CA1087339A - Branched block copolymers of a monovinyl-aromatic compound and a conjugated diene - Google Patents
Branched block copolymers of a monovinyl-aromatic compound and a conjugated dieneInfo
- Publication number
- CA1087339A CA1087339A CA264,020A CA264020A CA1087339A CA 1087339 A CA1087339 A CA 1087339A CA 264020 A CA264020 A CA 264020A CA 1087339 A CA1087339 A CA 1087339A
- Authority
- CA
- Canada
- Prior art keywords
- monovinyl
- weight
- block copolymers
- branched block
- aromatic compound
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F297/00—Macromolecular compounds obtained by successively polymerising different monomer systems using a catalyst of the ionic or coordination type without deactivating the intermediate polymer
- C08F297/02—Macromolecular compounds obtained by successively polymerising different monomer systems using a catalyst of the ionic or coordination type without deactivating the intermediate polymer using a catalyst of the anionic type
- C08F297/04—Macromolecular compounds obtained by successively polymerising different monomer systems using a catalyst of the ionic or coordination type without deactivating the intermediate polymer using a catalyst of the anionic type polymerising vinyl aromatic monomers and conjugated dienes
- C08F297/044—Macromolecular compounds obtained by successively polymerising different monomer systems using a catalyst of the ionic or coordination type without deactivating the intermediate polymer using a catalyst of the anionic type polymerising vinyl aromatic monomers and conjugated dienes using a coupling agent
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G81/00—Macromolecular compounds obtained by interreacting polymers in the absence of monomers, e.g. block polymers
- C08G81/02—Macromolecular compounds obtained by interreacting polymers in the absence of monomers, e.g. block polymers at least one of the polymers being obtained by reactions involving only carbon-to-carbon unsaturated bonds
- C08G81/021—Block or graft polymers containing only sequences of polymers of C08C or C08F
- C08G81/022—Block or graft polymers containing only sequences of polymers of C08C or C08F containing sequences of polymers of conjugated dienes and of polymers of alkenyl aromatic compounds
Abstract
ABSTRACT OF THE DISCLOSURE
Branched block copolymers of from 60 to 95 per cent by weight of a monovinyl-aromatic compound and from 40 to 5 per cent by weight of a conjugated diene.
The branched block copolymers have a structure of the general formula (A1-A2-B?A3)n-X-(A3?B-A2)m where the A's are non-elastomeric polymer segments based on the monovinyl-aromatic compound, the B's are elastomeric polymer seg-ments based on the conjugated diene, X is the radical of an at least trifunctional coupling agent and n and m are numbers.
The branched block copolymers may be used for the manufacture of highly transparent impact-resitant shaped articles, especially packaging materials.
Branched block copolymers of from 60 to 95 per cent by weight of a monovinyl-aromatic compound and from 40 to 5 per cent by weight of a conjugated diene.
The branched block copolymers have a structure of the general formula (A1-A2-B?A3)n-X-(A3?B-A2)m where the A's are non-elastomeric polymer segments based on the monovinyl-aromatic compound, the B's are elastomeric polymer seg-ments based on the conjugated diene, X is the radical of an at least trifunctional coupling agent and n and m are numbers.
The branched block copolymers may be used for the manufacture of highly transparent impact-resitant shaped articles, especially packaging materials.
Description
10~73~ o .z . 31,665 BRANCHED BLOCK COPOLYMERS AND THEIR MANUFACTURE
The present invention relates to branched block copolymers which are built up of a predominant proportion of a monovlnyl-aroma~
tic compound and a lesser proportion of a con~ugated diene, and which possess high transparency, high clarity and good mechanlcal properties, especially a high impact strength.
The manufacture, by polymerization of styrene and butadiene with lithium-hydrocarbons as initiators, of block copolymers ln which one or more non-elastomerlc polymer blocks are bonded to one or more elastomeric polymer blocks, has been disclosed. Dependlng on the content of the polymer blocks in the total polymer, these thermoplastic block copolymers exhibit non-elastomeric or elasto-meric properties. Successive polymerization of the monomers results in block copolymers having a linear structure. If such linear block r copolymers are coupled to one another by polyfunctional reactive compounds, branched block copolymers having a star-shaped structure result. Such branched block copolymers, described, for example, ln British Patent 985,614, have a symmetrical structure and in general exhiblt better processability than the linear block copolymers.
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~08~339 O.Z. ~1,665 It has also been disclosed that styrene-butadiene block copoly-mers having a high styrene content are clear thermoplastics having a high impact strength. Even though the block copolymers of this type, developed and proposed hitherto, have satisfactory properties in some respects, there are many practical requirements which they do not fulful. In particular, thelr physical and mechanical proper-ties leave something to be desired, or the products do not possess the transparency which is desirable for many appllcations.
German Laid-Open Appllcation 1,959,922 discloses branched --copolymers havlng a star-shaped structure, obtained from a pre-dominant proportion of styrene and a lesser proportion of a con~u-gated dlene, which are stated to combine impact strength, clarity, good processabllity and resistance to external factors, in one and the same polymer. These branched block copolymers are obtained by coupling styrene-diene two-block copolymers in which the termlnal polystyrene blocks have different block lengths. It is true that these products exhibit improved properties compared to the symmetri-¢al branched block copolymers, but they do not prove fully satis-factory in respect of their mechanical properties, especially thelr 2Q impact strength.
Unsymmetrical branched block copolymers are also described in German Laid-Open Application 2,125,~44. The advantage of these block copolymers, which possess a homopolymer block in at least one branch, over symmetrical block copolymers is stated to be the lower solution viscoslty of the polymers. In respect of their mechanical properties (impact strength), the polymers described in German-Laid Open Applicatlon 2~125,344, if based on a predominant proportlon of styrene, are as unsatisfactory as the products known from German Laid-Open Application 1,959,922.
~O It is an object of the present lnvention to improve the mecha-nlcal properties of styrene-butadiene block copolymers which comprise a predominant proportlon of styrene, and in particular to provlde products havlng an increased impact strength. In addition, thè pro-
The present invention relates to branched block copolymers which are built up of a predominant proportion of a monovlnyl-aroma~
tic compound and a lesser proportion of a con~ugated diene, and which possess high transparency, high clarity and good mechanlcal properties, especially a high impact strength.
The manufacture, by polymerization of styrene and butadiene with lithium-hydrocarbons as initiators, of block copolymers ln which one or more non-elastomerlc polymer blocks are bonded to one or more elastomeric polymer blocks, has been disclosed. Dependlng on the content of the polymer blocks in the total polymer, these thermoplastic block copolymers exhibit non-elastomeric or elasto-meric properties. Successive polymerization of the monomers results in block copolymers having a linear structure. If such linear block r copolymers are coupled to one another by polyfunctional reactive compounds, branched block copolymers having a star-shaped structure result. Such branched block copolymers, described, for example, ln British Patent 985,614, have a symmetrical structure and in general exhiblt better processability than the linear block copolymers.
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~08~339 O.Z. ~1,665 It has also been disclosed that styrene-butadiene block copoly-mers having a high styrene content are clear thermoplastics having a high impact strength. Even though the block copolymers of this type, developed and proposed hitherto, have satisfactory properties in some respects, there are many practical requirements which they do not fulful. In particular, thelr physical and mechanical proper-ties leave something to be desired, or the products do not possess the transparency which is desirable for many appllcations.
German Laid-Open Appllcation 1,959,922 discloses branched --copolymers havlng a star-shaped structure, obtained from a pre-dominant proportion of styrene and a lesser proportion of a con~u-gated dlene, which are stated to combine impact strength, clarity, good processabllity and resistance to external factors, in one and the same polymer. These branched block copolymers are obtained by coupling styrene-diene two-block copolymers in which the termlnal polystyrene blocks have different block lengths. It is true that these products exhibit improved properties compared to the symmetri-¢al branched block copolymers, but they do not prove fully satis-factory in respect of their mechanical properties, especially thelr 2Q impact strength.
Unsymmetrical branched block copolymers are also described in German Laid-Open Application 2,125,~44. The advantage of these block copolymers, which possess a homopolymer block in at least one branch, over symmetrical block copolymers is stated to be the lower solution viscoslty of the polymers. In respect of their mechanical properties (impact strength), the polymers described in German-Laid Open Applicatlon 2~125,344, if based on a predominant proportlon of styrene, are as unsatisfactory as the products known from German Laid-Open Application 1,959,922.
