Title of Invention

A PROCESS FOR PREPARATION OF LEATHER LIKE SHEET

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.

Documents:

752-DEL-2002-Abstract-(26-11-2007).pdf

752-del-2002-abstract.pdf

752-DEL-2002-Claims-(26-11-2007).pdf

752-del-2002-claims.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-1.pdf

752-del-2002-form-18.pdf

752-DEL-2002-Form-2-(26-11-2007).pdf

752-del-2002-form-2.pdf

752-DEL-2002-Form-3-(26-11-2007).pdf

752-del-2002-form-3.pdf


Patent Number 213629
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:
# Inventor's Name Inventor's Address
1 NAGARAJAN VEDARAMAN CENTRAL LEATHER RESEARCH INSTITUTE, ADYAR, CHENNAI-600020, INDIA.
2 THIRUMALAISAMY RANGASAMY CENTRAL LEATHER RESEARCH INSTITUTE, ADYAR, CHENNAI-600020, INDIA.
3 CHELLAPPA MURALIDHARAN CENTRAL LEATHER RESEARCH INSTITUTE, ADYAR, CHENNAI-600020, INDIA.
4 PARUCHURI GANGADHAR RAO CENTRAL LEATHER RESEARCH INSTITUTE, ADYAR, CHENNAI-600020, INDIA.
PCT International Classification Number D06N 3/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA