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...
Reexamination Certificate
2000-11-02
2003-04-22
Reddick, Judy M. (Department: 1713)
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...
C523S201000, C524S458000, C524S521000, C524S522000, C526S201000
Reexamination Certificate
active
06552116
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a multistage emulsion polymer particularly suitable as a binder for aqueous high gloss paints and to a coating composition comprising it.
DISCUSSION OF THE BACKGROUND
DE 44 39 459 discloses an aqueous polymer dispersion prepared by two-stage emulsion polymerization. The difference between the glass transition temperatures T
g
1
and T
g
2
of the individual stages be polymerized, from 0.1 to 10% by weight of a nitrogen-containing adhesion monomer are copolymerized, of which from 20 to 100 mol% are copolymerized in the first polymerization stage. It has been found that the polymer dispersions of DE 44 39 459 result in coating compositions whose gloss is insufficient for certain applications.
DE 12 20 613 discloses a process for preparing polymer emulsions by polymerizing at least one film-forming monomer, at least one non-film-forming monomer, and an unsaturated carboxylic acid. The polymerization takes place in two stages, at least 70% by weight of the overall amount of the film-forming monomer and up to 70% by weight of the overall amount of the non-film-forming monomer being copolymerized in the first stage and the remainder of the monomers being copolymerized in the second polymerization stage. Styrene is used as the preferred non-film-forming monomer. The polymer emulsion of DE 12 20 613, although it gives coating compositions of high gloss, has the disadvantage of inadequate blocking resistance and inadequate abrasion resistance.
U.S. Pat. No. 3,454,516 describes acrylate dispersions consisting of a soft phase and a hard phase, the soft phase consisting of ethyl acrylate, butyl methacrylate and methacrylic acid and the hard phase of methyl methacrylate, butyl methacrylate and methacrylic acid. The proportion of the soft phase is from 40 to 70% by weight.
EP 609 756 describes a coating composition comprising a multistage polymer having at least two polymer domains one polymer domain having a glass transition temperature in the range from −5 to −55° C. and constituting from 90 to 10% by weight of the overall monomer and the other polymer domain having a glass transition temperature in the range from 0 to +50° C. and constituting from 10 to 90% by weight of the overall polymer. The gloss properties of the coating composition are not addressed.
EP 0 379 892 discloses binders for aqueous gloss paints, these binders being composed of a core material having a glass transition temperature of more than 40° C. and a shell material having a glass transition temperature of less than 70° C. but at least 20 K below that of the core material, the particles having a diameter of less than 200 nm, and the composition of the shell material including a polymer with at least 4% by weight of an ethylenically unsaturated carboxylic acid and more than 80% by weight of one or more monomers from the group consisting of styrene and (meth)acrylic alkyl esters having at least 4 carbon atoms in the alkyl radical. The hard core material accounts for from 5 to 45% by weight of the emulsion polymer.
The known multistage emulsion polymers and, respectively, the coating compositions comprising them do not have a satisfactory, balanced profile of properties in respect of gloss, blocking resistance and abrasion resistance.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide emulsion polymers which lead to coating compositions having high gloss, high blocking resistance at low minimum film-forming temperature, and high abrasion resistance. Furthermore, the emulsion polymers are required to lend themselves well to thickening with associative thickeners.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
We have found that this object is achieved by a multistage emulsion polymer comprising at least one first domain having a glass transition temperature T
g
of from −10 to +40° C. and at least one second domain having a T
g
of from +50 to 120° C., the weight ratio of the first domain to the second domain being in the range from 90:10 to 50:50 and the first domain containing copolymerized units of
1a) from 5 to 60% by weight of methyl methacrylate and/or ethyl methacrylate,
1b) from 20 to 80% by weight of C
4
-C
12
alkyl acrylate,
1c) up to 50% by weight of vinylaromatic compounds,
1d) from 0.1 to 5% by weight of ethylenically unsaturated carboxylic acids,
1e) up to 5% by weight of ethylenically unsaturated carboxamides,
1f) up to 10% by weight of other ethylenically unsaturated monomers,
and the second domain containing copolymerized units of
2a) up to 99.9% by weight of methyl methacrylate and/or ethyl methacrylate,
2b) up to 99.9% by weight of vinylaromatic-compounds and/or C
4
-C
12
alkyl methacrylates,
2c) from 0.1 to 5% by weight of ethylenically unsaturated carboxylic acids,
2d) up to 10% by weight of ethylenically unsaturated carboxamides,
2e) up to 10% by weight of other ethylenically unsaturated monomers,
with the proviso that the first and/or the second domain contains from 0.1 to 10% by weight, preferably from 1 to 5% by weight, of a nitrogen-containing adhesion monomer and, further, that the first domain contains at least 10% by weight of vinylaromatic compounds and/or the second domain contains at least 15% by weight of vinylaromatic compounds and/or C
4
-C
12
alkyl methacrylates, all of the weights specified being based on the respective domain.
