Citrate ester compounds and processes for their preparation

Citrate ester compositions which are useful as compatible components in a resinous system for sheet molding compositions and have a general formula ##STR1## wherein X is selected from the group consisting of --OC.sub.3 H.sub.6).sub.3 --OCH.sub.3 and OH are disclosed. Also disclosed is a sheet molding composition which includes a four component resinous system comprising (a) an unsaturated polyester comprising a polycondensation product of one or more dihydric alcohols and one or more ethylenically unsaturated polycarboxylic acids; (b) one or more low-profile thermoplastic polymer additives which cause phase separation and internal voids during the curing reaction; (c) one or more olefinically unsaturated monomers which copolymerize with the unsaturated polyester; and, (d) one or more compatible components which remain compatible when the polyester and monomer cure and impart improved surface characteristics when added to typical low-profile resin systems.

The present invention provides improved surface smoothness in unsaturated 
polyester resin compositions that contain low-profile additives. More 
specifically, these unsaturated resin compositions contain low-profile 
additives and compatible compounds. The present invention relates in 
particular to citrate ester compatible compounds and the processes for 
their preparation. 
Unsaturated polyester resin compositions are finding increased use in the 
automotive industry as compositions from which component parts especially 
body panels can be molded. These compositions contain, in addition to the 
unsaturated polyesters, so-called "low-profile" additive components which 
are thermoplastic polymers that act to prevent undesirable shrinkage as 
the composition is being molded into a thermoset article. Low-profile 
additives are added to unsaturated polyester compositions for the purpose 
of obtaining a composition which can be molded into thermoset articles, 
where the surfaces of the molded articles truly reflect the surface 
characteristics of the mold. 
Two types of low-profile systems are commonly used commercially, one-pack 
and two-pack. In one-pack systems, the polyester, styrene and low-profile 
additive components are mutually compatible, i.e., no gross separation 
occurs when a mixture is allowed to stand. In contrast, two-pack systems 
form distinct phases if the components are allowed to stand. These need to 
be mixed immediately prior to use. In either case phenonmena occur that 
allow these resins to microscopically compensate for shrinkage. 
It is the ability of the low-profile resins to compensate for shrinkage 
that leads to the usefulness of these resins. This shrinkage compensation 
is largely a result of a micro-phase separation that occurs in these 
unsaturated polyester resin systems. The micro-phase separation occurs 
during the cure phase for both the one-pack and two-pack systems. 
Prior to cure the low-profile additive is at least partly soluble in the 
polyester/styrene solution. As the polyester/styrene mixture crosslinks, 
the low-profile thermoplastic additive and copolymer become increasingly 
less compatible and a two-phase (domain-matrix) type morphology results. 
This micro-phase separation leads to the formation of a porous structure 
as the opposing internal stresses of thermal expansion and polymerization 
shrinkage occur. In many unsaturated polyester resin compositions the 
porous structure is a result of microfracturing of the curing resins which 
gives rise to void formation. Unsaturated polyester resins have been 
developed which have essentially zero shrinkage and which, in fact, expand 
upon curing. 
In addition to unsaturated polyester resins, the sheet molding compound 
formulations typically contain other ingredients including, for example, 
chemical thickeners. In such systems, an alkaline material such as 
magnesium oxide or magnesium hydroxide is added to, for example, an 
uncured polyester along with fillers, glass fiber, and other standard 
materials. The alkaline material interacts with the residual acidity in 
the polyester and, usually, the low-profile additive to build viscosity. 
This process is referred to as maturation and usually takes several days. 
If two-pack resin systems are used, care has to be taken to avoid gross 
phase separation. After the maturation process is complete, the thickened 
systems are handlable and can easily be placed into compression molds 
either by hand or by machine. 
Although the use of low-profile additives as described as three component 
mixtures do effect some degree of improvement in the anti-shrinkage 
characteristics of the unsaturated polyester compositions, it has been 
found that significant improvements could yet be made on surface 
smoothness and processing characteristics. 
