Modified extender and a coating composition prepared therefrom

Abstract

The present disclosure relates to a modified extender and a process for its preparation. The modified extender of the present disclosure is used as a partial replacement of TiO2 in the coating composition thereby making the composition cost effective without affecting the properties. The present disclosure further provides a coating composition comprising the modified extender. Further, the coating composition of the present disclosure has excellent brightness and whiteness and has good opacity.

Description

[0001] MODIFIED EXTENDER AND A COATING COMPOSITION PREPARED THEREFROM FIELD

[0002] The present disclosure relates to coatings. Particularly, the present disclosure relates to a modified extender and its use in a coating composition.

[0003] DEFINITIONS

[0004] As used in the present disclosure, the following terms are generally intended to have the meaning as set forth below, except to the extent that the context in which they are used, indicate otherwise.

[0005] Opacity: The term “opacity” refers to the extent to which an object or surface impedes the transmission of light through it.

[0006] Wet hiding: The term “wet hiding” in paint or coating refers to the phenomenon that occurs when a coat of paint applied over a substrate is still wet and is able to hide / obliterate the surface beneath.

[0007] Dry hiding: The term “dry hiding” in paint or coating refers to the phenomenon that occurs when a coat of paint applied over a substrate has completely dried and is able to hide / obliterate the surface beneath.

[0008] Extender: The term “extender” in a coating composition refers to a pigment or filler used to increase the volume and bulk of the coating composition without significantly affecting its colour or properties.

[0009] Reducing strength: The term “reducing strength” refers to the ability of a material such as an extender, to reduce the effect or impact of another component in a coating, most commonly, the color strength or opacity of a pigment.

[0010] BACKGROUND

[0011] The background information herein below relates to the present disclosure but is not necessarily prior art. Coatings are used to protect the surface of materials against various corrosions along with their decorative purpose. There are various types of compositions available for coating such as solvent-based coating composition, water-based coating composition and the like. The use of water-based coating compositions has increased since these are environmentally friendly as compared to the solvent based coatings. The typical water-based coating compositions consist of maximum amount of pigments and minerals. Further, in a dry fdm, there are just pigment particles and polymer fibers to keep the particles on the surface. As a consequence, the type of pigment or mineral used in the coating composition directly affects the characteristics of the applied coat.

[0012] Titanium dioxide (Ti O2 ) is the main pigment used in the water-based coating composition due to its high refractive index and coverage capability. However, titanium dioxide is very expensive which leads to increase in the overall cost of the coating composition. Further, the extraction of titanium dioxide requires large amounts of energy thereby making the use of high amount of titanium dioxide uneconomical. Therefore, alternate pigments or minerals are used instead of the conventional titanium dioxide pigment. However, the use of these alternative pigments or minerals negatively impacts the physical and mechanical properties of the coating composition such as opacity, brightness and the like.

[0013] Therefore, there is felt a need to provide a modified extender and a coating composition thereof to mitigate the drawbacks mentioned hereinabove or at least provide a useful alternative. OBJECTS

[0014] Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:

[0015] It is an object of the present disclosure to ameliorate one or more problems of the background or to at least provide a useful alternative.

[0016] Another object of the present disclosure is to provide a modified extender.

[0017] Still another object of the present disclosure is to provide a modified extender for partial replacement of TiCf.

[0018] Yet another object of the present disclosure is to provide a modified extender for a partial replacement of TiCf in a coating composition. Still another object of the present disclosure is to provide a modified extender that is used as a partial replacement of TiCfi in a coating composition thereby making it cost effective without affecting the properties of the coating composition.

[0019] Yet another object of the present disclosure is to provide a coating composition.

[0020] Still another object of the present disclosure is to provide a coating composition comprising a modified extender.

[0021] Yet another object of the present disclosure is to provide a coating composition comprising a modified extender that has excellent brightness and whiteness.

[0022] Still another object of the present disclosure is to provide a coating composition comprising a modified extender that has good opacity.

[0023] Yet another object of the present disclosure is to provide a process for the preparation of a modified extender.

[0024] Still another object of the present disclosure is to provide a process for the preparation of a coating composition comprising a modified extender.

