Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2003-09-24
2004-12-14
Lu, Caixia (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...
C502S152000
Reexamination Certificate
active
06831135
ABSTRACT:
The present invention relates to a process for the selective hydrogenation of olefin double bonds present in homopolymers and copolymers of conjugated dienes.
Polymers obtained through the polymerization or copolymerization of conjugated dienes are widely used on industrial scale.
These (co)polymers have, in the polymeric chain, olefin double bonds which, although useful when vulcanization processes are effected, are responsible for a low resistance to stability, and particularly to oxidation.
In particular, the block copolymers obtained from conjugated dienes and vinyl-substituted aromatic hydrocarbons, are used in non-vulcanized form, as thermoplastic elastomers or impact strength transparent resins or modifiers of styrene or olefin resins. The above block copolymers have a low resistance to oxidation, ozone and atmospheric aging, due to the presence of olefin double bonds in the polymeric chain. This creates a great drawback for their application.
This low stability can be greatly reduced by the selective hydrogenation of the olefin double bonds of the above copolymers.
The known methods for the hydrogenation of polymers having olefin double bonds are based on (1) heterogeneous catalysts supported on inert carriers (for example, silica, alumina, carbon) on which a metal (for example nickel, palladium, platinum) is deposited and (2) non-supported heterogeneous catalysts obtained by reacting an organometallic compound of nickel, cobalt, titanium or the like, with a reducing compound such as an organo-aluminum, an organo-magnesium or an organo-lithium.
With respect to the supported heterogeneous catalysts (1), the non-supported catalysts (2) have the advantage of a higher reactivity. This is a great advantage, as it is possible to operate under lighter conditions and with lower 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 titanium bis-(cyclopentadienyl) derivative and (B) at least one organo-lithium derivative, the molar ratio between the lithium atoms and titanium atoms being 0.1/1 to 100/1.
EP-A-434,469 describes a catalytic composition which comprises at least one titanium bis-(cyclopentadienyl) derivative and at least one compound selected from those of general formula (i) M
2
(AlR
3
R
4
R
5
R
6
) and (ii) M
2
(MgR
3
R
4
R
6
) wherein M
2
is selected from lithium, sodium and potassium. Compound (i) can be obtained by reacting an organo-alkaline compound with an organo-aluminum compound, whereas compound (ii) can be obtained by reacting 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 of general formula Cp
2
Ti(PhOR)
2
or CP
2
Ti(CH
2
PPh
2
)
2
.
All these processes have various drawbacks. The process described in U.S. Pat. No. 4,501,857 is the simplest as it starts from a compound (titanium dicyclopentadienyl chloride) which is easily available on the market and involves only the addition of an organic lithium derivative. Unfortunately, the same data of this patent show that the process is very effective when applied to living polymers, but gives a low hydrogenation yield when applied to non-living polymers (see table III compared with table II).
EP-A-434,469, on the other hand, comprises the presence of compounds (i) and (ii), which require reaction, not included in U.S. Pat. No. 4,501,857, between an organo-alkaline derivative (usually an organo-lithium derivative) and an organo-aluminum or an organo-magnesium derivative, with the titanium compound. Similarly, the process described in EP-A-601,953 is also onerous, as it includes the preparation and isolation of particular titanium dicyclopentadienyl derivatives obtained starting from Cp
2
TiCl
2
.
In any case, all of the catalysts described above, have the disadvantage of being prepared in situ and not being stable to storage.
A hydrogenation process of olefin double bonds has now been found, which overcome the above drawbacks.
In accordance with this, the present invention relates to a process for the hydrogenation of olefin double bonds present in polymers and copolymers of conjugated dienes, which comprises putting the above polymer or copolymer of conjugated dienes in contact with hydrogen in an inert solvent, in the presence of a catalytic system, characterized in that the above catalytic system essentially consists of one or more titanium compounds selected from those having general formula (I)
wherein:
M is selected from Ti(III) and Ti(IV) and the relative mixtures;
R″ is selected from (i) an organic or inorganic radical of an anionic nature, different from cyclopentadienyl or cyclopentadienyl substituted, (ii) an oligomeric group having general formula (II);
the groups R
1
, R
2
, R
3
, R
4
, R
5
, each independently represent, atoms or radicals bound to the cyclopentadienyl group coordinated to the metal M, and are selected from hydrogen and any other suitable organic or inorganic substituent of said cyclopentadienyl group;
R
6
is selected from: (a) an inorganic anion, (b) a hydrocarbyl having from 1 to 20 carbon atoms, (c) R′, preferably selected from: cyclopentadiene, cyclopentadiene substituted, R′;
“w” has the value of 0 or 1, according to the valence of the titanium;
R′ consists of an oligomeric group having the following formula (II):
−(A
x
D
y
U
z
)R
I
(II)
wherein:
A represents any monomeric unit deriving from a vinylaromatic group polymerizable by means of anionic polymerization, having from 6 to 20 carbon atoms;
D represents any monomeric unit deriving from a conjugated diolefin polymerizable by means of anionic polymerization, having from 4 to 20 carbon atoms;
U represents any generic optional monomeric unit deriving from an unsaturated compound co-polymerizable with any of the above conjugated diolefins D or vinylaromatic compounds A;
R
I
represents a hydrocarbyl group having from 1 to 20 carbon atoms,
each index “x” and “y” can be independently zero or an integer, provided the sum (x+y) is equal to or higher than 2, preferably between 2 and 50, even more preferably between 2 and 25:
“z” can be zero or an integer ranging from 1 to 20.
The preparation of the compounds having general formula (I) is explained in the pending patent application in the name of the same applicant. The experimental part describes the preparation of some compounds having general formula (I) subsequently used in hydrogenation tests.
The term “suitable”—as used in the text and claims with reference to groups, radicals and substituents in the formula of organic and organometallic compounds—means that those groups, radicals and substituents are compatible with the stability characteristics of said compounds in the pure state, i.e. substantially inert towards any part of the molecule under examination, on the basis of the chemical reactivity characteristics generally known to average experts in the field.
The term “derivative” as used herein with reference to the monomeric units present in general formula (I), means the production of said units in accordance with one of the known anionic poly-addition reactions, both with a 1-2 mechanism and, when possible, with a 1-4 mechanism. The monomeric units thus obtained substantially have the same structure as the monomer from which they derive, but one unsaturation less, and are linked with a covalent bond to each end of the oligomeric chain.
The complex having formula (I), according to the present invention, is a metallocene complex of trivalent or tetravalent Titanium, and is characterized by a higher stability both in solution and in the pure state.
Without limiting the present invention in any way to any particular theory or interpretation, it is believed that the favorable and surprising characteristics of said complexes having formula (I), with respect to the mono- or bis-metallocene complexes of the known art, can be specifically attributed to the presence of at least one unsaturated group having formula (II) bound to metal M.
I
Masi Francesco
Santi Roberto
Sommazzi Anna
ENI S.p.A.
Lu Caixia
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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