PRIOR ART 
Low-profile resins have been described that contain unsaturated polyester 
resins, thermoplastic low-profile additives, and a polymerizable monomer, 
usually styrene. In addition to these components other materials have been 
added to low-profile systems to improve specific properties. 
The Iseler, et al. U.S. Pat. No. 4,622,354 describes "phase stabilizing 
agents" that comprise a selected group of compounds from three classes; 
fatty acids, dimer acids and polyester polyols. When used in an SMC 
formulation where the thermoplastic low-profile additive is 
polymethylmethacrylate and a urethane prepolymer is included, the phase 
stablizing agent reduces the gross separation that occurs during the 
maturation process. The resin compositions described by Iseler et al. are 
two-pack systems that formerly phase-separated during maturation prior to 
the addition of the phase stabilizers. 
The Ochsenbein et al. U.S. Pat. No. 4,473,544 describes an anti-shrink 
additive with a tri- or tetrafunctional polyether condensation product of 
propylene oxide on a triol or tetrol wherein the condensation product is 
acidified in such a manner that it possesses at least one terminal acidic 
functional group per elementary molecule. This material is used as a 
low-profile additive. 
The Atkins U.S. Pat. No. 4,555,534 describes low-shrink pigmentable 
unsaturated polyester resins which comprises a polyester resin comprising 
the reaction product of an olefinically unsaturated dicarboxylic acid or 
anhydride and a polyol, an olefinically unsaturated monomer, a thickening 
agent, a pigment, a carboxylated vinyl acetate polymer low-profile 
additive, and a surface active compound. The Atkins '534 patent describes 
low-shrink resins having improved uniformity of pigmentation in internally 
pigmented thickened polyestermodling compositions. These pigmentable resin 
systems are low-shrink, and not low-profile. The surface quality of these 
pigmentable systems is considerably inferior to surfaces required for 
automotive appearance applications. 
Although the use of low-profile additives and thickening agents, as 
described, do effect some degree of improvement in the antishrinkage and 
surface smoothness characteristics of the unsaturated polyester 
compositions, they are unable to achieve the degree of surface smoothness 
required of today's thermoset molded articles. 
SUMMARY OF THE INVENTION 
The present invention provides a means for improving the surface smoothness 
in low-profile resin compositions which are compression or injection 
molding into useful articles. In one aspect, the invention comprises an 
improved sheet molding composition that includes a four component resinous 
system comprising: 
(a) an unsaturated polyester comprising a poly condensation product of one 
or more dihydric alcohols and one or more ethylenically unsaturated 
polycarboxylic acids; 
(b) one or more low-profile additives comprising thermoplastic polymers 
which cause phase separation and internal voids during the curing 
reaction; 
(c) one or more olefinically unsaturated monomers which copolymerize with 
the unsaturated polyester; and, 
(d) one or more components that remain compatible when the polyester and 
monomer cure and contain one or more polyoxyethane substituents. 
In another aspect, the invention relates to novel compositions which are 
useful as compatible components in a resinous system for sheeting molding. 
The novel compounds are citrate ester compounds containing one or more 
polyoxyethane substituents having a general formula 
##STR2## 
wherein X is selected from the group consisting of --O--C.sub.3 
H.sub.6)OCH.sub.3 and OH. 
The four component resinous system imparts improved surface smoothness when 
used with other known conventional ingredients for low-profile resin 
systems used in making sheet molding compositions.

DESCRIPTION OF INVENTION 
The present invention relates to the discovery of the use in a group of 
components which remain compatible with a curing unsaturated polyester 
resin, and monomer used in a low-profile resin system. When these 
compatible components are included in combination with low-profile 
additives and used in sheet molding compositions, articles with very 
smooth surfaces may be molded. Additionally, the flow during the molding 
process is improved to the point that rapidly curing formulations may be 
composed, consequently the molding time is drastically reduced. Also, 
these compounds are helpful in controlling the thickening of SMC. 
The unsaturated polyester components of the four component resinous system 
comprises the polycondensation reaction product of one or more dihydric 
alcohols and one or more ethylenically unsaturated polycarboxylic acids. 
