FORM 2
THE PATENTS ACT, 1970
(39 OF 1970)
As amended by the Patents (Amendment) Act, 2005
&
THE PATENTS RULES, 2003
As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
Ethylene gas adsorbent material and method of making such material
APPLICANTS
Reliance Industries Limited, 3rd Floor, Maker Chamber IV, 222, Nariman Point, Mumbai 400021, Maharashtra, India, an Indian company
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed:

FIELD OF THE INVENTION
This invention relates to an ethylene gas adsorbent material and method of making such material.
BACKGROUND OF THE INVENTION
Ethylene is a natural plant hormone synthesized by all the plant tissues and certain microorganisms. It affects the growth, development, ripening and senescence (aging) of all the plants and binds to a number of different protein receptors. Many food plants produce ethylene as part of their normal metabolic cycle. During storage of perishable plant produce like fruits, vegetables or flowers, ethylene gas, which is a natural ripening agent, is released into the surrounding storage atmosphere. Most of the fruits and vegetables produce ethylene gas in small quantities. However, there are also fruits which produce large amount of ethylene during the ripening phase causing acceleration of the ripening process during storage thereof.
Concentrations of ethylene gas as low as 0.1 ppm can affect the ripening process and ethylene gas levels as low as 1 ppm can accelerate ripening and destroy a large quantity of fruits due to overripening in a single day. Unripe fruits show low ethylene concentrations (0.05-0. lppm) but the ethylene level increases 10 to 1000 times as the fruits begin to ripen. During ripening, ethylene levels increase to a maximum peak and then drop as fermentation occurs. Formation of ethylene during ripening of fruits is slowed down either by reducing the temperature of storage atmosphere or by removing

the formed ethylene from the storage atmosphere to keep the fruits fresh for longer periods.
Ethylene control from plant produce is well known in the industry for preservation of plant produce using various techniques and methods like chemical scrubbers, catalytic method, adsorptive ethylene removal methods, storage at reduced atmospheric pressure, cold storage at low temperatures or controlled atmosphere storage methods. Good ventilation conditions are induced by circulation of fresh air in order to reduce ethylene content in the storage atmosphere to enhance plant produce life. Controlled atmosphere signifies typical temperatures in the range of 0 to 5 °C, O2 concentration of about 3% and CO2 concentration in the range of 0-5%. During controlled atmosphere storage, it is important to maintain these optimal conditions depending upon the type of plant produce. Controlled atmosphere storage techniques are also employed during transport of tropical fruits in refrigerated containers or ships or during domestic storage of fruits. However, cold and controlled atmosphere storage spoil the taste of certain plant produce like apples due to low O2 content and high CO2 content in the storage atmosphere. (US 2001/0031299A1).
Removal of ethylene from plant produce storage facilities is reported to be carried out using oxidizing agents like activated carbons, potassium bromate supported on activated charcols, silver and aluminum chloride alumina, copper exchanged zeolite A, palladium chloride supported on carbon, sodium chloride saturated on silica and zeolites or sodium and potassium permanganate impregnated carrierss like activated carbon, alumina, zeolites

or diatomaceous earth (US 4906398 and US 5624478, EP 515764A2 and US 2006/0070523 Al).
Tetra ethyl ortho silicate (TEOS) is a known pore engineering agent for zeolite adsorbents. Either TEOS itself or its alkali metal derivative is reported to marginally reduce zeolite pore size to make it fit to adsorb smaller size gas molecules (WO2010109477 A2).
Permanganate coated materials are predominantly used in the industry for ethylene adsorption but their use is limited by low loading of permanganate ions thereby reducing the life of coated materials. Moreover the permanganate ions may leach out of the permanganate coated materials if they become wet which is a serious problem in the storage and transfer of plant produce since these are often accompanied by atmosphere of high humidity of 80-90% (US 2001/0031299). Ag+ and Cu2+ exchanged hydrophilic zeolites like Zeolite A and X are known for removal of ethylene from plant produce storage facilities but they have limited ethylene storage capacity and capability in the presence of high humidity during storage because of the affinity of hydrophilic zeolites for water.
In our Indian Patent Application No 384/MUM/2009 filed on 20 February 2009, we have described ethylene absorbent packaging for ethylene susceptible and perishable articles and ethylene absorbent barrier material and also methods of making the same. The ethylene absorbent packaging and ethylene absorbent barrier material comprises a textile

