ES2608806T3 - Sack with discontinuous longitudinal seam - Google Patents

Abstract

A pouch (100, 200) having an inner sheet (101) and an outer sheet (102, 202), wherein: the outer sheet (102, 202) forms an overlapping region (103, 203) of longitudinal extension comprising an inner layer (104) and an outer layer (105); a first end portion (106) of the outer sheet (102, 202) forms the inner layer (104) and a second end portion (107) of the outer sheet (102, 202) forms the outer layer (105); an inside (108) of the outer layer (105) is bonded (221) to an outside (109) of the inner layer (104) to form a discontinuous longitudinal seam (220); and an interior (110) of the first end portion (106) is glued (113a, 113b, 113c) to the inner sheet (101), so that air passes out from an interior space (111) between the inner sheet ( 101) and the outer (102, 202) through the channels (112, 212) in the discontinuous longitudinal seam (220), characterized in that the outer sheet (102, 202) is coated with a barrier against humidity and inner sheet (101) is porous to allow air penetration.

Description

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DESCRIPTION

Sack with discontinuous longitudinal seam Technical field

The present disclosure refers to bags. In particular, it refers to a bag for a hydraulic binder, such as cement.

Background

During the filling and storage of powdered material, such as cement, paper bags are required to meet high standards.

First, the paper bags must contain a considerable weight of material, that is, have a high tensile strength. For this purpose, the brown paper is a suitable bag wall material. The bags normally have two or more walls, that is, layers of paper material, to further reinforce the construction of the bag. A wall layer of a sack is often called a leaf. The production of sheet material (ie sack paper) is disclosed for example in WO 99/02772.

Second, a material such as cement is sensitive to moisture contamination during storage. Therefore, cement bags often require protection against the penetration of atmospheric water vapor through the sheets of the bags. Such protection is often achieved by a moisture barrier incorporated as an intermediate layer in the bag, that is, between two sheets of paper material. The moisture barrier is normally a plastic film ("free film") for example polyethylene (PE), which is impermeable to water. The free film can also improve fat resistance and prevent contamination by microorganisms.

Third, the paper bag should ventilate the air during filling. In detail, the air that accompanies the powdered material should effectively ventilate the bag as the filling machine that supplies the material operates at high production rates. Often, the ventilation capacity of the bag is the current limiting factor for the filling rate. Effective ventilation also prevents air from getting trapped in the bag and causes packages with little weight, bag breakage and problems when the bags are stacked for transport.

During the filling process, the only way for air to escape from inside the bag, in many bag constructions, has been through the walls of the bag. High porosity brown paper has often been used on the walls to facilitate air permeability. However, an increased porosity of the paper often results in a decrease in overall strength. In particular, the resistance can be significantly reduced if holes must be made in the paper material to achieve sufficient air permeability. In addition, the use of a free film can reduce deaeration during filling, since most such films are air permeable. Therefore, the free film layers are provided with slits or openings to facilitate deaeration.

US 2001/0021281 discloses a ventilated bag, which includes a length of sealed gas impermeable tubular material to be closed at least one end thereof by means of a plurality of separate sealing lines, each including a discontinuity near an end of the same. The discontinuities in adjacent ones of the sealing lines are arranged close to opposite ends of the lines whereby the discontinuities, the lines and the adjacent material form a tortuous channel that provides a communication between the inside of the bag and the outside of the bag.

Summary

The purpose of the present disclosure is to provide a bag concept that has improved air ventilation during filling.

The present disclosure provides a bag that has an inner sheet and an outer sheet, in which:

the outer sheet forms a longitudinally extending overlap region comprising an inner layer and an outer layer;

a first terminal portion of the outer sheet forms the inner layer and a second terminal portion of the outer sheet forms the outer layer;

an inside of the outer layer sticks to an outside of the inner layer to form a discontinuous longitudinal seam; Y

an inside of the first terminal portion sticks to the inner sheet,

so that the air can pass out from an interior space between the inner and outer leaf through channels in the discontinuous longitudinal seam,

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in which the outer sheet is coated with a moisture barrier and the inner sheet is porous to allow air penetration.

The present disclosure also provides a use of the above bag to package a granular or powdered material.

The present disclosure also provides a method of filling the above bag, which comprises the step of filling the bag with a granular or powdered material. Air ventilation through the longitudinal seam is thus allowed by tubing the outer sheet with a discontinuous longitudinal glue seam instead of a continuous seam found in the bags of the prior art. The gaps in the discontinuous seam form air ventilation channels that are activated (opened) by the overpressure formed inside the bag during filling. This construction is greatly improved when the outer sheet sticks to the inner sheet in the discontinuous longitudinal seam.

