Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~0~7~g :~
Background of the Invention
Field of the Invention: Tlle present invention relates to
pigment grinding vehicles and, more particularly, to resinous products
suitable for such use. In another aspect, the invention relates ta
cationic electrocoating empl~oying paints containing novel pigment -
grinding vehicles.
Brief Description of the Prior Art: In the formation of
paint compositions, and especially electrodepositable paint compositions,
an important factor is the introduction of pigments into the coating
composition. The pigments are typically ground in a pigment grinding
vehicle which acts as a dispersing agent to form a paste, and the
resultant pigment paste is incorporated illtO the coating composition
to give the coating composition proper color, opacity, application and
film properties.
Unfortunately, many of the pigment pastes for electrodeposition
are mixtures of water-soluble soaps or resins which are not electro-
depositable. These pastes remain in the aqueous phase where they pose
serious effluent problems.
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~L~9744~
The present invention overcomes this problem by providing a
pigment grinding vehicle which can be made electrodepositable and co-
depositable with the vehicle resin of the paint.
Summary of the Invention
In accordance with the present invention, a polymeric product
suitable for use as a pigment grinding vehicle is provided. The polymeric
product comprises the reaction product of an organic polyepoxide and an
organic amine containing alkyl aryl polyether moieties. Besides the
polymeric product, the invention also provides for a pigment paste
comprising the above-described product in combination with a pigment.
Additionally, the present invention provides for a method of electro-
coating an electrically-conductive surface serving as d cathode in an
electrical circuit comprising a cathode and an anode and an aqueous
electrodepositable compositlon ~herein the electrodepositable composition
comprises an aqueous dispersion of an amine salt-containing resin or a
quaternary ammonium group-containing resin and the aforementioned pigment
paste.
:
The polymeric products of the present invention, besides
providing outstanding pigment wetting properties, are co-depositable
with the vehicle resin of the electrodeposition paint and thus signi-
`~ ficantly minimize effluent problems.
''`` ~
Detailed Description
The organic polyepoxides can be a monomeric or polymericcompound or a mixture of compounds having a 1,2-epoxy equivalency
greater than 1.OJ that is, in which the average number of 1,2-epoxy
groups per molecule is greater than 1. It is preferred that the organic
polyepoxide be polymeric or resinous.
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1~974~9
The polyepoxide can be any of the well-knowrl epoxides. Examples
of these polyepoxides have, for example, been described in U. S. Patents
2,467,171; 2,615,007; 2,716,123; 3,030,336; 3,053,855; and 3,075,999.
A useful class of polyepoxides are the polyglycidyl ethers of polyphenols,
such as Bisphenol A. These may be prepared, for example, by etherification
of a poly~herlol with epichlorohydrin or dichlorohydrin in the presence of
an alkali. The phenolic compound may be bis(4-hydroxy-phenyl)2,2-propane,
4,4'-dihydroxybenzophenone, bis(4-hydroxy-phenyl)l,l-ethane, bis(4-hydroxy-
phenyl)l,l-isobutane; bis(4-hydroxy-tertiary-butyl-phenyl)2,2-propane,
bis(2-hydroxy-naphthyl)methane, 1,5-hydroxy-naphthalene, or the like.
Another quite useful class of polyepoxides are produced similarly from
novolak resins or similar polyphenol resins.
Also suitable are the similar polyglycidyl ethers of polyhydric
alcohols which may be derived from such polyhydric alcohols as ethylene
glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, -
1,4-butylene glycol, 1,5-pentanediol, 1,2,6-hexanetriol, glycerol,
bis-(4-hydroxy-cyclohexyl)2,2-propane, and the like.
There can also be employed polyglycidyl ethers of polycarboxylic
acids which are produced by the reaction of epichlorohydrin or a similar
epoxy compound with an aliphatic or aromatic polycarboxylic acid, such
as oxalic acid, succinic acid, glutaric acid, terephthalic acid, 2,6-
naphthalene dicarboxylic acid, dimerized linoleic acid, and the like.
~xamples are diglycidyl adipate and diglycidyl phthalate.
