Tooth whitening gel and preparation method thereof

Abstract

The invention discloses tooth whitening gel and a preparation method thereof, and relates to the technical field of tooth gel. The toothpaste comprises the following components: 2% of sodium carboxymethyl cellulose, 10% of glycerol, 4% of polyethylene glycol-400, 6% of urea peroxide, 1% of potassium nitrate, 0.5% of menthol, 3% of xylitol, a pH regulator for regulating the pH value to 6.5, and the balance of deionized water. The urea peroxide realizes nanoscale dispersion under a low-temperature wet grinding process, and cooperates with the potassium nitrate to block neural signal conduction through an ion channel, so that the whitening effect and dentin sensitivity problems are synchronously solved; xylitol can reduce irritation and form a'whitening-desensitization 'synergistic system; a three-time equal-component feeding method is combined with temperature control, so that sodium carboxymethyl cellulose is fully swelled and forms a stable net-shaped structure, and the caking defect caused by traditional one-time feeding is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of tooth gels, and in particular to a tooth whitening gel and a preparation method thereof. Background Art

[0002] Tooth discoloration is a common problem, primarily caused by factors such as dietary pigmentation, smoke stains, and aging-related thinning of tooth enamel. Traditional whitening methods, such as in-office cold light whitening, while effective, are limited by high cost, complex procedures, and post-procedural sensitivity. Commercially available at-home whitening products often cause gum irritation due to poor peroxide stability and uncontrolled pH levels, or their high viscosity prevents the active ingredients from evenly penetrating the microporous structure of the tooth surface.

[0003] Existing gel formulations often rely on simple physical mixing processes, which are prone to problems such as active ingredient agglomeration and sedimentation, system stratification, and residual bubbles, seriously affecting product permeability and safety. Furthermore, traditional formulations lack effective measures to inhibit dentin hypersensitivity, and long-term use may cause pulp damage.

[0004] After searching, the application scheme of Chinese patent application number CN202211550530.4 discloses a dual-function gel for tooth mineralization and antibacterial, its preparation method and application. The preparation method is as follows: dissolving a stabilizer, calcium salt and metal ion salt additive in a solvent to obtain a mixed solution, then adding a gelling agent, and swelling uniformly to prepare gel i; dissolving phosphate and fluoride in a solvent to obtain a mixed solution, adjusting the pH of the solution to 8-12, and then adding a gelling agent, and swelling uniformly to prepare gel ii. Gel i and gel ii are stirred and mixed in proportion to produce a hybrid amorphous calcium phosphate gel. The gel in the above patent is based on hybrid amorphous calcium phosphate, focusing on remineralizing tooth enamel and inhibiting bacterial growth, and has poor effects on whitening and desensitization. Summary of the Invention

[0005] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a tooth whitening gel and a preparation method thereof.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A teeth whitening gel comprises the following ingredients: 2% sodium carboxymethylcellulose, 10% glycerol, 4% polyethylene glycol-400, 6% urea peroxide, 1% potassium nitrate, 0.5% menthol, 3% xylitol, a pH regulator to adjust the pH value to 6.5, and the balance deionized water.

[0008] A method for preparing a teeth whitening gel comprises the following steps:

[0009] S1: Prepare the premixed solution by dividing the prepared deionized water into two parts. Add the first part of deionized water to a reactor equipped with a stirring device and start stirring at a low speed. Slowly sprinkle in sodium carboxymethyl cellulose powder and continue stirring for 30 minutes until it is completely swollen and forms a uniform colloid. Then, add glycerol, polyethylene glycol-400, and xylitol in sequence and continue mixing at the same speed for 15 minutes to obtain a transparent and viscous base solution A.

[0010] S2: Active ingredient dispersion treatment: Carbamide peroxide and potassium nitrate were mixed in appropriate proportions and passed through a sieve to remove lumps. The mixture was pre-dissolved in a second portion of deionized water in a separate container and ultrasonically shaken for 10 minutes to obtain suspension B. Suspension B was slowly poured into base solution A and homogenized.

[0011] S3: Finely blend and degas, add menthol solution pre-dissolved in a small amount of ethanol, and keep stirring; use an online pH meter to monitor the pH of the system, and add 5% citric acid or 1 mol / L NaOH solution to adjust to the target pH value of 6.5; start the vacuum degassing process to eliminate bubbles in the liquid;

[0012] S4: Aseptic filling and packaging.

