Environment-friendly degradable food packaging bag and preparation method thereof

Abstract

The application relates to the technical field of environment-friendly packaging bags, in particular to an environment-friendly degradable food packaging bag and a preparation method thereof, which comprises a high-density hydrophobic layer, an active barrier layer and an antibacterial fresh-keeping layer, the high-density hydrophobic layer is arranged as an outer layer of the packaging bag, the active barrier layer is arranged as a middle layer of the packaging bag, and the antibacterial fresh-keeping layer is arranged as an inner layer of the packaging bag. The application has the effect of improving the problems of a complicated manufacturing process of a traditional degradable packaging bag and a small amount of non-degradable substances.

Description

Technical Field

[0001] This invention relates to the technical field of environmentally friendly packaging bags, and in particular to an environmentally friendly biodegradable food packaging bag and its preparation method. Background Technology

[0002] Plastic bags are common items in daily life, characterized by their low price and ease of use. However, with the continuous development of human technology, people have realized the huge harm that non-degradable plastic bags cause to the environment. With the implementation of "plastic restriction orders" in various places, degradable plastic packaging bags have gradually appeared in our lives. However, the traditional degradable packaging bag manufacturing process is complicated and contains a small amount of non-degradable substances, which will still cause pollution to the environment if they accumulate. Summary of the Invention

[0003] To address the issues of complex manufacturing processes and the presence of small amounts of non-degradable substances in traditional biodegradable packaging bags, this application provides an environmentally friendly biodegradable food packaging bag and its preparation method.

[0004] This application provides an environmentally friendly and biodegradable food packaging bag and its preparation method, which adopts the following technical solution:

[0005] An environmentally friendly biodegradable food packaging bag and its preparation method are disclosed, comprising a high-density hydrophobic layer, an active barrier layer, and an antibacterial preservation layer. The high-density hydrophobic layer is configured as the outer layer of the packaging bag, the active barrier layer is configured as the middle layer of the packaging bag, and the antibacterial preservation layer is configured as the inner layer of the packaging bag.

[0006] Preferably, the preparation method specifically includes modified starch preparation, nanocellulose extraction, tea polyphenol grafted cellulose preparation, attapulgite modification, enzymatic hydrolysis pretreatment, low-temperature blending granulation, three-layer structure co-extrusion design, low-temperature blown film process, and post-processing steps.

[0007] Preferably, the modified starch is prepared as follows: corn starch and acetic anhydride (substituent) are mixed in a stainless steel reactor equipped with stirring and temperature control at a molar ratio of 1:0.3, and 0.5% sulfuric acid catalyst is added. The mixture is reacted at 50°C for 2 hours. The product is then washed and dried in a centrifugal dehydrator (to remove unreacted acetic anhydride and byproducts) and a vacuum drying oven to obtain acetylated crosslinked starch (degree of substitution 0.25-0.3).

[0008] Preferably, the method for extracting nanocellulose is as follows: bamboo fiber is immersed in an acid hydrolysis tank containing 64% sulfuric acid solution, hydrolyzed at 45°C for 30 minutes, centrifuged to remove acid, and the product is processed three times by a high-pressure homogenizer (120MPa) to obtain a nanocellulose suspension with a diameter of 50-100nm. The nanocellulose suspension is then placed in a freeze dryer to prepare nanocellulose powder.

[0009] Preferably, the method for preparing tea polyphenol-grafted cellulose is as follows: microcrystalline cellulose and tea polyphenols (mass ratio 1:0.5) are grafted in a grafting reactor at 60°C for 4 hours under the initiation of ammonium persulfate to generate antibacterial functional particles.

[0010] Preferably, the method for modifying attapulgite is as follows: attapulgite is soaked in a 5% silane coupling agent (KH550) ethanol solution for 24 hours to improve its gas adsorption performance.

[0011] Preferably, the enzymatic pretreatment method is as follows: modified starch and nanocellulose are mixed in a certain proportion, and a compound biological enzyme (cellulase:amylase = 2:1, total enzyme activity 0.5 U / g matrix) is added. The mixture is stirred and reacted in an enzymatic reaction vessel for 30 minutes at pH = 5.5 and temperature of 45°C. The enzymatic hydrolysis product is then inactivated at 80°C in an enzyme inactivation device.

