Linear polyether-polysiloxane copolymers, their preparation...

Details Linear polyether-polysiloxane copolymers, their preparation... Linear polyether-polysiloxane copolymers, their preparation...

1999-08-11

2001-02-13

Dawson, Robert (Department: 1712)

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

Synthetic resins

From silicon reactant having at least one...

C528S031000, C528S015000, C528S029000, C556S444000, C556S445000, C568S673000, C568S675000

Reexamination Certificate

active

06187891

ABSTRACT:

TECHNICAL FIELD
The present invention relates to linear polyether-polysiloxane copolymers in which linear polyether units and linear polysiloxane units are linked via Si—C bonds. The copolymers according to the invention can be used widely and can, for example, be used as additives for coatings or as emulsion stabilizers.
BACKGROUND ART
A large number of classes of compounds of polyether-polysiloxane copolymers are known. The suitability of each individual type of copolymer for a specific application depends considerably on the structure of the polysiloxane and polyether units, their ratio, and their arrangement relative to one another, and the type of linkage between these units. In this connection, the linking of the units can be distinguished, inter alia, by Si—O—C bonding or by Si—C bonding.
As is known, polysiloxane-polyether copolymers linked by Si—O—C bonds are prepared by reaction of OH—terminated polyethers with siloxanes containing halogen, hydroxyl, alkoxy or acetoxy groups, for example (cf. W. Noll, “Chemie und Technologie der Silicone”, Verlag Chemie, 1968, p. 321). These polyether-polysiloxane copolymers are known and available commercially.
Si—C-linked polysiloxane-polyether copolymers can, for example, be obtained by reaction of alkenyl-containing polyethers with polysiloxanes which contain Si—H groups with the help of a substance which accelerates the reaction of alkenyl compounds with Si—H bonds, e.g. Pt catalysts. For example, U.S. Pat. No. 5,625,023 describes compounds which are intended to prevent the formation of aerosols in silicone-based coatings which are to be applied quickly. These compounds are obtained by reacting an organohydrogensilicon compound with an oxyalkylene compound, a catalyst and a monohydric olefinic alcohol. The reaction can in this connection be carried out, inter alia, by hydrosilylation or by the addition reaction of the side and/or terminal SiH groups with the polyethers terminated at both ends with alkenyl groups, forming Si—C bonds between polyether and siloxane. The use of silicon compounds having Si—H side groups leads to branched copolymers. Using the process described it is not possible to prepare exclusively linear polyether-polysiloxane copolymers of defined molecular size.
EP 643 329 claims a large number of polyoxyalkylene-polysiloxane block copolymers for liquid radiation-curable compositions. In the general formula (II), Si—C bonds are present between polyether and polysiloxane units, one polysiloxane unit being a block in the middle of the molecule flanked by polyether groups, rather than two or more blocks or units being randomly distributed throughout the molecule.
DE 30 11 304 and DE 31 23 103 describe antifoam formulations for use in aqueous dispersions and solutions of synthetic resins which are free from mineral oxides, such as SiO
2
and Al
2
O
3
, and contain polysiloxane-polyether block polymers. These polymers, containing alternating polysiloxane and polyether units, are linked both via Si—C bonds and via Si—O—C bonds. In addition, DE 38 07 247 describes the use of polyoxyalkylene-polysiloxane block copolymers for the defoaming of aqueous dispersions, polysiloxane and polyoxyalkylene being linked exclusively via Si—O—C bonds.
Polysiloxane-polyether block copolymers in which polyether and polysiloxane units are linked via Si—O—C bonds have the disadvantage that these linkage sites can be cleaved in the presence of compounds containing free hydrogen atoms, such as, for example, alcohols, polyols or water (cf. W. Noll, “Chemie und Technologie der Silicone” [Chemistry and Technology of Silicones], Verlag Chemie, 1968, p. 323), the cleavage being accelerated considerably in particular by the presence of acidic or basic compounds. For example, in aqueous systems this leads to the hydrolysis, and in alcoholic systems to the alcoholysis of the polysiloxane-polyether block copolymers. This effect occurs in particular during storage of formulations which comprise such polysiloxane-polyether block copolymers and compounds containing free hydrogen atoms, and thus leads to an undesired negative change in the properties.
