Calcium hypochlorite sustained release tablet and preparation method thereof

Abstract

The invention discloses a calcium hypochlorite sustained-release tablet and a preparation method thereof, and relates to the field of calcium hypochlorite sustained-release agents.The calcium hypochlorite sustained-release tablet aims at solving the problem that in the prior art, the limited chlorine release period is short, and the adopted technical scheme is that the amount of calcium hypochlorite is increased to 50% or above, copper sulfate is added to improve the sterilization effect, the proportion of bentonite to carboxymethylcellulose is controlled, and the calcium hypochlorite sustained-release tablet is prepared. The raw materials are dried and sieved before being mixed, and finally calcium hydroxide and copper sulfate are added. Calcium hypochlorite is compounded into a slow-release system, so that the release of available chlorine is more uniform, the release period of available chlorine is prolonged, the release period of available chlorine can be further prolonged by high-content calcium hypochlorite, and the pH of the system can be more uniform by drying, sieving and adjusting the mixing sequence of raw materials.

Description

Technical Field

[0001] This invention relates to the field of calcium hypochlorite sustained-release pharmaceutical technology, specifically to a calcium hypochlorite sustained-release tablet and its preparation method. Background Technology

[0002] Traditional calcium hypochlorite products are mostly in powder form, which has obvious drawbacks: the effective chlorine release rate is too fast, resulting in a short disinfection duration and requiring frequent replenishment; excessively high local concentrations can easily cause secondary pollution and are corrosive to metals; they are easily decomposed during storage due to temperature and humidity, and the effective ingredients are lost quickly; they require manual mixing, which is cumbersome and the dosage is difficult to control accurately.

[0003] To address the aforementioned issues, existing technologies (such as Chinese patent CN107047614B) include methods for preparing slow-release disinfectants using calcium hypochlorite, hydroxides, bentonite, and carboxymethyl cellulose, which can effectively solve these problems. However, if the calcium hypochlorite content is low, the effective chlorine release duration is short. If the calcium hypochlorite content is increased (e.g., to over 50%), it is prone to premature decomposition of effective chlorine due to excessive local humidity after mixing with alkaline excipients (hydroxides). Furthermore, the soft material is prone to clumping and has poor flowability during granulation. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the existing defects and provide a calcium hypochlorite sustained-release tablet and its preparation method, which can effectively solve the problems in the background art.

[0005] To achieve the above objectives, the present invention first discloses a calcium hypochlorite sustained-release tablet, the technical solution of which comprises the following components:

[0006] Calcium hypochlorite, calcium hydroxide, copper sulfate, bentonite, carboxymethyl cellulose, adhesives, water-retaining agents;

[0007] The mass ratio of bentonite to carboxymethyl cellulose is 4:1; the calcium hydroxide controls the pH of the calcium hypochlorite sustained-release tablets at 8-9.

[0008] The effective chlorine loss rate of the calcium hypochlorite sustained-release tablets after mixing of each component does not exceed 2.5%, the effective chlorine release uniformity does not exceed 5%, the tablet hardness is 30-40 HR, the precipitation formation rate of the system does not exceed 1.5%, and the effective chlorine sustained-release period is not less than 30 hours.

[0009] The ratio of bentonite to carboxymethyl cellulose also affects the release rate of available chlorine. Too much bentonite leads to over-release, resulting in insufficient release of available chlorine. Conversely, too little bentonite or insufficient pretreatment of the bentonite and carboxymethyl cellulose can cause the sustained-release mechanism to fail, resulting in excessively rapid release of available chlorine and low tablet hardness. A suitable sustained-release effect can be achieved by controlling the mass ratio of bentonite to carboxymethyl cellulose.

[0010] As a preferred embodiment of the present invention, the adhesive is starch paste, with a mass fraction not exceeding 3%; the water-retaining agent is a microparticle aerogel water-retaining agent, which is obtained by compounding nano-silica and sodium polyacrylate.