[0012] Preferably, the low-temperature blending granulation method is as follows: the enzymatic hydrolysis product (85), chitosan (12), tributyl citrate (5), modified attapulgite (3) and tea polyphenol grafted cellulose (3) are mixed according to the weight ratio (parts by weight), and a co-rotating twin-screw extruder (length-to-diameter ratio L / D = 48) is used. The four temperature zones are set as follows: 80℃→85℃→90℃→85℃, and the screw speed is 120 rpm. After melt blending, the mixture is water-cooled and pelletized to obtain a three-layer special masterbatch.

[0013] Preferably, the three-layer co-extrusion design is as follows: High-density hydrophobic layer: 5% stearic acid modified silica (particle size 20nm) is added to the masterbatch to improve surface hydrophobicity (contact angle > 110°); Active barrier layer: The content of nanocellulose in the masterbatch is increased to 25%, and 3% montmorillonite intercalation structure is added to reduce oxygen permeability; Antibacterial preservation layer: The content of tea polyphenol grafted cellulose in the masterbatch is increased to 5%, which synergistically enhances antibacterial properties with chitosan.

[0014] Preferably, the low-temperature blown film process is as follows: a multi-layer co-extrusion blown film machine is used with a three-layer co-extrusion die (the temperature of the co-extrusion die is 90°C for the outer layer, 95°C for the middle layer, and 85°C for the inner layer, with an overall temperature gradient difference of ≤10°C), a blow-up ratio of 2.5:1, a traction speed of 15m / min, and an air ring cooling temperature of 20°C to form a three-layer composite film packaging bag with a thickness of 25±2μm.

[0015] Preferably, the post-processing method is as follows: the three-layer composite film packaging bag prepared in the low-temperature blown film process is subjected to corona treatment using a corona treatment machine, and finally the corona-treated three-layer composite film packaging bag is slit and wound up using a slitting and winding machine.

[0016] In summary, this application includes the following beneficial technical effects:

[0017] 1. The present invention provides an environmentally friendly biodegradable food packaging bag and its preparation method. By reducing the crystallinity of biological macromolecular chains through enzymatic pretreatment, the subsequent mechanical plasticizing temperature is reduced by 40-50℃, which effectively reduces production energy consumption (compared to traditional processes).

[0018] 2. The present invention provides an environmentally friendly biodegradable food packaging bag and its preparation method, which features a three-layer independent temperature-controlled die head design to avoid thermal degradation of chitosan while ensuring viscoelastic matching of the interlayer melt.

[0019] 3. The present invention provides an environmentally friendly biodegradable food packaging bag and its preparation method, which simultaneously completes the construction of antibacterial and barrier functions during the plasticizing process, eliminating the need for post-coating process and reducing production costs. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the environmentally friendly biodegradable food packaging bag and its preparation method in the embodiments of this application.

[0021] Explanation of reference numerals in the attached figures: Detailed Implementation

[0022] To enable those skilled in the art to better understand the present invention, the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0023] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation or specific orientational structure and operation. Therefore, they should not be construed as limitations on the invention. The terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, unless otherwise explicitly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0024] This application discloses an environmentally friendly and biodegradable food packaging bag, including a high-density hydrophobic layer, an active barrier layer, and an antibacterial preservation layer. The high-density hydrophobic layer is set as the outer layer of the packaging bag, the active barrier layer is set as the middle layer of the packaging bag, and the antibacterial preservation layer is set as the inner layer of the packaging bag.

[0025] Reference Figure 1 The specific preparation method of an environmentally friendly and biodegradable food packaging bag is as follows:

[0026] S1. Preparation of modified starch; S2. Extraction of nanocellulose; S3. Preparation of cellulose grafted with tea polyphenols; S4. Modification of attapulgite; S5. Enzymatic hydrolysis pretreatment; S6. Low-temperature blending and granulation; S7. Three-layer co-extrusion design; S8. Low-temperature blown film process; S9. Post-processing steps.

