CN115836010A

CN115836010A - Apparatus and method for forming flexible containers by heat sealing

Info

Publication number: CN115836010A
Application number: CN202180049018.9A
Authority: CN
Inventors: M·罗滕布勒
Original assignee: Societe des Produits Nestle SA
Current assignee: Societe des Produits Nestle SA
Priority date: 2020-07-16
Filing date: 2021-07-15
Publication date: 2023-03-21
Also published as: CL2023000125A1; BR112023000477A2; WO2022013402A1; EP4182233A1

Abstract

An apparatus for forming flexible containers from a sheet of laminate material is disclosed. The apparatus comprises: a dispensing system for supplying a sheet (1) of laminate material; a former (5) configured to fold the sheet of laminate material (1) into a longitudinal tubular shape; a side sealing bar (10) configured to weld adjacent edges (9) of the laminated material sheet (1) folded into a tubular shape by heat sealing; and a sealing device configured to squeeze the formed tube and form a transverse sealing strip (17) by heat sealing. The apparatus comprises a heating device (19) configured to heat the sheet of laminate material (1) upstream of the sealing device. The invention also relates to a system comprising such an apparatus and a sheet of laminate material, and to a corresponding method for packaging a product. The present invention enables flexible packaging to be produced at high speed, with enhanced seal quality and/or with materials that are easily recycled.

Description

Apparatus and method for forming flexible containers by heat sealing

Technical Field

The invention relates to the technical field of packaging. The invention relates more particularly to the field of packaging products in flexible packages formed from a sheet of material by heat sealing.

Such packages are commonly used for food products such as bulk food products in the form of chips, grains, seeds and many other powders, granules or small articles. Such packaging can also be used for many other products in the food industry (preserves, other liquid or pasty products) or in many other products in other industrial fields (for example for pharmaceutical or medical technical applications).

Such packages are also used, for example, for packaging small quantities of products, such as individual doses of sugar, freeze-dried coffee, concentrated milk. They are also used for packaging small quantities of candy, or for individually packaging small cakes and cookies. When such small packages have an elongated shape, they are generally referred to as "stick packs". Larger packages (e.g., for potato chips or cereals) are commonly referred to as "pillow bags".

The present invention therefore relates to a package hereinafter indicated by the expression "flexible container". In the present document, the expression relates to many types of packages, such as stick-shaped packages, obtained by heat-sealing at least one sheet of laminate material, and more generally to flexible containers or wrappers, sometimes also called pouches.

Background

To form such a package, a sheet (or several) of material is folded or assembled to form a volume (e.g., a bag) suitable for containing the product to be packaged. The assembly (if required) and closure of the package is by heat sealing (also known as heat sealing).

Typically, the sheets of material used to form such packages are multi-layer sheets, also referred to as "laminates" or sheets of laminated material. For example, they may include:

an outer layer, which will form the outer surface of the package, made of polyethylene terephthalate (PET),

-an intermediate layer made of aluminium,

-an inner layer, which will form the inner surface of the package, made of Polyethylene (PE).

In this document, laminate also includes coextruded multilayer materials or coated paper, or any other multilayer material suitable for forming flexible containers by heat sealing.

More specifically, the package may be formed as follows. The laminate is passed through a so-called former. In the forming machine, the laminate is folded into a tubular shape. The adjacent edges of the sheet forming the tube are heat sealed to close the walls of the tube. This is done by so-called side sealing bars which press adjacent edges of the laminate against each other and heat them so that they are joined by welding of their respective inner layers.

The tube then passes between sealing jaws (also referred to as sealing bars). The sealing jaws are brought together. These sealing jaws deform the tube of laminate material to squeeze the two opposite walls of the tube, thereby forming a transverse sealing strip by heat sealing. The jaws apply a large amount of heat to the sealing strip, which has the effect of welding the inner layer at this location.

This achieves a complete seal without the need for adhesive.

