US20070248291A1

US20070248291A1 - Vented plastic bag with filter medium

Info

Publication number: US20070248291A1
Application number: US11/407,622
Authority: US
Inventors: Rod Reeves; William Traywick
Original assignee: Exopack Thomasville LLC
Current assignee: Exopack Thomasville LLC
Priority date: 2006-04-20
Filing date: 2006-04-20
Publication date: 2007-10-25

Abstract

A vented plastic bag is adapted for containing a powdery product. The plastic bag includes a plurality of walls joined together and formed of a flexible plastic material. The walls define a fill opening for receiving the powdery product into the plastic bag. At least one of the bag walls defines a ventilation zone including a plurality of spaced-apart perforations. A filter medium overlies the ventilation zone and covers the plurality of perforations to substantially capture and retain the powdery product within the plastic bag during fill and ventilation.

Description

TECHNICAL FIELD AND BACKGROUND OF THE INVENTION

This invention relates generally to heavy duty plastic bags, and more specifically to a vented industrial shipping sack with an attached filter medium for capturing and retaining product, particularly during filling and venting. Vented bags are commonly used for packaging powdery products, such as powdered TiO2, ground gypsum, activated carbon, and the like. Such bags are typically fabricated from LD, HD, or LLD polyolefin sheet or tube stock, such as polyethylene or polypropylene having a thickness in the range of 3 to 12 mils. The sheet or tube stock may be coextruded or monoextruded, and may be a single ply or multi-ply material. The multi-ply material may be multiple thicknesses of the same sheet or tube stock, or different materials to provide particular characteristics, such as strength, flexibility, UV resistance, or color. The sheet stock may also be woven or non-woven synthetic or non-synthetic material. While the invention has particular application to vented bags with a capacity of from 20 to 100 pounds, the present concept can be applied to bags of any size and style.
There exists a present and long-felt need in the industry for a heavy duty industrial shipping sack for packaging powdery products. One primary advantage of traditional paper-like (or fibrous) shipping sacks is their inherent ability to filter product during the filling process. Drawbacks to such bags, however, are substantial. For example, many powdery products cannot tolerate fiber contamination common in a paper environment. Additionally, paper sacks are considerably weaker than plastic, and often cannot withstand the rigors of external, environmental conditions. While use of a plastic bag is generally preferable for increased strength and durability, common fill processes which force powdery product into the bag under pressure require effective ventilation and the ability to retain the product inside the bag during filling, venting, and shipping.
Prior art plastic shipping sacks with perforations have been used to package a variety of products, but have limited use for powdery products due to their inability to properly retain product during filling and ventilation. These bags typically have a rank-and-file arrangement of relatively large perforations. Plastic bags with much smaller perforations have had some success, but often either still allow small particles to exit the package, or worse, the small particles can plug the perforations and not allow the air to evacuate. Other prior art plastic bags comprise multiple layers with off-set perforations. While these type bags have had limited success, excessive powder is often either captured in-between the multiple layers or escapes from the bag altogether.
Outside of re-engineering the plastic bag, some in the industry have invested heavily in equipment designed to remove the air during packaging of powdery products. This equipment is expensive, and still often requires some sort of secondary ventilation.

