CN114286791B

CN114286791B - Method and apparatus for bag forming

Info

Publication number: CN114286791B
Application number: CN202080059989.7A
Authority: CN
Inventors: 高雷夫·罗希亚
Original assignee: Lohia Corp Ltd
Current assignee: Lohia Corp Ltd
Priority date: 2019-08-24
Filing date: 2020-08-19
Publication date: 2023-12-01
Anticipated expiration: 2040-08-19
Also published as: EP4017808A4; WO2021038387A1; EP4017808A1; CN114286791A

Abstract

The present invention relates to a process and apparatus for making bags from polymeric web materials, particularly polyolefins, using adhesive bonding. It is well known that the hot air welding/sewing systems used in such processes result in an undesirable and uncontrollable degradation of fabric strength. A process is disclosed wherein surface enhancement techniques are used on the surfaces to be joined prior to joining the surfaces together by use of an adhesive. The overall weight of the bag is reduced, the production speed is increased, and the joint adhesive strength is increased. The invention also discloses an apparatus having at least four stations: a first station (15), a second station (16), a third station (17) and a fourth station (18), wherein in each of said second station (16), third station (17) and fourth station (18) a sealing unit (19) is provided, which sealing unit (19) has at least one unit (3) for a surface-enhancing treatment and at least one adhesive applicator (8) for applying an adhesive as an attaching means to surfaces attached to each other.

Description

Method and apparatus for bag forming

Technical Field

The present invention relates to a bag made of a polymeric web material, in particular a bag made of polyolefin bonded using an adhesive.

Background

Bulk materials are contained in various bags, which can be broadly classified into pillow type and box type or block type. Pillow bags are typically made by sewing or stitching the bottom. The box or block shape is made by folding and bonding the bottom. The box shape allows for optimal utilization of the material surface, good stackability and increased volume utilization due to its brick shape. The pillow bag is arranged on one side, and the box bag is arranged on the other side.

Typically, the bag has a capacity of 10kg, 25kg, 100kg, 500kg and 1000 kg. Suitable materials include natural fiber fabrics (such as jute, paper), plastic sheets and plastic fabrics, nonwoven webs. Over the past few decades, bags made from natural fiber fabrics have been replaced with bags made from paper and plastic sheets and plastic fabrics, as these bags are cheaper and offer technical advantages. The paper has no moisture barrier or higher strength. For this reason, bags often comprise various paper layers, which increases material consumption. Furthermore, paper bags are not suitable for storing most chemicals widely used in the industry. However, it can be produced at low cost by using an inexpensive adhesive. Plastic sheets do not have high tear strength and thus thicker materials are used. Further, plastic sheets are dimensionally unstable and relatively sensitive to heat. The plastic sheet bag can be easily seam welded into pillow shape, but is not easily adhered into box-shaped bag or block-shaped bag.

Plastic woven fabrics comprising monoaxially drawn tapes have high strength and are dimensionally stable, in particular coated plastic woven fabrics. The raw material requirements of woven fabrics made from stretched tapes are much lower for the same load-bearing capacity than for unstretched plastic sheets. Bags made of plastic fabric are typically made in pillow shapes with seams. The block-shaped pockets of plastic fabric are made by using hot air welding/sewing techniques to form a connection on the top and bottom sides, as is known in the art from US5845995. However, it is well known that hot air welding/sewing systems result in an undesirable and uncontrollable degradation of fabric strength. The inability to control the process parameters of the hot air welding/sewing system results in uncontrolled variations in production quality. This results in a reduction in production speed.

Disclosure of Invention

The present invention provides an alternative bonding method for polymer webs/plastic woven fabrics/webs to form bulk bags with sufficient joint quality at higher processing speeds than conventional systems.

The object of the present invention is to overcome the limitations of the traditional box-shaped bag manufacturing process, in particular to create a bag and a method for producing a bag and a machine system for producing a bag, by means of which a bag can be produced faster and more easily. Further, the efficiency of producing bags is improved.

It is another object of the present invention to provide a process for manufacturing bags that uses surface enhancing techniques and an efficient gluing mode.

Accordingly, the process disclosed herein may be summarized as a process for bag forming comprising the steps of:

a. -feeding an optionally coated polymeric web material (1) and cutting it into pieces (1A) of suitable length;

b. opening at least one end of the cutting member (1A) to form a hexagon at either open end of the cutting member (1A), namely a first hexagon (10) and a second hexagon (10A), the two hexagons (10, 10A) having tabs (9) formed by folding the open ends, and the second hexagon (10A) having a first region (11) to receive an outer surface (14) of a valve pad (4), and supplying and attaching the valve pad (4) to the second hexagon (10A);

c. folding the flap (9) and forming block bottoms, i.e. a first block bottom (12) and a second block bottom (12A), at both ends of the cutting member (1A), the block bottoms (12 and 12A) having a second area (11A) to receive the outer surface of the cover sheet (4A);

d. a cover sheet is supplied at the second area (11A) and attached to the block bottom.

The characteristic elements of the process result from the step of providing a surface enhancing treatment in each of said step b and said step d and the step of applying an adhesive as an attaching means to surfaces attached or adhered to each other. Another characteristic aspect of the invention is in the form of a chill roll (19A), which chill roll (19A) is also provided as part of the apparatus after each of the sealing units (19). The dual function of the chill roll is to cool the sealing surface down to room temperature and also to apply pressure, helping the cut pieces to pass through the sealing unit (19) to the next station.

