A high-strength firework die compact based on in-situ whisker toughening and staged curing and a preparation method thereof

Abstract

This application relates to the field of fireworks molding technology, specifically disclosing a high-strength fireworks molding agglomerate based on in-situ whisker toughening and staged curing, and its preparation method. It includes the following components: calcium carbonate powder, micron-sized gypsum whiskers, virgin cassava flour, a gelatinization-coking regulator, wood fiber, lubricant, and water; the gelatinization-coking regulator is a compound of polyol and pH buffer salt. This solves the technical problem mentioned above where the existing fireworks molding agglomerates, due to the introduction of anhydrous gypsum and cassava flour, are prone to defects such as large bubbles, microcracks, or delamination during the production process, leading to defective products, low yield, and serious constraints on product quality stability.

Description

Technical Field

[0001] This application relates to the field of fireworks molding technology, and specifically discloses a high-strength fireworks molding mass based on in-situ whisker toughening and staged curing, and its preparation method. Background Technology

[0002] Fireworks typically consist of multiple independent paper tubes bundled and glued together to form a cylindrical array structure. Each paper tube is filled with propellant, effect powder (including opening powder, colored beads, etc.), and fuse. The main function of the paper tube wall is to withstand the instantaneous high pressure (approximately 5–10 MPa) generated by the combustion of gunpowder after the fireworks are ignited, achieving energy confinement and directional release. Because the production of fireworks paper tubes requires first manufacturing individual paper tubes and then bundling and gluing them together, the overall process is quite complex. Therefore, a new type of molded fireworks tube structure has emerged in the fireworks industry, generally referred to as a molded fireworks body. The molded fireworks body is an integrated cylindrical structure made primarily from plant fibers, calcium carbonate, cassava flour, etc., mixed and then pressed into shape using a high-temperature mold, replacing the method of bundling and assembling multiple paper tubes into a single firework tube.

[0003] Currently, the mainstream firework molded cylinders are mainly made of basic materials such as stone powder, calcium sulfate, and calcium carbonate, plus auxiliary materials such as pulp fiber, and are formed by pressing with molds. However, the firework molded cylinders produced in this way are not strong enough. In order to withstand the instantaneous high pressure during the explosion of fireworks, companies can only increase the thickness of the cylinder. As a result, the mainstream firework molded cylinders are heavy, bulky and difficult to transport, and use a lot of stone powder, which increases the cost.

[0004] To reduce weight and increase strength, the production of fireworks molded bodies has been improved in two main directions: first, finding substitutes for stone powder, such as using anhydrous gypsum; and second, adding adhesives, such as tapioca flour. For example, patent document CN118955078A discloses a fireworks molded body material and its preparation method, which includes anhydrous gypsum and tapioca flour in its raw material composition. By utilizing the hydration gel properties of anhydrous gypsum and the adhesive properties of tapioca flour, the strength of the fireworks molded body is improved, the use of stone powder is reduced, and the overall weight is reduced.

[0005] While the above-mentioned technologies have improved the bonding efficiency to a certain extent, it has been found in actual production that the fireworks molding products containing anhydrous gypsum and cassava flour are prone to defects such as large air bubbles, microcracks or delamination, resulting in defective products, low production yield, and seriously restricting the stability of product quality. Summary of the Invention

[0006] The purpose of this invention is to provide a high-strength fireworks molding body based on in-situ whisker toughening and staged curing, and its preparation method, in order to solve the technical problem mentioned above that the existing fireworks molding body, due to the introduction of anhydrous gypsum and cassava flour, is prone to defects such as large air bubbles, microcracks or delamination during the production process, resulting in defective products, low production yield, and serious restriction on product quality stability.

[0007] To solve the above problems, the technical solution adopted by the present invention is as follows: a high-strength fireworks molding body based on in-situ whisker toughening and staged curing, comprising the following components: calcium carbonate powder, micron-sized gypsum whiskers, virgin cassava flour, gelatinization-coking regulator, wood fiber, lubricant, and water; wherein the gelatinization-coking regulator is composed of polyol and pH buffer salt.