~O It is an object of the present lnvention to improve the mecha-nlcal properties of styrene-butadiene block copolymers which comprise a predominant proportlon of styrene, and in particular to provlde products havlng an increased impact strength. In addition, thè pro-
-2-10~37339 OOZ~ 31,665 ducts should be transparent and as clear as possible, and should possess good processability.
We have found that this object is achieved and that, surprising-ly, non-elastomeric branched block copolymers of a monovinyl-aromatic compound and a conjugated diene possessing a quite specific block composition and structure in the branches, exhibit better properties than comparable conventional block copolymers.
Accordlngly, the present invention relates to branched block copolymers of from 60 to 95 percent by wei.ght of a monovinyl-aroma-tlc compound and from 40 to 5 percent by weight of a conjugated diene of 4 to 8 carbon atoms, whlch are built up of non-elastomerlc :.
polymer segments based on the monovinyl-aromatic compound and elastomerlc polymer segments based on the con~ugated diene and which , are manufactured by anlonic solution polymerizatlon of the monomers :
i' by means of a monollthlum-hydrocarbon as the initiator, followed by ~ coupllng of the resulting linear blook copolymer with a polyfunc- ~:
We have found that this object is achieved and that, surprising-ly, non-elastomeric branched block copolymers of a monovinyl-aromatic compound and a conjugated diene possessing a quite specific block composition and structure in the branches, exhibit better properties than comparable conventional block copolymers.
Accordlngly, the present invention relates to branched block copolymers of from 60 to 95 percent by wei.ght of a monovinyl-aroma-tlc compound and from 40 to 5 percent by weight of a conjugated diene of 4 to 8 carbon atoms, whlch are built up of non-elastomerlc :.
polymer segments based on the monovinyl-aromatic compound and elastomerlc polymer segments based on the con~ugated diene and which , are manufactured by anlonic solution polymerizatlon of the monomers :
i' by means of a monollthlum-hydrocarbon as the initiator, followed by ~ coupllng of the resulting linear blook copolymer with a polyfunc- ~:
3, tional coupllng agent, whereln the average structure of the branched 1 block copolymers corresponds to the general formula ~-v , (Al-A2-B--A3 )n-X- (A3 ~B-A2 )m where Al, A2 and A3 are non-elastomeric polymer segments based on ~-' 20 the monovlnyl-aromatlc compound and the B's are elastomeric polymer segments based on the con~ugated diene, n and m are numbers, m being ~ equal to or greater than n and the sum of m and n belng at least 3 ;~ and X ls the radical of the polyfunctional coupling agent by means of which the polymer blocks which form the branches are chemically bonded to one another at the polymer segments A3, with the provisos.
that the polymer segment or segments A contains or contain from 50 to 80% by weight, and the polymer segments A from 1 to 30% by weight, but the polymer segments A and A together not more than 90% by weight, of the total monovlnyl-aromatic compound of the branched 30 block copolymer, as copolymerized units, the transition between the polymer segments A and B is sharp and the transition between the O.Z. ~1,665 polymer segments B and A3 is gradual.
Examples of monovinyl-aromatic compounds which can be used to syntheslze the branched block copolymers of the inventlon are styrene, styrenes which are alkylated in the side chain, eg. a-methyl-styrene, and nuclear-substituted styrenes, eg. vinyltoluene or ethyl-vinylbenzene. The monovinyl-aromatic compounds may be employed lndivldually or as mixtures with one another. Preferably, however, styrene alone is used. Examples of con~ugated dienes which can be employe~ according to the invention, individually or as mixtures with one another, for the manufacture of the branched block copoly-mers, are butadiene, isoprene and 2,3-dimethylbutadiene. Butadiene or lsoprene give particularly advantageous results, and of the two butadiene is preferred.
The bran¢hed block copolymers of the invention should ln total contaln from 60 to 95 percent by weight, especially from 60 to 95 percent by weight, especlally from 70 to 90 percent by weight, of the monovlnyl-aromatic compound and from 40 to 5 percent by weight, preferably from 30 to 10 percent by weight, of the conJugated diene (in each case based on the total monomers employed), as copolymerized 0 units. The molecular weight of the branched block copolymers is as - .
a rule from 100,000 to 1,000,000 and preferably from 150,000 to 500,000. These figures relate to the welght average molecular welght, determlned by vlscosity measurements in toluene at 25C.
The branched block copolymers of the invention are manufactured by successlve polymerization of the monomers in solutlon in the presence of a monolithium-hydrocarbon as the initlator, with stepwise addition of monomer and of lnltiator, followed by coupling of the resulting living linear block copolymers with a polyfunctional reac-tive compound as the coupllng agent, as follows:
In a flrst process stage, the non-elastomerlc polymer segment Al ls produced by polymerizing a substantlal portion of the total amount of the monovinyl-aromatic compound by means of a relatively small amount of the monolithium-hydrocarbon initiator in an inert ~ -4-O.Z. 31,665 solvent under conventlonal conditions. In this stage, from 50 to 80 percent by weight, preferably from 60 to 75 percent by weight, of the total amount of the monovinyl-aromatic compound employed, over-all, for the manufacture of the branched block copolymers should be used. The total amount of monovlnyl-aromatic compound used ~or the manufacture of the branched block copolymers ls from 60 to 95 percent by weight, in particular from 70 to 90 percent by weight, based on the total monomers used for the manufacture of the polymer.
The amount of the initlator employed in the first sta~e of the process depends, above all, on the desired molecular weight of the polymer and is generally from 0.1 to 10 millimoles per mole of the monovinyl-aromatic compounds employed in the said first process stage. Preferably, from 0.4 to 2.5 milllmoles of initlator per mole of the monovlnyl-aromatic compounds employed in the flrst proceæs stage are used ln the sald stage. The inltlators employed are the ¢onventlonal monollthlum-hydrocarbons of the general ~ormula RLi, .
where R ls an allphatic, cycloallphatic, aromatic or mixed alipha-tlc-aromatic hydrocarbon radical, whieh may be of 1 to about 12 carbon atoms. Examples of the llthlum-hydrocarbon inltiators to be , employed according to the lnventlon are methyl-lithlum, ethyl-llthlum, n-, sec.- and tert.-butyl-llth~um, isopropyl-llthium, .
cyclohexyl-lithium, phenyl-lithium and p-tolyl-lithlum. The mono-llthium-alkyl compounds where alkyl ls of 2 to 6 carbon atoms are ,. . . . .
preferred, n-butyl-llthium and sec.-butyl-lithium belng particularly preferred.
The polymerizatlon of the monovinyl-aromatic compounds is carried out in solution in an lnert organic hydrocarbon solvent.
Sultable hydrocarbon solvents are aliphatlc, cycloaliphatic or aromatlc hydrocarbons whlch are llquid under the reactlon conditions ~0 and are preferably of 4 to 12 carbon atoms. Examples are lsobutane, n-pentane, lsooctane, cyclopentane, cyclohexane, cycloheptane, benzene, toluene, the xylenes and others. Mlxtures of these solvents may also be employed. Furthermore, the polymerizatlon can be carried 1~7~39 o . z. 31,665 out in the presence of small amounts, ~n general from 10 ~ to 5 percent by weight, based on total solvents, of ethers, eg. tetra-hydrofuran, dimethoxyethane, phenyl methyl ether and others, where-by it is possible to influenceJ in the conventional manner, the rate of polymerization, the configuration of the butadlene polymer segment B and the statistical transition between the se~ments B and A~. Preferably, however, no ether is added. The concentration of ~-the monomers in the reaction solution is not critical and can be so chosen that any des$red apparatus can be used for the polymerization.
As a ruleJ the polymerization ls carried out in from 10 to ~0 per cent strength solutions ln the inert solvents.
The polymerization is carried out under the conventlonal con-ditions for anionlc polymerizations wlth lithium-organic compounds?
eg. in an lnert gas atmosphere, wlth exclusion of air and molsture !
The polymerization temperature may be from 0 to 120 C and is pre-ferably kept at from 40 to 80C.