To implement the above process, the invention also discloses an apparatus having at least four stations: a first station (15), a second station (16), a third station (17) and a fourth station (18) to perform steps a, b, c and d, respectively, disclosed in the above process. The characteristic elements of the apparatus come from the provision of a sealing unit (19) in each of said second station (16), said third station (17) and said fourth station (18), the sealing unit (19) having at least one unit (3) for a surface-enhancing treatment and at least one adhesive applicator (8) for applying adhesive as an attachment means to surfaces attached to each other.

Another characteristic aspect of the invention is in the form of a chill roll (19A), which chill roll (19A) is also provided as part of the apparatus after each of the sealing units (19). The dual function of the chill roll is to cool the sealing surface to bring it down to room temperature and also to apply pressure, helping the cut pieces to pass through the sealing unit (19) to the next station.

Drawings

Fig. 1 shows a schematic view of a process and apparatus for bag manufacturing.

Fig. 2A, 2B and 2C illustrate an embodiment of the present invention.

Fig. 3 shows a number of patterns in which adhesive may be applied.

Parts list:

1. a web material. 1A. Cutting elements of web material. 1B, finished product bag

2. Conveyor platform or table

3. Surface treatment unit

4. Valve pad or cover (4A)

5. A valve sheet or cover sheet main transfer roller; 5A secondary roller

6. Suction roll

7. Pressure roller

8. Adhesive applicator 8A adhesive nozzle

9. Wing panel

10. A first hexagon 10A. Second hexagon

11. A first region. 11A. Second region

12. First block bottom 12A. Second block bottom 12B-corner of block bottom

13. The outer surface of the block bottom

14. Outer region of valve pad or flap

15. First station

16. Second station

17. Third station

18. Fourth station

19. Sealing unit

19A sealing unit transfer roller

20. Bag stacking unit/transfer unit

Detailed Description

The present invention discloses a process for manufacturing bags made of a polymer web material (1), such as a nonwoven or woven fabric comprising uniaxially stretched tapes of a polymer, in particular a polyolefin, preferably polypropylene. The web material (1) may optionally be coated or laminated with a thermoplastic, in particular a polyolefin, on one or both sides. The web material (1) may be a seamless tubular fabric or a flat web sewn to form a tube, and wherein at least one end of a bag, particularly having the shape of a box or a right parallelepiped, is made by folding the fabric/web ends together with an adhesive to form a bottom (or block bottom) surface, preferably rectangular, and a process for producing such a bag.

In order to produce woven bulk bags from such web material (1), the folded bottom is typically subjected to a heat welding system. Maintaining the required strength of the bag in turn requires achieving a practically viable and high production speed, which is a complex operation. In view of maintaining the required bag/sewing strength and controlling the uniform production quality, it is a challenging task to increase the production speed to over 120 to 150 bags per minute. Increasing the speed of thermal welding in order to increase the overall speed of bag manufacture may lead to an increase in processing temperature, which leads to further deterioration of the fabric strength and its uniformity control at high speeds.

A bag manufacturing process and apparatus uses an adhesive applied to a desired bonding area at the bottom of the fold to form a bulk bag. Those skilled in the art know that polypropylene and polyethylene materials (typically forming fabrics) are difficult to bond strongly. Thus, in another aspect of the invention, the surfaces to be joined are pre-treated using a surface enhancing method, such as corona treatment, plasma treatment or similar thin surface roughening treatment. The applicant found through experiments that this pretreatment surprisingly greatly improves the adhesive strength. For example, joints made with web materials that have not been surface enhanced have adhesive strengths of about 40% to 60% of the original web/fabric strength. While when the web material is pre-treated with a surface enhancer, the final bond strength of the joint is about 90% -140% of the original web/fabric strength using the same binder and the same amount.

For the purposes of this disclosure, the terms surface enhancing treatment and pretreatment are used synonymously.

In one aspect of the invention, the web material (1) used to make the pouch of the invention comprises a woven fabric made from uniaxially stretched polyolefin tapes or a non-woven polyolefin material or a combination thereof. The tape is produced from a polyolefin sheet (or film) stretched to 4 to 10 times its original length, whereby molecular chains in the film longitudinal direction are oriented, so that about 6 to 10 times the strength of the original sheet is obtained in that direction. Thus, the tape produced by slitting the stretched film also has a strength 6 to 10 times that of the unstretched film. The slit film tape typically has a width of about 1.5mm to 10mm and a thickness of 20 microns to 80 microns. When these tapes are woven using a circular or flat loom to form a fabric, the fabric has a uniform high tensile strength in the warp direction and the weft direction, and tear strength is also improved.

The web material (1) may optionally be extrusion coated or laminated to provide protection against dust and moisture. Furthermore, the coating may have a desired slip resistant surface to achieve better stackability of bags made from such fabrics. Furthermore, in order to be able to fill the bulk bags of the invention with a powdery material like cement, the surface of the web material (1) or the bag surface has small perforations, typically of nano-to micrometer size, at the locations where air escape is required. In the case of a filling material, such as cement, transported by an air flow, it may be appropriate to have a venting system, such as perforations, in the web material (1) so that air trapped after or during the filling operation can escape. The size of the perforations is micro-or nano-sized, that is, the perforations are smaller than the particle size of the filler material. Thus, the bag becomes leak-proof to the stored material, but still allows air to escape.

