Note: Descriptions are shown in the official language in which they were submitted.
~ 2'~4(~
BACKGROU~ID OF THE INVENTION
The present invention is concerned with a multi-component
cathodic electrocoating composition comprising a cross-linking
agent, a polymer, an acid disperser and, optionally, a cross-linking
catalyst. The composition of the invention finds utility in
the preparation of coatings on conductive substrate and the present
invention also concerns methods for electrodepositing the com-
position on a substrate and heating the deposited coating to cure
it to form a thermoset coating.
- - Electrodepositable resin compositions are of course well known
in the art. For example, U.S. Patent 4,031,050 discloses cationic
electrodepositable compositions of blocked organic polyisocyanates
and an amine adduct of an epoxy resin. As disclosed in this patent,
electrodeposition of such compounds, which may optionally contain a
catalyst for urethane formation, can be carried out to provide
coatings on a conductive substrate, which coatings have desirable
properties. In this regard, see also U.S. Patents 3,984,299 and
4,031,050. ~owever, isocyanate compounds are toxic and highly
reactive, requiring suitable precautions in handling and
storing the same.
U.S. Patent 4,017,438 discloses an epoxy resin-derived,
cati~nic electrodepositable resin enhanced by the incorporation
of primary amine groups into the resin molecule, by reacting
certaln polyamine compounds having primary amine groups blocked by
ketimine. The ketimime groups when contacted with water, will
decompose to provide primary amine functionality as disclosed in
~hls patent. Capp~d isocyanates are disclosed in combination with
~ 274~
--2--
the amine-resin adduc~ to provide, together with a suitable catalyst,
a cationically electrodepositable resin system. The electro-
deposited coating, upon being heated to an elevaeed temperature,
us~ally in the presence of a cross-linking catalyst, undergoes
cross-linking through reaction of hydroxy and amino groups with blocked
isocyanate groups.
As well known, the "capped" or "blocked" isocyanates react
with hydroxy groups and amino groups under conditions of elevated
temperature to for~ urethane and urea cross-linkages.
Numerous literature references exist showing the reactions
of primary and secondary amines with, for example, propylene
carbonate to yield corresponding hydroxypropyl carbamates (Compt.
rend. 1142, 1954). The reaction of cyclic carbonates and
aromatic amines in the presence of certain zinc, tin or cobalt
catalysts to provide carbamate compounds is shown by U.S. Patent
4,268,684, with uses of the resulting carbamates disclosed in
U.S. Patents 3,919,279; 3,919,280 and 3,962,302. The literature
also shows that bishydroxyalkyl carbamates derived from corresponding
diamines have been further self-condensed, or transesterified with
other diols, to produce linear thermoplastic polyurethanes. For
example, see the article "The Preparation oE Polymeric and Cyclic
Urethans and Ureas from Ethylene Carbonate and Amines'` by Elizabeth
Dyer and Harvey Scott, J.A.C.S. (1956? pp 672 - 675. See also
the report "Polyurethane elastomers obtained without the use oE
diisocyanates'` by L. Ya. Rappoport, G.N. Pe~rov, I.I. T~ostyanskaya
and O.P. Gavrilova in Interna ~ cience and Technolo~,
~, N~. 1, 1981 and an ar~icle by Richard D. Cowell entitled:
~', .
~.2t7~ 3;~
"Thermoplastic Polyurethane Elastomers: Chemistry Properties and
Processing for the 80's" in the Journal of Elastomers and Plastics,
Vol. 14, (October, 1982) pages 195 - 203.
SU~MARY OF THE INVENTION
In accordance with the present invention there is provided
a cathodic electrocoating composition comprising (a) a hydrophobic
cross-linking agent having at least two carbamate groups selected
from the class consisting of one or both of (i) hydroxyalkyl
carbamate groups, and (ii) alkyl carbamate groups obtained by
capping the reaction product of a cyclic carbonate tsuch as ethylene
carbonate or propylene carbonate) and a polyamine; (b) a water-
insoluble and hydrophobic amino group-containing polymer; and (c)
an acid disperser (such as an inorganic acid or hydrophilic organic
acid) effective ~o provide cationic groups in the polymer (b)
whereby the polymer is rendered water-dispersible; and (d) optionally,
a cross-linking catalyst; the cross-linking agent (a) and the
polymer (b) being stable relative to each other in the composition
while at ambient temperature, and reactive wi~h each other at
elevated temperature.
