WO2007017769A1

WO2007017769A1 - Continuous web of the type used for making flexible wrappings

Info

Publication number: WO2007017769A1
Application number: PCT/IB2006/050755
Authority: WO
Inventors: Arturo Giusti
Original assignee: Policarta S.R.L.
Priority date: 2005-08-05
Filing date: 2006-03-10
Publication date: 2007-02-15
Also published as: EP1931577A1; ITRM20050424A1; ATE417793T1; EP1931577B1; DE602006004370D1

Abstract

A continuous composite web (1) for making flexible wrappings, in particular for food products (P), is of easy use on a reel and comprises at least one strip (2) of paper material and at least one strip (3) of basically see-through material, for making said web (1); a glue deposition (5) on a face of each of said strips (2, 3), so as to make an adhesive surface; and a continuous layer (6), laid on said adhesive surface so as to cover all of the web (1).

Description

CONTINUOUS WEB OF THE TYPE USED FOR MAKING FLEXIBLE

WRAPPINGS

DESCRIPTION The present invention relates to a continuous web of the type used for making flexible wrappings, in particular bags or the like for containing food products in general, like, e.g., bakery products such as bread just out of the oven or even partially cooled, fruits, vegetables. The web of the present invention comprises at least one strip of a paper material and at least one strip of substantially see-through material, arranged side-by-side to make said web.

Therefore, the continuous composite web is of the type having a face adhering onto itself, at predetermined portions thereof, to bond the wrappings made therewith. Usually, the abovementioned web is provided in coils that are inserted into an automated production cycle having, as end result, separate flexible wrappings each containing the respective food product, e.g. a loaf of bread, and suitably sealed to assure an adequate preservation of the organoleptic and hygienic properties of the contained product, from the production to the final consumption thereof.

An example of such a web is disclosed in the utility design application n° IT-RM92U000048. The web of Pat. Appl. n° IT-RM95A000356 has longitudinal strips that are overlapped at the longitudinal edges thereof to provide continuity to the web. It further comprises longitudinal edge depositions and transversal depositions of glue to implement each wrapping. In order to prevent edge overlapping from creating excessive thicknesses at which accidental adhering of said longitudinal and transversal depositions might have occurred into the coil, the latter depositions have been arranged in selected areas, i.e. preventing said thicknesses. In Pat. Appl. n⁰ IT-RM97A000517, a different way to prevent said drawback is disclosed: in fact, a continuous deposition of glue, made with a grid of thin glue lines, is provided on the entire web surface.

EP 1 031 515 describes a web consisting in a plastic support onto which paper strips are applied. The abovementioned strips and others to be found in the state of the art are such as to have anyhow a variable thickness on the respective transversal contour of the web. The thickenings and the depressions determined thereby cause, during coiling, zones that are anyhow more compressed thereamong and zones where the pressure is sensibly lower. However, notwithstanding the complex systems adopted to avoid this drawback, the adhesive zones of the web lying at higher-pressure zones tend to adhere permanently, then ripping at the time of unreeling.

Moreover, the adjoining zones between strips of different nature easily originate ruptures that propagate, during packaging or once the wrapping is made, thwarting the effects of the packaging itself.

The technical problem underlying the present invention is to provide a continuous composite web overcoming the drawbacks mentioned with reference to the known art.

Such a problem is solved by a composite web as specified above, characterized in that it comprises a deposition of glue on a face of each of said strips, so as to make an adhesive surface, and a continuous layer laid on said adhesive surface so as to cover the entire web.

The main advantage of the web according to the present invention lies in the elimination of the web thickenings and the overlappings between the edges of the different strips.

The present invention will hereinafter be described according to a preferred embodiment thereof, given by way of a non-limiting example, making reference to the annexed drawings, wherein:

* figure 1 shows a schematic and exploded perspective view of a length of the composite web according to the invention;

* figure 2 shows a cross section of the web of figure 1 ; and * figure 3 shows a perspective view of a step of making a wrapping with the web of figure 1.

Referring to the figures, a continuous composite web for making wrappings is generally denoted by 1. It comprises at least one strip of a paper material and at least one strip of basically see-through material side- by-side, for making said web 1. According to the present embodiment, in particular it comprises a pair of lateral strips 2 of laminated paper material, with a middle strip 3 of substantially transparent material interposed therebetween.

However, it is understood that different geometries are possible, providing a variable number, greater than or equal to one, for each type of strip.

The internal edges 4 of the side-by-side strips 2, 3 are into contact, yet not overlapped. On a face of each strip 2, 3 there is a deposition 5 of glue, lacquer, resin or of an equivalent adhesive material, so as to make an adhesive surface determined by placing said strips side-by-side.

It is understood that the deposition 5 of said glue may occur prior to placing the strips 2, 3 side-by-side. Advantageously, said strips could be provided in suitable coils with the applying of the layer of glue 5 directly downstream of the unreeling.

In the present embodiment, said glue deposition 5 is made by a continuous layer of glue, deposited by spreading, silk-screen or spraying, Glue thickness is such as not to excessively alter the transpirability of the underlying layers, in particular of the paper layer.

According to a variant, said glue deposition 5 is made by a grid of glue lines, so thick and uniformly distributed as to operate like a continuous layer. According to a further variant, said glue deposition 5 is made by an array of suitably distributed glue points.

The composite web 1 further comprises a continuous layer 6, laid on said adhesive surface determined by the depositions 5, of an extension such as to cover all of the web 1.

Suitably, said continuous layer 6 is made of basically transparent material, e.g. a plastic material, optionally of the same nature of that used for the middle strip 3.

