Note: Descriptions are shown in the official language in which they were submitted.
Mo-1843
POLYBUTYLENE TEREPHTHALATE/T~ERMOPLASTIC
POLYURETHANE MOLDING COMPOSITIONS
_
FIELD OP TH _ VENTIO
This invention relates to polymer blends and more
particularly to molding compositions comprising intimate
blends of polybutylene terephthalate and thermoplastic
polyurethanes.
BACKGROUND OF THE INVENTION
Thermoplastic polyurethanes have found utility in
many molding appllcations where good tensile strength,
tensile modulus, good ductility and elongation properties
are required. Molded articles of thermoplastic poly-
urethanes have, therefore, found considerable use and
success in the automobile industry, in the shoe industry,
in the electrical industry and in the mechanical equipment
industry, such as for pump stators, pump impellers and
gasket materials. ~owever, it has been found that thermo-
plastic polyurethanes may lack the requisite hardness
properties required in various applications for parts or
articles molded from these polymers.
Polybutylene terephthalate has been commercially
available since about 1970 and has recently found extensive
use in various molding applications due to its excellent
processibility, excellent resistance to chemicals and solvents,
excellent hardness, low coefficient of friction and wear
resistance, high heat distortion temperature, low water
absorptio~ and excellent electrical properties. The
combination of these interesting mechànical, thermal,
electrical and processibility properties make polybutylene
Mo-1843
terephthalate an attractive polymer for mokling applications.
However, it has been found that po1ybutylene terephthalate
may lack the necessary ductility properties (drop dart
impact prope~ti(C;) re(luired in various app~ications ~or
parts or articlcs molded fronl this polymer.
In accordance with tile present invention, molding
compositions comprising intimate blends of polybutylene
terephthalate and thermoplastic polyurethanes are provided
which exhibit overall physical properties superior to the
properties exhibited by either polymer individually.
Specifically, the ductility properties,of polybutylene
terephthalate are improved by intimately blending with an
effective amount of thermoplastic polyurethane, and the
hardness properties of a thermoplastic polyurethane are
improvecl by intimate blending with an effective a~ount of
polybutylene terephthalate.
SU~RY OF THE INVENTION
The present invention is directed to molding
compositions comprising intimate blends of polybutylene
terephthalate and thermoplastic polyurethane.
DET~ILED DESCRI~TION OF THE INVENTION
The thermoplastic polyurethanes of the invention
are those generally prepared from a diisocyanate, a polyester
or polyether and a chain extender. These thermoplastic poly-
urethanes are substantially linear and maintain thermoplastic
processing characteris-tics.
The thermoplastic polyurethanes may be synthesized
by methods disclosed in U. S. ~atent 3,214,411.
Mo-1843 - 2 -
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.
A particularly useful polyester resin
which may be used as a startincl material for the thermoplastic
polyurethanes is produced from adipic acid and a glycol having
at least one primary hydroxyl ~rou~. The aclipic acid is
condensed with a suitable glycol or mixture of glycols
which have at least one primary hydroxyl group. The
condensation is stopped when an acid number of from about 0.5
to about 2.0 is reached. The water formed durin~ the reaction
is removed simultaneously therewith or subsequently thereto
so that the final water content is from about 0.01 to about
0.02~, preferably from about 0.01 to O.OS%.
~ny suitable glycol may be used in reaction with the
adipic acid such as, for example, ethylene glycol, propylene
glycol, butylene glycol, hexanediol, bis-(hydroxymethylcyclo-
hexane), 1,4-butanediol, diethylene glycol, 2,2-dimethyl
propylene glyco', l,3-propylene glycol and the like. In
addition to the glycols, a small amQunt of trihydric alcohol,
up to about l~,may be used along with the glycols such as,
for example, trimethylolpropane, glycerine, hexanetriol and
the like. The resulting hydroxyl polyester may have a
molecular weight of at least about 600, a hydroxyl number of
about 25 to about 190 and preferably between about 40 and about
60, an acid number of between about 0.5 and about 2 and a
water content of about 0.01 to about 0.2~.
The organic diisocyanate to be used in the
preparation of the elastomer is preferably 4,4'-diphenyl-
methane diisocyanate. It is desired that the 4,4'-diphenyl-
methane diisocyanate contain less than about 5% of 2,4'-
diphenylmethane diisocyanate and less than about 2% of the
dimer of diphenylmethane diisocyanate. It is furthe- desired
Mo-1843 ~ 3
B
... ...... ........ . ..
that the acidity calculated as HCl be ~rom about 0.~001 to
~.2%. The acidity calculated as percent HCl is determined by
extracting the chloride from the isocyanate in a hot a~ueous
meth.anol solution or by liberating the chloride on hydrolysis
with water and titrating the extract with a standard silver
nitrate solution to obtain the chloride ion concentration
present.
