Composite slow-release coated environment-friendly deicing agent and preparation method thereof

Abstract

The application discloses a composite slow-release coated environment-friendly snow-melting agent and a preparation method thereof, and belongs to the technical field of snow-melting and deicing, and comprises sodium chloride and calcium chloride mixed salt, natural zeolite, coating material, a crosslinking and initiating system, an inhibitor and a proper amount of deionized water. Solid waste is utilized as a resource to produce a chlorinated salt, and through processes such as deep impurity removal, evaporation concentration, graft copolymerization, granulation coating and drying, a long-acting environment-friendly snow-melting agent is produced, which has a natural zeolite as a skeleton, is anti-caking and easy to construct, has a coating of a degradable polymer starch and arabic gum crosslinked slow-release layer, and has the functions of corrosion resistance protection of citric acid and sodium hexametaphosphate.

Description

Technical Field

[0001] This invention relates to a slow-release coated environmentally friendly snow-melting agent and its preparation method, belonging to the field of snow melting and de-icing technology. It is a technical method for producing snow-melting agents from solid waste resource utilization products through processes such as deep impurity removal, evaporation and concentration, granulation and drying. Background Technology

[0002] Persistent snow and ice in winter severely endanger road safety, easily causing traffic accidents and traffic paralysis, resulting in casualties and property damage. Currently, common snow removal and ice-breaking methods mainly include a combination of mechanical removal, thermal melting, and the application of de-icing agents. Among these, chloride-based de-icing agents are widely used due to their low cost, rapid ice melting, and significant effects. However, the chloride ions generated by the ionization of chloride-based de-icing agents are highly corrosive, posing a persistent threat to roads, bridges, vehicle steel reinforcement, and the surrounding ecological environment. How to prevent direct contact between chloride ions and metals and reduce the rate of metal corrosion has become the core of chloride-based de-icing agent research and development.

[0003] Snow and ice weather conditions are complex, with both continuous heavy snow and sleet, and severe icing after snowfall. Even with mechanical spreading, there are problems such as travel difficulties and operational safety. If a single spreading operation could efficiently melt ice and snow and provide a long-lasting effect, it would balance economy and safety.

[0004] While industrial by-product salts, as a source of chloride-based de-icing agents, have the potential for resource utilization, they also face potential environmental safety risks. These risks are mainly reflected in the lack of a sound regulatory standard system for recycled salt products, bottlenecks in safe disposal technologies, and the difficulty in removing organic pollutants and toxic and harmful substances.

[0005] Therefore, developing environmentally friendly snow-melting agents that combine high efficiency, low corrosion, long-lasting effect, and biodegradability has become an urgent need and an inevitable trend for solving the problem of solid waste resource utilization and promoting the sustainable development of the industry. Summary of the Invention

[0006] To address the aforementioned issues, this invention discloses a composite slow-release coated environmentally friendly de-icing agent and its preparation method. This invention develops an environmentally friendly de-icing agent with high efficiency, low corrosion, long-lasting slow release, and biodegradability. Compared with traditional chloride-based de-icing agents, it can significantly reduce corrosion to concrete and metals, as well as damage to surrounding vegetation and soil.

[0007] A composite slow-release coated environmentally friendly de-icing agent, wherein the de-icing agent is prepared from the following materials in parts by weight:

[0008] A mixed salt of sodium chloride and calcium chloride, 50%–65%.

[0009] The aforementioned skeletal system:

[0010] Natural zeolite (80-120 mesh) 12%-20%

[0011] The coating material:

[0012] Soluble starch 8%–12%

[0013] Gum arabic 2%–4%

[0014] Acrylic acid 4%–7%

[0015] Deionized water appropriate amount

[0016] The crosslinking and initiation system described above:

[0017] Citric acid 1%–2%

[0018] Sodium hexametaphosphate 0.5%–1%

[0019] Persulfate 0.5%–1%

[0020] Hydrogen peroxide (30%) 0.5%~1%

[0021] The corrosion inhibitor mentioned above:

[0022] Citric acid 0.5%–1%

[0023] Sodium hexametaphosphate 0.5%–1%

[0024] Furthermore, the de-icing agent has a particle size of 1 mm to 6 mm and a pH value of 6 to 8.