By polycarboxylic acid is generally meant the polycarboxylic or 
dicarboxylic acids or anhydrides, polycarboxylic or dicarboxylic acid 
halides, and polycarboxylic or dicarboxylic esters. Suitable unsaturated 
polycarboxylic acids, and the corresponding anhydrides and acids halides 
that contain polymerizable carbon-to-carbon double bonds may include 
maleic anhydride, maleic acid, and fumaric acid. A minor proportion of the 
unsaturated acid, up to about forty mole percent, may be replaced by 
dicarboxylic or polycarboxylic acid that does not contain a polymerizable 
carbon-to-carbon bond. Examples of which include O-phthalic, isophthalic, 
terephthalic, succinic, adipic, sebacic, methyl-succinic, and the like. 
Dihydric alcohols that are useful in preparing the polyesters include 
1,2-propane diol (hereinafter referred to as propylene glycol), 
dipropylene glycol, diethylene glycol, 1,3-butanediol, ethylene glycol, 
glycerol, and the like. Examples of suitable unsaturated polyesters are 
the polycondensation products of (1) propylene glycol and maleic and/or 
fumaric acids; (2) 1,3-butanediol and maleic and/or fumaric acids; (3) 
combinations of ethylene and propylene glycols (approximately 50 mole 
percent or less of ethylene glycol) and maleic and/or fumaric acid; (4) 
propylene glycol, maleic and/or fumaric acids and dicyclopentadiene 
reacted with water. In addition to the above described polyesters one may 
also use dicyclopentadiene modified unsaturated polyester resins as 
described in the Pratt et al. U.S. Pat. No. 3,883,612. These examples are 
intended to be illustrative of suitable polyesters and are not intended to 
be all-inclusive. The acid number to which the polymerizable unsaturated 
polyesters are condensed is not particularly critical with respect to the 
ability of the low-profile resin to be cured to the desired product. 
Polyesters which have been condensed to acid numbers of less than 100 are 
generally useful, but acid numbers less than 70 are preferred. The 
molecular weight of the polymerizable unsaturated polyester may vary over 
a considerable range, but ordinarily those polyesters useful in the 
practice of the present invention have a molecular weight ranging from 300 
to 5000, and more preferably, from about 500 to 5000. 
In preferred embodiments, the unsaturated polyester is present in amounts 
ranging from about 20 to 45 percent, by weight, based on the total four 
component resinous system comprising the unsaturated polyester, the 
low-profile additive, monomer and compatible component containing one or 
more polyxyethane substituents. Especially preferred concentrations of the 
unsaturated polyester are in the 28 to 35 percent, by weight, range. 
Low-profile additives are materials that when mixed in an unsaturated 
polyester and cured, result in a multiphase system. If the low-profile 
additive and the unsaturated polyester are compatible (from the standpoint 
that a gross phase separation does not take place) before cure, the system 
is known as a one-pack. Those mixtures which tend to separate into two or 
more layers on standing are known as a two-pack resin systems. This does, 
however, necessitate mixing immediately before use. Some polymers that are 
useful as low-profile additives include homopolymers and copolymers of 
acrylic and methacrylic acid esters, cellulose acetate butyrate, vinyl 
acetate homopolymers and copolymers, polyurethanes prepared from 
polyisocyanates, preferably diisocyanates, and polyether polyols, numerous 
saturated polyesters, polycaprolactone, styrenebutadiene copolymers, some 
modified celluloses, and certain alkyl oxide polymers. The above list of 
low-profile additives is not intended to list all low-profile additives 
but rather to show examples of materials which ave been used to cause the 
multiphase morphology present in low profile resins. In preferred 
embodiments the thermoplastic additive is present in amounts ranging from 
5 to 30 percent, by weight, based on the total four component resinous 
system. Especially preferred concentrations of thermoplastic additive are 
in the 7 to 20 percent, by weight range. 
