CA1260173A - Modified block copolymer process - Google Patents

Abstract

ABSTRACT
Process for the production of a thermally stable modi-fied selectively hydrogenated high 1,2 content block copolymer wherein a functional group is grafted to the block copolymer in the vinylarene block. The copolymers produced according to the process of the invention have excellent appearance characteristics and mechanical properties and are particularly useful in blending with other polymers obtained by modifying a block copolymer composed of a conjugated diene compound and an aromatic vinyl compound with a functional group.

Description

7 ~

- 1 - 63293-~678 MODIFIED BLOCK COPOLYMER PROCESS
This inven-tion relates to novel selectively hydrogenated functionalized block copolymers. More particularly, i-t relates to a process or the production of modified thermoplastic polymers with excellent appearance properties and mechanical properties particularly useful in blending with o-ther polymers obtained by modifying a block copolymer composed of a conjugated diene compound and an aromatic vinyl compound with a functional group.
This application is related to Canadian patent applica-tion Serial Number 513,448 which has been filed on July 10, 1986.
It is known that a block copoly.~er can be obtained by an anionic copolymerization of a conjugated diene compound and an aromatic vinyl compound by using an organic alkali metal initiator. These types of block copolymers are diversified in characteristics, depending on the content of the aromatic vinyl compound.
When the content of the aromatic vinyl compound issmall, the produced block copolymer is a so-called thermoplastic rubber. It is a very useful polymer which shows rubber elasticity in the unvulcani~ed state and is applicable for various uses such as mouldings of shoe sole, etc.; impact modifier for polystyrene resins; adhesive; binder; etc.
The block copolymers with a high aromatic vinyl compound content, such as more than 70~ by weight , provide a resin possessing both excellent impact resistance and transparency, and such a resin is widely used in the field of packaging. Many proposals have been made on processes for the preparation of these types of block copolymers (V.S. 3,639,517)~

The elastomeric properties of certain aromatic vlnyl polymers also appear to be due in part to their degree of branching. While the aromatic vinyl polymers have a basic straight carbon chain backbone, those with elastomeric properties always have pendent alkyl radicals. For example, EPR (ethylene-propylene rubber) has a structure of pendent methyl radicals which appear to provide elas~icity and other elastomeric properties. When an essentially unbranched straight chain polymer is formed, such as some psly-ethylenes, the resulting polymer is essentially non-elastomeric or in other words relatively rigid, and behaves like a typical thermoplastic without yield, low set or other properties charac-teristic of desirable elastomers.
Block copolymers have been produced, see U.S. Patent Xe 279145 which comprlse primarily those having a general structure A--B--A
wherein the two terminal polymer blocks A comprise thermoplastic polymer blocks of vinylarenes such as polystyrene, while block B
is a polymer block of a selectively hydrogenated conjugated diene.
The proportion of the thermoplastic terminal blocks to the centre elastomeric polymer block and the relative molecular weights of each of these blocks is balanced to obtain a rubber having an optimum combination of properties such that it behaves as a vulcanized rubber without requlring the actual step of vulca-nization. Moreover, these block copolymers can be deslgned not only with this important advantage but also so as to be handled in thermoplastic forming equipment and are soluble in a variety of relatively low cost solvents.
While these block copolymers have a number of outs~anding technical advantages, one of their principal limitations lies in their sensitivity to oxidation. Thls was due to their unsaturated character which can be minimized by hydrogenating the copolymer, especially ln the centre section comprising the polymeric diene block. Hydrogenation ~ay be effected selectively as disclosed in U.S. Patent Re 27,145. These polymers are hydrogenated block copolymers having a configuration, prior to hydrogenation, of A-B-A wherein each of the A's is an alkenyl-substituted aromatic hydrocarbon polymer block and B is a butadiene polymer block wherein 35-55 mol per cent of the condensed butadiene units ln the butadiene polymer block have 1,2 configuration.
Due to their hydrocarbon nature, these selectively hydrogenated ABA block copolymers are deficient in many applications in which adhes4on to a polar surface ls required. E~amples include the toughening and compatibilization of polar polymers such as the engineerln~ thermoplastics, the adhesion to high energy substrates by hydrogenated block copolymer elastomer based adhesives, sealants and coatings, and the use of hydrogenated elastomer in reinforced polymer systems. However, the placement onto the block copolymer of functional groups which can provide interactions not possible with hydrocarbon polymers solves the adhesion problem and extends the range of applicability of this material.
Beyond th very dramatic improvement in interface adhesion in polymer blends, a functionalized styrene ethylene/butylene-styrene (S-EB-S) component can also contribute substantially to the external adhesion characteristics often needed in polymer systems.
These include adhesion to fibres and fillers which reinforce the polymer system; adhesion to substrates in adhesives, sealants, and coatings based on functionalized S-EB-S polymers, adhesion of decorations such as printing inks, paints, primers, and metals of systems based on S-EB-S polymers; participation in chemical reactions such as binding proteins as heparin for blood compati-bility; surfactants in polar-nonpolar aqueous or non-aqueous dispersions.
Functionalized S-EB-S polymer can be described as basically 3~ commerc~ally produced S-EB-S poly~ers which are produced by hydrogenatlon of S-B-S polymer to which is chemically attached to either the styrene or the ethylene-butylene block, chemically functional moieties.

