Preparation Of Enzyme Modified Casein-Chitosan Oligosaccharide-Polyvinyl Alcohol Blend Fiber And Its Wet Spinning Process

Regenerated protein fiber is a kind of chemical fiber.It is a solution rich in protein extracted from natural animals and plants that already exist in nature.It is a green fiber that is considered to be able to replace synthetic fibers prepared by spinning.The advent of regenerated protein fiber not only alleviates people’s pollution to the environment,but also improves resource utilization.At present,the research on regenerated protein fibers is stuck in a bottleneck.The problem is that the protein content is low,the fiber strength is not high,and chemical cross-linking agents are still used in the textile process,etc.,which are not truly green and environmentally friendly fibers.In view of the above problems,In this study,we introduced a small amount of chitosan oligosaccharide and polyvinyl alcohol under the premise of casein content as the main factor,and replaced the post-treatment of chemical cross-linking agent with enzymatic pre-cross-linking to improve the spinnability of casein fibers.while improving its mechanical properties.In this study,we firstly prepared chitosan oligosaccharide/polyvinyl alcohol copolymer by boric acid complexation method,and then grafted it onto casein molecules by enzymatic modification.The glycosylation reaction of chitosan and casein was observed by PAS staining method;Fourier transform infrared spectroscopy（FT-IR）proved the complexation reaction of chitosan oligosaccharide and polyvinyl alcohol;The degree of complexation between chitosan oligosaccharide and polyvinyl alcohol was measured;at the same time,the viscosity of casein with different solid content and its blended spinning dope was measured uncrosslinking,crosslinking and aging.Next,the effect of different components in the coagulation bath on the fiber properties was investigated.The single factor results show that Ca²⁺is related to the formation of fibers,and only Ba²⁺has similar characteristics among the main group elements.The most suitable ratio of the coagulation bath was optimized by using an orthogonal experiment design,and the breaking strength of the fiber was used as an index.The results showed that factors such as barium chloride,calcium chloride,hydrochloric acid,and ethanol in the coagulation bath had an impact on the mechanical properties of the fiber.The optimum coagulation baths for casein fibers were 3%（w/v）BaCl₂,1%（w/v）CaCl₂,2%（w/v）HCl and 40%（w/v）ethanol.The optimum coagulation baths for casein-chitosan oligosaccharide-polyvinyl alcohol blend fibers were 2.5%（w/v）BaCl₂,1.5%（w/v）CaCl₂,1%（w/v）HCl and 55%（w/v）ethanol.The influence of the coagulation bath temperature on the breaking strength of the fibers was studied,and the results showed that the mechanical properties of the fibers were the strongest at room temperature.Finally,the optimal process affecting the drawing of casein and its blended fibers was studied by bench-top wet spinning machine.By changing the temperature of the spinning dope,it is found that the breaking strength of the fiber is the highest when the temperature is 35°C and the viscosity is about 40000m Pa·s.The maximum draw ratio of the fiber after nozzle drawing and post-drawing process is determined.The best drawing process of casein fiber is:the speed of drafting roller 1 is 70 r/min,the speed of drafting roller 2 is 80 r/min,the speed of drafting roller 3 is 90 r/min,and the maximum draw ratio is 5.31.The best process for stretching casein-chitosan oligosaccharide-polyvinyl alcohol blended fibers is:drafting roller 1 rotating speed 70 r/min,drafting roller 2 rotating speed 90 r/min,drafting roller 3 rotating speed 100r/min,the maximum drawing The elongation factor is 7.75.After stretching,the minimum diameter of casein and its blended fibers is 0.08mm,the maximum breaking strength of casein fibers is 144 MPa,and the maximum breaking strength of casein-chitosan oligosaccharide-polyvinyl alcohol blended fibers is 259 MPa.The surface morphology and structure of the fiber showed that the surface of the drawn casein-chitosan oligosaccharide-polyvinyl alcohol blend fiber was smoother and the structure was denser than that of pure casein fiber.