Coating processes – With post-treatment of coating or coating material – Heating or drying
Reexamination Certificate
2002-03-21
2004-06-22
Dawson, Robert (Department: 1712)
Coating processes
With post-treatment of coating or coating material
Heating or drying
C525S523000, C528S111000, C528S123000, C528S407000, C528S420000, C528S421000
Reexamination Certificate
active
06753040
ABSTRACT:
The present invention relates to alkyldipropylenetriamines and their adducts with epoxide compounds having on average at least one epoxide group per molecule as hardeners for epoxy resins and to the use of curable compositions based on these alkyldipropylenetriamines and adducts and epoxy resins for coating mineral and metallic substrates.
Curable compositions based on amine curing agents and epoxy resins are widely used in industry to coat and enhance metallic and mineral substrates. Amine curing agents used in particular are aliphatic, cycloaliphatic or aromatic amines and also polyaminoamides with or without imidazoline groups.
The mechanical and physical properties of the curable compositions based on these amines are adequate for numerous applications.
Especially for the coatings sector, however, there is a requirement for binder systems which are surface tolerant, i.e., which exhibit good adhesion even on substrates that are difficult to coat, such as moist substrates or unpretreated metal panels, for example, and which ensure the very best protection of the substrate, e.g. corrosion protection. There is also a requirement for rapid initial curing of the binder systems following application to the substrates, even at low temperatures, in order, for example, to ensure that the substrates can soon withstand loading or be coated further.
High early water resistance of the still uncured film (for example, by forming droplets at high relative atmospheric humidities) is an important criterion, as is a low viscosity of the binder, so that it can still be processed even at low temperatures.
Known hardeners for epoxy resins which afford relatively good corrosion protection and exhibit serviceable adhesion even on difficult substrates include polyaminoamides, which normally contain imidazoline groups. These compounds are prepared by condensing generally unsaturated, long-chain fatty acids with polyethylenepolyamines. The disadvantage of these compounds is their high viscosity at low temperatures (<15° C.) and also the slow rate of initial cure and/or through-cure. Moreover, compounds of this type possess relatively high colour numbers.
It was therefore an object of the present invention to eliminate these disadvantages.
This object is achieved through the use of the curable compositions of the invention, comprising alkyldipropylenetriamines and/or their adducts with epoxide compounds which contain on average at least one epoxide group per molecule with epoxy resins.
It has surprisingly been found that the alkyldipropylenetriamines and/or their adducts of the invention, although similar in structure to the polyaminoamides with or without imidazoline groups, possess a much higher rate of initial cure and/or through-cure, especially at low temperatures of <15° C. Moreover, these compounds have, in comparison, a much lower viscosity and colour number.
The invention provides curable compositions comprising
a) an epoxy resin having on average more than one epoxide group per molecule and
b1) an alkyrdipropylonetriamine of the general formula (I) and/or
b2) an adduct of an alkyidipropylenetriamine of the general formula (I) with b3) an epoxide compound having on average at least one epoxide group per molecule
in which R is a hydrocarbon radical having 8 to 22, preferably 10 to 20. carbon atoms.
The compounds of the formula (I) are normally prepared by cyanoethylation of amines (fatty amines) and subsequent hydrogenation in accordance with conventional methods. The amines or, respectively, fatty amines are reacted with acrylonitrle, and then the cyanide groups are hydrogenated in the presence of a catalyst. Schematically, the reaction sequence is as follows:
The fatty amines used preferably as reactants for the cyanoethylation are mixtures of long-chain primary alkylamines, obtained from mixed glycerol esters of medium and higher fatty acids with an even number of carbons, as occur in plant or animal bodies. For example, bovine tallow contains almost 100% (esterified) fatty acids having a carbon chain length of 14, 16 and 18 carbon atoms. The bovine tallow fatty amines obtained from bovine tallow are available commercially as tallow fatty amine, for example as Genamine® TA100 (Clariant). Therefore, if adducts of the invention are prepared starting from fatty amines of natural products, the products of the general formula (I) comprise mixtures of compounds with different chain lengths R. The chains R have approximately 8 to 20 carbon atoms, not more than approximately 22 carbon atoms, and may either be saturated or contain multiple bonds and may be either straight-chain or branched. Further examples of commercially available fatty amines which may be used in accordance with the invention, besides tallow fatty amine, are saturated straight-chain fatty amines such as dodecylamine, tetradecylamine, for example, saturated, branched fatty amines such as isotridecylamine, for example, unsaturated and saturated fatty amines and fatty amine mixtures, such as coconut fatty amine, oleylamine, rapeseed oil fatty amine, for example, or else stearylamine.
The present invention provides b2) adducts of compounds of the formula (I) with epoxide compounds containing on average at least one epoxide group per mole (b3). The adducts of the invention are prepared by known methods, by adding the epoxide compounds dropwise at 50° C.-100° C. with stirring to the initial charge of alkyldipropylenetrimine and then stirring the mixture at the same temperature for about 30 minutes until formation of adducts is as an end.
Also used are what are known as “isolated adducts”, which are prepared with an excess of alkyldipropylenetrlamine. In this case, from 1.5 to 10, preferably 4-6, times the molar amount of amine are introduced as the initial charge and the epoxide compound is added dropwise with stirring, judiciously at 50-100° C., Subsequently, the excess amine is removed by distillation under reduced pressure.
The further provides a process for preparing the adduct, which comprises heating an alkyldipropylenetrimine of the formula (I) to reaction temperature (50-100° C.), subsequently adding at least one epoxide compound having on average at least one epoxide group in the molecule, with continued stirring, and finally, after the formation of adducts has ended, removing any excess alkyldipropylenetrimine from the reaction mixture.
In accordance with the invention, both the compounds of the formula (I) and the adducts with epoxide compounds that have derived from the compounds of the general formula (I) may be used as hardeners for epoxide compounds. Similarly, mixtures comprising at least one compound of the formula I and at least one adduct of compounds of the formula I with epoxide compounds may be used as hardeners for epoxide compounds. Similarly, mixtures of compounds of the formula (I) or, respectively, their adducts may be used in which the compounds of the formula (I) may have hydrocarbon radicals R which are different in terms of the respective chain length (8 to 20 carbon atoms), degree of branching and bond order. Moreover, the curable compositions of the Invention may comprise further amine curing agents, with or without the use of solvents, plasticizers, UV stabilizers, dyes, pigments and fillers.
The invention therefore additionally provides curable compositions comprising
a) an epoxy resin having on average more than one epoxide group per molecule and
b1) an alkyldipropylenetrimine of the general formula (I) and/or
b2) an adduct of an alkyldipropylenetrimine of the general formula (I) with b3) an epoxide compound having on average at least one epoxide group per molecule
which R is a hydrocarbon radical having 8 to 22, preferably 10 to 20, carbon atoms, and, if desired, further optional components selected from
c) diluents, other amine components and other customary auxiliaries and additives.
The modifiers c) may be added equally to the hardener b) of the invention, to the resin a), with the exception of the amine component, or to the curable composition.
The curable compositions of the invention
Scherzer Wolfgang
Volle Jörg
Aylward David E.
Dawson Robert
Levato Tiffany A.
Neuman Kristin H.
Proskauer Rose LLP
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