Figure 1 schematically illustrates the process and apparatus for making bags of the present invention. It shows a roll of tubular web material (1), which roll of tubular web material (1) has passed through a series of feed rolls, which system feed rolls subject the web material (1) to several optional pre-cutting operations, such as perforation and spot perforation, and inspection of defect free portions (not shown) of the surface of the web material (1). Suitable cutting equipment at the first station (15) cuts the continuously arriving web material (1) into cut pieces (1A) of the desired length. As shown in fig. 1, the cut length (1A) of web material (1) is transferred onto a bag forming conveyor platform (2) with the aid of suitable gripping and conveying elements (not shown). The cutting member (1A) then passes through a second station (16), where the two cut ends of the cutting member (1A) are opened and folded into a preferably hexagonal shape, forming a first hexagon (10) and a second hexagon (10A) according to the desired/predetermined dimensions of the final bag. The terms hexagonal end and hexagon are synonymously used in this specification.

The first hexagon (10) and the second hexagon (10A) are eventually converted into box-shaped ends or block bottoms (12 and 12A) at one or both ends of the bag as desired. The tabs (9) of the first hexagon (10) and the second hexagon (10A) are folded such that portions thereof overlap each other, and the overlapping portions of the tabs (9) are connected together. In one embodiment of the invention, the surfaces of the fins (9) facing each other in the joining process are treated with a surface enhancer treatment, such as a plasma treatment or corona treatment. Adhesive is applied to these areas using suitable adhesive applicator units (8), each having a nozzle (8A).

For connecting the folded flaps (9) together, the cutting member (1A) with the folded ends (12 and 12A) is passed through a sealing unit (19). The sealing unit may comprise two rollers, one suction roller (6) and one pressure roller (7), the suction roller (6) and the pressure roller (7) rotating in opposite directions about their axes such that the cutting member (1A) is pushed out of the slit or gap formed between the two rollers (6 and 7) while the roller applies pressure to the cutting member (1A) passing through the rollers. A separate sealing unit (19) is provided at one or both ends of the cutting member (1A).

Once the substantially hexagonal shapes (10 and 10A) as shown in part (b) of fig. 1 are formed, they are further folded depending on whether a valve is required for filling the bag. Where a valve is provided, the valve is typically provided at one of the two ends of the bag. As shown in part (c) of fig. 1, the first region (11) of the second hexagon (10A) shown in part (b) is ready to receive a valve pad (4) at the second station (16). As shown in fig. 1, the first region (11) is positioned across the triangular portion of the second hexagon (10A) and the widest portion of the second hexagon (10A).

The pretreatment includes treating the first region (11) (hatched region in part (c)) shown in fig. 1 with a surface enhancement treatment. After the pretreatment, at a second station (16) an adhesive is applied to at least the first region (11). The valve pad (4) is also pre-treated and an adhesive is applied to an outer surface (14) of the valve pad (4) facing the first area (11) of the second hexagon (10A). As shown in part (d) of fig. 1, the valve pad (4) is then placed on the second hexagon (10A) such that it substantially covers the first area (11). Subsequently, in the second station (16), the two hexagonal ends (10 and 10A) of the cutting member, one with the valve pad (4) and one without the valve pad (4), are folded to close the first hexagon (10) and the second hexagon (10A) so that there is an overlap between the flaps (9) after the flaps (9) of the hexagons (10 and 10A) are folded. The adhesive is applied to the surfaces of the flaps (9) facing each other on the overlapping area.

After this step, at a third station (17), the folded ends pass through a sealing unit (19) having a set of suction rollers (6) and pressure rollers (7) such that a first block bottom (12) and a second block bottom (12A) are formed at the respective hexagonal ends (10 and 10A) of the cutting member (1A). Furthermore, in the third station (17), a surface pretreatment is applied to the second zone (11A) of the respective shaped end portions (12 and 12A) -indicated by the dashed line in part (f) of fig. 1. The second region (11A) is a rectangular region defined by the four corners of the first block bottom (12) and the second block bottom (12A).

After this step, at a fourth station (18), the coverslip (4A) is prepared by pre-treating the coverslip (4A). An adhesive is applied to the outer surface (14) of the cover sheet (4A) and to the second region (11A) of the block bottom (12 and 12A). Next the coverslip is placed on the pretreated second area (11A) of the block bottom and the two block bottoms (12 and 12A) carrying the coverslip (4A) are passed through the suction roll (6) and the pressure roll (7) of the sealing unit (19) to attach or seal the coverslip to the respective block bottoms (12 and 12A). After the cover sheet (4A) has been applied to the block bottom (12 and 12A), the finished bags travel to a bag stacking/transfer unit (20) of any other suitable downstream processing station.

