Note: Descriptions are shown in the official language in which they were submitted.
80~
SELF-CROSSLINKA8LE ~LECTROCOA~ RESINS PREPARED
BY ROOM TEMPERATURE REACTIONS OF EPOXY RESINS AND
POLYAMINES CONTAINING PRIMA~Y AND TERTIARY AMINE GROUPS
Technical Field
This invention relates to water dispersible,
cathodically electrodepositable, self-crosslinkable resins.
More particularly, these resins are amine-~unctional and
epoxide-functional and are the partially crosslinked, room
t~mpecature react~on product of epoxy resins and
polyamines, wherein the polyamines contain at least one
primary and at least one tertiary amine group.
Backqround Art
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The coating of electroconductive substrates by
electrodeposition is an important industrial process. In
this process, a conductive article is immersed as one
electrode in a coating composition made from an aqueous
dispersion o~ film-forming polymer. An electric current is
passed between the acticle and a counter electrode in
electrical contact with the aqueous dispersion until a
desired amount of coating is produced on the article. The
article to be coated can be made the anode or the cathode
depending upon the ionic nature of the coating system.
Cationic coating compositions generally are
derived from resinous compositions containing a basic
nitrogen atom which can be neutralized with an acid and
then be dissolved or dispersed ln water. Sufficient basic
nitrogen atoms should be present so that the dispersibility
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or solubility can be obtained with a minimum amount o~
acid.
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The most commonly employed type of cathodically
electrodepositable resins are made by ceacting polyepoxide
resins with amines at elevated temperatures, as exemplified
by U.S. Patent 4,137,140 to Belanger and U.S. Patent
4?182~ 831 to Hicks. Belanger teaches forming an
electrocoat resin by reacting polyepoxides with polyamines
and then modifying the product by reaction with a
monoepoxide or a monocarboxylic acid. In the Hicks patent,
the electrocoat resin is taught to be the reaction product
of polyepoxides, a mixture of primary amines, and a
monoepoxide. As illustrated by these patents, when forming
this type of resin the amount o~f amine reacted with the
epoxy group containing material is generally at least that
amount necessary to react all the epoxide groups and form a
hydroxyl amine resin. However, since these resins contain
essentially no unreacted epoxide groups available for later
crosslinking the amine during curing, they require a
crosslinking agent which is capable of reacting with the
hydroxyl or amine functionality of the resin duriny curing
to form a thermoset film. The crosslinking agent may be
present in the coating bath so as to codeposit with the
resin or it may be incorporated into the resin molecule.
Hicks and Belanger teach oodepositing the resin with a
ceosslinker such as an aminoplast or phenoplast resin. On
thè other hand, Jerabek et al in U.S. Patents 3,922,253 and
3,947,338 disclose reacting a partially block isocyanate
- with the epoxy resins and amines so as to incorporate the
crosslinker into the resin molecule. That electrocoat
resin product is thus able to self-crosslink during baking
to form a thermoset film.
Binders for cathodic electrodeposition have been
prepared by simply combining epoxy resins with amine
compounds. However, aqueous dispersions of these binders
are very unstable, becaue of the presence of free
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(unreacted) epoxide groups~ Thus, these two component
compositions are less than desirable for use as
electrodepositable coatings. Such compositions are taught
by Munn et al in British Patent 1,235,975 and in Room
Temperature Curing Electrodeposited Coatings, A.G. North,
J. Oil Colour Chem. Assoc., 53 (1970) 353. While it is
generally recognized in these references that stability of
the compositions in the coating bath is usually limited to
a few hours, one advantage of this type of coa ing, when
compared to prior art electrodepositable coatings, is
taught to be its ability to be cured at low temperatures,
e.g., room temperature.
