TECHNICAL FIELD

The present disclosure relates to welding/ sealing of plastic materials like polymer tape woven fabric or laminated polymer tape woven web & more particularly to ultrasonic welding / sealing method. Such kind of welding / sealing method are used for making bags/ pouches for packaging & storage of bulk products or for any such welding/ sealing application to prepare packages, or otherwise where welding / sealing is to be done for joining one or more members with woven fabric of tapes of polymers like polyolefin, polyesters etc.

BACKGROUND

The packages/ bags available for packaging of bulk products or heavy weight products are made of multi layer films or woven fabrics are difficult to handle, carrying, storing and particularly do not have sufficient strength at surface/edge joints to withstand drop test & similar impact in use. In case of multi layer film bags, the bags do not have sufficient strength to withstand the product load because they are generally heat sealed which can give away easily. These kinds of bags may get torn or puncture and are slippery on the surface, hence not suitable for large / bulk packaging.

Another kind of woven fabric bag is developed with increased strength. These bags were initially developed with only woven fabric tube which is subsequently laminated to enhance the load bearing strength, tear & puncture resistance. This method offers more and better options for colorful printing on bags, still finished by stitching. However such lamination process leaves two edges of two laminating films coming from the top & bottom of the pressed woven fabric tube during lamination & does not allow continuous or registered printing around the bag surface. The woven fabric is made from thin strips of Polyethylene or Polypropylene or any other suitable polymer or polymer blend in pre-defined size and weaved together. Use of conventional heat-sealing method for sealing/ joining two or more different surfaces, one essentially being woven fabric of the package together result in weakening of the tapes near the sealing band.

Packages made by stitching have a major disadvantage that the stitched area has through holes at a distance in chain. Although there is a thread passing through each hole but due to clearance & de- shaping of holes there are many small openings which allow passage for moisture, smell and also risk of entry of insects, mites etc. Threads made from natural means may not be hygienic for food contact. This kind of stitching can be done only by highly skilled tailors and the process is slow & expensive.

US 4373979 discloses a method for sealing together a first member and a second member of plastic material, at least one of which member is a fabric comprising a first plurality of parallel strips interwoven with a second plurality of parallel strips at right angles to the said first plurality, the strips of each plurality being of the same width and being of oriented plastic material whose orientation and strength are adversely affected by heat seal. However said method is dependent on the specific pattern^ which depends on the woven fabric pattern. Further, said method is useful for small packages or low volume and weight applications but it is found that when there is a layer of woven fabric to be sealed by ultrasonic welding with layer(s) of other components in the embodiment, the spot pattern on the ultrasonic horn digs through the woven fabric tapes and causes burning & displaces polymer in the spots resulting in reduction in seal strength, causing failure in drop tests or falls experienced in actual use and handling of packages for bulk applications.

SUMMARY

The present disclosure provides an ultrasonic sealing method which is common for woven fabrics of any tape size configuration, irrespective of the weaving pattern. In one embodiment the present disclosure provides an ultrasonic welding / sealing method for high sealing strength and low rejection rate for heavy weight carrying packages/bags. The method of sealing used in the present disclosure is an easy and improved process of sealing a woven fabric surface with another woven fabric surface or with any other embodiment surface of same polymer family.

In another embodiment the present disclosure provides a re-closable and reusable laminated woven bag with temper evidence member sealed with the woven fabric with sufficient strength. This method is also used for package closing after material filling.

To achieve the desired objective, one embodiment of the present disclosure describes a polymeric tape woven fabric bag comprising a package body having front and back walls, and top and bottom openings; a top closing means sealed with the front and back walls forming a sealing band at proximate to the top opening; and a polymeric sealing strip sealed on the outer sides of the front and back walls at the sealing band, the respective sealing surfaces of each of the top closing means, the front and back walls, and the polymeric sealing strip which are in contact with each other are made of same polymer or it's blend or from same polymeric family.

