Paper bag

Abstract

The invention relates to a paper bag comprising at least one first layer that consists of a first paper, the first layer of paper comprising a steam barrier in the form of a coating.

Description

[0001] Paper bag

[0002] The invention relates to a paper bag with a first paper layer made of a first paper and a second paper layer made of a second paper, wherein the first paper layer has a water vapor barrier in the form of a coating.

[0003] Paper sacks have long been known in the art and are used as packaging and transport containers for a wide variety of goods, such as bulk materials. Paper sacks are used, for example, to transport mortar, cement, or other building materials in powder form. These materials and goods should preferably be transported in such a way that they are adequately protected from moisture, as moisture can lead to the materials no longer being able to function for their original purpose.

[0004] It is therefore known from the prior art to provide at least one paper layer with a water vapor barrier in the form of a plastic coating. This prevents the penetration of moisture even when the paper sacks are stored outdoors and exposed to, for example, light rain or high humidity. The effectiveness of the coating usually ends when the moisture to which the paper sack is exposed is sufficient to decompose one or both paper layers to such an extent that the paper sack can no longer hold its contents. It is therefore technically sensible to apply the plastic coating to the outside of the paper sack, i.e. to the outside of the paper layer that forms the outer layer. The first paper layer and the second paper layer are arranged so that one paper layer forms the outer layer, which is visible from the outside.The other paper layer forms the inner layer, the inner side of which faces the interior of the paper bag and thus the material to be transported in the bag. Paper has a reputation for being an environmentally friendly and, to the greatest extent possible, recyclable packaging material. Therefore, the plastic coating is often not applied to the outside of the outer layer of the paper bag, so as not to suggest to the customer that it is a plastic bag and therefore a less environmentally friendly packaging material.

[0005] Such paper bags are generally not handled particularly carefully when filled. They are thrown or, for example, dragged across the back of a van. This exerts a force on the bag, often causing it to tear and the packaged goods to leak out. This is detrimental.

[0006] The invention is therefore based on the object of further developing a paper bag of the form described above so that it tears less easily.

[0007] The invention solves the stated problem by a paper bag with a first paper layer made of a first paper and a second paper layer made of a second paper, wherein the first paper layer has a water vapor barrier in the form of a coating, which is characterized in that the first paper layer is made of an expandable paper.

[0008] This allows the paper of the outer layer, which is formed by the first paper layer or the second paper layer, to better withstand forces acting on it through elastic deformation. Preferably, the first paper layer and the second paper layer are made of a stretchable paper, preferably the same paper.

[0009] One of the two paper layers forms the inner layer, and the other paper layer forms the outer layer. Preferably, the first paper layer forms the inner layer. The first paper layer is preferably arranged so that the coating is located on the outside of the first paper layer. If the first paper layer is the inner layer, the coating is consequently located on the side of the first paper layer that faces the second paper layer. This is advantageous but not necessary. In some embodiments, it is advantageous to arrange the coating on the inside of the inner layer.

[0010] In a preferred embodiment, the first paper layer is the outer layer of the paper sack. The coating is therefore arranged on the outer layer of the paper sack. The coating is preferably located on the inside of the outer layer, i.e., the side that corresponds to the inner layer and thus, when the paper sack is filled, to the product packaged in the paper sack. By arranging the coating on the inside of the outer layer, the coating is better protected against mechanical damage than if it were arranged on the outside of the outer layer. The inner layer of the paper sack is preferably made of perforated paper.

[0011] When filling a paper sack, especially with bulk material, any air contained within the sack must be able to escape to allow for rapid filling. A water vapor barrier applied to a layer of paper also reduces the paper's permeability to air. Therefore, when filling a paper sack, an adhesive seam, such as a longitudinal seam of the paper sack, often has to be opened in sections or left open to allow the air to escape from the sack quickly enough. However, this means that some of the bulk material can also escape, which can lead to material loss and contamination of the immediate surroundings, and often also to contamination of the outside of the paper sack.

[0012] If the inner layer is perforated, air can escape from the paper bag through the individual holes in the perforation without the need to open or leave a seam open. However, a water vapor barrier applied to this paper layer would also be perforated by such a perforation, making it less effective or even completely ineffective. Therefore, it has proven advantageous to perforate the inner layer of the paper bag rather than coat it with a water vapor barrier. The outer layer has a water vapor barrier coating applied to the inside of the outer layer.

