Coating compositions containing polyisocyanates and aldimines which have improved storage stability

The present invention relates to a coating composition having an improved pot life without a corresponding increase in dry time when cured under ambient conditions which contains PA0 a) a polyisocyanate component, PA0 b) an aldimine based on the reaction product of a polyamine having 2 or more primary amino groups with an aldehyde corresponding to the formula: EQU O.dbd.CHCH(R.sub.1)(R.sub.2) wherein R.sub.1 and R.sub.2 may be the same or different and represent optionally substituted hydrocarbon radicals, or R.sub.1 and R.sub.2 together with the .beta.-carbon atom form a cycloaliphatic or heterocyclic ring and PA0 c) 0.1 to 15 weight percent, based on the total weight of the coating composition, of a water-adsorbing zeolite, wherein components a) and b) are present in an amount sufficient to provide an equivalent ratio of isocyanate groups to aldimine groups of 0.5:1 to 20:1.

BACKGROUND OF THE INVENTION 
The present invention is directed to coating compositions based on 
polyisocyanates and aldimines which have improved pot lives without a 
corresponding increase in the dry times of the resulting coatings under 
ambient conditions. 
Coating compositions which may be cured at room temperature are known. 
One-component coating compositions contain fully reacted polyurethanes as 
the binder. These compositions have the advantage that they are available 
as fully formulated systems which may be directly applied to suitable 
substrates without any preliminary steps except for mild stirring. 
Disadvantages of these systems are that large amounts of organic solvents 
are needed to reduce the viscosity of fully reacted, i.e., high molecular 
weight, polyurethanes. The coating compositions are cured by evaporation 
of the solvent which is objectionable from an environmental perspective. 
In addition, in order to solubilize the polyurethanes in organic solvents, 
they must be essentially linear polyurethanes. While such polyurethanes 
possess properties which are suitable for many applications, they do not 
provide certain properties, e.g., solvent resistance which may be obtained 
from crosslinked polyurethanes. 
Two-component coating compositions are also known. These compositions come 
in two containers. The first contains a polyisocyanate, while the second 
contains an isocyanate-reactive component, generally a polyol. The 
components are not mixed until they are ready to be used. One advantage of 
these compositions is that because the components are not pre-reacted to 
form a high molecular weight polymer, a suitable processing viscosity can 
be achieved without the need for large amounts of organic solvents. In 
addition, higher functional components can be used to obtain highly 
crosslinked coatings which possess properties which surpass those 
possessed by one-component coatings. 
The disadvantages of these compositions is that they cannot be applied 
without a preliminary mixing step in which it is critical that the 
components are mixed in the right proportions. In addition, special 
metering and mixing equipment is needed to conduct this process on a 
commercial scale. If the components are mixed in the wrong proportions, 
then the properties of the resulting coatings can be substantially 
affected. In addition, after the components are mixed they must be used in 
a timely fashion. If not, they continue to react until an unusable solid 
is obtained. 
Coating compositions which possess the advantages of the known one- and 
two-component coating compositions without possessing their disadvantages 
have been disclosed in copending applications, U.S. Ser. Nos. 08/171,281 
and 08/171,550. Even though coatings prepared in accordance with these 
copending applications possess many desirable properties, further 
improvements are needed in the pot lives of the compositions. In 
particular, the viscosity of these compositions increases too rapidly 
prior to being applied to a substrate and cured. 
Accordingly, it is an object of the present invention to provide increased 
pot lives without significantly increasing the dry times of the resulting 
coatings and without altering any of the other desirable properties of the 
compositions. 
This object may be achieved with the coating compositions of the present 
invention which contain polyisocyanates and aldimines and also the 
water-adsorbing zeolites described hereinafter to increase the pot life. 
It is surprising that an increase in the pot life can be obtained by 
incorporating these zeolites because contrary to the prior art, the 
Applicants have discovered that water does not hydrolyze aldimines to the 
corresponding amine. 
