Note: Descriptions are shown in the official language in which they were submitted.
1085~83
BACKGROUND 0~ INVENTION
; This invention relates to thermoplastic molding
composition having an advantageous combination of charac-
teristics not readily attainable from competitive materials.
Heretofore prior technologists have established
that most thermoplastic polymers are insoluble in other
thermoplastic polymers. Most attempts to mix pellets of
different molding pellets at the time they are fed to an
extruder lead to extrudates having fracture lines at the
boundaries amongst the different compositions. Plastic
"alloys" which contain a plurality of thermoplastic composi-
tions have been discovered, but represent a minority of the
theoretical number of possible mixtures. As greater know-
ledge of attractive compatibilities of blends has accumulated
through the decades, some basis has evolved for selecting
plausible fields for research on thermoplastic blends.
Because incompatibility remains the dominating rule, any
` discovery of a useful blend of different thermoplastics
represents a pragmatic invention which could not have been
` 20 predicted on the basis of previous publications.
Example 7 of Elghani et al 3,882,192 describes a -
thermoplastic molding composition blended from 40 parts of
polycarbonates of a dihydric phenol and a derivative of
carbonic acid, 35 parts of polyvinylchloride, and 25 parts
of a copolymer of styrene and maleic anhydride (88:12 molar
ratio) having a Vicat temperature of 110C.
Maleimide, N-methyl maleimide, maleic diamide,
bis(N-methyl) maleic diamide, and related compounds have
been studied by scholars but have not been employed to a
significant extent in the production of copolymers, except
in research projects. Outstandingly advantageous properties
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have been discovered for copolymers of styrene and such
compounds, conveniently designated as styrene-maleimide
; copolymers. Notwithstanding the superior characteristics
of such styrene-maleimide copolymers, the market for such
" copolymers has been small enough that it has been efficient
to produce such copolymers by copolymerizing styrene and
maleic anhydride and thereafter treating the copolymer with
methyl amine or ammonia to obtain such styrene-maleimide
copolymers. DiGiulio 3,998,907 describes a method of pre-
paring maleimide-containing copolymers by reacting amine or
.. . .
,~ ammonia with particles of the copolymer comprising maleic
anhydride under autogenous pressure at 125 to 200 C.
,...
~ Notwithstanding the abundance of literature perti-
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' nent to polycarbonates and blends comprising polycarbonates,
there continued to be a persistent demand for a polycarbonate
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I blend suitable for molding items at a convenient temperature,
,' and a failure by others to meet such demand satisfactorily.
" SUMMARY OF INVENTION
In accordance with the present invention, an
advantageous thermoplastic composition is prepared by heat
; blending polycarbonate and the imino derivative of styrene-
` maleic anhydride, each thermoplastic component being present
^ in a concentration within the range from 10% to 90~.
;,.
The invention is further clarified by reference
to a plurality of examples.
Examples 1-3
A series of samples were prepared by melting
plastic pellets in an extruder, mixing much more thoroughly
in the extruder than is conventional, whereby a complete
blending of the thermoplastic materials was achieved, and
then extruding the thoroughly mixed thermoplastic compositions.
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Composition A was a polycarbonate prepared from
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the high molecular weight carbonate ester derivative of
bis(4 hydroxyphenyl)-2,-2-propane.
Composition B was a copolymer of styrene and about
8% maleimide prepared by the method of Example 1 of DiGiulio
3,998,907, using aqueous ammonia at a temperature of about
147C. for about 12 hours at a pressure of about 5 atm~s-
pheres.
Compositions C, D, and E were blends containing
25%, 50% and 75% respectively of styrene-maleimide (8%)
~j copolymer (Composition B) and the balance polycarbonate
~ (Composition A).
rl Data relating to the controls and examples are
shown in Table 1.
Table 1 -~
Control Example Control
JJ 1 2 3l K
Code composition A B
% polycarbonate100 75 50 25
% styrene-maleimide 0 255 50 75 100
Z~ 20
{, Tensile yield psi8,300 9,100 NA NA NA -~
Tensile break psi10,000 7,600 8,500 6,800 7,600
Tensile elong psi270 54 2.3 1.5 1.8
Modulus (105 psi)3.3 4.0 4.5 4.7 5.4
Flexure mod51us3.1 3.8 4.1 4.5 4.7
.' (10 pSi)
; Flexural break (psi) NA NA NA 13,300 13,000
Izod (ft lb/in)9.2 o.6 0-5 0.2 0.2
Vicat (F) 310 296 287 - 268 265
Said data establish that the transparent macromole- -
cular organic alloy has a high heat resistance and a highly
advantageous superior stiffness to that of polycarbonate.
Moreover, styrene-maleimide resin is less costly than
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1C~85~83
polycarbonate, whereby some of the advantages of polycarbon-
.,
ates can be utilized in the production of articles sold at
a price significantly below the price at which a molded pure
polycarbonate article would be expected to sell.
Example 4
Compositions are prepared from thermoplasticly
blended polycarbonates and styrene-maleimide using concen-
trations of polycarbonate within the 9-25% range, showing
many of the advantages of the 25% blend. Compositions are
prepared from thermoplastically blended polycarbonates and
styrene-maleimide concentrations of styrene-maleimide within
the 9-25% range, showing many of the advantages of the 25%
blend.
Example 5
Blends of 50~ polyphenylenecarbonate and 50% co-
polymer of styrene-maleimide containing about 8% maleimide
are prepared by preparing solutions of components in halo-
genated organic solvent, mixing such solutions, volatilizing
the solvents, and extruding the thus precipitated mixture.
A basis is thus established for the conclusion that the
advantageous results of Example 2 are attributable to the
advantageous alloying propensities of the components and
not primarily to the method of blending.
Example 6
Blends of polycarbonate and styrene-maleimide are
prepared throughout the 10 to 90% and 90 to 10% ranges,
using a series of styrene-maleimide copolymers. It is thus
established that the method of preparing the maleimide, the
use of ammonia, a lower alkyl primary amine, or mixtures
thereof, does not jeopardize the attainment of advantageous
results. The minimum amount of maleimide in the copolymer
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must be at least 5~, and lesser amounts fail to impart to
the blends the stiffness which characterize the blends of
the present invention. The maximum amount of maleimide in
the copolymer must not be greater than 35~ because the
extrudability of the hot mix is impaired by excessive con-
centrations of the maleimide. Some association of the ;~
, imide group of the copolymer chain and the carbonate group
of the polycarbonate chain is indicated as a synergistic
i~ advantage of the unique alloys of the present invention.
Example 7
;~ Blends of polycarbonate and styrene-maleimide
are prepared throughout the 10 to 90~ and 90 to 10~ ranges,
using a series of polycarbonates. Satis~actory results are
obtained only with polycarbonates which are predominantly
aromatic. Polycarbonates derived from hydroquinone, bis
4-hydroxy diphenylmethane, 2,6-dimethyl hydroquinone, and
other types of phenylene carbonate polymers are established
as useful polycarbonates for the advantageous blends of the
present invention.
Various modifications of the invention are possi-
ble without departn~ng from the scope of the invention as set
forth in the claims.
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