U.S. patent application number 09/793289 was filed with the patent office on 2002-08-29 for carbamate-functional resins and their use in high solids coating compositions.
Invention is credited to Campbell, Donald H., Green, Marvin L., Ohrbom, Walter H., Ramesh, Swaminathan.
Application Number | 20020119320 09/793289 |
Document ID | / |
Family ID | 25159570 |
Filed Date | 2002-08-29 |
United States Patent
Application |
20020119320 |
Kind Code |
A1 |
Ramesh, Swaminathan ; et
al. |
August 29, 2002 |
Carbamate-functional resins and their use in high solids coating
compositions
Abstract
The present invention provides a coating composition containing
1) a carbamate-functional resin having in its structure a
hyperbranched or star polyol core, a first chain extension based on
a polycarboxylic acid or anhydride, a second chain extension based
on an epoxy containing compound, and having carbamate functional
groups on the core, the second chain extension, or both; and 2) a
second resin containing functional groups reactive with the
carbamate groups on the carbamate-functional resin. In one
embodiment, the coating compositions are used as a clearcoat to be
applied over a basecoat to form a composite coating. The
compositions exhibit a combination of desirable properties, such as
scratch and mar resistance, resistance to environmental etch, good
intercoat adhesion, and high solids.
Inventors: |
Ramesh, Swaminathan;
(Canton, MI) ; Green, Marvin L.; (Brighton,
MI) ; Campbell, Donald H.; (Hartland, MI) ;
Ohrbom, Walter H.; (Hartland Township, MI) |
Correspondence
Address: |
BASF CORPORATION
ANNE GERRY SABOURIN
26701 TELEGRAPH ROAD
SOUTHFIELD
MI
48034-2442
US
|
Family ID: |
25159570 |
Appl. No.: |
09/793289 |
Filed: |
February 26, 2001 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09793289 |
Feb 26, 2001 |
|
|
|
09748643 |
Dec 22, 2000 |
|
|
|
Current U.S.
Class: |
428/423.1 |
Current CPC
Class: |
C09D 201/005 20130101;
Y10T 428/31551 20150401; C09D 201/025 20130101; Y10T 428/31511
20150401 |
Class at
Publication: |
428/423.1 |
International
Class: |
B32B 027/00 |
Claims
We claim:
1. A coating composition comprising a) a carbamate-functional resin
comprising a hyperbranched or star polyol core; a first chain
extension based on a polycarboxylic acid or anhydride; a second
chain extension based on an epoxide-containing compound; and
carbamate functional groups on the core, the second chain extension
or both, and b) a crosslinking resin comprising a plurality of
functional groups reactive with the carbamate groups on the
carbamate-functional resin.
2. A coating composition according to claim 1, wherein the core
comprises a hyperbranched polyol that is the reaction product of a
diol or triol and a compound with one carboxyl group and two or
more hydroxyl groups.
3. A coating composition according to claim 2, wherein the core
comprises a hyperbranched polyol that is the reaction product of a
triol and a compound with one carboxyl group and two hydroxyl
groups.
4. A composition according to claim 1, wherein the
carbamate-functional resin comprises a star polyol core, wherein
the star polyol core comprises a monomeric polyol with three or
more primary or secondary hydroxyl groups.
5. A composition according to claim 4, wherein the star polyol is
selected from the group consisting of trimethylolpropane,
trimethylolethane, glycerol, pentaerythritol, dipentaerythritol,
ditrimethylolpropane, and mixtures thereof.
6. A coating composition according to claim 1, wherein the first
extension is based on an anhydride of a cycloaliphatic dicarboxylic
acid having carboxylic acid groups on adjacent carbon atoms.
7. A composition according to claim 1, wherein the first extension
is selected from the group consisting of hexahydrophthalic
anhydride, methylhexahydrophthalic anhydride, tetrahydropthalic
anhydride, methyltetrahydropthalic anhydride, adipic anhydride,
glutaric anhydride, and mixtures thereof.
8. A composition according to claim 1, where the epoxide-containing
compound comprises a glycidyl ester of a C.sub.2-40 carboxylic
acid.
9. A composition according to claim 1, wherein the core comprises
pentaerythritol, the anhydride comprises hexahydrophthalic
anhydride, and the epoxide compound comprises a glycidyl ester of
neodecanoic acid.
10. A composition according to claim 1, wherein the coating
composition is a clearcoat composition.
11. A composition according to claim 1, wherein the crosslinking
resin comprises an amino resin.
12. A composition according to claim 11, wherein the amino resin
comprises a melamine formaldehyde resin.
13. A composition according to claim 11, wherein the amino resin
has an imino content of 10% or greater.
14. A composition according to claim 1, further comprising a
carbamate-functional acrylic resin.
15. A composition according to claim 14, wherein the crosslinking
resin comprises an amino resin having 10% or higher imino
content.
16. A carbamate functional resin, made by a process comprising the
steps of: reacting a core compound having three or more primary or
secondary hydroxyl groups with a carboxylic anhydride to form a
first intermediate containing at least one carboxylic functional
group and optionally containing primary hydroxyl groups; reacting
the first intermediate with a compound containing one epoxide group
to form a second intermediate containing at least one secondary
hydroxyl group; and reacting the second intermediate with a
carbamic compound to convert some or all of the secondary and
optional primary hydroxyl groups to a carbamate functional
group.
17. A resin according to claim 16, wherein the core compound
comprises a star polyol selected from the group consisting of
trimethylolpropane, trimethylolethane, glycerol, pentaerythritol,
ditrimethylolpropane, dipentaerythritol, and mixtures thereof.
18. A resin according to claim 16, wherein the core compound
comprises the reaction product of a) a first compound having two or
more hydroxyl groups; and b) a second compound having one carboxyl
group and two or more hydroxyl groups.
19. A resin according to claim 18, wherein the polydispersity of
the reaction product is greater than 1.0.
20. A resin according to claim 16, wherein the first intermediate
has at least one hydroxyl group.
21. A resin according to claim 16, wherein the carbamate-functional
resin contains secondary hydroxyl groups.
22. A resin according to claim 16, wherein the carbamate-functional
resin contains primary and secondary hydroxyl groups.
23. A coating composition comprising a carbamate-functional resin A
according to claim 16, and a compound B comprising a plurality of
functional groups reactive with the carbamate groups of the
carbamate-functional resin.
24. A composition according to claim 23, wherein the compound B
comprises an amino resin.
25. A composition according to claim 24, wherein the compound B
comprises a melamine formaldehyde resin.
26. A composition according to claim 24, wherein the amino resin
has an imino content greater than 10%.
27. A method for producing a composite coating on a substrate
comprising the steps of applying a basecoat composition to the
substrate; applying a clearcoat comprising a composition according
to claim 23 onto the basecoat; and baking the basecoat and topcoat
together to cure the composite coating.