Other diisocyanates may be used in preparing the
thermoplastic polyurethanes such as ethylene diisocyanate,
ethylidene diisocyanate, propylene diisocyanate, butylene
diisocyanate, cyclopentylene-1,3-diisocyanate, cyclohexylene- :
1,4-diisocyanate, cyclohexylene-1.,2-diisocyanate, 2,4-tolylene
diisocyanate, 2,6-tolylene diisocyanate, 2,2-diphenylpropane-
4,4'-diisocyanate, p-phenylene diisocyanate, m-phenylene
diisocyanate, xylylene diisocyanate, 1,4-napthylene diisocyan-
ate, l,S-naphthylene diisocyanate, diphenyl-4,4'-diisocyanate,
azobenzene-4,4'-diisocyanate, diphenyl sulfone-4,4'-diisocyan-
ate, dichlorohexamethylene diisocyanate, tetramethylene
diisocyanate, pentamethylene diisocyanate, hexamethylene
diisocyanate, 1-ahlorobenzene-2,4-diisocyanate, furfurylidene
diisocyanate and the like.
Any suitable chain extending agent having active
hydrogen containing groups reactive with isocyanate groups
may be used such as, for example, diols including ethylene
glycol, propylene glycol, butylene glycol, 1,4-butanediol,
butenediol, bytynediol, xylylene glycols, amylene glycols,
1,4-phenylene-bis-~-hydroxy ethyl ether, 1,3-phenylene-bis-
~-hydroxy ethyl ether, bis-(hydroxy-methyl-cyclohexane),
hexanediol, thiodiglycol and the like; diamines including
ethylene diamine, propylene diamine, butylene diamine,
Mo-1843 ~ 4 ~
hexametllyl~ne diamine, cyclohexalene diamine, phenylene
diamine, tolylene diamine, xylylene diamine, 3,3'-dichloro-
benzidine, 3,3'-dinitrobenzidine and the like; alkanol amines
such as, for example, ethanol amine, aminopropyl alcohol,
2,2-dimethyl propanol amine, 3-aminocyclohexyl alcohol,
p-aminobenzyl alcohol and the like. The difunctional chain
extenders mentioned in U. S. Patents 2,620,516, 2,621,166
and 2,729,618 may be
used. If desirable, a small amount of polyfunctional material
may be utilized. This polyfunctional chain extender, however,
should not be present in an amount grea~ter than about 1~ by
weight. Any suitable polyfunctional compound may be used in
this application such as, for example, glycerine, trimethylol-
propane, hexanetriol, pentaerythritol and the like.
The polyester, the organic diisocyanate and the chain
extender may be individually heated preferably to a temperature
of from about 60C. to about 135 and then the polyester and
chain extender may be substantially simultaneously mixed
with the diisocyanate. Preferably, the chain extender and
the polyester, each of which has been previously heated, are
first mixed and the resulting mixture is mixed with the
heated diisocyanate. This method is preferred for the reason
that the extender and the polyester will not react prior to
the introduction of diisocyanate and rapid mixing with the
diisocyanate is thus facilitated.
The mixing of the polyester, the chain extender and
diisocyanate may be suitably carried out by using any
mechanical mixer such as one equipped with a stirrer which
results in intimate mixing of the three ingredients in a
short period of time. If the material begins to become too
Mo-1843 - 5 -
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' ' ' ': ' ' ' ' ' ' :
thick, either the temperature may be lowere(l or a small amount
of citric acid or the like of from about 0.00l to 0.050 parts
by weight based on 100 parts of the polyester may be added
to slow down the reaction. Of course, to increase the rate
of reaction, any suitable catalyst may be added to the
reaction mixture such as tertiary amines and the like as set
forth in U. S. Patent Nos. 2,620,516, 2,621,166 and 2,729,618.
Additional processing techniques for the production of
thermoplastic polyurethanes useful in the present invention
are disclosed in the text Polyurethanes: Chemistry and
Technology, Vol. II, pages 299 - 452, by J. H. Saunders and
K. C. Frisch, Interscience Publishers, New York 1964 and in
the pamphlet ~ Processing Handbook for Texin Urethane Elasto-
plastic Materials, Mobay Chemical Corporation, Pittsburgh, PA.
Although adipate polyesters are preferred in producing
suitable thermoplastic polyurethanes, polyesters may be used
which are based on succinic acid, suberic acid, sebacic acid,
oxalic acidl methyl adipic acid, glutaric acid, pimelic
acid, azelaic acid, phthalic acid, tereL)hthalic acid, iso-
phthalic acid and the like.
