An ammonia gas control wet hydrogel, a preparation method and application thereof

Abstract

The application relates to the technical field of high polymer materials, in particular to ammonia-removing and humidity-controlling water gel as well as a preparation method and application thereof, which comprises the following raw materials: deionized water, AM, MBA, Gly, lithium chloride, 2-hydroxy-2-methyl propiophenone, magnesium chloride or magnesium oxide; the AM and the MBA are added into the deionized water, and polymerization is initiated by 2-hydroxy-2-methyl propiophenone and ultraviolet light to form a polyacrylamide network, so that the novel water gel can stably control humidity and effectively remove ammonia in long-term storage, effectively adsorb ammonia and provide molecular-level water molecules, and the required humidity of a cigar is maintained; secondly, the MBA is added into the water gel to form a more stable and porous three-dimensional crosslinking network, which can not only adjust the moisture absorption / relaxation rate of the water gel, realize humidity buffering, but also adsorb ammonia molecules through acid-base neutralization, ion exchange, hydrogen bonding, electrostatic interaction, so that the water gel can maintain the required humidity of the cigar for a long time and reduce the volatilization of ammonia.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to an ammonia-removing humidity-controlled hydrogel, its preparation method, and its application. Background Technology

[0002] During the storage, care, and warming process of cigars, they continuously release ammonia, a smell that severely interferes with the cigar enthusiast's experience. To address this issue, measures to remove ammonia become crucial. Furthermore, cigar care requires extremely high humidity levels; different cigar enthusiasts have different humidity preferences, with the ideal range typically between 50% and 90%. Cigars are also susceptible to humidity fluctuations, such as mold growth from excessive moisture or cracking from insufficient humidity. Therefore, an ammonia-removing and moisture-controlling hydrogel is needed to be applied during the care, warming, and storage of cigars, ensuring they are preserved in optimal condition. While existing hydrogel products can regulate humidity to some extent, they are difficult to remove ammonia effectively in the long term, and their ability to supply humidity is easily affected by the external environment, resulting in unstable humidity supply and difficulty in providing stable humidity for cigars in the long term. Summary of the Invention

[0003] The present invention aims to solve the problem that although existing hydrogel products can regulate humidity to a certain extent, they are difficult to remove ammonia effectively in the long term, and their ability to supply humidity is easily affected by the external environment, resulting in unstable humidity supply and difficulty in providing stable humidity for cigars in the long term.

[0004] To achieve the above objectives, the present invention provides the following technical solution: an ammonia-removing and moisture-controlling hydrogel, characterized in that it comprises the following raw materials in the indicated mass fractions: The composition is as follows: 30%–60% deionized water, 10%–30% AM (mass fraction), 0.02%–1% MBA (mass fraction), 1%–5% Gly (mass fraction), 5%–30% lithium chloride (mass fraction), 0.5%–2% 2-hydroxy-2-methylphenylacetone (mass fraction), and 5%–20% magnesium chloride or magnesium oxide (mass fraction).

[0005] A method for preparing an ammonia-removing and moisture-controlling hydrogel, characterized by comprising the following steps: Step 1: Weigh out each raw material with a total mass fraction of 100%: 43% deionized water, 18% AM, 0.8% MBA, 2% Gly, 23.3% lithium chloride, 1% 2-hydroxy-2-methylphenylacetone, and 15% magnesium chloride or magnesium oxide. Add 25% AM by mass to 43% deionized water in three portions, with a 5-minute interval between each addition. Use mechanical stirring at a speed of 200-400 rpm for 30 minutes until AM is completely dissolved to form a homogeneous solution, thus obtaining the first intermediate product. Step 2: Add 0.7% MBA by drop at a rate of 1-2 mL / min to the first intermediate product while mechanically stirring at a speed of 400-600 rpm to form the second intermediate product. Step 3: Add 3% Gly dropwise to the second intermediate while stirring at a speed of 300-500 rpm for 20 minutes until the Gly is completely dissolved to obtain the third intermediate. Step 4: Add 15% by mass of magnesium chloride or magnesium oxide to the third intermediate product and stir at 400-600 rpm for 30 minutes to form a precursor solution. Step 5: Transfer the precursor solution to a flask and purge with N2 to remove dissolved oxygen for 30 minutes. Add 1% (w / w) of 2-hydroxy-2-methylphenylacetone and pour the precursor solution into a custom mold. Initiate with ultraviolet light for 1 to 24 hours to form a hydrogel. Step 6, Lithium chloride solution preparation: Prepare lithium chloride solutions of different concentrations, divided into three levels according to the concentration gradient: 10% low, 20% medium, and 30% high. Step 7: Immerse the hydrogel in lithium chloride solutions of corresponding concentration gradients for 1-2 hours at low concentrations, 2-3 hours at intermediate concentrations, and 3-4 hours at high concentrations to ensure that lithium chloride fully penetrates into the gel network and obtains an ammonia-free, moisture-controlled hydrogel.

[0006] Preferably, in step six, the wavelength of the ultraviolet light is 100nm to 400nm, the light intensity is 20 to 200mW / cm², the illumination distance is 2 to 20cm, and the illumination time is 10min to 36h.

[0007] An application of an ammonia-removing and humidity-controlling hydrogel: Based on different humidity control needs of cigars, hydrogels soaked in lithium chloride solutions of different concentrations are precisely matched. Placing the hydrogel in a constant temperature box or cigar cabinet can adsorb the ammonia gas volatilized from the cigars and control humidity.

[0008] Compared with the prior art, the beneficial effects of the present invention are as follows: By adding AM and MBA to deionized water and initiating polymerization with 2-hydroxy-2-methylphenylacetone and ultraviolet light to form a polyacrylamide network, the novel hydrogel can stably control humidity and effectively remove ammonia during long-term storage, providing a high-quality storage environment for cigars; polyacrylamide has good water absorption and water retention properties, which can effectively adsorb and lock in moisture to maintain the humidity required by cigars; secondly, adding MBA to the hydrogel forms a more stable and porous three-dimensional cross-linked network, which can not only regulate the moisture absorption / release rate of the hydrogel and achieve humidity buffering, but also adsorb ammonia molecules through acid-base neutralization to form salts, ion exchange, hydrogen bonding, and electrostatic interaction, so that the hydrogel can maintain the humidity required by cigars for a long time and reduce the volatilization of ammonia; Finally, the zwitterionic groups of magnesium chloride in the hydrogel, such as –N + (CH3)2 － and –SO3 - Electrostatic attraction is formed between them, locking these ions in the hydrogel and preventing the decrease in hygroscopic performance caused by salting out; it enhances hygroscopic kinetics, reduces the differences in hygroscopic kinetics caused by uneven salting out, and improves the stability and recycling frequency of the hydrogel; Ammonia gas is captured by acidic groups (such as carboxyl groups) in the hydrogel or by H⁺ in the water, forming NH₄⁻. + NH4+ then reacts with magnesium ions to form ammonium salts; this process is reversible, and NH4+ can be heated or exposed to light to form ammonium salts. + It can decompose into NH3 and H⁺, releasing ammonia; the hydrogel can be reused; magnesium chloride contains Mg. 2+ Ionic crosslinking with negatively charged groups on the AM / MBA chain through ionic bonds enhances the three-dimensional structural stability of the hydrogel and improves the durability of the moisture absorption swelling-shrinkage cycle. This ionic crosslinking helps to form a more robust and stable polymer network, improving the hydrogel's pressure resistance and reliability for repeated use. Magnesium oxide captures ammonia through the physical adsorption of hydrogen bonds. Combined with the carboxyl groups (-COOH) of the polyacrylamide network, it enhances the capture of NH4+, achieving the effect of removing ammonia. This better meets the needs of cigar care, warming, and storage, effectively improving the quality of cigars and extending their shelf life. Detailed Implementation

[0009] The technical solutions in the embodiments of the present invention have been clearly and completely described. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0010] The present invention provides a technical solution: an ammonia-removing and moisture-controlling hydrogel, comprising the following raw materials by mass fraction: The composition is as follows: 30%–60% deionized water, 10%–30% AM (mass fraction), 0.02%–1% MBA (mass fraction), 1%–5% Gly (mass fraction), 5%–30% lithium chloride (mass fraction), 0.5%–2% 2-hydroxy-2-methylphenylacetone (mass fraction), and 5%–20% magnesium chloride or magnesium oxide (mass fraction).

