CN114805900B - A method for improving the gas barrier properties of a film substrate, film and application - Google Patents

Abstract

The invention discloses a method for improving the gas barrier properties of a matrix, and belongs to the technical field of bioplastic packaging. The technical solution adopted is: a certain mass fraction of cellulose acetate (CA) and glycerin solution is prepared by casting method to prepare cellulose acetate film, and combined with graphene oxide (GO) nanosheets under the action of molecular glue to form a dense composite film material (CA/GO), and then the transition metal oxide nanoparticles (NPs) prepared by the rapid reduction method at room temperature were riveted on the surface of the CA/GO film under the action of hydrogen bonds to achieve precise repair of GO defects, blocking the gas transmission channel, and then High gas barrier CA/GO‑NPs nanocomposite films were obtained. The invention has low energy consumption, simple process flow, easy mass production and large-area production, effectively reduces the permeability of oxygen and water vapor molecules, and is expected to be widely used in the fields of bioplastic-based packaging such as food preservation, pharmaceutical packaging, electronic product packaging, and agricultural packaging. widely used.

Description

A method for improving the gas barrier properties of a film substrate, film and application

technical field

The invention belongs to the technical field of bioplastic gas-resistant films, and in particular relates to a method for improving the gas barrier properties of a matrix.

Background technique

In recent years, with the promulgation of the "Plastic Ban" and people's increasing attention to environmental issues, natural materials as bioplastic packaging have attracted attention due to their biocompatibility, biodegradability, renewability and low cost. More and more attention. In particular, cellulose, the most abundant and renewable natural polysaccharide, can be efficiently isolated from various lignocellulosic biomasses, including wood or agricultural residues. Moreover, as one of the most promising derivatives of cellulose, cellulose acetate (CA) has been widely used in various daily consumer products, such as cigarette filters, textiles, and packaging film materials, etc. However, the high gas permeability of pure CA films severely limits its practical application in the field of bioplastic packaging to protect objects sensitive to oxygen and moisture, especially under high humidity conditions. An effective strategy to overcome this shortcoming is to incorporate appropriate nanofillers, such as montmorillonite, inorganic oxides, and carbonaceous nanomaterials (such as carbon nanotubes, reduced graphene oxide (rGO) and graphene oxide (GO) nanosheets). . Among them, two-dimensional (2D) graphene materials involving stacked GO and rGO nanosheets are considered as new stars among gas barrier materials due to the highly sp2 hybridized carbon framework structure and small lattice parameter of 0.246 nm. Theoretically, defect-free single-layer graphene nanosheets are impermeable to all gases, liquids, and corrosive chemicals. However, various defects, such as Stone-Wales defects, grain boundaries, vacancies, and macroscopic defects, are inevitably generated within the basal plane during the exfoliation process of pristine graphite and the subsequent reduction process, which lead to many microscopic gas transport channels and short gas permeation paths, resulting in poor gas barrier performance.

So far, various GOs and derivatives have been synthesized and introduced into CA film matrices to enhance barrier properties through physical mixing. However, this treatment method limits the progress to further optimize the fundamental physicochemical properties of nanocomposite membranes. Moreover, the dispersion of rGO usually involves the use of toxic organic solvents, causing pollution to the surrounding environment. Therefore, it is more practical to apply GO or rGO as multilayer coatings on different substrate surfaces by spraying, rod coating or dipping techniques, rather than as independent films. However, poor interfacial interactions can easily cause GO or rGO layers to detach from substrates under external physical forces such as bending, stretching, and folding, limiting practical applications. Therefore, it is highly desirable to fabricate robust bioplastic films with high gas resistance.

Contents of the invention

Based on this, it is an object of the present invention to provide a method for improving the gas barrier properties of a matrix.