The monomer component comprises materials that copolymerize with the 
unsaturated polyester. The olefinically unsaturated monomer that is 
copolymerizible with the unsaturated polyester is most generally styrene, 
however, methyl-styrene is also useful. In preferred embodiments the 
monomer is present in amounts ranging from 25 to 65 percent, by weight, 
based on the total four component resinous system. Especially preferred 
concentrations of monomer are in the 35 to 50 percent, by weight range. 
In the present invention one or more components are added which are 
compatible with the unsaturated polyester and monomer during cure. 
According to the present invention, these compatible components give the 
added benefits of surface smoothness and better flowability, when compared 
with low-profile resin compositions without the compatible components. In 
the preferred embodiments the compatible component is present in amounts 
ranging from 0.5 to 15 percent, by weight, based on the total four 
component resinous system. Especially preferred concentrations of the 
compatible components are in the 1 to 8 percent, by weight range. 
The compatible components of the present invention contains one or more 
polyoxyethane substituents having a general structure: 
##STR3## 
where R.sup.1, R.sup.2, R.sup.3, and R.sup.4, are selected from the group 
consisting of hydrogen, cycloalkyl, lower alkyl, phenyl, phenyl 
substituted by halogen, lower alkyl, acyl, or lower alkoxy; R.sup.1, 
R.sup.2, R.sup.3 and R.sup.4 may be the same or different; and a is an 
integer between about 1 and 200, and in some embodiments a is less than 
100 and in certain embodiments a is between 3 and 70. 
The following terms used herein: "lower alkyl", "lower alkoxy", lower 
phenyl", "cycloalkyl" and "acyl" generally contain from 1 to 50 carbons, 
as is well understood by those skilled in the art. 
One example of compatible components that contain polyoxyethane 
substituents are polymers such as apolyalkylene oxide which has a 
molecular weight of betwen about 200-5000. The molecular weight of the 
polyalkylene oxide polymer is such that the compatible component remains 
compatible with the curing unsaturated polyester and monomer. When the 
molecular weight of the polymer is too high, the polyalkylene oxide 
polymer is incompatible with the curing unsaturated polyester and monomer. 
At that point the polyalkylene oxide polymer acts like a low-profile 
additive component, which, by definition, is incompatible with the curing 
unsaturated polyester and monomer. Specific examples of polyalkylene oxide 
polymers useful as compatible components include polyethylene oxide having 
a molecular weight between about 200-1000 and polyethylene oxide having a 
mole weight between about 200-5000. 
Other examples of these compatible components include esters of citric 
acid, adipic acid and/or sebacic acid with tripropylene glycol monomethyl 
ether, dipropylene glycol monomethyl ether, diethylene glycol monomethyl 
ether, diethylene glycol monoethyl ether and the like. 
Examples of esters include triesters of a general structure: 
##STR4## 
wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7, 
R.sup.8, R.sup.9, R.sup.10, R.sup.11, R.sup.12, R.sup.13, R.sup.14, 
R.sup.15 and R.sup.16 are selected from the group consisting of hydrogen, 
cycloalkyl, lower alkyl, phenyl, phenyl substituted by halogen, lower 
alkyl, acyl, or lower alkoxy, and R.sup.1, R.sup.2, R.sup.3, R.sup.4, 
R.sup.5, R.sup.6, R.sup.7, R.sup.8, R.sup.9, R.sup.10, R.sup.11, R.sup.12, 
R.sup.13, R.sup.14, R.sup.15, and R.sup.16 may be the same or different, 
a, b, and c are integers between 1and about 200, and a, b and c may be the 
same or different. 
Specific examples of such triesters include wherein a=b.ltoreq.c=3, R.sup.1 
=R.sup.2 =R.sup.3 =R.sup.4 =R.sup.5 =R.sup.6 =R.sup.7 =R.sup.8 =R.sup.9 
=R.sup.10 =R.sup.11 =R.sup.12 =H, R.sup.13 =R.sup.14 =R.sup.15 =CH.sub.3, 
and R.sup.16 =H; and wherein a=b=c=3, R.sup.1 or R.sup.2 or R.sup.3 or 
R.sup.4 =CH.sub.3 and the others=H, R.sup.5 or R.sup.6 or R.sup.7 or 
R.sup.8 =CH.sub.3 and the others=H, R.sup.9 or R.sup.10 or R.sup.11 or 
R.sup.12 =CH.sub.3 and the others=H, R.sup.13 =R.sup.14 =R.sup.15 
=CH.sub.3 and R.sup.16 =H. 
