POLYESTER RESIN WITH CARBAMATE FUNCTIONALITY,
A METHOD OF PREPARING THE RESIN, AND A COATING
COMPOSITION UTILIZING THE RESIN
RELATED APPLICATIONS
[0001] This application is a continuation-in-part of co-pending United States
Patent Application Serial Nos. 10/122,509, 10/106,000, 09/793,289, and
09/747,474 which were filed on April 15, 2002, March 25, 2002, February 26,
2001, and December 22, 2000, respectively. Furthermore, this application is
related to assignee's copending United States Patent Application entitled
" heology Control Agent, A Method Of Preparing The Agent, And A Coating
Composition Utilizing The Agent" filed on the same date as the present
application. Each application is directed to different inventions.
FIELD OF THE INVENTION
[0002] The subject invention generally relates to a polyester resin for use in a
coating composition. More specifically, the subject invention relates to a
polyester resin having carbamate functionality. The subject invention also relates
to methods of preparing the polyester resin, and a coating composition utilizing
the resin.
BACKGROUND OF THE INVENTION
[0003] Polyester resins are known in their uses are known in the art. Polyester resins are incorporated into coating compositions, as either a primary or additive
resin, to participate in a cross-linking reaction with a cross-linking agent to form a
film of the coating composition on a substrate upon application and cure.
[0004] It is known throughout the art that certain convention polyester resins are
inadequate. More specifically, it is known that the inclusion of certain
conventional polyester resins in coating compositions, especially in clearcoat
coating compositions, sacrifices the overall integrity of the cured film. One
critical physical property that is representative of the overall integrity of the cured film is flexibility as evaluated by cold gravelometer, i.e., chipping, testing. The
flexibility of the cured film is particularly important as the substrate weathers and
as the substrate is repeatedly exposed to harsh environmental conditions, such as
exposure to stones, rocks, etc. It is also known that the cured films of clearcoat coating compositions, which incorporate certain conventional polyester resins, do
not maintain acceptable appearance over time due to inadequate gloss retention.
[0005] In sum, the polyester resins of the prior art are characterized by one or
more inadequacy, including those described above. Due to such inadequacies, it
is desirable to provide a novel polyester resin that improves the flexibility and
maintains the appearance of a cured film of a coating composition that incorporates the polyester resin. With the improved flexibility, the cured film
produced by the coating composition which incorporates the polyester resin of the
subject invention is more resilient to chip.
SUMMARY OF THE INVENTION [0006] A polyester resin is disclosed. The polyester resin of the subject invention
is used in a coating composition, such as a clearcoat coating composition, to
improve the flexibility and to maintain the appearance of a cured film of the coating composition. The polyester resin is the reaction product of a first compound comprising a plurality of hydroxyl groups, a lactone compound, a carboxylic acid anhydride, an epoxy compound comprising at least one epoxy group, and a carbamate compound.
[0007] A method of preparing the polyester resin is also disclosed. According to this method, the first compound is provided, and at least one of the hydroxyl groups of the first plurality is reacted with the lactone compound to form a first intermediate compound that terminates with a second plurality of hydroxyl groups. Once the first intermediate compound is formed, at least one of the hydroxyl groups of the second plurality is reacted with the carboxylic acid anhydride to form a second intermediate compound that terminates with at least one carboxyl group. Next, the at least one carboxyl group of the second intermediate compound is reacted with the epoxy compound, which comprises at least one epoxy group, to form a third intermediate compound. The third intermediate compound terminates with a third plurality of hydroxyl groups. At least one of the hydroxyl groups of the third plurality is then reacted with the carbamate compound, which comprises at least one carbamate group, to prepare the polyester resin of the subject invention, hi an alternative method of preparing the polyester resin, the carboxylic acid anhydride and the epoxy compound are reacted with the first compound to form the first and second intermediate compounds. Then, the lactone compound and the carbamate compound are reacted.
[0008] The polyester resin of the subject invention has improved flexibility
relative to conventional polyester resins. As such, the cured films of coating
compositions that incorporate this polyester resin have improved resistance to
chip and acceptable appearance, such as acceptable distinctiveness and gloss.
DETAILED DESCRIPTION OF THE INVENTION
[0009] The polyester resin of the subject invention, also referred to as the
polyester, is a carbamate-functional polyester that is used as a resin in a coating
composition to improve flexibility in a cured film of the coating composition.
More specifically, the polyester is included in the coating composition as either a
primary, i.e., sole, resin or as an additive resin, to participate in a cross-linking reaction with a cross-linking agent, which is also present in the coating
composition, to form the cured film of the coating composition on a substrate
after application and cure. The polyester resin includes an organic structure
having carbamate functionality which enables the polyester to chemically react,
i.e., cross-link, with the cross-linking agent of the coating composition. It is most preferred that the carbamate-functional polyester resin is used as a resin in a
solventborne clearcoat coating composition.
[0010] The polyester is generally the reaction product of a first compound
comprising a first plurality of hydroxyl groups, a lactone compound, a carboxylic
acid anhydride, an epoxy compound comprising at least one epoxy group, and a carbamate compound. The carbamate compound comprises at least one
carbamate group.
