|Title of Invention||
A METHOD FOR MANUFACTURING FIBRE REINFORCED CEMENT
|Abstract||A process for manufacturing fibre reinforced cement comprising homogenously mixing, of cut dry fibres of length 3 to 15mm with cement particles, by means of pressurized air at pressures ranging from 1 to 4 kg/cm.|
THE PATENT ACT, 1970
(39 of 1970)
THE PATENT RULES, 2003
(See section 10 and Rule 13)
MANUFACTURE OF FIBER CEMENT.
GRASIM INDUSTRIES LIMITED
An Indian Company
of Birlagram, Nagda-456 331, Madhya Pradesh,
THE FOLLOWING SPECIFICATION DESCRIBES THE INVENTION
This invention relates to a method of making fiber cement and an improved fiber cement composition made by this method.
FIELD OF INVENTION
This invention relates to fiber cement and a method of making fiber cement.
Fibre reinforced cement is an old concept and is widely available in the literature for the last 30 years. The fibres referred to are glass, polypropylene , polyester, nylon, bamboo, steel and other synthetic and natural materials. Presently, the fibres are mixed in cement at the time of application of cement along with sand, aggregate and water. Normally this is done at the site or in RMC plant. Only one case is known where Von Tech has patented a process where fibre is interground with the cement and fiber cement is produced. Normally all fibre manufacturers recommend that fibre should not get damaged. During intergrinding the fibre, the fibres when ground along with clinker to form cement are fully damaged. This has been tested and microscopically examined in laboratory.
BACKGROUND OF THE INVENTION
European patent 0275156A1 discloses dry milled fibre cement products manufactured by preparing fibres from a base cellulose stock such as wastepaper, which is first broken up into small pieces in a shredder and then disintegrated in a dry hammer mill such that the fibres are fibrillated. The fibres are mixed with cement water slurry and the water then dried off leaving a laminated wet web on a porous support which is then allowed to cure and harden. Synthetic organic fibres such as PVAc may also be incorporated.
International patent 9200927A1 discloses autoclaved fire resistant fibre cement products comprising, cellulose fibres, cementitious material, and 1 % to about 40 % of magnesite on a dry weight basis. The percentage of cellulose fibres is in the range from 7 % to 8.5 % and the magnesite in a
preferred range of between 25 % to 40 %. Silica and Portland cement may also be included.
International patent 04031093A1 discloses durable medium density fibre cement composite product and method of modifying the properties of a low or medium density FRC product by providing a predetermined pore size distribution. The pore size distribution is obtained such that in critical zones of the distribution, the pore volume is substantially equivalent to or less than the pore volume in a respective critical zone of a conventional high density FRC product. The resultant material provides improved properties over conventional medium density FRC products, in particular improved freeze/thaw durability and/or improved workability.
United States patent 20060182946 discloses durable high performance fibre cement product including a first major surface to which a carbonation reducing sealer is applied and a second generally opposing major surface to which a carbonation reducing sealer is applied, so as to reduce propensity for differential carbonation in the product. A method of manufacturing a durable fibre reinforced cement product, said method comprising steps of mixing a wet fibre reinforced cement formulation; forming from said formulation a green product defining first and second generally opposing major surfaces; curing the green product to form a cured product; and applying a carbonation reducing sealer to said first and second major surfaces, so as to reduce propensity for differential carbonation in the product. An engineered fibre reinforced cement product including a first major surface with a reduced propensity to differential carbonation,
wherein the product has a cement to silica ratio of between 0.29 and around 0.51 and a porosity of between 25% and around 45%.
United States patent 20030176593 discloses Building material comprising a fibrous or filament reinforcement with hydraulic binder. The reinforcement consists of synthetic yarns and fibres, modified by a dendritic polymer. The invention concerns for example fibre cements whereof the reinforcing fibers
consist of a composition comprising a polyamide and a dendritic polymer.
In the prior art the fibres are mixed in cement at the time of application of cement along with sand, aggregate and water. Normally this is done at the site or in RMC plant. In other processes fibre is interground with the cement. During intergrinding the fibre, the fibres when ground along with clinker to form cement are fully damaged. This creates a big weakness in final product of fibre cement.
OBJECT OF THE INVENTION
The object of the invention is to provide a method of making fiber cement.
Another object of the invention is to provide a process where fibre is not ground along with cement.
Yet another object of the invention is to provide uniform distribution of de aggregated fibre in fibre cement.
Yet another object of the invention is to provide intact fibres in fibre cement.
Still another object of the invention is to provide a fiber cement with improved properties.
SUMMARY OF THE INVENTION
According to this invention, therefore there is provided a process for making Fibre reinforced cement, typically comprising the following steps which are by way of example only,
a) Unwinding coiled roll of fibres by coiler motor at a predetermined rpm based on the proportion of fibre to be mixed in cement and the density of fibre to get uncoiled fibres,
b) Cutting Uncoiled fibres typically by a roll cutter as per desired length,
c) Receiving cut fibres in bulk collected in a specially designed
first storage system to facilitate the flow and having a opening at the bottom,
d) Extracting fibres from the bottom outlet of the first storage system at a desired mass flow rate (kg/hr) by specially designed first conveyer belt system with spikes on the surface,
e) Discharging extracted fibres into an the inlet of a second conveying system along with cement to form a fibre cement mixture and conveyed to second storage system.