[0025] The aforementioned composite slow-release coated environmentally friendly de-icing agent and its preparation method include the following steps:

[0026] (1) Add the deionized water, soluble starch and gum arabic in sequence to the reactor and heat until gelatinized;

[0027] Preferably, the heating temperature is 80℃~90℃;

[0028] Preferably, the gelatinization time is 20 to 40 minutes;

[0029] (2) Cool after gelatinization;

[0030] Preferably, the temperature is cooled to 50°C to 60°C;

[0031] (3) Inert gas is introduced for protection, and pretreated acrylic acid, citric acid and sodium hexametaphosphate are added in sequence. Sodium persulfate and hydrogen peroxide aqueous solution are slowly added dropwise, and the time of the dropwise process is controlled. After the reaction is completed, the temperature is kept warm and a viscous starch-acrylic acid graft copolymer solution is obtained.

[0032] Preferably, the inert gas is nitrogen;

[0033] Preferably, after pretreatment, the acrylic acid is neutralized to a degree of neutralization of 70%–80% in a water bath using a NaOH solution of a certain concentration.

[0034] Preferably, the reaction time is 1 hour to 2 hours;

[0035] Preferably, the heat preservation reaction lasts for 2 to 3 hours.

[0036] (3) Preheat the mixed salt of sodium chloride and calcium chloride, pump the copolymer colloid to the atomizing nozzle, and after the atomized droplets come into uniform contact with the mixed salt particles, a thin film is formed on their surface. Continue stirring until the particles are wet and independent.

[0037] Preferably, the mixed salt of calcium chloride and sodium chloride is a recycled product salt that utilizes by-product industrial salt resources;

[0038] Preferably, the preheating temperature is 40℃~60℃;

[0039] Preferably, the by-product industrial salt is obtained by sequentially undergoing low-temperature pyrolysis, salt dissolution, impurity removal with a subsaturated salt solution, and oxidative evaporation crystallization.

[0040] Preferably, the temperature for low-temperature pyrolysis is 350℃~500℃, and the pyrolysis time is 1h~2h.

[0041] Preferably, the mass fraction of the salt solution after the salt is dissolved is 200 g / L.

[0042] Preferably, the purification of impurities by subsaturated salt solution includes denitrification, defluorination, dephosphorization, removal of heavy metals, and deep oxidation.

[0043] Preferably, the denitrification agent is sodium hypochlorite, the defluorination and phosphorus removal agent is calcium hydroxide, the heavy metal removal agent is sodium sulfide, and the deep oxidation agent is hydrogen peroxide, ozone, or a combination of both.

[0044] Preferably, the oxidant used for oxidative evaporation crystallization is hydrogen peroxide, and the evaporation crystallization temperature is 80℃~90℃.

[0045] (4) The above-mentioned coated wet material is mixed with the pretreated natural zeolite powder to obtain a mixed and dispersed coated de-icing agent. After thermal cross-linking treatment, it is dried at low temperature and then crushed and sieved.

[0046] Preferably, the pretreated natural zeolite is successively crushed, sieved, soaked, and dried;

[0047] Preferably, the sieve mesh size is 40 to 60 mesh;

[0048] Preferably, the soaking solution is a mixed salt solution;

[0049] Preferably, the thermal crosslinking temperature is 120℃~140℃, and the reaction time is 1h~2h;

[0050] Preferably, the low-temperature drying temperature is 40℃~60℃.

[0051] The composite slow-release coated environmentally friendly de-icing agent and its preparation method of the present invention have the following advantages:

[0052] (1) After heat treatment, the hydrogen bonds of starch granules are destroyed and the molecular bonds form a viscous hydrophilic colloid. After pretreatment, the grafted acrylic acid not only reduces the acidity of the monomer to prevent starch hydrolysis, but also provides good water absorption and ion exchange capacity through the -COONa functional group. Under the dual oxidant system, the free radicals of the oxidant can capture hydrogen atoms of starch chains to form active free radical sites, which provides good conditions for acrylic acid / sodium acrylate to form comb-like graft copolymers. The added gum arabic carries carboxyl and hydroxyl functional groups to form hydrogen bonds with water to obtain a colloidal solution, which makes the de-icing agent less likely to be lost while improving the plasticity and flexibility of the starch film. The entire coating material is a biodegradable material, which combines the film-forming properties of starch with biodegradability, the high water absorption and swelling of polyacrylic acid and the colloidal flexibility of gum arabic, so that the film can absorb water and gel, and can control the release rate of chloride ions through swelling and diffusion, which is incomparable to simple starch solution coating.

