阅读说明：本技术 一种聚乳酸气体阻隔复合膜的制备方法 (Preparation method of polylactic acid gas barrier composite membrane ) 是由 张启纲 李沅鸿 王威威 蔡文彬 于 2020-12-14 设计创作，主要内容包括：一种聚乳酸气体阻隔复合膜的制备方法,涉及功能高分子材料技术领域,从降低气体分子在表面层的溶解和降低气体分子在聚乳酸材料中的迁移两个方面增强聚乳酸的气体阻隔性能,即在表面引入氧化石墨烯/乙二胺涂层,在聚乳酸材料中引入氨基功能化氧化石墨烯,制备聚乳酸气体阻隔复合膜。本发明有益效果：本发明的聚乳酸气体阻隔复合膜材料对水蒸气和氧气具有较高的阻隔能力,能够满足对气体阻隔要求较高的包装材料领域,具有产业上的广泛利用价值。(A preparation method of a polylactic acid gas barrier composite membrane relates to the technical field of functional polymer materials, and enhances the gas barrier performance of polylactic acid from two aspects of reducing the dissolution of gas molecules in a surface layer and reducing the migration of the gas molecules in the polylactic acid material, namely, a graphene oxide/ethylenediamine coating is introduced into the surface, and amino functionalized graphene oxide is introduced into the polylactic acid material to prepare the polylactic acid gas barrier composite membrane. The invention has the beneficial effects that: the polylactic acid gas barrier composite film material has high barrier capability to water vapor and oxygen, can meet the field of packaging materials with high gas barrier requirements, and has wide industrial utilization value.)

1. A preparation method of a polylactic acid gas barrier composite membrane is characterized by comprising the following steps: the method comprises the following steps:

(1) preparing a composite membrane: dissolving polylactic acid in a solvent, adding amino functionalized graphene oxide into the solvent, oscillating the mixture for 30 minutes by using ultrasonic waves to obtain a mixed solution, pouring the mixed solution into a flat plate mold, and volatilizing the solvent to obtain an amino functionalized graphene oxide/polylactic acid composite membrane;

(2) modification of the composite membrane: spraying a chloroform dispersion liquid of ethylenediamine and a chloroform dispersion liquid of graphene oxide on the surface of the amino functionalized graphene oxide/polylactic acid composite membrane prepared in the step (1) one by one to obtain an ethylenediamine/graphene oxide coating on the surface of the composite membrane;

(3) hot pressing treatment: and (3) carrying out hot-pressing treatment on the composite membrane modified in the step (2), and converting the graphene oxide sheet layer on the surface of the composite membrane into a graphene sheet layer subjected to thermal reduction, so as to obtain the polylactic acid gas barrier composite membrane.

2. The method for preparing a polylactic acid gas barrier composite film according to claim 1, wherein the method comprises the following steps: the solvent in the step (1) is chloroform, and the content of the amino functionalized graphene oxide in the prepared amino functionalized graphene oxide/polylactic acid composite membrane is 0.1% -5%.

3. The method for preparing a polylactic acid gas barrier composite film according to claim 1, wherein the method comprises the following steps: the preparation process of the amino functionalized graphene oxide in the step (1) comprises the following steps: under the condition of stirring at room temperature, dropwise adding a graphene oxide solution into an excessive ethylenediamine solution, wherein the mass ratio of graphene oxide to ethylenediamine is (0.1-0.3): 1.

4. the method for preparing a polylactic acid gas barrier composite film according to claim 1, wherein the method comprises the following steps: the mass concentrations of the chloroform dispersion liquid of the graphene oxide and the chloroform dispersion liquid of the ethylenediamine in the step (2) are both 0.1-0.5%.

5. The method for preparing a polylactic acid gas barrier composite film according to claim 1, wherein the method comprises the following steps: the number of layers of the ethylenediamine/graphene oxide coating in the step (2) is 10-30.

6. The method for preparing a polylactic acid gas barrier composite film according to claim 1, wherein the method comprises the following steps: the temperature of the hot pressing treatment in the step (3) is 150-165 ℃, the time is 2-5 minutes, and the pressure is 2-5 MPa.

Technical Field

The invention belongs to the technical field of functional polymer materials, and particularly relates to a preparation method of a polylactic acid gas barrier composite membrane.

Background

As a renewable material which is rich in source and can be completely and naturally degraded, the polylactic acid can be refined by using various agricultural products such as corn starch and polysaccharide. In addition, the polylactic acid has good processing performance, is a thermoplastic natural high polymer material, and has wide application value in the field of packaging materials. However, polylactic acid contains abundant carboxyl groups, so that the polylactic acid is sensitive to water vapor, the water vapor in the air can be dissolved in the polylactic acid and used as a plasticizer, the mechanical property and the gas barrier property of the polylactic acid are greatly reduced, and the application prospect of the polylactic acid is greatly limited by the defects. Therefore, the research on the gas barrier property, especially the water vapor barrier property, of the polylactic acid is a precondition for the wide application thereof.