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DiscIosure of the Invention
The coating compositions of this invention are
cathodically electrodepositable and are characterized in
that they comprise an aqueous dispersion of
self-crosslinkable resin which contains amine groups and
epoxide groups, the resin being prepared by reacting (A)
epoxide cesin having, on average, more than one and up to
about two epoxide groups per molecule and an epoxide
equivalent weight of between about 400 and about 4000,
preferably between about 450 and about 2000, with ~8)
polyamine containing at least one primary amine group and
at least one tertiary amine group per molecule and no other
groups capable of reacting with the epoxide groups. The
polyamine preferably contains a fatty portion which
comprises between about 12 and about 36 carbon atoms. The
epoxy resin and the polyamine are combined and reacted in
the presence of an organic solvent in which they are
mutually soluble~ The reaction solution mixture comprises
(i) a total of between about 70 and about 25 weight percent
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of reactants ~A) and (B) and between about 30 and about 75
weight percent solvent. The epoxy resin and the polyamine
are reacted in solution in amounts so as to provide between
about 0.25 and about l.0, preferably between about O.S and
about 1.0 primary amine groups of (a) for each epoxide
group of (A). The reaction is carried out at room
temperature~ i.e., at between about 18 and about 33C,
preferably between about 21 and about 27C, for a period
of time so as to react between about 20 and about 50
percent of the epoxide groups of the epoxy resin with
; active amine hydrogens to form partially crosslinked,
self-crosslinkable resin. This partially crosslinked,
self-crosslinkable resin has a weight average (Mw)
molecular weight of between about 1300 and about 12,000,
preferably between about 2400 and abou~ 6500.
In order to substantially limit further reaction
between the epoxide and amine groups, the amine groups of
the reaction mixture are neu~ralized with a water soluble
acid in an amount sufficient to neutralize at least S0
percent, preferably greater than 90 percent, most
preferably, essentially all of the amine groups present in
the mixture. The resin is then dispersed in water to form
a cathodically electrodepositable coating composition. The
~- coating composition may include such commonly mployed
materials as plasticizing agents and catalysts. While
crosslinking agents such as aminoplast resins or blocked
isocyanates may also be included in the coating composition
in a limited amount, it is preferable that such
crosslinking agents not be included in the composition.
~ 30 The coating composition may be cathodically
; electrodeposited on a metal substrate and subjected to
baking, during which it crosslinks to form a thermoset
film.
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Advantageously, these self-crosslinkable resins
when used, for example, as a primer coating on steel
possess exceptional adhesion to the steel and thus offer
excellent corrosion protection for the steel.
Yet another advantage of the partially crosslinked
resin of this invention is that they display excellent
stability in the coating bath. It has been found that
coating baths made according to the invention of this
application, wherein all the amine groups have been
neutralized, are stable in excess of six weeks and that
coatings made from these baths have excellent film qualilty
and corrosion resistance.
Significantly, the resins of this invention offer
t~e advantage that they are made by simpler methods of
manufacture and comprise simpler compositions than those of
fully epoxide reacted resins conventionally employed in
primer coatings. As described above, these conventionally
employed resins additionally need a crosslinking agent for
curing. Thus, the resins of this invention offer cost
advantages in their manu~acture, particularly since they
are made from materials rea~ted at room temperature,
wherein the reaction mixture need not be agitated during
the reaction process.
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Best Mode For Carryin~ Out The Invention
The invention of this application is directed to a
cathodically electrodepositable, self-crosslinkable resin
dispersed in water as has been describ~d briefly above.
In order to form the electrodepositable,
self-crosslinkable resin of the invention, an epoxy resin
and a polyamine are partially reacted at room temperature
in an organic solvent for both reactants. The reaction
m1xture is allowed to stand or may be stirred, although
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stirring is not necessary, for a period of time at room
temperature, so as to allow the reaction to take place.
When the desired number of epoxide groups have
reacted,about 20-50 percent, (corresponding to a reaction
time period of between about 12-36 hours), the reaction
mixture is neutralized with a water soluble acid so as to
limit the ongoing reaction between the epoxide and the
reactive amine groups of the reactants. The amount of acid
employed must be sufficient to neutralize at least 50
percent, preferably greater than 90 percent, most
preferably, essentially all of the amine groups in the
mixture~ which amine groups are either present on the
resin or on unreacted polyamine. However, it appears that
essentially all of the polyamine is incorporated to some
extent during the reaction period into the
~ self-crosslinkable resin by reaction of the polyamine with
; some of the epoxide groups of the epoxy resin. The
neutralized self-crosslinkable resin mixture is -then
dispersed in water to form a cathodically
electrodepositable coating composition comprising the
self-crosslinkable resins.
The epoxy resins useful in forming the
self-crosslinkable resin of this invention have, on
average, moce than one and up to about two epoxide groups
per molecule. These epoxy resins have an epoxide
equivalent weight of between about 400 and about 4000,
preferably be~ween about 450 and about 2000. Such
polyepoxide resins may be derived from a dihydric phenol or
i~ a dihydric alcohol and an epihalohydrin. Examples of
epihalohydrins are epichlorohydrin, epibromohydrin and
epiiodohydrin with epichlorohydrin being preferred.
