A solvent-free branched silicone oil preparation method and equipment

Abstract

This invention relates to the field of polymer compound preparation technology, and discloses a solvent-free method and equipment for preparing branched silicone oil. The preparation method includes hydrolysis condensation, equilibrium polymerization, and decolorization. A capping agent, cyclosiloxane, or dialkoxysilane is reacted with water and a protic acid catalyst to obtain a pre-hydrolyzed product. The product of the hydrolysis condensation reaction of the pre-hydrolyzed product and the trialkoxysilane is dried with a desiccant to obtain a hydrolysis condensation primary polymer S1. The hydrolysis condensation primary polymer S1 is then subjected to re-equilibrium polymerization under a protic acid catalyst and a Lewis acid catalyst. The resulting product is neutralized with a neutralizing agent, and then decolorized to obtain the branched silicone oil. This preparation method is simple, eliminates the need for water washing and large-volume solvent neutralization, effectively reduces waste liquid generation, and yields MDT branched silicone oil with high regularity, good stability, and higher yield, making it easy to promote and apply.

Description

Technical Field

[0001] This invention relates to the field of polymer compound preparation technology, and more specifically, to a solvent-free branched silicone oil preparation method and equipment. Background Technology

[0002] Branched silicone oils are liquid polyorganosiloxanes containing trifunctional or tetrafunctional chain segments as branching points within the linear silicone oil molecular chain. Due to the branched structure, the entanglement between molecular chains is greater than that of linear silicone oils, resulting in a shear-thinning effect that facilitates dispersion and flow. The introduction of branching also enhances the low-temperature performance (its freezing point can reach as low as -90℃) while retaining many of the excellent properties of silicone oils, making it widely used in personal care, textiles, low-temperature lubrication, LED silicone rubber, and other applications.

[0003] Common methods for preparing branched silicone oils include: (1) Alkylchlorosilane co-hydrolysis method: for example, trimethylchlorosilane, dimethyldichlorosilane, and methyltrichlorosilane are mixed and hydrolyzed to prepare MDT branched silicone oil, and MDT silicone oil is then subjected to ring-opening equilibrium reaction with cyclosiloxane to prepare MDT silicone oils of different viscosities. (2) Alkylalkoxysilane co-hydrolysis method: for example, methyltrimethoxysilane and dimethyldimethoxysilane are co-hydrolyzed in the presence of hexamethyldisiloxane and other capping agents to prepare branched silicone oil. (3) 1,1,1,3,5,7,7,7-octamethyl-3,5-dihydroxy-tetrasiloxane (MHTS) is subjected to equilibrium reaction with cyclosiloxane to prepare branched silicone oil.

[0004] Chinese invention patent CN100396715C involves adding phenylsilane and a capping agent dropwise to water and a catalyst. After hydrolysis, the oil layer is washed with alkali and water until neutral. Chinese invention patent CN110003473A involves adding 1-1.5 times the amount of ethanol to D4 and phenyltrichlorosilane, followed by water for hydrolysis and condensation. Chinese invention patent CN102329427B involves adding a mixture of methylchlorosilane dropwise to a mixture of methanol and water for hydrolysis. The generated hydrochloric acid is preferentially removed, requiring repeated addition of 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 obtain MDT silicone oil. Chinese invention patent CN103435806B involves adding phenyltriethoxysilane dropwise to a mixture containing a capping agent, an acidic catalyst, and water. After addition, the mixture is washed with water until neutral, dried, and then degraded under reduced pressure to obtain branched phenyl silicone oil.

[0005] Existing technologies all prepare branched silicone oils with T-structures through hydrolysis or a combination of hydrolysis and equilibration. Both the hydrolysis and neutralization processes require large amounts of solvents such as ethanol, isopropanol, and toluene. Furthermore, multiple water washes are necessary to remove acidic water, significantly complicating the manufacturing process. The use of large amounts of solvents not only increases costs but also necessitates wastewater treatment, which is both environmentally and safety-critical. In addition, there is a risk of solvent and catalyst residues causing unpleasant odors, which undoubtedly reduces product quality and prevents its widespread use in high-end applications such as cosmetics.

