Sealant capable of being stored stably in high-temperature environment and preparation method thereof

Abstract

The invention belongs to the technical field of sealants, and particularly discloses a sealant capable of being stored stably in a high-temperature environment and a preparation method of the sealant. The sealant is prepared from the following components in parts by weight: 100 parts of alkoxy-terminated polydimethylsiloxane; 20 to 80 parts of dimethyl silicone oil; 180 to 300 parts of an inorganic filler; 2-8 parts of a molecular sieve catalyst; 1-8 parts of a cross-linking agent; 0.5 to 1.5 parts of a coupling agent; the preparation method of the molecular sieve catalyst comprises the following steps: carrying out hydrothermal crystallization on a mixed solution containing dimethylamine, pseudo-boehmite, phosphoric acid and water, washing, and roasting to obtain a molecular sieve; the preparation method comprises the following steps: adding toluene and titanium diisopropoxy diacetoacetate into a flask in an inert atmosphere, stirring at a material temperature of 25-55 DEG C, adding a molecular sieve, stirring, filtering, and drying in vacuum to obtain the molecular sieve catalyst. The sealant disclosed by the invention has the advantages of excellent performance, high storage stability, no viscosity peak phenomenon in a sealant preparation process and the like.

Description

Technical Field

[0001] This invention relates to the field of sealant technology, and in particular to a sealant that is stable in storage at high temperatures and its preparation method. Background Technology

[0002] Silicone sealant is a polysiloxane-based adhesive, mixed with crosslinking agents, fillers, plasticizers, coupling agents, catalysts, and other additives under vacuum. Also known as organosilicon sealant, it cures to form a high-molecular-weight elastic silicone rubber. Due to its excellent weather resistance, temperature resistance, electrical insulation, and chemical stability, silicone sealant is widely used for sealing joints in the electronics, construction, automotive, and aerospace industries. With the rapid development of the construction market, some extremely hot regions and operating environments are placing higher demands on the high-temperature storage performance of sealants.

[0003] Patent application CN201710077333.8 provides a high-temperature resistant silicone sealant formulation. While the high-temperature resistance of the sealant is improved, the addition of excessive metal oxides significantly reduces its tensile properties. Patent application CN201810177897.3 also provides a high-temperature resistant silicone sealant formulation. By modifying nano-kaolin and silicone oil, and compounding with a silane coupling agent, the high-temperature resistance of the product is improved. This method involves a complex process, significantly increasing the production cost of the sealant, and resulting in poor product stability. Patent CN 110862801A provides a method for preparing a sealant with a long shelf life. This invention utilizes the compatibility of oxygen ether with hydrophilic silica and hydrophobic silicon materials to effectively remove moisture, thereby extending the sealant's shelf life. However, this method has high requirements for raw materials, severely limiting the types of sealants that can be prepared.

[0004] In the actual production of sealants, after the titanate catalyst is added to the base adhesive, the viscosity will rise sharply in a short period of time during the stirring and dispersion process, resulting in material climbing the rod and paddle. This process is called the viscosity peak of the sealant. The occurrence of the viscosity peak will affect the appearance and performance of the sealant in actual production, reduce the actual production efficiency and product qualification rate. At the same time, the material thickening due to the sharp increase in viscosity will cause the current of the dispersion motor to surge in a short time or even jam, seriously damaging the service life of the equipment. Summary of the Invention

[0005] In view of the above-mentioned problems, the present invention provides a sealant that is stable in storage under high temperature conditions and its preparation method. The sealant of the present invention has the advantages of excellent performance (tensile strength, elongation, surface drying time), strong storage stability, and no viscosity peak phenomenon during the compounding process.

