Water-based organic silicon resin capable of being dried to form film at low temperature of-5 DEG C and preparation method of water-based organic silicon resin

Abstract

The invention belongs to the technical field of organic silicon resin, and particularly discloses water-based organic silicon resin capable of being dried to form a film at the low temperature of-5 DEG C and a preparation method of the water-based organic silicon resin. The water-based organic silicon resin is prepared from the following components in parts by mass: 58 to 62 parts of mixed silane monomer, 7.5 to 8.5 parts of 2-acrylamido-2-methylpropanesulfonic acid, 14 to 16 parts of HYDROSIL 2926, 3.5 to 4.0 parts of ethylene glycol, 1.8 to 2.2 parts of ethanol, 1.4 to 1.6 parts of initiator and deionized water. The mixed silane monomer is prepared from the following components in percentage by mass: 45.5 to 48.0 percent of phenyl trimethoxy silane, 34.5 to 37.0 percent of methyl trimethoxy silane, 7.8 to 8.5 percent of diphenyl dimethoxy silane, 6.0 to 6.8 percent of dimethyl dimethoxy silane and 2.8 to 3.0 percent of vinyl trimethoxy silane, and the prepared resin can quickly form a film at the temperature of-5 DEG C and has excellent cold resistance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of silicone resins, and particularly relates to a water-based silicone resin capable of being dried and formed into a film at a low temperature of-5 DEG C and a preparation method thereof. BACKGROUND

[0002] With increasingly stringent environmental regulations, water-based silicone resins have become an important development direction in the field of industrial coatings due to their low VOC characteristics. However, the drying performance bottleneck at low temperatures (<5 DEG C) seriously limits the actual application: the rapid decrease in water evaporation rate leads to a significant extension of the film formation time (drying time at 0 DEG C can be more than 10 hours), and the uncured coating is prone to defects such as sagging and shrinkage, which directly affects the construction efficiency and coating quality. The existing technology usually improves the low-temperature performance by adding high-boiling-point organic solvents or reducing the crosslinking degree of the resin, but the mechanical strength and weather resistance of the coating are sacrificed. Therefore, it is urgent to develop a water-based silicone resin that can be quickly dried and formed into a film below 0 DEG C while maintaining excellent performance. SUMMARY

[0003] In view of the deficiencies of the prior art, the present application provides a water-based silicone resin capable of being dried and formed into a film at a low temperature of-5 DEG C and a preparation method thereof. The water-based silicone resin has a composition by mass fraction of 58-62 parts of mixed silane monomers, 7.5-8.5 parts of 2-acrylamido-2-methylpropanesulfonic acid, 14-16 parts of HYDROSIL 2926, 3.5-4.0 parts of ethylene glycol, 1.8-2.2 parts of ethanol, 1.4-1.6 parts of an initiator, and deionized water in an amount of 45-50% by non-volatile fraction.

[0004] Further, the mixed silane monomers are composed of raw materials in the following mass percentages: 45.5-48.0% of phenyltrimethoxysilane (PhTMS), 34.5-37.0% of methyltrimethoxysilane (MTMS), 7.8-8.5% of diphenyldimethoxysilane (DPhDMS), 6.0-6.8% of dimethyldimethoxysilane (DMDMS), and 2.8-3.0% of vinyltrimethoxysilane (VTMS).

[0005] The combination of mixed silane monomers adopts phenyltrimethoxysilane (PhTMS), methyltrimethoxysilane (MTMS), diphenyldimethoxysilane (DPhDMS), dimethyldimethoxysilane (DMDMS) and vinyltrimethoxysilane (VTMS), the R / Si ratio (R is a substituent) and the ratio of phenylsilane and methylsilane are optimized to ensure the balance between flexibility and crosslinking density; 2-acrylamido-2-methylpropanesulfonic acid (AMPS) is used as an emulsifier and is introduced by free radical grafting to give the resin self-emulsifying ability, avoid additional addition of surfactants, and reduce the chemical medium resistance and weather resistance caused by the residual surfactants; HYDROSIL 2926 is used as a crosslinking agent / solvent, which has the functions of crosslinking and resin dissolving, and improves the low-temperature reaction activity; ethylene glycol is used as an antifreezing agent to reduce the freezing point of the emulsion and prevent freezing at low temperature, and it is also a chain extender to improve the crosslinking density; the addition of N,N-dimethylformamide (DMF) and ethanol improves the resin solubility and stability.

[0006] Further, the initiator is BPO.

