Title of the Invention
A self-coloured magnetic leather for industrial applications and a process for the preparation
thereof.
Field of the Invention
The present invention relates to a self-coloured magnetic leather for industrial applications.
More particularly, the present invention provides a magnetic leather in different color range
useful in producing consumer products by incorporating the suitable magnetic
materials/nanoparticles within the leather matrix in-situ. Further, the present invention
provides a process for producing the said magnetic leather with desired color ranges
simultaneously by a single chemical treatment without employing synthetic or natural dyes
or pigments. The invention is anticipated to have significant application in leather product
industries catering to the consumer needs in terms of life-style accessories and garments.
Background of the Invention and Description of Prior Art
Leather has outstanding physical properties, which enables its usage for several
applications from wallet to wall covering. However, it lacks several functional properties
such as electrical conductivity, magnetism, etc, as reported by Kabat (US Patent 2,127,034,
1938) and Ashokkumar et al. (Carbon, 2012, 50, 5574); thus limiting its use in advanced
applications such as smart/interactive clothing, electromagnetic interference (EMI)
shielding, intelligent garments, adhesive-free wall covering, magnetic health care etc.
Collagen and most of the natural fiber based fabrics are diamagnetic and do not respond to
a magnetic field effectively, as reported by Ashokkumar et al. (Carbon, 2012, 50, 5574).
Although chromium tanned leather exhibits weak paramagnetic properties (0.05 emu/g), it is
not sufficient to fulfill the required application needs, as reported by Ashokkumar et al. (ACS
Sustainable Chem. Eng. 2013, 1, 619). Therefore, the augmentation of magnetism in
leather will open up new and advanced areas of application. A major area is smart products
with novel functionalities such as magnetism, flexibility, stretchability, lightweight, etc.
Magnetically responsive textiles and fabrics are known in the literature. Such materials have
found a wide variety of uses including functional or smart products and floor or wall
covering/tiles. Although there are reports to incorporate magnetic properties in collagen
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fibers, as reported by Thanikaivelan et al. (Scientific Reports, 2012, 2, 230) and
Ashokkumar et al. (Carbon, 2012, 50, 5574), currently there are no effective chemical
technologies available for leather matrix. However, physical methods do exist for leathers
and synthetic/PU/artificial leathers.
Many attempts, as detailed below, have been made to improve magnetic properties of
textile and leather materials.
Magnetically responsive textiles and fabrics are generally prepared by dipping/coating of
magnetic materials/nanoparticles into the fabric, as reported by Daoquan et al. (CN
101235594 B, 2010) or by incorporating magnetic yarns in the fabric, as reported by Jie et
al. (CN 203049165 U, 2013). Dipping polyester fabrics in ethanol solution containing
nanometer ferroferric oxide granules whose surface is modified by the oleic acid, and
utilizing excimer laser irradiation 222 nm to irradiate two surfaces of the polyester fabrics
after dipping resulted in superparamagnetic functional textile with comparatively high
fastness to washing, as reported by Daoquan et al. (CN 101235594 B, 2010), although
there was a small reduction in strength. Jie et al. (CN 203049165 U, 2013) disclosed a
functional textile fabric containing metal yarn and magnetic yarn. One of the metal yarn and
the magnetic yarn or a mixture of the metal yarn and the magnetic yarn is adopted by the
warp direction of the functional textile fabric, and one of metal yarn and the magnetic yarn
or the mixture of the metal yarn and the magnetic yarn is adopted by the widthwise direction
of the functional textile fabric. Due to the fact that the metal yarn and the magnetic yarn are
combined together, the functional textile fabric has a plurality of functions such as magnetic
health care, radiation protection, static electricity prevention, ultraviolet prevention,
bacterium prevention, odor removal etc.
