Note: Descriptions are shown in the official language in which they were submitted.
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20~5~ ~
IMPROV~D FILL~3R FOR POLYESLI5K MOLDING
COMPOUND AND ME~TEIOD
Field of the Invention
This invention relates to an improved polyester
molding compound and method, and more particularly,
this invention relates to an improved calcium car~onate
filler for use in the manufacture of polyester molding
compound.
Background of the Invention
Polyester molding compound is used in the
manufacture of light-weight, glass reinforcedpolyester
resin automotive parts and other general hardware which
is made in heated matched metal dies or molds.
Polyester molding compound is conventionally produced in
the form of sheet molding compound ( SMC) or bulk molding
compound (BMC).
Sheet molding compound is made by dropping glass
fibers onto the sur~ace of a polyethylene film which has
first been coated with a non-polymerized polyester resin
paste. A similarly coated polyethylene film is placed
~oating to coating o~er the fir~t film to form a
sandwich composite. This composite is then s~ueezed to
remove excess air and taken up onto a ~pool. This spool
is stored at 70~ - 90~F for one to ten days.
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203~ g7
During this curing period, thickeners in the resin
paste increase the paste viscosity from that of a
relatively low viscosity liquid until ultimately a dry
leather-like molding compound containing long glass
fihers randomly dispersed in two dimensions is produced.
In this manner fiber integrity is largely maintained
since no intensive mixing is involved in the process.
Fiber integrity is important in as much as the strength
of the fiber reinforced composite is a function of fiber
lo length, its dispersion, and its loading in the resin
In order to obtain consistent manufacturing
conditions, the initial paste viscosity of the polyester
resin paste must be held within certain defined limits.
The thickener in the resin is designed such that the
viscosity of the paste increases slowly until after the
glass fibers have had a chance to become coated or "wet
out" in the resin. After a sufficient time has been
allowed for thorough glass wet-out, the thickeners
present in the paste affect a rapid increase in
viscosity until approximately 20-60 million-centipoise
(MMcps) is attained. Thereafter, the rate of increase
in viscosity slows down. Accordingly, the initial
increase in viscosity must be slow and reproducible in
order to facilitate the manufacture of sheet molding
compound in a highly automated environment.
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2036~97
Bulk molding compounds are similar in chemical
composition to SMC compounds. The manufacturing process
differs in that low intensity mixers are used to gently
wet-out the glass fibers into the resin paste. This
process allows the use of higher viscosity pastes.
Thickeners may be used to obtain a further viscosity
increase in some situations. While mixing times are
kept as short as possible to minimize fiber degradation,
extensive degradation does occur w~th fibers longer than
0 l/41l in length. Thus, the BMC process typically employs
fibers of this length or smaller.
Calcium carbonate fillers are used at high levels
in polyester molding compounds to reduce costs, to
improve surfaoe finish by reducing resin shrinkage, and
to modify the rheological behaviors of the paste to
prevent segregation o~ the fiberglass during handling
and storage. Although fillers are typically viewed as
low cost bulking agents, they are critical to the
processing of polyester molding compounds. The physical
properties of the fillers must be maintained within
certain tightly controlled limits to produce composites
of consistent quality.
As the filler levels have increased through the
years to provide improved surface finish, it has been a
z5 disadvantage that minor variations in the chemical and
physical properties of the filler can cause significant
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( (' 203~97
variations in viscosity profile. This in turn results
in manufacturing difficulties when using highly
automated equipment. Further, variations in filler
moisture levels are especially serious in their effect
on the thickening rate o~ the polyester resin paste.
Because of its inherently low oil absorption, low
moisture content and low cost, the most preferred filler
used in polyester molding compound applications is
calcium carbonate. The ores from which finely ground
calcium carbonate fillers are produced for use in
polyester molding ~ompounds are found naturally in
several forms. Broadly speaking, these forms are chalk,
limestone, mar~le and dolomite. Precipitated calcium
carbonate, which is a synthetically prepared product, is
unacceptable for polyester molding compound applications
due to its excessively high oil absorption.