[0011] A method for preparing an ammonia-removing and moisture-controlling hydrogel includes the following steps: Step 1: Weigh out each raw material with a total mass fraction of 100%: 43% deionized water, 18% AM, 0.8% MBA, 2% Gly, 23.3% lithium chloride, 1% 2-hydroxy-2-methylphenylacetone, and 15% magnesium chloride or magnesium oxide. Add 25% AM by mass to 43% deionized water in three portions, with a 5-minute interval between each addition. Use mechanical stirring at a speed of 200-400 rpm for 30 minutes until AM is completely dissolved to form a homogeneous solution, thus obtaining the first intermediate product. By adding AM in batches and continuously stirring, we avoid localized high concentrations that could lead to AM agglomeration, ensuring that AM molecular chains are fully extended and providing a foundation for subsequent cross-linking. AM is added as the main monomer to MBA. This network has high water absorption and water retention properties, which can absorb and lock in moisture to maintain the humidity required for cigar storage. Step 2: Add 0.7% MBA by drop at a rate of 1-2 mL / min to the first intermediate product while mechanically stirring at a speed of 400-600 rpm and sonicating at a frequency of 40 kHz and a power of 100 W for 15 min to form the second intermediate product. MBA and AM can form a three-dimensional cross-linked network through their bifunctional properties, which enhances the mechanical strength and structural stability of the hydrogel. The reversible hydration of the hydrophilic groups in the cross-linked network can regulate the moisture absorption / release rate of the hydrogel, achieving humidity buffering, such as the dynamic balance of lithium chloride deliquescence / crystallization, ensuring that humidity fluctuations are ≤±5%RH (mainly due to the regulation of humidity by lithium chloride; of course, the three-dimensional structure also plays a role, but lithium chloride plays the main role). Step 3: Add 3% Gly dropwise to the second intermediate while stirring at a speed of 300-500 rpm for 20 minutes until the Gly is completely dissolved to obtain the third intermediate. Gly binds to water molecules through hydrogen bonds, reducing water evaporation and maintaining the long-term humidity stability of the gel. Gly forms hydrogen bonds with amide groups in the polyacrylamide network, serving as physical cross-linking points, which enhances the toughness of the gel, such as tear resistance and fatigue toughness, and extends the service life of the hydrogel. Step 4: Add 15% by mass of magnesium oxide or magnesium chloride to the third intermediate product and stir at 400-600 rpm for 30 minutes to form a precursor solution. Magnesium chloride forms reversible ammonium salts, which decompose under sunlight, allowing the hydrogel to be reused. The ion gradient distribution of lithium chloride and magnesium chloride optimizes the moisture absorption-desorption cycle performance of the hydrogel under different humidity environments, improving its durability for repeated use. Lithium chloride (Li) + ) and magnesium chloride (Mg 2+ Through ion exchange with zwitterionic groups such as –N in the hydrogel + (CH3)2 - and -SO3 - Electrostatic interaction occurs, forming a stable binary salt system, Li + With Cl - It is fixed by electrostatic interaction, preventing salting out, and at the same time enhancing the hygroscopic kinetics; The polymer network formed by magnesium chloride, AM, and MBA through ionic cross-linking enhances the three-dimensional structural stability of the hydrogel and improves the durability of the moisture absorption, expansion, and contraction cycle. MBA, as a chemical crosslinking agent, introduces covalent crosslinking points in polymerization through bisacrylamide groups; MgCl2 and lithium chloride further enhance network density through ionic crosslinking; the two form a dual network structure of "chemical covalent crosslinking + ionic physical crosslinking". In the hydrogel, ionic crosslinking, hydrogen bonding, and nanoparticle enhancement work synergistically to improve energy dissipation capacity. AM and MBA form linear / branched polymer chains through free radical polymerization. The bifunctional groups of MBA initiate inter-chain crosslinking to form a network structure. The ionic crosslinking of magnesium chloride introduces reversible ionic bonding sites into the network, giving the network dynamic responsiveness. Mg 2+ The introduction of Mg increases the surface polarity of nano-magnesium oxide / magnesium chloride, thereby enhancing the adsorption of polar ammonia molecules (NH3) through electrostatic interactions; 2+ It forms coordinate bonds with nitrogen atoms in ammonia molecules or achieves chemical adsorption through hydrogen bonds (hydroxyl groups -NH3 on the zeolite surface); the defect sites on the surface of nano-magnesium oxide further provide adsorption anchors, and its high specific surface area increases the probability of ammonia contact, thus synergistically improving the adsorption capacity. Step 5: Transfer the precursor solution to a flask and purge with N2 to remove dissolved oxygen for 30 minutes. Add 1% (w / w) of 2-hydroxy-2-methylphenylacetone and pour the precursor solution into a custom mold. Initiate with ultraviolet light for 1 to 24 hours to form a hydrogel. Among them, the ultraviolet light wavelength is 100nm~400nm, the light intensity is 20~200mW / cm², the illumination distance is 2~20cm, and the illumination time is 10min~36h; Step 8, Lithium chloride solution preparation: Prepare lithium chloride solutions of different concentrations, divided into three levels according to the concentration gradient: 10% low, 20% medium, and 30% high, to match the cigar humidity preference of 50% to 90% RH, with humidity fluctuations controlled within ±3% RH, so as to achieve adjustable humidification capacity. The humidification capacity is adjustable through gradient concentration design, corresponding to the 50% to 90% RH humidity preference of cigars; low concentration (10%) is suitable for low humidity preference scenarios, high concentration (30%) meets high humidity requirements, and the intermediate concentration (20%) gradient can accurately match the personalized preferences of cigar enthusiasts. Step 9: Immerse the hydrogel in lithium chloride solutions of corresponding concentration gradients. Immersion time is ≥1 hour for low concentrations, 2–3 hours for intermediate concentrations, and 3–4 hours for high concentrations to ensure that lithium chloride fully penetrates into the gel network and drives Li through the concentration gradient. + / Cl - The diffusion process forms a stable humidity-regulating layer, resulting in an ammonia-removing and humidity-controlled hydrogel.

