Title of Invention | A PROCESS FOR PREPARATION OF LEATHER LIKE SHEET |
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Abstract | A leather like sheet and its process of preparation by way of coating collagen us particle on fabric surface are disclosed, thereby providing not only an economic option for effective utilization of the solid wastes generated in leather industry, but also a suitable cost effective material for making different consumer products. |
Full Text | The present invention relates to a process for preparation of leather like sheet. More particularly, the present invention relates to a process for the preparation of leather like sheet using fabric and solid wastes generated during leather manufacture. The process of the invention has enormous potential application in leather processing industry for utilizing some of the solid wastes for making value added sheet and the sheet prepared thereby is envisaged to have application potential as excellent raw material in variety of consumer product industries. Significant quantities of solid wastes are generated during leather processing. As reported by Muralidharan et.al (Leather Research Industry Get-together Pre prints, pp 1-8, 1996 ) for every one gm. of hide processed, only 0.5 gm. of finished leather is obtained, which implies nearly 50% of leather forming material emanates as wastes. These wastes include raw hide trimmings, hair, fleshings, tanned leather trimmings, shavings and buffing dust. While raw hide trimmings and fleshings are being used for preparation of glue and gelatin, the tanned trimmings and shavings have been in use for manufacture of leather boards, which find application as base material in footwear and leather goods industries for making select group of products, because of the constraints exhibited in terms of flexibility. Buffing dust, a waste generated during cleansing of flesh side of leather, is primarily dumped as waste, thereby creating a major disposal problem of severe environmental concern. It is also sometimes used as fuel for boilers after conversion to briquettes, whereby it leads to formation of chromium (VI), which is a carcinogen. Hence, there exists a restriction for burning buffing dust. Consequently the disposal of buffing dust has remained an unresolved technological and environmental problem. On the other hand, there is a growing demand for leather in the consumer market for its elegance. But the supply does not commensurate with the demand. Being a natural material, leather has limitations with reference to its availability. This limitation in terms of the demand-supply gap on the one hand and the high price of leather on the other hand has prompted the consumer product industry to explore possibilities of using different materials, which are similar at least visually. Thus various efforts on producing leather like materials or synthetic leather through different approaches have been gaining significant recognition, thereby making visible impact on the consumer products industry. Most of these approaches involve coagulation of a polymeric matrix on fabrics and then printing them to various designs including the grain patterns, which are exhibited by genuine leather. These materials resemble leather because most of the leathers are finished using polymeric film forming materials on the surface of the leathers. Typically finishing involves, as reported in Leather Finishing Manual, Pp 34, prepared by Indofil Chemicals Ltd, formation of multi layer film on the surface of the leather using film forming polymer, which may optionally be used along with pigments, plasticisers and feel modifiers. The said ingredients are mixed in suitable proportions and then applied on the leather surface by spraying or brushing, thereby facilitating the formation of film thereon. The design of the coating film may be modified by embossing or plating. It is also a practice to apply a curing agent on top of the multi layer film in order to enhance the durability of the finish. While the major advantage of the leather like materials is that they are cheaper compared to leather, they are constrained by the absence of 'leathery' property because of the absence of collagen us materials in them. No prior art is available on the use of any collagenous material for making leather like sheet. The main objective of the present invention is to provide a process for preparation of leather like sheet, which obviates the limitations as stated above. Another objective of the present invention is to provide a cost effective product for fabrication of consumer articles with elegant appearance of leather. Yet another objective of the present invention is to provide a profitable method of solid waste disposal generated during leather manufacture. Accordingly the present invention provides a process for preparation of leather like sheet which comprises : (i) coating a fabric surface with a film forming polymer by conventional coating method , (ii) topping the above said coated fabric with tanned collagen us powder of particle size not exceeding 80 mesh, (iii) drying the above fabric obtained in step (ii), at a temperature not exceeding 80°C for a period of at least 10 minutes and removing unfixed powder by known method, (iv) repeating the steps (i) to (iii) for at least