CA1271280A - Transparent, impact-resistant styrene block polymers and their preparation - Google Patents

Abstract

Abstract of the Disclosure: Block polymers of vinylaro-matic compounds and conjugated dienes which possess acidic terminal groups, are present in the form of li-thium salts and form an aluminum complex. A process for the preparation of such complexes and the use of these block polymer complexes as molding materials and for modifying thermoplastic materials.

Description

~7~
. .
- 1 - O.Z. 0050/38064 rransparent~ impact-resistant styrene block poLymers and their preparation ~ _ , , ,~
The present invention relates to block polymers of vinylaromatics and conjugated dienes, which possess terminal acidic groups and are present in ~he form of lithium salts and complexes of an aluminum compound.
It is known that polymerization of styrene and butadiene with a lithium-hydrocarbon as an initia~or gives block copolymers in which one or more nonelasto-meric polymer blocks are associated with one or moreelastomeric polymer blocks. Depending on the content of polymer blocks in the total polymer, these thermo-plastic block copolymers possess nonelastomeric or elas-tomeric properties. Successive polymerization of the monomers gives block copolymers having a linear struc-ture~ If such linear block copolymers are coupled to one another via functional react;ve compounds, branched block copoly~ers result, as described in, for example, British Patent 985,614. These have a symmetrical struc-ture and generally exhibit improved processability com-pared with the linear block copolymers.
It is a~so known that styrene/butadiene block copolymers having a high styrene con~ent are transparent, impact-resistant thermoplastic products. Although the block copolymers of this type which have been developed and proposed to date have satisfactory properties in some respects, they still do not meet many of the requirements set in practice.
German Laid-Open Application DOS 1,959,922 des-cribes branched block copolymers ~hich have a star-shaped structure and consist of a predominant amount of styrene and a smaller amount of a conjugated diene, and are said to combine impact strength, transparency~ good processability and external stability in one polymer.
These branched block copolymers are obtained by coupling two-block styrene/diene copolymers in which the terminal polystyrene blocks have different block lengths, with ~ " ~, ~7~

- 2 - O.Z. 0050/38064 the result that an asymmetric structure is obtained in the branched block copolymers. Although these products have improved properties compared with the symmetric branched block copolymers, they are not completely satis-factory in respect of their mechanical properties, inparticular their impact strength.
~ lock polymers of styrene and butadiene which are obtained using a lithum-hydrocarbon as an initiator and carry terminal carboxyl groups are known. They are disclosed in, for example, German Laid-Open Application DOS 2,723,905, where these compounds are obtained by subjecting first styrene and then butadiene to anionic polymerization and then reacting the l;ving block poly-mer with an alkylene oxide, eg. ethylene oxide, and fin-ally subjecting the reaction product to a further reac-tion with a cyclic dicarboxylic anhydride. The block polymers obtained carry a terminal carboxyl group.
3lock polyners of this type have different properties, depending on the styrene content; for example, those 2Q which have a h;gh styrene content can be used as thermo-plastics. We have found that, although the mechanical and processing properties.in most cases are sufficient for a particular purpose, they are unsatisfactory for some applications.
It is an object of the present invention to im-prove the mechanical and processing properties of such block po~ymers, which possess terminal carboxyl groups and are present as lithium salts.
We have found that this object is achieved by block polymers ~hich possess terminal carboxyl groups and are present as salts of the general formula tRl-Y -x3] Li~ tAl(OR~)3~
a n where R1 is a block polymer of a monovinylaromatic compound and of a conjugated diene, which contains from 60 to 95% by weight of the former and from 40 to 5~ by weight of the latter as copolymerized units and has a s-tructure A-B, A-B-A or B-A-B, which can be repeated several times, where A is the polymer unit which contains the monovinylaromatic monomers as copolymerized units, and block B is the polymer component composed of the conjugated dienes; in this case, either block A or block B being bonded to an alkylene oxide unit Y, X is a group of the formula:

- C - R' - C - O
' in which R' is a divalent organic radical, R is hydrogen or alkyl, a is from 1 to 10 and n is from 0.3 to 3, as obtained by anionic polymerization of vinylaromatic compounds and conjugated dienes with a lithiumalkyl and reacting of the . resulting living block polymer with an alkylene oxide and a cyclic anhydride, and reacting the reaction product with an aluminum alcoholate or with an aluminum trialkyl and water.
The present invention furthermore relates to a process for the preparation of block polyrners of this type by anionic polymerization of vinylaromatics and conjugated dienes and reaction of the resulting block polymers with an alkylene oxide and a cyclic anhydride, wherein the reaction product obtained is further reacted with an aluminum compound.
The present invention furthermore relates to the use of such block polymers in thermoplastic materials, for example for modifying thermoplastic materials, or as a component of molding materials.
Other subjects of the invention are evident from the description below.
The novel block polymers possess high transparency and clarity, very good impact strength coupled with great rigidity, and good processability, for example to give

- 3~

films, so that they are particularly useful for the production of blown films. We have also found that the molding materials produced using such block polymers have a particularly small number of specks.
In the stated polymers, Rl is a radical of a block polymer of a vinylaromatic compound and a conjugated diene the said polymer being obtained by a lithiumalkyl-catalyzed reaction of the starting monomers. The starting materials for these block polymers are monovinylaromatic monomers, such as styrene, styrenes which are alkylated in the side chain, such as o~-methylstyrene, and styrenes which are substituted in the nucleus, such as vinyltoluene or ethylvinylbenzene. The _ ~-~7~

..
~ O.Z. 0050/38064 monovinylaromatic monomers may also be used as mixtures.
However, styrene is preferably used alone. Examples of conjugated dienes which are copolymerized ;n the block polymers are butadiene, isoprene and 2,3-dimethylbuta-diene. Butadiene and isoprene are particularly advantage-ous, butadiene being preferred.
The radicals R of the block copolymers of the invention should contain in total, as copolymerized units, from 60 to 95, in particular from 70 to 90, ~ by weight of the monavinylaromatic compound and from 40 to S, preferably from 30 to 1û, % by weight of the conjuga-ted diene, the percentages in each case being based on the total amount of monomers used. The molecular weight of the polymers is as a rule from 30,00~ to 500,000, pre-ferably from 50,000 to Z00,000. The stated molecularweights are weight average molecular weights, determined by viscosity ~easurements in ~oluene at 25C.
The novel block copolymers are prepared by suc-cessive polymerization of the monomers in solution in the presence of a monolithium-hydrocarbon as an initia-tor, with stepwise add;tion of the monomers and, where relevant, initiator, followed by success;ve react;on w;th an alkylene oxide, a cyclic anhydride and an aluminum compound.
The block polymer R1 can have a structure A-0, where A is the polymer un;t which contains the monovinyl-aromatic 00nomers as copolymerized units, and bLock ~ is the polymer component composed of the conjugated dienes.
In this case, either block A or block ~ can be bonded to the alkylene oxide unit Y. However, it is also Pos-sible to use block polymers of the A-B-A or B-A-~ type~
The groups of blocks can be repeated several times.
Preferred polymer units R1 are those which consist only of two blocks A and B, block B being bonded to the alky-lene ox;de unit Y. Polymer units R~ which consist ofthree A-8-A blocks and in which one of the blocks A is bonded to the alkylene oxide unit Y are part;cularly ~7~