[0053] (2) Citric acid and sodium hexametaphosphate were selected as crosslinking modifier and corrosion inhibitor. First, the esterification reaction of the carboxyl group of citric acid with the hydroxyl group of starch was used to construct a network structure, which increased the binding with the coating film. Second, sodium hexametaphosphate has the ability to coordinate with calcium ions, which complexes the precipitate to adhere to the metal surface and blocks the corrosion of chloride ions. Finally, a dual-effect design was achieved, which simplified the formula and reduced the cost.

[0054] (3) Natural zeolite has a large specific surface area and adsorption capacity. It adsorbs on the surface and gaps of wet particles, preventing direct contact between particles and improving the situation where the colloid easily clumps under the action of surface tension when the colloid is atomized and granulated. The pretreatment of soaking in salt solution allows it to come into contact with ice and snow first after spreading, providing a hydrophilic environment for subsequent coating. Moreover, the strong exchange and adsorption capacity of zeolite can also adsorb ammonia nitrogen in subsequent surface water bodies.

[0055] (4) By-product salt is pyrolyzed at low temperature to remove refractory organic matter, and after a series of physicochemical impurity removal methods, toxic and harmful impurities are deeply removed to obtain recycled industrial salt products, which meet the requirements of ensuring human health and ecological environment safety, and realize the safe resource utilization of hazardous waste. Attached Figure Description

[0056] Figure 1 The flowchart of this invention. Detailed Implementation

[0057] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. It should be noted that the terms "front," "rear," "left," "right," "up," and "down" used in the following description refer to directions in the accompanying drawings, and the terms "inner" and "outer" refer to directions toward or away from the geometric center of a specific component, respectively.

[0058] (a) such as Figure 1 The preparation method of a composite slow-release coated environmentally friendly de-icing agent is shown below:

[0059] (1) Weigh out industrial by-product waste salt and catalytically pyrolyze it at 550℃ for 1.5h to obtain pyrolysis waste salt. Prepare a 20%wt concentration subsaturated salt solution and remove impurities by denitrification, defluorination, dephosphorization, heavy metal removal, deep oxidation, etc. Finally, oxidize, evaporate and crystallize to obtain recycled industrial salt for later use.

[0060] (2) The natural zeolite powder was ground through a 40-mesh sieve. The material passing through the sieve was soaked in a 10% wt salt solution for 24 hours. After filtration, it was dried at 105°C to obtain the treated zeolite for later use.

[0061] (3) Take an appropriate amount of acrylic acid and place it in an ice-water bath. Slowly add 10 mol / L sodium hydroxide while stirring until the degree of neutralization is 75% for later use.

[0062] (4) Add measured amounts of deionized water, soluble starch and gum arabic to a three-necked flask. Stir at 300 rpm and heat to 85°C. Gelatinize at a constant temperature for 30 minutes. Cool the gelatinized liquid to 55°C and purge with nitrogen for 20 minutes. Add acrylic acid, citric acid and sodium hexametaphosphate from (3) in sequence. Stir at a constant speed under a nitrogen atmosphere. Slowly add a mixed aqueous solution of hydrogen peroxide and sodium persulfate over 1 hour. After the addition is complete, continue to react at 55°C for 2.5 hours to obtain the graft copolymerized gel for later use.

[0063] (5) After preheating the recycled industrial salt in (1) to 50°C, place it in a fluidized bed granulator. Pump the adhesive in (4) to the atomizing nozzle through a peristaltic pump and spray it onto the tumbling salt particles in the fluidized bed until the surface of the particles is wetted. Then stop atomizing to obtain wet particles for later use.

[0064] (6) Mix the zeolite in (2) with the moist particles in (5) for 10 min, spread the mixture evenly on a tray, and place it in a 130℃ drying oven for thermal crosslinking reaction for 1.5 h; after the crosslinking reaction is completed, transfer the material to a 50℃ vacuum drying oven to dry until constant temperature, then grind and lightly crush it through a 20 mesh sieve to obtain a composite slow-release coated environmentally friendly de-icing agent.

