Anti-floating coated urea based on water-soluble pigment and preparation method thereof

Abstract

The invention discloses anti-floating coated urea based on a water-soluble pigment and a preparation method of the anti-floating coated urea, and belongs to the technical field of slow-release fertilizers. Azone, dodecyl glucoside and polyvinyl alcohol are compounded to prepare a composite surfactant, then the composite surfactant is used for preparing the anti-floating coated urea based on the water-soluble pigment, and the anti-floating coated urea is specifically prepared from the following raw materials in parts by mass: 0.05-1 part of food-grade pigment, 0.5-5 parts of the composite surfactant, 900-1100 parts of urea and 5-20 parts of polyhydric alcohol. 5 to 20 parts of isocyanate; 5 to 20 parts of water; compared with the situation that the surfactant is not used or a single surfactant is used, the anti-floating capacity of the anti-floating coated urea is effectively enhanced. The anti-floating coated urea prepared by the invention is good in anti-floating property, controllable in nutrient release, good in environmental protection property and high in appearance identification degree, meets the development requirements of green and environment-friendly agriculture, and improves the market competitiveness of the product.

Description

Technical Field

[0001] This invention relates to the field of slow-release fertilizer technology, specifically to an anti-floating coated urea based on water-soluble pigments and its preparation method. Background Technology

[0002] Urea is a commonly used nitrogen fertilizer in agricultural production. However, ordinary urea suffers from rapid nutrient release and low utilization rate. A large amount of urea that is not absorbed by plants is lost or volatilized by rainwater, resulting in resource waste and potentially environmental pollution problems such as eutrophication of water bodies. Coated urea, with one or more layers of film material wrapped around the surface of urea granules, can effectively control the release rate of urea and improve fertilizer utilization.

[0003] However, existing coated urea products have some shortcomings. The appearance of commercially available coated urea products is relatively uniform, failing to meet users' needs for product distinctiveness. Adding pigments during fertilizer production can improve this issue. Most commonly used organic pigments in existing products are dispersed in resin, resulting in relatively high costs and difficulty in degradation. Furthermore, traditional pigments exhibit poor dispersibility during coating, making it difficult to bind well with the coating material, thus affecting the quality and performance of coated urea. Food-grade pigments refer to inorganic pigments that can dissolve in water to form a uniform, transparent or semi-transparent colored solution, suitable as dyes for coated fertilizers. However, due to the complex and diverse composition and sources of different food-grade pigments, uneven coating can also occur during production. Therefore, selecting suitable surfactants to improve their binding performance is a key research direction. Summary of the Invention

[0004] In view of the above-mentioned prior art, the purpose of this invention is to provide an anti-floating coated urea based on water-soluble pigments and its preparation method.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides an anti-floating coated urea based on a water-soluble pigment, comprising the following raw materials in parts by weight: 0.05-1 part food-grade pigment, 0.5-5 parts compound surfactant, 900-1100 parts urea, 5-20 parts polyol, 5-20 parts isocyanate, 5-20 parts water; The composite surfactant includes azone, dodecyl glucoside and polyvinyl alcohol, wherein the mass ratio of azone, dodecyl glucoside and polyvinyl alcohol is (1-4):(1-4):(0.5-2).

[0006] Furthermore, the composite surfactant is prepared by the following method: Azone and dodecyl glucoside are heated to 20-40℃ and mixed evenly. Then polyvinyl alcohol is added and stirred to dissolve, thus obtaining a composite surfactant.

[0007] Furthermore, the urea is large-particle urea with a particle size of 1mm-10mm.

[0008] Furthermore, the food-grade pigments include synthetic food colorings and natural food colorings.

[0009] Furthermore, the synthetic food colorings include amaranth red and its aluminum lake, carmine and its aluminum lake, tartrazine and its aluminum lake, sunset yellow and its aluminum lake, brilliant blue and its aluminum lake, allura red and its aluminum lake, and indigo and its aluminum lake.

[0010] Synthetic food colorings include amaranth and its aluminum lake, carmine and its aluminum lake (commonly known as "scarlet"), tartrazine and its aluminum lake (bright yellow), sunset yellow and its aluminum lake (orange yellow), brilliant blue and its aluminum lake (royal blue), allura red and its aluminum lake (red), and indigo and its aluminum lake (blue).

[0011] Furthermore, the natural pigments include erythrosine, curcumin, paprika oleoresin, gardenia yellow, gardenia blue, grape skin red, caramel color, titanium dioxide, and carbon black.