[0008] A method for preparing a high-strength fireworks molding compound includes the following steps: Step 1, Material preparation: Weigh out the following ingredients according to the weight ratio: calcium carbonate powder, active type II anhydrous gypsum, cassava flour, gelatinization-coking regulator, wood fiber, lubricant, and water. Step 2, Mixing: Heat the water to 60-80℃, mix the other ingredients evenly, add warm water and stir evenly to form a slurry; Step 3, hot pressing and curing: Inject the slurry into a mold with a temperature of 180-200℃, close the mold immediately, and heat and pressurize it in stages to form and cure it until no water vapor comes out of the outside of the mold. Step 4, Demolding: Open the mold and remove the molded product.

[0009] Furthermore, the weight proportions of each raw material are as follows: 500-600 parts calcium carbonate powder, 200-300 parts micron-sized gypsum whiskers, 50-65 parts virgin cassava flour, 0.15-0.7 parts gelatinization-coking regulator, 70-80 parts wood fiber, 4-6 parts lubricant, and 550-650 parts water.

[0010] Furthermore, the polyol is sorbitol, accounting for 0.1%-0.5% of the dry weight; the pH buffer salt is sodium dihydrogen phosphate, accounting for 0.05%-0.2% of the dry weight.

[0011] Furthermore, the micron-sized gypsum whiskers are generated by the hydration of active type II anhydrous gypsum and water at 60-80℃.

[0012] Furthermore, the active type II anhydrous gypsum is prepared by treating phosphogypsum using a medium-temperature crystallization method, with an oil absorption value ≤30g / 100g and a fineness D50 ≤20μm.

[0013] Furthermore, the intermediate-temperature crystallization method includes the following steps: S1, raw material pretreatment: adding lime to phosphate paste and mixing; S2, particle size optimization: grinding the neutralized phosphogypsum into particles with a concentrated particle size distribution and less than 5 μm; S3, calcination regime: placing the pretreated phosphogypsum in a muffle furnace, heating it to 500°C at a heating rate of 10°C / min, and holding it at that temperature for 1.5 hours; S4, rapid cooling: immediately removing the sample after calcination and cooling it in air to retain more lattice defects and improve surface energy.

[0014] Furthermore, the sample is placed in air and cooled at a rate >10°C / s.

[0015] Furthermore, the phased procedure in step 3 is as follows: Step 301, Low-pressure penetration period: Within 0-2 minutes after mold closing, apply a pressure of 3-5 MPa, and control the mold temperature at 180-200℃; Step 302, Pressure increase and curing period: Within 2-8 minutes after mold closing, gradually increase the pressure from the first stage pressure to 10-15 MPa, and simultaneously raise the mold temperature to 230-250℃; Step 303, Pressure holding and strengthening period: Within 8-12 minutes after mold closing, maintain a pressure of 10-15 MPa and a temperature of 230-250℃.

[0016] The beneficial effects of this implementation plan are as follows: 1. In the existing technology, the strength of the fireworks molding body is improved by utilizing the hydration gel properties of anhydrous gypsum and the adhesive properties of tapioca flour. However, after actual application and production, it was found that the fireworks molding body products with the introduction of anhydrous gypsum and tapioca flour are prone to defects such as large air bubbles, microcracks or delamination, which easily lead to defective products, resulting in a low production yield and seriously restricting the stability of product quality. In response, this application, through repeated experiments and reflection, discovered that due to the introduction of anhydrous gypsum and cassava flour, various chemical reactions occur in the slurry during the coagulation process (such as the gelatinization and coking of cassava flour, the hydration of gypsum, and van der Waals forces and electrostatic adsorption between water evaporation particles). This is different from the coagulation process of traditional slurry base materials such as stone powder, calcium sulfate, and calcium carbonate, plus auxiliary materials such as pulp fibers. When the slurry containing anhydrous gypsum and cassava flour is molded in a mold at 150°C, the rates of multiple chemical reactions, such as the evaporation of internal water, the gelatinization and coking of cassava flour, and the hydration of gypsum, are all different and mismatched. This leads to stress concentration inside the product, which in turn causes the slurry with different coagulation degrees to pull and squeeze each other, resulting in defects such as large bubbles, microcracks, or delamination. Based on the above findings, this application first modifies the original Type II anhydrous gypsum using a medium-temperature crystallization method to transform it into active Type II anhydrous gypsum. Active Type II anhydrous gypsum can be activated and hydrated in situ under 60-80℃ warm water conditions to generate micron-sized gypsum whiskers. Therefore, the micron-sized gypsum whiskers generated by the active Type II anhydrous gypsum in the slurry can play a role in fiber toughening, just like the steel bars in concrete. The generation of micron-sized gypsum whiskers significantly avoids defects such as microcracks or delamination in the final product, the fireworks molding mass. This application utilizes active Type II anhydrous gypsum to generate gypsum whiskers in situ, forming a three-dimensional network fiber skeleton, which fundamentally enhances the toughness of the mass, transforming it from a brittle material to a quasi-tough material.

