A granular desiccant and preparation method thereof

Abstract

The present application discloses a granular desiccant and a preparation method thereof, and relates to the technical field of desiccant. The granular desiccant comprises calcium oxide hygroscopic particles and a water-proof breathable membrane arranged from the inside to the outside. The calcium oxide hygroscopic particles are prepared by mixing calcium carbonate, sodium carbonate, aluminum hydroxide, aluminum oxide modified particles and water in a weight ratio of (60-80): (5-15): (10-30): (3-10): (20-25) and then extruding granulation, baking and calcining. The aluminum oxide modified particles are prepared by modifying aluminum oxide particles with methacryloxysilane, triethanolamine oleate and hexamethyldisiloxane. The water-proof breathable membrane is prepared by uniformly spraying a water-proof breathable material onto the outer surface of the calcium oxide hygroscopic particles and then cooling. The granular desiccant of the present application has the characteristics of high hygroscopicity and no risk of severe heat release.

Description

Technical Field

[0001] The present application relates to the technical field of desiccants, and in particular to a granular desiccant and a preparation method thereof. Background Art

[0002] Desiccant is widely used in food, medicine, industrial products and household products to ensure the suitability of storage conditions and prevent products from deteriorating in a humid environment. In recent years, as people's requirements for quality increase, efficient and safe desiccant has become the focus of market research and development.

[0003] Existing desiccants are mainly divided into two categories according to the principle of moisture absorption: physical moisture absorption type and chemical moisture absorption type. Physical moisture absorption type desiccants are generally silica gel desiccants, mineral desiccants, etc., which mainly achieve the drying function by absorbing moisture through the pore structure. Chemical moisture absorption type desiccants are generally calcium chloride, magnesium chloride and calcium oxide desiccants, which achieve moisture absorption through chemical reactions with water.

[0004] Among them, the moisture absorption rate of calcium oxide desiccant is only about 30%, which limits the application of calcium oxide desiccant in high humidity environments. In addition, calcium oxide easily releases high heat when it comes into contact with water, which poses certain safety hazards.

[0005] In order to solve the problem of low moisture absorption rate of calcium oxide desiccant, the related technology provides a process of calcium oxide granulation, wherein calcium hydroxide or calcium carbonate and some binding materials are added into water, stirred and granulated, and calcium oxide particles with a certain strength are manufactured by roasting, and the moisture absorption rate of the calcium oxide particles is improved by using the roasted calcium oxide and the microporous structure inside the particles. At present, the moisture absorption rate of the desiccant manufactured by this method can reach more than 50%, but the moisture absorption rate of the calcium oxide particles manufactured by this method is still very limited, and high heat is still released when it comes into contact with water, and the dangerous problem of the calcium oxide desiccant is not solved. Summary of the invention

[0006] In order to improve the problems of low moisture absorption rate and dangerous heat release of calcium oxide desiccant in the related art when it comes into contact with water, the present application provides a granular desiccant and a preparation method thereof.

[0007] In the first aspect, the present application provides a granular desiccant using the following technical solution:

[0008] A granular desiccant, comprising calcium oxide hygroscopic particles and a water-proof and breathable membrane arranged from the inside out. The calcium oxide hygroscopic particles are prepared by mixing calcium carbonate, sodium carbonate, aluminum hydroxide, aluminum oxide modified particles and water in a weight ratio of (60-80): (5-15): (10-30): (3-10): (20-25) and then subjected to extrusion granulation, baking and calcination. The aluminum oxide modified particles are prepared by modifying aluminum oxide particles with methacryloxysilane, triethanolamine oleate and hexamethyldisiloxane. The water-proof and breathable membrane is prepared by uniformly spraying a water-proof and breathable material onto the outer surface of the calcium oxide hygroscopic particles and then cooling them.

