Anti-adhesion fresh-keeping packaging material for cold pasta and preparation method of anti-adhesion fresh-keeping packaging material

Abstract

The invention relates to the technical field of packaging materials, in particular to an anti-adhesion fresh-keeping packaging material for cold pasta and a preparation method thereof.The anti-adhesion fresh-keeping packaging material is obtained by preparing a packaging base material from chain extension modified polylactic acid and introduced composite modified nano-silica particles and then compounding a layer of polytetrafluoroethylene coating material on the surface; the packaging material prepared by the invention is used for the cold pasta, not only has an excellent fresh-keeping effect, but also has an excellent anti-adhesion characteristic, and can better ensure the quality of the cold pasta. Polylactic acid is subjected to chain extension modification, so that the mechanical property of the polylactic acid is improved, the polylactic acid is easier to process and form in the preparation process of the packaging material, and the overall stability of the packaging material is enhanced. Meanwhile, the compatibility of the polylactic acid subjected to chain extension modification and other components is improved, a foundation is laid for subsequent uniform dispersion of composite modified nano silicon dioxide particles, and various requirements of packaging of the cold pasta noodles can be better met.

Description

Technical Field

[0001] The present invention relates to the technical field of packaging materials, and particularly to an anti-sticking and fresh-keeping packaging material for cold noodles and pasta and a preparation method thereof. Background Art

[0002] As a popular food, cold noodles and pasta are widely welcomed in the market due to their unique taste and convenient eating method.

[0003] However, cold noodles and pasta may also face some problems during storage and transportation, namely, they are prone to sticking. This is mainly due to the surface characteristics of cold noodles and pasta and the components such as starch they contain. Under the influence of external environmental factors such as temperature and humidity changes, the noodles are easily adhered to each other, seriously affecting the product quality and the consumer's eating experience. At present, there are various types of materials used for food packaging, but there are still many deficiencies in the special packaging materials for this special food of cold noodles and pasta. Common packaging materials mainly focus on basic barrier properties, such as preventing the intrusion of external substances such as oxygen and moisture to achieve a certain degree of fresh-keeping function. However, for cold noodles and pasta, only having a fresh-keeping function is far from enough. Its prominent sticking problem urgently needs a packaging material with anti-sticking characteristics to solve. Therefore, the present invention has developed an anti-sticking and fresh-keeping packaging material for cold noodles and pasta. Summary of the Invention

[0004] In view of the problems existing in the prior art, the present invention provides an anti-sticking and fresh-keeping packaging material for cold noodles and pasta and a preparation method thereof.

[0005] To achieve the above object, the present invention provides the following technical solutions: An anti-sticking and fresh-keeping packaging material for cold noodles and pasta is made by preparing a packaging substrate from chain-extended modified polylactic acid incorporated with composite modified nano-silica particles, and then obtaining it by surface-compositing a polytetrafluoroethylene coating material; In the packaging material, the addition amount of the composite modified nano-silica particles is 3wt%-4wt% of the mass of the modified polylactic acid; Among them, the polytetrafluoroethylene coating material further contains 8wt%-10wt% of polydimethylsiloxane.

[0006] As a further technical solution, the preparation method of the chain-extended modified polylactic acid is as follows: First, vacuum-dry polylactic acid at 90 - 95°C for 5 - 6 hours to remove moisture; Then add the dried polylactic acid, chain extender and plasticizer into a twin-screw extruder. The chain extender is a bifunctional epoxy compound, and its addition amount is 1.2wt%-1.5wt% of the mass of polylactic acid; The plasticizer is a citric acid ester plasticizer, and its addition amount is 5wt%-8wt% of the mass of polylactic acid; in a twin-screw extruder, the barrel temperature is sequentially set to 170°C, 180°C, 190°C, and 200°C from the feeding section to the head, and the screw speed is 120-180 r / min, so that polylactic acid, a chain extender, and a plasticizer react fully under high temperature and the shearing action of the screw, thereby completing the modification of polylactic acid; The weight-average molecular weight of the polylactic acid is 150,000-180,000.

[0007] As a further technical solution, the difunctional epoxy compound is bisphenol A diglycidyl ether; The plasticizer, which is a citric acid ester plasticizer, is tributyl acetylcitrate.

