| Ramie originated in China and is known as "China grass". It is major distributed in the Yangtze River basin. At present, China accounts for90percent of the world’s ramie production. The ramie has good spinnability, wearability, as well as good prospect of development. It is a kind of fine material of textile industry. The major ingredient of ramie is cellulose. In addition to this, the ramie also has a lot of gum, for example, hemicellulose, pectin, lignin and water soluble substances and so on. These non-cellulosic substances are known as gum. These gum need to be removed before the process of spinning. The process of making the ramie fiber separated from each other is called degumming.At present, the methods of ramie degumming are retting and chemical degumming. The retting can be divided into three kinds of methods:natural fermentation, bacteria degumming and enzyme degumming. Bacteria degumming, enzyme degumming and chemical degumming improve the quality of the degummed ramie fiber of natural fermentation to a certain extent. The efficiency of the chemical degumming is high, the time is short, and the quality is stable. However, the process of the chemical degumming is long, energy consumption is large and pollution is serious. Bacterial degumming and enzymatic degumming are usually time-consuming and high-cost. What’s worse, the quality is unstable. However, the bacteria degumming and enzyme degumming just require mild conditions and produce little environmental pollution.According to the characteristics of retting and chemical degumming, the traditional chemical degumming was researched and analyzed in this subject. There are so many problems in the chemical degumming, such as the process is long, the energy consumption is large and the pollution is high and so on. To deal with these issues, the environmentally friendly peroxide—sodium percarbonate is used in the oxidation degumming of ramie. The effects of the temperature, time and dosage of sodium percarbonate on the degumming are analyzed. The experimental results showed that the optimum process of sodium percarbonate degumming was as follows:the temperature is95℃, the time is150minutes, the dosage of sodium percarbonate is18%, chelating agent (EDTA) is2%, sodium tripolyphosphate is2%, alkali penetrating agent is2%, bath ratio is1:12. The optimal case was verified in hualong hemp industry co., LTD. Anhui province and star ramie co., LTD. Hunan province respectively. The results showed that compared with the traditional degumming, the breaking strength of degummed ramie fiber treated by sodium percarbonate degumming attained the level of92percent. Moreover, the doubling of the degummed ramie fiber is better than traditional chemical degumming. XRD analysis showed that the degree of crystallinity of the degummed ramie fiber treated by sodium percarbonate degumming is less than traditional chemical degumming. Thus, the breaking strength of the degummed ramie fiber treated by sodium percarbonate is lower than traditional chemical degumming, which can be explained by the XRD result. From the SEM pictures, readers can see that the gum coated with ramie fiber was removed after the sodium percarbonate degumming. But the cellulose surface was cracked; it meant that the fiber was damaged. The Na element test results also indicated that the cellulose was damaged and oxidized cellulose and alkali cellulose was produced. ATR analysis showed that the gum was removed after the sodium carbonate degumming. But the degummed ramie fiber contained hemicellulose and lignin. The results of the chemical composition of the degummed ramie fiber test results showed that the hemicellulose was still left. The results of the COD, pH and chromaticity test results showed that sodium percarbonate degumming pollution to the environment was far less than the traditional chemical degumming.Sodium percarbonate can produce sodium carbonate and hydrogen peroxide in aqueous solution. Therefore, the research on the decomposition velocity of sodium percarbonate and hydrogen peroxide plays a very important role in improving the effect of sodium percarbonate degumming. The reader found that hydrogen peroxide could maintain relatively stable state when the temperature was70℃under zero in neutral conditions. At the same time, the decomposition velocity of hydrogen peroxide rose with the increasing of the concentration of hydrogen peroxide. Alkaline condition was preferred to neutral condition in the results of the decomposition velocity of hydrogen peroxide. When the sodium hydroxide concentration was constant, the decomposition velocity of hydrogen peroxide rose with the increasing of the concentration of hydrogen peroxide. When the hydrogen peroxide concentration was constant, the decomposition velocity of hydrogen peroxide slowed down with the increasing of the concentration of sodium hydroxide. Therefore, when the hydrogen peroxide was used to bleach the raw materials, the advisable temperature was not less than70℃advisable under the neutral condition. While in alkaline condition, using hydrogen peroxide to treat the ramie, the concentration of hydrogen peroxide was no less than6g/L; along with the concentration of sodium hydroxide was2-4%. In the process of heating, when the ramie raw materials were put into the sodium percarbonate scouring solution, the decomposition velocity of sodium percarbonate was faster that of not adding ramie raw materials to the sodium percarbonate scouring solution. To some extent, this was due to the ramie raw materials containing more dust, metal and so on; these impurities will promoted the invalid decomposition of hydrogen peroxide. At the same time, sodium percarbonate also interacted with the ramie raw materials, thus, the decomposition of sodium percarbonate was faster that of not adding ramie raw materials to the sodium percarbonate scouring solution.In addition, in the process of heating, when the temperature was below80℃and when the ramie raw material was not put into the sodium percarbonate scouring solution, sodium percarbonate could maintain more stable state. As the temperature was rising from80℃to90℃, the decomposition of sodium percarbonate was significant. However, when the ramie raw materials were put into the sodium percarbonate scouring solution, no matter how the temperature changed, the decomposition of sodium percarbonate was obvious. Moreover, when the temperature was90℃, and remained the same temperature, the concentration of sodium percarbonate was close to zero after90minutes. Therefore, when using sodium percarbonate to treat the ramie raw material, the scouring time preferably was around90minutes.In order to make the decomposition speed of hydrogen peroxide stable, avoid or reduce hydrogen peroxide invalid decomposition and oxidation degree of cellulose during the sodium percarbonate degumming, the application of stabilizer on the sodium percarbonate degumming was analyzed in this subject. The results showed that compared with the process of not using the oxygen bleaching stabilize in sodium percarbonate degumming, breaking strength and breaking elongation of the degummed ramie fiber were improved after using the oxygen bleaching stabilizer P5. The results of the Edna group Jiangxi province also showed that the performance of the degummed ramie fiber improved after using the oxygen bleaching stabilizer P5during the process of sodium percarbonate degumming.In order to reduce the amount of sodium percarbonate and the damage of cellulose during the sodium percarbonate degumming, the pectate lyase was used in the process of pretreatment on the ramie degumming in this subject. At the same time, the writer used the oxidizing and bleaching property of sodium percarbonate to treat the ramie treated by pectate lyase. And the writer combined the three processes ("inactivation","scouring" and "bleaching") of the enzyme degumming of the ramie into one process ("sodium percarbonate degumming"). After these, the aim of shortening the process and improving the production efficiency was achieved. Readers found that the requirements of optimal pretreatment process of pectate Iyase-sodium percarbonate degumming were as follows:the temperature was60℃, the time was3hours, the pectate lyase was1.0g/L and the pH was8.5. According to the experimental results of the decomposition velocity of sodium percarbonate, during the process of sodium percarbonate degumming, the writer reduced the time from150minutes to120minutes, the dosage of sodium carbonate from18%to12%and the temperature from95℃to90℃. SEM images showed that the gum was removed after the ramie treated by pectate lyase-sodium percarbonate degumming. ATR analysis indicated that the pectin of the degummed ramie fiber was removed effectively after the pectate lyase-sodium percarbonate degumming. But there were still capable of hemicellulose in the degummed ramie fiber. The test results of the chemical composition of degummed ramie fiber proved the experimental results. XRD analysis results showed that the degree of crystallinity of degummed ramie fiber treated by pectate lyase-sodium percarbonate degumming was less than that of sodium percarbonate degumming. However, the amount of the pectin and the content of residual gum of the degummed ramie fiber were all reduced, and the effect of degumming was more thoroughly, so the breaking strength and the softness of the degummed ramie fiber were improved.To further reduce the content of hemicellulose and the content of residual gum of the degummed ramie fiber, as well as the dosage of sodium percarbonate and the cellulose damage and improve the efficiency of degumming and the quality of degummed ramie fiber, the peracetic acid was used in the process of pretreatment of the ramie degumming. Readers found the requirements of the optimum process of pretreatment of peracetic acid-sodium percarbonate degumming were as follows:the temperature was55℃; the pH was5.0; the time was1.5hours and the peracetic acid was2%. According to the experimental results of the decomposition velocity of sodium percarbonate, during the process of sodium percarbonate, the writer reduced the time from150minutes to120minutes, the dosage of sodium carbonate from18%to12%and the temperature from95℃to90℃. The experimental results showed that breaking strength, breaking elongation and specific breaking work of the degummed ramie fiber treated by peracetic acid-sodium percarbonate degumming were higher than that of the traditional chemical degumming process. But the softness of the degummed ramie fiber treated by traditional chemical degumming was the best-352.49twist/10cm. SEM images show that the gum was removed after the peracetic acid-sodium percarbonate degumming. The hemicellulose and lignin were removed effectively. ATR analysis showed that the content of hemicellulose and lignin had been further reduced. The experimental results of chemical composition have also proved these results. XRD results showed that the degree of crystallinity of degummed ramie fiber had further reduced after the peracetic acid-sodium percarbonate degumming. On account of the content of pectin and hemicellulose reducing, the content of residual gum of the degummed ramie fiber was all reduced significantly. Furthermore, the effect of degumming was more thoroughly, so the breaking strength and the softness of the degummed ramie fiber were further improved. |
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