Patent Application
20110089168
The present disclosure relates to microwavable bags.
Embodiments of microwavable bags for use with liquid oil, as well as methods for manufacturing the same, are disclosed. Particular features of various embodiments are disclosed herein and are recited in the appended claims, which are hereby incorporated by reference into this summary section.
The drawings are not necessarily to scale and thus, in some instances, layer thicknesses or other sizes may be exaggerated or otherwise altered.
Certain bags configured for use in heating food in a microwave oven can be particularly well-suited for popping popcorn. Microwavable popcorn bags are often formed from laminates that comprise two paper plies, and the laminates may be treated with a chemical barrier or a film former to provide the bags with grease resistance. The bags generally store a mixture of unpopped popcorn kernels and fats. The fats are solid at room temperature, as well as at elevated temperatures experienced during packaging and/or transport of the bags, and often include trans fats and/or hydrogenated oils. The bags are generally sealed via heat seals. Although the heat seals may adequately prevent solid fats from exiting the bags, the seals are not capable of preventing the escape of liquid oils.
Certain embodiments of microwavable bags disclosed herein are advantageously configured to retain liquid oils, such as, for example, oils that are free or substantially free of trans fat and/or oils that are in a liquid state at room temperature. In some embodiments, the microwavable bags include a body material that comprises one or more paper plies. The microwavable bags can have a pinch bottom closure in which portions of one or more gussets are sealed between a front wall and a rear wall of the bag. The pinch bottom closure can be sealed via a cold seal adhesive, which can prevent liquid oil from exiting the bag via the closure.
With reference to
In the illustrated embodiment, as shown in
In other embodiments, the body material 110 can comprise other structures and compositions. For example, more or fewer paper plies and/or layers of other materials may be included in the laminate. Examples of suitable body materials 110 and coatings are disclosed in U.S. patent application Ser. No. 10/843,760, which was filed on May 12, 2004 and published as U.S. Patent Application Publication No. 2005/008736 on Jan. 13, 2005. The portions of the foregoing application that relate to the structure and composition of body materials are hereby incorporated by reference herein as non-limiting examples.
With reference again to
The front wall 130 can comprise a left panel 130a and a right panel 130b that are joined to each other via a seam 152. In the illustrated embodiment, the seam 152 extends longitudinally from the upper end 122 to the lower end 124 of the tube 120. The seam 152 can comprise any suitable seal, such as, for example, a lap seal or a fin seal, and can be configured to prevent liquid oil from passing through the seal.
As further discussed below, the tube 120 can comprise a seal or a seam 154 at the upper end 122 and a seal or seam 156 at the lower end 124. Each seam 154, 156 can be configured to prevent liquid oil from passing through it. For example, a food product, such as unpopped popcorn kernels and oil or fats having a relatively low melting point, can be received within the interior cavity 150 of the tube 120 and sealed therein via the seams 154, 156, and each seam 154, 156 can prevent the liquid oil from exiting the interior cavity 150 via the upper and lower ends 122, 124 of the tube 120, respectively.
With continued reference to
The cold seal adhesive 160 can be applied to the body material 110 in any suitable fashion. For example, in some embodiments, a flexographic technique may be used in which the cold seal adhesive 160 is applied to the body material 110 via photopolymer plates. The cold seal adhesive 160 can be transferred to the body material 110 in a wet state and allowed to dry. In other embodiments, a rotogravure style press may be used to apply the cold seal adhesive 160 to the body material 110.
A cold seal adhesive 162 can be disposed at or near a bottom edge of the body material 110, and can extend substantially continuously between an edge of the left panel 130a and an edge of the right panel 130b. In the illustrated embodiment, sections 162a, 162b, 162c, 162d, 162e, 162f, and 162g of the cold seal adhesive 162 cover the bottom edges of the left panel 130a, the front panel 134a, the back panel 134b, the back wall 132, the back panel 136b, the front panel 136a, and the right panel 130b, respectively. The cold seal adhesive 162 can be applied to the body material 110 in any of the manners described above with respect to the adhesive 160.