In addition, in conventional pigmented, one-component, moisture-curing 
coating compositions containing polyisocyanates, water present in the 
pigments does affect the pot life. However, the pot life is still 
adequate, i.e., generally at least 12 to 24 hours, to provide sufficient 
time to apply the coating compositions before the viscosity increases to 
the point where it is not possible to apply the coating compositions using 
conventional spray equipment without adding additional solvent. 
To the contrary the examples of the subject application demonstrate that 
pigmented coating compositions containing polyisocyanates and aldimines, 
which are essentially blocked amines, increase in viscosity much more 
rapidly. Since water does not hydrolyze the aldimines to form the 
corresponding amines (which would then rapidly react with the 
polyisocyanate component), there is no reason to expect that water is the 
cause of the more rapid increase in viscosity and shortened pot life. 
Accordingly, it is surprising that the addition of the water-adsorbing 
zeolites described hereinafter would have any affect on increasing the pot 
life of the systems. 
For the preceding reasons, it would not be expected that the addition of 
zeolites would have any effect on increasing the pot life of the 
composition. 
U.S. Pat. Nos. 3,420,800 and 3,567,692 disclose coating compositions 
containing polyisocyanates and either aldimines or ketimines. However, 
these patents do not teach the use of zeolites to increase the pot life. 
In addition, U.S. Pat. No. 5,243,012 teaches that tin compounds may be 
used to increase the pot life of coating compositions containing 
polyisocyanates and polyaspartic acid derivatives that contain secondary 
amino groups. Copending application, U.S. Ser. No. 08/171,304, teaches 
that tin compounds may be used to increase the pot life of coating 
compositions containing polyisocyanates and aldimines. 
SUMMARY OF THE INVENTION 
The present invention relates to a coating composition having an improved 
pot life without a corresponding increase in dry time when cured under 
ambient conditions which contains 
a) a polyisocyanate component, 
b) an aldimine based on the reaction product of a polyamine having 2 or 
more primary amino groups with an aldehyde corresponding to the formula: 
EQU O.dbd.CHCH(R.sub.1)(R.sub.2) 
wherein R.sub.1 and R.sub.2 may be the same or different and represent 
optionally substituted hydrocarbon radicals, or R.sub.1 and R .sub.2 
together with the .beta.-carbon atom form a cycloaliphatic or heterocyclic 
ring and 
c) 0.1 to 15 weight percent, based on the total weight of the coating 
composition, of a water-adsorbing zeolite, 
wherein components a) and b) are present in an amount sufficient to provide 
an equivalent ratio of isocyanate groups to aldimine groups of 0.5:1 to 
20:1. 
DETAILED DESCRIPTION OF THE INVENTION 
Examples of suitable polyisocyanates which may be used as the 
polyisocyanate component in accordance with the present invention include 
monomeric diisocyanates, preferably NCO prepolymers and more preferably 
polyisocyanate adducts. Suitable monomeric diisocyanates may be 
represented by the formula 
EQU R(NCO).sub.2 
in which R represents an organic group obtained by removing the isocyanate 
groups from an organic diisocyanate having a molecular weight of about 112 
to 1,000, preferably about 140 to 400. Diisocyanates preferred for the 
process according to the invention are those represented by the above 
formula in which R represents a divalent aliphatic hydrocarbon group 
having 4 to 18 carbon atoms, a divalent cycloaliphatic hydrocarbon group 
having 5 to 15 carbon atoms, a divalent araliphatic hydrocarbon group 
having 7 to 15 carbon atoms or a divalent aromatic hydrocarbon group 
having 6 to 15 carbon atoms. 
