Cyanoacetic ester system

A process for preparing a crosslinked polymer comprises reacting a polycyanoacetic functional monomer or polymer with a poly .alpha.,.beta.-unsaturated ester in the presence of a catalytically effective amount of a metallic catalyst. A crosslinked polymer produced by this process is also described.

FIELD OF THE INVENTION 
The present invention relates to crosslinked polymers and to processes for 
the manufacture thereof. More particularly, the present invention relates 
to a crosslinked polymer system resulting from the reaction of a 
cyanoacetate ester and an .alpha.,.beta.-unsaturated ester group. 
BACKGROUND OF THE INVENTION 
Several disadvantages have been experienced with current ambient and 
thermosetting compositions and especially those formulated with melamine 
or urea-formaldehyde resins since during the curing cycle toxic volatiles, 
including free formaldehyde, are evolved. These compositions are generally 
cured at elevated temperatures, i.e. at about 275.degree. F. or higher. It 
has also been observed that while the use of isocyanates offers excellent 
cure at lower temperatures, i.e. from ambient temperature to about 
250.degree. F., nonetheless isocyanates are very toxic and compositions 
containing them, when cured at ambient or room temperature, produce 
undesirable side reactions, especially if moisture is present. Epoxy resin 
containing compositions can cure over a wide temperature range depending 
upon the type of curing agent employed. However, curing agents for epoxy 
resins are often very toxic and act as sensitizers to humans. Moreover, 
their exterior durability is unsatisfactory, limiting their use generally 
to primer applications. 
SUMMARY AND OBJECTS OF THE PRESENT INVENTION 
The present invention relates to a process for producing a crosslinked 
polymer. The process comprises reacting a polyfunctional cyanoacetic 
monomer or polymer with a polyfunctional .alpha.,.beta.-unsaturated ester 
in the presence of a catalytic amount of a metallic compound, preferably 
an organometallic compound. 
In one embodiment of the present invention, the process comprises 
transesterifying a monofunctional alkyl cyanoacetate with a hydroxy 
functional monomer or polymer having a functionality of two or greater in 
the presence or not of a transesterification catalyst so as to produce a 
polyfunctional cyanoacetic monomer or polymer and reacting the thus formed 
polyfunctional monomer or polymer with a polyfunctional 
.alpha.,.beta.-unsaturated ester in the presence of a metallic catalyst, 
preferably an organometallic compound. The present invention also relates 
to the crosslinked polymers produced by this process. 
It has been found that the disadvantages associated with other crosslinking 
systems can be avoided by the practice of the present invention which 
provides a crosslinking composition which is curable not only without the 
production of any toxic fumes or by-products during the cure cycle, but 
also at low temperatures, i.e. ambient temperature to about 350.degree. F. 
or higher without adverse side reactions. The quality of coatings produced 
using the crosslinked compositions of the present invention equals or 
exceeds that of current coatings in primer application or high durability 
top coats. The crosslinked compositions of the present invention, when 
used as a coating composition, also offer the advantage of being 
compliance coatings which meet the current Environmental Protection 
Agency's VOC (volatile organic compound) regulations. Coatings or films 
produced using the crosslinked compositions of the present invention 
exhibit excellent adhesion, excellent solvent resistance, good flexibility 
and excellent hardness. These properties are achieved when the polymer 
system is coated over numerous metallic and plastic substrates such as 
chromate treated aluminum, zinc and iron phosphate treated steel and 
various plastics such as polyamides, polycarbonates, ABS, and 
polyphenylene oxide. 
Polymers prepared from the composition of the present invention are useful 
as coatings for farm implements, automotive top coats, primers, aluminum 
extrusions, office furnishings and wood products. Industries having a use 
for such coatings have been in need of a high quality, non-toxic, low 
temperature cure coating meeting the EPA's VOC regulations and exhibiting 
good solvent resistance, hardness, flexibility and excellent gloss 
properties. The present invention fulfills such a need. 