A surface-enhancer treatment unit (3) is used to provide a surface-enhancer treatment according to the invention. A plurality of such surface enhancing units (3) are provided at each sealing unit (19), which surface enhancing units (3) are in turn arranged at a second station (16), a third station (17) and a fourth station (18) of the inventive device. The surface enhancer treatment includes a treatment (such as plasma or corona) for activating a desired area of the block bottom (12, 12A) to which the valve pad (4) or cover sheet (4) is adhered by means of a suitable adhesive. The adhesive is applied using a suitable adhesive applicator (8) having a nozzle (8A).

As discussed in the preceding paragraph, the process of the present invention discloses a surface enhancing unit (3) for a web cut (1A), wherein the cut (1A) is treated using the surface enhancing treatment unit (3). Further surface-enhancing units (3) for cover sheets (4A) or valve gaskets (4) are also disclosed, wherein the cover sheets (4A) or valve gaskets (4) are treated with a surface-enhancing treatment unit (3). Also disclosed is a sealing unit (19) for attaching two surfaces together, such as a fin (9) of a hexagon (10, 10A), or a flap/valve pad (4A/4) and a shaped block bottom (12, 12A). These are schematically illustrated in fig. 2A, 2B and 2C.

Fig. 2A, 2B and 2C show portions of the process where the valve gasket (4) and the cover sheet (4A) together with the first region (11) and the second region (11A) are treated with a surface enhancing treatment and passed through the sealing unit (19). These figures show that the web material (1) is conveyed by a pair of primary conveying rollers (5) and secondary conveying rollers (5A). The web material (1) is cut into suitable pieces using a cutting device (not shown), which pieces serve as valve gaskets or cover sheets (4 and 4A).

A separate sealing unit (19) is placed at the second station (16), the third station (17) and the fourth station (18) for the purpose of sealing any two surfaces together. Fig. 2A, 2B and 2C also show a surface-enhancer-treatment unit (3) provided in the process, and a sealing unit (19) comprising a suction roll (6) and a pressure roll (7) provided if necessary.

Separate sealing units (19) are provided at both ends of the web cutter (1A)/bag, wherein the surfaces are to be sealed.

The application of adhesive is also necessary wherever the attachment surfaces are desired. For this purpose, an adhesive applicator (8) is provided with a nozzle (8A). In any case where it is desired to apply the adhesive, they may be applied in continuous lines, or dots, spots, dashed lines, or in any other similar manner, as shown in FIG. 2.

Fig. 2A, 2B and 2C show alternative arrangements of nozzles (8A). When an adhesive is used to join two surfaces together, the adhesive may be applied to one or both of the surfaces. For example, as shown in part (e) of fig. 1, when the two fins (9) of each of the hexagons (10 and 10A) are connected together to form the block bottom (12, 12A), only one of the two fins (9) facing each other at each end of the cutting member (1A) may be applied with an adhesive, or both of the two fins (9) at each end may be applied with an adhesive. When the cover sheet (4A) is applied to the block bottom (12, 12A), the surface of the cover sheet (4A) or the block bottom (12, 12A), or both the cover sheet (4A) and the block bottom (12, 12A) may be applied with an adhesive.

Either or both surfaces that are joined together may be surface treated by a surface enhancing treatment. For example, when the cover sheet (4A) is applied to the block bottom (12, 12A), the joining surface of the cover sheet (4A) or the surface of the block bottom (12, 12A), or both the joining surface of the two cover sheets (4A) and the surface of the block bottom (12, 12A) may be subjected to an enhanced surface treatment.

In the example illustrated in fig. 2A, 2B and 2C, the valve pad/cover (4/4A) is conveyed using a set of primary conveying rollers (5) and secondary conveying rollers (5A) (only one set is shown in the figures, however, there may be more than one set of these rollers) and a pair of suction rollers (6) and pressure rollers (7).

With the aid of the surface-enhancer treatment unit (3), the valve pad (4) conveyed through the conveyor system is also subjected to a surface-activation treatment, such as corona or plasma, before it adheres to the location on the shaped hexagonal shape of the cut piece (1A) of the web, as shown in parts (c) and (d) of fig. 1. Fig. 2A shows a valve pad/cover sheet (4/4A) transporting a roller (5), which further has a cutting unit (not shown) and a further surface enhancer treatment (or simply surface activation) unit (3). A corona or plasma treated surface activation unit (3) activates or treats the side surface of the label/cover sheet to be superimposed on the shaped folded hexagonal shape with cut web length (1A).

Regarding the application of the adhesive, the process of the present invention discloses many alternatives. The adhesive may be applied to either one of the two surfaces that are joined together (as shown in fig. 2A and 2B), or to both surfaces (as shown in fig. 2C). Thus, as illustrated in FIG. 2A, an adhesive applicator (8) having a nozzle (8A) (or alternatively, a roller in place of the nozzle) is provided to apply adhesive to the valve pad/cover sheet (4/4A). Alternatively, as shown in fig. 2B, an adhesive applicator (8) having at least one nozzle (8A) is provided to apply adhesive to a desired location (e.g., block bottom) on the web cutter (1A). As a further alternative, as shown in fig. 2C, an adhesive applicator (8) with a nozzle (8A) is provided to apply adhesive to the valve pad/cover sheet (4/4A) and to the desired location (e.g. bottom of the block) on the web cutter (1A).

