A defoaming composition is composed of a composition E composed of a hydrogen bond donor polyether modified polysiloxane C and a hydrogen bond acceptor X, and a composition F composed of a hydrogen bond donor fatty alcohol polyether D and a hydrogen bond acceptor Y; and the polyether modified polysiloxane C is composed of a polyorganosiloxane A and an allyl polyether B. The general structural formula of the polyorganosiloxane A is R.sup.0.sub.2HSiO (Me.sub.2SiO).sub.aSiHR.sup.0.sub.2, where R.sup.0 is C1-12 alkyl, cycloalkyl or aryl, and a=10-100. The general structural formula of the allyl polyether B is CH.sub.2═CHCH.sub.2(OCH.sub.2CH.sub.2).sub.b(OCH.sub.2CHCH.sub.3).sub.cOH, where b=1-10, and c=10-100. The general structural formula of the fatty alcohol polyether D is R.sup.1(OCH.sub.2CH.sub.2).sub.m(OCH.sub.2CHCH.sub.3).sub.nOH, where R.sup.1 is C3-20 linear or branched alkyl, cycloalkyl or aralkyl; m=1-50; and n=10-100. The hydrogen bond acceptors X and Y are menthol, menthene, thymol, terpilenol, carveol or perillyl alcohol.

Effective defoamer compositions contain two different aryl-substituted organopolysiloxanes and filler particles, and show high defoaming capability.

Effective defoamer compositions contain two different aryl-substituted organopolysiloxanes and filler particles, and show high defoaming capability.

Provided is a silicone based anti-foaming agent oil compound that has not only superior anti-foaming speed but also anti-foaming performance that does not degrade with repeated use or use over a long period. The silicone based anti-foaming agent oil compound comprises: (A) an essentially hydrophobic organopolysiloxane with a viscosity at 25 C. of 2,500 to 50,000 mPa.Math.s: 20 to 80 parts by mass; (B) a hydrophobic organopolysiloxane or cyclic organopolysiloxane having silanol groups at least at both terminals: 20 to 80 parts by mass; (C) a silane or silane condensation product: 1 to 10 parts by mass; and (D) a fine powder silica with a specific surface area of 50 m.sup.2/g or more: 2 to 10 parts by mass; where the total amount of (A) and (B) combined is 100 parts by mass. Also provided is a method for manufacturing the silicone based anti-foaming agent oil compound.

A defoaming composition is composed of a composition E composed of a hydrogen bond donor polyether modified polysiloxane C and a hydrogen bond acceptor X, and a composition F composed of a hydrogen bond donor fatty alcohol polyether D and a hydrogen bond acceptor Y; and the polyether modified polysiloxane C is composed of a polyorganosiloxane A and an allyl polyether B. The general structural formula of the polyorganosiloxane A is R.sup.0.sub.2HSiO (Me.sub.2SiO).sub.aSiHR.sup.0.sub.2, where R.sup.0 is C1-12 alkyl, cycloalkyl or aryl, and a=10-100. The general structural formula of the allyl polyether B is CH.sub.2CHCH.sub.2(OCH.sub.2CH.sub.2).sub.b(OCH.sub.2CHCH.sub.3).sub.cOH, where b=1-10, and c=10-100. The general structural formula of the fatty alcohol polyether D is R.sup.1(OCH.sub.2CH.sub.2).sub.m(OCH.sub.2CHCH.sub.3).sub.nOH, where R.sup.1 is C3-20 linear or branched alkyl, cycloalkyl or aralkyl; m=1-50; and n=10-100. The hydrogen bond acceptors X and Y are menthol, menthene, thymol, terpilenol, carveol or perillyl alcohol.