The synthesis of rosin allyl ester and its UV-curing properties

The forest chemical industry has identified rosen as a potential renewable resource. A mixture of organic acids with high molecular weights and related materials. Resin acids, which include abietic acid, neoabietic acid, and palustric acid, are the acidic components of rosin. In addition to producing fine chemicals1, 2, 3 they are widely used as raw materials to produce functional polymers.4, 5, 6, 7, 8 Woo-Sik Kim5 developed a method to synthesize poly(vinylbenzyl abietate) using poly(vinylbenzyl chloride) and sodium abietate as raw materials. By reacting poly(glycidylmethacrylate) with abietic acid, Tae Hoon Kim6 reported the synthesis of polymethacrylate.

Neither of these methodologies used resin derivatives as monomers for polymerization. Thus, these polymers were made up of monomers other than resin derivatives. The final product did not provide a suitable resin structure; the reaction conversion was relatively low.5, 6 Moreover, a large amount of solvent was used to purify the product after reaction. Vinyl compounds are already well known for their photosensitive properties. In order to polymerize abietate derivatives, Woo-Sik Kim7 and Byoung-Woo Park8 introduced a vinylbenzyl group into the molecular structure. Due to its high boiling point (192 °C), vinylbenzyl chloride is difficult to remove by vacuum distillation, causing vinylbenzyl abietate to be thermally unstable.

The purpose of this study was to synthesize Rosin ester allyl ester by adding a vinyl group to the structure of the rosin monomer. Using thermogravimetry (TG), differential scanning calorimetry (DSC), and gel permeation chromatography (GPC), we evaluated the UV-curing reaction of the rosin allyl ester.

Experiment Description:

The materials used in this experiment were obtained from commercial sources without further purification. An IR spectrophotometer MAGNA-550 (Nicolet, Waltham, MA, USA) was used to obtain IR spectra (max in cm*1). The composition of resin acids and rosin allyl ester was examined using gas chromatography-mass spectrometry (GC-2010, Shimadzu, Kyoto, Japan). We separated the samples in an HP-5 column, 30 m * 0.25 mm * 0.25 *m, under the following conditions: 100 °C, 5 °C min−1 to 200 °C, 2 °C min to 250 °C, hold for 25 min. According to the China National Standard for testing rosin (GB/T 8146-2003), we used the Intelli-ray 600 (Shenzhen Wisbay M&E Co., Ltd., Shenzhen, China); a shuttered UV flood light (the Intelli-ray 600 is powered by a metal halide lamp and the radiation flux is 315–400 nm); a wave band of 315–400 nm; intensity 100%; and a timer at room temperature on an apparatus equipped with a refractive-index detector, the Waters 515 (Waters, Milford, MA, USA).

The columns used were Styragel HR1 (300 * 7.8 mm) and HR2 (300 * 8.3 mm). A flow rate of 1 ml min*1 was used as the eluent, which was high-purity liquid chromatography-grade tetrahydrofuran. Polystyrene standards with molecular weights in the range 580 to 1.96 * 104 g mol*1 (with NMD for 1.1) were used to calibrate the columns.

Rosin acids were purified using this technique.

After stirring at 60°C for 10 minutes, 20 grams of rosin were dissolved in 15 ml acetone. Once the mixture reached room temperature, it was cooled to form a solid. Two times in acetone, the solid obtained was filtered and recrystallized. The product yielded an acid value of 182.5 mg KOH per g (185.8 mg KOH per g according to theory) after purification.

 

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