~;i~Ei;6D~L'73 Many attempts have been made or the purpose of improving adhesiveness, green strength and other properties by functiona-lizing block copolymers, and various methods have been proposed for functionalizing synthetic conjugated diene rubbers.
Saito et al in U.S. 4,292,414 and U.S. 4J308~353 describe a monovinyl aryl/conjugated diene block copolymer with low 1,2 content grafted with a maleic acld compound. However, the process is limited to reaction conditions wherein the generation of free radicals is substantially inhibited by using free radical inhibitors or conventional stabilizers for example phenol type phosphorous type or amine type stabilizers. The processes are limited to thermal additlon reactions or the so-called 'tENE" reaction. This reaction scheme depends on unsaturation ln the base polymer for reaction sites. A reasonable amount of residual unsaturation must be present in order to obtain an advantageous degree of function-ality or grating onto the base polymer. A substantially completely hydrogenated base polymer would not react appreciably in the Saito et al process.
Hergenrother et al in U.S. 4,427,828 describe a similar modified block copolymer with high 1,2 content ho~ever, again produced by the 'ENE' reaction.
Tbe 'EME' process as described in the prior art results in a modified polymer product which i6 substi~uted at a position on the polymer backbone which is allylic to the double bond. The reaction can be shown for maleic anhydride as ollows:
a) to main chain unsaturation H H 3h H H H H H
- C - C = C~C- C ~ C - C = C- Allylic position H ~ H

' ~0/ \0/
:
~' 7~31 _ 5 63293-2678 b) to vinyl unsaturation H ~H H
-C~ C -C~) Allylic position H ¦ ¦ H ¦~
C-H \ C-H
pl -+ ~ ~-C~

O=C C=O O=C C=O
~O / 0/

wherein a) represents addition across a double bond in the main chain of the base polymer and b) represents addition across a double bond occurring in a side chain. After addition and iso-merization the substitution is positioned on a carbon allylic to the double bond.
The allylically substituted polymers are prone to thermal degradation due to their thermal instability. It is known in the art that allylic substituents can undergo what has been referred to as a retro ENE reaction, see B.C. Trivedi9 B.M. Culbertson, Maleic Anhydride, (Plenum Press, New York, 1982) pp. 172-173.
Further, because the ENE reaction requires a reasonable amount of unsaturation in the precursor base polymer, as discussed previously, the resulting functionalized copolymer product will have a significant amount of residual unsaturation and will be inherently unstable to oxidation.
According to the present invention, there is provided a process for the produceion of a thermally stable, modified, selectively hydrogenated, high 1,2 content block copolymer to which a functional group has been grafted primarily in the vinyl-arene block.
More preferably there is provided a process for producing graft copolymers comprisingn~tallatinghydrogenated block copo-lymers of conjugated dienes and monovinyl-substituted aromatic compounds with an alkyllithium compound, and a polar compound l ~ . ' ' ~26~31173 selected from the group consisting of tertiary amines and low molecular weight hydrocarbon ethers, to form a backbone polymer having active lithium atoms along the polymer chain, and therea~ter reacting said backbone polymer and at least one electrophile or graft-able m~lecule hav.ing electrophillc functional gr~ups to forn backkone polymers with grafted molecules attached wherein substantially all of said graftable molecules which have been grafted are grafted to the block copolymer in the vinylarene block.
The feature of this invention lies not only in providing a process for the industrial production of modified blo~k copolymers but also providing the modified block copolymers which are thermally stable; have a low residual unsaturation, are excellent in appearance characteristics, melt-flow characteristics, and mechanical properties such as tensile strength and impact resistance; etc.
The modified block copolymers produced according to the process of the present invention are substituted in the vinylarene block as shown in the exemplary reactions given below:
H RLi Amine ~ C02 H
--(CH2-C)n - (CH -C ~ para ... 'bl ~
~:02Li H

