Antifoaming compositions

Details Antifoaming compositions Antifoaming compositions

2000-02-29

2002-07-09

Metzmaier, Daniel S. (Department: 1712)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

At least one aryl ring which is part of a fused or bridged...

C524S588000, C524S757000, C524S762000, C516S074000, C516S076000, C516S117000, C516S118000, C516S124000

Reexamination Certificate

active

06417258

ABSTRACT:

This invention relates to antifoaming compositions having improved antifoaming properties, water dispersibility and stability.
BACKGROUND OF THE INVENTION
Because of their superior antifoaming properties, silicone base antifoaming agents are used in a variety of industrial areas covering synthetic resins, synthetic rubber, oils and fats, fermentation, foods, fibers, petroleum, and medicines. Among others, antifoaming compositions for use under rigorous conditions including high temperatures, high pH and high shear forces are known from JP-B 52-19836, JP-B 52-22638, and JP-B 55-23084. For these compositions, further improvements in antifoaming properties were desired. To meet such demands, JP-B 3-14481, JP-B 3-14482, JP-A 63-147507, JP-A 1-317505 and JP-A 3-188905 propose compositions primarily comprising an organopolysiloxane having crosslinking units incorporated therein. These compositions, however, lack stability.
More recently, JP-A 5-271689, JP-A 8-196811 and JP-A 8-309104 propose oil compounds primarily comprising an organopolysiloxane having branched units incorporated in its structure. The antifoaming properties of these compounds are fairly improved, but not yet satisfactory.
SUMMARY OF THE INVENTION
An object of the invention is to provide an antifoaming composition having improved antifoaming properties, water dispersibility and stability.
The invention provides an antifoaming composition comprising (A) 58 to 90% by weight of an oil compound and (B) 10 to 42% by weight of a mixture. The oil compound (A) consists essentially of (i) 80 to 99.9% by weight of an organopolysiloxane and (ii) 0.1 to 20% by weight of finely divided silica. The organopolysiloxane (i) is composed of R
1
3
SiO
1/2
units, R
1
2
SiO
2/2
units and R
1
SiO
3/2
units wherein R
1
is independently a monovalent organic group of 1 to 20 carbon atoms, has a structure giving a compositional ratio of R
1
3
SiO
1/2
units:R
1
2
SiO
2/2
units:R
1
SiO
2/3
units=(0.1 to 5):(90 to 99.8):(0.1 to 5) by mol %, and has a viscosity of 100 to 1,000,000 centipoise at 25° C. The mixture (B) consists essentially of (iii) 30 to 99% by weight of a polyoxyalkylene-modified silicone oil of the following structural formula (1) and having a viscosity of 5,000 to 1,000,000 centipoise at 25° C. and (iv) 1 to 70% by weight of a polyhydric alcohol alkyl ether having a molecular weight of 50 to 500.
In formula (1), R
2
is independently a monovalent organic group of 1 to 20 carbon atoms, A is a polyoxyalkylene-bearing group represented by —R
3
—O(CH
2
CH
2
O)
p
(CH
2
CH(CH
3
)O)
q
—R
4
wherein R
3
is a divalent hydrocarbon group of 1 to 4 carbon atoms, R
4
is hydrogen or an alkyl, acyl or isocyanate group of 1 to 6 carbon atoms, p and q are numbers satisfying 10≦p+q≦100 and 10/90≦p/q≦100/0, the letters a and b are numbers satisfying 10≦a+b≦1000 and 50/50≦a/b≦99/1, and c is equal to 0 or 1.
A surfactant other than the polyoxyalkylene-modified silicone oil may be blended in the antifoaming composition in an amount of 0.1 to 50 parts by weight per 100 parts by weight of components (A) and (B) combined. This antifoaming composition can be dispersed in an aqueous dispersion of a water-soluble polymer.
The antifoaming composition of the invention exhibits improved antifoaming properties, good water dispersibility and high stability.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Briefly stated, the antifoaming composition of the invention contains (A) an oil compound and (B) a mixture as main components. The oil compound (A) is a main component for endowing the composition with antifoaming properties. The oil compound (A) consists essentially of (i) an organopolysiloxane and (ii) finely divided silica.
The organopolysiloxane (i) used herein consists essentially of the following structural units.
R
1
3
SiO
1/2
