Block copolymers interpolymerized with in situ polystyrene and process for preparation thereof

A process for interpolymerizing a vinyl aromatic hydrocarbon polymer and a block polymer is disclosed. The process includes the following steps: (a) forming a block polymer precursor of at least one polymeric block containing conjugated diene monomer contributed units in the presence of an anionic initiator and in an inert diluent, the block polymer precursor having living ends; and (b) thereafter adding to the block polymer precursor a charge of a vinyl aromatic hydrocarbon monomer and an additional charge of an anionic initiator to simultaneously form (1) a block polymer having a terminal block formed from the charge of vinyl aromatic hydrocarbon monomer attached to the block polymer precursor and (2) a poly(vinyl aromatic hydrocarbon) polymer interpolymedzed with the block polymer. The practice of this process produces a vinyl aromatic hydrocarbon block terminated block polymer, such as SBS, interpolymerized with a polymer formed from vinyl aromatic hydrocarbon monomer, such as polystyrene. The resultant interpolymer has a high Gardner Impact strength and good processibility.

FIELD OF THE INVENTION 
This invention relates generally to processes for incorporating polystyrene 
in block copolymers and to the compositions produced thereby. More 
specifically, the invention relates to a process for producing a vinyl 
aromatic hydrocarbon block terminated block polymer, such as SBS, 
interpolymerized with a polymer formed from vinyl aromatic hydrocarbon 
monomer contributed units, such as polystyrene; and a product having a 
substantially improved Gardner impact strength, produced by such a 
process. 
BACKGROUND OF THE INVENTION 
The prior art has long strived to improve the physical properties of 
styrenic polymers. For instance, U.S. Pat. No. 4,267,283 to Whitehead 
teaches a two-component graft copolymer composition having improved 
toughness. The first graft polymer component is disclosed as consisting 
essentially of: from about 8.0 to about 16.0 parts by weight of a mixture 
of an ABA block copolymer and an A'B'A' tapered block copolymer in a 
weight ratio of the ABA copolymer to the A'B'A' copolymer of between about 
25:75 and about 75:25. Each A segment is an essentially pure polymer block 
of styrene having a number average molecular weight of between about 
14,000 and about 18,000. Each B segment is an essentially pure polymer 
block of butadiene having a number average molecular weight of between 
about 60,000 and about 80,000; the B block having a glass transition 
temperature of about -105.degree. C.+/-5.degree. C. The weight ratio of 
total A to B being between about 1:1.8 and about 1:2.7. Each A' segment 
represents essentially polymerized styrene. The balance of the A' segment 
is polymerized butadiene. The B' segment represents essentially 
polymerized butadiene. The balance of the B' segment is polymerized 
styrene. The weight ratio of total A' to B' being from about 1:2.6 to 
about 1:3.6, the number average molecular weight of said A'B'A' block 
copolymers being between about 400,000 and about 660,000. The B' block has 
a glass transition temperature of about -90.degree. C.+/-5.degree. C. The 
second graft component consists essentially of from about 92.0 to about 
84.0 parts by weight of monomeric styrene polymerized in the presence of 
the ABA and A'B'A' copolymers. 
Similarly, U.S. Pat. No. 3,954,696 to Roest, teaches a process for the 
preparation of block copolymers of the general formula A--B--C. This 
process includes the steps of polymerizing at least one monomer to form a 
living polymer block A; adding a further monomer and continuing 
polymerization to form polymer block B bound to polymer block A, and 
continuing polymerization while adding at least one monomer to form 
terminal polymer block C, so as to produce an A--B--C block copolymer. 
Each of the polymer blocks A and C consist of either a non-elastomer 
homopolymer or copolymer having a glass transition temperature over 
25.degree. C. and a number average molecular weight between 200 and 
100,000. The polymer block B consists of a conjugated diene, derived from 
preferably 1,3-butadiene or isoprene, having a glass transition 
temperature below -10.degree. C. and a number average molecular weight 
between 25,000 and 1,000,000. The contaminants contained in the monomers 
forming blocks A and C are thereafter deactivated. As his improvement over 
the prior art, Roest includes contaminants in the conjugated diene monomer 
forming polymer block B, that have not been deactivated and that are 
capable of killing 1-50% of the living polymer block A upon introduction 
of conjugated diene monomer to the reaction mass. Each of the polymer 
blocks A and C are disclosed as consisting of a non-elastomeric polymer 
block having a glass transition point over 50.degree. C. and a number 
average molecular weight between 500 and 50,000. The polymer block B is 
disclosed as consisting of an elastomeric polymer block having a glass 
transition point below -25.degree. C. and a number average molecular 
weight between 50,000 and 500,000. At least one of polymer blocks A and C 
is derived from a monovinylaromatic hydrocarbon. 
