FI102527B - Bag - Google Patents

Description

102527 Sack - Säck Field of technology

The invention relates to multilayer paper bags and relates in particular to reinforcing or stiffening their mouths.

Technology background

Sacks that can be closed by sewing are most easily torn under stress at the perforated jpmm seam. To prevent tearing, these bags generally use stronger paper or more layers of paper than would be necessary for the other parts of the bag.

FI-75318 discloses a way of reinforcing the stitching of a sealable paper bag by sewing. Accordingly, a separate paper reinforcement strip is glued to the seam.

Description of the invention A paper bag according to claim 1 has now been invented. Some advantages of the invention. . Additional applications are set out in the other claims.

The sack according to the invention is closed by a transverse seam so that in the seam the inner surface of the sheath comes into contact with the inner surface. At least two layers of the sack are glued together from the area of the sealing seam. This results in a substantially stronger seam of the paper; 20 without adding. In addition, the end result is cooler when there is no extra paper on the bag.

The gluing according to the invention also stiffens the sack, which is an advantage especially in automatic equipment when handling open sacks.

It is best to extend the adhesive strip around the entire sheath. However, sufficient strength can also be provided by two strips made in the middle of the side of the sheath.

One application of the invention is to open an openable bag by sewing. Another application is a valve bag with both mouths closed by sewing.

Sacks according to the invention can be made on conventional sack making lines which generally have suitable means for forming the adhesive strips according to the invention. The gluing can be performed, for example, in a line printing unit or in a cross-gluing unit.

The gluing is most preferably performed so that the glue does not protrude substantially into the paper.

Some embodiments of the invention are described in more detail below. In the drawings of the description, Figures 1a to 1e show a two-layer sack and Figure i shows the gluing of an adhesive strip of a three-layer sack on a line printing machine.

Figure 1a shows an empty, folded two-layer open sack with a flat bottom closed by gluing. The mouth is intended to be closed after filling by suturing. The location of the seam is marked with a dashed line 1. At the seam, the paper layers are glued to the entire circumference of the bag with an adhesive strip 2. A suitable width of the adhesive strip is about 2-6 cm. A suitable amount of adhesive is, for example, about 14 g / m 2 calculated as dry matter.

Fig. 1b shows a sack for filling when opened and Fig. 1b shows a sack filled and closed by sewing.

The strengths of modern sack papers have increased, making it possible to use thinner papers or fewer layers than before. However, this has also resulted in a reduction in the stiffness of the sacks, which has become on-20 gelms in filling machines. For example, in a conventional open bag closure line, the filling. The compressed mouth of the bag should remain upright as the bag passes to the sealing machine.

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The adhesive strip 2 also acts as a stiffener for the mouth of the sack. For this purpose, the adhesive strip can also be made wider than would be necessary to reinforce the seam point 25 alone. In a 50-60 cm wide sack with a height of about 80-100 cm when filled, a suitable stiffening strip width is, for example, 15-20 cm aligned with the beginning of the compression part of the sack. The stiffened compressed mouth does not tear to the side, but remains upright.

Instead of a strip extending around the entire sheath, adhesive strips made in the middle of the side, for example about 25-75% of the width of the side, can be used.

3 102527

Figure 2 shows the manufacture of a three-layer bag using a conventional production line line press. The inner layer consists of track 3, the middle layer of track 4 and the outer layer of track 5. The tracks are run on top of each other and then fed to a bag machine where a hose is formed by gluing the edges together longitudinally, the hose 5 is cut into pieces and the other end is closed.

The inner layer track is driven through the brush roller 6, the top folding roller 7 and the guide roller 8. The surface of the strip roll has a plate 9, by means of which a transverse adhesive strip is applied to the outer surface of the track at cutting intervals. Glue is introduced to the lubrication roll from the basin 10 by means of a lifting roll 11 and a sweeping roll 12. Of course, instead of a rotating roll, 10 rotating roll segments can also be used.

The adhesive is transferred to the surface of the web 3 without substantial compression so that it does not protrude into the paper. The folding roller 7 can be moved and thus the track tension and angle against the brush roller 6 can be adjusted. In this way, the brush is always optimized. An adhesive coating unit of the type described can be conveniently provided on sack lines in the conventional manner. line weight of the unit. However, when the printing unit is normally used for printing, the roll 8 is pressed against the roller 6. Such a printing unit 13 is also present in the apparatus according to Fig. 2. It is used to print the desired monochrome pattern on the outer layer web 5. The apparatus also has a third printing unit 14 which can be used to print a second color. If desired, this unit can also be converted into an adhesive-20 coating unit, in which case the outer layer and the middle layer can also be glued to each other. The gluing units are, of course, synchronized with the bag machine so that the gluing strip always comes in sync with the sealing and cutting point.

