Method for separating metal contaminants from organic polymers

A method for separating metal residues from a polymer wherein a solution or suspension of said polymer is contacted with an aqueous solution containing one or more inorganic acids in the presence of a monocarboxylic acid containing from about 6 to about 20 carbon atoms. The polymer solution or suspension will be contacted with an oxidizing agent either prior to or simultaneously with the contacting with the aqueous inorganic acid solution. The inorganic acid is, preferably, a mineral acid and the monocarboxylic acid is preferably a branched chain alkanoic acid having from about 6 to about 10 carbon atoms. When a monocarboxylic acid is used in combination with the inorganic acid, the amount of metal removed from the polymer is increased and the amount of the aqueous phase containing ionized metal entrained in the organic phase is sugnificantly reduced.

BACKGROUND 
1. Field of the Invention 
This invention relates to a method for separating various contaminants form 
organic polymers. More particularly, this invention relates to a method of 
separating metal contaminants from organic polymers. 
2. Prior Art 
It is, of course, well known in the prior art that various metal 
contaminants are, frequent]y, undesirable in organic polymers and organic 
polymer compositions since such contaminants frequently accelerate 
deterioration of the polymer and may interfere with subsequent curing 
reactions. Metals may be introduced into the polymer either as catalyst( 
during polymerization or as catalyst during a subsequent treatment such as 
hydrogenation of an unsaturated polymer. 
Heretofore several processes have been proposed for separating various 
metals from organic polymers. These processes generally involve reaction 
of the metal or a compound thereof with a reagent thereby forming a 
product which can then be separated. Generally, the product will be 
insoluble in the organic phase and may be removed therefrom either via 
extraction into an inorganic phase or by filtration or the like. Suitable 
reagents include mineral acids such as taught in U.S. Pat. No. 2,893,982 
as well as carboxylic acids such as taught in U.S. Pat. Nos. 2,893,982; 
3,780,138; 4,476,297 and 4,595,749. Other suitable reagents include the 
ammonium phosphates such as taught in U.S. Pat. Nos. 3,531,448 and 
3,793,306. Carboxylic acids may be used in combination with other reagents 
such as an anhydrous base as taught in U.S. Pat. No. 4,028,485 or an 
aliphatic alcohol as taught in U.S. Pat. No. 3,780,138. An oxidizing agent 
may also be used prior to or simultaneously with the reagent used to react 
with the metal or metal compound such as tau&ht in U.S. Pat. Nos. 
3,780,138; 3,793,306 and 4,595,749. 
As is well known, most, if not all, of the aforementioned processes are 
effective in significantly reducing the amount of metal remaining in the 
polymer after treatment. None, however, are effective in removing all of 
the metal and certain of these processes frequently leave more metal in 
the polymer than is desired in many end uses for the polymer. Moreover, 
those processes involving the use of an aqueous phase generally result in 
higher concentrations of metal in the polymer due to entrainment of the 
aqueous phase in the organic, polymer phase. In light of this, the need 
for an improved process for separating various metals from organic 
polymers is believed to be readily apparent. 
SUMMARY OF THE INVENTION 
It has now been discovered that the foregoing and other disadvantages of 
the prior art processes for separating various metals from polymeric 
materials can be avoided or at least significantly reduced with the method 
for separating metals from polymeric materials of this invention and an 
improved process for separating metals from polymeric materials provided 
thereby. It is, therefore, an object of this invention to provide an 
improved process for separating various metals from polymeric materials. 
It is another object of this invention to provide such an improved process 
wherein an aqueous phase is used with reduced entrainment thereof in the 
polymer phase. The foregoing and other objects and advantages will become 
apparent from the description of the invention set forth hereinafter and 
:rom the examples included therein. 
In accordance with the present invention, the foregoing and other objects 
and advantages are accomplished with a process wherein a higher molecular 
weight monocarboxylic acid is used in combination with an inorganic acid. 
It is important to the present invention that the polymer be dissolved or 
suspended in an organic media and that the metal component or components 
contained in the polymer be contacted with an oxidizing agent either prior 
to or simultaneously with the contacting with the mixture o: acids. 
Separation will be accomplished by contacting the polymer solution or 
suspension with an aqueous solution of an inorganic acid in the presence 
of a higher molecular weight monocarboxylic acid. The separation is 
accomplished such that the metal or metals to be separated from the 
polymer are ultimately dissolved in the aqueous phase as a reaction 
product of the inorganic acid while the higher molecular weight 
monocarboxylic acid remains in the organic phase with the polymer. The 
monocarboxylic acid may be subsequently separated from the organic phase 
and reused. 
