Method and equipment for preparing solvent-free branched chain silicone oil

Abstract

The invention relates to the technical field of preparation of high-molecular compounds, and discloses a preparation method and equipment of solvent-free branched-chain silicone oil. The preparation method comprises the following steps: carrying out hydrolytic condensation, carrying out balanced telomerization, removing low content and color, preparing a pre-hydrolysate from an end capping agent, cyclosiloxane or dialkoxysilane in the presence of water and a protonic acid catalyst, and drying a product obtained by carrying out hydrolytic condensation reaction on the pre-hydrolysate and trialkoxysilane by using a drying agent to obtain a hydrolytic condensation primary polymer S1; and carrying out rebalance telomerization on the hydrolytic condensation primary polymer S1 in the presence of a protonic acid catalyst and a Lewis acid catalyst, neutralizing the obtained product by using a neutralizer, and then removing low content and color to obtain the branched chain silicone oil. The preparation method is simple in process, washing is not needed, a large amount of solvent is not needed for neutralization, generation of waste liquid is effectively reduced, and the obtained MDT branched silicone oil is high in regularity, good in stability, higher in yield and convenient to apply and popularize.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer compound preparation, in particular to a method and equipment for preparing solvent-free branched silicone oil. Background Art

[0002] Branched silicone oils are liquid polyorganosiloxanes containing trifunctional or tetrafunctional segments as branching points within the linear silicone oil molecule. This branched structure creates greater intertwining between the molecules than with linear silicone oils, resulting in a shear-thinning effect that facilitates dispersion and flow. These branches enhance low-temperature resistance (with a freezing point as low as -90°C) while maintaining the many desirable properties of silicone oil. They are widely used in personal care, textiles, low-temperature lubrication, LED silicone rubber, and other applications.

[0003] Conventional methods for preparing branched silicone oils include: (1) Alkyl chlorosilane co-hydrolysis method: for example, trimethylchlorosilane, dimethyldichlorosilane, and methyltrichlorosilane are mixed and hydrolyzed to produce MDT branched silicone oil, and MDT silicone oil is then subjected to a ring-opening equilibrium reaction with cyclosiloxane to produce MDT silicone oils of different viscosities. (2) Alkyl alkoxysilane co-hydrolysis method: for example, methyltrimethoxysilane and dimethyldimethoxysilane are co-hydrolyzed in the presence of a capping agent such as hexamethyldisiloxane to produce branched silicone oil. (3) 1,1,1,3,5,7,7,7-octamethyl-3,5-dihydroxy-tetrasiloxane (MHTS) is subjected to an equilibrium reaction with cyclosiloxane to prepare branched silicone oil.

[0004] Chinese invention patent CN100396715C adds phenylsilane and a capping agent dropwise to water and a catalyst. After hydrolysis is complete, the oil layer is washed with alkali and water until neutral. Chinese invention patent CN110003473A adds 1-1.5 times the amount of ethanol to D4 and phenyltrichlorosilane, and then adds water for hydrolysis and condensation. Chinese invention patent CN102329427B adds a methylchlorosilane mixture dropwise to a mixture of methanol and water for hydrolysis, and then preferentially removes the generated hydrochloric acid. It is necessary to repeatedly add urea and 2-3 times the amount of water to promote acid-water separation. After the oil layer is neutral, a secondary equilibrium polymerization is performed under the action of tetramethylammonium hydroxide to produce MDT silicone oil. Chinese invention patent CN103435806B adds phenyltriethoxysilane dropwise to a mixture containing a capping agent, an acidic catalyst, and water, washes with water until neutral, and then evaporates under reduced pressure after drying to obtain branched phenyl silicone oil.

[0005] The existing technologies all prepare branched silicone oils with T structures by hydrolysis or hydrolysis followed by balancing. In the hydrolysis process and water washing and neutralization process of the branched silicone oil, a large amount of solvents such as ethanol, isopropanol, and toluene are required, and multiple water washing and stratification are required to remove the acid water, which undoubtedly brings inconvenience to the manufacturing process. The use of a large amount of solvents not only increases costs, but also requires the treatment of waste liquids, which is neither environmentally friendly nor safe. In addition, there is a risk of solvent and catalyst residues causing unpleasant odors, which will undoubtedly reduce product quality and prevent it from being widely used in high-end applications such as cosmetics.