Brief description of the drawings

The invention is now described, by way of example, in reference to the accompanying drawings, in which:

Figure 1 shows a schematic cross-sectional view of three embodiments of a bag according to the present disclosure.

Figure 2 is a schematic side view of an embodiment of an unfilled bag according to the present disclosure.

Figure 3 shows a schematic longitudinal sectional view of a region of superposition of a sack according to the present disclosure.

Figure 4 shows the results of measurements of the normalized air flow (y axis (Nm3 / dm2 * h)) at different pressure coffees (x axis (mbar, kPa)) for six different bags according to the present disclosure and a reference bag. Figure 4 also shows lines representing typical standardized air flows for filling with mixed mortar (0.55 Nm3 / dm2 * h), cement (0.80 Nm3 / dm2 * h) and finely ground powder (1.20 Nm3 / dm2 * h).

Detailed description

Referring to the figures, a bag 100, 200 is provided as a first aspect of the present disclosure.

The bag 100, 200 comprises an inner sheet 101 and an outer sheet 102, 202. The outer sheet 102, 202 forms a longitudinally overlapping region 103, 203. The overlapping region comprises an inner layer 104 and an outer layer 105. A first terminal portion 106 of the outer sheet 102 forms the inner layer 104 and a second terminal portion 107 of the outer sheet 102 forms the outer layer 105. An inner 108 of the outer layer 105 is glued 221 to an exterior 109 of the inner layer 104 to form a discontinuous longitudinal seam 220. An interior 110 of the first terminal portion 106 sticks 113a, 113b, 113c to the inner sheet 101. In this way , the air can pass outside from an interior space 111 between the inner sheet 101 and the outer sheet 102 through channels 112, 212 in the discontinuous longitudinal seam 220.

The bag 100, 200 comprises two ends, an upper end 231 and a lower end 232. The lower end 232 is normally closed by folding and glue, also before filling the bag 100, 200. The folding and gluing patterns to close a Sack ends are well known in the field. The upper end 231 may be open or partially closed before filling so that the bag can then be filled. Accordingly, the upper end 231 may comprise a valve opening for filling with a spigot. The bag of the present disclosure can thus be a valve bag.

"Longitudinally extending" means that it extends in the longitudinal direction of the bag 100, 200, which is the direction from the lower end 232 to the upper end 231 of the bag 100, 200. The longitudinal seam 220 thus extends between the ends 231,232 of the bag 100, 200.

As mentioned above, the interior 110 of the first terminal portion 106 is bonded 113a, 113b, 113c to the inner sheet 101. The specific parts of the interior 110 of the first terminal portion 106 that are attached to the inner sheet 101 may be completely within the overlap region 103 as shown in Figure 1a, partially within the overlay region 103 as shown in Figure 1b or outside the overlay region 103 as shown in Figure 1c. It is preferred that the specific parts in question are partially or completely within the region of overlap 103.

Accordingly, in an embodiment of the first aspect, an interior of the inner layer 104 of the overlap region 103 is bonded 113a to the inner sheet 101.

In one embodiment, the interior of the inner layer 104 of the overlap region 103 is bonded 113a, 113b to the inner sheet 101 in the channels 112, 212. In such an embodiment, at least some of the parts of the inner layer 104 are

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glue 113a, 113b to the inner sheet 101 on the inner faces of the channels 112 on the outside 109 (see Figure 3). Such a glue pattern can facilitate air ventilation as it allows channels 112 of larger cross section to be formed.

Accordingly, the inside of the inner layer 104 can be glued to the inner sheet 101 by a discontinuous glue bead. However, in an alternative embodiment, the interior of the inner layer 104 can be glued to the inner sheet 101 by a continuous glue cord.

The outer sheet 102 is coated with a moisture barrier. Therefore, the bag of the first aspect may not have a plastic film disposed between the outer sheet 102 and the inner one 101. Such a plastic film, which is also called "free film", is often used in bags of the prior art. to provide a moisture barrier.

Various moisture barrier coatings that can be applied to the sack paper are known to the person skilled in the art. The barrier coating may have one or more components. The coating weight of the barrier coating layer can be for example between 5-25 g / m2. When the barrier coating is applied, the water vapor transmission rate (WVTR, ISO 2528) of the outer sheet 102 is normally less than 1350 g / m2 * 24 h and preferably less than 1250 g / m2 * 24 h. For example, the WVTR of the multilayer paper material of the present disclosure may be between 750-1150 g / m2 * 24 h. However, the bag concept of the present disclosure can also be used with higher rates of water vapor transmission, such as 2500-3500 g / m2 * 24 h.

