A method for controlling viscosity peaks in the production process of dealcohol-based silicone sealants

Abstract

This invention discloses a method for controlling viscosity peaks during the production of dealcohol-type silicone sealants, comprising the following steps: α,ω-dihydroxy polysiloxane and fillers are added to a kneader; after the material reaches a predetermined temperature, it is dehydrated and mixed for at least 120 minutes; a hydrophobic modifier is then added, and stirring continues, followed by cooling to obtain a base material; at room temperature, the base material, dimethyl silicone oil, colorant, and other materials are added to a mixing device and pre-stirred and dispersed for a certain time; a viscosity peak control composition is added, and the mixture is stirred until the material temperature reaches 50-55°C; a crosslinking agent, coupling agent, and titanate catalyst are added, and the mixture is stirred until the material temperature is below 45°C, followed by continued dispersion for 30-90 minutes before discharge. This invention can significantly reduce the severity and duration of viscosity peaks during the production of dealcohol-type sealants, effectively improving product qualification rates and extending equipment lifespan.

Description

Technical Field

[0001] This invention relates to the field of silicone sealant technology, and specifically to a method for controlling the viscosity peak during the production process of de-alcoholized silicone sealant. Background Technology

[0002] Silicone sealants are a type of elastomer formed by the addition of linear polyorganosiloxanes as a base polymer, reinforcing fillers, crosslinking agents, coupling agents, and plasticizers. They absorb moisture from the air and undergo compounding and vulcanization. Currently, silicone materials are widely used in prefabricated buildings, aerospace, electronic and electrical insulation and sealing, rail transportation, and biomedicine. Among these, alcohol-based sealants, which release small-molecule alcohols during curing, are more non-corrosive and environmentally friendly compared to ketoxime-based and acid-based sealants, making them more popular in the market. In the construction sealant sector, the market share of alcohol-based sealants is increasing year by year, and the demand is also growing.

[0003] In the actual production process of dealcohol-type silicone sealants, when titanate catalysts are added to the base adhesive, the viscosity rises sharply in a short period of time, causing material to climb the dispensing rod and slurry. Continuous dispersion and stirring are required for the viscosity to return to normal; this process is called the viscosity peak of the dealcohol-type sealant. Poor control of the viscosity peak during production can affect the appearance and performance of the finished sealant, often requiring rework or even scrapping, impacting output and product qualification rate. Simultaneously, the thickening of the material during the viscosity peak can cause a short-term surge in the current of the dispersion motor, which in severe cases can lead to dispersion jamming, motor burnout, and damage to the lifespan of the machinery.

[0004] The main reason for the viscosity peak is that when the hydroxyl-terminated polysiloxane in the system comes into contact with titanate substances, the high concentration of titanate on the surface interacts with the polymer hydroxyl groups through hydrogen bonding, forming pseudo-crosslinks. This hydrogen bonding is similar to a chain reaction and can form in a very short time, so the viscosity increases exponentially and remains at the peak viscosity for a long time. Only under strong mechanical shear force can the titanate gradually penetrate into the interior of the polysiloxane, weakening and eventually breaking this hydrogen bonding before the viscosity returns to normal. At the same time, hydroxyl groups from other sources within the system can also make the viscosity peak more intense.

[0005] Currently, there are two main aspects to controlling or avoiding viscosity peaks in dealcohol-type sealants: First, it is necessary to control the content of other small-molecule hydroxyl compounds and moisture in the system to prevent the viscosity peak from being aggravated. The main raw materials for sealant production are polymers and fillers, and fillers are the main source of other small-molecule hydroxyl compounds and moisture in the system. Simple vacuum heating for dehydration has limited efficiency, and the base material has a certain degree of hygroscopicity, so the moisture content will also increase after storage. Second, it is necessary to reduce the hydroxyl content of the polymer, as polymer hydroxyl groups are the main cause of viscosity peaks. Using alkoxy-terminated polysiloxanes as raw materials avoids viscosity peaks because the high-viscosity polymer in the system does not contain hydroxyl groups and will not form hydrogen bonds with titanate catalysts. However, alkoxy-terminated polysiloxanes have high activity and poor stability, and can self-crosslink, resulting in easy thickening of the finished sealant and a short shelf life. At the same time, the cost is high, and the economic benefits are poor. Therefore, a process for controlling viscosity peaks in the production process of dealcohol-type silicone sealants has certain economic value, can improve yield, and extend equipment life. Summary of the Invention

[0006] In view of the above-mentioned shortcomings, the present invention provides a method for controlling the viscosity peak during the production process of de-alcoholized silicone sealant. The present invention modifies the powder by adding a hydrophobic modifier during the dehydration preparation stage, so that the prepared base material has a low water content and hygroscopicity, and the base material can maintain a low water content after storage. By adding a viscosity peak control composition during the production process, and in combination with the specific process and process parameters of the present invention, the severity of the viscosity peak during the production process of de-alcoholized sealant can be significantly reduced and the duration of the viscosity peak can be shortened, which can effectively improve the product qualification rate and extend the service life of equipment.

