Preparation and application of modified cellulose EVA film

Abstract

The invention discloses preparation and application of a modified cellulose EVA (Ethylene Vinyl Acetate) film. The preparation method of the modified cellulose EVA film comprises the following steps: adding butyrolactone and an amine catalyst into an ionic liquid solution containing cellulose acetate to obtain a reaction solution; carrying out heating reaction on the reaction liquid, and removing the ionic liquid to obtain modified cellulose; mixing the modified cellulose with an ethylene-vinyl acetate copolymer, and performing melt extrusion granulation to obtain composite particles; and carrying out hot pressing on the composite particles to obtain the modified cellulose EVA film. The modified cellulose EVA film is further applied to preparation of a breathable cell culture bag. The composite EVA film prepared by the invention has good air permeability and strength, good biocompatibility and low toxicity, can better meet the use requirements of the cell culture bag, and has a better application prospect.

Description

Technical Field

[0001] The invention relates to the preparation and application of a polymer film, in particular to the preparation and application of a modified cellulose EVA film. Background Art

[0002] Cell culture bags have important application value in the biomedical field, and they place higher demands on the performance of film materials. For example, they must have good biocompatibility and a certain degree of permeability to oxygen and carbon dioxide, which are related to cell growth. Polymer materials are the main raw materials for making cell culture bags. Traditional ethylene-vinyl acetate copolymer (EVA) films have low gas permeability, resulting in poor cell culture effects in cell culture bags. Since cell culture bags are a type of special packaging that has relatively stringent requirements on the strength and comprehensive performance of the membrane material (including the permeability of gases, moisture, and microorganisms), developing a membrane material that meets the requirements for cell culture bags has become a technical problem that needs to be solved urgently.

[0003] Adding natural cellulose to composite membranes can effectively improve their flexibility and reduce their weight. Due to its recyclability and biodegradability, natural cellulose has become a promising filler candidate for composite membranes. However, unchemically modified natural cellulose offers limited benefits in improving the membrane's air permeability, making it difficult to form gas transfer channels and failing to meet the requirements for cell culture bags.

[0004] In addition, due to the incompatibility between hydrophilic natural cellulose and hydrophobic EVA matrix, natural cellulose is difficult to be used in modified EVA membranes. In order to solve this problem, the existing technology uses modified cellulose to prepare EVA composite materials, such as modifying cellulose with acid anhydride and glycidyl methacrylate to improve the interfacial adhesion and compatibility of each component of the EVA composite material. Other studies modified nanocellulose crystallites (CNC) by surface grafting and then melt blended to prepare PHBV / CNC biocomposites. Experiments have shown that the difference in interfacial adhesion is between hydrophobic PHBV and hydrophilic CNC. In addition, the study also used palmitoyl chloride and ε-caprolactone to improve the lipophilicity of CNC. The results show that CMC has a heterogeneous nucleation effect on the crystallization process of PHBV, and the interfacial adhesion between CMC-g-CL and PHBV is better (References: Carbohydrate Polymers 242 (2020) 116399; International Journal of Biological Macromolecules, 235 (2023) 123785).

[0005] However, there has been no report on the preparation of high-strength and high-permeability EVA membranes using modified or unmodified cellulose. Summary of the Invention

[0006] Objectives of the Invention: This invention provides a method for preparing a modified cellulose EVA film, addressing the problem of producing a modified cellulose EVA film with high gas permeability and strength. Another objective of the invention is to propose the use of the modified cellulose EVA film in the preparation of breathable cell culture bags, addressing the problem of preparing breathable cell culture bags.

[0007] Technical solution: The method for preparing a modified cellulose EVA film according to the present invention is characterized in that it comprises the following steps:

[0008] (1) adding butyrolactone and an amine catalyst to an ionic liquid solution containing cellulose acetate to obtain a reaction solution;

[0009] (2) heating the reaction solution to react and removing the ionic liquid to obtain modified cellulose;

[0010] (3) mixing the modified cellulose with ethylene-vinyl acetate copolymer and then melt-extruding and granulating the mixture to obtain composite particles;

[0011] (4) The composite particles are hot-pressed to obtain a modified cellulose EVA film.

[0012] This invention modifies micron-sized cellulose through chemical grafting, improving the hydrophilicity / hydrophobicity of the fiber surface. By introducing a large number of ester groups through ring-opening butyrolactone polymerization, it effectively enhances the compatibility of cellulose with ester-rich EVA. Furthermore, the large molecular weight of the modified cellulose forms gas transmission channels within the EVA matrix, improving the air permeability of the EVA film.

