Porous composite gel drying agent and preparation method thereof

Abstract

The invention relates to the technical field of drying agents, in particular to a porous composite gel drying agent and a preparation method thereof. Conventional desiccants are difficult to give consideration to both stable chemical properties and high moisture absorption capacity. In order to solve the problems, the porous composite gel drying agent is provided, lithium chloride, calcium chloride and other hygroscopic salts are introduced to serve as additives in a porous polymerization network of the drying agent and are compounded with the polymer network, and the intrinsic moisture absorption capacity of the material is remarkably improved. The moisture absorption capacity of the obtained porous composite gel drying agent is far higher than that of traditional silica gel, the long-acting moisture absorption requirement in the high-humidity environment can be met, and the porous composite gel drying agent is particularly suitable for the high-end fields of precision electronics, new energy batteries, biological agents and the like with strict requirements for humidity control precision.

Description

Technical Field

[0001] This invention relates to the field of desiccant technology, specifically to a porous composite gel desiccant and its preparation method. Background Technology

[0002] Desiccants, functional materials that reduce environmental humidity and prevent moisture damage through physical or chemical adsorption, play a crucial role in numerous fields, including food, pharmaceuticals, electronic equipment, precision instruments, and warehousing and transportation. In the food industry, desiccants effectively prevent food from becoming damp and spoiling, extending its shelf life. In the pharmaceutical field, they ensure the stability and efficacy of medicines. For electronic equipment and precision instruments, they prevent short circuits and corrosion caused by excessive humidity, ensuring their normal operation. In warehousing and transportation, they help maintain the quality of goods and reduce losses. Therefore, the performance of desiccants directly affects the quality and safety of related products and is of great significance to economic development.

[0003] Silica gel is chemically stable, non-toxic, and inexpensive, making it the most widely used physical adsorption desiccant. However, it has significant drawbacks. Firstly, its moisture absorption rate is limited; for example, silica gel (SiO2·nH2O) has a moisture absorption rate of only 30%-40% of its own weight, making it unsuitable for long-term use in high-humidity environments and limiting its performance in humidity control applications. Secondly, regeneration requires high-temperature treatment at 120-150℃, with energy consumption per unit mass reaching 1.3-1.6 kW·h / kg, severely hindering the progress of green manufacturing.

[0004] While chemical desiccants such as calcium chloride significantly improve moisture absorption, they are prone to deliquescence and liquefaction. This characteristic poses a risk of corroding metals and polluting the environment, potentially damaging surrounding equipment and the environment during application, thus limiting their widespread use.

[0005] Montmorillonite-based mineral desiccants are biodegradable, offering certain environmental advantages. However, their moisture absorption efficiency is significantly affected by ambient temperature and they are difficult to recycle. This results in unstable performance under varying environmental conditions, failing to meet long-term, stable usage requirements.

[0006] With the increasing demands for humidity control precision in high-end fields such as precision electronic packaging, new energy battery module storage, and bioactive preparation transportation, traditional desiccants, limited by low moisture absorption capacity and irreversible structural degradation, are unable to meet the long-term humidity stability requirements under complex operating conditions. Developing novel desiccant material systems with high moisture absorption capacity, dynamic self-regulating properties, and customizable performance has become an urgent industry need. Summary of the Invention

[0007] Existing technologies have the problem that conventional desiccants struggle to balance chemical stability and high moisture absorption capacity. To address this issue, this invention provides a porous composite gel desiccant, the preparation method of which includes the following steps: (1) Using water-soluble lithium salt and water-soluble calcium salt as additives, under the action of an initiator, acrylamide, sodium acrylate and N,N'-methylenebisacrylamide crosslink and copolymerize in aqueous solution to form a gel polymer; (2) The above-mentioned gel polymer is freeze-dried to obtain a porous composite gel desiccant.

[0008] Preferably, the water-soluble lithium salt is lithium chloride.

[0009] Preferably, the water-soluble calcium salt is calcium chloride.

[0010] Preferably, the initiator is a persulfate.

[0011] Preferably, the initiator is ammonium persulfate.

[0012] Preferably, the temperature of the crosslinking copolymerization reaction is 70±2℃.

[0013] Preferably, the mass ratio of water-soluble lithium salt to water-soluble calcium salt is 2.6:0.6, the mass ratio of acrylamide to sodium acrylate is 1.4:0.6, the mass ratio of water-soluble lithium salt to acrylamide is 2.6:1.4, the amount of N,N'-methylenebisacrylamide added is 2‰-2.1‰ of the total mass of acrylamide and sodium acrylate, and the mass of the initiator is 2%-2.5% of the total mass of acrylamide and sodium acrylate.

