|Title of Invention||
NATURAL RUBBER MODIFIED BITUMEN
|Abstract||The present invention relates to Natural Rubber Modified Bitumen using crumb rubber powder obtained from ammoniated field latex, heat stabilizing agents, anti-oxidants, curing agents and rubber chemical dispersions.|
|Full Text||FIELD OF THE INVENTION
This invention relates to a Natural Rubber Modified Bitumen (NRMB) prepared from Crumb Rubber Powder produced from ammoniated field latex. The Natural Rubber Modified Bitumen (NRMB) described herein is useful in industrial applications such as road paving.
More specifically the subject invention relates to Natural Rubber Modified Bitumen (NRMB) prepared from ammoniated field latex, heat stabilizing agents, antioxidants, curing agents and rubber chemical dispersions.
Natural rubber has been widely employed in industrial articles such as automobile tires, belts and adhesives and domestic articles such as gloves.
In addition to its excellent mechanical properties as vulcanized rubber, natural rubber is a much superior in the raw rubber strength (green strength) to synthetic rubbers. Accordingly, natural rubber is excellent in processing characteristics in kneading, sheeting and various molding procedures. In the form of a latex, natural rubber has a high gel strength of solidification and thus can be easily formulated into a film, which makes natural rubber applicable to various products including condoms, surgical gloves and diverse catheters.
BACKGROUND OF THE INVENTION
The raw rubber is in the form of bales and other constituents of thje'vulcanizable mixture have to be incorporated in the rubber phase.
Communication of the bale and intimate mixing with fillers, mineral oil plasticizers and vulcanization auxiliaries on rolls or internal mixers in a number of process stages. Between the stages, the mixture is generally cooled on a batch-off system, laid out in milled sheet form on pallets, and put into intermediate
storage. Downstream of the internal mixers or rolls there are appropriate extrusion or calendaring processes.
For some time there have been discussions on the use of free-flowing rubber powders which allow rubber mixtures to be processed as simply and rapidly as thermoplastic powders or pallets.
The preparation of the rubbers usually used in the rubber industry, via polymerization of various monomers, is generally divided into two fundamentally different processes:
a) Polymerization in water (Emulsion Polymerization)
Known rubbers present in or prepared in water are natural rubber (NR), emulsion styrene-butadiene rubber (ESBR), nitrite-butadiene rubber (NBR) and chloroprene rubber (CR).
b) Polymerization in Organic Solvents
Examples of important rubbers prepared in organic solvents are styrene-butadiene rubber based on solution polymerization (SSBR), butadiene rubber (BR), butyl rubbers, halobutyl rubbers, and also ethylene-propylene rubbers with (EPDM) or without (EPM) a copolymerized tercomponent.
It was observed that natural rubber can not compete successfully with synthetic rubber which have specific characteristics e.g. nitrite rubber being excellent in oil resistance.
The importance for using modified bitumen was realized in the mid-90s for commercial application and to use it for improving quality of roads. Guidelines have been laid down for specifications of various types of modified bitumen
namely (1) Crumb Rubber Modified Bitumen (CRMB), (2) Polymer Modified Bitumen (PMB), and (3) Natural Rubber Modified Bitumen (NRMB).
Conventionally bitumen used as road paving material and other commercial applications are manufactured using the synthetic or crumb rubber mainly due to the fact that the available natural rubber latex is highly unstable for storage and production purpose. Also the water content in the natural rubber latex is quite high. It is therefore essential that natural rubber latex should be stabilized and water contents should be removed before the same can be mixed with bitumen.
Number of attempts have been made to modify natural latex so as to impart the characteristics of other rubbers thereto so that the same can be blended with bitumen. The present invention helps in manufacturing Natural Rubber Modified Bitumen (NRMB) as per the specification of Indian Road Congress vide their special publication no. IRC:SP:53:2002.
Therefore the object of the present invention is to provide a Natural Rubber Modified Bitumen composition which is cost effective.
The other object of the present invention is to provide a Natural Rubber Modified Bitumen which has increased softening point of at least 25%.
Yet other object of the present invention is to provide a Natural Rubber Modified Bitumen which has increased elastic recovery of at least 400%.
Still other object of the present invention is to provide a Natural Rubber Modified Bitumen which has lower penetration thereby resulting into harder grade of bitumen
Further other object of the present invention is to provide a Natural Rubber Modified Bitumen which is having better strength and stability
Another object of the present invention is to provide a Natural Rubber Modified E3iturnen which has improved aging characteristics
Yet another object of the present invention is to provide a Natural Rubber Modified Bitumen which reduces noise pollution.