DETAILED DESCRIPTION OF THE INVENTION 
The present invention provides both a method for preparing the cyanoacetate 
esters and .alpha.,.beta.-unsaturated ester components for a polymer as 
well as the crosslinked polymer itself. 
In one embodiment of the present invention the process for producing the 
crosslinked polymer comprises transesterifying a monofunctional alkyl 
cyanoacetate with a polyhydroxy functional monomer or polyhydroxy 
functional polymer in the presence or not of a transesterification 
catalyst so as to produce a polyfunctional cyanoacetate monomer or polymer 
and, subsequently, reacting the thus formed polyfunctional cyanoacetic 
monomer or polymer with an .alpha.,.beta.-unsaturated material in the 
presence of a metallic catalyst, preferably an organometallic catalyst. 
When a transesterification catalyst is employed, representative catalysts 
include, for instance dibutyl tin oxide, paratoluene sulfonic acid, 
methylsulfonic acid and sodium methoxide. Preferably, dibutyl tin oxide is 
employed since its use shortens the reaction time and produces lighter 
colored products. 
Monofunctional alkyl cyanoacetates suitable for transesterification 
include, for instance, methyl cyanoacetatate, ethyl cyanoacetate, propyl 
cyanoacetate, isopropyl cyanoacetate, n-butyl cyanoacetate, isobutyl 
cyanoacetate, tert. butyl cyanoacetate, 2-methoxyethyl cyanoacetate, 
methyl benzyl cyanoacetate and dodecyl cyanoacetate. 
Suitable polyhydroxy functional monomers and polymers include for instance 
diols and polyols. Representative diols include ethylene glycol, propylene 
glycol, diethylene glycol, 1,6-hexanediol, neopentyl glycol, cyclohexane 
dimethylol, trimethylpentanediol, 1,4-butanediol and 
2,2-dimethyl-3-hydroxy propyl-2,2-dimethyl-3-hydroxypropionate. 
Suitable polyols include, for instance, glycerine, trimethylolethane, 
trimethylolpropane, pentaerythritol and dipentaaerythritol. 
Additionally, there can be employed a hydroxy functional acrylic resin such 
as .alpha.-methyl styrene/hydroxyethyl acrylate modified with 
.epsilon.-caprolactone [Union Carbide's Tone 100.RTM.]/2-ethylhexyl 
acrylate with weight ratios 35/55/10 respectively, and a styrene/allyl 
alcohol copolymer sold under the trade designation RJ-100 by Monsanto. 
Saturated polyester and alkyd resins can also be employed as the source of 
polyhydroxy functionality for the said transesterification reaction. Epon 
resins such as Shell's Epon 1001 and 1004 as well as epoxyesters can be 
used to transesterify with the monofunctional alkyl cyanoacetates. 
Still other polyhydroxy functional materials include acrylic copolymers of 
2-hydroxyethylacrylate or 2-hydroxyethyl methacrylate or 2-hydroxypropyl 
acrylate or 2-hydroxypropyl methacrylate with styrene, vinyl toluene 
and/or other acrylic ester monomers. 
The poly .alpha.,.beta.-unsaturated ester employed to crosslink with the 
polycyanoacetic ester has, preferably, the following structure 
##STR1## 
wherein R represents, independently, hydrogen, methyl or 
##STR2## 
R' represents, independently, hydrogen, methyl or 
##STR3## 
Exemplary poly .alpha.,.beta.-unsaturated ester materials having a 
functionality of two or more include, for instance, hexanediol diacrylate, 
hexanediol dimethacrylate, trimethylolpropane triacrylate, 
trimethylolpropane trimethacrylate, neopentyl glycol diacrylate and the 
diacrylate and dicrotonate esters of Shell's Epon 828. 
