Note: Descriptions are shown in the official language in which they were submitted.
-~ 122`7/1310
1085079
!
FIELD OF INVENTION A~D BACKGROU~D
.
The present invention is directed to the preparation ofJ and coat-
ing compositions which are water-dilutable upon neutralization with acids,
The coating compositions are electrically depositable at the cathode of an
electrodeposition system and will crosslink through thermal polymerization,
Electrodeposition of synthetic resins and plastics, although known
for quite some time, has gained technical importance as a coating proces3
in only recent years. The coating compositions or binders primarily used
commercially for electrodeposition contain polycarboxylic acid resins neu-
tralized with bases. The products deposit at the anode of an electrodeposition
system. Owing to the acidic character of the resins, they are sensitive to
corroding influences exerted by salts and particularly by alkalis. Further-
more, coatings of the aforesaid compositions tend to undergo spot discolor-
ation or undergo other chemical changes as a result of the metal ions
anodically dissolved from the anode~ Accordingly, there is a desire to use
coating compositions which will deposit at the cathode of an electrodeposition
system.
There are a substantial number of binders disclosed in the liter-
ature carrying groupings neutralizable with acid9 which can be deposited on
cathodically wired objects of an electrodeposition system, Many have dis-
advantages prirnarily due to the need to have crosslinking additives in the
coating compositions which adversely affect film characteristics. Recently,
however, coating compositions have been provided which are self-cross-
linking through thermal polymerization. These selE-crosslinking binders
include bmders comprising -
- 3
.
- .. . . . ............ . - . .
~, ' , . . ' , . ' : ,. . . .
1085079
~A) the reaction products of diepoxy compounds with alpha,
beta-unsaturated acids and, optionally, long chain fatty acids, and basic
monoisocyanates;
(B) reaction products of diepoxy compounds with monoamines and,
optionally, fatty acids, and unsaturated monoisocyanates; and
~C) two ~oles of a diepoxy compound plus one mole of a primary-
tertiary or secondary~secondary diamine plus two moles of an alpha,beta-
unsaturated monocarboxylic acid and, optionally, an unsaturated fatty acid,
plus an unsaturatet monoisocyanate.
The aforesaid binders are highly desirable due to their ability to self-cross-
link through the presence of alpha,beta-unsaturation; their being water-
soluble in the presence of acids due to the basic nitrogen atoms, and their
ability to provide excellent films with good performance characteristics,
particularly regarding resistance to corroding influences. At times, how-
ever, these binders provide films having certain deficiencies as a result of
poor lev01ing of the coating composition on certain substrates and a gen-
erally reduced adhesion on certain substrates, particularly untreated steel.
OBJECTS OF THE INVENTION AND GENER~L DESCRIPTION
'I It has now been found that the above-noted disadvantages with
2- respect to leveling and lack of adhesion can be eliminated by emulsifying the
water-soluble cationic binders with select di- and/or triurethanes. It has
been found that not only is the leveling and adhesion characteristics of the
binders improved by emulsification with the select di- or triurethanes, but
surprisingly the emulsions obtained, without use of additional emulsifiers,
i have excellent stability even when water diluted for use in coating composi-
', tions to be applied at the cathode of an electrodeposition process. The
added select di- or triurethanes, however, exert a favorable influence on the
viseosity of the coating compositions and on the curing characteristics of
films deposited from the coating compositions, namely, enhanced corrosion re-
; 30 sistance, in addition to the improved leveling characteristic and adhesion
of the film to diverse substrates. Furthermore, the addition of the non-
-- 4 --
- ' :
~`~
1085079
water-soluble, fatty acid modified polyester resins permits regulation of
the deposition equivalent which in turn influences the formation of the film
on deposition.
