Classifications

• • C—CHEMISTRY; METALLURGY
  • C14—SKINS; HIDES; PELTS; LEATHER
  • C14C—CHEMICAL TREATMENT OF HIDES, SKINS OR LEATHER, e.g. TANNING, IMPREGNATING, FINISHING; APPARATUS THEREFOR; COMPOSITIONS FOR TANNING
  • C14C1/00—Chemical treatment prior to tanning
  • C14C1/06—Facilitating unhairing, e.g. by painting, by liming
  • C14C1/065—Enzymatic unhairing

Definitions

• ExaminerGary M. Nath AltorneyCurtis, Morris & Safford ABSTRACT Process for dehairing skins and hides by treatment thereof, at a pH less than 5, with a mold-fungus protease showing its optimum effect at a pH below 5, with pepsin, with papain, or with a combination of these enzymes.
• the present invention relates to processes for the enzymatic dehairing of skins and hides.
• the enzymatic dehairing of skins and hides has up till now been carried out in a weakly acid to weakly alkaline region with proteolytic enzymes which exert their optimum effect within this region.
• proteolytic enzymes include the majority of enzymes obtained from mold fungi or bacterial cultures, as well as pancreatic enzymes.
• the known dehairing processes have the disadvantage that the undesired growth of bacteria and fungi in the dehairing bath must be hindered by preservatives. This precaution is critically necessary, particularly in tropical countries, and leads to a corresponding increase in the cost of the process.
• a process for dehairing using proteolytic enzymes has now been found according to which skins and hides are treated under nonswelling conditions at pH values below 5 with proteolytic enzymes exhibiting their optimum effect at pH values below 5, and/or with pepsin, and/or with papain. The hair is subsequently removed.
• pepsin and papain are of particular importance. They can be used alone or together, optionally also in combination with other kinds of enzymes.
• the most favorable working region is between pH 3 and 5, and the optimum efficacy for the process of theinvention is observed at about pH 4.
• Papain is preferred in the pH region 4.0 to 5.0.
• the enzyme bath should contain, for example, from 0.1 to 0.5 percent, calculated on the softened weight of the hides, of an enzyme product having an enzyme activity of 55,000-60,000 EZA. At a working temperature of 40 C., hair can be removed in from 24 to 48 hours.
• EZA Enzyme activity, is determined using hemoglobin as a substrate.
• the substrate is prepared by suspending 4.6 grams of hemoglobin in 143.4 ml. of water. After hours standing at 5 C., 80 grams of urea are added to the mixture, which is heated to 25 C. and combined with 32 ml. of 0.5 N aqueous NaOH and 20 ml. of a 1 N aqueous KH P O, solution. The final mixture has a pH of 7.5.
• the process can be practiced in such a manner that the hides and skins are immersed in a nonswelling enzyme bath.
• a nonswelling enzyme bath it is also possible first to treat the hides and skins in an enzyme-free, acid, nonswelling bath adjusted to a pH below 5, and then to take them out of the bath and to treat them from the flesh side with an enzyme preparation in powder or paste form.
• a further advantage of the process is that it leads to a complete destruction of pigmentation while extensively preserving the skin substance.
• the process of the invention can advantageously be combined with oxidative dehairing, which also takes place in an acid region.
• oxidative dehairing For the dehairing of calf and goat skins, cowhide, pigskin and the like, a small residuum of hair often remains. This can be completely removed using about one third of the amount of sodium chlorite usually employed in the art for oxidative dehairing, whereby the grain is not attacked. [Oxidative dehairing processes are discussed in the article by K. Rosenbusch on pages 1 19-121 of Das Leder" 1964).]
• the weights of treating agent are expressed in percent by weight of the hides treated.
• the EZA values for the pepsin used in examples 1, 5, and 7 were determined at a pH of 4; the EZA of the commercial enzyme product of example 6 was determined at pH 5.
• the procedure used was as described earlier, but employed a buffer system other than NaOHlKH Po EXAMPLE 1
• the initial pH value of the bath was 3.0-3.3.
• the treatment time in the dehairing bath was 24 hours. After this period, the bath had a pH of 4.0-4.3.
• the skins were subsequently dehaired in the usual fashion.
• the treatment time amounted to 24 hours. During this time, the hides were paddled 3 or 4 times for S-minute periods. Dehairing was subsequently accomplished in the usual way.
• the bacterial protease comprised 15,000 Loehlein- Volhard units [cf. Gerschenemisches Taschenbuch, by A. Kuentzel, Verlag Th. Steinkopff, Dresden and Leipzig 1955 86.]86.
• a process as in clai r n l wh rei n said enzyme is papain.

Landscapes

• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Treatment And Processing Of Natural Fur Or Leather (AREA)
• Cosmetics (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=5700019

Family Applications (1)

Country Status (6)

Cited By (7)

Citations (3)

• 1969
  • 1969-01-09 CH CH19569A patent/CH515994A/de not_active IP Right Cessation
  • 1969-02-10 DK DK70169AA patent/DK126861B/da unknown
  • 1969-03-12 FR FR6906974A patent/FR2006170A1/fr not_active Withdrawn
  • 1969-04-10 US US815236A patent/US3623950A/en not_active Expired - Lifetime
  • 1969-04-11 CA CA048437A patent/CA919606A/en not_active Expired
  • 1969-04-14 GB GB09043/69A patent/GB1235422A/en not_active Expired

Patent Citations (3)

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