Zhongguo youzhi (Apr 2022)
精炼过程对漆蜡理化性质的影响 Effect of refining on physiochemical properties of lacquer wax
Abstract
毛漆蜡酸值高、色泽深，需要通过精炼提高其品质。对毛漆蜡进行脱酸、脱色和脱臭处理，对精炼前后漆蜡的酸值、过氧化值、色泽、甘油酯和脂肪酸组成进行了分析，采用X-射线衍射技术对漆蜡晶型进行测定，通过固体脂肪含量的测定和差示扫描量热法分析了漆蜡的热性质。结果表明：脱酸后漆蜡的酸值（KOH）由（35.06±0.05）mg/g降至（0.12±0.01）mg/g；精炼后，漆蜡色泽由深褐色变为乳白色，过氧化值为（0.28±0.04）mmol/kg。精炼过程中漆蜡的甘油酯和脂肪酸组成没有发生改变，但脱酸漆蜡的甘三酯含量显著增加，甘一酯和甘二酯含量显著降低，棕榈酸含量显著增加，油酸和亚油酸含量显著降低;脱色、脱臭对漆蜡的甘油酯和脂肪酸含量没有显著影响。固体脂肪含量分析表明，毛漆蜡的熔化范围为20~55 ℃，脱酸、脱色和脱臭漆蜡熔化范围为30~60 ℃；X-射线衍射数据显示，毛漆蜡以β晶型为主，并存在少量α晶型，精炼后α晶型消失；差示扫描量热分析表明，脱酸、脱色和脱臭漆蜡熔点有所升高。这些变化可能是精炼过程中毛漆蜡中的绝大部分游离脂肪酸、部分甘二酯和一些挥发性物质被除去所致。The crude lacquer wax should be refined to improve its quality because of its high acid value and dark color. The crude lacquer wax was deacidified, bleached and deodorized,and the acid value, peroxide value, color, glycerides and fatty acid composition of lacquer wax before and after refining were analyzed. The crystalline shape of lacquer wax was determined by X-ray diffraction technique, and the thermal properties of lacquer wax were analyzed by solid fat content determination and differential scanning calorimetry. The results showed that after deacidification, the acid value of lacquer wax decreased from (35.06±0.05)mgKOH/g to (0.12±0.01)mgKOH/g; after refining, the color changed from brown to milky white, and the peroxide value was (0.28±0.04) mmol/kg. The glycerides and fatty acid compositions of lacquer wax did not change in the refining process, but in deacidification process, the contents of triglycerides increased significantly, the contents of monoglyceride and diglyceride decreased significantly, and the palmitic acid content increased obviously, while the oleic acid and linoleic acid contents decreased obviously. There was no significant effect of bleaching and deodorization processes on the glycerides and fatty acid contents of lacquer wax. The solid fat content analysis showed that the melting range of crude lacquer wax was 20-55 ℃, and the melting range of deacidified, bleached and deodorized lacquer wax was 30-60 ℃. The X-ray diffraction data showed that the crude lacquer wax was dominated by β-type crystals, and a small amount of α-type crystals existed, while the α-type crystals disappeared after refining. The differential scanning calorimetric analysis showed that the melting points of deacidified, bleached and deodorized lacquer waxes increased. These changes might be due to the removal of most of the free fatty acids, some diglycerides and some volatile substances from the crude lacquer wax during refining.
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