[0007] Further, the preparation method of the aqueous organosilicon resin comprises the following steps: (1) Mix the mixed silane monomers, anhydrous ethanol and DMF, and cool to 2-6°C.

[0008] Preferably, the volume ratio of the anhydrous ethanol and DMF is 3-4:1.

[0009] (2) Slowly add 2-acrylamido-2-methylpropanesulfonic acid AMPS aqueous solution under nitrogen protection, control the temperature <15°C, and stir for 2.5-4 hours, the 2-acrylamido-2-methylpropanesulfonic acid AMPS aqueous solution is prepared by dissolving 2-acrylamido-2-methylpropanesulfonic acid in a mixed solvent of water and DMF, and the volume ratio of water and DMF in the mixed solvent of water and DMF is 3-4:1.

[0010] (3) Stop the nitrogen, vacuum ≥400mmHg, remove the methanol and small molecules for half an hour, then raise the vacuum to ≥700mmHg, gradually heat to 88-93°C for condensation, until no by-products (water and other small molecules) are evaporated, to obtain a transparent prepolymer.

[0011] (4) Heat to 69-72°C, add an initiator to initiate a grafting reaction, and keep the temperature for 2.5-3 hours, and monitor the viscosity to 2000-4000 mPa·s.

[0012] (5) Cool to 39-42°C, add HYDROSIL 2926 and 2926, ethylene glycol, ethanol and deionized water, and then high-speed shear emulsify.

[0013] Preferably, the high-speed shearing emulsification speed is 8000 rpm, and the time is 30 minutes.

[0014] (6) Adjust the pH to 7-8 with ammonia water, filter, and obtain the aqueous silicone resin with a solid content of 45-50%.

[0015] Advantages of the present application: The resin prepared by optimizing the combination of phenylsilane monomers, methylsilane monomers, introducing AMPS self-emulsifier, HYDROSIL 2926 crosslinking agent, and ethylene glycol antifreeze agent can still quickly form a film at-5℃, and has excellent cold resistance, mechanical strength, high temperature resistance, and weather resistance, can dry and form a film at-5℃, and the surface drying time is ≤4 hours. DETAILED DESCRIPTION

[0016] The present application will be further described below in conjunction with examples.

[0017] Example 1

[0018] (1) Mix 60 parts of mixed silane monomers, 90 parts of anhydrous ethanol, and 30 parts of DMF, and cool to 5℃; (2) Slowly drop 2-acrylamido-2-methylpropanesulfonic acid AMPS aqueous solution (pH 4-5) under nitrogen protection, control the temperature <15℃, and stir for 3 hours, wherein the 2-acrylamido-2-methylpropanesulfonic acid AMPS aqueous solution is prepared by dissolving 8 parts of 2-acrylamido-2-methylpropanesulfonic acid in a mixed solvent of 9 parts of water and 3 parts of DMF; (3) Stop the nitrogen, vacuum ≥400mmHg, remove the methanol and small molecules for half an hour, then raise the vacuum to ≥700mmHg, and gradually heat to 90℃ for condensation, until no by-products (water and other small molecules) are evaporated, to obtain a transparent prepolymer; (4) Heat to 70℃, add 1.5 parts of BPO to initiate grafting reaction, and heat for 3 hours, and monitor the viscosity to 2000-4000mPa·s; (5) Cool to 40℃, add 15 parts of HYDROSIL 2926 and 3.5 parts of ethylene glycol, 2 parts of ethanol, and deionized water, and then high-speed shearing emulsification (8000 rpm, 30 minutes); (6) Adjust the pH to 7-8 with ammonia water, filter, and obtain the aqueous silicone resin with a solid content of 45%.

[0019] The mixed silane monomer is composed of raw materials with the following mass percentages: 46.6% phenyltrimethoxysilane (PhTMS), 35.9% methyltrimethoxysilane (MTMS), 8.3% diphenyldimethoxysilane (DPhDMS), 6.3% dimethyldimethoxysilane (DMDMS), and 2.9% vinyltrimethoxysilane (VTMS).

[0020] The prepared aqueous silicone resin has a silica content of 52.8% (mass content) and a molecular weight Mw of 3200 (determined by GPC).

[0021] Example 2

[0022] The difference between Example 2 and Example 1 is that the mixed silane monomer is composed of raw materials with the following mass percentages: 46% phenyltrimethoxysilane (PhTMS), 36.5% methyltrimethoxysilane (MTMS), 8% diphenyldimethoxysilane (DPhDMS), 6.6% dimethyldimethoxysilane (DMDMS), and 2.9% vinyltrimethoxysilane (VTMS), and the rest is the same as in Example 1.