[0006] Chinese invention patent CN108892775B equilibrates an alkoxysilane with a cyclosiloxane and / or a hydroxypolydimethylsiloxane in the presence of an acidic catalyst, then adds water and a silicon-containing solvent to induce hydrolysis and condensation. The alcohol, water, and silicon-containing solvent are then removed, and finally neutralized and desalted to produce a branched silicone oil. This method uses cyclosiloxane, a raw material that provides D segments, as a solvent, which can replace solvents such as ethanol, isopropanol, and toluene. However, this method suffers from the high cost of using cyclosiloxane as a solvent. The preparation process also carries the risk of T segment crosslinking due to incomplete equilibration between the cyclosiloxane and alkoxysilane, resulting in different hydrolysis and condensation rates.

[0007] Chinese invention patent CN119241852A discloses a solvent-free hydrophilic block silicone oil and its preparation method. This method uses chloropropyl alkyl alkoxysilane and hydroxyl-terminated polydimethylsiloxane in an acidic catalyst through an equilibrium reaction to produce a linear silicone oil with chloropropyl alkyl alkoxy groups at both ends. The linear silicone oil is then neutralized and filtered before reacting with a tertiary amine to produce a quaternary ammonium salt-terminated hydrophilic block silicone oil. However, this method is not suitable for MDT branched silicone oils, as the preparation methods and reaction mechanisms of the two are significantly different.

[0008] In summary, the existing technologies all have the problem of needing to use additional solvents such as methanol, ethanol, and toluene, and requiring multiple water washings to generate a large amount of waste liquid. In addition, the use of cyclosiloxane as a solvent has the risk of cross-linking due to different hydrolysis and condensation rates, resulting in the risk of solvent and acid-base residues in the product, resulting in low product purity and reduced quality, which in turn limits its application in high-end applications such as cosmetics. Summary of the Invention

[0009] In response to the deficiencies in the prior art, the present invention provides a method and apparatus for preparing a solvent-free branched silicone oil. The preparation method has a simple process, does not require water washing or the use of a large amount of solvent for neutralization, effectively reduces the generation of waste liquid, and the obtained MDT branched silicone oil has high regularity and good stability.

[0010] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions: A method for preparing a solvent-free branched silicone oil, wherein the viscosity of the branched silicone oil is 1-1000 mPa.s and the chemical formula is (R1R2R3SiO 1 / 2 ) a ((R4)2SiO 2 / 2 ) b (R5SiO 3 / 2 ) c , where a+b+c=1, a=0.1-0.5, b=0.1-0.8, c=0.1-0.3; R1, R2, R3, R4, and R5 are H, C1-C 10 an alkyl or aralkyl group; The preparation method of the branched silicone oil comprises the following steps: 1) Hydrolysis and condensation: A capping agent, cyclosiloxane or dialkoxysilane, and water are mixed and pre-hydrolyzed under protonic acid catalyst conditions to obtain a pre-hydrolyzate; trialkoxysilane is then slowly added to the pre-hydrolyzate to carry out a hydrolysis and condensation reaction. After the reaction is completed, the mixture is allowed to stand and separate into layers. The oil layer is separated and dried with a desiccant to obtain a hydrolysis and condensation primary polymer S1; 2) Equilibrium telomerization: adding a protonic acid catalyst and a Lewis acid catalyst to the hydrolysis-condensation primary polymer S1 for re-equilibrium telomerization. After the reaction is completed, the stratification is allowed to stand, the oil layer is separated, a neutralizing agent is added for neutralization, and the equilibrium telomer S2 is obtained by filtration. 3) Decolorization: The equilibrium polymer S2 is vacuum decolorized and then filtered to remove color to obtain branched silicone oil.

[0011] Preferably, R1, R2, R3, R4, and R5 are one or more of H, methyl, vinyl, ethyl, propyl, phenyl, and α-phenyl.

[0012] Branched silicone oil (R1R2R3SiO 1 / 2 ) a ((R4)2SiO 2 / 2 ) b (R5SiO 3 / 2 ) c The M chain segment, linear chain segment D, and branched chain segment T are provided by capping agent, cyclosiloxane or dialkoxysilane, and trialkoxysilane, respectively, as follows.

[0013] The chemical formula of the sealing agent is R1R2R3-Si-O-Si-R1R2R3, where R1, R2, and R3 can be the same or different and are H, C1-C 10The alkyl or aralkyl group is preferably one or more of H, methyl, vinyl, ethyl, propyl, phenyl, and α-phenyl. More specifically, the capping agent can be one of tetramethyldisiloxane, hexamethyldisiloxane, 1,3-divinyldisiloxane, 1,3-diphenyldisiloxane, 1,3-diethyldisiloxane, and 1,3-diisopropyldisiloxane; preferably one of tetramethyldisiloxane, hexamethyldisiloxane, 1,3-divinyldisiloxane, and 1,3-diphenyldisiloxane.

[0014] The cyclosiloxane is specifically one or more of methylhydrogencyclosiloxane, dimethylcyclosiloxane, diethylcyclosiloxane, methylethylcyclosiloxane, methylvinylcyclosiloxane, methylphenylcyclosiloxane, diphenylcyclosiloxane, etc.; preferably one or more of methylhydrogencyclosiloxane, dimethylcyclosiloxane, methylvinylcyclosiloxane, methylphenylcyclosiloxane.

[0015] The chemical formula of dialkoxysilane is (R4)2Si(R6)2, where R4 is H, C1-C 10 alkyl or aralkyl, R6 is a hydrolyzable alkoxy group; preferably, R4 is one or more of H, methyl, vinyl, ethyl, propyl, phenyl, α-phenyl, etc., R6 is a hydrolyzable alkoxy group, and the alkoxy group is specifically one of methoxy, ethoxy, propoxy, butoxy, etc. More specifically, the dialkoxysilane is one or more of methylhydrogendimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, methylvinyldimethoxysilane, methylvinyldiethoxysilane, methylphenyldimethoxysilane, methylphenyldiethoxysilane, diphenyldimethoxysilane, and diphenyldiethoxysilane; preferably, it is one or more of methylhydrogendimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, and methylphenyldimethoxysilane.

[0016] The chemical formula of trialkoxysilane is R5Si(R7)3, where R5 is H, C1-C 10 alkyl or aralkyl, R7 is a hydrolyzable alkoxy group; preferably, R5 is H, methyl, vinyl, ethyl, propyl, phenyl or α-phenyl, and R7 is methoxy, ethoxy, propoxy or butoxy. More specifically, the trialkoxysilane is one or more of trimethoxysilane, triethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, methacrylatetrimethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, etc.; preferably, it is one or more of trimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, vinyltriethoxysilane, phenyltrimethoxysilane, and phenyltriethoxysilane.

[0017] Preferably, in the step 1) pre-hydrolysis reaction, the capping agent is first pre-hydrolyzed, and then the cyclosiloxane or dialkoxysilane is added dropwise to continue the pre-hydrolysis reaction; The pre-hydrolysis reaction temperature of the sealing agent is 20-40°C, the reaction time is 0.5-3h, and the stirring speed is 100-500r / min; Cyclosiloxane or dialkoxysilane is added dropwise at 20-60°C for 0.5-3h, and stirring is continued for 0.5-3h after the addition is completed to carry out a pre-hydrolysis reaction.

[0018] Preferably, in the hydrolysis condensation reaction of step 1), trialkoxysilane is slowly added dropwise to the pre-hydrolyzate, the addition time is 0.5-6 h, the addition speed is 100-300 kg / h, the hydrolysis condensation reaction temperature is 30-100° C., and the reaction time is 2-10 h.

[0019] Preferably, in step 2), the re-equilibrium polymerization temperature is 40-100° C., and the re-equilibrium polymerization time is 2-12 h; the neutralization temperature is 30-60° C., and the neutralization time is 3-10 h.

[0020] Preferably, in step 3), the vacuum degree is -0.1-0.4 MPa, the dehumidification temperature is 40-150°C, the dehumidification time is 3-12 hours, and the temperature is lowered to 30-60°C after dehumidification.

