A kind of monitoring camera, drying agent for car light and its preparation method
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HANGZHOU RONGHUI NEW MATERIALS CO LTD
- Filing Date
- 2026-05-29
- Publication Date
- 2026-06-30
Smart Images
Figure SMS_1
Abstract
Description
Technical Field
[0001] This application relates to a desiccant, specifically a desiccant for surveillance cameras and vehicle lights, and a method for preparing the same. Background Technology
[0002] Existing physical adsorption desiccants such as silica gel, zeolite, molecular sieves, and clay minerals generally have limited adsorption capacity at low to medium humidity (below 40% RH). Quicklime, on the other hand, reacts with water and can absorb approximately 30% of its own weight in water. Furthermore, when deliquescent salts (such as MgCl2 and CaCl2) are added to a carrier or hydrophilic polymer, they absorb moisture to form liquid water at low to medium humidity; at medium to high humidity, they become a saturated solution, continuously absorbing moisture from the air until the partial pressure of the moisture in the air reaches equilibrium, thus becoming a liquid desiccant. However, when the concentration reaches a certain level, there is a risk of leakage.
[0003] Conventional physical adsorption desiccants such as silica gel, molecular sieves, and zeolites have weak adsorption capacity at low to medium humidity levels and are easily affected by ambient temperature. When the temperature rises and the humidity decreases, the adsorbed moisture will be desorbed again. Although quicklime is not affected by the environment after absorbing moisture, CO2 in the air can easily react with its moisture-absorbing products (Ca(OH)2) to regenerate H2O and become damp again.
[0004] Currently, the most commonly used desiccants are mixtures of MgCl2 and MgO powders. For example, patent application JPH0256215A discloses a powder composition desiccant consisting of MgCl2 and MgO. However, although this desiccant is easy to mix evenly, it is prone to dust generation during production. At the same time, MgCl2 has a fast deliquescence rate and easily releases HCl gas when combined with H2O. Although the acidity can be reduced by adding alkali metal hydroxides to the system, the generation of HCl cannot be completely eliminated. HCl is extremely corrosive to the surfaces of precision instruments, metal parts, and other metal components, posing a great hazard.
[0005] Magnesium chloride desiccants exhibit volume expansion after absorbing moisture, typically exceeding 150%. They also solidify upon moisture absorption, forming hard lumps. Patent KR1022144262B1 incorporates polymer wax and SiO2 to reduce the strength of the solidified lumps. However, due to the volume expansion of the desiccant and the solidification of the product, the limited space for placing the desiccant can cause deformation of nearby devices and damage to its own packaging material, leading to a risk of leakage.
[0006] Furthermore, magnesium chloride desiccants are prone to deliquescent liquid "reversion" in high-temperature environments. Even with reduced MgCl2 content and the addition of inhibitors, it is difficult to achieve a dense crystal phase. Therefore, water-retaining stones, deliquescent salts, and hydrophilic polymers are added to prevent the formation of free deliquescent liquids and the risk of leakage. For example, patent CN113398874B protects a composite desiccant, which, by mass, consists of the following components: 25-75 parts heavy magnesium oxide; 5-48 parts active magnesium oxide; 1-17 parts anhydrous magnesium chloride; 5-62 parts anhydrous magnesium sulfate; and 0.01-5 parts water-resistant additives. The water-resistant additives include one or more of phosphoric acid, ferric sulfate, ethyl silicate, citric acid, and melamine resin. The water-resistant additives improve the stability of the magnesium chloride and magnesium sulfide crystal phases in water, preventing hydrolysis of the crystal phases even when water is adsorbed on the desiccant surface or under the influence of ambient water, thus preventing the formation of magnesium chloride hexahydrate. However, the desiccant in this patent is not suitable for use in small spaces in special industries such as surveillance cameras and car headlights.
[0007] Therefore, we will continue to develop desiccants that can be applied to special industries such as surveillance cameras and automotive headlights. Summary of the Invention
[0008] To at least partially achieve the above-mentioned objectives, this application provides the following technical solutions:
[0009] In a first aspect, this application provides a desiccant, the preparation method of which includes the following steps: hydrating the raw material and processing it into desiccant precursor particles, and then activating the desiccant precursor particles at 180-500°C.
[0010] The raw materials include the following substances in parts by weight:
[0011] Raw material A 30-70 parts
[0012] Raw material B 15-60 parts
[0013] Admixture 0.01 to 30 parts
[0014] The raw material A is selected from magnesium oxide and / or magnesium hydroxide, and the raw material B is selected from magnesium chloride and / or magnesium chloride hydrate;
[0015] The additives include one or more of the following: silica sol, silicate, phosphoric acid, phosphate, cement, alumina, molecular sieve, aluminate, glass fiber, silicone resin, and epoxy resin.
[0016] Secondly, this application also provides a method for preparing a desiccant, the method comprising:
[0017] The raw materials are hydrated and processed into desiccant precursor particles, and then the desiccant precursor particles are activated at 180-500°C.
[0018] Based on the above technical solutions, the desiccant and its preparation method of this application have the following beneficial effects compared with the prior art: the desiccant has a high adsorption capacity under low and medium humidity, thereby reducing or avoiding the "fogging" phenomenon of camera lenses and car headlight lenses. At the same time, the volume increase rate of the desiccant after absorbing moisture is extremely low, thereby avoiding deformation of working components in monitoring cameras and car headlights. Detailed Implementation
[0019] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with specific embodiments.
