Ethylene-vinyl alcohol copolymer composite material as well as preparation method and application thereof
Through the composite material of ethylene-vinyl alcohol copolymer and polyoxylate molecular clusters, the problem of degradation of gas barrier properties and complex processing in high humidity is solved, and low-cost and high-performance packaging material preparation is achieved, suitable for food and pharmaceutical packaging.
Patent Information
- Application Number
- CN202510639928.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-19
- Publication Date
- 2025-08-19
AI Technical Summary
The existing ethylene-vinyl alcohol copolymer (EVOH) has reduced gas barrier properties and complex processing technology and high production costs in high humidity environments, which limits its wide application.
A composite material of ethylene-vinyl alcohol copolymer and polyoxygenate molecular cluster is prepared by solution casting method, and the polyoxygenate molecular cluster forms hydrogen bond interaction with EVOH to improve compatibility, form a bicontinuous phase structure with stable structural structure, and improve gas barrier and mechanical properties.
The prepared composite materials still maintain excellent gas barrier properties under high humidity environments, have excellent mechanical properties, low production costs, and are suitable for large-scale industrial production and applications.
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Figure CN120504899A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of organic-inorganic composite materials, and in particular to an ethylene-vinyl alcohol copolymer composite material and a preparation method and application thereof. Background Art
[0002] Ethylene-vinyl alcohol copolymer (EVOH) is produced by copolymerizing ethylene and vinyl acetate and then hydrolyzing them. It possesses strong gas barrier properties (for example, strong barrier capabilities against gases such as oxygen, carbon dioxide, and nitrogen), high transparency, high gloss, and excellent oil and chemical resistance. It is an ideal packaging material for extending the shelf life of products in the food and pharmaceutical industries, and has broad application prospects.
[0003] However, because the polyvinyl alcohol (PVA) segments in EVOH contain a large number of hydroxyl groups, EVOH is sensitive to humidity. In high-humidity environments, EVOH's gas barrier properties significantly decrease. This problem is often overcome by combining it with other materials (e.g., polyethylene, polypropylene, etc.) to create a multilayer composite structure. However, the preparation of multilayer composite structures not only increases the process difficulty but also increases production costs. Furthermore, because EVOH itself has a strong eutectic nature (polyethylene and polyvinyl alcohol have a strong eutectic nature), the current industrial production of EVOH film primarily uses a melt extrusion process, which is relatively limited in processing methods and places high demands on processing equipment, severely restricting the expanded application of EVOH.
[0004] Therefore, it is of great significance to develop an ethylene-vinyl alcohol copolymer composite material with good gas barrier properties, excellent mechanical properties, good processing properties and low production cost. Summary of the Invention
[0005] The purpose of the present invention is to provide an ethylene-vinyl alcohol copolymer composite material and a preparation method and application thereof.
[0006] The technical solution adopted by the present invention is:
[0007] An ethylene-vinyl alcohol copolymer composite material comprises an ethylene-vinyl alcohol copolymer and a polyoxometalate molecular cluster.
[0008] Preferably, the mass ratio of the ethylene-vinyl alcohol copolymer to the polyoxometalate molecular cluster is 1:0.5-5.
[0009] Further preferably, the mass ratio of the ethylene-vinyl alcohol copolymer to the polyoxometalate molecular cluster is 1:1-3.
[0010] More preferably, the mass ratio of the ethylene-vinyl alcohol copolymer to the polyoxometalate molecular cluster is 1:2-3.
[0011] Preferably, the molar percentage of ethylene units in the ethylene-vinyl alcohol copolymer is 24 mol% to 44 mol%.
[0012] Preferably, the number average molecular weight of the ethylene-vinyl alcohol copolymer is 10,000 g / mol to 50,000 g / mol.
[0013] Preferably, the polyoxometalate molecular cluster is at least one of a Keggin-type polyoxometalate molecular cluster, a Dawson-type polyoxometalate molecular cluster, and a pentavanadate-type polyoxometalate molecular cluster.