[0065] Table 1 lists three typical embodiments, where the values ​​represent the weight percentage of each component in the de-icing agent.

[0066] Table 1. Composition of a composite slow-release coated environmentally friendly snow melting agent formulation

[0067]

[0068] (ii) Relative snow melting and ice-melting capacity

[0069] The de-icing agent described in the above examples was prepared into a test solution with a salt concentration of 20%. 25.00 mL of each solution was placed in a low-temperature incubator at -15℃ ± 1℃ for later use. A beaker containing ice was removed from the incubator, the outer wall was wiped dry, and the solution was quickly weighed at room temperature. The de-icing agent test solution was then quickly poured into the beaker containing ice, and the beaker was returned to the low-temperature incubator at -15℃ ± 1℃. After 0.5 hours, the beaker was removed, the liquid was immediately poured out, and the beaker and remaining ice were quickly weighed at room temperature. The amount of ice loss was calculated to compare the relative de-icing and snow-melting capabilities. Specific results are shown in Table 2.

[0070] Table 2. Relative snow melting and ice-melting capacity (ice loss in g)

[0071]

[0072] (III) Freezing point test

[0073] The de-icing agent described in the above embodiment was prepared into a solution with a salt concentration of 20%. A certain amount of the solution was measured and placed in an environment below the freezing point. A thermometer or temperature sensor was inserted, and a trend graph of temperature change over time was plotted. The point where the temperature tends to level off is the freezing point temperature of the salt solution. The specific results are shown in Table 3.

[0074] Table 3 Freezing point test results

[0075]

[0076] (iv) Corrosion rate test of carbon steel

[0077] The de-icing agent described in the above embodiment was prepared into a 20% salt concentration solution. The corrosion rate of metallic carbon steel was tested according to the GB / T 18175 test method. The standard corrosion test piece was made of No. 20 metallic carbon steel, with a sample size of 5cm × 2cm × 0.2cm. The corrosion test piece was pre-degreased, impurities removed, dried, and weighed for later use. A certain amount of de-icing agent solution was measured, and the corrosion test piece was completely immersed in it. After soaking for 72 hours, the surface rust was removed, and the sample was weighed. The corrosion rate υ and corrosion rate η were calculated. Specific results are shown in Table 4.

[0078] Table 4 Corrosion Rate and Corrosion Concentration Results of Carbon Steel

[0079]

[0080] (v) Sustained-release effect test

[0081] A measured amount of the de-icing agent from the above examples was weighed out, added to a certain volume of water, and stirred slowly. Samples were taken at 0.5h, 1h, 2h, and 4h to determine the chloride ion content in the solution. The specific results are shown in Table 5.

[0082] Table 5 Results of sustained-release effect test (chloride ion content, unit: g / L)

[0083]

[0084] Notes: (1) The stable chloride ion content over 4 hours is related to the component ratio of the de-icing agent in the initial example; (2) The test results fluctuated due to the dilution factor; (3) Some of the de-icing agent encapsulated under stirring conditions failed to dissolve completely.

[0085] It is not difficult to see from the content and embodiments of this invention:

[0086] (1) The relative snow melting and ice-melting capacity and freezing point of the coated environmentally friendly snow melting agent are superior to those of the traditional sodium chloride snow melting agent;

[0087] (2) The starch and gum arabic film of the slow-release coated environmentally friendly de-icing agent delays the release of salt, and the citric acid and sodium hexametaphosphate inside further block metal corrosion as corrosion inhibitors. Compared with the control group, its metal carbon steel corrosion rate and corrosion rate are the best.

[0088] The technical means disclosed in this invention are not limited to those disclosed in the above embodiments, but also include technical solutions composed of any combination of the above technical features.

Claims

1. A composite slow-release coated environmentally friendly de-icing agent, characterized in that: It includes a mixed salt of sodium chloride and calcium chloride, natural zeolite, coating material, crosslinking and initiation system, corrosion inhibitor, and an appropriate amount of deionized water.