Suitable po].yesters for the production of the thermo-
plastic polyurethanes also include those based on polymeriza-
tion products of lactones, for example caprolactones.
A polyether may be used instead of the polyester in
the preparation~of the thermoplastic polyurethane, preferably
polytetramethylene glycol, having an average molecular
: welght between about 600 and 2000 and preferably about 1000.
Other polyethers such as polypropylene glycol, polyethylene
glycol and thelike may be used providing their molecular
weight is above about 600.
Mo-1843
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The above and other thermoplastic polyurethanes
such as disclosed in U. S. Patents 2,621,166, 2,729,618,
3,214,411, 2,778,810; Canadian Patents 754,233, 733,577 and
842,325 may be used
to produce thermoplastic polyurethanes which can be intimately
blended with the polybutylene terephthalate.
"Thermoplastic polyurethane" as used herein means
block polymers prepared from a diisocyanate, a polyester
or polyether, and a chain extender and are processable by all
the standard techniques of compression or injection molding
or extrusion.
The polybutylene terephthalate polymers used in the
practice of the invention are those characterized by the
repeating structural formula:
H20C ~ CO ~
Generally, polybutylene terephthalate is produced by
the transesterification of dimethylterephthalate and 1,4-
butanediol or by the direct esterification of terephthalic
~ ,
acid and l,4-butanediol. Such processes are described in
2Q ~ U. S. Patent Nos. 2,647,885; 2,643,989; 2,534,028; 2,578,660;
2,742,494 and 2,901,466.
: .
Mo-1843 ~ 7 ~
B
.
.;.
Polybutylene terephthalates suitable in the invention
also include modified polybu~ylene terephthalates wherein the
diol component used to produce the polymer comprises at least
abc,ut 75 mol ~ of 1,4-butanediol, based on the total mols of
dic,l component used, and the dicarboxylic acid component or
corresponding dialkyl (preferably Cl-C6) ester component used
to produce the polymer comprises at least about 75 mol %
of terephthalic acid or dialkyl terephthalate, respectively,
based on the total mols of dicarboxylic acid component or
corresponding dialkyl ester component used. Thus, up to
about 25 mol ~ of diols other than 1,4-butanediol and up to
about 25 mol % of dicarboxylic acids or corresponding
dialkyl esters other than terephthalic acid or the corresponding
dialkyl terephthalates may be used.
E~amples of suitable diols other than 1,4-butanediol
that may be used include ethylene glycol, 1,3-propanediol,
2,2-dimethyl-1,3-propanediol,1,5-pentanediol and 1,6-hexane-
diol. Examples of suitable dicarboxylic acids-and corresponding
dialkyl esters other than terephthalic acid and the corres-
ponding dialkyl terephthalates that may be used include
aliphatic, cycloaliphatic and aromatic dicarboxylic acids such
as succinic acid, glutaric acid, adipic acid, pimetic acid,
suberic acid, azelaic acid, sebacic acid, 1,4-cyclohexane-
dicarboxylic acid, isophthalic acid, 1,5- and 1,6-naphthalene-
dicarboxylic acid, 4,4'-, 4,3'- and 3,3'-diphenyl-dicarboxylic
acid and 4,4'-, 4,3'- and 3,3'-diphenylsulphonedicarboxylic
acid, and the corresponding dialkyl esters produced from such
acids.
Preferably, the polybutylene terephthalates and
modified polybutylene terephthalates have an intrinsic
viscosity of about 0.5 to 1.5 and more preferably about 0.7
Mo-1843 - 8 -
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,
to 1.3 measured at 25C as a 0.1% solution in a 60/40 volume-
tric mixture of phenol/tetrachloroethane.
The thermoplastic polyurethane may be homogeneously
blended with the polybutylene terephthalate by melt homo-
genlzation, extrusion or a like method for intimately mixingthermoplastic polymers.
After the thermoplastic polyurethane has been
intimately blended with the polybutylene terephthalate,
it can be molded by injection molding techniques or other
techniques known to those skilled in the art.
During the blending process, it is also possible to
admix additives such as pigments, stabilizers, flame
retardants, flow agents, lubricants, antistatic agents and
mold release agents in a known manner.
In a preferred embodiment of the present in~ention,
the molding compositions comprise an intimate blend of
5-95% by weight of a polybutylene terephthalate with
95-5% by weight of a thermoplastic polyurethane, based on
the total weight of the molding composition.
In a more preferred embodiment of the present
invention, the molding compositions comprise an intimate blend
of thermoplastic polyurethane with an effective amount of
polybutylene terephthalate to improve the hardness properties
of the thermoplastic polyurethane. In general, 5 to 30%
by weight of polybutylene terephthalate, based on the total
weight of the molding composition, has been found to be an
effective amount.
