Packaging material under ultralow-temperature liquid nitrogen environment and preparation method thereof

Abstract

The invention relates to the technical field of high polymer materials, in particular to a packaging material under an ultralow-temperature liquid nitrogen environment and a preparation method thereof, and the packaging material comprises the following components in parts by weight: 40-60 parts of poly-D-polylactic acid, 10-30 parts of poly-racemic polylactic acid and 10-30 parts of polypropylene. 1-5 parts of a butylene succinate-butylene adipate copolymer / halloysite nano composite material, 1-5 parts of poly-L-lactic acid, and 1-4 parts of poly (vinyl phenol). The packaging material prepared by the invention can be kept stable in a liquid nitrogen environment, and is suitable for articles needing to be stored at an extremely low temperature, such as biological samples and special medicines; the low-temperature-resistant characteristic of the material ensures the integrity and activity of the material in the storage and transportation processes. The preparation method of the packaging material comprises the processes of melting and banburying, extrusion, film casting and the like, the optimization of the processes enables the material to be efficiently processed and formed, and the packaging material is suitable for large-scale production.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and particularly relates to a packaging material under an ultra-low temperature liquid nitrogen environment and a preparation method thereof. Background Art

[0002] With the vigorous development of the modern social economy, plastic packaging has been widely used in various fields and has become an indispensable part of our daily life. It has many remarkable advantages, such as high flexibility and extremely light weight. In the field of food packaging, its lightness not only facilitates transportation and storage, but also can effectively reduce fuel consumption during transportation, thereby reducing carbon dioxide emissions and contributing to environmental protection. Its good barrier performance can effectively extend the shelf life of food, reduce waste caused by food spoilage, and ensure the safety of food, providing consumers with healthier and more reliable food protection.

[0003] However, with the continuous progress of society and the increasing pace of people's lives, in the packaging of frozen foods and the cold chain transportation process, the packaging material needs to have excellent cold resistance, be able to maintain good flexibility and elasticity under low temperature conditions, not harden or crack due to low temperature, and not adhere to the food itself, affecting the quality and appearance of the food. At the same time, the packaging material should also avoid emitting odors in a low temperature environment to ensure that the taste and flavor of the food are not affected.

[0004] Therefore, it is particularly important to develop a new type of packaging material with high and low temperature resistance. In the packaging of frozen foods, this packaging material can effectively prevent the quality decline of foods caused by the deterioration of the packaging material during the freezing process; in the cold chain transportation process, it ensures the integrity of the packaging, reduces the loss of foods during transportation, improves the safety and freshness of foods, provides consumers with better quality and safer food choices, and meets the needs of people for convenient, safe and high-quality packaged foods in modern fast-paced life. Summary of the Invention

[0005] In order to solve the problems existing in the prior art, the present invention provides a packaging material under an ultra-low temperature liquid nitrogen environment and a preparation method thereof.

[0006] A packaging material under ultra-low temperature liquid nitrogen environment, by weight, includes 40-60 parts of poly-D-lactic acid, 10-30 parts of poly-rac-lactic acid, 10-30 parts of polypropylene; 1-5 parts of butylene succinate-adipate copolymer / halloysite nanotube composite material, 1-5 parts of poly-L-lactic acid, 1-4 parts of poly(vinylphenol). Further, by weight, it includes 50 parts of poly-D-lactic acid, 20 parts of poly-rac-lactic acid, 10 parts of polypropylene; 1-5 parts of butylene succinate-adipate copolymer / halloysite nanotube composite material, 1-5 parts of poly-L-lactic acid, 4 parts of poly(vinylphenol). Further, the mass ratio of the butylene succinate-adipate copolymer / halloysite nanotube composite material to poly-L-lactic acid is 1:1. Further, the mass parts of the butylene succinate-adipate copolymer / halloysite nanotube composite material and poly-L-lactic acid are 3 parts respectively.

[0007] Further, the preparation method of the butylene succinate-adipate copolymer / halloysite nanotube composite material is: stirring the butylene succinate-adipate copolymer and halloysite at 110°C for 60 min, with a stirring speed of 80 rpm, and the mass ratio of halloysite to the butylene succinate-adipate copolymer is 5:95.

[0008] Further, the average Mn of poly-L-lactic acid is 40000; the average Mn of poly-D-lactic acid is 10000; the Mw of poly-rac-lactic acid is 18000-28000; the average Mw of polypropylene is 250000, and the average Mn is 67000; the average Mw of poly(vinylphenol) is 25000; the average Mw of the butylene succinate-adipate copolymer is 10 kDa. Halloysite, with a diameter of 30-70 nm.