(CH2 I~~n meta : in which: RLi = Alkyl-Lithium C2Li -tCH2 C ~ benzylic b` (minor product) The structure of the substituted block copolymer specifically determined by the location of the functionality on the polymer ~2~a~ 7~

- 7 - 63293~2678 backbone in the vinylarene block gives the block copolymer a substantially greater degree of thermal stability.
Selectively Hydrogenated Block Copoly~er Base Polymer Block copolymers of conjugated dienes and vinyl aromatic hydrocarbons which may be utilized include any of those which exhibit elastomeric properties and those which have l,2-micro-structure contents prior to hydrogenation suitably in the range of ~rom about 7% to about 100% and preferably of from 35% to 50%.
Such block copolymers may be multiblock copolymers of varying structures containing various ratios of conjugated dienes to vinyl aromatic hydrocarbons including those containing up to 60 per cent by weight of vinyl-aromatic hydrocarbon. Thus, multiblock copolymers may be utilized which are linear or radial symmetric or asymmetric and which have structures represented by the formulae A-B, A-B-A, A-B-~-B, B-A. B-A-B, B-A-B-A, (AB)o 1 2 BA and the like wherein A is a polymer biock of a vinyl aromatic hydrocarbon or a conjugated diene/vinyl aromatic hydrocarbon tapered copolymer block and B is a polymer block of a conjugated diene.
Block A preferably has an average molecular weight in the range of from 500 to 60,000 and block B preferably has an average molecular weight in the range of from 35,000 to 150,000.
The block copolymers may be produced by any well known block polymerization or copolymerization procedures including the well known sequential addition of monomer techniques, incremental addition of monomer technique or coupling technique as illustrated in, for example, UOS. Patent Nos. 3,251,905; 3,390,207; 3,598,887 and 4,219,627. As is well known in the block copolymer art, tapered copolymer blocks can be incorporated in the multiblock copolymer by copolymerizing a mixture of conjugated diene and vinyl aromatic hydrocarbon monomers utilizing the difference in their copolymerization reactivity rates. Various-patents describe the prepara~ion of multiblock copolymers containing tapered copolymer blocks including U.S. Patent Nos. 3,251,905; 3,265,765;
3,639,521 and 4,208,356 ~2~
~ 8 - 63293-2678 Conjugated dienes which may be utilized to prepare the polymers and copolymers are those having from 4 to 8 carbon atoms per molecule and include 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, and the like. Mixtures of such conjugated dienes may also be used. The preferred conjugated diene is 1,3-butadiene.
The polymer blocks A are prior to hydrogenation preferably polymer blocks of a monoalkenyl-aromatic hydrocarbon,more pre~erably of a vinyl-aromatic hydrocarbon.
Vinyl aromatic hydrocarbons which may be utilized to prepare copolymers include styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, alpha-methylstyrene, vinylnaphthalene,vinylanthracene and the like. The preferred vinyl aromatic hydrocarbon is styrene. The block copolymer is preferably a styrene-ethylene/butylene styrene block copolymer.
It should be observed that the above-described polymers and copolymers may, if desired, be readily prepared by the methods set forth hereinbefore.However, since many of these polymers and copolymers are commercially available, it is usually preferred to employ the commercially available polymer as this serves to reduce the number of processing steps involved in the overall process.
The hydrogenation of these polymers and copolymers may be carried out by a variety of well established processes including hydro-genation in the presence of such catalysts as Raney B'~.

