WO2009033197A1

WO2009033197A1 - Plastic bag

Info

Publication number: WO2009033197A1
Application number: PCT/AT2008/000318
Authority: WO
Inventors: Herbert Fürst; Peter Skopek
Original assignee: Starlinger & Co Gesellschaft M.B.H.
Priority date: 2007-09-10
Filing date: 2008-09-08
Publication date: 2009-03-19
Also published as: AT9643U3; AT9643U2

Abstract

A plastic bag (10, 10') has a tubular bag base (1, 1') which is configured from a tubular round material or a flat material the longitudinal edges of which are connected to give a tubular structure. At least one end section of the bag base is folded to give a generally rectangular end surface. The plastic bag also comprises a cover sheet (3, 6) which is connected to the end surface of the bag base via an intermediate layer under the effect of heat, said intermediate layer being produced from a polyolefin, preferably polyethylene material. The bag base (1, 1') and/or the cover sheet (3, 6) comprises an imprintable plastic film (13, 20, 30).

Description

Plastic bag

In addition to bags made of paper, plastic film and paper-foil composites, packaging bags made of tissue from uniaxially stretched plastic tapes have made a triumphal march around the world over the last decade due to their advantageous properties. Such packaging bags, which are shaped as box sacks or quasi-box sacks, are e.g. from document WO 95/30598 A1. The fabric of these bags consists of monoaxially stretched polymer tapes, in particular Polyolefϊnbändchen, wherein the fabric may be coated on one or both surfaces with a thermoplastic material, in particular a polyolefin. The fabric is either a tube-like tubular fabric made on a circular loom, or a flat woven fabric connected to a tube by means of a longitudinal welding or adhesive seam.

According to WO 95/30598 A1, a bag is produced by using the above-described fabric of uniaxially stretched plastic tapes as a bag body by forming at least one end of the bag body into a rectangular bottom surface by folding the fabric ends, in particular via an intermediate layer of thermoplastic material Polyolefin or polypropylene material, is thermally bonded to a cover sheet of fabric monoaxially drawn polymer ribbon, wherein the heat is applied so that less than 30% of the material thickness of the fabric bands of the bottom surface and the cover sheet due to the heat of disoriented polymer molecules in the rest of the material area Molecular orientation but remains. Instead of a separate cover sheet, a flap of the bag body tissue overlapping the bottom surface can also serve as the cover sheet.

The known from WO 95/30598 Al bags have been proven in practice for many years. In particular, the webs of monoaxially stretched plastic tapes have shown the highest tear resistance. The problem with them, however, has been the poor printability of the fabric surface, which does not allow a detailed print.

The present invention is therefore based on the object to provide a plastic packaging bag, which has both high tear resistance and excellent printability. This object is achieved by a bag with the features of claim 1. Advantageous embodiments of the invention are set forth in the subclaims.

The invention comprises a bag with a tubular bag body, which is formed from a tube-like round material or a flat material connected to a tube at the longitudinal edges, wherein at least one end portion of the bag body is formed by folding into a generally rectangular end surface, and with a cover sheet, the has been connected by an intermediate layer of thermoplastic material, in particular polyolefin, preferably polyethylene material under the action of heat with the end face of the bag body. The bag body and / or the cover sheet comprise a printable plastic film. By means of this embodiment of the bag, tear-resistant materials, such as the known fabric of monoaxially stretched plastic tapes, can be combined with easily printable plastic films to form a bag which has both the advantages of the tear-resistant material and the advantages of the readily printable material without negative effects to adjust.

The bag according to the invention is designed as a box bag with two opposite rectangular end faces or as a quasi-box bag with a rectangular end face (bottom face). The basic structure of such bags is described in detail in WO 95/30598, which is hereby incorporated by reference into the present application. In these case bags, the topsheet may be formed either as a separate element, or the topsheet is formed by corresponding folding of the end surface by overlapping end face tabs as a constituent of the bag body.

