Unsaturated polyester resin compositions containing compatible polysiloxane compounds

A sheet molding composition is disclosed which includes a four component resinous system which comprises (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 additives which are thermoplastic polymers which cause phase separation and porosity during the curing reaction; (c) one or more olefinically unsaturated monomers which copolymerize with the unsaturated polyester; and, (d) one or more compatible components comprising at least one polysiloxane polyalkylene copolymer. The compatible components are compatible with the reacted unsaturated polyester and monomer during cure and impart improved surface characteristics when added to low-profile resin systems.

TECHNICAL FIELD 
The present invention provides unsaturated polyester resin compositions 
that contain one or more unsaturated polyesters, ethylenically unsaturated 
monomers that copolymerize with the unsaturated polymer, thermoplastic 
low-profile additives and compatible compounds. 
Unsaturated polyester resin compositions are finding increased use of the 
automotive industry as sheet molding compound (SMC) formulations from 
which component parts especially body panels can be molded. The 
unsaturated polyester resin composition contain, in addition to the 
unsaturated polyesters and monomer components, 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 resin 
compositions in order to obtain a composition which can be used in a sheet 
molding formulation and molded into thermoset articles. 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 unsaturated polyester, monomer and 
low-profile additive components are mutually compatible, i.e., no gross 
separation occurs when a mixture of the components is allowed to stand. In 
contrast, two-pack systems form distinct phases if the components are 
allowed to stand after being mixed. As such, the components need to be 
mixed immediately prior to use. In both systems, phenomena 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/monomer solution. As the polyester/monomer mixture crosslinks, 
the low-profile thermoplastic additive and copolymer (of polyester and 
monomer) 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 resin compositions 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 formulations, a chemical thickener such as an 
alkaline material (for example, magnesium oxide or magnesium hydroxide) is 
added to 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 
increase the viscosity of the composition. 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 formulations are handleable 
and can easily be placed into compression molds either by hand or by 
machine. 
Although the use of low-profile additives does effect some degree of 
improvement in the anti-shrinkage characteristics of the unsaturated 
polyester compositions, it has now been found that significant 
improvements in surface smoothness and processing characteristics can be 
achieved by adding a component which is compatible with the reacted 
unsaturated polyester and monomer during cure. 
BACKGROUND 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 select 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 
stabilizing 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 or 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 polyester molding compositions. These pigmentable 
resin systems are low-shrink and not low-profile. The surface quality of 
these pigmentable systems is considerably inferior to surface 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 anti-shrinkage and 
surface smoothness characteristics of the unsaturated polyester 
compositions, it is still not possible to achieve the degree of surface 
smoothness required of today's thermoset molded articles. 
DISCLOSURE OF INVENTION 
The present invention provides low-profile resin compositions having 
improved surface smoothness which are useful for 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 polycondensation 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 porosity during the curing reaction; 
(c) one or more olefinically unsaturated monomers which copolymerize with 
the unsaturated polyester; and, 
(d) one or more polysiloxane components which are compatible with the 
reacted unsaturated polyester and monomer during cure. 
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. 
BEST MODE OF CARRYING OUT INVENTION 
The present invention relates to the discovery of the use in a low-profile 
system of components which are compatible with the reacted unsaturated 
polyester and monomer during cure. 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 of the sheet molding composition during the molding 
process is improved to the point that rapidly curing formulations may be 
composed. As a result, the molding time is drastically reduced. 
The unsaturated polyester component 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 the acid 
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, methylsuccinic, 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. Especially 
preferred concentrations of the unsaturated polyester are in the 28 to 35 
percent, by weight, range. 
The low-profile additive component of the four component resinous system 
comprises thermoplastic polymers which cause phase separation and porosity 
during the curing reaction. 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 
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 polyioscyanates, preferably diisocyanates, and 
polyether polyols, numerous saturated polyesters, polycaprolactone, 
styrene-butadiene 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 have 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 7-20 percent, by weight range. 
In addition, low-profile additives such as the composition comprising 
ethylene glycol, at least one nonpolar diol, adipic acid and trimellitic 
anhydride, as disclosed in copending and commonly owned patent application 
Ser. No. 07/555,884, filed May 2, 1990, which is expressly incorporated 
herein by reference, may also be used in the present invention. 
The monomer component of the resinous system comprises materials that 
copolymerize with the unsaturated polyester. The olefinically unsaturated 
monomer that is copolymerizible with the unsaturated polyester is most 
generally styrene, however, methylstyrene 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. 
The compatible component of the four component resinous system comprises 
one or more materials which are compatible with the reacted unsaturated 
polyester and monomer during cure. The compatible component, when added to 
the unsaturated polyester/monomer combination does not cause the necessary 
micro-phase separation that occurs with low-profile systems; that is, the 
compatible component does not act like a low-profile additive. 
Examples of other useful compatible components are those compatible 
components containing one or more polyoxyethane substituents, as disclosed 
in the copending and commonly owned patent applications, Ser. No. 428,548, 
filed Oct. 30, 1989; Ser. No. 07/517,775, filed May 2, 1990 and Ser. No. 
07/517,863, filed May 2, 1990, which are expressly incorporated herein by 
reference. These examples are intended to be illustrative of suitable 
compatible components and are not intended to be all inclusive. 
In the present invention one or more components are added which are 
compatible with the unsaturated polyester and monomer during cure. That 
is, they do not act as low-profile additives. They do not cause a 
micro-phase separation 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 contain one or more 
polysiloxane polymers. One example of a compatible component is a 
polysiloxane polyalkyl copolymer such as Abilwax 9800. 
The polysiloxane polyalkylene copolymer represented by the formula: 
##STR1## 
wherein each R, which can be the same or different, is an alkyl group 
containing 1 to 20 carbon atoms, x is an integer ranging from 1 to 10 and 
y is an integer ranging from 1 to 10. Preferably, each R group is an alkyl 
group containing 1 to 12 carbon atoms, x is an integer ranging from 1 to 5 
and y is an integer ranging from 1 to 5. More preferably, each R group is 
an alkyl radical containing 1 to 8 carbon atoms. 
The best mode of carrying out our invention is with a polysiloxane 
polyalkylene copolymer represented by the formula: 
##STR2## 
wherein each R is an alkyl group having 1 to 8 carbon atoms, x is an 
integer ranging from 1 to 5 and y is an integer ranging from 1 to 5. 
It is desirable that the molecular weight of the compatible component be 
less than about 4000 and in certain embodiments be less than about 3000. 
The molecular weight of the compatible compound is such that the compatible 
component is compatible with the reacted unsaturated polyester and monomer 
during cure. Compatibility generally means that the combination of 
unsaturated polyester and compatible additive do not cause the microporous 
structure widely accepted as necessary for the low-profile phenomenon. 
Low-profile additive components, by definition, are incompatible with the 
curing unsaturated polyester and monomer, and cause phase separation. 
The four component resinous system of this invention 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 
alkoxides 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. 
Table I below illustrates the preferred ranges for the four component 
mixture described in this invention. 
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. In preferred embodiments, the mold release 
agents are present in amounts ranging from about 0.5 to about 6.0 parts, 
by weight, based on one hundred parts of the four component resinous 
system. 
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 about 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 component resinous system. 
In one aspect of the present invention 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 or secondary monomer is added to the B-side 
formulation in which the thickener is suspended. In preferred embodiments 
the additional monomer comprises 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 of the present invention 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 sill, of course, 
depend upon the exact composition being molded. In preferred embodiments 
suitable molding cycles are conducted at temperatures ranging from about 
120.degree.-177.degree. C. for periods of time ranging from 1/3 to about 5 
minutes.