- 8a - 63293-2678 ~ickel,noble metals such as platinum, palladium and the like and soluble transition metal catalys-ts. Suitable hydrogenation processes which can be used are ones wherein the diene-containing polymer or copolymer is dissolved is an inert hydrocarbon diluent such as cyclohexane and hydrogenated by reaction with hydrogen in the presence of a soluble hydrogenation catalyst. Such processes are disclosed in U.S. Patent Nos. 3,113,986 and 4,226,952. The polymers and copolymers are hydrogenated in such a manner as to produce hydrogenated polymers and copolymers having a residual unsaturation content in the polydiene block of from 0.5 to 20 `^`` ~6~ 3 and more preferably from 0.5 to 10 per cent of their orlginal unsaturation content prior to hydrogenation. Most preferably the unsaturation of block B has been reduced to a value of less than 5 per cent of its original value.
In general, any materials having the ability to react with the lithiated base polymer, are operable for the purposes of this invention.
In order to incorporate functional groups into the base polymer9 reactants capable of reacting with the lithiated base polymer are necessary. These reactants may be polymerizable or nonpolymeriæable, however, preferred reactants are nonpolymerizable or slowly polymerizing.
The graft reaction involves nucleophilic attack of a polymer bound lithium alkyl on an electrophile.
The class of preferred electrophiles which will form graft polymers within the scope of the present invention include reactants from the following groups: carbon dioxide, ethylene oxide, aldehydes, ketones, carboxylic acid salts, their esters and halides, epoxides, sulphur, boron alkoxides, isocyanates and various silicon compounds.
These electrophiles may contain appended functional groups as in the case of N,N-dimethyl-p-aminobenzaldehyde where the amine is an appended functional group and the aldehyde is the reactive electrophile. Alternati~ely, the electrophile may react to become the functional site itself; as an example, carbon dioxide ~electro-phile) reacts with the metalated polymer to form a carboxylate functional group. By these routes, polymers could be prepared containing grafted sites sele&ted from one or more of the following groups of functionality type carboxylic acids, their salts and esters, ketones, alcohols and alkoxides, amines, amides, thiols, borates, and functional groups containing a silicon atom.
These ~unctionalities can be subsequently reacted with other ; modifying materials to produce new functional groups. For example, 7:31 the grafted c~rboxylic acid described hereinbefore could be suitably modified by esterifying the resulting acid groups in the graft by appropriate reaction with hydroxy-containing compounds of varying carbon atoms lengths. In some cases, the reaction could take place simultaneously with the grafting process but in most examples it would be practised in subsequent post modification reaction.
The grafted polymer will usually contain in the range from 0.02 to 20, preferably 0.1 to 1b, and most preferably 0.2 to 5 ~eight per cent of grafted portion.
The block copolymers, as modified, can still be used for any purpose for which an unmodified material (base polymer) was formerly used. That is, they can be used for adhesives and sealants, or compounded and extruded and moulded in any convenient manner.
An example of a method to incorporate functional groups into the base polymer primarily in the vinylarene block is metalation.
Metalation is conveniently carried out by means of a complex formed by the combination of a lithium component which can be represented by R'(Li) with a polar metalation promoter. The polar compound and the lithium component can be added separately or can be premixed or pre-reacted to form an adduct prior to addition to the solution of the hydrogenated copolymer. In the compounds represented by R'(Li) , the R' is usually a saturated hydrocarbon radical of any length whatsoever, but ordinarily containing up to 20 carbon atoms, and can be a saturated cyclic hydrocarbon radical of e.g. 5 to 7 carbon atoms. In the formula, R'(~i) x is an integer of 1 to 3. Representative species include, for example:
methyllithium, isopropyll~thium, sec-butyllithium, n-butyllithium, t-butyllithium, n-dodecyllithium, 1,4-dilithiobutane, 1,3,5,-tri-lithiopentane, and the like. The lithium alkyls must be more basic than the product metalated alkyl. Of course, other alkali metal or alkaline earth metal alXyls could be used but the ~6~ 73 lithium alkyls are preferred due to their ready commercial availa-bility. In a similar way, metal hydrides could be employed as the metalation reagent but the hydrides have only limited solubility in the appropriate solvents. The metal alkyls are preferred for their greater solubility which makes them easier to process.
Lit~ium compounds alone usually metalate copolymers containing aromatic and olefinic functional groups with considerable difficulty and under high temperatures ~hich may tend to degrade the copolymer.
~owever, in the presence of tertiary diamines and bridgehead monoamines~ metalation proceeds rapidly and smoothly. Some lithium compounds can be used alone effectively, notably the methyllithium types.
It has been shown that the metalation occurs at a carbon to which an aromatic group is attached, or on an aromatic group, or in more than one of these positions. In any event, it has been shown that a very large number of lithium atoms are positioned variously along the polymer chain, attached to internal carbon atoms away from the polymer terminal carbon atoms, either along the backbone of the polymer or on groups pendant therefrom, or both, in a manner depending upon the distribution of reactive or lithiatable positions. This distinguishes the lithiated copolymer from simple terminally reactive polymers prepared by usin~ a lithium or even a polylithium initiator in polymerizat~on thus limiting the number and the location of the positions avallable for subsequent attachment. With the metalation procedure described herein, the extent of the lithiation will depend upon the amount of metalating agent used and/or the groups available for metalation.
The use of a more basic lithium alkyl such as tert-butyllithium may not require the use of a polar metalation promoter.
The polar compound promoters include a variety of tertiary amines, bridgehead amine~, ethers, and metal alko~ides.

~21Ei~7~

The tertiary amines useful in the metalation step have three saturated aliphatic hydrocarbon groups attached to each nitrogen and include, for example:
(a) Chelating tertiary diamines, preferably those of the formula (R )2N-C H2y~~N(R )2 in which each R2 can be the same or different straight- or branched-chain alkyl group of any chain length containing up to 20 carbon atoms or more all of which are included herein and y can be any whole number from

2 to 10, and particularly the ethylene diamines in which all alkyl substituents are the same. These include, for example:
tetramethylethylenediamine (which is preferred~, tetraethyl-ethylenediamine, tetradecylenediamine, tetraoctylhexylenedi-amine, tetra-(mixed alkyl) ethylenediamines, and the like.
(b) Cyclic diamines can be used, such as, for example, the N,N,~',N'-tetraalkyl 1,2-diamino cyclohexanes, the N,~,N',N',-tetraalkyl 1~4 diamino cyclohexanes, ~,N'-dimethylpiperazine, and the like.
(c) The useful bridgehead diamines include, for example, sparteine, triethylenediamine, and the like.
Tertiary monoamiDes such as triethylenediamine are generally not as effective in the lithiation react-lon. However, bridgehead monoamines such as l-azabicyclo~2.2.2~ octane and its substituted homologs are effective.
Ethers and the alkali metal alkoxides are presently less preferred than the chelating amines as activators for the me~alation reaction due to somewhat lower levels of incorporation of functional group containing compounds onto the copolymer backbone in the subsequent grafting reaction.
Polar metalation promoters may be present ln an amount sufficient to enable metalation to occur, e.g. amounts between 0,01 and 100 or more preferably between 0.1 and 10 and most preferably between 1 and 3 equivalents per equivalent of lithium alkyl.

7~

The equivalenes of lithlum employed for the desired amount of lithiation generally range from such as 0.001 to 3 per vinyl-arene unit in the copolymer, presently preferably 0.01 to 1.0 equivalents per vinyl-arene unit in the copolymer to be modified. The molar ratio of active lithium to the polar promoter can vary from such as 0.01 to 10Ø A preferred ratio is 0.5.
The amount of alkyl lithium employed can be expressed in terms of the Li/vinylarene molar ratio. This ratio may range from a value of 1 (one lithium alkyl per vinylarene unit) to as low as 1 x 1~ 3 (1 lithium alkyl per 1000 vinylarene units).
In general, it is most desirable to carry out the lithiation reaction in an inert solvent such as saturated hydrocarbons.
Aromatic solverlts such as benzene are lithiatable and may interfere with the desired lithiation of the hydrogenated copolymer. The solvent/copolymer weight ratio which is convenient generally is in the range of about 5:1 to 20:1. Solvents such as chlorinated hydrocarbons, ketones, and alcohols, should not be used because they destroy the lithiating compound.
The process of lithiation can be carried out at temperatures in the range of such as about -70 C to ~150 C, presently preferably in the range of about 25 C to 80 C, the upper temperatures being limited by the thermal stability of the lithium compounds~ The lower temperatures are limited by considerations of production cost, the cost of cooling these reactants becoming high at low temperatures. The length of time necessary to complete the lithiation and subsequent reactions is largely dependent upon the mixing conditions and the temperature. Generally the time can range from a few seconds to about 72 hours, presently preferably from about 1 minute to 1 hour.
The next step in the process of preparing the modified block copolymer is the treatment of the lithiated hydrogenated copolymer, in solution, without quenching in any manner which would destroy the lithium sites, with a species capable of reacting w~th a lithium anion. These reactive species are selected q3 from the class of molecules called electrophiles. The most preferred electrophiles have been listed above in the section hereinbefore.
These electrophiles either contain or form upon reaction with the polymer bound lithium anion the desired functional groups~ such functional groups include but are not limited to -C-O- carboxyl C-~R2 Amine C-OH hydroxyl ~-NR2 Amide C-OR ether C-SH Thiol o -C-R ~etone C-B(OR)2 Borane^containing -C-H aldehyde C-Si- Silicone-containing The process also includes further chemistry on the modified block copolymer. For example, converting of a carboxylic acid salt containing modified block copolymer to the carboxylic acid form can be easily accomplished.
EXAMPLES
Example 1 The base polymer used in this example was an S-E¦B-S type block copolymer (herein referred to as reactant polymer A).
Reactant polymer A had a molecular weight of about 50,000 and contained 30% polystyrene.
In a typical experiment, 45.36 kg of a polymer cement containing Polymer A in cyclohexane (5~ solids) was lithlated at 60 ~C using a diamine (eetramethylethylenediamine, TMEDA) promoted sec-butyl-Li reagent (1.1 mol base, 1.8 mol promoter). A rapid metalation reaction afford~d a thixotropic, semlsolid cement which immobllized the reactor's stirring mechanism (auger type) within

