A gradient cooling medical self-cooling ice bag and a preparation method thereof

Abstract

This invention discloses a gradient cooling medical self-cooling ice pack and its preparation method, belonging to the technical field of medical cold compress consumables. The ice pack includes a primary instant cooling source matrix and a secondary delayed cooling effect microspheres, which are physically mixed and then packaged in a medical packaging bag. The bag contains an independent activation water pack. The primary matrix is ​​composed of urea, ammonium chloride, medical superabsorbent resin, sodium carboxymethyl cellulose and purified water. The secondary microspheres have urea / superabsorbent resin as the core and calcium alginate as the water-soluble shell. They can dissolve and cool in 60±15 minutes. This invention constructs a dual gradient cooling system of "instant rapid cooling-constant temperature buffer-secondary continued cooling". The temperature can be kept stable below 10℃ for more than 2 hours throughout the process, avoiding sudden frostbite and rapid decay of cooling effect. All raw materials are medical grade, which is safe and non-irritating. The system is stable and leak-free. The process is simple and easy to mass-produce. It is highly innovative and suitable for various medical cold compress scenarios.

Description

Technical Field

[0001] This invention belongs to the field of medical cold compress consumables technology, specifically relating to a gradient cooling medical self-cooling ice pack, and also to its preparation method. Background Technology

[0002] Medical cold compresses are a commonly used physical therapy method in clinical practice, which can achieve effects such as reducing swelling, relieving pain, and local cooling. Self-cooling ice packs are widely used in clinical nursing, sports injuries, and emergency cooling scenarios because they do not require prior refrigeration or rubbing to activate.

[0003] Currently, medical self-cooling ice packs on the market are mainly divided into single rapid cooling type and simple cooling type. The core of most of them uses a single cold source system (such as a mixture of urea and ammonium chloride, or a combination of ammonium nitrate and water) with a basic thickener to achieve cooling. Although they can meet basic cold compress needs, there are still the following areas for improvement in clinical applications: Firstly, the cooling mode is singular and cannot achieve gradient temperature control. Existing self-cooling ice packs mostly exhibit a cooling curve of "instantaneous rapid cooling + rapid decay". After being rubbed and activated, the temperature drops sharply in a short period of time, which can easily cause frostbite to the skin. They are especially unsuitable for special medical scenarios such as postoperative wounds, infants, and sensitive skin. At the same time, the cooling effect decays too quickly. The temperature usually rises back to room temperature quickly after 30 minutes, which cannot meet the need for long-term constant temperature cold compresses of more than 2 hours, making it difficult to achieve the clinical effect of continuous swelling reduction and pain relief.

[0004] Secondly, some products pose significant safety hazards and lack medical compatibility. Some ice packs use corrosive and irritating hazardous chemicals such as ammonium nitrate as a cold source in pursuit of cooling intensity. If the packaging is damaged and leaks occur, contact with the skin can easily cause redness, swelling, and burns, and there is also a risk of accidental ingestion. This does not meet the safety standards for medical consumables. Other ice packs use a single ordinary ammonium salt system, which slightly improves safety, but the cooling intensity is insufficient and there is no antibacterial design. Bacteria can easily grow during the cold compress process, increasing the risk of skin infection.

[0005] Third, the system has poor stability and is prone to leakage and stratification. Most existing ice packs use sodium carboxymethyl cellulose (CMC) as a single thickening and water-locking component. If the amount of thickener is too high, the system viscosity will be too high and the free water content will be insufficient, which will not meet the requirements for the full dissolution of the cold source components. If the amount is too low, leakage and stratification will easily occur, affecting the user experience and the cooling effect.

[0006] Fourth, the core formulas of existing self-cooling ice packs are mostly simple combinations of "cold source + single thickener + water", with highly overlapping ratio ranges. They do not involve time-sequential gradient cooling design, nor do they adopt a safe delayed cold source system, resulting in serious homogenization of technical solutions. Summary of the Invention

