TITLE:
An improved process for manufacturing non-asbestos cement roofing fiber sheets.
FIELD OF THE INVENTION:
The present invention relates to an improved process for manufacturing non-asbestos cement roofing fiber sheets.
BACKGROUND OF THE INVENTION:
In the past asbestos-cement compositions have been formed into products such as flat sheets, corrugated sheets, boards, panels and the like. These sheets generally contained Portland cement in the amount of 43 to 55%, silica and / or filler in the amount of about 30 to 35% and asbestos fibres in the amount of about 10 to 12%. The products had many desirable qualities, including high strength, exterior durability and easy application. Asbestos is a naturally occurring mining product. But day by day the availability of quality fibers is reduced tremendously. Hence it is essential to develop corrugated sheeting product with alternative fibers with similar strength of asbestos based and cost effective.

Conventionally, the wood pulp has also been used as an alternate to asbestos due to its unique characteristic of good dispersion in cementicious / water slurry because of its hydrophilic nature. In this process, the wood pulp and synthetic fibers such as Poly vinyl alcohol fibers intimately mixed with the cement particles and remained in suspension without settling out or floating to the top of the slurry. Non-asbestos fibre cement compositions have been formed into products such as flat sheets, corrugated sheet, boards, panels and the like. These sheets generally contained Portland cement in the amount of 70 to 80%, silica and / or filler in the amount of about 10 to 20% and synthetic fibers and wood pulp in the amount of about 4 to 8%.
The above combination of fiber and fillers the end product can't be subjected for hydrothermal curing (autoclave) only Air cured/ water cured method to be adopted.
Conventionally the sheets generally contained the Portland cement in the amount of 70 to 80% and it is known that when one ton cement is produced, consequently one ton of carbon dioxide (C02) is emitted into the atmosphere from cement manufacturing industries. Replacement of cement with fly ash and Ground granulated blast furnace slag (GGBS) protects environment by reducing Green House Gas (GHG) emission (according to the International Energy

Agency, cement production accounts for 7% of total global C02 emission).
An attempt has been made replacing Poly Vinyl Alcohol fibers which cannot with stand autoclave conditions due to low melting point and glass transition with new modified polyethylene terephthalate (PET) fibers and natural mineral fibers like Wollastonite.
As attempt has been made replacing Asbestos fibers or wood pulp in combination of PVA fibers with Cellulose pulp, Modified PET fibers and Wollastonite/modified wollastonite.
An attempt has been made to partly replacing cement in non asbestos fibre cement products with fly ash and GGBS which are generated as waste by product 'from thermal power and steel plants. Inhalation of Quartz is known to cause silicosis and is also a known to develop carcinogenesis. In other words replacing silica with fly ash minimizes the health hazard.
As attempt has been made replacing conventional curing such as Air cured or water curing with hydrothermal (autoclave) curing this improve the dimensional stability of the product.

A product replacing asbestos fibres and PVA fibers, silica and partly replacing cement with suitable materials makes it unique Green product in many ways. The present invention provides the method to Manufacture of Non asbestos fiber cement sheet (corrugated) comprising of the processing reinforced fibers such as herein described
It also reduces the emission of other common air pollutants such as NOx and SOx, associated with cement production by the same proportion. Apart from this cement substitution with fly ash/GGBS saves natural resources such as lime stone, coal which are being used for the manufacturing of cement. Mining of lime stone, coal and cement production needs energy and they are polluting the environment to great extent. So cement replacement helps in energy conservation and environment protection.
OBJECTS OF THE INVENTION:
An object of the present invention is to replace asbestos fibers, wood pulp, PVA
fibers and part replacement of cement to make Non Asbestos Cement Roofing sheets.
Another object of the present invention is to use materials like PET fibers, Wollastonite/modified wollastonite to replace asbestos fibers and PVA fibers.