[0027] S1. The method for preparing modified starch is as follows: Corn starch and acetic anhydride (substituent) are mixed in a stainless steel reactor equipped with stirring and temperature control at a molar ratio of 1:0.3, and 0.5% sulfuric acid catalyst is added. The mixture is reacted at 50°C for 2 hours. The product is then washed and dried in a centrifugal dehydrator (to remove unreacted acetic anhydride and by-products) and a vacuum drying oven to obtain acetylated cross-linked starch (degree of substitution 0.25-0.3).

[0028] S2. The method for extracting nanocellulose is as follows: bamboo fiber is immersed in an acid hydrolysis tank with 64% sulfuric acid solution, hydrolyzed at 45°C for 30 minutes, centrifuged to remove acid, and the product is processed three times by a high-pressure homogenizer (120MPa) to obtain a nanocellulose suspension with a diameter of 50-100nm. The nanocellulose suspension is then placed in a freeze dryer to prepare nanocellulose dry powder.

[0029] S3. The method for preparing tea polyphenol grafted cellulose is as follows: microcrystalline cellulose and tea polyphenol (mass ratio 1:0.5) are grafted in a grafting reactor at 60°C for 4 hours under the initiation of ammonium persulfate to generate antibacterial functional particles.

[0030] S4. The method for modifying attapulgite is as follows: attapulgite is soaked in a 5% silane coupling agent (KH550) ethanol solution for 24 hours to improve its gas adsorption performance.

[0031] S5. The enzymatic pretreatment method is as follows: The modified starch and nanocellulose in S1 and S2 are mixed in proportion, and a compound biological enzyme (cellulase:amylase = 2:1, total enzyme activity 0.5U / g matrix) is added. Under the conditions of pH = 5.5 and temperature of 45℃, the mixture is stirred and reacted in the enzymatic reaction vessel for 30 minutes. The enzymatic hydrolysis product is then inactivated at 80℃ in an enzyme inactivation device.

[0032] S6. The method of low-temperature blending and granulation is as follows: The enzymatic hydrolysis product (85), chitosan (12), tributyl citrate (5), modified attapulgite (3) and tea polyphenol grafted cellulose (3) are mixed according to the weight ratio (parts by weight). A co-rotating twin-screw extruder (length-to-diameter ratio L / D = 48) is used, and the four temperature zones are set as follows: 80℃→85℃→90℃→85℃, and the screw speed is 120 rpm. After melt blending, the mixture is water-cooled and pelletized to obtain a three-layer special masterbatch.

[0033] S7, the three-layer co-extrusion design is as follows: High-density hydrophobic layer: 5% stearic acid modified silica (particle size 20nm) is added to the masterbatch to improve surface hydrophobicity (contact angle > 110°); Active barrier layer: The content of nanocellulose in the masterbatch is increased to 25%, and 3% montmorillonite intercalation structure is added to reduce oxygen permeability; Antibacterial preservation layer: The content of tea polyphenol grafted cellulose in the masterbatch is increased to 5%, which synergistically enhances antibacterial properties with chitosan.

[0034] S8. The low-temperature blown film process is as follows: A multi-layer co-extrusion blown film machine is equipped with a three-layer co-extrusion die (the temperature of the co-extrusion die is 90℃ for the outer layer, 95℃ for the middle layer, and 85℃ for the inner layer, with an overall temperature gradient difference of ≤10℃ for the die), a blow-up ratio of 2.5:1, a traction speed of 15m / min, and an air ring cooling temperature of 20℃ to form a three-layer composite film packaging bag with a thickness of 25±2μm.

[0035] S9. The post-processing method is as follows: The three-layer composite film packaging bag prepared in the low-temperature blown film process is corona treated with a corona treatment machine, and finally the corona-treated three-layer composite film packaging bag is cut and wound up with a slitting and winding machine.

