Paper, paper sack, use, and production method

Abstract

The invention relates to a paper being made from a suspension consisting of: a fibrous composition, water, a sizing agent, and optionally one or more further additives, wherein at least 80 wt.-% based on dry mass of the fibrous composition is unbleached Kraft pulp; wherein the paper has a grammage of less than 120 g / m², in particular of from 70 g / m² to 90 g / m², a stretch at break in machine direction and in cross direction of at least 4%, and a Gurley air resistance of at most 10 s, wherein the paper contains a rosin sizing agent in an amount of from 1.0 to 2.5 kg / t of dry fiber. The invention also relates to a paper sack, a use, and a method.

Description

[0001] 65470 / MB / - Mondi AG, Marxergasse 4A, 1030 Wien (AT)

[0002] Paper, paper sack, use, and production method

[0003] The present invention relates to the technical field of packaging solutions, specifically to a paper as such, a paper sack, a use, and a production method as defined in the independent patent claims. The invention particularly relates to these aspects in combination with paper, which is disintegrate in water, at least partially and / or under certain conditions.

[0004] In various industries, particularly in the construction sector, powdery materials such as cement are commonly packaged in paper bags. Traditional packaging methods often involve the use of bags that require manual opening and disposal, leading to increased waste, contributions to environmental concerns, and potential contamination at construction sites. Furthermore, the disposal of such packaging contributes to environmental concerns and additional costs.

[0005] The need for efficient, waste-reducing packaging solutions has led to the development of water-soluble bags that disintegrate when brought into contact with aqueous media and thus can be introduced directly into mixing equipment. These bags allow the packaged material to integrate fully into the mix without the need for bag removal or disposal. This approach not only streamlines the mixing process but also minimizes waste and enhances site cleanliness.65470 / MB / - Mondi AG, Marxergasse 4A, 1030 Wien (AT) Existing solutions have attempted to address these issues; however, challenges remain in achieving the necessary balance between sack strength during handling, rapid solubility during mixing, and environmental friendliness.

[0006] Therefore, there exists a need for an improved disintegrate paper sack that overcomes at least some drawbacks of prior art solutions. A general object of the invention can therefore be seen in providing an improved and / or environmentally friendlier paper sack.

[0007] The invention particularly relates to a paper sack, which is made from unbleached ( / .e., brown) Kraft paper. This way, bleaching of the pulp can be omitted, leading to increased environmental friendliness of paper production. However, the invention also relates to a paper perse, as well as to other aspects, as will become apparent below.

[0008] It is preferred that the paper contains a rosin sizing agent, which has shown to provide excellent disintegration characteristics when immersing the paper in an aqueous medium, especially if the pH value of the aqueous medium is highly alkaline, which is typically achieved when building materials such as cement are mixed with water.

[0009] Said sizing agent is commonly known to improve wet strength properties of paper. It is therefore surprising and completely against the expectations that the disintegration characteristics can be improved using such sizing agent.

[0010] The sizing agent is particularly an acidic rosin sizing agent, containing abietic, dehydroabietic, and / or pimaric acids.

[0011] The paper is particularly a sack Kraft paper, which may be characterized by its high mechanical strength, such as stretch at break, tensile strength, or tensile energy absorption. The paper may also be highly porous, without being perforated. Depending on the specific use, the paper sack may contain the paper in one-ply, two-ply paper, or multi-ply form.

[0012] The paper may additionally contain aluminum, which originates from the addition of aluminum sulphate (also known as alum) during the paper production process in order65470 / MB / - Mondi AG, Marxergasse 4A, 1030 Wien (AT) to act as a precipitating agent and to adjust the pH value of the fiber suspension, from which the paper is prepared. In conjunction with using the rosin sizing agent, it may be beneficial to adjust the pH value of the suspension to lie in an acidic range, i.e., below 7.

[0013] It has additionally been found that addition of starch to the paper may be beneficial to improve paper strength and fiber bonding. However, to achieve the desired effects, lower amounts of starch addition may be required as is usual, which adds up to the resource-efficient characteristics of the present invention.