[0007] To achieve the above objectives, the present invention provides a method for controlling viscosity peaks during the production process of alcohol-free silicone sealants, comprising the following steps:

[0008] Step 1: Add α,ω-dihydroxy polysiloxane and filler to a kneader. After the material reaches the predetermined temperature, dehydrate and mix for at least 120 minutes. Then add hydrophobic modifier and continue stirring for a certain time. Finally, cool down to obtain the base material.

[0009] Step 2: At room temperature, add the above base material, dimethyl silicone oil, colorant and other materials into the mixing equipment and stir and disperse for a certain period of time beforehand;

[0010] Step 3: Add the viscosity peak control composition to a stirring device and stir until the material temperature reaches 50-55℃; wherein, by mass parts, the components of the viscosity peak control composition are: 100 parts of monohydroxy-terminated polydimethylsiloxane, 40-80 parts of titanate mixture, 20-40 parts of dehydrating agent, and 10-20 parts of stabilizer; the structural formula of the monohydroxy-terminated polydimethylsiloxane is shown in Formula 1 below:

[0011]

[0012] In Equation 1, n ≥ 2;

[0013] Step 4: Add the crosslinking agent, coupling agent and titanate catalyst required for the sealant to the mixing equipment, stir until the material temperature is below 45℃, and then continue to disperse for 30-90 minutes before discharging.

[0014] It should be noted that the mixing equipment is a planetary mixer or a high-speed dispersion mixer.

[0015] According to one aspect of the present invention, the hydrophobic modifier comprises one or two of the following: triglycerides of fatty acids with a chain of sixteen carbons or more and propylene glycol esters of fatty acids with a chain of sixteen carbons or more.

[0016] The general structural formula of the fatty acid triglycerides with a chain of sixteen or more carbons is shown in Formula 2 below:

[0017]

[0018] The general structural formula of the propylene glycol ester of fatty acids with a chain of sixteen or more carbons is shown in Formula 3 below:

[0019]

[0020] According to one aspect of the present invention, the amount of the hydrophobic modifier added is 0.3 wt% to 1.5 wt% of the base material; the amount of the viscosity peak control composition added is 2 wt% to 4 wt% of the base material.

[0021] According to one aspect of the present invention, in step 1, the temperature of the kneader is 120-150°C, the vacuum degree is 0.06-0.099 MPa, the stirring time is 30 min, and the predetermined temperature reached by the material is the temperature of the kneader.

[0022] According to one aspect of the present invention, in step 2, the vacuum degree of pre-stirring dispersion is -0.095 MPa or higher, the pre-stirring dispersion speed is 100 to 150 rpm, and the pre-stirring dispersion time is 30 min.

[0023] According to one aspect of the present invention, in step 3, the stirring process specifically involves: first stirring for 10 to 15 minutes under a vacuum of -0.06 MPa and a rotation speed of 70 to 90 rpm; then stirring until the material temperature reaches 50 to 55°C under a vacuum of -0.095 MPa and a rotation speed of 350 to 500 rpm.

[0024] According to one aspect of the present invention, in step 4, the stirring process specifically involves: first stirring for 5 minutes under a vacuum of -0.06 MPa and a rotation speed of 70 to 90 rpm; then stirring until the material temperature is below 45°C under a vacuum of -0.095 MPa, a rotation speed of 100 to 150 rpm, and cooling water flowing through the reactor.

[0025] According to one aspect of the present invention, the method for preparing the viscosity peak control composition is as follows:

[0026] Add the monohydroxy-terminated polydimethylsiloxane to the reactor according to the specified ratio, and add the titanate mixture while stirring under a nitrogen atmosphere. Stop the nitrogen atmosphere after the addition is complete.

[0027] Continue stirring for 20 minutes at a vacuum level above -0.095 MPa;

[0028] After refilling with nitrogen and adding a dehydrating agent and stabilizer, the mixture is stirred under a vacuum of 0.06 MPa for 10 minutes to obtain a viscosity peak control composition.

[0029] According to one aspect of the present invention, the monohydroxy-terminated polydimethylsiloxane has a viscosity of 350 mPa·s to 1500 mPa·s at 25°C.

[0030] According to one aspect of the present invention, in step 3, the titanate mixture is a mixture of isopropoxytris(dodecylbenzenesulfonyloxy) titanate, bis(ethyl acetoacetate) titanate diisopropyl ester and tetraisopropyl titanate, wherein the mass ratio of isopropoxytris(dodecylbenzenesulfonyloxy) titanate, bis(ethyl acetoacetate) titanate diisopropyl ester and tetraisopropyl titanate is (15-30):(30-60):(40-60); the dehydrating agent includes at least one of vinylmethyltrimethoxysilane, hexamethyldisilazane, and hexamethylcyclotrisilazane; the stabilizer includes at least one of vinylmethoxysilane hydrolyzed oligomer, vinylmethoxyethoxysilane hydrolyzed oligomer, and vinylethoxysilane hydrolyzed oligomer.

[0031] The beneficial effects of this invention are:

[0032] (1) The present invention uses a hydrophobic modifier to modify the surface of the filler during the preparation of the base adhesive. The hydrophobic modifier can be adsorbed by the filler under high temperature melting and form a hydrophobic film on its surface, so that the base adhesive produced has a low water content and hygroscopicity. The water content of the base material is kept at a low level both initially and after storage, which is beneficial to the production of de-alcoholized sealant and the storage resistance of the finished adhesive.

[0033] (2) This invention uses a viscosity peak control composition. The composition uses a single-hydroxyl-terminated polydimethylsiloxane with low viscosity. At the same time, the titanate adsorbed and encapsulated by the low-viscosity polysiloxane enhances its compatibility with the high-viscosity polymer, so that the titanate catalyst added later can penetrate into the base material very quickly, reducing the degree of pseudo-crosslinking formed between the titanate and the base material on the two-phase surface due to hydrogen bonding. This reduces and shortens the degree and time of the viscosity peak. The dehydrating agent in the composition can extend the shelf life of the composition. After the sealant is added, it can also remove the water vapor and hydroxyl groups brought in by other materials and production operations, reducing the degree of the viscosity peak. The stabilizer ensures that the single-hydroxyl-terminated polydimethylsiloxane in the composition will not affect the curing and crosslinking of the original sealant.

[0034] (3) This invention achieves relatively effective control. This invention uses a vacuum degree of -0.06 MPa as the critical point for vacuuming and degassing the material, ensuring that the air trapped in the material during stirring is balanced with the air discharged from the vacuum. This effectively isolates the material from moisture in the environment while also controlling the material's level within the reactor. Temperature control is also crucial. Lower material temperatures increase system viscosity and intensify viscosity peaks, while excessively high temperatures lead to rapid evaporation of additives, affecting product performance. Furthermore, high temperatures can cause sealant curing during discharge. Increasing the material temperature to approximately 50-55°C before adding additives effectively reduces system viscosity, significantly lowering the viscosity peak. Once the viscosity is normal, cooling the material to below 45°C with cooling water effectively controls additive evaporation while allowing sufficient margin for discharge. Detailed Implementation

[0035] 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.

[0036] The equipment used in both the examples and comparative examples was a 20L planetary hybrid mixer with a total feed amount of 18 kg. The dispersing rod, 400 mm in length, was connected to the top of the equipment. The intensity of the viscosity peak could be evaluated by measuring the height of the clean section on the dispersing rod during sealant discharge; a higher value indicates less material climbing the rod and a lower viscosity peak intensity, and vice versa. The duration of the viscosity peak was evaluated by recording the duration of the current increase in the equipment. The current value of the planetary hybrid mixer is positively correlated with the material viscosity; the longer the material thickens, the longer the current increase lasts.

[0037] Example 1

[0038] A method for controlling viscosity peaks during the production process of alcohol-free silicone sealants:

[0039] Step 1: Add 150 parts of α,ω-dihydroxypolysiloxane (viscosity of 50000 mPa.s at 25℃) and 150 parts of nano-calcium carbonate to a kneader. After reaching the predetermined temperature (120℃), dehydrate and mix for at least 120 minutes. Then add 1.5 parts of triglyceride oleate and 1.5 parts of propylene glycol oleate and continue stirring for 30 minutes. Finally, cool down to obtain the base material.

[0040] Step 2: At room temperature, add the above base material, 10 parts of dimethyl silicone oil (viscosity of 350 mPa.s at 25°C), and 10 parts of colorant into a planetary hybrid mixer. The vacuum degree is above -0.095 MPa, the dispersion speed is 125 rpm, and the mixture is pre-stirred and dispersed for 30 minutes.

