Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
Field of the Invention
The invention concerns the field of reinforced
reaction lnjection molded polyurethanes (RRIM).
Description of the Prior Art
Reaction Injection Molding (RIM) is a technique for
the rapid mixing and molding of large, fast curing urethane
parts. RIM polyurethane parts are used in a variety of
exterior body applications on automobiles where their light
weight contributes to energy conservation. RIM parts are
generally made by rapidly mixing active hydrogen containing
materials with polyisocyanate and placing the mixture into a
mold where reaction proceeds. These active hydrogen
containing materials comprise a high molecular weight
polyhydric polyether and a low molecular weight active
hydrogen containing compound. The low molecular weight
active hydrogen containing compounds are ethylene glycol,
1,4-butane diol or similar materials known to those skilled
in the art.
Generally, the active hydrogen containing ma-
terials, both high and low molecular weight, are mixed
together with catalyst and other optional materials in one
tank and the polyisocyanate is contained in another tank.
When t~ese two streams are brought together in a mold, re-
action is effected, and the RIM part is m~de. In many cases,
in order to improve the strength properties of the RIM
product, a reinforcing material such as chopped or milled
glass or other mineral fibers is incorporated into the RIM
formulation by placing the inert filler material in the
unreacted components. Prior to our invention, the filler
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material has been placed in the active hydrogen containing
material side, that is, the polyol side or split between the
polyol side and the polyisocyanate side before the polyol and
the isocyanate streams are mixed together.
It has been surprisingly discovered that properties
are considerably improved if all of the inert filler material
is placed in the isocyanate side prior to reaction.
SUMMARY OF 1~ INVENTION
The invention is a method of improving certain
physical properties of inert fiber reinforced reaction
injection molded polyurethane elastomers (RRIM) made by the
reaction of two streams, one containing polyisocyanate and
one containing active hydrogen containing materials. The
method involves placing all of the inert filler material in
the isocyanate containing stream prior to mixing and reaction
with the active hydrogen containing stream and then reactins
the streams in a conventional manner.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The polyols useful in the RIM elastomers of this
invention include polyether polyols, polyester diols, triols,
tetrols, etc., having an equivalent weight of from about
1,000 to about 3,000. Those polyether polyols based on
trihydric initiators which have hydroxyl numbers ranging from
about 56 to about 24 are especially preferred. The
polyethers may be prepared from lower alkylene oxides such as
ethylene oxide, propylene oxide, butylene oxide or mixtures
of propylene, butylene and/or ethylene oxide. In order to
achieve the rapid reaction rates which are normally required
for molding RIM polyurethane elastomers, it is preferable
that the polyol be capped with enough ethylene oxide to
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increase the reaction rate of the polyurethane mixture.
Normally at least 50% primary hydroxyl is preferred, although
amounts of primary hydroxyl less than this are acceptable if
the reaction rate is rapid enough to be useful in industrial
application.
The chain-extenders useful in the process of this
invention are preferably difunctional. ~ixtures of di-
functional and trifunctional chain-extenders are also useful
in this invention. The chain-extenders useful in this
invention include diols, amino alcohols, diamines or mixtures
thereof. Low molecular weight linear diols such as 1,4-
butanediol and ethylene glycol have been found suitable for
use in this invention. Ethylene glycol is especially
preferred. Other chain-extenders including cyclic diols such
as 1,4-cyclohexane diol and ring containing diols such as
bishydroxyethylhydroquinone, amide or ester containing diols
or amino alcohols, aromatic diamines and aliphatic amines
would also be suitable as chain-extenders in the practice of
this invention.
A wide variety of aromatic polyisocyanates may be
used here. Typical aromatic polyisocyanates include p-
phenylene diisocyanate, polymethylene polyphenylisocyanate,
2,6-toluene diisocyanate, dianisidine diisocyanate, bitolylene
diisocyanate, napthalene-1,4-diisocyanate, bis(4-isocyanato-
phenyl)methane, bis(3-methyl-3-isocyantophenyl~methane, bis-
(3-methyl-4-isocyanatophenyl)methane, and 4,4'-diphenyl-
propane diisocyanate.
Other aromatic polyisocyanates used in the practice
of the invention are methylene-bridged polyphenyl
polyisocyanate mixtures which have a functionality of from
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about 2 to about 4. These latter isocyanate compounds are
generally produced by the phosgenation of corresponding
methylene bridged polyphenyl polyamines, which are con-
ventionally produced by the reaction of formaldehyde and
primary aromatic amines, such as aniline, in the presence of
hydrochloric acid and/or other acidic catalysts. Known
processes for preparing polyamines and corresponding me-
thylene-bridged polyphenyl polyisocyanates therefrom are
déscribed in the literature and in many patents, for example,
U.S. Patents 2,683,730; 2,950,263; 3,012,008; 3,344,162 and
3,362,979.
