A method for producing a polyvinyl alcohol-based foam
By regulating the polyvinyl alcohol chain through the synergistic effect of small organic molecule polyols and inorganic salts, a biodegradable foam material was prepared, solving the problems of difficult foam degradation and high energy consumption, and realizing a simple preparation method and excellent performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-09-28
- Publication Date
- 2026-04-14
AI Technical Summary
Existing foam materials suffer from problems such as difficulty in degradation, high production costs, and high energy consumption during the production process.
Polyvinyl alcohol was used as a raw material. The Hoffmann effect of organic small molecule polyol and inorganic salt was utilized to regulate the polymerization morphology of polyvinyl alcohol chains. Foam materials were prepared by room temperature gelation and room temperature drying.
The preparation of biodegradable foam materials simplifies equipment investment, reduces energy consumption, and possesses excellent mechanical properties, good solar reflectivity, and thermal insulation properties, showing great application potential.
Smart Images
Figure CN117050373B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of polymer material preparation technology, specifically relating to a method for preparing polyvinyl alcohol-based foam material. Background Technology
[0002] Foam, with its unique characteristics of low density, high specific surface area, extremely high porosity, and low thermal conductivity, is widely used in packaging, insulation, shock absorption, and vibration damping. The production and use of foam materials have grown rapidly over the past few decades. However, most commercial foams, such as polystyrene and polypropylene-based foams, are typically made from petroleum-based feedstocks, which can take hundreds of years to degrade in the environment. Furthermore, the production of polyethylene glycol (PED) foam materials often involves freeze-drying and supercritical drying processes, which not only require expensive facilities but also involve intensive energy consumption and greenhouse gas emissions. This poses multiple threats to the sustainable development of human society and has potential harm to human society and health. Therefore, developing biodegradable foam materials through energy-efficient drying methods is urgently needed. Summary of the Invention
[0003] This invention addresses the problems of existing foams being difficult to degrade, having high production costs, and consuming a lot of energy during the production process by providing a method for preparing polyvinyl alcohol-based foam materials. This method solves the problems of high energy consumption in the foam production process, large investment in equipment for traditional production processes, and the difficulty in degrading traditional foam materials.
[0004] To achieve the above objectives, the present invention adopts the following technical solution:
[0005] A polyvinyl alcohol-based foam material is prepared by using polyvinyl alcohol as a raw material and utilizing the synergistic effect of the Hofmannst effect of organic small molecule polyols and inorganic salts to regulate the polymerization morphology of polyvinyl alcohol chains; its preparation method includes the following steps:
[0006] 1) Dissolve polyvinyl alcohol in a binary composite solvent composed of deionized water and small molecule polyol, and stir at 95 °C until completely dissolved to prepare a composite solution;
[0007] 2) Add an inorganic salt with salt-dissolving effect and a pre-prepared inorganic salt solution with salting-out effect to the composite solution obtained in step 1), and continue stirring until completely dissolved;
[0008] 3) Pour the solution obtained in step 2) into a mold and let it polymerize at -20℃ to room temperature for 1 to 10 hours to obtain polyvinyl alcohol-based gel material;
[0009] 4) The polyvinyl alcohol-based gel material obtained in step 3) is dried at room temperature to obtain the polyvinyl alcohol-based foam material.
[0010] Furthermore, the polyvinyl alcohol may be selected from one or more of the grades 1788, 1799, 2088, 2099, 2488, 2499, 2688, and 2699.
[0011] Furthermore, the content of small molecule polyol in the binary composite solvent is 10-35%; the small molecule polyol is selected from one or more of ethylene glycol, glycerol, sorbitol, polyethylene glycol 200, polyethylene glycol 400, and polyethylene glycol 600.
[0012] Furthermore, the concentration of polyvinyl alcohol in the resulting composite solution is 5-20 wt%.
[0013] Furthermore, the inorganic salt with salt-dissolving effect is selected from one or more of lithium chloride, calcium chloride, magnesium chloride, zinc chloride, calcium nitrate, zinc nitrate, and magnesium nitrate; its addition amount is 5 to 20% of the weight of the polyvinyl alcohol used.
[0014] Furthermore, the concentration of the inorganic salt solution with salting-out effect is 20-40 wt%, and its amount is 2-4 times the weight of the polyvinyl alcohol used; the inorganic salt used is selected from one or more of sodium chloride, sodium carbonate, and sodium citrate.
[0015] Furthermore, the drying process includes any one of room temperature drying, freeze drying, and hot air drying.
[0016] The above-mentioned polyvinyl alcohol-based foam materials are used as outer packaging materials for goods or as thermal insulation materials in buildings.
