SEALABLE REPULPABLE VALVE BAG AND METHOD OF ASSEMBLING

Abstract

A valve tube assembly for a repulpable bag having a valve end portion includes, in an exemplary embodiment, a valve tube member formed from a repulpable paper material, wherein the valve tube member includes a first end, a second end, an inside surface, and an outside surface, and a water dispersible hot melt adhesive layer deposited on at least a portion of the inside surface adjacent the first end by a timed application, with a remainder of the inside surface being free of the water dispersible hot melt adhesive. The valve tube member is sized to extend into the valve end portion of the repulpable bag with the second end positioned inside the repulpable bag.

Description

BACKGROUND OF THE INVENTION

The field of the invention relates generally to paper bags, and more particularly to a sealable repulpable valve bag.

A valve bag is a container having a body portion of substantially tubular configuration, which has an outer layer of at least one ply, and an inner layer of at least one ply. The plies may be made from a relatively stiff and sturdy paper material. The first end of the bag (usually the end the ultimate consumer opens) may be cut in a stepped end pattern, folded over and sealed, to form what is called a pinch-bottom bag. Alternatively, the first end may be formed with two sets of flaps, arranged in opposed pairs. The first pair of opposed flaps are folded inwardly toward one another (in-folded flaps). The two other flaps (outer flaps), typically oriented perpendicular to the in-folded flaps, would be folded over the already folded flaps and glued in place to close that end of the bag, such that when the bag is filled, the bottom of the bag will assume a square-bottomed shape.

Rather than leave the second end of the bag completely open for filling the valve bag, the bag can be filled with the second end of the bag substantially closed, when a valve is provided. In a valved bag, the second end is closed using in-folded flaps as described above. The tubular bag form is flattened somewhat, and the in-folded flaps correspond to the two opposite “short” sides of the bag. The in-folded flaps may or may not overlap. The outer flaps, which correspond to the “long” sides of the bag, are then folded over one another, and glued to each other. In addition, one of the in-folded flaps may be glued to the outer flaps. The remaining in-folded flap is not glued to either the outer flaps or the other in-folded flap, and so a channel can be formed, upon outward deflection of the glued and overlapped outer flaps, leading to the interior of the bag. If the in-folded flaps overlap, the valve is located on the side of the “under” flap. Filling can be accomplished by the insertion of an appropriately configured nozzle, which will extend to the gap between the in-folded flaps, to drop material into the interior of the bag, or if the in-folded flaps overlap, the nozzle will project under the “over” flap and into the bag far enough to clear the “under” flap and access the interior of the bag.

There are two general kinds of valved bags, those which cannot be sealed, and those which can be sealed. The bag described above, is an unsealed bag, as once filling has been accomplished, there can be no further gluing, or other sealing procedure which can be done without potentially disturbing or contaminating the contents of the bag, since the gap between the outer flaps and the unglued in-folded flap would have to be re-opened to place a seal between them.

In some instances, it is desirable to be able to fully seal the bag, after filling by the valve method. In such instances, an outwardly extending valve tube can be used in sealing the bag. In such a bag, the valve extension is a tube, formed from the stiff paper bag material previously described. The tube is positioned inside the valve area, so as to extend outwardly, well past the side of the bag, and inwardly, to a position substantially even with the inner edge of the valve side in-folded flap. The entire inner surfaces of the tube are coated with an adhesive/sealing material, such as a heat activatable glue, or an adhesive which may be activated by ultrasonic means. During the filling process, the valve tube is opened, and a filling nozzle is inserted. Due to the stiffness of the combined paper and the adhesive/sealing material, the valve tube may tend to remain slightly open, even after removal of the filling nozzle.

Once filled, the valve is typically flattened, and the end of the valve tube is sealed, either by application of heat or ultrasonic vibrations, to activate the sealing adhesive. In other valve tube bag constructions, a tab on the “upper” portion of the outwardly extending tube extends further than the “lower” portion, and instead of relying upon an adhesive lined tube, an applicator puts a hot melt glue on the underside of the tab, and a wiper presses the valve tube downward against the side of the filled bag, simultaneously closing the bag and affixing the tube against the bag side.