[0013] Preferably, in step (1), the preparation method of the ionic liquid solution containing cellulose acetate is:

[0014] The cellulose powder is dissolved in an ionic solution, and then acetic anhydride is added and heated to react to obtain an ionic liquid solution containing cellulose acetate.

[0015] Furthermore, the ionic liquid includes at least one of 1-alkyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium bromide, 1-alkyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium chloride, and methylallylimidazolium chloride.

[0016] Furthermore, the mass ratio of the cellulose powder to the ionic liquid to the acetic anhydride is 0.2-1:3-7:0.5-2, and the heating reaction is carried out at 60-100°C for 4-24 hours. The reaction temperature is preferably 80-100°C.

[0017] Preferably, in step (1), the amine catalyst includes at least one of 4-dimethylaminopyridine or pyridine.

[0018] Preferably, in step (1), the weight ratio of butyrolactone, amine catalyst and ionic liquid solution containing cellulose acetate is 2-6:0.05-0.5:30-80.

[0019] Preferably, in step (2), the reaction solution is heated at 60-150°C for 2-12 hours. The ionic liquid is removed by adding water to the reactants, filtering and washing, removing the ionic liquid, and drying the solid to obtain the modified cellulose. The heating reaction temperature is preferably 80-100°C.

[0020] Preferably, in step (3), the mass ratio of the modified cellulose to the ethylene-vinyl acetate copolymer is 2-5:100; the melting point of the ethylene-vinyl acetate copolymer is 60-90°C, the melt extrusion conditions are twin-screw extrusion at 90-180°C and a rotation speed of 40-80 rpm, and the particle size of the composite particles is 0.5-5 mm.

[0021] Preferably, in step (4), the hot pressing conditions are 135-165° C. and 0.4-0.8 MPa pressure for 20-30 min.

[0022] Another aspect of the present invention discloses the use of the modified cellulose EVA film prepared by the above preparation method in the preparation of a breathable cell culture bag.

[0023] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0024] The composite EVA film produced by the present invention exhibits excellent air permeability and strength, good biocompatibility, and low toxicity, effectively meeting the requirements for cell culture bags and possessing promising application prospects. At normal operating temperatures, the EVA matrix filled with cellulose-grafted polybutyrolactone exhibits good gas permeability. FTIR spectroscopy further confirms the successful production of cellulose-grafted polybutyrolactone. Experimental results demonstrate that the cellulose-grafted polybutyrolactone is uniformly distributed throughout the EVA and is non-toxic, making it suitable for the production of cell culture bags. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is the infrared spectrum of cellulose;

[0026] Figure 2 IR spectrum of cellulose grafted polybutyrolactone (MC-g-GBL) in Example 1;

[0027] Figure 3is the H NMR spectrum of cellulose grafted polybutyrolactone (MC-g-GBL) in Example 1;

[0028] Figure 4 This is a picture of cell culture using the modified cellulose / EVA film in Example 1. DETAILED DESCRIPTION

[0029] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0030] Example 1: A method for preparing a modified cellulose / EVA film is as follows:

[0031] (1) Preparation of cellulose grafted poly-γ-butyrolactone (MC-g-GBL):

[0032] Dissolve 4g of dry micronized cellulose powder in a three-necked flask containing 40g of 1-alkyl-3-methylimidazolium chloride, heat to 80°C, stir for half an hour to obtain a uniform and transparent solution, then add 8g of acetic anhydride and react at 80°C for 12h. After the reaction is complete, add 4g of γ-butyrolactone and 0.25g of 4-dimethylaminopyridine. After reacting at 90°C for 3 hours, add a large amount of deionized water to the reactant, filter and wash it several times to remove the ionic liquid. Place the washed solid in a vacuum oven and dry it to constant weight to obtain the product MC-g-GBL. Its characterization results are shown as follows: Figure 2 and Figure 3 The characterization results of micron-sized cellulose powder are shown in Figure 1 shown.

[0033] (2) The preparation method of the EVA film of this embodiment is as follows:

[0034] In a high-speed mixer, 40g of MC-g-GBL powder was added to 1000g of EVA powder pellets (melting point 75°C) at 400rpm and thoroughly mixed. The EVA / modified cellulose mixture was then added to a twin-screw extruder, heated to 150°C for melt mixing at 60rpm. After cooling and pelletization, composite pellets with a diameter of approximately 1mm were produced.

[0035] (3) Hot pressing the composite particles: 20 g of the composite particles were added to a mold. The hot pressing temperature was 150° C., the pressure was 0.55 MPa, and the time was 20 min. The thickness of the composite film was 0.1 mm.