Still more examples of esters include diesters of a general structure: 
##STR5## 
wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7, 
R.sup.8, R.sup.9, R.sup.10, R.sup.11 and R.sup.12 are selected from the 
group consisting of hydrogen, cycloalkyl, lower alkyl, phenyl, phenyl 
substituted by halogen, lower alkyl, acyl, or lower alkoxy, and R.sup.1, 
R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7, R.sup.8, R.sup.9, 
R.sup.10, R.sup.11 and R.sup.12 may be the same or different, a and b are 
integers between 1 and about 200 and b may be the same or different. 
Specific examples of such diesters include wherein a=b=3, R.sup.1 =R.sup.2 
=R.sup.3 =R.sup.4 =R.sup.5 =R.sup.6 =R.sup.7 =R.sup.8 =H, R.sup.9 
=R.sup.10 =CH.sub.3 and R.sup.11 =R.sup.12 =H; and wherein a=b=3, R.sup.1 
or R.sup.2 or R.sup.3 or R.sup.4 =CH.sub.3 and the others=H, R.sup.5 or 
R.sup.6 or R.sup.7 or R.sup.8 =CH.sub.3 and the others=H, R.sup.9 
=R.sup.10 =CH.sub.3 and R.sup.4 =R.sup.12 =H. 
Still more specific examples of esters include diesters of a general 
structure; 
##STR6## 
wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7, 
R.sup.8, R.sup.9, R.sup.10, R.sup.11 and R.sup.12 are selected from the 
group consisting of hydrogen, cycloalkyl, lower alkyl, phenyl, phenyl 
substituted by halogen, lower alkyl, acyl, or lower alkoxy, and R.sup.1, 
R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7, R.sup.8, R.sup.9, 
R.sup.10, R.sup.11 and R.sup.12 may be the same or different, a and b are 
integers between 1 and about 200 and b may be the same or different. 
Specific examples of such diesters include wherein a=b=3, R.sup.1 =R.sup.2 
=R.sup.3 =R.sup.4 =R.sup.5 =R.sup.6 =R.sup.7 =R.sup.8 =H, R.sup.9 
=R.sup.10 =CH.sub.3 and R.sup.11 =R.sup.12 =H; and wherein a=b=3, R.sup.1 
or R.sup.2 or R.sup.3 or R.sup.4 =CH.sub.3 and the others=H, R.sup.5 or 
R.sup.6 or R.sup.7 or R.sup.8 =CH.sub.3 and the others=H, R.sup.9 
=R.sup.10 =CH.sub.3 and R.sup.11 =R.sup.12 =H. 
Still more specific examples of esters include monoesters of a general 
structure: 
##STR7## 
R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7 and R.sup.8 
are selected from the group consisting of hydrogen, cycloalkyl, lower 
alkyl, phenyl phenyl substituted by halogen, lower alkyl, acyl, or lower 
alkoxy, and R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7 
and R.sup.8 may be the same or different, and a is an integer bewteen 1 
and about 200. 
Specific examples of such monoesters include wherein a=3, R.sup.1 =R.sup.2 
=R.sup.3 =R.sup.4 =H, R.sup.5 =CH.sub.3 and R.sup.6 =R.sup.7 =R.sup.8 =H; 
and wherein a=3, R.sup.1 or R.sup.2 or R.sup.3 or R.sup.4 =CH.sub.3 and 
the others=H, R.sup.5 =CH.sub.3 and R.sup.6 =R.sup.7 =R.sup.8 =H. 
Still more specific examples of esters include monoesters of a general 
structure: 
##STR8## 
R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7 and R.sup.8 
are selected from the group consisting of hydrogen, cycloalkyl, lower 
alkyl, phenyl, phenyl substituted by halogen, lower alkyl, acyl, or lower 
alkoxy, and R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7 
and R.sup.8 may be the same or different, and a is an integer between 1 
and about 200. 