Examples of the suitable organic diisocyanates include 1,4-tetramethylene 
diisocyanate, 1,6-hexamethylene diisocyanate, 
2,2,4-trimethyl-1,6-hexamethylene diisocyanate, 1,12-dodecamethylene 
diisocyanate, cyclohexane-1,3- and -1 ,4-diisocyanate, 
1-isocyanato-2-isocyanatomethyl cyclopentane, 
1-isocyanato-3-isocyanatomethyl-3,5,5-trimethyl-cyclohexane (isophorone 
diisocyanate or IPDI), bis-(4-isocyanatocyclohexyl)-methane, 
2,4'-dicyclohexyl-methane diisocyanate, 1,3-and 
1,4-bis-(isocyanatomethyl)-cyclohexane, 
bis-(4-isocyanato-3-methyl-cyclohexyl)-methane, .alpha., .alpha., 
.alpha.', .alpha.'-tetramethyl-1,3-and/or 1,4-xylyene diisocyanate, 
1-isocyanato-l-methyl-4(3)-isocyanatomethyl cyclohexane, 2,4- and/or 
2,6-hexahydrotoluylene diisocyanate, 1.3- and/or 1,4-phenylene 
diisocyanate, 2,4- and/or 2,6-toluylene diisocyanate, 2,4-and/or 
4,4'-diphenyl-methane diisocyanate, 1.5-diisocyanato naphthalene and 
mixtures thereof. Aromatic polyisocyanates containing 3 or more isocyanate 
groups such as 4,4',4"-triphenylmethane diisocyanate and polyphenyl 
polymethylene polyisocyanates obtained by phosgenating 
aniline/formaldehyde condensates may also be used. 
In accordance with the present invention the polyisocyanate component is 
preferably in the form of an NCO prepolymer or a polyisocyanate adduct, 
more preferably a polyisocyanate adduct. Suitable polyisocyanate adducts 
are those containing isocyanurate, uretdione, biuret, urethane, 
allophanate, carbodiimide and/or oxadiazinetrione groups. The 
polyisocyanates adducts have an average functionality of 2 to 6 and an NCO 
content of 5 to 30% by weight. 
1 ) Isocyanurate group-containing polyisocyanates which may be prepared as 
set forth in DE-PS 2,616,416, EP-OS 3,765, EPOS 10,589, EP-OS 47,452, U.S. 
Pat. No. 4,288,586 and U.S. Pat. No. 4,324,879. The 
isocyanato-isocyanurates generally have an average NCO functionality of 3 
to 3.5 and an NCO content of 5 to 30%, preferably 10 to 25% and most 
preferably 15 to 25% by weight. 
2) Uretdione diisocyanates which may be prepared by oligomerizing a portion 
of the isocyanate groups of a diisocyanate in the presence of a trialkyl 
phosphine catalyst and which may be used in admixture with other aliphatic 
and/or cycloaliphatic polyisocyanates, particularly the isocyanurate 
group-containing polyisocyanates set forth under (1) above. 
3) Biuret group-containing polyisocyanates which may be prepared according 
to the processes disclosed in U.S. Pat. Nos. 3,124,605; 3,358,010; 
3,644,490; 3,862,973; 3,906,126; 3,903,127; 4,051,165; 4,147,714; or 
4,220,749 by using co-reactants such as water, tertiary alcohols, primary 
and secondary monoamines, and primary and/or secondary diamines. These 
polyisocyanates preferably have an NCO content of 18 to 22% by weight and 
an average NCO functionality of 3 to 3.5. 
4) Urethane group-containing polyisocyanates which may be prepared in 
accordance with the process disclosed in U.S. Pat. No. 3,183,112 by 
reacting excess quantities of polyisocyanates, preferably diisocyanates, 
with low molecular weight glycols and polyols having molecular weights of 
less than 400, such as trimethylol propane, glycerine, 1,2-dihydroxy 
propane and mixtures thereof. The urethane group-containing 
polyisocyanates have a most preferred NCO content of 12 to 20% by weight 
and an (average) NCO functionality of 2.5 to 3. 
5) Allophanate group-containing polyisocyanates which may be prepared 
according to the processes disclosed in U.S. Pat. Nos. 3,769,318, 
4,160,080 and 4,177,342. The allophanate group-containing polyisocyanates 
have a most preferred NCO content of 12 to 21% by weight and an (average) 
NCO functionality of 2 to 4.5. 
