CA1050191A - Method for producing transparent block copolymer resin from a vinyl aromatic compound and a conjugated diene - Google Patents

Abstract

METHOD FOR PRODUCING TRANSPARENT
BLOCK COPOLYMER RESIN

ABSTRACT OF THE DISCLOSURE
By block-copolymerizing a vinyl aromatic compound and a conjugated diene in a hydrocarbon solvent with an organolithium compound as initiator, there is obtained a block copolymer which comprises in the molecule three blocks of homopolymerized vinyl aromatic compound, randomly copolymerized vinyl aromatic compound and conjugated diene, and homopolymerized diene, respec-tively. The resulting block copolymer is transparent and excellent in mechanical properties, and is suitable for use in the manufacture of sheeting, film , and various molded articles.

Description

~C)50~L9l 1 .This invention relates to a method for pro-ducing a novel block copolymer resin which is transparent and excellent in mechanical properties~ More particularly, it relates to a novel method for producing a block co-polymer resin which is transparent 9 excellent in mechanical properties, particularly in elongation and impact resist-ance 9 and not susceptible to flexural stress clouding.
It has heretofore been known that block copolymers.of various structures are obtained by co-polymerizing vinyl aromatic compounds and conjugateddienes with an alkali metal or an organo-alkali-metal compound as inltiator. There has.been disclosed, for example, in Japanese Patent Publication NoO 19,286/61, a method for block-copolymerizing styrene 9 butadiene, etc., in two stages using a lithium compound; in Japanese Patent Publication No. 2,423/73, a method for synthesizing a three-blocks copolymer in two stages . using similar monomers; in Japanese Patent Publication ~os. 3,252/72 and 28 9 915/72, methods for preparing a transparent resin by feeding similar monomers alter-nately in four or five stages; and in Japanese Patent Application ~aid-Open ("Kokai") No. 7,597/71, German Patent Application Iaid-Open (Offenlegungsshri~t) No. 2,120,232 9 and Japanese Patent Publication No.
20,038/73, methods for preparing a transparent resin by single stage polymerization from similar monomers.
These methods employ a.s the polymerization initiator an organolithium compound generally known as one-end initiation type or that known as both-ends initiation type In either case 9 these methods are . - 1 --111)5019~L
1 characterized by forming a polymer by means of a living anionic polymerization technique so tha-t each polymer molecule may comprise a plastic block composed chiefly of polymerized vinyl ar~matic compound and an elastomeric block composed chiefly of polymerized conjugated dieneO
It has been known9 however, that when the elastomeric block is composed exclusively of a homopolymer of a conjugated diene, the block copolymer obtained is not sufficient for practical use in elongation, impact strength, and resistance to flexure among mechanical properties (~xample 11 in Japanese Patent Publication ~oO 19,286/61; Japanese Patent Publication ~o. 2,42~/73), giving rise to a disadvantage of the block copolymer in practical application as a resin. On the other hand 9 in a method where a monomer mixture is added all at a time [Japancse Patent ~pplication ~aid-Open ("Kokai") ~o. 7,597/71; German Patent Application ~aid-Open (9'0ffenlegungsschrift") No. 2,120,Z32; Japanese Patent Publication NoO 20,038/73], there is always formed a copolymer block between the plastic block composed chiefly of polymerized vinyl aromatic compound and the ela~tomeric block composed chiefly of conjugated diene owing to the difference in monomer reactivites. In this case, however, a technical difficulty is encountered

2~ in removing a large quantity o* heat evolved from the polymerization of monomers which have been added all at a time. Such a difficulty would certainly be deterrent to the co~mercialization of the method.
The present inventors had conducted exten-sive investigations to develop a method for producing iO:~L9~lL
1 from a vinyl aromatic compound monomer and a conjugated diene monomer as starting materials a transparent resin which is excellent in mechanical properties, particular-ly in impact resistance, and susceptible to nei~her flexural stress clouding nor reduction in mechanical properties at low temperatures. As a resultS it was found that the above object can be achieved by a method for producing a block copolymer by means of an anionic living polymerization technique using an organolithium compound as initiator, which method comprises forming the block copolymer so as to contain in the molecule at least one plas.tic block composed of homopolymerized vinyl aromatic compound and at least one elastomeric block partly composed of randomly co-polymeriz.ed vinyl aromatic compound and conjugateddiene in a specified ratio. ~ased on this ~inding, the present mvention has been accomplished.
. An object of this invention is.to provide :~ a novel resin9 which is transparent and excellent in mechanical properties, obtained from a vinyl aromatic compound monomer and a conjugated diene monomer as starting materials and a method ~or preparing same.
Other objects and advantages of this inven-tion will become apparent from the followlng descrip-25 tion. . - .
This invention provides a method for producing a transparent block copolymer resin, which is characterized by the following five essential conditions in block-. copolymerizing 90 to 65 parts by weight of a vinyl aromatic compound monomer and lO to 35 parts by weight : - 3 -, . . .

1050~L9~.
1 of a conjugated diene monomer in a hydrocarbon solvent with an organolithium compound as initiator: (1) formation of a block copolymer having i~ the moleculc at least one plastic block composed of homopolymerized ~inyl aromatic compound and at least one elastomeric block composed of randomly copolymerized vinyl aromatic compound and conjugated diene, (2) formation of said plastic block composed of homopolymerized vinyl aromatic compound by use of 50 to 90 % by weight of the vinyl aromatic compound monomer, (3) formation of said elastomeric block in such a manner that it may con-tain a randomly copolymerized segment formed by con-tinuously feeding to the polymerizing system a monomer mi~ture of the vinyl aromatic compound and the conjugated diene in a fixed ra-tio in the range from 0.1 to 3.0, a homopolymerized conjugated diene segment, and/or a randomly copolymerized segment formed by feeding all :. . .
at a time or continuously to the polymerization system a monomer mixture of the vinyl aromatic compound and the conjugated diene in a fixed weight ratio of less - than 0.1, preferably in the range from 0.001 to 0.1;
the first named randomly copolymerized segment occupy-ing 50 % by weight or more of the elastomeric block, (4) formation of the block copolymer having an average molecular weight of 0.35 to 1.8 dl/g in terms of intrinsic viscosity, as measured in toluene at 30C., and (5) the polymerization conducted in the presence or absence of 0.01 to 5 mole-% based on total monomer - of a Iewis base compound. The present method would present no particular difficulty in commercializ~tion.

