The present invention provides room temperature curable epoxy coating compositions prepared by reacting (1) a saturated epoxy resin, (2) a curing amount of a polyamide and (3) a cellulose acetate butyrate in the presence of an organic solvent.

FIELD OF THE INVENTION 
The present invention is directed to the preparation of room temperature 
curable saturated epoxy resin compositions. 
BACKGROUND OF THE INVENTION 
It is generally known that epoxy resins such as the diglycidyl ethers of 
2,2-bis(4-hydroxyphenyl)propane can be cured with aliphatic and aromatic 
amines to produce acceptable coatings. It is also known that with the use 
of aliphatic amines, low-temperature curing systems can be obtained. When, 
however, saturated epoxy resins are reacted with aliphatic amines, the 
resulting coatings do not readily cure, i.e., remain wet or tacky for 
extended periods of time. A process was developed that produced tough, 
hard film using saturated epoxy resins and aliphatic amines at low baking 
temperatures. Such low-temperature curable saturated epoxy resin 
compositions and their methods of preparation are described in U.S. Pat. 
No. 4,108,824, issued Aug. 22, 1978. While these compositions offer 
significantly improved low-temperature curing epoxy compositions, there is 
still a need to improve the pot life and viscosity control. Also, ketone 
solvents are not operable in these compositions. It is generally known by 
those skilled in the coatings art that polyamides offer better 
flexibility, better substrate wetting characteristics, longer pot life and 
less sensitivity to stoichiometry than the aliphatic amines. It is also 
known that ketones offer better control of the pot life and viscosity than 
conventional oxygenated solvents. It would therefore be highly desirable 
to develop a low-temperature saturated epoxy curing system utilizing 
polyamides and ketone solvents. 
SUMMARY OF THE INVENTION 
The present invention provides curable epoxy coating compositions prepared 
by reacting (1) a saturated epoxy resin (2) a curing amount of a 
polyamide, and (3) from about 5% to about 50% by weight based on total 
weight of the epoxy resin and polyamide of a cellulose acetate butyrate, 
for from about 15 to 60 minutes in the presence of an organic solvent, 
before applying the composition to a suitable substrate. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In general, the present compositions provide excellent bond, tough coatings 
and are prepared by reacting (1) a saturated epoxy resin, preferably a 
diglycidyl polyether of a hydrogenated polyphenol, (2) a curing amount of 
a polyamide, and (3) from about 5% to about 50% by weight based on (1) and 
(2) of a cellulose acetate butyrate in the presence of an organic solvent. 
In other words, the instant compositions are simply prepared by 
pre-reacting the components for a period of from about 15 to 60 minutes at 
ambient temperature. This pre-reaction period is sometimes referred to as 
the "sweat-in" period or time. After the components have been pre-reacted 
for a sufficient "sweat-in" time, the resulting one-package composition is 
applied by well-known techniques to a suitable substrate and cured to 
produce a uniform, hard, tough surface coating or film. 
Saturated Epoxy Resins 
The epoxy compounds useful in the present compositions include those 
compounds derived from polyhydric phenols and having at least one vicinal 
epoxy group wherein the carbon-to-carbon bonds within the six-membered 
ring are saturated. Such epoxy resins may be obtained by two well-known 
techniques, i.e., (1) by the hydrogenation of glycidyl polyethers of 
polyhydric phenols, or (2) by the reaction of hydrogenated polyhydric 
phenols with epichlohydrin in the presence of a Lewis Acid catalyst and a 
subsequent dehydrochlorination in an alkaline medium. The method of 
preparation forms no part of the present invention and the resulting 
saturated epoxy resins derived by either method are suitable in the 
present compositions. 
Briefly, the first method comprises the hydrogenation of glycidyl 
polyethers of polyhydric phenols with hydrogen in the presence of a 
catalyst consisting of rhodium or ruthenium supported on an inert carrier 
at a temperature below about 50.degree. C. This method is thoroughly 
disclosed in U.S. Pat. No. 3,336,241, and is suitable for use in preparing 
saturated epoxy resins. Accordingly, the relevant disclosure of U.S. Pat. 
