INCREASING THE TEAR RESISTANCE OF A MULTI-LAYERED FILM

Abstract

The invention relates to a method of increasing the tear resistance of a multi-layered film. This multi-layered film includes at least one barrier arrangement that has a total thickness for reducing gas permeability. According to the invention, the barrier arrangement is divided into at least two layers, to increase tear resistance.

Claims

1. A method for increasing a tear resistance of a multilayer film, having a barrier arrangement which has a total thickness for reducing a gas permeability, the method comprising: sub-dividing the barrier arrangement into at least two layers in the multilayer film.

2. The method as claimed in claim 1, further comprising: increasing the tear resistance as a result of the subdivision by a factor of 1.5 or more.

3. The method as claimed in claim 1, further comprising after the subdivision of the barrier arrangement, providing the film with a same total thickness, and providing the film with an oxygen permeability similar to that before the subdivision of the barrier arrangement, the oxygen permeability being determined according to DIN 53380-3 at 23 C. and 50% relative humidity, and the oxygen permeability after the subdivision deviates from the oxygen permeability before the subdivision by not more than 30%.

4. The method as claimed in claim 1, further comprising: sub-dividing the barrier arrangement into layers having individual thicknesses which are situated in relation to one another between a ratio of 1:1 up to a ratio of 1:10.

5. The method as claimed in claim 1, further comprising: providing all the layers of the barrier arrangement with similar individual thicknesses, the deviation being not more than 20%.

6. The method as claimed in claim 1, further comprising: forming the barrier arrangement of at least 50 wt % of materials from the group consisting of at least one of: a polyamide, a copolyamide, a polyester, a copolyester, polyethylene-vinyl alcohol, polyvinyl alcohol or mixtures thereof.

7. The method as claimed in claim 1, further comprising: forming the film with outer layers of a polyolefin.

8. The method as claimed in claim 1, further comprising: forming the barrier arrangement from at least one of the materials in the group including a polyamide, a copolyamide, a polyester, a copolyester, polyethylene-vinyl alcohol, polyvinyl alcohol, or mixtures thereof, and at most 20 wt % of further polymeric constituents.

9. The method as claimed in claim 1, further comprising: forming the barrier arrangement of at least one of a polyamide or a copolyamide.

10. The method as claimed in claim 1, further comprising: forming the film with a thickness of less than 200 m and more than 10 m.

11. An apparatus for agricultural use, comprising a multilayer film including a barrier arrangement having a total thickness to reduce a gas permeability, and the barrier arrangement is subdivided into at least two layers, a DIN 53128 Elmendorf tear resistance of the film in at least one of a machine direction (MD) or transverse direction (TD) being more than $10.Math.\frac{g}{m},$

12. The apparatus as claimed in claim 11, wherein the film has an oxygen permeability of at most 500 cm.sup.2/m.sup.2.Math.d.Math.bar determined according to DIN 53380-3 at 23 C. and 50% relative humidity.

13. The apparatus as claimed in claim 11 individual thicknesses of the at least two layers relative to one another is between a ratio of 1:1 up to a ratio of 1:10.

14. The apparatus as claimed in claim 11, wherein the layers of the barrier arrangement all have similar individual thicknesses, with a deviation being preferably not more than 20% between the layers.

15. The apparatus as claimed in claim 11, wherein the barrier arrangement is formed of at least 50 wt % of materials from the group including at least one of: a polyamide, a copolyamide, a polyester, a copolyester, polyethylene-vinyl alcohol, polyvinyl alcohol, or mixtures thereof.

16. The apparatus as claimed in claim 11, wherein the film further comprises outer layers of a polyolefin.

17. The apparatus as claimed in claim 11, wherein the barrier arrangement is formed from at least one of the materials in the group including at least one of a polyamide, a copolyamide, a polyester, a copolyester, polyvinyl, polyethylene-vinyl alcohol, polyvinyl alcohol, or mixtures thereof, and at most 20 wt % of further polymeric constituents.

18. The apparatus as claimed in claim 11, wherein the barrier arrangement is comprised of at least one of a polyamide or a copolyamide.

19. The apparatus as claimed in claim 11, wherein a thickness of the film is less than 200 m and more than 10 m.

20. The apparatus of claim 16, wherein the polyolefin is a product of a polymerization process which uses a metallocene catalyst.

Description

DETAILED DESCRIPTION

[0028] Further features and advantages of the invention are apparent from the description of working examples.

