Claims:
1. A fiber cement coloured roofing sheet having in-built anti-algal, anti-fungal and water repellent properties wherein the coloured roofing sheet manufactured by an automated process comprising steps of:
(a) forming multiple layers of fiber cement films using endless felt on plurality of separate sieve cylinders (100) simultaneously;
(b) transferring the formed layers of fiber cement films on a rotating metallic drum in order to form a roofing sheet of a desired thickness;
(c) removing excess water from the roofing sheet on a moving felt (600) using a plurality of vacuum boxes (300) and by squeezing the layer between a forming drum and a press roller;
(d) colouring the roofing sheet by spraying colour coating composition through an automated atomiser coating system (400) on the last layer of the roofing sheet; and
(e) removing excess water from the roofing sheet by adjusting vacuum in a suction box (500);
wherein a colour coating composition is added to a last layer of the roofing sheet.

2. The roofing sheet according to claim 1 further comprises incorporating additional layer of binder along with water on top of the colour coating composition by using an additional spray system to give an additional binding and water repellent effect to the product.

3. The roofing sheet according to claim 1 & 2 further comprises
(a) converting the flat sheet into a profile sheet using a corrugators pad;
(b) hardening the profile sheets by placing between two templates for 8-10 hours; and
(c) de-stacking and curing the partially hardened profile sheet for 21 days in a covered area to prepare the final product.

4. The roofing sheet according to claim 2, wherein the additional layer of binder is selected from thermosetting or thermoplastic cross-linkable polymers.

5. The roofing sheet according to claim 4, wherein the thermosetting or thermoplastic cross-linkable polymer is selected from, but not limited to, acrylic, epoxy, polyurethane or copolymer or in-combination thereof.

6. The roofing sheet according to claim 2, wherein the additional binder is in ratio of 1:10 with water.

7. The roofing sheet according to claim 1, wherein the colour coating composition comprises a water repellent additive, an anti-fungal and anti-algal additive, a coloured pigment, an extender and a binder.

8. The roofing sheet according to claim 1, wherein the formation of multiple layers of cement films on the plurality of separate sieve cylinders is synchronised with each other.

9. The roofing sheet according to claim 1, wherein the automated spray coating by the atomiser coating system (400) is decided on factors including, but not limited to, depth of coating required, variations of colour paste viscosity.

10. The roofing sheet according to claim 1, wherein the colour coating composition is sprayed to the last layer of the sheet by means of an automated atomiser coating system.

11. The roofing sheet according to claim 1, wherein the colour coating composition comprises of Colour pigment in an amount of 2-45%, water repellent additive in 0.1-1.5%, an anti-fungal & anti-algal additives in 0.2-1.5%, an extender in 1-30%, a binder in 5-35%, and water.

12. The roofing sheet according to claim 11, wherein the colour pigments are inorganic or organic pigments or combination thereof.

13. The roofing sheet according to claim 11, wherein the water repellent additives are selected from, but are not limited to, Siliconates, Silane-siloxanes, active silicates of sodium or potassium or combination thereof.

14. The roofing sheet according to claim 11, wherein the anti-fungal & anti-algal additives are selected from, but are not limited to, Zinc-pyrithione, Idopropynyl butyl carbamet (IPBC), Carbendazim, Diuron, Octyl Iso Thiazolin (OIT) or a mixture thereof.

15. The roofing sheet according to claim 11, wherein the extender may be selected from, but not limited to, calcium carbonate, calcium magnesium carbonate, barium sulphate, talc, kaolin, carbonates of alkaline earth metals or combination thereof.

16. The roofing sheet according to claim 11, wherein the binder is selected from, but is not limited to, ordinary Portland cement, Portland Pozzolana cement, ground granulated blast-furnace slag or combination thereof.

17. The roofing sheet according to claim 1, wherein the roofing sheet composition comprises of Mineral fibers in an amount of 0-13%, Polymeric fibers in 0-13%, Cement binder in 30-60%, Pozzolonic material in 30-60%, and Cellulosic pulp in 0-13%.

18. The roofing sheet according to claim 17, wherein the mineral fibers are selected from, but are not limited to, chrysotile, wollastonite and such.

19. The roofing sheet according to claim 17, wherein the polymeric fiber are selected from, but not limited to, polyester, polyvinyl alcohol, polypropylene or combination thereof.

20. The roofing sheet according to claim 17, wherein the cement fiber is selected from, but not limited to, ordinary Portland cement, Portland Pozzolana cement, ground granulated blast-furnace slag or combination thereof.

