MXPA00002848A - Open mesh bag - Google Patents

Abstract

The present invention provides an improved open mesh bag (10) comprising an open, mesh-like fabric. The bag (10) has a closed end (12) formed by folding the fabric, an opposing end and longitudinal, heat-sealed side seams (14, 16) extending from the closed end (12) to the opposing end (11). The bags (10) are used for packaging articles for which visibility and/or breathability of the bag (10) fabric are useful characteristics. In a preferred embodiment, the bags (10) are also suited for manufacture and filling using high speed, automated bagmaking equipment.

Description

OPEN MESH BAG Field of the Invention The invention relates to open mesh bags suitable for packing goods and articles Background of the Invention Previously, open mesh bags have been used for several packaging applications including those in which the breathability and visibility of the contents of the bags are important characteristics. Examples include the production of bags for fruits, vegetables and other agricultural products and bags for sports equipment, toys, blocks and various other solid objects of small to medium size. Such bags have been made of solid plastic films, tubular packing materials, such as VEXAR originated by E.l. du Pont de Nemours and Company, woven fabrics of gauze back, interwoven fabrics and woven fabrics. Each of these has disadvantages. For example, tubular materials require the investment of special equipment to prepare the bags therefrom (see, e.g., U.S. 4,091,595). Interwoven and woven packaging materials, while avoiding the complexities associated with tubular goods, are disadvantageous, because they are typically sewn to form seams. This adds cost. Nonwoven tiles rarely achieve a practical balance of resistance and visibility contents and are often difficult to sew with the proper strength. Plastic films lack breathability; the attempt to overcome this limitation, such as by perforation, adds cost, can impart resistance and in general is not performed satisfactorily.

Beyond the additional attributes of bag production, including breathability resistance and sufficient transparency or aperture to allow the observation of its contents, automated and high-speed bag making and filling equipment has imposed additional requirements. At the eye of the process needle in the high-speed bag making equipment, the substrates of the bags must follow the path precisely through the equipment and remain in register during the entire sequence of the stages of making the bags. The substrate must remain precisely in register through the repeated accelerations and decelerations, so that each stage of the operation of the elaboration of the bag, eg, sewing, application of the label, cut of the die, finished of the cut of the bag , perform in the precisely correct position in the bag. The dimensional stability of a bag substrate is important for such operations from the point of view to maintain the record and prevent deformation as the material begins and stops rapidly during its progress through the bag making equipment.

The substrate must also be a material that can be sewn with adequate strength to overcome filling, transportation and handling operations. Bags made from open mesh fabrics can be problematic in this respect, particularly those comprising a delicate, net-like material and / or only the limited surface area available for sewing. The limited area for contact between the opposing layers of the fabric tends to make the seams sealed by weak heat, if effective at all. Sewing with adhesives does not tend to be aesthetically attractive. The stitching of the seams adds cost and often is not effective due to the small surface area of the open mesh fabric.

The U.S. No. 3,123,279 discloses an open-mesh plastic bag having a thermoplastic film bonded to a thermoplastic mesh along three margins of the film made by folding the film over the mesh and sealing the film through the mesh.

There is a need for improved open mesh bags, and particularly bags that have the traditional attributes of conventional open mesh bags, such as breathability and content visibility, and also meet the criteria for high-speed bag making machines. .

Brief Description of the Invention Briefly, this invention provides a pouch comprising an open mesh fabric and having a closed end, an opposite end and at least two longitudinal seams extending from the terminal end to the opposite end, wherein the end end is It is formed by a fold in the fabric on a central axis and each seam comprises a section of fabric on each side of the fold to which a thermoplastic sealing tape is heat sealed. The thermoplastic sealing tape to which the fabric is sealed comprises a resin or blend of thermoplastic resins having a melting temperature or thermal seal temperature less than the melting point of the fabric. Optionally, a label, printed band or other decorative elements can be attached to the bag.

Importantly, inventive open mesh bags can be easily manufactured in high-speed automated industrial bag making equipment. Heat sealed film tapes comprising a thermoplastic resin are preferably applied by lightly heat sealing the tapes through approximately one half the width of the fabric, preferably in the transverse direction of the machine, so that when the fabric is folded on a central axis the film ribbon extends perpendicular towards the fold and along the height or total length of the bag. In addition, the invented bags are very suitable for use in automated bag filling operations due to their dimensional stability and ability to bend. Significantly, these attributes are achieved without loss of other important features that include strength, flexibility, breathability and visibility of contents.

Brief Description of the Drawings Subsequently, the non-limiting modalities of the invention are described in detail with reference to the accompanying drawings in which: FIG. 1 is a perspective view of an open mesh bag according to the invention.

FIG. 2 is a cross-sectional view of the open mesh bag of FIG. 1; Y FIG. 3 is a perspective view of a section of open mesh fabric to which the tapes of the thermoplastic film for subsequent heat sealing have been applied to form the seams.