In this first stage of the process, the polymerization is taken to virtually complete conversion of the monovinyl-aromatic compounds employed. This gives a solution of non~elastomeric, llving polymers of the monovinyl-aromatic compounds (polymer segment Al) with actlve termlnal lithium-carbon bonds capable of further addl-tion of monomers.
In the second stage of the process, a further amount of initla-tor, and a further 1 to ~0% by weight, preferably 5 to 25% by weight, of the total amount of the monovinyl-aromatic compounds used for the manufacture of the branched block copolymers are added to the above solutlon of the non-elastomeric living polymers based on the monovinyl-aromatic compounds and having lithium-termlnated chain ends capable of further polymerlzatlon. The sum of the amount of monovlnyl-aromatic compound employed ln the first and second stages of the process should however be at most 90% by welght of the total amount of monovinyl-aromatic compound used for the manufacture of the branched block copolymers. The amount of fresh initiator which 10~37339 o o z o ~1 3 665 is added to the reaction solutlon in the second stage of the process should be at least as great, or greater, than the original amount of initiator which has been employed in the flrs~ stage of the polymerization process~ Pre~erably~ the amount o~ fresh initiator added in the second stage of the process is from 1 to 15 times, and in particular from 1 to 10 times, the amount of lnitiator added originally. It is particularly advantageous to add from 1 to 5 times the amount, expecially when, as e~plained in more detail below, trlfunctional or tetrafunctional coupling agents are employed in the subsequent coupling reaction. Suitable lnitiators are the monolithium-hydrocarbons, which can also be employed ln the first stage of the process; preferably, the initiator used is identical to that used in the first stage of the process. It is advantageous to add the fresh initiator to the reaction solutlon before the further proportion of the monovinyl-aromatic compound is added.
In the second process stage, the same polymerization condi-tlons are malntained as in the first stage, and here again polymerl-zation is taken to virtually complete conversion of the added monovinyl-aromatic compound. In this polymerlzation, the monomers added in the second stage of the process are added onto the active llthium-termlnated chain ends of the polymer segments Al previously formed in the first stage of the process, but new chains of living ! .
polymers are also formed by the fresh lnitiator added.
After complete polymerization of the monomers ln the second process stage, the solution obtained thus contalns livlng polymers the monovinyl-aromatic compound, wlth, on average, two differ-ent chain lengths. The reactlon solution contalns, on the one hand, the active? living non-elastomeric polymer segments of the type (Al-A2)-Ll, which have been formed by addition of the monomer used ~O in the second stage of the process onto the active living polymer segments Al-Ll formed beforehand in the first stage of the process, and also containsJ on the other hand, actlve, livlng non-elasto-meric polymer segments of the type A -Li, ~hich have been formed by 10~7339 o~z~ 31,665 polymerizlng the monomer used ln the second stage of the process by means of the additional fresh initiator. The ratio in whlch these two types of non-elastomeric polymer segments based on the monovinyl-aromatic compounds are present in the reaction solution accordingly corresponds to the ratio of the amounts of initlator ln the first and second stages of the process~ Both types of polymer segments (Al-A2) and A2 have, at one of their chain ends, active, reactive lithium-carbon bonds capable of further addition of monomer.
In a third stage of the process, the polymer segments B are polymerized onto the active chain ends of the two types of non-elastomeric polymer segments, (Al-A2)-Li and A2-Li, and thereafter the polymer segments A~ are polymerized on, to form the polymer blocks (Al-A2-B-~ A~) and (A2-B-~A~), which form the branches of the block copolymers of the invention. For this purpose, a monomer mixture of the remaining monovinyl-aromatic compound and the total amount of the con~ugated diene is added to the fully polymerized reaction solution from the second stage of the process. The amount of oon~ugated diene is from 5 to 40% by welght, preferably from lO
2~ to 30% by weight, of the total monomer employed for the manufacture of the branched block copolymers of the lnventlon. The monomer mix-ture ls polymerized - agaln to vlrtually complete conversion of the monomers - under the same polymerization conditions as apply to the first two stages of the process.
Because of the different copolymerization parameters, the con-~ugated dienes polymerize substantlally more rapldly than the monovinyl-aromatlc compounds, so that, after addition of the monomer mixture in the thlrd stage of the process, it is first predominantly the con~ugated dienes which undergo polymerlzation, and only occasio-3 nally are units of the monovinyl-aromatic compounds copolymerized.
Only towards the end of the diene polymerization, le. when almost all the con~ugated diene has polymerized, does the polymerization of the monovinyl-aromatlc compounds commence to a significant degree, 7339 O a Z ~ 665 so that the predominant proportion - as a rule more than 70~ by weight, and in most cases up to 80% by welght - of the monovinyl-aromatic compounds contalned in the monomer mlxture only polymeri-zes after the conjugated dlenes have been consumed.
Accordingly, in the thlrd stage of the process an elastomeric polymer segment B, based on the con~ugated dienes, is flrst poly-merized onto the non-elastomerlc polymer segments (Al-A2) or A2, this elastomeric segment being a copolymer of a predomlnant propor-tion of the con~ugated diene with small amounts of the monovinyl-aromatic compound, after which a non-elastomeric polymer segment A3 is formed, which is made up of the monovinyl-aromatic compounds only. Since the proportion of the monovinyl-aromatic compounds pro-gressively increases towards the end of the polymer segment B and the proportion of the conjugated diene correspondingly progressively decreases, the transition between the polymer segments B and A3 thus formed is not sharp and instead occurs gradually; this is therefore also frequently described as a blurred transition between the segments. This fact is taken into account, in the general formula for the branched block copolymers of the invention, by the use of the symbol ~ O
After complete polymerization of the monomer mixture in the third stage of th;e process9 the reaction solution contains a mix-ture of living linear block copolymers of the type (Al-A2-B--~ A3)-Li and (A2-B-~ A3)-Li with active, reactive lithium-carbon bonds in each case at the free end of the polymer segments A3.
The mixture of these two types of active living linear block copolymers is then reacted in a further stage of the process, in which is added a polyfunctional reactive compound to act as the coupling agent. The polyfunctional coupling agent used should be at least trifunctional, ie. it should be capable of reacting with at least three of the active livlng block copolymer chains, at the terminal lithium-carbon bonds of these, to form a chemical bond, so that a slngle coupled and accordingly branched block copolymer _9_ 10~339 o .z . ~1,665 is formed. The coupling of lithium-terminated living polymers with polyfunctional coupling agents ls known ln the art and disclosed, for example, ln the publications clted init~ally, especially British Patent 985,6140 Examples of suitable coupling agents for the manufacture of the branched block copolymers of the invention are polyepoxides, eg.
epoxidized linseed oil, polyisocynaates~ eg. benzo-1,2,4-triiso-cyanate, polyketones, eg. 1,~,6-hexanetrione or 1,4,9,10-anthra-cenetetrone, polyanhydrides, egO the dianhydride of pyromellitic .
acid, or polyhalides. Dicarboxylic acid esters, eg. dlethyl adipate or the like, can equally be used as coupllng agents. A further preferred group of coupling agents comprises the silicon halides, especially silicon tetrachloride, silicon tetrabromide, trichloro-ethylsilane or 1,2-bis-(methyldichlorosilyl)-ethane. Further coupling agents which can be employed are polyvinyl-aromatics, especially dlvinylbenzene, as described, eg., in U.S. Patent ~,220,084. In thls case, some divinylbenzene units add on, producing crosslinking and formlng a bra~ching center, through which the preformed polymer blocks are bonded to one another.
The nature of the polyfunctlonal coupling agent used is not critical provided it doas not significantly detract from the desired propertie~ of the end product. The use of a trifunctional or tetra-functional coupling agent of the above type, or of divinylbenzene, is preferred. In general, the polyfunctional coupling agent is added to the reaction solution in amounts equivalent to the total amount of the "living" polymer blocks, ie. equivalent to the number of active llthium-carbon bonds in the preformed linear block copolymers.
The reaction of the livlng linear block copolymers with the poly-functional coupling agent is preferably carried out under the same reaction conditions as the precedlng polymerization of the monomers.
The resulting branched block copolymers are lsolated from the reac-tion solution by conventional methods, eg. by preclpitating the polymer from the reaction solution, and filtering it off.