substrate impregnated with a solution of zeolite, crosslinker and binder. The zeolite is of class 3A, 4A, 5A, ZSM, X or Y of sodium aluminosilicate (Kirk-Othmer Encyclopedia of Chemical Technology, 5th ed Vol 16, John Wiley and sons Inc, NJ, P 811 to 853) and may be ionized, for instance, with Ag or Zn ions so as to impart antibacterial / antifungal activity to the substrate or with NH4 ions to bring about polarity changes in the substrate. The crosslinker is melanine formaldehyde and the binder is acrylic polymer or copolymer. The solution is formed with water or a mixture of water and an organic solvent like isopropyl alcohol.
Preservation of perishable plant produce like vegetables and fruits for long periods is of utmost importance. There is thus need for ethylene adsorbent materials or ethylene barriers or ethylene separators having high ethylene adsorption capacity, especially under high humidity conditions in order to increase the shelf and storage life of perishable plant produce like fruits or vegetables.
DESCRIPTION OF THE INVENTION
According to the invention there is provided an ethylene gas adsorbent material comprising a fabric material coated with silver ion exchanged hydrophobic ZSM-5 zeolite, wherein the coating of the silver ion exchanged hydrophobic ZSM-5 zeolite is carried out with an aqueous solution of the silver ion exchanged hydrophobic ZSM-5 zeolite and an inorganic silicate binder selected from the group consisting of sodium salt of silicate, potassium salt of silicate or colloidal silica followed by drying the coated fabric material at 130-170°C.

According to the invention there is also provided a method of making ethylene gas adsorbent material comprising applying a coating of an aqueous solution of silver ion exchanged hydrophobic ZSM-5 zeolite and an inorganic silicate binder selected from the group consisting of sodium salt of silicate, potassium salt of silicate or colloidal silica on a fabric material followed by drying the coated fabric material at 130 to 170°C.
The fabric material comprises woven or non-woven polymer, preferably polyester. According to a variation of the invention, the coating of the aqueous solution of silver ion exchanged hydrophobic ZSM-5 zeolite and the binder is applied on the fabric material by dip coating the fabric material in the aqueous solution. According to another variation of the invention, the coating of the aqueous solution of silver ion exchanged hydrophobic ZSM-5 zeolite and the binder is applied on the fabric material by spraying the aqueous solution on the fabric material. Preferably, the spraying is carried out with a liquid spray gun. Preferably, the coating of the silver ion exchanged hydrophobic ZSM-5 zeolite comprises 1-5 wt% zeolite loading and the zeolite comprises Si/Al weight ratio of 25 to 1000 and particle sizes of 1 to 5 microns. Preferably, the coating of silver ion exchanged hydrophobic ZSM-5 zeolite comprises 2 wt% zeolite loading. The zeolite coated fabric material is dried and cured at 130 - 170°C in order to chemically bond the zeolite coating to the fabric material with the inorganic silicates. Preferably, the drying of the coated fabric is carried out at 150°C.

Inorganic silicates, known as water glass, are transparent and brittle materials, generally used as sealants and binders in metallurgy or in cement or automotive industry. It has been found out by us extensive research and experimentation that inorganic silicates can be used as binders for zeolite in order to produce zeolite coated fabric material having enhanced ethylene adsorption and that the ethylene adsorption varies from one counter cation of silicate to another (Na-NHU-K), especially under very high humid conditions without having the adverse effect of pore size reduction associated with TEOS. Therefore, the zeolite coated fabric material of the invention can be advantageously used as a ethylene adsorbent packaging material for increasing the shelf or storage life of plant produce like fruits or vegetables, especially under high humidity conditions. Because of the chemical bonding of the zeolite to the fabric material with the binder, the coating is durable thereby increasing the life of the coated fabric material and maintaining its ethylene adsorption capacity for a long period. Further the coated fabric material is cost effective in that the method of making the coated fabric material is simple, easy and economical to practise.
It is to be noted that the ethylene adsorbent material of the invention also can be effectively used as a barrier or as a separator for ethylene gas in other areas where ethylene separation or prevention is required, especially under high humidity conditions.