[0011] In one particular embodiment, the carbamate-functional polyester is more
specifically the reaction product of a star polyol comprising a first plurality of
hydroxyl groups, the lactone compound, the carboxylic acid anhydride, the epoxy
compound, and the carbamate compound. The lactone compound is reactive with
the first plurality of hydroxyl groups to form a first intermediate compound that
terminates with a second plurality of hydroxyl groups. The carboxylic acid anhydride is reactive with the second plurality of hydroxyl groups to form a
second intermediate compound that terminates with at least one carboxyl group.
The epoxy compound is reactive with the at least one carboxyl group to form a
third intermediate compound that terminates with a third plurality of hydroxyl
groups. The carbamate compound is reactive with the third plurality of hydroxyl
groups to form the polyester resin with carbamate functionality.
[0012] In a preferred method of preparing the polyester, the first compound is
provided, and at least one of the hydroxyl groups of the first plurality is reacted with the lactone compound to form the first intermediate compound that
terminates with the second plurality of hydroxyl groups. Next, at least one of the
hydroxyl groups of the second plurality is reacted with the carboxylic acid
anhydride to form the second intermediate compound that terminates with the at
least one carboxyl group. The at least one carboxyl group of the second
intermediate compound is then reacted with the epoxy compound, specifically with the epoxy group or groups of the epoxy compound, to form the third
intermediate compound that terminates with the third plurality of hydroxyl groups.
Next, at least one of the hydroxyl groups of the third plurality is reacted with the carbamate compound to prepare the polyester resin.
[0013] In an alternative method of preparing the polyester resin of the subject
invention, at least one of the hydroxyl groups of the first plurality is reacted with
the carboxylic acid anhydride to form the first intermediate compound that
terminates with the at least one carboxyl group. In this alternative method, the at
least one carboxyl group of the first intermediate compound is then reacted with
the epoxy compound to form the second intermediate compound that terminates
with the second plurality of hydroxyl groups. Next, at least one of the hydroxyl
groups of the second plurality is reacted with the lactone compound to form the
third intermediate compound that terminates with the third plurality of hydroxyl
groups. At least one of the hydroxyl groups of the third plurality is then reacted
with the carbamate compound to prepare an alternative form of the polyester
resin. In either method, the steps are preferably conducted at temperatures
between 50°C and 200°C, more preferably between 110°C and 160°C. The subject invention is described below primarily in the context of the preferred
method.
[0014] To prepare the polyester of the subject invention, the first compound is
selected to maximize the number of hydroxyl groups, i.e., the hydroxyl
functionality, present in the first compound while establishing a foundation for the organic structure of the polyester. The hydroxyl groups of the first compound can
be primary, secondary, and/or tertiary hydroxyl groups. Although not required, it
is preferred that the plurality of hydroxyl groups of the first compound is at least
three hydroxyl groups. Preferably, the first compound is present in the polyester
in an amount from 1 to 10, more preferably from 2 to 8, parts by weight based on
100 parts by weight of the polyester.
[0015] hi one embodiment of the subject invention, the first compound is at least
one of a diol, triol, tetrol, or sugar alcohol. Therefore, in this embodiment it is
implicit that the first compound can also be any blend of the diols, triols, tetrols,
or sugar alcohols. Furthermore, in this embodiment, the first compound can
suitably be an aliphatic, a cycloaliphatic, or an aromatic diol, triol, or tetrol.
[0016] Diols suitable as the first compound include straight chain 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. Other suitable diols include, but are not limited to, diethylene glycol, triethylene glycol,
polyethylene glycol, dipropylene glycol, tripropylene glycol, and polypropylene
glycol.
[0017] The diols can also be branched such as, for instance, dimethylolpropane,
neopentyl glycol, 2-propyl-2-methyl- 1,3-propanediol, 2-butyl-2-ethyl-l,3-
propanediol, 2,2-diethyl-l,3-propanediol, 2,2,4-trimethylpentane-l,3-diol,
trimethylhexane-l,6-diol, and 2-methyl-l,3-propanediol.
[0018] Cycloaliphatic diols such as cyclohexane dimethanol and cyclic formals of
pentaerythritol such as, for instance, l,3-dioxane-5,5-dimethanol can also be used.
[0019] Aromatic diols, for instance 1,4-xylylene glycol and l-phenyl-1,2-
ethanediol, as well as reaction products of polyfunctional phenolic compounds
and alkylene oxides or derivatives thereof, can furthermore be employed.
Bisphenol A, hydroquinone, and resorcinol may also be used.
[0020] Diols of the ester type, for example neopentylhydroxypivalate, are also suitable diols.
[0021] As substitute for a 1,2-diol, the corresponding 1,2-epoxide or an α-olefin
oxide can be used. Ethylene oxide, propylene oxide, 1 ,2-butylene oxide, and styrene oxide can serve as examples of such compounds.
[0022] 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.
[0023] 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.
[0024] In other embodiments, the first compound is at least one of erythritol,
pentaerythritol, dipentaerythritol, trimethylolethane, trimethylolpropane, trimethylolbutane, glycerol, ditrimethylolethane, ditrimethylolpropane, diglycerol,
dulcitol, threitol, sorbitol, and mannitol.
[0025] In the most preferred embodiment of the subject invention, the first
compound comprises pentaerythritol. For descriptive purposes, a chemical
representation of pentaerythritol is disclosed below.
[0026] In view of the characteristics described above for the first compound, other equivalent compounds include, but are not limited to, ethylene glycol and
propylene glycol, which each provide two hydroxyl groups, and glycerol, which
provides three hydroxyl groups. Other alcohols, sugars, and acids providing a
plurality of hydroxyl groups are also suitable as the first compound. Examples of
such acids include, but are not limited to, dimethylpropionic acid (DMPA),
tartaric acid, and citric acid.
