A hydrophobic sustained-release sodium silicate microcapsule and its preparation method

Abstract

This invention provides a hydrophobic sustained-release sodium silicate microcapsule and its preparation method, belonging to the field of microcapsules. The invention provides a core-shell structure for the hydrophobic sustained-release sodium silicate microcapsule, with the core being sodium silicate modified with a coupling agent and the shell being polystyrene. This invention achieves double hydrophobic protection by modifying sodium silicate with a coupling agent and using polystyrene for coating, completely altering the hydrophilic surface of sodium silicate. This effectively blocks the contact between water molecules and sodium silicate, significantly reducing the solubility of sodium silicate in water. At room temperature, the solubility of sodium silicate in water decreases from approximately 40 g / 100 g to 2.2 g / 100 g after 24 hours. This invention also modifies sodium silicate with a coupling agent using silicic acid, greatly improving the interfacial bonding between the highly polar sodium silicate and polystyrene, solving the key problem of poor bonding between the two, resulting in a more uniform, dense, and complete polystyrene coating, avoiding coating layer defects.

Description

Technical Field

[0001] This invention relates to the field of microcapsules, specifically to a hydrophobic sustained-release sodium silicate microcapsule and its preparation method. Background Technology

[0002] Sodium silicate is an important inorganic chemical product widely used in various fields, such as for improving the strength of concrete materials and for slow-release repair of pores, and for bonding and foaming in fire-retardant coatings for steel structures. However, the inherent strong hydrophilicity and high solubility of sodium silicate limit its use in humid environments or in situations requiring isolation from water.

[0003] Microencapsulation technology is a technique that uses film-forming wall materials to encapsulate solid, liquid, or gaseous core materials into tiny particles. This effectively protects the core material from environmental factors and improves or enhances its properties. Currently, most existing sodium silicate microencapsulation technologies focus on direct encapsulation. The main technical challenge in effectively encapsulating highly polar sodium silicate particles while simultaneously imparting excellent hydrophobicity lies in the significant polarity difference between sodium silicate and polystyrene, resulting in poor interfacial bonding and difficulty in forming a complete and dense encapsulation layer. This leads to high solubility, poor water resistance, and short release time in sodium silicate microcapsules. Summary of the Invention

[0004] This invention provides a hydrophobic sustained-release sodium silicate microcapsule and its preparation method. The hydrophobic sustained-release sodium silicate microcapsule of this invention has low solubility, excellent water resistance, and long sustained-release time.

[0005] This invention provides a hydrophobic sustained-release sodium silicate microcapsule with a core-shell structure, wherein the core is sodium silicate modified with a coupling agent and the shell is polystyrene.

[0006] Preferably, the preparation of the coupling agent-modified sodium silicate includes the following steps: Sodium silicate, a coupling agent, water, and an alcohol solvent are mixed and modified to obtain sodium silicate modified with the coupling agent.

[0007] Preferably, the sodium silicate has a modulus of 2 to 3 and a particle size of less than 100 μm.

[0008] Preferably, the mass ratio of sodium silicate to coupling agent is 100:8~10; the coupling agent includes alkylsilane coupling agents, and the alkylsilane coupling agents include hexadecyltrimethoxysilane or phenyltrimethoxysilane.

[0009] Preferably, the mass ratio of sodium silicate to alcohol solvent is 1:1.5~2; the alcohol solvent includes ethanol.

[0010] Preferably, the mass ratio of sodium silicate to water is 100:1~2.

[0011] Preferably, the modification temperature is 50~70℃ and the time is 2~4h.

[0012] Preferably, the mass ratio of the shell to the core is 0.1 to 0.2:1.

[0013] This invention also provides a method for preparing the hydrophobic sustained-release sodium silicate microcapsules described in the above technical solution, comprising the following steps: A solution of sodium silicate modified with a coupling agent was mixed and then added dropwise to a poor solvent for polystyrene to obtain the hydrophobic sustained-release sodium silicate microcapsules.

[0014] The present invention also provides a fire-retardant coating, comprising the following components by mass fraction: The hydrophobic sustained-release sodium silicate microcapsules described in the above technical solution or the preparation method described in the above technical solution contain 35-45% aluminum hydroxide, 35-45% magnesium hydroxide, 5-15% low melting point glass powder, 1-5% latex powder, and 1-5% additives.

