Composite material, packaging product and method

Abstract

The invention relates to a composite material comprising or consisting of a cellulose-based carrier (1); and a coating (3) arranged on a first surface (2) of the carrier (1), the coating (3) being a polymer material, in particular an extruded polymer material, the coating (3) being designed as at least one coating strip (4), the longitudinal extension direction (6) of which runs substantially parallel to two opposite side edges (5) of the carrier (1), the width of the coating strip (4) being smaller than the width of the carrier (1), such that the carrier (1) has at least one uncoated region (7). The invention further relates to a packaging product and to a method.

Description

[0001] 64969

[0002] Mondi AG, Marxergasse 4A, 1030 Vienna (AT)

[0003] Composite material, packaging product and process

[0004] The present invention relates to a composite material, a packaging product, and a method for producing a composite material. In particular, the invention relates, among other things, to a composite material comprising at least two layers, comprising a cellulose-based carrier and a coating arranged on a surface of the carrier.

[0005] Multilayer composite materials of the type mentioned above are known in the prior art. For example, the substrate can be made of or comprise paper or a paper-like material. However, these materials typically exhibit high permeability to gases such as water vapor and / or oxygen, which makes them unsuitable for numerous applications.

[0006] To reduce gas permeability, the supports can be coated, for example using extruded polymer materials.

[0007] In processes known in the prior art, the coating is carried out by polymer extrusion in such a way that paper webs are coated over their entire width and a 64969 is formed on both sides of the longitudinal edges of the paper web.

[0008] Mondi AG, Marxergasse 4A, 1030 Vienna (AT)

[0009] Excess coating material remains. In other words, the width of the coating is greater than the width of the paper web.

[0010] The coating webs are typically wound onto rolls until further processing, with the excess material remaining on the web material.

[0011] The coated paper sheets can then be used to create packaging products such as sacks or bags by joining the material along opposite edges, in particular by gluing. The excess material can be trimmed off.

[0012] Within the scope of the present invention, it has now been found that, among other things, the use of water-based starch adhesives is not suitable for the manufacture of such packaging products, since contact with water leads to the coating detaching from the substrate.

[0013] To overcome the problem of detachment, other adhesives can be used, such as solvent-based synthetic adhesives, but these are less environmentally friendly compared to water-based starch adhesives.

[0014] The aforementioned problems result in a conflict of objectives, which the present invention aims to resolve. The invention may also solve further or alternative problems.

[0015] Surprisingly, it was found in the present invention that said conflict of objectives can be overcome in particular by providing a coated carrier which has a web-like coating, i.e. in which uncoated areas are provided.

[0016] This is surprising, among other reasons, because the prevailing assumption in the prior art is that the extrusion of polymers onto web-like carrier materials must be carried out with the overhangs described above in order to obtain a satisfactorily uniform coating thickness and width. 64969

[0017] Mondi AG, Marxergasse 4A, 1030 Vienna (AT)

[0018] The coated web materials produced in this way can advantageously be further processed into packaging products by bonding uncoated areas together using starch adhesive. Provided that the starch adhesive or the water it contains does not come into contact with coated areas, there is no risk of the coating material detaching.

[0019] In general, various configurations of area- or strip-by-strip coating are conceivable; however, it is typically intended that a strip of coating material runs in the longitudinal direction of the carrier strip. The side edges of the coating material can therefore run essentially parallel to the longitudinal edges of the carrier strip.

[0020] The substrate has at least one uncoated area. However, it is advantageous to have two or more uncoated areas. In one embodiment, two uncoated areas are provided that extend along two longitudinal edges of the substrate material, with the coating being located in a central area of ​​the substrate material.

[0021] The carrier web is primarily paper or another cellulose-based material, specifically a cellulose-based nonwoven fabric. The raw material from which the cellulose is derived is primarily wood, but can also be another ignitable renewable raw material or recycled paper.

[0022] The coating consists of, or comprises, a polymer material. In one version, the polymer material is a thermoplastic polymer, such as a polyolefin. The polyolefin can be polyethylene.

[0023] The substrate and / or coating generally have a substantially rectangular shape with a length many times greater than its width. In particular, the long edges of the substrate and / or coating are substantially straight. Mondi AG, Marxergasse 4A, 1030 Vienna (AT)

[0024] In the context of the present invention, the term "width" refers in particular to the dimension that lies in the plane of the composite material transversely to the longitudinal direction. In particular, the width refers to the average width over the entire length of the composite material.

