RU2691364C2 - Brown bag paper capable of decomposition - Google Patents

Abstract

FIELD: manufacturing technology.SUBSTANCE: invention relates to bag paper and its production. Bag fabrication method involves stages where unbleached cellulose is mixed with bleached cellulose to produce a mixture of cellulose and sack paper is formed from said cellulose mixture. Starch is added in amount of 1–7 kg/t of paper. Ratio of weight in dry state of unbleached cellulose to weight in dry state of bleached cellulose in mixture of cellulose ranges from 7:1 to 1:1. Produced paper has porosity by Gurley method (according to ISO 5636-5) of less than 25 s.EFFECT: improved degradability of bag paper.27 cl, 1 dwg, 5 tbl

Description

TECHNICAL FIELD

This invention relates to the field of bag paper and its production.

BACKGROUND

During the filling and storage of powdered material, such as cement, paper bags, as a rule, must meet high requirements.

Paper bags often have to withstand considerable material weight, which requires high tensile strength and tensile properties. For this purpose, kraft paper is a suitable material as bag walls. Bags usually have two or more walls, that is, layers of paper material to further strengthen the bag structure. The bag wall layer is often called simply a layer. The manufacture of a layered material (i.e. bag paper) is described, for example, in the publication of international patent application WO 99/02772. In the production method disclosed in international patent application WO 99/02772, sulphate pulp is milled at a high consistency, after which a filled polymer is added to the resulting mass, for example, starch in an amount of at least 8 kg (calculated as starch) per ton paper for paper, which is both durable and porous at the same time (to allow air to be released during bag filling).

For years, it was assumed that construction workers opened cement bags and added their contents to the mixer. However, some alternative solutions have been proposed.

GB 2448486 discusses a soluble bag made of paper or other soluble materials containing building materials that require mixing, such as cement, lime or gypsum. It is argued that a soluble bag can be introduced directly into the mixer, in which the bag quickly dissolves when water is added, which reduces spillage, loss, contamination and effects on construction products. Packages are put together in a waterproof package to ensure that the product remains dry during storage or during transport.

International patent application WO 2004052746 proposes spraying or dipping an impermeable water-repellent coating on the entire outer surface of already filled bags. In addition, it is proposed to place the bag in the mixer, also containing some water, while the flow of water into the bag causes the water-soluble inner layer of the bag to dissolve, thereby allowing the water-repellent outer shell of the bag to be destroyed in the mixture. In the publication of international patent application WO 2004052746 does not disclose the invention of any materials for the inner and outer layers of the bag.

In the application for the grant of patent US 2011/0315272 states that the bag, which dissolves in a humid environment, can be obtained using dextrin glue, which is used to glue the folded ends of the bag. Templates for folding and gluing the ends of the bag are also discussed. The waterproofing layer in the bag is not discussed.

JP 5085565 A proposes that a cement bag adapted to be inserted directly into the mixer consists of a water-soluble material, such as polyvinyl alcohol (PVA), having a thickness of 20-70 microns. FR 2874598 discloses a similar solution.

SUMMARY OF INVENTION

Brown (i.e., unbleached) sack paper is often stronger than white (i.e., bleached) sack paper. In addition, brown paper may be preferable to white paper, since the bleaching process can be costly and cause environmental problems. In addition, bleaching can reduce the yield of products.

The authors of this invention have turned their attention to the need for decomposable brown sack paper, that is, paper designed to be introduced into the mixer along with its contents, such as cement, and then decomposition in this mixer.

Accordingly, there would be no need to open such a bag and empty its contents into the mixer. Since the bags are heavy and their contents dusty, the working conditions of construction workers can be significantly improved.

In addition, the inventors of the present invention were convinced that brown sack papers corresponding to the prior art, such as brown sack paper produced in accordance with the application WO 99/02772, or Billerud Korsnas brown commercial sack paper QuickFill® are not sufficiently capable of decomposition.

Thus, the purpose of this disclosure is to provide brown sack paper, which, after being formed into a bag layer, which is filled with contents and introduced into a mixer for preparing cement slurry together with the contents and water, disintegrates in this mixer.

The authors of this invention have found that the degradability of brown sack paper can be significantly improved by adding bleached pulp to unbleached pulp used to make brown sack paper. The authors of this invention have also found that the degradability of brown sack paper can be significantly improved by reducing the kappa number and the degree of grinding at low consistency (NC) of unbleached pulp used to make brown sack paper.

The following detailed list presents various embodiments of the present invention.

1. A method of manufacturing bag paper with porosity according to the Gurley method (in accordance with ISO 5636-5) of less than 25 s, comprising the steps of:

a) mix the unbleached pulp with bleached pulp to obtain a mixture of cellulose in such proportions that the dry weight ratio of unbleached pulp to weight in a dry state of bleached pulp in a mixture of pulp is from 7: 1 to 1: 1; and

b) form the bag paper from the specified mixture of cellulose.

2. The method according to p. 1, characterized in that the porosity by the method of Gerley (in accordance with ISO 5636-5) bag paper is less than 20 s, such as less than 15 s, such as less than 10 s, such as less less than 8 s, such as less than 7 s, such as less than 6 s.

3. The method according to p. 1 or 2, characterized in that the Kapla number (in accordance with SCAN-C 1:00) bleached pulp is less than 10, such as less than 7, such as less than 4, such as less than 2

4. The method according to any of the preceding paragraphs, characterized in that the whiteness in accordance with ISO (ISO 2470-1) of bleached pulp is at least 60, such as at least 70, such as at least 80, such as at least least 85.

5. The method according to any of the preceding paragraphs, characterized in that the Kappa number (in accordance with SCAN-C 1:00) unbleached pulp is less than 70, such as less than 60, such as less than 55, such as less than 50 , such as less than 40, such as less than 35.

6. The method according to any of the preceding paragraphs, characterized in that the whiteness in accordance with ISO (ISO 2470-1) of the bag paper is less than 30, such as less than 25, such as less than 22.

7. The method according to any of the preceding paragraphs, characterized in that the ratio of unbleached pulp to bleached pulp in a mixture of pulp is in the range from 6: 1 to 1: 1, such as from 5: 1 to 1: 1, such as from 4: 1 to 1: 1, such as from 3.5: 1 to 1.1: 1, such as from 3: 1 to 1.2: 1, such as from 2.8: 1 to 1.3: 1.

