A metal oxide / metal ion crosslinked polyvinyl alcohol porous composite material and preparation method thereof

Abstract

The present invention discloses a metal oxide / metal ion crosslinked polyvinyl alcohol porous composite material and a preparation method thereof. A functionalized metal oxide and a surfactant are added to a polyvinyl alcohol solution, and after stirring evenly, an alkali solution containing metal ions is added. After high-speed stirring and foaming, curing is carried out to obtain a metal oxide / metal ion crosslinked polyvinyl alcohol porous composite material; the functionalized metal oxide is a metal oxide with carboxyl groups. The present invention uses surface-functionalized Fe3O4@-COOH powder and Na + as a green composite crosslinking agent to replace aldehydes and interact with PVA macromolecules to form a crosslinked network structure. The present invention does not require the addition of aldehyde substances as crosslinking agents and does not require acids as catalysts for polymerization reactions, solving the problems of high residual aldehyde content and difficulty in completely removing aldehydes in PVA porous materials, as well as the problems of generating highly acidic cleaning waste liquid that requires a large amount of water for washing and causing environmental pollution.

Description

Technical Field

[0001] The present invention relates to the technical field of PVA porous materials, and particularly relates to a metal oxide / metal ion cross-linked polyvinyl alcohol porous composite material and a preparation method thereof. Background Art

[0002] Polyvinyl alcohol (PVA) is a water-soluble linear polymer. Each repeating unit side chain contains a hydrophilic hydroxyl group, and it has good film-forming property, adhesiveness, and biocompatibility. It can be prepared into products with various morphologies through different cross-linking processes and undergo condensation reactions with aldehydes (formaldehyde, acetaldehyde, butyraldehyde) to prepare various polymers, and is widely used. Among them, PVA porous materials (sponges) are widely used in medical polymer materials and the cleaning industry because they are soft and have excellent elasticity after absorbing water and have good biocompatibility.

[0003] Currently, the widely used PVA porous materials are prepared by acetalization of PVA and aldehyde monomers under an acidic catalyst. Under acidic conditions, the carbonyl group of formaldehyde is protonated by H + ⁺, and then forms a hemiacetal structure with the hydroxyl oxygen. The -OH of the hemiacetal is unstable and undergoes dehydration condensation with the hydroxyl hydrogen on PVA to form a cyclic 1,3-dioxane. In addition, the carbonyl group of the aldehyde may also undergo an acetal reaction with one hydroxyl group each in two PVA macromolecules to form a cross-linked network structure between macromolecules, thereby obtaining a polyvinyl alcohol acetal polymer. For example, the patent with the application number 202211246234.5 discloses a PVA composite porous material and its application, and a PVA composite porous material is prepared by reacting and cross-linking PVA with formaldehyde and a polyurethane prepolymer in a solution. However, the existing methods for preparing PVA porous materials by acetalization have the following disadvantages: (1) A large amount of aldehyde compounds such as formaldehyde, acetaldehyde, and butyraldehyde are used as cross-linking agents for condensation reactions during the preparation process, and a large amount of aldehyde remains in the produced porous materials and is difficult to remove completely, which causes great harm to human health during use; (2) Acids such as sulfuric acid and hydrochloric acid are used as catalysts during the preparation process, and a relatively high acid addition amount is required to achieve acetalization. The acidity of the obtained sample after curing is very high, and a large amount of water is required for washing, generating highly acidic cleaning waste liquid, causing environmental pollution and being difficult to post-treat. Therefore, synthesizing a polyvinyl alcohol porous composite material without aldehyde, without acid, and with excellent water absorption and mechanical properties has important theoretical value and practical application value. Summary of the Invention

[0004] Aiming at the above-mentioned prior art, the purpose of the present invention is to provide a metal oxide / metal ion cross-linked polyvinyl alcohol porous composite material and a preparation method thereof. The present invention uses surface-functionalized Fe3O4@-COOH powder and Na +As a green composite crosslinking agent, it replaces aldehydes and interacts with PVA macromolecules to form a crosslinked network structure. In the present invention, there is no need to add aldehyde substances as crosslinking agents and no need for acids as catalysts for polymerization reactions, solving the problems of high residual aldehyde content in PVA porous materials and the difficulty in completely removing them, as well as the problem of generating highly acidic cleaning waste liquid that requires a large amount of water for washing and causes environmental pollution.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] In the first aspect of the present invention, a method for preparing a metal oxide / metal ion crosslinked polyvinyl alcohol porous composite material is provided, which is characterized by including the following steps:

[0007] Add a functionalized metal oxide and a surfactant to a polyvinyl alcohol solution, stir evenly, then add an alkali solution containing metal ions, and after high-speed stirring and foaming, carry out curing to obtain a metal oxide / metal ion crosslinked polyvinyl alcohol porous composite material;

[0008] The functionalized metal oxide is a metal oxide with carboxyl groups.

