WO2012093371A1 - Co-extruded multi-layer film substrate for use in packaging fresh vegetables - Google Patents

Abstract

The invention relates to a co-extruded multi-layer film substrate for use in the packaging of fresh vegetables, which enables modulation of the permeability of the gases generated during the respiration of said fresh vegetables, wherein said substrate comprises: a first sealing layer (2) formed, by at least 55 wt %, of a polyethylene that is at least 0.925 g/cm3, the difference consisting of another polyethylene, which is a thermoplastic having a significant number of short branches up to no more than 0.935 g/cm3; a second nucleus layer (3) formed of a polymer matrix that includes a film-forming polymer, wherein the polymer matrix of said second nucleus layer (3) comprises from 88 % of a suitable thermoplastic polymer having a low degree of branching and greater than 0.940 g/cm3, the difference consisting of a suitable thermoplastic polymer having a significant number of short branches of up to 0.935 g/cm3; and a third outer layer (4) formed, by at least 55 wt %, of a polyethylene of at least 0.925 g/cm3, the difference consisting of another polyethylene that is a thermoplastic having a significant number of short branches of up to no more than 0.935 g/cm3.

Description

 DESCRIPTIVE MEMORY

 SUBSTRATE OF COEXTRUDED MULTI-PAPER FILM FOR USE IN FRESH VEGETABLE PACKAGING.

TECHNICAL FIELD OF THE INVENTION

 The present invention relates to a coextruded multilayer film substrate for use in the packaging of fresh vegetables, which has a low branching polyolefin layer and greater than 0.940 g / cm3 and a polyolefin layer of about 0.925 g / cm3, symmetric in cross section, where said layers can be exempted in similar or equal symmetric thicknesses. The resulting film has sufficient permeation capacity of the gases involved in respiration such as the dehydration of fresh vegetables making them very suitable to slow senescence and prolong the shelf life of fresh vegetables packaged with them.

BACKGROUND OF THE INVENTION

 Vegetables use the energy that is stored in the chemical bonds of the molecules generated by photosynthesis. To be used this energy have developed mechanisms that allow to oxidize organic molecules, to reduce them to carbon dioxide plus water. This oxidation is called breathing.

 Breathing in vegetables is a metabolic process that involves the oxidation of sugars, starch and organic acids among other compounds. This raw material is subjected to enzymatic oxidation, finally transforming it into simpler compounds such as carbon dioxide and water vapor.

 This implies that the vegetable requires and consumes oxygen to perform such oxidation.

 These considerations should be taken into account when designing containers for the maintenance of vegetables, during storage and transport.

On the other hand, many vegetables are stored and transported in boxes one above the other, as shown in Figures 1 and 2. In the box (14) the vegetables (5) are placed on each other, so when a vegetable (5 ) suffer attack For pathogens that initiate the rotting process, it is usual for this rot to spread to other vegetables generating decomposed vegetables (5 '), which can continue to damage the rest of the vegetables (5) contained in the box (14).

 Therefore, there have been attempts to obtain coatings of vegetables (5) in a group or individual way.

 The coating of fruits with multilayer films has been known for several years to increase the life of the vegetables when they are transported from their packing place to the consumer markets.

 There are usually two types of packaging for vegetables. Intelligent packaging and active packaging.

 Intelligent packaging can be defined as packaging techniques that contain, externally or internally, an indicator to generate an active product history and determine its quality. In general, smart packaging has time-temperature indicators, leakage indicators, oxygen indicators, carbon dioxide indicators.

 Active packaging focuses on the need for protection and conservation granted by the container, protecting the food from both mechanical damage during handling and from deterioration due to the different environments through which the container will pass during its distribution and storage. Unlike smart packaging, which aims to provide product information. In general, active packaging includes the generation of modified atmosphere packages that have internal atmosphere controllers, oxygen trappers, carbon dioxide producers or trappers, moisture removers, ethylene removers, additive release agents, antimicrobials and fungicides, among others. .

 Many of these packages use substrates of multilayer films, which are known in the art.