[0009] The present invention also provides a preparation method of a packaging material under ultra-low temperature liquid nitrogen environment, which is characterized by including the following steps: Step S1: Heating poly-D-lactic acid, poly-rac-lactic acid, and polypropylene to 100°C and stirring for 10 min; Step S2: Adding the butylene succinate-adipate copolymer / halloysite nanotube composite material, poly-L-lactic acid, and poly(vinylphenol) into a DMF solution, refluxing and heating to 70°C, and heating for 4 h; then heating to evaporate DMF; Step S3: Melting and kneading the products obtained in Step S1 and Step S2, controlling the temperature between 175°C and 190°C, and simultaneously dehydrating under vacuum; then extruding through an extruder, casting into a film, cooling and casting, stretching, heat setting, winding, and slitting, where the stretching ratio is 1.3-1.6, the stretching temperature is 70-75°C, and the heat setting temperature is 180-220°C.

[0010] Further, in the step S2, the volume ratio of the DMF solution to the butylene succinate - butylene adipate copolymer / halloysite nanotube composite material is 10:1.

[0011] Compared with the prior art, the present invention has the following advantages and beneficial effects: The packaging material prepared by the present invention can remain stable in a liquid nitrogen environment and is suitable for items that need to be stored at extremely low temperatures, such as biological samples, special drugs, etc.; its low - temperature resistance ensures the integrity and activity of the items during storage and transportation. The preparation method of this packaging material includes processes such as melting and kneading, extrusion, and casting into a film. The optimization of these processes enables the material to be efficiently processed and formed, suitable for large - scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a bright - field TEM image of the butylene succinate - butylene adipate copolymer / halloysite nanotube composite material in Example 1 of the present invention, 100 nm.

[0013] Figure 2 It is a bright - field TEM image of the butylene succinate - butylene adipate copolymer / halloysite nanotube composite material in Example 1 of the present invention, 200 nm. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0014] To make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the embodiments. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and do not limit the present invention.

[0015] All reagents in the present invention are purchased from commercially available products without further treatment. Among them, poly - L - lactic acid PLLA has an average Mn of 40000; poly - D - lactic acid PDLA has an average Mn of 10000; poly - DL - lactic acid PDLLA has an Mw of 18000 - 28000; polypropylene has an average Mw of 250000 and an average Mn of 67000; poly(vinylphenol) has an average Mw of 25000; butylene succinate - butylene adipate copolymer PBSA has an average Mw of 10 kDa; halloysite has a diameter of 30 - 70 nm; montmorillonite has a diameter ≤20 μm.

[0016] The preparation method of the butylene succinate - butylene adipate copolymer / halloysite nanotube composite material in the present invention is as follows: The butylene succinate - butylene adipate copolymer and halloysite are stirred at 110 °C for 60 min, the stirring speed is 80 rpm, and the mass ratio of halloysite to the butylene succinate - butylene adipate copolymer is 5:95.

[0017] The preparation method of the butylene succinate - butylene adipate copolymer / montmorillonite nanocomposite in the present invention is as follows: The butylene succinate - butylene adipate copolymer and montmorillonite are stirred at 110 °C for 60 min at a stirring speed of 80 rpm. The mass ratio of montmorillonite to the butylene succinate - butylene adipate copolymer is 5:95.

[0018] Example 1 A packaging material under an ultra - low - temperature liquid nitrogen environment comprises, by weight, 50 parts of poly - D - lactic acid, 20 parts of poly - DL - lactic acid, and 10 parts of polypropylene; 5 parts of butylene succinate - butylene adipate copolymer / halloysite nanotube nanocomposite, 5 parts of poly - L - lactic acid, and 4 parts of poly(vinylphenol); Figure 1 This is the bright - field TEM image of the butylene succinate - butylene adipate copolymer / halloysite nanotube nanocomposite in Example 1 of the present invention; Figure 2 This is the bright - field TEM image of the butylene succinate - butylene adipate copolymer / halloysite nanotube nanocomposite in Example 1 of the present invention; The preparation method of a packaging material under an ultra - low - temperature liquid nitrogen environment is as follows: Step S1: Heat poly - D - lactic acid, poly - DL - lactic acid, and polypropylene to 100 °C and stir for 10 min; Step S2: Add the butylene succinate - butylene adipate copolymer / halloysite nanotube nanocomposite, poly - L - lactic acid, and poly(vinylphenol) into a DMF solution, reflux and heat to 70 °C, and heat for 4 h; then heat to evaporate DMF; here, DMF serves as a solvent, and the volume ratio of DMF to the butylene succinate - butylene adipate copolymer / halloysite nanotube nanocomposite is 10:1; Step S3: Melt and knead the products obtained in Step S1 and Step S2, control the temperature between 175 °C and 190 °C, and simultaneously dehydrate under vacuum; then extrude through an extruder, cast into a film by casting, cool and form a sheet, stretch, heat - set, wind up, and slit to obtain the double - layer packaging material of the present invention, where the stretching ratio is 1.3 - 1.6, the stretching temperature is 70 - 75 °C, and the heat - setting temperature is 180 - 220 °C.