Detailed description of the invention The open mesh bag of the present invention is formed of an open mesh fabric. With reference to FIG. 1, an open mesh bag 10 is shown. The bag 10 is constructed of a mesh-like fabric, open and has a lower or terminal end 12 formed by a fold in the fabric on a central axis between the side seams 14 and 16 The fabric on each side of the fold extends from the fold and ends at the opposite end 11 of the bag. The opposite end can be opened, for example before filling it, or it can be closed, for example after filling the bag. Any suitable means for effecting such closure, such as sewing, lacing and lashing, sewing with thin strands, the use of adhesives, heat sealing and the use of slide or bending type closures, may be used. With reference again to FIG. 1, the side seams 14 and 16 of the bag 10 are heat sealed. The end and opposite ends of the bag, together with the heat sealed seams, define a space or volume to receive and accommodate the contents of the bag. Although not shown in FIG. 1, having the benefit of this description it will be appreciated that a label or band can be attached to the open mesh bag, for example sealing by heat, with adhesives or by sewing. The label or band could be pre-printed or it could be a material suitable for subsequent printing.

In more detail, FIG further illustrates the construction of the pouch of FIG. 1. In particular, the front 8 and the back 20 of the bag 10 are shown with the side seams 14 and 16. The edges 22 and 32 of the front 18 and the edges 28 and 38 of the backrest 20 are also shown. The tapes 26 and 36 are sealed to the fabric at the edges to form the longitudinal seams. The side seam 14 is shown with the edge 22 of the front 18 having the tape 26 heat sealed thereto. The tape 26 is also heat sealed to the edge 28 of the back 20 of the bag 10. In a similar manner, the side seam 16 is shown with the edge 32 of the front 18 having a heat seal between the edge 32. and the tape 36. The tape 36 also has a heat seal between the tape 36 and the edge 38 of the backing 20 By virtue of the heat sealing of the seam, the edges of the fabric forming the seam are engaged in the thermoplastic seal tape, so that strength is provided despite the low surface area of the open mesh fabric in the seam. .

The heat sealed side seams 14 and 16 can be as wide as necessary to effectively join the fabric to the seams. Seam widths of about 1/4 inch to about 1 inch are preferred, with seam widths of about 1/4 inch to about 1 inch that are most appropriate for bags up to approximately 10 pounds of capacity and widths of about 1 inch to about 1 inch which are more suitable for bags in the range of about 10 to about 20 pounds of capacity. As will be appreciated by those skilled in the art who have the benefit of the description provided herein, the optimum widths of the seams will vary depending on the size, construction and intended use of a bag.

While the bag illustrated in Figures 1 and 2 represents a preferred construction for some terminal uses, it will be appreciated that a wide range of modifications and alternatives are contemplated for such construction according to the invention. In an alternative embodiment, referred to as an edge bag, the open mesh fabric at the open end is much shorter on one side of the bag than on the other to facilitate the use of the bags in automated filling operations; this can also facilitate closing the open end of the bag, because the additional fabric on the longer side of the bag provides a convenient flange that can simply be folded over the shorter side and heat sealed, sewn or otherwise sealed to form an effective closing for the bag. In yet another embodiment, gussets can be incorporated into the structure of the final bag such as by bending during the formation of the bags.

According to another embodiment of the invention, the invented bags can be provided in the form of a stack made of a plurality of bags arranged in a porthole. The wicket in general is in the form of a wire or roller having two angled curvatures to the right and adapted to receive and house the bags in place by perforated or otherwise made holes in one end of the bags, and more preferably on the longer side of a bag with edges at the open end thereof. Advantageously, the dimensional stability of the fabric of the bag assists in keeping the holes in register and also avoids the wear of the fabric due to the holes.

The open mesh bag of the present invention can be constructed, in general, from any open mesh fabric to which a thermoplastic tape can be heat sealed to form a seam. The non-woven fabrics and extruded, woven, interlaced, light-diffusing mesh may be used provided they have sufficient construction opening to allow adequate visibility of the contents of the bag. Preferably, the open mesh fabric is also suitable for processing in bags using high speed bag making equipment. For such a purpose, fabrics having a coefficient of friction according to ASTM 3334-80 Section 15 of less than about 30 ° and dimensional stability such that the fabric, when folded and sewn, can overcome a force of at least 20%, are especially preferred. less approximately one g without additional de-registration. Most preferred fabrics have coefficients of friction of about 15 ° to about 25 ° and can exceed forces of at least 2 g without substantial de-registration.

