A soft capsule gradient drying method based on capsule shell moisture properties

Abstract

The application belongs to the technical field of pharmacy, and discloses a soft capsule gradient drying method based on the moisture properties of the capsule shell. The method monitors the moisture content of the capsule shell in real time, uses the measured moisture value as the basis for stage division and parameter control, divides the drying process into several continuous moisture stages, dynamically matches the drying temperature, relative humidity and cage rotation speed according to the physical properties of the capsule shell, such as elasticity, hardness and plasticity in each stage. Compared with the traditional fixed parameter drying or open-loop control method based on the time axis, the application realizes the technical transformation from "empirical fixed time drying" to "closed-loop precise control based on material state", solves the problem of uneven drying inside and outside from the mass transfer mechanism, shortens the drying period by more than 30%, reduces the waste pellet rate by more than 50%, and can stably control the capsule shell moisture in the best range of 7% to 10%, which has significant industrial application value.

Description

Technical Field

[0001] This invention belongs to the field of pharmaceutical technology, specifically relating to a soft capsule drying process, and more particularly to a gradient drying method for soft capsules based on real-time monitoring of capsule shell moisture. Background Technology

[0002] Soft capsules are a type of capsule formulation made by sealing liquid or suspension drugs in a soft shell (rubber). They are widely used in the pharmaceutical and health product industries due to their advantages such as accurate dosage, masking of odors, high bioavailability, and good stability. The capsule shell is typically made from gelatin, glycerin (plasticizer), and water as the main raw materials, mixed and melted to form a gel, which is then cooled and solidified. Because freshly pressed capsule shells have a high water content (usually around 30%–50% initially), the capsules are relatively soft and must undergo a drying process to remove moisture and harden the shells for subsequent production and storage. The moisture content of the capsule shell directly determines its elasticity, hardness, and stability. Studies have shown that a moisture content of 8%–12% after drying is suitable for soft capsules, with the optimal range being 7%–10%. Excessive moisture can lead to adhesion, deformation, microbial growth, and oil leakage, while insufficient moisture may cause shell cracking and content degradation, resulting in quality problems.

[0003] Currently, the mainstream soft capsule drying process in the industry is a single-stage or two-stage open-loop drying process with fixed parameters, controlling the temperature and humidity of the room environment. For example, CN104873393B discloses a soft capsule drying device that divides an eight-section rotary drum into three drying stages: a shaping stage (two sections), a pre-drying stage (three sections), and a final drying stage (three sections). The temperature in the shaping stage is fixed at 20±0.5℃, and the humidity is controlled by a solution dehumidifier connected to the rotary drum. The overall process is an open-loop predefined stage control, with the stage division based on the mechanical structure layout of the rotary drum, rather than on the real-time moisture status of the capsules. Another example is CN216222342U, which discloses a capsule heating drying tunnel that divides the tunnel into multiple sections to achieve a gradual increase in temperature. However, this solution is designed for a hard capsule drying tunnel structure and does not involve the coordinated control of moisture monitoring and drying parameters.

[0004] The above-mentioned existing technologies generally have the following technical defects: (1) Ignoring the differences in properties of capsules at different moisture stages. Changes in the moisture content of the capsule shell will cause significant changes in its elasticity, hardness, plasticity and other physical properties. When the initial moisture content is 30%~50%, the capsule shell is soft and has strong adhesion. When the moisture content is 20%~30%, the elasticity reaches its peak. When the moisture content is 12%~20%, the hardness increases and the plasticity decreases. When the moisture content is 7%~12%, the performance tends to be stable. However, the existing process uses the same temperature and humidity treatment for each stage, which leads to an imbalance in the internal and external drying rates, generating internal stress and causing defects such as adhesion, brittleness, oil leakage, water return and deformation. Studies have shown that excessively high temperature or excessively fast rotation speed in the early stage of drying will cause the surface of the soft capsule to form a skin and the internal moisture to be unable to be discharged, resulting in external dryness and internal moisture, which is prone to mold after storage. (2) The precise correspondence between moisture content and temperature and humidity control parameters has not been established, and the drying cycle is long. Tray drying requires 24~34 hours. Although rotary drying can be shortened to about 16 hours, it is still operated empirically according to fixed time. The moisture control stability is poor and the yield is low. (3) The environmental temperature and humidity control accuracy is low, and the moisture content of the capsule shell is difficult to reach the ideal range of 7%~10%, which affects the stability of product quality. Summary of the Invention

[0005] The present invention aims to overcome the above-mentioned defects in the prior art and provide a gradient drying method for soft capsules based on the moisture properties of the capsule shell, which can dynamically adjust the temperature and humidity control parameters to achieve a high-efficiency and low-defect drying effect.