21. The roofing sheet according to claim 17, wherein the pozzolonic material is selected from, but not limited to, fly ash, silica or combination thereof.
, Description:REFERENCE:
The present invention is a Divisional Patent Application to originally filed Patent Application No. 201721021072 dated 16/06/2017.

FIELD OF INVENTION:
The present invention relates to a Coloured Roofing Sheet having anti-fungal and anti-algal properties, and high aesthetic value. More particularly, the present invention relates to the said coloured roofing sheets and a method of preparing the same by on-line atomiser process and the product made thereof.

BACKGROUND & PRIOR ART:
Coloured Roofing Sheets having anti-fungal and anti-algal properties have been disclosed in pending patent application no. 3168/MUM/2013 and 33/MUM/2013, filed by the applicant of the present invention. In the said applications, colour pigment additives are incorporated during manufacturing by mass pigmentation within Hatschek process. The colour pigments such as colour oxides or organic / inorganic colouring ingredients are incorporated into the roofing sheet composition in the last vat of the machine.

In order to enhance and prolong the colour aesthetics of the roofing sheets, the inventors of the present invention have invented a novel approach of on-line atomiser based pigment impregnation method on Hatscheck process, in a very economical way.

US20130095293 discloses a coloured roofing coverings and a method for manufacturing the same. A fiberglass mat has upper and lower surfaces provided with an asphalt coating layer to make the mat waterproof. Onto the said coating layer is disposed a layer of top surfacing material comprises of individual granules. Thereafter, a colour coating layer is disposed on top of the said top surfacing layer. The colour coating layer is a spray painted layer or ink injected layer, wherein the spray coating or ink injecting is computer controlled.
US2111761 relates to the process and apparatus for applying coating material, such as asphalt, bitumen or other coating material mixed with bronzing powder or other pigments, to a roofing sheet or other plane surface. The coating material is directly applied to a moving roofing sheet by means of a spraying device. The spraying device can be manipulated to apply in spaced parallel bands or at any desired angle. Different coloured grits can be applied to the continuous portion of the same strip to obtain any desired ornamental appearance. The apparatus is also provided with a regulating valve to control the flow of coating material and a means of circulating the excess coating material back to the supply of source.

Even though, above mentioned inventions are related to atomized coloration of roofing components, these processes do not relate to the Hatscheck process integration, as well as inorganic coloration of multi-layered cement fiber sheets.

SUMMARY OF INVENTION:
The present invention discloses a fiber cement coloured roofing sheet having anti-fungal and anti-algal properties, excellent water repellent effect and high aesthetic value.

According to the present invention, the fiber cement coloured roofing sheet is prepared by a method , which comprises steps of:
(a) forming multiple layers of fibre cement films using endless felt on plurality of separate sieve cylinders simultaneously;
(b) transferring the formed layers of cement sheets / films on a rotating metallic drum in order to form a roofing sheet of a desired thickness;
(c) removing excess water from the roofing sheet on a moving felt using vacuum system and also by squeezing the layer between forming drum and press roller; and
(d) colouring the roofing sheet by automated spray coated atomiser on the last layer of the roofing sheet;

The method further comprises transferring the sheet by using conveyor and then further converting the flat sheet into profile sheet using corrugators pad; stacking the sheets between two templates and keeping for 8-10 hours within the template to complete the initial hardening process; destacking the sheets from the template and curing for 21 days in a covered area. After curing the sheets are checked for quality parameters and are ready for despatch.

In an embodiment, a colour coating having anti-fungal, anti-algal properties for the roofing sheets is disclosed. The colour coating composition comprises of Colour pigment in an amount of 2-45%, water repellent additive in 0.1-1.5%, an anti-fungal & anti-algal additives in 0.2-1.5%, an extender in 1-30%, a binder in 5-35%, and water to achieve sprayability. The colour pigment may be inorganic or organic pigments or combination thereof. The water repellent additives are selected from, but are not limited to, Siliconates, Silane-siloxanes, active silicates of sodium or potassium or combination thereof. The anti-fungal & anti-algal additives are selected from, but are not limited to, Zinc-pyrithione, Idopropynyl butyl carbamet (IPBC), Carbendazim, Diuron, Octyl Iso Thiazolin (OIT) or a mixture thereof. The extender may be selected from, but not limited to, calcium carbonate, calcium magnesium carbonate, barium sulphate, talc, kaolin, carbonates of alkaline earth metals or combination thereof. The binder is selected from, but is not limited to, ordinary Portland cement, Portland Pozzolana cement, ground granulated blast-furnace slag or combination thereof.

