Suspensions, a process for their preparation, and the use...

Details Suspensions, a process for their preparation, and the use... Suspensions, a process for their preparation, and the use...

1999-05-24

2001-05-01

Dawson, Robert (Department: 1712)

Coating processes

With post-treatment of coating or coating material

Heating or drying

C528S037000, C528S015000, C528S032000, C556S458000, C556S464000, C524S837000

Reexamination Certificate

active

06224946

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to novel suspensions and their preparation and use.
The demands placed on modem lacquer binders include high hardness with at the same time high elasticity, good weather resistance and chemical resistance as well as a possibly low emission of volatile organic substances during application and curing. Meanwhile, water-based organic binders are highly developed; lacquer systems based on acrylate, polyester and polyurethane are used in the lacquering of wood, for example, in furniture lacquering as well as metals and plastics, for example, in the lacquering of automobiles, railway vehicles, ships and in industrial lacquering. Aqueous binders based on polyorganosilicones are also known. Because of their chemical structure, silicones substituted with methyl groups in particular have an outstanding weather resistance and water repellency. Their water repellency in particular renders them efficient constituents of paints, for example, on the exteriors of buildings.
Multifunctional carbosilanes, which are described in DE-A 19,711,650 and DE-A 19,603,241, are also suitable coating materials. Such compounds combine the hardness and elasticity of high-quality organic lacquer binders with the high weather resistance and low tendency to yellowing of methylsilicones. But the processing of multifunctional carbosilanes is subject to difficulties. Thus it has not been possible to use them as binders in aqueous lacquer formulations. Moreover, prior to application these binders have had to be aged in solvent-containing catalyst formulations and then processed within a certain period of time.
The object of the present invention was to provide aqueous suspensions (dispersions or emulsions) which are based on these carbosilanes and are stable in storage.
It has now been found that the object stated above could be achieved using suspensions (emulsions or dispersions) according to the invention, when these contain particular siloxanes or silanes, emulsifiers, and optionally conventional additives and auxiliary substances in particular proportions in water. This is surprising, as those skilled in the art would have to assume that these multifunctional carbosilanes or siloxanes in water would become unusable in time, owing to progressive hydrolysis and condensation reactions. The suspensions according to the invention nevertheless exhibit a very high stability in storage.
For the purpose of this invention, the term “suspensions” includes emulsions as well as dispersions.
SUMMARY OF THE INVENTION
The invention accordingly provides suspensions comprising
(a) 30 to 95 wt. % (preferably 50 to 80 wt. %) of water,
(b) 70 to 5 wt. % (preferably 60 to 30 wt. %) of at least one silane or siloxane having at least two groups corresponding to formula (I)
—(CH
2
)
m
SiR
n
X
3-n
  (I)
 wherein
R denotes C
1
-C
8
alkyl or C
6
-C
20
aryl (preferably C
1
-C
8
alkyl),
X denotes OH, C
1
-C
4
alkoxy, C
6
-C
20
aryloxy, C
1
-C
6
acyloxy, or hydrogen (preferably OH, methoxy, or ethoxy),
m is 1 to 6, (preferably 2 or 3) and
n is 0 to 2,
(c) 0.1 to 30 wt. % (preferably 0.5 to 10 wt. %) of at least one emulsifier, and
(d) 0 to 20 wt. % (preferably 0 to 2 wt. %) of one or more additives and/or auxiliary substances,
with the proviso that the sum of components (a) to (d) totals 100 wt. %.
In a preferred embodiment of the invention, the silane, which has at least two groups corresponding to formula (I), is a compound corresponding to formula (II)
R
4-p
Si[O
t
(CH
2
)
m
SiR
1
n
X
3-n
]
p
  (II)
wherein
t is 0 or 1,
p is 4, 3, or 2 (preferably 4),
m is 1 to 6 (preferably 2 or 3),
n is 0 to 2,
R denotes C
1
-C
18
alkyl and/or C
6
-C
20
aryl (preferably C
1
-C
8
alkyl),
R
1
denotes unsubstituted C
1
-C
18
hydrocarbon (preferably methyl or ethyl) or a C
1
-C
18