[0036] Example 2: A method for preparing a modified cellulose / EVA film is as follows:

[0037] (1) Preparation of cellulose grafted poly-γ-butyrolactone (MC-g-GBL):

[0038] Dissolve 1.6g of dry micronized cellulose powder in a three-necked flask containing 24g of 1-ethyl-3-methylimidazolium bromide. Heat to 80°C and stir for half an hour to obtain a homogeneous, transparent solution. Add 4g of acetic anhydride and allow the reaction to continue at 100°C for 4 hours. After completion, add 2g of γ-butyrolactone and 0.05g of 4-dimethylaminopyridine. After reacting at 120°C for 2 hours, add a large amount of deionized water to the reaction mixture. Filter and wash the mixture several times to remove the ionic liquid. The washed solid is then placed in a vacuum oven and dried to a constant weight to obtain the product, MC-g-GBL.

[0039] (2) The preparation method of the EVA film of this embodiment is as follows:

[0040] In a high-speed mixer at 400 rpm, 50 g of MC-g-GBL powder was added to 1000 g of EVA powder pellets (melting point 80°C) and mixed thoroughly. The EVA / modified cellulose mixture was then added to a twin-screw extruder, heated to 160°C, and melt-mixed at 80 rpm. After cooling and pelletization, composite pellets with a diameter of approximately 5 mm were produced.

[0041] (3) Hot pressing the composite particles: 20 g of the composite particles were added to a mold. The hot pressing temperature was 165° C., the pressure was 0.4 MPa, and the time was 30 min. The thickness of the composite film was 0.1 mm.

[0042] Example 3: A method for preparing a modified cellulose / EVA film is as follows:

[0043] (1) Preparation of cellulose grafted poly-γ-butyrolactone (MC-g-GBL):

[0044] 8g of dry micronized cellulose powder was dissolved in a three-necked flask containing 56g of 1-butyl-3-methylimidazolium chloride. The temperature was raised to 60°C and stirred for half an hour to obtain a homogeneous, transparent solution. 16g of acetic anhydride was then added, and the reaction was maintained at 60°C for 24 hours. After completion of the reaction, 6g of γ-butyrolactone and 0.5g of 4-dimethylaminopyridine were added. After reacting at 150°C for 5 hours, a large amount of deionized water was added to the reaction mixture, and the ionic liquid was removed by repeated filtration and washing. The washed solid was placed in a vacuum oven and dried to a constant weight to obtain the product MC-g-GBL.

[0045] (2) The preparation method of the EVA film of this embodiment is as follows:

[0046] In a high-speed mixer at 400 rpm, 20 g of MC-g-GBL powder was added to 1000 g of EVA powder pellets (melting point 60°C) and mixed thoroughly. The EVA / modified cellulose mixture was then added to a twin-screw extruder, heated to 90°C, and melt-mixed at 40 rpm. After cooling and pelletization, composite pellets with a diameter of approximately 2 mm were produced.

[0047] (3) Hot pressing the composite particles: 20 g of the composite particles were added to a mold. The hot pressing temperature was 135° C., the pressure was 0.8 MPa, and the time was 25 min. The thickness of the composite film was 0.1 mm.

[0048] Example 4: A method for preparing a modified cellulose / EVA film is as follows:

[0049] (1) Preparation of cellulose grafted poly-γ-butyrolactone (MC-g-GBL):

[0050] Dissolve 6g of dry micronized cellulose powder in a three-necked flask containing 50g of methylallylimidazole chloride. Heat the mixture to 90°C and stir for half an hour to obtain a homogeneous, transparent solution. Add 10g of acetic anhydride and allow the reaction to continue at 100°C for 6 hours. After completion, add 5g of γ-butyrolactone and 0.1g of 4-dimethylaminopyridine. After reacting at 100°C for 10 hours, add a large amount of deionized water to the reaction mixture. Filter and wash the mixture several times to remove the ionic liquid. The washed solid is then placed in a vacuum oven and dried to a constant weight to obtain the product, MC-g-GBL.

[0051] (2) The preparation method of the EVA film of this embodiment is as follows:

[0052] In a high-speed mixer at 400 rpm, 30 g of MC-g-GBL powder was added to 1000 g of EVA powder pellets (melting point 90°C) and mixed thoroughly. The EVA / modified cellulose mixture was then added to a twin-screw extruder, heated to 165°C, and melt-mixed at 70 rpm. After cooling and pelletization, composite pellets with a particle size of approximately 0.5 mm were produced.