In some embodiments, the amount of cold seal adhesive 160, 162 applied to the body material 110 can be greater than the amount of heat seal adhesive used for bags of comparable capacity. For example, for some bags, a heat seal adhesive for closing both ends of a bag is used in an amount of from about 3 pounds to about 3.5 pounds per ream, when dry, or from about 6 pounds to about 7 pounds per ream when wet. In contrast, in various embodiments of bags configured to retain liquid oil, the amount of cold seal adhesive 162 applied to the body material 110 for sealing both ends of a bag 100 can be in a range of from about 8 pounds to about 12 pounds or can be no less than about 8 pounds, no less than about 9 pounds, no less than about 10 pounds, no less than 11 pounds, or no less than about 12 pounds per ream when the cold seal adhesive 162 is dry. The amount of cold seal adhesive 162 can be in a range of from about 16 pounds to about 24 pounds or can be no less than about 16 pounds, no less than about 18 pounds, no less than about 20 pounds, no less than about 22 pounds, or no less than about 24 pounds per ream when wet.
Cold seal adhesives are generally configured to form a seal when separate portions of the adhesive are brought into contact with each other and pressure is applied. Unlike heat seal adhesives, cold seal adhesives can create the seal without the additional application of heat. However, as discussed below, it can be desirable to heat the cold seal adhesive when forming a seal in some instances. A variety of existing cold seal adhesives can be used or readily modified for use with embodiments of the bag 100. For example, cold seal adhesives produced by Ashland Inc. of Covington, Ky.; H.B. Fuller Co. of Vadnais Heights, Minnesota; Henkel Corporation of Rocky Hill, Conn.; and Rohm and Haas Company of Philadelphia, Pa. may be used or modified.
Cold seal adhesives can include an adhesive component combined with an elastomer. The adhesive component can comprise, for example, one or more of vinyl acetate polymers and copolymers and acrylic polymers. The elastomer can comprise one or more of natural rubber latex and synthetic elastomers, such as, for example, styrene butadiene rubber, polycholroprene, and butyl rubber.
Cold seal adhesives can have “hard” or “soft” characteristics. Hard cold seal adhesives are generally less tacky and can require greater pressure to create a seal, as compared with soft cold seal adhesives. In some embodiments, a balance between the features of hard and soft varieties of cold seal adhesives can be desirable. For example, in some instances, the cold seal adhesives 160, 162 are applied and the lower seam 156 is sealed at a first manufacturing facility. However, the upper seam 154 may be sealed at a second facility after a food product has been introduced into the semi-formed bag 100. In such instances, it may be desirable for the cold seal adhesive 160 to be relatively hard to prevent premature formation of the upper seam 154 during transport of the semi-formed bag 100 from the first facility to the second facility. In other instances, it can be desirable for the cold seal adhesive 160 to be relatively soft. This may allow for simpler application of the cold seal adhesive 160 to the bag material 110 (which may result from better deformation properties of soft adhesives) and/or quicker or easier formation of the seal (which may result from the tackier properties of soft adhesives). In some embodiments, it can be desirable for one or both of the cold seal adhesives 160, 162 to have hard characteristics at relatively low temperatures (e.g., room temperature) and to behave in a softer manner at elevated temperatures (e.g., about 100 degrees Fahrenheit to about 250 degrees Fahrenheit) such that the adhesives 160, 162 can be resistant to prematurely forming a seal 154, 156 during storage, transport, and/or early stages of conversion, but may readily form the seal 154, 156 upon application of heat and pressure at a desired stage of a conversion process or other bag sealing process.