28. A method according to claim 27, wherein the basecoat
composition is a waterbome composition.
29. A carbamate-functional resin, comprising the reaction product
of a) a core compound having three or more primary hydroxyl groups;
and b) a second compound having an isocyanate group and a carbamate
group.
30. A resin according to claim 29, wherein the second compound
comprises the reaction product of an organic diisocyanate and a
difunctional compound having a hydroxyl and a carbamate group.
31. A resin according to claim 30, wherein the difunctional
compound comprises the reaction product of ammonia or a primary
amine with an alkylene carbonate.
32. A resin according to claim 29, wherein the second compound and
the core compound are reacted in about a one-to-one ratio of
isocyanate groups to hydroxyl groups.
33. A resin according to claim 29, wherein the resin contains
primary hydroxyl groups.
34. A resin according to claim 29, wherein the core compound
comprises the reaction product of 1) a first compound having two or
more hydroxyl groups; and 2) a second compound having one carboxyl
and two or more hydroxyl groups.
35. A resin according to claim 34, wherein the first compound has
three hydroxyl groups and the second compound has one carboxyl
group and two hydroxyl groups.
36. A coating composition comprising a carbamate-functional resin
according to claim 29; and a second resin having a plurality of
functional groups reactive with the carbamate groups on the
carbamate-functional resin.
37. A coating composition according to claim 36, wherein the second
resin comprises an amino resin.
38. A coating composition according to claim 37, wherein the amino
resin comprises a melamine formaldehyde resin with an imino content
of 10% or greater.
39. A composite coating comprising a) basecoat comprising a cured
organic coating; and b) a topcoat applied to the basecoat,
comprising a coating composition according to claim 36.
40. A composite coating according to claim 39, wherein the basecoat
is a waterbome basecoat.
41. A carbamate-functional resin comprising a hyperbranched or star
polyol core; a first chain extension based on a polycarboxylic acid
or anhydride; a second chain extension based on an
epoxide-containing compound; and carbamate functional groups on the
core, the second chain extension or both.
42. A resin according to claim 41, wherein the core comprises a
hyperbranched polyol that is the reaction product of a diol or
triol and a compound with one carboxyl group and two or more
hydroxyl groups.
43. A resin according to claim 42, wherein the core comprises a
hyperbranched polyol that is the reaction product of a triol and a
compound with one carboxyl group and two hydroxyl groups.
44. A resin according to claim 41, wherein the carbamate-functional
resin comprises a star polyol core, wherein the star polyol core
comprises a monomeric polyol with three or more primary or
secondary hydroxyl groups.
45. A resin according to claim 44, wherein the star polyol is
selected from the group consisting of trimethylolpropane,
trimethylolethane, glycerol, pentaerythritol, dipentaerythritol,
ditrimethylolpropane, and mixtures thereof.
46. A resin according to claim 41, wherein the first extension is
based on an anhydride of a cycloaliphatic dicarboxylic acid having
carboxylic acid groups on adjacent carbon atoms.
47. A resin according to claim 41, wherein the first extension is
selected from the group consisting of hexahydrophthalic anhydride,
methylhexahydrophthalic anhydride, tetrahydropthalic anhydride,
methyltetrahydropthalic anhydride, adipic anhydride, glutaric
anhydride, and mixtures thereof.
48. A resin according to claim 41, where the epoxide-containing
compound comprises a glycidyl ester of a C.sub.2-40 carboxylic
acid.
49. A resin according to claim 41, wherein the core comprises
pentaerythritol, the anhydride comprises hexahydrophthalic
anhydride, and the epoxide compound comprises a glycidyl ester of
neodecanoic acid.
Description
[0001] This application is a continuation-in-part of application
Ser. No. 09/748,643 filed on Dec. 22, 2000.
FIELD OF THE INVENTION
[0002] The present invention relates to carbamate-functional resins
and their use in high solids coating compositions. More
specifically it relates to carbamate functionalized star or
hyperbranched polyols as reactive resins in coatings.
BACKGROUND OF THE INVENTION
[0003] Coating compositions based on carbamate-functional acrylic
polymers and aminoplast cross-linking agents are desirable as
automotive topcoats because they have excellent durability,
hardness, gloss, appearance, and resistance to environmental etch.
As such, they are highly suitable for use as a clearcoat layer
applied over a basecoat layer in a color plus clear composite
coating.
[0004] A problem associated with curable coating compositions based
on acrylic polymers containing pendant carbamate groups and
aminoplast curing agents is that the compositions do not have
particularly good intercoat adhesion. This problem presents itself
when the compositions are used as clearcoats and composite color
plus clear coatings, especially during repair procedures which
involve applying the clear film forming composition to a flawed
area of a previously applied color plus clear composite
coating.
[0005] Another area for improvement in the use of
carbamate-functional acrylic polymers with amino resins systems as
cross-linkers is compatibility with waterborne basecoats. The
waterborne basecoats contain amines used to salt the resin into
water. During baking, the amine is released from the basecoat and
travels through the clearcoat to the surface, where it is released
into the atmosphere. The concentration of amine at the bottom of
the clearcoat is greater than the concentration at the top, which
sets up a pH gradient in the clearcoat. Because the cure rate is a
function of the pH, a so called cure gradient forms in the
clearcoat. This leads to an appearance defect known as
wrinkling.
[0006] The curable carbamate-functional compositions are generally
formulated with a low-imino amino resin so as to achieve high
solids, which is desirable for economic and environmental reasons.
If instead high-imino amino resins are used, the cure gradient is
minimized along with the wrinkling. This is because the dependency
on pH of the cure rate of a high-imino amino resin is not as great
as that of a low-imino resin.
[0007] However, when high-imino resins are used, the solids content
of the coating becomes unacceptably low. Thus, it would be
desirable to provide a coating composition based on
carbamate-functional resins and amino resin crosslinkers that have
a combination of high solids and compatibility with waterbome
basecoats. Preferably, such a composition would also exhibit
improved intercoat adhesion.
[0008] U.S. Pat. No. 5,759,694 to Mayo has addressed the intercoat
adhesion problem by providing a polyester made by copolymerizing a
diol, optional triol, a hydroxyl functional and acidic functional
material, and a polyacid, followed by reaction with a monoepoxide
and carbamoylation. The polyester is combined with a
carbamate-functional acrylic resin and an aminoplast to yield a
film forming composition. Mayo does not directly address the
problem of compatibility of the film forming composition with a
waterborne basecoat.
[0009] U.S. Pat. No. 5,693,723 to Green describes a
carbamate-functional resin prepared by reacting a compound having
at least one hydroxyl group and one carboxyl group with an epoxy
compound, and then carbamoylating the reaction product. High solids
coating compositions are obtained, but there is no discussion of
how to improve intercoat adhesion.