[0015] This invention modifies sodium silicate with a coupling agent and coats it with polystyrene to achieve double hydrophobic protection. This completely changes the hydrophilic surface of sodium silicate, making it hydrophobic and increasing the contact angle from 17.2° to about 152.1°. This effectively blocks water molecules from contacting sodium silicate and significantly reduces the solubility of sodium silicate in water. At room temperature, the solubility of sodium silicate in water after 24 hours is reduced from about 40 g / 100 g to 2.2 g / 100 g.

[0016] This invention modifies sodium silicate with a coupling agent, which greatly improves the interfacial bonding between highly polar sodium silicate and polystyrene, solving the key problem of poor bonding between the two. This results in a more uniform, dense, and complete polystyrene coating, avoiding coating layer defects.

[0017] The preparation method of this invention is simple, operates under mild conditions, and is easy to operate and scale up. The wall material can be recycled polystyrene foam, which is inexpensive, and the solvent can be recycled, which is beneficial for industrial production. Attached Figure Description

[0018] Figure 1 The infrared spectra of sodium silicate, modified sodium silicate, and sodium silicate microcapsules in Example 1 are compared. Figure 2 These are scanning electron microscope images of sodium silicate, modified sodium silicate, and sodium silicate microcapsules from Example 1; Figure 3 This is a comparison diagram of the water contact angles of sodium silicate, modified sodium silicate, and sodium silicate microcapsules in Example 1; Figure 4This is a comparison chart of the solubility of sodium silicate, modified sodium silicate, and sodium silicate microcapsules in Example 1; Figure 5 The images show the effect of sodium silicate microcapsules on the surface hydrophobicity of fire-retardant coatings before and after application in Examples 1 and 2. Detailed Implementation

[0019] This invention provides a hydrophobic sustained-release sodium silicate microcapsule with a core-shell structure, wherein the core is sodium silicate modified with a coupling agent and the shell is polystyrene.

[0020] In this invention, the average particle size of the hydrophobic sustained-release sodium silicate microcapsules is preferably 0.2 mm. In this invention, the mass ratio of the shell to the core is preferably 0.1 to 0.2:1, and in a specific embodiment of this invention, it can be 0.15:1.

[0021] In this invention, the preparation of the coupling agent-modified sodium silicate preferably includes the following steps: Sodium silicate, a coupling agent, water, and an alcohol solvent are mixed and modified to obtain sodium silicate modified with the coupling agent.

[0022] In this invention, the mixing preferably includes dispersing sodium silicate in a portion of an alcohol solvent to obtain a dispersion; mixing water with the remaining alcohol solvent and then sequentially mixing the dispersion and the coupling agent. The preferred mass ratio of the partial alcohol solvent to the remaining alcohol solvent is 1.5 to 4:1.

[0023] In this invention, the mass ratio of sodium silicate to coupling agent is preferably 100:8~10, and in specific embodiments of this invention it can be 100:8.5, 100:9 or 100:9.5; the coupling agent preferably includes an alkylsilane coupling agent, and the silane coupling agent preferably includes hexadecyltrimethoxysilane or phenyltrimethoxysilane; the modulus of the sodium silicate is preferably 2.0-3.0 and the particle size is preferably less than 100μm.

[0024] In this invention, the mass ratio of sodium silicate to alcohol solvent is preferably 1:1.5 to 3, and in specific embodiments of this invention it can be 1:1.6, 1:1.7, 1:1.8, 1:2, 1:2.2, 1:2.5 or 1:2.8; the alcohol solvent preferably includes ethanol.

[0025] In this invention, the mass ratio of sodium silicate to water is preferably 100:1~2, and in specific embodiments of this invention it can be 1:1.2, 1:1.5 or 1:1.8.

[0026] In this invention, the preferred temperature for modification is 50~70℃, and the preferred time is 2~4h. In specific embodiments of this invention, the temperature for modification can be 55℃, 60℃ or 65℃, and the time can be 2.5h, 3h or 3.5h.

[0027] After modification, the present invention preferably filters the modified system and then dries the resulting solid.

[0028] This invention also provides a method for preparing the hydrophobic sustained-release sodium silicate microcapsules described in the above technical solution, comprising the following steps: A solution of sodium silicate modified with a coupling agent was mixed and then added dropwise to a poor solvent for polystyrene to obtain the hydrophobic sustained-release sodium silicate microcapsules.

