Low VOC unsaturated polyester systems and uses thereof

This invention relates to a polyester resin comprising (A) from about 5% to about 50% by weight reactive diluent and (B) from about 50% to about 95% by weight of an unsaturated polyester resin prepared from at least one component selected from the group consisting of (i) from about 0.5% up to about 8% by mole of a polyhydric alcohol, having at least three hydroxyl groups, and at least one transesterification catalyst, (ii) from about 2% up to about 12% by mole of a reaction product of a polyol and a fatty carboxylic acid, and (iii) from about 2% up to about 12% by mole of a fatty reactant selected from the group consisting of a fatty primary alcohol, a fatty epoxide, a fatty monocarboxylic acid and mixtures thereof, wherein each member of the group has up to about 100 carbon atoms. In another aspect, the invention relates to mixtures of the above polyester resins with conventional polyester resins. Methods of reducing volatile organic compound emissions are also part of the invention. The present invention provide resins and methods which have low emissions of volatile organic compounds and when used in curable compositions have good gel times and final cured properties.

FIELD OF THE INVENTION 
This invention relates to unsaturated polyester resins systems and methods 
of using the same. 
BACKGROUND THE INVENTION 
Unsaturated polyester resins are typically used together with a reactive 
diluent, usually a volatile unsaturated organic monomer, which is 
generally referred to as a reactive diluent. The unsaturated organic 
monomer copolymerizes with the polyester resins to form a gelcoating and 
may be used in other applications such as pultrusion, resin lamination, 
sheet molding compounding, bulk molding compounding, etc. 
During curing some of the volatile organic monomer is lost to the 
atmosphere. Due to environmental concerns of such organic compounds, 
legislation has been passed which requires reduction in the amount of 
volatile organic compounds which may be released to the atmosphere. 
One method of reducing such VOC emission is replacement of the reactive 
diluent with a less volatile reactive diluent. However, this approach has 
led to slower curing times and/or incomplete curing at normal ambient 
temperatures. Another approach is the reduction in the amount of reactive 
diluent. This approach has led to increases in viscosity beyond useable 
values. If viscosity increase is compensated by use of a lower molecular 
weight polyester, then poor final gelcoat properties have resulted. 
Another approach has been the use of a suppressant which reduces the loss 
of VOCs. The suppressants are often waxes which lead to a reduction in 
interlaminar adhesion of the gelcoat. It is desirable to have a gelcoat 
product which has reduced VOC and also which has acceptable gel time and 
good final gelcoat properties. 
SUMMARY OF THE INVENTION 
This invention relates to a polyester resin comprising (A) from about 5% to 
about 50% by weight reactive diluent and (B) from about 50% to about 95% 
by weight of an unsaturated polyester resin prepared from at least one 
component selected from the group consisting of (i) from about 0.5% up to 
about 8% by mole of a polyhydric alcohol, having at least three hydroxyl 
groups, and at least one transesterification catalyst, (ii) from about 2% 
up to about 12% by mole of a reaction product of a polyol and a fatty 
carboxylic acid, and (iii) from about 2% up to about 12% by mole of a 
fatty reactant selected from the group consisting of a fatty primary 
alcohol, a fatty epoxide, a fatty monocarboxylic acid and mixtures 
thereof, wherein each member of the group has up to about 100 carbon 
atoms. In another aspect, the invention relates to gelcoats having 
mixtures of the above polyester resins with conventional polyester resins. 
In another aspect, the invention relates to the addition of suppressants 
which reduce volatile organic compound emissions. Methods of reducing 
emissions volatile organic compounds are also part of the invention. The 
present invention provide resins and methods which have low emissions of 
volatile organic compounds and which have good gel times and final cured 
properties. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In the specification and appended claims, the term polyester resin system 
refers to the combination of an unsaturated polyester resin and a reactive 
diluent. The term gelcoat refers to compositions containing the 
unsaturated polyester system and other gelcoat components such as 
thixotropic agents, copromoters, pigments, air release agents, etc. 
The use of the term "conventional" polyester resin refers to unsaturated 
polyester resins in reactive diluent which are available commercially. The 
conventional polyester is separate and distinct from the unsaturated 
polyester resin systems described herein. The conventional polyesters are 
described below including commercial examples. 
The term surface tension relates to a measure of the surface energy of the 
cured gelcoat. The surface tension is determined using water and methyl 
iodine. A drop is placed on a cured gelcoat and the contact angle is 
measured by a goniometer (Model 100-00 from Rame-Hart Inc.). The contact 
angle may be used to determine the total surface tension, as well as polar 
and dispersive surface tensions. The equations for determining the surface 
tension from contact angle are found in S. Wu, Polymer Interfaces and 
Adhesion, Marcel Dekker, Inc., New York (1982). The sections related to 
surface tension and its measurement are hereby incorporated by reference. 