[0009] Preferably, the metal oxide with carboxyl groups is an iron oxide with surface carboxylation; the alkali solution containing metal ions is an alkali solution containing Na + ions.

[0010] Preferably, the iron oxide with surface carboxylation is carboxylated Fe3O4; the alkali solution containing Na + ions is a NaOH solution, a sodium carbonate solution or a sodium bicarbonate solution.

[0011] Preferably, the addition amount of the carboxylated Fe3O4 accounts for 0.5 - 20% of the mass of the polyvinyl alcohol solution; the mass concentration of the NaOH solution is 15 - 30%, and the addition amount of the NaOH solution accounts for 40 - 120% of the mass of the polyvinyl alcohol solution.

[0012] Preferably, the polyvinyl alcohol solution is obtained by adding polyvinyl alcohol to distilled water and heating and stirring in a constant temperature water bath until the polyvinyl alcohol is completely dissolved; the concentration of the polyvinyl alcohol solution is 0.15 - 0.23 g / mL.

[0013] Preferably, the surfactant is an anionic surfactant; the anionic surfactant is selected from at least one of sodium fatty acid methyl taurate, sodium coconut methyl taurate, and sodium lauroyl methyl taurate; the addition amount of the surfactant accounts for 0.05 - 2.0% of the mass of the polyvinyl alcohol solution.

[0014] The selected anionic surfactant in the present invention has strong foaming ability. The hydrophilic group and hydrophobic group in its molecular structure act together to significantly reduce the surface tension of the solution during the foaming process, making it easier for gas to form stable bubbles in the liquid.

[0015] Preferably, the stirring time is 1 - 6 h.

[0016] Preferably, the high-speed stirring and foaming time is 1 - 3 min, and the stirring speed for high-speed stirring and foaming is 1000 - 3000 r / min; the curing temperature is 70 - 90 °C, and the curing time is 5 - 15 h.

[0017] In the second aspect of the present invention, there is provided a metal oxide / metal ion cross-linked polyvinyl alcohol porous composite material obtained by the above preparation method.

[0018] In the third aspect of the present invention, there is provided the application of the metal oxide / metal ion cross-linked polyvinyl alcohol porous composite material in improving the mechanical properties and water absorption of the cross-linked polyvinyl alcohol porous composite material.

[0019] Advantages of the present invention:

[0020] (1) The present invention uses surface-functionalized Fe3O4@-COOH powder and Na + as a green composite cross-linking agent to interact with PVA macromolecules instead of aldehydes to form a cross-linked network structure, solving the problems of high residual aldehyde content and difficulty in complete removal in PVA porous materials.

[0021] (2) The present invention does not require an acid as a catalyst for the polymerization reaction, eliminating the influence brought by the acid catalyst and solving the problem that due to the high acidity of PVA porous materials, a large amount of water is needed for washing, generating highly acidic cleaning waste liquid and causing environmental pollution.

[0022] (3) The PVA porous material prepared by the present invention is aldehyde-free and acid-free, simple to wash and pollution-free, and has excellent mechanical properties and water absorption properties. Description of the Drawings

[0023] Figure 1 : Preparation mechanism diagram of the Fe3O4 / Na + / PVA porous composite material prepared by the present invention;

[0024] Figure 2 : Physical diagram of the Fe3O4 / Na + / PVA porous composite material in Example 2;

[0025] Figure 3 : Cell morphology (SEM photo) of the Fe3O4 / Na + / PVA porous composite material in Example 2;

[0026] Figure 4 : XRD pattern of the Fe3O4 / Na + / PVA porous composite of Example 2;

[0027] Figure 5 : Tensile stress-strain curve of the Fe3O4 / Na + / PVA porous composite of Example 2;

[0028] Figure 6 : DSC test chart of the Fe3O4 / Na + / PVA porous composite of Example 2;

[0029] Figure 7 : Water absorption rate curve of the Fe3O4 / Na + / PVA porous composite of Example 2. Detailed implementation mode

[0030] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present application belongs.

