A biodegradable and environmentally friendly food preservative film and its manufacturing method

Abstract

The present invention relates to the technical field of fresh-keeping films, and discloses a biodegradable and environment-friendly food fresh-keeping film and a manufacturing method thereof. This kind of food fresh-keeping film uses polybutylene adipate / terephthalate as the base material, and polylactic acid composite and biological antibacterial agent as auxiliary materials. It is made through processes of mixing, extrusion, and blown film. The polylactic acid composite is a graft product of palm fiber and polylactic acid. The reinforcing effect of the palm fiber can be efficiently exerted to achieve the transfer and diffusion of stress loads, thereby effectively improving the mechanical properties of the fresh-keeping film. The biological antibacterial agent can participate in subsequent expansion reactions and thus enter the matrix of the fresh-keeping film, making the structure of the fresh-keeping film denser and the porosity lower, thereby preventing oxygen from entering and causing food spoilage. In addition, it can also effectively extend the retention time of the natural antibacterial agent caffeic acid in the fresh-keeping film, ensuring the antibacterial persistence of the fresh-keeping film.

Description

Technical Field

[0001] The present invention relates to the technical field of food wrap, and particularly relates to a biodegradable and environmentally friendly food wrap and a manufacturing method thereof. Background Art

[0002] In modern life, as a common packaging material, food wrap is widely used in the processes of food preservation, transportation and sales. However, traditional plastic food wraps based on petroleum-based materials such as polyethylene are gradually phased out of the market due to their difficult-to-degrade characteristics. Among them, poly(butylene adipate-co-terephthalate) (PBAT) and polylactic acid (PLA), as two important environmentally friendly degradable materials, show broad application prospects in the field of food wrap.

[0003] Due to the relatively high price of polylactic acid, polylactic acid is generally not directly used as the base material of food wrap at present stage. It can be added as an auxiliary material by blending with PBAT. Compared with traditional polyethylene-based food wraps, the strength of PBAT-based food wraps is relatively low. In addition, since PBAT itself does not have antibacterial properties, the antibacterial performance of PBAT-based food wraps is poor, which is very disadvantageous for food preservation. Therefore, there are still relatively large problems in practical applications.

[0004] The invention patent with the publication number of CN106751568B discloses an antibacterial PBAT / PLA composite film and a preparation method thereof. By designing and synthesizing an antibacterial compatibilizer, the composite film is given good comprehensive properties such as antibacterial property. Therefore, the properties of PBAT can be improved by adding functional additives. However, conventional quaternary ammonium salt-based small molecule antibacterial agents have poor stability and are prone to volatilization and migration, resulting in the inability to ensure the antibacterial persistence of the material. Based on this, the present invention provides a biodegradable and environmentally friendly food wrap with good antibacterial and other functional properties, which can solve the problems existing in the prior art. Summary of the Invention

[0005] In order to solve the problems mentioned in the background art, the purpose of the present invention is to provide a biodegradable and environmentally friendly food wrap and a manufacturing method thereof.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A manufacturing method of a biodegradable and environmentally friendly food wrap, characterized in that the food wrap is made of raw materials including the following parts by weight:

[0008] Poly(butylene adipate-co-terephthalate) 55 - 65 parts;

[0009] Polylactic acid complex 5 - 12 parts;

[0010] 2.5 - 4 parts of biological antibacterial agent;

[0011] 0.5 - 1 part of chain extender;

[0012] 0.5 - 1.5 parts of lubricant;

[0013] 0.5 - 1 part of antioxidant;

[0014] The manufacturing method includes the following steps:

[0015] First step: Weigh each raw material according to the formula amount and set aside;

[0016] Second step: Add polybutylene adipate / terephthalate, polylactic acid composite, and biological antibacterial agent into the mixing kettle, control the stirring rate at 1000 - 1200 r / min, mechanically stir and mix for 30 - 60 min, then add the chain extender, lubricant, and antioxidant into the mixing kettle. After adding, continue mechanical stirring for 20 - 30 min, and discharge to form a premix;

[0017] Third step: Feed the premix into the extruder, control the extruder temperature at 160 - 180 °C, and after the melt extrusion process, blow it into a film.