[0009] The granular desiccant of the present application has the characteristics of high hygroscopicity and no risk of violent heat release. Among them, the calcium oxide hygroscopic particles are prepared by mixing calcium carbonate, sodium carbonate, aluminum hydroxide and aluminum oxide modified particles in a specific proportion. Calcium carbonate, sodium carbonate and aluminum hydroxide generate gas and water vapor after calcination, which can form microporous channels inside the granular desiccant. In addition, the addition of sodium carbonate can also passivate the calcium oxide hygroscopic particles in the granular desiccant, which can inhibit the problem of high heat generation of calcium oxide hygroscopic particles in the granular desiccant when they come into contact with water. The aluminum oxide modified particles are obtained by modifying aluminum oxide particles by methacryloxysilane, triethanolamine oleate and hexamethyldisiloxane, and have a large specific surface area and pore frame effect. The role of the aluminum oxide modified particles is mainly to improve the internal microporous framework of the calcium oxide hygroscopic particles by using the ultra-high specific surface area to form a channel that penetrates the inside to enhance the hygroscopic speed and hygroscopic capacity of the granular desiccant for water molecules. The aluminum oxide obtained after calcining aluminum hydroxide can be used as a matrix material to increase the strength of the granular desiccant. The water-proof and breathable membrane is made by evenly spraying a water-proof and breathable material on the surface of the calcium oxide hygroscopic particles and then cooling it. The water-proof and breathable membrane can allow water vapor molecules to pass through, while isolating water on the outside of the calcium oxide hygroscopic particles, preventing the calcium oxide hygroscopic particles in the granular desiccant from reacting violently and releasing heat when in contact with water, thereby solving the safety hazard problems of the traditional calcium oxide desiccant's low moisture absorption rate and violent heat release when in contact with water.

[0010] Preferably, the method for preparing the alumina modified particles comprises the following steps:

[0011] Under the catalytic action of ammonium trifluoroacetate, methacryloxysilane and alumina particles are coupled to obtain preliminary product particles;

[0012] Under the catalytic action of cerium sulfate, triethanolamine oleate is coupled with the preliminary product particles to obtain an intermediate product;

[0013] The intermediate product is mixed with an alcohol solution of hexamethyldisiloxane to react and obtain aluminum oxide modified particles.

[0014] In the present application, alumina particles are subjected to a coupling reaction with methacryloxysilane under the catalysis of ammonium trifluoroacetate to obtain preliminary product particles, the preliminary product particles are further subjected to a coupling reaction with triethanolamine oleate under the catalysis of cerium sulfate to obtain an intermediate product, and finally the intermediate product is mixed with an alcohol solution of hexamethyldisiloxane to obtain alumina modified particles. The alumina modified particles have an ultra-large specific surface area and a pore frame effect, and can form a channel for penetrating the interior of the calcium oxide hygroscopic particles, thereby significantly improving the moisture absorption rate and moisture absorption capacity of the granular desiccant.

[0015] Specifically, the methacryloxysilane may be γ-methacryloxypropyltrimethoxysilane.

[0016] The alcohol solution of hexamethyldisiloxane may be a glycerol solution of hexamethyldisiloxane, and the mass concentration of hexamethyldisiloxane in the glycerol solution of hexamethyldisiloxane is 5-10%.

[0017] Preferably, the water-proof and breathable material is prepared by heating and melting microcrystalline wax, a dispersant and modified calcium carbonate particles uniformly and then cooling.

[0018] In the present application, a water-proof and breathable material is prepared by heating and melting microcrystalline wax, a dispersant and modified calcium carbonate particles uniformly and then cooling them. The addition of the dispersant can improve the dispersibility of the modified calcium carbonate particles in the microcrystalline wax, and a water-proof and breathable membrane with good air permeability and water-proof effect can be obtained, ensuring that water vapor molecules can pass through the water-proof and breathable membrane into the interior of the calcium oxide hygroscopic particles, thereby achieving the hygroscopic effect of the granular desiccant. At the same time, the water-proof and breathable membrane can effectively isolate the calcium oxide hygroscopic particles from water, preventing the occurrence of violent heat release when the calcium oxide hygroscopic particles meet water, thereby improving the safety of the granular desiccant.

[0019] Preferably, the weight ratio of the microcrystalline wax, the dispersant and the modified calcium carbonate particles is (15-25): (1-3): (1-2).

[0020] In the present application, when the water-proof and breathable material is prepared using raw materials within the above-mentioned ratio range, the water-proof and breathable film formed on the surface of the calcium oxide hygroscopic particles has better air permeability and water-proof properties, which is beneficial to increasing the moisture absorption rate of the granular desiccant, and further improves the heat release phenomenon of the granular desiccant when it comes into contact with water, thereby enhancing the safety and use effect of the granular desiccant.

[0021] Preferably, the modified calcium carbonate particles are silicon-containing calcium carbonate particles.

[0022] In the present application, the silicon-containing calcium carbonate particles can significantly improve the stability and air permeability of the water-proof and breathable membrane, thereby enhancing the moisture absorption rate of the granular desiccant, while blocking water and effectively preventing the granular desiccant from releasing heat violently when it comes into contact with water.