As shown in these fig. 2A, 2B and 2C, another set of sealing unit transfer rollers (19A) that cool the sealing surface is also provided. At least one cooling roller (19A) is provided at each stage, if necessary. The chill roll (19A) is operated with a suitable coolant, such as chilled water, and the temperature of the chill roll (19A) is brought below room temperature so that the sealing surface cools.

Fig. 2A, 2B and 2C illustrate various stages of the bag making process of the present disclosure. For this purpose, the second (16), third (17) and fourth (18) stations are represented according to which stage of the bagging process the cut pieces are at any given time. For example, when the cutting member (1A) is at the second station (16), the arrow representing the input cutting member shows that the cutting member is being conveyed from the previous station (indicated by 'from 15/16/17'). The figure also shows a specific station (indicated by' 16/17/18) for machining the cut pieces and providing a sealing unit (19). Finally, these figures also show the station (denoted by "to 17/18/20") to which the cutting member (1A) next travels.

The adhesive applicator (8) is activated by an electronic control unit (not shown) for applying the required gauge and predetermined amount of adhesive/glue to the folded surface of the cut web such that the valve pad/cover sheet (4/4A) is adhered to the glue area. The control unit controls the release amount and release rate (volume/min) of the adhesive.

The pressure roller (7) and sealing unit transfer roller (19A) further promote bonding of the valve pad/flap to the folded web structure, thereby converting the cut web length into a bottom-of-block pouch. Alternatively, the conveying roller may be more than one, and any one may be forcibly cooled.

b. opening the end of the cutting member (1A) to form a hexagon at either open end of the cutting member (1A), namely a first hexagon (10) and a second hexagon (10A), the two hexagons (10 and 10A) having tabs (9) formed by folding the open ends, and the second hexagon (10A) having a first region (11) to receive an outer surface (14) of a valve pad (4), and supplying and attaching the valve pad (4) to the second hexagon (10A);

c. folding the flaps (9) and forming at the respective ends of the cut pieces (1A) a block bottom, a first block bottom (12) and a second block bottom (12A), the block bottoms (12 and 12A) having a second area (11A) to receive the outer surface (14) of the cover sheet (4A);

The characteristic elements of the process result from the step of providing a surface enhancing treatment in each of said step b and said step d and the step of applying an adhesive as an attaching means to surfaces attached or adhered to each other.

In addition, the web material (1) is passed through any or all of the precutting operations, such as perforating and spot perforation, and inspecting the non-defective portions of the web surface.

To implement the above process, the present invention also discloses an apparatus as illustrated in fig. 1. It has at least four stations: a first station (15), a second station (16), a third station (17) and a fourth station (18) to perform steps a, b, c and d, respectively, disclosed in the above process. The characteristic elements of the apparatus come from the provision of a sealing unit (19) in each of said second (16), third (17) and fourth (18) stations, the sealing unit (19) having at least one unit (3) for a surface-enhancing treatment and at least one unit (8) for applying an adhesive as an attachment means to surfaces attached to each other.

Another characteristic aspect of the invention is in the form of a chill roll (19A) which is also provided as part of the apparatus after each of the sealing units (19). The dual function of the chill roll is to cool the sealing surface down to room temperature and also to apply pressure, helping the cut pieces to pass through the sealing unit (19) to the next station.

Many other configurations are made in the device of the present invention. The adhesive applicator (8) is capable of applying adhesive in a pattern selected from the group consisting of dot or dashed lines, or zigzagged lines or straight lines, or any combination thereof. The sealing unit (19) is provided with a set of rollers comprising a suction roller (6) and a pressure roller (7), the cutting member (1A) passing under pressure through a gap between the suction roller (6) and the pressure roller (7). In order to apply a surface enhancing treatment with the surface enhancing treatment unit (3), a number of different types of units may be selected depending on whether the selected treatment is a corona treatment, or a plasma treatment or a similar thin surface roughening treatment. In this case, the selected treatment is a corona treatment, which is performed by passing the cutting member (1A) requiring the corona treatment between an electrode in the corona treatment unit (3) and the metal plate. Where the process is a plasma process, this is performed by supplying energy in the form of radio frequency electromagnetic radiation to ionize a process gas, which may be oxygen, nitrogen, argon, helium, or combinations thereof, to produce a plasma of electrons, ions, and other high energy metastable species.

In the aforementioned bagging process using the aforementioned apparatus, the web material (1) used is tubular. In another aspect of the invention, the process disclosed herein may be used where the starting point is a flat web from which the tubular web is made. In this scenario, a surface enhancer unit (3) is used to treat the edges of the flat web, after which an adhesive may be applied to the edge regions of the flat web, so that the tubular web may be formed by rolling the flat web and overlapping the edge regions with each other and passing the rolled web through a set of pressure rollers.

The valve pad and/or flap (4/4A) are made of the same material as the bag or any of them may alternatively be made of a material different from the fabric web material. The alternative material may be a single layer of thermoplastic web material, or one may use a composite material or a combination of coatings or laminates from a substrate such as paper, fabric, printed or non-printed film, or a nonwoven web material.

