Method for beaching shellac using chlorine dioxide and alcohol solvent, and application thereof

Abstract

The invention discloses a method for beaching shellac using chlorine dioxide and an alcohol solvent. The method comprises the following steps of: dissolving shellac using the alcohol solvent into solution, adding chlorine dioxide to the solution under the condition of constant temperature and stirring the solution for bleaching for certain time, thereby obtaining bleached shellac solution; adding dilute sulphuric acid to the bleached shellac solution so that the bleached shellac is separated out, and then repeatedly washing the bleached shellac until the pH of washing water is neutral; and drying the shellac at the room temperature, thus obtaining the bleached shellac, wherein the absorbance of the ethanol solution in the position of 490 nm can be reduced to 1.6% of the raw material shellac, while the color index thereof can be reduced to be less than 0.5#; and other technical indexes are capable of meeting the requirements of the refined bleached shellac level I. The method is characterized in that: bleaching conditions are mild; a non-alkaline condition is adopted; the bleaching temperature is low; the dosage of an acidic precipitator is low; the color index of the obtained bleached shellac is low; and accurate control and regulation can be performed by adjusting the dosage of the chlorine dioxide, etc; therefore, the application of the bleached shellac in special fields can be extended.

Description

Technical field [0001] The invention relates to a method for bleaching shellac with chlorohydrin solvents and its application. Background technique [0002] Shellac is also called shellac. It is a purple-red colloid secreted by lac insects parasitic on the host plant after absorbing the sap. It is a natural condensate formed by components such as tungoleic acid and shellac. Because of its brownish-red color, film-forming properties and water vapor permeability, it is often used to extract natural pigments, make furniture paints and insulating materials. [0003] Shellac contains slightly different components depending on the place of production, but usually contains about 67.9% of C, 9.1% of H and 23.0% of O, and its molecular formula meets the empirical formula (C 4 H 6 O) n , The relative molecular mass of fresh shellac (uncured shellac) is about 1000, so it can be inferred that the value of n in the molecular formula of shellac is about 15, generally 6-22. On averag...

AI Technical Summary

Problems solved by technology

However, this technology has high requirements on the control accuracy of the pH value of the colloid analysis. If the pH value of the colloid analysis is too high, it will increase the consumption of shellac and increase the difficulty of subsequent dehydration. If the pH value of the colloid analysis is too low, the product life will be shorter.

The third type of technology represented by Chinese patent application (92105048.8) uses sodium chlorate to bleach shellac in an ethanol system. The mild condition also reduces the bleaching temperature at the same time, and the mildness of the bleaching condition makes the color index of the bleached shellac low and the thermal stability improved, but the problem is that the used bleaching agent sodium chlorate

[0007] The low solubility in ethanol affects the bleaching efficiency of the system and prolongs the bleaching time

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