Chalk is a soft, amorphous carbonate made up of the
fossil shells of millions of tiny marine organisms.
Accordingly, while the individual particles are rounded
2~ and quite strong in themselves, the bonding between
particles is weak and easily broken. Hence, the
comminution of chalk is essentially a process of gently
breaking down the mineral into its fundamental
particles. This may be accomplished either by dry
grinding the chalk or wet grinding the chalk in a water
slurry and segregating the desired fraction using water
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2 0 3 ~
flotation techniques. Historically, the term "whiting"was used to describe finely pulverized chalk This term
is n~w inconsistently used to describe any finely ground
calcium carbonate from any source, and therefore, for
clarity this term is ~est avoided.
Limestone, mar~le, and dolomite are generally
crystalline rocks whose particles and grinding display
the characteristic rhom~ohedral structure of compact but
pointed particles. Marble, limestone and dolomite are
conventionally processed by one of two methods. The
first and most energy efficient is dry grinding.
Dry-ground limestone has been found unacceptable for use
in polyester molding compounds because of excessive
resin demand and excessive variation in the rate of
viscosity increase in the manufacturing process.
The second method for processing limestone or
marhle is wet grinding wherein the limestone is crushed,
made into a slurry with water and ground to the desired
particle size. Thereafter, the limestone is filtered
from the slurry and dried t~ produce a calcium car~onate
filler. Wet ground calcium carbonates are the preferred
filler in polyester molding compounds.
The wet grinding process requires the removal of
substantial ~uantities of water from the processed
Z5 slurry and, consequently, this process requires
substantially more energy than the dry grinding method.
- 5 -
It is generally accepted that wet grinding calciumcarbonate is between 15~ to 25~ more expensive than the
dry grinding technique. Accordingly, it has long been
desired to develop a dry-ground calcium carbonate which
has the thickening consistency and loading capa~ility of
wet ground products. Although attempts have been made
to surface treat many of the above calcium carbonate
fillers With silanes or fatty acids, Such as stearic
acid, these treatments have not been entirely successful
although dispersion and oil absorption have been
mproved .
In the manufacture of polyester molding compound,
two grades or types of calcium car~onate filler are
used. The first is termed a Class I filler. Class I
calcium carbonate fillers are a finely ground material
having a median particle size between 2.0 to 4.0 microns
and with at least 90% by weight less than lO microns.
This fine particle size filler is used in applications
where surface finish is the most critical. However,
20 because of the f ine particle size, f iller loadings must
necessarily be restricted to lower levels. This is
because of the higher oil absorption and resin demand of
smaller particle size fillers. Class I fillers are
known to produce composites having higher strength and
superior surface finish.
2 0 3 ~ ~ 9
The second type of filler is termed a Class II
~roduct. A ~lass II filler has a median particle size
~etween approxima~ely 5 to 10 microns with at least 98~
by weight finer than 44 microns. A Class II filler has
a lower surface area than the Class I filler and hence
has a lower oil absorption and resin demand.
Accordingly, ~lass II fillers may be placed in polyester
molding compounds at much higher loading levels. The
fraction ~reater than 44 microns must ~e kept below two
o percent to minimize imperfections in the composite
surface. Therefore, samples made according to the
present invention were fcrmed into fillers of both the
Class I and Class II variety for comparison with other
fillers of the same class.
While calcium carbonate deposits are widely
dispersed throughout the world, only a very few meet the
exacting requirements necessary for a polyester molding
compound ~iller. In the United States only high purity
marble fillers have gained any significant usage. In
Europe the high purity limestone from the Orgon deposit
in France is preferred. Chalks, despite their wide
spread availability, their ease of processing, and their
high calcium carbonate content have not found extensive
application as polyester molding compound filler~ at the
more preferred high loadings because of their extremely
3~ ~ 9 ~
high oil absorption and moisture pickup values. Both of
these f actors follow from their extreme fineness and
porosity.