The air permeability of the outer sheet 102 is normally very low when the moisture barrier coating is applied, but that is not a problem since air can escape through the channels 112, 212 in the discontinuous seam 220.

The inner sheet 101 is porous to allow air penetration. The air resistance according to Gurley (ISO 5636/5) is a measurement of the time it takes for 100 ml of air to pass through a specific area of a sheet of paper. A short time means a high porosity paper.

The Gurley porosity (ISO 5636/5) of the inner sheet 101 is preferably less than 15 s. For example, it can be less than 10 s, such as 2-8 s, such as 3-7 s.

The weight of the inner sheet 101 is for example 50-140 g / m2. Preferably, it is 50-130 g / m2, such as 60-120 g / m2, such as 60-110 g / m2, such as 70-110 g / m2.

The weight of the outer sheet 102, which may comprise the barrier coating, is for example 50-150 g / m2. Preferably, it is 50-140 g / m2, such as 60-130 g / m2, such as 60-120 g / m2, such as 70-120 g / m2.

Tensile strength is the maximum force that a paper will withstand before breaking. In the standard ISO 1924/3 test to measure the parameter, a 15 mm wide and 100 mm long strip was used with a constant elongation index. Tensile strength is a parameter in the measurement of tensile energy absorption (ASD). In the same test, tensile strength, stretching and TEA value are obtained.

The TEA is sometimes considered as the property of the paper that best represents the relevant resistance of the wall of the paper sack. This is supported by the correlation between ASD and coffee tests. When you drop a sack, the goods that fill it will move when you reach the ground. This movement means a tension in the wall of the sack. To withstand the tension, the ASD should be high, which means that a combination of high tensile strength and good stretching on the paper will absorb the energy.

If the index of a paper property is necessary, it should be calculated by dividing the current value by the weight for the paper in question.

Pleated paper improves the stretchability in the machine direction (MD) and therefore the TEA index. Accordingly, the inner sheet 101 and / or the outer sheet 102 of the present disclosure can be pleated.

In embodiments of the present disclosure, the rate of tensile energy absorption (ISO 1924-3) of the inner sheet 101 and / or the outer sheet 102 may be for example at least 1.8 J / g, such as at least 2 J / G, such as at least 2.2 J / g, both in the machine direction (MD) and in the transverse direction (CD). In addition, the tensile index of the inner sheet 101 and / or the outer sheet 102 may for example be at least 50 kNm / kg (ISO 1924/3), such as at least 60 kNm / kg, in the machine direction ( MD) and at least 35 kNm / kg, such as at least 38 kNm / kg, in the transverse direction (CD).

To further facilitate the formation of channels 112, 212, the expandability of the outer sheet 102 may be greater than the expandability of the inner sheet 101. This can also be expressed as that the tensile stiffness (ISO 1924-3) of the inner sheet 101 is greater than the tensile stiffness of the outer sheet 102.

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The above strength properties can, for example, be obtained by selecting a bleached and / or unbleached brown bag paper for the inner sheet 101 and / or the outer sheet 102. Such brown bag papers are for example sold by BillerudKorsnas AB under the name QuickFill ®.

In one embodiment, the discontinuous seam 220 comprises at least one glued portion 221 and at least one unglued portion having a length in the longitudinal direction of at least 10 mm, such as at least 15 mm. For example, the discontinuous seam 220 may comprise at least two, such as at least three or four, glued portions 221 separated by unglued portions. In addition, the discontinuous seam 220 may comprise at least two, such as at least three or four, unglued portions separated by glued portions 221. A glued portion 221 may have a length in the longitudinal direction of 5-100 mm, such as 10 -50 mm A portion not attached can have a length in the longitudinal direction of at least 5 mm, such as at least 10 mm, such as 10-100 mm, such as 15-100 mm, such as 15-80 mm.

In one embodiment, the discontinuous seam 220 may comprise at least one unglued portion having a length in the longitudinal direction of at least 40 mm, such as at least 50 mm.

Bags are usually filled from the bottom to the top. Accordingly, it may be beneficial to provide at least one portion not glued near the upper end 231 of the bag 100, 200. In one embodiment, the discontinuous seam 220 thus comprises an upper half and a lower half, in which the upper half is closer to the upper end 231 and comprises at least one of the unglued portions, such as an unglued portion having a length in the longitudinal direction of at least 40 mm.

