PROCESS FOR TANNING FISH SKIN

Abstract: A process for tanning fish skin, which process comprises the steps of: a) introducing into the drum-tumbler or any other similar ap­ paratus for the processing of skins, cold water in weight amounts variable between one time and eight times the weight amount of skins to be processed and an amount of salt variable between 2 % and 30 % by weight of the weight of the skins; b) putting said drum-tumbler into rotation for a time period variable between 2 and 45 minutes; c) introducing the skins into said drum-tumbler and let the drum to rotate for a period variable between 5 minutes and one hour; d) introducing into the drum-tumbler an amount variable between 1 % and 10 % by weight of the skins to be processed of a disin­ fectant having preservation properties with regards to said skins and which is compatible with the same, and causing the drum to ro­ tate for a period variable between 5 minutes and one hour; e) introducing into the drum-tumbler an emulsifying agent in amounts 0.3 and 5 % by weight of the skins to be processed and causing the drum to rotate for a period variable between 5 minutes and one hour; f) unloading the whole amount from said drum-tumbler; g) subjecting the skins so treated to an internal cleaning action by removal of the flesh residues attached to the skins; h) weighing the skins so obtained; i) introducing the skins into the drum-tumbler together with an amount of water between 0.5 and 6 times as large as the weight of the skins according to the step h) and with an amount of salt such as to obtain a degree Baumé (B E ) of about 6.5; l) putting the drum into rotation for a period variable between 2 and 30 minutes; m) introducing formic acid progressively till a pH value is obtained between 3 and 4, and causing the drum to rotate further for a period variable between 10 minutes and one hour; n) introducing into the drum-tumbler while it is at a stand­ still an amount of chromium variable between 3 and 30 % by weight of the skins according to the step h); o) causing the drum-tumbler to rotate for a time variable between 1 hour and 20 hours; p) keeping the whole mass at rest about overnight; q) washing the same with running water; and r) arranging the skins so tanned on a beam or the like at rest for at least 36 hours.

Description: The present invention relates to a process for tanning fish skin. More particularly, the present invention relates to a process which allows tanned fish skin to be obtained having optimal characteristics as regards workability and finishing so that finished products can be made from the same which are perfect from a commercial Standpoint. It is well known that the trade of skin articles such as shoes, bags, wallets and the like is ever increasing and is addressing to a definitely large and industrial market. Various different types of animal skins are tanned at the present time on an industrial scale, such as for instance skins of lizards, crocodiles, and a lot of others. The major problems that cause the production costs to increase and accordingly which cause the retail prices to increase also, consist more particularly in difficulties involved in the obtainment of raw material. Moreover, in a number of cases the industrial effort tries to find out new kinds of proposals for customers so as to succeed in acquiring additional market possibilities. As regards this attitude, the competition is increasingly keen and the articles available at the present time do not give many possibilities of changing the production. In WO 84/03718 it is described a process for tanning fish skins comprising the steps of a) contacting dry fish skins with an aqueous solution of a neutral salt said solution having a pH adjusted into the range 1.5 to 3.5; b) subjecting said fish skins to a two step tanning operation wherein after said first tanning step said skins are washed at a temperature of not more than 35°C and the second tanning step is carried out using a more concentrated solution than the first tanning step at a temperature of not less than 35°C; and c) washing the tanned skins and treating them in an aqueous bath with an anionic grease and then an oil and then with an alkali metal salt of a weak organic acid followed by an alkali to raise the pH to at least 6. The object of the present invention is that of providing a process for tanning fish skin, which allows a skin to be exploited as raw material which is available at definitely lower prices with respect to the skins employed at the present time, such as for instance lizard, reptile or crocodile skins. This kind of process allows the skin to be exploited of animals caught for food purposes, so as to avoid killing animals to the only aim of obtaining their skins. Moreover, tanned fish skin is characterized by typical ornamental motifs which, being new with respect to the motifs of the skins processed at the present time can be advantageously exploited for advertisement purposes. Accordingly, it is an object of the present invention that of supplying a fundamental technical teaching for the realization of a process for tanning skin of fish of any kind, and in particular of fish typical of northern seas because of their strength. Skin tanned with the process of the present invention can be both the fresh type and of the type preserved in the