[0011] As a preferred embodiment of the present invention, the components are proportioned by weight as follows:

[0012] 55 parts calcium hypochlorite, 20 parts calcium hydroxide, 3 parts copper sulfate, 12 parts bentonite, 3 parts carboxymethyl cellulose, 2 parts adhesive, and 5 parts water-retaining agent.

[0013] This invention also discloses a method for preparing the above-mentioned calcium hypochlorite sustained-release tablets, the technical solution of which includes the following steps:

[0014] Step 1, Raw material pretreatment,

[0015] Calcium hypochlorite powder, calcium hydroxide, and copper sulfate were dried and sieved separately, with the moisture content of calcium hypochlorite controlled to be no higher than 2%; bentonite was ground, sieved, and dried; carboxymethyl cellulose was ground and sieved.

[0016] Step 2, mix the ingredients.

[0017] Weigh out calcium hypochlorite, calcium hydroxide, copper sulfate, bentonite, carboxymethyl cellulose, and water-retaining agent according to the weight parts, and mix them evenly to obtain a mixed powder. When mixing, first dry mix calcium hypochlorite with bentonite and carboxymethyl cellulose to obtain the main mixing system, then premix copper sulfate with water-retaining agent, and finally add calcium hydroxide, copper sulfate, and water-retaining agent to the main mixing system and continue to dry mix until uniform.

[0018] Step 3, granulation.

[0019] Add binder to the mixed powder obtained in step 2, stir to form a moist soft material, and extrude to granulate to obtain moist particles with uniform particle size.

[0020] Step 4, drying.

[0021] The moist particles obtained in step 3 are dried to a moisture content of 3%-4%.

[0022] By drying, grinding, and sieving the raw materials during the pretreatment stage, and mixing calcium hypochlorite, bentonite, and carboxymethyl cellulose first to obtain a large-volume main mixture before adding calcium hydroxide, excessive local alkalinity can be avoided. Premixing copper sulfate with a water-retaining agent before adding it to the main mixture can effectively prevent copper sulfate agglomeration when using adhesives for fixation. Mixing the main mixture thoroughly first and then adding calcium hydroxide and copper sulfate last can improve mixing efficiency, shorten mixing time, and thus shorten the contact time between copper sulfate and calcium hydroxide, significantly reducing the possibility of precipitation.

[0023] As a preferred embodiment of the present invention, in step 1, a starch slurry with a mass concentration of 10% is also prepared.

[0024] As a preferred technical solution of the present invention, in step 1, the calcium hypochlorite powder is passed through a 200-mesh sieve to remove large particulate impurities and lumps, and then dried in a drying oven at 50-55℃ for 3 hours to control the moisture content to ≤2% for later use.

[0025] Calcium hydroxide and copper sulfate were passed through an 180-mesh sieve and dried for later use.

[0026] After grinding, the bentonite is passed through a 180-mesh sieve and dried at 60°C for 2 hours for later use.

[0027] Carboxymethyl cellulose was ground through a 180-mesh sieve and set aside.

[0028] As a preferred technical solution of the present invention, in step 2, dry mixing is carried out in a high-speed mixer. The high-speed mixer rotates at a speed of 300 rpm. First, calcium hypochlorite, bentonite, and carboxymethyl cellulose are dry mixed for 10 minutes, and then calcium hydroxide, copper sulfate, and water-retaining agent are added. The total dry mixing time is extended to 15-20 minutes.

[0029] As a preferred embodiment of the present invention, in step 3, the moistened soft material is extruded and granulated through a 16-mesh sieve.

[0030] In a preferred embodiment of the present invention, after removing fine powder and lumps from the dried granules obtained in step 4, the granules are fed into a tablet press, and the tableting pressure is adjusted to 7-9 MPa to compress them into tablets. The drying of bentonite enhances its adsorption properties. Combined with the grinding and sieving of carboxymethyl cellulose, tableting pressure, granule moisture content, and the ratio of bentonite to carboxymethyl cellulose, a balance is achieved between sustained-release performance and mechanical strength.