Magnetic leather is currently prepared by attaching a magnetic substrate with leather
laminates using adhesives and used widely as magnetic leather tiles for interior decoration
applications such as wall and floor tiling. Manchee (US20050276982 A1, 2005; CA 2470778
A1, 2005) has invented a flexible composite tile comprising a leather lamina affixed to the
magnetic substrate to form a tile. Preferably, the leather lamina is adhesively affixed
completely to the magnetic substrate. The composite tile is used as a floor tile or as a wall
tile. Preferably, the leather is vegetable-tanned and is of a grade and thickness similar to
leather for shoe soles. The leather may be dyed or colored, and may have debossed
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features. The composite tile preferably has a relatively thick leather lamina and a relatively
thin magnetic substrate. The leather lamina may also be recycled leather (in the form of
leather board). Leather may also be decorated with color finishes and impressed with
debossings to give different color and grain characters. For instance, aniline dyes may be
used, which come in a variety of colors. Wax finishes may also be used, alone, or in
conjunction with dyes.
Jincong (CN 202610622 U, 2012) has disclosed polyurethane (PU) leather with a
suspension magnetic three dimensional (3D) pearl effect. The PU leather is characterized
by comprising a basic cloth layer. A suspension magnetic 3D pearl powder layer is arranged
on the basic cloth layer, and a PU surface layer is arranged on the suspension magnetic 3D
pearl powder layer. The suspension magnetic 3D pearl powder is added into polyamine
ethyl ester and then is arranged on the basic cloth layer to form the suspension magnetic
3D pearl powder layer so as to obtain the suspension magnetic 3D pearl effect. Relative
technology of a suspension train is applied to the PU leather in order to form a top-speed
and glaring illusion 3D effect, and then effectively improve quality of products. In addition,
since magnetic pearl powder is added, the PU leather has certain magnetic therapy effect.
Esposito (WO 2008121806 A1, 2008) disclosed a tile comprising a top layer preferably
natural or synthetic leather, a bottom magnetic flexible layer, and at least one intermediate
textile lamina with adhesive means to affix to both the top layer and the bottom magnetic
flexible layer, wherein the top layer has peripheral edges extending downwardly around
corresponding edges of the bottom magnetic flexible layer. The coverings of the invention
even may be used in applications under wet conditions and water such as in swimming
pools, shower spaces, bathrooms, kitchens.
Vulgar and Bin (CN 2626362 Y, 2004) have disclosed a thermal magnetic leather pillow,
characterized in that the pillow into headrest and occipital, occipital portion of said curved
bulge, and in the side with two magnet headrest for smaller flat-shaped or curved bulge in
the distribution of the strip in the subcutaneous pillow pillow bags, pillow bags under the
heating wire distribution. As a result of the above structure, curved occipital bulge just
supporting the neck, and by the magnet on the acupoint massage, can prevent and treat
cervical spondylosis.
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Although coating of magnetic nanoparticles on the leather surface through a conventional
finishing technique seems feasible, it cannot provide magnetic and colored leather across
the entire thickness of the leather consisting of a three dimensional fibrous network.
As can be seen in the prior art, magnetic substrate is physically attached to previously
colored natural leather, wherein coloration was achieved by the introduction of a colored
pigment, synthetic dye or natural dyes, or synthetic/PU leather. Further, they do not provide
bi-functionality namely, magnetic property and color, in a single chemical treatment
throughout the 3D structure of leather. Therefore, there exists a dire need to provide a
method of producing magnetic self-colored leathers eliminating the aforementioned
problems.
Objects of invention:
The main objective of the present invention is to provide a self-coloured magnetic leather for
industrial applications, which obviates the limitations as stated above.
Another objective of the invention is to provide magnetic leather in different colour range
without utilizing pigments or dyes.
Yet another objective of the present invention is to provide magnetic leather with different
colors using a single chemical treatment.
Still another objective of the present invention is to provide an economical process free from
the use of expensive equipments.
Still another objective of the present invention is to prepare the leather with higher response
to magnetization and related applications.
Summary of the invention:
Accordingly, the present invention provides a self-coloured magnetic leather, characterized
by leather matrix incorporated with magnetic nanoparticles and molecules in-situ throughout
the 3D structure of leather, the said leather exhibiting magnetization in the range of 0.1 to
10 emu/g, the said leather being available in single or multiple colours.
