A dry volatile control method

Abstract

The application discloses a drying and volatilization control method, comprising the following steps: S1, placing a screen glass into a cavity of a vacuum drying machine main body, and performing vacuumizing treatment on the cavity of the vacuum drying machine main body; S2, heating the screen glass, and adjusting the distance between a condensing plate and the screen glass to a minimum distance state; and S3, adjusting the distance between the condensing plate and the screen glass and / or adjusting the vacuum air pressure in the cavity of the vacuum drying machine main body under the heating state of the screen glass. The application provides a drying and volatilization control method, which can stabilize the volatilization speed and improve the product forming quality.

Description

Technical Field

[0001] This invention relates to the field of vacuum drying technology, and more specifically, to a method for controlling volatilization during drying. Background Technology

[0002] Currently, after cleaning, etching, and surface coating pretreatment, volatile solvents such as pure water and isopropanol adhere to the surface of screen glass. The industry generally uses vacuum drying technology to remove these solvents. Vacuum dryers are equipped with a heating main board and a low-temperature condensing plate. They rely on a low-pressure environment to lower the boiling point of the solvent, and the condensing plate liquefies and recovers the vapor, thus achieving low-temperature drying.

[0003] In existing vacuum drying processes, due to the lack of buffering and speed control mechanisms in the initial drying stage, the solvent on the surface of the glass film in localized areas evaporates rapidly. A significant amount of heat is carried away from the surface of the film, creating a substantial temperature difference between the surface and the interior. This rapid evaporation causes solutes and impurities on the surface to precipitate and accumulate quickly, while the outer layer of the film solidifies rapidly, forming a dense barrier layer. This solidified layer hinders the outward diffusion and evaporation of the solvent from the deeper layers of the film, preventing the inner solvent from properly desorbing. After drying, localized solvent residue, hazy marks, uneven spots, uneven film thickness, or other appearance defects appear on the glass surface, affecting the quality of subsequent film formation and product yield. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a drying and evaporation control method to stabilize the evaporation rate and improve the product molding quality.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a drying and evaporation control method, comprising the following steps: Step S1, placing the screen glass into the cavity of the vacuum dryer body and evacuating the cavity of the vacuum dryer body; Step S2, installing a condenser plate inside the vacuum dryer body, the condenser plate being located above the screen glass, heating the screen glass to cause the solvent on the surface of the screen glass to evaporate, and adjusting the distance between the condenser plate and the screen glass to the minimum distance state, the minimum distance between the condenser plate and the screen glass being 3mm to 5mm; Step S3, while the screen glass is continuously heated, adjusting the distance between the condenser plate and the screen glass and / or adjusting the vacuum pressure inside the cavity of the vacuum dryer body to ensure that the concentration of the evaporated solvent gas in the space between the condenser plate and the screen glass is in an unsaturated state.

[0006] The present invention is further configured such that the vacuum pressure adjustment range of the cavity of the vacuum dryer body is 0.0001 Pa to 10 Pa. In step S1, the vacuum process reaches the minimum vacuum pressure value. In step S2, while the screen glass is heated, the vacuum pressure value is gradually increased to 5 Pa.

[0007] The present invention is further configured such that, in step S3, the distance between the condenser plate and the screen glass is adjusted to the maximum distance state, and the distance value of the maximum distance state is controlled between 8mm and 50mm.

[0008] The present invention is further configured such that the distance between the condenser plate and the screen glass adopts a step-by-step adjustment mode, with each adjustment step ranging from 0.1mm to 10mm, and the first distance adjustment is to increase the distance.

[0009] The present invention is further configured such that the distance between the condenser plate and the screen glass is adjusted in steps within a preset adjustment range, the preset adjustment range being the minimum distance to the maximum distance between the condenser plate and the screen glass, the maximum distance between the condenser plate and the screen glass being limited to 8mm to 50mm, and the minimum distance being limited to 3mm to 5mm.

[0010] The present invention is further configured such that, in step S3, after each adjustment of the distance between the condenser plate and the screen glass, the vacuum pressure inside the cavity of the vacuum dryer body is adjusted so that the concentration of solvent gas in the space between the condenser plate and the screen glass is in an unsaturated state. The specific adjustment method is as follows: Step S31, obtain the actual concentration difference: in the space between the condenser plate and the screen glass, the concentration at the bottom of the condenser plate is collected and recorded as Ctop, and the concentration at the top of the screen glass is collected and recorded as Cbot. The concentration difference Cver = Cbot - Ctop; Step S32, compare the actual concentration difference with the saturated concentration difference and adjust the vacuum pressure: if Cver ≥ 0.7Csat, then gradually increase the vacuum pressure inside the cavity of the vacuum dryer body; if Cver ≤ 0.35Csat, then gradually decrease the vacuum pressure inside the cavity of the vacuum dryer body. Wherein, Csat is the saturated concentration of the solvent gas volatilized at the current pressure and temperature.

[0011] The present invention is further configured such that after each adjustment of the vacuum air pressure value inside the cavity of the vacuum dryer body, a wait of 1 second to 30 seconds is made before repeating steps S31 and S32.

[0012] The present invention is further configured such that, in step S32, the vacuum pressure value inside the cavity of the vacuum dryer body increases or decreases by a step of 0.01 Pa to 0.3 Pa.

[0013] The present invention is further configured such that, for every three consecutive decreases or increases in the vacuum air pressure value inside the cavity of the vacuum dryer body, the distance between the condenser plate and the screen glass is increased or decreased once.

[0014] In summary, the present invention has the following beneficial effects:

[0015] 1. In the initial drying stage, adjust the distance between the condenser plate and the screen glass to the minimum, allowing the local solvent vapor to quickly reach near saturation, reducing the vapor pressure difference between the liquid film and the gas phase on the glass surface, and actively suppressing solvent explosive evaporation. Slow vaporization and heat absorption result in a small temperature difference between the surface and interior of the liquid film, preventing impurities and solutes dissolved in the solvent from instantly accumulating on the surface to form a dense, solidified barrier layer. This ensures synchronous and uniform drying across all areas of the glass, avoiding localized instantaneous drying that can cause fogging, ring-shaped halos, dotted dry spots, and uneven film thickness, thus guaranteeing the optical appearance quality of the screen glass and reducing product scrap rates.

[0016] 2. By adjusting the distance between the condenser plate and the screen glass and by implementing graded vacuum control, the concentration of volatile gases between the condenser plate and the screen glass is continuously controlled within the unsaturated range. A stable mass transfer partial pressure difference always exists between the liquid film and the gas phase, allowing the solvent to evaporate continuously without gas-liquid balance or evaporation stagnation, thus ensuring drying efficiency. Attached Figure Description

[0017] Figure 1 This is a three-dimensional schematic diagram of the vacuum dryer in the embodiment;

[0018] Figure 2 This is a diagram showing the positional relationship between the heating motherboard, screen glass, and condenser plate in the embodiment.

[0019] Figure 3 This is a flowchart of the evaporation control method in the embodiment.

[0020] Reference numerals: heating main board 1, screen glass 4, vacuum dryer body 8, condenser plate 81, concentration detection element 82. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1:

[0023] like Figures 1-3 As shown, a method for controlling drying and volatilization includes the following steps:

[0024] Step S1, loading: Place the screen glass 4 into the vacuum dryer body 8. The vacuum dryer body 8 is equipped with a heating main board 1, which can be raised and lowered. The screen glass 4 is placed on the upper surface of the heating main board 1 (after placement, it will enter the initial preheating state).

[0025] A condenser plate 81 is fixedly installed on the top of the cavity of the vacuum dryer body 8. The condenser plate 81 is located above the heating plate 1. The medium that evaporates from the surface of the screen glass 4 due to heating is condensed and collected by the condenser plate 81. The condenser plate 81 is cleaned regularly. Cooling pipes are provided inside the condenser plate 81 to keep the condenser plate 81 at a temperature of about 10°C.

[0026] A threaded rod is mounted on the bottom of the heating main board 1 and is controlled by a servo drive (lead screw drive) to move up and down, thereby adjusting the distance between the screen glass 4 located at the upper end of the heating main board 1 and the condenser plate 81. The heating main board 1 uses flow channel heating or electric heating wire conduction heating.