[0021] Preferably, the protonic acid catalyst is one or more of sulfuric acid, hydrochloric acid, sulfonic acid, and phosphoric acid, preferably one or more of sulfuric acid, sulfonic acid, and phosphoric acid. The addition amount is 0.1-20% of the total reactant amount, preferably 0.1-6%.

[0022] Preferably, the Lewis acid catalyst is one or more of aluminum chloride, ferric chloride, boron fluoride, and magnesium sulfate, preferably aluminum chloride or ferric chloride. The addition amount is 0.1-10% of the total reactant amount, preferably 0.1-5%.

[0023] Preferably, the desiccant is silica gel, molecular sieve, calcium chloride, mineral desiccant or activated alumina, preferably silica gel, molecular sieve or calcium chloride. The amount added is 0.1-20% of the total amount of the reactants, preferably 1-10%.

[0024] Preferably, the neutralizing agent is one or more of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, sodium hydroxide, and potassium hydroxide, preferably one or more of sodium carbonate, sodium bicarbonate, potassium carbonate, and potassium bicarbonate. The addition amount is 0.1-20% of the total amount of the reactants, preferably 0.1-8%.

[0025] Furthermore, the present invention also discloses a solvent-free branched silicone oil preparation device, which is used to implement the solvent-free branched silicone oil preparation method, including a hydrolysis reactor I, an equilibrium reactor II, a desulfurization reactor III and a finished product storage tank connected to each other in sequence, a desiccant is provided in the pipeline between the hydrolysis reactor I and the equilibrium reactor II, a filter is provided between the equilibrium reactor II and the desulfurization reactor III, and an adsorbent is provided in the pipeline between the desulfurization reactor III and the finished product storage tank.

[0026] The preparation method principle of the present invention is as follows: First, a capping agent, providing the M segments, and a cyclosiloxane or dialkoxysilane, providing the linear segments D, are pre-hydrolyzed in the presence of a protonic acid catalyst and water to produce sufficient Si-OH and HO-Si-OH groups. A trialkoxysilane, providing the branched segments T, is then slowly added dropwise to the pre-hydrolyzed material. Upon contact with water, it rapidly hydrolyzes to Si-(OH)3. The hydrolyzed T segments then condense and cap with the abundant M and D units, achieving dynamic equilibrium. Due to the different hydrolysis rates of M, D, and T, with the T segment hydrolyzing at a rate far greater than that of both M and D, the co-hydrolysis method poses the risk of rapid T segment hydrolysis followed by slow M and D segment hydrolysis, leading to condensation and crosslinking of the T segments themselves. Therefore, a step-by-step hydrolysis method is employed to mitigate the network-forming effect of the T segment condensation and crosslinking reaction. The T segments, added to the pre-hydrolyzed material, are surrounded by the pre-hydrolyzed M and D segments, effectively forming the MDT branched silicone oil structure. After the hydrolysis is completed, the upper acid-water layer is removed by standing and stratification, and the oil layer is dried through a pipe filled with a desiccant. Then, a protonic acid catalyst and a Lewis acid catalyst (equilibrium co-catalyst) are added to carry out a secondary equilibrium polymerization at 30-100°C to make up for the difference in D and T chain scission efficiency, so that the MDT silicone oil can be deeply condensed and more regular. Then, the acid catalyst is removed by stratification. Finally, an alkaline substance is added for neutralization, and then filtered to remove salt, and the oil layer is decolorized to obtain the branched silicone oil.

[0027] The beneficial effects of the present invention are: (1) The preparation process of the present invention does not require a solvent, and fully utilizes the alcohol and linear M and D segments after hydrolysis as cosolvents to promote hydrolysis and decomposition; (2) The preparation method of the present invention does not require a large amount of solvent for neutralization and water washing. After the secondary equilibrium polymerization, neutralization and acid removal, filtration and desalination are carried out, and no large amount of waste liquid is generated, which is safer and more environmentally friendly. (3) The preparation process of the present invention adopts a step-by-step hydrolysis method to avoid excessive condensation and cross-linking of the T chain itself due to the different hydrolysis rates of the M, D, and T chain segments, so that the prepared branched silicone oil has fewer by-products and higher purity; (4) The preparation process of the present invention adds a secondary balancing process, which uses a combination of proton acid and Lewis acid for rebalancing, and supplements the chain breakage and rearrangement of the D segment, which can effectively reduce the Si-OH and Si-alkoxy groups generated by incomplete hydrolysis. The obtained branched silicone oil has higher regularity and better stability, does not require additional raw materials, and has a simpler process and higher yield, which is convenient for promotion and application. DETAILED DESCRIPTION

[0028] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts are within the scope of protection of the present invention.