6) Isocyanurate and allophanate group-containing polyisocyanates which may 
be prepared in accordance with the processes set forth in U.S. Pat. Nos. 
5,124,427, 5,208,334 and 5,235,018; the disclosures of which are herein 
incorporated by reference. 
7) Carbodiimide group-containing polyisocyanates which may be prepared by 
oligomerizing di- or polyisocyanates in the presence of known 
carbodiimidization catalysts as described in DE-PS 1,092,007, U.S. Pat. 
No. 3,152,162 and DE-OS 2,504,400, 2,537,685 and 2,552,350. 
8) Polyisocyanates containing oxadiazinetrione groups and containing the 
reaction product of two moles of a diisocyanate and one mole of carbon 
dioxide. 
Preferred polyisocyanate adducts are the polyisocyanates containing 
isocyanurate groups, biuret groups or mixtures of isocyanurate and 
allophanate groups. 
The NCO prepolymers, which may also be used as the polyisocyanate component 
in accordance with the present invention, are prepared from the previously 
described monomeric polyisocyanates or polyisocyanate adducts, preferably 
monomeric diisocyanates, and organic compounds containing at least two 
isocyanate-reactive groups, preferably at least two hydroxy groups. These 
organic compounds include high molecular weight compounds having molecular 
weights of 400 to about 6,000, preferably 800 to about 3,000, and 
optionally low molecular weight compounds with molecular weights below 
400. The molecular weights are number average molecular weights (M.sub.n) 
and are determined by end group analysis (OH number). Products obtained by 
reacting polyisocyanates exclusively with low molecular weight compounds 
are polyisocyanates adducts containing urethane groups and are not 
considered to be NCO prepolymers. 
Examples of the high molecular weight compounds are polyester polyols, 
polyether polyols, polyhydroxy polycarbonates, polyhydroxy polyacetals, 
polyhydroxy polyacrylates, polyhydroxy polyester amides and polyhydroxy 
polythioethers. The polyester polyols, polyether polyols and polyhydroxy 
polycarbonates are preferred. Further details concerning the low molecular 
weight compounds and the starting materials and methods for preparing the 
high molecular weight polyhydroxy compounds are disclosed in U.S. Pat. No. 
4,701,480, herein incorporated by reference. 
These NCO prepolymers generally have an isocyanate content of about 0.5 to 
30% by weight, preferably about 1 to 20% by weight, and are prepared in 
known manner by the reaction of the above mentioned starting materials at 
an NCO/OH equivalent ratio of about 1.05:1 to 10:1 preferably about 1.1:1 
to 3:1. This reaction may take place in a suitable solvent which may 
optionally be removed by distillation after the reaction along with any 
unreacted volatile starling polyisocyanates still present. In accordance 
with the present invention NCO prepolymers also include NCO 
semi-prepolymers which contain unreacted starting polyisocyanates in 
addition to the urethane group-containing prepolymers. 
As disclosed in copending application, U.S. Ser. No. 08/171,281, the 
compatibility between the polyisocyanates and the aldimines as well as the 
optical properties of the resulting coatings may be improved by the use of 
polyisocyanates containing a monoallophanate group, i.e., a polyisocyanate 
containing one aliophanate group and formed from two isocyanate molecules 
and 1 monoalcohol molecule. In mixtures with monomeric polyisocyanates, 
polyisocyanate adducts or NCO prepolymers, the polyisocyanates containing 
allophanate groups should be present in an amount of at least 5% by 
weight, preferably at least 25% by weight and more preferably at least 40% 
by weight, based on the solids content of the polyisocyanate component. 
Suitable aldimines for use in combination with the polyisocyanate mixtures 
include those prepared from an aldehyde and polyamines containing two or 
more, preferably 2 to 6 and more preferably 2 to 4, primary amino groups. 
