EP2356030B1

EP2356030B1 - A method for making form fill seal pouches

Info

Publication number: EP2356030B1
Application number: EP09751863A
Authority: EP
Inventors: Krishnaprakash Nurani Dharmaraj Iyer; Vaibhavi Amit Khedekar; Endah Sulistyowati; Pardeep Kaur Surinder Singh Vilkhu
Original assignee: Unilever PLC; Unilever NV
Current assignee: Unilever PLC; Unilever NV
Priority date: 2008-12-12
Filing date: 2009-10-30
Publication date: 2012-08-01
Anticipated expiration: 2029-10-30
Also published as: BRPI0922072B1; BRPI0922072A2; CN102245475B; WO2010066509A1; AR074666A1; CN102245475A; ES2392682T3; EP2356030A1

Abstract

The invention relates to a method and a system of continuously forming, filling and sealing side-gusseted flexible pouches with product, comprising the steps of : (i) providing a continuous sheet of film; (ii) drawing said sheet over a pouch-former to form a film tube having an overlapped vertical film edge; (iii) sealing said overlapped vertical film edge with a vertical sealer to form a vertical seal, while said film-tube is continuously pulled along machine direction; (iv) forming gussets on both lateral sides of the tube; (v) effecting a horizontal seal across said film- tube, with horizontal sealing jaws, at a predetermined location below said vertical sealer to form the top horizontal seal of a filled pouch and the bottom horizontal seal of a pouch to be filled, optionally with perforations there-between; (vi) feeding said product within said film-tube; and, (vii) sealing open end of said film-tube with said horizontal sealing jaws at a pre-determined location, where at the intersection of the horizontal seal with inner ends of the gussets, an un-sealed pocket extending on either sides of the intersection is formed, wherein width of the un-sealed pocket is in the range of 25 to 50 % of the total width of the gusset.

Description

FIELD OF INVENTION

The present invention relates to a method for making flexible side-gusseted pouches on a form-fill-seal machine.
The invention has been developed primarily for use in detergent powders and will be described hereinafter with reference to this application. However, it will be appreciated that the invention is not limited to this particular field of use.