[0027] As described initially above, the star polyol may be included in the
reaction to prepare the carbamate-functional polyester. That is, the first
compound may be a star polyol. Star polyols are frequently described in different
manners. For instance, a star polyol can be described as a monomeric polyol
containing four or more primary or secondary hydroxyl groups. Alternatively, a
star polyol can be described as a macromolecule containing a single branch point
from which linear chains, or arms, emanate. A star polyol can also be described as a macromolecule containing a constitutional unit from which more than two
chains, or arms, emanate.
[0028] Examples of star polyols include, without limitation, pentaerythritol,
ditrimethylolpropane, dipentaerythritol, tetrakis (2-hydroxyethyl) methane,
diglycerol, trimethylolethane, xylitol, glucitol, dulcitol, and sucrose. Mixtures of
star polyols may also form the hydroxy initiating compound of the carbamate-
functional polyester of the present invention.
[0029] Alternatively, the first compound may be based on a hyperbranched polyol
that is prepared by the reaction of an initial 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 the hyperbranched polyol.
[0030] As initially described above, the polyester of the subject invention is also
the reaction product of the lactone compound. More specifically, the lactone
compound reacts with at least one of the hydroxyl groups of the first plurality to
form the first intermediate compound which terminates with the second plurality
of hydroxyl groups. The lactone compound is present in the polyester in an
amount from 5 to 50, more preferably from 10 to 45, parts by weight based on 100 parts by weight of the polyester.
[0031] In one embodiment, the lactone compound can be described to have the
general formula
wherein n is a positive integer from 1 to 7, and R is one or more hydrogen atoms,
or substituted or unsubstituted alkyl groups having from 1 to 7 carbon atoms, hi
alternative embodiments, the lactone compound is at least one of ε-caprolactone,
γ-caprolactone, β -butyrolactone, β-propiolactone, γ-butyrolactone, α-methyl-γ-
butyrolactone, β-methyl-γ-butyrolactone, γ-valerolactone, δ-valerolactone, γ-
nonanoic lactone, γ-octanoic lactone, and pentolactone.
[0032] In the most preferred embodiment of the subject invention, the lactone
compound comprises ε-caprolactone. For descriptive purposes, a chemical
representation of ε-caprolactone is disclosed below.
[0033] At least one of the hydroxyl groups of the first compound, in the most
preferred embodiment, pentaerythritol, is reacted with the lactone compound, in
the most preferred embodiment ε-caprolactone, to form the first intermediate
compound. As described above, the first intermediate compound terminates with
the second plurality of hydroxyl groups, i this reaction, the molar ratio of the
lactone compound to the first compound is from 2 : 1 to 20 : 1, more preferably
[0034] When pentaerythritol is utilized as the first compound, it is preferred that
either four moles of ε-caprolactone or 8 moles of ε-caprolactone are reacted with
the pentaerythritol. For descriptive purposes, a chemical representation of the first
intermediate compound resulting from the reaction of one mole of pentaerythritol
and four moles of ε-caprolactone is disclosed below.
[0035] Of course, it is understood by those of ordinary skill in the art that the
above chemical representation is ideal in that it assumes that one mole of ε-
caprolactone reacts with each of the four hydroxyl groups of the pentaerythritol.
Although not disclosed in a chemical representation such as that disclosed immediately above, alternative embodiments could include more than one mole of
ε-caprolactone reacting at one of the hydroxyl groups such that at least one of the
hydroxyl groups of the pentaerythritol remains unreacted.
[0036] The chemical representation of the first intermediate compound resulting
from the reaction of one mole of pentaerythritol and eight moles of ε-caprolactone
is disclosed below.
[0037] Of course, it is understood by those of ordinary skill in the art that the
above chemical representation is ideal in that it assumes that two moles of ε-
caprolactone react with each of the four hydroxyl groups of the pentaerythritol.
Although not disclosed in a chemical representation such as that disclosed
immediately above, alternative embodiments could include more than two moles
of ε-caprolactone reacting at one of the hydroxyl groups such that at least one of
the hydroxyl groups of the pentaerythritol remains unreacted.
[0038] The two chemical representations of the first intermediate compound
disclosed above are merely illustrative of the subject invention. The first
intermediate compound disclosed above has a four-branch organic structure
originally derived from the organic structure of the pentaerythritol. It is to be
understood that if an alternative first compound is selected, such as dipentaerythritol which provides six hydroxyl groups, then the first intermediate
compound would have a six-branch organic structure derived from the structure of
the dipentaerythritol. Of course, either six or twelve moles of the lactone
compound then would be selected to react with the six hydroxyl groups of the dipentaerythritol.
[0039] As described above, the carboxylic acid anhydride reacts with at least one
of the hydroxyl groups of the second plurality to form the second intermediate
compound which terminates with the at least one carboxyl group. The carboxylic acid anhydride that is polymerized with the first intermediate compound to form
the second intermediate compound is selected to maximize the number of carboxylic acid groups, i.e., the acid functionality, that can be formed in the
second intermediate compound without increasing the molecular weight too much or imparting too much crystalinity. The carboxylic acid anhydride may be either an aromatic or non-aromatic cyclic anhydride.
