Thermoplastic PU-PS Graft Copolymers

Title: POLYURETHANE-BASED POLYMER COMPOSITION

 Number/Link: WO2014/147194

Applicant/Assignee: BASF

Publication date: 25-09-2014

Gist”: TPU microparticles react with styrene monomer resulting in a TPU-PS copolymer.

Why it is interesting: Blends of TPU with polystyrene are known, but compatibility is low and PS to TPU ratio therefore needs to be low as well  to prevent ‘delamination’ of injection moulded parts.  According to this patent application it is however possible to graft the PS onto TPU such that much higher PS/TPU ratio’s can be obtained. The TPU needs to be MDI-based and have a relatively low hardblock content and softening temperature. Apparently the PS grafts onto the MDI methylene groups which form radicals easily. In an example TPU micropellets are swollen in styrene monomer at low temperature together with dicumulperoxide as a radical initiator. The swollen particles are then dispersed in water together with an emulsifier and heated under pressure to form a 60-40 TPU-PS copolymer. A solvent-based process is also exemplified.  The resulting polymers are especially useful for injection moulded parts such as spring-aids.

MDI radical

MDI radical

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