[0020] Regarding the first aspect of this application, the purpose of this application is to provide a special desiccant suitable for special scenarios such as surveillance cameras and automotive headlights. The special desiccant exhibits good hygroscopicity at low to medium humidity levels (e.g., 30°C, 40%RH), thereby effectively removing moisture from surveillance cameras and automotive headlights in these special scenarios and ensuring the normal operation of the equipment.
[0021] Currently, desiccants used in industries such as surveillance cameras and automotive headlights have the following problems: when these devices are operating, "fogging" easily occurs on the inner surfaces of camera lenses and headlight lenses, leading to quality issues. Simply put, in a confined space, the temperature rises, and the hot air heats the components and desiccant. This temperature increase causes H2O to escape, resulting in an increase in absolute humidity. The area around camera lenses and headlight lenses, which are connected to the external environment, reaches relative humidity saturation, causing "fogging" on the inner surfaces of the lenses. It is necessary to maintain a low humidity level in the confined space for extended periods, so that when humidity rises, less H2O escapes from the components and desiccant, preventing the relative humidity from reaching saturation. Therefore, the desiccant must have a high adsorption capacity at low to medium humidity, i.e., "effective adsorption."
[0022] To solve the aforementioned technical problems, the inventors, through dedicated research, discovered that using magnesium oxychloride cementitious material (hereinafter referred to as MOC) as a precursor for a desiccant, followed by high-temperature activation, yields a desiccant with excellent moisture absorption capacity in medium to low humidity conditions, thus solving the aforementioned problems. MOC is a cementitious material produced by the reaction (i.e., hydration) of magnesium oxide, magnesium chloride, and water. It possesses low density and a low coefficient of thermal expansion, as well as good mechanical strength. At room temperature, hydrated MOC mainly comprises two phase structures: a 3-phase structure (3Mg(OH)₂·MgCl₂·8H₂O) and a 5-phase structure (5Mg(OH)₂·MgCl₂·8H₂O). However, while directly drying MOC and using it as a granular desiccant can achieve extremely high particle strength, its moisture absorption capacity in low humidity conditions is poor, failing to meet the moisture absorption requirements of industries such as surveillance cameras and automotive headlights. The inventors discovered that by fully activating MOC at high temperatures (180–500°C), the MOC product will release moisture at high temperatures, but the structure of the desiccant remains that of the MOC product. When the desiccant absorbs water in a humid environment, the moisture will refill the voids in the MOC structure, forming a relatively stable magnesium oxychloride gel material. This significantly improves the hygroscopicity of the desiccant in low to medium humidity conditions. At the same time, the size of the desiccant particles hardly expands, and its volume increase rate is extremely low, making the desiccant suitable for industries such as surveillance cameras and automotive headlights.
[0023] Raw material A is selected from magnesium oxide and / or magnesium hydroxide, and raw material B is selected from magnesium chloride and / or magnesium chloride hydrate. Raw materials A and B are the core raw materials of this application, which can react with water (i.e., hydrate) to obtain MOC, thereby providing precursor particles for subsequent activation. To ensure sufficient MOC, raw material A should be 30-70 parts and raw material B should be 15-60 parts. Raw material A can specifically be 32 parts, 34 parts, 36 parts, 38 parts, 40 parts, 42 parts, 44 parts, 46 parts, 47 parts, 48 parts, 50 parts, 52 parts, 54 parts, 56 parts, 58 parts, 60 parts, 62 parts, 64 parts, 66 parts, or 68 parts; raw material A is preferably 40-68 parts, more preferably 50-67 parts, and most preferably 55-65 parts. Raw material B can be specifically 16 parts, 18 parts, 20 parts, 22 parts, 24 parts, 26 parts, 28 parts, 30 parts, 32 parts, 34 parts, 36 parts, 38 parts, 40 parts, 42 parts, 44 parts, 46 parts, 47 parts, 48 parts, 50 parts, 52 parts, 54 parts, 56 parts, or 58 parts; raw material B is preferably 20 to 55 parts, more preferably 30 to 50 parts, and most preferably 35 to 45 parts.
[0024] The admixture is also a core raw material of this application. During the activation process, the desiccant precursor particles undergo high-temperature treatment at 180–500°C, resulting in a certain loss of particle strength. This may lead to particle breakage during subsequent processing, introducing dust into the desiccant particles, which is detrimental to their use in industries such as surveillance cameras and automotive headlights. Therefore, by introducing an admixture, the desiccant precursor particles can maintain the required strength after high-temperature activation. Through extensive research and development, the inventors have discovered that admixtures meeting activation requirements include one or more of the following: sol, silicate, phosphoric acid, phosphate, cement, alumina, molecular sieve, aluminate, glass fiber, silicone resin, and epoxy resin. The cement can be various types of cement, such as silicate cement, sulfate cement, and composite cement, while the amount of admixture added needs to be between 0.01 and 30 parts. Below 0.01 parts, the admixture's effect of improving particle strength cannot be achieved; above 30 parts, it will affect the hygroscopicity of the desiccant. The amount of the additive can be specifically 0.02 parts, 0.03 parts, 0.05 parts, 0.08 parts, 0.09 parts, 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1.0 parts, 1.2 parts, 1.5 parts, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 12 parts, 14 parts, 15 parts, 16 parts, 18 parts, 20 parts, 22 parts, 24 parts, 26 parts, or 28 parts, etc.; the amount of the additive is preferably 0.02 to 25 parts, more preferably 0.03 to 20 parts, and most preferably 0.04 to 15 parts.