[0014] Preferably, the general structural formula of the Keggin-type polyoxometalate molecular cluster is as follows: n [XM 12 O 40 ] n- ·mH2O, wherein X represents the central atom, X is selected from at least one of P, Si, Co, and Al, Y represents the counter ion, Y is selected from at least one of H, Li, Na, and K, M represents the coordinating atom, M is selected from at least one of Nb, W, and Mo, m represents the number of crystal waters, the number of m depends on the self-bound water and the specific environmental humidity, m is an integer from 0 to 40, and n represents the number of charges carried by the polyanion / the number of counter ions, and n is 3, 4, or 6.
[0015] Further preferably, the Keggin type polyoxometalate molecular cluster is a silicotungstic acid molecular cluster (X4[SiW 12 O 40 ] 4- ·mH2O), phosphotungstic acid molecular clusters (X3[PW 12 O 40 ] 3- ·mH2O), cobalt tungstate molecular clusters (X6[CoW 12 O 40 ] 6- ·mH2O).
[0016] More preferably, the Keggin-type polyoxometalate molecular cluster is a silicotungstic acid molecular cluster H4[SiW 12 O 40 ] 4- ·26H2O (abbreviated as SiW 12 ).
[0017] Preferably, the general structural formula of the Dawson type polyoxometalate molecular cluster is as follows: n [X2M 18 O 62 ] n-·mH2O, wherein X represents the central atom, X is selected from at least one of P, Si, Co, and Al, Y represents the counter ion, Y is selected from at least one of H, Li, Na, and K, M represents the coordinating atom, M is selected from at least one of Nb, W, and Mo, m represents the number of crystallization waters, the number of m depends on the self-bound water and the specific environmental humidity, m is an integer from 0 to 60, and n represents the number of charges carried by the polyanion / the number of counter ions, and n is 3, 4, 6, or 8.
[0018] Further preferably, the Dawson type polyoxometalate molecular cluster is H6[P2W 18 O 62 ] 6- 14H2O (abbreviated as P2W 18 ).
[0019] Preferably, the structural formula of the pentavanadate-type polyoxometalate molecular cluster is Li7[V 15 O 36 (CO3)]·39H2O.
[0020] A preparation method of the ethylene-vinyl alcohol copolymer composite material as described above comprises the following steps: dispersing the ethylene-vinyl alcohol copolymer and polyoxometalate molecular clusters in a solvent to prepare a casting solution, coating the casting solution on a substrate to form a film, and drying to obtain the ethylene-vinyl alcohol copolymer composite material.
[0021] Preferably, the dispersion is carried out at a temperature of 50°C to 100°C.
[0022] Preferably, the solvent is at least one of water, methanol, ethanol, n-propanol, N,N-dimethylformamide, and dimethyl sulfoxide.
[0023] Preferably, the coating method is at least one of spin coating, drop coating, blade coating, and dip coating.
[0024] Preferably, the substrate is one of a PMMA substrate, a PS substrate, a PTFE substrate and a glass substrate.
[0025] Preferably, the drying comprises the following process: first drying at a temperature of 35°C to 45°C for 4h to 8h, and then vacuum drying at a temperature of 70°C to 80°C for 4h to 8h.
[0026] A gas barrier film comprises the ethylene-vinyl alcohol copolymer composite material.
[0027] A use of the ethylene-vinyl alcohol copolymer composite material as described above in the preparation of food packaging, pharmaceutical packaging, oil tanks or floor heating pipes.
[0028] The beneficial effects of the present invention are as follows: the ethylene-vinyl alcohol copolymer composite material of the present invention has the advantages of good gas barrier properties, excellent mechanical properties, good processing properties, etc., and is suitable for use as a packaging material in the fields of food, medicine, etc., and its preparation method is simple and the production cost is low, and it is suitable for large-scale industrial production and application.
[0029] Specifically:
[0030] 1) The present invention utilizes hydrogen bonding interactions between polyoxometalate molecular clusters and the hydrophilic domains of EVOH (amphiphilic), thereby improving the compatibility of EVOH with solvents. Thus, ethylene-vinyl alcohol copolymer composites can be prepared by solution casting. This method is simple, has low production costs, and is easy to recycle. Furthermore, the polyoxometalate molecular clusters can complex with EVOH through supramolecular interactions to induce the formation of a structurally stable bicontinuous phase structure, effectively improving the elastic modulus of the composite material, ultimately resulting in a composite material with both high gas barrier properties and excellent mechanical properties.
[0031] 2) The ethylene-vinyl alcohol copolymer composite material of the present invention is in a uniform solid film state in a dry state, and has excellent gas barrier properties even in a high humidity environment, and is suitable for use as a packaging material in the fields of food, medicine, etc.;
[0032] 3) The raw materials for preparing the ethylene-vinyl alcohol copolymer composite material of the present invention are green, non-toxic and harmless EVOH and polyoxometalate molecular clusters, which have the advantages of being green, environmentally friendly and highly safe;
[0033] 4) The preparation method of the ethylene-vinyl alcohol copolymer composite material of the present invention is simple and easy. It only requires dissolving the polyoxometalate molecular clusters and EVOH in a solvent to prepare a solution and then casting the solution into a film. The product process quality is easy to control, which is conducive to large-scale industrial production and application. BRIEF DESCRIPTION OF THE DRAWINGS
[0034] Figure 1 This is a physical picture of the ethylene-vinyl alcohol copolymer composite material of Example 3.
[0035] Figure 2 This is the TEM image of the ethylene-vinyl alcohol copolymer composite material of Example 3.
[0036] Figure 3 SWAXS graphs of the ethylene-vinyl alcohol copolymer composite material, silicotungstic acid and EVOH of Examples 1 to 3.
[0037] Figure 4 These are stress-strain curves of the ethylene-vinyl alcohol copolymer composite material and the EVOH film of Examples 1 to 4.
[0038] Figure 5 These are TGA curves of the ethylene-vinyl alcohol copolymer composite material of Example 2, the ethylene-vinyl alcohol copolymer composite material of Example 3, and EVOH.
[0039] Figure 6 Graph showing the gas barrier properties test results of the ethylene-vinyl alcohol copolymer composite material and EVOH film of Example 3.
[0040] Figure 7 Graph showing the gas barrier properties test results of the ethylene-vinyl alcohol copolymer composite material and EVOH film of Example 4 in a high humidity environment. DETAILED DESCRIPTION
[0041] The present invention will be further explained and illustrated below with reference to specific embodiments.
[0042] Example 1:
[0043] An ethylene-vinyl alcohol copolymer composite material, the preparation method of which is as follows:
[0044] 1g of ethylene-vinyl alcohol copolymer (the molar percentage of ethylene units is 32mol%, and the number average molecular weight is 44000g / mol) and 1g of silicotungstic acid molecular clusters H4[SiW 12 O 40 ] 4- ·26H2O(SiW 12 ) was added into 20 mL of a n-propanol-water mixed solvent (the volume ratio of n-propanol to water was 1:1), and then stirred at 80°C for 3 h to prepare a casting liquid (a clear and transparent solution). The casting liquid was then scraped onto the surface of a PS plastic plate, and then dried at 40°C for 5 h, and then vacuum-dried at 80°C for 8 h to obtain an ethylene-vinyl alcohol copolymer composite material.
[0045] Example 2:
[0046] An ethylene-vinyl alcohol copolymer composite material, the preparation method of which is as follows:
[0047] 1g of ethylene-vinyl alcohol copolymer (the molar percentage of ethylene units is 32mol%, and the number average molecular weight is 44000g / mol) and 2g of silicotungstic acid molecular clusters H4[SiW 12 O 40 ] 4- ·26H2O(SiW 12) was added into 20 mL of a n-propanol-water mixed solvent (the volume ratio of n-propanol to water was 1:1), and then stirred at 80°C for 3 h to prepare a casting liquid (a clear and transparent solution). The casting liquid was then scraped onto the surface of a PS plastic plate, and then dried at 40°C for 5 h, and then vacuum-dried at 80°C for 8 h to obtain an ethylene-vinyl alcohol copolymer composite material.