[0008] As a further technical solution, the preparation method of the composite modified nano-silica particles is as follows: Disperse nano-silica and nano-zinc oxide in anhydrous ethanol with a mass 5 times that of the total mixture, add 1.2wt% of γ-aminopropyltriethoxysilane, stir and react at 70°C-78°C for 3h-4h, and then obtain the product through filtration, washing, and drying; The particle size of the nano-silica particles is 20nm-30nm; The particle size of the nano-zinc oxide is 10-15nm; The mass ratio of the nano-silica to the nano-zinc oxide is 10:1.

[0009] As a further technical solution, the preparation method of the polytetrafluoroethylene coating material is as follows: First, melt the polytetrafluoroethylene resin particles at 330-340°C to obtain a melt; then add polydimethylsiloxane to the melt, stir at 300-325°C at a stirring speed of 250-300 r / min for 20-30 minutes to make the polydimethylsiloxane fully dispersed in the polytetrafluoroethylene melt, and finally granulate through a twin-screw extruder to obtain the polytetrafluoroethylene coating material masterbatch; Among them, in the twin-screw extruder, the barrel temperature is sequentially set to 300°C, 310°C, 320°C, and 330°C from the feeding section to the head, and the screw speed is 220-250 r / min;<D Add the polytetrafluoroethylene coating material masterbatch to a solvent at a mass ratio of 1:5-6. The solvent is ethyl acetate, and stir at 60-65°C at a stirring speed of 300-325 r / min for 40-50 minutes to obtain the polytetrafluoroethylene coating material.

[0010] The preparation method of the anti-sticking and fresh-keeping packaging material for cold pasta includes the following steps: Step 1: Obtain chain-extended modified polylactic acid; Step 2: Mix the composite modified nano-silica particles and the chain-extended modified polylactic acid evenly in a high-speed mixer to obtain a mixed material. The mixing temperature is 130°C - 135°C, and the mixing time is 15 min - 20 min; Step 3: Extrude and pelletize the mixed material obtained in Step 2 through a single-screw extruder. The extrusion temperature is 190°C - 200°C to obtain composite pellets; Step 4: Blow the composite pellets into a film. The blow-up ratio is 2.5 - 3; Step 5: Coat one side of the film with a polytetrafluoroethylene coating material. The coating thickness is 8 μm - 10 μm, and then cure for 8 min - 10 min to obtain the anti-sticking fresh-keeping packaging material for cold pasta.

[0011] As a further technical solution, in Step 2, the rotation speed of the high-speed mixer is 1100 r / min - 1200 r / min.

[0012] As a further technical solution, in Step 3, the length-diameter ratio of the screw of the single-screw extruder is 28:1.

[0013] As a further technical solution, in Step 5, the coating method is spraying, and the spraying pressure is 0.22 MPa - 0.25 MPa.

[0014] As a further technical solution, the curing temperature in Step 5 is 155°C - 160°C.

[0015] Compared with the prior art, the beneficial effects of the present invention are: The packaging material prepared by the present invention is used for cold pasta, not only has excellent fresh-keeping effect, but also has excellent anti-sticking characteristics, and can better ensure the quality of cold pasta.

