Method for extruding and labelling a cylindrical product

The present application is a United States national stage application of International patent application PCT/IB2017/055515 filed on Sep. 13, 2017 that is designating the United States, and claims foreign priority to European patent application EP 16188491.1 filed on Sep. 13, 2016, the contents of both documents being herewith incorporated by reference in their entirety.

The invention is situated in the field of tubes or cylinders, and more particularly in the field of packaging tubes for liquid or viscous products, such as toothpastes and creams, the skirt of which is obtained by extrusion of material.

Flexible packaging tubes generally have two distinct parts, namely a flexible cylindrical body or skirt connected to a head including a neck that is closed by a cap. The skirt of the tube is obtained either by extrusion of a tubular body or by welding of a multilayer film that is rolled up to form this tubular body before welding it edge to edge or with an overlap.

A number of methods exist for adding and fixing a tube head to the end of a previously extruded skirt. The tube head may be compression or injection molded and conjointly welded to the skirt by an overmolding process. Another method consists in prefabricating the tube head by injection or compression molding and then assembling the tube head to the skirt by welding.

The tube formed in this way is then decorated at the level of the skirt, notably by the end user of the tube, and printing techniques are routinely used to add the required decoration. When the skirt is obtained by extrusion of a tubular body, the printing operation is carried out before or after the assembly of the skirt and the tube head. This printing operation has a number of disadvantages linked to the fact that the printing is not carried out flat but on the tubular geometry of the skirt. This generally leads to a process of greater complexity and consequently costly equipment, lower production rates, and reduced flexibility of the manufacturing process. The lack of flexibility of printing machines leads for example to reworking operations for complex decorations such as screenprinting or a hot decoration process.

In order to overcome the difficulties of decoration by printing, one alternative method consists in applying a preprinted adhesive label to the tube. The label, which is associated with a support film generally made of PET, is separated from the support upon application to the external surface of the tube. The label is precoated with a sticky adhesive that bonds the label to the surface of the tube. The adhesive layer is protected by the support film before application of the label to the tube.

For example, the method disclosed in the patent application WO 2007/092652 consists in applying a thin label that is not suck to a support film before use. In this method, the operation of coating or of activation of the adhesive layer takes place at the moment of application of the label to the surface of the tube. A variant of this method consists in applying the adhesive layer to the label at the moment of application. Another variant consists in applying the adhesive layer to the surface of the tube before application of the label. The method described in WO 2007/082652 has a number of disadvantages, however. The addition of an adhesive layer by coating at the moment of application of the label or the addition of an activation step makes the manufacturing process more complex, in particular when applied on a line for continuous tube extrusion (FIG. 2 of WO 2007/092652). Another disadvantage lies in the very short activation time of the adhesive layer that this method requires, which can lead to a restricted and costly choice of adhesives. Another disadvantage is situated at the level of the packaging: the label that is added to the surface of the tube is not an integral part of the wall of the packaging. The edges of the label are sometimes visible or detectable by touch and compromise the decorative and esthetic properties of the packaging.

The patent application EP 0 457 561 describes a method and a device for the making up of extruded tubular bodies having a laminated surface film. This method consists in forming a first tubular body from a film, extruding a liner inside said tubular body, drawing the liner radially, pressing the liner against the tubular body. This method has a number of disadvantages. A first disadvantage is linked to the fact that the liner must be extruded inside the tubular body formed by the film. This operation requires a tube diameter sufficiently large to place in the tube the tools necessary for the extrusion and radial drawing of the extruded liner. The method proposed in this prior art does not enable the production of tubes of small diameter and in particular of tubes with a diameter less than 35 mm. EP 0 457 561 also proposes internal calibration of the diameter of the tube. Apart from the issues of bulk cited above, this method has the disadvantage of generating small variations of the outside diameter of the tube. These variations, which depend on the regularity of the throughput of the extruder, can generate decoration defects. Indeed, to obtain decoration of high quality, the edges of the decorative film on the external surface of the tubular body must be butt jointed. Now, the extrusion rate variations cited above have the effect of varying the outside diameter of the tubular body, and thus of moving the edges of the decorative film closer together or farther apart. These variations generate visual defects at the level of the junction of the edges of the decorative film.

Similar disadvantages are found in the methods and devices described in the patent applications DE 1 504 918 and DE 10 2006 006 993 for example.

U.S. Pat. No. 4,261,777 describes a method and a device for the production of a hollow synthetic structural section at least one side of which is covered by a single-layer film, the side of the structural section covered by the film having a plane surface. The film can be of paper or metal or again a synthetic material.