The present inv0ntion provides a coating composition which is ::
; cathodically deposited when used in an electrodeposition process comprising ;
as the coating binder an aqueous emulsion of
(I) 98 - 50 % by weight of at least one selfcrosslinking cationic
binder based on a modified epoxy compound from the group comprising: ~ :
(A) the reaction products of diepoxy compounds with alpha,beta- :
; 10 unsaturated acids and, optionally, long chain fatty acids, and
: basic monoisocyanates;
(B) reaction products of diepoxy compounds with monoamines and, -
optionally, fatty acids, and unsaturated monoisocyanates;
(C) two moles of a diepoxy compound plus one mole of a primary-tertiary :
or secondary-secondary diamine plus two moles of an alpha,beta-
unsaturated monocarboxylic acid and, optionally, an unsaturated
fatty acid, plus an unsaturated monoisocyanate and
; (II) 2 - 50 % by weight of a urethane obtained by reacting one
isocyanate group of a di- or triisocyanate with a hydroxy ethyl(meth)acrylate
or a hydroxypropyl(~eth)acrylate, and the remaining isocyanate groups with a
saturated or unsaturated aliphatic monohydric alcohol with at least 6 carbon
atoms or a monohydroxyalkoxy(meth)acrylate or a saturated or unsaturated
aliphatic monocarboxylic acid with at least 6 carbon atoms.
i! The present invention also provides a process of preparation of
. cathodically electrodepositable coating compositions which comprises
emulsifying :~
.. (I) 98 - 50 % by weight of at least one selfcrosslinking cationic
~: binder based on a modified epoxy compound from the group comprising:
(A) the reaction products of diepoxy compounds with alpha,beta-
:~' 30 unsaturated acids and, optionally, long chain fatty acids, and basic
-I monoisocyanates;
:'`
- 5 -
. ~
' ~Uii
.
:
` 1085079
~B) reaction products of diepoxy compounds with monoamines and, .
optionally, fatty acids, and unsaturated monoisocyanates;
~C) two moles of a diepoxy compound plus one mole of a primary-tertiary
or seconda~y-secondary diamine plus two moles of an alpha,beta-
unsaturated monocarboxylic acid and, optionally, an unsaturated
fatty acid, plus an unsaturated monoisocyanate and
~ II) 2 - 50 % by weight of a urethane obtained by reacting one
isocyanate group of a di- or triisocyanate with a hydroxy ethyl~meth)acrylate
or a hydroxypropyl(meth)acrylate, and the remaining isocyanate groups with a
saturated or unsaturated aliphatic monohydric alcohol with at least 6 carbon
atoms or a monohydroxyalkoxy(meth)acrylate or a saturated or unsaturated
aliphatic monocarboxylic acid with at least 6 carbon atoms.
The cathodically depositable binders for coating compositions which
can be emulsified with the non-water-soluble, di- or triurethanes are self-
crosslinking binders based on modified epoxy compounds~ and particularly
binders comprising -
(A) the reaction products of diepoxy compounds with alpha,beta-
unsaturated acids and, optionally, long chain fatty acids, ant basic
monoisocyanates;
(B) reaction products of diepoxy compounds with mono-amines and,
optionally, fatty acids, and unsaturated monoisocyanates; and
(C) two moles of a diepoxy compound plus one mole of a primary-tertiary
or secondary-secondary diamine plus two moles of an alpha,beta-unsaturated
monocarboxylic acid and, optionally, an unsaturated fatty acid, plus an
unsaturated monoisocyanate.
The di- or triurethanes emulsified in or with the water-soluble
cationic resins as hereinbefore described have the general formula -
Rl - C - MH - R - (NH - C ~ ~ )n
wherein R represents an aromatic (preferably phenyl ornaphthyl),cycloaliphatic,
or aliphatic (preferably of 2 to 10 carbon atoms) hydrocarbon radical;
Rl stands for a hydroxyethyl(meth)acrylate or a hydroxypropyl-
-- 6 --
,
--~ 1227/1310 1085079
(meth)acrylate radical; ~2 is the radical of a saturated and/or unsaturated
aliphatic monoalcohol with at least 6 carbon atoms and/or an alkyl or
aLkylene radical with at least 6 carbon atoms, and n is an integer of 1 or 2.