Woven and knitted fabrics can be constructed and prepared in any appropriate manner. From a cost and development point of view, so-called strips or strings of film strips are preferred for such fabrics. Any suitable fabric or knit can be used that provides an appropriate level of opening to impart breathability of the fabric and visibility of the contents of the bag. Examples include plain woven and gauze fabrics and knits. Such fabrics can also be used with heat sealings or seals to provide improved dimensional stability and wear resistance thereto. Of course, any coating must be applied to the fabric in a discontinuous manner, that is, so that less of the total surface of the fabric is coated, to ensure that the coated fabrics have adequate breathability. Various techniques for the discontinuous coating of fabrics are well known. An example is the strip coating as described in U.S. 4,557,958. The heat seal can also be used to improve the dimensional stability of such fabrics, as will be appreciated by those skilled in the art. In the case of these fabrics, if a back gauze, plain woven, knitted or other fabric, the threads of the fabric or such threads and any covering, will generally comprise a thermoplastic resin composition. It is also contemplated to form the coated fabric or fabric of the thermoplastic resin compositions having different melting points, with a higher melting resin being present to provide strength and integrity to the fabric and a lower melting resin that it is present either as a discontinuous coating on the surface of the fabric or laminate or as part of the threads thereof, eg, as co-extruded tapes, to provide heat bonding of the threads of the fabric to another and, in contrast , dimensional stability and superior wear resistance. Similar considerations are applicable to light diffusing fabrics.

Non-woven mesh-like fabrics, netting and extruded gauze fabrics are also suitable as mesh fabrics for invented bags. These materials typically have a grid-like or mesh-like structure, with a plurality of intersecting, intersecting fibers or ridges defining a plurality of open spaces. The fibrils are preferably arranged in a regular pattern, whereby a mesh is formed that defines the open spaces. Depending on the pattern formed by the fibrils, the open spaces could all be of the same size and shape or could be of different sizes and / or shapes. Mesh-like networks comprise one or more thermoplastic resin compositions or formulations. These materials can be made by various means such as thermally bonding a series of filaments established in a predetermined pattern, of opening and / or splitting and controlled elongation of the compositions of the thermoplastic film-forming resin to achieve a mesh-like structure and others. Lamination of two or more such structures, preferably with at least two layers thereof arranged such that the machine direction of one is essentially perpendicular to the machine direction of the other, may be used to provide the materials of greatest resistance than simple layer structures.

If the fabric is a woven, knitted or woven back or nonwoven fabric, the resins are therefore polyesters and polyolefins such as polypropylene, polyethylene and copolymers of propylene and polyethylene. The polyethylenes of high, medium, low and linear density, such as the so-called metallocene polyolefins, are contemplated. Preferred combinations of the resins are polypropylene or polyethylene terephthalate for the strength or load bearing components of the fabric and polyethylene or mixtures thereof with polypropylene for the heat sealed components thereof and high density polyethylene for the components of resistance or load bearing and low density polyethylene for the components sealed by heat.

More preferably, the bags are formed of cross-laminated non-woven fabric made of coextruded film that has been cut and stretched. Such fabrics can comprise any suitable thermoplastic film-forming resin. Among the film-forming materials that can be used in the manufacture of the cross-laminated thermoplastic mesh-like networks are polyolefin thermoplastic synthetic polymers such as low density polyethylene, linear low density polyethylene, polypropylene, high density polyethylene, polyethylene metallocene, random copolymers of ethylene and propylene and combinations of these polymers; polyesters; polyamides; polyvinyl polymers such as polyvinyl alcohol, polyvinyl chloride, polyvinyl acetate, polyvinylidene chloride and copolymers of the monomers of these polymers. Preferred materials are polyesters and polyolefins such as polypropylene, random copolymers of propylene and ethylene, and a combination of high density polyethylene and low density polyethylene. Especially preferred resins are polyethylenes and combinations thereof such as a high density polyethylene layer and a low density polyethylene layer.

These synthetic thermoplastic polymers could contain additives such as stabilizers, plasticizers, colorants, pigments, anti-slip agents and foam-forming materials for foam films and the like.

To form the thermoplastic material, open-mesh, non-woven fabric of cross lamination, it can be formed into a film by extrusion, co-extrusion, molding, blowing or other film-forming methods. The thickness of the film can be any working thickness with a typical thickness in the range of about 0.3 to about 20 mil. Co-extruded films can be used containing two or more layers of thermoplastic material, such as a polypropylene layer and a low density polyethylene layer, wherein one layer provides about 5 to about 95% of the thickness of the film and the second layer provides the remaining thickness. Such coextruded structures are more preferably formed from the first and second thermoplastic resin compositions, wherein the first composition is a higher melting point resin component that provides the strength and load bearing capacity to the fabric and the second composition is a lower melting point resin which has good adhesion to the first component and can also provide thermal sealing of the fabric to the other materials.