- 5 - o.z~ 0050/3806 preferred. The polymer blocks or segments A have a molecular weight of from 1500 to 150,000, preferably from 5000 to 100,000, and the polymer blocks or segments 8 have a moLecular we;ght of from 2000 to 200,000, pre-ferably from 20,000 to 100,000. The transition betweentwo polymer blocks A and 8 can be abrupt (sharply sepa-rated blocks) or gradual (indistinct or conical blocks).
Such block polymers containing indistinct or coni-cal blocks are obtained if mixtures of, for example, sty-rene and butadiene are polymerized~ However, it is alsopossible to use block polymers in ~hich the blocks A and B are copolymers of the monov;nylaromatic monomers and the conjugated dienes. The glass transition temperature of the polymer blocks or segments A in such polymers is greater than 0C, preferably greater than 20C. The polymer blocks or seg~ents 8 have a gLass transition temperature of less than 0C, preferably less than -15C. In the block polymer component R1, it is also possible for some or all of the olefinic double bonds derived from the diene building blocks to be hydrogena-ted.
In the preferred embodiment, the nonelastomeric polymer segment A1 is first prepared by polymerizing a substant;al part of the total amount of the monovinyl-aromatic compound by means of a relat;vely small amountof the monolithium-hydrocarbon initiator in an inert solvent under convent;onal conditions. In this proce-dure, tro~ 50 to 80, preferably from 60 to 75, % by weight of the total amount of the monovinylaromatic com-pound used for the preparat;on of the branched blockcopolymers should be employed.
The amount of initiator used in the first pro-cess stage depends in particular on the desired molecu-lar weight of the polymer and is generally from 0.1 to 10 millimoles per mol of the monovinylaromatic compounds used in this first process stage. For the polymerization in this stage, 0~2-1.5 millimoles of initiator are ~'7~

- 6 - O.Z. 0~50/38064 preferably used per mole of the monov;nylaromat;c compounds used here. Suitable initiators are the known monolithium-hydrocarbons of the general formula ~Li where R is an aliphatic, cycloaliphatic, aromatic or aral;phatic hy-drocarbon radical of 1 to about 12 carbon atoms. Ex-amples of lithium-hydrocarbon initiators employed accor-ding to the invention are methyllithium, ethyllithium, n-, sec- and tert-butyllithium, isopropyllithium, cyclo-hexyllithium, phenyllithium and p-tolyllithium. The monoLithiumalkyl compounds where alkyl is of 2 to 6 car-bon atoms are preferably used, n-butyllithium and sec-butyllithium being particularly preferred.
The polymerization of the monovinylaromatic com-pounds is carried out in solution in an inert organic hydrocarbon solv~nt. Suitable hydrocarbon solvents are aliphatic, cycloaliphatic or aromatic hydrocarbons which are liquid under the reaction conditions and are prefer-ably o~ 4 to 12 carbon atoms~ Examples of suitable sol-vents are benzene, toluene, the xylenes, etc. Mixtures of these solvents may also be used. It is also possible to carry out the polymerization in the presence of small amounts, in general from 10 3 to 5% by weight, based on the total amount of solvent, of ethers, such as tetrahy-drofuran, dimethoxyethane, phenyl methyl ether, etc.
This makes it possible to influence the polymerlzation rate, the configuration of the butadiene polymer seg-ments ~ and the random transition between the segments and A3 in a known manner. However~ the reaction is preferably carried out without the addition of an ether.
The concentration of the monomers in the reaction sol-ution is not critical and may be such that any desired apparatus can be used for the polymerization.
Usually, polymerization is carried out using from 10 to 30% strength solutions in the inert solvent.
The polymerization is effected under the condi-tions conventionally used for anionic polymerization with organolithium compounds, for example an inert gas - 7 - O.Z. 0050/3~064 atmosphere and the absence of air and moisture. The polymerization temperature can be from 0 to 12~C but is preferably kept at from 40 to 80C.
The polymerization in this first process stage is continued until virtually complete conversion of the monovinylaromatic compounds used. This gives a solution of nonelastomeric living polymers of the monovinylaroma-tic compounds (polymer segment A1) possessing active, terminal lithium-hydrocarbon bonds which are capable of undergoing further addition reactions with the monomers.
- In the second process stage, a further amount of initiator and a further 1-30, preferably 5 25, % by ~eight of the total amount of the monovinylaromatic compounds used for the preparation of the branched block copolymers are added to this solut;on of the nonelastomeric living polymers based on the monovinylaromat;c compounds possess-ing the lithium-term;nated chain ends capable of under-going polymerization. Ho~ever, the sum of the amounts of monovinylaromatic compounds used in the first and second Z0 process stages should not exceed 90~ by weight, based on the total amount of the mono-vinylaromatic compound used for the preparation of the branched block copolymers.
The amoun~ of fresh initiator which is addit;on-ally added to the reaction solution in the second pro-cess stage is preferably the same as or larger than theinitial amount of initiator which was employed in the first process stage of the polymerization. In the se-cond process stage, it is particularly preferable if the amount of further fresh initiator added is from 1 to 15, particularly advantageously from 3 to 7, times the amount of initiator initially used. Suitable initiators are the monolithium-hydrocarbons, ~hich can also be used in the first process stage; preferably, the initiator used is the same as that employed in the first process stage~ It is advantageous if the additional of fresh initiator is added to the reaction solution before the further a~ount '7~

