CA1090034A - Blend of resinous radial copolymers of a monovinyl- substituted aromatic compound and a conjugated diene - Google Patents

Abstract

BLEND OF RESINOUS RADIAL COPOLYMERS OF A MONOVINYL-SUBSTITUTED AROMATIC COMPOUND AND A CONJUGATED DIENE Abstract of the Disclosure A composition comprising a blend of at least two resinous radial copolymers of a monovinyl-substituted aromatic compound and a conjugated diene, said blend having a heterogeneity index of polymerized monovinyl-substituted aromatic compound blocks within the range of about 2.8 to 3.5. The heterogeneity index is the ratio of weight average to number average molecular weight. Such compositions exhibit high strength and are made by blending at least two resinous radial block copolymers made under different conditions so as to give different lengths of the polymerized monovinyl-substituted aromatic compound blocks. These compositions are particularly useful in applications such as injection molded articles where high impact strength is desirable.

Description

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'.~;, 1 B~END OF R~SINO~S RADIAL COPOLYMERS OF A MONOVINYL-SUBSTITUTED AROMATIC COMPoUNml AND~ A~ CONJUGATE~ DI~NE
Cross Refereuce to Related Application . This is a divisional of copending application, Serial No.
258,971, filed August 12, 1976.
Background of the Invention This invention relates to high impact resinous linear copolymers of a monovinyl-substituted aromatic compound and a conjugated diene. In another aspect this invention relates to high impact blends of monovinyl-sub6tituted aromatic compound/conjugated diene block copolymers.
` 10 It is well known to produce impact polystyrene by blending a rubber with the polystyrene. This results in improvement in the impact of the polystyrene with a substantial sacrifice with respect to other properties. It is also known that some but not all radial block copolymers exhibit high impact strength, see for instance Kitchen et al, U. S. 3,639,517.
It would be desirable to achieve a linear polymer having high ~ impact strength without the disadvantages associated with rubber .~ reinforced polystyrene.
Summary of the Invention It is an object of this invention to provide high i~pact linear ` block copolymers of a monovinyl-substituted aromatic compound and a conjugated diene.
It is a further object of this invention to provide high impact ` block copolymer without the necessity o~ multiple addition of initiator and monovinyl-substituted aromatic compound; and ,. .
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It is yet a further object of this invention to provide an improved blend of monovinyl-substituted aromatic compound/conjugated diene copolymers.
In accordance with this invention there is provided a linear monovinyl-substituted aromatic compolmd/conjugated diene block copolymer composition characterized by a heterogeneity index of blocks of polymerized monovinyl-substi-tuted aromatic compound within the range of ;~; about 2.3 to 4.5, preferably 2.4 to 4.5. In another aspect of this invention, there is provided a blend of two resinous radial copolymers of monovinyl-substituted aromatic compound/conjugated diene which blend has a heterogeneity index for the monovinyl-substituted aromatic compound blocks of at least about 2.8, pxeferably within the range of about 2.8 to 3.5.
Description of the Preferred ~mbodiments It has been found that the high impact strength of resinous radial block copolymers made with incremental addition of the monovinyl-substituted aromatic compound and initiator is related to the morphology. Specifically, with a very low heterogeneity index for the monovinyl-substituted aromatic compound block, i.e., less than abou-t

2.8, the morphology is characterized by spheres of the diene component in the monovinyl-substituted aromatic compound component. At a heterogeneity index above about 3.5 the morphology exhibits an inverted structure having spheres or eIlipsoids of the monovinyl-substituted aromatic component in a continuum of the diene component. This structure gives a cheesy (weak and crumbly) product. This change in property above a heterogeneity index of about 3.5 may also be affected by ; incompatibility due to great differences in the molecular weights of the : block. However, within the desired range of heterogeneity index of about 2.8 to 3.5 for the monovinyl-substituted aromatic compound block of the ~ 30 radial polymer blends, there is present an alternating lamellar - structure comprising alternate layers of conjugated diene blocks and layers of monovinyl-substituted aromatic compound blocks.
With linear polymers, samples having a heterogeneity index of the monovinyl-substituted aromatic compound block of less than 2.3 tend to have the morphology characterized by spheres of the polymerized diene embedded in a continuum of polystyrene. On impact the polystyrene phase ';, takes most of the load and hence low impact values are obtained whereas with the lamellar configuration there are alternating layers of , ~.
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polymerized styrene blocks and polymerized diene blocks which act in a reinforcing manner. With a heterogeneity index of greater than about 4.5 the morphology for linear block copolymer i8 inverted with spheres or - ellipsoids of polymerized monovinyl-substituted aromatic compound being found in a continuum of polymerized diene. This structure gives a cheesy (weak and crumbly) product. This change in properties above a heterogeneity index of 4.5 may also be affected by incompatibility due to great variations in the molecular wei,~hts of the blocks.
Thus in accordance with the invention there is provided linear block copolymer compositions having a heterogeneity index within the range of about 2.3 to 4.5 for the polymerized monovinyl-substituted aromatic component blocks. In accordance with another aspect o~ this instant invention, there is provided blends of two block copolymers each of which has a heterogeneity index for the monovinyl-substituted aromatic compound blocks outside the range of about 2.8 to 3.5, the blend being within this range.
The heterogeneity index is the ratio of weigh~ average to ` number average molecular weight and is expressed by the formula WlSlMSl ~ W2S2MS2 w/Mn WlSl W2S2 1 Sl N2MS2 ' Nl + N2 ` where:
: W is weight of fraction (1 = Ma~or, 2 = minor~.
S is styrene content o$ the fraction.
N is moles styrene blocks in the fraction.
S is molecular weight of styrene block in the ~raction.
The weight average and ~umber average molecular weights used in the abo~e formula are calculated assuming monodispersity, which is a