[0006] To address the above problems, the present invention provides a sealant that is stable in high-temperature environments, comprising the following components by weight:

[0007] 100 parts of alkoxy-terminated polydimethylsiloxane;

[0008] 20-80 parts of dimethyl silicone oil;

[0009] Inorganic filler 180-300 parts;

[0010] 2-8 parts of molecular sieve catalyst;

[0011] 1-8 parts of crosslinking agent;

[0012] 0.5-1.5 parts of coupling agent;

[0013] The preparation method of the molecular sieve catalyst includes the following steps:

[0014] S1. A molecular sieve is obtained by hydrothermal crystallization of a mixture containing dimethylamine, boehmite, phosphoric acid and water, followed by washing and calcination.

[0015] S2. Under an inert atmosphere, toluene and ethyl diisopropoxydiacetate titanium were added to a flask and stirred at a material temperature of 25-55℃ for 0.5-5 h. Then, the molecular sieve was added, and the mixture was stirred for 3-10 h. After filtration and vacuum drying, the molecular sieve catalyst was obtained. The mass ratio of toluene to ethyl diisopropoxydiacetate titanium was 3-6:1, and the mass ratio of molecular sieve to ethyl diisopropoxydiacetate titanium was 1-2:1.

[0016] Preferably, in step S1, the molar ratio of dimethylamine, boehmite, phosphoric acid and water is 2.0-4.8:0.4-1.2:1:50-150.

[0017] Preferably, in step S1, the hydrothermal crystallization temperature is 120-200℃ and the time is 12-30h.

[0018] Preferably, in step S1, the calcination temperature is 450-650℃ and the time is 4-8h.

[0019] Preferably, the alkoxy-terminated polydimethylsiloxane has a viscosity of 5000-50000 mPa·s at 25°C.

[0020] Preferably, the dimethyl silicone oil has a viscosity of 100-2000 mPa·s at 25°C.

[0021] Preferably, the inorganic filler is at least one of activated nano calcium carbonate, heavy calcium carbonate, carbon black, and silica.

[0022] Preferably, the crosslinking agent is at least one selected from methyltrimethoxysilane, propyltrimethoxysilane, octyltrimethoxysilane, phenyltrimethoxysilane, and vinyltrimethoxysilane.

[0023] Preferably, the coupling agent is at least one of γ-(2,3-epoxypropoxy)propyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-aminopropyltriethoxysilane, and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane.

[0024] Based on the same inventive concept, this invention also discloses a method for preparing any of the above-mentioned high-temperature stable sealants, comprising the following steps:

[0025] The alkoxy-terminated polydimethylsiloxane, dimethyl silicone oil, and inorganic filler are added to a reactor. After low-speed stirring to absorb the powder, the material temperature is set to 60-110℃, the rotation speed to 400-1000 rpm, and the vacuum degree to -0.08~-0.099 MPa. The mixture is stirred, dehydrated, and blended for 20-200 min. The vacuum is then released with nitrogen, and the material is cooled with cooling water until it does not exceed 40℃. The crosslinking agent, coupling agent, and molecular sieve catalyst are added. The mixture is stirred under a nitrogen atmosphere for 10-100 min, followed by vacuum stirring at a vacuum degree of -0.08~-0.099 MPa. The material temperature is maintained below 40℃, the rotation speed is 200-400 rpm, and the stirring time is 40-120 min. The mixture is then degassed and discharged.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] (1) The molecular sieve prepared by the present invention has a large specific surface area. The hydroxyl groups on its surface react with diisopropoxydiacetoacetate titanium, and some diisopropoxydiacetoacetate titanium is adsorbed in the molecular sieve pores. As a result, the prepared molecular sieve catalyst is slowly released during the storage of the sealant, and the sealant curing performance remains good.

[0028] (2) Compared with traditional liquid catalysts, the molecular sieve catalyst prepared by the present invention can avoid the viscosity peak phenomenon caused by the catalyst when the liquid catalyst is added to the slurry during the preparation process; at the same time, due to the pore effect of the molecular sieve, the molecular sieve catalyst prepared by the present invention can effectively adsorb small alcohol molecules released during the curing process of the sealant, which further improves the storage stability of the sealant. Detailed Implementation

[0029] To make the present invention easier to understand, specific embodiments are described below to further illustrate the invention. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical terms used below have the same meaning as understood by those skilled in the art; unless otherwise specified, the raw materials and reagents involved herein can be purchased commercially or obtained by known methods.