[0019] Example 2 A packaging material under an ultra - low - temperature liquid nitrogen environment comprises, by weight, 50 parts of poly - D - lactic acid, 20 parts of poly - DL - lactic acid, and 10 parts of polypropylene; 4 parts of butylene succinate - butylene adipate copolymer / halloysite nanotube nanocomposite, 4 parts of poly - L - lactic acid, and 4 parts of poly(vinylphenol); The preparation method of a packaging material under an ultra - low - temperature liquid nitrogen environment is the same as that in Example 1.

[0020] Example 3 A packaging material under ultra-low temperature liquid nitrogen environment, by weight, includes 50 parts of poly-D-lactic acid, 20 parts of poly-rac-lactic acid, 10 parts of polypropylene; 3 parts of butylene succinate-butylene adipate copolymer / halloysite nanotube composite material, 3 parts of poly-L-lactic acid, 4 parts of poly(vinylphenol); The preparation method of a packaging material under ultra-low temperature liquid nitrogen environment is the same as that of Example 1.

[0021] Example 4 A packaging material under ultra-low temperature liquid nitrogen environment, by weight, includes 50 parts of poly-D-lactic acid, 20 parts of poly-rac-lactic acid, 10 parts of polypropylene; 2 parts of butylene succinate-butylene adipate copolymer / halloysite nanotube composite material, 2 parts of poly-L-lactic acid, 4 parts of poly(vinylphenol); The preparation method of a packaging material under ultra-low temperature liquid nitrogen environment is the same as that of Example 1.

[0022] Example 5 A packaging material under ultra-low temperature liquid nitrogen environment, by weight, includes 50 parts of poly-D-lactic acid, 20 parts of poly-rac-lactic acid, 10 parts of polypropylene; 1 part of butylene succinate-butylene adipate copolymer / halloysite nanotube composite material, 1 part of poly-L-lactic acid, 4 parts of poly(vinylphenol); The preparation method of a packaging material under ultra-low temperature liquid nitrogen environment is the same as that of Example 1.

[0023] Comparative Example 1 A packaging material under ultra-low temperature liquid nitrogen environment, by weight, includes 50 parts of poly-D-lactic acid, 20 parts of poly-rac-lactic acid, 10 parts of polypropylene; 5 parts of butylene succinate-butylene adipate copolymer / halloysite nanotube composite material, 1 part of poly-L-lactic acid, 4 parts of poly(vinylphenol); The preparation method of a packaging material under ultra-low temperature liquid nitrogen environment is as follows: Step S1: Heat poly-D-lactic acid, poly-rac-lactic acid, and polypropylene to 100°C and stir for 10 min; Step S2: Add butylene succinate-butylene adipate copolymer / halloysite nanotube composite material, poly-L-lactic acid, and poly(vinylphenol) to the DMF solution, reflux and heat to 70°C, and heat for 4 h; then heat to evaporate DMF; here DMF acts as a solvent, and the volume ratio of DMF to butylene succinate-butylene adipate copolymer / halloysite nanotube composite material is 10:1; Step S3: Melt and knead the products obtained in Step S1 and Step S2 at a temperature controlled between 175°C and 190°C, while dehydrating under vacuum; then extrude through an extruder, cast into a film, cool and cast the sheet, stretch, thermally set, wind up, and slit to obtain the double-layer packaging material of the present invention, where the stretching ratio is 1.3 - 1.6, the stretching temperature is 70 - 75°C, and the thermally setting temperature is 180 - 220°C.