[0027] Before the screen glass 4 is placed into the vacuum dryer body 8, the vacuum dryer body 8 is maintained at atmospheric pressure. After the screen glass 4 is placed, the vacuum dryer body 8 closes the chamber sealing door and performs vacuum treatment on the inner cavity. The vacuum pressure adjustment range of the inner cavity of the vacuum dryer body 8 is 0.0001 Pa to 10 Pa (molecular pump pressure adjustment range). In this step, the vacuum is evacuated to a pressure close to 0.0001 Pa. Under near-vacuum conditions, the evaporation efficiency of the medium solvent on the surface of the screen glass 4 is higher.

[0028] In a non-high vacuum environment, a large amount of nitrogen, oxygen, water vapor, and trace particulate impurities remain in the chamber. During subsequent heating and volatilization, these air molecules and impurities will fill the gap between the glass and the condenser plate, causing interference. Therefore, by first evacuating to an ultimate high vacuum, the original air can be almost completely removed. The gas phase environment after subsequent pressurization is mainly composed of pure solvent vapor and filled dry nitrogen, greatly improving process controllability.

[0029] Step S2, First stage heating (heating time 120-200 seconds): Adjust the interlayer spacing between the condenser plate 81 and the screen glass 4 to the minimum spacing state, with the minimum spacing set to 3mm to 5mm. A preferred minimum spacing value is 4.5mm. A smaller spacing setting can compress the space volume between the condenser plate 81 and the screen glass 4, accelerating the rapid accumulation of evaporating solvent gas, allowing the evaporating solvent gas in the space between the condenser plate 81 and the screen glass 4 to quickly reach saturation.

[0030] In the initial heating stage, the overall solvent volume is at its maximum. As the screen glass 4 gradually heats up, different areas of the screen glass 4 have varying solvent distributions. Some areas of the screen glass 4 experience rapid solvent heating and violent evaporation, leading to phenomena such as boiling over. By controlling the distance between the condenser plate 81 and the screen glass 4, the solvent gas between them quickly reaches saturation, significantly reducing the partial pressure difference between the gas and liquid phases. This significantly lowers the mass transfer flux of solvent molecules detaching from the liquid film on the surface of the screen glass 4, preventing unrestrained and violent evaporation. If a large distance is used initially, the gas partial pressure is extremely low, and the partial pressure difference between the gas and liquid phases is extremely large. This causes a large amount of solvent on the surface of some screen glass 4 to vaporize instantly, easily leading to liquid film boiling, microbubbles, and rapid drying of localized solvents. This results in stains, halos, and uneven drying on the surface of the screen glass 4, affecting the molding quality.

[0031] In the minimum spacing state, the heating motherboard 1 continuously heats the screen glass 4. During the heating process, the vacuum pressure is gradually increased to 5Pa (the pressure increase time is 30-40 seconds, and the gas introduced is dry nitrogen). The lower vacuum pressure in the initial stage is conducive to the rapid evaporation of the solvent gas to reach saturation. The subsequent gradual increase of the vacuum pressure (5Pa) is conducive to suppressing evaporation and controlling the evaporation rate.

[0032] Step S3, the second stage of heating, maintains the heating state of the main board 1 on the screen glass 4, increases the distance between the condenser plate 81 and the screen glass 4, so as to break the solvent gas concentration saturation state formed in step S2.

[0033] The reason for disrupting the solvent gas saturation state is that the core driving force for solvent evaporation from the surface of the screen glass is the vapor partial pressure difference between the liquid film and the gas phase on the glass surface. If the gas phase concentration reaches saturation, the gas-liquid partial pressure difference is very low, and the evaporation efficiency is very low. Maintaining an unsaturated state, with a continuous stable partial pressure difference, allows the solvent to evaporate more quickly, thereby improving drying efficiency.

[0034] The maximum distance between the condenser plate 81 and the screen glass 4 is limited to 8mm to 50mm, and the minimum distance is limited to 3mm to 5mm. In this step, the distance between the condenser plate 81 and the screen glass 4 is adjusted to 8mm-50mm, preferably 20mm. By increasing the distance, it is easier to maintain the concentration gradient of the solvent gas in the interlayer between the condenser plate 81 and the screen glass 4, preventing the solvent gas at the bottom from reaching concentration saturation. This is beneficial for increasing the evaporation rate of the solvent on the surface of the screen glass 4 and improving the drying efficiency.

[0035] Step S4: After drying is complete, remove the screen glass 4 to complete the unloading.