Usually methylene-bridged polyphenyl polyiso-
cyanate mixtures contain about 20 to about 100 weight percent
methylene diphenyldiisocyanate isomers, with the remainder
being polymethylene polyphenyl diisocyanates having higher
functionalities and higher molecular weights. Typical of
these are polyphenyl polyisocyanate mixtures containing about
20 to 100 weight percent methylene diphenyldiisocyanate
isomers, of which 20 to about 95 weight percent thereof is
the 4,4'-isomer with the remainder being polymethylene
polyphenyl polyisocyanates of higher molecular weight and
functionality that have an average functionality of from
about 2.1 to about 3.5. These isocyanate mixtures are known,
commercially available materials and can be prepared by the
process described in U.S. Patent, 3,362,979, issued January
9, 1968 to Floyd E. Bentley.
By far the most preferred aromatic polyisocyanate
is methylene bis(4-phenylisocyanate) or MDI. Pure MDI,
quasi- prepolymers of MDI, modified pure MDI, etc. Materials
of this type may be used to prepare suitable RIM elastomers.
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Since pure MDI is a solid and, thus, often inconvenient to
use, liquid products based on MDI are often used and are
included in the scope of the terms MDI or methylene bis(4-
phenylisocyanate) used herein. U.S. Patent 3,394,164 is an
example of a liquid MDI product. More generally uretonimine
modified pure MDI is included also. This product is made by
heating pure distilled MDI in the presence of a catalyst.
The liquid product is a mixture of pure MDI and modified MDI:
2[0CN ~ CH2 ~ NCO]
~Catalyst
O~N ~ CH2 ~ ~=C=N ~ CH2 ~ NCO + C02
C~arbodiimide
OCN ~ CH2 ~ N-C=N @ CH2 ~ NCo
O=C-N ~ CH2 ~ NCO
Uretonimine
Examples of commercial materials of this type are Upjohn's
ISONATE~125M (pure MDI) and ISONATE~143L ("liguid" MDI).
Preferably the amount of isocyanates used is the
stoichiometric amount based on all the ingredients in the
formulation or greater than the stoichiometric amount.
In one embodiment of the invention, the polyiso-
cyanate not prereacted with any active hydrogen containing
compounds such as polyols before the polyisocyanate stream
and polyol streams are mixed to form the RRIM part.
In another embodiment, the polyisocyanate stream
may comprise a quasi-prepolymer. A quasi-prepolymer is the
reaction product of a polyol with more than the
stoichiometric amount of polyisocyanate.
Catalysts can be present to accelerate the re-
action. Among those most frequently employed in this art are
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the amine catalysts and the organo methallic compounds. For
example, trimethylamine, N-methylmorpholine,
N,N,N',N'-tetramethyl-1,3-butanediamine, 1,4-
diazabicyclo[2.2.1]octane, dibutyltin dilaurate, stannous
octoate, dioctyltin diacetate, lead octoate, lead naphthe-
nate, lead oleate, etc. Also useful are other known
catalysts such as the tertiary phosphines, the alkali and
alkaline earth metal hydroxides or alkoxides, the acidic
metal salts of strong acids, salts of various metals, etc.
These catalysts are well known in the art and are employed in
catalytic quantities, for example, from 0.001 percent to
about 5 percent, based on the weight of the reaction mixture.
The RIM formulation includes a great number of
other recognized ingredients such as additional cross-
linkers, catalysts, extenders, blowing agents and the like.Blowing agents may include halogenated low-boiling hydro-
carbons, such as trichloromonofluoromethane and methylene
chloride, carbon dioxide, nitrogen, etc., used.
Other conventional formulation ingredients may
also be employed, such as, for example, foam stabilizers,
also known as silicone oils or emulsifiers. The foam
stabilizer may be an organic silane or siloxane. For ex-
ample, compounds may be used having the formula:
RSi[O-~R2SiO)n~(oxyalkylene)mR]3
wherein R is an alkyl group containing from 1 to 4 carbon
atoms; n is an integer of from 4 to 8; m is an integer of from
20 to 40; and the oxyalkylene groups are derived from
propylene oxide and ethylene oxide. See, for example, U.S.
Patent 3,194,773.
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The reinforcing materials useful in the practice of
our invention are those which are useful and known to those
skilled in the art. For example, chopped or milled glass
fibers, chopped or milled carpet fibers and/or other mineral
fibers are useful. The invention herein lies not in which
inert fiber is useful but in the method of its incorporation
in the reaction medium. That is, invention concerns placing
all of the inert fibers or fillers in the isocyanate portion
prior to reaction with the active hydrogen containing
portion.
In a particularily preferred embodiment, a 5500
molecular weight polyether polyol based on a trihydric
initiator ~hydroxyl number of about 33), ethylene glycol,
silicone fluid and catalysts are mixed and comprise the
polyol stream. The polyisocyanate stream comprises a quasi-
prepolymer of the 5500 molecular weight polyol described
above and liquid MDI. Glass fibers are placed in the
polyisocyanate stream. The polyol stream and the
polyisocyanate stream are mixed and reacted in a RRIM machine
resulting in a RRIM elastomer which is cured at 250F for
about 30 minutes.
The examples which follow exemplify the improvement
obtained by the process of the invention. However, these
examples are not intended to limit the scope of the
invention.
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GLOSSARY OF TERMS AND MATERIALS
THANOL~SF-5505 - a 5500 molecular weight polyether triol
containing approximately 80% primary hydroxyl
groups.