lO SO ~L9 1 1 The block copolymer resin thus produced is characterized by transparency, excellent mechanical properties 9 particuiarly a high impact resistance, little sus-ceptibility to flexural stress clouding9 and good processability, permitting the resin to be used in manufacturing sheeting, filmg usual molded articles, and in other fields where ordinary resins are used.
The method of this invention is explained below in detail.
The ~inyl aromatic compounds for use in this invention are styrene and ~-methylstyrene, vinyl-naphthalene, and nucleus-substituted styrenes such as vinyltoluene, and mixtures of these. The conjugated dienes to be used are 1,3-butadiene and substituted butadienes such as isoprene, piperylene, 2,3-dimethyl-l,~-butadiene, l-phenyl-1,3-butadiene, and mixtures of these. Particularly, styrene among vinyl aromatic compounds and 1,3-butadiene among con~ugated dienes are preferable because of their availability and effectiveness.
The monomer composition in this inven-tion is 90 to 65 parts by weight of a vinyl aromatic com-pound for 10 to 35 parts by weight of a conjugated diene. If the ~inyl aromatic compound is used in excess o~ 90 parts by weLght, the elongation and impact strength among mechanical properties of the resin become inferior, while if its amount is reduced below 65 parts by weight, the tensile strength is decreased and the processability becomes inferior. In the present method, the block copolymer obtained has in the molecule at least one plastic block composcd of homopolymerized vinyl aromatic compound.

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1 In forming said plastic block, are used 50 to 90 %
o~ the total vinyl aromatic compound monomer.
The inert hydrocarbons for use in this invention as solvent are aromatic hydrocarbons such as benzene 9 toluene, xylene, and ethylbenzene, aliphatic hydrocarbons such as hexane and heptane, and cyclo-aliphatic hydrocarbons such as cyclopentane, cyclo-hexane, and methylcyclohexaneO These are used each alone or in mix-tures of two or more~ It is preferable to use generally 1 to 20 parts by weight of a hydro-carbon as solvent for one part by weight of the total~
monomer. It is necessary in advance to sufficiently remove from the above-mentioned solvents and monomers the substances such as water, oxygen, carbon dioxide, some kind of sulfur compounds and acetylenes which destroy the initiators and active ends used in the present inve~tionO As a variation in the present method, it is also possible to obtain the block co-polymer in the form of suspension in a solvent instead of the form o~ solution, by suitably selecting the solvent and the order of addition of the monomers.
$he organolithium compound used in the present method is generally known as an anionic polymerization initiator of the one~end initiation type or of the both-ends initiation type. Examples of the individual compounds include ethyllithium, propyllithium, butyl-lithium, amyllithium, trimethylenedilithium, tetra-methylenedilithi~m, hexyllithium, cyclohexyllithium, phenyllithium, tolyllithium, naphthyllithium, condensed-ring or non-condensed-ring aromatic lithium complexes, .

~ 5~
1 and oligobutadienyldilithium or oligoisoprenyldilithium in living form. These organolithium compounds are used in an amount of generally 0.002 to 5 mole-%, preferably 0.005 to 1.5 mole-% based on total monomer.
~he organolithium compounds are used each alone or in mixtures of two or more.
In the present method; as a part of the elastomeric block in the molecule, there is formed at least one random copolymer segment comprising a vinyl aromatic compound and a conjugated diene and such a segment occupies at least 50 ~0 by weight of - the elastomeric blockO In order to allow the poly-.
merization in this stage to proceed s~oothly, it is also possible to use specified amounts of a ~ewis base compound such as, for example, an ether compound or a tertiary amine compound. Examples o~ effective ether - compounds are cyclic ethers such as tetrahydro~uran and tetrahydropyrane; aliphatic monoethers such as diethyl ether and dibutyl ether; and aliphatic poly-ethers such as diethylene glycol dimethyl ether and diethylene glycol diethyl ether. Examples o~ tertiary amine compounds are triethylamine, tripropylamine, tributylamine, N,N'-dimethylaniline, pyridine, and quinoline. When ~uch a ~ewis base compound is used, the amount to be added is 0.01 to 5 mole-%, preferably 0.05 to 2 mole-% based on total monomer. If it is used in an amount exceeding the upper limit, content of vinyl-bond in the copolymer block composed of vinyl aromatic compound and conju~ated diene and in the homopolymeriæed conjugated diene block becomes markedly :~05~
1 high, resulting in marked deterioration in mechanical properties of the resin, particularly at low tem-peratures. The ~ewis base compound can be added without any particular restriction to the polymerization system at any time prior to the stage where the copolymer region is formed.
In the present method 7 a vinyl aromatic compound monomer and a conjugated diene monomer are block-copolymerized in the presence of an organolithium - ;
compound. The block copolymer thus formed should have in the molecule at least one plastic block composed o~ homopolymerized vinyl aromatic compound and at least one elas-tomeric block containing a segment formed by copolymerization of a vinyl aromatic compound and a conjugated diene in a speoified ratio. A block co~
- polymer of a structure in which a homopolymerized vinyl aromatic compound block is absent or less than 50 %
by weight of the vinyl aromatic compound monomer are used in forming the homopolymerized block is undesirable because of defects in mechanical properties, particular-ly in tensile strength and hardness of the resin. On the other hand, a block copolymer of a structure in which more than 90 %9 particularly 100 % by weight, of the vinyl aromatic compound monomer form the homopolymerized block is not called a useful resin because it is inferior in elongation and impact strength among mechanical pro-perties and easily susceptible to flexural stress clouding. In a block copolymer of a structure in which two or more homopolymerized vinyl aromatic compound blocks are present, sum of the vinyl aromatic compound 1 ~ 5 ~ ~ 9 ~
l used in each homopolymerized block should be 50 to 90 %
by weight o~ the total vinyl aromatic compound monomer.
In the present method, formation of the elastomeric block from a vinyl aromatic compound and a conjugated diene should be conducted in such a manner that the elastomeric block may contain a randomly co-polymerized segment formed by continuously feeding to the polymeriæation system a monomer mixture of the vinyl aromatic compound and the conjugated diene in lO a fixed ratio in the range from 0.1 to 3.0, a homo-polymerized conjugated diene segment, and/or a randomly copolymeri~ed segment formed by feeding all at a time or continuously to the polymerization system a monomer mixture of the vinyl aromatic compound and the con-jugated diene in a fixed weight ratio of less than 0.1,pre~erably in the range from OoOOl to 0.1. The seg-ments composing the elastomeric block are not necessarily linked directly to one another but can be distributed separately throughout the block copolymerO ~he random-ly copolymerized segment in the elastomeric block shouldbe formed from a continuously fed monomer mixture of the vinyl aromatic compound and the conjugated diene in a fixed ratio in the range from 0.1 to 3Ø If the ratio is decreased below 0.1, the impact resistance among mechanical properties of the resulting block co-polymer resin is deteriorated and the susceptibility to flexural stress clouding is increased 9 while if the ratio is increased beyond 3.0, the tensile strength - and hardness of the resin become inferior, both cases being undesir~ble.