[0006] Chinese invention patent CN108892775B describes a method for preparing branched silicone oil by first equilibrating alkoxysilanes with cyclosiloxanes and / or hydroxyl polydimethylsiloxanes under an acidic catalyst, then adding water and a silicon-containing solvent to initiate hydrolysis and condensation, followed by removal of alcohol, water, and the silicon-containing solvent, and finally neutralization and desalting. This method uses cyclosiloxanes, which provide D-units, as a solvent, which can replace solvents such as ethanol, isopropanol, and toluene. However, this method suffers from the high cost of using cyclosiloxanes as solvents, and the preparation process also carries the risk of T-unit crosslinking due to incomplete equilibration between cyclosiloxanes and alkoxysilanes and the different hydrolysis and polycondensation rates.

[0007] Chinese invention patent CN119241852A discloses a solvent-free hydrophilic block silicone oil and its preparation method. This method uses chloropropyl alkylalkoxysilane and hydroxyl-terminated polydimethylsiloxane. In an acidic catalyst, a linear silicone oil with chloropropyl alkylalkoxy structures at both ends is first prepared through an equilibrium reaction. The linear silicone oil is then neutralized, filtered, and reacted with a tertiary amine to obtain a quaternary ammonium salt-terminated hydrophilic block silicone oil. However, this method is not applicable to MDT branched silicone oils, as their preparation methods and reaction mechanisms differ significantly.

[0008] In summary, existing technologies all suffer from the problems of requiring additional solvents such as methanol, ethanol, and toluene, as well as generating large amounts of waste liquid through multiple water washings. Furthermore, the use of cyclosiloxanes as solvents carries the risk of crosslinking due to different hydrolysis and polycondensation rates, resulting in solvent and acid / alkali residues in the products. This leads to low product purity and reduced quality, thus limiting their application in high-end applications such as cosmetics. Summary of the Invention

[0009] To address the shortcomings of existing technologies, this invention provides a solvent-free branched silicone oil preparation method and equipment. This preparation method is simple, requires no water washing or large-volume solvent neutralization, effectively reduces waste liquid generation, and yields MDT branched silicone oil with high regularity and good stability.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] A method for preparing solvent-free branched silicone oil, wherein the branched silicone oil has a viscosity of 1-1000 mPa·s and a chemical formula of (R1R2R3SiO2). 1 / 2 ) a (R4)2SiO 2 / 2 ) b (R5SiO) 3 / 2 ) c In the formula, a + b + c = 1, a = 0.1 - 0.5, b = 0.1 - 0.8, and c = 0.1 - 0.3;

[0012] R1, R2, R3, R4, and R5 are H and C1-C, respectively. 10 Alkyl or aralkyl groups;

[0013] The preparation method of this branched silicone oil includes the following steps:

[0014] 1) Hydrolysis condensation: The capping agent, cyclosiloxane or dialkoxysilane and water are mixed and pre-hydrolyzed under the condition of protic acid catalyst to obtain pre-hydrolyzed product; then, trialkoxysilane is slowly added to the pre-hydrolyzed product to carry out hydrolysis 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 hydrolysis condensation primary polymer S1.

[0015] 2) Equilibrium telomerization: Protic acid catalyst and Lewis acid catalyst are added to the hydrolysis condensation primary polymer S1 for reequilibrium telomerization. After the reaction is completed, the mixture is allowed to stand and separate into layers. The oil layer is separated, neutralized by adding a neutralizing agent, and filtered to obtain equilibrium telomer S2.

[0016] 3) Degradation and decolorization: Vacuum degradation is performed on the equilibrium telomer S2, followed by filtration and decolorization to obtain branched silicone oil.

[0017] Preferably, R1, R2, R3, R4, and R5 are one or more of H, methyl, vinyl, ethyl, propyl, phenyl, and α-phenyl.