Disclosure of Invention

The invention aims to solve the technical problem of providing a preparation method of a polylactic acid gas barrier composite film, and solves the problems of polylactic acid in gas barrier, especially water vapor barrier.

The technical scheme adopted by the invention for solving the technical problems is as follows: a preparation method of a polylactic acid gas barrier composite membrane comprises the following steps:

(1) preparing a composite membrane: dissolving polylactic acid in a solvent, adding amino functionalized graphene oxide into the solvent, oscillating the mixture for 30 minutes by using ultrasonic waves to obtain a mixed solution, pouring the mixed solution into a flat plate mold, and volatilizing the solvent to obtain an amino functionalized graphene oxide/polylactic acid composite membrane;

(2) modification of the composite membrane: spraying a chloroform dispersion liquid of ethylenediamine and a chloroform dispersion liquid of graphene oxide on the surface of the amino functionalized graphene oxide/polylactic acid composite membrane prepared in the step (1) in sequence to obtain an ethylenediamine/graphene oxide coating on the surface of the composite membrane;

(3) hot pressing treatment: and (3) carrying out hot-pressing treatment on the composite membrane modified in the step (2), converting the graphene oxide sheet layer on the surface of the composite membrane into a graphene sheet layer subjected to thermal reduction, improving the hydrophobicity of the material, and obtaining the polylactic acid gas barrier composite membrane.

The solvent in the step (1) is chloroform, and the content of the amino functionalized graphene oxide in the prepared amino functionalized graphene oxide/polylactic acid composite membrane is 0.1-5%.

The preparation process of the amino functionalized graphene oxide in the step (1) comprises the following steps: under the condition of stirring at room temperature, dropwise adding a graphene oxide solution into an excessive ethylenediamine solution, wherein the mass ratio of graphene oxide to ethylenediamine is (0.1-0.3): 1.

the preparation process of the amino functionalized graphene oxide comprises the following steps of dropwise adding a graphene oxide solution into an excessive ethylenediamine solution under stirring at room temperature, wherein the mass ratio of the graphene oxide solution to the excessive ethylenediamine solution is as follows: and (3) graphene oxide: and (3) ethylenediamine = 0.1-0.3: 1, and if the temperature is increased to more than 50 ℃, the ethylenediamine-reduced graphene is obtained, and the content of oxygen in the graphene is reduced, so that the compatibility of the amino-functionalized graphene oxide and the matrix polylactic acid is poor, and the influence of the temperature on the amino-functionalized graphene oxide is large. And dropwise adding the graphene oxide solution into an excessive ethylenediamine solution at room temperature to obtain a clear brown yellow amino functionalized graphene oxide solution, and raising the reaction temperature to be higher than 50 ℃ to obtain a black ethylenediamine reduced graphene dispersion liquid. The dropping sequence of the sample is dropping the graphene oxide solution into the excess ethylenediamine solution.

In the step (2), the mass concentrations of the chloroform dispersion liquid of the graphene oxide and the chloroform dispersion liquid of the ethylenediamine are both 0.1-0.5%.

The number of layers of the ethylenediamine/graphene oxide coating in the step (2) is 10-30.

The temperature of the hot-pressing treatment in the step (3) is 150-165 ℃, the time is 2-5 minutes, and the pressure is 2-5 MPa.

The invention has the beneficial effects that: the polylactic acid gas barrier composite film material has high barrier capability to water vapor and oxygen, can meet the field of packaging materials with high gas barrier requirements, and has wide industrial utilization value, and specifically comprises the following components: (1) the amino functionalized graphene oxide lamella prolongs the permeation path of gas molecules, so that the gas barrier property of the material is enhanced; (2) the amino, hydroxyl and carboxyl of the amino functionalized graphene oxide lamellar layer can form hydrogen bonds with the carboxyl of polylactic acid, so that the interfacial tension is enhanced, and the phase separation of the amino functionalized graphene oxide is reduced; (3) after polylactic acid and amino functionalized graphene oxide are formed into a film by a solution pouring method, a graphene oxide coating and an ethylene diamine coating are introduced on the surface of the film by a spraying method, so that the gas barrier property of the polylactic acid film is further enhanced; (4) the hot-pressing treatment can reduce graphene oxide sheets on the surface of the composite membrane into graphene sheets to improve the hydrophobicity of the membrane, and promote the arrangement ordering of the graphene sheets to further improve the gas barrier property of the composite membrane.

Detailed Description

The technical solution of the present invention is further illustrated by the following specific examples.