3~ reasonable approximation since the molecular weight distribution of each polymer produced is extremely narrow. Then the number o$ moles of initiator is divided into the number of grams of monomer to give grams of polymer per mole or the number average molecular weight which is essentially the same as the weight average molecular weight.
Past experience based on actually digesting a copolymer in peroxide to leave only the polymerized styrene block which was then analyzed using gel permeation chromatography has shown the calculated values to agree closely with the measured values.
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MSl = 75 x 103 ; MS2 = 17 x 103 Wl = 0-58 - W2 = 0.42 Sl - 75 x 10 = 0.862 87 x 103 S2 = 17 x 1o3 = 0.58 29 x 103 Nl ~ 0.862 x 58 = 0.667 x 10 3 75 x 10 N = 0.586 x 42 = 1.45 x 10 3 ` 17 x 103 ; 15 .58 x .862 x 75 x 103 + .42 x .586 x 17 x 103 .58 x .862 + .42 x .586 HI
667 x 75 x 1o3 * 1 45 x 17 x 103 (37 50 + 4 18) x 103 41 68 ~ 103 ,.,; .
= = = 55.87 x 103 = 1.58 ~: 35.36 x 103 2.112 2.112 Althou~h the formula is directed to the combination of two ~ polymers either blended together or produced in situ, it should be noted , that three or more polymers can be used. The expression as well as the x'~ following preparative methods encompass such expansion. The block copolymers of this invention are produced from a monovinyl-substituted , aromatic compound and a conjugated diene.
The term resinous is used in the conventional sense to mean a normally solid material not having rubbery properties. Generally, such ~., materials ~ill have a Shore D hardness ~ASTM D-1706-61) of 8reater than '~, 35 62, generally greater than 65. Th~se final compositions of the invention ;~ and the constituent components will have from 50 to ~5 weight percent polymerized monovinyl-substituted aromatic component.

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` 5 ., ~ uitable monovinyl-substituted aromatic compounds are those containing 8 to 18 carbon atoms per molecule. Examples oE suitable compounds include styrene, 3-methylstyrene, 4-n-propylstyrene, 4-cyclohexylstyrene, 4~decylstyrene, 2-ethyl-4-benzylstyrene, 4-p-tolylstyrene, 4-(4-phenyl-n-butyl)styrene, l-vinylnaphthalene, 2-vinylnaphthalene, and the like and mixtures ~hereof. Styrene is the preferred monovinyl-substituted aromatic compound and for the sake of simplicity the invention hereinater will be described in terms of utilizing styrene, it being understood that the invention is not limited to the use of styrene as the monovinyl-substituted aromatic compound.
Suitable conjugated dienes or mixtures thereo~ that can be used in this invention include those having 4 to 12 carbon atoms per molecule, those containing 4 to 8 carbon atoms being preferred.
'~ Exemplary of sui-table compounds are 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, piperylene, 3-butyl-1,3-octadiene, and the like.
The preferred diene is 1,3-butadiene and the invention hereinafter will ; be described in terms of butadiene, it being understood that butadiene hereinafter is referred to as exemplary only and the invention is not ; intended to be limited thereto.
~ .i -- 20 The polymerization initiators employed according to this , invention are well known in the art and can be broadly depicted as ;~ organolithium initiators. Those preferred are hydrocarbyl monolithium compounds and can be represented by the formula RLi where R is a hydrocarbon radical selected from aliphatic, cycloaliphatic, or aromatic ~-- 25 radicals containin~ from about 1 to 20 carbon atoms per molecule.
Exemplary initiators suitable for use according to this invention include: n-butyllithium, æec-butyllithium, methyllithium, phenyllithium, naphthyllithium, p-tolyllithium, cyclohexyllithium, eicosyllithium, and the like. Because it is particularly effective, n-butyllithium is presently preferred.
Polymerization of the linear copolymers is carried out by initially adding styrene and initiator which results irl the formation of polymerized styrene blocks having a terminal lithium atom. Thereafter if - additional styrene and initiator are added new polymerized styrene blocks are begun utilizing part of the newly added styrene with the remainder serving to increase the length of the existing polymerized ' styrene blocks. Thereafter butadiene is added which forms a block of ; polymerized bu-tadiene between the polymerized styrene block and the :.~, . ~ :
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terminal lithium atom. At this point additional styrene can be added to complete the polymer by forming a polymerized styrene block between the polymeriæed butadiene and the terminal lithium atom to give s-tyrene-butadiene-styrene. Alternatively a difunctional coupling agent can be added so as to couple two of the styrene-butadiene blocks to give styrene-butadiene-butadiene-styrene. Difunctional coupling agents are known in the art and any of these known coupling agents can be u~ilized.
Suitable difunctional coupling agents include the diisocyanates, diimines (diaziridinyl), dialdehydes, dihalides, and the like.
; 10 Exemplary compounds are: benzene-].,4-diisocyanate; naphthalene-2,6-diisocyanate; naphthalene-1,3-diisocyanate; di(l-aziridinyl)ethyl ~ phosphine oxide; di(2-phenyl-1-aziridinyl)propyl phosphine oxide;
: di(2,3-dimethyl-aziridinyl)hexyl phosphine sulfide; 1,4-naphthalene ~ dicarboxyaldehyde; l,9-anthracene dicarboxyaldehyde; 2,4-hexanedione;
l,10-anthracenedione; dichlorodiethylsilane; dibromodibutylsilane;
difluorodicyclohexylsilane; di-n-hexyldifluorotin; diphenyldibromotin;
diethyldiallyltin; dicyclohexyldichlorotin; didodecylchlorobromotin;
di(3-methylphenyl)chloroallyltin; and the like.
Another suitable difunctional treating agent is carbon dioxide.
The preferred difunctional coupling agents are esters of the formula ' RC - OR' .:' "
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The final linear block copolymer compositions of this invention contain 50 to 95 weight percent polymerized monovinyl-substituted aromatic component and exhibit a falling dart impact ,~ strength of greater than 20 in.-lbs. (2.2 joules), preferably greater than 25 in.-lbs. (2.8 joules). The separate constituents of the final - composition also individually contain 50 to 95 weight percent polymerized monovinyl-substituted aromatic component but have a lower impact strength. The term resinous is used in a conventional sense to .

