Note: Descriptions are shown in the official language in which they were submitted.
2~75~1
PHOTODEGRADATION-RESISTANT ~LECTRODEPOSITABLE
PRIMER COMPOSITIONS
FIELD OF THE TNV~TION
~ This invention relates to an electrodepositable primer
_ - composition. More particularly, this composition i8 well suited for
~ reducing or eliminating delamination between topcoats and primer coats
as a result of photodegradation of primer compositions.
~AC1CGROUND OF THE TNVENTION
Electrodepositable primer coating compositions, particularIy
in the automotive industry, are typically corrosion resistant
epoxy-based compositions and are typically crosslinked with aromatic
15 isocyanates. If exposed to sunlight, such compositions undergo
photodegradation from ultraviolet light. In some automotive-
applications, a spray applied primer surfacer is applied to the
electrocoat before topcoating to provide protection from
photodegradation. In other automotive applications, topcoats are
~- 20 applied directly to the electrocoat and in these instances, the
topcoat usually prevents W radiation from resching the prlmer
surface. However, if a topcoat does not provide sufficient protection,
extensive photodegradation of the electrocoat can result in a loose
-. :
_powdery surface being formed on the primer. In such a case,
- 25 delamination between the primer coat and the topcoat results from the
formation of the loose powdery layer.
Typically, if a topcoat is sufficiently opaque to W light by
being filled with pigment and/or light-absorbing compounds, no
ultraviolet light penetrates to the surface of epoxy-based primers to
30 cause photodegradation. However, in the case of a thin topcoat and/or
a topcoat which is not W light absorbing, ultraviolet light can pass
through the topcoat and cause photodegradation of an epoxy-based
primer. The photodegradation results in delamination of the topcoat
from the primer coat which produces catastrophic failure of the
35 coating system. This problem is particularly likely to occur when a
topcoat is lightly pigmented with metal flake pigments which tend to
allow radiation to pass through to the primer.
J
20~5~51
-- 2 --
Typically, the best way to avoid photodegradation of primer
coatings is by formulating topcoats to prevent transmission of
ultraviolet light to the primer surface~ For example, the use of
thick topcoats or opaque topcoats is sufficient. Also, the use of
5 component6 in the topcoat to prevent transmission of ultraviolet
light, such as ultraviolet light absorbers, is a successful strategy
for avoiding photodegradation of the primer. However, reliance on
proper formulation of topcoats can be unsatisfactory in the painting
operatlon because of variatlons ln the quallty of topcoats.
10 Accordingly, there is a need for a primer composition which retards
photodegradatlon and subsequent delamination independent of the
quality of the topcoat.
Other factors can aggravate the photosensitivity of an
epoxy-based primer and can contribute to delamination of a topcoat
15 from a primer coat, such a~ use of aromatic isocyanate crosslinkers or
of T102 as a pigment in electrodeposltion coatings. Addltionally,
overbake of the electrodepositable coating at excesslve tlmes or
temperatures or baking in an oxidizing atmosphere can aggravate the
problem.
SUMMAR~ OF THE INVENTION
The present composition ls directed toward an
electrodepositable fllm-forming primer composltion which includes an
ionlc resin and a hlndered aminoether light stabilizer. In a
25 preferred embodlment, the hindered aminoether llght stabillzer is
bis-(l-octyloxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate. In a
further preferred embodlment of the composition, the composition also
includes ultraviolet light absorbers and/or antioxldants.
The present invention also includes a process for coating a
30 substrate whlch includes applying a film-formlng prlmer composltion
having an ionic resin and a hindered amine light stabilizer to a
substrate by electrodeposition and subsequently applying a
film-forming topcoat compositlon to the prlmer composition. The
hindered amine light stabilizer is preferably a hindered aminoether
35 light stabilizer.
2~7~65~
- 3 -
DETAIL~D D~SCRIPTION OF THE T~VFNTION
The present primer composition addresses the problem of
delamination of topcoats caused by photodegradation of epoxy-based
primers by including in the primer composition a hindered amine light
5 stabilizer (HALS) and particularly, a hindered aminoether light
-- stabilizer. In this manner, topcoat quality variations in the ability
-- to screen ultraviolet light are at least partially compensated for by
~- the present invention. Therefore, the present primer composition is
- particularly well suited for use with a wide variety of topcoats.
~ 10 The primary component of the electrodeposition primer
,'- composition of the present invention is a hindered amine light
- . -
- stabilizer, a preferred embodiment of which is a hindered aminoether
light stabilizer. The hindered amine light stabilizer is included in
the present composition in an amount sufficient to substantially
."
15 reduce photodegradation of the composition and delamination of any
-~ subsequently applied topcoat as compared with the composition without
the hindered amine light stabilizer. Typically, the hindered amine
light stabilizer is present in the composition in amounts between
about 0.1 % and about 5 %, more preferably betwçen about 0.2 % and
20 about 3 % and most preferably between about 0.5 ~ and 2 % based on
total weight of resin solids. As is known, the ultraviolet region of
sunlight (300 nanometers - 400 nanometers) initiates free radicals in
organic coatings which can cause degradation of the coating by several
known or suggested mech~n~Pms.
The hindered amine light stabilizers of the present
invention are a recognized class of compounds which act as free
radical scavengers to reduce photodegradation of a composition by
ultraviolet light, such as the class of compounds which are
N-substituted 2,2,6,6-tetraalkylpiperidines. HALS include compounds
30 having a group of the formula (I)
- ~ - --
~ ~ ? ~ z~
_ 4 -
C - CH
Rl N\ CH-
/ C \ CH2
S RCH2 CH3
wherein R represents a hydrogen or methyl and Rl represents Cl-Cl8
alkyl, Cl-C6 hydroxyalkyl, C3-C8 alkenyl, C3-C8 slkynyl, C7-C12
aralkyl which is unsubstituted or substituted ln the alkyl moiety by
10 hydroxyl, or Cl-C18 alkanoyl or C3-C5 alkenoyl. Representative
7~ m
commercially available HALS are identified as TIN W IN 770, TINWIN 292
7~
and TIN W IN 440 and are sold by Ciba-Geigy Corporation.