[0031] Compared with the prior art, the beneficial effects of the present invention are: by incorporating calcium hypochlorite into the slow-release system, the present invention makes the release of available chlorine more uniform and extends the release cycle of available chlorine. The high content of calcium hypochlorite can further extend the release cycle of available chlorine. Furthermore, by drying, sieving, and adjusting the mixing order of raw materials, the pH of the system can be made more uniform.

[0032] Furthermore, by controlling the ratio of bentonite and carboxymethyl cellulose, and combining drying, grinding, and sieving, a superior release rate of available chlorine can be achieved. Subsequent tableting balances sustained-release performance and mechanical strength, while also producing tablets for rapid administration. The high tablet hardness allows the tablets to maintain their shape even when absorbing moisture, preventing disintegration.

[0033] Furthermore, when mixing raw materials, the non-reactive raw materials are mixed first, and then the potentially reactive components are added. After rapid mixing, the binder is added, which can reduce the contact time between copper sulfate and calcium hydroxide and reduce the formation of precipitate. The binder is made of starch paste, which can coat the raw materials, further reducing the contact time between copper sulfate and calcium hydroxide.

[0034] Furthermore, the effective chlorine release period of this invention reaches 36-48 hours, which is 6-8 times longer than that of traditional calcium hypochlorite powder (≤6 hours), and the concentration remains stable at 0.3-0.48 mg / L (meeting disinfection standards); the removal rate of bacteria (Escherichia coli, Staphylococcus aureus, etc.) is ≥99.9% after 24 hours, and the removal rate of algae is 95% after 72 hours (the algae inhibition rate of traditional calcium hypochlorite is only about 60%); the effective chlorine retention rate is ≥82% after 6 months of storage at room temperature, which is 32% higher than that of traditional powder (62%), and the tablets have excellent mechanical strength (30-40 hours) and no moisture absorption or disintegration. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the effective chlorine release cycle of the present invention. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Example 1

[0038] This embodiment discloses a first implementation of the present invention. First, it discloses a calcium hypochlorite sustained-release tablet, which adopts a technical solution comprising the following components:

[0039] 55 parts calcium hypochlorite, 20 parts calcium hydroxide, 3 parts copper sulfate, 12 parts bentonite, 3 parts carboxymethyl cellulose, 2 parts adhesive, and 5 parts water-retaining agent.

[0040] The preparation method of the above-mentioned calcium hypochlorite sustained-release tablets is as follows:

[0041] Step 1, Raw material pretreatment,

[0042] Take calcium hypochlorite powder, pass it through a 200-mesh sieve, and dry it at 50℃ for 3 hours, controlling the moisture content to ≤2%, and set it aside for later use; this operation is to avoid the decomposition of available chlorine due to high temperature later;

[0043] Dry calcium hydroxide and copper sulfate separately by passing them through an 180-mesh sieve and set them aside for later use.

[0044] Take bentonite, grind it, pass it through a 180-mesh sieve, and dry it at 60℃ for 2 hours for later use; this operation is to enhance the adsorption and slow-release performance.

[0045] Take carboxymethyl cellulose and pass it through an 180-mesh sieve;

[0046] Prepare a 10% starch slurry using distilled water, heat it to 80°C, stir until it becomes transparent, and cool it to room temperature for later use.

[0047] Step 2, mix the ingredients.

[0048] Weigh out 55 parts of calcium hypochlorite powder, 20 parts of calcium hydroxide, 3 parts of copper sulfate, 12 parts of bentonite, 3 parts of carboxymethyl cellulose, and 2 parts of starch paste after the pretreatment in step 1; then weigh out 5 parts of microparticle aerogel water-retaining agent.