U.S. Pat. No. 3,265,765 to Holden et al, discloses an unvulcanized 
elastomeric block copolymer having the general configuration A--B--A. 
Holden discloses that block A is an independently selected non-elastomeric 
monovinyl aromatic hydrocarbon polymer block having an average molecular 
weight of 2,000-100,000 and a glass transition temperature above about 
25.degree. C. The total block A content being 10-50% by weight of the 
copolymer. Block B is an elastomeric conjugated diene polymer block having 
an average molecular weight between about 25,000 and 1,000,000 and a glass 
transition temperature below about 10.degree. C. The copolymer is prepared 
with a lithium-based catalyst and has a tensile strength at 23.degree. C., 
in excess of about 1400 pounds per square inch. 
In yet another similar U.S. Pat. No. 3,231,635 to Holden et al, an 
unvulcanized elastomeric block copolymer having the general configuration 
A--B--A is disclosed. Block A is an independently selected non-elastomeric 
monovinyl aromatic hydrocarbon polymer block having an average molecular 
weight of 2,000-100,000 and a glass transition temperature above about 
25.degree. C. The total block A content being 10-50% by weight of the 
copolymer. Block B is an elastomeric conjugated diene polymer block having 
an average molecular weight between about 25,000 and 1,000,000 and a glass 
transition temperature below about 10.degree. C. The copolymer is prepared 
with a lithium-based catalyst and has a tensile strength at 23.degree. C., 
in excess of about 1400 pounds per square inch. 
U.S. Pat. No. 3,239,478 to Harlan, teaches an adhesive composition that 
comprises components. The first component of the composition comprises 100 
parts by weight of a block copolymer having the general configuration 
A--B--A. Each A block is an independently selected polymer block of a 
vinyl arene. The average molecular weight of each A block is between about 
5,000 and about 125,000. The B block is a polymer block of a conjugated 
diene. The average molecular weight of the B block is between about 15,000 
and about 250,000. The total of the A blocks is less than about 80% by 
weight of the copolymer. The second component of the composition comprises 
about 25-300 parts by weight of a tackifying resin. Finally, the third 
component of the composition comprises 5-200 parts by weight of an 
extender oil. The oil is substantially compatible with homopolymers of the 
conjugated diene. 
Finally, U.S. Pat. No. 3,149,182 to Porter teaches a process for preparing 
an elastomeric three component block copolymer. The copolymer comprises 
the first step of: contacting a monomer of the group consisting of 
diolefins containing from 4 to 10 carbon atoms, mono alkenyl-substituted 
aromatic hydrocarbons and mono-alkenyl-substituted pryidine compounds with 
a hydrocarbon lithium compound in an inert atmosphere and under 
substantially anhydrous conditions until the unpolymerized monomer in the 
reaction mixture is consumed. Next, without further treating the reaction, 
adding a monomer of the above group which is similar to that used in the 
initial reaction. Thereafter, continuing the polymerization under the 
above conditions until the dissimilar monomer has been polymerized. Next, 
without further treatment of the reaction mixture, adding a third monomer 
which is different from the aforementioned dissimilar monomer and selected 
from the above group of monomers. Finally, the polymerization is continued 
under the aforedescribed conditions until the third monomer has been 
completely consumed. At least one of the foregoing monomers is a diolefin. 
Despite the foregoing prior art, there nonetheless exists a long felt need 
for a process for predicably producing styrenic polymers exhibiting high 
Gardner impact strengths in excess of at least 60 ft lb/in, as well as 
such other polymers and articles produce therefrom. 
Surprisingly, the instant inventors have discovered that by merely 
manipulating the weight proportions of the respective polymers of the 
interpolymer mix, dramatic increases in the Gardner Impact Strength of the 
product may be achieved. 