The surface activation/enhancement system is applied to obtain sufficient adhesion on the polyolefin or polypropylene, in particular to pretreat the web before the adhesion is applied. The aim is to optimise the wetting and adhesion process. One way to perform this result is to apply a high frequency discharge, such as corona treatment, towards the film surface. The result is an improved chemical bond (in dynes/cm) between the plastic/polyolefin web and the molecules in the applied adhesive/glue. The corona surface treatment does not reduce or alter the strength of the web nor does it alter the appearance of the web. Information for using corona surface treatment on plastic films can be found in a number of references, including U.S. patent No.7,074,476, which is incorporated herein by reference.

The effectiveness of the corona treatment depends on the particular film used. There is no limitation on the materials that can be corona treated. However, the required treatment strength (watts/min/square meter) may vary significantly. The process level can be calculated-the exact value can be best determined by testing the actual web sample for the particular application. The corona treatment may be performed by passing the web between an electrode and a metal plate in the corona treatment unit (3). The width of the electrodes may correspond to the width of the folded/covered area such that only the desired area of the web receives the treatment. The cutting member (1A) may travel in the longitudinal direction through the corona treatment unit (3). The amount of corona treatment received by the fold is determined by the length of the electrode, the speed of travel of the web between the electrode and the plate, and the amount of potential generated between the electrode and the plate.

Alternatively, the selective energy treatment surface activation may be a selective plasma treatment. As previously described, in a typical plasma processing process, the plasma is generated from a supply of energy in the form of radio frequency electromagnetic radiation to ionize a process gas, which may be, for example, oxygen, nitrogen, argon, helium, or a combination thereof. Plasmas include electrons, ions and other high energy metastable species. The energy of the individual plasma particles may be in the range of about 3 ev to 20 ev. When these energetic particles contact the surface of the polyolefin web, the surface is energized via ionization or chemical reaction (typically oxidation).

The plasma may condition the substrate for receiving other materials. In this case, the substrate is a polymer, more specifically a polyolefin polymer. Plasma treatment provides a better surface for sealing the polymer to other surfaces and enhances the ability of the adhesive to remain on the polymer treated with the plasma. The plasma treatment provides a strong bond of the polymer and other materials. The plasma treatment uses only electricity and compressed air, and can treat heat-sensitive materials. Thus, the plasma treatment can be readily applied to various areas of the continuous web or sheet of polymeric material that is subsequently formed into bags. The polymer web may also be a combination of woven polymer with non-woven polypropylene and other materials, such as an intermediate or extruded layer of paper or aluminum sheet and an inner layer of a material suitable for shrinking the contents of the bag to be formed. Plasma treatment can be used at high speeds for flat materials such as polymer webs used to form bags.

Further, the invention may be intended to bond the valve and cover gaskets (4/4A) to the surface of the folded cut piece (1A) at the desired location, in particular where there is a hot/glue or cold glue. The hot melt adhesive/melt adhesive may comprise at least one of the following components: base polymer, resin, stabilizer, wax, and nucleation means. The base polymer may be selected from, for example, PA (polyamide), PE (polyethylene), APAO (amorphous polyalphaolefin), EVAC (ethylene vinyl acetate copolymer), TPE-E (thermoplastic polyester elastomer), TPE-U (thermoplastic polyurethane elastomer), TPE-a (thermoplastic copolyamide elastomer). For example, rosin and/or terpene and/or hydrocarbon resins may be used as the resin.

According to the invention, stabilizers, such as antioxidants and/or metal deactivators and/or light stabilizers, may be used. By using a hot glue, the advantage is that different materials can be glued to each other. Further, the unevenness of the surface to be glued can be easily compensated.

The advantage of using cold glue is that cold glue technology can achieve high speed operation of the machine. Further, the cold glue can be applied relatively easily.

The adhesive/glue is applied to the desired substrate or predetermined area of the moving web in a pattern as shown in fig. 3, comprising at least two points or lines extending transversely to each other parallel to the direction of movement of the substrate.

According to the invention, the adhesive is applied in a pattern parallel or perpendicular to the direction of movement of the substrate/web or a combination thereof by a combination of operations. As the substrate web moves under the orifice of the nozzle (8A) of the adhesive applicator (8), the adhesive is applied in the form of a linear or beaded or rotary spray by extrusion or hydraulic injection in accordance with a predetermined time burst. Further, the adhesive flows out in at least the required amount and maintains a clear shape, which may be a sharp line or a bead.

The device according to the invention for applying adhesive comprises a conveyor for moving a substrate through an adhesive application station, the adhesive application device comprising at least one nozzle (8A) or orifice provided to an adhesive applicator (8) adjacent to the path of movement of the substrate for depositing adhesive in a pattern parallel to the direction of movement of the substrate, thereby forming the desired pattern. A timing means is provided for actuating the applicator (8) for a selected period of time to provide the required length of glue/adhesive. The timer may be pulsed or cycled to provide a bead-gap-bead pattern, i.e., a stitched or intermittent line. The adhesive application device also includes a gun having a flat spray nozzle in the station for spraying the adhesive as a transverse liquid sheet directed at a plane that is angled to the direction of movement of the substrate. A timing device is provided for actuating the adhesive apertures to run for a selected period of time such that adhesive from the adhesive apertures will be deposited as a pattern on the substrate with a width substantially less than its length. Various embodiments are shown in fig. 3. Fig. 3 shows several patterns, labeled (a), (b), (c), (d), (e) and (f). Among them, it has been found that pattern (b) and pattern (c) are most effective in terms of adhesive strength, resulting in a fabric strength of about 1.2 to 1.5 times. Further, patterns (d), (e) and (f) in fig. 3 show sufficient adhesive strength, measured as the amount of adhesive required per unit area, with the best use of adhesive being about 3% to 7% lower than the other patterns.