R
1
2
SiO
2/2
R
1
SiO
3/2
Herein R
1
is independently selected from substituted or unsubstituted monovalent organic (hydrocarbon) groups of 1 to 20 carbon atoms, for example, alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl, tetradecyl, hexadecyl, and octadecyl; cycloalkyl groups such as cyclohexyl; alkenyl groups such as vinyl and allyl; aryl groups such as phenyl and tolyl; and substituted ones of these groups in which some or all of the hydrogen atoms attached to carbon atoms are replaced by halogen atoms, cyano groups, etc. such as chloromethyl, 3-chloropropyl, 3,3,3-trifluoropropyl, and cyanoethyl. It is recommended that methyl account for at least 90 mol % of the entire R
1
groups.
Appropriate amounts of the R
1
3
SiO
1/2
, R
1
2
SiO
2/2
and R
1
SiO
3/2
units are combined to constitute the organopolysiloxane. If the quantity of R
1
3
SiO
1/2
units is less than 0.1 mol %, the organopolysiloxane has a too high viscosity to handle. If the quantity of R
1
3
SiO
1/2
units exceeds 5 mol %, the organo-polysiloxane has a too low viscosity to reduce foaming. If the quantity of R
1
2
SiO
2/2
units is less than 90 mol %, the organopolysiloxane has a too low viscosity to reduce foaming. If the quantity of R
1
2
SiO
2/2
units exceeds 99.8 mol %, the organopolysiloxane has a too high viscosity to handle. If the quantity of R
1
SiO
3/2
units is less than 0.1 mol %, antifoaming properties become poor. If the quantity of R
1
SiO
3/2
units exceeds 5 mol %, the organopolysiloxane has a too high viscosity to handle. For this reason, these units are contained to give a compositional ratio of R
1
3
SiO
1/2
units:R
1
2
SiO
2/2
units:R
1
SiO
3/2
units =(0.1 to 5):(90 to 99.8):(0.1 to 5), and preferably (1 to 3):(94 to 98):(1 to 3) as expressed in mol %.
A lower viscosity is desirable from the standpoints of ease of dispersion and working of the organopolysiloxane, while a higher viscosity is desirable from the standpoint of foam suppression. With a viscosity of less than 100 centipoise, the resulting composition becomes less antifoaming. With a viscosity in excess of 1,000,000 centipoise, it becomes difficult to work the organopoly-siloxane into an emulsion. Then the organopolysiloxane should have a viscosity of 100 to 1,000,000 centipoise at 25° C. and preferably 1,000 to 100,000 centipoise at 25° C.
Finely divided silica (ii) used herein may be any well-known silica including wet silica and dry silica. Examples of silica powder include precipitated silica, silica xerogel, and fumed silica, which may be further surface treated to be hydrophobic. They are commercially available under the trade name of Aerosil from Nippon Aerosil K.K., Nipsil from Nippon Silica K.K., Cabosil from Cabonet, and Santocel from Monsanto Industrial Chemicals Co. Since better antifoaming properties are achieved with silica having a greater specific surface area, silica should preferably have a specific surface area of at least 100 m
2
/g, and more preferably at least 200 m
2
/g, as measured by the BET method.
If the amount of finely divided silica blended is less than 0.1% by weight of the oil compound (A), foam suppression becomes poor. If the amount of silica is more than 20% by weight, the oil compound has a too high viscosity to handle. For this reason, the amount of finely divided silica blended is 0.1% to 20% by weight, and preferably 1% to 10% by weight based on the oil compound (A).
The oil compound (A) can be prepared by mixing predetermined amounts of the organopolysiloxane and silica powder in a mixer having an appropriate agitating mechanism, heat treating the mixture at 60 to 200° C. while mixing, and optionally, distilling off low-boiling fractions. Inorganic ammonium salts, organosilicon compounds and siloxane resins may be added, if desired, for the purpose of improving the retention of antifoaming ability, high-temperature performance, and dilution stability (see JP-B 4-42043, JP-A 5-261206 and JP-A 5-261207).
In the antifoaming composition of the invention, the mixture (B) consisting essentially of (iii) a polyoxyalkylene-modified silicone oil and (iv) a polyhydric alcohol alkyl ether helps emulsify and disperse the oil compound (A) in

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