[0007] In view of the above-mentioned shortcomings of the existing technology, one of the objectives of the present invention is to provide a gradient cooling medical self-cooling ice pack, which constructs a dual gradient cooling system of "instant rapid cooling + delayed continuous cooling", which is safe and non-irritating, with precise and controllable cooling, good system stability, and can meet the needs of long-term medical cold compress. The second objective of the present invention is to provide its preparation method, which is simple and controllable in process, low in raw material cost, and suitable for large-scale industrial production.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a gradient cooling medical self-cooling ice pack, comprising a primary instant cold source matrix and a secondary delayed cooling effect microspheres, which are physically mixed and then sealed in a medical-grade packaging bag, wherein the packaging bag also contains an independently sealed water bag for activating the cold source; The primary instant cold source matrix is ​​composed of the following components in parts by weight: 45-60 parts urea, 15-25 parts ammonium chloride, 0.1-0.5 parts medical superabsorbent resin, 1-3 parts sodium carboxymethyl cellulose, and 100-130 parts purified water. Urea and ammonium chloride are combined as the main cold source, and the dissolution endothermics achieve rapid cooling. The medical superabsorbent resin and sodium carboxymethyl cellulose are combined as a composite thickening and water-locking component to adjust the viscosity and specific heat capacity of the system and delay the temperature rise. Purified water serves as the medium for dissolving the cold source and provides moisture for the swelling and cold release of the secondary microspheres. The secondary delayed-release cooling microspheres use a mixture of urea and medical-grade superabsorbent resin as the core and calcium alginate as the water-soluble shell. The shell can completely swell and disintegrate to release the core contents in 60±15 minutes under normal temperature and cold water conditions. The secondary delayed-release cooling microspheres account for 3%-15% of the total mass of the ice pack's cooling components. Among them, the core urea serves as a secondary cold source, dissolving and absorbing heat after release to achieve secondary cooling. The medical-grade superabsorbent resin can lock in moisture to ensure a stable dissolution process. The calcium alginate shell is a water-soluble controlled-release structure, controlling the timing of the contents release through the swelling rate to achieve sequential continuous cooling.

[0009] Preferably, in the primary instant cooling source matrix, purified water accounts for more than 60% of the total mass of the primary instant cooling source matrix. By reducing the total amount of sodium carboxymethyl cellulose and medical superabsorbent resin, the initial state of the primary instant cooling source matrix is ​​a thin paste, retaining sufficient free water. This design ensures that the microsphere shell has sufficient water to fully swell and dissolve, and also ensures that there is enough water to participate in the dissolution of the core contents after release. At the same time, it avoids the problems of insufficient cooling effect due to excessive viscosity and leakage and stratification due to excessive thinness.

[0010] Preferably, the particle size of the secondary delayed cooling microspheres is 0.5-3mm, the mass ratio of urea to medical superabsorbent resin in the core is 10:1, and the mass of sodium alginate in the shell accounts for 5%-10% of the total mass of the core. Under these parameters, the microsphere shell thickness is uniform, the swelling rate is stable, and the release timing can be precisely controlled.

[0011] Preferably, the secondary delayed cooling microspheres are prepared by a semi-dry granulation and embedding method. The preparation steps include: mixing urea and medical superabsorbent resin, low-speed shaking and water spraying granulation, sieving and rolling with sodium alginate dry powder, adding calcium chloride solution for cross-linking and curing, washing with anhydrous ethanol, drying at a constant temperature of 40°C, and screening the particle size to obtain the finished product. During the preparation process, the medical superabsorbent resin is not ground. The semi-dry granulation process can avoid urea crystal precipitation that punctures the shell, ensuring the integrity of the microsphere structure. Not grinding the superabsorbent resin can avoid the destruction of its cross-linking network, ensuring water-locking and swelling performance.

[0012] Preferably, the self-cooling ice pack achieves three-stage gradient cooling after activation: The first 15 minutes are the instant cooling phase. Urea and ammonium chloride in the primary instant cooling source matrix dissolve and absorb heat rapidly, and the system temperature drops quickly to the appropriate temperature for cold compress, meeting the needs for immediate swelling reduction and pain relief. At this time, the system is in a thin paste state with sufficient free water content.

[0013] The 15-60 minute period is a constant temperature buffer phase. During this phase, the cooling effect of the primary cold source gradually decreases, and the system temperature rises slightly and steadily. During this process, the free water in the system continues to slowly permeate the microsphere shell, causing the water-absorbing resin in the core to gradually absorb water and swell. However, the shell does not disintegrate, and the contents are not released prematurely, thus maintaining the system temperature at a relatively stable level.