In accordance with one aspect of the invention the cross-
linking catalyst is selected from the class consisting of metal-
containing catalysts, quaternary compounds and ternary compounts,
preferably Çrom the class consisting of one or more of tin, ~inc,
and titanium compounds and/or Çrom the class consisting of
quaternary ammonium, phosphonium and arsonium compounds and
ternary sulfonium compounds.
, ~, '. :'
~ ~ 7~)33
In one aspect of the invention, the cross-linking agent
(a), the polymer (b), the acid disperser tc), and, when present,
the catalyst (d) are present in weight proportion, per 100 parts
by weight of the solids of (a), tb), tc), and (d), of at least
about 5, preferably from about 5 to about 50 parts (a), at least
about 40, preferably from about 40 to about 90, parts (b), at
least about 1, preferably from about 1 to about 10, parts (c), and,
when present, at least about 0.1 to 10, preferably from about 1 to
about 5, parts (d).
In another aspect of the invention, the polymer (b) contains
one or more functional groups which are reactive at elevated
temperature with the hydroxyalkyl carbamate groups of the cross-
linking agent (a). These functional groups may comprise one or more
of amino, amide, hydroxy and ester functional groups, preferably
one or both of amino and hydroxy groups. The polymer (b) may com-
prise from about 0.25 to about 30~ by weight a~ino groups and from
about 0.5 to about 20~ by weight hydroxy groups, based on the weight
of polymer (b) solids.
One aspect of the invention provides that the hydrophobic
cross-linking agent (a) contains one or more hydroxyalkYl car-
bamate ~roups or alkyl carbamate groups capped by a moiety selected
from the class consisting of ester, urethane, thiocarbamate, sulfonic
ester, sulfona~ate ester, and ether groups.
In accordance with the present invention there is further
provided a method Oe forming a cross-linked coating on a substrate
comprisin8 immersing the substrate in an alectrodeposition bath
comprlsing the composition (a), (b), (c~ and, optionally, ~d~
~ ~7~3;~
--5--
above, cathodically èlectrodepositing a coating of the composltion
from the bath onto the substrate, removing the coated substrate
from the bath, and heating the coated substrate at an elevated
temperature and for a time sufficient to cure the deposited
coating.
In one aspect of the invention, the catalyst (d) is employed
in the bath. In another aspect of the invention, the method
includes heating the coated substrate at an elevated temperature
of from about 200 to about 400F (about 93 to 204C).
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The compositions of the invention comprise three essential
and one optional component which may be present in a composition
which has good bath stability at ambient temperature and which may be
cathodically electrodeposited upon a substrat~ by conventional
techniques and the deposited coating then heated to an elevated
temperature for a time sufficient to cure it by a cross-linking
reaction between components of the composition.
As mentioned above, the essential components of the
electrodepositable composition, which is diluted in water to
comPris& an electrodeposition bath, are (a) a capped or uncapped
hydroxyalkyl carbamate cross-linking agent, (b) a cationically-
charged, non-gelled polymer and (c) an acid solubilizer ar disperser
to render the polymer water-dispersible. The optional compenent
is (d), a cross-linking catalyst.
The Hydroxyalky~--arbamate Cross-LinkinR Agent
Cyclic carbonates such as ethylene or propylene carbonate
react with amines to form hydroxyalkyl carbamates, according to
the following typical example, in which Ra i5 assu~ed to be hydrogen:
..
:.':, .,. :
'' ' ~ :
'~
--6--
(1) R1~
a Ib
_ CH R ~ N - C - O - CH CH 2 OH
R2~ ~ b
~N - C - O - CH CHOH
d
where Rb is hydrogen for ethylene carbonate and methyl for propylene
carbonate. The reaction may be run with or without solvent and, if
so desired, protic solvenes such as water or alcohols may be used.
h~en either Rc or Rd is hydrogen, as in an unhindered primary
amine, the reaction takes place at room or slightly elevated tem-
peratures whereas secondary or hindered primary amines usually
require heating and/or the use of catalysts for significant reaction.
Hydroxyalkyl carbamate-containing compounds as illustrated in
equation (1) above are useful in this invention if they are
sufficiently hydrophobic to be co-electrodeposited with a
cationic polymer by conventional techniques. In some cases, in
order to attain the requisite degree of hydrophobicity of the cross-
linking agent, the hydroxy groups may be reacted with other,
hydrophobic capping agents to incorporate the latter into the cross-
linking agent.
