Claims:1. An automated process of preparation of anti-algal, anti-fungal and water repellent fiber Cement coloured roofing sheets 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).

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

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

7. The process 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 process 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 process 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. An automated system for preparation of anti-algal, anti-fungal and water repellent fiber Cement coloured roofing sheets comprising:
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.

11. The system according to claim 10, wherein the plurality of separate sieve cylinders (100) is synchronised.

12. The system according to claim 10, wherein automated spray coated atomiser (400) comprises one or more sets of nozzles depending on depth of coating required and a controller integrated with programmable 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.

13. A fiber cement coloured roofing sheet having in-built anti-algal, anti-fungal and water repellent properties manufactured according to any of the preceding claim, wherein a colour coating composition is added to a last layer of the roofing sheet.

14. The sheet according to claim 13, wherein the colour coating composition is sprayed to the last layer of the sheet by means of an automated atomiser coating system.

15. The sheet according to claim 13, 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.
, Description: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 a method of manufacturing the Coloured Roofing Sheet 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 application, 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 method for preparation of an fiber cement coloured roofing sheet having anti-fungal and anti-algal properties, excellent water repellent effect and high aesthetic value.

Accordingly, the method of preparation of anti-algal, anti-fungal and water repellent fiber Cement coloured roofing sheet using conventional Hatschek process, 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 said colour coating composition for the roofing sheets comprises a water repellent additive, an anti-fungal additive, an anti-algal additive, a coloured pigment, an extender and a binder. Preferably, the extender may be readily available carbonates of alkaline earth metals and a binder may be chosen from high opaque cementitious material.

In an embodiment, 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. The binder with a ratio 1: 10 along with water is incorporated on top layer by using additional spray system on top of the coating to give an additional binding and water repellent effect to the product. The binder is selected from, the thermosetting or thermoplastic cross-linkable polymer, which is selected from, but not limited to, acrylic, epoxy, polyurethane or copolymer or in-combination thereof. The fibre material may be selected from wood pulp, fibrous magnesium silicates and aluminum silicates, alkali resistant polymeric fibers or mixture thereof.

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 another embodiment, an automated system for preparation of a fibre cement coloured roofing sheet having in-built anti-algal, anti-fungal and water repellent properties is disclosed. It comprises plurality of sieve cylinders in synchronisation with each other to form layers of 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 to remove additional water from the roofing sheet, an automated spray coating atomiser system for colouring roofing sheet, and a suction box to remove excess water from the roofing sheet and a hood to collect the fumes generated during the spray

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 sheet having anti-fungal, anti-algal properties and high aesthetic value. The said roofing sheet comprises a colour coating wherein said colour coating composition comprises a water repellent additive, an anti-fungal additive, and anti-algal additive, a coloured pigment, an extender and a binder.

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.

An automated process of preparation of anti-algal, anti-fungal and water repellent fiber Cement coloured roofing sheets is disclosed herein. It comprises steps of: forming multiple layers of fiber cement films using endless felt on plurality of separate sieve cylinders (100) simultaneously; transferring the formed layers of fiber cement films on a rotating metallic drum in order to form a roofing sheet of a desired thickness; 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; 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 removing excess water from the roofing sheet by adjusting vacuum in a suction box (500).

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 another embodiment, the said roofing sheet comprises a colour coating wherein said colour coating composition comprises a water repellent additive, an anti-fungal additive, an anti-algal additive, a coloured pigment, an extender and a binder. The fibre material may be selected from wood pulp, fibrous magnesium silicates and aluminum silicates, alkali resistant polymeric fibers or mixture thereof.

In yet another embodiment, the present invention discloses a coloured roofing sheet having anti-fungal, anti-algal properties and high aesthetic value. The said roofing sheet comprises a colour coating wherein said colour coating composition comprises a water repellent additive, an anti-fungal additive, an anti-algal additive, a coloured pigment, an extender and a binder. The extender may be readily available carbonates of alkaline earth metals. The binder may be opaque cementitious materials. The said coloured roofing sheet is prepared by Hatschek process wherein the aforesaid colour coating composition is incorporated into the roofing sheet during formation of the topmost layer of the sheet.

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.