Antibacterial preservative film bag

Abstract

The invention relates to an antibacterial preservative film bag, the antibacterial preservative film bag is prepared by mixing antibacterial master batch and linear low density polyethylene through a film blowing process, and the antibacterial master batch is prepared from the following components in parts by weight: 20-30 parts of antibacterial powder, 65-75 parts of linear low density polyethylene and 4-7 parts of coupling agent. 1-2 parts of an antioxidant and 3-4 parts of a dispersing agent are uniformly mixed and then are subjected to melt extrusion to prepare the composite material. The antibacterial powder is a natural antibacterial agent containing a cashew nut shell extract. The antibacterial preservative film bag has the antibacterial rate of more than or equal to 99%, has the characteristics of efficient antibacterial property, long-term mildew resistance and food safety, can remarkably prolong the preservation period of food, and has an extremely good market application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of food storage and preservation, specifically to polyethylene fresh-keeping film bags, and particularly to an antibacterial fresh-keeping film bag. Background Art

[0002] Polyethylene (PE) fresh-keeping film bags have become the mainstream material in the food packaging field due to their excellent ductility, transparency and water barrier properties. According to statistics, the annual global consumption of polyethylene fresh-keeping film exceeds 5 million tons, and more than 60% of which is used for the packaging of fresh fruits and vegetables, meats and ready-to-eat foods. However, traditional PE film bags lack the active antibacterial function and only rely on physical barriers to delay food spoilage. In a humid and nutrient-rich packaging microenvironment, microorganisms (such as Gram-negative / positive bacteria like Escherichia coli, Staphylococcus aureus, Salmonella, etc., and fungi like Aspergillus, Penicillium, etc.) can rapidly multiply through membrane surface adsorption or packaging process contamination, resulting in food spoilage. Experimental data shows that fresh-cut fruits packaged in PE film without antibacterial treatment can only maintain freshness for 48 hours at 25°C, and obvious sensory deterioration occurs when the total colony count exceeds 10^6 CFU / g. Therefore, although polyethylene fresh-keeping film bags are widely used, they have deficiencies in antibacterial performance.

[0003] To improve the antibacterial performance of PE film bags, the industry has tried to introduce chemically synthesized antibacterial agents, mainly including quaternary ammonium salts (such as cetyltrimethylammonium bromide), silver-based compounds (such as silver nanoparticles) and organohalogens (such as triclosan). These materials achieve bacteriostasis by destroying the microbial cell membrane or interfering with the metabolic process, and the initial antibacterial rate can reach over 99%. However, their applications have significant limitations. For example, there are biosafety risks. Quaternary ammonium salts and organohalogens are prone to migrate from the film material to the food. Research by the European Food Safety Authority (EFSA) shows that long-term intake of more than 0.5 mg / kg of quaternary ammonium salts can induce intestinal flora disorders; triclosan has been proven to have endocrine disrupting properties. When adding silver-based compounds, silver ions are easily oxidized and agglomerated at the high temperature of PE processing, resulting in a 20%-30% decrease in the light transmittance of the film material; halogen-based antibacterial agents may release HCl gas, corroding production equipment.

[0004] Based on the concept of "green packaging", researchers have turned to developing natural antibacterial agents, such as plant extracts (tea tree essential oil, cinnamaldehyde, tea polyphenols), animal-derived antibacterial peptides (lactoferrin, lysozyme) and mineral materials (zinc oxide, montmorillonite). Although these components have the advantages of low toxicity and biodegradability, their applicability in the industrial production of PE film bags is restricted by the following:

[0005] First, insufficient thermal stability: The processing of PE masterbatch requires high-temperature extrusion at 160°C - 250°C, while the thermal decomposition temperature of most natural active ingredients is lower than 160°C. For example, the inactivation rate of tea polyphenols reaches 92% within 30 seconds at 190°C, and cinnamaldehyde undergoes cyclization reaction at 200°C, losing its antibacterial efficacy.

[0006] Second, poor compatibility: The polarity difference between natural antibacterial agents and the PE matrix leads to uneven dispersion. When unmodified tea tree essential oil is directly added, micron-sized aggregates are formed in the PE film, reducing the tensile strength of the film by more than 40%.