Reactive Diluent 
The reactive diluent typically comprises from about 5% to about 50%, or 
preferably from about 10% to about 45%, or more preferably from about 15% 
to about 35% by weight of the unsaturated polyester system. Here as well 
as through the specification and claims, the range and ratio limits may be 
combined. The reactive diluent is preferably an ethylenically unsaturated, 
monomeric compound, which include allyl and vinyl compounds conventionally 
used for the preparation of unsaturated polyester moldings, impregnating 
and coating compositions. Examples of reactive diluents include styrene, 
substituted styrenes, e.g., methoxystyrene, divinylbenzene, 
4-ethylstyrene, 4-methylstyrene, 4-t-butylstyrene, p-chlorostyrene or 
vinyltoluene, esters of acrylic acid and methacrylic acid with alcohols or 
polyols (such as those described herein) each having from 1 to 18 carbon 
atoms, e.g., methyl methacrylate, butylacrylate, ethylhexyl acrylate, 
hydroxpropyl acrylate, lauryl acrylate, stearyl methacrylate, lauryl 
methacrylate, butanediol diacrylate, and trimethylolpropane triacrylate, 
allyl esters, e.g., diallyl phthalate, and vinyl esters, e.g., vinyl 
ethylhexanoate, vinyl pivalate, limonene, dipentene, vinyl ethers, indene, 
allyl benzene, and the like. Mixtures of these compounds may be used. 
Preferred components are styrene, .alpha.-methylstyrene, vinyltoluene, and 
divinyl-benzene. 
In one embodiment, the reactive diluent is a mixture of styrene and less 
volatile organic monomers. The styrene is generally present in a majority 
(e.g., greater than 50%) amount preferably up to about 70%, or up to about 
80% by weight) of the reactive diluent. The remainder of the reactive 
diluent are less volatile monomers such as those above reactive diluents 
with a lower vapor pressure, and preferably .alpha.-methylstyrene, 
vinyltoluene, divinyl-benzene and methyl methacrylate. 
Polyester Resin 
The polyester resin is typically the condensation product of a 
polycarboxylic acid or its derivative (anhydrides, C.sub.1-8 alkyl esters, 
etc.) and a polyhydric alcohol. The polyester resin usually encompasses 
from about 50% to about 95%, or preferably from about 55% to about 90%, or 
more preferably from about 60% to about 85% by weight of the unsaturated 
polyester resin system. The inventors have discovered that polyester resin 
having lower acid numbers, such as less than about 30, with about 20 or 
less being preferred, have good spraying properties in applications where 
the unsaturated polyester resin system is applied by spraying. In one 
embodiment, the polyester has a narrow molecular weight distribution 
(Mw/Mn). The molecular weight distribution is typically from about 2 to 
about 8, or preferably from about 2.5 to about 5. In one embodiment, the 
polyester resin is free of dicyclopentadiene olefins, alcohols or acids. 
As described above, the polyester resins may be prepared with at least one 
component selected from the group consisting of (i) from about 0.5% up to 
about 8% by mole of a polyhydric alcohol, having at least three hydroxyl 
groups, and at least one transesterification catalyst, (ii) from about 2% 
up to about 12% by mole of a reaction product of a polyol and a fatty 
carboxylic acid, and (iii) from about 2% up to about 12% by mole of a 
fatty reactant selected from the group consisting of a fatty primary 
alcohol, a fatty epoxide, a fatty monocarboxylic acid and mixtures 
thereof, wherein each member of the group has up to about 100 carbon 
atoms. The polyhydric alcohols typically have from about 4 to about 12, 
preferably from about 4 to about 8 carbon atoms. In one embodiment, the 
polyhydric alcohols have a neo structure, e.g. a carbon atom bonded solely 
to other carbon atoms. Examples of the polyhydric alcohols are listed 
below and include glycerol, pentaerythritol, dipentaerythritol, 
tripentaerythritol, trimethylolethane, trimethylolpropane, and 
di-trimethylolpropane. These polyhydric alcohols are generally present in 
an amount from about 1% to about 6%, more preferably from about 2% to 
about 5% by mole. 
In one embodiment, the polyester resin is prepared with a 
transesterification catalyst. The catalyst is present in an amount from 
about 0.05% to about 2% by weight. Transesterification catalyst include 
metal-containing catalysts metal glycoxides, such as antimony glycoxide; 
alkali metal borohydrides, such as sodium borohydride, potassium 
borohydride, magnesium borohydride, calcium borohydride, aluminum 
borohydride, titanium borohydride, and tin borohydride; metal oxides, such 
as beryllium oxide, magnesium oxide, antimony trioxide, tin(IV) oxide, and 
dibutyltin oxide; metal hydroxides, such as magnesium hydroxide, metal 
acetates such as magnesium acetate, manganese acetate, tin(IV) acetate, 
metal carbonates, such as lithium carbonate, sodium carbonate, potassium 
carbonate, magnesium carbonate, tin(IV) carbonate, tetraalkyl metals, such 
as tetraalkyl titanate, such as tetraisopropyl titanate, tetra-n-butyl 
titanate, and tetrakis (2-ethylhexyl) titanate, and tetraalkyl zirconate, 
such tetraisopropyl zirconate, tetra-n-butyl zirconate, tetrakis 
(2-ethylhexyl) zirconate; and metal nitrates, such as tin(IV) nitrate. 