[0014] After 60 minutes, the second cooling phase begins. Under the continuous immersion of free water, the microsphere shell completely swells and disintegrates, releasing the urea inside and coming into contact with the free water. This rapid dissolution and heat absorption achieves a second cooling, lowering the system temperature again and maintaining it stably below 10°C. This significantly extends the duration of constant temperature cold compresses, meeting the clinical needs of long-term physiotherapy and postoperative swelling reduction.

[0015] The present invention also provides a method for preparing the above-mentioned gradient cooling medical self-cooling ice pack, including the following steps: S1: preparing a primary instant cold source substrate: at room temperature, urea, ammonium chloride, medical superabsorbent resin and sodium carboxymethyl cellulose are added into a mixing container according to the ratio and stirred until uniformly mixed to obtain a primary cold base solid mixture. At the same time, purified water is packaged according to the ratio to prepare an independent water bag for later use.

[0016] S2: Preparation of secondary delayed cooling microspheres: prepared by semi-dry granulation and embedding method, and then dried and screened for particle size before use.

[0017] S3: Finished product filling and packaging: At room temperature, add the secondary delayed cooling microspheres to the primary cold base solid mixture and stir until the microspheres are evenly dispersed and there are no broken microspheres. Then fill the mixture into a medical-grade packaging bag, put in an individual water bag and seal it to obtain the finished product of gradient cooling medical self-cooling ice pack.

[0018] Compared with the prior art, the beneficial effects of the present invention are: (1) The gradient cooling medical self-cooling ice pack and its preparation method are highly safe for medical use and have a wide range of applications. All components of the solution use medical-grade or food-grade raw materials and do not use hazardous chemicals such as ammonium nitrate. The system is non-toxic, non-irritating, and non-corrosive. Even if the packaging is damaged and leaks, it will not cause harm when it comes into contact with the skin. Antibacterial components can be added as needed to prevent bacterial growth during the cold compress process. It fully complies with the safety standards for medical cold compress consumables and is suitable for various medical cold compress scenarios such as postoperative wounds, infants, and sensitive skin.

[0019] (2) The gradient cooling medical self-cooling ice pack and its preparation method have precise and controllable gradient cooling, which solves the core pain points of the industry. By constructing a dual-gradient cooling system of "first-level instant rapid cooling + second-level delayed cooling", a three-stage cooling curve of "instant rapid cooling - constant temperature buffer - second-level continued cooling" is formed. It not only meets the rapid cooling needs of instant cold compress, but also achieves long-term constant temperature cold compress through delayed release of cold. The overall temperature can be stably maintained below 10℃ for more than 2 hours, which effectively avoids the dual defects of "sudden frostbite" and "rapid decay of cooling effect" of existing ice packs, and is suitable for clinical needs such as long-term physiotherapy and postoperative swelling reduction.

[0020] (3) The gradient cooling medical self-cooling ice pack and its preparation method have excellent system stability and no leakage or stratification problems. By optimizing the amount of composite thickener and the ratio of purified water, the initial state of the primary matrix is ​​a thin paste, which retains sufficient free water. This ensures the water requirements for the swelling of microspheres and the dissolution of the secondary cold source, and avoids the problems of insufficient cooling effect due to excessive thickness and leakage and stratification due to excessive thinness. The colloidal stability is strong and the user experience is good.

[0021] (4) The gradient cooling medical self-cooling ice pack and its preparation method are significantly different from the existing single cold source ice packs by using a pioneering dual safety gradient cooling system of "urea + ammonium chloride instant cold source + urea delayed microsphere cold source" combined with microsphere precise controlled release technology and moisture retention design.

[0022] (5) The gradient cooling medical self-cooling ice pack and its preparation method are simple to prepare, cost controllable and easy to mass-produce. The raw materials used are all common medical / food grade raw materials on the market, which are inexpensive and easy to purchase. The preparation process is simple and does not require complicated production equipment. Stable production can be achieved by controlling the process parameters. It is suitable for large-scale industrial production. The product has good storage stability and can be stored for a long time under normal temperature and light protection conditions without the risk of premature failure. Attached Figure Description

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 This is a schematic diagram of the temperature change curves for different proportions of the present invention; Figure 2 This is a schematic diagram of the structure of the three sets of temperature change curves of the present invention. Detailed Implementation Example 1

[0024] This invention provides a technical solution: a gradient cooling medical self-cooling ice pack, with a total mass of 200 parts for the cooling components, including 193 parts for the primary instant cold source matrix and 7 parts for the secondary delayed cooling microspheres (accounting for 3.5% of the total mass); the packaging bag contains an independently sealed purified water bag.