Numerous polyamines, including, for example~ 4,4'-diamino-
dicyclohexyl methane, 4,4'-diaminodicyclohexyl propane, and
hexamethylene diamine may be used for the formation of carbamate
~: '
". ,
,
,: :; : ' ` ; ;
- , :
~7~:)3~
cross-linking agents by reaction with cyclic carbonates. Suitable
polyamines include, by way of example and not limitation, simple
diamines such as those of the formula
(2) RlHN-R2-NHR3
where Rl is independently H, CH3 or C2 to C20 al~yl, R2 is
independently -CH2 or C2 to C20 alkyl fragments which may con-
tain aromatic or saturated rings and wherein ~1~ R2, and R3 may
also contain other functional groups which do not interfere with
the amine-carbonate reaction, including, for example, esters,
am`ides, nitriles, ethers, hydroxys, phenolics, ~etones, etc., and
R3 is independently H, CH3 or C2 to C20 alkyl.
A suitable class of monomers/polymers usable to react with a
cyclic carbonate to form a carbamate-containing cross-linking agent
comprises vi~yls/polyvinyls, acrylicslpolyacrylics, methacrylics/
polymethacrylics, esters/polyesters, amides/polyamides, imides/
polyimides, ethers/polyeehers, or mixtures or capolymers oÇ these
which contain an average of two or more pendant amine groups per
molecule.
As indicated above, the a~ines utilized in accordance with
the present invention to react with one or more cyclic carbonates
to provide hydro~yalkyl carbamate-containing cross-linking agents
may be any one oÇ a lar~e number oÇ compounds and, generally, may
comprise polyflmines containing straight chain or branched alkyl,
cycloalkyl or allcyl aromatic moieties? most preferably Cl to C20
: " ~. ~:.
.: "~" ., . -
'','- : ::
- :
~2~
alkyl, cycl`oalkyl or alkyl aro~atic moieties and such moieties
containing, in addition to at least one carbon atom, one or more
heteroatoms. Such moieties containing one or more heteroatoms
include, for example, those containing thio groups and organo-
silicon moieties, in addition to the groups mentioned above in
connection with formula (2).
As will be appreciated by those skilled in the art, a certain
degree of hydrophobicity is required of a cathodically electro-
depositable material such as the cross-linking agent employed in
this invention. Therefore, it is preferred that the polyamines
(as used herein and in the claims, the term "polyamines" is deemed
to include diamines) utilized be selected so that after reaction
with the cylic carbonates the resulting carbamate cross-linking
agents are water insoluble or only partly water soluble. However,
water soluble carbamate cross-linking agents, otherwise suitable~
may be ~odified to render them water insoluble or par~ly water
soluble. This may be accomplished by capping or blocking the
hydroxyalkyl carbamate groups by reacting them with a suitable
capping agent which, when the deposited composition is heated to
cure, will enter into the cross-linking reaction. Generally, ehe
capping agents may be any suitable reagen~s which will react
with the hydroxy groups of the hydroxyalkyl carbamate moiety
to form an ester, urethane, thiocarbamate, sul~onic ester,
sulfonamate ester, ether, or the like, whereby the cross-linking
agent is rendered water-lnsoluble. Among suitable cappin~
agentS are the clas5eg o~ compounds set forth in the ~ollowing list,
~7~3~
which also shows the class of the moiety resulting from capping the
hydroxy moiety of the hydroxyalkyl group of the hydroxyalkyl
carbamate.
Cappin~ Agent Resultant Capping Moiety
1. Aliphatic and aromatic
carboxylic acids Esters
2. Aliphatic and aromatic
carboxylic acid halides Esters
3. Aliphatic and aromatic
carboxylic acid anhydrides Esters
4. Aliphatic and aromatic
carboxylic esters Esters
5. Isoalkylenyl Esters (e.g.,
isopropenyl acetate, etc.) Esters
6. Ketenes (e.g., ketene, mono or
disubstituted ketenes, etc.) . Esters
7. Ureas (e.g., urea, mono-,di-, or
tri-substituted ureas, etc.) Urethanes
8. Aliphatic and aromatic
isocyanates Urethanes
9. Cyanic Acid Urethanes
10. Aliphatic and aromatic
isothiocyanates Thiocarb~mates
11. Aliphatic and aromatic
sulfonyl halides Sulfonic Esters
12. Aliphatic and aromatic
sulfamoyl halides Sulfonamate Esters
13. Aliphatic and Alkyl aromatic
alkyl halides Esters
. ~ , .
"" ~' " ' ' ~
33
--10--
The above list of capping agents is merely illustrative
and not limiting, as will be appreciated by those .skilled in
the art. For e~ample, alcohols, including diols and polyols
(see Example 4, below), mercaptans, amines and polyamines may
also be employed as capping agents to render the hydroxyalkyl
carbamate cross-linking agent water-insoluble. By way of example,
capping the hydroxyalkyl carbamate moiety of the cross linking
agent with a polyol is illustrated by the following reaction.