[0024] Comparative Example 2 A packaging material under an ultra-low temperature liquid nitrogen environment includes, by weight, 50 parts of poly-D-lactic acid, 20 parts of poly-DL-lactic acid, 10 parts of polypropylene; 5 parts of a butylene succinate-butylene adipate copolymer / halloysite nanotube composite material, 2 parts of poly-L-lactic acid, and 4 parts of poly(vinylphenol); The preparation method of a packaging material under an ultra-low temperature liquid nitrogen environment is the same as that of Comparative Example 1.

[0025] Comparative Example 3 A packaging material under an ultra-low temperature liquid nitrogen environment includes, by weight, 50 parts of poly-D-lactic acid, 20 parts of poly-DL-lactic acid, 10 parts of polypropylene; 5 parts of a butylene succinate-butylene adipate copolymer / halloysite nanotube composite material, 3 parts of poly-L-lactic acid, and 4 parts of poly(vinylphenol); The preparation method of a packaging material under an ultra-low temperature liquid nitrogen environment is the same as that of Comparative Example 1.

[0026] Comparative Example 4 A packaging material under an ultra-low temperature liquid nitrogen environment includes, by weight, 50 parts of poly-D-lactic acid, 20 parts of poly-DL-lactic acid, 10 parts of polypropylene; 3 parts of a butylene succinate-butylene adipate copolymer / montmorillonite nanocomposite material, 3 parts of poly-L-lactic acid, and 4 parts of poly(vinylphenol); The preparation method of a packaging material under an ultra-low temperature liquid nitrogen environment is as follows: Step S1: Heat poly-D-lactic acid, poly-DL-lactic acid, and polypropylene to 100°C and stir for 10 min; Step S2: Add a butylene succinate-butylene adipate copolymer / montmorillonite nanocomposite material, poly-L-lactic acid, and poly(vinylphenol) to a DMF solution, reflux and heat to 70°C, and heat for 4 h; then heat to evaporate DMF; here, DMF acts as a solvent, and the volume ratio of DMF to the butylene succinate-butylene adipate copolymer / montmorillonite nanocomposite material is 10:1; Step S3: Melt and knead the products obtained in Step S1 and Step S2, control the temperature between 175°C and 190°C, and dehydrate under vacuum at the same time; then extrude through an extruder, cast into a film by casting, cool and cast the film, stretch, heat set, wind up, and slit to obtain the double-layer packaging material of the present invention, wherein the stretching ratio is 1.3 to 1.6, the stretching temperature is 70 to 75°C, and the heat setting temperature is 180 to 220°C.

[0027] Comparative Example 5 A packaging material under an ultra-low temperature liquid nitrogen environment, by weight, includes 50 parts of poly-D-lactic acid, 20 parts of poly-rac-lactic acid, and 10 parts of polypropylene; 2 parts of butylene succinate-adipate copolymer, 3 parts of halloysite nanocomposite, 3 parts of poly-L-lactic acid, and 4 parts of poly(vinylphenol); A preparation method of a packaging material under an ultra-low temperature liquid nitrogen environment is as follows: Step S1: Heat poly-D-lactic acid, poly-rac-lactic acid, and polypropylene to 100°C and stir for 10 min; Step S2: Add butylene succinate-adipate copolymer, halloysite nanocomposite, poly-L-lactic acid, and poly(vinylphenol) to the DMF solution, reflux and heat to 70°C, and heat for 4 h; then heat to evaporate DMF; here DMF acts as a solvent, and the volume ratio of DMF to butylene succinate-adipate copolymer / halloysite nanocomposite is 10:1; Step S3: Melt and knead the products obtained in Step S1 and Step S2, control the temperature between 175°C and 190°C, and dehydrate under vacuum at the same time; then extrude through an extruder, cast into a film by casting, cool and cast the film, stretch, heat set, wind up, and slit to obtain the double-layer packaging material of the present invention, wherein the stretching ratio is 1.3 to 1.6, the stretching temperature is 70 to 75°C, and the heat setting temperature is 180 to 220°C.

[0028] Test Example 1 Place the packaging materials prepared in each example and comparative example in a liquid nitrogen quick-freezing box for 24 h first, and then measure their tensile strength after waiting for the packaging materials to return to room temperature, wherein the temperature of the liquid nitrogen quick-freezing box is -70°C.