[0049] Copper sulfate is premixed and dispersed with a water-retaining agent;

[0050] Turn on the high-speed mixer and put the calcium hypochlorite powder, bentonite, and carboxymethyl cellulose into the high-speed mixer. Dry mix at 300 rpm for 10 minutes to obtain the main mixing system. Finally, add calcium hydroxide, copper sulfate, and water-retaining agent to the main mixing system and continue to dry mix for a total dry mixing time of 15 minutes until the ingredients are evenly mixed. Take out the mixture.

[0051] Step 3, granulation.

[0052] Add starch slurry to the mixture and stir at 250 r / min for 10 min to make a moist soft material that can be formed into a ball by hand and crumbles easily when touched.

[0053] The moist soft material is extruded and granulated through a 16-mesh sieve to obtain moist particles with uniform particle size.

[0054] Step 4: Drying and granulation.

[0055] The wet granules were spread evenly on a tray and placed in a vacuum drying oven at 50℃ for 2.5 hours to dry them, controlling the moisture content of the granules to 3.5% (to avoid decomposition of the active ingredients at high temperatures). The dried granules were then granulated through a 20-mesh sieve to remove fine powder and lumps. The dried granules were collected and set aside for later use.

[0056] Step 5, tableting.

[0057] The dried granules obtained in step 4 are placed into a tablet press, and the tableting pressure is adjusted to 7 MPa. The tablets are then pressed into round tablets with a diameter of 18 mm and a thickness of 4 mm. The tablet weight is controlled at 2.75 g / tablet, the Rockwell hardness is 32 HR, and there is no powdering or disintegration. This yields sustained-release tablets.

[0058] Step 6, Post-processing and packaging.

[0059] Place the compressed sustained-release tablets in a dry, ventilated place to cool to room temperature;

[0060] The calcium hypochlorite sustained-release tablets are individually packaged using an aluminum foil composite film to prevent moisture absorption.

[0061] Example 2

[0062] The difference between this embodiment and Embodiment 1 is that in step 1, the calcium hypochlorite powder is dried at 52°C for 3 hours.

[0063] In step 2, the total dry mixing time is 18 minutes;

[0064] In step 3, the stirring time is 11 minutes;

[0065] In step 4, the particles are dried in a vacuum drying oven at 50°C for 2 hours to control the moisture content of the particles to 3%.

[0066] In step 5, tablets are compressed under 8 MPa pressure to produce tablets with a diameter of 18 mm, a thickness of 3 mm, a weight of 1.9 g, and a hardness of 36 HR.

[0067] Performance testing was conducted on Example 2.

[0068] Comparative Example 1: The difference between this comparative example and Example 2 is that copper sulfate is not present;

[0069] Comparative Example 2: The difference between this comparative example and Example 2 is that calcium hydroxide is not present;

[0070] Comparative Example 3: The difference between this comparative example and Example 2 is that it does not contain carboxymethyl cellulose;

[0071] Comparative Example 4: Traditional calcium hypochlorite powder;

[0072] Comparative Example 5: Chinese Patent CN107047614B.

[0073] The test results include sustained-release performance test, disinfection effect test, and stability test.

[0074] Sustained-release performance test: The calcium hypochlorite sustained-release tablets obtained in Example 2 and the samples of Comparative Examples 1-4 were placed in 1L of deionized water according to the principle of equal mass (e.g., 2.7g each), and stirred at a constant temperature of 25°C. The effective chlorine concentration was detected periodically using a high-performance liquid chromatograph.

[0075] Disinfection efficacy test: One tablet each of the calcium hypochlorite sustained-release tablets obtained in Example 2 and the samples from Comparative Examples 1-4 (3g was added for Comparative Example 4) were added to 1L of solution containing Escherichia coli (initial concentration). In simulated wastewater containing (CFU / mL); one tablet each of the calcium hypochlorite sustained-release tablets obtained in Example 2 and the samples from Comparative Examples 1-4 (3g corresponding to Comparative Example 4) were added to 1L of wastewater containing algae (initial concentration). The concentration of algae was measured in simulated wastewater at a concentration of (number of algae / mL) periodically using an ultraviolet spectrophotometer, and the concentration of Escherichia coli was measured using plate counting or other microbiological methods. In this embodiment, plate counting was used.