8. The method according to any of the preceding paragraphs, characterized in that the index of energy expended during the geometric tension (in accordance with ISO 1924-3) of sack paper is at least 2 J / g, such as at least 2.4 J / g, such as at least 2.8 J / g, such as at least 3.2 J / g.

9. The method according to any of the preceding paragraphs, characterized in that the density (in accordance with ISO 536) of the sack paper is 50-140 g / m ² , such as 60-120 g / m ² , such as 60-110 g / m ² , such as 70-110 g / m ² , such as 75-100 g / m ² .

10. The method according to any of the preceding paragraphs, characterized in that the unbleached pulp is a chemical pulp, such as Kraft pulp.

11. The method according to any of the preceding paragraphs, characterized in that the bleached pulp is a chemical pulp, such as Kraft pulp.

12. The method according to any of the preceding paragraphs, characterized in that at least 50%, such as at least 60%, 70%, 80% or 90%, of the dry weight of unbleached pulp is coniferous wood pulp.

13. A method according to any one of the preceding claims, characterized in that at least 50%, such as at least 60%, 70%, 80% or 90%, of the dry weight of the bleached pulp is softwood pulp.

14. The method according to any of the preceding paragraphs, further comprising a stage in which bleaching is carried out to obtain bleached pulp.

15. The method according to p. 14, characterized in that the bleaching process includes oxygen separation of lignin.

16. The method according to p. 15, characterized in that the cellulose subjected to the oxygen separation of lignin, has a Kappa number (in accordance with SCAN-C 1:00) below 60, such as below 45, such as 20-40.

17. A method according to any one of claims. 14-16, characterized in that the bleaching process includes bleaching with ozone.

18. A method according to any one of claims. 14-17, characterized in that the bleaching process includes bleaching with chlorine dioxide.

19. A method according to any one of claims. 14-18, characterized in that the bleaching process includes bleaching with alkaline hydrogen peroxide and / or peracetic acid (PAA).

20. A method according to any one of claims. 14-19, characterized in that the bleaching process includes alkaline extraction, such as sodium hydroxide extraction.

21. The method according to any of paragraphs 14-20, characterized in that the bleaching process includes bleaching with sodium dithionite.

22. The method according to any of the preceding paragraphs, wherein step b) involves creping.

23. The method according to any of the preceding paragraphs, characterized in that a hydrophobic additive is added in an amount of less than 2.0 kg / ton of paper.

24. The method according to any of the preceding paragraphs, characterized in that a hydrophobic additive is added in an amount of less than 1.5 kg / ton of paper.

25. The method according to any of the preceding paragraphs, characterized in that a hydrophobic additive is added in an amount of less than 1.0 kg / ton of paper.

26. The method according to any of the preceding paragraphs, characterized in that a hydrophobic additive is added in an amount of less than 0.5 kg / ton of paper.

27. The method according to any of the preceding paragraphs, characterized in that a hydrophobic additive is added in an amount of less than 0.3 kg / ton of paper.

28. The method according to any of the preceding paragraphs, characterized in that starch is added in an amount of 1-7 kg / ton of paper, such as 1-5 kg / ton of paper, such as 2-5 kg / ton of paper.

29. Sack paper, having a porosity according to the Gurley method (in accordance with ISO 5636-5) less than 25 s, consisting of a mixture of unbleached fibers and bleached fibers, in which the dry weight ratio of unbleached fibers to bleached fibers in the mixture ranges from 7: 1 to 1: 1.

30. Sack paper according to claim 29, characterized in that the porosity according to the Gurley method (in accordance with ISO 5636-5) is less than 20 s, such as less than 15 s, such as less than 10 s, such as less than 8 s, such as less than 7 s, such as less than 6 s.

31. Sack paper according to any one of paragraphs. 29-30, characterized in that the whiteness in accordance with ISO bag paper is less than 30, such as less than 25, such as less than 22.

32. Sack paper according to any one of paragraphs. 29-31, characterized in that the dry weight ratio of unbleached fibers to bleached fibers in the mixture is in the range from 6: 1 to 1: 1, such as from 5: 1 to 1: 1, such as from 4: 1 to 1: 1, such as from 3.5: 1 to 1.1: 1, such as from 3: 1 to 1.2: 1, such as from 2.8: 1 to 1.3: 1.

33. Sack paper according to any one of paragraphs. 29-32, characterized in that the index of energy expended in geometric tension (in accordance with ISO 1924-3) of sack paper is at least 2 J / g, such as at least 2.4 J / g, such as at least 2.8 J / g, such as at least 3.2 J / g.

34. Sack paper to any of paragraphs. 29-33, characterized in that the density (in accordance with ISO 536) of bag paper is 50-140 g / m ² , such as 60-120 g / m ² , such as 60-110 g / m ² , such as 70 -110 g / m ² , such as 75-100 g / m ² .

35. Sack paper according to any one of paragraphs. 29-34, characterized in that it undergoes creping.

36. Sack paper according to any one of paragraphs. 29-35, obtained in the paper manufacturing process, to which a hydrophobic additive was added in an amount of less than 2 kg / ton of paper.

37. Sack paper according to any one of paragraphs. 29-36, obtained in the paper manufacturing process, to which a hydrophobic additive was added in an amount of less than 1.5 kg / ton of paper.

38. Sack paper according to any one of paragraphs. 29-37, obtained in the paper making process, to which a hydrophobic additive was added in an amount of less than 1.0 kg / ton of paper.

39. Sack paper according to any one of paragraphs. 29-38, obtained in the paper making process, to which a hydrophobic additive was added in an amount of less than 0.5 kg / ton of paper, such as less than 0.3 kg / ton of paper.

40. Sack paper according to any one of p. 29-39, which does not contain a hydrophobic additive.

41. Sack paper according to any one of paragraphs. 29-40, obtained in the process of making paper, to which starch was added in an amount of 1-7 kg / ton, such as 1-5 kg / ton, such as 2-5 kg / ton.

42. Bag for hydraulic binder, such as cement, which contains a layer consisting of bag paper according to any one of paragraphs. 29-41.

43. Multi-layer bag for hydraulic binder, such as cement, which contains an inner layer consisting of bag paper according to any one of paragraphs. 29-41.