Another type of coextruded film construction comprises a three layer construction. Each of the three layers may be a different thermoplastic polymer. However, more frequently, the three layer coextruded film is made with the same material for the two outer layers and a different polymer for the inner layer. The inner layer can provide about 5 to about 95% of the thickness of the film. Preferably, the inner layer provides from about 50 to about 80% of the thickness and the two outer layers made from about 20 to about 50% of the thickness, the two outer layers preferably having approximately equal thicknesses. Co-extruded films are typically used for the manufacture of cross-laminated thermoplastic mesh-like networks in which a layer of the film is cross-laminated and is bonded to a second layer of the film with the outer layers of the films containing materials easily bonded and compatible thermoplastics, such as low density polyethylene or linear low density polyethylene, The film can be guided by any appropriate orientation process. Typical elongation ratios are from about 1.5 to about 15 depending on factors such as the thermoplastic used and the like. The temperature range for orienting the film and the speed at which the film is oriented are intimately related and depend on the thermoplastic used to make the film and other parameters of the process such as the elongation ratio, as is well known from the art. experts in art.

A particularly preferred non-woven mesh-like fabric for invented bags is a "thin cross-laminated fabric", also known as Nippon Pet rochemical Company Ltd. trademark CLAF®. This material can be characterized as a mesh-like or non-woven network and is described in detail in the commonly assigned U.S. 5,182,162 which is incorporated herein by reference. As described in such patent, such fabrics have a network-like structure comprising a multiplicity of fibril-like elements or aligned thermoplastic ribs, wherein the first elements are aligned at an angle of about 45 ° to about 90 ° with respect to the second elements and the elements define edges for multiple empty areas of the network-like non-woven structures. The edges defining the empty areas may be of a parallelogram shape such as a square, rectangular or diamond shape, such as a circle or ellipse, depending on the network-like formation process. The elements that define the edges can be in the same plane or different planes. The elements in the different planes can be laminated with each other. A preferred thermoplastic mesh-like network is a cross-laminated thermoplastic mesh-like network having a uniaxially oriented thermoplastic mesh laminated network to a second oriented mesh or network of a thermoplastic, so that the angle between the orientation direction of each film is from about 45 ° to about 90 °. The networks may be continuous or discontinuous slits to form the empty areas of the mesh-like network and may be formed by any suitable fibrillation or slit process. The mesh-like structure can also be formed by other means such as the formation on one side of the thermoplastic film a plurality of parallel continuous main beats and the formation on the opposite side of the film a plurality of discontinuous bends parallel with the film being formed. remove in one or two directions to open the film in a network structure, perforate or stamp the material of a film to form a pattern of holes in the film and stretch the film to lengthen the spaces between the holes. The network-like structure can also be formed by extrusion with the mesh oriented by an elongation operation.

Networks similar to cross-laminated thermoplastic meshes can be made by joining two or more layers of network structures oriented uniaxially together, wherein at an angle between the direction of the uniaxial orientation of the oriented films is between about 45 ° to about 90 °. to obtain good wear and strength resistance properties in more than one direction. The orientation and / or formation of the structure of the network in the films can be completed before the joining operation or can be done during the joining process. The joining of two or more layers of the films of the structure of the network can be done by applying an adhesive between the layers and passing the layers through a heating chamber and calendering cylinders to join the layers, or passing the layers through. heated calendering cylinders for thermally bonding the layers, or using ultrasonic bonding, spot bonding or any other suitable joining technique.

As described in U.S. No. 4,929,303, networks similar to cross-laminated meshes can be fabrics of non-woven cross-laminated fibrillated films as described in U.S. 4,681,781. Cross-laminated fibrillated films are described as high density polyethylene (HDPE) films having the outer layers of coextruded ethylene-vinyl acetate on the side of the HDPE or heat seal layers. The films are fibrillated, and the resultant filament-like elements extend in at least two transverse directions in a bead count of about 6-10 per inch. The spread fibers are then laminated by cross-over by application of heat to produce a 3-5 mil thick nonwoven fabric with approximately equal machine direction and cross direction direction properties very suitable for open mesh fabrics, Thin with exceptional strength and durability. As described in U.S. No. 4,929,303, the open mesh fabric is suitable for bonding with other materials, such as papers, films, sheets, foams and other materials, by laminating or extrusion coating techniques, or by sewing or by heat sealing. The fabric could be of any suitable material, but preferably it is made of low density polyethylene, linear low density polyethylene, polypropylene, mixtures of these polymers or polyesters. Open mesh fabrics generally have an elongation (ASTM D1682) of less than about 30%; a cutting effort of Elmendorf (ASTM D689) of at least about 300 g; and a rupture load (ASTM D1682) of at least about 15 Ib / inch. The reported uses of cross-laminated fibrillated film fabrics include navigation bags for cement, fertilizers and resins, shopping bags, beach bags and cargo bags, consumer and industrial packaging such as sachet bags, forms, fillings and seals, and backing of adhesive tapes, disposable clothes and sheets, construction film and wraps, insulation and reinforcement backing for reflective sheets, waxing, tents and geotextiles and covers for agricultural land, insulation and shade clothing.