Other suitable transesterification catalysts include, for example, 
Bronsted acids such as sulfuric acid and Lewis acids such as aluminum 
triisopropoxide. Preferred transesterification catalysts are antimony 
glycoxide, (Sb.sub.2 (OCH.sub.2 CH.sub.2 O).sub.3), and manganese acetate 
in about equal portions. 
In another embodiment, the polyester resin is prepared using (ii) from 
about 2% up to about 12% by mole of a reaction product of a polyol and a 
fatty carboxylic acid. The reaction product may contain an average of two, 
three or more, preferably two, residual hydroxyl groups which may be used 
in the preparation of the polyester resin. Residual hydroxyl groups are 
those remaining after the reaction of the polyol and the fatty acid. The 
residual hydroxyl groups are reacted in preparing the unsaturated 
polyester systems. The polyols include those which have three or more 
hydroxyl groups, such as those listed herein, and have from about three to 
about 12, preferably from about 3 to about 8 carbon atoms. The fatty acids 
include those having from about 8 to about 30, preferably from about 12 to 
about 24, more preferably from about 14 to about 22 carbon atoms. Examples 
of fatty acids include dodecanoic acid, hexadecanoic acid, stearic acid, 
palmitic acid, oleic acid, etc. The preferred reaction products are 
glycerol based, such as glycerol monostearate. In one embodiment, the 
fatty acids are saturated fatty acids. 
In another embodiment, the polyester resin may be prepared from (iii) from 
about 2% up to about 12% by mole of at least one fatty reactant selected 
from the group consisting of a fatty primary alcohol, a fatty epoxide, a 
fatty monocarboxylic acid and mixtures thereof, wherein each member of the 
group has up to about 100 carbon atoms. In one embodiment, (iii) contains 
from about 12 to about 90, or from about 25 to about 80 carbon atoms. In 
one embodiment, (iii) is saturated. Generally, (iii) may contain up to 
about 25% by weight of nonfunctional hydrocarbon diluent. Component (iii) 
is typically present in an amount from about 3% to about 12%, more 
preferably from about 4% to about 10% by mole. Examples of fatty alcohols 
include oleyl alcohol, lauryl alcohol, stearyl alcohol, UNILIN 425 (a 
C.sub.30 avg. linear primary alcohol), UNILIN 550 (a C.sub.40 avg. linear 
primary alcohol), and UNILIN 700 (a C.sub.50 avg. primary alcohol). UNILIN 
alcohols are available from Petrolite Corporation. The fatty epoxides 
include epoxidized fatty alcohols, such as oleyl epoxide, stearyl epoxide, 
epoxidized soybean oil, epoxidized linseed oil, epoxidized C.sub.8-50 
alpha-olefins, etc. The fatty acids may be any of the monocarboxylic acids 
discussed herein. 
Polyester resin are typically reaction products of polybasic carboxylic 
acids or their derivatives and polybasic alcohols, and, in this invention, 
include one or more of the above described components B (i) through (iii). 
The carboxylic acids and their derivatives are typically dibasic 
unsaturated, preferably .alpha., .beta.-olefinically unsaturated, 
carboxylic acids or their derivatives. Examples of these carboxylic acid 
and their derivatives include maleic acid, fumaric acid, chloromaleic 
acid, itaconic acid, citraconic acid, methyleneglutaric acid and mesaconic 
acid and their esters or preferably their anhydrides, as well as succinic 
acid, glutaric acid, d-methylglutaric acid, adipic acid, sebacic acid, 
pimelic acid, phthalic anhydride, o-phthalic acid, isophthalic acid, 
terephthalic acid, dihydrophthalic acid, tetrahydrophthalic acid, 
tetrachlorophthalic acid, dodecanedicarboxylic acids, nadic anhydride, 
cis-5-norbornene-2,3-dicarboxylic acid or anhydride, 
dimethyl-2,6-naphthenic dicarboxylate, dimethyl-2,6-naphthenic 
dicarboxylic acid, naphthenic dicarboxylic acid or anhydride and 
1,4-cyclohexane dicarboxylic acid. Monobasic, tribasic or higher polybasic 
carboxylic acids, for example ethylhexanoic acid, methacrylic acid, 
propionic acid, benzoic acid, 1,2,4-benzenetricarboxylic acid or 
1,2,4,5-benzenetetracarboxylic acid may also be used in preparing the 
polyester resins. 