[0040] In certain embodiments, the carboxylic acid anhydride is at least one of
maleic anhydride, hexahydrophthalic anhydride, methyl-hexahydrophthalic
anhydride, tetrahydrophthalic anhydride, phthalic anhydride, succinic anhydride,
dodecenylsuccinic anhydride, trimellitic anhydride, and methyl tetrahydrophthalic
anhydride. Other anhydrides useful in the invention include, without limitation,
adipic anhydride, glutaric anhydride, malonic anhydride, and the like.
Polycarboxylic acids may also be used in place of the carboxylic acid anhydride.
[0041] In the most preferred embodiment of the subject invention, the carboxylic
acid anhydride comprises hexahydrophthalic anhydride. For descriptive purposes,
a chemical representation of hexahydrophthalic anhydride is disclosed below.
As shown above, the hexahydrophthalic anhydride provides an acid functionality
whereby one carboxylic acid group can be formed into the second intermediate
compound per mole of the carboxylic acid anhydride introduced.
[0042] The carboxylic acid anhydride is present in the polyester resin in an
amount from 5 to 25, preferably from 7.5 to 20, parts by weight based on 100
parts by weight of the polyester resin. Also, in preferred embodiments, the molar
ratio of the carboxylic acid anhydride to the first compound present in the polyester resin is from 1 : 1 to 4 : 1. In the most preferred embodiment, this molar
ratio is 2 : 1. That is, two moles of hexahydrophthalic anhydride react with the
first intermediate compound, specifically with the hydroxyl groups of the second plurality, to form the second intermediate compound. The most preferred first intermediate compound is formed with one mole of pentaerythritol and either four
or eight moles of ε-caprolactone.
[0043] For descriptive purposes, a chemical representation of the second intermediate compound formed by the reaction of one mole pentaerythritol, eight
moles of ε-caprolactone, and two moles of hexahydrophthalic anhydride is
disclosed below.
As disclosed above, the second intermediate compound that is formed with the reactants of the most preferred embodiment terminates with at least one carboxyl group. More specifically, this second intermediate compound is a di-carboxylic acid compound, i.e., a compound including two carboxylic acid groups or an acid functionality of two. These two carboxyl or carboxylic acid groups of the second intermediate compound are formed when the anhydride rings of the two moles of hexahydrophthalic anhydride open forming ester linkages with the first intermediate compound, and the hydrogen atoms from the hydroxyl groups of the second plurality react with the oxygen atoms originally from the anhydride rings
of the two moles of hexahydrophthalic anhydride thereby forming the di-
carboxylic acid intermediate compound, i.e., the second intermediate compound,
according to the preferred embodiment. As stated above, the second intermediate
compound of the preferred embodiment has an acid functionality of two. Of
course, it is to be understood that the acid functionality can decrease or increase
depending upon the selection of the particular first compound and of the particular
carboxylic acid anhydride, and upon the equivalent weight ratios between the first
compound and the carboxylic anhydride.
[0044] The chemical representation of the second intermediate compound
disclosed above is merely illustrative of the subject invention. The second
intermediate compound disclosed above has a four-branch organic structure originally derived from the organic structure of the pentaerythritol. This four-
branch organic structure is only one of many possible structures that can be
derived from the organic structure of the pentaerythritol. It is to be understood
that if an alternative first compound is selected, such as dipentaerythritol which provides six hydroxyl groups, then the second intermediate compound would have
a six-branch organic structure derived from the structure of the dipentaerythritol.
Of course, the number of moles of the hexahydrophthalic anhydride would then
also be modified.
[0045] The at least one carboxyl group of the second intermediate compound is
reacted with the epoxy compound to form the third intermediate compound which terminates with the third plurality of hydroxyl groups. The epoxy compound is
selected to include at least one epoxy group. A wide variety of epoxy compounds
may be used in the practice of the present invention. Epoxy compounds are well-
known in the art, and may be characterized by the general formula:
where Rl5 R2, R3 and R* are each independently hydrogen (with the proviso that at least one of Ri^ is other than hydrogen), an organic radical, which may be
polymeric or non-polymeric and may contain unsaturation and/or heteroatoms, or
one of Ri or R together with one of R3 or R4 may form a cyclic ring, which may
contain unsaturation and/or heteroatoms.
[0046] Useful epoxy compounds 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.
[0047] In one preferred embodiment, the epoxy compound is a monoepoxide
preferably an epoxy ester, also known as a glycidyl ester. In fact, the most
preferred epoxy compound is an ester, CARDURA® E 10S, which is described
additionally below. 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 glycidyl esters is a branched neo-acid such as, without
limitation, neodecanoic or neononanoic acid. Glycidyl esters are commercially
available, e.g., as Cardura® E from Shell Oil Company, Glydexx® N-10 from
Exxon, or Araldite® PT910 from Ciba-Geigy. Glycidyl esters may be described
by the formula:
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.
[0048] 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® product family from CVC Specialties.
[0049] Preferably the epoxy compound is reacted in a molar ratio of about 1:1
with respect to carboxyl groups on the second intermediate compound. 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 functionality in the second intermediate compound may be used.