four times followed by conventional finishing of the surface to obtain leather like sheet. In an embodiment of the present invention, the film forming polymer used may be selected from poly acrylate, polyurethane, polybutadiene. In another embodiment of the present invention, the method for coating of film forming polymer may be selected from spraying, brushing. In yet another embodiment of the present invention, the fabric used may be selected from knitted, woven. In another embodiment of the invention the film forming polymer used may be at least 5 ml per square ft. In still another embodiment of the invention the film forming polymer may be used as aqueous emulsion of concentration of at least 50 % v/v. In still another embodiment of the present invention, the method used for topping by tanned collagen us powder may be selected from sprinkling, spreading In yet another embodiment of the present invention, the collagen us powder used may be selected from buffing dust, leather powder either individually or in combination. In still another embodiment of the present invention, the method used for removal of unfixed collagen us powder may be selected from brushing .shaking. Accordingly the present invention provides a leather like sheet, prepared by the above process. The process of the present invention is described below in detail. A fabric surface is coated with at least 5 ml of film forming polymer, which is used either as such or as aqueous emulsion of concentration not less than 50% v/v, for every sq.ft of fabric by conventional method. The coated fabric surface is then topped with 3-6 gms of tanned collagen us powder of particle size not exceeding 80 mesh, per sq. ft of the fabric by known method. The resulting material is dried by known method at a temperature not exceeding 80°C for a period of not less than 10 minutes and the unfixed particles are removed conventionally. The above steps are repeated for not less than four times. Finally, the coated fabric is finished by conventional method of leather finishing to obtain leather like sheet. Novelty as well as non-obviousness of the present invention lies in the fixing of tanned collagen us powder of particle size restricted to a maximum of 80 mesh on fabric surface with the help of film forming polymer in such a way as to form a continuous coating thereon, resulting in a value added leather like sheet thereby suggesting a method of gainful utilization of solid waste. The invention is described in detail with reference to the examples given below which should not however be construed to limit the scope of the present invention. 50ml of acrylic binder was mixed with 50 ml of water and applied on 10 sq.ft of a knitted fabric by brushing. 30 gms of buffing dust, collected after screening through 80 mesh screen was then sprinkled and rubbed manually on the fabric. The composite was then air dried for a period of 30 minutes at 35 °C. The unfixed buffing dust was removed by shaking. The process of binder application and subsequent buffing dust adhesion continued for 5 times. Then the buffing dust coated fabric was finished in the following way. The finishing coat was prepared in a beaker using the following composition. Three full cross-coats of the above finishing mixture were sprayed on the buffing dust coated side of the fabric manually with intermittent drying. The coated fabrics were then sprayed manually with topcoat of following composition. Lacquer emulsion (Table Removed) Finally, the coated fabric was subjected to air drying followed by plain plating at 80°C. The resulting leather like sheet was stored for making products. Example 2 100ml of polyurethane binder was sprayed on 20 sq.ft of a knitted fabric. 120 gms of leather powder collected after screening through 80 mesh screen was then spread and rubbed on the fabric. The composite was then dried for a period of 10 minutes in hot air room at 80° C. The unfixed leather powder was then removed by brushing. The process of binder application and subsequent leather powder adhesion continued for 4 times. Then the leather powder coated fabric was finished in the following way. The finishing coat was prepared in a beaker using the following composition. (Table Removed) Four full cross-coats of the above finishing mixture were sprayed on the buffing dust coated side of the fabric manually with intermittent drying. The coated fabrics were then sprayed manually with topcoat of following Finally, the finished coated fabrics were subjected to air-drying followed by printing with goat grain at 75°C. The resulting leather like sheet was stored for making products. Example 3 100 ml of Butadiene binder were mixed with 100ml of water and sprayed on sq.ft of a woven fabric. 