[0014] In general, the brown Kraft paper in the context of the invention can be produced as is known in the art of paper-making from a suspension containing a fibrous composition (i.e., pulp), water, and one or more, typically non-fibrous, additives. The rosin sizing agent, the aluminum sulphate, and the starch may be such additives. The fibrous composition is typically 100% unbleached Kraft pulp, but in certain cases, fractions of other pulp types may be present, without departing from the general concept of the invention. Thus, the fibrous composition of said suspension may contain at least 80 wt.-%, such as at least 90 wt.-%, unbleached Kraft pulp.

[0015] The paper sack may be a flush cut-type or a stepped end-type paper sack.

[0016] A flush cut-type paper sack particularly refers to a paper sack in which all plies of the sack body are cut to the same length at the open end, resulting in a uniform, level edge.

[0017] A stepped end-type paper sack particularly refers to a paper sack in which the individual plies or layers are deliberately cut at different lengths, producing a staggered or stepped profile. This configuration enables progressive folding, pasting, or sealing of the sack end.

[0018] The paper sack may also be equipped with a valve sleeve, which may be formed from the paper according to the invention. The paper sack may thus a valve-type paper sack, which typically has at least one corner with an opening fitted with a valve sleeve. The valve may particularly be of the internal, external, or sealable external type.65470 / MB / - Mondi AG, Marxergasse 4A, 1030 Wien (AT) In order to prepare a paper sack from a paper, typically a glue or adhesive is required to attach parts of the paper to each other.

[0019] The adhesive used in the paper sack of the invention particularly is a starch-based adhesive, which may be particularly based on com starch. Using a starch-based adhesive provides the advantage that the glue connections are disintegrate upon contact with an aqueous medium, supporting the overall disintegrability of the paper sack according to the invention.

[0020] In this context, it may be preferable to provide gluing sections, which are formed by areas to which adhesive is applied interspersed by areas without adhesive application. This may aid the penetration of water, further improving disintegrability. An area to which adhesive is applied may be referred to as “adhesive area”, whereas an area without adhesive application may be referred to as “non-adhesive area”.

[0021] Adhesive areas may be lines, dots or other shapes with adhesive application, while the non-adhesive area can occupies the space between. Typically, there is a multiplicity of adjacent adhesive areas, which are not connected to each other.

[0022] A gluing section may also be formed by an adhesive area, which has a full-surface application of the adhesive, wherein the adhesive area is partially interspersed by non-adhesive areas.

[0023] A gluing section may also have a larger central part, which is free from adhesive.

[0024] In general, a gluing section may be present on every part or area of a paper sack, which requires the bonding of two layers of paper. The requirements on the exact nature of the gluing section can be defined by a skilled person, depending on the type of sack and the part or area, to which the gluing section is applied.

[0025] The invention particularly relates to a paper being made from a suspension consisting of: a fibrous composition, water, a sizing agent, and optionally one or more further additives, wherein at least 80 wt.-% based on dry mass, particularly at least 90 wt.-%65470 / MB / - Mondi AG, Marxergasse 4A, 1030 Wien (AT) based on dry mass, of the fibrous composition is unbleached Kraft pulp; wherein the paper has a grammage of less than 120 g / m2, in particular of from 70 g / m2to 90 g / m2, determined in accordance with ISO 536:2019, a stretch at break in machine direction and in cross direction of at least 4% determined in accordance with ISO 1924-3:2005, and a Gurley air resistance of at most 10 s determined in accordance with ISO 5636-5:2013.

[0026] Preferably, it is provided that the paper contains a rosin sizing agent in an amount of from 0.6 to 2.5 kg / t of dry fiber, in particular from 1.0 to 1.5 kg / t of dry fiber.

[0027] It may be provided that the suspension contains aluminum sulphate in an amount of from 4.0 to 8.0 kg / t of dry fiber, in particular from 5.5 to 7.5 kg / t of dry fiber.

[0028] It may be provided that the the suspension has a pH lower than 7.0, preferably of from 4.5 to 5.5.

[0029] It may be provided that the paper contains starch in an amount of from 8.0 to 13.0 kg / t of dry fiber.

[0030] It may be provided that the Kraft pulp is softwood pulp.

[0031] It may be provided that the fibrous composition has a Kappa number of more than 25 determined in accordance with ISO 302:2015.

[0032] It may be provided that the paper has a tensile energy absorption index in machine direction and in cross direction of at least 2.5 J / g, such as at least 3.0 J / g, determined in accordance with ISO 1924-3:2005.