No. 3,336,241 is incorporated herein by reference. 
The second method comprises the condensation of a hydrogenated polyphenol 
with an epihalohydrin, such as epichlorohydrin, in the presence of a 
suitable catalyst such as BF.sub.3, followed by the dehydrohalogenation in 
the presence of caustic. When the phenol is hydrogenated bisphenol A, the 
resulting saturated epoxy compound is sometimes referred to as 
"diepoxidized hydrogenated bisphenol A", or more properly as the 
diglycidyl ether of 2,2-bis(4-cyclohexanol)propane. 
In any event, the term "saturated epxoy resin", as used herein shall be 
deemed to mean the glycidyl ethers of polyhydric phenols wherein the 
aromatic ring structure of the phenols is or has been saturated. 
An idealized structural formula representing the preferred saturated epoxy 
compounds is as follows: 
##STR1## 
wherein n has a value so that the average molecular weight of the 
saturated polyepoxide is from about 350 to about 2500. 
Polyamides 
Polyamides which are useful in the present compositions are those derived 
from polymeric fatty acids and aliphatic polyamines. Polyamides of this 
type are disclosed in U.S. Pat. No. 2,450,940. Typically, these polyamides 
are those made from polymeric fatty acids containing up to about 22 carbon 
atoms in a monomeric acid with ethylene diamine and/or diethylene 
triamine. It will be appreciated that polyamide resins having terminal 
amine groups or terminal carobxyl groups or in which some of the terminal 
groups are amine groups while others are carboxyl groups. 
The polymeric fatty acids employed in preparing the polyamides are those 
resulting from the polymerization of drying or semi-drying oils, or the 
free acids or simply aliphatic alcohol esters of such acids. Suitable 
drying or semi-drying oils include soybean, linseed, tung, perilla, 
oiticica, cottonseed, corn, tall, sunflower, safflower, dehydrated castor 
oil, and the like. In the polymerization process for the preparation of 
the polymeric fatty acids, the fatty acids with sufficient double bond 
functionality combine for the most part, probably by a Diels Alder 
mechanism, to provide a mixture of dibasic and higher polymeric acids. The 
acids with insufficient functionality to react remain as monomers and may 
be wholly or partially removed, for example by distillation. The residue 
after distillation consists of the desired polymeric acids and this 
mixture is used for the preparation of the polyamide resin. In place of 
this method of polymerization, any other method of polymerization may be 
employed whether the resultant polymer possesses residual unsaturation or 
not. The term "polymeric fatty acids" as used herein, is intended to 
include the polymerized mixture of acids obtained, which mixture usually 
contains a predominant portion of dimeric acids, a smaller quantity of 
trimeric and higher polymeric acids, and some residual monomer. 
These polymeric fatty acids may be reacted with a variety of aliphatic 
polyamines for the production of the polyamide. The amidification reaction 
may be carried out under the usual conditions employed for this purpose, 
as will be evident from the examples. Polyamides of this type generally 
have molecular weights varying from 1,000 to 10,000 and are resistant to 
the corrosive action of water, alkali, acids, oils, greases, and organic 
solvents. The melting points vary, depending upon the reactants and the 
reaction conditions. Where aliphatic diamines, such as ethylene diamine, 
are employed for the preparation of the polyamide the resin may melt 
within the approximate range of 100.degree.-120.degree. C., and usually 
within the range of 100.degree.-105.degree. C. 
Higher melting polyamide resins, for example melting within the range of 
130.degree.-215.degree. C., may be made by employing a mixture of 
polymeric fatty acids and other polybasic acids, the latter having at 
least two carboxyl groups which are separated by at least 3 and not more 
than 8 carbon atoms. Typical of these polybasic acids are the aliphatic 
acids, glutaric, adipic, pimelic, suberic, azelaic, and sebacic, and the 
aromatic acids, terephthalic, and isophthalic acids. The melting point of 
the copolymer resin may vary within the range previously indicated, 
depending upon the particular reactants, relative ratios thereof, as well 
as the reaction conditions. 