The polyester molding compound maturation process
is extremely moisture sensitive, and accordingly, the
moisture content of the filler must be kept below .1%.
This extreme moisture sensitivity leads to process
stability problems. These process stability problems
are especially severe during seasonal variations in
Io temperature and relative humidity. Because the filler
moisture ~ontent is a function of the relative humidity
of the filler storage area which is substantially
uncontrollable, compounders have attempted to overcome
these process consistency problems by numerous methods.
Compounders tried developing special seasonal
recipes, purchasing resins to which f ree water has been
added to a constant level or limiting the filler loading
such that they o~tain satisfactory glass wet-out and
thickening even under the most adverse relative
humidities encountered. These are less than optimum
solutions since relative humidities only roughly follow
seasonal patterns and limiting filler levels to cover
worst case conditions unnecessarily increase the cost of
the final resin-aglass composite.
2036597
These and other disadvantages of the prior art are overcome
by the product and process of the present invention which is set
forth in the following detailed description.
Summary of the Invention
5It is a discovery of the pre~ent invention that a unique,
high purity calcium carbonate of sedimentary origin, commonly
known as ~aribbean limestone, may be utilized to produce a filler
which is acceptable for polyester molding compound applications.
Carib~ean limestone is an almost chalk-like calcium carbonate
10which is very soft and breaks readily into very fine particles.
Calcium carbonates which are of sedimentary origin include
reef limestone, which is made up of reef-existing fossil
fragments; betrital limestone, which is made up of fibrous
skeletal and non-skeletal grains, including pelloids, ooids and
15infraclasts; micrite, which is a naturally precipitated calcium
carbonate which forms into beds or is found in a matrix with
betrital limestones and chalk, which is made up of disarticulated
caccolith fragments. Caribbean limestone is sedimentary in
origin and exists as combinations of all of the above types, i.e.
20reefs, betritals, micrites and chalk. This Caribbean limestone,
or as referred to herein as micritic limestone, is extremely pure
with some deposits ha~ing calcium carbonate contents in excess
of 98~ and generally containing no alpha quartz.
~xtremely pure limestones are relatively uncommon. One
25known high purity limestone formation is the Orgon deposit in
France. Although the existence of the micritic limestone
deposits have been known for many years, they have heretofore
been thought to possess no ~ommercial utility because of their
perceived close ~imilarity to chalk which is ab~ndant throughout
_ 9 _
2036597
the world at high purity levels.
It is a discovery of the present invention that these
heretofore commercially undesirable limestones when dry ground
can produce a calcium carbonate filler which may be utilized in
polyester molding compound applications at loading levels
heretofore unattainable without degradation of composite
performance.
Deposits of micritic limestone are found throughout the
Caribbean basin with significant deposits found on the islands
0 of Haiti and Jamaica.
More particularly, the invention provides a Class I calcium
carbonate filler suitable for use in a polyester molding
compound, the filler comprising a finely divided dry-ground
micritic Caribbean limestone having a CaCO3 content of at least
about 95~ by weight with the dry-ground filler having a median
particle size in the range of 2 to 4 microns, a Process Stability
Index (PSI - as set out further herein) less than about 150~ and
a Standard 30-Minute Viscosity (S 30-M V as set out further
herein) of less than about 0.5 MMcps.
The invention also comprehends a Class II calcium carbonate
filler suitable for use in polyester molding compound, the filler
comprising a finely divided, dry-ground micritic limestone havin~
a CaC03 content of at least about 95~ by weight with the filler
having a median particle size in the range of about 4 to lo
microns with at lea~t 98~ by weight of the filler less than about
44 microns and having a Process Stability Index les8 than about
15~ and a standard ~-Minute Vis~osity of less than about .07
MMcpS.