44. The multi-ply bag of claim 43, further comprising an outer layer consisting of white sack paper.

45. The multi-ply bag of claim 44, wherein the white sack paper contains a layer of waterproofing coating.

46. The multi-ply bag of claim 43, further comprising an outer layer consisting of bag paper according to any one of claims. 29-41.

47. Bag according to any one of paragraphs. 42-46, containing a hydraulic binder, such as cement.

48. A bag according to claim 47, wherein the amount of hydraulic binder is 20-60 kg.

49. A method for producing a hydraulic composition comprising the step of injecting water and a bag according to any one of claims 4 to the mixer. 47-48 and provide the possibility of decomposition of the material layer of the bag during mixing in the mixer.

50. A method of manufacturing bag paper having porosity according to the Gurley method (in accordance with ISO 5636-5) of less than 25 seconds, comprising the steps of:

a) receive a pulp having a Kappa number (in accordance with SCAN-C 1:00), equal to 15-40;

b) grind the pulp at a high consistency (VC) and, optionally, at a low consistency (NC) to obtain a refined pulp, while the specific energy consumption for grinding at NC is less than 120 kWh / ton of paper; and

c) form the bag paper from the above mixture of cellulose,

however, the amount of added starch is 1-7 kg / ton of paper, and the amount of added hydrophobic additive is less than 2 kg / ton of paper.

51. The method according to claim 50, wherein the porosity according to the Gurley method (in accordance with ISO 5636-5) of bag paper is less than 20 seconds, such as less than 15 seconds, such as less than 10 seconds, such as less less than 8 s, such as less than 7 s, such as less than 6 s.

52. The method according to p. 50 or p. 51, in which the Kappa number (in accordance with SCAN-C 1:00) cellulose, obtained in step a), is the value of 20-35.

53. The method according to any one of paragraphs. 50-52, characterized in that the index of energy expended by geometric stretching (in accordance with ISO 1924-3) of sack paper is at least 2 J / g, such as at least 2.4 J / g, such as at least 2.8 J / g, such as at least 3.2 J / g.

54. The method according to any one of paragraphs. 50-53, characterized in that the density (in accordance with ISO 536) of bag paper is 50-140 g / m ² , such as 60-120 g / m ² , such as 60-110 g / m ² , such as 70 -110 g / m ² , such as 75-100 g / m ² .

55. The method according to any one of paragraphs. 50-54, characterized in that the pulp obtained in step a) is a chemical pulp, such as kraft pulp.

56. The method according to any one of paragraphs. 50-55, characterized in that at least 50%, such as at least 60%, 70%, 80% or 90% by weight in the dry state of the pulp obtained in step a), is a pulp from coniferous wood.

57. The method according to any one of paragraphs. 50-56, characterized in that stage C) includes creping.

58. The method according to any one of paragraphs. 50-57, characterized in that the amount of hydrophobic additive is less than 1.5 kg / ton of paper, such as less than 1.0 kg / ton of paper, such as less than 0.5 kg / ton of paper, such as less than 0.3 kg / ton of paper, such as 0 kg / ton of paper.

59. The method according to any one of paragraphs. 50-58, characterized in that the amount of starch is 1-5 kg / ton of paper, such as 2-5 kg / ton of paper.

60. The method according to any one of paragraphs. 50-59, characterized in that step a) includes the conversion of wood into cellulose, having a Kappa number (in accordance with SCAN-C 1:00), equal to 25-40 using sulphate pulping.

61. The method according to any one of paragraphs. 50-60, characterized in that the specific energy consumption for grinding at NC is less than 110 kWh / ton of paper, such as less than 100 kWh / ton of paper.

DETAILED DESCRIPTION OF THE INVENTION

As a first aspect of the present invention, a method for manufacturing bag paper is provided. "Sack paper" is a paper intended for the manufacture of a paper bag, for example a paper bag for a hydraulic binder. The hydraulic binder in accordance with this invention is intended for use in a hydraulic mixture. Examples of hydraulic mixtures are discussed below.

The paper bag must release air during filling. In more detail, the air that accompanies the powdered material should be promptly released from the bag, since the filling machines that serve the material for filling the bags work with high throughput. Often, the maximum air removal rate from the bag is the actual limiting factor for the filling rate. Effective ventilation also prevents air from being trapped in the bag and causes underloading of the container, bag rupture, and problems placing the bags on top of each other for transport. During the filling process, the only way for air to escape from the inside of the bag in many bag designs is to pass through the inside wall or layer of the bag. For air that has passed through the inner wall or layer of the bag, the prior art provides various alternatives for its further exit. In some bags, the outer layer is also porous to facilitate further air release. Based on the foregoing, it should be understood that, in accordance with this invention, bag paper, which is mainly intended for the inner layer, but can also be used for the outer layer, has less resistance to air flow (or higher porosity) than many other types of paper. .

In addition, from the above explanation, it should be understood that the bag containing the bag paper according to the first aspect of the present invention, in most cases, is a bag with a flap.

Resistance to air flow according to the Gurley method (in accordance with ISO 5636-5) is a measurement of time (in seconds “s”), spent on the passage of 100 ml of air through a given area of a sheet of paper. Short time means highly porous paper.

Sack paper in accordance with this invention has a Gurley porosity (in accordance with ISO 5636-5) of less than 25 s. In a preferred embodiment of the invention, it is less than 20 seconds. In some embodiments of the invention, it is less than 15 s, such as less than 10 s, such as less than 8 s, 7 s, or 6 s. Sack paper having a porosity according to the Gurley method of less than 2 s or 3 s often has insufficient strength. Consequently, the porosity according to the method of the Gurley bag of the present invention in its preferred embodiment is at least 2 s or 3 s. In some embodiments of the invention, it is at least 4 s. Typical porosity ranges according to the Gurley method for this invention are therefore 3-15 seconds, preferably 4-10 seconds, such as 4-8 seconds, 4-7 seconds, or 4-6.5 seconds.

The method according to the first aspect of the present invention includes the step of:

a) mix unbleached pulp with bleached pulp to obtain a mixture of pulp.

Unbleached pulp in the preferred embodiment of the invention is a chemical pulp. The reason for choosing chemical pulp is that, as a result, in most cases it produces stronger paper than that obtained from waste paper or mechanical pulp. Chemical pulp can be, for example, kraft pulp or sulfite pulp. Kraft pulp is the preferred option. As is well known to an experienced specialist, Kraft pulp is obtained by sulphate pulping.