[0018] Branched silicone oil (R1R2R3SiO) 1 / 2 ) a (R4)2SiO 2 / 2 ) b (R5SiO) 3 / 2 ) c The M-linkage, linear linker D, and branched linker T are provided by a capping agent, cyclosiloxane or dialkoxysilane, or trialkoxysilane, as detailed below.

[0019] The chemical formula of the end-capping agent is R1R2R3-Si-O-Si-R1R2R3, where R1, R2, and R3 can be the same or different, and can be H, Cl-C. 10The alkyl or aralkyl group; preferably one or more of H, methyl, vinyl, ethyl, propyl, phenyl, and α-phenyl. More specifically, the end-capping agent can be one of tetramethyldisiloxane, hexamethyldisiloxane, 1,3-divinyldisiloxane, 1,3-diphenyldisiloxane, 1,3-diethyldisiloxane, 1,3-diisopropyldisiloxane, etc.; preferably one of tetramethyldisiloxane, hexamethyldisiloxane, 1,3-divinyldisiloxane, and 1,3-diphenyldisiloxane.

[0020] The cyclosiloxane is specifically one or more of methylhydrocyclosiloxane, dimethylcyclosiloxane, diethylcyclosiloxane, methylethylcyclosiloxane, methylvinylcyclosiloxane, methylphenylcyclosiloxane, and diphenylcyclosiloxane; preferably one or more of methylhydrocyclosiloxane, dimethylcyclosiloxane, methylvinylcyclosiloxane, and methylphenylcyclosiloxane.

[0021] The chemical formula for diekoxysilane is (R4)2Si(R6)2, where R4 is H, C1-C. 10 The alkyl or aralkyl group, wherein R6 is a hydrolyzable alkoxy group; preferably, R4 is one or more of H, methyl, vinyl, ethyl, propyl, phenyl, α-phenyl, etc., and R6 is a hydrolyzable alkoxy group, specifically one of methoxy, ethoxy, propoxy, butoxy, etc. More specifically, the dialkoxysilane is one or more of methylhydrodimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, methylvinyldimethoxysilane, methylvinyldiethoxysilane, methylphenyldimethoxysilane, methylphenyldiethoxysilane, diphenyldimethoxysilane, and diphenyldiethoxysilane; preferably one or more of methylhydrodimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, and methylphenyldimethoxysilane.

[0022] The chemical formula for trialkoxysilane is R5Si(R7)3, where R5 is H, C1-C. 10 The alkyl or aralkyl group, wherein 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, methacrylate-based trimethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, etc.; preferably one or more of trimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, vinyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane.

[0023] Preferably, in step 1), the pre-hydrolysis reaction is performed first, and then cyclosiloxane or dialkoxysilane is added dropwise to continue the pre-hydrolysis reaction.

[0024] The pre-hydrolysis reaction temperature of the end-capping agent is 20-40℃, the reaction time is 0.5-3h, and the stirring speed is 100-500r / min;

[0025] Cyclosiloxane or dialkoxysilane is added dropwise at 20-60℃ for 0.5-3 hours, and then stirred for another 0.5-3 hours after the addition is complete to carry out the pre-hydrolysis reaction.

[0026] Preferably, in step 1) the hydrolysis-condensation reaction, the trialkoxysilane is slowly added dropwise to the pre-hydrolysate for 0.5-6 h at a rate of 100-300 kg / h, and the hydrolysis-condensation reaction temperature is 30-100 °C for 2-10 h.

[0027] Preferably, in step 2), the rebalancing polymerization temperature is 40-100℃ and the rebalancing polymerization time is 2-12h; the neutralization temperature is 30-60℃ and the neutralization time is 3-10h.

[0028] Preferably, in step 3), the vacuum degree is -0.1~-0.4MPa, the de-lowering temperature is 40-150℃, the de-lowering time is 3-12h, and the temperature is lowered to 30-60℃ after de-lowering.

[0029] Preferably, the protic acid catalyst is one or more of sulfuric acid, hydrochloric acid, sulfonic acid, and phosphoric acid, and more preferably one or more of sulfuric acid, sulfonic acid, and phosphoric acid. The amount added is 0.1-20% of the total reactants, preferably 0.1-6%.

