Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Patent
1992-01-24
1993-07-06
Kight, III, John
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
528 49, 528 76, 528 78, 528 85, 528363, C08G 6300, C08G 6700, C08G 6900, C08G 6344
Patent
active
052255190
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to the field of resinous binders suitable for application as coatings on various metallic and non-metallic substrates, in particular for the finishing of body parts in the automobile industry.
More specifically, the invention regards a coating composition which can harden at low temperatures, thus being useful for forming coatings on body components also having plastic parts, as well as more generally for forming protective coatings on various substrates in industry in general.
BACKGROUND ART
Among the resinous binders known to be in widespread use nowadays as coatings, in particular in the finishing of body parts in the automobile industry, are those based on polyisocyanate which are known to be highly toxic.
DISCLOSURE OF THE INVENTION
The principle aim of the present invention is to obtain a new coating composition as an alternative to those available nowadays based on polyisocyanate, and which may have faster cross-linking properties at low temperatures such as to permit a notable time-savings in production cycles.
Still another aim of the invention is to obtain a coating composition that can provide coatings with excellent chemical resistance and durability.
WAYS OF CARRYING OUT THE INVENTION
These and other aims which will become more apparent hereinafter are achieved by a coating composition characterized by the fact of comprising at least one polycarbodiimide component having at least two carbodiimide groups per molecule, at least one anhydride component having at least one carboxylic acid anhydride group per molecule, and a hydroxylic reagent capable of reacting with said anhydride component to generate free carboxylic polyacids, at least one among said components and reagents being suitable for forming films.
The polycarbodiimide component useful in the present composition can be a compound by itself or it can be incorporated together with the above-mentioned anhydride or no longer carrying the carbodiimide functionality.
In the first case, one uses a polycarbodiimide of the general formula: hydrocarbon radicals or aromatic radicals, without functional groups capable of reacting with the carbodiimide group.
The polycarbodiimide of the formula (1) can be an oligomeric compound, but as a rule it is a polymer.
Such polymer can have any molecular weight provided that the solid residue is not excessively limited and both the solubility in common solvents and the compatibility with the remaining components in the system are not compromised. Preferably, polycarbodiimides of molecular weight 1500-3000 are used.
Among those polycarbodiimides which can be utilized, some which can be cited for illustrative purposes only are, for example, polycarbodiimides available from Union Carbide (USA) under the trademark Ucarlink XL 20, XL 25 SE, and XL 27 HS or else polycarbodiimides available from Bayer (Germany) under the trademark Bayderm Fix PCL.
The anhydrides useful in the composition according to the invention can be of low molecular weight or polymeric, monofunctional or polyfunctional, but the polymeric polyanhydrides are preferred.
According to a first embodiment of the invention linear polymeric polyanhydrides are used and are of the formula ##STR1## in which X.sub.a and X.sub.b are selected from among atoms of hydrogen, linear or branched aliphatic hydrocarbon radicals, and aromatic hydrocarbon radicals, derived from monofunctional carboxylic acids.
R.sub.1, R.sub.2 . . . R.sub.n are selected from linear or branched aliphatic, cycloaliphatic, heterocyclic, or aromatic hydrocarbon radicals, having any functionality provided that it is not reactive with the anhydride group, such radicals being derived from polyfunctional carboxylic acids.
n.sub.1, n.sub.2 . . . n are whole numbers that each vary from 0 to 30. Usually, the sum of n.sub.1, n.sub.2 . . . n is less than or equal to 30 even if greater values are possible provided that they do not excessively limit the dry residue and do not compromise the solubility in common solvents and the compatibility w
REFERENCES:
patent: 4192926 (1980-03-01), Schafer et al.
patent: 4954577 (1990-09-01), Dunwald et al.
Industrie Vernici Italiane S.p.A.
Kight III John
Mosley T.
Pingitore Linda
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