[0076] Stability test: One sample of calcium hypochlorite sustained-release tablets obtained in Example 2 and one sample of Comparative Examples 1-4 (3g corresponding to Comparative Example 4) were sealed and stored at room temperature for 6 months.

[0077] The test results are as follows:

[0078]

[0079] The sustained-release performance test results of Example 2 are as follows: Figure 1 As shown, the effective chlorine concentration remained between 0.3 and 0.48 mg / L within 36 hours, and remained above 0.05 mg / L after 48 hours. Its release characteristics exhibited a periodic fluctuation and slow decay within 36 hours, with a peak of 0.48 ppm and a trough of 0.31 ppm. This phenomenon stems from the dynamic changes of "water absorption and swelling-crack closure" in the bentonite-carboxymethyl cellulose gel skeleton, a typical characteristic of this type of sustained-release formulation.

[0080] Example 2 was further compared with Comparative Example 5. The experimental conditions for Staphylococcus aureus were: ambient temperature of 25°C, 1L of simulated wastewater (prepared with distilled water, COD=55mg / L, total bacterial count...). The effective chlorine dosage in the samples was consistent (0.5 g / L). The algae concentration was periodically measured using a UV spectrophotometer. The Staphylococcus aureus concentration was measured using the plate count method or other microbiological methods. In this embodiment, the plate count method was used. The metal corrosion test was conducted using 304 stainless steel test pieces in a corrosion test chamber.

[0081] The test results are as follows:

[0082]

[0083] The above comparison shows that Comparative Example 5 has poor uniformity of available chlorine release, a short release cycle, and its disinfection effect and stability are not as good as Example 2, and its metal corrosion rate is faster.

[0084] Then, mechanical performance tests were conducted on Example 2: The hardness of the calcium hypochlorite sustained-release tablet sample obtained in Example 2 was 36HR (measured by a hardness tester). When dropped onto a cement floor (height 1m), there was no disintegration or powdering, indicating good molding stability.

[0085] Compared with Comparative Examples 1-5, Example 2 has better sustained-release performance, longer effective chlorine release time, and more stable concentration; higher disinfection efficiency and wider disinfection range, especially for stubborn pollutants such as algae; stronger storage stability and ease of use, no need for secondary processing, and is suitable for large-scale application.

[0086] The reasons for the above-mentioned effects in Example 2 were analyzed as follows: Calcium hydroxide (20%) adjusted the pH of the system to a slightly alkaline state (pH 8-9), which precisely inhibited the hydrolysis and decomposition of calcium hypochlorite, while providing a stable environment for the bentonite-carboxymethyl cellulose composite framework; Copper sulfate (3%) and calcium hypochlorite formed a synergistic disinfection system: the effective chlorine released by calcium hypochlorite destroyed the bacterial cell membrane, and the copper ions in copper sulfate penetrated the cell wall and bound to enzyme proteins, enhancing the bactericidal and bacteriostatic effects, especially against stubborn microorganisms such as algae; the layered adsorption structure of bentonite (12%) and the gel blocking effect of carboxymethyl cellulose (3%) complemented each other, forming a "adsorption-slow release" dual channel, which delayed the dissolution of effective chlorine; starch paste (2%) and water-retaining agent (5%) controlled the particle humidity and formability, ensuring the stability of the tablet structure and further extending the sustained-release period.

[0087] However, if copper sulfate is added directly to the raw materials to improve the disinfection effect, it is easy to agglomerate when mixed with other solid components because copper sulfate is a water-soluble salt, resulting in uneven disinfection effect. It may also react slightly with calcium hydroxide to form a precipitate, affecting the stability of the system. Therefore, it cannot be simply added to the reaction system.

[0088] Furthermore, the effectiveness of the preparation method was verified.

