Water-insoluble poly(oxy-1,4-butanediyl)-containing...

Details Water-insoluble poly(oxy-1,4-butanediyl)-containing... Water-insoluble poly(oxy-1,4-butanediyl)-containing...

2002-02-19

2003-02-25

Metzmaier, Daniel S. (Department: 1712)

Colloid systems and wetting agents; subcombinations thereof; pro

Compositions containing an agent for breaking ; processes of...

Continuous liquid phase colloid system and discontinuous gas...

C516S119000, C516S121000, C516S124000, C508S208000, C524S188000, C524S267000, C524S588000, C106S031250

Reexamination Certificate

active

06525103

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to the use of water-insoluble poly(oxy-1,4-butanediyl)-containing 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, 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 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 always, however, the continually repeating sequence of the two carbon atoms and one oxygen atom along the polyoxy-alkylene chain. Nor is this principle altered by the use of epoxides of longer-chain olefins.
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
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
Surprisingly, this object is achieved by the use of water-insoluble poly(oxy-1,4-butanediyl)-containing 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 being especially preferred.
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
l
—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
(CH
2
—CH
2
—CH
2
—CH
2-c
R
10
c
O)
d—
 where
R
9
is identical or different alkyl radicals, preferably having 1 to 4 carbon atoms.
R
10
is an alkyl radical, preferably having 1 to 6 carbon atoms,
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 0 to 3,
b is from 0 to 200,
c is from 0 to 2,
d is from 2 to 40,
the sum (b+d)=3 to 240
and the sequence of the individual polyoxyalkylene segments —(C
2
H
4-a
R
9
a
O)
b
— and —(CH
2
—CH
2
—CH
2
—CH
2-c
R
10
c
O)
d
— 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 from 0 or 1,
x is from 0 or 1,
y is from 0 to 200,
and, if y=0, R
1
and/or
R
7
are/is —[R
4
]
w
—[R
5
]
x
—[R
6
]—R
8
.
DETAILED DESCRIPTION OF THE INVENTION
In many cases, polyoxyalkylene-polysiloxane block copolymers, which have proven highly suitable, are those obtained by means of combinations of two 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 diffe

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