[0025] In a preferred embodiment, the phosphate is selected from one or more of alkali metal phosphates, alkaline earth metal phosphates, transition metal phosphates, aluminum dihydrogen phosphate, aluminum orthophosphate, aluminum metaphosphate, and aluminum polyphosphate.
[0026] To further improve the performance of the desiccant, in a preferred embodiment, the desiccant precursor particles contain 20% to 99.9% by mass of magnesium oxychloride cementitious material (MOC). Controlling the MOC content in the desiccant precursor particles to above 20% by mass ensures that the structure of the activated desiccant particles meets the hygroscopic requirements, resulting in excellent hygroscopic performance of the desiccant under low to medium humidity conditions. Higher MOC content in the desiccant precursor particles is preferable; preferably, it is above 40% by mass, more preferably above 60% by mass, most preferably above 80% by mass, and can reach a maximum of 99.9% by mass.
[0027] In a preferred embodiment, the magnesium oxide is selected from one or more of calcined magnesium oxide, light-calcined magnesium oxide, and molten magnesium oxide. The MgO content in the magnesium oxide is 85% by mass or more. The magnesium chloride is selected from anhydrous magnesium chloride, magnesium chloride hexahydrate, magnesium chloride dihydrate, etc. Regardless of the raw material selected, the effective component in raw material A is MgO, and the effective component in raw material B is MgCl2. To better utilize the effective components in raw material A and raw material B, the mass ratio of effective MgO to effective MgCl2 in raw material A and raw material B is preferably 30~70:15~60, more preferably 40~65:20~55, particularly preferably 50~65:30~55, and most preferably 55~65:35~45; wherein the effective MgO is the mass of raw material A converted to MgO, for example, the mass of Mg(OH)2 converted to MgO, and the effective MgCl2 is similar, for example, the mass of hydrated MgCl2 converted to MgCl2.
[0028] In a preferred embodiment, the desiccant comprises component AB, wherein component AB is selected from Mg(H2O)Cl2, MgO, MgCl2, Mg(OH)Cl, Mg(H2O)Cl2•3MgO, Mg(H2O)2Cl2•3MgO, Mg(H2O)Cl2•5MgO, Mg(H2O)2Cl2•5MgO, Mg(OH)Cl•3MgO, Mg(OH)Cl•5MgO, 3Mg(OH)2•MgCl2, 3Mg(OH)2•Mg(H2O)Cl2, 3[ One or more of the following: Mg(H2O)(OH)2]•Mg(H2O)Cl2, 3Mg(OH)2•Mg(H2O)2Cl2, 3[Mg(H2O)(OH)2]•Mg(H2O)2Cl2, 5Mg(OH)2•MgCl2, 5Mg(OH)2•Mg(H2O)2Cl2, 5[Mg(H2O)(OH)2]•Mg(H2O)2Cl2, 5Mg(OH)2•Mg(H2O)Cl2, 5[Mg(H2O)(OH)2]•Mg(H2O)Cl2. High-temperature activation can appropriately decompose the MOC in the desiccant precursor particles, especially the 3-phase and 5-phase in the MOC. As the activation temperature increases, for example, above 180°C, the water of crystallization begins to detach, and the activation products are, for example: 3Mg(OH)2•MgCl2, 3Mg(OH)2•Mg(H2O)2Cl2, 3[Mg(H2O)(OH)2]•Mg(H2O)2Cl2, 3Mg(OH)2•Mg(H2O)Cl2, 3[Mg(H2O)(OH)2]•Mg(H2O)Cl2, 5Mg(OH)2•MgCl2, 5Mg(OH)2•Mg(H2O)2Cl2, 5[Mg(H2O)(OH)2]•Mg(H2O)2Cl2, 5Mg(OH)2•Mg(H2O)Cl2, 5[Mg(H2O)(OH)2]•Mg(H2O)Cl2. When the temperature rises further, for example, above 300℃ or even 350℃, Mg(OH)2 also begins to decompose, and its activation products include: Mg(H2O)Cl2 and MgO, Mg(OH)Cl and MgO, Mg(H2O)Cl2•3MgO, Mg(H2O)2Cl2•3MgO, Mg(H2O)Cl2•5MgO, Mg(H2O)2Cl2•5MgO, Mg(OH)Cl•3MgO, and Mg(OH)Cl•5MgO. Through high-temperature activation, the MOC gel structure formed after the raw material hydration is maintained, and the material can fully absorb moisture from the air during actual use, thus achieving better hygroscopic properties at low to medium humidity levels.From the perspective of improving hygroscopicity, the higher the content of component AB, the better. Its content is at least 20% by mass, and can account for 20-99.9% by mass of the desiccant. For example, it can be 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 960%, 97%, 98%, 99%, 99.1%, 99.2%, 99.5%, 99.7%, or 99.8% by mass. The content of component AB is preferably 40% by mass or more, more preferably 60% by mass or more, most preferably 80% by mass or more, and can reach a maximum of 99.9% by mass.
[0029] In a preferred embodiment, the moisture absorption rate of the desiccant is: 45%–80% after 168 hours at 30°C and 40% RH; preferably, 46%–78% after 168 hours; and more preferably, 48%–76% after 168 hours. The moisture absorption rate can specifically be 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, etc.