BACKGROUND AND RELATED ART

Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of the common general knowledge in the field.
Pouches, or bags made of plastic films are used for packaging various products like creams, powders, liquids, tablets, noodles, granular detergents and pastes. Pouches enable packaging and sale of these products in small, as well as large quantities, typically in the range of 200g to 10kg.
In the case of pouches or bags made from a single sheet of a film, or a laminate, the structure of the pouch is such that it does not expand during filling but has a generally similar shape and configuration, when empty or full. To increase the available space for filling, it is very common to have pouches with side-gussets along both its longitudinal sides, connecting the front and back surfaces of the pouch. Gussets allow the front and rear surfaces to expand away from each other when the pouch is filled. The gusset structure is advantageous, since it permits the unfilled pouch to be substantially flat when empty, and then to expand to a full depth as the pouch is filled with material. Side gusseted pouches are described in US 2008/137998 A1 (KONINKL PHILIPS ELECTRONICS)
One of the problems of side-gusseted pouches is that when such pouches are filled, especially with high bulk-density detergent powders, it is commonly observed that the pouches show an un-acceptably high rate of failure in the "Bag Drop" test. In this test, filled pouches are dropped from a pre-determined height to the ground, and it is checked whether any seal of the pouch opens up (fails) as a result of the impact. The particular areas of concern are the four inner corners of the pouches. In these corners, due to the gussets, four layers of the film/laminate come together to be sealed. It is generally believed that the reason for failure lies in the difficulty to ensure a cohesive seal between the four layers. In addition, there is a lot of stress that gets generated at these corners which leads to rupture (failure). From a commercial point-of-view, it is preferred that the rate of failure is less than 5 %, and more preferably less than 1 %.
Some attempts have been carried out in the past to solve this problem. The easiest way is to use a thicker laminate, typically a 3-ply film. However, this is not a cost-effective solution.
WO 1995/10566 A1 (DUPONT CANADA INC) describes a process for making pouches on a vertical FFS machine, which show low rate of failure in the Bag Drop-Test. In this case, the laminate has one layer of a blown film formed from a blend which includes a linear polymer of ethylene with at least one C₄-C₁₀ alpha-olefin, which is manufactured in a single-site catalyst polymerization process. The laminate also includes at least one of a linear polymer of ethylene with at least one C₄-C₁₀ alpha-olefin made by a multi-site catalyst polymerization process; a high pressure low density polyethylene; and additives selected from the group consisting of stabilizers, anti-block additives and extrusion aids. A limitation of this process is that one needs to have the special grade of laminated films, and the process would not work with any other material.
JP/2006/264765A (DAINIPPON PRINTING CO LTD) describes a process to prevent a gusset bag from being broken and generating a pin-hole at its gusset part, in which the sheet forming the gussets is folded into two and inserted between the front and back panels of the pouch, so as to extend along their one side. It is said that with this type of sealing arrangement; stress that tends to be concentrated at the crossing point is dispersed and the bag is prevented from being broken. A drawback of this disclosure is that the extra folds of gussets mean utilisation of higher amount of packaging material. This would therefore, be a relatively expensive route and also not practical on a VFFS (Vertical Form-Fill-Seal) machine.
JP/2005/104572A (FUJITA KIKAI KK; HAYASHI SANGYO KK) describes a square-cornered pouch, in which, in addition to the lower horizontal seal, there are two additional vertical seals near the bottom of the pouch (one adjacent to each gusset) such that this extra sealing lines extend vertically to the upper end of the pouch for some distance, whereafter the sealing lines are inclined at 45 degrees with respect to the gusset folds. The pouches also have reinforcing seals having a circular arc which are provided by piling four films of the front face and back face of the bag and the gusset fold and bonding them integrally by fusion. The arcuate seals are adjacent to the inner edges of the gusset fold, and it contacts the extra sealing lines that extend vertically upward. A primary drawback of such pouches is that, as the entire width of the pouch is sealed in the horizontal seal, it becomes essential that either the outermost layer of the laminated film has to be of heat-sealable grade, or a special type of lacquer is used to seal the layer in case the outermost layer is not heat-sealable. This limits the use of this process.
Japanese unexamined Patent Application No. JP/02/173149A (YUKAWA SEITAI, Co. Ltd, 2002) aims to solve the same problem of pre-formed plastic pouches with side gussets, where failure occurs at the points where the horizontal seal meets the inner ends of the gussets. This has been solved by providing non-sealed curved pockets at the points of intersection. It is known that while using pre-formed pouches for filling and packaging of products, the overall speed of filling and packaging is low as the pouches are formed at one station, and then filled and sealed at a different station. Further, in the case of such pre-formed pouches, as only one bag is handled at a time, there is relatively little shift in the relative alignment of the gussets with the sealing jaws during the sealing operation. Further, as the bags have already been manufactured offline, very little shift in the centre-line of the gussets is observed. On the other hand, in the case where plurality of side-gusseted pouches are made in an on-line method using VFFS machines; as the pouches are made in a continuous manner at high throughput rates and efficiency, there is an appreciable shift in the relative alignment of the gussets with the sealing jaws, as well as an appreciable shift in the centre-line of the gussets. This is further compounded by the fact that due to the fall-height of product, especially in the case of fills over 1 kg; where gravity acts on the filled and suspended pouch; the pouches deviate from their ideal mean positions, and this therefore, affects the seal strength at the four inner corners of the pouch. This may be further complicated by the stiffness and thickness of the laminate and the machine settings, including its speed. The appreciable shift in the relative alignment of the gussets with the sealing jaw, as well as the appreciable shift in the centre-line of the gussets, would therefore nullify the effect of the presence of the curved pocket provided in the horizontal seals at the inner corners. Thus there would still be a significant amount of failure in the Bag Drop-Test.
Thus, there is a need for a method for making side-gusseted pouches on a vertical form, fill, seal machine which takes care of the shift in the relative alignment of the gussets with the sealing jaws, as well as the shift in the centre-line of the gussets, where the pouches show relatively lower rate of failure in the Bag Drop-Test.

OBJECT OF THE INVENTION

It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art.
It is an object of the present invention to provide a method for making relatively stronger side-gusseted pouches on a vertical form, fill, seal machine.
Other objects of the present invention will become apparent to those skilled in the art by reference to the specification.

