic material is less than or equal to 20 g / m2. In the context of the present invention, the term "impermeable" is used, applied to water in any of its states, to indicate that there is no appreciable migration of water molecules through the walls of the receptacle that forms the envelope of the invention. , in long periods of time, that is, approximately between one and three months.

In embodiments of the invention, the stiffening sheet made of a noxious gas permeable material is a cellulose sheet or a sheet of nonwoven fabric or other gas permeable material.

In embodiments of the invention, the plastic material impermeable to water and permeable to harmful gases is chosen from the following plastic materials: ethylene-vinyl acetate (EVA), ultra-low-density polyethylene, low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, polypropylene, polybutylene, ionomers, polystyrene (PS) and their mixtures.

In embodiments of the invention, the plastic material has been bonded to the rigid sheet by extrusion, coextrusion, heat, molten plastic coating, spraying, spraying, or spray impregnation.

In embodiments of the invention, the grammage of the plastic material is less than or equal to 20 g / m2, such as less than or equal to 15 g / m2, or between 5 and 12 g / m2, or between 6 and 12 g / m2, or between 6 and 11 g / m2, or between 7 and 11 g / m2, or between 7 and 10 g / m2, or between 8 and 10 g / m2.

In embodiments of the invention, the thickness of the plastic material is less than 25 pm, such as between 5 and 25 pm, or between 5 and 20 pm, or between 5 and 15 pm, or between 5 and 12 pm, or between 8 and 12 pm, or between 10 and 12 pm.

In embodiments of the invention, the stiffening sheet of gas-permeable material has a grammage ranging between 30 and 80 g / m2, such as between 40 and 70 g / m2 or between 40 and 60 g / m2 or between 45 and 55 g / m2.

In embodiments of the invention, for the union or integration of the sheet that provides rigidity and the plastic material, no type of adhesive or any other material is used.

In embodiments of the invention, a noxious gas permeable adhesive is used for bonding or integrating the stiffening sheet and the plastic material.

In embodiments of the invention, the filter material comprises a porous substrate provided with an impregnation. The filter material can be granules or powder.

In embodiments of the invention, the filter material comprises a granulate formed by grains whose diameter varies between 1 and 7 mm.

In embodiments of the invention, the plastic material remains on the inside of the receptacle, in contact with the filtering material, with the sheet that provides rigidity on the outside of the receptacle, in contact with the gases to be absorbed.

In another aspect of the present invention, a package is provided for packaging perishable products comprising an envelope as described above.

Among the advantages of the envelope of the invention, it stands out that it is possible to increase the permeability to gases to be eliminated, such as ethylene, without reducing the desired impermeability to water in any of its states (solid, liquid and gaseous). In addition, the amount of plastic material used is reduced, with the consequent environmental impact. As if that were not enough, by reducing the amount of plastic used, the integration of the plastic in the support sheet is facilitated, to the point that the use of adhesives can be dispensed with, which, in addition to the obvious advantage derived from the simplification of the product and Respect for the environment, adds the advantage of facilitating the evaluation of gas permeability and water impermeability, by eliminating the effect that adhesives may have on said evaluation. In addition, as with respect to conventional envelopes, such as those made of Tyvek®, the envelope of the present invention is impervious not only to water in the liquid, but also water vapor. Thus, a more efficient envelope is achieved from the point of view of the elimination of harmful gases and the water saturation of the active material contained inside the envelope is avoided, which makes it possible to reduce the amount of it without reducing the effectiveness. of the set. In other words, it has been observed that the permeability to water vapor, which is avoided in the envelope of the invention, reduces the effectiveness of the absorption of unwanted gases, such as ethylene, due to the condensation of water inside the packaging of perishable products and, therefore, to the presence of water inside the envelope.

Additional advantages and features of the invention will be apparent from the detailed description that follows and will be pointed out in particular from the appended claims.

BRIEF DESCRIPTION OF THE FIGURES

To complement the description and in order to help a better understanding of the characteristics of the invention, according to an example of a practical embodiment thereof, a set of figures is attached as an integral part of the description, in which with character Illustrative and not limiting, the following has been represented:

Figure 1 shows a gas absorption envelope according to a possible embodiment of the invention. One end of the envelope is open to reveal the granular filter material that is housed inside the envelope.