In one embodiment, the carboxylic acids and their derivatives are the 
combination of a non-aromatic carboxylic acid or derivative and an 
aromatic carboxylic acid or derivative. Examples of the various acids and 
their derivatives are disclosed above. The non-aromatic acid is typically 
present in an amount from about 40% to about 70%, preferably from about 
40% to about 65%, or more preferably from about 45% to about 60% by mole 
of non-aromatic carboxylic acid or derivative. These carboxylic acids 
typically have from about 3 to about 12, or from about 3 to about 8, or 
from about 4 to about 6 carbon atoms. Preferred acids or derivatives are 
maleic or fumaric acids or esters and maleic anhydride. 
The aromatic carboxylic acids or their derivatives are generally present in 
an amount from about 30% to about 60% by mole, preferably from about 35% 
to about 60%, or more preferably from about 40% to about 55% by mole. The 
aromatic carboxylic acid or their derivatives have from about 8 to about 
18, preferably from about 8 to about 12 carbon atoms. The aromatic 
carboxylic acids and their derivatives are disclosed above. The aromatic 
carboxylic acids and derivatives are disclosed above and preferred 
aromatic carboxylic acid and derivatives, include phthalic anhydride, 
o-phthalic acid, iso-phthalic acid, etc. 
As described above the polyester resin is prepared from polyhydric 
alcohols, preferably glycols. Suitable polyhydric alcohols include 
alkanediols and oxa-alkanediols, for example, ethyleneglycol, 
1,2-propyleneglycol, propane-1,3-diol, 1,3-butyleneglycol, butene- 
1,4-diol, hexane- 1,6-diol, 2,2-dimethylpropane- 1,3-diol, 
diethyleneglycol, triethyleneglycol, polyethyleneglycol, cyclohexane- 
1,2-diol, 2,2-bis-(p-hydroxycyclohexyl)-propane, butene-1,4-diol, 
5-norbornene-2,2-dimethylol, 2.3-norbornene diol, and cyclohexane 
dimethanol. Preferably the polyhydric alcohols are neopentyl glycol and 
propyleneglycol. 
In one embodiment, the polyester resin is prepared from polyhydric alcohols 
where from about 45% to about 70%, preferably from about 50% to about 65% 
by mole of the polyhydric alcohols are those having a neo structure. 
Examples of such alcohols include neopentylglycol, 
dimethylpropane-1,3-diol, 2,2-dimethylheptanediol, 2,2-dimethyloctanediol, 
2,2-dimethyl-1,3-propanediol, pentaerythritol, dipentaerythritol, 
tripentaerythritol, trimethylolpropane, di-trimethylolpropane, 
2,2,4-trimethyl- 1,3-pentanediol, 2-butyl-2-ethyl- 1,3 -propanediol, 
3-hydroxy-2,2-dimethylpropyl 3-hydroxy-2,2-dimethyl propanate, etc. 
In another embodiment, the unsaturated polyester is prepared from alcohols 
having a neo structure. In this embodiment, preferably greater than 80%, 
or greater than 90% by mole or all of the polyhydric alcohols have a neo 
structure. Examples of neo structure containing a polyhydric alcohols are 
discussed above. 
Conventional Polyesters 
The conventional unsaturated polyesters are those which are available 
commercially and contain reactive diluent. They are prepared from one or 
more of the above polycarboxylic acids or derivatives and one or more of 
the above polyhydric alcohols. In one embodiment, the conventional 
polyester is prepared from a combination of a non-aromatic and an aromatic 
carboxylic acid or derivative thereof, preferably phthalic acid and maleic 
anhydride. The polyol is typically neopentylglycol and propyleneglycol. 
The conventional polyester generally contains from about 20% to about 45% 
or preferably from about 30 to 38% reactive diluent such as those 
described above. The unsaturated polyester resin is typically present in 
an amount from about 55% to about 85%. 
Commercial polyester resins are available as ortho or iso polyester from 
many companies. Examples of these companies include Reichhold Chemical, 
Ashland Chemical, Huls AG, and Alpha Resin. 
Suppressants 
In another embodiment of the present invention the polyester resin 
compositions systems may include a suppressant. The suppressant acts to 
reduce volatile organic emissions. The suppressants include polyethers, 
polyether block copolymers and polyether polysiloxane block copolymers as 
well as alkoxylated alcohols, alkoxylated fatty acids and 
polyalkoxypolysiloxanes. The suppressants are generally present in an 
amount from about 0.05% to about 4% or from about 0.25% to about 3%, or 
from about 0.5% to about 2%. Examples of useful suppressants include but 
are not limited to polyethers in particular poly-(ethylene glycols) (PEG) 
having at least five oxyethylene units, poly-(propylene glycols) (PPG), 
monoalkoxyl-poly-(propylene glycols), monomethoxy-poly(ethylene glycols) 
(MPEG) having at least five oxyethylene units and the like; polyether 
block copolymers in particular poly-(ethylene glycol)-poly-(propylene 
glycol) block copolymers (PEG-b-PPG), and the like; and 
polyether-polysiloxane block copolymers, in particular 
polyl(alkylsiloxane)-polyether block copolymers, 
poly-(alkylarysiloxane)-polyether block copolymers, and the like. Vinyl 
functional derivatives of the polymers include but are not limited to 
polyoxyethylene maleate half-acid esters of five or more oxyethylene 
units, in particular monoalkoxy poly-(ethylene glycols) of five or more 
oxyethylene units, poly-(dimethylsiloxane)-polyether block copolymers 
(PDMS-b-polyethylene glycol/polypropylene glycol) and the like. 