[0014] Beneficial effects: (1) This invention introduces hygroscopic salts such as lithium chloride and calcium chloride as additives in the porous polymer network of the desiccant and combines them with the polymer network, which significantly improves the intrinsic moisture absorption capacity of the material. The resulting porous composite gel desiccant has a moisture absorption capacity much higher than that of traditional silica gel (30%-40% of its own weight), which can meet the long-term moisture absorption requirements in high humidity environments, and is especially suitable for high-end fields such as precision electronics, new energy batteries, and biological agents where humidity control accuracy is critical. (2) This invention constructs a unique "lithium-calcium synergistic" mechanism in a polymer network by introducing a specific ion combination of lithium chloride and calcium chloride and controlling their ratio. Among them, lithium ions (Li... + With its extremely high charge density, calcium ions act as a highly efficient "osmotic pressure engine" and "hydration anchor," generating strong osmotic pressure and firmly binding a large number of water molecules. This is the core driving force behind the breakthrough increase in hygroscopic capacity (far exceeding 1.5 g / g); while calcium ions (Ca... 2+The main function of the desiccant is as a "structural cross-linking lock," which effectively enhances the mechanical strength of the gel network by forming ionic cross-links with carboxylate groups on the polymer chain, preventing it from excessively swelling or disintegrating after absorbing moisture. This synergistic effect overcomes the shortcomings of insufficient moisture absorption (difficult to reach 1.5 g / g) when using calcium salt alone or the potential for weak structure when using lithium salt alone. For the first time, it simultaneously achieves near-chemical desiccant high moisture absorption capacity and physical desiccant structural stability in a single material system. (3) The hygroscopic salts are firmly bound in the three-dimensional network structure of the cross-linked polymer, effectively avoiding the deliquescence and liquefaction phenomena that are prone to occur in chemical desiccants such as pure calcium chloride. This structural characteristic eliminates the risk of leakage, prevents corrosion of metal devices and pollution of the surrounding environment, and eliminates the potential corrosion and pollution risks to precision electronic components, metal packaging or storage environment, greatly expanding the safety of applications in high-end precision occasions.

[0015] (4) The main body of the material is a polymer gel, which forms a porous structure through freeze drying. Its regeneration temperature requirement (60℃) is much lower than that required for silica gel (120-150℃). This characteristic greatly reduces the energy consumption in the desiccant regeneration process, which is in line with the development direction of green manufacturing. At the same time, the porous structure is conducive to the adsorption and desorption of moisture, ensuring the performance stability during recycling. Attached Figure Description

[0016] Figure 1 Results of the moisture absorption stability test of the porous composite gel desiccant obtained in Example 3. Detailed Implementation

[0017] The present invention will be described in detail below with reference to embodiments. However, it should be understood that the following embodiments are merely illustrative examples of implementation of the present invention and are not intended to limit the scope of the present invention.

[0018] Example 1

[0019] A porous composite gel desiccant is prepared as follows: (1) First, dissolve 0.6g of anhydrous lithium chloride and 2.6g of anhydrous calcium chloride powder in 6.4mL of distilled water and stir and mix at 30℃ for 30 minutes to obtain an inorganic salt mixture. (2) 1.4 g of acrylamide, 0.6 g of sodium acrylate powder and 520 μL of N,N'-methylenebisacrylamide aqueous solution with a mass concentration of 0.008 g / mL were added to the above inorganic salt mixture in sequence and stirred and mixed evenly to obtain a polymer monomer solution. (3) Add 220 μL of ammonium persulfate initiator solution with a mass concentration of 0.2 g / mL to the monomer solution and continue stirring for 30 minutes to make the ammonium persulfate initiator uniformly dispersed in the system to obtain the prepolymer solution; (4) Transfer 2.5 mL of prepolymer solution to a plastic mold using a pipette. Seal the plastic mold with a sealed container and purge it with nitrogen. Then place the plastic mold in an oven at 70°C and let it stand for 3 hours. Sodium acrylate reacts with acrylamide and crosslinking agent to form a three-dimensional network structure composite gel polymer. (During the crosslinking copolymerization process, LiCl contains Li...) + Ca in CaCl2 2+ (It complexes with carboxylic acid groups in the resin matrix, significantly enhancing the crosslinking network strength). (5) The above composite gel polymer was frozen at -40°C for 72 hours, and then transferred to a freeze dryer for 96 hours to obtain a porous composite gel desiccant with a porous three-dimensional network skeleton structure.