SUMMARY OF THE INVENTION

The present invention provides a method of continuously forming, filling and sealing side-gusseted flexible pouches with product, comprising the steps of:

(i) providing a continuous sheet of film;
(ii) drawing said sheet over a pouch-former to form a film tube having an overlapped vertical film edge;
(iii) sealing said overlapped vertical film edge with a vertical sealer to form a vertical seal, while said film-tube is continuously pulled along machine direction;
(iv) forming gussets on both lateral sides of the tube;
(v) effecting a horizontal seal across said film-tube, with horizontal sealing jaws, at a predetermined location below said vertical sealer tc form the top horizontal seal of a filled pouch and the bottom horizontal seal of a pouch to be filled, optionally with perforations there-between;
(vi) feeding said product within said film-tube; and,
(vii) sealing open end of said film-tube with said horizontal sealing jaws at a pre-determined location,

Width of the un-sealed pocket is in the range of more than 26.55 % to upto 40 %, further more preferably in the range of 30 to 40 %, and most preferably 33 % of the total width of the gusset. It is preferred that the un-sealed pocket is free of sharp corners or bends, and more preferably the corners are rounded-off. It is preferred that the un-sealed pocket is formed at least three inner corners of the pouch. It is preferred that the profile of the unsealed pocket is semi-circular, oval or ellipsoidal, more preferably semi-circular.
The terms "pouch" and "bag" have been used interchangeably throughout the specification.
The present inventors have observed that the maximum shift in the centre-line of the gussets is 13.33 % of its total width. Thus for example, for a total gusset width of 60 mm, the ideal situation is when the centre-line of the gusset is at 30 mm, i.e. width of both gusset ears is 30 mm each. However, the present inventors have found that the maximum shift in the centre-line could be by 8 mm, which amounts to 13.33 % of the total gusset width. This means that the centre-line of the gussets could be anywhere between 22 to 38 mm, when measured from one end of the gusset. In this case, the width of the individual gussets would be different and not 30 mm each. It is preferred that the width of the un-sealed pocket is more than 200 % of the maximum shift in the centre-line of the gussets, more preferably at least 250 % and upto 300 % of the shift in the centre-line of the gusset. It is highly preferred that the width is 250 % of the maximum shift in the centre-line of the gussets. Thus, for example, where the maximum shift in the centre-line of the gusset is 8 mm, the width of the un-sealed pocket is more than 16 mm, more preferably, at least 20 mm, and upto 24 mm. It is highly preferred that the width of the un-sealed pocket is 20 mm, which is 250 % of 8 mm.
It is preferred that the height of the un-sealed pocket is less than 35 % of the height of the horizontal seal, preferably in the range of 10 to 30 %, and more preferably in the range of 10 to 20 %. Excessive height may weaken the horizontal seal. While the method can be used to form pouches with the un-sealed pockets formed at least three corners of the pouch, it is possible to form the pockets at all four corners. It is preferred that the height of the horizontal seal, preferably the top horizontal seal, at one end is in the range of 167 to 240 % of the general height of the seal, wherein a notch/slit is provided on both or one side of the gussets-ears at the end, the notch/slit being positioned below the un-sealed pocket at the opposite end of the horizontal seal. Thus, for example, when the general height of the horizontal seal is 15 mm; the seal height at the end of the seal, where the notch/slit is to be provided, is preferably in the range of 25.05 to 36 mm, more preferably 30 mm. It is preferred that the notch is provided 5 to 10 mm, preferably 5 mm below the un-sealed pocket at the opposite end of the same horizontal seal.
Preferably, the gusset ears are not sealed to each other. Having introduced the un-sealed pockets, it is not essential to seal the gusset-ears to each other for low rate of failure in Bag-Drop test. However, in a less preferred embodiment, if the outermost layer of the laminated film is of heat-sealable grade, or a special type of lacquer is used to seal the layer, in case the outermost layer is not heat-sealable, the gusset-ears could be sealed to each other, thereby further reducing the rate of failure.
Pouches may be manufactured from a variety of materials. It is particularly advantageous, however, that they be constructed, at least partly, from relatively thin, strong material such as Polyethyleneterepthalate (PET), which is polyester; biaxially oriented nylon (BON), linear low density polyethylene (LLDPE), commonly abbreviated as PET/BON/LLDPE film. For example, the following combinations, some with multiple layers or ply of the same material, may be used for making the pouches. It is preferred that 2-ply laminates are used, but, if desired, 3-ply laminates can also be used, although these laminates are less preferred because of their cost.

