Adhesive for stacking and reinforcing plastic packaging bags as well as preparation method and application of adhesive

Abstract

The invention provides an adhesive for stacking and reinforcing plastic packaging bags as well as a preparation method and application of the adhesive, and belongs to the technical field of adhesives. The adhesive for stacking and reinforcing the plastic packaging bag, provided by the invention, is prepared from the following components in percentage by mass: 10 to 30 percent of maltodextrin, 1 to 10 percent of oligosaccharide, 3 to 15 percent of maltose, 3 to 15 percent of glucose, 0.1 to 0.5 percent of carboxymethylcellulose, 5 to 15 percent of alcohol reagent and the balance of water. The adhesive provided by the invention has the characteristic that the adhesive can be adhered again after being separated for multiple times when being used for stacking and reinforcing plastic packages.

Description

Technical Field

[0001] This invention relates to the field of adhesive technology, and in particular to an adhesive for reinforcing the stacking of plastic packaging bags, its preparation method, and its application. Background Technology

[0002] In modern logistics and warehousing, goods are typically stored and transported using pallets. To ensure the stability and safety of pallets and prevent goods from collapsing or sliding during transportation or storage, packaging reinforcement is necessary. Traditional packaging materials such as stretch film and strapping, while providing palletizing reinforcement, have limitations including environmental concerns, high costs, and unsuitability for all types of goods. Therefore, developing a new, environmentally friendly, and efficient anti-slip adhesive for palletizing has become a focus of industry attention.

[0003] Currently, there are few technologies related to anti-slip adhesives for palletizing, and those that exist often only focus on the initial adhesion effect. During logistics transportation and warehousing, goods are often depalletized and repalletized. To ensure stability during multiple palletizing operations, anti-slip adhesives for palletizing need to possess the ability to re-adhere after multiple separations following depalletizing. Currently, there are no reports on anti-slip adhesives with such properties in existing technologies. Summary of the Invention

[0004] The purpose of this invention is to provide an adhesive for reinforcing the stacking of plastic packaging bags, its preparation method, and its application. The adhesive provided by this invention has the characteristic of being able to be re-adhere after multiple separations when used for reinforcing the stacking of plastic packaging bags.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides an adhesive for reinforcing the stacking of plastic packaging bags, comprising the following components by mass fraction: Maltodextrin 10-30%, oligosaccharides 1-10%, maltose 3-15%, glucose 3-15%, carboxymethyl cellulose 0.1-0.5%, alcohol reagent 5-15%, and the balance water.

[0006] Preferably, the adhesive for stacking and reinforcing plastic packaging bags comprises the following components by mass fraction: Maltodextrin 10-15%, oligosaccharides 2-10%, maltose 3-11%, glucose 5-10%, carboxymethyl cellulose 0.2-0.3%, alcohol reagent 5-10%, and the balance water.

[0007] Preferably, the degree of polymerization of the oligosaccharide is 3 to 4.

[0008] Preferably, the alcohol reagent includes ethanol or isopropanol.

[0009] This invention provides a method for preparing the adhesive for stacking and reinforcing plastic packaging bags as described in the above technical solution, comprising the following steps: Maltodextrin, oligosaccharides, maltose, glucose, carboxymethyl cellulose, alcohol reagent, and water are mixed to obtain the adhesive for stacking and reinforcing plastic packaging bags.

[0010] This invention provides a method for preparing the adhesive for stacking and reinforcing plastic packaging bags as described in the above technical solution, comprising the following steps: Corn starch, amylase, and water are mixed and subjected to enzymatic hydrolysis to obtain an enzymatic hydrolysate; the enzymatic hydrolysis reaction takes 2-3 hours; the enzymatic hydrolysate includes maltodextrin, oligosaccharides, maltose, and glucose. The enzymatic hydrolysate, carboxymethyl cellulose, and alcohol reagent are mixed to obtain the adhesive for stacking and reinforcing plastic packaging bags. The mass ratio of corn starch, amylase and carboxymethyl cellulose is 10~40:2~4:0.1~0.5.

[0011] Preferably, the temperature of the enzymatic hydrolysis reaction is 70~80℃.