[0016] In the present invention, the polylactic acid is chain-extended and modified. Bisphenol A diglycidyl ether is selected as the chain extender. Under certain conditions, it reacts with the polylactic acid. By adding the chain extender, chemical bond connections can be formed between the polylactic acid molecular chains, thereby increasing the length and molecular weight of the molecular chains. This not only improves the mechanical properties of the polylactic acid, making it easier to process and form during the preparation of the packaging material, but also enhances the overall stability of the packaging material. At the same time, the compatibility between the chain-extended modified polylactic acid and other components is improved, laying a foundation for the uniform dispersion of the subsequent composite modified nano-silica particles. In addition, the addition of tributyl acetylcitrate as a plasticizer reduces the intermolecular force between the polylactic acid molecular chains, improves the flexibility and plasticity of the material, and enables the packaging material to better meet the various requirements of cold pasta packaging while having good mechanical properties. The composite modified nano-silica particles introduced in the packaging material of the present invention are composed of nano-silica and nano-zinc oxide with specific particle sizes, and are treated with γ-aminopropyltriethoxysilane. Nano-silica has a large specific surface area and surface activity, and can form a physical barrier layer in the packaging material, reducing the volatilization of moisture, ensuring a relatively high moisture content, and thus playing a good anti-sticking role. Nano-zinc oxide has certain antibacterial properties and can inhibit the growth and reproduction of microorganisms, further enhancing the fresh-keeping function of the packaging material. The use of γ-aminopropyltriethoxysilane enables nano-silica and nano-zinc oxide to better combine with chain-extended modified polylactic acid, improving the dispersion stability of the composite particles in the polylactic acid matrix and enhancing the synergistic effect among the components. Due to the characteristic of the extremely low surface energy of the polytetrafluoroethylene coating material, a smooth coating is formed on the surface of the packaging material, greatly reducing the friction between the cold noodles and the packaging material, and effectively preventing the adhesion of the cold noodles. The addition of polydimethylsiloxane further optimizes the performance of the polytetrafluoroethylene coating. Polydimethylsiloxane composed of potassium perfluorooctanesulfonate and sodium perfluorohexanesulfonate in a specific mass ratio can reduce the surface tension of the polytetrafluoroethylene melt, making it more evenly distributed on the surface of the packaging material during the coating process, improving the quality and integrity of the coating. At the same time, there is a synergistic effect between polydimethylsiloxane and polytetrafluoroethylene, enhancing the stability and durability of the coating, and further improving the anti-sticking and fresh-keeping properties of the packaging material. In the present invention, the components such as chain-extended modified polylactic acid, composite modified nano-silica particles, and polytetrafluoroethylene coating material cooperate with each other, greatly improving the comprehensive performance of the packaging material. The chain-extended modified polylactic acid provides a good matrix for other components, enabling each component to be evenly dispersed and play a synergistic role. The anti-sticking effect of the packaging material is significantly improved. At the same time, the antibacterial property of nano-zinc oxide and the overall barrier property of the packaging material cooperate to effectively extend the fresh-keeping period of the cold noodles, ensuring that the product maintains good quality during storage and transportation. Description of the Drawings

[0017] Figure 1 It is a statistical chart of moisture in the fresh-keeping test of the present invention. Detailed Embodiments

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0019] The present invention provides an anti-sticking and fresh-keeping packaging material for cold noodles and pasta and a preparation method thereof.

[0020] Among them, the anti-sticking and fresh-keeping packaging material for cold noodles and pasta of the present invention is made by introducing composite modified nano-silica particles into chain-extended modified polylactic acid to form a packaging substrate, and then surface-composite coating a polytetrafluoroethylene coating material. In the packaging material, the addition amount of the composite modified nano-silica particles is 3wt%-4wt% of the mass of the modified polylactic acid; the polytetrafluoroethylene coating material also contains 8wt%-10wt% of polydimethylsiloxane.

[0021] The preparation method of the chain-extended modified polylactic acid is as follows: First, polylactic acid with a weight-average molecular weight of 150,000-180,000 is vacuum-dried at 90-95°C for 5-6 hours to remove moisture; then the dried polylactic acid, chain extender and plasticizer are added to a twin-screw extruder. The chain extender is bisphenol A diglycidyl ether, and the addition amount is 1.2wt%-1.5wt% of the mass of the polylactic acid; the plasticizer is tributyl acetylcitrate, and the addition amount is 5wt%-8wt% of the mass of the polylactic acid. In the twin-screw extruder, the barrel temperature is set to 170°C, 180°C, 190°C, 200°C in sequence from the feeding section to the head, and the screw speed is 120-180r / min, so that the polylactic acid, chain extender and plasticizer react fully under the action of high temperature and screw shear to complete the modification of the polylactic acid.

[0022] The preparation method of the composite modified nano-silica particles is as follows: Nano-silica with a particle size of 20nm-30nm and nano-zinc oxide with a particle size of 10-15nm are dispersed in anhydrous ethanol with 5 times the total mass of the mixture. The mass ratio of nano-silica to nano-zinc oxide is 10:1, and 1.2wt% of γ-aminopropyltriethoxysilane is added, and the mixture is stirred and reacted at 70°C-78°C for 3h-4h, and then obtained through filtration, washing and drying.