[0023] Preferably, the preparation of the silicon-containing calcium carbonate particles comprises the following steps:

[0024] The calcium carbonate particles are added into the organic silicon ethylene glycol solution, heated to 180-220°C for reaction, and then kept warm, filtered, washed and dried to obtain silicon-containing calcium carbonate particles.

[0025] The silicon-containing calcium carbonate particles in the present application can be better dispersed in the microcrystalline wax, reducing agglomeration, allowing the water-proof and breathable membrane to smoothly allow water vapor molecules to pass through and block water, which is beneficial to improving the hygroscopic performance of the granular desiccant while ensuring the safety performance of the granular desiccant.

[0026] The ethylene glycol solution of organic silicon contains 4-6 wt % of organic silicon, and the organic silicon can be any one of epoxy silane and vinyl silane.

[0027] Preferably, the preparation of the silicon-containing calcium carbonate particles further includes a step of preparing calcium carbonate particles, and the step of preparing the calcium carbonate particles is as follows:

[0028] Calcium chloride and sodium carbonate are added to an ethanol solution of methyl oleate, and the temperature is raised to 130-170° C. for reaction, followed by filtering, washing and drying to obtain calcium carbonate particles.

[0029] The above technical scheme of the present application first uses calcium chloride and sodium carbonate to react in an ethanol solution of methyl oleate to prepare calcium carbonate particles. The calcium carbonate particles have better dispersibility in the silicone glycol solution, which can promote the uniform modification of the calcium carbonate particles, help the water-proof and breathable membrane to form a uniform microporous structure, thereby further improving the air permeability of the water-proof and breathable membrane and improving the moisture absorption rate of the granular desiccant.

[0030] Wherein, in the ethanol solution of methyl oleate, the mass concentration of methyl oleate is 8-12%.

[0031] In a second aspect, the present application provides a method for preparing a granular desiccant using the following technical solution:

[0032] A method for preparing a granular desiccant, based on preparing any one of the granular desiccant described above, comprises the following steps:

[0033] Calcium carbonate, sodium carbonate, aluminum hydroxide and aluminum oxide modified particles are mixed in proportion, stirred, then water is added and stirred and mixed to form, and then extruded into granules, baked and calcined to obtain calcium oxide hygroscopic particles;

[0034] The water-proof and breathable material is evenly sprayed onto the surface of the calcium oxide hygroscopic particles, and then cooled to obtain a granular desiccant.

[0035] By adopting the above technical scheme, a permeable channel can be formed inside the calcium oxide hygroscopic particles to enhance the moisture absorption rate and moisture absorption capacity. At the same time, by spraying the waterproof and breathable film, the occurrence of violent heat release of the calcium oxide particle desiccant when it comes into contact with water is improved, thereby improving the safety and practicality of the calcium oxide particle desiccant.

[0036] Preferably, the baking adopts a continuous temperature rise mode with a temperature range of 150-300°C, and the calcination temperature is 900-1200°C.

[0037] By adopting the above technical solution, a continuous temperature rise mode is used for baking, and the temperature range is controlled at 150-300°C, which ensures that the calcium oxide hygroscopic particles are evenly heated during the baking process, avoiding the problem of particle structure destruction or decreased hygroscopic performance due to excessively high or low temperature; the calcination temperature is set at 900-1200°C, which ensures the stability of the calcium oxide hygroscopic particles at high temperatures and effectively improves the hygroscopic capacity and durability of the particles.

[0038] Preferably, when spraying the water-proof and breathable material, the water-proof and breathable material is added into a high-temperature spraying device, and the calcium oxide hygroscopic particles are allowed to fall into a hollow spraying chamber, and the water-proof and breathable material is sprayed at high temperature from all sides of the spraying chamber, and cooled to obtain a granular desiccant.

[0039] When spraying the waterproof and breathable material, add the waterproof and breathable material into the high-temperature spraying equipment, and allow the calcium oxide hygroscopic particles to fall into the hollow spray chamber. Spray the waterproof and breathable material at high temperature from all sides of the spray chamber to form a uniform and dense waterproof and breathable film on the outer surface of the calcium oxide hygroscopic particles, thereby improving the air permeability and waterproofing properties of the waterproof and breathable film.

