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
2000-05-11
2002-12-10
Cain, Edward J. (Department: 1714)
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...
C524S502000, C524S507000, C524S510000, C524S519000, C524S521000, C524S523000
Reexamination Certificate
active
06492451
ABSTRACT:
The present invention relates to pigment-comprising formulations which comprise as binder at least one aqueous polymer dispersion whose polymer is functionalized with phosphonate groups.
Pigmented formulations are employed widely in the form of emulsion paints, synthetic-resin-bound plasters (dispersion plasters), sealing compounds or filling compositions for purposes of architectural protection or for decorative purposes. Pigmented formulations generally include as binder a film-forming polymer, at least one inorganic pigment with or without one or more inorganic fillers, and also customary auxiliaries. The quality of the coatings formed from pigmented formulations depends critically on the ability of the film-forming polymer to bind, equally, the nonfilm-forming constituents, the pigments and inorganic fillers.
A low pigment-binding capacity leads to poor mechanical stability of the coating, which is manifested, for example, in a low wet abrasion resistance. The desire, however, is for high wet abrasion resistance, especially in the case of washable emulsion
The pigment-binding capacity of the binder plays a particularly important part in formulations having a high content of inorganic pigments and fillers which is generally reflected in a pigment volume concentration (p.v.c.) of >40%. The p.v.c. is usually defined as the percentage quotient of the overall volume of the solid inorganic constituents (pigment+fillers) divided by the overall volume of the solid inorganic constituents and of the polymer particles of the aqueous binder polymer dispersion; see Ullmanns Enzyklopädie der technischen Chemie, 4th Edition, Volume 15, p. 668.
In the case of exterior applications in particular, the coating compositions should be stable to environmental influences such as sunlight, moisture and fluctuations in temperature. In addition, the coating composition must adhere well to a variety of substrates, which again depends on the chosen binder polymer.
Another property dependent on the binder polymer is the blocking resistance of the coatings.
EP-A-184 091 describes coating compositions based on aqueous polymer dispersions which have a low film-forming temperature and form films of high blocking resistance. The polymer dispersions disclosed therein may also comprise, in copolymerized form, monomers having a crosslinking action. The coating materials described include only small amounts of inorganic substances and pigments.
EP-A-327 006 and EP-A-327 376 describe aqueous polymer dispersions comprising siloxane-functional monomers in copolymerized form. Such monomers, however, are expensive, with even a small amount pushing up the binder preparation costs sharply. It must also be reckoned that hydrolysis of the siloxane groups will alter the properties of the binder in the course of storage.
U.S. Pat. No. 4,219,454 describes binders for coating materials which are based on aqueous polymer dispersions comprising, in copolymerized form, urea-functional monomers for improving the adhesion of the coatings in the moist state. The coatings described therein, however, have only low pigment contents. The problem of the wet abrasion resistance of coating materials is not adequately solved by the polymers described therein.
GB 1,189,560 discloses latex paints (=emulsion paints) to which low molecular mass alkyl phosphates or alkyl phosphonates are added to improve the dispersion of the inorganic pigments.
EP-A-625 541 and WO 93/11181 disclose titanium dioxide-containing formulations comprising as binder aqueous polymer dispersions whose polymers have phosphate groups. The phosphate groups improve the adsorption of the latex particles on the surface of the pigment particles. The storage life of the formulations disclosed therein, however, leaves much to be desired, since their viscosity increases over the course of time.
U.S. Pat. No. 4,110,285 proposes polymers containing phosphate groups as binders for high-gloss emulsion paints. Here too, the problem of storage life arises.
The prior art binders are able to go only some of the way toward meeting the requirements that are placed on coating materials.
It is an object of the present invention to provide pigmented formulations possessing a high pigment-binding capacity, and hence a high wet abrasion resistance, good wet adhesion to a very wide variety of substrates, and good blocking resistance. These properties must also be retained at relatively high pigment volume concentrations, ie. p.v.c. >40%. In addition, the formulations are required to be stable on storage; in other words, their viscosity should show little or no increase even on prolonged storage.
We have found that this object is achieved by using, for the formulations, binders based on aqueous dispersions whose polymers have been modified with phosphonate groups.
The present invention accordingly provides formulations for coating substrates, comprising
i) at least one polymer P which has phosphonate groups, as binder,
ii) at least one inorganic pigment,
iii)if desired, one or more inorganic fillers, and
iv) customary auxiliaries.
The phosphonate-functional polymers P to be used in the formulations of the invention are in principle obtainable in a variety of ways. For instance, the phosphonate groups can be generated in a conventional polymer by means of polymer-analogous reaction. The sole prerequisite for this is that the polymer has reactive functional groups that are amenable to a polymer-analogous reaction. One possible procedure, for example, is to react a reactive functional group of the polymer in a polymer-analogous reaction with a phosphonate-functional compound which in turn possesses a reactive functional group that is complementary to the reactive group on the polymer. An example is the reaction of polymers having glycidyl groups with compounds that contain phosphonate groups and additionally have amino groups, and vice versa. The reaction of phosphonate groups can take place, for example, in the manner of a Moedritzer reaction (Moedritzer et al., J. Org. Chem. 31 (1966) 1603) by reacting amino-containing polymers with phosphorous acid in the presence of formaldehyde.
The preparation of phosphonate-functional polymers P, and the preparation of appropriate prepolymers, which are converted only subsequently by polymer-analogous reaction into the phosphonate-functional polymers P, can in principle take place by all known polymerization techniques for ethylenically unsaturated monomers, such as bulk, solution, precipitation, suspension or emulsion polymerization. Preparation takes place preferably by means of emulsion polymerization. This is particularly appropriate when the phosphonate groups are introduced by copolymerizing appropriate phosphonate-functional monomers into the polymer P.
In general, the polymers P are used in the form of aqueous dispersions in the pigmented formulations of the invention. It is not least for this reason that free-radical aqueous emulsion polymerization is advisable for preparing the polymers P. Polymers P obtainable in another way can be converted to aqueous dispersions by means of suitable measures that are known from the prior art (and are then known as secondary dispersions).
Preferably, the aqueous polymer dispersions employed in the formulations of the invention are obtainable by free-radical aqueous emulsion polymerization of ethylenically unsaturated monomers, in which at least one monomer a and at least one different monomer b of the formula I
where
R
1
is hydrogen, C
1
-C
4
-alkyl, COOH, —CO
2
-Alk-OH or —CO
2
-Alk-P(O)(OH)
2
and
R
2
is hydrogen, alkyl, —CH
2
—CO
2
H, —CH
2
—CO
2
-Alk-OH or CH
2
—CO
2
-Alk-P(O)(OH)
2
, in which
Alk is C
1
-C
4
-alkylene,
X is a single bond, alkylene, arylene, —R
3
—Z—O—R
4
— or —R
3
—Z—NH—R
4
—, in which
R
3
is attached to a carbon of the double bond and is a single bond, alkylene or arylene,
R
4
is alkylene or arylene and
Z is CO or SO
2
or a salt thereof are reacted with one another.
In the text below alkyl is preferably linear or branched C
1
-C
12
-alkyl, especially C
1
-C
8
-al
Dersch Rolf
Roser Joachim
Schlarb Bernhard
Zhao Cheng-Le
BASF - Aktiengesellschaft
Cain Edward J.
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