[0025] The primary instantaneous cooling source matrix consists of the following components by mass: 54 parts urea, 18 parts ammonium chloride, 0.2 parts medical superabsorbent resin, 1.8 parts sodium carboxymethyl cellulose, and 119 parts purified water. Purified water accounts for 61.66% of the total mass of the primary matrix. The system is initially a thin paste with sufficient free water.

[0026] The secondary delayed cooling microspheres have a particle size of 0.5-3mm. The core is composed of urea and medical superabsorbent resin (mass ratio 10:1), and the shell is composed of calcium alginate. The amount of sodium alginate accounts for 9.09% of the total mass of the core. The shell completely swells and disintegrates in about 60 minutes under normal temperature and cold water conditions.

[0027] The preparation method of the gradient cooling medical self-cooling ice pack in this embodiment is as follows: S1: Preparation of primary instant cold source matrix: At room temperature, weigh 54 parts of urea, 18 parts of ammonium chloride, 0.2 parts of medical superabsorbent resin, and 1.8 parts of sodium carboxymethyl cellulose according to the ratio, put them into a mixing container and stir until completely mixed to obtain a primary cold base solid mixture. Separately weigh 119 parts of purified water and seal it into an independent water bag for later use.

[0028] S2: Preparation of secondary delayed cooling microspheres: prepared by semi-dry granulation and encapsulation method. The specific process is as follows: weigh the core raw materials according to the mass parts: 10 parts of urea and 1 part of medical superabsorbent resin (the superabsorbent resin is not ground), put them into the granulator and mix them evenly; keep the granulation at room temperature and shake it at low speed, slowly sprinkle in a total of 3 parts of purified water in 5 times, and continue to shake the granulation for 15 minutes to form wet particles with uniform particle size. The wet granules are sieved to remove oversized particles. The sieved granules are returned to the granulator and shaken at low speed. One part of sodium alginate dry powder is added in three batches to make sodium alginate evenly coat the surface of the core granules and form a uniform shell. After the shell is rolled, the coated particles are added one by one to a 2% calcium chloride curing solution and left to cure at room temperature for 25 minutes to allow the sodium alginate to crosslink and form a stable calcium alginate semi-permeable shell structure. After curing, the microspheres are removed and washed three times with anhydrous ethanol to remove residual impurities on the surface. Then, they are placed in a 40℃ constant temperature forced-air drying oven for 3 hours. After drying, the finished microspheres with a particle size of 0.5-3mm are collected by screening with a standard sieve for later use.

[0029] S3: Finished product preparation: At room temperature, weigh 7 portions of the prepared secondary delayed cooling microspheres and add them to the primary cold base solid mixture. Stir at low speed until the microspheres are evenly dispersed and there are no broken microspheres. Then fill the mixture into medical-grade packaging bags, put in an individual water bag and seal the bag to obtain the finished product of gradient cooling medical self-cooling ice pack.

[0030] Performance testing: The ice pack was activated at room temperature (25℃), and the temperature change of the system was tested. After activation, the system temperature dropped to 8.2℃ in 10 minutes (instantaneous rapid cooling). The temperature slowly rose within 15-60 minutes, reaching 9.7℃ at 60 minutes (constant temperature buffer). After 60 minutes, the microspheres disintegrated and cooled, and the temperature dropped again, reaching 7.5℃ at 70 minutes and 9.3℃ at 120 minutes. The cooling time below 10℃ can reach 2.5 hours, and the gradient cooling effect is significant. Example 2

[0031] This embodiment of the gradient cooling medical self-cooling ice pack has a total mass of 200 parts for the cooling components, including 190 parts for the primary instant cold source matrix and 10 parts for the secondary delayed cooling microspheres (accounting for 5% of the total mass). The packaging bag contains an independently sealed purified water packet.

[0032] The primary instantaneous cold source matrix is ​​composed of the following components in parts by weight: 48 parts urea, 22 parts ammonium chloride, 0.3 parts medical superabsorbent resin, 2.2 parts sodium carboxymethyl cellulose, and 117.5 parts purified water. The purified water accounts for 61.84% of the total mass of the primary matrix. The system is initially in a thin paste state with sufficient free water.