[0025] Yet another object of the present disclosure is to provide a simple and economical process for the preparation of a coating composition comprising a modified extender.

[0026] Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure. SUMMARY

[0027] The present disclosure relates to a modified extender and a process for its preparation.

[0028] In an aspect, the present disclosure provides a modified extender comprises a blend of scalenohedral calcium carbonate and a titanium dioxide pigment.

[0029] In an embodiment of the present disclosure, the modified extender is characterized by having at least one of the following:

[0030] • particle size (D50) below 5 microns; and

[0031] • refractive index (RI) in the range of 1.6 to 2.2. In an embodiment of the present disclosure, a mass ratio of the scalenohedral calcium carbonate to the titanium dioxide pigment is in the range of 10:90 to 40:60.

[0032] In an embodiment of the present disclosure, the titanium dioxide pigment is in a form selected from titanium dioxide rutile grade and titanium dioxide anatase grade.

[0033] In an embodiment of the present disclosure, the modified extender of the present disclosure is used in a coating composition.

[0034] In another aspect, the present disclosure provides a process for the preparation of a modified extender. The process comprises the following steps:

[0035] i. mixing titanium dioxide pigment and scalenohedral calcium carbonate in a predetermined mass ratio at a stirring speed in the range of 20 rpm to 60 rpm at a temperature in the range of 30 °C to 40 °C in a ribbon blender to obtain a mixture; and

[0036] ii. maintaining the mixture for a time period in the range of 15 minutes to 30 minutes to obtain the modified extender.

[0037] In an embodiment of the present disclosure, the predetermined mass ratio of the scalenohedral calcium carbonate to the titanium dioxide pigment is in the range of 10:90 to 40:60.

[0038] In an embodiment of the present disclosure, the titanium dioxide pigment is in a form selected from titanium dioxide rutile grade and titanium dioxide anatase grade.

[0039] In still another aspect, the present disclosure provides a coating composition. The coating composition comprises:

[0040] • a modified extender in an amount in the range in the range of 2 mass% to 8 mass%;

[0041] • at least one dispersing agent in an amount in the range of 1 mass% to 2 mass%;

[0042] • at least one wetting agent in an amount in the range of0.5 mass% to 1.5 mass%;

[0043] • at least one defoamer in an amount in the range of 0.2 mass% to 0.8 mass%;

[0044] • at least one biocide in an amount in the range of 0.2 mass% to 0.8 mass%;

[0045] • at least one pH neutralizer in an amount in the range of 0.2 mass% to 0.8 mass%;

[0046] • at least one thickening agent in an amount in the range of 0.2 mass% to 0.8 mass%; • at least one pigment in an amount in the range of 6 mass% to 10 mass%;

[0047] • at least one filler in an amount in the range of 40 mass% to 50 mass%;

[0048] • at least one binder in an amount in the range of 8 mass% to 12 mass%;

[0049] • at least one coalescing agent in an amount in the range of 1 mass% to 2 mass%;

[0050] • at least one co-solvent in an amount in the range of 0.5 mass% to 1 mass%;

[0051] and

[0052] • water in an amount in the range of 20 mass% to 30 mass%,

[0053] wherein the mass% of each ingredient is with respect to the total mass of the coating composition.

[0054] In an embodiment of the present disclosure,

[0055] • the modified extender comprises a blend of scalenohedral calcium carbonate and a titanium dioxide pigment;

[0056] • the dispersing agent is selected from ammonium polyacrylate and sodium polyacrylate;

[0057] • the wetting agent is alkyl polyethylene glycol ether;

[0058] • the defoamer is a mineral oil based defoamer;

[0059] • the biocide is methylisothiazolinone;

[0060] • the pH neutralizer is a mixture of amines;

[0061] • the thickening agent is hydroxyethyl cellulose;

[0062] • the pigment is selected from titanium dioxide rutile grade and titanium dioxide anatase grade;

[0063] • the filler is selected from the group consisting of steatite, calcium carbonate, talc, dolomite and a combination thereof;

[0064] • the binder is styrene acrylic emulsion;

[0065] • the coalescing agent is 3-hydroxy-2,2,4-trimethylpentyl 2-methylpropanoate;

[0066] and

[0067] • the co-solvent is selected from monoethylene glycol and diethylene glycol. The coating composition of the present disclosure is characterized by having at least one of the following:

[0068] whiteness index is in the range of 80 % to 95 %; brightness index is in the range of 80 % to 95 %;

[0069] contrast ratio is greater than 95; and

[0070] reducing strength is greater than 100.

