Radiant energy curable acrylic urethane prepolymer resin compositions and method

An acrylic urethane prepolymer composition and an unsaturated polyester resin composition to which the prepolymer has been added. The prepolymer composition includes an acrylic urethane prepolymer prepared by the reaction of diisocyanate, like MDI, with an hydroxyl-containing acrylate monomer, such as a pentaerythritol triacrylate. The prepolymer composition contains a styrene monomer and an inhibitor, such as benzoquinone, to retard the reaction of the prepolymer and styrene monomer prior to the addition of the prepolymer composition into the polyester resin composition and a photoinitiator to promote the polymerization of the resin by exposure to radiant energy. The employment of the urethane prepolymer composition provides for the reduction in the amount of styrene monomer used in the unsaturated resin composition and also provides for improved chemical and physical properties of the photocured, unsaturated resin composition.

BACKGROUND OF THE INVENTION 
Polyester resins are polycondensation products of a dicarboxylic acid with 
dihydroxy alcohols. Such polyester resins catalyze to cure or harden, 
generally at room temperatures, to make a wide variety of products. 
Unsaturated polyester resins are widely used today to make products for 
use in the marine, transportation and building industries, and in 
particular, fiber or particulate reinforced products, such as glass fiber 
reinforced laminate-type products. Unsaturated polyester resins generally 
contain ethylenic unsaturation introduced by the employment of unsaturated 
diacids, thus comprising thermosetting-type resins. As such, unsaturated 
resins generally employ maleic and fumaric unsaturated acids, although 
saturated acids, phthalic and adipic acid may also be included to control 
or reduce the amount of unsaturation in the final unsaturated polyester 
resin and to control the physical properties. Dihydroxy alcohols most 
generally used are typically ethylene, propylene, diethylene and 
dipropylene glycols. Crosslinking agents may be employed with the 
unsaturated polyester resins. Generally, styrene monomers and di-allyl 
phthalate are the most common crosslinking agents. The styrene monomers 
are used to reduce the viscosity of the polyester resin and to act also as 
a crosslinker in the polyester resins. 
It is desirable, particularly in view of the toxicity of the styrene 
monomer and government regulations, to reduce the concentration levels of 
the styrene monomer from the usual 40% to 50% by weight of the polyester 
resin to below 35% or 30% by weight. However, reductions in styrene 
monomer concentrations present problems in the polyester resins with the 
increased viscosity of the resin, causing difficulties in applying the 
resins, such as causing spray problems and glass roll-out when the resin 
is sprayed or used in conjunction with glass fibers. The reduced styrene 
monomer polyester resin does not wet the glass in preparing glass fiber 
laminates, and therefore, the surface of the sprayed glass fiber polyester 
resin typically must be contacted with a roller to prevent glass fibers 
from sticking out of the surface. In addition, the physical properties of 
the styrene monomer-reduced polyester resins are also greatly reduced 
without the use of additional, supplemental crosslinkers in the polyester 
resin. The aromatic nature of styrene monomers in the unsaturated polyols 
improves the hydrolytic stability and increases the chemical resistance to 
water, detergents and corrosion in the final, cured polyester resin 
product. 
Acrylic monomers, such as methyl methacrylate (MMA) have been added to low 
or reduced styrene monomer polyester resins for marine grade gel coats and 
for outdoor applications. However, and unfortunately, MMA has a strong 
odor, is a skin and eye irritant and results in a slowing of the cure rate 
of a polyester resin. However, such acrylic monomers usually improve UV, 
water and chemical resistance. Therefore, it is not desirable to 
substitute MMA monomer for the styrene monomer or to add it with the 
styrene monomer, since MMA is also a hazardous material. 
It is therefore desirable to provide new and improved, photoinitiated, 
crosslinkable resin compositions to replace or reduce styrene monomer in 
unsaturated resins, to provide unsaturated, cured resins with better 
physical and chemical properties and to provide an unsaturated polyester 
resin composition having reduced styrene monomer therein. 
SUMMARY OF THE INVENTION 
The invention relates to a modified acrylic urethane prepolymer concentrate 
for use and admixture with radiation curable, unsaturated polyester resin 
compositions and to the unsaturated resin compositions containing the 
concentrate as a diluent and a crosslinking composition and to the 
photocured unsaturated polyester resin compositions and their uses in and 
the method of preparing laminates and resin products. 