The polyamines include high molecular weight amines having molecular 
weights of 400 to about 10,000, preferably 800 to about 6,000, and low 
molecular weight amines having molecular weights below 400. The molecular 
weights are number average molecular weights (M.sub.n) and are determined 
by end group analysis (NH number). Examples of these polyamines are those 
wherein the amino groups are attached to aliphatic, cycloaliphatic, 
araliphatic and/or aromatic carbon atoms. 
Suitable low molecular polyamines starting compounds include tetramethylene 
diamine, ethylene diamine, 1,2- and 1,3-propane diamine, 
2-methyl-1,2-propane diamine, 2,2-dimethyl-l,3-propane diamine, 1,3- and 
1,4-butane diamine, 1,3- and 1,5-pentane diamine, 2-methyl-1,5-pentane 
diamine, 1,6-hexane diamine, 1,7-heptane diamine, 1,8-octane diamine, 
1,9-nonane diamine, 1,10-decane diamine, 1,11-dodecane diamine, 
1-amino-3-aminomethyl-3,5,5-trimethyl cyclohexane, bis-( 
4-aminocyclohexyl)-methane, bis-(4-amino-3-methylcyclohexyl)-methane, 1,2- 
and/or 1,4-cyclohexane diamine, 1,3-bis(methylamino)-cyclohexane, 
1,8-p-menthane diamine, hydrazine, hydrazides of semicarbazido carboxylic 
acids, bis-hydrazides, bis-semicarbazides, phenylene diamine, 2,4- and 
2,6-toluylene diamine, 2,3- and 3,4-toluylene diamine, polyphenylene 
polymethylene polyamines of the kind obtained by the aniline/formaldehyde 
condensation reaction, N,N,N-tris-(2-aminoethyl)-amine, guanidine, 
melamine, N-(2-aminoethyl)-1,3-propane diamine, 3,3'-diamino-benzidine, 
polyoxypropylene amines, polyoxyethylene amines, 
2,4-bis-(4'-aminobenzyl)-aniline and mixtures thereof. 
Preferred polyamines are 1-amino-3-aminomethyl-3,5,5-trimeethyl-cyclohexane 
(isophorone diamine or IPDA), bis-(4-aminocyclohexyl)-methane, 
bis-(4-amino-3-methylcyclohexyl)-methane, 1,6-diaminohexane, 2-methyl 
pentamethylene diamine and ethylene diamine. 
Suitable high molecular weight polyamines correspond to the polyhydroxyl 
compounds used to prepare the NCO prepolymers with the exception that the 
terminal hydroxy groups are converted to amino groups, either by amination 
or by reacting the hydroxy groups with a diisocyanate and subsequently 
hydrolyzing the terminal isocyanate group to an amino group. Preferred 
high molecular weight polyamines are amine-terminated polyethers such as 
the Jeffamine resins available from Texaco. 
Suitable aldehydes are those corresponding to the formula 
EQU O.dbd.CHCH(R.sub.1)(R.sub.2) 
wherein 
R.sub.1 and R.sub.2 may be the same or different and represent optionally 
substituted hydrocarbon radicals, preferably containing 1 to 10, more 
preferably 1 to 6, carbon atoms, or R.sub.1 and R.sub.2 together with the 
.beta.-carbon atom form a cycloaliphatic or heterocyclic ring. 
Examples of suitable aldehydes include isobutyraldehyde, 2-ethyl hexanal, 
2-methyl butyraldehyde, 2-ethyl butyraldehyde, 2-methyl valeraldehyde, 
2,3-dimethyl valeraldehyde, 2-methyl undecanal and cyclohexane 
carboxyaldehyde. 
The aldimines may be prepared in known manner by reacting the polyamines 
with the aldehydes either in stoichiometric amounts or with an excess of 
aldehyde. The excess aldehyde and the water which is produced can be 
removed by distillation. The reactions may also be carried out in 
solvents, other than ketones. The solvents may also be removed by 
distillation after completion of the reaction. 