Sack 100, 200 of the present disclosure can be designed to allow "superior deaeration" in addition to "longitudinal deaeration" through channels 112, 212 in discontinuous longitudinal seam 220. In comparison to deaeration that depends on pores on the outer sheet, the "upper deaeration" and the "longitudinal deaeration" are both compatible with an outer sheet 102, 202 coated with a moisture barrier.

In one embodiment of the bag 100, 200, the upper end 231 is thus formed by folding and optionally gluing the sheets 101, 102 so that a portion of the upper end 231 is not sealed. In such an embodiment, the folding and optional gluing are such that the air can escape through the unsealed portion during filling of the bag 100, 200.

The width of the overlap region 103, 203 may be for example 0.3-7 cm, such as 0.5-5 cm. A width of 1-3 cm is preferred since it is sufficient overlap to provide reliable sewing and is compatible with most of the conversion process. If the width is above 3 cm, it may be difficult for channels 112, 212 to open during filling. In addition, paper consumption increases with a greater overlap.

The width of the glued portions 221 of the discontinuous longitudinal seam 220 may be for example 0.5-1.5 cm. On each side of the glued portions, the distance to the end of the overlap region may be 0.2-1 cm, such as 0.3-0.7 cm. Accordingly, the width of the overlap region may be 0.9-3.5 cm and preferably 1.1-2.9 cm when the width of the glued portions 221 of the discontinuous longitudinal seam 220 is 0.5-1 , 5 cm

The sack of the first aspect may be filled, for example, with goods having a fineness (measured in accordance with ASTM C204-11) above 4000 cm2 / g, such as above 5000 cm2 / g. An example of such fine goods is high blaine cement.

As a second aspect of the present disclosure, a use of a sack according to the first aspect for packaging a granular or powder material is provided. Examples of granular or powdered material are hydraulic binders that include cement and other building materials such as powdered goods for the construction industry and ready-to-mix building materials. Additional examples are chemicals, minerals, garden fertilizers or animal foods.

In a preferred embodiment of the second aspect, the use is for packaging cement or finely ground goods, such as carbon black. The cement can for example be high blaine cement, in which the fineness (measured in accordance with ASTM C204-11) is above 4000 cm2 / g, such as above 5000 cm2 / g. Similarly, the fineness of finely ground goods can be above 4000 cm2 / g, such as above 5000 cm2 / g, such as above 6000 cm2 / g. The sack of the first aspect allows the filling of such fine material with a satisfactory filling rate.

As a third aspect of the present disclosure, a method of filling a bag according to the first aspect is provided, which comprises the step of filling the bag with a granular or powdered material. Examples of granular or powder material have been provided before in relation to the second aspect.

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Examples

Tests were carried out with paper bags that had an inner sheet and an outer sheet. The inner sheet of the sacks was highly porous (Gurley 3-6 seconds). In addition, the bags did not have a free film. Instead, the outer sheet of the bags was coated with a moisture barrier. Such a barrier significantly limited air penetrability. The outer sheet of the bags formed a region of overlap of longitudinal extension with a width of 20 mm. In the overlap region, two ends of the outer sheet were glued together by a longitudinal discontinuous seam. The glue pattern of the discontinuous seam differed between the sacks tested, as shown in the table below. For each bag, the longitudinal seam was glued 50 mm from both sides of the tuber to have a robust construction. In between, there were regions not stuck and stuck in a repetitive pattern. In addition, a bag with a continuous longitudinal seam was included as a reference. The lower ends of the bags were completely closed by folding and gluing in a conventional manner. In comparison, the upper ends did not close completely to allow superior deaeration during filling.

 Bag No.

 Length of each region not pasted (mm) Length of each region pasted (mm)

 one

 25 50

 2

 20 20

 3

 30 30

 4

 40 40

 5

 40 20

 6

 70 mm, below the valve, only one region not attached All except the 70 mm opening

 Reference

 - The entire length was pasted

Air permeability was measured in a Haver Airflow Tester® (Mega Gurley) that measures the air flow in m3 / h at different pressure coffees. These results were standardized for the bag sizes and specifically the area of the bags that normally allows air ventilation according to the following formula: [Bag width * Bag length * 2]. The results of the measurements are shown in Figure 4, which also indicates the desired normalized flow rates for filling with mixed mortar, cement and finely ground powder, respectively.

