Continuous cracking method for dimethyl polysiloxane with end sealed by hydroxyl group and rectifying method for the same to preparing cyclosiloxane
A technology of polydimethylsiloxane and octamethylcyclotetrasiloxane is applied in the field of continuous cracking and rectification to prepare cyclosiloxane, and achieves the advantages of solving the problem of solvent treatment, improving the yield of the ring body and the quality of the product. Effect
Inactive Publication Date: 2011-05-04
JIANGXI BLUESTAR XINGHUO SILICONE CO LTD
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[0003] The technical problem to be solved by the present invention is to provide a solvent-free hydroxyl-terminated poly The continuous cracking and rectification of dimethylsiloxane to prepare cyclosiloxane, which not only solves the problem of solvent treatment, but also improves the yield of ring body and product quality
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[0027] Hydroxy-terminated polydimethylsiloxane F1=2644kg / h, composition (wt): MM: 0.06%, D3: 0.5%, D4: 50%, D5: 10%, D6: 2.14%, line body: 37.3 % And alkali catalyst (50% KOH aqueous solution), according to the proportion of R=50% KOH aqueous solution: hydroxyl-terminated polydimethylsiloxane F1 (wt) = 1:100, continuous feeding to the cracking tank 1a, control The reaction temperature of the cracking kettle is 135℃, and the reaction pressure is 0.005MPa-A. The vapor phase V1 of the mixture obtained from cracking is fed from the cracking kettle 1a into the cracking tower 1t with a pressure of 0.002MPa-A and a top temperature of 95°C. The cracking tower 1t is a plate type. The column is used for vapor-liquid exchange with the reflux liquid on the tray, and the line body is returned to the cracking tank 1a for re-cracking. The mixed ring body G1 mainly composed of octamethylcyclotetrasiloxane obtained at the top of the tower is condensed by the condenser for 1h , One part of reflu...
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The present invention discloses a process for preparing cyclic siloxane including continuous cracking and rectification of hydroxyl group terminated polydimethyl siloxane. Under the condition of alkali catalyst and vacuum, a line body of the hydroxyl group terminated polydimethyl siloxane is continuously cracked and broken in chain to oligomeric ring siloxane, namely mixed ring body, the distilled vapor phase enters a cracking tower from a cracking kettle, and is carried out vapor-liquid exchange with refluxing liquid of a condenser. The line body is recracked after returning the cracking kettle, and the mixed ring body with octamethylcyclotetrasiloxane as main component is obtained at top of the cracking tower. The mixed ring body is continuously distilled under vacuum through double tower, the continuous discharging at the side line, tower top and tower bottom is realized, and the required cyclic siloxane is obtained. The present invention carries out cracking under the condition of no solvent, which not only solves the solvent processing problem, but also improves cyclic siloxane yield and product quality, and overcomes the inconvenience for the operation caused by batch feed.
Description
technical field [0001] The invention relates to a method for continuously cracking and rectifying hydroxyl-terminated polydimethylsiloxane to prepare cyclosiloxane. Background technique [0002] Some people in China use dimethyldichlorosilane hydrolyzate hydroxyl-terminated polydimethylsiloxane evaporation, cracking, evaporation to dryness and ring body washing process to prepare cyclosiloxane, but this process has low ring body yield, Poor quality, short production slag discharge cycle, high alkali consumption, and difficulty in device enlargement. Since the early 1980s, there have been reports on the preparation of cyclic siloxane by solvent cracking of dimethyldichlorosilane hydrolyzate in foreign countries. The Jihua Research Institute also published the "Chemical Industry "Science and Technology", 2001 Vol.9 No.2 P.63-65 published "Continuous Cracking Process Development of Dimethyldichlorosilane Hydrolyzate by Solvent Method", which is about the preparation of cyclic...
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IPC IPC(8): C07F7/21
Inventor 郭守涛吕永雄王继忠尹跃龙陈晓明
Owner JIANGXI BLUESTAR XINGHUO SILICONE CO LTD