A process for the preparation of platelet-shaped sodium hydrosulfide

Abstract

The present application relates to chemical product preparation technical field, disclose a kind of preparation flaky sodium hydrosulfide process, raw material preparation, reaction synthesis, concentration crystallization, separation and drying, sheet forming and surface modification, surface modification includes: surface modification forms hydrophobic protective film, plasma pretreatment activates surface, chemical vapor modification forms bonding layer, ultraviolet curing stable structure and partition isolation continuous production processing etc. Step.The present application is through the synergistic effect of each step and partition isolation continuous production process, significantly improve the moisture resistance and mechanical strength of flaky sodium hydrosulfide product, solve the problem of mutual interference between processes, improve production efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of chemical products, more particularly, it relates to a process for preparing flaky sodium hydrosulfide. BACKGROUND

[0002] Sodium hydrosulfide is an important raw material and intermediate in chemical production, and is widely used in many industrial fields. Flaky sodium hydrosulfide has special value in actual production due to its large specific surface area and high reactivity. However, the traditional flaky sodium hydrosulfide has the following technical problems:

[0003] The easy deliquescence property leads to poor storage stability, and it is easy to absorb moisture and deliquesce in a humid environment, affecting product quality and service life;

[0004] The protective film formed by the existing surface modification technology has insufficient bonding strength, long curing time, and limited moisture-proof effect;

[0005] The processes such as plasma pretreatment, chemical vapor modification, and ultraviolet curing interfere with each other in continuous production, resulting in unstable product quality;

[0006] There are many transfer and intermediate storage links between processes in the process flow, which not only reduces production efficiency, but also increases energy consumption.

[0007] Although single surface modification methods are used in the prior art to try to solve the moisture-proof problem of sodium hydrosulfide, there are generally defects such as poor protection effect, poor process stability, and inability to realize continuous production, which cannot meet the demand of industrial production for high-quality flaky sodium hydrosulfide products. SUMMARY

[0008] In order to solve the above technical problems, the present application provides a process for preparing flaky sodium hydrosulfide, which comprises raw material preparation, reaction synthesis, concentration crystallization, separation and drying, flaky molding and surface modification. The surface modification comprises the following steps:

[0009] The production line is divided into three functional areas: plasma pretreatment area, chemical vapor modification area and ultraviolet curing area;

[0010] A gas flow barrier system is provided between adjacent functional areas to prevent the mutual mixing and contamination of gases in different areas;

[0011] A pressure gradient is established in the entire production line, so that the gas flow direction is from the plasma pretreatment area to the ultraviolet curing area;

[0012] The flaky sodium hydrosulfide product is transferred from one functional area to the next functional area by a continuous conveying system;

[0013] The surface of the flaky sodium hydrosulfide product is activated to form active sites in the plasma pretreatment zone;

[0014] A chemical bond modification layer is formed by the reaction of the precursor gas with the active sites in the chemical vapor modification zone;

[0015] The chemical modification layer is cured by ultraviolet irradiation in the ultraviolet curing zone to form a moisture-proof protective film.

[0016] Preferably, the airflow direction in the airflow barrier system is perpendicular to the product transmission direction, the first airflow barrier airflow speed is 0.5-2.0 m / s, and the second airflow barrier airflow speed is 0.5-1.5 m / s.

[0017] Preferably, the pressure gradient satisfies the relationship P1>P2>P3, where P1 is the pressure in the plasma pretreatment zone, P2 is the pressure in the chemical vapor modification zone, and P3 is the pressure in the ultraviolet curing zone, and the pressure difference between adjacent zones is 20-50 Pa.

[0018] Preferably, the plasma pretreatment uses a low-temperature plasma method, the temperature is controlled within the range of 40-60℃, the plasma gas source is argon or oxygen, the power density is 0.1-0.5 W / cm², and the treatment time is 5-30 seconds.

[0019] Preferably, the precursor in the chemical vapor modification is an organosilicon or organofluorine compound with hydrophobic groups and active reaction groups, and the reaction temperature is 60-80℃.

[0020] Preferably, the organosilicon or organofluorine compound is octamethylcyclotetrasiloxane, hexamethyldisiloxane, or perfluorobutyl ethylene.

[0021] Preferably, the ultraviolet curing treatment uses a combined light source with wavelengths of 254 nm and 365 nm, the light intensity is 50-200 mW / cm², the irradiation time is 3-15 seconds, and the curing process is carried out under inert gas protection.

[0022] Preferably, the gas used in the airflow barrier system is nitrogen or argon.

[0023] Preferably, the modification layer formed by the chemical vapor modification has a thickness of 50-200 nm and a surface contact angle of 110°-150°.

[0024] Preferably, the process further includes a product quality control step, and the detection indicators include: the moisture absorption rate is less than 0.5% after being placed at a temperature of 25℃ and a relative humidity of 90% for 7 days; the compressive strength of the modified product is not less than 130% of the initial value; the surface contact angle is greater than 110°; the peeling rate of the modification layer after tape peeling test is less than 5%; and the effective ingredient utilization rate of the modified product is not less than 95%.

[0025] Preferably, the raw material preparation includes: taking sodium hydroxide and hydrogen sulfide as the main raw materials, preparing solid sodium hydroxide with a purity of not less than 98% and hydrogen sulfide gas with a purity of not less than 99.5%.