SUMMARY OF INVENTION

Therefore, it is an object of the invention to provide a vented industrial shipping bag with an attached filter medium for capturing and retaining powdery product during filling and venting.
It is another object of the invention to provide a vented plastic shipping bag which is fabricated from plastic sheet or tube stock.
It is another object of the invention to provide a vented plastic bag which incorporates a fibrous, air-release filter medium.
It is another object of the invention to provide a vented plastic bag which incorporates a filter medium comprising a random arrangement of variable-size filter openings which resist clogging.
It is another object of the invention to provide a vented plastic bag which can withstand higher packaging temperatures (as compared to standard polyethylene shipping sacks).
It is another object of the invention to provide a vented plastic bag which incorporates a fibrous and absorbent filter medium that acts to draw and trap moisture away from the packaged product, while allowing air release.
It is another object of the invention to provide a vented plastic bag which is applicable for packaging powdery products that can be readily dissolved along with the bag without ever opening the package.
It is another object of the invention to provide a vented plastic bag which is available in a version such that end users could incorporate their own selected micron-rated filter-ply films to custom manufacture, fill and seal their own packaging.
It is another object of the invention to provide a multi-layer packaging composite which is applicable for use with automatic form/fill/seal machines.
It is another object of the invention to provide a method for filling a plastic bag with a powdery product.
These and other objects of the present invention are achieved in the preferred embodiments disclosed below by providing a vented plastic bag adapted for containing a powdery product. The term “powdery product” refers to any loose product composed of or similar to powder and which may contain fines or other small particulate matter. The plastic bag includes a plurality of walls joined together and formed of a flexible plastic material. The term “joined” means either two formerly separate sheets connected together, or integrally formed by, for example, folding over a sheet to form an edge. The walls define a fill opening for receiving the powdery product into the plastic bag. At least one of the plastic bag walls defines a ventilation zone comprising a plurality of spaced-apart perforations. A fibrous filter medium overlies the ventilation zone and covers the plurality of perforations to substantially capture and retain the powdery product within the plastic bag during fill and ventilation. The term “fibrous” is defined broadly herein to mean any material containing, consisting of, or resembling fibers. Alternatively, the filter medium may comprise any non-fibrous material which defines a similar random arrangement of variable-size filtration openings.
Preferably, the filter medium comprises a single-ply filter panel.
According to one preferred embodiment of the invention, the filter panel is affixed to the plastic bag along welded seams (and without needle openings).
Preferably, the filter medium comprises a non-woven material.
According to one preferred embodiment of the invention, the filter medium comprises a fibrous material selected from a group consisting of polyester felt, polypropylene microfiber, nylon monofilament, polyethylene, and PTFE.
Preferably, the micron rating of the filter medium is less than the micron rating of the perforations of the ventilation zone.
According to one preferred embodiment of the invention, the filter medium has a nominal micron rating of less than 100.
According to another preferred embodiment of the invention, the perforations of the ventilation zone have a nominal micron rating greater than 500.
Preferably, the filter medium is positioned to reside between the powdery product and ventilation zone. Alternatively, the filter medium may reside adjacent the ventilation zone on an outside surface of the bag wall.
According to one preferred embodiment of the invention, a product-side surface of said filter medium is glazed to reduce fiber contamination of the powdery product.
In another embodiment, the invention is a method for filling a plastic bag with a powdery product. The method includes the steps of inserting the powdery product into the plastic bag, and venting the plastic bag. During ventilation, air exiting the plastic bag is filtered using a fibrous filter medium to substantially capture and retain the powdery product within the plastic bag.

BRIEF DESCRIPTION OF THE DRAWINGS

Some of the objects of the invention have been set forth above. Other objects and advantages of the invention will appear as the description proceeds when taken in conjunction with the following drawings, in which:
FIG. 1 is a perspective view of a powder-filled plastic vented bag according to one preferred embodiment of the present invention;
FIG. 2 is a view of the vented bag laid flat prior to filling;
FIG. 3 is a fragmentary view of the vented bag with one bag wall cut away and the filter medium partially pulled from the opposite, perforated bag wall;
FIG. 4 is a further fragmentary view of the vented bag with various layers shown in cross-section, and demonstrating the escape of air through the filter medium and perforated bag wall.