[0029] In this invention, the mass ratio of polystyrene to solvent in the polystyrene solution is preferably 1:7.5~35, and in specific embodiments of this invention, it can be 1:8, 1:10, 1:12, 1:15, 1:18, 1:20, 1:25, 1:28, 1:30 or 1:32; the solvent preferably includes ethyl acetate.

[0030] In this invention, the dripping speed is preferably 0.5 to 2 drops / second, and in specific embodiments of this invention, it can be 1 drop / second or 1.5 drops / second.

[0031] In this invention, the undesirable solvent preferably includes ethanol.

[0032] After the addition is complete, the present invention preferably heats the resulting system and then filters it, and then washes, dries and grinds the resulting solid.

[0033] In this invention, the preferred temperature for the heat treatment is 76-77°C, and the preferred time is 30 minutes. The heat treatment can solidify the shell.

[0034] After heat treatment, one-third to one-half of the solvent in the polystyrene solution evaporates.

[0035] The present invention also provides a fire-retardant coating, comprising the following components by mass fraction: The hydrophobic sustained-release sodium silicate microcapsules described in the above technical solution or the preparation method described in the above technical solution contain 35-45% aluminum hydroxide, 35-45% low melting point glass powder, 5-10% magnesium hydroxide, 1-5% latex powder, and 1-5% additives.

[0036] By mass fraction, the fire-retardant coating of the present invention comprises 35-45% hydrophobic slow-release sodium silicate microcapsules, which may be 36%, 37%, 38%, 39%, 40%, 41%, 42% or 43% in specific embodiments of the present invention.

[0037] The fire-retardant coating of the present invention comprises 35-45% aluminum hydroxide by mass fraction, which may be 36%, 37%, 38%, 39%, 40%, 41%, 42% or 43% in specific embodiments of the present invention.

[0038] The fire-retardant coating of the present invention comprises 5-15% magnesium hydroxide by mass fraction, which may be 6%, 7%, 8%, 9%, 10%, 11%, 12% or 13% in specific embodiments of the present invention.

[0039] The fire-retardant coating of the present invention comprises 5-10% low-melting-point glass powder by mass fraction, which may be 6%, 7%, 8% or 9% in specific embodiments of the present invention; the glass powder preferably comprises Bi2O3-B2O3-ZnO low-melting-point glass powder.

[0040] The fire-retardant coating of the present invention comprises 1 to 5% latex powder by mass fraction, which may be 2%, 3% or 4% in specific embodiments of the present invention.

[0041] The fire-retardant coating of the present invention comprises 1-5% additives by mass fraction, which may be 2%, 3% or 4% in specific embodiments of the present invention. The additives preferably include one or more of dispersants, defoamers and waterproofing agents. The dispersant preferably includes Zhonglianbang DK-70 dispersant; the defoamer preferably includes BASF DF9010F defoamer; and the waterproofing agent preferably includes Yilaitai SEAL81 silicone water-repellent agent.

[0042] The following detailed description of the hydrophobic sustained-release sodium silicate microcapsules and their preparation method provided by the present invention, with reference to the embodiments, should not be construed as limiting the scope of protection of the present invention.

[0043] Example 1 S1. Surface modification of sodium silicate: 20g of ball-milled sodium silicate powder (modulus 2-3, particle size 75μm) was weighed and mixed with 25mL of anhydrous ethanol in a three-necked flask. After stirring at 30℃ for 30min, a mixture of 25mL of anhydrous ethanol and 0.3g of deionized water was added, and stirring continued. Then, 2g of hexadecyltrimethoxysilane (HDTMS) was slowly added dropwise. The temperature was raised to 60℃ and the reaction was maintained at this temperature for 3h. After the reaction was completed, the mixture was filtered, washed with ethanol, and the resulting solid was dried under vacuum at 60℃ for 2h to obtain HDTMS hydrolytically polymerized pre-modified hydrophobic sodium silicate powder.

[0044] S2. Preparation of wall material solution: Weigh 0.75g of polystyrene (EPS) foam particles into a beaker, add 25mL of ethyl acetate, and stir magnetically at room temperature until the EPS is completely dissolved to form a transparent polystyrene solution.

