TECHNICAL FIELD

The present description relates to a sheet, in particular a sheet that can be used to manufacture packaging for wrapping and cooking food, such as gluten-free bread, which requires special care during its production. The present description also relates to a packaging comprising this sheet, as well as processes for manufacturing this sheet or this packaging.

FRAMEWORK OF THE DESCRIPTION

When cooking allergen-free food, such as gluten-free bread for celiac consumers, the food must not come into contact with the environment of the oven, if the oven or any other machine in the production chain are used, as it happens in most cases, also for the preparation of products containing the allergen in question.

Faced with this need, in the case of gluten-free bread baking, the standard procedure involves the use of perfectly sealed packaging, which, however, if put in the oven, does not allow heat exchange and the release of steam from the internal space. As a result, the product is particularly wet during cooking because it reabsorbs the water trapped in the packaging, thus deteriorating the organoleptic properties of the final product, which is thus often soft and unappetizing. This problem could be solved by puncturing micro-holes in the packaging or by punching holes or incisions, however the presence of a direct passage leads to the risk of contact between the inside and the outside of the packaging, with the entry of dust of products containing gluten. Moreover, in this case there would not be an optimal release of steam, which instead requires the creation of larger openings.

EP 2070831 and EP 3028953 describe sheets and packaging comprising openings provided with grids to see food contained in these packaging. These known sheets and packaging cannot be used to contain bread or other foods, since their grids can be crossed by contaminants. US 2997224 describes a sheet and a packaging for containing sterile products, such as for example cotton balls, bandage items and the like, wherein some openings are closed by germ-resistant paper. Such known sheet and packaging cannot withstand heat.

SUMMARY OF THE DESCRIPTION

Object of the present description is therefore to provide a packaging free from said drawbacks. Said object is achieved with a sheet, a packaging and processes for their manufacture, the main features of which are specified in the appended claims.

In particular, said object is achieved through a packaging formed by a multilayer sheet comprising at least one polymeric layer having one or more openings covered with a filter paper. This filter paper allows the exchange of heat, humidity and air between the inside and the outside of the packaging and at the same time prevents the entry of particles that could lead to physical contamination. Unlike the solution currently used, which involves the use of an airtight bag, the present packaging therefore allows optimal cooking and the achievement of a more fragrant bread.

The filter paper is preferably made of cellulose and/or other natural fibres and both the filter paper and the polymeric layer can withstand the temperatures required for baking bread. The particular combinations of substances, thicknesses and/or weights of the polymeric layer, of the adhesive layer and/or of the filter paper layer allow to obtain sheets and packaging that withstands temperatures above 150 °C, i.e. the cooking temperature of food, and preferably also of 200 °C, i.e, the baking temperature of the bread.

The fibrous content in the filter paper is preferably greater than 80%, so that its resistance to high temperatures increases, since in the filter papers of common use the residual percentage of substances, for example plastic substances, deteriorates at lower temperatures, thus also deteriorating the filter paper.

In one embodiment, the filter paper is bonded in bands over the polymeric layer, thus leaving uncovered portions of the polymeric layer, preferably transparent to see the contents, so as to allow an optimal heat-sealing of the packaging.

In another embodiment, the filter paper is arranged between two polymeric layers in order to obtain a packaging with a greater mechanical strength and with the possibility of applying writings on the outer polymeric layer. Also in this embodiment the polymeric layers are preferably transparent to allow viewing of the contents through an intermediate portion.

Thanks to the resistance to temperatures of an oven, a food can be cooked directly in the packaging.

A primer is preferably applied to the filter paper, so as to gather the fibres of the paper and improve the penetration of the layer of adhesive therein, thus preventing overheating and deterioration of the fibres when the sheet is heated.

The sheet and the packaging according to the present description can also be manufactured with relatively simple, cheap and fast processes, preferably with a series production.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages and characteristics of the sheet, the packaging and the processes according to the present description will be apparent to those skilled in the art from the following detailed and non-limiting description of some of embodiments thereof with reference to the attached drawings in which:

figure 1 shows a top view of a first embodiment of the sheet;

figure 2 shows a bottom view of the sheet of figure 1;

figure 3 shows section III-III of figure 2;

figure 4 shows a scheme of the manufacturing process of the sheet of figure 1; figure 5 shows a front view of a packaging comprising the sheet of figure 1 during a phase of the manufacturing process of the packaging;