[0029] Table 1 Performance Test Tensile strength (MPa) Example 1 72.1 Example 2 78.3 Example 3 87.1 Example 4 79.2 Example 5 77.2 Comparative Example 1 61.5 Comparative Example 2 67.7 Comparative Example 3 63.2 Comparative Example 4 59.2 Comparative Example 5 61.3 As can be seen from Table 1, the tensile strengths of Examples 1 to 5 are all relatively excellent, among which the tensile strength of Example 3 is the highest, reaching 87.1 MPa. The tensile strength data of the comparative examples are relatively low and are all lower than those of the examples. This indicates that the packaging materials used in the examples have better tensile strength in mechanical properties after low-temperature treatment, can better withstand tensile forces, reduce the possible cracking or damage of the packaging during use, thus better protecting the items inside the packaging, extending their shelf life, and reducing food waste. At the same time, the higher tensile strength also helps the packaging materials maintain integrity during transportation and storage, reducing transportation costs and losses.

[0030] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above description is only the specific embodiments of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A packaging material for ultra-low temperature liquid nitrogen environment, characterized in that: The invention comprises, by weight, 40 to 60 parts of poly(dextrorotatory) poly(lactic acid), 10 to 30 parts of poly(racemic) poly(lactic acid), 10 to 30 parts of polypropylene; 1 to 5 parts of butylene succinate-butylene adipate copolymer / halloysite nanocomposite material, 1 to 5 parts of poly(l-lactic acid), and 1 to 4 parts of poly(vinyl phenol).

2. The packaging material for ultra-low temperature liquid nitrogen environment as claimed in claim 1, characterized in that: The invention comprises, by weight, 50 parts of poly(dextrorotatory) poly(lactic acid), 20 parts of poly(racemic) poly(lactic acid), 10 parts of polypropylene; 1-5 parts of butylene succinate-butylene adipate copolymer / halloysite nanocomposite material, 1-5 parts of poly(l-lactic acid), and 4 parts of poly(vinyl phenol).

3. The packaging material for ultra-low temperature liquid nitrogen environment as claimed in claim 2, characterized in that: The mass ratio of the butylene succinate-butylene adipate copolymer / halloysite nanocomposite material to poly (L-lactic acid) is 1:

1.

4. The packaging material for ultra-low temperature liquid nitrogen environment as claimed in claim 3, characterized in that: The mass proportions of the butylene succinate-butylene adipate copolymer / halloysite nanocomposite material and poly-L-lactic acid are 3 parts respectively.

5. The packaging material for ultra-low temperature liquid nitrogen environment as claimed in claim 1, characterized in that: The preparation method of the butylene succinate-butylene adipate copolymer / halloysite nanocomposite material is as follows: butylene succinate-butylene adipate copolymer and halloysite are stirred at 110° C. for 60 minutes at a stirring speed of 80 rpm, and the mass ratio of halloysite to butylene succinate-butylene adipate copolymer is 5:

95.

6. The packaging material for ultra-low temperature liquid nitrogen environment as claimed in claim 1, characterized in that: The average Mn of the poly-L-lactic acid is 40,000; the average Mn of the poly-D-lactic acid is 10,000; the Mw of the poly-racemic poly-lactic acid is 18,000-28,000; the average Mw of polypropylene is 250,000 and the average Mn is 67,000; the average Mw of poly(vinyl phenol) is 25,000; and the average Mw of the butylene succinate-butylene adipate copolymer is 10 kDa.

7. The packaging material for ultra-low temperature liquid nitrogen environment as claimed in claim 6, characterized in that: The halloysite has a diameter of 30-70 nm.

8. A method for preparing a packaging material in an ultra-low temperature liquid nitrogen environment according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step S1: heat poly(d-lactic acid), poly(d-lactic acid) and polypropylene to 100° C. and stir for 10 min; Step S2: adding butylene succinate-butylene adipate copolymer / halloysite nanocomposite, poly (L-lactic acid) and poly (vinyl phenol) into a DMF solution, heating under reflux at 70° C. for 4 h; then heating to evaporate the DMF; Step S3: melt and knead the products obtained in step S1 and step S2, control the temperature between 175°C and 190°C, and vacuum dehydrate them at the same time; then extrude them through an extruder, cast them into films, cool the cast sheets, stretch them, heat-set them, roll them up, and cut them, wherein the stretching ratio is 1.3-1.6, the stretching temperature is 70-75°C, and the heat-setting temperature is 180-220°C.

9. The preparation method as claimed in claim 8, characterized in that The volume ratio of the DMF solution in step S2 to the butylene succinate-butylene adipate copolymer / halloysite nanocomposite material is 10:1.

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