[0017] The significant advantages of this invention are:
[0018] (1) This invention utilizes the synergistic effect of the Hoffmann effect of organic small molecule polyols and inorganic salts to regulate the polymerization morphology of polyvinyl alcohol chains, and prepares foam materials by room temperature gelation and room temperature drying. The preparation method is simple, does not require high equipment investment, and solves the problem of high energy consumption in the foam production process.
[0019] (2) The polyvinyl alcohol-based foam material prepared by the present invention has excellent mechanical properties, good solar reflectivity, good thermal insulation performance and shock absorption capacity, and has great application potential in energy-saving building materials. Moreover, the polyvinyl alcohol material is degradable, which makes up for the defects of traditional foam that is difficult to degrade. Attached Figure Description
[0020] Figure 1 These are photographs of the foam material obtained in Example 1 in different shapes and states.
[0021] Figure 2Porosity and average pore size (a), shrinkage and density (b), and SEM comparison images (c, d) of the foam materials obtained in Examples 1 and 2.
[0022] Figure 3 This is a comparison chart of the mechanical properties of the foam materials obtained in Example 1 and Example 2.
[0023] Figure 4 The images show a comparison of the physical samples (a), porosity and average pore size (b), shrinkage rate and density (c) of the foam materials obtained in Examples 1, 3 and 4, as well as a comparison image (df) using SEM.
[0024] Figure 5 The diagram shows a comparison of the mechanical properties of the foam materials obtained in Examples 1, 3, and 4 (ac), and a demonstration diagram of the shock absorption and cushioning performance of Example 1 (d).
[0025] Figure 6 The test apparatus and results comparison diagram (bd) show the thermal conductivity (a) and heat insulation and heat insulation capabilities of the foam material obtained in Example 1 and the EPE foam material obtained in the comparative example. Detailed Implementation
[0026] A polyvinyl alcohol-based foam material, the preparation method of which includes the following steps:
[0027] 1) Dissolve polyvinyl alcohol in a binary composite solvent composed of deionized water and a small molecule polyol, and stir at 95 °C until completely dissolved to prepare a composite solution with a concentration of 5-20 wt%; the content of the small molecule polyol in the binary composite solvent is 10-35%;
[0028] 2) Add 5-20% by weight of polyvinyl alcohol and an inorganic salt with salt-dissolving effect to the composite solution obtained in step 1), and 2-4 times the weight of polyvinyl alcohol and an inorganic salt solution with salting-out effect at a concentration of 20-40 wt%, and continue stirring until completely dissolved.
[0029] 3) Pour the solution obtained in step 2) into a mold and let it polymerize at -20℃ to room temperature for 1 to 10 hours to obtain polyvinyl alcohol-based gel material;
[0030] 4) The polyvinyl alcohol-based gel material obtained in step 3) is dried at room temperature, freeze-dried, or hot-air dried to obtain the polyvinyl alcohol-based foam material.
[0031] The polyvinyl alcohol may be selected from one or more of the grades 1788, 1799, 2088, 2099, 2488, 2499, 2688, and 2699. The small molecule polyol may be selected from one or more of ethylene glycol, glycerol, sorbitol, polyethylene glycol 200, polyethylene glycol 400, and polyethylene glycol 600. The inorganic salt with salt-soluble properties may be selected from one or more of lithium chloride, calcium chloride, magnesium chloride, zinc chloride, calcium nitrate, zinc nitrate, and magnesium nitrate. The inorganic salt used may be selected from one or more of sodium chloride, sodium carbonate, and sodium citrate.
[0032] To make the content of this invention easier to understand, the technical solution of this invention will be further described below with reference to specific embodiments, but this invention is not limited thereto.
[0033] Example 1
[0034] A method for preparing polyvinyl alcohol-based foam material:
[0035] By weight, 1 part polyvinyl alcohol and 2 parts glycerol were added to 6 parts distilled water and stirred at 95 °C until dissolved. Then, 0.2 parts calcium chloride and 3.2 parts sodium citrate solution with a mass concentration of 37.5% were added sequentially, and stirring was continued until dissolved. The resulting homogeneous solution was then poured into a mold and left at room temperature for 2 hours to obtain a gel material. Finally, the obtained gel material was further dried at room temperature to constant weight to obtain a polyvinyl alcohol-based foam material.
[0036] The pore structure of the foam material was tested as follows: the foam sample was cut into small pieces with tweezers and a knife and sputtered with gold using an ion sputtering instrument. Finally, the microstructure of the cross-section of the aerogel sample was photographed using a scanning electron microscope. The SEM images were then processed using ImageJ software, and the porosity of the foam was found to be 32.2%, with an average pore size of 116.5 μm.
[0037] The density and shrinkage rate of the foam material were tested as follows: Based on the diameter, height, and weight of the gel samples before and after drying, the apparent density of the foam sample was determined to be 0.53 g / cm³. 3 The shrinkage rate was 51.12%.