Depending on the material of the bag body and the cover sheet, two different connection methods for flat, intimate connection of bag body and cover sheet are used. On the one hand, this is a hot air welding process in which said intermediate layer is formed from at least one sealing layer which is provided on the surface of the bag body facing the cover sheet and / or on the surface of the cover sheet facing the bag body, wherein when the bag body is joined to the cover sheet the sealing layer or sealing layers are heated by hot air until plasticization, the bag body and the cover sheet are pressed against each other and then cooled. The hot air causes a melting of the facing sealing layers of the bag body and the cover sheet. The temperature of the hot air and the heating time are adjusted so that only the sealing layers melt, possibly also any existing adhesive layers, but not (or only in one too negligible extent) the load-bearing layers of bag body and cover sheet, in particular tissue.

If the material of the bag body and the cover sheet has no sealing layers, then the surface, intimate connection of bag body and cover sheet by means of an extrusion process, in which by a slot die or the like. A melt of thermoplastic plastic, especially polyolefin, preferably polyethylene material, as Intermediate layer is introduced between the bag body and the cover sheet, the bag body and the cover sheet are pressed against each other and then cooled. The temperature of the melt and the process parameters are adjusted so that the bearing layers of bag body and cover sheet are not melted (or only to a negligible extent).

In one embodiment of the bag according to the invention, the bag body and / or the cover sheet comprise a woven-film composite having a construction of a web of monoaxially drawn polymer tapes, in particular polyolefin or polyester tapes, preferably polypropylene or polyethylene terephthalate tapes, an OPP (Oriented Poly Propylene) film and an intermediate bonding layer of thermoplastic or adhesive, wherein the OPP film is printed on the fabric-facing surface. Such a material structure shows both high strength (through the fabric) and excellent printability (through the OPP film). Since the OPP film is stretched, it also has a very good dimensional stability. Advantageously, BOPP films can also be used, which are so-called Biaxially Oriented Polypropylene propylene films. To facilitate the connection with other tissues, tissue-film composites or films, it is expedient to provide an OPP film for the fabric-film composite, which (at least) has a film-sealing layer on its surface facing away from the tissue. For the same reason, it is expedient if the fabric of the fabric-film composite is coated on one or both sides with a fabric sealing layer made of a thermoplastic material. In order that the tissue is not damaged in the production of the tissue-film composite or in the bonding process of the sack body and cover sheet, at least one of which consists of the tissue-film composite, it is advantageous if the film seal layer and / or the tissue sealing layer has a melting point which is below the crystallite melting point of the fabric ribbon material and the OPP film.

The production of the fabric-film composite according to the invention is carried out by providing a fabric of monoaxially stretched polymer ribbon, in particular Polyolefm or polyester ribbons, preferably polypropylene or polyethylene terephthalate, eg a fabric as described in WO 95/30598, and an OPP film. The OPP film is printed on its fabric-facing surface, ie the inside. Subsequently, the fabric and the OPP film are laminated to one another by introducing a plastic extrudate from a slot die placed therebetween, whereupon the fabric and the OPP film are pulled together through a cooled pair of rollers so that the extrudate solidifies. The big advantage of this tissue-film composite is that the print layer is inside and therefore protected against scratching. Very suitable as an extrudate, for example, is the product LOTADER® 4503 produced by Arkema, which is a terpolymer of ethylene, acrylic ester and maleic anhydride.

In an alternative embodiment of a bag according to the invention, it is provided that at least either the bag body or the cover sheet comprises a multilayer film which has a core layer of polyethylene or a polyolefin and printable film seal layers on the surfaces of the core layer.

In a variant of this embodiment, at least one of the bag body or the cover sheet comprises a film composite which comprises at least a first film of OPP and a second film of polyethylene or a polyolefin which are connected to one another via a bonding layer of thermoplastic material or an adhesive, preferably both films are provided on their outer surfaces with a film sealing layer of a thermoplastic material and wherein on one of the films on the inside of a pressure layer is provided.

Thus, the following combination possibilities arise for the production of a bag: bag body of multilayer film combined with a cover sheet of multilayer film; Bag body of multilayer film combined with a cover sheet of film composite; Bag body of film composite combined with a cover sheet of multilayer film; and bag body of film composite combined with a cover sheet of film composite. Although these embodiments of the bag do not offer the same high strength as the use of a fabric of monoaxially stretched plastic tapes, but this disadvantage can be mitigated by increasing the number of foil layers.