The compounds are prepared by stepwise or simultaneous reaction of 1 mole
of a corresponding di- or triisocyanate with 1 mole of hydroxyethyl acrylate
or hydroxypropyl acrylate or of the corresponding methacrylates and 1 or 2
moles of the longer chain saturated or unsaturated monoalcohol or a cor-
responding monocarboxylic acid at 20 to 80 C., optionally in the presence
of an isocyanate inert solvent. Suitable di- or triisocyanates are, e.g.,
aromatic isocyanates, such as 2, 4- or 2, 6-toluene diisocyanate; 4, 4'-
diphenylmethane diisocyanate; or cycloaliphatic isocyanates such as iso-
phorone diisocyanate and cyclohexane-1,4-diisocyanate as well as aliphatic
isocyanates such as trimethyl -hexamethylene-1, 6-diisocyanate and trishexa-
methylene-triisocyanate. As used herein, the di- and triisocyanates~are at
, 15 times referred to as polyisocyanates. Any long chain monoalcohol with at
least 6 carbon atoms in the chain is suitable. Saturated alcohols in this
' group include the n-alcanols, particularly saturated fatty alcohols. Suitable
unsaturated alcohols include, on the one hand, those with an alpha,beta-
ethylenic double bond, such as esters of acrylic and methacrylic acid with
a di- or triol or a polyglycol, and, on the other hand, unsaturated fatty
alcohols. Furthermore, saturated or unsaturated fatty acids with at least
6 carbon atoms are suitable, such as pelargonic acid, lauric acid, stearic
acid, oleic acid, linolenic acid, as well as mixtures of these acids as are
obtained from the natural olls. During the reaction of fatty acids with the
isocyanate, as is known, CO2 is set free.
The basic groups (amine groups) of the cationic components are
~~ - 1227 / 1310
1085079
partially or totally neutralized with organic and/or inorganic acids, e.g.,
formic acid, acetic acid, lactic acid, phosphoric acid, etc. The degree of
neutralization depends upon the properties of the binder employed in each
individual case. In general, sufficient acid is added to provide dispersion
or dilution with water of the coating composition at a pH-value of from 4 to
9, preferably from 6 to 8.
The combination, admixing, or emulsifying of the components
advantageously is carried out in order that the binders are homogenized
thoroughly, optionally at elevated temperature, prior to the addition of
water. Subsequently, the neutralizing agent is stirred in and the batch is
; diluted with water to application viscosity, usually after milling the resin
blend together with pigments and extenders.
The concentration of the binder in water depends upon the para-
meters of the electrodeposition process and may range fror~ 3 to 30 percent
by weight, preferably from 5 to 15 percent by weight. Upon electrodeposi-
tion, the binder of the invention as a vehicle of the aqueous coating composi-
tion is wired to a conductive anode and cathode, the surface of the cathode
being coated with the coating composition. The conductive substrates to be
!
coated may be any of a variety of materials, and particularly metals such
as steel, alu~nnurn, copper, or the like. Other metalized materials or
materials rendered conductive through a conductive coating can be employed.
After deposition, the coating is cured at a stoving temperature of from about
130 to 200 C., preferably 150 to 180 C~ ~ for from about 5 to 30 minutes,
preferab`ly 10 to 25 minutes.
The following examples illustrate the invention without limiting
its scope.
~ 1 227 / 1 3 10
i 1085079
Water-Dilutable Cationic Resins I - III
The composition of the water-dilutable cationic resins are tabu-
lated in Table 1 wherein all quantities are parts by weight. The resins were
prepared as follows:
S A reaction vessel is equipped with stirrer, addition funnel,
thermometer, and reflux condensor. The epoxy compound listed in Table 1,
solubilized in an isocyanate inert solvent such as monoethylene glycol mono-
ethylether acetate (ethylglycol acetate), is charged to the vessel; and, upon
addition of hydroquinone as an inhibitor, if desired, the monocarboxylic acid
10 is added at elevated temperature. The reaction is carried to an acid value of
below 5 mg KOH/g at 100 to 110C. Epoxy resins with low melting points
can be reacted without addition of solvents. The reaction product is mixed
with the basic monoisocyanate intermediate designated in the table and is ;
reacted at 60 to 70 C. to an NCO-value of 0. Access of moixture is avoided
15 during the reaction.
.
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. ,
1085079
TA BLE
Epoxy Resin, Solvent, Monocarbo~ylic Basic
Inhibitor __ Acids Monoisocyanates
1000 EPH B 224 TFS 832 B (iso)
560 AEGLLAC 86. 5 ACS
0.2 HY
II 1000 EPH B -144 ACS 705 B ~iso)
492 AEGLAC
0.2 HY
III 520 EPH C 564 HE 750 A (iso)
465 AEGLAC
0.3 HY
.. . .
,~ EPH B - a solid epoxy resin based on Bisphenol A having a melting
range of 65 to 75C., an epoxy-equivalent of 485 - 510,
and a molecular weight of about 1000.
. .
