A METHOD AND AN ARRANGEMENT FOR THE MANUFACTURE OF A LAMINATED MATERIAL STRIP

Abstract: A method and an arrangement for the manufacture of a laminated material strip which comprises a foil (4) of gas barrier material, e.g. aluminium foil, enclosed in a liquid-­ tight manner between two external films (2,3). In accordance with the invention a first film (2) is provided with transverse irregularities (9), e.g. folds or elevations, whereafter the foil (4) and the film are sealed to one another. After transverse cutting of the foil (4) at the irregularities (9) the film (2) is stretched and a second film is applied over the foil (4). The method is carried out with the help of an arrangement which comprises co-operating pairs of rolls (5,6; 12,14; 16) for forming the irregularities and cutting and stretching of the film, together with conventional arrangements for heating and laminating.

Description: The present invention relates to a method for the manufacture of a laminated material strip comprising an inner foil wholly enclosed between two external films, and an arrangement for the manufacture of such a material strip. When packing containers of a non-returnable type are manufactured through folding and heat-sealing of flexible packing laminate which comprises a carrier layer of paper, absorption of the contents at the edges is prevented by sealing off the cut edges which will be located inside the packing containers with the help of material strips of thermoplastic material, which is heat-sealed to the inside of the packing material. In packing containers of the aseptic type of when for other reasons extremely high demands are made on the imperviousness to gas and light the strip cannot simply be manufactured from thermoplastic material but has to contain also a suitable barrier layer,e.g. an aluminium foil. Since contact with certain acid contents, e.g. fruit juices or wine, may involve precipitation of aluminium into the contents, the foil has to be wholly covered by layers of thermoplastic material strip. Strips of this kind are known which comprise a relatively narrow layer of aluminium foil which on both sides is surrounded by layers of thermoplastic material, whose edges extend beyond the edges of the aluminium foil and which are sealed in liquid-tight manner to one another. A method of manufacturing such a strip is known from US-A-4119452. On cutting of a material strip of this type, however, the aluminium foil is exposed once again in the cut surfaces and it has not been possible up to now to manufacture in a rational manner a strip of the required length in which an internal layer of barrier material, e.g. aluminium foil, is wholly enclosed by surrounding layers on all four edges of the strip. It is an object of the present invention, therefore, to provide a method for manufacturing such a strip, and for this method to be highly suitable for rapid manufacture by machine. It is a further object of the present invention to provide a method for the manufacture of a laminated material strip comprising an inner foil wholly enclosed between two external films, this method being simple and reliable and not subject to the disadvantages of previously known methods. These and other objects have been achieved in accordance with the invention in that a method of the type mentioned in the introduction has been given the characteristic that a weblike first film is provided at equal intervals with transverse irregularities in the form of folds or elevations projecting from one side of the film, whereafter the weblike inner foil is laminated to the first film and is cut off right opposite the irregularities which thereafter are flattened out by stretching of the film web before the second film is applied against the free surface of the inner foil now divided into transverse strips and against parts of the first film situated in between, in which the films then are cut in transverse direction. Preferred embodiments of the method in accordance with the invention have been given, moreover, the characteristics which are evident from subsidiary claims 2-5. It is a further object of the present invention to provide an arrangement for the carrying out of the method, this arrangement being of a simple and reliable design which permits a high rate of production. It is a further object of the present invention to provide an arrangement for the carrying out of the method, in which arrangement all the material layers included are introduced in the form of webs. These and other objects have been achieved in accordance with the invention in that an arrangement for the manufacture of a material strip comprising an internal foil wholly enclosed between two external films has been given the characteristic that it comprises a work roll with transverse recesses arranged in its peripheral surface and a mating roll provided with corresponding projections, means for controlling of a first film web between the rolls and for joining it to a foil web, cutting means for dividing the foil web into individual strips, rolls for flattening out of the irregularities and means for laminating of a second film web. Preferred embodiments of the arrangement in accordance with the invention have been given, moreover, the characteristics which are evident from subsidiary claims 7-10. Through the method and the arrangement in