[0013] Preferably, the first paper layer is stretchable by at least 3%, preferably by at least 4%, particularly preferably by at least 5% in the longitudinal direction and / or in the transverse direction.

[0014] The coating is preferably an extrusion coating. Alternatively, the coating is a dispersion coating.

[0015] The coating is preferably a polyethylene coating, an acrylate coating, and / or a polyvinyl alcohol coating. A polyethylene coating is preferably applied as an extrusion coating. A coating with acrylate and / or polyvinyl alcohol is preferably applied as a dispersion coating. The use of polyvinyl alcohol, in particular, has the advantage that the coating can be made water-soluble, making the paper bag recyclable.

[0016] In a preferred embodiment, the paper bag has at least one venting channel through which air can escape from the paper bag. This ensures that the air contained therein can escape quickly enough, especially when filling the paper bag, even if the air permeability of the paper in the first and second paper layers is reduced by the coating.

[0017] The first paper layer preferably forms the inner layer of the paper bag. The coating preferably has a chemical component, for example a polyvinyl alcohol, and a starch component. This component is preferably at least 10% by weight, particularly preferably at least 20% by weight. In a particularly preferred embodiment, the starch component is 25% by weight of the entire coating. It has proven advantageous if the proportion of the chemical component of the coating to the total mass of the coated paper is less than 5%. This makes it possible to achieve water vapor permeability of less than 50 grams per square meter per day, preferably less than 30 grams per square meter per day.

[0018] Preferably, a paper with a grammage of at least 70 g / m 2 , preferably at least 100 g / m 2 , particularly preferably at least 120 g / m 2used, which is coated. The higher the paper weight, the greater the mechanical stress the paper can withstand. Burst resistances of more than 350 kPa, preferably more than 500 kPa, and particularly preferably more than 700 kPa can be achieved. Tear resistance also depends on the weight. For example, tear resistances in the machine direction of more than 14 mN m can be achieved. 2 / g and in the transverse direction of more than 16 mN m 2 / g.

[0019] Paper has a front side and an opposite back side. These are created during the paper production process. During production, the paper lies on a screen or screen through which excess water can drain away. The paper fibers are held back by the screen or screen. As a result, the side opposite the screen or screen has greater smoothness or, to put it another way, a lower surface roughness. This is why it is called the "front side." The side opposite the front side lies against the screen or screen and is therefore the back side. The coating is preferably applied to the front side. Surprisingly, this results in better properties, in particular better and therefore lower water vapor permeability.

Claims

Patent claims 1. A paper bag with at least one first paper layer made of a first paper, characterized in that the first paper layer has a water vapor barrier in the form of a coating.

2. Paper bag according to claim 1, characterized in that the coating of the first paper layer has an extrusion coating.

3. Paper bag according to claim 1 or 2, characterized in that the coating of the first paper layer has a dispersion coating.

4. Paper bag according to one of the preceding claims, characterized in that the coating is a polyethylene coating, an acrylate coating and / or a polyvinyl alcohol coating.

5. Paper bag according to one of the preceding claims, characterized in that the paper bag has at least one venting channel through which air can escape from the paper bag.

6. Paper bag according to one of the preceding claims, characterized in that the paper bag has at least a second paper layer.

7. Paper bag according to one of the preceding claims, characterized in that the paper bag has an inner side facing an interior of the paper bag and an outer side opposite the inner side, wherein the coating does not form the outer side of the paper bag.

8. Paper bag according to one of the preceding claims, characterized in that the first paper layer is an inner layer of the paper bag.

9. Paper bag according to one of claims 1 to 7, characterized in that the first paper layer is an outer layer of the paper bag, wherein the coating is preferably applied to the inside of the outer layer.

10. Paper bag according to one of the preceding claims, characterized in that the coating is applied to a front side of the paper.

11. Paper bag according to one of the preceding claims, characterized in that the coating has a starch content which is preferably at least 10% by weight, particularly preferably at least 20% by weight, further preferably 25% by weight.