Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1229/1340 109470~3
FIELD OF INVENTION AND BACKGROUND
The present invention is directed to the preparation of, and
coating compositions which are water-dilutable upon neutralization with
acids. The coating compositions are electrically depositable at the cathode
of an electrodeposition system and will crosslink through thermal polymer-
ization.
Electrodeposition of synthetic resins and plasticsJ although
known for substantial time, has gained technic~l importance as a coating
process in only recent years. The coating compositions or binders pri-
marily used for commercial electrodeposition contain polycarbo~ylic acid
resins neutralized with bases. The products deposit at the anode of an
- electrodeposition system. Owing to the acidic character of the resins,
they are sensitive to corroding influences exerted by salts and particularly
by alkalis. Furthermore, coatings of the aforesaid compositions tend to
undergo spot discoloration or undergo other chemical changes as a result
of the metal ions anodically dissolved from the anode. Accordingly, there
has been a desire to use coating compositions which will deposit at the
cathode of an electrodeposition system.
A substantial number of binders are disclosed in the literature
carrying groupings neutralizable with acids which can be deposited on
cathodically wired ob~ects of an electrodeposition system. Many have dis-
advantages primarily due to the need to have crosslinking additives in the
c~oating compositions which adversely affect film characteristics. Re-
cently, however, coating compositions have been provided which are self-
crosslinking through thermal polymerization. These self-crossl;nking
binders include binders comprising -
-- 3 --
109~70B
(A) the reaction products of diepoxy compounds with alpha,
beta-unsaturated acids and, optionally, long chain fatty acids, and
basic monoisocyanates as described in copending Canadian appli- `
cation No. 282,996 filed July 18, 1977, assigned to the assignee of the
present application;
(B) reaction products of diepo~y compounds with monoamines
and, optionally, fatty acids, and unsaturated monoisocyanates as de-
scribed in copending Canadian application No. 282,900 filed July 18,
1977, assigned to the assignee of the present application; and
(C) two moles of a diepoxy compound plus one mole of a pri-
mary-tertiary or secondary-secondary diamine plus two moles of an
alpha,beta-unsaturated monocarboxylic acid and, optionally, an unsat-
urated fatty acid, plus an unsaturated monoisocyanate as described in
copending Canadian application No. 290,406 filed November 8, 1977,
assigned to the assignee of the present application.
The aforesaid binders are highly desirable due to their
ability to self-crosslink through the presence of alpha,beta-unsatura-
tion; their being water-soluble in the presence of acids due to the
basic nitrogen atoms, and their ability to provide excellent films with
good performance characteristics, particularly regarding resistance to
corroding influences. The aforesaid binders, however, utilize expensive
components and, accordingly~ cannot be used for many applications be-
cause of cost.
OBJECTS OF THE INVENTION AND GENERAL DESCRIPTION
It has now been found that components containing basic func-
tional nitrogen groups for neutralization with inorganic or organic acids
can be derived rrom components which are rela~ively inexpensive, but
which
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IL~ - 4 -
~0~ ~708
provide coating compositions having excellent resistance to water,
chemicals, and corrosion. The relatively low cost of the components
permits the use of cathodic electrodeposition on a substantially wider
scale than heretofore possible.
The basic functional nitrogen atoms according to this inven-
tion are introduced into substantially non-saponifiable diene polymers
having a main polymer chain of co-valent carbon atoms carrying free
hydroxyl groups to form the basis for a thermosetting aqueous binder
for cathodically depositable coatings, such binders, in accordance with
the invention comprise essentially the reaction product of (A) a hydroxyl
group containing diene polymer having a hydroxyl number of at least about
40 mg KOH/g and an average maximum molecular weight of 4000; and ~B)
compounds carrying per molecule an average of from 0.8 to 1.5, and pre-
ferably one free isocyanate group and at least one basic aliphatically
bound nitrogen atom, neutralized with an organic or inorganic acid.
Optionally, there can be present a compound ~C) carrying per molecule an
average of from 0.8 to about 15, and preferably one free isocyanate group
and from l to 3 ethylenically unsaturated double bonds per molecule.