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mean a normally solid material not having rubbery properties. Generally, such materials will have a Shore D hardness of greater than 62, generally greater than 65.
The linear compositions of the invention can be produced by three techniques. In each instance sufficient time is allowed after the - introduction of each monomer for the substantially complete - polymerization thereof before the adclition of the next monomer.
- Technique one encompasses multiple sequential addition of monomers and catalyst and no coupling i8 involved. The order of addition of components is styrene, initiator; initiator, styrene; butadiene;
styrene (neglecting charging of solvent, modifier, e-tc.). Linear, block copolymers are prepared. By regulating the quantity of styrene ~S) charged in each increment aæ well as quantity of butadiene (B) charged, a mixture of polymers is formed in situ of Sl-S2-B-S3 and S2-B-S3, which in combination satisfy the required HI index. Each subscript refers to a separately charged styrene increment.
Technique two encompasses multiple sequential addition of . .
monomers and initiator and coupling of the resulting products with a difunctional coupling agent (X) to obtain a mixture of linear polymers ` 20 t d as S -S -B-X-B-s2-sl' S1-S2-B X B S2 2 2 taken together satisfies the required HI index. The order of addition, ~ neglecting solvent and modifier, is styrene, initiator; initiator, .^ styrene; butadiene; coupling agent.
Technique three encompasses in the first instance mixing two or more difunctionally coupled styrene-butadiene diblock copolymers, each coupled polymer separately prepared, to obtain a final blend which ; satis~ies the required HI index or in the second instance mixing two or more separately prepared block copolymers prepared by multiple addition of styrene and initiator. The blend, using previous terminology, can be -- 30 represented as a mixture of Sl-Bl-X-Bl-Sl and S2-~2-X-B2-S2 in the first or Sl-s2-Bl-s3 plus S2-B1-s3 and S4-ss-Bz-s6 plus S -B -S6 in ~ the second instance, where Bl and B2 represent butadiene blocks of -; different molecular weights. However, the difference in number average molecular weights of the butadiene blocks preferably should not exceed about 10,000 in order to obtain the proper morphology. The order of addition in each reactor in the first instance, neglecting solvent and ; modifier, is styrene, initiator; butadiene; coupling agent. In the second instance, it is styrene, initiator; initiator, styrene;
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butadiene; styrene. The polymer æolutions are -then combined and mixed ; before recovering the final product. Alternately, polymers previously ;~ recovered can be blended together by suitable means (roll mills, etc.).
It is also within the scope of this invention to mix a polymer :~ 5 prepared by means of technique one with one prepared by technique two or technique three and a polymer prepared by technique two with one of technique three to obtain a final blend which satisfies the required HI
index range.
A general method of pre]para-tion of the various linear polymers, subject to the limitations of this invention, is described in . S. Patent 3,639,517 in which sequential polymerization of styrene or other monovinyl-substituted aromatic hydrocarbon and butadiene or other conjugated diene is employed.
'. The radial polymers of this invention are individnally s 15 prepared according to the method described in Kitchen et al U. S.
;~ 3,639,517 except that multiple addition of the monovinyl-substituted aromatic compound is not necessary. Briefly, in accordance with the - procedure outlined therein, sequential polymerization of styrene or ; other monovinyl-substituted aromatic hydrocarbon and butadiene or other ~ 20 conjugated diene is carried out and thereafter the resulting lithium-.'.'.3 terminated polymer is coupled with a polyfunctional treating agent. Asnoted hereinabove, only a single charge of monovinyl-substituted aromatic compound and initiator is required for each individual polymer used to prepare the radial copolymer blends of this invention. Styrene '~! 25 and 1,3-butadiene are the presently preferred monomers in this aspect of the invention also.
In this aæpect of the invention also, the polymer solutions resulting from two separate polymerizations as described above are combined and mixed to form an intimate mixture of the polymer solutions.
: 30 Subsequently, the mixture is recovered following the procedures described in said Kitchen et al patent. It is within the scope of this aspect of the invention to form mixtures of separately recovered polymers by intensive mixing in Banbury mixers, extrusion compounding, roll .l milling, solution blending, and the like.
~- 35 The general method of preparing the high impact polymers of X; this invention is summarized by giving the charge order for forming two polymers, each polymer having different block lengths, followed by mixing as follows:

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Reactor one Reactor two a) cyclohexane cyclohexane b) styrene styrene c) tetrahydrofuran tetrahydrofuran : 5 d) n-butyllithium n-butyllithium e) polymerize at 50-60C polymerize at 50-60C
f) butadiene butadiene g) polymerize at 50-60C polymerize at 50-60C
h) polyfunctional treating agent polyfunctional treatin~ agent i) combine solutions .
j) add stabilizer system k) devolatilize 1) finish (form granules or pellets) `; The sequence given above in each reactor is for making diblocks which are coupled by the polyfunctional treating agent to form a polymer which can be expressed as: tstyrene-butadiene3nY where Y is the polyfunctional treating agent and n is an inte8er of 3-7 or more. It is -;; within the scope of this invention to employ as one or more components of the blend one or more polymers made by multiple addition of monovinyl-substituted aromatic hydrocarbon and initiator wherein or some reason ; the resulting polymer is off specification, i.e., has a heterogeneity ` index outside the range of about 2.8 to 3.5. Broadly, then this aspect ., .
of the invention involving radial polymer resides in the blending of two ~: radial block copolymers of a monovinyl-substituted aroMatic compound and ,~ 25 a conjugated diene each having a heterogeneity index ou-tside the range of about 2.8 to 3.5 with at least one less than 2.8 to give a blend having a heterogeneity index within the range of 2.8 to 3.5.
Exemplary polyfunctional treating agents that can be used in accordance with this aspect of the invention in the preparation of the branched block (radial) copolymers are the polyepoxides such as epoxidized linseed oil, epoxidized soybean oil, and 1,2,5,6,9,10-triepoxydecane; polyimines such as tri(l-aziridinyl)phosphine oxide;
polyisocyanates such as benzene-1,2,4-tri-isocyanate; polyaldehydes such as 1,4,7-naphthalenetricarboxyaldehyde; polyhalides such as silicon 35 tetrachloride or polyketones such as 1,4,9,10-anthracenetetrone and polyalkoxysilanes such as methyltrimetho~ysilane.
The compositions of this invention can, of conrse, contain conventional additives such as antioxidants, UV stabilizers, fillers, pigments, and the like.

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' 10 `- In the following Examples, Examples I to III relate to the . first aspect of this invention (linear copolymer blends) and Example IV
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. Example I
.: 5 Polymers made according to technique one, previously a described, were prepared by conducting each polymerization in 32 ounce (0.95 liter) glass beverage bottles. In each run, the following . materials were added to the bottle, whlle under nitrogen, in the order ` shown:
10 (1) cyclohexane (CyC6), then first increment of styrene (S) (2) purge 5 minutes with nitrogen, cap and fill with nitrogen ~3) tetrahydrofuran (THE) -~ (4) first initiator charge, n-butyllithium (BuLi), 0.023 g/cm3 ;.-; in cyclohexane ~,.
:~ 15 (5) react at 60C for 30 minutes (60 minutes in run 2) (6) second initiator charge .j (7) second increment of styrene (8) react at 60C for 15 minutes (60 minutes in run 2) (9) butadiene (B) "..¢
,~J 20 (10) react at 60C for 30 minutes (60 minutes in run 2) ~ (11) third increment of styrene ;- (12) react at 60C for 30 minutes (60 minutes in run 2) - (13) stabilizer system, 2 parts by weight per 100 parts by weight monomer (phm) The quantities of each component used in the polymerizations are given in the-Following Table IA.
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f3~ ~4 After the stabilizer system was mixed with the polymer ~; solution, each solution was devolatiliæed in a vacuum oven at 100C and the resulting dried product was milled on a roll mill at 285F (140C) for 3 minutes, after banding commenced, to further homogeniæe and densify the sample.
The mel-t flow, glass transition temperature (Tg) (by diEferential thermal analysis, DTA), falling dart impact strength, elongation, dynamic modulus and loss was determined, when applicable, for each sample. The melt flow was determlned in accordance with ASTM
10 D1238-62T at 200C and a 5 kg load. Tg was determined by DTA using a DuPont Thermal Analyzer, Model 900, equipped with a DSC cell. Dart ~ impact strength was ascertained by noting the height in inches at which a - free falling bullet-shaped brass dart weighing 1.123 lbs (0.509 kg) inpacting a test sample broke 2 Ollt of 4 samples tested at that height.
The samples were made by injection molding slabs having the dimensions 1 1/4" x 1 3/4" x 0.100" (3.2 cm x 4.4 cm x 0.25 cm). Each slab was positioned so that it was supported around its perimeter during the impact test and each sample was tested only once. The dynamic modulus and loss values were determined by means of a Vibron Direct Reading Viscoelastometer, Model D W -II (Vibron is a trademark of Toyo Instruments Co., Tokyo, Japan). The direct reading viscoelastometer , experiments were made on test samples cut from compression molded film having dimensions about 1/8" wide (0.05 cm), 1.2" long (3 cm) and about ; 10 mils (0.025 cm) in thickness. Each teæt sample was measured at 35 Hz 25 at temperatures ranging irom about -100C to about 20C. The physical properties of each pclymer sample and the test results are given in the iollowing Table Ib.