BRIEF DECRIPTION OF THE DRAWINGS
Fig 1 of the accompanying drawings is a graphical representation of comparative study of ethylene adsorption of various fabrics; and
Fig 2 1 of the accompanying drawings is a graphical representation of comparative study of preservation of tomatoes with hydrophobic and hydrophilic zeolite coated fabrics.
The following experimental examples are illustrative of the invention but note limitative of the scope thereof:
Example 1
10 g of hydrophobic ZSM-5 zeolite powder (Si/Al 400) of 1 to 5 microns sizes was mixed with 500 ml of 0.3 wt% aqueous solution of AgNC>3 at 80°C in a flask under constant stirring for 4 hrs. The solid material was filtered out and washed with distilled hot water at 80°C until free of Ag+ ions as tested with sodium chloride solution. Filter cake was oven dried at 120°C and the soft lumps formed were powdered.
Example 2
5 g of the Ag+ exchanged zeolite powder as prepared in Example 1 was dip coated on 50 g of non-woven polyester fabric material of 12 inch size and 0.5 mm thickness prepared by hydroentanglement route using an aqueous solution of 2 wt% of Ag+ exchanged zeolite powder and 1 wt% of sodium silicate. The dip coated fabric was passed between

a pair of rotating squeeze rollers to remove excess solution of zeolite and sodium silicate. The fabric was fixed on stenter frames and passed through a hot air chamber at 150 °C for 60 sees to dry and cure the coating on the fabric material.
Dip coated fabric adsorbed 0.083 wt% of ethylene at 30°C and 1 mmHg pressure. Polyester fabric without Ag-ZSM5 coating absorbed 0.05 wt% of ethylene at 30°C and 1 mmHg pressure.
Example 3
The ethylene adsorption efficiency of the coated fabrics of Example 2 was compared with virgin fabric and fabric coated similarly with potassium silicate, colloidal silica and TEOS at 1 torr pressure and at 30°C and the results were as shown in Fig 1 of the accompanying drawings and as shown in the Table below:

Table

Adsorbent Ethylene adsorption wt% Binder wt
% Zeolite wt %
Virgin Fabric 0.05 - -
Sodium silicate coated fabric where coating was carried out after fabric was made 0.083 1 2
Colloidal silica coated fabric where coating was carried out after fabric was made 0.089 1 2
Potassium silicate coated fabric where coating was carried out after fabric was made 0.104 1 2
TEOS coated fabric where coating was carried out after fabric was made 0.08 1 2
The increase in the ethylene adsorption in the case of the fabric material coated with silver ion exchanged hydrophobic ZSM-5 zeolite and fixed with the inorganic silicates according to the invention is of significance when the fabric material is used as a packaging material for ethylene adsorption or as ethylene barrier or separator. It also clearly shows that the inorganic silicate binder do not affect the pore size of the zeolites.
Example 4
Efficacy of hydrophobic zeolite (Ag ZSM-5 Si/Al 900) and hydrophilic zeolite (Ag Zeolite A) coated polyester fabrics for storage of tomatoes was tested in sealed containers at 30 °C and 80% relative humidity with 10 gm of coated fabrics for 500 g of tomatoes. The dip coated fabrics each had 2 wt% zeolite loading. The tomatoes were medium size and oblong shape and showed 30-40% of total surface ripeness with