Yet another object of the present invention is to use materials like Cellulose pulp in virgin or processed cotton rag to replace both asbestos and natural wood pulp.
Still another object of the present invention is to use materials like pulverized fly ash and GGBS as pozzolanic ingredient for part replacement of cement to enhance the strength properties, protect environment and minimize health hazardous.
Yet another object of the present invention to avoid 28 days air cured/ water cured by hydrothermal (Autoclaving) curing for 1 Day.
Another objective of the present invention, method of manufacturing building product generally similar in strength and other properties to the product manufacturing using Asbestos fiber cement roofing sheet, Wood pulp and PVA fibers cement roofing sheet.
BRIEF DESCRIPTION OF THE INVENTION:
According to this invention there is provided an improved process for
manufacturing non-asbestos cement roofing fiber sheets comprising; preparing a slurry; subjecting the said slurry to the step of forming thin films, applying the said thin films on accumulator rolls, curing the arranged product.

DETAILED DESCRIPTION OF THE INVENTION:
The present invention relates to Non asbestos cement roofing fiber product which
does not contains asbestos, PVA and virgin wood pulp and silica powder but which contains other fibres and the combination of Cellulose, Modified PET Fibers, wollastonite/modified wollastonite, cement and siliceous material such as fly ash and GGBS so as to permit satisfactory production thereof on a machine in which a slurry is formed on a screen and subsequently vacuum-filtered through a screen and or felt.
In the following paragraphs, wherein the fly ash is referred, it mean the fly ash, (it is a burnt and powdery derivative of inorganic mineral matter) that generates during the combustion of pulverized coal in the thermal power plant. Similarly wherein the term cellulose pulp is referred, it the cellulose pulp, which is obtained by mechanical pulping of cotton in loose or cloth form. In the following paragraphs, when inventor refers Non-asbestos fiber cement sheets, that is the new and invented non-asbestos fiber cement sheets which are environment friendly products as is described in the present claim invention.
Cellulose pulp is obtained from natural cotton or processing the waste cotton rags. Modified PET Fibers are having high molecular weight with good water dispersion and compatible with cement. Wollastonite is natural occurring mineral

fiber having very good aspect ratio to attain strength and durability. Conventional fiber cement sheets are cured either air cured or water cured which is tedious and long period of curing (28days) needs good amount of water which is natural resource. The present invention by hydrothermal curing (autoclaving) the curing process completes in one day and no further curing is required it saves time and as well as precious water.
Due to this invention we have achieved the strength similar to asbestos based fiber cement sheets.
The process of the invention and its advantage will now be explained in greater detail with reference to the known method of manufacture of such sheets for clear and better understanding of the invention.
STEP 1- PREPARING THE SLURRY
According to the present invention, an improved process for manufacture of Non Asbestos Cement Roofing Fiber cement sheets comprising of the processing reinforced fibres is provided.

The said reinforcing fibers essentially included Cellulose Pulp having fiber opening Deg.SR 12-50 used in an amount of 3-15%, PET fibers and wollastonite/modified wollastonite in an amount of 0.25 to 6%, Portland cement in an amount of 20 to 55%, Siliceous material in the binder essentially pulverized fly ash having surface area of 2000-8000 cm2/gm used in an amount of 15 -50%, Ground granulated blast furnace slag having surface area greater than 3000 cm2/gm in an amount of 2 to 20% and fillers and additives in an amount of 0.25 to 5% by weight of the total mixing comprising or the reinforcing fibres, cement, fillers and additives.
The mixing the above mentioned fibers with water to form a fiber slurry, adding binders comprising basically Ordinary Portland Cement, GGBS and siliceous materials such as herein described optionally with fillers and additives such as herein described to said fiber slurry followed by feeding the mixture thus formed to sheet forming machine such as herein described, demoulding and subsequently curing by hydrothermal method at 90 to 130 psi pressure for 10 to 15 hours.
While making slurry, care was taken to ensure there was homogeneous mixing of siliceous material, additives, GGBS and cement with reinforcing fibers.

Mixing/holding system ensured that solids are not separated from the aqueous solution, i.e. solids do not settle so that the lamination having uniform distribution of the binder and the reinforcing fibers is obtained in the process.
STEP 2: APPLICATION OF SLURRY
The recipe thus obtained in respect of the above formulations were independently run on pilot plant sheet forming machine such as HATSCHECK MACHINE where thin films are picked up and superimposed on accumulator roll. The composite is cut upon after building up to desired thickness and laid flat and or conveyed for corrugation and stacking before pre curing. Over a period of time and at predetermined temperature, the initial curing in the composite make it strong and acquire enough strength for demoulding.
STEP 3: CURING THE ARRANGED PRODUCT.
Demoulded articles are then arranged on a trolley and cured under Autoclave maintaining the steam pressure for 90 to 130psi and duration of 10 to 15 hours. After curing is over, cured material in the trolleys is pulled out and stacked in ambient condition for further inspection and dispatch.