[0029] Example 1: Step 1: Hydrolysis and condensation 360 parts of the capping agent hexamethyldisiloxane were pumped into the dry hydrolysis reactor I, 120 parts of concentrated hydrochloric acid and 60 parts of water were added dropwise, and stirred at 30°C for 1 hour at a stirring speed of 300 r / min. Then, 560 parts of dimethyldimethoxysilane were added dropwise, and the temperature was kept at 30°C and the addition was continued for 1 hour. After the addition was completed, stirring was continued for 3 hours to carry out the pre-hydrolysis reaction.

[0030] Then, 280 parts of methyltrimethoxysilane were slowly added dropwise to the pre-hydrolyzate for 1.5 hours. After the addition was completed, the temperature was controlled at 60°C to continue the hydrolysis condensation reaction for 5 hours. The reaction was then stopped and allowed to stand for 10 hours to separate the layers. The upper acid-water layer was removed, and the lower oil layer was dried through a pipe filled with a desiccant to obtain the dried hydrolysis condensation primary polymer S1.

[0031] Step 2: Balanced polymerization The hydrolysis condensation primary polymer S1 is pumped into a dry equilibrium reactor II, and 24 parts of concentrated sulfuric acid and 12 parts of AlCl3 are added dropwise with stirring. The temperature is raised to 80°C for re-equilibrium polymerization for 8 hours. The reaction is then stopped and allowed to stand for 6 hours for stratification. The lower acid layer is removed, and the oil layer is retained in the reactor. 12 parts of sodium carbonate are added with stirring, and the mixture is heated to 40°C for neutralization for 4 hours. The material is pumped through a filter equipped with a filter aid for filtration and desalination to obtain the equilibrium polymer S2.

[0032] Step 3: Remove color The resulting equilibrium telomer S2 was pumped into a dry desulfurization reactor III. Under nitrogen protection, stirring and vacuum were initiated, and the vacuum was controlled at -0.1 MPa. The material was then heated to 80°C for 6 hours to remove low-carbon components under vacuum. After the desulfurization was stopped, the temperature was lowered to 50°C and pumped through a pipeline containing an adsorbent for filtration and color removal. The material was then pumped into a finished product storage tank to obtain the finished branched silicone oil. The branched silicone oil was colorless, transparent, and odorless, with a viscosity of 28 mPa·s and an acid value of 1.08 μg / g.

[0033] Example 2: Step 1: Hydrolysis and condensation 180 parts of tetramethyldisiloxane, a capping agent, was pumped into a dry hydrolysis reactor I, 20 parts of sulfonic acid and 30 parts of water were added dropwise, and stirred at 30°C for 1 hour at a stirring speed of 300 r / min. Then, 880 parts of octamethylcyclotetrasiloxane was added dropwise, and the mixture was kept at 30°C and added dropwise for 1 hour. After the addition was completed, stirring was continued for 3 hours to carry out a pre-hydrolysis reaction.

[0034] Then, 360 parts of phenyltriethoxysilane were slowly added dropwise to the pre-hydrolyzate for 2 hours. After the addition was completed, the temperature was controlled at 40°C and the hydrolysis condensation reaction was continued for 8 hours. The reaction was then stopped and allowed to stand for 10 hours to separate the layers. The upper acid-water layer was removed, and the lower oil layer was dried through a pipe filled with a desiccant to obtain the dried hydrolysis condensation primary polymer S1.