R O H
~3) 3HOCH2CHoc-N-Rl + R2(OH)3 ~,
R O H H O R
11 l I li I
[ HOCH2CHOC-N-Rl-N-C-0] 3-R2 ~ 3HOCH2CHoH
In the above reaction r~l must also contain the following
hydroxyalkyl carbamate group.
HOCH2CHO~
R O H
As shown by reaction (3), three moles of a biscarbamate
pr~pared by reacting 1,6-hexanediamine and propylene carbonate per
reaction (1) above, are condensed with one mole of trimethylol
propane to prepare a liquid, organic solvent-soluble, trifunctional
cross-linker suitable for use in a cationic electrocoating co~-
positlon in accordance with the present invention. The starting
biscarb3mate is a water soluble, difunctional, crystalline
material. Its water solubility prevents its use in cationic
electrocoating because it will not codeposit with the resin. The
capping of the bi5carba~ate with the polyol provides a hydrophobic
,,~',",:,. "' : ,. ' '
;
~2~4~33~
composition well suited for use in the present invention.
The cyclic carbonates which are to be reacted with the amines
may comprise any suitable cyclic carbonate, including bis-carbonates,
which are reactive with one or more of the amine groups of a multi-
functional amine. Generally, five-me~ber ring organic carbonates
are preferred as compared to six-member ring organic carbonates
because the latter are relatively morP expensive and difficult to
prepare. Accordingly, a preferred cyclic carbonate utilizable in
the present invention has the formula shown in the equation (1) above,
- wherein R and Rb may be the same or dif~erent, and each may comprise
H, or a Cl to C8 aliphat~c, cycloaliphatic, aromatic or heterocyclic
compound. Ethylene carbonate and propylene carbonate are readily
available and have been successfully employed and to this extent
are preferred reactants.
The Amino Group-Containing ~olvmer
The amino group-containing polymer is a water-dispersible,
non-gelled polymeric material carrying a cationic charge. The
polymeric material may con~ain several dif~erent types o~ functio~al
groups. For example, the presence of hydroxy groups in the poly-
meric material is hlghly desirable for reac~ion with the carbamate
cross-lin~ing agents. However, the carbamate-conCaining cross-
linking agents will also cross-link through amine groups~ The
..~: .: . . . .
:, . : -
., - ~
~ ;~7~3
-
- 12 - 611~9-7362
presence of amino groups is essentlal, however~ to impart cationic character to
the polymer and to obtain stable dispersion in water in the presence of an acid
solubilizer or disperser.
A wide variety of amino group-containing polymers may be utilized in
the composition of the present invention. Polymers suitable for use in the
present invention are the amine adducts of epoxy group-containing resins as
disclosed in U.S. Patent 4,031,050 of Robert D. Jerabek.
A large number and variety of amino group-containing polymeric mater-
lals are suitable for use as the cationic polymeric component of the invention,
so long as such materials are non-gelled, water-dispersible, polymeric in na-
ture, and capable of carrying a cationic charge. It is also necessary that
these polymeric materials co-deposit with the carbamate-containing cross-link-
ing agent and when used, the optional cross-linking catalyst on the metal sur-
face upon passage of an electric current between a cathode comprising the sur-
face and an anode immersed in the electrodeposition bath. In this way, the
electrodeposited composition can be converted to the cross-linked state by the
application of heat. Cationic polymeric materials such as those identiEied as
cationic Polymeric Materials A through F in U~S. Patent 4,026~855 may be
utilized as the amino group-containing polymers of the present
~7~3~3
-13-
invention. Generally, in addition to bisphenol-A based epoxy
cationic materials, novalac epoxy based cationic materials may
be utilized.
The Acid Solubilizer
The acid solubilizer or disperser may comprise one or more
organic or inorganic acids which are water soluble or at least
water dispersible and which will convert the amino group-containing
polymer to a weter-dispersible material carrying a cationic charge.
The acid solubilizer is a water soluble (or at least water disper-
sible) material, so that the counterion formed when the acid is
added to the cationic polymer facilitates the water dispersion
or solubilization of the cationic polymer. Generally, the acid
solubilizer may be any suitable acid which will impart a cationic
charge to the polymer and will not interfere with the stability
or cross-linking reaction of the composition.
