ITMI20130935A1 - HIGH GAS FILM PERMEABILITY, SUITABLE FOR PACKAGING LIQUID FOODS THAT REQUIRE A GASSOUS EXTERNAL EXTERNAL EXCHANGE, IN PARTICULARLY SUITABLE FOR PACKAGING CREAM YEAST - Google Patents

Description

Description of the invention entitled:

"FILM WITH HIGH GAS PERMEABILITY, SUITABLE FOR THE PACKAGING OF LIQUID FOODS THAT REQUIRE GASEOUS EXCHANGE WITH THE EXTERNAL, IN PARTICULAR SUITABLE FOR THE PACKAGING OF YEAST IN CREAM"

DESCRIPTION

The present invention refers to a film with high gas permeability for the packaging of liquid / creamy foods that produce gas, such as yeast in cream.

The marketing of baker's yeast in liquid or creamy form instead of the more traditional compressed or dry forms, appears to be an absolutely convenient solution for several reasons.

From the point of view of the producer, the compression or drying operations are eliminated with indisputable economic advantages such as reduction of production times and lower energy consumption (reduction of C02) because the process is shorter, also reducing the risks of pollution and contamination associated with the drying and compression processes.

From the point of view of the user (bakery), the use of liquid or creamy yeast is convenient as it is a readily available form, facilitates the operation in the dough (allows greater automation), has a greater gasifying power, in addition to being more effective the relative dosage.

The distribution of this form of yeast in large volumes currently takes place through refrigerated tanks but only at an industrial level, while it is not applicable in the commercialization at an artisanal level where the quantity typically required for the batch is 10 liters (or at most 20 liters).

This quantity typically requires a "bag in box" type of packaging where the product is packaged in a flexible sachet inserted into a cardboard box with the sole purpose of maintaining a more regular shape of the package, allowing for easier handling and storage. easy.

The difficulties in this type of packaging, still not resolved today, lie in the extreme difficulty in making the sachet with adequate containment capacity for the cream and at the same time with sufficient "breathability" for the carbon dioxide produced in large quantities and speed by the fermentation of the yeast itself.

It should also be taken into account that the continuous search for yeast strains with greater gasifying power and greater effectiveness in action increasingly lead to obtaining yeasts with irrepressible CO2 production.

It is in fact very frequent that the bags containing the liquid / creamy yeast swell quickly and considerably (depending a lot on the type of yeast, on the free head space above the liquid phase, on the storage conditions of the yeast) until they burst, creating liquid / cream spillage which damages all adjacent carton packs.

And even if the bag does not break, the unsightly swelling of the cardboard box, which inevitably yields under the pressure of the yeast and deforms, creates a bad image and prejudices on the freshness of the product as well as returned to the supplier.

Currently the liquid / creamy yeast is packaged using various solutions among which we can mention the following:

- Tetrabrick (rectangular or square structure formed by a multilayer material perfectly impenetrable to gases consisting of Aluminum, Polyethylene, paper, variously sequenced) with a vent opening for the C02 formed by an upper cut. This solution (which is not a "bag in box"), however, shows the strong limit that due to the normal handling of the liquid during transport, the opening is blocked by the yeast cream which, solidifying, occludes this opening, so the most of the packs have an unsightly swelling that appears too high;

- Bag in box with poly-coated paper envelope (or sack) which, however, appears overall fragile and not very resistant to normal handling and not able to pass the "crash test", a widely used empirical test which consists in dropping a bag of 10 liters from a height of 1 m, then evaluating the condition of the bag (there must be no breakage or the slightest crack);

- Bag in box with double polyethylene bag, one of which is thinner inside and one macro-perforated outside: even in this case, however, the escape of the gas is not effective because the contact of the cardboard box with the holes prevents an effective escape of CO2 ;

- Bag in box with double and single bags (the latter in high thickness), generally in polyethylene, with relief valves in the upper part of the bag; although this is the most used solution today, it does not seem satisfactory due to the occlusion that occurs as mentioned above.

The object of the present invention is to overcome, at least in part, the disadvantages of the known art by providing a package for liquid / creamy foods that produce gas, in particular for liquid or cream yeast, which does not require openings and / or relief valves and / or micro-perforations, which has sufficient "breathability" with high permeability to gases, in particular to C02, and which is mechanically resistant to handling, in particular resistant to the "crash test".