[0040] In summary, the present application includes at least one of the following beneficial technical effects:

[0041] (1) The present application prepares calcium oxide hygroscopic particles by using calcium carbonate, sodium carbonate, aluminum hydroxide and aluminum oxide modified particles in a specific ratio, thereby forming a permeable channel inside the calcium oxide hygroscopic particles, thereby significantly improving the hygroscopic capacity of the calcium oxide hygroscopic particles;

[0042] (2) The present application provides a water-proof and breathable membrane on the outer surface of the calcium oxide hygroscopic particles. The water-proof and breathable membrane is made of microcrystalline wax, dispersant and modified calcium carbonate particles. The water-proof and breathable membrane has excellent air permeability and can prevent the direct contact between the calcium oxide hygroscopic particles inside the granular desiccant and water. In addition, the passivation effect of sodium carbonate on the calcium oxide in the granular desiccant effectively prevents the problem of calcium oxide in the granular desiccant releasing heat violently when it comes into contact with water, thereby enhancing the safety of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1This is a schematic diagram of the structure of a granular desiccant according to an embodiment of the present application.

[0044] Reference numerals:

[0045] 1. Calcium oxide hygroscopic particles; 2. Water-proof and breathable membrane. DETAILED DESCRIPTION

[0046] The present application discloses a granular desiccant, referring to Figure 1 , including calcium oxide hygroscopic particles 1 and a water-proof and breathable membrane 2 arranged from the inside to the outside. The calcium oxide hygroscopic particles 1 are prepared by mixing calcium carbonate, sodium carbonate, aluminum hydroxide, aluminum oxide modified particles and water in a weight ratio of (60-80): (5-15): (10-30): (3-10): (20-25) and then extruding, granulating, baking and calcining.

[0047] The aluminum oxide modified particles are obtained by modifying the aluminum oxide particles with methacryloxysilane, triethanolamine oleate and hexamethyldisiloxane. Specifically, the preparation method of the aluminum oxide modified particles includes the following steps:

[0048] Alumina particles are added to dimethyl sulfoxide, and then ammonium trifluoroacetate and methacryloxysilane are added, the temperature is raised to 75-85° C., and the reaction is heated for 1.8-2.2 hours, followed by filtering, washing, and drying to obtain preliminary product particles;

[0049] Add cerium sulfate, triethanolamine oleate and citric acid to deionized water and stir evenly, then add to a high-pressure reactor, gradually heat to 175-185°C, stir and react for 1.5-2.5 hours, add preliminary product particles, continue to react for 10-14 hours, then filter, wash and dry to obtain an intermediate product;

[0050] The intermediate product is added to glycerol, heated to 95-105° C., and then a glycerol solution of hexamethyldisiloxane is added dropwise. After reacting for 2.5-3.5 hours, the mixture is kept warm for 1 hour, and then filtered, washed, and dried to obtain alumina modified particles.

[0051] The water-proof and breathable membrane 2 is obtained by uniformly spraying a water-proof and breathable material onto the outer surface of the calcium oxide hygroscopic particles and then cooling. The water-proof and breathable membrane 2 is a thin film that allows water vapor molecules to pass through while blocking water from passing through. For example, the water-proof and breathable membrane 2 can be prepared by using a water-proof and breathable material obtained by uniformly heating and melting microcrystalline wax, a dispersant, and modified calcium carbonate particles and cooling them. The preparation method of the water-proof and breathable material specifically includes the following steps:

[0052] After heating and melting 15-25 parts by weight of microcrystalline wax, add 1-3 parts by weight of dispersant and 1-2 parts by weight of modified calcium carbonate particles, then stir at 75-85°C and 140-160r / min until uniformly mixed, cool, and obtain a waterproof and breathable material.

[0053] The dispersant is at least one of sodium dodecylbenzene sulfonate and sodium dodecyl sulfate.

[0054] The preparation method of modified calcium carbonate particles comprises the following steps:

[0055] Add 40-50 parts by weight of calcium chloride and 40-50 parts by weight of sodium carbonate to 1000 parts by weight of methyl oleate ethanol solution, raise the temperature to 145-155° C., stir and heat to react for 4.5-5.5 hours, filter, wash and dry the product after the reaction to obtain calcium carbonate particles;

[0056] 45-55 parts by weight of calcium carbonate particles are added to 500 parts by weight of ethylene glycol solution of silicone, heated to 195-205° C. in a reactor, reacted for 2.8-3.2 hours and then kept warm for 1 hour, and the product after the reaction is filtered, washed and dried to obtain modified calcium carbonate particles.

