1. A gas permselective packaging film characterized by: which comprises the following components:

60-90 wt% of poly (butylene adipate)/terephthalate,

8 to 30 weight percent of ethylene acrylic acid copolymer,

2-10 wt% of sodium sulfite.

2. The gas permselective packaging film according to claim 1, characterized in that: the mass ratio of the ethylene acrylic acid copolymer to the sodium sulfite is (3-4): 1.

3. a method of producing a gas permselective packaging film according to claim 1 or 2, wherein: which comprises the following steps:

(1) mixing the ethylene acrylic acid copolymer with sodium sulfite, carrying out melt extrusion, cooling, and then carrying out grain cutting to obtain master batches;

(2) and mixing the poly (butylene adipate)/terephthalate and the master batch to obtain a mixture, and performing melt extrusion casting to obtain the gas selective permeability packaging film.

4. The production method according to claim 3, characterized in that: in the step (1), the mass ratio of the ethylene acrylic acid copolymer to the sodium sulfite is (3-4): 1.

5. the production method according to claim 3, characterized in that: in the step (1), in the melt extrusion process, the temperatures from a first zone to a seventh zone in the double-screw extruder are respectively 160 ℃, 165 ℃, 170 ℃, 175 ℃ and 170 ℃, and the rotating speed is 20-40 r/min.

6. The production method according to claim 3, characterized in that: in the step (2), the mass ratio of the polybutylene adipate/terephthalate to the master batch is (3-23): (1-3.75).

7. The production method according to claim 3, characterized in that: in the step (2), in the melt extrusion casting process, the temperatures from a first zone to a seventh zone in a single-screw extrusion casting machine are respectively 130 ℃, 140 ℃, 155 ℃, 170 ℃, 175 ℃ and 170 ℃, the rotating speed is 20-40r/min, and the rotating speed of the traction of the casting machine is 2-4 r/min.

Background

The food package plays an important role in protecting food, and the shelf life of the food can be prolonged and the waste and loss of the food can be reduced through reasonable package. The breathability of food packaging materials has a great influence on the quality of the food during storage. In the fresh-keeping of fresh fruits and vegetables, the packaging material can play an important role in adjusting the atmosphere composition inside the package. Fruits and vegetables are used as special food, and after being harvested, the fruits and vegetables still carry out life activities, carry out physiological metabolism depending on gas supply of a storage environment, absorb oxygen from the external environment, and carry out oxidative decomposition on organic substrates under the action of enzymes through respiration to maintain life activities, so that the quality of the fruits and vegetables is reduced, and the storage life is shortened. The spontaneous modified atmosphere packaging means that in the storage process, the gas components in the packaging are completely regulated through the selective permeability of the film to gas and the respiration of fruits and vegetables without any manual operation, finally the dynamic balance is achieved, the stable and proper atmosphere in the packaging is maintained, the physiological metabolism of the fruits and vegetables can be effectively inhibited, the senescence is delayed, the operation is convenient and fast, the preservation effect is obvious, and the flavor and the nutrient substances are greatly reserved while the shelf life is prolonged.

The current common packaging materials on the market are polyethylene, polypropylene, polyvinyl chloride and the like, the selective permeability of the packaging materials to carbon dioxide and oxygen is not high, and the permeability ratio of the carbon dioxide to the oxygen is about (3-6): 1, the packaging material can be used for packaging fresh fruits and vegetables but cannot meet the requirements of ideal modified atmosphere packaging materials, the atmosphere in the packaging cannot reach the ideal modified atmosphere level of the fruits and vegetables, alcoholism and other phenomena caused by anaerobic respiration are easily caused, and the quality reduction of the fruits and vegetables is accelerated. The research shows that the permeation ratio of the fresh fruit and vegetable packaging film material to carbon dioxide and oxygen is (8-10): preferably 1. For some fruit and vegetable products with higher respiratory strength, the packaging material is required to have higher carbon dioxide and oxygen permeability ratio. In addition, due to exhaustion of petroleum resources and increasing environmental pollution, biodegradable packaging film materials become the focus of research and development at home and abroad and the development trend in the future. The biodegradable material with superior performance is selected and used for packaging fresh food, thereby meeting the dietary pursuit of safety, nutrition and health of people and simultaneously conforming to the green environmental protection concept.

Disclosure of Invention

In view of the deficiencies of the prior art, it is a primary object of the present invention to provide a gas permselective packaging film.