[0018] As a further scheme of the present invention, the specific preparation method of the polylactic acid composite is as follows:

[0019] Step one: Add alkalized palm fiber into tetrahydrofuran, ultrasonically disperse it evenly, then add isocyanate monomer into the formed dispersion liquid. After adding, stir at room temperature for 4 - 6 h, discharge, and centrifuge to obtain solid material to prepare functionalized palm fiber;

[0020] Step two: Uniformly disperse the functionalized palm fiber in toluene, then add hydroxyl - terminated polylactic acid and catalyst. After adding, gradually raise the temperature to 60 - 70 °C, keep it warm for 6 - 8 h, and separate the material to obtain the polylactic acid composite.

[0021] As a further scheme of the present invention, in step one, the isocyanate monomer is selected from 4 - isocyanatobenzoyl chloride or 3 - isocyanatoxybenzoyl chloride.

[0022] As a further scheme of the present invention, in step one, the preparation method of the alkalized palm fiber is: Immerse the palm fiber in a sodium hydroxide solution with a mass fraction of 5 - 20%, control the temperature at 50 - 60 °C, take it out after 0.5 - 1.5 h, wash it to neutrality, and then perform drying treatment.

[0023] As a further scheme of the present invention, in step two, the catalyst is selected from stannous octoate or dibutyltin dilaurate.

[0024] In the above technical solution, first, the palm fiber is alkalized to expose a large number of active hydroxyl functional groups on its surface. Then, isocyanate monomers are used, and the active acyl chloride substituents in the isocyanate monomer structure are used to modify the surface of the alkalized palm fiber to obtain palm fiber modified with isocyanate active substituents, that is, functionalized palm fiber. Next, under the action of a catalyst, hydroxyl-terminated polylactic acid is used to carry out a further grafting reaction with the functionalized palm fiber to obtain palm fiber grafted with polylactic acid, that is, a polylactic acid composite.

[0025] As a further solution of the present invention, the specific preparation method of the biological antibacterial agent is as follows:

[0026] Mix caffeic acid and dimethyl sulfoxide, stir evenly mechanically, then add a composite catalyst. After adding, raise the temperature to 40 - 50 °C and keep stirring for 1 - 2 h to form an activation solution. Then add guar gum to the activation solution. After adding, stir at room temperature for 8 - 12 h, and discharge to obtain the biological antibacterial agent.

[0027] As a further solution of the present invention, the composite catalyst is a mixture of 4-dimethylaminopyridine and dicyclohexylcarbodiimide, and the mass ratio is 1:3 - 4.

[0028] As a further solution of the present invention, the mass ratio of caffeic acid to guar gum is 0.2 - 0.3:1.

[0029] In the above technical solution, first, the active carboxyl substituents in the caffeic acid structure are activated by a composite catalyst, and then esterification condensation is carried out with the active hydroxyl substituents in the guar gum structure to obtain a guar gum derivative containing the natural antibacterial agent caffeic acid in its structure, that is, the biological antibacterial agent.

[0030] As a further solution of the present invention, the chain extender is chain extender KL-E, the lubricant is selected from stearic acid, paraffin wax or polyethylene wax; the antioxidant is selected from antioxidant 1010 or antioxidant 168.

[0031] A biodegradable and environmentally friendly food preservative film is prepared by the above manufacturing method.

[0032] The beneficial effects of the present invention:

[0033] (1) The polylactic acid composite prepared by the present invention is a graft product of palm fiber and polylactic acid. Through chemical bonding, the interfacial compatibility between the palm fiber and the material matrix can be greatly improved, and it can exist in the material matrix in the form of a chemical cross-linking core, forming a mechanical connection structure similar to a "snap fastener", so that the reinforcing effect of the palm fiber can be efficiently exerted, realizing the transfer and diffusion of stress loads, thereby effectively improving the mechanical properties of the preservative film.