[0007] Third, low sustained-release efficacy: Although some natural ingredients (such as lysozyme) can tolerate the processing temperature, they cannot achieve long-term sustained release. Experiments show that the antibacterial activity of a PE film containing 1% lysozyme decays by 80% within 7 days, making it difficult to meet the requirements of the food shelf life (usually 14 - 30 days).

[0008] In response to the above problems, many improvement schemes have been proposed in existing research, but none have completely broken through the technical bottleneck. For example, the microcapsule coating technology uses β-cyclodextrin or gelatin to wrap the antibacterial agent to improve thermal stability. However, the addition amount of the wall material needs to reach more than 30% to achieve effective protection, resulting in a 50% decrease in the melt index of the masterbatch, making it difficult to meet the requirements of the blown film process.

[0009] Using a nano-carrier composite antibacterial agent, for example, loading the natural antibacterial agent cinnamaldehyde through mesoporous silica or layered clay can increase the thermal decomposition temperature of cinnamaldehyde to 210°C, but the nano-particles are likely to block the filter screen of the extruder, increasing the production line downtime rate by 15% - 20%.

[0010] In summary, there is an urgent need to develop a new type of high-temperature resistant composite antibacterial masterbatch, which can retain the antibacterial active ingredients during high-temperature extrusion at 180°C - 210°C, while improving the compatibility during the processing and the antibacterial durability of plastic film products. Summary of the Invention

[0011] The purpose of the present invention is to overcome the lack of antibacterial properties in existing PE food wraps, and provide an antibacterial food wrap bag. A composite antibacterial powder is prepared by compounding natural cashew shell extract with a porous carrier, and further the antibacterial agent powder is loaded onto LLDPE to form an antibacterial masterbatch. The antibacterial masterbatch is added to LLDPE to prepare the antibacterial food wrap bag. The film bag has high antibacterial efficiency (bacteriostatic rate ≥ 99%), long-term mildew prevention, and food safety characteristics, and can significantly extend the food preservation period.

[0012] The specific solutions are as follows:

[0013] An antibacterial fresh-keeping film bag is prepared by mixing an antibacterial masterbatch and linear low-density polyethylene through a blown film process. Among them, the antibacterial masterbatch is prepared by uniformly mixing 20-30 parts by weight of antibacterial powder, 65-75 parts by weight of linear low-density polyethylene, 4-7 parts of coupling agent, 1-2 parts of antioxidant and 3-4 parts of dispersant, and then through melt extrusion; the preparation method of the antibacterial powder includes:

[0014] S1. Crush the cashew nut shell and sieve it, add n-hexane for heating and ultrasonic treatment, and then dry it to obtain defatted cashew nut shell powder;

[0015] S2. Mix the defatted cashew nut shell powder with ethanol, heat for condensation reflux extraction, then filter, collect the filtrate for concentration to obtain cashew nut concentrated liquid;

[0016] S3. Mix the cashew nut concentrated liquid with a porous carrier, heat, then filter, take the solid phase for spray drying to obtain the antibacterial powder.

[0017] Further, the aperture of the sieve in S1 is <100 mesh, the heating temperature is 50-60°C, and the ultrasonic treatment time is 20-60 minutes.

[0018] Further, the material-liquid ratio of the defatted cashew nut shell powder and ethanol in S2 is 1:10-20, and the extraction temperature is 70-80°C.

[0019] Further, the concentration in S2 uses a rotary evaporator, the temperature is 50-60°C, the vacuum degree is -0.05 to -0.1 MPa, and it is concentrated to 1 / 4 to 1 / 5 of the original volume.

[0020] Further, the porous carrier in S3 is glass powder.

[0021] Further, the coupling agent is silane coupling agent or magnesium stearate, the antioxidant is antioxidant 1010 or antioxidant 168, and the dispersant is PE wax.

[0022] Further, the temperature of the melt extrusion is 180°C - 210°C. Preferably, the extrusion temperature range distribution is T1: 190°C, T2: 190°C, T3-T6: 200°C, T7-T9: 210°C.

[0023] Further, the weight ratio of the antibacterial masterbatch to the linear low-density polyethylene is (5-10):(90-95).

[0024] Further, the blown film process includes temperature settings: the feeding zone is 130-140°C, the melting zone is 160-165°C, the die head is 170-175°C, the blow-up ratio is 2.5-2.9, and the film thickness is 10-100 um.