[0041] Step 3: At room temperature, add 8 parts of the viscosity peak control composition to a planetary hybrid mixer. First, maintain a vacuum of approximately -0.06 MPa and a speed of 90 rpm for 15 minutes. Then, increase the vacuum to above -0.095 MPa and increase the speed to 350 rpm for rapid stirring until the material temperature reaches 50°C. The preparation process of the viscosity peak control composition is as follows: Add 100 parts of monohydroxy-terminated polydimethylsiloxane (viscosity of 1000 mPa·s at 25°C) to the reactor according to the formula and purge with nitrogen. While stirring under a nitrogen atmosphere, add 60 parts of the titanate mixture in the above proportion. After the addition is completed, stop the nitrogen purge, maintain a vacuum of above -0.095 MPa, and continue stirring for 20 minutes. Then, purge with nitrogen again and add 10 parts of hexamethyldisilazane, 30 parts of vinylmethyltrimethoxysilane, and 20 parts of vinylethoxysilane hydrolysate oligomer. After stirring under a vacuum of 0.06 MPa for 10 minutes, the viscosity peak control composition is obtained. The mass ratio of isopropoxytris(dodecylbenzenesulfonyloxy) titanate, bis(ethyl acetoacetate) titanate diisopropyl ester and tetraisopropyl titanate in the titanate mixture is 20:30:45.

[0042] Step 4: Add 8 parts of methyltrimethoxysilane, 1 part of γ-aminopropylethoxysilane, and 6 parts of titanate catalyst to a planetary hybrid mixer. First, set the vacuum to approximately -0.06 MPa and the speed to 90 rpm. After stirring for 5 minutes, adjust the vacuum to -0.095 MPa and the speed to 125 rpm. Circulate cooling water through the reactor and maintain the material temperature at 43°C by adjusting the cooling water flow rate and temperature. Continue dispersing for 50 minutes before discharging.

[0043] Example 2

[0044] A method for controlling viscosity peaks during the production process of alcohol-free silicone sealants:

[0045] Step 1: Add 130 parts of α,ω-dihydroxypolysiloxane (viscosity of 50000 mPa.s at 25℃), 30 parts of dimethyl silicone oil (viscosity of 350 mPa.s at 25℃), and 150 parts of nano-calcium carbonate to a kneader. The temperature is 120℃ and the vacuum degree is 0.099 MPa. After reaching the predetermined temperature, dehydrate and mix for at least 120 minutes. Then add 3 parts of propylene glycol stearate and continue stirring for 30 minutes. Finally, cool down to obtain the base material.

[0046] Step 2: At room temperature, add the above base material, 10 parts of dimethyl silicone oil (viscosity of 350 mPa.s at 25°C), and 10 parts of colorant into a planetary hybrid mixer. The vacuum degree is above -0.095 MPa, the dispersion speed is 125 rpm, and the mixture is pre-stirred and dispersed for 30 minutes.

[0047] Step 3: At room temperature, add 12 parts of the viscosity peak control composition to a planetary hybrid mixer. First, maintain a vacuum of approximately -0.06 MPa and a speed of 70 rpm for 15 minutes. Then, increase the vacuum to above -0.095 MPa and increase the speed to 500 rpm for rapid stirring until the material temperature reaches 55°C. The preparation process of the viscosity peak control composition is as follows: Add 100 parts of monohydroxy-terminated polydimethylsiloxane (viscosity of 350 mPa·s at 25°C) to the reactor according to the formula and purge with nitrogen. While stirring under a nitrogen atmosphere, add 40 parts of the titanate mixture in the above proportion. After the addition is completed, stop the nitrogen purge, maintain a vacuum of above -0.095 MPa, and continue stirring for 20 minutes. Then, purge with nitrogen again and add 20 parts of hexamethylcyclotrisilazane and 20 parts of vinylmethoxyethoxysilane hydrolysate oligomer. Stir under a vacuum of 0.06 MPa for 10 minutes to obtain the viscosity peak control composition. The mass ratio of isopropoxytris(dodecylbenzenesulfonyloxy) titanate, bis(ethyl acetoacetate) titanate, and tetraisopropyl titanate in the titanate mixture is 30:30:50.

[0048] Step 4: Add 8 parts of methyltrimethoxysilane, 1 part of γ-aminopropylethoxysilane, and 6 parts of titanate catalyst to a planetary hybrid mixer. First, set the vacuum to approximately -0.05 MPa and the speed to 90 rpm. After stirring for 5 minutes, adjust the vacuum to -0.095 MPa and the speed to 125 rpm. Circulate cooling water through the reactor and maintain the material temperature at 45°C by adjusting the cooling water flow rate and temperature. Discharge the material after continuous dispersion for 50 minutes.