Cross-laminated thermoplastic mesh-like networks are available from Amoco-Nis seki CLAF, Inc. under the designation CLAF®, with examples of product designations including CLAF S, CLAF SS, CLAF HS and CLAF MS. Such fabrics are available in various styles and weights. The designated style MS is a preferred fabric for invented bags. The MS CLAF® style has a basis weight of approximately 18 g / m2 and a thickness of approximately 7.8 millionths, as determined by ASTM D3776 and ASTM D1777, respectively. The properties of CLAF® fabrics that make them very suitable construction materials for the manufacture of invented bags using automated bag making equipment, high speed, include coefficients of friction of about 15 ° to about 25 ° and sufficient dimensional stability to overcome the acceleration of at least about 2 g without significant de-registration. As an indicator of such dimensional stability, the grip traction test according to ASTM 5034-95 can be used with the cutting of the test specimens at an angle of 45 ° with respect to the direction of the fabric machine, with loads at 10% elongation at approximately 2.5 pounds that characterizes the fabrics. Other typical properties of this fabric include the grip strength of the machine direction of approximately 35 pounds and elongation of approximately 15% according to ASTM 5034-95 The thermoplastic tapes to which the open mesh fabric of the invented bags are heat sealed to form longitudinal seams comprising at least one thermoplastic resin composition having a melting or softening point that is lower than that of a mesh fabric open In the case of open mesh fabrics composed of two or more resin compositions with different melting temperatures, the ribbon resin preferably melts at a lower temperature than the upper melting components of the fabric. Preferably, the melting point of the ribbon resin is at least about 10 ° below the melting point of the resin of the fabric, to facilitate heat sealing without melting or softening the fabric. More preferably, the melting point differential is from about 30 ° to about 60 °. The resin of the seam tape should also provide sufficient strength and adhesion to the seal, so that the bags maintain the product without rupture or failure or adjacent to the seams during filling, handling and use. Preferably, the open mesh fabric and the thermoplastic tapes are composed of resins and are thus configured to provide the longitudinal seams having a strength of at least about 5.0 lbs / 2 inches, as measured by ASTM D 5035-95. More preferably, the strength of the seam is at least about 8 lbs / 2 inches.

The choice of thermoplastic resin for the tapes depends in part on the amount of heat and pressure that can be applied thereto on the seam side of the open mesh bag without impacting the integrity of the bag. The resin for the tapes will also depend on the choice of resin for the open mesh fabric. The thermoplastic resin could be a single resin or a mixture of two or more compatible resins. In the case where HDPE is used as the top melting temperature component of the mesh-like fabric, the tape of the thermoplastic film is preferably an ethylene alpha-olefin polymer or copolymer or blends of compatible polymers having a temperature of fusion lower than HDPE. The thermoplastic synthetic polymer resins may contain additives such as stabilizers, colorants, pigments, anti-lightening agents, foaming agents and the like.

The invented bags are manufactured by a process comprising the steps of applying to an open mesh fabric on the high position ribbons of a thermoplastic resin to which the fabric is heat sealed, folding the open mesh fabric along the a central axis, where the axis and the tapes are arranged perpendicularly, and heat seal the fabric from both sides of the fold to the tapes. In one embodiment, the bags are particularly suitable for manufacturing using automated or high-speed bag-forming equipment, although other bag-making machinery can also be used. The process may also comprise additional steps that include applying a label to the fabric, cutting the fabric, before or after bending or sealing by heat, in the individual bags or the appropriate sizes for the individual bags, distributing and stacking.

In greater detail, the film tapes are generally applied to the open mesh fabric. The tapes can be secured to the fabric by any effective means to provide sufficient bond strength between the fabric and the tapes to maintain the bag making steps downstream. Preferably, the tapes are lightly heat sealed to the fabric using a sealing bar or other tape application equipment. More preferably, the heat-sealed material in the form of thermoplastic film tapes is fixed to the fabric in the transverse direction of the machine at evenly spaced intervals and at a distance of about half the width of the fabric.

Film tapes are preferably applied to approximately half the width of the fabric, so that when the fabric is folded, the film tape will extend longitudinally along the total length or height of the bag. The exact length of the film tape across the width of the fabric will depend on the locking mechanism used for closing the bag with the length of the tape being much less than half the width of the fabric, if used a coating of the fabric material of the bag to close the open end of the bag. In the case where the bags are joined by reinforcement with an inch of depth of the joint, for example, the film tape is preferably applied at a distance of about one inch more than half the width of the fabric, so that each layer in the reinforcement junction touches the film.

The width and thickness of the film tape should be sufficient for the effective heat seal to form the side seams of the open mesh bag. In one embodiment of the bag making process, the film tapes are generally greater than twice the desired width of the seal for the side seam of the finished bags, whereby the bags are allowed to open on the side of the bag. sewing to reduce the frequency of application of the tapes to the open mesh fabric in the bag making operation. For example, they could be used with a one-inch-wide stamp bar, a 1 to 1/4 inch wide film tape, and the seam opening to form half-inch wide side seams. The slightly wider film tape is used to ensure that only the fabric with the heat-sealed film between the layers of the fabric is exposed to the heat seal bar.