DESCRIPTION OF A WAY OF CARRYING OUT THE INVENTION

The description that follows is not to be taken in a limited sense, but is provided solely for the purpose of describing broad principles of the invention. The following embodiments of the invention will be described by way of example, with reference to the figures cited above, which show devices and results according to the invention.

The envelope of the present invention optimizes its permeability to harmful gases and impermeability to water in any of its states towards the interior of the envelope, reducing the amount of plastic used, making the envelope much more environmentally friendly by reducing the amount of plastic used in its manufacture. In addition, by increasing its effectiveness, derived from the optimized impermeability to harmful gases and impermeability to water, it is possible to reduce the amount of active material inside.

In figure 1 an envelope 1 for gas absorption according to a possible embodiment of the invention is shown. The envelope 1 is made up of a receptacle 2 inside which a filter material, product or composition 3 is housed. The receptacle 2 is formed by two sheets, walls or flat surfaces, of the same size, made of the same material, joined or sealed by its edges, so that they form a hollow or closed interior volume. That is, the receptacle is multilayer, specifically bilayer. In Figure 1, the shape of the envelope 1, imposed by the shape of the receptacle 2, is square or rectangular. However, the envelope 1 can take any other shape, such as circular or oval, or any other. In figure 1 one of the edges of the receptacle 2 is shown open so that the filter material 3 inside it can be seen.

The receptacle 2 of the envelope 1, that is to say, the walls or delimiting surfaces of the envelope 1, is made of a first sheet of a gas-permeable material, in which an impermeable plastic material has been added, applied, bonded or integrated. water in any of its solid, liquid or gaseous states, and permeable to harmful or unwanted gases, such as ethylene, ethanol, acetaldehyde and hydrogen sulfide. The first sheet provides rigidity to the assembly and, to allow the filtering material 3 to absorb harmful gases, it must be permeable to these gases. The plastic material provides, among others, the functionality of impermeability to water, including water vapor. In this way, the gases to be absorbed by the filtering material 3 are able to enter the interior of the envelope 1, but the water cannot do so. Note that inside containers of perishable products it is common for water to condense. Other functions of the plastic material are resistance to tearing, resistance to abrasion or ability to seal, for example by application of heat. Thus, the assembly is permeable to harmful gases and impermeable to water, so that the gases to be filtered enter the envelope 1 but the water does not. The plastic material remains on the inside of the receptacle 2, in contact with the filter material 3, leaving the sheet that provides rigidity on the outside of the receptacle 2, in contact with the gases to be absorbed. Note that although the outer sheet can be moistened with water, it does not pass through the plastic material of the inner surface of the receptacle 2.

The plastic material is applied, joined, added or integrated in the form of a sheet or layer or of treatment or deposit applied on the first sheet. In embodiments of the invention, the two materials (first sheet of gas-permeable material and second sheet or reservoir of plastic material) are adhered, coupled or integrated without using any adhesive that alters the properties of the whole. Non-limiting examples of forms of coupling are extrusion, coextrusion, heat, molten plastic coating, spraying, spraying, or spray impregnation, among others. Possible removal or reduction of adhesives simplifies the final product and makes it more environmentally friendly. In addition, the elimination or reduction of adhesives facilitates the evaluation of the gas permeability and impermeability to water of the envelope, by eliminating the effect that adhesives may have on said evaluation. In the event that the plastic material is added, integrated or attached to the sheet that provides rigidity, by means of an adhesive, an adhesive permeable to harmful gases is chosen.

In a preferred embodiment, the first sheet is made of cellulose. Alternatively, the first sheet can be made of any other gas-permeable and stiffening material, such as non-woven fabric or Tyvek®.

The plastic material included in the receptacle 2 - added to, or integrated into, the support sheet - can be chosen from the following plastic materials: ethylene vinyl acetate (EVA), ultra-low-density polyethylene, low-density polyethylene, medium-sized polyethylene density, high-density polyethylene, linear low-density polyethylene, polypropylene, polybutylene, ionomers, polystyrene (PS) and their mixtures, or any other plastic material that is impermeable to water in any of its states and permeable to harmful gases.