[0034] (2) The bio - antibacterial agent prepared by the present invention is a guar gum derivative containing caffeic acid, a natural antibacterial agent, in its structure. Since the guar gum structure contains a large number of active hydroxyl substituents, it can participate in the chain - extension reaction during the subsequent chain - extension process and thus enter the matrix of the fresh - keeping film. On the one hand, this chain - extension method can convert PBAT from a linear structure into a three - dimensional network structure, making the structure of the fresh - keeping film denser and the porosity lower, thereby preventing oxygen from entering and causing food spoilage. In addition, it can also effectively extend the residence time of the natural antibacterial agent caffeic acid in the fresh - keeping film and ensure the antibacterial persistence of the fresh - keeping film.

[0035] Of course, it is not necessary for any product implementing the present invention to achieve all the above - mentioned advantages simultaneously. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for describing the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0037] Figure 1 It is the FT - IR diagram of the bio - antibacterial agent. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0039] Preparation Example 1

[0040] Preparation of the polylactic acid composite:

[0041] Step 1: Immerse 5 g of palm fibers in a sodium hydroxide solution with a mass fraction of 10%, control the temperature at 55 °C, take them out after 1 h, wash until neutral, and then dry them to obtain alkalized palm fibers.

[0042] Step 2: Add 3.5 g of alkalized palm fibers to tetrahydrofuran, disperse them evenly by ultrasonic treatment, and then add 0.6 g of 4 - isocyanatobenzoyl chloride to the formed dispersion. After adding, stir at room temperature for 6 h, discharge the material, and centrifuge to obtain solid materials to obtain functionalized palm fibers.

[0043] According to the hydrochloric acid - dibutylamine titration test method, the functionalized palm fiber was correspondingly tested to measure the percentage content of isocyanate groups on its surface. Taking 0.1 g of the functionalized palm fiber as the titration sample and 0.5 mol / L hydrochloric acid as the standard solution, the titration test results showed that the percentage content of isocyanate groups was 4.147%;

[0044] Step 3: Uniformly disperse 2.6 g of the functionalized palm fiber in toluene, then add 12 g of hydroxyl - terminated polylactic acid and 0.1 g of dibutyltin dilaurate. After adding, gradually raise the temperature to 65 °C, keep warm for 6 h, and then separate the material to obtain the polylactic acid composite.

[0045] Take another 0.1 g of the polylactic acid composite as the titration test sample and conduct the same titration test as in Step 2. The results showed that the percentage content of isocyanate groups was 0.381%, indicating that a large amount of isocyanate groups were consumed during the reaction with hydroxyl - terminated polylactic acid.

[0046] Preparation Example 2

[0047] Preparation of the biological antibacterial agent:

[0048] Mix 0.8 g of caffeic acid with dimethyl sulfoxide, stir evenly mechanically, then add 0.1 g of 4 - dimethylaminopyridine and 0.3 g of dicyclohexylcarbodiimide. After adding, raise the temperature to 40 °C, keep warm and stir for 2 h to form an activation solution. Then add 3 g of guar gum to the activation solution. After adding, stir at room temperature for 9 h, and discharge to obtain the biological antibacterial agent.

[0049] Make the biological antibacterial agent into a potassium bromide tablet and conduct infrared analysis test. The results are shown in Figure 1 , as Figure 1 shown, the characteristic absorption peak at 3308 cm -1 is the characteristic absorption peak of the unreacted hydroxyl group in the guar gum structure, the characteristic absorption peak at 3000 - 3100 cm -1 is the characteristic absorption peak of the carbon - hydrogen bond of the benzene ring, the characteristic absorption peak at 1725 cm -1 is the characteristic absorption peak of the carbon - oxygen double bond of the ester group generated by the esterification condensation reaction, and the characteristic absorption peak at 1088 cm -1 is the characteristic absorption peak of the ether bond. Example