[0012] Preferably, the mixing of corn starch, amylase, and water includes: dissolving corn starch in water, adjusting the pH of the resulting starch aqueous solution to 6-7, and then mixing it with amylase.

[0013] This invention provides the application of the adhesive for reinforcing stacked plastic packaging bags described in the above-described technical solution or the adhesive for reinforcing stacked plastic packaging bags prepared by the preparation method described in the above-described technical solution in the reinforcement of stacked plastic packaging.

[0014] Preferably, the plastic packaging includes PE film bags, PP coated woven bags, or aluminum foil bags.

[0015] Beneficial Effects: The adhesive provided by this invention is suitable for commonly used plastic packaging in the packaging field, such as PE film bags, PP coated woven bags, and aluminum foil bags. It features the characteristic of being able to be re-bonded after multiple separations, meaning that even after the upper and lower layers of packaging materials are separated, the adhesive still possesses a certain degree of continuous adhesion, enabling multiple separations and re-bonding. This effectively improves the stacking height and stability during transportation and warehousing. Simultaneously, the adhesive of this invention has moderate lateral shear strength, low vertical peel strength, and is easy to peel up and down. Specifically, the main effective components of the adhesive of this invention are maltodextrin, oligosaccharides, maltose, and glucose. Maltodextrin has a long molecular chain, and the cross-linking between molecules gives the adhesive good film-forming properties, easily forming a continuous film on plastic packaging materials, while also possessing moderate lateral shear strength. Oligosaccharides, maltose, and glucose, due to their different molecular sizes and the number of hydroxyl groups, can be combined to fill and adhere to the microstructures of different sizes on the surface of plastic packaging materials through intermolecular forces. This results in a sustained adhesion to the plastic packaging materials within a certain time frame, i.e., a separation and re-adhesion effect. In the field of logistics packaging, this allows plastic packaging bags to maintain a certain degree of anti-slip performance after multiple handling and stacking, improving the safety and stability during stacking and warehousing.

[0016] Furthermore, the adhesive described in this invention is easy to apply, easy to clean, does not damage packaging materials, and leaves minimal adhesive residue. Moreover, the polysaccharide raw materials used in the adhesive of this invention are widely available, have mature preparation processes, and are low in cost.

[0017] This invention provides a method for preparing the adhesive, which is simple to operate. By adjusting the raw material ratio and reaction conditions, the mechanical properties and number of repeated bonding cycles of the adhesive can be adjusted, making it suitable for a variety of plastic packaging materials. Attached Figure Description

[0018] Figure 1 This is a diagram showing the adhesive application pattern of the packaging material in Test Example 2; Figure 2 The diagram shows the test results for transverse shear force and vertical peel force in Test Example 2. Detailed Implementation

[0019] This invention provides an adhesive for reinforcing the stacking of plastic packaging bags, comprising the following components by mass fraction: Maltodextrin 10-30%, oligosaccharides 1-10%, maltose 3-15%, glucose 3-15%, carboxymethyl cellulose 0.1-0.5%, alcohol reagent 5-15%, and the balance water.

[0020] In this invention, unless otherwise specified, all raw materials used are commercially available products well known to those skilled in the art or prepared using methods well known to those skilled in the art.

[0021] The adhesive for palletizing and reinforcing plastic packaging bags according to the present invention comprises 10-30% maltodextrin by mass fraction, specifically 10%, 12%, 15%, 18%, 20%, 25%, or 30%. In one embodiment of the present invention, the DE value of the maltodextrin can be 4-20. In this invention, if the maltodextrin content is low, the film-forming properties of the adhesive are poor; if the content is high, the viscosity of the adhesive is high, which is also detrimental to film formation.

[0022] The adhesive for palletizing and reinforcing plastic packaging bags according to the present invention comprises 1-10% oligosaccharides by mass fraction, specifically 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%. In one embodiment of the present invention, the degree of polymerization of the oligosaccharides is 3-4. In this invention, if the oligosaccharide content is low, the adhesive strength of the adhesive is low; if the content is high, the production cost of the adhesive is high.

