N-alkoxymethyl (meth)acrylamide functional polymers and their use in self-crosslinkable coating compositions

Self-crosslinkable film-forming compositions and a process for preparing multi-layered coated articles coated with a pigmented or colored base coat and a transparent or clear topcoat containing a self-crosslinkable film-forming composition are disclosed. The self-crosslinkable film-forming composition comprises a non-gelled addition polymer which is the free radical initiated reaction product of an N-alkoxymethyl(meth)acrylamide and at least one other ethylenically unsaturated monomer. The topcoat composition may be aqueous based. The transparent topcoat provides a composite coating with improved acid etch resistance and mar resistance, making the composite coating particularly useful as a topcoat for automotive parts.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to self-crosslinkable film-forming 
compositions, and to the use of such compositions in a process for 
preparing multi-layered coated articles comprising a pigmented or colored 
base coat and a transparent or clear topcoat. 
2. Brief Description of the Prior Art 
Color-plus-clear coating systems involving the application of a colored or 
pigmented base coat to a substrate followed by the application of a 
transparent or clear topcoat to the base coat have become conventional as 
original finishes for automobiles. The clear coat imparts outstanding 
gloss and distinctness of image (DOI) to the color-plus-clear systems, and 
serves to protect the base coat from environmental attack. 
Because many geographic areas encounter acidic precipitation, resistance to 
etching by atmospheric acid precipitation ("acid etch resistance") is 
becoming an increasingly desirable property for coatings, particularly 
automotive original equipment coatings. Original equipment manufacturers 
are requiring that coating systems demonstrate acid etch resistance. In 
response to this requirement, coating compositions based on functional 
polymers cured with a crosslinking agent have been developed for use in 
color-plus-clear coating systems. 
Coatings cured with aminoplast crosslinking agents such as polymeric 
polyol-aminoplast systems are known to provide many excellent coating 
properties. They are inexpensive, durable, and attractive. However, it is 
widely recognized that such coatings, particularly clear coats, have poor 
resistance to etching by atmospheric acidic pollutants. Polymeric 
polyol-aminoplast coating systems of the prior art are not highly 
effective for providing protection against etching caused by acid rain. 
Clear coat compositions comprising polyols such as polyester polyols, 
polyurethane polyols, and acrylic polyols cured with polyisocyanate 
crosslinking agents yield coatings with outstanding gloss and distinctness 
of image. However, such systems do not provide optimum mar and abrasion 
resistance. In addition, the isocyanates are difficult to handle because 
they are sensitive to moisture and require cumbersome safety precautions 
because of their toxicity. 
It would be desirable to provide a color-plus-clear coating system which 
avoids the problems of the prior art by providing improved acid etch 
resistance and mar resistance properties, and which does not have the 
drawbacks associated with crosslinking agents of the prior art. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, a self-crosslinkable film-forming 
composition is provided comprising a non-gelled addition polymer which is 
the free radical initiated reaction product of the following polymerizable 
ethylenically unsaturated monomers: 
a) about 40 to 80% by weight of an N-alkoxymethyl(meth)acrylamide; i.e., an 
N-alkoxymethylacrylamide or N-alkoxymethylmethacrylamide; and 
b) about 20 to 60% total by weight of at least one polymerizable 
ethylenically unsaturated monomer selected from the group consisting of 
styrene, methyl styrene dimer, methyl (meth)acrylate; i.e., methyl 
acrylate or methyl methacrylate, butyl (meth)acrylate, cyclohexyl 
(meth)acrylate, and mixtures thereof; the percentage by weight being based 
on total weight of the polymerizable ethylenically unsaturated monomers 
used in preparing the polymer. The polymer typically has a weight average 
molecular weight of about 1800 to 80,000 as determined by gel permeation 
chromatography using a polystyrene standard. The film-forming composition 
may be organic solvent or aqueous based. 
By "non-gelled" or ungelled is meant that the resin is substantially free 
from crosslinking, and the resin has a measurable intrinsic viscosity when 
dissolved in a suitable solvent. In contrast, a gelled resin, having an 
essentially infinite molecular weight, would have an intrinsic viscosity 
too high to measure by gel permeation chromatography. 
The invention further provides a method for applying a composite coating to 
a substrate which comprises applying to the substrate a colored 
film-forming composition to form a base coat and applying to the base coat 
a clear film-forming composition to form a transparent top coat over the 
base coat. The main resinous ingredient of the clear film-forming 
composition is a self-crosslinkable film-forming composition of the type 
described above. 
The reaction products of the invention, because of the relatively high 
level of N-alkoxymethyl(meth)acrylamide, are difficult to prepare without 
gelling the reaction mixture. However, if precautions are taken as 
described herein gelation can be avoided. 
Somewhat surprisingly, it has been found that the reaction products of the 
present invention, when used as the main resinous ingredient of a clear 
film-forming composition for use over base coats in color-plus-clear 
composite coatings, provide cured clear coats with excellent resistance to 
acid etching and to marring. 
DETAILED DESCRIPTION 
The polymer mentioned above used in the self-crosslinkable film-forming 
composition of the present invention may be prepared by reacting an 
N-alkoxymethyl(meth)acrylamide with at least one other ethylenically 
unsaturated monomer via free radical initiated addition polymerization 
techniques. 
The N-alkoxymethyl(meth)acrylamide typically has 1 to 6, preferably 1 to 4 
carbon atoms in the alkoxy group. Examples include 
N-ethoxymethyl(meth)acrylamide and N-butoxymethyl(meth)acrylamide. 