Thus, for example, document CL 38270 (Forrester) of April 20, 1992, discloses a laminar article, comprising a combination of a polyolefin, an ethylene-vinyl alcohol copolymer with a melting point at least about 5 ° C. high than that of polyolefin, and a compatibilizer of a compatible polyolefin structure grafted with fractions of cyclic anhydrides, where the ethylene-vinyl alcohol copolymer is present within the polyolefin as multiple thin, substantially parallel and overlapping strata. These items exhibit barrier properties and improved mechanical strength.

 Document CL 2018-1997 (Wilson) published on August 4, 1998, discloses a laminate and production method thereof, said laminate comprises a first structural layer of polyolefin or an interpolymer thereof which is of low melt index and a sealant layer containing a second polyolefin or an interpolymer thereof and structural layer. By mixing a first polyolefin, or an interpolymer thereof, which is of low melt index and is multimodal in terms of molecular weight distribution, with a homogeneous polyolefin that is compatible in molten mixing with said first polyolefin and co- by extruding or extruding the mixture through a flat groove matrix, with or without a second polyolefin, or an interpolymer thereof, a laminar material or a monolayer is obtained. The sheet material comprises a structural layer constituted by the first polyolefin, or the interpolymer thereof and a sealant layer constituted by the second polyolefin, or the interpolymer thereof and a sealant layer constituted by the second polyolefin, or the interpolymer of the same, which has a sealing start temperature lower than the start sealing temperature, or at least the thermoforming plateau temperature of the structural layer and compatible with molten mixing with the structural layer. The monolayer or laminate is particularly suitable for thermoforming in containers.

EP 1658973 (Lischefski et al.) Published on May 24, 2006, describes a thermoformable coextruded film suitable for use in packaging applications having at least one first polymeric layer that serves as an outermost outermost film layer and comprising a cycloaliphatic polyester, an aromatic polyester or mixtures thereof; a second polymeric layer that serves as an auxiliary thermoforming layer and comprising a polyolefin; and a third polymeric layer that serves as a more inward outer film layer and comprising a polyolefinic material that seals by hot. The films of the present invention are permeable to oxygen, since they exhibit an oxygen transmission rate between 2-1000 cm. 3/100 in. 2/24 h. atm. (31 -15,500 cm. 3 / m. 2/24 h).

 None of the prior art documents disclose a film substrate that has a modulated permeability, where a part, and not all, of the carbon dioxide generated in the breath can permeate or leave from the space generated by the skin of the plant and the internal surface of the coextruded multilayer film substrate. Therefore, if the rate of permeability in the substrate for carbon dioxide is lower than the rate of production of carbon dioxide resulting from the respiration of the plant, then in this space a greater amount of carbon dioxide will remain. In general, this coextruded multilayer film substrate has the capacity to modulate the permeation of the gases involved in respiration and control the dehydration of fresh vegetables by making the packages formed by said multilayer film substrate very suitable to retard senescence and prolong the shelf life of fresh vegetables packed with them.

SUMMARY OF THE INVENTION

 The present invention relates to a coextruded multilayer film substrate for use in the packaging of fresh vegetables, which has a low branching polyolefin layer and greater than 0.940 g / cm3 and a polyolefin layer around 0.925 g / cm3, symmetrical in cross section. Both layers can be exempted in similar or equal symmetrical thicknesses.

The structure of the multilayer film substrate is constructed of symmetrical layers in its cross-section, and hermetically heat sealable for use in the packaging of fresh vegetables in relative time according to the respiration rate, which includes a layer more functional than symmetrical ones, a) a first sealing layer that is biaxially oriented; b) a second core layer that is biaxially oriented having a melt index of 6.3 to 12.3 (g / 10 min), where the second core layer is oriented in at least a first direction, the direction of the machine (longitudinal) to a degree of 1: 1 to 3: 1, preferably 1: 1 to 2: 1, and oriented in a second direction stretched in the transverse (lateral) direction to a degree of 2: 1 to 4: 1, preferably 2: 1 to 3: 1; and c) a third layer printed or not that is biaxially oriented, so that the film can also be modified in another way for example by corona discharge treatment. The structure of the multilayer coextruded film preferably requires a thickness comprised between approximately one third for the symmetric layer, the difference being structured by the core more preferably between approximately 8 μιτι and approximately 30 μιτι. However, the optimum thickness of the film will depend on the physiology of the vegetable to be packaged.

