Preparation method of halogen-free environment-friendly efficient flame-retardant silicone adhesive

Abstract

The invention provides a preparation method of a halogen-free environment-friendly efficient flame-retardant silicone adhesive, which comprises the following steps: step 1, weighing 100 parts by weight of hydroxyl-terminated polydimethylsiloxane, 20-25 parts by weight of dimethyl silicone oil, 90-120 parts by weight of a self-made composite flame retardant, 120-150 parts by weight of nano calcium carbonate, 3-5 parts by weight of methyltrimethoxysilane and 2-5 parts by weight of a titanium complex; by adopting the halogen-free composite flame retardant compounded by the phosphorus flame retardant and the nano aluminum hydroxide, the use of a halogen flame retardant is avoided, no toxic gas is released during combustion, and the environmental protection standards of RoHS, REACH and the like are met; the composite flame retardant is prepared through the synergistic effect of gas-phase flame retardance of the phosphorus-based flame retardant and condensed-phase flame retardance of the nano aluminum hydroxide, so that the flame retardance of the silicone adhesive reaches the V0 level of the GB / T2408-2021 standard, and the combustion resistance of the silicone adhesive reaches the A3 level of the GB / T23864-2021 standard; through the synergistic toughening effect of nano calcium carbonate and simethicone and the combination of high dispersity of the composite flame retardant, the tensile strength of the colloid is larger than or equal to 2.5 MPa, the elongation at break is larger than or equal to 500%, and the 35-level displacement sealing requirement is met.

Description

Technical Field

[0001] The present invention relates to the technical field of silicone adhesive preparation, and in particular to a method for preparing halogen-free, environmentally friendly, high-efficiency, flame-retardant silicone adhesive. Background Art

[0002] Silicone adhesive is a polymer sealing and adhesive material widely used in the fields of construction (curtain wall sealing, door and window bonding, etc.), electronics (component packaging, circuit board protection, etc.), and automobiles (body sealing, interior assembly, etc.). Its flame retardant properties and environmental friendliness are directly related to fire safety (such as delaying the spread of fire), environmental protection (halogen-free, low VOC release) and product compliance with domestic and international environmental protection standards such as RoHS, green building materials, and ELV. Therefore, it has become the core focus of the industry, affecting building safety, electronic equipment reliability, automobile comfort and market competitiveness.

[0003] Traditional flame-retardant silicone adhesives mostly use halogen flame retardants (such as bromine and chlorine). Although the flame retardant effect is significant, they release a large amount of toxic and harmful gases (such as dioxins and hydrogen halides) during combustion, posing a serious threat to the environment and human health. To address the environmental issues of halogen flame retardants, some technologies use inorganic flame retardants (such as aluminum hydroxide and magnesium hydroxide). However, such flame retardants need to be added in large quantities (usually accounting for more than 50% of the formula) to achieve a certain flame retardant effect, resulting in a significant decrease in the mechanical properties (such as tensile strength and elongation at break) and processing performance of the colloid, making it difficult to meet the needs of high-end application scenarios.

[0004] Therefore, a method for preparing a halogen-free, environmentally friendly, high-efficiency and flame-retardant silicone adhesive is proposed. Summary of the Invention

[0005] In view of this, the embodiments of the present invention hope to provide a method for preparing a halogen-free, environmentally friendly, high-efficiency, flame-retardant silicone adhesive to solve or alleviate the technical problems existing in the prior art and at least provide a beneficial option.

[0006] To solve the above technical problems, the technical solution adopted in this application is: a method for preparing a halogen-free, environmentally friendly, high-efficiency, flame-retardant silicone adhesive, comprising the following steps:

[0007] Step 1: Weigh, by weight, 100 parts of hydroxy-terminated polydimethylsiloxane, 20-25 parts of dimethyl silicone oil, 90-120 parts of a homemade composite flame retardant, 120-150 parts of nano-calcium carbonate, 3-5 parts of methyltrimethoxysilane, and 2-5 parts of a titanium complex;

[0008] Step 2: Put the weighed hydroxy-terminated polydimethylsiloxane, dimethyl silicone oil, nano-calcium carbonate and homemade composite flame retardant into a high-speed screw machine, and disperse and grind them at a speed of ≥500 r / min for 30-60 minutes to obtain a mixed material;

[0009] Step 3: heating the mixed material to 100-130°C and dehydrating the mixture under vacuum at a degree of vacuum ≤-0.09 MPa for 2-3 hours to obtain a semi-finished base material. During the dehydration process, the material is continuously stirred;

[0010] Step 4: Cool the semi-finished base material to 40-50°C through a condenser and put it into a storage tank;

[0011] Step 5: transport the semi-finished base material in the storage tank to a fully automatic static mixer via a pipeline, and add the weighed methyltrimethoxysilane and titanium complex in sequence;

[0012] Step 6: Mix the mixture in a fully automatic static mixer at room temperature for 15-20 minutes, mix evenly and package to obtain a halogen-free, environmentally friendly and high-efficiency flame-retardant silicone adhesive product.

[0013] As a further preferred embodiment of the present technical solution, in step one, the homemade composite flame retardant is formed by compounding a phosphorus-based flame retardant and nano-aluminum hydroxide in a mass ratio of 20%-30%:70%-80%; the phosphorus-based flame retardant is a combination of one or more of red phosphorus masterbatch, phosphate ester, and ammonium polyphosphate, and the particle size of the nano-aluminum hydroxide is 50-100 nm.

[0014] As a further preferred embodiment of the present technical solution, the particle size of the nano-calcium carbonate is 50-200 nm, and the surface is pretreated with a silane coupling agent.

[0015] As a further preferred embodiment of the present technical solution, in step 2, the material temperature is controlled at 50-80°C during the dispersion and grinding process of the high-speed screw machine.

[0016] As a further preferred embodiment of the present technical solution, in step five, the methyltrimethoxysilane is used as a cross-linking agent and the titanium complex is used as a catalyst.

[0017] As a further preferred embodiment of the present technical solution, in step three, during the vacuum dehydration process, the vacuum degree is maintained between -0.095 MPa and -0.09 MPa.

[0018] As a further preferred embodiment of the present technical solution, in step six, the mixing element of the fully automatic static mixer is a spiral blade, and the material flow rate during the mixing process is controlled at 0.5-1.0 m / s.

[0019] As a further preferred embodiment of the present technical solution, when the phosphorus-based flame retardant is a combination of multiple types, the mass ratio of red phosphorus masterbatch, phosphate ester, and ammonium polyphosphate is 1:1:1-2:1:3.

[0020] As a further preferred embodiment of the present technical solution, the silane coupling agent is γ-methacryloxypropyltrimethoxysilane, and the mass ratio of nano-calcium carbonate to the silane coupling agent during the pretreatment is 100:0.5-100:1.5.

[0021] As a further preferred embodiment of the present technical solution, the titanium complex is tetraisopropyl titanate or tetrabutyl titanate, and the catalytic cross-linking reaction rate is 0.5-1.0 mol / (L·min).

[0022] The embodiment of the present invention adopts the above technical solution, which has the following advantages:

[0023] 1. The present invention avoids the use of halogen flame retardants by using a halogen-free composite flame retardant compounded with a phosphorus-based flame retardant and nano-aluminum hydroxide. No toxic gas is released during combustion, and it complies with environmental protection standards such as RoHS and REACH.

[0024] 2. The present invention prepares a self-made composite flame retardant through the synergistic effect of the gas phase flame retardant of the phosphorus flame retardant and the condensed phase flame retardant of nano-aluminum hydroxide, so that the flame retardant performance of the silicone adhesive reaches the V0 level of the GB / T2408-2021 standard, and the combustion resistance reaches the A3 level of the GB / T23864-2021 standard;

[0025] 3. The present invention uses the synergistic toughening effect of nano-calcium carbonate and dimethyl silicone oil, combined with the high dispersibility of the composite flame retardant, to make the colloid tensile strength ≥2.5MPa and the elongation at break ≥500%, meeting the 35-level displacement sealing requirements.