In the present invention, crumb rubber powder is first obtained from ammoniated natural rubber latex and the same is blended with conventional grades of bitumen giving better strength, stability and longer life, it also helps in providing harder grade of bitumen giving additional strength to roads and reducing water damage consequently reducing noise pollution . The crumb rubber powder described herein increases the elastic recovery of bitumen by 400% and softening point by
at lest 25%.
Ammoniated latex is blended with dispersions of rubber chemicals namely vulcanizing chemical dispersion, antioxidant chemical dispersions and rubber processing chemical dispersions by stirring in the drum and kept for maturing at ambient temperature for the at least 24 hours . The mixture which is in liquid from is then put in trays and kept in heated oven/smoke houses for curing and removal of water for 10-20 hours at temperature of 110°C - 140°C. The semicured natural rubber sheets are further grinded into fine powder of size 30 to 50 Mesh.
he Crumb rubber powder along with the natural asphalt is mixed with the bitumen in a tank equipped with agitators, heating system and circulation pumps
he stirrers are designed to disperse the modifier uniformly. Dispersion is the key to proper functioning of natural rubber modified asphalt.
According to the present invention, a Natural Rubber Modified Bitumen comprising Crumb Rubber obtained from ammoniated natural rubber latex Natural asphalt
Bitumen heated and blended in the ratio of 6:4:90::3:4:93::2:3:95
Accordingly, another embodiment of the present invention relates to Crumb
Rubber Powder comprises:
ammoniated natural rubber latex (33% dry rubber content) 300 parts
vulcanizing chemical dispersion 4.5-13.5
stabilizing agents 2-6
rubber chemicals 1.5-4.5
DETAILED DESCRIPTION OF THE INVENTION
The subject invention relates to Natural Rubber Modified Bitumen (NRMB) prepared from ammoniated field latex, heat stabilizing agents , antioxidants, curing agents and rubber chemical dispersions.
These heat stabilizing agents are KOH solution , TDQ (Polymerised 2,2, 4-trimethyl-1,2 dilhydroquinoline ) dispersion or a mixture thereof , the curing agents are sulphur dispersions, ZDC (Zinc diethyl dithiocarbamate) dispersions, ZMBT (Zinc Salt of 2-mercapto-benzothiazole) dispersion or a mixture thereof and antioxidant is SP(Styrenated Phenol (SPH) Predominantly 2, 4-di-(alpha-phenylethyl)-phenol.) emulsion.
The Natural Rubber Modified Bitumen comprises of the crumb rubber powder having the following composition :
Arnoniated field latex ( compounded of 33% DRC (Dry Rubber Containts) approx.)
Or ammoniated centrifuged latex (60% Dry Rubber Containts) - 167
-10% Potassium Hydroxide solution 1.0-3.0
along with 10% Potassium Casin
-50% Sulphur dispersion 2.0-8.0
-50% Pilcure ZDC (Zinc diethyl dithiocarbamate) dispersion 20 - 5.0
-50% Pilcure ZMBT (Zinc Salt of 2-mercapto-benzothiazole) dispersion 0.4 - 5.0
-20% Pilnox TDQ (Polymerised 2,2, 4-trimethyl-1,2 dilhydroquinoline ) 1.0- 5.0
-50% Zinc oxide dispersion 1.0-7.0
-50% PILNOX SP (Styrenated Phenol (SPH) Predominantly 2, 4-di-
(alpha-phenylethyl)-phenol.) Emulsion.(Anti-oxidant) 2.0 - 3.0
natural asphalt and bitumen of grades 80/100 or 60/70 blended in the ratio of 6:4:90::3:4:93::2:3:95
The process for the manufacture of a crumb rubber powder from ammoniated natural rubber latex involves the following steps:-
The material is transferred into aluminum trays (normally used for making natural rubber sheets) and put in heated oven/smoke house at the temperature between 100-110°C for curing for 5-20 hours. The semicured rubber sheets free from water are removed from the oven and are ready for grinding/powdering which again involves two steps: In first step the sheets are broken into smaller pieces in cracker grinder/rubber shredder and in the second step the small pieces of rubber are put into roller grinder/disc grinder for fine powdering of 30 Mesh to 50 Mesh size
The grinded crumb rubber can be used either directly for modification of bitumen or by making a blend of latex crumb rubber powder with natural asphalt powder The natural rubber latex crumb powder singularly or along with natural asphalt is tnen packed in HOPE bags for storage.
To Manufacture Natural Rubber Modified Bitumen (NRMB) the natural rubber latex crumb powder is blended along with the bitumen.
The bitumen of specific grades i.e.80/100 or 60/70 is taken into the mixing tank through a direct pipeline or bitumen tankers. The quantity of bitumen taken is checked through a caliberated dipping rod. The total quantity of bitumen taken is only 2/3rd of the capacity of the tank. Each tank is fitted with at least two agitators of a specific design and a pair of circulation pumps for the mixing.