N-butoxymethyl(meth)acrylamide is preferred. The N-alkoxymethyl 
(meth)acrylamide is typically present in the polymer at about 40 to 80% by 
weight, preferably at about 40 to 50% by weight, based on total weight of 
the polymerizable ethylenically unsaturated monomers used in preparing the 
polymer. Amounts below about 40% by weight do not provide coatings with 
sufficient mar resistance, and amounts above about 80% by weight can lead 
to gelation of the reaction mixture during polymerization and have poor 
resistance to acid etching. 
The other ethylenically unsaturated monomers used in the polymer include 
vinyl aromatic monomers such as styrene, alphamethyl styrene, and tertiary 
butyl styrene; vinyl aliphatic monomers such as ethylene, propylene, and 
1,3-butadiene; and alkyl esters of acrylic and methacrylic acid having 
from 1 to 17 carbon atoms in the alkyl group, including methyl 
(meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, cyclohexyl 
(meth)acrylate, 2-ethylhexyl (meth)acrylate, isobornyl (meth)acrylate and 
lauryl (meth)acrylate. The ethylenically unsaturated monomers are 
typically present in the polymer at about 20 to 60% total by weight, 
preferably 50 to 60% total by weight, based on total weight of the 
polymerizable ethylenically unsaturated monomers used in preparing the 
polymer. 
Preferably, the ethylenically unsaturated monomer present in the polymer is 
selected from the group consisting of styrene, methyl (meth)acrylate, 
butyl (meth)acrylate, cyclohexyl (meth)acrylate, and mixtures thereof. 
These monomers are preferred because they provide for better humidity 
resistance in the cured coating composition. 
The polymer may also include up to 15% by weight, based on total weight of 
the polymerizable ethylenically unsaturated monomers used in preparing the 
polymer, of an epoxy functional ethylenically unsaturated monomer such as 
glycidyl (meth)acrylate. 
The polymer may further include up to 10% by weight, based on total weight 
of the polymerizable ethylenically unsaturated monomers used in preparing 
the polymer, of a hydroxyl functional ethylenically unsaturated monomer 
selected from the group consisting of hydroxypropyl (meth)acrylate, 
hydroxyethyl (meth)acrylate, and hydroxybutyl (meth)acrylate. Such 
monomers are preferred in organic solvent based systems because they 
result in improved cured film properties by increasing the crosslink 
density. 
The polymer may further include up to 5% by weight, based on total weight 
of the polymerizable ethylenically unsaturated monomers used in preparing 
the polymer, of an acid functional ethylenically unsaturated monomer such 
as acrylic and methacrylic acid in order to improve resistance to marring, 
but higher levels are not recommended because of a tendency to gel the 
reaction mixture and to decrease the solids content of the coating 
composition. 
The polymers described above can be prepared by free radical initiated 
addition polymerization of a mixture of the monomers by organic solution 
polymerization techniques. The monomers are typically dissolved in an 
organic solvent or mixture of solvents including ketones such as methyl 
ethyl ketone, esters such as butyl acetate, the acetate of propylene 
glycol, and hexyl acetate, alcohols such as ethanol and butanol, ethers 
such as propylene glycol monopropyl ether and ethyl-3-ethoxypropionate, 
and aromatic solvents such as xylene and SOLVESSO 100, a mixture of high 
boiling hydrocarbon solvents available from Exxon Chemical Co. The solvent 
is first heated to reflux, usually 110.degree. to 160.degree. C., and a 
mixture of monomers and free radical initiator is slowly added to the 
refluxing solvent, over a period of about 1 to 5, preferably 1 to 3 hours. 
Adding the monomers too quickly may cause poor conversion or a high and 
rapid exotherm, which is a safety hazard. Adding the monomers over a 
period greater than 5 hours yields a polymer with an undesirably high 
molecular weight. Suitable free radical initiators include t-amyl 
peroxyacetate, which is preferred, di-t-amyl peroxyacetate, and 
2,2'-Azobis(2-methylbutanenitrile). The free radical initiator is 
typically present in the reaction mixture at about 2 to 10%, based on 
total weight of the monomers. 
The polymer prepared by the above described technique is non-gelled or 
ungelled and preferably has a weight average molecular weight of about 
2000 to 8500, more preferably 2000 to 6000. Lower molecular weight 
polymers (less than about 3000 weight average molecular weight) may be 
prepared by synthesizing the polymer in high boiling solvents at a 
relatively low solids content (about 30-40 percent by weight, based on 
total weight of the reaction mixture). After the reaction, the excess 
solvents are removed from the reaction mixture under reduced pressure to 
yield a product with a relatively high solids content (at least about 60 
weight percent solids). This technique is described in detail in Example 
M. 
The polymers prepared by the techniques described above may be used in 
organic solvent based film-forming compositions; that is, film-forming 
compositions containing less than about 5% by weight water, based on total 
weight of the film-forming composition. 
The polymers can also be prepared by free radical initiated polymerization 
of the mixture of monomers by aqueous emulsion polymerization techniques. 
Suitable free radical initiators include ammonium persulfate, which is 
preferred, hydrogen peroxide, and azo-bis(isobutyronitrile), available 
from E. I. du Pont de Nemours and Co. as VAZO 64. The free radical 
initiator may be present in the reaction mixture at about 0.1 to 3%, based 
on total weight of the monomers. Addition of a chain transfer agent such 
as tertiary dodecyl mercaptan or methyl styrene dimer to control molecular 
weight is also preferred. 
