Organosilicon sealant and preparation method thereof

Abstract

The invention belongs to the technical field of sealants, and particularly relates to an organic silicon sealant and a preparation method thereof.The preparation method comprises the steps that polysiloxane, calcium carbonate and a plasticizer are mixed and dehydrated, and a matrix is obtained; respectively dehydrating the modified calcium carbonate and the modified titanium dioxide to obtain dehydrated calcium carbonate and dehydrated titanium dioxide; after the temperature is reduced to below 50 DEG C, uniformly mixing dehydrated calcium carbonate and an amino-containing silane coupling agent, adding the mixture into a matrix, uniformly mixing dehydrated titanium dioxide and an amino-free silane coupling agent, and adding the mixture into the matrix; and fully mixing and dispersing, continuously adding the catalyst and the auxiliary agent, and stirring and mixing. The organic silicon sealant provided by the invention can be anti-aging in multiple aspects while ensuring the strength of the sealant, and the service life of the product is prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of sealants, and in particular relates to an organosilicon sealant and a preparation method thereof. Background Art

[0002] Silicone sealants are generally composed of base glue, reinforcing fillers, crosslinking agents, catalysts, additives and pigments. They are very commonly used adhesives in the fields of machinery, construction, medical, aerospace and electronics. The organic silica in silicone sealants is mainly a type of silicone resin with alternating silicon atoms and carbon atoms in the main chain, which has the dual characteristics of organic and inorganic substances. It exhibits extremely high adhesion, high permeability and excellent sealing and bonding properties for special materials. It also has the characteristics of high and low temperature resistance, excellent stability in extreme environments and chemical stress. However, compared with other organic resins, silicone resins have the disadvantages of softening after curing and poor bonding properties. Silicone sealants are easily affected by water, heat, light and stress and age, causing the appearance and physical properties of the material to deteriorate, resulting in a shortened service life of silicone sealants. These aging factors first damage the colloid edge with less material, causing aging to often start from the edge of the bonding interface, and the adhesive at the interface loses its function first. This phenomenon has little effect on adhesives for general purposes and will not immediately lose its use value. However, for sealants, once interface separation occurs somewhere, the sealing effect is lost. This aging phenomenon has a great impact on the working life of the sealant. Summary of the invention

[0003] The present invention mainly provides an organic silicon sealant and a preparation method thereof, so as to overcome the problem in the prior art that the organic silicon sealant is easily affected by water, heat, light and stress and ages, thus affecting the sealing effect. The technical scheme is as follows:

[0004] A method for preparing the above-mentioned organic silicon sealant comprises the following steps: mixing polysiloxane, calcium carbonate and a plasticizer and dehydrating them to obtain a matrix; then dehydrating modified calcium carbonate and modified titanium dioxide respectively to obtain dehydrated calcium carbonate and dehydrated titanium dioxide; after the temperature drops below 50°C, mixing the dehydrated calcium carbonate and an amino-containing silane coupling agent, mixing them uniformly and then adding them to the matrix; mixing the dehydrated titanium dioxide and a non-amino-containing silane coupling agent, mixing them uniformly and then adding them to the matrix; fully mixing and dispersing, continuing to add a catalyst and an auxiliary agent, stirring and mixing, and obtaining the sealant.

[0005] Furthermore, the dehydration is performed under vacuum at 105-120° C. for 2-3 hours.

[0006] Further, the preparation of the modified calcium carbonate comprises the following steps: dispersing calcium chloride and ammonium carbonate in an aqueous solution of ethanol, then adding hydroxypropyl-β-cyclodextrin and stirring for 10 - 30 min, and then adding methylimidazolium salt and stirring for reaction for 2 - 4 h; filtering, washing the precipitate with water and drying to obtain the modified calcium carbonate.

[0007] Further, the molar ratio of the calcium chloride to the ammonium carbonate is 1:

[0008] 1.2 - 1.5; the mass ratio of the hydroxypropyl-β-cyclodextrin to the 1-hydroxyethyl-3-methylimidazolium salt is 1:0.5 - 2; the mass ratio of the hydroxypropyl-β-cyclodextrin to the calcium chloride is 1:20 - 50; the volume concentration of ethanol in the aqueous solution of ethanol is 40 - 60%.