Among suitable acid solubilizers are inorganic acids such as;
hydrohalic acids, nitric, sulfuric, phosphoric, carboxylic acids
such as acetic, butyric, pentanoic, formic, lactic and citric ac~ds
or the like, or polycarboxylic acids such as: adipic, oxalic,
malonic, succinic, maleic, or fumaric acids or the like.
The Cross-Linkin~ Catalyst
The optional componenc of the composition of the present
invention is a catalyst effective to lower the cure temperature of
the other components of the composition after they have been
electrodeposited upon a substrate. The catalyst accordin~ly must
co-electrodepo9it with the other ingredients in the cathodic
electrodeposition process. ~yplcally, a suitable cross-linking
:,
., . '', -. .
' .: .
,
~274~ 3
-14-
catalyst will lower the cure temperature of the electrodeposieed
materials from about 400 to 600F (about 204 to 316C), the
cure temperature without the catalyst, to about 200 to 400F
(about 93 to 204C). In order to attain sufficient co-deposition
of the cross-linking catalysts with the other components of the
electrodeposition composition, the cross-linking catalysts are
preferably water insoluble or, at most, only partially soluble
in water. Further, in order to insure efficient co-deposition of
the catalyst, it is preferably at least partially soluble in the
cross-linking a~ent and in the amino group-containing polymer.
Typical catalysts include organo tin compounds such as dibutyltin-
dilaurate, organo zinc compounds, organo titanium compounds,
quaternary ammonium compounds and the like, including quaternary
phosphonium and arsonium compounds and ternary sulfonium compounds.
Other suitable catalysts include organo tin compounds such as
dialkytin compounds, e.g., dibutyltindilaurate, organo ~inc com-
pounds such as zinc octoate, zinc bu~yrate, etc., some organo
titanium compounds, tetraalkyl ammonium compounds where the alkyl
groups are selected so that quaternary ammonium compounds are
water insoluble lor at most, water dispersible~ and co-deposit
with the other components of the composition. In general, the
catalysts are selected so that they are sufficiently hydrophobic to
co-deposit with the carbamate cross-linking agent and amino group -
containlng polymer components at least in amounts suficient to
reduce the cure temperature o~ the electrodeposited compasltion.
A9 k~own ln the art, the catalygts may be lncorporated into the
" ~' ' '
~7~ 3
--15--
backbone of the poly~er (b) during preparation of the polymer.
Usually, sufficient catalyst is co-deposited to reduce the
cure temperatu~e from about 400 to about 600F tabout 204 to
316C) to from about 200 to about 400F tabout 93 to 204C)
or even less, e.g., from about 200 to about 250F tabout 93 to
121C).
The efficacy of the specific embodiments of the invention is
illustrated by the following Examples, in which Examples 1-4
illustrate the preparation of suitable carbamate-containing
cross-linking agents.
EXAMPLE
Carbamate Cross-Linkin~ Agent I
To a suitably equipped flask under a nitrogen atmosphere was charged
436.8 grams (2.1 moles) of 4,4'-diaminodicyclohexyl methane (mixture
of isomers), 435.4 grams (4.3 moles) of propylene carbonate, and
262 grams of tert-butyl alcohol. The ~ixture was brought ~o
reflux and the progress of the reaction was followed by titrating
~he remaining amine with O.lN HCl using phenol red indicator. After
3 days at reflux 95% conversion was reached and the mixture was
cooled to 50C and 500 ml of acetone was added. After cooling to
room tel~perature the mixture converted to a slurry of white
crystals. The mixture was then warmed to 60C and fil~ered. To
the filtrate was added small portions of e~hylacetate-heptane
(2 to 1 by volume) until no more solid separated. Refiltration,
combining the collected solid with that obtained previously, and
drying at 40qC overnlght afforded 125 grams ~14.5%) of high melting
"",
'":. '~" ' . . . '
.: : . ' ' '
',; ., .;.
~L274(~3~
-16- 61109~7362
(19Z to 198C) isomers of bis(2-hydroxy-1-methylethyl~ (methylenedi
-4,1-cyclohexanediyl)biscarbamate, herein referred to as "Carbamate
Cross-Linking A~ent I" which gave satisfactory spectral
analyses but were not deemed suitable for use in cathodic electro-
coating compositions due to their high melting range. Accordingly,
to the clear filtrate was added enough cationic exchange resin
(Dowex SOW-X~ manufactured by Dow Chemical Co.) to remove all
residual free amine as determined by checking with phenol red
indicator from time to time. After all free amine had been removed,
the ion exchange resin was filtered off and the solvents were
vacuum distilled with steam bath heating, the last traces of which
were removed at 5 mm of pressure. The resulting clear, light
yellow, low me:Lting semi-solid gave satisfactory spectral analyses
for a mixture of isomers of Carbamate Cross-Linking Agent I.