According to the principle of diffusion of gas molecules in polymers, gas molecules first dissolve in the surface layer of the polymer, then permeate and migrate in the polymer, and finally escape from the polymer. The invention simultaneously enhances the gas barrier property of the polylactic acid from the following two aspects: (1) reducing the dissolution of gas molecules in the surface layer; (2) the migration rate of gas molecules in the polylactic acid material is reduced. Specifically, a graphene oxide/ethylene diamine coating is introduced on the surface. Because gas molecules cannot be dissolved in the graphene sheet layer, the dissolution of the gas molecules in the surface layer of the material is reduced, and in order to reduce the affinity of the surface layer to water vapor, a hot-pressing treatment process is adopted to reduce the graphene oxide of the coating into a hydrophobic graphene sheet layer, so that the material is changed from hydrophilicity to hydrophobicity; amino functionalized graphene oxide is introduced into the polylactic acid material, and due to the physical barrier effect of the modified graphene, gas molecules have to adopt a more curved permeation route in the composite material, so that the barrier property of the material is improved;

example 1

Dispersing 10 g of polylactic acid (PLA) and 0.01 g of ethylenediamine modified graphene oxide (namely amino functionalized graphene oxide) in 50 ml of chloroform, performing ultrasonic oscillation for 30 minutes, pouring the dispersion liquid in a flat plate mold, and volatilizing a solvent to obtain an amino functionalized graphene oxide/polylactic acid composite film; spraying Ethylenediamine (EDA) chloroform dispersion liquid with the mass concentration of 0.1% on the surface of the amino functionalized graphene oxide/polylactic acid composite membrane, horizontally standing for 5 minutes, and continuously spraying the chloroform dispersion liquid with the mass concentration of 0.1% on the surface of the membrane0.1% Graphene Oxide (GO) chloroform dispersion liquid is horizontally stood for 5 minutes to obtain an ethylene diamine/graphene oxide coating, and the operation is repeated to make the number of the coatings be 10; finally, the composite film with the coating is subjected to hot pressing treatment, the composite film is preheated in a 160 ℃ oven for 3 minutes and is placed in a 160 ℃ oven^oAnd C, pressing for 2 minutes under the pressure of 5MPa under a hot press to obtain the polylactic acid gas barrier composite membrane.

Example 2.

Dispersing 10 g of polylactic acid and 0.1 g of amino functionalized graphene oxide in 50 ml of chloroform, pouring the dispersion liquid in a flat plate mold after ultrasonic oscillation for 30 minutes, and volatilizing a solvent to obtain an amino functionalized graphene oxide/polylactic acid composite membrane; spraying chloroform dispersion liquid of ethylenediamine with the mass concentration of 0.1% on the surface of the amino functionalized graphene oxide/polylactic acid composite membrane, after horizontally standing for 5 minutes, continuously spraying chloroform dispersion liquid of graphene oxide with the mass concentration of 0.1% on the surface of the amino functionalized graphene oxide/polylactic acid composite membrane, horizontally standing for 5 minutes to obtain an ethylenediamine/graphene oxide coating, and repeating the operation to enable the number of the ethylenediamine/graphene oxide coatings to be 10; finally, the polylactic acid composite membrane is subjected to hot pressing treatment, and the composite membrane is treated at 160 DEG^oPreheating in oven C for 3 min, and placing in 160^oAnd C, pressing for 5 minutes under the pressure of 2 MPa by a hot press to obtain the polylactic acid gas barrier composite membrane.

Example 3.

Dispersing 10 g of polylactic acid and 0.1 g of amino functionalized graphene oxide in 50 ml of chloroform, pouring the dispersion liquid in a flat plate mold after ultrasonic oscillation for 30 minutes, and volatilizing a solvent to obtain an amino functionalized graphene oxide/polylactic acid composite membrane; spraying chloroform dispersion liquid of ethylenediamine with the mass concentration of 0.1% on the surface of the amino functionalized graphene oxide/polylactic acid composite membrane, horizontally standing for 5 minutes, spraying chloroform dispersion liquid of graphene oxide with the mass concentration of 0.1% on the surface of the amino functionalized graphene oxide/polylactic acid composite membrane, horizontally standing for 5 minutes to obtain an ethylenediamine/graphene oxide coating, and repeating the operation to enable the number of the ethylenediamine/graphene oxide coatings to be 30; finally, carrying out hot pressing on the amino functionalized graphene oxide/polylactic acid composite membraneTreating the composite film at 160^oPreheating in oven C for 3 min, and placing in 160^oAnd C, pressing for 3 minutes under the pressure of 5MPa by a hot press to obtain the polylactic acid gas barrier composite membrane.

Example 4.

