BR122020007252B1 - HIGHLY ORIENTED POLYPROPYLENE FABRIC BULK BAG - Google Patents

Abstract

The present invention relates to a method of producing flexible polypropylene fabric bags with heat-fused seams comprising providing fabric pieces, wherein each fabric piece has a coated side and an uncoated side; positioning fabric pieces so that a coated side of one fabric piece faces a coated side of another fabric piece; selecting an area of fabric to be joined for forming a seam or joint; applying heat to the area to be joined that is lower than the melting point of the fabrics, to form one or more seams or joints and wherein the heat-fused seams or joints of a resulting polypropylene bag retain at least 85% of the strength of the fabric without using sewing machines.

Description

CROSS-REFERENCE TO RELATED ORDERS

[001] The priority of U.S. Provisional Patent Application Serial No. 61/831,476, filed June 5, 2013; U.S. Provisional Patent Application Serial No. 61/890,664, filed October 14, 2013; U.S. Provisional Patent Application Serial No. 61/909,737, filed November 27, 2013 and U.S. Provisional Patent Application No. 61/994,642, filed May 16, 2014, each of which is hereby incorporated herein by reference, is hereby claimed.

[002] U.S. Patent Application Serial No. 14/297,331, filed June 5, 2014, is hereby incorporated herein by reference.

STATEMENT ON FEDERAL GOVERNMENT-SPONSORED RESEARCH OR DEVELOPMENT

[003] Not applicable

REFERENCE TO A "MICROFICHE ANNEX"

[004] Not applicable

BACKGROUND OF THE INVENTION 1. Field of Invention

[005] The present invention relates to the bulk bag industry and the technique for producing bulk bags without the use of sewing machines and seams. The invention further relates to the production of flexible fabric packages, bags or containers with no contamination of the thread and minimal human contact with the interior of the package, fabric or container to help eliminate concerns regarding bacterial contamination. The invention further relates to the production of nearly air-tight flexible fabric packages, bags or containers that contain no stitching or holes.

2. General Background of the Invention

[006] Polypropylene woven fabrics have long been the fabric of choice in certain industries, including the bulk bag industry, due to the strength, cost and flexibility of the fabrics. Although polypropylene woven fabrics and some similar fabrics are very strong, they are also very chemically inert. Polypropylene fabrics are highly oriented through a heat and stretch process to achieve maximum strength while maintaining the necessary fabric flexibility to meet market needs. Because of these properties, it is very difficult to find a method of joining two polypropylene fabrics together without damaging the fabric itself, thereby significantly reducing the strength and usefulness of the fabrics.

[007] The bulk bag industry is now over 40 years old. The first bulk bags were constructed by combining various configurations of woven fabrics and braided webbing and sewing them together to achieve the required strength.

[008] Now, stitching remains almost the exclusive method for connecting construction materials when making bulk bags. Determining which fabrics to use and which stitching patterns and threads to use to combine these parts to create the most economical bulk bag container is well known and has been studied in great detail.

[009] However, the basic methods cannot produce the most economical container since the act of sewing reduces the strength of the fabric through needle puncture. The average stitch in these high strength polypropylene woven fabrics creates seams that are typically about 63% of the strength of unstitched fabrics.

[010] Therefore, in order for the seams to be strong enough, the fabrics themselves must be constructed thicker and stronger to compensate for the loss of strength in the seam.

[011] Much effort has been made to find an acceptable alternative to sewing polypropylene fabrics for several reasons. 1. The act of sewing creates thread ends that must be trimmed from the end of each seam line. These ends often become loose and can become unwanted contamination without bags. 2. Due to the high heat generated by the needles passing through this tough polypropylene fabric, the threads often break. This causes production to stop momentarily while the thread is rethreaded into the machine. 3. Sewing machines can run at speeds of several thousand stitches per minute. At this high speed with many mechanical parts, there is a high incidence of part breakage and needle breakage that stops production on that machine while it is being repaired.

[012] Due to points 2 & 3, the production of bulk bags, for example, requires a high amount of labor to operate these machines and deal with these issues. Global bulk bag production has largely occurred outside the United States, being produced in countries with abundant sources of low-wage labor.

[013] Additionally, seams reduce the strength of polypropylene or other similar fabrics as the needle puncture breaks the fibers in the area and reduces the overall strength of the fabric. The number of stitches in each inch or centimeter of the seam, the size of the needle, and the thickness of the thread used to make the stitch all play a role in the overall strength of the resulting seam. Often, these seams produce a joint that is about 63 to 70% of the strength of the unstitched fabric. Due to the weakening of the fabrics, fabrics that are 30% stronger than would theoretically be necessary to carry the very heavy weights that bulk bags are designed to carry may be used. For all of these reasons, an alternative to sewing has been desired and sought after within the industry for many years.

[014] Thus, for many years, the industry has sought an alternative to sewing as a method of bulk bag construction. Various glues and welding methods have been tried. Contact adhesives have proven unsuccessful due to: 1. Poor peel resistance; 2. Lack of a permanent bond (contact adhesives remain active so that they can be peeled and reattached again and again); 3. A bond that is easily affected by temperature changes (the adhesive often melts at very low temperatures and becomes inactive at colder temperatures); 4. Cut resistance that is only achieved with very large area type coverage. Solvent adhesives have also failed due to the following: a. The joints are brittle and inflexible; b. They often involve hazardous elements not permitted in food packaging; and c. The strength of the fabric is reduced by molecular reconfiguration.

[015] Heat welding has been attempted and largely rejected because heat welding, as in the prior art, must reach the melting point of the polypropylene fabrics to bond them. However, polypropylene fabrics are highly oriented and placing them at this temperature level results in a loss of tensile strength of the fabric of approximately 50%.

[016] Laser welding has been tried and has shown some marginal success, but this method is not economically feasible due to low production rates and very high capital costs.

[017] The basic problem has always been that bulk bags must safely carry enormous weights, e.g. in some cases up to 3,300 (1,497 kilograms) or 4,400 pounds (1,996 kilograms). Many previous efforts have shown that joints can be achieved, but nothing in the prior art has shown that they are capable of carrying the enormous weights with the required 5 to 1 lifting safety in the resulting containers.

[018] Therefore, after 40 years of production, sewing still remains the basic method of bulk bag production. Bulk bags are still largely manufactured by the original methods of sewing woven polypropylene fabrics together to form the bag and its lifting components. As discussed above, polypropylene has been the primary fabric of choice due to its combination of strength, flexibility, and cost.

[019] The heat sealing technique is well known in the fabric and plastics industries such as those industries using polyethylene or PVC fabrics. The prior art method was simple. Heat the fabric to any temperature greater than the melting temperature of polyethylene then knock the fabric pieces apart with sufficient force to eliminate any melt laminate coatings between the fabrics and allow the fabrics to bond directly together. Heat sealing equipment is useful in that it is significantly more amenable to automation than sewing machines. It has far fewer moving parts and can be electronically monitored for reliable repeatability.

[020] In the prior art, polyethylene fabrics are heated past their melting point, then squeezed with sufficient pressure (e.g., 20 psi (137.8 kilopascals)) to ensure that the fabrics meet and bond within a predetermined amount of time, and the joint is made. This joint is typically around 80 to 85% of the materials original strength. Since these materials are not as highly oriented as compared to polypropylene, this high heat method results in an acceptable joint. In the prior art, pressure can generally be applied at approximately 20 psi (137.8 kilopascals) across the entire joint area to eliminate laminations. The heat is applied at temperatures significantly above the melting point of the polyethylene fabric so that the laminations would become liquefied and the surface of the woven pieces would also become fused. The liquefied lamination was then squeezed out of the fabrics and the molten surfaces of the fabrics themselves were used to make the joint. Exemplary melting points of some polyethylene fabrics may be 235 or 265 degrees Fahrenheit (112.8 or 129.4 degrees Celsius). High and low density polyethylene fabrics are made in the prior art and different polyethylene fabrics may have different melting points, with low density polyethylene generally having a lower melting point than high density polyethylene. Temperatures of, for example, 425 to 500 degrees Fahrenheit (218.3 to 260 degrees Celsius) are used in the prior art to fuse the laminated film and the polyethylene fabric. Additionally, polyethylene has about 30% less tensile strength than polypropylene of similar size and a much greater amount of stretch. Therefore, polyethylene has not been a useful alternative fabric when making bags to carry the large weights of bulk bags (up to 4,400 pounds (1,996 kilograms) for example).

[021] However, polypropylene is so highly oriented that the use of current or standard heat sealing procedures, which call for temperatures exceeding the melting point of the fabrics, results in the strength of the fabric itself being greatly deteriorated. Testing conducted in connection with the development of the present invention has shown an average loss of tensile strength of approximately 50% when polypropylene fabric is joined by standard heat sealing methods, wherein the fabric is heated to a temperature exceeding the melting point of the fabric. This then results in strengths that are significantly lower than the strengths currently available through the sewing of polypropylene fabrics. Thicker and stronger fabrics may therefore be preferred to be used so that the final strength of a resulting product will safely support the required weights needed for the product. Furthermore, such joints produced by heat sealing polypropylene fabric with standard heat sealing methods show a measure of crystallization in the joint area which also reduces the flexibility of the fabrics in the joint areas.

[022] There is a need in the industry to produce products comprising polyethylene fabrics with stronger heat-sealed seams or joints than what is achieved by prior art methods of heat-sealing polyethylene fabrics.

[023] There is a need in the industry to produce products comprising polypropylene fabrics, including bulk fabric bags, by sealing rather than sewing the fabric parts or pieces together, since needles frequently break and sewing requires an operator to replace the needle and repair stitches that were not applied properly.

[024] There is also a need in the industry to produce products comprising polypropylene or polyethylene fabrics, including woven bulk bags, by sealing rather than sewing the pieces together. The use of sewing machines for bulk bag production, for example, involves high amounts of labor, contamination of the thread will always be a possibility, and leakage of powders through the seams will always be a concern.

[025] Although sewing machines may be capable of being automated, they have not been able to operate in an automated manner. Threads break as heat builds up and an operator is required to resequence the machine with new thread. These machines operate at high speeds and frequently skip stitches. This requires an operator to see this quality problem and repair it immediately.

[026] The following prior art references are incorporated herein by reference.