 The functional layer comprises a polymer matrix comprising a film-forming polymer having properties suitable for extrusion and biaxial orientation, stretching the extruded material in the machine direction and in the transverse direction. The polymer matrix of the core layer may be constituted from 88% of suitable thermoplastic polymer of low branching degree and greater than 0.940 g / cm 3, the difference being structured by appropriate thermoplastic polymer with significant number of short branches of up to 0.935 g / cm 3, where a) and c) are both hermetically heat sealable and include at least 55% by weight of a polyethylene of about 0.925 g / cm3, the difference being complemented with another polyethylene, being a unilinear thermoplastic with a significant number of short branches of up to no more than 0.935 g / cm3. The film of the invention has superior properties having a good degree of transparency and hindering gas permeability and water vapor, reducing dehydration due to water loss and reduced respiration.

BRIEF DESCRIPTION OF THE DRAWINGS

 The accompanying drawings are included to provide greater understanding of the invention, and together with the description serve to explain the general principles of this invention.

 Figure 1 shows a diagram of a storage and transport box with healthy vegetables, according to the prior art.

Figure 2 shows a scheme of a storage and transport box with healthy vegetables and some attacked by pathogens. Figure 3 shows a schematic of the structure of the coextruded multilayer film substrate.

 Figure 4 shows a scheme of the film substrate wrapping a vegetable, with its breathing mechanism.

 Figure 5 shows a scheme of the film substrate wrapping a fraction of vegetable unit.

 Figure 6 shows a scheme of the film substrate wrapping a group of vegetables.

 Figures 7 show photographs of the tests performed with the coextruded multilayer film substrate of the present invention, which has been used to wrap artichokes.

 Figures 8 show photographs of the tests performed with the coextruded multilayer film substrate of the present invention, which has been used to wrap broccoli.

 Figures 9 show photographs of the tests performed with the coextruded multilayer film substrate of the present invention, which has been used to wrap peach.

 Figures 10 show photographs of the tests performed with the coextruded multilayer film substrate of the present invention, which has been used to wrap pear.

 Figures 1 1 show photographs of the tests performed with the coextruded multilayer film substrate of the present invention, which has been used to wrap carrot.

DESCRIPTION OF THE INVENTION

The present invention relates to a coextruded multilayer film substrate for use in the packaging of fresh vegetables, which has a low branching polyolefin layer and greater than 0.940 g / cm3 and a polyolefin layer of about 0.925 g / cm3, symmetric in cross section that can be exempted in similar or equal symmetrical thicknesses. The resulting film substrate has sufficient permeation capacity of the gases involved in respiration such as dehydration of fresh vegetables, making packaging made with said substrate very suitable to delay senescence and prolong the shelf life of fresh vegetables packed with them.

 Referring to Figure 3, the structure is of a multilayer film substrate (1) constructed of symmetrical layers in the cross section, and hermetically heat sealable, for use in the packaging of fresh vegetables that allows a modulation of the gases generated in the respiration of the vegetables, where said modulation will depend on the relative packing time, according to the respiration rate and the storage T °.

 The first sealing layer (2) is a layer that is biaxially oriented. The second core layer (3) is biaxially oriented and has a melt index of 6.3 to 12.3 (g / 10 min), where the second core layer (3) is oriented in at least a first direction, the machine direction (longitudinal) to a degree of 1: 1 to 3: 1, preferably 1: 1 to 2: 1, and oriented in a second direction stretched in the transverse (lateral) direction to a degree of 2 : 1 to 4: 1, preferably 2: 1 to 3: 1. The third outer layer (4) printed or not, is biaxially oriented. In this way, the multilayer film (1) can also be modified in another way, for example, by corona discharge treatment.

 The structure of the multilayer coextruded film (1), preferably requires a thickness "E" comprised between approximately one third for each symmetric layer being the difference of the remaining third structured by the second core layer (3), as seen in Figure 3. Thus, the similar or equal thickness, for first sealing layer (2); the second core layer (3); and the third outer layer (4), wherein the thickness "A" is equal to or approximately equal to the thickness "B"; and the thickness "B" is equal to or approximately equal to the thickness Ί ", wherein said thickness is in a range between about 8 μιτι and approximately 30 μιτι. However, the optimum thickness of the film will depend on the physiology of the plant a package.