A solution of water, a buffer, and one or more surfactants is prepared 
first. Suitable buffers include sodium bicarbonate, present in the 
solution at about 0.05 to 0.2% by weight. Suitable surfactants include 
anionic and nonionic surfactants and mixtures thereof. Examples of anionic 
surfactants include sodium lauryl sulfate; sodium dioctyl sulfosuccinate, 
available from American Cyanamid Co. as AEROSOL OT-75; and ammonium 
alkylphenoxypolyethoxy sulfosuccinate, available from Rhone-Poulenc Co. as 
ALI CO-436. Examples of nonionic surfactants include IGE CO-897, an 
ethoxylated nonyl phenol available from Rhone-Poulenc Co.; and TRITON 
N-101, a nonyl phenoxypolyethoxy ethanol available from Union Carbide Co. 
ALI CO-436 is the preferred surfactant. The surfactants are typically 
present in the water solution at about 0.1 to 0.2% total by weight, based 
on weight of monomers. 
A mixture of the monomers and free radical initiator is then added to a 
second water solution like that described above, forming a monomer 
emulsion. During the reaction, the first water solution is heated to about 
80.degree. C. and "seeded"; that is, about 3% of the total monomer 
emulsion is added to the water solution. This is done to control particle 
size, which is approximately 800 to 1100 .ANG., preferably about 1000 
.ANG.. Larger particle sizes result in poor appearance of the final 
coating and instability of the coating composition; i.e., separation of 
phases. After seeding, the rest of the monomer emulsion is added slowly to 
the water solution over a period of about 1 to 3 hours so as to avoid 
rapid exotherm and gellation. The reaction is conducted in a temperature 
range of about 50.degree. to 85.degree. C. 
When the polymer is prepared by aqueous emulsion polymerization techniques, 
N-butoxymethyl(meth)acrylamide is the preferred N-alkoxymethyl 
(meth)acrylamide used in the polymer. Lower alkoxy groups are very 
reactive in an aqueous medium and tend to gel the reaction mixture. 
The amount of N-butoxymethyl(meth)acrylamide present in the polymer when 
prepared by aqueous emulsion polymerization techniques is preferably about 
40 to 50% by weight, based on total weight of the polymerizable 
ethylenically unsaturated monomers used in preparing the polymer. More 
than about 80% by weight tends to gel the reaction mixture. 
The polymer, when prepared by aqueous emulsion polymerization techniques, 
may further include up to 0.2% by weight, based on total weight of the 
polymerizable ethylenically unsaturated monomers used in preparing the 
polymer, of an acid functional ethylenically unsaturated monomer such as 
acrylic and methacrylic acid, but their use is not preferred because of a 
tendency to gel the reaction mixture. 
The polymers prepared by aqueous emulsion polymerization techniques are 
non-gelled and typically have a weight average molecular weight of about 
25,000 to 70,000, preferably about 25,000 to 40,000. 
The polymers prepared by the techniques described above may be used in 
aqueous based film-forming compositions. By aqueous based is meant that 
the film-forming compositions contain at least about 20% by weight water, 
based on total weight of the film-forming composition. 
Usually the film-forming composition will also preferably contain catalysts 
to accelerate cure. Examples of suitable catalysts are acidic materials 
and include phenyl acid phosphate, sulfonic acid, or a substituted 
sulfonic acid such as paratoluene sulfonic acid and dodecyl benzene 
sulfonic acid. The catalyst is usually present in an amount of about 0.5 
to 1.5 percent by weight, preferably about 0.75 to 1.2 percent by weight, 
based on total weight of resin solids. 
Optional ingredients such as, for example, cosolvents, plasticizers, flow 
control agents, anti-oxidants, UV light absorbers and similar additives 
conventional in the art may be included in the composition. Aminoplast 
crosslinking agents may also be added, particularly when the polymer 
contains hydroxyl functionality, but their use is not preferred. These 
ingredients are typically present at up to 25% by weight based on total 
weight of resin solids. 
The film-forming composition of the present invention is preferably used as 
the clear coat layer in a "color-plus-clear" coating system. The 
film-forming composition of the base coat in the color-plus-clear system 
can be any of the compositions useful in coatings applications, 
particularly automotive applications. The film-forming composition of the 
base coat comprises a resinous binder and a pigment to act as the 
colorant. Particularly useful resinous binders are acrylic polymers, 
polyesters, including alkyds, and polyurethanes. 
The base coat compositions may be solventborne or waterborne. Water-based 
base coats in color-plus-clear compositions are disclosed in U.S. Pat. No. 
4,403,003, and the resinous compositions used in preparing these base 
coats can be used in the practice of this invention. Also, water-based 
polyurethanes such as those prepared in accordance with U.S. Pat. No. 
4,147,679 can be used as the resinous binder in the base coat. Further, 
waterbased coatings such as those described in U.S. Pat. No. 5,071,904 can 
be used as the base coat. 
The base coat also contains pigments to give it color. Compositions 
containing metallic flake pigmentation are useful for the production of 
so-called "glamour metallic" finishes chiefly upon the surface of 
automobile bodies. Suitable metallic pigments include in particular 
aluminum flake, copper bronze flake and metal oxide coated mica. 
Besides the metallic pigments, the base coating compositions of the present 
invention may contain non-metallic color pigments conventionally used in 
surface coatings including inorganic pigments such as titanium dioxide, 
iron oxide, chromium oxide, lead chromate, and carbon black, and organic 
pigments such as phthalocyanine blue and phthalocyanine green. In general, 
the pigment is incorporated into the coating composition in amounts of 
about 1 to 80 percent by weight based on weight of coating solids. The 
metallic pigment is employed in amounts of about 0.5 to 25 percent by 
weight based on weight of coating solids. 