figure 6 shows a side view of the packaging of figure 5 during a subsequent phase of the manufacturing process of the packaging;

figure 7 shows a section view of a second embodiment of the sheet;

figure 8 shows a scheme of the manufacturing process of the sheet of figure 7; figure 9 shows a top view of a third embodiment of the sheet;

figure 10 shows a bottom view of the sheet of figure 9;

figure 11 shows a top view of a fourth embodiment of the sheet; figure 12 shows a bottom view of the sheet of figure 11;

figure 13 shows a top view of a fifth embodiment of the sheet;

figure 14 shows a bottom view of the sheet of figure 13;

figure 15 shows a top view of a sixth embodiment of the sheet;

figure 16 shows a bottom view of the sheet of figure 15.

EXEMPLARY EMBODIMENTS

With reference to figures 1 to 3, it is seen that the sheet 1 according to a first embodiment comprises at least one polymeric layer 2 having two surfaces. One or more layers of filter paper 4 are applied to a surface, for example the upper surface, of the polymeric layer 2 by at least one adhesive layer 3.

The layers of filter paper 4 preferably cover only some areas of the polymeric layer 2 so that one or more portions 2a, 2b of the polymeric layer 2 are not covered by a layer of filter paper 4.

The polymeric layer 2 is further provided with at least one incision 5 which connects the two surfaces of the polymeric layer 2. In particular, the incision 5 can be rectilinear or curved or, as in the present embodiment, closed so as to define in the layer polymeric 2 at least one opening, in particular four openings having a substantially elliptical shape. The adhesive layer 3 is preferably applied to the polymeric layer 2 only in the portions covered by the layers of filter paper 4, thus leaving the uncovered portions 2a, 2b without adhesive.

The layers of filter paper 4 cover the incisions 5, so that gases, for example water vapor, can pass through the sheet 1 through the layers of filter paper 4 and the incisions 5.

The polymeric layer 2 and/or the layers of filter paper 4 have a preferably rectangular shape. In particular, one or more non-overlapping layers of filter paper 4 are applied to the polymeric layer 2 so as to form one or more substantially parallel bands which extend between two opposite edges of the polymeric layer 2. Such bands preferably define at least two lateral portions 2a and/or at least one intermediate portion 2b in which the polymeric layer 2 is not covered by the layers of filter paper 4. The lateral portions 2a can be arranged along the shorter sides, as in the present embodiment, and/or along the longer sides of the polymeric sheet 2, to favour the closing of the sheet 1 to form a packaging. The polymeric layer 2 is preferably transparent.

The filter paper 4 preferably comprises at least 80% by weight of a fibrous material, in particular natural fibres, more particularly cellulose. The weight of the filter paper 4 is between 30 and 90 g/m ² , in particular between 40 and 70 g/m ² , preferably between 48 and 51 g/m ² . The thickness of the filter paper layer 4 is between 50 and 250 microns. The polymeric layer 2, the adhesive layer 3 and the filter paper layer 4 preferably withstand the temperatures of the food ovens, in particular at least 150 °C, more particularly at least 200 °C. This heat resistance can be obtained for example by means of a chemical bath in sulfuric acid or in zinc chloride and/or in any substance suitable for creating a reticulated structure within the polymeric chains of which the cellulose is composed. The filter paper 4 may be coated with a material with high thermal resistance, for example a silicone rubber, which may be provided with pores for the passage of gas. The filter paper 4 may comprise other natural fibres such as alpaca fibres and/or artificial fibres such as rayon fibres.

The filter paper 4 may have different conformations and mechanical resistances depending on whether it is produced, for example, in a smooth, rough or crinkled conformation. Among these, rough paper and crepe paper generally provide a greater filtration area and offer high filtration rates. Crepe paper preferably also offers a higher ability to retain particulates than smooth paper.

The polymeric layer 2 can be obtained using one or more layers of PET, PA, PP cast or coextruded PP. In particular, the polymeric layer 2 preferably comprises PET with a Mylar coating, on which two layers of filter paper 4 made of cellulose treated and joined to rayon fibres are applied by means of a layer of adhesive 3.

The adhesive layer 3 may consist for example of a dispersion in a water-based solvent or alcohol, a monocomponent polyester-based adhesive, or a two-component adhesive with polyester and reagent. In particular, a primer, preferably a water-based acrylic primer, is applied to at least one portion of the layer of filter paper 4, preferably in an amount of 2 to 6 g/m ² , after which the polymeric layer 2 is joined to the portion of filter paper 4 provided with primer by means of the adhesive layer 3, preferably a one- component polyester-based adhesive and/or applied in an amount of 2 to 10 g/m ² .