[0048] Example 3:
[0049] An ethylene-vinyl alcohol copolymer composite material, the preparation method of which is as follows:
[0050] 0.7 g of ethylene-vinyl alcohol copolymer (the molar percentage of ethylene units is 32 mol%, and the number average molecular weight is 44000 g / mol) and 2.1 g of silicotungstic acid molecular clusters H4[SiW 12 O 40 ] 4- ·26H2O(SiW 12 ) was added to 20 mL of a n-propanol-water mixed solvent (the volume ratio of n-propanol to water was 1:1), and then stirred at 80 ° C for 3 h to prepare a casting solution (a clear and transparent solution). The casting solution was then scraped onto the surface of a PS plastic plate, and then dried at 40 ° C for 5 h, and then vacuum dried at 80 ° C for 8 h to obtain an ethylene-vinyl alcohol copolymer composite material (as shown in the actual picture). Figure 1 shown).
[0051] The transmission electron microscope (TEM) image of the ethylene-vinyl alcohol copolymer composite material of this embodiment is as follows: Figure 2 shown.
[0052] Depend on Figure 2 It can be seen that the hydrophilic domain (dark part in the figure) and the hydrophobic domain (light part in the figure) in the ethylene-vinyl alcohol copolymer composite material form a microphase separation structure.
[0053] Example 4:
[0054] An ethylene-vinyl alcohol copolymer composite material, the preparation method of which is as follows:
[0055] 1g of ethylene-vinyl alcohol copolymer (the molar percentage of ethylene units is 32mol%, and the number average molecular weight is 44000g / mol) and 2g of Dawson type polyoxometalate molecular cluster H6[P2W 18 O 62 ] 6- 14H2O(P2W 18) was added into 20 mL of a n-propanol-water mixed solvent (the volume ratio of n-propanol to water was 1:1), and then stirred at 80°C for 3 h to prepare a casting liquid (a clear and transparent solution). The casting liquid was then scraped onto the surface of a PS plastic plate, and then dried at 40°C for 5 h, and then vacuum-dried at 80°C for 8 h to obtain an ethylene-vinyl alcohol copolymer composite material.
[0056] Performance testing:
[0057] 1) The ethylene-vinyl alcohol copolymer composite materials of Examples 1 to 3, the silicotungstic acid molecular cluster H4[SiW 12 O 40 ] 4- The small angle and wide angle X-ray scattering (SWAXS) patterns of 26H2O (referred to as silicotungstic acid) and ethylene-vinyl alcohol copolymer (EVOH) in Example 1 are as follows: Figure 3 shown.
[0058] Depend on Figure 3 It can be seen that the silicotungstic acid molecular clusters are uniformly dispersed in the EVOH polymer matrix without aggregation, and with the addition of silicotungstic acid molecular clusters, the crystallization of EVOH is inhibited.
[0059] 2) The ethylene-vinyl alcohol copolymer composite materials of Examples 1 to 4 and EVOH film (EVOH for short; made of the ethylene-vinyl alcohol copolymer in Example 1, with the same thickness as the ethylene-vinyl alcohol copolymer composite material in Example 1) were subjected to tensile testing (tensile rate of 2 mm / min), and the obtained stress-strain curves are shown in FIG. Figure 4 The test results of elastic modulus, tensile strength and elongation at break are shown in the following table:
[0060] Table 1 Test results of elastic modulus, tensile strength and elongation at break
[0061] Test items EVOH film Example 1 Example 2 Example 3 Example 4 Elastic modulus (MPa) 1362.3 1013.8 1759.0 1705.8 1401.5 Tensile strength (MPa) 54.00 18.14 67.43 68.34 73.74 Elongation at break (%) 18.1 8.6 8.0 5.6 7.8
[0062] Depend on Figure 4As shown in Table 1, after adding polyoxometalate molecular clusters to EVOH, the abundant hydrogen bonding sites on its surface play a cross-linking role in the EVOH matrix. In Example 1, since the amount of added polyoxometalate molecular clusters is too small, the hydrophobic part of the polymer is too separated from the hydrophilic clusters, and it is easy to break from the uneven part during stretching, resulting in a significant decrease in mechanical strength. The ethylene-vinyl alcohol copolymer composites of Examples 2 to 4 with more polyoxometalate molecular clusters added have significantly improved tensile strength and elastic modulus compared with the EVOH film. After the polyoxometalate molecular clusters are cross-linked, the movement between the chain segments is suppressed, so the elongation at break is reduced, indicating that the ethylene-vinyl alcohol copolymer composites of the present invention have excellent mechanical properties.