wet state and pickled. Accordingly, it a specific object of the present invention a process for tanning fish skin, said process comprising the steps of: a) introducing into a drum-tumbler cold water in weight amounts variable between 1 time and 8 times the weight amount of the skins to be processed and an amount of salt variable in weight between 2 % and 30 % of the weight of said skins; b) causing the drum-tumbler to rotate for a time period variable between 2 and 45 minutes; c) introducing the skins into the drum-tumbler and causing the drum to rotate for a period variable between 5 minutes and 1 hour; d) introducing into the drum-tumbler an amount variable between 1 % and 10 % by weight of the skins to be processed of a disinfectant having preservation properties with respect to said skins and which is compatible with the same, and causing the drum-tumbler to rotate for a period variable between 5 minutes and one hour; e) introducing into the drum-tumbler an emulsifying agent in amounts between 0.3 an 5 % by weight of the skins to be processed, and causing said drum to rotate for a period variable between 5 § minutes and 1 hour; f) unloading the whole mass from the drum-tumbler; g) subjecting the skins so treated to an internal cleaning action so as to remove the flesh residues attached to the same; h) weighing the skins so obtained; i) introducing the skins into the drum-tumbler together with an amount of water between 0.5 and 6 times the weight amount of the skins according to the step h) and with an amount of salt such as to obtain a degree Baumé (B E ) of about 6.5; l) putting the drum-tumbler into rotation for a period variable between 2 and 30 minutes; m) introducing formic acid progressively till a pH value is obtained between 3 and 4, and causing the drum-tumbler to rotate further for a period between 10 minutes and 1 hour; n) introducing into the drum-tumbler while it is at a standstill an amount of chromium between 3 and 30 % by weight of the skins according to the step h); o) putting the drum-tumbler into rotation for a period variable between 1 hour and 20 hours; p) keeping the whole mass at rest about overnight; q) washing with running water; and r) arranging the skins so tanned on a beam or on any other similar device at rest for at least 36 hours. Thus an optimal product has been obtained which is very suitable for being subjected to the usual retanning treatments in the expected periods. Preferably according to the present invention after step p) a further rotation can be carried out for a period of about 30 minutes. Again according to the present invention, said step a) is performed with a water amount at a temperature of 10°C which is four times as large as the weight of the skins to be processed, whereas the amount of salt employed in said step is preferably 10 % by weight of said skins. The rotation time of the step b) is preferably, in the process according to the present invention, of 10 minutes, whereas the rotation of the drum-tumbler according to the step c) of the same process is carried out preferably for 15 minutes. Further according to the present invention, the disinfectant introduced into the drum-tumbler according to step d) is about 3.5 % by weight of the skins and the drum-tumbler is caused to rotate preferably for a period of 15 minutes. More particularly, said disinfectant can be the same as that commercially available under the names of SOLANA S ® (a non-ionic compound made up of emulsifying agents and solvents having the function of detergent, soaking and degreasing) or IMEROLO SJ ® (an ethyleneoxide derivative combined with solvents having the function of detergent, soaking and degreasing). In addition, the emulsifying agent introduced according to the step e) is supplied in amounts of 1 % by weight of the skins to be processed and the drum-tumbler is made to rotate preferably for a time of 15 minutes in order to complete step e). Again according to the present invention, the cleaning action performed on the skins so treated and unloaded after step g) can be carried out by fleshing, by hanging on nails and by shaving or pressing and shaving. Step i) of the process according to the present invention can be performed advantageously with water at a temperature lower than 10°C and in amounts of 2.5 times the weight amount of the skins according to step h) and with an amount of salt of 15 % by weight of the skins. Moreover, said step l) in which the drum-tumbler is made to rotate can be performed for a period of 10 minutes. The progressive introduction of formic acid can be carried out according to the present invention till a pH value is obtained of 3.5 and step m) can comprise preferably a 30 minutes rotation. Further according to the present invention, chromium introduced in step n) can be of the self-alkalizing type (for instance, the product commercially available under the name of BAICROM F ® (chromium basic sulfate) in amounts of 15 % by weight of the skins according to step h) In addition, the rotation of step o) can occur for a period of 8 hours. The rest period of the skins tanned by means of the process according to the present invention can be preferably of 48 hours. With the process according to the present invention, tanned fish skins are obtained which are ready for being subjected to retanning and dyeing treatments. More