~ A preferred class of HALS are hindered aminoether light
-~ stabllizers. Such compounds have a group of the formula (II)
RCH2 CH3 / R
/C/ CX\
Rl ~ N \ / CH-
C--CX2
RCH2 C~3
wherein Rl and R are as discussed above. Hindered aminoether light
stabilizers are believed to be particularly effective as HALS because
no oxidation of the compound is required to make it an active radical
25 trap as i6 necessary for non-~minoether type HALS. A representative
commercially available hindered aminoether light stabilizer i8
identified as TIN W IN-123 and is sold by Ciba-Geigy Corporation. The
aminoether of TIN W IN-123 is bis-(1-octyloxy-2,2,6,6-tetramethyl-
4-piperidinyl) sebacate and has the formula (III)
2a7~6~l
~ - 5 -
:-~ CH3 CH3
C ~ C CH2 1l 0 CH C - CH
H17C8~-N ~ / CH-0-C-(CH2)g-C-0-CH \ / N-OC8H17
CH3 Cl - CH2 CH2 - IC CH3
.- 5 CH3 CH3
- Without intending to be bound by theory, it is believed that
hindered amine light stabilizer6 are particularly effective when the
hindered amine light stabilizers are relatively non-volatile. In this
10 manner, upon heating o~ the applied composition for cure and
particularly in the event of overbake, a greater percentage of the
HALS is likely to remain in the cured composition as compared to a
more volatile HALS. For this reason, another preferred asp~ct of the
invention is the use of a non-volatile HALS. As used herein, the term
15 non-volatile generally refers to a HALS which ha6 less than about a 5%
weight loss after 30 minutes at 175~C, more preferably less than about
- a 4% weight loss and most preferably less than about a 3% weight loss.
In a further preferred embodiment of the invention, the HALS
component has a pKb>7. In this manner, the HALS is particularly
; 20 compatible with a subsequently applied topcoat when the topcoat
includes an acid-catalyzed aminoplast cros81inker. Since 8uch a HALS
is a weak base, it will not inhibit the acid-catalyzed cure.
The ionic resin of the present composition can be any
standard cationic or anionic resin commonly available to the art.
25 Preferably, the present ionic resin is cationic. The cationic resins
are typically acid-solubilized polyepoxides which are combined with a
crosslinking agent.
The polyepoxides which are used in the practice of the
invention are polymers having a 1,2-epoxy equivalency greater thsn one
30 and preferably about two, that is, polyepoxides which have on an
average basis two epoxy groups per molecule. The preferred
polyepoxides are polyglycidyl ethers of cyclic polyols. Particularly
preferred are polyglycidyl ethers of polyhydric phenols such as
- 6 - 2 0 ~ 65 1
bisphenol A. These polyepoxides can be produced by etherification of
polyhydric phenols with epihalohydrin or dihalohydrin 6uch as
epichlorohydrin or dichlorohydrin in the presence of alkali. Examples
of polyhydric phenols are 2,2-bis-(4-hydroxyphenyl)propsne, l,l-bis-
S (4-hydroxyphenyl)ethane, 2-methyl-1,1-bis-(4-hydroxyphenyl)propane,
2,2-bi~-(4-hydroxy-3-tertiarybutylphenyl)propane,
bis-(2-hydroxynaphthyl) methane or the like.
Besides polyhydric phenols, other cyclic polyols can be used
ln preparing the polyglycidyl ethers of cyclic polyol derivati~es.
10 Ex~mples of other cyclic polyols would alicyclic polyols, particularly
cycloaliphatic polyols, such as 1,2-cyclohexanediol,
1,4-cyclohexanediol, 1,2-bis-(hydroxymethyl)cyclohexane,
1,3-bis-(hydroxymethyl)cyclohexane and hydrogenated bisphenol A.
The polyepoxides have molecular weights of at least 200 and
15 preferably within the range of 200 to 2000, and more preferably about
340 to 2000.
The polyepoxides are preferably chain extended with a
polyether or a polyester polyol which increase6 rupture voltage of the
- composition and enhances flow and coalescence. Examples of polyether
f 20 polyols and conditions for chain extension are disclosed in U.S.
- Patent No. 4,468,307, column 2, line 67, to column 4, line 52.
Examples of polyester polyols for chain extension are disclosed in U.S. Patent
No. 4,148,772, column 4, line 42, to column 5, line 53.
The polyepoxide is reacted with a cationic group former, for
example, an amine and acid. The amine can be a primary. secondary or
tertiary amine and mixtures of thereof.
The preferred amines are monoAmines, particularly
hydroxyl-containing amines. Although monoamines are preferred,
polyamines such as ethylene diamine, diethylamine triamine,
triethylene tetramine, N-(2-aminoethyl)ethanolamine and piperazine can
be used but their use in large amounts is not preferred because they
~re multlfunctional and h~ve a greater tendency to gel the reaction
mixture than monoamines.
.~
._, .. ,_ . .....
2 0 7 ~
-- 7 --
- ~ Tertiary and secondary amines are preferred to primary amines
because the primary amines are polyfunctional with regard to reaction
with epoxy groups and have a greater tendency to gel the reaction
imixture. When using polyamine6 or primary amines, special precautions
5 should be taken to avoid gelation. For example, excess amine can be
used and the excess can be vacuum stripped at the completion of the
reaction. Also, the polyepoxide resin can be added to the amine to
insure that excess amine will be present.
Examples of hydroxyl-containing amines are alkanolamines,
10 dialkanolamines, trialkanolamines, alkylalkanolamines,
arylalkanolamines and arylalkylalkanolamines containing from 2 to 18
carbon atoms in the alkanol, alkyl and aryl substituents. Specific
examples include ethanolamine, N-methylethanolamine, diethanolamine,
N-phenylethanolamine, N,N-dimethylethanolamine, N-methyldiethanolamine
15 and triethanolamine.
Amines which do not contain hydroxyl groups such as mono, di
and tri-alkyl amines and mixed alkyl-aryl amines and substituted
amines in which the substituents are other than hydroxyl and in which
the substituents do not detrimentally affect the epoxy-amine reaction
20 can also be used. Specific examples of these amines are ethylamine,
propylamine, methylethylamine, diethylamine, N,N-dimethylcyclohexyl-
amine, triethylamine, N-benzyldimethylamine, dimethylcocamine and
dimethyltallowamine. Also, amines such as hydrazine and propylene
imine can be used. Ammonia can also be used and is considered for the
25 purposes of this application to be an amine.
Mixtures of the various amines described above can be used.
The reaction of the primary and/or secondary amine with the
polyepoxide resin takes place upon mixing the amine with the product.
The reaction can be conducted neat, or, optionally in the presence of
30 a suitable solvent. Reaction may be exothermic and cooling may be
desired. However, heating to a moderate temperature, that is, within
the range of 50~ to 150~C., may be used to hasten the reaction.
The reaction product of the primary or secondary amine with
the polyepoxide resin attains it~ cationic character by at least
35 partial neutralization with acid. A group of preferred acids which
- 8 -
are u6ed in preparlng the electrocoating composition of the invention
are sulfamlc acid and derivatlves thereof, this is, those acids of the
-~ structure:
R
H - ~ - S03H
where R is H or Cl to C4 alkyl. Preferably, the scid is sulfamic acld
itself. Hereafter, when "sulfamic acid" is used, not only sulfamic
10 acid itself but also its derivatives as depicted by the abo~e
;, structure are intended. The use of sulfamic acid for neutralization
is discussed in detail in U.S. Patent No. 4,933,056. Exarnples of
other suitable acids include organic and inorganic acids such as formic acid,
acetic acid, lactic acid, phosphoric àcid and carbonic acid. The extent of
neutrallzation will depend upon the particular product invol~ed. It
is only necessary that sufficient acid be used to disperse the product
in water. Typically, the amount of acid used will be sufficient to
provide at least 30 percent of the total theoretical neutralization.