[0031] As introduced in the background art section, polyvinyl alcohol porous materials are prepared by acetalization of PVA and aldehyde monomers under an acidic catalyst. Aldehyde compounds are used as cross-linking agents for the condensation reaction, and a large amount of aldehyde remains in the produced porous materials and is difficult to completely remove, which causes great harm to human health during use; in the preparation process, acids such as sulfuric acid and hydrochloric acid are used as catalysts, and a relatively high amount of acid is required to achieve acetalization. The resulting sample has a high acidity after curing and requires a large amount of water for washing, generating highly acidic cleaning waste liquid, causing environmental pollution and being difficult to post-treat.

[0032] Based on this, the object of the present invention is to provide a metal oxide / metal ion cross-linked polyvinyl alcohol porous composite material and a preparation method thereof. The present invention uses surface-functionalized Fe3O4@-COOH powder and metal sodium ions Na + as a green composite cross-linking agent to cross-link with PVA to prepare a porous material. A large number of -OH groups are contained in the PVA macromolecular chain, and the surface-modified functionalized Fe3O4 powder has a large number of -COOH groups, which generate esterification reaction, coordination and hydrogen bond interaction with the PVA macromolecules under alkaline conditions. At the same time, the OH - ions in the NaOH solution attack the -OH on the PVA macromolecular chain to be deprotonated to form a part of O - groups, and combine with the free Na +Ionic interactions form complexes, in short, with functionalized Fe3O4 and Na + The synergistic effect forms a multi-crosslinked network structure with PVA macromolecules. At the same time, anionic surfactants are used to reduce the surface tension of the solution, thereby forming a PVA porous material with a uniform and stable pore structure. Figure 1 The cross-linking degree and performance of the porous material can be controlled by adjusting the amount of functionalized Fe3O4 and the concentration of NaOH solution.

[0033] In order to enable those skilled in the art to more clearly understand the technical solution of the present application, the technical solution of the present application will be described in detail below in conjunction with specific embodiments.

[0034] Note: The functionalized Fe3O4 in the present invention is Fe3O4@-COOH, and its preparation method is as follows:

[0035] 20 g of Fe3O4 was dissolved in 100 mL of anhydrous ethanol and dispersed by ultrasonication, and then 1 g of malonic acid was added. After ultrasonic stirring, the mixture was dried at 85°C for about 5 h to obtain surface functionalized Fe3O4@-COOH powder.

[0036] The test materials used in the examples of the present invention are all conventional test materials in the art and can be purchased through commercial channels.

[0037] Embodiment 1:

[0038] In this example, the amount of functionalized Fe3O4 is 9 g, and 15% NaOH solution is used. The preparation steps are as follows:

[0039] (1) Place a four-necked flask equipped with a thermometer, a stirring paddle, and a condenser in a constant temperature water bath. Take 17 g of polyvinyl alcohol granules and add them to the four-necked flask. Add 83 g of distilled water to the four-necked flask. Mechanically stir and dissolve the polyvinyl alcohol in a constant temperature water bath at 90°C for 10 hours until the polyvinyl alcohol is completely dissolved. Reduce the temperature and cool to obtain a completely dissolved viscous and transparent polyvinyl alcohol solution.

[0040] (2) Take 60 g of the completely dissolved polyvinyl alcohol solution in step (1), add 0.05 g of sodium methyl taurine and 9 g of functionalized Fe3O4, and stir thoroughly at a stirring speed of 100 r / min to evenly mix the polyvinyl alcohol, surfactant and functionalized Fe3O4.

[0041] (3) Add 25 g of 15% NaOH solution to the mixed solution in step (2), stir and disperse at 1000 r / min for 2 min to foam, and quickly put the melt into an oven for curing at 80° C. for 10 h after foaming. After curing, wash the material with distilled water to obtain a metal oxide / metal ion cross-linked polyvinyl alcohol porous composite material (denoted as Fe3O4 / Na + / PVA porous composite material).