Specific examples of such monoesters include wherein a=3, R.sup.1 =R.sup.2 
=R.sup.3 =R.sup.4 =H, R.sup.5 =CH.sub.3 and R.sup.6 =R.sup.7 =R.sup.8 =H; 
and wherein a=3, R.sup.1 or R.sup.2 or R.sup.3 or R.sup.4 =CH.sub.3 and 
the others=H, R.sup.5 =CH.sub.3 and R.sup.6 =R.sup.7 =R.sup.8 =H. 
The invention also relates to a process for making citrate ester compounds 
of the general formula 
##STR9## 
wherein X is selected from the group consisting of --O-C.sub.3 
H.sub.6).sub.3 --OCH.sub.3 and OH. The process comprises adding together 
approximately 25-30 percent, by weight, of citric acid and approximately 
70-75 percent, by weight, of tripropylene glycol monomethyl ether, heating 
to a temperature in the range of about 190.degree.-240.degree. C. with a 
nitrogen sparge to remove water. The resulting product comprises 
approximately 5-50 and preferably about 32-42 percent, by weight of 
2-hydroxy-1,2,3-propane tricarboxylic acid-tripropylene glycol 
monomethylether triester, approximately 5-95 and preferably about 46-57 
percent, by weight, of 2-hydroxy-1,2,3-propane tricarboxylic 
acid-tripropylene glycol monomethylether diester, and approximately 5-50 
and preferably about 5-5 percent, by weight, of 2-hydroxy-1,2,3-propane 
tricarboxylic acid-tripopylene glycol monomethylether monoester. 
The citrate esters described in this invention may also be useful as 
plasticizers for thermoplastic polymers such as polyvinyl chloride, or 
polystyrene. 
The four components resinous system is suitable for mixing with other 
ingredients in order to form a sheet molding composition. For example, the 
four component resinous system is suitable for mixing with chemical 
thickeners which are physically mixed into the resin emulsion. The 
chemical thickeners generally include metal oxides, hydroxides and 
aldoxides of Group II, III or IV from the Periodic Table. Calcium oxide 
and magnesium oxide or the respective hydroxides are most often employed 
with four component resin compositions of the present invention. In 
preferred embodiments, the thickener is present in amounts ranging from 
about 0.5 to about 6 parts, by weight, based on the four component 
resinous system. The thickener is generally suspended in a carrier resin, 
as is known in the art. In preferred embodiments the carrier material 
comprises a composition which does not react with the thickener such as, 
for example, polymethylmethacrylate, polyvinylacetate, saturated or 
unsaturated polyesters, and similar materials well-known in the art. In 
preferred embodiments the carrier resin is present in amounts ranging from 
about 0.5 to about 8 parts, by weight, based on one hundred parts of the 
four component resinous system. 
Catalysts are incorporated in small amounts into thermosetting polyester 
resins containing ethylenically unsaturated monomer to aid in curing or 
crosslinking the unsaturated polyester with the monomer. Such catalysts 
are well known and may be similarly utilized in this invention to aid in 
curing the unsaturated polyester and monomer mixed with the low-profile 
thermoplastic polymer. Typical catalysts, for example, include organic 
peroxides and peracids such as tertiary butyl perbenzoate, tertiary butyl 
peroctoate, benzoyl peroxide and the like. The amounts of catalysts may be 
varied with the molding process and similarly varied with the level and 
types of inhibitors utilized, in a manner well known in the art. In 
preferred embodiments the catalyst is present in amounts ranging from 
about 0.5 to about 2.5 parts, by weight, based on one hundred parts of the 
four component resinous system. 
Curing of the composition is carried out under heat and pressure typically, 
in closed, preferably positive pressure type molds. Mold release agents 
may be added to the compositions to perform their normal function, as is 
well understood in the art. 