The invention concerns an improved, liquid modified, acrylic urethane 
prepolymer concentrate adapted for addition to unsaturated resin 
compositions to provide improved cured resin properties and to provide 
unsaturated polyester resin compositions of reduced styrene monomer 
content. The liquid concentration comprises a modified acrylic urethane 
prepolymer or oligomer prepared by the reaction of a polyisocyanate, such 
as an aromatic isocyanate, like MDI, or an aliphatic isocyanate, usually 
in a stoichiometric amount or in a slight excess, with a 
hydroxyl-containing acrylate monomer with or without the presence of a 
catalyst and a diluent monomer, like a styrene monomer, generally in an 
amount of less than 40% by weight of the unsaturated polyester resin 
composition to which the concentrate is added, and an inhibitor, such as a 
quinone compound, such as benzoquinone, to retard any prereaction of the 
prepolymer and the styrene monomer in the concentrate. 
The invention is also concerned with unsaturated resin compositions subject 
to curing in the presence of a catalyst, typically a peroxide alone or 
with a metal promoter, like a metal carboxylate, such as a cobalt or 
copper salt, alone or in combination with various accelerators, which are 
amine or amide accelerators. The catalytic amount of the peroxide compound 
added just prior to use with the resin composition contains a promoting 
amount of a metal promoter salt at room temperatures in order to provide 
sufficient exothermic heat to cure the unsaturated polyester resin 
composition containing the concentrate. An unsaturated polyester resin 
composition is usually employed either alone or typically in conjunction 
with filler material, such as particles or fiber materials, like clay, 
quartz, sand, limestone, mica, pigments or fibers, like glass fibers, and 
in some cases flame retardants like aluminum trihydrate, viscosity control 
agents and modifiers like formed silica and flow control agents, or 
combinations in amounts of about 0% to 30% by weight of the resin in order 
to prepare cured laminates of the unsaturated polyester resin, such as a 
spray laminate, containing glass fibers admixed with the polyester resin. 
It has been found further that the resin composition of the invention may 
be cured either alone by photoinitiation or in combination with a peroxide 
promoter where a dual curing reaction is desired. The employment of 
radiation compounds by the use of one or more photoinitiators added to the 
prepolymer used with an unsaturated resin or to the prepolymer (oligomer) 
concentrate-unsaturated resin composition provides many advantages in the 
shelf life, storage, handling and processing of the composition and in the 
resultant radiation cured resin and resin products produced thereby. 
The photoinitiators employed may vary, depending on the intensity and type 
of radiation to be used, and typically are selected to promote or initiate 
the curing-polymerization reaction of the composition, such as by the 
generation of free radicals. The radiant energy employed may include high 
energy radiation beams, but more particularly include visible light 
(sunlight) or UV light. The selection of the photoinitiator is usually 
based on the optimum absorption surges, e.g, 250 to 450 nm or to which the 
curable composition either as centering or molded product is to be 
exposed. The photoinitiator should be compatible with and admix with the 
prepolymer-oligomer concentrate and the resin composition. 
The photoinitiators are used in a sufficient amount to initiate and promote 
polymerization, which amount may vary depending on the number and type of 
photoinitiators and whether the composition also contains chemical curing 
agents and promotion and the material used in the composition, the 
thickness of the composition and the radiant energy to be used. 
For example, the photoinitiator may be used in amounts of from about 0.01 
to 5.0 percent by weight of the unstructured resin composition, such as 
1.5 to 3.0 percent by weight. 
The photoinitiators may be used alone or in various combinations and 
generally are organic compounds like, but not limited to benzoins, ketals, 
ketones, phenones, and thioxanthones, and benzoates. Typical specific 
photometric compounds are: benzildimethyl ketal, 60% solution of 
benzildimethyl ketal, mixture of benzoin normal butyl ethers, 
trimethylbenzophenone blend, alpha hydroxy ketone, blend of 
trimethylbenzophenone blend and alpha hydroxy ketone, 
isopropylthioxanthone, blend of isopropylthioxanthone and 
trimethylbenzophenone blend, ethyl 4-(dimethylamino) benzoate, and 
benzophenone. 