Excess acid beyond that required for 100 percent total theoretical
20 neutrallzation can also be used.
~ "
-- In the reaction of the tertiary amine with the polyepoxide
- resin, the tertiary am~ne can be prereacted with the acid such as
- I tho6e mentioned above to form the amine salt and the salt reacted with
the polyepoxide to form the quaternary ammonium salt group-containing
~ 25 resin. The reaction is conducted by mixing the amine salt and the
: polyepoxide resin together in the presence of water. Typically, the
water is employed on the bas i8 of about 1.75 to about 20 percent by
weight baged on total reaction mixture solids.
., Alternately, the tertiary amine can be reacted with the30 polyepoxide resin in the presence of water to form a quaternary
ammonium hydroxide group-containing polymer which, if desired, may be
subsequently acidified. The quaternary ammonium hydroxide-containing
polymers can also be used without acid, although their use i8 not
preferred.
20756~ l
- _ 9 _
In forming the quaternary ammonium base group-containing
polymers, the reaction temperature can be varied between the lowest
temperature at which reaction reasonably proceeds, for example, room
temperature, or in the usual case, slightly above room temperature, to
5 a maximum temperature of 100~C (at atmospheric pres6ure). At greater
than atmospheric pressure, higher reaction temperatures can be used.
Preferably, the reaction temperature ranges between about 60~ to
100~C. Solvent for the reaction i8 usually not necessary, although a
solvent such as a sterically hlndered ester, ether or sterically
10 hindered ketone may be used if desired.
In atdition to the primary, secondary and tertiary amines
. :~
-~ disclosed abo~e, a portion of the amine which is reacted with the
- :-
polyepoxide-polyether polyol product can be the ketimine of a
polyamine. This is described in V.S. Patent No. 4,104,147 in column
15 6, llne 23, to column 7, line 23~ The ketimine groups will decolllpose upon
dispersing the amine-epoxy reaction product in water resulting in free
primary amine groups which would be reactive with curing agents which
are described in more detall below.
Besides reslns containing amine salts and quaternary ammonium
20base groups, resins contalning other cationic groups can be used in
the prsctice of this invention. Examples of other cationic resins are
quaternary phosphonium resins and ternary sulfonium resins. However,
resins containing amine salt groups and quaternary ammonium base
groups are preferred and the amine salt group-containing re6ins are
25the most preferred.
The extent of cationic group formation of the resin should be
selected 80 that when the resin is mixed With aqueous medium, a stable
dispersion will form. A stable dispersion is one which does not
~ settle or is one whlch is easily redispersible if some sedimentation
- 30 occurs. In atdition, the dispersion should be of sufficient cationic
character that the dispersed resin particles will migrate towards the
cathode when an electrical potential is impressed between an anode and
a cathode immer~ed in the aqueous dispersion.
2 0 ~ 5 6 5 ~
-- -- 10 --
In general, most of the cationic resins prepared by the
- process of the lnvention contain from about 0.1 to 3.0, preferably
- from about 0.3 to 1.0 milliequivalents of cationic group per gram of resin solids.
The cationic resinous binders should preferably have weight
average molecular weights, as determined by gel permeation
chromatography using a polystyrene standard, of less than 100,000,
more preferably less than 75,000 and most preferably less than 50,000
in order to achieve high flowability.
- 10 The preferred crosslinkers in the present composition are
blocked isocyanates which are employed in the coating compositions of
- the invention and are organic polyisocyanates and can be those in
whlch the isocyanato groups have been reacted with a compount 80 that
~ ,, .
-- the resultant blocked or capped isocyanate is stable to acti~e
15 hydrogens at room temperature but reactive with active hydrogens at
elevated temperatures, usually between 90~ and 200~C. Aromatlc and
aliphatic, including cycloaliphatic, polyisocyanates may be used and
representative examples include diphenylmethane-4,4'-diisocyanate
- (MDI), 2,4- or 2,6-toluene diisocyanate including mixtures thereof
20 (TDl), p-phenylene diisocyanate, tetramethylene and hexamethylene
diisocyanates, dicyclohexylmethane-4,4'-diisocyanate, isophorone
diisocyanate, mixture6 of diphenylmethane-4,4'-diisocyanate and
polymethylene polyphenylisocyanate. Higher polyisocyanate~ such as
~ triisocyanates can be used. An example would include triphenylmethane-
- ~ 25 4,4',4"-triisocyanate. NCO-prepolymers such as reaction products of
polyisocyanates with polyols such as neopentyl glycol and
- trimethylolpropane and with polymerlc polyols such as polycaprolactone
diol6 and triol6 (NCO/OH equivalent ratio greater than 1) can also be
used. Preferred polyisocyanates are mixtures of diphenylmethane-
~- 30 4,4'-dii60cyanate and polymethylene polyphenylisocyanates. Such
-~ mixture6 are commonly referred to as crude MDI or polymeric MDl. A
particularly preferred mixture is available from Mobay Chemical Co. as
MONDUR MRS 2.77Y
'
-
- 207~
Some isocyanate crosslinkers are preferred from the
standpoint of preventing delamination because, in the event of
accidental extreme cure times and temperatures, i.e., overbake, they
volatilize before thermally breaking down and causing delamination.
5 Illustrative of such volatile polyisocyanates is TDI. In the case of
non-volatile polyisocyanates, such as polymeric MDI, the potential for
delamination can be reduced by limiting the amount of the
polyisocyanate in the formulation as much as possible.
The blocked polyisocyanate can be used in two similar ways.
10 The polyisocyanate can be fully blocked, that is, no free isocyanate
groups remain and then added to the cationic polymer to form a
two-component resin. Or, the polyisocyanate can be partially blocked,
for example, half-blocked diisocyanate, so that there is one remaining
reactive isocyanate group. The half-blocked isocyanate can then be
15 reacted with active hydrogen groups in the polymer backbone under
conditions which will not unblock the blocked isocyanate group. This
reaction makes the isocyanate part of the polymer molecule and a
one-component resin.
Whether fully blocked or partially blocked, sufficient
20 polyisocyanate is present with the cationic polymer so that there are
about 0.1 to about 1.2 isocyanate groups for each active hydrogen,
i.e., hydroxyl, primary and secondary amino and thiol.
Preferably, the molecular weight of the crosslinker, measured
as viscosity average molecular weight, is less than 40,000 in order to
25 achieve high flowability.
The cationic resin and the blocked isocyanate are the
principal resinous ingredients in the electrocoating compositions.
They are usually present in amounts of about 50 to 100 percent by
weight of resin solids.
Preferably, the electrodepositable coating compositions of
the present invention are of the high film build type, that is, they
are capable of being electrodeposited and cured as a substantially
-~ continuous thick film. By thick is meant a film having a dry film
~ thickness of at least 25 and usually from about 25 to 75 microns.
35 Preferably, the film will have a thickness of at least 30 and more
preferably of at least 35 microns.