7339 o.z. ~1,665 If desired, the branched block copolymer can be hydrogenated following the coupllng reaction and, advantageously, before isolat-lng the product from the reactlon solutionO rrhe hydrogenation may be carried out selectively or non-selectively and is normally effected with the aid of molecular hydrogen and catalysts based on metals, or salts of metals, of group 8 of the periodic table. The hydrogenation can be carried out in a homogeneous phase with cata-lysts based on salts, especlally the carboxylates, alkoxldes or enolates of cobalt, nickel or iron, which have been reduced with metal alkyls, especially aluminum alkyls, as disclosed, for example, in U.S. Patent ~ ,986, German Published Applicatlon 1,222,260 or German Laid-Open Application 2,013,26~. In these reactions, the olefinic double bonds are hydrogenated under mild conditlons at hydrogen pressures of from 1 to 100 bars, and at from 25 to 150 C.
The hydrogenatlon can also be carrled out in a heterogeneous phase, with metallic nickel or a platlnum metal as catalyst, at hydrogen pressures of from 20 to 300 bars and at from 40 to 300C (for example, by the method of German Published Applicatlon 1,106?961 or German Laid-Open Application 1,595,~45). In thls reaction, not only the olefinic double bonds but also the aromatic double bonds are hydrogenated. If the hydrogenation is carried out ln solution, it is advantageously effected in the same solvent as the preceding polymerization. The branched block copolymer may be hydrogenated partlally or completelyO If a hydrogenation is carried out, it is - preferred selectively to hydrogenate the olefinic double bonds of the polymer, so that the hydrogenated branched copolymers obtained preferably only contain less than 10%, and especially less than ~, of olefinic double bonds.
The hydrogenation is preferably carried out on branched block ~0 copolymers which have been manufactured in the presence of small amounts of ethers durlng the polymerization.
The process of manufacture decides the composition and struc-ture of the branched block copolymers of the invention. If, for example, a tetrafunctional coupling agent is used and the ratio, 1~7339 o . z ~ ~1, 665 in the fully polymerized reaction solution from the third stage of the process, of the two types of polymer blocks which form the branches, namely the ratio of (Al-A2-B-~A~)-Li to (A2-B _ A3)-Li, is, for examplg 1:1 or 1:3, the resulting branched block copolymer will on average (most probable structure) possess a structure of the formula (Al-A -B--~A3)2-X-(A3~--B-A2)2 or (Al-A2-B--~ A3)1-X-(A3~--B-A2)~. In the case of a trifunctional coupling agent and a ratlo of the two types of branches (Al-A2-B-~A3)-Li to (A2-B-~ A~)-Li of 1:2, the most probable average structure of the branched block copolymer is 3 10 (Al-A2-B-~ A3)1-X-(A3~- B-A2)2; in each of the formulae, X is the radical of the polyfunctional coupling agent.
In general, the most probable average structure of the branched block copolymers manufactured according to the invention corresponds to the general formula (Al-A2-B ~A3)n-X-(A3~B-A2)m where m and n are integers, and the sum of n and m corresponds to the polyfunctionality of the coupling agent and is thus at least three, in general from 3 to 10 and preferably 3 or 4. m is at least equal to or greater than n. The non-elastomeric polymer segment Al, which con-tains from 50 to 80% by weight, preferably from 60 to 75% by weight, 20 of the total monovinyl-aromatic compound, employed for the manufacture of the branched block copolymer, as polymerized units, preferably only consists of the monovinyl-aromatic compounds and is, in particular, a homopolystyrene segment. Its molecular weight depends particularly on the envisaged end use and is preferably from 50,000 to 250,000.
The polymer segments A2 correspond to the polymer segments Al except that they have a lower molecular weight, usually from 5,000 to 50,000.
They contain from 1 to 30% by weight, and preferably from 5 to 25% by weight, of the total monovinyl-aromatic compound as polymerized units.
The elastomeric polymer segment B is, as has been mentioned, a copoly-30 mer block consisting essentlally of the con~ugated diene with a small proportion of monovinyl-aromatic compoundJ in which block the olefinic double bonds may or may not be selectively hydrogenated. The proportion ~0~7339 o O z . 31,665 of the monovinyl-aromatic compound in the polymer segment B is in general less than about 30% by weight and in particular less than about 20% by weight, based on the amount of monovinyl-aromatic not contained in the polymer se~ments Al and A2. The non-elastomeric polymer segments A3, like the polymer segments Al and A2, preferably are built up of the monovinyl-aromatic compound alone and in parti-cular are homopolystyrene. The molecular weight of the polymer blocks (Al-A2-B - A3) is preferably from 100,000 to 500,000, whilst that of the polymer blocks (A2-B-~ A3) is from 10,000 to 100,000.
The branched block copolymers of the invention possess high .
transparency and clarity and good mechanical properties; in parti-cular they are superior, in respect of impact strength and yield stress, to the conventional products described in German Laid-Open Application 1,959,922. This was not foreseeable and was all the more surprising since, according to German Laid-Open Application 1,959,92?, all non-elastomeric polymer segments must be in terminal positions lf satisfactory mechanlcal properties are to be achieved.
Hydrogenation in particular improves the aging resistance of the~
products, though it may result in some reduction in their trans-2Q parency. The branched block copolymers of the invention can easilybe processed by the conventional processing methods for thermo-plastics, eg. extrusion, deep-drawing or injection molding, and are above all suitable for the manufacture of moldings and packaglng materlals.
The Examples which follow illustrate the lnvention. The vls-cosity number, measured ln 005% strength solution in toluene at 25C, ls quoted as a measure of the molecular weight. The impact strength an and notched impact strength ak were determlned on a molded speci-men according to DIN 53,453. The yield stress Y, tensile strength Z and elongation at break D were measured on a molded dumbbell-shaped bar according to DIN 5~,455.
6 kg of toluene and 430 g of styrene were introduced into a -1~-1~7339 oOzO 31,665 10 1 pressure kettle and titrated, under an lnert gas atmosphere, with a 1.5~ strength n-butyl-lithium solution until polymerization just commenced. 7 millimoles of n-butyl-lithium (as a 3~ strength solution in hexane) were then added and the mixture was polymerized at from 50 to 60C for about one hour, untll the monomer had been virtually completely converted~ The polymer had a vls¢osity number of 34.7 ~cm~/g~. A further 7 millimoles of n-butyl-lithium (as a 3%
strength solution in hexane) were added to the active reaction solu-tlon, 80 g of styrene were then added and the mixture was fully polymerized at from 50 to 60C. A~ter this stage, the viscosity number was 33.1 [cm3/g~. A mixture of 120 g of styrene and 210 g of butadiene was now added and polymerlzation was again carried out until the monomers had been virtually completely converted, which requlred about two hours at from 50 to 60C. ~.5 millimoles of silicon tetrachloride were then added. The resulting branched block copolymer was precipitated by adding methanol, and filtered of~.
It had a viscosity number of 84.3 [cm3/g] and the approximate struc-ture (Al-A2-B-~ A3)2-Si-(A3~--B-A2)2 where the A's are polystyrene segments and the B poly(butadiene/styrene) segments. The mechanical properties are shown in the Table.
The procedure followed was as described in Example 1, but in this case 450 g of styrene in 6 kg of toluene were initlally intro-duced into the reactor, and, after titration, were polymerized with 3.8 millimoles of n-butyl-lithlum at 50C. A viscosity number of 49.1 Ccm~/g~ resulted. A further 1104 millimoles of n-butyl-lithium were then added and 60 g of styrene were polymerized at from 50 to 60C. The vlscosity number was now 46.3 ~m3/g } A mixture of 120 g of styrene and 210 g of butadiene was now added and polymerization was now added and polymerization was again carried out? at 60C, until the monomers were virtually completely converted. The product was then coupled by means of 3.8 mllllmoles of sillcon tetrachloride to glve a branched block copolymerO It had the average structure (Al-A2-B-~ A3)1-Si-(A3~--B-Al)3 where the A's are polystyrene seg-ments and the B's poly(butadiene/styrene)segments~ The viscoslty number was 79.~ tcm/g]. The mechanical properties are shown in the Table.