It has been discovered that unsaturated polyester resins and acrylic 
urethane oligomers made by reacting pentaerythriol triacrylate and either 
MDI or HDI adducts provide improved physical properties and cycle time. 
These hybrid resins, as described, are catalyzed using MEKP (methyl ethyl 
ketone peroxide) and promoted with cobalt octoate (12%) and DMAA (Dimethyl 
Aceto Acetamide). 
It has now been discovered that these peroxide cured resin hybrids can now 
be cured using photoinitiators (PI) and radiant energy, such as UV or 
visible light, e.g. 365-450 nanometers. For PI compositions, cycle times 
can be reduced to 2-3 minutes at 50-120 mils in thickness and up to 50% 
glass reinforcement. However, glass reinforcement is not necessary when 
used as a coating. 
It has been found that the photoinitiating curable prepolymer-resin 
composition will provide many and significant advantages over the 
peroxide-curable prepolymer-resin composition. One advantage is the 
increased shelf or container life of the PI composition, since once in the 
container and free of radiant energy, a significant increase in shelf and 
container life is possible over the peroxide-containing prepolymer resin 
compositions, which are subject to low reaction over time. Thus, the PI 
compositions may be stored for long periods and are quickly ready for use. 
Another advantage is that the PI compositions, particularly where used in 
enclosed areas, have an absence of any peroxide or promoter odor. Also, 
the PI curable compositions often have improved physical properties over 
the peroxide curable prepolymer resin compositions and exhibit better 
processing properties as regards to curing and cycle time. For example, 
where conventional unsaturated polyester resin compositions often take one 
to two hours or more to cure and the peroxide-curable prepolymer-resin 
compositions have reduced cure and cycle times, for example, of as low as 
five minutes, the PI curable compositions provide cycle times generally of 
less than about five minutes, such as reduced to 1-3 minutes, and coating 
thicknesses of about 50 to 120 mils. The PI curable compositions permit 
complete cures in reduced time, and therefore promote mold efficiencies, 
since the molded products have been partially cured by radiant energy, and 
may be rapidly demolded from the mold without waiting for the full cure to 
take place, as in the peroxide-curing compositions. 
The curable prepolymer-resin compositions may be employed with flow 
modifying agents such as wetting agents, which wet the surface to which 
the curable composition is to be applied, either in a mold or by spray, 
and to prevent or reduce the development of "fish eyes" or other 
deformations in the cured resin surface. It has also been discovered that 
the PI curable compositions can contain significant amounts of, for 
example, up to about 15% by weight of particulate flame-retardant 
materials, such as, but not limited to, aluminum trihydrate, and still be 
effectively cured by the exposure of the curable composition to radiant 
energy, thus providing a relatively inexpensive, flame retardant, cured 
resin product. The PI-curable compositions may also contain minor amounts, 
as desired, for example, 1-20% or more by weight, of light-reflective 
materials, such as metal, for example, aluminum particles, glitter and 
flakes, which provide further disseminating of the radiant energy 
throughout the curable composition, and increases the efficiency of the 
time of the radiant cure, and provides a metallic or glitter-looking cured 
resin surface, for example, for the use on such as boats, or in traffic 
marking lanes or traffic or other road signs. Where the prepolymer-resin 
composition is to be employed on a vertical or sloping surface such as in 
a spraying or coating operation, it is often desirable to add a 
viscosity-modifying amount of a viscosity-modifying agent to the curable 
composition to prevent resin flow on the surface prior to cure, especially 
by the employment of various selected fixative compositions, for example, 
but not limited to, fumed silica, in the amount of 0.01 to 5% by weight of 
the curable composition. 
