Solubilized collagen fibers and method for producing the same

Abstract

Provided are novel solubilized collagen fibers with which solubilized collagen can be obtained by instantaneous uniform dissolution in water at the time of use. The solubilized collagen fibers are formed from a solubilized collagen solid content of 66 to 87 wt %, buffer salt content of 2 to 6 wt %, water content of 10 to 22 wt %, and a residual hydrophilic organic solvent content of a trace amount of up to 6 wt % (totaling 100 wt %). The solubilized collagen fibers have an average fineness of 3 to 10 dtx, an isoionic point of 4.5 to 5.0, a water content of 10 to 22 wt %, and residual hydrophilic organic solvent content of a trace amount of up to 6.0 wt %. The solubilized collagen fibers are present uniformly in the direction of fiber length. The buffer salt is selected from sodium citrate, sodium lactate, and sodium phosphate.

1 . A method of producing a solubilized collagen fiber bundle, which comprises:
 (i) a step of subjecting a product obtained by decomposing a skin sample containing insoluble collagen fibers under alkaline conditions to a neutralization and desalting treatment, separating a neutralized and desalted skin sample, and subsequently extracting a solubilized collagen aqueous solution having an isoionic point of pH 5.0 or less, and a step of adjusting pH of the solubilized collagen aqueous solution in presence of a buffer salt to a value within a range from 6.0 to 7.5 which is greater than the isoionic point, thus preparing a solubilized collagen aqueous solution that functions as a solubilized collagen fiber raw material;   (ii) a step of discharging the solubilized collagen aqueous solution obtained in the step (i) into an organic solvent in a thread-like form, spinning the solubilized collagen into a fiber bundle, drawing the spun solubilized collagen fiber bundle by winding, and then immersing the drawn solubilized collagen fiber bundle in a hydrophilic organic solvent; and   (iii) a step of drying the solubilized collagen fiber bundle from the step (ii) by passing the solubilized collagen fiber bundle through nip rollers, introducing a thus obtained solubilized collagen fiber bundle having a reduced water content and a reduced concentration of the hydrophilic organic solvent into a drying tube, forming a moving bed of air inside the tube by blowing sterilized air having a temperature of 30° C. or lower and a relative humidity of 70% or lower into the tube, using the moving bed of air to move and dry the solubilized collagen fiber bundle inside the tube, and then extracting the solubilized collagen fiber bundle from the tube.   
     
     
         2 . A method of producing a solubilized collagen fiber bundle, which comprises:
 (i) a step of decomposing a skin sample containing insoluble collagen fibers using a protein degrading enzyme (protease) and extracting a solubilized collagen aqueous solution having an isoionic point of 7 to 8, and a step of adding an alkali to the solubilized collagen aqueous solution to adjust pH to 9 to 10, using a carboxylic anhydride to succinylate the solubilized collagen and reduce an isoionic point to a pH of 5 or less, subsequently precipitating and separating the solubilized collagen, and then adding an alkali in presence of a buffer salt to adjust pH to a value within a range from 6.0 to 7.5 which is greater than the isoionic point, thus preparing a solubilized collagen aqueous solution that functions as a solubilized collagen fiber raw material;   (ii) a step of discharging the solubilized collagen aqueous solution obtained in the step (i) into an organic solvent in a thread-like form, spinning the solubilized collagen into a fiber bundle, drawing the spun solubilized collagen fiber bundle by winding, and then immersing the drawn solubilized collagen fiber bundle in a hydrophilic organic solvent; and   (iii) a step of drying the solubilized collagen fiber bundle from the step (ii) by passing the solubilized collagen fiber bundle through nip rollers, introducing a thus obtained solubilized collagen fiber bundle having a reduced water content and a reduced concentration of the hydrophilic organic solvent into a drying tube, forming a moving bed of air inside the tube by blowing sterilized air having a temperature of 30° C. or lower into the tube, using the moving bed of air to move and dry the solubilized collagen fiber bundle inside the tube, and then extracting the solubilized collagen fiber bundle from the tube   
     
     
         3 . The method according to  claim 1 , which further comprises: (iv) a step of opening the solubilized collagen fiber bundle obtained in the step (iii). 
     
     
         4 . The method according to  claim 2 , which further comprises: (iv) a step of opening the solubilized collagen fiber bundle obtained in the step (iii).