Suitable zeolites c) include those which are capable of adsorbing water, 
preferably those which adsorb water without adsorbing any of the other 
components of the coating composition. These preferred zeolites have a 
pore diameter of less than 10.ANG., preferably less than 5.ANG.. Examples 
of suitable zeolites are sodium aluminosilicates and potassium sodium 
aluminosilicates, such as those available from Miles as Baylith T powder 
and Baylith L powder. 
The zeolites are added to the coating compositions in an amount sufficient 
to adsorb 20 to 100%, preferably 60 to 100% and more preferably 100%, of 
the water present in the coating compositions. Excess amounts may be 
added, but do not provide any significant benefits. The amount of zeolite 
which is necessary can be calculated based on the water adsorption ability 
of the zeolite. For example, the preceding Baylith powders are capable of 
adsorbing about 25% of their weight in water. 
Generally, the preceding guidelines can be achieved if zeolite c) is added 
in a minimum amount of at least 0.1 weight percent, preferably at least 
0.5 weight percent and more preferably at least 1 weight percent, based on 
the total weight of the coating composition, up to a maximum amount of 15 
weight percent, preferably 10 weight percent and more preferably 7 weight 
percent, based on the weight of the total weight of the coating 
composition. 
The binders present in the coating compositions according to the invention 
contain polyisocyanate component a), aldimine component b) and zeolite c). 
While the coating compositions may also contain other isocyanate-reactive 
components, such as the polyols commonly used in polyurethane coating 
compositions, their presence is not preferred. Components a) and b) are 
used in amounts sufficient to provide an equivalent ratio of isocyanate 
groups to aldimine groups of 0.5:1 to 20:1, preferably 0.8:1 to 3:1 and 
more preferably 1:1 to 2:1. 
The binders to be used according to the invention are prepared by mixing 
all of the individual components together or by premixing two of the 
components before adding the third component. For example, zeolite c) may 
be initially blended with the component a) or component b), preferably 
component b) before the addition of the other component. 
Preparation of the binders is carried out solvent-free or in the presence 
of the solvents conventionally used in polyurethane or polyurea coatings. 
It is an advantage of the process according to the invention that the 
quantity of solvent used may be greatly reduced when compared with that 
required in conventional two-component systems. 
Examples of suitable solvents include xylene, butyl acetate, methyl 
isobutyl ketone, methoxypropyl acetate, N-methyl pyrrolidone, Solvesso 
solvent, petroleum hydrocarbons and mixtures of such solvents. 
In the coating compositions to be used for the process according to the 
invention, the ratio by weight of the total quantity of binder components 
a) and b) to the quantity of solvent is about 40:60 to 100:0, preferably 
about 60:40 to 100:0. 
In addition to the binder components and component c), the coating 
compositions may also contain the known additives from coatings 
technology, such as fillers, pigments, softeners, high-boiling liquids, 
catalysts, UV stabilizers, anti-oxidants, microbiocides, algicides, 
dehydrators, thixotropic agents, wetting agents, flow enhancers, matting 
agents, anti-slip agents, aerators and extenders. Coating compositions 
containing pigments and/or fillers are especially suitable for the present 
invention due to the difficulty of removing all of the moisture from these 
additives. 
It is also possible to incorporate other additives which increase the pot 
life of compositions containing polyisocyanates and aldimines, such as the 
tin compounds disclosed in copending application, U.S. Ser. No. 
08/171,304, and in U.S. Pat. No. 5,243,012, the disclosures of which are 
herein incorporated by reference. 
The additives are chosen based on the requirements of the particular 
application and their compatibility with components a) and b). The coating 
compositions may be applied to the substrate to be coated by conventional 
methods such as painting, rolling, pouring or spraying. 
The coating compositions according to the invention have good storage 
stability and provide coatings which have relatively fast dry times. The 
coatings are also characterized by high hardness, elasticity, very good 
resistance to chemicals, high gloss, good weather resistance, good 
environmental etch resistance and good pigmenting qualities. 