[0033] The secondary delayed cooling microspheres have a particle size of 0.5-3mm. The core is composed of urea and medical superabsorbent resin (mass ratio 10:1), and the shell is composed of calcium alginate. Sodium alginate accounts for 7% of the total mass of the core. The shell completely swells and disintegrates in about 55 minutes under normal temperature and cold water conditions.

[0034] The preparation method of this embodiment is basically the same as that of Example 1, except that: the calcium chloride curing time in step S2 is 22 minutes, and the performance test is: the ice pack is activated at room temperature of 25°C, and the temperature change of the system is tested: the system temperature drops to 7.8°C after 10 minutes of activation, and the temperature is 9.5°C at 55 minutes. The temperature drops again after the microspheres release cold, and the temperature is 8.9°C at 120 minutes. The cold compress time below 10°C can reach 2.8 hours, and the secondary cooling intensity is better than that of Example 1. Example 3

[0035] This embodiment of the gradient cooling medical self-cooling ice pack has a total mass of 200 parts for the cooling components, including 192 parts for the primary instant cold source matrix and 8 parts for the secondary delayed cooling microspheres (accounting for 4% of the total mass). The packaging bag contains an independently sealed purified water packet.

[0036] The primary instantaneous cooling source matrix is ​​composed of the following components by weight: 58 parts urea, 16 parts ammonium chloride, 0.15 parts medical superabsorbent resin, 1.2 parts sodium carboxymethyl cellulose, and 116.65 parts purified water. Among them, purified water accounts for 60.76% of the total mass of the primary matrix, and the system is initially in a thin paste state with sufficient free water.

[0037] The secondary delayed cooling microspheres have a particle size of 0.5-3mm. The core is composed of urea and medical superabsorbent resin (mass ratio 10:1), and the shell is composed of calcium alginate. Sodium alginate accounts for 6% of the total mass of the core. The shell completely swells and disintegrates in about 65 minutes under normal temperature and cold water conditions.

[0038] The preparation method of this embodiment is basically the same as that of Example 1, except that: the calcium chloride curing time in step S2 is 28 minutes, and the performance test is: the ice pack is activated at room temperature of 25°C, and the temperature change of the system is tested: the system temperature drops to 8.5°C after 10 minutes of activation, and the temperature is 9.6°C after 65 minutes. The temperature drops again after the microspheres release cold, and the temperature is 9.1°C after 120 minutes. The cold compress time below 10°C can reach 2.6 hours.

[0039] Comparative Example 1 (Existing ordinary quick-cooling ice pack) A single cold source system is used, consisting of 54 parts urea, 18 parts ammonium chloride, 2 parts sodium carboxymethyl cellulose, and 126 parts purified water, without secondary delay microspheres.

[0040] Performance test: Activated at room temperature of 25℃, the temperature dropped to 8.0℃ in 10 minutes, rose back to 11.2℃ in 30 minutes, and rose to 15.8℃ in 45 minutes. The cooling effect lasted only about 35 minutes below 10℃, with rapid decay of cooling effect and no gradient cooling effect.

[0041] As can be seen from the comparison of the above embodiments and comparative examples, the present invention can achieve three-stage gradient cooling by combining a primary instant cold source with a secondary time-delay microsphere, which greatly extends the effective cooling time and the cooling process is gradual, avoiding sudden cold stimulation and fully meeting the needs of medical cold compresses.

[0042] Please see Figure 1-2 Add the prepared microspheres (curing time is 23 minutes) to deionized water at a mass ratio of 1:10, ensuring that the water can cover the microspheres. At 50-70 minutes, take 10 microspheres at each two-minute interval, observe whether the microspheres break and record the results, and add a parallel set.

[0043] The results are as follows:

[0044] The above results confirm that the disintegration time of the secondary delayed cooling microspheres prepared by this method meets the design requirements, and the contents can be released within a preset time to achieve gradient temperature control. The technical solution can be stably and repeatedly implemented.

[0045] After activating ice packs with different formulations at 25°C, attach thermometers to the surface of the ice packs, measure and record the temperatures, as shown in the table below:

[0046] Combining the above table with Figure 1 Analysis of temperature changes clearly shows a three-stage gradient cooling characteristic of "instantaneous rapid cooling - constant temperature buffering - secondary cooling" for different ratios. Selecting the appropriate ratio can stably maintain the system temperature in the suitable cold compress range below 10℃, which can fully meet the needs of long-term clinical physiotherapy, swelling reduction and analgesia.