The yield of Carbamate Cross-Linking Agent I was 683.1 grams (80%
of theory; the total yield of all dicarbamates was 93.7% of theory).
E~A~PLE 2
Carbamate Cross-Linkin~ A~ent II
To a suitable reactor under a nitrogen atmosphere was charged
95.36 grams (0.4 moles) of 2,2'-~is(4-amino cyclohexyl) propane,
83.72 grams (0.82 moles) of propylene carbonate, and 53.72 grams of
tert-butyl alcohol and the whole was brought to reflu~. The
progress of the reaction was followed by titrating the remaining
amine with O.lN HCl using phenol red indicator. 95% conversion
was obtained after three days of refluxing after which the viscous
reactlon mixture was c`oclecl to SOQC and 54 grams of methanol was
added. ~nou~h o~ the same ca~ionic exchan~e resin as used in ~xample
* 7'rqr~Q M~l rl~
~2
; ~ .
7~3~3
1 was added to remove ~ree amine and the solution was filtered.
Evaporation of all solvents under vacuum using steam bath heating
afforded 163 grams (91% of theory~ of a mixture of isomers of
bis(2-hydroxy-1-methylethyl), [~l-methylethylidene)di-4,1-
cyclohexanediyl]biscarbamate, herein referred to as "Carbamate
Cross-Linking Agent III'. The structure was confirmed by spectral
analyses. Carbamate Cross-Linking Agent II softens by about 60C
and begins to melt at about 80C.
Hexane-1,6-bis(hydroxypropyl~carbamate
as a starting material for Cathodic Electrocoating Compositions
Hexane-1,6-bis(hydroxypropyl) carbamate is completely water
soluble and cherefore unsuitabie as a carbamate cross-linking agent
for cathodic electrocoating. Hexane-1,6-bis(hydroxypropyl)
carbamate was prepared as described in the literature (Na;er, ~1.,
Chabrier, P., and Guidicelli, R., Compt. rend. 238 690 tl9S4)~ by
the reaction of hexamethylene diamine, and propylene carbonate
and subsequently fully purified. This bishydroxypropyl carbamate
was then chemically modified by "capping" or "blocking" the
hydroxyalkyl carbamate groups in order to produce wa~er insoluble
carbamate cross-linking agents for cathodic electrocoating as
described below.
~X~ E 3
. Carbamate Cross-Linking A~ent III
. _ _
To a suitable reactor under a nitrogen atmosphere was charged 50.0
grams o~ dry pyridine and 8.72 grams tO.04 moles) of hexane-1,6-bis-
(h~droxypropyl~ carbamate prepared as described above. The well
stirred solutian was then caoled to a 3C and ace~ic anhydride
t8.98 Brams; 0.88 moles~ was slowly added keeping the temperature
:. .:. . ,
~ '
- .
3~
below 10C while efficiently stirring. After complete addition the
mixture was stirred overnight at room temperature. At this
point thin layer chromatography (TLC-Analtech precoated Silica
Gel GF 250 micron plates 2.5 x lOcm; eluent 10/90 V~V MeOH/CHC13
followed by oven drying at 105C for 30 minutes to remove pyridine
and pyridine acetate; visualization with iodine) showed only one
product spot at Rf 0.73 (pure hexane-1,6-bis(hydroxypropyl)
carbamate has Rf 0.53 under the same conditions. Most of ehe
solvent pyridine was then removed at aboutlO mm of pressure with
a flask temperature of 40 to 80C. The reaction residue containing
product was then dissolved in CHC13 ~100 ml) and washed with three
25 ml portions of 25% w/w NH4Cl solution, then with two25:ml portions
of water, followed by a25 ml portion of brine. The CHCl3 solution
of product was then dried (Na2S04), filtered, and evaporated under
vacuum to afford 10.77 grams (99%) of a light yellow liquid which
solidified to a low melting solid on standing. This product was
insoluble in water, homogeneous by TLC and gave IR and PMR spectra
consistent with the diacetate of hexane-1,6-bis(hydroxypropyl)
carbamate,. hereinafter referred to as "Carbamate Cross-Linking
Agent III".