[0045] S3. Preparation of microcapsules: Take 5g of the modified sodium silicate powder prepared in step S1 and add it to the polystyrene solution in step S2. Sonicate the solution for 20 minutes to ensure thorough dispersion. Then, under magnetic stirring, slowly add the mixed suspension dropwise to 50mL of 100mL of anhydrous ethanol at a rate of approximately 1 drop / second. After the addition is complete, slowly raise the system temperature to 76-77℃ and continue stirring for 30 minutes to allow the solvent to fully evaporate and the wall material to solidify. Finally, filter the product, vacuum dry it at 60℃, and grind it into powder to obtain the final hydrophobic sustained-release sodium silicate microcapsules.

[0046] The components of the coating, by mass fraction, are: The composition includes: 43% hydrophobic slow-release sodium silicate microcapsules (or sodium silicate), 36% aluminum hydroxide, 10% magnesium hydroxide, 8% Taizhen Mineral Products 599 low melting point glass powder (purchased from Taizhen Mineral Products Processing Plant in Lingshou County), 2% Wacker 328N latex powder, 0.25% Zhonglianbang DK-70 dispersant, 0.25% BASF DF9010F defoamer, and 0.5% Yilaitai SEAL81 organosilicon hydrophobic agent.

[0047] Example 2 S1. Surface modification of sodium silicate: 20g of ball-milled sodium silicate powder (modulus 2-3, particle size 75μm) was weighed and mixed with 25mL of anhydrous ethanol in a three-necked flask. After stirring at 30℃ for 30min, a mixture of 25mL of anhydrous ethanol and 0.3g of deionized water was added, and stirring continued. Then, 2g of phenyltrimethoxysilane (PTMS) was slowly added dropwise, and the temperature was raised to 60℃ and reacted at this temperature for 3h. After the reaction was completed, the mixture was filtered, washed with ethanol, and the resulting solid was dried under vacuum at 60℃ for 2h to obtain PTMS hydrolytically polymerized pre-modified hydrophobic sodium silicate powder.

[0048] S2. Preparation of wall material solution: Weigh 0.75g of polystyrene (EPS) foam particles into a beaker, add 25mL of ethyl acetate, and stir magnetically at room temperature until the EPS is completely dissolved to form a transparent polystyrene solution.

[0049] S3. Preparation of microcapsules: Take 5g of the modified sodium silicate powder prepared in step S1 and add it to the polystyrene solution in step S2. Sonicate the solution for 20 minutes to ensure thorough dispersion. Then, under magnetic stirring, slowly add the mixed suspension dropwise to 50mL of 100mL of anhydrous ethanol at a rate of approximately 1 drop / second. After the addition is complete, slowly raise the system temperature to 76-77℃ and continue stirring for 30 minutes to allow the solvent to fully evaporate and the wall material to solidify. Finally, filter the product, vacuum dry it at 60℃, and grind it into powder to obtain the final hydrophobic sustained-release sodium silicate microcapsules.

[0050] The components of the coating, by mass fraction, are: The formula consists of 43% hydrophobic slow-release sodium silicate microcapsules, 36% aluminum hydroxide, 10% magnesium hydroxide, 8% Taizhen Mineral Products 599 low melting point glass powder, 2% Wacker 328N latex powder, 0.25% Zhonglianbang DK-70 dispersant, 0.25% BASF DF9010F defoamer, and 0.5% Yilaitai SEAL81 organosilicon hydrophobic agent. Performance tests were conducted to characterize the sodium silicate, modified sodium silicate, and sodium silicate microcapsules prepared above: Figure 1 The image shows a comparison of the infrared spectra of sodium silicate, modified sodium silicate, and sodium silicate microcapsules in Example 1.

[0051] Depend on Figure 1 It can be seen that the modified sodium silicate at 2919 cm⁻¹ -1 and 2850 cm -1 Characteristic peaks of -CH3 and -CH2 appeared at 750 cm⁻¹, and at 750 cm⁻¹... -1 The presence of characteristic Si-O-Si absorption peaks at 1600 cm⁻¹ confirms the successful grafting of polysiloxane. Sodium silicate microcapsules showed absorption peaks at 1600 cm⁻¹. -1 1493 cm -1 1450 cm -1 The presence of benzene ring characteristic peaks of polystyrene in various locations indicates that polystyrene has been successfully coated.

[0052] Figure 2 The images shown are scanning electron microscope (SEM) images of sodium silicate, modified sodium silicate, and sodium silicate microcapsules from Example 1.