BRIEF SUMMARY OF THE INVENTION

[027] The apparatus and method of the present invention solve the problems confronted in the art in a simple and objective manner. What is provided is an alternative method of joining polypropylene woven fabrics or similar fabrics without the use of sewing machines and sewing thread. Also provided is a method for joining polyethylene fabrics without the use of sewing machines and sewing thread. The present invention is useful in the production of bulk bags, and will also be applicable to any product in which it is desired to join polypropylene fabrics, polyethylene fabrics, or similar fabrics without the use of sewing machines. This invention also relates to the ability to produce products involving the joining of polypropylene fabrics or similar fabrics, including bulk bags, with minimal labor, thereby allowing such products to be made in all areas of the world where the products are needed, versus only being produced in volume in those areas of the world with large amounts of low wage labor.

[028] It is thus an object of the present invention to provide an alternative to sewing polypropylene or similar fabrics in the production of bulk bags and other flexible fabric products or containers. The present invention seeks to provide an alternative method of joining polypropylene or similar woven fabrics without the use of sewing machines and sewing thread. Although this invention is useful in the production of bulk bags, it will be applicable to any product where it is desired to join polypropylene or similar fabrics without the use of sewing machines. For example, the present invention may also be useful with smaller bags (to hold 25 to 100 pounds (11 to 45 kilograms)).

[029] Another objective of this invention is to design a sealing system that can use simple robots for automation in the construction of flexible fabric containers.

[030] It is a further object of the present invention that a flexible fabric bag or product made by heat sealing versus sewing has many advantages as follows, lower wage content, reduced or eliminated contamination of the sewing thread, new needle holes to allow for product leakage or moisture and contamination in a more consistent quality controlled by computerized production rather than being made by hand with all the attendant consistency problems that such a method creates.

[031] It is a further object of the present invention that flexible fabric products made by heat sealing have great commercial appeal to those companies for whom any contamination of the thread would compromise the quality of their product. Such companies would be in the food or electronics or medical or pharmaceutical industries. These bags would not have any threads that would endanger things since there is no stitching.

[032] It is a further object that the present invention provides a flexible fabric product that has broad appeal to those companies that are concerned about their product leaking through needle holes left by the sewing process. Such companies may include carbon black companies, where minute amounts of their product can be very messy. Other companies may include companies whose products are going into sensitive end-user environments, where small amounts of their product would contaminate the area.

[033] It is a further object of the present invention to provide a flexible fabric product that would not require a polyethylene coating. This would be useful to companies that are using polyethylene coatings to prevent leakage and contamination. Coatings make bulk bags, for example, more difficult to work with and add a notable amount of cost to the overall product.

[034] It is a further object that the present invention provides a method that enables companies to proceed with full automation for the production of woven fabric product.

[035] It is a further object of the present invention to provide heat-sealed joints with minimal damage to the original fabric to allow for lower costs by facilitating automated production to reduce labor costs and also by facilitating the reduction of fabric weights and thicknesses while providing similar overall strengths through greater sewing efficiencies.

[036] It is a further object of the present invention to use heat sealing equipment, which can be automated, to produce polypropylene products without requiring seams or sewing machines. It is also an object of the present invention to use heat sealing methods to produce products comprising polypropylene-like fabrics, without requiring seams or sewing machines.

[037] Another object of the present invention is to facilitate a robotic or automated system for the production of large fabric bags, e.g. polypropylene bulk bags or barrier cells, for the formation of a flood barrier, e.g. when filled with sand or the like, using robots or another automated system.

[038] An additional object of the present invention is to provide a heat-sealed polypropylene product that can be manufactured without human touch to the interior of the product, so as to maintain a sterile product and help eliminate a concern regarding bacterial contamination of polypropylene storage products, as well as eliminate the possibility of leakage through seam holes, so that the product can be used in medical applications, for example, in the pharmaceutical industry.

[039] In developing the present invention, testing and experimentation were conducted. For example, testing and experimentation with heat-sealable polypropylene fabric was conducted. The test results showed that these fabrics are highly oriented for strength. This high orientation and the molecular structure of polypropylene made efforts to join two pieces of this material difficult. To join the polypropylene fabric pieces required such a level of heat that the polypropylene fabric simply crystallized, rendering it brittle and not useful for the purpose of lifting large weights, a purpose for which bulk bags, for example, are routinely used.

[040] In addition to crystallization of the fabric, heat sealing polypropylene fabric using standard procedures known in the art has resulted in seams with two distinctly different strengths. In sewing operations, including sewing, there is a "cut strength" and a "peel strength". For example, the lifting handles sewn to the side walls of a bulk bag have incredible strength when pulled upwards since this movement utilizes the cut strength of this joint, where the entire joint is sharing the load at all times. But if the bag is sitting on its side and it is picked up by a handle, the joint is temporarily placed in a position where the peel strength becomes critical, where one edge of the joint is clamped. Thus, in the cut strength position, the entire joint is sharing the load at all times. In the peel strength position, only one edge of the joint is clamped or carrying the load. As one edge fails, the next edge and then the next edge fail in sequence.

[041] This problem of cut versus peel resistance was considered when experimenting with heat-sealable polypropylene fabric to construct bulk bags, for example, because any interior panel that can be heat-sealed into a bulk bag can be held by the weight of the fill material on both sides. It is also difficult to control all fill situations in the field. An object of the present invention is to create a seam that works in both directions. An object of the present invention was also to develop different seam configurations that would always have cut resistance in their favor.

[042] In testing panels for the interior, a fabric container for flood wall use, for example, an upside down “T” shaped seam construction was developed and used. The test revealed that if the load came from the right side of the ‘T’, the right side of the seal or joint would be in shear and the left side would be in peel. But the right side would protect the left side with all its shear resistance. If the load or force came from the left side, the seam would work in reverse with the shear resistance on the left protecting the peel on the right.

[043] In additional testing conducted with polypropylene fabrics, different glues were tested to make the joints usable with polypropylene fabric. The test results using Super Glue showed that the Super Glue did not achieve a cut resistance of 20 pounds (9 kilograms).

[044] Testing was also conducted using different types of fabric. Polyethylene fabric is similar to polypropylene, but is not as highly oriented, and many products comprising polyethylene have been made using standard heat sealing methods.

[045] Testing and experimentation with polyethylene fabric showed that polyethylene fabrics were generally about 30% weaker than polypropylene fabrics. The testing was conducted on heat-sealing polyethylene fabric to produce a bulk bag. As discussed earlier, polypropylene fabric has been preferred in the bulk bag industry because of its greater strength.

[046] Prior art heat sealing methods generally involve high enough heat and high enough applied pressure to melt the base fabrics and bond them together. This method purposefully melts any applied coating and blows it apart through high pressure levels so that the woven materials in the base can be bonded together. This method has been successful with polyethylene fabrics and was necessary because the strength being relied upon came from the woven fabrics. The coatings were generally applied for the purpose of providing dust and/or moisture control. The technology at the time of application in the laminations did not provide reliably strong bonds of the coating to the fabric by itself. Therefore, the technique of bonding the fabrics intentionally fused the laminated materials by melting and squeezing them between the fabrics.

[047] In the prior art, the standard method discussed above has been applied to woven fabrics having a thin layer of laminated film on at least one side, e.g., a layer of 1 or 2 mils (0.0254 or 0.0508 mm). For polyethylene fabrics, the standard laminated film or coating is often comprised of polyethylene or a blend of polyethylene and other additives. Standard prior art methods apply pressure to remove the laminated film or coating from between the layers of polyethylene fabric to allow the fabric pieces to fuse and bond. Traditionally in the art, the laminated film or coating has not been very securely attached to the woven fabrics. Therefore, if the joint included the laminated film itself, the lamination became the cause of joint failure due to its poor attachment to the woven fabrics.

[048] To determine strength, laminated woven fabrics can be tensile tested before being joined to provide a reference fabric strength. For example, a fabric may tear at 200 lbs. per inch (3,572 kilograms per meter) in its raw state. Two pieces of this fabric may then be joined together and then shredded again. A resulting strength of, for example, 160 to 165 lbs. per inch (2,857 to 2,946 kilograms/meter) would mean that the resulting joint would have lost 17 to 20% of the total fabric strength as a result of being sealed together. While this strength may be sufficient based on current industry standards, it represents a significant cost of inefficiency.

[049] In one embodiment of the method of the present invention, the method provides a heat-fused joint between the polyethylene fabric pieces by bonding the laminations rather than by bonding the fabrics. Current lamination methods now produce a bond or connection between the woven fabric and the lamination that is very strong and reliable. By leaving the lamination in place between the fabrics and not bonding the fabric pieces, the improved sealing method of the present invention adds the strength of the lamination to the total strength of the joint. Additionally, since the method of the present invention does not damage the fabric when fusing the woven pieces, the sealed joint retains virtually all of the basic strength of the woven fabrics. The small percentage of strength loss, e.g., two or three percent strength that may be lost, is the result of minimal damage to the laminated film through the fusion and melting that occurs in the present method.

[050] In the prior art, pressure may generally be applied at approximately 20 psi (137.8 kilopascals) across the entire joint area to eliminate the laminations. Heat is applied at temperatures significantly above the melting point of the polyethylene fabric so that the laminations become liquefied and the surface of the woven pieces also becomes fused. The liquefied lamination is then eliminated from between the fabrics and the fused surfaces of the fabrics themselves are used to make the joint. Exemplary melting points of some polyethylene fabrics may be 235 or 265 degrees Fahrenheit (112.8 or 129.4 degrees Celsius). Both high and low density polyethylene fabrics are made in the prior art, and different polyethylene fabrics may have different melting points, with low density polyethylene generally having a lower melting point than high density polyethylene. Temperatures, for example, of 425 to 500 degrees Fahrenheit (218.3 to 260 degrees Celsius) are applied in the prior art to fuse the laminated film and the polyethylene fabric.

[051] One embodiment of the method of the present invention comprises joining polyethylene fabrics using controlled amounts of heat, time and pressure that leave the base or braid materials unfused and undamaged while still fusing the laminations. The pressure levels are kept light enough to leave the lightly fused lamination in place rather than purposefully eliminating it from between the braided pieces of the joint.

[052] Another embodiment of the present invention comprises a method of heat sealing polyethylene fabric comprising joining the polyethylene fabrics using controlled amounts of heat, time and pressure that leave the base or braid materials unfused and undamaged by further fusing the laminations.

