Study On Biological Modification Of Chitin Size

Chitin and chitosan are natural macromolecular polymers, which belong to amylase of carbohydrate. At present, chitosan is usually used as chitin size. Chitin size owns many excellent properties, for instance, it can form strong film, and it has good abrasion resistance. Besides, it has good biodegradation and biological activity, eminent antibacterial and bacteriostasic activity. However, chitosan is a kind of long chain polymers whose water solubility is bad. Chitosan can only be solved in acidic solution which pH value is about 4.0, which will result in damage to sizing fiber and machine. Furthermore, chitin size has low concentration but high viscosity. Only concentration is 1%～2%, its viscosity will be in direct proportion with concentration. When concentration goes up, the increasing rate of viscosity is much bigger than that of concentration, which result that the size has bad penetration towards sizing fiber. Therefore, it is very meaningful to study how to use enzyme to improve the water solubility of the size and reduce its viscosity properly.At present, there are about three ways to improve the water solubility of the chitin size. First, utilizing the reactive activity of the -OH and -NH₂, chitosan reacts with chemical agents to produce ramifications which have better water-soluble properties. Second, the deacetylation degree (D.D.) of chitosan is controlled at about 50% in mild and homogeneous environment to produce water-soluble chitosan. Last, the long chain of chitosan is cut properly to get water-soluble product, which contain three ways, chemical degradation, physical degradation and biological enzymatic degradation. Compared with other methods, biological enzymatic degradation uses less chemical agents, and has less pollution. Besides, the reactive process and the molecular weight of products can be easily controlled. Enzymatic degradation is a way to use special or non-special enzyme to cut the chain of chitosan properly. Compared with expensive special enzyme, non-special enzyme is cheaper and has broader source. It's more practical to use non-special enzyme in industry.Abundant solid and liquid enzymes were chosen to do the experiments, and liquid cellulase, pectinase and proteinase were found to have obvious effects. Multiple enzymes were made according to the"co-operative effect" between those different hydrolyze enzymes. Lots of experiments and analyses showed that, when multiple enzymes made from cellulase and proteinase deal with chitin size, the pH value of size liquor can be upgraded to around the neuter, and the viscosity of size liquor can be controlled in proper scope. The proper conditions of enzymatic treatment were studied, such as temperature, pH value, react time and the dosage of enzyme. Then the slashing experiment with modified size was done. The performance of size liquor, size film and sized yarns were tested. Besides, the sizing properties of the mixture of chitosan and another size were examined. The reasonable sizing technics were groped for, so as to satisfy the demand of improving the sizing performance of chitin size.Mathematics analyses on experiments data showed that, when multiple enzymes with cellulase and proteinase in the proportion of 2:1 react with chitosan in the condition that the react temperature is 55℃, the ration between enzyme and substrate is 1: 25, and the react time is about 2 hours, chitosan can be dissolved in acetum whose pH value is 6.5, thus water solubility of the size improves a lot. Besides, the viscosity can be easily dominated through controlling the reactive time. Tests showed that the performance of the size liquor, size film, sized yarns were very good, and the sizing performance of chitin size improved.