[0038] The mechanical properties of the foam material were tested as follows: Cylindrical foam samples were placed on a universal testing machine, and the compression speed was set to 5 mm / min. Each sample was tested at least three times to obtain the average value. The compressive strength of the foam was measured to be 0.63 MPa.
[0039] Example 2
[0040] By weight, 1 part polyvinyl alcohol and 2 parts glycerol were added to 6 parts distilled water and stirred at 95 °C until dissolved. Then, 0.2 parts calcium chloride and 3.2 parts sodium citrate solution with a mass concentration of 37.5% were added sequentially, and stirring was continued until dissolved. The resulting homogeneous solution was then poured into a mold and placed at -20 °C for 3 hours to obtain a gel material. Finally, the obtained gel material was placed at room temperature for further drying to obtain a polyvinyl alcohol-based foam material.
[0041] The pore structure, density, shrinkage rate, and mechanical properties of the obtained sample were tested according to the method described in Example 1. The results were as follows: porosity of 33.3%, average pore size of 116.5 μm, and apparent density of 0.53 g / cm³. 3 The shrinkage rate is 50.78%, and the compressive strength is 0.66 MPa.
[0042] Example 3
[0043] By weight, 1 part polyvinyl alcohol and 2 parts glycerol were added to 6 parts distilled water and stirred at 95 °C until dissolved. Then, 0.2 parts calcium chloride and 3.2 parts sodium citrate solution with a mass concentration of 37.5% were added sequentially, and stirring was continued until dissolved. The resulting homogeneous solution was then poured into a mold and left at room temperature for 6 hours to obtain a gel material. Finally, the obtained gel material was further dried in a freeze dryer to obtain a polyvinyl alcohol-based foam material.
[0044] The pore structure, density, shrinkage rate, and mechanical properties of the obtained sample were tested according to the method described in Example 1. The results were as follows: porosity of 33.3%, average pore size of 113.3 μm, and apparent density of 0.53 g / cm³. 3 The shrinkage rate is 50.35%, and the compressive strength is 0.65 MPa.
[0045] Example 4
[0046] By weight, 1 part polyvinyl alcohol and 2 parts glycerol were added to 6 parts distilled water and stirred at 95 °C until dissolved. Then, 0.2 parts calcium chloride and 3.2 parts sodium citrate solution (37.5% by mass) were added sequentially, and stirring continued until dissolved. The resulting homogeneous solution was then poured into a mold and left at room temperature for 6 hours to obtain a gel material. Finally, the obtained gel material was further dried in a dryer at 60 °C to obtain a polyvinyl alcohol-based foam material.
[0047] The pore structure, density, shrinkage rate, and mechanical properties of the obtained sample were tested according to the method described in Example 1. The results were as follows: porosity of 32.2%, average pore size of 116.5 μm, and apparent density of 0.53 g / cm³. 3The shrinkage rate is 50.78%, and the compressive strength is 0.66 MPa.
[0048] Comparative Example
[0049] The EPE foam material was purchased directly.
[0050] Figure 1 The figures show photographs of the foam material obtained in Example 1 in different shapes and states. As can be seen from the figures, the prepared polyvinyl alcohol-based foam material has a low density and can be placed on slender bamboo leaves without falling off (a). In addition to the conventional cubic shape, the prepared polyvinyl alcohol-based foam material can also be molded into complex shapes using mold design (b), and due to the simplicity of the preparation process, large-scale production of foams of different shapes is also possible. Furthermore, when the foam sample is folded twice and then unfolded, the sample quickly returns to its original shape, and no cracks were found on the sample surface, demonstrating outstanding flexibility and foldability (c).
[0051] Figure 2 The figures show the porosity and average pore size (a), shrinkage rate and density (b), and SEM comparison images (c, d) of the foam materials obtained in Examples 1 and 2. As can be seen from the figures, the polyvinyl alcohol-based foam materials prepared by different gelation methods have almost the same pore structure, density, and shrinkage rate, indicating that the polyvinyl alcohol-based foam material can be prepared at room temperature, and its preparation method is simple and energy-saving.
[0052] Figure 3 The graph shows a comparison of the mechanical properties of the foam materials obtained in Examples 1 and 2. As can be seen from the graph, the compressive strength of the polyvinyl alcohol-based foams prepared by different gelation methods is basically the same (a, b). Furthermore, both foam materials prepared by different gelation methods exhibit excellent recovery after 10 repeated compression loading-unloading cycles (c, d), further confirming the feasibility of preparing this polyvinyl alcohol-based foam at room temperature.