The plastic material added to or integrated into the sheet may consist of one of the above materials. In a preferred embodiment, the material is a low density polyethylene (LDPE).

The inventors have observed that reducing the amount of plastic material applied or added on the sheet of gas-permeable material, such as cellulose, increases the permeability to noxious gases, thus facilitating the entry of these gases into the envelope for absorption. by granulate 3, while maintains the impermeability to water in any of its states. In this way, it is possible to improve the permeability of the receptacle 2, while reducing the amount of plastic used, with respect to conventional receptacles, formed by two superimposed sheets (a sheet of gas-permeable material, such as cellulose, and another sheet of plastic material, such as LDPE, at least 35 microns), typically bonded by an adhesive. Thus, the layer or deposit of plastic material of the present invention has a grammage or surface density less than or equal to 20 g / m2 (grams per square meter), such as less than 15 g / m2, or between 5 and 12 g / m2, or between 6 and 12 g / m2, or between 6 and 11 g / m2, or between 7 and 11 g / m2, or between 7 and 10 g / m2, or between 8 and 10 g / m2, inclusive . It has been observed that by choosing a plastic sheet with a grammage less than or equal to 20 g / m2, the permeability to gases of the receptacle 2 is increased, without impairing the impermeability to water in any of its states.

In embodiments of the invention, the thickness of the plastic sheet or reservoir is chosen less than 25 µm (microns, 10 "6 m). In embodiments of the invention, this thickness ranges between 5 and 25 µm, such as between 5 and 20 pm, or between 5 and 15 pm, or between 5 and 12 pm, or between 8 and 12 pm, or between 10 and 12 pm, both inclusive.

The thickness of the plastic sheet or reservoir can be constant or uneven. In the case of being irregular, the previous thickness value ranges are mean values of the plastic sheet of irregular thickness.

In embodiments of the invention, the first sheet, that is, the sheet that provides rigidity to the receptacle 2, while being permeable to gases, has a grammage or surface density that varies between 30 and 80 g / m2, such as between 40 and 70 g / m2, or as between 40 and 60 g / m2, or as between 45 and 55 g / m2.

In a possible implementation, in which the sheet of gas-permeable material is cellulose and the added plastic is LDPE, the receptacle 2 has an amount of 50 g / m2 of cellulose and 10 g / m2 of LDPE.

The inside of the envelope 1 is filled with a filter material 3 formed by a porous substrate provided with an impregnation. In embodiments of the invention, for joining the sheet, for example cellulose, and the plastic material, for example polyethylene, no type of adhesive or any other material is used.

Returning to figure 1, inside the envelope 1 a plurality of grains or granules have been introduced, or in other words, a granulate 3. Alternatively, the filter material 3 housed in the receptacle 2 is dust of said material. The granulate or plurality of grains or granules 3, or powder, provide the filtering capacity of the envelope 1, that is, they absorb unwanted gases. Therefore, it is necessary that said gases penetrate through the walls 2 of the envelope 1, that is, the cellulose sheet with polyethylene in the case that the walls 2 are made of these materials, with the highest possible permeability.

As said, the granulate or plurality of grains or granules 3 comprise a porous substrate and an impregnation of the porous substrate. The porous substrate used to form the granulate can be made from the following materials: diatomaceous earth; natural or synthetic zeolites of any kind; molecular sieve; celite; perlite; aluminas and active aluminas; mica; magnesium aluminate; aluminosilicate; magnesium silicate; activated carbon; absorbent clays, such as bentonite, sepiolite, attapulgite, vermiculite, etc .; kaolin; activated bauxite; silica gel; or mixtures of the above materials. The impregnation that is applied to the filter granulate can vary in percentage. The impregnation can be of the following types: potassium permanganate; sodium permanganate; lithium permanganate; magnesium permanganate; calcium permanganate; barium permanganate; or any purple colored permanganate. Alternatively, the granules 3 can be obtained by combining impregnated substrates with non-impregnated substrates, from among the substrates mentioned above; adding other chemical compounds as impregnating agents (eg, bicarbonate) as long as a permanganate is added; combining substrates impregnated with permanganate (and adding some or no chemical compounds) with substrates with other impregnations (such as KOH, NaOH or others); or by combining the various possibilities described above (for example, by mixing three or more types of granules together).