[0030] Preferably, the Lewis acid catalyst is one or more of aluminum trichloride, ferric chloride, boron fluoride, and magnesium sulfate, with aluminum trichloride or ferric chloride being the most preferred. The amount added is 0.1-10% of the total reactants, preferably 0.1-5%.

[0031] Preferably, the desiccant is silica gel, molecular sieve, calcium chloride, mineral desiccant, or activated alumina, with silica gel, molecular sieve, or calcium chloride being more preferred. The amount added is 0.1-20% of the total reactants, preferably 1-10%.

[0032] Preferably, the neutralizing agent is one or more of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, sodium hydroxide, and potassium hydroxide, and more preferably one or more of sodium carbonate, sodium bicarbonate, potassium carbonate, and potassium bicarbonate. The amount added is 0.1-20% of the total reactants, preferably 0.1-8%.

[0033] Furthermore, the present invention also discloses a solvent-free branched silicone oil preparation device, which is used to realize the solvent-free branched silicone oil preparation method, including a hydrolysis reactor I, an equilibrium reactor II, a descaling reactor III and a finished product storage tank connected 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 descaling reactor III, and an adsorbent is provided in the pipeline between the descaling reactor III and the finished product storage tank.

[0034] The principle of the preparation method of this invention is as follows:

[0035] First, the capping agent providing the M-chain segments and the cyclosiloxane or dialkoxysilane providing the linear D-chain segments are pre-hydrolyzed in the presence of a protic acid catalyst and water to provide sufficient Si-OH and HO-Si-OH. Then, the trialkoxysilane providing the branched T-chain segments is slowly added dropwise to the pre-hydrolyzed material, where it rapidly hydrolyzes into Si-(OH)3 upon contact with water. The hydrolyzed T-chain segments then condense and cap with the abundant M and D units to reach dynamic equilibrium. Because the hydrolysis rates of M, D, and T are different, the hydrolysis rate of T is often much greater than that of M and D. The co-hydrolysis method suffers from the risk of rapid hydrolysis of T-chain segments followed by slow hydrolysis of M and D, leading to condensation and cross-linking reactions of the T-chain segments themselves. Therefore, a stepwise hydrolysis method is used to avoid the network structure caused by the condensation and cross-linking reactions of the T-chain segments themselves. When the T-chain segments are added to the pre-hydrolyzed material, they are surrounded by the atmosphere of pre-hydrolyzed M and D-chain segments, effectively forming an MDT branched silicone oil structure. After hydrolysis, the oil layer is allowed to stand and separate into layers to remove the upper acidic water layer. The oil layer is then dried through a pipe containing a desiccant. A protic acid catalyst and a Lewis acid catalyst (equilibrium co-catalyst) are added and subjected to a second equilibrium polymerization at 30-100℃ to compensate for the difference in chain scission efficiency between D and T, allowing the MDT silicone oil to undergo deep condensation while becoming more regular. The acidic catalyst is then removed in layers. Finally, an alkaline substance is added for neutralization, followed by filtration and desalting. The oil layer is then decolorized and de-saturated to obtain the branched silicone oil.

[0036] The beneficial effects of this invention are as follows:

[0037] (1) The preparation process of this invention does not require solvents, and makes full use of the hydrolyzed alcohol and linear M and D chain units as co-solvents to promote hydrolysis and stratification;

[0038] (2) The preparation method of the present invention does not require a large amount of solvent for neutralization and water washing. After secondary equilibrium polymerization, neutralization and deacidification and filtration and desalination are carried out, without generating a large amount of waste liquid, which is safer and more environmentally friendly.

[0039] (3) The preparation process of the present invention adopts a stepwise hydrolysis method to avoid excessive condensation and crosslinking of the T chain segment itself due to the different hydrolysis rates of M, D and T chain segments, so that the prepared branched silicone oil has fewer by-products and higher purity.