It has been discovered that the replacement or reduction in amount of a 
styrene monomer as a diluent and cross-linking additive to unsaturated 
polyester resin compositions may be accomplished by employment of modified 
acrylic urethane prepolymers which result in improved properties to the 
cured polyester, better handling in preparing laminates as regards to 
roll-out of the laminate, and permits reduction of the styrene monomer, 
typically to amounts lower than 40%, for example from 0% to 30% by weight 
of the polyester resin composition. Particularly, it has been discovered 
that higher functionality acrylic monomers improve the polyester 
properties of the cured polyester composition. When a polyisocyanate, like 
MDI, is added to unsaturated polyester resin compositions by itself, such 
MDI tends to react with the hydroxyl group unsaturated polyester resin 
composition leading to increased and high viscosity which greatly reduces 
the feasibility of employing the unsaturated polyester resin composition 
as a diluent additive. Employment of a MMA monomer itself provides certain 
disadvantages. Therefore, the employment of a modified acrylic urethane 
prepolymer, a liquid concentrate, either alone or together with a styrene 
monomer and an inhibitor, may be used as a diluent additive to unsaturated 
polyester resin compositions to improve properties and to prepare 
compositions of reduced styrene monomer content. 
In particular, it has been discovered that the high functionality aliphatic 
urethane prepolymers provide for a variety of improved cure properties of 
a polyester resin as set forth, for example, in Table I. 
TABLE I 
______________________________________ 
Properties Mono Di Tri Tetra Penta 
______________________________________ 
Cure Speed Slow .fwdarw. 
.fwdarw. 
.fwdarw. 
.fwdarw. 
.fwdarw. 
Fast 
Flexibility High .rarw. 
.rarw. 
.rarw. 
.rarw. 
.rarw. 
Low 
Hardness Low .fwdarw. 
.fwdarw. 
.fwdarw. 
.fwdarw. 
.fwdarw. 
High 
Solvent Resistance 
Low .fwdarw. 
.fwdarw. 
.fwdarw. 
.fwdarw. 
.fwdarw. 
High 
Crosslink Density 
Low .fwdarw. 
.fwdarw. 
.fwdarw. 
.fwdarw. 
.fwdarw. 
High 
______________________________________ 
The employment of a special hydroxyl containing high functionality acrylic 
monomer, that is, an acrylic monomer with hydroxyl groups, being made into 
a prepolymer by the employment of a polyisocyanate, either aromatic or 
aliphatic diisocyanate, and which prepolymer so prepared in a preferred 
embodiment remains in a liquid condition. This liquid concentrate can be 
added to the low level styrene monomer unsaturated polyester resin 
compositions and produces a stable polyester resin composition, which does 
not react unless and until the peroxide catalysts or a 
catalyst-accelerator promoter combination is added to the unsaturated 
polyester resin composition. The addition of the catalytic curing 
composition, such as the use of methyl ethyl ketone peroxide as one 
example, provides for rapid cure of the polyester without significant loss 
of unreacted styrene monomer, so that the resulting unsaturated polyester 
resin with the liquid concentrate wets glass fiber with excellent 
efficiency and significantly reducing the need to roll-out the glass, 
where the unsaturated polyester resin composition is sprayed with glass 
fibers to form a glass fiber reinforced laminate. 
The concentrate includes in one example a hydroxyl alkyl, such C.sub.2 
-C.sub.6 acrylic monomer, which is reacted with a diisocyanate to provide 
the modified acrylic urethane prepolymer for use in the concentrate. Low 
functionality acrylic monomers, while not the preferred embodiment, 
provide for improved cure, chemical and physical properties of the 
polyester resin, since such low functionality modified acrylic urethane 
prepolymers with the low functionality used therein provide for solidified 
prepolymers or prepolymers which rapidly gel, and a liquid concentrate is 
the preferred embodiment. Some representative types of the acrylic 
monomers useful in the invention would include 2-hydroxy ethyl acrylate; 
hydroxy propyl acrylate; 2-hydroxy ethyl methacrylate; 2-hydroxy ethyl 
propyl methacrylate; and acrylic urethane prepolymers made from having an 
100 index down to a 20 index with solidification occurring in most 
prepolymers, except for the prepolymers having a 20 or below index. 
A preferred acrylic polymer which provides for a liquid concentrate 
comprises a pentaerythritol acrylate composed of tri-, tetra- and 
pentacrylate, which acrylic monomer has an hydroxyl group or an active 
hydrogen for reaction with the diisocyanate. Reaction of this 
pentaerythritol polyacrylate with diisocyanate, such as MDI, at different 
levels produces a stable liquid prepolymer, which does not react when 
added to an unsaturated polyester resin prior to the peroxide agent 
addition to the promoted unsaturated resin. For example, with a 
pentaerythritol triacrylate made up of tetra- and pentacrylate, the 
molecular weight of the acrylic monomer is 298 with a hydroxyl number of 
298, which is reacted with MDI with 32% NCO and a 2.3 functionality with 
the MDI containing both 4--4 and 2-4 isomers. 