In an embodiment, the roofing sheet composition comprises of Mineral fibers in an amount of 0-13%, Polymeric fibers in 0-13%, Cement binder in 30-60%, Pozzolonic material in 30-60%, and Cellulosic pulp in 0-13%. The mineral fibers may include, but are not limited to, chrysotile, wollastonite and such. The polymeric fiber are selected from, but not limited to, polyester, polyvinyl alcohol, polypropylene or combination thereof. The cement fiber may include, but not limited to, ordinary Portland cement, Portland Pozzolana cement, ground granulated blast-furnace slag or combination thereof. The pozzolonic material is selected from, but not limited to, fly ash, silica or combination thereof. The said composition is diluted with water for achieving flowability and film formation.

In an embodiment, the formation of multiple layers of cement films on the plurality of separate sieve cylinders is synchronised with each other. The automated spray coating by atomiser is decided on factors including, but not limited to, depth of coating required, variations of colour paste viscosity.

In yet another embodiment, the present invention discloses an fiber cement roofing sheet with in-built anti-fungal and anti-algal biocide additives, colour pigmentation additives and water repellent additives; wherein said biocide additives, colour pigmentation additives and water repellent additives are incorporated into said fibre cement roofing sheet during Hatscheck process based multi-layered manufacturing by an online atomiser system to enhance the durability and resistance to wide range of fungi and algae and to enhance aesthetics and water repellency of the product, respectively. The online atomiser system is integrated with the Hatscheck process using novel programmable circuit controller.

The coloured roofing sheets produced by the method of the present invention exhibits no seepage properties as well as a lotus effect on the top surface, at any given point of time when it is in use.

BRIEF DESCRIPTION OF DRAWINGS:
Fig. 1 illustrates a diagrammatical representation of an automatic raw material feeding system for pigment preparation.

Fig. 2 illustrates a process of the present invention by which anti-fungal, anti-algal, coloured roofing sheet are prepared.

DETAILED DESCRIPTION OF INVENTION:
The present invention may be comprehended in detail with reference to figures and illustration, which are described below. However, the figures and illustrations demonstrate various embodiments of the invention and do not restrict the invention to the figures. For the person skilled in the art, any minor variations may be viewed as falling into the scope of the invention.

The present invention describes fiber cement coloured roofing sheets, which have in-built anti-fungal and anti-algal properties, excellent water repellent effect and high aesthetic value. The coloured roofing sheet is prepared by an automated process comprising steps of:
(a) forming multiple layers of fiber cement films using endless felt on plurality of separate sieve cylinders simultaneously;
(b) transferring the formed layers of fiber cement films on a rotating metallic drum in order to form a roofing sheet of a desired thickness;
(c) removing excess water from the roofing sheet on a moving felt using a plurality of vacuum boxes and by squeezing the layer between a forming drum and a press roller;
(d) colouring the roofing sheet by spraying colour coating composition through an automated atomiser coating system on the last layer of the roofing sheet; and
(e) removing excess water from the roofing sheet by adjusting vacuum in a suction box; wherein a colour coating composition is added to a last layer of the roofing sheet.

The method further comprises incorporating additional layer of binder along with water on top of the colour coating composition by using an additional spray system to give an additional binding and water repellent effect to the product.
Furthermore, the method comprises:
(a) converting the flat sheet into a profile sheet using a corrugators pad;
(b) hardening the profile sheets by placing between two templates for 8-10 hours; and
(c) de-stacking and curing the partially hardened profile sheet for 21 days in a covered area to prepare the final product.

The additional layer of binder is selected from thermosetting or thermoplastic cross-linkable polymers. The thermosetting or thermoplastic cross-linkable polymer is selected from, but not limited to, acrylic, epoxy, polyurethane or copolymer or in-combination thereof. The additional binder is in ratio of 1:10 with water.

The colour coating composition comprises a water repellent additive, an anti-fungal and anti-algal additive, a coloured pigment, an extender and a binder. The colour coating composition is sprayed to the last layer of the sheet by means of an automated atomiser coating system.

Further, the formation of multiple layers of cement films on the plurality of separate sieve cylinders is synchronised with each other.

Further, the automated spray coating by the atomiser coating system is decided on factors including, but not limited to, depth of coating required, variations of colour paste viscosity.