Polyester/adhesive (or Extrusion Poly)/ Linear Low Density P.E film (2-ply)
Polyester/ adhesive (or Extrusion Poly)/ Polyester/ adhesive (or Extrusion)/ Linear Low Density P.E. film (3-ply)
Polyester/adhesive (or Extrusion poly)/ Aluminium foil/adhesive (or Extrusion poly)/LLDPE (3-ply)
Polyester/adhesive/Metallised Polyester/adhesive/LLDPE (3-ply)
Polyester/adhesive/Nylon/adhesive/LLDPE (3-ply)
Polyester/adhesive/Nylon/adhesive/Aluminium foil /adhesive/LLDPE
Nylon/adhesive/LLDPE (2-ply)
Nylon/adhesive/Metallised Polyester/adhesive/LLDPE (3-ply)
Nylon/adhesive/ Aluminium Foil/adhesive/LLDPE (3-ply)
Nylon/adhesive/Nylon/adhesive/LLDPE (3-ply)
Nylon/adhesive/Nylon/adhesive/Aluminium Foil/ LLDPE (3-ply)

Other materials such as Polypropylene may also be used in place of the above or in combination with the other materials. Material thickness may also vary.
It is preferred that the sheet of film is a 2-ply laminate of 10/12 micron Polyethyleneterepthalate and 70/80 micron Polyethylene. Alternatively, and more preferably, a 2-ply laminate of 10/12 micron Polyethyleneterepthalate and 70/80 micron Easy-tear Polyethylene is used to make the pouches.
In an alternate embodiment, the method according to this invention may be used to make "Quad-packs". The general method for making quad-packs is well-known to a person skilled in the art.
The term "comprising" is meant not to be limiting to any subsequently stated elements but rather to encompass non-specified elements of major or minor functional importance. In other words the listed steps, elements or options need not be exhaustive. Whenever the words "including" or "having" are used, these terms are meant to be equivalent to "comprising" as defined above.
Except in the operating and comparative examples, or where otherwise explicitly indicated, all numbers in this description indicating amounts of material ought to be understood as modified by the word "about".
It should be noted that in specifying any range of concentration or amount, any particular upper concentration can be associated with any particular lower concentration or amount.
For a more complete understanding of the above and other features and advantages of the invention, reference should be made to the following detailed description of preferred embodiments.

BRIEF DESCRIPTION OF THE FIGURES

A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying figures in which:

Figure 1 is the isometric view of a system for carrying out the method according to the invention; and
Figure 2 is front view of a horizontal sealing jaw of the system of Figure-1.
Figure-3 is front view of a pouch formed in the system of Figure-1.
Figure-4 is side-view of the pouch of Figure-3 with the gussets ears opened up.
Figure-5 is the isometric view of another embodiment of a pouch formed by a system according to the invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