[0030] In a preferred embodiment, the moisture absorption rate of the desiccant is: 100%–140% after 168 hours at 35°C and 90%RH, preferably 105%–135%, and more preferably 110%–130%. The moisture absorption rate can specifically be 111%, 112%, 113%, 114%, 115%, 116%, 117%, 118%, 119%, 120%, 121%, 122%, 123%, 124%, 125%, 126%, 127%, 128%, 129%, etc. For lenses in camera equipment and vehicle lights, due to the continuous infiltration of outside air into the sealed space over a long period, the humidity inside the space will continuously rise. At this time, the inside of the lens is in a high-humidity environment (e.g., 35°C, 90%RH). Existing desiccants typically have a high adsorption capacity at high humidity, and this adsorption is usually physical adsorption. As the equipment operates, the internal temperature rises, leading to an increase in the amount of H2O escaping from the desiccant. This can cause fogging, resulting in relatively saturated humidity, near camera lenses and headlight lenses—a harmful form of ineffective moisture absorption. The inventors discovered that by adjusting the desiccant's formulation and the final effective components, the desiccant's moisture absorption rate under high humidity conditions is lower than that of existing desiccants. The preferred desiccant of this application achieves unexpected results.
[0031] In a preferred embodiment, the desiccant is granular with a particle size of 0.1 mm to 5 mm, specifically 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.2 mm, 1.5 mm, 1.8 mm, 2.0 mm, 2.2 mm, 2.5 mm, 3 mm, 3.5 mm, 4.0 mm, 4.5 mm, etc., which can be conventional particle sizes in the field of desiccants.
[0032] In a preferred embodiment, the desiccant particle strength is 1.0N to 25N, preferably 1.1N to 20N, and more preferably 1.2N to 15N. The particle strength of the desiccant can specifically be 1.3N, 1.4N, 1.5N, 1.6N, 1.7N, 1.8N, 1.9N, 2.0N, 2.2N, 2.5N, 2.8N, 3.0N, 3.2N, 3.5N, 3.8N, 4.0N, 4.5N, 5.0N, 5.5N, 6.0N, 6.5N, 7.0N, 7.5N, 8.0N, 9.0N, 10.0N, 11.0N, 12.0N, 13.0N, or 14.0N, etc. The inventors have found through testing that controlling the desiccant particle strength within a suitable range yields better technical results. Controlling the strength of desiccant particles to a certain level, such as above 1.0N, avoids particle breakage during production and packaging, which would generate dust and affect the use of the desiccant in the final equipment; at the same time, it can also ensure the structural strength of the particles themselves, so that the volume increase rate of the desiccant is small after fully absorbing water.
[0033] In a preferred embodiment, the volume increase rate of the desiccant at 30°C and 40%RH is 0.1%–19.9% over 168 hours. The inventors have discovered that by adjusting the desiccant formulation and the final effective components, the volume increase rate of the desiccant after moisture absorption is significantly lower than that of existing desiccants. This is because after high-temperature activation, moisture escapes from the MOC (Metal-Oxide-Cell Composite), while the desiccant retains the MOC structure. When the desiccant absorbs surrounding moisture, the moisture fills the gaps in the desiccant structure, resulting in extremely low particle expansion and minimal impact on devices near the desiccant. This avoids deformation of surrounding devices caused by desiccant expansion. Therefore, the preferred desiccant of this application is particularly suitable for applications such as surveillance cameras and automotive headlights used in small spaces. Preferably, the volume increase rate of the desiccant at 30°C and 40%RH is 0.2%–18.0% over 168 hours; more preferably, the volume increase rate is 0.3%–15.0% over 168 hours at 30°C and 40%RH. Specifically, the volume increase rate can be 0.5%, 0.8%, 1.0%, 1.2%, 1.5%, 1.8%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 6.0%, 7.0%, 8.0%, 9.0%, 10.0%, 11.0%, 12.0%, 13.0%, 14.0%, etc.
[0034] In a preferred embodiment, the raw material further contains 0-30 parts of excipients, which are selected from one or more of sulfates, hydrogen peroxide, wood flour, cellulose, silica, sepiolite, glycerol, dicyandiamide, calcium fluoride, ethanol, and polymer-modified mortar. The addition of these excipients can form fine interconnected channels in the desiccant, which helps increase the porosity of the desiccant and accelerate moisture adsorption. The preferred amount of excipients is 0.01 to 28 parts, more preferably 0.05 to 25 parts, and can also be 0.1, 0.2, 0.3, 0.4, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.7, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 12.0, 15.0, 17.0, 20.0, or 22.0 parts, etc.
[0035] In a preferred embodiment, the raw material may further contain 0-100 parts of recycled magnesium oxychloride gelling material. By adding a certain amount of recycled magnesium oxychloride gelling material, the cost of the desiccant can be further reduced. The recycled magnesium oxychloride gelling material can be the crushed and recycled material from waste magnesium oxychloride gelling material products, and its source is not specifically limited. The preferred amount of recycled magnesium oxychloride gelling material added is 0.01-90 parts, more preferably 0.05-80 parts, and can also be 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1.0 parts, 1.1 parts, 1.2 parts, 1.3 parts, 1.4 parts, 1.5 parts, 1.7 parts, 2.0 parts, 2.5 parts, 3.0 parts, etc. The quantities are available in parts, such as 3.5 parts, 4.0 parts, 4.5 parts, 5.0 parts, 6.0 parts, 7.0 parts, 8.0 parts, 9.0 parts, 10.0 parts, 12.0 parts, 15.0 parts, 20.0 parts, 25.0 parts, 30.0 parts, 35.0 parts, 40.0 parts, 45.0 parts, 50.0 parts, 55.0 parts, 60.0 parts, 65.0 parts, 70.0 parts, or 75.0 parts. The higher the purity of the recycled magnesium oxychloride gelling material, the better; for example, it can be above 50%, preferably above 60%, more preferably above 70%, and most preferably above 80%. The recycled magnesium oxychloride gelling material added to the raw materials can be ground into powder for better compatibility with other raw materials and to prepare the final desiccant.