3-4 minutes. An aliquot of the lithiated-polymer cement was quenched with D20. The remainder was transferred through a 3.8 cm diameter line to a vessel containing an excess of C02 (1.36 kg) in g~ 73 tetrahydrofuran (THF). The carboxylated product was treated with acetic acid (85 g, 1.4 mol) and finished by steam coagulation affording over 1.81 kg of white, functionalized polymer crumb.
Analyses of the carboxylated product found 0.84% wt - C02H and 0.29% wt ~ CO2 - for a total polymer bound carboxylate content of 1.13% wt.
A deuterium (D) NMR analysis of the D20 treated aliquot found the D resided primarily at aromatic sites, at meta and para positions on the ring, ~90% of total D), with the remainder of the tag or label being at either benzylic or allylic positions (10% of total D~. The technique cannot discern between allylic and benzylic locations. Thus, the label resided principally, at least 90%, and most likely entirely in the polystyrene block of the polymer. We infer Erom this labelling experiment that essentially all of the lithiation reaction, at least 90%, occurred in the polystyrene ~lock. Therefore, essentially all of the carboxylation must occur at these sites as well.
Eor this experiment, 50% of the reactant sec-butyl Li was converted into polymer bound carboxylate as found in the product (lithiation efficiency). The product, as finlshed, contained 7 parts of acid (-CO2H) to every 26 parts of salt (-CO2-).
Examples 2-14 Examples 2-14 were conducted as outlined in Example 1. Some modifications were used as outlined in Table 1.
Reactant polymer B was similar to polymer A with the molecular weight being about 67,000. Reactant polymer C was similar to polymer A ~ith the ~olecular weight ~eing ahout 181,000 and a polystyrene content of 33%. Reactant polymer D was an S-E/P type of block copolymer with a total molecular weight of about 98,000 and a polystyrene content of 37%.
The lithiation of polymers A, B and C proceeded with a rapid rise in viscosity in all examples. In some examples, the lithiated product was allowed to digest for longer periods without stirring.
The lithiation of polymer D proceeded with no observable increase in cement viscosity.

As found in Example 1, deuterium NMR analyses of D20 quenched aliquots of the various products found the label to be predominantly in the polystyrene block of the polymer. These results are summari7ed in Table 2.
Each of the deuterated samples was analyzed by Gel Permeation Chromatography. The resulting molecular weight information did not differ significantly from that for the starting unmetalated polymer. This indicates that the metalation technique did not induce any degradation, for example, chain scission or crosslinking in these polymers.
Control experiments using the reaction technique of Example 1 and S-rubber-S block copolymers where the rubber is substantially unsaturated showed that these reactants were lithiated indiscri-minately in both the styrene block (about 50%) and the rubber block (about 50%). These randomly functionalized products were not preferred.