[0026] The above summary is for illustrative purposes only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments and features described above, further aspects, embodiments and features of the present invention will be readily apparent by reference to the accompanying drawings and the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or technical descriptions. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1 This is a schematic flow chart of a method for preparing a halogen-free, environmentally friendly, high-efficiency, flame-retardant silicone adhesive according to the present invention;

[0029] Figure 2 This is a comparison chart of experimental data results provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0030] The embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.

[0031] It should be clear that the following embodiments of the present disclosure are described through specific concrete examples, and those skilled in the art can easily understand other advantages and effects of the present disclosure from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all the embodiments. The present disclosure can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present disclosure. It should be noted that the following embodiments and features in the embodiments can be combined with each other in the absence of conflict. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present disclosure.

[0032] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on this disclosure, it should be understood by those skilled in the art that an aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects described herein can be used to implement the device and / or practice the method. In addition, other structures and / or functionalities other than one or more of the aspects described herein can be used to implement this device and / or practice this method.

[0033] It should also be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present disclosure. The illustrations only show components related to the present disclosure and are not drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component can be changed at will, and the component layout type may also be more complicated.

[0034] Additionally, in the following description, specific details are provided to provide a thorough understanding of the examples. However, one skilled in the art will appreciate that the aspects described can be practiced without these specific details.

[0035] Figure 1 This is a flow chart of a method for preparing a halogen-free, environmentally friendly, high-efficiency, flame-retardant silicone adhesive according to an embodiment of the present invention. It should be noted that if there are substantially the same results, the method of this application is not based on Figure 1 The process sequence shown is limited. Figure 1 As shown: The embodiment of the present invention provides a method for preparing a halogen-free, environmentally friendly, high-efficiency, flame-retardant silicone adhesive, comprising the following steps:

[0036] Step 1: Weigh, by weight, 100 parts of hydroxy-terminated polydimethylsiloxane, 20-25 parts of dimethyl silicone oil, 90-120 parts of a homemade composite flame retardant, 120-150 parts of nano-calcium carbonate, 3-5 parts of methyltrimethoxysilane, and 2-5 parts of a titanium complex;

[0037] For hydroxy-terminated polydimethylsiloxane, purchase products that meet industry quality standards, have a purity of ≥99%, and a viscosity within a certain range (e.g., 5,000-10,000 mPa·s, depending on product requirements). Store in a cool, dry, well-ventilated warehouse, away from direct sunlight, and at a temperature between 5°C and 30°C to prevent molecular chain degradation due to high temperatures or fluidity loss due to low temperatures.

[0038] Dimethyl silicone oil: Select dimethyl silicone oil with an appropriate kinematic viscosity (e.g., 20-1000 mPa·s) based on the desired degree of toughening and improvement in processing properties. Storage conditions are the same as for hydroxy-terminated polydimethylsiloxane, and it must be stored separately from other chemicals to prevent contamination.

[0039] Self-made composite flame retardant: compound in advance according to the mass ratio of phosphorus flame retardant and nano-aluminum hydroxide 20%-30%:70%-80%; the compounding process is carried out in a dry and clean environment, and stirring equipment is used to fully mix and ensure the dispersion of the flame retardant;

[0040] Nano calcium carbonate: Use nano calcium carbonate with a particle size of 50-200 nm and that has been pretreated with a silane coupling agent (the silane coupling agent is γ-methacryloxypropyltrimethoxysilane, with a mass ratio of 100:0.5-100:1.5). Keep it away from moisture during storage to prevent the nanoparticles from agglomerating.

[0041] Methyltrimethoxysilane: Purchase analytical grade or industrial grade high purity (≥98%) products and store them in sealed containers in a cool, dark place to prevent hydrolysis and ineffectiveness;

[0042] Titanium complexes (such as tetraisopropyl titanate or tetrabutyl titanate): Select products with a catalytic cross-linking reaction rate of 0.5-1.0 mol / (L·min) and store them in a dry, low-temperature environment (0-10°C) to avoid prolonged contact with water and air to prevent deterioration.

[0043] The specific steps of the weighing operation are as follows:

[0044] First, based on the production scale and accuracy requirements, select an electronic balance or automatic weighing equipment equipped with a load cell with an accuracy of ±0.1g (pilot scale) or ±1g (pilot and mass production scale); and calibrate the balance or weighing equipment before each weighing to ensure accurate weighing. You can use standard weights for calibration and follow the steps in the equipment manual.

[0045] Then, weigh each raw material in sequence according to the formula ratio; first weigh the end-hydroxy polydimethylsiloxane. Since it is a viscous liquid, it can be transferred to the reaction vessel or intermediate storage container by pouring and scraping the wall to ensure complete transfer; then weigh the dimethyl silicone oil, and also pay attention to the residual problem during the transfer process; when weighing the homemade composite flame retardant, since the powdered substance is easy to fly, it can be operated in a relatively closed environment (such as a fume hood), and stirred while adding (if weighed directly in the reactor) to prevent local accumulation; when weighing nano calcium carbonate, pay attention to avoid it being exposed to the air for too long to cause agglomeration, and weigh it quickly and put it into the subsequent process as soon as possible; the amount of methyltrimethoxysilane and titanium complex is relatively small, and a micro-injector or a small-scale measuring cylinder with higher precision can be used to assist in weighing to ensure accurate measurement. After weighing, quickly transfer to the designated container to prevent volatile loss;

[0046] At the same time, during the weighing process, detailed records of the name, specifications, actual weighing amount, weighing time, operator and other information of each raw material are recorded to form a complete production record file;

[0047] Finally, after weighing is completed, another person will review the weighed amount of each raw material to ensure that it is consistent with the formula requirements. If there is any deviation, the cause will be found and corrected in time, and re-weighed if necessary.

[0048] Step 2: Put the weighed hydroxy-terminated polydimethylsiloxane, dimethyl silicone oil, nano-calcium carbonate and homemade composite flame retardant into a high-speed screw machine, and disperse and grind them at a speed of ≥500 r / min for 30-60 minutes to obtain a mixed material;

[0049] Specifically, first, according to the production scale (small-scale test, pilot test or mass production), select a high-speed screw machine of appropriate specifications; for example, a small screw machine with a volume of 5-10L can be selected for a small-scale test, and a larger volume model can be selected for pilot test and mass production according to the output requirements. Ensure that the equipment is installed on a stable and level foundation, and reserve enough space around it for operation, maintenance and repair; and before use, thoroughly check the mechanical components of the high-speed screw machine, such as the screw, barrel, seals, etc. to see if they are intact and the connections are tight. Check whether the motor, transmission device, temperature control system, lubrication system, etc. are operating normally. Start the equipment for no-load debugging, observe whether the screw rotates smoothly, and whether there is any abnormal noise or vibration to ensure that the equipment is in good working condition;

[0050] Then, the end-hydroxy polydimethylsiloxane, dimethyl silicone oil, nano-calcium carbonate, and homemade composite flame retardant are sequentially added into the high-speed screw machine; since the end-hydroxy polydimethylsiloxane and dimethyl silicone oil are liquid, they can be directly poured through the feed port or added by pipeline; the nano-calcium carbonate and homemade composite flame retardant are powdery, and to prevent them from flying, they can be slowly added with the help of a funnel, while the screw machine is turned on at a low speed (about 100-200r / min) to allow the raw materials to be preliminarily mixed and brought into the barrel by the screw;

[0051] Next, according to the raw material characteristics and the expected dispersion effect, the screw machine speed is set to ≥500r / min. Generally speaking, for situations with high nano-filler content and strict requirements on dispersion uniformity, the speed can be appropriately increased to 600-800r / min. However, it should be noted that too high a speed may cause problems such as increased material heating and increased equipment wear. During the commissioning stage, the speed can be gradually increased and the material state and equipment operation can be observed to determine the optimal speed parameters.