[0026] Preferably, the reaction synthesis includes:

[0027] In a sealed reaction kettle, sodium hydroxide is dissolved in deionized water to prepare a solution with a concentration of 45-55%, and the temperature is controlled in the range of 20-30℃. Hydrogen sulfide gas is introduced to react with the sodium hydroxide solution, and the reaction equation is: NaOH + H2S → NaHS + H2O. Stirring is maintained during the reaction to ensure that the reaction proceeds completely, and the pH value of the solution reaches 8.5-9.5, indicating that the reaction is basically complete.

[0028] Preferably, the concentration and crystallization include:

[0029] The sodium hydrosulfide solution obtained by reaction is pumped into an evaporator for concentration, and the temperature is controlled in the range of 65-75℃, and evaporated under negative pressure conditions (0.05-0.08MPa) until the solution concentration reaches 70-75%. The concentrated solution is sent to the crystallizer to cool to 20-25℃ to promote the precipitation of sodium hydrosulfide crystals.

[0030] Preferably, the separation and drying include:

[0031] The slurry containing crystals is sent to a centrifugal separator for solid-liquid separation, and the wet crystals separated are transferred to a vacuum drying device, and the temperature is controlled at 50-60℃, and dried to a moisture content of less than 0.5%.

[0032] Preferably, the sheet forming includes:

[0033] The dried sodium hydrosulfide powder is prepared into sheet-shaped products of the required specifications by mechanical tabletting or hot pressing forming, and the thickness is controlled to be 0.5-2.0mm, and the diameter or side length is set according to actual needs.

[0034] The beneficial effects of the present application are:

[0035] The sheet-shaped sodium hydrosulfide prepared by the process has the following effects:

[0036] Moisture resistance: The sheet-shaped sodium hydrosulfide product treated by the process has a moisture absorption rate of less than 0.5% after being stored in an environment with a relative humidity of 90% for 30 days, while the traditional product has a moisture absorption rate of 8-15% under the same conditions. This moisture resistance allows the product to maintain good physical state and chemical activity in a high-humidity environment.

[0037] High bonding strength protective layer: Through the synergistic effect of plasma pretreatment, chemical vapor modification and ultraviolet curing, the moisture-proof protective layer formed has a bonding strength of 3-5 MPa with the sodium hydrosulfide substrate, which is 3-5 times that of traditional surface modification methods, ensuring that the protective layer is not easily detached or damaged during use.

[0038] Mechanical strength improvement: The protective layer gives the product surface additional mechanical protection, increasing the compressive strength of the flaky sodium hydrosulfide product by 30-50% and the impact resistance by 40-60%, improving the stability of the product during transportation and use.

[0039] Chemical activity retention: The surface protective layer formed by this process provides moisture-proof function without affecting the chemical activity of the product. Tests show that the effective ingredient utilization rate of the modified product remains above 95%, meeting the needs of various application scenarios.

[0040] The process of the present application has the following effects:

[0041] Solution to interference between processes: Through zoned isolation continuous production process, the problems of contamination of plasma residues on chemical vapor deposition, interference of gas phase precursors on ultraviolet curing, etc. are solved. Tests show that the gas cross-contamination between adjacent processes is reduced by more than 95%, and each process step can operate independently under optimal conditions.

[0042] Production efficiency improvement: The zoned isolation continuous production process eliminates the transfer and intermediate storage links between processes, and the ultraviolet curing replaces the traditional thermal curing, so that the entire production cycle is shortened from 30-60 minutes to 1-3 minutes, and the production efficiency is improved by 10-20 times.

[0043] Energy consumption reduction: Low-temperature plasma pretreatment and ultraviolet curing process reduce energy demand. Compared with traditional thermal treatment process, energy consumption per ton of product is reduced by 60-70%, reducing production cost.

[0044] Improved product quality stability: By controlling the process parameters and environmental conditions of each functional zone, the consistency between batches of product quality is improved. Test data shows that the variation coefficient of the modified layer thickness is less than 5%, and the variation coefficient of the hydrophobic performance is less than 3%, which is better than 15-20% of the traditional process.

[0045] The present application combines plasma pretreatment, chemical vapor modification and ultraviolet curing, and introduces zoned isolation continuous production process, solves the technical problems of traditional flaky sodium hydrosulfide such as hygroscopicity, insufficient surface modification bonding strength and mutual interference between processes, realizes the improvement of product performance and production efficiency, has technical innovation value and application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 is the moisture absorption rate comparison of different products of the present application in a high humidity environment (25℃, 90% RH);

[0047] Figure 2 is the trace gas concentration distribution comparison of each area of the production line of the present application;

[0048] Figure 3 is the active retention rate change curve of the flaky sodium hydrosulfide product under different conditions of the present application. DETAILED DESCRIPTION

[0049] The subject matter described herein will now be discussed with reference to example implementations. It should be understood that discussions of these implementations are merely provided to enable those skilled in the art to better understand subject matter and should not be taken to limit the scope of the claims in any way. Various processes or components can be omitted, substituted, or added as desired. Additionally, features described with respect to one example can be combined in any manner with features described with respect to another example.

[0050] Example 1

[0051] A process for preparing flaky sodium hydrosulfide is proposed in this example, including raw material preparation, reaction synthesis, concentration crystallization, separation and drying, flaky molding, and surface modification, which includes the following steps:

[0052] The production line is divided into three functional areas: plasma pretreatment area, chemical vapor modification area, and ultraviolet curing area;

[0053] A gas flow barrier system is provided between adjacent functional areas to prevent the mixing and contamination of gases from different areas;

[0054] A pressure gradient is established throughout the production line, with the gas flow direction being from the plasma pretreatment area to the ultraviolet curing area;

[0055] A continuous conveying system is used to transport the flaky sodium hydrosulfide product from one functional area to the next;

[0056] The surface of the flaky sodium hydrosulfide product is activated in the plasma pretreatment area to form active sites;

[0057] In the chemical vapor modification area, the active sites react with the precursor gas to form a chemically bonded modification layer;

[0058] In the ultraviolet curing area, the chemical modification layer is subjected to ultraviolet irradiation and curing treatment to form a moisture-proof protective film.

[0059] Wherein:

[0060] The airflow direction of the airflow barrier system is perpendicular to the product conveying direction, the airflow speed of the first airflow barrier is 0.5 m / s, and the airflow speed of the second airflow barrier is 0.5 m / s.

[0061] The pressure gradient satisfies the relationship P1>P2>P3, wherein P1 is the pressure of the plasma pretreatment zone, P2 is the pressure of the chemical vapor modification zone, and P3 is the pressure of the ultraviolet curing zone, and the pressure difference between adjacent zones is 20 Pa.

[0062] The plasma pretreatment adopts a low-temperature plasma method, the temperature is controlled at 40°C, the plasma gas source is argon or oxygen, the power density is 0.1 W / cm², and the treatment time is 5 seconds.

[0063] The precursor in the chemical vapor modification is selected to be an organosilicon with hydrophobic groups and active reaction groups, and the reaction temperature is 60°C.

[0064] The organosilicon is octamethylcyclotetrasiloxane or hexamethyldisiloxane.

[0065] The ultraviolet curing treatment adopts a combined light source with wavelengths of 254 nm and 365 nm, the light intensity is 50 mW / cm², the irradiation time is 3 seconds, and the curing process is carried out under the protection of inert gas.

[0066] The gas used in the airflow barrier system is nitrogen.

[0067] The thickness of the modified layer formed by the chemical vapor modification is 50 nm, and the surface contact angle is 110°.

[0068] The process also includes a product quality control step, and the detection indicators include: the moisture absorption rate is less than 0.5% after being placed at a temperature of 25°C and a relative humidity of 90% for 7 days; the compressive strength of the modified product is not less than 130% of the initial value; the surface contact angle is greater than 110°; the peeling rate of the modified layer after the tape peeling test is less than 5%; and the effective ingredient utilization rate of the modified product is not less than 95%.

[0069] The raw material preparation includes: using sodium hydroxide and hydrogen sulfide as main raw materials, preparing solid sodium hydroxide with a purity of not less than 98% and hydrogen sulfide gas with a purity of not less than 99.5%.

[0070] The reaction synthesis includes:

[0071] In a sealed reaction kettle, sodium hydroxide is dissolved in deionized water to prepare a solution with a concentration of 45-55%, and the temperature is controlled within the range of 20-30°C. Hydrogen sulfide gas is introduced to fully react with the sodium hydroxide solution, and the reaction equation is: NaOH + H2S → NaHS + H2O. Stirring is maintained during the reaction to ensure that the reaction proceeds completely, and the pH value of the solution reaches 8.5-9.5, indicating that the reaction is basically complete.

[0072] Concentrating and crystallizing includes:

[0073] The sodium hydrosulfide solution obtained from the reaction is pumped into an evaporator for concentration, the temperature is controlled within the range of 65-75°C, and evaporation is carried out under negative pressure (0.05-0.08 MPa) until the concentration of the solution reaches 70-75%. The concentrated solution is sent into a crystallizer for cooling to 20-25°C to promote the precipitation of sodium hydrosulfide crystals.

[0074] Separating and drying includes:

[0075] The slurry containing crystals is sent into a centrifugal separator for solid-liquid separation, and the separated wet crystals are transferred into a vacuum drying device, the temperature is controlled within the range of 50-60°C, and drying is carried out until the moisture content is less than 0.5%.

[0076] Sheet forming includes:

[0077] The dried sodium hydrosulfide powder is prepared into sheet products of the required specifications by mechanical tabletting or hot-pressing forming, the thickness of the tablets is controlled within the range of 0.5-2.0 mm, and the diameter or side length is set according to actual requirements.

[0078] Example 2

[0079] The difference between this example and Example 1 is that:

[0080] The airflow direction in the airflow barrier system is perpendicular to the product transmission direction, the airflow speed of the first airflow barrier is 1.2 m / s, and the airflow speed of the second airflow barrier is 1.0 m / s.

[0081] The pressure gradient satisfies the relationship P1>P2>P3, wherein P1 is the pressure of the plasma pretreatment zone, P2 is the pressure of the chemical vapor modification zone, and P3 is the pressure of the ultraviolet curing zone, and the pressure difference between adjacent zones is 35 Pa.

[0082] The plasma pretreatment adopts a low-temperature plasma method, the temperature is controlled at 50°C, the plasma gas source is argon or oxygen, the power density is 0.3 W / cm², and the treatment time is 18 seconds.

[0083] The precursor in the chemical vapor modification is an organic fluorine compound with hydrophobic groups and active reaction groups, and the reaction temperature is 70°C.

[0084] The organic fluorine compound is perfluorobutyl ethylene.

[0085] The ultraviolet curing treatment adopts a light intensity of 125 mW / cm² and an irradiation time of 9 seconds.

[0086] The gas used in the airflow barrier system is argon.

[0087] Example 3

[0088] The difference between this embodiment and embodiment 1 is that:

[0089] The airflow direction in the airflow barrier system is perpendicular to the product transmission direction, the airflow speed of the first airflow barrier is 2.0 m / s, and the airflow speed of the second airflow barrier is 1.5 m / s.

[0090] The pressure gradient satisfies the relationship P1>P2>P3, wherein P1 is the pressure of the plasma pretreatment zone, P2 is the pressure of the chemical vapor modification zone, and P3 is the pressure of the ultraviolet curing zone, and the pressure difference between adjacent regions is 50 Pa.

[0091] The plasma pretreatment adopts a low-temperature plasma method, the temperature is controlled at 60°C, the plasma gas source is argon or oxygen, the power density is 0.5 W / cm², and the processing time is 30 seconds.

[0092] The ultraviolet curing treatment adopts, the light intensity is 200 mW / cm², and the irradiation time is 15 seconds.

[0093] Example 4

[0094] A surface modification method in a process for preparing flaky sodium hydrosulfide is proposed in this embodiment, which comprises the following steps:

[0095] 1. Raw material preparation

[0096] The flaky sodium hydrosulfide product produced by the conventional process is subjected to surface impurity removal and drying treatment to obtain a flaky sodium hydrosulfide product with clean surface and water content meeting the requirements, which is used as the raw material of the process.

[0097] 2. Construction of a continuous production line with partitioned isolation

[0098] 2.1. Partitioned construction

[0099] The production line is divided into three independent functional areas: a plasma pretreatment zone, a chemical vapor modification zone, and an ultraviolet curing zone, and the three areas are organically connected through a continuous transmission system. The three areas are independent of each other in physical space, but closely connected in process flow, forming a whole continuous production system.

[0100] 2.2. Construction of an airflow barrier system

[0101] An airflow barrier system is provided between adjacent functional areas. This system forms a directional airflow layer at the junction of the areas to prevent the mixing and contamination of gases in different areas. In specific implementation:

[0102] A first airflow barrier is provided between the plasma pretreatment zone and the chemical vapor modification zone, the airflow direction is perpendicular to the product transmission direction, and the airflow speed is 1.2 m / s;

[0103] A second airflow barrier is arranged between the chemical vapor modification zone and the ultraviolet curing zone, and the airflow direction is also perpendicular to the product transmission direction, and the airflow speed is 1.0 m / s;

[0104] The gas used by the airflow barrier is clean inert gas (nitrogen), which ensures that it does not react with the process gas in each functional zone.

[0105] 2.3, pressure gradient isolation system construction

[0106] A reasonable pressure gradient is established in the entire production line to ensure that the gas flow direction is controllable and reverse diffusion is prevented. In specific implementation:

[0107] The pressure of the plasma pretreatment zone is set to P1, the pressure of the chemical vapor modification zone is set to P2, and the pressure of the ultraviolet curing zone is set to P3;

[0108] The pressure gradient relationship of P1>P2>P3 is maintained, so that the overall gas flow direction is from the plasma pretreatment zone to the ultraviolet curing zone;

[0109] The pressure difference is controlled at 35 Pa to ensure that it is sufficient to maintain directional gas flow, but does not affect the continuous transmission of the product.

[0110] 2.4, continuous transmission system construction

[0111] A continuous transmission system suitable for sheet sodium hydrosulfide is adopted to realize uninterrupted transmission of the product between different functional areas. The system meets the following requirements:

[0112] The transmission system material is selected from materials that do not react with sodium hydrosulfide;

[0113] The transmission speed can be adjusted to meet the processing needs under different process conditions;

[0114] The transmission system ensures that the product surface is uniformly exposed to the processing environment of each functional zone;

[0115] The transmission system structure ensures that the product is not disturbed by the airflow when passing through the airflow barrier, and maintains stable transmission.

[0116] 3, plasma pretreatment

[0117] 3.1, plasma activation treatment

[0118] Plasma pretreatment is carried out in the first functional zone to activate the surface of the sheet sodium hydrosulfide product. In specific implementation of this step:

[0119] Low-temperature plasma method is used, and the temperature is controlled at 50°C to avoid decomposition of sodium hydrosulfide caused by high temperature;

[0120] The plasma gas source is selected from argon or oxygen, which can be adjusted according to specific needs;

[0121] Plasma power density is controlled at 0.3 W / cm²;

[0122] The processing time is controlled at 18 seconds, adjusted according to product characteristics and subsequent processing requirements.

[0123] 3.2, Formation of surface active sites

[0124] During the plasma pretreatment process, the plasma interacts with the surface of sodium hydrosulfide, forming active sites. This process is the basis for subsequent chemical vapor modification, with the following specific features:

[0125] The activation process mainly occurs in the product surface 30 nm deep, without affecting the internal structure and performance of the product;

[0126] The active site density reaches 1012-1014 / cm², improving the surface reactivity;

[0127] The activated surface is uniform, with uniform distribution of active sites, which is beneficial to the formation of a uniform moisture-proof film in the subsequent modification layer.

[0128] 4, Chemical vapor modification

[0129] 1, Precursor gas phase introduction

[0130] Chemical vapor modification is carried out in the second functional zone to chemically modify the surface of the product activated by plasma. In this step, appropriate precursor gas is selected to form a chemically bonded modification layer on the activated surface through gas phase reaction:

[0131] The precursor gas is introduced into the reaction zone through a controlled flow system;

[0132] The precursor is selected to be an organosilicon with hydrophobic groups and active reaction groups: octamethylcyclotetrasiloxane (D4), hexamethyldisiloxane (HMDS);

[0133] The gas phase concentration is kept stable to ensure uniform thickness of the formed modification layer;

[0134] The reaction temperature is controlled at 70°C to optimize the reaction efficiency of gas phase molecules and surface active sites.

[0135] 4.2, Formation of chemically bonded layer

[0136] The precursor gas molecules react with the surface active sites to form a firm chemically bonded layer. This process has the following characteristics:

[0137] The reaction mainly forms through covalent bonds, with higher bonding strength than physical adsorption;

[0138] The thickness of the formed modification layer is controlled at 125 nm, with uniformity;

[0139] The modified layer surface exhibits hydrophobicity, with a contact angle of 110°-150°;

[0140] A stable interface structure is formed between the modified layer and the sodium hydrosulfide substrate, and peeling is not easy.

[0141] 5. UV curing treatment

[0142] 5.1. UV light irradiation treatment

[0143] UV curing treatment is carried out in the third functional area to quickly cure the chemical modification layer. This step uses a UV light source with a suitable wavelength combination to achieve rapid and efficient curing:

[0144] The UV light source uses a combination of 254 nm and 365 nm wavelength light sources to achieve full-depth curing. The 254 nm wavelength UV light can effectively excite the photosensitive groups on the surface of the modified layer to initiate crosslinking, while the 365 nm wavelength UV light has strong penetration and can promote crosslinking reactions in the deep part of the modified layer. The combination of the two ensures uniform curing of the entire modified layer;

[0145] The UV light intensity is controlled at 125 mW / cm² to provide the energy required for curing;

[0146] The irradiation time is controlled at 9 seconds, which shortens the time required for traditional thermal curing;

[0147] The curing process is carried out under inert gas protection to prevent oxygen from inhibiting the curing reaction.

[0148] 5.2. Formation of crosslinked network structure

[0149] UV light irradiation induces crosslinking reactions of photosensitive groups in the modified layer, forming a stable three-dimensional network structure. This process has the following characteristics:

[0150] The crosslinking reaction is completed within a few seconds, improving production efficiency;

[0151] The crosslinked network structure formed has mechanical strength and chemical stability;

[0152] The orientation of the hydrophobic groups is preserved in the crosslinked network, ensuring moisture-proof function;

[0153] The crosslinking density reaches 70%-90%, forming a dense moisture-proof layer.

[0154] 6. Product quality control and acceptance

[0155] The sheet-shaped sodium hydrosulfide product after surface modification treatment is subjected to quality detection, including the following specific detection indicators:

[0156] Moisture resistance test: According to GB / T 2423.3 standard method, place the product in a constant temperature and humidity chamber at 25℃ and 90% relative humidity for 7 days. The moisture absorption rate should be less than 0.5%;

[0157] Mechanical strength test: According to GB / T 17671 test method, the compressive strength of the modified product should be not less than 130% of the initial value;

[0158] Hydrophobicity test: Using contact angle measurement method, the contact angle of water droplets on the surface of the product should be greater than 110°;

[0159] Bonding strength test: Using tape peeling method, the peeling rate of the surface modification layer after 3M tape peeling test should be less than 5%;

[0160] Chemical activity test: According to enterprise standard test method, the utilization rate of active ingredients of the modified product should be not less than 95%.

[0161] The qualified products are vacuum packaged, labeled with production date, batch number and shelf life (18-24 months), and the entire process is completed.

[0162] Experimental verification

[0163] In order to verify the technical effect of this process, a series of experiments were carried out, and the results are as follows:

[0164] 1. Moisture resistance test

[0165] 1.1 Purpose of the experiment

[0166] To verify the moisture resistance of the flaky sodium hydrosulfide product treated by the process of zoned isolation continuous plasma pretreatment-chemical vapor modification-ultraviolet curing composite surface modification.

[0167] 1.2 Experimental materials and equipment

[0168] Flaky sodium hydrosulfide sample treated by this process;

[0169] Unmodified flaky sodium hydrosulfide sample produced by traditional process (control group);

[0170] Constant temperature and humidity chamber (temperature control accuracy: ±0.5℃, humidity control accuracy: ±3%RH);

[0171] Analytical balance (accuracy: 0.0001g);

[0172] Drier;

[0173] Standard tray.

[0174] 1.3 Experimental steps

[0175] Take 5 samples of 10 g each of the surface-modified flaky sodium hydrosulfide sample and untreated sample, and label them respectively.

[0176] Accurately weigh the initial mass m of each sample using an analytical balance o .

[0177] Adjust the constant temperature and humidity chamber to 25±0.5℃ and relative humidity 90±3% RH.

[0178] Put all samples into the constant temperature and humidity chamber, and take them out after 1 day, 3 days, 7 days, 15 days and 30 days respectively, and cool them in a desiccator for 30 minutes.

[0179] Measure the mass m1 of each sample using an analytical balance.

[0180] Calculate the moisture absorption rate: Moisture absorption rate (%) = (m1-m o ) / m o × 100%.

[0181] 1.4 Experimental results

[0182] Table 1 Comparison of moisture absorption rates of flaky sodium hydrosulfide products under different conditions

[0183]

[0184] Figure 1 Comparison of moisture absorption rates of different products in a high humidity environment (25℃, 90% RH).

[0185] The experimental results show that the moisture absorption rate of the flaky sodium hydrosulfide product treated by the process is only 0.48% after 30 days in a high humidity environment, which is much lower than the traditional product of 14.83%, verifying the significant effect of the process in improving the moisture resistance of the product.

[0186] 2. Protective layer bonding strength test

[0187] 2.1 Purpose of the experiment

[0188] Determine the bonding strength between the protective layer formed by the plasma pretreatment-chemical vapor modification-ultraviolet curing composite surface modification process and the sodium hydrosulfide substrate, and compare it with the traditional surface modification method.

[0189] 2.2 Experimental materials and equipment

[0190] Flaky sodium hydrosulfide sample treated by the process;

[0191] Flaky sodium hydrosulfide sample treated by traditional method (dip coating method);

[0192] Flaky sodium hydrosulfide sample treated by single surface modification method;

[0193] Microcomputer-controlled electronic universal testing machine;

[0194] Special tensile clamp (matched with sample shape);

[0195] Epoxy adhesive;

[0196] Metal substrate plate;

[0197] Sample pretreatment equipment.

[0198] 2.3 Experimental steps

[0199] Sample preparation: cut each group of sheet-shaped sodium hydrosulfide samples into standard test size of 10 mm x 10 mm x 2 mm, and prepare 10 parallel samples for each group.

[0200] Grind the standard metal substrate plate with sandpaper and clean it with alcohol to ensure the surface is clean.

[0201] Use epoxy adhesive to paste one side of the sample on the metal substrate plate, and paste the other side with a tensile joint.

[0202] Cure at room temperature for 24 hours to ensure that the adhesive interface strength is higher than the test interface strength.

[0203] Fix the test sample on the microcomputer-controlled electronic universal testing machine.

[0204] Set the tensile rate to 2 mm / min and record the force-displacement curve during the tensile process.

[0205] Record the maximum tensile force F when the sample interface breaks.

[0206] Calculate the bonding strength σ = F / A, where A is the surface area of the sample (100 mm²).

[0207] Observe the surface of the damaged sample to determine the failure mode (interfacial failure or cohesive failure).

[0208] 2.4 Experimental results

[0209] Table 2 Comparison of protective layer bonding strength formed by different surface modification methods

[0210]

[0211] The experimental results show that the average bonding strength between the protective layer formed by the process and the sodium hydrosulfide substrate reaches 4.23 MPa, which is about 4 times that of the traditional dip coating method, 2.3 times that of the single vapor deposition method, 4.5 times that of the single plasma treatment, and 3.1 times that of the single UV curing coating. In addition, the protective layer formed by the process mainly shows cohesive failure, indicating that the interfacial bonding strength is better than the strength of the material itself, which confirms that the synergistic effect of plasma pretreatment-chemical vapor modification-UV curing significantly improves the bonding strength of the protective layer.

[0212] 3. Interference control test between processes

[0213] 3.1. Purpose of the experiment

[0214] To evaluate the effectiveness of the zoned isolation continuous production process in controlling cross-contamination between processes and analyze its impact on product quality.

[0215] 3.2. Experimental materials and equipment

[0216] Zoned isolation continuous production line on a pilot scale;

[0217] Traditional non-isolated production line (control group);

[0218] Gas mass spectrometer;

[0219] Tracer gas (low concentration of tetrafluoromethane CF4);

[0220] Gas sampler;

[0221] Sample collection points (set at key locations in each zone);

[0222] Gas flow meter;

[0223] Pressure sensor;

[0224] 3.3. Experimental steps

[0225] System configuration: Set up the zoned isolation continuous production line and the traditional non-isolated production line respectively, ensuring that the production parameters (except for isolation measures) of the two production lines remain consistent.

[0226] Tracer gas introduction: Add low-concentration tetrafluoromethane (CF4) as a tracer gas in the plasma pretreatment zone, with an initial concentration of 100 ppm.

[0227] Sampling site setting: Set sampling points in each zone of the production line, including:

[0228] Inside the plasma pretreatment zone (P1);

[0229] Interface between the plasma pretreatment zone and the chemical vapor modification zone (P2);

[0230] Inside the chemical vapor modification zone (P3);

[0231] The junction between the chemical vapor modification zone and the ultraviolet curing zone (P4);

[0232] Inside the ultraviolet curing zone (P5);

[0233] Run the production line, and after 30 minutes of stable operation, use a gas sampler to collect gas samples at each sampling point.

[0234] Use a gas mass spectrometer to measure the concentration of CF4 tracer gas in each sample.

[0235] Calculate the gas cross-contamination rate: Contamination rate (%) = (CF4 concentration at this point / CF4 concentration at P1 point) x 100%.

[0236] Repeat steps 4-6 under the isolation system open and closed conditions respectively, and compare the cross-contamination rates under the two conditions.

[0237] Collect the finished products produced by the two production lines, and test the product performance according to the methods of 1 and 2.

[0238] 3.4, Experimental results

[0239] Table 3 Tracer gas concentration and contamination rate at each sampling point under different production line configurations

[0240]

[0241] Figure 2 Comparison of tracer gas concentration distribution in each area of the production line.

[0242] Table 4 Product performance comparison under different production line configurations

[0243]

[0244] The experimental results show that the partition isolation continuous production process effectively controls the cross-contamination of gases between processes, and the contamination rates in the chemical vapor modification zone and the ultraviolet curing zone are reduced by 95.2% and 98.6% respectively. Gas mass spectrometry shows that after using the partition isolation system, the diffusion of tracer gas CF4 between functional areas is effectively prevented. This process isolation has a significant impact on product performance, with the uniformity of the modified layer thickness improved by 77.0%, the surface contact angle improved by 50.1%, the modified layer coverage improved by 14.7%, and the ultraviolet curing degree improved by 31.3%. The experiment verifies the significant effect of the partition isolation continuous production process in solving the mutual interference between processes.

[0245] 4, Production efficiency comparison test

[0246] 4.1, Purpose of the experiment

[0247] Compare the differences in production efficiency, energy consumption, and product consistency between the partition-isolated continuous production process and the traditional step-by-step production process, and verify the technical advantages of this process.

[0248] 4.2, Experimental materials and equipment

[0249] Partition-isolated continuous production line

[0250] Traditional step-by-step production line (equipment includes independent plasma processing equipment, chemical vapor deposition equipment, and ultraviolet curing equipment);

[0251] Energy consumption monitoring system;

[0252] Timing device;

[0253] Product testing equipment (thickness gauge, contact angle gauge, etc.);

[0254] Sheet-shaped sodium hydrosulfide raw material (same batch);

[0255] Temperature monitoring system;

[0256] Manual operation recording system.

[0257] 4.3, Experimental steps

[0258] System preparation: Adjust the partition-isolated continuous production line and the traditional step-by-step production line to the best working state, and ensure that the operators are familiar with the operation process.

[0259] Production parameter setting: Set the same process parameters on both production lines, including plasma power, chemical vapor modification precursor, ultraviolet light intensity, etc.

[0260] Test run:

[0261] Produce continuously on the partition-isolated continuous production line for 2 hours, record the output, energy consumption, and process switching time.

[0262] Produce the same amount of product on the traditional step-by-step production line, record the total production time, energy consumption, and each process transfer and waiting time.

[0263] Production efficiency calculation:

[0264] Unit time output (kg / h) = total output / total production time;

[0265] Unit product processing time (min / kg) = total production time / total output.

[0266] Energy efficiency calculation:

[0267] Energy consumption per unit product (kWh / kg) = Total energy consumption / Total production.

[0268] Human resource efficiency calculation:

[0269] Labor hours per unit product (h / kg) = Total labor hours / Total production.

[0270] Product consistency evaluation: 20 samples were randomly selected from two production lines, and key quality indicators (modified layer thickness, contact angle, curing degree, etc.) were measured to calculate the coefficient of variation.

[0271] Start-stop conversion efficiency: Record the time from start to reach stable production state, and the time from stop command to complete stop.

[0272] 4.4, Experimental results

[0273] Table 5 Comparison of efficiency of two production processes

[0274]

[0275] Table 6 Comparison of energy consumption of two production processes

[0276]

[0277] Table 7 Comparison of product quality consistency of two production processes

[0278]

[0279] The experimental results show that the partition isolation continuous production process is significantly better than the traditional step-by-step production process in all aspects: the output per unit time is increased by 12.2 times, the processing time per unit product is shortened by 12.3 times; The material transfer time is completely eliminated, and the process switching time is reduced from the traditional 685 seconds to less than 1 second; the energy consumption per unit product is reduced by 69.9%; the consistency of product quality is significantly improved, and the coefficient of variation of each index is reduced by an average of 77.1%. These data verify the significant advantages of the partition isolation continuous production process in production efficiency, energy consumption and product quality stability, providing strong support for industrial production.

[0280] 6.5, Product shelf life acceleration test

[0281] 6.5.1, Purpose of the experiment

[0282] To evaluate the shelf life extension effect of flaky sodium hydrosulfide product treated by this process, and verify its stability under different storage conditions.

[0283] 6.5.2, Experimental materials and equipment

[0284] Sample of flaky sodium hydrosulfide treated by the process;

[0285] Sample of unmodified flaky sodium hydrosulfide produced by conventional process (control group);

[0286] Accelerated aging test chamber (adjustable temperature, humidity);

[0287] Analytical balance (accuracy: 0.0001 g);

[0288] Sealing packaging materials (aluminum-plastic composite bag, plastic sealing bag);

[0289] Component analysis equipment (infrared spectrometer, X-ray diffractometer, etc.);

[0290] Mechanical strength test equipment;

[0291] Data recording system.

[0292] 6.5.3, Experimental steps

[0293] Sample preparation: The sample of flaky sodium hydrosulfide treated by the process and the sample of conventional process are each divided into 5 groups, 5 portions per group, and each portion is 50 g.

[0294] Storage condition setting: 5 different storage conditions are set:

[0295] Condition A: 25℃, relative humidity 50% (standard condition);

[0296] Condition B: 40℃, relative humidity 75% (accelerated condition 1);

[0297] Condition C: 55℃, relative humidity 80% (accelerated condition 2);

[0298] Condition D: 25℃, relative humidity 90% (high humidity condition);

[0299] Condition E: Cyclic condition (25℃ / 50%RH and 40℃ / 75%RH alternate every 12 hours).

[0300] Packaging method: The samples under each condition are packaged as follows:

[0301] No packaging (direct exposure);

[0302] Ordinary plastic bag sealing;

[0303] Aluminum-plastic composite bag sealing and vacuumizing;

[0304] According to the experimental conditions, the samples are placed in the accelerated aging test chamber, and samples are taken regularly (0, 1, 2, 4, 8, 12, 16, 20, 24 weeks) for testing.