[0025] As mentioned above, the composite material, or a part of the composite material, can be used to manufacture a packaging product. The packaging product could be, for example, a bag or a sack, and generally has at least a partially enclosed interior suitable for containing packaged goods.

[0026] In this packaging product, two uncoated areas of the composite material can be joined together, in particular by adhesive bonding. A starch-based adhesive, which can be cured by heat, is used for this purpose.

[0027] The coating of the composite material can face the interior of the packaging product, i.e., be inside.

[0028] The coating of the composite material can form a continuous layer in the packaging product. This is particularly the case when two edges of the coating are arranged so that they abut each other, or when areas of the coating overlap.

[0029] Furthermore, a method for producing a composite material as described herein is disclosed.

[0030] In this process, the coating can be extruded as a strip onto a surface of the substrate.

[0031] An extrusion device equipped with a slot die can be used for this purpose. Mondi AG, Marxergasse 4A, 1030 Vienna (AT)

[0032] The width of the extrusion die is generally greater than the width of the substrate to be coated. By using a capping or baffle device, the die outlet width, and thus the width of the coating path, can be adjusted.

[0033] The capping device can be inserted into the outlet gap of the extrusion nozzle.

[0034] The invention may relate to a composite material comprising or consisting of: a cellulose-based carrier; and a coating arranged on a first surface of the carrier.

[0035] The coating may comprise or consist of a polymer material, in particular an extruded polymer material.

[0036] Optionally, the coating may be designed as at least one coating strip whose longitudinal direction is substantially parallel to two opposite side edges of the carrier, wherein the width of the coating strip is smaller than the width of the carrier, so that the carrier has at least one uncoated area.

[0037] If necessary, the coating is provided for to be formed from a coating strip.

[0038] If necessary, the coating is provided to consist of several coating strips that are opposed to each other and run essentially parallel to each other.

[0039] If necessary, the width of the coating strip(s) is provided for to be essentially constant.

[0040] If necessary, the support is provided to have at least two uncoated areas, each located between a side edge of the support and a Mondi AG, Marxergasse 4A, 1030 Vienna (AT)

[0041] The side edge of the coating strip runs, with the width of the uncoated areas being between 5 mm and 30 mm, the uncoated areas being in particular the edges of the carrier.

[0042] If necessary, the carrier is provided for to have at least one uncoated area running between two coating strips.

[0043] If necessary, the carrier is made of paper, in particular kraft paper and preferably sack kraft paper, the machine direction of which runs in particular along the longitudinal extension direction of the coating strip.

[0044] If necessary, the carrier is provided for to be a track material whose length-to-width ratio is at least 100:1, in particular 1000:1.

[0045] If applicable, it is stipulated that the beam has a length of at least 1000 m, and / or that the beam has a width between 0.5 m and 3.5 m.

[0046] If necessary, the carrier is intended to have a basis weight between 20 g / m². 2 and 150 g / m² 2 determined according to ISO 536:2019, and / or that the coating (3) has a basis weight between 0.5 g / m² 2 and 30 g / m² 2 , especially between 2.0 g / m³ 2 and 7.0 g / m² 2 , exhibits.

[0047] Optionally, it is provided that the basis weight of the coating is at most 20%, preferably at most 10%, more preferably at most 5%, of the basis weight of the substrate, wherein the basis weight of the substrate is determined according to ISO 536:2019.

[0048] If applicable, the polymer material of the coating may comprise or be a polyolefin, in particular polyethylene.

[0049] If necessary, the composite material in the coating area is designed to have a water vapor permeability of no more than 40 g / m². 2 / t, preferably not more than 30 g / m² 2 / t, preferably not more than 25 g / m² 2 / t, where Mondi AG, Marxergasse 4A, 1030 Vienna (AT)

[0050] Water vapor permeability is determined at a temperature of 23°C and a relative humidity of 50% according to ASTM F1927.

[0051] The invention may relate to a packaging product, in particular a bag or sack, comprising a composite material as described herein, wherein two layers of the composite material are joined together, in particular glued, at the uncoated areas.

[0052] If necessary, the uncoated areas are to be bonded with starch adhesive.

[0053] If applicable, the packaging product is provided to have an interior space, with the coating facing the interior space.