The invention also provides a polyester molding compound
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2D365 97
containing a polyester resin, chopped fiber and a calcium
carbonate filler, wherein the filler comprises a finely divided,
dry-ground micritic Caribbean limestone having a CaC03 content of
at least 98~ by weight, less than 1~ MgCO3 by weight, less than
50.5~ acid insoluble by weight and less than o.1~ silica by
weight.
The invention also provides processes for making the ~lass
I and Class II carbonate fillers.
Accordingly, the present invention seeks to provide a
10calcium carbonate filler by dry grinding which is suitable for
use in a polyester molding compound at high filler loadings
without adversely effecting the composite quality.
Further, the present invention seeks to provide a calcium
carbonate filler which may be incorporated into a polyester
15molding compound at higher loadings without adversely effecting
either the proce~s ~or making the polyester molding compound or
the quality of the final composite.
Still further, the present invention seeks to provide a
calcium carbonate filler which is less sensitive to variation~
20in relative humidity.
Further still, the present invention seeks to provide a
calcium carhonate filler which does not promote premature
viscosity increase in the polyester resin paste to allow time for
adequate wet-out of the reinforcing chopped glass fibers.
25Moreover, the present invention seeks to pr~vide a calcium
carbonate filler that improves ~urface qu~lity when ~sed in a
polyester molding ~ompound composite and that improves impact
resistance when used in a polyester molding compound composite.
These and other feature~ and aspects of the present
20365q7
invention will become apparent when reference is made to the
following detailed description.
Detailed Descri~tion of Preferred Embodiments and Examples
Particularly preferred embodiments of the Class I calcium
carbonate fillers referred to in the Summary of the Invention
above include fillers:
- wherein the micritic limestone is at least 98~ CaCO3 by
weight and has less than 0.3~ acid insoluble, less
than 0.1~ silica and less than l~ MaC03;
- wherein the S 30-M V is less than about 0.25 MMcps;
- wherein the median particle size is in the range of
2.5 to 3.5 microns; and
- wherein the PSI is less than 100~ and more preferably
less than about 50~. ~
Particularly preferred embodiments of the Class II calcium
carbonate fillers referred to in the Summary of the Invention
above include fillers:
- wherein the micritic limestone is at least 98~ CaCO3 by
weight and has less than 0.3~ acid insoluble, less
than 0.1~ silica and less than l~ MaCO3;
- wherein the filler has a median particle size in the
range of 4.5 to 8 microns; and
- wherein the median particle size range is 4 to lO
microns with at least 98~ by weight of the filler
being less than about 44 microns and more preferably
having a PSI less than about 8~.
A method for producing the product of the present
invention includes the steps of taking a high purity
(greater than 95~ and preferably greater than 98
- L~ -
~ 3~ 7J
calcium carbonate) ~amai~an micritic limestone as
described above and crushing into nugge~s approximately
2 inches in diameter to obtain an easily workable crude
feedstock. At this point the micritic Caribb~an
limestone contains approximately 14% by weight moisture.
This crushed Jamaican micritic limestone is then
fed into a Raymond roller mill equippe~ with a mill
furnace to remo~e superf icial moisture and
conventionally dry ground to a desired particle size
o Upon leaving the roller mill, the pulverized limestone
is split into two streams. The coarser of the two
streams, which is 98% less than 44 microns, is collected
in a cyclone to form Example 2 which is a Class II
filler. The finer, second stream, which has a median
particle size of approximately ~ microns, is collected
in a bag filter to form ~xample 1, which is a Class I
filler. The mill furnace is operated to ensure that
moisture levels of all samples are ~elow .05~. Using
this method, a Haitian micritic limestone was dry ground
to prepare a Class II filler, Example 4, and a Class I
filler, Example 3. These sample calcium carbonate
fillers were packaged into perf orated kraft bags to
allow free exchange with the atmosphere's moisture.