[0050] A biodegradable and environment - friendly food preservative film is made of the following raw materials by weight:

[0051] Polybutylene adipate / terephthalate 55 parts;

[0052] Polylactic acid composite 5 parts;

[0053] Biological antibacterial agent: 2.5 parts;

[0054] Chain extender KL-E: 0.5 part;

[0055] Stearic acid: 0.5 part;

[0056] Antioxidant 1010: 0.5 part;

[0057] The manufacturing method includes the following steps:

[0058] First step, weigh each raw material according to the formula amount and set aside;

[0059] Second step, add polybutylene adipate / terephthalate, polylactic acid complex, and biological antibacterial agent into the mixing kettle, control the stirring rate at 1000 r / min, mechanically stir and mix for 60 min, then add chain extender KL-E, stearic acid, and antioxidant 1010 into the mixing kettle. After adding, continue mechanical stirring for 30 min, and discharge to form a premix;

[0060] Third step, feed the premix into an extruder, control the extruder temperature at 160 °C, and after the melt extrusion process, blow it into a film.

[0061] The preparation method of the polylactic acid complex can be seen in Preparation Example 1; the preparation method of the biological antibacterial agent can be seen in Preparation Example 2, and the same applies hereinafter. Example

[0062] An environmentally friendly biodegradable food fresh-keeping film is made of raw materials including the following weight parts:

[0063] Polybutylene adipate / terephthalate: 62 parts;

[0064] Polylactic acid complex: 9 parts;

[0065] Biological antibacterial agent: 3 parts;

[0066] Chain extender KL-E: 0.6 part;

[0067] Polyethylene wax: 1 part;

[0068] Antioxidant 168: 0.8 part;

[0069] The manufacturing method includes the following steps:

[0070] First step, weigh each raw material according to the formula amount and set aside;

[0071] Step 2: Add polybutylene adipate / terephthalate, polylactic acid composite, and bio-antibacterial agent into a mixing kettle, control the stirring rate at 1200 r / min, mechanically stir and mix for 40 min, then add chain extender KL-E, polyethylene wax, and antioxidant 168 into the mixing kettle. After adding, continue mechanical stirring for 20 min, and discharge to form a premix.

[0072] Step 3: Feed the premix into an extruder, control the extruder temperature at 170 °C, and after the melt extrusion process, blow it into a film. Example

[0073] An environmentally friendly biodegradable food fresh-keeping film is made of raw materials including the following parts by weight:

[0074] Polybutylene adipate / terephthalate 65 parts;

[0075] Polylactic acid composite 12 parts;

[0076] Bio-antibacterial agent 4 parts;

[0077] Chain extender KL-E 1 part;

[0078] Paraffin wax 1.5 parts;

[0079] Antioxidant 168 1 part;

[0080] The manufacturing method includes the following steps:

[0081] Step 1: Weigh each raw material according to the formula amount and set aside.

[0082] Step 2: Add polybutylene adipate / terephthalate, polylactic acid composite, and bio-antibacterial agent into a mixing kettle, control the stirring rate at 1200 r / min, mechanically stir and mix for 30 min, then add chain extender KL-E, paraffin wax, and antioxidant 168 into the mixing kettle. After adding, continue mechanical stirring for 20 min, and discharge to form a premix.

[0083] Step 3: Feed the premix into an extruder, control the extruder temperature at 180 °C, and after the melt extrusion process, blow it into a film.