yellowish or pinkish colour. The tomatoes did not show any kind of physiological, fungal or mechanical damage and were from the central region of the Gujarat State.
The evolution of the ethylene content in the sealed containers was determined periodically by extracting 1 ml of gas through airtight septum fixed on the containers using a Hamilton air tight gas syringe and analyzed by gas chromatograph. Ethylene content of the sealed container containing the fabric coated with Ag ZSM-5 Si/Al 900 reduced to <0.5 ppm at the end of 8 days, whereas in the case of the container containing fabric coated with Ag-Zeolite A, the ethylene content remained at 6 ppm at the end of 8 days. Tomatoes remained fresh for 4 weeks for the Ag ZSM-5 Si/Al coated fabrics and 2 weeks for the Ag-Zeolite A coated fabrics. In the case of Ag-Zeolite A, the tomatoes were distinctively very soft and wrinkled with 70% weight loss, whereas in the case of Ag ZSM-5 Si/Al, the tomatoes were fresh with only 10% weight loss. The study results were as shown in Fig 2 of the accompanying drawings. It is seen from Fig 2 that the zeolite coated fabric of the invention showed high ethylene gas adsorption at high humidity conditions of 80%.

We claim:
1. Ethylene gas adsorbent material comprising a fabric material coated with silver ion exchanged hydrophobic ZSM-5 zeolite, wherein the coating of the silver ion exchanged hydrophobic ZSM-5 zeolite is carried out with an aqueous solution of silver ion exchanged hydrophobic ZSM-5 zeolite and an inorganic silicate binder selected from the group consisting of sodium salt of silicate, potassium salt of silicate or colloidal silica followed by drying the coated fabric material at 130 -170°C.
2. Ethylene gas adsorbent material as claimed in claim 1, wherein the fabric material comprises woven or non-woven polymer.
3. Ethylene gas adsorbent material as claimed in claim 2, wherein the polymer is polyester.
4. Ethylene gas adsorbent material as claimed in claim 1, 2 or 3, wherein the coating of the silver ion exchanged hydrophobic ZSM-5 zeolite comprises 1-5 wt% zeolite loading and the zeolite comprises Si/Al weight ratio of 25 to 1000 and particle sizes of 1 to 5 microns.
5. Ethylene gas adsorbent material as claimed in claim 4, wherein the coating of silver ion exchanged hydrophobic ZSM-5 zeolite comprises 2 wt% zeolite loading.
6. Ethylene gas adsorbent material as claimed in anyone of claims 1 to 5, wherein the
coated fabric material is dried at 150°C.
7. A method of making an ethylene gas adsorbent material comprising applying coating
of an aqueous solution of silver ion exchanged hydrophobic ZSM-5 zeolite and an
inorganic silicate binder selected from the group consisting of sodium salt of

silicate, potassium salt of silicate or colloidal silica on a fabric material followed by drying the coated fabric material at 130 to 170°C.
8. The method as claimed in claim 7, wherein the fabric material comprises woven or
non-woven polymer.
9. The method as claimed in claim 8, wherein the polymer is polyester.
10. The method as claimed in claim 7, 8 or 9, wherein the coating of the silver ion exchanged hydrophobic ZSM-5 zeolite comprises 1-5 wt% zeolite loading and the zeolite comprises Si/Al weight ratio of 25 to 1000 and particle sizes of 1 to 5 microns.
11. The method as claimed in claim 10, wherein the coating of silver ion exchanged hydrophobic ZSM-5 zeolite comprises 2 wt% zeolite loading.
12. The method as claimed in anyone of claims 7 to 11, wherein the drying of the coated fabric material is carried out at 150°C.
13. The method as claimed in anyone of claims 7 to 12, wherein the coating of the
aqueous solution of silver ion exchanged hydrophobic ZSM-5 zeolite and the binder
is applied on the fabric material by dip coating the aqueous solution on the fabric
material.
14. The method as claimed in anyone of claims 7 to 12, wherein the coating of the
aqueous solution of silver ion exchanged hydrophobic ZSM-5 zeolite and the binder

is applied on the fabric material by spraying the aqueous solution on the fabric material.