Method for improving lubricant antifoaming performance and filterability

A lubricating oil having a composition comprising a lubricating oil base stock as a major component;

• and at least one antifoam agent, as a minor component;
• wherein the antifoam agent comprises a silicone composition having the formula:
• wherein:
• R1 are independently selected from the group consisting of:
• an alkyl having 1-5 carbon atoms, a substituted alkyl having 1-5 carbon atoms optionally substituted by one or more fluorine atoms, and a phenyl, and R2 is selected from the group consisting of:
• hydrogen, alkyl of 1 to 45 carbon atoms, substituted alkyl of 1 to 45 carbon atoms optionally substituted by one or more fluorine atoms, aryl, a partially esterified ester-containing group represented by the formula:
• and a reverse ester thereof represented by the formula:
• and the formula:
• and a reverse ester thereof represented by the formula:
• provided that if R1 is anything but methyl or ethyl, then R2 must be a methyl, ethyl or butyl, R3 is derived from a partially esterified ester residue;
• R8 is selected from the group consisting of:
• hydrogen, alkyl of 1 to 45 carbon atoms, substituted alkyl of 1 to 45 carbon atoms optionally substituted by one or more fluorine atoms, aryl and a group derived from a partially esterified ester residue;
• R9 is selected from the group consisting of:
• an arylene, an alkylene of 1 to 22 carbon atoms, substituted alkylene of 1 to 22 carbon atoms optionally substituted by one or more fluorine atoms and arylene;
• R4 is selected from the group consisting of:
• alkyl of 1 to 45 carbon atoms, substituted alkyl of 1 to 45 carbon atoms optionally substituted by one or more fluorine atoms, aryl, said ester-containing group and said group derived from reverse esters thereof, m is an integer between about 5 to about 22;
• and x is an integer between about 0 to about 1000;
• wherein said composition has at least 1 compound derived from said partially esterified ester-containing group or said reverse ester thereof;
• and
• wherein the antifoam agent is provided to the lubricating oil in the form of a defoamant concentrate present in an amount of from about 0.05 weight percent to about 0.5 weight percent, based on the total weight of the lubricating oil, to yield less than 100 ppm of total insoluble defoamant to the lubricating oil.

A method for improving antifoaming performance, while maintaining or improving filterability, of a lubricating oil in an engine or other mechanical component lubricated with the lubricating oil by using as the lubricating oil a formulated oil, said formulated oil having a composition comprising a lubricating oil base stock as a major component;

• and at least one antifoam agent, as a minor component;
• wherein the antifoam agent comprises a silicone composition having the formula:
• wherein:
• R1 are independently selected from the group consisting of:
• an alkyl having 1-5 carbon atoms, a substituted alkyl having 1-5 carbon atoms optionally substituted by one or more fluorine atoms, and a phenyl, and R2 is selected from the group consisting of:
• hydrogen, alkyl of 1 to 45 carbon atoms, substituted alkyl of 1 to 45 carbon atoms optionally substituted by one or more fluorine atoms, aryl, a partially esterified ester-containing group represented by the formula:
• and a reverse ester thereof represented by the formula:
• and the formula:
• and a reverse ester thereof represented by the formula:
• provided that if R1 is anything but methyl or ethyl, then R2 must be a methyl, ethyl or butyl, R3 is derived from a partially esterified ester residue;
• R8 is selected from the group consisting of:
• hydrogen, alkyl of 1 to 45 carbon atoms, substituted alkyl of 1 to 45 carbon atoms optionally substituted by one or more fluorine atoms, aryl and a group derived from a partially esterified ester residue;
• R9 is selected from the group consisting of:
• an arylene, an alkylene of 1 to 22 carbon atoms, substituted alkylene of 1 to 22 carbon atoms optionally substituted by one or more fluorine atoms and arylene;
• R4 is selected from the group consisting of:
• alkyl of 1 to 45 carbon atoms, substituted alkyl of 1 to 45 carbon atoms optionally substituted by one or more fluorine atoms, aryl, said ester-containing group and said group derived from reverse esters thereof, m is an integer between about 5 to about 22;
• and x is an integer between about 0 to about 1000;
• wherein said composition has at least 1 compound derived from said partially esterified ester-containing group or said reverse ester thereof;
• and
• wherein the antifoam agent is provided to the lubricating oil in the form of a defoamant concentrate present in an amount of from about 0.05 weight percent to about 0.5 weight percent, based on the total weight of the lubricating oil, to yield less than 100 ppm of total insoluble defoamant to the lubricating oil.