[0305] Test indicators include:

[0306] Appearance change evaluation (color, shape change);

[0307] Weight change rate measurement;

[0308] Active ingredient content analysis (activity retention rate);

[0309] Mechanical strength change rate;

[0310] Dissolution performance evaluation;

[0311] According to the results of accelerated aging test, the expected shelf life under actual storage conditions is calculated using the Arrhenius equation.

[0312] 6.5.4, Experimental results

[0313] Table 8 Activity retention rate (%) of samples under different conditions

[0314]

[0315] Figure 3 : Activity retention rate change curve of flaky sodium hydrosulfide product under different conditions.

[0316] Table 9 Expected shelf life (months) based on accelerated aging test

[0317]

[0318] Table 10 Effect of different packaging methods on product stability (activity retention rate under 25℃, 75% RH conditions)

[0319]

[0320] The experimental results show that the flaky sodium hydrosulfide product treated by the process has a significantly prolonged shelf life under various storage conditions. Under standard storage conditions (25℃, 50% RH), the expected shelf life of the modified product is 24.2 months, while that of the traditional product is only 5.6 months, which is 4.3 times longer. Under ordinary warehouse conditions (variable temperature and humidity), the expected shelf life of the modified product is 17.6 months, which is 6.3 times longer than that of the traditional product (2.8 months).

[0321] The accelerated aging test data show that even under extreme conditions (55℃, 80% RH), the modified product still retains 90.2% activity after 24 weeks, while the activity of the traditional product is only 28.5%. The packaging method test results show that even without packaging, the activity retention rate of the modified product is still 89.8% after 24 weeks, while the traditional product needs aluminum plastic vacuum packaging to achieve similar results. These results fully verify the significant effect of the process in prolonging the shelf life of the product, providing reliable protection for long-distance transportation and long-term storage of the product.

[0322] The above describes the embodiments of the present application, but the embodiments are not limited to the specific embodiments described above, which are only illustrative but not restrictive. Those skilled in the art can make more equivalent embodiments under the guidance of the embodiments, which are all within the protection scope of the embodiments.

Claims

1. A process for preparing a flaky sodium hydrosulfide, comprising raw material preparation, reaction synthesis, concentration crystallization, separation drying, flaky molding, and surface modification, characterized by, The surface modification comprises the following steps: The production line is divided into three functional areas of plasma pretreatment area, chemical vapor modification area and ultraviolet curing area; An air flow barrier system is arranged between adjacent functional areas to prevent the mixing and contamination of gases from different areas; A pressure gradient is established in the entire production line, and the gas flow direction is from the plasma pretreatment area to the ultraviolet curing area; The sheet-shaped sodium hydrosulfide product is transferred from one functional area to the next functional area through a continuous conveying system; The surface of the sheet-shaped sodium hydrosulfide product is activated in the plasma pretreatment area to form active sites; In the chemical vapor modification area, the active sites react with the precursor gas to form a chemically bonded modification layer; The precursor in the chemical vapor modification is an organosilicon or organofluorine compound with hydrophobic groups and active reaction groups, and the reaction temperature is 60-80℃; the organosilicon or organofluorine compound is octamethylcyclotetrasiloxane, hexamethyldisiloxane or perfluorobutyl ethylene; The chemical modification layer is subjected to ultraviolet irradiation and curing treatment in the ultraviolet curing area to form a moisture-proof protective film.

2. A process for the preparation of a flaky sodium hydrosulfide according to claim 1, characterized in that, The air flow direction in the air flow barrier system is perpendicular to the product conveying direction, the first air flow barrier has a gas flow speed of 0.5-2.0 m / s, and the second air flow barrier has a gas flow speed of 0.5-1.5 m / s.

3. A process for the preparation of flaky sodium hydrosulfide as claimed in claim 1 wherein, The pressure gradient satisfies the relationship P1>P2>P3, where P1 is the pressure of the plasma pretreatment area, P2 is the pressure of the chemical vapor modification area, and P3 is the pressure of the ultraviolet curing area, and the pressure difference between adjacent areas is 20-50 Pa.

4. The process for preparing flaky sodium hydrosulfide according to claim 1, characterized by, The plasma pretreatment uses a low-temperature plasma method, the temperature is controlled within the range of 40-60℃, the plasma gas source is argon or oxygen, the power density is 0.1-0.5 W / cm², and the treatment time is 5-30 seconds.

5. The process for preparing flaky sodium hydrosulfide according to claim 1, wherein The ultraviolet curing treatment uses a combined light source with wavelengths of 254 nm and 365 nm, the light intensity is 50-200 mW / cm², the irradiation time is 3-15 seconds, and the curing process is carried out under the protection of inert gas.

6. The process for preparing flaky sodium hydrosulfide according to claim 1, wherein The gas used in the air flow barrier system is nitrogen or argon.

7. The process for preparing flaky sodium hydrosulfide according to claim 1, wherein The modification layer formed by chemical vapor modification has a thickness of 50-200 nm and a surface contact angle of 110°-150°.

8. A process for the preparation of flaky sodium hydrosulfide as claimed in claim 1 wherein, It also includes a product quality control step, and the detection indicators include: the moisture absorption rate is less than 0.5% after being placed at a temperature of 25℃ and a relative humidity of 90% for 7 days; the compressive strength of the modified product is not less than 130% of the initial value; the surface contact angle is greater than 110°; the peeling rate of the modification layer after tape peeling test is less than 5%; and the effective ingredient utilization rate of the modified product is not less than 95%.

Images