[0025] Furthermore, the antibacterial fresh-keeping film bag has at least one of the following (1) to (3):

[0026] (1) The antibacterial rate against Escherichia coli is 99%, and the antibacterial rate against Staphylococcus aureus is 99%;

[0027] (2) When heated in a microwave oven at a power of 800 W for 30 seconds, the antibacterial rate of the heated antibacterial fresh-keeping film bag against Escherichia coli and Staphylococcus aureus is 99%;

[0028] (3) After the antibacterial fresh-keeping film bag wraps the fish cake and is stored at 4°C for 12 days, the fish cake has a fresh smell and no visible mold to the naked eye.

[0029] Beneficial effects: The antibacterial fresh-keeping film bag provided by the present invention contains natural cashew shell extract. By degreasing the cashew shell, the high-temperature resistance of the product can be improved, so that it can maintain antibacterial properties during the processing of masterbatch and the preparation of the film, and the film bag still has an antibacterial rate of 99% against Escherichia coli and Staphylococcus aureus after microwave heating.

[0030] Secondly, the antibacterial fresh-keeping film bag provided by the present invention can achieve long-lasting antibacterial through the porous carrier compounded with cashew shell extract, meeting the requirement of a 30-day food shelf life.

[0031] Furthermore, the antibacterial fresh-keeping film bag provided by the present invention solves the compatibility problem between the antibacterial powder and linear low-density polyethylene through the cooperation of the coupling agent and the dispersant, making the antibacterial fresh-keeping film bag have good mechanical properties.

[0032] In summary, the antibacterial fresh-keeping film bag provided by the present invention not only has high antibacterial performance, but also has long-lasting antibacterial performance, meeting the requirements of the food shelf life; at the same time, under high-temperature heating conditions, the antibacterial performance is maintained and it has high-temperature resistance, thus promoting the upgrading and development of PE fresh-keeping film bags towards high-efficiency antibacterial, heat-resistant durability and environmental friendliness. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the present invention, the drawings will be briefly introduced below. Obviously, the drawings in the following description only relate to some embodiments of the present invention and do not limit the present invention.

[0034] Figure 1 is a photo of the antibacterial powder provided by Embodiment 1 of the present invention;

[0035] Figure 2 is a photo of the antibacterial masterbatch provided by Embodiment 1 of the present invention;

[0036] Figure 3 is an unfolded state diagram of the antibacterial fresh-keeping film bag provided by Embodiment 2 of the present invention;

[0037] Figure 4 It is a winding state diagram of the antibacterial fresh-keeping film bag provided by Embodiment 2 of the present invention;

[0038] Figure 5 It is a photo of the fish cake after 12 days wrapped with the ordinary fresh-keeping film provided by the present invention;

[0039] Figure 6 It is a photo of the fish cake after 12 days wrapped with the commercially available fresh-keeping film containing silver antibacterial additive provided by the present invention;

[0040] Figure 7 It is a photo of the fish cake after 12 days wrapped with the fresh-keeping film bag containing natural composite antibacterial additive provided by the present invention. Detailed implementation manners

[0041] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. For those where specific techniques or conditions are not indicated in the examples, the techniques or conditions described in the literature in the relevant field or according to the product specifications are followed. For reagents or instruments whose manufacturers are not indicated, they are all conventional products that can be obtained through commercial purchase. In the following examples, unless otherwise specified, "%" refers to weight percentage.

[0042] Example 1: Preparation of antibacterial PE masterbatch

[0043] (1) Take 500 g of dry cashew nutshells, crush them to a particle size of 0.5 - 1 mm with a pulverizer, and then sieve (<100 mesh) to remove the powder to obtain crushed material; mix the crushed material with n-hexane at a ratio of 1:8 (w / v), perform ultrasonic treatment at 50 °C for 30 minutes, repeat 3 times until the solvent is colorless, and then dry in an oven at 60 °C to constant weight (about 4 hours) to obtain defatted cashew nutshell powder; weigh 100 g of defatted cashew nutshell powder, add ethanol solution at a material-liquid ratio of 1:15, stir with a glass rod until completely wetted, set the temperature of the water bath at 75 ± 2 °C, install a condensing reflux device, perform constant-temperature extraction for 2 hours, then filter, collect the filtrate and perform rotary evaporation at a temperature of 50 °C and a vacuum degree of -0.085 MPa until it is concentrated to 1 / 5 of the original volume (about 300 mL) to obtain cashew nut concentrate.