Example 1

[0029] Table 1 shows two multilayer films each with a thickness of 70 m; the right-hand column lists the mechanical properties of the film before the subdivision, and the left-hand column the mechanical properties of the film after subdivision of the barrier arrangement.

TABLE-US-00001 70 m 70 m 2 5 m PA 1 10 m PA Dart drop (g) 1780 1760 Tensile strength (MPa) MD 49.7 45.0 TD 47.4 39.7 Elongation at break (%) MD 535 520 TD 555 525 [00008]$\mathrm{Tear}.Math..Math.\mathrm{resistance}.Math.\frac{g}{\mathrm{.Math.m}}.Math.M.Math..Math.D$ 39.7 12.6 TD 51.2 14.8

[0030] The barrier arrangement of the film comprises a PA layer having a total thickness of 10 m. The DIN 53128 Elmendorf tear resistance in machine direction (MD) is

[00009]$12.6.Math..Math.\frac{g}{\mathrm{.Math.m}}.$

The DIN 53128 Elmendorf tear resistance in transverse direction, TD, is

[00010]$14.8.Math..Math.\frac{g}{\mathrm{.Math.m}}.$

[0031] By using the method of the invention, the polyamide barrier arrangement is subdivided into two layers each with an individual thickness of 5 m. The sum of the individual thicknesses of the barrier layers add up again to give the total density of the barrier arrangement. Surprisingly it has been found that the subdivision of the barrier arrangement significantly raises the tear resistance of the film.

[0032] In working example 1, the DIN 53128 Elmendorf tear resistance in machine direction (MD) increases from

[00011]$12.6.Math..Math.\frac{g}{\mathrm{.Math.m}}$

(right-hand column) to

[00012]$39.7.Math..Math.\frac{g}{\mathrm{.Math.m}}$

(left-hand column). Accordingly, through use of the method of the invention, the tear resistance in machine direction (MD) rises by a factor of 3.15.

[0033] The DIN 53128 Elmendorf tear resistance in transverse direction (TD) increases from

[00013]$14.8.Math..Math.\frac{g}{\mathrm{.Math.m}}.Math..Math.\mathrm{to}.Math..Math.51.2.Math..Math.\frac{g}{\mathrm{.Math.m}}$

by a factor of 3.46.

[0034] All tear resistances specified are DIN 53128 Elmendorf values.

[0035] Prior to the subdivision of the barrier arrangement in accordance with example 1 (right-hand column), the construction of the individual layers in the film is as follows:

[0036] 12.7 vol % metallocene-LLDPE with additives, especially antiblock additives

[0037] 13 vol % metallocene-LLDPE

[0038] 17 vol % tie layermetallocene LLDPE

[0039] 14.3 vol % barrier arrangement, copolyamide PA6/6.6

[0040] 17 vol % tie layermetallocene LLDPE

[0041] 13 vol % metallocene-LLDPE

[0042] 13 vol % metallocene-LLDPE with additives, especially antiblock additives

[0043] After the subdivision of the barrier arrangement in accordance with example 1 (left-hand column), the construction of the individual layers in the film is as follows:

[0044] 17 vol % metallocene-LLDPE with additives, especially antiblock additives

[0045] 17 vol % tie layermetallocene LLDPE

[0046] 7.15 vol % barrier arrangement, copolyamide PA6/6.6

[0047] 17.7 vol % tie layermetallocene LLDPE

[0048] 7.15 vol % barrier arrangement, copolyamide 6/6.6

[0049] 17 vol % tie layermetallocene LLDPE

[0050] 17 vol % metallocene-LLDPE with additives, especially antiblock additives

Example 2

[0051] Table 2 shows a multilayer film with a thickness of 85 m; the right-hand column lists the mechanical properties of the film before the subdivision, and the left-hand column the mechanical properties of the subdivision of the film after subdivision.

TABLE-US-00002 85 m 85 m 2 8.5 m PA 1 17 m PA Dart drop (g) >1690 >1690 (g/m) >20.4 >20.6 Tensile strength (MPa) MD 45.2 45.5 TD 45.9 43.8 Elongation at break (%) MD 480 470 TD 460 450 [00014]$\mathrm{Tear}.Math..Math.\mathrm{resistance}.Math.\frac{g}{\mathrm{.Math.m}}.Math.M.Math..Math.D$ 53.2 6.3 TD 56.1 8.1

[0052] The barrier arrangement of the film comprises a PA layer of 17 m (right-hand column). The tear resistance in machine direction (MD) is

[00015]$6.3.Math..Math.\frac{g}{\mathrm{.Math.m}}.$

[0053] By using the method of the invention, the polyamide barrier arrangement is subdivided into two layers each with an individual thickness of 8.5 m. The sum of the individual thicknesses of the barrier layers add up again to give the total thickness of the barrier arrangement. Here as well, it was surprisingly found that the subdivision of the barrier arrangement significantly raises the tear resistance of the film.