EXAMPL~ 4
Carbamate Cross-Linking Agene IV
In a suitably equipped flast was charged Trimethylol propane
(13.4 grams) hexane-1,6-bis(hydroxyprQpyl)~carbamate prepared as
descrlbed above (96 grams)~ and dibutyltindilaurate catalyst
(0.6 grams). Th~ reaction mixture was stirred and heated under
: ;
4 [)~
- 19 - 61109-7362
reduced pressure (approximately 20 mm of Hg) to 175 to 190C Eor a perlod of
about one hour. During this period about 10 grams oE distillate was collected
which by GPC proved to mostly propylene glycol. The clear resinous product in
the Elask was soluble in alcohol, Cellosolve, and insoluble in water. The
resulting condensation product of hexane-1,6-bis(hydroxypropyl)carbamate with
trimethylol propane is herein referred to as "Carbamate Cross-Linking A~ent
IV". The product was diluted with 20 grams of Cellosolve to 77% solids.
The following Examples 5-7 illustrate the preparation of cationic
polymers usable in the composition of the invention.
IO EXAMPLE 5
Cationic P~ol'ymeric'Mat'erial V
Cationic polymeric material V is prepared by reacting n-butyl acrylate, sty-
rene, N,N-dimethyl amino ethyl methacrylate, 2-hydroxyethylacrylate, the reac-
t:lon product oE acrylic acid and a methoxypolyethyleneglycol having a molecular
weight oE 550, N-dodecyl mercaptan, and azobisisobutyronitrile in the amounts
and according to the procedure described in U.S. Patent 4,026,855 Eor the pre-
paration of the material therein described as "Polymeric Material E". The
final reæin is about 71% solids and has an hydroxy number oE about 90 and an
amine number of about 45.
EXAMPLE'6
Cationi'c Polymeric Mat'_ial VI
Catlonic polymerlc material VI, a cationic epoxy resin, was prepared by
reacting EPON* 1004 (a product of Shell Chemical Co.
*Trade-mark
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comprising the reaction produce of bisphenol-A and epichlorohydrin) with the
diketimine of t~e diethylenetriamine (prepared as described in U.S. Patent
3,523,925) and diethyla~ine according to the procedure described in U.S. Patent
3,984,299 Eor the preparation of the material therein described as adduct C.
The final cationic resin was 75% solids. The analysis o~ the resin corrected
to 100% solids showed the following: t-amine: 1 meq per gram, primary amine
(after hydrolysis): 0.2 meq per gram, and calculated hydroxy content 3.7 to 4
meq per gram.
EXAMPLE 7
Cationlc`Polymeric Material VII
Cationic Polymeric Material VII, an epoxy material, was prepared from the
ingredients and processes described below:
Pa~rts`by Weight Equivalents
EPON 1004* 1017.0 1.0
~ethyl isobutyl ketone 176.0 --
(MIBK)
Diketimine 69.4 0.~6
Diethylamlne 57.5 0.79
Propa80l P** 163.0 --
*Shell Chemical Co. reaction product of epichlorohydrin and bisphenol-A
**Union Carbide Corp, trade mark for propoxypropanol
The EPON 1004 and MIBK were charged to a suitable reactor under nitrogen havlng
a decantlng trap in the dlstillate return line. The mixture was heated to
reflux with stlrring in order to remo~e any water
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present. After cooling to 80C the Propasol P was added followed
by the diketi~ine (derived from one mole of diethylenetriamine
and 2 moles oE MIBK as described in U.S. Patent 3,523,925). The
mixture was held at 80C for one hour and then cooled to 60C and
the diethylamine was slowly added keeping the temperature below 65C
(exotherm) so that no diethylamine was lost by volatilization.
After complete addition the mixture was refluxed for one hour and
then 100 parts more of Propasol P was added. The same amount of
Propasol P was then removed by two vacuum distillations at 100 to
125C in order to remove any residual free diethylamine. The final
cationic resin was 78~ solids. The analysis of the resin corrected
to 100% solids showed the following: t-amine: 0.84 meq per gram;
primary amine (after hydrolysis): 0.45 meq per gram and calculated
hydroxy content: 3.6 to 3.8 meq per gram.
The following Examples 8-12 illustrate the preparation and
use of cathodic electrocoating baths in accordance with specific
embodiments of the present invention. All references in the
following Examples to "parts" means parts by weight.
EXA~PL~ 8
A cathodic electrocoating bath is prepased by combining 50 parts
of the Cationic Polymeric Material V, lS parts of t~e Carbamate.