Fibers, fillers and pigments normally added to resin compositions can be 
likewise used in formulating the sheet molding composition of this 
invention. Reinforcing fibers or fibrous reinforcement is taken to mean 
glass fibers in one form or another, such as glass fabrics, chopped glass 
strands, chopped or continuous strand glass fiber mat; however, the terms 
also include reinforcing agents which may also be used if desired, for 
example asbestos, cotton, synthetic organic fibers and metals. Fillers, 
usually inert, and inorganic material useful with the compositions of the 
present invention include, for example, clay, talc, calcium carbonate, 
silica, calcium silicate, and the like. In preferred embodiments the 
fillers are present in amounts ranging from the 165 to about 250 parts, by 
weight, based on one hundred parts of the four component resinous system. 
Examples of pigments include carbon black, iron oxide, titanium dioxide, 
and the like, as well as organic pigments. In preferred embodiments the 
pigments are present in amounts ranging from about 0 to about 4 parts, by 
weight, based on one hundred parts of the four components resinous system. 
The preparation of the sheet molding composition is generally carried out 
by blending together a first portion comprising the unsaturated polyester, 
the low-profile additive, the monomer, the compatible component, and such 
additives as a catalyst, mold release agent and fillers. This is generally 
known in the industry as the A-side formulation. The second portion 
(generally known as the B-side formulation) comprises the thickening agent 
and a carrier resin therefor, and such additives as pigments and mold 
release agents. In another aspect of the invention an additional monomer 
is added to the B-side formulation in which the thickener is suspended. In 
preferred embodiments the additional monomer comprised vinyl toluene or 
styrene. In preferred embodiments, the additional monomer is present in 
amounts ranging from about 1 to about 8 parts, by weight, based on one 
hundred parts of the four component resinous system. 
The sheet molding composition can be prepared by mixing the components in a 
suitable apparatus at temperatures which are conventional and known to 
those skilled in the art. Once the sheet molding composition is 
formulated, the composition can be molded into thermoset articles having a 
desired shape. The actual molding cycle will, or course, depend upon the 
exact composition being molded. In preferred embodiments suitable molding 
cycles are conducted at temperatures ranging from about 
250.degree.-350.degree. F. for periods of time ranging from about 1/3 to 
about 5 minutes. 
The following formulations are provided to illustrate examples of the 
compositions of the present invention and are not intended to restrict the 
scope thereof. All parts are parts by weight, unless otherwise expressly 
specified. 
TABLE I 
______________________________________ 
Resin Compositions 
Preferred 
Ingredients Range (wt. %) 
Range (wt. %) 
______________________________________ 
Unsaturated polyester 
20-45 28-35 
Thermoplastic additive 
5-30 7-20 
(low-profile) 
Monomer 25-65 35-50 
Compatible component 
0.5-15 1-8 
100 100 
______________________________________ 
TABLE II 
______________________________________ 
Typical Sheet Molding Composition Formulation 
Formulations 
Ingredients A B C D 
______________________________________ 
Resin 100 100 100 100 
Catalyst 1.5 1.5 1.5 1.5 
Release agent 
5.0 4.5 5.0 4.5 
Filler 230 220 225 225 
Thickener 4.0 5.0 4.5 4.8 
Pigment 0.1 0.2 0.1 0.1 
Carrier 1.55 -- 1.5 1.6 
Secondary monomer 
5.6 -- 5.5 5.5 
______________________________________ 
The sheet molding compositions of the above formulations have shown 
unexpected improvements in surface aesthetics and mold fillout. These 
improvements are especially significant for use in sheet molding compounds 
(SMC). Moreover, increasingly thinner automobile parts are able to be 
molded with smoother surfaces than by any known systems. 
For formulation A the unsaturated polyester comprises maleic anhydride and 
propylene glycol; the low-profile additive comprises a saturated polyester 
made from ethylene glycol and propylene glycol and adipic acid; the 
monomer comprises styrene; the compatible component comprises a 
polypropylene oxide having a molecule weight between about 200 and 2000; 
the catalyst comprises tertiary butyl perbenzoate; added to the A-side, 
the release agent comprises calcium stearate and zinc stearate; the filler 
comprises calcium carbonate; the thickener comprises magnesium hydroxide; 
the carrier comprises polymethylmethacrylate; the pigment comprises a 
carbon black pigment suspension; and the secondary monomer comprises vinyl 
toluene. 
