Patent Application
20070047853
1. Field of the Invention
The present invention relates generally to the bags or packaging industry, and more particularly, to grease-resistant bags having an adhesive closure and related methods.
2. Description of the Related Art
Consumer packaging is important in today's marketplace. Not only do the products within the packaging have to be fresh, but the outside portions of the packaging must be aesthetically appealing. Traditionally, the focus has been to either sacrifice external appearance for internal protection, or sacrifice internal protection for external appearance, but seldom are the concerns with both external appearance and internal protection addressed with a single bag.
Furthermore, foods such as pet foods can exhibit an increased grease or fat component. The grease component of these foods in the past tended to penetrate the layers of the bag or gradually led to deterioration of the bag over time. The increasing grease content has created a desire in the art for a food bag with greater grease resistant properties and yet can be aesthetically appealing. Problems have also persisted regarding adequate sealing measures for the bag ends of the bags.
In view of the foregoing, embodiments of the present invention advantageously provide an enhanced bag that prevents grease from penetrating therethrough. Embodiments of the present invention also advantageously provide a method for constructing a bag that prevents grease from penetrating therethrough. Embodiments of the present invention further advantageously include a bag body and a pair of bag ends adapted to retain a food element, as well as any grease component associated with the food element, within the inner confines of the bag body. Embodiments of the invention allow the bag to carry over twenty-five pounds of a product, such as pet food, with relative ease.
For example, an embodiment of the present invention advantageously provides a bag to carry a food element having a grease component so that grease from the grease component is advantageously prevented from penetrating from within the bag to outside the bag. Additionally, for example, grease from other grease components not associated with the bag is advantageously prevented from penetrating from outside the bag to within the bag. An embodiment of the bag, for example, can include a tubular bag body having pair of opposing open bag ends and an inner face of an outer ply abuttingly adhering to an outer face of an inner ply. The outer ply includes an inner face of a grease-resistant polyester film abuttingly adhered to an outer face of a paper layer with a tie layer that can include a solventless adhesive. For example, the paper layer can advantageously have a greater bending stiffness than the polyester film. Also, for example, the paper layer can advantageously have a greater thickness than the polyester film. The bag can also include the inner face of the polyester film having printed indicia thereon to advantageously enhance visual appearance of the bag, and the polyester film can be adapted to allow an amount of light to advantageously transmit therethrough to thereby allow viewing of the printed indicia from outside of the bag.
An embodiment of the food bag, for example, can further include an inner ply having an inner face of a first film abuttingly adhered to an outer face of a grease-resistant material and an inner face of the grease-resistant material abuttingly adhered to an outer face of a second film. The embodiment can include a portion of the second film overlying a portion of the polyester film to define an overlapping seam of the tubular bag body extending along a longitudinal extent of the bag. The outer ply can have a substantially similar longitudinal length from one bag end to the other bag end along a circumferential periphery of each of the opposing bag ends, and the inner ply can have a substantially similar longitudinal length from the one bag end to the other bag end along a circumferential periphery of each of the opposing bag ends. Also, for example, a portion of at least one of the inner and outer plies of at least one of the opposing bag ends can foldingly and adheringly overlie another portion of the one bag end to define an overlapping seam extending along substantially an entire transverse extent of the one bag end to thereby closingly seal the one bag end so that the food element when positioned therein is retained within inner confines of the bag between the opposing pair of bag ends.
A further embodiment of the bag, for example, can include a bag body having a pair of opposing open bag ends and an inner face of an outer ply abuttingly adhering to an outer face of an inner ply. For example, the outer ply can include an inner face of a grease-resistant polyester film abuttingly adhered to an outer face of a paper layer. Also, for example, the paper layer can have a greater bending stiffness than the polyester film. The inner ply can include a grease-resistant material. Also, for example, an end portion of at least one of the inner and outer plies of at least one of the opposing bag ends can adheringly overlie another portion of the same bag end to define an overlapping seam substantially extending along a transverse extent of the same bag end to thereby closingly seal the bag end.
