Copolymerization of conjugated dienes with non-conjugated...

Details Copolymerization of conjugated dienes with non-conjugated... Copolymerization of conjugated dienes with non-conjugated...

2003-04-21

2004-03-16

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...

C526S129000, C526S130000, C526S134000, C526S164000, C526S308000, C526S337000, C526S339000, C526S340000

Reexamination Certificate

active

06706830

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a process for the copolymerisation of conjugated diolefins with non-conjugated olefins in the presence of rare earth metal catalysts.
BACKGROUND OF THE INVENTION
The polymerisation of conjugated diolefins has been known for a long time and is described for example by W. Hoffmann, Rubber Technology Handbook, Hanser Publishers (Carl Hanser Verlag), Munich, Vienna, New York, 1989. Thus, for example, polybutadiene is nowadays mainly produced by solution polymerisation using Ziegler-Natta type co-ordination catalysts, for example based on titanium, cobalt, nickel and neodymium compounds, or in the presence of alkyllithium compounds. The solvent that is used in each case depends largely on the type of catalyst that is employed. Benzene or toluene as well as aliphatic or cycloaliphatic hydrocarbons are preferably used.
In contrast to the respective homopolymerisation, there are however few references to the copolymerisation of conjugated diolefins with non-conjugated olefins.
From U.S. Pat. No. 4,540,744 it is known to use anionic initiators for the polymerisation of butadiene and styrene in hexane. The disadvantage of the described process is that it is possible only to a limited extent to control the cis/trans ratio in the butadiene fraction and to obtain relatively high cis contents. However, high cis contents are advantageous for applications in the tyre and plastics modification sectors.
The disadvantage of the anionic initiators is that butadiene-styrene copolymers (SBR) are formed that permit only a slight control of the microstructure in relation to the butadiene units. It is not possible to obtain economically with anionic initiators a high cis-content SBR in which the 1,4-cis content is above 50%. Only the proportion of 1,2-units can be raised by adding modifiers, the 1,2-content leading to an increase in the glass transition temperature of the polymer. This is particularly disadvantageous on account of the fact that SBR is formed in this process, in which with increasing styrene content there is, in contrast to homopolymeric polybutadiene (BR), a further rise in the glass transition temperature. However, if the rubber is to be used for impact shock modification of for example HIPS or ABS, a high glass transition temperature of the rubber has a deleterious effect on the low temperature toughness of the material, and accordingly rubbers having low glass transition temperatures are preferred.
Furthermore, Kobayashi et al., for example in J. Polym. Sci., Part A, Polym. Chem., 33 (1995) 2175 and 36 (1998) 241 and Yingtai et al., for example in Polymere, 37/2 (1996) 349-352 have described a catalyst system consisting of halogenated acetates of the rare earth metals, such as for example Nd(OCOCCl
3
)
3
or Gd(OCOCF
3
)
3
, with tri(isobutyl)aluminium and diethylaluminium chloride, which enables butadiene and styrene to be copolymerised in the inert solvent hexane. The disadvantage of these catalysts is that the catalyst activity falls to below 10 g polymer/mmole catalyst/hr. even at a low styrene incorporation of about 5 mole %, and that the 1,4-cis content of the polymer drops significantly with increasing styrene content.
Bodrova et al. describes for example in Polymer Sci., Ser. A 39/12 (1997) 1259-1265 a catalyst system consisting of NdCl
3
-3 ROH and trisisobutyl aluminium, with which in the polymerisation of mixtures of isoprene and styrene in various inert solvents polymers are formed that have an overall styrene content of less than 10% as detected by H-NMR spectroscopy. The polymerisations were carried out at 60° C. over a period of 30 hours. In our own experiments however we were able to show that the polymerised styrene is mainly polystyrene that was formed during the long polymerisation time in, for example, a thermally induced secondary reaction.
In U.S. Pat. No. 5,096,970 and EP-A-304088 a process is described for the production of polybutadiene in styrene using catalysts based on neodymium phosphonates, organic aluminium compounds such as di(isobutyl)aluminium hydride (DIBAH), and based on a halogenated Lewis acid such as ethyl aluminium sesquichloride, in which the butadiene is converted in styrene to a 1,4-cis-polybutadiene without further addition of inert solvents. The disadvantage of this catalyst is that it is not possible to form styrene-butadiene copolymers in this case. A comparable catalyst system based on a rare earth metal carboxylate, an aluminium alkyl and a halogenated Lewis acid is described in EP-A 11184 as a particularly advantageous catalyst system for the production of polybutadiene with a high proportion of cis-1,4 units in aliphatic solvents.
It is furthermore known that allyl complexes of the rare earth metals in combination with co-catalysts, preferably with alumoxanes, in non-polar solvents such as toluene and n-heptane are suitable catalysts for the polymerisation of butadiene with a high content of 1,4-cis double bonds [R. Taube, H. Windisch, S. Maiwald, Makromol. Symp. 89 (1995) 393-409].
SUMMARY OF THE INVENTION
The object of the present invention was accordingly to provide a process for the copolymerisation of conjugated diolefins and non-conjugated olefins such as vinyl aromatic monomers, by means of which copolymers are obtained in which the polymer composition may be varied as regards the content of for example vinyl aromatic compounds and diolefins and with respect to the selectivity of the polymerised diolefins, i.e. for example the content of cis-positional double bonds and 1,2 units with side-chain vinyl groups.
With the catalyst systems according to the invention it is possible to adjust the cis content and thus the ratio of the cis to trans fractions independently of the styrene content. This possibility of varying the cis content is not possible with the known alkyllithium-based catalyst systems used in industry, in which the cis/trans ratios are moreover fixed.
It is known that the compounds used for tyre mixtures, in particular for the tread, consist of several rubbers in order to optimise the properties such as for example rolling resistance, wear and non-skid behaviour in the wet. These rubbers as a rule comprise natural rubber and synthetic rubbers such as polybutadiene, butadiene-styrene rubber or polyisoprene. A problem when using rubber mixtures is that incompatibilities may arise between the individual types of rubber. Such incompatibilities are reflected in increased tyre wear, low tear propagation resistance and short working life of the tyre.
It has now surprisingly been found that catalysts based on structurally defined allyl complexes of the rare earth metals are suitable for the copolymerisation of conjugated dienes with non-conjugated olefins, wherein compared to the hitherto known catalysts higher catalytic activities combined with a high variation range of the copolymerisation parameters and the selectivity of the diolefin can be achieved on the one hand, and the nature of the non-conjugated olefin can be widely varied on the other hand.
DETAILED DESCRIPTION OF THE INVENTION
The present invention accordingly provides a process for the copolymerisation of conjugated dienes with non-conjugated olefins, which is characterised in that the copolymerisation is carried out in the presence of catalysts consisting of:
(a) at least one allyl compound of the rare earth metals,
or consisting of
(a) at least one allyl compound of the rare earth metals and
(b) at least one activator
at temperatures of −30 to +160° C. in aromatic, aliphatic or cycloaliphatic solvents, wherein the molar ratio of the catalyst components (a):(b) is in the range from 1:0.1 to 1000, the component (a) of the catalyst is employed in amounts of 1 &mgr;mole to 10 mmoles, referred to 100 g of the conjugated diolefins that are used, and the non-conjugated olefin is employed in amounts of 5 g to 1000 g, referred to 100 g of the conjugated diolefins that are used.
As conjugated diolefins (dienes) there may for example be used in the process according to the invention 1,3-buta

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