Also useful are polyepoxides derived from the epoxidation of
an olefinically unsaturated alicyclic compound. Included are diepoxides
comprising, in part, one or more monoepoxides. These polyepoxides are
non-phenolic and obtained by epoxidation of alicyclic olefins, for
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7445~
example, by oxygen and selected metal catalyst, by perbenzoic acid, by
acid aldehyde monoperacetate or by peracetic acid. ~mong the poly-
epoxides are the epoxy alicyclic ethers and esters which are well known
in the art.
Other epoxies which may be employed are acrylic polymers
containing epoxy groups and hydroxyl groups. Preferably, these acrylic
polymers are polymers produced by copolymerizing an unsaturated epoxy-
containing monomer, such as, for example, glycidyl acrylate or methacrylate,
a hydroxyl-containing unsaturated monomer and at least one other unsaturated
monomer .
Any polymerizable monomeric compound containing at least one
CH2=C~ group, preferably in the terminal position, may be polymerized
with the unsaturated glycidyl compounds. Examples of such monomers
include aromatic compounds such as phenyl compounds, for example, styrene,
alpha-metllyl styrene, vinyl toluene and the like. ~lso, aliphatic
compounds such as olefinic acids and esters, such as acrylic acid, methyl
acrylate, ethyl acrylate, methyl methacrylate and the like may be employed.
In carrying out the polymerization reaction, techniques well
known in the art may be employed. ~ peroxygen-type catalyst is ordinarily
utili~ed; diazo compounds or redox catalyst systems can also be employed
as catalysts.
The preferred hydroxy-containing unsaturated monomers are
hydroxyalkyl acrylates, for example? hydroxyethyl acrylate or methacrylate
or hydroxypropyl acrylate or methacrylate may be used.
Another method of producing acrylic polymers which may be
utilized in the present invention is to react an acrylic polymer containing
reactive sites, including hydroxyl groups, with an epoxy-containing compound
such as diglycidyl ether of Bisphenol ~ or other polyepoxides as enumerated
1~97449
elsewhere herein, to provide epoxy group-containing hydroxyl group-
containing acrylic polymers.
The organic amine containing alkyl aryl polyether moieties
can be a secondary amine or a tertiary amine acid salt which is capable
of reacting with and opening the epoxide moiety to form basic nitrogen-
containing adducts. In the case of secondary amines, the adduct contains
tertiary amine groups and in the case of tertiary amine acid salts,
quaternary ammonium-containing adducts are formed. The tertiary amine-
containing adducts are usually insoluble in water and can be solubilized
by treating with acid.
The acid used Eor solubilizlng the tertiary amine adduct and
the acids of the tertiary amine acid salts preferably are acids having a
PKa less than 5 such as hydrochloric acid, sulfuric acid and boric acid. r
Preferably, the acid is an organic acid such as acetic acid and lactic
acid, with lactic acid being the most preferred.
As has been mentioned above, the organic amine contains alkyl
aryl polyether moieties, typical of which are represented by the following
structural formula:
R \ ~ ~ (OCll2 - CH)x ~ o~
`,
wllere R is an alkyl radical containing from 1 to 30 carbon atoms and
R' is hydrogen or lower alkyl containing from 1 to 5 carbon atoms and
x is equal to 3 to 20. Preferably, R is a branched alkyl group contain-
ing secondary, tertiary or both secondary and tertiary carbon atoms. In
the most preferred embodiment, R is octyl.
~g791~
In the above structural formula, the aryl radical is repre-
sented by the phenyl ring. It should be appreciated, nowever, that
other aryl radicals such as naphthyl, phenanthryl and anantnryl can
be used.
In one embodiment oE the invention, the organic amine contain-
ing alkyl aryl polyet^her moieties can be prepared by reacting an alkyl
aryl polyether which contains an active hydrogen such as hydroxyl with
an organic diisocyanate to form a half-capped isocyanate product. An
organic amine containing active hydrogens such as a hydroxyl-containing
tertiary amine can then be reacted with a half~capped isocyanate to form
the desired adduct. In a preferred embodiment of the invention, toluene
diisocyanate is half-capped with an octyl phenol-ethylene oxide adduct
having the following structural formula: .