Figure 4 shows that for the normalized flow associated with filling with mixed mortar (0.55 Nm3 / dm2 * h), the pressure coffee was lower for all bags with a discontinuous seam (bags 1-6) than for the reference bag with a continuous seam. For the standard flow rate associated with filling with cement (0.80 Nm3 / dm2 * h), the pressure coffee was at least 30% lower for all bags with a discontinuous seam (bags 1-6) than for the bag reference. A lower pressure coffe means that a shorter filling time can be obtained.

Figure 4 also shows that the normalized flow associated with filling with finely ground powder (1.20 Nm3 / dm2 * h) cannot be reached at a pressure of 10 kPa (100 mbar) for the reference bag, while For all bags with a discontinuous seam (bags 1-6), a pressure coffee below 10 kPa (100 mbar) was sufficient.

Figure 4 also shows a 50-90% improvement in deaeration at 10 kPa (100 mbar) for bags with a discontinuous seam compared to the reference bag.

Finally, Figure 4 shows that bags 1 and 2 had the best deaeration values at an overpressure of 5 kPa (50 mbar). The other bags showed progressive behaviors with improved deaeration with increased overpressure above 5 kPa (50 mbar). The best result at 10 kPa (100 mbar) was obtained for bag 5, which had 118% better deaeration compared to the reference bag.

Claims (13)

5 10 fifteen twenty 25 30 35 40 Four. Five fifty 55 1. A bag (100, 200) having an inner sheet (101) and an outer sheet (102, 202), in which: the outer sheet (102, 202) forms a longitudinally overlapping region (103, 203) comprising an inner layer (104) and an outer layer (105); a first terminal portion (106) of the outer sheet (102, 202) forms the inner layer (104) and a second terminal portion (107) of the outer sheet (102, 202) forms the outer layer (105); an interior (108) of the outer layer (105) is glued (221) to an exterior (109) of the inner layer (104) to form a discontinuous longitudinal seam (220); Y an interior (110) of the first terminal portion (106) is glued (113a, 113b, 113c) to the inner sheet (101), so that the air passes out from an inner space (111) between the inner sheet (101) ) and the outside (102, 202) through the channels (112, 212) in the discontinuous longitudinal seam (220), characterized in that the outer sheet (102, 202) is coated with a moisture barrier and the inner sheet (101) is porous to allow air penetration. 2. The bag according to claim 1, wherein the Gurley porosity (ISO 5636/5) of the inner sheet (101) is less than 15 s, such as less than 10 s, such as 2-8 s , such as 3-7 s. 3. The sack of any one of claims 1-2, wherein a plastic film between the inner sheet (101) and the outer sheet (102) is not provided. 4. The sack of any one of claims 1-3, wherein the discontinuous seam (220) comprises at least one glued portion (221) and at least one unglued portion having a length in the longitudinal direction of at least 10 mm, such as at least 15 mm. 5. The sack of claim 4, wherein the discontinuous seam (220) comprises at least two, such as at least three, separate non-glued portions, each with a length in the longitudinal direction of at least 10 mm, such at least 15 mm 6. The bag of claim 4, wherein the discontinuous seam (220) comprises at least one portion not glued with a length in the longitudinal direction of at least 40 mm, such as at least 50 mm. 7. The sack of any one of the preceding claims, wherein the sack comprises an upper end (231) through which it is filled and the discontinuous seam (220) comprises an upper half and a lower half, wherein the upper half is closer to the upper end (231) and comprises at least one portion not attached. The bag of any one of the preceding claims, wherein the bag comprises an upper end (231) formed by folding and gluing the sheets, in which a portion of the upper end (231) is not sealed by gluing so that the air can escape through the unsealed portion during the filling of the bag. 9. The sack of any one of the preceding claims, wherein the width of the overlap region (103, 203) is 0.3-7 cm, such as 0.5-5 cm, such as 1-5 cm , such as 1.5-3 cm, such as 1-3 cm. 10. Use of a sack (100, 200) according to any one of the preceding claims for packaging a granular or powdered material, such as cement, building materials, powdered goods for the construction industry, building materials ready to mix, chemicals, minerals or garden fertilizers. 11. Use of a bag (100, 200) according to claim 10 for packaging cement. 12. Method for filling a bag (100, 200) according to any one of claims 1 to 9, comprising the step of filling the bag with a granular or powder material. 13. Method according to claim 12, wherein the fineness measured in accordance with ASTM C204-11 of 2 1 2 powder material is above 4000 cm / g, such as above 5000 cm / g.