Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Graphite – coal – or elemental carbon
Reexamination Certificate
2000-05-11
2002-05-21
Metzmaier, Daniel S. (Department: 1712)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Graphite, coal, or elemental carbon
C524S267000, C524S588000, C516S118000, C516S119000, C516S121000, C516S124000, C508S208000, C106S031130
Reexamination Certificate
active
06391831
ABSTRACT:
RELATED APPLICATIONS
This application claims priority to German application No. 199 22 351.3, filed May 14, 1999, herein incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to the use of water-insoluble polyoxyarylene-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, organomodified siloxanes, hydrophobic polyoxyalkylenes, mineral oils, natural oils and other hydrophobic liquids as defoaming substances. Frequently, the above-mentioned substances are used in combinations with hydrophobic solids, such as pyrogenic 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 to weaken them until they collapse. 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 hydrophobicity/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 above-mentioned 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. Furthermore, it is also possible to use epoxides of longer-chain olefins as well.
Typically, however, polyoxyethylenes and polyoxy-propylenes 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 these basic units described above, however, in many cases it has not been possible to date to find the optimum incompatibility/compatibility balance required for certain defoamers.
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 as has been possible to date.
SUMMARY OF THE INVENTION
This object is surprisingly achieved by the use of water-insoluble polyoxyarylene-polysiloxane block copolymers for defoaming aqueous media 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, especially phenyl.
R
4
—is a divalent radical of the formula —O—, —NH—, —NR
2
—, —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
f
—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−a
R
9
a
O)
b
(C
2
H
4−a
R
10
a
O)
c
—, where
R
9
is identical or different alkyl radicals having 1 to 4 carbon atoms and
R
10
is a radical of the general formula II
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, and
R
11
can be identical or different and is a hydrogen, a hydrocarbon radical, preferably having 1 to 12 carbon atoms, or a halogen atom,
a is from 0 to 3,
b is from 0 to 100,
c is from 1 to 100, and
the sum (b+c) is from 3 to 200
and the sequence of the individual polyoxyalkylene and/or polyoxyarylene segments —(C
2
H
4−a
R
9
a
O)
b
— and —(C
2
H
4−a
R
10
a
O)
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 from 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
.
As evident from the description given above, the polyoxyarylene-polysiloxane block copolymers described in the context of this invention can also include polyoxyalkylene units in addition to the polyoxyarylene units.
DETAILED DESCRIPTION OF THIS INVENTION
In many cases, polyoxyarylene-polysiloxane block copolymers which have proven highly suitable are those obtained by means of combinations of two polyoxyarylene units with one or more polysiloxane copolymers. In that case, the distinction in the case of the polyoxyarylene 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 polyoxyarylene 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 w
Ebbrecht Thomas
Josten Wolfgang
Keup Michael
Silber Stefan
Sucker Roland
Frommer & Lawrence & Haug LLP
Goldschmidt AG
Metzmaier Daniel S.
LandOfFree
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