Cross-Linking Agent I, 1.7 parts of 88% lactic acid, and 1.5 parts
of dibutyltindilaurate in a suitable mixing vessel equipped with a
Cowels stirrer. These ingredients are rapidly mixed while 466
parts of the deioni~ed water is slowly added to produce a bath
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contalning approxim~tely lO,' solids. The final cathodic elec~ro-
oating bath has a pH of 4.8. Af~cr a~in~ the b~th overni~ht,
electrodeposition of the composition on aluminum panels serving as
the cathode at lOOV for 60 seconds afforded, after rinsing and curing
at 175C for 20 minutes, cured films which are glossy,
smooth, and have very good solven~ resistance and mechanical
propèreies.
EX~YoeLE 9
The procedure of Example 8 was repeated in all essential respects
using the following ingredients:
Parts by Weight
Cationic Polymeric ~aterial VII 49.0
Carbamace Cross-Linking Agent I 14.4
Hexyl Cellosolve* (1) 5.0
Butyl Cellosolve** 5.0
Lactic Acid (88%) 2.8
Dibutyltindilaurate 1.2
Deionized Water 485.0
*Monohexyl ether of ethylene glycol - a flowing agent
**Monobutyl ether of ethylene glycol - a co-solvent
The final cathodic electrocoating bath was lOZo solids and had a pH
of 5.8 and a conductivity of 700 micro mho cm 1. APter aging the
bath cvernight, electrodeposition of the composition on aluminum
panels serving as a cathode at 75V for 20 seconds produced, after
rinsing and then curing at 175aC for 20 minutes, films with thick-
nesses oP 0.2 to 0.25 mil. All panels were smooth, glossy, had 4H
pencil hardness, passed 40 in-lb impact tests, znd resisted greater
~harl 200 methyl ethyl ke~orle doub~le rubs. rhis cachodic electro-
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coating bath proved stable for greater than 3 months.
EYA~LE lO
The procedure of Example 8 and the ingredients of Example 9 were
repeated, except that 15.3 parts of the Carbamate Cross-Linking
Agent II was substituted in place of the 14.4 parts of Carbamate
Cross-Linking Agent I. The resulting cathodic electrocoating bath
had a pH of 5.8, a conductivity of 700 micro mho cm , and was
approximately lO~ solids. Aging the bath overnight followed by
electrodeposition on aluminum panels serving as the cathode at
75V for 20 seconds afforded, after rinsing and curing at 175C for
20 minutes, film builds of 0.2 to 0.5 mil. The coatings on all
panels were smooth, glossy, had 4H pencil hardness, passed 40 in-lb
impact tests and resisted greater than 200 methyl ethyl ketone double
rubs. The electrocoating bath was stable for more than three months
in storage at ambient temperatures.
EXA~PLE ll
The procedure of Example 8 and the ingredients of Example 9 were
repeated except that 9.4 parts of Carbamate Cross-Linking Agent III
was substituted for Carbamate Cross-Linking Agent I and 440 parts
of deionized water was used. The resulting cathodic electrocoating
bath was 10~ solids, had a pH of 5.5, and a conductivity of 780
micro mho cm l The bath was then aged overnight and aluminum
panels servlng as the cathode were electrocoated at 75V for 20
seconds. The electrocoated panels were then rinsed and cured at
175~C Eor 20 minutes. The cured ~ilms were 0.2 to 0.25 mil thick,
had 4~ pencil hardness, passed 40 in-lb impact tests, were smooth and
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glossy, and resisted greater than 200 methyl ethyl ketone double
rubs. The bath ~as still stable after three months aging at
ambient temperature.
EXAMPLE 12
Using the mixing procedure of Example 8, 47 parts of Cationic
Polymeric Material VI, 19.5 parts of Carbamate Cross-Linking
Agent IV, 3 parts of hexyl Cellosolve, 1.2 parts of dibutyltindilaurate,
and 3.6 parts of 88~ lactic acid were emulsified to 10% solids with
470 parts of deionized water. A milky white emulsion was obtained
having a pH of 5.8 and a conductivity of 1225 micro mho cm . After
aging the cathodic electrocoating bath overnight, aluminum panels
serving as the cathode were electrocoated at 50V and lOOV for
30 seconds. The electrocoated panels were rinsed with water and
then cured at 175C for 20 minutes. After the cure, the electrocoated
films were solvent resistant, had thickness of 0.6 to 0.7 ~il,
passed 40 in-lb impact tests, and had pencil hardness of 4H to 5H.
Generally reference herein and in the claims to hydroxyalkyl
carbamates and compounds containing the same, including structural
formulas of the same, is intended to include the various isomeric
species thereof, if any.
While the invention has been described with respect to
specific preferred embodiments, it will be apparent to one skilled
in the art that numerous variations may be made to the embodiments
without departing from the spirit and scope of the invention.