- _ 9 _ .

,.

1~51~19~
1 In the case of a block copolymer having a molecular structure in which two or more copolymer segments formed from a monomer mixture of the vinyl aromatic compound and the conjugated diene in the specified ratio as mentioned above are present, each of the segments should be formed from the monomer in the specified ratio and the ratio between the sum of the vinyl aromatic compound and the sum of the con-jugated diene used in forming said segments should be maintained within the specified range from O.l to 3.0;
the monomer ratio in forming each of the segments can be the same or different from one another~
The random copolymer segment formed by con-tinuous feeding of a monomer mixture of the vinyl aromatic compound and the conjugated diene in a weight ratio of 0.1 to 3.0 should occupy 50 % by weight or more of the total elastomeric block. If the proportion o~ random copolymer segment in the elastomeric block ~ is below 50 ~ by weight, particularly if it is null, such a block copolymer is undesirable because of its reduced impact resistance and elongation among mechanical properties and its enhanced susceptibility to flexural stress clouding. On the other hand, if the homopoly-merized conjugated diene segment and/or the copolymer segment formed from a monomer mixture of the vinyl aromatic compound and the conjugated diene in a weigh ratio of less than 0.1, preferably in the range of OoOOl to 0.1, is absent in the elastomeric block, such - a block copolymer shows unsatisfactory mechanical pro-~0 perties, particularly at low temperatures. A preferable -- 10 -- , ~050~gl 1 proportion of the random copolymer segment formed froma monomer mixture of the vinyl aroma-tic compound and the conjugated diene in a weight ratio of 0.1 to 3.0 is in the range from 50 to 90 % by weight of the total elastomeric block. When two or more segments are present ln the elastomeric block, the sum of the segments formed from a monomer mixture of the vinyl aromatic compound and the conjugated diene in a weight ratio of 0.1 to 3.0 should be 50 % by weight or more of the elastomeric block.
- In forming the randomly copolymerized seg-~ent by continuous addition of a vinyl aromatic compound and a conjugated diene, both monomers can be fed either i~ a mixture or separately, maintaining a fixed monomer ratlo within the aforesaid range. In either case, it i8 necessary to feed both monomers in a fixed ratio continuously or substantially continuously to the poly-merization system under such conditions of polymeriza-tion temperature and feeding rate that both monomers will not remain unreacted in the system.
The present method permits to adopt continuous feeding of the monomers in each stage of forming a block copolymer. This is one of the characteristic features of the present method, which allows effective removal of a large quantity of heat evolved from the polymeri-zation reaction when carried out on an industrial scale and, moreover, prevents occurrence of side reactions such as gelation accompanying the heat evolution.
- - Although the block copolymer formed accord-ing to the present invention has no restriction placed ~L~SOl91 ~ .
1 on its structure so long as the conditions mentioned in the foregoing are satisfied~ examples of particularly . preferred structures are given below, wherein Sl, S2, and S3 represent homopolymerized vinyl aromatic com-pound block, (S/B)ls (S/B)29 and ~S/B)~ represent - randomly copolymerized vinyl aromatic compound and conjugated diene block, and Bl and~B2 represent homo- -polymerized conjugated diene block or a block formed from a monomer mixture of a vinyl aromatic compound and a conjugated diene in a weight ratio of less than 0.1, preferably in the range from 0.001 to 0.1.

1) Sl - (S/B)l - Bi : 2) Sl - Bl - (S/~)l ~) 51 - (S/B)l - Bl - S2 . 4~) Sl - (S/B)l - B1 - (S/B)2 ~ S2 . . 5) Sl - Bl - (S/B)l - B2 ~ S2 6) Sl - (S/B)l - (S/B)2 - Bl - S2 7) ~1 - (S/B)l - Bl - (S/B)2 - B2 - (SjB)3 - S2 - 8) Sl - (S/B)l - S2 - (S/B)2 ~ Bl - S3 Z 9) Sl - (S/B)l - Bl - S2 - ~2 - ($/B)2 S3 10) Sl - (S/B)l - S2 ~ Bl - tS/B)2 11) 'Sl - (S/B)l - S2 - (S/B)2 - Bl The present method is carried out by way of multistage polymerization. In each stage, addition of the monomer may be conducted a-t any time after the con-version in the preceding stage has reached substantially 100 %. In the present method, it is possible to obtain an overall converslon of substantially 100 %.
In the present method, the mean molecular - 12 _ 105~)~91 1 wei~ht of the block copolymer resin to be formed is regulated by the amount of an initiator used. Accord-ing to this invention9 the mean molecular weight of the block copolymer should have a value in the range from 0.35 to 1.8 dl/g in terms of intrinsic viscosity {~ , as measured in toluene at 30C. A block co-polymer of low molecular weight, which has an intrinsic viscosity below 0O~5 dl/g~ is undesirable because of decreased mechanical properties 9 while a resin of ex-cessively high molecular weight, which shows an intrinsic ~iscosity exceeding 1.8 dl/g9 is also undesirable be-cause of deterioration in transparency and in pro- -cessability.
The polymerization according to this invention is carried out at a temperature from -20 to 150C., prefe~ably from 20 to 120C. The polymerization pressure is selected from those which are sufficient to keep the monomer and solvent in liquid phase at ~ the polymerization temperature. A sufficient poly-merization time is 1 to 48 hours, usually 1 to 24 hours, though depending on polymerization conditions.
After the polymerization is completed, to the polymerization mixture is added sufficient amount of water, methanol, ethanol, or ispropanol to deactivate the active terminal of the polymer and the residual initiator. After adding, if necessary, a small amount of an antioxidant such as, for example, 4-methyl-2,6-di-tert-butylphenol, the polymer can be precipitated and recovered by use of an excess of methanol, ethanol, or isopropanol. ~n alternative procedure is to recover so~
1 the polymer by directly heating the polymerizate solu-tion to dryness or by contacting the polymerizate solution with steam to remove the solvent by distilla-tion.
The block copolymer obtained according to this invention can be processed by conventional pro-cessing techniques to be used in the field where the conventional resins have been used. The copolymer can also be compounded with conventional stabilizers, reinforcing agents, fillers, and various other addi-tivesO
As mentioned in the for,egoing, the presentinvention provides a novel method for producing a co-polymer resin, transparent and excellent in mechanical propertie,s 9 from 90 to 65 parts by weight of a vinyl aromatic compound monomer and 10 to 35 parts by weight of a conjugated diene monomer, both used as starting materials, by adding to the polymerizatlon system said monomers in specified sequence and in specified combina-tions using an organolithium compound as initiator. The present method may be easily carried out on a commercial scale and the resin obtained is characterized by trans-parency and excellent mechanical characteristics so that it may be used even in the field where conventional resins could not be succe-ssfully used.
~ he invention is illustrated below in detail with reference to Examples, but the invention is not limited to these examples.