2. The composite slow-release coated environmentally friendly de-icing agent according to claim 1, characterized in that: The de-icing agent is prepared from the following materials in parts by weight: A mixed salt of sodium chloride and calcium chloride, comprising 50%–65%. Natural zeolite 12%–20% Covering material: Soluble starch 8%–12% Gum arabic 2%–4% Acrylic acid 4%–7% Crosslinking and initiation system: Citric acid 1%–2% Sodium hexametaphosphate 0.5%–1% Persulfate 0.5%–1% Hydrogen peroxide (30%) 0.5%~1% Corrosion inhibitor: Citric acid 0.5%–1% Sodium hexametaphosphate 0.5%–1% Add an appropriate amount of deionized water.

3. The composite slow-release coated environmentally friendly de-icing agent according to claim 1, characterized in that: The de-icing agent has a particle size of 1 mm to 6 mm and a pH value of 6 to 8.

4. The composite slow-release coated environmentally friendly de-icing agent according to claim 1, characterized in that: The sodium chloride and calcium chloride mixed salt is a regenerated salt obtained by low-temperature pyrolysis, salt dissolution, impurity removal, and oxidative evaporation crystallization of industrial by-product salt.

5. The preparation method of a composite slow-release coated environmentally friendly de-icing agent according to any one of claims 1-4, characterized in that: Includes the following steps: Step (1) Add the deionized water, soluble starch and gum arabic in the formula to the reactor in sequence, and heat until gelatinization; heating temperature 80℃~90℃; gelatinization time 20 minutes~40 minutes; Step (2) After gelatinization, cool to 50℃~60℃; Step (3) Under inert gas protection, pre-neutralized acrylic acid, citric acid and sodium hexametaphosphate are added, and persulfate and hydrogen peroxide aqueous solution are added dropwise. The reaction is kept at the temperature for 2 to 3 hours. After the reaction is completed, a viscous starch-acrylic acid graft copolymer solution is obtained. Step (3) Preheat the mixed salt of sodium chloride and calcium chloride to 40℃~60℃; pump the copolymer colloid to the atomizing nozzle, and after the atomized droplets come into uniform contact with the mixed salt particles, a thin film is formed on their surface. Continue stirring until the particles are wet and independent. Step (4) The above-mentioned coated wet material is mixed with the pretreated natural zeolite powder to obtain a mixed and dispersed coated de-icing agent. After thermal cross-linking treatment, it is dried at low temperature and then crushed and sieved. Low-temperature drying temperature: 40℃~60℃.

6. The preparation method of the composite slow-release coated environmentally friendly de-icing agent according to claim 5, characterized in that: The inert gas is nitrogen.

7. The preparation method of the composite slow-release coated environmentally friendly de-icing agent according to claim 5, characterized in that: After pretreatment, the acrylic acid is neutralized to a degree of 70%–80% in a water bath with a certain concentration of NaOH solution.

8. The preparation method of the composite slow-release coated environmentally friendly de-icing agent according to claim 5, characterized in that: The pretreated natural zeolite is successively crushed, sieved, soaked, and dried; the sieve mesh size is 40-60 mesh; the soaking solution is a mixed salt solution; the thermal crosslinking temperature is 120℃-140℃, and the reaction time is 1h-2h.

9. The preparation method of the composite slow-release coated environmentally friendly de-icing agent according to claim 5, characterized in that: The mixed salt of calcium chloride and sodium chloride is a recycled product of the by-product industrial salt. The by-product industrial salt is obtained by low-temperature pyrolysis, salt dissolution, impurity removal in subsaturated salt solution, and oxidative evaporation crystallization. The low-temperature pyrolysis temperature is 350℃~500℃, and the pyrolysis time is 1h~2h. The mass fraction of the salt solution after salt dissolution is 200g / L. Impurity removal in subsaturated salt solution includes denitrification, defluorination, dephosphorization, removal of heavy metals, and deep oxidation. The oxidant for oxidative evaporation crystallization is hydrogen peroxide, and the evaporation crystallization temperature is 80℃~90℃.

10. The preparation method of the composite slow-release coated environmentally friendly de-icing agent according to claim 5, characterized in that: The denitrification agent is sodium hypochlorite, the defluorination and phosphorus removal agent is calcium hydroxide, the heavy metal removal agent is sodium sulfide, and the deep oxidation agent is hydrogen peroxide, ozone, or a combination of both.

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