In the detailed description, like numerals have been used to indicate like features.
Figure-1 is the isometric view of a system for continuously forming, filling and sealing side-gusseted flexible pouches with product according to the method of the invention. The system is constructed in the form of an enclosed frame on which all parts for the forming, filling, and sealing of the pouches are mounted.
In this figure, a continuous sheet of film 1 is un-wound from a roll (not shown) and is drawn/conveyed over conveying Aluminium rollers 2 and 3. It then reaches a forming shoulder 4 and later on, a pouch-former 5 (also called a forming tube). In this pouch-former, the sheet of film 1 is folded over itself so that the opposite longitudinal edges 6 and 7 are juxtaposed to form a common vertical film edge. A vertical sealer 8 then seals this common overlapped vertical film edge to form a film-tube. Pulling means (not shown) then continuously pull the film-tube 9 along machine direction, (shown by a solid arrow) as set on a stroke length lever (not shown). A pair of gusset pins 10 and 11 (means for forming gussets), disposed on either lateral sides of the film-tube than form gussets on both lateral sides of the film-tube. The film-tube is then sealed in the horizontal direction by a pair of horizontal sealing jaws 12 and 13 at a predetermined location below the vertical sealer 8. The horizontal sealing jaws have depressed areas, both represented by common numeral 14 which form un-sealed pockets at the intersection of the horizontal seal with inner ends of the gussets of the pouch. The same features are present in the other horizontal sealing jaw 12 (features not seen in this view). The horizontal sealing jaws simultaneously define the top horizontal seal 15 of the filled pouch 16, and the bottom horizontal seal 18 of the pouch to be filled 19. Perforations 20 are formed between the top horizontal seal 15 and the bottom horizontal seal 18 for later severing the filled and sealed pouches to form individual pouches therefrom. In heat-sealing system, which is used for majority of films/laminates, this severing action takes place separately, whereas in the Poly heat-sealing system, the sealing and severing actions take place at the same time, because knives are mounted on the sealing jaws itself. In the pouch to be filled 19, a product is continuously fed through means in the form of a tube 21, below the vertical sealer 8 and above the pair of horizontal sealing jaws 12 and 13. The open end of the film-tube is then sealed with the horizontal sealing jaws, at a pre-determined location, which corresponds to a distance of one bag length. The cycle is repeated to form plurality of pouches.
Referring now to Figure-2 which shows the front view of the horizontal sealing jaw 13 of the system of Figure-1, the jaw has a bottom-sealing section in the form of seal bar 22 and a top-sealing section in the form of another seal bar 23 with a knife-edge 24 there-between. At three corners, the jaw is provided with curved/semi-circular depressed areas, all represented by common numeral 14, with their corners rounded-off, so as to minimise sharp corners. The gusset alignment area is shown as L in the figure. At one end of the seal bar 23, the height of the seal bar "H-1" is greater than the general height of the seal bar "H". This feature gives extra sealing height to the pouch in the top-horizontal seal, so that an easy-tear notch can be formed in this sealed region with the cavity 25.
Turning now to Figures 3 and 4, the pouch 16 has a top horizontal seal 15 and a bottom horizontal seal 18. The seal height of a portion of the top horizontal seal 15 at one end 27 is greater than the general seal-height of the top-horizontal seal. Both corners of 27 are rounded-off. Three curved semi-circular pockets, all represented by the common numeral 26 can be seen at the three inner corners of the pouch, at the intersection of the horizontal seal with the inner ends of the gussets represented by the centre line of the gussets 28. Figure-4 shows the pouch of Figure-3 in a side view, where the gusset-ears have been opened up, to show the total width of the gusset "W". Common numeral 28 indicates the centre-lines of the gussets, and the pockets 26 extend across this line. Both corners of each pocket are rounded-off.
Figure-5 shows another embodiment of a pouch formed by a system according to the invention. The pouch has a top and bottom horizontal seals 15 and 18 respectively, with gusset-ears at one end shown by the common numeral 29. The seal height of a portion of the top horizontal seal 15 at one end 27 is greater than the general seal-height of the top-horizontal seal. Both corners of 27 are rounded-off. An easy-tear notch 30 is provided in this region, and the notch is positioned below the un-sealed pocket 26 at the opposite end of the same horizontal seal. Three curved semi-circular pockets; all represented by the common numeral 26, can be seen at the three inner corners of the pouch, and at the intersection of the horizontal seal with the inner ends of the gussets, which are the centre-lines of the gussets 28. The pockets 26 extend across their respective centre-lines. The gusset-ears have been opened up to show the total width of the gusset "W". Both corners of each un-sealed pocket 26 are rounded-off; so as to further reduce stress at the points by reducing sharp corners.
The invention will now be described in greater details with the help of the following non-limiting examples.

EXAMPLES

EXAMPLE-1

2250 pouches were made by the method in accordance with the invention and as described with reference to Figure-5. The pouches were made from a 2-ply laminate (10/12 micron Polyethyleneterepthalate and 70/80 micron easy-tear Polyethylene). Of the 2250 pouches, 1500 pouches were filled with 1 kg high bulk-density (BD) detergent powder, and 750 pouches were filled with 500 g of a low BD detergent powder. Specifications of the pouches were as follows:

Table-1

Total width of the gussets	60 mm
Width of the semi-circular pockets	20 mm (33% of the width of the gusset)
Height of the semi-circular pockets	4.5 mm
Shift in the centre-line of the gussets	There was a shift of 7 mm; gusset-ears were 23 mm and 37 mm respectively
Height of the top horizontal seal	15 mm
Height of the top horizontal seal at the end where easy-tear notch was provided	30 mm
Height of the bottom horizontal seal	15 mm

Of these 1500 pouches, 100 (from each set) were randomly selected for the Bag Drop-Test. The selected pouches were dropped on the floor from a height of four feet, four times, such that they fell on the bottom horizontal seal, so that the inner corners of the seal experienced the stress. The number of pouches which opened at least one gusset seal was recorded. For the control experiment, 1000 pouches were made from the same laminate, of which 500 were filled with 500 g low BD detergent powder, the remaining were filled with 1 kg high BD powder. The control pouches did not have any un-sealed pocket, other specifications being identical to the pouches according to the invention. Of the 1000 control bags, 100 (from each set) were also subjected to bag-drop test. The results are provided in Table-2 below. Table-2

Pouch code Number of pouches tested Number of pouches failing % failure

Control 100 (of each set) 8 (in both sets) 8 %

Invention 100 (of each set) 1 (in both sets) 1 %
The data in the above table indicates that the % failure in the case of inventive pouches was only 1 %, which is highly desirable.

