Bladderless dunnage bag apparatus and method for manufacturing same

Abstract

A bladderless dunnage bag is provided in which the primary material used for construction is a dunnage material based upon a paper substrate in which one or both of its outer surfaces are coated with a resin material that is impermeable to air and is heat sealable. By use of heat sealable coating materials, a center seal and the end seals of the dunnage bag can be formed in a moving process, and the heat-sealable joints or seals are stronger than the paper substrate material itself, since the heat seals are comprised of the coating material being adhered to itself, rather than the use of an adhesive applied to a paper material as in conventional dunnage bags. In a preferred construction, the dunnage material has a resin coating on both the top and bottom surfaces of the paper substrate, and both lap joints and fin joints can be formed by a heat sealable process that adheres the coating materials together, and does not depend upon the paper material for strength. Moreover, the end joints can be formed by double folding, and again the heat sealable process is used to cause the coating materials to be melted together to form the seal, and not depend upon the strength of the paper substrate. The preferred dunnage bags are constructed of a single ply of dunnage material, or can be constructed of a multi-ply material in which the coated dunnage material is the inner layer; further middle and outer layers can be added made of paper or other materials to improve the bag's bursting strength. A new coating resin material is provided consisting of a low density polyethylene and a metalacene process polyethylene, in a mixture so as to benefit from the metalacene polyethylene while also providing sufficient low density polyethylene to make the material extrudable while being applied to the paper substrate. Therefore, the paper substrate can be coated with the extrudable compound while in motion in a rolling process, and further center seals can also be formed while the material is in a rolling process.

1 . A material used to construct bags, comprising: 
 a flexible paper substrate, said paper substrate having a first surface and a second surface;    a first coating material substantially covering the entire first surface of said paper substrate, said first coating material comprising a compound consisting of a low density polyethylene and a metalacene process polyethylene; and    a second coating material substantially covering the entire second surface of said paper substrate, said second coating material comprising a compound consisting of a low density polyethylene and a metalacene process polyethylene.    
     
     
         2 . The material as recited in  claim 1 , wherein said paper substrate comprises extensible kraft paper, and wherein said first coating material and said second coating material each exhibit properties of being extrudable, impermeable to air, heat sealable, able to absorb shock energy, and usable as a coating on extensible kraft paper.  
     
     
         3 . The material as recited in  claim 2 , wherein said material is used for constructing a bladderless dunnage bag, such that said first coating material acts as a bladder layer in the interior portions of said bladderless dunnage bag.  
     
     
         4 . The material as recited in  claim 2 , wherein said first coating material and said second coating material each comprise: 10% to 20% low density polyethylene, and 80% to 90% metalacene process polyethylene.  
     
     
         5 . A material used to construct bags, comprising: 
 a flexible paper substrate, said paper substrate having a first surface and a second surface; and    a coating material substantially covering the entire first surface of said paper substrate, said coating material comprising a compound consisting of a low density polyethylene and a metalacene process polyethylene.    
     
     
         6 . The material as recited in  claim 5 , wherein said paper substrate comprises extensible kraft paper, and wherein said coating material exhibits properties of being extrudable, impermeable to air, heat sealable, able to absorb shock energy, and usable as a coating on extensible kraft paper; and wherein said material is used for constructing a bladderless dunnage bag, such that said coating material acts as a bladder layer in the interior portions of said bladderless dunnage bag.  
     
     
         7 . The material as recited in  claim 6 , wherein said coating material comprises: 10% to 20% low density polyethylene, and 80% to 90% metalacene process polyethylene.  
     
     
         8 . A bladderless dunnage bag, comprising: 
 a flexible sheet material having a substrate with a coating on at least one surface of said substrate, said substrate comprising an extensible material, said coating comprising a material that is impermeable to air, heat sealable, and able to absorb shock energy; and    said flexible sheet material being formed into a dunnage bag shape by use of at least one seal along a longitudinal axis of said dunnage bag, and at least one seal along a transverse axis which is substantially perpendicular to said longitudinal axis; 
 wherein said coating forms an inner surface of said dunnage bag.  
   