A further object is to provide such a package which also shows a rapid gaseous exchange with the outside, preferably a gaseous exchange rate with the outside greater than the fermentation rate of the yeast itself so as to quickly dispose of the large amount of carbon dioxide. produced in a short time.

Still a further object is to provide such a package which is easily obtainable and / or workable with known methods, on an industrial scale, for example by blown extrusion, and which can be produced with a high containment capacity, for example in packs of 10 to 20 liters.

Yet another object of the present invention is to provide such a package with high sealing strengths and not subject to the opening of the sealing, in particular in the case of a multilayer film (for example according to the ASTMF88 standard).

These and other purposes are achieved by the package in accordance with the invention made with a film suitable for contact with food having the characteristics listed in the attached independent claim 1.

Advantageous embodiments of the invention appear from the dependent claims.

An object of the present invention relates to a package for liquid / creamy foods that produce gas, which in no way makes use of cuts, slits, holes, vent valves or micro-perforations, to facilitate the escape of gases but resorts to the use of a material or a combination of polymeric materials that is highly permeable to gases, for example having an OTR (oxygen transmission rate, ASTM D3985) greater than or equal to 3000 cm <3> / (m <2> 24h bar), and in particular that it has a high specific permeability towards C02.

Furthermore, this material or this combination of materials has been found to possess sufficient mechanical properties such as to allow the creation of a package capable of passing the so-called "crash test" without having any break or the slightest crack.

In particular, the object of the present invention consists of a multilayer film as defined above formed by at least one central or internal layer comprising styrene-based polymers or copolymers, optionally mixed with thermoplastic polyolefins.

More specifically, the object of the present invention is a co-extruded film formed by at least three layers (three-layer), but also by a greater number of layers, where the two outermost layers opposite each other are made with polyolefin polymers / copolymers with high welding capacity (heat-sealable) while the central or intermediate internal layer is based on styrenic polymers, preferably polystyrene or styrene copolymers, optionally mixed with thermoplastic polyolefins.

Alternatively, said extruded film can be a monolayer formed by a blend of styrene-based polymers or copolymers mixed with the thermoplastic polyolefins or thermoplastic polymers based on polyolefins indicated for the two outermost layers of the aforementioned three-layer.

Further features of the invention will become clearer from the detailed description that follows, referring to a purely exemplary, and therefore non-limiting, embodiment illustrated in the attached drawings, in which:

Figure 1 is an enlarged view of a vertical section of a first embodiment of a multilayer film according to the invention;

Figure 2 is an enlarged view of a vertical section of a second embodiment of a multilayer film according to the invention;

figure 3 is a perspective view of a bag for cream yeast obtainable from the film of fig. 1.

With reference to Figure 1, the film object of the present invention, indicated as a whole with the numerical reference 10, is a flexible film particularly suitable for making a flexible sachet / bag for containing liquid / creamy foods that produce gas, for example by fermentation, as in the case of liquid / creamy yeast.

Said film 10 comprises an external layer 1 (i.e. the one intended to be in contact with the atmosphere and / or external environment) and an internal layer 3 (i.e. the one intended to be in contact with the liquid / creamy yeast, also referred to here as external layer opposed to the external layer 1), both made of thermoplastic or polyolefin-based thermoplastic polymers, the same or different from each other but highly heat-sealable.

The thermoplastic polyolefms or the polyolefin-based thermoplastic polymers of layer 1 and / or layer 3 are preferably selected from the group formed by

- non-polar polyolefms, such as PP, LD-PE, LLD-PE (linear low density polyethylene), HD-PE (high density polyethylene), MD-PE (medium density polyethylene), VLD-PE (very low density polyethylene) , ULD-PE (ultra low density polyethylene) and the like; ethylene-propylene copolymers, cyclo-olefin copolymers (COC), polybutylene; or a copolymer of ethylene such as polyethylenes comprising α-olefins all these polymers obtained with various types of catalysis / known production technologies as long as they can be thermoplastically processed, for example by extrusion;

- polar copolymers of the above, such as for example EVA (ethylene-vinyl acetate copolymer), EMA (ethylene-methylacrylate copolymer), EAA (ethylene-acrylic acid copolymer), EBA (ethylene-butylacrylate copolymer), Ionomers and the like, as long as they can be thermoplastically processed, for example by extrusion (and having a polyethylene content such as to result in a non-sticky material);

- their blends.

The polar copolymers EVA, EMA, EAA, EBA, Ionomers are “thermoplastic workable” when the polar comonomer content is preferably less than 60%.