DETAILED DESCRIPTION OF THE INVENTION 
As indicated supra, the present invention is drawn to a method for 
separating metals from polymeric materials. It is important to the present 
invention that the polymeric material containing the metal or metals be 
dissolved or suspended in an organic media. Separation of the metal or 
metals is accomplished by contacting the polymer solution or suspension 
with an aqueous solution comprising at least one inorganic acid in the 
presence of at least one relatively high molecular weight monocarboxylic 
acid. The metal or metals to be separated will be contacted with a 
suitable oxidizing agent either prior to contacting with the aqueous 
inorganic acid solution or simultaneously therewith. Separation of the 
metal or metals from the polymer is accomplished such that the metal or 
metals become dissolved in the aqueous phase as reaction products of the 
inorganic acid or acids while the higher molecular weight monocarboxylic 
acid or acids remain with the polymer in the organic media. The relatively 
high molecular weight monocarboxylic acid may then, subsequently, be 
separated from the organic media and reused in the separation process. 
In general, the method of this invention can be used to separate any of the 
metals commonly found in polymers so long as the polymer may be either 
dissolved or suspended in an organic media. Metals which may be separated 
include: the metals of Group IA of the Table of Periodic Properties of the 
Elements, particularly sodium and lithium which are frequently used as 
anionic polymerization initiators; the metals of Groups IIA and IIIB, 
particularly magnesium and aluminum which are frequently contained as a 
component (the reducing agent) in a hydrogenation catalyst; the metals of 
Group IVA, particularly titanium and zirconia which are frequently 
contained in cationic polymerization initiators; and the metals of Groups 
V8, V18 and VIIIA, particularly cobalt, nickel and molybdenum which are 
frequently used as hydrogenation catalyst. All reference to Groups of the 
Table of Periodic Properties of the Elements herein will be to the Table 
of Periodic Properties of the Elements as published and copyrighted by 
Sargent-Welch Scientific Company in 1980. It will, of course, be 
appreciated that any metal which will react with the inorganic acids 
useful in the method of this invention can also be separated from a 
solution or suspension of a polymer using the method of this invention. 
Metals other than those specifically mentioned are, however, less commonly 
found in such polymers. 
In general, the method of this invention may be used to separate metals 
from any of the polymers known in the art which can be either dissolved or 
suspended in an organic media. The method of this invention can, then, be 
used to separate metals from such polymers as those containing alpha 
olefin monomer units, diolefin monomer units, monoalkenyl aromatic 
hydrocarbon monomer units, polyalkenyl aromatic hydrocarbon monomer units 
and the like. The method of the present invention is particularly 
effective for separating metal residues from polymers which have been 
prepared with cationic initiators, metal residues from polymers which have 
been prepared via anionic initiation and metal residues in polymers which 
have been hydrogenated in the presence of a metal containing catalyst. 
Polymers commonly prepared via cationic initiation include homopolymers of 
the various alpha olefins, copolymers of two or more different 
alphaolefins and copolymers of at least one alphaolefin and at least one 
polyolefin. Polymers prepared via anionic initiation include homopolymers 
of the conjugated diolefins, copolymers of two or more conjugated 
diolefins, copolymers of one or more conjugated diolefins and one or more 
monoalkenyl aromatic hydrocarbons, homopolymers of monoalkenyl aromatic 
hydrocarbons and copolymers of monoalkenyl aromatic hydrocarbons. 
Unsaturated polymers which are frequently hydrogenated include 
homopolymers of conjugated diolefins, copolymers of two or more conjugated 
diolefins, copolymers of at least one conjugated diolefin and at least one 
monoalkenyl aromatic hydrocarbon and the like. The polymer may be random, 
tapered or block. 
In general, any inorganic acid may be used in the method of the present 
invention to effectively react with and separate the metal atoms contained 
in the polymer solution or suspension. The inorganic acid may be 
monoprotic or polyproprotic. It is, however, important that the ionization 
constant for at least one hydrogen atom contained in the acid be greater 
than or equal to about 1.times.10.sup.-5. Suitable inorganic acids include 
but are not limited to, the hydrogen halides such as hydrogen chloride, 
hydrogen bromide, hydrogen fluoride and the like, the various sulfur 
containing acids such as sulfurous acid, sulfuric acid and the like; the 
various phosphorus containing acids such as phosphorus acid, phosphoric 
acid and the like, nitric acid, chloric acid, perchloric acid and the 
like. The mineral acids such as hydrochloric acid, nitric acid, phosphoric 
acid, sulfuric acid and the like, are particularly effective when used in 
the method of this invention and are, therefore, preferred. 