[0009] Further, the methylimidazolium salt is one of 1-hydroxyethyl-3-methylimidazolium salt, 1-hydroxypropyl-3-methylimidazolium salt, 1-aminopropyl-3-methylimidazolium salt, and 1-aminoethyl-3-methylimidazolium salt.

[0010] Further, the preparation of the modified titanium dioxide comprises the following steps: mixing potassium carbonate and titanium dioxide with ethanol uniformly; taking liquid polyethylene glycol and adding water, then adding it into the system and grinding for 1 - 2 h; then calcining at 750 - 850 °C for 8 - 12 h to obtain a solid powder; placing the solid powder in a dilute hydrochloric acid solution and stirring for reaction for 4 - 8 h, separating the solid, and repeating the treatment with a new dilute hydrochloric acid solution to obtain a titanium dioxide precursor;

[0011] Dispersing the titanium dioxide precursor and magnesium stearate in an aqueous solution of ethanol, reacting in boiling water for 0.5 - 1 h, then continuing to react at 80 - 90 °C for 1 - 2 h, naturally cooling at room temperature, separating the precipitate, and drying to obtain the product.

[0012] Further, the molar ratio of the potassium carbonate to the titanium dioxide is 1:1.5 - 2.5; the mass ratio of the liquid polyethylene glycol to the titanium dioxide is 1:5 - 8; the mass ratio of the water to the potassium carbonate is 0.2 - 0.6:1.

[0013] Further, the concentration of the dilute hydrochloric acid is 1 - 2 mol / L; the mass ratio of the magnesium stearate to the titanium dioxide is 1:60 - 80.

[0014] An organosilicon sealant prepared by the above preparation method comprises 80 - 120 parts of polysiloxane, 100 - 120 parts of calcium carbonate, 5 - 15 parts of modified calcium carbonate, 5 - 10 parts of modified titanium dioxide, 20 - 30 parts of plasticizer, 5 - 10 parts of silane coupling agent, 3 - 5 parts of crosslinking agent, 0.5 - 1.5 parts of catalyst, and 0.5 - 1 part of auxiliary agent.

[0015] Further, by mass parts, the auxiliary agent includes one or more of ultraviolet absorbers, light stabilizers or antioxidants.

[0016] Adopting the above solution, the method of the present invention has the following advantages:

[0017] 1. The sealant of the present invention has high bonding strength, high dispersibility of filler particles, good thixotropic performance and mechanical properties, and produces small color change after aging, overcoming the problem that polymers containing amino groups are prone to yellowing. And the cyclodextrin compounded on the modified calcium carbonate can form hydrogen bond interaction with the hydroxyl groups on the silane-modified polyether resin, forming physical crosslinking, dispersing stress when being stretched, and reducing the influence of stress on the service life of the sealant.

[0018] 2. The present invention adds titanium dioxide particles with nanoscale size to directly scatter and reflect ultraviolet light, which can greatly reduce the damage of ultraviolet light to the sealant, keep it with high transparency, and extend the service life.

[0019] 3. The present invention first mixes the modified calcium carbonate with the amino-containing silane coupling agent, and at the same time mixes the modified titanium dioxide with the amino-free hydrophobic silane coupling agent, so that the modified calcium carbonate and modified titanium dioxide particles are first dispersed, and the interfacial compatibility between the particles and the organic polymer rubber matrix is improved, solving the problems of easy agglomeration of particles, poor interfacial compatibility of the bonding interface, long mixing period and high energy consumption during direct mixing.

[0020] 5. The lower end and outer wall of the cyclodextrin of the present invention attract calcium carbonate to enrich and grow, and the imidazole at the opening of the cyclodextrin can control the growth of calcium carbonate, promote the dispersion of calcium carbonate crystals, and avoid the over-large particle size of the grown calcium carbonate crystals.

