Bag for packing moisture-sensitive materials

Flexible bags – Free-standing

Patent

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Details

383120, 383125, B65D 3016, B65D 3018

Patent

active

057555141

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

This invention relates to a bag, and more particularly to a bag for packing moisture-sensitive materials, having a front wall and a back wall, and having sidewalls which form longitudinal outer edges with the front wall and the back wall.


BACKGROUND OF THE INVESTIGATION

Bags of this type, which are used for packing building materials or washing powders for example, generally consist of thick paper or of cardboard in order to ensure their dimensional stability and to ensure that they can be stacked. In order to prevent the ingress of moisture the bags are provided with a water-tight or vapour-tight layer, which may consist of a plastic coating or a coat of lacquer and which is bonded to the paper bag in a suitable manner.
Packages comprising composite materials such as these are not only expensive to manufacture but are also difficult to dispose of in a manner which takes due account of the environment, since the different materials of the bag have to be separated from each other before they can be appropriately re-utilised.


SUMMARY OF THE INVENTION

The object of this invention is to construct a dimensionally stable, moisture-repellent bag in such a way that it can be manufactured simply and inexpensively, and can easily be disposed of and re-utilised.
This object is achieved by means of the invention in that the bag completely consists of a liquid- and vapour-tight plastic film which has a thickness of at least 50 .mu.m and at most 300 .mu.m, and that the longitudinal seam of the bag is not welded, but is adhesively bonded.
This form of construction has the advantage that re-utilisation of the plastic of the bag can be effected directly after use. The use of a plastic film more than 50 .mu.m thick enables the bag to be manufactured and folded by machine. The adhesive bonding of the longitudinal seam prevents the shrinkages which occur during welding, which is otherwise customary, so that the bag has a high degree of dimensional accuracy and stability.
The bag is advantageously a block-base bag having at least four transverse outer edges on one end face, along which edges parts of the front wall, the back wall and the sidewalls are folded over in order to form a block base. Block-base bags of this type can be stacked particularly easily and safely.
The bag may also be a bag with side folds, which can be manufactured particularly simply and inexpensively.
The plastic film is preferably a polyethylene film of high density (HDPE) which has a thickness of about 100 .mu.m. A thick HDPE film of this type is particularly tear-resistant and enables the edges of the bag to be folded easily. It is also possible to use a plastic composite film comprising a polyethylene film of high density (HDPE) and a polyethylene film of low density (LDPE), which are both classed as polyolefines, and the chemical composition of which is similar so that their combined re-utilisation is possible without problems.
It is advantageous if the bag is also adhesively bonded at overlapping portions of the film in its base region. By this means, shrinkages due to welding are also reliably prevented at the base of the block-base bag or at the closed end of the bag with side folds.
The block base of the block-base bag is advantageously provided with a covering of plastic film which approximately corresponds to the dimensions of the block base and is adhesively bonded to the base from the outside. By this means additional stiffness is imparted to the block-base bag, and it has a homogeneous surface on its bottom face, which can easily be printed on.
It is particularly advantageous if the base of the block-base bag is adhesively bonded by means of two mutually parallel beads of adhesive which have a length which at least corresponds to the width of a longitudinal side, and if the covering is adhesively bonded all over to the base. By this means the flaps of the block base can be adhesively bonded to each other with just a little adhesive. The all-over adhesive bonding of the covering to the base ensures a particularly good

REFERENCES:
patent: 2996238 (1961-08-01), Linde
patent: 3485438 (1969-12-01), McCall et al.
patent: 3519195 (1970-07-01), Kuhnle
patent: 4808421 (1989-02-01), Mendenhall et al.

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