Title of Invention

A PROCESS OF MAKING OZONE RESISTANT NATURAL RUBBER

Abstract

A process for making natural rubber ozone resistant by, i)Passing natural rubber through two roll mixing mill to reduce viscosity in a Range of 40 to 45; ii)Mixing this rubber in two roll mixing mill with activator, accelerator, Curative, fillers and plasticizers only; iii)The mix is kept at 50ºC in electrically heated oven for 1 hr. then it is cooled at room temperature and kept for maturation for 24 hrs; iv)Followed by refining 10-15 times to ensure proper dispersion of all the ingredints in rubber matrix. v)Moulding the mix as per requirement.

Full Text

FORM 2 THE PATENTS ACT, 1970 (39 of 1970) COMPLETE SPECIFICATION 1. Title of the invention : "A Process of making ozone resistant natural rubber " (a) Name in full Mrs. Anushree Dukhande (b) Address Indian Rubber Manufacturers Research Association, B-88, Road No.24/U-2, Wagle Industrial Estate, Thane - 400 604, Maharashtra, India. (c) Nationality Indian (a) Name in full Dr. Madhu Sudan Banerji (b) Address Indian Rubber Manufacturers Research Association, B-88, Road No.24/U-2, Wagle Industrial Estate, Thane - 400 604, Maharashtra, India. (c) Nationality Indian 2. The following specification particularly describes the nature of the invention and the manner in which it is to be performed. Signature Mrs. Anushree Dukhande Dr. Madhu Sudan Banerji Date: 22.02.2005 To The Controller of Patents, The Patent Office, At Mumbai ORIGINAL 101MUM/2004 30-01-04 Title of invention: A process of making Ozone resistant natural rubber. Field of Invention: The invention relates to a process of Improvement of ozone resistance of natural rubber. More particularly the invention relates to a process of making ozone resistant natural rubber without use of antioxidants which gives equal industrial applicability like synthetic saturated rubber etc. Background of invention: India is one of the very few countries which have the status of being both a leading producer and consumer of natural rubber. The beauty of natural rubber is that it possesses combination of various properties and thereby it can be used in variety of applications. There are more than 30,000 products for which natural rubber is a raw material. Tire and automobile are the major sectors which consumes natural rubber. Inherent character of Natural rubber is to provide good tensile properties, resistance to tear and abrasion, good shock absorption, resistance to mechanical properties. It is a very rare combination of so many properties in one polymer. One of the main types of aging of elastomers, in service under natural conditions, is caused by atmospheric ozone. Ozone is generated in nature by electrical discharge and also by solar radiation in the stratosphere. The ground-level ozone concentration in normal air is in the range of 1 - 5 parts per hundred million (pphm). In urban environment, however, ozone reaches much higher levels, up to 25 pphm, due to ultraviolet photolysis of pollutants. A major problem associated with the use of natural rubber, is the surface degradation, typically exemplified by cracking, caused by ozone. {1 .Encyclopedia of Chemical Technology, " Vol.3, 4th ed, .I.Kroschwitz, Ed., John Wiley, New York 1992,p.448) 2.M.P.Anachkov, etallnt. J.Polym. Mater. 14, 79 (1990)) Deterioration has been observed to occur when small surface cracks grow rapidly into deep, disruptive fissures. Fissures of this sort can significantly shorten the serviceable life of an article made from natural rubber. In order to overcome this problem of ozone attack, several approaches have been undertaken like A. Proper selection of polymer: (1) Chemically saturated type (Natural rubber is unsaturated type) (2) Stearically hindered type; B. Proper compounding and use; (1) Wrappers-paper or plastic films (2) Paints films - flexible films of ozone resistant rubber or plastic, and (3) Chemical films - antiozonant in solvent; C. Proper compounding and use; (1) Chemical antiozonats, (2) Waxes (3) High set and low modulus compounds and (4) Storage of items in unstressed state. To overcome the problem of ozone resistance especially in natural rubber following attempts were made. 1. Addition of micro crystalline paraffin waxes: Waxes when present in a vulcanisate at a level exceeding its solubility, some of it will migrate to the rubber surface where it can form a physical barrier to prevent the penetration of ozone. (l.Braden and A.N.Gent, Rubber Chem. Technol, 35:200 (1962); 2.Braden and A.N.Gent, J.Appl. Polym. Sci, 7:1003 (1963)) As waxes are not reactive to ozone, it gives protection to rubber from ozone. Use of waxes was not found suitable for dynamic application. 2. Use of anti ozonants: Anti ozonants are the chemicals which protect the rubber against ozone deterioration by chemical reaction with polymer chain. They need to be used in high doses for natural rubber to get ozone resistance thereby creating problem of bleeding on the surface. Due to problems like staining were found with the anti ozonants use is limited to black products. 