Enclosed between the inner layer 3 and the outer layer 1, there is an intermediate or central layer 2 which is made up of a styrene-based polymer or copolymer or its derivatives, preferably selected from PS (polystyrene), SBS (styrenebutadiene / styrene ), SEBS (styrene-ethylene / butylene-styrene), SBBS (styrene / butadiene / butylene / styrene), SIS (styrene-isoprene), and the like.

Said layer 2 can also be a blend of one or more styrene-based (co) polymers mixed with one or more polyolefin polymers of layer 1, 3 in order to favor compatibilization between the different polymers in the extrusion phase (for example EVA , mLLD-PE).

Said outermost layers 1,3 have a high sealing capacity which favors the tightness of the seal of the bag which will be obtained from the present film.

In another embodiment (not shown in the figures) the film 10 can be in the form of a single layer formed by a blend between one or more polymers of the layer 1 or 3, and one or more polymers of the central layer 2.

In a further embodiment, illustrated in Figure 2, the film of the present invention, indicated with the numerical reference 20, can be made with a number of layers greater than three, providing additional layers 4, 5 (but the number can also be greater) arranged between the outer layer 1 and / or the inner layer 3 and the intermediate layer 2. Said interposition layers 4, 5 also consist of the polyolefin materials listed above or of their combination / mixture with (co) polymers styrene based.

It is understood that it is also possible to make a co-extruded film according to the invention formed by more than five layers, for example seven or nine (but even more), provided that the two outermost opposing layers, 1 and 3, are made. with polyolefin polymers (to ensure a high sealing capacity which favors the sealing of the sack obtained from the film) and to create at least one internal layer 2 with styrene-based polymers: obviously the layers interposed between the outermost layers 1, 3 and the inner layer 2 can be made indifferently of thermoplastic polyolefin polymers and / or styrene-based polymers, alternating with each other, so as to originate a multilayer where, for example, the polyolefin layer is alternated with the styrenic one for seven, nine or more layers, in a polyolefmic / styrene / polyolefin / styrene / layer type scheme. . . .

It should be noted that one or more of the layers 1, 2, 3, and / or the additional layers 4, 5 (and others) forming the multilayer film 10, 20 or the single-layer film may also contain one or more additives useful for some specific properties, such as for example slipping, antiblocking, antistatic, antifog, antiUV, and the like, normally used in the sector of films suitable for contact with food.

Furthermore, said layers can optionally also contain monomers / polymers which favor gas permeability.

The thicknesses of each layer 1,2, 3, 4, 5 (and others), are not binding for the purposes of the present invention and can range from a few my up to several tens of my, while the total thickness of the film of the present invention can vary from 20 to 250 microns.

The film according to the invention is obtained by extrusion if single-layer or, in the case of multilayer film, by co-extrusion of the polymers or blends of polymers indicated above according to the known technique, preferably by bubble co-extrusion.

The monolayer film according to the invention is also obtained by extrusion of the blend, preferably by blown extrusion.

Subsequently, said film according to the invention (single-layer or multi-layer) is processed in the form of a bag or sachet 100 for the containment of liquid / creamy yeast, as illustrated for example in Figure 3, by making appropriate perimeter welds 11.

Said bag 100 is preferably a conventional bag for liquid / creamy yeast with a capacity generally of 10 or 20 liters, which has strong perimeter seals thanks to the fact that the polymer based on the inner layer 3 and the outer layer 1 is an extremely heat-sealable polymer. .

The same high heat-sealability also occurs in the case of single-layer films as the mixture that forms said layer contains heat-sealable.

The Applicant has found that surprisingly 10-liter, 20-liter bags made with the film according to the present invention and filled with liquid / creamy yeast have a slight swelling just immediately after closing which quickly vanishes within a few minutes, as if , after this period, the sac began to "breathe" expelling the excess carbon dioxide that caused the initial swelling to the outside.

This phenomenon was surprising in that styrene-based polymers are known to have a gas permeability comparable to that of.

Without wishing to bind to any theory, it is presumed that the presence of styrene-based polymers and / or the present combination of layers as defined above leads to a specific "breathability" towards carbon dioxide as well as greater speed and speed of gaseous exchange with the 'external compared to bags in polyethylene only, through diffusion mechanisms not investigated.

It is therefore presumed that the film of the present invention is able to determine a faster release of the CO2 under the pressure gradient, thus allowing to reach the equilibrium in the gaseous exchange between the outside and inside of the bag more quickly.

