Abstract: The invention relates to a dental composition which is suitable as a fissure sealant, dental glaze, bonding agent or orthodontic adhesive and which is a mixture of a selected vinyl urethane prepolymer, selected comonomer, and visible light cure catalyst comprising an organic amine and selected .alpha.-diketone.

Abstract: The invention relates to a dental composition which is suitable as a fissure sealant, dental glaze, bonding agent or orthodontic adhesive and which is a mixture of a selected vinyl urethane prepolymer, selected comonomer, and visible light cure catalyst comprising an organic amine and selected .alpha.-diketone.

Abstract: A titanium trihalide is ground with an organic Lewis Base compound which contains at least one phosphorus atom, and optionally at least one nitrogen atom, and a titanium tetrahalide, the Lewis Base and the titanium tetrahalide being used in amounts of 5 to 75, preferably 5 to 50%, molar and 1 to 50, preferably 5 to 30% molar respectively relative to the titanium trihalide. The materials are conveniently milled together and the milled product can be used as a component of an olefine polymerization catalyst and when such catalysts are used to polymerize propylene a high activity is achieved together with satisfactory stereospecificity.

Abstract: An olefine polymerisation catalyst comprises a titanium trichloride component of high surface area, an organo-metallic component, a Lewis Base component and optionally a polyene. The TiCl.sub.3 component which may have a high porosity is conveniently obtained by the reaction of TiCl.sub.4 and an organo-aluminium compound, treating the reaction product with a complexing agent and then contacting this product with TiCl.sub.4. The organo-metallic component is preferably aluminium triethyl, the Lewis Base component hexamethylphosphoric triamide and the polyene is cycloheptatriene. This system has high polymerisation activity combined with good stereospecificity. Polypropylene can be obtained in high yield thereby giving low catalyst residues and the polymer has a high stiffness modulus.