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Further, the present invention provides a process for preparing a self-coloured magnetic
leather for industrial and smart product applications, which comprises:
i. taking 10 to 15000% w/w, of magnetic raw materials based on the weight of leather,
and dissolving it in 100 to 5000%) v/w, of solvent based on the weight of leather,
under stirring condition
ii. adding undyed crust leather in the solution, as obtained in step (i), for a period in the
range of 20 to 180 minutes under stirring condition at 20 to 60°C,
iii. adjusting the pH of the mixture as obtained in step (ii) up to pH 11, by employing a
reducing agent dissolved in water, at a temperature range 20 to 60°C for a time
period of 20 to 150 minutes to obtain magnetic and colored leather in-situ,
iv. subjecting the in-situ magnetic and colored leather, as obtained in step (iii), to
aqueous washing at a pH in the range of 6-8 followed by drying at a temperature in
the range of 20-40°C to obtain novel bi-functional leather.
In an embodiment of the present invention, the magnetic raw materials used may be
selected from iron(lll) chloride, iron(ll) sulphate heptahydrate, cobalt(ll) acetate,
cobalt(ll) chloride hexahydrate, nickel(ll) acetate, nickel(ll) chloride hexahydrate.
In another embodiment of the present invention, the solvent used may be selected from
water, acetone, ethanol, either individually or in any combination.
In yet another embodiment of the present invention, the reducing agent used may be
such as ammonia, sodium carbonate, sodium borohydride, hydrazine, either individually
or in any combination.
Detailed description of the invention
The invention is described below in detail:
Natural undyed crust leather is selected for the purpose of the present invention.
10 to 15000% w/w, of magnetic raw materials based on the weight of leather is dissolved in
100 to 5000% v/w, of solvent under stirring condition. Undyed crust leather is added to the
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said solution under continuous stirring for a period in the range of 20 to 180 minutes at 20 to
60°C.The pH of the said mixture is adjusted up to 11 by employing a reducing agent
dissolved in water, at 20 to 60°C for 20 to 150 minutes. The resulting in-situ magnetic and
colored leather is subjected to aqueous washing at a pH in the range of 6-8 followed by
drying at a temperature in the range of 20-40°C to obtain novel bi-functional leather.
The self-coloured magnetic leather exhibits the following characteristics:
Average magnetization value: 0.1 to 10 emu/g.
Color of leather: Single or multiple colours
The following examples are given by way of illustration only and therefore should not be
construed to limit the scope of the present invention.
EXAMPLE 1
120 g of iron(lll) chloride and 30 g of iron(ll) sulphate heptahydrate were dissolved in 50 ml
water and stirred for 20 minutes. 1 g white crust leather was soaked in the above solution
for 3 h with continuous stirring at 60°C. Ammonia solution was added to the above solution
drop wise to adjust the pH to 10 at 60°C for 2.5 h. Resultant in-situ magnetic and colored
leather was washed with water at a pH 8 for 2 times and air dried at 40°C for 24 h to obtain
brown coloured magnetic leather.
The leather was then subjected to characterization. It was found to exhibit the following
characteristics:
Average magnetization value: 0.75 emu/g.
The colour of leather was found to be brown.
EXAMPLE 2
0.2 g of nickel(ll) acetate was dissolved in 1.5 ml water and 0.5 ml acetone mixture and
stirred for 10 minutes. 2 g white crust leather was soaked in the above solution for
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20minutes with continuous stirring at 20°C. Hydrazine was added to the above solution drop
wise to adjust the pH to 11 at 20°C for 20 minutes. Resultant in-situ magnetic and colored
leather was washed with water at a pH 6 and air dried at 20°C for 48 h to obtain greyish
black coloured magnetic leather.
The leather was then subjected to characterization. It was found to exhibit the following
characteristics:
Average magnetization value: 0.1 emu/g.
The colour of leather was found to be greyish black.
EXAMPLE 3
0.2 g of cobalt(ll) acetate and 0.02 g of cobalt(ll) chloride hexahydrate were dissolved in 10
ml water and stirred for 20 minutes. 1.6 g white crust leather was soaked in the above
solution for 1 h with continuous stirring at 30°C. Sodium borohydride (0.1 g in 10 ml distilled
water) was added to the above solution drop wise to adjust the pH to 10 at 30°C for 90
minutes. Resultant in-situ magnetic and colored leather was washed with water at a pH 7
for 2 times and air dried at 30°C for 36 h to obtain yellowish green colored magnetic leather.
The leather was then subjected to characterization. It was found to exhibit the following
characteristics:
Average magnetization value: 0.26 emu/g.