COMPARATIVE EXAMPLES
(according to German Laid-Open Application 1,959,922) 2.7 kg of cyclohexane and 525 g of styrene were titrated with sec.-butyl-lithium in a 6 1 pressure kettle under an inert gas atmosphere and then polymerized for 30 mlnutes with 0.33 g of sec.-butyl-lithium. The initial temperature was 54C~ 0.22 kg of cyclo-hexane, 0.9 g of sec.-butyl-lithium and 225 g of styrene were added to the active reaction solutlon at 71C, polymerization was carried out for one hour, and 250 g of butadiene were then polymerized onto the product ln the course of one hour at about 74 C. Finally, coup~g -was carried out with lQ-ml of Epoxol 9-5*in 150 ml of toluene. The product was preclpitated fromlsopropanol. The viscoslty number was 91.9 Em3/g~ .
!' TABLE
cmkp/cm2 cmkp/cm2 kp/cm2 kp/ 2 D
; ~,, ' Example 1 2~.0 7~1 310 260 7 Example 2 32.012.1 205 154 132 Comparatlve Example 15.1 5.4 170 190 91 . ~ , * Trademark for an epoxidized linseed oil.
.:
,:~
, .. . . . . .
that the polymer segment or segments A contains or contain from 50 to 80% by weight, and the polymer segments A from 1 to 30% by weight, but the polymer segments A and A together not more than 90% by weight, of the total monovlnyl-aromatic compound of the branched 30 block copolymer, as copolymerized units, the transition between the polymer segments A and B is sharp and the transition between the O.Z. ~1,665 polymer segments B and A3 is gradual.
Examples of monovinyl-aromatic compounds which can be used to syntheslze the branched block copolymers of the inventlon are styrene, styrenes which are alkylated in the side chain, eg. a-methyl-styrene, and nuclear-substituted styrenes, eg. vinyltoluene or ethyl-vinylbenzene. The monovinyl-aromatic compounds may be employed lndivldually or as mixtures with one another. Preferably, however, styrene alone is used. Examples of con~ugated dienes which can be employe~ according to the invention, individually or as mixtures with one another, for the manufacture of the branched block copoly-mers, are butadiene, isoprene and 2,3-dimethylbutadiene. Butadiene or lsoprene give particularly advantageous results, and of the two butadiene is preferred.
The bran¢hed block copolymers of the invention should ln total contaln from 60 to 95 percent by weight, especially from 60 to 95 percent by weight, especlally from 70 to 90 percent by weight, of the monovlnyl-aromatic compound and from 40 to 5 percent by weight, preferably from 30 to 10 percent by weight, of the conJugated diene (in each case based on the total monomers employed), as copolymerized 0 units. The molecular weight of the branched block copolymers is as - .
a rule from 100,000 to 1,000,000 and preferably from 150,000 to 500,000. These figures relate to the welght average molecular welght, determlned by vlscosity measurements in toluene at 25C.
The branched block copolymers of the invention are manufactured by successlve polymerization of the monomers in solutlon in the presence of a monolithium-hydrocarbon as the initlator, with stepwise addition of monomer and of lnltiator, followed by coupling of the resulting living linear block copolymers with a polyfunctional reac-tive compound as the coupllng agent, as follows:
In a flrst process stage, the non-elastomerlc polymer segment Al ls produced by polymerizing a substantlal portion of the total amount of the monovinyl-aromatic compound by means of a relatively small amount of the monolithium-hydrocarbon initiator in an inert ~ -4-O.Z. 31,665 solvent under conventlonal conditions. In this stage, from 50 to 80 percent by weight, preferably from 60 to 75 percent by weight, of the total amount of the monovinyl-aromatic compound employed, over-all, for the manufacture of the branched block copolymers should be used. The total amount of monovlnyl-aromatic compound used ~or the manufacture of the branched block copolymers ls from 60 to 95 percent by weight, in particular from 70 to 90 percent by weight, based on the total monomers used for the manufacture of the polymer.
The amount of the initlator employed in the first sta~e of the process depends, above all, on the desired molecular weight of the polymer and is generally from 0.1 to 10 millimoles per mole of the monovinyl-aromatic compounds employed in the said first process stage. Preferably, from 0.4 to 2.5 milllmoles of initlator per mole of the monovlnyl-aromatic compounds employed in the flrst proceæs stage are used ln the sald stage. The inltlators employed are the ¢onventlonal monollthlum-hydrocarbons of the general ~ormula RLi, .
where R ls an allphatic, cycloallphatic, aromatic or mixed alipha-tlc-aromatic hydrocarbon radical, whieh may be of 1 to about 12 carbon atoms. Examples of the llthlum-hydrocarbon inltiators to be , employed according to the lnventlon are methyl-lithlum, ethyl-llthlum, n-, sec.- and tert.-butyl-llth~um, isopropyl-llthium, .
cyclohexyl-lithium, phenyl-lithium and p-tolyl-lithlum. The mono-llthium-alkyl compounds where alkyl ls of 2 to 6 carbon atoms are ,. . . . .
preferred, n-butyl-llthium and sec.-butyl-lithium belng particularly preferred.
The polymerizatlon of the monovinyl-aromatic compounds is carried out in solution in an lnert organic hydrocarbon solvent.
Sultable hydrocarbon solvents are aliphatlc, cycloaliphatic or aromatlc hydrocarbons whlch are llquid under the reactlon conditions ~0 and are preferably of 4 to 12 carbon atoms. Examples are lsobutane, n-pentane, lsooctane, cyclopentane, cyclohexane, cycloheptane, benzene, toluene, the xylenes and others. Mlxtures of these solvents may also be employed. Furthermore, the polymerizatlon can be carried 1~7~39 o . z. 31,665 out in the presence of small amounts, ~n general from 10 ~ to 5 percent by weight, based on total solvents, of ethers, eg. tetra-hydrofuran, dimethoxyethane, phenyl methyl ether and others, where-by it is possible to influenceJ in the conventional manner, the rate of polymerization, the configuration of the butadlene polymer segment B and the statistical transition between the se~ments B and A~. Preferably, however, no ether is added. The concentration of ~-the monomers in the reaction solution is not critical and can be so chosen that any des$red apparatus can be used for the polymerization.
As a ruleJ the polymerization ls carried out in from 10 to ~0 per cent strength solutions ln the inert solvents.
The polymerization is carried out under the conventlonal con-ditions for anionlc polymerizations wlth lithium-organic compounds?
eg. in an lnert gas atmosphere, wlth exclusion of air and molsture !
The polymerization temperature may be from 0 to 120 C and is pre-ferably kept at from 40 to 80C.
In this first stage of the process, the polymerization is taken to virtually complete conversion of the monovinyl-aromatic compounds employed. This gives a solution of non~elastomeric, llving polymers of the monovinyl-aromatic compounds (polymer segment Al) with actlve termlnal lithium-carbon bonds capable of further addl-tion of monomers.
In the second stage of the process, a further amount of initla-tor, and a further 1 to ~0% by weight, preferably 5 to 25% by weight, of the total amount of the monovinyl-aromatic compounds used for the manufacture of the branched block copolymers are added to the above solutlon of the non-elastomeric living polymers based on the monovinyl-aromatic compounds and having lithium-termlnated chain ends capable of further polymerlzatlon. The sum of the amount of monovlnyl-aromatic compound employed ln the first and second stages of the process should however be at most 90% by welght of the total amount of monovinyl-aromatic compound used for the manufacture of the branched block copolymers. The amount of fresh initiator which 10~37339 o o z o ~1 3 665 is added to the reaction solutlon in the second stage of the process should be at least as great, or greater, than the original amount of initiator which has been employed in the flrs~ stage of the polymerization process~ Pre~erably~ the amount o~ fresh initiator added in the second stage of the process is from 1 to 15 times, and in particular from 1 to 10 times, the amount of lnitiator added originally. It is particularly advantageous to add from 1 to 5 times the amount, expecially when, as e~plained in more detail below, trlfunctional or tetrafunctional coupling agents are employed in the subsequent coupling reaction. Suitable lnitiators are the monolithium-hydrocarbons, which can also be employed ln the first stage of the process; preferably, the initiator used is identical to that used in the first stage of the process. It is advantageous to add the fresh initiator to the reaction solutlon before the further proportion of the monovinyl-aromatic compound is added.