In a further embodiment of a bag according to the invention, which is characterized by high strength and excellent handling in the manufacture, comprises Sack body a coated fabric, which has a structure of a fabric of monoaxially stretched polymer tapes, in particular Polyolefϊn- or polyester tapes, preferably polypropylene or polyethylene terephthalate, which tissue is coated on one or both sides with a fabric sealing layer of a thermoplastic material. The tissue-sealing layers can be easily joined by hot-air welding to tissue-sealing layers of adjacent coated tissues. In order to minimize thermal stress on the bands of the fabric during hot air welding, it is advantageous if the fabric sealing layer consists of a thermoplastic whose melting point is below the crystallite melting point of the fabric band material.

A problem that arises in providing the sealant layer on the web of monoaxially drawn polymer ribbons of the invention is that this sealant layer may poorly adhere to the web of monoaxially drawn polymer ribbons. In particular, pure polyethylene having a sufficiently low melting point does not adhere to tapes made of polypropylene. In order to be able to use special materials which are not only available on the market for the sealing layer and which have both sufficient adhesion to the ribbon material and a sufficiently low melting point, a variant of the invention is provided between the fabric of monoaxially drawn polymer ribbon and the sealing layer To arrange an adhesive layer of a polymer material with good adhesion to both the fabric and the sealing layer. For improved handleability in welding, the adhesive layer should preferably have a melting point higher than that of the sealant layer. High degrees of freedom in setting the welding process parameters is provided by another embodiment of the coated fabric of the present invention wherein the fabric ribbon material has a crystallite melting point greater than 120 ° C.

A bag body of the above fabric composite can be excellently combined with a cover sheet consisting of the above-described multilayer film or the film composite described above. The bag thus produced has high strength and good printability.

Similarly, a bag body of the above-described fabric can be combined with a cover sheet of the above-described multilayer film or the above-described film composite to obtain a bag having high strength and good printability of the cover sheet. The invention will now be described by way of non-limiting exemplary embodiments with reference to the drawings. In the drawings show:

1 shows a bag made of coated round fabric according to the invention in perspective.

2 shows a bag according to the invention made of coated flat fabric with longitudinal seam;

3 shows a section of an embodiment of a bag according to the invention;

4 shows a section of a second embodiment of a bag according to the invention;

5 shows a section of a third embodiment of a bag according to the invention;

6 shows a section of a fourth embodiment of a bag according to the invention; and

Fig. 7 shows a detail of a fifth embodiment of a bag according to the invention.

FIG. 1 shows a basic form of a box-shaped bag 10 as disclosed, for example, in WO 95/30598. The bag 10 consists of a bag body 1 of a flexible sheet material according to the present invention. The candidate materials according to the invention will be explained in more detail below. In the present embodiment, the flexible sheet material is designed as a round material. The end surfaces, ie bottom and top surface of this box bag are formed by folding tabs 4, 4 ', 5, 5' of the bag body 1. As indicated by dashed lines, the tabs 4 and 5 tower each other only slightly. Between the lobes 5 'and 4 and 5, a valve 2 is further arranged, which consists of sheet or tubular materials such as fabrics or films and through which the filling of the bag is made. If the bag 10 is filled, then the valve 2 closes by the pressure of the filling material against the end face. On the tabs 4, 5 a cover sheet 3 is welded, which also consists of a flexible sheet material according to the invention, as will be explained in more detail below. For the connection of bag body 1 and cover sheet 3 either the hot air welding method explained above or the extrusion of an intermediate layer of thermoplastic material is used, as also explained in the introduction. The particular method chosen is carried out so that the strength of the flexible sheet material at least the bag body 1, preferably also the cover sheet 3 is not or only slightly affected. This means in particular that optionally contained in the web materials fabric of monoaxially stretched plastic tapes are thermally so low charged that after the welding of the cover sheet 3, the molecular chains in the ribbon essentially maintain their orientation. FIG. 2 shows a variant of a box bag 10 '. This differs from the variant shown in FIG. 1 above all in that, on the one hand, a flexible flat material has been formed into a tube by connecting its longitudinal edges to a tube by joining its longitudinal edges with a longitudinal welding or adhesive seam, and on the other hand, the tabs 6 and 7, from which the rectangular end surface has been formed, almost completely overlap, so that the flap 6 fulfills the function of the cover sheet and therefore can be dispensed with a separate cover sheet. The two tabs 6 and 7 are welded or glued together. The side flaps 6 'and T are folded according to the tabs 4' and 5 'of Fig. 1. Between the tabs T and 6 or 7, a hose valve 2 is again arranged.