[0020] Example 2 is the same as Example 1, except that the mass of anhydrous lithium chloride added in Example 2 is 1.6g, and the mass of anhydrous calcium chloride powder added is 1.6g.

[0021] Example 3 is the same as Example 1, except that the mass of anhydrous lithium chloride added in Example 3 is 2.6g, and the mass of anhydrous calcium chloride powder added is 0.6g.

[0022] Example 4 is the same as Example 1, except that the mass of anhydrous lithium chloride added in Example 4 is 1.2g and the mass of anhydrous calcium chloride powder added is 2g.

[0023] Comparative Example 1

[0024] A porous composite gel desiccant is prepared as follows: (1) 1.4 g of acrylamide, 0.6 g of sodium acrylate powder and 520 μL of N,N'-methylenebisacrylamide aqueous solution with a mass concentration of 0.008 g / mL were added to the above inorganic salt mixture in sequence and stirred and mixed evenly to obtain a polymer monomer solution. (2) 220 μL of ammonium persulfate initiator solution with a mass concentration of 0.2 g / mL was added to the monomer solution and stirred for 30 minutes to make the ammonium persulfate initiator uniformly dispersed in the system to obtain the prepolymer solution; (3) Transfer 2.5 mL of prepolymer liquid to a plastic mold using a pipette, seal the plastic mold with a sealed container and fill it with nitrogen, then place the plastic mold in an oven and control the temperature at 70°C. Let it stand for 3 hours to react. Sodium acrylate reacts with acrylamide and crosslinking agent to form a three-dimensional network structure composite gel polymer. (4) The above composite gel polymer was frozen at -40°C for 72 hours, and then transferred to a freeze dryer for 96 hours to obtain a porous composite gel desiccant with a porous three-dimensional network skeleton structure.

[0025] Comparative Example 2 is the same as Example 3, except that the mass of anhydrous calcium chloride powder added in Comparative Example 2 is 3.2g, and no anhydrous lithium chloride is added.

[0026] Comparative Example 3 is the same as Example 3, except that the mass of anhydrous lithium chloride added in Comparative Example 3 is 3.2g, and no anhydrous calcium chloride powder is added.

[0027] Performance testing

[0028] The porous composite gel desiccants obtained in Examples 1-4 and Comparative Examples 1-3 of the present invention were subjected to relevant performance tests, and the specific test results are shown in Table 1.

[0029] Moisture absorption rate: Weigh the sample to be tested and record the weight as m. 0, The sample was then placed in the appropriate temperature and humidity environment, and after a predetermined time, it was removed and weighed. The weight was recorded as m. t. Formula for calculating moisture absorption rate: (m t - m0) / m0.

[0030] Moisture absorption stability: Moisture absorption cycle performance tests were conducted on different desiccants: they were stored at 90%RH and 10℃-50℃ for 48 hours to fully absorb moisture, and then dried at 60℃ for 24 hours. The results showed that the composite gel obtained in Example 1 could be restored to its initial mass, enabling repeated moisture absorption and use; and at 30℃ and 90%RH, its maximum moisture absorption capacity reached 2.61 g / g.

[0031] Table 1

[0032] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A porous composite gel desiccant, characterized by, The preparation method comprises the following steps: (1) using water-soluble lithium salt and water-soluble calcium salt as additives, under the action of an initiator, acrylamide, sodium acrylate and N,N'-methylene bisacrylamide are cross-linked and copolymerized in an aqueous solution to form a gel polymer; (2) the gel polymer is freeze-dried to obtain a porous composite gel desiccant.

2. The porous composite gel desiccant of claim 1, wherein, The water-soluble lithium salt is lithium chloride.

3. The porous composite gel desiccant of claim 1, wherein, The water-soluble calcium salt is calcium chloride.

4. The porous composite gel desiccant of claim 1, wherein, The initiator is a persulfate salt.

5. A composite porous gel desiccant according to claim 4, wherein The initiator is ammonium persulfate.

6. The composite porous gel desiccant of claim 1, wherein, The temperature of the cross-linking and copolymerization reaction is 70±2℃.

7. The composite porous gel desiccant of claim 1, wherein, The mass ratio of the water-soluble lithium salt to the water-soluble calcium salt is 2.6:0.6, the mass ratio of the acrylamide to the sodium acrylate is 1.4:0.6, the mass ratio of the water-soluble lithium salt to the acrylamide is 2.6:1.4, the addition amount of the N,N'-methylene bisacrylamide is 2‰-2.1‰ of the total mass of the acrylamide and the sodium acrylate, and the mass of the initiator is 2%-2.5% of the total mass of the acrylamide and the sodium acrylate.

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