,, .
~ ' -''.
.
'.- ' .
~ 2b 75651
- 12 -
. ,
..,
In a preferred embodiment of the present composition
~- including an ionic resin and a hindered amine light stabilizer, the
composition further includes a compound selected from the group
~-~ consisting of ultraviolet light absorbers, antioxidants ànd mixtures
-- j 5 thereof. Typically, such compounds are present in the composition in
. amounts of between about .05 weight percent and about 5 weight
~,; percent, and more preferably between about 0.1 weight percent and
about 3 weight percent, and most preferably between about 0.1 weight
percent and about 1.0 weight percent based on total weight of resin
10 solids.
Ultraviolet light absorbers function by absorbing ultraviolet
radiation and disposing of the energy without interacting with the
polymers in the coating compositlon in any harmful way. Recognized
classes of ultraviolet radiation absorbers include derivatives of
15 2-hydroxybenzophenone, 2-(2-H-benzotriazol-2-yl) phenols, phenyl
esters and substituted cinnamic acid derivatives.
Antioxldants reduce or prevent photodegradation of polymers
i by retarding atmospherlc oxidation of polymers in the coating
composition. The present invention includes the use of commonly known
20 antioxidants. A suitable commercial antioxidant is available from
Ciba Geigy and is identified as Irganox 101077~which is a hindered
phenol.
The electrodepo6itable composition of the present invention
also usually contains a pigment which is incorporated into the
25 composition in the form of a paste. The pigment paste is prepared by
grinding or disper6ing a pigment into a grinding vehicle and optional
ingredients such as wetting agents, surfactants and defoamer6.
Grinding i8 usually accomplished by the use of ball mills, Cowles
- dissolvers, continuous attritors and the like until the pigment has
30 been reduced to the desired size and has been wetted by and dispersed
by the grinding vehicle. After grinding, the particle size of the
pigment should be as small as practical, generally, a Hegman grinding
gauge rating of about 6 to 8 is usually employed. Suitable pigment
- grinding vehicles can be selected from those known in the art.
~" :
207~51
- 13 -
Pigments which can be employed in the practice of the
invention include titanium dioxide, basic lead silicate, carbon black,
strontium chromate, iron oxide, clay and phthalocyanine blue.
Pigments with hlgh surface areas and oil absorbencies should be used
5 judiciously because they can have an undesirable effect on coalescence
and flow.
In addition to the above-described components, the present
- composition can also include various additives such as surfactants,
wetting agents, catalysts, film build additives, and additives to
10 enhance flow and appearance of the composition. Such additives are
typically ln the composition in amounts of about 0.01 to about 70
percent by weight based on total weight of resin solids.
The present invention is also directed to a process for
coating a substrate which includes applying the electrodepositable
- 15 film-forming primers, as broadlg described above, to a substrate and
subsequently applying a film-forming resin which transmits ultraviolet
radiation, i.e. radiation having a wavelength less than about 400
nanometers, to the primer composition. Such a process is particularly
useful because the primer reduces the effect of photodegradation
20 caused by transmission of ultraviolet light through the topcoat.
In the electrodeposition process for applying the electro-
depositable film-forming primer of the present invention, the primer
is placed in contact with an electrically conductive anode and an
-electrically conductive cathode. If the ionic resin in the primer
25 composition contains cationic groups, the surface to be coated is the
cathode. If the ionic resin contains anionic groups, the surface to
be coated is the anode. Upon passage of electric current between the
anode and the cathode, while in contact with the bath containing the
primer composition, an adherent film of the composition i8 deposited
30 on the surface to be coated. In the present invention, the resin is
preferably a cationic resin.
:~ The conditions under which the electrodeposition is carried
out are, in general, those used in electrodeposition of other types of
coatings. The applied voltage may be varied greatly and can be, for
35 example, as low as one volt or as high as several thousand volts,
although typically between 50 volts and 500 volts. The current
~'~7,''''''''.
,.. t
2~756~
- 14 -
density is usually between about 1.0 ampere and 15 amperes per square
foot, and tends to decrease during electrodeposition. The method of
the invention is applicable to the coating of any electrically
conductive substrate, and especially metals such as steel, aluminum,
5 copper and the like.
After deposition, the primer coating is cured at elevated
temperatures by any convenient method such as in baking ovens or with
~ banks of infrared heat lamps. Typically, cure is obtained at
temperatures of about 200~F to about 400~F.
After electrodeposltion of the primer coating and either
- - before or after cure of the primer, a subsequent topcoat is applied to
~ .
- the primed substrate. The topcoat is typically a pigmented composition
~ .
and can be a single pigmented layer or a "color-plus-clear" two
component system. The topcoat is then cured. Although a preferred
15 embodiment of the present process includes the application of a
- topcoat over the primer, it should be noted that a composition in
accordance with the present primer composition can be used as a single
coat system and is believed to have improved durability.
An alternative to the above-described process is to coat a
20 substrate with a standard electrodepositable primer which does not
include a hindered amine light stabilizer and to subsequently apply a
HALS to the electrocoated substrate. Application of a HALS can be
accomplished by dipping or spraylng the substrate in a solution of the
HALS. This process further includes curing the electrocoated
25 substrate after the additional HALS coating has been applied.
Preferred embodiments of this process include the use of hindered
aminoether light stabilizers as the HALS in the solution or the
additional use of W absorbers or antioxidants in the solution.
A HALS solution, in accord with the present invention, can be
- 30 prepared with any suitable solvent at a concentration sufficient to
obtain reduced photodegradation and improved delamination results.
For example, suitable solvents include acetone, butoxyethanol, and
xylene and the HALS can be present in amounts between about 0.1 volume
percent and about 100 volume percent and more preferably between about
35 0.1 volume percent and about 10 volume percent based on total volume
of the HALS solution.
2 0 7S65 1
- 15 -
As discussed above, the foregoing process is particularly
useful when the topcoat does not adequately screen ultraviolet light
which passes through the topcoat to impinge on the primer. Due to the
hindered amine light stabilizer in the primer, photodegradation of the
5 primer is significantly reduced or prevented.
The following examples are provided for the purpose of
illustration of the present invention and are not intended to limit
the scope of the invention, as claimed below.
"
_ .
,,
. ", . . . , -
,.
, .
'
:~
- 16 - ~ ~7 5 6
FXAMP~ I
This example illustrates the use of application of a hindered
amine light stabilizer to an electrocoated substrate.
A solution was prepared comprising 1070 by volume TINUVIN 123
5 in acetone.
Smooth zinc-phosphated panels were electrocoatet with 1.2
mils of ED4, an electrodepositable epoxy amine resin, with a polymeric
MDI crosslinker, commercially available from PPG Industries, Inc. The
panels were treated in three different ways:
- 10 A - Untreated
B - Dipped in 10~ TIN W IN 123 in acetone, for 2
seconds, before baking
C - Dipped in 10% TIN W IN 123 in acetone, for 2
seconds, after baking
The panels were cured at three different temperatures in a
gas-fired oven.