[053] In another embodiment of the polyethylene fabric heat sealing method, the pressure levels are kept light enough to leave a slightly fused lamination in place rather than eliminating it from between the woven pieces of the joint.

[054] In another embodiment of the polyethylene fabric heat sealing method, the seals provide 90% to 97% resistance in the cut direction.

[055] In another embodiment of the method of heat sealing the polyethylene fabric, the seal comprises a strength of 92 to 95%.

[056] In another embodiment of the method of heat sealing the polyethylene fabric the seal comprises a strength of 96 to 97%.

[057] In another embodiment of the method of heat sealing polyethylene fabric, the method comprises heating a laminated film or coating on direct polyethylene fabric pieces at or rarely above the melting point of the polyethylene fabrics so that only the lamination is melted and liquefied. Then, light pressures, e.g., 5 to 6 psi (34.5 to 41.4 kilopascals), are used to join the laminations of the fabric pieces, rather than pushing them together and joining the underlying fabrics. In another embodiment of the method of heat sealing polyethylene fabric, the method provides a heat fused polyethylene seal or joint having 90 to 97% strength as compared to the strength of the original fabric.

[058] Another embodiment of the present invention comprises heat-fusing polyethylene fabrics to produce a bulk bag. In one embodiment of the polyethylene bulk bag of the present invention, the bag would include lifting loops, but would include fabric tunnels that would use the strength of the entire bag fabrics for lifting versus lifting loop bags that use only a small portion of the fabric for lifting. Test results in one embodiment of the present invention showed that a heat-sealed bulk bag constructed from the polyethylene fabric held up to 18,000 lbs (8,165 kilograms) of hydraulic pressure before failing. At a safety ratio of 5 to 1, this bag could be useful for applications carrying up to 3,600 lbs (1,633 kilograms). In this embodiment, the method used the entire fabric on two sides of the bag. Additionally, the fabric was folded so the heat seal would be at the bottom of the bag and protected from any potential peeling forces. Although the heat-melt polyethylene bag had almost 50% more materials, this type of bag still eliminated a large portion of the labor associated with producing bulk woven bags through sewing methods.

[059] In another embodiment of the polyethylene fabric heat sealing method, impulse heat sealing equipment is used to deliver controlled amounts of heat for controlled amounts of time to specified portions of the fabric resulting in a two inch wide seal. In another embodiment of the polyethylene fabric heat sealing method, these seals provide 90% to 97% resistance in the cut direction.

[060] In another embodiment of the method of heat sealing polyethylene fabric, the heat sealing equipment may be automated and sensors may be attached to monitor time, heat and pressure. These readings may be transferred to a monitoring station in a control room. Robots may move materials from workstation to workstation and the fabric may be positioned and sealed robotically.

[061] In another embodiment of the polyethylene fabric heat sealing method, using relatively low heat and low pressure, only the coating itself is being joined. This leaves the fabric completely undamaged and unweakened. In fact, the strength of the coating now adds to the overall strength rather than being eliminated in current methods. With the resulting strengths, one is now able to lift greater weights with less material than can be done with current commonly used fabric stitching methods.

[062] In developing an embodiment of a polyethylene heat-sealed bulk bag, the following factors were considered. First, there are many changes in direction and different or special shapes for heat sealing equipment may be required for the production of bulk bags. Second, the security levels for polyethylene bulk bags would preferably be similar to the security levels of polypropylene woven bulk bags, which are 30% stronger.

[063] When testing one embodiment of a polyethylene heat-sealed bulk bag, the results showed 93% gasket efficiency.

[064] In one embodiment of a polyethylene bulk bag of the present invention, the lifting loops have been eliminated and replaced with fabric tunnels that would use the strength of the entire bag fabrics for lifting versus lifting loop bags that use only a small portion of the fabric for lifting.

[065] Experimental models were constructed to identify and evaluate any practical problems. In one embodiment, test results showed that a heat-sealed bulk bag constructed of polyethylene fabric held up to 18,000 lbs (8,164 kg) of hydraulic pressure before failure. At a safety ratio of 5 to 1, this bag could have been sold for applications carrying up to 3,600 lbs (1,632 kg). In this embodiment, the method used all of the fabric on two sides of the bag. Additionally, the fabric was folded so that the heat seal would be at the bottom of the bag and protected from any potential peeling forces. This meant that the heat-sealed polyethylene bag had nearly 50% more material. This bag embodiment, however, still eliminated a large portion of the labor associated with producing fabric bulk bags via sewing methods.

[066] One embodiment of the method of the present invention is a method for producing bulk bags or any flexible fabric container comprising polypropylene fabrics in a manner that can result in seams that are heat sealed in such a manner that the natural stresses on each heat sealed seam will be applied to the seam or seam in the cutting direction for greatest strength. In the preferred embodiment, a method of producing polypropylene bulk bags would utilize a blend of a minimum of 70% pure VERSIFY™ 3000 (Trademark of The Dow Chemical Company) and 25% Polyethylene and 5% other additives such as pigments or Ultraviolet (UV) inhibitors. Other potential additives may include antistatic protection. Properly sealed this system will produce heat sealed seams resulting in an average strength of 92% of the strength of standard 5 ounces per square yard (169.53 grams per square meter) woven polypropylene.

[067] Another embodiment of the present invention comprises a method of joining highly oriented polypropylene woven fabrics by the following steps: coating the fabrics with materials, wherein one piece of fabric to be joined is coated with materials comprising VERSIFY™ 3000, which has a lower melting point than the polypropylene fabric, and wherein the other piece of fabric to be joined is coated with an industry standard coating; heating the coating comprising VERSIFY™ 3000 to its lower melting point; and joining the coatings with pressure light enough to allow the coating to stay in place and generally prevent the woven fabrics from being touched.

[068] In one embodiment of the present invention, the strength of the coating adds to the overall strength and the resulting strengths allow one to lift greater weights with less material than can be done with current commonly used fabric sewing methods.

[069] In another embodiment of the present invention, a coating comprising a suitable percentage of VERSIFY™ 3000 or another suitable propylene elastomer or plastomer coating having a melting point lower than the melting point of polypropylene fabrics will be applied to at least one side of a piece of polypropylene fabric and an industry standard coating will be applied to at least one side of another piece of polypropylene fabric. Industry standard coatings for polypropylene fabric generally comprise a majority percentage of polypropylene and a small percentage of polyethylene. The piece of fabric comprising the VERSIFY™ 3000 coating or another suitable propylene elastomer or plastomer having a melting point below the melting point of the polypropylene fabric will be positioned overlapping the piece of fabric comprising the standard coating and positioned so that the coating layers are in contact. Low heat and low pressure will be applied to melt the coating and form a joint between the polypropylene fabric coatings. This embodiment of the present invention is cost effective because standard coatings cost less than coating comprising VERSIFY™ 3000, for example. Test results have shown similar seam strengths when joining a fabric comprising a VERSIFY™ 3000 coating and joining another fabric comprising a standard coating. A considerable amount of money can be saved since the standard coating is much less expensive. In a preferred embodiment, both the VERSIFY™ coating or other suitable propylene elastomer or plastomer with a melting point below the melting point of the polypropylene fabrics and the standard coating will be applied at a thickness of 2.5 mils (0.0635 mm). In a preferred embodiment of the present invention, the coating is applied at a thickness of 2.5 mils (0.0635 mm). Typically in the prior art, industry standard coatings are applied at a thickness of 1 mil (0.0254 mm).

[070] In one embodiment of the method of the present invention, the method is for creating a new form of heat-welded seam for polypropylene fabrics that provides as high as 95% seam strength in the cut position. An object of the present invention is to use that seam method to create a securely improved bulk bag that is competitive in the marketplace.

[071] Another embodiment of the method of producing flexible fabric bags, comprising the steps of coating a polypropylene fabric with 100% VERSIFY™ 3000 or a combination of VERSIFY™ 3000 and polyethylene and joining the fabrics (not specifically just the edges) using a combination of heat and minimal pressure in such a manner that only the coatings are welded and not the fabrics. Thus, producing a joint that has a higher strength than the original uncoated fabric.

[072] One embodiment of the method of the present invention comprises using heat to combine laminated coatings of fabrics versus attempting to combine the fabrics themselves. Since coatings have a marginally lower melting point than the fabric itself, this invention joins polypropylene fabrics without damaging the tensile strength of the original fabrics.

[073] In one embodiment of the present invention, impulse heat sealing equipment is used to deliver controlled amounts of heat for controlled amounts of time to specified portions of the fabric resulting in a 2 inch wide (5.08 cm) seal. In one embodiment of the present invention, these seals provide 85% to 96% resistance in the cut direction.

[074] In one embodiment of the present invention, the heat sealing equipment may be automated and sensors may be attached to monitor time, heat and pressure. These readings may be transferred to a monitoring station in a control room. Robots may move materials from workstation to workstation and the fabric may be positioned and sealed robotically.

[075] One embodiment of the method of the present invention allows for the production of a robotically manufactured bulk bag that requires very little labor, wherein the bulk bags will have no human touch inside the bag so as to prevent contamination by human bacteria.

[076] One embodiment of the present invention comprises a robotic or automated system for producing large fabric bags, e.g., polypropylene bulk bags or barrier cells, for forming a flood barrier, e.g., when filled with sand or the like using robots or other automated system.

[077] Another embodiment of the present invention comprises a simple robotic or automated system that can fit into a 40-foot (12.19 m) export container or other suitable means of transportation, which one could then take to any potential flood site or project site and begin producing 500-foot (152.4 m) lengths of fabric bags or containers or cells on-site, for example. The robotic or automated system would be similar to a system used to make endless rain gutters for homes and apartments, for example. In another embodiment of the present invention, the automated or robotic system would also allow for the production of other polypropylene or similar fabric products on-site, in various length measurements as may be suitable for a particular purpose or project.

[078] In another embodiment of the present invention, what is provided is a method of producing flexible fabric bags, comprising the steps of coating a polypropylene fabric bag with heat-fused seams comprising: a combination of VERSIFY™ 3000 or other propylene elastomer or plastomer having a melting point below the melting point of the polypropylene fabric, and comprising polyethylene; providing fabric pieces, wherein each fabric piece has a coated side and an uncoated side; positioning fabric pieces so that a coated side of one fabric piece is face to face with a coated side of another fabric piece; selecting an area of fabrics to be joined for forming one or more seams or joints; and applying heat to the coated fabric at the joint under an area-to-be-joined pressure that is less than 2 psi (13.8 kilopascals), to form a joint with at least a 90% joint efficiency in a joint tensile test.