Thus, according to the above invention, bottom-of-block bags made from the polymer web (1) can be manufactured with a relatively high processing speed of 200 bags per minute using a suitable adhesive. While in the illustrated embodiment of the invention the bag is shown in each case as being formed from a single layer of thermoplastic web material, it should be understood that one or more layers may be used without departing from the scope of the invention. Further, it should also be appreciated that instead of a single layer of thermoplastic web material, one may use a composite material or a combination coated or laminated from a substrate such as paper, fabric, film or nonwoven web as web material (1) for bag forming.

Examples: using the disclosed process and apparatus, a 500mm wide and 600mm long bottom pocket is made of about 60gsm woven polypropylene fabric coated with a 12 micron polyolefin receiver sealed with conventional hot melt adhesive, spray/applied at about 10 to 12 grams per square meter, showing adhesive strength of about 68 to 72kgf at the top and bottom ends of the bottom pocket, and production rates of about 160 to 180 pockets/minute.

The present invention has a number of advantages. Some of which are listed here, however, other advantages will be apparent to those skilled in the art. First, the coating thickness/linear weight on the fabric can be reduced by 20% to 50% compared to the heat sealed block bottom pouch, since heat sealing is not involved. This results in a 10% to 30% reduction in the overall weight of the bag over conventional bags, ultimately resulting in a commercial advantage of about 5% to 15%. Further, since no external heating process is involved during the conversion of the fabric into a bag, the conversion speed can be 20% to 50% higher than the bottom conversion of the heat seal block. Furthermore, since the polyolefin is substantially hydrophobic, it is known to those skilled in the art that surface activation is necessary to enhance the adhesion of external substances such as glue or adhesive, which has heretofore been impossible. The system of the present invention allows this. Finally, the adhesive strength obtained using the system of the present invention is about 0.75 to 1.8 times the fabric strength.

While several different embodiments of the present invention have been described, those skilled in the art will appreciate that other changes and modifications may be made without departing from the scope of the invention as defined in the appended claims.

Claims

1. A process for bag forming, the process comprising the steps of:

a. supplying a tubular polymeric web material and cutting it into cut pieces (1A) of suitable length;

b. opening the end of the cutting member (1A) to form a hexagon at either open end of the cutting member (1A), namely a first hexagon (10) and a second hexagon (10A), the two hexagons (10, 10A) having tabs (9) formed by folding the open ends, and the second hexagon (10A) having a first region (11) to receive the outer surface of a valve pad (4) and supplying and attaching the valve pad (4) to the second hexagon (10A);

c. folding the flap (9) and forming block bottoms, i.e. a first block bottom (12) and a second block bottom (12A), at both ends of the cutting member (1A), the block bottoms (12, 12A) having a second area (11A) to receive the outer surface of the cover sheet (4A);

d. -supplying and attaching the cover sheet (4A) to the block bottom (12, 12A) at the second area (11A);

Characterized in that in each of said step b and said step d a surface enhancing treatment is introduced, the step of applying a surface enhancing treatment to said first region (11) and said second region (11A) and to the outer surfaces (14) of said valve pad (4) and said cover sheet (4A) and the step of applying an adhesive as attachment means to said first region (11) and said second region (11A) and to the outer surfaces (14) of said valve pad (4) and said cover sheet (4A).

2. A process according to claim 1, wherein the first region (11) is positioned across the triangular portion of the second hexagon (10A) and the widest portion of the second hexagon (10A), and the second region (11A) is a rectangular region defined by the four corners of the first block bottom (12) and the second block bottom (12A).

3. A process according to claim 2, wherein the step of surface enhancing treatment comprises the step of providing at least one surface enhancing treatment unit (3) capable of providing a corona treatment, or a plasma treatment or a thin surface roughening treatment.

4. A process according to claim 3, wherein the surface-enhancing treatment unit (3) is provided at the stage of forming the bottom of the block, wherein the surface-enhancing treatment unit (3) treats those areas of the fins (9) of the hexagons (10, 10A) formed at the ends of the cut pieces (1A), the areas of the fins (9) overlapping each other after folding the fins (9) of the hexagons (10, 10A).

5. A process according to claim 3 or 4, wherein the surface enhancing treatment unit (3) is provided to treat the first region (11) before folding the fins (9) to form the block bottom (12, 12A).

6. A process according to claim 3 or 4, wherein the at least one surface enhancing treatment unit (3) is provided to treat an outer surface (14) of the valve pad (4) or the cover sheet (4A).

7. A process according to claim 3 or 4, wherein the at least one surface-enhancing treatment unit (3) is provided to treat the outer surface of the block bottom (12, 12A) to which the cover sheet (4A) is attached.

8. A process according to any one of claims 1 to 4, wherein the predetermined adhesion area comprises the overlapped area of the flap (9), the outer surface of the block bottom (12, 12A) formed and the outer surfaces of the valve pad (4) and the cover sheet (4A).