Dihydric phenols and dihydric alcohols are exemplified by
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resorcinol, hydroquinone, Bisphenol A, p,p'-dihydroxy
; benzol phenone, p,p'~dihydroxy phenol, p,p'-dihydroxy
diphenol ethane, bis-(2-hydroxy naphtha) methane,
1,5-dihydroxy naphthaline, ethylene glycol, propylene
glycol, 1,4-butane diol, hydrogenated Bisphenol A,
1,4-cyclohexane diol, 1,3-cyclopentane diol, cyclo-
hexane dimethanol, and the like. These polyepoxide
resins are well known in the art and are made in the
desired molecular weights by reacting the epihalohydrin
-10 and the diols in various ratios, or by reacting a
dihydric phenol with a lower molecular weight poly-
epoxide resin. Preferred polyepoxide resins are the
glycidyl polyethers of Bisphenol A having the equivalent
weight stated above. Examples of epoxy resins which are
commercially available and suitable for use in this
invention include Epon* lOOlF, 1002F, 1004F, 1007F,
lOO9F, available from and a trademark of Shell Chemical
Company tHoustcn; Texas), Araldite* 6084, 6097, 6099
7072 and 7097 available from Ciba-Geigy (Ardsley, N.Y.~,
and DER* 661, 664, 667 and 669 available from Dow
Chemical Company (Midland, ~ichigan). Mixtures of these
epoxy resins may also be employed as the epoxy resin
reactant useful in forming the self-crosslinking resin
of this invention.
The polyamines used in this invention contain at
least one primary amine group and at least one tertiary
amine group per molecule. The polyamine may also
contain secondary amine groups. Preferably, the
polyamine contains two primary amine groups and, only
one tertiary amine group. During the formation of the
self-crosslinkable resin, reaction will take place
between active amine hydrogens of the polyamine and
epoxide groups of the epoxy resin. In a preferred
embodiment, the polyamine, is a fatty polyamine, wherein
the fatty portion of the fatty polyamine comprises
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between about 12-36 carbon atoms, preferably between
about 12-18 carbon atoms, most preferably between about
16 18 carbon atoms. The fatty portion may be skraight
chain or branched, and may be substituted with
non-interfering functionality.
The polyamine may not contain any other type of
functionality which could react with the epoxide groups
of the epoxv resin. That is, no other functionality
should be present on the polyamine which would interfere
with the reaction of the amine and epoxide groups of the
reactants of the mixture. However, groups not reactive
with epoxide may be included in the polyamine. One such
group which may be present is amide.
Preferably, the polyamine has a weight average (Mw)
molecular weight of between about 300 and about 1000,
more preferably between about 350 and about 550.
Suitable commercially available polyamines which may be
employed in this invention include 3-dimethylamino
propylamine and 3-diethylamino propylamine with 3-
dimethylamino propylamine being preferred. Other
polyamines ~may include diethylaminobutylamine,
dibutylaminoethylamine, etc. r (available from BASF
Wyandotte Corp., Wyandotte, Michigan). Suitable
commercially available fatty polyamine which may be
;~ 25 employed in this invention include N-Tallow
Bis(aminopropyl) amine (XC95*) from Henkel Corporation,
Minneapolis, Minn. Mixtures of polyamines as described
above could also be employed in this invention as the
polyamine reactant.
The epoxy resin and the polyamine are combined in
the reaction mixture in amounts so as to provide between
about 0.25 and about 1.0, preferably between about 0.5
and about 1.0 primary amine groups present on the
polyamine resin for each epoxide group present on
* - Trademark
the epoxide resin. The reactants are dissolved in an
organic solvent in which both reactant are soluble. The
reaction mixture comprises (i) between about 30 and
about 75 weight percent solvent and (ii) a total of
between about 70 and about 25 weight percent reactants
(A) and (B), preferably between about 40 and about 60
weight percent solvent and between about 60 and about 40
weight percent total of reactants (A) and (8). The
reaction temperatuxe of the mixture is between about 18
and about 33C, preferably between about 21 and about
27C.
Suitable solvents incIude alcohols, ethers,
ketones, as well as aromatic hydrocarbons and
phthalates. Exemplary of the alcohols are butanol,
isopropanol, hexanol, etc. Ethers which may be used
include, but are not limited to, propylene glycol methyl
ether, dipropylene glycol methyl ether and ethylene
glycol ether acetate, with the Cellosolve* type ethers
being preferred. Ketones which may be so employed
include methyl butyl ketone, methylisobutyl ketone,
methyl propyl ketone, methyl ethyl ketone, etc. Useful
aromatic solvents incIude xylene, toluene, ethyl
benzene, etc. Phthalates useful as solvents in this
invention include dimethyl, dipropyl, dibutyl, and
dioctyl phthalates. Preferably, blends of such solvents
are employed as the solvent in this invention. While
solvents which may be used have been disclosed above,
this disclosure is not meant to be limiting. Other
suitable organic solvents which may be used to dissolve
the reactant and form the reaction mixture will be
apparent to those skilled in the art.
