Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic compound containing silicon
Reexamination Certificate
2002-03-18
2004-02-03
Metzmaier, Daniel S. (Department: 1712)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Organic compound containing silicon
C516S074000, C516S076000, C516S118000, C516S119000, C516S121000, C516S124000, C524S188000, C524S267000, C524S588000, C106S031250
Reexamination Certificate
active
06686320
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to the use of water-insoluble polyoxyalkylene-polysiloxane block copolymers for defoaming aqueous media.
In numerous industrial processes, aqueous formulations use surface-active substances in order, for example, to emulsify water-insoluble substances or to reduce the interfacial tension and so achieve better wetting characteristics. An unwanted accompanying effect of these surface-active substances, however, is that air introduced during the preparation and processing of such water-based formulations is stabilized as foam. Examples of processes in which such problems occur include papermaking, wastewater treatment, emulsion polymerization, and the manufacture and application of water-dilutable coating systems.
Foam of this kind, produced in the course of stirring or dispersing operations during manufacture or filling, prolongs production times and reduces the effective capacity of the production plant Foam is disruptive to the application of coating materials since it leads to unwanted surface defects. As a result, the use of antifoams or defoamers in virtually all water-based systems is widespread and often indispensable.
In the past, a large number of formulations have been described which envisage the use of, for example, silicone oils, organo modified siloxanes, hydrophobic polyoxyalkylenes, mineral oils, natural oils and other hydrophobic liquids as defoaming substances. Frequently, the above-mentioned substances are used in combination with hydrophobic solids, such as silicas, metal stearates or fatty acid amides, for example, which often intensify the foam inhibiting or defoaming effect.
In accordance with the present state of knowledge, it is critical to the defoaming action of a defoamer that it is able to penetrate into the foam lamellae and so to weaken them until they collapse (cf. K. Koezo, J. K. Koezone, D. T. Wasan, J. Colloid Interface Sci. 166, 225-238 (1994)). To achieve this requires a controlled incompatibility (hydrophobicity) with the aqueous phase to be defoamed: if a defoamer is too compatible (hydrophilic), it will not be able to be very effective since it does not penetrate preferentially into the foam lamella. If the degree of incompatibility is too great, then defoaming is generally very good but there are frequently the unwanted side effects of surface defects, deterioration in wetting characteristics, and separation phenomena.
Consequently, the search for a suitable defoamer is always a search for the correct incompatibility/compatibility balance for the system to be defoamed, with the aim of getting as close as possible to the target hydropbobicity/hydrophilicity equilibrium
2. Description of the Related Art
In the past, polyoxyalkylene-polysiloxane block copolymers have proven suitable for allowing this equilibrium to be established in a particularly variable manner, as is described, inter alia, in U.S. Pat. No. 3,763,021.
When polyoxyalkylene-polysiloxane block copolymers are used, advantage is taken of the fact that the polysiloxane blocks can be modified in a targeted manner with polyoxyalkylene units which, by virtue of their composition from hydrophilic and hydrophobic polyoxyalkylene units, can be adapted, in interplay with the polysiloxane block, to the abovementioned desired hydrophobicity/hydrophilicity equilibrium.
The prior art, an example of which that may be mentioned here is DE-C-1 012 602, includes polyoxyalkylene-polysiloxane block copolymers in which the polyoxyalkylene block is defined as (C
n
H
2n
O)
x
. The index n is an integer from 2 to 4, it being essential that these polyoxyalkylene blocks always include —CH
2
—CHR—O— groups as a common structural element, R being a hydrogen atom, a methyl group or an ethyl group. Such polyoxyalkylene blocks are prepared by ionic addition polymerization of oxirane derivatives, such as ethylene oxide, propylene oxide and butylene oxide. The basic structure of the properties-determining polyoxyalkylene chain is distinguished, however, by generally the combination of only two different polyoxyalkylene units in a polyoxyalkylene chain. Typically, polyoxyethylenes and polyoxypropylenes are used in the polyoxyalkylene-polysiloxane block copolymers of the prior art.