[0053] Figure 4 The figures show a comparison of the physical samples (a), porosity and average pore size (b), shrinkage and density (c), and SEM images (df) of the foam materials obtained in Examples 1, 3, and 4. As can be seen from the figures, the polyvinyl alcohol-based foam materials prepared by different drying methods have almost identical appearance, pore structure, density, and shrinkage, indicating that the polyvinyl alcohol-based foam material can be obtained by room temperature drying, and its preparation method is simpler, more energy-efficient, and has lower production costs.
[0054] Figure 5Figures show a comparison of the mechanical properties of the foam materials obtained in Examples 1, 3, and 4 (ac) and a demonstration of the shock absorption performance of Example 1 (d). As shown in the figures, the foam material prepared by this invention can quickly recover to its original shape after one load-unload cycle (a). Furthermore, by comparing the compressive stress-strain curves of polyvinyl alcohol-based foam materials prepared by different drying methods, it can be seen that the compressive strength of polyvinyl alcohol-based foams prepared by different drying methods is basically the same (b, c), indicating that this foam material only needs to be dried at room temperature to prepare a foam material with excellent mechanical properties. In addition, a drop test of a brittle glass sheet was conducted on the foam material prepared by this invention. The glass sheet encased in foam survived the test (d), indicating that the foam material prepared by this invention has great potential in protecting fragile objects from impact.
[0055] The thermal stability of the foam material was tested as follows: The foam material (a cuboid with a height of 2 mm, a length of 15 mm, and a width of 10 mm) was placed on a heating platform at 120 ℃ and heated for 1 min. Thermal images of the prepared foam and commercial plastic foam were collected at 25 ℃ and 250 ℃ using an infrared thermal imager to demonstrate their thermal stability. Simultaneously, parallel experiments were conducted using commercial EPE foam as a control to test its thermal insulation properties. Two different model houses were prepared by attaching 5 mm thick EPE foam material and the foam material prepared according to this invention to one side of a model house with a length of 20 cm, a width of 10 cm, and a height of 14 cm, respectively, with the rest of the parts identical. These two model houses were then placed sequentially in high-temperature (35 ℃) and low-temperature (-20 ℃) environments, and the real-time temperature changes inside the model houses were recorded using thermocouples.
[0056] Figure 6 The figures show the testing apparatus and results (bd) for the thermal conductivity (a) and heat insulation capabilities of the foam material obtained in Example 1 and the EPE foam material obtained in the comparative example. As shown in the figures, the foam material prepared in this invention and the EPE foam material were simultaneously placed on a heating platform at 120 °C and heated for 1 min. The heating rate of the EPE foam material was significantly higher than that of the foam material in this invention (a). Meanwhile, the model house with the foam material of this invention attached exhibited a more gradual temperature change, confirming its great application potential in heat insulation and thermal insulation (c, d).
[0057] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.
Claims
1. A method for preparing a polyvinyl alcohol-based foam material, characterized in that: Using polyvinyl alcohol as raw material, a composite solution is prepared by dissolving polyvinyl alcohol in a binary composite solvent composed of deionized water and small molecule polyol. Then, an inorganic salt solution with salt-dissolving effect and an inorganic salt solution with salting-out effect are added. After stirring evenly, the solution is poured into a mold and placed at -20℃ to room temperature for 1 to 10 hours. The polymerization morphology of the polyvinyl alcohol chain is adjusted by the synergistic effect of the Hofmannst effect of organic small molecule polyol and inorganic salt. After drying, the polyvinyl alcohol-based foam material is obtained. The content of small molecule polyol in the binary composite solvent is 10-35%; the small molecule polyol is selected from one or more of ethylene glycol, glycerol, sorbitol, polyethylene glycol 200, polyethylene glycol 400, and polyethylene glycol 600. The inorganic salt with salt-dissolving effect is selected from one or more of lithium chloride, calcium chloride, magnesium chloride, zinc chloride, calcium nitrate, zinc nitrate, and magnesium nitrate; its addition amount is 5-20% of the weight of polyvinyl alcohol used; The concentration of the inorganic salt solution with salting-out effect is 20-40 wt%, and its amount is 2-4 times the weight of the polyvinyl alcohol used; the inorganic salt used is selected from one or more of sodium chloride, sodium carbonate, and sodium citrate.
2. The method for preparing a polyvinyl alcohol-based foam material according to claim 1, characterized in that: The concentration of polyvinyl alcohol in the resulting composite solution is 5-20 wt%.
3. The method for preparing a polyvinyl alcohol-based foam material according to claim 1, characterized in that: The drying process includes any one of room temperature drying, freeze drying, and hot air drying.
4. A polyvinyl alcohol-based foam material prepared by the method described in any one of claims 1 to 3.
5. The application of the polyvinyl alcohol-based foam material as described in claim 4 as an outer packaging material for articles or as a thermal insulation material in buildings.