DESCRIPTION OF THE PREFERRED EMBODIMENT AND BEST MODE

The present invention is described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be operative and enabling. Like numbers refer to like elements throughout. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. Unless otherwise expressly defined herein, such terms are intended to be given their broad ordinary and customary meaning not inconsistent with that applicable in the relevant industry and without restriction to any specific embodiment hereinafter described.
Referring now specifically to the drawings, a plastic vented bag according to a preferred embodiment of the present invention is illustrated in FIG. 1 and shown generally at reference numeral 10. The vented bag 10 is especially applicable for packaging powdery products, such as powdered chemicals. The vented bag 10 may be formed in any desired size and style including satchel-style valve bags, pillow-style valve bags, open mouth bags, and film type bags used by automatic form-fill-seal machines.
In the embodiment shown, the vented bag 10 comprises a valve bag which is satchel-style pasted at both ends during its manufacture. The bag 10 is preferably machine-fabricated from heavy duty polyolefin tube stock, and comprises opposing integrally-formed walls 1 1 and 12 defining a top 14, bottom 15 and sides 16 and 17. When the bag walls 11, 12 are sealed to form the closed ends 14, 15, a tape of plastic is added to create the filling valve (not shown) in one of the corners of the bag 10. A flexible plastic sleeve 18 extends out of the valve and cooperates with a valve packer (e.g., air, auger, impeller, belt) to load product into the bag 10. After filling, the sleeve 18 is typically folded and tucked into the valve. The valve bag 10 may be closed using a self-closing internal valve, ultrasonic sealing, or other suitable means.
As best shown in FIGS. 1 and 2, in order to allow venting during filling, a number of spaced-apart perforations 21 are formed in the bag 10 in an area of the wall 11 The perforations 21 are preferably spaced in a rank-and-file arrangement defining a ventilation zone which covers a majority of the wall 11 of the bag 10. According to one embodiment, the ventilation zone occupies greater than 25% of the entire surface area of the bag walls 11, 12. The size or “micron rating” of each perforation 21 is relatively large to promote rapid expulsion of air. Preferably, the nominal micron rating is at least 100, and more preferably, greater than 500. The “nominal” rating means that the bag wall 11 will capture substantially all particles larger than 100 micron, but will allow some percentage of particles larger than 100 microns to by-pass the perforations.
Referring to FIGS. 3 and 4, to prevent the escape of powdery product “P” through the relatively large perforations 21 during filling and venting of the bag 10, a fibrous non-woven filter ply 25 is affixed to the plastic wall 11 by fabric welding, adhesive, or other means (outside of sewing). The filter ply 25 is preferably joined to the bag 10 by continuous seams 27 and 28 along its longitudinal edges, and along its end edges by welded end seams (not shown). Because there are no sewn holes in the bag 10 there is no particle by-pass through the seams 27, 28. The filter ply 25 overlies the ventilation zone on either an inside or outside of the perforated plastic wall 11, and completely covers each of the perforations 21 such that air exiting the vented bag 10 is first filtered to substantially capture and retain product “P” within the bag 10. FIG. 4 demonstrates the evacuation of air “A” through the filter ply 25 and perforated bag wall 11.
According to one preferred embodiment, the filter ply 25 comprises a spunbonded, non-woven polypropylene microfiber. Alternatively, the filter ply 25 may comprise other fibrous or fiber-like materials including paper, melt-blown polyethylene, nylon monofilament, polyester felt, or PTFE. The filter ply 25 may also comprise a non-fibrous, mechanically perforated, 2- or 3-dimensional substrate which defines a similar random arrangement of clog-resistant, variable-size openings. Preferably, the filter ply 25 is a self-supported or scrim-supported material. To avoid fiber contamination, the product-side surface 25A of the filter ply 25 may be singed or glazed.
While the micron rating of the filter ply 25 will vary depending on user requirements, the size of the filter openings in all cases will likely be smaller than the wall perforations 21. For most powders, the nominal micron rating will be less than 100. As indicated above, the micron rating selected determines the size of the particles captured as the product is filtered.
A plastic vented bag is described above. Various details of the invention may be changed without departing from its scope. Furthermore, the foregoing description of the preferred embodiment of the invention and the best mode of practicing the invention are provided for the purpose of illustration only and not for the purpose of limitation-the invention being defined by the claims.

Claims

1. A vented plastic bag adapted for containing a powdery product, said plastic bag comprising:

a plurality of walls joined together and formed of a flexible plastic material, said walls defining a fill opening for receiving the powdery product into said plastic bag;

at least one of said bag walls defining a ventilation zone comprising a plurality of spaced-apart perforations; and

a fibrous filter medium overlying said ventilation zone and covering said plurality of perforations to substantially capture and retain the powdery product within said plastic bag during fill and ventilation.

2. A vented plastic bag according to claim 1, wherein said filter medium comprises a single-ply filter panel.

3. A vented plastic bag according to claim 2, wherein said filter panel is affixed to said plastic bag along welded seams.

4. A vented plastic bag according to claim 1, wherein said filter medium comprises a non-woven material.

5. A vented plastic bag according to claim 1, wherein said filter medium comprises a fibrous material selected from a group consisting of polyester felt, polypropylene microfiber, nylon monofilament, polyethylene, and PTFE.

6. A vented plastic bag according to claim 1, wherein said filter medium has a nominal micron rating of less than 100.

7. A vented plastic bag according to claim 6, wherein the perforations of said ventilation zone have a nominal micron rating greater than 500.

8. A vented plastic bag according to claim 1, wherein said filter medium is positioned to reside between the powdery product and ventilation zone.