In order to achieve the above object, the technical scheme adopted in the present invention is:

A certain mass fraction of cellulose acetate and glycerol solution was prepared by casting method to prepare cellulose acetate film, which was combined with GO nanosheets under the action of molecular glue to form a dense composite film material (CA/GO), which was then prepared by rapid reduction method at room temperature Under the action of hydrogen bonds, transition metal oxide nanoparticles (NPs) can be riveted on the surface of CA/GO film to achieve precise repair of GO defects and block the gas transmission channel, so that CA/GO-NPs with high gas barrier properties can be obtained. Composite film material.

The cellulose acetate film prepared by casting a certain mass fraction of cellulose acetate and glycerin solution is to prepare the cellulose acetate film with a mass fraction of 6-18wt.% and a mass fraction of 3wt.%-12wt.%. The plasticizer is dispersed in the acetic acid solution and stirred evenly, and the plasticizer is glycerin.

The specific preparation method is as follows: 1) preparing cellulose acetate film by casting cellulose acetate (CA) and glycerin solution;

2) Combined with graphene oxide (GO) nanosheets under the action of molecular glue to form a dense composite film material (CA/GO);

3) The transition metal oxide nanoparticles (NPs) prepared by the rapid reduction method at room temperature were then riveted on the surface of the CA/GO film under the action of hydrogen bonds of the oxygen-containing groups on the surface of GO in the solution, thereby obtaining a high gas barrier CA /GO-NPs composite films.

The step (1) prepares the cellulose acetate film by casting the cellulose acetate and glycerin solution, and adopts the preparation process of the casting raw material as follows: according to the mass fraction, the cellulose acetate is 6-18wt.% (preferably 10-13wt%) The plasticizer and mass fraction of 3wt.%～12wt.% (preferably 4-7wt.%) are dispersed in the acetic acid solution, stirred evenly, and the plasticizer is glycerol; the thickness of the cellulose acetate film prepared by casting method is 80 -100 μm.

The step (2) is combined with GO nanosheets with a thickness of 1-2nm under the action of molecular glue to form a dense composite film material, and the operation process is:

1) Soak the cellulose acetate film in the chitosan aqueous solution, the film quality is 2-8g (preferably 4-6g), the solution volume is 10-30mL (preferably 20-25mL), the molecular glue action temperature is 40～100°C (preferably 50-70℃), the action time is 5-48h (preferably 20-26h), the type of molecular glue is one or more of chitosan, polyvinyl alcohol, polyethyleneimine and ethylenediaminetetraacetic acid, the concentration 1.0～5wt.% (preferably 2-4wt.%);

2) Take out the film, wash it with water to remove the unreacted molecular glue, and then immerse it in the GO aqueous solution at a temperature of 40-100°C (preferably 50-70°C), and the action time is 5-48h (preferably 20-26h); take out the film , wash with water to remove unfixed GO, and dry at room temperature to obtain a CA/GO film; the concentration of GO in the aqueous solution is 0.1-2 mg/mL (preferably 0.8-1.2 mg/mL), and the volume of GO solution is 10-30 mL (preferably 20- 25mL).

The transition metal oxide nanoparticles (NPs) prepared by the rapid reduction method at room temperature in the step (3) is to obtain a transition metal oxide nanoparticle solution by rapidly reducing transition metal salt ions in a solvent using sodium borohydride at room temperature, and the transition metal One or more of iron, cobalt and nickel, the solvent is ethylene glycol, and the obtained nanoparticles are one or more of iron oxide, cobalt oxide and nickel oxide.

The anion of the transition metal salt is one or two or more of acetate ions, chloride ions, and nitrate ions. The transition metal ion concentration in 10mL of solvent is 10-120mM (preferably 40-60mM), the amount of sodium borohydride added is 50-300mg (preferably 80-120mg), and the reaction temperature is 20-30°C (preferably 24-28°C). The rivet under the action of hydrogen bonds can realize the precise repair of GO defects on the surface of the CA/GO film. The specific process is to soak the prepared CA/GO composite film in the prepared NPs solution, and the film quality is 3-9g (preferably 5g. -7g) The volume of the solution is 5-30mL (preferably 10-15mL), the soaking time is 1-10h (preferably 1.5-3h), and the temperature is 20-30°C, preferably 24-28°C.