Suppressants include BYK S-740 (believed to be a hydroxy polyester with 
paraffin wax), available from BYK Chemie USA, and STYRID (believed to be a 
wax in a mineral oil) available from Specialty Products Company, Jersey 
City, N.J. 
In one embodiment, the above unsaturated polyester resin systems are used 
as suppressants in gelcoats containing a polyester resin, such as the 
conventional polyester resins. The unsaturated polyester resin systems are 
generally present in an amount from about 5% to about 40%, or from about 
10% to about 30% by weight. The unsaturated polyester resin systems, when 
used as a suppressant, are added to the gelcoat which already contains 
another polyester. Preferred suppressant unsaturated polyester resin 
system are those designated as B(ii) and B(iii) above. 
Surface Tension Agents 
In one embodiment, of the invention, the unsaturated polyester resin system 
contains a surface tension agent. The surface tension agent is generally 
present in an amount from about 0.001% up to about 1%, or from about 0.01% 
up to about 0.5% by weight. These agents act to reduce the polar surface 
tension to a value below the dispersive surface tension. The surface 
tension agent lowers the surface tension at the surface of the cured 
gelcoat. Examples of surface tension agents silicone and fluorocarbon 
surfactants. Examples of silicone surfactants include dimethyl silicones, 
liquid condensation products of dimethylsilane diol, methyl hydrogen 
polysiloxanes, liquid condensation products of methyl hydrogen silane 
diols, dimethysilicones, aminopropyltriethoxysilane, and methyl hydrogen 
polysiloxanes. In one embodiment, the silicone surfactant is a 
polysiloxane preferably a polydimethylsiloxane block polyether, such as 
BYK-306 available from BYK Chemie USA. The inventors have discovered that 
these surfactants also control formation of fish eyes in brushed 
applications. These surfactants are sold under the tradename DOW CORNING 
fluids and additives from Dow Corning Chemical and SF-69 and SF-99 from 
General Electric, and BYK polysiloxanes available from BYK Chemie USA. 
Fluorocarbon surfactants, such as fluorinated potassium alkyl carboxylates, 
fluorinated alkyl quaternary ammonium iodides, ammonium perfluoroalkyl 
carboxylates, fluorinated alkyl polyoxyethylene ethanols, fluorinated 
alkyl alkoxylates, fluorinated alkyl esters, and ammonium perfluoroalkyl 
sulfonate sold under the FLUORAD tradename of 3M Company. 
Polyester Resin Preparation 
The polyester resins may be prepared by usual esterification means known to 
those skilled in the art. In one embodiment, the polyester resins are 
prepared by mixing the carboxylic acids or their derivatives with a polyol 
and heating the mixture to about 120.degree. C. to about 160.degree. C. 
The mixture heats exothermically by about 30 degrees, for instance to 
170.degree. C. The mixture is heated to 175.degree. C. to about 15.degree. 
C. or higher. The reaction is continued until the desired acid number is 
reached. When the above described polyol having three or more hydroxyl 
groups are used, then the polyol is added together with the acids or their 
derivatives and reacted before addition of any other polyols used to make 
the polyester. When using the polyol with three or more hydroxyl groups, a 
transesterification catalyst is added when about 50% of the theoretical 
water is removed from the reaction. 
When isophthalic acid and maleic anhydride are used in preparing the 
polyester resin, then the above procedure is modified by adding all acids 
and alcohols except maleic anhydride. Maleic anhydride is added when the 
reaction mixture is clear (about 50% of the theoretic water is removed). 
Acid number is a reflection of the extent of esterification and molecular 
weight of the polyester resin. The esterification is typically continued 
until the polyester has the acid number corresponding to the desired 
molecular weight. In one embodiment, the final acid number is in the range 
less than 30, preferably less than 20. For applications which require 
spray application, the inventors have discovered that polyester resin with 
acid number less than about 30 are preferred and less than about 25 are 
more preferred. 