Low melting polyamide resins melting within the approximate range of 
25.degree.-90.degree. C. may be prepared from polymeric fatty acids and 
aliphatic polyamines having at least 3 atoms intervening between the amine 
groups principally involved in the amidification reaction. These three 
atoms may be carbon atoms or hetero atoms. Typical of the polyamines which 
may be used are diethylene triamine, triethylene tetramine, tetraethylene 
pentamine, 1,4-diaminobutane, 1,3-diaminobutane, hexamethylene diamine, 
3-(N-isopropylamino)propylamine, 3,3'-imino-bispropylamine, and the like. 
A preferred group of these low melting polyamides are derived from 
polymeric fatty acids, and diethylene triamine and are liquid at room 
temperature. 
Suitable such polyamides are commercially available under the trade 
designation of VERSAMID.RTM. Polyamide resins and are amber-colored 
polyamides having a molecular weight ranging from about 3000 to about 
10,000 and a softening point from about below room temperature to 
190.degree. C. and prepared by condensing polymerized unsaturated fatty 
acids (e.g., dilinoleic acid) with aliphatic polyamines such as diethylene 
triamine. 
The preparation of such VERSAMID.RTM. polyamide resins is well-known and by 
varying the acid and/or the functionality of the polyamine, a great 
variety of viscosities, molecular weights and levels of active amino 
groups spaced along the resin molecule can be obtained. Typically, the 
VERSAMID.RTM. polyamide resin have amine values from about 50 to 400; 
Gardner color (max.) of 8-10; and viscosities of from about 1 to 30 
poises. 
Organic Solvents 
Suitable solvents include the aliphatic alcohols and glycols containing up 
to about 6 carbon atoms and at least one OH group. Examples of such 
solvents include methanol, ethanol, propanol, isopropanol, n-butanol, 
iso-butanol, hexanediol, ethylene glycol and propylene glycol. 
Other suitable solvents include the so-called glycol ethers such as tht 
methyl, ethyl and butyl ethers of ethylene glycol or propylene glycol. 
Such glycol ethers are commercially available under the trade designation 
of OXITOL.RTM. such as methyl OXITOL.RTM. glycol ether, CELLOSOLVE.RTM. 
and methyl CELLOXOLVE.RTM., and PROPASOL.RTM. B. 
Still other suitable solvents include the ketones such as acetone methyl 
ethyl keton (MEK), diethyl ketone, methyl iso-butyl ketone (MIBK), etc. 
Cellulose Acetate Butyrate 
The preparation of the cellulose acetate butyrate resins forms no part of 
the instant invention and are available commercially. Accordingly, the 
cellulose acetate butyrate resins (CAB resins) which are suitable for use 
in the present compositions possess the following typical properties: 
______________________________________ 
Butyryl content: 37 to 55% by weight 
Acetyl content: 2 to 15% by weight 
Hydroxyl content*: 1.5 to 2% by weight 
Viscosity Grade 
(ASTM D-1343-54T) 0.01 to 0.5 seconds 
Softening Point: 125.degree. to 200.degree. C. 
______________________________________ 
*approximately one OH group for each four anhydroglucose units 
The instant compositions are conveniently prepared by reacting the 
saturated epoxy resin with an approximately stoichiometric amount of the 
polyamide, although a slight excess of either reactant may be employed 
under certain circumstances. In general, about a 20% excess may be 
employed. To this composition is added from about 5% to about 50% by 
weight of epoxy resin and polyamide of the cellulose acetate butyrate, 
with from about 5% to about 15% by weight being preferred. Sufficient 
organic solvent is used to produce a system having up to 98% by weight of 
binder or vehicle (epoxy resin+polyamide+cellulose acetate butyrate). 
Expressed another way, at least 2% by weight of organic solvent is 
required. Preferably, the solution will contain from about 25% to about 
95% by weight binder or vehicle. 
