Method for copolymerization and resulting copolymers

Details Method for copolymerization and resulting copolymers Method for copolymerization and resulting copolymers

2002-07-15

2004-05-04

Acquah, Samuel A. (Department: 1711)

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

Synthetic resins

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

C525S268000, C525S269000, C525S323000, C525S333700, C526S159000

Reexamination Certificate

active

06730744

ABSTRACT:

This application claims priority to PCT/FR00/00614 filed Mar. 14, 2000, which claims priority to French Patent Application No. 9903669 filed Mar. 24, 1999.
The present invention relates to a novel method of preparing block copolymers, and to certain of these block copolymers.
Block copolymers are widely known. However, it is also known that it is difficult to prepare block copolymers one of whose blocks is a polyolefin (PO), especially if the desire is that the alpha-olefin should be inserted in a regular manner in order to give a stereoregular and/or regioregular copolymer. It is also known that it is (virtually) impossible to prepare block copolymers whose two blocks are polyolefins, whether crystalline or amorphous.
Yamahiro et al., Macromol. Chem. Phys. 200, 134-141 (1999), describes a process of stopped-flow polymerization for obtaining “true” PP/EP block copolymers. However, the copolymers produced are limited in terms of molecular mass, since they have a molecular weight Mn of less than or equal to 16 000 and a polydispersity index of between 3.0 and 3.3. Other molecular mass characteristics are excluded by this type of technique: in particular, higher molecular masses cannot be attained, since they are a function of the polymerization time, which can only be short (of the order of from 0.1 to 0.2 s) and in any case less than the growth time of a chain; in particular, also, lower polydispersity indexes cannot be attained, since stopped-flow polymerization is not a true polymerization with living species, but comprises a large number of transfer reactions.
Therefore, there is to date no true PP/EP copolymer, with a PP block and an EP block linked together, which has a sufficient molecular mass. This PP/EP copolymer is a crystalline PO/amorphous PO copolymer, which would find advantageous application in PP/EP polymer blends. In these blends, the crystalline PP forms the continuous phase, which is modified by the addition of EP copolymer (more specifically EPR, which is elastomeric) which forms a nodular disperse phase. A true copolymer added to this blend would play a part similar to that played by an emulsifier in emulsions, improving the compatibility of the phases, and ultimately would enhance the impact/rigidity trade-off.
This same problem of difficulty in preparing “true” block copolymers occurs with copolymers one of whose blocks is a block of a polar monomer, such as MMA.
The patent application EP-A-0634429 in the name of Mitsui describes the preparation of block copolymers, one block being a polyolefin and one block being derived from a vinyl, vinylidene or lactone monomer. The catalyst used is an alkyl complex of a metal from the rare earth group, with bridged cyclopentadiene rings (bridged by a dimethylsilylene group). This document describes in particular the catalyst Me
2
Si(2-Me
3
Si,4-tBuCp)
2
YCH(SiMe
3
)
2
, with—optionally—a THF-type donor complexed to the metal. The copolymers obtained, however, are not satisfactory, since the polyolefin fraction represents too low a fraction of the final copolymer. Moreover, if the polydispersity values appear to be acceptable, it is only because these values are derived from the PMMA fraction, representing the quasitotality of the copolymer. Moreover, the catalysts do not in fact provide true copolymers. In effect, extensive transfer reactions (that is, the reactions which put an end to the living nature of the polymerization) lead to the formation not of true copolymers but of a mixture of homopolymers and copolymers. Moreover, the reaction times are fairly long.
The article by Yasuda et al., Tetrahedron, Vol. 51, No. 15, pp. 4563-4570, 1995, describes hydride derivatives of lanthanides in the form of a complex with bridged cyclopentadiene rings (bridged by a dimethylsilylene group), these cyclopentadiene rings carrying substituents which have a significant steric bulk (“bulky substituent”). This document describes in particular the hydride catalyst Me
2
Si(2-Me
3
Si, 4-Me
2
tBuSiCp)
3
YH (represented in its dimer form). These compounds are obtained in situ by hydrogenolysis of the starting alkyl derivative, and are then used for the polymerization of alpha-olefins. Although such compounds are described as having an alpha-olefin polymerization activity greater than that of the alkyl derivatives from which they are derived, the polymerization times are still very long, of the order of half a day or a day.
These hydride catalysts also have the classic disadvantage of hydrides, namely that hydride derivatives are known to be unstable and to break down rapidly at high temperature.
The search is therefore on for an effective method of preparing block copolymers: particularly, on the one hand, copolymers one of whose blocks includes a polar fraction, and, on the other hand, copolymers whose two blocks are polyolefins.
The invention accordingly provides a method of preparing block copolymers, comprising the steps of polymerizing a first monomer using an organolanthanide catalyst in which said catalyst is in the form of a hydride complex of a trivalent metal from the rare earth group, then polymerizing at least one second monomer.
In one embodiment, the hydride complex of a trivalent metal from the rare earth group has the formula I:
which:
Cp is a cyclopentadienyl radical;
R
1
, identical or different at each occurrence, is a substituent of the cyclopentadienyl group and is an alkyl radical or a silicon-containing hydrocarbon radical, containing from 1 to 20 carbon atoms, and with the Cp ring to which it is linked optionally forming an indenyl or fluorenyl ring system, it being possible optionally for each R
1
to be substituted;
j, identical or different at each occurrence, is an integer from 1 to 5 inclusive;
X is a divalent alkylene radical or a divalent, silicon-containing hydrocarbon radical, containing from 1 to 20 carbon atoms, optionally containing other heteroatoms such as oxygen;
y is 1 or 2;
Ln is a trivalent metal from the rare earth group, selected from Y, Sc, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu.
In one embodiment, in the formula I, X is Si(R)
2
in which R is an alkyl radical having from 1 to 4 carbon atoms.
In one embodiment, in the formula I, R
1
is an alkyl radical or a silicon-containing hydrocarbon radical, containing from 1 to 6 carbon atoms, which is unbubstituted, and j is 1, 2 or 3.
In one embodiment, in the formula I, R
1j
Cp is the group 2-Me
3
Si, 4-Me
2
tBuSiCp or the group 2-Me
3
Si, 4-tBuCp.
In one embodiment, in the formula I, Ln is Y or Sm.
In one embodiment, the catalyst is Me
2
Si(2-Me
3
Si, 4-Me
2
tBuSiCp)
2
YH or Me
2
Si(2-Me
3
Si, 4-tBuCp)
2
SmH.
In one embodiment, the catalyst is racemic.
In one embodiment, the catalyst is generated in situ in the presence of at least one portion of the first monomer.
In one embodiment, the blocks are homopolymers or random copolymers.
In one embodiment, the block copolymer comprises a block of the first monomer which is an alpha-olefin and a block of the second monomer which is a vinyl, vinylidene or lactone compound.
In this embodiment, the vinyl or vinylidene compound is represented by the formula
H
2
C═CR′Z
in which R′ is hydrogen or an alkyl radical having from 1 to 12 carbon atoms and Z is an electron-withdrawing radical.
In this embodiment, the vinyl or vinylidene compound is an ester of an unsaturated carboxylic acid.
In this embodiment, the polyolefin is crystalline.
In one embodiment, the second monomer is polar.
In one embodiment, the method is for preparing a PO/PMMA or PO/PL copolymer.
In this embodiment, the PO block is an iPO block.
In one embodiment, the block copolymer comprises a block of the first monomer which is a first alpha-olefin and a block of the second monomer which is a second alpha-olefin.
In a variant of this embodiment, the first polyolefin is crystalline and the second polyolefin is crystalline.
In this variant, the copolymer is a PP/PE copolymer.
In another variant of this embodiment, the first polyolefin is crystalline and the second polyolefin is amorphous.
In this variant,

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