[0053] Depend on Figure 2 It can be seen that sodium silicate has a rough surface, and a dense polymer film can be observed on the surface of sodium silicate microcapsules, with a regular morphology and a clear core-shell structure.

[0054] Figure 3 This is a comparison diagram of the water contact angles of sodium silicate, modified sodium silicate, and sodium silicate microcapsules in Example 1. Figure 3It is known that sodium silicate has strong hydrophilicity and a very small contact angle; after modification, the contact angle increases to about 127.3°; the contact angle of sodium silicate microcapsules further increases to about 152.1°, showing excellent hydrophobicity.

[0055] Figure 4 The chart shows a comparison of the solubility of sodium silicate, modified sodium silicate, and sodium silicate microcapsules in Example 1. The test method was to soak 5g of the sample in deionized water at room temperature for 24 hours.

[0056] Depend on Figure 4 It can be seen that the solubility of sodium silicate microcapsules is only about 2.2 g / 100g water, and the water resistance is significantly improved.

[0057] Mix all components of the fire-retardant coating evenly, add an appropriate amount of water and stir until it is smooth and uniform, then apply it evenly to the sample. According to GB 14907-2018 "Fire-retardant Coatings for Steel Structures" standard, the sample was cured for 14 days under the conditions of ambient temperature of 25~30 ℃ and relative humidity of 50~80% before the hydrophobicity was tested.

[0058] Figure 5 The images show the effect of sodium silicate microcapsules on the surface hydrophobicity of fire-retardant coatings before and after application in Examples 1 and 2.

[0059] Before the use of sodium silicate microcapsules in fire-retardant coatings, it referred to sodium silicate itself. After the use of sodium silicate microcapsules in fire-retardant coatings, it refers to the replacement of sodium silicate with sodium silicate by sodium silicate microcapsules.

[0060] Depend on Figure 5 It can be seen that the hydrophobicity of the coating surface has been improved, and the water absorption rate after 12 hours has decreased from 25.6% to 17.3%.

[0061] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A hydrophobic sustained-release sodium silicate microcapsule, characterized in that, It has a core-shell structure, with the core being sodium silicate modified with a coupling agent and the shell being polystyrene.

2. The hydrophobic sustained-release sodium silicate microcapsule according to claim 1, characterized in that, The preparation of the coupling agent-modified sodium silicate includes the following steps: Sodium silicate, a coupling agent, water, and an alcohol solvent are mixed and modified to obtain sodium silicate modified with the coupling agent.

3. The hydrophobic sustained-release sodium silicate microcapsule according to claim 2, characterized in that, The sodium silicate has a modulus of 2 to 3 and a particle size of less than 100 μm.

4. The hydrophobic sustained-release sodium silicate microcapsule according to claim 2, characterized in that, The mass ratio of sodium silicate to coupling agent is 100:8~10; the coupling agent includes alkylsilane coupling agents, and the alkylsilane coupling agents include hexadecyltrimethoxysilane or phenyltrimethoxysilane.

5. The hydrophobic sustained-release sodium silicate microcapsule according to claim 2, characterized in that, The mass ratio of sodium silicate to alcohol solvent is 1:1.5~2; the alcohol solvent includes ethanol.

6. The hydrophobic sustained-release sodium silicate microcapsule according to claim 2, characterized in that, The mass ratio of sodium silicate to water is 100:1~2.

7. The hydrophobic sustained-release sodium silicate microcapsule according to claim 2, characterized in that, The modification temperature is 50~70℃, and the time is 2~4h.

8. The hydrophobic sustained-release sodium silicate microcapsule according to claim 1, characterized in that, The mass ratio of the shell to the core is 0.1 to 0.2:

1.

9. A method for preparing the hydrophobic sustained-release sodium silicate microcapsules according to any one of claims 1 to 8, characterized in that, Includes the following steps: A solution of sodium silicate modified with a coupling agent was mixed and then added dropwise to a poor solvent for polystyrene to obtain the hydrophobic sustained-release sodium silicate microcapsules.

10. A fire-retardant coating, characterized in that, By mass fraction, it includes the following components: The hydrophobic sustained-release sodium silicate microcapsules according to any one of claims 1 to 8 or the hydrophobic sustained-release sodium silicate microcapsules prepared by the preparation method according to claim 9 contain 35-45% aluminum hydroxide, 35-45% magnesium hydroxide, 5-15% low melting point glass powder, 5-10% latex powder, and 1-5% additives.

Images