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As can be seen, invention Run 2 representing the invention had a high impact strength similar to that of the best of the radial ;: polymers as exemplified by control Run 4, and much better than that of ;~ ordinary radial polymer as exemplified by control Run 3. Impact was not ; 5 determined on invention Run l, however, the tempera-ture of tangent~ max was -80C., which is a value associated with good impact as will be ~l discussed in more detail in the discussion following Table IIIC. Thus these data show surprisingly that linear polymer produced by multiple addition of initiator and styrene, having a heterogeneity index of the polymerized styrene blocks within the range of about 2.3 to 4.5 has an ' impact strength as good as or better than the best radial polymer. Runs 3 and 4 contained 76 percent polymerized styrene and Runs l and 2, 75 percent, i.e.~ they were essentially equal.
Example II
. 15 Polymers made according to techniquP two, previously ; described, were prepared by conducting a series of individual polymerizations with variable quantities of monomers and coupling the ~- resulting polymers with ethyl acetate as an example of a difunctional coupling agent. Each polymerization of the first 9 runs was conducted in ` 20 a 32 ounce (0.95 liter) glass beverage bottle. Each component used was `~ added to the bottle in a nitrogen atmosphere. Preparation details are given in Table IIA.

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.~, Run 10 Run 11 . ,, _ _ _ ~, 5 First charge:
cyclohexane 14.7 lbs (6.7 kg) 14.7 lbs (6.7 kg) ~, tetrahydrofuran 0.84 cm3 0.84 cm3 styrene 1.59 kg 1.59 kg ~-^ n-butyllithium (as solution cyclohexane) 0.90 g 0.87 g ' initial temperature 107F (42C) 110F (43C) ' polymerization time, minutes 37 44 Second charge:
cyclohexane 0.3 lb (0.14 kg) 0.3 lb (0.14 kg) n-butyllithium 3.6 g 3.1 g ~- styrene 0.69 kg 0.69 kg initial temperature 156F (69C) 166F (74C) ~ polymerization time, minutes 24 21 ,~ Third charge:
cyclohexane 0.1 lb (0.045 kg) 0.1 lb (0.045 kg) butadiene 0.72 kg 0.72 kg initial temperature 161F (72C) 166F (74C) polymerization time, minutes 21 20 Fourth charge:
~: Z5 cyclohéxane 0.2 lb (0.09 kg) 0.2 lb (0.09 kg) ethyl acetate in C C6 (Q.l~ g/cm3) 31 cm3 28 cm3 ; initia~ temperature 216F (102C) 218F (103C) . reaction time, minutes 20 20 ~; Each polymer solution was treated with 6 cm3 water and the - 30 reactor pressured up to llO psig (758 kPa gage) with carbon dioxide to improve the color of the polymer. Xun 10 was C02 treated 20 minutes at 216F ~102C) and run 11 was C02 treated 30 minutes at 216F also. A 50 ~, weight percent stabilizer solution containing tris(monylphenyl)phosphite ~i~ and 2,6-di-t-butyl-4-methylphenol dissolved in cyclohexane was then '' ~- 35 added to each polymer solution such that 1.5 parts by weight phosphite , per lO0 parts by weight total monomers (phm) and 0.5 phm phenol was ~,: present. Each polymer solution was flashed at 332F (167~C) to remove , ~
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9r3~34 The physical properties of the polymers are presented in Table IIB. A general discussion of the test results is given following Table IIIC.