~1~5~
1 Example 1 Into a 2.5-liter glass autoclave provided with a stirrer, after the air in which had been re-placed by argon, were charged 1.5 liters of purified, dried cyclohexane 9 1 17 g of tetrahydrofuran~ 125 g of purified styrene 9 and a hexane solution containing 6.5 millimoles of n-butyllithium. The autoclave was externally heated to 60C~ to conduct the first stage polymerization for one hour. Into the autoclave was then added under an argon pressure a mixture of 125 g - of styrene and 75 g of butadiene~ continuously for a period of about 2 hours to con-tinue the second stage polymerization for 3 hours in total. Then, 50 g of butadiene was added into the autoclave to continue the third stage polymerization for one hour. After addition of another 125 g of styrene, the fourth stage polymerization was carried out for 1.5 hours~ hfter a total of 6.5 hours 9 the polymerization ~as terminated by addition of 50 ml of methanol as terminating a~ent.
The resulting solution was poured into a large amount of methanol to precipitate a polymer. The polymer obtained in a yield of 98.5 % had an intrinsic viscosity ~ of` 0.68 dl/g, as measured in toluene at ~0C.
A mixture of 100 parts by weight of the polymer, 005 part of 4-methyl-2,6-di-tert-butylphenol and 0.5 part of tris(nonylphenyl) phosphite, both used as antioxidant, was pelletized by means of an extruder and the pellets were injection molded to prepare specimens for testing physical properties. The molded specimen had an attractive appearance and a hi~h transparency~ The ., ..... .. .. .. , ..................... . .. .. _.~,~

50~L9~
1 results of test were as shown in Table 1.

Table _ . .
Intrinsic viscosity(l), dl/g 0.68 _ __ . _ .
Melt index(2) 9 g/10 minutes 1.96 _ _ _ _ .
. Tensile strength (yield point)(3), kg/cm2 171 , _ __ _ . _ _ .
Tensile strength (breaking point)(3), kg/cm2 239 Elongation(3), ~o 359 ~ .
Izod impact strength(4) 9 Xg-cm/cm2 > 100 . _ _ __ Haze value(5), % 7.5 .

~ote: (1) Measured on the polymer before pelleti~ation, ln toluene at 30C. by means of an Ubbelohde viscometer.
(2) Measured according to JIS K 6760.
. (3) Measured according to JIS K 6871 at 20C.
and at a speed of testing of 5 mm/minuts.
(4) Measured according to JIS K 6871 on un-. notched specimens at 20C.
(5) Measured according to ASTM D 100~.

Examples 2 to 4 Polymerization was conducted by use of the same apparatus and in the same manner as in Example 1, except that combinations o~ the monomers were as shown in Table 2. In each Example, 1.17 g o~

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1 tetrahydrofuran were used as the ~ewis base com-pound.

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, . . :

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~ ~, O ~J N ~J . ..
O ~0 .
'~- ' '~h~a~ _ '~ O O O .
h ~ h ~ h --- O O O, . '' ~ j h o~ ¦ ~ ;

E~ _ . '~bD ~DC =~ ~ : ' .
O ~ rl ~ ~ ~ o rd . _ U~ ~ l ~Q ~
. 1::- O O O

- -. ~æ N 1~ _ .: . .

~os~9~l 1 ~ The polymer obtained was treated in the same manner as in Example 1. Results of test for physical properties were as shown in Table ~.

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P~ o o o ~ r-- ,0~ N
N
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O C~ St ~ IS~ O O . ..
N ~ ~1 ~_1 H ~h .~ A ~
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rl ~
t'rl bD ' S~ l O O O
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1 Example 5 In a manner similar to that in Example 1, five.-stage polymerization was carried out using the monomer combination as shown below. Polymerization in the second and fourth stages was conducted while feeding the monomer mixture under an argon pressure continuously for a period of 1.5 hours. The amounts of tetrahydro~uran and n-butyllithium were the same as in Example 1.

Monomer in the first stage: Styrene. 125 g Monomer in the 2nd stage: Styrene 62.5 g Butadiene 37.5 g Monomer in the 3rd stage: Butadiene 50 g Monomer in the 4th stage: Styrene 62.5 g ' . . Butadiene 37.5 g .Monomer in the 5th stage: Styrene 125 g . . The polymerization procedure in Example 1 . was ~ollowed and the polymerizate obtained was treated .
in the same manner as in Example 1. The results of .,test for physical properties were as shown in Table 4.

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1 ~ Table 4 Int,rinsic ViSCos1ty, dl/g 0.69 Melt index, g/10 minutes 0.91 Tensile strength (yield point)~ kg/cm2 205 Tensile strength (breaking point) 9 kg/cm2 2~3 Elongation, % ' 384 . Izod impact strength9 kg~cm/cm2 > 100 Haze value 9 % . 9 5 ~ . _ Examples 6 to 8 Polymerization was carried out in the same manner as in Example 5, except that the monomer com-binations used were,as shown in Table 5. ~he amountsof n-butyllithium (as initiator) and tetrahydrofuran ewis base compound) were the same as in Example 5.