Optionally, the sealing jaws may also cut the so formed sealing strips to separate the individual containers. More specifically, the sealing jaw may be configured to form two parallel sealing strips. The separation of the containers can be carried out by cutting between two parallel sealing strips thus formed.

Optionally, the cutting may be performed using a device other than a sealing jaw. The known embodiments provide the possibility to cut only some of the sealing strips to provide groups of flexible containers connected to each other at the location of the uncut sealing strips.

The sealing jaws apply heat to the laminate from the outside thereof (i.e. on the outer layer of the laminate) to finally heat and thus seal the inner layer of the laminate. Therefore, the material must allow heat to pass through its thickness.

The heat transfer required to obtain a good seal is difficult to achieve. In fact, in the region of the adjacent edges of the sheets of laminate material welded to form the tube, heat must pass through the four layers of laminate material. In addition, the overlapping of the four plies of laminate material creates an excess thickness in this region that can create thickness variations between the sealing jaws. These thickness variations (also referred to as "thickness jumps") impair the heat transfer from the sealing jaws to the inner layer.

Since the material cannot be heated beyond a certain temperature, which would damage it, the speed of the packaging line is usually limited by this sealing step of the sealing jaws. Beyond a certain speed of the production line, the packages may present quality problems, in particular because their closure by welding may be defective.

Furthermore, laminates consisting of different materials have the important disadvantage that they are difficult to recycle.

An alternative to standard multi-material laminates are polyolefin laminates. The polyolefin laminate may be recycled mechanically. However, they also have disadvantages, particularly when used in large-scale, high-speed production lines.

The polyolefin laminate is thicker than a comparable multi-material laminate to ensure equivalent barrier and mechanical properties.

Due to the nature of the material itself and due to the required thickness of the polyolefin laminate, heat transfer within the polyolefin laminate is slower than within the multi-material laminate (i.e. from the outside of the package where heat is applied to the inside of the package where sufficient heat must be applied to ensure sealing). A longer dwell time, i.e. sealing time, is required in the sealing jaws.

Due to the nature of some of their layers (e.g. PET and/or aluminium layers), multi-material laminates are stable at higher sealing temperatures than polyolefin laminates. Therefore, polyolefin laminates cannot be heated to as high a temperature as multi-material laminates.

All these cases lead to slower production speeds when using polyolefin laminates, in particular because the sealing step by means of the sealing jaws is usually a step limiting the speed of the packaging line, as described above.

In addition to material composition, the form and shape of the formed bag may further affect the heat transfer problems described above. This is the case, for example, with so-called "gusseted bags". Gusseted bags include gussets, i.e., materials added to the flexible bag to create more space and strengthen its structure. However, this increases the number of "thickness jumps" along the seal, which impairs heat transfer.

It is an object of the present invention to provide an apparatus and a method for producing flexible packages from a sheet of laminated material, which allow the speed of the packaging line to be unrestricted by the step of sealing by means of sealing jaws (and eventually accelerate the packaging line) and/or which allow the use of sheets of material having poorer heat transfer characteristics or thermal stability characteristics than the commonly used multi-material laminates, such as polyolefin laminates, without limiting the packaging speed.

Disclosure of Invention

The present invention therefore relates to an apparatus for forming flexible containers from a sheet of laminate material as it passes through the apparatus. The apparatus comprises: a dispensing system configured to supply the laminate sheet to the former; a former configured to fold the laminate sheet into a longitudinal tubular shape by placing opposite edges of the laminate sheet in adjacent positions; a side sealing bar configured to weld adjacent edges of the sheet of laminate material folded into a tube; and a sealing device configured to compress the tube formed by the sheet of laminate material and form transverse sealing strips, thereby forming a closed volume of the flexible container between two successive sealing strips. The apparatus according to the invention comprises a heating apparatus configured to heat the sheet of laminate material upstream of the sealing device without coming into contact with the product.