In some embodiments, one or both of the cold seal adhesives 160, 162 are relatively resistant to blocking. A variety of tests are available to determine the blocking resistance of a cold seal adhesive 160, 162. For example, in some embodiments, the ASTM D918 Standard Test for Blocking Resistance of Paper and Paperboard, as this test is understood by those skilled in the art, may be used to characterize the blocking resistance. In further embodiments, it can be possible to use a test similar to ASTM D918, but with altered testing conditions (e.g., altered environmental temperatures and humidity, increased pressures applied to the samples, shorter dwell times, etc.) to more closely simulate actual conditions to which the cold seal adhesives 160, 162 may be exposed during conversion and/or transport. For example, rather than operating at 140 degrees Fahrenheit and applying a pressure of 1 psi to test specimens for 24 hours, lower temperatures (e.g., room temperature), higher pressures, and/or shorter dwell times may be employed.
The blocking resistance of some embodiments of the cold seal adhesives 160, 162 can be tested using specialized equipment, such as a Kohler Block Tester. Such a test can be conducted on test specimens or test samples in a manner resembling that set forth in ASTM D918. The test can include providing ten or more two-inch by two-inch samples of a body material 110 that has a cold seal adhesive 160, 162 disposed thereon. The samples are divided into sets of two, with the cold seal adhesive portions of the samples placed in contact with each other. Three-inch by two-inch foil sheets can be provided for use as interleaving sheets that are placed between adjacent sets of samples. The sets of samples are stacked on top of each other, with one sheet of foil between adjacent sample sets. The stacked samples are then placed on the bottom plate of a Kohler Block Tester. A centering plate of the Kohler Block Tester is placed over the samples, and then an appropriate spring is selected to provide the desired pressure to the samples. Examples of springs that may be used include those listed in the following table (Table 1), which identifies the serial number of the spring for use with a Kohler Block Tester and the loads each spring can provide:
1 lb.-15 lbs.
1 lb.-15 lbs.
1 lb.-15 lbs.
With the desired spring in place and the centering plate in position, pressure is applied to the stack of samples by turning a pressure screw to the predetermined distance to achieve the desired pressure via the spring. The samples are left under the desired pressure conditions for the desired amount of time and under the desired environmental conditions. After the desired time has elapsed, the pressure is released from the sets of samples and the interleaving foil sheets are removed. Where an elevated temperature has been used for an environmental simulation, the sample sets can be allowed to cool. The samples are then separated from each other, and their resistance to blocking is evaluated. A rating or description of the blocking can be provided according to the following table (Table 2):
A cold seal adhesive 160, 162 can be tested for dynamic loading conditions, such as may be experienced during or between stages of a converting process that precede a seam-forming stage (e.g., pinching that may occur as a web of body material 110 is fed through a converter). In one such test, the pressure is maintained for a dwell time of 1 second, the ambient temperature is maintained at 73 degrees Fahrenheit, and the relative humidity of the testing environment is maintained at 50%. Under these conditions, various embodiments of the cold seal adhesives 160, 162 can withstand loading pressures within a range of from about 100 psi to about 436 psi, of no more than about 100 psi, no more than about 150 psi, no more than about 200 psi, no more than about 250 psi, no more than about 300 psi, no more than about 350 psi, no more than about 400 psi, or no more than about 436 psi, no less than about 100 psi, no less than about 200 psi, no less than about 300 psi, or no less than about 400 psi with no more than “slight blocking” (i.e., with a blocking rating of 0, 1, or 2, as defined in Table 2). Certain of such embodiments can be advantageous, as it is believed that blocking either will not be encountered or will not pose significant difficulties during conversion of the bags under normal handling conditions prior to the desired sealing of such bags 100 using elevated temperatures.