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' -~ bD LL~ C- ~ GO r-~ ~ ~ ~ ~ V~ ~
~ ~ o lo o `:
~ ~ ~ ~
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æ~ f~ ~
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10501~

1 . The polymerizate obtained was treated in the 8ame way as in Example 1. The results of test for physical properties were as shown in Table 6.

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.

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N
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N p~ ~ . .
H ~ ~ ~ .
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~ . N t~ l ~1 ~O
U~ ~ ~1 Ir~ O t~ C~J ' h~,, P.

rl ~ a) ~ O N d-~ ~1 o cr~ 1 E-l P-~ ~ N N
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H ~
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1~50:~9~ -1 Examples 9 and 10 Polymerization was carried out in the same manner as in Example 1, except t`hat the monomer com-binations were as shown in Table 70 As the ~ewis base compound, 009 g of tetrahydrofuran was used.
.
_ ~05~9~ -~ . . _ ~3~ D
' ~
_ _ ~bO ~0 O ~ .- .

~ ¦ a~ ~D ¦ a a ¦ a ~, ¦
H 9 N r N

~` ~ ¦ a ¦ a j- a ¦;

~1 _ - I ' ~ ~__ ~50~1 1 The polymerizate obtained was treated in the same manner as in Example 1. The results of test for physical properties were as shown in Table 8~ -,. .. : .

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. N ~ h ~ -~ ' . ' O ~ ~O , ~0 1~1 ~ a~ a ~ ~1 ~

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cq.,~ b~ O ~
.~ o ~ O O
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1 ~Example 11 In the present Example 9 oligoisoprenyldi-lithium compound was synthesized in the following manner and used as an organolithium compound of the both-ends initiation type.
Into a 300-ml four-necked flask, after the air in which had been replaced with argon, were charged 50 ml of purified tetrahydrofuran and 0.35 g (0.05 mole) o~ dispersed metallic lithium~ Into -the flask was added with stirring 6O4 g (0.05 mole) of naphthalene dissolved in 150 ml of tetrahydrofuran through a dropping funnel and allowed to react for 24 hours.
To the reaction solution, after having been cooled .. . .... .
to -40 to -50C., was added gradually 40 ml of isoprene with a period of about 6 hours. Thereafter, the flask was warmed slowly to room temperature and further heated under reduce pressure to remove tetra-hydrofuran by distillation. The contents of flask ~ere dissolved by adding 400 ml of purified benzene, and the resulting benzene solution was subdivided into small portions and stored in ampoules to be used later in polymerization.
The polymerization according to this invention was carried out by use of the same apparatus as in Example 1 in the following way.
Into the reactor, were added 1.5 liters of cyclohexane, 0.9 g of tetrahydrofuran, 50 g of . ~ .
_ 30 -~1~5~L9~

1 butadiene, and 120 ml of oligoisoprenyldilithium initiator solution, and allowed to react at 60C~
for 2 hours. To the reaction mi~ture9 was added continuously a mixture of 125 g of styrene and 75 g of butadiene to continue the polymerization for 3 hoursO Then9 250 g of s-tyrene was added and poly-merization was allowed to proceed for 1.5 hours.
After termination o~ the polymerization9 the poly-merizate mixture was treated in the same manner as in Example 1. Physical properties of the polymer obtained were as shown in Table 9 Table 9 _ _ . . I -Intrinsic viscosity, dl/g - 0.73 .
Tensile strength (yield point), kg/cm2 197 Tensile strength ~breaking point)9 kg/cm2 228 Elongation, % ~72 I~od impact strength9 kg.cm/cm2> 100 Haze value, % lO.S
.

Comparative Examples 1 to 4 Polymerization and after-treatment were carried out in the same manner as in Example 19 except that the combinations of monomer and a I.ewis base compound were as shown in Table 10. The results obtained were as shown in Table 11.

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_ _ = _ _ ~
-q~ ~ 3 ~ ~

,, o 0 o o ,~ ,, V V ~ ~
_ ___ o O O h o __ æ ~ h O h h ~I> ~ \ \ ~ ~
. a~D \ \ ~" s~
_ _ ~ ^ o o o o ~ o O~ h ~ ~ d s~ s:~
,. ~ o~ :~ ~ ~ 01 E~ ~ U~ U~ ~ U~ ~
.~ '. . . ~ O O- O O--~ ~ ~D ~ rl rl rl ~ N _ ~1 ~q Irl _ o o o a~
h ~c~l cu r-l ~1 a~ ~ a) a) ~
~D ~I :: ~ , ~:
~- _ _ "a _ _ _ ~

.

.. .

1050~91 '' ~.. ~' __ _ ? ~
N
H
__ rl .
~1 ~ ¦ - l !
,~.

~ ,~

o :~, .
W~I I

. _ .

~ P ~ ~ C~ ' ~ ;
_~ ~ . _ .