It is a second object of the present invention to provide a method for producing the above-mentioned gas permselective packaging film.

In order to achieve the above primary object, the solution of the present invention is:

a gas permselective packaging film comprising the following components:

60-90 wt% of poly (butylene adipate terephthalate) (PBAT),

8-30 wt% of ethylene acrylic acid copolymer (EAA),

sodium sulfite (Na)₂SO₃) 2-10wt％。

Wherein PBAT is German Basff C1200, EAA is US Dow 5990I, Na₂SO₃For analytical grade.

Further, the mass ratio of the ethylene acrylic acid copolymer to the sodium sulfite is (3-4): 1.

in order to achieve the second objective, the solution of the invention is:

the preparation method of the gas permselective packaging film comprises the following steps:

(1) mixing the ethylene acrylic acid copolymer with sodium sulfite, carrying out melt extrusion, cooling, and then carrying out grain cutting to obtain master batches;

(2) and mixing the poly (butylene adipate)/terephthalate and the master batch to obtain a mixture, and performing melt extrusion casting to obtain the gas selective permeability packaging film.

Further, in the step (1), the mass ratio of the ethylene acrylic acid copolymer to the sodium sulfite is (3-4): 1.

further, in the step (1), in the process of melt extrusion, the temperature of each temperature zone (from one zone to seven zones) in the double-screw extruder is 160 ℃, 165 ℃, 170 ℃, 175 ℃ and 170 ℃ respectively, and the rotating speed is 20-40 r/min.

Further, in the step (2), the mass ratio of the poly (butylene adipate)/terephthalate to the master batch is (3-23): (1-3.75).

Further, in the step (2), in the process of melt extrusion casting, the temperature of each temperature zone (from one zone to seven zones) in the single-screw extrusion casting machine is 130 ℃, 140 ℃, 155 ℃, 170 ℃, 175 ℃ and 170 ℃, the rotating speed is 20-40r/min, and the rotating speed of the traction of the casting machine is 2-4 r/min.

Due to the adoption of the scheme, the invention has the beneficial effects that:

the active film with the gas selective permeation function adopts the ethylene acrylic acid copolymer and the sodium sulfite with specific mass ratio, and can help maintain or quickly establish an ideal microenvironment with low oxygen and high carbon dioxide atmosphere in the fruit and vegetable package by utilizing the selective permeability of the film to gas molecules such as oxygen, carbon dioxide and the like, thereby effectively inhibiting the respiration of fruits and vegetables and further achieving a better fresh-keeping effect. Meanwhile, the main base material of the film is a biodegradable material, and the film is used for packaging fresh food, meets the dietary pursuit of safety, nutrition and health of people, and accords with the green environmental protection concept.

Detailed Description

The invention provides a gas selective permeability packaging film and a preparation method thereof, wherein the gas selective permeability packaging film mainly comprises PBAT, EAA and Na₂SO₃And (4) forming.

< packaging film having gas Selective permeation >

The gas permselective packaging film of the present invention comprises the following components:

60-90 wt% of poly (butylene adipate terephthalate) (PBAT),

8-30 wt% of ethylene acrylic acid copolymer (EAA),

sodium sulfite (Na)₂SO₃) 2-10wt％。

Wherein, EAA resin and Na₂SO₃In a mass ratio of(3-4)：1。

< method for producing gas permselective packaging film >

The preparation method of the gas selective permeability packaging film comprises the following steps:

(1)、EAA/Na₂SO₃preparing master batch: mixing EAA resin with Na₂SO₃According to the mass ratio of (3-4): 1, uniformly mixing, adding the mixed material into a double-screw extruder for melt extrusion, cooling by cold water, and then obtaining master batches by a granulator;

(2) and preparing a film: mixing PBAT resin and EAA/Na₂SO₃The master batch is prepared from the following components in percentage by mass (3-23): (1-3.75), uniformly mixing, adding the mixture into a single-screw extrusion casting machine, and carrying out melt extrusion casting to obtain the gas selective permeability packaging film.

Wherein, in the step (1), during the melt extrusion, the temperature of each temperature zone (one zone to seven zones) in the double-screw extruder is 160 ℃, 165 ℃, 170 ℃, 175 ℃ and 170 ℃, and the rotating speed can be 20-40r/min, preferably 30 r/min.