As has been stated above, the reactants are reacted
for a period of time so as to react between about 20 and
about 50 percent of the epoxide groups present in the
reaction mixture. The completeness of
* - Trademark
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the epoxide reaction can be cletermined by means such as
Infrared Absorption. At the desired percent conversion
of epoxide groups, the amine groups present in the
reaction mixture are neutralized with water soluble
5 acid. The amount of acid used must be more than that
needed to simply disperse the resin. Rather, sufficient
acid must be employed so as to neutralize at least 50
percent, preferably greater than 90 percent, most
preferably, essentially all of the amine groups in the
` 10 mixture. This neutralizing substantially limits or, in
the most preferred embodiment where essentially all the
amine groups are neutralized, stops any further reaction
of amine and epoxide groups. Acids which may be so
employed include water soluble monocarboxylic acids such
15 as formic, propionic, lactic, acetic, and butanoic, just
to name a few, with lactic acid being preferred.
Optionally, other commonly employed materials may
~ be included in ~he coating composition comprising the
f dispersed self-crosslinkable rasin disclosed in this
20 application. These optional constituents are generally
mix d into the reaction mixture prior to the addition of
the water soluble acid althou~h they may be added after
~r ~ the addition of the acid. Such optional constituents
include, but are not limited to, plastlcizers, pigments,
25 catalysts and crosslinking agents. Such plasticizers
include dioctylphthalate, polyhydroxy polyethers (e.g.,
G ~
~ ~ Eponol* 52B40 or ~panol* 57B40, Shell Chemical, Houston,
`~ Texas~, hydroxy acrylate (e.g., G-Cure* 868 Rohm & Haas
Company, Philadelphia, Pa), etc. Pigments when included
30 generally comprise up to about 4 weight percent of the
coating composition bath. Crosslinking agents may
include blocked polyisocyanates, aminoplast resins or
; phenoplast resins. Thus, in addition to the resins
ability to self-thermoset, the amine and hydroxyl group
35 of the resin (the hydroxyl being produced by the
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amine~epoxide reactions) can crosslink wi.th blocked
isoc~anate at elevated temperatures to form polyurethane
and polyurea. The hydroxyl groups can
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also crosslink with aminoplast or phenoplast crosslinkers
at elevated temperatures. However, while c~osslinking
agents may be included in the coating composition, it is
preferred not to employ any additional crosslinking agents.
It has been found tha~ the cationic self-crosslinking resin
coatings of this invention, when used without additional
crosslinking agents, posess greater throwing power than
uch cationic coating compositions which contain additional
crosslinking- agents~ If however, additional crosslinking
agents are employed, they would preferably not comprise
more than 6.5 weight percent of the coating bath.
9election of such commonly employed crosslinking agents of
the types mentioned above, will be well within the skill of
one in the art.
lS The coatings comprising the dispersed resin of
this invention may be coated onto metal substrates by
cathodic electrodeposition methods well known to those
skilled in the art. Generally, voltages of between about
300 and about 400 volts are employed~for between about 2
`; 20 and about 3 minutes so as to provide coatings betwèen about12 and about 40 microns~ Selection of optimal coating
condition would be well within the skill of one in the art,
~ and those described above are not meant to be limiting to
;~ the invention of this application.
The invention will be further understood by
referring to the following detailed examples. It should be
understood that the specific examples are presented by way
of illustration and not by way of limitation.
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12~30~34;2
12
Example 1
A fatty tertiary amine group containing self-
crosslinking amine epoxy cathodic electrocoat primer was
prepared as follows:
(A) 445 grams Epon 1007Fl and
(B) 111 grams Epon lOOlFl were dissolved in a
mixture of
~C) 414 grams Dowanol DPM2,
(D) 114 grams Hexyl Cellosolve, and
10 (E) 130 grams Dioctylphthalate.
(F) 44 grams N-Tallow bis(amino propyl) amine
having an amine equivalent weight of
95 were reacted with the resin
solution (A) - (E) for 16 hours at
room temperature (about 22-25C).