In general, any monocarboxylic acid that is significantly more soluble in 
an organic media than in an inorganic media such as water can be used as 
the monocarboxylic acid in the method of this invention. In this regard, 
it is important to the method of this invention that at least about 90 wt 
% of the monocarboxylic acid remain in the organic media in which the 
polymer is either dissolved or suspended after the separation of the metal 
or metals is completed and that not more than about 10 wt % of said 
monocarboxylic acid be contained in the aqueous phase when the separation 
is completed. Suitable monocarboxylic acids may be represented by the 
following general formula: 
EQU RCO.sub.2 H 
wherein: R is a hydrocarbyl radical containing from about 6 to about 20 
carbon atoms. The hydrocarbyl radical may be a linear or branched alkyl 
radical, a cyclic hydrocarbyl radical, an alkyl-substituted cyclic 
hydrocarbyl radical, an aromatic radical, an alkyl-substituted aromatic 
radical and the like. Suitable monocarboxylic acids include, but are not 
limited to, linear aliphatic monocarboxylic acids such as caproic, 
enanthic, caprylic, pelargonic, capric, undecanoic, lauric and the like; 
branched chained monocarboxylic acids such as methylpentanoic acid, 
methyl- and ethylhexanoic methyl and ethylheptanoic acids, methyl- and 
ethyloctanoic acids, methyl- and ethylnonanoic acids, methyl- and 
ethyldecancic acids, and the like; cyclic monocarboxylic acids such as 
cyclohexanoic acid, cyclohexanoic acid, cyclooctanoic acid and the like; 
alkyl-substituted cyclic monocarboxylic acids such as methyl- and 
ethylcyclohexanoic acids, methyl- and ethylcylcoheptanoic acids, methyl- 
and ethylcyclooctanoic acids and the like; aromatic acids such as benzoic 
acid and the like; alkyl-substituted aromatic acids such as the toluic 
acids, p-t-butylbenzoic acid and the like. 
In general, any hydrocarbon which is liquid at the conditions at which the 
separation of the metal or metals is accomplished may be used as the 
organic media in which the polymer is either dissolved or suspended in the 
method of this invention. Suitable hydrocarbons which are useful either as 
a solvent or diluent, then, include, but are not limited to straight and 
branched chained aliphatic hydrocarbons, cyclic hydrocarbons, substituted 
cyclic hydrocarbons, aromatic hydrocarbons, substituted aromatic 
hydrocarbons and the like. Representative examples of useful hydrocarbons 
include pentane, hexane, heptane, octane, cyclopentane, cyclohexane, 
cycloheptane, benzene, toluene, xylene and the like. 
As indicated supra, the inorganic acid and the monocarboxylic acid will be 
used in combination with a suitable oxidizing agent. As also indicated 
supra, the oxidizing agent may be used prior to or simultaneously with the 
acid mixture. In general, the particular oxidizing agent selected is not 
critical to the present invention and any known oxidizing agent may be 
used. Suitable oxidizing agents include air, oxygen, peroxides, 
hydroperoxides and the like. Suitable peroxides and hydroperoxides 
include, but are not limited to, hydrogen peroxides and the primary, 
secondary or tertiary alkyl and aryl peroxides and hydroperoxides. Alkyl 
hydroperoxides such as ethyl hydroperoxide, butyl hydroperoxide, isopropyl 
hydroperoxide, tertiary butyl hydroperoxide and the like are particularly 
useful as oxidizing agents in the present invention. 
As indicated supra, the inorganic acid will be used in aqueous solution. 
Obviously, a mixture of such acids could be used. Also, the inorganic acid 
or acids and the monocarboxylic acid or acids may, initially, be combined 
into the aqueous solutions or separate solutions of each could be prepared 
and then combined prior to contacting with the polymer solution or 
suspension or the separate solutions may be separately contacted with the 
polymer solution or suspension. In this regard, it should be noted that 
the monocarboxylic acid or acids could also be added directly to the 
polymer solution or suspension or the monocarboxylic acid or acids could 
first be dissolved in an organic solvent, which may be the same as the 
organic media used in the polymer solution or suspension, and then 
contacted with the polymer solution or suspension. 
In general, the concentration of inorganic acid in the aqueous solution is 
not critical to the present invention. It is, however, important to the 
method of this invention that a sufficient amount of water be present 
during contact to insure that the reaction product of the metal or metals 
to be separated and the inorganic acid or acids is dissolved in said 
aqueous phase prior to its separation from the organic phase containing 
the polymer. It is also important in the method of the present invention 
that sufficient inorganic acid be used to insure complete reaction of the 
inorganic acid or acids with the metal or metals to be separated. When 
good contacting between the organic phase and the aqueous phase is 
maintained, the reaction between the metal or metals and the inorganic 
acid will occur stoichiometrically. Use of a amount of inorganic acid just 
slightly in excess of this stoichiometric amount will, then, generally be 
sufficient to insure at least substantially complete reaction and 
subsequent separation of the metal or metals contained in the polymer 
solution or suspension. 