The second core layer (3) comprises a polymeric matrix comprising a film-forming polymer having properties suitable for extrusion and biaxial orientation, stretching the extruded material in the machine direction and in the transverse direction. The polymer matrix of the core layer (3) can be constituted from 88% of appropriate thermoplastic polymer of low branching degree and greater than 0.940 g / cm3, the difference being structured by appropriate thermoplastic polymer with a significant number of short branches of up to 0.935 g / cm3, where the first sealing layer (2 ) and the third outer layer (4) are both hermetically heat sealable and include at least 55% by weight of a polyethylene around 0.925 g / cm3, the difference being complemented with another polyethylene being a thermoplastic with a significant number of short branches up to not more than 0.935 g / cm3.

 The film of the invention has superior properties having adequate transparency, hindering gas permeability and water vapor and decreasing dehydration due to water loss and reduced respiration.

 This is achieved according to what is shown in figure 2. In said figure, a vegetable (5), such as a fruit, is shown. The vegetable (5) is surrounded by a gasket (6) formed by the multilayer coextruded film (1). On the outside of the package is the oxygen (8) contained in the air that represents approximately 21% of it. Also, in the environment there is of the order of 0.03% of carbon dioxide (7), in addition to water vapor (9), product of the humidity of the environment.

 Inside, between the inner surface of the packaging (6) and the skin of the vegetable (5) a chamber or head space (10) is generated, in which oxygen (8) decreases as a function of time and the effect of the respiration rate of the vegetable (5). Likewise, carbon dioxide (7) increases as a function of time and according to the rate of respiration of the vegetable (5), and there may also be ethylene generation (1 1). In addition, water vapor (9) is produced within the chamber or head space (10), product of the vegetable's respiration (5).

The gasket (6) is made up of the multilayer coextruded film (1) which modulates the flow of the chamber (10) inwards, from the oxygen (8), outwards of the carbon dioxide (7), ethylene 1 1) and water vapor (9), allowing oxygen (8) to decrease in the chamber (10), increasing carbon dioxide (7) which decreases ethylene production (1 1). Additionally the film protects from dehydration. This means that the multilayer coextruded film substrate (1) has a modulated permeability. That is, a fraction of the oxygen (8) consumed in the respiration of the vegetable (5), permeates from the outside of the package (6) into the chamber (10). Therefore, oxygen (8) decreases in the head space. On the other hand, a fraction of the carbon dioxide (7) generated in the breath permeates or exits from the chamber (10) towards the outside of the gasket (6). Therefore, carbon dioxide (7), the product of vegetable respiration (5), increases in the head space.

 According to what is shown in figures 4, 5 and 6, the packages formed with the multilayer coextruded film (1), can be used in vegetables in unit form (figure 4), in unit fractions (figure 5) or in several units (Figure 6), being useful for packing in storage and export of vegetables, for domestic use, and packed in retail stores among others.

 In the photographs shown in Figures 7, 8, 9 10 and 1 1, different vegetables are observed packed with the packaging of the present invention and kept refrigerated at 6-7 ° C, for the time indicated for each case. Figure 7, artichokes (30 days), figure 8 broccoli (30 days), figure 9 peach (30 days), figure 10 pear (76 days) and figure 1 1 carrot (53 days). As the volume of the head space decreases, the container collapses on the vegetable's epidermis, as if it were a second skin, which optically resembles the presentation of vacuum-packed products. This is because after a variable time, depending on the rate of respiration of the plant, cooling temperature and thickness of the film used, in the chamber or head space (10), the volume decreases proportionally to the oxygen consumed by the vegetable.