Still other useful poly .alpha.,.beta.-unsaturated esters include the 
acrylate, methacrylate, crotonate, maleate and itaconate esters of acrylic 
copolymers, oil free polyesters, alkyd resins, Epons and epoxy esters. A 
suitable maleic modified polyester is one having a maleic anhydride to 
propylene glycol molar ratio of 1.0/1.1 and being reduced to 60% 
nonvolatiles in methyl amyl ketone. A suitable crotonic acid modified 
acrylic is one obtained by reacting crotonic acid with an acrylic resin 
containing glycidyl methacrylate (GMA)/butylacrylate 
(BA)/methylmethatrylate (MMA)/styrene (S) in weight ratios, respectively, 
of 25/25/20/30 and having a 60% nonvolatiles content in xylene. A suitable 
acrylate functional acrylate can be obtained by reacting acrylic acid with 
a glycidyl methacrylate/butyl acrylate/styrene/methyl methacrylate 
copolymer wherein the weight ratios are, respectively, 25/25/30/20. 
The ratio of the polyfunctional cyanoacetic compound to the poly 
.alpha.,.beta.-unsaturated ester material ranges from 0.03-1.50 to 
1.50-0.03 and preferably from about 1.0 to 0.8. 
Examples of suitable organometallic compounds for use to catalyze the 
cyanoacetate-.alpha.,.beta.-unsaturated ester reaction include the 2-ethyl 
hexanoates or octoates of lead, cobalt, manganese, zinc, calcium, iron, 
zirconium, potassium, and vanadium; the naphthenates of lead, cobalt, 
manganese, zinc, calcium, iron, potassium and cerium; the tallates of 
lead, cobalt, manganese, calcium and iron; and the neodecanoates, 
isononanoates and heptanoates of calcium, cobalt, lead, manganese, zinc, 
zirconium and iron; or a mixture thereof. Also included are the metallic 
acetoacetonates of manganese (II), (III), cobalt (II), (IV), chromium, 
lead, potassium, etc, and mixtures thereof. 
The amount of catalyst employed in the present process will range, for 
example, between about 0.02 percent and about 0.80 percent and, 
preferably, between about 0.04 percent and 0.25 percent, based on total 
vehicle solids. The amount and type of organometallic catalyst will depend 
on the reactivity of the cyanoacetic group with the 
.alpha.,.beta.-unsaturated ester material, whether an air dry or bake 
system is used, as well as the time and temperature of the bake cycle. 
The curing step may be conducted between room temperature and 350.degree. 
F., preferably between 250.degree. and 300.degree. F.

EXAMPLES 
The following non-limiting examples illustrate the present process. 
Examples I-VII illustrate exemplary polyfunctional cyanoacetic materials 
and the process for their preparation. Example I. 
A one liter reaction vessel equipped with a thermometer, and inert gas 
delivery tube, a Barrett distilling receiver and a water condenser, is 
charged with 236 grams of 1,6-hexanediol, 396 grams of methyl cyanoacetate 
and 3 grams of dibutyl tin oxide. The mixture is heated under a light 
nitrogen blanket to 95.degree. C. at which point methanol starts to 
distill over. The temperature increases as the methanol is removed to a 
maximum of 135.degree. C. The nitrogen blanket is replaced by a nitrogen 
blow to remove the last traces of methanol. The product, hexanediol 
dicyanoacetate has a N Gardner-Holdt viscosity at 100% nonvolatiles and a 
126 equivalent weight. 
EXAMPLE II 
Trimethylolpropane tricyanoacetate was prepared by the same process as in 
Example I. 268 grams of trimethylolpropane was reacted with 594 grams of 
methyl cyanoacetate and 6 grams of dibutyl tin oxide. The product was 
semi-solid at 100% nonvolatiles and has a 112 equivalent weight. 
EXAMPLE III 
Using the method of Example I, 526 grams of Monsanto's styrene/allyl 
alcohol copolymer, RJ-100, were reacted with 173 grams of methyl 
cyanoacetate and 1.4 grams of dibutyl tin oxide. The product was reduced 
to 70% nonvolatiles in a 1:1 mixture of methyl isobutyl ketone and xylene. 