[0013] Preferably, the first portion of deionized water accounts for 70% of the total amount of deionized water, and the second portion of deionized water accounts for 30% of the total amount of deionized water.

[0014] Preferably, in S2, the mesh size of the sieve is 200 meshes; the stirring speed of the homogenization treatment is controlled at 400 rpm for 20 minutes; and in S3, the menthol solution dissolved in a small amount of ethanol has an ethanol content of no more than 0.1% of the total system.

[0015] Preferably: in said S4, the aseptic filling and packaging is filtered through a 0.22 μm microporous filter membrane and then transferred into a clean stainless steel storage tank; a fully automatic piston filling machine is used for filling, and a medical grade polyethylene hose is used for sealing; Co 60 Irradiation sterilization, outer packaging uses light-proof aluminum foil composite film bag.

[0016] Preferably, in S1, the premix solution is prepared as follows:

[0017] S11: Prepare deionized water, take 70% of the total amount of deionized water and inject it into the jacketed reactor with a temperature sensor, start the constant temperature circulation system and raise the temperature to 28℃±0.5℃;

[0018] S12: Add the high molecular weight polymer in batches, and accurately weigh the sodium carboxymethyl cellulose according to the formula; add the materials by sprinkling equal amounts three times;

[0019] S13: The polyol complex solvent is blended, and a dual-channel metering pump is simultaneously activated to deliver glycerol and polyethylene glycol-400, respectively: glycerol is injected at a linear flow rate of 50 mL / min, and a scraper and diversion device is simultaneously activated to prevent local excessive concentration; PEG-400 is added in a pulsed manner, and a vacuum negative pressure environment is used to eliminate bubbles; after mixing, samples are taken for refractive index detection;

[0020] S14: To enhance the dissolution of natural sweeteners, xylitol and a portion of deionized water were pre-mixed into a saturated mother liquor, which was then processed using a high-shear homogenizer to obtain a milky white suspension. The suspension was slowly introduced into the main system, and an ultrasonic cell disruptor was activated. The treatment was continued until the particle size analyzer indicated that D90 was ≤ 2 μm.

[0021] S15: Temporary storage management of the intermediate. After completing the above operations, a translucent colloidal intermediate is obtained, which is transferred to a nitrogen-sealed storage tank for storage; the storage tank is equipped with a magnetic stirrer to maintain low-speed stirring, and dry nitrogen is introduced to maintain positive pressure.

[0022] Preferably, in S12, the materials are added by sprinkling equal amounts three times, as follows:

[0023] For the first time, add 40% of the total amount, stir at a low speed of 200 rpm to form a vortex, and then let it stand and soak for 15 minutes; for the second time, add 30%, increase the speed to 300 rpm and shear and disperse for 10 minutes to break up lumps; for the last 30%, sprinkle evenly and maintain high-speed stirring at 400 rpm until the system shows obvious climbing phenomenon.

[0024] Preferably, in S2, the active ingredient dispersion treatment is specifically as follows:

[0025] S21: Oxidant pretreatment process: The urea peroxide raw material is pretreated in a jet mill to a particle size of D50 = 8 μm, and the particle size distribution is verified by laser diffraction. The raw material is mixed with potassium nitrate in a certain proportion, and 0.2% by weight of magnesium stearate is added as a flow aid. The mixture is processed in a rotary three-dimensional motion mixer for 30 minutes.

[0026] S22: Low-temperature wet grinding, with a 15% by volume ethanol solution as the grinding medium, and a sand milling circulation loop established: a 70% filling rate of zirconia beads was used, and the slurry flow rate was controlled at 8 L / h; the grinding chamber temperature was controlled below 10°C by a cooling unit.