Other high functionality hydroxyl acrylic monomers suitable for use would 
include ethoxylated or propoxylated trimethylol propane or glycerol 
polyacrylate, e.g., tri acrylate monomers. Specific high functionality 
acrylic monomers suitable for use include ethoxylated trimethylol propane 
triacrylate; pentaerythritol tri, tetra and pentaacrylate, propoxylated 
trimethylolpropane triacrylate; propoxylated glycerol triacrylate; di-tri 
methylol propane tetracrylate; dipentaerythritol pentacrylate; and 
ethoxylated pentaerythritol tetracrylate and combinations thereof. 
The prepolymer is made by reacting with or without a catalyst the 
hydroxyl-containing acrylic monomer with polyisocyanate, more 
particularly, an aliphatic or aromatic diisocyanate, such as, but not 
limited to an aromatic diisocyanate, like MDI, or an aliphatic isocyanate, 
such as trimerized HDI (hexamethyl diisocyanate) or trimerized IPDI 
(isophenyl diisocyanate), or other acceptable diisocyantes or prepolymers 
which will react with the hydroxyl groups in the acrylic monomer. The 
compound, pentaerythritol triacrylate is a commercial product known as SR 
444 of Sartomer Company, Inc. of Exton, Pa. 
The prepolymer is added to an unsaturated resin composition, either alone 
or preferably in the concentrate form, known to contain some styrene 
monomer for viscosity control purposes, and thereby needing a reduction of 
the styrene monomer employed in the unsaturated polyester resin. The total 
amount of styrene monomer in the unsaturated resin composition would be 
less than 30% by weight. The prepolymer concentrate would also generally 
contain an inhibiting agent to provide for storage stability of the liquid 
concentrate, such as to maintain at least two-weeks' stability at 
120.degree. F., and which inhibitor generally comprises a quinone 
compound, such as parabenzonequinone. 
The prepolymer concentrate is employed as an additive diluent to 
unsaturated polyester resin compositions, such as those unsaturated resin 
compositions, but not limited to polyester resins prepared by reacting 
dicyclopentadiene (DCPD) with orthophthalic and maleic acid, the reaction 
of propylene glycol with maleic acid anhydride; and the reaction of 
isophthalic acid-maleic anhydride with neo pentyl glycol, or other known 
unsaturated polyester resin compositions. 
Generally, the unsaturated resin compositions contain an inhibitor to 
prevent prereaction until a promoter or catalyst is added to effect cure 
in the polyester resin after the addition of the prepolymer concentrate. 
The unsaturated polyester resin compositions contain a monomer for 
crosslinking therewith, such as a diluent styrene monomer at reduced 
levels, where a concentrate prepolymer is employed. A cure is effected by 
employing an organic peroxide compound, and typically a metal salt, such 
as a fatty acid salt, like a cobalt octoate or potassium octoate, is 
employed in combination with an organic ketone, such as methyl ethyl 
ketone peroxide, to provide for an exothermic curing reaction. The 
promoter and catalyst composition may also contain amide-type compounds 
for acceleration purposes, such as the dimethyl acetamide. Generally, the 
peroxide, metals salts, amines and amides are employed at low levels with 
the peroxide employed from about 0.1% to 2.5% by weight and the metal 
salts ranging from about 0.05% to 0.5% by weight and the amine or amide 
from about 0.05% to about 0.5% by weight. It has been found that after 
addition of the concentrate prepolymer to the unsaturated polyester resin 
composition used to prepare laminates, that the roll-out time was reduced, 
for example, to less than five minutes. The polyester resin composition 
without the concentrate prepolymer, even though such composition gelled in 
ten minutes, tended to stay rubbery for five minutes or more until a peak 
exotherm occurred, while with the use of the concentrate prepolymer, cure 
of the polyester resins to a rigid physical condition occurred in less 
than five minutes. 