[0035] Step 2: Balanced polymerization The hydrolysis condensation primary polymer S1 is pumped into a dry equilibrium reactor II, 20 parts of concentrated sulfuric acid and 10 parts of FeCl3 are added dropwise with stirring, the temperature is raised to 60°C for re-equilibrium polymerization for 10 hours, the reaction is then stopped, and the mixture is allowed to stand for 6 hours for stratification, the lower acid layer is removed, and the oil layer is retained in the reactor, 10 parts of potassium carbonate are added with stirring, and the mixture is heated to 40°C for neutralization for 4 hours. The material is pumped through a filter equipped with a filter aid for filtration and desalination to obtain the equilibrium polymer S2.

[0036] Step 3: Remove color The resulting equilibrium telomer S2 was pumped into a dry desulfurization reactor III. Under nitrogen protection, stirring and vacuum were initiated, and the vacuum was controlled at -0.1 MPa. The material was then heated to 100°C for 6 hours to remove low-carbon components under vacuum. After the desulfurization was stopped, the temperature was lowered to 50°C and pumped through a pipeline containing an adsorbent for filtration and color removal. The material was then pumped into a finished product storage tank to obtain the finished branched silicone oil. The branched silicone oil was colorless, transparent, and odorless, with a viscosity of 496 mPa·s and an acid value of 0.76 μg / g.

[0037] Example 3: Step 1: Hydrolysis and condensation 93 parts of divinyldisiloxane, a capping agent, was pumped into a dry hydrolysis reactor I, 36 parts of phosphoric acid and 120 parts of water were added dropwise, and stirred at 30°C for 1 hour at a stirring speed of 300 r / min. Then, 1280 parts of methyldimethoxysilane was added dropwise, and the temperature was kept at 50°C for 1 hour. After the addition was completed, stirring was continued for 3 hours to carry out a pre-hydrolysis reaction.

[0038] Then, 240 parts of octyltriethoxysilane were slowly added dropwise to the pre-hydrolyzate for 1 hour. After the addition was completed, the temperature was controlled at 80°C to continue the hydrolysis condensation reaction for 8 hours. The reaction was then stopped and allowed to stand for 10 hours to separate the layers. The upper acid-water layer was removed, and the lower oil layer was dried through a pipe filled with a desiccant to obtain the dried hydrolysis condensation primary polymer S1.

[0039] Step 2: Balanced polymerization The hydrolysis condensation primary polymer S1 was pumped into a dry equilibrium reactor II, and 16 parts of concentrated sulfuric acid and 8 parts of BBF3 were added dropwise under stirring. The temperature was raised to 80°C for re-equilibrium polymerization for 8 hours. The reaction was then stopped and allowed to stand for 6 hours for stratification. The lower acid layer was removed, and the oil layer was retained in the reactor. 8 parts of sodium bicarbonate were added under stirring, and the mixture was heated to 40°C for neutralization for 4 hours. The material was pumped through a filter equipped with a filter aid for filtration and desalination to obtain the equilibrium polymer S2.

[0040] Step 3: Remove color The resulting equilibrium telomer S2 was pumped into a dry desulfurization reactor III. Under nitrogen protection, stirring and vacuum were initiated, with the vacuum maintained at -0.1 MPa. The material was then heated to 130°C for 6 hours to remove the low-carbon components. After the desulfurization was stopped, the temperature was lowered to 50°C and pumped through a pipeline containing an adsorbent for filtration and color removal before being pumped into a finished product storage tank to obtain the finished branched silicone oil. The branched silicone oil was colorless, transparent, and odorless, with a viscosity of 823 mPa·s and an acid value of 1.29 μg / g.

[0041] Comparative Example 1 (C-1): Traditional co-hydrolysis-ethanol solvent method Step 1: Hexamethyldisiloxane, dimethyldimethoxysilane, and methyltrimethoxysilane were added at once; then 30 wt% excess anhydrous ethanol, concentrated hydrochloric acid, and water were added and hydrolyzed for 6 h.

[0042] Step 2: Wash with water three times until pH ≈ 7, and dealcoholize under reduced pressure. No secondary equilibrium polymerization was performed.

[0043] Result: The product was light yellow, with residual ethanol of 740 ppm and acid value of 22.4 μg g -1 The viscosity at 30°C was 41 mPa·s, but it increased by 18% after 30 days. The amount of water-washing wastewater was approximately 4.2 kg.