accordance with the invention it is made possible to manufacture rapidly and reliably laminated strips comprising a wholly enclosed inner foil, these strips being highly suitable for use in packing machines of known type. The strips can be manufactured from weblike material which simplifies the feed of the arrangement in accordance with the invention. After the manufacture the laminated material strip may be supplied to the packing machine either in the form of individual pieces of strip or in the form of a continuous web which is divided into individual pieces of strip only in connection with its application to the packing material. A preferred embodiment of the method as well as of the arrangement in accordance with the invention will now be described in more detail with special reference to the attached, schematic drawing which only shows the details indispensable for an understanding of the invention. Fig.1 shows a material strip of the type the manufacture of which is the object of the method as well as of the arrangement in accordance with the invention. Fig.2 shows the arrangement in accordance with the invention in perspective representation. A material strip of the type which is intended to be manufactured with the help of the method and the arrangement in accordance with the present invention is illustrated in Fig.1. The strip comprises at least three layers laminated to one another, namely two external films 2,3 of thermoplastic material, e.g. polythene, and an inner foil 4 of a so-called barrier material which is impervious to gas and/or light, e.g. aluminium foil. The inner foil is of a somewhat smaller length and width than the two outer films 2,3 which are sealed to one another around all four edges of the inner foil 4 so that the foil is enclosed in a water-tight matter between the two films 2,3. The first and the second film 2,3 preferably are also laminated to the respective surface of the foil 4 which may be covered with any suitable bonding agent, not shown here, e.g. thermoplastic material of the same type as the films 2,3 are made of. The dash-dotted lines in Fig.1 indicate the longitudinal edges of the two material or film webs which constitute the two outer films 2,3 and it is thus evident that the material strip extends transversely across the said webs. Naturally, the material strip may also extend lengthwise on the material webs. This depends only on the mutual proportions of the material strip and the webs. The material strip 1 may be separated from the webs after manufacture, but it is also possible to allow the material strip wholly or partly to retain its contact with adjoining material strips, so that a coherent web is maintained which is used for feeding the material strips in a simple manner into the machine where subsequently they are going to be used, e.g. for sealing off a pouring opening or a sealing join in a packing containers. Strips of similar type are used e.g. for the sealing of a longitudinal join in a packing container of known type, which is manufactured by conversion of weblike packing material to a tube, which thereafter is filled with contents and is sealed off transversely at equal intervals. The material strip is then heat-sealed along one longitudinal cut edge of the packing material web so that the latter is sealed off towards the interior of the packing container after the conversion of the packing material web to tubular shape. The length of the material strip here will coincide with the the length of the packing container, so that the cut ends of the material strip, where the central layer of the material strip actually is exposed, do not come into contact with the packed contents and thus do not cause a problem. However, if a material strip of this type is intended to be used for sealing off e.g. the cut edge around a pouring opening, the end edges of the material strips do not come into contact with the contents, and for this reason up to now the range of application has been limited to contents of the type which do not react with, or are affected adversely by the barrier layer of aluminium foil of the material strip. The total enclosure of the barrier layer of the material strip which is achieved in accordance with the method and arrangement according to the invention eliminates this problem. An arrangement for the carrying-out of the method in accordance with the invention is illustrated in Fig.2., from which it is evident how three material webs with the help of the arrangement by means of processing and laminating are converted to a material strip of the type described above. As mentioned earlier, the material strip 1 in accordance with the invention is manufactured in its simplest form from three different material layers which are supplied in the form of webs to the arrangement in accordance with the invention. The first film 2 consisting of thermoplastic material, such as polythene, is fed substantially vertically downwards to the nip between a work roll 5 and a mating roll 6 which rotate in opposite directions as indicated by arrows and thereby contribute to the advance of the film 2 through the nip of the rolls. The main shape of the work roll 5 is cylindrical and its circumferential surface possesses a number of U-shaped grooves or recesses 7 which extend transversely over the whole work surface of the roll. A number of