A further embodiment of the bag, for example, can include a bag body having a pair of opposing open bag ends and an inner face of an outer ply abuttingly adhering to an outer face of an inner ply. For example, the outer ply can include a grease-resistant film, and the inner ply can include a grease-resistant material. Also, for example, an end portion of at least one of the inner and outer plies of at least one of the opposing bag ends can adheringly overlie another portion of the same bag end with an adhesive including components of rosin ester and ethylene vinyl acetate so that the grease resistant film of the outer ply contacts the adhesive and the grease resistant material of the inner ply contacts the adhesive to thereby define an overlapping seam substantially extending along a transverse extent of the same bag end.
Another embodiment of the bag, for example, can include a bag body having an inner face of an outer ply abuttingly adhering to an outer face of an inner ply. Also, for example, the outer ply can include a polyester material, and the inner ply can include a polymeric material. Also, for example, a portion of at least one of the inner and outer plies can adheringly overlie another portion of the same bag end with an adhesive including components of rosin ester and ethylene vinyl acetate so that the polyester material of the outer ply contacts the adhesive and the polymeric material of the inner ply contacts the adhesive to thereby define a bag closure.
An embodiment of the bag, for example, can include a method of constructing a bag. For example, the method can include adhering an inner face of a grease-resistant polyester film with an outer face of a paper layer to create an outer ply. The method can also include, for example, adhering an inner face of a first film to an outer face of a grease-resistant material and adhering an inner face of the grease-resistant material to an outer face of a second film to create a multi-layer inner ply. The method can also include, for example, adhering an inner face of the outer ply to an outer face of the inner ply to create a laminate with a pair of opposing ends. The method can also include, for example, adheringly overlying a portion of an inner face of the inner ply located at one lateral side of the laminate onto a portion of an outer face of the outer ply located at another lateral side of the laminate to define an overlapping seam extending along a longitudinal extent of a tubular portion of the bag. The method can also include, for example, adheringly overlying an end portion of at least one of the inner and outer plies of at least one of the opposing bag ends onto another portion of the same bag end with an adhesive including components of rosin ester and ethylene vinyl acetate to define an overlapping seam substantially extending along a transverse extent of the same bag end to thereby closingly seal the bag end.
Embodiments of the present invention advantageously combine the use of polymeric structures and paper, thereby combining the advantages of the thickness and bending stiffness of paper with the puncture-resistant and grease-resistant properties of polyester. Embodiments of the present invention further advantageously combine the use of grease-resistant or polymeric structures in the form of a mono-layer or multi-layer coextruded film, thereby combining the advantages of the thickness and bending stiffness of paper with the puncture-resistant and grease-resistant properties of grease-resistant or polymeric materials. Embodiments of the present invention also provide increased barrier protections from grease, endurance, strength, physical integrity, thickness, stiffness, resistance to stretching from pressure from food elements within the bag, and heat-sealable characteristics not offered with other bags. The bag advantageously prevents problems customarily associated with greasy products such as pet food, for example, and eliminates the absorption and penetrable effect of the grease component included in such foods as pet food. Various bags are often used in other settings where greasy elements are contained within the bags, and the present invention advantageously contributes to solving such problematic concerns attributable to the grease. Other applications of the bag may include dry foods, beverages, feed, soil, lawn and garden, building materials, and other markets to advantageously prevent grease from penetrating from outside the bag to within the bag and to prevent grease from penetrating from within the bag to outside the bag.
Embodiments of the present invention offer the further advantages of the adhesive including components of rosin ester and ethylene vinyl acetate adhering a portion of at least one of the inner and outer plies of at least one of the opposing bag ends to another portion of the same bag end to define an overlapping seam substantially extending along a transverse extent of at least one of the pair of bag ends. For example, the adhesive can adhere a grease-resistant material to another grease-resistant material. Also, for example, the adhesive can adhere a polyester material with a type of polymeric material. Even further, for example, layers of materials, such as polyethylene or oriented polypropylene (OPP) can be heat-sealed in order to closingly seal the bag.
A further advantage of the present invention is the environmentally friendly composition of the structure of the present invention by producing bags 18 that are less toxic and increasingly biodegradable, while maintaining inexpensive costs relative to other types of potentially environmentally friendly bags 18. Further, the bag 15 can advantageously be manufactured on existing equipment previously utilized for manufacturing bags 18, so there is no necessity to invest in new and expensive bag 15 manufacturing equipment.
Embodiments of the invention can have many alternative bag styles in addition to the embodiments described, such as for example bag styles of a gusseted pinch-bottom bag, a pinch-bottom bag not gusseted, other various pinch-bottom styles of bags, heat-sealable bags of various constructs, and block-bottom bags of various constructs. Such features are interchangeable, as understood by those skilled in the art, and are determined by the requirements of the marketplace. Regardless of what type of bag is to be constructed, another advantage of embodiments of the present invention is that each can be run on conventional bag producing machines, as understood by those skilled in the art. Embodiments of the bags manufactured in this way using the described construction and materials also offers the advantage of allowing the bag to be made containing consumer features such as easy-carry handles, reclosable zippers, and easy-to-open features, and cost-effective measures.
Some of the features, advantages, and benefits of the present invention having been stated, others will become apparent as the description proceeds when taken in conjunction with the accompanying drawings, in which:
The present invention will now be described more fully hereinafter with reference to the accompanying drawings, which illustrate embodiments of the invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the illustrated embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. The prime notation, if used, indicates similar elements in alternative embodiments.
An embodiment of the bag 15 has an outer ply 31 and an inner ply 51, as shown for example in all embodiments of
In one embodiment, the polyester film 33, for example, can advantageously be treated with a coating 27 on the outer face of the outer ply 31 to advantageously provide enhanced barrier protection from grease penetrating from outside the bag 15 to within the bag 15, protecting against abrasion and moisture, and providing an attractive gloss finish. The coatings 27 can also include printed indicia 29 as well. The coatings 27 can include, for example, flexography coatings 27, proprietary coatings 27, or other suitable coatings 27. In an embodiment, for example, the coatings 27 can utilize Repellence™ barrier coatings or Aqua Crystal™ film coatings, both of which are manufactured by Exopack, LLC of Spartanburg, S.C., as understood by those skilled in the art. The coatings can facilitate adhesion and bonding and can enhance the coefficient of friction of the bag.
The coating 27 provided on the outer face of the polyester film 33 of the outer ply 31 provides oil, grease, and water resistance without the use of inferior traditional films and/or foils. The coatings 27 effectively preserve the quality of the package contents as well as the physical integrity of the bag 15 as a whole. The Repellence™ coating 27, for example, is particularly advantageous for products that contain oil or grease and to bags 18 that may occasionally be subjected to rain or other elements 19. The Aqua Crystal™ film coating 27, for example, is advantageous in part because of its clarity and gloss thereby enhancing the appearance to consumers.
In one embodiment, the outer face of the polyester film 33, for example, can have a coefficient of friction in a range of about 0.5 to about 0.9, as understood by those skilled in the art, but can alternatively feature differing ranges of coefficients of friction depending on the specific type of polyester film 33 employed in each instance and/or other applications. The coefficient of friction, for example, in a pet food bag application can advantageously be high enough so that the finished product does not have the tendency to slip or slide when positioned on a shelf or cabinet. An embodiment of the polyester film 33 may have a thickness varying from 36 gauge to 48 gauge, for example, but alternatively may have thicknesses above or below that range.
In one embodiment, the inner face of the grease-resistant film 33 of the outer ply 31 can advantageously include printed indicia 29 thereupon to enhance visual appearance of the bag 15. The polyester film 33 is adapted to allow an amount of light to transmit therethrough, as understood by those skilled in the art, to thereby allow viewing of the printed indicia 29 from outside of the bag 15. The polyester film 33 can be an amorphous classification which is highly transparent and colorless, or can alternatively be a semi-crystalline classification which is translucent or opaque with an off-white coloring. Amorphous polyester films 33 generally have better ductility than semi-crystalline polyesters, but less hardness and stiffness than the semi-crystalline type. The polyester film 33, for example, can be printed with solvent-based inks or water based inks, and can be printed overall with a flood coat of white ink, which may advantageously allow for better graphics. The embodiment featuring the flood coat of white ink may also advantageously impart the ability to mask grease if it somehow penetrated through a cut or crack in the polyester film 33. Also, for example, portions of the polyester film 33 can be treated with an acrylic chemical suitable for adhering to solvent based inks, water based inks, or other inks. In alternative embodiments, instead of reverse printing printed indicia 29 on the inner face of the polyester film 33, printed indicia 29 can be surface printed on the outer face of the polyester film 33, or otherwise can be left clear without any printed indicia 29 featured thereupon.
Embodiments of the invention can feature the paper layer 35 of the outer ply 31, for example, advantageously having a greater bending stiffness or tensile stiffness than the polyester film 33 of the outer ply 31. Also, for example, embodiments of the invention can feature the paper layer 35 of the outer ply 31 having a greater thickness than the polyester film 33 of the outer ply 31, which additionally contributes to enhanced bending stiffness, modulus, and/or tensile strength of the paper layer 35 and increased stabilization of the bag, as understood by those skilled in the art. The range of thickness for the paper layer 35 can be generally in the range of about 1.75 millimeters to about 10 millimeters. For example, the minimum thickness of one embodiment includes a paper thickness of about 1.9 millimeters, which is relatively flimsy compared to paper 35 with advantageously greater thickness. For example, embodiments of the invention can feature a paper layer 35 of the outer ply 31 having a thickness in the range of about 3.5 millimeters to about 4.5 millimeters. The range of thickness for the polyester film 33 of the outer ply 31 can be generally in the range of about 0.25 millimeters to about 0.75 millimeters. For example, embodiments of the invention can feature a polyester film 33 of the outer ply 31 of about 48 gauge and/or having a thickness in the range of about 0.475 millimeters to about 0.485 millimeters. As understood by those skilled in the art, an increased thickness of the paper layer 35 or the polyester film 33 can provide for increased bending stiffness and increased stabilization of the bag.
Stiffness, in this regard, is generally understood to be bending stiffness or tensile stiffness, although other suitable measurements of stiffness can also be utilized in accordance with the present invention, such as droop stiffness, folding endurance, or other alternative measurements. Bending stiffness, for example, is an expression of the rigidity of paper or paperboard and is a function of the cube of the caliper thickness. As understood by those skilled in the art, this property of bending stiffness is to some extent related to the modulus of elasticity of the product and its thickness. The bending stiffness of the paper layer generally increases as the thickness of the paper layer is increased, as understood by those skilled in the art.
There are several instruments in use in the industry that measure stiffness, and they all operate in such a manner to bend the product as a way of measuring stiffness. As understood by those skilled in the art, there are generally 2-point bending instruments and 4-point bending instruments. Solid fiber board and small fluted combined board (to be used in folding cartons) is typically measured with 2-point bending instruments. Commonly used instruments include Taber, Gurley, and L&W instruments to measure bending stiffness. In the United States, Taber Stiffness is the most common stiffness measurement, and Gurley Stiffness is also used quite often. L&W instruments are more common in European countries to measure stiffness. As such, in accordance with the present invention, Taber Stiffness and Gurley Stiffness are therefore two methods of measuring bending stiffness for the particular applications and thicknesses of the paper layer 35 and the polyester film 33 in the ordinary course, as understood by those skilled in the art.
With respect to the bending stiffness measurements, as understood by those skilled in the art, the TAPPI (Technical Association of the Pulp and Paper Industry) has industry standards for measuring stiffness that are utilized, acknowledged, and/or implemented in embodiments of the present invention. The Gurley Stiffness Value is measured using a Gurley Stiffness Testor, manufactured by W. and L. E. Gurley of Troy, N.Y. In essence, as understood by those skilled in the art, this instrument measures the externally applied moment required to produce a given deflection of a strip of material of specific dimensions fixed at one end and having a concentrated load applied to the other end. The results are obtained as “Gurley Stiffness” values in units of grams. There is a reasonable correlation between Gurley Stiffness and Taber Stiffness for paperboard grades, as understood by those skilled in the art. As referenced in TAPPI Test Method T-543, paragraph 4.1.5, the full range of Gurley values range from approximately 1.39 to 56,888 Gurley Stiffness units, which after using the proper conversion equation roughly corresponds to Taber values ranging from approximately 0 to 806.3 Taber Stiffness units, as understood by those skilled in the art.
The Tables 1-3 in
For example, in Tables 1-4, particularly in the raw data included within Table 4 of
In this manner, in some embodiments of the invention, the paper layer 35 advantageously enhances the appearance of the bag 15 as a whole, and also advantageously enhances durability and product handling by consumers. Various base-weights of paper can be utilized, for example, ranging from about 30 lbs.-force per square inch to about 50 lbs.-force per square inch, as understood by those skilled in the art. Embodiments of the paper layer 35, for example, also can be clay-coated and bleached, as understood by those skilled in the art, or alternatively can be manufactured without clay-coating and without bleach. Embodiments of the paper layer 35 can also be treated with a fluorocarbon chemical to improve grease-resistance, as understood by those skilled in the art, or alternatively can be manufactured without applying a fluorocarbon chemical treatment or with applying a non-fluorocarbon treatment in some applications, for example. Also, for example, portions of the outer face of the paper layer 35 by illustrate printed indicia 29 printed thereupon. Procedures for printing printed indicia 29 can include process printing, rotogravure printing, innovative flexographic printing, or other processes of printing as understood by those skilled in the art. The paper layer 35 can also be treated with a chemical to advantageously provide enhanced protection from grease penetrating through the paper layer 35 of the bag 15.
The technical requirements of the paper layer 35 may be reduced because the grease-resistant polyester and nylon layers solve the grease problem. Thus, even though grease-resistant paper 35 may still be utilized in certain embodiments, it is no longer necessary to utilize grades of paper layers 35 that have some degree of grease-resistant properties, because the other layers prevent grease penetration. As a result, other less expensive grades of paper that don't offer any grease-resistance may be utilized. In accordance with embodiments of the present invention, a paper layer 35 can be selected having a sufficient thickness that advantageously contributes to the bending stiffness and stability of the bag 15 without having to address concerns of grease-resistance which are duly addressed by the polyester film 33. Paper bags 18 are also more difficult to attach zippers and handles thereto.
The adhesive abuttingly adhering the paper layer 35 to the grease-resistant film 33, for example, can be is preferably a tie layer 37, but can alternatively be a solvent-based adhesive. The tie layer 37 can advantageously include an element 19 of polyurethane to better adhere the paper layer 35 to the polyester film 33, if desired.
An embodiment of the inner ply 51′, shown for example in
A polypropylene film mono-layer for the inner ply 51′ shown in
Another alternative embodiment of the inner ply 51, shown for example in
Embodiments of the first and second films 53, 54 of the inner ply 51 include a material, for example, selected from the group consisting of: polyethylene (PE) and oriented polypropylene (OPP). These films 53, 54, for example, are heat-sealable and are advantageously capable of melting and bonding together to form a sealable closure in various applications. Embodiments of the grease-resistant material 55 of the inner ply 51 include a material selected from the group consisting of: nylon and polypropylene. Other grease-resistant materials 55 can alternatively be utilized, such as for example, metalized films, ethylene vinyl alcohol, polyester, or other specialty resins. These grease-resistant materials, for example, are advantageously capable of resisting and preventing penetration or absorption of grease, mineral oils, solvents, and acids. The first and second films 53, 54 are adhered to the grease-resistant material 55 of the inner ply 51, for example, by tie layers 57 of chemical bond. One embodiment of the tie layers 57 that can be utilized in securing the grease-resistant material 55 between the films 53, 54 is solvent-based petroleum distolate. Alternatively, other suitable adhesives can be utilized as the tie layers 57 as understood by those skilled in the art.
After the inner face of the outer ply 31 is abuttingly adhered to the outer face of the inner ply 51 with an adhesive 38, as shown in
As shown, for example, in
Additionally, such as shown in
Another embodiment of the bag 15, as shown for example in
Another embodiment of the bag 15, as shown for example in
Within the adhesives industry, hot melts, for example, have good performance and usage benefits, as understood by those skilled in the art. Hot melt adhesives are solvent-free adhesives, that are characteristically solid at temperatures below 180 degrees F. (° F.), are low viscosity fluids above 180° F., and rapidly set upon cooling. The development of hot melt adhesive technology stemmed from the previous use of molten wax for bonding. Hot melt adhesives are used in a variety of manufacturing processes. There are a number of hot melt adhesives in use, with the most common being those used for hot melt pressure sensitive adhesive applications: ethylene vinyl acetate (EVA) copolymers, compatible with paraffin, the original hot melt; styrene-isoprene-styrene (SIS) copolymers; styrene-butadiene-styrene (SBS) copolymers; ethylene ethyl acrylate copolymers (EEA); and polyurethane reactive (PUR).
Generally, these polymers do not exhibit the full range of performance characteristics required for an end product by themselves. For this reason, for example, a variety of tackifying resins, waxes, antioxidants, plasticizers, viscosity reducers, and other materials can be added to the adhesive formulation to enhance the polymer performance, as understood by those skilled in the art.
For example, one of the most recent hot melt adhesive advances is the PUR adhesive, which is a 100 percent solid, one-component urethane prepolymer that behaves like a standard hot melt until it reacts with moisture to crosslink or chain extend, forming a new polyurethane polymer. By curing the polymer in this way, PURs have performance characteristics that are more enhanced than those of standard hot melts. Unlike many of the other hot melts, which require a slot die or roll coater, PURs are applied to a substrate as a dot or a thin glue line, set in seconds, and are structurally rigid in minutes, following a final set. These adhesives have been accepted in many manufacturing industries, for example, where they can be applied in small bond points to eliminate use of mechanical fasteners, such as staples, screws, rivets, clips, snaps, nails or stitching.
Furthermore, for example, all groups of pine chemicals, except generally plant sterols, can also be used by the adhesives and sealants industry. Pine chemicals are renewable, naturally occurring materials derived from the pine tree (genus Pinus). The range of chemical classes obtained from pine trees includes numerous plant sterols, terpenes (or turpentine), resin acids (or rosin) and fatty acids. Rosin resins, including esters and polymerized rosins, are used as tackifiers to modify the properties of selected polymers to produce adhesives and sealants. Polyterpene resins are used to modify non-polar polymers for these same applications. Tall oil fatty acids can be dimerized to produce dimer fatty acids that, in turn, are the major ingredient in thermoplastic polyamide adhesives.
For example, as understood by those skilled in the art, there can be three major classes of tackifier resins for the adhesives industry: terpene, hydrocarbon and rosin resins. Terpene resins (pine-based) and hydrocarbon resins (petrochemical-based) are both hydrocarbons; that is, they contain only carbon and hydrogen. Although they are somewhat similar in that respect, they impart somewhat different properties to the resultant adhesives. Terpene-based resins are more diverse than petrochemical hydrocarbons in that these resins are readily modified with other chemicals (e.g., phenol) to produce an array of products. Notably, for example, rosin resins significantly differ from the previous two types in that they contain carboxylic acid and/or ester groups. These resins are generally more polar and narrower in molecular weight, for example, making them good tackifiers for a variety of end-use applications.
Within the adhesives industry, hot melts have excellent performance and usage benefits. New polymer and tackifier technologies are available to formulators, thus allowing adhesives that can be applied outside traditional paper and non-woven bonding. New uses in publishing, graphics, electronics and semi-structural applications will drive growth of hot melts.
End users, for example, can expect hot-melt packaging adhesives to run faster in some applications and perform on a range of substrates. Terpene phenolic resins, derivatives of alpha-pinene, can deliver enhanced adhesion qualities to difficult substrates such as recycled cardboard. They offer better green strength, making them useful for high-speed packaging lines with short set times. Rosin esters are commonly used to increase adhesion and the temperature performance range of ethylene vinyl acetate (EVA) based adhesives, but Applicant has advantageously recognized that this combination of elements in a hot melt adhesive can advantageously be used as a closure (e.g., end, sides, or other overlap region) for a bag in applications, for example, of a polyester or grease-resistant material facing another polymeric or grease resistant material. Rosin esters have the added benefit of being compatible with a range of polymers, thus limiting formulating complexity.
As understood by those skilled in the art, ethylene vinyl acetate (EVA), for example, can be produced by the random copolymerization of ethylene and vinyl acetate in predetermined ratio. The presence of VA reduces the crystallinity as the large acetoxy group distorts the chain structure. The stiffness of EVA varies with VA content. However, beyond about 60 percent VA, the stiffness rises sharply as pure vinyl acetate is a glass-like substance at room temperature. The practical limit for “mechanical” uses of EVA is about 20 percent VA content; however, for “adhesive” uses higher levels of VA can be used. High VA level copolymers are typically used in adhesive applications, while lower vinyl acetate containing copolymers, whose tensile moduli and surface hardness are greater, find greatest use in films, profile extrusions and injection molding. The higher percent VA resins have a good compatibility with other materials. Thus, EVA is widely used in blends and compounds. One main application, for example, is hot melt adhesives, where the EVA is blended with tackifier and paraffin wax.