The thickness of the film may vary depending on whether the film is a single layer or multilayer film. For single layer films, the appropriate thicknesses are such that they effectively seal the seams by heat. For multi-layer films, the thicknesses will vary depending on the expected characteristics of the film to provide the heat sealed seams. For example, a multi-layer film could comprise two outer layers of a lower melting temperature resin to improve the characteristics of the heat seal and an inner layer of a lower melting temperature resin to reinforce the seam.

With reference now to FIG. 3, a section of an open mesh fabric with seal tapes applied to it is illustrated. As seen from the figure, the heat sealed tapes 52, 54 and 56 are secured to the open mesh fabric 50 at substantially regular intervals. The tapes are conveniently formed from a thermoplastic film and are sealed or lightly bonded by heat to the fabric 50. In general, the heat-sealed film tapes are approximately twice the desired width at the side seams of the bags. open mesh for the bags formed in the bag making equipment at high speed. The base or the terminal end of the bag is formed by folding the fabric into a central axis, so that each side seam of the bag comprises a section of the fabric on each side of the fold in the fabric and the heat-sealed tapes are of about half the width and spaced over the fabric so that the side seams of the bag are formed from the fabric by heat sealing and cutting the fabric. Each tape of the film 52, 54 and 56 in this manner is cut in half lengthwise as the bags are formed and each of the tapes in this manner provides two side seams.

The heat sealing of the fabric to the heat sealed tapes is carried out after the tapes are properly positioned with respect to the side seams. The tapes, preferably superposed between the fabric of each side of the fold, they are subjected to sufficient heat and pressure to soften or melt the tape to effect a heat seal with the fabric. The temperatures and pressures effective to provide heat sealing will depend in part on the particular thermoplastic tapes and the open mesh fabric used in the manufacture of the open mesh bag as well as the thickness of the tapes and the fabric. The heat and applied pressure, of course, should not be too great to destroy the integrity of the bag. In a preferred embodiment of the invented process, wherein a MS-grade CLAF® fabric and an alpha-olefin polymer of ethylene such as Affinity PF 1140 or mixtures thereof with polyethylenes are used for the heat-sealed tapes, the temperatures of about 360 ° to 400 ° F and pressures of approximately 40 to 60 psi provide effective heat sealing at short heating times in the order of half a second or less.

In heat sealing, heat sealed tapes and open mesh fabric to form the side seams, any suitable heat sealing means can be used. Examples include seal rods, heat sealing frames and the like. In general, when a seal bar is used, temperatures of about 200 ° to about 450 ° F, pressures of about 30 to about 75 psi and dwell times of about 0.2 to about 2 seconds are preferred, to form a seam that has substantial resistance when using fabrics similar to open-mesh, non-woven, cross-laminated fabrics such as CLAF® fabrics for open-mesh bag cloth.

Optionally, a printing band or label can be attached to the bag. Preferably, such labels are heat sealed to the fabric. The printing web could conveniently be made from commercially available printable polymer films, such as composed of three layers of, for example, a high density polyethylene / po 1 iet linear low density polyethylene / high density polyethylene blend and acetate of ethylene vinyl. Such films are available, for example, from Inpak Inc., in 2 and 3 millionths of thickness. Similarly, the printing web could be made of a film comprising linear low density polyethylene / polyester or oriented polypropylene film coated with linear or low density polyethylene. A label made of linear low density polyethylene of 1.25 millionths and 0.5 millionth polyester has been found to have acceptable performance properties in this application. Depending on the economy, only a linear low density polyethylene film can also be used, although the printing of such a film is not as good as that of some composite films.

Invented bags are very suitable as bags for products for packaging, transportation, storage and exhibition of agricultural products such as potatoes, onions, apples, oranges, etc. They can also be used for toys, games, blocks, sporting goods and other solid items, as well as canned and bottled and semi-solid liquids, e.g., multi-use packaging of canned products, bottled beverages and the like.

The following examples illustrate the invention, but are not intended to limit the scope.