[0033] It may be provided that the paper has a wet strength index in machine direction and in cross direction of at least 0.3 Nm / g determined in accordance with ISO 3781 :2011.

[0034] It may be provided that the paper is unperforated.65470 / MB / - Mondi AG, Marxergasse 4A, 1030 Wien (AT) The invention particularly also relates to a paper sack made of paper as described herein, wherein the sack is a flush cut-type or a stepped end-type paper sack.

[0035] It may be provided that the sack is a one-ply or a two-ply paper sack.

[0036] It may be provided that the sack is glued using a starch-based adhesive.

[0037] It may be provided that at least one gluing section is provided, which has a multiplicity of adhesive areas, in which adhesive is applied, interspersed by at a non-adhesive area, which is free from adhesive.

[0038] It may be provided that at least one gluing section is provided, which has at least an adhesive area, in which adhesive is applied, interspersed by a multiplicity of non-adhesive areas, which are free from adhesive.

[0039] It may be provided that at least a part of the outer contour of the gluing section is interrupted by non-adhesive areas, which non-adhesive areas particularly form channels within the adhesive area.

[0040] It may be provided that the adhesive areas are provided as dots and / or lines.

[0041] It may be provided that a central part of the gluing section is free from adhesive.

[0042] It may be provided that the gluing section is one of the following: a length pasting section of the sack; a main pasting section on the bottom side of the paper sack; a main pasting section on the valve side of the paper sack; a valve pasting section of the paper sack; a bottom patch gluing section of the paper sack.

[0043] It may be provided that the paper sack has a valve sleeve and / or a bottom closure, wherein the valve sleeve and / or the bottom closure, if provided, are made of the paper as described herein.65470 / MB / - Mondi AG, Marxergasse 4A, 1030 Wien (AT) The invention particularly also relates to a use of the paper as described herein for packaging of a powdered or granular material, such as cement.

[0044] The invention particularly also relates to a method for producing a paper by forming and drying a web from a suspension consisting of: a fibrous composition, water, a sizing agent, and optionally one or more further additives, wherein at least 80 wt.-% based on dry mass, particularly at least 90 wt.-% based on dry mass, of the fibrous composition is unbleached Kraft pulp; wherein the paper has a grammage of less than 120 g / m2determined in accordance with ISO 536:2019, a stretch at break in machine direction and in cross direction of at least 4% determined in accordance with ISO 1924-3:2005, and a Gurley air resistance of at most 10 s determined in accordance with ISO 5636-5:2013

[0045] Preferably, it is provided that the sizing agent is a rosin sizing agent added to the suspension in an amount of from 1.0 to 2.5 kg / t of dry fiber, in particular from 1.0 to 1.5 kg / t of dry fiber.

[0046] It may be provided that aluminum sulphate is added to the suspension in an amount of from 4.0 to 7.0 kg / t of dry fiber, in particular from 6.0 to 7.5 kg / t of dry fiber.

[0047] It may be provided that the suspension has a pH lower than 7.0, preferably of from 4.5 to 5.5.

[0048] It may be provided that starch is added to the suspension in an amount of from 8.0 to 13.0 kg / t of dry fiber.

[0049] It may be provided that the unbleached Kraft pulp is subjected to low consistency refining at an energy input of below 110 kWh / t, or below 40 kWh / t dry pulp, and / or that the unbleached Kraft pulp is subjected to high consistency refining at an energy input of below 350 kWh / t dry pulp.

[0050] Further features of the invention will become apparent from the claims, the drawings, and the description of the exemplary embodiment. In the following, specific benefits will65470 / MB / - Mondi AG, Marxergasse 4A, 1030 Wien (AT) be described by making reference to exemplary embodiments of the invention, which is not intended to limit the scope of protection defined by the patent claims.

[0051] In the drawings:

[0052] Fig. 1 shows a schematic view of a gluing section according to a first embodiment; Fig. 2 shows a schematic view of a gluing section according to a second embodiment; Fig. 3 shows a schematic view of a gluing section according to a third embodiment; and Fig. 4 shows a schematic view of a gluing section according to a fourth embodiment. Except otherwise mentioned or clearly apparent from the context, the drawings show the following features: gluing section 1 ; adhesive area 2; non-adhesive area 3; outer contour 4 (of the gluing section 1 ); central part 5 (of the gluing section 1 ).