[0023] The adhesive for palletizing and reinforcing plastic packaging bags according to the present invention comprises 3-15% maltose by mass fraction, specifically 3%, 5%, 8%, 10%, 11%, 13%, or 15%. In one embodiment of the present invention, the dry matter content of the maltose is 75 wt%. In this invention, if the maltose content is low, the adhesive strength of the adhesive is low; if the content is high, the vertical peel force of the adhesive on the packaging material is large, which is not conducive to cargo handling.

[0024] The adhesive for palletizing and reinforcing plastic packaging bags according to the present invention comprises 3-15% glucose by mass fraction, specifically 3%, 5%, 8%, 10%, 11%, 13%, or 15%. In one embodiment of the present invention, the dry matter content of the glucose can be 99 wt%. In this invention, if the glucose content is low, the adhesive strength of the adhesive will be low; if the content is high, the vertical peel force of the adhesive on the packaging material will be large, which is not conducive to cargo handling.

[0025] The adhesive for palletizing and reinforcing plastic packaging bags according to the present invention comprises 0.1-0.5% carboxymethyl cellulose by mass fraction, specifically 0.1%, 0.2%, 0.3%, 0.4%, or 0.5%. In one embodiment of the present invention, the degree of substitution of the carboxymethyl cellulose is ≥0.6. In this invention, if the content of carboxymethyl cellulose is low, the adhesive has low viscosity and poor film-forming properties; if the content is high, the adhesive has high viscosity, which is not conducive to application.

[0026] The adhesive for palletizing and reinforcing plastic packaging bags according to the present invention comprises 5-15% alcohol reagent by mass fraction, specifically 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15%. In one embodiment of the present invention, the alcohol reagent may include ethanol or isopropanol, preferably ethanol. The alcohol reagent of the present invention has bactericidal and preservative effects, which is beneficial for improving the storage time of the adhesive; moreover, it can control the evaporation rate of the solvent and the onset time of the adhesive.

[0027] By mass fraction, the adhesive for stacking and reinforcing plastic packaging bags of the present invention includes a surplus of water, which may be deionized water.

[0028] The adhesive for stacking and reinforcing plastic packaging bags described in this invention is a light yellow, semi-transparent liquid; its pH value is 6.4~6.6, specifically 6.4, 6.5, or 6.6; and its density is 1.08~1.09 g / cm³. 3； The viscosity is 9~11 mPa·s, specifically 9 mPa·s, 10 mPa·s, 10.5 mPa·s or 11 mPa·s.

[0029] This invention provides a method for preparing the adhesive for palletizing and reinforcing plastic packaging bags as described in the above technical solution. The adhesive for palletizing and reinforcing plastic packaging bags described in this invention can be prepared by two methods, which will be described in detail below.

[0030] The preparation method of the adhesive for stacking and reinforcing plastic packaging bags according to the present invention includes the following steps: Maltodextrin, oligosaccharides, maltose, glucose, carboxymethyl cellulose, alcohol reagent, and water are mixed to obtain the adhesive for stacking and reinforcing plastic packaging bags.

[0031] As one embodiment of the present invention, the mixing of maltodextrin, oligosaccharides, maltose, glucose, carboxymethyl cellulose, alcohol reagent, and water may include: heating water to 40-60°C, adding maltodextrin, oligosaccharides, maltose, glucose, and carboxymethyl cellulose at a stirring speed of 250-300 rpm, and after the addition is complete, continuing to stir at a stirring speed of 100-150 rpm until the solid components are completely dissolved, then cooling to room temperature, and mixing the resulting material with the alcohol reagent until uniform.

[0032] Alternatively, the preparation method of the adhesive for stacking and reinforcing plastic packaging bags according to the present invention includes the following steps: Corn starch, amylase, and water are mixed and subjected to enzymatic hydrolysis to obtain an enzymatic hydrolysate; the enzymatic hydrolysis reaction takes 2-3 hours; the enzymatic hydrolysate includes maltodextrin, oligosaccharides, maltose, and glucose. The enzymatic hydrolysate, carboxymethyl cellulose, and alcohol reagent are mixed to obtain the adhesive for stacking and reinforcing plastic packaging bags. The mass ratio of corn starch, amylase and carboxymethyl cellulose is 10~40:2~4:0.1~0.5.