Polystyrene is a well-known thermoplastic material finding a wide variety 
of uses. It is often added to polymers including block copolymers to 
increase the mold flow characteristic of the polymer, thus preventing the 
polymer from sticking to the injection molder cavity. Heretofore, 
polystyrene has been blended with block copolymers to increase the 
processability of the block copolymer. U.S. Pat. No. 4,308,358 to Miller, 
discloses a process for making high impact polystyrene comprising mixing, 
at an elevated temperature, an AB block copolymer and a styrene polymer. 
This blending process creates disadvantageous properties in the blend, 
namely the impact strength of the block copolymer is severely reduced upon 
the addition of as low as 1.5% by weight of crystal polystyrene to the 
block copolymer. While not wishing to be bound by any particular theory, 
Applicants believe that the lower impact strength resulting from the 
blending of polystyrene and block copolymer is due to the different 
molecular weights and physical properties of the components thereby 
causing phase separation to occur in the resulting product. The poor 
interphase adhesion characteristic of highly incompatible blends usually 
results in very poor mechanical properties, e.g., tensile strength, 
elongation and impact strength. 
It is therefore an object of the present invention to provide a process for 
producing an interpolymer of polystyrene and a block copolymer exhibiting 
good mechanical properties. It is a further object of this invention to 
provide polystyrene and block copolymer products exhibiting high impact 
strength. 
SUMMARY OF THE INVENTION 
In contrast to the foregoing prior art, the instant invention provides a 
process for interpolymerizing a blend of a vinyl aromatic hydrocarbon 
polymer and copolymer product is disclosed. The process includes the 
following steps: 
(a) forming in a suitable diluent a block polymer precursor having a living 
end and having at least one polymeric block containing conjugated diene 
monomer contributed units in the presence of an anionic initiator; 
(b) thereafter adding to the block polymer precursor a charge of vinyl 
aromatic hydrocarbon monomer and an additional amount of anionic initiator 
to simultaneously form (1) a block polymer having a terminal block, formed 
from the vinyl aromatic hydrocarbon monomer, attached to the block polymer 
precursor and (2) poly(vinyl aromatic hydrocarbon) interpolymerized with 
the block polymer of (1). 
The practice of this process produces a vinyl aromatic hydrocarbon block 
terminated block polymer, such as SBS, interpolymerized with a polymer 
formed from vinyl aromatic hydrocarbon monomer contributed units, such as 
polystyrene. 
Surprisingly, the instant inventors have discovered that by merely 
manipulating the weight proportions of the respective block polymer and 
polyvinyl aromatic hydrocarbon polymer of the interpolymer mix, dramatic 
increases of in excess of about 60 ft lb/in to at least about 200 ft lb/in 
of the Gardner Impact Strength of the final product may be achieved.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The process of the present invention prepares an interpolymer of (1) a 
block polymer having a precursor polymer block attached to a terminal 
block of a poly(vinyl aromatic hydrocarbon) and (2) a poly(vinyl aromatic 
hydrocarbon). The precursor polymer block of the block polymer preferably 
contains diene monomer contributed block units, and optionally contains 
vinyl aromatic monomer (VAM) contributed units including random blocks of 
butadiene and styrene (B/S). 
The block polymers to be interpolymerized in accordance with the present 
invention preferably contain conjugated diene monomers and vinyl 
substituted aromatic hydrocarbons contributed units. Polymerizable 
1,3-diene monomers that can be employed in the production of the 
copolymers of the present invention are one or more 1,3-conjugated dienes 
containing from four to twelve, inclusive, carbon atoms per molecule. 
Exemplary monomers include 1,3-butadiene; isoprene; 
2,3-dimethyl-1,3-butadiene; 1,3-pentadiene (piperylene); 
2-methyl-3-ethyl-1,3-butadiene; 3-methyl-1,3-pentadiene; 1,3-hexadiene; 
2-methyl-1,3-hexadiene; 3-butyl-1,3-octadiene; and the like. Among the 
dialkyl-1,3-butadienes, it is preferred that the alkyl groups contain from 
one to three carbon atoms. The preferred 1,3-diene monomer for use in the 
process of the present invention is 1,3-butadiene. 