In the paper manufacturing industry, it is well known to use dry additives, such as the whitening agent titanium dioxide, which are shipped in large paper bags which must be individually opened and dumped into the pulp mixture. Typically such additives are added to an ambient temperature mixture, for example, 60° F. to 80° F. Some dry additives that are used in the paper making industry are packaged in “beater bags” which are substantially closed across the top, using conventional water soluble bag manufacturing adhesives, except for a fold-in spout through which the bag is filled. In the case of “beater bags”, the entire bag is then added to the pulp mixture for making a batch of paper. The bag disintegrates, becoming incorporated into the pulp mixture along with its contents. Such “beater bags” have the disadvantage, however, that filling through the spout is difficult and that after filling and folding in of the spout, the bag remains unsealed and therefore allows for leakage of the contents during shipping and handling. It is known to utilize hot melt adhesives to seal bags of dry bulk chemicals but the known adhesives used for this purpose have been incompatible with the pulp mixture and can cause discoloration or spotting of the manufactured paper, or can contaminate the dry chemicals. It is also known to apply a heat activated adhesive to the entire inner surfaces of the spout, but such adhesives are also incompatible with the pulp mixture, or seal prematurely when they are exposed to moisture from the sealing of the bottom of the bag.

BRIEF DESCRIPTION OF THE INVENTION

In one aspect, a valve tube assembly for a repulpable bag having a valve end portion is provided. The valve tube assembly includes a valve tube member formed from a repulpable paper material, wherein the valve tube member includes a first end, a second end, an inside surface, and an outside surface. A water dispersible hot melt adhesive layer is deposited on at least a portion of the inside surface adjacent the first end by a timed application, with a remainder of the inside surface being free of the water dispersible hot melt adhesive. The valve tube member is sized to extend into the valve end portion of the repulpable bag with the second end positioned inside the repulpable bag.

In another aspect, a method of assembling a valve tube assembly for a repulpable bag having a valve end portion is provided. The method includes providing a roll of repulpable paper material having an inside surface and an outer surface, applying a water dispersible hot melt adhesive to at least a portion of the inside surface of the repulpable paper material, and cutting the repulpable paper material to a predetermined length to form a valve tube blank. The valve tube blank includes a first end and a second end, wherein the water dispersible hot melt adhesive applied to the inside surface is located adjacent the first end of the valve tube blank.

In another aspect, a method of assembling a sealable repulpable valve bag is provided. The repulpable bag includes a front wall, a rear wall, opposing side walls, and a valve end portion. The method includes providing a repulpable valve bag having a first outer flap, an opposing second outer flap, a first in-folded flap and a second in-folded flap, and assembling a valve tube assembly. The valve tube is assembled by providing a roll of repulpable paper material having an inside surface and an outer surface, applying a water dispersible hot melt adhesive to at least a portion of the inside surface of the repulpable paper material, cutting the repulpable paper material to a predetermined length to form a valve tube blank, with the valve tube blank including a first end and a second end, wherein the water dispersible hot melt adhesive applied to the inside surface is located adjacent the first end of the valve tube blank. The method also includes forming a tubular valve tube assembly from one valve tube blank wherein the inside surface of the repulpable paper material forms the inside surface of the valve tube assembly. The method further includes attaching the valve tube assembly to the first in-folded flap so that the first end of the valve tube assembly is located outside the repulpable valve bag and the second end of the valve tube assembly is located inside the repulpable valve bag, and folding the first and second outer flaps and attaching the outer flaps to each other, the valve tube assembly, and the second in-folded flap.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a repulpable valve bag in accordance with an embodiment of the present invention.

FIG. 2 is a side elevation in section, of the repulpable valve bag shown in FIG. 1.