SUMMARY OF THE INVENTION
[0010] The present invention provides a coating composition
containing
[0011] 1) a carbamate-functional resin having in its structure a
hyperbranched or star polyol core, a first chain extension based on
a polycarboxylic acid or anhydride, a second chain extension based
on an epoxy-containing compound, and having carbamate functional
groups on the core, the second chain extension, or both; and
[0012] 2) a second resin containing functional groups reactive with
the carbamate groups on the carbamate-functional resin.
[0013] In one embodiment, the coating compositions are used as
clearcoats applied over basecoats to form composite coatings. The
compositions exhibit a combination of desirable properties, such as
scratch and mar resistance, resistance to environmental etch, good
intercoat adhesion, and high solids.
[0014] In another embodiment, the coating compositions also contain
a carbamate-functional acrylic resin. In this embodiment, the
carbamate-functional resin of the invention may act as a reactive
diluent. Methods are also provided to synthesize the
carbamate-functional resins of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0015] The terms "carbamate group", "carbamate-functional", and the
like, as used in connection with the present invention refer to a
group having a structure: 1
[0016] in which R is H or alkyl, preferably R is H or alkyl of from
1 to about 8 carbon atoms, more preferably R is H or alkyl of from
1 to about 4 carbon atoms, and yet more preferably R is H. When R
is H, the carbamate group is referred to herein as a primary
carbamate group.
[0017] The carbamate-functional resin of the invention is based on
a star or hyperbranched core and contains carbamate functionality.
The carbamate functionality can be introduced onto the core by
reacting the core with a compound containing a carbamate group and
a functional group reactive with the hydroxyl groups on the core.
Alternatively, it can be introduced by a series of extension steps
with a polycarboxylic acid or anhydride and epoxy compound,
followed by carbamoylation. The degree of carbamoylation and the
number of extensions can be selected so as to obtain desirable
properties of coatings prepared from the resin.
[0018] The carbamate-functional resins of the invention can be
formulated with another resin having functional groups reactive
with the carbamate groups to form curable coating compositions
particularly useful as a topcoat or as a clearcoat component of a
basecoat-clearcoat composite coating. The coating compositions of
the invention can further contain a carbamate-functional acrylic
resin.
[0019] The star core is a structure based on a star polyol. A star
polyol is a monomeric polyol containing three or more primary or
secondary hydroxyl groups. In a preferred embodiment, the star
polyol has four or more hydroxyl groups. Examples of star polyols
include, without limitation, glycerol, trimethylolpropane,
trimethylolethane, pentaerythritol, ditrimethylolpropane,
dipentaerythritol, tetrakis (2-hydroxyethyl) methane, diglycerol,
trimethylolethane, xylitol, glucitol, dulcitol, and sucrose.
Mixtures of star polyols may also form the star core of the
carbamate-functional resin of the invention.
[0020] A hyperbranched core is a structure based on hyperbranched
polyols. Hyperbranched polyols are prepared by the reaction of a
first compound having two or more hydroxyl groups and a second
compound having one carboxyl group and two or more hydroxyl groups.
The first and second compounds can be reacted to form a first
generation hyperbranched polyol. Alternatively, the second compound
can be reacted with the first generation hyperbranched polyol to
form a second generation and, if desired, subsequent generations.
Preferably, a first generation or second generation hyperbranched
polyol is used as the hyperbranched core of the
carbamate-functional resin of the invention.
[0021] The first compound can suitably be an aliphatic, a
cycloaliphatic, or an aromatic diol, triol, or tetrol, a sugar
alcohol such as sorbitol and mannitol, dipentaerythritol, an
.alpha.-alkylglucoside such as (.alpha.-methylglucoside, or an
alkoxylate polymer having a molecular weight of at most about 8,000
that is produced by a reaction between an alkylene oxide or a
derivative thereof and one or more hydroxyl groups from any of the
alcohols mentioned above. Mixtures of these can also be used as the
first compound.
[0022] Diols suitable as the first compound include straight diols
with 2-18 carbon atoms. Examples include, without limitation,
1,3-propanediol, 1,2-ethanediol, 1,4-butanediol, 1,5-pentanediol,
and 1,6-hexanediol.
[0023] The diols can also be branched such as, for instance,
dimethylolpropane, neopentyl glycol,
2-propyl-2-methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol,
2,2-diethyl-1,3-propanediol, 2,2,4-trimethylpentane-1,3-diol,
trimethylhexane-1,6-diol, and 2-methyl-1,3-propanediol. Other
suitable diols include, without limitation, diethylene glycol,
triethylene glycol, polyethylene glycols, dipropylene glycol,
tripropylene glycol and polypropylene glycols.
[0024] Cycloaliphatic diols such as cyclohexane dimethanol and
cyclic formals of pentaerythritol such as, for instance,
1,3-dioxane-5,5-dimetha- nol can also be used.
[0025] Aromatic diols, for instance 1,4-xylylene glycol and
1-phenyl-1,2-ethanediol, as well as reaction products of
polyfunctional phenolic compounds and alyklene oxides or
derivatives thereof, can furthermore be employed. Bisphenol A,
hydroquinone, and resorcinol may also be used.
[0026] Diols of the ester type, for example
neopentylhydroxypivalate, are also suitable diols.
[0027] As substitute for a 1,2-diol, the corresponding 1,2-epoxide
or an .alpha.-olefin oxide can be used. Ethylene oxide, proplyene
oxide, 1,2-butylene oxide, and styrene oxide can serve as examples
of such compounds.
[0028] Suitable triols can contain three primary hydroxyl groups.
Trimethylolpropane, trimethylolethane, trimethylobutane, and
3,5,5-trimethyl-2,2-dihydroxymethylhexane-1-ol are examples of this
type of triols. Other suitable triols are those having two types of
hydroxyl groups, primary as well as secondary hydroxyl groups, as
for instance glycerol and 1,2,6-hexanetriol. It is also possible to
use cycloaliphatic and aromatic triols and/or corresponding adducts
with alkylene oxides or derivatives thereof.
[0029] Suitable tetrols for use as the first compound include,
without limitation, pentaerythritol, ditrimethylolpropane,
diglycerol and ditrimethylolethane. It is also possible to use
cycloaliphatic and aromatic tetrols as well as corresponding
adducts with alkylene oxides or derivatives thereof.
[0030] The second compound used to prepare the hyperbranched polyol
can be a monofunctional carboxylic acid having at least two
hydroxyl groups. Examples include, without limitation
.alpha.,.alpha.-bis(hydroxymethyl)pr- opionic acid (dimethylol
propionic acid),.alpha.,.alpha.-bis(hydroxymethyl- )butyric acid,
.alpha.,.alpha.,.alpha.-tris(hydroxymethyl)acetic acid,
.alpha.,.alpha.-bis(hydroxymethyl)valeric acid,
.alpha.,.alpha.-bis(hydro- xyethyl)propionic acid or
.alpha.-phenylcarboxylic acids having at least two hydroxyl groups
directly pendant to the phenyl ring (phenolic hydroxyl groups) such
as 3,5-dihydroxybenzoic acid.