[0036] Regarding the second aspect of this application, the purpose of this application is to provide a method for preparing a special desiccant suitable for special scenarios such as surveillance cameras and automotive headlights.
[0037] In a preferred embodiment, the process of hydrating the raw material and processing it into desiccant precursor particles specifically involves: selecting powdered raw materials, mixing the raw materials, adding water and stirring, and then sequentially performing granulation, sieving, settling, and drying; the settling time is 2.5 h to 2400 h. In another preferred embodiment, the process of hydrating the raw material and processing it into desiccant precursor particles specifically involves: selecting powdered raw materials, adding water and mixing, and then sequentially performing granulation, sieving, settling, and drying; the settling time is 2.5 h to 2400 h. When the specific raw material is solid, it is preferably powdered. Furthermore, stirring and granulation can be performed simultaneously. The purpose of settling is to allow the raw material to hydrate with water, thereby obtaining MOC in the desiccant precursor particles. To ensure the required MOC is obtained, the settling time should be at least 2.5 h; less than this time, the hydration process cannot be fully realized, and a satisfactory desiccant cannot be obtained. A longer settling time is better, but considering cost, the settling time should preferably not exceed 2400 h. Preferably, the settling time is 3h to 2200h, more preferably, the settling time is 4h to 2000h, even more preferably, the settling time is 6h to 1800h, and the preferred settling time is 240h. The settling time can be specifically 8h, 10h, 12h, 15h, 20h, 25h, 30h, 35h, 40h, 45h, 50h, 60h, 70h, 80h, 90h, 100h, 110h, 120h, 130h, 140h, 150h, 160h, 170h, 180h, 200h, 220h, 240h, 300h, 400h, 500h, 600h, 700h, 800h, 900h, 1000h, 1200h, 1400h, 1500h, 1600h, or 1700h, etc.
[0038] In a preferred embodiment, the drying temperature is 40~120℃, and the drying time is sufficient to ensure that the precursor particles are fully dehydrated.
[0039] The amount of water required for the hydration process of the raw materials is only needed to ensure that the raw materials can be fully hydrated and granulated. To improve the performance of the desiccant, the preferred amount of water added is 80 to 150 parts, for example, 82 parts, 84 parts, 86 parts, 88 parts, 90 parts, 92 parts, 94 parts, 96 parts, 98 parts, 100 parts, 102 parts, 104 parts, 106 parts, 108 parts, 110 parts, 115 parts, 120 parts, 125 parts, 130 parts, 135 parts, 140 parts, or 145 parts, etc.
[0040] Activation temperature is crucial for desiccants. If the activation temperature is below 180℃, the MOC (Modified Organic Compound) cannot decompose, resulting in extremely poor hygroscopicity of the desiccant at low to medium humidity, making it unsuitable for applications such as surveillance cameras and automotive headlights. Conversely, if the activation temperature is too high, such as exceeding 500℃, the MOC will undergo excessive decomposition, leading to an excessively high rate of moisture absorption by the desiccant, which fails to meet requirements. In a preferred embodiment, the activation temperature is preferably 200~480℃, more preferably 220~460℃, and most preferably 250~450℃. The activation temperature can specifically be 260℃, 270℃, 280℃, 290℃, 300℃, 310℃, 320℃, 330℃, 340℃, 350℃, 360℃, 370℃, 380℃, 390℃, 400℃, 410℃, 420℃, 430℃, or 440℃, etc.
[0041] In a preferred embodiment, the activation treatment time is preferably 30 min to 600 min. An activation treatment time of 30 min or more ensures the activation of the MOC. Furthermore, for cost reasons and to avoid over-activation of the precursor, the activation time can be less than 600 min. Specific activation treatment times can be 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, 120 min, 130 min, 140 min, 150 min, 160 min, 170 min, 180 min, 190 min, 200 min, 220 min, 250 min, 300 min, 350 min, 400 min, 450 min, 500 min, or 550 min. Of course, if the activation temperature is lower, the activation time can be slightly longer; conversely, if the activation temperature is higher, the activation time can be controlled to be slightly shorter to avoid over-activation of the precursor. In addition, the temperature during the activation process can be kept constant, or it can be increased or decreased in stages, or other forms of temperature change, as long as the activation effect is guaranteed.
[0042] In a preferred embodiment, the preparation method includes the following steps:
[0043] 1) Select powdered raw materials, stir the raw materials to obtain mixed raw materials;
[0044] 2) Add the mixed raw materials and water to the granulation equipment for granulation;
[0045] 3) After granulation, the formed granules are sieved and optionally polished;
[0046] 4) Allow the sieved particles to stand for 2.5h to 2400h;
[0047] 5) Dry the granules after they have been left to stand at 40~120℃ to obtain the desiccant precursor;
[0048] 6) The desiccant precursor is activated at 180–500°C to obtain the desiccant.