[0030] To address the problems existing in the background technology, this invention provides a sealant that is stable in storage under high temperature conditions and its preparation method. The sealant of this invention has advantages such as excellent performance (tensile strength, elongation, surface drying time), strong storage stability, and no viscosity peak phenomenon during the mixing process.

[0031] The following examples and comparative models further illustrate this point.

[0032] Example 1

[0033] A method for preparing a molecular sieve catalyst includes the following steps:

[0034] (1) Add deionized water to a certain amount of phosphoric acid, and add boehmite while stirring. After stirring evenly, slowly add the template agent dimethylamine and stir for 24 hours to obtain a mixture. The molar ratio of each substance in the mixture is 3.2:0.8:1:80 for (CH3)2NH4, Al2O3, P2O5 and H2O. After the solution is fully mixed, pour the mixture into a stainless steel hydrothermal reactor lined with polytetrafluoroethylene and seal it. Hydrothermal crystallize it in an oven at 160℃ for 20 hours to obtain the molecular sieve precursor. Wash the obtained precursor molecular sieve with deionized water and centrifuge until it is nearly neutral. Calcine it in a muffle furnace at 550℃ for 7 hours to remove the template agent. The product obtained is the molecular sieve.

[0035] Under nitrogen protection, 200g of toluene and 40g of diisopropoxydiacetoacetate titanium were added to a flask and stirred at 45°C for 1 hour. Then, 40g of the molecular sieve prepared above was added and stirred for 5 hours. The remaining solvent was filtered off and the resulting product was collected and dried completely under vacuum to obtain the molecular sieve catalyst.

[0036] Example 2

[0037] A method for preparing a sealant that is stable in high-temperature environments includes the following steps:

[0038] 100 parts of alkoxy-terminated polydimethylsiloxane with a viscosity of 50000 mPa·s, 40 parts of dimethyl silicone oil with a viscosity of 200 mPa·s, 130 parts of active nano-calcium carbonate, and 110 parts of heavy calcium carbonate were added to a reactor. After the powder was absorbed by low-speed stirring, the material temperature was set to 80℃, the rotation speed to 600 rpm, and the vacuum degree to -0.085 MPa. The mixture was stirred, dehydrated, and blended for 60 minutes. The vacuum was released with nitrogen, and the material was cooled to 35℃ with cooling water. 5 parts of methyltrimethoxysilane, 1 part of γ-(2,3-epoxypropoxy)propyltrimethoxysilane, and 5 parts of molecular sieve catalyst (Example 1) were added. The mixture was stirred for 30 minutes under a nitrogen atmosphere, and then vacuum stirred at a vacuum degree of -0.095 MPa. The material temperature was maintained at 35℃, the rotation speed to 240 rpm, and the mixture was stirred for 50 minutes. The mixture was then degassed and discharged. The product performance indicators are shown in Table 1-2.

[0039] Example 3

[0040] 100 parts of alkoxy-terminated polydimethylsiloxane with a viscosity of 50000 mPa·s, 60 parts of dimethyl silicone oil with a viscosity of 200 mPa·s, 80 parts of silica, and 130 parts of heavy calcium carbonate were added to a reactor. After the powder was absorbed by low-speed stirring, the material temperature was set to 80℃, the rotation speed to 600 rpm, and the vacuum degree to -0.085 MPa. The mixture was stirred, dehydrated, and blended for 60 minutes. The vacuum was released with nitrogen, and the material was cooled to 35℃ with cooling water. Then, 3 parts of vinyltrimethoxysilane, 0.2 parts of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, 0.5 parts of γ-aminopropyltriethoxysilane, and 4 parts of molecular sieve catalyst (Example 1) were added. The mixture was stirred for 30 minutes under a nitrogen atmosphere, and then vacuum stirred at -0.095 MPa. The material temperature was maintained at 35℃, the rotation speed was 240 rpm, and the mixture was stirred for 60 minutes. The mixture was then degassed and discharged. The product performance indicators are shown in Table 1-2.