Claims

 1 .- A multilayer film substrate coextruded for use in the packaging of fresh vegetables, which allows modulating the permeability of the gases generated during the respiration of said fresh vegetables, CHARACTERIZED because it is constituted by:  a first sealing layer (2) formed by at least 55% by weight of a polyethylene of at least 0.925 g / cm 3, the difference being complemented by another polyethylene, being a thermoplastic with a significant number of short branches of not more than more than 0.935 g / cm3;  a second core layer (3) formed by a polymeric matrix comprising a film-forming polymer, wherein the polymeric matrix of said second core layer (3) is constituted from 88% of appropriate thermoplastic polymer of low branching degree and greater than 0.940 g / cm3 the difference being structured by appropriate thermoplastic polymer with a significant number of short branches of up to 0.935 g / cm3; Y  a third outer layer (4) formed by at least 55% by weight of a polyethylene of at least 0.925 g / cm3, the difference being complemented with another polyethylene, being a thermoplastic with a significant number of short branches of not more than more of 0.935 g / cm3.  2. A coextruded multilayer film substrate, according to claim 1, CHARACTERIZED because said first sealing layer (2) is a layer that is biaxially oriented.  3. - A coextruded multilayer film substrate, according to claim 1 or 2, CHARACTERIZED in that the polymer matrix of said second core layer (3) comprises a film-forming polymer having appropriate properties for extrusion and biaxial orientation, stretching the material extruded in machine direction and in transverse direction. 4. - A coextruded multilayer film substrate, according to claim 1, 2 or 3, CHARACTERIZED because said second core layer (3) is biaxially oriented and has a melt index of 6.3 to 12.3 g / 10 min. , wherein said second core layer (3) is oriented in at least a first direction, the machine direction (longitudinal) to a degree of 1: 1 to 3: 1, preferably 1: 1 to 2: 1, and oriented in a second direction stretched in the transverse (lateral) direction to a degree of 2: 1 to 4: 1, preferably 2: 1 to 3: 1.  5. - A coextruded multilayer film substrate, according to any of the preceding claims, CHARACTERIZED because said third outer layer (4) is biaxially oriented.  6. - A coextruded multilayer film substrate, according to claim 1 or 5, CHARACTERIZED because said third outer layer (4) is printed.  7. - A coextruded multilayer film substrate, according to claim 1 or 5, CHARACTERIZED because said third outer layer (4) is not printed.  8. - A coextruded multilayer film substrate according to claim I, CHARACTERIZED because said coextruded multilayer film substrate (1) is modified by corona discharge treatment.  9. - A coextruded multilayer film substrate, according to any of the preceding claims, CHARACTERIZED because a first sealing layer (2) and the third outer layer (4) are both hermetically heat sealable  10. - A coextruded multilayer film substrate, according to any of the preceding claims, CHARACTERIZED because the structure of said multilayer coextruded film substrate (1) requires a thickness "E" comprised between approximately one third for each symmetrical layer being the difference of the remaining third structured by the second core layer (3).  eleven . - A coextruded multilayer film substrate, according to claim 10, CHARACTERIZED in that the thicknesses of: the first sealing layer (2), second core layer layer (3) and the third outer layer (4) are similar or equal.  12. - A coextruded multilayer film substrate according to claim I I, CHARACTERIZED because said thickness is in a range between approximately 8 μιτι and approximately 30 μιτι. 13. - A coextruded multilayer film substrate, according to any of claims 10 to 12, CHARACTERIZED because the optimum thickness of the film depends on the physiology of the vegetable to be packaged. 14. - Use of the coextruded multilayer film substrate, according to any one of claims 1 to 13, CHARACTERIZED because it serves to manufacture a package (6) intended to wrap vegetables in a unitary manner.  15. - Use of the coextruded multilayer film substrate, according to any of claims 1 to 13, CHARACTERIZED because it serves to manufacture a package (6) intended to wrap vegetables in unit fractions.  16. - Use of the coextruded multilayer film substrate, according to any of claims 1 to 13, CHARACTERIZED because it serves to manufacture a package (6) intended to wrap vegetables in several units.  17. Use of the packaging according to any of claims 14 to 16, CHARACTERIZED because it is used for packaging in storage and export of vegetables.  18. Use of the packaging according to any of claims 14 to 16, CHARACTERIZED because it is used for domestic use.  19.- Use of the packaging according to any of claims 14 to 16, CHARACTERIZED because it is used for packaging in retail stores.