EP3575233B1

EP3575233B1 - Paper bag for food

Info

Publication number: EP3575233B1
Application number: EP19176825.8A
Authority: EP
Inventors: Gabriele Gava
Original assignee: Cartotecnica Postumia SpA
Current assignee: Cartotecnica Postumia SpA
Priority date: 2018-05-28
Filing date: 2019-05-27
Publication date: 2021-03-03
Anticipated expiration: 2039-05-27
Also published as: IT201800005788A1; EP3575233A1; ES2877780T3; PT3575233T

Description

The object of this invention relates to a paper bag for packaging food that can be mechanically closed in a hermetical manner.

Prior Art

The packaging of food products inside paper bags is well known. The food products particularly suited to being contained in paper bags are: flour, rice, sugar, etc., namely dry foods, in a powdery or granular form.
This paper is a paper for foodstuffs that must not release a whole series of substances that are dangerous for food to the contents with which it comes into contact
The advantage of packaging food in a paper bag is that there is a high gaseous exchange with the environment outside the bag, thereby preventing the formation of mould or other conditions that could damage the product.
To obtain other performances of paper bags, such as the possibility of containing foods that are moist or containing water, it would be possible to couple the paper with a plastic film such as PP or PE, however in this case the packaging would no longer be recyclable as paper, and there would be a high impermeability to ventilation.
A considerable advantage of the above-mentioned combination is that it is easy to heat-seal the opening of the bag, thereby ensuring it is completely moisture proof.
One of the drawbacks of packaging food in paper-only bags, for example flour, consists in the difficulty of completely closing the top opening, with the escape of a small part of the powdery food product, creating a dusting on shop shelves; moreover, since there is no complete seal, it is possible that external elements in theory could enter the closed bag.
Indeed, currently the (non-hermetic) closure of the paper bag is carried out by automatic machines that, after opening the bag and filling it with food material, close it by folding the top flap and after one or more folds glue the folded part to the outside of the bag; this type of closure is defined as a brick and in fact it is the standard in industrial packaging.
Another method for creating the closure required, however, a manual intervention: it was a matter of applying a heat-sealing lacquer to the mouth of the bag and heating the lacquered flaps after bringing them together; however the heat treatment times did not permit sealing at speeds compatible with automated packaging, the heat-sealing lacquer had to be spread over the entire inner circumference of the bag and subsequently it was not possible to fold up the upper edges of the mouth, so the package remained with the upper edges straight, the so-called heat seal fin, a very unwelcome method for the subsequent and automated processing. Furthermore, the complete treatment with this heat-sealing lacquer inside the bag had other drawbacks: the bag often breaking when the user opened it, and the blocking effect, namely during the storage of the bags, the continuous and total internal sticking that did not allow the automated re-opening of the empty bag prior to the filling phase on automatic machinery.
The bag breaking when opened by the user is an additional drawback which is a problem with all the bags made of PP or PE, plastic or technopolymer film, if they are sealed near the opening edges.
This aforementioned breaking in reality occurs even if the relative flaps are thermally bonded, given the necessary chemical affinity of the materials to be bonded with the relative adhesive, whether it is a generic heat-sealing glue or else heat-sealing lacquers, which melt the material of the bag also at low temperatures from 80° to 150°, lower than the melting point of the material of the bag.
In addition, we can avoid using heat-sealing glues or lacquers for bonding the opening edges of bags for packaging food products if they are toxic or have one or more component that can be absorbed through the skin From document DE 10 2010 051579 A1 , a conventional paper bag is known, having a band of hot-melt adhesive glue on its internal walls, situated near the opening edges of the bag.