If desired, the base coat composition may contain additional materials well 
known in the art of formulated surface coatings. These would include 
surfactants, flow control agents, thixotropic agents, fillers, 
anti-gassing agents, organic cosolvents, catalysts, and other customary 
auxiliaries. These materials can constitute up to 40 percent by weight of 
the total weight of the coating composition. 
The base coating compositions can be applied to various substrates to which 
they adhere. The compositions can be applied by conventional means 
including brushing, dipping, flow coating, spraying and the like, but they 
are most often applied by spraying. The usual spray techniques and 
equipment for air spraying and electrostatic spraying and either manual or 
automatic methods can be used. 
The coating compositions of the present invention may be applied to various 
substrates including wood, metals, glass, cloth, plastic, including 
elastomeric substrates, foam, and the like. They are particularly useful 
in applications over metal substrates found on motor vehicles. 
During application of the base coat composition to the substrate, a film of 
the base coat is formed on the substrate. Typically, the base coat 
thickness will be about 0.01 to 5, preferably 0.1 to 2 mils in thickness. 
After application of the base coat to the substrate, a film is formed on 
the surface of the substrate by driving solvent, i.e., organic solvent or 
water, out of the base coat film by heating or by an air drying period. 
Preferably, the heating will only be for a short period of time, 
sufficient to ensure that the clear coat can be applied to the base coat 
without the former dissolving the base coat composition. Suitable drying 
conditions will depend on the particular base coat composition, and on the 
ambient humidity with certain waterbased compositions, but in general a 
drying time of from about 1 to 5 minutes at a temperature of about 
80.degree.-250.degree. F. (20.degree.-121.degree. C.) will be adequate to 
ensure that mixing of the two coats is minimized. At the same time, the 
base coat film is adequately wetted by the clear coat composition so that 
satisfactory intercoat adhesion is obtained. Also, more than one base coat 
and multiple clear coats may be applied to develop the optimum appearance. 
Usually between coats, the previously applied coat is flashed; that is, 
exposed to ambient conditions for about 1 to 20 minutes. 
The clear topcoat composition may be applied to the base coated substrate 
by any conventional coating technique such as brushing, spraying, dipping 
or flowing, but spray applications are preferred because of superior 
gloss. Any of the known spraying techniques may be employed such as 
compressed air spraying, electrostatic spraying and either manual or 
automatic methods. 
After application of the clear coat composition to the base coat, the 
coated substrate is heated to cure the coating layers. In the curing 
operation, solvents are driven off and the film-forming materials of the 
clear coat and the base coat are each crosslinked. The heating or curing 
operation is usually carried out at a temperature in the range of from 
160.degree.-350.degree. F. (71.degree.-177.degree. C.), preferably 
230.degree.-285.degree. F. (110.degree.-140.degree. C.) but if needed, 
lower or higher temperatures may be used as necessary to activate 
crosslinking mechanisms. The thickness of the clear coat is usually from 
about 0.5-5, preferably 1.2-3 mils.

The invention will be further described by reference to the following 
examples. Unless otherwise indicated, all parts are by weight. 
The following examples (A to O) show the preparation of various free 
radical initiated N-alkoxymethyl (meth)acrylamide addition polymers. 
Example P shows the preparation of a free radical initiated addition 
polymer having hydroxyl functionality. 
EXAMPLE A (COMATIVE) 
A 30% NBMA (N-(n-butoxymethyl)acrylamide) functional acrylic polymer was 
prepared as follows: 
______________________________________ 
Weight in grams 
______________________________________ 
Charge I 
Ektapro EEP.sup.1 209.6 
Xylene 52.4 
Charge II 
NBMA (55% in 8% xylene and 37% butanol) 
427.4 
Butyl acrylate 157.9 
Butyl methacrylate 236.8 
Styrene 78.9 
alpha-methyl styrene dimer 
78.9 
Charge III 
Ektapro EEP 68.5 
Lupersol 555 M 60.sup.2 109.1 
Charge IV 
Ektapro EEP 5.6 
Lupersol 555 M 60 9.6 
______________________________________ 
.sup.1 ethoxy 3ethyl propionate, available from Eastman Chemical Co. 
.sup.2 tamyl peracetate, available from E. I. Du Pont de Nemours and Co. 
Charge I was added to a suitable reactor and heated to reflux. At reflux, 
charges II and III were added over 2 hours. Upon the completion of these 
charges, Charge IV was added over 15 minutes. The reaction contents were 
held at reflux for 30 minutes. The product was then cooled to room 
temperature. The finished product had theoretical solids of 60%, and a 
weight average molecular weight of 3905. 
EXAMPLE B 
A 40% NBMA functional acrylic polymer was prepared in the same way as the 
polymer in Example A, except that 10% butyl methacrylate was replaced by 
NBMA; i.e., an amount of butyl methacrylate equaling 10% of the total 
monomer content was replaced by NBMA. The finished product had a weight 
average molecular weight of 4415. 
EXAMPLE C 
A 45% NBMA functional acrylic polymer was prepared in the same way as the 
polymer in Example A, except that 15% butyl methacrylate was replaced by 
NBMA. The finished product had a weight average molecular weight of 5122. 
EXAMPLE D 
A 50% NBMA functional acrylic polymer was prepared in the same way as the 
polymer in Example A, except that 20% butyl methacrylate was replaced by 
NBMA. The finished product had a weight average molecular weight of 5621. 
EXAMPLE E 
A 60% NBMA functional acrylic polymer was prepared in the same way as the 
polymer in Example A, except that 20% butyl methacrylate and 10% butyl 
acrylate were replaced by NBMA. The finished product had a weight average 
molecular weight of 3648. 