1 - 30 minutes at 340~F~
2 - 30 minutes at 375~F.
3 - 30 minutes at 400~F.
Panels were subsequently topcoated with 1.8 mils of URC-600177
a melamlne cured acrylic clearcoat with sufficient W protection at
25 1.8 mils to provide 80% transmi~sion of radiation at 400 nm wavelength,
commercially available from PPG Industries, Inc., and baked for 30
minutes at 250-F. The topcoated panels were exposed in Florida (Fort
Lauterdale) at 45~ from horizontal facing south. After times to be
specified, they were returned to the laboratory where they were
30 cross-hatched with a tool having 6 teeth 2 mm. apart, rated for
adhesion 108s on a scale from 0 = worst to 10 - best, then placed in
100~F at 100% relative humidity for 24 hours, then recross-hatched and
rerated.
,....
2~75651
- 17 -
Table 1
Time inCross-~tch Rat;n~
5 Electrocoat Treatment Bake FloridaInitisl After Humiditv
ED4 A 30' @ 340~F. 5 weeks 4 0
ED4 B " " 10 0
ED4 C " " 5 0
~ 10 ED4 A 30' @ 375~F. 7 days 0 0
-,, ED4 B " " 10 10
~-- ED4 C " " 4 ~
. .;
~- ED4 A 30' @ 400~F. 7 days 0 0
'''
- - ED4 B " " 10 _ 10
-- 15 ED4 C " " 0 0
The results in Table 1 illustrate an improvement in adhesion of
ED4 when subjected to rinsing with TINWIN 123 before baking.
~: .
EXAMPLE II
This example compares the effect of applying various
concentrations of TINWIN 123 in acetone to an electrocoated
substrate, before baking.
The following solutions were prepared:
A - Acetone only
B - 10% TINWIN 123 in acetone
C - 1% TINWIN 123 in acetone
D - 0.1% TINWIN 123 in acetone
ED4 was electrocoated onto smooth, zinc-phosphated steel at
30 1. 2 mil6 and subjected to the described dip-rinse6 for 2 seconds
1 before being cured at the following temperatures:
1 - 30 minutes at 375~F. (gas oven)
2 - 30 minutes at 400~F. (gas oven)
237~
- 18 -
Panels were subsequently topcoated with 1.8 mils of URC-6001
as described in Example 1, baked 30' @ 250~F., and exposed at 45~
south in Fort Lauderdale for 7, 14 and 21 days.
Table 2
Dip Time in Cross-H~tch A~hesion
- ~lectrocoat Sol~tion Bake Florida Initial After HumiditY
ED4 none 30' @ 375~F. 7 days 10 10
" A " " 10 10
" B " " 10 10
" C " " 10 10
15 " D " " 10 8
ED4 none " 14 days 1 0
: " A " " 9 ~
" B " " 10 10
C " " 10 10
: 20 " D " " 9 0
ED4 none " 21 days 0 --
" B " " 10 9
" C " " 10 2
ED4 none 30' @ 400~F. 7 days 0 --
25 " A " " 7 0
" B " " 10 10
" C " " 10 2
" D " " 7 0
ED4 none " 14 days 0 --
30 " A " " 0
" B " " 10 10
7 0
' ~ -
- 19 - ~ u 1 5 6 5 1
The results in Table 2 illustrate that improved adhesion
results are obtained at higher concentrations of TINWIN 123.
EXAMP~F III
- - 5 The following example compares applying TINWIN 123 to
-- ~ electrocoated substrates with applying TINWIN 292, a normal hindered
--~ amine light stabilizer (NH terminated) of high basicity.
Solutions were prepared as follows:
A - 10% TINWIN 292 in acetone (to compare to previous
example)
B - 1% TINWIN 292 in 2-butoxyethanol
C - 1% TINWIN 123 in 2-butoxyethanol
Smooth zinc-phosphated steel panels were electrocoa~ed with
- 1.2 mils ED4, subjected to 2 second dips in the described solutions,
-~ and compared for delamination resistance at the following bakes:
1 - 30 minutes at 375~F. (gas oven)
- 2 - 30 minutes at 400~F. (gas oven)
- Panels were topcoated with 1.8 mils URC~6001 as descrlbed in
Example 1, baked 30' @ 250~F., and exposed at 45~ south in Fort
,,,- Lauderdale for 7 days.
Table 3
~- Dip Time in Cross-Hatch Adhesion30 Electrocoat Solution ~8 Els~LL~ Initial After Humiditv
ED4 none 30' @ 375~F.7 days 7 0
" A " " 10 10
" B " " 10 4
" C " " 10 10
ED4 none 30' @ 400~F.7 days 2 0
" A " " 10 4
" B " " 4 0
" C " " 10 10
.
:-:
~! ~
~, . __ . .
_
- 20 - ~ ~ 75 65 ~
The results in Table 3 illu6trate that use of a hindered
aminoether light stabilizer (TIN W IN 123) provides better adhesion
results than a standard HALS (TIN W IN 292).
EXAMPL~ IV
This example illustrates the effect of incorporating a
hindered amine light stabllizer into an electrocoat composition. This
embodiment i8 compared at different concentrations of HALS, and with
two different means of incorporation.
- : Pre~aration of Fil~-For~inF Resin 4A
Film-forming resin 4A was prepared from the following mixture
of ingredients:
JngredientsParts by Weight
EPON 828 1023.0
20 : Bisphenol A-ethylene oxide
-- adduct (1/6 molar ratio) 365.0
Bisphenol A 297.0
Methyl isobutyl ketone 88.7
Benzyldimethylamine1.4
_ Benzyldimethylamine4.2
Crossllnkerl 1783.9
Diketimine2 115.6
,~ 35 N-methylethanolamine98.6
:; 88% lactic acid110.1
Surfactant3 51.6
Deionized Water2252.7
- Deionized Water1360.4
Deionized Water2137.7
~, . .
,,
~ - 21 - 2~7 S 65 ~
1 The capped polyisocyanate crosslinker was prepared from the
following mixture of ingredients:
- 5 IngredientsParts by Wei~ht
Polyisocyanatea 4095.0
Methyl lsobutyl ketone 2199.6
Dlbutyltin dllaurate 6.2
10 2-(2-Butoxyethoxy)ethanol . 3353.0
Trlmethylolpropane 356.1
2-(2-Butoxyethoxy~ethanol 464.2
a Polymerlc~ DI available from Mobay Chemical Company as
15 MONDUR MRS-4.
The polyisocyanate, methyl isobutyl ketone and dibutyltin dilaurate
were charged to a reaction flask and heated under a nitrogen atmosphere
- ~ 20 to 30~C. The first portion of the 2-(2-butoxyethoxy)cthanol wa8 added
slowly while holding the temperature between 60 and 65~C. Upon
- completion of the addltlon the reaction mixture was held at 65~C for
-~ 90 minutes. The trimethylolpropane was then added and the mixture
heated to llO-C and held for three hours whereupon the final portion
25 of the 2-(2-butoxyethoxy)ethanol was added. The 110~C hold was
continued until infrared analysls indicated no unreacted NCO.