Fig. 3 shows in cross section a section of an embodiment of a bag according to the invention, in which the bag body 1 of a fabric-film composite 15 and the cover sheet 3 also consists of a fabric-film composite 15 '. The construction of the fabric-film composite of the bag body consists of a fabric 11 of monoaxially drawn polymer tapes, in particular polyolefin or polyester tapes, preferably polypropylene or polyethylene terephthalate tapes. The fabric 1 1 forms an outer layer of the fabric-film composite 15. On the inside of the fabric 1 1, a bonding layer 12 of thermoplastic material or adhesive is applied, the fabric 1 1 with an OPP (Oriented Poly Propylene) film thirteenth combines. The OPP film 13 is well printable and has, on its surface facing the fabric 11, a print layer 16 which was produced before the OPP film 13 was joined to the fabric 11 by the bonding layer 12. Such a fabric-film composite 15 exhibits both high strength (through the fabric 11) and excellent printability (through the OPP film 13). The fabric-film composite 15 'of the cover sheet 3 has a similar structure as the fabric-film composite 15 of the bag body 1, but here the fabric is still coated with an optional layer 14 of a thermoplastic material with a low melting point to the To facilitate connection with the fabric-film composite 15 of the bag body 1. It should be noted that the fabric-film composites 15, 15 'are arranged one above the other in the same orientation for connection to one another, ie the OPP film 13 of the fabric-film composite 15 is followed by the fabric 11 (or the optional Thermoplastic layer 14) of the fabric-film composite 15 'at. To facilitate the connection with other fabrics, fabric-film composites or films, it is expedient for the fabric-film composites 15, 15 'to provide OPP films which (at least) have a film seal layer (at least) on their surface facing away from the fabric 11. not shown). Of course, OPP films with sealing layers on both surfaces can also be used. The film seal layer 14 and / or the Fabric coating has a melting point that is below the crystallite melting point of the fabric ribbon material and the OPP film. The connection of the two fabric-film composites 15, 15 'by means of hot air welding or introducing a symbolically shown intermediate layer 17 made of thermoplastic material. Since the print layer 16 is located inside the fabric-film composite 15, 15 ^* , it is protected against mechanical damage. The OPP film 13 has a glossy surface which gives the bag produced a very attractive design.

To produce the fabric-film composite 15, first the fabric 11 of monoaxially drawn polymer tapes, in particular polyolefin or polyester tapes, preferably polypropylene or polyethylene terephthalate tapes, and the OPP film 13 are provided. The OPP film 13 is on its surface facing the fabric 1 1, i. the inside, provided with the print layer 16. Subsequently, the fabric 1 1 and the OPP film 13 are laminated together by the connecting layer 12 is introduced from a plastic extrudate from an interposed slot die, whereupon the fabric 1 1 and the OPP film 13 are pulled together through a pair of cooled rollers, so that the bonding layer 12 solidifies. As the plastic for the bonding layer 12, e.g. the LOTADER® 4503 product made by Arkema which is a terpolymer of ethylene, acrylic ester and maleic anhydride. This product adheres very well to both the printed OPP sheet 13 and the fabric 1 1. Alternatively, the tie layer 12 can be made from a coextrudate comprising a first layer facing the OPP sheet 13, e.g. a special polymer that bonds well with the printed OPP film 13 (e.g., LOT ADER), and a second layer of thermoplastic that adheres well to the fabric and to the specialty polymer. This may be a polypropylene layer.

4 shows in cross-section a section of a further embodiment of a bag body 1 or a cover sheet 3 of a bag according to the invention. In this embodiment, the bag body 1 and / or the cover sheet 3 comprise a multilayer film 20 having a core layer 23 of polyethylene or a polyolefin and printable film seal layers 22, 24 on the surfaces of the core layer 23. In the illustration of FIG. 4, the upper film-sealing layer 22 is provided with a printing layer 21.