EXAMPLE F 
A 70% NBMA functional acrylic polymer was prepared in the same way as the 
polymer in Example A, except that 10% butyl acrylate, 10% styrene and 20% 
butyl methacrylate were replaced with NBMA. The finished product had a 
weight average molecular weight of 5465. 
EXAMPLE G 
An 80% NBMA functional acrylic polymer was prepared in the same way as the 
polymer in Example A, except that all the butyl acrylate and butyl 
methacrylate were replaced by NBMA. The finished product had a weight 
average molecular weight of 4599. 
EXAMPLE H (COMATIVE) 
A 90% NBMA functional acrylic polymer was prepared in the same way as the 
polymer in Example A, except that all the butyl methacrylate, butyl 
acrylate, and styrene were replaced by NBMA. The finished product had a 
weight average molecular weight of 4421. 
EXAMPLE I 
A 50% NBMA and 1% acrylic acid functional polymer was prepared in the same 
way as the polymer in Example D, except that 1% butyl acrylate was 
replaced by acrylic acid. The product had a weight average molecular 
weight of 6,443. 
EXAMPLE J 
A 50% NBMA and 2% acrylic acid functional polymer was prepared in the same 
way as the polymer in Example D, except that 2% butyl acrylate was 
replaced by acrylic acid. The product had a weight average molecular 
weight of 6,795. 
EXAMPLE K 
A 50% NBMA and 5% acrylic acid functional was prepared in the same way as 
the polymer in Example D, except that 5% butyl acrylate was replaced by 
acrylic acid. The product had a weight average molecular weight of 8,261. 
EXAMPLE L 
A 50% NBMA functional polymer was prepared in the same way as the polymer 
in Example D, except that butyl acrylate was replaced by butyl 
methacrylate. The product had a weight average molecular weight of 5,149. 
EXAMPLE M 
A low molecular weight 50% NBMA functional polymer was prepared by 
synthesizing the polymer at 40% solids (instead of at 60% solids as in 
other examples) and then stripping the solvents under reduced pressure, as 
follows: 
______________________________________ 
Weight in grams 
______________________________________ 
Charge I 
SOLVESSO 100.sup.1 960.9 
Charge II 
Styrene 66.1 
Butyl methacrylate 198.2 
NBMA 347.9 
alpha-methyl styrene dimer 
66.0 
Charge III 
SOLVESSO 100 57.3 
Lupersol 555 M60 91.4 
Charge IV 
SOLVESSO 100 4.7 
Lupersol 555 M60 7.7 
______________________________________ 
.sup.1 SOLVESSO 100 is a mixture of high boiling hydrocarbon solvents and 
is available from Union Carbide. 
Charge I was added to a suitable reactor and heated to reflux. At reflux, 
charges II and III were added over 2 hours. Upon completion of these 
charges, charge IV was added over 15 minutes followed by cooling to room 
temperature. The solids were increased to about 72% by distilling the 
solvents under reduced pressure. The product had a weight average 
molecular weight of 2,299. 
EXAMPLE N 
A polymer containing 25% NBMA and 25% NEMA (N-(n-ethoxymethyl) acrylamide, 
91% active, available from American Cyanamid Co.) was prepared in the same 
way as the polymer in Example L, except that half of the NBMA (based on 
solids) was replaced with NEMA. The product had a weight average molecular 
weight of 2,818, and a solids content of 63.88%. 
EXAMPLE O 
A 50% NBMA functional waterborne polymer was prepared as follows: 
______________________________________ 
Weight in grams 
______________________________________ 
Charge I 
Deionized water 407.4 
ALI CO 436.sup.1 4.34 
Sodium bicarbonate 0.52 
Charge II 
NBMA (95% active in butanol) 
177.7 
Styrene 50.7 
Butyl acrylate 67.5 
Butyl methacrylate 50.7 
Tridecyl mercaptan 5.07 
ALI CO 436 4.86 
Deionized water 198.50 
Charge III 
Deionized water 32.02 
Ammonium persulfate 0.73 
______________________________________ 
.sup.1 ALI CO 436 is an anionic surfactant and is available from 
RhonePoulenc Co. 
Charge I was added to a suitable reactor and heated to 80.degree. C. At 
this temperature, 13 grams of charge II was added. Five minutes later 
Charge III was added and the mixture was held for 20 minutes. The 
remainder of Charge II was then added over 3 hours, and the mixture was 
held for 2 hours before cooling. The product had a theoretical solids 
content of 35%, a pH of 6.22, and a weight average molecular weight of 
27,211. 
EXAMPLE P (CONTROL) 
A 40% HEA (hydroxyethyl acrylate) functional acrylic polymer was prepared 
in the same way as the polymer in Example B, except that the NBMA was 
replaced by HEA. 
The following examples (1-15) show the preparation of various clear 
film-forming compositions containing the N-alkoxymethyl (meth)acrylamide 
addition polymers of Examples A-N. Examples 16 and 17 are included as 
controls for comparative purposes. The clear film-forming compositions 
were evaluated as clear coats in color-plus-clear composite coatings for 
appearance, mar resistance, and resistance to acid etch. 