3. Blending: It was proved that blending unsaturated rubber with saturated rubber gives ozone resistance. This was found to be at the cost of physical properties (i. P.M. Lewis,poly.degrad.stab,l 5:33(1986) 2. Z.T.Ossefort and E.W.Bergstrom, Rubber age, 10(9).47(1969) 3J.R.Dunn, Dev, Polym. Stab. 4:223 (1981)) . Object of invention: The primary object of the invention is to provide a process of making Ozone resistant natural rubber without use of any extra additives. Still further objective of this invention is to provide an Ozone resistant natural rubber which can be used in place of synthetic rubber particularly without any ozone cracking. From extensive study it has been observed that the combination of cure system dose play an important role in the above mentioned property. Summary of work The present invention relates to a process of making ozone resistant natural rubber without use of any extra additives (i.e. Antiozonants) Industrial applicability Our present invention can be used to make the various articles from natural rubber which are being made from saturated rubbers like EPDM, butyl. We would currently expect the major commercial use in the near term to be in the areas of tiers, conveyor belts and elastomeric hoses. Advantages of work 1. The present invention will allow the producers to use natural rubber in the application where ozone resistance is required. So that consumption of natural rubber in the country will increase. 2. Cost of products will also be reduced as costly synthetic rubbers will be replaced by less expensive and easily available natural rubber 3. Natural rubber can be used any where without the fear of ozone cracking. 4. Commonly available additives are used. 5. As no other rubber is blended with NR, no compromise is made with physical properties. Detailed description of the invention: All above means are having limitation. In our present work we have not used any one of above means to provide ozone resistance to natural rubber. For this work, all the ingredients were accurately weighed. Natural rubber of grade ISNR (Indian Standard Natural Rubber) was banded over slow roll of two roll mixing mill to reduce the viscosity. The viscosity was checked by Mooney viscometer. The viscosity was adjusted in the range of 40 to 45.Then ZnO was added on rubber and mixed by making one % cut from each side. Next carbon black was added along with plasticizer to rubber. When about half the black was incorporated the stearic acid was added on the rubber and mixed by making one 3A cut from each side. Then remainder of the carbon black was added on the rubber and mixed properly. Accelerators and sulphur were added on the rubber mix. Four % cuts were made so that all the ingredients get mixed properly. /The mix was heated at 50° C for I hr in electrically heated oven. Further the mix was cooled at room temperature and kept for maturation for 24 hrs. After the maturation period was over, the mix was refined 10-15 times in two roll mixing mill to ensure proper dispersion of all the ingredients in rubber matrix; finally the rubber stock was passed through the mill endwise six times to make a sheet. The Rheograph was recorded of the mix at 150°C. Optimum cure time (t90) was calculated by the Rheograph. The rubber stock was molded at 150°C for optimum cure time in the form of 6 x 6 inches slab. Test pieces were tested for ozone resistance as per standard procedure. It has been observed that the absence of conventional antioxidants / anti ozonants which is supposed to be protecting from weather and with the use of certain doses of accelerator the NR gets ozone resistance up to 50 pphm at 40°C under 20% strain. We claim 1. A process for making natural rubber ozone resistant by, i) Passing natural rubber through two roll mixing mill to reduce viscosity in a Range of 40 to 45; ii) Mixing this rubber in two roll mixing mill with activator, accelerator, Curative, fillers and plasticizers only ; iii) The mix is kept at 50°C in electrically heated oven for 1 hr. then it is cooled at room temperature and kept for maturation for 24 hrs; iv) Followed by refining 10-15 times to ensure proper dispersion of all the ingredients in rubber matrix. v) Moulding the mix as per requirement. 2. The process of claim 1, wherein the rubber composition contains natural rubber preferably of grade ISNR (Indian Standard Natural Rubber) in 100 parts by weight 3. The process of claim 1, wherein the rubber composition contains the activator used is ZnO in 0-5 parts by weight. 4. The process of claim 1, wherein the rubber composition contains black filler preferably HAF (High Abrasion Black) black in 50 - 70 parts by weight. 5. The process of claim 1, wherein the rubber composition contains processing oil preferably aromatic oil in 5 - 10 parts by weight. 6. The process of claim 1, wherein the rubber composition contains curative in 1 -3 parts by weight of sulphur. 7. The process of claim 1, wherein the rubber composition contains an accelerator preferably sulphenamide type accelerator in 0.5 - 2 parts by weight. Signature Mrs. Anushree Dukhande: Dr.Madhu Sudan Banerji: Date :22.02.2005

Documents:

101-mum-2004-cancelled pages(23-02-2005).pdf

101-mum-2004-claims(granted)-(23-02-2005).doc

101-mum-2004-claims(granted)-(23-02-2005).pdf

101-mum-2004-correspondence(22-02-2005).pdf

101-mum-2004-correspondence(ipo)-(18-04-2007).pdf

101-mum-2004-form 1(23-02-2005).pdf

101-mum-2004-form 1(30-01-2004).pdf

101-mum-2004-form 13(23-02-2005).pdf

101-mum-2004-form 19(30-01-2004).pdf

101-mum-2004-form 2(granted)-(23-02-2005).doc

101-mum-2004-form 2(granted)-(23-02-2005).pdf

101-mum-2004-form 3(30-01-2004).pdf

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