[0049] Example 3

[0050] A method for controlling viscosity peaks during the production process of alcohol-free silicone sealants:

[0051] Step 1: Add 130 parts of α,ω-dihydroxypolysiloxane (viscosity of 50000 mPa.s at 25℃), 20 parts of dimethyl silicone oil (viscosity of 350 mPa.s at 25℃), and 150 parts of nano-calcium carbonate to a kneader. The temperature is 120℃ and the vacuum degree is 0.099 MPa. After reaching the predetermined temperature, dehydrate and mix for at least 120 minutes. Then add 2 parts of triglyceride stearate and continue stirring for 30 minutes. Finally, cool down to obtain the base material.

[0052] Step 2: At room temperature, add the above base material, 10 parts of dimethyl silicone oil (viscosity of 350 mPa.s at 25°C), and 10 parts of colorant into a planetary hybrid mixer. The vacuum degree is above -0.095 MPa, the dispersion speed is 125 rpm, and the mixture is pre-stirred and dispersed for 30 minutes.

[0053] Step 3: At room temperature, add 7 parts of the viscosity peak control composition to a planetary hybrid mixer. First, maintain a vacuum of approximately -0.06 MPa and a speed of 80 rpm for 15 minutes. Then, increase the vacuum to above -0.095 MPa and increase the speed to 400 rpm for rapid stirring until the material temperature reaches 52°C. The preparation process of the viscosity peak control composition is as follows: Add 100 parts of monohydroxy-terminated polydimethylsiloxane (viscosity of 7500 mPa·s at 25°C) to the reactor according to the formula and purge with nitrogen. While stirring under a nitrogen atmosphere, add 60 parts of the titanate mixture in the above proportion. After the addition is completed, stop the nitrogen purge, maintain a vacuum of above -0.095 MPa, and continue stirring for 20 minutes. Then, purge with nitrogen again and add 30 parts of hexamethyldisilazane and 15 parts of vinyl methoxy hydrolyzed oligomer. Stir for 10 minutes under a vacuum of 0.06 MPa to obtain the viscosity peak control composition. The mass ratio of isopropoxytris(dodecylbenzenesulfonyloxy)titanate, diisopropyl bis(ethyl acetoacetate)titanate and tetraisopropyl titanate in the titanate mixture is 25:50:55.

[0054] Step 4: Add 8 parts of methyltrimethoxysilane, 1 part of γ-aminopropylethoxysilane, and 6 parts of titanate catalyst to a planetary hybrid mixer. First, set the vacuum to approximately -0.07 MPa and the speed to 70 rpm. After stirring for 5 minutes, adjust the vacuum to -0.095 MPa and the speed to 125 rpm. Circulate cooling water through the reactor and maintain the material temperature at 43°C by adjusting the cooling water flow rate and temperature. Discharge the material after continuous dispersion for 50 minutes.

[0055] Example 4

[0056] A method for controlling viscosity peaks during the production process of alcohol-free silicone sealants:

[0057] Step 1: Add 150 parts of α,ω-dihydroxypolysiloxane (viscosity of 50000 mPa.s at 25℃) and 150 parts of nano-calcium carbonate to a kneader at 120℃ and 0.099 MPa. After reaching the predetermined temperature, dehydrate and mix for at least 120 minutes. Then add 4 parts of palmitic acid triglyceride and continue stirring for 30 minutes. Finally, cool down to obtain the base material.

[0058] Step 2: At room temperature, add the above base material, 10 parts of dimethyl silicone oil (viscosity of 350 mPa.s at 25°C), and 10 parts of colorant into a planetary hybrid mixer. The vacuum degree is above -0.095 MPa, the dispersion speed is 125 rpm, and the mixture is pre-stirred and dispersed for 30 minutes.

[0059] Step 3: At room temperature, add 6 parts of the viscosity peak control composition to a planetary hybrid mixer. First, maintain a vacuum of approximately -0.06 MPa and a speed of 80 rpm for 10 minutes. Then, increase the vacuum to above -0.095 MPa and increase the speed to 350 rpm for rapid stirring until the material temperature reaches 50°C. The preparation process of the viscosity peak control composition is as follows: Add 100 parts of monohydroxy-terminated polydimethylsiloxane (viscosity of 1500 mPa·s at 25°C) to the reactor according to the formula and purge with nitrogen. While stirring under a nitrogen atmosphere, add 80 parts of the titanate mixture in the above proportion. After the addition is completed, stop the nitrogen purge, maintain a vacuum of above -0.095 MPa, and continue stirring for 20 minutes. Then, purge with nitrogen again and add 15 parts of hexamethyldisilazane, 5 parts of hexamethylcyclotrisilazane, and 10 parts of vinyl methoxy hydrolyzed oligomer. After stirring under a vacuum of 0.06 MPa for 10 minutes, the viscosity peak control composition is obtained. The mass ratio of isopropoxytris(dodecylbenzenesulfonyloxy) titanate, bis(ethyl acetoacetate) titanate, and tetraisopropyl titanate in the titanate mixture is 15:40:50.