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5 values of 48.3 to >80 for the linear polymer of invention ~uns 7, 9, 10 and 11 compares favorably with the best of the radial polymers as ;~ exemplified by control Run 4 of Example I and represents a dramatic improvement compared with linear polymer having a heterogeneity index below 2.4 AS by control Runs 1-3 as well as a dramatic improvement compared with ordinary radial polymer as exemplified by control Run 3 of ; Example I. While impact was not determined on Runs 6 and 8, these runs exhibited a temperature of tangent ~ maximum and tangent ~ maximum ` associated with high impact strenpth as discussed in connection with Example III hereinbelow.
Example III
; Polymers made according to technique three, previously described wherein the order of addition was styrene, ini-tiator, butadiene, coupling agent ? were prepared by conducting a series of ,; .
individual polymerizations to form diblock polymers each of which was coupled with ethyl acetate as the difunctional coupling agent. The resulting solutions were mixed as shown in Tables IIIA and IIIB to form a mixture. Each mixture was treated with stabilizer solution as previously - described, recovered by devolatilization in vacuo at 100C for the bottle samples or by flashing at 332F (167C) to remove solvent for the larger ~ 25 preparations.
The preparation details are presented in Tables IIIA and B.
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Pre~aration of Individual Diblock, Dlfunctionally Coupled Copolymers ~ Ef~ective Ethyl ; Run CyC6 S Compone t T~F Bu~3 B Component Acetate No. (cm ) (~) (cm ) (8) (cm ) (g) (cm ) (g) Comments 1 325 34 37.70.023 0.6311 18.2 1.0 ` 2 220 22.5 24.9 .015 4.47 7.5 12.3 6.6 3 325 34 37.70.023 0.6311 18.2 1.0 Run 1 duplicate 4 220 22.5 24.9 .015 4.47 7.5 12.3 6.6 Run 2 duplicate 325 34 37.70.023 0.9411 18.2 1.5

6 220 22.5 24.9 .015 4.47 7.5 12.3 6.6

7 325 36.3 39.9 .023 0.49 8.7 14.3 0.29 . 8 220 19.9 21.9 .015 1.83 10.1 16.6 1.33 9 325 37.5 41.2 .023 0.3d 7.5 12.3 0.30 220 18.8 20.7 .015 1.75 11.2 18.5 1.25 ` 11 325 38.8 42.6 .023 0.31 6.2 10.2 0.31 ~- 12 220 17.5 19.2 .015 1.67 12.5 20.6 1.17 13 325 40.9 45.0 .023 0.33 4.1 6.8 0.33 14 220 15.4 16.9 .015 1.53 14.6 24.0 1.03 295 37.4 41.5 .020 0.79 3.2 5.3 0.25 i 16 250 18.9 21.0 .017 3.70 15.6 25.9 1.26 17 295 37.0 41.0 .020 0.60 2.8 4.7 0.22 b' 18 250 19.3 21.4 .018 3.75 16.0 26.5 1.28 ,` 19 295 40.9 45.0 .023 0.91 4.1 6.8 0.33 250 15.4 16.9 .015 3.06 14.6 24.0 1.0 ", 1C~90034 . . ;, i`

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Effective Ethyl 5 Run C C6 _ S Component ~ BuLi B Component Acet~te No. (Pounds)Y ~ (k~? __ (cm ) (~?_ (kg) (cm ) 21 9.4 4.3 1.254 0.40 0.93 0.171 6.4 2~ 7.1 3.2 0.624 0.31 2.97 0.451 20.0 23 ~.9 4.0 1.161 0.38 0.63 0.189 4.4 24 7.6 3.4 0.725 0.32 3.10 0.425 21.0 ' 25 9.4 4.3 1.254 0.41 0.67 0.171 4.6 ' 26 7.1 3.2 0.624 0.31 2.66 0.451 18.0 27 9.9 4.5 1.335 0.42 O.g2 0.165 6.9 28 6.6 3.0 0.550 0.28 2.33 0.450 16.0 - 15 29 8.9 4.0 1.242 U.38 0.52 0.108 4.1 ' 30 7.6 3.4 0.621 0 32 2.68 0.529 18.4 .
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` The magnitude and temperature of the tan ~ maximum corresponding to the glass transition temperature of the polybutadiene ` blocks are used as criteria of polymer morphology. Samples exhibiting high tan ~ max values, i.e., from about 0.045 up to about 0.200 or more along with T(tan ~max) values ranging from about -87 to about 75C are shown in the tables to have good impact properties as determined by the falling dart tests. Such samples have impact values in the dart test ranging from about 20 in.-lbs. to greater than 80 in.-lbs. (the limit of ~ the test). Micrographs taken of se~veral radial polymers made using - lO multiple styrene and initiator addition as is exemplified in control Run 4, Table IB, having a tan ~ max of 0.149, T(tan ~ max) of -78C, dart impact oi 53.0 in.-lbs. and HI of 3.0 are shown to possess lamellar morphology. Such polymers have alternating layers of polybutadiene and polystyrene. Since the invention samples have high test values for the criteria descxibed above, it is reasoned that they all exhibit lamellar morphology.
On the other hand, ordinary radial polymers are illustrative of copolymers exhibiting good but not outstanding impact values; control Run 3, Table IB is an example. This sample has a tan~ max of 0.027, a T(tan ~max) of -93C, a dart impact of qO in.-lbs. and a HI of 1Ø
Micrographs taken of similar ordinary radial polymers show them to possess a spherical morphology in which spheres of polybutadiene are embedded in a continuum of polystyrene. On impact, the polystyrene phase takes most of the load, hence relatively low impact values are to be ; 25 expected which correlate with the Vibron results.
~ Inspection of the data presented in Table IIIC, shows that some -~ polymer mixtures exhibiting a styrene block HI index in the desired range of about 2.3 to about 3.9 do not appear to have lamellar morphology based on low impact values, and/or low tan ~ max values. The polymers of Runs 1, 2, and 4-8 illustrate this. It should be noted that the polymer mixture of Run 6 also possesæes a T(tan ~ max) of -87C which is in the desired range. This is because in mixtures of polymers another requirement i9 also needed, namely, tha~ the butadiene blocks of each polymer in the mixture have similar enough molecular weights to be compatible. In Runs 1, 2, and 4-8, the difference between the molecular weights of the butadiene block ranges from about 19,000 to about 128,000.
: The incompatibility apparently influences the morphology of the mixed polymers, thus the desired lamellar morphology is not realized and oo3g~