When the filter material is a granulate, the grains or granules 3 can take any shape, such as spherical, cylindrical, pellet-shaped or irregularly shaped. When the grains are spherical, their diameter can vary between 1 and 7 mm (millimeters, 10-3 meters), such as between 3 and 5 mm.

The envelope 1 filled with a filter material 3, and whose walls 2 are formed by a sheet of material permeable to harmful gases, such as cellulose, to which has been

1

Joined, added, integrated or impregnated, for example by extrusion or coextrusion, a plastic material that is impermeable to water in any of its states and permeable to harmful gases, such as low-density polyethylene, provides greater permeability to gases, in particular to ethylene, maintaining the impermeability to water in any of its states, with respect to the envelopes formed by the adhesion of a cellulose sheet and a polyethylene sheet of at least 35 pm thickness.

The following experiment has been carried out: Several envelopes made of a 50 g / m2 cellulose sheet attached to or integrated with a 10 LDPE sheet have been introduced into an airtight container with an ethylene emission source (high emission fruit). g / m2, and various conventional envelopes, that is, formed by a 40 g / m2 cellulose sheet adhered to a 35 pm thick LDPE sheet. All the sachets had the same batch and quantity of filter granules inside. It is known that the small difference in the amount of cellulose of the two types of envelopes has no impact on the permeability of the envelopes to harmful gases and impermeability to water. With the passage of time (48 hours), the degree of saturation of the granules housed inside the sachets, expressed by color change, was observed. Thus, the envelopes whose plastic was 10 g / m2 showed higher granulate saturation compared to conventional envelopes. Thus, a measure of the permeability of the envelopes of the invention was obtained in comparison with conventional envelopes. Note that all the envelopes were housed in the same container, so that the various variables, such as pressure or gas concentrations, were identical for all of them. A remarkable increase in permeability to ethylene was observed in the sachets of the invention. It thus follows that the permeability to ethylene, and therefore the effectiveness of the envelope, derives both from the thickness of the layers thereof, and from its permeability to water, including the permeability to water vapor.

The following experiment was also carried out to evaluate the migration of water molecules into the envelope in contact with water: Several envelopes formed by a 50 g / m2 cellulose sheet attached to or integrated with a sheet of LDPE of different weights that vary between 10 g / m2 and 6 g / m2. All the sachets had the same batch and quantity of filter granules inside. It was waited more than a month to see if the water turned purple due to the migration of the water with permanganate. In all cases it was observed that the water did not it was stained purple, that is, it was concluded that there was no migration of water into the envelope. In fact, it was observed that the water molecules seem to only migrate through the envelope when there is a break in the envelope, regardless of the weight of the LDPE.

Lastly, the migration of water molecules into Tyvek® sachets in contact with water has been evaluated by the following experiment: Several conventional Tyvek® sachets containing a filter granulate containing permanganate have been immersed in containers with water. It was waited more than a month and a slow migration of water molecules through the Tyvek® was observed, observing that the granules got wet, ceasing to be effective, and that water with permanganate migrated to the outside of the envelope.

The described harmful gas absorption envelope 1 is intended to be inserted inside a packaging (bags, boxes, etc.) in which perishable products have been stored or packed.

In this text, the term "comprises" and its derivations (such as "comprising", etc.) should not be understood in an exclusive sense, that is, these terms should not be interpreted as excluding the possibility that what is described and it is defined to include elements, additional stages, etc.

In the context of the present invention, the term "approximately" and terms of its family (such as "approximate", etc.) should be interpreted as indicating values very close to those that accompany said term. That is, a deviation within reasonable limits from an exact value should be accepted, because a person skilled in the art will understand that such a deviation from the indicated values may be unavoidable due to measurement inaccuracies, etc. The same applies to the terms "about", "about" and "substantially".

The invention is not obviously limited to the specific embodiment (s) described, but also encompasses any variation that may be considered by any person skilled in the art (for example, in relation to the choice of materials, dimensions, components, configuration, etc.), within the general scope of the invention as defined in the claims.