The heating device enables the laminate to be heated before it reaches the sealing means. Thus, the amount of energy that needs to be brought to the laminate sheet by the sealing device to cause sealing and fluid tightness (by welding, i.e. by partially melting and then solidifying the inner layers of the laminate sheet) is lower than when the laminate sheet is cold (i.e. at around ambient temperature) when it reaches the device.

This makes it possible to reduce the sealing time or residence time in the sealing device compared to the prior art, or for the same sealing time:

to use thicker laminate sheets, and/or

To use a laminate sheet having a lower thermal conductivity from its outer layer to its inner layer, and/or

To use a laminate sheet of lower thermal stability, and/or

To reduce or maintain the temperature of the sealing means to obtain a seal, and/or

The pressure exerted by the sealing means is to be reduced, thus solving the risk of deformation of the container.

Finally, this enables the use of mechanically recyclable sheets of laminate material, such as polyolefin laminates, while maintaining the same high production (i.e. packaging) speed.

1. The heating device is preferably configured to heat the laminate sheet by convection or radiation. The heating apparatus may comprise a heating chamber through or adjacent to which the sheet of laminate material folded into a tube passes. Preferably, this is done without contact with the filling product. The heating apparatus may include a hot air blower and a duct between the hot air blower and the heating chamber so that the heating chamber may be supplied with hot air by the hot air blower. The heating chamber may comprise at least one heating resistor. The heating device may be configured to generate air heated to a temperature of, for example, between 70 ℃ and 100 ℃ around or near the sheet of laminate material folded into the longitudinal tube.

Many types of heating devices may be used in the present invention. Creating at least one heating chamber in or around the portion of the tubular folded laminate sheet is an efficient way of heating it with little energy loss. Since hot air is blown around the laminate, convenient and efficient heating is achieved. The heating temperature is preferably selected to be close to but below the melting temperature of the inner layers of the laminate. In addition, the melting temperature must not significantly affect the barrier and optical properties of the material.

The heating apparatus may be configured to heat the laminate sheet between the side sealing apparatus and the sealing device.

Heating the laminate just before the sealing means provides an optimum supply of thermal energy. Most importantly, this is such that the laminate's coefficient of friction (which increases with its temperature) is not increased prematurely, which would generate friction in the packaging machine that would impair its passage and possibly damage the laminate.

Typically, in a vertical seal packaging machine, heat is applied in areas where the coefficient of friction is not important to machinability.

According to a preferred embodiment of the invention, the sealing means is a sealing jaw. The sealing jaw is configured to form a seal strip by heat sealing. According to alternative embodiments, an ultrasonic welding device, a vibration welding device, or a laser welding device may be used.

The invention also relates to a system comprising an apparatus as described above and a sheet of laminate material, wherein the laminate material is a polyolefin-based laminate.

Polyolefin laminates can be recycled, whereas laminates currently used to form flexible containers such as stick packs and bags are not recyclable or are difficult to recycle. Polyolefins provide a better working window (thermal stability curve and sealing temperature). The apparatus allows the use of homopolymer (sometimes also referred to as homopolymer) laminates. These laminates provide better material purity for recycling. The polyolefin laminate may have a thickness of, for example, between 50 and 1500 microns, preferably between 70 and 100 microns.

Such thicknesses provide sufficient barrier properties for the polyolefin laminate. Polyolefin laminates having such thicknesses are one of the best alternatives to the standard laminates currently used to form flexible containers in terms of barrier properties.

The polyolefin laminate may comprise:

an outer layer of oriented polypropylene (e.g., OPP 12), and

an inner layer of polyethylene (e.g., PE 50).

The polyolefin laminate may also comprise an intermediate layer of uniaxially oriented polypropylene (e.g. MOPP 15).

Alternatively, the polyolefin laminate may be a single material PE laminate or a single material PP (polypropylene) laminate.