CH - C - CH2 - C ~(OCH2C112)XOH
CH3 CH3
where x is equal to 12 to 13. The half-capped adduct is then fully
capped with dimethyl ethanolamine to form a tertlary amine adduct con-
taining alkyl aryl polyether moieties which also contains urethane linkages.
To make the polymeric product of the invention, preferably
two moles of the organic monoamine containing alkyl aryl polyether
moieties are reacted with one mole of an organic diepoxide to form an
adduct in which the alkyl aryl polyether groups are in the terminal
position on the polymer chain. This provides a polymeric product with
the most desirable pigment dispersing properties. The reaction proceeds
at room temperature in most cases and, in some cases, exothermically,
so that moderate cooling may be necessary. In some cases, moderately
~09744~
elevated temperature can be used and is preferred. Typically, the
reaction is conducted between about 50C. and 100C. The reaction
may be conducted in the presence of a solvent if desired. If a solvent
is employed, preferably it is capable of being used in the ultimate
composition which is formed. For example, alcohols, ketones and glycol
ethers may be used.
For suitable pigment pastes for use in electrodeposition, the
amounts of organic polyepoxide and organic amine containing alkyl aryl
polyether moieties should be selected so that the final polymeric product
contains about 0.3 to 1.5, preferably 0.4 to 0.7 milliequivalents of
basic nitrogen per gram of resin. Iower milliequivalents of basic nitrogen
j~ per gram of resin, i.e., lower than 0.3, are undesirable because the
resin will have poor pigment wetting properties, whereas higher milli-
equivalents of basic nitrogen per gram of resin, i.e., higiler than 1.5,
are undesirable because the resin may become too water soluble.
; The pigment pastes of the present invention are prepared by
grinding or dispersing a pigment into the polymeric products described
above in a manner well known in the art. The pigment paste comprises
as essential ingredients basic nitrogen-containing adducts of the
invention and at least one pigment; however, the paste may, in addition,
contain optional ingredients such as plasticizers, wetting agents,
surfactants or àefoamers.
Grinding is usually accomplished by the use of ball mills,
sand mills, Cowles dissolvers, continuous attritors and the like until
the pigment has been reduced to the desired size and preferably has been
wet by and dispersed by the grinding vehicle. After grinding, the particle
size of the pigment should be in the range of 10 microns or less, preferably
.
11~974~9
as small as practicable. Generally, a Hegman grind gauge reading of
about 6-8 is usually employed.
Preferably, grinding is conducted in an aqueous dispersion of
the vehicle. The amount of water present in the aqueous grind should
be sufficient to produce a continuous aqueous phase. Tlle aqueous grind
usually contains about 30 to 70 percent total solids. The use of more
water merely reduces the effective capacity of the mill and, while less
water can be employed, higher resultant viscosity may create problems in
certain instances. Although the pigment paste is usually prepared in the
presence of water, water is not absolutely necessary and in fact the pigment
dispersants of the present invention can be used to prepare non-aqueous
pigment pastes ~hich are subsequently dispersible in water-based compositions.
` The pigment-binder ratio in the grinding step is usually
;~ maintained within the range of about 2/l to 7/1.
Pigments which may be employed in the practice of the invention
are pigments ~ell known in the art. Generally titanium dioxide i8 the
sole or chief white pigment; other white pigments and/or extender pigments
include antimony oxide, zinc oxide, basic lead carbonate, basic lead
sulfate, barium carbonate, China clay, calcium carbonate, aluminum silica,
silica, magnesium carbonate, magnesium silica, among others. Color
pigments may also be employed, for example, cadmium yellow, cadmium red,
carbon black, phthalocyanine blue, chrome yellow, toluidine red, hydrated
iron oxide, among others.
For a general review of pigment grinding and paint formulation,
reference may be had to: -
! D. H. Parker, PrinciPles of Surface Coatin~ Technology,
Interscience Publishers, New York (1965)
! R. L. Yates, Electropainting, Robert Draper Ltd.,
Teddington, England (1966)
H. F. Payne, Or~anic Coating Technology, Vol. 2,
Wiley and Sons, New York ~1961).