hydrocarbon which contains at least O, N, S, or P (preferably methoxyethyl), with each R
1
within the molecule being identical or different, and
X denotes OH, C
1
-C
4
alkoxy, C
6
-C
20
aryloxy, C
1
-C
6
acyloxy, and/or hydrogen (preferably OH, methoxy, or ethoxy).
Compounds corresponding to formula (II) are prepared preferably by hydrosilylation of the corresponding vinyl, allyl, or higher alkenyl compounds with correspondingly functionalized silanes bearing H-Si-groups or siloxanes with correspondingly functionalized silanes bearing vinyl, allyl or higher alkenyl groups.
In other embodiments of the invention, the siloxane contains at least two structural units selected from M, D, and T units and optionally also Q units and/or its condensation products and/or partial condensation products. In the nomenclature familiar to the person skilled in the art, M denotes R
3
SiO
1/2
, D denotes R
2
SiO
2/2
, T denotes RSiO
3/2
, Q denotes SiO
4/2
, and R has the meanings given above.
Here, the siloxane has a preferred molecular weight (number average) of from 308 to 5,000.
In another preferred embodiment of the invention, the siloxane has the formula (III)
wherein a is 3 to 6 (preferably 4), or corresponds to its condensation products or partial condensation products, all other indices n, m, R, and X having the meanings already given above.
Particularly preferred siloxanes are
and/or their condensation products or partial condensation products.
Compounds corresponding to formula (III) (e.g., of formulas (IIIa) and (IIIb)) are preferably prepared by the process described in DE-A 19,603,241 or DE 19,711,650, by hydrosilylation of the corresponding vinyl compound with a chlorosilane and subsequent hydrolysis or alcoholysis.
For the purpose of this invention, condensation products and partial condensation products mean those compounds that are formed, for example, through reaction of two groups corresponding to the general formula (1), with splitting off of water or alcohol.
For the purpose of this invention, emulsifiers (c) are preferably anionic, cationic, or neutral low-molecular, oligomeric or polymeric emulsifiers, surfactants, or protective colloids.
Examples of anionic low-molecular, oligomeric, or polymeric emulsifiers or surfactants are alkali metal salts or alkaline-earth salts of fatty acids, for example, sodium salts of saturated fatty acids having 10 to 21 carbon atoms, sodium salts of unsaturated fatty acids having 12 to 18 carbon atoms, alkyl ether sulfonates, such as ethers of &agr;-sulfo-&ohgr;-hydroxypolyethylene glycols with, for example, 1-methylphenylethylphenol, nonylphenol or alkyl ethers having 12 to 18 carbon atoms, arylalkyl sulfonates such as, for example, naphthalenesulfonic acids provided with straightchain or branched butyl groups, or alkyl sulfates, such as the sodium salts of long-chain alkyl sulfate esters.
Examples of cationic low-molecular, oligomeric, or polymeric emulsifiers or surfactants are the salts of amines bearing long-chain alkane groups having 8 to 22 carbon atoms in which the amines have been converted to the ammonium compounds with acids or by alkylation, as well as similar phosphorus compounds and sulfur compounds.
Examples of nonionic oligomeric or polymeric emulsifiers or surfactants are alkyl polyglycol ethers or alkyl polyglycol esters, such as ethoxylated long-chain alcohols having, for example, 12 to 18 carbon atoms, containing saturated or unsaturated bonds, ethoxylated castor oil, ethoxylated (coconut) fatty acids, ethoxylated soy bean oil, ethoxylated resin acids or rosin acids, ethoxylated and optionally propoxylated butyl diglycol, ethoxylated alkyl aryl ethers, such as ethoxylated straight-chain and/or branched nonylphenol or octylphenol or benzylated p-hydroxybiphenyl, ethoxylated tri- and diglycerides and alkyl polyglycosides.
Also suitable as emulsifiers or surfactants are ethoxylated long-chain alkylamines or alkenylamines, lecithin, reaction products of polyethylene glycols and diisocyanates modified by long-chain alkyl isocyanates, reaction products of rape-seed oil and diethanolamine or ethoxylated reaction products of sorbitan and long-chain alkanecarboxylic acids or alkenecarboxylic acids.
So-called protective co

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