Alternatively, the laminate may be a coated paper. Such coated papers may include a paper layer about 80 microns thick with an HDPE (high density polyethylene) coating or an acrylic coating to improve sealability and sealing. Acrylic coatings are preferred.

In fact, many types of coatings can be used in the present invention to obtain coated paper as a laminate.

Liquid coatings may be used. Liquid coatings comprise aqueous dispersions of any kind of polymer. Such coatings are applied in liquid form on a paper substrate and then dried to form a sealant layer.

Alternatively, the coated paper may be obtained by extrusion coating (i.e. by applying molten plastic on a paper substrate).

For example, the following polymers may be used: polyethylene (PE), polypropylene (PP), ethylene vinyl alcohol (EVOH), P-hydroxystyrene (PHS or 4-vinylphenol), polyethylene terephthalate (PET), PET-g (glucose-modified PET).

The coated paper can be recycled by pulping, which allows the cellulose to be separated from the coating material.

Applicants have successfully tested these exemplary materials. Many other laminates may be used. However, the laminate used in the present invention is preferably easily recyclable. The apparatus provided in the present invention also advantageously increases the tightness on current laminates (which hitherto have been commonly used for forming packages).

Typically, the laminate has an outer layer and an optional intermediate layer that protect the contained product from air and optional light, and an inner layer that can easily melt to weld on itself. The laminate must generally be suitable for food contact.

The invention also relates to a method for packaging a product in a flexible container, comprising the steps of:

providing a system as described above;

folding the laminate sheet into a longitudinal tubular shape by placing opposite edges of the laminate sheet in adjacent positions;

welding by heat-sealing the adjacent edges of the sheet folded into a tubular shape;

introducing the product into the tube thus formed, the product falling onto the previously formed transverse sealing strip which forms the bottom of the flexible container formed;

advancing the sheet of laminated material (1) folded into a tube through a device for forming flexible containers of given length; and

closing the flexible container by forming a transverse seal.

The method enables packaging of products, preferably food products such as, for example, potato chips, cereals, seeds, sugar, candy, freeze-dried coffee, food products in any powder, granular or granular form, cakes, biscuits, preserves, liquid or pasty food products, at high speed and/or in a manner that is easy to recycle materials. The method may also be used for packaging any other product, such as a medical product or a technical product.

Drawings

Figure 1 is a schematic three-dimensional view of an apparatus for forming flexible containers from a sheet of laminate material according to the prior art;

figure 2 is a schematic three-dimensional view of an apparatus for forming flexible containers from a sheet of laminate material according to an embodiment of the invention;

FIG. 3 is a schematic three-dimensional view of the apparatus of FIG. 2 in operation;

figure 4 is a diagram illustrating the principle and meaning of the invention.

Detailed Description

For a complete understanding of the present invention and the advantages thereof, reference is made to the following detailed description of the invention.

It is to be understood that the embodiments of the invention may be combined with other embodiments of the invention and are merely illustrative of specific ways to make and use the invention and do not limit the scope of the invention when considered in the claims and the following detailed description.

As used in this specification, the terms "comprises," "comprising," and the like are not to be construed in an exclusive or exhaustive sense. In other words, these words are intended to mean "including, but not limited to".

The invention will be further described with reference to the exemplary embodiments shown. It should be understood that the claimed invention is not intended to be limited in any way by these examples.

Fig. 1 depicts an apparatus for forming flexible containers from a sheet of laminate material according to the prior art.

The apparatus comprises a dispensing system for dispensing a sheet 1 of laminate material. The laminate sheet 1 may have the form of a roll 2. The apparatus comprises a reel 3 and a guide 4, enabling the laminate web to be supplied to the machine with a desired orientation and mechanical tension. In known apparatuses, for example for forming rod-shaped packages, the laminate web dispensed by the dispensing system is cut longitudinally into several webs of smaller width, which can each be considered individually as a laminate web 1.