[0017] 2. Since the active type II anhydrous gypsum of this application needs to be activated by hydration under 60-80℃ warm water conditions to generate micron-sized gypsum whiskers in situ, this application directly uses 60-80℃ to mix the raw materials of each component when preparing the fireworks body. At the same time as the mixture is uniform, the micron-sized gypsum whiskers are also generated. The generated gypsum whiskers are essentially a flow guide rod in the slurry. During the stirring process, water easily flows along the gypsum whiskers. At this time, the original cassava flour has not gelatinized and is very easy to absorb water and expand to gelatinize. Therefore, water flows along the gypsum whiskers under the flow guide effect of the gypsum whiskers. Through the water, a large amount of cassava flour that needs to absorb water and expand is adsorbed on the gypsum whiskers, which coats the newly generated gypsum whiskers. In the subsequent process, when the temperature reaches the gelatinization temperature of the cassava flour, the cassava flour gelatinizes rapidly, forming a high-viscosity colloid on the gypsum whiskers to coat the gypsum whiskers and enhance the toughness of the gypsum whiskers. Furthermore, some cassava flour, after gelatinization in warm water, can form a viscoelastic matrix. This matrix acts as a dispersant to prevent whisker agglomeration and also reacts with Ca through hydroxyl groups.2+ The coordination effect guides the whiskers to grow oriented along the c-axis. Therefore, the toughening effect of the fibers in the adhesive of this application is not just the effect of gypsum whiskers alone, but a combined effect of gypsum whiskers and gelatinized tapioca flour.

[0018] 3. This application also adds a gelatinization-coking regulator. Through the synergistic effect of the gelatinization-coking regulator, the reaction rate of cassava flour at high temperature is precisely controlled, resulting in a fine and uniformly distributed closed-cell structure inside the cassava mass. This avoids the formation of large bubbles and cracks, significantly improving the uniformity and strength of the product. Furthermore, by using the gelatinization-coking regulator to match the reaction rate of cassava flour during hot pressing with the hydration rate, and combined with a staged hot pressing curing process, the gelatinization, hydration, and staged curing work synergistically. The temperature-pressure curve of the staged hot pressing curing process perfectly matches the chemical reaction kinetics of the material, effectively avoiding internal stress concentration and defects caused by reaction rate mismatch. Ultimately, a high-quality fireworks molded mass with low cassava flour content (≤6.5%), high compressive strength, uniform internal structure, and a drop test pass rate greater than 99.5% is produced.

[0019] 4. Under the same conditions, the amount of cassava flour can be reduced to below 6.5%, while the compressive strength of the product is increased by more than 30%, and the drop test pass rate is stable at over 99.5%, achieving the dual goals of reducing costs and improving performance. Attached Figure Description

[0020] Figure 1 This is a process flow diagram of this application; Detailed Implementation The following detailed description illustrates the specific implementation method: Methodology Overview: Step 1, Material preparation: Weigh out the following ingredients according to the weight ratio: calcium carbonate powder, active type II anhydrous gypsum, cassava flour, gelatinization-coking regulator, wood fiber, lubricant, and water. Step 2, Mixing: Heat the water to 60-80℃, mix the other ingredients evenly, add warm water and stir evenly to form a slurry; Step 3, hot pressing and curing: Inject the slurry into a mold with a temperature of 180-200℃, close the mold immediately, and heat and pressurize it in stages to form and cure it until no water vapor comes out of the outside of the mold. Step 301, Low-pressure penetration period: Within 0-2 minutes after mold closing, apply a pressure of 3-5 MPa, and control the mold temperature at 180-200℃; Step 302, Pressure Increasing and Curing Period: Within 2-8 minutes after mold closing, gradually increase the pressure from Stage 1 pressure to 10-15MPa, and simultaneously raise the mold temperature to 230-250℃; Step 303, Pressure Holding and Strengthening Period: Maintain a pressure of 10-15 MPa and a temperature of 230-250℃ for 8-12 minutes after mold closing; Step 4, Demolding: Open the mold and remove the molded product.