[0089] Comparative Example 6: The difference between this comparative example and Example 2 is that the pretreatment in step 1 is not performed. In step 2, all raw materials are added to the high-speed mixer at the same time without any order and are dry mixed at a rate of 300 r / min for 18 min.

[0090] The test results are as follows:

[0091]

[0092] Note: RSD is the relative standard deviation. The smaller the value, the better the uniformity.

[0093] As can be seen from the above comparison, the pretreatment in step 1 and the optimization of the mixing order in step 2 significantly reduced the loss of available chlorine, improved the uniformity of available chlorine release, and resulted in tablets with higher hardness, less disintegration, better flowability of the soft material, and less clumping. Calcium hydroxide and copper sulfate were added to the mixing system last, resulting in a shorter contact time and a lower precipitation rate.

[0094] The microparticle aerogel water-retaining agent is obtained by compounding nano-silica and sodium polyacrylate, which is an existing technology.

[0095] The advantage of this water-retaining agent lies in the synergistic effect of the inorganic framework of nano-silica aerogel, the dispersion advantage of microparticle morphology, and the high water absorption properties of sodium polyacrylate. This perfectly solves the core problems of traditional pure sodium polyacrylate water-retaining agents (as well as some starch-grafted water-retaining agents and polyacrylamide-based water-retaining agents) in terms of poor salt resistance and weak water retention durability, as detailed below:

[0096] 1. The precise sustained-release and controlled release of the nanoporous framework prolongs the effective chlorine action time. This is the core unique advantage of this water-retaining agent, perfectly solving the key pain points of calcium hypochlorite reacting rapidly with water, instantaneous release of effective chlorine, and short duration of action. Mechanism of action: The three-dimensional continuous nanoporous framework formed by nano-silica aerogel can uniformly load and encapsulate calcium hypochlorite particles in the pores like a "microcapsule / drug storage tank." Sodium polyacrylate is a hydrophilic polymer that slowly swells (rather than rapidly dissolves) upon contact with water. By regulating the rate of water molecule penetration into the tablet, water gradually contacts the calcium hypochlorite within the pores, thereby controlling the hydrolysis rate of calcium hypochlorite and achieving a slow, continuous, and quantitative release of hypochlorous acid (the core form of effective chlorine). Practical value: Compared to traditional excipients (such as starch which rapidly disintegrates upon contact with water, causing calcium hypochlorite to be released instantly, and the available chlorine to be lost within a few hours), this water-retaining agent can extend the release period of available chlorine by 3-10 times (the specific amount can be controlled by adjusting the proportion of water-retaining agent and the porosity of aerogel), making it suitable for the needs of long-term slow release in sewage treatment, water disinfection, soil disinfection, etc., and avoiding frequent addition.

[0097] 2. Selective moisture-absorbing and water-locking stabilization significantly improves storage and usage stability. The core weakness of calcium hypochlorite is its susceptibility to moisture absorption and decomposition: even trace amounts of moisture in the environment will prematurely hydrolyze it, leading to the loss of available chlorine. Temperature and humidity changes during storage also accelerate its decomposition. This water-retaining agent addresses this problem at its source, a unique property not found in traditional excipients. Storage stability: The nanoporous structure of the aerogel has a high specific surface area and selective adsorption, adsorbing trace amounts of free moisture within the packaging and locking them in the inorganic framework pores, preventing direct contact between moisture and calcium hypochlorite. The high-molecular network of sodium polyacrylate also fixes trace amounts of moisture through hydrogen bonds, forming a "dry protective layer" that prevents premature deliquescence and decomposition of calcium hypochlorite, extending the shelf life of the sustained-release tablets by 2-5 times and reducing the available chlorine storage loss rate from the traditional 30%-50% to below 5%.