In order to compare Examp~e~ 1-4 of the present
invention with prior art calcium carbonate fillers, a
standardized group of measurement procedures were
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- 20~6597
developed. These tests, to the extent practicable, reflect
actual processing conditions which are of concern. Chosen to be
the standard resin system was an unsaturated polyester resin sold
under the trademark OCF4297-5 and available from Owens Corning
Fiberglass of Granville, Ohio. ThiS resin was selected among
many resin systems commercially available because it is highly
moisture sensitive and may be handled conveniently in a
laboratory. The measurements developed are termed the ~tandard
30-Minute Viscosity and the Processing Stability Index.
To measure the Standard 30-Minute Viscosity of a calcium
carbonate filler, 100 parts by weight of OCF4297-5 polyester
resin is poured into a pint can and 2.5 parts by weight of
testiary butyl perbenzoate (TBPB) catalyst is carefully metered
in with a syringe. In a separate container a series of dry
powders are preblended. These dry powders are lso phr of the
filler which has been preconditioned at 75~ relative humidity for
24 hours, 2 phr VR-3 a viscosity reducing additive from Union
Carbide of Danbury, Connecticut, 4 phr zinc stearate, 3 phr Merck
Marinco ~H~, a magnesium hydroxide thickener available from
Merck Chemical of San Francisco, California and 0.4 small PHR
Merck Maglite~ A, a magnesium oxide thickener also from Merck
Chemical.
* Trade Mark
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,~
.~
2 0 3 ~ 9 7
These preblended dry powders are slowly added to
the resin and catalyst mixture while the mixture is
being stirred at 2500 RPM by a Cowles dissolver. The
mixing is continued until a temperature of 90~F is
obtained. All viscosi~ies are measured using a
Brookfield HBT viscometer with a No. 5 spindle. The
initial visc~sity measurement is taken 4 minutes after
the dry powders have been added to the resin. All other
times are incremental from this initial point. The
lo sealed pint cans are thereafter placed in a 9~~F oven
for the maturation process and periodically the
viscosity is measured. After a 30-minute time increment,
the viscosity is measured and this number, expressed in
MMCPS, is the Standard 30-Min.ute Viscosity (V7~).
1~ The significance of the Standard 30-Minute
viscosity is that different calcium carbonate fillers
used in polyester molding compound applications produce
different rates of viscosity increase over time. It is
important to the polyester molding ~ompound
manufacturing process that the viscosity of the
polyester resin paste be sufficiently low at the e~rly
stages of the process to permit adequate wetting of the
chopped glass fiber and adequate dispersion of the
~al~ium carbonate filler. Thereafter, the viscosity
should rapidly increase with time until a tough
leather-like polye~ter molding compound i~ formed. In
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(- ( 203~9~
order to provide a safety margin in the processing of
the polyester molding compound, it is conventional in
the industry to add no more filler than will produce an
accepta~le viscosity duriny the initial glass wetting
period, For thiS reason, together with the pronoun~ed
variations due to relative humidity, less calcium
carbonate ~iller is used than would be economically
desirable.
Another procedure established to measure calcium
carbonate filler performance is the Processing Stability
Index. In this test a calcium carbonate filler sample
is divided into two portions. Each portion is
preconditioned in a constant relative humidity chamber
for 24 hours at 50~ relative humidity and 75% relative
humidity, respectively. Each filler portion is
compounded at 190 phr into a OCF4297-5 polyester resin
as described a~ove. After a 30-minute increment, the
viscosity is measured. The difference between the 75
RH viscosity (V7$)and the 50% RH viscosity (V50) is
divided by the 50% RH viscosity and then multiplied by
100 to be expressed as a percent.