[0060] Step 4: Add 8 parts of methyltrimethoxysilane, 1 part of γ-aminopropylethoxysilane, and 6 parts of titanate catalyst to a planetary hybrid mixer. First, set the vacuum to approximately -0.05 MPa and the speed to 90 rpm. After stirring for 5 minutes, adjust the vacuum to -0.095 MPa and the speed to 125 rpm. Circulate cooling water through the reactor and maintain the material temperature at 42°C by adjusting the cooling water flow rate and water temperature. Discharge the material after continuous dispersion for 50 minutes.

[0061] Example 5

[0062] A method for controlling viscosity peaks during the production process of alcohol-free silicone sealants:

[0063] The difference between this embodiment and embodiment 4 is that the dimethyl silicone oil and colorant added in step 2 are all replaced with α,ω-dihydroxy polysiloxane (viscosity at 25°C is 12000 mPa·s), while the other steps and parameters are the same as in embodiment 4.

[0064] Example 6

[0065] A method for controlling viscosity peaks during the production process of alcohol-free silicone sealants:

[0066] The difference between this embodiment and Example 4 is that in step 4, there are 6 parts of methyltrimethoxysilane and 9 parts of titanate catalyst, while the other steps and parameters are the same as in Example 4.

[0067] Comparative Example 1

[0068] A method for preparing a dealcohol-free silicone sealant:

[0069] Step 1: Add 150 parts of α,ω-dihydroxypolysiloxane (viscosity of 50000 mPa.s at 25℃) and 150 parts of nano-calcium carbonate to a kneader. The temperature is 120℃ and the vacuum degree is 0.099 MPa. After reaching the predetermined temperature, dehydrate and blend for at least 120 minutes, and then cool down to obtain the base material.

[0070] Step 2: At room temperature, add the above base material, 10 parts of dimethyl silicone oil (viscosity of 350 mPa.s at 25°C), and 10 parts of colorant into a planetary hybrid mixer. The vacuum degree is above -0.095 MPa, the dispersion speed is 125 rpm, and the mixture is pre-stirred and dispersed for 30 minutes.

[0071] Step 3: Add 8 parts of methyltrimethoxysilane, 1 part of γ-aminopropylethoxysilane, and 6 parts of titanate catalyst to a planetary hybrid mixer. First, apply a vacuum of approximately -0.095 MPa and a rotation speed of 125 rpm, and continue dispersing for 50 minutes before discharging.

[0072] Comparative Example 2

[0073] A method for preparing a dealcohol-free silicone sealant:

[0074] The difference between this comparative example and Example 4 is that the viscosity peak composition is not added, while the other steps and parameters are the same as in Example 4.

[0075] Comparative Example 3

[0076] A method for preparing a dealcohol-free silicone sealant:

[0077] Step 1: Add 150 parts of α,ω-dihydroxypolysiloxane (viscosity of 50000 mPa.s at 25℃) and 150 parts of nano-calcium carbonate to a kneader. The temperature is 120℃ and the vacuum degree is 0.099 MPa. After reaching the predetermined temperature, dehydrate and blend for at least 120 minutes, and then cool down to obtain the base material.

[0078] Step 2: At room temperature, add the above base material, 10 parts of dimethyl silicone oil (viscosity of 350 mPa.s at 25°C), and 10 parts of colorant into a planetary hybrid mixer. The vacuum degree is above -0.095 MPa, the dispersion speed is 125 rpm, and the mixture is pre-stirred and dispersed for 30 minutes.