FIG. 3 is a plan view of a roll of paper material for forming the valve tube shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

A sealable repulpable valve bag that can be used in paper making processes is described below in detail. The repulpable bag disintegrates, becoming incorporated into the pulp mixture along with its contents when added to a pulp mixture used for making a batch of paper. The repulpable bag utilizes a water dispersible hot melt adhesive which may be activated by heat and/or ultrasonic energy to seal the bag's valve tube. The water dispersible hot melt adhesive and any other water soluble adhesives used to manufacture the valve bag are compatible with the pulp mixture used in paper making processes.

A repulpable valve bag 50 capable of being sealed is shown in FIGS., 1-3. In an exemplary embodiment, valve bag 50 includes opposing side walls 52 and 54, opposing in-folded flaps 56 and 57, and outer flaps 58 and 60. Bag 50 is fabricated from three layers of bag material, outer layer A, and inner layers B and C. In alternate embodiments, bag 50 may be formed with greater or fewer than three layers. Layers A, B, and C are adhered together, at least in portions, by layers of adhesive D. In order to facilitate filling and subsequent sealing of bag 50, a valve tube 62 is provided. Valve tube 62 is an integral unit that includes a valve tube member 64 formed from a repulpable paper material and is secured in bag 50 during manufacture. Valve tube member 64 has a uniform length, from its inside end 61, to its outside end 63, around its complete circumference. Valve tube member 64 is affixed to in-folded flap 56 and outer flaps 58 and 60 by adhesive layer D. Adhesive layer D is formed from a water soluble starch based adhesive that is compatible with pulp mixtures used in paper making processes. Valve tube member 64 is coated on its interior surface 65 along outside end 63 with an adhesive material 66. Adhesive material 66 is a water dispersible hot melt adhesive which may be activated by heat and/or ultrasonic energy. Adhesive material 66 should be compatible with pulp mixtures used in paper making processes. Any suitable water dispersible hot melt adhesive material may be used, for example, a water dispersible polyamide hot melt adhesive, NP-2068, commercially available from H. B. Fuller, St. Paul, Minn.

Referring also to FIG. 3, valve tube member 64 is formed from a continuous roll of paper stock 70. Valve tube member 64 is cut to length along cut lines 72. Hot melt adhesive material 66 is deposited on adjacent outside end 63 of valve tube member 64 along cut line 72. Because cut line 72 defines outside end 63 and inside end 61 of adjacent valve tube members 64, the timing of the adhesive application to outside end 63 as the continuous roll of paper stock 70 moves past an adhesive applicator is controlled to prevent the application of adhesive material 66 to inside end 61 of valve tube member 64 of an adjacent valve tube member 64 along cut line 72.

If adhesive material 66 is applied to both inside end 61 and outside end 63, valve tube member 64 might be sealed at inside end 61 during the activation of adhesive layer D used to attach valve tube member 64 to in-folded flap 56 and outer flaps 58 and 60. In addition, if adhesive material 66 extends too far inwardly from outside end 63, adhesive material 66 can pick up moisture from adhesive layer D and prematurely seal valve tube member 64. Thus, adhesive material 66 is strategically applied to outside end 63 of valve tube member 64. In the exemplary embodiment, adhesive material 66 extends approximately one-quarter inch (⅛″) plus or minus one-eighth inch (±⅛″) to approximately three inches (3″) plus or minus one-eighth inch (±⅛″) or beyond from outside end 63 of valve tube member 64. More specifically, in the exemplary embodiment, adhesive material 66 extends approximately three-quarter inch (¾″) plus or minus one-eighth inch (±⅛″) to approximately one and one-quarter inches (1¼″) plus or minus one-eighth inch (±⅛″) from outside end 63 of valve tube member 64. The distance of adhesive material 66 from outside end 63 towards inside end 61 may be variable between production lots. Final dimensions of bag 50 and valve tube member 64 may also be variable between production lots, thus causing the need for different areas of adhesive material 66 coverage extending from outside end 63 to inside end 61. In some configurations, adhesive material 66 could extend toward inside end 61 where moisture from adhesive layer D may prematurely seal valve tube member 64. The premature seal point can vary between production lots. For most, but not all applications, adhesive material extends approximately one-quarter inch (⅛″) plus or minus one-eighth inch (±⅛″) to approximately three inches (3″) plus or minus one-eighth inch (±⅛″) from outside end 63 of valve tube member 64.

