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Method for determining bleaching degree of shellac

A method of determination, the technology of shellac, is applied in the field of determination of the degree of bleaching of shellac, which can solve the problems of difference in color sensitivity measurement results, time-consuming and labor-consuming, cumbersome procedures, etc., to meet product grading requirements, accurate quantification, and simple operation Effect

Inactive Publication Date: 2012-02-22
KUNMING UNIV OF SCI & TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

In addition, these two methods use the visual dilution method for color comparison, which will introduce additional differences in measurement results due to the difference in sensitivity to color by the naked eye, and samples with small color differences or very light color cannot pass the color index or color test. In the determination operation, it is necessary to prepare and dilute standard substances of various concentrations and bleached shellac solutions, which has the problems of cumbersome procedures, time-consuming and labor-intensive

Method used

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  • Method for determining bleaching degree of shellac
  • Method for determining bleaching degree of shellac
  • Method for determining bleaching degree of shellac

Examples

Experimental program
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Effect test

Embodiment 1

[0040] Use industrial grade I dewaxed shellac flakes (raw shellac, color index ≤ 18) to prepare a shellac ethanol solution with a concentration of 7.7g / L, and measure the absorbance at 490nm with a 1cm cuvette A is 0.831, according to E 0 = A 0 / C 0 Calculate the absorbance per unit concentration E is 0.1079, which E 490 =100%, p =0 (see Table 1 for details), the absorption spectrum curve is shown in figure 2 .

Embodiment 2

[0042] Bleached shellac with chlorine dioxide of industrial grade I dewaxed shellac sheet (raw shellac, color index ≤ 18), No. 2, and prepared bleached shellac ethanol solution with a concentration of 16.0g / L, using a 1cm cuvette The absorbance at 490nm was measured A is 0.782, according to E b = A b / C b Calculate the unit concentration of bleached lac ethanol solution

[0043] Absorbance E is 0.0489, according to E 490 = A b C 0 / C b A 0 ×100% and p= 1 - E 490 calculate its E 490 =45.2%, p =54.8%, and the color index measured by the shellac product inspection method (GB8140-87) is No. 11 (see Table 1 for details).

Embodiment 3

[0045] The method is the same as that in Example 2, except that chlorine dioxide is used to bleach shellac 3, and the preparation concentration is 51.7g / L bleached shellac ethanol solution, and the absorbance at 490nm is measured A is 0.790, the absorbance per unit concentration E is 0.0153, which E 490 =14.1%, p =85.9%, the color index is measured as No. 4 (see Table 1 for details), and the absorption spectrum curve is shown in figure 2 .

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Abstract

The invention relates to a method for determining the bleaching degree of shellac, in particular to a method for determining the values of an absorbancy retention ratio E490 and a decoloring degree p of a bleached shellac ethanol solution by using a spectrophotometric method. The method comprises the following steps of: preparing a shellac solution with concentration of C0 and a bleached shellac ethanol solution with concentration of Cb; respectively measuring the absorbancies A0 and Ab at 490nm; calculating the values of the E490 and the decoloring degree p according to the formulas as follows: E490 = AbC0 / CbA0*100% and p = 1-E490, and then taking the calculated values as the bleaching parameters for quantitatively characterizing the bleaching degree and decoloring degree of the shellac. Compared with the existing dilution and visual colorimetry method for determining color indexes and the existing Gardner chromaticity method, by using the method disclosed by the invention, the differences between absorption spectrums of a shellac and a standard colorimetric substance and the differences between determining results caused by different color-sensitive degrees of the visual colorimetry method can be eliminated, and a quantitative evaluation on the colors of bleached shellacs with extremely-low color indexes or with slightly delicate differences between color indexes can be performed; the method is accurate in quantitation, easy to operate and quick in detection, and can realize the online measurement on the bleaching degree of bleached shellac in the actual production process; and through online control of the decoloring degree, the method can meet the productive process control and product grading requirements of bleached shellac with different color indexes.

Description

technical field [0001] The invention relates to a method for measuring the bleaching degree of shellac, in particular to measuring the absorbance retention rate ( E 490 ) and degree of decolorization ( p ) method, which belongs to the technical field of natural product processing. Background technique [0002] Shellac, also known as shellac, is a purple-red gum secreted by lac insects parasitic on host plants after absorbing sap. It is a natural condensation product formed by tung oil acid, shellac acid and other components. Because it contains lac red pigment (also known as shellac acid, see general structural formula I), it has a brownish red color. [0003] [0004] (I) [0005] With the expansion of the use of light-colored shellac in food, medicine, cosmetics, dyes, paints, fresh-keeping and adhesives, the demand for bleached shellac in the market is increasing day by day. Bleaching shellac is a product that uses bleaching agen...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N21/31
Inventor 唐辉黄喜坚张晓春
Owner KUNMING UNIV OF SCI & TECH
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