[0033] This invention utilizes amylase to enzymatically hydrolyze corn starch to produce maltodextrin, oligosaccharides, maltose, and glucose. Based on this, carboxymethyl cellulose and an alcohol reagent are then combined to obtain the adhesive for stacking and reinforcing plastic packaging bags. The mass ratio of corn starch, amylase, and carboxymethyl cellulose in this invention can be 10~40:2~4:0.1~0.5, more preferably 25~35:2.5~3.5:0.2~0.3, and specifically 30:3:0.2. The method of this invention is described in detail below.

[0034] This invention involves mixing corn starch, amylase, and water to perform an enzymatic hydrolysis reaction, yielding an enzymatic hydrolysate. In one embodiment of this invention, the amylase activity can be 1000 U / g. In another embodiment, mixing the corn starch, amylase, and water may include: dissolving the corn starch in water, adjusting the pH of the resulting starch solution to 6-7, and then mixing it with the amylase; the water temperature can be 70-80℃, specifically 70℃, 73℃, 75℃, 78℃, or 80℃; after dissolution, the process further includes: filtering the resulting starch solution, collecting the filtrate, cooling it to room temperature, and then adjusting the pH of the resulting starch solution to 6-7; the reagent used to adjust the pH can be citric acid. This invention adjusts the pH of the starch solution to the above range, which is beneficial for ensuring the smooth progress of the enzymatic hydrolysis reaction. In one embodiment of the present invention, the temperature of the enzymatic hydrolysis reaction can be 70-80°C, specifically 70°C, 73°C, 75°C, 78°C, or 80°C; the time is 2-3 hours, specifically 2 hours, 2.5 hours, or 3 hours. If the enzymatic hydrolysis reaction time is too short, the content of effective components in the enzymatic hydrolysate will be low, resulting in low mechanical properties of the adhesive. In another embodiment of the present invention, the enzymatic hydrolysis reaction preferably further includes: cooling the obtained product system to room temperature, filtering, and collecting the filtrate to obtain the enzymatic hydrolysate.

[0035] After obtaining the enzymatic hydrolysate, the present invention mixes the enzymatic hydrolysate, carboxymethyl cellulose, and alcohol reagent to obtain the adhesive for stacking and reinforcing plastic packaging bags. The present invention does not have specific limitations on the mixing method of the enzymatic hydrolysate, carboxymethyl cellulose, and alcohol reagent, as long as the components are mixed evenly; for example, the components can be stirred and mixed.

[0036] This invention provides the application of the adhesive for reinforcing plastic packaging bags described in the above technical solution in the reinforcement of plastic packaging stacking.

[0037] As one embodiment of the present invention, the plastic packaging may include PE film bags, PP coated woven bags or aluminum foil bags; the aluminum foil bags mentioned in the present invention specifically refer to aluminum-plastic composite bags, that is, bags made of aluminum foil and plastic film, and the material of the plastic film may include one or more of PET, BOPP and PE.

[0038] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0039] The parameters or requirements of some raw materials used in the following experiments are shown in Table 1. All of them are commercially available products.

[0040] Table 1 Raw material parameters and sources

[0041] Example 1 By mass, 30 parts of corn starch were dissolved in 56.8 parts of water at 75°C. The resulting starch solution was filtered, the filtrate was collected and cooled to room temperature, and the pH of the resulting starch solution was adjusted to 6.5 with citric acid. Then, 3 parts of amylase were added and reacted at 75°C for 2 hours. The resulting product system was cooled to room temperature, filtered, and the filtrate was collected to obtain an enzymatic hydrolysate. The enzymatic hydrolysate was mixed evenly with 0.2 parts of carboxymethyl cellulose and 10 parts of ethanol to obtain an adhesive.

[0042] The composition of the adhesive prepared in this embodiment was detected (specifically, the sample was extracted, dried or ignited at high temperature, and analyzed by instruments such as FTIR, GCMS, HSGCMS, PYGCMS, and HPLC), and the results are shown in Table 2.