[0027] Preferably, in S3, the fine mixing and degassing are specifically as follows:

[0028] S31: Constructing a flavor sustained-release carrier: dissolving menthol in a small amount of propylene glycol to prepare a concentrated solution; adding β-cyclodextrin as a molecular encapsulation material, and performing a kneading inclusion reaction at a molar ratio of 1:5; spray drying to obtain a spherical microcapsule powder;

[0029] S32: pH precision titration system, based on an automatic titrator, automatically matches the citric acid / sodium carbonate binary regulator ratio according to a preset buffer curve; gradually increases the pH value from an initial 4.2 to 6.5;

[0030] S33: Vacuum gradient degassing method, implementing three-stage decompression procedures in stages;

[0031] S34: Rheological property correction: Brookfield viscometer is used to test the apparent viscosity at different shear rates; the thickener dosage is adjusted according to the power law equation fitting results.

[0032] Preferably, in said S33, the three-stage decompression procedure is implemented in sections as follows:

[0033] First-stage rough removal: the pressure drops to -0.06MPa in a short time to quickly remove large-diameter bubbles;

[0034] Secondary fine stripping: Maintain a constant pressure of -0.08 MPa for 20 minutes to eliminate tiny gaps;

[0035] Tertiary balance: slowly return to normal pressure while filling in inert gas to replace residual gas components.

[0036] The beneficial effects of the present invention are:

[0037] 1. The carbamide peroxide of the present invention is nano-dispersed under a low-temperature wet grinding process, and is combined with potassium nitrate to block nerve signal conduction through ion channels, thereby simultaneously solving the problems of whitening effect and dentin sensitivity; xylitol can reduce irritation, forming a "whitening-desensitization" synergistic system.

[0038] 2. The present invention adopts a three-amount equal-dose feeding method combined with temperature control to ensure that the sodium carboxymethyl cellulose is fully swollen and forms a stable network structure, avoiding the agglomeration defect caused by traditional one-time feeding; the dual-channel metering pump realizes linear and pulsed composite delivery of glycerol / PEG-400, and cooperates with the scraping device to eliminate concentration gradients and improve the uniformity of the base liquid.

[0039] 3. The present invention refines the particle size of urea peroxide to submicron level through air flow crushing pretreatment and sand grinding circulation loop, significantly improving its suspension stability in colloid and tooth surface contact efficiency.

[0040] 4. This invention uses the buffer curve matching technology of the automatic titrator to achieve a precise increase in pH value from 4.2 to 6.5; the three-stage gradient vacuum degassing method completely eliminates bubbles, and combined with rheological correction, ensures the smoothness of the product's coating at different shear rates. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a flow chart of a method for preparing a tooth whitening gel proposed in the present invention;

[0042] Figure 2 This is a flow chart of the preparation of a premixed solution in the method for preparing a tooth whitening gel proposed in the present invention;

[0043] Figure 3 This is a flow chart of the active ingredient dispersion process in the preparation method of the tooth whitening gel proposed in the present invention;

[0044] Figure 4 The present invention provides a flow chart of fine mixing and degassing in the preparation method of a tooth whitening gel. DETAILED DESCRIPTION

[0045] The technical solution of the present invention will be further described in detail below in conjunction with specific implementation methods.

[0046] Example 1:

[0047] A teeth whitening gel comprising the following ingredients:

[0048]

[0049] The preparation method of the tooth whitening gel comprises the following steps:

[0050] S1: Preparation of premixed solution (room temperature, 25°C ± 2°C)

[0051] Add 70% of the total amount of deionized water to a reactor equipped with a stirring device and start low-speed stirring (set to 200 rpm); slowly sprinkle in sodium carboxymethyl cellulose powder and continue stirring for 30 minutes until it is completely swollen to form a uniform colloid; add glycerol, polyethylene glycol-400, and xylitol in sequence and continue mixing at the same speed for 15 minutes to obtain a transparent viscous base liquid A.

[0052] S2: Active ingredient dispersion

[0053] Urea peroxide and potassium nitrate were mixed in appropriate proportions and passed through a 200-mesh sieve to remove lumps. The mixture was pre-dissolved in the remaining 30% deionized water in a separate container and ultrasonically shaken (40 kHz, 80 W) for 10 minutes to obtain a suspension B. Suspension B was slowly poured into base solution A while increasing the stirring speed to 400 rpm and homogenized for 20 minutes.

[0054] S3: Fine mixing and degassing

[0055] Add a menthol solution pre-dissolved in a small amount of ethanol (ethanol accounts for no more than 0.1% of the total system) and keep stirring; use an online pH meter to monitor the pH of the system, and add 5% citric acid or 1 mol / L NaOH solution dropwise to adjust to the target pH value of 6.5; start the vacuum degassing program (vacuum degree -0.09 MPa, duration 15 minutes) to eliminate bubbles in the liquid.