The viscosity of this material was Z4+ and has a 370 equivalent weight of 
solids. 
EXAMPLE IV 
A cyanoacetic functional alkyd resin was prepared by first reacting 204.8 
grams of coconut oil and 51.2 grams pentaerythritol in the presence of 0.8 
gram calcium octoate. After alcoholysis takes place 216.8 grams of 
phthalic anhydride and 139.2 grams of pentaerythritol are added. 40 grams 
of xylene were then added to remove the water by azeotropic distillation. 
After this alkyd portion is reacted down to a maximum acid number of ten, 
the alkyd is cooled to 100.degree. C. and 187.2 grams of methyl 
cyanoacetate and 2.0 grams of dibutyl tin oxide are added. The by-product 
of the transesterification is removed as in Example I. The resin, reduced 
to 59% nonvolatiles in xylene, has a Z3-viscosity and a 377 equivalent 
weight on solids. 
EXAMPLE V 
A cyanoacetic functional acrylic was prepared by first reacting 106.5 grams 
of styrene (S), 138.6 grams of butyl methacrylate (BMA), 25.0 grams of 
butyl acrylate (BA) and 145.8 grams of hydroxy ethylacrylate (HEA) in the 
presence of 203.4 grams of xylene and 36.6 grams of di-tertiary-butyl 
peroxide. The poly hydroxy functional acrylic resin that is formed is then 
reacted with 140 grams of methyl cyanoacetate and 4 grams of dibutyl tin 
oxide. The methanol was removed by the procedure in Example I. The 
cyanoacetic functional acrylic, at 66% nonvolatiles, has a Z5 viscosity 
and a 427 equivalent weight. 
EXAMPLE VI 
A cyanoacetic functional oil free polyester is prepared by first reacting 
326.4 grams of trimethylpentanediol, 27.2 grams of trimethylol propane, 
280 grams of isophthalic acid and 0.8 grams of butyl stannoic acid. The 
mixture is esterified to a maximum acid number of ten. The resin is cooled 
to 100.degree. C. and 164.8 grams of methyl cyanoacetate and 0.8 gram of 
dibutyl tin oxide are added. The methanol was removed as in Example I. The 
cyanoacetic functional polyester has a S+ viscosity at 68% nonvolatiles in 
xylene and a 412 equivalent weight. 
EXAMPLE VII 
A cyanoacetic functional epoxy ester was prepared by first reacting 393.6 
grams of tall oil fatty acid with 267.2 grams of Shell Chemical's Epon 
828. The mixture is reacted to a maximum acid number of three. The epoxy 
ester is cooled to 120.degree. C. at which time 138.4 grams of methyl 
cyanoacetate and 0.8 gram of dibutyl tin oxide are added. The methyl 
alcohol was removed as in Example I. The resin has a V+ viscosity at 80.5% 
nonvolatiles in xylene and a 540 equivalent weight. 
Examples VIII-XVIII demonstrate the curing properties of the various 
polyfunctional cyanoacetate materials with poly .alpha.,.beta.-unsaturated 
esters. The stoichiometric ratio of the blend is 1:1 with a catalyst level 
of 0.12% manganese octoate on total solids. Films (0.8-1.1 mil dry) were 
baked at 250.degree. F. and/or 300.degree. F. or thirty minutes on cold 
rolled steel panels. 
EXAMPLES VIII-XVIII 
______________________________________ 
Cyano- Bake MEK Film Reverse 
.alpha.,.beta.-Unsaturated 
acetate Temp. Resis- 
Hard- Impact, 
Ester Example (.degree.F.) 
tance ness in. lb. 