SUMMARY OF THE INVENTION
The object of the present invention was to provide linear polyether-polysiloxane copolymers in which linear polyether and linear polysiloxane units are linked via Si—C bonds, and processes for their preparation. The polymers according to the invention are be stable in the presence of compounds containing free hydrogen atoms and are suitable for use as foam stabilizers, antifoams and/or in formulations which act as antifoams, as additives for solvent-based coatings, low-solvent coatings, and solvent-free aqueous coatings, construction chemicals, pastes and other preparations, and/or as emulsion stabilizers.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The invention provides linear polyether-polysiloxane copolymers in which linear polyether and linear polysiloxane units are linked via Si—C bonds and which conform to the general formula
A(BC)
n
BA  (I),
in which n is ≧1, preferably from 1 to 20, and
A is a group of the general formula
R
1
—O—[CH
2
CH
2
O]
a
[CH
2
CH(CH
3
)O]
b
[CH
2
CH(CH
2
CH
3
)O]
c
—(C
m
H
2m
)—  (II),
where R
1
independently of one another is either hydrogen, alkyl, aralkyl, aryl or an R
2
—C(O)— radical, and R
2
is a substituted or unsubstituted alkyl radical having from 1 to 8 carbon atoms, m is an integer between 3 and 8, and a, b and c independently of one another are integers between 0 and 200, with the proviso that the sum (a+b+c) is from 2 to 300,
B is a group of the general formula
—(R
3
2
Si—O)
d
—R
3
2
Si—  (III),
where R
3
independently of one another are substituted and/or unsubstituted, saturated and/or unsaturated hydrocarbon radicals having from 1 to 20 carbon atoms, and d is an integer between 1 and 400, and C is a group of the general formula
—(C
m
H
2m
)—O—[CH
2
CH
2
O]
a
[CH
2
CH(CH
3
)O]
b
[CH
2
CH(CH
2
CH
3
)O]
c
—(C
m
H
2m
)  (IV),
where m, a, b and c have the values given above.
In the polyether-polysiloxane copolymer according to the invention, the polyether moieties are bonded to the diorganopolysiloxane units via —(C
m
H
2m
)—groups, which can be linear or branched and consists of from 3 to 8, preferably from 3 to 6, carbon atoms.
In the general formula (I), the group A is a polyether unit of the general formula (II) which is notable for the fact that it is constructed from at least two polyoxyalkylene units and usually no more than 200 polyoxyalkylene units where, preferably, in the general formula (II) m assumes values between 3 and 6, a and b assume values between 0 and 40, and c assumes values between 0 and 30, with the proviso that the sum (a+b+c) is from 2 to 60. The polyoxyalkylene units may be derived from the polymerization of ethylene oxide and/or propylene oxide and/or butylene oxide. The ethylene oxide, propylene oxide and butylene oxide units may be distributed randomly, or may be in the form of block copolymers. The polyether unit of the general formula (II) may be constructed from just one alkylene oxide or a copolymer of two of the alkylene oxides mentioned. Terpolyethers containing all three repeating oxyalkyl moieties are also possible.
The polyether or polyoxyalkylene unit A is terminated by the group R
1
. The nature of this group is unimportant for the purposes according to the invention. For example, the polyether unit can be terminated by a hydroxyl group (R
1
is a hydrogen atom), by an ether group (R
1
is a monovalent, straight-chain, or branched alkyl radical, aralkyl radical or else aryl radical, such as, for example, methyl, ethyl, n-propyl, i-propyl, butyl, hexyl, decyl, dodecyl, 2-phenylethyl, phenyl) or a carboxyl group in the form of an ester (such as, for example, acetyl), or else by a carbonic acid group or by an isocyanate group.
Group B in the general formula (I) is a linear diorganopolysiloxane unit of the general formula (III) which consists of at least two diorganosil

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