FIELD OF INVENTION
This invention in general pertains to Leather Industry. More particularly the invention is concerned with manufacturing value added leather. Especially this invention is concerned with manufacturing value added leather from Fish skin.
This invention is unique as it utilizes waste material to make value added products. The upper thick skin of Stingray fish is not eaten. The pebbles on the dorsal side of the skin are made of keratin, which is not digestible, hence not consumed for food. Several thousand tons of ray fish are caught annually and the raw material is available in plenty in our country. Sting Ray species Dasyatis bleekeri has a very thick skin on the dorsal side with regularly arranged pebbles. We have developed an invention by way of a novel process to make leather out of this skin.
Stingray leather is not only a major value-addition to the fish skin, but also
a unique leather by itself. Its properties are unique. It is the toughest and strongest leather. This
leather scratch proof and fire proof unlike the cow, goat and sheep leather.
For want of technical know-how this value-added product could not be developed so far. Technical expertise is required in every step from de-skinning to tanning. At the fish landing centers, the skin of this fish should be removed carefully without damage. Any flay cut while removing the skin or any deep cut in the skin while de-skinning makes the skin useless. The skin should then be preserved carefully so that its shelf-life should be at least 15 days because it has to be taken to a tannery for further processing. Care should be taken to remove the anterior portion of the skin carefully as it is attached with the bone and cartilage of the fish, similarly the portion near the eyeballs should also be carefully handled while removing the skin. A small portion of tail can be removed along with the skin. Only the pebbled or the stone area of the skin is useful. Other portion of the skin is not removed.
It is the primary object of the invention is to develop a novel process of manufacturing value added exotic (new) leather from Fish Skin.
It is another object of the invention is to develop a novel process of manufacturing value added leather product from Fish Skin wherein the manufactured leather is scratch proof
It is another object of the invention is to develop a novel process of manufacturing value added leather products from Fish Skin wherein the manufactured leather is the fire proof.
Further object of the invention will be clear from the following description:
The nature of the invention and the manner in which it is to be performed will be clearly described in the following specification. The entire process of manufacturing value added product from waste material such as fish skin is clearly explained. Further the advantages of the invention will be clearly stated.

The invention was not thought off earlier because; the leather technology was in the hands of traditionalist. All the R&D efforts were focused on the finish quality of conventional leathers and also on product development. Nobody could think on non-conventional innovative resources. There are still many non-conventional resources, which can be tapped to make quality leather like the viscera of animals, skin of birds etc.
The major impediment in the development of this technology is to make the skin soft. This skin is very hard, thick, tough and rough. Once it is turned into leather it becomes more hard and un-pliable. Our major effort was to makes this skin more flexible, pliable through our process. Besides sophistication it required patience to develop ray fish skin leather. It is a painstaking effort to test different processing and tanning chemicals in different concentration for different periods.
PROCESS
There are different stages in the process:
1. De-Skinning the fish: the usable pebbled area alone is removed
2. Curing and Preservation of skin in brine
3. Soaking - Prolong soaking with bactericidal compound
4. Liming ~ Quick liming
5. Degreasing with kerosene
6. De-Liming - with Ammonium sulphate
7. Pickling - with two acid combination
8. Eco - Friendly tanning using multifunctional phosphonium compound.
9. Dyeing to make value added finished leather
The entire sequence of the process of manufacturing value added leather from skin of fish is shown in the form of flowchart which is as follows:

SALIENT FEATURES
Salient feature of the invention is the use of multifunctional phosphonium compound at 2-4% concentration. The end result of this process is the production of WET WHITE in contrast to the conventional 'Wet Blue'.
Another salient feature is the using of alkaline bate of higher activity in two doses of concentration ranging from 1-2%. The strength/activity of the bate is 1500-3000 IU. The detail procedure is shown in the table of 'Fish Leather Process' annexed here and above.
Further salient feature is the use of Kerosene as a degreasing agent. This reduces the cost and also effective for ray fish skin.
ADVANTAGES
Stingray fish skin is though small but very strong and durable. Therefore, it can be utilized in different ways. Many leather articles can be made out of it. We can make leather wallets, ladies bags, belts and shoes. Many innovative articles can also be made. These skins can be used for making motorcycle seats, can be used on furniture and at many other decorative places. This leather can be used as padding leather for sportsmen wear to prevent injury. The most import use is that the Wet White can be used to dye the leather in very light pleasant colours
Once produced commercially, this leather has an export market. It can be a major foreign exchange earner for the country. This leather industry when developed can also given employment to fisher women and many poor families in tanneries.

We Claim:
1. We claim a process of manufacturing leather from Stingray fish skin,
Dasyatis bleekeri (also known as Himantura bleekeri) is characterised
that it comprises of the following.
a.Using Eco-friendly non-metallic tanning agent for tanning fish skin, b.Using Kerosene as a cheaper degreasing agent. c.Low concentration of lime and high concentration of bate. d.Two acid combination during pickling.
2. We claim a process according to claim 1 in the production of fish leather wherin eco-
friendly non-metallic tanning compound used is a multifunctional phosphonium
compound which is relatively non toxic than the chrome or aluminium metal compounds
usually used for tanning animal skins. This phosphonium compound is technically a
hydroxy methyl phosphonium. This is photodegradable, biodegradable and breaks
down by hydrolysis and oxidation also.
3. We claim a process in claim 2 where in the phosphonium compound used in to 2-4%
concentration to give softness to the fish skin besides tanning it in white. The resultant
product of this tanning is called WET WHITE (the conventional chrome tanning results
in "Wet Blue"). The Phosphonium chrome-free tanning process starts at pH 4.5 and
completes at pH 5.5 with basification.
4. We claim in the process of claim I wherein commercial (domestic grade)
Kerosene is used as a degreasing agent for fish skin, which is cheaper and better
functional in the case of Dasyatis bleekeri.
5. A process according to claim 4 wherein the concentration of Kerosene used
as degreasing agent is 2-3%.
6. We claim a process in claim 1 wherein the pH at pickling is brought down
below 3.5 by a combination of two acids.
7. We claim a process according to claim 6 wherein the acid combinations used are sulphuric acid (inorganic acid) and formic acid (organic acid) in 1-2% and 2-4% concentration respectively.
8. We claim a process of manufacturing leather from fish skin as given in the complete specification.