[079] Another embodiment of the method of producing flexible fabric bags comprises the steps of coating a polypropylene fabric with a combination of VERSIFY™ 3000 or other suitable propylene elastomer or plastomer having a melting point below the melting point of the polypropylene and polyethylene fabric; joining the edges of the coated fabric, applying heat to the coated fabric at the joint under a pressure of less than 2 psi (13.8 kilopascals), to form a joint having at least a 90% joint efficiency in a joint tensile test.

[080] Another embodiment of the method of producing flexible fabric bags comprises the steps of coating a polypropylene fabric with 100% VERSIFY™ 3000 or other suitable propylene elastomer or plastomer having a melting point lower than the melting point of the polypropylene fabric or coating the fabrics with a combination of VERSIFY™ 3000 or other suitable propylene elastomer or plastomer having a melting point below the melting point of the polypropylene and polyethylene fabric and joining the fabrics (not specifically just edges) using a combination of heat and minimal pressure in such a manner that only the coatings are welded and not the fabrics, thereby producing a joint that will have a higher strength than the original uncoated fabric.

[081] In another embodiment of the present invention, all weight-bearing points on the flexible bag are designed so that the welded joint will be stressed in the direction of the cut when the bag is being used properly.

[082] In another embodiment of the present invention, if lifting handles are provided, the lifting handles are further protected against peeling forces with an additional piece of protective material applied over the top of the lifting handle seam to protect against peeling pressures.

[083] One embodiment of the present invention comprises a method of producing a flexible polypropylene fabric bag with heat-fused seams comprising: providing fabric pieces, wherein each fabric piece has a coated side and an uncoated side; positioning fabric pieces so that a coated side of one fabric piece faces a coated side of another fabric piece; selecting an area of fabrics to be joined for forming one or more seams or joints; applying heat to the area to be joined that is lower than the melting point of the fabrics, for forming one or more seams or joints.

[084] In another embodiment of the method of the present invention, the seams or joints between the fabric pieces are formed one at a time to produce a flexible polypropylene fabric bulk bag.

[085] In another embodiment of the method of the present invention, the seams or joints between the fabric pieces are joined in a single step to produce the main body of the flexible polypropylene fabric bulk bag.

[086] In another embodiment of the method of the present invention, the seams or joints of the flexible polypropylene fabric bulk bag retain at least 85% of the fabric strength without using sewing machines.

[087] In another embodiment of the method of the present invention, the seams or joints of the flexible polypropylene fabric bulk bag retain at least 90% of the fabric strength.

[088] In another embodiment of the method of the present invention, the seams or joints of the flexible polypropylene fabric bulk bag retain at least 96% of the fabric strength.

[089] In another embodiment of the method of the present invention, they retain at least 100% of the fabric strength without using sewing machines.

[090] In another embodiment of the method of the present invention, for each seam or joint, a joined coated portion of one piece of fabric forms one half of a seam or joint, and a joined coated portion of another piece of fabric comprises a second half of the same seam or joint.

[091] Another embodiment of the present invention comprises a method of producing flexible fabric bags with heat-fused seams in a single step, comprising: a. providing 8 layers of flexible fabric, including: i. a top layer for a top panel, having a flat side; ii. a second layer for a body panel, having a flat side; iii. a third layer for a body panel, having a gusset side; iv. a fourth layer for a top panel, having a gusset side; v. a fifth layer for a top panel, having a gusset side; vi. a sixth layer for a body panel, having a gusset side; vii. a seventh layer for a body panel, having a flat side; viii. an eighth layer, for a top panel having a flat side; b. wherein the fabric layers comprise a coating layer; c. positioning the layers of flexible fabric so that all areas intended to be joined are coated face to coated face and all areas intended not to be joined are uncoated fabrics facing the uncoated fabrics; d. positioning the layers of fabric so that there is an overlap of the layers of fabric; e. centering the overlapping portions of fabric under the sealing bar; and f. applying low heat and low pressure to create heat-fused seams.

[092] In another embodiment of the method of the present invention, the method comprises pulse heating.

[093] In another embodiment of the method of the present invention, heat is applied from upper and lower directions to the flexible fabric layers.

[094] In another embodiment of the method of the present invention, heat is applied from one direction to the flexible fabric layers.

[095] Another embodiment of the present invention comprises a polypropylene container comprising heat-fused seams, wherein the seams comprise a “T” shape and wherein the right side of the “T” seam in a cut position allows protection of the left side in a peeling position when force is applied in the right direction, and wherein the left side of the “T” seam in a cut position allows protection of the right side in a peeling position when force is applied in the left side direction.

[096] Another embodiment of the present invention comprises an automated production method for producing flexible fabric bags with heat-fused seams comprising: a. providing layers of flexible fabric, including tubular flexible fabric, wherein some layers are folded and some layers are flat, and wherein the flexible fabric layers comprise a facing layer; b. positioning the tubular flexible fabric layers such that the folded layers comprise facing on the outside and the flat fabric layers comprise facing on the inside of their gussets; c. positioning the fabric layers such that one layer overlaps an adjacent layer; and d. applying low heat and low pressure to the overlapping portions of the fabric layers to create heat-fused seams.

[097] Another embodiment of the method of producing flexible fabric bags with heat-fused seams comprises: a. providing fabric pieces, wherein each fabric piece has a coated side and an uncoated side; b. applying heat that is less than the melting point of the fabric pieces to be joined to the joining of fabric pieces to create one or more seams or joints wherein for each seam or joint, a coated side of one fabric piece will form one half of the seam and will face a coated side of another fabric piece to form the other half of the seam.

[098] In another embodiment of the present invention, the one or more joints have a joint strength equal to or greater than 85% of the fabric.

[099] In another embodiment of the present invention, the one or more joints have a joint strength equal to or greater than 85% of the fabric without using sewing machines.

[100] In another embodiment of the present invention, the overlapping fabric portions are 1.5 inches (3.81 cm) and the overlapping fabric portions are centered under a 2 inch (5.08 cm) wide sealing bar.

BRIEF DESCRIPTION OF THE VARIOUS VIEWS OF THE DRAWINGS

[101] For a further understanding of the nature, objects and advantages of the present invention, reference should be made to the following detailed description, read in conjunction with the accompanying drawings, in which like reference numerals denote like elements and in which:

[102] Figure 1A and 1B are a graph showing comparative data of prior art sewing test results for bulk bag construction using standard sewn sewing methods on both the weft and warp yarns of the fabric.

[103] Figure 2 illustrates a prior art simple sewn seam.

[104] Figure 3A illustrates a prior art pre-hemmed seam.

[105] Figure 3B illustrates a prior art pre-hemmed seam of a bag in a filled position.

[106] Figure 4 is a graph showing test results of a heat-fusion seamed bulk bag of the present invention.

[107] Figure 5 is a perspective view of a bulk bag of the present invention with heat-fused seams.

[108] Figures 6-7 are prior art views of a sewn seam bag and the prior art sewing process.

[109] Figure 8 illustrates the position of a prior art seam as sewn.

[110] Figure 9 illustrates the position of a prior art sewn seam when a bag is filled.

[111] Figure 10 illustrates a heat fusion seam of one embodiment of the present invention.

[112] Figure 11 illustrates the use of a heat seal bar in one embodiment of the heat fusion sealing method of the present invention.

[113] Figure 12A illustrates a filling or discharge spout of one embodiment of a heat melt seal bag of the present invention.

[114] Figure 12B illustrates a top or bottom panel of one embodiment of a heat-melt seal bag of the present invention.

[115] Figure 12C illustrates a tubular body panel of one embodiment of a heat-melt seal bag of the present invention.

[116] Figure 13A illustrates an end view of a folded filling or discharge spout of one embodiment of a heat melt seal bag of the present invention.

[117] Figure 13B illustrates an end view of a folded top or bottom panel of one embodiment of a heat melt seal bag of the present invention.

[118] Figure 13C illustrates an end view of a folded bag body of one embodiment of a heat-melt seal bag of the present invention.

[119] Figure 13D illustrates a side view of a folded top or bottom panel of one embodiment of a heat melt seal bag of the present invention.

[120] Figure 14 illustrates a general view of an embodiment of a heat-fusion sealed bag of the present invention.

[121] Figure 15 illustrates the layering of fabrics in one embodiment of the heat fusion sealing method of the present invention.

[122] Figure 16 illustrates the layering of fabrics in one embodiment of the heat fusion sealing method of the present invention.

[123] Figure 17 illustrates a sample of a heat fused seam of the present invention in which the wall fabric is folded.

[124] Figure 18 illustrates a general view of a fusion heat sealed fabric bag of the present invention.

[125] Figure 19 illustrates an isolated view of a heat-fused seal of the present invention in which the edges of the fabric at the point of sealing are overlapped.

DETAILED DESCRIPTION OF THE INVENTION

[126] In the method of the present invention, what is provided is a heat sealing method that does not substantially damage the strength of the polypropylene fabric and yet achieves an ultimate strength equal to or exceeding the strength of current sewing methods. During testing, products produced using the method of the present invention achieved strengths of 90 to 102% of the strength of polypropylene fabrics which is considerably above the seam joint strengths achieved through sewing.

[127] In one embodiment of the present invention, the invention will aid in and enable the automation of bulk bag production, thereby freeing up the location of factories around the world. Due to the improved strength, this invention will enable the use of thinner materials to perform lifting of similar weights.

[128] In one embodiment of the present invention, a suitable coating, e.g., VERSIFY™ 3000, a product produced by The Dow Chemical Company, is applied to polypropylene or similar fabrics and provides up to 240 lbs of adhesion or grip per linear inch (4.286 kilogram/meter) to the polypropylene fabric from a 1.5 inch (3.81 cm) heat seal across the joint area. In another embodiment, a coating, e.g., VERSIFY™ 3000, a product produced by The Dow Chemical Company, is applied to polypropylene or similar fabrics and provides up to 200 lbs of adhesion or grip per linear inch (3.572 kilogram/meter). In a preferred embodiment, the coating has a melting point that is lower than the melting point of the fabrics being joined together. The heat sealing method is an improvement over the technique known in the woven fabric industry today.