Components ~A) and (B~, and optionally (C), are reacted at from about 10
to 100C., and preferably from about 50 to 80C., to an NCO-value of
substantially zero. The reactionJ if desired, can be carried out in the
presence of an isocyanate inert solvent. Catalyst can be included if
desired. The reaction product is partially or totally neutralized with
inorganic or organic acids.
Unsaturated polymers of dienes with free hydroxy groups, suit-
able for use in the present invention, include copolymers of alkane di-
enes or cycloalkanedienes with hydroxy groups containing monovinyl com-
pounds and, optionally, subordinate quantities of other monovinyl com-
pounds. Suitable diene compounds include 1,3-butadiene, 1-3-penta-
diene, cyclo-
B _ 5 _
1229/13~0 1094708
pentadiene or isoprene, while hydroxy group containing monovinyl com-
pounds are allyl alcohol or hydroxy alkyl esters or hydroxyalkylene oxide
esters of acrylic or methacrylic acid. Another known method to introduce
preferably chain ending hydroxyl groups into diene polymers is the reaction
of so-called "living polymers" with alkylene oxides, preferably ethylene
oxide. A group of diene polymers with latent hydroxy groups are epoxidation
products of diene polymers. The products are prepared in known manner
, through treatment of liquid diene polymers with per-formic acid or per-
acetic acid. In oxirane structures, the oxirane group is considered a latent
hydroxy group since a hydroxy group is set free upon reaction with a com-
pound carrying an active hydrogen atom, The reaction can be carried out
~~ at temperatures of up to 1~0~ C., either with monocarboxylic acids orsaturated or unsaturated fatty acids, benzoic acid, p-tert.-butylbenzoic
acid, sorbic acid, and the like, and may optionally be accelerated by alka-
line catalysts. Another manner of releasing free hydroxy groups from
partially epoxidized diene polymers which is an advantage for the use of
the products produced according to the invention is the reaction of the
epoxy group with secondary alkylamines or secondary alkanol amines,
such as diethylamine, diethanol arnine, diisopropylamine. The introduc-
tion of the nitrogen atom into the polymer chain increases the basic char-
acter of the macromolecule in the desired way. The secondary hydroxy
group which forms on the opening of the oxirane ring is used according to
the invention for reaction with the isocyanate containing components.
The basic nitrogen atorns are introduced into the diene polymer
containing free hydroxyl groups according to this invention by reaction
with compounds carrying per molecule an average Or from 0. 8 to 1.5
1229/1340 109470t3
isocyanate groups and at least one tertiary basic nitrogen atom. Prefer-
ably the compounds contain an average of about one isocyanate group in the
molecule.
The compounds containing the basic nitrogen atom are pre-
pared in a separate step by reacting diisocyanates or polyisocyanates with
less than a stoichiometric quantity of an amine of the formula -
,R
R - N~
R being an alkanol or hydroxyphenyl radical, and Rl and R2 being alkyl
radicals or cycloalkyl radicals. Dialkylalkanol amines are preferred in-
~; 10 cluding dimethylethanol amine, diethylethanol amine or higher homologues and isomers thereof.
Suitable polyisocyanates for use in preparing the intermediate
basic nitrogen carrying component are aromatic isocyanates such as 2,4-
or 2, 6-toluylene diisocyanate or mixtures thereof, 4,4'-diphenyl-methane-
diisocSranate or cycloaliphatic isocyanates such as isophorone diisocyanate,
cyclohexane-1,4-diisocyanate, as well as aliphatic isocyanates, such as
trimethylhexamethylene-1,6-diisocyanate; tris-hexamethylene-triisocyanate.