[0052] The dispersion grinding time is controlled within 30-60 minutes; the initial stage can be set to 30 minutes, and then the dispersion effect can be judged by sampling and observing the uniformity of the material (such as using a microscope to observe the dispersion of nanoparticles) and testing relevant performance indicators (such as viscosity changes); if the ideal effect is not achieved, the grinding time can be appropriately extended, but it should not be too long to avoid excessive grinding leading to degradation of material performance (such as molecular chain breakage);

[0053] During the dispersion and grinding process, the material temperature is monitored in real time by the screw machine's jacket temperature control device to control the temperature at 50-80°C. If the temperature rises too quickly and approaches or exceeds the upper limit, the temperature can be lowered by reducing the screw speed, increasing the jacket cooling medium flow rate, etc. If the temperature is too low, the jacket heating temperature can be appropriately increased or the material residence time in the screw machine can be extended to ensure that the temperature is within the appropriate range, which is conducive to the dispersion of nanoparticles and prevents adverse changes such as thermal degradation of the raw materials.

[0054] Finally, when the dispersion grinding reaches the predetermined time and the material state meets the requirements, open the screw machine discharge port and transport the mixed material to the storage container or reactor of the subsequent process. During the discharge process, pay attention to observe the fluidity and uniformity of the material. If any abnormality occurs (such as material agglomeration, poor discharge), analyze the cause in time and take corresponding measures (such as cleaning the discharge port and adjusting the material properties).

[0055] Step 3: heating the mixed material to 100-130°C and dehydrating the mixture under vacuum at a degree of vacuum ≤-0.09 MPa for 2-3 hours to obtain a semi-finished base material. During the dehydration process, the material is continuously stirred;

[0056] Specifically, first, according to the amount of mixed materials, select a reactor with a suitable volume, and ensure that the volume of the materials does not exceed 2 / 3 of the volume of the reactor, so that there is enough space for stirring and to prevent the materials from overflowing. The reactor must have good sealing and corrosion resistance, and be equipped with reliable heating, temperature control, vacuum and stirring devices; for example, a stainless steel reactor can be selected, which can adapt to a variety of chemical environments and is easy to clean and maintain; at the same time, check the heating device of the reactor (such as electric heating rods, jacket heating, etc.) to ensure that it can stably heat up and accurately control the temperature. According to the temperature control range and accuracy requirements of the reactor, calibrate the temperature sensor and control system, set the heating rate (generally controllable at 5-10℃ / min), and avoid Rapid heating causes local overheating of the material; and conduct a comprehensive inspection of the vacuum system (vacuum pump, vacuum pipeline, vacuum gauge, etc.) to confirm that the vacuum pump is in good performance and can achieve the required vacuum degree (≤-0.09MPa), and check whether the vacuum pipeline is well sealed and there is no air leakage. Leak detection can be performed by applying soapy water, etc., and the vacuum gauge is calibrated to ensure accurate measurement; also check the operation of the agitator to ensure that the stirring blades are firmly installed and without deformation, and the stirring motor is operating normally. According to the size of the reactor and the characteristics of the material, select the appropriate stirring blade type (such as anchor type, paddle type, turbine type, etc.) to ensure that the material can be evenly mixed and heated during the stirring process, and adjust the stirring speed to ensure that it can operate stably during the dehydration process;

[0057] Then, carefully transfer the mixed material obtained in step 2 to the reactor, turn on the heating device of the reactor, and heat the mixed material to 100-130°C at the set heating rate. During the heating process, pay close attention to the temperature changes and record the temperature value every certain time (such as 5-10 minutes). When the temperature approaches the target range, appropriately reduce the heating rate and make fine adjustments to ensure that the temperature is stable within the set range. For example, if the target temperature is 120°C, when the temperature rises to about 115°C, adjust the heating rate to 1-2°C / min until it reaches and stabilizes at 120°C.

[0058] When the temperature of the mixed material reaches the predetermined range, start the vacuum pump to perform vacuum operation, and slowly adjust the vacuum valve to gradually reduce the vacuum degree to ≤-0.09MPa. During the vacuuming process, closely observe the value changes of the vacuum gauge to prevent the vacuum degree from dropping too quickly, causing material splashing or other abnormal conditions;

[0059] After the vacuum degree reaches the requirement, start the timer and perform vacuum dehydration for 2-3 hours. The dehydration time can be adjusted appropriately according to the moisture content of the material and the actual dehydration effect. For example, if the test shows that the moisture content of the material decreases slowly, the dehydration time can be appropriately extended to 3.5 hours. However, it should be noted that excessive vacuum dehydration may affect certain properties of the material, such as causing the volatilization loss of some low-boiling point components.

[0060] During the entire vacuum dehydration process, keep the material stirred continuously. The stirring speed can generally be controlled at 50-150r / min, which can be adjusted according to the viscosity of the material and the stirring effect. The purpose of stirring is to make the material heated evenly and the water can escape more fully, while preventing the material from being overheated or coking locally.

[0061] Then, after the dehydration is completed, turn off the vacuum pump and heating device, stop stirring, and judge whether the dehydration has achieved the expected effect by detecting the water content of the material (Karl Fischer titration method, etc. can be used) or observing the appearance of the material (such as whether it is clear, whether there are bubbles, etc.). If the water content is still high or the material state does not meet the requirements, decide whether to perform secondary dehydration according to the situation; if the semi-finished base material meets the requirements, carefully transfer it from the reactor to a clean, sealed storage container, and place the storage container in a cool, dry environment, waiting for use in the next process.

[0062] Step 4: Cool the semi-finished base material to 40-50°C through a condenser and put it into a storage tank;

[0063] Specifically, first, select the appropriate type and specification of condenser based on the output of semi-finished base materials, temperature requirements, and site conditions. Common types include shell-and-tube condensers and plate condensers. If the base material output is large and high heat exchange efficiency is required, a plate condenser can be selected. If the base material is corrosive, a shell-and-tube condenser made of corrosion-resistant materials (such as titanium) should be selected. Ensure that the heat exchange area and cooling medium flow rate of the condenser can meet the requirements of reducing the base material temperature from the current temperature to 40-50°C.

[0064] Then, connect the reactor and the condenser through the pipe, ensuring that the connection is firm and well sealed to prevent leakage of the base material. During the connection process, pay attention to the slope of the pipe to avoid liquid accumulation. Open the discharge valve of the reactor to allow the semi-finished base material to slowly flow into the condenser. When introducing the base material, closely observe the flow of the base material to prevent blockage.

[0065] Next, according to the initial temperature, flow rate and target temperature range (40-50°C) of the base material, adjust the flow rate and temperature of the cooling medium. If the initial temperature of the base material is high, the flow rate of the cooling medium can be appropriately increased or the temperature of the cooling medium can be lowered. However, it is necessary to avoid problems such as solidification, crystallization or stress concentration of the base material caused by excessive cooling. For example, when the initial temperature of the base material is around 100°C, the temperature of the cooling medium can be set to 20-30°C first, and the flow rate can be adjusted so that the residence time of the base material in the condenser can ensure that it is cooled to the target range. During the cooling process, the temperature change of the base material is monitored in real time through the temperature monitoring point on the condenser, and the temperature data is recorded at regular intervals (such as 2-5 minutes). According to the temperature change, the flow rate or temperature of the cooling medium is fine-tuned in time to ensure that the base material temperature is stable at 40-50°C.

[0066] Finally, select a storage tank of suitable material (such as stainless steel, plastic, etc., selected according to the characteristics of the base material) and capacity, ensure that the storage tank is clean, dry and free of impurities, and clean and disinfect the storage tank before use, such as rinsing with clean water, steam sterilization (if applicable), etc., to prevent residual substances in the tank from contaminating the base material; the base material cooled to 40-50℃ is transported to the storage tank through a pipeline. During the transportation process, a pump (such as a centrifugal pump, screw pump, etc., select a suitable pump type according to the viscosity of the base material) can be used for transportation, and the flow and pressure of the pump can be controlled to avoid excessive shear force on the base material during transportation, which will affect the base material performance; while the base material is being pumped into the storage tank, observe the changes in the liquid level of the tank to avoid overflow caused by excessive liquid level; when the tank reaches the appropriate liquid level (generally not exceeding 80% of the tank volume), stop transportation, close the tank inlet and outlet valves, and place the tank in the specified storage area. The storage area should be kept cool, dry, and well ventilated to avoid direct sunlight and high temperature environment.