[0006] The core technical concept of this invention lies in: by real-time monitoring of the moisture content of the soft capsule shell, using the measured moisture value as the direct basis for stage division and parameter control, and dynamically matching the drying temperature, relative humidity, and drum speed according to the physical properties (elasticity, hardness, plasticity, etc.) of the shell under different moisture ranges, a technological leap is achieved from empirical fixed-time drying to closed-loop precise control based on material state, thereby fundamentally solving the mass transfer problem of uneven drying inside and outside, significantly shortening the drying cycle, and reducing the product defect rate.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: The first aspect of the present invention provides a gradient drying method for soft capsules based on the moisture properties of the capsule shell, comprising the following steps: (1) Obtain the real-time moisture content of the soft capsule shell; (2) Based on the real-time moisture content, the drying process is divided into several continuous moisture stages; (3) For each moisture stage, at least one drying parameter is dynamically adjusted according to the shell characteristics corresponding to that stage. The drying parameter is selected from one or more of drying temperature, relative humidity, and drum rotation speed. (4) Repeat steps (1) to (3) until the moisture content of the capsule reaches the target range.

[0008] Preferably, the plurality of consecutive moisture stages include four stages: First moisture stage (high moisture soft and sticky stage): The moisture content of the shell is 30%~50%. The shell is soft, highly malleable, and easily deformed and stuck together. Control the drying temperature at 18~22℃, relative humidity at 40%~55%, and drum speed at 10~12 rpm. The second moisture stage (medium-high moisture elasticity stage): the moisture content of the shell is 20%~30%, the shell elasticity reaches its peak and the tensile strength is strong. The drying temperature is controlled at 24~28℃, the relative humidity is 30%~40%, and the drum speed is 8~10 rpm. The third moisture stage (medium-low moisture acceleration period): the moisture content of the shell is 12%~20%, the hardness of the shell increases and the plasticity decreases. The drying temperature is controlled at 30~35℃, the relative humidity is <25%, and the drum speed is 6~8 rpm. Fourth moisture stage (low moisture stabilization period): The moisture content of the shell is 7%~12%, and the shell performance tends to be stable. The drying temperature is controlled at 20~24℃, the relative humidity is <25%, and the drum speed is 6~8 rpm.

[0009] The aforementioned moisture stage division values ​​were determined through experimental research based on a capsule formulation with a gelatin:glycerol ratio ranging from 1:0.3 to 1:0.6. Taking a gelatin:glycerol ratio of 1:0.3 as an example: Stage 1: 30%–50%, Stage 2: 20%–30%, Stage 3: 12%–20%, Stage 4: 7%–12%. When the gelatin-glycerol ratio, capsule thickness, or contents properties change, the moisture stage thresholds and corresponding drying parameters can be adaptively adjusted within the above value range. Such adaptive adjustments are within the scope of the technical solution of this invention.

[0010] The present invention also provides a gradient drying system for soft capsules based on the moisture properties of the capsule shell, characterized in that it comprises: (a) At least one closed drying drum unit with independent temperature and humidity control for holding soft capsules to be dried; (b) A moisture monitoring device for measuring the real-time moisture content of the capsule shell; (c) A control unit configured to perform the soft capsule gradient drying method described in any of the preceding claims.

