Graft polymers that may be obtained by graft polymerization of vinylaromatic monomers and vinyl nitrites on ethylene/α-olefin rubbers or ethylene/α-olefin-diene rubbers are known in principle and as a rule are designated graft polymers of the AES type. Graft polymers of the AES type are described for example in GB 2 059 427, DE 30 36 921 A1, EP 0 286 071 A2, EP 0 096 527 A2, WO 86/06733, EP 0 054 148 and U.S. Pat. No. 3,876,727.
Compared to graft polymers of the ABS type, they are characterised by an improved weathering stability.
The graft polymers of the AES type known from the prior art all have deficiencies however in at least one category of surface properties and mechanical and polymer-physical properties.
The object therefore existed, as before, of providing graft polymers based on ethylene/α-olefin rubbers that have a balanced ratio of surface properties and mechanical and polymer-physical properties.
It is furthermore known that blends that contain graft polymers of the AES type are resistant to weathering, whereas their mechanical properties in the low temperature range are however unsatisfactory. At temperatures below 0° C. these blends become brittle and exhibit unsatisfactory toughness properties. Accordingly the use of these molding compositions is restricted at low temperatures. In particular the notched-bar impact strength of AES blends in the low temperature range is poor, especially compared to acrylonitrile/butadiene/styrene (ABS) blends.
EP-A 0 502 367 relates to the production of AES graft polymers and a copolymer, the copolymer containing 60 to 76 wt. % of a vinyl type aromatic monomer and 40 to 24 wt. % of an aliphatic copolymer. Vinylaromatic compounds and/or nuclear-substituted vinylaromatic compounds and vinyl cyanides and/or (meth)acrylic acid (C1–C8) alkyl esters are grafted on. These thermoplastic copolymers are said to exhibit, inter alia, a good impact strength in addition to the desired good properties relating to surface gloss, weathering resistance and sliding properties.
JP-A 50 109 247 describes polycarbonate blends with AES that contains 0.1 to 10 wt. % of paraffin oil. JP-A 58 098 354 describes polycarbonate blends with AES and 0.5 to 20 wt. % of plasticisers for vinyl polymers. It is not known whether the use of special additives that specifically concentrate in the plasticised phase lead to a significant improvement of the low temperature properties in polycarbonate/AES blends.
The object of the present invention is accordingly also to modify AES blends so that they have an improved property profile, in particular also an improved notched-bar impact strength, while maintaining their weathering resistance in the low temperature range.
It has now surprisingly been found that the aforementioned objects may be achieved by the AES graft polymers according to the invention and molding compositions containing these AES graft polymers according to the invention.