[0012] Natural pigments include erythrosine (pink), beetroot red (extracted from red beets, pink), curcumin (extracted from turmeric rhizomes, yellow), capsicum red (extracted from red peppers, orange-red), gardenia yellow / gardenia blue (extracted from gardenia fruit, can be mixed to produce yellow, green, and blue), grape skin red (purple-red), caramel color (made by heating and caramelizing sugars, brown), titanium dioxide (mineral source, white), and carbon black (plant carbonization, black).

[0013] A second aspect of the present invention provides a method for preparing the aforementioned water-soluble pigment-based anti-floating coated urea, comprising the following steps: (1) Add food-grade pigment to water and stir continuously until dissolved, then add composite surfactant, stir evenly and heat to obtain pigment solution; (2) The pigment solution obtained in step (1) is evenly sprayed onto the surface of heated granular urea, and after being kept warm and dried, the dyed fertilizer core is obtained. (3) The heated isocyanate and polyol are evenly sprayed onto the surface of the fertilizer core, stirred continuously, and dried to obtain anti-floating coated urea based on water-soluble pigments.

[0014] Furthermore, in step (1), the heating temperature is 35-45℃.

[0015] Furthermore, in step (2), the heat preservation temperature is 65-75℃, and the drying method is hot air drying.

[0016] Furthermore, in step (3), the temperature of the isocyanate and polyol is 55-65℃, the drying method is hot air drying, and the drying time is 3-10 minutes.

[0017] The beneficial effects of this invention are: Excellent anti-floating properties: The composite surfactant added to the urea surface can disperse to the coated urea surface, thereby playing an anti-floating role. The composite surfactant prepared by combining azone, dodecyl glucoside and polyvinyl alcohol in this invention has an effectively enhanced anti-floating ability compared to not using a surfactant or using a single surfactant.

[0018] Controllable nutrient release: By adjusting the thickness of the coating layer, the release rate of urea can be effectively controlled, matching it with the nutrient requirements of plants at different growth stages, thereby improving fertilizer utilization and reducing fertilizer waste and environmental pollution.

[0019] It is environmentally friendly: it uses biodegradable pigments that can gradually decompose in the soil, reducing the burden on the soil environment and meeting the development requirements of green and environmentally friendly agriculture.

[0020] High visual distinctiveness: Water-soluble pigments are evenly dispersed on the outermost layer of urea particles, giving coated urea a distinct color characteristic. This makes it easy for users to identify and distinguish the product during storage, transportation, and use, avoiding confusion. It can also serve as a way to brand the product and enhance its market competitiveness. Detailed Implementation

[0021] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0022] To enable those skilled in the art to better understand the technical solution of this application, the technical solution of this application will be described in detail below with reference to specific embodiments.

[0023] Unless otherwise specified, all test materials used in the embodiments of this invention are conventional test materials in the art and can be purchased through commercial channels. The CAS number for isocyanate is 103-72-0, for polyol is 9003-11-6, for azone is 59227-89-3, for dodecyl glucoside is 110615-47-9, and for polyvinyl alcohol is 9002-89-5. The diameter d of the granular urea used ranges from 2.0 mm to 4.75 mm.

[0024] Example 1 Preparation of composite surfactants 2 kg of azone and 1.5 kg of dodecyl glucoside were heated to 30°C and mixed evenly. Then, 1.0 kg of polyvinyl alcohol was added and stirred to dissolve, thus obtaining a composite surfactant.

[0025] Example 2 Add 0.3 kg of water-soluble blue dye, Gardenia Blue, to 10 kg of water and stir until completely dissolved. Then add 2 kg of composite surfactant, stir evenly, and heat to 40°C. Heat 1000 kg of granular urea to 70°C. Spray the aqueous solution containing the pigment and surfactant onto the surface of the granular urea, start stirring, and circulate hot air to maintain the urea temperature at 70°C. Heat 11 kg of polyol and 10 kg of isocyanate to 60°C respectively. After the urea surface is dry, spray the polyol and isocyanate onto the urea surface separately, stirring continuously and circulating hot air continuously to ensure that the polyol and isocyanate are evenly distributed on the urea surface. After reacting for 5 minutes, the coated urea product is obtained.