Fig. 5 shows in cross section a section of another embodiment of a Sackköpers 1 and a cover sheet 3 of a bag according to the invention. In this variant At least either the bag body 1 or the cover sheet 3 comprises a film composite 30, which has at least a first film 31 with an OPP layer 34 and a second film 32 with a polyethylene or polyolefin layer 37, which together via a connecting layer 36 made of thermoplastic material or an adhesive are connected. In the illustrated embodiment, the first film 31 is provided on the outer surface of the OPP layer 34 with a film sealing layer 33 made of a thermoplastic material. Similarly, the second film 32 on the outer surface of the polyethylene or polyolefin layer 37 is provided with a film sealing layer 38 of a thermoplastic. Both the OPP layer 34 of the first film 31 and the polyethylene or polyolefin layer 37 of the second film 32 are printable, wherein in the illustrated embodiment, the inside of the OPP layer 34 of the first film 31 is provided with a print layer 35.

The embodiments according to FIGS. 4 and 5 can be combined with one another as desired. Thus, the following combination possibilities result for a bag 10 or 10 'according to the invention:

Bag body 1 of multilayer film 20 combined with a cover sheet 3 of multilayer film 20;

• Sack body 1 of multilayer film 20 combined with a cover sheet 3 of film composite 30;

• Sack body 1 made of film composite 30 combined with a cover sheet 3 of multilayer film 20;

Sack body 1 made of film composite 30 combined with a cover sheet of film composite 30th

Although these above embodiments of the bag do not provide the same high strength as the use of a film-fabric composite 15 as in the embodiment of Figure 3, this disadvantage can be alleviated by increasing the number of film layers.

In a further embodiment, which is shown in cross-section in FIG. 6, cover sheet 3 made of a multilayer film 20 according to FIG. 4 is combined with a bag body 1 comprising a coated fabric 50 known in a similar manner from document WO 95/30598 , The coated fabric 50 comprises a fabric 51 of monoaxially drawn polymer tapes, in particular polyolefin or polyester tapes, preferably polypropylene or polyethylene terephthalate tapes, and a fabric sealing layer 52 of a thermoplastic whose melting point is below the crystallite melting point of the fabric tape material. The crystallite melting point of Tissue tape material is above 120 ° C. The bonding of multilayer film 20 and coated web 50 is accomplished by hot air blasting wherein the fabric seal layer 52 and the film seal layer 24 are fused, but not the fabric layer 51. The fabric seal layer 52 is printable as illustrated by the print layer 21. It should be noted that in a variant of this embodiment, not shown, the multilayer film 20 can be replaced by a film composite 30, as shown in Fig. 5.

A variant of the embodiment of a bag according to FIG. 6 is shown in FIG. 7. This variant differs from the previous embodiment in that in a coated fabric 50 'between the fabric 51 and the fabric seal layer 52, an adhesive layer 53 of a polymer material with good adhesion to both the fabric 51 and the fabric seal layer 52 is disposed. For improved handleability in welding, the adhesive layer 53 should preferably have a melting point higher than that of the tissue-sealing layer 52.

The invention allows a very wide variety of combinations of the materials described above for bag bodies and cover sheets of a bag according to the invention. For example, a bag body 1 from the fabric composite 15 shown in FIG. 3 can be excellently combined with a cover sheet 3 that consists of the above-described multilayer film 20 or the film composite 30 described above. The bag thus produced has high strength and good printability.

Similarly, a bag body 1 of the coated fabric 50, 50 'shown in Figs. 6 and 7 can be combined with a cover sheet 3 of the multilayer film 20 or the film composite 30 to form a high-strength bag.

Claims

Claims:

1. bag (10, 10 ') with a tubular bag body (1, 1'), which is formed from a tubular round material or a longitudinally connected to a tube flat material, wherein at least one end portion of the bag body by folding to a generally rectangular Endface is formed, and with a cover sheet (3, 6) which has been connected via an intermediate layer (17) made of thermoplastic material, in particular polyolefin, preferably polyethylene material under heat to the end face of the bag body, characterized in that the bag body (1 , 1 ') and / or the cover sheet (3, 6) comprise / comprises a printable plastic film (13, 20, 30).

2. Sack according to claim 1, characterized in that the intermediate layer is formed from at least one sealing layer, which on the cover sheet facing surface of the bag body (1, 1 ') and / or on the bag body facing surface of the cover sheet (3, 6 ) is provided, wherein when sealing the bag body with the cover sheet, the sealing layer or sealing layers are heated by hot air to plasticization, the bag body and the cover sheet are pressed together and then cooled.