[0049] The preparation method of the desiccant of this application is further described below with reference to specific embodiments. Those skilled in the art can refer to the content of this application and appropriately improve the process parameters to achieve the desired result. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included within the scope of this application. The methods and applications of this application have been described through preferred embodiments. Those skilled in the art can obviously modify or appropriately change and combine the methods and applications described in this application without departing from the content, spirit, and scope of this application to realize and apply the technology of this application.
[0050] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.
[0051] Example 1
[0052] A desiccant is prepared from the following raw materials: 60g of lightly calcined magnesium oxide powder A, 40g of anhydrous magnesium chloride powder B, and 1g of silicate cement powder C. The preparation method includes: mixing the powdered raw materials A, B, and C to obtain a mixture; weighing 125g of water; adding the mixture and water to a granulator for stirring and granulation; after granulation, placing the formed granules into a vibrating screen for sieving to obtain granules with a diameter of 1.5–2 mm; allowing the sieved granules to stand for 72 hours; then drying the standing granules at 110°C for 1.5 hours in a dryer to obtain desiccant precursor granules; subsequently, activating the desiccant precursor granules in a heating furnace at 310°C for 30 minutes and 370°C for 60 minutes sequentially to finally obtain desiccant granules 1.
[0053] Example 2
[0054] A desiccant is prepared from the following raw materials: 60g of lightly calcined magnesium oxide powder A, 40g of anhydrous magnesium chloride powder B, and 1.5g of molecular sieve powder C. The preparation method includes: mixing the powdered raw materials A, B, and C to obtain a mixture; weighing 125g of water; adding the mixture and water to a granulator for stirring and granulation; after granulation, placing the formed granules into a vibrating screen for sieving to obtain granules with a diameter of 1.5–2mm; allowing the sieved granules to stand for 144 hours; then drying the standing granules in a dryer at 90℃ for 2 hours to obtain desiccant precursor granules; subsequently, activating the desiccant precursor granules in a heating furnace at 400℃ for 40 minutes to finally obtain desiccant granules 2.
[0055] Example 3
[0056] A desiccant is prepared from the following raw materials: 60g of lightly calcined magnesium oxide powder A, 40g of anhydrous magnesium chloride powder B, and 2g of 30% silica sol C. The preparation method includes: mixing raw materials A, B, and C to obtain a mixture; weighing 125g of water; adding the mixture and water to a granulator for stirring and granulation; after granulation, placing the formed granules into a vibrating screen for sieving to obtain granules with a diameter of 1.5–2mm; allowing the sieved granules to stand for 144h; then drying the standing granules in a dryer at 90℃ for 2h to obtain desiccant precursor granules; subsequently, activating the desiccant precursor granules in a heating furnace at 400℃ for 40min to finally obtain desiccant granules 3.
[0057] Example 4
[0058] A desiccant is prepared from the following raw materials: 60g of lightly calcined magnesium oxide powder A, 40g of anhydrous magnesium chloride powder B, and 0.5g of organosilicon resin C. The preparation method includes: mixing raw materials A, B, and C to obtain a mixture; weighing 125g of water; adding the mixture and water to a granulator for stirring and granulation; after granulation, placing the formed granules into a vibrating screen for sieving to obtain granules with a diameter of 1.5–2mm; allowing the sieved granules to stand for 144h; then drying the standing granules in a dryer at 80℃ for 2h to obtain desiccant precursor granules; subsequently activating the desiccant precursor granules in a heating furnace sequentially at 220℃ / 30min, 310℃ / 30min, and 360℃ / 60min to finally obtain desiccant granules 4.
[0059] Example 5
[0060] A desiccant is prepared from the following raw materials: 65g of lightly calcined magnesium oxide powder A, 35g of anhydrous magnesium chloride powder B, and 1g of phosphoric acid C. The preparation method includes: mixing raw materials A, B, and C to obtain a mixture; weighing 100g of water; adding the mixture and water to a granulator for stirring and granulation; after granulation, placing the formed granules into a vibrating screen for sieving to obtain granules with a diameter of 1.5–2mm; allowing the sieved granules to stand for 144h; then drying the standing granules in a dryer at 80℃ for 2h to obtain desiccant precursor granules; subsequently, activating the desiccant precursor granules in a heating furnace at 370℃ for 60min to finally obtain desiccant granules.
[0061] Example 6
[0062] A desiccant is prepared from the following raw materials: 40g of lightly calcined magnesium oxide powder A1, 29g of magnesium hydroxide A2, 85g of magnesium chloride hexahydrate B, 1g of glass fiber powder C, and 0.3g of sepiolite powder D. The preparation method includes: mixing raw materials A1, A2, B, C, and D to obtain a mixture; weighing 80g of water; adding the mixture and water to a granulator for stirring and granulation; after granulation, placing the formed granules into a vibrating screen for sieving to obtain granules with a diameter of 1.5–2mm; allowing the sieved granules to stand for 120 hours; then drying the standing granules at 100℃ for 1 hour in a dryer to obtain desiccant precursor granules; subsequently, activating the desiccant precursor granules in a heating furnace at 220℃ / 30min, 310℃ / 30min, and 380℃ / 30min sequentially to finally obtain desiccant granules 6.