The colour of leather was found to be yellowish green.
EXAMPLE 4
24 g of cobalt(ll) acetate was dissolved in 80 ml water and stirred for 30 minutes. 4 g white
crust leather was soaked in the above solution for 2 h with continuous stirring at 50°C.
Sodium borohydride (1 g in 20 ml distilled water) was added to the above solution drop wise
to adjust the pH to 10 at 50°C for 90 minutes. Resultant in-situ magnetic and colored leather
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was washed with water at a pH 7 and air dried at 35°C for 36 h to obtain green coloured
magnetic leather.
The leather was then subjected to characterization. It was found to exhibit the following
characteristics:
Average magnetization value: 10 emu/g.
The colour of leather was found to be green.
EXAMPLE 5
1.77 g of nickel(ll) acetate and 0.2 g of nickel(ll) chloride hexahydrate were dissolved in 10
ml water and 2 ml ethanol mixture and stirred for 15 minutes. 0.5 g white crust leather was
soaked in the above solution for 90 minutes with continuous stirring at 40°C. Sodium
borohydride (1 g in 10 ml distilled water) and sodium carbonate (0.4 g in 10 ml distilled
water) were added to the above solution drop wise to adjust the pH to 10 at 40°C for 60
minutes. Resultant in-situ magnetic and colored leather was washed with water at a pH 7
and air dried at 40°C for 24 h to obtain black coloured magnetic leather.
The leather was then subjected to characterization. It was found to exhibit the following
characteristics:
Average magnetization value: 0.14 emu/g.
The colour of leather was found to be black.
Advantages of the Invention:
The following are the advantages of the present invention:
• The product of invention used for production of smart product such as
smart/interactive clothing, electromagnetic interference (EMI) shielding, intelligent
garments, adhesive-free wall covering, magnetic health care etc
• The process of invention is easy and convenient.
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#
• The process provides magnetic and colored leather throughout the cross section of
leather
• Avoids toxic and expensive dyes
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e\, /&. fe-i n - •_ •*"
We claim:
1. A self-coloured magnetic leather, characterized by leather matrix incorporated with
magnetic nanoparticles and molecules in-situ throughout the 3D structure of leather, the said
leather exhibiting magnetization in the range of 0.1 to 10 emu/g, the said leather being
available in single or multiple colours.
2. A process for preparing a self-coloured magnetic leather for industrial applications, which
comprises:
i. taking 10 to 15000% w/w, of magnetic raw materials based on the weight of leather,
and dissolving it in 100 to 5000% v/w, of solvent based on the weight of leather,
under stirring condition
ii. adding undyed crust leather in the solution, as obtained in step (i), for a period in the
range of 20 to 180 minutes under stirring condition at 20 to 60°C,
iii. adjusting the pH of the mixture as obtained in step (ii) up to pH 11, by employing a
reducing agent dissolved in water, at temperature range 20 to 60°C for a period of
20 to 150 minutes to obtain magnetic and colored leather in-situ,
iv. subjecting the in-situ magnetic and colored leather, as obtained in step (iii), to
aqueous washing at a pH in the range of 6-8 followed by drying at a temperature in
the range of 20-40°C to obtain self-coloured magnetic leather.
3. A process, as claimed in Claim 2, wherein the magnetic raw materials used is selected
from iron(lll) chloride, iron(ll) sulphate heptahydrate, cobalt(ll) acetate, cobalt(ll) chloride
hexahydrate, nickel(ll) acetate, nickel(ll) chloride hexahydrate.
4. A process, as claimed in Claim 2, wherein the solvent used is selected from water,
acetone, ethanol, either individually or in any combination.
5. A process, as claimed in Claim 2, wherein the reducing agent used is such as ammonia,
sodium carbonate, sodium borohydride, hydrazine, either individually or in any combination.
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6. A process for preparing a self-coloured magnetic leather for industrial applications,
substantially as herein described with reference to the examples.
Dated this 29th day of August 2014
Chief Scientist
ST. 3T5HT «r^m / Dr. Anjana Baruah
g©J tsnf^W ^ aga / Chief Scientist & Head
14, ;H?m ft?R 'Wf. ^ ftetft-110067
Council of Scientific ^aaffWSsrtl,rSr^esy9r(9flhi-110067
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