     
     
         9 . The bladderless dunnage bag as recited in  claim 8 , wherein: said coating is extrudable, and improves the bag's bursting strength, puncture resistance, tear resistance, tensile strength, wet strength properties, and energy absorption properties.  
     
     
         10 . The bladderless dunnage bag as recited in  claim 8 , wherein said flexible sheet material comprises a single ply of dunnage material having a paper substrate with a resin coating on both surfaces of said paper substrate, which is used throughout the entire bag structure.  
     
     
         11 . The bladderless dunnage bag as recited in  claim 10 , further comprising at least one additional ply of material that is formed on the outer surface of said dunnage material, wherein said at least one additional ply of material comprises one of: a film material; a woven material; a non-woven material; or at least one additional ply of said dunnage material.  
     
     
         12 . The bladderless dunnage bag as recited in  claim 8 , wherein: 
 said substrate comprises extensible kraft paper;    said coating material comprises a compound consisting of 10% to 20% low density polyethylene and 80% to 90% metalacene process polyethylene;    said at least one longitudinal seal comprises a center seal formed along substantially the length of said dunnage bag before said flexible sheet material is shaped into a slightly spaced-apart form;    said at least one transverse seal comprises two end seals formed to close opposite end openings of said flexible sheet material after said center seal has been formed, thereby forming an enclosed bag structure; and    further comprising an air inlet valve located in said flexible sheet material.    
     
     
         13 . The bladderless dunnage bag as recited in  claim 12 , wherein: said flexible sheet material with center seal initially exhibits a substantially flat form while said end seals are formed, and later said bag structure is inflated into an air pillow form by use of said air inlet valve.  
     
     
         14 . The bladderless dunnage bag as recited in  claim 8 , wherein said at least one longitudinal seal comprises a fin seal constructed by: first forming said flexible sheet material into a slightly spaced-apart profile, then by folding said flexible sheet material at a substantially right angle along a first edge of the flexible sheet material, folding said flexible sheet material at a substantially right angle along a second edge of the flexible sheet material, the folds at both said first and second edges being made such that the coating on said substrate at the first edge faces and makes contact against the coating on said substrate at the second edge, then heating said flexible sheet material at said first and second edges until said coating melts, and then cooling said flexible sheet material at said first and second edges until said coating solidifies, thereby creating the fin seal.  
     
     
         15 . The bladderless dunnage bag as recited in  claim 14 , wherein: said flexible sheet material either is coated on a single surface, or is coated on both surfaces.  
     
     
         16 . The bladderless dunnage bag as recited in  claim 14 , wherein said slightly spaced-apart profile, when viewed from an open end, has the appearance of a relatively flat oval in which said first edge of the flexible sheet material abuts said second edge of the flexible sheet material.  
     
     
         17 . The bladderless dunnage bag as recited in  claim 8 , wherein said at least one longitudinal seal comprises a lap seal constructed by: first forming said flexible sheet material into a slightly spaced-apart profile, then by placing an area along a first edge of the flexible sheet material proximal to an area along a second edge of the flexible sheet material, such that the coating on a first surface of said substrate along said first edge comes into contact with the coating on a second surface of said substrate along said second edge, then heating said flexible sheet material at said first and second edges until said coatings on both said first and second surfaces melt, and then cooling said flexible sheet material at said first and second edges until said coatings on both said first and second surfaces solidify, thereby creating the lap seal.  
     
     
         18 . The bladderless dunnage bag as recited in  claim 17 , wherein said slightly spaced-apart profile, when viewed from an open end, has the appearance of a relatively flat oval in which said first edge of the flexible sheet material overlaps said second edge of the flexible sheet material.  
     
     
         19 . The bladderless dunnage bag as recited in  claim 8 , wherein said at least one transverse seal comprises an end seal constructed by: first forming said flexible sheet material into a slightly spaced-apart profile and forming a center seal; 
 bringing together a first sheet portion and a second sheet portion of said flexible sheet material at an open end of the bag structure, and directing both first and second sheet portions in a substantially parallel configuration through multiple folds while maintaining contact between the coating on the surface of said first sheet portion and the coating on the surface of said second sheet portion; and    heating said flexible sheet material in the area of said open end of the bag structure until the coatings on the surfaces of both said first and second sheet portions melt, and then cooling said flexible sheet material in the area of open end of the bag structure until said coatings on both said first and second surfaces solidify, thereby creating the end seal.    
     
     
         20 . The bladderless dunnage bag as recited in  claim 19 , wherein said flexible sheet material comprises a single ply of dunnage material having a paper substrate with a resin coating on both surfaces of said paper substrate.  
     
     
         21 . The bladderless dunnage bag as recited in  claim 20 , wherein the end seal construction includes a fold-over member formed from said an area of said first sheet portion, and wherein said fold-over member covers a portion of the outer coating of said second sheet portion.  
     
     
         22 . The bladderless dunnage bag as recited in  claim 19 , further comprising: a second ply of material which comprises one of: a film material; a woven material; or a non-woven material; and wherein the second ply of material covers the flexible sheet material of both said first and second sheet portions, and exhibits said substantially parallel configuration through multiple folds along with said first and second sheet portions; and 
 wherein the end seal construction includes a fold-over member formed from said second ply of material, wherein said fold-over member covers a portion of the outer coating of one of the first or second sheet portions.    
     
     
         23 . The bladderless dunnage bag as recited in  claim 8 , wherein a strength of said bag is limited by said coating material, not by said substrate material.  
     
     
         24 . A method for constructing a bladderless dunnage bag, comprising: 
 providing a flexible sheet material having a substrate with a coating on at least one surface of said substrate, said substrate comprising an extensible material, said coating comprising a material that is (a) impermeable to air, (b) heat sealable, and (c) able to absorb shock energy;    folding said flexible sheet material over upon itself to begin its shaping into a dunnage bag form;    forming at least one seal along a longitudinal axis of said dunnage bag form; and    forming at least one seal along a transverse axis which is substantially perpendicular to said longitudinal axis; 
 wherein said coating forms an inner surface of said dunnage bag.  
   
     
     
         25 . The method as recited in  claim 24 , wherein the step of forming at least one longitudinal seal comprises: 
 forming a center seal of either a lap seal or a fin seal, by first forming said flexible sheet material into a slightly spaced-apart profile in a continuous loop so that a first edge of said flexible sheet material is placed proximal to a second edge of said flexible sheet material, such that the coating on said substrate at or near the first edge faces and makes contact against the coating on said substrate at or near the second edge; and    heating said flexible sheet material at or near said first and second edges until said coating melts, and then cooling said flexible sheet material at said first and second edges until said coating solidifies, thereby creating the center seal.    
     
     
         26 . The method as recited in  claim 24 , wherein the step of forming at least one transverse seal comprises: 
 after forming a center seal to shape the flexible sheet material into a preliminary dunnage bag structure, forming at least one end seal by:    bringing together a first sheet portion and a second sheet portion of said flexible sheet material at an open end of the bag structure, and directing both first and second sheet portions in a substantially parallel configuration through multiple folds while maintaining contact between the coating on the surface of said first sheet portion and the coating on the surface of said second sheet portion; and    heating said flexible sheet material in the area of said open end of the bag structure until the coatings on the surfaces of both said first and second sheet portions melt, and then cooling said flexible sheet material in the area of open end of the bag structure until said coatings on both said first and second surfaces solidify, thereby creating said at least one end seal.    
     
     
         27 . The method as recited in  claim 26 , wherein the step of making multiple folds in said first and second sheet portions includes: 
 slitting side edges proximal to said open end of the bag structure;    folding said first sheet portion along a crease line between said slit side edges;    sealing said folded first sheet portion to create an inner end seal;    folding both said first and second sheet portions onto themselves along a line proximal to said inner end seal; and    sealing both said folded first and second sheet portions to create an outer seal.    
     