[0023] The preparation method of the polytetrafluoroethylene coating material is as follows: First, melt the polytetrafluoroethylene resin particles at 330 - 340 °C to obtain a melt; add polydimethylsiloxane composed of potassium perfluorooctanesulfonate and sodium perfluorocaprylate in a mass ratio of 1:1 to the melt, stir at a stirring speed of 250 - 300 r / min at 300 - 325 °C for 20 - 30 minutes to fully disperse the polydimethylsiloxane in the polytetrafluoroethylene melt, and finally granulate through a twin-screw extruder to obtain the polytetrafluoroethylene coating material masterbatch. In the twin-screw extruder, the barrel temperature is set to 300 °C, 310 °C, 320 °C, and 330 °C in sequence from the feeding section to the head, and the screw speed is 220 - 250 r / min. Add the polytetrafluoroethylene coating material masterbatch to ethyl acetate in a mass ratio of 1:5 - 6, stir at a stirring speed of 300 - 325 r / min at 60 - 65 °C for 40 - 50 minutes to obtain the polytetrafluoroethylene coating material.

[0024] The preparation method of the anti-sticking and fresh-keeping packaging material for cold pasta includes the following steps: Step 1: Obtain chain-extended modified polylactic acid according to the above method; Step 2: Mix the composite modified nano-silica particles and the chain-extended modified polylactic acid evenly in a high-speed mixer at a mixing temperature of 130 °C - 135 °C, a mixing time of 15 min - 20 min, and a mixer speed of 1100 r / min - 1200 r / min to obtain a mixed material; Step 3: Extrude and granulate the mixed material obtained in Step 2 through a single-screw extruder at an extrusion temperature of 190 °C - 200 °C, and the length-diameter ratio of the screw of the single-screw extruder is 28:1 to obtain composite particles; Step 4: Blow the composite particles into a film, and the blow-up ratio is 2.5 - 3; Step 5: Coating the polytetrafluoroethylene coating material on one side of the film by spraying, with a spraying pressure of 0.22 MPa - 0.25 MPa and a coating thickness of 8 μm - 10 μm, and then curing at 155 °C - 160 °C for 8 min - 10 min to obtain the anti-sticking and fresh-keeping packaging material for cold pasta.

[0025] The raw materials or reagents used in the following examples are all commercially available. Example 1

[0026] Preparation of chain-extended modified polylactic acid: Take polylactic acid with a weight-average molecular weight of 150,000 and vacuum dry it at 90 °C for 5 hours. Add the dried polylactic acid, bisphenol A diglycidyl ether accounting for 1.2 wt% of the mass of polylactic acid, and tributyl acetylcitrate accounting for 5 wt% of the mass of polylactic acid to a twin-screw extruder. The barrel temperature of the twin-screw extruder from the feeding section to the head is 170 °C, 180 °C, 190 °C, 200 °C in sequence, the screw speed is 120 r / min, and chain-extended modified polylactic acid is obtained after the reaction.

[0027] Preparation of composite modified nano-silica particles: Disperse nano-silica with a particle size of 20 nm and nano-zinc oxide with a particle size of 10 nm in anhydrous ethanol at a mass ratio of 10:1, which is 5 times the total mass of the mixture. Add 1.2 wt% γ-aminopropyltriethoxysilane and stir and react at 70 °C for 3 hours. After filtration, washing, and drying, composite modified nano-silica particles are obtained.

[0028] Preparation of polytetrafluoroethylene coating material: Melt polytetrafluoroethylene resin particles at 330 °C, add polydimethylsiloxane composed of potassium perfluorooctanesulfonate and sodium perfluorohexanesulfonate at a mass ratio of 1:1, which accounts for 8 wt% of the mass of polytetrafluoroethylene, and stir at 300 °C at 250 r / min for 20 minutes. Granulate through a twin-screw extruder to obtain masterbatch. The barrel temperature of the twin-screw extruder from the feeding section to the head is 300 °C, 310 °C, 320 °C, 330 °C in sequence, and the screw speed is 220 r / min. Add the masterbatch to ethyl acetate at a mass ratio of 1:5 and stir at 60 °C at 300 r / min for 40 minutes to obtain polytetrafluoroethylene coating material.