In the second process stage, the same polymerization condi-tlons are malntained as in the first stage, and here again polymerl-zation is taken to virtually complete conversion of the added monovinyl-aromatic compound. In this polymerlzation, the monomers added in the second stage of the process are added onto the active llthium-termlnated chain ends of the polymer segments Al previously formed in the first stage of the process, but new chains of living ! .
polymers are also formed by the fresh lnitiator added.
After complete polymerization of the monomers ln the second process stage, the solution obtained thus contalns livlng polymers the monovinyl-aromatic compound, wlth, on average, two differ-ent chain lengths. The reactlon solution contalns, on the one hand, the active? living non-elastomeric polymer segments of the type (Al-A2)-Ll, which have been formed by addition of the monomer used ~O in the second stage of the process onto the active living polymer segments Al-Ll formed beforehand in the first stage of the process, and also containsJ on the other hand, actlve, livlng non-elasto-meric polymer segments of the type A -Li, ~hich have been formed by 10~7339 o~z~ 31,665 polymerizlng the monomer used ln the second stage of the process by means of the additional fresh initiator. The ratio in whlch these two types of non-elastomeric polymer segments based on the monovinyl-aromatic compounds are present in the reaction solution accordingly corresponds to the ratio of the amounts of initlator ln the first and second stages of the process~ Both types of polymer segments (Al-A2) and A2 have, at one of their chain ends, active, reactive lithium-carbon bonds capable of further addition of monomer.
In a third stage of the process, the polymer segments B are polymerized onto the active chain ends of the two types of non-elastomeric polymer segments, (Al-A2)-Li and A2-Li, and thereafter the polymer segments A~ are polymerized on, to form the polymer blocks (Al-A2-B-~ A~) and (A2-B-~A~), which form the branches of the block copolymers of the invention. For this purpose, a monomer mixture of the remaining monovinyl-aromatic compound and the total amount of the con~ugated diene is added to the fully polymerized reaction solution from the second stage of the process. The amount of oon~ugated diene is from 5 to 40% by welght, preferably from lO
2~ to 30% by weight, of the total monomer employed for the manufacture of the branched block copolymers of the lnventlon. The monomer mix-ture ls polymerized - agaln to vlrtually complete conversion of the monomers - under the same polymerization conditions as apply to the first two stages of the process.
Because of the different copolymerization parameters, the con-~ugated dienes polymerize substantlally more rapldly than the monovinyl-aromatlc compounds, so that, after addition of the monomer mixture in the thlrd stage of the process, it is first predominantly the con~ugated dienes which undergo polymerlzation, and only occasio-3 nally are units of the monovinyl-aromatic compounds copolymerized.
Only towards the end of the diene polymerization, le. when almost all the con~ugated diene has polymerized, does the polymerization of the monovinyl-aromatlc compounds commence to a significant degree, 7339 O a Z ~ 665 so that the predominant proportion - as a rule more than 70~ by weight, and in most cases up to 80% by welght - of the monovinyl-aromatic compounds contalned in the monomer mlxture only polymeri-zes after the conjugated dlenes have been consumed.
Accordingly, in the thlrd stage of the process an elastomeric polymer segment B, based on the con~ugated dienes, is flrst poly-merized onto the non-elastomerlc polymer segments (Al-A2) or A2, this elastomeric segment being a copolymer of a predomlnant propor-tion of the con~ugated diene with small amounts of the monovinyl-aromatic compound, after which a non-elastomeric polymer segment A3 is formed, which is made up of the monovinyl-aromatic compounds only. Since the proportion of the monovinyl-aromatic compounds pro-gressively increases towards the end of the polymer segment B and the proportion of the conjugated diene correspondingly progressively decreases, the transition between the polymer segments B and A3 thus formed is not sharp and instead occurs gradually; this is therefore also frequently described as a blurred transition between the segments. This fact is taken into account, in the general formula for the branched block copolymers of the invention, by the use of the symbol ~ O
After complete polymerization of the monomer mixture in the third stage of th;e process9 the reaction solution contains a mix-ture of living linear block copolymers of the type (Al-A2-B--~ A3)-Li and (A2-B-~ A3)-Li with active, reactive lithium-carbon bonds in each case at the free end of the polymer segments A3.
The mixture of these two types of active living linear block copolymers is then reacted in a further stage of the process, in which is added a polyfunctional reactive compound to act as the coupling agent. The polyfunctional coupling agent used should be at least trifunctional, ie. it should be capable of reacting with at least three of the active livlng block copolymer chains, at the terminal lithium-carbon bonds of these, to form a chemical bond, so that a slngle coupled and accordingly branched block copolymer _9_ 10~339 o .z . ~1,665 is formed. The coupling of lithium-terminated living polymers with polyfunctional coupling agents ls known ln the art and disclosed, for example, ln the publications clted init~ally, especially British Patent 985,6140 Examples of suitable coupling agents for the manufacture of the branched block copolymers of the invention are polyepoxides, eg.
epoxidized linseed oil, polyisocynaates~ eg. benzo-1,2,4-triiso-cyanate, polyketones, eg. 1,~,6-hexanetrione or 1,4,9,10-anthra-cenetetrone, polyanhydrides, egO the dianhydride of pyromellitic .
acid, or polyhalides. Dicarboxylic acid esters, eg. dlethyl adipate or the like, can equally be used as coupllng agents. A further preferred group of coupling agents comprises the silicon halides, especially silicon tetrachloride, silicon tetrabromide, trichloro-ethylsilane or 1,2-bis-(methyldichlorosilyl)-ethane. Further coupling agents which can be employed are polyvinyl-aromatics, especially dlvinylbenzene, as described, eg., in U.S. Patent ~,220,084. In thls case, some divinylbenzene units add on, producing crosslinking and formlng a bra~ching center, through which the preformed polymer blocks are bonded to one another.
The nature of the polyfunctlonal coupling agent used is not critical provided it doas not significantly detract from the desired propertie~ of the end product. The use of a trifunctional or tetra-functional coupling agent of the above type, or of divinylbenzene, is preferred. In general, the polyfunctional coupling agent is added to the reaction solution in amounts equivalent to the total amount of the "living" polymer blocks, ie. equivalent to the number of active llthium-carbon bonds in the preformed linear block copolymers.
The reaction of the livlng linear block copolymers with the poly-functional coupling agent is preferably carried out under the same reaction conditions as the precedlng polymerization of the monomers.
The resulting branched block copolymers are lsolated from the reac-tion solution by conventional methods, eg. by preclpitating the polymer from the reaction solution, and filtering it off.
7339 o.z. ~1,665 If desired, the branched block copolymer can be hydrogenated following the coupllng reaction and, advantageously, before isolat-lng the product from the reactlon solutionO rrhe hydrogenation may be carried out selectively or non-selectively and is normally effected with the aid of molecular hydrogen and catalysts based on metals, or salts of metals, of group 8 of the periodic table. The hydrogenation can be carried out in a homogeneous phase with cata-lysts based on salts, especlally the carboxylates, alkoxldes or enolates of cobalt, nickel or iron, which have been reduced with metal alkyls, especially aluminum alkyls, as disclosed, for example, in U.S. Patent ~ ,986, German Published Applicatlon 1,222,260 or German Laid-Open Application 2,013,26~. In these reactions, the olefinic double bonds are hydrogenated under mild conditlons at hydrogen pressures of from 1 to 100 bars, and at from 25 to 150 C.
The hydrogenatlon can also be carrled out in a heterogeneous phase, with metallic nickel or a platlnum metal as catalyst, at hydrogen pressures of from 20 to 300 bars and at from 40 to 300C (for example, by the method of German Published Applicatlon 1,106?961 or German Laid-Open Application 1,595,~45). In thls reaction, not only the olefinic double bonds but also the aromatic double bonds are hydrogenated. If the hydrogenation is carried out ln solution, it is advantageously effected in the same solvent as the preceding polymerization. The branched block copolymer may be hydrogenated partlally or completelyO If a hydrogenation is carried out, it is - preferred selectively to hydrogenate the olefinic double bonds of the polymer, so that the hydrogenated branched copolymers obtained preferably only contain less than 10%, and especially less than ~, of olefinic double bonds.