[0021] 6. The methyl group on the 3-methylimidazolium salt of the present invention extends into the hydrophobic inner cavity of the cyclodextrin, while the imidazole part is located at the opening of the cyclodextrin. During the growth process of calcium carbonate, the methyl group is wrapped, forming a stable amphiphilic composite structure, controlling the growth size of calcium carbonate while forming amino modification on calcium carbonate, and improving the dispersibility of the calcium carbonate complex and its affinity with the rubber matrix.

[0022] 7. Polyethylene glycol is added during the preparation of the lamellar potassium titanate composite. The ether bond on the polyethylene glycol controls crystal growth, avoids over-large particles, improves the strength of the colloid, and makes the particles finer, so that a good anti-ultraviolet effect can be achieved by adding a small amount of titanium dioxide.

[0023] 8. The present invention uses magnesium stearate to treat the replaced titanium dioxide, so that anions are tightly loaded on the titanium dioxide, improving the affinity between the titanium dioxide and the rubber matrix and reducing the agglomeration of titanium dioxide.

[0024] 9. An electrostatic interaction occurs between the anions on the modified titanium dioxide of the present invention and the cations on the modified calcium carbonate. Under the action of the hydroxyl groups on the modified calcium carbonate, the interfacial compatibility of titanium dioxide and calcium carbonate with the rubber matrix is improved, further reducing the agglomeration of particles. Moreover, under the connection of the modified titanium dioxide and the modified calcium carbonate, the lubricating effect of magnesium stearate can simultaneously affect the modified titanium dioxide and calcium carbonate, reducing the viscosity of the system and enabling the system to accommodate more fillers. Detailed implementation manners

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0026] Example 1: (1) By mass, take 10 parts of calcium chloride and 10 parts of ammonium carbonate and disperse them sufficiently in an aqueous solution of ethanol with a volume concentration of 40%. Then add 0.3 part of hydroxypropyl-β-cyclodextrin and stir for 20 min. Continue to add 1 part of 1-hydroxyethyl-3-methylimidazolium chloride and stir and react for 3 h. After filtration, wash the precipitate with water and dry it to obtain modified calcium carbonate;

[0027] (2) By mass, mix 14 parts of potassium carbonate and 16 parts of titanium dioxide with ethanol evenly. After mixing 3 parts of liquid polyethylene glycol and 5 parts of water, add them to the system and grind for 2 h. Then calcine at 800 °C for 10 h to obtain a solid powder. Place the solid powder in a 1.5 mol / L dilute hydrochloric acid solution and stir and react for 6 h. Separate the solid and repeat the treatment 3 times with a new dilute hydrochloric acid solution to obtain a titanium dioxide precursor;

[0028] (3) By mass, disperse 60 parts of the titanium dioxide precursor and 1 part of magnesium stearate in an aqueous solution of ethanol with a volume concentration of 60%. React in boiling water for 1 h, and then continue to react at 80-90 °C for 2 h. After natural cooling at room temperature, separate the precipitate and dry it to obtain the product;

[0029] (4) Mix 100 parts of α, ω-dihydroxy polydimethylsiloxane, 110 parts of calcium carbonate and 25 parts of dimethyl silicone oil by mass, and dehydrate them under vacuum at 110-120° C. for 2-3 hours to obtain a matrix; then dehydrate 10 parts of modified calcium carbonate and 8 parts of modified titanium dioxide to obtain dehydrated calcium carbonate and dehydrated titanium dioxide respectively; after the temperature drops below 50° C., mix the dehydrated calcium carbonate and 5 parts of N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, mix them evenly and add them to the matrix; mix the dehydrated titanium dioxide and 3 parts of γ-(2,3-epoxypropoxy)propyltrimethoxysilane, mix them evenly and add them to the matrix; mix and disperse them thoroughly, and then continue to add 1 part of dibutyltin dilaurate, 0.5 parts of Tinuvin326 and 0.2 parts of Tinuvin770DF and 4 parts of vinyltrimethoxysilane, stir and mix to obtain.

[0030] Embodiment 2: The difference from Embodiment 1 is that:

[0031] (1) Taking 10 parts by mass of calcium chloride and 10 parts of ammonium carbonate, dispersing them fully in an aqueous solution of ethanol with a volume concentration of 40%, then adding 0.3 parts of hydroxypropyl-β-cyclodextrin, stirring for 10 to 30 minutes, and then adding 0.25 parts of 1-hydroxyethyl-3-methylimidazolium chloride, stirring and reacting for 2 to 4 hours; after filtering, washing the precipitate with water and drying it to obtain modified calcium carbonate.