[0067] Step 5: transport the semi-finished base material in the storage tank to a fully automatic static mixer via a pipeline, and add the weighed methyltrimethoxysilane and titanium complex in sequence;

[0068] Specifically, first, according to the properties of the semi-finished base material (such as viscosity, corrosiveness, etc.) and the conveying volume, select pipes of appropriate material and diameter; for example, for general silicone adhesive semi-finished base materials, stainless steel pipes or corrosion-resistant plastic pipes (such as polyethylene, polypropylene, etc.) can be selected to ensure that the inner diameter of the pipe can meet the conveying flow requirements of the base material to avoid the situation where the flow rate is too fast or too slow; and connect the discharge port of the storage tank with the feed port of the fully automatic static mixer through a pipe. During the connection process, use appropriate pipe fittings (such as elbows, tees, flanges, etc.) to ensure that the pipe connection is tight and there are no leaks; seal the joints with materials such as sealing gaskets and sealants to prevent leakage of the base material; after the connection is completed, pressure test the pipeline system to check for leaks;

[0069] Then, according to the formula requirements, accurately weigh methyltrimethoxysilane and titanium complex, place the weighed methyltrimethoxysilane and titanium complex in appropriate containers, and mark them to prevent confusion;

[0070] Then, according to the process requirements, methyltrimethoxysilane and titanium complex are added to the fully automatic static mixer in sequence. Generally, methyltrimethoxysilane is added first, and after it is preliminarily mixed with the base material, the titanium complex is added. During the addition process, attention should be paid to controlling the addition speed to avoid adding too quickly, which may lead to excessive local concentration or uneven reaction. The addition method of methyltrimethoxysilane and titanium complex can be selected according to the specific situation. For liquid methyltrimethoxysilane, it can be directly transported to the mixer through a pipeline. For solid titanium complexes (such as tetraisopropyl titanate or tetrabutyl titanate), First dissolve it in an appropriate amount of solvent, and then add it to the mixer through a pipe or other means; during the addition process, ensure that the additive can be evenly dispersed in the base material; at the same time, when the base material is transported to the fully automatic static mixer, the base material delivery flow rate is accurately controlled by a flow meter or other flow control device. According to the design requirements and process parameters of the mixer, the base material flow rate is controlled within an appropriate range to ensure mixing effect and production efficiency; for example, if the optimal operating flow range of the mixer is 5-10L / min, the base material delivery flow rate is controlled within this range.

[0071] Step 6: Mix the mixture in a fully automatic static mixer at room temperature for 15-20 minutes, mix evenly and pack to obtain a halogen-free, environmentally friendly and high-efficiency flame-retardant silicone adhesive product;

[0072] Specifically, after adding the semi-finished base material, methyltrimethoxysilane and titanium complex into the fully automatic static mixer, start the mixer drive motor to make the mixer start running at the preset speed; and use the mixer's built-in time control system or external timer to accurately set the mixing time to 15-20 minutes; during the mixing process, the operator needs to pay close attention to the time and cannot change the mixing time at will; if the mixing is interrupted due to special circumstances (such as a temporary equipment failure), the mixing time needs to be re-evaluated or the mixing operation needs to be repeated; for example, if the equipment is temporarily powered off at 10 minutes of mixing, the mixing time needs to be recalculated after the power is restored to ensure that the total mixing time is within the specified range;

[0073] During the mixing process, observe the operating status of the mixer every 3-5 minutes to check for material leakage, abnormal noise or increased vibration. At the same time, observe the uniformity of the material mixing through the sight glass or sampling port on the mixer. For example, observe whether the material color is uniform and whether there is obvious stratification or particle agglomeration. If uneven mixing is found, extend the mixing time appropriately or check whether there are any problems with the internal structure of the mixer.

[0074] When the mixing time reaches 15-20 minutes and the materials are confirmed to be evenly mixed, open the discharge port of the mixer and use the filling machine to quantitatively fill the silicone rubber product into the packaging container; during the filling process, the filling speed must be controlled to avoid material overflow or inaccurate filling volume; after filling is completed, immediately use the sealing machine to seal the package. For plastic flexible packaging, use heat sealing to ensure that the seal is flat, firm and leak-free; for plastic barrels or metal barrels, tighten the barrel lid to ensure a good seal.

[0075] After packaging, affix a product label to the container. The label should include information such as product name, model, specifications, production date, shelf life, manufacturer, implementation standards, instructions for use, and precautions. Ensure that the label is clearly and securely affixed, and the information is legible for easy identification and use.

[0076] In one embodiment, specifically: in step 1, the self-made composite flame retardant is compounded by a phosphorus-based flame retardant and nano-aluminum hydroxide in a mass ratio of 20%-30%:70%-80%;

[0077] Specifically, the homemade composite flame retardant is compounded by phosphorus flame retardant and nano aluminum hydroxide in a specific mass ratio, with phosphorus flame retardant accounting for 20%-30% and nano aluminum hydroxide accounting for 70%-80%; this ratio setting is obtained through a large number of experimental verifications, and is intended to achieve synergistic effect of the two flame retardant ingredients; phosphorus flame retardant will play a role in the gas phase during combustion, forming phosphoric acid or polyphosphoric acid to cover the surface of the burning material, isolating oxygen and inhibiting the combustion reaction; nano aluminum hydroxide will decompose and absorb heat when heated, reducing the surface temperature of the material, and the water vapor produced by the decomposition can also dilute the oxygen concentration in the combustion area, playing a condensed phase flame retardant effect; the two are compounded in this ratio, which can not only give full play to the high-efficiency gas phase flame retardant properties of phosphorus flame retardant, but also utilize the good condensed phase flame retardant effect of nano aluminum hydroxide, thereby reducing the total amount of flame retardant while ensuring the flame retardant effect, and avoiding the negative impact of large amounts of flame retardant on other properties of silicone adhesive (such as mechanical properties);

[0078] The phosphorus-based flame retardant is one or more combinations of red phosphorus masterbatch, phosphate ester, and ammonium polyphosphate;

[0079] Specifically, red phosphorus masterbatch has high flame retardant efficiency and relatively low cost, but it has the problems of easy moisture absorption and poor stability; phosphate ester has good solubility and processing properties, and is more compatible with the silicone adhesive matrix; ammonium polyphosphate has good thermal stability and a high decomposition temperature, and can form a stable carbon layer at high temperatures to enhance the flame retardant effect; selecting one or more flame retardants for combination can comprehensively utilize their advantages and make up for the shortcomings of a single flame retardant; for example, combining red phosphorus masterbatch with phosphate ester can not only improve the flame retardant efficiency, but also improve the dispersibility and stability of the red phosphorus masterbatch; combining ammonium polyphosphate with phosphate ester can exert a flame retardant effect at different temperature stages and improve the flame retardant properties of silicone adhesive;

[0080] The particle size of nano aluminum hydroxide is 50-100nm;

[0081] Specifically, nano-aluminum hydroxide with a particle size of 50-100nm is selected. Compared with ordinary aluminum hydroxide, the nano-scale particle size gives it a larger specific surface area and higher activity; in the silicone adhesive system, smaller particles can be more evenly dispersed in the matrix and fully contact with other components, thereby enhancing the flame retardant effect and mechanical properties; the small particle size of nano-aluminum hydroxide can also improve its synergistic efficiency with phosphorus-based flame retardants, allowing the composite flame retardant to form a denser flame retardant network structure in the silicone adhesive, effectively preventing the transfer of heat and oxygen, and further improving the flame retardant properties of the silicone adhesive.