[0098] 3. The synergistic organic-inorganic molding and toughening effect enhances the mechanical strength and breakage resistance of tablets. Calcium hypochlorite is an inorganic powder with no binding properties. Traditional sustained-release tablets often rely on organic binders such as starch and carboxymethyl cellulose for molding, but this results in low tablet hardness, easy breakage, and easy disintegration during use. This water-retaining agent combines binding properties with rigid support, achieving a dual improvement in molding properties and mechanical strength. Binding properties: The long polymer chains of sodium polyacrylate have entanglement and binding properties, which can encapsulate the microparticles of calcium hypochlorite and the water-retaining agent itself, forming a continuous organic binder phase. This replaces traditional binders, making tablets easier to mold during compression without the need for additional binder excipients, simplifying the formulation. Rigid support: The inorganic framework of nano-silica aerogel provides rigid support for tablets, making up for the shortcomings of traditional organic binders (such as starch) that are "soft and brittle" after molding. This increases the compressive strength of tablets by 2-4 times, making them less prone to breakage during storage and transportation. They also do not rapidly disintegrate into powder in water / soil, avoiding secondary pollution caused by excessively high local concentrations, while ensuring the consistency of sustained-release effect.

[0099] 4. The uniformity of the microparticle-dispersed system avoids localized burst releases and component agglomeration. Calcium hypochlorite powder has a small particle size and is prone to agglomeration. When traditional excipients are mixed with calcium hypochlorite, uneven local concentrations can easily occur. At agglomerated areas, calcium hypochlorite reacts rapidly with water, forming a "localized burst release," which not only reduces the sustained-release effect but also causes problems such as sudden pH changes in water and excessive killing of beneficial microorganisms due to excessively high local hypochlorous acid concentrations. Mechanism of action: This water-retaining agent is in microparticle form (particle size matched to calcium hypochlorite powder), and the nano-silica surface has a slight charge, which can prevent calcium hypochlorite particles from agglomerating through electrostatic repulsion. The polymer chains of sodium polyacrylate can be adsorbed on the surface of calcium hypochlorite particles, forming steric hindrance, allowing the calcium hypochlorite particles to be uniformly dispersed in the organic-inorganic composite system of the water-retaining agent, resulting in a uniform distribution of components within the tablet. Practical value: It achieves uniform release of available chlorine throughout the entire process without localized bursts, ensuring stable pH and available chlorine concentration in the disinfection / treatment system, improving safety and consistency of performance, and is especially suitable for precision water purification, laboratory wastewater treatment and other scenarios.

[0100] 5. Environmentally friendly with no side effects, and also possessing auxiliary functions, simplifying the formulation system. This water-retaining agent is highly compatible with the application scenarios of calcium hypochlorite sustained-release tablets (water, soil, environmental disinfection), causes no secondary pollution, and can achieve "one material for multiple uses," replacing multiple components in traditional excipients such as sustained-release agents, binders, anti-caking agents, and stabilizers, simplifying tablet formulation. No secondary pollution: Nano-silica is an inorganic inert material, non-toxic, and biodegradable (ultimately transforming into silicon oxide, harmless to water / soil); sodium polyacrylate is a food-grade / environmentally friendly polymer with good biocompatibility, no residue, and no release of organic solvents. Neither reacts with the degradation products of calcium hypochlorite, nor does it accumulate in the environment. Auxiliary functions: In soil disinfection, the water-retaining properties of sodium polyacrylate can improve soil water holding capacity, and the porous structure of nano-silica can improve soil porosity, thus taking into account both soil disinfection and soil improvement; In water disinfection, the microparticle structure of the water-retaining agent will not cause water turbidity, and can adsorb a small amount of suspended impurities in the water, thereby improving water clarity.

[0101] The water-retaining agent used in this application differs from traditional pure sodium polyacrylate water-retaining agents as follows:

[0102]

[0103] As can be seen from the above comparison, the microparticle aerogel water-retaining agent, through organic-inorganic composite modification and microparticle morphology design, has overcome the core pain points of traditional pure sodium polyacrylate water-retaining agent, such as poor salt resistance, weak water retention durability, and low gel strength, and has achieved a comprehensive performance improvement of "high water absorption and retention + salt resistance and structural stability".