[0026] Example 3 Add 0.3 kg of water-soluble yellow dye, tartrazine, to 10 kg of water and stir until completely dissolved. Then add 2 kg of composite surfactant, stir evenly, and heat to 40°C. Heat 1000 kg of granular urea to 70°C. Spray the aqueous solution containing the pigment and surfactant onto the surface of the granular urea, start stirring, and circulate hot air to maintain the urea temperature at 70°C. Heat 11 kg of polyol and 10 kg of isocyanate to 60°C respectively. After the urea surface is dry, spray the polyol and isocyanate onto the urea surface separately, stirring continuously and circulating hot air continuously to ensure that the polyol and isocyanate are evenly distributed on the urea surface. After reacting for 5 minutes, the coated urea product is obtained.

[0027] Example 4 0.3 kg of water-soluble purple grape skin red dye was added to 10 kg of water and stirred until completely dissolved. Then, 2 kg of composite surfactant was added and stirred evenly, and the mixture was heated to 40°C. 1000 kg of granular urea was heated to 70°C. The aqueous solution containing the pigment and surfactant was sprayed onto the surface of the granular urea. Stirring was started and hot air was introduced to maintain the urea temperature at 70°C. 11 kg of polyol and 10 kg of isocyanate were heated to 60°C respectively. After the urea surface was dried, the polyol and isocyanate were sprayed onto the urea surface separately. Stirring was continued and hot air was continuously introduced to ensure that the polyol and isocyanate were evenly distributed on the urea surface. After reacting for 5 minutes, the coated urea product was obtained.

[0028] Comparative Example 1 The difference between Comparative Example 1 and Example 2 is that no surfactant is used.

[0029] The preparation method is as follows: Add 0.3 kg of water-soluble blue dye, Gardenia Blue, to 10 kg of water and stir until completely dissolved. Then add 2 kg of water, stir evenly, and heat to 40°C. Heat 1000 kg of granular urea to 70°C. Spray the aqueous solution containing the pigment and surfactant onto the surface of the granular urea, start stirring, and circulate hot air to maintain the urea temperature at 70°C. Heat 11 kg of polyol and 10 kg of isocyanate to 60°C respectively. After the urea surface is dry, spray the polyol and isocyanate onto the urea surface separately, stirring continuously and circulating hot air continuously to ensure that the polyol and isocyanate are evenly distributed on the urea surface. After reacting for 5 minutes, the coated urea product is obtained.

[0030] Comparative Example 2 The difference between Comparative Example 1 and Example 2 is that the surfactant used is azone.

[0031] The preparation method is as follows: Add 0.3 kg of water-soluble blue dye, Gardenia Blue, to 10 kg of water and stir until completely dissolved. Then add 2 kg of azone and stir until homogeneous. Heat to 40°C. Heat 1000 kg of granular urea to 70°C. Spray an aqueous solution containing pigment and surfactant onto the surface of the granular urea, start stirring, and circulate hot air to maintain the urea temperature at 70°C. Heat 11 kg of polyol and 10 kg of isocyanate to 60°C respectively. After the urea surface is dry, spray the polyol and isocyanate onto the urea surface separately, stirring continuously and circulating hot air continuously to ensure that the polyol and isocyanate are evenly distributed on the urea surface. After reacting for 5 minutes, the coated urea product is obtained.

[0032] Comparative Example 3 The difference between Comparative Example 3 and Example 2 is that the surfactant used is dodecyl glucoside.

[0033] The preparation method is as follows: Add 0.3 kg of water-soluble blue dye, Gardenia Blue, to 10 kg of water and stir until completely dissolved. Then add 2 kg of dodecyl glucoside, stir evenly, and heat to 40°C. Heat 1000 kg of granular urea to 70°C. Spray an aqueous solution containing pigment and surfactant onto the surface of the granular urea, start stirring, and circulate hot air to maintain the urea temperature at 70°C. Heat 11 kg of polyol and 10 kg of isocyanate to 60°C respectively. After the urea surface is dry, spray the polyol and isocyanate onto the urea surface separately, stirring continuously and circulating hot air continuously to ensure that the polyol and isocyanate are evenly distributed on the urea surface. After reacting for 5 minutes, the coated urea product is obtained.

[0034] Comparative Example 4 The difference between Comparative Example 4 and Example 2 is that polyvinyl alcohol is used as the surfactant.