[0029] Preparation of packaging material: Mix composite modified nano-silica particles with an addition amount of 3 wt% of the mass of modified polylactic acid and chain-extended modified polylactic acid in a high-speed mixer at 130 °C for 15 minutes. The rotation speed of the mixer is 1100 r / min to obtain a mixed material. The mixed material is extruded and granulated at 190 °C through a single-screw extruder, and the length-diameter ratio of the screw is 28:1 to obtain composite particles. The composite particles are blown into a film with a blow-up ratio of 2.5. Spray polytetrafluoroethylene coating material on one side of the film, the spraying pressure is 0.22 MPa, the coating thickness is 8 μm, and it is cured at 155 °C for 8 minutes to obtain the packaging material. Example 2

[0030] Preparation of chain-extended modified polylactic acid: Take polylactic acid with a weight-average molecular weight of 160,000 and vacuum dry it at 92 °C for 5.5 hours. Add the dried polylactic acid, bisphenol A diglycidyl ether accounting for 1.3 wt% of the mass of polylactic acid, and tributyl acetylcitrate accounting for 6 wt% of the mass of polylactic acid to a twin-screw extruder. The barrel temperature of the twin-screw extruder from the feeding section to the head is 175 °C, 185 °C, 195 °C, 200 °C in sequence, the screw speed is 150 r / min, and chain-extended modified polylactic acid is obtained after the reaction.

[0031] Preparation of composite modified nano-silica particles: Disperse nano-silica with a particle size of 20 nm and nano-zinc oxide with a particle size of 10 nm in anhydrous ethanol at a mass ratio of 10:1, which is 5 times the total mass of the mixture. Add 1.2 wt% γ-aminopropyltriethoxysilane and stir and react at 75 °C for 3.5 hours. After filtration, washing, and drying, composite modified nano-silica particles are obtained.

[0032] Preparation of polytetrafluoroethylene coating material: Melt polytetrafluoroethylene resin particles at 335 °C, add polydimethylsiloxane composed of potassium perfluorooctanesulfonate and sodium perfluorohexanesulfonate at a mass ratio of 1:1 and accounting for 9 wt% of the mass of polytetrafluoroethylene, stir at 315 °C at 280 r / min for 25 minutes, and obtain masterbatch by pelletizing through a twin-screw extruder. The barrel temperature of the twin-screw extruder from the feeding section to the head is 305 °C, 315 °C, 325 °C, 330 °C in sequence, and the screw speed is 230 r / min. Add the masterbatch to ethyl acetate at a mass ratio of 1:5.5, stir at 62 °C at 310 r / min for 45 minutes to obtain polytetrafluoroethylene coating material.

[0033] Preparation of packaging material: Mix composite modified nano-silica particles with an addition amount of 3.5 wt% of the mass of modified polylactic acid and chain-extended modified polylactic acid in a high-speed mixer at 132 °C for 17 minutes, and the rotation speed of the mixer is 1150 r / min to obtain a mixed material. The mixed material is extruded and pelletized at 195 °C through a single-screw extruder, and the length-diameter ratio of the screw is 28:1 to obtain composite particles. The composite particles are blown into a film with a blow-up ratio of 2.8. Spray polytetrafluoroethylene coating material on one side of the film, the spraying pressure is 0.23 MPa, the coating thickness is 9 μm, and it is cured at 158 °C for 9 minutes to obtain the packaging material. Example 3

[0034] Preparation of chain-extended modified polylactic acid: Take polylactic acid with a weight-average molecular weight of 180,000 and vacuum dry it at 95 °C for 6 hours. Add the dried polylactic acid, bisphenol A diglycidyl ether accounting for 1.5 wt% of the mass of polylactic acid, and tributyl acetylcitrate accounting for 8 wt% of the mass of polylactic acid to a twin-screw extruder. The barrel temperature of the twin-screw extruder from the feeding section to the head is 180 °C, 190 °C, 200 °C, 200 °C in sequence, the screw speed is 180 r / min, and chain-extended modified polylactic acid is obtained after the reaction.

[0035] Preparation of composite modified nano-silica particles: Disperse nano-silica with a particle size of 20 nm and nano-zinc oxide with a particle size of 10 nm in anhydrous ethanol with a mass 5 times that of the total mixture at a mass ratio of 10:1. Add 1.2 wt% γ-aminopropyltriethoxysilane and stir and react at 78 °C for 4 hours. After filtration, washing, and drying, composite modified nano-silica particles are obtained.