[0053] A paper has been prepared according to an embodiment of the invention. This paper is made from a suspension containing 100% unbleached Kraft pulp made from softwood. The following additives were dosed to the suspension: an acidic rosin sizing agent in an amount of approx. 1.3 kg / t dry pulp, alum in an amount of approx. 6.5 kg / t dry pulp, starch in an amount of approx. 11 kg / t dry pulp. The pH value of the suspension was approx. 5.0.

[0054] The suspension was processed in a paper machine applying process parameters as commonly known in the art to obtain the paper, which has the parameters as listed in Table 1 below.

[0055] Table 1: Parameters of the paper according to the first embodiment

[0056]

[0057] 65470 / MB / - Mondi AG, Marxergasse 4A, 1030 Wien (AT)

[0058]

[0059] Measurements performed 5 min soaking time in water, without artificial aging

[0060] The paper shows good disintegration characteristics when immersed in an aqueous solution with an approximately neutral pH value. At a pH value of 13, simulating the conditions when preparing cement, disintegration is even more pronounced.

[0061] A paper has been prepared according to a further embodiment of the invention, with the difference compared to the first embodiment that the rosin sizing agent was used in an amount of approx. 2.1 kg / t dry fiber weight. The paper had similar mechanical characteristics as compared to the first embodiment.

[0062] The paper shows satisfactory disintegration characteristics when immersed in an aqueous solution with an approximately neutral pH value, but disintegration is weaker than for the first embodiment. At a pH value of 13, simulating the conditions when preparing cement, disintegration is more pronounced.

[0063] The paper according to the two embodiments described above is used for preparing cement sacks. Figs. 1 to 4 show schematic views of a gluing sections 1 according to a first to fourth embodiment.

[0064] The first to third embodiment show gluing sections 1 , which are used as part of the main pasting on the bottom side of a sack, and the fourth embodiment shows a gluing section, which is used for attaching the bottom patch to the sack. A potato starch-based adhesive is used.

[0065] The gluing sections 1 of all embodiments have an outer contour 4. In the first, third and fourth embodiment, the gluing sections 1 are formed by a multiplicity of adhesive areas65470 / MB / - Mondi AG, Marxergasse 4A, 1030 Wien (AT) 2, formed as dots, interspersed by a non-adhesive area 3. The size of the dots is such that a continuous non-adhesive area 3 is retained during the production process of the sack.

[0066] The gluing section 1 of the third and fourth embodiment additionally have a central part 5, which is free from adhesive.

[0067] In contrast to the other embodiments, the gluing section 1 of the second embodiment has an adhesive area 2 with adhesive continuously applied thereto. Multiple non-adhesive areas 3 are formed as channels within the gluing section 1, wherein each of the channels interrupts the outer contour 4 of the gluing section 1.

[0068] In all embodiments, the intermittent arrangement of adhesive areas 2 and non-adhesive areas 3 allows for an improved penetration of water, this accelerating the disintegration process in connection with the starch-based adhesive and the paper of the invention.

Claims

65470 / MB / - Mondi AG, Marxergasse 4A, 1030 Wien (AT) Claims1. A paper being made from a suspension consisting of: a fibrous composition, water, a sizing agent, and optionally one or more further additives, wherein at least 80 wt.-% based on dry mass, particularly at least 90 wt.-% based on dry mass, of the fibrous composition is unbleached Kraft pulp; wherein the paper has a grammage of less than 120 g / m2, in particular of from 70 g / m2to 90 g / m2, determined in accordance with ISO 536:2019, a stretch at break in machine direction and in cross direction of at least 4% determined in accordance with ISO 1924-3:2005, and a Gurley air resistance of at most 10 s determined in accordance with ISO 5636-5:2013, characterized in that the paper contains a rosin sizing agent in an amount of from 1.0 to 2.5 kg / t of dry fiber, in particular from 1.0 to 1.5 kg / t of dry fiber.

2. The paper according to claim 1 , wherein the suspension contains aluminum sulphate in an amount of from 4.0 to 8.0 kg / t of dry fiber, in particular from 5.5 to 7.5 kg / t of dry fiber, and / or wherein the suspension has a pH lower than 7.0, preferably of from 4.5 to 5.5.