[0044] (2) Add the cashew nut concentrate to heat-resistant porous carrier glass powder, heat and react at 80 °C for 1 - 2 hours, then filter, and then prepare heat-resistant natural composite antibacterial powder through spray drying.

[0045] The heat-resistant natural composite antibacterial powder is as Figure 1 shown. The powder is yellow, with fine particles and uniform dispersion.

[0046] (3) Mix 20 parts of the prepared high-temperature resistant natural composite antibacterial powder, 70 parts of linear low-density polyethylene (LLDPE), 5 parts of silane coupling agent, 1 part of antioxidant 168, and 4 parts of dispersant PE wax evenly. In a twin-screw extruder, extrude and pelletize at 180°C - 210°C (the extrusion temperature range is distributed as T1: 190°C, T2: 190°C, T3 - T6: 200°C, T7 - T9: 210°C, and the head temperature is 220°C) with a screw speed of 200 rpm - 500 rpm to obtain the antibacterial masterbatch.

[0047] The antibacterial masterbatch is as Figure 2 shown and is in the state of brown particles.

[0048] Example 2: Preparation of antibacterial PE masterbatch

[0049] (1) Take 500 g of dry cashew nutshells, crush them with a crusher to a particle size of 0.5 - 1 mm, and then sieve (<100 mesh) to remove the powder to obtain the crushed material; mix the crushed material with n-hexane at a ratio of 1:8 (w / v), ultrasonically treat it at 50°C for 30 minutes, repeat 3 times until the solvent is colorless, and then dry it in an oven at 60°C to constant weight (about 4 hours) to obtain the defatted cashew nutshell powder; weigh 100 g of the defatted cashew nutshell powder, add an ethanol solution according to the solid-liquid ratio of 1:15, stir with a glass rod until completely wetted, set the temperature of the water bath at 75 ± 2°C, install a condensing reflux device, extract at a constant temperature for 2 hours, then filter, collect the filtrate and perform rotary evaporation at a temperature of 50°C and a vacuum degree of -0.085 MPa until it is concentrated to 1 / 5 of the original volume (about 300 mL) to obtain the cashew nut concentrate.

[0050] (2) Add the cashew nut concentrate to the high-temperature resistant porous carrier glass powder, heat and react at 80°C for 1 - 2 hours, then filter, and then prepare the high-temperature resistant natural composite antibacterial powder by spray drying.

[0051] (3) Mix 20 parts of the prepared high-temperature resistant natural composite antibacterial powder, 70 parts of linear low-density polyethylene (LLDPE), 5 parts of magnesium stearate, 1 part of antioxidant 168, and 4 parts of dispersant PE wax evenly. In a twin-screw extruder, extrude and pelletize at 180°C - 210°C (the extrusion temperature range is distributed as T1: 190°C, T2: 190°C, T3 - T6: 200°C, T7 - T9: 210°C, and the head temperature is 220°C) with a screw speed of 200 rpm - 500 rpm to obtain the antibacterial masterbatch, which is in the state of brown particles.

[0052] Example 3: Preparation of antibacterial PE masterbatch

[0053] (1) Take 500 g of dry cashew nut shells, crush them with a crusher to a particle size of 0.5 - 1 mm, then sieve (<100 mesh) to remove the powder, obtaining a crushed material; mix the crushed material with n - hexane at a ratio of 1:8 (w / v), perform ultrasonic treatment at 50 °C for 30 minutes, repeat 3 times until the solvent is colorless, and then dry in an oven at 60 °C to constant weight (about 4 hours) to obtain defatted cashew nut shell powder; weigh 100 g of defatted cashew nut shell powder, add an ethanol solution according to a solid - liquid ratio of 1:15, stir with a glass rod until completely wetted, set the water bath temperature at 75 ± 2 °C, install a condensing reflux device, perform constant - temperature extraction for 2 hours, then filter, collect the filtrate and perform rotary evaporation at a temperature of 50 °C and a vacuum of - 0.085 MPa, concentrate to 1 / 5 of the original volume (about 300 mL) to obtain a cashew nut concentrate.

