Process for the hydrogenation of diene (co)polymers

Details Process for the hydrogenation of diene (co)polymers Process for the hydrogenation of diene (co)polymers

1998-11-02

2001-05-08

Lipman, Bernard (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

C502S104000, C502S115000, C502S117000, C525S332800, C525S332900, C525S333100, C525S333200, C525S339000

Reexamination Certificate

active

06228952

ABSTRACT:

The present invention relates to a catalytic composition which can be used for the hydrogenation of olefinically unsaturated compounds, particularly for the selective hydrogenation of polymers and copolymers of conjugated dienes.
Polymers obtained by the (co)polymerization of conjugated dienes are widely used on a commercial scale.
In the polymeric chain these (co)polymers have olefinic double bonds which, useful when used in vulcanization, are responsible for a poor stability, particularly resistance to oxidation.
In particular, the block copolymers obtained starting from conjugated dienes and vinyl substituted aromatic hydrocarbons are adopted non-vulcanized as thermoplastic elastomers or as shock-resistant transparent resins or as modifiers of styrene resins or olefinic resins. Owing to the presence of unsaturated double bonds in the polymeric chain, the above block copolymers have a poor resistance to oxidation, ozone and atmospheric aging. This is a great disadvantage for their application.
This lack of stability can be greatly reduced by selectively hydrogenating the olefinic double bonds of the above copolymers.
The known methods for hydrogenating polymers having olefinic double bonds are based on (1) supported heterogeneous catalysts consisting of inert carriers (for example silica, alumina, carbon) on which a metal such as nickel, platinum, palladium, etc. is deposited and (2) non-supported homogeneous catalysts obtained by reacting an organometallic compound of nickel, cobalt, titanium or the like, with a reducing compound such as an organo-aluminum, an organomagnesium or an organolithium.
With respect to supported heterogeneous catalysts (
1
), non-supported catalysts (
2
) have the quality of a greater activity. This is a considerable advantage as it allows blander hydrogenation conditions to be adopted, with smaller quantities of catalyst.
U.S. Pat. No. 4,501,857 describes a hydrogenation process of non-living polymers carried out in the presence of (A) a bis-(cyclopentadienyl) titanium derivative and (B) at least one organolithium derivative, the molar ratio between lithium atoms and titanium atoms being from 0.1 to 100.
EP-A-434.469 describes a catalytic composition which comprises (a) at least one titanium bis-cyclopentadienyl derivative and (b) at least one compound selected from those having general formula (i) M
2
(AlR
a
R
b
R
c
R
d
) and (ii) M
2
(MgR
e
R
f
R
g
), wherein M
2
, is selected from lithium, sodium and potassium. Compound (i) can be obtained by the reaction of an organ-alkaline compound with an organo-aluminum compound, whereas compound (ii) can be obtained by the reaction of an organo-alkaline compound with an organo-magnesium derivative.
EP-A-601.953 describes a hydrogenation process carried out in the presence of a catalyst having the general formula Cp
2
Ti(PhOR)
2
or Cp
2
Ti(CH
2
PPh
2
)
2
.
All the above processes differ in reality not so much in the hydrogenation reaction as in the preparation process of the catalytic species.
The process described in U.S. Pat. No. 4,501,857 is the simplest among those mentioned as it starts from a compound which is easily available on the market (titaniumdicyclopentadienylchloride) and involves only the addition of an organic lithium derivative. Unfortunately the data provided by this patent show how the process, which is very effective when applied to living polymers, gives a poor hydrogenation yield when applied to non-living polymers (see Table III compared with Table II).
On the other hand, EP-A-434.469 comprises the presence of compounds (i) or (ii), which require the reaction, not included in U.S. Pat. No. 4,501,857, between an organo-alkaline derivative (usually an organolithium derivative) and an organo-aluminum or organo-magnesium derivative, with the Titanium compound.
The process of EP-A-601.953 is also complex as it involves the preparation and isolation of particular titanium dicyclopentadienyl derivatives obtained starting from Cp
2
TiCl
2
.
In any case all the catalysts of the prior art have the disadvantage of requiring high quantities of Titanium; in addition the hydrogenation rates are unsatisfactory.
A catalytic composition has now been found which can be used in the selective hydrogenation of olefinic double bonds which overcomes the above drawbacks as it is simple to prepare and is also much more active than the catalysts described in the above patents.
In accordance with this, the present invention relates to a catalytic composition effective in the hydrogenation of olefinic double bonds, particularly in the selective hydrogenation of olefinic double bonds present in copolymers between dienes and vinylbenzenes, even more particularly styrene-butadiene and styrene-isoprene block copolymers, prepared by reaction between:
(A) at least one cyclopentadienyl complex of a transition metal having general formula (I) (R)(R
1
)M
1
(R
2
)(R
3
)
wherein
R is an anion containing an &eegr;
5
-cyclopentadienyl ring coordinated to M
1
and is preferably cyclopentadienyl;
M
1
is selected from titanium, zirconium and hafnium, preferably titanium;
R
2
and R
3
1
the same or different, are organic or inorganic anion groups bound to M
1
, preferably selected from hydride, halide, C
1
-C
8
alkyl group, C
5
-C
8
cycloalkyl group, C
6
-C
10
aryl group, C
1
-C
8
alkoxyl group, C
1
-C
8
carboxyl group; even more preferably they are both equal to chloride;
R
1
is selected from cyclopentadienyl and R
2
;
with
(B) an alkylating composition essentially consisting of:
(b1) an organometallic compound having general formula (II) M
2
(R
4
)(R
5
), wherein M
2
is selected from Zn and Mg and is preferably Mg, R
4
is selected from aliphatic or aromatic hydrocarbon radicals having from 1 to 20 carbon atoms, preferably C
1
-C
16
aliphatic hydrocarbon radicals, even more preferably C
1
-C
8
; R
5
is a halogen or is equal to R
4
;
(b2) an organoderivative of Aluminum having general formula (III) Al(R
6
)
31
wherein R
6
is a C
1
-C
16
aliphatic hydrocarbon radical, preferably C
1
-C
8
.
The preparation of the catalytic composition of the present invention takes place by mixing the cyclopentadienyl derivative having general formula (I) with alkyating agents (b1) and (b2). In the preferred embodiment, all the components are dissolved in inert solvents. More specifically the alkylating composition can be dissolved in a single solvent.
In the preferred embodiment the molar ratio between the compound having general formula (I) and the alkylating compound (b1) is from 1/1 to 1/10, preferably from 1/3 to 1/7; the molar ratio between (b2) and (I) is less than 1, preferably from 0.3/1 to 0.9/1.
As specified above, in the preferred embodiment, in the compound having general formula (I), M
1
is Ti, R
1
is cyclopentadienyl, whereas R
2
and R
3
are halides, preferably chlorides. Other non-limiting examples of compounds having general formula (I) are listed below:
(&eegr;
5
-C
5
H
5
)TiCl
3
, (&eegr;
5
-THInd)TiCl
3
(&eegr;
5
-Ind)Ti(NMe
2
)
3
, (&eegr;
5
-Flu)TiCl
3
(&eegr;
5
-C
5
Me
5
)TiC
3
, (&eegr;
5
-C
5
H
5
)TiCl
2
Me
(&eegr;
5
-Ind)Ti(OMe)
3
, (&eegr;
5
-Ind)TiCl
3
(&eegr;
5
-C
5
H
5
)TiCl
2
Ph, (&eegr;
5
-Flu)Ti(OBu)
3
(&eegr;
5
-C
5
H
5
)
2
TiCl
2
, (&eegr;
5
-THInd)
2
TiCl
2
(&eegr;
5
-Ind)
2
Ti(NMe
2
)
2
, (&eegr;
5
-Flu)
2
TiCl
2
(&eegr;
5
-C
5
Me
5
)
2
TiCl
2
, (&eegr;
5
-C
5
H
5
)
2
TiClMe
(&eegr;
5
-Ind)
2
Ti(OMe)
2
, (&eegr;
5
-Ind)
2
TiCl
2
(&eegr;
5
-C
5
H
5
)
2
TiClPh, (&eegr;
5
-Flu)
2
Ti(OBu)
2
The following abbreviations were used in the above formulae: Me=methyl, Bu=butyl, Ind=indenyl, THInd=4,5,6,7-tetrahydro-indenyl, Flu=fluorenyl, Ph=phenyl, Et=ethyl.
The alkylating component (b
1
) is preferably selected from alkylmagnesium halides, normally known as Grignard compounds, and Magnesium dialkyls. Both groups of products are well known and there are numerous methods for their preparation. Many organometallic compounds having general formula (II) M
2
(R
4
)(R
5
), wherein M
2
is selected from Zn and Mg, are commercial products, normally

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