[0082] In one embodiment, specifically: the particle size of the nano calcium carbonate is 50-200 nm, and the surface is pre-treated with a silane coupling agent;

[0083] Specifically, the particle size of nano calcium carbonate in the range of 50-200nm is of great significance. At this particle size, it has good compatibility and dispersibility with the silicone adhesive matrix, can be evenly distributed between polymer molecular chains, effectively transfer stress, prevent crack propagation, and greatly improve the mechanical properties of silicone adhesive such as tensile strength and elongation at break. Compared with ordinary calcium carbonate, the tensile strength can be increased by 20%-30%, and the smaller particle size increases the contact area with the matrix, enhancing the interaction force, and has significant advantages in high-stress and high-sealing requirements such as building curtain wall sealing and automotive component sealing. At the same time, this particle size range also helps to improve the processing performance of silicone adhesive, plays a role similar to that of a plasticizer, reduces the viscosity of the system, makes silicone adhesive easier to flow and form during processing, improves production efficiency, reduces processing energy consumption, and is more evenly distributed in processes such as coating and extrusion. For example, during extrusion molding, it can make silicone adhesive extrusion smoother, reduce bubbles and defects, and improve product appearance quality and dimensional accuracy.

[0084] The effect of pre-treatment of nano-calcium carbonate with silane coupling agent is significant. Its molecular structure is unique. One end is chemically bonded to the hydroxyl group on the surface of nano-calcium carbonate, and the other end is compatible with the organic molecules of the silicone adhesive matrix. It effectively improves the dispersibility of nano-calcium carbonate in silicone adhesive, avoids agglomeration, makes it evenly distributed, enhances the improvement of the mechanical properties of silicone adhesive and makes the performance more stable and consistent. Scanning electron microscopy shows that the pre-treated nano-calcium carbonate is more evenly dispersed; at the same time, the silane coupling agent forms a transition layer between the two, enhancing the interfacial bonding force, so that the nano-calcium carbonate and the matrix can cooperate to resist external forces, significantly improving the mechanical properties of silicone adhesive such as impact strength and tear strength, and reducing the risk of failure in applications such as sealing and bonding of automotive parts that are subjected to impact loads; in addition, pre-treatment forms a protective film on the surface of nano-calcium carbonate to prevent contact with moisture and chemicals, improve the water resistance and chemical resistance of silicone adhesive, and enable it to maintain stable performance in humid or corrosive environments such as building exterior wall sealing, thereby extending its service life.

[0085] In one embodiment, specifically: in step 2, during the high-speed screw machine dispersion and grinding process, the material temperature is controlled at 50-80°C;

[0086] Specifically, by precisely controlling the material temperature at 50-80°C, material fluidity is optimized, the viscosity of liquid raw materials such as end-hydroxy polydimethylsiloxane and dimethyl silicone oil is reduced, and solid particles such as nano-calcium carbonate and the homemade composite flame retardant are easier to disperse, effectively reducing the agglomeration of nano-calcium carbonate. Experiments show that the number of agglomerates is reduced by 30%-40% compared with dispersion at room temperature, greatly improving the uniformity and stability of the silicone adhesive. At the same time, this temperature creates favorable conditions for weak chemical reactions or physical adsorption between the raw materials. For example, the phosphorus-based flame retardant in the composite flame retardant will interact with nano-aluminum hydroxide at the interface. Thermal analysis experiments show that the flame retardant efficiency of the treated composite flame retardant can be increased by 10%-15%, significantly enhancing the flame retardant properties of the final product. In addition, the 50-80°C temperature effectively protects the raw material properties, preventing excessive temperatures from causing oxidative decomposition of dimethyl silicone oil and ineffectiveness of the composite flame retardant components, and preventing excessive temperatures from causing excessive viscosity and difficulty in dispersion, ensuring the stable function of each raw material and laying a solid foundation for the final high-quality silicone adhesive product.

[0087] In one embodiment, specifically: in step 5, methyltrimethoxysilane is used as a cross-linking agent and a titanium complex is used as a catalyst;

[0088] Among them, methyltrimethoxysilane is used as a crosslinking agent. Its unique chemical structure makes it play the role of a "bridge builder" in the silicone adhesive system. The methoxy group (-OCH3) in its molecule has high reactivity and can be hydrolyzed to form silanol groups (-SiOH) under certain conditions. These silanol groups can undergo condensation reactions with the hydroxyl groups (-OH) on the terminal hydroxyl polydimethylsiloxane molecular chain, thereby forming chemical bonds between different molecular chains and constructing a three-dimensional network cross-linked structure. The formation of this cross-linked structure greatly changes the physical and chemical properties of silicone adhesives. On the one hand, it enhances the cohesive force of silicone adhesive, making the silicone adhesive have higher strength and hardness after curing, which can better resist the influence of external forces and is less prone to deformation and cracking. For example, in the sealing application of building curtain walls, cross-linked silicone adhesive can withstand greater wind pressure and displacement, ensuring the sealing and safety of the curtain wall. On the other hand, the cross-linked structure also improves the chemical corrosion resistance and weather resistance of silicone adhesive. Due to the close connection between the molecular chains, it is more difficult for chemical substances and external environmental factors to penetrate into the interior of the silicone adhesive, reducing the risk of aging and degradation of the silicone adhesive due to erosion, and extending its service life.

[0089] As a catalyst, titanium complex plays an important role in accelerating the cross-linking reaction of silicone glue. The rate of the cross-linking reaction itself is relatively slow. If it relies solely on natural reactions, it may take a long time for the silicone glue to reach the ideal degree of curing, which is unrealistic in actual production. The addition of titanium complex can reduce the activation energy of the cross-linking reaction, making the reaction easier to occur, greatly shortening the curing time of silicone glue. It changes the reaction pathway by forming a specific intermediate complex with the reactant molecules, so that the condensation reaction between methyltrimethoxysilane and end-hydroxy polydimethylsiloxane can be completed in a shorter time. In actual production, this not only improves production efficiency, but also ensures the stability of the quality of silicone glue products. Because the fast and stable curing process can reduce product performance differences caused by excessive reaction time or fluctuations in reaction conditions. At the same time, the catalytic effect of the titanium complex can also make the cross-linking reaction more complete, further optimize the cross-linking structure of the silicone glue, and improve its overall performance.

[0090] In one embodiment, specifically: in step 3, during the vacuum dehydration process, the vacuum degree is maintained between -0.095 MPa and -0.09 MPa;

[0091] Specifically, from the perspective of dehydration efficiency, the vacuum range of -0.095MPa to -0.09MPa creates favorable conditions for the rapid escape of moisture. In this negative pressure environment, the boiling point of water is significantly reduced. For example, under standard atmospheric pressure, the boiling point of water is 100°C, while under a vacuum of -0.095MPa to -0.09MPa, the boiling point of water can drop to around 40°C or even lower, which allows the moisture in the mixed material to quickly vaporize into water vapor at a relatively low temperature. After the mixed material is heated to 100-130°C, at this vacuum, moisture can be more efficiently separated from the material, greatly shortening the dehydration time and improving production efficiency. Compared with dehydration under a lower vacuum, it can save about 30%-40% of the dehydration time, ensuring the efficient advancement of the production process.

[0092] From the perspective of product quality, stable vacuum plays a decisive role in ensuring the performance of silicone adhesive. If the vacuum degree is too low, moisture cannot be fully removed, and the residual moisture will generate bubbles during the subsequent curing process of the silicone adhesive. These bubbles will reduce the strength, sealing performance and appearance quality of the silicone adhesive. For example, in electronic component packaging applications, silicone adhesive containing bubbles may cause uneven heat dissipation of components, affecting the stability and service life of electronic equipment. Maintaining a vacuum degree between -0.095MPa and -0.09MPa can control the moisture content at an extremely low level, effectively avoiding the generation of bubbles and improving the overall quality of silicone adhesive. In addition, the appropriate vacuum degree can also prevent the oxidation and decomposition of materials at high temperatures. In a high vacuum environment, the oxygen content is extremely low, reducing the chance of material contact with oxygen, thereby reducing the risk of performance degradation due to oxidation and ensuring the chemical stability of the silicone adhesive and the consistency of physical properties.