[0040] (4) The preparation process of this invention incorporates a secondary balancing process, which uses a combination of protic acid and Lewis acid to rebalance the D-chain segment and supplement the chain breakage and rearrangement. This effectively reduces the Si-OH and Si-alkoxy groups generated by incomplete hydrolysis, resulting in a branched silicone oil with higher regularity and better stability. No additional raw materials are required, the process is simpler, the yield is higher, and it is easier to promote and apply. Detailed Implementation

[0041] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present invention.

[0042] Example 1:

[0043] Step 1: Hydrolysis and Condensation

[0044] 360 parts of the capping agent hexamethyldisiloxane were pumped into a dry hydrolysis reactor I, and 120 parts of concentrated hydrochloric acid and 60 parts of water were added dropwise. The mixture was 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 mixture was kept at 30°C for 1 hour. After the addition was complete, the mixture was stirred for another 3 hours to carry out the pre-hydrolysis reaction.

[0045] Then, 280 parts of methyltrimethoxysilane were slowly added dropwise to the pre-hydrolysate for 1.5 hours. After the addition was completed, the temperature was controlled at 60°C and the hydrolysis condensation reaction was continued for 5 hours. Then the reaction was stopped and the mixture was allowed to stand for 10 hours to separate into layers. The upper acidic water layer was removed and the lower oil layer was dried through a pipe containing a desiccant to obtain the dried hydrolysis condensation primary polymer S1.

[0046] Step 2: Balancing and Tilting

[0047] The hydrolyzed condensation primary polymer S1 was pumped into a dry equilibrium reactor II. 24 parts concentrated sulfuric acid and 12 parts AlCl3 were added dropwise with stirring. The temperature was raised to 80°C for reequilibrium polymerization for 8 hours. The reaction was then stopped, and the mixture was allowed to stand for 6 hours to separate into layers. The lower acid layer was removed, while the oil layer remained in the reactor. 12 parts sodium carbonate were added with stirring, and the mixture was heated to 40°C for neutralization for 4 hours. The material was then pumped through a filter equipped with a filter aid to remove salt, yielding the equilibrium polymer S2.

[0048] Step 3: Decolorization

[0049] The obtained equilibrium polymer S2 was pumped into a dry de-lowering reactor III. Under nitrogen protection, stirring and vacuum were started, and the vacuum was controlled at -0.1 MPa. The material was then heated to 80°C for vacuum de-lowering of low-grade components for 6 hours. After de-lowering was stopped, the temperature was lowered to 50°C, and the material was pumped through a pipeline containing adsorbent for filtration and decolorization before being pumped into a finished product storage tank to obtain the branched silicone oil. The branched silicone oil is colorless, transparent, and odorless, with a viscosity of 28 mPa·s and an acid value of 1.08 μg / g.

[0050] Example 2:

[0051] Step 1: Hydrolysis and Condensation

[0052] 180 parts of the end-capping agent tetramethyldisiloxane were pumped into a dry hydrolysis reactor I. 20 parts of sulfonic acid and 30 parts of water were added dropwise. The mixture was stirred at 30°C for 1 hour at a stirring speed of 300 r / min. Then, 880 parts of octamethylcyclotetrasiloxane were added dropwise. The mixture was kept at 30°C for 1 hour. After the addition was complete, the mixture was stirred for another 3 hours to carry out the pre-hydrolysis reaction.

[0053] Then, 360 parts of phenyltriethoxysilane were slowly added dropwise to the pre-hydrolysate 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. Then the reaction was stopped and the mixture was allowed to stand for 10 hours to separate into layers. The upper acidic water layer was removed and the lower oil layer was dried through a pipe containing a desiccant to obtain the dried hydrolysis condensation primary polymer S1.