~0 X 100 = PSI%
V50
The significance of this Processing Stability Index
25 i5 that it measures the susceptibility of the calclum
~arbonate filler t~ vary the paste ~iscoslty as the
- 16 -
~ 4
r~lative humidity of the storage environment changes. Afiller with a lower Processing Stability Index will
effect a significant improvement ln the manu~acturing of
polyester molding compounds during periods of c~anging
climatic conditions.
In order to compare calcium carbonate fillers of
the present invention with those of the prior art a
series of representative samples of available calcium
carbonate fillers were obtained. The chemical
composition of various ~alcium carbonate ores was
determined by standard ASTM ~ethods used in the mineral
filler industry and the results are set forth in Table
I, below. Unless otherwise specified all percentages
are percentages by weight.
TABLE I
Acid Silica,
Ore Type CaC03,% MgCo3,~ Insol,% %
Maryland Marble 91.0 6.6 2.3 0.8
Alabama Marble 96.4 2.1 1.2 0.98
20English Chalk 97.4 1.0 1.5 0.68
French orgon
Limestone 98.7 0.43 0.16 n . 02
Jamaican Micrite
Limestone 99. 4 0.41 0.17 0.02
Haitian Micrite
L}mestone 99.6 o 30 o.oo 0.04
Dominican Rep.
Micrite LLmestone 99.4 0.43 0 16 0.00
20365~7
In comparing the calcium carbonate ores from which
the fillers are made, it may be seen that the micrite
limestone o~ the present in~ention has a very high
calcium carbonate content with very low impurities of
magnesium, silica and acid insoluble material, Only the
very high purity French orgon limestone approaches the
purity of the micritic limestone. It should be noted
that marble ore, which is the source o~ most
commercially available calcium carbonate fillers, has
significantly higher impurities.
Class I fillers made according to the present
invention, Examples 1 and 3, were compared to
commercially available Class I fillers of the prior art.
Similarly, Class II fillers made according to the
present invention, Examples 2 and 4, were compare~ to
Class II fillers of the prior art. Particle size was
determined by Quantachrome Microscan analyzer and
moisture content, measured after coming to e~uili~rium
in a controlled relative humidity cabinet, was
determined by a Carl-Fischer moisture analyzer.
The prior art ~lass I fillers evaluated were as
follows;
SNOWCAL 60, a dry ground ~nglish chalk available
from Rlue Circle Company;
* Trade Mark
2036597
-
CAMELWITE, a wet ground high purity marble
available from Genstar Corporation of Texas, Maryland;
and
MILLICARB, a wet ground high purity Orgon limestone
available from Pluess-Stauffer of Paris,France.
Of the above Calss I fillers, SNOWCAL 60 is
generally not acceptable to the polyester molding
compound industry.
The prior art Class II fillers compared were as
follows:
CAMEL-FIL, a wet ground high purity marble,
CAMEL-CARB, a dry ground high purity marble, and
CAMEL-TEX, a dry ground high purity marhle, all
available from Genstar Corp. of Texas, Maryland;
GAMA PLUS, a dry ground high purity marble,
CALWHITE II, a wet ground high purity marble, both
available from Georgia Marble of Atlanta, Georgia
SNOWFLAKE, a wet ground, high purity marble
available from Engish China Clay of Atlanta, Georgia;
OMYA BL, a wet ground, high purity Orgon limestone
available from Pluess-Stauffer of Paris, France
Of the above Class II fillers, only OMYA BL,
SNOWFLAKE, CALWHITE II, and CAMEL-FIL are generally
acceptable to the polyester molding industry. Physical
properties of these fillers, along with Examples l, 2,
and 4 were determined and results are set forth in
Tables 2 and 3.
* Trade Marks
,.
2036597
TABLE 2
Class I Fillers
Median Particle Moisture Content, %
Filler Size, % 50% R.H. 75% R.H.
Example 1 3.0 .0S% .073%
MILLICARE~ 2 . 8 . 0896 .144
SNOWCAL 60 2 . 8 . 09% .17%
CAMEL-WITE 2 .7 .11% .131%
MICROCARB 5 2 . 4 . 26% . 32%
TABI.E; 3
Class II Fillers
Median Equilibrium
Particle Moisture Content, %
Filler Size, Microns 50% R.H.75% R.H.