[0044] Using external solvents and no secondary balance, the residual alcohol and residual acid are high, the stability is poor, and there is a lot of waste liquid.

[0045] Comparative Example 2 (C-2): Cyclosiloxane as Solvent Method (CN108892775B Route) 1000 g of octamethylcyclotetrasiloxane (D4) was pre-added as the reaction medium; the remaining procedures were identical to those in Example 2, except that the stepwise additions were omitted. The product required 8 h of decyclization at 120°C and −0.08 MPa, with 2.9 wt% of D4 remaining.

[0046] Result: light yellow and transparent, acid value 8.7 μg g -1 , viscosity at 30 ℃ was 495 mPa·s; 3 vol% gel appeared after freezing at -20 ℃ for 24 h; raw material cost increased by 18%.

[0047] It can be seen that the use of large doses of cyclosiloxane solvents is costly, difficult to remove the ring, and has a high risk of gelation.

[0048] Comparative Example 3 (C-3): One-time co-hydrolysis without stepwise addition Mix all trialkoxysilanes with a capping agent, dimethyldimethoxysilane, water, and hydrochloric acid at once and hydrolyze at 30°C for 8 hours. Allow to stand for stratification, filter coarsely, and then vacuum degas.

[0049] Results: The system showed flocculent gel after 3 h of hydrolysis and could not be pumped; a semi-solid-semi-liquid product was finally filtered out, and the acid value could not be accurately determined, which was considered a preparation failure.

[0050] It can be seen that if “step-by-step hydrolysis” is not adopted, the T chain segments will self-condense and cross-link severely, and fluid MDT branched silicone oil cannot be obtained.

[0051] Comparative Example 4 (C-4): Omitting the Secondary Equilibrium Polymerization S1 was obtained by the step-by-step hydrolysis process of Example 1; neutralization-filtration-desulfurization was performed directly without adding protonic acid / Lewis acid for rebalancing.

[0052] Result: Colorless appearance, but Si-OH residue 0.68 wt% ( 1 H-NMR), acid value 11.3 μg g -1 After aging at 45 °C for 7 days, the product became turbid and its viscosity increased by 23%.

[0053] It can be seen that there is a lack of rebalancing, insufficient compensation for chain breaks, many residual active groups, and poor heat-storage stability.

[0054] Comparative Example 5 (C-5): Rebalancing with protic acid only, without Lewis acid 0.8 wt% concentrated sulfuric acid (without AlCl 3 ) was added to S1 of Example 1, and the mixture was equilibrated at 80° C. for 8 h. The rest of the reaction was the same as in Example 1.

[0055] Result: Acid value 6.2 µg g -1 , Si-OH residue 0.19 wt%, viscosity 30 mPa·s at 30 ℃; but the molecular weight distribution (GPC, Mw / Mn) = 2.6, which is wider than 1.8 in Example 1, and the viscosity fluctuates by 12% after storage for 30 days.

[0056] It can be seen that there is a lack of Lewis acid co-catalysis, insufficient chain scission-rearrangement, a wide molecular weight distribution, and poor regularity and long-term stability.

[0057] Table 1 Comparison of experimental data

[0058] As can be seen from Table 1, the examples of the present invention have the lowest acid value, the least residual Si-OH, the most stable long-term viscosity, no solvent residue, and zero wastewater, fully demonstrating the significant technical benefits brought about by the synergistic effect of solvent-free, step-by-step hydrolysis, and protonic acid / Lewis acid dual catalytic secondary equilibrium. The omission of each item in the comparative examples leads to significant performance degradation or outright preparation failure, objectively demonstrating the inventiveness and superiority of the present invention.