3. The paper according to claims 1 or 2, containing starch in an amount of from 8.0 to 13.0 kg / t of dry fiber.

4. The paper according to any of claims 1 to 3, wherein the Kraft pulp is softwood pulp, and / or wherein the fibrous composition has a Kappa number of more than 25 determined in accordance with ISO 302:2015.

5. The paper according to any of claims 1 to 4, having a tensile energy absorption index in machine direction and in cross direction of at least 2.5 J / g, such as at least 3.0 J / g, determined in accordance with ISO 1924-3:2005, and / or having a wet strength index in machine direction and in cross direction of at least 0.3 Nm / g determined in accordance with ISO 3781 :2011.

6. The paper according to any of claims 1 to 5, being unperforated.65470 / MB / - Mondi AG, Marxergasse 4A, 1030 Wien (AT) 7. A paper sack made of paper according to any of claims 1 to 6, wherein the sack is a flush cut-type or a stepped end-type paper sack.

8. The paper sack according to claim 7, being a one-ply or a two-ply paper sack.

9. The paper sack according to claim 7 or 8, wherein the sack is glued using a starch-based adhesive.

10. The paper sack according to any of claims 7 to 9, wherein at least one gluing section (1) is provided, which has a multiplicity of adhesive areas (2), in which adhesive is applied, interspersed by at a non-adhesive area (3), which is free from adhesive, and / or wherein at least one gluing section (1) is provided, which has at least an adhesive area (2), in which adhesive is applied, interspersed by a multiplicity of non-adhesive areas (3), which are free from adhesive.

11. The paper sack according to claim 10, wherein at least a part of the outer contour (4) of the gluing section (1) is interrupted by non-adhesive areas (3), which non- adhesive areas (3) particularly form channels within the adhesive area (2).

12. The paper sack according to claim 10 or 11 , wherein the adhesive areas (2) are provided as dots and / or lines.

13. The paper sack according to any of claims 10 to 12, wherein a central part (5) of the gluing section (1) is free from adhesive.

14. The paper sack according to any of claims 10 to 13, wherein the gluing section (1) is one of the following: a length pasting section of the sack; a main pasting section on the bottom side of the paper sack; a main pasting section on the valve side of the paper sack; a valve pasting section of the paper sack; a bottom patch gluing section of the paper sack.

15. The paper sack according to any of claims 7 to 14, having a valve sleeve and / or a bottom closure, wherein the valve sleeve and / or the bottom closure, if provided, are made of the paper according to any of claims 1 to 6.65470 / MB / - Mondi AG, Marxergasse 4A, 1030 Wien (AT)16. A use of the paper according to any of claims 1 to 6 for packaging of a powdered or granular material, such as cement.

17. A method for producing a paper by forming and drying a web from a suspension consisting of: a fibrous composition, water, a sizing agent, and optionally one or more further additives, wherein at least 80 wt.-% based on dry mass, particularly at least 90 wt.-% based on dry mass, of the fibrous composition is unbleached Kraft pulp; wherein the paper has a grammage of less than 120 g / m2determined in accordance with ISO 536:2019, a stretch at break in machine direction and in cross direction of at least 4% determined in accordance with ISO 1924-3:2005, and a Gurley air resistance of at most 10 s determined in accordance with ISO 5636-5:2013, characterized in that the sizing agent is a rosin sizing agent added to the suspension in an amount of from 1.0 to 2.5 kg / t of dry fiber, in particular from 1.0 to 1.5 kg / t of dry fiber.

18. The method according to claim 17, wherein aluminum sulphate is added to the suspension in an amount of from 4.0 to 7.0 kg / t of dry fiber, in particular from 6.0 to 7.5 kg / t of dry fiber, and / or wherein the suspension has a pH lower than 7.0, preferably of from 4.5 to 5.5.

19. The method according to claim 17 or 18, wherein starch is added to the suspension in an amount of from 8.0 to 13.0 kg / t of dry fiber.

20. The method according to any of claims 17 to 19, wherein the unbleached Kraft pulp is subjected to low consistency refining at an energy input of below 110 kWh / t dry pulp, or below 40 kWh / t dry pulp, and / or that the unbleached Kraft pulp is subjected to high consistency refining at an energy input of below 350 kWh / t dry pulp.

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