[0054] (2) Add the cashew nut concentrate to heat - resistant porous carrier glass powder, heat - react at 80 °C for 1 - 2 hours, then filter, and then prepare heat - resistant natural composite antibacterial powder through spray drying.

[0055] (3) Mix 30 parts of the prepared heat - resistant natural composite antibacterial powder, 70 parts of linear low - density polyethylene (LLDPE), 5 parts of silane coupling agent, 1 part of antioxidant 168, and 4 parts of dispersant PE wax evenly, and in a twin - screw extruder, extrude and pelletize at 180 °C - 210 °C (the extrusion temperature range is distributed as T1: 190 °C, T2: 190 °C, T3 - T6: 200 °C, T7 - T9: 210 °C, and the head temperature is 220 °C), with a screw speed of 200 rpm - 500 rpm to obtain an antibacterial masterbatch, which is in the state of brown particles.

[0056] Comparative Example 1:

[0057] (1) Take 500 g of dry cashew nut shells, crush them with a crusher to a particle size of 0.5 - 1 mm, then sieve (<100 mesh) to remove the powder, obtaining a crushed material; take 100 g of the crushed material, add an ethanol solution according to a solid - liquid ratio of 1:15, stir with a glass rod until completely wetted, set the water bath temperature at 75 ± 2 °C, install a condensing reflux device, perform constant - temperature extraction for 2 hours, then filter, collect the filtrate and perform rotary evaporation at a temperature of 50 °C and a vacuum of - 0.085 MPa, concentrate to 1 / 5 of the original volume (about 300 mL) to obtain a cashew nut concentrate.

[0058] (2) Add the cashew nut concentrate to heat - resistant porous carrier glass powder, heat - react at 80 °C for 1 - 2 hours, then filter, and then prepare antibacterial powder through spray drying.

[0059] (3) Mix 20 parts of the prepared antibacterial powder, 70 parts of linear low-density polyethylene (LLDPE), 5 parts of silane coupling agent, 1 part of antioxidant 168, and 4 parts of dispersant PE wax evenly. In a twin-screw extruder, extrude and pelletize at 180°C - 210°C (the extrusion temperature range is distributed as T1: 190°C, T2: 190°C, T3 - T6: 200°C, T7 - T9: 210°C, and the head temperature is 220°C), with a screw speed of 200 rpm - 500 rpm to obtain the antibacterial masterbatch.

[0060] Comparative Example 2: Preparation of Antibacterial PE Masterbatch

[0061] (1) Take 500 g of dry cashew nutshells, crush them with a crusher to a particle size of 0.5 - 1 mm, and then screen (<100 mesh) to remove the powder to obtain the crushed material; mix the crushed material with n-hexane at a ratio of 1:8 (w / v), ultrasonically treat it at 50°C for 30 minutes, repeat 3 times until the solvent is colorless, and then dry it in an oven at 60°C to constant weight (about 4 hours) to obtain defatted cashew nutshell powder; weigh 100 g of defatted cashew nutshell powder, add an ethanol solution at a material-liquid ratio of 1:15, stir with a glass rod until completely wetted, set the water bath temperature at 75 ± 2°C, install a condensing reflux device, extract at a constant temperature for 2 hours, then filter, collect the filtrate and perform rotary evaporation at a temperature of 50°C and a vacuum degree of -0.085 MPa until it is concentrated to 1 / 5 of the original volume (about 300 mL) to obtain the cashew nut concentrate.

[0062] (2) Add the cashew nut concentrate to heat-resistant porous carrier glass powder, heat and react at 80°C for 1 - 2 hours, then filter, and then prepare a heat-resistant natural composite antibacterial powder through spray drying.

[0063] (3) Mix 35 parts of the prepared heat-resistant natural composite antibacterial powder, 60 parts of linear low-density polyethylene (LLDPE), 5 parts of silane coupling agent, 1 part of antioxidant 168, and 4 parts of dispersant PE wax evenly. In a twin-screw extruder, extrude and pelletize at 180°C - 210°C (the extrusion temperature range is distributed as T1: 190°C, T2: 190°C, T3 - T6: 200°C, T7 - T9: 210°C, and the head temperature is 220°C), with a screw speed of 200 rpm - 500 rpm to obtain the antibacterial masterbatch, which is in a brown granular state.