Another advantage of choosing chemical pulp is that it contains much less lignin than mechanical pulp. For example, prior to bleaching, chemical pulp may contain less than 5% lignin, compared with about 30% in the case of mechanical pulp. The inventors have found that reducing the lignin content of cellulose in most cases improves its ability to decompose.

The kappa number of unbleached chemical pulp may be, for example, 45-60. The advantage of making pulp with such a relatively high Kappa number is the relatively high yield. However, it may be advisable to increase the duration of the cooking process to produce pulp with a lower kappa number, such as with a kappa number of 20-45 or 25-40. Despite the fact that longer cooking times reduce the yield of the product, they may be of practical importance. The reason for this is that the authors of the present invention realized that lower Kappa numbers in unbleached pulp according to the method in accordance with the first aspect of the present invention in most cases are associated with an improved ability to decompose the finished sack paper.

The relatively low Kappa number (i.e. 20-45) unbleached pulp can also provide a relatively low proportion of bleached pulp in the pulp mixture, i.e. a ratio from 7: 1 to 1.5: 1.

Kappa number can be measured in accordance with SCAN-C 1:00 or ISO 302: 2004.

Also preferred is that the bleached pulp is a chemical pulp, such as kraft pulp or sulfite pulp. As for unbleached pulp, the advantages of choosing chemical pulp are relatively strong paper and relatively low Kappa numbers after the cooking process.

In a preferred embodiment of the invention, the Kappa number of bleached pulp is less than 10, such as less than 7, such as less than 4, such as less than 2. The inventors believe that at least to some extent lower values of Kappa numbers in bleached pulp associated with increased ability to decompose the finished bag paper.

Cellulose whiteness is a measure of the degree of bleaching. Regarding the Kappa number, the inventors believe that, at least to some extent, the higher whiteness of the bleached pulp is associated with an increased ability to decompose the finished sack paper. For example, the whiteness in accordance with ISO (ISO 2470-1) of bleached pulp may therefore be at least 60. The preferred whiteness of bleached pulp in accordance with ISO may be at least 70. In some embodiments of the invention, it may be at least 80 or 85. However, from an economic and environmental point of view, it may be preferable not to bleach the pulp to ISO whiteness of 80 or 85. Accordingly, in some embodiments of the invention, whiteness is ISO is less than 85, such as 50-80.

As understood by an experienced specialist, a sheet is molded from the bleached pulp to facilitate the measurement of its whiteness in accordance with ISO.

Different types of softwood pulp are in most cases associated with the presence of long fibers, resulting in durable paper. In this regard, unbleached pulp and / or bleached pulp in accordance with this invention may contain at least 50% (in terms of weight in a dry state) pulp from coniferous wood. The proportion of softwood pulp can be, for example, at least 75% or 90% (based on weight in the dry state) in unbleached pulp and / or in bleached pulp.

As is clear from the above discussion, the method of the first aspect may further include a bleaching process for preparing bleached pulp. Such a bleaching process may include, for example, oxygen separation of lignin.

Oxygen separation of lignin can be, for example, the first step in the bleaching process. In accordance with this, the pulp obtained during the cooking process may be subjected to oxygen separation of lignin. Such cellulose, which leaves the cooking process and undergoes oxygen separation of the lignin, may have a kappa number, for example, below 45, such as 20-40, before the oxygen separation of the lignin.

Accordingly, the cooking process used in the preparation of bleached pulp may result, for example, in a lower Kapp number than in the cooking process used in the preparation of unbleached pulp.

Alternatively, the same cooking process is used in the preparation of both types of pulp.

As a supplement or alternative to the oxygen separation of lignin (“O”), the bleaching process may include one of the following steps (which are all well known to an experienced technician):

chlorine dioxide bleaching ("D")

ozone bleaching (“Z”);

extraction using sodium hydroxide (“E”);

bleaching with alkaline hydrogen peroxide (“P”);

bleaching with peracetic acid ("PAA"); and

bleaching with sodium dithionite also (known as sodium hydrosulfite) (“Y”).

In one embodiment of the invention, the bleaching process contains O and at least two or three of D, Z, E, P, PAA and Y.

In step a) of the method according to the first aspect of the present invention, the pulp (i.e., unbleached pulp and bleached pulp) are mixed in such proportions that the dry weight ratio of unbleached pulp to bleached pulp in the pulp mixture is between 7: 1 and 1: 1 , preferably from 6: 1 to 1: 1, such as from 5: 1 to 1: 1, such as from 4: 1 to 1: 1, such as from 3.5: 1 to 1.1: 1, such as from 3: 1 to 1.2: 1, such as from 2.8: 1 to 1.3: 1.

If the proportion of bleached pulp is too low, the decomposition capacity of the resulting paper will be too low. However, if the proportion of bleached pulp is too high, the cost of production may be too high.

The method according to the first aspect of the present invention further includes the step of:

b) form the bag paper from the specified mixture of cellulose.

Generally, step b) includes standard pulp paper forming operations, such as forming a paper web on a net in a grid part of a paper machine, pressing a paper web in a press section of a paper machine and drying the paper web in a dryer part of the paper machine.

Bag paper from step b) is still considered brown sack paper. In accordance with this, the whiteness according to ISO of the bag paper in a preferred embodiment of the invention is less than 30, such as less than 25, such as less than 22.

Bag paper properties are often measured in the machine direction (MN) and in the transverse direction (PN), since there can be significant differences in properties depending on the flow of oriented fiber from the headbox on the paper machine.

The index of a specific paper property is calculated by dividing the actual value by the density of the paper in question.

The paper weight (sometimes referred to as the basis weight or 1 m ^{2 of} paper weight) is measured by weight and surface area, for example, in accordance with ISO 536.

Tensile strength is the maximum force that the paper will withstand before breaking. The standard test in accordance with ISO 1924-3 uses a strip of paper 15 mm wide and 100 mm long with a constant elongation rate. Tensile strength is one of the parameters for measuring the cost of energy in the gap (ZER). In the course of the same test, tensile strength, tensile strength and ZER value are obtained.