The prepared product has the advantages of simple operation, low energy consumption, good repeatability between batches, easy large-scale production, excellent gas barrier performance, etc., and can effectively reduce the permeability of oxygen and water vapor molecules.

Compared with the prior art, the preparation method provided by the invention has the following advantages:

1. The present invention proposes for the first time the simultaneous use of molecular glue and nano-repair strategies to prepare a bioplastic film with stable structure and high barrier properties, which is expected to be widely used in the fields of bioplastic-based packaging such as food preservation, pharmaceutical packaging, electronic product packaging, and agricultural packaging. .

2. The production process for preparing bioplastic film involved in the present invention has low energy consumption, simple process, and is easy to batch and large-scale production.

The following examples are provided in order to further understand the present invention better, are not limited to the best implementation mode, and do not limit the content and protection scope of the present invention, anyone under the inspiration of the present invention or use the present invention Any product identical or similar to the present invention obtained by combining features of other prior art falls within the protection scope of the present invention.

The specific experimental steps or conditions are not indicated in the examples, and all are carried out according to the operation or conditions of the conventional experimental steps described in the literature in this field. The reagents or instruments used were not indicated by the manufacturer, but were commercially available conventional reagents.

Example 1

1) Accurately weigh 12g of cellulose acetate and 5mL of glycerin and dissolve them in 95mL of acetic acid solution, stir well until they are completely dissolved. The cellulose acetate film was obtained by casting method, and dried naturally at room temperature to obtain a CA film with a film thickness of 100 μm.

2) Soak 5 g of cellulose acetate film in 20 mL of chitosan aqueous solution with a concentration of 3 wt.%, and keep it warm at 60° C. for 24 h.

The film was taken out and rinsed with deionized water to remove unreacted molecular glue; then immersed in 20 mL of GO (thickness 1-2 nm) aqueous solution with a concentration of 1 mg/ml, and kept at 60 °C for 24 h. The film was taken out, rinsed with deionized water to remove unfixed GO, and dried at room temperature to obtain a CA/GO film.

3) Accurately weigh 0.18g of cobalt acetate tetrahydrate and dissolve it in 10mL of ethylene glycol, and slowly add 100mg of sodium borohydride under stirring to obtain a uniformly dispersed ethylene glycol solution of cobalt nanoparticles (particle size 2-3nm) .

Soak 6g of CA/GO film in 10mL of the ethylene glycol solution after the above reaction, take it out after 8h, rinse with deionized water to remove the unriveted nanoparticles, and then obtain the CA/GO-NPs composite film.

Example 2

1) Accurately weigh 15g of cellulose acetate and 5mL of glycerin and dissolve them in 95mL of acetic acid solution, stir well until they are completely dissolved. The cellulose acetate film was obtained by casting method, and dried naturally at room temperature to obtain a CA film with a film thickness of 100 μm.

2) Soak 4g of cellulose acetate film in 20mL of 2wt.% polyvinyl alcohol aqueous solution and keep it warm at 90°C for 12h. The film was taken out, rinsed with deionized water to remove unreacted molecular glue, and then immersed in 20 mL of 2 mg/ml GO (thickness 1-2 nm) aqueous solution, and kept at 60 ° C for 10 h. The film was taken out, rinsed with deionized water to remove unfixed GO, and dried at room temperature to obtain a CA/GO film.

3) Accurately weigh 0.18g of nickel acetate tetrahydrate and dissolve it in 10mL of ethylene glycol, slowly add 150mg of sodium borohydride under stirring to obtain a uniformly dispersed ethylene glycol solution of nickel nanoparticles (particle size 2-3nm) .