The present disclosure also describes A method of manufacturing a polymeric tape woven fabric bag comprising forming a package body having front and back walls, and top and bottom openings; sealing a top closing means with the front and back walls by forming a sealing band at proximate to the top opening; and sealing a polymeric sealing strip on the outer sides of the opposite front and back walls at the sealing band, the respective sealing surfaces of each of the top closing means, the front and back walls and the polymeric sealing strip which are in contact with each other are made of same polymer or it's blend or from same polymeric family.

The ultrasonic sealing of laminated or un-laminated woven fabric members with each other or such members with any other member offering high seal strength for different applications, typically for making packages / bags for bulk or heavy weight packaging. This method of ultrasonic sealing is devised for sealing combination of substrates essentially having at least one layer of woven fabric made from the weaving longitudinal and cross tapes of equal or unequal widths. Such sealing joints are capable of withstanding impact and / or tensile forces during handling, transportation, storage of packages and sustaining the drop tests as applicable. In an embodiment the laminated or un-laminated woven fabric is sandwiched between a single layer or multiple layer polymer strips on one side and another polymer surface like extruded zipper on other side. The said combination is pressed by ultrasonic sealing horn against a fixed flat surface or a surface with some pattern, with simultaneous application of controlled ultrasonic energy for validated and pre-set duration, to get a firm joint.

The ultrasonic sealing horn is used on either side depending upon the requirement of the product or product / process limitation. The face of the horn has pattern suitable to achieve desired results in terms of seal strength and aesthetic. The combination to be sealed having plurality of layers of different substrates. Individual layer of substrate may be made of single layer of polymer or blend or has multiple layers with the condition that any two surfaces coming in contact with each other during the sealing should be of some polymer or polymeric family in order to achieve adequate sealing strength since cross polymer sealing by ultrasonic does not give good sealing qualities.

The advantage of using polymer strip on one side of woven fabric is to get enhanced seal strength since the polymer strip also gets sealed as integral member of the sealing band and avoids burning of the woven fabric tapes. The polymer from the polymer strips melts and fills the displaced or eroded material from the woven fabric where the pattern on the horn presses.

This method gives sealing performance with least rejection and requirement of minimal skill offering reliable and high strength joints with woven fabric at faster speed, which is applied for the manufacturing of packages, bags or for any other application. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS FIGS. IA, IB and 1C: Show the arrangement of polymeric layers and the polymeric tape woven fabric layers to be welded/sealed together using ultrasonic sealing process according to an exemplary embodiment of the present disclosure.

FIG. 2: shows the woven fabric layer sealed between other two polymeric layers, and location of the seal on a pouch/bag according to an exemplary embodiment of the present disclosure.

DETAILED DESCRIPTION The embodiments of the present disclosure are described in detail with reference to the accompanying drawings. However, the present disclosure is not limited to these embodiments, which are only provided to explain more clearly the present disclosure to the ordinarily skilled in the art of the present disclosure. In the accompanying drawings, like reference numerals are used to indicate like components.

FIG. IA illustrates the arrangement of different polymeric layers under the ultrasonic welding method as per the present disclosure. The ultrasonic horn "1" as shown in the FIG. IA moves up and down over the polymeric layers. The ultrasonic horn "1" is the part of an ultrasonic welding machine through which controlled ultrasonic energy is applied to the objects to be sealed. The up and down movement is precisely controlled for speed, distance, duration of pressing & pressure. The ultrasonic horn "1" may be moving up and down type having fixed shape and size with desired pattern on the face thereof. Alternatively, the ultrasonic horn "1" may be of rotary type like a sewing machine having desired pattern for continuous sealing.

As shown in FIG. IA a single or multilayer polymeric film "4", like flap of extruded zipper and/or temper evidence diaphragm which is required to serve an specific purpose, is placed over the laminated or un-laminated woven fabric "7". There is another single or multilayer polymer sealing strip "10" below the woven fabric "7" which gets sealed with the woven fabric "7" during the sealing process. A supporting block "11" of the ultrasonic welding machine is provided to support the polymeric layers against the ultrasonic horn's pressure.