[0043] Table 2. Test results of the main components of the adhesive prepared in Example 1

[0044] Example 2 By mass, 59.8 parts of water were heated to 45°C, and 13 parts of maltodextrin, 2 parts of oligosaccharide, 10 parts of maltose, 5 parts of glucose and 0.2 parts of carboxymethyl cellulose were added at a stirring speed of 300 rpm. After the addition was complete, the mixture was stirred at a stirring speed of 150 rpm until the solid components were completely dissolved. The mixture was then cooled to room temperature, and the resulting material was mixed with 10 parts of ethanol until homogeneous to obtain the adhesive.

[0045] Example 3 The adhesive was prepared according to the method of Example 2, except that the adhesive formulation in this example is: 10 parts maltodextrin, 10 parts oligosaccharide, 5 parts maltose, 5 parts glucose, 0.2 parts carboxymethyl cellulose, 10 parts ethanol and 59.8 parts water.

[0046] Example 4 The adhesive was prepared according to the method of Example 2, except that the adhesive formulation in this example is as follows: 13 parts maltodextrin, 2 parts oligosaccharide, 5 parts maltose, 10 parts glucose, 0.3 parts carboxymethyl cellulose, 10 parts ethanol and 59.7 parts water.

[0047] Comparative Example 1 The adhesive was prepared according to the method of Example 1, except that the reaction time was shortened to 1 hour.

[0048] Comparative Example 2 The adhesive was prepared according to the method of Example 2, except that the adhesive formulation in this example is: 0 parts maltodextrin, 2 parts oligosaccharide, 10 parts maltose, 5 parts glucose, 0.2 parts carboxymethyl cellulose, 10 parts ethanol and 72.8 parts water.

[0049] Comparative Example 3 The adhesive was prepared according to the method of Example 2, except that the adhesive formulation in this example is: 10 parts maltodextrin, 10 parts oligosaccharide, 0 parts maltose, 5 parts glucose, 0.2 parts carboxymethyl cellulose, 10 parts ethanol and 64.8 parts water.

[0050] Comparative Example 4 The adhesive was prepared according to the method of Example 2, except that the adhesive formulation in this example is as follows: 15 parts maltodextrin, 2 parts oligosaccharide, 5 parts maltose, 0 parts glucose, 0.2 parts carboxymethyl cellulose, 10 parts ethanol, and 67.8 parts water.

[0051] Test Example 1 The adhesive parameters in each embodiment and comparative example were tested. Density was measured using a liquid density meter, and viscosity was measured using a rotational viscometer (25°C). The results are shown in Table 3. It can be seen that the adhesive prepared in the examples is a light yellow, semi-transparent liquid with a pH of 6.4–6.6 and a density of 1.08–1.09 g / cm³. 3 The viscosity is 9~11 mPa·s.

[0052] Table 3. Indicator parameters of the adhesives in each embodiment and comparative example.

[0053] Test Example 2 In the examples and comparative examples, one drop (approximately 0.02g) of the adhesive was applied using a dropper to three packaging materials: a PE film bag, a PP laminated woven bag, and an aluminum foil bag (specifically, a bag made of aluminum foil and PE plastic film). The adhesive was then spread evenly over an area of ​​4cm x 4cm. Figure 1 (As shown); then place another packaging material of the same specifications on its upper surface for the first bonding, and let it stand for 1 hour and 12 hours under a pressure of 200g (as shown). Figure 2 As shown in the figure, the lateral shear strength (anti-slip property), vertical peel strength (ease of peeling property), and the ratio of lateral shear strength to vertical peel strength of the adhesive material are tested. The larger the ratio, the better the anti-slip property of the adhesive on the packaging material, and the easier it is to unpack and handle. The ratio of lateral shear strength to vertical peel strength is calculated according to the following formula: The ratio of transverse shear force to vertical peel force = (transverse shear force of 1h + transverse shear force of 12h) / (vertical peel force of 1h + vertical peel force of 12h).

[0054] After the first test, the two peeled packaging materials were placed in an air atmosphere at a temperature of 25°C and a relative humidity of 60% for 12 hours. After the placement time, the two peeled packaging materials were directly stacked and bonded for a second time (the adhesive surfaces of the packaging materials were in contact). After standing for 1 hour and 12 hours under a pressure of 200g, their transverse shear strength (anti-slip property), vertical peel strength (ease of peeling property), and the ratio of transverse shear strength to vertical peel strength were tested.