[0036] Example 2: Figures 1-3As shown, the difference from Embodiment 1 is that in step S3, the distance between the condenser plate 81 and the screen glass 4 is adjusted in steps within a preset adjustment range. The preset adjustment range is from the minimum distance to the maximum distance between the condenser plate 81 and the screen glass 4. The maximum distance between the condenser plate 81 and the screen glass 4 is limited to 8mm to 50mm, and the minimum distance is limited to 3mm to 5mm. Preferably, the maximum distance between the condenser plate 81 and the screen glass 4 is set to 20mm, and the minimum distance is set to 3mm.

[0037] The spacing value is adjusted in increments of 0.1 mm to 10 mm, with a preferred increment of 1 mm. The first adjustment increases the spacing. After each adjustment, the vacuum level is adjusted to control the evaporation rate.

[0038] The vacuum dryer body 8 is equipped with a concentration detection element 82, which is used to detect the gas concentration in the lower area of ​​the condenser plate 81 and the upper area of ​​the screen glass 4.

[0039] The concentration detection element 82 uses laser to collect concentration. The transmitter and receiver of the concentration detection element 82 are located on both sides of the space between the condenser plate 81 and the screen glass 4.

[0040] The specific method for adjusting the vacuum level is as follows:

[0041] Step S31, obtain the actual concentration difference:

[0042] In the space between the condenser plate 81 and the screen glass 4, the concentration at the bottom of the condenser plate 81 is recorded as Ctop, and the concentration at the top of the screen glass 4 is recorded as Cbot. The concentration difference Cver = Cbot - Ctop.

[0043] Step S32: Compare the actual concentration difference with the saturation concentration difference and adjust the gas pressure:

[0044] If Cver ≥ 0.7Csat, it indicates that the vertical concentration gradient is too large, where Csat is the saturation concentration of the solvent gas that evaporates at the current pressure.

[0045] Since the gas evaporating from the solvent on the surface of the screen glass 4 preferentially fills the cavity space between the condenser plate 81 and the screen glass 4, the vertical concentration gradient is too large, indicating that the gas diffusion rate in the cavity space between the gas condenser plate 81 and the screen glass 4 is relatively fast. This results in the solvent evaporation rate on the surface of the screen glass 4 being too fast. A large amount of solvent evaporates in a short time, which can easily cause local solvent to dry quickly, forming a halo and dry spots on the surface of the screen glass 4. Therefore, the vacuum pressure in the cavity is gradually increased and the vacuum degree is reduced to slow down the evaporation rate.

[0046] By finely adjusting the total gas pressure within the cavity between the condenser plate 81 and the screen glass 4, the density in the gas phase increases, molecular collisions become more frequent, and the mass transfer resistance of solvent vapor diffusion outwards significantly increases. Solvent molecules diffuse outwards more slowly after detaching from the liquid film, macroscopically manifested as a decrease in the overall evaporation rate, thus inhibiting evaporation.

[0047] If 0.7Csat≥Cver≥0.35Csat, then maintain the vacuum pressure value inside the cavity.

[0048] If Cver ≤ 0.35Csat, it indicates a small vertical concentration gradient, meaning the concentration in the cavity between the condenser plate 81 and the screen glass 4 is close to saturation, resulting in a significant reduction in the evaporation rate of the solvent on the surface of the screen glass 4. Therefore, by finely adjusting and reducing the vacuum pressure inside the cavity to increase the vacuum level, some of the solvent vapors are removed, increasing the evaporation rate.

[0049] The single pressure adjustment step is limited to 0.01Pa to 0.3Pa, preferably 0.2Pa. After each pressure adjustment, the chamber is allowed to stand for 1s to 30s (preferably 16 seconds) to allow sufficient time for the chamber pressure to balance, avoid the controller from frequently adjusting the pressure due to instantaneous concentration fluctuations, reduce the continuous oscillation of the chamber pressure, and ensure stable evaporation of solvent on the surface of the screen glass 4.

[0050] By adjusting the evaporation rate, the stability and uniformity of the evaporation rate can be ensured, thereby improving the product molding quality.

[0051] Repeat steps S31 and S32 after each voltage adjustment.