In the device, a film is therefore applied to the plane surface of the structural section, and vacuum is preferably applied to the formed structural section with atmospheric pressure maintained in the structural section to press it against the film. The profiles produced are not cylindrical but rectangular and include said single-layer film on at least one plane face. The film therefore does not need to be conformed in any particular manner, and it suffices to unroll it and to apply it to the provided plane surface. If it is wished to apply a film to two plane surfaces of the structural section, then two films are unrolled and individually applied to the surface of the structural section.

The application EP 0 182 763 describes a method and a system for the production of an extrudable material tube surrounded by a metal film. In the method described, the tube is formed first, after which it enters a module in which it is surrounded by the metal film. Said film comprises an adhesive layer and the tube-film assembly is laminated to produce the final product.

The application JP 2001 226476 describes products formed of polyester compositions.

The application DE 39 20 854 describes extruded plastic profiles, in particular surfaces of window or door frames with wood decorative finishes. The extruded structural section is joined to a film and to a particular wood grain. The structural section has a “T” shape and the surfaces to which the film is applied are plane. In the production machine, a film is applied to the required plane surfaces once the structural section has been extruded and the structural section-film assembly is then calibrated and cooled to form the end product. As the surfaces to which the film is applied are plane, it is not necessary to shape the film, it suffices to unroll it and to apply it to the intended surface.

The international application WO 2015/159234 in the name of AISAPACK HOLDING SA describes a method and a device for extruding and labeling a packaging tube obtained by extrusion, this publication being incorporated by reference in its entirety into the present application.

The method described in the above publication enables the decoration of skirts of extruded tubes thanks to an economical and flexible method. It consists in associating extrusion operations with labeling operations in order to end up with a decorated tubular body. The label is formed by a decorative film comprising at least two layers. The decorative film is integrated into the packaging during extrusion of the tubular body in the molten state, so that the exterior surface of the decorated packaging forms a continuous surface with no sharp edges. Thanks to the method from the above publication the decorative film forms an integral part of the packaging in contrast to a label of the usual kind added to packaging already formed.

In WO 2015/159234, the decorative film that forms all or part of the external surface of the tubular body is preferably welded to the tubular body thanks to the heat of the extruded resin. In one embodiment, the decorative film comes into contact with the molten extrudate before the cooling phase, before the calibration step.

The method according to WO 2015/159234 is the result of combining an extrusion process and a labeling process. The method consists in bringing the label into contact around the tubular body in the molten state, preferably after the operation of shaping the film into a tubular geometry. The resulting multilayer tubular structure is advantageously calibrated and cooled in order to obtain a decorated extruded tube.

In one embodiment from WO 2015/159234, the method includes a first step of shaping the film into a partially or totally tubular geometry, followed by a second step of extrusion of a tubular body in the molten state; thereafter a third step consists in bringing the external surface of the tubular body in the molten state into contact against the (concave) internal surface of the label and finally a calibration fourth step consisting in applying the external surface of the label intended to form the external surface of the tube against the internal surface of the calibration element. The third step is performed by means of a pressure difference between the internal and external surfaces of the tubular body. The fourth step employs a pressure difference between the internal surface and the external surface of the tube.

The method according to WO 2015/159234 therefore consists in producing an extruded tubular body having a decorative film label that may compose all of its external surface. Thus the tubular body is completely enveloped in the label when it enters the calibration element and the successive cooling tanks. The molten material does not rub on the cooled tools, which enables improvement of the esthetics of the packaging produced and its resistance to impact and to stress cracks.

In WO 2015/159234, a first pressure difference is used to bring the tubular body and the label into contact. This first pressure difference is exerted at least between the extrudate outlet of the nozzle of the tool and the zone of contact between the internal surface of the film and the external surface of the extrudate. This first pressure difference makes it possible to prevent air bubbles from being trapped between the label and the external surface of the tubular body. In one embodiment of the invention, the pressure difference is created by a positive air pressure inside the tube. An alternative way to create this pressure difference consists in creating a reduced pressure chamber between the extruder and the calibration element. In one embodiment, the tubular body and the label are brought into contact immediately after shaping the tube into a tubular geometry.

In a variant of the method the film is shaped into a tubular geometry conjointly with the inflation of the tubular body onto the internal surface of the film. In this variant, the plane of contact (the plane formed by the contact zone) between the film and the tubular body is inclined relative to the axis of the tube in contrast to the prior art in which the contact plane is always perpendicular to the axis of the tube.