The apparatus comprises a former 5, also called "lapel former". The former 5 folds the laminate sheet 1 into a tubular shape. To achieve this, the sheet is slid along a dome member 6 formed around a fill tube 7.

Sufficient space is provided between dome member 6 and fill tube 7 for laminate sheet 1 to pass through.

Dome member 6 also comprises a converging guide surface 8 which places two side edges 9 of the laminate sheet in adjacent contact with each other. In this way, a tube is formed from the laminate sheet 1 around the filling tube 7.

A fill tube 7 extends below dome member 6 (as shown in fig. 2). The laminate tube slides along the filling tube 7.

The adjacent edges of the sheet forming the tube are heat sealed together to close the walls of the tube of laminate material. This is done in side sealing bars 9 which press the adjacent side edges 9 of the laminate sheets 1 against each other and heat them so that they are joined by welding of their respective inner layers. Alternatively, adjacent edges may be placed overlapping and the inner layer of the overlying layer sealed to the outer surface of the other edge to form a so-called "lap seal".

The filling tube 7 allows the product to be packaged to be introduced into a tube formed by the sheets of laminate material constituting the package to be filled. In the example shown, this filling is performed by means of a funnel 11 located in the upper part of the filling tube 7.

To form the container, the tube formed from the laminate sheet must be closed at its bottom and its top in a direction transverse to the direction of filling the tube, the direction of the tube formed from the sheet and the direction of the edge 9 of the sheet. As described below, during the closing of the top of the previously formed flexible container, a closure at the bottom of the flexible container is formed by heat sealing.

To achieve this closure, a tube formed from the laminate sheet is passed between the sealing means. In the preferred embodiment shown, the sealing means is a sealing jaw 12 (also referred to as a sealing bar). The sealing jaw 12 brought to an elevated temperature compresses the tube formed by the laminate sheet 1. The sealing jaw 12 thus deforms the tube of laminate material 1 in order to lay it flat. The two opposite walls of the tube of laminate are thus pressed against each other. The inner layer of the laminate sheet 1, which is pressed between the sealing jaws, is at least partially melted in order to form a welding or sealing strip for closing the tube.

In the example shown here, the sealing jaws 12 each have two parallel sealing portions lying one above the other.

The upper sealing portion 13 of the sealing jaw 12 closes the bottom of the container currently being formed (before the container is filled by introducing the product through the filling tube 7), while the lower sealing portion 14 of the sealing jaw closes the top of the previously formed container 15. Thus, the sealing jaws are configured to form two parallel sealing strips 17. The top of the previous pack and the bottom of the next pack are thus closed simultaneously.

A slot 16 is formed between the upper sealing portion 13 and the lower sealing portion 14 of the sealing jaw 12. The slot 16 is configured to allow a cutting device to pass through to separate the containers. The separation of the flexible containers can be carried out by cutting between two parallel sealing strips thus formed. According to other embodiments, the cutting device may be a separate device.

As mentioned above, the difficulty with this system is to correctly close the flexible container, particularly in the thick region 18 of the container where the adjacent edge 9 of the laminate sheet 1 is folded down. This locally forms four layers of laminate material between the sealing jaws 12.

In addition, the thick region 18 creates a thickness variation (which may be referred to as a "jump in thickness") in the region to be welded to close the container. This thickness variation impairs good heat transfer between the sealing jaws 12.

The exemplary bag shown is a pillow bag. In such examples, there are a double layer region, a four layer region (thick region 18), and a double layer region along each seal strip. In gusseted bags, the situation is even more complicated and detrimental to heat transfer because there are four zones (due to the first side gusset), two zones, four zones (thick zone 18), two zones and four zones (due to the second side gusset) along each sealing strip. The speed of the packaging plant and the packaging line comprising the plant is generally limited by this sealing step for closing the containers, since the heat transfer is difficult in the four-layer zone, the jump in thickness zone and the double-layer zone located between the four-layer zones (in which case the pressure exerted by the sealing jaws is reduced in the double-layer zone), and since the temperature of the sealing jaws is limited by the thermal stability of the material used to form the containers.