[0055] After the second test, the two peeled packaging materials were placed in an air atmosphere at a temperature of 25°C and a relative humidity of 60% for 12 hours. After the placement time, the two peeled packaging materials were directly stacked and bonded three times (the adhesive surfaces of the packaging materials were in contact). After standing for 1 hour and 12 hours under a pressure of 200g, their transverse shear strength (anti-slip property), vertical peel strength (ease of peeling property), and the ratio of transverse shear strength to vertical peel strength were tested.

[0056] Table 4 shows the test results of the adhesive used in PE film bags in each embodiment and comparative example; Table 5 shows the test results of the adhesive used in PP coated woven bags in each embodiment and comparative example; and Table 6 shows the test results of the adhesive used in aluminum foil bags in each embodiment and comparative example. It can be seen that the adhesive of the present invention has good anti-slip properties and easy peelability for PE film bags, PP coated woven bags, and aluminum foil bags. After peeling, it also has a certain degree of secondary and tertiary adhesion, which can effectively improve the stability and safety of packaging materials during stacking, transportation, and storage.

[0057] Table 4. Test results of adhesives used in PE film bags in each embodiment and comparative example.

[0058] Table 5. Test results of adhesives used in PP coated woven bags in each embodiment and comparative example.

[0059] Table 6. Test results of adhesives used in aluminum foil bags in each embodiment and comparative example.

[0060] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An adhesive for stacking and reinforcing plastic packaging bags, comprising the following components by mass fraction: Maltodextrin 10-30%, oligosaccharides 1-10%, maltose 3-15%, glucose 3-15%, carboxymethyl cellulose 0.1-0.5%, alcohol reagent 5-15%, and the balance water.

2. The adhesive for stacking and reinforcing plastic packaging bags according to claim 1, characterized in that, By mass fraction, it includes the following components: Maltodextrin 10-15%, oligosaccharides 2-10%, maltose 3-11%, glucose 5-10%, carboxymethyl cellulose 0.2-0.3%, alcohol reagent 5-10%, and the balance water.

3. The adhesive for stacking and reinforcing plastic packaging bags according to claim 1 or 2, characterized in that, The degree of polymerization of the oligosaccharide is 3 to 4.

4. The adhesive for stacking and reinforcing plastic packaging bags according to claim 1 or 2, characterized in that, The alcohol reagent includes ethanol or isopropanol.

5. A method for preparing the adhesive for stacking and reinforcing plastic packaging bags according to any one of claims 1 to 4, comprising the following steps: Maltodextrin, oligosaccharides, maltose, glucose, carboxymethyl cellulose, alcohol reagent, and water are mixed to obtain the adhesive for stacking and reinforcing plastic packaging bags.

6. A method for preparing the adhesive for stacking and reinforcing plastic packaging bags according to any one of claims 1 to 4, comprising the following steps: Corn starch, amylase, and water are mixed and subjected to enzymatic hydrolysis to obtain an enzymatic hydrolysate; the enzymatic hydrolysis reaction takes 2-3 hours; the enzymatic hydrolysate includes maltodextrin, oligosaccharides, maltose, and glucose. The enzymatic hydrolysate, carboxymethyl cellulose, and alcohol reagent are mixed to obtain the adhesive for stacking and reinforcing plastic packaging bags. The mass ratio of corn starch, amylase and carboxymethyl cellulose is 10~40:2~4:0.1~0.

5.

7. The preparation method according to claim 6, characterized in that, The temperature of the enzymatic hydrolysis reaction is 70~80℃.

8. The preparation method according to claim 6 or 7, characterized in that, The process of mixing corn starch, amylase, and water includes: dissolving corn starch in water, adjusting the pH of the resulting starch aqueous solution to 6-7, and then mixing it with amylase.

9. The application of the adhesive for reinforcing stacked plastic packaging bags according to any one of claims 1 to 4 or the adhesive for reinforcing stacked plastic packaging bags prepared by the preparation method according to any one of claims 5 to 8 in the reinforcement of stacked plastic packaging.

10. The application according to claim 9, characterized in that, The plastic packaging includes PE film bags, PP coated woven bags, or aluminum foil bags.

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