[0057] The present application also discloses a method for preparing the above-mentioned granular desiccant, comprising the following steps:

[0058] (1) Calcium carbonate, sodium carbonate, aluminum hydroxide, and aluminum oxide modified particles are mixed in proportion, stirred, and then water is added to continue stirring and mixing to form, and then extruded into granules, baked, and calcined to obtain calcium oxide hygroscopic particles 1;

[0059] (2) The water-proof and breathable material is uniformly sprayed onto the surface of the calcium oxide hygroscopic particles 1 and cooled to obtain a granular desiccant.

[0060] The baking in step (1) adopts a continuous heating mode with a temperature range of 150-300°C.

[0061] The calcination temperature in step (1) is 900-1200°C.

[0062] The present application is further described below in conjunction with specific experiments.

[0063] Preparation example of alumina modified particles

[0064] [Preparation Example 1-1]

[0065] A kind of aluminum oxide modified particles, the preparation method thereof is as follows:

[0066] S1. Add 5 kg of alumina particles to 10 kg of dimethyl sulfoxide, then add 0.1 kg of ammonium trifluoroacetate and 1 kg of γ-methacryloxypropyltrimethoxysilane, raise the temperature to 80° C., heat to react for 2 hours, then filter, wash, and dry to obtain preliminary product particles; wherein the alumina particles were purchased from Jinan Zhiheng Zhiyuan Chemical Technology Co., Ltd.;

[0067] S2, adding 0.01kg of cerium sulfate, 1.5kg of triethanolamine oleate and 0.5kg of citric acid to 20kg of deionized water and stirring evenly, then adding to a high-pressure reactor, gradually heating to 180°C, stirring and reacting for 2h, adding 4.2kg of preliminary product particles, continuing the reaction for 12h, then filtering, washing and drying to obtain an intermediate product;

[0068] S3, add 4 kg of the intermediate product to 10 kg of glycerol, heat to 100°C, then drop 5 kg of hexamethyldisiloxane glycerol solution, react for 3 hours, keep warm for 1 hour, then filter, wash, and dry to obtain alumina modified particles. The mass concentration of hexamethyldisiloxane in the glycerol solution of hexamethyldisiloxane is 7.5%.

[0069] [Preparation Example 1-2]

[0070] An alumina modified particle, which differs from [Preparation Example 1-1] in that:

[0071] Step S1 was omitted, and the preliminary product particles in step S2 were replaced by an equal amount of alumina particles. In this preparation example, the alumina particles used in step S1 were purchased from Jinan Zhiheng Zhiyuan Chemical Technology Co., Ltd.

[0072] [Preparation Example 1-3]

[0073] An alumina modified particle, which differs from [Preparation Example 1-1] in that:

[0074] Step S2 is omitted, and the intermediate product in step S3 is replaced by an equal amount of the preliminary product particles prepared in step S1.

[0075] [Preparation Example 1-4]

[0076] An alumina modified particle, which differs from [Preparation Example 1-1] in that:

[0077] The S3 step is omitted, and the intermediate product is directly used as the alumina modified particles.

[0078] Preparation example of modified calcium carbonate particles

[0079] [Preparation Example 2-1]

[0080] A modified calcium carbonate particle, the preparation method of which is as follows:

[0081] 50 kg of calcium carbonate particles were added to 500 kg of ethylene glycol solution of organosilicon, heated to 200 ° C in a reactor, reacted for 3 hours and then kept warm for 1 hour, and the product after the reaction was filtered, washed, and dried to obtain modified calcium carbonate particles. Among them, the ethylene glycol solution of organosilicon is an ethylene glycol solution of γ-(2,3-epoxypropoxy)propyltrimethoxysilane, and the mass content of γ-(2,3-epoxypropoxy)propyltrimethoxysilane is 5%. In this preparation example, calcium carbonate particles were purchased from Lingshou County Wanzhu Mineral Products Co., Ltd.

[0082] [Preparation Example 2-2]

[0083] A modified calcium carbonate particle, the preparation method of which is as follows:

[0084] 50 kg of calcium chloride and 50 kg of sodium carbonate are added to 1000 kg of methyl oleate ethanol solution, the temperature is raised to 150°C, stirred and heated for reaction for 5 hours, and the product after the reaction is filtered, washed and dried to obtain calcium carbonate particles; wherein the mass content of methyl oleate in the methyl oleate ethanol solution is 10%;

[0085] 50 kg of calcium carbonate particles were added to 500 kg of ethylene glycol solution of organosilicon, heated to 200°C in a reactor, reacted for 3 hours and then kept warm for 1 hour, and the product after the reaction was filtered, washed and dried to obtain modified calcium carbonate particles. The ethylene glycol solution of organosilicon was an ethylene glycol solution of γ-(2,3-epoxypropoxy)propyltrimethoxysilane, and the mass content of γ-(2,3-epoxypropoxy)propyltrimethoxysilane was 5%. Example