[0012] An application of an ammonia-removing and humidity-controlling hydrogel: Based on different cigar humidity control needs, hydrogels soaked in lithium chloride solutions of different concentrations are precisely matched. Placing the hydrogel in a constant temperature box or cigar cabinet can adsorb the ammonia gas volatilized from the cigars and control humidity. Specifically, by utilizing the synergistic effect of nano-magnesium oxide / magnesium chloride and polyacrylamide three-dimensional network, a three-stage ammonia removal system of "chemical adsorption-physical adsorption-ion exchange" is formed, which significantly improves the long-term ammonia removal efficiency and avoids secondary release after adsorption saturation, providing stable and efficient ammonia control for cigar storage. A dynamic humidity regulation system is formed through ion diffusion and hydrogen bonding. When the ambient humidity is lower than the set value, lithium chloride releases water molecules; when the humidity is too high, the gel adsorbs excess moisture, achieving humidity fluctuation control of ±3%RH.

[0013] The following table shows the effects of different mass fraction combinations of components on ammonia removal and humidity control: Compare the three sets of experiments above: In the three sets of experiments, AM and MBA formed a three-dimensional polyacrylamide network through chemical cross-linking, Gly acted as a moisturizing factor to lock in water through hydrogen bonds, and lithium chloride achieved bidirectional humidity regulation (moisture absorption / moisture release) through ion hydration, forming a three-level synergistic system of "network-moisturizing-humidity regulation". In Experiment 1, magnesium oxide captured ammonia gas through electrostatic adsorption and pores, and the carboxyl groups (-COOH) of the polyacrylamide network enhanced its ability to capture NH4+. + The capture of these substances creates a synergistic ammonia removal effect; In Experiment 2, lithium chloride (20.3%) and magnesium chloride (15%) formed a dual-salt synergistic system, which improved the ammonia removal efficiency compared to the single-salt system in the moisture absorption rate test. Cl in magnesium chloride - The moisture absorption rate is enhanced by ion exchange, magnesium chloride forms a reversible ammonium salt, and the ammonium salt decomposes when exposed to the sun. The hydrogel can be reused, reducing the cost of use. Mg in magnesium chloride 2+ The three-dimensional structural stability of the hydrogel is enhanced by forming magnetic crosslinks with the negatively charged groups on the AM / MBA chain through ionic bonds, which improves the durability of the moisture absorption swelling-shrinkage cycle. In Experiment 3, without magnesium chloride / magnesium chloride, intelligent humidity control of 65%RH±5% can be achieved, but there is no ammonia removal function.