[0036] Finally, it should be noted that the above description is only a preferred embodiment of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be pointed out that for those skilled in the art, any improvements and modifications made without departing from the principle of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. An environmentally friendly and biodegradable food packaging bag, characterized in that: The packaging bag comprises a high-density hydrophobic layer, an active barrier layer, and an antibacterial preservation layer. The high-density hydrophobic layer is the outer layer of the packaging bag, the active barrier layer is the middle layer, and the antibacterial preservation layer is the inner layer. The packaging bag is a three-layer composite film packaging bag with a thickness of 25±2μm formed by three-layer co-extrusion of a three-layer special masterbatch. The three-layer special masterbatch comprises, by weight, 85 parts of enzymatic hydrolysis product, 12 parts of chitosan, 5 parts of tributyl citrate, 3 parts of modified attapulgite clay, and 3 parts of tea polyphenol-grafted cellulose. The enzymatic hydrolysis product is prepared by: mixing modified starch and nanofiber... Vitamins are mixed in a certain proportion, and a compound biological enzyme is added and stirred to react. The compound biological enzyme consists of cellulase:amylase = 2:1, with a total enzyme activity of 0.5 U / g matrix. 5% stearic acid modified silica is added to the masterbatch of the high-density hydrophobic layer. The stearic acid modified silica has a particle size of 20 nm, and the contact angle of the high-density hydrophobic layer is greater than 110°. The masterbatch of the active barrier layer contains 25% nanocellulose and 3% montmorillonite intercalation structure. The masterbatch of the antibacterial and preservative layer contains 5% tea polyphenol-grafted cellulose, which synergistically enhances antibacterial properties with the chitosan.

2. The method for preparing an environmentally friendly biodegradable food packaging bag according to claim 1, characterized in that, The preparation steps include the following: (1) Preparation of modified starch: Corn starch and acetic anhydride were mixed in a stainless steel reactor with stirring and temperature control at a molar ratio of 1:0.3, and 0.5% sulfuric acid catalyst was added. The mixture was reacted at 50°C for 2 hours. The product was washed and dried by a centrifugal dehydrator and a vacuum drying oven to obtain acetylated cross-linked starch. (2) Extraction of nanocellulose: Bamboo fiber is immersed in an acid hydrolysis tank of 64% sulfuric acid solution, hydrolyzed at 45°C for 30 minutes, centrifuged to remove acid, and the product is processed three times by a high-pressure homogenizer to obtain a nanocellulose suspension with a diameter of 50-100nm. The nanocellulose suspension is then placed in a freeze dryer to prepare nanocellulose powder. (3) Preparation of tea polyphenol grafted cellulose: microcrystalline cellulose and tea polyphenols were grafted at a mass ratio of 1:0.5 in a grafting reactor at 60°C for 4 hours under the initiation of ammonium persulfate to generate antibacterial functional particles. (4) Attapulgite modification: Attapulgite was soaked in 5% silane coupling agent KH550-ethanol solution for 24 hours to improve gas adsorption performance; (5) Enzymatic hydrolysis pretreatment: Modified starch and nanocellulose are mixed in proportion, and compound biological enzyme is added. The compound biological enzyme consists of cellulase:amylase = 2:1, with a total enzyme activity of 0.5 U / g matrix. Under the conditions of pH = 5.5 and temperature of 45℃, the mixture is stirred and reacted in the enzymatic hydrolysis reaction vessel for 30 minutes. The enzymatic hydrolysis product is then inactivated at 80℃ in the enzyme inactivation device. (6) Low-temperature blending and granulation: A co-rotating twin-screw extruder was used, with four temperature zones set: 80℃→85℃→90℃→85℃ and screw speed 120rpm. After melt blending, the mixture was water-cooled and pelletized to obtain a three-layer special masterbatch. (7) Low temperature blown film: A multi-layer co-extrusion blown film machine equipped with a three-layer co-extrusion die head is used, with a blow-up ratio of 2.5:1, a traction speed of 15m / min, and an air ring cooling temperature of 20℃; (8) Post-processing: The three-layer composite film packaging bags prepared in the low-temperature blown film process are subjected to corona treatment using a corona treatment machine, and finally the corona-treated three-layer composite film packaging bags are cut and wound using a slitting and winding machine.

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