[0079] Step 3: At room temperature, add 8 parts of the viscosity peak control composition to a planetary hybrid mixer, with a vacuum of approximately -0.095 MPa and a speed of 125 rpm, and stir for 15 minutes. The preparation process of the viscosity peak control composition is as follows: 100 parts of monohydroxy-terminated polydimethylsiloxane (viscosity of 1500 mPa.s at 25°C) are added to the reactor according to the formula, and nitrogen is purged. Under a nitrogen atmosphere, 80 parts of the titanate mixture in the above proportion are added while stirring. After the addition is completed, the nitrogen is stopped, the vacuum is maintained above -0.095 MPa, and stirring is continued for 20 minutes. Then, 15 parts of hexamethyldisilazane, 5 parts of hexamethylcyclotrisilazane, and 10 parts of vinyl methoxy hydrolyzed oligomer are added under nitrogen purging. After stirring under a vacuum of 0.06 MPa for 10 minutes, the viscosity peak control composition is obtained. The mass ratio of isopropoxytris(dodecylbenzenesulfonyloxy) titanate, bis(ethyl acetoacetate) titanate, and tetraisopropyl titanate in the titanate mixture is 15:40:50.

[0080] Step 4: Add 8 parts of methyltrimethoxysilane, 1 part of γ-aminopropylethoxysilane, and 6 parts of titanate catalyst to a planetary hybrid mixer. First, apply a vacuum of approximately -0.095 MPa and a rotation speed of 125 rpm, and continue dispersing for 50 minutes before discharging.

[0081] Performance checks and results analysis:

[0082] Methods for evaluating the intensity of viscosity peaks:

[0083] When discharging sealant in Examples 1-6 and Comparative Examples 1-3, after the planetary hybrid mixer is raised, first mark the highest material position of the sealant on the planetary mixer's dispersing rod with a marker. Then, complete the sealant discharge and sealing and equipment cleaning work according to the normal discharge operation. Take care not to damage the marker mark on the dispersing rod. Finally, measure the height of the mark from the connection between the dispersing rod and the top of the equipment, and record the measured height.

[0084] Methods for evaluating the duration of viscosity peaks:

[0085] After adding titanate catalyst and other additives and lowering the planetary machine, start the planetary machine. When the machine reaches the specified vacuum and speed and runs stably (about 10 seconds after startup), start timing and record the initial current value. Then, due to the high viscosity, the current value will continue to fluctuate and rise, maintaining a peak current for a period of time before gradually decreasing and returning to near the initial current value (initial current ±2A). Stop timing and record the timing time.

[0086] The results of the above measurements are shown in Table 1 below:

[0087] Table 1:

[0088] Dispersion rod clean height, mm Duration of current increase, s Example 1 103 180 Example 2 120 65 Example 3 112 246 Example 4 107 185 Example 5 84 320 Example 6 99 298 Comparative Example 1 0 589 Comparative Example 2 36 475 Comparative Example 3 21 362

[0089] As shown in Table 1, the process of this invention can effectively reduce the intensity and duration of viscosity peaks in the production of de-alcoholized sealants. Among them, Example 2 shows the best effect. Examples 1-4 generally have good control over the intensity of viscosity peaks, while the duration of viscosity peaks varies. This is because different viscosities of monohydroxy-terminated polysiloxanes are used. The lower the viscosity, the better the penetration and dispersion ability, and therefore the shorter the duration. Although Examples 1 and 3 use monohydroxy-terminated polysiloxanes of different viscosities, the difference in dosage makes the duration of their viscosity peaks similar. Example 5 shows that although the content of α,ω-dihydroxy polysiloxane in the formulation is increased, the degree and duration of the viscosity peak are still controlled within a good range, indicating that the process has a high upper limit. Example 6 shows that increasing the amount of titanate catalyst under this process only appropriately prolongs the duration of the viscosity peak, also indicating that it has a good upper limit. Comparative Example 1 was prepared using a conventional dealcoholized sealant process, and its material reached the top of the machine, with the longest duration of viscosity peak. Comparative Example 2 did not use a viscosity peak control composition, but its material underwent hydrophobic discharge, and its process followed the present invention. Due to the longer duration of the viscosity peak, it exhibited higher rod climbing, but this was significantly improved compared to Comparative Example 1. Comparative Example 3 used only a viscosity peak control composition in its preparation process, following a conventional dealcoholized sealant process. Its results were similar to Comparative Example 2, also showing high rod climbing, but with a shorter duration. The data results from the above examples and comparative examples demonstrate the synergistic relationship between the various technical points in this invention, which can effectively control and reduce the viscosity peak problem in the dealcoholized sealant production process, thereby improving the enterprise's production qualification rate and efficiency, and extending the service life of equipment.