Exemplary vinyl substituted aromatic hydrocarbon monomers, commonly 
referred to as vinyl aromatic hydrocarbon monomers or VAM, for use in 
either the preparation the block polymer precursor and/or the terminal 
block and the poly(vinyl aromatic hydrocarbon), include: styrene, 
alpha-methylstyrene; 1-vinylnaphthalene; 2-vinyl-naphthalene; 
1-alpha-methylvinylnaphthalene; 2-alphamethyl-vinylnaphthalene; and 
mixtures of these as well as alkyl, cycloalkyl, aryl, alkaryl and aralkyl 
derivatives thereof in which the total number of carbon atoms in the 
combined hydrocarbon is generally not greater than 12. Examples of these 
latter compounds include: 4-methylstyrene; vinyl toluene; 
3,5-diethylstyrene; 2-ethyl-4-benzylstyrene; 4-phenylstyrene; 
4-para-tolylstyrene; and 4,5-dimethyl-1-vinylnaphthalene. Occasionally, 
di- and tri-vinyl aromatic hydrocarbons are used in small amounts in 
addition with mono-vinyl aromatic hydrocarbons. The preferred vinyl 
aromatic hydrocarbon is styrene. 
The total amount of vinyl aromatic hydrocarbon monomer in the final monomer 
charge used to prepare both the terminal vinyl aromatic block and the 
interpolymerized poly(vinyl aromatic hydrocarbon) is an amount of from 6.3 
to 70.2% by weight, preferably from 28.3 to 61.7% by weight, more 
preferably from 50.6 to 57.6% by weight, based on the total weight of the 
block polymer. The weight percent of interpolymerized vinyl aromatic 
hydrocarbon polymer of the total amount of both of the terminal poly(vinyl 
aromatic hydrocarbon) block and vinyl aromatic hydrocarbon polymer is in 
the range of from 5 to 35% by weight, preferably from 9 to 26% by weight, 
more preferably from 10 to 20% by weight. These weight percentages reflect 
the percentage of monomer, such as styrene, of the final monomer charge 
that is polymerized due to the additional charge of anionic initiator to 
the reaction zone. The final monomer charge is used to prepare both the 
terminal block added onto the block polymer precursor and the 
interpolymerized poly(vinyl aromatic monomer). 
The block polymers produced according to the instant invention must 
terminate in a vinyl aromatic hydrocarbon block. The resulting structure 
of the block polymers may be linear, branched, tapered, or star as long as 
the structure has a live end. Exemplary block precursors include block 
polymers containing at least one polymeric block, a diblock polymer, 
triblock polymers and tetrablock polymers, random copolymer blocks, 
graft-copolymers blocks, block-copolymers of a conjugated diolefin and a 
vinyl aromatic hydrocarbon, and mixtures thereof. Typical examples of the 
various structures of the block polymer precursors useful in the present 
invention are as follows: 
______________________________________ 
(B--S).sub.n -- linear, 
S--(B--S).sub.n -- linear, 
B--(S--B).sub.n -- linear, 
B/S--B--S-- linear, 
[B(S)--B--B(S)--B--B(S)--B--B].sub.n -- 
branched, 
B--, S--B--, S--(B--S).sub.n --B--, (B--S).sub.n --B--, (B/S).sub.n 
--B--, 
B--(B/S).sub.n --, S--(B/S).sub.n --, and (B/S).sub.n --; 
______________________________________ 
wherein S is a polymer block primarily containing vinyl aromatic 
hydrocarbon monomer contributed units, B is a polymer block primarily 
containing conjugated diene monomer contributed units, and n is an integer 
of one or more. The rubbery diene portion of the polymer may contain some 
copolymer vinyl aromatic hydrocarbon in order to adjust the glass 
transition temperature (T.sub.g) or the solubility parameter. The block 
polymers produced in accordance with the present invention are represented 
by any of the above-discussed block polymer precursor structures 
additionally containing a terminal block formed from vinyl aromatic 
hydrocarbon contributed units. 
The process according to the present invention is performed in the 
following manner. First, any desirable block polymer precursor is prepared 
in a reactor or reaction zone by polymerizing suitable monomers, 
particularly diene monomers and/or vinyl aromatic monomers, to form one or 
more blocks in a suitable diluent in the presence of an anionic initiator. 