It has been found that the employment of the prepolymer concentrate of the 
invention helps in reducing roll-out where the unsaturated resin 
composition is employed with fiberglass, such as in a spray or mold 
operation, so that in the preparation of cured polyester fiberglass 
laminates with the use of the liquid concentrate prepolymer, no rolling of 
the concentrate was required when the concentrate was employed. Further, 
it has been noted that the polyester resin systems, with the liquid 
prepolymer concentrate added thereto, had little or no styrene monomer 
smell within three to four minutes after the spraying of the resin 
composition, which is believed to occur as a result of the cross linking 
taking place and tying up the styrene monomer. 
The invention will be described for the purposes of illustration only in 
connection with certain embodiments; however, it is recognized that those 
persons skilled in the art may make various modifications, changes, 
additions and improvements to the illustrated embodiments, without 
departing from the spirit and scope of the invention. 
EMBODIMENTS OF THE INVENTION

EXAMPLE 1 
A liquid concentrate prepolymer prepared by admixing together 500 parts per 
weight of pentaerythritol triacrylate (acrylate SR-444) and 100 parts per 
weight of MDI (Papi 94, a trademark of Dow Chemical Company) and slowly 
reacted together without the present of catalyst to provide a liquid 
pentaerythritol acrylic urethane. Four hundred parts per weight of a 
styrene monomer were added to the liquid prepolymer and together with 50 
ppm of an inhibitor, parabenzoquinone. Employment of straight 
uretonomini-isocyanate (like Dow L143) and polymeric MDI (like Papi 27) 
were also employed with the acrylate SR-444. Prepolymer solidification 
took place while heating the mixture in the oven. Low functionality 
hydroxyl-containing acrylic acrylates were tried employing diisocyanates 
of Papi-94 (Dow L143 and Papi 27); however, all these low functionality 
monomers solidified when the prepolymers were made. 
EXAMPLE 2 
The liquid prepolymer concentrate was added to different types of 
unsaturated polyester resins, such as a general purpose orthophthalic 
resin containing 30% styrene monomer and NPG orthoresin containing 30% 
styrene monomer, an NPG isophthalic resin containing 30% styrene monomer 
and DCPD ortho resin blends containing 30% styrene monomer. The 
unsaturated resin composition contained 50 ppm of an hydroquinone 
inhibitor with the mixing in of the liquid prepolymer concentrate, 
catalysts and promoters were admixed as follows: 2% catalyst of methyl 
ethyl ketone peroxide (containing 9% oxygen); 0.2 parts per weight of 12% 
cobalt octuate as a promoter; 0.2 parts per weight of dimethyl acetyl 
acetamide (DMAA); and 0.1 parts per weight of potassium octuate (15%). Ten 
percent of the liquid prepolymer concentrate was added to each resin. Gel 
time without the concentrate was about 10 minutes, while with the 
concentrate added, gel time was reduced to 2.5 to 2.8 minutes. All samples 
prepared without the concentrate, even though they gelled in ten minutes, 
stayed rubbery for five minutes until a peak exotherm occurred, while the 
same polyester resin samples with the 10% liquid prepolymer concentrate 
became rigid in less than five minutes. 
EXAMPLE 3 
The unsaturated polyester resin samples containing the 10% liquid 
prepolymer concentrate were put on a Binks B-8 fiberglass spray machine 
and sprayed with a Binks Century gun with external mix catalyst above and 
the fiberglass at about 22% by weight was sprayed at 3/4 inch fiber length 
employing a four by four foot plate mold. With each unsaturated polyester 
resin system used without the liquid prepolymer concentrate on the 
surface, the glass required rolling to make an acceptable laminate without 
air. The liquid prepolymer concentrate added at 10% and sprayed provided 
for a fiberglass polyester cured laminate requiring no roll out. Further, 
the resin systems with the liquid concentrate had no styrene monomer smell 
within three to four minutes of spraying of the polyester resin as a 
result of cross linking taking place with the styrene monomer. 
Physical testing was done on all the polyester resin compositions, with or 
without the liquid prepolymer concentrate as added at 10%, and the test 
oligomers are shown on the accompanying Table II. 