Immediately afterwards
(G) 152 grams Eponol 53B40 (Shell Chemical) were
added to the reacted resin from (F),
and immediately thereafter
20 (H) 47.3 grams 88% lactic~acid were worked into the
reacted resin mixture from (F) to
neutralize all the amine groups in
the reaction mixture.
(I) 30 grams carbon black were worked into (H)
using various blending methods (ball
milling, roll milling, etc.). The
pigmented resin mixture from (I) was
dispersed with deionized water to a
4000 gram coating bath.
The bath was placed in a stainless steel container
; and stirred for at least 24 hours. A zinc phosphated
steel panel cathode electrode was coated at 350 volts
for 2 minutes at 23C. After the panel is baked at
180C air temperature for 25 minutes, the panel had a
17.8 micron thick coating. Additional panels were
similarly coated and baked and then salt spray tested
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according to ASTM Test Method B-117. The panels after
500 hours testing showed no signs of failure. The bath
from (I) showed excellent stability in excess of six
weeks and provided cured coatings with excellent film
quality and corrosion resistance.
Trademark of Shell Chemical Company
2Trademark Dow Chemical Company, Midland, MI.
Example 2
A fatty tertiary amine group containing self-
crosslinking amine epoxy cathodic electrocoat primer
paint was prepared as follows:
(A) 387 grams Epon lOO9F1 and
(8) 166 grams Epon lOOlF1 were dissolved into a
mixture of
(C) 414 grams Dowanol DPM2,
(D) 114 grams Hexyl Cellosolve, and
tE) 130 grams Dioctylphthalate.
(F) 47 grams F a t t y a m i n e , N - T a l l o w
bis(aminopropyl) amine were reacted
at 23C with the resin solution (A)
; - ~E) for about 16 hours.
Immediately afterwards
(G) 152 grams Eponol 53B-40 (Shell Chemical) were
~ added to the reacted resin from (F).
(H) 47 grams 88~ lactic acid w@re worked into the
~ mixture from (G) to neutralize all
- the amine groups.
(I) 60 grams Alcoblak 3383 carbon black pigment
were worked into ~he neutralized
~ reaction mixture from (H).
;~ Deionized water was worked into the
pigmented resin mixture from (I) to
prepare 4000 grams electrocoat bath.
` 35 The bath from (I) was placed in a stainless
steel container and stirred for at least 24 hours. As
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in Example 1, a zinc phosphate panel used as the
cathode, was coated in the bath at 300 volts for 2 ~
minutes. After baking the panel at 180C ~or 25
minutes, the panel had a 22.5 micron thick coating.
Additional panels that were coated and baked as above
showed no signs of failure after 500 hours salt spray
testing.
1Trademark of Shell Chemical Company
2Trademark Dow Chemical Company, Midland, MI.
3Trademark of Borden Chemical, Cincinnati, Ohio.
Example 3
The same bath was prepared as in Example 2
except that the lactic acid of (H) is replaced with 27.4
gram of acetic acid.
Zinc phosphated panels were coated as in
Example 2. After baking the coated panels for 25
minutes at 150C, the panels had 20.5 micron thick
coatings. The panels showed 500 hours resistance to
salt spray corrosion.
Example 4
A cathodic self-crosslinking electrocoat paint
~ was prepared as follows:
;~ (A) 545.5 grams Epon 1004El are dissolved in a
mixture of
25 (8) 414 grams Propylene glycol methyl ether,
(C) 114 grams Hexyl Cellosolve, and
(D) 130 grams Dibutylphthalate.
(E) 54.5 grams N-Tallow bis(amino propyl) amine are
reacted with the resin solution (A)
- (D) for 18 hours at about
20-25C. Immediately afterwards
(F) 76 grams Eponol 52B-40 (Shell Chemical) are
~ added to the resin from (E).
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Immediately a~terwards
(G) 58.7 gxams 886 lactic acid are worked into the
resin mixture from (F) to neutralize
all the amine groups in the mixture.
30 grams Carbon black are worked into the
resin from (G). Deionized water is
worked into the resin mixture from
(H) until a 4000 gram bath is
yielded.
10 The bath ~rom (H) is placed into a steel
container and placed under mild agitation by stirring.
Zinc phosphate panels, electrocoated at 300 volts for 2~
minutes at 27C and baked at 180C for 20 minutes, had
18.5 micron ;thick coatings. The bath also displayed
excellent corrosion~protection for more complex shaped
lectrocoated zinc phosphated articles~
Trademark of Shell Chemical Company
Example 5
A fatty tertia ry am ine reacted
self-crosslinkable epoxy cathodic electrocoat primer
paint was prepared as follows: ~
(A) 545.5 grams Epon 1004Fl were dissolved in a
mixture of
(B) 414 grams Dowanol DPM2,
25 (C) 114 grams ~ Hexyl Cellosolve, and
(D) 130 grams Dioctylphthalate.