In the step (2), in the process of melt extrusion casting, the temperature of each temperature zone (from one zone to seven zones) in the single-screw extrusion casting machine is 130 ℃, 140 ℃, 155 ℃, 170 ℃, 175 ℃ and 170 ℃, and the rotating speed can be 20-40r/min, preferably 30 r/min; the rotational speed of the casting machine can be 2 to 4r/min, preferably 2.5 r/min.

The present invention will be further described with reference to examples and comparative examples.

The composition ratios of the examples corresponding to the comparative examples are shown in Table 1.

TABLE 1 contents of components of examples and comparative examples

Example 1:

the method for producing a gas permselective packaging film according to this example comprises the steps of:

(1)、EAA/Na₂SO₃preparing master batch: mixing EAA resin with Na₂SO₃Uniformly mixing according to the mass ratio of 4:1, adding the mixed material into a double-screw extruder for melt extrusion, cooling by cold water, and then obtaining master batches by a granulator; wherein the temperature of each temperature zone (one zone to seven zones) in the double-screw extruder is respectively 160 ℃, 165 ℃, 170 ℃, 175 ℃ and 170 ℃, and the rotating speed is 30 r/min.

(2) And preparing a film: mixing PBAT resin and EAA/Na₂SO₃Uniformly mixing the master batches according to the mass ratio of 9:1, adding the mixed material into a single-screw extrusion casting machine for melt extrusion casting to obtain a gas selective permeability packaging film; wherein the temperature of each temperature zone (one zone to seven zones) in the single screw extrusion casting machine is respectively 130 ℃, 140 ℃, 155 ℃, 170 ℃, 175 ℃ and 170 ℃, the rotating speed is 30r/min, and the rotating speed of the traction of the casting machine is 2.5 r/min.

Example 2:

the method for producing a gas permselective packaging film according to this example comprises the steps of:

(1)、EAA/Na₂SO₃preparing master batch: mixing EAA resin with Na₂SO₃Uniformly mixing according to the mass ratio of 4:1, adding the mixed material into a double-screw extruder for melt extrusion, cooling by cold water, and then obtaining master batches by a granulator; wherein the temperature of each temperature zone (one zone to seven zones) in the double-screw extruder is respectively 160 ℃, 165 ℃, 170 ℃, 175 ℃ and 170 ℃, and the rotating speed is 30 r/min.

(2) And preparing a film: mixing PBAT resin and EAA/Na₂SO₃Uniformly mixing the master batches according to the mass ratio of 3:1, adding the mixed material into a single-screw extrusion casting machine for melt extrusion casting to obtain a gas selective permeability packaging film; wherein the temperature of each temperature zone (one zone to seven zones) in the single screw extrusion casting machine is respectively 130 ℃, 140 ℃, 155 ℃, 170 ℃, 175 ℃ and 170 ℃, the rotating speed is 30r/min, and the rotating speed of the traction of the casting machine is 2 r/min.

Example 3:

the method for producing a gas permselective packaging film according to this example comprises the steps of:

(1)、EAA/Na₂SO₃preparing master batch: mixing EAA resin with Na₂SO₃Uniformly mixing according to the mass ratio of 4:1, adding the mixed material into a double-screw extruder for melt extrusion, cooling by cold water, and then obtaining master batches by a granulator; wherein the temperature of each temperature zone (one zone to seven zones) in the double-screw extruder is respectively 160 ℃, 165 ℃, 170 ℃, 175 ℃ and 170 ℃, and the rotating speed is 30 r/min.

(2) And preparing a film: mixing PBAT resin and EAA/Na₂SO₃Uniformly mixing the master batches according to the mass ratio of 6.25:3.75, adding the mixed material into a single-screw extrusion casting machine for melt extrusion casting to obtain a gas selective permeability packaging film; wherein the temperature of each temperature zone (one zone to seven zones) in the single screw extrusion casting machine is respectively 130 ℃, 140 ℃, 155 ℃, 170 ℃, 175 ℃ and 170 ℃, the rotating speed is 30r/min, and the rotating speed of the traction of the casting machine is 4 r/min.

Example 4:

the method for producing a gas permselective packaging film according to this example comprises the steps of:

(1)、EAA/Na₂SO₃preparing master batch: mixing EAA resin with Na₂SO₃Uniformly mixing according to the mass ratio of 3:1, adding the mixed material into a double-screw extruder for melt extrusion, cooling by cold water, and then obtaining master batches by a granulator; wherein the temperature of each temperature zone (one zone to seven zones) in the double-screw extruder is respectively 160 ℃, 165 ℃, 170 ℃, 175 ℃ and 170 ℃, and the rotating speed is 30 r/min.