[129] A suitable coating may be a propylene plastomer and elastomer, for example, Versify™ 3000. The coating may contain, for example, 50% to 90% polypropylene-based polymer and 10%-50% polyethylene, by weight.

[130] In a coating to be used in a preferred method of the present invention for heat bonding polypropylene fabric, 10-99%, preferably 20-95%, more preferably 30-95% and most preferably 75-90% of plastomers, propylene elastomers or combinations thereof may be used.

[131] 0-5% additives may be used for color, antistatic or other purposes (these do not materially affect the coating performance and are typically minimized since they are more expensive than propylene and polyethylene).

[132] The balance is preferably plastomers, polyethylene elastomers or combinations thereof.

[133] Preferably, the plastomers, propylene elastomers or combinations thereof have a density of 0.915 to 0.80 grams per cc and more preferably 0.905 to 0.80 grams per cc. Preferably, the polyethylene plastomers, elastomers or combinations thereof have a density of 0.91 to 0.925 grams per cc. Typically, at least 5% low density polyethylene should be used to make the coating work and preferably at least 10%.

EXAMPLE

[134] In a preferred embodiment of the present invention, the fabrics are only being heated to a melting point of the coating that is lower than the melting point of the fabrics being joined. In a preferred embodiment of the present invention, the joining temperatures are at least 5 degrees lower than the melting point of the polypropylene fabrics to be joined. Different polypropylene fabrics will have different melting points, and in one embodiment of the method of the present invention, the joining temperatures are at least 5 degrees lower than the melting point of the particular polypropylene fabrics to be joined. An exemplary polypropylene fabric may have a melting point of 320 degrees Fahrenheit (176.7 degrees Celsius), and thus in one embodiment of the present invention, the coating will be heated to 315 degrees Fahrenheit (157.22 degrees Celsius). By using a lower heat than polypropylene fabrics, the method of the present invention does not damage or reduce the strength of the fabric as is typically the case when using prior art high heat welding formulas. Additionally, in one embodiment of the present invention, the clamping pressure used to make the seal is designed to be low enough (e.g., 7 psi (48.3 kilopascals)) to leave the coating largely in place and the materials to be joined largely separated by the coatings. Clamping pressures may also be lower, e.g., under 2 psi (13.8 kilopascals). Typically, in prior art heat sealing methods, the clamping process is designed to purposefully melt and set aside any coatings on the fabric and join the fabric strands directly. When any portion of the fabric strands is heated past its melting point and that is combined with high pressure (e.g., 20 psi (137.8 kilopascals)), the strands are thinned, weakened, and partially crystallized.

[135] It is an object of the present invention to heat fabrics by melting. In a preferred embodiment of the present invention, the fabrics are not being heated until after their melting points, which is useful in preventing degradation of the fabric strength. In a preferred embodiment of the present invention, the fabrics are only being heated to the melting point of the coating which is lower than the melting point of the fabrics being joined. In one embodiment of the present invention, the joining temperatures are at least 5 degrees lower than the melting point of the polypropylene fabrics to be joined. Different polypropylene fabrics will have different melting points, and in one embodiment of the method of the present invention, the joining temperatures are at least 5 degrees lower than the melting point of the polypropylene fabrics to be joined. (An exemplary polypropylene fabric may have a melting point of 320 degrees Fahrenheit (176.7 degrees Celsius) and thus, in one embodiment of the present invention, the coating will be heated to 315 degrees Fahrenheit (157.22 degrees Celsius).) By using a lower heat than polypropylene fabrics, the method of the present invention does not damage or reduce the strength of the fabric as typically occurs when using prior art high-heat heat welding formulas. Additionally, in one embodiment of the present invention, the clamping pressure used to make the seal is designed to be low enough (e.g., 7 psi (48.3 kilopascals)) to leave the coating largely in place and the materials to be joined largely separated by the coatings. Clamping pressures may also be lower, e.g., under 2 psi (13.8 kilopascals). Typically, in prior art heat sealing methods, the prior art clamping process is designed to purposefully melt and set aside any coatings on the fabric and bond the fabric strands directly. Naturally, when any portion of the fabric strands is heated past its melting point and that is combined with high pressure (e.g., 20 psi (137.8 kilopascals)), the strands are thinned, weakened, and partially crystallized.

[136] In the present invention, using low heat and low pressure, only the coating itself is being joined. This leaves the fabric completely intact and strengthened. In fact, the strength of the coating can now add to the overall strength rather than being eliminated in current methods. With the resulting strengths, the present invention allows for the lifting of greater weights with less material than can be done with prior art methods of sewing fabrics together.

[137] As previously discussed, in a preferred embodiment, the coating materials have a lower melting point than the fabrics to be joined. In a preferred embodiment, the coating materials in the process may be any suitable material or materials that can be used to successfully carry out the process, and may be selected from a range of coating materials. A suitable coating, for example, may be a propylene elastomer and plastomer, e.g., VERSIFY™ 3000, a product manufactured by The Dow Chemical Company. A suitable coating may contain 50% to 90% polypropylene based polymer and 10%-50% polyethylene by weight. VERSIFY™ is a registered trademark of The Dow Chemical Company for propylene-ethylene copolymers, used as raw materials in the manufacture of films, fibers, and a wide variety of molded plastic objects; propylene-ethylene copolymers used as raw materials in the manufacture of compounds to make coated fabrics, artificial leather, soft-touch grippers, shoe insoles and flexible waterproofing membranes.

[138] In one embodiment of the present invention, the method would use a mixture of a minimum of 70% pure VERSIFY™ 3000 and 25% polyethylene and 5% additives such as colors and UV protection. Using 100% pure VERSIFY™ 3000, the method of the present invention achieved up to 96% to 102% joint efficiency in a shear joint tensile test, while at 70% VERSIFY™ 3000 91% to 95% joint efficiency was achieved in the same test. (The resulting percentages are based on the average strength of the fabric tested. There is generally approximately a 5% variable strength in any section of the fabric tested.)

[139] Turning now to the figures, the graph shown in Figures 1A and 1B illustrates the comparative test data and results of the seams made for bulk bag construction using both standard stitched seam methods on both the weft and warp threads of the fabric. There are several ways of making prior art seams in the bulk bag industry. In Figures 2-3, the most common seams are depicted.

[140] Figure 2 depicts a simple seam. In Figure 2, fabric 13 is shown with sewn seam 11, and fabric fold 15, where the fabric is folded over itself to create a seam. As shown, the simple seam is simply a back fold of the two pieces of fabric to be sewn together. This simple seam prevents the interwoven web from simply slipping off the edge of the fabric under the extreme pressures that are often encountered in bulk bag use. This seam typically creates a strength of about 58%.

[141] Figure 3A depicts a pre-hem seam, which is created by not only folding the fabric before making the join, but by sewing the folded portion of the fabric to itself. Figure 3A shows fabric 13 with the seam of stitching stitches 11 and hem holding stitch 12, where the folded back is sewn to the fabric itself. This extra step typically creates a seam with an average strength of 63%. 63% over 58% is an 8.5% increase in strength. Even though there is extra work involved in hemming the fabrics, a gain in strength of this size is often considered significant in the industry.

[142] After the bag is made and filled, the pre-hem seam will be in the position shown in Figure 3B. Figure 3B depicts the heat seal joint 14. This means that most of the time, the seam is basically in a peeling position, the strength of which is largely determined by the strength of the yarn being used. But when the seams are only capable of withstanding forces equal to 63% of the fabrics, then the fabrics must be reassembled to account for the inefficiency of the seam.

[143] When labor is also taken into consideration, it is easily observed that the sewing operation is a very large factor in determining the final cost of manufacturing bulk bags.

[144] Considering the same fabrics, and using the fusion heat sealing seam method of the present invention, the graph shown in Figure 4 shows that the seam strengths obtained over 4 sets of tests yielded 95.75% strength retention. This is a significant increase in strength retention with these fabrics.

[145] When 95% of the original strength is being maintained through the fabric connections, equal fabrics can be used to carry heavier loads, or less fabric can be used to carry the same load. One embodiment of the present invention, therefore, can provide a 50% gain in strength over sewn seams.

[146] The fusion heat sealed seam not only creates a strong seal, but it does so in a significantly different way. The fusion heat sealed seam of the present invention enables new bulk bag designs that will meet the needs of the bulk bag industry.

[147] In the prior art, due to the nature of the sewing machines and the size of the bulk bags, most seams must be sewn in an edge-to-edge peeling position. The passage of a sewing machine is not large enough to allow a bulk bag to easily pass through the machine passage. Therefore, the seam is typically designed to place all seams in an edge-to-edge position, as shown in FIG. 7. FIG. 5 depicts a fusion heat seal seam 16 of fusion heat seal bag 10. FIG. 6 illustrates a prior art sewn seam 11.

[148] Once a prior art sewn-sewn bag is made and stuffed, the sewn seam is then placed in a peeling position which depends entirely on the strength of the combination of the thread and needle-punched fabrics.

[149] In Fig. 8, the positions of the fabric as it was sewn by the machine above Fig. 7 can be seen. The seam of stitch 11 is shown sewing together the bag side wall 17 and the bag bottom wall 18. The folds of fabric 15 are positioned so that the fold of fabric 15 of the side wall 17 is in contact with the fold of fabric 15 of the bottom wall 18. In Fig. 9 the position of the stitch and the seam when the bag is in use are shown. The stitching point 11 and the joint 14 are shown, to which the side wall 17 and bottom wall 18 are attached. The folds of fabric 15 of each wall, 17, 18 are shown on an interior of the bag. Typically, a minimum fold of fabric 15 will be 2 inches (5.08 cm) deep on each side. This means that the average seam is 4 inches (10.16 cm) of doubled fabric.

[150] The fusion heat seal seam of the present invention is formed by overlapping the fabrics to give the seal a wide cutting area for strength. In one embodiment of the present invention, the fusion seam will have 95% of the original strength of the fabric. In a preferred embodiment, there will be an overlap of 1.5 to 2 inches (3.81 cm to 5.08 cm). This saves a minimum of 2 inches (5.08 cm) of fabric at each joint, since the prior art sewing method has 2 inches of double layers of fabric on both sides of a seam.