The reaction between the amine and the polyisocyanate is
carried out at from 0 to 80 C., preferably at from 2û to 50 C. The weight
ratios between the reaction partners are chosen in order that the formed
- compound carries from about 0. 8 to 1. 5, and preferably one free isocyanate
g-roup~, This product is at times herein designated as the "basic isocyanate
intermediate. "
In order to enhance the thermal crosslinking reaction of the
cathodically deposited film, it is desirable to react the reaction products
1229/13ds0
~09470B
of the hydroxy containing diene polymer and basic isocyanate intermediate
with compounds carrying from about 0.8 to 1. 5 free isocyanate groups in
the molecule and from 1 to 3 olefinically unsaturated double bonds. These
compounds are prepared in a separate reaction step from the aforemen-
tioned polyisocyanates and a reaction partner which carries at least one
isocyanate reactive hydrogen atom and from 1 to 3 olefinic double bonds.
Suitable unsaturated compounds include hydroxyalkyl esters of acrylic acid
or methacrylic acid, triethyleneglycol mono(meth3acrylate, trimethylol-
propanedi(meth)acrylate, allyl alcohol, tripropyleneglycol manoabietate,
oleyl alcohoLor linoleyl alcohol. The reaction between the polyisocyanate
and the isocyanate reactive olefinically unsaturated compound is carried
-- out, optionally in an isocyanate inert solvent, at temperatures of from 10
to 100 C., and preferably from about 50 to 80 C. Organic stannous com-
pounds, as catalysts, can be advantageously used. The weight ratios of
the reactants are chosen such that the formed compound carries from about
0.8 to 1.5, and preferably one free isocyanate group in the molecule. The
compound is at times herein designated as the "olefinically unsaturated
isocyanate intermediate. "
The reaction components used in preparing the binders of the
~0 present invention are effected in order that the hydroxy group containing
unsaturated diene polymers, preferably dissolved in isocyanate-inert
solvents, are reacted at from 10 to 100 C., preferably at from 50 to 80 C.,
with the desired quantity of the basic isocyanate intermediate and, option-
ally, with the olefinically unsaturated isocyanate intermediate, optionally
in the presence of organic stannous compounds as catalysts, until an
NCO-value of zero is obtained. The quantity of basic isocyanate interme-
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1229/ 1340
~094708
diate is chosen in order that the basicity of the binder upon neutralization
with the acid will provide sufficient water dilutability at a pH-value of from
4 to 9, and preferably 6 to 8. The reaction between the hydroxy group
containing polycondensates, the basic isocyanate intermediate, and the
olefinically unsaturated intermediate may be effected in random sequence,
separately or jointly.
In order to reduce the stoving temperatures or to obtain a par-
ticular corrosion protection it can be of advant age, although not essential,
to co-employ additional known crosslinking agents, such as melamine- or
phRnol-formaldehyde condensates. Such resins are prepared according to
known methods by alkaline condensation of formaldehyde or of formaldehyde-
splitting substances with urea, melamine, benzoguanamine? acetoguanarnine,
phenolJ cresol, p.-tert. -butylphenol, Bishpenol A, and the like. The
methylol compounds may be optionally etherified with alcohols. A preferred
product in this group is the reaction product of phenol with formaldehyde
- carrying allyl ether groups. If the crosslinking agents are non-water-
soluble, it is advantageous to combine them by careful condensation with
the binder of the invention at temperatures of from 50 to 120 C. The reac-
tion is carried out until excellent dilutability with water of the reaction
mass upon neutralization with low molecular weight organic acids is ob-
tained.
The basic nitrogen atoms of the coating compositions of the
invention are partially or totally neutralized with organic and~or inorganic
acids such as formic acid, acetic acid, lactic acid, and phosphoric acid.
The degree of neutralization in the individual case depends upon the prop-
erties of the binder employed. In generalJ sufficient acid is added to allow
1229/1340
, 10947B
dispersion or dilution with water at a pH-value of the coating of from
about 4 to 9, and preferably of from about 6 to 8.
The concentration in water of the binder depends upon the para-
meters of electrodeposition and may lie in a range of between about 3 to
30 percent by weight, preferably at from about 5 to 15 percent by weight.