[0050] The epoxy compound is present in the polyester resin in an amount from 5 to 40, preferably from 10 to 35, parts by weight based on 100 parts by weight of the polyester resin. The molar ratio of the carboxylic acid anhydride to the epoxy compound is from 1 : 2 to 2 : 1, more preferably this molar ratio is 1 : 1. The epoxy compound is further selected to include from 6 to 20, preferably from 10 to 15, carbon atoms such that the miscibility between the polyester resin and other resins present in the coating composition (if the polyester resin of the subject invention is utilized as an additive resin) is maximized. As such, it is preferred that the epoxy compound comprises at least one of glycidylneodecanoate, dodecyl oxide, tetradecyl oxide, octadecyl oxide, and cyclohexene oxide. In view of the above characteristics of the epoxy compound, other equivalent compounds include, but are not limited to, epoxy-containing aromatic hydrocarbons such as bisphenol A monoglycidyl ether.
[0051] In the most preferred embodiment of the subject invention, the epoxy compound comprises glycidylneodecanoate. As is known in the art, glycidylneodecanoate is commercially available from Shell Chemical Company under its CARDURA® product line, as CARDURA E 10S. For descriptive purposes, a chemical representation of glycidylneodecanoate is disclosed below.
As shown above, glycidylneodecanoate includes one epoxy group. Preferably, two moles of glycidylneodecanoate are reacted with the two carboxyl groups of
the second intermediate compound such that one epoxy group reacts with each
carboxylic acid group. As described above, it is the epoxy group of the epoxy
compound that reacts with the carboxyl groups of the second intermediate
compound. More specifically, the epoxy ring of the glycidylneodecanoate opens
such that one of the two carbon atoms, originally in the epoxy ring of the
glycidylneodecanoate, reacts and bonds with a single-bonded oxygen atom from
the carboxyl groups. It is to be understood that in the reaction, the epoxy ring can
open in one of two manners such that either one of the carbon atoms of the epoxy
ring reacts and bonds with the oxygen atom from the carboxyl group. In one
manner, the third intermediate compound, disclosed below, includes a primary
hydroxyl, and in a second manner, the third intermediate compound includes a
secondary hydroxyl. These two manners of epoxy ring opening are disclosed
below in the chemical representation of the third intermediate compound.
[0052] Next, at least one of the hydroxyl groups of the third plurality is reacted with the carbamate compound to prepare the polyester resin. More specifically, the carbamate compound includes at least one carbamate group, and it is the carbamate group or groups of the carbamate compound that react with the hydroxyl groups. The carbamate compound is present in the polyester in an amount from 5 to 25, preferably from 7.5 to 20, parts by weight based on 100 parts by weight of the polyester. Also, in this reaction, the molar ratio of the carbamate compound to the lactone compound is from 1 : 8 to 2 : 1.
Alternatively, the amount of the carbamate compound present in the polyester
may be described as introducing a number of moles of the carbamate compound
equal to the number of hydroxyl groups present in the third intermediate
compound. For example, there are four hydroxyl groups present in the above
chemical representation of the third intermediate compound. In this case, it is
most preferred to use four moles of the carbamate compound.
[0053] In one embodiment, the carbamate compound is an alkyl carbamate having
from 1 to 20 carbon atoms in the alkyl chain. For example, the carbamate
compound may be genetically defined as
O
R O C NH2
where R is an alkyl chain having from 1 to 20 carbon atoms. In alternative
embodiments, the carbamate compound more specifically includes at least one of
methyl carbamate, ethyl carbamate, propyl carbamate, and butyl carbamate.
[0054] In the most preferred embodiment of the subject invention, the carbamate
compound comprises methyl carbamate [CH OC(O)NH ]. Other carbamate
compounds include, but are not limited to, propylene glycol monocarbamate, and the like.
[0055] The completed polyester resin, prepared from one mole of pentaerythritol,
eight moles of ε-caprolactone, two moles of hexahydrophthalic anhydride, two
moles of glycidylneodecanoate, and four moles of methyl carbamate, is disclosed below.
The completed polyester set forth immediately above assumes that one of the four moles of methyl carbamate reacts with each of the four hydroxyl groups of the third plurality, i.e., of the third intermediate compound. Of course, it is to be understood that these parameters are ideal reaction conditions that do not always occur such that some of the hydroxyl groups of the third plurality may remain unreacted. The completed polyester resin, disclosed above, is a carbamate-
functional polyester, a polyester tetracarbamate, having a four-branch organic
structure.
[0056] Of course, in terms of the preferred embodiment, after the four moles of
methyl carbamate react with the hydroxyl groups of the third intermediate
compound to prepare the polyester, four moles of methanol are produced as a side
product. The number of moles of methanol that are produced as a side product
vary depending on the number of moles of the carbamate compound, preferably
the methyl carbamate, that are reacted with the intermediate compound.
[0057] In either of the embodiments, it is preferred that the total number of moles
of the carbamate compound is generally equal to the number of hydroxyl groups
present in the third intermediate compound such that all of the hydroxyl groups
are reacted, hi the event the total number of moles of the carbamate compound is
less than the number of hydroxyl groups in the third intermediate compound,
some of the hydroxyl groups will remain unreacted and the completed polyester will have both hydroxyl and carbamate functionality.
[0058] As described above an alternative polyester resin prepared according to an
alternative method of the present invention reacts the carboxylic acid anhydride
and the epoxy compound with the first compound to form the first and second
intermediate compounds. As such, in this alternative embodiment, the first and
second intermediate compounds will not be equivalent to the first and second
intermediate compounds described above in the context of the preferred
embodiment. After the carboxylic acid anhydride is reacted with the first compound to form the first intermediate compound, and after the epoxy compound is reacted with the first intermediate compound to form the second
intermediate compound, the lactone compound and the carbamate compound are
then reacted.