ZER is sometimes considered a property of paper that best reflects the real strength of the wall of the paper bag. This opinion is based on the correlation between the AED and the test by dropping from a height. When the bag is dropped, the products that fill the bag will move when the bag reaches the floor. This movement causes the deformation of the bag wall. In order for the wall of the bag to withstand the deformation, ZER must have a high value. This means that the combination of high tensile strength and good tensile properties in paper absorbs energy.

The density (in accordance with ISO 536) of the sack paper in accordance with this invention is in most cases in the range from 50 to 140 g / m ² . It is generally preferable to add another layer of paper to the bag instead of increasing the density of the layer above 140 g / m ² . The preferred density value (in accordance with ISO 536) of bag paper in accordance with this invention is 50-130 g / m ² , such as 60-120 g / m ² , such as 60-110 g / m ² , such as 70- 110 g / m ² , such as 75-100 g / m ² .

To take into account the ZER in both MN and MON, the geometric index ZER can be calculated as the square root of the product of ZER in MN and ZER in MO (ZER (geometrical) = √ (ZER (MN) × ZER (MO)).

The geometric index ZED (in accordance with ISO 1924-3) of sack paper in accordance with this invention is preferably at least 2 J / g. For example, it may be at least 2.4 J / g, such as at least 2.8 J / g, such as at least 3.2 J / g.

The creping of the paper improves the stretchability and, therefore, the ZER index. Accordingly, in one embodiment of the method according to the first aspect of the invention, step b) includes creping.

The inventors also realized that the ability to break down can be improved by reducing the amount of hydrophobic additive added in this process, such as alkyl ketene dimer (alkyl alcohol), alkyl nucleonic anhydride (AAN) and / or rosin. In one embodiment of this invention, the amount of hydrophobic additive is less than 2 kg / ton of paper. For example, this amount may be less than 1.5 kg / ton of paper, such as less than 1 kg / ton of paper, such as less than 0.5 kg / ton of paper, such as less than 0.3 kg / ton of paper. In one embodiment of the method, the hydrophobic component is not added.

In addition, the inventors realized that the ability to break can be improved by minimizing the amount of starch. In one embodiment of this invention, the amount of starch added in the process is less than 7 kg / ton of paper, such as less than 5 kg / ton of paper, such as less than 4 kg / ton of paper. In order to obtain sufficient strength in spite of this, the minimum amount of starch to be added may, by way of example, be at least 1 kg / ton of paper, such as at least 2 kg / ton of paper, such as at least 3 kg / ton of paper. In this case, "starch" contains in its composition starch of any charge.

In a preferred embodiment of the present invention, the starch is added before step b).

In the context of this invention, “kg / ton of paper” refers to kg per ton of dried paper obtained from the paper making process. Such dried paper in most cases has a dry matter content (mass fraction) of 90-95%.

As a second aspect of the present invention, bag paper is proposed having a porosity according to the Gurley method (in accordance with ISO 5636-5) of less than 25 s, which consists of a mixture of unbleached fibers and bleached fibers, while the ratio of the mass of the substance in the dry state of unbleached fibers to bleached the fibers in the mixture range from 7: 1 to 1: 1.

Sack paper according to the second aspect of the present invention can be manufactured using the method according to the first aspect. Accordingly, embodiments of the invention and examples of the first aspect are applied with due regard for the necessary changes to the second aspect.

In addition, a bag is provided for a hydraulic binder, such as cement, comprising a layer consisting of sack paper according to a second aspect.

The bag in accordance with this invention in most cases is a bag with a valve.

By way of example, the bag may be a multi-layer bag comprising an inner layer consisting of bag paper in accordance with the second aspect.

In a multi-layered bag with a flap, each layer of paper may have, for example, a density of 50-100 g / m ² , such as 60-90 g / m ² .

The multi-ply bag may further comprise an outer layer consisting of white sack paper. An example of a suitable white sack paper for this purpose is described in patent application EP 14175729.4. In some embodiments of this invention, such white sack paper contains a protective layer of waterproofing coating. Experienced specialist known various waterproofing coatings. The weight of the protective layer of the waterproofing coating may be, for example, 5-30 g / m ² . Waterproofing coatings can be considered sufficient if the water vapor penetration rate (WVTR according to ISO 2528, measured at 38 ° C and relative humidity of 90% (tropical climate)) is less than 1400 g / m ² in 24 hours, preferably less than 1200 g / m ² in 24 hours. For example, a WVTR bag paper containing a protective layer of a waterproofing coating may be 700-1200 g / m ² in 24 hours. In a preferred embodiment of the present invention, the white bag paper forming the outer layer is capable of to decomposition, in th number, if it is provided with a protective layer of waterproofing coating. An example of such coated paper is described in patent application EP 14175736.9.

If the outer layer is provided with a protective layer of waterproofing coating, it is often practically impermeable to air. In such a case, in order to ensure that air is removed during the filling process, the bag may comprise an upper end formed by bending and gluing the material of the layer so that a portion of the upper end does not close hermetically by gluing. In such an embodiment of the present invention, folding and gluing are performed in such a way that air can escape through the unsealed portion of the bag during its filling with a hydraulic binder. In a preferred embodiment of the present invention, such a bag is designed in such a way that air penetrates into the innermost layer, and then exits through the unsealed part of the bag during its filling with material at high speed.

Alternatively, the multi-ply bag may comprise an outer layer consisting of sack paper in accordance with the second aspect. For example, all layers of a multi-ply bag may consist of sack paper in accordance with the second aspect. From an economic point of view, it is advantageous if all the paper required for the bag can be made using a single paper making method.

The bag volume in accordance with this invention may be, for example, 8-45 liters, such as 15-45 liters.

The bag in accordance with this invention may, for example, contain a hydraulic binder, such as cement. The amount of hydraulic binder may be, for example, 20-60 kg. For example, bags with a capacity of 25 kg, 35 kg and 50 kg are in demand in the market and can be manufactured in accordance with this description of the invention. The dimensions of the filled 25 kg bag may be, for example, 400 × 450 × 110 mm. A “25 kg bag” can usually be filled with approximately 17.4 liters of material, while a “50 kg bag” can usually be filled with approximately 35 liters of material.

To provide protection against the penetration of atmospheric water vapor, many bags of the prior art contain plastic film located between two paper layers of the bags. Such a film, which in most cases consists of polyethylene, is often called "free film." A plastic free film does not easily break up in a mixer for preparing cement mortar. In this regard, it is preferred that the bag according to this invention does not contain a free plastic film.

