PAINT CAN AHD METHCX) OF MANUFACTURING A PAINT CAN

The invention relates to a can, in particular a can intended for being filled with a liquid, such as paint, containing at least 3% volatile organic substances, comprising a circumferential wall, a first end wall and a second end wall. The can may also have the shape of a bottle, in which case an end wall is for example provided with a screw cap opening, for storing volatile organic substances, for example.

Such a can is known from Dutch patent publication NL 1028302, which can is made of plastic material. Also other paint cans of this kind are generally known, for example paint cans entirely made of a metal. There are essentially two variants of paints. The first variant concerns paint based on organic solvents, in which the liquid component is essentially an organic volatile solvent. The second variant concerns water-based paint, in which the liquid component is essentially water, but which still contains about 5-20% organic volatile solvent. It is very important in connection with the shelf life of the paint and in order to prevent undesirable odours and harmful substances in the space where the paint can is stored that said volatile substances cannot escape from the paint can.

The object of the invention is to provide a can of the kind referred to in the introduction which can be manufactured at low cost, which makes it possible to realise a long shelf life of the liquid, which is not harmful to public health and/or which is environmentally friendly.

According to the invention, the circumferential wall of the can to that end consists of a laminate, which laminate, viewed from the outside to the inside, comprises at least one layer of cardboard, an adhesive layer, a layer of a metal foil, and a layer of plastic material.

Within the framework of the invention, the term "cardboard" is to be understood to include (multilayer) paper as well. Cardboard is an inexpensive and environmentally friendly packaging material in comparison with plastic and metal. The cardboard is preferably Kraft cardboard. Preferably, the layer of cardboard has a thickness between 300 μm and 2500 μm, more preferably between 400 μm and 1200 μm. In the preferred embodiment, the layer of cardboard is about 600 μm thick. Preferably, the layer of cardboard is made up of several layers of glued-together cardboard. In the preferred embodiment, the layer of cardboard consists of two layers of Kraft cardboard, each having a thickness of 300 μm, and one layer of 50-gram Kraft paper, which are fixed together by means of an adhesive layer. Such a multilayer structure imparts strength to the wall.

Preferably, the adhesive layer between the metal foil and the cardboard likewise comprises a glue. In an alternative embodiment, this is polyethylene, and a strong bond is obtained by melting said polyethylene during the production of the laminate. Preferably, the polyethylene adhesive layer has a thickness between 3 μm and 60 μm, more preferably between 5 μm and 30 μm. In the alternative preferred embodiment, the polyethylene layer has a thickness of about 13 μm.

Preferably, the layer of metal foil consists of aluminium foil. The layer of metal foil preferably has a thickness between 3 μm and 50 μm, more preferably between 4 μm and 20 μm. In the preferred embodiment, the layer of metal foil has a thickness of about 9 μm.

The volatile organic substances in the liquid may for example comprise one or more substances from the group consisting of toluene, xylene, benzene, turpentine, hexane, thinner, white spirit, dry cleaning naphta, ketone, ester, glycol ether, alcohol, in particular butyl glycol, butyl diglycol, ethyl glycol and methyl glycol. All these substances are well-known solvents for paint. The plastic on the inner side of the wall is preferably a plastic such as a polyalkene, for example polypropylene or polyethylene, or polyethylene terephthalate, which exhibits sustained resistance to the volatile organic substances. Other resistant plastics are also conceivable, however. The layer of plastic preferably has a thickness between 5 μm and 100 μm, more preferably between 10 μm and 50 μm. In the preferred embodiment, the layer of plastic consists of polypropylene and has a thickness of about 25 μm.

The metal foil, as well as the layer of plastic, and in particular the combination thereof, provides adequate imperviousness to air, volatile organic substances, water and water vapour.

In the preferred embodiment, one of the end walls of the can is an upper wall consisting of a ring portion provided with an opening and a lid that fits therein. In the preferred embodiment, the end walls of the circumferential wall are separate parts, which are connected to the circumferential

wall. The end walls are preferably made of a plastic, such as polypropylene, preferably by means of an injection moulding technique. In that respect the preferred embodiment is the same as the preferred embodiment as disclosed in NL 1028302, from which the preferred embodiment disclosed herein is only different as regards the composition and structure of the circumferential wall. Consequently, the manner in which the end walls are connected to the circumferential wall is identical to the manner described in said document. Because of the presence of the layer of plastic on the inside, the bond obtained between the polypropylene end walls and the circumferential wall by using a glue or an ultrasonic welding technique is a very strong one.