[0064] Example 4: Preparation of Antibacterial Fresh-keeping Film Bags

[0065] (1) Take 5 parts of the antibacterial masterbatch prepared in Example 1 and mix it with 95 parts of LLDPE resin (with a melt index of 3 g / 10 min or higher), and disperse it evenly with a high-speed mixer (500 rpm, 5 minutes).

[0066] (2) Extrusion in a blown film machine, with temperature settings: feeding zone 130°C, melting zone 160°C, die head 170°C, blow-up ratio 2.8, film thickness 30 μm;

[0067] (3) Cooling (cooling roll at 25°C), cutting, and heat-sealing to make a fresh-keeping film bag (size 20 cm × 30 cm).

[0068] The physical object of the fresh-keeping film bag prepared in this example is as Figure 3 , Figure 4 shown. This fresh-keeping film bag has a certain light transmittance and is also coffee-colored.

[0069] Example 5: Preparation of an antibacterial fresh-keeping film bag

[0070] (1) Take 5 parts of the antibacterial masterbatch prepared in Example 2 and mix it with 95 parts of LLDPE resin (with a melt index of 3 g / 10 min or higher), and disperse it evenly with a high-speed mixer (500 rpm, 5 minutes);

[0071] (2) Extrusion in a blown film machine, with temperature settings: feeding zone 130°C, melting zone 160°C, die head 170°C, blow-up ratio 2.8, film thickness 30 μm;

[0072] (3) Cooling (cooling roll at 25°C), cutting, and heat-sealing to make a fresh-keeping film bag (size 20 cm × 30 cm).

[0073] Example 6: Preparation of an antibacterial fresh-keeping film bag

[0074] (1) Take 5 parts of the antibacterial masterbatch prepared in Example 3 and mix it with 95 parts of LLDPE resin (with a melt index of 3 g / 10 min or higher), and disperse it evenly with a high-speed mixer (500 rpm, 5 minutes);

[0075] (2) Extrusion in a blown film machine, with temperature settings: feeding zone 130°C, melting zone 160°C, die head 170°C, blow-up ratio 2.8, film thickness 30 μm;

[0076] (3) Cooling (cooling roll at 25°C), cutting, and heat-sealing to make a fresh-keeping film bag (size 20 cm × 30 cm). Comparative Example 3: Preparation of an antibacterial fresh-keeping film bag

[0077] (1) Take 5 parts of the antibacterial masterbatch prepared in Comparative Example 1 and mix it with 95 parts of LLDPE resin (with a melt index of 3 g / 10 min or higher), and disperse it evenly with a high-speed mixer (500 rpm, 5 minutes);

[0078] (2) Extrusion in a blown film machine, with temperature settings: feeding zone 130°C, melting zone 160°C, die head 170°C, blow-up ratio 2.8, film thickness 30 μm;

[0079] (3) Cooling (cooling roller at 25 °C), cutting, and heat-sealing to make a fresh-keeping film bag (size 20 cm × 30 cm). Comparative Example 4: Preparation of an antibacterial fresh-keeping film bag

[0080] (1) Take 5 parts of the antibacterial masterbatch prepared in Comparative Example 2 and mix it with 95 parts of LLDPE resin (melt index of 3 g / 10 min or higher), and disperse it evenly with a high-speed mixer (500 rpm, 5 minutes);

[0081] (2) Extrude in a blown film machine, with the temperature settings: feeding zone at 130 °C, melting zone at 160 °C, die head at 170 °C, blow-up ratio of 2.8, and film thickness of 30 μm;

[0082] (3) Cooling (cooling roller at 25 °C), cutting, and heat-sealing to make a fresh-keeping film bag (size 20 cm × 30 cm).

[0083] Performance Test

[0084] (1) Test the antibacterial performance of the antibacterial fresh-keeping film bag. Take the fresh-keeping film bag prepared in Example 4 and test it according to "GB / T 31402-2023 Determination of Antibacterial Activity on the Surface of Plastics and Other Non-porous Materials". The antibacterial results are shown in Table 1.