With reference to figure 4, it is seen that in a first operative step of the manufacturing process of the sheet 1 according to the first embodiment, a strip 6, of the same material of the polymeric layer 2 and preferably wound in a reel 7, is pulled in the direction of the arrows from one or more auxiliary rollers 13. One or more rollers 10 create notches 5 in the strip 6 at regular intervals by means of suitable punches, removing excess material, while at least one suitably shaped roller 11 rotates inside a tank 12 containing an adhesive to apply an adhesive layer 3 to the lower surface of the strip 6 or portions thereof. One or more substantially parallel strips 8 wound on reels 9 are pulled by the rollers 13 in the direction of the arrows and joined to the strip 6 thanks to the adhesive layer 3. The thus obtained laminated strip 14 is preferably wound onto a reel 15. In a subsequent operating step, the laminated strip 14 can be taken from the reel 15 and cut to obtain one or more sheets 1 according to the first embodiment.

With reference to figure 5, it can be seen that a sheet 1 can be used to form a packaging suitable to contain one or more articles, for example a piece of bread 16. In a first operative step the sheet 1 is folded, preferably with the layer of filter paper 4 on the outside, after which the edges corresponding to the two lateral portions 2a of the polymeric layer 2 are heat-sealed, thus creating a substantially tubular structure having the open ends and a longitudinal rib corresponding to the two lateral portions 2a joined together. The piece of bread 16 is then inserted into the substantially tubular structure through an open base.

With reference to figure 6, it is seen that in a subsequent manufacturing step of the packaging, the two openings at the ends of the substantially tubular structure are closed by joining together and then heat-sealing two portions of both other edges of the polymeric layer 2, thus forming two further ribs 17 which complete the closure of the packaging.

An alternative process for manufacturing the packaging, not shown in the figures, comprises instead the folding and overlapping of two halves of the laminated strip 14 along the longitudinal axis, preferably leaving the filter paper 4 on the outside, so that the lateral portions 2a of the polymeric layer 2 coincide. Subsequently, the lateral portions 2a are heat-sealed and a further transverse seal is obtained, i.e. substantially perpendicular to the edges of the laminated strip 14, so as to create a pocket in which at least one article is inserted. A further transverse seal is formed in the laminated strip 14, so as to form a closed packaging containing the article. This closed packaging can then be separated from the rest of the laminated strip 14 by a transverse cut, for example performed by an automatic cutter.

With reference to figure 7, it is seen that the sheet 1 according to a second embodiment is similar to the first embodiment but comprises at least two polymeric layers

2 provided with one or more incisions 5. One or more layers of filter paper 4 are arranged between the two polymeric layers 2 and are joined thereto by at least two adhesive layers

3 applied to the surfaces of the polymeric layers 2 in contact with the layers of filter paper 4. The incisions 5 are covered by the layers of filter paper 4, so that gas can pass through the sheet 1 through at least two incisions 5 and a layer of filter paper 4 arranged between these two incisions 5.

With reference to figure 8, it can be seen that in a first operative phase of the manufacturing process of the second embodiment of the sheet 1, two strips 6, of the same material as the polymeric layer 2 and preferably wound in two reels 7, are pulled in the direction of the arrows from one or more auxiliary rollers 13. The reels 7 are preferably arranged at different heights and the two strips 6 thus form an upper branch and a lower branch which are pulled by the auxiliary rollers 13, so that the strips 6 can be joined to one or more strips 8 of filter paper after an adhesive layer 3 is applied thereto. The laminated strip 18 thus obtained is preferably wound on a reel 15 and can be used to make a packaging similar to that obtained with the first embodiment of the sheet 1.

Figures 9 to 16 show further embodiments of the sheet 1, with one or more filter papers 4 and incisions 5 having different shapes, dimensions and/or arrangements on the polymeric layer 2. In the sheet of figures 9 and 10 the layer of filter paper 4 has substantially the same extension as the polymeric layer 2 and has a plurality of incisions 5 having the shape of pores.

Possible variations or additions can be made by those skilled in the art to the embodiments described and illustrated herein, remaining within the scope of the following claims. Further embodiments may comprise the technical characteristics of one of the following claims with the addition of one or more technical features described in the text or illustrated in the drawings, taken individually or in any mutual combination thereof.