The applied coating composition can optionally contain various additives,
such as pigments, extenders, surface active agents~ etc. Upon electro-
deposition, the binder of the invention as a vehicle of the aqueous coating
composition is wired to a conductive anode and cathode, the surface of the
cathode being coated with the coating composition. The conductive sub-
strates to be coated may be of a variety of materials, and particularly
-- metals such as ~teel, aluminum, copper, or the like. Other metalized
materials or materials rendered conductive through a conductive coating
can be employed. AMer deposition, the coating is cured at a stoving tem-
perature of from about 130 to 200C., preferably 150 to 180C. for about
5 to 30 minutes, preferably 10 to 25 minutes.
The following examples illustrate the invention without limiting
its scope.
Description Of The Intermediates Used In The Exarnples
~A) HydroxylGroup Containing Diene Polymers_
Intermediate (A 1): Commercially available liquid polybutadiene
with a hydroxyl number of 67 mg KoHJg. a molec~ar weight of about 1400
and a microstructure of about 90 percent 1, 2-vinyl- and about 10 percent
1, 4-trans configuration is used. (Polybutadiene G 1000 manufactured by
Nippon Soda Co. Ltd. )
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j 10~ ~708
Intermediate (A 2): Commercially available liquid polybutadiene
with a hydroxyl number of 47 mg KOH/g, a molecular weight of about 2800
and a microstructure of about 20 percent 1, 2-vinyl- and about 60 percent
1, 4-trans and 20 percent 1> 4-cis- configuration. (Polybutadiene R 45 HT
manufactured by Arco Chemical Company)
Intermediate (A 3): In a three-neck llask equipped with stirrer, inert
gas duct and reflux condensor, 1000 g of an epoxidized polybutadiene (1) are
heated to 100~C. and mixed with 885 g of p-tert.-butylbenzoic acid and 2 g
of triethylamine. The temperature is raised to 180 C. and the reaction is
carried to an acid value of below 3 mg KOH/g. Hydroxyl number of the end
product is approximately 200 mg KOH/g. The epoxidized polybutadiene
-- has a molecular weight of about 1500, an epoxy equivalent of about 160,
and a microstructure of 75 percent of 1, 4-cis and 25 percent of 1, 4-trans
configuration.
Intermediate (A 4): 1000 g of the epoxidized polybutadiene used for
.
intermediate (A 3) are heated to 180C. within 3 hours together with 525 g
of diethanol amine, maintaining reflux condensation and inert gas protection.
After another three hours at this temperature, 95 percent of the used amine
has reacted. A product with a hydroxyl number of about 600 mg KOH/g
20 results~
(B) Basic Isocyanate Intermediates
Intermediate (B 1): 174 g OI toluylene diisocyanate (a blend of 80
-
percent of 2> 4- and 20 percent of 2, 6-isomers) are charged to a three-
neck flask equipped with reflux condensor and inert gas duct, and, with
25 absolute protection from moisture and effective cooling, 89 g of dimethyl-
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1229/1340 109~'~708
ethanol arnine, 60 percent in ethyleneglycol monoethylether acetate,
are continuously added. The reaction temperature is held below 25C.
The reaction is finished when the theoretical isocyanate value is 16 percent
or lower.
S Intermediate (B 2): 174 g of toluylene diisocyanate (a blend of 80
percent of 2, 4- and 20 percent of 2, 6-isomers) are mixed with 194 g of
ethyleneglycol monoethylether acetate in a three-neck flask equipped with
reflux condensor and inert gas duct. Access of moisture is absolutely
prevented. With intense cooling, 117 g of diethylethanolamine are added
continuously within one hour at a temperature of below 25 C. The iso-
cyanate value of the final product is 14.4 percent.
-
(C) Olefinically Unsaturated Isocyanate Intermediates
~ = . . .
Intermediate (C 1): 168 g of hexamethylene diisocyanate are mixed
-
with 200 g of ethyleneglycol monoethylether acetate in a three-neck flask
with reflux condensor and inert gas duct and, while maintaining total pre-
vention of moisture access, is heated to 60 C. At the stated temperature
a blend of 130 g of hydroxyethylmethacrylate, stabilized with 0.1 g of
hydroquinone, are added dropwise. The reaction is finished, about 2 hours,
when the isocyanate value has attained 14.1 percent or slightly less.