[151] Figure 10 depicts a fusion heat seal seam of the present invention. In Figure 10, the fabric 13 is shown as a dark line. The coating or lamination 19 of the fabrics is shown as a dotted line. Line 20 depicts the sealed or joined area of the fabric, which may be 1.5 to 2 inches (3.81 cm to 5.08 cm).

[152] In one embodiment of the present invention the width of the overlap may be much smaller, for example 0.5 inches (1.25 cm) to save even more tissue.

[153] It is preferable that the seams be sealed so that no scrapable edges are left on any external seam of the bag. This will discourage any attempt to unpick the seal in the peeling position, which is the weak direction of the fusion joint.

[154] In one embodiment of the present invention, the preferred method is to overlap the fabrics only 1.5 inches (3.81 cm) and center them under a 2 inch (1.25 cm) wide, e.g., seal bar 21 as shown in FIG. 11. In FIG. 11, line 20 depicts the sealed area, which may be 1.5 inches (3.81 cm) wide. This intentionally leaves a 1/2 inch (0.64 cm) gap or transitional area, represented by arrow 22, on either side of the joint or sealed area 20. This ensures that the end edges of the two halves of the seal are sealed to the edge. This does not allow the scrape edge to create an easily peeled area.

[155] The % inch (0.64 cm) transitional area is small enough to prevent damaging heat from overcoming the volume of the smaller single layer material and to allow a small offset of the fabric edge to align.

[156] In one embodiment of the method of the present invention, a pulse heating process is used. Using pulse heat, the high temperature can be controlled and maintained at a desired amount of heat for a desired amount of time. This then allows the process to bring the material to temperatures up to the desired level without going so high as to damage the tissues, but also to maintain it long enough to allow for complete and uniform heating of the joint area.

[157] It is also helpful to the process to maintain equal amounts of materials under the seal at all times. The pulse heating process is to inject equal heat throughout the sealing process. If an uneven amount of materials under the seal bar is too diverse, then areas with less material may absorb more heat than desired and material damage may occur.

[158] In Figure 10, with only a single seal being made, the amount of heat applied is minimal enough that the 22 % inch (0.64 cm) gap or transient area allows sufficient heat dissipation to provide a very good seal without damage to the surrounding materials.

[159] One embodiment of the present invention involves stacking this process and creating multiple seals simultaneously. When stacking the process, the placement of the materials must be considered and keeping the amounts of material the same throughout the process will allow for safe repeatability of the sealing process.

[160] What has been described and shown so far is the difference between seaming and heat sealing to make a simple seam using polypropylene fabrics. Hereafter, the construction of bulk bags, which can routinely carry a ton of dry fluid materials, for example, will be discussed.

[161] An object of the present invention is to find ways to reduce the cost of making a product commonly referred to by various names. Such names include bulk bags, Flexible Intermediate Bulk Containers, FIBCs, Big Bags or even Super Bags (a trademark of B.A.G. Corporation). In this document, the product has been and will be referred to most often as bulk bags.

[162] The present invention has useful applications with bulk bag production, and is also useful with a number of other packages or products, for example, smaller bags used to carry 25 to 100 pounds (11 to 45 kilograms). Other products that will benefit from the present invention include products stored or transported in flexible fabric packaging, where an airtight and sterile packaging is preferred.

[163] Current bulk bag technology using sewing machines typically passes stitch by stitch around every inch of seam on each part of the bag on an individual basis. In one embodiment of the present invention, the invention will simplify this process to create a production system that can seal or join the fill spout to the top sheet, the top sheet to the bag body, the bottom sheet to the bag body, and the bottom discharge spout to the bottom sheet in a single step or step. This eliminates a tremendous amount of labor and time.

[164] Furthermore, in one embodiment of the present invention each heat-sealed seam can be approximately 50% stronger than a sewn seam. Because each joint requires fewer stitches than a sewn seam, the present invention allows for the production of a fabric bag that is demonstrably less expensive and more economical to make.

[165] The use of heat sealing is known in the art. No matter what shape the seal is to be made, heat bars can be shaped to obtain such a seal and such a shape. In one embodiment of the present invention, a heat bar and square-shaped structures to hold the fabric in place to allow joining of the bottom of the bag to the side walls will be used to make a gasket. Such equipment, however, can be large, bulky and expensive. Additional steps to complete the product and machinery may be required.

[166] In one embodiment of the present invention, the method comprises using the heat fusion sealing method of the present invention for producing bulk bags, wherein the seams are sealed sequentially, one after the other. In another embodiment of the present invention, fewer steps and machines are used in heat fusion sealing the bulk bag. An objective of the present invention is to simplify the number of steps in producing a bulk bag, compared to prior art sewing methods.

[167] There are many prior art designs on the bulk bag market, but most of these designs fall into two basic categories. The bag body may be made from numerous pieces of flat panels sewn together, or the bag body may be made from a single piece of tubular fabric that has no vertical seams.

[168] All of the basic designs can be made using the system of the present invention. A preferred embodiment of the present invention will begin with a tubular fabric body.

[169] Many bulk bags have a filling spout, a top panel, a circular fabric body panel, a bottom panel, and a discharge spout. The two spouts may be made of seamless tubular fabric. The body of the bag may be made of seamless tubular fabric. The bottom and top panels are generally flat square panels with a hole cut to accommodate the spouts that must be attached to them. Figure 12A depicts a discharge or filling spout 23. Line 24 represents, for example, a width of 22 inches for a flat (55.88 cm) spout tube. Line 25 represents, for example, an 18-inch (45.72 cm) long discharge or filling spout.

[170] Figure 12B depicts example upper or lower panels 26. In Figure 12B the upper or lower panel 26 is relatively square with sides being 41 inches (104.14 cm), for example, as represented by lines 29. Area 30 represents a connection area for the discharge or fill spout, with lines 28 being 11 inches (27.94 cm), for example.

[171] Figure 12C depicts a seamless tubular fabric 27. Line 31 may represent a height of 45 inches (114.30 cm), for example, and line 32 may represent a width of 74 inches (187.96 cm), when the tubular fabric is flat.

[172] Thus, Figures 12A-12C depict five potential fabric pieces, a fill spout 13, a discharge spout 13, a top panel 23, a bottom panel 23, and a tubular fabric piece 26.

[173] In one embodiment of the present invention, a bulk bag can be produced using a fusion heat sealing process in a single step. In a preferred embodiment, the fabric pieces will be reinforced and placed in position for the fusion heat sealing process. Figures 13A-13D depict the final shape of the fabrics in a preferred embodiment, just prior to making the basic bag.

[174] In a preferred embodiment, the side facing of the fabrics is on the outside of the tubes and on the inside of the flat panels, such that the facings face each other when the bag is formed.

[175] These coating positions may be reversed and placed on the inside of the tubes and outside of the flat panels for the bottom and top, but since the coating naturally enters the outside of the tubular fabric, the preferred method is that shown in the drawings.

[176] Figures 13A-13C depict the folding of bulk bag parts prior to heat sealing in a single step. As shown in Figures 13A-13C, the folded shape of each part is essentially the same shape. Figure 13A depicts an end view of folded fill or discharge spouts 23, where the liner or lamination 19 is on the exterior. Line 33 depicts an area 11 inches (27.94 cm) wide, for example. Figure 13B illustrates an end view of top and bottom panels 26, where the liner or lamination 19 is on the interior. Line 45 depicts an area 41 inches (104.14 cm), for example. Figure 13C illustrates an end view of a folded tubular bag body 27, where the liner or lamination 19 is on the exterior. Line 46 depicts an area of 37 inches (93.98 cm), for example. Figure 13D depicts a side view of a folded top and bottom, in which the liner 19 is on the inside. The dotted line 34 represents a future fold line. Corner cuts 35 are also shown. Approximately a 45 degree angle can be formed.

[177] The folding arrangement as described above allows each part to fit inside or around the part that will be connected in the production process.

[178] Once the shapes are placed together, the bag is ready for sealing, as shown in Figure 14. At each of the four seams or heat-fusion seal areas 41, the pieces are positioned with the outside having the liner 19 facing inward and the inside having the liner 19 facing outward, as shown in Figures 15-16.

[179] This results in a total of 8 layers of fabric at all points from bottom to top. In figures 15-16, layers 1-8 are shown.

[180] Example; Connection of the upper part to the Body of the bag. 1. Top layer Top panel Flat side 2. Second layer Body panel Flat side 3. Third layer Body panel Gusset side 4. Fourth layer Top panel Gusset side 5. Fifth layer Top panel Gusset side 6. Sixth layer Body panel Gusset side 7. Seventh layer Body panel Flat side 8. Eighth layer Top panel Flat side

[181] By aligning multiple layers in this manner, the heat fusion method of the present invention is capable of completely bonding the upper to the body panel in a single action. When the structure as depicted in Figures 15-16 is collapsed, the structure is always facing 19 to facing 19 to create a joint and fabric 13 to fabric 13 so as not to create a joint. In the drawings, the gussets may be positioned so as to interlock and during production, the fabrics are collapsed to a flat condition.

[182] All four joints are made in the same way.

[183] The method of the present invention using impulse sealing to make joints through multiple layers without exceeding the safe temperature limit comprises controlled heating that will not rise above the desired level that is less than the melting point of the polypropylene fabrics.

[184] In a preferred embodiment, in order to get the entire group of intended joints to the right temperature level without damaging the strength of the fabric, time will be employed to allow the necessary heat to become universal throughout the 8 layers of materials.

[185] Additionally, it would be helpful if the heat mechanisms were mirrored at the top and bottom so that the heat would only need to pass through 50% of the total thickness. This process could also be achieved with a heating element using a longer time for the heat to pass through the entire stack of fabric. A preferred method uses heating elements at the top and bottom of the stack.

[186] In one embodiment of the present invention, a single machine with 4 heating elements on the top and four heating elements on the bottom can effectively seal, in a single action, all four seams shown in Figure 14 of the completed bag.

[187] The fabrics may be placed and positioned under the sealing mechanisms so that the heat seal bars cover the area to be joined plus a 1/2 inch (0.64 cm) overlap, for example, to allow all edges to be sealed and also to make them non-scratchable. In one embodiment of the present invention, the mechanisms may control heat, time and pressure. When this is done, the bags may be put together in a completely dependable and repeatable manner, at this stage of production requiring a single automatable machine.