Soak 6g of CA/GO film in 10mL of the ethylene glycol solution after the above reaction, take it out after 2h, rinse with deionized water to remove unriveted nanoparticles, and obtain CA/GO-NPs composite film.

Example 3

1) Accurately weigh 6g of cellulose acetate and 10mL of glycerin and dissolve them in 90mL of acetic acid solution, stir well until they are completely dissolved. The cellulose acetate film was obtained by casting method, and dried naturally at room temperature to obtain a CA film with a film thickness of 90 μm.

2) Soak 5 g of cellulose acetate film in 20 mL of polyethyleneimine aqueous solution with a concentration of 2 wt.%, and keep it warm at 40° C. for 5 h. The film was taken out, rinsed with deionized water to remove unreacted molecular glue, and then immersed in 20 mL of 2 mg/ml GO (thickness 1-2 nm) aqueous solution, and kept at 50 ° C for 6 h. The film was taken out, rinsed with deionized water to remove unfixed GO, and dried at room temperature to obtain a CA/GO film.

3) Accurately weigh 0.18g of ferric acetate tetrahydrate and dissolve it in 10mL of ethylene glycol, slowly add 300mg of sodium borohydride under stirring to obtain a uniformly dispersed ethylene glycol solution of iron nanoparticles (particle size 2-3nm) .

Soak 6g of CA/GO film in 10mL of the ethylene glycol solution after the above reaction, take it out after 7h, rinse with deionized water to remove unriveted nanoparticles, and then obtain CA/GO-NPs.

Example 4

1) Accurately weigh 12g of cellulose acetate and 8mL of glycerin and dissolve them in 92mL of acetic acid solution, stir well until they are completely dissolved. The cellulose acetate film was obtained by casting method, and dried naturally at room temperature to obtain a CA film with a film thickness of 100 μm.

2) Soak 6g of cellulose acetate film in 20mL of 2wt.% polyethyleneimine aqueous solution, and keep it warm at 70°C for 12h. The film was taken out, rinsed with deionized water to remove unreacted molecular glue, and then immersed in 20 mL of 2 mg/ml GO (thickness 1-2 nm) aqueous solution, and kept at 70 ° C for 12 h. The film was taken out, rinsed with deionized water to remove unfixed GO, and dried at room temperature to obtain a CA/GO film.

3) Accurately weigh 0.09g of iron acetate tetrahydrate and 0.09g of cobalt acetate tetrahydrate and dissolve them in 10mL of ethylene glycol, and slowly add 100mg of sodium borohydride under stirring to obtain iron-cobalt nanoparticles (particle size 2-3nm ) uniformly dispersed ethylene glycol solution.

Soak 6g of CA/GO film in 10mL of the ethylene glycol solution after the above reaction, take it out after 3h, rinse with deionized water to remove unriveted nanoparticles, and then obtain CA/GO-NPs.

Example 5

1) Accurately weigh 14g of cellulose acetate and 8mL of glycerin and dissolve them in 92mL of acetic acid solution, stir well until they are completely dissolved. The cellulose acetate film was obtained by casting method, and dried naturally at room temperature to obtain a CA film with a film thickness of 100 μm.

2) Soak 5g of cellulose acetate film in 20mL of 2wt.% polyethyleneimine aqueous solution, and keep it warm at 80°C for 10h. The film was taken out, rinsed with deionized water to remove unreacted molecular glue, and then immersed in 20 mL of 1 mg/ml GO (thickness 1-2 nm) aqueous solution, and kept at 80 ° C for 10 h. The film was taken out, rinsed with deionized water to remove unfixed GO, and dried at room temperature to obtain a CA/GO film.

3) Accurately weigh 0.18g of ferric acetate tetrahydrate and dissolve it in 10mL of ethylene glycol, slowly add 50mg of sodium borohydride under stirring to obtain a uniformly dispersed ethylene glycol solution of iron nanoparticles (particle size 2-3nm) .

