| Hemp fiber is one of the earliest textile fibers people can use and China is the first country of the hemp cultivation.In recent years,with the development of the concept of "green textiles",low toxicity hemp fiber(the content of THC is less than 0.3%)with excellent performance attracts the people's attention once again,such as excellent bactericidal and antibacterial properties,perspiration moisture absorption,soft and comfortable,but the presence of a large number of non-cellulose ingredients such as pectin,hemicellulose and lignin,etc.had a great impact on the development of the hemp fiber.The single hemp fiber with the length of 12 ~ 25 mm is short,the colloid can be used as the adhesive to make the length of the hemp fiber increased,which means that some colloids should be retained in the degumming process.Therefore the refined degumming treatment of the hemp fiber is the basis for the development of hemp fiber.In this paper,the bio-chemical degumming treatment of the hemp fiber was studied in order to realize the controllable degumming with low consumption and high efficienc,especially for the controllable treatment of lignin with stable chemical property in colloids.In the biological treatment stage,lignin-degrading enzyme-laccase was used to degrade lignin in the hemp fiber and its different influencing factors and controllable conditions were analyzed.At the stage of chemical treatment,The optimum selection of different additives in pretreatments and the scouring liquid can not only ensure the cellulose from damage but also ensure the full removal of colloids.It can be divided into four stages: pretreatment,laccase treatment,alkali treatment and degumming treatment.The main contents and conclusions are as follows: Pretreatment: The chemical and physical treatment conditions were optimized and the components of the treated hemp fiber were analyzed.The effects of different pretreatment schemes on the different components of hemp fiber were obtained.The pretreatment included alkali treatment,oxidation treatment and ultrasonic treatment.In the alkali treatment,the orthogonal design experiment method was used with the variables of concentration,temperature,time and liquor ratio.Temperature as the variable was considered in the oxidation treatment and frequency and time as variables in the ultrasonic treatment.The removal rate of gum was taken as the pretreatment measure to express the degumming effect.After getting the best solution of each pretreatment,the treated fibers were analyzed respectively.Finally,it can be concluded that alkali trearment can reach a comprehensive high level in the degumming.Biological enzyme treatment: Based on the above pretreatments,the effect of laccase on the lignin of hemp fiber was studied.The variables of laccase concentration,time,bath ratio and mediator concentration were set up.First,single factor tests were conducted respectively and the lignin content of the treated fibers was used as a measure,it was found that the lignin removal degree showed a positive correlation with laccase concentration and time respectively,and showed a quadratic function relationship with the bath ratio,and the mediator had a great effect on lignin removal while the mediator concentrations had hardly effect on it..Through the optimization test,it was found that the lignin content could reach the expected level.And then by the analysis of Fourier Transform Infrared Spectroscopy on the fibers treated by alkali and laccase,it was found that the colliods especially lignin which had a great influence on the post-processing,had a great degree of degradation and the degradation degree of the cellulose was much smaller.It could be seen that the treated fiber surface became smooth in the SEM photographs.Chemical treatment: Based on the pretreatment of hemp fiber,the effects of different additives on the colloid removal in alkaline boiling solution were investigated.In the experiment,phosphate chelating agent and reducing agent were selected to optimize and the weight loss rate was used as the standard.Trisodium phosphate,sodium tripolyphosphate and sodium pyrophosphate were selected as the chelating agents.It was found that sodium pyrophosphate could achieve good degumming effect under laboratory conditions.The optimization of reducing agent was based on the theory of sulphate cooking,the weight loss rate and fiber tensile strength of hemp fiber were studied respectively after alkali treament with different concentrations of ammonium sulfide and sodium sulfide.Finally,the comprehensive treatment of hemp fiber was carried out.On the basis of the above experiments,hemp fiber was synthetically degummed by biochemical method,and the advantages and disadvantages of biological enzyme-chemical and chemical-biological enzyme treatment were discussed respectively.Gelatin content and lignin content was used to evaluate the degumming effect of hemp fibers and the properties of degummed fibers were characterized by fineness and elongation.In the end the best comprehensive treatment method of hemp fiber was obtained. |
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