After paper stock 70 is formed as a continuous roll with hot melt adhesive material 66 being strategically positioned on outside end 63, each valve tube member 64 included on the continuous roll of paper stock 70 is folded, and cut into an individual valve tube member 64 by an automated bag forming machine. The bag forming machine then inserts and adheres folded valve tube member 64 to bag 50. When forming bag 50, the bag forming machine automatically cuts paper stock 70 along cut lines 72 to form individual valve tube member 64. Each valve tube member 64 is folded, cut and inserted into partially formed bag 50 and is properly positioned on in-folded flap 56 of bag 50. Once valve tube member 64 is positioned and adhered to in-folded flap 56, the bag forming machine then folds outer flaps 58 and 60, which in turn causes valve tube member 64 to be further adhered to bag 50.

More specifically, upon cutting paper stock 70 along cut lines 72, a plurality of valve tube member blanks 73 are formed. The bag forming machine for forming bag 50 includes an electronic drive system which controls the tension of paper stock 70 as the material is folded into valve tube member 64 and fed into a cutting device. An electronic contrast sensor system measures contrast differences between the valve tube member 64 and the adhesive material 66, which enables the bag forming machine to properly cut each valve tube member 64. In the example embodiment, the contrast sensor systems measures the contrast between adhesive material 66 and paper stock 70. In another embodiment, a fluorescent additive is added to adhesive material 66 such that the fluorescent additive is detectible by a fluorescent sensor for determining the proper location for cutting valve tube member 64. In another embodiment, a colorant additive is added to adhesive material 66 such that the colorant additive is detectible using a reflectance measurement for determining the proper location for cutting valve tube member 64.

An individually folded and cut valve tube member 64 is then positioned by the bag forming machine on in-folded flap 56. The position of valve tube member 64 on in-folded flap 56 is controlled by the contrast sensor and the electronic drive system of the bag forming machine. Valve tube member 64 is formed into a substantially tubular shape by affixing a first side edge 74 to a second side edge 76 in an overlapped arrangement with adhesive layer D.

In the process of making bag 50, valve tube member 64 is positioned and affixed onto in-folded flap 56 of bag 50 before outer flaps 58 and 60 are folded down and glued into place. Valve tube member 64 is further attached to bag 50 by folding outer flaps 58 and 60 into contact with valve tube member 64. Adhesive layer D is applied to the upper side of valve tube member 64, among other areas, and outer flaps 58 and 60 are folded over each other and also secured to in-folded flap 57.

Filling of bag 50 is accomplished by inserting a nozzle into a valve passage 78 and bag filling material is discharged into the interior 80 of bag 50. Upon completion of filling, bag 50 is sealed by sealing valve passage 78 closed. In one embodiment, bag 50 is sealed by applying heat to adhesive material 66. In another embodiment, an ultrasonic generator head 68 and anvil 82 combination is positioned adjacent to outside end 63 of valve tube member 64. Outside end 63 of valve tube member 64 is positioned between generator head 68 and anvil 82, which then come together, closing outside end 63, and applying ultrasonic energy to activate adhesive material 66 to seal the valve tube member 64.

While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.

Claims

1. A valve tube assembly for a repulpable bag having a valve end portion, said valve tube assembly comprising:

a valve tube member formed from a repulpable paper material, said valve tube member comprising a first end, a second end, an inside surface, and an outside surface; and

a water dispersible hot melt adhesive layer deposited on at least a portion of said inside surface adjacent said first end by a timed application, a remainder of said inside surface being free of said water dispersible hot melt adhesive;

said valve tube member sized to extend into the valve end portion of the repulpable bag with said second end positioned inside the repulpable bag.

2. A valve tube assembly in accordance with claim 1 wherein said water dispersible hot melt adhesive layer comprises a water dispersible hot melt polyamid adhesive, said water dispersible hot melt polyamid adhesive repulpable and dispersible into a pulp mixture of a paper making process.