[0047] By adjusting the curing time and amount of the secondary delayed cooling microspheres and the amount of water added, the start time and cooling range of the secondary cooling can be precisely controlled, adapting to the cooling needs of different people and different scenarios: shortening the curing time can start the secondary cooling earlier, extending the curing time can delay the release of cold, and adjusting the amount of microspheres added can change the range of secondary cooling. The solution is flexible, adjustable, and highly adaptable.

[0048] Take three ice packs with the optimal mixing ratio, activate them at 25°C, attach a thermometer to the surface of the ice packs, and measure and record the temperature, as shown in the table below:

[0049] Combining the above table with Figure 2 The results of the three sets of repeated tests show that the formulation scheme has good stability and high repeatability, and the cooling sequence and temperature control deviation of different batches of finished products are all within the design allowable range.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

[0051] The contents or structures not described in detail in this specification are existing technologies known to those skilled in the art, and therefore will not be elaborated upon further.

[0052] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A gradient cooling medical self-cooling ice pack, characterized in that: It includes a primary instant cold source matrix and a secondary delayed cooling effect microspheres, which are physically mixed and then sealed in a medical-grade packaging bag. The packaging bag also contains a water bag for activating the cold source. The primary instant cold source matrix is ​​composed of the following components in parts by weight: 45-60 parts urea, 15-25 parts ammonium chloride, 0.1-0.5 parts medical superabsorbent resin, 1-3 parts sodium carboxymethyl cellulose, and 100-130 parts purified water. The secondary delayed cooling microspheres use a mixture of urea and medical superabsorbent resin as the core and calcium alginate as the water-soluble shell. The shell can completely swell and disintegrate to release the contents of the core in 60±15 minutes under normal temperature and cold water conditions. The secondary delayed cooling microspheres account for 3%-15% of the total mass of the ice pack's cooling components.

2. The gradient cooling medical self-cooling ice pack according to claim 1, characterized in that: In the primary instant cooling source matrix, purified water accounts for more than 60% of the total mass of the primary instant cooling source matrix; by reducing the total amount of sodium carboxymethyl cellulose and medical superabsorbent resin, the initial state of the primary instant cooling source matrix is ​​a thin paste, retaining sufficient free water.

3. The gradient cooling medical self-cooling ice pack according to claim 2, characterized in that: The secondary delayed cooling microspheres have a particle size of 0.5-3 mm, the mass ratio of urea to medical superabsorbent resin in the core is 10:1, and the mass of sodium alginate in the shell accounts for 5%-10% of the total mass of the core.

4. The gradient cooling medical self-cooling ice pack according to claim 3, characterized in that: The secondary delayed cooling microspheres are prepared by a semi-dry granulation and encapsulation method. The preparation steps include: mixing urea and medical superabsorbent resin, low-speed shaking and water spraying granulation, sieving and rolling sodium alginate dry powder, adding calcium chloride solution for cross-linking and curing, washing with anhydrous ethanol, drying at 40°C, and screening the particle size to obtain the finished product. The medical superabsorbent resin is not ground during the preparation process.

5. A gradient cooling medical self-cooling ice pack according to claim 4, characterized in that: After activation, a three-stage gradient cooling is achieved: 0-15 minutes is the instant rapid cooling stage, where the cold source components in the primary instant cold source matrix dissolve and absorb heat to achieve rapid cooling; 15-60 minutes is the constant temperature buffer stage, where the cooling effect of the primary cold source slowly decays, free water slowly permeates and swells the microsphere shell, and the core contents are not released prematurely. After 60 minutes, the second cooling stage begins. The microsphere shell swells and disintegrates, while the urea core dissolves and absorbs heat to achieve a second cooling. The system temperature is then stably maintained below 10°C.

6. A method for preparing a gradient cooling medical self-cooling ice pack, characterized in that, Includes the following steps: S1: At room temperature, the solid components of the primary instant cold source matrix are mixed evenly to obtain the primary cold base, and an independently packaged water bag is prepared for later use. S2: Secondary delayed-effect cooling microspheres were prepared by a semi-dry granulation and encapsulation method, and then dried and screened for particle size before use. S3: Add the secondary delayed cooling microspheres to the primary cold base and mix evenly. Fill the mixture into medical-grade packaging bags, place them in a water bag, and seal to obtain the finished product.

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