[0042] Example 2

[0043] In this embodiment, the amount of functionalized Fe3O4 is 7 g, and 20% NaOH solution is used. The preparation steps are as follows:

[0044] (1) Place a four-necked flask equipped with a thermometer, a stirring paddle, and a condenser in a constant temperature water bath. Take 17 g of polyvinyl alcohol granules and add them to the four-necked flask. Add 83 g of distilled water to the four-necked flask. Mechanically stir and dissolve the polyvinyl alcohol in a constant temperature water bath at 90°C for 10 hours until the polyvinyl alcohol is completely dissolved. Reduce the temperature and cool to obtain a completely dissolved viscous and transparent polyvinyl alcohol solution.

[0045] (2) Take 60 g of the completely dissolved polyvinyl alcohol solution in step (1), add 0.05 g of sodium methyl taurine and 7 g of functionalized Fe3O4, and stir thoroughly at a stirring speed of 100 r / min to evenly mix the polyvinyl alcohol, surfactant and functionalized Fe3O4.

[0046] (3) Add 25 g of 20% NaOH solution to the mixed solution in step (2), stir and foam for 2 min using a high-speed stirring disperser at 1000 r / min, and quickly put the melt into an oven for curing at 90° C. for 10 h after foaming. After curing, wash the material with distilled water to obtain a metal oxide / metal ion cross-linked polyvinyl alcohol porous composite material (denoted as Fe3O4 / Na + / PVA porous composite material).

[0047] Example 3

[0048] In this embodiment, the amount of functionalized Fe3O4 is 5 g, and 25% NaOH solution is used. The preparation steps are as follows:

[0049] (1) Place a four-necked flask equipped with a thermometer, a stirring paddle, and a condenser in a constant temperature water bath. Take 17 g of polyvinyl alcohol granules and add them to the four-necked flask. Add 83 g of distilled water to the four-necked flask. Mechanically stir and dissolve the polyvinyl alcohol in a constant temperature water bath at 90°C for 10 hours until the polyvinyl alcohol is completely dissolved. Reduce the temperature and cool to obtain a completely dissolved viscous and transparent polyvinyl alcohol solution.

[0050] (2) Take 60 g of the completely dissolved polyvinyl alcohol solution from step (1), add 0.05 g of sodium cocoyl methyl taurate and 5 g of functionalized Fe3O4, and stir well at a stirring speed of 100 r / min to uniformly mix the polyvinyl alcohol with the surfactant and functionalized Fe3O4.

[0051] (3) Add 25 g of 25% NaOH solution to the mixed solution in step (2), stir and foam for 2 min at 1000 r / min using a high-speed stirring disperser. After foaming, quickly put the melt into an oven for curing at 70 °C for 10 h. After curing, wash the material with distilled water to obtain a metal oxide / metal ion cross-linked polyvinyl alcohol porous composite material (denoted as Fe3O4 / Na + / PVA porous composite material).

[0052] Example 4

[0053] In this example, the amount of functionalized Fe3O4 used is 3 g, and 30% NaOH solution is used. The preparation steps are as follows:

[0054] (1) Install a four-necked flask equipped with a thermometer, a stirring paddle, and a condenser in a constant temperature water bath. Take 17 g of polyvinyl alcohol particles and add them to the four-necked flask. Add 83 g of distilled water to the four-necked flask, and mechanically stir and dissolve in a constant temperature water bath at 90 °C for 10 h until the polyvinyl alcohol is completely dissolved. Cool down to obtain a completely dissolved viscous and transparent polyvinyl alcohol solution.

[0055] (2) Take 60 g of the completely dissolved polyvinyl alcohol solution from step (1), add 0.05 g of sodium lauroyl methyl taurate and 3 g of functionalized Fe3O4, and stir well at a stirring speed of 100 r / min to uniformly mix the polyvinyl alcohol with the surfactant and functionalized Fe3O4.

[0056] (3) Add 25 g of 30% NaOH solution to the mixed solution in step (2), stir and foam for 2 min at 1000 r / min using a high-speed stirring disperser. After foaming, quickly put the melt into an oven for curing at 80 °C for 10 h. After curing, wash the material with distilled water to obtain a metal oxide / metal ion cross-linked polyvinyl alcohol porous composite material (denoted as Fe3O4 / Na + / PVA porous composite material).

[0057] Comparative Example 1

[0058] The difference from Example 2 is that no functionalized Fe3O4 is added, and finally a metal ion cross-linked polyvinyl alcohol porous composite material (denoted as Na + / PVA composite material) is obtained.