[0093] In one embodiment, specifically: in step six, the mixing element of the fully automatic static mixer is a spiral blade, and the material flow rate during the mixing process is controlled at 0.5-1.0 m / s;

[0094] Specifically, the unique structural design of the spiral blades provides an excellent foundation for material mixing. The blades form a complex and orderly flow path within the mixer, and the materials are continuously divided, merged, and redistributed as they pass through. When the semi-finished base material containing methyltrimethoxysilane and titanium complex enters the mixer, the spiral blades guide the material along a specific path, allowing for full contact between the different components. Compared with mixing elements of other shapes, spiral blades can generate stronger shear forces and dispersion effects, ensuring uniform mixing of various raw materials. For example, in some electronic applications that require extremely high mixing uniformity, static mixers using spiral blades can allow additives to be evenly dispersed in silicone adhesives down to the microscopic scale, avoiding local concentrations that are too high or too low, thereby ensuring the consistency of silicone adhesive product performance.

[0095] Controlling the material flow rate between 0.5 and 1.0 m / s is the optimal range determined after comprehensive consideration of mixing effect and production efficiency. If the flow rate is too low, the material will stay in the mixer for too long, which, although conducive to uniform mixing, will reduce production efficiency and increase production costs. If the flow rate is too high, the material will be discharged from the mixer before it has time to be fully mixed, resulting in uneven mixing and affecting product quality. Within this flow rate range, it can ensure that the material is subjected to sufficient shear and stirring when passing through the spiral blades to achieve uniform mixing while maintaining a certain level of production efficiency. For example, through experimental comparison, it was found that when the flow rate was controlled at 0.8 m / s, the mixing uniformity of the various components in the silicone adhesive reached over 98%, and a certain amount of finished product could be produced per hour, meeting the needs of industrial production. In addition, a stable flow rate also helps ensure the stability and repeatability of the production process, facilitates the control and management of the production process, and provides a strong guarantee for the large-scale production of high-quality halogen-free, environmentally friendly, and highly efficient flame-retardant silicone adhesives.

[0096] In one embodiment, specifically: when the phosphorus-based flame retardant is a combination of multiple types, the mass ratio of red phosphorus masterbatch, phosphate ester, and ammonium polyphosphate is 1:1:1-2:1:3;

[0097] Specifically, when these three flame retardants are used in combination according to a mass ratio of 1:1:1-2:1:3, their advantages can be comprehensively utilized to make up for their respective shortcomings; for example, at a lower ratio (such as 1:1:1), red phosphorus masterbatch provides basic flame retardancy, phosphate ensures good dispersion and processing performance of the flame retardant in silicone adhesive, and ammonium polyphosphate plays a role in stabilizing the carbon layer at high temperature, so that the silicone adhesive can have a certain flame retardant effect in different combustion stages; with the appropriate increase of the ratio of red phosphorus masterbatch and ammonium polyphosphate (such as 2:1:3), the flame retardant effect of the three flame retardants can be effectively controlled. ), the overall flame retardant performance of silicone adhesive will be further improved, especially in terms of flame retardant grade and combustion resistance; within this ratio range, through synergistic effect, the flame retardant grade of silicone adhesive can reach GB / T2408-2021 standard V0 level, and the combustion resistance can reach GB / T23864-2021 standard A3 level. At the same time, while maintaining good flame retardant performance, it can ensure that the mechanical properties and processing performance of silicone adhesive are not greatly affected, and meet the requirements of different application scenarios for the flame retardant performance and comprehensive performance of silicone adhesive.

[0098] In one embodiment, specifically: the silane coupling agent is γ-methacryloxypropyltrimethoxysilane, and the mass ratio of nano-calcium carbonate to the silane coupling agent during pretreatment is 100:0.5-100:1.5;

[0099] Specifically, γ-methacryloxypropyltrimethoxysilane has a unique chemical structure. Its molecule contains both a hydrolyzable methoxy group and an unsaturated double bond. The methoxy group can undergo a hydrolysis reaction in the presence of water to generate a silanol group, which can undergo a condensation reaction with the hydroxyl groups on the surface of nano-calcium carbonate, thereby tightly binding to the surface of the nano-calcium carbonate. The unsaturated double bond can chemically react or physically entangle with the organic components in the silicone adhesive matrix, forming a strong connection between the nano-calcium carbonate and the silicone adhesive matrix.

[0100] During the pretreatment process, the mass ratio of nano-calcium carbonate to γ-methacryloxypropyltrimethoxysilane is controlled at 100:0.5-100:1.5 to achieve the best modification effect. If the amount of silane coupling agent used is too small, less than 100:0.5, the hydroxyl groups on the surface of the nano-calcium carbonate cannot be fully covered, and the connection with the silicone adhesive matrix is ​​not tight enough, which cannot effectively improve the dispersibility and interfacial bonding strength of the nano-calcium carbonate in the silicone adhesive, resulting in limited improvement in the mechanical properties of the silicone adhesive, such as no significant increase in tensile strength and elongation at break. On the contrary, if the amount of silane coupling agent used is too much, exceeding 100:1.5, the excess silane coupling agent may self-polymerize in the system, which not only causes waste, but may also affect the curing process and final performance of the silicone adhesive, such as causing the silicone adhesive to cure more slowly or causing problems such as surface stickiness after curing. Within this mass ratio range, the treated nano-calcium carbonate is evenly dispersed in the silicone adhesive, which can effectively enhance the tensile strength, elongation at break, water resistance and other properties of the silicone adhesive, meeting the application requirements of silicone adhesive in different fields such as building sealing and electronic packaging.

[0101] In one embodiment, specifically: the titanium complex is tetraisopropyl titanate or tetrabutyl titanate, and the catalytic cross-linking reaction rate is 0.5-1.0 mol / (L·min);

[0102] Specifically, the molecular structures of tetraisopropyl titanate and tetrabutyl titanate contain titanyl bonds that easily coordinate with silanol groups. In the silicone adhesive system, they can accurately combine with the silanol groups produced by the hydrolysis of methyltrimethoxysilane and the hydroxyl groups of hydroxy-terminated polydimethylsiloxane to form active intermediates, significantly reducing the activation energy of the cross-linking reaction. This effectively promotes the condensation reaction of the silanol bonds and prompts the linear molecular chains to quickly build a three-dimensional network cross-linked structure.

[0103] Strictly controlling the catalytic cross-linking reaction rate within 0.5-1.0 mol / (L·min) is based on the dual considerations of production efficiency and product quality. If the reaction rate is too slow, below 0.5 mol / (L·min), the silicone adhesive curing time will be significantly prolonged, seriously reducing production efficiency, increasing energy consumption and time costs, and may also introduce impurities due to prolonged exposure to the environment, affecting product purity. On the other hand, if the reaction rate is too fast, exceeding 1.0 mol / (L·min), it may cause the reaction to run away, leading to localized excessive cross-linking and gelation. This will make the silicone adhesive's internal structure uneven, resulting in differences in hardness distribution and reduced mechanical properties, such as reduced tensile strength and poor toughness. These problems make it difficult to meet the stringent mechanical property and stability requirements of silicone adhesives in applications such as building sealing and electronic packaging. Within the rate range of 0.5-1.0 mol / (L·min), the silicone adhesive can complete cross-linking and curing within a reasonable time, achieving efficient production, while also ensuring that the cross-linking reaction proceeds uniformly and fully, giving the silicone adhesive excellent and stable overall properties, such as high strength, high elasticity, and good weather resistance.

[0104] In summary, the present invention successfully solves the flame retardant and environmental protection problems of traditional silicone adhesives by adopting a preparation method of a halogen-free, environmentally friendly and high-efficiency flame retardant silicone adhesive provided by the above embodiment; the method selects a variety of raw materials such as terminal hydroxyl polydimethylsiloxane and dimethyl silicone oil of specific specifications, and the homemade composite flame retardant is compounded by a phosphorus-based flame retardant and nano-aluminum hydroxide in an optimized ratio, and the nano-calcium carbonate is pretreated with a silane coupling agent, which ensures the product performance from the source; the parameters of each preparation step are precise, such as the speed, temperature and time control during the high-speed screw machine dispersion grinding, and the temperature, vacuum degree and time setting of the vacuum dehydration, all of which ensure that the materials are fully mixed and the performance is stable; methyltrimethoxysilane is used as a cross-linking agent and a titanium complex is used as a catalyst to promote the formation of an ideal cross-linked structure of the silicone adhesive under suitable reaction conditions; the silicone adhesive finally prepared not only releases no toxic gas during combustion, meets international environmental protection standards, but also has excellent flame retardant properties and excellent mechanical properties. It can be widely used in fields such as construction, electronics, and automobiles that have strict requirements on the performance of silicone adhesives, has significant economic and social benefits, and provides a new direction for the development of silicone adhesive preparation technology.

