Coating processes – Applying superposed diverse coating or coating a coated base – Synthetic resin coating
Reexamination Certificate
2001-03-28
2002-12-31
Yoon, Tae H. (Department: 1714)
Coating processes
Applying superposed diverse coating or coating a coated base
Synthetic resin coating
C427S393600, C428S688000, C524S804000, C524S806000, C524S831000, C524S833000
Reexamination Certificate
active
06500492
ABSTRACT:
The present invention relates to the use of aqueous film-forming formulations comprising at least one crosslinked copolymer P in dispersed form for coating shaped mineral articles and to a process for coating shaped mineral articles.
By shaped mineral articles are meant, here and below, shaped articles which comprise mineral aggregates, such as sand, clay, crushed rock, etc., and a mineral binder, and also, if desired, customary additives. Mineral binders are common knowledge. They comprise, for example, finely divided inorganic substances, such as lime, gypsum, clay and/or cement, which can be shaped in the wet state and which, when left to themselves, harden after a certain time, either in air or underwater, with or without the action of elevated temperature, to give a stonelike mass.
The aggregates consist in general of granular or fibrous, natural or synthetic stone (gravel, sand, mineral fibers), including in special cases metals as well, or organic material or mixtures of said aggregates, with grain sizes or fiber lengths that are adapted in a conventional manner to the specific application intended. In many cases, color pigments are also used as aggregates, for the purpose of coloring.
Examples of shaped mineral articles that can be coated in accordance with the invention are concrete pipes, as used to transport waste water, for example, concrete roof tiles or curb stones, steps, base slabs, and plinth tiles based on mineral binders, and also fiber cement slabs, i.e. flat shaped mineral articles which may be filled with inorganic or organic fibers, such as polyester fibers or nylon fibers, for example.
A disadvantage of shaped mineral articles is that under the influence of weathering (especially exposure to water) the cationic constituents, such as Ca
2+
, are leached out over the course of time, reducing the strength of the articles. This is often accompanied by efflorescence phenomena. These are probably attributable to the fact that cations with a valency of two or more, such as Ca
2+
, react with the carbon dioxide from the air and so form, on the surface of the shaped mineral articles, white spots of lime. Efflorescence may also appear during the hardening of freshly prepared shaped mineral articles.
In order to avoid these disadvantages, the shaped mineral articles are often provided with a protective coat. For this purpose use is now generally made of aqueous coating systems whose film-forming constituent (binder) comprises an aqueous polymer dispersion. Customary binders include styrene-acrylate copolymers, vinyl acetate homo- and copolymers, pure acrylates and the like (cf. for example DE 21 64 256). However, the coatings obtainable with these binders are unable to prevent satisfactorily the emergence of the cationic constituents (efflorescence). Furthermore, such coatings are easily soiled.
It has proven possible to improve the protection of shaped mineral articles from the efflorescence described above by means, inter alia, of coating compositions based on styrene-acrylate dispersions or all-acrylate dispersions of EP-A-469 295 and DE-A-195 14 266. EP-A-469 295 recommends for this purpose the use of a specific anionic emulsifier, and DE-A-195 14 266 the use of polymers whose incorporated monomers include specific, sulfonate-functional monomers, while DE 197 49 642.3 recommends using polymers containing itaconic acid in copolymerized form.
EP-A-279 067 discloses clear varnishes for coating wood which comprise alkyl methacrylate-based polymers crosslinked with divinylaromatics, diol di(meth)acrylates or diallyl phthalates. On weathering, such coatings lose their gloss and become brittle over time. DE-198 10 050.7 discloses the use of aqueous, film-forming formulations based on alkyl methacrylate copolymers which contain not more than 1% by weight of monomers having two or more ethylenically unsaturated double bonds. There is no mention whatsoever of suitable polyunsaturated monomers, and the examples are devoid of polyethylenically unsaturated monomers.
It is an object of the present invention to provide coatings for shaped mineral articles which feature improved gloss stability and long-term durability in outdoor use, provide effective protection against efflorescence, and show good adhesion properties to mineral substrates.
We have found that this object is achieved and that aqueous formulations comprising copolymers P as film-forming constituent, which are composed essentially of (meth)acrylates and/or vinylaromatics and include from 0.01 to 1.9% by weight of specific diethylenically unsaturated (meth)acrylates having a crosslinking action result in coatings of increased gloss stability, high long-term durability, and good adhesion properties in outdoor use.