As a third aspect of the present invention, there is provided a method for producing a hydraulic composition comprising introducing water and a bag in accordance with the invention into a mixer and ensuring decomposition of the material of the bag layer during mixing in the mixer.

Thus, the hydraulic composition is a mixture containing a water-curing binder and water (often referred to as mixing water). The composition may, by way of example, additionally contain one or more aggregates, one or several additives, and / or one or several mineral additives. An example of a filler is sand, which may have different particle sizes. The hydraulic composition in accordance with this invention is preferably a cement mortar, mortar, concrete, gypsum dough or a suspension of hydraulic lime. In one of the embodiments of the present invention, the water-solidifying composition is selected from cement mortar, mortar and concrete.

In another aspect of the present invention, bleached fibers are optionally mixed with unbleached fibers. Alternatively, the production of degradable sack paper is based on the use of pulp having a Kapp number, which is relatively low compared with many unbleached pulps. To this can be added that the addition of starch, the addition of hydrophobic glue and the grinding in NCs are maintained at relatively low levels. A “low kappa pulp” cellulose can be obtained by mixing unbleached pulp with bleached pulp, as in the first aspect, or using a cooking process that is designed to produce “low kappa pulp pulp”. For example, the duration or residence time of the pulp during the cooking process can be adapted to produce unbleached pulp having the required Kappa number (as indicated above, a longer cooking time in most cases results in smaller Kappa numbers). In addition, to reduce the Kappa number to a value below 25 or 30, oxygen lignin can be used.

In this regard, as a fourth aspect of the present invention, a method for manufacturing bag paper having a porosity by the Gurley method (in accordance with ISO 5636-5) of less than 25 s is proposed, which includes the steps of:

a) receive cellulose having a Kappa number (in accordance with SCAN-C 1:00) 15-40;

b) grind the pulp at high consistency (VC), and not necessarily at low consistency (NC) to obtain purified cellulose, while the energy consumption for grinding at NC is less than 120 kWh per ton of paper; and

c) bag paper is formed from said cellulose mixture, in which the amount of starch added is 1-7 kg / ton of paper, and the amount of added hydrophobic glue is less than 2 kg / ton of paper.

Grinding at VK in most cases is carried out at the consistency of a fibrous suspension, which is 15 mass. % or higher, such as from 5 to 45 mass. % Grinding at NC in most cases is carried out at the consistency of a fibrous suspension, which is 10 mass. % or lower, such as 2% -10%.

For example, the specific energy consumption for grinding with VC can be from 100 to 320 kWh / ton of paper, and in the preferred embodiment of the present invention it can be from 150 to 300 kWh / ton of paper, such as from 170 to 300 kW .h / t paper.

As indicated above, the specific energy consumption for milling is less than 120 kWh per ton of paper (for example, 10-120 kWh per ton of paper) if grinding is performed at NC. Preferably, the specific energy consumption for milling at NC is less than 110 kWh per ton of paper, for example, 10-110 kWh per ton of paper, and more preferably it is less than 100 kWh per ton of paper, such as 10- 100 kWh per ton of paper.

The Gurley porosity (in accordance with ISO 5636-5) of bag paper in accordance with the fourth aspect in a preferred embodiment of the present invention is less than 20 seconds, such as less than 15 seconds, such as, for example, 10 seconds or less. In some embodiments of this invention, it is less than 8 seconds, such as less than 7 seconds, such as less than 6 seconds.

In a preferred embodiment of the present invention, step a) comprises kraft pulping, which means that pulping pulp is used to turn wood into pulp, which has a Kapp number (according to SCAN-C 1:00) equal to 25-40 . Preferably, at least 50% by weight of the dry wood used in such kraft pulping is softwood. More preferably, at least 60%, 70%, 80% or 90% of the dry weight of the wood is softwood. If the kappa number is required to be below 25 or 30, then the cooking can be combined with the subsequent oxygen separation of the lignin.

In a preferred embodiment of the present invention, the kappa number (in accordance with SCAN-C 1:00) of the pulp provided in step a) is 20-35. An experienced specialist knows how to adjust the cooking process to get such a kapp number.

The amount of hydrophobic additive in the method in accordance with the fourth aspect, in a preferred embodiment of the present invention, is less than 1.5 kg / ton of paper, such as less than 1.0 kg / ton of paper, such as less than 0.5 kg / ton paper, such as less than 0.3 kg / ton of paper. In one of the embodiments of the present invention, the hydrophobic additive in this method is completely excluded.

The amount of starch is preferably kept relatively low to improve the degradability of the paper. At the same time, the strength of the resulting paper may be too low if no starch is added at all. In this regard, the amount of starch added in the method in accordance with the fourth aspect, in the preferred embodiment of the present invention is 1-5 kg / ton of paper, such as 2-5 kg / ton of paper.

In other cases, embodiments of the present invention and examples of the first aspect, taking into account the necessary changes, are applicable to the fourth aspect, if they do not contradict each other.

BRIEF DESCRIPTION OF GRAPHIC MATERIALS

FIG. 1 is a graph showing the degradability of various types of paper.

EXAMPLES

For the tests presented below, “kg / ton” means “kg per ton of paper”.

Full scale test

, Швеция. В ходе испытания способность к разложению бумаги, полученной из смеси небеленой целлюлозы (57 масс. %) и отбеленной целлюлозы (43 масс. %), сравнивалась со способностью к разложению стандартной бумаги, выбранной для сравнения, которая была получена только из небеленой целлюлозы. Плотность обоих бумаг была одинаковой и составляла 90 г/м².A full-scale test was conducted on a paper machine 9 (PM9) at the mill of Billerud Korsnas AB in the city

, Sweden. During the test, the degradability of paper obtained from a mixture of unbleached pulp (57 wt.%) And bleached pulp (43 wt.%) Was compared with the degradability of standard paper chosen for comparison, which was obtained only from unbleached pulp. The density of both papers was the same and was 90 g / m ² .

Both types of pulp were softwood kraft pulp, subjected to grinding at VK (specific energy consumption for grinding was about 120 kWh / t) and grinding at NC (specific energy consumption for grinding 20 kWh / t) to which starch (8 kg / t), polyacrylamide of the brand Fennosil 517 (0.25 kg / t) and ASA hydrophobic additive (1 kg / t) were added. The kappa number (in accordance with SCAN-C 1:00) unbleached pulp was 50. The whiteness in accordance with ISO (ISO 2470-1) bleached pulp was 90.

