Method for preparing low-chlorine bleach lac

A technology for bleaching shellac and shellac, which is applied in the field of preparation of bleached shellac with low chlorine content, can solve the problems of poor storage performance and shorten the shelf life of products, and achieve the effect of expanding market prospects

Inactive Publication Date: 2008-04-09
KUNMING UNIV OF SCI & TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Until now, poor storage performance is still the Achilles heel of bleaching glue, so manufacturers generally only promise a product shelf life of about six months
During the bleaching process of lac, free chlorine mainly enters the double bond of lac cyclic components through free radical addition (Zhou Hao, Gan Qigui. A study on the bleaching mechanism of lac resin chain components lac jaulic acid. Forest Product Chemistry and Industry , 1994, 14(1): 9-13), thereby combining chlorine on the shellac molecule, the presence of chlorine not only reduces the shelf life of the product, but also limits its use in the food and pharmaceutical industries. The bleached shellac requires a chlorine content of less than 1.0% (wt%) (GB8140-87 Bleached Shellac, 1987)

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0011] 4000mL of sodium carbonate solution with a concentration of 1.0% (wt%) was warmed up to a temperature of 85°C, and after adding 500g of natural particle shellac to dissolve completely, it was placed in a cold water bath and cooled to a temperature of 50°C, using a sieve diameter of 0.175mm Filter the insoluble matter through a stainless steel screen to remove most of the wax and mechanical impurities in the shellac; the resulting filtrate is bleached by adding sodium hypochlorite with an available chlorine content of 3% (wt%) at a temperature of 30°C for 12 hours, and the color index reaches 1.0 Stop; warm up the bleached shellac alkaline solution to a temperature of 90°C, add a mixture of 18g of sodium ethoxide and 90mL of ethanol and react with stirring for 60min; after the reaction, cool the solution to a temperature of 30°C, slowly Add dropwise 15mL of sodium hypochlorite solution with an available chlorine content of 3% (wt%) for bleaching for 10min, the color index...

Embodiment 2

[0013] 3000mL of sodium carbonate solution with a concentration of 1.5% (wt%) is warmed up to a temperature of 90°C, and after adding 500g of natural particle shellac to dissolve completely, it is placed in a cold water bath and cooled to a temperature of 45°C. Filter the insoluble matter through a sieve to remove most of the wax and mechanical impurities in the shellac; the obtained filtrate is bleached for 16 hours by adding sodium hypochlorite with an available chlorine content of 3% (wt%) at a temperature of 30° C., and stops when the color index reaches 1.0; After the bleached alkaline solution of shellac is heated to 80°C, add 6g of sodium metal and 100mL of absolute ethanol to react for 60min under stirring; after the reaction, cool the solution to a temperature of 30°C, drop Add 18mL of sodium hypochlorite solution with an available chlorine content of 3% (wt%) to bleach for 15min, the color index is 0.8, then filter with diatomaceous earth filter aid; the gained filtra...

Embodiment 3

[0015] 3500mL of sodium carbonate solution with a concentration of 3.0% (wt%) is warmed up to a temperature of 80°C, and after adding 500g of natural particle shellac to dissolve completely, it is placed in a cold water bath and cooled to a temperature of 50°C. Screen filter insolubles to remove most of the wax and mechanical impurities in the shellac; the gained filtrate is added with sodium hypochlorite with an available chlorine content of 3% (wt%) at 30°C to bleach for 8 hours, and stop when the color index reaches 0.8; After the final shellac alkaline solution is warmed up to a temperature of 85°C, add 20g of sodium ethylate and react for 90min under stirring; (wt%) sodium hypochlorite solution bleaching 20min, color index is 0.8, then filters with diatomaceous earth filter aid; Gained filtrate adds the dilute sulfuric acid of 5% (wt%) to precipitate shellac resin, and the control end point pH value is lower than 4.0; the precipitated white shellac resin was washed, vacuu...

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PUM

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Abstract

A preparation method of less chlorine bleaching lac: first, lac grains are put into sodium carbonate solution under the temperature of 60 DEG C to 100 DEG C and are completely dissolved. And then the solution is cooled below 70 DEG C and waxiness and insoluble content in the lac are filtrated; the filtrated solution under the temperature of 20 DEG C to 40 DEG C is added with sodium hypochlorite to blanch, then the temperature is increased to 70 DEG C to 100 DEG C. Next, sodium ethoxide is put into the solution to react. After the solution being cooled to room temperature or below 30 DEG C, sodium hypochlorite solution is dropped into the solution to blanch. Then the solution is filtrated with filtration aids such as white mud, diatomite and so on; the filtrated solution is added with dilute sulphuric acid or dilute hydrochloric acid to precipitate. The precipitation is dried by heat air after being washed and solid / liquid separation. In the end, the less chlorine bleaching lac which is white or slight yellow powder can be gotten. The product can satisfy the demand for food industry and pharmacy. The chlorine content in the product is less than 0.3 percent (wt percent). The time for thermal polymerization under the temperature of 170 DEG C plus or minus 1 DEG C amounts to above 5 minutes. The storage period is more than 2 years.

Description

1. Technical field [0001] The invention relates to a deep-processing and refining process of natural lac, in particular to a method for preparing bleached lac with low chlorine content that can meet the requirements for use in the food and pharmaceutical industries. 2. Background technology [0002] Lac, also known as shellac, is a lac insect parasitic on some leguminous or moraceous plants, such as Dalbergia, Yangqing (Simao Dalbergia), matchlock tree, three-leaf bean, big-leaved banyan, bull ribs and other trees that suck tree. A red substance secreted after juice. Shellac is a natural resin and the only animal resin. Due to its stable chemical performance, non-toxic, non-irritating, good electrical insulation performance, oil resistance, acid resistance, waterproof, moisture-proof, UV protection, plasticity, film-forming and strong adhesion, etc., it is widely used in national defense, electrical appliances, coatings, Machinery, rubber, plastics, medicine, leather, pape...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C09F1/02A23L1/056A23L29/275
Inventor 廖亚龙
Owner KUNMING UNIV OF SCI & TECH
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