Objects of the invention

The object of this invention is to make available a paper bag for high productivity foods that overcomes one or more of the drawbacks of the known art.
A further object of this invention is to make available a paper bag for high productivity foods which overcomes the drawbacks described above.
A different object of this invention is to make available a paper bag for high productivity foodstuffs which provides simple automated processing.
An important object of this invention is to make available a paper bag for high productivity foods which provides a completely moisture proof closure.
An interesting object of this invention is to make available a paper bag for high productivity foods that provides a closure with folded over flaps.
A valuable object of this invention is to make available a paper bag for high productivity foods that is free of the blocking effect.
An important object of this invention is to make available a paper bag for high productivity foods which can be opened without tearing the paper.
A further object of this invention is to make available a paper bag formed from a single layer of paper that can be glued in its opening flaps.
A further object of this invention is to make available a paper bag for foods whose adhesive glue of its opening flaps is suitable for foods or non-toxic.
Another object of this invention is to make available a paper bag for foods whose adhesive gluing of its opening flaps can be free of aromatic components and/or components that can be absorbed through the skin.
A different object of this invention is to make available e a paper bag for foods whose adhesive gluing of its opening edges can be in such a quantity as to make the process for making the bag and its packaging automated.
Within the ambit of the preceding object, this invention avoids the use of amounts of glue greater than 1.35 mg/sq.cm, which would dirty the machines due to the release of glue against the various parts of the machines that would come into contact with the glue; and still within the scope of the previous object, this invention avoids the use of a glue whose time to create the gluing was greater than 1 second per bag, namely a time which if exceeded would make automated production economically unsustainable.

Explanation of the invention

These objects and those which will appear better in the following description are achieved by a paper bag for high productivity foods as described and characterised in the appended claims.
In particular, the object of the invention consists of a paper bag for high-productivity foods that has a strip of food-grade or non-toxic hot-melt glue near the opening edges in its internal walls. 0.0005 to 0.00135 gr/cm2, and preferably from 0.0009 to 0.00125 gr/cm2 of dry residue, thereby capable of being defined suitable to come into contact with foodstuffs, and where said band of adhesive glue is on at least one fold line for a crosswise turn-up of the opening edges for the brick folding of the single-layer paper bag.

Advantageous characteristics of the invention

Advantageously, said strip of glue is not continuous but is interrupted on one or more of the longitudinal folding corners of the bag, avoiding the drawback that occurs following the spreading of the glue during the folding and bag construction phase; in fact the passage of the bag on the forming plates with the abrasion of the film of glue generated a heating of the glue itself and a detrimental stickiness on the inside.
Advantageously, said strip of glue is not continuous but is interrupted on one or more of the longitudinal folding corners of the bag, thereby avoiding the drawback of continuous sticking along the entire edge, which prevents the mechanised treatment of the automated re-opening of the empty bag before the filling phase on automated machines.
Advantageously, said strip of glue is not continuous but is interrupted on each longitudinal folding corner of the bag, preventing that during the hot-melt subsequent to the filling of the bag, with the thermal expansion/enlargement of the glue there is an excess of material at the folded over folds that would tend to bring the folded edge to open towards a fin configuration. Advantageously, said strip of glue is not continuous but is interrupted at each folding corner of the bag, so it is possible to adjust the positioning of the folding profile at the centre of the interruption or adjacent to the interruption of the strip itself, in consideration of the granulometry of the food material packaged within the bag itself, thereby avoiding paper parts not glued to the opening of the bag, larger than said granulometry. Advantageously, said limited thickness of the glue is necessary to ensure it is completely moisture proof even in the corners, even if they do not have any of it, given the thermal enlargement of the glue which also arrives at surfaces not previously covered with glue.
Advantageously, with said limited thickness of the glue it is possible to create the relative hot-melting within a time of 0.7 and 1 second, making the mechanised process economically sustainable and in line with the speed of the industrial production process for packaging, without excessive temperatures beyond the 250°C, but preferably not over 230°C, which would leave a sign of carbonisation on the outer surface of the paper.
Advantageously, the hot-melt temperature of said glue is between 170°C and 230°C, avoiding the aforementioned drawback, but guaranteeing melting of said glue within the times of 0.7-1 seconds for the secure gluing of the flaps for opening the bag. Advantageously, said limited glue thickness is necessary so that the melting glue does not penetrate into the weft of the paper, entailing the risk of the user breaking the bag when opening it, but it may be opened while maintaining the continuity of the paper structure in its upper folding near the opening mouth. Advantageously, the tile folding of the top ends of the free flaps near the opening of the bag is maintained without the need for gluing to the outside of the bag, due to the additional thickness of the paper with added hot-melt glue on the inner walls of the bag and on at least one crosswise turn-up fold of the opening edges, which maintains the folding after cooling of the hot-melting.
These and other objects are all attained by the high productivity food paper bag of this invention according to the appended claims.