Comparative Examples A series of open-mesh cloth bags of a cross-laminated thermoplastic mesh-like mesh fabric available from Amoco-Nisseki CLAF, Inc. under the designation CLAF® was made with the fabric folded so that the fold extends into the fabric. Machine direction (MD) of the fabric. The side seams of the bags were heat sealed, without any heat-sealed material between the layers of fabrics, using a heat sealer from Custom Design & Development, Inc. (CDDI) that is half an inch wide, superior heat sealing metal bar and a silicone plastic pad heated at the base. The samples tested are summarized in the following table. 12-inch-wide bags with heat-sealed side seam resistances measured on two-inch tensile test tapes were manufactured according to ASTM D 5035-95 (The standard test method for the strength of fabric rupture and elongation textiles - tape traction method). The test samples of the tensile belts were prepared with the seam in the center of the sample and perpendicular to the direction of the test. Samples A to D were prepared from CLAF® fabrics described below which include color and weight of the fabric expressed in units of grams per square meter (g / m2). The fabric of Sample A was a dark orange CLAF® fabric having a weight of approximately 27.1 g / m2 with a multi-layer construction comprising an inner layer of HDPE (melting point = 145 ° C) and the layers exteriors of an ethereal resin to the affinity resin that melts at about 95-105 ° C. The fabric of sample B was a natural-colored CLAF® fabric having a weight of approximately 16 g / m2. The fabric of sample C was a natural-colored CLAF® fabric having a weight of approximately 18 g / m2 and the fabric of sample D was a red CLAF® fabric having a weight of approximately 22 g / m2. Fabrics of samples B, C and D had an internal layer of HDPE with a melting point of 145 ° C and external LDPE layers of resin that melted at 110 ° C. The side seams of samples A-D were sealed by heat with the seal bar by heat maintained at temperatures of 310 ° or 320 ° F, a pressure of 60 psi and resting time of 0.75 or 1.25 seconds. The indication is also given in the following table as "inner side" which refers to the side of the fabric, which has MD strands and CD strands laminated to one another, was placed inward as the seam was sealed by heat. Seam resistances were found in the range of 1.1 to 3.1 lbs / 2-in.

Table 1 Test Conditions Sample Temp. ° F Side Resistance time of internal rest, seam seg lbs / 2 -inch A 310 CD 0.75 2.0 A 310 MD 0.75 2.8 A 310 CD 1.25 1.9 A 310 MD 1.25 2.8 A 320 CD 0.75 1.8 A 320 MD 0.75 3.1 B 310 CD 0.75 1.9 B 310 CD 1.25 2.5 B 320 CD 1.25 2.3 Sample Temp. ° F Side Resistance time of internal rest, seam seg lbs / 2 -inch B 320 CD 0.75 2.1 C 310 CD 0.75 1.1 C 310 CD 1.25 1.1 C 320 CD 1.25 1.2 D 310 CD 1.25 1.1 D 310 MD 1.25 2..4 D 320 CD 0.75 1.3 The emplos A series of 10-pound open mesh bags were made using the side seam construction illustrated in FIG. 1 and FIG. 2. The bag material was a network fabric similar to thermoplastic cross-laminated mesh from Amoco-Nisseki CLAF, Inc. under the designation CLAF®. The layer of the film tape of the heat sealed material was an ethylene alpha-olefin resin available from Dow. In Examples Al to A4, the bags were made of a dark orange CLAF® fabric having a weight of approximately 30 g / m2. For Examples Bl to B5, the bags were made of a natural color CLAF® fabric having a weight of about 18 g / m2 and for Examples Cl to C4 the bags were made of a green CLAF® fabric having a weight of approximately 18 g / m2. The heat-sealed film that was used to form the side seams for Examples Al to B3 was a one-inch-wide strip of blown film of two millionths of Affinity PF 1140 ethylene alpha-olefin resin from Dow having a melting point of 94 ° C according to the manufacturer's literature. For Examples B4 to C4, the heat-sealed film was a one-inch tape of a 1.25 millionths blown film of a 1: 1 blend of Affinity PF 1140 resin and a linear low density polyethylene available from C &H Packaging ( Merrill, Wl). The melting point of the fabric resins were 145 ° C for the HDPE layers and 110 ° C for the outer LDPE layers. The side seams of the bags were made with CLAF® fabric strands next to the heat-sealed film in the machine direction and the seams were heat sealed with the CDDI heat sealer described above with the temperature of the metal bar seal, varied top and temperature of the lower silicone plastic pad maintained at 200 ° F using a half inch wide seal bar. For the examples tested and summarized in Table 2 below, the 12-inch wide bags were manufactured with the heat-sealed side seam resistances tested on the two-inch tensile test tapes according to ASTM D 5035-95 . The tensile test tapes were prepared so that the seam was in the center of the sample and perpendicular to the test direction. The entry "2 x 0.13" in the standstill column in Table 2 indicates that the side seam was heat sealed once at 60 psi for 0.13 sec, then the bag was turned, and the reverse side of the seam was sealed by heat for another 0.13 sec at 60 psi. This process was used to stimulate heat sealing in commercial equipment, which has two heat sealed sections in series with the first section, which has a heat seal bar on top and a silicone pad on the base and the second section that has the positions of the reverse bar and pad. The "1 x 0.13" entry indicates heat sealing with a simple exposure for 0.13 seconds at 60 psi. Examples Bl-B5 and comparative sample C were manufactured from the same manufacturer. The resistances of the side seams of Examples Bl-B5 with a heat-sealed material using between the fabric layers of the seams were 1.9 to 12.1 lbs / 2-inches, while the seam resistances of the Comparative Sample C were from 1.1 to 1.2 lbs / 2-inches, demonstrating the improvement of the strength of the side seam with the addition of heat-sealed film tapes.