Example 2 6.6 .04% .06%
~xample 4 7.8 .03% .05%
OMYA BL 5 . 4 ~ 05% - 07%
CAMEL-FIL 6 . 6 . 06% . Os%
SNOWFLARE 5.0 .04% .09%
CALWHITE II 6.4 .04~ .09%
*
C~MEL-CARB 9.O .05% .10%
CAMEL-TEX 5.4 .09% .13%
GAMA P~AS 7.1 . 06% .10%
Trade Marks
-- 20 --
20 ~6~
It may be seen by looking at the equili~rium
moisture content at 50% and 75~ relati~e humidity,
respectively, that the dry ground English chalk and the
dry-ground marbles pick up substantially more mQisture
than the other fillers and for this reason are not
a~cepted by industry as desirable for use in high
loading polyester molding compound applicatio~s.
The Standard ~O-Minute Vis~osity and the Pro~essing
Stability Index were determined according to the methods
lo previously described and set forth in Table 4 and 5.
TABLE 4
Pro~ec.c;n~ St~h;l;ty Tn~;~ec for Various Class I Fillers
30 Min. Yiscosity, MMcps
Filler 50% R.H. 75% R.H. PSI%
Example 1 .131 .173 32
*
MIILIC~RB . 211 . 640 203
C~MEL-WITE . 240 1.18 392
SNOWCAL 60 . 544 ~ . 20 488
* Trade Marks
.~
.~
203659'7
TABLE 5
Pr~rç?~:-ci n~ Stability TnAi r~: of Variou~; Class II Fillers
30 Min. Viscosity, ~Mcps
Filler 5~)96 R.H.7~% R.H. PSI%
Es~ample 4 . 036 . 038 5 . 5
Example 2 . 054 . 056 3 . 7
CAMEL-CARB . û85 . 099 19 . 3
SNOWFLA~ . 0 48 . 07 3 5 2 . 1
CAMEL-TEX . 115 . 147 27 . 8
OMYA Bl. . 074 lol 36 .
*
GAMA PI,AS . 0 8 5 . 112 3d~ . 9
CAMEL-FIL . 066 110 66 . 7
In order to illustrate the resin paste viscosity
increase found in a typical SMC molding formulation,
~xample 4, a Class II filler made from Haitian micritic
limestone as described previously, was compared to
* ~
SNOWFLAKE and CAM~L-FIL calcium carbonate Class II
fillers of the prior art. These fillers were
preconditioned at 20%, 70% and 90% respectively and 235
zO
phr filler was compounded into an unsaturated polyester
resin sold under the name OCF ATRYL availa~le from
owens-Corning Fiberglass of Granville, Ohio. The
viscosity of each sample was measured periodically and
the results set forth in Table 6.
2~
* Trade Marks
- 22 -
2~5~7
TABLE 6
Effect o$ Filler Pre-Conditioning
Class II Filler on SMC Thickpnin~
(OCF Atryl Resin, 235 prh)
~reconditioned
at RelatiYe ~ille~ snc Paste Visc~sity, H cps
Hwu~ti~ Mo~t~e, % Init. 30H~. 60~n. 24 ~.
SNOWFLA~ 0 . 07 44 86 120785
7Q .11 46.8 104194 1,008
. 13 61 201 3365,400
CAMEL-FIL 20 .06 41 72 1~5825
.11 42.4 101190 1,016
. 14 54 230 3846,800
Ex~e 2 20 .04 37 46 59214
. 06 37 48 61256
. 08 38 48 64368
It may be seen that the rate of resin paste viscosity
increase with time using the filler of the present
invention is much less pronounced and less subject to
variation with changes in the relative humidity of the
environment. Accordingly, it is believed that the
filler content of this resin paste system could be
increased by 5 - 10~ without the early viscosity of the
paste detrimentally effecting the wetting of the glass
fibers in an SMC compound. Further an adequate saf ety
margin to compensate for variations in relative
humidity would be provided even at these higher filler
loading levels.