2 Dlketimlne derlved from dlethylene triamine and methyl isobutyl
ketone, 72% solids in methyl isobutyl ketone.
3 Surfactant prepared from 51.5 Glacial acetic acid
316.17 2-butoxyetha~ol
316.17 Surfynol 104 ~acetylenic diol from
Air Products ~ Chemicals Inc.
316.17 Gelgy Amine C alkyl imidazoline,
Ciba-Geigy Corp.
1000 . O
The EPON 828, bisphenol A-ethylene oxide adduct, bisphenol A
and methyl lsobutyl ketone were char~ed into a reaction ~essel and
heated under a nitrogen atmosphere to 140~C. The first portion of the
benzyldimethylamine was added and the reaction mixture allowed to
exotherm to about 185~C and refluxed to azeotropically remove any
45 water present. The reaction mixture was cooled to 160~C, held for one
half hour, cooled further to 145~C and the second portion of
benzyldimethylamine added. The reaction was held at 145~C until a
reduced Gardner-Holdt visc06ity (50 percent resin solids in
2-methoxypropanol) of P-Q was obtained. At this point, the
2~756~1
- 22 -
crosslinker, the diketimine and N-methylethanolamine were added in
succession. The mixture was allowed to exotherm and then a
temperature of 125~C was established. After one hour at 125~C, the
resin was dispersed in aqueous medium by adding it to a mixture of the
5 lactic acid, surfactant and the first portion of deionized water. The
dispersion was further thinned in stages with the second and third
portions of deionized water and vacuum stripped to remove organic
solvent to give a dispersion having a solids content of 36.0 percent
and a particle size of 825 A.
Preparation of Modifv;n~ Resin 4B
Modifying Resin 4B is a polyepoxidepolyoxyalkylenediamine
adduct for subsequent addition to a cationic electrodeposition bath to
provide better appearance in the cured coating. In order to prepare
15 the adduct, an intermediate polyepoxide was prepared from the
following mixture of ingredients:
Ingredients Parts by Weight
EPON 828 1000.0
Bisphenol A 308.1
Ethyltriphenyl
phosphonium iodide 1.3
2-Butoxyethanol 413.5
, ,
The EPON 828 and bisphenol A were charged to a reaction
vessel under a nitrogen blanket and heated to 110~C. The reaction
mixture was held- at 110~C until all the bisphenol A had dissolved
whereupon the ethyltriphenyl phosphonium iodide catalyst was added and
the reaction mixture was heated to 160~C to initiate reaction. The
35 mixture was allowed to exotherm to 180~C and then cooled to 160~C
where it was held for an hour to complete reaction. When the hold was
j over, the 2-butoxyethanol was added to give a solids content of 76;~ percent and an epoxy equivalent weight of 504 (based on solids).
The adduct was then prepared from the following mixture of
40 ingredients:
-
- 23 _ 2~7~
Ingredients Parts by Weight
JEFFAMINE D-20007~ 2362.2
Polyepoxide intermediate
prepared as described above1141.6
2-Butoxyethanol 296.1
88% Aqueous lactic acid solution 96.6
Deionized Water 5279.1
A polyoxypropylenediamine having a molecular weight of 2000
and commercially available from Texaco Chemical Company as JEFFAMINE
D-2000 was reacted with the polyepoxide intermediate as follows: The
JEFFAMINE D-2000 was charged to a reaction vessel under a nitrogen
atmosphere and heated to 90~C. The polyepoxide intermediate and the
20 butoxyethanol were added over a one half hour period. At the
completion of the addition, the reaction mixture was heated to 130~C
and held there for three hours. The resin was then dispersed by
pouring it into a mixture of the 88% aqueous lactic acid solution and
deionized water. The resulting reaction product had a solids content
25 of 36.0 percent.
:
M~n Film Forming Resin 4C Incor~orating Tinuv~n 123
A main film-forming resin 4C containing Tinuvin 123 was
~ prepared from the following mixture of ingredients:
- 30
~n~redients Parts br Wei~ht
EPON 828 1019.25
Bisphenol A-ethyleneoxide lt6 366.08
Bisphenol A 297.45
Methyl isobutyl ketone 88.65
Benzyl dimethyl amine 1.44
Benzyl dimethyl amine 4.28
2~7~51
- 24 -
Crosslinkerl 1779.19
,~ Diketimine2 112.28
_- ~ 5 Methyl ethanolamine 98.42
Tinuvin 123 101.04
Sulfamic acid 92.99
Deionized Water 2167.23
Deionized Water 1359.95
Deionized Water 2137.07
1 Crosslinker as described in resin 4A
20 2 Diketimine as described in resin 4A
The EPON 828, blsphenol A-ethyleneoxide adduct, bisphenol A,
and methylisobutyl ketone were charged into a reaction vessel and
25 heated under a nitrogen atmosphere to 140~C. The first portion of the
benzyldimethylamine was added and the resction allowed to exotherm
with azeotropic removal of water, then cooled to 160~C and held for
one half hour. The reaction mixture was then cooled to 145~C and the
second portion of benzyldimethylamine added. The reaction was held
30 until a reduced Gardner-Holdt viscosity (50% solids in
2-methoxypropanol) of P+ was attained at which point the crosslinker,
diketimine, and methylethanolamine were added in succession. The
reaction was then completed during a hold of 1 hour at 125~C. The
Tinuvin 123 was then added to the reaction mixture, and the entire
35 mixture was then partially dispersed by pouring it into an agitated
mixture of sulfamic acid and the first portion of deionized water.
The dispersion was further thinned in stages with the second and third
portions of deionized water and vacuum stripped to remove organic
solvent, yielding a final dispersion of 39.8% solids and 963 A
40 particle size.
; ~
.
-
- 25 - 2~7~51
Modifvin~ Resins 4D-1 and 4D-2 IncorRoratin~ Tinuvin 123
A modifying resin 4D-l was prepared from the following
ingredients:
Tn~redients Parts bv Weight
JEFFAMINE D-2000 2159.3
Polyepoxide intermediate prepared
as in Resin 4B, 75% solids 1093.4
2-Butoxyethanol 254.8
The polyoxypropylenediamine was charged to a reaction vessel
under a nitrogen atmosphere and heated to 90~C. 1051.4 parts of the
polyepoxide intermediate were added, the mixture was heated and held
at 130~C for 3 hours and 40 minutes, and 22 parts more epoxide
intermediate was added. After 4 more hours at 130~C, the
20 butoxyethanol and 20 parts more epoxide intermediate were added, and
after 3 hours and 15 minutes longer at 130~C the desired Gardner-Holdt
viscosity of Z at 50% solids in 2-methoxy propanol was achieved. The
resulting cooled product 4D-1 had a solids content of 86.7%.
A solubilized mixture of the above adduct and Tinuvin 123 was
25 designated 4D-2 and prepared as follows.