EXAMPLE 4 
Compression-molded fiberglass trays were prepared employing an isophthalic 
polyester resin with a heat-activated catalyst, such as tertiary butyl 
perbenzoate, and added to a 33% glass fiber mat, with mold temperatures at 
280.degree. F., a cycle time of 90 seconds and with 10% of the liquid 
prepolymer concentrate added to the polyester resin. Upon addition of the 
liquid prepolymer concentrate, cycle times for curing were reducing to 60 
seconds. The glass fiber wet-out was improved, styrene emissions were 
reduced and the laminate had improved physical properties and chemical 
resistance. 
EXAMPLE 5 
Further tests were carried out with other polyester resins with and without 
a styrene monomer added and to which 10% by weight of the liquid 
concentrate of Example 1 was added. The cycle times of the polyester resin 
increased to 10 to 12 minutes on all types of polyester resins, and when 
each polyester resin system was sprayed with the fiberglass, no 
improvement was seen over the same polyester resin without the presence of 
the liquid prepolymer concentrate of the invention. 
TABLE II 
Urethane Oligomers 
Aliphatic urethane acrylate and 2- (2 Ethoxyethoxy) 
Ethyl acrylate ester (Craynor 961-H) 
Epoxy acrylate oligomer plus 1, 6 Hexanediol 
diacrylate ester (Craynor 120 B) 
Aromatic urethane oligomer plus 1, 6 Hexanediol 
diacrylate ester (Craynor 970) 
EXAMPLE 6 
In the marine and bathtub industry in the preparation of fiberglass 
laminate, water absorption is critical to the success of the end product. 
Extensive boiling tests were run on samples of polyester resins of DCPD, 
G.P.-Ortho, NPG-Ortho and NPG-Iso polyester resins, both with and without 
the liquid prepolymer concentrate added. The following Table III shows the 
percent water absorption at 80.degree. C. for 160 hours. 
TABLE III 
__________________________________________________________________________ 
Type Resin 
DCPD DCPD + C* 
PG 
PG + C 
NPG-Ortho 
+ C 
NPG-ISO + C 
__________________________________________________________________________ 
% H.sub.2 O 
3.2 1.6 3.1 
1.4 2.9 1.4 
2.0 1.2 
Absorption 
__________________________________________________________________________ 
*C = 10% concentrate made from SR444. 
The above results indicate that all unsaturated polyester resin 
compositions showed significant improvement in water absorption when the 
liquid prepolymer concentrate was added at a level of 10% parts by weight. 
Thus, the modified prepolymer concentrate prepared by the employment of 
pentaerythritol triacrylate, MDI and a styrene monomer with an inhibitor 
when added to unsaturated polyester resin compositions results in 
improvement in the physical and chemical properties, such as decrease in 
cure time, reduction in styrene emissions, reduction in styrene odor when 
sprayed, reduction in roll-out of molded or sprayed laminates, reduction 
in water absorption, increased chemical resistance, higher heat distortion 
temperatures and higher impact strength. 
The unsaturated polyester resin composition with the modified 
acrylic-urethane prepolymer or oligomer and with a styrene monomer of less 
than about 30% by weight may be cured with a methyl ethyl ketone peroxide 
(1.5%-2.0%) and a cobalt salt (0.1-0.5%). The composition can be sprayed 
as a glass-fiber barrier coat behind a polyester or polyesteracrylic gel 
coat with a very fast cure time and with rapid cure. The barrier coat 
strengthens the gel coat and reduces water absorption and lowers water and 
vapor transmission. The composition may be sprayed or used with charged 
glass fibers in an open or closed mold, so that a no-roll surface without 
air entrapment can be prepared. After the gel coat is applied and a 
barrier coat is added (prior to resin and glass application), no glass 
fibers are visible on the gel coat side, eliminating veil mats, to provide 
a class A finish where a class A mold is used. 
EXAMPLE 7 
HP 1161 unsaturated polyester resin was used as a base material. This base 
material is a NPG orthophthalic resin with 30% styrene monomer, and a 10% 
by weight acrylic oligomer made by reacting pentaerythritol triacrylate 
and a low functionally MDI adduct and blended with 2% by weight of 
photoinitiator KB-1 (Benzil dimethyl ketal). No peroxide or promoters were 
used. The PI containing composition material was applied to a piece of 
wood at 50 mil thickness. The wood sample was taken outside in sunlight. 