[0031] The hyperbranched polyols can be prepared by reacting the
first compound and second compound under esterification conditions.
The temperature of reaction is generally from 0 to 300.degree. C.,
preferably 50 to 280.degree. C., and most preferably 100 to
250.degree. C.
[0032] A first generation intermediate is prepared by reacting the
first compound and second compound in an equivalent molar ratio of
hydroxyls on the first compound to carboxyl groups on the second
compound of between about 1:2 and about 2:1. Preferably the
equivalent ratio will be from about 1:1.5 to about 1.5:1, and even
more preferably from about 1:1.2 to about 1.2:1.
[0033] The functionality and polydispersity of the first generation
intermediate, and of any subsequent generation, depend on the
equivalent ratio of hydroxyl groups to carboxyl groups of the
reactants in each step. The functionality of the hyperbranched
polyol, whether first generation or subsequent generation, should
be four hydroxyl groups or greater. Hyperbranched polyols with a
wide range of polydispersities are useful. It is preferred that the
polydispersity be less than about 2.5, preferably less than about
2.0, and most preferably less than about 1.8.
[0034] To make the resins of the invention, the core polyol, either
star or hyperbranched as described above, is next reacted with a
polycarboxylic acid or anhydride to form a first chain extension
containing an ester linkage and a free carboxyl group. Preferred as
the polycarboxylic acid or anhydride are cyclic carboxylic
anhydrides. Anhydrides are advantageous for this step because the
ring-opening esterification is faster than reaction of remaining
hydroxyl groups on the core polyol with the carboxyl group
liberated by the ring opening reaction. As a consequence the first
chain extension is a half acid ester with little polymerization or
polyester formation.
[0035] Suitable anhydrides include, without limitation, anhydrides
of dicarboxylic acids with carboxyl groups on adjacent carbons. The
anhydrides can be aliphatic, cycloaliphatic, or aromatic. Examples
include without limitation, maleic anhydride, succinic anhydride,
phthlalic anhydride, hexahydrophthalic anhydride,
tetrahydrophthalic anhydride, methyl tetrahydrophthalic anhydride,
methylhexahydrophthalic anhydride, and trimellitic anhydride. Other
anhydrides useful in the invention include, without limitation,
adipic anhydride, glutaric anhydride, malonic anhydride, and the
like.
[0036] The reaction of the polycarboxylic acid or anhydride with
the core polyol results in formation of a first intermediate that
has carboxyl functionality and may contain some primary or
secondary hydroxyl groups that result from any unreacted hydroxyl
groups on the core polyol.
[0037] The stoichiometry is chosen so that at least one primary
hydroxyl group of the core polyol reacts with the polycarboxylic
acid or anhydride. Preferably at least two hydroxyl groups on the
core polyol will be reacted. In some embodiments the molar ratio of
hydroxyl on the core polyol to carboxyl group on the polycarboxylic
acid or anhydride will be approximately 1:1, so that essentially
every hydroxyl group on the core polyol is esterified.
[0038] The first intermediate, which contains at least one carboxyl
group and optionally has primary or secondary hydroxyl groups as
noted above, is next reacted with a compound containing an epoxide
group to form a second intermediate having a chain extension based
on an epoxide-containing compound.
[0039] A wide variety of epoxide containing compounds may be used
in the practice of the present invention. Epoxides are well-known
in the art, and may be characterized by the general formula: 2
[0040] where R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are each
independently hydrogen (with the proviso that at least one of
R.sub.1-R.sub.4 is other than hydrogen), an organic radical, which
may be polymeric or non-polymeric and may contain unsaturation
and/or heteroatoms, or one of R.sub.1 or R.sub.2 together with one
of R.sub.3 or R.sub.4 may form a cyclic ring, which may contain
unsaturation and/or heteroatoms.
[0041] Useful epoxides can be prepared from monofunctional
alcohols, e.g., butanol and hexanol, by reaction with an
epihalohydrin (e.g., epichlorohydrin) or by reaction of an allyl
group with peroxide. For example, a monoepoxide can be prepared by
reacting a mono-alcohol or mono-acid with an epihalohydrin or a
monounsaturate with peroxide.
[0042] In one preferred embodiment, the epoxide is a monoepoxide
preferably an epoxy ester, also known as a glycidyl ester. Glycidyl
esters can be prepared by reacting a monofunctional carboxylic acid
(e.g., octanoic acid, benzoic acid, benzylic acid, cyclohexane
carboxylic acid) with an epihalohydrin (e.g., epichlorohydrin)
under conditions well-known in the art. In a preferred embodiment,
the monofunctional carboxylic used to produce the glycidy esters is
a branched neo-acid such as, without limitation, neodecanoic or
neononanoic acid. Glycidyl esters are commercially available, e.g.,
as Cardura.RTM. E from Shell Oil Company, Glydexx.RTM. N-10 from
Exxon, or Araldite.RTM. PT910 from Ciba-Geigy. Glycidyl esters may
be described by the formula: 3
[0043] wherein R is a hydrocarbon group of from 1 to about 40
carbon atoms, preferably from about 1 to about 20 carbon atoms, and
most preferably from about 1 to about 12 carbon atoms. This
hydrocarbon group may be substituted, as is known in the art. In a
preferred embodiment, the
[0044] Another useful class of monoepoxides is glycidyl ethers.
Glycidyl ethers can be prepared by the reaction of monofunctional
alcohols (e.g., n-butanol, propanol, 2-ethylhexanol, dodecanol,
phenol, cresol, cyclohexanol, benzyl alcohol) with an epihalohydrin
(e.g., epichlorohydrin). Useful glycidyl ethers include the
glycidyl ether of 2-ethylhexanol, the glycidyl ether of dodecanol,
the glycidyl ether of phenol, and the like. These compounds are
commercially available under the Erisys.RTM. product family from
CVC Specialties.
[0045] The reaction of the epoxide compound with the first
intermediate is preferably carried out without catalyst. In this
case, the epoxide group of the epoxide-containing compound reacts
faster with the carboxyl group than with any primary or secondary
hydroxyl groups that may be present on the first intermediate.
Therefore, a relatively clean chain extension is achieved to form a
second intermediate that contains secondary hydroxyl groups
resulting from ring opening of the epoxide, as well as any primary
or secondary hydroxyl groups that remained unreacted in the
formation of the first intermediate, above.
[0046] Preferably the epoxy containing compound is reacted in a
molar ratio of about 1:1 with respect to carboxyl groups on the
first intermediate. However, if carboxyl groups are desired in the
final product (for example for salting with amines to provide a
water dispersible coating), an excess of carboxyl functional first
intermediate may be used.