[0104] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A calcium hypochlorite sustained-release tablet, characterized in that, Includes the following components: Calcium hypochlorite, calcium hydroxide, copper sulfate, bentonite, carboxymethyl cellulose, adhesives, water-retaining agents; The mass ratio of bentonite to carboxymethyl cellulose is 4:1; the calcium hydroxide controls the pH of the calcium hypochlorite sustained-release tablets at 8-9. The effective chlorine loss rate of the calcium hypochlorite sustained-release tablets after mixing of each component does not exceed 2.5%, the effective chlorine release uniformity does not exceed 5%, the tablet hardness is 30-40 HR, the precipitation formation rate of the system does not exceed 1.5%, and the effective chlorine sustained-release period is not less than 30 hours.

2. The calcium hypochlorite sustained-release tablet according to claim 1, characterized in that: The adhesive is a starch paste, with a mass fraction not exceeding 3%; the water-retaining agent is a microparticle aerogel water-retaining agent, which is obtained by compounding nano-silica and sodium polyacrylate.

3. The calcium hypochlorite sustained-release tablet according to claim 1 or 2, characterized in that, The components are proportioned by weight as follows: 55 parts calcium hypochlorite, 20 parts calcium hydroxide, 3 parts copper sulfate, 12 parts bentonite, 3 parts carboxymethyl cellulose, 2 parts adhesive, and 5 parts water-retaining agent.

4. A method for preparing calcium hypochlorite sustained-release tablets as described in claim 1, characterized in that, Includes the following steps: Step 1, Raw material pretreatment, Calcium hypochlorite powder, calcium hydroxide, and copper sulfate were dried and sieved separately, with the moisture content of calcium hypochlorite controlled to be no higher than 2%; bentonite was ground, sieved, and dried; carboxymethyl cellulose was ground and sieved. Step 2, mix the ingredients. Weigh out calcium hypochlorite, calcium hydroxide, copper sulfate, bentonite, carboxymethyl cellulose, and water-retaining agent according to the weight parts, and mix them evenly to obtain a mixed powder. When mixing, first dry mix calcium hypochlorite with bentonite and carboxymethyl cellulose to obtain the main mixing system, then premix copper sulfate with water-retaining agent, and finally add calcium hydroxide, copper sulfate, and water-retaining agent to the main mixing system and continue to dry mix until uniform. Step 3, granulation. Add binder to the mixed powder obtained in step 2, stir to form a moist soft material, and extrude to granulate to obtain moist particles with uniform particle size. Step 4, drying. The moist particles obtained in step 3 are dried to a moisture content of 3%-4%.

5. The method according to claim 4, characterized in that: In step 1, a starch slurry with a mass concentration of 10% was also prepared.

6. The method according to claim 4, characterized in that: In step 1, the calcium hypochlorite powder is passed through a 200-mesh sieve to remove large particles and lumps, and then dried in a drying oven at 50-55℃ for 3 hours, with the moisture content controlled to ≤2%, for later use. Calcium hydroxide and copper sulfate were passed through an 180-mesh sieve and dried for later use. After grinding, the bentonite is passed through a 180-mesh sieve and dried at 60°C for 2 hours for later use. Carboxymethyl cellulose was ground through a 180-mesh sieve and set aside.

7. The method according to claim 4, characterized in that: In step 2, dry mixing is carried out in a high-speed mixer. The high-speed mixer rotates at a speed of 300 rpm. First, calcium hypochlorite, bentonite, and carboxymethyl cellulose are dry mixed for 10 minutes. Then, calcium hydroxide, copper sulfate, and water-retaining agent are added, and the total dry mixing time is extended to 15-20 minutes.

8. The method according to claim 4, characterized in that: In step 3, the moist soft material is extruded and granulated through a 16-mesh sieve.

9. The method according to claim 4, characterized in that: After removing fine powder and clumps from the dried granules obtained in step 4, they are fed into a tablet press, and the tableting pressure is adjusted to 7-9 MPa to compress them into tablets.

Images