80 gms of collagen us powder containing both buffing dust and leather powder was then sprinkled and rubbed on the fabric. The composite was then dried for a period of 20 minutes in hot air room at 50 ° C. Th unfixed collagen us powder was then removed by brushing. The process of binder application and subsequent collagen us powder adhesion continued for times. Then the coated fabric was finished in the following way. The finishing coat was prepared in a beaker using the following composition. Three full cross-coats of the above finishing mixture were sprayed on the buffing dust coated side of the fabric manually with intermittent drying. The coated fabrics were then sprayed manually with topcoat of following composition. (Table Removed) finally, the finished coated fabrics were subjected to air-drying followed by printing with cow grain print at 80°C. The resulting leather like sheet was stored for making products. The leather like sheets prepared as per examples 1,2 and 3 were subjected to physical characteristics evaluation similar to that for leather meant for similar purpose. The values obtained for the leather like sheets of the present are given below . corresponding data for conventional nappa leather are also cited in the following table since the leather like sheets prepared are envisaged to be used for making products which are usually made from nappa leather. (Table Removed) Presently promerics , rexins etc. are considered as synthetic leather materials which are prepared by depositing polymers on the fabrics surface and printed with different designs to appear like leather. But so far as feel and other physical characteristics are concerned they are far from leather . But in the present invention , the caliginous powder (leather powder) is applied on the fabric using binders to produce a leather like feel and appearance . The product of the present invention is thus much closer to leather because of the use of collagen use matter on the fabric . Apart from the product resembling leather in organoleptic and strength properties . The process provides a lucrative and viable solution for disposal of solid waste generated during leather manufacturing. The advantages of the present invention are the following 1. The process methodology is simple and cost effective. 2. The technology while providing a process for preparation of leather like sheets solves one of the major solid waste disposal problem of leather processing industry. 3. The process has high degree of reproducibility. 4. The technology does not call for use of any sophisticated machinery or specialty chemicals. We claim 1. A process of preparation of leather like sheet which comprises: (i) coating a fabric surface with a film forming polymer by conventional coating method , (ii) topping the above said coated fabric with tanned collagen us powder of particle size not exceeding 80 mesh (iii) drying the above fabric obtained in step (ii), at a temperature not exceeding 80°C for a period of at least 10 minutes and removing unfixed powder by known method, (iv) repeating the steps (i) to (iii) for at least four times followed by conventional finishing of the surface to obtain leather like sheet. 2. A process, as claimed in claim 1, wherein the method for coating of film forming polymer is selected from spraying, brushing 3. A process, as claimed in claims 1 and 2, wherein the film forming polymer used is selected from poly acrylate, polyurethane, polybutadiene. 4. A process, as claimed in claims 1 to 3, wherein the fabric used is selected from knitted, woven. 5. A process as claimed in claims 1to 4 wherein invention the film forming polymer used is at least 5 ml per square ft. 6. A process as claimed in claims 1 to 5 wherein the film forming polymer used is as aqueous emulsion of concentration of at least 50 % v/v. 7. A process, as claimed in claims 1 to 6, wherein the method used for topping by tanned collagen us powder is selected from sprinkling, spreading. 8. A leather like sheet prepared by the process as claimed in claims 1 to 7 , wherein the collagen us powder used is selected from buffing dust, leather powder, either individually or in combination. 9. A leather like sheet prepared by the process as claimed in claims 1 to 8, wherein the method used for removal of unfixed collagen us powder is selected from brushing .shaking. 10. A leather like sheet, as prepared by the process as claimed in claims 1 to 9. 11. A process for preparation of leather like sheet, substantially as herein described with reference to the examples. 12. A leather like sheet substantially as herein described with reference to the examples. |
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752-DEL-2002-Abstract-(26-11-2007).pdf
752-DEL-2002-Claims-(26-11-2007).pdf
752-DEL-2002-Correspondence-Others-(26-11-2007).pdf
752-del-2002-correspondence-others.pdf
752-del-2002-correspondence-po.pdf
752-DEL-2002-Description (Complete)-(26-11-2007).pdf
752-del-2002-description (complete).pdf
752-DEL-2002-Form-2-(26-11-2007).pdf
752-DEL-2002-Form-3-(26-11-2007).pdf
Patent Number | 213629 | |||||||||||||||
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Indian Patent Application Number | 752/DEL/2002 | |||||||||||||||
PG Journal Number | 03/2008 | |||||||||||||||
Publication Date | 18-Jan-2008 | |||||||||||||||
Grant Date | 09-Jan-2008 | |||||||||||||||
Date of Filing | 16-Jul-2002 | |||||||||||||||
Name of Patentee | COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH | |||||||||||||||
Applicant Address | RAFI MARG, NEW DELHI-110001, INDIA | |||||||||||||||
Inventors:
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PCT International Classification Number | D06N 3/00 | |||||||||||||||
PCT International Application Number | N/A | |||||||||||||||
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PCT Conventions:
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