[0047] The next step in preparing the resin of the invention is to
add carbamate groups to the second intermediate. As discussed
above, the second intermediate contains at least secondary hydroxyl
groups resulting from the ring opening of the epoxy containing
compound. It may also contain primary or secondary hydroxyl groups
on the core, if less than a molecular equivalent of polycarboxylic
compound was used to react with the core polyol.
[0048] Techniques for adding carbamate groups to the second
intermediate are known in the art and are described, for example,
in P. Adams and F. Barren "Esters of Carbamate Acid", Chemical
Review, Vol. 65 (1965). For example, a carbamate group may be added
to the second intermediate by reacting the second intermediate with
phosgene and then ammonia to form a compound having primary
carbamate groups, or by reaction of the second intermediate with
phosgene and then a primary amine to form a compound having
secondary carbamate groups. Alternatively, the second intermediate
may be reacted with one or more ureas to form a compound with
secondary carbamate groups (i.e., N-alkyl carbamates). This
reaction is accomplished by heating a mixture of the second
intermediate and urea. Another technique is the reaction of the
second intermediate with a monoisocyanate, for example
methylisocyanate, to form a compound with secondary carbamate
groups.
[0049] The second intermediate can be reacted with a carbamate
compound to form the carbamate-functional second intermediate. In
one embodiment, the carbamate compound is cyanic acid, which may be
formed by the well-known reaction of the thermal decomposition of
urea or by other methods, such as described in the U.S. Pat. Nos.
4,389,386 or 4,364,913. In another embodiment, the carbamate
compound is a compound comprising a carbamate group. In this
embodiment, the reaction between the second intermediate and the
carbamate compound is believed to be a transesterification between
the hydroxyl groups on the second intermediate and the carbamate
ester on the carbamate compound. The carbamate compound can be any
compound having a carbamate group capable of undergoing a
transesterification with the hydroxyl groups on the second
intermediate. These include, without limitation, methyl carbamate,
butyl carbamate, propyl carbamate, 2-ethylhexyl carbamate,
cyclohexyl carbamate, phenyl carbamate, hydroxypropyl carbamate,
hydroxyethyl carbamate, and the like. Useful carbamate compounds
can be characterized by the formula: 4
[0050] wherein R.sub.1 is substituted or unsubstituted alkyl
(preferably of 1-8 carbon atoms) and R.sub.2 is H, substituted or
unsubstituted alkyl (preferably of 1-8 carbon atoms, substituted or
unsubstituted cycloalkyl (preferably of 6-10 carbon atoms), or
substituted or unsubstituted aryl (preferably of 6-10 carbon
atoms). Preferably, R.sub.2 is H.
[0051] The transesterification reaction between the second
intermediate and the carbamate compound can be conducted under
typical transesterification conditions, e.g., temperatures from
room temperature to 150.degree. C. with transesterification
catalysts such as calcium octoate, metal hydroxides (e.g., KOH),
Group I or II metals (e.g., Na, Li), or metal carbonates (e.g.,
K.sub.2CO.sub.3). These may be enhanced by use in combination with
crown ethers, metal oxides (e.g., dibutyltin oxide), metal
alkoxides (e.g., NaOCH.sub.3, Al(OC.sub.3H.sub.7).sub.3), metal
carboxylic acid salts (e.g., stannous octoate, calcium octoate),
protic acids (e.g., H.sub.2SO.sub.4), MgCO.sub.3, or Ph.sub.4SbI.
The reaction may also be conducted at room temperature with a
polymer-supported catalyst such as Amberlyst-15.RTM. (Rohm &
Haas) as described by R. Anand, Synthetic Communications, 24(19),
2743-47 (1994), the disclosure of which is incorporated herein by
reference.
[0052] In another embodiment, the carbamate compound comprises a
molecule with an isocyanate group and a carbamate group. Such a
molecule can be prepared for example by reacting an organic
diisocyanate with a difunctional compound that contains, in
addition to a carbamate group, a reactive hydroxyl or amino group.
The difunctional molecule can be, for example, a hydroxycarbamate
that is the reaction product of ammonia or a primary amine with an
alkylene carbonate, which is well known in the art.
[0053] Diisocyanates suitable for reaction with the difunctional
compound to form the carbamate compound include aliphatic or
cycloaliphatic diisocyanates, such as 1,11-diisocyanatoundecane,
1,12-diisocyanatododeca- ne, 2,2,4- and
2,4,4-trimethyl-1,6-diisocyanatohexane,
1,3-diisocyanatocyclobutane,
4,4'-bis-(isocyanatocyclohexyl)-methane, hexamethylene diisocyanate
(HMDI), 1,2-bis-(isocyanatomethyl)-cyclobutane- , 1,3- and
1,4-bis-(isocyanatomethyl)cyclohexane, hexahydro-2,4- and/or
-2,6-diisocyanatotoluene, 1-isocyanato-2-isocyanatomethyl
cyclopentane,
1-isocyanato-3-isocyanatomethyl-3,5,5-trimethyl-cylohexane,
2,4'-dicyclohexyl-methane diisocyanate, and
1-isocyanato-4(3)-isocyanatom- ethyl-1-methyl cyclohexane.
[0054] Other suitable diisocyanates include aromatic diisocyanates,
such as, without limitation, tetramethyl-1,3- and/or -1,4-xylylene
diisocyanate, 1,3- and/or 1,4-phenylene diisocyanate, 2,4- and/or
2,6-toluene diisocyanate, 2,4- and/or 4,4'-diphenyl-methane
diisocyanate, 1,5-diisocyanato naphthalene, p-xylylene diisocyanate
and mixtures thereof.
[0055] Suitable diisocyanates are also understood to include those
containing modification groups such as biuret, uretdione,
isocyanurate, allophanate and/or carbodiimide groups, as long as
they contain two isocyanate groups.
[0056] The carbamate compound can be prepared by converting one of
the isocyanate groups of the diisocyanate to a carbamate group by
reacting the diisocyanate with the difunctional compound. To make
it easier to convert just one isocyanate group, it is preferred to
use a diisocyanate compound that has isocyanate groups of different
reactivity. In this situation, one of the isocyanates will react
preferentially with the difunctional compound.
[0057] Examples of diisocyanates having isocyanate groups of
different reactivity include, without limitation,
1-isocyanato-3-isocyanatomethyl-3- ,5,5-trimethylcyclohexane (also
known as isophorone diisocyanate),
1-isocyanato-2-isocyanatomethylcyclopentane,
1-isocyanato-1-methyl-4(3)-i- socyanatomethylcyclohexane,
2,3-toluenediisocyanate, and 2,4-toluenediisocyanate. In a
preferred embodiment, isophorone diisocyanate is used.
