MADE THEREOF

FIELD OF THE INVENTION The invention generally relates to packaging bags and more particularly to packaging bags made of woven multi-layered tapes flexible substrates.

BACKGROUND OF THE INVENTION

In flexible packaging industry, there are various methods of making a package / bag from different substrates. Woven substrates such as Woven Polypropylene (WPP) fabrics are widely used as they have high bursting and puncture strength, good chemical and wear resistance, and are light in weight as compared to non-woven substrates.

Woven fabric is made in a tubular form and converted to bags after lamination and printing by flattening the tube. In some processes of making a bag, an essential step is to make the tube. The process of making the tube from a web involves overlapping and sealing together the longitudinal edges of the woven substrate after lamination and printing.

One of the ways of sealing is by using hot air. However, using hot air sealing method is disadvantageous because the method requires very high temperature in the range of 700 deg. C. Further, the sealing achieved is not so good as the material of the woven substrate such as WPP has poor sealing property. The overall speed of the process is slow to achieve proper sealing.

Another method of sealing is using hot melt adhesive. However, the hot melt adhesive has a tendency to overflow and leaves excess material overflowing out of the center seal band. However, the sealing strength is not enough for heavy bags.

Another method of sealing is by ultrasonic method. However, sealing by ultrasonic method is very sensitive and hermetic sealing is not ensured due to less compatible properties of material of woven fabric for ultrasonic sealing and speed of the sealing operation is also slow.

Yet another method of sealing is by extrusion lamination. However, the strength of the seal is lower than what is desired especially for heavy bags and speed of the process of sealing is also slow.

Few common disadvantages with the known methods of center sealing the web to make the tube are that the quality of sealing is not good and it is very difficult to achieve hermetic sealing at high speeds.

Therefore, there exists a need to develop an improved method for making tube while forming bag made up of woven tapes substrate such as WPP that ensures proper sealing as well high processing speed offering hermetic sealing and overcomes the disadvantages listed above.

SUMMARY OF THE INVENTION

According to an aspect of the present invention a co-extruded multi- layered tape is provided. The multi-layered tape includes a middle polymeric layer coextruded with at least one external layer configured on each side of the middle polymeric layer. The external layers are coextruded with a low temperature sealable material, such that the external layers on each side of the middle polymeric layer have same sealing properties.

According to another aspect of the present invention, a woven substrate is provided. The woven substrate includes a plurality of multi- layered tapes woven to form the woven substrate. Each of the multi-layered tapes include a middle polymeric layer coextruded with at least one external layer configured on each side of the middle polymeric layer. The external layers are coextruded with a low temperature sealable material, such that the external layers on each side of the middle polymeric layer have same sealing properties.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages and features of the present invention shall be better understood with reference to the following detailed description taken in conjunction with the accompanying drawings, wherein like elements are identified with like symbols and in which:

FIG. 1 is a cross sectional view of a co-extruded multi-layered tape, in accordance with an embodiment of the present invention.

FIGS. 2A-2C show various embodiments of a woven substrate made up of the co-extruded multilayered tape, in accordance with an embodiment of the present invention.

FIG. 3 illustrates a pictorial representation of an exemplary method of forming a continuous tube from a web of the woven substrate made up of the co-extruded multilayered tapes, in accordance with an embodiment of the present invention.

FIG. 4 illustrates an exemplary bag formed from the tube made by overlapping the longitudinal edges of the web, in accordance with an embodiment of the invention.

Like reference numerals refer to like parts throughout the description of several views of the drawings. DETAILED DESCRIPTION OF THE DRAWINGS

A method for manufacturing co-extruded multi-layered tapes and packages / bags made from flexible woven substrate made thereof is disclosed.

The method includes extruding a multilayered film such that one extruder forms a middle layer (102) of said multilayered film and the separate extruder(s) form external co-extruded layers (104a and 104b) of the multilayered film. External layers (104a and 104b) are co-extruded with low temperature sealable material such as pure metallocene PE or a mixture of metallocene PE mixed with EVA or any other polymeric material, on both sides. The co-extruded external layers are meant for efficient sealing purpose. In various other embodiments, the low temperature sealable material may be in pure form or in a combination of one or more of Polypropylene copolymer, Polypropylene ter-polymer, elastomers, ethylene- vinyl acetate (EVA), modified Polypropylene or Modified Polyethylene modified to provide suitable sealing properties.