[0054] If necessary, the coating is designed to form a continuous layer in the interior.

[0055] The invention may optionally relate to a method for producing a composite material comprising or consisting of a cellulose-based support and a coating arranged on a first surface of the support, wherein the coating comprises or consists of a polymer material.

[0056] If necessary, the process includes the following steps: providing the carrier; applying the coating to the first surface of the carrier using an extrusion device.

[0057] Optionally, the coating is applied as at least one coating strip, the longitudinal direction of which extends substantially parallel to two opposite side edges of the substrate, the width of the coating strip being smaller than the width of the substrate, so that the substrate has at least one uncoated area. 64969

[0058] Mondi AG, Marxergasse 4A, 1030 Vienna (AT)

[0059] If necessary, the coating is extruded onto the first surface of the carrier, with the application direction corresponding to the longitudinal extension direction of the coating strip.

[0060] Optionally, the extrusion device may have an extrusion die whose outlet width is greater than the width of the carrier, and at least one covering device may be provided to adjust the width of the coating strip by reducing the outlet width of the extrusion die.

[0061] Optionally, the substrate is provided to be paper, in particular kraft paper and preferably sack kraft paper, which is supplied as roll stock, and optionally, the substrate is unwound from the roll for coating and wound onto a product roll after coating.

[0062] Further features can be found in the patent claims, the figures and the description of the exemplary embodiments.

[0063] Certain aspects of the present invention are explained in more detail below using an exemplary embodiment and with reference to the figures. This serves only to illustrate advantageous effects of the invention and is not intended to limit the scope of protection defined by the patent claims.

[0064] They show:

[0065] Fig. 1 shows a schematic top view of a composite material according to a first embodiment;

[0066] Fig. 2 shows a schematic sectional view of the composite material according to the first embodiment;

[0067] Fig. 3 shows a schematic sectional view of a composite material according to a second embodiment;

[0068] Fig. 4 shows a schematic sectional view of the composite material according to the second embodiment. Mondi AG, Marxergasse 4A, 1030 Vienna (AT)

[0069] Unless otherwise specified or apparent from the context, the following features and elements are depicted in the figures: carrier 1, first surface 2, coating 3, coating strip 4, side edge 5 (of the carrier 1), longitudinal direction 6, uncoated area 7, side edge 8 (of the coating strip 4).

[0070] Fig. 1 shows a schematic top view of a composite material according to a first embodiment, and Fig. 2 shows a schematic sectional view of the same composite material, with the section plane running in the width direction of the composite material. These two figures are explained together for clarity.

[0071] The composite material shown in Figures 1 and 2 is supplied in roll form, of which only a small section is shown. The substrate 1 is sack kraft paper, which is provided on a first surface 2 with a coating 3 of extruded polyethylene.

[0072] In this embodiment, the second surface 9 opposite the first surface 2 of the carrier 3 is uncoated.

[0073] The coating 3 extends as a coating strip 4 or web over the substrate 3, such that it has a longitudinal direction 6. The longitudinal direction 6 of the coating strip 4 is generally the direction that corresponds to the greatest geometric extent of the coating strip 4. The side edges 8 of the coating strip 4 run along the longitudinal direction 6.

[0074] As can be seen in Fig. 1, the side edges 8 of the coating strip 4 run essentially parallel to the side edges 5 of the substrate 1. Furthermore, both side edges 8 of the coating strip 4 are spaced apart from the side edges 5 of the substrate 1, so that uncoated areas 7 are formed at both edges of the composite material, in which the first surface 2 is free of the coating 3. The uncoated areas 7 can also be seen in Fig. 2. Mondi AG, Marxergasse 4A, 1030 Vienna (AT)

[0075] In this embodiment, the uncoated areas have a width of approximately 10 mm, with tolerances of approximately ± 5 mm being deemed acceptable. The side edges 8 of the coating strip 3 are typically not perfectly straight.

[0076] The properties of the composite material described here are as follows in detail:

[0077] Carrier material: brown kraft paper

[0078] Paper weight of carrier: 70 g / m² 2

[0079] Beam width: 990 mm

[0080] Beam length: approx. 11,000 m

[0081] Coating material: Low-density polyethylene (LDPE)

[0082] Coating weight: approx. 5 g / m² 2

[0083] Water vapor permeability: approx. 25 g / m² 2 / t at 23°C and 50% rH

[0084] The material for coating 3 was extruded onto the carrier web moving at a speed of approximately 240 m / min at an extrusion die temperature of approximately 320°C. The resulting composite material was then cooled and wound onto a roll.

[0085] The coating 3 showed good adhesion to the substrate 1.

[0086] Pieces of the composite material can be cut from the roll and used to manufacture packaging products. By bonding the opposing uncoated areas 7 together, a tubular intermediate product can be formed, which can then be processed into a bag or sack by sealing one open end of the tube.

[0087] A starch-based adhesive can be advantageously used for bonding.

[0088] Fig. 3 shows a schematic sectional view of a composite material according to a second embodiment and Fig. 4 shows a schematic top view of the same 64969

[0089] Mondi AG, Marxergasse 4A, 1030 Vienna (AT)

[0090] Composite material. The section plane of the illustration in Fig. 3 runs in the width direction of the composite material. These two figures are explained together for better understanding.

[0091] The composite material shown in Figures 3 and 4, as in the first embodiment, is a roll material, of which only a small section is shown. As in the first embodiment, the carrier 1 in the second embodiment is sack kraft paper with a coating 3 of extruded polyethylene on a first surface 2. The second surface 9 is uncoated.

[0092] In contrast to the first embodiment, this second embodiment provides two coating strips 4 which run essentially parallel to each other. The longitudinal direction 6 of the two coating strips 4 is also essentially parallel to the side edges 5 of the carrier 1. The side edges 8 of the two coating strips 4 run along the longitudinal direction 6.

[0093] Between the outer side edges 8 of the coating strips 4 and the side edges 5 of the carrier 1, an uncoated area 7 is formed at the edges of the composite material, in which the first surface 2 is free of the coating 3.

[0094] Furthermore, between the inner side edges 8 of the coating strips 4, which point towards each other, a further, third, uncoated area 7 is formed.

[0095] In this embodiment, the outer uncoated areas 7 have a width of approximately 20 mm, with tolerances of approximately ± 5 mm being deemed acceptable. The inner uncoated area 7 has a width of approximately 40 mm, with the same tolerances. The side edges 8 of the coating strip 3 are typically not perfectly straight.

[0096] The properties of the composite material described here are as follows in detail: 64969

[0097] Mondi AG, Marxergasse 4A, 1030 Vienna (AT)

[0098] Carrier material: white kraft paper

[0099] Carrier weight: 80 g / m² 2

[0100] Beam width: 829 mm

[0101] Beam length: approx. 11,000 m

[0102] Coating material: Low-density polyethylene (LDPE)

[0103] Coating weight: approx. 4 g / m² 2

[0104] Water vapor permeability: approx. 22 g / m² 2 / t at 23°C and 50% rH

[0105] The material for coating 3 was extruded onto the carrier web moving at a speed of approximately 240 m / min at an extrusion die temperature of approximately 320°C. The resulting composite material was then cooled and wound onto a roll.

[0106] The coating 3 showed good adhesion to the substrate 1.

[0107] Pieces of the composite material can be cut from the roll and used to manufacture packaging products. The composite material can be cut lengthwise along the inner uncoated areas 7 to form webs of the composite material that are approximately half the width of the original material.

[0108] By bonding the opposing uncoated areas 7, a tubular intermediate product can be formed, as in the first embodiment, which can subsequently be processed into a bag or sack by closing an open end of the tube.

Claims

64969 Mondi AG, Marxergasse 4A, 1030 Vienna (AT) Patent claims 1. Composite material comprising or consisting of - a cellulose-based carrier (1 ) and - a coating (3) arranged on a first surface (2) of the carrier (1), wherein the coating (3) comprises or consists of a polymer material, in particular an extruded polymer material, characterized in that the coating (3) is formed as at least one coating strip (4) whose longitudinal extension direction (6) is substantially parallel to two opposite side edges (5) of the carrier (1), wherein the width of the coating strip (4) is smaller than the width of the carrier (1), such that the carrier (1) has at least one uncoated area (7).

2. Composite material according to claim 1, characterized in that, - that the coating (3) is formed from a coating strip (4), or - that the coating (3) is formed from several coating strips (4) that are opposed to each other and run essentially parallel to each other.

3. Composite material according to claim 1 or 2, characterized in that the width of the coating strip(s) (4) is essentially constant.