The advantages of the film of the present invention and the bags / sacks for cream yeast obtainable therefrom can be summarized as follows:

- High gas permeability, generally evaluated as OTR greater than or equal to 3000 cm <3> / (m <2> 24h bar);

- High permeability to C02 with high speed of reaching the state of equilibrium with the outside;

- High resistance to handling (does not break and does not tear) thanks to the good mechanical properties of this film which has a breaking load greater than or equal to 15 N / mm, preferably equal to or greater than 20 N / mm (determined according to ASTM D882) and mechanical properties such as to pass the crash test (drop test from a height of 1m);

- Exceptional welding capacity, absence of micro-cracks and high welding strengths; for high sealing strengths those in which in the execution of the test according to internal methods or according to the ASTM F88 standard there is no opening of the seal, but breakage of the film, i.e. the cohesion of the welded films together at temperatures> 130 ° C and "fused" one on the other is such as not to yield, so that the film is preferably broken / tearing;

- High runnability on the lines that pack the bags and excellent bubble extrudability so as to be an easily obtainable bag.

The present invention is not limited to the particular embodiments previously described and illustrated in the annexed drawings, but numerous detailed modifications can be made to it, within the reach of the person skilled in the art, without thereby departing from the scope of the invention itself, such as defined in the appended claims.

Claims (10)

CLAIMS 1. Plastic film (10; 20) with high permeability to gases and suitable for the packaging of liquid / creamy foods that produce gas, in the form of a multilayer comprising at least a central layer (2) and two outermost opposing layers (1,3 ), characterized in that said central layer (2) comprises styrene-based polymers, optionally mixed with thermoplastic polyolefins, said outermost layers (1) and / or (3), the same or different from each other, being formed by thermoplastic polyolefins or from thermoplastic polymers based on polyolefms. 2. Film according to claim 1 characterized in that it is a multilayer film obtained by coextrusion, preferably in a blown film. 3. Films according to claim 1 or 2 wherein the thermoplastics or thermoplastic polymers based on polyolefms of the outermost layers (1) and / or (3) are selected from the group formed by - non-polar, such as for example PP, LD-PE, LLD-PE (linear low density polyethylene), HD-PE (high density polyethylene), MD-PE (medium density polyethylene), VLD-PE (very low density polyethylene), ULD-PE (ultra low density polyethylene) and the like; ethylene-propylene copolymers, cyclo-olefmic copolymers (COC), polybutylene; or a copolymer of ethylene such as polyethylenes comprising a-olefins, all these polymers obtained with various types of catalysis / known production technologies as long as they are thermoplastic workable, for example by extrusion; - polar copolymers of the aforementioned polyolefms, such as for example EVA (ethylene-vinyl acetate copolymer), EMA (ethylene-methylacrylate copolymer), EAA (ethylene-acrylic acid copolymer), EBA (ethylene-butylacrylate copolymer), Ionomers and the like, as long as they can be thermoplastically processed example by extrusion; - their blends. 4. Film according to any one of the preceding claims in which the layer (2) is formed by a styrene-based polymer or copolymer or its derivatives, preferably selected from PS, SBS, SEBS, SIS, SBBS and the like, optionally in mixture ( blend) with one or more polymers indicated for layer (1) and / or (3). 5. Film according to any one of the preceding claims in which one or more layers (4,5), the same or different from each other, are provided, arranged between the outer layers (1; 3) and the intermediate layer (2), said further layers (4, 5) also being made up of polyolefin-based and / or styrene-based polymers. 6. Film according to any one of the preceding claims, in which one or more of the layers also contains one or more additives useful for imparting specific properties to said film, preferably slipping, antiblocking, antistatic, antifog, antiUV, and the like, used in the film sector suitable for contact with food and / or monomers / polymers that favor gas permeability. 7. Film according to any one of the preceding claims in the form of a monolayer (2) instead of a multilayer, said monolayer (2) being formed by a blend of styrene-based polymers mixed with thermoplastics or thermoplastic polymers based on oleofms as defined for the outermost layers (1) and (3) of the multilayer (10, 20). Package (100), in the form of a flexible sack or sachet, for liquid / creamy foods that produce gas comprising, over its entire surface, the multilayer (10, 20) or single-layer film as defined by the preceding claims. Packaging (100) according to claim 8 characterized in that it provides perimeter heat-sealing (11). 10. Package (100) according to claim 8 and / or 9 characterized by having a containment capacity of between 10 and 20 liters.