[0053] (3) Hot pressing the composite particles: 20 g of the composite particles were added to a mold. The hot pressing temperature was 140° C., the pressure was 0.7 MPa, and the time was 20 min. The thickness of the composite film was 0.1 mm.

[0054] Comparative Example 1: The rest are the same as Example 1, except that:

[0055] When preparing the EVA film, no MC-g-GBL powder was added, and only EVA powder pellets were used to prepare the film by hot pressing.

[0056] Comparative Example 2: All other aspects are the same as in Example 1, except that:

[0057] When preparing EVA film, MC-g-GBL powder was replaced with micron-sized cellulose powder raw material.

[0058] Comparative Example 3: The rest are the same as Example 1, except that:

[0059] When preparing the EVA film, 40 g of MC-g-GBL powder was replaced with 20 g of micronized cellulose powder and 20 g of poly-γ-butyrolactone (Mw=50,000).

[0060] Comparative Example 4: All other aspects are the same as in Example 1, except that:

[0061] γ-Butyrolactone was replaced by caprolactone.

[0062] Comparative Example 5: The rest are the same as Example 1, except that:

[0063] The EVA powder pellets were replaced with polyethylene terephthalate pellets.

[0064] Comparative Example 6: All other aspects are the same as in Example 1, except that:

[0065] The EVA powder pellets were replaced with polyvinyl chloride pellets.

[0066] Comparative Example 7: The rest are the same as Example 1, except that:

[0067] 4-Dimethylaminopyridine was replaced by tetraisopropoxytitanium.

[0068] The properties of the composite film prepared in Examples 1-4 and Comparative Examples 1-7 were tested as follows:

[0069] Oxygen permeability test:

[0070] The OTR value is measured using an air permeability recorder manufactured by DTS FAAR (Model N 500) in accordance with ASTM 1434.

[0071] The tensile strength of the film was measured according to GB / T 1040.3-2006. The test results are as follows:

[0072] Table 1 Performance test results of EVA films prepared by different methods

[0073] Group <![CDATA[OTR(×10 -5 mL / m 2 )]]> Water absorption (%) Tensile strength (MPa) Example 1 4.78 0.12 16.24 Example 2 4.68 0.13 16.33 Example 3 4.39 0.14 16.52 Example 4 4.53 0.12 16.16 Comparative Example 1 2.24 0.12 16.48 Comparative Example 2 2.17 0.11 2.27 Comparative Example 3 2.04 0.15 0.71 Comparative Example 4 1.86 0.13 11.46 Comparative Example 5 1.31 0.16 4.58 Comparative Example 6 1.94 0.14 6.77 Comparative Example 7 2.52 0.15 2.84

[0074] In the results of Table 1, Comparative Example 1 shows that the air permeability of pure EVA membrane is poor. When MC-g-GBL is added, the air permeability of the films obtained in Examples 1-4 is greatly increased, and the strength of the composite film is not affected. However, as shown in the results of Comparative Example 2, when unmodified cellulose is added to the EVA membrane, not only does it fail to improve the air permeability, but it also causes the strength of the EVA membrane to be greatly reduced. This is mainly due to the agglomeration of unmodified cellulose in the EVA matrix, which is unevenly dispersed, resulting in a significant reduction in the mechanical properties and air permeability of the composite film. Comparative Example 3 shows that pre-polymerized γ-butyrolactone not only does not alleviate the agglomeration of unmodified cellulose in the EVA matrix, but also further hinders the formation of gas channels, causing the air permeability of the composite film to further decrease, while worsening the strength of the composite film. The modified MC-g-GBL can improve the compatibility of cellulose with the EVA matrix and avoid the decline in mechanical properties caused by cellulose agglomeration.

[0075] Comparative Example 4 shows that the effect of acylcellulose grafted with butyrolactone on improving the air permeability of EVA composite film is significantly higher than that of acylcellulose grafted with caprolactone. The reason is the length and structure of the grafted side chain and its influence on the free volume, hydrophilicity and crystallinity of the film. The shorter polybutyrolactone side chain has a higher chain end concentration and higher segment mobility. The chain end and the segment with high mobility are the main contributors to the free volume in the polymer. This larger free volume provides more diffusion channels and dissolution space for gas molecules (including oxygen, carbon dioxide, water vapor, etc.). At the same time, the PBL segment is shorter and has a higher ester group content. Its graft is more compatible with EVA. At the same time, the short side chain has weak crystallization ability, maintains a high amorphous ratio, and reduces the crystallization barrier to gas diffusion. Therefore, the long side chain graft modification strategy of cellulose is not suitable for performance improvement of EVA film.