In accordance with one embodiment of the invention, the fibres consists of at least one fibrous material selected from a group of fibrous materials consisting of glass, polypropylene , polyester, nylon, aramid, polyamide, Teflon, acrylate, bamboo, steel, Virgin Wood Pulp, Bamboo pulp, Hardwood, Softwood, Jungle wood, Cotton yarn, paper, rice straw, wheat straw and husk.
In accordance with another embodiment of the invention, the first storage system is designed with at least one material selected from a group of materials consisting of steel, copper, wood, concret, plastic and brass In accordance with another embodiment of the invention, the bottom outlet of the first storage system is equipped with at least one device selected from a group of devices consisting of rotary air lock, drum with spikes, vibro feeder, ping gate and vacuum suction.
In accordance with another embodiment of the invention, the second conveying system is at least one system selected from a group of systems consisting of pneumatic Conveying system, FK Pump, Fluxo Pump, Air Lift,
Mechanical Conveying System, Screw Conveyor and Bucket elevator.
In accordance with another embodiment of the invention, the second
conveying system is preferably pneumatic Conveying system.
In accordance with another embodiment of the invention, the third conveying system is at least one system selected from a group of systems consisting of screw conveyor and bucket elevator.
In accordance with another embodiment of the invention, the compressed air pressure ranges from 1 to 4 kg/cm2.
DETAILED DESCRIPTION OF THE INVENTION
The fibres can be collected from fibre manufacturers in one of the two forms:
(a) Coiled roll of fibres
(b)Cut fibres of varying length from 3 mm to 15 mm.
For coiled roll of fibres, the 1st stage of the manufacturing process in accordance with this invention is as under:
The coil is connected to a variable speed motor attached with a PLC. This motor unwinds the coil and the fibres are sent out to a roll cutter (used in fibre plants) for cutting the fibres as per the desired length. The coiler motor uncoils the fibre at a pre-determined rpm based on the proportion of fibre to be mixed in cement and the density of fibre. This process will ensure that the fibre is extracted, cut and fed to the process at a desired mass flow rate (kg/hour).
For cut fibres, the 1st stage of manufacturing process is as under:
The fibres received in bulk are emptied in a hopper. Most of the varieties of these fibres are sticky and form lumps and thus are difficult to disperse from each other. The hopper is especially designed with steel or any other material to facilitate the flow. At the bottom of the hopper, there is an opening, where a conveying belt equipped with beltware is installed. This belt is specially designed belt with spikes on the surface to extract fibres from the hopper. The beltware is connected to a PLC and the conveyor has a variable speed motor connected to the same PLC. The motor speed is varied through PLC based on readings of beltware to ensure the flow of fibres at a desired mass flow rate (kg/hr). The outlet of hopper may also be equipped with devices like rotary air lock, drum with spikes, vibro
feeder, ping gate, vacuum suction or other extraction devices.
Once, the fibres are extracted, based on any of the above two methods, the fibres are discharged into the inlet of any of the following devices along with cement:
Pneumatic Conveying system - FK Pump, Fluxo Pump, Air Lift or similar
Mechanical Conveying System - Screw Conveyor, Bucket elevator or similar
The pneumatic system is the most preferred way in view of uniform mixing of fibre and cement. The pressurized air ensures mixing of fibre and cement uniformly. The higher the pressure of the air and density of air-cement mixture, the better is the mixing.
This mixture is directly conveyed to a storage system - silo, hopper etc. The fibre cement so produced and stored is extracted from the bottom of silo/hopper by means of compressed air and conveyed through mechanical conveying system (screw conveyor/bucket elevator) is sent to another hopper at height (called packer hopper). Conveying by air slide should be avoided as it may segregate fibres. The screen (any size) which is always installed at the discharge of the packer hopper for segregating nibs must not be installed or bypassed for fibre cement. It was found that even if the size of the screen is >4 mm, it can segregate the fibres which are much smaller in size.
This hopper can be connected to bulk loading system (already available in the market) or one spout mechanical packer for bagging the same. The mechanical packer available in the market will require some modifications -the size of the nozzle will have to enlarged and it requires connection with 1-4 kg/cm2 compressed air connection.
Thus it is apparent that there has been provided, in accordance with the invention, a product and process that fully satisfies the objects, aims, and advantages set forth above. While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations
will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations. For instance, the fibres may undergo a drying process before introduction so that the moisture in the fiber is less than 1%.
|Indian Patent Application Number||2118/MUM/2006|
|PG Journal Number||08/2011|
|Date of Filing||22-Dec-2006|
|Name of Patentee||GRASIM INDUSTRIES LIMITED|
|Applicant Address||BIRLAGRAM, NAGDA 456 331,|
|PCT International Classification Number||B32B5/18,B29C41/04|
|PCT International Application Number||N/A|
|PCT International Filing date|