[0011] The present invention adopts the above technical solution and has the following technical effects compared with the prior art: (1) Solve the problem of uneven drying inside and outside from the perspective of mass transfer mechanism: By accurately matching the drying parameters with the shell properties at different moisture stages, the moisture migration rate at each stage is effectively controlled, avoiding surface crusting and internal stress generation, and reducing defects such as adhesion, brittleness, oil leakage, and water return from the root cause; and experimental data show that after the implementation of this invention, the waste shot rate is reduced from 0.55% in the traditional process to 0.23%, and the defect rate is reduced by 58.2%.

[0012] (2) The drying efficiency is significantly improved and the cycle is significantly shortened: Through precise matching of moisture and parameters, the drying rate of each stage is significantly improved; the drying cycle of the isotretinoin soft capsules in this embodiment is shortened from 26 hours in the traditional process to 16 hours, and the efficiency is improved by 38.5%.

[0013] (3) Energy saving: The drying process of soft capsules is one of the main sources of energy consumption in production. This invention shortens the drying time and adopts independent temperature and humidity control of the equipment, which effectively reduces the energy consumption of water, electricity and gas.

[0014] (4) High precision in moisture control: The present invention can stably control the final moisture content of the capsule shell within the optimal range of 7.0% to 9.0%, and the batch-to-batch uniformity is significantly better than that of traditional processes, thus improving product stability.

[0015] (5) High versatility: This invention is applicable to the industrial production of various types of soft capsules such as fat-soluble, suspension, and water-soluble. The thresholds and parameters of each stage can be flexibly adjusted according to the gelatin / glycerin ratio, capsule shell thickness, and contents properties to meet diverse production needs.

[0016] (6) Parameters can be quantified and scaled up: This invention achieves closed-loop control based on real-time moisture monitoring, rather than empirical fixed-time drying. All drying parameters can be quantified, recorded and replicated, which can meet GMP production requirements and industrial scale-up needs. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the process flow for the gradient drying method for soft capsules of the present invention.

[0018] Figure 2 This is a graph showing the change in moisture content of the capsule shell over drying time in the method of this invention and in the traditional process. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. The numerical ranges described in this invention include their endpoint values ​​and any values ​​between the endpoint values, and each value has a technical effect equivalent to the endpoint value.

[0020] The drying equipment used in this invention is a series of sealable units that can independently control temperature and humidity (temperature control accuracy ±1℃, relative humidity control accuracy ±3%) and drum rotation speed, such as the Wuxi Zhongyi ZL300B intelligent drying drum. Each drying unit has a cylindrical drum for storing capsules, with guide plates on the inner wall. As the drum rotates in different directions and at different speeds, the capsules can be dried within a single unit or transferred to subsequent units. The units are independently temperature and humidity controlled, preventing moisture interference between capsules produced earlier and later.

[0021] The moisture content of the capsules is determined using a rapid moisture analyzer employing the drying method (such as the Shenzhen Guanya WL series capsule rapid moisture analyzer, which can complete the test within 5-6 minutes). During the test, the capsule shell is cut open, the contents are wiped clean, and the shell is placed inside the moisture analyzer. The capsule is then heated and dried to constant weight according to the instrument's operating procedures. The moisture content is automatically calculated and displayed. Moisture monitoring is performed once per hour (or at shorter intervals), and the data is input to the control unit in real time.

[0022] The core of the gradient drying method for soft capsules in this invention lies in dividing the drying process into four stages based on the real-time moisture content of the capsule shell, with the drying parameters for each stage precisely matched to the capsule's properties. The following detailed description, in conjunction with specific embodiments, illustrates this point.

[0023] Example 1: Gradient drying of isotretinoin soft capsules

[0024] This embodiment uses isotretinoin soft capsules (containing an oil-based suspension) as an example of gradient drying. The capsule shell formulation uses gelatin:glycerol = 1:0.3 (mass ratio). After granulation, the initial moisture content of the capsules is approximately 38%~42%. Figure 1 As shown, drying is carried out in the following four stages: Stage 1 (High Moisture, Soft and Adhesive Stage): The initial moisture content of the capsule shell is 30%~50% (average measured value is approximately 40%). During this stage, the shell is soft, highly malleable, and easily deforms and sticks together. Control the drying temperature at 18~22℃ (preferably 20℃), relative humidity at 40%~55% (preferably 48%), and drum speed at 10~12 rpm (preferably 11 rpm). Low-temperature, normal-humidity forced-air drying conditions quickly remove surface free water, fix the capsule shape, and prevent shell sticking; the faster drum rotation helps prevent the capsule from deforming under pressure. Real-time moisture monitoring shows that after approximately 3 hours, the capsule shell moisture content drops to approximately 26%, entering the next stage.