[0085] Table 1 Test Results of Antibacterial Performance of Antibacterial Fresh-keeping Film Bags

[0086]

[0087] As can be seen from Table 1, the antibacterial rate of this antibacterial fresh-keeping film bag against Escherichia coli is 99%, and the antibacterial rate against Staphylococcus aureus is 99%.

[0088] According to the same test method, test the antibacterial properties of the fresh-keeping film bags prepared in Example 5, Example 6, Comparative Example 3, and Comparative Example 4, and the same antibacterial properties are shown.

[0089] (2) High-temperature resistance test: Place the film bags prepared in Example 4, Example 5, Example 6, and Comparative Example 3 in a microwave oven for heating (800 W, 30 seconds) respectively, and test that the antibacterial performance against Staphylococcus aureus has no significant decrease. The results are shown in Table 2.

[0090] Table 2 Test Results of High-temperature Resistance

[0091] Sample Initial antibacterial rate % Antibacterial rate after heating % Example 4 99 99 Example 5 99 99 Example 6 99 99 Comparative Example 3 99 74

[0092] As can be seen from Table 2, after heating, the antibacterial rates of the film bags prepared in Examples 4, 5, and 6 of the present invention against Staphylococcus aureus still reached 99%, while that of the film bag prepared in Comparative Example 3 decreased to 74%, and the antibacterial performance decreased significantly. This shows that degreasing treatment during the extraction process of cashew shells can improve the thermal stability of the fresh-keeping film bags, enabling them to still maintain significant antibacterial properties after being heated.

[0093] (3) Mechanical property test:

[0094] Tensile strength tests were carried out on the fresh-keeping film bags prepared in Examples 4, 5, 6 and Comparative Examples 3, 4, and the results are shown in Table 3.

[0095] Table 3 Test results of the mechanical properties of the fresh-keeping film bags

[0096] Sample Transverse tensile strength MPa Longitudinal tensile strength MPa Example 4 18 23 Example 5 17 21 Example 6 12 20 Comparative Example 3 10 17 Comparative Example 4 6 10

[0097] As can be seen from Table 3, the fresh-keeping film bags prepared in Examples 4, 5, and 6 of the present invention have relatively high tensile strength, indicating that the compatibility of the antibacterial powder and linear low-density polyethylene achieved by adding coupling agents and dispersants in this system is relatively high. In Comparative Example 3, the cashew extraction was not subjected to degreasing treatment, which is not conducive to the fusion of the antibacterial powder and polyethylene, showing slightly inferior mechanical strength. In Comparative Example 4, due to the excessively high addition amount of the antibacterial powder, it is also not conducive to the uniform dispersion of the antibacterial powder and linear low-density polyethylene.

[0098] (4) Food fresh-keeping test: The same fish cakes were wrapped with a common fresh-keeping film without antibacterial additives, a commercially available fresh-keeping film with silver antibacterial additives, and the fresh-keeping film bag with natural composite antibacterial additives prepared in Example 4, respectively. The samples were stored at 4°C for 12 days, and then sensory evaluation and bacterial count tests were carried out. The calculation of the antibacterial effect was based on the common fresh-keeping film without antibacterial additives as a reference, and the calculation formula was: antibacterial rate = [(number of viable bacteria in the control sample - number of viable bacteria in the antibacterial sample) / number of viable bacteria in the control sample] × 100%. The number of viable bacteria in the control sample is the number of bacteria in the common fresh-keeping film without antibacterial additives, and the test results are shown in Table 4.

[0099] Among them, the photo of the fish cake wrapped with the common fresh-keeping film after 12 days is shown in Figure 5 , the photo of the fish cake wrapped with the commercially available fresh-keeping film with silver antibacterial additives after 12 days is shown in Figure 6 , and the photo of the fish cake wrapped with the fresh-keeping film bag with natural composite antibacterial additives after 12 days is shown in Figure 7 .