The reaction is performed at ambient temperatures, i.e., from about 
15.degree. to 30.degree. C., for a period from about 15 to 60 minutes. 
This reaction time or period will sometimes be referred to herein as the 
"sweat-in" time. 
Before or during a suitable sweat-in period, conventional additives such as 
pigments, fillers, etc., may be added and resulting formulation applied by 
suitable means to a substrate and the coacting or film cured. 
In general, if a pigmented system is desired, one or more pigments 
conventionally employed in surface coatings may be added to produce a 
pigment volume concentration of from about 15 to 25%. 
The present coating compositions may be applied to a suitable substrate by 
any suitable means such as spraying, dipping, painting, doctor blade, or 
the like. The thickness of the film will depend on many circumstances, 
particularly the end-use of such baked coatings, e.g., as primers or as 
surface coatings. 
The applied coating can be cured at ambient temperature or at higher 
temperatures. In general, the film will cure in 7 to 10 days at ambient 
(room) temperature, i.e., so-called "air-dry" cure. On the other hand, the 
film can be conveniently cured by baking at 80.degree. to 120.degree. C. 
for 10 to 30 minutes. A very acceptable cure cycle is 20 minutes at 
93.degree.-95.degree. C. 
The advantages of the instant compositions are illustrated by the following 
illustrative examples. The reactants, their proportions, and other 
specific ingredients are presented as typical and various modifications 
can be made in view of the foregoing disclosure and discussion without 
departing from the spirit or scope of the disclosure or of the claims. 
Unless otherwise specified, parts and percentages are by weight. 
Polyether A is a diglycidyl polyether of hydrogenated 
2,2-bis(4-hydroxyphenyl)propane having an average molecular weight of 426 
and a weight per epoxy (WPE) of 234. 
Polyamide A is VERSAMID.RTM. 1540 [a commercially available polyamide 
derived from the condensation of a dimer fatty acid and a polyamine having 
an amine value of 370-400, a Gardner color of 3 max and a viscosity at 
40.degree. C. of 25-40 poise, a viscosity at 25.degree. C. or 120 poise 
and a specific gravity at 25.degree. C. of 1.03 (8.58#/gal)]. 
The cellulose acetate butyrate (CAB) resins had the following properties: 
______________________________________ 
CONTENT 
Viscosity 
CAB Hydroxyl, % w 
Butyryl, % w 
Acetyl, % w 
Grade 
______________________________________ 
CAB-1 1.7 37.0 13.0 0.1 
CAB-2 1.6 53.0 2.0 0.2 
CAB-3 1.6 53.0 3.0 0.01 
CAB-4 50/50 mixture of CAB-2 + CAB-3 
______________________________________

EXAMPLE I 
This example illustrates the properties of enamels prepared from the 
instant compositions. 
In a 1-quart container were mixed the following: 
______________________________________ 
Component Part by Weight 
______________________________________ 
TiO.sub.2 447.2 
Polyether A 250.5 
Suspending/Thixotropic Agent 
(Bentone 27-NL Industries) 
5.0 
Methanol 1.7 
Flow Control Agent (Urea-Formaldehyde 
Resin - BEETLE 216-8 -- American Cyanamid) 
12.5 
______________________________________ 
The above mixture was dispersed in a Cowles dissolver at 4,000 rpm for 10 
minutes. This blended composition is hereinafter referred to a "Mill Base 
A". 
To 716.9 parts by weight of "Mill Base A" were added several CAB resin 
solutions (and one control) having the following compositions: 
______________________________________ 
CAB RESIN SOLUTION, 
Con- TS BY WEIGHT 
Components trol A B C D 
______________________________________ 
CAB-1 -- 62.6 -- -- -- 
CAB-2 -- -- 62.6 -- -- 
CAB-3 -- -- -- 62.6 -- 
CAB-4 -- -- -- -- 62.6 
Polyether A 40.4 -- -- -- -- 
MEK 13.9 13.9 13.9 13.9 13.9 
BUTYL OXITOL.RTM. 