- 8 - O.Z. On50/3806 of the monov;nylaromatic compound is introduced~
In the second process st3ge, the same polymeri-zation conditions are maintained as in the f;rst process stage, polymerization in this case too be;ng cont;nued S until virtually complete conversion of the added mono-vinylaromatic compound is achieved.
The monomers added in the second process stage undergo addition at the active, lithium-term;nated cha;n ends of the polymer segments A1 formed beforehand ;n the first process stage, and furthermore new chains of l;v-ing polymers are formed by the addition of fresh ;n;t;a-tor.
After complete polymerization of the monomers in the second process stage, the solution present contains the living polymers of the monovinylaromatic compound with on average two different chain lengths. The reac-tion solution contains, on the one hand, the active, living nonelastomeric polymer segments of type (A1-A2)-Li, which have been formed as a result of the monomers of the second process stage undergoing an addition reac-tion w;th the active, living polymer segments A1-Li pre-viously formed in the first process stage, and on the other hand active, living nonelastomeric polymer seg-ments of type A2-Li, which have been formed by polymeriza-tion of the monomers Qf the second process stage with theadditionally introduced, fresh ;nitiator. The ratio in which these two types of nonelastomeric polymer segments based on monovinylaromatic compounds are present in the reaction solution accordingly depends on the ratio of the amounts of initiator in the first and second process stages. aoth types of polymer segments ~A1-A2) and A2 have, at one of their chain ends, active, reactive lith-ium-carbon bonds capable of undergoing further addition reactions with monomers.
In a third process stage, the polymer segments 8 and, after this, the polymer segments A3 are 7~ 36~

- 9 - o.z~ 0050/38064 polymer;zed onto the active chain ends of the two types of nonelastomeric polymer segments (A1-A2)-Li and AZ-Li, with formation of the polymer blocks (A1-A2-a~A3) and (AZ-~-A3), which form the branches of the block copolymer.
To do this, a monomer mixture consisting of the remain-ing monovinylaromatic compound and the total amount of conjugated diene is added to the completely polymerized reaction solution within the second process stage. The amount of conjugated diene is from 5 to 40, preferably from 10 to 30, % by weight, based on the total amount of monomers used for the preparat;on of the novel bran-ched block copolymers. The monomer mixture is polymer-ized under the same conditions as for the two first pro-cess stagesO once again until virtually complete conver-sion of the monomers is achieved.
8ecause of the different copolymerization para-meters, the conjugated dienes polymeri2e substantially more rapidly than the monovinylaromatic compounds, so that, after the addition of the monomer mixture in the third process stage, initially the conjugated dienes are predominantly polymerized, and the monovinylaromatic compounds are polymerized only in isolated areas.
Only toward the end of the diene polymerization, ie. when virtually all of the conjugated diene has been ZS polymerized, does polymerization of the monovinylaromatic compounds occur to any noticeable e~tent, so that the pre-dominant amount (as a rule more than 70X by weight and predom;nantly more than 80% by we;ght) of the monovinyl-aromat;c compounds present in the monomer mi~ture are 3U polymerized only after the conjugated dienes have been cûnsumed.
In the third process stage, therefore, an elas-tomeric polymer segment ~ based on the conjugated dienes is first polymerized onto the nonelastomeric polymer segments (A1~A2) and A2, the said polymer segment ~ be-ing a copolymer which consists mainly of the conjugated diene and small amounts of the monovinylaromatic - ~ .
- 10 - O.Z. OOS0/38064 compound; ~hereafter, a nonelastomeric polymer segment A3 which is composed only of the monovinylaromatic compounds is formed. Since, toward the end of the poly-mer segment a, the amount of monovinylaromatic compounds increases steadily and the amount of conjugated diene accordingly shows a steady decrease, the transition be-tween the polymer segments B and A3 formed in this way is not sharp but gradual; hence, this is also frequently referred to as an indistinct transition between the seg-ments. This fact is taken into account in the generalformula of the novel branched block copolymers by the symbol --->.
After complete polymerization of the monomer mixture in the third process stage, the reaction solu-tion contains a mixture of liv;ng, linear block copoly-mers of type (A1-A2-~ ---> A3)-Li and (AZ-B ---> A3)-Li possessing active reactive lithium-carbon bonds at the free end of poly~er segment A3.
In a less pre~erable embodiment which is si~pler but does not give optimum results, the polymerization may also be effected in only two process stages by ini-tially taking the total amount of catalyst and, after process stage 1, polymerizing the total remaining amount of diene and styrene onto the hard segment A1 as descri-bed ;n process stage 3. In this case, the resultingblock copolymers are of uniform length.
The active, living linear block copolymers are then first reacted with an alkylene oxide in order to incorporate the alkylene oxide unit. Examples of suit-able alkylene oxides are propylene oxide and higher -straight-chain or branched alkylene oxides. Ethylene oxide is preferred, this being the only alkylene oxide which forms a primary terminal Li alcoholate group in this reaction; such groups are more suitable for the subsequent reaction with cyclic anhydrides than the ,e-condary alcoholate groups formed from other alkylene oxides.