As understood by those skilled in the art, the polarity of the VA molecule makes the copolymers receptive to high filler loadings and to combination with tackifiers and other adhesive components. The addition of the rosin ester to EVA produces a compatible mixture. The increase in the VA amount decreases the crystallinity of EVA and the elastic and viscous modules, but increases the peel strength and the tack. The tackifier improves the adhesion and increases the “open time” of the formulation.
In a further embodiment in which the bag ends or other bag closures are heat-sealed, each of the pair of bag ends 23, 25 is adapted to be positioned so that opposingly facing first and second portions of the inner ply 51 are compressed between opposingly facing first and second portions of the outer ply 31 to define a compressed lip 71, as shown in
Each of the materials used to construct the bag 15 can have a different range of melting temperatures. The polyester film 33 of the outer ply 31, for example, has a melting point temperature greater than the heat-sealable film 53 of the inner ply 51. In one embodiment, the polyester film 33 of the outer ply 31 has a melting temperature in the range of about 300 degrees Fahrenheit to about 475 degrees Fahrenheit, and preferably greater than 425 degrees Fahrenheit. In one embodiment, the heat-sealable film 53 of the inner ply 51 has a melting point temperature in the range of about 220 degrees Fahrenheit to about 300 degrees Fahrenheit, and preferably greater than 240 degrees Fahrenheit. As understood by those skilled in the art, the polyethylene heat-sealable film 53 of the inner ply 51 has a lower melting temperature and therefore melts easier and at lower temperatures than the grease-resistant polyester film 33 of the outer ply 31. A sufficiently low melting point temperature for the heat-sealable film 53 of the inner ply 51 advantageously allows for the melting and bonding of the second heat-sealable film 54 to closingly seal the bag end 23, 25, as understood by those skilled in the art.
For example, as understood by those skilled in the art, heat-sealing bag machine performs the function of forming and shaping the multi-layered structure into a bag 15 by accordingly compressing and melting the bag ends 23, 25 to closingly seal the bag ends 23, 25. The heat-sealing bag machine has an extended heater belt and/or heated jaws that carry out the heat-sealing procedure. The heat can alternatively be applied, for example, by heated rollers, a heated wire/wires, or a heated air zone that adequately melts the heat-sealable film 53, as understood by those skilled in the art. The extended heater belt and/or heated jaws can mass-produce the heat-sealed products through a continuous high-speed operation, which manufactures a quality product in massive quantities to be delivered to customers in the ordinary course of business. In some applications, for example, the bag manufacturer typically heat-seals one end of each bag and delivers the bag to a customer, and the customer fills the bag with the proper elements and ultimately heat-seals the other end of the bag. The heat-sealing process can form bags with a lip as herein described, or can alternatively form bags that have a flattened top end and flattened bottom end to thereby provide the capability of stacking multiple bags neatly on top of one another.
To describe the heat-sealing process more specifically, for example, the polyethylene portion of the heat-sealable film 53 of the inner ply 51 at the bag ends 23, 25 is heated to a melting point temperature of at least 220 degrees Fahrenheit, in one embodiment for example, to melt the heat-sealable polyethylene film of the bag ends 23, 25. Alternatively, the temperature could be raised in excess of 300 degrees Fahrenheit, in one embodiment for example, to melt not only portions of the polyethylene heat-sealable films 53 together but also to melt portions of the polyester films 33 together as well, thus advantageously forming an even tighter closed seal at the bag ends 23, 25. In one embodiment, for example, the manufacturer utilizing the heat-sealing bag machine will seal only one end 23, 25 portion of the bag 15, thereby leaving another end 23, 25 portion of the bag 15 open to eventually fill the bag 15 with food or other elements 19. The distributor of the goods, for example, then fills the bag 15 with the food or other elements 19, and thereafter seals the other end 23, 25 portion of the bag 15 after the bag 15 is full.
As illustrated in
Embodiments of the method of the present invention of constructing a bag 15, for example, can include adhering an inner face of a grease-resistant polyester film 33 with an outer face of a paper layer 35 to create an outer ply 31. The method can also include adhering an inner face of a first film 54 to an outer face of a grease-resistant material 55 and adhering an inner face of the grease-resistant material 55 to an outer face of a second film 53 to create a multi-layer inner ply 51. The method can also include adhering an inner face of the outer ply 31 to an outer face of the inner ply 51 to create a laminate with a pair of opposing ends 23, 25. The method can also include overlying a portion of an inner face of the inner ply 51 located at one lateral side of the laminate onto a portion of an outer face of the outer ply 31 located at another lateral side of the laminate to define an overlapping seam extending along a longitudinal extent of a tubular portion of the bag. The method can also include adheringly overlying an end portion of at least one of the inner and outer plies 51, 31 of at least one of the opposing bag ends 23 onto another portion of the same bag end 23 with an adhesive 64 including components of rosin ester and ethylene vinyl acetate to define an overlapping seam substantially extending along a transverse extent of the same bag end 23 to thereby closingly seal the bag end 23.