[0032] Embodiment 3: The difference from Embodiment 1 is that:

[0033] (1) Taking 10 parts by mass of calcium chloride and 10 parts of ammonium carbonate, dispersing them fully in an aqueous solution of ethanol with a volume concentration of 40%, then adding 0.3 parts of hydroxypropyl-β-cyclodextrin, stirring for 10 to 30 minutes, and then adding 2 parts of 1-hydroxyethyl-3-methylimidazolium chloride, stirring and reacting for 2 to 4 hours; after filtering, washing the precipitate with water and drying it to obtain modified calcium carbonate.

[0034] Embodiment 4: The difference from Embodiment 1 is that:

[0035] (2) By mass, 14 parts of potassium carbonate, 16 parts of titanium dioxide and ethanol were mixed evenly; 3 parts of liquid polyethylene glycol were mixed with 3 parts of water, added to the system, and ground for 2 hours; then calcined at 800°C for 10 hours to obtain a solid powder; the solid powder was placed in a 1.5 mol / L dilute hydrochloric acid solution and stirred for 6 hours, the solid was separated, and the treatment was repeated with a new dilute hydrochloric acid solution to obtain a titanium dioxide precursor.

[0036] Embodiment 5: The difference from Embodiment 1 is that:

[0037] (2) By mass, 14 parts of potassium carbonate, 16 parts of titanium dioxide and ethanol were mixed evenly; 3 parts of liquid polyethylene glycol were mixed with 7 parts of water, added to the system, and ground for 2 hours; then calcined at 800°C for 10 hours to obtain a solid powder; the solid powder was placed in a 1.5 mol / L dilute hydrochloric acid solution and stirred for 6 hours, the solid was separated, and the treatment was repeated with a new dilute hydrochloric acid solution to obtain a titanium dioxide precursor.

[0038] Embodiment 6: The difference from Embodiment 1 is that:

[0039] (3) By weight, 80 parts of titanium dioxide precursor and 1 part of magnesium stearate are dispersed in an aqueous solution of ethanol with a volume concentration of 60%, reacted in boiling water for 1 hour, and then continued to react at 80-90°C for 2 hours. After natural cooling at room temperature, the precipitate is separated and dried to obtain the product.

[0040] Comparative Example 1: The difference from Example 1 is:

[0041] (2) By mass, 14 parts of potassium carbonate, 16 parts of titanium dioxide and ethanol were mixed evenly; 5 parts of water were mixed, added to the system, and ground for 2 hours; then calcined at 800°C for 10 hours to obtain a solid powder; the solid powder was placed in a 1.5 mol / L dilute hydrochloric acid solution and stirred for 6 hours, the solid was separated, and the treatment was repeated with a new dilute hydrochloric acid solution to obtain a titanium dioxide precursor.

[0042] Comparative Example 2: The difference from Example 1 is:

[0043] In parts by mass, 100 parts of α, ω-dihydroxy polydimethylsiloxane, 110 parts of calcium carbonate and 25 parts of dimethyl silicone oil are mixed, and vacuum dehydrated at 110-120° C. for 2-3 hours to obtain a matrix; then 10 parts of modified calcium carbonate are dehydrated to obtain dehydrated calcium carbonate; after the temperature drops below 50° C., the dehydrated calcium carbonate and 5 parts of N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane are mixed, and the mixture is added to the matrix after being evenly mixed; the mixture is fully mixed and dispersed, and 1 part of dibutyltin dilaurate, 0.5 part of Tinuvin326 and 0.2 part of Tinuvin770DF and 3 parts of γ-(2,3-epoxypropoxy)propyltrimethoxysilane and 4 parts of vinyltrimethoxysilane are continuously added, and the mixture is stirred and mixed to obtain the product.

