(+-)-alpha-Pinene → (+)-Limonene

Participants

Reaction Steps

To a 1.0 Liter flask is charged 140 g of xylene and 5.7 g of anhydrous aluminum chloride and the suspension is stirred under a nitrogen atmosphere at ambient temperature. The suspension is then warmed to 45° C. Using an addition funnel, 175 grams of a blend of alpha pinene, beta pinene and styrene (30:40:30 weight ratio) is introduced into the flask over a period of 60 minutes, while maintaining the polymerization temperature at 45-47° C. (cooling externally, as needed, using a water-ice mixture). After the blend has been fed, the reaction contents are quenched (catalyst is neutralized) with 100 g cold water. The contents are stirred and heated to 75-80° C. After stirring at 75-80° C. for 10 minutes, the aqueous layer is removed and the organic solution is washed with 100 g of water. The contents are heated again to 75-80° C. and the aqueous and organic layers separated. The organic layer constitutes the resin solution. This resin solution is then heated under a nitrogen atmosphere to 240° C. Most solvent and low boiling by-products are distilled between 140-200° C. Once the temperature reaches 240° C., a sample of the molten resin is collected and its softening point measured. The resin is stripped further using a nitrogen sparge (to remove low molecular weight by-products) till the desired s.p. is achieved. The maximum softening achieved was 91.1° C. At this point, the molten resin is poured into a container for storage. Resin had a neat color=2+Gardner, and overall yield was 84%. If required, the resin can be bleached, to lighten its color, at 240° C. during the stripping process, by introducing of a solution of iodine in xylene and stirring for 15 minutes. The iodine is 300 ppm by weight of total molten resin in the flask. Bleaching results in a resin neat color of about 1+.

Provenance & Evidence