EXAMPLE 1 (COMATIVE) 
A clear film-forming composition was prepared by mixing together at low 
shear the following ingredients in the order indicated: 
______________________________________ 
Solid Solution 
weight in 
weight in 
Ingredients grams grams 
______________________________________ 
NBMA containing polymer 
100.0 174.4 
of Example A 
TINUVIN 328.sup.1 3.0 3.0 
Polybutyl acrylate.sup.2 
0.4 0.6 
Phenyl acid phosphate 
1.0 1.3 
ethanol -- 9.0 
methyl n-amyl ketone 
-- 3.0 
______________________________________ 
.sup.1 Substituted benzotriazole UV stabilizer available from Ciba Geigy 
Corporation 
.sup.2 a flow control agent having a Mw of about 6,700 and a Mn of about 
2,600 made in xylene at 62.5% solids 
EXAMPLE 2 
A clear film-forming composition was prepared as in Example 1 from the 
following ingredients: 
______________________________________ 
Solid Solution 
weight in 
weight in 
Ingredients grams grams 
______________________________________ 
NBMA containing polymer 
100.0 166.7 
of Example B 
TINUVIN 328 3.0 3.0 
Polybutyl acrylate 0.4 0.6 
Phenyl acid phosphate 
1.0 1.3 
ethanol -- 9.0 
methyl n-amyl ketone 
-- 5.0 
______________________________________ 
EXAMPLE 3 
A clear film-forming composition was prepared as in Example 1 from the 
following ingredients: 
______________________________________ 
Solid Solution 
weight in 
weight in 
Ingredients grams grams 
______________________________________ 
NBMA containing 100.0 166.7 
polymer of Example C 
TINUVIN 328 3.0 3.0 
Polybutyl acrylate 
0.4 0.6 
Phenyl acid phosphate 
1.0 1.3 
ethanol -- 9.0 
methyl n-amyl ketone 
-- 9.2 
______________________________________ 
EXAMPLE 4 
A clear film-forming composition was prepared as in Example 1 from the 
following ingredients: 
______________________________________ 
Solid 
weight in 
Weight in 
Ingredients grams grams 
______________________________________ 
NBMA containing 100.0 166.7 
polymer of Example D 
TINUVIN 328 3.0 3.0 
Polybutyl acrylate 
0.4 0.6 
Phenyl acid phosphate 
1.0 1.3 
ethanol -- 9.0 
methyl n-amyl ketone 
-- 9.2 
______________________________________ 
EXAMPLE 5 
A clear film-forming composition was prepared as in Example 1 from the 
following ingredients: 
______________________________________ 
Solid Solution 
weight in 
weight in 
Ingredients grams grams 
______________________________________ 
NBMA containing 100.0 167.2 
polymer of Example E 
TINUVIN 328 3.0 3.0 
Polybutyl acrylate 
0.4 0.6 
Phenyl acid phosphate 
1.0 1.3 
ethanol -- 9.0 
methyl n-amyl ketone 
-- 10.0 
______________________________________ 
EXAMPLE 6 
A clear film-forming composition was prepared as in Example 1 from the 
following ingredients: 
______________________________________ 
Solid Solution 
weight in 
weight in 
Ingredients grams grams 
______________________________________ 
NBMA containing 100.0 163.4 
polymer of Example F 
TINUVIN 328 3.0 3.0 
Polybutyl acrylate 
0.4 0.6 
Phenyl acid phosphate 
1.0 1.3 
ethanol -- 9.0 
methyl n-amyl ketone 
-- 31.5 
______________________________________ 
EXAMPLE 7 
A clear film-forming composition was prepared as in Example 1 from the 
following ingredients: 
______________________________________ 
Solid Solution 
weight in 
weight in 
Ingredients grams grams 
______________________________________ 
NBMA containing 100.0 165.1 
polymer of Example G 
TINUVIN 328 3.0 3.0 
Polybutyl acrylate 
0.4 0.6 
Phenyl acid phosphate 
1.0 1.3 
ethanol -- 9.0 
methyl n-amyl ketone 
-- 29.8 
______________________________________ 
EXAMPLE 8 (COMATIVE) 
A clear film-forming composition was prepared as in Example 1 from the 
following ingredients: 
______________________________________ 
Solid Solution 
weight in 
weight in 
Ingredients grams grams 
______________________________________ 
NBMA containing 100.0 167.1 
polymer of Example H 
TINUVIN 328 3.0 3.0 
Polybutyl acrylate 
0.4 0.6 
Phenyl acid phosphate 
1.0 1.3 
ethanol -- 9.0 
methyl n-amyl ketone 
-- 37.0 
______________________________________ 
EXAMPLE 9 
A clear film-forming composition was prepared as in Example 1 from the 
following ingredients: 
______________________________________ 
Solid Solution 
weight in 
weight in 
Ingredients grams grams 
______________________________________ 
NBMA containing 100.0 166.7 
polymer of Example D 
TINUVIN 328 3.0 3.0 
Polybutyl acrylate 
0.4 0.6 
Phenyl acid phosphate 
1.0 1.3 
Ektapro EEP -- 11.6 
Xylene -- 9.0 
______________________________________ 
EXAMPLE 10 
A clear film-forming composition was prepared as in Example 1 from the 
following ingredients: 
______________________________________ 
Solid Solution 
weight in 
weight in 
Ingredients grams grams 
______________________________________ 
NBMA and acrylic acid 
100.0 166.7 
containing polymer of 
Example I 
TINUVIN 328 3.0 3.0 
Polybutyl acrylate 
0.4 0.6 
Phenyl acid phosphate 
1.0 1.3 
Ektapro EEP -- 11.6 
Xylene -- 15.0 
______________________________________ 
EXAMPLE 11 
A clear film-forming composition was prepared as in Example 1 from the 
following ingredients: 
______________________________________ 
Solid Solution 
weight in 
weight in 
Ingredients grams grams 
______________________________________ 
NBMA and acrylic acid 