. , ..... .,.~,~.. _ 1 As is apparent from Table 11, those block copolymers which have in the molecule an elastomeric block composed of polymerized conjugated diene alone 7 are inferior in physical properties (Comparative 5 Examples 1 and 2). It was also found that when the monomer mixture was added all at a time and poly-merization was carried out in the absence of a ~ewis base compound such as tetrahydrofuran, mechanical pro-perties of the resulting polymer become markedly 10 inferior (Comparative Example 3). It was further found that a block copoly~er having elastomeric blocks in which the copolymerized conjugated diene and vinyl aromatic compound segments occupy less than 50 ~ by weight is inferior in mechanical properties to the 15 block copolymer prepared according to this invention (Comparative Example 4).
: ' . .
~xample 12 ~ Into a 2.5-liter glass autoclave, after the 20 air in which had been replaced with argon~ were charged 1~5 liters of purified, dried, and deaerated cyclohexane and i50 g of styrene. A n-butyllithium solution diluted with n-hexane to a predetermined concentration was added dropwise into the stirred autoclave until a pale 25 orange color characteristic of a polystyryl anion appeared. Thereafter, 6.5 millimoles of n-butylli~hium was added as an initiator into the autoclaveO The - autoclave was heated to 100C. and stirrin~ was con-- tinued for one hour. ~ mixture prepared from 50 g of 30 styrene and 30 g of purified dry butadiene was added 1 to the polymerization system, maintained at 100C., continuously at a rate of 1 g per minute. After the addition, stirring was continued for 30 minutes. `t' Then, 40 g of butadiene was added and polymerization was continued for one hour. To the polymerization system was further added a mixture of 50 g of styrene and 30 g of butadiene continuously at a rate of 1 g per minuteO After the addition 9 stirring was con-tinued for ~0 minutes and then 150 g of styrene was added to continue the polymerization for further one hour at 100C.
The polymerization was terminated by addi-tion of 50 ml of methanol and the resulting poly-merizate solution was poured into a large amount of methanol containing 4-methyl-2,6-di-tert-butylphenol as antioxidant, to precipitate a polymer. The pre-cipitated polymer was collected by filtration and dried in vacuo to obtain a dry polymer in a yield of 98.6 ~. The polymer had an intrinsic viscosity ~ of 0.70 dl/g, as measured in toluene at 30C. A mixture of 100 parts by weight of the polymer, 0.5 part of 4-methyl-2,6-di-tert-butylphenol and 0.5 part of tris(nonylphenyl) phosphite, both used as antioxidant, was pelletized by means of an extruder. The pellets were injection molded to prepare specimens for testing physical properties. The molded specimen had an attrac-tive apperance and a high transparency. The resul-ts of test were as shown in Table 120 ~050~L91 1 Table lZ
. . . _. _ Intrinsic viscositytl), dl/g 0.70 Melt index(2) 9 g/10 minutes 0.81 Tensile strength(3), kg/cm2 279 Elongation(3) 9 % 220 Izod impact strength(4), unnothced 9 kg - cm/cm2 45.0 Flexural stress clouding , mm 3.3 ~lass transition temperature(6), C. -58 . _ _ _ __ _ ~ote: (1) Measured on the polymer before pelletization, i~ toluene at 30C. by use of Ubbelohde viscometer.
(2) Measured in accordance with JIS K 6760.
1 (3) Measured in accordance with JIS E 6871.
(4) Measured in accordance with JIS K 6871, at 20C., unnotched.-- (~5) ~ specimen9 38 mm 2 13 mm, was cut out o~ a press-molded sheet, 1 mm in thickness, and annealed at 80C~ for 3 hours. ~he annealed specimen, without incision, was mounted on a holder specified in JIS Z 1703, left standing ln the air at room temperature for 24 hours and the width of cracks dis-tribution developed due to the stress was measured.
(6) Calculated from the kinetic viscoelasticity data as a function of temperature.

' ' '' -'"'`''~F

~s~

1 iExamples 13 and 14 . Polymerization was carried out in the same manner as in Example 12, except that monomer combina-tions were as shown in Table 13.

,.... ...... ~

1~50~
- - - o '~ b~ ,~ ,~
S~ ~d a) ~
~ ~ ~ . i ~
~ ~ h _ ~ , U~ U~
N 1~ C-- i~
5 bD ~ , t~ ~
~ ~ ~ a) .

¦ i~ ~ ¦ h :~ h ~ ¦ ;
, . _ '~'~0` ~ U~ .
El ~q bD ~ - ~1 G~ ~ ~ ~ . ~ I ~
~1 _ 00 E~ . L~ Ll~
t~ c- c-s~ ~ ~ t-~ ~
,. El~qbD ~I~ s:~
s:: ~ a) ~ Q) ~ ~ ~
, ~:~ ~ ~ ~ ~, ' O ' h 0 . ~1 'o~ ~ ~ .
~1 ,~ ~ ~ .' ~- ~ ~
X~; . .,. , '';

.
. .

. .... .... ... _.

~)5(~1g~
1 The polymerizate obtained was treated in the ; 5ame manner as in Example 12. Phys~cal .properties o~
the polymer were as shown in Table 14.

' .. :

, , , , -:~

; . _ 39 -:
...... - ~-,..... _ _ .
,..... - ' ~ ~ .
~: h ~Q bD t~ O
~ . ~
$~ J
~1 :

c) ~
~ ~ O t~
~ ~\
H U~ Yl ' ~ _ . .
-1 '~

. ~ .

C ~ Uo~ ,~ ~
. ~ 5: h ~ c~ J
. -- -L . ~ ~
' ' . ~0 O O
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. ' ~ 0 H P O O
~ I .
t~ ;~j ..
.. '. . ~. ' ' ;. :

.. _ ... ~r~

9LQ50~9~1L
1 ~Example 15 In a manner similar to that in Example 12, four-stage polymerization was carried out by use of the monomer combinations shown below. Polymerization in each of the first, third, and fourth stages was conducted for one hour. The copolymer segment of styrene with butadiene was formed in the second stage while feeding the monomer mixture continuously at a rate of 1 g per minute.
1~ . .
~onomer in the first stage: styrene 150 g Monomer in the second stage: styrene 100 g butadiene 60 g Monomer in the third stage: butadiene 40 g Monomer in the fourth stage: styrene 150 g The amount of n-butyllithium used as the initiator was 6.5 millimoles. The polymerizate obtained was treated in the same manner as in ~xample 12. ~he results of test physical properties were as shown in Table 15.

Table 15 Intrinsic viscosity, dl/g 0.71 Melt index, g/lO minutes 0.55 Tensile strength, kg/cm2 258 Elongation, % 213 ~
Izod impact strength, unnotched, kg-cm/cm242 0 Flexural stress clouding, mm 3.1 . : . -D

105~
1 Example 16 . In a manner similar to that in Example 12, seven-stage polymerization was carried out by use of the monomer combinations as shown below.

5Monomer in the first stage: styrene 150 g Monomer in the second stage: styrene 25 g butadiene 25 g Monomer in the third stage: butadiene 25 g Monomer in the fourth stage: styrene 25 g 10butadiene 25 g Monomer in the fifth stage: butadiene 25 g - Monomer in the sixth stage: styrene 25 g . - ~ butadiene 25 g Monomer in the seventh stage: styrene 150 g ' The amount of the initiator used was 6.5 millimoles 9 as in Example 12. Polymerization was con-ducted for one hour in each of the first and seventh stages and for 30 minutes in each of the third and fifth stages. In the second and fourth stages, the monomer mixture was continuously fed at a rate of 1 g per minute. In Table 16 were shown physical properties of the polymer obtained after the treatment similar to that in Example 12~
, `

1~5C7~L91 1 Table 16 , . . .
Intrinsic viscosity, dl/g . 0.70 Melt index, g/10 minutes 0.60 Tensile strength, kg/cm2 23~
Elongation, % . 297 .
Izod impact strength, unnotched, kg cm/cm2 50.3 Flexural stress clouding, mm 4.6 .