~7~
\
- 11 - O.Z. 0050/38064 The reaction of lithium-terminated living poly-mers with ethylene axide is well known and is described in, for example, German Laid-Open Application DOS
2,723,905. In general, it is sufficient to add not less than 1 mole, preferably from 1.5 to 2 moles, of alkylene oxide per mole of l;ving polymer. In order to avoid un-desirable side react;ons, the reaction should be carried out at from O to 70C, preferably from 20 to 50C. It is complete when the intense orange color of the living polystyryl anion changes to colorless or pale yellow.
For the subsequent reaction with cyclic anhyd-rides, cyclic dicarboxylic anhydrides are preferred.
Examples of these are succinic anhydride and its alkyl-substituted and halogen-substituted derivatives, maleic anhydride, glutaric anhydride, methylenesuccinic anhyd-ride, dimethylenesuccinic anhydride, phthalic anhydride, the various naphthalenedicarboxylic anhydrides, cyclo-hexenedicarboxylic anhydride, etc. This list is not complete. In principle~ all cyclic anhydrides of dicar-boxylic acids which are capable of forming the group Xdefined above are suitable.
For the reaction of the polymeric Li alcoholates w;th the cycl;c anhydride~ it is n~cessary in general to use more than the stoichiometric amount of anhydride per mole of polymer in order to achieve an adequate con-version. A conversion of not less than 50% is suffic1-ent, but 60% is preferable and conversions > 7ûX are optimal. Such conversions are achieved if not less than 1.25, preferably 1.75~ equivalents of cyclic anhydride are employed per mole of polymer. The optimum reaction temperature is 4~-6UC, a reaction time of about 1 hour being sufficiènt~ However, the excess of cyclic anhyd-ride should be kept as small as possible since this has an adverse effect on the properties of the end product.
The reaction with the aluminum compound follows, a complex being formed between this compound and the ~7~
, - 12 - O.Z. 0050/3~06 polymer. Particularly suitable aluminum compounds are the alcoholates, which are read;ly soluble in organic solvents~ such as toluene, and are reacted in this form.
An example of a particularly suitable compound is Al triisopropylate~ Instead of the alcoholates, it is also possible to react aluminum-trialkyls, in which case, however, subsequent addition of water is necessary.
This gives an aluminum hydroxide complex~ Tha addition of small amounts of water to the reaction solution may also be advantageous when the alcoholates are used.
Formation of the Al complex is evident from a sharp increase in the solution viscosity, which general-ly reaches a limiting value when 3 moles of aluminum compound are present per mole of polymer. Hence, the amount of aluminum compound used should be not less ~han 0.3 mole and preferably not more than 1 mole. this com-plexing of the terminal groups results in a dramatic im-provement in the properties of the end products.
8efore being reacted with the aluminum compound, the block copolymer possessing carboxyl functional groups may be hydrogena~ed~ Hydrogenation may be effected selec-tively or nonselectively and is usually carried out with the aid of molecular hydrogen and a catalyst based on a metal or metal salt of group 8 of the Period;c Table. It may be effected in the homogeneous phase using a catalyst based on a salt, in particular a carboxylate, alkoxide or enolate of cobalt, nickel or iron, which is reduced with a metal alkyl, in part;cular an aluminumalkyl~ as described in~ for example, U.S. Patent 3,113,986, German Published Application QAS 1,222,260 or GPrman Laid-Open Application DOS 2,013,Z63. The olefinic double bonds are hydrogenated under mild conditions under a hydrogen pressure of from 1 to 100 bar and at 25 to 15ûC.
Hydrogenation may also be carried out in the heterogeneous phase using a nickeL or platinum metal as a catalyst, under a hydrogen pressure of from 20 to 3QO