As described above the progress of the reaction may be followed by acid 
number. The acid number may be reduced by increasing temperature and/or 
maintaining the reaction temperature until the acid number is reduced to 
the desired level. In one embodiment, the acid number may be reduced by 
using an acid neutralizer. The acid neutralizer is added in an amount 
sufficient to lower the acid number to the desired level. In one 
embodiment, the acid neutralizer is added when the acid number is in the 
range of about 40 to about 70, preferably from about 45 to 65, more 
preferably from about 50 to about 60. Examples of acid neutralizers 
include ethylene carbonate, glycidyl neodecanate (Cardura E-10, available 
from Shell Chemical Co.), carbodimides, isocyanates, MTMI 
(benzene-1-(1-isocyanato-1methylethyl)-3-(1-methylethenyl-a,a-dimethyl-met 
a-isopropenyl-benzoisocyanate) from Cyanamid, glycidyl methacrylate, fatty 
primary alcohols, fatty epoxides, and mixtures thereof. 
Applications 
The above unsaturated polyester systems may be used in a variety of 
applications which include gelcoating, resin lamination, pultrusion, sheet 
molding compounding, bulk molding compounding, etc. The coating and 
articles of manufacture include sinks, countertops, shower stalls/tubs, 
spas, boat hulls, patio brick coatings, etc. 
The unsaturated polyester system may be used together with other additives 
to form gelcoats and polyester articles. The applications may include the 
spray up manufacture of coating and articles. In this method, one or more 
of the above unsaturated polyester system is fed into a spray gun along 
with fillers, such as chopped fiberglass, mica and/or thixotropic agents, 
such as fumed silica or precipitated silica. The unsaturated polyester 
system may be mixed with the fibers internal or external to the spray gun. 
Another method of using unsaturated polyester systems is the hand lay up 
method of fabrication. In this method the fiberglass, as roving or chopped 
fibers are added to an open mold and the unsaturated polyester system is 
wetted out on the fiberglass by hand rollers, brushes and squeegees. 
Pultrusion involve pulling roving fiberglass strands through a unsaturated 
polyester system bath and through a heated die. 
Gelcoats 
Gelcoats are curable compositions which contain one or more of the above 
unsaturated polyester systems along with other additives. These other 
additives include thixotropic agents, suppressants, surface tension 
agents, copromoters, air release agents, fillers and optionally pigments. 
The thixotropic agents include silica compounds (including fumed silica and 
precipitated silica), and inorganic clays (including bentonite and 
hectorite clay). Precipitated silica is preferred for non-aqueous 
applications and for its abilities to reduce volatile organic emissions. 
These agents are typically present in an amount from about 0.5 to about 5, 
or from about 1 to about 4 parts per 100 parts of neat polyester resin. 
The gelcoat may also contain fillers, such as pyrex glass, chopped 
fiberglass, flint and crown glasses, talc, silicone dioxide, titanium 
dioxide, calcium carbonate, magnesium carbonate, barium carbonate, calcium 
sulfate, magnesium sulfate, and barium sulfate. The fillers are present in 
an amount from about 5 to about 40, or from about 10 to about 35 parts per 
100 parts of neat polyester resin. 
Promoters are any electron donating species which helps in the 
decompositions of the catalyst. The promoters are usually added to 
unsaturated polyester resin systems to accelerate the decomposition of a 
peroxide initiator to free radicals and thereby initiate or speed the 
curing of the composition at relatively low temperatures, i.e., at 
temperatures in the range of 0.degree. to 30.degree. C. The promoters are 
generally used from about 0.01% to about 1%, or from about 0.03% to about 
0.5%, preferably about 0.06% by weight. Among the materials that have been 
reported as being effective promoter are metal compounds, such as cobalt, 
manganese, iron, vanadium, copper, and aluminum salts of organic acids; 
amines, such as dimethylaniline, diethylaniline, and 2-aminopyridine; 
Lewis acids, such as boron fluoride dihydrate and ferric chloride; bases, 
such as tetramethyl ammonium hydroxide; quaternary ammonium salts, such as 
trimethylbenzyl ammonium chloride and tetrakismethylol phosphonium 
chloride; and sulfur compounds, such as dodecyl mercaptan and 
2-mercaptoethanol; dimethyl acetoacetamide; and methyl acetoacetate. 
Cobalt salts of organic acids are the most widely-used accelerators for 
the low temperature decomposition of peroxide catalysts and the curing of 
unsaturated polyester resin compositions. It is generally preferred that 
cobalt and potassium salts of aliphatic monocarboxylic acids having 5 to 
about 20, or from about 8 to about 12 carbon atoms or alicyclic acids 
having about 5 to about 7 carbon atoms be present in the promoter systems. 
Particularly useful promoter include COBALT HEXCHEM (cobalt octanoate) and 
POTASSIUM HEXCHEM (potassium octanoate), dimethyl acetoacetamide; and 
methyl acetoacetate. 
The alkyl acrylate or methacrylate is typically used in combination with a 
vinyl aromatic monomer. The alkylacrylate or methacrylate is usually 
present in an amount up to 20%, from about 0.5% to about 15%, or from 
about 1% to about 10%, or from about 1% to about 5% by weight of gelcoat. 