[0086] [Example 1]

[0087] A granular desiccant comprises calcium oxide hygroscopic particles 1 and a water-proof and breathable membrane 2 arranged from the inside to the outside, wherein the raw materials for preparing the calcium oxide hygroscopic particles 1 comprise 60kg of calcium carbonate, 5kg of sodium carbonate, 30kg of aluminum hydroxide, 5kg of aluminum oxide modified particles obtained in [Preparation Example 1-1] and 20kg of water, and the raw materials for preparing the water-proof and breathable material used in the water-proof and breathable membrane 2 comprise 15kg of microcrystalline wax (BASF Luwax AF29), 1kg of sodium dodecylbenzene sulfonate and 1kg of modified calcium carbonate particles obtained in Preparation Example [2-1].

[0088] In this embodiment, the preparation method of the granular desiccant comprises the following steps:

[0089] Calcium carbonate, sodium carbonate, aluminum hydroxide and aluminum oxide modified particles are mixed in proportion, stirred, then water is added and stirred to form the mixture, then extruded into granules, then sent into a furnace at a temperature of 150° C., and continuously heated to 300° C. for 45 minutes, and finally calcined at 900° C. to obtain calcium oxide hygroscopic particles 1;

[0090] After heating and melting the microcrystalline wax, add sodium dodecylbenzene sulfonate and modified calcium carbonate particles, then stir at 80°C and 150r / min until evenly mixed, cool to obtain a water-proof and breathable material, then put the water-proof and breathable material into a high-temperature spraying device, and allow the calcium oxide hygroscopic particles 1 to fall into the hollow spray chamber, spray the water-proof and breathable material at high temperature from all around the spray chamber, cool to obtain a granular desiccant.

[0091] [Example 2]

[0092] A granular desiccant, which differs from [Example 1] in that:

[0093] The raw materials for preparing the calcium oxide hygroscopic particles 1 include 70kg of calcium carbonate, 10kg of sodium carbonate, 10kg of aluminum hydroxide, 10kg of modified aluminum oxide particles obtained in [Preparation Example 1-1] and 25kg of water. The raw materials for preparing the water-proof and breathable material used in the water-proof and breathable membrane 2 include 20kg of microcrystalline wax (BASF Luwax AF29), 2kg of sodium dodecylbenzene sulfonate and 1.5kg of modified calcium carbonate particles obtained in Preparation Example [2-1].

[0094] [Example 3]

[0095] A granular desiccant, which differs from [Example 1] in that:

[0096] The raw materials for preparing the calcium oxide hygroscopic particles 1 include 80kg of calcium carbonate, 5kg of sodium carbonate, 10kg of aluminum hydroxide, 5kg of modified aluminum oxide particles obtained in [Preparation Example 1-1] and 25kg of water. The raw materials for preparing the water-proof and breathable material used in the water-proof and breathable membrane 2 include 25kg of microcrystalline wax (BASF Luwax AF29), 3kg of sodium dodecylbenzene sulfonate and 2kg of modified calcium carbonate particles obtained in Preparation Example [2-1].

[0097] [Example 4]

[0098] A granular desiccant, which differs from [Example 1] in that: in the water-proof and breathable membrane 2, the modified calcium carbonate particles are the modified calcium carbonate particles prepared in [Preparation Example 2-2].

[0099] Comparative Example

[0100] [Comparative Example 1]

[0101] A granular desiccant, which differs from [Example 1] in that the sodium carbonate in the calcium oxide hygroscopic particles 1 is replaced by an equal amount of calcium carbonate.

[0102] [Comparative Example 2]

[0103] A granular desiccant, which differs from [Example 1] in that the alumina modified particles in the calcium oxide hygroscopic particles 1 are replaced by an equal amount of alumina particles.

[0104] [Comparative Example 3]

[0105] A granular desiccant, which differs from [Example 1] in that the alumina modified particles in the calcium oxide hygroscopic particles 1 are replaced by an equal amount of alumina modified particles prepared in [Preparation Example 1-2].

[0106] [Comparative Example 4]

[0107] A granular desiccant, which differs from [Example 1] in that the alumina modified particles in the calcium oxide hygroscopic particles 1 are replaced by an equal amount of alumina modified particles prepared in [Preparation Examples 1-3].