7 ~
- 13 - O.Z. OOSO/38064 bar and at from 40 to 300C (for example as described in German Published Application DAS 1,106,961 or Ger-man Laid-Open Application 1,595,345). In this proce-dure~ the aromatic double bonds too are hydrogenated, after the olefinic double bonds. The solvent used for the hydrogenation is preferably the same as that used in the precedin3 polymerization. The block copolymer may be partially or completely hydrogenated~ Preferab-ly, the olefinic double bonds of the polymer are selec-tively hydrogenated, and the hydrogenated block copoly-mers preferably contain less than 10~, in particular less than 3%, of olefinic double bonds.
After the reaction with the aluminum compound, ~he block copolymer is isolated from the reaction solu-tion in a convent;onal manner, for example by precipita-ting and filtering off the polymer from the reaction solut;on.
In the polymers according to the invention, the complexed chain ends are probably aggregated. The in-creased solution viscosity corresponds to an increasein the apparent molecular weight to 3-6 times the value for ~he starting polymer.
The novel block copolymers, while possessing the same solution viscos;ty, have high transparency, clar-;ty, impact strength and yield stress as well as unex-pectedly high flow in comparison with conventional poly-mers~ If novel polymers possessing a higher intrinsic viscosity are compared with known polymers of the same composition but of lower intrinsic viscosity, it is found that the polymers according to the invention have better nechanical properties coupled with good process-ability. They are therefore particularly suitable for the production of blown fiLms, where they produce few specks and have little tendency to tear~ wh;ch ;s a dis-advantage of conventional polymers. Moreover, the dienecontent can be reduced to a greater extent than in the case of conventional polymers, the mechanical properties - 14 - O.Z. 0050/38064 remaln;ng slmilar.
The Fxamples which follo~ ;llustrate the ;nven-tion. The intrinsic viscosity, measured on a sample taken before the reaction with ethylene oxide, in 0.5 strength solution in toluene at 25C, is a measure of the molecular weight. The notched impact strength aLK
~as determined according to DIN 53,753 on compression-molded specimens. The yield stress Gs~ tensile strength GR and elongation ER were measured on compression-molded dumbell-shaped bars according to DIN 53,455.
Specks ~ere assessed by counting on a 70 ~m thick blown film produced in a Troster MP 30 extruder at a through-put of 10 kg/h and a melt temperature of 200C.