[0036] Preparation of polytetrafluoroethylene coating material: Melt polytetrafluoroethylene resin particles at 340 °C, add polydimethylsiloxane composed of potassium perfluorooctane sulfonate and sodium perfluorohexane sulfonate at a mass ratio of 1:1 accounting for 10 wt% of the mass of polytetrafluoroethylene, stir at 325 °C at 300 r / min for 30 minutes, and granulate through a twin-screw extruder to obtain masterbatch. The barrel temperature of the twin-screw extruder from the feeding section to the head is 310 °C, 320 °C, 330 °C, 330 °C in sequence, and the screw speed is 250 r / min. Add the masterbatch to ethyl acetate at a mass ratio of 1:6 and stir at 65 °C at 325 r / min for 50 minutes to obtain polytetrafluoroethylene coating material.

[0037] Preparation of packaging material: Mix composite modified nano-silica particles with an addition amount of 4 wt% of the mass of modified polylactic acid and chain-extended modified polylactic acid in a high-speed mixer at 135 °C for 20 minutes, with the mixer speed of 1200 r / min to obtain a mixed material. The mixed material is extruded and granulated at 200 °C through a single-screw extruder with a screw length-diameter ratio of 28:1 to obtain composite particles. The composite particles are blown into a film with a blow-up ratio of 3. Spray polytetrafluoroethylene coating material on one side of the film with a spraying pressure of 0.25 MPa and a coating thickness of 10 μm, and cure at 160 °C for 10 minutes to obtain the packaging material.

[0038] Comparative Example 1 Based on Example 1, the difference from Example 1 is that the chain extension modification of polylactic acid is not carried out, and unmodified polylactic acid is directly used to prepare the packaging material.

[0039] Comparative Example 2 Based on Example 1, the difference from Example 1 is that composite modified nano-silica particles are not added, and only chain-extended modified polylactic acid is used to prepare the packaging material.

[0040] Comparative Example 3 Based on Example 1, the difference from Example 1 is that the polytetrafluoroethylene coating material is not sprayed.

[0041] Test: Anti-sticking performance test: Equal amounts of cold noodle pasta samples were respectively packaged with the packaging materials of the examples and comparative examples. After being placed in the same environment for 24 hours, the sticking situation of the cold noodle pasta samples was observed and rated. The rating criteria are as follows: No sticking is rated as level 5, slight sticking that can be easily separated is rated as level 4, moderate sticking that requires a little force to separate is rated as level 3, severe sticking that is difficult to separate is rated as level 2, and complete sticking is rated as level 1. The results are shown in Table 1: Anti - adhesion level / level Example 1 5 Example 2 5 Example 3 5 Comparative Example 1 3 Comparative Example 2 4 Comparative Example 3 3 As can be seen from Table 1, the packaging material prepared by the present invention has excellent anti-sticking performance.

[0042] Fresh-keeping performance test: [[ID=!23]] Cold noodle pasta samples with the same weight and freshness were respectively packaged with the packaging materials of the examples and comparative examples. They were stored for 7 days under the same refrigeration conditions (4°C, relative humidity 70%), and then the moisture content and total number of microbial colonies of the cold noodle pasta samples were detected. The higher the moisture content and the lower the total number of microbial colonies, the better the fresh-keeping performance. As shown in Table 2: Moisture % Total number of microbial colonies cfu / g Example 1 75.0 500 Example 2 73.9 520 Example 3 73.5 510 Comparative Example 1 67.6 630 Comparative Example 2 70.5 950 Comparative Example 3 72.1 550 As can be seen from Table 2, the packaging material prepared by the present invention has excellent fresh-keeping function.

[0043] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor limit the invention to the specific embodiments described. Obviously, many modifications and variations can be made according to the content of this specification.

Claims

1. An anti-sticking and fresh-keeping packaging material for cold pasta, characterized in that, It is obtained by making a packaging substrate from chain-extended modified polylactic acid and introducing composite modified nano-silica particles, and then surface-compositing a layer of polytetrafluoroethylene coating material; In the said packaging material, the addition amount of the composite modified nano-silica particles is 3wt%-4wt% of the mass of the modified polylactic acid; Among them, the polytetrafluoroethylene coating material also contains 8wt%-10wt% of polydimethylsiloxane.