As it is evident in figure 2, the thickness of the resulting web 1 is absolutely uniform, therefore void of thickenings or depressions.

The resulting coupling of a paper material, glue deposition 5 thereon and continuous layer 6 is suitably permeable to steam, in order to allow the packaged product to breathe.

Onto the continuous layer 6 an exposed surface 7 is defined, intended to come into contact with the product to be packaged in the wrapping produced with the web 1. Onto said exposed surface 7, and at the external longitudinal edges 9 of the above described composite web 1 , the latter comprises longitudinal glue depositions 8 for forming wrappings in a continuous process.

According to a variant, said continuous layer 6 does not extend to the rim of said lateral edges 9 but leaves uncovered a continuous band, where it is possible to provide said longitudinal deposition 8. In a further variant, the longitudinal deposition 8 itself consists of the glue deposition 5 left uncovered at a longitudinal bar. The web 1 may comprise even a single longitudinal glue deposition 8.

Moreover, the above described composite web 1 comprises transversal glue depositions 10 spaced at a fixed pitch onto the exposed surface 7 of said continuous layer 6, for making wrappings in a continuous process.

In figure 3 there can be seen a food product P, e.g. a loaf of bread just out of the oven, in a packaging step in which the wrapping W enveloping it is made. The longitudinal depositions 8 are overlapped according to a flow- pack configuration. Then, the transversal depositions 10 folded on themselves are bonded. Adhesion may occur by pressure, heat-bonding or a combination of both.

Optionally, said longitudinal 8 and transversal 10 depositions may be provided after the unreeling of the coiled web, just upstream of the packaging process, by a suitable machine. In a further variant, the depositions 8, 10 are not employed, yet the continuous layer 6 is heat-bondable in selected areas during the making of the wrapping.

The above described coupling system provides novel features to the composite web 1: the reeling takes place in a basically planar manner, preventing differentiated pressures among the various zones of the web; the construction mode adopted implies an improved bondability of the cross section, thanks to the basically planar surface of the web making uniform the pressure and/or the heat provided in the bonding area along the entire transversal contour; and the construction mode employed allows the use of a continuous layer 6, even very thin and of simpler finding on the market with respect to those commonly used to date, as the web see-through zone is reinforced by the presence of a two-fold material structure that, obviously, could also be of a different nature with respect to the film used in the coupling to paper, thereby providing features different and differentiated among the various web zones.

Lastly, the use of thin films is of difficult application in most cases, due to their delicacy in use and the high likelihood of ruptures ensuing, both during the packaging step and in the use of the package itself, due to the following reasons: a) in the packaging step, owing to the two-fold thickness generated by paper overlapping to the film, in order to make a satisfactory bonding of the window zone, it is necessary to exert a strong pressure of the ~~ O ~~ bonding masses, in order to transfer into the central zone as well an adequate contact between surfaces, such as to produce a satisfactorily tight bonding. Thus, however, if the film of which the window zone is made does not exhibit sufficient strength, fractures are produced onto the web surface, such as to prejudice the package tightness. b) in the package-using step, in case a satisfactory package has been made even by using a paper-coupled thin film, at the opening of the package, by effect of the action exerted in the detaching of the transversal bonding, usually a longitudinal rupturing of the film takes place in the window zone, making the package not bondable anymore.

Therefore, the above described web solves these problems:

1) Film planarity, improved behavior in packaging machine, improved bondability of the transversal closures, improved manufacturing of gas-tight packages. 2) Abatement of the cost of the materials used in the making of the packages, thanks to the lesser amount of material required.

3) Absence of the longitudinal rupturing of the window zone at the opening of the package.

To the above described continuous composite web a person skilled in the art, in order to satisfy further and contingent needs, may effect several further modifications and variants, all however encompassed by the protective scope of the present invention, as defined by the appended claims.

Claims

1. A continuous composite web (1) for making flexible wrappings, in particular for food products (P), comprising at least one strip (2) of paper material and at least one strip (3) of substantially transparent material arranged side-by-side, for making said web (1), and further comprising:

- a glue deposition (5) onto a face of each of said strips (2, 3), so as to form an adhesive surface; and

- a continuous layer (6), laid on said adhesive surface so as to cover all the web (1).

2. The composite web (1) according to claim 1 , wherein said continuous layer (6) is of substantially transparent material.

3. The composite web (1) according to claim 1 or 2, comprising longitudinal glue depositions (8) onto the exposed surface (7) of said continuous layer (6), at the longitudinal edges (9) of the web (1), for forming wrappings in a continuous process.

4. The composite web (1) according to one of the preceding claims, comprising transversal glue depositions (10) onto the exposed surface (7) of said continuous layer (6), for forming wrappings in a continuous process.

5. The composite web (1) according to one of the preceding claims, wherein the resulting coupling of paper material, glue deposition (5) thereon and continuous layer (6) is permeable to steam.

6. The composite web (1) according to one of the preceding claims, comprising a pair of strips (2) of paper material with a strip (3) of basically transparent material interposed therebetween.

7. The composite web (1) according to one of the preceding claims, wherein said glue deposition on a face of each of said strips (2, 3) is made by a continuous layer of glue (5).

8. The composite web (1) according to one of the claims 1 to 6, wherein said glue deposition on a face of each of said strips (2, 3) is made by a grid of glue lines.

9. The composite web (1) according to one of the claims 1 to 6, wherein said glue deposition on a face of each of said strips (2, 3) is made by an array of uniformly distributed glue points.