The degradability of the test papers was tested according to the following instructions:

1. Cut the paper (dry weight 30.0 g) into pieces approximately 1.5 cm × 1.5 cm in size and place them in water with a temperature of 20 ° C and a volume of 2 liters;

2. After 2 minutes, place the paper-water mixture in a laboratory defibrator (brand L &W);

3. Turn on the defibrator at a speed of 5000 revolutions per minute;

4. Place the contents of the defibrator onto a laboratory sieve having a hole size of 0.15 mm and pass the contents of the defibrator through the sieve for 15 minutes;

5. After filtration is complete, collect the concentrate;

6. Dry the concentrate at 105 ° C;

7. Weigh the dried concentrate; and

8. Calculate the degradability (in%) using the formula ((30-w) / 30) × 100, where w is the mass (g) of the dried concentrate.

Paper porosity was also measured by the Gurley method. The results are presented below in table 1.

Laboratory tests

First of all, the order of laboratory tests was evaluated and a sufficient correlation was found with full-scale testing.

Bleached and unbleached pulp for laboratory tests were obtained from paper mills.

Test 1

Unbleached pulp consisted of unbleached softwood Kraft pulp, subjected to grinding at VK (specific energy consumption for grinding 250 kWh / t) and grinding at NC (specific energy consumption for grinding 18 kWh / t). Kappa number (according to SCAN-C 1:00) unbleached pulp was 50. Bleached pulp was bleached softwood Kraft pulp, subjected to grinding at VK (specific energy consumption for grinding 150 kWh / t) and grinding at NK (specific energy consumption for grinding 16 kWh / t). The whiteness according to ISO (ISO 2470-1) of the bleached pulp was 90.

. Способность к разложению этих листов бумаги, которая также демонстрируется в таблице 2 ниже, была испытана так же, как и в полномасштабном испытании, описанном выше.For the formation of sheets of paper were prepared various types of pulp in accordance with table 2 below. Laboratory sheets of paper with a density of 80 g / m ² were prepared on a dynamic paper machine according to Billerad's own method.

. The degradability of these sheets of paper, which is also demonstrated in Table 2 below, was tested in the same way as in the full scale test described above.

From Tables 1 and 2 it can be concluded that adding bleached pulp to unbleached pulp significantly improves the decomposition ability of the paper obtained, in particular, if the mixture of pulp from which the paper is molded contains more than 10% bleached pulp or at least 20% bleached pulp . In addition, table 2 demonstrates that the ability to decompose is significantly improved by reducing the amount of ASA (hydrophobic additive) added to cellulose.

The results from tables 1 and 2 are also presented in FIG. one.

Test 2

Unbleached pulp and bleached pulp were the same as in test 1, except that for unbleached pulp, the specific energy consumption for grinding at VK was 258 kWh / t, and the specific energy consumption for grinding at NC was 41 kW .h / t

. Способность к разложению этих листов бумаги, которая также демонстрируется в таблице 3 ниже, была испытана так же, как и в полномасштабном испытании, описанном выше.For the formation of sheets of paper were prepared various types of pulp in accordance with table 3 below. As in experiment 1, Fennosil 517 (kg / t) was added in an amount of 0.25 kg / t. In test 2, the ASA was not added. Laboratory sheets of paper having a density of 80 g / m ² were obtained on a dynamic paper machine in accordance with Billerud’s own method

. The degradability of these sheets of paper, which is also shown in Table 3 below, was tested in the same way as in the full scale test described above.

The data in Table 3 prove that adding bleached pulp (BP) to unbleached pulp (UBP) significantly improves the degradability (D) of the paper produced. In addition, table 3 demonstrates that the ability to decompose (D) is significantly improved by reducing the amount of starch (S) added to the pulp. Ultimately, a comparison of the values for 8 kg / t of starch in table 3 with the values in table 2 demonstrates that the decomposition capacity (D) was lower when the degree of milling at NC unbleached pulp was higher.

Tests 3 and 4

In test 3, unbleached pulp was unbleached softwood kraft pulp that was milled at a BK with a specific energy consumption for grinding of 177 kWh / t and milled at NC with a specific energy consumption for grinding of 131 kWh / t. In test 4, unbleached pulp of the same type of unbleached softwood kraft pulp was used, subjected to grinding with a BK with a specific energy consumption for grinding of 210 kWh / t and grinding with a NC with a specific energy consumption for grinding of 95 kWh / t. The kapp number (according to SCAN-C 1:00) of unbleached pulp was 30 in both test 3 and test 4. Bleached pulp was the same as in test 1.

Test 3 and test 4 were carried out under different circumstances.

. Способность к разложению этих листов бумаги, которая такжеDifferent types of pulp for forming sheets of paper were prepared in accordance with tables 4 and 5, which are listed below. As in Test 1, Fennosil 517 (kg / ton) was added in an amount of 0.25 kg / ton. In tests 3 and 4, the ASA was not added. Laboratory sheets of paper, having a density of 80 g / m ² , were obtained on a dynamic paper machine in accordance with Billerud’s own method

. The ability to decompose these sheets of paper, which also

shown in Tables 4 and 5 below, was tested in the same way as in the full-scale test described above.

The data in Table 4 prove that adding bleached pulp (BP) to unbleached pulp (UBP) significantly improves the degradation capacity (D) of the paper produced and that the degradability (D) is significantly improved by reducing the amount of starch (S) added to the pulp. . It should also be noted that the data on decomposition capacity (D) given in Table 4, which were obtained using unbleached pulp with a Kappa number of 30, are in most cases higher than the data shown in Table 3, which were obtained using unbleached pulp. with a kappa number of 50. As an example, the degradability for 32% of bleached pulp and 5 kg / ton of starch in table 4 is 95% compared with 85% in table 3

Comparing the values in table 5 with the values in table 4 shows that the decomposition capacity (D) was higher if the degree of milling at NC unbleached pulp was lower. In addition, table 5 demonstrates that if the values of both the kappa numbers, the milling degrees in the NC and the starch amounts are kept at a relatively low level, there is no need to add bleached pulp to achieve high degradation values (> 95%). Nevertheless, the positive effect of the addition of bleached pulp in table 5 is still observed.