[0063] 3) The thermogravimetric (TGA) curves of the ethylene-vinyl alcohol copolymer composite material of Example 2, the ethylene-vinyl alcohol copolymer composite material of Example 3, and the ethylene-vinyl alcohol copolymer (EVOH) are as follows: Figure 5 (heating rate is 10℃ / min, temperature range is 0℃~800℃).
[0064] Depend on Figure 5 It can be seen that the decomposition temperature of the ethylene-vinyl alcohol copolymer composite materials of Examples 2 and 3 is about 130° C., which is very stable at general use temperature, indicating that the ethylene-vinyl alcohol copolymer composite materials of the present invention have good thermal stability.
[0065] 4) The ethylene-vinyl alcohol copolymer composite material of Example 3 and an EVOH film (EVOH for short; made of the ethylene-vinyl alcohol copolymer of Example 3 and having the same thickness as the ethylene-vinyl alcohol copolymer composite material of Example 3) are placed between the two chambers of the test chamber, sealed, and then the lower chamber is evacuated, while the upper chamber is maintained with a certain pressure of test gas. As gas molecules pass through the ethylene-vinyl alcohol copolymer composite material, the pressure in the lower chamber gradually increases. This change is monitored by a high-precision pressure sensor, and the gas permeation per unit area per unit time is calculated. The obtained gas barrier test results are shown as follows: Figure 6 shown.
[0066] Depend on Figure 6 It can be seen that EVOH film has very strong gas barrier properties for O2, N2, H2 and CO2 gases, and the gas permeability of O2, N2, H2 and CO2 is 4.27×10 -3 barrer, 5.14×10 -3 barrer, 1.16×10 -2 Barrer and 3.86×10 -3barrer, and although the overall gas barrier performance of the ethylene-vinyl alcohol copolymer composite material of Example 3 has declined, it still has strong gas barrier performance, with the permeability of O2, N2, H2 and CO2 gases being 6.65×10 -3 barrer, 4.41×10 -3 barrer, 2.42×10 -2 Barrer and 5.12×10 -3 Barrer, the gas permeability values of the ethylene-vinyl alcohol copolymer composite material of Example 3 and the EVOH film are in the same order of magnitude, indicating that the addition of polyoxometalate molecular clusters does not have much effect on the gas barrier properties of the system, and the obtained ethylene-vinyl alcohol copolymer composite material still has excellent gas barrier properties.
[0067] In addition, the same test shows that the ethylene-vinyl alcohol copolymer composite materials of Examples 1, 2 and 4 have excellent gas barrier properties.
[0068] 5) The gas barrier properties of the ethylene-vinyl alcohol copolymer composite material of Example 4 and the EVOH film (EVOH for short; made of the ethylene-vinyl alcohol copolymer in Example 4 and having the same thickness as the ethylene-vinyl alcohol copolymer composite material of Example 4) were tested in a high humidity environment (temperature of 25°C and relative humidity of 100%) (test method is the same as above). The results are as follows: Figure 7 shown.