[0108] [Comparative Example 5]

[0109] A granular desiccant, which differs from [Example 1] in that the alumina modified particles in the calcium oxide hygroscopic particles 1 are replaced by an equal amount of alumina modified particles prepared in [Preparation Examples 1-4].

[0110] [Comparative Example 6]

[0111] A granular desiccant, which differs from [Example 1] in that: the water-proof and breathable film 2 is not sprayed on the outer surface of the calcium oxide hygroscopic particles 1.

[0112] Performance testing

[0113] Moisture absorption rate test: refer to Section 6.1 of BB / T 0049-2021 to test the moisture absorption rate of 8g of granular desiccant in each embodiment and comparative example in a constant temperature and humidity chamber at a temperature of 25°C and a relative humidity of 90%.

[0114] Adsorption speed test: After the granular desiccant in each embodiment and comparative example is sealed with a breathable packaging bag, the amount of water vapor that the granular desiccant can absorb in 72 hours is tested in a constant temperature and humidity chamber at a temperature of 25°C and a relative humidity of 90%. During the test, the sample is hung or placed overhead in the constant temperature and humidity chamber, allowing air to flow freely on all surfaces of the bag containing the desiccant, and the inner wall of the test chamber must not contact any part of the bag. Among them, the breathable packaging bags used in the test have the same specifications and the same water vapor permeability. The weight of the granular desiccant packaged in the breathable packaging bag is 40g. The water vapor absorption of each sample after 72 hours is recorded. The greater the water vapor absorption, the faster the moisture absorption speed of the granular desiccant.

[0115] Particle strength test: refer to "Measurement of Particle Compressive Strength" for testing, the unit is N.

[0116] Exothermic temperature when in contact with water: Take 20g of the granular desiccant in each embodiment and comparative example, put it into 100g of water at a temperature of 20°C, stir for 5 minutes, test the temperature of the water mixed with the granular desiccant, and record the exothermic temperature (i.e., temperature increment) of the granular desiccant in the following Table 1.

[0117] Table 1

[0118]

[0119] The difference between Comparative Example 1 and Example 1 is that the sodium carbonate in the calcium oxide hygroscopic particles 1 is replaced by an equal amount of calcium carbonate. Combined with the test results in Table 1, it can be seen that when no sodium carbonate is added to the calcium oxide hygroscopic particles 1, the passivation of the calcium oxide hygroscopic particles cannot be achieved. Even with the presence of a water-proof and breathable membrane 2, the problem of the calcium oxide desiccant particles releasing heat violently when in contact with water cannot be improved.

[0120] The difference between Comparative Example 2 and Example 1 is that the alumina modified particles in the calcium oxide hygroscopic particles 1 are replaced by an equal amount of alumina particles. Combined with the test results in Table 1, it can be seen that compared with traditional alumina particles, the alumina modified particles have an ultra-large specific surface area and pore frame effect, which can improve the internal microporous framework of the calcium oxide hygroscopic particles 1 and form channels that penetrate the interior to enhance the hygroscopic rate and hygroscopic capacity of the granular desiccant for water molecules.

[0121] The difference between Comparative Examples 3-5 and Example 1 is that the alumina modified particles are modified with any two of methacryloxysilane, triethanolamine oleate and hexamethyldisiloxane to obtain alumina modified particles. Combined with the test results in Table 1, it can be seen that the alumina modified particles obtained by modifying the alumina particles with methacryloxysilane, triethanolamine oleate and hexamethyldisiloxane have an ultra-large specific surface area and pore frame effect, thereby achieving the purpose of improving the internal microporous framework of the calcium oxide hygroscopic particles 1 and forming a channel for penetrating the interior, so as to enhance the moisture absorption rate and moisture absorption capacity of the granular desiccant for water molecules.

[0122] The difference between Comparative Example 6 and Example 1 is that the water-proof and breathable film 2 is not sprayed on the outer surface of the calcium oxide hygroscopic particles 1. Combined with the test results in Table 1, it can be seen that when the granular desiccant lacks an external water-proof and breathable film 2, even with the passivation effect of sodium carbonate, it cannot improve the problem that the calcium oxide desiccant particles easily release heat when in contact with water.