Cure time was two minutes with a tack free surface. Total cure and 
hardness occurred in five minutes. 
The same composition was promoted using cobalt octoate 12% and DMAA at 
levels of 0.1 and 0.3% respectively. 
The PI promoted composition was coated on a wood sample at 50 mils 
thickness and placed outside. No difference in cure was seen. The promoted 
resin systems and photoinitiator was cured using 2% MEKP (925 Norac 9% 
O.sub.2). 
A 3" disc 120 mils thick was cast of the PI-promoted composition and cured 
in five minutes. This resin system was taken outside after being applied 
at 50 mils to a wood sample. The sample was cut in half and half was 
placed in direct sunlight and half in indirect light. Results showed the 
direct sunlight sample cured in 2-3 minutes and the indirect light sample 
cured in 10 minutes, but remained tacky at the surface. It is well known 
that unsaturated polyester resins in their films usually have paraffin wax 
added to prevent air inhibition. It is also known that acrylic oligomers 
and monomers will not cure when exposed to air in their films. 
EXAMPLE 8 
The hybrid resin composition with its acrylic oligomers and the 
photoinitiator was added to 50% glass cloth. Two glass plates were used to 
contain the resin and glass to form a sandwich. The plates were taken 
outside and exposed to direct sunlight, and after five minutes the plates 
were removed. A stiff tackfree resin-covered glass laminate resulted. It 
should be noted that no smell of styrene monomer was present. 
The same resin composition with promoters and catalyzed with MEKP at 2% was 
added to 50% glass cloth. The sample was allowed to cure for five minutes 
and removed. The sample was rubbery and had a styrene monomer and peroxide 
smell. Ten minutes after the sample was removed, the sample was cured and 
stiff. 
The unsaturated polyester resin HP 1161 was tried without the acrylic 
oligomer. The photoinitiator was added at the same level, 50 mils was 
added on a wood sample. The sample was taken outside and exposed to direct 
sunlight. The sample cured in 12 minutes and remained sticky for 20 
minutes. The hardness was never reached when compared to the same material 
with the acrylic oligomer added. 
A standard acrylic oligomer produced by Sartomer Company, Inc. of Exton, 
Pa., called CN 975 was tried. The material was cut in 1,6 hexane 
diacrylate to reduce the viscosity at a 60/40 ratio. Ten percent of the 
oligomer was added to 1164 resin with the photoinitiator. The sample was 
placed outside on the wood sample. Cure was quick but the surface remained 
wet for 30 minutes. Stickiness never disappeared. 
The same standard oligomer from Sartomer, CN 975, was tried by itself. Two 
percent KP-1 PI was added at 50 mils to a wood sample. This sample was 
exposed to direct sunlight. The sample did not cure on the surface, but 
did cure under the surface. The wetness did not go away. 
It should be noted that the PI prepolymer-resin composition also cures well 
when using 0.5 to 1 mil thickness and high intensity light on a commercial 
UV curable machine. 
The new hybrid PI compositions, using HP 1161 resin and the special 
oligomers (prepolymers), are a superior coating or laminating resin. 
EXAMPLE 9 
The PI composition was spray applied at 50 mils thickness to concrete and 
asphalt surfaces. The hybrid PI composition cured in 2-3 minutes with a 
beautiful high gloss coating. For vertical surfaces a 1-2% fumed silica 
was added as a viscosity control agent. No differences in cure were seen. 
CaCO.sub.3 and aluminum trihydrate were tried at levels up to 50% in the PI 
hybrid composition in direct sunlight. The PI composition still cured 
rapidly without tackiness. 
EXAMPLE 10 
The hybrid resin was sprayed as a gel coat 20 mils on a waxed fiberglass 
mold. The mold was exposed to direct sunlight for three minutes. The PI 
hybrid composition was put through a standard fiberglass machine where 30% 
of 1" chopped glass was added to the spray pattern. The PI resin 
composition was sprayed 125 mils over the 20 mil coating. No rolling was 
necessary, because of the low surface tension of the resin composition. 
The mold was again taken outside and exposed to direct sunlight. The 
sample was left for five minutes in the mold and removed. A cured 
fiberglass laminate was made without MEKP or styrene odor.