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relatively low impact values are found in molded articles made from these polymer blends. It is thought that these polymer blends may exhibit cylindrical morphology, i.e., cylinders of butadiene blocks in a . .
continuum of styrene blocks.
:~: 5 Invention Runs 10, 11, 12 and 15 of Table IIIC meet all the desired criteria including compatib:ility of butadiene blocks. Run 14 is : on the borderline between those blends that have the greatly improved ; impact strength and those that do not. The difference in molecular;~ weights of the butadiene blocks in 1:hese blends ranges from about 0 to ;~ 10 about g,000. Thus, for a final criterion, the molecular weight difference between butadiene blocks of mixed linear polymers (blends) ~! should be less than about 10,000.
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Example IV - Part I
A series of dlblock polymers containing polymerized styrene 15 and polymerized butadiene was prepared in 32 ounce (0.95 litre) glass beverage bottles and coupled with epoxidized soybean oil containing an average of 4 epoxide groups per molecule. In each run, the following materials were added to the bottle, while under nitrogen, in the order shown:
1) cyclohexane ~CyC6) then first increment of styrene (S) - 2) purge 5 minutes with nitrogen, cap and fill with nitrogen 3) tetrahydrofuran (T~) 4) n-butyllithium (0.023 g/cm3 in cyclohexane) BuLi 5) react at 60C for 30 minutes 6) second increment of styrene (if used) and react 60C for 30 minutes - no~e that no additional initiator is added so this is not a multiple addition of styrene in the sense contemplated by said Kitchen et al patent.
- 7) butadiene (B), react at 60~C for 30 minutes

8) epoxidized soybean oil (ES0) and react at 60C for 30 minutes

9) stabilizer system 2 parts by weight per 100 parts by weight monomer (phm).
The quantities of each component used are given in the following table:

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Individual Radial Block Co~olymer Formation Efflective(a) n C~C6 First S THE BuLi Second S__ B ES0 No. (cm ) (g) (cm ) (g) ~,cm ) (g) (cm ) 5~ (cm ) (g~
1 400 26.5 29.10.073 2.0 ~ 0 27.5 45.4 0.27 2 400 50.0 55.00.0~3 3.2 28.7 31.5 7.3 12.0 0.~3 3 400 31.9 35.00.013 2.0 0 0 23.1 38.1 0.27 4 400 50.0 55.00.023 3.2 23.1 25.4 ll.g 19.6 0.43 400 36.2 39.80.013 2.0 0 0 17.8 29.4 0.27 6 400 50.0 35.00.023 3.2 18.8 20.6 17.2 28.4 0.43 7 220 27.7 30.50.013 6.7 0 0 23.0 28.0 0.25 8 400 50.0 55.00.023 1.7 2~.0 30.8 12.2 20.0 0.45 9 220 32.4 35.60.013 6.7 0 0 18.4 30.4 0.25 15 10 600 50.0 55.00.023 1.7 23.0 25.3 16.9 27.7 0.45 11 220 38.4 ~12.1 0.013 6.7 0 0 12.7 21.0 0.25 12 600 50.0 55.00.023 1.7 17.5 19.2 22.5 37.1 0.45 13 220 2~.0 26.40.013 6.7 0 0 26.0 43.0 0.25 14 400 50.0 55.00.023 1.7 32.3 35.5 7.7 12.7 0.45 20 15 400 40.5 44.50.013 2.0 0 0 15.5 22.3 0.27 16 400 50.0 55.00.023 3.2 14.5 15.9 21.5 35.5 0.43 17 175 11.6 12.80.006 3.2 0 0 12.5 20.6 0.27 l 18 310 39.0 42.90.011 0.8 0 0 3.9 6.4 0.07 -', 19 175 15.4 16.90.006 3.2 0 0 8.7 14.3 0.27 25 20 310 35.2 38.70.011 0.8 0 0 7.7 12.7 0.07 ~,~ (a) Slightly more than this was used depending on the measured catalyst ~I
poisons. The effective amount is the cc of the solution used in .
~, addition to a small amount needed to scavenge poisons.
Notes: The styrene in each even numbered run was added in two portions because of safety considerations. After the firæt portion polymeri~ed, the remainder was charged and allowed to polymerize. Thus, a single polystyrene block was formed from two styrene portions, i.e.~ it was not multiple addi~:ions as defined hereinbefore because no additional initiator was added.
The THF and ES0 were each added as a solution in cyclohexane, having 0.034 gram of compound per cm3 solvent.
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`` 109~ q . 26 The stabilizer system consisted of 1.5 phm tri(mixed mono- and ~ dinonylphenyl) phosphite (Wytox 312), and 0.5 phm 2,S-di-t-butyl-4-'~ methylphenol contained in cyclohexane.
~` Example IV - Part II
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in pairs, i.e., runs 1 and 2, 3 and 4, S and 6, etc.,-to obtain a cement, in each instance, except for two cc.ntrol runs, containing a mixture of ~` polymers of differing polystyrene block molecular weights. Each cement : mixture was thoroughly blended together, devolatilized in a vacuum oven at 210F (99C), and the dried material was milled on a roll mill at 280F (138C) for 3 minutes after banding commenced to further homogenize and densify the sample. Film samples for the dynamic viscoelastic ~ measurements were prepared by compression molding 1 g samples at 5000 `~ psig (34.47 MPa g) for 4 minutes and then for 1 minute at 30,000 psig (206.8 MPa g). The samples were cooled in about 10-15 minutes to about 190F (88C~ under the 30,000 psig initial pressure by passing cooling ; water through the press and then removed. The measurements of dynamic ' modulus and loss argle were carried out by means of a Vibron Direct ` Reading Viscoelastometer, Model DW-II (Toyo Instruments Co., Tokyo, ;-~ 20 Japan). All experiments were made on test samples cut from the compression mold~d film which were about 1/8" wide (0.05 cm), 1.2" long (3 cm) and about 10 mils (0.025 cm3 in thickness. The samyles were ` tested at 35 H at temperatures ranging from about -100C to about 20C.
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In discussing the test results, especially the Vibron results, it is to be noted that the magnitude of the maximum loss tangent (tan max) and the temperature at which the tan ~ max occurs for the - polybutadiene blocks are used as criteria of polymex morphology. From work on other polymers it is observed that test samples exhi~iting high tan ~ max values, i.e., from about 0.045 to about 0.200 or more along with T(tan ~ max) ranging from about -87 to about -75C have dart impact values ranging from about 20 to greater than the test limit of 80 in.-lbs. Micrographs taken of multiple addition polymers of the type described in said Kitchen et al patent as exemplified in control run 12, . having a tan ~ max of 0.149, T(tan ~ max) of -78C, dart impact of 53.0 in.-lbs. and a HI of 3.0 are shown to possess lamellar morphology. Since the i~vention polymers of runs 8, 9 and 10 possess the requisite HI
values (2.8 to 3.1), the requisite tan ~ max values (0.0625 to 0.1050) and requisite T(tan ~ max) values of (-87 to -81) it is reasoned that these polymers would exhibit lamellar morphology and that therefore ~- their dart impact values, if run, would fall between 20 and 80 in.-lbs.
- Control run 11 illustrates properties of a typical single styrene and initiator addition polymer which exhibits relatively low impact strength co~pared to the multiple addition polymers of said -~ Kitchen et al patent and the blends of this invention. Mlcrographs taken ~ of single addition polymers show them to possess a spherical morphology i;~ in which spheres of polybutadiene are embedded i~ a continuum of . polystyrene. On impact, the polystyrene phase takes most of the load, ,~ 25 hence these polymers exhibit relatively low impact values. Control runs 1 to 7 are illustrative of polymers also possessing the spherical morphology of the polymer of control run 11, by analogy, since the HI
~:- values of each polymer are less than 2.8. The ~ibron test results, i.e., ~- ~ tan ~ max of less than about 0.045 along with T(tan ~ max) values of less than about -88C for control runs 1 to 7 are typical of polymers exhibiting the spherical morphology.
While this invention has been described in detail for the purpose of illustration it is not to be construed as limited thereby but is intended to cover all changes and modifications within the spirit and .. :..
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Claims (10)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A composition comprising a blend of at least two resinous radial copolymers of a monovinyl-substituted aromatic compound and a conjugated diene, said blend having a heterogeneity index of polymerized monovinyl-substituted aromatic compound blocks within the range of about 2.8 to 3.5.

2. A composition according to claim 1 wherein said copolymers are each copolymers of styrene and 1,3-butadiene.

3. A composition according to claim 2 wherein said copolymers are made by multiple addition of styrene and initiator and wherein said copolymers each have a heterogeneity index of the styrene block thereof outside the range of about 2.8 to 3.5.

4. A composition according to claim 2 wherein said copolymers are prepared by introducing initiator and said styrene into a polymerization zone in a single portion.

5. A composition according to claim 2 wherein said blend exhibits a morphology characterized by an alternating lamellar configuration.

6. A composition according to claim 2 wherein the heterogeneity index of the polymerized styrene block of each of said at least two resinous radial polymers is outside the range of about 2.8 to 3.5.

7. A resinous composition comprising a blend of two resinous copolymers, each copolymer being prepared by the sequential addition of a monovinyl-substituted aromatic compound and an initiator, a conjugated diene, and a polyfunctional coupling agent, said blend having a heterogeneity index of polymerized monovinyl-substituted aromatic compound blocks within the range of about 2.8 to 3.5.

8. A composition according to claim 7 wherein said monovinyl-substituted aromatic compound is styrene and said conjugated diene is 1,3-butadiene.

9. A composition according to claim 7 wherein said coupling agent is selected from the group consisting of polyepoxides, polyimines, polyisocyanates, polyhalides, and polyketones.

10. A composition according to claim 7 wherein said coupling agent is epoxidized soybean oil.