[0071] In yet another aspect, there is provided a process for the preparation of a coating composition. The process comprises the following steps:

[0072] i. mixing predetermined amounts of a first portion of water, a dispersing agent, a wetting agent, a biocide and a defoamer in a reactor at a temperature in the range of 30 °C to 40 °C under stirring at a speed in the range of 8 m / s to 15 m / s to obtain a first mixture;

[0073] ii. adding predetermined amounts of a pigment, a modified extender and a filler in the first mixture under stirring at8 m / s to 15 m / s for a time period in the range of 5 minutes to 20 minutes to obtain a second mixture;

[0074] iii . adding predetermined amounts of a thickening agent and a pH neutralizer in the second mixture under stirring at a speed in the range of 15 m / s to 30 m / s for a time period in the range of 20 minutes to 50 minutes to obtain a third mixture; and

[0075] iv. maintaining the third mixture under stirring at a speed in the range of 8 m / s to 15 m / s followed by adding predetermined amounts of a coalescing agent, a cosolvent, a binder and a second portion of water in the third mixture to obtain the coating composition.

[0076] In an embodiment of the present disclosure,

[0077] • the first portion of water is in an amount in the range of 20 mass% to 25 mass%;

[0078] • the dispersing agent is present in an amount in the range of 1 mass% to 2 mass%;

[0079] • the wetting agent is present in an amount in the range of 0.5 mass% to 1.5 mass%;

[0080] • the biocide is present in an amount in the range of 0.2 mass% to 0.8mass%;

[0081] • the defoamer is present in an amount in the range of 0.2 mass% to 0.8 mass%;

[0082] • the pigment is present in an amount in the range of 6 mass% to 10 mass%;

[0083] • the modified extender is present in an amount in the range in the range of 2 mass% to 8 mass%;

[0084] • the filler is present in an amount in the range of 40 mass% to 50 mass%; • the thickening agent is present in an amount in the range of 0.2 mass% to 0.8 mass%;

[0085] • the pH neutralizer is present in an amount in the range of 0.2 mass% to 0.8 mass%;

[0086] • the coalescing agent is present in an amount in the range of 1 mass% to 2 mass%;

[0087] • the co-solvent is present in an amount in the range of 0.5 mass% to 1 mass%;

[0088] • the binder is present in an amount in the range of 8 mass% to 12 mass%;

[0089] and

[0090] • the second portion of water is in an amount in the range of 1 mass% to 5 mass% wherein the mass% of each ingredient is with respect to the total mass of the coating composition.

[0091] In an embodiment of the present disclosure,

[0092] • the dispersing agent is selected from ammonium polyacrylate and sodium polyacrylate;

[0093] • the wetting agent is alkyl polyethylene glycol ether;

[0094] • the biocide is methylisothiazolinone;

[0095] • the defoamer is a mineral oil based defoamer;

[0096] • the pigment is selected from titanium dioxide rutile grade and titanium dioxide anatase grade;

[0097] • the modified extender comprises a blend of scalenohedral calcium carbonate and a titanium dioxide pigment;

[0098] • the filler is selected from the group consisting of steatite, calcium carbonate, talc, dolomite and a combination thereof;

[0099] • the thickening agent is hydroxyethyl cellulose;

[0100] • the pH neutralizer is a mixture of amines;

[0101] • the coalescing agent is 3 -hydroxy-2, 2, 4-trimethylpentyl 2-methylpropanoate;

[0102] • the co-solvent is selected from monoethylene glycol and diethylene glycol; and • the binder is styrene acrylic emulsion. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING

[0103] The present disclosure will now be described with the help of the accompanying drawing, in which:

[0104] Figure 1 illustrates a schematic representation of the mechanism of partial replacement of titanium dioxide (TiO2) by using a modified extender (calcium carbonate (CaCO?) coated with titanium dioxide), in accordance with the present disclosure;

[0105] Figure 2 illustrates a Scanning Electron Microscope (SEM) image of scalenohedral calcium carbonate in accordance with the present disclosure;

[0106] Figure 3 illustrates a SEM image of titanium dioxide in accordance with the present disclosure; and

[0107] Figure 4 illustrates a SEM image of the modified extender in accordance with the present disclosure.