particularly, a process is suggested according to the present invention of retanning and dyeing of fish skins obtained through the process of the present invention, by which retanning and dyeing procedure a finished product can be obtained that is ready for the refinish procedure and has optimal features, considering that it is possible to treat the products obtained through said procedure by means of the usual retanning and dyeing treatments so as to obtain equally good quality skins that are ready for the refinish treatment. Moreover, it is also an object of the present invention a retanning treatment of fish skins obtained through the procedure disclosed above, which treatment comprises the step of: 1) blubbering the skins in water at a temperature between 20°C and 50°C in amounts of 0.5-8 times as large as the weight of the skins according to step h) of the process, with a blubbering agent in amounts between 0.5 and 10 % by weight of skins according to step h), causing the drum-tumbler to rotate for a period variable between 10 minutes and 2 hours; 2) unloading the drum-tumbler by taking out the liquid and leaving the skins behind; 3) introducing into the drum-tumbler a water amount of 0.5-8 times the weight amount of the skins according to step h), at a temperature between 20°C and 60°C, and adding an amount between 0.5 and 10 % by weight of said skins of a neutralizing agent and causing the drum-tumbler to rotate for a time between 5 minutes and 2 hours; 4) adding an amount of a product of a tannin -base vegetable origin in amounts between 1 and 10 % by weight of the skins according to step h) and causing the drum-tumbler to rotate for a time variable between 10 minutes and 1 hour; 5) unloading the bath; 6) washing the skins in running water for a time variable between 5 and 10 minutes and unloading the bath; 7) blubbering (padding or stuffing) the skins so obtained by introducing a water amount at a temperature between 20°C and 80°C, said amount being variable between 1.5 and 8 times the weight amount of the skins according to step h), and with an amount variable between 1.5 and 30 % of said weight of the skins of a softening agent; 8) causing the drum-tumbler to rotate for a period between 5 minutes and 2 hours; 9) carrying out a vegetable retanning by adding an amount variable between 2 % and 50 % by weight of the skins according to step h) of the process, of a tannin-base vegetable product and causing the drum-tumbler to rotate for a period variable between 5 minutes and 2 hours. At that point the skins so obtained are completely finished so that the bath can be unloaded and the dyeing treatment can be performed next or otherwise the dyeing treatment can be carried out in the bath itself without unloading the same. Preferably, the dyeing process is carried out through the following steps: 10) adding dyes to the bath; 11) adding formic acid in amounts variable between 0.5 and 10 % by weight of said weight of the skins and causing the drum-tumbler to rotate for a time variable between 10 minutes and 2 hours; 12) unloading the bath. Preferably according to the present invention the blubbering of the skins can be performed with water at a temperature of 35°C, water being present in amounts twice as large as said weight, and with an amount of the blubbering agent equal to 2 % of that weight, and causing the drum-tumbler to rotate for 40 minutes. Again according to the present invention, step 3) of the retanning process can be carried out with water at 40°C in amounts twice as large as the weight of the skins according to step h) and with an amount of the neutralizing agent equal to 2 % of the same weight, and causing the drum-tumbler to rotate for 20 minutes. In addition, the tannin-base product can be added according to step 4) in amounts of 5 % by weight and the rotation can be performed for 40 minutes, said product being for instance the TAMOL GA ® (chromium salt). Further according to the present invention the blubbering (padding or stuffing) operation of the skin can be carried out with amounts of water at 55°C three times as large as the weight of the skins as defined above and employing an amount of 8 % by weight of the softening agent. Sais softener can be made up of 5 % of GLICERMAX 52 ® (lubricating oil) and 3 % of SERIDOL 82 ® (lubricating oil). The first of said products acts as a softening agent whereas the second one avoids the fact that the so-called "grain" or the top part of the skin itself be affected too much by the action of the first product. The rotation for realizing the blubbering step may last by preference 30 minutes. The vegetable retanning according to step 9) can be carried out by adding preferably an amount of the vegetable product equal to 13 % of the weight of the skins as defined above and causing the drum-tumbler to rotate for 30 minutes. More particularly the retanning can be performed by adding 5 % by weight of TAMOL GA ® and 8 % by weight of TANIGAN OS ® (methylene linkage condensate of hydroxides and arylsulphonic acids). In the dyeing step formic acid can be preferably added in amounts equal to 2 % by weight of the skins according to step h) causing the drum-tumbler to rotate for about 40 minutes. At that point the product is completely finished and it is ready for being subjected to the usual refinish operations.