2. The anti-sticking and freshness-preserving packaging material for cold noodles and Italian noodles according to claim 1, characterized in that The preparation method of the chain-extended modified polylactic acid is as follows: First, vacuum-dry polylactic acid at 90-95 °C for 5-6 hours to remove moisture; Then add the dried polylactic acid, chain extender and plasticizer into a twin-screw extruder. The chain extender is a bifunctional epoxy compound, and its addition amount is 1.2wt%-1.5wt% of the mass of polylactic acid; The plasticizer is a citric acid ester plasticizer, and its addition amount is 5wt%-8wt% of the mass of polylactic acid; In the twin-screw extruder, the barrel temperature is set to 170 °C, 180 °C, 190 °C, 200 °C in sequence from the feeding section to the head, and the screw speed is 120-180 r / min, so that polylactic acid, chain extender and plasticizer react fully under the action of high temperature and screw shear, thus completing the modification of polylactic acid; The weight-average molecular weight of the polylactic acid is 150,000-180,000.

3. The anti-sticking and fresh-keeping packaging material for cold noodles and pasta according to claim 2, characterized in that The bifunctional epoxy compound is bisphenol A diglycidyl ether; The plasticizer is acetyl tributyl citrate as the citric acid ester plasticizer.

4. The anti-sticking and fresh-keeping packaging material for cold noodles and Italian noodles according to claim 1, characterized in that, The preparation method of the composite modified nano-silica particles is as follows: Disperse nano-silica and nano-zinc oxide in anhydrous ethanol with 5 times the total mass of the mixture, add 1.2wt% of γ-aminopropyltriethoxysilane, stir and react at 70 °C - 78 °C for 3h - 4h, and then obtain it through filtration, washing and drying; The particle size of the nano-silica particles is 20nm - 30nm; The particle size of the nano-zinc oxide is 10 - 15nm; The mass ratio of the nano-silica to the nano-zinc oxide is 10:

1.

5. The anti-sticking and freshness-preserving packaging material for cold noodles and pasta according to claim 1, characterized in that, The preparation method of the polytetrafluoroethylene coating material is as follows: First, melt-treat polytetrafluoroethylene resin particles at 330 - 340 °C to obtain a melt; then add polydimethylsiloxane to the melt, stir at a stirring speed of 250 - 300 r / min at 300 - 325 °C for 20 - 30 minutes, so that polydimethylsiloxane is fully dispersed in the polytetrafluoroethylene melt, and finally granulate through a twin-screw extruder to obtain the polytetrafluoroethylene coating material masterbatch; Among them, in the twin-screw extruder, the barrel temperature is set to 300 °C, 310 °C, 320 °C, 330 °C in sequence from the feeding section to the head, and the screw speed is 220 - 250 r / min; ​ 6. A preparation method of an anti-sticking and fresh-keeping packaging material for cold noodles and pasta according to any one of claims 1-5, characterized in that, ​ ​ Step 2: Mix the composite modified nano-silica particles and the chain-extended modified polylactic acid evenly in a high-speed mixer to obtain a mixed material. The mixing temperature is 130°C - 135°C, and the mixing time is 15 min - 20 min; Step 3: Extrude and pelletize the mixed material obtained in Step 2 through a single-screw extruder. The extrusion temperature is 190°C - 200°C to obtain composite particles; Step 4: Blow the composite particles into a film. The blow-up ratio is 2.5 - 3; Step 5: Coat one side of the film with a polytetrafluoroethylene coating material. The coating thickness is 8 μm - 10 μm, and then cure for 8 min - 10 min to obtain the anti-sticking and fresh-keeping packaging material for cold pasta.

7. The preparation method according to claim 6, characterized in that, In Step 2, the rotation speed of the high-speed mixer is 1100 r / min - 1200 r / min.

8. The preparation method according to claim 6, characterized in that, In Step 3, the length-diameter ratio of the screw of the single-screw extruder is 28:

1.

9. The preparation method according to claim 6, wherein, In Step 5, the coating method is spraying, and the spraying pressure is 0.22 MPa - 0.25 MPa.

10. The preparation method according to claim 6, wherein In Step 5, the curing temperature is 155°C - 160°C.

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