Ingredients Parts bv Weight
Adduct 4D-1 500.0
Tinuvin 123 144.5
88% Lactic Acid 34.1
Deionized Water 972.8
The first three ingredients were mixed well, before adding
the deionized water slowly under strong agitation. The solids content
40 of the dispersion 4D-2 was 35%.
Electrocoating composition 4E was prepared as follows.
:
~07~
- 26 -
.
In~redients Parts bv Weight
Resin 4B 296
Paraplex WPll 72
~- Deionized Water 130
- ~ (Mix well for 30 minutes)
~ 10 Resin 4A 2836
--. Deionized Water 3890
E5994 Paste 2 776
1 Plasticizer available from Rohm and Haas
2 Available from PPG Industries as a milled dispersion of titanium
dioxide (46.2 weight percent of pigment paste), carbon black (1.5
weight percent of pigment paste) basic lead silicate (3.4 weight
percent of pigment paste), and dibutyltin oxide (2.6 weight percent
of pigment paste)
~ Electrocoating composition 4F, containing 2.170 Tinuvin 123 on
- resin solids dispersed in modifying resin was prepared as follows.
In~redients Parts bv Weight
Resin 4D-2 304
Paraplex WPl 72
J 35 Deionized Water 130
(Mix well for 30 minutes)
Resin 4A 2836
Deionized Water 3882
~5994 Paste 776
Electrocoating composition 4G, containing 2.6% Tinuvin 123 on
resin solids dispersed in the main film-forming resin, was prepared as
follows.
2075~51
Ingredients Parts br Weight
Resin 4B 296
Paraplex WPl 72
Deionized Water 130
(Mix well for 30 minutes)
10 Resin 4C 2566
Deionized Water 4160
E5g94 Paste 776
Electrocoating compositions 4H~ 4I, 4J, 4K, 4L, and 4M were
prepared by blending 4E, 4F and 4G as follows.
20 Composition Parts 4E Parts 4F Parts 4G
4H 1700 1700 O
4I 2550 850 O
4J 3060 340 0
4K 2093 0 1307
4L 2747 0 653
4M 3139 0 261
- 35 The makeup of electrocoat compositions 4E-M in terms of %
Tinuvin 123 and method of incorporation of Tinuvin 123 i~ summarized
below
-
- : % Tinuvin 123 Incorporation Method
40 CompositionOn Resin Solids of Tinuvin 123
4E 0 None
4F 2.1 Modifying Resin
4H 1.0 " "
4I 0.5 " "
4J 0.2 " "
.~ ' .
207~
, _ .. . . ....
- 28 -
4G 2.6Main Film-Forming Resin
4K 1.0 " " " "
4L 0.5 " " " "
4M 0.2 " " " "
Smooth zinc-phosphated steel panels were electrocoated with
the above compositions under conditions to produce 1.2 mils baked
film. They were baked at the following conditions:
1. 30 minutes at 375~F (gas oven).
2. 30 minutes at 400~F (gas oven).
_,_ 15 A portion of the panels were topcoated with 1.8 mils URC-6001
~ as described in hxample 1, and baked 30 minutes at 250~F. Thesepanels were exposed in Florida at 45~ South, for one, two, and three
week5~ then returned for adhesion evaluations.
Another portion of panels was topcoated with 0.35 mils of a
20 basecoat which is a 50/50 blend of HBAL-9264 (melamine-cured acrylic
blue basecoat available from PPG Industries) and E5697 (melamine cured
acrylic clearcoat available from PPG Industries, Inc.), plus 1.8 mils
of h5697 clearcoat. The above system was designed to have 20%
transmission of radiation at 400 nanometers when cured 30 minutes at
25 250~F. Panels were exposed for 2, 4, 6, 8, and 10 weeks at 5~ South,
then reviewed for topcoat adhesion ratings as described in Example I.
The results are shown below in Table 4.1 and 4.2.
20756~1
- 29 -
Table 4.1
Time inCrosshatch Adhesion
5 Electrocoat To~coat Bake Fla.Initial After Humiditv
4E URC-6001 30'@3751 week lO 0
4F " " " 10 10
4H " " " 10 9
4I " " " 10 10
4J " " " 9
4G " " " 10 9
4K " " " 10 10
4L " " " 10
- 15 4M " " " 9 2
4E " 30'@4001 week 8 0
4F " " " 10 10
4H " " " 9 2
4I " " " 10
4J " " " 8 0
4G " " " 10 ,10
4K " " " 10 10
4L " " " 9 0
" ~ r ~ 4M " " " 8
~ 25 4E " 30'@3752 weeks 7 0
4F " " " 10 10
4H " " " 10 0
4I " " " 6 0
:. 4J " " " 2 0
- 30 4G " " " 10 10
4K " " " 10 10
.- 4L " " " 9 0
4M " " " 8
4E " 30'@400 " 1 0
4F " " " 10 7
4H " " " 4 0
4I " " " 5 0
4J " " " 2 0
4G " " " 9
4K " " " 8 0
4L " " " 1 0
4M " " " 1 0
4F URC-6001 30'@3753 weeks 10 10
4H " " " 9 0
- 45 4G " " " 10 10
4K " " " 9 0
.~ ~
-
207~
--30--
~1 ~ ~~~~~~~~~~~~~~~~~~
~ +
o.,~
~q ~ ~ ~ o~ o o o~ o~ ~ o o ~ o o oo ~ o o
~- 3 1
. ~
-
.
~e C
.- ,_
,--
o ~ o~ o~ o o~ o o~ oO
~ ~: ~ ,~
~ E~ 3 -
n~
o~ o o~ o o~ o~ o o o o~ a~
2,
U~ O
~" o
o o
r~
r~
~o
~ U~
o
o
E u~
C
r
f
-
- 31 - ~75651
The results in Tables 4.1 and 4.2 illustrate the
effectiveness in crosshatch adheslon of incorporating Tinuvin 123
into re6in compositions.
EXAMPIF V
~ This example illustrates the effect of combining Tinuvin 123
with an antioxidant.
ADDITIVE DISPERSION 5A
Unsolub~lized Modifying Resin 4D-l
of Example IV at 86.77O Solids116.6
887~ Lactic Acld 7.9
Deionized Water 271.4
Irganox 10101 240.0
The above dispersion was milled to a 7+ Hegman reading on a
laboratory sand mill.
O 1 A hindered phenolic antioxidant compound available from Ciba-Geigy
r~ Corporation.
~, "
: ' '
q,: .
