ANTIFOAMING AGENT AND LUBRICANT COMPOSITION
FIG1 is an explanatory view of the structure of a homogenizer test machine that is used for the evaluation of defoaming performance 
Defoaming performance of each of the prepared lubricating oil compositions was evaluated by a homogenizer test machine shown in FIG1. The homogenizer test machine shown in FIG1 includes a homogenizer 1, a cylindrical heater for heating 2, a temperature adjuster 3, a thermocouple for oil temperature measurement 4, an electric power source for the heater 5, a glass cylinder corresponding to an oil tank 6 (graduated cylindrical glass vessel, 40 mm in inner diameter, 300 mm in depth, 2 mL grading divisions from 0 to 250 mL), and an air blow tube (air blow rate: 30 mL/min) 7.
explanatory view
5
than
2
general formula
1
general formula
['1. A defoaming agent comprising a polymer, the polymer comprising: at least one first polymer chain comprising a polysiloxane structure, the polysiloxane structure being represented by the following general formula (1) and having a polymerization degree of 5 to 2000; and at least one second polymer chain comprising a repeating unit, the repeating unit being represented by the following general formula (2), the second polymer chain being bonded to the first polymer chain: wherein in the general formula (1), polysiloxane repeating units may be in any order; each of R 1  and R 2  is independently a C 1-18  organic group comprising no fluorine atom; each of R 3  and R 4  is independently a C 1-18  organic group comprising no less than 3 fluorine atoms or a C 1-18  organic group comprising no fluorine atom, wherein at least one of R 3  and R 4  is the organic group comprising no less than 3 fluorine atoms; n is an integer of no less than 0; m is an integer of no less than 1; and n+m is 5 to 2000, wherein in the general formula (2), X 1  is a repeating unit obtainable by polymerization of an ethylenic unsaturated group; Y 1  is a side chain consisting of a substituted or unsubstituted C 1-40  hydrocarbyl group; and Z 1  is a linking group linking the repeating unit X 1  and the side chain Y 1 .']