The resulting block polymer precursor is "living", because a catalytically 
active anion is present at the terminal end of the block polymer 
precursor. The anion is capable of initiating polymerization of further 
monomers in the reaction zone. 
After formation of the block polymer precursor, charges of additional 
anionic initiator and vinyl aromatic hydrocarbon monomer are 
simultaneously or sequentially added to the reaction zone containing the 
"living" block polymer precursor. A portion of the vinyl aromatic 
hydrocarbon monomer charge attaches to the "living" block polymer 
precursor. The additional charge of anionic initiator initiates 
polymerization of an equimolar amount the additionally charged vinyl 
aromatic hydrocarbon monomer thereby creating "living" vinyl aromatic 
hydrocarbon polymers. Thus, the additional anionic initiator is added to 
create competition for the additional charge of vinyl aromatic hydrocarbon 
monomer resulting in the simultaneous production of (1) a terminal block 
of vinyl aromatic hydrocarbon monomer contributed units attaching to the 
"living" block polymer precursor and (2) poly(vinyl aromatic hydrocarbon) 
having a living end. The resulting interpolymer is an interpolymerized 
blend of a block polymer and a poly(vinyl aromatic hydrocarbon) having 
living ends. 
The reaction mixture is then treated to inactivate the living ends and 
recover the interpolymer product. While it is to be understood that any 
suitable treating method can be employed, one method for accomplishing the 
desired treatment comprises adding a catalyst-inactivating material. 
Exemplary catalyst-inactivating materials include water, alcohol, an 
organic acid, an inorganic acid, or the like. It is generally preferred to 
add only an amount of the catalyst-inactivating material sufficient to 
deactivate the catalyst without causing precipitation of the dissolved 
polymer. It has also been found to be advantageous to add an antioxidant 
to the polymer solution prior to isolation of the polymer. After the 
addition of the catalyst-inactivating material and the antioxidant, the 
polymer present in the solution can then be precipitated by the addition 
of an excess of the catalyst-inactivating material or isolated by flashing 
the solvent. Deactivation of the catalyst and precipitation of the polymer 
can be accomplished in a single step. The precipitated polymer can then be 
recovered by filtration, delectation, or the like. In order to purify the 
polymer, the separated polymer can be redissolved in a solvent, such as 
those suitable for the polymerization, and again precipitated by the 
addition of an alcohol. Thereafter, the polymer is again recovered by a 
suitable separation means, as indicated hereinbefore, and dried. The 
solvent and alcohol can be separated, for example, by fractional 
distillation, and recycled. The antioxidant can be added to the reaction 
mixture prior to precipitation of the polymer, to the solution of 
redissolved polymer, or to the solvent in which the polymer is to be 
subsequently redissolved. Polymerization can be carried out at any 
convenient temperature employed in the polymerization arts. Exemplary 
temperatures lie in the range of from less than about 0 to 200.degree. C., 
or more, preferably polymerization temperatures range from about 
40.degree. to 100.degree. C., for each step. The pressures employed can be 
convenient, and preferably are pressures sufficient to maintain monomers 
and diluents substantially in the liquid phase. The polymerization times 
can vary widely as may be convenient, and will, of course, be affected by 
polymerization temperatures chosen. The times should be chosen, for each 
step, such that substantially complete polymerization is obtained. 
Any anionic initiator that is known in the art as useful in the 
copolymerization of diene monomers with vinyl aromatic hydrocarbons can be 
employed in the process of the instant invention. Exemplary organo-lithium 
catalysts include lithium compounds having the formula R(Li).sub.x, 
wherein R represents a hydrocarbyl radical of 1 to 20, preferably 2 to 8, 
carbon atoms per R group and x is an integer from 1 to 4. Typical R groups 
include aliphatic radicals and cycloaliphatic radicals, such as alkyl, 
cycloalkyl, cycloalkylalkyl, alkylcycloalkyl, aryl and alkylaryl radicals. 
Specific examples of R groups for substitution in the above formulas 
include primary, secondary and tertiary groups such as methyl, ethyl, 
n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, n-amyl, isoamyl, n-hexyl, 
n-octyl, n-decyl, cyclopentyl-methyl, cyclohexyl-ethyl, cyclopentyl-ethyl, 
methylcyclopentylethyl, cyclopentyl, dimethylcyclopentyl, 
ethylcyclopentyl, methylcyclohexyl, dimethylcyclohexyl, ethylcyclohexyl, 
isopropylcyclohexyl, and the like. 