~L2~09 ,, a~ ~ o r~ ~ o 1~- ~ O~ 00 ~ ~ ~ ~D
~~ ~ ~ ~ o ~ O ~ ~ 3 ~ ~~ oo ~ u~ ~ ~ cn o~ ~D O~ CO G~ CO
E~ ~'4 E~ ~ .~ ~ ~ c~l O ~ ~ ~ 5 ,, o b~ ~ ~ ~ ~ O O~ O ~ C~
~ ~ _~ o _~ o _l o o o o ~ o _ C~
V
C~
V ~ _I ~ ~D i ~ ~ ~ ~ C~ ~ ~ Ul Z ;~ _ -I O O I O O O O O O O ~ O
,_1 H ~ a~ ¢
.5 ~_ ~ ~
~i ~ '` '` '`

~ ~ ~ ~ O O O ~ C`l O O ~ O O O O O
a~z t~ ~ ~3 ~O ~O ~
E~

~ ~ O ~
zi g ;q ~3 ~ ~ 1 0 0 0 0 H ~ t~ ¦

~u ~ ~ ~ ~: ~C ~ m td O E~
P~

~ ~ ~ ~ U~ O

TABLE II
Location of Deuterated Site Example Location of Deuterium Label (Carboxylate) Number Aromatic Benzylic, Allylic (%) (%)

4 92 8 Example 15 The modified block copolymer in Example 14 was converted to the carboxylic acid salt formed by the following procedure: 50 g of polymer was dissolved in 500 g of a 90:10 mixture of cyclohexane:THF.
Next, 4.3 g of a 1 molar aqueous LiOH solution was added. The mixture was allowed to stand 24 hours. The polymer was then recovered by precipitztion with methanol and dried at sub-atmospheric pressure.
By IR analysis, the sample showed complete conversion of acid functionality to lithium salt functionality. The absorbance band of the salt occurs at 1560-1600 cm 1, while that of the acid occurs at 16~0 ~
Example 16 In this example, hydroxyl functionality was placed on the base polymer. The base polymer used was Reactant Polymer B.
Base polymer (100 g) was dissolved in 100 ml of cyclohexane in a glass reactor under an argon purge. 1.02 meq TMEDA per g of polymer was then added. Impurities in the mixture were then removed by titration with sec-butyllithium. The reactor contents were heated to 50 C, and 0.51 meq of additional sec-butyllithium per g of polymer were added. 1000 ml of distilled THF was added and this solution was stirred at 25 ~C for 16 hours. This mixture was maintained at 40-45 C for 70 minutes. Next, ethylene oxide was bubbled into the vessel and the mixture was stirred for 10 minutes at 45 ~C. Finally, 1 meq of HCl (in methanol) per g of polymer was ~6~ l73 added to the reactor. The polymer WAS recovered by coagulation into 2-propanol and washed with methanol. A portion of the polymer was dried at sub-atmospheric pressure at 40 C.
In order to analy~e this hydroxylated polymer, thP OH func-tionality was converted to acid by reaction with maleic anhydride at 150-160 ~C in diisopropylbenzeneO The reaction product was precipitated into me~hanol and washed with 70 C water to remove unreacted maleic anhydride. IR measurement showed carbonyl bands at 1730 cm 1 characteristic of a maleic ester.
The polymer was then dried at sub-atmospheric pressure at 50 C. Titration for the half maleic acid ester using potassium methoxide in methanol together with a phenolphthalein indicator gave 0.18 meq acid per g polymer, showing that the original modified block copolymer contained 0.18 meq OH groups per g polymer.

Claims (35)

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

1. A process for producing graft copolymers comprising metallating hydrogenated block copolymers of conjugated dienes and monovinyl-substituted aromatic compounds with an alkyllithium compound, and a polar compound selected from the group consisting of tertiary amines and low molecular weight hydrocarbon ethers, to form a backbone polymer having active lithium atoms along the polymer chain, and thereafter reacting said backbone polymer and at least one electro-phile or graftable molecule having electrophilic functional groups to form backbone polymers with grafted molecules attached wherein substan-tially all of said graftable molecules which have been grafted are grafted to the block copolymer in the vinylarene block.