EPH C - a highly viscous epoxy resin based on Bisphènol A having
an epoxy-equivalent of about 260.
A (iso) - reaction product of 1 mole toluene diisocyanate and 1 mole ;;
dimethyl ethanolamine, 70 percent, dissolved in ethyl-
acetate.
B (iso) - -reaction product of 1 mole toluene diisocyanate and 1 mole
diethylethanolarnine, 70 percent, dissolved in ethyl-
acetate.
HY - hydroquinone (an inhibitor).
TFS - tall oil fatty acids (with about 2 percent rosin acids).
',
~ ACS - acrylic acid.
'~
HE _ semi-ester of tetrahydrophthalic acid and hydroxyethyl
methacrylate.
AEGLAC - ethylene glycol monoethylether acetate.
.,
:-
. j .
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1085079
Non-Water-Soluble Urethane Compounds
Compound A: 174 g (1 mole) toluene diisocyanate is charged
to a reaction vessel and reacted at 25 to 40 C. with 130 g hydroxyethyl-
methacrylate and 350 g tetrapropylene glycol monomethacrylate, the latter
being added dropwise and simultaneously. The batch is finally heated to
70 C. and reacted to an NCO-value of 0.
Cornpound B: Analogous to Compound A, 174 g of toluene di-
isocyanate are reacted with 130 g of hydroxypropylacrylate and 266 g of
linoleyl alcohol.
Compound C: Analogous to Compound A, 504 g of tris-hexa-
methylene triisocyanate are reacted with 130 g of hydroxypropylacrylate
and 532 g of oleyl alcohol.
Compound D: To 174 g (1 mole) of toluene diisocyanateJ 280 g
linseed oil fatty acids are added at 80C., and, after cooling the batch to
40~C., 130 g of hydroxyethylmethacrylate are added dropwise. The batch
is reheated to 70C. and reacted to an NCO-value of 0.
, .
E:xamples 1 - 4
In accordance with Table 2, homogeneous blends of the above-
described water-soluble cationic resins and non-water-soluble urethanes
20 were prepared. Each ioo parts (resin solids) of the resin blends were
; thereafter milled on a triple roll mill together with 22 parts aluminum
silicate pigment, 2 parts carbon black, and 1 part lead chromate. The
paint pastes were mixed with the listed neutralizing agents and diluted with
deionized water to a solids content of 12.5 percent by weight. Electro-
25 deposition of the blends was carried out in a plastic tank with a bath tem-
perature of 30C. and a deposition time of 60 C. The anode was a carbon
'
. . : . .
'
.. . . :
1227 / 1310
1085079
plate. The cathodically wired suhstrate was untreated steel panels or
iron phosphated steel plates as designated in Table 3. The deposited films
were cured at 180 C. for 30 minutes in an air circulation oven.
TA BLE 2
Cationic Resin Polyester Resin Neutralizing Agent
Example I II III A B C D ES MS
- - 30 - - - 0. 08
2 - 95 - - 5 - - - 0. 08
3 - - 82 - - 18 - 0. 08
4 - 78 - - - - 22 0~ 08
The resin quantities referred to are based on 100% resin sdids.
The quantity of neutralizing agent is in moles for 100 g resin solids.
ES - acetic acid.
MS - lactic acid, ;
Deposition conditions and test results are as listed in Table 3
as follow9:
.
;'. . " -.: . ~ .
.
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- 1085079
TABLE 3
_ _ .
u~Untreated Steel Iron-Phosphated Steel
120 201 7.1 250 1-2 ~ 250
2 200 201-2 4.3 275 1 280
i' 1 3 140 221-2 6.6 255 2 250
!
4 180 211-2 5.4 250 1-2 255
,
surface evaluation - I = excellent
2 = slightly wavy
10 salt spray evaluation - 1 = no visible attack
2 = slight corrosion underneath
Adhesion in all cases is from Gt O B to 1 B according to DIN 53 151,
which is excellent.
In the above illustrative examples the cationic water-solubIe
15 resin and non-water-soluble urethane component can be modified and/or the
amounts varied within the bounds herein designated with enhanced results
being obtainable. Additionally. the cationic water-soluble resin can be
replaced with other cationic water-soluble resins which are of the self-
crosslinl~ing type and which are based on a modified diepoxide system.
20 These and other modifications being within the ability of one skilled in the
art are within the scope OI the present invention.
- 13 -
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