EP1657180B1 - Improvements on multi-ply paperbags, comprising an airtight film or equivalent, which is interposed between two paper layers - Google Patents

Abstract

The bag has a polyethylene film (4) impermeable to air and interposed between two paper folds (2, 3). The film is folded to form a sleeve with two contactless edges spaced by an interval (5) for permitting free passage of the air for deaeration, during filling of the bag. The fold (2) has a band (6) impermeable to air to impose a path to the air such that air penetrates between the fold and the film, and evacuates towards outside.

Description

The present invention relates to multi-ply paper bags comprising a film or the like, of an air impermeable material interposed between two folds of paper.

Paper bags of this type, in particular with valves and sleeves, are widely used in the art for the packaging of powdery products, for example cements, lime, coatings and all other powdered products, and the like. airtight film, usually made of plastic material, most often made of polyethylene, is intended to preserve the contents of the bag against dampness and possible splashing.

In place of a plastic film, it is also known to coat a film of an air-impermeable material with one side of a paper fold of the bag.

The invention is concerned with these two types of paper bag and the term "air-impermeable film or the like" here includes both films separated from the paper folds, as well as coatings of an impermeable material. air, sheathing one side of one of these folds.

A disadvantage of these films impervious to air is that, when filling the bag, they do not have pores allowing free passage of air deaeration bag, which slows the filling rate thereof.

To overcome this disadvantage, bag manufacturers generally cut or puncture the plastic bag, but, of course, the notched or perforated film has a lesser ability to protect packaged products from moisture.

The present invention aims to avoid this problem of the prior art by providing a paper bag having a film or a coating of a material impervious to air, which nevertheless allows excellent deaeration of the bag during its filling, while ensuring a better protection against moisture of the packaged powder product than plastic bags perforated or cut of the usual technique.

We already know, by US 4,093,114 A and by FR 2 316 138 A which corresponds to it partially, a valve bag which aims to provide "a significantly improved safety for the valve, so that the bags can be used for the packaging of semi-solid liquids that can flow, even when the bags have a large capacity "(page 2, lines 12-18, of the application French 2,316,138 ), which is completely different from the purpose of the present invention.

The invention which is the subject of the aforementioned US patent and French application seems to be (see bottom of page 3 of the French application) "the adaptation [consisting] of ensuring the admission of other strips or pellets of the film between the appropriate layers of the overlapping panels ". But nowhere is it indicated that the film inserted between the two folds of the paper is not joined, that is to say does not completely around the bag and that, to provide protection against moisture, a an airtight band is arranged opposite the space separating the two adjacent edges of the film.

The present invention relates to a multi-ply paper bag, comprising a film or the like impervious to air interposed between two folds of paper, the film being folded so as to form a sheath comprising two contiguous longitudinal edges, which bag being characterized in that these contiguous edges of the film are not contiguous, but leave between them a gap sufficient to allow a free passage of air deaeration, when filling the bag, and in that the fold of paper disposed inside the bag has, on one of its faces and opposite the gap separating the adjacent edges of the film or the attached film of air-impermeable material, an impervious band, imposing on the air of deaeration of the bag a baffle path bypassing this band so that it can access between the fold of paper and the film or the attached film and be discharged to the outside, when bagging the product packaged, while ensuring protection of the product against moisture.

As indicated above, this definition of the invention also encompasses the case where the air impervious film is replaced by a coating with a film of an impermeable material of one of the faces of a fold. of the paper of the bag, this film here being discontinuous and then comprising on the coated side of the paper fold a longitudinal zone devoid of the air-impermeable film, in such a way to allow a free passage of air through the pores of the paper and satisfactory deaeration of the bag during its filling.

The invention therefore considerably improves the bag's de-aeration capacity at the time of bagging and, consequently, the filling rate, which results in an appreciable gain in productivity.

Far from being diminished, the protection of the packaged product against any moisture recovery is enhanced, due to the total or partial elimination of the perforations of the impermeable film, and this increased protection makes it possible to increase the duration of storage bags filled with powdery product, without fear of deterioration of their contents.

The cleanliness of the bags, after the bagging, is another advantage of the invention, because the powdery product is no longer likely to escape during filling by the holes usually made during the manufacture of the bag.

Finally, the bag has an external appearance more pleasing to the eye, due to the lack of perforations of the outer paper fold.

• la figure 1 est une vue en perspective avec arrachements d'un sac en papier multi-plis conforme à l'invention ;
• la figure 2 est une coupe transversale de ce sac.