[0023] Example 3

[0024] The difference between Example 3 and Example 1 is that the mixed silane monomer is composed of raw materials with the following mass percentages: 47.5% phenyltrimethoxysilane (PhTMS), 35% methyltrimethoxysilane (MTMS), 8.3% diphenyldimethoxysilane (DPhDMS), 6.3% dimethyldimethoxysilane (DMDMS), and 2.9% vinyltrimethoxysilane (VTMS), and the rest is the same as in Example 1.

[0025] Example 4

[0026] The difference between Example 4 and Example 1 is that the aqueous silicone resin has the following mass fraction composition: 58 parts of mixed silane monomer, 8.5 parts of 2-acrylamido-2-methylpropanesulfonic acid, 16 parts of HYDROSIL 2926, 3.5 parts of ethylene glycol, 2.2 parts of ethanol, 1.6 parts of BPO, and the amount of deionized water is controlled to be 45% non-volatile parts, and the rest is the same as in Example 1.

[0027] Example 5

[0028] The difference between Example 5 and Example 1 is that the aqueous silicone resin has the following mass fraction composition: 62 parts of mixed silane monomer, 7.5 parts of 2-acrylamido-2-methylpropanesulfonic acid, 14 parts of HYDROSIL 2926, 4.0 parts of ethylene glycol, 1.8 parts of ethanol, 1.4 parts of BPO, and the amount of deionized water is controlled to be 45% non-volatile parts.

[0029] Comparative Example 1

[0030] The difference between Comparative Example 1 and Example 1 is that the mixed silane monomer is composed of the following raw materials in the following mass percentages: 48.5% phenyltrimethoxysilane (PhTMS), 34.2% methyltrimethoxysilane (MTMS), 8.3% diphenyldimethoxysilane (DPhDMS), 6.3% dimethyldimethoxysilane (DMDMS), and 2.9% vinyltrimethoxysilane (VTMS).

[0031] Comparative Example 2

[0032] The difference between Comparative Example 2 and Example 1 is that the mixed silane monomer is composed of the following raw materials in the following mass percentages: 36.5% phenyltrimethoxysilane (PhTMS), 40.0% methyltrimethoxysilane (MTMS), 8.0% diphenyldimethoxysilane (DPhDMS), 12.5% ​​dimethyldimethoxysilane (DMDMS), and 3% vinyltrimethoxysilane (VTMS).

[0033] Comparative Example 3

[0034] The difference between Comparative Example 3 and Example 1 is that HYDROSIL 2926 is replaced with KH-570, otherwise it is the same as Example 1.

[0035] Comparative Example 4

[0036] The difference between Comparative Example 4 and Example 1 is that HYDROSIL 2926 is replaced with KH-560, otherwise it is the same as Example 1.

[0037] Comparative Example 5

[0038] The difference between Comparative Example 5 and Example 1 is that HYDROSIL 2926 is replaced with A-171, otherwise it is the same as Example 1.

[0039] The low-temperature film-forming properties and cold resistance of the waterborne organosilicon resins prepared in Comparative Examples 1-4 and Examples 1-5 were tested.

[0040] The test method for low-temperature film formation is as follows: water-based silicone resin is uniformly coated on a clean tinplate, and the wet film thickness is controlled at 20 μm. The coated test plate is placed in an environment of -5±0.5℃. The film surface is lightly touched with a finger every 15 minutes. The time is recorded when no emulsion adheres to the finger and no fingerprint remains.

[0041] The cold resistance test method is as follows: water-based silicone resin is coated on a standard Q235 steel plate with a wet film thickness of 50 μm and cured at -5℃ for 7 days; then it is placed at -30±2℃ for 4 hours, transferred to 25±2℃ and left to stand for 2 hours to complete one cycle, and a total of 10 cycles are performed; after the cycle, the coating surface is observed with a 10x magnifying glass, and the phenomena (no cracking, micro-cracks or obvious cracking) and the maximum crack length are recorded.

[0042] The test results are as follows.