The alkylacrylates or methacrylates are described above. 
Typically, the gelcoat is prepared by blending a polyester resin system 
with the gelcoat components as is known to those in the art. After 
addition of the additives the gelcoat compositions is diluted with 
reactive diluent to a Brookfield viscosity from about 2,000-4,000, or from 
about 3000-4000, or from about 3500-3600 cPs at 77.degree. F, using 
spindle #4. The gel time of a small portion of the gelcoat is determined. 
If the gel time is too short, then inhibitors, such as phenols like 
hydroquinone and hydroquinone methyl ester material are added to make the 
gel time increase. If the gel time is too long, then one or more of the 
above promoters is added to decrease the gel time. 
A pigmented gelcoat, for example, is prepared by adding 12 parts titanium 
dioxide, 0.25 parts of ethyleneglycol, 0.5 parts of 5% hydroquinone 
solution, 15 parts of talc, 3 parts of styrene monomer, 1.7 parts of fumed 
silica, 3 parts of methyl methacrylate, 0.26 parts of potassium octanoate, 
8 parts of styrene monomer, 0.14 parts of cobalt octanoate (12%), 0.3 
parts of air release agent, 3 parts of styrene monomer, and 0.1 parts of 
methyl methacrylate to 43 parts of unsaturated polyester resin system.

The following example relates to unsaturated polyester resins and 
unsaturated polyester systems. Unless otherwise specified, in the examples 
as well as elsewhere in the specification and claims, amounts and 
percentages are by weight, the temperature is in degrees Celsius, and 
pressure is atmospheric pressure. 
EXAMPLE 1 
(a) A reaction vessel is charged with 30.8 grams (0.5 mole) of 
trimethylolpropane, 238.2 grams (3.5 moles) of phthalic anhydride, and 
236.1 grams (5.3 moles) of maleic anhydride under a nitrogen sparge. The 
mixture is heated and the final temperature is 190.degree. C. The reaction 
mixture is cooled to 140.degree. C. where 113.26 (3.2 moles) of 
propyleneglycol and 241.8 grams (5.1 moles) of neopentylglycol are added 
to the reaction vessel. The reaction mixture is heated to 205.degree. C. 
when 35 grams of water are evolved then 0.5 grams of manganese acetate and 
0.50 grams of Sb.sub.2 (OCH.sub.2 CH.sub.2 O).sub.3 are added to the 
reaction vessel. The reaction temperature is maintained until 52 grams of 
water distillate is collected. The acid number is 56 and 80 grams of 
ethylene carbonate are added to the reaction vessel. The temperature is 
heated to 205.degree. C until the acid number is 20. The resin has 
Mw=3198, Mn=881 and Mw/Mn=3.6. 
(b) The above resin is diluted with styrene to a concentration of 80% resin 
and 20% styrene. 
EXAMPLE 2 
(a) A reaction vessel is charged with 168.1 grams (3.5 moles) of maleic 
anhydride, 159.1 (2.2 moles) of phthalic anhydride, 265.8 grams (1.5 
moles) of glycerol monostearate under a nitrogen sparge. The mixture is 
heated to 140.degree. C. where 75.7 grams of propyleneglycol and 161.6 
grams (3.2 moles) of neopentylglycol are added to the reaction vessel. The 
reaction temperature is increased to 180.degree. C. under a nitrogen flow 
of 350 cc/min and the temperature is maintained for 2 hours. Then, 0.3 
grams each of manganese acetate and Sb.sub.2 (OCH.sub.2 CH.sub.2 O).sub.3 
are added to the reaction vessel. The reaction temperature is raised to 
190.degree. C. and the temperature is maintained for 4 hours. The nitrogen 
flow is increased to 500 cc/min. and the temperature is maintained for 1 
hour. The nitrogen flow is increased to 800 cc/min. and the temperature is 
maintained at 205.degree. C. for 1 hour. The total aqueous distillate 
collected is 47 grams. The final resin has an acid number of 12. The 
temperature is heated to 205.degree. C. until the acid number is 20. The 
resin has Mw=4520, Mn=1410 and Mw/Mn=3.1. 
(b) The above resin is diluted with styrene to a concentration of 80% resin 
and 20% styrene. 
EXAMPLE 3 
(a) A reaction vessel is charged with 109.5 grams of UNILIN 700, 38.3 grams 
of maleic anhydride, 267.5 grams of phthalic anhydride under a nitrogen 
sparge. The reaction mixture is heated until clear at 158.degree. C. The 
reaction mixture is cooled to 140.degree. C. where 297.6 grams of 
neopentylglycol and 139.5 grams of propyleneglycol are added to the 
reaction vessel. The temperature is heated to 190.degree. C. and 
maintained for 8 hours while 73 grams of water distillate is collected. 