[0021] The preparation of active type II anhydrous gypsum using the intermediate-temperature crystallization method for phosphogypsum includes the following steps: S1. Raw material pretreatment: Add lime to the phosphate paste and mix. S2. Particle size optimization: Grinding the neutralized phosphogypsum into particles with a concentrated particle size distribution and less than 5μm can significantly improve its specific surface area and surface activity, providing more sites for crystal nucleation. S3. Calcination process: The pretreated phosphogypsum is placed in a muffle furnace and heated to 500°C at a rate of 10°C / min, and then calcined for 1.5 hours. S4. Rapid cooling: After calcination, the sample is immediately removed and placed in air for rapid cooling to retain more lattice defects and improve surface energy; specifically, dry cold air is used for convection cooling on the sample surface, and the cooling rate must be >10℃ / s.

[0022] Implementation, for example, attached Figure 1 As shown: Example 1 A high-strength fireworks molding compound is composed of the following raw materials (parts by weight): 550 parts calcium carbonate powder, 250 parts active type II anhydrous gypsum, 60 parts virgin cassava flour, 0.4 parts gelatinization-coking regulator (0.3 parts sorbitol + 0.1 parts sodium dihydrogen phosphate), 75 parts wood fiber, 5 parts zinc stearate lubricant, and 600 parts water.

[0023] The active type II anhydrous gypsum is a type II anhydrous gypsum powder obtained by medium-temperature crystallization of phosphogypsum, with an oil absorption value of 28g / 100g and a D50 of 18μm.

[0024] During preparation, water is heated to 70℃. Other raw materials are dry-mixed until homogeneous, then warm water is added and stirred to form a uniform slurry. During the mixing process, the active type II anhydrous gypsum hydrates to form micron-sized gypsum whiskers. The slurry is poured into a mold preheated to 190℃, and the mold is immediately closed. Curing is performed according to the following procedure: 0-2 minutes, pressure 4MPa, temperature 190℃; 2-8 minutes, pressure gradually increases to 12MPa, temperature simultaneously increases to 240℃; 8-12 minutes, maintaining 12MPa and 240℃ until no steam escapes from the mold. Finally, the mold is opened and the product is removed.

[0025] Example 2 A high-strength fireworks molding compound is composed of the following raw materials (parts by weight): 520 parts calcium carbonate powder, 280 parts active type II anhydrous gypsum, 55 parts virgin cassava flour, 0.33 parts gelatinization-coking regulator (0.25 parts sorbitol + 0.08 parts sodium dihydrogen phosphate), 78 parts wood fiber, 4.5 parts zinc stearate lubricant, and 620 parts water.

[0026] The preparation process is the same as in Example 1, except that the parameters in stage two are adjusted so that the pressure is increased to 13 MPa and the temperature is increased to 235 °C.

[0027] Example 3 A high-strength fireworks molding compound is composed of the following raw materials (parts by weight): 580 parts calcium carbonate powder, 220 parts active type II anhydrous gypsum, 62 parts virgin cassava flour, 0.47 parts gelatinization-coking regulator (0.35 parts sorbitol + 0.12 parts sodium dihydrogen phosphate), 72 parts wood fiber, 5.5 parts zinc stearate lubricant, and 580 parts water.

[0028] The preparation process is the same as in Example 1, except that the parameters in Stage 2 are adjusted so that the pressure is increased to 11 MPa and the temperature is increased to 245°C.

[0029] Comparative Example 1 It is prepared using a traditional formula: 795 parts stone powder, 100 parts cassava flour, 100 parts wood fiber, 5 parts stearic acid, 70-80% hot water, and a traditional one-step hot pressing process (constant pressure 12MPa, temperature 240℃).