recesses 7 is distributed at equal intervals around the circumference of the roll and the bottom of the recesses 7 may be provided with a number of holes which via vacuum ducts (not shown) situated inside the work roll 5 communicate with an external vacuum source of conventional type. The mating roll 6 too is of a shape which is mainly cylindrical but is provided with projections 8 corresponding to the recesses 7, which extend transversely over the work surface of the mating roll 6 and are at a mutual distance which corresponds to the distance between two consecutive recesses 7 on the work roll 5. On rotation of the rolls 5,6 the projections will press a part of the film 2 into the recesses 7 in the work roll 5 so that a transverse irregularity 9 across the film web originates. The irregularities 9 are in the shape of folds or elevations which are impressed into the film 2, and depending on the film material these folds or elevations will be more or less permanent. To prevent the irregularities 9 from being smoothed out through tension in the film web after the projection 8 has left the corresponding recess 7, the recess 7, as mentioned earlier, may be connected to a vacuum source which ensures that the irregularities retain their shape even when the film web during the continuing rotation of the work roll 5 passes, and is heated by, a heat source of the radiant type which is placed along the periphery of the work roll 5 and serves for heating the thermoplastic film 2 to softening or laminating temperature. After the first film 2 has been provided with transverse irregularities 9 and has been heated to lamination temperature it is combined with the foil 4 which, likewise in web form, is introduced into the arrangement in accordance with the invention so that it can be fed in between the work roll 5 mentioned earlier and a further mating roll or laminating roll 20. The foil 4 preferably consists of a layer of aluminium foil which in advance has been provided on both sides with a suitable heat-meltable bonding agent, e.g. polythene of the same type as the material in the film 2. The foil web 4 possibly may also be heated prior to the lamination, and when a suitable lamination temperature has been attained the foil 4 is combined with the film 2 in the nip between the work roll 5 and the laminating roll 20 so that they are durably joined to one another. The foil web 4 here is of a slightly smaller width than the film web 2 which means that the film 2 will extend somewhat beyond the edges of the foil 3, as will be explained in more detail later. Since the transverse irregularities 9 of the film 2 remain in the recesses 7 in the work roll 5 even during the course of the lamination, the film 2 after lamination to the foil 4 will have still the said irregularities at which the foil is not laminated to the film 2 owing to the absence of lamination pressure. Right opposite of the irregularities the foil instead extends in a substantially plane manner between edges of the irregularities so that a space appears between the folded or elevated film and the plane foil 4, and this space is used for making possible repeated transverse cutting off of the foil web with the help of the succeeding cutting means 11. The cutting means 11 comprises a cutting roll 12 which is provided with edges 13 and is located at the side of the laminated material where the foil 4 is situated. The cutting roll 12 co-operates with a mating roll 14 which is situated at the opposite side of the laminated web. The mating roll 14 is provided with grooves 15 for accomodating the transverse irregularities 9, these grooves 15 being adapted so as to co-operate with the cutting edges 13 of the cutting roll 12. The two rolls 12 and 14, like the rolls 5,6 referred to earlier, are coupled together in pairs for synchronous driving in opposite directions. When the web consisting of the film 2 and the foil 4 passes the cutting means in the nip between the cutting roll 12 and the mating roll 14 the cutting edges 13 will cut the foil 4 transversely right opposite the place of each irregularity. In this way the foil can be cut off completely without the cutting edge reaching as far as, or damaging the film 2, and the individual foil strips formed remain joined to the film 2 to which they are laminated over substantially their entire surface, apart from very narrow edge regions along the cutting edges. The film 2 with adherent strips of the foil,4 continues from the cutting means 11 towards the right in Figure 2 and in so doing passes first into the nip between a pair of clamping rolls 16 and thereafter a driving roll 17 which is situated right opposite, and co-operates with, a further laminating roll 18. The clamping rolls 16 as well as the driving rolls 17 are driven by means of e.g. electric motors, the driving rolls 17 having a slightly higher peripheral speed than the clamping rolls 16. The clamping rolls 16 are coated with a resilient material of a high friction coefficient, e.g. rubber, which means that the film 2, when it passes between the clamping rolls 16 and the driving roll 17, is stretched so that the transverse irregularities 9 are flattened out and the interval between the cut edges of the foil 4 produced by the cutting edges 13 is increased. The foil web 4 thus has been converted to separate foil strips extending transversely