In one embodiment where the polymeric film "4" is a multiple layer structure and the woven polymer fabric "7" is a laminated web then the surface layer "3" and the laminated layer "5" has to be of same polymer or from same polymeric family to ensure good sealing strength. Where polymeric sealing strip "10" is a multilayer structure, then the surface layer "8" of the polymeric sealing strip "10" has to be same polymer or from same polymeric family as the laminated layer "6" of the woven fabric.

In an embodiment if the woven fabric is single un-laminated surface then polymer of the woven fabric "7", the surface in contact of single or multilayer polymeric film "4" and the surface in contact of single or multilayer polymeric sealing strip "10" has to be of same polymer or of same polymeric family for good sealing strength.

As shown in FIG. IB the arrangement of polymeric sealing strip "10" and the single or multilayer polymeric film "4" in respect of woven fabric "7" placed for ultrasonic sealing may be reversed depending upon the application requirement.

FIG. 1C shows the top view of the flat woven fabric surface after ultrasonic sealing and before forming a package or a bag product or in any other application. Such ultrasonic sealing is shown as a sealing band "12" in the figure.

FIG. 2 shows a typical embodiment of forming a pouch or bag (A) with a temper proof evidence member "13" and a top closing means "15" are sealed together by ultrasonic sealing as per the present disclosure. The pouch or bag (A) as shown in FIG. 2 includes a package (B) having at top and bottom walls (C) and (D), and top and bottom openings (E) and (F). The top closing means "15" may be either a zipper-slider assembly or a press to lock zipper for reclosing and opening, or may be one time openable sealed member. Further, where the top closing member "15" is the sealed member, then the sealed member is made from a polymeric film or a polymer blend or a laminate having sealability with the contact surfaces of the front and back walls of the pouch or bag (A). For the purpose of the explanation, in FIG. 2, the top closing means "15" is a re-closable zipper-slider assembly and wherein a re-closable zipper is referred by the numeral "15" and slider is referred by numeral "14". The zipper-slider assembly "15" includes polymeric flap "15a" similar to polymer structure "4" as explained in FIGS. IA & IB. As shown in the figure, the woven fabric layer "7" and the temper proof evidence "13" are sandwiched between the polymeric sealing strip "10" and polymeric flap "15a". In this embodiment, the temper proof evidence "13" which is a film or multiplayer laminate, required to be sealed along with the other embodiment "15a", "7", and "10" to act as a temper proof evidence. Further the reclosable zipper "15" along with the slider "14" is used for re-closing and re-opening the zipper profile. Similar combination may be welded/sealed without the temper proof evidence "13". The polymeric surfaces of various substrates in contact with each other to be welded/sealed together should be of same polymer, it's blend as major constituent or of the same polymer family.

Further, the bottom opening (F) is also sealed by sealing the front and back walls (D) and (C) either directly or by providing a sealing layer in between the front and back walls (D) and (C) or outside of the front and back walls (D) and (C) or both in between and outsides of the front and back walls (D) and (C).

The bag or pouch (A) shown in FIG. 2 may be either formed by sealing overlapping ends of the woven web or formed by butt sealing edges of the woven web by providing strip(s) overlapping on one or both side of the end to end edges of the woven web. Further, The bag or pouch (A) may be made from one of both side laminated polymeric tape woven web having plurality of layers of same or different polymeric material or made from un-laminated polymeric tape woven web depending upon requirement.

All documents cited in the description are incorporated herein by reference. The present invention is not to be limited in scope by the specific embodiments and examples, which are intended as illustrations of a number of aspects of the invention and embodiments which are functionally equivalent are within the scope of this invention. Those skilled in the art will know or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. These and all other equivalents are intended to be encompassed by the following claims.