The invention also relates to a method of manufacturing a can of plastic material, such as a paint can, comprising the provision of a circumferential wall, a first end wall and a second end wall, wherein the can is filled with a liquid, such as paint, containing at least 3% volatile organic substances, and wherein the circumferential wall is made of a laminate, which laminate, viewed from the outside to the inside, comprises at least one layer of cardboard, an adhesive layer, a layer of aluminium foil, and a layer of plastic material.

The present invention will be explained in more detail in the description below with reference to the appended illustrations of embodiments thereof.

Figure 1 is a longitudinal sectional view of a first embodiment of a can according to the invention, in which certain parts are not shown.

Figure 2 shows the can of figure 1, parts of which are shown in exploded view.

The can 1 shown in figures 1 and 2 comprises a circumferential wall 3, a first end wall in the form of a bottom 12, and a second end wall or upper wall 5 consisting of a ring portion with an opening 6 for a lid that fits therein. The upper wall 5 comprises a circumferential surface 9, which terminates in a slot 8 at the top of the upper wall 5. The circumferential wall 3 is slid into the upper wall 5, in such a manner that the surface 9 abuts against the inner side of the circumferential wall 3 and the upper edge of the circumferential wall extends into the slot 8. The upper wall 5 is accommodated in the circumferential wall 3 in a liquid-tight manner, for example as a result of the presence of an adhesive layer between the surface 9 and the circumferential wall. The connection may also be realised in a different manner, for example by ultrasonic welding. In a particularly preferred embodiment, the end walls are connected to the circumferential wall by means of an APOA hot melt.

The upper wall 5 is provided with a wall 7 that slopes towards the opening 6, which wall 7 ensures that the entire contents can flow out when the can 1 is being emptied. In this way an environmentally friendly aspect is realised. The can 1, which must eventually be processed as waste, will contain hardly any remnants of the original contents of the can 1, if at all.

The bottom 12 comprises a slot 13, in which the bottom edge of the circumferential wall 3 is accommodated. The

connection between the bottom 12 and the circumferential wall 3 can be realised in a suitable manner, for example by glueing or by ultrasonic welding, or by means of the aforesaid APOA hot melt .

The bottom 12 comprises a portion which extends along a curved path from the horizontal bottom surface to the circumferential wall 3 with a fillet radius 14, which likewise contributes towards an adequate discharge of the contents of the can.

Although figures 1 and 2 show a preferred embodiment, the invention is not limited to this embodiment. The upper wall and the bottom may be configured in different ways.

According to the invention, the circumferential wall 3 of the can is made of a laminate which, viewed from the outside to the inside, comprises at least one layer of cardboard, an adhesive layer, a layer of a metal foil, and a layer of plastic material.

In the preferred embodiment described herein, the laminate, viewed from the outside to the inside, consists of the following layers. - Kraft cardboard (300 μm, 200 g/m ² )

- glue (1.5 g/m ² )

- Kraft cardboard (300 μm, 200 g/m ² )

- glue (1.5 g/m ² )

- Kraft paper (50 g/m ² ) - glue (1.5 g/m ² )

- aluminium foil (9 μm, 24 g/m ² )

- glue (1.5 g/m ² )

- polypropylene (25 μm, 25 g/m ² )

The circumferential wall is for example made by glueing a sheet of aluminium foil to a sheet of polypropylene and to arrange the glued-together assembly around a cylindrical mandrel. The seam where the ends overlap is sealed by means of heat, so that the polypropylene will melt. Then the Kraft paper and cardboard layers are wound around the whole, with a glue being applied between the layers.

The glue that is used is for example Euroflex (TM) 2038/4 from EOC Belgium Adhesive Division, a glue based on vinyl acetate polymer and polyvinyl alcohol.

The Kraft paper and the Kraft cardboard impart strength to the wall, and the aluminium foil and the polypropylene provide an adequate seal action against air, water as well as the volatile substances in the paint.