:~:
::
2075~51
RESIN DISPERSION 5B
Paraplex WPl 62
Tinuvin 123 25
(Mix, Dissolve)
Resin 4B 316
(Mix well for 30 minutes)
Resin 4A 2554
Deionized Water 543
(Mix well)
RESIN DISPERSION 5C
Resin 4B 316
Deionized Water 125
Paraplex WPl 62
(Mix well for 30 minutes)
Resin 4A 2554
Deionized Water 443
(Mix well)
E~ECTROCOAT COMPOSITIONS 5D~ 5E~ 5F~ 5G
Composition 5D 5E 5F _~Ç_
Resin Dispersion 5C 1682 0 841 841
Resin Dispersion 5B O 1682 841 841
Deionized Water19311931 1931 1929
: E5994 Paste 387 387 387 387
Additive Dispersion 5AO O 0 2
~756~ ~
- 33 -
The four prepared electrocoats have the following contents of
Tinuvin 123 and Irganox 1010:
% Tlnuvin 123 ~ IRGANOX 1010
C~ ~ ~ition on Resin Solids on Resin Solids
5D O O
5~ 2.0 0
5F 1.0 0
- 15 5G 1.0 0.1
The above composltions were electrocoated onto smooth zlnc
: phosphated steel under conditions producing 1.2 mils baked film. They
20 were baked 30 minutes at 375~F in a gas oven.
The panels were topcoated with 1.8 mils URC-6001~ 80%
transmission at 400 nanometers) clearcoat, baked 30 minutes at 250~F,
--: and exposed in Florida at 5~ South for 4, 8, 12,. 16 and 20 days. They
were subsequently evaluated for topcoat adhesion as described in
25 Example I. The results are shown in Table 5:
.
-
Table S
Time in Florida/Crosshatch Adhesion
4 Days 8 Days 12 Days 16 Days 20 Days
Electrocoat Topcoat Bake Init. +~UM.Init. +HUM.Init. +~UM.Init. +~UM. Init. +~UM.
5D URC-6001 30'@375~F 10 10 4 0 0 0 0 0 0 0
5E " " 10 10 10 10 9 3 9 0 9 0
5F " " 10 10 9 8 8 0 1 0 1 0
5G " " 10 10 10 10 10 0 lO 0 9 0
-
- 35 _ ~ 6 5
~XAMPLE VI
This example illustrates a preferred way to incorporate both
j Tinu~in 123 and Irganox 1010 into an electrocoat bath at 1-0~ and 0.1%
; of resin solids respectively. The formulation i6 further optimized
5 for delamination in that it contains a relatively low level of
titanium dioxide and employs a toluene diisocyanate (TDI) as opposed
to a polymethylene polyphenyl isocyanate (polymeric MDI) based
crosslinker.
~ain Film-Forming Resin 6A
The cationic resin is prepared from the following mixture of
ingredients:
Ingredients Parts b~ Wei~ht (~rams)
EPON 828 524.0
Bisphenol A-ethylene oxide
adduct tl/6 molar ratio)189.0
Xylene 46.0
Bisphenol A 152.0
Benzyldimethylamine (catalyst) 0.39
Benzyldimethylamine 0.97
Crosslinker2 694
Diketimine3 59.0
- 35 N-methylethanolamine 50
DOWANOL PPH4 7~ 43
88% Aqueo~s lactic acid 47.5
- Deionized Water 2457
-
r
3 6 ~ r~ ~ ' 6
1 Epoxy resin solution made from reacting epichlorohydrin and
bisphenol A having an epoxy equivalent of about 188, commercially
available from Shell Chemical Company.
5 2 Ihe crosslinker which was formed from half-capping toluene
diisocyanate (80/20 2,4t2,6-isomer mixture) with 2-hexoxyethanol and
reacting this product with trimethylolpropane in a 3:1 molar ra~io.
The crosslinker was present as a 70 percent solids solution in
methyl isobutyl ketone and butanol (9:1 weight ratio).
3 Diketimine derived from diethylenetriamine and methyl isobutyl
ketone (73% solids in methyl isobutyl ketone).
4 1-Phenoxy-2-propanol from Dow Chemical Co.
The EPON 828, bisphenol A-ethylene oxide adduct, bisphenol A,
and methyl isobutyl ketone are charged to a reaction vessel and heated
together under a nitrogen atmosphere at 140~C. The first portion of
20 benzyldimethylamine is added and the reaction mlxture allowed to
exotherm to 183~C and refluxed under reduced pressure to azeotropically
remove any water present. ~he reaction mixture iB cooled to 160~C,
held for one-half hour, cooled further to 145~C, and the second portion
of benzyldimethylamine is added. The reaction mixture is held at 145~C
25 for two hours at which time a reduced Gardner-Holdt viscosity (50
percent resin solids in 2-methoxypropanol) of Q-R is obtained. The
polyurethane crosslinker, diketimine derivative, and N-methylethanol-
~amine are added and the temperature of the reaction mixture brought to118~C and held at this temperature for 1.5 hours. The DOWANOL PPH ~ s
j30 added and the reaction mixture i9 dispersed in a mixture of the lactic
acid and the first portion of deionized water. Further portions of
the water are gradually added to bring the resin solids to 33
percent. Stripping in vacuum to remove organic solvent 8i~es a
dispersion having a solids content of 36.0 percent. The crosslinker
35 comprises about 35 percent of the resin solids.
2375~1
Modifving Resin 6B Containing Tinuvin 123 and Irganox 1010
IngredientsParts bv Wei~ht
Jeffamine D2000 2380.0
,_--- Polyepoxide Intermediate
- Prepared As In Example IV,
Resin 4B, at 75% Solids 1267.0
2-Butoxyethanol 273.0
Tinuvin 123 827.1
Irganox 1010 83.0
Glacial Acetic Acid 25.5
Deionized Water 1273.0
Deionized Water 333.3
The polyoxypropylene diamine is charged to a reaction vessel
under a nitrogen atmosphere and heated to 90~C. 1188.3 parts of the
polyepoxide intermediate are added, plus the 2-butoxyethanol, and the
mixture is heated to 130~C~ and held for 3 hours and 20 min. 24.5
parts polyepoxide intermediate is added and the mixture held for one
30 hour and 40 minutes. 54.2 parts polyepoxide intermediate is added,
and the reaction mixture held for one hour and 15 minutes more to
attain a desired Gardner-Holdt viscosity at 50% solids in 2-methoxy-
propanol of Y+. The mixture is cooled to 115~C. and the Tinuvin 123
and Irganox 1010 are added and stirred until the Irganox 1010 is
35 dissolved. The resin is then dispersed by pouring into an agitated
mixture of acetic acid and the first-portion of deionized water.
After thorough mixing, the second portion of deionized water is added
and thoroughly mixed. The resulting resin dispersion has a solids
content of 35.8%.
-
207~6~1
Electrocoat Composition 6C
Ingredients Pa~ts bv Weight
Resin 4B 88.9
Modifying Resin 6B 89.4
Paraplex WPl 38.4
Deionized Water 75 9
- (Mix Well for 30 Minutes)
~ Main Film-Forming Resin 6A1492.2
Deionized Water 1508.0
E6064 Pastel 207.2
1 A paste commercially available from PPG containing 27.2% titanium
dioxide, 1.470 carbon black, 15.9% aluminum silicate, 5.7% basic lead
silicate, and 3.8% dibutyl tin oxide.
i: -