Claims (32)

1. A method of manufacturing bag paper having porosity according to the Gurley method (in accordance with ISO 5636-5) of less than 25 s, comprising the steps of: a) mix the unbleached pulp with bleached pulp to obtain a mixture of cellulose in such proportions that the dry weight ratio of unbleached pulp to weight in a dry state of bleached pulp in a mixture of pulp is from 7: 1 to 1: 1; and b) form the bag paper from the specified mixture of cellulose. 2. The method according to p. 1, characterized in that the porosity by the method of Gerley (in accordance with ISO 5636-5) bag paper is less than 20 s, such as less than 15 s, such as less than 10 s, such as less less than 8 s, such as less than 7 s, such as less than 6 s. 3. The method according to any of the preceding paragraphs, characterized in that the whiteness in accordance with ISO (ISO 2470-1) of bleached pulp is at least 60, such as at least 70, such as at least 80, such as at least least 85. 4. The method according to any of the preceding paragraphs, characterized in that the ratio of unbleached pulp to bleached pulp in a mixture of pulp is in the range from 6: 1 to 1: 1, such as from 5: 1 to 1: 1, such as from 4: 1 to 1: 1, such as from 3.5: 1 to 1.1: 1, such as from 3: 1 to 1.2: 1, such as from 2.8: 1 to 1.3: 1. 5. The method according to any of the preceding paragraphs, characterized in that the density (in accordance with ISO 536) of the sack paper is 50-140 g / m ² , such as 60-120 g / m ² , such as 60-110 g / m ² , such as 70-110 g / m ² , such as 75-100 g / m ² . 6. The method according to any of the preceding paragraphs, characterized in that a hydrophobic additive is added in an amount of less than 1.0 kg / ton of paper. 7. The method according to any of the preceding paragraphs, characterized in that starch is added in an amount of 1-5 kg / ton of paper, such as 2-5 kg / ton of paper. 8. Sack paper, having a porosity according to the Gurley method (in accordance with ISO 5636-5) less than 25 s, consisting of a mixture of unbleached fibers and bleached fibers, in which the dry weight ratio of unbleached fibers to bleached fibers in the mixture ranges from 7: 1 to 1: 1. 9. Bag paper according to claim. 8, characterized in that the porosity of the Gurley method (in accordance with ISO 5636-5) of bag paper is less than 20 s, such as less than 15 s, such as less than 10 s, such as less than 8 s, such as less than 7 s, such as less than 6 s. 10. Sack paper according to any one of paragraphs. 8-9, characterized in that the dry weight ratio of unbleached fibers to bleached fibers in the mixture ranges from 3.5: 1 to 1.1: 1, such as from 3: 1 to 1.2: 1, such as from 2.8: 1 to 1.3: 1. 11. Sack paper according to any one of paragraphs. 8-10, characterized in that the density (in accordance with ISO 536) of bag paper is 50-140 g / m ² , such as 60-120 g / m ² , such as 60-110 g / m ² , such as 70 -110 g / m ² , such as 75-100 g / m ² . 12. Sack paper according to any one of paragraphs. 8-11, characterized in that it undergoes creping. 13. Bag for hydraulic binder, such as cement, containing a layer consisting of bag paper according to any one of paragraphs. 8-12. 14. A bag according to claim 13, comprising a hydraulic binder, such as cement. 15. A method of obtaining a hydraulic composition, comprising the step of introducing water and a bag according to claim 14 to the mixer and allow the material of the bag layer to decompose during mixing in the mixer. 16. A method of manufacturing bag paper having porosity according to the Gurley method (in accordance with ISO 5636-5) of less than 25 s, comprising the steps of: a) receive a pulp having a Kappa number (in accordance with SCAN-C 1:00), equal to 15-40; b) grind the pulp at a high consistency (VC) and, optionally, at a low consistency (NK) to obtain a refined pulp, while the specific energy consumption for milling at NK is less than 120 kWh / ton of paper; and c) bag paper is formed from said cellulose mixture, wherein the amount of starch added is 1-7 kg / ton of paper, and the amount of added hydrophobic additive is less than 2 kg / ton of paper. 17. The method according to p. 16, characterized in that the porosity by the method of Gurley (in accordance with ISO 5636-5) bag paper is less than 20 s, such as less than 15 s, such as less than 10 s, such as less less than 8 s, such as less than 7 s, such as less than 6 s. 18. The method according to p. 16 or 17, characterized in that the Kappa number (in accordance with SCAN-C 1:00) cellulose, obtained in step a), is 20-35. 19. A method according to any one of claims. 16-18, characterized in that the index of energy expended by geometric stretching (in accordance with ISO 1924-3) of sack paper is at least 2 J / g, such as at least 2.4 J / g, such as at least 2.8 J / g, such as at least 3.2 J / g. 20. A method according to any one of claims. 16-19, characterized in that the density (in accordance with ISO 536) of bag paper is 50-140 g / m ² , such as 60-120 g / m ² , such as 60-110 g / m ² , such as 70 -110 g / m ² , such as 75-100 g / m ² . 21. A method according to any one of claims. 16-20, characterized in that the pulp obtained in step a), is a chemical pulp, such as Kraft pulp. 22. A method according to any one of claims. 16-21, characterized in that at least 50%, such as at least 60%, 70%, 80% or 90% by weight in the dry state of the pulp obtained in step a), is a softwood pulp. 23. A method according to any one of claims. 16-22, characterized in that step c) includes creping. 24. A method according to any one of claims. 16-23, characterized in that the amount of hydrophobic additive is less than 1.5 kg / ton of paper, such as less than 1.0 kg / ton of paper, such as less than 0.5 kg / ton of paper, such as less than 0.3 kg / ton of paper, such as 0 kg / ton of paper. 25. The method according to any one of paragraphs. 16-24, characterized in that the amount of starch is 1-5 kg / ton of paper, such as 2-5 kg / ton of paper. 26. A method according to any one of claims. 16-25, characterized in that step a) includes the conversion of wood into pulp having a Kapp number (in accordance with SCAN-C 1:00), equal to 25-40 using sulphate pulping. 27. The method according to any one of paragraphs. 16-26, characterized in that the specific energy consumption for grinding at NC is less than 110 kWh / ton of paper, such as less than 100 kWh / ton of paper.

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