[0044] Comparative Example 3: The difference from Example 1 is:

[0045] By mass, 100 parts of α, ω-dihydroxy polydimethylsiloxane, 110 parts of calcium carbonate and 25 parts of dimethyl silicone oil were mixed and vacuum dehydrated at 110°C for 2-3 hours to obtain a matrix; 8 parts of modified titanium dioxide were dehydrated to obtain dehydrated titanium dioxide; after the temperature dropped below 50°C, the dehydrated titanium dioxide was mixed with 3 parts of γ-(2,3-epoxypropoxy)propyltrimethoxysilane, and the mixture was added to the matrix after being mixed evenly; after being fully mixed and dispersed, 1 part of dibutyltin dilaurate, 0.5 parts of Tinuvin326 and 0.2 parts of Tinuvin770DF, 5 parts of N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane and 4 parts of vinyltrimethoxysilane were added and stirred to obtain the product. .

[0046] Example sample test:

[0047] The tensile strength and elongation at break were measured according to GB / T 528-2009. The surface drying time was measured according to GB / T 13477.5-2002. A transparent plastic sealed tube containing potting glue was placed in it, and after drying for 12 hours, it was allowed to cool naturally, and then placed in a UV irradiation test box for 3 days. After aging, the glue layer color was observed and its surface drying time was measured.

[0048] Table 1:

[0049]

[0050] It can be seen from the above table that, compared with Example 1 and Examples 2 to 3, adding less 1-hydroxyethyl-3-methylimidazolium chloride will significantly reduce the strength of the colloid and affect the surface drying time and aging resistance. However, after reaching the limit of the effect improvement, adding more 1-hydroxyethyl-3-methylimidazolium chloride has limited effect on the strength of the sealant and even begins to have a negative impact on the yellowing resistance.

[0051] When preparing a layered potassium titanate composite, adding water during the grinding process can promote the dispersion of potassium ions and their full contact with titanium dioxide. Example 4 adds less water, while Example 5 adds more water. The aging resistance of Examples 4 and 5 has decreased, indicating that adding too much water is not conducive to morphology control and affects the particle size, or affects the formation of the lamellae and the load of anions. These factors will affect the dispersion of the modified titanium dioxide. When titanium dioxide is modified with magnesium stearate, the magnesium stearate content of Example 6 is relatively less, and the performance of the sealant product is reduced, especially the elongation at break is significantly reduced, indicating that the modification of magnesium stearate is beneficial to improve the toughness of the sealant and improve its ability to withstand stress. The decline in aging resistance in Example 6 shows that magnesium stearate has a significant dispersing effect on titanium dioxide.

[0052] Comparative Example 1 does not add polyethylene glycol to participate in the preparation of modified titanium dioxide, and the strength and elongation at break of the obtained product decrease, especially the yellowing degree after aging is higher, indicating that the polyethylene glycol here has a significant effect on the modified titanium dioxide, and adding polyethylene glycol to participate in the reaction is helpful to improve the aging resistance of the sealant. Comparative Example 2 does not add modified titanium dioxide, and the performance of the obtained sealant decreases, especially the yellowing is obvious after aging, and the surface drying time is significantly increased, indicating that titanium dioxide has a significant effect on the aging resistance of the sealant. Comparative Example 3 does not add modified calcium carbonate, and there is no interaction between modified calcium carbonate and the matrix, and the elongation at break of the sealant decreases significantly, indicating that the stress resistance of the sealant decreases. And the yellow color of Comparative Example 3 after aging is deeper than that of each embodiment, and the surface drying time is also longer, indicating that its aging resistance is also significantly reduced. Combining Comparative Example 2 and Comparative Example 3, it can be seen that the application of modified calcium carbonate and modified titanium dioxide alone cannot comprehensively improve the aging resistance of the sealant. Only by combining modified calcium carbonate and modified titanium dioxide can we obtain a silicone sealant with excellent aging resistance to the greatest extent.

