Bleaching and dyeing; fluid treatment and chemical modification – Treatment of hides – skins – feathers and animal tissues – Tanning
Patent
1995-07-10
1996-07-02
Willis, Jr., Prince
Bleaching and dyeing; fluid treatment and chemical modification
Treatment of hides, skins, feathers and animal tissues
Tanning
8 9418, 427338, 427389, 252 857, 4284782, 428473, C14C 1100
Patent
active
055317952
DESCRIPTION:
BRIEF SUMMARY
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a 371 of PCT/DK93/00412 filed Dec. 8, 1993, which is incorporated herein by reference.
The invention comprises a method for casein finishing of leather.
It belongs to the prior art that leather can be supplied with a finish of casein which is hardened by means of a hardening agent, such as an aldehyde, an aziridine or an isocyanate. These prior art hardening agents, however, suffer from the disadvantage that they are toxic or even very toxic. This is a most unwanted disadvantage, because operators in leather finishing plants tend to acquire allergy and have their mucous membranes attacked.
Thus, the purpose of the invention is the provision of a method for casein finishing of leather, in which a hardening agent is used which do not suffer from the above indicated disadvantages.
The method according to the invention for casein finishing of leather is characterized by the fact that transglutaminase is added to a solution of casein or partially decomposed casein, and that the transglutaminase containing solution is applied to leather as a coat, whereafter the finished leather is dried.
Thus, in the method according to the invention transglutaminase is used as the hardening agent. Transglutaminase is not a toxic material.
Usually, the addition of transglutaminase to the solution is carried out at a pH value between 5 and 9 and at a peak temperature between 10.degree. and 50.degree. C.
Transglutaminase of all origins can be used in the invention.
It goes without saying that the concentration of Ca.sup.++ in the solution should be at least 0.1-10 mmolar in order to secure a satisfactory activity of the transglutaminase.
In this specification with claims partially decomposed casein means a casein (alpha, beta, and/or Kappa casein) with a degree of hydrolysis (DH) up to 15%, the DH being defined e.g. in "Enzymic Hydrolysis of Food Proteins" by Jens Adler-Nissen, Elsevier Applied Science Publishers Ltd., 1986, page 12-13.
In this specification with claims the term "is applied to leather as a coat" covers one or more of the following types of coats: a base coat, a top coat, and an intermediate coat.
It appears from the above that the method according to the invention comprises three steps: 1 ) addition of transglutaminase to the solution, 2) application of the transglutaminase containing solution to leather, and 3) drying of the finished leather. These three steps may be carried out directly after each other, or some time may elapse between steps 1) and 2) and/or step 2) and 3). If some time elapses between steps 1) and 2), and if in step 2) the viscosity of the solution tends to be too high for easy handling, it may be necessary or recommendable to inactivate the transglutaminase in order to prevent any further viscosity increase. After the end of the application step (i.e. step 2)) ordinarily it is not recommended to inactivate the transglutaminase, because the characteristics of the casein finishing are improved with increasing degree of polymerization. During step 3), the drying step, the transglutaminase will be inactivated, however, if the drying is carried out at high temperature. Usually it is preferred to perform step 1 ), wait for around an hour, and then perform step 2), and immediately thereafter step 3).
It is admitted that it also belongs to the prior art that casein can form a gel by addition of transglutaminase, vide unexamined Japanese patent publication no. 58-149645. However, no indication whatsoever is present in this Japanese patent publication that this process can be used in the leather field.
A preferred embodiment of the method according to the invention is characterized by the fact that the solution of casein or partially decomposed casein also contains one or more normal additives in leather finishing compositions. Typical examples of normal additives in leather finishing compositions are polyurethanes (binders or lacquers), acrylates (lacquers), waxes (agents for generation of a wax or silk like feel), emulsifiers and thickening
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Mollgaard Annette
Petersen Bent R.
Rasmussen Lars
Sorensen Niels H.
Diamond Alan D.
Lambiris Elias J.
Novo Nordisk A S
Willis Jr. Prince
Zelson Steve T.
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