Furthermore, the use of thicker materials (especially materials that are easy to recycle) would require even longer sealing times, which is unacceptable in industrial processes. Furthermore, the materials envisaged for easy recycling are not as thermally stable as the commonly used materials, so that they cannot be heated to the high temperatures normally used.

Fig. 2 depicts an apparatus for forming flexible containers from a laminate sheet according to an embodiment of the present invention. The apparatus shown in fig. 2 is substantially the same as the apparatus shown in fig. 1, so that the above description of the apparatus of fig. 1 applies to the apparatus of fig. 2. The apparatus of fig. 2 differs from the apparatus of fig. 1, however, in that it comprises a heating device 19, which is described in detail below.

In fig. 2, the apparatus is shown when the laminate sheet 1 is not fully engaged on the filling tube 7. Thus, the lower part of the filling tube 7 is visible.

In the exemplary embodiment shown, the heating device 19 essentially comprises two parts. The heating device 19 thus comprises a heating chamber 20. The heating system 19 further comprises a heat generator 21. In the example shown, the heat generator 21 generates hot air. The heat generator 21 is fluidly connected to the heating chamber 20.

The hot air is thus delivered from the heat generator 21 to the heating chamber 20.

The heating chamber 20 is located between the lower part of the filling tube 7 and the sealing jaw 12.

The heating chamber 20 has an inlet 22 and an outlet 23. The heating chamber 20 is configured to be traversed by a tube formed by the sheet of laminate 1 downstream of the forming machine 5 and the filling tube 7. This situation is shown in fig. 3.

The heating chamber 20 is intended to provide thermal energy to the laminate tube passing through it. The supply of thermal energy is carried out upstream of the sealing jaw. Thus, the laminate is preheated before reaching the sealing nip 12. Thus, the amount of energy brought to the material by the sealing jaws in order to obtain a good closure of the container is reduced.

The heating chamber 20 may, for example, have a cylindrical shape or a frustoconical shape. Such shapes are particularly suitable for obtaining a good heat distribution. However, the heating chamber may have many other shapes.

In the present invention, the use of a heating chamber is optional. However, the following aspects are important.

The supply of thermal energy must be carried out as contactless as possible, i.e. by convection or radiation.

Thus, at least the following heating techniques may be used: hot air heating, radiant heating, laser heating, and any other non-contact heating technique. For example, heating resistors may be provided in the heating chamber instead of or in addition to introducing hot air into the chamber.

In fact, the coefficient of friction of the material used to make the flexible container increases very significantly when it is heated.

If the material is heated by conduction (i.e., by contact with the heating element), it will rub strongly against the heating element and may deform or break. In addition, strong forces may be required to push the material through the heating element.

For this reason, in the present invention, the position where the preheating is performed in the apparatus for forming the flexible container is also important.

The preheating must be carried out before the tube of laminate material reaches the sealing nip 12. However, the preheating must preferably be performed after the tube of laminate leaves the filling tube 7. Otherwise, the material will rub strongly along the filling tube 7. It may also rub on wheels provided for propelling the material along the filling tube 7.

Due to the heating means used in the present invention, the laminate has been heated when it reaches the sealing nip (as shown in fig. 3).

The principle implemented in the present invention is summarized in fig. 4. FIG. 4 is a schematic diagram schematically depicting the energy required to obtain a good seal during the manufacture of a flexible container. Fig. 4 is a schematic diagram which does not correspond exactly to physical reality, but shows in a simple manner the parameters used when sealing the container.

Two triangles are shown in fig. 4. Each corner of these triangles corresponds to an important parameter when sealing the flexible container.

The first angle corresponds to the temperature of the sealing jaw.