A cold seal adhesive 160, 162 can be tested for static loading conditions, such as may be experienced during storage or transport of the body material 110 or the bags 100. For example, the cold seal adhesive 160, 162 may be applied to a web of the body material 110 that is subsequently rolled upon itself prior to its conversion of the into bags 100. As another example, a bag 100 may be only partially formed during the conversion, with one end thereof having a cold seal adhesive 160, 162 applied thereto but not yet sealed shut, and it thus can be desirable for this bag end to remain open until the bag 100 is filled with a desired product. In one test simulating storage and/or transport conditions, the pressure is maintained for a dwell time of 10 seconds, the ambient temperature is maintained at 130 degrees Fahrenheit, and the relative humidity of the testing environment is maintained at 50%. Under these conditions, various embodiments of the cold seal adhesives 160, 162 can withstand loading pressures within a range of from about 100 psi to about 436 psi, of no more than about 100 psi, no more than about 150 psi, no more than about 200 psi, no more than about 250 psi, no more than about 300 psi, no more than about 350 psi, no more than about 400 psi, or no more than about 436 psi, no less than about 100 psi, no less than about 200 psi, no less than about 300 psi, or no less than about 400 psi with no more than “slight blocking” (i.e., with a blocking rating of 0, 1, or 2, as defined in Table 2). Certain of such embodiments can be advantageous, as it is believed that blocking either will not be encountered or will not pose significant difficulties during conversion of the bags under normal handling conditions prior to the desired sealing of such bags 100 using elevated temperatures.
In some embodiments, the cold seal adhesives 160, 162 comprise the same composition (e.g., the adhesives are substantially the same), and in other embodiments, the cold seal adhesives 160, 162 have different compositions. For example, in some embodiments, the adhesive 160 may be harder than the cold seal adhesive 162.
With continued reference to
With reference to
The resulting bond can be sufficiently strong to maintain the bag 100 in a closed orientation during the final stages of manufacture and subsequent transport. However, the bond can also be configured to weaken or release upon heating the bag 100 and/or the contents thereof. For example, heating the bag can raise the temperature of the adhesive 164, and steam from the contents of the bag 100 likewise can raise the temperature of the adhesive 164. Sufficient pressure from steam within the heated bag 100 can cause at least a portion of the adhesive 164 to separate from a wall of the bag 100 so as to permit venting of the steam. The bond can also be configured to permit relative easy opening of the bag 100 to allow access to its contents.
With reference to
The step-down area can include a gap or a channel 170, which can be at least partially defined by the crease 142 of the side wall 136 and by the front and back walls 130, 132. As shown in
As mentioned above, previously known microwavable popcorn bags having a pinch-bottom closure are not suitable for retaining liquid oil. The Applicants have discovered that at least one reason for this unsuitability is that the channels 170 of these bags are not adequately obstructed. Rather, the channels 170 remain sufficiently open to permit liquid oil to pass through them.
With continued reference to
A food product can be introduced into the bag 100 prior to sealing the upper seam 154. In the embodiment illustrated in
After introduction of the food product into the bag 100, the upper seam 154 can be sealed. Referring again to
In other embodiments, one or more of the amounts or weights of adhesives used, sealing pressures, and sealing dwell times discussed above with respect to the lower seam 156 may be different for each seam 154, 156. For example, in some embodiments, the bond strength for one of the seams 154, 156 is lower than it is for the other seam 154, 156, which may facilitate opening of the bag 100 to access the cooked contents of the bag 100. In some embodiments, one of the seams 154, 156 can include a crimp seal (not shown), while the other seam 154, 156 does not include a crimp seal. In certain of such embodiments, the seam 154, 156 that is not crimp sealed can be at the end of a bag 100 that is intended for opening by a consumer, whereas the crimp sealed seam 154, 156 does include a crimp seal such that the crimp sealed end of the bag 100 is more difficult to open. Creation of a crimp sealed seam can involve, for example, application of a different amount of pressure to the seam 154, 156.
As shown in
It will be understood by those having skill in the art that many changes may be made to the details of the above-described embodiments without departing from the underlying principles of the present invention. The scope of the present invention should, therefore, be determined only by the following claims. Recitation in the claims of the term “first” with respect to a feature or element does not necessarily imply the existence of a second or additional such feature or element.