: Comparative Examples 5 to 8 .

Polymerization was carried out in the same manner as in Example 12, except that the monomer com- :
binations and methods of feeding monomers in forming the copolymer segments of styrene with butadiene and . the homopolymerized butadl.ene segments were as shown - in Table 170 - ., .

. . 43 ~LOS~
_ F~. a) ~ O ~ a) Q) h O
Q) Q) ~ c) I ~ ~ 'H ~D
h ~ O O +' ~d ,~ ,~h Q) O o ~
h ~ E 'd El h::~ O bO +' a) ' o h El ~ bD ~3 rd ,D ~ . tn :~ ~3 rd O ;~D O ~ Q~ a) ~ ~ r~ . Q cd '~ -~H Q> ~ ~H c~ ~ E3 ^~H
~ a C~ ~d 5~ c~ ~ ~D ~ O ~ ~1 O ~H S:~ ~ +~ ~: ~ +~ C) (D ta cd t~i +~
, ~ . O~ ~ E3 sl 'H ~ ~ ~ o E3 Q~ ~ ~ Q~ o X ~ bD~ ~ ~ ~ ~ ~ s~
~ ~rl ,D t~ ~ H 3 +~ ~1H ;~ ~d H ~ ~ H E3 ~ ~ .
_ ~^ g O O
~ ~J rl l . ~bD .1 ~ S:~ Q~

h h U~ h ~_ ,01 ,01~ 00 . E3 ~ l Q) ~ ~ Q
. N +~ ,Q) ~d h . ~q ~ ~ ~ m : _ _ .
~ o $ $ o o~
~-1 d- ~--I N ~--I ~1 h

3 ~q bD d s~ S:

--I :~ h ~ ' P~
V~ 1~1 U~ U~ V~
. _ _.
P
.
h ~ ~2; If~ ~ t--~ . .
C~ . .
_ _ _ ' 105~91 1 -After having been treated in the same manner as in Example 12, the polymer obtained was tested for physical properties. The results obtained were as shown ln Table 18.

. "' , '.
.

, . I~5 S~
_ . _ _ ,,.. -. .
, .~ ..
~ U~ ~ ~ . W L~ I
:, ~ V ~ ~ 0~ 1 ~1 u~ a) o C~ .
, _ _ _ __ s~ ~

r~ ~ O ~ ~, ~ N
X Ql ~ ,!d~ l ~D ~ O O
C~ ~d _ .
O U~
~bD~ O t~ ~ O .
o ~ E~ O r~ O
C~ ~> C) ~ ~
O ~ S~ ~
_ , ,CD 1~ .

,D O O vt ~ d I ~ ~
E-~ . _ . _ . ~ ' 'I ~ O t~
~1 ~ , E~ 1 ~ 0~ ' . _ _ . :
..
a~
. ~'~ ~ C~
.. ''10 ~I ~ o ~
~'l ~i o o ~ ., ~:~
. . _ oP.
d o~ w Lr~ ~
~ O, o o o H P .
__ '.
~ ~1 .
~, o .
. ~r~ ~ O U~
~ ;
C~ F~l ~ _ o ` . ... . ,.~

Sl~iL9~L
1 It is seen from the results that if the co-polymer lacks in homopolymerized styrene block, as in Comparative Example 5, tensile strength of the resin becomes markedly low, while if in the second s~tage butadiene was homopolymerized or styrene and butadiene were copolymerized to form less randomly copolymerized segment by feeding the monomer mixture all at a time, as in Comparative Examples 6 and 7, the resulting block copolymers become lnferior in elongation and impact strength9 and more susceptible to flexural stress clouding. Therefore, such copoly-mers are undesirable.
On the other hand, if in the second stage styrene and butadiene were randomly copolymerized by continuously feeding the monomer mixture and no homo--polymerized butadiene segment was formed, as in Com-parative ~xample 8, the resulting polymer becomes ~uperior in impact strength and less susceptible to flexural stress clouding, whereas the glass transi-tion point becomes higher, indicating deterioratedmechanical properties at low temperatures.

; 47 -. ~ r~

Claims (31)

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

1. In a process for forming a block copolymer having in the molecule at least one plastic block composed of a homopolymer of a vinyl aromatic com-pound and at least one elastomeric block composed of a vinyl aromatic compound and a conjugated diene by block-copolymerizing 90 to 65 parts by weight of a vinyl aromatic compound monomer and 10 to 35 parts by weight of a conjugated diene monomer in a hydro-carbon as solvent with an organolithium compound as initiator in the presence or absence of 0.01 to 5 mole-% based on total monomer of a Lewis base compound, the improvement whereby a transparent block copolymer resin is formed, which comprises forming a block co-polymer which has a plastic block formed by homo-polymerizing 50 to 90 % by weight of total vinyl aromatic compound monomer and an elastomeric block composed of (1) a segment formed by continuously feed-ing to the polymerization system a monomer mixture of a vinyl aromatic compound and a conjugated diene in a fixed weight ratio in the range from 0.1 to 3.0 and at least one of (2) a segment formed by homopolymerizing a conjugated diene, and (3) a copolymer segment formed by feed-ing a monomer mixture of a vinyl aromatic compound and a conjugated diene in a fixed weight ratio of less than 0.1 continuously or all at a time to the poly-merization system; said segment (1) occupying 50 %
by weight or more of said elastomeric block; said block copolymer having an average molecular weight of 0.35 to 1.8 dl/g in terms of intrinsic viscosity as measured in toluene at 30°C.

2. A process according to Claim 1, wherein the vinyl aromatic compound is at least one member selected from the group consisting of styrene, .alpha.-methylstyrene and vinyltoluene.