` 1097449
The pigment paste of the present invention is usually combined
with an amine group-containing resinous vehicle known in the art for
cationic electrodeposition. The amine group-containing cationic electro-
depositable resins are well known in the art and need not be described ~ ;
in any detail. Examples of suitable resins include those described in
U. S. Patent 3,799,854 to Jerabek and U. S. Patent 3,839,252 to ~3Osso et al.
. :
,
`~ Enough of the pigment paste is used so that the final electro-
depositable composition (electrodepositable resin plus pigment paste)
has the properties required for electrodeposition. In most instances,
the final electrodepositable cotnposition has a pigment-to-binder (electro-
depositable resin plus pigment dispersant) ratio of between about 0.05 to
about 0.5.
For electrodeposition, a bath containing about 5 to 25 percent
by weight solids, that is, pigment plus resinous vehicle, is usually
employed. This aqueous composition is then placed in contact with an
electrically-conductive anode and an electrically-conductive cathode in
an electric circuit. ~hile in contact with the bath containing the
coating composition, an adherent film of the coating composition is
deposited on the cathode.
The conditions under which the electrodeposition is carried out
are, in general, similar to those used in electrodeposition of other types
of coatings. The applied voltage may be varied greatly and can be, for
example, as low as one volt or as high as several thousand volts, although
typically between 50 volts and 500 volts are usually employed. The current
density is usually between about 0.25 ampere and 15 amperes per square foot,
and tends to decrease during electrodeposition.
~974~9
The method of the invention is applicable to the coating of
any conductive substrate and especially metal, such as steel, aluminum,
copper and the like.
After deposition, the coating is cured at elevated temperatures
by any convenient method, such as in baking ovens or with banks of
infrared heat lamps.
The final electrodepositable composition may contain, in addition
to the pigment dispersion and the electrodeposition resin, adjuvant resins
such as aminoplast resins for crosslinking, solvents, anti-oxidants,
surfactants and other adjuvants typically employed in an electrodeposition
process.
Illustrating the invention are the following examples which are
not to be construed as limiting the invention to their details. All parts
and percentages in the examples, as well as throughout the specification,
are by weight unless otherwise speciEied.
Example I
A polymeric product suitable for use as a pigment grinding
vehicle was prepared from the following charge:
Charge ~ y___~ Solids
EPON 829 400 383.8
Bisphenol A 136.8 136.8
Organic amine containing alkyl aryl
polyether moieties2 792 792
Aqueous lactic acid solution 96 72
Deionized water 113.7
Epoxy resin solution made from reacting epichlorohydrin and Bisphenol A,
~ T~de rr~ark
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10~449
having an epoxy equivaient of approximately 193-203 and commercially
available from Shell Chemical Company.
2This component was made by charging 174 parts by weight of toluene
diisocyanate and 727`parts by weight of an alkyl aryl polyether having
the following structure: -
CH3 CH ~ (OCH2CH2)xOH
:; CH3 CH3
where x is equal to 12 to 13, commercially available from Rohm and Haas
as TRITON X-102, to a reaction vessel. The reaction was permitted to
exotherm at 30-35C. with Stirring for two hours~ after which time 89
parts ~y weight of dimethyl ethanolamitle was added. The reaction mixture
was again permitted to exotherm for an additional two hours to form the
desired reaction product.
The EPON 829 and the ~isphenol A were charged to a suitable
reaction vessel and heated to 155-160C. and permitted to exotherm for
one hour. The organic amine, lactic acid and deionized water were then
added and the reaction mixture held for one hour at 80-85C. to form the
desired reaction product.
Example II
A pigment paste ground to a }legman No. 7 containing the
polymeric product of Example I was prepared from the following charge: -
~ Tr~ na~
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7~4S~
Parts by Weight
. Resin of Example I125.0
: Titanium dioxide 592.2
Red iron oxide 2.5
Carbon black 5.1
Dibutyltin diacetate7.2
Deionized water 315
Example III
A cationic electrodepositable resin was prepared Erom the
following charge: _
Char&~ Parts by Weight Solids
EPON 829 5428 5208.3
Bisphenol ~ 1752.3 1752.3
2-Ethylhexyl-half capped toluene
diisocyanate 3705.5 3705.5
PCP-02001 1424.8 1424.8
TEXANOL 1167.3
Dimethyl ethanolamine25.8 25.8
Aqueous lactic acid solution 52.3 39.5
Phenyl CELLOSOLVE1830.5
Ethyl CELLOSOLVE 857.0
FOAM KILL 639 66.5 66.5
Aqueous dimethyl cyclohexyl amine-
lactic acid salt solution 1600.7 1200.5
Deionized water 857.0 - -
Polycaprolactone diol having a molecular weight of 540 formed from ring
-12 _
/~
J4t~
opening epsilon-caprolactone with diethylene glycol, commercially available
from ~nion Carbide Corporation.