Brief description of the drawings

The technical characteristics of the invention, according to the aforesaid objects, can clearly be seen in the content of the claims below, and its advantages will become more readily apparent in the detailed description that follows, made with reference to the accompanying drawings, which illustrate a preferred embodiment, which is purely exemplary and not limiting, in which:

Fig. 1 shows a perspective view of the paper bag for foodstuffs that is the object of the invention opened in the upper part so as to highlight the presence and the arrangement of the band of glue near the opening with interruptions along the folding edges.
Fig. 2 shows a perspective view of the bag of fig. 1 flattened, in the configuration in which it is supplied by the bag manufacturers to their buyers, who, after opening the bag, package the food product inside.
Fig. 3 shows a plan view of the length of the bag with the band of glue indicated, possible interruptions and in an indicative manner the fold edges.
Fig. 4 shows a perspective view of a paper bag filled with food product and closed at the top with a folded over fold of the top flaps, assuming the so-called brick configuration.

Detailed description of an example of a preferred embodiment

With reference to the figures, the paper bag 1 of the invention is intended to be filled with food and closed at the top by the hot-melting of the band of glue near the free edges of the opening 3. The closure can be made mechanically and the top edge can be folded over, along the crosswise fold lines 10, giving the closed bag the classic brick configuration 2.
After this bag 1 is made it is then supplied by the manufacturers to their customers in a flattened configuration 4. Since these bags are prepared for mechanised opening, filling and closing, all the parts must be able to come into contact with the food without any drawbacks and/or limitations.
For this reason, in the past the glue or the sealing lacquer that were not certified to come into contact with the food contained in the bags, had to be present only on the outside of the bag. Only with the hot-melt glue 5 for foodstuffs, which is non-toxic, was it possible to proceed with their preparation inside the bag 1, namely near the free edges of the opening 3 on the internal walls. However, this caused the big drawback of blocking, which could only be resolved manually to avoid jamming during the mechanised opening.
By placing the hot-melt glue in a band 6 with at least one interruption 7, it has been possible to overcome this drawback, since at least on this interruption 7, preferably centred on a folding edge 8, certainly a free area 9 is configured and free from the aforementioned problem, on which to create the initial opening of the flattened bag.
It is very important that the band 6 of glue 5 is in the amount of 0.0005 to 0.00135 gr/cm2 of dry residue so that the relative closure can be carried out mechanically, without the risk of leaving glue residue on the parts of the machinery for the automated processing of the bag itself.
Moreover, with this amount of glue 5, the time taken for the relative hot-melting is between 0.7 and 1 second, which makes it possible to have no slowdowns during the packaging production process, making it economically viable.
Preferably the amount of glue of the band 6 is between 0.0009 to 0.00125 gr/cm2 of dry residue, ensuring that the glue does not enter the paper weft with the risk that the bag may break during opening.
Furthermore, it is very important that this amount of glue 5 is that envisaged for maintaining the melting temperature lower than 250°C, and preferably at 230°C, to avoid the surface carbonisation of the paper, while it is important that the melting temperature does not fall below 170°C, avoiding the risk that parts may be glued in an unreliable manner.
With a time of 0.7 to 1 second and with a temperature of 170°C to 230°C, the envisaged amount of glue is between 0.0005 and 0.00135 gr/cm2, and preferably between 0.0009 and 0.00125 gr/cm2 of dry residue.
With the aforesaid amount of glue we avoid, during the hot-melting, the glue penetrating the weft of the paper, which would break the upper edges of the bag when being opened by the end user.
A very important aspect of the invention relates to where the strip of glue on the inner walls, and near the upper edges, is positioned; in fact, the strip of hot-melt adhesive glue must be positioned on at least one crosswise fold line 10 of the opening edges for the tile configuration of the single-layer paper bag, ensuring that the bag is kept closed.
In fact, the amount of glue set out above and the position on at least one crosswise fold line 10 is enough to provide sufficient solidity and rigidity to the folded over assembly of the crosswise upper edges 10, after the glue subjected to the hot-melt process has cooled, maintaining the various crosswise folds of 10 against and close to the bag with a brick closure.
Finally, this amount of glue 5 is sufficient to achieve the closure of the longitudinal fold edges during the hot-melting thermal expansion.
Eventually the longitudinal fold edges can be positioned both at the centre of the breaks of the band of glue, but they can also be adjacent to this band, with a view to realising a closure that is sufficient to hold the packaged food product according to the granulometry that it has.
Finally for an even greater speed of the automation of the closure, with the hot-melting of the glue on at least one crosswise fold line 10, and with greater security in the management of the forming of the bag and avoiding any possible drawbacks during the opening of the bag for the filling of the food material before the closure, the glue interruptions or its arrangement are such as not to have overlaps of two layers of glue, but making only a hot-melt of a layer of glue directly on the paper not covered with glue.