100.0 166.7 
containing polymer of 
Example J 
TINUVIN 328 3.0 3.0 
Polybutyl acrylate 
0.4 0.6 
Phenyl acid phosphate 
1.0 1.3 
Ektapro EEP -- 11.6 
Xylene -- 17.5 
______________________________________ 
EXAMPLE 12 
A clear film-forming composition was prepared as in Example 1 from the 
following ingredients: 
______________________________________ 
Solid Solution 
weight in 
weight in 
Ingredients grams grams 
______________________________________ 
NBMA and acrylic acid 
100.0 166.7 
containing polymer of 
Example K 
TINUVIN 328 3.0 3.0 
Polybutyl acrylate 
0.4 0.6 
Phenyl acid phosphate 
1.0 1.3 
Ektapro EEP -- 11.6 
Xylene -- 35.5 
______________________________________ 
EXAMPLE 13 
A clear film-forming composition was prepared as in Example 1 from the 
following ingredients: 
______________________________________ 
Solution 
Solid weight 
weight in 
Ingredient in grams grams 
______________________________________ 
NBMA and butyl 100.0 177.9 
methacrylate containing 
polymer of Example L 
TINUVIN 328 3.0 3.0 
Polybutyl acrylate 
0.4 0.6 
Phenyl acid phosphate 
1.0 1.3 
ethanol -- 7.5 
methyl n-amyl ketone 
-- 26.5 
______________________________________ 
EXAMPLE 14 
A clear film-forming composition was prepared as in Example 1 from the 
following ingredients: 
______________________________________ 
Solid weight 
weight in 
Ingredient in grams grams 
______________________________________ 
low molecular weight 
100.0 138.3 
NBMA containing 
polymer of Example M 
TINUVIN 328 3.0 3.0 
Polybutyl acrylate 
0.4 0.6 
Phenyl acid phosphate 
1.0 1.3 
ethanol -- 7.5 
methyl n-amyl ketone 
-- 30.2 
______________________________________ 
EXAMPLE 15 
A clear film-forming composition was prepared as in Example 1 from the 
following ingredients: 
______________________________________ 
Solution 
Solid weight 
weight in 
Ingredient in grams grams 
______________________________________ 
NBMA/NEMA containing 
100.0 168.7 
polymer of Example N 
TINUVIN 328 3.0 3.0 
Polybutyl acrylate 
0.4 0.6 
Phenyl acid phosphate 
1.0 1.3 
ethanol -- 7.5 
methyl n-amyl ketone 
-- 31.7 
______________________________________ 
EXAMPLE 16 (CONTROL) 
A clear film-forming composition was prepared as in Example 1 from the 
following ingredients: 
______________________________________ 
Solid Solution 
weight in 
weight in 
Ingredient grams grams 
______________________________________ 
ethanol -- 10.0 
TINUVIN 328 3.0 3.0 
Polybutyl acrylate 0.4 0.7 
HEA containing polymer 
60.6 97.7 
of Example P 
MR-225.sup.1 35.0 53.8 
AEROSIL R812 5.4 12.6 
dispersion.sup.2 
Phenyl acid phosphate 
1.5 2.0 
TINUVIN 123.sup.3 0.2 0.2 
______________________________________ 
.sup.1 Butylated melamineformaldehyde resin prepared by reacting together 
6.0 moles formaldehyde, 6.5 moles nbutanol, and 1.0 mole melamine. The 
resulting resin is 64.5% solids in a solvent mixture of 15% nbutanol and 
85% xylene. Available from Monsanto Chemical Co. 
.sup.2 8 parts by weight (pbw) of a highly dispersed hydrophobic amorphou 
silicon dioxide available from Degussa Corporation; 50 pbw of a solution 
of hydroxyl functional acrylic polymer having a peak molecular weight of 
8000, Mw of 9000, Mn of 3500 (determined by gel permeation chromatography 
using a polystyrene standard) made from 40% hydroxypropyl acrylate, 20% 
styrene, 19% butyl acrylate, 18.5% butyl methacrylate, 0.5% methyl 
methacrylate, 2% acrylic acid at 70% solids in isobutanol, xylene, and 
SOLVESSO 100; 48.75 pbw xylene; 1.5 pbw isobutanol; 6.75 pbw SOLVESSO 100 
.sup.3 Sterically hindered tertiary amine light stabilizer available from 
CibaGeigy Corp. 
EXAMPLE 17 (CONTROL) 
A clear film-forming composition was prepared as in Example 1 from the 
following ingredients: 
______________________________________ 
Solid Solution 
weight in 
weight in 
Ingredient grams grams 
______________________________________ 
ethanol -- 10.0 
TINUVIN 328 3.0 3.0 
Polybutyl acrylate 0.4 0.7 
HEA containing polymer 
100.0 161.2 
of Example P 
TINUVIN 123 0.2 0.2 
______________________________________ 
The clear film-forming compositions of Examples 1-17 were applied to a 
pigmented base coat to form color-plus-clear composite coatings over 
electrocoated steel substrates. The electrocoat used on the steel is 
commercially available from PPG Industries, Inc. and is identified as 
ED-5000. The pigmented base coat is commercially available from PPG 
Industries, Inc. and is identified as R732N401. The base coat was 
pigmented black in color. 
The base coat was spray applied in two coats to electrocoated steel panels 
at a temperature of about 75.degree. F. (24.degree. C.). A ten second 
flash time was allowed between the two base coat applications. After the 
second base coat application, a flash time of approximately five minutes 
was allowed at 75.degree. F. (24.degree. C.) before the application of the 
clear coating composition. The clear film-forming compositions of Examples 
1-17 were each applied to a base coated panel in two coats with a ninety 
second flash at 75.degree. F. (24.degree. C.) allowed between coats. The 
composite coating was allowed to air flash at 75.degree. F. (24.degree. 