Mo-1843 ~ 9 ~
In a second more preferred embodiment of the present
invention, the molding compositions comprise an intimate blend
of polybutylene terephthalate with an effective amount of
thexmoplastic polyurethane to improve the ductility properties
of the polybutylene terephthalate. In general 5 to 30~ by
weight of thermoplastic polyurethane, based on the total
weight of the molding composition, has been found to be an
effective amount.
The invention will be further illustrated by the
following examples.
:
.
Mo-1843 - lO -
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.
EXAMPLES
The following thermoplastic polyurethanes were
used in the examples:
POLYURETHANE A
This thermop~astic polyurethane was prepared by
reacting butylene adipate (MW of 2000), 1,4-butanediol and
methylene di-para-phenylene diisocyanate (MDI).
POLYURETHANE B
This thermoplastic polyurethane was prepared by
reacting butylene adipate (MW of 2000), ethylene glycol
and methylene di~para-phenylene diisocyanate (MDI).
POLYURETHANE C
This thermoplastic polyurethane was prepared by
reacting butylene adipate (MW of 2000), para-phenylene-di
(~-oxyethylether) and methylene di-para~phenylene diisocyanate.
EXAMPLE 1
- 100 parts by weight of thermoplastic Polyurethane A
were extruded and then cut into 1/8" X 1/8" granules. The
granules were then molded into test specimens. The properties
~20 of this molding composition are reported in Tables 1 and 2.
EXAMPLE 2
85 parts by weight of thermoplastic Polyurethane A
were intimately blended with 15 parts by weight of a polybutylene
terephthalate having an intrinsic visc06ity of about 0.80 in
a single screw laboratory extruder. The intimately blended
polymers were cut into 1/8" X 1/8" granules and molded into
Mo-1843 - 11 -
: . -
test specimens. The properties of this molding composition
are reported in Tables 1 and 2.
EX~PLES 3-26
These examples were conducted in a manner similar
to that of Examples 1 and 2 except for the fact that various
thermoplastic polyurethanes and polybutylene terephthalates
of various intrinsic viscosities were used. The properties
of these compositions are reported in Tables 1 and 2.
Mo-1843 - 12 -
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Mo-1843 - 16 -
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LEGEND FOR TABLES 1 AND 2
. .
ASTM D-412: Unless otherwise noted, ASTM "D" dumb-
bells (.125" wide) die cut from 0.80" thick slabs
were used and were tested at 20"/minute.
~ ASTM D-2240 -
Drop dart impact strength was measured by dropping
a 10.5 lb. weight with a contact surface of a 1"
diameter hemisphere upon a 0.10" thick, 4" diameter,
securely clamped, molded specimen. The drop height
corresponding to a 50% breakage of the specimen is
proportional to the impact resistance of the test
specimen.
ASTM D-256
~ ASTM D-256: With the notched samples struck on the
unnotched (i.e.,"reverse") side.
These molding compositions were molded into dumbbells
0.263" wide and 0.127" thick due to their hardness.
These molding materials were tested at 2"/minute due
to their plastic-like nature.
~ These molding materials were molded into dumbbells
0.500" wide and 0.125" thick and were tested at 2"/
minute.
B = break
NB = no break
~ PBT = polybutylene terephthalate
Mo-1843 - 17 -
, ~ , : -.: ' . , ' . - , -
,,': -. , ' ' ' '' ~ ' . . '. ~
~ . :
PU = thermoplastlc polyurethane
RT - room temperature
These samples yielded and necked like conventional
plastic.
:~: ::
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Mo-}843 - 18 - ~
" . : ~ ., . .
~ . . , - - ~ - .-
A review of the properties of the compositions of the
above examples reveals that the intimate blends of the thermo-
plastic polyurethanes and the various polybutylene terephtha-
lates exhibit overall physical properties superior to the
properties exhibited by either polymer individually.
Specifically, it is noted that the ductility (as represented
by drop dart impact values) of polybutylene terephthalate
i5 improved by intimately blending with thermoplastic poly-
urethanes and the hardness (as measured by Shore hardness)
of the thermoplastic polyurethanes are improved by intimately
blending with polybutylene terephthalates. Such improved
properties of the blends of the invention were unexpected
because it was in no way predictable that the blends of these
polymers would exhibit overall physical properties superior
to those exhibited by either polymer alone.
Although the invention has been described in detail
in the foregoing for the purpose of illustration, it is to
be understood that such detail is solely for that purpose
and that variations can be made therein by those skilled in
the art without departing from the spirit and scope of the
invention except as it may be limited by the claims.
' ':
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Mo-1843 - 19 -
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