Additive composition, method of blending same and a low haze polyolefin material and preparation thereof

A nucleating and clarifying additive composition comprises one or more optical brighteners, bis-3,4-dimethylbenzylidene sorbitol, and bis-p­ethylbenzylidene sorbitol, wherein the weight ratio of bis-3,4-dimethylbenzylidene sorbitol to bis-p-­ethylbenzylidene sorbitol is 45:55 to 25:75. In a method of forming a polyolefin material, the additive composition is mixed with a polyolefin resin to form a polyolefin composition, which is then processed to form the polyolefin material. The processing step preferably comprises moulding, such as injection or extrusion moulding, at 180-245ºC or at no more than 200ºC. The polyolefin may be polypropylene or a copolymer thereof. The optical brightener(s) may be phenylcoumarins, methylcoumarins, bis-(styryl)biphenyls, or bis-benzoxazoles, which may be present in an amount of 0.05-5 wt.% based on the combined weight of bis-3,4-dimethylbenzylidene sorbitol and bis-p-­ethylbenzylidene sorbitol. In preferred embodiments, the optical brighteners are selected from 2,5-bis(5-tert-butyl-benzoxazol-2-yl)thiophene, 4,4-bis-benzoxazolylstilbene, 3-phenyl-7-(4-methyl-6-butyloxybenzoxazole)coumarin, and 4-methyl-7-diethylamincoumarin.