1.2 the low hydrogen silicone oil is prepared by the polymerization method [3]. 111.5g DMC, 6.5g high hydrogen silicone oil and 2.2gmm were added to the reactor, and concentrated sulfuric acid was used as catalyst to react at 60-65 ℃ for 3-5h; then, they were reduced to room temperature, neutralized and filtered with sodium bicarbonate, and the low boiling matter was removed by vacuum distillation at 110 ℃, and the low hydrogen silicone oil with active hydrogen content of 0.09% was obtained.








Synthesis of 1.3-terminal allyl polyoxyalkylene ether






In the high-pressure reactor, add a certain amount of propylene alcohol and alkali catalyst, press the cover of the reactor tightly, and replace it with N2 for three times; evacuate and heat up, stir and add ethylene oxide and propylene oxide at the temperature of 90-110 ℃; after feeding, the pressure in the reactor is negative pressure; cool the discharge; after neutralization, bleaching and decolorization, filter and dehydrate the product to obtain allyl polyoxyene ether.








1.4 synthesis of polyether modified polysiloxane






Under the action of catalyst, Si-H group in hydrogenated silicone oil can react with double bond in allyl polyoxyalkylene ether to produce Si-C polyether modified polysiloxane. The addition reaction is as follows:






In a four port flask, the reaction raw materials (low hydrogen silicone oil, allyl polyoxyalkylene ether) and 25% toluene were azeotropically dehydrated, then the isopropanol chloroplatinate solution with 30 × 10-6 platinum content was used as catalyst, heated to 100 ℃ in nitrogen atmosphere, reacted for 4-4.5h, and the polyether modified polysiloxane was obtained after the solvent was evaporated.






1.5 preparation of polyether modified polysiloxane defoamer


A certain proportion of hydrophobic fumed silica and polyether modified polysiloxane were stirred at 160-180 ℃ for 3h, then dropped to room temperature to obtain silica paste; then a certain amount of emulsifier and thickener were added, stirred and heated to make the emulsifier completely dissolved. Continue stirring about 2h, then get the crude emulsion; then stir it with high speed homogenizer for about 10min to get a stable emulsion product.






1.6 performance evaluation of defoamer






1.6.1 stability






Centrifugal stability: centrifuge at high speed, centrifuge at a speed of 4000 r/min centrifuge 30min to observe whether the emulsion is stratified or bleached. Thermal stability: store 48h at (85 + 2) C to observe whether the emulsion is demulsifying.






Particle size of 1.6.2 defoamer emulsion






The particle size and its distribution were observed by zetasizey 3000 dynamic light scattering instrument of maiven company.






1.6.3 defoamer performance






Defoaming includes two aspects: the elimination of the generated foam, called defoaming, and prevention of foam formation, called bubble suppression.






In a 600ml graduated tube, add 100ml of sodium dodecylbenzene sulfonate aqueous solution with a mass fraction of 2.5% as the foaming solution, and the N2 gas continuously passes through the immersion at a gas speed of 3L / min When the foam volume reaches 500mL, add a certain amount of defoamer (0.05% of the foaming liquid quality) to the foam head and start the time, and record the time of foam elimination. The shorter the time is, the better the defoamer is. Next, record the time required for foam volume to reach 500mL again. The longer the time is, the better the antifoam is.