Soak 7g of CA/GO film in 10mL of the ethylene glycol solution after the above reaction, take it out after 5h, rinse with deionized water to remove unriveted nanoparticles, and then obtain CA/GO-NPs.

Composite film gas barrier and stability performance test:

1. Laboratory evaluation method:

1) According to the ASTM D 3985 standard, the oxygen transmission rate (OTR) was measured with a differential pressure gas permeameter (BASIC201, China) at an ambient temperature of 23±2°C and a relative humidity of 50±5%;

2) Water vapor permeability (WVP) was measured by a water vapor permeability tester (PERMEW3/010, LABTHINK, China) at 38±0.5°C and 90±1% relative humidity according to the standard method (ASTM E398).

2. Performance testing

The effects of the three membranes prepared in the above-mentioned Example 1 are compared, and the results are shown in Table 1.

Table 1 Embodiment 1 effect comparison

It can be seen from Table 1 that the barrier effect of the obtained CA/GO-NPs composite film is better than that of other comparative examples, and the oxygen and water vapor transmission rates are significantly lower than those of other comparative examples.

The barrier effects of CA/GO-NPs composite films prepared in the above different examples are compared, and the results are shown in Table 2.

Table 2 Comparison of barrier effects of CA/GO-NPs composite films prepared in different examples

It can be seen from Table 2 that the barrier effect of the CA/GO-NPs composite film obtained in Example 1 is better than that of other examples, and the oxygen and water vapor transmission rates are significantly lower than those of other examples. However, the gas barrier properties of the composite films prepared in Examples 2-5 are better than those of the original CA films, and the oxygen and water vapor transmission rates are significantly lower than the original CA films. On the surface, the inventive method can significantly improve the gas barrier properties of the CA films.

3. Product stability test

The CA/GO-NPs composite film prepared in Example 1 was used to check the stability of the product, and the results are shown in Table 3.

Table 3 Example 1 prepares CA/GO-NPs film stability

It can be seen from Table 3 that the product has excellent structural stability and meets the actual application requirements of bioplastic films. The films prepared in Examples 2-5 also have good stability, and the films have no obvious delamination after continuous bending for 100 times.

The invention discloses a method for improving the gas barrier properties of a substrate, which belongs to the technical field of bioplastic packaging. The experimental results show that the oxygen and water vapor barrier performance of the prepared composite film is better than that of the same type of products, the cost is lower, and the system is stable without delamination.

Claims (13)

1. A method for improving the gas barrier properties of a film substrate, comprising:

1) Preparing a cellulose acetate film from a Cellulose Acetate (CA) solution and a glycerol solution by a tape casting method;

2) Combining with Graphene Oxide (GO) nano sheets under the action of molecular glue to form a compact composite film material (CA/GO);

3) And then, in a solution, the transition metal oxide Nano Particles (NPs) prepared by a rapid reduction method at room temperature are riveted on the surface of the CA/GO film under the action of hydrogen bonds containing oxygen groups on the surface of the GO, so that the high-gas-barrier CA/GO-NPs composite film is obtained.

2. A method according to claim 1, characterized in that: the preparation process of the cellulose acetate film prepared by a casting method through the cellulose acetate and glycerol solution and adopting the casting raw material comprises the steps of dispersing 6-18 wt.% of cellulose acetate and 3-12 wt wt.% of plasticizer in the acetic acid solution according to mass fraction, uniformly stirring, wherein the plasticizer is glycerol; the thickness of the cellulose acetate film prepared by the tape casting method is 80-100 mu m.

3. A method according to claim 2, characterized in that: the preparation process of the cellulose acetate film prepared by the casting method through the cellulose acetate and glycerol solution and adopting the casting raw material comprises the steps of dispersing 10-13% by mass of wt% of cellulose acetate and 4-7% by mass of wt% of plasticizer in the acetic acid solution, and uniformly stirring.