[0059] The polyester of the subject invention preferably has a theoretical weight-
average molecular weight, Mw, of from 500 to 4000, more preferably from 1000
to 3000, and most preferably from 1500 to 2500. Additionally, the completed
polyester according to the subject invention has a non- volatile content of from 60
to 80, preferably from 65 to 75, percent non-volatile by weight.
[0060] As understood by those skilled in the art, the polyester may optionally
include additives to effect the reaction or to effect certain properties of the
polyester and of the coating composition. Such additives include, but are not
limited to, solvents, catalysts, and combinations thereof. As a non-limiting, specific example, the polyester may include stannous octoate or di-butyltin oxide
as a catalyst, and solvents such as toluene.
[0061] If the polyester resin of the subject invention is utilized in the coating
composition as the primary resin, then the coating composition includes the polyester resin of the subject invention and the cross-linking agent. On the other
hand, if the polyester resin of the subject invention is utilized in the coating
composition as an additive resin, then the coating composition includes a second
resin different from the resin of the subject invention. This second resin is cross- linkable with the cross-linking agent like. If present, this second resin may
include an oligomer such as a dimer, trimer, or tetramer. As known to those
skilled in the art, oligomers are polymer molecules having only a few monomer
units and generally have low molecular weights. As a non-limiting example, certain polyester resins may be the oligomer. Alternatively, if present, this second
resin may include at least one of acrylic resin, epoxy resin, phenolic resin, polyester
resin, polyurethane resin, acrylate resin, methacrylate resin, and polysiloxane resin.
As understood by those skilled in the art, each of these types of resins contains a respective functional group. Specific examples of these resins include epoxy esters,
fluoropolymers such as fluorinated acrylic resins, and various resins having silicone
appendages.
[0062] Whether the polyester resin of the present invention is utilized as a primary
resin or as an additive resin, it is present in the coating composition in an amount
from 10 to 90, preferably from 20 to 75, parts by weight based on 100 parts by
weight of the coating composition. Of course, if the polyester resin is utilized as a
primary resin, then the polyester resin will be present in a greater amount as
compared to its presence in a coating composition where it is merely utilized as an additive resin.
[0063] The cross-linking agent, which is reactive with the polyester resin of the
present invention, may include at least one of a polyacid, polyanhydride,
polyisocyanate, polyamine, acetoacetate, polyaziridine, and polysiloxane. More
specific examples of such cross-linking agents include, but are not limited to, polycarboxylic acids, acid anhydrides, and blocked and unblocked isocyanates.
Preferably, however, the cross-linking agent comprises an aminoplast resin.
Aminoplast resins include urea resins and melamine formaldehyde resins, hi the
present invention, the most preferred cross-linking agent utilized in the coating composition that incorporates the polyester described above is a melamine formaldehyde resin. The cross-linking agent is present in the coating composition in
an amount from 1 to 20, preferably from 2 to 10, and more preferably from 4 to 8,
parts by weight based on 100 parts by weight of the coating composition.
[0064] The melamine formaldehyde resins of the preferred embodiment include
either a methylol group, CH2OH, an alkoxymethyl group, or both. The
alkoxymethyl group is of the general formula — CH ORl5 where Ri is an alkyl
chain having from 1 to 20 carbon atoms. As understood by those skilled in the
art, the methylol groups and the alkoxymethyl groups are reactive with the
carbamate functional groups present in the completed polyester. Thus, the
polyester resin of the present invention is able to participate in the cross-linking reaction with the cross-linking agent.
[0065] Other cross-linking agents that are aminoplasts include benzaquanimine
and glycolurals. Further possible cross-linking agents include, but are not limited
to, monomeric and polymeric melamine formaldehyde resins, including both
partially and fully alkylated melamines such as methylated melamines, butylated melamines, and methylated/butylated melamines. Other cross-linking agents that
are urea resins include methylol ureas such as urea formaldehyde resins, and
alkoxy ureas such as butylated urea formaldehyde resin.
[0066] The preferred embodiment of the subject invention includes hexamethoxymethyl melamine (HMMM). HMMM is commercially available
from Monsanto (Solutia) under its Resimene Amino Crosslinker Resins as
Resimene 747. HMMM is shown in the following chemical representation.
[0067] Upon addition, the carbamate groups present in the completed polyester
react with some of the alkoxymethyl, i.e., ether, groups of the HMMM,
specifically the CH2OCH3 groups, thereby establishing urethane ( — NH — CO —
O — ) linkages. Upon application and cure of the coating composition, the cross-
linking agent, in the preferred embodiment HMMM, cross-links with the
functional groups of the polyester resin to form a cured film of the coating composition.
[0068] It is to be understood that all of the preceding chemical representations are merely two-dimensional chemical representations and that the structure of these
chemical representations may be other than as indicated. It is also to be
understood that the subject invention is not intended to be limited only to the
preferred reactants disclosed in these chemical representations.
[0069] The following examples illustrating the formation of and the use of the
carbamate-functional polyester of the subject invention, as presented herein, are intended to illustrate and not limit the invention.
EXAMPLE 1:
[0070] In Example 1, the polyester resin was prepared by adding and reacting the
following parts, by weight, unless otherwise indicated.