Specific example of other suitable lithium catalysts include: 
p-tolyllithium, 4-phenylbutyl-lithium, 4-butylcyclohexyllithium, 
4-cyclohexylbutyl-lithium, lithium dialkyl amines, lithium dialkyl 
phosphines, lithium alkyl aryl phosphine, lithium diaryl phosphines and 
the like. 
The preferred catalyst for use in the present invention is n-butyllithium 
and sec-butyllithium. 
In accordance with the process of the present invention, two separate 
charges of anionic initiator must be made into the reaction zone. The 
first charge of anionic initiator is used to initiate polymerization of 
the monomer charges used to prepare the block polymer precursor of the 
present invention. The second charge of anionic initiator is added to the 
reaction zone containing the formed block polymer precursor in solution 
prior to or simultaneously with the final charge of vinyl aromatic monomer 
used to simultaneously prepare the terminal block onto the block polymer 
precursor and the interpolymerized poly(vinyl aromatic hydrocarbon). The 
amounts of anionic initiator employed in both: (1) the preparation of the 
block polymer precursor and (2) the preparation of the terminal block and 
interpolymerized poly(vinyl aromatic hydrocarbon) can vary over a broad 
range. In general, the first charge or amount of initiator used to 
initiate polymerization of the block polymer precursor will be in the 
range of from 01. to 5 milliequivalents of initiator per 100 parts by 
weight of total amount of monomer charged into the reaction zone and will 
preferably be in the range of from 0.4 to 2 milliequivalents of initiator 
per 100 parts by weight of total monomer charged. Likewise, the amount of 
additional anionic initiator used to initiate polymerization of a portion 
of the final vinyl aromatic hydrocarbon monomer charge will be in the 
range of from 0.01 to 30 milliequivalents of initiator per 100 parts by 
weight of the monomers charged and will preferably be in the range of from 
0.05 to 7.6 milliequivalents of initiator per 100 parts by weight of the 
monomer charged into the reaction zone. Variance of the amount of the 
second charge of the anionic initiator is used to control the amount of 
poly(vinyl aromatic hydrocarbon) interpolymerized with the block polymer. 
A 1,2-microstructure controlling agent or randomizing modifier can be used 
during formation of the polymer blocks to control the 1,2-microstructure 
in the diene contributed units and to randomize the amount of vinyl 
aromatic monomers, such as styrene, incorporated with the diene monomer, 
such as butadiene, in the rubbery phase. Suitable modifiers include, but 
are not limited to, tetramethylenediamine (TMEDA), oligomeric oxolanyl 
propanes (OOPS), 2,2-bis-(4-methyl dioxane) (BMD), tetrahydrofuran (THF), 
bistetrahydrofuryl propane and the like. One or more randomizing, 
modifiers can be used. The amount of the modifier to the weight of the 
monomers in the reactor can vary from a minimum as low as 0 to a maximum 
as great as 400 millimoles, preferably 0.01 to 300.0 millimoles, of 
modifier per hundred grams of monomer currently charged into the reactor. 
As the modifier charge increases, the percentage of 1,2-microstructure 
increases in the diene monomer contributed units. A polar organic compound 
such as ether, polyether, tertiary amine, polyamine, thioether and 
hexamethylphosphortriamide may be used to control the vinyl linkage 
content in the conjugated diene component. The vinyl linkage content can 
be controlled by the amount added of the polar organic compound, and by 
the polymerization temperature. 
Modifiers such as tetramethyl THF can be used to increase initiation of the 
first polystyrene block without effecting microstructure of the rubber 
block if low levels are used. 
The process of this invention is preferably carried out in the presence of 
a hydrocarbon diluent. Aliphatic, aromatic hydrocarbons, paraffins, and 
cycloparaffins may be employed. The preferred hydrocarbons are those 
containing from 3 to 12, inclusive, carbon atoms, particularly n-hexane. 
Examples of diluents include propane, isobutene, n-pentane, isooctane, 
n-dodecane, cyclopentane, cyclohexane, methylcyclohexane, benzene, 
toluene, xylene, and the like. Mixtures of two or more of these 
hydrocarbons may also be used. 
The polymerization process may be conducted under batch or semi-batch 
conditions. 
The polymers of this invention may be compounded further with other 
polymers, oils, fillers, reinforcements, antioxidants, stabilizers, fire 
retardants, tackifiers, vulcanization accelerators, vulcanizing agents, 
processing aids, antiblocking agents and other rubber plastic compounding 
ingredients without departing from the scope of this invention. These 
compounding ingredients are incorporated in suitable amounts depending 
upon the contemplated use of the product. 
A reinforcement may be defined as the material that is added to a resinous 
matrix to improve the strength of the polymer. Most of these reinforcing 
materials are inorganic or organic products of high molecular weight. 
Various examples include glass fibers, asbestos, boron fibers, carbon and 
graphite fibers, whiskers, quartz and silica fibers, ceramic fibers, metal 
fibers, natural organic fibers, and synthetic organic fibers. 
The interpolymers of the instant invention can be used as is or can be 
incorporated into injection molding resins or in any other compositions 
typically containing high impact polymers. Particularly, the interpolymers 
of the present invention have improved processability over prior art 
blends of polystyrene and block polymers. The interpolymers produced 
according to the process of the present invention possess a Gardner Impact 
Strength of at least 60 ft-lb/inch, preferably at least 100 ft-lb/inch, 
more preferably at least 150 ft-lb/inch, and most preferably at least 200 
ft-lb/inch. 
The following examples are presented for purposes of illustration only and 
are not to be construed in a limiting sense. All percentages are by weight 
unless otherwise specified. 
EXAMPLE 1 
An interpolymer was produced according to the present invention. The 
structural characteristics of the triblock polymer produced by anionic 
polymerization are displayed in Table 1. The first block of this triblock 
polymer was prepared by charging a stirred reactor with (1) 18.2 lbs. of a 
33% by weight charge of styrene in hexane, (2) 10.9 lbs. of hexane, (3) 
0.69 kg of a 3% solution of n-butyllithium in hexane together with 1.634 
grams of modifier, 10.0 kg of a 15% solution of a styrene/butadiene 
diblock dispersant. This mixture was heated at 120.degree. F. for 30 
minutes and then cooled to 110.degree. F. to produce a first block as 
displayed in Table 1. A charge of 40.0 lbs. of a 33% by weight solution of 
1,3-butadiene in hexane was added to the reactor as the temperature of the 
reactor was raised to 170.degree. F. and heated until 30 minutes after 
peak temperature. The composition of the second block is disclosed in 
Table 1. The reactor was then additionally charged with 0.07 kg of a 3% 
solution of n-butyllithium in hexane followed by a charge of 134.8 lbs. of 
a 33% solution of styrene in hexane. The contents of the reactor was 
heated to 170.degree. F. for thirty minutes after reaching the peak 
temperature. The reaction was terminated by adding 272.4 grams of a 3% 
aqueous solution of boric acid, and a 5.55 lbs of a hexane solution 
containing antioxidant was added. The molecular weight of the third block 
of the triblock polymer as displayed in Table 1 was 56,470. The molecular 
weight of the polystyrene produced in situ was also 56,470. 
EXAMPLE 2 
An interpolymer was produced according to the procedure of Example 1. The 
first block of this triblock polymer was prepared by charging a reactor 
with (1) 25.8 lbs. of a 33% by weight charge of styrene in hexane, (2) 
33.6 lbs. of hexane, (3) 0.81 kg of a 3% solution of n-butyllithium in 
hexane together with 10 grams of modifier, 14.1 kg of a styrene/butadiene 
diblock dispersant. This mixture was heated at 120.degree. F. for 30 
minutes and then cooled to 100.degree. F. to produce a first block as 
displayed in Table 1. Separate charges of 56.7 lbs. of a 33% by weight 
solutions of 1,3-butadiene in hexane and styrene in hexane were added to 
the reactor as the temperature of the reactor was raised to 170.degree. F. 