4. Composite material according to one of claims 1 to 3, characterized in that the carrier (1 ) has at least two uncoated areas (7) which each extend between a side edge (5) of the carrier (1 ) and a side edge (8) of the coating strip (4), wherein the width of the uncoated areas (7) is between 5 mm and 30 mm, wherein the uncoated areas (7) are in particular the edges of the carrier (1 ). 64969 Mondi AG, Marxergasse 4A, 1030 Vienna (AT) 5. Composite material according to one of claims 1 to 4, characterized in that the carrier (1 ) has at least one uncoated area (7) which runs between two coating strips (4).

6. Composite material according to one of claims 1 to 5, characterized in that the carrier (1 ) is made of paper, in particular kraft paper and preferably sack kraft paper, the machine direction of which runs in particular along the longitudinal extension direction (6) of the coating strip (4).

7. Composite material according to one of claims 1 to 6, characterized in that the carrier (1 ) is a web material whose ratio between length and width is at least 100:1, in particular 1000:1 .

8. Composite material according to one of claims 1 to 7, characterized in that the support (1 ) has a length of at least 1000 m, and / or that the support (1 ) has a width between 0.5 m and 3.5 m.

9. Composite material according to one of claims 1 to 8, characterized in that the carrier (1 ) has a basis weight between 20 g / m² 2 and 150 g / m² 2 determined according to ISO 536:2019, and / or that the coating (3) has a basis weight between 0.5 g / m² 2 and 30 g / m² 2 , especially between 2.0 g / m³ 2 and 7.0 g / m² 2 , exhibits.

10. Composite material according to one of claims 1 to 9, characterized in that the basis weight of the coating (3) is at most 20%, preferably at most 10%, more preferably at most 5%, of the basis weight of the substrate (1 ), wherein the basis weight of the substrate (1 ) is determined according to ISO 536:2019.

11. Composite material according to one of claims 1 to 10, characterized in that the polymer material of the coating (3) comprises or is a polyolefin, in particular polyethylene. 64969 Mondi AG, Marxergasse 4A, 1030 Vienna (AT) 12. Composite material according to one of claims 1 to 11, characterized in that the composite material has a water vapor permeability of at most 40 g / m² in the area of ​​the coating (3). 2 / t, preferably not more than 30 g / m² 2 / t, preferably not more than 25 g / m² 2 / t, where the water vapor permeability is determined at a temperature of 23°C and a relative humidity of 50% according to ASTM F1927.

13. Packaging product, in particular bag or sack, comprising a composite material according to one of claims 1 to 12, characterized in that two layers of the composite material are joined together at the uncoated areas (7), in particular glued.

14. Packaging product according to claim 13, characterized in that the uncoated areas (7) are bonded with starch adhesive.

15. Packaging product according to claim 13 or 14, characterized in that the packaging product has an interior (8), wherein the coating (3) points towards the interior (8).

16. Packaging product according to claim 15, characterized in that the coating (3) forms a continuous layer in the interior (8).

17. Method for producing a composite material comprising or consisting of a cellulose-based support (1 ) and a coating (3) arranged on a first surface (2) of the support (1 ), wherein the coating (3) comprises or consists of a polymer material, the method comprising the following steps: - Provision of the carrier (1 ), - Applying the coating (3) to the first surface (2) of the carrier (1) using an extrusion device, characterized in that the coating (3) is applied as at least one coating strip (4) whose longitudinal extension direction (6) extends substantially parallel to two opposite side edges (5) of the carrier (1), wherein the width of the coating strip (4) is smaller Mondi AG, Marxergasse 4A, 1030 Vienna (AT) as the width of the support (1) such that the support (1) has at least one uncoated area (7).

18. Method according to claim 17, characterized in that the coating (3) is extruded onto the first surface (2) of the carrier (1), wherein the application direction corresponds to the longitudinal extension direction (6) of the coating strip (4).

19. Method according to claim 18, characterized in that the extrusion device has an extrusion die whose outlet width is greater than the width of the carrier (1 ), and that at least one covering device is provided for adjusting the width of the coating strip (4) which reduces the outlet width of the extrusion die.

20. Method according to one of claims 17 to 19, characterized in that the carrier (1) is paper, in particular kraft paper and preferably sack kraft paper, which is provided as roll stock, wherein it is optionally provided that the carrier (1) is unwound from the roll for coating and wound onto a product roll after coating.

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