Claims (28)

1. - An envelope for gas absorption (1) comprising a receptacle (2) inside which a filtering material (3) is housed to absorb harmful gases, characterized in that the receptacle (2) is formed by a sheet that provides rigidity, said sheet being made of a material permeable to harmful gases, attached to or integrated with a plastic material that is impermeable to water and permeable to harmful gases, the grammage being of plastic material less than or equal to 20 g / m2. 2. - The envelope (1) of claim 1, wherein said sheet that provides rigidity, of a material permeable to harmful gases, is a cellulose sheet or a sheet of non-woven fabric. 3. - The envelope (1) of any one of claims 1 or 2, in which the plastic material impermeable to water and permeable to harmful gases is chosen from the following plastic materials: ethylene-vinyl-acetate (EVA) , ultra low-density polyethylene, low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, polypropylene, polybutylene, ionomers, polystyrene (PS) and their mixtures. 4. - The envelope (1) of any one of the preceding claims, in which the plastic material has been joined to the sheet that provides rigidity by extrusion, coextrusion, heat, molten plastic coating, spraying, spraying or impregnation by spray . 5. - The envelope (1) of any one of the preceding claims, wherein the grammage of the plastic material is less than or equal to 15 g / m2. 6. - The envelope (1) of claim 5, wherein the grammage of the plastic material varies between 5 and 12 g / m2. 7. - The envelope (1) of claim 6, wherein the grammage of the plastic material varies between 6 and 12 g / m2. 8. - The envelope (1) of claim 7, wherein the grammage of the plastic material varies between 6 and 11 g / m2. 9. - The envelope (1) of claim 8, in which the weight of the plastic material varies between 7 and 11 g / m2. 10. - The envelope (1) of claim 9, wherein the grammage of the plastic material varies between 7 and 10 g / m2. 11. - The envelope (1) of claim 10, wherein the grammage of the plastic material varies between 8 and 10 g / m2. 12. - The envelope (1) of any one of claims 1-4, wherein the thickness of the plastic material is less than 25 pm. 13. - The envelope (1) of claim 12, wherein the thickness of the plastic material varies between 5 and 25 pm. 14. - The envelope (1) of claim 13, wherein the thickness of the plastic material varies between 5 and 20 pm. 15. - The envelope (1) of claim 14, wherein the thickness of the plastic material varies between 5 and 15 pm. 16. - The envelope (1) of claim 15, wherein the thickness of the plastic material varies between 5 and 12 pm. 17. - The envelope (1) of claim 16, wherein the thickness of the plastic material varies between 8 and 12 pm. 18. - The envelope (1) of claim 17, wherein the thickness of the plastic material varies between 10 and 12 pm. 19. - The envelope (1) of any one of the preceding claims, wherein the sheet that provides rigidity, made of gas-permeable material, has a grammage that varies between 30 and 80 g / m2. 20. - The envelope (1) of claim 19, wherein said grammage varies between 40 and 70 g / m2. 21. - The envelope (1) of claim 20, wherein said grammage varies between 40 and 60 g / m2. 22. - The envelope (1) of claim 21, wherein said grammage varies between 45 and 55 g / m2. 23. - The envelope (1) of any one of claims 1-22, wherein for the union or integration of the sheet that provides rigidity and the plastic material, an adhesive permeable to harmful gases is used. 24. - The envelope (1) of any one of the preceding claims, wherein the filter material (3) comprises a porous substrate provided with an impregnation. 25. - The envelope (1) of any one of the preceding claims, wherein the filtering material (3) is a granulate or powder. 26. - The envelope (1) of any one of the preceding claims, wherein the filtering material (3) comprises a granulate formed by grains whose diameter varies between 1 and 7 mm. 27. - The envelope (1) of any one of the preceding claims, in which the plastic material remains on the inside of the receptacle (2), in contact with the filtering material (3), leaving the sheet that provides rigidity in the outer part of the receptacle (2), in contact with the gases to be absorbed. 28. A package for packaging perishable products comprising an envelope (1) according to any one of the preceding claims. 1