[0054] Step 2: Balancing and Tilting

[0055] The hydrolyzed condensation primary polymer S1 was pumped into a dry equilibrium reactor II. 20 parts concentrated sulfuric acid and 10 parts FeCl3 were added dropwise with stirring. The temperature was raised to 60°C for reequilibrium polymerization for 10 hours. The reaction was then stopped, and the mixture was allowed to stand for 6 hours to separate into layers. The lower acid layer was removed, while the oil layer remained in the reactor. 10 parts potassium carbonate were added with stirring, and the mixture was heated to 40°C for neutralization for 4 hours. The material was then pumped through a filter equipped with a filter aid to remove salt, yielding the equilibrium polymer S2.

[0056] Step 3: Decolorization

[0057] The obtained equilibrium polymer S2 was pumped into a dry de-lowering reactor III. Under nitrogen protection, stirring and vacuum were started, and the vacuum was controlled at -0.1 MPa. The material was then heated to 100°C for vacuum de-lowering of low-grade components for 6 hours. After de-lowering was stopped, the temperature was lowered to 50°C, and the material was pumped through a pipeline containing adsorbent for filtration and decolorization before being pumped into a finished product storage tank to obtain the branched silicone oil product. The branched silicone oil is colorless, transparent, and odorless, with a viscosity of 496 mPa·s and an acid value of 0.76 μg / g.

[0058] Example 3:

[0059] Step 1: Hydrolysis and Condensation

[0060] 93 parts of the end-capping agent divinyldisiloxane were pumped into a dry hydrolysis reactor I, and 36 parts of phosphoric acid and 120 parts of water were added dropwise. The mixture was stirred at 30°C for 1 hour at a stirring speed of 300 r / min. Then, 1280 parts of methyldimethoxysilane were added dropwise, and the mixture was kept at 50°C for 1 hour. After the addition was complete, the mixture was stirred for another 3 hours to carry out the pre-hydrolysis reaction.

[0061] Then, 240 parts of octyltriethoxysilane were slowly added dropwise to the pre-hydrolysate for 1 hour. After the addition was completed, the temperature was controlled at 80°C and the hydrolysis condensation reaction was continued for 8 hours. Then the reaction was stopped and the mixture was allowed to stand for 10 hours to separate into layers. The upper acidic water layer was removed and the lower oil layer was dried through a pipe containing a desiccant to obtain the dried hydrolysis condensation primary polymer S1.

[0062] Step 2: Balancing and Tilting

[0063] The hydrolyzed condensation primary polymer S1 was pumped into a dry equilibrium reactor II. 16 parts concentrated sulfuric acid and 8 parts BBF3 were added dropwise with stirring. The temperature was raised to 80°C for reequilibrium polymerization for 8 hours. The reaction was then stopped, and the mixture was allowed to stand for 6 hours to separate into layers. The lower acid layer was removed, while the oil layer remained in the reactor. 8 parts sodium bicarbonate were added with stirring, and the mixture was heated to 40°C for neutralization for 4 hours. The material was then pumped through a filter equipped with a filter aid to remove salt, yielding the equilibrium polymer S2.

[0064] Step 3: Decolorization

[0065] The obtained equilibrium polymer S2 was pumped into a dry de-lowering reactor III. Under nitrogen protection, stirring and vacuum were started, and the vacuum was controlled at -0.1 MPa. The material was then heated to 130°C for vacuum de-lowering of low-grade components for 6 hours. After de-lowering was stopped, the temperature was lowered to 50°C, and the material was pumped through a pipeline containing adsorbent for filtration and decolorization before being pumped into a finished product storage tank to obtain the branched silicone oil product. The branched silicone oil is colorless, transparent, and odorless, with a viscosity of 823 mPa·s and an acid value of 1.29 μg / g.

[0066] Comparative Example 1 (C-1): Traditional co-hydrolysis-ethanol solvent method

[0067] Step 1: Add hexamethyldisiloxane, dimethyldimethoxysilane, and methyltrimethoxysilane all at once; then add 30 wt% excess anhydrous ethanol, concentrated hydrochloric acid, and water for co-hydrolysis for 6 h.

[0068] Step 2: Wash three times with water until pH≈7, then perform de-alcoholization under reduced pressure. No secondary equilibration polymerization was performed.