[0054] In working example 2, the tear resistance in machine direction (MD) increases from

[00016]$6.3.Math..Math.\frac{g}{\mathrm{.Math.m}}$

(right-hand column) to

[00017]$53.2.Math..Math.\frac{g}{\mathrm{.Math.m}}$

(left-hand column). Accordingly, through use of the method of the invention, the tear resistance in machine direction (MD) rises by a factor of 8.44. The tear resistance in transverse direction (TD) increases from

[00018]$8.1.Math..Math.\frac{g}{\mathrm{.Math.m}}.Math..Math.\mathrm{to}.Math..Math..Math.56.1.Math..Math.\frac{g}{\mathrm{.Math.m}}$

by a factor of 6.93.

[0055] Prior to the subdivision of the barrier arrangement (right-hand column), the construction of the individual layers in the film is as follows:

[0056] 12 vol % metallocene-LLDPE with additives

[0057] 16 vol % tie layercopolymer EBA

[0058] 20 vol % barrier arrangement, copolyamide 6/6.6

[0059] 14 vol % tie layerLLDPE

[0060] 10 vol % copolymer EBA

[0061] 16 vol % copolymer EBA

[0062] 12 vol % metallocene-LLDPE with additives

[0063] After the subdivision of the barrier arrangement in accordance with example 2 (left-hand column), the construction of the individual layers in the film is as follows:

[0064] 12 vol % metallocene-LLDPE with additives

[0065] 21 vol % tie layercopolymer EBA

[0066] 10 vol % barrier arrangement, copolyamide PA6/6.6

[0067] 14 vol % tie layermetallocene LLDPE

[0068] 10 vol % barrier arrangement, copolyamide 6/6.6

[0069] 21 vol % tie layercopolymer EBA

[0070] 12 vol % metallocene-LLDPE with additives

Example 3

[0071] Table 3 shows multilayer films having a thickness of 115 m. The left-hand column lists the mechanical properties of the film before the subdivision. The middle and right-hand columns list the mechanical properties of the films after subdivision.

TABLE-US-00003 115 m 115 m 115 m 4 m PA & 1 14 m PA 2 7 m PA 10 m PA Dart drop (g) 1385 >1670 >1670 (g/m) 11.3 >14.5 >14.9 Tensile strength (MPa) MD 44.6 47.6 42.7 TD 39.6 36.6 43.9 Elongation at break (%) MD 520 545 525 TD 450 480 520 [00019]$\mathrm{Tear}.Math..Math.\mathrm{resistance}.Math.\frac{g}{\mathrm{.Math.m}}.Math.M.Math..Math.D$ 13.2 >44.4 15.1 TD 19.2 >47.1 23.6

[0072] The barrier arrangement of the film comprises a PA layer having a total thickness of 14 m. Prior to the subdivision of the barrier arrangement, the tear resistance in machine direction (MD) is

[00020]$13.2.Math..Math.\frac{g}{\mathrm{.Math.m}}.$

The tear resistance in transverse direction, TD, is

[00021]$19.2.Math..Math.\frac{g}{\mathrm{.Math.m}}.$

[0073] Through use of the method of the invention, the barrier arrangement is subdivided into two layers in each case.

[0074] In the middle column, the barrier arrangement is subdivided into two layers of equal thickness, having an individual thickness of 7 m in each case. In this case the tear resistance increases from

[00022]$13.2.Math..Math.\frac{g}{\mathrm{.Math.m}}$

to more than

[00023]$44.4.Math..Math.\frac{g}{\mathrm{.Math.m}}$

in machine direction, by a factor of 3.36, and in the transverse direction, TD, from

[00024]$19.2.Math..Math.\frac{g}{\mathrm{.Math.m}}$

to more than

[00025]$47.1.Math.\frac{g}{m}$

by a factor of 2.45.

[0075] In accordance with the right-hand column, the barrier arrangement is subdivided into a layer having a thickness of 4 m and a layer having a thickness of 10 m. The barrier layer is therefore subdivided in a ratio of 1:2.5. The tear resistance increases in machine direction from

[00026]$13.2.Math.\frac{g}{m}.Math..Math.\mathrm{to}.Math..Math.15.1.Math.\frac{g}{m}$

by a factor of 1.14 and in transverse direction from 19.2 m to 23.26 m, by a factor of 1.23.