3. Sack according to claim 1, characterized in that when connecting the bag body (1, 1 ') with the cover sheet (3, 6) a melt of thermoplastic plastic, in particular polyolefin, preferably polyethylene material, as an intermediate layer (17) between the Sack body and the cover sheet is introduced, the bag body and the cover sheet pressed together and then cooled.

4. bag (10) according to one of claims 1 to 3, characterized in that the cover sheet (3) is formed as a separate element, wherein preferably the bag body parts folded to an end surface not or not substantially overlap each other.

5. bag (10 ') according to any one of claims 1 to 3, characterized in that the cover sheet (6) is a part of the bag body, which is formed in the folding of the end surface by overlapping with Endflächenlappen.

6. Sack according to one of claims 1 to 5, characterized in that the bag body (1, 1 ') and / or the cover sheet (3, 6) comprises a fabric-film composite (15, 15') / comprises, the a structure of a fabric (11) of monoaxially drawn polymer ribbon, in particular polyolefin or polyester ribbon, preferably polypropylene or Polyethylenterephthalatbändchen, an OPP (Oriented Poly Propylene) film (13) and an intermediate connection layer (12) made of thermoplastic material or adhesive, wherein the OPP film (13) on the fabric (1 1) facing surface is printed.

7. Sack according to claim 6, characterized in that the OPP film (13) of the fabric-film composite (15 ') on its side facing away from the fabric (11) surface or on both sides of a film seal layer (14).

8. Sack according to claim 6 or 7, characterized in that the tissue (1 1) of the fabric-film composite (15, 15 ') on one or both sides with a fabric sealing layer of a thermoplastic plastic coated.

9. A bag according to claim 7 or 8, characterized in that the film seal layer (14) and / or the fabric seal layer have a melting point which is below the crystallite melting point of the fabric ribbon material and the OPP film.

10. Sack according to one of claims 1 to 5, characterized in that the bag body (1, 1 ') and / or the cover sheet (3, 6) comprise / comprises a multilayer film (20) comprising a core layer (23) Polyethylene or a polyolefin and have printable film seal layers (22, 24) on the surfaces of the core layer.

1 1. Sack according to one of claims 1 to 5, characterized in that the bag body (1, 1 ') and / or the cover sheet (3, 6) comprises a film composite (30) / which comprises at least a first film (31 OPP and a second film (32) of polyethylene or a polyolefin, which are connected to each other via a connecting layer (36) made of thermoplastic material or an adhesive, preferably both films on their outer surfaces with a film seal layer (33, 38) a thermoplastic material are provided and wherein on one of the films on the inside thereof, a printing layer (35) is provided.

12. Sack according to claim 10 or 11, characterized in that either the bag body (1) the film composite (30) and the cover sheet (3) comprises the multilayer film (20), or the bag body (1) the multilayer film (20) and the cover sheet (3) comprises the film composite (30).

13. Sack according to one of claims 1 to 5, characterized in that the bag body (1) comprises a coated fabric (50, 50 ') having a structure of a fabric (51) of monoaxially stretched polymer tapes, in particular polyolefin or polyester tapes , preferably polypropylene or polyethylene terephthalate, which tissue is coated on one or both sides with a fabric sealing layer (52) made of a thermoplastic plastic having.

14. Sack according to claim 13, characterized in that the fabric sealing layer (52) consists of a thermoplastic material whose melting point is below the crystallite melting point of the fabric ribbon material.

A sack according to any one of claims 13 or 14, characterized in that between the fabric (51) of monoaxially drawn polymer ribbon and the fabric seal layer (52) is an adhesive layer (53) of a polymeric material having good adhesion to both the fabric and the sealant layer is arranged, wherein the adhesive layer preferably has a melting point which is higher than that of the sealing layer.

16. Sack according to one of claims 1 to 4, wherein the bag body (1) comprises a film-fabric composite (15) according to any one of claims 6 to 9 and a cover sheet (3) of a multilayer film (20) according to claim 10 or of a film composite (30) according to claim 1 1 or 12.

17. Sack according to one of claims 1 to 4, wherein the bag body (1) a coated fabric (50, 50 ') according to any one of claims 13 to 15 and a cover sheet (3) of a multilayer film (20) according to claim 10 or from a film composite (30) according to claim 11 or 12.