[188] By making bulk bags in this manner, different bag sizes can be made simply by changing the length of the body panel. This would only require moving two heating elements to match the new distance between the top and bottom panel fittings. The distance or relationship between the spout joints and the top and bottom panel would be unchanged.

[189] The method of the present invention can also be used to create different designs of bulk bags, for example, baffled bags or bags with lifting handles, with heat-fused gaskets or seals.

[190] This system eliminates the need for threads and the resulting contamination that often occurs when a piece of cut thread is left inside the bag. It reduces contamination from sewing machines, which come into contact with various parts of the bag. It reduces human contact with the internal surfaces of the bag.

[191] Since the seams are solid without any needle holes, this system eliminates any need for leak proofing that is often required for sewn bulk bags. The method of the present invention provides a bag that is nearly impermeable to air.

[192] Due to the air tightness and cleanability, it is clear that this production system can eliminate the need for polyethylene liners, which are often added to the inside of the bulk bag for moisture control and/or cleanliness. This will reduce the amount of plastic used in the industry and therefore reduce the amount of materials that eventually enter the landfill.

[193] Notably, all four seams shown in the preferred embodiment place the end seams in the cut position to withstand the forces of the weights that the bulk bags carry. Furthermore, the act of carrying the weight will always stress these seams only in the cut position.

[194] Thus, in the method of the present invention for automating the production of flexible bags, packages or containers, it should be understood that this method would cover all types of flexible bags, packages or containers.

[195] As discussed previously, the bulk bag industry uses a highly oriented woven polypropylene fabric. This is based on a cost versus strength matrix. Polypropylene is historically lower in cost per pound (kilogram) and historically stronger than similar polyethylene by about 30% in tensile strength. While it has always been possible to use a thicker polyethylene material to make bulk bags, there has been limited interest in using such a material due to the cost involved in achieving the required strength. Additionally, polyethylene fabrics have a lower melting point than polypropylene fabrics, so again, polypropylene has been a preferred material for nearly 40 years in this industry. Polypropylene is also a very inert material. It is unaffected by almost all chemicals. This also makes it a good choice for making packaging bags. With all these benefits to the industry, one area where polypropylene has been inferior to polyethylene has been as a result of polypropylene’s inertness and its strength due to high levels of orientation.

[196] Because of this inertia, the entire industry relied on a physical connection of materials for container construction. This relied on almost 100% sewing as the construction method.

[197] One of the common alternative methods of joining to seams that is automatable has been to use heat to form seams. When PE fabrics are used, this is very common. However, polypropylene crystallizes at the level of heat required to form a seam. This crystallization destroys the strength, rendering this previously unusable method. There are currently no known heat sealing methods for joining polypropylene fabrics that create seams useful for the construction of polypropylene bags, such as bulk bags.

[198] As stated earlier, the sewing process is very labor intensive and poorly suited to any form of automation. Sewing machines have very high-speed parts, moving to allow stitches to be applied at thousands of stitches per minute. At these speeds, even if the machines were operated robotically, the needles and threads would still break and require human repair to be put back into working order. Therefore, due to the inability to perform without constant human support, the bulk bag industry has never been able to automate its production in a profitable and efficient manner. This has led to the loss of all these jobs to foreign industries located in countries with low labor costs.

[199] Therefore, there is a need for an automatable bag construction system that will reduce the high levels of labor currently required in bulk bag construction. This will allow production to be positioned close to end users and eliminate the extremely long lead times and high inventory requirements that the industry suffers under current seam construction methods.

[200] One embodiment of the method of the present invention comprises a method of constructing woven fabric bags using a novel and unique heat sealing method. The use of a heat sealing process is well known and quite common in the joining of woven polyethylene fabrics. It is commonly understood that a joint efficiency of 80% to 85% is an extremely good joint efficiency level. Many operations accept lower joint efficiencies that range below 70 percent efficiency.

[201] In sewn seams, the efficiency is often only 65%. The strength of the polypropylene fabric takes these joint efficiencies into account when selecting the strength of the fabric that will be used in the construction of the final container.

[202] Current heat sealing methods typically involve high enough heat and high enough applied pressure to melt the base fabrics and bond them together. This method purposefully melts any applied coating and presses it through high levels of pressure so that the base woven materials can be bonded together. This method has been successful with polyethylene fabrics, for example, for several decades. It was necessary because the strength being applied came from the woven fabrics. The coatings, which were usually applied, were applied for the purpose of providing moisture and/or dust control.

[203] Because polypropylene is very inert, the coating to be applied has low bond strength to the woven fabrics. Therefore, if the applied coatings were to be used as the bonding point by welding the applied coatings together, the resulting bond strength would have no real relationship to the strength of the fabric. The resulting bond strength would only be related to the bond strength of the coating to the woven fabrics. In tests relating to the present invention, of making joints that depended on the bond strength of the coating using the present technology, the results showed about 27% joint efficiency in the specific bond strength of the materials tested. In these tests, it was never the fabric that failed. It was always the coating that had come off the fabric that caused the joint to fail.

[204] In the present invention, a coating that can be applied in a standard extrusion coating method is so fully bonded to polypropylene fabrics that it is no longer necessary to apply high pressure that will eliminate the coating under the heated jaws of the sealing mechanism. In fact, when sealing at less than 10 psi (68.9 kilopascals), it is an object of this invention to use the strength of the applied coating as part of the final heat seal strength. The fabric itself is virtually intact during this heat sealing method. In one embodiment of the present invention, only the coating is intended to be melted to create the joint. Test results have shown that strengths of over 90% have been achieved. Some test results have reached over 100% strength of coated materials that have not been sealed.

[205] However, the resulting strength of the joints often exceeds the strength of the original fabric itself before it was coated.

[206] Therefore in one embodiment of the method of the present invention, the heat sealing method creates seams that are sometimes actually stronger than the original fabric before any process begins. Whereas current methods are working with sewn seams that have a joint efficiency of 65%, it is an object of the present invention that this heat sealing method makes heated joints with minimal damage to the original fabric and allows not only to reduce costs through automation to reduce labor costs, but provides many opportunities to reduce fabric weights and thicknesses while providing similar overall strengths through greater seam efficiencies. An example would be as follows; if the sewn fabric had a tensile strength of 200 pounds per inch (3,572 kilograms/meter), after being sewn the seam would have a strength of 65% of the 200 pounds per inch (3,572 kilograms/meter) or only 130 pounds (58 kilograms). At 90% seam efficiency, a fabric that had an original strength of 150 lbs./in. (2,678 kg/m.) would still create a seam strength of 135 lbs./in. (2,410 kg/m.). This would allow for a 25% reduction in fabric strength to create an equal seam. This will obviously lead to long-term reductions in the amount of fabric needed with this system to create bags with similar strengths.

[207] All seams have at least two measurements that are critical to their success. These are often called peel and cut tests.

[208] In shear testing, the joint is made by attaching two ends of the material to be joined to opposite ends of the joint area. When the free ends of the materials are pulled in opposite directions, the entire sealed area supports the joint efficiently. This results in the highest possible demonstration of sealed joint efficiency.

[209] In the peel test, two free ends of the test materials are on the same side of the joint. In this case, when the two free ends are separated, only one edge of the seal is stressed at least once at any given time. This results in peeling of the joint as the ends are separated. This typically results in lower joint efficiency.

[210] One embodiment of the present invention is illustrated in Figures 17-19. Figure 17 depicts a joint in which the fabric wall is duplicated in an upside-down “T” shaped construction. As the fabric meets the back wall, one leg goes to each side, and the pressure from both sides protects the opposite side with its cut resistance. In Figure 18, a fusion heat sealed bulk bag 10 may be designed so that seam laps as shown may be used. The product will always push the joint in the cut direction, as illustrated by arrows 44 in Figure 19, which depict the pressure to be applied from the product held within a bag. PARTS LISTPart Descriptionlayerlayerlayerlayerlayerlayerlayerlayerlayerlayerlayersbulk bag with heat fusion seamstitch seamseam to secure hemfabricsewn jointfabric foldheat fusion sealed seamside wallbottom walllining/laminationlineheat seal bartransition gapfill/discharge spoutlinelinetop/bottom panelbodysewn seamline30 area31 line32 line33 line34 future fold line35 corner cut36 folded fill spout37 folded fill spout38 folded body39 folded bottom panel40 folded discharge spout41 fusion seal area42 double fabric wall43 lap seam44 bag content pressure45 line46 line

[211] All measurements described here are at standard temperature and pressure, at sea level on Earth, unless otherwise noted. All materials used or intended for use on a human being are biocompatible unless otherwise noted.

[212] The foregoing embodiments are presented by way of example only; the scope of the present invention is to be limited only by the following claims.