[0076] Prior to the subdivision of the barrier arrangement (left-hand column), the construction of the individual layers of the film is as follows:

[0077] 24 vol % LLDPE bimodal with additives

[0078] 10 vol % LLDPE bimodal

[0079] 10 vol % tie layerLLDPE bimodal

[0080] 12 vol % barrier arrangement, copolyamide 6/6.6

[0081] 10 vol % tie layerLLDPE bimodal

[0082] 10 vol % LLDPE bimodal

[0083] 24 vol % LLDPE bimodal with additives

[0084] After subdivision of the barrier arrangement into two layers of equal thickness, each of 7 m, the construction of the individual layers of the film is as follows:

[0085] 24 vol % LLDPE bimodal with additives

[0086] 13 vol % tie layerLLDPE bimodal

[0087] 6 vol % barrier arrangement, copolyamide 6/6.6

[0088] 14 vol % tie layerLLDPE bimodal

[0089] 6 vol % barrier arrangement, copolyamide PA 6/6.6

[0090] 13 vol % tie layerLLDPE bimodal

[0091] 24 vol % LLDPE bimodal with additives

[0092] After the subdivision according to example 3 (right-hand column) into layers of different thickness, with in each case one layer having a thickness of 4 m and a further layer of the barrier arrangement having a thickness of 10 m, the construction of the individual layers in the film is as follows:

[0093] 24 vol % LLDPE bimodal with additives

[0094] 13 vol % tie layerLLDPE bimodal

[0095] 3 vol % barrier arrangement, copolyamide 6/6.6

[0096] 14 vol % tie layerLLDPE bimodal

[0097] 9 vol % barrier arrangement, copolyamide PA 6/6.6

[0098] 13 vol % tie layerLLDPE bimodal

[0099] 24 vol % LLDPE bimodal with additives

Example 4

[0100] Through use of the method of the invention, an apparatus provided is a silage tube of the invention which comprises a multilayer film which has at least one barrier arrangement having a total thickness for reducing a gas permeability, wherein the barrier arrangement is subdivided into at least two layers, the silage tube having a 53128 Elmendorf tear resistance in machine direction (MD) and/or transverse direction, TD, of more than

[00027]$10.Math.\frac{g}{m},$

preferably more than

[00028]$20.Math.\frac{g}{m},$

more particularly more than

[00029]$30.Math.\frac{g}{m},$

the film having an oxygen permeability of at most

[00030]$500.Math.\frac{{\mathrm{cm}}^3}{m^2.Math.d.Math.\mathrm{bar}},$

preferably

[00031]$250.Math.\frac{{\mathrm{cm}}^3}{m^2.Math.d.Math.\mathrm{bar}},$

more particularly

[00032]$100.Math.\frac{{\mathrm{cm}}^3}{m^2.Math.d.Math.\mathrm{bar}},$

the oxygen permeability being determined according to DIN 53380-3 at 23 C. and 50% relative humidity, and the thickness of the film being less than 150 m, preferably less than 125 m, more particularly less than 100 m.

Example 5

[0101] In the case of another variant, through use of the method of the invention, an apparatus provided is a disinfection film of the invention which has at least one barrier arrangement having a total thickness for reducing a gas permeability, wherein in accordance with the invention the barrier arrangement is subdivided, for increasing the tear resistance, into at least two layers, so that the DIN 53128 Elmendorf tear resistance of the disinfection film in machine direction, MD, and/or transverse direction, TD, is more than

[00033]$10.Math.\frac{g}{m},$

preferably more than

[00034]$20.Math.\frac{g}{m},$

more particularly more than

[00035]$30.Math.\frac{g}{m},$

the film having an oxygen permeability of at most

[00036]$500.Math.\frac{{\mathrm{cm}}^3}{m^2.Math.d.Math.\mathrm{bar}},$

preferably

[00037]$250.Math.\frac{{\mathrm{cm}}^3}{m^2.Math.d.Math.\mathrm{bar}},$

more particularly

[00038]$100.Math.\frac{{\mathrm{cm}}^3}{m^2.Math.d.Math.\mathrm{bar}},$

the oxygen permeability being determined according to DIN 53380-3 at 23 C. and 50% relative humidity, and the thickness of the film being less than 150 m, preferably less than 125 m, more particularly less than 100 m.