[0030] Performance test results comparison:

[0031] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific structures and characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A high-strength fireworks molding compound based on in-situ whisker toughening and staged curing, characterized in that, It comprises the following components: calcium carbonate powder, micron-sized gypsum whiskers, virgin cassava flour, gelatinization-coking regulator, lignocellulose, lubricant, and water; wherein the gelatinization-coking regulator is a compound of polyol and pH buffer salt.

2. The high-strength fireworks molding compound based on in-situ whisker toughening and staged curing according to claim 1, characterized in that, The weight proportions of each raw material are as follows: 500-600 parts calcium carbonate powder, 200-300 parts micron-sized gypsum whiskers, 50-65 parts virgin cassava flour, 0.15-0.7 parts gelatinization-coking regulator, 70-80 parts wood fiber, 4-6 parts lubricant, and 550-650 parts water.

3. The high-strength fireworks molding compound based on in-situ whisker toughening and staged curing according to claim 1, characterized in that: The polyol is sorbitol, accounting for 0.1%-0.5% of the dry weight; the pH buffer salt is sodium dihydrogen phosphate, accounting for 0.05%-0.2% of the dry weight.

4. The high-strength fireworks molding compound based on in-situ whisker toughening and staged curing according to claim 1, characterized in that: The micron-sized gypsum whiskers are generated by hydration of active type II anhydrous gypsum and water at 60-80℃.

5. The high-strength fireworks molding mass based on in-situ whisker toughening and staged curing according to claim 4, characterized in that: The active type II anhydrous gypsum is prepared by treating phosphogypsum using a medium-temperature crystallization method. Its oil absorption value is ≤30g / 100g and its fineness D50 is ≤20μm.

6. The high-strength fireworks molding compound based on in-situ whisker toughening and staged curing according to claim 5, characterized in that, The intermediate-temperature crystallization method includes the following steps: S1. Raw material pretreatment: Add lime to the phosphate paste and mix. S2. Particle size optimization: Grind the neutralized phosphogypsum into particles with a concentrated particle size distribution and less than 5μm. S3. Calcination process: The pretreated phosphogypsum is placed in a muffle furnace and heated to 500°C at a rate of 10°C / min, and then calcined for 1.5 hours. S4. Rapid cooling: After calcination, the sample is immediately removed and placed in air to cool, retaining more lattice defects to improve surface energy.

7. The high-strength fireworks molding compound based on in-situ whisker toughening and staged curing according to claim 1, characterized in that: The sample was placed in air and cooled at a rate >10℃ / s.

8. A method for preparing a high-strength fireworks molding compound based on in-situ whisker toughening and staged curing as described in any one of claims 1-7, characterized in that, Includes the following steps: Step 1, Material preparation: Weigh out the following ingredients according to the weight ratio: calcium carbonate powder, active type II anhydrous gypsum, cassava flour, gelatinization-coking regulator, wood fiber, lubricant, and water. Step 2, Mixing: Heat the water to 60-80℃, mix the other ingredients evenly, add warm water and stir evenly to form a slurry; Step 3, hot pressing and curing: Inject the slurry into a mold with a temperature of 180-200℃, close the mold immediately, and gradually increase the temperature and pressure to 250℃ and 15MPa to form and cure it until no water vapor comes out of the outside of the mold. Step 4, Demolding: Open the mold and remove the molded product.

9. The high-strength fireworks molding compound based on in-situ whisker toughening and staged curing according to claim 8, characterized in that, The phased procedure in step 3 is as follows: Step 301, Low-pressure penetration period: Within 0-2 minutes after mold closing, apply a pressure of 3-5 MPa, and control the mold temperature at 180-200℃; Step 302, Pressure Increasing and Curing Period: Within 2-8 minutes after mold closing, gradually increase the pressure from Stage 1 pressure to 10-15MPa, and simultaneously raise the mold temperature to 230-250℃; Step 303, Pressure Holding and Strengthening Period: Maintain a pressure of 10-15 MPa and a temperature of 230-250℃ for 8-12 minutes after mold closing.

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