[0058] The product of such a reaction is a compound with an
isocyanate group and a carbamate group. As an illustration, when
the diisocyanate is isophorone diisocyanate, and the difunctional
molecule is a reaction product of ammonia and propylene carbonate,
one isomer of the carbamate compound can be represented by the
idealized structure. 5
[0059] The idealized structure illustrates the preferential
reaction of the difunctional compound with the primary isocyanate
on isophorone diisocyanate. The actual product of such a reaction
statistically will include some product substituted on the
secondary isocyanate, as well as disubstitued diisocyanate and some
unreacted diisocyanate. The product can then be reacted with the
second intermediate to provide the resin of the invention.
[0060] The resin of the invention can contain carbamate groups on
the core, on the second chain extension, or both. It follows from
the discussion above that any carbamate groups on the core will be
attached to primary or secondary hydroxyl carbamate groups, while
any carbamate groups on the second chain extension will be attached
to secondary hydroxyl groups.
[0061] In one embodiment, the presence of at least some free
hydroxyl groups on the carbamate-functional resin is preferred to
increase intercoat adhesion by allowing for hydrogen bonding. For
example, all or a portion of the primary hydroxyl groups on the
second intermediate may be selectively carbamoylated, leaving
unsubstituted secondary hydroxyl groups on the resin of the
invention. The reaction rate of a primary hydroxyl group with the
carbamate compound is greater than that of a secondary hydroxyl
group. Selective carbamoylation of the primary groups is
straightforward because the carbamate compound reacts
preferentially with the primary hydroxyl group.
[0062] On the other hand, in another embodiment, all of the
available hydroxyl groups on the second intermediate are converted
to carbamate groups. This is desirable when greater crosslinking
density is desired in the resin.
[0063] In another embodiment, the carbamate-functional resin of the
invention can be prepared by direct carbamoylation of the core
polyol itself. The primary hydroxyl groups of the core may be
converted to carbamate functionality by any of the techniques noted
above. To make the resin soluble in organic solvents, it is
preferred that at least one of the primary hydroxyl groups on the
core polyol be converted by reaction with a second compound having
an isocyanate group and a carbamate group. Such compounds are
prepared from organic diisocyanates as discussed above. Preferably,
most or all of the primary or secondary hydroxyl groups on the core
polyol are reacted with the second molecule to form a highly
carbamate-functional resin.
[0064] In a non-limiting example, a hyperbranched core polyol is
made by reacting trimethylolpropane and dimethylol propionic acid
in a 1:3 molar ratio such that there are equal equivalents of
hydroxyl groups on the trimethylolpropane to carboxyl groups on the
dimethylolpropionic acid. A core polyol results that has six
primary hydroxyl groups. The core polyol is reacted with a
carbamate-functional isocyanate molecule, which is in turn prepared
by the reaction of isophorone diisocyanate with a hydroxy
carbamate.
[0065] High solids coating compositions can be prepared by
combining the carbamate-functional resin (A) of the invention with
a compound (B) containing a plurality of functional groups that are
reactive with the carbamate groups on the carbamate-functional
resin. Such reactive groups include siloxane, silane, and anhydride
groups, as well as active alkylol or alkoxyalkyl groups on
aminoplast crosslinking agents or on other compounds such as
phenol/formaldehyde adducts.
[0066] Examples of compounds (B) include, without limitation,
melamine formaldehyde resin including monomeric or polymeric
melamine resin and partially or fully alkylated melamine resin,
urea resins (e.g., methylol ureas such as urea formaldehyde resin
and alkoxy ureas such as butylated urea formaldehyde resin),
N-methylol acrylamide emulsions, isobutoxy methacrylamide
emulsions, polyanhydrides (e.g., polysuccinic anhydride), and
siloxanes or silanes (e.g., dimethyldimethoxy silane). Aminoplast
resins such as melamine formaldehyde resin or urea formaldehyde
resin are especially preferred. Also useful are aminoplast resins
where one or more of the amino nitrogens is substituted with a
carbamate group for use in a process with a curing temperature
below 150.degree. C., as described in U.S. Pat. No. 5,300,328.
[0067] Aminoplast resins useful as compound B in the coating
compositions of the invention can be highly alkylated or partially
alkylated amino resins formed by the reaction of an amine with an
aldehyde. Preferred amino resins include those which are reaction
products of amines such as urea or melamine with an aldehyde such
as formaldehyde. Such aminoplast resins are characterized by a
degree of alkylation, degree of self crosslinking or a degree of
polymerization, alkylol content, and imino content. Imino groups
and amino groups on an aminoplast resin arise from the incomplete
reaction of the aldehyde with the amine. Aminoplast resins are
characterized as low-imino if the imino content is less than about
10%, that is, if less than about 10% of the functional groups on
the resin consist of imino or amino groups. Commonly, low-imino
aminoplast resins contain less than 5% imino content. On the other
hand, if the imino content of an aminoplast resin is greater than
about 10%, it can be characterized as high-imino. More commonly,
the imino content of a high imino resin is 15% or higher.
Commercial high imino melamine resins, for example, are available
with up to about 35% imino content.
[0068] In another embodiment, the coating compositions of the
invention can further comprise a carbamate-functional acrylic
resin. Carbamate-functional resins are known in the art to be
useful in clearcoat compositions. They include a plurality of
carbamate functional groups on an acrylic backbone. The carbamate
groups are introduced into the resin by transcarbamation of a
hydroxyl-functional resin following polymerization of acrylic
monomers, and can also be prepared from acrylic monomers containing
carbamate functional groups. Such carbamate-functional acrylic
resins are described, for example, in U.S. Pat. No. 5,605,965 to
Rehfuss et al., the disclosure of which is hereby expressly
incorporated by reference.
[0069] In this embodiment, the coating compositions of the
invention comprise two carbamate-functional resins and at least one
compound containing a plurality of functional groups reactive with
the carbamate groups. The carbamate-functional acrylic resin, if
present, makes up from between about 5 and about 95% by weight of
the total carbamate resin in the composition.
[0070] A solvent may optionally be utilized in the coating
composition used in the practice of the present invention. The
coating composition according to the present invention can be
applied without solvent. However, in many cases, it is desirable to
use a solvent in the coating composition as well. This solvent
should act as a solvent with respect to both the
carbamate-functional resin or resins as well as the component (B).
In general, depending on the solubility characteristics of
components (A) and (B), the solvent can be any organic solvent
and/or water. In one preferred embodiment, the solvent is a polar
organic solvent. More preferably, the solvent is a polar aliphatic
solvent or polar aromatic solvent. Still more preferably, the
solvent includes a ketone, ester, acetate, aprotic amide, aprotic
sulfoxide, or aprotic amine. Examples of useful solvents include,
without limitation, methyl ethyl ketone, methyl isobutyl ketone,
amyl acetate, ethylene glycol butyl ether-acetate, propylene glycol
monomethyl ether acetate, xylene, N-methylpyrrolidone, or blends of
aromatic hydrocarbons. In another embodiment, the solvent can be
water or a mixture of water with co-solvents.