The present invention therefore provides for the use of aqueous film-forming formulations comprising in dispersed form at least one copolymer P composed of ethylenically unsaturated monomers, said copolymer P comprising in copolymerized form
a) from 80 to 99.89% by weight of at least one monomer selected from esters of acrylic acid with C
1
-C
12
-alkanols, esters of methacrylic acid with C
1
-C
8
-alkanols and monovinylaromatics,
b) from 0.1 to 19.99% by weight of at least one monomer different from a), selected from &agr;,&bgr;-ethylenically unsaturated C
3
-C
6
monocarboxylic and dicarboxylic acids, the amides, N-alkyl amides and nitriles of these carboxylic acids, monoesters of &agr;,&bgr;-monoethylenically unsaturated C
4
-C
8
dicarboxylic acids with C
1
-C
12
-alkanols, vinyl esters of aliphatic C
1
-C
18
carboxylic acids, &agr;,&bgr;-monoethylenically unsaturated sulfonic acids and sulfonic esters, and &agr;,&bgr;-monoethylenically unsaturated siloxanes, and
c) from 0.01 to 1.9% by weight of at least one crosslinking monomer selected from esters of acrylic or methacrylic acid with linear or branched C
3
-C
6
-alkenols, cyclic C
5
-C
7
-alkenols and polycylic C
7
- to C
12
-alkenols,
the total content of monomers bearing free acid groups, based on the total amount of all copolymerized monomers, being less than 5% by weight, for coating shaped mineral articles.
Examples of suitable esters of acrylic acid with C
1
-C
12
-alkanols are methyl, ethyl, n-propyl, isopropyl, n-butyl, 2-butyl, isobutyl, tert-butyl-, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 1,1-dimethylbutyl, 2,2-dimethylbutyl, n-pentyl, 1-methylpentyl, 2-methylpentyl, 2-ethylpentyl, n-hexyl, 1-methylhexyl, 2-methylhexyl, 2-ethylhexyl, n-heptyl, 1-methylheptyl, 2-methylheptyl, 2-propylheptyl, n-octyl, 1-methyloctyl, 2-methyloctyl, n-decyl and n-dodecyl acrylate. Preference is given to the esters of acrylic acid with alkanols having 2 to 8 carbon atoms, i.e., ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, n-pentyl, n-hexyl and 2-ethylhexyl acrylate. Of these, n-butyl acrylate and 2-ethylhexyl acrylate are particularly preferred.
Examples of suitable esters of methacrylic acid with C
1
-C
18
-alkanols are methyl, ethyl, n-propyl, isopropyl, n-butyl-, 2-butyl, isobutyl, tert-butyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 1,1-dimethylbutyl, 2,2-dimethylbutyl, n-pentyl, 1-methylpentyl, 2-methylpentyl, 2-ethylpentyl, n-hexyl, 1-methylhexyl, 2-methylhexyl, 2-ethylhexyl, n-heptyl, 1-methylheptyl, 2-methylheptyl and n-octyl methacrylate. Preference is given to the esters of methacrylic acid with alkanols having 1 to 4 carbon atoms, i.e., methyl, ethyl, n-propyl, isopropyl, n-butyl and tert-butyl methacrylate. Of these, methyl methacrylate and n-butyl methacrylate are particularly preferred.
Examples of suitable vinylaromatic monomers are styrene, &agr;-methylstyrene, o-chlorostyrene and vinyltoluene; styrene is preferred.
Based on the total monomer amount, the copolymers P contain preferably from 90 to 98.99% by weight and, with particular preference, from 95 to 98.49% by weight of the abovementioned monomers (monomers a)) in copolymerized form.
In addition to the abovementioned monomers, the copolymers P include, based on the total monomer amount, from 0.1 to 19.99% by weight, preferably from 1.0 to 9.9% by weight and, with
Bechert Bertold
Hümmer Wolfgang
Schwartz Manfred
Wiese Harm
BASF - Aktiengesellschaft
Yoon Tae H.
LandOfFree
Aqueous, film forming preparations for coating mineral... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Aqueous, film forming preparations for coating mineral..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Aqueous, film forming preparations for coating mineral... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2993782