EXAMPLES
Using the above said slurry and process of manufacturing the claimed Non Asbestos Cement Roofing fiber cement sheet, The various trials were conducted in order to replace the Asbestos fibers, PVA fibers and part replacement of cement with fly ash and GGBS.. Some typical examples and test results are as follows:
Example 1 Present invention

Curing: Hydrothermal curing(Autoclave) 90 to 130 psi for 10 to 15 hours.


Example 2 Present invention

Curing: Hydrothermal curing (Autoclave) 90 to 130 psi for 10 to 15 hours.


It is obvious to mention that the above process / recipe was run on pilot plant sheet forming machine and so-called process is known as "HATSCHECK". In this process invented slurry of reinforcing fibers used are subjected to conventional treatment for opening up where in necessary amount of water is added to the slurry so obtained, Portland cement, GGBS, siliceous materials, fillers and other additives are mixed together.
APPLICATION OF CONVENTIONAL FORUMULATIONS IN SIMILAR CIRCUMSTANCES

In order to determined the difference between the invented product and the product manufactured by using conventional formulations and by using similai machines and following similar steps, a typical conventional formulation of mi> was used for preparation of non-asbestos fibre cement sheets and received the following results:-

It has been determined by way of compression of the conventional sheets with the sheets claimed in the present inventions that the claimed invented sheets are significantly improved and having better in strength in comparison to conventional sheets. Further use of the claimed slurry and process, there is a successful attempt to reduce the use of soft wood pulp along with cement.

WE CLAIM:
1. An improved process for manufacturing non-asbestos cement roofing fiber
sheets comprising;
preparing a slurry;
subjecting the said slurry to the step of forming thin films applying the said thin films on accumulator rolls, curing the arranged product.
2. The process as claimed in claim 1, wherein the said slurry is a homogeneous mixture of silicones material, additives, ground granulated blast furnace slag (GGBS) and cement with reinforcing fibers.
3. The process as claimed in claim 1 wherein the said GGBS is present in an amount of 2 to 20% having surface area greater than 3000 cm2/gm.
4. The process as claimed in claim 1, wherein the step of curing is preferred under autoclave maintaining the steam pressure for 90 to 130 psi and duration of 10 to 15 hours.

5. A process as claimed in claim 4 wherein the said reinforcing fibers is Cellulose pulp from virgin cotton or waste cotton rags used alone or in combination with man made (synthetic) fibers such as modified Polyethylene Terephthalate(PET), ceramic fibers, Glass fibers, mineral wool and ceramic wool. The natural mineral fibers such as wollastonite/modified wollastonite either alone or in combination.
6. A process as claimed in anyone of claims 1-5 wherein the said reinforcing fibres is Cellulose pulp is preferably processed to opening Deg.SR 12-50, used in an amount of 3-15% by weight of the total mix.
7. A process as claimed in anyone of claims 1-6 wherein the said reinforcing man made (synthetic) fibers modified Polyethylene Terephthalate(PET), ceramic fibers, Glass fibers, mineral wool and ceramic wool used individual or in combination in an amount of 0.25-6% by weight of the total mix.
8. A process as claimed in anyone of claims 1-7 wherein the said reinforcing natural occurring mineral fibers such as wollastonite/ modified wollastonite either alone or in combination in an amount of 0.25 to 6% by weight of the total mix.

9. A process as claimed in anyone of claims 1-8 wherein the pulverized fly ash used has a fineness of 2000-8000 cm2/gm, in an amount of 15-50% by weight of the total mix.
10. A process as claimed in anyone of claims 1-9 wherein the filler used amorphous silica (micro silica) in an amount of 0.25 to 5% by weight of the total mix.
11. A process as claimed in anyone of claims 1-10 wherein the additives used bentonite, pangel, flocculating agents, defoamers, water reducing admixtures of silicone or acrylic base in an amount of 0.25 to 5% by weight of the total mix.