2. The process of claim 1 wherein the block copolymer is a selectively hydrogenated block copolymer having at least 1 B mid block and at least two A end blocks wherein, (1) each A is predominantly a polymerized monoalkenyl aromatic hydrocarbon block having an average molecular weight of 100 to 115,000;
(2) each B prior to hydrogenation is predominantly a polymerized conjugated diene hydrocarbon block having an average molecular weight of 20,000 to 450,000;
(3) the blocks A constituting 1-95 weight per cent of the copolymer;
(4) the unsaturation of the block B is less than 10% of the original unsaturation;
i (5) the unsaturation of the A blocks is above 50% of the original unsaturation.

3. The process of claim 1 wherein the functional groups of the graftable molecule are selected from the group consisting of carboxyls, alcohols, ethers, amines, ketones, amides, thiols, aldehydes, borane containing groups and silicon containing groups.

4. The process of claim 1 wherein the block copolymer is a styrene-ethylene/butylene-styrene block copolymer.

5. The process of claim 2 wherein prior to hydrogenation, the polymeric blocks A are polymer blocks of a monoalkenyl-aromatic hydrocarbon.

6. The process of claim 2 wherein the blocks A comprise 1-40 per cent by weight of the copolymer, the unsaturation of block B is reduced to less than 5% of its original value and the average aliphatic unsaturation of the hydrogenated block copolymer is reduced to less than 20% of its original value.

7. The process of claim 4 wherein the styrene block has an average molecular weight of between 500 to 60,000.

8. The process of claim 2 wherein B is a polymerized butadiene block having an average molecular weight of between 35,000 and 150,000, 35%-50% of the condensed butadiene units having 1,2-confi-guration.

9. The process of claim 1 wherein the electrophile is carbon dioxide.

10. The process of claim 1 wherein the electrophile is ethylene oxide.

11. The process of claim 1 wherein the electrophiles are selected from the group consisting of aldehydes, ketones and acid salts and esters.

12. The process of claim 1 wherein the electrophiles are epoxides.

13. The process of claim 1 wherein the electrophile is sulphur.

14. The process of claim 1 wherein the electrophile is a boron alkoxide.

15. The process of claim 1 wherein the electrophile is an isocyanate.

16. The process of claim 1 wherein the electrophile is a molecule containing silicon.

17. The process of claim 1 wherein the polar compound is present at between 0.1 and 10.0 equivalents per equivalent of lithium alkyl.

18. The process of claim 1 wherein the functional groups are carboxylic acids, their salts and esters.

19. The process of claim 1 wherein the functional groups are ketones.

20. The process of claim 1 wherein the functional groups are alcohols and alkoxides.

21. The process of claim 1 wherein the functional groups are amines.

22. The process of claim 1 wherein the functional groups are functional groups containing a silicon atom.

23. The process of claim 1 wherein the functional groups are thiols.

24. The process of claim 1 wherein the functional groups are borates.

25. The process of claim 1 wherein the functional groups are amides.

26. A process of claim 1 wherein the polar compound is N,N,N',N'-tetramethylethylenediamine.

27. The process of claim 1 wherein the molar ratio of said alkyl-lithium compound to vinylarene units ranges from 3 to 1x10-3 and the amount of said polar compound is 0.1 to 10.0 equivalents per equivalent of lithium alkyl.

28. The process of claim 1 wherein the molar ratio of said alkyl lithium compound to vinylarene unit ranges from 1 to 1x10-2.

29. The process of claim 1 wherein said alkyllithium compound is sec-butyllithium.

30. The process of claim 1 wherein said metallating is performed at a temperature in the range of 25 to 80 °C for a period of 1 minute to 50 hours.

31. The process of claim 1 wherein the polar compound is present at between 1 and 3 equivalents per equivalent of lithium alkyl.

32. A process for producing graft copolymers comprising contacting hydrogenated block copolymers of conjugated dienes and monovinyl-substituted aromatic compounds with tert-butyllithium to form a backbone polymer having active lithium atoms along the polymer chain, and thereafter contacting at least one electrophilic graftable molecule which upon reaction with the active lithium atoms will produce functional groups selected from the group consisting of carboxyls, alcohols and ethers wherein substantially all of said molecules are grafted to the block copolymer in the vinylarene block.

33. The block copolymer produced by the process of claim 1.

34. The block copolymer produced by the process of claim 2.

35. The block copolymer produced by the process of claim 32.