By varying the oxyalkylene units, and in particular by modifying their respective proportions and their sequence in the polymer (random and/or in blocks), a large number of polyoxyalkylene-polysiloxane block copolymers are obtainable.
Because of the restriction to only two polyoxyalkylene units, however, in many cases it has not been possible to date to find the optimum incompatibility/compatibility balance required for certain defoamers, and especially not when their random distribution is permitted.
OBJECT OF THE INVENTION
It is therefore an object of the present invention to provide particularly suitable polyoxyalkylene-polysiloxane block copolymers for defoaming aqueous media, said copolymers making it possible to establish the above-described desired incompatibility/compatibility balance in a targeted manner better than has been possible to date.
SUMMARY OF THE INVENTION
This object is surprisingly achieved by the use of water-insoluble polyoxyalkylene-polysiloxane block copolymers of the general average formula I:
where
R
1
and/or R
7
are R
2
or —[R
4
]
w
—[R
5
]
x
—[R
6
]—R
8
,
R
2
and R
3
are identical or different alkyl radicals, preferably having 1 to 24 carbon atoms or are unsubstituted or substituted aryl radicals, preferably having up to 24 carbon atoms, with phenyl especially preferred,
R
4
is a divalent radical of the formula —O—, —NH—, —NR
2
— or —S— or of the formula
—[O—Si(CH
3
)
2
]
u
—,
where
u is from 2 to 200,
R
5
is identical or different alkylene radicals, preferably having 1 to 24 carbon atoms, or is
—C
n
H
2n-f
R
2
1
—O—C
m
H
2m-g
R
2
g
—,
where
f is from 0 to 12,
g is from 0 to 12,
n is from 1 to 18,
m is from 1 to 18,
R
6
is identical or different radicals of the general formula
—O—(C
2
H
4
O)
a
(CH
2
—CH(CH
3
)O)
b
(CH
2
—CR
9
R
10
O)
c
—,
where
R
9
and R
10
are a methyl radical or
R
9
is a hydrogen atom and R
10
is an ethyl radical,
but where, taking into account all radicals R
6
, the proportion of C
2
H
4
O groups among the total of all radicals R
6
does not exceed 40% by weight,
a is from 2 to 30,
b is from 2 to 50,
c is from 2 to 40, and
the sum (a+b+c) is from 6 to 100
and the sequence of the individual polyoxyalkylene segments —(C
2
H
4
O)
a
— and —(CH
2
—CH(CH
3
)O)
b
— and —(CH
2
—CR
9
R
10
0)
c
— can be as desired and, in particular, embraces block copolymers, such as random polymers and combinations thereof,
R
8
is a hydrogen, a substituted or unsubstituted alkyl radical, preferably having 1 to 6 carbon atoms, or an acyl radical,
v is from 3 to 200,
w is 0 or 1,
x is 0 or 1,
y is from 0 to 200,
and, if y is 0, R
1
and/or R
7
are/is —[R
4
]
w
—[R
5
]
x
—[R
6
]—R
8
for defoaming aqueous media.
In many cases, polyoxyalkylene-polysiloxane block copolymers which have proven highly suitable are those obtained by means of combinations of two or more polyoxyalkylene units with one or more polysiloxane copolymers. In that case, the distinction in the case of the polyoxyalkylene copolymers can be a distinction in relation either to the relative proportion of the units used for the preparation of this copolymer or to the molecular weight of the whole polyoxyalkylene unit, or else can lie in its functionality.
Different polysiloxane copolymers can be distinguished in accordance with both their molecular mass and their degree of branching or the number and/or relative position of the reactive groups used which are available for linkage.
The mode of action of the compounds of the invention is expressly not that they bring about particularly good compatibilization between constituents of a mixture that differ in polarity. Rather, it is the case that they themselves are just compatible enough not to induce any unwa
Ebbrecht Thomas
Josten Wolfgang
Keup Michael
Silber Stefan
Sucker Roland
Frommer & Lawrence & Haug LLP
Goldschmidt AG
Metzmaier Daniel S.
LandOfFree
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