The second angle corresponds to the pressure exerted by the sealing jaw.

The third angle corresponds to the time required for sealing.

The area of the triangle corresponds to the total energy required for sealing, which must be brought to the position of the sealing jaws. Ultimately, it is this amount of energy that is important in order to obtain a good seal. The total amount of energy required depends on the laminate used. Which depends inter alia on the thickness and composition of the laminate.

The isosceles triangle corresponds to the situation according to the prior art, i.e. the sealing of a flexible container formed from conventional laminate materials.

The other triangle shown in fig. 4 corresponds to the situation when it is desired to use another laminate, for example based on polyolefin. For this illustration presented in fig. 4, the thermal conductivity of the material is considered unchanged from the reference case. The thermal stability of the material is lower than that of the materials normally used, and the temperature of the sealing jaws must be lower than in the reference case. Depending on the mechanical configuration of the machine, the pressure applied by the jaws cannot be varied. In addition, excessive pressure may damage the material of the flexible container. Since the total necessary energy represented by the area of the triangle must be maintained, the only parameter that can be changed is the duration of the seal, which must therefore be increased.

In order to reduce the sealing time to the nominal time required in the reference case (isosceles triangle), it is therefore necessary to supply the energy represented by the hatched area of fig. 4 by means other than the sealing jaws. The energy supply is achieved by the heating device provided in the present invention.

Thus, when using less thermally conductive materials, the preheating provided in the present invention may enable a reduction in sealing time, and/or a reduction in the temperature of the sealing jaws and/or maintenance of these parameters. The invention is therefore of interest for the manufacture of flexible containers both from materials currently in use and from new materials, in particular materials which are easy to recycle.

For example, the inventors obtained experimental results in which a standard laminate comprising an outer layer of PET12, an intermediate layer of aluminum 7 and an inner layer of PE70, has a total thickness of about 89 μm.

Tests were conducted at several seal jaw temperatures with and without energy input through the heating system. The heating system used for the test was a hot air device. Which brings 100 degrees of air into the heating chamber at a flow rate of 500 liters/minute.

During these tests, the maximum production speed was determined, allowing to obtain 100% correctly sealed containers.

At a sealing jaw temperature of 100 degrees celsius, a maximum of five units per minute are available without energy supplied by the heating system, and a maximum of eight units per minute are available when energy is supplied by the heating system.

At a sealing jaw temperature of 110 degrees celsius, a maximum of sixteen units per minute are available without energy being supplied by the heating system, and a maximum of twenty-three units per minute are available with energy being supplied by the heating system.

At a sealing jaw temperature of 120 degrees celsius, a maximum of twenty-eight cells per minute are available without energy supplied by the heating system, and a maximum of thirty-five cells per minute are available when energy is supplied by the heating system.

At a sealing jaw temperature of 130 degrees celsius, a maximum of thirty-three units per minute is available without energy supplied by the heating system, and a maximum of forty-five units per minute is available when energy is supplied by the heating system.

An increase in productivity of about 40% can thus be achieved.

Thus, the present invention allows for example the formation of flexible containers using materials such as laminates comprising an outer layer of oriented polypropylene, an intermediate layer of uniaxially oriented polypropylene and an inner layer of polyethylene at production speeds equal to or higher than those obtained with machines without heating systems and standard laminate materials as used in the above tests. Successful testing has been performed on laminates comprising:

an outer layer of OPP 12 (oriented polypropylene 12),

-an intermediate layer of MOPP15 (mono-oriented polypropylene 15), and

-an inner layer of PE 50 (polyethylene 50).

The invention may also be of particular interest for two-layer laminates.

It is understood that various embodiments of devices may be constructed in accordance with the present invention.

Various configurations of heating systems may be used. The parameters used in the present invention must obviously be adjusted according to the laminate used to form the container and, in some cases, according to the product to be packaged. For example, chocolate cannot be packaged at high temperatures.

