Emulsion type defoamer is a general-purpose silicone defoamer, which is made of low foaming emulsifier such as Span, Tween, Polyethylene glycol ether and other emulsified silicone oil/silicone oil. /W) type emulsion. It is characterized by
It is easily dispersed in water system and can be widely used as defoaming of aqueous phase system. It is sensitive to the temperature, acid, alkali and salt of foaming liquid, easy to cause oil or demulsification, and has poor dilution stability and durability. Dimethyl silicone oil will gradually precipitate out, thus losing the ability to defoam, which will pollute the system for systems that cannot contain oil.
Example of emulsion type antifoaming agent: (containing 30% of active material) 1 Firstly made of silica gel: (as described in 2.1) 25 ° C, 500 cp Dimethicone 45.0 g 25 ° C, 1000 cp Dimethicone 45.0g fumed silica (Jibi HL-200) 10.0g total 100.0g
2 Preparation of emulsion: mixing the silica gel and the composite emulsifier to 60-70 ° C, stirring for 1 hour, slowly adding 50 ° C water under high-speed stirring, stirring for about 15 minutes, adding thickener to adjust to the appropriate Viscosity, filtered to obtain an emulsion.
Silica black silicone paste (ibid.) 30.0g S-80 6.0g T-80 2.0g polyoxyethylene (20) alkyl alcohol ether 2.0g water 60.0g thickener 0.5-1.0g total 100.0g