The bitumen taken in the tank is heated to a temperature 150°C - 170°C under controlled conditions by means of indirect heating with steam/ thermic oil
The crumb rubber powder along with the natural asphalt is fed through a rubber conveyor at the controlled speed of 1 MT per 30 minutes approximately . The ratio of crumb rubber modifier and natural asphalt to bitumen is 6:4:90/3:2:95. The different proportions are used for making different grades of the end product i.e. Natural Rubber Modified Bitumen as per Indian Road Congress Publication
Three stirrers attached with each tank are started simultaneously while mixing the modifier and the blend is allowed to mix for a period of 1-2 hours from the time of feeding of the modifier. The stirring is done at a controlled speed of 140-195 RPM per minute to obtain the crumb rubber modified bitumen.
300 parts of ammoniated natural latex (32-33% of dry rubber content) is impregnated with 10-30 parts of dispersion of rubber chemicals namely vulcanizing chemical dispersions, antioxidant chemical dispersions, rubber processing chemical dispersions and stabilizing chemical dispersions by stirring in the drum and kept for maturing at ambient temperature for at least 24 hours.
Items Formulation I Formulation II
Amoniated field latex 300 300
33% DRC (Dry Rubber Content) Approx .
10% Potatium Hydroxide solution 1.0 1.5
alongwith 10% Polatium Casin
-50% Sulphur dispersion 2.0 3.5
-50% Pilcure ZDC (Zinc diethyl dithiocarbamate) dispersion 2.0 2.0
50% Pilcure ZMBT(Zinc Salt of 2-mercapto-benzothiazole) 0.4 0.4
20% Pilcure TDQ (Polymerised 2,2, 4-trimethyl-1,2 1.0 1.0
dilhydroquinoline ) dispersion
50% Zinc oxide dispersion 1.0 2.0
-50% PIL NOX SP (Styrenated Phenol) 20 3.0
Curing the matured blend placed in an open container in an oven at the temperature between 140°C for 8 hours to obtain rubber sheets. The cured sheets are then crushed to fine powder of mesh size.35 thus obtaining crushed rubber powder.
Bitumen of grade 80/100 is filled into a tank fitted with agitators and circulation pumps and heated to a temperature of 155°C by indirect heating. After the bitumen is heated the crumb rubber modifier made from natural rubber latex along with the natural asphalt is fed to the tank wherein the ratio of crumb rubber modifier and natural asphalt to bitumen is 5:3:92. By thoroughly mixing it for a period of at least one hour by stirring it at a speed of 145 RPM a blend of natural rubber modified bitumen is obtained.
The subject application is a statement of invention, wherein various alterations and modification are possible without deviating from the scope of the claimed invention, hence the same should not be construed to restrict the scope of the invention.
1 A Natural Rubber Modified Bitumen comprising crumb rubber powder
obtained from ammoniated natural rubber latex as herein described
natural asphalt and
bitumen as herein described
heated to a temperature of 150°C - 170°C by indirect heating blended in the ratio of 6:4:90::3:4:90:2:3:95
2 A Natural Rubber Modified Bitumen as claimed in claim 1, wherein the
Bitumen used is selected from 80/100 grade and 67/100 grade.
3 A.Natural Rubber Modified Bitumen as claimed in claim 1 wherein the said
Crumb Rubber Powder comprises :
ammoniated natural rubber latex (33% dry rubber content) 300 parts
curing agents 4.5-13.5
stabilizing agents 2-6
rubber chemicals 1.5-4.5
4 A Natural Rubber Modified Bitumen as claimed in claim 3, wherein the said
curing agents are selected from 50% sulphur dispersion ,50% pilcure ZDC
(Zinc diethyl dithiocarbamate) dispersion ,50% pilcure ZMBT (Zinc Salt of 2-
mercapto-benzothiazole) dispersion and / or a mixture thereof.
5 A Natural Rubber Modified Bitumen as claimed in claim 3, wherein the said
antioxidant agent is 50% PILNOX SP(Styrenated Phenol (SPH) Predominantly 2,
6 A Natural Rubber Modified Bitumen as claimed in claim 3 , wherein the said
stabilizing dispersions are selected from 10% KOH solution along with 10%
7 A Natural Rubber Modified Bitumen as claimed in claim 3, wherein the said
rubber processing chemicals are Zinc oxide dispersions .
8. A Natural Rubber Modified Bitumen substantially as hereinbefore described with reference to the given examples.
|Indian Patent Application Number||97/DEL/2005|
|PG Journal Number||38/2008|
|Date of Filing||17-Jan-2005|
|Name of Patentee||VIJAY SEKHRI|
|Applicant Address||C-295, DEFENCE COLONY, NEW DELHI -110024.|
|PCT International Classification Number||B05D|
|PCT International Application Number||N/A|
|PCT International Filing date|