Dispersing 10 g of polylactic acid and 0.5 g of amino functionalized graphene oxide in 50 ml of chloroform, pouring the dispersion liquid in a flat plate mold after ultrasonic oscillation for 30 minutes, and volatilizing a solvent to obtain an amino functionalized graphene oxide/polylactic acid composite membrane; spraying ethylenediamine chloroform dispersion (with the mass concentration of 0.1%) on the surface of the amino functionalized graphene oxide/polylactic acid composite membrane, horizontally standing for 5 minutes, spraying graphene oxide chloroform dispersion (with the mass concentration of 0.1%) on the surface of the amino functionalized graphene oxide/polylactic acid composite membrane, horizontally standing for 5 minutes to obtain an ethylenediamine/graphene oxide coating, and repeating the operation to enable the number of the coatings to be 10; finally, carrying out hot pressing treatment on the amino functionalized graphene oxide/polylactic acid composite membrane, and putting the composite membrane at 160 DEG C^oPreheating in oven C for 3 min, and placing at 150 deg.C^oAnd C, pressing for 2 minutes under the pressure of 5MPa by a hot press to obtain the polylactic acid gas barrier composite membrane.

Example 5.

Dispersing 10 g of polylactic acid and 0.5 g of amino functionalized graphene oxide in 50 ml of chloroform, pouring the dispersion liquid in a flat plate mold after ultrasonic oscillation for 30 minutes, and volatilizing a solvent to obtain an amino functionalized graphene oxide/polylactic acid composite membrane; spraying ethylenediamine chloroform dispersion (with the mass concentration of 0.1%) on the surface of the amino functionalized graphene oxide/polylactic acid composite membrane, horizontally standing for 5 minutes, spraying graphene oxide chloroform dispersion (with the mass concentration of 0.1%) on the surface of the amino functionalized graphene oxide/polylactic acid composite membrane, horizontally standing for 5 minutes to obtain an ethylenediamine/graphene oxide coating, and repeating the operation to enable the number of the ethylenediamine/graphene oxide coatings to be 30; finally, carrying out hot-pressing treatment on the amino functionalized graphene oxide/polylactic acid composite membrane, and carrying out 160% hot-pressing treatment on the amino functionalized graphene oxide/polylactic acid composite membrane^oPreheating in oven C for 3 min, and placing at 150 deg.C^oAnd C, pressing for 5 minutes under the pressure of 5MPa by a hot press to obtain the polylactic acid gas barrier composite membrane.

Comparative example: dissolving 10 g of polylactic acid in 50 ml of chloroform, performing ultrasonic oscillation for 30 minutes, pouring the dispersion liquid in a flat plate mold, and volatilizing the solvent to obtain an amino functionalized graphene oxide/polylactic acid composite membrane; the composite film is arranged at 160^oPreheating in oven C for 3 min, and placing in 160^oAnd C, pressing for 2 minutes under the pressure of 5MPa under a hot press to obtain the polylactic acid gas barrier film.

Oxygen transmission rate measurement: the method is implemented according to the national standard GB/T10382000; the water vapour transmission rate is performed according to GB/T10371988.

Table 1 is a table for measuring the oxygen transmission rate and the water vapor transmission rate of the polylactic acid gas barrier composite film according to each example of the present invention and the polylactic acid gas barrier film according to the comparative example.

Table 1 table for measuring oxygen transmission rate and water vapor transmission rate of polylactic acid gas barrier film in each example and comparative example

	Example 1	Example 2	Example 3	Example 4	Example 5	Comparative example
							Oxygen transmission rate (g.m)-2·d-1)	0.153	0.095	0.061	0.053	0.017	0.230
Water vapor transmission rate (g.m)-2·d-1)	0.155	0.098	0.072	0.066	0.033	0.382

As can be seen from the results in table 1, the introduction of the amino functionalized graphene oxide and the surface coating significantly reduces the oxygen and water vapor permeation rate of the polylactic acid, and the excellent oxygen and water vapor barrier properties of example 5 are derived from the dual barrier effect of the surface barrier coating and the internal modified graphene. Due to the reduced graphene sheet layer on the surface, the surface of the polylactic acid has a hydrophobic characteristic, and the method that the graphene sheet layer blocks oxygen and water vapor from being dissolved in the polylactic acid fundamentally cuts off the permeation source of gas; on the other hand, a small amount of gas molecules dissolved in the polylactic acid are blocked by a plurality of modified graphene sheets (amino functionalized graphene oxide), so that the permeation path of the gas molecules is prolonged, the permeation difficulty is increased, and the gas barrier property of the material is improved.

The above embodiments are only preferred embodiments of the present invention, and the present invention is not limited thereto in any way, and any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention are within the scope of the technical solution of the present invention without departing from the content of the technical solution of the present invention.