9. Process according to any one of claims 1 to 4, wherein the actual affixing in step b and step d is performed in a separate sealing unit (19), said sealing unit (19) being provided in each of said step b and step d and at each end of said cutting member (1A).

10. Process according to claim 9, wherein the sealing unit comprises a set of rollers comprising a suction roller (6) and a pressure roller (7), the cutting member (1A) passing under pressure through a gap between the suction roller (6) and the pressure roller (7).

11. The process according to any one of claims 1 to 4, wherein the adhesive is applied by an adhesive applicator (8), the adhesive applicator (8) being provided in each of the steps b and d.

12. Process according to claim 11, wherein the adhesive applicator (8) is provided with at least one nozzle (8A), which nozzle (8A) is capable of discharging adhesive at a desired rate and a desired pattern.

13. The process of claim 12, wherein the desired pattern comprises dots or dashed lines, or zig-zag lines or straight lines, or any combination thereof.

14. The process of any one of claims 1 to 4, wherein the adhesive comprises at least one of the following components: base polymer, resin, stabilizer, wax, and nucleation means.

15. The process of claim 14, wherein the base polymer is selected from the group consisting of polyamides, polyethylenes, amorphous poly-alpha-olefins, ethylene vinyl acetate copolymers, thermoplastic polyester elastomers, thermoplastic polyurethane elastomers, and thermoplastic copolyamide elastomers.

16. The process of claim 14, wherein the resin is a hydrocarbon resin compound.

17. A process according to claim 3, wherein the corona treatment is carried out by passing the cutting member requiring corona treatment between an electrode in a corona treatment station and a metal sheet to ensure that only a desired region of the cutting member is subjected to the corona treatment.

18. The process of claim 3, wherein the plasma treatment is performed by supplying energy in the form of radio frequency electromagnetic radiation to ionize a process gas, which can be oxygen, nitrogen, argon, helium, or combinations thereof, to generate a plasma of electrons, ions, and other high energy metastable species.

19. Process according to any one of claims 1 to 4, wherein in step 'a' of claim 1, the web material (1) can be a flat fabric, which is converted into a tubular web before being cut into pieces of suitable length for further processing according to step 'b'.

20. The process of any one of claims 1 to 4, wherein the adhesive can be a hot melt adhesive or a cold glue.

21. Process according to claim 9, wherein at least one cooling roller (19A) cools the sealing surface of the cut piece (1A) coming out of the sealing unit (19).

22. A process according to any one of claims 1 to 4, wherein the polymeric web material (1) is pre-coated or laminated with a thermoplastic on one or both sides.

23. The process of claim 22, wherein the thermoplastic is a polyolefin.

24. An apparatus for bag forming, the apparatus comprising:

-a first station (15) for supplying the web material (1) and cutting it into cut pieces (1A) of suitable length;

-a second station (16) for opening the ends of the cutting member (1A) to form a first hexagon (10) and a second hexagon (10A) at the respective ends of the cutting member (1A), the hexagons (10, 10A) having fins (9) and supplying a valve pad (4) and affixing the valve pad (4) to the second hexagon (10A);

-a third station (17) for folding the flaps (9) and forming a first block bottom (12) and a second block bottom (12A) at respective ends of the cut pieces (1A);

-a fourth station (18) for supplying a cover sheet (4A) and attaching said cover sheet (4A) to said block bottom (12, 12A) at a predetermined position;

characterized in that in each of the second station (16), the third station (17) and the fourth station (18) there is provided (i) at least one surface-enhancing treatment unit (3) for applying a surface-enhancing treatment to the cutting member (1A), the valve pad (4) and the cover sheet (4A), and (ii) a separate sealing unit (19) provided for each end of the cutting member (1A), the sealing unit (19) comprising at least one adhesive applicator (8) for applying an adhesive as an attachment means to the first and second areas (11) and (11A) and to the outer surfaces (14) of the valve pad (4) and the cover sheet (4A).

25. The apparatus of claim 24, wherein the adhesive applicator (8) is capable of applying adhesive in a pattern selected from the group consisting of dots or broken lines, or zigzagged lines or straight lines, or any combination thereof.

26. Apparatus according to claim 24 or 25, wherein at least one cooling roller (19A) is provided to cool the sealing area of the flap (4A) coming out of the sealing unit (19).

27. The apparatus according to claim 24 or 25, wherein the sealing unit comprises a set of rollers comprising a suction roller (6) and a pressure roller (7), the cutting member (1A) passing under pressure through a gap between the suction roller (6) and the pressure roller (7).

28. The apparatus according to claim 24 or 25, wherein the surface enhancing treatment unit (3) is a corona treatment, or a plasma treatment or a thin surface roughening treatment.

29. The apparatus according to claim 28, wherein the corona treatment is performed by passing the cutting member (1A) requiring corona treatment between an electrode in a corona treatment station and a metal plate.

30. The apparatus of claim 28, wherein the plasma treatment of the cutting member (1A) is performed by supplying energy in the form of radio frequency electromagnetic radiation to ionize a process gas, which may be oxygen, nitrogen, argon, helium or a combination thereof, to generate a plasma of electrons, ions and other high energy metastable species.

31. Apparatus according to claim 24 or 25, wherein the adhesive applicator (8) is activated by an electronic control unit for applying adhesive in a desired pattern and at a predetermined amount and rate.