3. A process according to Claim 2, wherein the vinyl aromatic compound is styrene.

4. A process according to Claim 1, wherein the conjugated diene is at least one member selected from the group consisting of 1,3-butadiene, isoprene and piperylene.

5. A process according to Claim 4, wherein the conjugated diene is 1,3-butadiene.

6. A process according to Claim 1, wherein the hydrocarbon is at least one member selected from the group consisting of paraffinic, naphthenic and aromatic hydrocarbons having 3 to 20 carbon atoms.

7. A process according to Claim 6, wherein the hydrocarbon is at least one member selected from the group consisting of hexane, heptane, cyclohexane, methylcyclohexane, benzene and toluene.

8. A process according to Claim 1, wherein the hydrocarbon is used in a proportion of 1 to 20 parts by weight per part by weight of the total monomer.

9. A process according to Claim 1, wherein the Lewis base compound is at least one member selected from the group consisting of an ether compound and a tertiary amine compound.

10. A process according to Claim 9, wherein the ether compound is at least one member selected from the group consisting of cyclic ethers, aliphatic monoethers and aliphatic polyethers.

11. A process according to Claim 10, wherein the ether compound is at least one member selected from the group consisting of tetrahydrofuran, tetra-hydropyran, diethyl ether, dibutyl ether, ethylene glycol dimethyl ether and diethyleneglycol diethyl ether.

12. A process according to Claim 9, wherein the tertiary amine compound is at least one member selected from the group consisting of triethylamine, tripropylamine, tributylamine, N,N'-dimethylaniline and pyridine.

13. A process according to Claim 1, wherein the Lewis base compound is used in a proportion of 0.05 to 2 mole-% based on the total monomer.

14. A process according to Claim 1, wherein the Lewis base compound is not used.

15. A process according to Claim 1, wherein the organolithium compound is at least one member selected from the group consisting of an organo-monolithium compound and an organodilithium compound.

16. A process according to Claim 15, wherein the organomonolithium compound is at least one member selected from the group consisting of ethyllithium, propyllithium, butyllithium, amyllithium, hexyllithium, 2-ethylhexyllithium, cyclohexyllithium, decyllithium, dodecyllithium, phenyllithium, tolyllithium, xylyl-lithium and naphthyllithium.

17. A process according to Claim 16, wherein the organomonolithium compound is butyllithium.

18. A process according to Claim 15, wherein the organodilithium compound is at least one member selected from the group consisting of trimethylene-dilithium, tetramethylenedilithium, pentamethylene-dilithium, naphthalene-lithium complex, stilbene-lithium complex, diphenyl-lithium complex, oligo-butadienyldilithium and oligoisoprenyldilithium.

19. A process according to Claim 18, wherein the organodilithium compound is at least one member selected from the group consisting of oligobutadienyl-dilithium and oligoisoprenyldilithium.

20. A process according to Claim 1, wherein the organolithium compound is used in a proportion of 0.002 to 5 mole-% based on the total monomer.

21. A process according to Claim 1, wherein in forming in the molecule two or more plastic blocks composed of vinyl aromatic compound homopolymer, the sum of the vinyl aromatic compound used in each plastic block is 50 to 90 % by weight of the total monomer.

22. A process according to Claim 1, wherein in forming in the molecule two or more elastomeric blocks composed of a random copolymer of a vinyl aromatic compound and a conjugated diene, the weight ratio between the vinyl aromatic compound and the conjugated diene used in forming each elastomeric block is in the range from 0.1 to 3.0 and the weight ratio between the vinyl aromatic compound and the con-jugated diene used in forming all of the elastomeric blocks is also in the range from 0.1 to 3Ø

23. A process according to Claim 22, wherein in forming in the molecule two or more elastomeric blocks by feeding continuously a vinyl aromatic com-pound and a conjugated diene in a fixed ratio, said fixed ratio is different in each of the elastomeric blocks.

24. A process according to Claim 22, wherein in forming the elastomeric block, the vinyl aromatic compound and the conjugated diene are fed in a fixed ratio continuously or consecutively deemed as sub-stantially continuously.

25. A process according to Claim 24, wherein the monomer mixture is fed at such a rate that the monomers which were fed may polymerize substantially instantly under the polymerization conditions and not remain unpolymerized in the polymerization system.

26. A process according to Claim 1, wherein the conjugated diene homopolymer segment occupies less than 50 % by weight of the elastomeric block.

27. A process according to Claim 1, wherein less than 50 % by weight of the elastomeric block are occupied by the segment formed by feeding a monomer mixture of a conjugated diene and a vinyl aromatic compound in a fixed weight ratio in the range from 0.001 to 0.1, all at a time or continuously to the polymerization system.

28. A process according to Claim 1, wherein in forming all blocks, the monomer or the monomer mix-ture is fed continuously.

29. A process according to Claim 1, wherein the structure of the block copolymer is represented by any of the following formulas:

(1) S1 - (S/B)1 - B1 (2) S1 - B1 - (S/B)1 (3) S1 - (S/B)1 - B1 - S2 (4) S1 - (S/B)1 - B1 - (S/B)2 - S2 (5) S1 B1 - (S/B)1 - B2 - S2 (6) S1 - (S/B)1 - B1 - (S/B)2 - B1 - S2 (7) S1 - (S/B)1 - B1 - (S/B)2 - B2 - (S/B)3 - S2 (8) S1 - (S/B)1 - S2 - (S/B)2 - B1 - S3 (9) S1 - (S/B)1 - B1 - S2 - B2 - (S/B)2 - S3 (10) S1 - (S/B)1 - S2 - B1 - (S/B)2 (11) S1 - (S/B)1 - S2 - (S/B)2 - B1 wherein S1, S2, and S3 represent homopolymerized vinyl aromatic compound blocks, (S/B)1, (S/B)2, and (S/B)3 represent randomly copolymerized vinyl aromatic and conjugated diene segments, and B1 and B2 represent homopolymerized conjugated diene segments or segments formed by feeding a vinyl aromatic compound and a conjugated diene in a weight ratio in the range from 0.001 to 0.1.

30. A process according to Claim 1, wherein the polymerization is effected at a temperature in the range from 20° to 120°C.

31. A process according to Claim 1, wherein after completion of the polymerization, the poly-merization solution is contacted with excess of a lower alcohol, or directly heated to dryness, or mixed with steam, thereby removing the solvent to recover the polymer.