The gluing according to the invention can also be performed by cross-gluing the hose machine. group. In this case, free cross-adhesive groups must be used, which can be applied to gluing on the same principles as the line printing devices described above.

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A suitable starch glue can be used for gluing, which is preferred and is normally used for gluing sacks. However, other adhesives can also be used. For example, synthetic dispersion adhesives (such as polyvinyl acetate, PVAC) provide an even better reinforcing effect. Adhesive mixtures can also be used.

Table 1 below compares, by way of example, the mutual tear strengths (mN) of the seam seams of different sacks in both the track direction (MD) and the cross direction (RD) when the seam point was not glued or glued with starch or PVAC glue according to the invention. The paper was sack paper, basis weights 80, 95 and 100 g / m. All layers were glued together. The width of the adhesive strip was about 4 cm and the amount of adhesive in the dry matter was 2-4 g / m 2. Tear strength was determined according to SCAN methods.

Table 1 __Number and basis weight of paper layers_ __3 * 100 g / m2__4 * 80 g / m2__2 * 95 g / m2

__MD mN CD mN MD mN CD mN MD mN CD mN

No glue 940 1000 1050 1200 650 780 Starch 1200 1520 2260 2060 945 1015 PVAC 1270 1630 2270 2440 5 It is noted that gluing the paper layers together significantly increased the strength of the seam.

As an example, Table 2 compares the bending resistance of different open sacks in the MD direction. All layers of the sack were glued together. The width of the adhesive strip was about 15 cm and the amount of adhesive in dry matter was 1-3 g / m. The bending resistance was determined according to SCAN methods.

Table 2 __Number of paper layers and basis weight __3 * 80 g / m2 4 ♦ 70 g / m2 2 ♦ 80 g / m2

__mN__mN__mN

No glue__170__105__120. Starch__1385__1100__475. !!!: PVAC 1325__1035__460

It is noted that gluing the paper layers together increased the stiffness of the mouth quite substantially.

15 When using adhesive reinforcement, thinner papers or fewer paper layers can be used, which naturally reduces material costs.

Claims (10)

102527 A paper bag with a tubular sheath comprising at least two layers of paper, which is intended to be closed by a transverse seam (1) so that the inner surface of the sheath abuts the inner surface in the seam, characterized in that at least two of the sheath layers are glued together in a transverse adhesive strip (2). ). A sack according to claim 1, which is intended to be closed by a transverse seam (1). A flat-bottomed open sack according to claim 1 or 2, the mouth of which is intended to be closed by a seam (1). Sack according to one of Claims 1 to 3, characterized in that the adhesive strip • '(2) extends around the entire casing. Sack according to one of Claims 1 to 4, characterized in that the width of the adhesive strip (2) is 2 to 6 cm. Sack according to one of Claims 1 to 4, characterized in that the adhesive strip the width is 15-20 cm. 7. A method of making a paper bag, comprising forming a tubular sheath comprising at least two layers of paper and a transverse closure region thereon through which the bag is intended to be sealed so that the inner surface of the sheath abuts the inner surface, characterized in that the paper layers: ... 20 are glued together with a transverse adhesive strip. A method according to claim 7, wherein the tubular sheath is formed of at least two paper webs which are driven on top of each other and folded and joined at their edges into a hose, characterized in that to form an adhesive strip on the at least one paper web against the other paper web. a transverse adhesive strip is applied to the incoming surface 25 at regular intervals so that the adhesive does not imprint on the surface of the web. Method according to Claim 8, characterized in that the adhesive strip is brushed by means of a rotating roller. 10. A method of making, filling and sealing a paper bag, the method comprising forming a tubular sheath comprising at least two layers of paper, closing one end thereof as a base, leaving an open mouth at the other end, filling the bag orally and closing the mouth by sealing the inner surface comes against the inner surface, characterized in that at least two layers of paper are glued together in the mouth of the sheath with a transverse adhesive strip and the mouth is closed by sealing at this adhesive strip. 5 Patentkrav