The final resin has an acid number of 15. 
(b) The above resin is diluted with styrene to a concentration of 80% resin 
and 20% styrene. 
EXAMPLE 4 
A polyester resin is prepared as described in Example 1 except 20% of the 
styrene is replaced with divinyl benzene. 
EXAMPLE 5 
A polyester resin is prepared as described in Example 1 except 630 grams of 
UNILIN 700 is used in place of ethylene carbonate. 
EXAMPLE 6 
A conventional unsaturated polyester has 35% styrene and the polyester is 
prepared from 26.9% maleic anhydride, 20% phthalic anhydride, 20.8% 
propyleneglycol, and 32.2% neopentylglycol. 
The following table relates to examples of polyester resins and polyesters 
resin systems prepared as described above. The percentages of the 
ingredients for the polyesters are by mole. The polyester resins are then 
blended with styrene to the proportions indicated. 
TABLE 1 
______________________________________ 
Example 7 
Example 8 
Example 9 
______________________________________ 
Polyester 57 80 80 
maleic anhydride 
30 27 26.3 
phthalic anhydride 
20 20 19.2 
propyleneglycol 
18 18 17.8 
neopentylglycol 
29 28 27.7 
trimethylolpropane 
3 -- -- 
manganese acetate 
0.2 -- -- 
Sb.sub.2 (OCH.sub.2 CH.sub.2 O).sub.3 
0.2 -- -- 
glycerol -- 7 -- 
monostearate 
UNILIN 700 -- 8.8 
Styrene 43% 20% 20% 
______________________________________ 
The following Examples relate to gelcoat compositions. The gelcoat 
compositions are prepared from a clear gelcoat composition. The gelcoat 
composition has 45.7% styrene and contains 0.5 parts of polysiloxane, 0.2 
parts of ethyleneglycol, 4.4 parts of fumed silica, 0.44 parts of a UV 
stabilizer, 0.08 parts of potassium octanoate, 0.12 parts of cobalt 
octanoate (12%), 0.04 parts dimethylacetoacetamide, 0.5 parts methyl 
methacrylate per 100 parts of neat unsaturated polyester resin. 
EXAMPLE A 
A gelcoat is prepared by blending the resin system of Example 6 with the 
above gelcoat composition. 
EXAMPLE B 
A gelcoat is prepared by blending the resin system of Example 1 with the 
above gelcoat composition. 
EXAMPLE C 
A gelcoat is prepared by blending the polyester resin system of Example 1 
with the above gelcoat compositions. Then 24 parts of the polyester resin 
system of Example 6 is added to 76 parts the gelcoat. 
EXAMPLE D 
A gelcoat is prepared by blending the resin of Example 6 with the above 
gelcoat composition. Then, 20 parts of the resin of Example 8 is blended 
with 80 parts of the gelcoat. 
EXAMPLE E 
A gelcoat is prepared by blending the resin of Example 6 with the above 
gelcoat composition. Then, 20 parts of the resin of Example 9 is blended 
with 80 parts of the gelcoat. 
EXAMPLE F 
A gelcoat is prepared by blending the resin of Example 1 with the above 
gelcoat composition. Then 1 part STYRID styrene suppressant is added to 
100 parts of the gelcoat. 
EXAMPLE G 
A gelcoat is prepared by blending the resin of Example 1 with the above 
gelcoat composition. Then 1 part of BYK-306 (a polydimethylsiloxane 
polyether) available from BYK Chemie USA is added to 100 parts of gelcoat. 
EXAMPLE H 
A gelcoat is prepared as described in Example B except the gelcoat 
additionally contains 0.01% by weight of Dow Corning 65 additive, 
available from Dow Coming Chemical. 
EXAMPLE I 
A gelcoat is prepared as described in Example B except 20% of the styrene 
is replaced with p-t-butylstyrene. 
The following table contains test emission data for the above gelcoats. The 
reduction in volatile emissions is determined by the California Can Lid 
Test performed in accordance with Proposed Rule 1162 (South Coast Air 
Quality Management District). The gelcoats were cured using Lupersol DDM-9 
peroxide initiator. 
TABLE 2 
______________________________________ 
Volatile 
emission 
Resin System 
(g/m.sup.2) 
Gel time (min) 
______________________________________ 
Example A Example 6 154 10 
Example B Example 1 89 9.9 
Example C Example 10 44.2 8.5 
Example D Example 11 102 10 
Example E Example 12 87.8 9.0 
______________________________________ 
As can be seen from the above table, gelcoat compositions prepared with the 
inventive polyesters have improved emissions over convention polyesters 
resins. 
While the invention has been explained in relation to its preferred 
embodiments, it is to be understood that various modifications thereof 
will become apparent to those skilled in the art upon reading the 
specification. Therefore, it is to be understood that the invention 
disclosed herein is intended to cover such modifications as fall within 
the scope of the appended claims.