* Trade Marks
_ 23 -
203~597
In order to compare composites made ~y the
polyester molding compound of the present invention with
prior art composites, test composite panels were made
using Example 2, a Class II filler of the present
invention. Chosen as a comparison composite was
CALWHITE II in a structured SMC resin system
manufactured by Ashland Chemical Company of Dublin,
Ohio. Upon evaluation using standard techniques of the
industry, it was observed that the composite using
Example 2, the filler of the present invention, attained
a lower initial thickening, comparable ultimate
thickening, comparable shrinkage, a 34~ improvement in
surface ~uality, a 35% Lmprovement in tensile strength,
a 18~ improvement in modulus, a slightly improved
flexual strength and an improvement in izod impact
toughness of 48~. Accordingly, it may be seen that the
filler of the present invention met or exceeded the
performance ~haracteristics of the more energy intensive
typical wet ground sample of the prior art.
In order to more fully compare the filler of the
present invention to prior art fillers, Examples 1 and 3
were compared with another Class. I and Class II filler-
in a PHASE ALPHA resin system of Ashland Chemical
Corporation of Dublin, Ohio. The results are set forth
in Table 7.
* Trade Marks
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2036597
TABLE 7
Effect of Filler on Physical Properties of C~c~tes
Class I Class II
Example l Example 4
vs. CAMEL-WITE vs. SNOWF~AKE
LOADING +15% +10%
Tensile Str. (psi) +26% +13.6%
Tensile Mod. (psi~ +10.7~ +33%
% Elongation +15.6% -7.0%
Flex Str. (psi) +18.4% +13.1%
Flex Modulus (psi) +4% +1%
IZOD:
Notched (ft-lb/in) +8.6% -4.9%
Unnotched (ft-lb/in~ +22.1% +l9.9%
It may be seen that substantial increase in filler
loading was attained using Examples l and 2 without
reduction in composite performance.
In order to further compare the present invention
with calcium carbonate fillers of the prior art in BMC
composite applications, a bulk molding compound
composite was made by mixi~g l00 phr OCF4297-5 polyester
resin with 0.5 MAGLITE A, l.5 phr TBPB, and 5 phr zinc
stearate and a specified amount of filler, for two
minutes in a high speed cowles dissolver. After cooling
the paste below 90~F, the paste was poured into a
slow-speed sigma blade mixer along with sufficient ll4''
chopped fiberglass to give a nominal 20% glass content
* Trade Marks ~
2036~57
and mixed for a further tw~
minutes. After sitting for 24 hours the compound was
injection molded at 300~F to produce final composites
for testing. The data are set forth in Ta~le 8 ~elow.
TABLE 8
Izod Impact Data on BMC ~ Y;tes
~OCF 4297-5 Re~; n )
L~g P~e Notch~ U~wt~d T~e
Filler phrVi~cosityIltlpact, ft/l~ Impa~t. ft/lb (p~i)
CAMEL-WITE 17664,000 4.57 6.01 5.05
Example 1 18036,8~0 6.25 8.07 4.78
SNOWFLAKE 20064 ,000 4 .11 4 .18 4 . S2
CAMEL-FIL 20054,400 3.89 4.61 3.92
HUBERCARB W4 200 44,800 4.77 5.51 4.35
Example 2 20044,000 5.17 6.18 3.72
Example 4 20038,400 5.77 5.58 3.09
( Haitian )
Accordingly it is seen that composites using the
Examples of the present invention obtain substantial
improvements in physical properties at similar loading
levels as o~tained using conventional wet ground calcium
carbonate fillers.
* Trade Mark~
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