[0069] Results: The product was pale yellow, with residual ethanol of 740 ppm and an acid value of 22.4 µg / g. -1The viscosity at 30 °C was 41 mPa·s, but increased by 18% after 30 days. The wastewater from the washing process was approximately 4.2 kg.

[0070] The use of external solvents without secondary equilibration results in high levels of residual alcohol and acid, poor stability, and a large amount of waste liquid.

[0071] Comparative Example 2 (C-2): Cyclosiloxane as Solvent Method (CN108892775B Route)

[0072] 1000 g of octamethylcyclotetrasiloxane (D4) was used as the reaction medium beforehand; the rest of the operation was the same as in Example 2, but the addition was not done in steps. The product required decyclization at 120 °C and −0.08 MPa for 8 h, and 2.9 wt% of D4 remained.

[0073] Results: Pale yellow and transparent, acid value 8.7 µg g -1 The viscosity at 30 °C was 495 mPa·s; after freezing at -20 °C for 24 h, 3 vol% gel appeared; the raw material cost increased by 18%.

[0074] It is evident that using cyclosiloxanes with large doses of solvent is costly, difficult to de-ring, and carries a high risk of gelation.

[0075] Comparative Example 3 (C-3): One-time co-hydrolysis without stepwise addition

[0076] All trialkoxysilanes were mixed with a capping agent, dimethyldimethoxysilane, water, and hydrochloric acid in one step and hydrolyzed at 30 °C for 8 h. After standing and separating into layers, and coarse filtration, vacuum descaling was performed.

[0077] Results: The system formed a flocculent gel after 3 hours of hydrolysis and could not be pumped; the final filtered product was a semi-solid-semi-liquid substance, and the acid value could not be accurately determined, so it was considered a preparation failure.

[0078] It is evident that without the use of "stepwise hydrolysis," the T-chain segments undergo severe self-condensation and cross-linking, making it impossible to obtain fluid-like MDT branched silicone oil.

[0079] Comparative Example 4 (C-4): Secondary equilibrium tunable polymerization omitted

[0080] S1 was obtained according to the stepwise hydrolysis process of Example 1; direct neutralization-filtration-de-lowering, without adding protic acid / Lewis acid for rebalancing.

[0081] Result: Colorless appearance, but Si-OH residue 0.68 wt% ( 1 H-NMR), acid value 11.3 µg g -1 After aging at 45 ℃ for 7 days, turbidity appeared and the viscosity increased by 23%.

[0082] It is evident that there is a lack of rebalancing, insufficient chain breakage compensation, a large number of residual active groups, and poor thermal-storage stability.

[0083] Comparative Example 5 (C-5): Reequilibration using only protic acids, without Lewis acid synergy.

[0084] Add 0.8 wt% concentrated sulfuric acid (without AlCl3) to S1 according to Example 1, re-equilibrate at 80 °C for 8 h, and the rest is the same as in Example 1.

[0085] Result: Acid value 6.2 µg g -1 The residual Si-OH content is 0.19 wt%, and the viscosity at 30 °C is 30 mPa·s; however, the molecular weight distribution (GPC, Mw / Mn) is 2.6, which is wider than 1.8 in Example 1, and the viscosity fluctuates by 12% after 30 days of storage.

[0086] It is evident that the lack of Lewis acid co-catalysis results in insufficient chain scission-rearrangement, a wide molecular weight distribution, and inferior regularity and long-term stability.

[0087] Table 1 Comparison of Experimental Data

[0088]

[0089] As shown in Table 1, the embodiments of the present invention exhibit 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 effects brought about by the solvent-free, stepwise hydrolysis, and the synergistic effect of the protonic acid / Lewis acid dual-catalytic secondary equilibrium. The omission of each item in the comparative examples leads to significant performance degradation or direct preparation failure, thus objectively proving the inventiveness and superiority of the present invention.

[0090] The foregoing description of embodiments of the present invention, through which those skilled in the art are able to implement or use the present invention, will be readily apparent to those skilled in the art. Various modifications to these embodiments will be readily apparent to those skilled in the art. The general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novelty disclosed herein.