[0105] The present invention is further described below by means of specific examples:

[0106] Example 1

[0107] Raw material ratio:

[0108] Hydroxyl-terminated polydimethylsiloxane (100 parts)

[0109] Dimethyl silicone oil (20 parts)

[0110] Homemade composite flame retardant (0 copies)

[0111] Nano calcium carbonate (120 parts)

[0112] Methyltrimethoxysilane (3 parts)

[0113] Titanium complex (2 parts)

[0114] Preparation steps:

[0115] Put the hydroxy-terminated polydimethylsiloxane, dimethyl silicone oil and nano calcium carbonate into a high-speed screw machine and grind them at a speed of 500 r / min for 30 minutes. During this process, the material temperature is controlled at 50°C by a jacket temperature control device;

[0116] The mixture was heated to 100°C and dehydrated under vacuum at -0.09 MPa for 2 hours, with continuous stirring during the dehydration process.

[0117] The semi-finished base material is cooled to 40°C through a condenser and pumped into a storage tank;

[0118] The semi-finished base material in the storage tank is transported to a fully automatic static mixer through a pipeline, and methyltrimethoxysilane and titanium complex are added in sequence;

[0119] The mixture was mixed in a fully automatic static mixer at room temperature for 15 minutes, and packaged after being evenly mixed to obtain a finished silicone adhesive product.

[0120] Example 2

[0121] Raw material ratio:

[0122] Hydroxyl-terminated polydimethylsiloxane (100 parts)

[0123] Dimethyl silicone oil (22 parts)

[0124] Homemade composite flame retardant (30 parts, including 6 parts of phosphorus flame retardant and 24 parts of nano-aluminum hydroxide)

[0125] Nano calcium carbonate (130 parts)

[0126] Methyltrimethoxysilane (4 parts)

[0127] Titanium complex (3 parts)

[0128] Preparation steps:

[0129] Hydroxyl-terminated polydimethylsiloxane, dimethyl silicone oil, nano-calcium carbonate and homemade composite flame retardant were put into a high-speed screw machine and dispersed and ground at a speed of 550 r / min for 40 minutes. The material temperature was controlled at 60°C.

[0130] The mixture was heated to 110°C and dehydrated under vacuum at -0.092 MPa for 2.5 hours, with continuous stirring during the dehydration process;

[0131] The semi-finished base material is cooled to 45°C through a condenser and pumped into a storage tank;

[0132] The semi-finished base material in the storage tank is transported to a fully automatic static mixer through a pipeline, and methyltrimethoxysilane and titanium complex are added in sequence;

[0133] The mixture was mixed in a fully automatic static mixer at room temperature for 18 minutes, and packaged after being evenly mixed to obtain a finished silicone adhesive product.

[0134] Example 3

[0135] Raw material ratio:

[0136] Hydroxyl-terminated polydimethylsiloxane (100 parts)

[0137] Dimethyl silicone oil (23 parts)

[0138] Homemade composite flame retardant (60 parts, including 15 parts of phosphorus flame retardant and 45 parts of nano-aluminum hydroxide)

[0139] Nano calcium carbonate (135 parts)

[0140] Methyltrimethoxysilane (4 parts)

[0141] Titanium complex (3 parts)

[0142] Preparation steps:

[0143] The relevant raw materials were put into a high-speed screw machine and dispersed and ground at a speed of 580r / min for 45 minutes. The material temperature was controlled at 65°C;

[0144] The mixture was heated to 115°C and dehydrated under vacuum at -0.093 MPa for 2.5 hours with continuous stirring.

[0145] Cool down to 45℃ through condenser and pump into storage tank;

[0146] The semi-finished base material in the storage tank is transported to a fully automatic static mixer through a pipeline, and methyltrimethoxysilane and titanium complex are added in sequence;

[0147] The mixture was mixed in a fully automatic static mixer at room temperature for 18 minutes, and packaged after being evenly mixed to obtain a finished silicone adhesive product.

[0148] Example 4

[0149] Raw material ratio:

[0150] Hydroxyl-terminated polydimethylsiloxane (100 parts)

[0151] Dimethyl silicone oil (24 parts)

[0152] Homemade composite flame retardant (90 parts, including 20 parts of phosphorus flame retardant and 70 parts of nano-aluminum hydroxide)

[0153] Nano calcium carbonate (140 parts)

[0154] Methyltrimethoxysilane (4 parts)

[0155] Titanium complex (4 parts)

[0156] Preparation steps:

[0157] The raw materials were put into a high-speed screw machine and dispersed and ground at a speed of 600 r / min for 50 minutes. The material temperature was controlled at 70°C.

[0158] The mixture was heated to 120°C and dehydrated under vacuum at -0.095 MPa for 2.5 hours with continuous stirring.

[0159] Cool down to 45℃ through condenser and pump into storage tank;

[0160] The semi-finished base material in the storage tank is transported to a fully automatic static mixer through a pipeline, and methyltrimethoxysilane and titanium complex are added in sequence;

[0161] The mixture was mixed in a fully automatic static mixer at room temperature for 18 minutes, and packaged after being evenly mixed to obtain a finished silicone adhesive product.

[0162] Example 5

[0163] Raw material ratio:

[0164] Hydroxyl-terminated polydimethylsiloxane (100 parts)

[0165] Dimethyl silicone oil (25 parts)

[0166] Homemade composite flame retardant (120 parts, including 30 parts of phosphorus flame retardant and 90 parts of nano-aluminum hydroxide)

[0167] Nano calcium carbonate (150 parts)

[0168] Methyltrimethoxysilane (5 parts)

[0169] Titanium complex (5 parts)

[0170] Preparation steps:

[0171] The raw materials were put into a high-speed screw machine and dispersed and ground at a speed of 600 r / min for 60 minutes. The material temperature was controlled at 80°C.

[0172] The mixture was heated to 130°C and dehydrated under vacuum at -0.095 MPa for 3 hours with continuous stirring.

[0173] Cool down to 50℃ through condenser and pump into storage tank;

[0174] The semi-finished base material in the storage tank is transported to a fully automatic static mixer through a pipeline, and methyltrimethoxysilane and titanium complex are added in sequence;

[0175] The mixture was mixed in a fully automatic static mixer at room temperature for 20 minutes, and packaged after being evenly mixed to obtain a finished silicone adhesive.

[0176] Example 6

[0177] Raw material ratio:

[0178] Hydroxyl-terminated polydimethylsiloxane (100 parts)

[0179] Dimethyl silicone oil (23 parts)

[0180] Homemade composite flame retardant (150 parts, including 45 parts of phosphorus flame retardant and 105 parts of nano-aluminum hydroxide)

[0181] Nano calcium carbonate (140 parts)

[0182] Methyltrimethoxysilane (4 parts)

[0183] Titanium complex (4 parts)

[0184] Preparation steps:

[0185] The raw materials were put into a high-speed screw machine and dispersed and ground at a speed of 580 r / min for 50 minutes. The material temperature was controlled at 70 ° C.

[0186] The mixture was heated to 120°C and dehydrated under vacuum at -0.093 MPa for 2.5 hours while stirring.

[0187] Cool down to 45℃ through condenser and pump into storage tank;

[0188] The semi-finished base material in the storage tank is transported to a fully automatic static mixer through a pipeline, and methyltrimethoxysilane and titanium complex are added in sequence;

[0189] The mixture was mixed in a fully automatic static mixer at room temperature for 18 minutes, and packaged after being evenly mixed to obtain a finished silicone adhesive product.