[0084] Comparative Example 1

[0085] An environmentally friendly biodegradable food fresh-keeping film is made of raw materials including the following parts by weight:

[0086] Polybutylene adipate / terephthalate 62 parts;

[0087] Palm fiber 9 parts;

[0088] Bio-antibacterial agent 3 parts;

[0089] Chain extender KL-E: 0.6 parts;

[0090] Polyethylene wax: 1 part;

[0091] Antioxidant 168: 0.8 parts;

[0092] The manufacturing method includes the following steps:

[0093] First step, weigh each raw material according to the formula amount and set aside;

[0094] Second step, add polybutylene adipate / terephthalate, palm fiber, and bio-antibacterial agent into the mixing kettle, control the stirring rate at 1200 r / min, mechanically stir and mix for 40 min, then add chain extender KL-E, polyethylene wax, and antioxidant 168 into the mixing kettle. After adding, continue to mechanically stir for 20 min, and discharge to form a premix;

[0095] Third step, feed the premix into an extruder, control the extruder temperature at 170 °C, and after the melt extrusion process, blow it into a film.

[0096] Comparative Example 2

[0097] A biodegradable and environmentally friendly food fresh-keeping film is made of raw materials including the following weight parts:

[0098] Polybutylene adipate / terephthalate: 62 parts;

[0099] Polylactic acid composite: 9 parts;

[0100] Caffeic acid: 3 parts;

[0101] Chain extender KL-E: 0.6 parts;

[0102] Polyethylene wax: 1 part;

[0103] Antioxidant 168: 0.8 parts;

[0104] The manufacturing method includes the following steps:

[0105] First step, weigh each raw material according to the formula amount and set aside;

[0106] Second step, add polybutylene adipate / terephthalate, polylactic acid composite, and caffeic acid into the mixing kettle, control the stirring rate at 1200 r / min, mechanically stir and mix for 40 min, then add chain extender KL-E, polyethylene wax, and antioxidant 168 into the mixing kettle. After adding, continue to mechanically stir for 20 min, and discharge to form a premix;

[0107] Step 3: Feed the premix into an extruder, control the temperature of the extruder at 170 °C, and after the melt extrusion process, blow it into a film, and that's it.

[0108] Comparative Example 3

[0109] A biodegradable and environmentally friendly food preservative film is made of raw materials including the following parts by weight:

[0110] Butylene adipate / terephthalate 62 parts;

[0111] Polylactic acid composite 9 parts;

[0112] Chain extender KL-E 0.6 part;

[0113] Polyethylene wax 1 part;

[0114] Antioxidant 168 0.8 part;

[0115] The manufacturing method includes the following steps:

[0116] Step 1: Weigh each raw material according to the formula amount and set aside;

[0117] Step 2: Add butylene adipate / terephthalate and polylactic acid composite to a mixing kettle, control the stirring rate at 1200 r / min, mechanically stir and mix for 40 min, then add chain extender KL-E, polyethylene wax and antioxidant 168 to the mixing kettle. After adding, continue mechanical stirring for 20 min, and discharge to form a premix;

[0118] Step 3: Feed the premix into an extruder, control the temperature of the extruder at 170 °C, and after the melt extrusion process, blow it into a film, and that's it.

[0119] Test Example

[0120] Make the preservative films in the examples and comparative examples into various test samples and conduct various performance tests. The test results are recorded in Table 1:

[0121] Table 1 - Performance Test Results

[0122]

[0123] Among them, the reference standard for the tensile property test is GB / T 1040.3-2006; the reference standard for the oxygen transmission rate test method is GB / T 1038.1-2022; the reference standard for the antibacterial rate test is according to the standard QB / T 2591-2003, and the test time is after the sample is placed at room temperature for 2 months.

[0124] Analysis of the test results shows that by using the polylactic acid composite in Preparation Example 1 and the biological antibacterial agent in Preparation Example 2 of the present invention as additives, a PBAT-based food preservative film with excellent mechanical properties, low air permeability and strong antibacterial properties can be prepared.

[0125] After replacing the polylactic acid composite with palm fibers, due to obvious interface problems, the reinforcing effect of palm fibers cannot be fully exerted, so the mechanical properties decline significantly.

[0126] After replacing the biological antibacterial agent with caffeic acid, it may be due to the volatilization and migration phenomenon during storage, resulting in an obvious decrease in the antibacterial performance of the preservative film. Moreover, due to the loss of the cross-linking effect of guar gum, the cross-linking density of the preservative film decreases, which directly affects the mechanical properties and oxygen barrier properties of the preservative film. After completely removing the biological antibacterial agent, the antibacterial performance is further reduced.