over the film as illustrated in Figure 1. After the foil web 4 has been cut and the strips obtained have been separated, the second film 3 is introduced from underneath so that after heating by means of a further heat source 19 it is fed into the nip between the laminating roll 18 and the driving roll 17, where it is pressed against the film 2 covered with foil strips 4 and is laminated to it in the interspace between the individual foil strips along longitudinal edges of the film 2 and to the free surface of the individual thermoplastic-covered foil strips. The two films 2,3 are now sealed to one another in a liquid-tight seal around each individual foil strip, and the laminated material strips produced can now be separated from one another through transverse cuts in the interspace between the individual foil strips. This may be done in a succeeding operation, not shown, by means of a conventional cutting unit, but it is also possible, of course, to keep the material strips in the form of a web so as to perform the final separation in the packing machine at the same time as the application at the desired place of the material strips to the packing material. This is probably preferred in many cases but constitutes a known, conventional technique which is not described in any detail in this context. As mentioned already the cutting roll 12 of the cutting means 11 co-operates with the mating roll 14, but it is also possible to place the cutting roll 12 adjoining the work roll 5 (after the laminating roll 20 seen in the direction of movement of the webs) so that the work roll 5 can serve also as mating roll for the cutting of the foil web 4. The arrangement becomes a little more complicated, but at the same time more compact which in certain cases may be preferred. Another possible variation of the preferred embodiment of the invention shown consists in retaining the irregularities 9 formed in the film 2 with the help of mechanical devices instead of the conventional vacuum method described. Thus the projection 8 may be replaced by movable fingers or rods which form the irregularities and accompany them during the lamination of the film 2 to the foil web 4. After cutting of the foil web 4, during which the rods may possibly serve as holding-up tool for the cutting edge, the rods can be withdrawn again and returned with the help of an endless chain or the like.

Claims: A method for the manufacture of a laminated material strip comprising an inner foil (4) wholly enclosed between two external films (2,3) characterized in that a weblike first film (2) is provided at equal intervals with transverse irregularities (9) in the form of folds or elevations projecting from one side of the film, whereafter the weblike inner foil (4) is laminated to the first film (2) and is cut right opposite of the irregularities (9), which thereafter are flattened out through stretching of the film web before the second film (3) is applied to the free surface of the inner foil (4) now divided into transverse strips against parts of the first film (2) situated in between, in which subsequently the films are cut in transverse direction. A method in accordance with claim 1, characterized in that the transverse irregularities (9) provide a free, unsealed region for the cutting of the inner foil (4). A method in accordance with claim 1 or 2, characterized in that the material webs (2, 3, 4) are joined to one another by heat-sealing. A method in accordance with one or more of the preceding claims, characterized in that the foil web (4) prior to lamination is provided on both sides with a suitable bonding agent. A method in accordance with one or more of the preceding claims, characterized in that the foil (4) consists of aluminium foil and that the films (2, 3) are made of thermoplastic material. An arrangement for the manufacture of a material strip comprising an internal foil wholly enclosed between two external films, characterized in that it comprises a work roll (5) with transverse recesses (7) arranged on its peripheral surface and with a mating roll (6) provided with corresponding projections (8), means (10, 20) for controlling a first film web between the rolls (5,6) and joining it with a foil web (4), cutting means (11) for dividing the foil web into individual strips, rolls for the flattening out of the irregularities (16,17) and means (18,19) for the lamination of the second film web. An arrangement in accordance with claim 6, characterized in that the recesses (7) of the work roll (5) can be connected to a vacuum source. An arrangement in accordance with claim 6 or 7, characterized in that the cutting means (11) is synchronized with the rotation of the work roll (5). An arrangement in accordance with one or more of claims 6-8, characterized in that the cutting means (11) is constituted of a roll (12) with transverse cutting edges (13), the distance between two edges (13) succeeding one another being equal to the distance between two recesses (7) in the work roll (5) succeeding one another. An arrangement in accordance with one or more of claims 7-9 characterized in that the work roll (5) serves as a mating roll for the cutting roll (12).

Inventors: CARLSSON, LARS, MARTENSSON, KJELL
Applicants: AB PROFOR
Application year: 1989
Main classification: B29D9
IPC codes: B32B15, B32B37, B32B43, B26D1, B26D7, B29C65