C.) for five minutes before baking at 285.degree. F. (141.degree. C.) for 
25 minutes to cure both the base coat and the clear coat. The panels were 
baked in a horizontal position. The properties of the composite coatings 
are reported in Tables I to III below. 
TABLE I 
______________________________________ 
Percent 
Percent Original 20.degree. gloss 
weight Acid 
Example NBMA 20.degree. gloss.sup.1 
after mar.sup.2 
solids.sup.3 
etch.sup.4 
______________________________________ 
1 30 87.8 18.9 50.9 2 
(comparative) 
2 40 90.4 53.6 48.3 2 
3 45 90.8 75.1 47.6 2 
4 50 91.5 75.0 45.4 3 
5 60 93.0 82.1 48.1 4 
6 70 94.3 83.3 44.1 4 
7 80 96.3 86.9 44.7 5 
8 90 91.5 83.8 43.5 7 
(comparative) 
16 (control) 
0 87.0 84.0 51.4 8 
17 (control) 
0 note.sup.5 
-- -- -- 
______________________________________ 
.sup.1 Measured with a 20.degree. BYK Gardner Glossgard II glossmeter, 
available from Gardner Instrument Co. 
.sup.2 Coated panels are marred by applying a dry abrasive powder cleanse 
(Bon Ami .TM. cleanser, Faultless Starch/Bon Ami Co.) followed by ten 
double rubs to the surface with a wool felt cloth using a Crockmeter mar 
tester(available from Atlas Electric Devices Company). 20.degree. gloss i 
read on marred area of panel after being washed with water and patted dry 
.sup.3 Determined by weight loss after 1 hour at 230.degree. F. 
(110.degree. C.). 
.sup.4 Panels were sprayed with a sulfurous acid solution (350 grams 
deionized water, 12 grams sulfurous acid to give a pH of 2.0 plus or minu 
0.1) using a polyethylene spray bottle, giving a distribution of drop 
sizes up to one quarter inch. Approximately 2.5 to 3.0 grams of solution 
were applied per 4 .times. 3 inch panel. The panels were then placed in a 
oven at 120.degree. F. for twenty minutes. The panels were then removed 
from the oven and the spray/bake procedure was repeated two more times to 
give a total of 60 minutes at 120.degree. F. After the third cycle the 
panels were washed with soap and water and dried, then rated for degree o 
acid etch resistance on a scale of 0-10 (0 = no observable etching; 10 = 
severe etching) 
.sup.5 Properties not tested; coating did not cure. 
The results reported in Table I indicate that mar resistance improves with 
increasing NBMA levels, although solids and acid etch resistance decrease, 
and that film-forming compositions containing polymers with about 40% to 
about 50% NBMA provide the optimum combination of properties. Control 
Example 16, although exhibiting excellent mar resistance, showed poor acid 
etch resistance. Control Example 17 did not cure. 
TABLE II 
______________________________________ 
Percent Percent 
acrylic Original 20.degree. gloss 
weight 
Example acid 20.degree. gloss 
after mar 
solids Acid etch 
______________________________________ 
9 0 92.0 75.1 44.3 3 
10 1 92.0 80.1 43.4 3 
11 2 91.7 80.4 43.2 3 
12 5 91.5 83.5 40.9 5 
______________________________________ 
The results reported in Table II indicate that mar resistance improves with 
increasing acrylic acid levels, although solids decrease. 
TABLE III 
______________________________________ 
20.degree. 
gloss 
Percent 
NBMA NEMA Original 
after 
weight Acid 
Example level level 20.degree. gloss 
mar solids etch 
______________________________________ 
13 50 0 88.1 70.7 44.7 1 
14 50 0 89.1 45.1 49.7 2 
15 25 25 88.2 74.7 45.4 3 
16 (control) 
0 0 87.0 84.0 51.4 8 
17 (control) 
0 note.sup.1 
-- -- -- -- 
______________________________________ 
.sup.1 Properties not tested; coating did not cure. 
The results reported in Table III for Examples 13 and 14 indicate that 
decreasing the molecular weight of the 50% NBMA functional polymer 
decreases the mar resistance and acid etch resistance but increases the 
solids content. The results reported for Examples 13 and 15 indicate that 
replacing half of the NBMA with NEMA increases the mar resistance and only 
slightly decreases the acid etch resistance. NBMA/NEMA containing systems 
are superior to hydroxyl-aminoplast cured systems for acid etch 
resistance. 
EXAMPLE 18 
An aqueous-based, clear film-forming composition was prepared from the 
following mixture of ingredients: 
______________________________________ 
Solution 
Solid weight 
weight in 
Ingredient in grams grams 
______________________________________ 
waterborne NBMA 200.0 571.4 
containing acrylic of 
Example O 
Dodecylbenzene 2.0 2.0 
sulfonic acid 
______________________________________ 
The above ingredients were mixed together and a film 2 mils (50.8 microns) 
thick was drawn on a glass panel with a "Straddle" wet film applicator No. 
14 (available from P. G. & T. Co.) The panel was placed in an oven at 
140.degree. C. for 30 minutes. The properties are reported in Table IV 
below. 
TABLE IV 
______________________________________ 
Percent 
NMBA Original 20.degree. gloss 
weight Acid 
Example level 20.degree. gloss 
after mar 
solids etch 
______________________________________ 
17 50 70 50 34.9 5 
______________________________________