[0090] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for controlling the viscosity peak during the production process of dealcoholized silicone sealant, characterized in that, Includes the following steps: Step 1: Add α,ω-dihydroxy polysiloxane and filler to a kneader. After the material reaches the predetermined temperature, dehydrate and mix for at least 120 minutes. Then add hydrophobic modifier and continue stirring for a certain time. Finally, cool down to obtain the base material. Step 2: At room temperature, add the above base material, dimethyl silicone oil, colorant and other materials into the mixing equipment and stir and disperse for a certain period of time beforehand; Step 3: Add the viscosity peak control composition to the stirring equipment and stir until the material temperature reaches 50-55℃; wherein, by mass parts, the components of the viscosity peak control composition are: 100 parts of monohydroxy-terminated polydimethylsiloxane, 40-80 parts of titanate mixture, 20-40 parts of dehydrating agent, and 10-20 parts of stabilizer; Step 4: Add the crosslinking agent, coupling agent and titanate catalyst required for the sealant to the mixing equipment, stir until the material temperature is below 45℃, and then continue to disperse for 30-90 minutes before discharging.

2. The method for controlling the viscosity peak during the production process of de-alcoholized silicone sealant according to claim 1, characterized in that, The hydrophobic modifier includes one or two of the following: triglycerides of fatty acids with a chain of sixteen carbons or more, and propylene glycol esters of fatty acids with a chain of sixteen carbons or more.

3. The method for controlling the viscosity peak during the production process of de-alcoholized silicone sealant according to claim 1, characterized in that, The amount of the hydrophobic modifier added is 0.3wt% to 1.5wt% of the base material; the amount of the viscosity peak control composition added is 2wt% to 4wt% of the base material.

4. The method for controlling the viscosity peak during the production process of de-alcoholized silicone sealant according to claim 1, characterized in that, In step 1, the temperature of the kneader is 120-150℃, the vacuum degree is 0.06-0.099MPa, the stirring time is 30min, and the predetermined temperature reached by the material is the temperature of the kneader.

5. The method for controlling the viscosity peak during the production process of dealcoholized silicone sealant according to claim 1, characterized in that, In step 2, the vacuum degree of pre-stirring dispersion is above -0.095MPa, the pre-stirring dispersion speed is 100-150rpm, and the pre-stirring dispersion time is 30min.

6. The method for controlling the viscosity peak during the production process of de-alcoholized silicone sealant according to claim 1, characterized in that, In step 3, the stirring process is as follows: first, stir for 10 to 15 minutes under a vacuum of -0.06 MPa and a rotation speed of 70 to 90 rpm; then, stir until the material temperature reaches 50 to 55°C under a vacuum of -0.095 MPa and a rotation speed of 350 to 500 rpm.

7. The method for controlling the viscosity peak during the production process of dealcoholized silicone sealant according to claim 1, characterized in that, In step 4, the stirring process is as follows: first, stir for 5 minutes under a vacuum of -0.06MPa and a rotation speed of 70-90rpm; then, stir until the material temperature is below 45℃ under a vacuum of -0.095MPa, a rotation speed of 100-150rpm, and cooling water is circulated through the reactor.

8. The method for controlling the viscosity peak during the production process of dealcoholized silicone sealant according to claim 1, characterized in that, The preparation method of the viscosity peak control composition is as follows: Add the monohydroxy-terminated polydimethylsiloxane to the reactor according to the specified ratio, and add the titanate mixture while stirring under a nitrogen atmosphere. Stop the nitrogen atmosphere after the addition is complete. Continue stirring for 20 minutes at a vacuum level above -0.095 MPa; After refilling with nitrogen and adding a dehydrating agent and stabilizer, the mixture is stirred under a vacuum of 0.06 MPa for 10 minutes to obtain a viscosity peak control composition.

9. The method for controlling the viscosity peak during the production process of de-alcoholized silicone sealant according to claim 1, characterized in that, The viscosity of the monohydroxy-terminated polydimethylsiloxane at 25°C is 350 mPa·s to 1500 mPa·s.

10. The method for controlling the viscosity peak during the production process of de-alcoholized silicone sealant according to claim 1, characterized in that, In step 3, the titanate mixture is a mixture of isopropoxytris(dodecylbenzenesulfonyloxy) titanate, bis(ethyl acetoacetate) titanate diisopropyl ester, and tetraisopropyl titanate, wherein the mass ratio of isopropoxytris(dodecylbenzenesulfonyloxy) titanate, bis(ethyl acetoacetate) titanate diisopropyl ester, and tetraisopropyl titanate is (15-30):(30-60):(40-60); the dehydrating agent includes at least one of vinylmethyltrimethoxysilane, hexamethyldisilazane, and hexamethylcyclotrisilazane; the stabilizer includes at least one of vinylmethoxysilane hydrolyzed oligomer, vinylmethoxyethoxysilane hydrolyzed oligomer, and vinylethoxysilane hydrolyzed oligomer.

Images