and heated until 30 minutes after peak temperature. The reactor was then 
additionally charged with 0.16 kg of a 3% solution of n-butyllithium in 
hexane (20% of the initial catalyst charge) followed by a charge of 142.2 
lbs. of a 33% solution of styrene in hexane. The contents of the reactor 
was heated to 170.degree. F. for thirty minutes after reaching the peak 
temperature. The reaction was terminated by adding 11.57 grams of boric 
acid and 374 grams of water, followed by the addition of a 6.80 lbs. of a 
hexane solution containing antioxidant. As can be easily recognized from 
the results displayed in FIG. 1, all interpolymers produced according to 
the process of the present invention possess measured Gardner Impact 
Strengths exceeding 200 ft-lb/inch. The amount of crystal polystyrene 
incorporated in the interpolymer varied in amount ranging from 9.0% to 
26.0%, by weight of the final styrene monomer charge. The amount of in 
situ polystyrene present in the interpolymer did not adversely affect the 
Gardner Impact Strength (measured in ft-lb/inch) of the interpolymer, nor 
did the interpolymer stick in the injection molder cavity. 
TABLE 1 
__________________________________________________________________________ 
Physical Characteristics of the Triblock Polymer 
Produced According to the Instant Invention 
First Block Second Block 
Third Block 
Example % % % Total 
Total 
No. MW.sup.1 
STY.sup.2 
MW STY MW STY MW % STY 
__________________________________________________________________________ 
1 8,420 
100 18,530 
0 56,470 
100 83,420 
77.8 
2 10,160 
100 44,690 
50 46,720 
100 101,570 
78.0 
__________________________________________________________________________ 
.sup.1 Molecular Weight 
.sup.2 Percent Styrene Remainder Butadiene 
Comparative Example A 
A triblock polymer was prepared by anionic polymerization techniques having 
the structural characteristics displayed in Table 2. The triblock polymer 
exhibited a Gardner Impact of about 175 ft-lb/inch, but the polymer 
adhered to the injection molder cavity. Crystal polystyrene was physically 
blended with the triblock polymer in amounts ranging from 1.5% to 7.0% by 
weight in order to improve the mold flow characteristics of the block 
polymer. The Gardner Impact Strength of the block polymer after the 
addition by blending of the crystal polystyrene was measured. The Gardner 
Impact Strength of the blend of triblock polymer of Table 2 and the 
crystalline polystyrene versus the percent by weight of crystalline 
polystyrene added to the triblock polymer is depicted in FIG. 2 in units 
of ft-lb/inch. The Gardner Impact Strength of the polymer blend was less 
than 25 ft-lb/inch upon the addition by blending of 1.5% by weight or more 
of the crystal polystyrene. 
TABLE 2 
______________________________________ 
Physical Characteristics of Block Polymer 
Utilized in Comparative Example A 
First Second Third 
Block Block Block Total 
% % % Total % 
MW.sup.1 
STY.sup.2 
MW STY MW STY MW STY 
______________________________________ 
8,980 
99 37,330 47.6 42,670 
100 88,980 
77.9 
______________________________________ 
.sup.1 Molecular Weight 
.sup.2 Percent Styrene Remainder Butadiene 
Comparative Example B 
A triblock polymer was prepared by anionic polymerization techniques having 
the structural characteristics displayed in Table 3. The block polymer 
exhibited a Gardner Impact of about 200 ft-lb/inch, but the polymer 
adhered to the injection molder cavity. Crystal polystyrene was physically 
blended with the block polymer in amounts ranging from 1.5% to 7.0% by 
weight in order to improve the mold flow characteristics of the triblock 
polymer. The Gardner Impact Strength of the triblock polymer decreased 
dramatically upon the addition by blending of 1.5% by weight or more of 
crystal polystyrene. The Gardner Impact Strengths of the polymer blends of 
Comparative Example B were about 20 ft-lb/inch and are displayed in FIG. 3 
as measured in ft-lb/inch. The addition of polystyrene to the triblock 
polymer resulted in a loss of approximately 90% of the Gardner Impact 
Strength of the original triblock polymer. 
TABLE 3 
______________________________________ 
Physical Characteristics of Block Polymer 
Utilized in Comparative Example B 
First Second Third 
Block Block Block Total 
% % % Total % 
MW.sup.1 
STY.sup.2 
MW STY MW STY MW STY 
______________________________________ 
8,620 
99 37,540 50 39,250 
100 85,410 
77.9 
______________________________________ 
.sup.1 Molecular Weight 
.sup.2 Percent Styrene Remainder Butadiene