Claims: A process for tanning fish skin comprising the steps of: a) introducing into a drum-tumbler cold water in weight amounts between 1 time and 8 times the weight of the skins to be processed and an amount of salt variable between 2 % and 30 % by weight of the weight of the skins; b) putting the drum-tumbler in rotation for a time between 2 and 45 minutes; c) introducing the skins into the drum-tumbler and causing the same to rotate for a time between 5 minutes and 1 hour; d) introducing into the drum-tumbler an amount between 1 % and 10 % by weight of the skins to be processed of a disinfectant having preservation properties with respect to the skins and which is compatible with the same, and causing the drum-tumbler to rotate for a period variable between 5 minutes and 1 hour; e) introducing into the drum-tumbler an emulsifying agent in amounts between 0.3 and 5 % by weight of the skins to be processed and causing the drum-tumbler to rotate for a period between 5 minutes and 1 hour; f) unloading the whole mass from the drum-tumbler; g) subjecting the skins so treated to an internal cleaning action by removing the flesh residues attached to the same; h) weighing the skins so obtained; i) introducing the skins into the drum-tumbler together with an amount of water between 0.5 and 6 times the weight of the skins according to the step h) and together with an amount of salt such as to obtain a degree Baumé (B E ) of about 6.5; l) putting the drum-tumbler in rotation for a period between 2 and 30 minutes; m) introducing formic acid progressively till a pH value is obtained between 3 and 4, and causing the drum-tumbler to rotate further for a period between 10 minutes and 1 hour; n) introducing into the drum-tumbler while it is at a standstill an amount of chromium between 3 % and 30 % of the weight of the skins according to the step h); o) putting the drum-tumbler in rotation for a period between 1 hour and 20 hours; p) keeping the whole mass at rest about overnight; q) washing with running water; and r) arranging the skins so tanned on a beam or any other similar device at rest for at least 36 hours. A process according to claim 1, wherein after step p) a rotation of the drum-tumbler is performed for a period of about 30 minutes. A process according to claim 1, wherein said step a) is carried out by introducing water at a temperature of 10°C in amounts of 4 times the weight amount of the skins to be processed and an amount of salt of 10 % by weight of the skins. A process according to claim 1, wherein the rotation according to step b) is performed for 10 minutes. A process according to claim 1, wherein the rotation according to step c) is carried out for 15 minutes. A process according to claim 1 wherein step d) is carried out by introducing an amount of a disinfectant equal to 3.5 % by weight of the skins and by rotating the drum-tumbler for 15 minutes. A process according to claim 1, wherein said step e) is performed by introducing an amount of the emulsifying agent equal to 1 % by weight of the skins to be processed and causing the drum-tumbler to rotate for about 15 minutes. A process according to claim 1, wherein the cleaning action according to step g) is carried out through the operations of fleshing, hanging on nails and shaving or pressing and shaving. A process according to claim 1 wherein step i) is carried out by introducing into the drum-tumbler, together with said skins, also an amount of water at a temperature lower than 10°C, equal to 2.5 times the weight of the skins according to the step h) and an amount of salt equal to 15 % by weight according to step h). A process according to claim 1, wherein the rotation according to step 1) is carried out for about 10 minutes. A process according to claim 1 wherein step m) is carried out through the introduction of formic acid in amounts equal to those that are required to obtain a pH value of the bath of 3.5, and causing the drum-tumbler to rotate for 30 minutes. A process according to claim 1, wherein step n) is carried out through the introduction of an amount of chromium equal to 15 % by weight of the skins according to step h). A process according to claim 1 or 13, wherein said chromium is of the self-alkalizing type. A process according to claim 1, wherein the rotation of the drum-tumbler according to step o) is performed for a time of 8 hours. A process according to claim 1, wherein the rest period according to step r) lasts 48 hours. A