[0025] Phase Two (Medium-High Moisture Elasticity Stage): Capsule moisture content is 20%~30%. During this stage, the capsule shell elasticity reaches its peak, exhibiting the strongest tensile strength. The temperature is increased to 24~28℃ (preferably 26℃), and the relative humidity is reduced to 30%~40% (preferably 35%). The drum rotation speed is reduced to 8~10 rpm (preferably 9 rpm). These lower temperature and humidity conditions accelerate the migration of internal moisture to the outside, maintaining the balance of internal and external water loss and capsule shell elasticity. As the capsule shell gradually hardens, the rotation speed is appropriately reduced to decrease friction between capsules. After approximately 4 hours, the capsule shell moisture content drops to approximately 18%, entering the next stage.

[0026] Phase Three (Accelerated Drying Period with Low to Medium Moisture): Capsule moisture content is 12%–20%. During this phase, the rate of water loss decreases, the capsule shell hardness increases, and plasticity decreases. The temperature is raised to 30–35°C (preferably 32°C), and the relative humidity drops to <25% (preferably 20%). The drum rotation speed is further reduced to 6–8 rpm (preferably 7 rpm). High-temperature, low-humidity airflow accelerates the capsule drying rate; as the capsule shell hardens and its flexibility decreases, the impact buffering between the capsule and the drum guide plate decreases, and the friction between capsules increases. Further reducing the rotation speed prevents breakage and ensures gloss. After approximately 5 hours, the capsule shell moisture content drops to approximately 11%, entering the next phase.

[0027] Phase Four (Low Moisture Stabilization Period): Capsule moisture content is 7%~12%. During this phase, the capsule shell properties tend to stabilize. Cool to 20~24℃ (preferably 22℃), maintain relative humidity <25% (preferably 20%), and maintain drum speed at 6~8 rpm (preferably 7 rpm). Perform final equilibration drying under low temperature and low humidity conditions to ensure uniform moisture content inside and outside the capsule, preventing the capsule shell from softening and deforming due to water reabsorption. When real-time moisture monitoring shows that the capsule shell moisture content has dropped to 7%~9%, end the drying process and unload the capsules.

[0028] In this embodiment, the total drying time was approximately 16 hours. After drying, the average moisture content of the capsule shells was 8.77%, and the waste rate was 0.23%.

[0029] Example 2: Gradient drying of fish oil soft capsules

[0030] This embodiment uses fish oil soft capsules as the subject of gradient drying. The capsule shell formulation uses gelatin:glycerin:water = 1:0.5:1. After granulation, the initial moisture content of the capsules is approximately 35%~45%. Given that the contents of fish oil have good fat solubility and are relatively sensitive to temperature, in stage one (30%~50%), the temperature is controlled at 19~21℃ (slightly lower than in Example 1 to reduce the risk of fish oil oxidation), and the relative humidity is 45%~55%; in stage two (20%~30%), the temperature is increased to 25~27℃, the relative humidity is 35%~40%, and the rotation speed is 8~10 rpm; in stage three (12%~20%), the temperature is increased to 30~32℃, the relative humidity is <25%, and the rotation speed is 6~8 rpm; in stage four (7%~12%), the temperature is decreased to 20~22℃, the relative humidity is <25%, and the rotation speed is 6~8 rpm.

[0031] The total drying time in this embodiment was approximately 14 hours. After drying, the average moisture content of the capsule shell was 8.2%, and the waste capsule rate was 0.18%. The results show that the method of the present invention is also applicable to soft capsules with oily contents. Furthermore, the slightly low temperature design in stage one effectively reduces the risk of fish oil oxidation and deterioration, demonstrating the versatility and flexible parameter adjustment capability of the present invention.