The attached schematic drawings illustrate, by way of example, an embodiment of the invention. On these drawings:

• Figure 1 is a cutaway perspective view of a multi-ply paper bag according to the invention;
• Figure 2 is a cross section of this bag.

The bag 1 shown in Figure 1 is a multi-ply paper bag, valve or sleeve, of a usual type, which will not be described in detail.

It comprises conventionally two paper plies, one inside 2, the other outside 3, folded to form a continuous sheath, whose contiguous longitudinal edges overlap and are assembled by gluing. Between these two plies 2 and 3 is interposed a film 4 of an impervious plastic material, which is intended to ensure the protection of the powder product contained in the bag against moisture recovery. This film 4 is for example polyethylene.

While the film 4 is usually folded similarly to the folds 2 and 3 to form a continuous sheath, with its contiguous edges overlapping and weldable, in the present case and according to an essential characteristic of the invention, the contiguous longitudinal edges of the film 4 are not contiguous, but are instead separated by an interval 5 extending along the length of the bag, this interval being sufficient to pass the air escaping from the bag during the filling thereof, the air deaeration first passing through the pores of the inner paper bag 2, then through the gap 5 and finally through the pores of the bag external paper 3, to be evacuated to the outside.

The gap 5 between the adjacent edges of the impermeable film 4 may have a width of a few centimeters and the film 4 thus does not provide protection against moisture at this level. In order nevertheless to maintain a perfectly satisfactory protection of the powdery product contained in the bag, one of the faces of the fold 2 of the bag, facing the gap 5, is advantageously glued to a strip of the same film or another film. impervious to air, so as to allow air to escape from the bag, during bagging, following a baffled path illustrated by arrows in Figure 2, while providing excellent protection against returns moisture from the outside of the bag, since the film is devoid of perforations at locations other than that of the gap 5.

As has been explained above, in the case of a bag with two folds of paper with an impermeable film, it would be possible, in a known manner, to substitute for the plastic film 4 a coating of a film of film. a product impervious to air on the face turned towards the inside of the bag of the fold 3, while providing, according to the invention, a localized interruption of this coating, so as to leave on this fold 3 a longitudinal zone not coated, having a role equivalent to that of the interval 5 described in the previous embodiment and allowing a free passage of air deaeration through the pores of the fold paper 3.

As before, the ply 2, on the side of this ply facing the inside of the bag and facing the zone devoid of an impervious film, will be provided with an impervious band imposing a baffled path in the air of aeration. This strip may also be made by coating the fold 2 with an impervious material to air.

It should be noted that the bag according to the invention comprises only the usual components of the paper bags known in the art and that the arrangements made to them according to the invention entail practically no increase in the cost of the raw materials necessary for the manufacture of these bags.

Claims (4)

1. A multi-ply paper bag, comprising a film (4) or the like impermeable to air, which is interposed between two plies (2,3) of paper, the film (4) being folded so as to form a sheath comprising two adjacent longitudinal edges, said bag being characterised in that the adjacent edges of the film (4) are not contiguous but leave between them a gap (5) which is sufficient to allow the free passage of escaping air when the bag is being filled, and in that the paper ply (2) disposed inside the bag comprises, on one of its sides and opposite the gap (5) separating the adjacent edges of the film (4), a strip (6) which is impermeable to air and which constrains the air escaping from the bag to follow a deflected path passing around said strip so that it can pass between the paper ply (2) and the film (4) and be evacuated towards the outside, during the bagging of the product to be packaged, while subsequently ensuring that the latter is protected from humidity.
2. A multi-ply paper bag according to claim 1, characterised in that the paper ply (3) disposed on the exterior of the bag comprises on one of its sides a coating of a film consisting of a material which is impermeable to air and which replaces the previously mentioned film impermeable to air, this bag being characterised in that the ply (3) includes a longitudinal zone which is not provided with the film of material impermeable to air and which, therefore, allows the passage of air escaping from the bag through the pores of this ply (3), which are disposed at the level of this longitudinal zone.
3. A bag according to claim 2, characterised in that, opposite the zone of the ply (3) not provided with the film of material impermeable to air, the inner ply (2) includes on one of its sides an associated strip which is impermeable to air and which constrains the air escaping from the bag to follow a deflected path so that it can escape towards the outside when the bag is being filled.
4. A bag according to claim 3, characterised in that the strip which is impermeable to air is formed by a film consisting of a material which is impermeable to air and deposited by coating on said inner ply (2).

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