     
         28 . A method of manufacturing a bladderless dunnage bag, comprising: 
 roll rewinding of a flexible sheet material having a substrate with a coating on at least one surface of said substrate, said substrate comprising an extensible material, said coating comprising a material that is impermeable to air, heat sealable, and able to absorb shock energy;    folding said flexible sheet material over upon itself to begin its shaping into a dunnage bag form, and forming a center seal;    forming said flexible sheet material into a spaced-apart configuration using a tube forming station;    punching a hole in said flexible sheet material and installing and sealing thereto an air inlet valve;    slitting side edges proximal to an open end of the dunnage bag form;    creasing and folding said first sheet portion along a crease line between said slit side edges;    sealing said folded first sheet portion to create an inner end seal;    double creasing and double folding both said first and second sheet portions onto themselves along a line proximal to said inner end seal; and    sealing both said folded first and second sheet portions to create an outer seal at sufficient locations of said flexible sheet material to achieve an air-tight dunnage bag.    
     
     
         29 . The method as recited in  claim 28 , further comprising: filling said dunnage bag with air while creating said outer seal.  
     
     
         30 . The method as recited in  claim 28 , further comprising: filling said dunnage bag with air after creating said outer seal through an air inlet valve.  
     
     
         31 . A method of manufacturing dunnage material for use in a bladderless dunnage bag, said method comprising: 
 combining a low density polyethylene material with a metalacene process polyethylene to create a coating resin that is extrudable;    providing a roll of uncoated extensible paper, and unwinding that roll such that the extensible paper forms a web that passes an inner coating station and an outer coating station;    at said inner and outer coating stations, applying said coating resin to both surfaces of the paper web using an extrusion process; and    winding said coated paper web onto a second roll.    
     
     
         32 . The method as recited in  claim 31 , wherein said coated paper web comprises: a coated substrate of extensible kraft paper, said coating resin comprising 10% to 20% low density polyethylene, and 80% to 90% a metalacene process polyethylene; and which coated paper exhibits properties of being extrudable, impermeable to air, heat sealable, and able to absorb shock energy.  
     
     
         33 . A method of manufacturing a bladderless dunnage bag, comprising: 
 combining a low density polyethylene material with a metalacene process polyethylene to create a coating resin that is extrudable;    providing a roll of uncoated extensible paper, and unwinding that roll such that the extensible paper forms a web that passes an inner coating station and an outer coating station;    at said inner and outer coating stations, applying said coating resin to both surfaces of the paper web using an extrusion process;    winding said coated paper web onto a second roll;    unwinding said coated paper web from said second roll and directing it to a center seal station where said flexible sheet material is folded over upon itself to form a center seal and to begin its shaping into a dunnage bag form;    forming said flexible sheet material into a spaced-apart configuration using a tube forming station; and    forming at least one end seal by use of a creasing and folding operation.    
     
     
         34 . The method as recited in  claim 33 , further comprising: punching a hole in said flexible sheet material and installing and sealing thereto an air inlet valve.  
     
     
         35 . The method as recited in  claim 33 , wherein said end seal forming step comprises: 
 slitting side edges proximal to an open end of the dunnage bag form;    creasing and folding said first sheet portion along a crease line between said slit side edges;    sealing said folded first sheet portion to create an inner end seal;    double creasing and double folding both said first and second sheet portions onto themselves along a line proximal to said inner end seal; and    sealing both said folded first and second sheet portions to create an outer seal.    
     
     
         36 . The method as recited in  claim 33 , wherein said steps of folding and forming a center seal, forming said flexible sheet material into a spaced-apart configuration, and forming at least one end seal are all performed while said flexible sheet material is in motion, and wherein said center seal and at least one end seal are formed in a continuous heat sealing operation.  
     
     
         37 . The method as recited in  claim 33 , wherein said coated paper web comprises: a coated substrate of extensible kraft paper, said coating resin comprising 10% to 20% low density polyethylene, and 80% to 90% a metalacene process polyethylene; and which coated paper exhibits properties of being extrudable, impermeable to air, heat scalable, and able to absorb shock energy, and said coating resin improves the bag's bursting strength, puncture resistance, tear resistance, tensile strength, wet strength properties, and energy absorption properties.  
     
     
         38 . The method as recited in  claim 36 , wherein said heat sealing operation uses a heating mechanism comprising one of: hot air, open flame, ultrasonic vibrations, induction heating, or electromagnetic radiation.