INDUSTRIAL APPLICABILITY 
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 
______________________________________ 
Various formulations using the sheet molding composition formulation shown 
in Table II below were made. 
TABLE II 
______________________________________ 
Typical Sheet Molding Composition Formulation 
Ingredients Amount 
______________________________________ 
Resin 100 
Catalyst 1.4 
Release agent 4.2 
Filler 215 
Thickener 3.7 
Pigment 0.2 
Carrier 1.9 
Secondary monomer 
3.7 
______________________________________ 
The ingredients comprised: 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 Abilwax 9800 which is a polysiloxane polyalkyl copolymer; the 
catalyst comprises tertiary butyl perbenzoate; the release agent comprises 
calcium stearate and zinc stearate; the filler comprises calcium 
carbonate; the thickener comprises magnesium hydroxide; the carrier 
comprising polymethylmethacrylate; the pigment comprises a carbon black 
pigment suspension; and the secondary monomer comprises vinyl toluene. 
Compression molded panels were made with the above formulation with 27 
percent, by weight, of 2.54 cm 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 about 
79, 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. In preferred embodiments, it 
is contemplated that the surface smoothness values of the four component 
resinous systems containing compatible components, be about 80 or less, as 
measured using a LORIA.RTM. surface smoothness index instrument. 
In addition, 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 
compound (SMC). Moreover, increasingly thinner automobile parts are able 
to be molded with smoother surfaces than by any known systems. 
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.