[0063] Example 7
[0064] A desiccant is prepared from the following raw materials: 50g of lightly calcined magnesium oxide powder A, 50g of anhydrous magnesium chloride powder B, and 1g of epoxy resin C. The preparation method includes: mixing powdered raw materials A, B, and C to obtain a mixture; weighing 125g of water; adding the mixture and water to a granulator for stirring and granulation; after granulation, placing the formed granules into a vibrating screen for sieving to obtain granules with a diameter of 1.5–2mm; allowing the sieved granules to stand for 72 hours; then drying the standing granules at 100℃ for 2 hours in a dryer to obtain desiccant precursor granules; subsequently, activating the desiccant precursor granules in a heating furnace at 310℃ for 30 minutes and 370℃ for 1 hour sequentially to finally obtain desiccant granules 7.
[0065] Example 8
[0066] A desiccant is prepared from the following raw materials: 40g of lightly calcined magnesium oxide powder A, 60g of anhydrous magnesium chloride powder B, and 1g of silicate. The preparation method includes: mixing powdered raw materials A, B, and C to obtain a mixture; weighing 125g of water; adding the mixture and water to a granulator for stirring and granulation; after granulation, placing the formed granules into a vibrating screen for sieving to obtain granules with a diameter of 1.5–2mm; allowing the sieved granules to stand for 72 hours; then drying the standing granules at 100℃ for 2 hours in a dryer to obtain desiccant precursor granules; subsequently, activating the desiccant precursor granules in a heating furnace at 310℃ / 30min and 370℃ / 60min sequentially to finally obtain desiccant granules 8.
[0067] Comparative Example 1
[0068] A desiccant is prepared from the following raw materials: 60g of lightly calcined magnesium oxide powder A, 40g of anhydrous magnesium chloride powder B, and 1g of silicate cement powder C. The preparation method includes: mixing the powdered raw materials A, B, and C to obtain a mixture; weighing 125g of water; adding the mixture and water to a granulator for stirring and granulation; after granulation, placing the formed granules into a vibrating screen for sieving to obtain granules with a diameter of 1.5–2mm; drying the sieved granules in a dryer at 100℃ for 2 hours within 2 hours to obtain desiccant precursor granules; subsequently heating the desiccant precursor granules in a heating furnace sequentially at 310℃ / 30min and 370℃ / 60min to finally obtain desiccant granules D1.
[0069] Comparative Example 2
[0070] A desiccant is prepared from 60g of lightly calcined magnesium oxide powder A and 40g of anhydrous magnesium chloride powder B. The particle size of the powders is 100-200 mesh. The powdered raw materials A and B are mixed to obtain desiccant D2.
[0071] Comparative Example 3
[0072] A desiccant is prepared from the following raw materials: 40g magnesium hydroxide A, 45g magnesium chloride hexahydrate B, 13g alumina powder C, 0.7g lignin D, 0.7 parts carboxymethyl cellulose E, and 0.6g glass fiber F. The preparation method includes: mixing raw materials A to F to obtain a mixture; weighing 125g of water; adding the mixture and water to a granulator for stirring and granulation; after granulation, placing the formed granules into a vibrating screen for sieving to obtain granules with a diameter of 1.5–2mm; drying the sieved granules in a desiccant for 1 hour within 2 hours; the temperature distribution of the dryer is a trapezoidal increase from the inlet to the outlet of 80–120℃ to obtain desiccant precursor granules; adding the desiccant precursor granules into a calcination furnace for calcination; the calcination temperature of the calcination furnace is a trapezoidal increase from 100–420℃ for 120 minutes to finally obtain desiccant granules D3.
[0073] Comparative Example 4
[0074] A desiccant is prepared from 60g of lightly calcined magnesium oxide powder A and 40g of anhydrous magnesium chloride powder B. The preparation method includes: mixing powdered raw materials A and B to obtain a mixture; weighing 125g of water; adding the mixture and water to a granulator for stirring and granulation; after granulation, placing the formed granules into a vibrating screen for sieving to obtain granules with a diameter of 1.5–2mm; allowing the sieved granules to stand for 72 hours to obtain precursor granules; then heating the precursor granules in a furnace at 105℃ for 120 minutes to finally obtain desiccant granules D4.
[0075] Comparative Example 5
[0076] A desiccant is prepared from the following raw materials: 30g of lightly calcined magnesium oxide powder A, 15g of magnesium hydroxide C, and 50g of anhydrous magnesium chloride powder C. The preparation method includes: mixing raw materials A, B, and C to obtain a mixture; weighing 100g of water; thoroughly stirring the mixture and water; allowing it to stand for 144 hours; crushing and grinding the agglomerated material after standing to obtain a 120-mesh desiccant precursor powder; and then heating the desiccant precursor powder in a furnace at 105℃ for 120 minutes to finally obtain desiccant powder D5.
[0077] The desiccant particle strength (N), hygroscopicity (%), volume gain rate, and state of Examples 1-8 and Comparative Examples 1-5 were tested respectively. The specific testing methods are as follows:
[0078] Desiccant particle strength (expressed as crushing resistance index) (N): Tested according to the crushing resistance determination method in the chemical industry standard: HG / T2783~2020 "Test Method for Crushing Resistance of Molecular Sieve".
[0079] Hygroscopicity (%): Tested according to the hygroscopicity test method in the packaging industry standard BB / T0049 "Desiccant for Packaging"; the test conditions include two types: 35℃, 90%RH and 30℃, 40%RH.