______________________________________ 
Itaconate I 250 35 3B 100 
Polyester (A) 300 50 HB-F 100 
(A) III 250 15 HB 20 
300 50 H 20 
Crotonate III 300 15 HB 20 
Functional 
Acrylic (B) 
Trimethylol 
IV 300 30 2B-B 20 
propane 
triacrylate 
(TMPTA) 
(A) IV 300 50 HB-F 20 
Acrylate IV 300 35 B 20 
Functional 
Acrylic (C) 
TMPTA V 250 15 HB 20 
300 50 F 20 
(A) V 250 3 HB 20 
300 50 H 20 
(C) V 300 38 H-2H 20 
(A) VI 300 50 HB 20 
(C) VI 300 30 HB 20 
______________________________________ 
(A) Itaconic Acid/2,2dimethyl-3-hydroxypropyl, 2,2dimethyl-3-hydroxy 
propionate (5/4 molar ratio) polyester, 350 equivalent weight. 
(B) Crotonic acid reacted with a glycidyl methacrylate functional acrylat 
resin containing a 25/25/30/20 ratio of glycidyl methacrylate/butyl 
acrylate/styrene/methyl 
(C) Acrylic acid reacted with a glycidyl methacrylate functional acrylic 
resin containing a 25/25/30/20 ratio of glycidyl methacrylate/butyl 
acrylate/styrene/methyl methacrylate respectively, 640 equivalent weight. 
The following examples demonstrate the cure and film properties of two 
gloss enamels based on cyanoacetic functional resins. 
EXAMPLE XVIII 
The cyanoacetic modified alkyd of Example IV was blended 1:1 on an 
equivalent basis with the itaconic acid/2,2-dimethyl-3-hydroxypropyl 
2,2-dimethyl-3-hydroxypropionate polyester (A). The mixture was pigmented 
to a gloss white enamel with a PVC of 18% at a volume solids of 45%. The 
system was catalyzed with 0.06% manganese octoate and 0.10% zinc octoate. 
The coating was applied four mils wet to a cold rolled steel panel and 
baked for 20 minutes at 300.degree. F. The coating had the following 
properties: 
Gloss--84/60.degree., 64/20.degree. 
Pencil Hardness--F 
Impact--100 in. lbs. reverse 
MEK resistance--50 double rubs 
Tape Adhesion--Excellent--no loss 
EXAMPLE XIX 
The cyanoacetic functional epoxy ester of Example VII was blended 1:1 on an 
equivalent basis with a 1,6-hexanediol itaconate polyester. The polyester 
was prepared by reacting four moles of 1,6-hexanediol with three moles of 
itaconic acid to a maximum acid number of two. The resin has a Z viscosity 
at 92.5% nonvolatiles in xylene and a 271 equivalent weight. 
The cyanoacetic modified epoxy ester/itaconate polyester blend was 
pigmented to a semi-gloss black baking enamel. The enamel was formulated 
at a PVC of 16.4% at a volume solids of 54.14%. The coating was catalyzed 
with 0.06% manganese metal and 0.010% zinc metal based on vehicle solids. 
The coating was sprayed onto a cold rolled steel panel and baked for 20 
minutes at 300.degree. F. The coating had the following properties: 
Gloss--69/60.degree., 26/20.degree. 
Pencil Hardness--B 
Impact--40 in. lbs. reverse 
MEK Resistance--50 double rubs 
Tape Adhesion--Excellent--no loss 
The Chemical Abstract Service registry number for Epon 1001, 1004 and 828 
is 25068-38-6. Their chemical formula is reported to be (C.sub.15 H.sub.16 
O.sub.2.C.sub.3 H.sub.5 ClO).sub.x. Their ring system data is 
(01)(nr=01; sr=3; ar=C20.01; fr=OC2.01; ir=1-30-1) (02)(nr=01; sr=6; 
ar=fr=C6.01; ir=46-150-18) 
Their Chemical Abstracts names are; 
HP=Phenol (9Cl), SB=4,4'-(1-methylethylidene)bis-NM=polymer with 
(chloromethyl)oxirane. 
Synonyms include: 2,2-bis(p-hydroxyphenyl)propaneepichorohydrin condensate.