[0056] S4: Aseptic filling and packaging

[0057] After being filtered through a 0.22μm microporous membrane, the product is transferred to a clean stainless steel storage tank. It is filled using a fully automatic piston filling machine (the error in each bottle's capacity is ≤±1%) and sealed with a medical-grade polyethylene hose. 60 Irradiation sterilization (dose not exceeding 5kGy), outer packaging uses light-proof aluminum foil composite film bag.

[0058] Wherein, in said S1, the premix solution is prepared specifically as follows:

[0059] S11: Deionized water preheating and water quality verification

[0060] A Milli-Q ultrapure water system was used to prepare water for injection with a resistivity ≥18.2 MΩ·cm. 70% of the total water volume was injected into a jacketed reactor equipped with a temperature sensor. The constant temperature circulation system was activated to raise the temperature to 28°C ± 0.5°C (to avoid slow dissolution of CMC due to low temperatures). An online conductivity meter was used to monitor the product and confirm the absence of residual ionic impurities (the alarm threshold was set to <5 μS / cm).

[0061] S12: Batch feeding of polymers

[0062] Accurately weigh sodium carboxymethyl cellulose (CMC-Na) according to the formula and spread it on a stainless steel tray;

[0063] Use the three-times equal-amount sprinkling method: first add 40% of the total amount, stir at a low speed of 200 rpm to form a vortex, and then let it stand and soak for 15 minutes;

[0064] Add 30% for the second time, increase the speed to 300 rpm and shear and disperse for 10 minutes to break up lumps; sprinkle the last 30% evenly and maintain high-speed stirring at 400 rpm until the system shows obvious climbing phenomenon (visual viscosity increases sharply).

[0065] S13: Polyol Complex Solvent Fusion

[0066] At the same time, the dual-channel metering pumps were turned on to deliver glycerol and polyethylene glycol-400 respectively: glycerol was injected at a linear flow rate of 50 mL / min, and the scraper and diversion device was turned on simultaneously to prevent local excessive concentration; PEG-400 was added in a pulsed manner (5 mL each time with an interval of 2 minutes), and a vacuum negative pressure environment was used to eliminate bubbles; after mixing, samples were taken for refractive index detection (target value RI = 1.472 ± 0.003).

[0067] S14: Natural sweetener dissolution enhancement

[0068] Xylitol and part of deionized water were pre-prepared into a saturated mother liquor (solid-liquid ratio of 1:3), and a milky white suspension was obtained by using a high shear homogenizer. The suspension was slowly introduced into the main system, and an ultrasonic cell disruptor was turned on (the probe depth was 5 cm from the liquid surface, and the power density did not exceed 0.5 W / mL). The treatment was continued until the particle size analyzer showed D90 ≤ 2 μm.

[0069] S15: Intermediate storage management

[0070] After completing the above operations, a translucent colloidal intermediate was obtained, which was transferred to a nitrogen-sealed storage tank for storage; the tank was equipped with a magnetic stirrer to maintain low-speed stirring (50 rpm), and dry nitrogen was introduced to maintain positive pressure (gauge pressure 0.02 MPa); the material batch number, temperature curve, and viscosity change map were recorded for traceability.

[0071] Among them, in said S2, the active ingredient dispersion treatment is specifically as follows:

[0072] S21: Oxidant pretreatment process

[0073] The urea peroxide raw material was pretreated by a jet mill to a D50 of 8 μm, and the particle size distribution was verified by laser diffraction. It was mixed with potassium nitrate in a certain proportion, and 0.2% by weight of magnesium stearate was added as a flow aid. The mixture was processed in a rotary three-dimensional motion mixer (speed adjustable range 0–30 r / min) for 30 minutes.

[0074] S22: Low temperature wet grinding

[0075] A 15% ethanol solution by volume was prepared as the grinding medium, and a sand milling circulation loop was established: zirconia beads (0.3 mm diameter) were used with a fill rate of 70%, and the slurry flow rate was controlled at 8 L / h. The grinding chamber temperature was controlled below 10°C by a cooling unit to prevent thermal decomposition. Samples were taken after each cycle for high-performance liquid chromatography analysis to monitor the integrity of the urea group (area-normalized purity ≥99.5%).