In the method belo~, the preparation of novel transparent impact resistant block polymers containing a) 25% (Example 1), b) 15% (Example Z) and c) 10% (Ex-ample 3) of butadiene is described. The amounts of re-actants in each case are accordingly designated by a), b) and c).
5390 m3 of cyclohexane and a) 539 g, b) 612 9, c) 648 9 of styrene are initially taken in a 10 l pres-sure kettLe and are titrated ~ith a 1.5% strength sec-butyllithium solution under an inert gas atmosphere un til polymerization just begins. Thereafter, 3 milli-moles of sec-butyllithium (as a 1.5 M solution in hex-ane) are added, and polymerization is carried out at from 50 to 60C for abaut one hour until conversion is complete~ A further 15 millimoles of sec-butyllithium are added to the active reaction solution, after which a) 326 9, b) 373 g, c) 395 9 are adcled, a) a mixture of 179 9 of styrene and 375 9 of butadiene, b) 205 9 of butadiene, c) a mixture of 217 9 of styrene and 140 9 of butadiene is added, and polymerization i, again carried out at from 50 to 60C until complete conversion of the monomers has occurred. This takes 1 hour. The intrin-sic viscosity in toluene is a) 7S, b) 73 and c) 72.

~7~
. ~
- 15 - O.Z. 0050/38064 Thereafter, 36 mill;moles of ethylane oxide are added at 40C and the m;xture ;s stirred for a further hour.
36 millimoles of succinic anhydride in the form of a fineLy divided suspension in cyclohexane, prepared by S treatment in an Ultra-Turrax mixer for 30 minutes or milling in a ball mill, are then added, and st;rr;ng is continued for a further hour at 40CO The ;ntr;ns;c v;scosity increases to a) 103, b) 105 and c) 99. 36 millimoles of aluminum triisopropylate are then mixed in, the intrinsic viscosity increasing to a) 115, b) 120 and c) 112. After the addition of 15 9 of di-tert-butyl-p-cresol, the polymers are precipitated by pouring the mixture into about 20 l of methanol with thorough st;r-ring, and are then dried. The properties are shown in the table below.
The designations d, e and f are used ;n the com-parative Examples 1, 2 and 3 below.
COMPARISONS
53~0 m3 of cyclohexane and d) 535 9, e) 612 9, f) 648 9 of styrene are initially taken in a 10 l pres-sure kettle and titrated with sec-butyllithium under an inert gas atmosphere until polymerization just begins.
Thereafter, d) 6 millimoles, b) 4.2 millimoles, f) 3.5 milli~oles of sec-butyllithium are added and polymeriza-tion is carried out for 1 hour. A further d) 30, e)Z1.3, f) 17.5 m;llimoles of sec-butyllith;um are then added, follo~ed by d) 326 9, e) 373 9, f) 395 g of sty-rene, and polymerization is continued at 50-60C. A mix-ture of d) 179 9 of styrene and 375 g of butadiene, e) 205 9 of styrene and 210 g of butadiene and f) Z17 9 of styrene and 140 g of butadiene is then added and poly-merization is continued for about 2.5 hours at 50-60C.
Thereafter, d) 4.9 9, e) 3.8 9, f) 286 9 of an epoxidiz-ed linseed oil (tradename: Edenol from Henkel, Dussel-dorf) are added and the m;xture is stirred for 15 min-utes at 60C. It is treated overnight ~ith carbon di-oxide, while stirring, stabilized with di-tert-butyl p-- 16 - O.Z. 0050/3806~
cresol, as described in Examples 1 to 3, and then w~rked up by prec;pitation w;th methanol and drying under re-duced pressure.