[0032] Example 3: Gradient drying of water-soluble contents soft capsules

[0033] This embodiment uses water-soluble vitamin soft capsules as the subject of gradient drying. The capsule shell formulation uses gelatin:glycerin = 1:0.4, and the initial moisture content of the capsules after compression is approximately 40%~45%. Water-soluble contents are more sensitive to moisture migration, therefore, humidity control in stages two and three is more critical. Stage one (30%~50%): temperature 18~22℃, humidity 40%~50% to adapt to the water-soluble formulation; Stage two (20%~30%): temperature 24~26℃, humidity 35%~40% to ensure a balance between the internal moisture migration rate and the surface water loss rate; Stage three (12%~20%): temperature 30~33℃, humidity <25% to accelerate drying while avoiding localized overheating of the contents; Stage four (7%~12%): temperature 20~22℃, humidity <25% for stabilization.

[0034] In this embodiment, the total drying time was approximately 17 hours. After drying, the average moisture content of the capsule shell was 8.5%, and the waste rate was 0.21%.

[0035] Comparative Example 1: Dry environment in traditional two-level rooms

[0036] This comparative example uses the most common two-level room temperature and humidity control method in the industry to dry isotretinoin soft capsules (the contents of which are oil-based suspensions) as a control of the method of the present invention.

[0037] Drying conditions are set as follows: Level 1: Room temperature is controlled at approximately 22℃, relative humidity at 40%~55%, drying time is 6 hours; Level 2: Temperature is increased to approximately 30℃, relative humidity is <30%, drying continues until the standard is met. Due to significant deviations in room temperature and humidity control, the actual drying time in production sometimes needs to approach 30 hours.

[0038] Drying process monitoring: Samples were taken starting at the 22nd hour of the total drying time, and the moisture content of the capsule shells was measured using a rapid moisture analyzer. The results showed that at the 22nd hour, the average moisture content of the three batches of capsule shells was 14.77%, indicating that drying was not complete; at the 24th hour, the average moisture content of the three batches was 11.62%, reaching the industry's wide-range drying standard (7%~12%) for the first time; at the 26th hour, the average moisture content of the three batches was 10.68%, failing to stably dry to the optimal range of 7%~10%.

[0039] After the pellet sorting was completed, the average scrap rate of the three batches was 0.55%.

[0040] Comparative Example 2: The three-stage drying apparatus method described in CN104873393B

[0041] This comparative example refers to the technical solution disclosed in CN104873393B to dry isotretinoin soft capsules: the 8-section drum is divided into three stages - the shaping stage (the first two sections, the temperature is controlled at 20±0.5℃, and the humidity is controlled by a solution dehumidifier connected to the drum), the pre-drying stage (the middle three sections), and the final drying stage (the last three sections). The temperature parameters of each stage are preset according to the equipment structure. The stage is switched based on the spatial position rather than the moisture content. The humidity parameter is only clearly controlled in the first stage. The drum speed is not adjusted differently in each stage.

[0042] Drying process monitoring: Sampling began at the 20th hour. At the 24th hour, the average moisture content of the three batches was approximately 12.3%, at the 26th hour approximately 11.5%, and at the 30th hour approximately 10.2%, all failing to consistently reach the optimal range of 7%~10%. The total drying time was approximately 28~30 hours, with an average waste rate of 0.48% across the three batches.

[0043] Test Item 1: Comparison of Drying Cycles .

[0044] The above test results show that, compared with the traditional process in Comparative Example 1, such as Figure 2As shown, the drying cycle of Embodiment 1 of the present invention is shortened by approximately 38.5% (from 26 hours to 16 hours), and the moisture content can be stably controlled below 9%, resulting in a significant improvement in drying efficiency. Compared to the three-stage spatial division drying method of CN104873393B, the four-stage drying method driven by the measured moisture content of the present invention shortens the drying time by approximately 44% to 47%, demonstrating the significant advantage of the control logic of the present invention, which is based on the material state, over the prior art based on spatial division.