[0014] Under the same conditions, magnesium chloride is more effective at removing ammonia than magnesium oxide, and the reagent cost is lower; therefore, Experiment 2 is the optimal formulation.

[0015] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A hydrogel for removing ammonia and controlling humidity, characterized in that: Raw materials including the following mass fractions: The composition is as follows: 30%–60% deionized water, 10%–30% AM (mass fraction), 0.02%–1% MBA (mass fraction), 1%–5% Gly (mass fraction), 5%–30% lithium chloride (mass fraction), 0.5%–2% 2-hydroxy-2-methylphenylacetone (mass fraction), and 5%–20% magnesium chloride or magnesium oxide (mass fraction).

2. The method for preparing an ammonia-removing and moisture-controlled hydrogel as described in claim 1, characterized in that, Includes the following steps: Step 1: Weigh out each raw material with a total mass fraction of 100%: 43% deionized water, 18% AM, 0.8% MBA, 2% Gly, 23.3% lithium chloride, 1% 2-hydroxy-2-methylphenylacetone, and 15% magnesium chloride or magnesium oxide. Add 25% AM by mass to 43% deionized water in three portions, with a 5-minute interval between each addition. Use mechanical stirring at a speed of 200-400 rpm for 30 minutes until AM is completely dissolved to form a homogeneous solution, thus obtaining the first intermediate product. Step 2: Add 0.7% MBA by drop at a rate of 1-2 mL / min to the first intermediate product while mechanically stirring at a speed of 400-600 rpm to form the second intermediate product. Step 3: Add 3% Gly dropwise to the second intermediate while stirring at a speed of 300-500 rpm for 20 minutes until the Gly is completely dissolved to obtain the third intermediate. Step 4: Add 15% by mass of magnesium chloride or magnesium oxide to the third intermediate product and stir at 400-600 rpm for 30 minutes to form a precursor solution. Step 5: Transfer the precursor solution to a flask and purge with N2 to remove dissolved oxygen for 30 minutes. Add 1% (w / w) of 2-hydroxy-2-methylphenylacetone and pour the precursor solution into a custom mold. Initiate with ultraviolet light for 1 to 24 hours to form a hydrogel. Step 6, Lithium chloride solution preparation: Prepare lithium chloride solutions of different concentrations, divided into three levels according to the concentration gradient: 10% low, 20% medium, and 30% high. Step 7: Immerse the hydrogel in lithium chloride solutions of corresponding concentration gradients for 1-2 hours at low concentrations, 2-3 hours at intermediate concentrations, and 3-4 hours at high concentrations to ensure that lithium chloride fully penetrates into the gel network and obtains an ammonia-free, moisture-controlled hydrogel.

3. The method for preparing an ammonia-removing and moisture-controlled hydrogel as described in claim 2, characterized in that, In step six, the ultraviolet light wavelength is 100nm to 400nm, the light intensity is 20 to 200mW / cm², the illumination distance is 2 to 20cm, and the illumination time is 10min to 36h.

4. The application of the ammonia-removing and moisture-controlling hydrogel as described in claim 1, characterized in that, Depending on the different humidity control requirements of cigars, hydrogels soaked in lithium chloride solutions of different concentrations are precisely matched. Placing the hydrogels in a constant temperature box or cigar cabinet can absorb the ammonia gas volatilized from the cigars and control humidity.

Images