Intermediate (C 2): In a three-neck ilask equipped with reflux
condensor and inert gas duct, with no possible access of moisture, 222 g
of isophorone diisocyanate are blended with 325 g of ethyleneglycol mono-
ethylether acetate and heated to 40C. 265 g of linoleyl alcohol are then
added continuously and, after the end of the addition, the temperature is
raised to 90 C. and held, until the isocyanate value has attained 8. 6.
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1229/1340
i ~ 1094708
Examples 1 - 4: In a reaction vessel equipped with stirrer,
addîtion funnel, thermometer and reflux condensorJ the hydroxy-rich diene
polymer (Intermediate A), in the presence of ethylene glycol monoethylether
acetate, an isocyanate inert solvent, is blended with a basic isocyanate
intermediate (Intermediate B), preventing access of moisture, and is re-
acted at 40 to 100 C. to an NCO-value of approximately zero. Swbsequently,
the reaction product is optionally mixed with an alpha, beta-olefinically
unsaturated isocyanate intermediate (Intermediate C) and reacted, also at
from 40 to 100 C., until an NCO-value of zero is obtained.
The reaction of Intermediate A with Intermediate B and Inter-
mediate C may also be effected in one reaction step at from 40 to 100 C.,
- with the same results.
It is also possible to blend the described reaction products with
crosslinking agents such as urea resins, melamine resins, or phenol-
formaldehyde resins and carefully reacted until substantial water dilutability
is attained.
The quantities of the Intermediates and the reactions conditions
for Examples 1 - 4 are tabulated in Table 1.
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1229/1340 109470~
TABLE 1
Reaction
Intermediates (g) ) Crosslinkers +) Conditions h/C.
1000 A 1 485 B2 - - - 1 /55
2 1000 A 2 352 B1 - - - 1/40
3 1887 A 3 485 B2 249 Cl 580 BP - 1/80 ~)
4 1525 A 4 220 Bl 253 C2 - 452 PA 3/60 I t 1)
+) All quantities refer to resin solids
~) Subsequent reaction with Intermediates B and C
+++) Simultaneous reaction with Intermediates B and C
Key to abbreviations in Table 1:
PE~ : Bisphenol A-formaldehyde resin
PA : Phenol-formaldehyde resin with allyl ether groups
(Methylon 75108 manufactured by General E:lectric)
15 Eval uation Of The Binders
Of the binders each 100 g resin solids samples were mixed with
the corresponding quantity of acid and made up to 1000 g with deionized
water while stirring. The 10 percent solutions were deposited using direct
current on steel panels as the cathode. Deposition time in all cases was
20 60 secondsO The coated substrates were rinsed with deionized water and
cured at elevated temperature, Average film thich~ess o~ the cured ~ilms
was between 13 to 17 ~am. Table 2 gives a summary of the evaluation.
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12291l340 10~4708
u, TABLE 2
Neutralization Deposition Evaluation
Q tity1) Type2) pH3) Volt Min/ C 4) Inde5n)ta- Resis
1 3.8 E 6.0 190 20/190 165 7.8 320/120
2 3.5 M 5,8 180 30/180 155 7.2 320/240
3 4.0 M 6.2 240 30/170 185 8.1 320/360
4 3.8 E 6.0 220 25/180 170 8.3 ~80/360
1) quantity of acid in g added to 100 g of resin solids
2) E: acetic acid; M: lactic acid
3) measured as a 10% aqueous solution
4) Konig pendulum hardness MN 53 157 (sec)
5) Erichsen indentation DIN 53 156 (mm)
6) hours of water soak at 40~C. until corrosion or blistering
become visible
-- 7) salt spray ASTM-B 117-64: 2 mm of corrosion at the cross
incision after the stated hours
For the evaluation degreased non-pretreated steel panels were
coated with a pigmented paint consisting of 100 parts by weight of resin
20 solids, 20 parts by weight of aluminum silicate pigment and 2 parts by
weight of carbon black.
In the above illustrative examples various modifications can
be made falling within the scope of the claimed invention. Such modifica-
tions being within the abi~ity of one sl~illed in the art are within the scope
25 of the present invention.
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