Claims (21)

1. A highly oriented polypropylene woven fabric bulk bag of the type capable of containing from 2,000 to 4,400 pounds (907 to 1,996 kilograms) of bulk material comprising weight-bearing heat-fused gaskets, and wherein at least each weight-bearing heat-fused gasket forming a containment area of the polypropylene bulk bag comprises the following four directly adjacent layers: (i) a first layer of polypropylene woven fabric (13); (ii) an industry standard coating (19) for the polypropylene fabric; (iii) a heat-seal coating (19); (eiv) a second layer of woven polypropylene fabric (13); wherein each weight-bearing heat-sealed joint is formed by forming a bond between the industry standard coating for the polypropylene fabric and the heat seal coating while the four layers are under heat and pressure; characterized in that the heat seal coating comprises propylene-based plastomers, propylene-based elastomers, or a combination thereof, and has a melting point below the melting point of the first and second layers of polypropylene fabric; and the industry standard coating for the polypropylene fabric being different from the top heat seal coating and comprising a majority percentage of polypropylene. 2. The highly oriented polypropylene woven fabric bulk bag of the type capable of containing from 2,000 to 4,400 pounds (907 to 1,996 kilograms) of bulk material, with heat-fused seams, according to claim 1 comprising: a. a highly oriented polypropylene woven fabric top (13) comprising a butt joint portion having a top heat seal coating (19) at least on the butt joint portion, the top heat seal coating comprising propylene-based plastomers, propylene-based elastomers, or a combination thereof; b. a highly oriented polypropylene woven fabric body (13) comprising lower and upper body joint portions having an industry standard coating for the polypropylene fabric (19) at least on the lower and upper body joint portions; c. a highly oriented polypropylene woven fabric bottom (13) comprising a bottom joint portion having a bottom heat seal coating (19) at least on the bottom joint portion, the bottom heat seal coating comprising propylene-based plastomers, propylene-based elastomers, or a combination thereof; d. a first heat-sealed joint providing at least one hermetic seal between the top and the body formed by positioning the top joint portion such that the top heat seal coating (19) is in contact with the industry standard coating for the polypropylene fabric (13) of the upper body joint portion and applying heat and pressure such that the top heat seal coating (19) and the industry standard coating for the polypropylene fabric (13) form a first bond to define the first heat-sealed joint; e. a second heat-sealed gasket providing at least one hermetic seal between the body and the bottom formed by positioning the bottom gasket portion of the body such that the industry standard coating (19) for the polypropylene fabric of the bottom gasket portion of the body is in contact with the bottom heat-seal coating and applying heat and pressure so that the bottom heat-seal coating (19) and the industry standard coating (19) for the polypropylene fabric form a second bond to define the second heat-sealed gasket; f. wherein the first heat-sealed joint has the following layers directly adjacent to the first bond formed between the top heat seal coating and the standard polypropylene coating of the joint portion of the upper body: (i) top highly oriented polypropylene woven fabric (13), (ii) top heat seal coating (19), (iii) industry standard coating (19) for the polypropylene fabric of the joint portion of the upper body, and (iv) highly oriented polypropylene woven fabric of the body (13); e.g. wherein the second heat-sealed joint has the following layers directly adjacent with the second bond formed between the bottom heat seal coating (19) and the industry standard coating (19) for the polypropylene fabric of the joint portion of the lower body: (i) bottom highly oriented polypropylene woven fabric (13), (ii) bottom heat seal coating (19), (iii) industry standard coating (19) for the polypropylene fabric of the lower body joint portion, and (iv) body highly oriented polypropylene woven fabric (13); characterized in that the heat seal coating comprises propylene-based plastomers, propylene-based elastomers, or a combination thereof and has a melting point below the melting point of the first and second layers of polypropylene fabric; and the industry standard coating for the polypropylene fabric being different from the top heat seal coating and comprising a majority percentage of polypropylene. 3. The bulk bag of claim 2, wherein the top heat seal coating has 50% to 90% propylene-based plastomers, propylene-based elastomers, or mixtures thereof, the industry standard polypropylene fabric body coating has a majority percentage of polypropylene and a minority percentage of polyethylene, and the bottom heat seal coating has 50% to 90% propylene-based plastomers, propylene-based elastomers, or mixtures thereof. 4. The bulk bag of claim 2, wherein each of the top, body, and bottom is folded into a two-dimensional configuration when forming the first and second joints, and wherein the top heat seal coating is on an interior surface of the top in the two-dimensional folded configuration, the industry standard coating (19) for the polypropylene fabric is on an exterior surface of the body in the two-dimensional folded configuration, and the bottom heat seal coating is on an interior surface of the bottom in the two-dimensional folded configuration. 5. The bulk bag of claim 4, wherein each of the top, body, and bottom portions is folded to form gussets to establish a two-dimensional configuration of each of the top, body, and bottom portions, and wherein the upper seam portion of the body including gussets is positioned within the top including gussets to establish contact between the top heat seal coating and the industry standard coating (19) for the polypropylene fabric of the upper seam portion of the body, and wherein the lower seam portion of the body including gussets is positioned within the bottom to establish contact between the bottom heat seal coating and the industry standard coating (19) for the polypropylene fabric of the lower seam portion of the body. 6. The bulk bag of claim 5, wherein each of the first and second heat seal gaskets extends around an entire circumference of the body and the first and second heat seal gaskets are formed simultaneously. 7. The bulk bag of claim 2, further comprising a fill spout and a third, nearly airtight heat-sealed joint connecting the top and the fill spout, and further comprising a discharge spout and a fourth, nearly airtight heat-sealed joint connecting the bottom and the discharge spout, the fill spout and the discharge spout each having an industry standard coating (19) for the polypropylene fabric in a fill spout joint area and a discharge tube joint area, respectively. 8. The bulk bag of claim 7, wherein each of the first, second, third and fourth joints is adapted to be stressed in a shear position when the bag is filled with bulk material. 9. Bulk bag according to claim 2, characterized in that it further comprises one or more lifting loops. 10. The bulk bag of claim 2, wherein the bag has no point holes in a containment area of the bag. 11. Bulk bag according to claim 2, characterized in that one containment area is at least hermetically sealed. 12. The bulk bag of claim 2, which is devoid of an interior liner to prevent sifting of bulk contents from a containment area. 13. The bulk bag of claim 2, wherein each of the first and second heat-sealed joints retains at least 80-85% of the strength of the highly oriented polypropylene woven fabric. 14. The bulk bag of claim 2, wherein each of the first and second heat-sealed joints retains at least 90% of the strength of the highly oriented polypropylene woven fabric. 15. The bulk bag of claim 2, wherein each of the first and second heat-sealed joints retains at least 96% of the strength of the highly oriented polypropylene woven fabric. 16. The bulk bag of claim 2, wherein each of the first and second heat-sealed joints retains 96% to 102% of the strength of the highly oriented polypropylene woven fabric. 17. The bulk bag of claim 2, wherein each of the first and second heat-sealed joints retains at least 100% of the strength of the highly oriented polypropylene woven fabric. 18. The bulk bag of claim 2, wherein each of the first and second heat-sealed joints retains at least 102% of the strength of the highly oriented polypropylene woven fabric. 19. The bulk bag of claim 2, wherein each of the first and second joints does not have scrapable edges. 20. The highly oriented polypropylene woven fabric bulk bag of the type capable of holding 2,000 to 4,400 pounds (907 to 1,996 kilograms) with heat-fused seams according to claim 1, comprising: a. a spout top formed from a continuous piece of a highly oriented polypropylene woven fabric (13) including a first inner surface and a first outer surface, with a first unsealed top and a first unsealed bottom, the spout top having a first heat seal coating over at least a portion of the first outer surface; b. a top formed from a continuous piece of highly oriented polypropylene woven fabric (13) and including a second inner surface and a second outer surface, with a second unsealed top and a second unsealed bottom, the top having an industry standard first coating (19) for the polypropylene woven fabric over at least a portion of the second inner surface; c. a body formed from a continuous piece of highly oriented polypropylene woven fabric (13) having a third inner surface and a third outer surface with a third unsealed top and a third unsealed bottom, the body having a second heat seal coating (19) over at least a portion of the third outer surface; d. a bottom formed from a continuous piece of highly oriented polypropylene woven fabric (13) and including a fourth inner surface and a fourth outer surface with a fourth unsealed top and a fourth unsealed bottom, the bottom having an industry standard second coating (19) for the polypropylene fabric over at least a portion of the fourth inner surface; e. a bottom spout formed from a continuous piece of highly oriented polypropylene woven fabric (13) and including a fifth inner surface and fifth outer surface, a fifth unsealed top portion and fifth unsealed bottom portion, the bottom spout having a third heat seal coating (19) over at least a portion of the fifth outer surface of the bottom tube;f. a first heat-fused joint connecting the top spout and the top with a first bond formed between the first heat seal coating (19) and the first industry standard coating (19) for the polypropylene fabric that extends a distance along the first outer surface and second inner surface without overlap to extend along the first inner surface and/or second outer surface, the first heat-fused joint having the following directly adjacent layers: (i) highly oriented polypropylene woven fabric (13) of the top spout, (ii) first heat seal coating (19), (iii) first industry standard coating (19) for the polypropylene fabric, and (iv) highly oriented polypropylene woven fabric (13) of the top; a second heat-fused gasket connecting the top and the body with a second bond formed between the second heat-seal coating (19) and the first industry standard coating (19) for the polypropylene fabric extending a distance along the second inner surface and third outer surface without overlap to extend along the second outer surface and/or third inner surface, the second heat-fused gasket having the following directly adjacent layers: (i) highly oriented polypropylene woven fabric (13) of the body, (ii) second heat-seal coating (19), (iii) first industry standard coating (19) for the polypropylene fabric, and (iv) highly oriented polypropylene woven fabric (13) of the top; h. a third heat-fused joint connecting the bottom and the body with a third bond formed between the second heat-seal coating (19) and the second industry standard coating (19) for the polypropylene fabric extending a distance along the fourth inner surface and third outer surface without overlap to extend along the fourth outer surface and/or third inner surface, the third heat-fused joint having the following directly adjacent layers: (i) highly oriented polypropylene woven fabric (13) of the body, (ii) second heat-seal coating (19), (iii) second industry standard coating (19) for the polypropylene fabric, and (iv) highly oriented polypropylene woven fabric (13) of the bottom; and 1. a fourth heat-fused joint connecting the bottom and the bottom spout with a fourth bond formed between the third heat-seal coating (19) and the second industry standard coating (19) for the polypropylene fabric extending a distance along the fourth inner surface and fifth outer surface without overlap to extend along the fourth outer surface and/or fifth inner surface, the fourth heat-fused joint having the following directly adjacent layers: (i) highly oriented polypropylene woven fabric (13) of the bottom spout, (ii) third heat-seal coating (19), (iii) second industry standard coating (19) for the polypropylene fabric, and (iv) highly oriented polypropylene woven fabric (13) of the bottom; characterized in that the first heat-seal coating, the second heat-seal coating, and the third heat-seal coating comprise propylene-based plastomers, propylene-based elastomers, or a combination thereof, and have a melting point below the melting point of the polypropylene fabric layers; and wherein the industry standard first coating for the polypropylene fabric and the industry standard second coating for the polypropylene fabric are different from the first heat seal coating, the second heat seal coating and the third heat seal coating, and wherein the industry standard first coating for the polypropylene fabric and the industry standard second coating for the polypropylene fabric comprise a majority percentage of polypropylene and a small percentage of polyethylene. 21. The bulk bag of claim 20, wherein each of the first, second, and third bonding coatings includes 50% to 90% propylene-based plastomers, propylene-based elastomers, or mixtures thereof, and each of the first and second standard fabric coatings includes a majority percentage of polypropylene and a minority percentage of polyethylene.