Claims

1. A method for preparing solvent-free branched silicone oil, characterized in that, The branched silicone oil has a viscosity of 1-1000 mPa·s and a chemical formula of (R1R2R3SiO2). 1 / 2 ) a (R4)2SiO 2 / 2 ) b (R5SiO) 3 / 2 ) c In the formula, a + b + c = 1, a = 0.1 - 0.5, b = 0.1 - 0.8, and c = 0.1 - 0.3; R1, R2, R3, R4, and R5 are H and C1-C, respectively. 10 Alkyl, vinyl, or aralkyl; The preparation method of this branched silicone oil includes the following steps: 1) Hydrolysis condensation: The capping agent, cyclosiloxane or dialkoxysilane and water are mixed and pre-hydrolyzed under the condition of protic acid catalyst to obtain pre-hydrolyzed product; then, trialkoxysilane is slowly added to the pre-hydrolyzed product to carry out hydrolysis 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 hydrolysis condensation primary polymer S1. 2) Equilibrium telomerization: Protic acid catalyst and Lewis acid catalyst are added to the hydrolysis condensation primary polymer S1 for reequilibrium telomerization. After the reaction is completed, the mixture is allowed to stand and separate into layers. The oil layer is separated, neutralized by adding a neutralizing agent, and filtered to obtain equilibrium telomer S2. 3) Degradation and decolorization: Vacuum degradation is performed on the equilibrium telomer S2, followed by filtration and decolorization to obtain branched silicone oil; In the pre-hydrolysis reaction, the capping agent undergoes a pre-hydrolysis reaction first, and then cyclosiloxane or dialkoxysilane is added dropwise to continue the pre-hydrolysis reaction.

2. The method for preparing solvent-free branched silicone oil according to claim 1, characterized in that, 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 solvent-free branched silicone oil according to claim 1, characterized in that, In step 1), the pre-hydrolysis reaction is carried out first, and then cyclosiloxane or dialkoxysilane is added dropwise to continue the pre-hydrolysis reaction. The pre-hydrolysis reaction temperature of the end-capping agent is 20-40℃, the reaction time is 0.5-3h, and the stirring speed is 100-500r / min; Cyclosiloxane or dialkoxysilane is added dropwise at 20-60℃ for 0.5-3 hours, and stirring is continued for another 0.5-3 hours after the addition is complete to carry out the pre-hydrolysis reaction; And / or, in step 1) the hydrolysis-condensation reaction, the trialkoxysilane is slowly added dropwise to the pre-hydrolysate for 0.5-6 h, the hydrolysis-condensation reaction temperature is 30-100 °C, and the reaction time is 2-10 h.

4. The method for preparing solvent-free branched silicone oil according to claim 1, characterized in that, In step 2), the rebalancing temperature is 40-100℃ and the rebalancing time is 2-12h; the neutralization temperature is 30-60℃ and the neutralization time is 3-10h.

5. The method for preparing solvent-free branched silicone oil according to claim 1, characterized in that, In step 3), the vacuum degree is -0.1~-0.4MPa, the de-lowering temperature is 40-150℃, the de-lowering time is 3-12h, and the temperature is lowered to 30-60℃ after de-lowering.

6. The method for preparing solvent-free branched silicone oil according to claim 1, characterized in that, The protic 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, characterized in that, The Lewis acid catalyst is one or more of aluminum trichloride, ferric trichloride, boron fluoride, and magnesium sulfate.

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

9. The method for preparing solvent-free branched silicone oil according to claim 1, characterized in that, 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 apparatus, characterized in that, The equipment is used to implement the preparation method according to any one of claims 1-9, comprising a hydrolysis reactor I, a equilibration reactor II, a descaling reactor III, and a finished product storage tank connected in sequence to each other, wherein a desiccant is provided in the pipeline between the hydrolysis reactor I and the equilibration reactor II, a filter is provided between the equilibration reactor II and the descaling reactor III, and an adsorbent is provided in the pipeline between the descaling reactor III and the finished product storage tank.

Images