The weight ratio of the first domain to the second domain is preferably in the range from 80:20 to 60:40.
Preferred emulsion polymers of
the invention contain in the first
domain:
from 5 to 30% by weight of
methyl methacrylate and/or ethyl
methacrylate,
from 30 to 60% by weight of
C
4
-C
12
alkyl acrylate,
from 15 to 50% by weight of
vinylaromatic compounds,
from 0.1 to 5% by weight of
ethylenically unsaturated
carboxylic acid,
up to 5% by weight of
ethylenically unsaturated
carboxamide,
up to 10% by weight of
other ethylenically unsaturated
monomers,
and in the second domain:
from 45 to 99.9% by weight of
methyl methacrylate and/or ethyl
methacrylate,
if desired
from 1.0 to 50% by weight of
vinylaromatic compounds and/or C
4
to C
12
alkyl methacrylate,
from 0.1 to 5% by weight of
ethylenically unsaturated
carboxylic acid,
up to 10% by weight of
ethylenically unsaturated
carboxamide,
up to 10% by weight of
other ethylenically unsaturated
monomers.
Other preferred emulsion
polymers of the invention
contain in the first domain:
from 5 to 50% by weight of
methyl methacrylate and/or ethyl
methacrylate,
from 30 to 60% by weight of
C
4
-C
12
alkyl acrylate,
from 0.1 to 5% by weight of
ethylenically unsaturated
carboxylic acid,
up to 5% by weight of
ethylenically unsaturated
carboxamide,
up to 10% by weight of
other ethylenically unsaturated
monomers,
and in the second domain:
up to 84.9% by weight of
methyl methacrylate and/or ethyl
methacrylate,
from 15 to 99.9% by weight of
vinylaromatic compounds and/or
C
4
-C
12
alkyl methacrylates,
from 0.1 to 5% by weight of
ethylenically unsaturated
carboxylic acid,
up to 10% by weight of
ethylenically unsaturated
carboxamide,
up to 10% by weight of
other ethylenically unsaturated
monomers.
For obtaining the desired glass transition temperatures T
g
by selecting appropriate types and amounts of monomers it is useful to use the formula of Fox (T. G. Fox, Bull. Amer. Phys. Soc. (Ser. II) 1 (1956) 123), according to which the glass transition temperature T
g
of copolymers is given in good approximation by:
1
T
g
=
X
1
T
g
1
+
X
2
T
g
2
+
…
+
X
S
T
g
S
where X
1
, X
2
. . . X
s
are the mass fractions of the monomers and T
g
1
, T
g
2
. . . T
g
s
are the glass transition temperatures of the homopolymers composed in each case of only one of the monomers 1,2, . . . S, in degrees Kelvin.
The glass transition temperatures of the homopolymers of the customary monomers are known and are listed, for example, in J. Brandrup and E. H. Immergut, Polymer Handbook, 2nd edition, J. Wiley Verlag, New York 1995.
The C
4
-C
12
alkyl acrylates are selected preferably from n-butyl acrylate, 2-ethylhe
Dittrich Uwe
Gulbins Erich
Pakusch Joachim
Röckel Harald
Smith Alan
BASF Aktiengesellchaft
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Reddick Judy M.
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