Reducing and bleaching composition for pulp from decoloured waste paper and its bleaching method

A technology for deinking pulp and composition of waste paper, applied in pulp bleaching and other directions, can solve the problems of poor stability, little increase in bleaching whiteness, affecting bleaching effect, etc., achieve good bleaching effect, reduce ineffective decomposition, improve The effect of bleaching efficiency

Inactive Publication Date: 2004-06-30
SOUTH CHINA UNIV OF TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Hydrogen peroxide is the most widely used bleaching agent with the best effect in pollution-free bleaching. It is mainly used for waste paper pulp (such as old newspapers) with high wood pulp content in bleaching machines, but there are also many shortcomings: the decolorization ability is relatively low. Poor; due to the use of H in the pulping process 2 o 2 , then use H 2 o 2 The value-added value of bleaching whiteness is not large, only 2-3% ISO; the cost of bleaching is relatively high; there are varying degrees of negative effects on the strength and opacity of paper fibers
The bleaching effect of FAS is better, and the wastewater is non-polluting, but the cost of bleaching is higher, and the application is limited
Sodium dithionite bleaching is easy to operate, the bleaching cost per unit of whiteness is low, and the decolorization ability is strong, and H 2 o 2 Combined use of bleaching can most effectively obtain pulp with high brightness, and bleaching with sodium dithionite can improve the brightness of pulp without any negative effect on the fiber strength and opacity of paper. Therefore, sodium dithionite is very effective Bleaching agent for secondary fiber pulp, but there are also some shortcomings: poor stability, if it encounters air or dissolved oxygen in the pulp, it will promote its ineffective decomposition, and heavy metal ions in waste paper deinking pulp and circulating white water will also catalyze the decomposition. Sodium disulfite affects the bleaching effect. The ineffective decomposition products of sodium dithionite will also corrode pipeline equipment, shorten the service life of equipment and pipelines, fail to achieve the expected increase in whiteness and yellowing of pulp after bleaching, etc.
Metal ions in deinked pulp not only catalyze the decomposition of sodium dithionite, but also cause the yellowing of bleached pulp
Some studies have tried to add chelating agent before bleaching or sodium bisulfite before storage, which has a certain effect, but not obvious

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0018] The waste paper deinking pulp reduction bleaching composition is formed by uniformly mixing 10% sodium dithionite, 2.5% sodium tripolyphosphate, 1% sodium hydroxide and 86.5% water, adding a thin layer of kerosene to make It is isolated from the air. During bleaching, take by weighing original whiteness and be 55.2%ISO waste newsprint deinking pulp 25g (absolutely dry weight), add tap water to regulate and treat that bleaching pulp concentration is 4%; Add H 2 SO 3 Or NaOH solution to adjust the initial pH. The conditions of the bleaching process are: bleaching temperature 70° C., bleaching time 45 minutes, initial pH value 6.5. At the same time, 0.025 g of sodium metabisulfite and 2.5 g of reducing bleaching composition were added. Stir vigorously and control the bleaching time. After bleaching, rinse 2-3 times. As described above, the present invention can be preferably realized. The brightness of bleached pulp is 64.5% ISO, and the value-added of brightness is ...

Embodiment 2

[0020] The waste paper deinking pulp reduction bleaching composition is prepared by uniformly mixing 5% sodium dithionite, 1.25% disodium edetate, 0.25% sodium carbonate and 93.5% water, adding a thin layer of solvent Oil, so that it is isolated from the air. During bleaching, take by weighing original whiteness and be 55.2%ISO waste newsprint deinking pulp 25g (absolutely dry weight), add tap water to regulate and treat that bleaching pulp concentration is 4%; Add H 2 SO 3 Or NaOH solution to adjust the initial pH. The conditions of the bleaching process are: bleaching temperature 65° C., bleaching time 60 minutes, initial pH value 5.5. First add 0.04 g of sodium sulfite for treatment, and then add 4 g of reduction bleaching composition. Stir vigorously and control the bleaching time. After bleaching, rinse 2-3 times. As described above, the present invention can be preferably realized.

Embodiment 3

[0022] The waste paper deinking pulp reduction bleaching composition consists of 15% sodium dithionite, 1.5% tetrasodium edetate, 1% sodium tripolyphosphate, 2% sodium carbonate, 1% sodium hydroxide and 79.5 % of water evenly mixed, adding a thin layer of compressor oil, so that it is isolated from the air. During bleaching, take by weighing original whiteness and be 55.2%ISO waste newsprint deinking pulp 25g (absolutely dry weight), add tap water to regulate and treat that bleaching pulp concentration is 4%; Add H 2 SO 3 Or NaOH solution to adjust the initial pH. The conditions of the bleaching process are: bleaching temperature 80° C., bleaching time 40 minutes, initial pH value 7.5. At the same time, 0.148 g of sodium bisulfite and 3.3 g of reducing bleaching composition were added. Stir vigorously and control the bleaching time. After bleaching, rinse 2-3 times. As described above, the present invention can be preferably realized.

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Abstract

A reducing and bleaching composition for decoloured waste pulp is prepared from sodium dithionite (5-15 wt.%), chelating agent (1.25-15), sodium carbonate or sodium hydroxide or their mixture (0.25-3) and water (79.5-93.5) through uniform mixing. Its bleaching method features that the stabilizer and said composition are cooperated, and the oil or solvent not dissolved in water is added to isolate air, so improving the stability of bleaching liquid, reducing consumption of sodium dithionite and improving bleaching effect. Its advantages include less damage to strength and opaqueness of paper fibres, less corrosion to pipeline, less pollution and low cost.

Description

(1) Technical field [0001] The invention relates to waste paper pulping technology, in particular to a waste paper deinked pulp reduction bleaching composition and a bleaching method thereof. (2) Background technology [0002] For recycled waste paper, it is difficult to produce deinked pulp with the same brightness as virgin fiber pulp only by purification and deinking technology. In order to obtain deinked pulp with high brightness, a post-bleaching process must be arranged after deinking. Removes all colors. Color can be caused by residual lignin in deinked pulp, such as newsprint made from high-interest rate pulp, which has a high lignin content; it can also be caused by dyes, pigments, inks and Caused by other chromogenic compounds. The technical process and conditions of waste paper bleaching are generally determined according to the waste paper raw materials to be processed, the types of paper to be copied and the requirements of environmental protection. People us...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): D21C9/10
Inventor 钱宇谭本祝江燕斌梁一鹏
Owner SOUTH CHINA UNIV OF TECH
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