Claims

A paper bag for high productivity food processing, comprising near the opening edges (3) in its internal walls, a band (6) of hot-melt adhesive glue (5), characterized in that the glue is of a food or non-toxic variety, with a quantity of 0.0005 to 0.00135 gr/cm2, and preferably from 0.0009 to 0.00125 gr/cm2 of dry residue, where everything is suitable for coming into contact with foodstuffs, and where said band of adhesive glue is on at least one crosswise fold line (10) of the opening edges for the brick folding of the single-layer paper bag.
A paper bag for high productivity food processing according to claim 1, characterised by the fact that said band (6) of glue (5) has interruptions (7) with sections (9) free of glue on one or more of the folding edges (8) of the bag.
A paper bag for high productivity food processing according to claim 2, characterised by the fact that at least a positioning of the fold profile of the folding edges (8) is set approximately at the centre of at least one of said interruptions (7) of the band (6) of glue (5), in the free sections (9).
A paper bag for high productivity food processing according to claim 2, characterised by the fact that least one positioning of the fold profile is set adjacent to the interruption (7) of the band (6) of glue (5).
A paper bag for high productivity food processing according to claims 4 or 5, characterised by the fact that the quantity of glue (5) next to the interruptions (7) is sufficient to expand, during the hot-melting, for the complete hermetic sealing of the closing of the mouth opening of said bag (1).
A paper bag for high productivity food processing according to one or more of the previous claims, characterised by the fact that the quantity of glue (5) during the hot-melting is thermofused to close the opening of said bag (1) from 0.7 to 1 second.
A paper bag for high productivity food processing according to one or more of the previous claims, characterised by the fact the quantity of glue (5) during the hot-melting is thermofused to close the opening of said bag (1) with a temperature lower than 250°C, and preferably between 170° and 230°C.
A paper bag for high productivity food processing according to one or more of the previous claims, characterised by the fact the quantity of glue (5) during the hot-melting is thermofused remaining on the surface with respect to the paper texture of the bag (1).
A paper bag for high productivity food processing according to one or more of the previous claims, characterised by the fact the quantity of glue (5), cooled after the hot-melting, provides the crosswise folds (10) of the free ends of the opening with a solidity that keeps the crosswise folds (10) of the bag (1) in the brick configuration (2).
A paper bag for high productivity food processing according to one or more of the preceding claims, characterised by the fact that the said band (6) of adhesive hot-melt adhesive glue (5) has interruptions so as to avoid overlapping two layers of glue, but making only a hot-melt of a layer of glue directly on the paper not covered with glue.