[0053] For those skilled in the art, various other corresponding changes and deformations can be made according to the technical solutions and concepts described above, and all of these changes and deformations should fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing an organosilicon sealant, characterized in that: The polysiloxane, calcium carbonate and plasticizer are mixed and dehydrated to obtain a matrix; then the modified calcium carbonate and modified titanium dioxide are dehydrated respectively to obtain dehydrated calcium carbonate and dehydrated titanium dioxide; after the temperature drops below 50°C, the dehydrated calcium carbonate and the amino-containing silane coupling agent are mixed, and after mixing evenly, the mixture is added to the matrix; the dehydrated titanium dioxide and the non-amino-containing silane coupling agent are mixed, and after mixing evenly, the mixture is added to the matrix; the mixture is fully mixed and dispersed, and a catalyst and an auxiliary agent are continuously added, and the mixture is stirred and mixed to obtain the product.

2. The method for preparing the organosilicon sealant according to claim 1, characterized in that: The dehydration is performed under vacuum at 105-120° C. for 2-3 hours.

3. The method for preparing the organosilicon sealant according to claim 1, characterized in that: The preparation of the modified calcium carbonate comprises the following steps: fully dispersing calcium chloride and ammonium carbonate in an ethanol aqueous solution, then adding hydroxypropyl-β-cyclodextrin, stirring for 10 to 30 minutes, continuously adding methylimidazole salt, stirring and reacting for 2 to 4 hours; after filtering, washing the precipitate with water and drying to obtain the modified calcium carbonate.

4. The method for preparing the organosilicon sealant according to claim 3, characterized in that: The molar ratio of the calcium chloride and ammonium carbonate is 1:1.2-1.5; the mass ratio of the hydroxypropyl-β-cyclodextrin and 1-hydroxyethyl-3-methylimidazolium salt is 1:0.5-2; the mass ratio of the hydroxypropyl-β-cyclodextrin and calcium chloride is 1:20-50; and the volume concentration of ethanol in the ethanol aqueous solution is 40-60%.

5. The method for preparing the organosilicon sealant according to claim 3, characterized in that: The methyl imidazole salt is one of 1-hydroxyethyl-3-methyl imidazole salt, 1-hydroxypropyl-3-methyl imidazole salt, 1-aminopropyl-3-methyl imidazole salt and 1-aminoethyl-3-methyl imidazole salt.

6. The method for preparing the organosilicon sealant according to claim 1, characterized in that: The preparation of the modified titanium dioxide comprises the following steps: Mix potassium carbonate, titanium dioxide and ethanol evenly; take liquid polyethylene glycol and add water, then add it to the system and grind for 1 to 2 hours; then calcine at 750 to 850°C for 8 to 12 hours to obtain a solid powder; place the solid powder in a dilute hydrochloric acid solution and stir to react for 4 to 8 hours, separate the solid, and repeat the treatment with a new dilute hydrochloric acid solution to obtain a titanium dioxide precursor; The titanium dioxide precursor and magnesium stearate are dispersed in an aqueous solution of ethanol, reacted in boiling water for 0.5 to 1 hour, and then continued to react at 80 to 90°C for 1 to 2 hours. After natural cooling at room temperature, the precipitate is separated and dried to obtain the product.

7. The method for preparing the organosilicon sealant according to claim 6, characterized in that: The mass ratio of the potassium carbonate to the titanium dioxide is 1:1.5-2.5; the mass ratio of the liquid polyethylene glycol to the titanium dioxide is 1:5-8; and the mass ratio of the water to the potassium carbonate is 0.2-0.6:

1.

8. The method for preparing the organosilicon sealant according to claim 6, characterized in that: The concentration of the dilute hydrochloric acid is 1-2 mol / L; the mass ratio of the magnesium stearate to titanium dioxide is 1:60-80.

9. An organic silicon sealant prepared by the preparation method according to any one of claims 1 to 8, characterized in that: It comprises 80-120 parts of polysiloxane, 100-120 parts of calcium carbonate, 5-15 parts of modified calcium carbonate, 5-10 parts of modified titanium dioxide, 20-30 parts of plasticizer, 5-10 parts of silane coupling agent, 3-5 parts of cross-linking agent, 0.5-1.5 parts of catalyst and 0.5-1 part of auxiliary agent.

10. The organic silicon sealant according to claim 9, characterized in that: In parts by mass, the auxiliary agent includes one or more of a UV absorber, a light stabilizer or an antioxidant.

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