While the inventor does not wish to be bound by any particular theory, it 
is believed that the monocarboxylic acid acts simply as a phase transfer 
catalyst thereby facilitating movement of the metal or a reaction product 
thereof, such as the reaction product formed with the inorganic acid, from 
the organic phase to the aqueous phase. To the extent that the metal or 
metals do not react with one or more of the inorganic acids present during 
contacting in the organic phase such a reaction could then occur in the 
aqueous phase. To the extent that the anion of the monocarboxylic acid 
combines with a metal and then moves to the aqueous phase reaction of the 
organic salt with an inorganic acid would restore the monocarboxylic acid, 
thereby enabling the return of the monocarboxylic acid to the organic 
phase where further reaction or phase transfer could be effected. In any 
case, it has been determined that all, or at least substantially all (90 
wt %) of the monocarboxylic acid or acids used during the separation will 
be in the organic phase as the acid after the organic phase is separated 
from the aqueous phase. The metal or metals separated from the polymer, on 
the other hand, will be contained in the aqueous phase as a salt formed by 
reaction with an anion contained in the inorganic acid or acids used. 
Surprisingly, it has been discovered that the amount of metal or metals 
actually separated is significantly increased when a monocarboxylic acid 
is used in combination with one or more inorganic acids even though the 
monocarboxylic acid remains chemically unchanged after the separation has 
been completed. 
Since the monocarboxylic acid apparently acts only as a phase transfer 
catalyst, the amount of such acid used during the contacting step may be 
significantly less than the amount of inorganic acid used (on a molar or 
equivalent basis). In fact, improved separation of the metal or metal 
components from the polymer will be realized when as little as 0.05 
equivalents of monocarboxylic acid per equivalent of total metal to be 
separated is present. The nominal holding time required to achieve the 
improved results will, however, continue to reduce until the amount of 
monocarboxylic acid actually present is within the range from about 0.1 to 
about 2.25 equivalents of monocarboxylic acid per mole of total metal to 
be separated. Use of an amount of monocarboxylic acid within this range 
is, therefore, preferred. The maximum amount of monocarboxylic acid that 
may be used is, of course, limited by the solubility of the monocarboxylic 
acid in the organic media in which the polymer is either dissolved or 
suspended. 
In general, the metal or metals to be separated may be present in the 
polymer in virtually any form. For example, the metal or metals may be 
present as the metal per se or as a compound of the metal or metals which 
may be either soluble or insoluble in the organic media used to dissolve 
or suspend the polymer. Examples of metal compounds which would be 
insoluble in the organic media are the metal oxides, the metal halides, 
certain metal alkyl halides and the like. Examples of metal compounds that 
would be soluble in the organic media are certain metal alkyls, certain 
metal alkyl halides, various metal alkoxides, various metal carboxylates, 
various metal carbonyls and the like. 
In general, any of the polymeric materials known in the prior art and 
containing one or more metals can be treated to separate the metals 
therefrom with the method of the present invention. As is well known, 
several polymers are prepared directly in either a solution or suspension 
process and polymers of this type may be treated directly after 
preparation thereof in accordance with the method of the present 
invention. The polymers prepared in bulk, in an organic reaction medium, 
or in the vapor phase would first have to be dissolved or suspended in a 
suitable organic medium prior to treatment in accordance with the method 
of the present invention. As is also well known, polymers prepared via any 
of these techniques may be further treated in solution, suspension or in 
bulk. Again, those polymers subsequently treated in either solution or 
suspension may be treated directly to separate metals therefrom using the 
method of the present invention. Polymers subsequently treated in bulk, 
however, must be dissolved or suspended in a suitable organic media prior 
to treatment in accordance with the method of this invention. 
In general, the polymeric solutions and suspensions treated to separate 
metal or metals therefrom with the method of the present invention will 
comprise from about 5 wt % to about 50 wt % polymer and from about 95 wt % 
to about 50 wt % organic media. Generally, the polymeric solution or 
suspension will contain from about 100 to about 2,000 ppm by weight, of 
one or more metals, based on polymer. 
As indicated supra, the polymeric solution or suspension will be contacted 
with an oxidizing agent either prior to or simultaneously with the 
contacting with the aqueous inorganic acid solution. When the polymer 
solution or suspension is contacted with the oxidizing agent prior to the 
contacting with the aqueous inorganic acid solution the contacting will be 
accomplished at a temperature within the range from about 50.degree. to 
about 100.degree. C., a pressure within the range from about 0 to about 
100 psig and at a nominal holding time within the range from about 10 to 
about 90 minutes. When the oxidizing agent is a gaseous oxidizing agent, 
the contacting may be accomplished simply by bubbling the oxidizing agent 
through the polymer solution or suspension. When the oxidizing agent is 
liquid or a solid soluble in the organic media, the contacting may be 
accomplished simply by adding the oxidizing agent to the polymer solution 
or suspension. To facilitate contacting between the oxidizing agent and 
the metal or metal compounds, suitable agitation means may be employed. 
While as indicated supra, the concentration of inorganic acid in aqueous 
solution is not critical so long as a sufficient amount of inorganic acid 
is used to effect the desired degree of metal separation, the aqueous 
solution will, generally, be from about 0.01 to about 1 normal in 
inorganic acid concentration and when the monocarboxylic acid is 
incorporated into the same or a different media, the monocarboxylic acid 
concentration will, generally, be within the range from about 0.001to 
about 0.02 normal. As also indicated supra, the monocarboxylic acid may be 
added directly to the polymer solution or suspension or the same may first 
be dissolved in an organic solvent and then contacted with the polymer 
solution or suspension. In any case, a sufficient amount of inorganic 
aqueous solution will be contacted with the polymer solution or suspension 
to effect the desired extent of metal separation. Generally, the amount of 
aqueous solution contacted with the polymer solution or suspension will be 
at least that required to effect complete conversion of the metal or 
metals to be separated on a stoichiometric basis although lesser amounts 
could be used if less than complete metal separation were desired. As also 
indicated supra, a sufficient amount of monocarboxylic acid will, 
generally, be added to provide from about 0.1 to about 2.25 mols of 
monocarboxylic acid per equivalent of total metal to be separated. 
In general, contacting between the polymer solution or suspension and the 
inorganic acid or acids and the monocarboxylic acid or acids will be 
accomplished at a temperature within the range from about 50.degree. to 
about 100.degree. C. at a pressure sufficient to maintain the organic 
media in the liquid phase, generally, a pressure within the range from 
about 0 to about 100 psig. In general, contacting of the inorganic acid or 
acids and the monocarboxylic acid or acids with the polymer solution or 
suspension will be maintained for a nominal holding time within the range 
from about 10 to about 90 minutes. Sufficient agitation will be used to 
insure good contacting between the metal or metals and the inorganic acid 
or acids and the monocarboxylic acid or acids. 
While the inventors still do not wish to be bound by any particular theory, 
it is believed that during the contacting of the polymer solution or 
suspension with an aqueous solution of an inorganic acid or acids in the 
presence of one or more monocarboxylic acids reaction occurs between the 
inorganic acid and acids and the metal or metals to form a salt. The salt, 
which is generally insoluble in the organic media is then transferred to 
the aqueous phase where it is soluble. While the monocarboxylic acid might 
also react with the metal or metals to be separated and passed into the 
aqueous phase, the salt formed with the monocarboxylic acid would be only 
slightly soluble in the aqueous media. As a result, the monocarboxylic 
acid salt anion would be displaced by an anion from the inorganic acid and 
the monocarboxylic acid would be restored. The monocarboxylic acid would 
then return to the organic phase where it would be soluble and where it 
could again react with a metal or metal compound. After such reaction, the 
monocarboxylic acid salt would again pass to the aqueous phase, surrender 
its metal ion to an inorganic acid anion and return to the organic media. 
The monocarboxylic acid or acids thus function as a phase transfer 
catalyst in the separation of the metal from the organic phase and 
transferring it to the aqueous phase. It will, of course, be appreciated 
that other mechanisms through which the monocarboxylic acid might 
facilitate transfer of the metal to the aqueous phase could be advocated 
but such mechanism is not critical to the present invention. 
To the extent that contacting with the oxidizing agent is accomplished 
simultaneously with the contacting of the inorganic acid or acids and the 
monocarboxylic acid or acids with the polymer solution or suspension, the 
contacting may be accomplished simply by bubbling a gaseous oxidizing 
agent through the reaction medium during the contacting or simply by 
combining a liquid or soluble solid oxidizing agent into the reaction 
medium. Such addition could be effected separately or the oxidizing agent 
could be combined with the inorganic acid or acids and/or the 
monocarboxylic acid or acids. In any case, contacting with the oxidizing 
agent would be accomplished at the same conditions used to effect the 
contacting between the polymer solution or suspension and the inorganic 
acid or acids in the presence of a monocarboxylic acid or acids. 
After the contacting between the polymer solution or suspension and the 
aqueous solution of at least the inorganic acid or acids, it will then be 
necessary to separate the aqueous phase which will contain most, if not 
all, of the metal or metals to be separated and the organic phase which 
will contain the polymer and the monocarboxylic acid or acids. In general, 
this separation may be accomplished using any of the means well known in 
the prior art. Such means include, but are not limited to, filtration, 
centrifugation, the use of a coalescing fibrous material and the like. To 
the extent that sufficient agitation was used during contacting to form an 
emulsion deemulsifying techniques known in the prior art may also be used. 
Such means include, but are not limited to, addition of one or more 
deemulsifying agents, such as methanol, isopropanol, and the like. 
After separation of the organic phase and the aqueous phase has been 
completed, both the polymer and the monocarboxylic acid or acids may be 
recovered from the organic phase using conventional technology. For 
example, if the polymer is suspended in the organic media, the polymer may 
be separated simply by filtration. Similarly, if the polymer is dissolved 
in the organic media, the same generally, may be precipitated and then 
separated via filtration. Alternatively, the polymer may be recovered 
using flashing techniques, distillation and the like. The monocarboxylic 
acid or acids on the other hand, may be precipitated as a salt or similar 
compound and then separated via filtration, centrifugation, and the like. 
The recovered product may then be converted back to the monocarboxylic 
acid or acids and the monocarboxylic acid or acids thus produced reused in 
the separation process of this invention. Alternatively, the 
monocarboxylic acid or acids may be recovered directly using flashing 
techniques, distillation and the like. 
As indicated supra, a surprising discovery of this invention is that the 
amount of water containing ionized metal entrained in the hydrocarbon 
phase after the organic and aqueous phases have been separated is 
significantly reduced when compared to the amount of aqueous phase 
containing ionized metal entrained in prior art separation techniques 
wherein an aqueous phase has been used. While the inventor does not wish 
to be bound by any particular theory, it is believed that the reduction in 
the amount of entrained aqueous phase is attributable directly to the 
presence of the higher molecular weight monocarboxylic acid or acids in 
the organic phase. 
PREFERRED EMBODIMENT OF THE INVENTION 
In a preferred embodiment of the present invention, a branched chain 
alkanoic acid containing from about 6 to about 10 carbon atoms, most 
preferably ethyl hexanoic acid, will be used in combination with a mineral 
acid, most preferably sulfuric acid, to separate a hydrogenation catalyst 
from a hydrogenated conjugated diolefin polymer, most preferably a block 
copolymer comprising at least one polymeric block containing predominantly 
monoalkenyl aromatic hydrocarbon monomer units and at least one polymeric 
block containing predominantly hydrogenated conjugated diolefin monomer 
units and even more preferably a block copolymer comprising a single 
styrene homopolymer block and a single isoprene homopolymer block. 
Polymers of this type are, of course, well known in the prior art and are 
described, for example in such patents as U.S. Pat. Nos. 3,554,911; 
3,668,125; 3,772,196; 3,775,329; 3,835,053; 4,116,917 and 4,156,673, the 
disclosure of which patents are herein incorporated by reference. 
In the preferred embodiment of the present invention, the polymer will be 
in solution when contacted with the inorganic acid and the monocarboxylic 
acid. Most preferably, the polymer will be dissolved in the same solvent 
that was used during hydrogenation. Preferred solvents includes aliphatic 
hydrocarbons such as pentane, hexane, heptane octane, 2-ethyl hexane, 
nonane and the like cyclic hydrocarbons such as cyclohexane, 
methylcyclohexane and the like and aromatic hydrocarbons such as benzene, 
toluene, ethyl benzene, xylene and the like. Cyclohexane will be used as 
the solvent in a most preferred embodiment of the present invention. 
In the preferred embodiment, the method of this invention may be used to 
separate any of the hydrogenation catalysts known in the prior art. The 
method of this invention will, most preferably, be used to separate both 
metal components contained in hydrogenation catalyst such as those 
described in U.K. Patent Specification No. 1,030,306, the disclosure of 
which patent specification is herein incorporated by reference, and U.S. 
Pat. No. 3,700,633, the disclosure of which patent is herein incorporated 
by reference. The catalyst taught in the U.S. patent is, of course, the 
product obtained by combining a nickel or cobalt carboxylate or alkoxide 
with an aluminum alkyl. The method of this invention will, effectively, 
separate both metal components. Moreover, and to the extent that the 
polymer solution actually treated also contains the polymerization 
catalyst or catalyst residue, the method of this invention will also, 
effectively, reduce the content of such metal or metals in the polymer 
solution. 
In the preferred embodiment of this invention, the branched chain alkanoic 
acid will be added directly to the polymer solution before the polymer 
solution is contacted with an aqueous solution containing the mineral 
acid. Air will be used as the oxidizing agent and contacting with the 
oxidizing agent will be accomplished simultaneously with the contacting 
with the aqueous inorganic acid solution. The contacting will be 
accomplished by, in effect, bubbling air or oxygen through the reaction 
medium. 
In the preferred embodiment, from about 0.1 to about 0.5 mols of 
monocarboxylic acid per equivalent of total metal will be added to the 
polymer solution. The aqueous solution containing the inorganic, mineral, 
acid will be from about 0.01 to about 0.1 normal in acid. In the preferred 
embodiment, a sufficient amount of aqueous solution containing the 
inorganic acid will be used to provide from about 1 to about 10 times the 
stoichiometric amount of inorganic acid required to react with all of the 
metals contained in the polymer solution. 
In the preferred embodiment, contacting between the polymer solution and 
the aqueous solution containing the inorganic acid will be accomplished at 
a temperature within the range from about 50.degree. to about 100.degree. 
C. at a pressure within the range from about 0 to about 100 psig. In the 
preferred embodiment, the partial pressure of oxygen will be maintained at 
a value within the range from about 0.1 to about 10 psig. In the preferred 
embodiment, contacting between the polymeric solution and the aqueous 
solution of the inorganic acid will be accomplished with sufficient 
agitation to insure good contacting between the polymer solution and the 
aqueous inorganic solution but the amount of agitation will not be 
sufficient to form an emulsion. In the preferred embodiment, contacting 
between the polymer solution and the inorganic acid aqueous solution will 
be maintained for a nominal holding (time within the range from about 10 
to about 90 minutes. 
Having thus broadly described the present invention, a preferred and most 
preferred embodiment thereof, it is believed that the invention will 
become even more apparent by reference to the following examples. It will 
be appreciated, however, that the examples are presented solely for 
purposes of illustration and should not be construed as limiting the 
invention.

EXAMPLE 1 
In this Example, two runs were completed, in batch equipment, to separate a 
hydrogenation catalyst from a freshly hydrogenated polymer cement 
containing said catalyst. Each run consisted of a first contacting step 
followed by separation o: the two phases, and a second contacting step 
followed by separation of the two phases. In both contacting steps of the 
first of these runs, ethyl hexanoic acid was used in combination with 
sulfuric acid and in both contacting steps of the second run, which was 
completed for comparison purposes only, only sulfuric acid was used. In 
both runs, the freshly hydrogenated polymer was a star-shaped polymer 
having about 20 polyisoprene arms having a weight average molecular weight 
of about 80,000. The nucleus of the star was formed with a commercial 
grade divinyl benzene. At the start of both runs, 100 grams of the 
hydrogenated polymer cement containing 10 wt % polymer dissolved in 90 
grams of cyclohexane were charged to a shaker which was operated at a low 
speed. In both runs, the polymer cement initially contained 2400 ppm, by 
weight, nickel, based on polymer, and 2,500 ppm, by weight, based on 
polymer, of aluminum. In both contacting steps of both runs, the polymer 
cement was contacted with a sufficient amount of aqueous sulfuric acid 
solution to provide 5 moles of sulfuric acid per equivalent of combined 
nickel and aluminum, initially. The volume ratio of aqueous phase to 
organic phase in both contacting steps of both runs was 0.5. In the first 
of these two runs, 0.2 grams of ethyl hexanoic acid was combined with the 
polymer cement before the sulfuric acid solution was added to the shaker 
and before both contacting steps. In the second run, the sulfuric acid 
aqueous solution was used alone in both contacting steps. In both runs, 
the contacting was continued for 30 minutes in each contacting step and 
the organic and aqueous phases were then separated by decanting after the 
mixture was allowed to settle for 60 minutes. In both runs, each 
contacting step was accomplished at room temperature and pressure. The 
viscosity of the polymer solution used in both runs was 760 cp at room 
temperature. After this first contacting step was completed and the phases 
separated, the organic phase was tested to determine the amount of nickel 
remaining after the first contacting and then the entire procedure 
repeated. After the second separation step was completed, the organic 
phase was again tested to determine the amount of nickel remaining therein 
and to determine the amount of aqueous phase entrained in the organic 
phase. In the first run, the amount of nickel remaining in the organic 
phase after the first separation was 39 ppm, by weight, based on polymer. 
After the second contacting, the amount of nickel remaining in the organic 
phase was determined to be 40 ppm by weight, based on polymer. 0.2 wt % of 
the aqueous phase was entrained in the organic phase after the second 
separation was completed. In the second run, 517 ppm, by weight, based on 
polymer, of nickel remained in the organic phase after the first 
contacting. After the second contacting, 150 ppm, by weight, based on 
polymer, of nickel remained in the organic phase. 2.7 wt % of the aqueous 
phase was entrained in the organic phase after separation. As will be 
readily apparent from these results, the addition of 20,000 ppm, by 
weight, based on a polymer, of 2-ethyl hexanoic acid significantly 
increases the amount of nickel separated from the polymer solution and at 
the same time significantly reduces the amount of the aqueous phase 
entrained in the organic phase. In both runs, and during both contacting 
periods, oxygen was supplied through equilibration of the gas cap with the 
reaction medium. 
EXAMPLE 2 
In this Example, four runs, each involving two contacting steps, were 
completed. In all four runs, an aqueous solution containing sulfuric acid 
was contacted with a hydrogenated polymer cement containing residues of a 
catalyst formed by combining nickel octoate with triethyl aluminum. The 
polymer cement was identical to that used in Example 1 except that its 
viscosity was only 420 cp and it contained only 2,200 ppm, by weight, 
based on polymer of nickel and 2,300 ppm, by weight, based on polymer of 
aluminum. In both contacting steps of all four runs, a sufficient amount 
of an aqueous solution containing sulfuric acid was contacted with the 
polymer cement to provide 4 mols of sulfuric acid per equivalent of 
combined metal (nickel+aluminum) initially present in the polymer cement. 
All four runs were completed by charging 35 pounds of the polymer cement 
to a 30 gal mixer and then adding the aqueous sulfuric acid solution. In 
the first run, 32 grams of ethyl hexanoic acid were added to the polymer 
cement before the aqueous sulfuric acid solution was added and before both 
contacting steps. In the second run, only 8 gms of ethyl hexanoic acid 
were added before each contacting step was completed. In the third run, 8 
grams of ethyl hexanol, an alcohol frequently used to prevent entrainment 
of the aqueous phase in the organic phase, was added to the polymer cement 
before the aqueous sulfuric acid solution was added in both contacting 
steps. In the fourth run, the aqueous solution of sulfuric acid was the 
only reagent added during both contacting steps. In all four runs, oxygen 
was bubbled through the reaction mixture during both contacting steps. In 
all four runs, the impeller was operated at a speed of 200 rpm. Again, two 
contacting steps were completed in each run and the organic and aqueous 
phases were separated alter each contacting period. In all of the runs, 
each of the contacting periods was continued for 30 minutes and separation 
of the organic phase and the aqueous phase was accomplished by decanting 
after settling for 60 minutes. After each contacting period was completed, 
the amount of nickel remaining in the organic phase and the amount of 
aqueous phase entrained in the organic phase was determined. The amount of 
nickel remaining in the organic phase after each contacting was as 
follows: 62 ppm, by weight, based on polymer and 38 ppm, by weight, based 
on polymer, respectively, in the first run when 2-ethyl hexanoic acid was 
used at 25,000 ppm by weight, based on polymer; 38 ppm, by weight, based 
on polymer and 12 ppm, by weight, based on polymer, respectively, in the 
second run where 6,200 ppm, by weight, based on polymer, of 2-ethyl 
hexanoic acid was used; 225 ppm, by weight, based on polymer and 62 ppm, 
by weight, based on polymer, respectively, in run three when 6,200 ppm, by 
weight, based on polymer, of 2-ethyl hexanol was used; and 312 ppm, by 
weight, based on polymer, and 62 ppm by weight, based on polymer 
respectively, when sulfuric acid alone was used. The amount of aqueous 
phase entrained in the organic phase after each contacting period was as 
follows: 0.1 wt % and 0.4 wt %, respectively, in run 1 when 25,000 ppm, 
by weight, based on polymer, of 2-ethyl hexanoic acid was used; 0.6 wt % 
and 0.4 wt % respectively, in run 2 when 6,200 ppm, by weight, based on 
polymer of 2-ethyl hexanoic acid was used; 1.2 wt % and 0.6 wt %, 
respectively, in run three when 6,200 ppm of 2-ethyl hexanol was used; and 
b 1.5 wt % and 0.6 wt % respectively, in run 4 where sulfuric acid was 
used alone. As will be apparent from this data, 2-ethyl hexanoic acid 
significantly increases the amount of nickel separated from :he organic 
phase and significantly reduces the amount of the aqueous phase entrained 
in the organic phase at both concentrations at which 2-ethyl hexanoic acid 
was used. 
While the present invention has been described and illustrated by reference 
to particular embodiments thereof, it will be appreciated by those of 
ordinary skill in the art that the same lends itself to variations not 
necessarily described or illustrated herein. For this reason, then, 
reference should be made solely to the appended claims for purposes of 
determining the true scope of this invention.