[0071] The coating composition used in the practice of the
invention may include a catalyst to enhance the cure reaction. For
example, when aminoplast compounds, especially monomeric melamines,
are used as component (B), a strong acid catalyst may be utilized
to enhance the cure reaction. Such catalysts are well-known in the
art and include, for example, p-toluenesulfonic acid,
dinonylnaphthalene disulfonic acid, dodecylbenzenesulfonic acid,
phenyl acid phosphate, monobutyl maleate, butyl phosphate, and
hydroxy phosphate ester. Other catalysts that may be useful in the
composition of the invention include Lewis acids, zinc salts, and
tin salts.
[0072] Additional agents, for example surfactants, fillers,
stabilizers, wetting agents, dispersing agents, adhesion promoters,
UV absorbers, HALS, etc., may be incorporated into the coating
composition. While the agents are well-known in the prior art, the
amount used must be controlled to avoid adversely affecting the
coating characteristics.
[0073] Coating compositions can be coated on the article by any of
a number of techniques well-known in the art. These include, for
example, spray coating, dip coating, roll coating, curtain coating,
and the like. The coatings can be cured at about 200.degree. F. to
350.degree. F. for a period of about 10 to 60 minutes.
[0074] In one preferred embodiment, the coating composition
according to the invention is preferably utilized in a high-gloss
coating and/or as the clearcoat of a composite color-plus-clear
coating. High-gloss coatings as used herein are coatings having a
20.degree. gloss (ASTM D523-89) or a DOI (ASTM E430-91) of at least
80. In other preferred embodiments, the coating composition may be
utilized to prepare high-gloss or low-gloss primer or enamel
coatings.
[0075] When the coating composition according to the invention is
used as the clearcoat of a composite color-plus-clear coating, the
pigmented basecoat composition may be any of a number of types
well-known in the art, and does not require explanation in detail
herein. Polymers known in the art to be useful in basecoat
compositions include acrylics, vinyls, polyurethances,
polycarbonates, polysters, alkyds, and siloxanes. Preferred
polymers include acrylics and polyurethanes. In one preferred
embodiment of the invention, the basecoat composition also utilizes
a carbamate-functional acrylic polymer. Basecoat polymers are
preferably crosslinkable, and thus comprise one or more type of
crosslinkable, functional groups. Such groups include, for example,
hydroxy, isocyanate, amine, epoxy, acrylate, vinyl, silane, and
acetoacetate groups. These groups may be masked or blocked in such
a way so that they are unblocked and available for the
cross-linking reaction under the desired curing conditions,
generally elevated temperatures. Useful cross-linkable functional
groups include hydroxy, epoxy, acid, anhydride, silane, and
acetoacetate groups. Preferred cross-linkable functional groups
include hydroxy functional groups and amino functions groups.
[0076] Basecoat polymers may be self cross-linkable, or may require
a separate cross-linking agent that is reactive with the functional
groups of the polymer. When the polymer comprises hydroxy
functional groups, for example, the crosslinking agent may be an
aminoplast resin, isocyanate and blocked isocyanates (including
isocyanurates), and acid or anhydride functional cross-linking
agents.
[0077] The carbamate functional resins and coating compositions of
the invention have been described above with respect to preferred
embodiments. The following examples give further non-limiting
descriptions of the use of the carbamate-functional resins in the
coatings of the invention.
EXAMPLES
Resin preparation 1A
[0078] In a first step, a hyperbranched polyol was prepared. 67 g
of trimethylolpropane (TMP) and 201 g of dimethylolpropionic acid
(DMPA) were combined in a 3-neck flask with 0.2 g of sulfuric acid
as a catalyst and heated to reflux with stirring and with a stream
of nitrogen. The course of the reaction was followed by removing
the water liberated (27 g). Toward the end of the reaction, vacuum
was applied to remove the final traces of water. The reaction was
complete after 5 hours. The hydroxyl number was 690-710 mg KOH/g
and the equivalent weight was 79-81 g/hydroxyl group. The acid
number was less than 5 mg KOH/g.
[0079] In a separate flask, 102 g of propylene carbonate was heated
with 80 g of 20% ammonia in methanol with stirring at 60-70.degree.
C. for 3 hours. Excess ammonium hydroxide was removed under vacuum
with N.sub.2 stripping. 115 g of dry hydroxypropyl carbamate (HPC)
was produced. To this, 222 g of isophorone diisocyanate (IPDI) and
50 g of butyl acetate was added and heated at 80-100.degree. C. The
reaction was monitored by determining the isocyanate content left.
At the end of 4 hours, the isocyanate content did not change over
30 minutes and was 10.5% (starting value 21.5%). The theoretical
equivalent weight was 349 g/isocyanate/NV.
[0080] 200 g of the reaction product of IPDI and HPC were added to
40 g of the hyperbranched polyol and stirred at 80-100.degree. C.
for 3 hours. At the end of the reaction, the isocyanate content was
determined to be less than 0.1% and the product was a
hexafunctional carbamate compound. Butyl acetate was added to
produce a final percent non-volatiles of 70% by weight.
Resin preparation 1B
[0081] A carbamate-functional resin was prepared as in resin
preparation 1A, except that 100 g of the reaction product of IPDI
and HPC were reacted with 40 g of the hyperbranced polyol. At the
end of the reaction, isocyanate content was determined to be less
than 0.1% and the product was a trifunctional carbamate.
Resin Preparation 2.
[0082] Trimethylolpropane and dimethylolpropionic acid were reacted
as in 1A to form a hyperbranched polyol. 240 g of the hyperbranched
polyol were reacted with 231 g of hexahydrophthalic anhydride (3
equivalents of hydroxyl to 1.5 equivalents of anhydride) in 50 g of
Aromatic 100 solvent. An exotherm started at 130.degree. C. and
ended at 150.degree. C. After 1 hour, infrared analysis showed no
anhydride and the acid number was determined to be ca. 170-185 mg
KOH/g NV. To this, 360 g of Cardura.RTM. E (1.5 equivalents) was
added at 130.degree. C. The temperature first increased to
150.degree. C. and on cooling was maintained at 120.degree. C. for
4 hours. IR showed no epoxide left. The measured weight per epoxide
was greater than 5000 g/epoxide. The acid number was less than 0.1
mg KOH/g.