[0076] Among them, in said S3, fine preparation and degassing are specifically as follows:

[0077] S31: Construction of flavor sustained-release carrier

[0078] Menthol was dissolved in a small amount of propylene glycol to prepare a concentrated solution; β-cyclodextrin was added as a molecular encapsulation material and kneaded and included in a molar ratio of 1:5; and spherical microcapsule powder was obtained by spray drying (yield ≥ 85%, and the UV absorption value of the drug loading determination was consistent with the standard curve).

[0079] S32: pH precision titration system

[0080] A Mettler Toledo autotitrator equipped with a composite glass electrode and a reference electrode was installed; the citric acid / sodium carbonate binary regulator ratio was automatically matched according to a preset buffer curve; and a smooth transition process from an initial pH value of 4.2 to the target pH of 6.5 was achieved.

[0081] S33: Vacuum gradient degassing method

[0082] Implement three-level decompression procedures in stages:

[0083] First-stage rough removal: the pressure drops to -0.06MPa in a short time to quickly remove large-diameter bubbles;

[0084] Secondary fine stripping: Maintain a constant pressure of -0.08 MPa for 20 minutes to eliminate tiny gaps;

[0085] Tertiary balance: slowly return to normal pressure while filling in inert gas to replace residual gas components.

[0086] S34: Rheological correction

[0087] A Brookfield viscometer was used to test the apparent viscosity at different shear rates. The thickener dosage was adjusted based on the power law equation fitting results to ensure that the product had both toothpaste-like uprightness and good extrusion ductility.

[0088] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A tooth whitening gel, characterized in that: The ingredients include: 2% sodium carboxymethyl cellulose, 10% glycerol, 4% polyethylene glycol-400, 6% urea peroxide, 1% potassium nitrate, 0.5% menthol, 3% xylitol, a pH regulator to adjust the pH value to 6.5, and the balance deionized water.

2. A method for preparing a tooth whitening gel, characterized in that: The steps include: S1: Prepare the premixed solution by dividing the prepared deionized water into two parts. Add the first part of deionized water to a reactor equipped with a stirring device and start stirring at a low speed. Slowly sprinkle in sodium carboxymethyl cellulose powder and continue stirring for 30 minutes until it is completely swollen and forms a uniform colloid. Then, add glycerol, polyethylene glycol-400, and xylitol in sequence and continue mixing at the same speed for 15 minutes to obtain a transparent and viscous base solution A. S2: Active ingredient dispersion treatment: Carbamide peroxide and potassium nitrate were mixed in appropriate proportions and passed through a sieve to remove lumps. The mixture was pre-dissolved in a second portion of deionized water in a separate container and ultrasonically shaken for 10 minutes to obtain suspension B. Suspension B was slowly poured into base solution A and homogenized. S3: Finely blend and degas, add menthol solution pre-dissolved in a small amount of ethanol, and keep stirring; use an online pH meter to monitor the pH of the system, and add 5% citric acid or 1 mol / L NaOH solution to adjust to the target pH value of 6.5; start the vacuum degassing process to eliminate bubbles in the liquid; S4: Aseptic filling and packaging.

3. The method for preparing a tooth whitening gel according to claim 2, wherein: The first portion of deionized water accounts for 70% of the total amount of deionized water, and the second portion of deionized water accounts for 30% of the total amount of deionized water.

4. The method for preparing a tooth whitening gel according to claim 2, wherein: In said S2, the mesh size of the sieve is 200 meshes; the stirring speed of the homogenization treatment is controlled at 400 rpm, and the time is 20 minutes; in said S3, the menthol solution dissolved in a small amount of ethanol, the proportion of ethanol in the total system does not exceed 0.1%.

5. The method for preparing a tooth whitening gel according to claim 2, wherein: In the S4, the aseptic filling and packaging are filtered through a 0.22 μm microporous filter membrane and then transferred into a clean stainless steel storage tank; a fully automatic piston filling machine is used for filling, and a medical grade polyethylene hose is used for sealing; Co 60 Irradiation sterilization, outer packaging uses light-proof aluminum foil composite film bag.