(E) 54~.5 grams N-Tallow ~bis(amino propyl) amine
were reacted with the resin mixture
from (Aj-(D) for 16 hours at 23~C to
about 25C. Immediately afterwards
(F) 61.5 qrams Desmodur 24123, blocked diisocyanate
crosslinking agent (Mobay Chemical
of Pittsburgh, PA.) were worked into
the reaction mixture from (E).
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(G) 34.3 grams Acetic acid are worked into the
resin from (F) to neutralized the
amine groups.
(H) 30 grams Carbon black are worked into the
resin from (G). Deionized water is
added to the paint paste from (H)
until a 4000 gram emulsion paint
bath is obtained.
The bath from (H) was placed into a stainless
steel container. As in Examples 1 through 4, a zinc
phosphated steel panel was cathodically electrocoated
and then baked at 180C for 25 minutes, the panels had a
15.3 micron thick coating. The coatings provide
excellent resistance against corrosion after being
exposed to salt spray test conditions for 500 hours.
Throw power tests conducted on a scaled up batch of the
; paint showed lower throw power than its
self-crosslinking counterpart, shown in Examples
through 4.
lTrademark of Shell Chemical Company
2Trademark Dow Chemical Company, Midland, MI.
;~ 3Trademark Mobay Chemical Company, Pittsburgh, PA
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A fakty tertiary amine reacted epoxy cathodic
electroaoat paint primer was prepared as in Example 5,
except the blocked diisocyanate crosslinker in (F) of
Example 5, was replaced by a urea formaldehyde resin
Beetle* 80 crosslinking agent, manufactured by American
Cyanamide of Wayne, New Jersey.
The bath prepared in Example 6 is placed in a
stainless steel container and agitated by mild stirring.
As in Example I through 5, zinc phosphated steel panel
electrode cathodes are coated at 300 volts for 2B
minutes and 23-25C. After baking at 180C for 25
minutes, the panels had 20.3 micron thick coatings which
passed accelerated laboratory test for electrocoat
~ 15 primer paints.
; Example 7
;~; A fatty tertiary amine group containing
self-crosslinking unstable amine epoxy cathodic
electrocoat primer was prepared as follows:
20 (A) 445 grams Epon 1007Fl and
(B) 111 grams Epon lOOlF1:were dissolved in a
-~ mixture of
(C) 414 grams Propylene glycol methyl ether,
(D) 114 grams Hexyl Cellosolve, and
(E) 130 grams Dioctylphthalate.
F) 44 grams N-Tallow bis(amino propyl) amine were
worked into the resin solution from
(A) - (E) as in Example 1. This
reaction mixture was permitted to
stand for 18 hours at 23-25C.
Immediately afterwards,
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~G) 23.7 grams 88% lactic acid ~that amount of acid
required to neutrali2e about half of
the amine groups o the mixture) were
blended into the resin mixture from (F).
(H) 30 gEams Carbon black are blended into the
partially neutralized resin from (G).
Deionized water was worked into the
pigmented, partially neutralized paint
from (H), to give a 4000 gram coating
bath.
The bath from (H) was placed into a stainless
steel contalner and stirred for at least 24 hours. A zinc
phosphated steel panel cathode was coated at 350 volts for
2 minutes and then baked at 180C for 25 minutes. The
baked panel had a 20 micron thick, glossy, smooth, coating
which showed~ no signs of; failure a:fter 500 hours salt
corrosion testing. After the bath was stirred for about 3
week~s,~ ano~ther~ æinc~ phosphated steel panel cathode
; electrode was coated in the bath.~ The baked panel (180C
~or 25 minutesl ylelded a non-uniform, thick, rough,
non-glossy coating. The~coating also showed poor adhesion
to the steel substrate and failed 500 hour salt spray
corrosion testing.
Trademark of Shell~Chemical Company
Industrial_APplicability
It should be apparent from the foregoing, that the
cathodically electrodepositable coating compositions of
this invention find application as, for example, primer
coatings for`metals to prevent corrosion.
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In view of the disclosure, many modifications of
this invention will be apparent to those skilled in the
art~ It is intended that all such modiications which ~all
within the true scope of this invention be included within
the terms o~ the appended claims.
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