L5430 Silicone Oil - a silicone glycol copolymer surfactant
containing reactive hydroxyl groups. Product of
Union Carbide.
THANCAT~DMDEE - Dimorpholinodiethylether
FOMREZ~UL-29 - a stannic diester of a thiol acid. The
exact composition is unknown. Product of Witco
Chemical Co.
ISONATE~143L - pure MDI isocyanate modified so that it is
a liguid at temperatures where WDI crystallizes -
product of the Upjohn Co.
5 Quasi-prepolymer L-55-0 - A quasi-prepolymer formed by
reacting weights of Isonate 143L and THANOL SF-
5505.
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E X A M P L E
THANOL~SF-5505 (16.0 pbw.), ethylene glycol (6.44
pbw) L-5430 silicone fluid (O.20 pbw.), THANCAT~DMDEE (O.25
pbw.), FOMREZ~UL-29 (0.025 pbw.), and dibutyltin dilaurate
(0.015 pbw.) were premixed and charged into the polyol
component working tank of an Accuratio VR-100 RRIM machine.
ISONATE~143L (29.66 pbw.), L 55-0 quasi-prepolymer (5.75
pbw.) and Owens/Corning Fiberglass P 117B 1/16" milled glass
fiber (14.6 pbw.) were premixed and charged into the
isocyanate component working tank of the machine. The amount
of glass dispersed in the isocyanate component represented 20
per cent of the resulting elastomer. The isocyanate
component was adjusted to 90F and the polyol component
adjusted to 120F. The machine was adjusted so that the
isocyanate/polyol ratio was 2.18 by weight at a total
throughput of 60 lb./min.
At the above conditions, the components were
injected through the impingement mix head into an 18" x 18" x
0.125" steel mold preheated to 160F. The parts were
released in one minute. Some of the samples received no post
cure while others were post cured 30 minutes at 250F and
still others at 325F. The dimension of the parts post
treated under the three conditions were accurately measured
and compared to the dimensions of the mold. Then, after
conditioning for one week, mechanical properties were
obtained both parallel and perpendicular to the flow of glass
fiber filled components into the mold.
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E X A M P L E I I
The formulation of Example I was repeated except
that in this case, 20 per cent by weight OCF P117B 1/16l'
milled glass was added to each component (5.73 pbw in the
polyol component and 8.85 pbw. in the isocyanate component).
The filled plaques were molded under exactly the same
conditions as in Example I except that in this case, the
weight ratio of the isocyanate/polyol component was 1.544.
These were cured and tested according to the conditions
outlined in Example I.
E X A M P L E I I I
The formulation of Example I was repeated, except
that in this case, all the milled glass fiber (14.6 pbw) was
dispersed in the polyol component. The filled plaques were
molded under exactly the same conditions as Example I except
that in this case, the weight ratio of the isocyanate/polyol
components was 0.944. These were cured and tested according
to the conditions outlined in Example I.
Thus, the composition of the three elastomers de-
scribed in Examples I, II and III is exactly the same. Theonly difference among them i~ in which component or
components the glass was dispersed before reaction.
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Table I gives the properties of the three elasto-
mers. Note that all properties are best for the elastomer of
Example I where all the glass is dispersed in the Isocyanate
component. In particular, tensile strength is improved by
the practice of this invention. In Table II, the shrink-
age/expansion properties of the three elastomers as shown as
a function of annealing temperature. Note that the elastomer
of Example I is least affected by temperature. Example III,
where all the glass is dispersed in the polyol component,
displays the greatest sensitivity to temperature. In fact,
when this elastomer is annealed at 325F for 1/2 hour ~Table
II), it actually expands versus the mold size. Since it is
very desirable, that RRIM elastomers be insensitive to
temperature changes, it is clear that the elastomer of
Example I is the best.
TABLE I
Properties as a Function of the Distribution
of Glass in the Polyol and Isocyanate ~iquid Components
Example I* Example II* Example III*
Paral- Perpen- Paral- Perpen- Paral- Perpen-
Flow Directionlel dicular lel dicular lel dicular
Tensile strength,
psi 5100 4500 4500 4400 4050 3800
Elongation, ~ 42 48 28 64 30 65
25 Flexural Modulus, psi
at 77F 245000 155000 235000 150000230000 150000
Heat Sag., in.
6" overhang
1/2 hr. at 325F 0.22 0.31 0.24 0.54 0.~9 0.36
Isocyanate Index = 1.02, all parts annealed 1/2 hr. at
325F.
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TA~LE II
~.
Shrinkage/Expansion as a Function of the
Distribution of Glass in the Polyol and Isocyanate Components
Example I Example II Example III
Annealing Condition
No annealing -0.35 -0.35 -0.35
Annealed 1/2 hr.
at 250F -0-57 ~0-57 ~0 35
Annealed 1/2 hr.
at 325F -0.24 -0.13 +0.31
Shrinkage is reported as a negative (-) % and expansion is
represented as a positive (+) % versus cold steel mold
dimensions. Data is reported in the direction perpendicu-
lar to the flow direction since this is where differences
are most exaggerated.
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