(trade mark) 2,2,4-trimethylpentanediol-1,3-monoisobutyrate.
3(trade mark) Ethylene glycol monophenyl ether.
(trade mark) Ethylene glycol monoethyl ether.
(trade mark) Hydrocarbon oil-containing diatomaceous earth surfactant.
The resin was prepared by charging the EPON 829 and Bisphenol
to a suitable reaction vessel and heating to exotllerm, the higllest
temperature being 215C. Reaction was controlled at 150-215C. for one
hour and the reaction mixture cooled to 125C. and charged with the half-
capped toluene diisocyanate. The reactlon mixture was held for one hour
at 120C. followed by the acldition of the PCP-0200 and the TE~Y~NOL. ~fter
the addition of these ingredients, the dimethyl ethanolamine was added
and the reaction mixture maintained at 125-130C. for seven hours until
the Gardner-Ho]dt viscosity was ~l+ a~ 25C. The lactic acid, phenyl
CELLOSOLVE, ethyl CELLOSOLVE and FO~I KILL 639 were then charged over a
period of 30 minutes followed by the addition of the dimethyl cyclohexylamine-
lactic acid salt. The reaction mixture was digested at 90-95C. for two
hours to form and clarify tile resinous product oE the invention which had
a solids content of 46.3 percent.
The above-described vehicle was combined with the ?igment paste
of Example II and deionized water in the following charge ratio to form
a 10 percent solids electrodeposition bath.
*Trade Mark
,. . ~
1C~9~4~3
Resin Pigment
Charge Parts by Weight Solids Solids
Cationic electrodepositable
resin 351.0 263.2
Pigment paste of Example II 145.0 13.8 83.0
Deionized water 3104.0
Zinc phosphated steel panels were coated with this bath at a
temperature of 27C. at 400 volts for 90 seconds to produce continuous
films.
Example IV
A pigment paste ground to a Hegman No. 7 was prepared from
the following charge:
ChargeParts by Weight Solids
Pigment grinding vehicle oE
Exa~ple I 121.7 100
Titanium dioxide472.2 472.2
Aluminum silicate120.0 120.0
Red iron oxide 2.5 2.5
Carbon black 5.1 5.1
Deionized water 284.7
Example V
An electrodeposition bath containing 10 percent total solids was
prepared from the thermosetting cationic composition described in Example III
and the pigment paste oE Example IV in the following charge ratio:
- 14 -
lOg7449
Resin Pigment
Charge Parts by Weight Solids Solids
Cationic electrodepositable
resin of Example III 717.6 502
Pigment paste of Example IV 312.8 31.1 186.6
Dibutyltin diacetate6.0
Deionized water 6163.0
When the electrodeposition bath at a temperature of 27C. was
used to coat zinc phosphated steel panels at 300 volts for 90 seconds,
continuous films were produced which, after curing for 20 minutes at
196C., were glossy~ hard and acetone-resistant.
Example VI
~ polymeric product similar to Example I and suitable for use
as a pigment grinding vehicle was prepared Erom the following charge:
Charge Parts by Weight Solids
EPO~ 829 400 383.8
Bisphenol A 136.8 136.8
Organic amine containing alkyl aryl
polyether moieties of Example I 673~4 673.4
Aqueous lactic acid solution 78 58.5
Deionized wat~r 62.6
Methyl ethyl ketone 214.8
The EPON 829 and the Bisphenol A were charged to a suitable
reaction vessel and heated to exotherm at 155C. and held for one hour.
