A defoaming agent obtainable by a process that includes: polymerizing (A) at least one polymerizable monomer in a composition, the composition comprising (C) a solvent and (B) at least one non-polymerizable polysiloxane dissolved in the (C) solvent, wherein the component (A) optionally comprises at least one Si-atom-containing monomer in an amount of less than 10 mass % on the basis of the total mass of the component (A).

A lubricating oil composition including: a lubricating base oil; (A) a first defoaming agent, the first defoaming agent being (A1) a first polymer, or (A2) a second polymer, or any combination thereof; and (B) a second defoaming agent, the second defoaming agent being a silicone defoaming agent, the (A1) first polymer including: a first polymer chain including a polysiloxane structure, the polysiloxane structure having a polymerization degree of 5 to 2000 and being represented by the following general formula (1); and a second polymer chain bonded with the first polymer chain, the second polymer chain including a repeating unit represented by the following general formula (2), the (A2) second polymer being a copolymer of a first monomer component and a second monomer component, the first monomer component represented by the general formula (7) or (8), the second monomer component represented by the general formula (9).

##STR00001##

A lubricating oil composition including: a lubricating base oil; (A) a first defoaming agent, the first defoaming agent being (A1) a first polymer, or (A2) a second polymer, or any combination thereof; and (B) a second defoaming agent, the second defoaming agent being a silicone defoaming agent, the (A1) first polymer including: a first polymer chain including a polysiloxane structure, the polysiloxane structure having a polymerization degree of 5 to 2000 and being represented by the following general formula (1); and a second polymer chain bonded with the first polymer chain, the second polymer chain including a repeating unit represented by the following general formula (2), the (A2) second polymer being a copolymer of a first monomer component and a second monomer component, the first monomer component represented by the general formula (7) or (8), the second monomer component represented by the general formula (9). ##STR00001##

A defoaming agent including a polymer, the polymer including: at least one first polymer chain including a polysiloxane structure represented by the following general formula (1); and at least one second polymer chain including a repeating unit represented by the following general formula (2) and bonded to the first polymer chain: ##STR00001##
wherein in the formula (1), repeating units may be in any order; each of R.sup.1 and R.sup.2 is independently a C.sub.1-18 organic group comprising no fluorine atom; at least one of R.sup.3 and R.sup.4 is the organic group comprising no less than 3 fluorine atoms; m is an integer of no less than 1; and n+m is 5 to 2000, ##STR00002##
wherein in the formula (2), X.sup.1 is a repeating unit obtainable by polymerization of an ethylenic unsaturated group; Y.sup.1 is a substituted or unsubstituted C.sub.1-40 hydrocarbyl group; and Z.sup.1 is a linking group linking X.sup.1 and Y.sup.1.

Reaction products of an optionally alkoxylated alcohol, a polyalkylene alcohol and a linker can be used in various applications such as defoamers. Methods of making the reaction products and defoamer compositions including the reaction products, and methods of using the reaction products to reduce or prevent foam in a composition are also disclosed. The reaction products can be used with an organic solvent or without an organic solvent to provide low VOC compositions.

A defoaming agent including a polymer, the polymer including: at least one first polymer chain including a polysiloxane structure represented by the following general formula (1); and at least one second polymer chain including a repeating unit represented by the following general formula (2) and bonded to the first polymer chain:

##STR00001##

wherein in the formula (1), repeating units may be in any order; each of R.sup.1 and R.sup.2 is independently a C.sub.1-18 organic group comprising no fluorine atom; at least one of R.sup.3 and R.sup.4 is the organic group comprising no less than 3 fluorine atoms; m is an integer of no less than 1; and n+m is 5 to 2000,

##STR00002##

wherein in the formula (2), X.sup.1 is a repeating unit obtainable by polymerization of an ethylenic unsaturated group; Y.sup.1 is a substituted or unsubstituted hydrocarbyl group; and Z.sup.1 is a linking group linking X.sup.1 and Y.sup.1.

A defoaming agent obtainable by a process that includes: polymerizing (A) at least one polymerizable monomer in a composition, the composition comprising (C) a solvent and (B) at least one non-polymerizable polysiloxane dissolved in the (C) solvent, wherein the component (A) optionally comprises at least one Si-atom-containing monomer in an amount of less than 10 mass % on the basis of the total mass of the component (A).

Reaction products of an optionally alkoxylated alcohol, a polyalkylene alcohol and a linker can be used in various applications such as defoamers. Methods of making the reaction products and defoamer compositions including the reaction products, and methods of using the reaction products to reduce or prevent foam in a composition are also disclosed. The reaction products can be used with an organic solvent or without an organic solvent to provide low VOC compositions.