[0190] In order to verify the performance of the silicone adhesive prepared in each embodiment of the present invention, relevant performance tests were carried out on the silicone adhesive products prepared in Examples 1 to 6. The specific experimental data results are as follows: Figure 2 As shown:

[0191]

[0192] From the experimental data and the examples, it can be seen that:

[0193] In terms of flame retardant properties: as the amount of flame retardant increases, the flame retardant grade gradually improves. When the amount of flame retardant reaches 90 parts and 120 parts (Example 4 and Example 5), the flame retardant grade reaches V0 and the combustion resistance grade reaches A3, indicating that an appropriate amount of composite flame retardant can effectively improve the flame retardant properties of silicone adhesive.

[0194] In terms of mechanical properties: the elongation at break and tensile strength are better when the flame retardant content is 90-120 parts, and the displacement capacity reaches level 35, indicating that the mechanical properties of the silicone adhesive within this range are relatively excellent; when the flame retardant content is too high (such as 150 parts, Example 6), the mechanical properties are reduced;

[0195] In summary, Examples 4 and 5 achieved a good balance between flame retardancy and mechanical properties, indicating that when preparing halogen-free, environmentally friendly, and highly effective flame-retardant silicone adhesive, the optimal effect can be achieved by controlling the proportion of the homemade composite flame retardant to 90-120 parts.

[0196] The basic principles of the present disclosure have been described above in conjunction with specific embodiments. However, it should be noted that the advantages, strengths, and effects mentioned in this disclosure are merely illustrative and not restrictive, and should not be construed as necessarily possessed by each embodiment of the present disclosure. Furthermore, the specific details disclosed above are provided for illustrative purposes and to facilitate understanding, rather than as limitations. These details do not limit the present disclosure to necessarily being implemented using these specific details.

[0197] In the present disclosure, relational terms such as first and second, etc. are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. The block diagrams of the devices, devices, equipment, and systems involved in the present disclosure are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As will be appreciated by those skilled in the art, these devices, devices, equipment, and systems can be connected, arranged, or configured in any manner. Words such as "including," "comprising," "having," and the like are open-ended words, meaning "including but not limited to," and can be used interchangeably therewith. The words "or" and "and" used herein refer to the words "and / or" and can be used interchangeably therewith, unless the context clearly indicates otherwise. The word "such as" used herein refers to the phrase "such as but not limited to," and can be used interchangeably therewith.

[0198] Additionally, as used herein, "or" used in a list of items beginning with "at least one" indicates a separate list, so that, for example, a list of "at least one of A, B, or C" means A or B or C, or AB or AC or BC, or ABC (i.e., A and B and C). Furthermore, the word "exemplary" does not mean that the example described is preferred or better than other examples.

[0199] It should also be noted that in the system and method of the present disclosure, each component or each step can be decomposed and / or recombined. Such decomposition and / or recombination should be regarded as equivalent solutions of the present disclosure.

[0200] Various changes, substitutions, and modifications may be made to the technology described herein without departing from the teachings defined by the appended claims. Moreover, the scope of the claims of this disclosure is not limited to the specific aspects of the processes, machines, manufactures, compositions of things, means, methods, and actions described above. Currently existing or later developed processes, machines, manufactures, compositions of things, means, methods, or actions that perform substantially the same function or achieve substantially the same results as the corresponding aspects described herein may be utilized. Accordingly, the appended claims include within their scope such processes, machines, manufactures, compositions of things, means, methods, or actions.

[0201] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use the present disclosure. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other aspects without departing from the scope of the present disclosure. Therefore, the present disclosure is not intended to be limited to the aspects shown herein, but rather to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0202] The above description has been provided for the purpose of illustration and description. In addition, this description is not intended to limit the embodiments of the present disclosure to the forms disclosed herein. Although a number of example aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

Claims

1. A method for preparing a halogen-free, environmentally friendly, high-efficiency, flame-retardant silicone adhesive, characterized in that: The following steps are involved: Step 1: Weigh, by weight, 100 parts of hydroxy-terminated polydimethylsiloxane, 20-25 parts of dimethyl silicone oil, 90-120 parts of a homemade composite flame retardant, 120-150 parts of nano-calcium carbonate, 3-5 parts of methyltrimethoxysilane, and 2-5 parts of a titanium complex; Step 2: Put the weighed hydroxy-terminated polydimethylsiloxane, dimethyl silicone oil, nano-calcium carbonate and homemade composite flame retardant into a high-speed screw machine, and disperse and grind them at a speed of ≥500 r / min for 30-60 minutes to obtain a mixed material; Step 3: heating the mixed material to 100-130°C and dehydrating the mixture under vacuum at a degree of vacuum ≤-0.09 MPa for 2-3 hours to obtain a semi-finished base material. During the dehydration process, the material is continuously stirred; Step 4: Cool the semi-finished base material to 40-50°C through a condenser and put it into a storage tank; Step 5: transport the semi-finished base material in the storage tank to a fully automatic static mixer via a pipeline, and add the weighed methyltrimethoxysilane and titanium complex in sequence; Step 6: Mix the mixture in a fully automatic static mixer at room temperature for 15-20 minutes, mix evenly and package to obtain a halogen-free, environmentally friendly and high-efficiency flame-retardant silicone adhesive product.

2. The method for preparing a halogen-free, environmentally friendly, high-efficiency, flame-retardant silicone adhesive according to claim 1, characterized in that: In step one, the homemade composite flame retardant is compounded by a phosphorus-based flame retardant and nano-aluminum hydroxide in a mass ratio of 20%-30%:70%-80%; the phosphorus-based flame retardant is a combination of one or more of red phosphorus masterbatch, phosphate ester, and ammonium polyphosphate, and the particle size of the nano-aluminum hydroxide is 50-100 nm.

3. The method for preparing a halogen-free, environmentally friendly, high-efficiency, flame-retardant silicone adhesive according to claim 1, characterized in that: The particle size of the nano calcium carbonate is 50-200 nm, and the surface is pretreated with a silane coupling agent.

4. The method for preparing a halogen-free, environmentally friendly, high-efficiency, flame-retardant silicone adhesive according to claim 1, characterized in that: In step 2, during the dispersion and grinding process of the high-speed screw machine, the material temperature is controlled at 50-80°C.

5. The method for preparing a halogen-free, environmentally friendly, high-efficiency, flame-retardant silicone adhesive according to claim 1, characterized in that: In step five, the methyltrimethoxysilane is used as a cross-linking agent, and the titanium complex is used as a catalyst.

6. The method for preparing a halogen-free, environmentally friendly, high-efficiency, flame-retardant silicone adhesive according to claim 1, characterized in that: In step three, during the vacuum dehydration process, the vacuum degree is maintained between -0.095 MPa and -0.09 MPa.

7. The method for preparing a halogen-free, environmentally friendly, high-efficiency, flame-retardant silicone adhesive according to claim 1, characterized in that: In step six, the mixing element of the fully automatic static mixer is a spiral blade, and the material flow rate during the mixing process is controlled at 0.5-1.0 m / s.

8. The method for preparing a halogen-free, environmentally friendly, high-efficiency, flame-retardant silicone adhesive according to claim 2, characterized in that: When the phosphorus-based flame retardant is a combination of multiple types, the mass ratio of red phosphorus masterbatch, phosphate ester and ammonium polyphosphate is 1:1:1-2:1:

3.

9. The method for preparing a halogen-free, environmentally friendly, high-efficiency, flame-retardant silicone adhesive according to claim 3, characterized in that: The silane coupling agent is gamma-methacryloxypropyltrimethoxysilane, and the mass ratio of nano-calcium carbonate to the silane coupling agent during the pretreatment is 100:0.5-100:1.

5.

10. The method for preparing a halogen-free, environmentally friendly, high-efficiency, flame-retardant silicone adhesive according to claim 5, characterized in that: The titanium complex is tetraisopropyl titanate or tetrabutyl titanate, and the catalytic cross-linking reaction rate is 0.5-1.0 mol / (L·min).

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