The hydrogenation is preferably carried out on branched block ~0 copolymers which have been manufactured in the presence of small amounts of ethers durlng the polymerization.
The process of manufacture decides the composition and struc-ture of the branched block copolymers of the invention. If, for example, a tetrafunctional coupling agent is used and the ratio, 1~7339 o . z ~ ~1, 665 in the fully polymerized reaction solution from the third stage of the process, of the two types of polymer blocks which form the branches, namely the ratio of (Al-A2-B-~A~)-Li to (A2-B _ A3)-Li, is, for examplg 1:1 or 1:3, the resulting branched block copolymer will on average (most probable structure) possess a structure of the formula (Al-A -B--~A3)2-X-(A3~--B-A2)2 or (Al-A2-B--~ A3)1-X-(A3~--B-A2)~. In the case of a trifunctional coupling agent and a ratlo of the two types of branches (Al-A2-B-~A3)-Li to (A2-B-~ A~)-Li of 1:2, the most probable average structure of the branched block copolymer is 3 10 (Al-A2-B-~ A3)1-X-(A3~- B-A2)2; in each of the formulae, X is the radical of the polyfunctional coupling agent.
In general, the most probable average structure of the branched block copolymers manufactured according to the invention corresponds to the general formula (Al-A2-B ~A3)n-X-(A3~B-A2)m where m and n are integers, and the sum of n and m corresponds to the polyfunctionality of the coupling agent and is thus at least three, in general from 3 to 10 and preferably 3 or 4. m is at least equal to or greater than n. The non-elastomeric polymer segment Al, which con-tains from 50 to 80% by weight, preferably from 60 to 75% by weight, 20 of the total monovinyl-aromatic compound, employed for the manufacture of the branched block copolymer, as polymerized units, preferably only consists of the monovinyl-aromatic compounds and is, in particular, a homopolystyrene segment. Its molecular weight depends particularly on the envisaged end use and is preferably from 50,000 to 250,000.
The polymer segments A2 correspond to the polymer segments Al except that they have a lower molecular weight, usually from 5,000 to 50,000.
They contain from 1 to 30% by weight, and preferably from 5 to 25% by weight, of the total monovinyl-aromatic compound as polymerized units.
The elastomeric polymer segment B is, as has been mentioned, a copoly-30 mer block consisting essentlally of the con~ugated diene with a small proportion of monovinyl-aromatic compoundJ in which block the olefinic double bonds may or may not be selectively hydrogenated. The proportion ~0~7339 o O z . 31,665 of the monovinyl-aromatic compound in the polymer segment B is in general less than about 30% by weight and in particular less than about 20% by weight, based on the amount of monovinyl-aromatic not contained in the polymer se~ments Al and A2. The non-elastomeric polymer segments A3, like the polymer segments Al and A2, preferably are built up of the monovinyl-aromatic compound alone and in parti-cular are homopolystyrene. The molecular weight of the polymer blocks (Al-A2-B - A3) is preferably from 100,000 to 500,000, whilst that of the polymer blocks (A2-B-~ A3) is from 10,000 to 100,000.
The branched block copolymers of the invention possess high .
transparency and clarity and good mechanical properties; in parti-cular they are superior, in respect of impact strength and yield stress, to the conventional products described in German Laid-Open Application 1,959,922. This was not foreseeable and was all the more surprising since, according to German Laid-Open Application 1,959,92?, all non-elastomeric polymer segments must be in terminal positions lf satisfactory mechanlcal properties are to be achieved.
Hydrogenation in particular improves the aging resistance of the~
products, though it may result in some reduction in their trans-2Q parency. The branched block copolymers of the invention can easilybe processed by the conventional processing methods for thermo-plastics, eg. extrusion, deep-drawing or injection molding, and are above all suitable for the manufacture of moldings and packaglng materlals.
The Examples which follow illustrate the lnvention. The vls-cosity number, measured ln 005% strength solution in toluene at 25C, ls quoted as a measure of the molecular weight. The impact strength an and notched impact strength ak were determlned on a molded speci-men according to DIN 53,453. The yield stress Y, tensile strength Z and elongation at break D were measured on a molded dumbbell-shaped bar according to DIN 5~,455.
6 kg of toluene and 430 g of styrene were introduced into a -1~-1~7339 oOzO 31,665 10 1 pressure kettle and titrated, under an lnert gas atmosphere, with a 1.5~ strength n-butyl-lithium solution until polymerization just commenced. 7 millimoles of n-butyl-lithium (as a 3~ strength solution in hexane) were then added and the mixture was polymerized at from 50 to 60C for about one hour, untll the monomer had been virtually completely converted~ The polymer had a vls¢osity number of 34.7 ~cm~/g~. A further 7 millimoles of n-butyl-lithium (as a 3%
strength solution in hexane) were added to the active reaction solu-tlon, 80 g of styrene were then added and the mixture was fully polymerized at from 50 to 60C. A~ter this stage, the viscosity number was 33.1 [cm3/g~. A mixture of 120 g of styrene and 210 g of butadiene was now added and polymerlzation was again carried out until the monomers had been virtually completely converted, which requlred about two hours at from 50 to 60C. ~.5 millimoles of silicon tetrachloride were then added. The resulting branched block copolymer was precipitated by adding methanol, and filtered of~.
It had a viscosity number of 84.3 [cm3/g] and the approximate struc-ture (Al-A2-B-~ A3)2-Si-(A3~--B-A2)2 where the A's are polystyrene segments and the B poly(butadiene/styrene) segments. The mechanical properties are shown in the Table.
The procedure followed was as described in Example 1, but in this case 450 g of styrene in 6 kg of toluene were initlally intro-duced into the reactor, and, after titration, were polymerized with 3.8 millimoles of n-butyl-lithlum at 50C. A viscosity number of 49.1 Ccm~/g~ resulted. A further 1104 millimoles of n-butyl-lithium were then added and 60 g of styrene were polymerized at from 50 to 60C. The vlscosity number was now 46.3 ~m3/g } A mixture of 120 g of styrene and 210 g of butadiene was now added and polymerization was now added and polymerization was again carried out? at 60C, until the monomers were virtually completely converted. The product was then coupled by means of 3.8 mllllmoles of sillcon tetrachloride to glve a branched block copolymerO It had the average structure (Al-A2-B-~ A3)1-Si-(A3~--B-Al)3 where the A's are polystyrene seg-ments and the B's poly(butadiene/styrene)segments~ The viscoslty number was 79.~ tcm/g]. The mechanical properties are shown in the Table.
COMPARATIVE EXAMPLES
(according to German Laid-Open Application 1,959,922) 2.7 kg of cyclohexane and 525 g of styrene were titrated with sec.-butyl-lithium in a 6 1 pressure kettle under an inert gas atmosphere and then polymerized for 30 mlnutes with 0.33 g of sec.-butyl-lithium. The initial temperature was 54C~ 0.22 kg of cyclo-hexane, 0.9 g of sec.-butyl-lithium and 225 g of styrene were added to the active reaction solutlon at 71C, polymerization was carried out for one hour, and 250 g of butadiene were then polymerized onto the product ln the course of one hour at about 74 C. Finally, coup~g -was carried out with lQ-ml of Epoxol 9-5*in 150 ml of toluene. The product was preclpitated fromlsopropanol. The viscoslty number was 91.9 Em3/g~ .
!' TABLE
cmkp/cm2 cmkp/cm2 kp/cm2 kp/ 2 D
; ~,, ' Example 1 2~.0 7~1 310 260 7 Example 2 32.012.1 205 154 132 Comparatlve Example 15.1 5.4 170 190 91 . ~ , * Trademark for an epoxidized linseed oil.
.:
,:~
, .. . . . . .
Claims (4)
1. Branched block copolymers of from 60 to 95 per cent by weight of a monovinyl-aromatic compound and from 40 to 5 per cent by weight of a conjugated diene of 4 to 8 carbon atoms, which have an average structure of the general formula (A1-A2-B?A3)n-X-(A3?B-A2)m where A1, A2 and A3 are non-elastomeric polymer segments based on the monovinyl-aromatic compound and the B's are elastomeric polymer segments based on the conjugated diene, m and n are numbers, m being equal to or greater than n and the sum of m and n being at least 3, and X is the radical of a polyfunctional coupling agent by means of which the linear polymer blocks (A1-A2-B?A3) and (A2-B?A3), which form the branches, are chemically bonded to one another at the polymer segments A3, with the provisos that the poly-mer segment or segments Al contains or contain from 50 to 80 per cent by weight, the polymer segments A2 from 1 to 30 per cent by weight, but the polymer segments Al and A2 together not more than 90 per cent by weight, of the total monovinyl-aromatic compound of the branched block copolymer, as copolymerized units, the transition between the polymer segments A2 and B is sharp and the transition between the polymer segments B and A3 is gradual.