[0080] The volume increase rate was measured after 168 hours of hygroscopicity testing at 30℃ and 40% RH. The increase rate was represented by the number of stars (★), where ★ indicates a volume increase rate of 0% to less than 5%, ★★ indicates a volume increase rate of 5% to less than 10%, ★★★ indicates a volume increase rate of 10% to less than 20%, ★★★★ indicates a volume increase rate of 20% to less than 50%, ★★★★★ indicates a volume increase rate of 50% to less than 100%, and ★★★★★★ indicates a volume increase rate of more than 100%.
[0081] The condition of the key desiccant was determined after a 168-hour moisture absorption test at 35°C and 90% RH.
[0082] The specific test results are shown in Table 1:
[0083] Table 1
[0084] As shown in Table 1, the desiccant in Comparative Example 1, due to insufficient settling, had extremely low MOC content in its precursor particles and a volume increase rate exceeding 20%, failing to meet usage requirements. Comparative Example 2, being a powdered desiccant, lacked particle strength; however, its volume increase rate exceeded 100%, failing to meet usage requirements and generating dust and other defects. Comparative Example 3, similar to Comparative Example 1, although subjected to high-temperature treatment, still suffered from insufficient settling time, resulting in extremely low MOC content in its precursor particles and a volume increase rate exceeding 20%, failing to meet usage requirements. Comparative Example 4, lacking high-temperature activation treatment, contained a large amount of MOC, resulting in poor hygroscopicity and failing to meet requirements. Comparative Example 5 exhibited poor hygroscopicity and a high volume expansion rate, failing to meet requirements.
[0085] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.
Claims
1. A desiccant, characterized in that, The preparation method of the desiccant includes the following steps: hydrating the raw material and processing it into desiccant precursor particles, and then activating the desiccant precursor particles at 180-500°C. The raw materials include the following substances in parts by weight: Raw material A 30-70 parts Raw material B 15-60 parts Admixture 0.01 to 30 parts The raw material A is selected from magnesium oxide and / or magnesium hydroxide, and the raw material B is selected from magnesium chloride and / or magnesium chloride hydrate; The additives include one or more of the following: silica sol, silicate, phosphoric acid, phosphate, cement, alumina, molecular sieve, aluminate, glass fiber, silicone resin, and epoxy resin.
2. The desiccant according to claim 1, characterized in that, The desiccant precursor particles contain 20% to 99.9% by mass of magnesium oxychloride cementitious material.
3. The desiccant according to claim 1, characterized in that, The magnesium oxide is selected from one or more of the following: calcined magnesium oxide, light-calcined magnesium oxide, and molten magnesium oxide, and / or... The magnesium oxide contains MgO content of 85% by mass or more, and / or, The magnesium chloride is selected from one or more of anhydrous magnesium chloride, magnesium chloride hexahydrate, and magnesium chloride dihydrate, and / or... In raw materials A and B, the mass ratio of available MgO to available MgCl2 is 30~70:15~60, and / or, The phosphate is selected from one or more of alkali metal phosphates, alkaline earth metal phosphates, transition metal phosphates, aluminum dihydrogen phosphate, aluminum orthophosphate, aluminum metaphosphate, and aluminum polyphosphate.
4. The desiccant according to any one of claims 1 to 3, characterized in that, The volume increase rate of the desiccant at 30°C and 40%RH for 168 hours is 0.1% to 19.9%.
5. The desiccant according to any one of claims 1 to 3, characterized in that, The desiccant has a moisture absorption rate of 45%–80% after 168 hours at 30°C and 40% RH, and / or, The desiccant has a moisture absorption rate of 100%–140% at 35°C and 90% RH for 168 hours, and / or, The volume increase rate of the desiccant at 30°C and 40%RH for 168 hours is 0.1% to 19.9%.
6. The desiccant according to any one of claims 1 to 3, characterized in that, The desiccant is in granular form with a particle size of 0.5 to 5 mm, and / or the particle strength of the desiccant is 1.0 to 25 N.
7. The desiccant according to any one of claims 1 to 3, characterized in that, The raw material also contains 0.01 to 30 parts of auxiliary materials, which are selected from one or more of sulfate, hydrogen peroxide, wood flour, cellulose, silica, sepiolite, glycerol, dicyandiamide, calcium fluoride, ethanol, and polymer-modified mortar, and / or the raw material contains 0.01 to 100 parts of recycled magnesium oxychloride cementitious material.
8. A method for preparing a desiccant as described in any one of claims 1 to 7, characterized in that, The preparation method includes: The raw materials are hydrated and processed into desiccant precursor particles, and then the desiccant precursor particles are activated at 180-500°C.
9. The method for preparing the desiccant according to claim 8, characterized in that, The specific steps involved in processing the raw materials and water into a desiccant precursor are as follows: Select powdered raw materials, mix them, add water and stir, then granulate, sieve, let stand, and dry in sequence; the standing time is 2.5h to 2400h, or... Select powdered raw materials, add water and mix, then granulate, sieve, stand, and dry in sequence; the standing time is 2.5 to 2400 hours.
10. The method for preparing the desiccant according to claim 8, characterized in that, The preparation method includes the following steps: 1) Select powdered raw materials, mix them to obtain the mixed raw materials; 2) Add the mixed raw materials and water to the granulation equipment for granulation; 3) After granulation, the formed granules are sieved and optionally polished; 4) Allow the sieved particles to stand for 2.5h to 2400h; 5) Dry the granules after they have been left to stand at 40~120℃ to obtain the desiccant precursor; 6) The desiccant precursor is activated at 180–500°C to obtain the desiccant.