A second pressure difference is advantageously employed to press the external surface of the tube against the internal surface of the calibration element and to prevent shrinkage of the tube during cooling. This so-called calibration step enables accurate adjustment of the outside diameter of the tube. In the method according to WO 2015/159234, the external surface of the tube is formed by the label that comes to slide on the internal surface of the calibration element. The tube is then cooled, cut, using the usual methods.

Nevertheless, it has proven that improvements to the known methods could be employed to enhance the quality of the products obtained and to reduce production defects.

In the present text the term “labeling” refers to fixing a film, said film also being denoted a “decorative film” or “label”, onto a tube. The term “decoration” refers to an information and/or esthetic and/or safety visual element (such as a marking) notably present on the film.

The term “tubular body” is used to designate the extruded material in the molten state that is pressed against the decorative film.

The term “tube” is used to designate the product formed by the decorative film and the extruded material. The term “tube” applies from the moment at which the extruded body is pressed against the decorative film.

One object of the invention is therefore to improve the methods of producing tubes including a label.

Another object of the invention is to propose a method of producing tubes by extrusion inside a label of tubular shape that is improved compared to that known from WO 2015/159234 and to the products obtained with this prior art method.

The theory of the method according to the present invention is similar to that described in the publication WO 2015/159234 which is incorporated by reference into the present application, to which method important modifications have been made as described hereinafter.

In one embodiment, the invention concerns a method of extruding and labeling a packaging tube comprising the following successive steps carried out on an extrusion-labeling line:

a) formation of a partially or totally tubular label from a film in a shaper;

b) introduction of the label into a calibration element;

c) extrusion of a tubular body on the side of the concave face of the label in an extrusion head;

d) bringing the external face of the extruded tubular body into contact with the concave face of the label, in which method the label comprises at least one layer the melting point of which is at least 20° C. higher than the melting point of the extruded tubular body.

In one embodiment, the step d) is carried out by means of a jet of air.

In one embodiment, the step d) is also carried out by means of a first pressure difference (ΔP) that is created between the interior and the exterior of the tubular body. Assuming that the exterior of the tubular body is at atmospheric pressure, this first pressure difference is created by a raised pressure in the tubular body, i.e. by the formation of a pressure higher than atmospheric pressure in the tubular body.

In one embodiment the first pressure difference (ΔP) is generated by a first plug situated downstream of the shaper that at least partially obstructs the escape of air via the interior of the tubular body.

In one embodiment, the first pressure difference is also generated by a controlled escape of air from the upstream side of the shaper, via the extrusion head.

In one embodiment, the plug is retained inside the tube by magnetic forces.

In one embodiment, the first plug is situated after means for pulling on the tube.

In one embodiment, a second plug is connected to the extrusion head during the starting phase.

In one embodiment, after the starting phase the second plug is released from the extrusion head and transported by the moving tube until it comes to abut against the first plug or against some other appropriate means.

The first pressure difference (ΔP) therefore facilitates pulling of the tube by the pulling means.

In one embodiment, a second pressure difference ΔPis established between the interior and the exterior of the tube.

In one embodiment, the second pressure difference ΔPis created by a reduced pressure in a vacuum tank, i.e. by establishing an outside pressure lower than that in the tube.

The conjoint use of a first pressure difference (ΔP) at the level of the tubular body and a second pressure difference (ΔP) at the level of the tube enables reduction of the variations in diameter of the tube. Indeed, in one preferred embodiment of the invention, the pressure inside the tubular body (higher than atmospheric pressure) and the pressure outside the tube (lower than atmospheric pressure) are controlled throughout the process of manufacturing the tube. Controlling the internal raised pressure and the external lowered pressure makes it possible to circumvent variations in atmospheric pressure during production and consequently to guarantee very small variations of diameter of the tubes produced. In conventional extrusion devices, only the pressure outside the tube or inside the tube is controlled, which makes the method dependent on variations in atmospheric pressure. To prevent variations in tube diameter, there are added to conventional extrusion devices pressure regulation systems based on continuous measurement of the diameter of the tube. The invention makes it possible to do away with these costly regulation devices by directly adjusting the value of the pressure inside and outside the tube.

The tubes obtained using the method according to the invention are very accurate. In particular, the diameter of the tube is very accurate. The variations in the diameter of the tubes during production have been measured and very small variations in diameter have been observed. Numerically, these small variations represent a standard deviation less than 5 hundredths of a millimeter and preferably less than 2 hundredths of a millimeter.

In one embodiment, the step c) is carried out in the calibration element.

In one embodiment, the calibration element is cooled.