Compression molded panels were made with each formulation with 27 percent, 
by weight, of 1" chopped glass fibers. When measured on a surface 
smoothness index instrument (LORIA.RTM. registered trademark of the 
Ashland Chemical Co.) the panels gave the LORIA.RTM. number of 60-70 as 
compared to the same formulation but without any compatible component 
which gave a number of 80-90. On the LORIA.RTM. instrument, the lower the 
number, the smoother the surface. 
For formulation B the unsaturated polyester comprises maleic anhydride and 
propylene glycol; the low-profile additive comprises a saturated polyester 
made from ethylene glycol and propylene glycol and adipic acid; the 
monomer comprises styrene; the compatible component comprises a triester 
of citric acid with tripropylene glycol monomethyl ether; the catalyst 
comprises tertiary butyl perbenzoate; the release agent comprises calcium 
stearate; the filler comprises calcium carbonate; the thickener comprises 
magnesium hydroxide; and the pigment comprises a carbon black pigment 
suspension. 
Compression molded panels made with Formulation B with 27 percent, by 
weight, of 1" chopped glass fibers. When measured on a surface smoothness 
index instrument (LORIA.RTM.) the panels gave a number of 55-60 as 
compared to the same formulation but without he compatible component which 
gave a number 80-90. 
For formulation C the unsaturated polyester comprises maleic anhydride and 
propylene glycol; the low-profile additive comprises a saturated polyester 
made from ethylene glycol and propylene glycol and adipic acid; the 
monomer comprises styrene; the compatible component comprises 
polypropylene oxide having a molecular weight of approximately 700 and 
citrate esters of the general formulae III, IV-A and IV-B, and V-A and 
V-B, wherein the polypropylene oxide comprises approximately 3 percent and 
the citrate esters comprise approximately 4 percent, by weight, of the 
resin formulation; the catalyst comprises tertiary butyl perbenzoate; the 
release agent comprises zinc stearate; the filler comprises calcium 
carbonate; the thickener comprises magnesium hydroxide; the carrier 
comprises polymethylmethacrylate; the pigment comprises a carbon black 
pigment suspension; and the secondary monomer comprises vinyl toluene. 
Compression molded panels were made with formulation C with 27 percent, by 
weight, 1" chopped glass fibers. When measured on a surface smoothness 
index instrument, LORIA.RTM., the panels gave a number of 50 as compared 
to the same formulation without he compatible component which gave a 
number of 80-90. 
For formulation D the unsaturated polyester comprises maleic anhydride and 
propylene glycol; the low profile additive comprises a saturated polyester 
made from ethylene glycol and propyleneglycol and adipic acid; the monomer 
comprises styrene; the compatible component comprises polypropylene oxide 
having a molecular weight of approximately 700 and citrate esters of the 
general formulae III, IV-A, IV-B and V-A and V-B wherein the polypropylene 
oxide comprises approximately 3 percent and the citrate esters comprise 
approximately 4 percent, by weight, of the resin formulation; the catalyst 
comprises tertiary butyl perbenzoate; the release agent comprises calcium 
stearate; the filler comprises calcium carbonate; the thickener comprises 
4 parts per hundred resin magnesium hydroxide and 0.8 parts per hundred 
magnesium oxide; the carrier comprises polyvinylacetate; the pigment 
comprises a carbon black pigment suspension; and the secondary monomer 
comprises vinyl toluene. 
Compression molded panels were made with formulation D with 27 percent, by 
weight, of 1" chopped glass fibers. When measured on a surface smoothness 
index instrument, LORIA.RTM., the panels gave an umber of 48 as compared 
to the same formulation without he compatible components which gave a 
number of 80-90. 
Although the invention has been described in its preferred form with a 
certain degree of particularity, it is understood that the present 
disclosure has been made only by way of example, and that numerous changes 
can be made without departing from the spirit of the scope of the 
invention.