The reaction mixture was cooled to 100C. and the methyl ethyl ketone
added. The reaction mixture was agitated and heated to reflux followed
- 15 -
1~197449
by the addition of the amine, lactic acid and deionized water. The
reaction mixture was further heated at 80-90C. for about one hour
to form the desired reaction product.
Example VII
A pigment paste ground to a Hegman No. 7 and containing the
polymeric product of Example VI was prepared from the following charge:
Charge Parts by Weight Solids
: ~A~ Resin of Example ~ 121.7 100
Titanium dioxide 472.2 472~2
Aluminum silicate 120.0 120
Red iron oxide 2.5 2.5
Carbon black 5.1 5.1
Deionized water 309.7
Example VI:[I
A cationic electrodepositable resin was prepared from the
following charge:
1~9~44~
Charge Parts by ~eight Solids
= ~ ~
EPON 829 1203.5 1155.7
Bisphenol A 207.0 207.0
Polypropylene glycol (molecular
weight = 625) 542.3 542.3
Dimethyl ethanolamine 3.6 3.56
75% by wei~ht aqueous lactic acid
solution 7.1 6.0
FOAM KILL 639 12.6 12.6
TEX~NOL 402.2 - -
Isopropanol 55.0
Dlmethyl ethanolamille lactic acid
salt (75% solids in isopropanol) 96.0 71.98
Deionized water 92.0
Boric acid 5.0 5.0
Deionized water 2550
Boric acid 5.9 5,9
X~1-11231 326.2 326.2
Isopropanol 69.0
METHLYON 75202 197.0 128.0
Isopropanol 58.3
XM-1123 (trade mark) benzoguanamine-fom~aldehyde resin commercially
available from American Cyanamid Company.
(trade mark) Unsaturated methylol phenol ether commercially available
from General Electric Company.
The EPON 829 and Bisphenol A were charged to a suitable reaction
vessel and heated to 150C. to exotherm with the highest temperature being
, ~ ., .
3.0~449
160C. The reaction temperature was controlled between 150-160C. for
one hour, after which time the polypropylene glycol was charged to the
reaction vessel followed by the addition of the dimethyl ethanolamine.
The reaction temperature was held at about 135C. for about six hours
until the Gardner-Holdt viscosity at 25C. was M+. The reaction mixture
was then charged with TEXANOL, isopropanol and FOAM KILL and digested for
45 minutes at 115-130C. The lactic acid was then charged and the reaction
mixture cooled to 98C., followed by the addition of the dimethyl ethanol-
amine lactic, the first portion of deionized water and boric acid. After
the addition of these ingredients, the temperature was held at 90-95C.
for 4S minutes, lowered to 70C. and the second portion of deionized
water and boric acid added. After this addition, the reaction mixture
was charged with XM-1123 and the first portion of isopropanol. The reaction
mixture was digested for 30 minutes at 65C. and then charged with the
METHLYON and the second portion of isopropanol. The reaction mlxture
was further digested for four hours at 56-62C. to clarify the reaction
product. The final product contained 71.2 percent total solids and had a
Brookfield viscosity of 22,000 centipoises (No. 7 spindle at 20 rpm's).
The above resin was combined with the pigment paste of Example
VII and deionized water to form a 10 percent solids electrodeposition
bath. The charge ratio for forming the bath was as follows:
Resin Pigment
Charge Parts by Weight Solids Solids
Cationic electrodepositable
resin 376.0 263.2
Pigment paste of Example VII 142.5 13.8 83.0
Deionized water 3081.6
18 -
~9~4~
The above bath when used to coat ~inc phosphated steel panels
at 200 volts for 90 seconds (bath temperature 27C.) produced continuous
films which when baked at 246C. for 20 minutes were hard and acetone-
resistant films of a thickness of approximately 0.70 mil.
Example IX
A non-aqueous pigment paste ground to a ~egman No. 7 containing
the polymeric product of Lxample I was prepared from the following charge:
Charge Parts by Weight
Resin of Example I 97.4
Butyl CELLOSOLVE 230
T:itanium dioxide 342
Chrome yellow pigment 38.2
Medium chrome yellow pigment 9.5
Etllylene glycol monobutyl ether.
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