15.6 15.6 15.6 15.6 15.6 
glycol ether 
n-Butyl Alcohol 
44.5 44.5 44.5 44.5 44.5 
Toluene 70.6 70.6 70.6 70.6 70.6 
185.0 207.3 207.3 207.3 207.3 
______________________________________ 
To each of the above mixtures were added the following: 
______________________________________ 
CAB Resin Solution 
Control + 
Component Mill Base A, Pbw 
Mill Base A, Pbw 
______________________________________ 
VERSAMID 1540 137.7 159.9 
MEK 9.2 9.2 
Butyl OXITOL glycol 
10.4 10.4 
ether 
n-butanol 30.6 30.6 
Toluene 46.7 46.7 
234.6 256.8 
______________________________________ 
The enamel had the following properties: 
______________________________________ 
Pigment to Binder ratio of 1:1 
Total Solids 78.6% w 
Total Solids 64.5% v 
Pigment Volume (PV) Concentration 21.3% v 
______________________________________ 
The epoxy enamels modified with the CAB resins are hereinafter designated 
as Enamel A, B, C, D and Control, corresponding to the enamels containing 
CAB-1, etc. 
The above enamels were allowed to set for 1 hour and then applied to cold 
roll steel panels and dried at room temperature. 
The drying times for the respective enamels were as follows: 
______________________________________ 
Enamel Set to touch, Cotton-free, hours 
______________________________________ 
A 0:10 3:40 
B 0:35 3:20 
C 3:00 &gt;5:00 
D 0:20 &gt;5:00 
Control &gt;5:00 &gt;5:00 
______________________________________ 
EXAMPLE II 
The procedure of Example I were repeated wherein the amounts of CAB resins 
were varied while maintaining the Pigment to Binder Ratio and solids 
content the same as Example I. Accordingly, Mill Base A composition was 
adjusted by reducing the amount of Polyether A and flow control agent with 
a corresponding increase in the CAB resin to form other Mill Base 
compositions as follows: 
______________________________________ 
Mill Base Compositions 
Components B C D 
______________________________________ 
TiO.sub.2 447.2 447.2 447.2 
Polyether A 262.7 271.8 281.1 
Bentone 27 5.0 5.0 5.0 
Methanol 1.7 1.7 1.7 
Beetle 216-8 
13.1 13.6 14.1 
______________________________________ 
To the above Mill Base compositions were added the following CAB Resin 
Solutions as hereinafter described: 
______________________________________ 
CAB Resin 
Solution, Parts by Weight 
Components E F G H 
______________________________________ 
CAB-2 62.6 43.5 29.0 14.5 
MEK 26.9 26.9 26.9 26.9 
Butyl OXITOL glycol ether 
13.9 13.9 13.9 13.9 
IPA 15.3 15.3 15.3 15.3 
Toluene 88.5 88.5 88.5 88.5 
______________________________________ 
Various curing agent mixtures for blending with the previously prepared 
Mill Base/CAB Resin Solution blends were prepared as follows: 
______________________________________ 
Curing Agent, Parts by Weight 
Component A B C D 
______________________________________ 
VERSAMID 1540 137.7 144.4 149.5 154.5 
MEK 18.0 18.0 18.0 18.0 
Butyl OXITOL glycol ether 
9.2 9.2 9.2 9.2 
IPA 10.3 10.3 10.3 10.3 
Toluene 59.3 59.3 59.3 59.3 
______________________________________ 
Enamels were then prepared from the above compositions as follows: 
______________________________________ 
Composition 
Mill Base CAB Resin Solution 
Curing Agent 
Enamel 
______________________________________ 
A E A E 
B F B F 
C G C G 
D H D H 
______________________________________ 
Films were prepared from the above enamels (after an induction period of 1 
hour) as in Example I. Drying times of the enamels are as follows: 
______________________________________ 
Enamel Set to Touch, hours 
______________________________________ 
E 0:30 
F -- 
G 2:00 
H 4:54 
Control &gt;6:00 
______________________________________