- 17 - O.Z. 0050/38064 I >~
L a) L J
., ~ ~ aJ
U~ O
-- ~
~ ~TJ ~ _ L V 0 11 O ~ ~ ~ ~ a, ~ ~a, ~_ ~ O a~ 3J c~
CL. ~a ~ Y 5 ~ ~ ~ F
N v t/) v_ E ~n O ~ v L U~ a~ V U~
a~ Y
O O O O O O ~J
E QJ u~ r~ ~ o O O
~ Q ~)N r~J O
Z V~ , r~
, Z
N
5~ . q~
0~ ~ ~ U~ O
tU Y U~ N N ~ ~ ~ ~
~ ~ ~) X ~ ::
* O
* O O 0~ O ~ c_ ~ L
V~ 00 In ~ON n ~ N O
w~ r~l N N
_O ~ ~
_ 1-- Y M
~1 ~_ E ., ~s_ E ~ ~ O ~
ac ~ N N N e-- ~-- ~ ~J ~ D
bZ C ~O
_ N .
tt E ~ ~ OO ~ ~ ~ c u~
E N~1 ~ NN I y _ t3 1 _ ~ ~n O
Z '-- E
E O C z E -- ~-- O
o~
O ~ v) ~
O O ~ u o N O r E L ~ .i N~I . 7~ Q
~ . . ~~ r-- ~rJ O E Q C5 Q ~) ~ ~ ~ _ O --,_, 1~ U~ O
S _ ~
a~ o o ~ 4 ~_ o ~_ ~1 ~
W ~ C
rl V~ O N
_ O ~ ~ N ~- N O ~ O ~ E
L U ~ ,~ ~00 r~ V L ~) aJ ~1 U~ r~) (~J O r_ L
~ ~ E ~ ~ ~
1--1 ~ L` D ~ a~ L
1~ ~ ~
~n ~ ~ ~ ~ ~"
aJ Y O Q E
a~ ~ ~ ~ a) ~, ~ a v ~
ul u~ ~ O u~u~ O ~n ~ ov, L a rrJ ~ ~ r~ J ~ ~ O,~ L Q~ ~ E
~ ~ L ~ ~
~ O ~ O O' m v a a~
L t C~ ~ 1~ ._ " ~_ D O u~
o e ~ o c c tn ~ ' O aJ ~ O
QJ ._ Z ~ ~ ~ ~ Z
L
Q ~I) E ~ ~ ~::L ~ N ~ lt ~1~ ' e *
X o o ~ * *
U~ Z ~ ~ ~ *

Claims (6)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A block polymer of vinylaromatic compounds and conjugated dienes which possesses acidic terminal groups, the said polymer being in the form of a complex of the formula:

where R1 is a block polymer of a monovinylaromatic compound and a conjugated diene, which contains from 60 to 95% by weight of the former and from 40 to 5% by weight of the latter as copolymerized units and has a structure A-B, A-B-A
or B-A-B, which can be repeated several times, where A is the polymer unit which contains the monovinylaromatic monomers as copolymerized units, and block B is the polymer component composed of the conjugated dienes; in this case, either block A or block B being bonded to an alkylene oxide unit Y, X is a group of the formula:

in which R' is a divalent organic radical, R2 is hydrogen or alkyl, a is from 1 to 10 and n is from 0.3 to 3.

2. A block polymer as claimed in claim 1, wherein R' is and these radicals in turn may be substituted by short alkyl chains and/or halogen.

3. A process for the preparation of a block polymer of vinylaromatic compounds and conjugated dienes by anionic polymerization of these compounds with a lithium-alkyl and reaction of the resulting living block polymer with an alkylene oxide and a cyclic anhydride, wherein the reaction product obtained is reacted with an aluminum alcoholate or with an aluminum trialkyl and water.

4. A molding material, including a block polymer as claimed in claim 1 as an additive.

5. A modifying thermoplastic material, including a block polymer as claimed in claim 1 as an additive.

6. A block polymer of vinylaromatic compounds and conjugated dienes which possesses acidic terminal groups, the said polymer being in the form of 2 complex of the formula:

where R1 is a block polymer of a monovinylaromatic compound and a conjugated diene, which contains from 60 to 95% by weight of the former and from 40 to 5% by weight of the latter as copolymerized units and has a structure A-B, A-B-A
or B-A-B, which can be repeated several times, where A is the polymer unit which contains the monovinylaromatic monomers as copolymerized units, and block B is the polymer component composed of the conjugated dienes; in this case, either block A or block B being bonded to an alkylene oxide unit Y, Z is a group of the formula:

in which R' is a divalent organic radical, R2 is hydrogen or alkyl, a is from 1 to 10 and n is from 0.3 to 3, as obtained by anionic polymerization of vinylaromatic compounds and conjugated dienes with a lithiumalky and reacting of the resulting living block polymer with an alkylene oxide and a cyclic anhydride, and reacting the reaction product with an aluminum alcoholate or with an aluminium trialkyl and water.