[0083] To this, 125 g of methylcarbamate was added along with 2 g
of dibutyltin dioxide (DBTO) and 300 g of toluene. The reaction
mixture was heated to 120-130.degree. C. At 123.degree. C.,
methanol byproduct of the transesterification started to azeotrope
along with toluene. The reaction was monitored by titrating for the
hydroxyl number. The starting hydroxyl number was 200 mg KOH/g/NV
and the reaction was continued until the number dropped to about 18
mg KOH/g NV for a 90% conversion. Total time for the conversion was
about 10 hours.
Resin Preparation 3.
[0084] 136 g of pentaerythritol (99% pure grade, 1 mole) was heated
with 616 g of hexahydrophthalic anhydride (4 moles) to 125.degree.
C. to form a first intermediate. An exotherm starts and peaks
around 160.degree. C. On returning back to 125.degree. C. (1 hour),
the acid number was determined to be 290-310 mg KOH/g. To this,
1000 g of Cardura.RTM. E was added (eq.wt 250 g/epoxide, 4 moles)
to form a second intermediate. An exotherm peaks at 150.degree. C.
The reaction cooled back to 130.degree. C. and reaction continued
until the acid number was <3 mg KOH/g.
[0085] 360 g of methylcarbamate, 4 g of DBTO, 900 g of toluene and
200 g of xylene were added to the second intermediate and heated to
120-130.degree. C. At 123.degree. C., methanol byproduct of the
transesterification started to azeotrope along with toluene. The
reaction was monitored by titrating for the hydroxyl number. The
starting hydroxyl number was 128 mg KOH/g NV and the reaction was
continued until the number dropped to about 13 mg KOH/g NV. The
theoretical conversion was about 90%. The total time for the
conversion was about 10 hours. Gel permeation chromatography
analysis showed a molecular weight of 1900-2100 and a
polydispersity of 1.1-1.2
Resin Preparation 3B.
[0086] 876 g of the second intermediate of Resin preparation 3A was
reacted with 600 g of the reaction product of IPDI and HPC
described in Resin preparation 1A (4 hydroxy equivalents to 3
isocyanate equivalents) in 600 g of amyl acetate to produce resin
3B at 70% by weight solids. The product was a
tricarbamate-functional resin with one primary hydroxyl group.
Resin Preparation 4A
[0087] 182 g of dulcitol and 616 g of HHPA are reacted by heating
the mixture to 125.degree. C. After an exotherm to 150.degree. C.,
the acid number is 410-430 mg KOH g. To the reaction mixture, 1000
g of Cardura.RTM. E is added and the mixture is heated to
130.degree. C. An exotherm occurs to 150.degree. C. After 5 hours,
the acid number is 3 mg KOH/g. The hydroxyl number is 180-200 mg
KOH/g.
[0088] The Cardura.RTM. E reaction product is transesterified at
120-130.degree. C. with 540 g of methylcarbamate, in the presence
of 5 g of dibutyltin oxide, 700 g toluene, and 300 g xylene. The
final hydroxyl number is less than 20 mg KOH/g NV, indicating a 90%
conversion. The resin was a hexacarbamate with a polydispersity of
1.1-1.3.
Resin preparation 4B.
[0089] Prepartion of the resin is carried out as in 4A, except that
360 g of methylcarbamate was used in the transesterfication step.
The reaction product had four carbamate functional groups and two
hydroxyls, with a polydispersity of 1.2-1.4.
[0090] In all Examples 1A-4A and 1B-4B, the carbamate-functional
resins of the respective resin preparations were taken up into
solvent with a melamine crosslinking resin. The solvent containing
composition was drawn down as a film on a phosphated steel plate.
The film was cured for 30 minutes at 260.degree. F. The cured films
of Examples 1A-4A and 1B-4B gave more than 200 MEK rubs.
[0091] The carbamate-functional resins of Resin Preparations 1A and
3A were formulated into clearcoat compositions as illustrated in
Examples 5-8. To make the clearcoat compositions, the ingredients
were added in the order specified in the Examples with agitation.
Following addition, they were reduced to a spray viscosity of about
35 seconds in a No. 4 Ford viscosity cup at 80.degree. F.
[0092] The clearcoat compositions of Examples 6-8 were applied with
an air atomized spray gun, wet-on-wet, over a conventional black,
medium solid solvent based basecoat. The basecoats were sprayed
over a 4".times.12" electrocoated steel panel. The basecoat film
thickness was 0.7 mils, and the clearcoat film builds were from
about 1.8 to about 2.0 mils. After application, the panels were
allowed to flash at ambient temperature for 10 minutes, then baked
in a gas fired convection oven for 25 minutes at 275.degree. F.
metal temperature.
[0093] Next the clearcoat compositions of Examples 6-8 were sprayed
over a waterborne basecoat. The waterborne basecoats were sprayed
over steel panels, and were allowed to flash at 140.degree. F. for
5 minutes to remove water. The clearcoats were applied as above.
The clearcoat basecoat was flashed at ambient temperature for 10
minutes and baked in a gas fired convection oven for 25 minutes at
275.degree. F. metal temperature.
[0094] The following components are used the Examples:
1 Carbamate functional resin carbamate functional resin of the
invention, prepared according to Preparation 1A or 3A as indicated
in the first row carbamate acrylic resin carbamate functional
acrylic polymer, equivalent weight 404, resin solids 68% by weight
melamine resin butylated polymeric melamine formaldehyde resin,
provided as a 61.6% solids solution. Iso crosslinker blocked
polyisocyanate UV absorber triazine UV absorber from Ciba-Geigy
HALS hindered amine light stabilizer from Clariant surfactant 1
surface control agent surfactant 2 silicone surfactant DDBSA a
blocked dodecylbenzenesulfonic acid catalyst Solvent 1 Exxate 1000,
a C10 alkyl acetate solvent from Exxon Solvent 2 Exxate 600, a C6
alkyl acetate solvent from Exxon Spray Viscosity Viscosity in a No.
4 Ford cup at 80.degree. F.
[0095]
2 5 6 7 8 Resin of Preparation -- 1A 1A 3A Carbamate functional
resin -- 54.1 106.1 45.9 Carbamate acrylic resin 104.8 51.3 -- 53.3
Melamine resin 29.1 25.2 21.1 27.1 Iso crosslinker 6.7 6.7 6.7 6.7
UV absorber 3.5 3.5 3.5 3.5 HALS 1.5 1.5 1.5 1.5 Surfactant 1 .25
.25 .25 .25 Surfactant 2 .05 .05 .05 .05 DDBSA 4.8 4.8 4.8 4.8
Solvent 1 7.0 7.0 7.0 7.0 Solvent 2 50.6 41.20 32.76 42.2 Spray
viscosity 34 34 35 35 Solids 48 51.1 54.4 52
[0096] The invention has been described in detail with respect to
preferred embodiments. It is to be understood, however, that
variations and modifications may be made by persons of skill in the
art based on the disclosure herein that are within the spirit and
scope of the invention.
* * * * *