[0069] Depend on Figure 7 It can be seen that: since the polyvinyl alcohol segments in EVOH are highly hydrophilic and contain a large number of hydroxyl groups, moisture in high humidity conditions will cause the free volume of the amorphous region of the EVOH film to increase, thereby increasing the gas permeability of the EVOH film. The gas permeabilities of O2, N2, H2 and CO2 are 0.050 barrer, 0.061 barrer, 0.121 barrer and 0.053 barrer, respectively. Although the gas permeability of the ethylene-vinyl alcohol copolymer composite material of Example 4 will also increase, the value is still at the same order of magnitude as that of the EVOH film. The gas permeabilities of O2, N2, H2 and CO2 are 0.065 barrer, 0.051 barrer, 0.252 barrer and 0.041 barrer, respectively, indicating that the ethylene-vinyl alcohol copolymer composite material of Example 4 can be used under high humidity conditions.
[0070] In addition, the same test shows that the ethylene-vinyl alcohol copolymer composite materials of Examples 1 to 3 can be used under high humidity conditions.
[0071] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.
Claims
1. An ethylene-vinyl alcohol copolymer composite material, characterized in that: The composition includes ethylene-vinyl alcohol copolymer and polyoxometalate molecular clusters.
2. The ethylene-vinyl alcohol copolymer composite material according to claim 1, characterized in that: The mass ratio of the ethylene-vinyl alcohol copolymer to the polyoxometalate molecular cluster is 1:0.5-5.
3. The ethylene-vinyl alcohol copolymer composite material according to claim 1 or 2, characterized in that: The molar percentage of ethylene units in the ethylene-vinyl alcohol copolymer is 24 mol% to 44 mol%.
4. The ethylene-vinyl alcohol copolymer composite material according to claim 1 or 2, characterized in that: The number average molecular weight of the ethylene-vinyl alcohol copolymer is 10,000 g / mol to 50,000 g / mol.
5. The ethylene-vinyl alcohol copolymer composite material according to claim 1 or 2, characterized in that: The polyoxometalate molecular cluster is at least one of a Keggin-type polyoxometalate molecular cluster, a Dawson-type polyoxometalate molecular cluster, and a pentavanadate-type polyoxometalate molecular cluster.
6. The ethylene-vinyl alcohol copolymer composite material according to claim 5, characterized in that: The general structural formula of the Keggin-type polyoxometalate molecular cluster is as follows: n [XM 12 O 40 ] n- ·mH2O, wherein X represents the central atom, X is selected from at least one of P, Si, Co, and Al, Y represents the counter ion, Y is selected from at least one of H, Li, Na, and K, M represents the coordinating atom, M is selected from at least one of Nb, W, and Mo, m represents the number of crystal waters, the number of m depends on the self-bound water and the specific environmental humidity, m is an integer from 0 to 40, and n represents the number of charges carried by the polyanion / the number of counter ions, and n is 3, 4, or 6.
7. The ethylene-vinyl alcohol copolymer composite material according to claim 5, characterized in that: The general structural formula of the Dawson type polyoxometalate molecular cluster is as follows: n [X2M 18 O 62 ] n- mH2O, wherein X represents a central atom, X is selected from at least one of P, Si, Co, and Al, Y represents a counter ion, Y is selected from at least one of H, Li, Na, and K, M represents a coordinating atom, M is selected from at least one of Nb, W, and Mo, m represents the number of crystal waters, the number of m depends on the bound water itself and the specific environmental humidity, m is an integer of 0 to 60, n represents the number of charges carried by the polyanion / the number of counter ions, and n is 3, 4, 6, or 8; the structural formula of the pentavanadate-type polyoxometalate molecular cluster is Li7[V 15 O 36 (CO3)]·39H2O.
8. A method for preparing the ethylene-vinyl alcohol copolymer composite material according to any one of claims 1 to 7, characterized in that: The following steps are involved: The ethylene-vinyl alcohol copolymer and the polyoxometalate molecular cluster are dispersed in a solvent to prepare a casting solution, and the casting solution is then coated on a substrate to form a film, and dried to obtain an ethylene-vinyl alcohol copolymer composite material.
9. A gas barrier film, characterized in that: A composite material comprising the ethylene-vinyl alcohol copolymer according to any one of claims 1 to 7.
10. Use of the ethylene-vinyl alcohol copolymer composite material according to any one of claims 1 to 7 in the preparation of food packaging, pharmaceutical packaging, oil tanks or floor heating pipes.