The invention is further illustrated, but is not intended to be limited by 
the following examples in which all parts and percentages are by weight 
unless otherwise specified.

EXAMPLES 
The following starling materials were used in the examples: 
Polyisocyanate 1 
To a 500 ml 3-neck flask equipped with a gas bubbler, mechanical stirrer, 
thermometer and condenser was added 301.7 parts of hexamethylene 
diisocyanate and 13.3 parts of 1-butanol. The stirred mixture was heated 
for 1 hour at 60.degree. C. while dry nitrogen was bubbled through the 
reaction mixture. The temperature of the reaction mixture was then raised 
to 90.degree. C. To the reaction mixture at 90.degree. C. was added 0.214 
parts of a 4.4% solution of N,N,N-trimethyl-N-benzyl-ammonium hydroxide in 
1-butanol. When the reaction mixture reached an NCO content of 34.8%, the 
reaction was stopped by adding 0.214 parts of di-(2-ethylhexyl)-phosphate. 
The excess monomer was removed by thin film evaporation to provide an 
almost colorless clear liquid having a viscosity of 630 mPa.s (25.degree. 
C.), an NCO content of 19.7% and a free monomer (HDI) content of 0.35%. 
The yield was 48.6%. 
Aldimine 1 
The aldimine of bis-(4-aminocyclohexyl)-methane and isobutyraldehyde was 
prepared by initially charging 1514.3 parts (21 equivalents) of 
isobutyraldehyde and then slowly charging 2104.0 parts (20 equivalents) of 
bis-(4-aminocyclohexyl)-methane over a period of thirty minutes to avoid 
an exotherm. After the addition of the diamine the reaction mixture was 
stirred for one hour. At this time stirring was stopped and water was 
allowed to settle to the bottom of the reactor. As much water as possible 
was drained from the bottom of the reactor. The reaction mixture was then 
heated to 100.degree. C. to remove excess isobutyraldeyde. While 
maintaining a temperature of 100.degree. C., a vacuum of approximately 20 
mm Hg was applied to remove any final traces of aldehyde. Thereafter the 
vacuum was increased to 1 mm Hg to remove water until the water content 
was less than 0.05% (approximately 1 to 3 hours.) The aldimine had a 
viscosity of 100 mPa.s at 25.degree. C., an equivalent weight of 159.3, an 
APHA color of 70, a purity as determined by GPC of 93.5% and a water 
content of less than 0.05%. 
Aldimine 2 
The aldimine of 2-methyl pentamethylene diamine and isobutyraldehyde was 
prepared using the procedure described for aldimine 1. 
Additive A - Dibutyltin dilaurate (T-12, available from Air Products) 
Zeolite A - Baylith L powder, available from Miles) 
Pigment A - titanium dioxide (Ti-Pure R-960, available from DuPont) 
Pigment Dispersant A - Anti-Terra U, available from Byk Chemie 
Polyol A - a polyesterether polyol (Desmophen 1150, available from Miles) 
Example 1 
Effect of Zeolite A on two-component, pigmented coating compositions based 
on Polyisocyanate 1 and Aldimine 1 or Polyol A 
Component 1 was prepared by adding pigment A, additive A and zeolite A 
powder to the amount of Aldimine 1 or Polyol A set forth in Table 1 and 
dispersed using a high speed cowles type disperser. Pigment A was added at 
an amount equal to a pigment to binder ratio of 0.5:1. Additive A was 
added in an amount of 0.30% based on the total weight of the coating 
composition. Zeolite A was added in an amount of 7%, based on the weight 
of Pigment A. The mixture was allowed to set overnight (minimum of 8 
hours) at a temperature of 25.degree. C. Then, the amount of 
polyisocyanate 1 set forth in Table 1, also at 25.degree. C., was added to 
component 1 (NCO/NH equivalent ratio 1.1:1). The mixture was immediately 
poured into 8 oz. bottles and capped until needed for viscosity 
measurements on a Brookfield Viscometer. The results of the viscosity 
measurements are set forth in Table 2. 