[0041] Example 4

[0042] 100 parts of alkoxy-terminated polydimethylsiloxane with a viscosity of 50000 mPa·s, 30 parts of dimethyl silicone oil with a viscosity of 200 mPa·s, 150 parts of active nano-calcium carbonate, and 50 parts of carbon black were added to a reactor. After the powder was absorbed by low-speed stirring, the material temperature was set to 80℃, the rotation speed to 600 rpm, and the vacuum degree to -0.085 MPa. The mixture was stirred, dehydrated, and blended for 60 minutes. The vacuum was released by nitrogen, and the material was cooled to 35℃ by cooling water. 6.5 parts of octyltrimethoxysilane, 1.2 parts of β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and 7 parts of molecular sieve catalyst (Example 1) were added. The mixture was stirred for 30 minutes under a nitrogen atmosphere, and then vacuum stirred at a vacuum degree of -0.095 MPa. The material temperature was maintained at 35℃, the rotation speed was 240 rpm, and the mixture was stirred for 80 minutes. The mixture was then degassed and discharged. The product performance indicators are shown in Table 1-2.

[0043] Comparative Example 1

[0044] The difference between this comparative example and Example 2 is that 5 parts of the molecular sieve catalyst were replaced with 2.5 parts of the molecular sieve from Example 1 and 2.5 parts of ethyl diisopropoxybisacetoacetate titanium. Other steps and parameters were the same as in Example 1. Product performance indicators are shown in Tables 1-2.

[0045] Comparative Example 2

[0046] The difference between this comparative example and Example 2 is that 5 parts of molecular sieve catalyst were replaced with 5 parts of commercially available 4A molecular sieve. Other steps and parameters are the same as in Example 1. Product performance indicators are shown in Table 1.

[0047] Comparative Example 3

[0048] The difference between this comparative example and Example 2 is that 5 parts of molecular sieve catalyst were replaced with 5 parts of diisopropoxydiacetoethyl titanium. Other steps and parameters are the same as in Example 1. Product performance indicators are shown in Tables 1-2.

[0049] Table 1:

[0050]

[0051] Performance testing and results analysis:

[0052] The properties of the high-temperature stable sealants prepared in Examples 2-4 and the ketone sealants prepared in Comparative Examples 1-3 were tested using the following methods;

[0053] (1) Tensile strength shall be determined in accordance with the provisions of GB / T 528-2009;

[0054] (2) The maximum elongation at break shall be determined in accordance with the provisions of GB / T 528-2009;

[0055] (3) The surface drying time shall be determined in accordance with the provisions of GB / T 13477.5-2002;

[0056] (4) Viscosity peak determination method: Viscosity peak refers to the rapid increase in viscosity in a short period of time after adding titanate catalyst to the base adhesive, resulting in material climbing the pole and paddle. Specific determination method: During the adhesive preparation process, after adding the catalyst, observe whether the climbing of the pole and paddle occurs during the stirring process; if the climbing of the pole does not occur during the stirring process, it is judged that there is no viscosity peak phenomenon; if the climbing of the pole occurs during the stirring process, it is judged that there is a viscosity peak phenomenon.

[0057] The sealant was stored at different temperatures, and the performance test results are shown in Table 1; the viscosity peak determination results are shown in Table 2.

[0058] Table 2:

[0059]

[0060] Table 1 shows that the sealant's performance deteriorates more severely at higher curing temperatures. Analysis of Example 2 and the comparative data shows that the sealant prepared from the self-made molecular sieve catalyst maintained good mechanical properties and surface drying time after curing at 90℃ for 10 days. This indicates that compared to conventional molecular sieves, the sealant prepared by the self-synthesized molecular sieve catalyst of this invention exhibits significantly better storage stability at high temperatures, and the prepared sealant demonstrates superior performance. Table 2 shows that, compared to liquid catalysts, the molecular sieve catalyst of this invention does not exhibit viscosity peaks during the sealant preparation process.

[0061] As can be seen from the above, molecular sieve catalysts not only avoid the viscosity peak problem in the sealant production process, but also play a very important role in the storage stability of sealants under high temperature environments.

[0062] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the inventive concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A sealant that is stable in high-temperature environments, characterized in that, The sealant comprises the following components by weight: 100 parts of alkoxy-terminated polydimethylsiloxane; 20-80 parts of dimethyl silicone oil; Inorganic filler 180-300 parts; 2-8 parts of molecular sieve catalyst; 1-8 parts of crosslinking agent; 0.5-1.5 parts of coupling agent; The preparation method of the molecular sieve catalyst includes the following steps: S1. A molecular sieve is obtained by hydrothermal crystallization of a mixture containing dimethylamine, boehmite, phosphoric acid and water, followed by washing and calcination. S2. Under an inert atmosphere, toluene and ethyl diisopropoxydiacetate titanium were added to a flask and stirred at a material temperature of 25-55℃ for 0.5-5 h. Then, the molecular sieve was added, and the mixture was stirred for 3-10 h. After filtration and vacuum drying, the molecular sieve catalyst was obtained. The mass ratio of toluene to ethyl diisopropoxydiacetate titanium was 3-6:1, and the mass ratio of molecular sieve to ethyl diisopropoxydiacetate titanium was 1-2:

1.

2. The high-temperature stable sealant according to claim 1, characterized in that, In step S1, the molar ratio of dimethylamine, boehmite, phosphoric acid and water is 2.0-4.8:0.4-1.2:1:50-150.

3. The high-temperature stable sealant according to claim 1, characterized in that, In step S1, the hydrothermal crystallization temperature is 120-200℃ and the time is 12-30h.

4. The high-temperature stable sealant according to claim 1, characterized in that, In step S1, the calcination temperature is 450-650℃ and the time is 4-8h.

5. The high-temperature stable sealant according to claim 1, characterized in that, The alkoxy-terminated polydimethylsiloxane has a viscosity of 5000-50000 mPa·s at 25°C.

6. The high-temperature stable sealant according to claim 1, characterized in that, The viscosity of the dimethyl silicone oil at 25°C is 100-2000 mPa·s.

7. The high-temperature stable sealant according to claim 1, characterized in that, The inorganic filler is at least one of activated nano calcium carbonate, heavy calcium carbonate, carbon black, and silica.

8. The high-temperature stable sealant according to claim 1, characterized in that, The crosslinking agent is at least one of methyltrimethoxysilane, propyltrimethoxysilane, octyltrimethoxysilane, phenyltrimethoxysilane, and vinyltrimethoxysilane.

9. The high-temperature stable sealant according to claim 1, characterized in that, The coupling agent is at least one of γ-(2,3-epoxypropoxy)propyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-aminopropyltriethoxysilane, and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane.

10. The method for preparing a high-temperature stable sealant according to any one of claims 1-9, characterized in that, Includes the following steps: The alkoxy-terminated polydimethylsiloxane, dimethyl silicone oil, and inorganic filler are added to a reactor. After stirring and absorbing the powder, the material temperature is set to 60-110℃, the rotation speed to 400-1000 rpm, and the vacuum degree to -0.08~-0.099 MPa. The mixture is stirred, dehydrated, and blended for 20-200 min. The vacuum is then released with nitrogen, and the material is cooled with cooling water until it does not exceed 40℃. The crosslinking agent, coupling agent, and molecular sieve catalyst are added. The mixture is stirred under a nitrogen atmosphere for 10-100 min, followed by vacuum stirring at a vacuum degree of -0.08~-0.099 MPa. The material temperature is maintained below 40℃, the rotation speed is 200-400 rpm, and the stirring time is 40-120 min. The mixture is then degassed and discharged.

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