Table 2 Test conditions Seam strength, lbs / 2- inch Use Temp. F Average Time Dev. rest, be. Standard Al 390 2 X 0.13 12.9 1.8 A2 400 2 X 0.13 11.9 2.1 A3 410 2 X 0.13 12.8 1.5 A4 420 2 X 0.13 12.8 1.6 Bl 350 2 X 0.13 12.1 0.9 B2 340 2 X 0.13 7.8 2.8 B3 340 1 X 0.13 7.3 3.8 B4 340 2 X 0.13 1.9 0.8 Test conditions Seam strength, lbs / 2-inch B5 340 2 x 0.23 3.1 1.2 Cl 400 2 x 0.13 4.9 4.0 C2 350 2 x 0.13 2.1 2.2 C3 375 2 x 0.13 7.1 3.3 C4 340 2 x 0.13 3.2 3.2 The bags of Examples A1 to A4 were then subjected to a series of drop tests. In these tests, each bag was filled with 20 baseballs weighing approximately 180 to 190 grams per piece for a total bag weight of approximately 8.3 pounds. The bags were then dropped from their terminal ends of a height of 3.5 feet onto a concrete surface. The tabulated results are the number of falls a bag went through before the failure of a side seam. Of the eleven bags of Example A2 tested, two bags were dropped ten or more times before failure of the side seam occurred. These bags with heat-sealed side seams with heat-sealed film tapes between the layers of the open-mesh fabric, all passed three or more times before the failure of the side seam. The other thirteen bags of Examples Al, A3 and A4 were tested for dropping and the results are also summarized below. Only one bag out of the 24 tested of Examples Al - A4 failed in the initial drop.

Table 3 Falls Bags of the Example Example A2 Bags Al, A3 v A4 7 1 6 1 1 5 3 1 4 2 2 3 1 1 2 2 1 1 0 1 In a second drop test battery, the bags of Example A2 were subjected to a drop test with 10 lbs of potatoes. Drop tests were dropped from 3.5 feet on a concrete surface. Of the nine bags tested, all the bags had four or more falls. The specific results were four bags with four falls, three bags with five falls, a bag with six falls and a bag with seven falls.

In another Example (D), a commercially available bag having polypropylene back gauze fabric (melting point at about 160 ° C) was obtained and the sewn seams were cut and released with two millionths blown film made of Affinity PF 1140 resin as the heat-sealed material between the fabric layers. The CDDI heat sealer was used with the temperature of the upper bar at 360 ° F and the temperature of the silicone pad lower than 200 ° F, a pressure of 60 psi and 2 resting times of 0.15 seconds each. The strength of the seam was tested by ASTM D 5035-95 and an average strength of 1.70 lbs / 2-inch was measured. The example demonstrates that the present invention is also applicable to woven fabrics, but the strengths of the seams were lower than for the preceding examples. A wider seam or use of a sealing tape having a seal initiation temperature closer to the melting point of the polypropylene would provide superior lateral seam strength.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Having described the invention as above, the content of the following is claimed as property.

Claims (10)

REIV NDICAC ONES

1. A bag that is breathable and allows observation of its contents, comprising an open mesh fabric with heat sealed seams, characterized in that the bag has a closed end, an opposite end and at least two longitudinal seams extending from the terminal end to the opposite end, wherein the terminal end is formed by a fold in the open mesh fabric and at least two seams are heat sealed seams having a section of open mesh fabric on each side of the fold joined with a thermoplastic sealing tape.

2. The bag of claim 1, characterized in that the fabric comprises a non-woven fabric.

3. The bag of claim 1, characterized in that the fabric comprises a woven fabric.

4. The bag of claim 1, characterized in that the fabric comprises a knitted fabric.

The bag of claim 1, characterized in that the fabric comprises a light diffusing or extruded mesh.

6. The bag of any of claims 1-5, characterized in that the longitudinal seams have a strength of at least about 5.0 lbs / 2-inches as measured by ASTM D 5035-95.

7. A process for manufacturing a bag that is breathable and allows the observation of its contents, in which an open mesh fabric is sealed by heat to form the seams, characterized in that the bag has at least two longitudinal seams and one terminal end formed by a fold in an open mesh fabric and formed by the steps comprising applying to an open mesh fabric in the selected positions corresponding to at least the longitudinal seams, the tapes of a thermoplastic resin to which the fabric of Open mesh is heat sealed, fold the open mesh fabric along an axis to form the bag's terminal end, and heat seal the open mesh fabric on both sides of the fold towards the tapes to form the longitudinal seams .

8. The process of claim 7, characterized in that the tapes are applied to approximately half the width of the fabric.

9. The process of claim 7 or 8, characterized in that the fold in the fabric is along the machine direction thereof.

10. A bag, characterized in that it is made by the process of any of claims 7-9.