Table 1
[0071] Per the above table, Table 1, 680.0 grams of PE, 4560.0 grams of E-cap,
600.0 grams of toluene, and 6.1 grams of DBTO were added in a reaction flask to
form the first intermediate compound. The reaction flask was heated with a
conventional heat supply to an initial temperature of 150°C and held for
approximately 4 hours. At this point, the first intermediate compound was 89.5%
non-volatiles, and IR Specfroscopy showed that no lactone groups remained present such that the formation of the first intermediate compound was complete.
The heat supply was then removed overnight and the reaction mixture cooled.
Next, the reaction flask was heated to 120°C and 1540.0 grams of HHPA were
added to the first intermediate compound in the reaction flask to form the second
intermediate compound. Initially, there was an exotherm, but cooling was applied
to maintain the exotherm below 128°C. The reaction flask was maintained at
approximately 120°C for approximately 2 hours. Titration for the acid number
resulted in 85.4 mg KOH/g, which is 657 g/COOH. The theoretical equivalent
weight would be 678 g/COOH. Next, 2476.0 grams of CE10S were added to the second intermediate compound to form the third intermediate compound. The
reaction flask, including the reactants for the third intermediate compound, was
heated to 130°C. When an exotherm began, the temperature of the reactants was
not permitted to exceed 138°C. The reaction flask was held for approximately 3 hours at 140°C until the acid number fell below 3 mg KOH/g. The third
intermediate compound had a hydroxyl number of 127 mg KOH/g (theory 123 mg
KOH/g). The contents of the reaction flask were cooled to 120°C and 1650.0
grams of MC, 600.0 grams of toluene, and 13.5 grams of DBTO were then added to the third intermediate compound in the reaction flask to form the complete
polyester resin of the subject invention. The MC was reacted from 130°C to
140°C for approximately 11 hours to prepare the polyester resin, a polyester
carbamate.
[0072] The course of the reaction was followed by monitoring the hydroxyl
number of the product. When the hydroxyl number fell below 15 mg KOH/g (ca.
88% conversion), the contents of the reaction flask were cooled to 125°C and
connected to a vacuum to strip off toluene and excess MC. Stripping was then continued until the residual MC in the product was less than 0.2%. The product was then dissolved in 2400 g of propylene glycol methyl ether to obtain a resin
with a final solids content of 79% NV. GPC analysis showed the molecular
weight to be Mn=1730, Mw=2550, and d (polydispersity)=1.5
EXAMPLE 2:
[0073] In Example 2, the polyester resin was prepared by adding and reacting the
following parts, by weight, unless otherwise indicated.
Table 2
[0074] Per the above table, Table 2, 1000.0 grams of the first intermediate
compound were added to a reaction flask. In this example, the first intermediate
compound was previously prepared and the reactants included 116.4 grams of PE,
782.3 grams of E-cap, 100.4 grams of toluene, and .9 grams of stannous octoate reacted at 150°C. 261.8 grams of HHPA and 50.0 grams of toluene were added to
the first intermediate compound to form the second intermediate compound and
the reaction flask was heated with a conventional heat supply to a temperature of from 120°C to 140°C and held for approximately 3 hours. The heat supply was then removed overnight and the reaction mixture cooled. Next, the reaction flask was heated to 125°C and 416.5 grams of CE10S were added to the second intermediate compound to form the third intermediate compound. After approximately 5 hours, 282.0 grams of MC, 200.0 grams of toluene, and 2.0 grams of DBTO were added to react with the third intermediate compound and form the complete polyester resin of the subject invention in about 12 hours. The reaction flask was heated to a temperature of from 120°C to 140°C and held for approximately 2 hours until the final hydroxyl number was below 15 mg KOH/g. Vacuum stripping was then carried out as described above to remove excess MC and toluene. The resulting polyester resin was dissolved in 700 grams of propylene glycol methyl ether for a final solids content of 70% NV.
EXAMPLE 3;
[0075] hi Example 3, the polyester resin was prepared by adding and reacting the following parts, by weight, unless otherwise indicated.
Table 3
[0076] Per the above table, Table 3, 650.1 grams of the first intermediate
compound were added to a reaction flask. In this example, the first intermediate compound was previously prepared and the reactants included 133.6 grams of PE,
451.8 grams of E-cap, 64.3 grams of toluene, and .4 grams of stannous octoate
reacted at 150°C. 308.0 grams of HHPA and 30.0 grams of toluene were added to
the first intermediate compound to form the second intermediate compound and the reaction flask was heated with a conventional heat supply to a temperature of
120°C and held for approximately 2 hours. Next, 490.0 grams of CE10S were
added to the second intermediate compound to form the third intermediate
compound. After approximately 1 hour, the heat supply was removed overnight
and the reaction mixture cooled. Next, the reaction flask was heated to 135°C, until the acid number fell below 3 mg KOH/g. Next, 330.0 grams of MC, 50.0 grams of toluene, and .9 grams of DBTO were added to the third intermediate
compound in the reaction flask to form the complete polyester resin of the subject
invention. The MC was reacted from 125°C to -140°C for approximately 12
hours until the hydroxyl number fell below 15 mg KOH/g, for a 91% conversion.
Vacuum stripping was applied to remove excess MC and solvent. The resulting
polyester resin was dissolved in 400 g of propylene glycol methyl ether to achieve
a final solids content of 76% NV.
EXAMPLE 4:
[0077] In Example 4, the polyester resin was prepared, according to the
alternative method, by adding and reacting the following parts, by weight, unless
otherwise indicated.