EXAMPLE-2

In another experiment, pouches were made from different materials and had variation in the width of the semi-circular un-sealed pockets. The total width of the gusset in all cases was 60 mm and shift in the centre-line of the gusset was 8 mm, i.e. one gusset-ear was 38 mm, while the other was 22 mm. The pouches were filled with 1 kg high BD detergent powder. Some pouches were filled with 1 kg low BD powder. The pouches were subjected to drop-test as in Example-1 above. Details of the pouches and the results are shown in Table-3 below.

Table-3

Expt	Laminate Structure	Width of Pocket/mm	Width of pocket as % of total gusset width	Width of pocket as % of shift in centre-line	% failure
1*	A	NIL	-	-	2
	B	12	20	150	19
	B	NIL	-	-	18
2*	A	NIL	-	-	2
	B	15	25	187	7
	B	NIL	-	-	15
3*	A	NIL	-	-	2
	C	20	33	250	1
	B	20	33	250	1
	C	NIL	-	-	16
3**	C	20	33	250	1
	C	NIL	-	-	16

Note: In the above Table
Expt stands for Experiment
Laminate structure A was 10 PET / 10 PET / 70 Poly (3-ply)
Laminate structure B was 12 PET / 70 Poly (2-ply)
Laminate structure C was 12 PET / 80 Poly (2-ply)
* pouches were filled with 1 kg low BD detergent powder
** pouches were filled with 1 kg high BD detergent powder

Thus it can be seen from the results in the above table that pouches made in accordance with the preferred aspects of the method according to the invention showed only 1% failure in Bag Drop-Test.
It will be appreciated that the illustrated examples provide a method for making relatively stronger side-gusseted pouches on a vertical form, fill, seal machine.
It will be appreciated that the illustrated examples provide a method for making side-gusseted pouches on a form, fill, seal machine where the rate of failure of pouches in the Bag Drop-Test is relatively lower.
It should be understood that the specific forms of the invention herein illustrated and described are intended to be representative only as certain changes may be made therein without departing from the clear teachings of the disclosure.
Although the invention has been described with reference to specific embodiments, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.

Claims

A method of continuously forming, filling and sealing side-gusseted flexible pouches with product, comprising the steps of:
(i) providing a continuous sheet of film;

(ii) drawing said sheet over a pouch-former to form a film tube having an overlapped vertical film edge;

(iii) sealing said overlapped vertical film edge with a vertical sealer to form a vertical seal, while said film-tube is continuously pulled along machine direction;

(iv) forming gussets on both lateral sides of the tube;

(v) effecting a horizontal seal across said film-tube, with horizontal sealing jaws, at a predetermined location below said vertical sealer to form the top horizontal seal of a filled pouch and the bottom horizontal seal of a pouch to be filled, optionally with perforations there-between;

(vi) feeding said product within said film-tube;

(vii) sealing open end of said film-tube with said horizontal sealing jaws at a pre-determined location; and,

(viii) optionally severing filled and sealed pouches to form individual pouches therefrom,
where at the intersection of the horizontal seal with inner ends of the gussets, an un-sealed pocket extending on either sides of the intersection is formed, wherein width of the un-sealed pocket is in the range of more than 26.66 % to up to 40% of the total width of the gusset, and wherein maximum shift in the centre-line of said gusset is 13.33 % of its total width, and width of the unsealed pocket is more than 200 % to up to 300 % of said maximum shift.
A method as claimed in claim 1 where said un-sealed pocket is devoid of a sharp corners or bends.
A method as claimed in any one of the preceding claims wherein height of the un-sealed pocket is less than 35 % of the height of the horizontal seal.
A method as claimed in any one of the preceding claims wherein the profile of the unsealed pocket is semi-circular, oval or ellipsoidal.
A method as claimed in any one of the preceding claims wherein the un-sealed pocket is formed at at least three corners of the pouch.
A method as claimed in any one of the preceding claims where the height of the horizontal seal at one end is in the range of 167 to 240 % of the general height of said seal, wherein a notch/slit is provided on both the gussets-ears at said end, said notch/slit being positioned below the un-sealed pocket at the opposite end of the horizontal seal.
A method as claimed in claim 8 wherein said notch/slit is provided 5 to 10mm below said un-sealed pocket.
A method as claimed in any one of the preceding claims wherein gusset ears are not sealed to each other.
A method as claimed in any one of the preceding claims wherein said sheet of film is a 2-ply laminate of 10 micron Polyethyleneterepthalate and 70 micron Polyethylene.