[0076] Comparative Examples 5 and 6 show that MC-g-GBL cannot be used to improve the permeability of substrates such as PET and PVC. This is primarily due to the poor compatibility of MC-g-GBL with these substrates, which prevents agglomeration and prevents the formation of gas diffusion channels. Consequently, the mechanical properties and permeability of the composite films are relatively low.

[0077] Comparative Example 7 shows that the catalytic efficiency of the metal catalyst for the grafting modification reaction is low, the modified cellulose in the product is less, and the unmodified cellulose accounts for a larger proportion. Therefore, the positive effect of the modified cellulose cannot offset the negative effect of the unmodified cellulose. Therefore, the strength and air permeability of the composite film cannot meet the application requirements of the cell culture bag.

[0078] Since gas diffusion in polymers occurs through the cavities in the volume occupied by molecules, the modified cellulose in this invention increases the available molecular surface area, which positively enhances gas diffusion. Furthermore, the impermeable modified fiber molecules have a larger displacement space, reducing the distance gas molecules must travel, making it easier for them to pass through the membrane surrounding the modified cellulose molecules. By filling EVA with MC-g-GBL, the interpenetrating free space increases, allowing oxygen penetrating the matrix to travel along the free volume surrounding the MC-g-GBL.

[0079] The highly breathable composite film prepared in Example 1 was used in a cell culture experiment. The results are as follows: Figure 4 As shown in the figure, the membrane material has low toxicity and good gas permeability, and is suitable for cell culture and proliferation. Taking all factors into consideration, the composite membrane is suitable for use as a membrane substrate for cell culture bags.

Claims

1. A method for preparing a modified cellulose EVA film, characterized in that: The steps include: (1) adding butyrolactone and an amine catalyst to an ionic liquid solution containing cellulose acetate to obtain a reaction solution; (2) heating the reaction solution to react and removing the ionic liquid to obtain modified cellulose; (3) mixing the modified cellulose with ethylene-vinyl acetate copolymer and then melt-extruding and granulating the mixture to obtain composite particles; (4) The composite particles are hot-pressed to obtain a modified cellulose EVA film.

2. The method for preparing the modified cellulose EVA film according to claim 1, wherein In step (1), the preparation method of the ionic liquid solution containing cellulose acetate is: The cellulose powder is dissolved in an ionic solution, and then acetic anhydride is added and heated to react to obtain an ionic liquid solution containing cellulose acetate.

3. The method for preparing the modified cellulose EVA film according to claim 2, wherein The ionic liquid includes at least one of 1-alkyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium bromide, 1-alkyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium chloride, and methylallylimidazolium chloride.

4. The method for preparing the modified cellulose EVA film according to claim 2, wherein The mass ratio of the cellulose powder to the ionic liquid and the acetic anhydride is 0.2-1:3-7:0.5-2, and the heating reaction condition is 60-100° C. for 4-24 hours.

5. The method for preparing the modified cellulose EVA film according to claim 1, wherein In step (1), the amine catalyst includes at least one of 4-dimethylaminopyridine or pyridine.

6. The method for preparing the modified cellulose EVA film according to claim 1, wherein In step (1), the weight ratio of the butyrolactone, the amine catalyst and the ionic liquid solution containing cellulose acetate is 2-6:0.05-0.5:30-80.

7. The method for preparing the modified cellulose EVA film according to claim 1, characterized in that: In step (2), the reaction liquid is heated at 60-150° C. for 2-12 hours. The method for removing the ionic liquid is as follows: water is added to the reactant, filtered and washed, and after removing the ionic liquid, the solid is dried to obtain the modified cellulose.

8. The method for preparing the modified cellulose EVA film according to claim 1, wherein: In step (3), the mass ratio of the modified cellulose to the ethylene-vinyl acetate copolymer is 2-5:100; the melting point of the ethylene-vinyl acetate copolymer is 60-90°C, the melt extrusion conditions are twin-screw extrusion at 90-180°C and a rotation speed of 40-80 rpm, and the particle size of the composite particles is 0.5-5 mm.

9. The method for preparing the modified cellulose EVA film according to claim 1, wherein: In step (4), the hot pressing conditions are 135-165° C. and 0.4-0.8 MPa pressure for 20-30 min.

10. Use of the modified cellulose EVA film prepared according to the preparation method according to any one of claims 1 to 9 in the preparation of a breathable cell culture bag.

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