Table 4
[0078] Per the above table, Table 4, 338.2 grams of the second intermediate
compound were added to a reaction flask. In this example, the first and second
intermediate compound were previously prepared, according to the alternative
method described above, with the reactants including 28.5 grams of PE, 103.4
grams of HHPA, 41.9 grams of xylene, and 164.4 grams of CE10S. The reaction
flask was heated with a conventional heat supply to an initial temperature of
100°C for approximately 0.5 hours. 61.1 grams of E-cap, .5 grams of stannous
octoate, and 8.7 grams of toluene were added to the alternative second
intermediate compound to form the third intermediate compound of this
alternative embodiment. The reaction flask was heated to a temperature of 120°C to 140°C and held for approximately 6 hours until IR Specfroscopy showed the
complete absence of lactone groups (i.e., no lactone peak). The heat supply was
removed overnight and the reaction mixture cooled. Next, the reaction flask was
heated to 120°C, and 64.3 grams of MC, 1.0 gram of DBTO, and 70.0 grams of toluene were reacted with the third intermediate compound to form the completed
polyester resin. The MC was reacted from 125°C to -140°C for approximately 15
hours to prepare the polyester resin until the hydroxyl number was below 15 mg
KOH/g (88% conversion). Vacuum stripping was then applied to remove excess
MC and solvent. The completed resin was then dissolved in 170 g of propylene glycol methyl ether to achieve a final solids content of 68% NV.
EXAMPLES 5 AND 6:
[0079] Examples 5 and 6 were prepared essentially as described above.
[0080] Example 5 is a polyester resin of 1 PE / 3.3 HHPA / 3.3 CE10S / 4 E-cap / 4
MC.
[0081] Example 6 is a polyester resin of 1 PE / 2 HHPA / 2 CE10S / 8 E-cap / 4 MC.
EXAMPLE 7: [0082] In Example 7, coating compositions, specifically two clearcoat coating compositions, including the polyester resin from Examples 1 and 2 were prepared by adding and reacting the following parts, by weight, unless otherwise indicated.
[0083]
Table 5
[0084] In Example 7A, the resin is the polyester resin prepared in Example 1 above.
[0085] In Example 7B, the resin is the polyester resin prepared in Example 2 above.
[0086] Cross-Linking Agent is a melamme-formaldehyde resin commercially
available as Resimene® 747 from Monsanto (Solutia).
[0087] Light Stabilizers A and B are ultra-violet light absorbers and are
commercially available from Ciba Specialty Chemicals as Tinuvin® 928 and
Tinuvin® 123, respectively.
[0088] Flow Additive is a polysiloxane flow additive.
[0089] Catalyst is a blocked acid catalyst (DDBSA) commercially available from
King Industries as Nacure 5225.
[0090] Solvent A is Exxate 1000 (oxo-decyl acetate), Solvent B is methyl propyl
ketone, and Solvent C is Exxate 500.
EXAMPLES 8 AND 9:
[0090] For Example 8, a coating composition was prepared as described above
using the polyester resin of Example 5, and for Example 9, a coating composition
was prepared as described above using the polyester resin of Example 6.
[0091] After standard solvent reduction to optimize spray viscosity, the
solventbome clearcoat coating compositions of Examples 7A-9 were was sprayed
onto panels over a black waterborne basecoat (WBBC) commercially available as E202KW706 from BASF Coφoration, Southfield, Michigan to evaluate certain
properties as described below. The properties described below were evaluated
versus an acrylic-based solventbome clearcoat control, which was sprayed over the
same WBBC. This acrylic-based control is also commercially available from the BASF Corporation as E10CG062.
Table 6
[0092] For 140 QCT, i.e., Cleveland Condensing Cabinet testing known in the art, the panels were exposed to 140°F humidity for 24 hours and rated from 1 to 5, with
1 being the best.
[0093] For Scratch/Mar, the panels were exposed to 10 double rubs with 3M
polishing paper on an ASTM Crockmeter and were measured for % gloss retention.
[0094] For Cold Gravelometer 275°F and 300°F, panels were prepared with an OEM basecoat/clearcoat and then with 2 basecoat/clearcoat repairs. Next, the panels were baked at either 25 X 275°F or 90 X 300°F. The Gravelometer testing equipment was run at -20°F and 70 PSI. The panels were rated from 1 to 10 with 10 being the best.
[0095] For QUV, the panels were measured for % gloss retention after 3500 hours exposure according to GM 8/4 Cycle Testing as is known in the art, where the panels are repeatedly and cyclically exposed to UV light for 8 hours and then to 4 hours of condensing humidity.
[0096] For WOM, the panels were measured for % gloss retention with an Atlas Xenon weatherometer, an instrument known in the art.
[0097] For JAX, the panels were exposed in testing facilities in Jacksonville, Florida for etch exposure and rated from 1 to 10, with 1 being the best. [0098] As the data included in Table 6 reveals, coating compositions which incoφorate the polyester resins of the subject invention are comparable to the acrylic based control coating composition in most properties. Furthermore, with respect to the flexibility of the cured films of the coating compositions, as evaluated by Cold Gravelometer, the polyester resins of the subject invention are significantly more resilient to chip relative to the control. [0099] The invention has been described in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Obviously, many modifications and variations of the present invention are possible in light of the
above teachings, and the invention may be practiced otherwise than as specifically described.