[0043] Table 1. Performance test results of the waterborne organosilicon resins prepared in Comparative Examples 1-4 and Examples 1-5

[0044] Comparing the data in Table 1, the waterborne silicone resins of Examples 1-5 showed excellent overall performance in the low-temperature performance test: the surface drying time of all examples at -5°C was 3.0 to 4.0 hours, with Examples 3 and 5 having the shortest time of 3.0 hours, and no cracking after freezing cycles at -30°C. The micro-defects of <0.1 mm in Example 2 were still within the safe range. Comparative Example 1 increased the phenyl content (increasing the amount of phenyl silane monomer added and decreasing the amount of methyl silane monomer added). Due to the excessive phenyl content, insufficient crosslinking occurred, resulting in prolonged surface drying time and poor cold resistance. The surface drying time was extended to 5.5 hours, and a significant crack of 2 mm was induced. Comparative Example 2 increased the methyl content (increasing the amount of methyl silane monomer added and decreasing the amount of phenyl silane monomer added). Due to the excessive rigid monomer and the imbalance of flexibility, brittleness was induced, resulting in a sharp increase in surface drying time to 8 hours and the formation of a deep crack of 4 mm. Comparative Examples 3-5 replaced HYDROSIL 2926 with KH-570 / KH-560 / A-171. Due to the lack of flexible buffering capacity of the rigid crosslinking agent, the surface drying time was delayed to 5.5-7.5 hours and a through crack of >2.5 mm was caused. In Comparative Example 4, the epoxy shrinkage of KH-560 reached >5.0 mm. These consequences collectively confirm that only under the formulation system defined in this application can both rapid surface drying and extreme cold resistance without cracking during -30°C cycling be achieved simultaneously. Any deviation of any component will lead to a decrease in low-temperature film formation and cold resistance.

[0045] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A water-based organosilicon resin that can be dried and formed into a film at -5°C, characterized in that: The waterborne silicone resin comprises, by weight, 58-62 parts mixed silane monomers, 7.5-8.5 parts 2-acrylamido-2-methylpropanesulfonic acid, 14-16 parts HYDROSIL 2926, 3.5-4.0 parts ethylene glycol, 1.8-2.2 parts ethanol, 1.4-1.6 parts initiator, and deionized water with a non-volatile content controlled at 45-50%. The mixed silane monomer is composed of the following raw materials in the following mass percentages: 45.5~48.0% phenyltrimethoxysilane, 34.5~37.0% methyltrimethoxysilane, 7.8~8.5% diphenyldimethoxysilane, 6.0~6.8% dimethyldimethoxysilane, and 2.8~3.0% vinyltrimethoxysilane.

2. The aqueous organosilicon resin that can be dried and formed into a film at -5°C as described in claim 1, characterized in that: The initiator is BPO.

3. A method for preparing an aqueous organosilicon resin that can be dried and formed into a film at -5°C as described in claim 1, characterized in that, Includes the following steps: (1) Mix the mixed silane monomers, anhydrous ethanol and DMF, and cool to 2~6℃; (2) Under nitrogen protection, slowly add 2-acrylamido-2-methylpropanesulfonic acid AMPS aqueous solution, control the temperature <15℃, and stir for 2.5~4 hours; (3) Stop the nitrogen gas flow, evacuate to a vacuum of ≥400 mmHg, remove methanol and small molecules and maintain for half an hour, then raise the vacuum to ≥700 mmHg, gradually raise the temperature to 88~93℃ for polycondensation until no by-products are distilled out, and obtain a transparent prepolymer. (4) Heat to 69~72℃, add initiator to initiate grafting reaction, keep warm for 2.5~3 hours, and monitor viscosity to 2000-4000mPa·s; (5) Cool down to 39~42℃, add HYDROSIL 2926, ethylene glycol, ethanol, and deionized water, and then emulsify by high-speed shearing; (6) Adjust the pH to 7-8 with ammonia water, filter, and obtain the water-based organosilicon resin.

4. The method for preparing an aqueous organosilicon resin that can be dried and formed into a film at -5°C as described in claim 3, characterized in that, The volume ratio of anhydrous ethanol to DMF in step (1) is 3~4:

1.

5. The method for preparing the aqueous organosilicon resin that can be dried and formed into a film at -5℃ as described in claim 3, characterized in that, The 2-acrylamido-2-methylpropanesulfonic acid AMPS aqueous solution in step (2) is prepared by dissolving 2-acrylamido-2-methylpropanesulfonic acid in a mixed solvent of water and DMF; the volume ratio of water to DMF in the mixed solvent of water and DMF is 3~4:

1.

6. The method for preparing the aqueous organosilicon resin that can be dried and formed into a film at -5℃ as described in claim 3, characterized in that, The high-speed shear emulsification in step (5) is performed at a speed of 8000 rpm for 30 minutes.

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