[0100] Table 4 Test results of food fresh-keeping

[0101]

[0102] From Figure 5, Figure 6 and Figure 7 From the comparison with Figure 6 and Figure 7 , when the fresh-keeping film bag containing the natural composite antibacterial additive prepared by the present invention is used to wrap the fish cake, the golden appearance of the fish cake can be maintained; while for the fish cakes wrapped with the other two kinds of fresh-keeping films, mildew occurs to varying degrees. Further bacterial counting confirms that the ordinary fresh-keeping film has no antibacterial property, and compared with the ordinary fresh-keeping film, the fresh-keeping film bag containing the natural composite antibacterial additive prepared by the present invention can exert a remarkable antibacterial effect.

[0103] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0104] In addition, it should be noted that, in the case of no contradiction, the various specific technical features described in the above specific embodiments can be combined in any appropriate way. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods.

[0105] In addition, any combination can be made between various different embodiments of the present invention, as long as it does not violate the idea of the present invention, it should also be regarded as the content disclosed by the present invention.

Claims

1. An antibacterial fresh-keeping plastic bag, characterized in that: It is prepared by mixing an antibacterial masterbatch and linear low-density polyethylene through a blown film process. Among them, the antibacterial masterbatch is prepared by uniformly mixing 20-30 parts by weight of antibacterial powder, 65-75 parts by weight of linear low-density polyethylene, 4-7 parts of coupling agent, 1-2 parts of antioxidant and 3-4 parts of dispersant, and then melt-extruding; the preparation method of the antibacterial powder includes: S1. Crush the cashew nut shell and sieve it, add n-hexane for heating and ultrasonic treatment, and then dry it to obtain defatted cashew nut shell powder; S2. Mix the defatted cashew nut shell powder with ethanol, heat for condensation reflux extraction, then filter, collect the filtrate and concentrate it to obtain a cashew nut concentrate; S3. Mix the cashew nut concentrate with a porous carrier, heat it, then filter, take the solid phase and spray dry it to obtain the antibacterial powder.

2. The antibacterial fresh-keeping plastic film bag according to claim 1, wherein: In S1, the aperture of the sieve is <100 mesh, the heating temperature is 50-60 °C, and the ultrasonic treatment time is 20-60 minutes.

3. The antibacterial fresh-keeping film bag according to claim 1, wherein: In S2, the material-liquid ratio of the defatted cashew nut shell powder and ethanol is 1:10-20, and the extraction temperature is 70-80 °C.

4. The antibacterial fresh-keeping film bag according to claim 3, characterized in that: In S2, the concentration is carried out by a rotary evaporator, the temperature is 50-60 °C, the vacuum degree is -0.05 to -0.1 MPa, and the concentration is to 1 / 4-1 / 5 of the original volume.

5. The antibacterial fresh-keeping plastic film bag according to claim 4, wherein: In S3, the porous carrier is glass powder.

6. The antibacterial fresh-keeping plastic film bag according to any one of claims 1-5, characterized in that: The coupling agent is a silane coupling agent or magnesium stearate, the antioxidant is antioxidant 1010 or antioxidant 168, and the dispersant is PE wax.

7. The antibacterial fresh-keeping plastic film bag according to claim 6, wherein: The temperature of the melt extrusion is 180 °C - 210 °C. Preferably, the extrusion temperature range is distributed as T1: 190 °C, T2: 190 °C, T3-T6: 200 °C, T7-T9: 210 °C.

8. The antibacterial fresh-keeping plastic film bag according to any one of claims 1-5, characterized in that: The weight ratio of the antibacterial masterbatch to linear low-density polyethylene is (5-10):(90-95).

9. The antibacterial fresh-keeping plastic film bag according to claim 8, wherein: The blown film process includes temperature settings: the feeding zone is 130-140 °C, the melting zone is 160-165 °C, the die head is 170-175 °C, the blow-up ratio is 2.5-2.9, and the film thickness is 10-100 um.

10. The antibacterial fresh-keeping plastic film bag according to any one of claims 1-5, characterized in that: It has at least one of the following (1)-(3): (1) The antibacterial rate against Escherichia coli is 99%, and the antibacterial rate against Staphylococcus aureus is 99%; (2) When heated in a microwave oven with a power of 800 W for 30 seconds, the antibacterial rate of the heated antibacterial food wrap bag against Escherichia coli and Staphylococcus aureus is 99%; (3) After the fish cake is wrapped with the antibacterial food wrap bag and stored at 4 °C for 12 days, the fish cake has a fresh smell and no visible mold to the naked eye.

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