9. A vented plastic bag according to claim 8, wherein a product-side surface of said filter medium is glazed to reduce fiber contamination of the powdery product.

10. A vented plastic bag adapted for containing a powdery product, said plastic bag comprising:

a filter medium overlying said ventilation zone and covering said plurality of perforations to substantially capture and retain the powdery product within said plastic bag during fill and ventilation, said filter medium defining a random arrangement of variable-size filtration openings.

11. A vented plastic bag according to claim 10, wherein said filter medium comprises a single-ply filter panel.

12. A vented plastic bag according to claim 11, wherein said filter panel is affixed to said plastic bag along welded seams.

13. A vented plastic bag according to claim 10, wherein said filter medium comprises a non-woven material.

14. A vented plastic bag according to claim 10, wherein said filter medium comprises a fibrous material selected from a group consisting of polyester felt, polypropylene microfiber, nylon monofilament, polyethylene, and PTFE.

15. A vented plastic bag according to claim 10, wherein said filter medium has a nominal micron rating of less than 100.

16. A vented plastic bag according to claim 15, wherein the perforations of said ventilation zone have a nominal micron rating greater than 500.

17. A vented plastic bag according to claim 10, wherein said filter medium is positioned to reside between the powdery product and ventilation zone.

18. A vented plastic bag according to claim 17, wherein a product-side surface of said filter medium is glazed to reduce fiber contamination of the powdery product.

19. A method for filling a plastic bag with a powdery product, said method comprising the steps of:

inserting the powdery product into the plastic bag;

venting the plastic bag; and

during ventilation, filtering air exiting the plastic bag using a fibrous filter medium to substantially capture and retain the powdery product within the plastic bag.

20. A method according to claim 19, and comprising venting the plastic bag through a plurality of perforations formed with a wall of the bag.

21. A method for filling a plastic bag with a powdery product, said method comprising the steps of:

inserting the powdery product into the plastic bag;

venting the plastic bag; and

during ventilation, filtering air exiting the plastic bag using a filter medium to substantially capture and retain the powdery product within the plastic bag, the filter medium defining a random arrangement of variable-size filtration openings.

22. A method according to claim 21, and comprising venting the plastic bag through a plurality of perforations formed with a wall of the bag.

23. A multi-layer packaging composite, comprising:

a flexible plastic sheet material comprising a plurality of spaced-apart perforations; and

a fibrous filter medium overlying said sheet material and covering said plurality of perforations.

24. A packaging composite according to claim 23, wherein said filter medium comprises a single-ply filter panel.

25. A packaging composite according to claim 24, wherein said filter panel is affixed to said plastic sheet material along welded seams.

26. A packaging composite according to claim 23, wherein said filter medium comprises a non-woven material.

27. A packaging composite according to claim 23, wherein said filter medium comprises a fibrous material selected from a group consisting of polyester felt, polypropylene microfiber, nylon monofilament, polyethylene, and PTFE.

28. A packaging composite according to claim 23, wherein said filter medium has a nominal micron rating of less than 100.

29. A packaging composite according to claim 28, wherein the perforations of said plastic sheet material have a nominal micron rating greater than 500.

30. A packaging composite according to claim 23, wherein said filter medium comprising an inside surface residing adjacent said plastic sheet material and a glazed outside surface.

31. A multi-layer packaging composite, comprising:

a filter medium overlying said sheet material and covering said plurality of perforations, said filter medium defining a random arrangement of variable-size filtration openings.

32. A packaging composite according to claim 31, wherein said filter medium comprises a single-ply filter panel.

33. A packaging composite according to claim 32, wherein said filter panel is affixed to said plastic sheet material along welded seams.

34. A packaging composite according to claim 31, wherein said filter medium comprises a non-woven material.

35. A packaging composite according to claim 31, wherein said filter medium comprises a fibrous material selected from a group consisting of polyester felt, polypropylene microfiber, nylon monofilament, polyethylene, and PTFE.

36. A packaging composite according to claim 31, wherein said filter medium has a nominal micron rating of less than 100.

37. A packaging composite according to claim 36, wherein the perforations of said plastic sheet material have a nominal micron rating greater than 500.

38. A packaging composite according to claim 31, wherein said filter medium comprising an inside surface residing adjacent said plastic sheet material and a glazed outside surface.