(2) And preparing a film: mixing PBAT resin and EAA/Na₂SO₃Uniformly mixing the master batches according to the mass ratio of 23:2, adding the mixed material into a single-screw extrusion casting machine for melt extrusion casting to obtain a gas selective permeability packaging film; wherein the temperature of each temperature zone (one zone to seven zones) in the single-screw extrusion casting machine is 130 ℃, 140 ℃, 155 ℃, 170 ℃, 175℃,The rotation speed is 30r/min at 175 ℃ and 170 ℃ and the rotation speed of the traction of the casting machine is 2.5 r/min.

Example 5:

the method for producing a gas permselective packaging film according to this example comprises the steps of:

(1)、EAA/Na₂SO₃preparing master batch: mixing EAA resin with Na₂SO₃Uniformly mixing according to the mass ratio of 3:1, adding the mixed material into a double-screw extruder for melt extrusion, cooling by cold water, and then obtaining master batches by a granulator; wherein the temperature of each temperature zone (one zone to seven zones) in the double-screw extruder is respectively 160 ℃, 165 ℃, 170 ℃, 175 ℃ and 170 ℃, and the rotating speed is 30 r/min.

(2) And preparing a film: mixing PBAT resin and EAA/Na₂SO₃Uniformly mixing the master batches according to the mass ratio of 4:1, adding the mixed material into a single-screw extrusion casting machine for melt extrusion casting to obtain a gas selective permeability packaging film; wherein the temperature of each temperature zone (one zone to seven zones) in the single screw extrusion casting machine is respectively 130 ℃, 140 ℃, 155 ℃, 170 ℃, 175 ℃ and 170 ℃, the rotating speed is 30r/min, and the rotating speed of the traction of the casting machine is 2 r/min.

Example 6:

the method for producing a gas permselective packaging film according to this example comprises the steps of:

(1)、EAA/Na₂SO₃preparing master batch: mixing EAA resin with Na₂SO₃Uniformly mixing according to the mass ratio of 3:1, adding the mixed material into a double-screw extruder for melt extrusion, cooling by cold water, and then obtaining master batches by a granulator; wherein the temperature of each temperature zone (one zone to seven zones) in the double-screw extruder is respectively 160 ℃, 165 ℃, 170 ℃, 175 ℃ and 170 ℃, and the rotating speed is 30 r/min.

(2) And preparing a film: mixing PBAT resin and EAA/Na₂SO₃Uniformly mixing the master batches according to the mass ratio of 3:2, adding the mixed material into a single-screw extrusion casting machine for melt extrusion casting to obtain a gas selective permeability packaging film; whereinThe temperature of each temperature zone (one zone to seven zones) in the single-screw extrusion casting machine is 130 ℃, 140 ℃, 155 ℃, 170 ℃, 175 ℃ and 170 ℃, the rotating speed is 30r/min, and the rotating speed of the traction of the casting machine is 4 r/min.

Comparative example 1:

the method for producing the gas permselective packaging film of the present comparative example comprises the steps of:

(1)、EAA/Na₂SO₃preparing master batch: mixing EAA resin with Na₂SO₃Uniformly mixing according to the mass ratio of 9:2, adding the mixed material into a double-screw extruder for melt extrusion, cooling by cold water, and then obtaining master batches by a granulator; wherein the temperature of each temperature zone (one zone to seven zones) in the double-screw extruder is respectively 160 ℃, 165 ℃, 170 ℃, 175 ℃ and 170 ℃, and the rotating speed is 30 r/min.

(2) And preparing a film: mixing PBAT resin and EAA/Na₂SO₃Uniformly mixing the master batches according to the mass ratio of 89:11, adding the mixed material into a single-screw extrusion casting machine for melt extrusion casting to obtain a gas selective permeability packaging film; wherein the temperature of each temperature zone (one zone to seven zones) in the single screw extrusion casting machine is respectively 130 ℃, 140 ℃, 155 ℃, 170 ℃, 175 ℃ and 170 ℃, the rotating speed is 30r/min, and the rotating speed of the traction of the casting machine is 2.5 r/min.