In an embodiment, the colour coating composition comprises of Colour pigment in an amount of 2-45%, water repellent additive in 0.1-1.5%, an anti-fungal & anti-algal additives in 0.2-1.5%, an extender in 1-30%, a binder in 5-35%, and water to achieve sprayability. The colour pigment may be inorganic or organic pigments or combination thereof. The water repellent additives are selected from, but are not limited to, Siliconates, Silane-siloxanes, active silicates of sodium or potassium or combination thereof. The anti-fungal & anti-algal additives are selected from, but are not limited to, Zinc-pyrithione, Idopropynyl butyl carbamet (IPBC), Carbendazim, Diuron, Octyl Iso Thiazolin (OIT) or a mixture thereof. The extender may be selected from, but not limited to, calcium carbonate, calcium magnesium carbonate, barium sulphate, talc, kaolin, carbonates of alkaline earth metals or combination thereof. The binder is selected from, but is not limited to, ordinary Portland cement, Portland Pozzolana cement, ground granulated blast-furnace slag or combination thereof.

In an embodiment, the roofing sheet composition comprises of Mineral fibers in an amount of 0-13%, Polymeric fibers in 0-13%, Cement binder in 30-60%, Pozzolonic material in 30-60%, and Cellulosic pulp in 0-13%. The mineral fibers may include, but are not limited to, chrysotile, wollastonite and such. The polymeric fiber are selected from, but not limited to, polyester, polyvinyl alcohol, polypropylene or combination thereof. The cement fiber may include, but not limited to, ordinary Portland cement, Portland Pozzolana cement, ground granulated blast-furnace slag or combination thereof. The pozzolonic material is selected from, but not limited to, fly ash, silica or combination thereof. The said composition is diluted with water for achieving flowability and film formation.

Figure 1 illustrates an automatic raw material feeding system for the preparation of pigment slurry. The raw materials are stored in different tanks and the raw materials are mixed in first Pigment preparation tank (1). In Fig 1, (2) and (3) indicate second tank and third tank, each of equal capacity for holding water repellent addictive and anti-fungal addictive respectively. An extender hopper (4) and a binder hopper (6) are also connected to the first Pigment preparation tank (1).

In an embodiment, a method of preparation of coloured roofing sheet having anti-fungal, anti-algal properties is disclosed. Pluralities of tanks are used for the preparation of the roofing sheets. Preferably, three tanks are brought into practice for the said preparation. Raw material which forms the composition of the colour coating is mixed in a first Pigment preparation Tank 1. The said coating composition includes a water repellent additive, an anti-fungal additive, an anti-algal additive, an extender and a binder. The stainless steel is preferred due to its non-corrosive nature. In a preferred embodiment, extender may be readily available carbonates of alkaline earth metals. The binder may be opaque cementitious materials. Subsequently, the said composition is transferred to the storage or holding second tank (2), having similar capacity as that of third tank (3), to store the said mixed composition.

While the roofing sheet is being manufactured by Hatschek process, that is layer by layer formation, the said composition is transferred from second tank (2) to third tank (3), which in turn feed the said coating composition to an automated atomiser system. The automated atomiser system sprays the said coating composition during manufacturing of the top layer of the roofing sheet, which is being produced by the Hatschek process, as stated earlier.

The color coating or atomizer system employed in the present invention comprises set of nozzles attached to color paste fluid system, pneumatic control system and compressor system to generate variable pressure suitable for the online atomizer. The color coating system comprises one or more sets of nozzles depending on the depth of coating required and atomizer controller is integrated with programmable circuit controller of the Hatscheck process to define the different coating parameters, including but not limited to coating thickness, time period of nozzle operations, number of layers being coated, variations of color paste viscosity etc.

Further, the invention discloses herein an automated system for preparation of anti-algal, anti-fungal and water repellent fiber Cement coloured roofing sheets. It comprises plurality of sieve cylinders (100) in synchronisation with each other to form layers of fiber cement films simultaneously, a rotating metallic drum to receive formed layers of cement sheets / films to form a roofing sheet of a desired thickness, plurality of vacuum boxes (300) to remove additional water from the roofing sheet, an automated spray coating atomiser system (400) for colouring roofing sheet, and a suction box (500) to remove excess colour from the coloured roofing sheet.