6. The method for preparing a tooth whitening gel according to claim 2, wherein: In S1, the premix solution is prepared as follows: S11: Prepare deionized water, take 70% of the total amount of deionized water and inject it into the jacketed reactor with a temperature sensor, start the constant temperature circulation system and raise the temperature to 28℃±0.5℃; S12: Add the high molecular weight polymer in batches, and accurately weigh the sodium carboxymethyl cellulose according to the formula; add the materials by sprinkling equal amounts three times; S13: The polyol complex solvent is blended, and a dual-channel metering pump is simultaneously activated to deliver glycerol and polyethylene glycol-400, respectively: glycerol is injected at a linear flow rate of 50 mL / min, and a scraper and diversion device is simultaneously activated to prevent local excessive concentration; PEG-400 is added in a pulsed manner, and a vacuum negative pressure environment is used to eliminate bubbles; after mixing, samples are taken for refractive index detection; S14: To enhance the dissolution of natural sweeteners, xylitol and a portion of deionized water were pre-mixed into a saturated mother liquor, which was then processed using a high-shear homogenizer to obtain a milky white suspension. The suspension was slowly introduced into the main system, and an ultrasonic cell disruptor was activated. The treatment was continued until the particle size analyzer indicated that D90 was ≤ 2 μm. S15: Temporary storage management of the intermediate. After completing the above operations, a translucent colloidal intermediate is obtained, which is transferred to a nitrogen-sealed storage tank for storage; the storage tank is equipped with a magnetic stirrer to maintain low-speed stirring, and dry nitrogen is introduced to maintain positive pressure.

7. The method for preparing a tooth whitening gel according to claim 2, wherein: In S12, materials are added by sprinkling equal amounts three times, specifically as follows: For the first time, add 40% of the total amount, stir at a low speed of 200 rpm to form a vortex, and then let it stand and soak for 15 minutes; for the second time, add 30%, increase the speed to 300 rpm and shear and disperse for 10 minutes to break up lumps; for the last 30%, sprinkle evenly and maintain high-speed stirring at 400 rpm until the system shows obvious climbing phenomenon.

8. The method for preparing a tooth whitening gel according to claim 2, wherein: In S2, the active ingredient dispersion process is specifically as follows: S21: Oxidant pretreatment process: The urea peroxide raw material is pretreated in a jet mill to a particle size of D50 = 8 μm, and the particle size distribution is verified by laser diffraction. The raw material is mixed with potassium nitrate in a certain proportion, and 0.2% by weight of magnesium stearate is added as a flow aid. The mixture is processed in a rotary three-dimensional motion mixer for 30 minutes. S22: Low-temperature wet grinding, with a 15% by volume ethanol solution as the grinding medium, and a sand milling circulation loop established: a 70% filling rate of zirconia beads was used, and the slurry flow rate was controlled at 8 L / h; the grinding chamber temperature was controlled below 10°C by a cooling unit.

9. The method for preparing a tooth whitening gel according to claim 2, wherein: In S3, fine blending and degassing are specifically as follows: S31: Constructing a flavor sustained-release carrier: dissolving menthol in a small amount of propylene glycol to prepare a concentrated solution; adding β-cyclodextrin as a molecular encapsulation material, and performing a kneading inclusion reaction at a molar ratio of 1:5; spray drying to obtain a spherical microcapsule powder; S32: pH precision titration system, based on an automatic titrator, automatically matches the citric acid / sodium carbonate binary regulator ratio according to a preset buffer curve; gradually increases the pH value from an initial 4.2 to 6.5; S33: Vacuum gradient degassing method, implementing three-stage decompression procedures in stages; S34: Rheological property correction: Brookfield viscometer is used to test the apparent viscosity at different shear rates; the thickener dosage is adjusted according to the power law equation fitting results.

10. The method for preparing a tooth whitening gel according to claim 2, wherein: In S33, the three-stage decompression procedure is implemented in sections as follows: First-stage rough removal: the pressure drops to -0.06MPa in a short time to quickly remove large-diameter bubbles; Secondary fine stripping: Maintain a constant pressure of -0.08 MPa for 20 minutes to eliminate tiny gaps; Tertiary balance: slowly return to normal pressure while filling in inert gas to replace residual gas components.

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