[0035] The preparation method is as follows: Add 0.3 kg of water-soluble blue dye, Gardenia Blue, to 10 kg of water and stir until completely dissolved. Then add 2 kg of polyvinyl alcohol, stir evenly, and heat to 40°C. Heat 1000 kg of granular urea to 70°C. Spray an aqueous solution containing pigment and surfactant onto the surface of the granular urea, start stirring, and circulate hot air to maintain the urea temperature at 70°C. Heat 11 kg of polyol and 10 kg of isocyanate to 60°C respectively. After the urea surface is dry, spray the polyol and isocyanate onto the urea surface separately, stirring continuously and circulating hot air continuously to ensure that the polyol and isocyanate are evenly distributed on the urea surface. After reacting for 5 minutes, the coated urea product is obtained.

[0036] Experimental example: The coated urea products prepared in Example 1 and Comparative Examples 1-4 were subjected to an anti-floating test. The specific steps are as follows: Take a transparent beaker and fill it halfway with tap water. Weigh out 200 coated urea granules and evenly sprinkle them into the beaker from a certain height above the water surface, allowing the granules to fall freely from the center of the water. Observation and recording: After the granules have been in the water for 1 minute, record the number of granules floating on the surface. Repeat the experiment multiple times and take the average value to improve accuracy. The results are shown in Table 1. The specific formula for calculating the buoyancy rate is as follows: Floating rate (%) = (Number of floating particles / Total number of particles fed) × 100% Table 1 Fertilizer Quantity Floating Rate As shown in Table 1, Example 2 had the lowest number of floating rates, which was better than Comparative Examples 1-4. This indicates that the composite surfactant prepared by mixing azone, dodecyl glucoside and polyvinyl alcohol can better combine with food-grade pigments when used in the preparation of coated urea, which is beneficial to improving the anti-floating performance of coated fertilizers.

[0037] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A water-soluble pigment-based anti-floating coated urea, characterized in that, The raw materials include the following parts by weight: 0.05-1 part food-grade pigment, 0.5-5 parts compound surfactant, 900-1100 parts urea, 5-20 parts polyol, 5-20 parts isocyanate, 5-20 parts water; The composite surfactant includes azone, dodecyl glucoside and polyvinyl alcohol, wherein the mass ratio of azone, dodecyl glucoside and polyvinyl alcohol is (1-4):(1-4):(0.5-2).

2. The anti-floating coated urea based on water-soluble pigments according to claim 1, characterized in that, The composite surfactant is prepared by the following method: Azone and dodecyl glucoside are heated to 20-40℃ and mixed evenly. Then polyvinyl alcohol is added and stirred to dissolve, thus obtaining a composite surfactant.

3. The anti-floating coated urea based on water-soluble pigments according to claim 1, characterized in that, The urea is large-particle urea with a particle size of 1mm-10mm.

4. The anti-floating coated urea based on water-soluble pigments according to claim 1, characterized in that, The food-grade pigments mentioned include synthetic food colorings and natural food colorings.

5. The anti-floating coated urea based on water-soluble pigments according to claim 4, characterized in that, The synthetic food colorings include amaranth and its aluminum lake, carmine and its aluminum lake, tartrazine and its aluminum lake, sunset yellow and its aluminum lake, brilliant blue and its aluminum lake, allura red and its aluminum lake, and indigo and its aluminum lake.

6. The anti-floating coated urea based on water-soluble pigments according to claim 4, characterized in that, The natural pigments mentioned include erythrosine, curcumin, paprika oleoresin, gardenia yellow, gardenia blue, grape skin red, caramel color, titanium dioxide, and carbon black.

7. The method for preparing anti-floating coated urea based on water-soluble pigments according to any one of claims 1-6, characterized in that, Includes the following steps: (1) Add food-grade pigment to water and stir continuously until dissolved, then add composite surfactant, stir evenly and heat to obtain pigment solution; (2) The pigment solution obtained in step (1) is evenly sprayed onto the surface of heated granular urea, and after being kept warm and dried, the dyed fertilizer core is obtained. (3) The heated isocyanate and polyol are evenly sprayed onto the surface of the fertilizer core, stirred continuously, and dried to obtain anti-floating coated urea based on water-soluble pigments.

8. The method for preparing anti-floating coated urea based on water-soluble pigments according to claim 7, characterized in that, In step (1), the heating temperature is 35-45℃.

9. The method for preparing anti-floating coated urea based on water-soluble pigments according to claim 7, characterized in that, In step (2), the heat preservation temperature is 65-75℃, and the drying method is hot air drying.

10. The method for preparing anti-floating coated urea based on water-soluble pigments according to claim 7, characterized in that, In step (3), the temperature of isocyanate and polyol is 55-65℃, the drying method is hot air drying, and the drying time is 3-10 minutes.

Images