2. Branched block copolymers as claimed in claim 1, which have a weight-average molecular weight of from 100,000 to 1,000,000.
3. Branched block copolymers as claimed in claim 1, which are partially or completely hydrogenated.
4. A process for the manufacture of branched block copolymers of from 60 to 95 per cent by weight of a monovinyl aromatic compound and from 40 to 5 per cent by weight of a conjugated diene of from 4 to 8 carbon atoms, wherein, in a first stage of the process, from 50 to 80 per cent by weight of the total amount of monovinyl-aroma-tic compound are polymerized in an inert solvent, in the presence of a relatively small amount of a monolithium-hydrocarbon as the initiator, until conversion is virtually complete, thereafter, in a second stage of the process, a further amount of monolithium-hydro-carbons, which is equal to or greater than the amount of initiator originally employed, is added to the reaction solution, followed by a further 1 to 30 per cent by weight of the total amount of the monovinyl-aromatic compound, the sum of the amount of monovinyl-aromatic compound added in the first and second stage of the process being at most 90 per cent by weight of the total amount of monovinyl-aromatic compound employed overall for the manufacture of the branched block copolymers, the monovinyl-aromatic compounds added in the second stage of the process are also polymerized until conversion is vir-tually complete, thereafter, in a third stage of the process, a mixture of the remaining monovinyl-aromatic compound and the whole of the conjugated diene is added to the reaction solution and polymerized, whereupon, when the monomers have been virtually completely converted, the mixture of the re-sulting linear block copolymers with active terminal lithium-carbon bonds is subjected to a coupling reaction, by adding an equivalent amount of a polyfunctional coupling agent, to form a branched block copolymer and finally the branched block copolymer is isolated from the reaction solution.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19752550227 DE2550227C2 (en) | 1975-11-08 | 1975-11-08 | Branched block copolymers and process for their preparation |
| DEP2550227.6 | 1975-11-08 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1087339A true CA1087339A (en) | 1980-10-07 |
Family
ID=5961264
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA264,020A Expired CA1087339A (en) | 1975-11-08 | 1976-10-21 | Branched block copolymers of a monovinyl-aromatic compound and a conjugated diene |
Country Status (8)
| Country | Link |
|---|---|
| JP (1) | JPS6035922B2 (en) |
| BE (1) | BE848028A (en) |
| CA (1) | CA1087339A (en) |
| DE (1) | DE2550227C2 (en) |
| FR (1) | FR2330706A1 (en) |
| GB (1) | GB1556234A (en) |
| IT (1) | IT1068944B (en) |
| NL (1) | NL183193C (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8129455B2 (en) | 2007-07-10 | 2012-03-06 | Styrolution GmbH | Flame retardant thermoplastic molding compositions |
| US8536279B2 (en) | 2008-12-23 | 2013-09-17 | Styrolution GmbH | Phase-separating block or graft copolymers comprising incompatible hard blocks and moulding compositions having a high stiffness |
| US8575269B2 (en) | 2007-09-14 | 2013-11-05 | Styrolution GmbH | Transparent, tough and rigid molding compositions based on styrene-butadiene block copolymer mixtures |
Families Citing this family (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3032832A1 (en) * | 1980-08-30 | 1982-04-22 | Basf Ag, 6700 Ludwigshafen | METHOD FOR PRODUCING BRANCHED BLOCK COPOLYMERS, USE THEREOF AND MOLDED PARTS THEREOF |
| DE3520103A1 (en) * | 1985-06-05 | 1986-12-11 | Basf Ag, 6700 Ludwigshafen | Process for the treatment of catalysts and/or residues of initiator-containing polymers or solutions thereof |
| IT1196517B (en) * | 1986-07-17 | 1988-11-16 | Montedipe Spa | RADIAL AND BIMODAL BLOCK COPOLYMERS HAVING EXCELLENT OPTICAL PROPERTIES AND IMPACT RESISTANCE AND PROCESS FOR THEIR PREPARATION |
| DE3921677A1 (en) * | 1989-07-01 | 1991-01-10 | Basf Ag | SEALABLE PLASTIC FILM |
| US5227419A (en) * | 1990-12-20 | 1993-07-13 | Phillips Petroleum Company | Tapered block styrene/butadiene copolymers |
| CA2134026C (en) * | 1993-11-15 | 1998-06-09 | William J. Trepka | Tapered block copolymers of monovinylarenes and conjugated dienes |
| DE4420769A1 (en) * | 1994-06-15 | 1995-12-21 | Basf Ag | Styrene / butadiene block copolymers stabilized with alpha-tocopherol |
| DE19914075A1 (en) | 1999-03-27 | 2000-09-28 | Basf Ag | Transparent high-impact styrene-butadiene block copolymers comprises at least two hard blocks and a soft block with a low 1,2-vinyl content for improved thermal stability |
| US6593430B1 (en) | 1999-03-27 | 2003-07-15 | Basf Aktiengesellschaft | Transparent, impact-resistant polystyrene on a styrene-butadiene block copolymer basis |
| DE10107423B4 (en) * | 2001-02-14 | 2007-02-15 | Dilo Trading Ag | Use of an anionically produced 3-block polymer as adhesion promoter and lithium polymer battery |
| DE10109737B4 (en) * | 2001-02-28 | 2005-10-20 | Dilo Trading Ag Zug | Anionically prepared modified polystyrene copolymers and process therefor |
| DE10306891B4 (en) * | 2003-02-18 | 2016-07-14 | Ineos Styrolution Europe Gmbh | Transparent block copolymers of vinylaromatics and dienes |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3778490A (en) * | 1969-04-23 | 1973-12-11 | Phillips Petroleum Co | Polar compound adjuvants for improved block polymers prepared with primary hydrocarbyllithium initiators |
-
1975
- 1975-11-08 DE DE19752550227 patent/DE2550227C2/en not_active Expired
-
1976
- 1976-10-14 IT IT2833876A patent/IT1068944B/en active
- 1976-10-21 CA CA264,020A patent/CA1087339A/en not_active Expired
- 1976-11-04 FR FR7633302A patent/FR2330706A1/en active Granted
- 1976-11-05 NL NL7612330A patent/NL183193C/en not_active IP Right Cessation
- 1976-11-05 BE BE172106A patent/BE848028A/en not_active IP Right Cessation
- 1976-11-05 GB GB4613576A patent/GB1556234A/en not_active Expired
- 1976-11-08 JP JP13330976A patent/JPS6035922B2/en not_active Expired
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8129455B2 (en) | 2007-07-10 | 2012-03-06 | Styrolution GmbH | Flame retardant thermoplastic molding compositions |
| US8575269B2 (en) | 2007-09-14 | 2013-11-05 | Styrolution GmbH | Transparent, tough and rigid molding compositions based on styrene-butadiene block copolymer mixtures |
| US8536279B2 (en) | 2008-12-23 | 2013-09-17 | Styrolution GmbH | Phase-separating block or graft copolymers comprising incompatible hard blocks and moulding compositions having a high stiffness |
Also Published As
| Publication number | Publication date |
|---|---|
| DE2550227A1 (en) | 1977-05-18 |
| BE848028A (en) | 1977-05-05 |
| NL183193C (en) | 1988-08-16 |
| DE2550227C2 (en) | 1984-12-20 |
| NL7612330A (en) | 1977-05-10 |
| JPS5258788A (en) | 1977-05-14 |
| FR2330706A1 (en) | 1977-06-03 |
| FR2330706B1 (en) | 1980-08-01 |
| JPS6035922B2 (en) | 1985-08-17 |
| IT1068944B (en) | 1985-03-21 |
| GB1556234A (en) | 1979-11-21 |
| NL183193B (en) | 1988-03-16 |
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