[0059] The above is a description of the embodiments of the present invention. The above description of the disclosed embodiments will enable professionals in the field to implement or use the present invention. Various modifications to these embodiments will be apparent to professionals in the field. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but should conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a solvent-free branched silicone oil, characterized in that: The viscosity of the branched silicone oil is 1-1000mPa.s, and the chemical formula is (R1R2R3SiO 1 / 2 ) a ((R4)2SiO 2 / 2 ) b (R5SiO 3 / 2 ) c , where a+b+c=1, a=0.1-0.5, b=0.1-0.8, c=0.1-0.3; R1, R2, R3, R4, and R5 are H, C1-C 10 an alkyl or aralkyl group; The preparation method of the branched silicone oil comprises the following steps: 1) Hydrolysis and condensation: A capping agent, cyclosiloxane or dialkoxysilane, and water are mixed and pre-hydrolyzed under protonic acid catalyst conditions to obtain a pre-hydrolyzate; trialkoxysilane is then slowly added to the pre-hydrolyzate to carry out a hydrolysis and condensation reaction. After the reaction is completed, the mixture is allowed to stand and separate into layers. The oil layer is separated and dried with a desiccant to obtain a hydrolysis and condensation primary polymer S1; 2) Equilibrium telomerization: adding a protonic acid catalyst and a Lewis acid catalyst to the hydrolysis-condensation primary polymer S1 for re-equilibrium telomerization. After the reaction is completed, the stratification is allowed to stand, the oil layer is separated, a neutralizing agent is added for neutralization, and the equilibrium telomer S2 is obtained by filtration. 3) Decolorization: The equilibrium polymer S2 is vacuum decolorized and then filtered to remove color to obtain branched silicone oil.

2. The method for preparing a solvent-free branched silicone oil according to claim 1, wherein: The R1, R2, R3, R4, and R5 are one or more of H, methyl, vinyl, ethyl, propyl, phenyl, and α-phenyl.

3. The method for preparing a solvent-free branched silicone oil according to claim 1, wherein: In the step 1) pre-hydrolysis reaction, the capping agent is first pre-hydrolyzed, and then the cyclosiloxane or dialkoxysilane is added dropwise to continue the pre-hydrolysis reaction; The pre-hydrolysis reaction temperature of the head sealing agent is 20-40°C, the reaction time is 0.5-3h, and the stirring speed is 100-500r / min; Cyclosiloxane or dialkoxysilane is added dropwise at 20-60°C for 0.5-3 hours, and then stirred for 0.5-3 hours to perform a pre-hydrolysis reaction; And / or, in step 1) the hydrolysis condensation reaction, trialkoxysilane is slowly added dropwise to the pre-hydrolyzate, the addition time is 0.5-6 hours, the hydrolysis condensation reaction temperature is 30-100° C., and the reaction time is 2-10 hours.

4. The method for preparing a solvent-free branched silicone oil according to claim 1, wherein: In the step 2), the re-equilibrium polymerization temperature is 40-100° C., and the re-equilibrium polymerization time is 2-12 hours; the neutralization temperature is 30-60° C., and the neutralization time is 3-10 hours.

5. The method for preparing a solvent-free branched silicone oil according to claim 1, wherein: In the step 3), the vacuum degree is -0.1-0.4 MPa, the dehumidification temperature is 40-150° C., the dehumidification time is 3-12 hours, and the temperature is lowered to 30-60° C. after dehumidification.

6. The method for preparing a solvent-free branched silicone oil according to claim 1, wherein: The protonic acid catalyst is one or more of sulfuric acid, hydrochloric acid, sulfonic acid, and phosphoric acid.

7. The method for preparing a solvent-free branched silicone oil according to claim 1, wherein: The Lewis acid catalyst is one or more of aluminum trichloride, ferric chloride, boron fluoride, and magnesium sulfate.

8. The method for preparing a solvent-free branched silicone oil according to claim 1, wherein: The desiccant is silica gel, molecular sieve, calcium chloride, mineral desiccant or activated alumina.

9. The method for preparing a solvent-free branched silicone oil according to claim 1, wherein: The neutralizing agent is one or more of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, sodium hydroxide, and potassium hydroxide.

10. A solvent-free branched silicone oil preparation device, characterized in that: The equipment is used to implement the preparation method described in any one of claims 1 to 9, comprising a hydrolysis reactor I, an equilibrium reactor II, a desulfurization reactor III and a finished product storage tank connected to each other in sequence, a desiccant is provided in the pipeline between the hydrolysis reactor I and the equilibrium reactor II, a filter is provided between the equilibrium reactor II and the desulfurization reactor III, and an adsorbent is provided in the pipeline between the desulfurization reactor III and the finished product storage tank.

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