3. A valve tube assembly in accordance with claim 1 wherein said valve tube member comprises a valve passage extending therethrough.

4. A method of assembling a valve tube assembly for a repulpable bag having a valve end portion, said method comprising:

providing a roll of repulpable paper material having an inside surface and an outer surface;

applying a water dispersible hot melt adhesive to at least a portion of the inside surface of the repulpable paper material; and

cutting the repulpable paper material to a predetermined length to form a valve tube blank, the valve tube blank comprising a first end and a second end, wherein the water dispersible hot melt adhesive applied to the inside surface is located adjacent the first end of the valve tube blank.

5. A method in accordance with claim 4 wherein applying a water dispersible hot melt adhesive to at least a portion of the inside surface of the repulpable paper material comprises timing the application of the water dispersible hot melt adhesive so that the water dispersible hot melt adhesive is applied adjacent a predetermined cut line that defines the first end of one valve tube blank and the second end of an adjacent valve tube blank, wherein the water dispersible hot melt adhesive is not applied to the second end of the adjacent valve tube blank.

6. A method in accordance with claim 4 further comprising forming a tubular valve tube assembly from one valve tube blank wherein the inside surface of the repulpable paper material forms the inside surface of the valve tube assembly.

7. A method in accordance with claim 6 wherein the inside surface of the valve tube assembly defines a valve passage extending through the valve tube assembly.

8. A method in accordance with claim 6 wherein the valve tube assembly formed from the valve tube blank is repulpable and dispersible into a pulp mixture of a paper making process.

9. A method in accordance with claim 4 wherein cutting the repulpable paper material to a predetermined length to form a valve tube blank comprises cutting the repulpable paper material to a length that permits one end of the valve tube assembly to be positioned inside the valve end portion of the repulpable bag while an opposing end of the valve tube assembly is positioned outside the repulpable bag.

10. A method of assembling a sealable repulpable valve bag, the repulpable bag having a front wall, a rear wall, and opposing side walls, and a valve end portion, said method comprising:

providing a repulpable valve bag having a first outer flap, an opposing second outer flap, a first in-folded flap and a second in-folded flap;

assembling a valve tube assembly by:

providing a roll of repulpable paper material having an inside surface and an outer surface;

applying a water dispersible hot melt adhesive to at least a portion of the inside surface of the repulpable paper material; and

cutting the repulpable paper material to a predetermined length to form a valve tube blank, the valve tube blank comprising a first end and a second end, wherein the water dispersible hot melt adhesive applied to the inside surface is located adjacent the first end of the valve tube blank; and

forming a tubular valve tube assembly from one valve tube blank wherein the inside surface of the repulpable paper material forms the inside surface of the valve tube assembly;

attaching the valve tube assembly to the first in-folded flap so that the first end of the valve tube assembly is located outside the repulpable valve bag and the second end of the valve tube assembly is located inside the repulpable valve bag; and

folding the first and second outer flaps and attaching the outer flaps to each other, the valve tube assembly and the second in-folded flap.

11. A method in accordance with claim 10 wherein applying a water dispersible hot melt adhesive to at least a portion of the inside surface of the repulpable paper material comprises timing the application of the water dispersible hot melt adhesive so that the water dispersible hot melt adhesive is applied adjacent a predetermined cut line that defines the first end of one valve tube blank and the second end of an adjacent valve tube blank, wherein the water dispersible hot melt adhesive is not applied to the second end of the adjacent valve tube blank.

12. A method in accordance with claim 10 wherein the valve bag and the valve tube assembly formed from the valve tube blank is repulpable and dispersible into a pulp mixture of a paper making process.

13. A method in accordance with claim 10 wherein providing a repulpable valve bag comprises providing a repulpable valve bag having at least two layers of repulpable paper.

14. A method in accordance with claim 10 wherein the inside surface of the valve tube assembly defines a valve passage extending through the valve tube assembly.