[0052] For every three consecutive increases or decreases in the vacuum pressure within the cavity of the vacuum dryer body 8, the distance between the condenser plate 81 and the screen glass 4 is correspondingly decreased or increased once. Specifically, decreasing the distance between the condenser plate 81 and the screen glass 4 compresses the space, increases the gas density, and slows evaporation. This works in conjunction with increasing the vacuum pressure to prevent the pressure from rapidly approaching a critical value, thus preventing adjustment failure. Conversely, increasing the distance between the condenser plate 81 and the screen glass 4 expands the space, reduces the gas density, and promotes evaporation. When the vacuum pressure reaches 10 Pa and further increases are needed, only the distance is adjusted.

[0053] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for controlling drying and volatilization, characterized in that, Includes the following steps: Step S1: Place the screen glass (4) into the cavity of the vacuum dryer body (8) and perform vacuum treatment on the cavity of the vacuum dryer body (8); Step S2: A condenser plate (81) is installed inside the vacuum dryer body (8). The condenser plate (81) is located above the screen glass (4). The screen glass (4) is heated to evaporate the solvent on the surface of the screen glass (4). The distance between the condenser plate (81) and the screen glass (4) is adjusted to the minimum distance state. The minimum distance between the condenser plate (81) and the screen glass (4) is 3mm to 5mm. Step S3: Under continuous heating, the distance between the condenser plate (81) and the screen glass (4) is adjusted and / or the vacuum pressure in the cavity of the vacuum dryer body (8) is adjusted so that the concentration of the solvent gas volatilized in the space between the condenser plate (81) and the screen glass (4) is in an unsaturated state. In step S3, the distance between the condenser plate (81) and the screen glass (4) is adjusted in a stepwise manner, with each adjustment step ranging from 0.1mm to 10mm. The first adjustment is to increase the distance. In step S3, after each adjustment of the distance between the condenser plate (81) and the screen glass (4), the vacuum pressure inside the cavity of the vacuum dryer body (8) is adjusted so that the concentration of solvent gas in the space between the condenser plate (81) and the screen glass (4) is in an unsaturated state. The specific adjustment method is as follows: Step S31, obtain the actual concentration difference: In the space between the condenser plate (81) and the screen glass (4), the concentration at the bottom of the condenser plate (81) is recorded as Ctop, and the concentration at the top of the screen glass (4) is recorded as Cbot. The concentration difference Cver = Cbot - Ctop. Step S32: Compare the actual concentration difference with the saturation concentration difference and adjust the vacuum pressure: If Cver ≥ 0.7Csat, the vacuum pressure inside the cavity of the vacuum dryer body (8) is gradually increased; if Cver ≤ 0.35Csat, the vacuum pressure inside the cavity of the vacuum dryer body (8) is gradually decreased, where Csat is the saturation concentration of the solvent gas volatilized at the current pressure and temperature.

2. The drying and volatilization control method according to claim 1, characterized in that, The vacuum pressure adjustment range of the cavity of the main body (8) of the vacuum dryer is 0.0001 Pa to 10 Pa. In step S1, the vacuum process reaches the minimum vacuum pressure value. In step S2, while the screen glass (4) is heated, the vacuum pressure value is gradually increased to 5 Pa.

3. The drying and volatilization control method according to claim 1, characterized in that, The distance between the condenser plate (81) and the screen glass (4) is adjusted in steps within a preset adjustment range. The preset adjustment range is the minimum distance to the maximum distance between the condenser plate (81) and the screen glass (4). The maximum distance between the condenser plate (81) and the screen glass (4) is limited to 8mm to 50mm, and the minimum distance is limited to 3mm to 5mm.

4. The drying and volatilization control method according to claim 1, characterized in that, After each adjustment of the vacuum air pressure value inside the cavity of the main body (8) of the vacuum dryer, wait for 1 to 30 seconds, and then repeat steps S31 and S32.

5. The drying and volatilization control method according to claim 1, characterized in that, In step S32, the vacuum air pressure value inside the cavity of the vacuum dryer body (8) increases or decreases by a step of 0.01 Pa to 0.3 Pa.

6. The drying and volatilization control method according to claim 1, characterized in that, For every three consecutive decreases or increases in the vacuum air pressure value inside the cavity of the main body (8) of the vacuum dryer, the distance between the condenser plate (81) and the screen glass (4) is increased or decreased once.

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