[0045] Example 2, due to the fat-soluble and temperature-sensitive nature of its contents, employed a slightly lower drying temperature. However, it achieved better drying efficiency than Example 1. This is likely because the fish oil contents have lower water activity and less resistance to internal water migration. Example 3, due to the special properties of its water-soluble contents, had a slightly longer drying cycle than Examples 1 and 2, but it still represented a significant improvement over the 26 hours of Comparative Example 1 and the 28-30 hours of the method in CN104873393B.

[0046] Test Item 2: Comparison of Waste Pellet Rate

[0047] The reject rate is defined as the percentage of defective capsules removed during the sorting process out of the total number of capsules before drying. Defective capsules mainly include adhered capsules, deformed capsules, oil-leaking capsules, and brittle capsules.

[0048]

[0049] The test results above show that the average waste rate of Example 1 of the present invention is 0.23%, which is 58.2% lower than that of the traditional process (0.55%) and approximately 52.1% lower than that of the method in CN104873393B (0.48%). The waste rates of Examples 2 and 3 are both lower than those of Example 1, further verifying the adaptability and versatility of the method of the present invention for soft capsules with different formulations.

[0050] The significant reduction in waste shot rate is mainly attributed to the precise matching of parameters and shell properties at each stage of the invention. Stage 1, low temperature and normal humidity with high rotation speed, prevents adhesion and deformation. Stage 2, heating and dehumidification to maintain elasticity and avoid early brittleness caused by internal stress accumulation. Stage 3, high temperature and low humidity with low speed, prevents frictional cracking of the capsules during the hardening period. Stage 4, cooling and balancing, ensures uniform internal and external moisture and prevents water return and deformation.

[0051] Test Item 3: Comparison of Moisture Control Accuracy

[0052] The above test results show that the method of the present invention can stably control the moisture content of the capsule shells at the end of drying within the optimal range of 7.0% to 9.0%, with a significantly lower batch-to-batch relative standard deviation than the traditional process, and a significant improvement in moisture uniformity. The method in CN104873393B, lacking a closed-loop feedback mechanism, has consistently failed to achieve the control precision of the present invention. The improvement in moisture control precision is due to the establishment of a closed-loop feedback mechanism—using measured moisture content to drive parameter adjustment, rather than operating in an open-loop manner with fixed parameters.

[0053] Test Item 4: Parameter Adaptability Verification for Different Capsule Ratios

[0054] This experiment used four gelatin:glycerol mass ratio formulations: 1:0.25 (harder gelatin shell), 1:0.3 (conventional), 1:0.5 (conventional), and 1:0.7 (softer gelatin shell). Gradient drying was carried out according to the method of Example 1 of this invention to investigate whether the parameters needed to be adjusted and the adjustment level under different ratios.

[0055]

[0056] The above experimental results show that the moisture stage threshold and drying parameters need to be adaptively adjusted for different gelatin:glycerol ratios, but the core control logic—dividing stages based on real-time moisture content and matching temperature, humidity, and rotation speed step by step—remains unchanged. The adjustment range varies with the ratio, but all are within a reasonable range that can be determined by a person skilled in the art through conventional experiments. It should be noted that when the gelatin:glycerol ratio deviates from the conventional range of 1:0.3 to 1:0.6, the glass transition temperature, elastic modulus, and other physical properties of the capsule shell will change significantly. In this case, the technical solution described in this invention is still applicable, but the moisture stage threshold and drying parameters need to be adjusted accordingly. This adjustment should be considered as something that can be achieved through conventional experimental methods under the guidance of the technical solution of this invention, and should not be considered a substantial deviation from this invention.

[0057] The core protection scope of this invention does not depend on a specific shell formulation. The above embodiments primarily used a gelatin:glycerol mass ratio of 1:0.3 to 1:0.6 for main research and verification. However, the technical solution of this invention is also applicable to various soft capsules with other gelatin / glycerol ratios, different shell thicknesses, and different contents (lipid-soluble, suspension, water-soluble). When the shell formulation changes significantly, the shell moisture threshold and the corresponding temperature, humidity, and rotation speed ranges at each stage can be adaptively adjusted based on the information disclosed in this invention. The basic principles and adjustment ranges are as follows: (1) When the proportion of glycerol in the gelatin:glycerol ratio is too high (the gelatin shell is too soft), the upper limit threshold of moisture in stage one can be lowered to 45%, and the temperature of stage two and stage three can be appropriately reduced by 1~2℃ to prevent the gelatin shell from softening too much; when the proportion of glycerol is too low (the gelatin shell is too hard), the lower limit threshold of moisture in stage one can be raised to 35%, and the temperature of each stage can be appropriately increased by 1~2℃ to promote moisture migration.

[0058] (2) When the thickness of the capsule increases, the internal moisture migration path is extended, and the drying time of stage two and stage three should be appropriately extended. The temperature of stage three can be appropriately increased within the range of 30~35℃.

[0059] (3) When the contents are water-soluble, special attention should be paid to humidity control in stages two and three to prevent excessive water activity gradient from causing the contents to precipitate or the permeability of the gel shell to change; when the contents are fat-soluble, the time of stage two can be appropriately shortened to accelerate the overall drying process.

[0060] The specific embodiments of the present invention have been described in detail above, but they are merely examples, and the present invention is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications and substitutions to the present invention are also within the scope of the present invention. Therefore, all equivalent transformations and modifications made without departing from the spirit and scope of the present invention should be covered within the scope of the present invention.

Claims

1. A gradient drying method for soft capsules based on the moisture properties of the capsule shell, characterized in that, Includes the following steps: (1) Obtain the real-time moisture content of the soft capsule shell; (2) Based on the real-time moisture content, the drying process is divided into several continuous moisture stages; (3) For each moisture stage, at least one drying parameter is dynamically adjusted according to the shell characteristics corresponding to that stage. The drying parameter is selected from one or more of drying temperature, relative humidity, and drum rotation speed. (4) Repeat steps (1) to (3) until the moisture content of the capsule reaches the target range.

2. The method according to claim 1, characterized in that, The aforementioned consecutive moisture stages include four stages: First moisture stage: The moisture content of the capsule shell is 30%~50%; Second moisture stage: The moisture content of the capsule shell is 20%~30%; Third moisture stage: The moisture content of the capsule shell is 12%~20%; Fourth moisture stage: The moisture content of the capsule is 7%~12%; The method controls the drying temperature, relative humidity, and drum rotation speed at each moisture stage.

3. The method according to claim 2, characterized in that: In the first moisture stage, the drying temperature is controlled at 18~22℃, the relative humidity at 40%~55%, and the drum speed at 10~12 rpm; In the second moisture stage, the drying temperature is controlled at 24~28℃, the relative humidity at 30%~40%, and the drum speed at 8~10 rpm; In the third moisture stage, the drying temperature is controlled at 30~35℃, the relative humidity is <25%, and the drum speed is 6~8 rpm; In the fourth moisture stage, the drying temperature is controlled at 20~24℃, the relative humidity is <25%, and the drum speed is 6~8 rpm.

4. The method according to claim 1, characterized in that, The frequency of obtaining the real-time moisture content of the capsule shell in step (1) is no less than once per hour.

5. The method according to claim 1, characterized in that, The initial formulation of the capsule contains gelatin in a mass ratio of 1:0.3 to 1:0.6 to glycerin.

6. The method according to claim 1, characterized in that, The target range is when the moisture content of the capsule reaches 7% to 10%.

7. The method according to claim 1, characterized in that, The drying parameters also include rotation speed.

8. A gradient drying system for soft capsules based on the moisture properties of the capsule shell, characterized in that, include: (a) At least one closed drying drum unit with independent temperature and humidity control for holding soft capsules to be dried; (b) A moisture monitoring device for measuring the real-time moisture content of the capsule shell; (c) A control unit configured to perform the soft capsule gradient drying method according to any one of claims 1 to 7.

9. The system according to claim 8, characterized in that, The drying drum unit is a drying system consisting of multiple sealable units connected in series, with each unit having independent temperature and humidity control.

10. The system according to claim 8, characterized in that, The control unit automatically divides the drying process into moisture stages based on real-time moisture data fed back by the moisture monitoring device and matches the corresponding temperature, humidity and drum rotation speed parameters to achieve closed-loop automatic control.

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