Embodiments of the method of the present invention can further include adhering an inner face of the inner ply 51 of at least one of the opposing bag ends 23 against an outer face of the outer ply 31 of the same bag end 23 to define an overlapping seam substantially extending along a transverse extent of the bag end 23. The method can further include closingly sealing the overlapping seam responsive to the adhering to thereby prevent grease from penetrating from within the bag 15 to outside the bag 15 and prevent grease from penetrating from outside the bag 15 to within the bag 15.
The method can also include adhering an outer face of the outer ply 31 of at least one of the opposing bag ends 23 against the same outer face of the same outer ply 31 of the same bag end 23 to define an overlapping seam substantially extending along a transverse extent of the bag end 23. The method can further include closingly sealing the overlapping seam responsive to the adhering to thereby prevent grease from penetrating from within the bag 15 to outside the bag 15 and prevent grease from penetrating from outside the bag 15 to within the bag 15.
Embodiments of the bags and methods of the present invention have important benefits and advantages. The combined use of polymeric structures and paper, for example, combines the advantages of the thickness and bending stiffness of paper with the puncture-resistant and grease-resistant properties of polyester, including in some embodiments the heat-sealable characteristics of films such as polyethylene. Furthermore, the grease-resistant properties of the inner ply 51, 51′ offer enhanced grease-resistance in addition to the grease-resistance properties of the outer ply 31, both of which contribute to the advantageous quality of the invention. Embodiments of the bag provide increased barrier protections from grease, endurance, strength, physical integrity, and heat-sealable characteristics not offered with other bags 18. The bag 15 advantageously prevents problems customarily associated with greasy products such as pet food, for example, and eliminates the absorption and penetrable effect of the grease component included in such foods as pet food. Various bags 18 are often used in other settings where greasy elements 19 are contained within the bags 18, and embodiments of the bag advantageously contribute to solving such problematic concerns attributable to the grease. Other applications of the bag 15 may include dry foods, beverages, feed, soil, lawn and garden, building materials, and other markets to advantageously prevent grease from penetrating from outside the bag 15 to within the bag 15 and to prevent grease from penetrating from within the bag 15 to outside the bag 15. Furthermore, embodiments of the invention offer enhanced strength to allow the bag to carry over twenty-five pounds of pet food with relative ease.
A further advantage of the present invention is the advantages of the adhesive 64 including components of rosin ester and ethylene vinyl acetate adhering a portion of at least one of the inner and outer plies 51, 31 of at least one of the opposing bag ends 23 to another portion of the same bag end 23 to define an overlapping seam substantially extending along a transverse extent of at least one of the pair of bag ends 23.
A further advantage of the present invention is the environmentally friendly composition of the structure of the present invention by producing bags 18 that are less toxic and increasingly biodegradable, while maintaining inexpensive costs relative to other types of potentially environmentally friendly bags 18. Further, the bag 15 can advantageously be manufactured on existing equipment previously utilized for manufacturing bags 18, so there is no necessity to invest in new and expensive bag 15 manufacturing equipment.
Embodiments of the invention can have many alternative bag styles in addition to the embodiments described, such as for example bag styles of a gusseted pinch-bottom bag, a pinch-bottom bag not gusseted, other various pinch-bottom styles of bags, and block-bottom bags of various constructs. Such features are interchangeable, as understood by those skilled in the art, and are determined by the requirements of the marketplace.
In the drawings and specification, there have been disclosed embodiments of the present invention, and although specific terms are employed, the terms are used in a descriptive sense only and not for purposes of limitation, the scope of the invention being set forth in the following claims. The invention has been described in considerable detail with specific reference to the illustrated embodiments. It will be apparent, however, that various modifications and changes can be made within the spirit and scope of the invention as described in the foregoing specification.