[0123] The difference between Example 4 and Example 1 is that the modified calcium carbonate particles are different. Among them, the modified calcium carbonate particles in Example 4 increase the production step of calcium carbonate particles, specifically using calcium chloride and sodium carbonate in an ethanol solution of methyl oleate to generate calcium carbonate particles to react with the ethylene glycol solution of silicone. Combined with the test results in Table 1, it can be seen that in the water-proof and breathable membrane 2, the use of the modified calcium carbonate particles in Example 4 is more conducive to the formation of a uniform microporous structure of the water-proof and breathable membrane 2, so that the water-proof and breathable membrane 2 smoothly allows water vapor to pass through and blocks water, which is conducive to further improving the moisture absorption rate of the granular desiccant.

[0124] This specific implementation manner is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the specific implementation manner as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A granular desiccant, characterized in that: The granular desiccant comprises calcium oxide hygroscopic particles (1) and a water-proof and breathable membrane (2) arranged from the inside to the outside. The calcium oxide hygroscopic particles (1) are prepared by mixing calcium carbonate, sodium carbonate, aluminum hydroxide, aluminum oxide modified particles and water in a weight ratio of (60-80): (5-15): (10-30): (3-10): (20-25), followed by extrusion granulation, baking and calcining. The baking adopts a continuous temperature rise mode with a temperature range of 150-300°C, and the calcining temperature is 900-1200°C. The preparation method of the aluminum oxide modified particles comprises the following steps: Under the catalytic action of ammonium trifluoroacetate, methacryloxysilane and alumina particles are coupled to obtain preliminary product particles; Under the catalytic action of cerium sulfate, triethanolamine oleate is coupled with the preliminary product particles to obtain an intermediate product; The intermediate product is mixed with an alcohol solution of hexamethyldisiloxane to react to obtain aluminum oxide modified particles; The water-proof and breathable film (2) is obtained by uniformly spraying a water-proof and breathable material onto the outer surface of the calcium oxide moisture-absorbing particles (1) and then cooling; the water-proof and breathable material is obtained by uniformly melting microcrystalline wax, a dispersant and modified calcium carbonate particles by heating and cooling; The modified calcium carbonate particles are silicon-containing calcium carbonate particles, and the preparation of the silicon-containing calcium carbonate particles comprises the following steps: The calcium carbonate particles are added into the organic silicon ethylene glycol solution, heated to 180-220°C for reaction, then kept warm, filtered, washed and dried to obtain silicon-containing calcium carbonate particles.

2. The granular desiccant according to claim 1, characterized in that: The weight ratio of the microcrystalline wax, the dispersant and the modified calcium carbonate particles is (15-25): (1-3): (1-2).

3. The granular desiccant according to claim 1, characterized in that: The preparation of the silicon-containing calcium carbonate particles also includes the steps of preparing the calcium carbonate particles. The steps of preparing the calcium carbonate particles are as follows: Calcium chloride and sodium carbonate are added to an ethanol solution of methyl oleate, and the temperature is raised to 130-170° C. for reaction, followed by filtering, washing and drying to obtain calcium carbonate particles.

4. A method for preparing the granular desiccant according to any one of claims 1 to 3, characterized in that: The following steps are involved: Calcium carbonate, sodium carbonate, aluminum hydroxide, and aluminum oxide modified particles are mixed in proportion, stirred, and then water is added to continue stirring and mixing to form, and then extruded into granules, baked, and calcined to obtain calcium oxide hygroscopic particles (1); the weight ratio of calcium carbonate, sodium carbonate, aluminum hydroxide, aluminum oxide modified particles, and water is (60-80): (5-15): (10-30): (3-10): (20-25); the baking adopts a continuous heating mode with a temperature range of 150-300°C, and the calcination temperature is 900-1200°C; The water-proof and breathable material is evenly sprayed onto the surface of the calcium oxide hygroscopic particles (1), and cooled to obtain a granular desiccant; The method for preparing the alumina modified particles comprises the following steps: Under the catalytic action of ammonium trifluoroacetate, methacryloxysilane and alumina particles are coupled to obtain preliminary product particles; Under the catalytic action of cerium sulfate, triethanolamine oleate is coupled with the preliminary product particles to obtain an intermediate product; The intermediate product is mixed with an alcohol solution of hexamethyldisiloxane to react to obtain aluminum oxide modified particles; The water-proof and breathable material is prepared by heating and melting microcrystalline wax, a dispersant and modified calcium carbonate particles uniformly and cooling them; The modified calcium carbonate particles are silicon-containing calcium carbonate particles, and the preparation of the silicon-containing calcium carbonate particles comprises the following steps: The calcium carbonate particles are added into the organic silicon ethylene glycol solution, heated to 180-220°C for reaction, then kept warm, filtered, washed and dried to obtain silicon-containing calcium carbonate particles.

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