JPH0160111B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical field] The present invention uses a sulfur-free and chlorine-free cooking chemical.
The present invention relates to a method for producing high-whiteness chemical pulp from bast at a high yield without going through a bleaching process using stage cooking. [Prior Art] The fibers contained in the bast of mitsumata, kozo, gampi, hemp, flax, etc. are composed of pectocellulose containing a small amount of lignin. If these basts are digested at 80 to 130°C using conventional pulping methods, long fiber pulp can be obtained relatively easily. The pulp of these basts is strong and elegant and has been prized as a raw material for banknote paper, securities paper, and Japanese paper. However, in order to obtain pulp with even higher whiteness, it has been necessary to perform one or two stages of bleaching using a chlorine bleach.
The bleaching yield was usually 90 to 95%, and loss of raw material was inevitable. Therefore, many attempts have been made to increase the yield of pulping, to eliminate sulfur, and to eliminate chlorine during bleaching. However, there have been no reports of success in producing pulp with high brightness by only one-stage cooking using sulfur-free and chlorine-free chemicals without bleaching during pulp production. [Purpose] The present invention aims to simultaneously reduce pollution, save resources, save energy, improve quality, and save labor in the bast pulping process. By subjecting the raw bast to a single stage of cooking at a relatively low temperature in an almost neutral range using a cooking chemical, it is possible to produce a pulp that is at least as high as that obtained by one or two additional stages of bleaching after pulping. The purpose of the present invention is to provide a method for obtaining chemical pulp with higher whiteness than conventional methods. [Structure] The present inventors have been conducting intensive research for many years in order to rationalize the method for producing bast pulp. This time table-1
As shown in Figure 2, a mixture of the common reagents sodium oxalate, hydrogen peroxide, sodium carbonate, a chelating agent, and water, or a mixture of anthraquinones added thereto, is used as a new cooking chemical solution. When purified white bark of mitsumata was treated at 90°C under normal pressure for 5 hours (one-stage cooking), depectinization and delignification of the raw material progressed, and pulping and bleaching occurred in parallel. We have developed a new type of pure white chemical pulp that has not been seen in previous research reports (cut par value 24.3~
22.5, Hunter whiteness 84.6% to 84.8%) was obtained in high yield (74.2% to 74.6%) [hereinafter referred to as
The pulping method of the present invention is the NPO method (neutral hydrogen peroxide-oxalate method), and the resulting pulp is abbreviated as NPOP (neutral hydrogen peroxide-oxalate pulp). In addition, the refined white bark of Mitsumata from the same lot is used as conventional NSP.
(neutral sulfite method) and alkaline method using sodium carbonate (AP()), but Table 1
As shown in , Hunter whiteness is 64.1 respectively.
% and 47.1%. In addition, as shown in Table 2, among sodium hydroxide, sodium oxalate, and sodium sulfite, sodium hydroxide alone (P
()) or a combination of sodium oxalate and sodium sulfite (SOP) as the cooking chemical, pulping is not easy, the yield is low, and the whiteness of the resulting pulp is low. It was also low. In other words, when cooking at 140-150℃ for 1-2 hours, the yield of selected pulp from Mitsumata white bark is 13.4~13.4~
The total yield including the lees ratio of 28.0% was 51.8 to 59.3%. The whiteness of the obtained pulp was 49.1 to 58.1.
%, which was extremely low. In addition, when cooking with an alkaline solution of hydrogen peroxide at 150℃ for 2 hours (PA), pulping progressed well, but the yield of selected pulp was low.
64.4%, Hunter whiteness 62.0%, both NPO
It has been shown that it is inferior to the law.

【table】

【table】

〔Effect of the invention〕

The scope of application of the present invention is wide, and the expected effect on streamlining the pulp manufacturing process is extremely large. That is, (1) As shown in Table 3, according to the present invention, the bast of various plants is used as a raw material and processed under very mild conditions to produce bast pulp with high whiteness and high quality at a high yield. Now I can get it. In other words, when comparing the purified mitsumata white bark from the same lot as a sample,
NPOP achieved Hunter whiteness of 84.6%, but
This indicates that the whiteness is comparable to or even whiter than bleached pulp obtained by conventional methods. Moreover, the pulp yield at that time was 74.2%, which is 7 to 22% higher than the unbleached pulp produced by the conventional method.
Since NPO cooking can be carried out without any problems at normal pressure and below 100°C, there is no need to use a pressure-resistant reactor, making it possible to significantly save resources and streamline factory construction.

[Cooking chemical composition]

Hydrogen peroxide 0.221 mol Sodium oxalate 0.112 mol Chelating agent 0.225 g/Anthraquinones 0.750 g/Sodium carbonate 0.0708 g/The pH at the end of the reaction was 7.75. After the reaction, the chemical solution was collected, the pulp was washed, and it was screened using a 12/1000 cut flat screen, and the following experimental results were obtained. [Experimental results] Selected pulp yield 72.4% Lees ratio 1.8% Total yield 74.2% Katsupar number 22.7 Hunter whiteness 84.6% Example 2 300g of crude white bark of Aoganpi as shown in Table 3
(as an absolute dry amount) was taken and pulped under the same conditions as in Example 1. The pH at the end of the reaction was 7.80. The experimental results are shown below. [Experimental results] Selected pulp yield 42.5% Lees rate 1.5% Total yield 44.0% Katsupar number 24.3 Hunter whiteness 82.1% Example 3 As shown in Table 3, 300 g of refined white bark of mulberry (as absolute dry amount) was taken and pulped under the same conditions as in Example 1. The pH at the end of the reaction was 7.57. The experimental results were as follows. [Experiment results] Selected pulp yield 73.0% Residue rate 2.1% Total yield 75.1% Katsupar number 25.2 Hunter whiteness 83.4% Example 4 An experiment was conducted in the same manner as in Example 1 except that anthraquinones were not used, and the following results were obtained. The experimental results were obtained. [Experimental results] Selected pulp yield 72.6% Residue rate 2.0% Total yield 74.6% Cut par value 22.5 Hunter whiteness 84.8%

Claims (1)

[Claims] 1 Bast raw materials are mixed with a mixture of oxalic acid or oxalate, hydrogen peroxide or a hydrogen peroxide generator, an alkali metal carbonate, a chelating agent, and water, or a mixture with anthraquinones added thereto. using 60
A method for producing high yield unbleached chemical pulp from bast without bleaching, characterized by carrying out cooking at a temperature of ~130°C.