[0059] Comparative Example 2

[0060] The difference from Example 2 is that no 20% NaOH solution is added, and finally a metal oxide cross-linked polyvinyl alcohol composite material (denoted as Fe3O4 / PVA composite material) is obtained.

[0061] Comparative Example 3

[0062] The difference from Example 2 is that the 20% NaOH solution is replaced with an equal amount of 5% NaOH solution, and finally a cross-linked polyvinyl alcohol composite material is obtained.

[0063] Comparative Example 4

[0064] The difference from Example 2 is that the 20% NaOH solution is replaced with an equal amount of 40% NaOH solution, and finally a cross-linked polyvinyl alcohol porous composite material is obtained.

[0065] Comparative Example 5

[0066] According to the patent with the application number CN200410014019.8, in this comparative example, formaldehyde is used as a cross-linking agent, and sulfuric acid is added for foaming to obtain a cross-linked polyvinyl alcohol porous material. The preparation steps are as follows:

[0067] (1) Install a four-necked flask equipped with a thermometer, a stirring paddle, and a condenser in a constant temperature water bath. Take 17 g of polyvinyl alcohol particles and add them to the four-necked flask. Add 83 g of distilled water to the four-necked flask, and mechanically stir and dissolve in a 90°C constant temperature water bath for 10 h until the polyvinyl alcohol is completely dissolved. Cool down and obtain a viscous, transparent, and completely dissolved polyvinyl alcohol solution.

[0068] (2) Take 60 g of the completely dissolved polyvinyl alcohol solution from step (1), add 0.05 g of sodium lauroyl methyl taurate and 14 g of liquid formaldehyde, and stir well at a stirring speed of 100 r / min to mix the polyvinyl alcohol, surfactant, and liquid formaldehyde evenly.

[0069] (3) Add 10 g of 62% H2SO4 solution to the mixed solution in step (2), stir and foam at 1000 r / min with a high-speed stirring disperser for 2 min. After foaming, quickly put the melt into an oven for curing at 80°C for 18 h. After curing, wash the material with distilled water to obtain a polyvinyl formal porous composite material (denoted as PVA formaldehyde porous composite material).

[0070] Test Example

[0071] 1. Mechanical property testing

[0072] The Instron-5569 electronic universal tensile testing machine was used to test the tensile properties of the PVA porous composites prepared in Examples 1-4 and Comparative Examples 1-5. The PVA porous materials were made into regular cuboids (length 25 mm, width 10 mm, thickness 2 mm) for tensile property testing.

[0073] 2. Water absorption rate test

[0074] Referring to GB / T8810-2005 for the water absorption rate test of samples, after drying the PVA porous composites prepared in Examples 1-4 and Comparative Examples 1-5 in an oven, small pieces of samples were taken and weighed with an electronic balance for their mass. m 0 . Without external force, the PVA porous composites were allowed to absorb water freely. After the materials were completely saturated with water, the mass of the sponge was weighed at this time. m c , and the water absorption rate was calculated using Equation 1-1.

[0075] .

[0076] 3. DSC test

[0077] The 910S differential thermal analyzer was used to test the glass transition temperature (Tg) of the PVA porous composites prepared in Examples 1-4 and Comparative Examples 1-5. After drying the PVA porous composites in an oven, they were taken out and cut into thin slices. Then, about 10 mg of the sample was weighed and placed in an aluminum crucible. The initial temperature was set at room temperature, the final temperature was 150 °C, and the programmed heating rate was 5 °C / min.

[0078] The results of the above three tests are shown in Table 1.

[0079] Table 1 Performance test results of the polyvinyl alcohol composites prepared in Examples 1-4 and Comparative Examples 1-5

[0080]

[0081] As can be seen from Comparative Examples 1-2 in Table 1, in the absence of NaOH solution, the materials prepared from functionalized Fe3O4 and PVA have no pores, and at the same time, the porous materials formed by simply using Na + as a crosslinking agent with PVA only contain a small number of pores. Therefore, the present invention uses surface-functionalized Fe3O4 metal oxide and metal sodium ion Na + as a green composite crosslinking agent to prepare polyvinyl alcohol porous materials.

[0082] As can be seen from Comparative Examples 3-4 in Table 1, when the concentration of the NaOH solution is relatively low or relatively high, the prepared porous materials only contain a small number of pores. Therefore, the concentration of the NaOH solution is 15-30%.

[0083] It can be seen from Figure 1 that the Fe3O4 / Na + / PVA porous composite prepared by the present invention forms a stable network structure through multiple crosslinkings.

[0084] It can be seen from Figure 2 and Figure 3 that the Fe3O4 / Na + / PVA porous composite prepared in Example 2 has a three-dimensional network porous structure.

[0085] It can be seen from Figure 4 that in Example 2, the functionalized Fe3O4 and PVA are successfully compounded to prepare the Fe3O4 / Na + / PVA porous composite.

[0086] It can be seen from Figures 5 to 7 that the Fe3O4 / Na + / PVA porous composite prepared in Example 2 has a relatively high crosslinking degree, excellent mechanical properties, and at the same time, due to its porous structure, it has excellent water absorption properties.

[0087] The present invention uses functionalized Fe3O4 and Na + as green composite crosslinking agents for polyvinyl alcohol, replacing aldehydes to interact with polyvinyl alcohol macromolecules to form a crosslinked network structure. Under alkaline conditions, an esterification reaction, coordination, and hydrogen bond interaction occur between the functionalized Fe3O4 and polyvinyl alcohol macromolecules. At the same time, the introduction of metal ions Na + produces a complexation effect with the polyvinyl alcohol macromolecular chain. The synergistic effect of the composite crosslinking agents enables it to form a stable multiple crosslinked network structure, thereby preparing a polyvinyl alcohol porous composite without aldehydes and acids, with simple washing and no pollution, and excellent mechanical properties and water absorption properties.

[0088] The above are only the preferred embodiments of the present application and are not used to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A metal oxide / metal ion cross-linked polyvinyl alcohol porous composite material, characterized in that, Prepared by the following method: Adding a functionalized metal oxide and a surfactant to a polyvinyl alcohol solution, uniformly stirring, then adding an alkaline solution containing metal ions, and performing solidification after high-speed stirring and foaming to obtain a metal oxide / metal ion cross-linked polyvinyl alcohol porous composite material; The functionalized metal oxide is a metal oxide with carboxyl groups; The metal oxide with carboxyl groups is iron oxide with surface carboxylation; the alkaline solution containing metal ions is an alkaline solution containing Na + ; The surface carboxylated iron oxide is carboxylated Fe3O4; the lye containing Na + is NaOH solution, sodium carbonate solution or sodium bicarbonate solution; The addition amount of the carboxylated Fe3O4 accounts for 0.5-20% of the mass of the polyvinyl alcohol solution; the mass concentration of the NaOH solution is 15-30%, and the addition amount of the NaOH solution accounts for 40-120% of the mass of the polyvinyl alcohol solution; The mass concentration of the polyvinyl alcohol solution is 0.15-0.23 g / mL.

2. The metal oxide / metal ion crosslinked polyvinyl alcohol porous composite material according to claim 1, wherein The polyvinyl alcohol solution is obtained by adding polyvinyl alcohol to distilled water and heating and stirring in a constant temperature water bath until the polyvinyl alcohol is completely dissolved.

3. The metal oxide / metal ion crosslinked polyvinyl alcohol porous composite material according to claim 1, wherein The surfactant is an anionic surfactant; the anionic surfactant is selected from at least one of sodium fatty acid methyl taurate, sodium coconut oil methyl taurate, and sodium lauroyl methyl taurate; the addition amount of the surfactant accounts for 0.05-2.0% of the mass of the polyvinyl alcohol solution.

4. The metal oxide / metal ion crosslinked polyvinyl alcohol porous composite material according to claim 1, characterized in that, The stirring time is 1-6 h.

5. The metal oxide / metal ion crosslinked polyvinyl alcohol porous composite material according to claim 1, characterized in that, The time for high-speed stirring and foaming is 1-3 min, and the stirring speed for high-speed stirring and foaming is 1000-3000 r / min; the solidification temperature is 70-90 °C, and the solidification time is 5-15 h.

6. Use of the metal oxide / metal ion cross-linked polyvinyl alcohol porous composite material according to any one of claims 1-5 in improving the mechanical properties and water absorption of the cross-linked polyvinyl alcohol porous composite material.

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