retanning treatment of fish skins obtained by means of the process according to any one of claims 1-15, said retanning treatment comprising the steps of: 1) blubbering the skins in water at a temperature between 20°C and 50°C in amounts between 0.5 and 8 times the weight amount of the skins according to step h) of the process, introducing a blubbering agent in amounts variable between 0.5 and 10 % by weight of the skins according to step h) and causing the drum-tumbler to rotate for a period variable between 10 minutes and 2 hours; 2) unloading the drum-tumbler taking out the liquid out of the same and leaving the skins behind; 3) introducing into the drum-tumbler a water amount between 0.5 and 8 times as large as the weight of the skins according to step h) and having a temperature between 20°C and 60°C, adding an amount variable between 0.5 and 10 % by weight of said skins according to step h) of a neutralizing agent and causing the drum-tumbler to rotate for a period variable between 5 minutes and 2 hours; 4) adding an amount of tannin-base vegetable origin product variable between 1 and 10 % by weight of the skins according to step h) and causing the drum-tumbler to rotate for a period variable between 10 minutes and 1 hour; 5) unloading the bath; 6) washing the skins with running water for a period between 5 minutes and 10 minutes and unloading the bath; 7) blubbering the skins so obtained introducing water at a temperature between 20°C and 80°C in amounts between 1.5 and 8 times as large as the weight of the skins according to step h) and an amount between 1.5 and 30 % by weight of the skins according to step h) of a softening agent; 8) causing the drum-tumbler to rotate for a period between 5 minutes and 2 hours; 9) retanning the material by means of a vegetable retanning process through the addition of an amount of a tannin-base vegetable origin product between 2 % by weight and 50 % by weight of the skins according to step h) and causing the drum-tumbler to rotate for a period between 5 minutes and 2 hours. A treatment according to claim 16, wherein the blubbering step 1) is performed with water at a temperature of 35°C and in amounts twice as large as the weight amount of said skins and with an amount of the blubbering agent equal to 2 % of the same weight of the skins, causing the drum-tumbler to rotate for 40 minutes. A treatment according to claim 16, wherein step 3) is carried out by the introduction of water at 40°C in amounts twice as large as the weight amount of the skins according to step h) and of an amount of a neutralizing agent equal to 2 % of the same weight, and causing the drum-tumbler to rotate for 20 minutes. A treatment according to claim 16, wherein step 4) is performed by the addition of an amount of 5 % by weight of the skins according to step h) of the tannin-base vegetable origin product and causing the drum-tumbler to rotate for 40 minutes. A treatment according to claim 16, wherein step 7) is performed through the introduction into said drum-tumbler of an amount of water at 55°C three times as large as the weight amount of the skins according to step h) and of an amount of the softener equal to 8 % by weight of the weight amount of said skins. A treatment according to claims 16 or 20, wherein the rotation according to step 8) is carried out for a period of 30 minutes. A treatment according to claim 16, wherein step 9) is performed through the addition of a tannin-base vegetable origin product in amounts equal to 13 % by weight of the weight amount of the skins according to step h) and causing the drum-tumbler to rotate for 30 minutes. A treatment according to one of claims 16-22, wherein a dyeing process is carried out after step 9), said dyeing process comprising the steps of: 10) adding the dyeing agents into the bath; 11) adding formic acid in amounts variable between 0.5 and 10 % by weight of the skins according to step h) and causing the drum-tumbler to rotate for a time between 10 minutes and 2 hours; and 12) unloading the bath from the drum. A treatment according to claim 23, wherein step 11) is performed introducing an amount of formic acid of 2 % by weight of the weight amount of skins according to step h) and causing the drum-tumbler to rotate for 40 minutes.

Inventors: DEL GAUDIO, ANTONIO, RENZULLI, FRANCESCO, RENZULLI, PIERO
Applicants: CO.GE.IT COSTRUZIONI GENERALI ITALIANE S.R.L.
Application year: 1987
Main classification: C14C13
IPC codes: C14C3, C14C13