Method for (CO)polymerizing polar and non-polar monomers

Details Method for (CO)polymerizing polar and non-polar monomers Method for (CO)polymerizing polar and non-polar monomers

2002-05-23

2003-07-29

Teskin, Fred (Department: 1713)

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

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S113000, C526S126000, C526S134000, C526S346000, C526S347000, C525S269000, C525S299000

Reexamination Certificate

active

06599996

ABSTRACT:

The present invention relates to a process for the transition-metal-catalyzed preparation of polymers having a syndiotactic or predominantly syndiotactic structure from vinylaromatic monomers and to a process for preparing block copolymers from vinylaromatic monomers and olefinically unsaturated polar monomers. The invention further relates to the block copolymers obtained by the process mentioned and to their use as impact modifiers in the production of fibers, films or moldings. The invention also relates to fibers, films or moldings comprising the abovementioned block copolymers.
Transition metal complexes based on rare earth metals have recently been examined to an increasing extent for their suitability as catalysts for the coordinative polymerization of nonpolar or polar olefinically unsaturated monomers (cf. H. Yasuda, E. Ihara, Bull. Chem. Soc. Jpn., 1997, 70, pp. 1745 to 1767). Depending on the monomer used in each case, use is made of metal complexes having one or two metal centers, with satisfactory results frequently only being achieved when a suitable cocatalyst is additionally used. According to Yasuda and Ihara, the polymerization of, for example, styrene can be carried out in the presence of a catalyst mixture comprising complexes of the formula Sm(O-i-Pr)
3
or Nd(acac)
3
and trialkylaluminum compounds. The polymerization of styrene was able to be carried out using the bimetallic complex [(t-BuCp)
2
NdMe]
2
(Cp=cyclopentadienyl) in the absence of a cocatalyst. Although styrene could also be polymerized using monometallic samarium and lanthanum complexes without using a cocatalyst, only atactic polystyrene was obtained. Cocatalyst-free samarium or yttrium catalyst systems have hitherto displayed only a very low activity, if any, in the polymerization of styrene. To prepare syndiotactic polystyrene or polystyrene having a high syndiotactic content, the advice has hitherto been to use catalyst systems comprising cyclopentadienyltitanium complexes and suitable aluminoxane compounds (cf. Ishihara et al., Macromolecules, 1988, 21, p. 3356).
Syndiotactic polystyrene, i.e. polystyrene having an rr triad content of >70%, is suitable for use as a thermoplastic material owing to its good mechanical properties and its thermal stability. However, since syndiotactic polystyrene is frequently not compatible with other polymeric materials, it would be desirable to be able to prepare suitable blends with the aid of compatibilizers so as to combine the advantageous properties of different polymer materials in one material. Block copolymers and graft copolymers have proven to be useful as compatibilizers and impact modifiers in polymer blends. Block copolymers can be obtained, for example, by means of anionic polymerization, in which the coupling of two or more copolymer blocks comprising nonpolar monomer units, e.g. butadiene and styrene, is unproblematical but the block copolymerization of styrene and polar monomers, e.g. acrylates, has not been able to be brought about.
Wakatsuki et al. (Macromolecules 1998, 31, pp. 8650 to 8652) were able to obtain block copolymers comprising polystyrene and polyethylene blocks with the aid of a monocyclopentadienylsamarium phenoxide complex. However, the incorporation of block components comprising polar monomer units is not described. Although Yasuda et al., Bull. Chem. Soc. Jpn. 1997, 70, pp. 1745 to 1767, show that block copolymers of ethene and polar monomers such as methyl methacrylate can be prepared in the presence of binary hydride-bridged samarium complexes, the monometallic and bimetallic complexes described are not suitable for the block copolymerization of styrene with polar monomers. In addition, Yasuda et al. disclose the preparation of polystyrene having an increased syndiotactic content using defined neodymium complexes in the presence of aluminum alkyl compounds as coactivators. Many further lanthanide complexes gave only atactic polystyrene when no cocatalysts were employed.
According to EPA 0 634 429, only block copolymers made up of polyolefin blocks and blocks consisting of polar monomer units can be prepared in the presence of defined biscyclopentadienyllanthanum complexes, i.e. in the absence of a cocatalyst. Schaverien, Organometallics, 1994, 13, pp. 69 to 82, describe numerous dimeric alkyl- and hydride-bridged lanthanide complexes in terms of their preparation and properties. However, these compounds display polymerization activity only toward &agr;-olefins.
It would be desirable to have a process for preparing block copolymers which enables not only nonpolar monomers such as olefins but also vinylaromatic monomers to be copolymerized with polar monomer units.
It is an object of the present invention to provide a preparatively simple block copolymerization process for preparing block copolymers comprising vinylaromatic and polar monomer units.
We have found that this object is achieved by a process for the transition-metal-catalyzed preparation of block copolymers, in which vinylaromatic monomers and olefinically unsaturated polar monomers are polymerized sequentially in the presence of a transition metal compound of the formula (I)
where the substituents and indices have the following meanings:
M is scandium, yttrium, lanthanum or a lanthanide metal,
R is hydrogen, halogen, C
1
-C
20
-alkyl, C
3
-C
10
-cycloalkyl, C
6
-C
15
-aryl or C
3
-C
30
-organosilyl, where two adjacent radicals R may form a saturated or unsaturated, cyclic or heterocyclic group having from 4 to 18 carbon atoms,
Z is —SiR′
2
—, —CR′
2
—, —GeR′
2
—, —SnR′
2
—, —BR′— or —O—,
R′ is C
1
-C
20
-alkyl, C
3
-C
10
-cycloalkyl, C
6
-C
15
-aryl or alkylaryl having from 1 to 10 carbon atoms in the alkyl part and from 6 to 10 carbon atoms in the aryl part,
X is —O—, —S—, —NR″—, —PR″—, —OR″, —SR″, —NR″
2
or —PR″
2
,
R″ is hydrogen, C
1
-C
20
-alkyl, C
3
-C
10
-cycloalkyl, C
6
-C
15
-aryl, alkylaryl having from 1 to 10 carbon atoms in the alkyl part and from 6 to 10 carbon atoms in the aryl part or C
3
-C
30
-organosilyl,
R′″ is &mgr;-C
3
-C
20
-alkyl,
p is a natural number greater than 1,
L is a low molecular weight, organic compound having Lewis basicity, n=1 or 0 and at least one n in (I) is 0,
m is 1 or 2.
Preference is given to using metal hydride complexes (I) in which the substituents and indices have the following meanings:
M is yttrium, terbium or erbium
R is C
1
-C
10
-alkyl or C
3
-C
21
-organosilyl, where two adjacent radicals R may also form a fused-on aromatic ring,
Z is —SiR′
2
— or —CR′
2
—,
R′ is C
1
-C
10
-alkyl or C
6
-C
10
-aryl,
m is 1,
X is —NR″— or —PR″—,
R″ is C
1
-C
10
-alkyl, C
6
-C
10
-aryl or alkylaryl having from 1 to 6 carbon atoms in the alkyl part and from 6 to 10 carbon atoms in the aryl part and
R′″ is &mgr;-C
4
-C
10
-alkyl,
p is a natural number greater than 1
L is tetrahydrofuran, a 2,5-dialkyltetrahydrofuran, dioxane, a dialkyl ether, acetonitrile, a triarylphosphine or halogenated triarylphosphine.
Furthermore, we have found a process for preparing polymers of vinylaromatic monomers having a syndiotactic or predominantly syndiotactic structure, in which the starting monomers are polymerized in the presence of the abovementioned transition metal compound (I). In addition, the block copolymers obtainable by the abovementioned process and their use as impact modifiers or compatibilizers have been found. Finally, fibers, films and moldings comprising essentially the block copolymers mentioned have also been found.
In the processes of the present invention, use is made of binuclear or polynuclear complexes (I) based on rare earth metals. Suitable central metals M are accordingly scandium, yttrium, lanthanum or lanthanide metals such as cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium (Cf. Lehrbuch der anorganischen Chemie, Hollemann-wiberg, de Gruyter, Berlin,

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