Comparative example 2:

the method for producing the gas permselective packaging film of the present comparative example comprises the steps of:

(1)、EAA/Na₂SO₃preparing master batch: mixing EAA resin with Na₂SO₃Uniformly mixing according to the mass ratio of 5:2, adding the mixed material into a double-screw extruder for melt extrusion, cooling by cold water, and then obtaining master batches by a granulator; wherein the temperature of each temperature zone (one zone to seven zones) in the double-screw extruder is respectively 160 ℃, 165 ℃, 170 ℃, 175 ℃ and 170 ℃, and the rotating speed is 30 r/min.

(2) And preparing a film: mixing PBAT resin and EAA/Na₂SO₃The master batch is uniformly mixed according to the mass ratio of 13:7,adding the mixed material into a single-screw extrusion casting machine for melt extrusion casting to obtain a gas selective permeability packaging film; wherein the temperature of each temperature zone (one zone to seven zones) in the single screw extrusion casting machine is respectively 130 ℃, 140 ℃, 155 ℃, 170 ℃, 175 ℃ and 170 ℃, the rotating speed is 30r/min, and the rotating speed of the traction of the casting machine is 2.5 r/min.

Comparative example 3:

the method of preparing the PBAT film of this comparative example included:

adding the PBAT resin into a single-screw extrusion casting machine for melt extrusion casting to obtain a PBAT film, wherein the temperature of each temperature zone (from one zone to seven zones) in the single-screw extrusion casting machine is 130 ℃, 140 ℃, 155 ℃, 170 ℃, 175 ℃ and 170 ℃, the rotating speed is 30r/min, and the rotating speed dragged by the casting machine is 2.5 r/min.

The packaging films of the above examples and comparative examples were subjected to gas (oxygen and carbon dioxide) permeability measurement. The experimental results are shown in table 2:

TABLE 2 gas permeability of different films

As can be seen from Table 2, the carbon dioxide to oxygen transmission ratio (P) of the pure PBAT film (comparative example 3)_CO2/O2) Is 6.58, EAA/Na₂SO₃The permeation ratio of the PBAT film is greatly improved by adding the master batch, and the packaging film of the embodiment is increased to 7.92-12.48. In examples 1 to 6, P of PBAT film_CO2/O2With EAA/Na in the film₂SO₃The content of the master batch is increased; when Na is contained in the film₂SO₃P corresponding to examples 4 to 6 in the same content_CO2/O2Higher than in examples 1 to 3, respectively, indicating the preparation of EAA/Na₂SO₃In the case of master batch, EAA resin and Na₂SO₃The mass ratio of 3:1 is more beneficial to increasing the P of the PBAT film than the mass ratio of 4:1_CO2/O2. P for the comparative example 1 and comparative example 2 films compared to a pure PBAT film (comparative example 3)_CO2/O2Slightly increased. Comparative example 1 and comparative example 1, example 2 and comparative example 2, the difference between them being the preparation of EAA/Na₂SO₃In the case of master batch, EAA resin and Na₂SO₃Different mass ratio, but P of the film_CO2/O2A large difference indicates EAA resin and Na₂SO₃The mass ratio is controlled to be (3-4): 1, it is advantageous to adjust the carbon dioxide to oxygen transmission ratio of the film over a wide range, otherwise it is not helpful to improve the carbon dioxide to oxygen transmission ratio of the film. In conclusion, the PBAT film has the function of gas selective permeation, and the permeability of the PBAT film to oxygen and carbon dioxide can be regulated and controlled. By utilizing the selective permeability of the film to gas molecules such as oxygen, carbon dioxide and the like, the ideal microenvironment of low oxygen and high carbon dioxide atmosphere can be maintained or quickly established in the fruit and vegetable package, the respiration of the fruit and vegetable can be effectively inhibited, and the better fresh-keeping effect can be achieved.

Specifically, when the permeability and the selective permeability of the fruit and vegetable packaging material are proper and oxygen in the package cannot meet the breathing requirement, a certain amount of oxygen enters the package through the film to supplement the breathing consumption under the promotion of concentration difference and the control of the permeability of the film. Meanwhile, carbon dioxide generated by respiratory metabolism can be discharged through the film in time, and a microenvironment combining proper humidity with low oxygen and high carbon dioxide in the package is maintained, so that the effect of modified atmosphere preservation is achieved.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. It will be readily apparent to those skilled in the art that various modifications to these embodiments and the generic principles defined herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above-described embodiments. Those skilled in the art should appreciate that many modifications and variations are possible in light of the above teaching without departing from the scope of the invention.