FIG. 1 shows a cross sectional view of the exemplary co-extruded multilayered tape (100) obtained after co-extruding the layers (104a and 104b) with the middle layer (102). In an exemplary embodiment, the middle

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layer (102) may be a single layer of polyolefins such as polypropylene (PP) or High Density Polyethylene (HDPE) or other suitable polymeric materials.

The co-extruded multi-layered film is further slit into tapes of predefined dimension such as length, width, thickness, denier etc., on a tape line and stretching and tempering operations are performed inline. The final co- extruded multi layered tapes are wound on bobbins for weaving the woven substrate on the looms thereby forming the woven fabric / substrate of co- extruded tapes (100).

The co-extruded multi-layered tapes typically have a width between 1.5 mm to 7 mm, and a denier between 300 and 2,500. It may be contemplated that the woven substrate is either woven as a tube, flattened by pinching, cut on both sides to get two flat webs on rolls or directly flat web is woven to roll. The coextruded multi layered tapes have same sealing layers, so as to have same sealing properties on both sides since it is not possible to ensure that the tapes winding on the bobbins or during weaving on looms have a same layer always on one side of the fabric.

FIGS. 2A-2C shows various embodiments of woven substrates (200a, 200b, and 200c) of the co-extruded tapes. FIG. 2A shows a woven substrate (200a) made up of the multi-layered co-extruded tapes without any additional layer coated or laminated to it. FIG. 2B shows another woven substrate (200b) made up of the co- extruded multi-layered tapes is extrusion laminated with a molten layer (202) on its surface extruded through a flat extrusion die (210) and a roller (204), according to an alternate embodiment of the present invention. Molten layer (202) fills in the gaps and troughs on the woven fabric surface thereby ensuring a smooth surface. It also makes the woven fabric (200b) hermetic. The plain and smooth surface provides a conducive surface for printing. The molten layer (202) comprises Polypropylene or Polyethylene or a combination of both.

FIG. 2C shows yet another woven substrate (200c) of the co-extruded tapes laminated with a film of reverse printed BOPP/PET film (208). BOPP/PET film (208) has a reverse printed layer (208a), according to another embodiment of the present invention. The reverse printed BOPP/PET film (208) may be laminated with the woven substrate (200c) by extrusion lamination, or adhesive lamination.

It may be apparent to person skilled in the art that other known surface treatments may also be applied to the woven substrate of the co-extruded multi-layered tapes over printing such as Ultraviolet curing, E-beam curing and the like to provide rub resistance, increase gloss or enhance barrier properties. FIGS. 2A-2C show some of the embodiments of the many such possibilities.

FIG. 3 illustrates a pictorial representation of an exemplary method of forming a continuous tube (312) from a web of woven fabric (314), hereinafter referred to as the web (314) of co-extruded multi-layered tapes. In the method, overlapping and sealing of two longitudinal edges (L1 and L2) of the web (314) is done to form tube (312). In an exemplary embodiment, sealing of the two longitudinal edges (L1 , L2) is achieved by blowing hot air through a nozzle (310). The nozzle (310) is positioned such that as the longitudinal edges (L1 and L2) overlap, hot air from the nozzle (310) is blown between the overlapping longitudinal edges (L1 , L2). In an embodiment of the present invention, the hot air nozzle (310) is connected to a hot air generator (311 ). Subsequently, the edges (L1 , L2) are pressed and cooled to form the continuous tube (312). The continuous tube (312) may be wound in the form of a roll for further processing or may be slit / perforated inline into cut pieces of required bag length.

The tube (312) so formed is further processed and finished to make bags / packages of various designs and shapes such as valve bags, gusset bags, pinch bottom bags, stitched bags, standup bags etc. In accordance with an alternative embodiment of the present invention, the sealing of the two longitudinal edges (L1 and L2) can also be done by hot melt adhesive, ultrasonic sealing method or extrusion lamination method. In all these methods of sealing the two longitudinal edges (L1 and L2) is achieved at lower temperatures by virtue of the low temperature sealable material of the multi-layer tape (100) thereby providing easy and effective sealing.

FIG. 4 shows a bag (400) which is formed after the formation of the continuous tube (312) with a longitudinal seal (402). During the process of longitudinal sealing (402) while making tube (312) using such a woven substrate / flat fabric, the sealing obtained is hermetic and the sealing can be performed at much lower temperature and much higher speeds and thus production rate increases in various methods of sealing.

The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof.