Research On One-Bath Alkali-H₂O₂ Of Degumming And Bleaching Of Hemp

The hemp fiber is the most prospective cellulosic fibre. It has many natural healthcare functions such as good bacterial repellency & inhibition, good absorption-air permeability, shielding radiation, it is emollient, frash and comfortable. What's more, hemp has the ecology-safe-productivity and end-product-recycling, it is the real "green product", many environmental protective textile and non-textile products can be developed from hemp fiber.To make a comprehensive survey, there are three methods for the hemp dugumming: natural fermentation, chemical dugumming and biological degumming. The natural fermentation has many disadvantages such as long processing time, much dependence on the circumstance and having not enough quality assurance; chemical degumming often uses methods of ramie degumming, namely the processes of degumming and bleaching in two steps or more, which has the disadvantages of long process and long treatment time, high cost and consumption; though the biological degumming has little energy consumption, the degumming is incomplete, it need secondary chemical degumming. So new shorten process of one-bath alkali-H2O2 of degumming & bleaching is studied in this paper, the two steps of degumming and bleaching are shortened in one step, which has high efficiency and low consumption. The paper mainly deals with the following:a) On the basis of studying some chemical degumming processes of other bast fibres, a new shorten process of degumming & bleaching in one step will be given.b) A series of tentative optimized experiments are carried out to get the best range of the three parameters: the concentrations of NaOH and H2O2, the treatment time.c) Using the universal rotatable experimental design to obtain the regression equation with high precision and the relations between the main parameters (NaOH and H2O2 concentration and treatment time and the efficiency of cooking off gum and lignin; finding the best degumming technique.d) Analyzing the reaction principles between the reagents such as NaOH and H2O2 and the components of the bast of hemp such as cellulose, semi-cellulose, lignin and pectin, and some tentative experiments are carried out about the principle of alkali and hydrogen peroxide in one bath.After the above researches and experiments, the conclusions could be obtained as follows:1. The new process can not only shorten the degumming time and steps that has achieved the expected "shorten process", but also has an apparent influence to the degumming and can increase spinnability of hemp fiber.2. The three parameters: NaOH and H2O2 concentration and treatment time all apparently affect the percent of gum content in degummed hemp.3. H2O2 density has the apparent influence to the percent of residual lignin in degummed hemp, namely, it mainly affects the content of residual lignin; the influence of NaOH concentration and treatment time are not so obvious to the residual lignin comparatively, especially for the treatment time, it has little influence.4. The best combination of those parameters for the degumming and bleaching of hemp is: H2O2 9.5-10g/1, NaOH 10-11lg/1, treatment time 120-130min.