Figure 2 illustrates production of the coloured fiber roofing sheets by employing the system claimed in the instant invention. Layers which are simultaneously formed on plurality of sieve cylinders (100) are transferred to moving felt (600). All of the layers are transferred therein to a continuous rotating metallic drum and placed one above other till the desired thickness of sheet is achieved. Additional water is removed from the sheet by means of vacuum boxes (300). Once desired thickness achieved, the sheets are removed from a metallic drum. The spray coating atomiser system (400) is installed at the end of the Hatschek machine in such a way that the spraying of color pigment is effected on a sheet to give a coating only on top layer of sheet. Excess water is removed from a suction box (500) by adjusting vacuum. The color spray coating system (400) starts and stops in such a way that it covers only top surface layer of sheet formation.

The color spray coating atomiser system (400) and Hatcheck machine are synchronized through PLC system. For this purpose, two inputs provided from Hatcheck machine to online spray system for synchronization. One of the input is employed for resetting the cycle and the remaining input is employed to calculate rounds after resetting the cycle. For instance, if machine runs on 4 laminations, the spray starts after 3 rounds. For 5 laminations, the spray starts after 4 rounds and for 6 laminations, the spray starts after 5 rounds. A Selector switch is provided for lamination input.

To addition that final spray of additive can be done on color sheet surface before corrugation to improve water repellency, reduction in color fastness and to reduce lime leach out.

In order to demonstrate advantages of the present invention, the examples are produced herein:

Example 1: Fungi growth
For the testing, the asbestos cement coloured roofing sheets were placed in a sterile petriplate and covered with the culture solution of 106 organisms/ml, with initial culture taken on agar. The culture solution was chosen from Aspergillus Brastelensis and the media was chosen from Sabarauds Dextrose Agar.

Petriplate were incubated at 2500 c for 7 days. Same procedure was followed for a normal asbestos roofing sheet. It was observed that the normal asbestos sheet showed fungi growth after two days whereas asbestos sheet of the present invention showed fungi growth after seven days. In conclusion, the asbestos sheet of the present invention shows 3 to 4 times more inhibition against the fungus than normal corrugated sheet.

This data is reproduced in tabular form as follows:

Table 1:
Product Tested Total hours
Tjnder
Observation Fungal
Growth
Observed Generic
Fungal
Observed
Normal asbestos cement sheet 7 days 2nd day Aspergillus sp.
Sheet of the present invention 7 days After 7 days Aspergillus sp.

Example 2: Temperature gradient
The temperature gradient, in case of the sheet of the present invention and a normal sheet, is tested when both the sheets are exposed to infrared radiation. Both sides, viz. top as well as bottom surfaces, of the sheets are subjected to infrared radiation for 10 minutes. It was observed that the surface temperature of the normal sheet rises significantly after 10 minutes compared to the sheet of the present invention.

Following table summarises this test result.

Table 2:
Minutes of Infrared Exposure Surface of the sheet Temperature of Normal sheet (deg. C) Temperature of Sheet of the Present Invention (deg.C)
0 Top 33.5 34
Bottom 33.8 33.8
10 Top 52.6 47.5
Bottom 48.7 45

The product so formed exhibits following properties:
• The coloured roofing sheets exhibit excellent water repellent property.
• The coloured roofing sheets so produced have shown no sign of wetness after observation of one month of impermeability test (according to Indian standard 5913)
• No erosion of the colour of the roofing sheets is recorded even after 100 cycles of heat/rain cycle.
• Natural weathering performances have shown no formation of fungal and algal growth on the sheets.
• The said coloured roofing sheet is protected from efflorescences.
• The said coloured roofing sheets prepared by the method of the present invention exhibits Lotus effect that is the said coloured coating display self-cleaning phenomenon with super hydrophobicity.
• The aesthetic, anti-fungal and anti-algal properties of the said roofing sheets are guaranteed for 10 years.

Advantages of the invention:
• The method of the present invention forms a complete and continuous membrane.
• The coating applied by the present invention penetrates better into the pits and crevices.
• With the method of the present invention, uniform thick coating is produced, reducing the number of coatings required.
• The method ensures good adhesion to the surface
• Since the method is automated, over spraying is avoided.
• Highly cost effective coating system i.e. almost 4 times less requirement of pigmentation.
• The product has high durability and long lasting aesthetic look.
• Top layer on the product with high intensity of pigmentation has shown better thermal insulation effect than normal roofing sheets.
• As the anti-fungal additives are also present in the top layer coat, results have shown additional longevity of anti-fungal effect, resulting in long-lasting color beauty.
• Extra top coat provides better color or wash fastness as well as abrasion resistance during handling.