TABLE 1 
______________________________________ 
Formulations A-D 
A (Comp) 
B C (Comp) D (Comp) 
______________________________________ 
Component 1 
Aldimine 1 298.2 298.2 -- -- 
Polyol A -- -- 448.8 448.8 
Pigment A 377.7 377.7 385.5 385.5 
Zeolite A -- 26.4 -- 27.0 
Additive A 2.3 2.3 2.3 2.3 
Component 2 
Polyisocyanate 1 
457.1 457.1 322.3 322.3 
______________________________________ 
TABLE 2 
______________________________________ 
Viscosity (in mPa.s) 
Formulations A-D 
A (Comp) B C (Comp) D (Comp) 
______________________________________ 
Initial 3600 2600 3600 3900 
15 Minutes 
2300 3300 4700 5300 
50 Minutes 
2200 3900 22,000 11,000 
1.5 hours 
2600 4200 Gelled Gelled 
2 hours 2900 4200 -- -- 
3 hours 3700 4200 
8 hours 9000 3300 
23 hours 30,000 4800 
______________________________________ 
A comparison of formulation A with B demonstrates the improved pot life 
which may achieved in accordance with the present invention. However, a 
comparison of formulation C with D indicates that zeolites do not improve 
the pot lives of systems containing polyisocyanates and polyols in the 
same manner that they improve the pot lives of systems containing 
polyisocyanates and aldimines. 
Example 2 
Effect of Zeolite A on two-component, pigmented coating compositions based 
on Polyisocyanate 1 and Aldimine 1 or Aldimine 2 
Component 1 was prepared by adding pigment A, pigment dispersant A and 
zeolite A to the amount of Aldimine 1 or Aldimine 2 set forth in Table 3 
and dispersed using a high speed cowles type disperser. Pigment A was 
added at an amount equal to a pigment to binder ratio of 0.6:1. Zeolite A 
was added in an amount of 10%, based on the weight of Pigment A. The 
mixture was allowed to set overnight (minimum of 8 hours) at a temperature 
of 25.degree. C. Then, the amount of polyisocyanate 1 set forth in Table 
3, also at 25.degree. C. was added to component 1 (NCO/NH equivalent ratio 
1.05:1). The mixture was immediately poured into 8 oz. bottles and capped 
until needed for viscosity measurements on a Brookfield Viscometer. The 
results of the viscosity measurements are set forth in Table 4. 
TABLE 3 
______________________________________ 
Formulations E-H 
E (Comp) F G (Comp) H 
______________________________________ 
Component 1 
Aldimine 1 300 300 -- -- 
Aldimine 2 -- -- 250 250 
Pigment A 444 444 462 462 
Zeolite A -- 44 -- 46 
Pigment 9 9 9 9 
Dispersant A 
Component 2 
Polyisocyanate 1 
440 440 520 520 
______________________________________ 
TABLE 4 
______________________________________ 
Viscosity (in mPa.s) 
Formulations E-H 
E (Comp) F G (Comp) H 
______________________________________ 
Initial 5200 3900 800 900 
1 hour 11,200 4600 1700 660 
2 hours gelled 4200 2000 660 
4 hours -- 3500 2800 800 
6 hours -- 4200 3700 960 
24 hours 
-- 50,000 20,000 3280 
______________________________________ 
A comparison of formulation E with F and formulation G with H demonstrates 
the improved pot life which may achieved in accordance with the present 
invention. 
Example 3 
Aldimine 1 and water in an equivalent ratio of 1:2 were dissolved in 
tetrahydrofuran and monitored by IR. After 6 days at ambient temperature, 
no evidence of aldimine hydrolysis was observed by IR. This result 
illustrates the hydrolytic stability of an aldimine. 
Although the invention has been described in detail in the foregoing for 
the purpose of illustration, it is to be understood that such detail is 
solely for that purpose and that variations can be made therein by those 
skilled in the art without departing from the spirit and scope of the 
invention except as it may be limited by the claims.