[0127] In this article, specific examples are used to elaborate on the principle and implementation mode of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention, including the best mode, and also enables any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that for those of ordinary skill in the art in the technical field, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention. The protection scope of the present invention patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to the literal description of the claims, or if they include equivalent structural elements that have no substantial difference from the literal description of the claims, then these other embodiments should also be included within the scope of the claims.

[0128] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements will not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for producing a biodegradable and environment-friendly food preservative film, characterized in that: The food preservative film is made of the following raw materials in parts by weight: Polybutylene adipate / terephthalate 55-65 parts; 5-12 parts of polylactic acid compound; 2.5-4 parts of biological antibacterial agent; Chain extender 0.5-1 part; Lubricant 0.5-1.5 parts; Antioxidant 0.5-1 part; The manufacturing method comprises the following steps: The first step is to weigh each raw material according to the formula and set aside; Step 2: Add polybutylene adipate / terephthalate, polylactic acid composite and bioantibacterial agent into the mixing kettle, control the stirring rate to 1000-1200r / min, mechanically stir and mix for 30-60min, then add chain extender, lubricant and antioxidant into the mixing kettle, continue mechanical stirring for 20-30min, discharge and form a premix; The third step is to feed the premix into the extruder, control the extruder temperature to 160-180°C, and after the melt extrusion process, blow mold into a film. The specific preparation method of the polylactic acid composite is as follows: Step 1: using isocyanate monomer to graft modify alkalized palm fiber to obtain functionalized palm fiber; Step 2: Using toluene as a medium and in the presence of a catalyst, the hydroxy-terminated polylactic acid and the functionalized palm fiber are further reacted to obtain a polylactic acid composite; The specific preparation method of the biological antibacterial agent is as follows: Caffeic acid and dimethyl sulfoxide are mixed, mechanically stirred evenly, and then the composite catalyst is added. After the addition, the temperature is increased to 40-50°C, and the mixture is stirred for 1-2 hours to form an activation solution. Then, guar gum is added to the activation solution. After the addition is completed, the mixture is stirred at room temperature for 8-12 hours and the bioantimicrobial agent is obtained.

2. The method for manufacturing a biodegradable and environment-friendly food preservative film according to claim 1, characterized in that: In step 1, the isocyanate monomer is selected from 4-isocyanobenzoyl chloride or 3-isocyanatobenzoyl chloride.

3. The method for manufacturing a biodegradable and environment-friendly food preservative film according to claim 1, characterized in that: In step 1, the preparation method of the alkalized palm fiber is: immerse the palm fiber in a sodium hydroxide solution with a mass fraction of 5-20%, control the temperature to 50-60° C., take it out after 0.5-1.5 hours, wash it to neutrality, and then dry it.

4. The method for producing a biodegradable and environment-friendly food preservative film according to claim 1, characterized in that: In step 2, the catalyst is selected from stannous octoate or dibutyltin dilaurate.

5. The method for manufacturing a biodegradable and environment-friendly food preservative film according to claim 1, characterized in that: The composite catalyst is a mixture of 4-dimethylaminopyridine and dicyclohexylcarbodiimide, with a mass ratio of 1:3-4.

6. The method for manufacturing a biodegradable and environment-friendly food preservative film according to claim 1, characterized in that: The mass ratio of caffeic acid to guar gum is 0.2-0.3:

1.

7. The method for manufacturing a biodegradable and environment-friendly food preservative film according to claim 1, characterized in that: The chain extender is chain extender KL-E, the lubricant is selected from stearic acid, paraffin or polyethylene wax; and the antioxidant is selected from antioxidant 1010 or antioxidant 168.

8. A biodegradable and environment-friendly food preservative film, characterized in that: The method is prepared by the manufacturing method according to any one of claims 1 to 7.

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