In other embodiments, the present invention provides a method for packaging a product in a flexible container using the above-described apparatus.

The present invention therefore provides improvements to the apparatus and process for obtaining flexible containers by heat-sealing. This improves the productivity of the packaging line. This also enables the use of materials that are easy to recycle in industrial packaging lines. This allows in particular the use of polyolefin-based laminates.

Claims

1. Apparatus for forming a flexible container from a sheet of laminate material (1) as it passes through the apparatus, the apparatus comprising:

-a dispensing system configured to supply the sheet of laminate material (1) to a former;

-a former (5) configured to fold the sheet of laminate material (1) into a longitudinal tubular shape by placing opposite edges (9) of the sheet of laminate material (1) in adjacent positions;

-side sealing bars (10) configured to weld the adjacent edges (9) of the sheet of laminate material (1) folded into a tube;

-sealing means configured to press the tube formed by the sheet of laminate material (1) and to form transverse sealing strips (17) so as to form a closed volume of the flexible container between two successive sealing strips,

wherein the apparatus comprises a heating apparatus (19) configured to heat the laminate sheet (1) upstream of the sealing device.

2. The apparatus according to claim 1, wherein the heating apparatus (19) is configured to heat the laminate sheet (1) by convection or radiation.

3. Apparatus according to claim 1 or claim 2, wherein the heating apparatus comprises at least one heating chamber (20) through or close to which the sheet of laminate material (1) folded into a tube passes, preferably without contact with a filling product (20).

4. The apparatus according to claim 3, wherein the heating apparatus comprises at least one hot air blower and a duct between the hot air blower and the heating chamber (20) such that the heating chamber can be supplied with hot air by the hot air blower.

5. The apparatus of claim 2 or claim 3, wherein the heating chamber (20) comprises at least one heating resistor.

6. The apparatus according to any one of the preceding claims, wherein the heating apparatus (19) is configured to generate air heated to a temperature between 70 ℃ and 100 ℃ around or in the vicinity of the sheet of laminate material (1) folded into a longitudinal tube.

7. The apparatus according to any one of the preceding claims, wherein the heating apparatus is configured to heat the laminate sheet (1) between the side sealing apparatus and the sealing device.

8. The apparatus according to any of the preceding claims, wherein the sealing device comprises a sealing jaw (12), an ultrasonic welding device, a vibration welding device or a laser welding device.

9. System comprising an apparatus according to any of the preceding claims and a laminate sheet (1), wherein the laminate is a polyolefin based laminate.

10. The system of claim 9, wherein the polyolefin laminate has a thickness of between 50 and 150 microns, more preferably between 70 and 100 microns.

11. The system according to claim 9 or claim 10, wherein the polyolefin laminate is a polymer laminate, preferably based on one main polymer family.

12. The system of claim 9 or claim 10, wherein the polyolefin laminate comprises:

an outer layer of oriented polypropylene, for example an outer layer of OPP 12, and

inner polyethylene layers, for example inner PE 50 layers.

13. The system of claim 12, wherein the polyolefin laminate further comprises a uniaxially oriented polypropylene interlayer, such as a MOPP15 interlayer.

14. System comprising an apparatus according to any one of claims 1 to 8 and a laminate sheet (1), wherein the laminate is coated paper.

15. A method for packaging a product in a flexible container, the method comprising the steps of:

-providing a system according to any one of claims 9 to 14;

-folding the laminate sheet (1) into a longitudinal tubular shape by placing opposite edges (9) of the laminate sheet (1) in adjacent positions;

-welding said adjacent edges of said sheet folded into a tubular shape;

-introducing the product into the tube thus formed, the product falling onto a previously formed transverse sealing strip (17) forming the bottom of the flexible container formed;

-advancing the laminated material sheet (1) folded into a tube through the apparatus for forming flexible containers of given length; and

-closing the flexible container by forming a transverse sealing strip.