4. A method according to claim 1, characterized in that:

the step (2) is combined with GO nano sheets with the thickness of 1-2nm under the action of molecular glue to form a compact composite film material, and the operation process is as follows:

1) Soaking cellulose acetate film inIn the chitosan aqueous solution, the film mass is 2-8g, the solution volume is 10-30mL molecules, and the glue action temperature is 40-100 ^o C, the acting time is 5-48 h, the molecular glue is one or more of chitosan, polyvinyl alcohol, polyethyleneimine and ethylenediamine tetraacetic acid, and the concentration is 1.0-5 wt%;

2) Taking out the film, washing with water to remove unreacted molecular glue, then immersing in GO aqueous solution at 40-100 DEG C ^o C, the acting time is 5-48 hours; taking out the film, washing with water to remove unfixed GO, and drying at room temperature to obtain a CA/GO film; the concentration of GO in the aqueous solution is 0.1-2mg/mL, and the volume of the GO solution is 10-30 mL.

5. The method of claim 4, wherein:

the step (2) is combined with GO nano sheets with the thickness of 1-2nm under the action of molecular glue to form a compact composite film material, and the operation process is as follows:

1) Soaking cellulose acetate film in chitosan water solution at a film mass of 4-6g, a solution volume of 20-25mL molecules and a glue action temperature of 50-70 ^o C, the acting time is 20-26h, the molecular glue is one or more of chitosan, polyvinyl alcohol, polyethyleneimine and ethylenediamine tetraacetic acid, and the concentration is 2-4 wt%;

2) Taking out the film, washing with water to remove unreacted molecular glue, then immersing in GO aqueous solution at 50-70 deg.C ^o C, the acting time is 20-26 h; taking out the film, washing with water to remove unfixed GO, and drying at room temperature to obtain a CA/GO film; the concentration of GO in the aqueous solution is 0.8-1.2mg/mL, and the volume of the GO solution is 20-25 mL.

6. A method according to claim 1, characterized in that:

the transition metal oxide Nano Particles (NPs) prepared by adopting a rapid reduction method at room temperature in the step (3) are transition metal oxide nano particle solutions obtained by rapidly reducing transition metal salt ions in a solvent at room temperature by adopting sodium borohydride, wherein one or more than two of transition metal iron, cobalt and nickel are obtained, the solvent is ethylene glycol, and the obtained nano particles are one or more than two of ferric oxide, cobalt oxide and nickel oxide.

7. The method of claim 6, wherein: 10 The concentration of transition metal ion in the mL solvent is 10-120mM, the dosage of sodium borohydride is 50-300mg, and the reaction temperature is 20-30 ^o C。

8. The method of claim 7, wherein: 10 The concentration of transition metal ions in the mL solvent is 40-60mM, the dosage of sodium borohydride added is 80-120mg, and the reaction temperature is 24-28 ^o C。

9. The method of claim 6, wherein:

the anions of the transition metal salt are one or more than two of acetate ions, chloride ions and nitrate ions.

10. A method according to claim 1, characterized in that: the rivet can realize GO defect level accurate repair on the surface of the CA/GO film under the action of hydrogen bond, and the specific process comprises the steps of soaking the prepared CA/GO composite film in the prepared NPs solution, wherein the mass of the film is 3-9g, the volume of the solution is 5-30mL, the soaking time is 1-10h, and the temperature is 20-30 ^o C。

11. The method of claim 10, wherein: the rivet can realize GO defect level accurate repair on the surface of the CA/GO film under the action of hydrogen bond, and the specific process comprises the steps of soaking the prepared CA/GO composite film in the prepared NPs solution, wherein the mass of the film is 5-7g, the volume of the solution is 10-15mL, the soaking time is 1.5-3h, and the temperature is 24-28 ^o C。

12. A film prepared by the method of any one of claims 1-11.

13. Use of the film of claim 12 as a packaging film in food preservation, pharmaceutical packaging, electronic product packaging or agricultural product packaging.