[0108] DETAILED DESCRIPTION

[0109] The present disclosure relates to coatings. Particularly, the present disclosure relates to a modified extender and its use in a coating composition.

[0110] Embodiments, of the present disclosure, will now be described with reference to the accompanying drawing.

[0111] Embodiments, of the present disclosure, will now be described herein. Embodiments are provided to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, apparatus structures, and techniques are not described in detail.

[0112] The terminology used, in the present disclosure, is only to explain a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms “comprises”, “comprising,” “including,” and “having,” are open-ended transitional phrases and therefore specify the presence of stated features, integers, steps, operations, elements, modules, units, and / or components, but do not forbid the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. The order of steps disclosed in the method and process of the present disclosure is not to be construed as necessarily requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed.

[0113] As used herein, the term "and / or" includes all combinations of one or more of the associated listed elements.

[0114] The terms first, second, third, etc., should not be construed to limit the scope of the present disclosure as the aforementioned terms may be only used to distinguish one element, component, region, layer or section from another component, region, layer or section. Terms such as first, second, third etc., when used herein do not imply a specific sequence or order unless clearly suggested by the present disclosure.

[0115] Titanium dioxide (Ti O2 ) is the main pigment used in the water-based coating composition due to its high refractive index and coverage capability. However, the titanium dioxide is very expensive which leads to increase the overall cost of the coating composition. In view of high cost, some alternate pigments or minerals are used instead of conventional pigments but it leads to affect the physical and mechanical properties of the coating composition such as opacity, brightness and the like. Further, the extraction of titanium dioxide from the earth requires large amounts of energy thereby making the use of high amount of titanium dioxide is uneconomical. Therefore, there is felt a need to provide a modified extender having lower cost and provides improved properties of coating composition prepared thereof.

[0116] The present disclosure relates to a modified extender and a process for its preparation.

[0117] In an aspect, the present disclosure provides a modified extender comprising a blend of scalenohedral calcium carbonate and a titanium dioxide pigment.

[0118] In an embodiment of the present disclosure, the modified extender is characterized by at least one of the following:

[0119] • particle size (D50) below 5 microns; and

[0120] • refractive index (RI) in the range of 1.6 to 2.2. In an embodiment of the present disclosure, a mass ratio of the scalenohedral calcium carbonate to the titanium dioxide pigment is in the range of 10:90 to 40:60. In an exemplary embodiment of the present disclosure, the mass ratio of the scalenohedral calcium carbonate to the titanium dioxide pigment is 30:70.

[0121] In an embodiment of the present disclosure, the titanium dioxide pigment is in a form selected from titanium dioxide rutile grade and titanium dioxide anatase grade. In an exemplary embodiment of the present disclosure, the titanium dioxide pigment is in the form of titanium dioxide rutile grade.

[0122] In an embodiment of the present disclosure, the modified extender is used in a coating composition.

[0123] In an embodiment of the present disclosure, the modified extender is used for the preparation of coating composition in the form of a high pigment volume concentration (PVC) paint, and can be used in mid PVC paint and low PVC paint. In an exemplary embodiment of the present disclosure, the modified extender is used for the preparation of a coating composition in the form of a high pigment volume concentration (PVC) emulsion paint (PVC of 65 to 75).

[0124] In an embodiment of the present disclosure, the modified extender is used for partial replacement of the titanium dioxide pigment in a coating composition.

[0125] In an embodiment of the present disclosure, the modified extender is used for complete / whole replacement of the titanium dioxide pigment in a coating composition depending on PVC. In an embodiment of the present disclosure, the partial replacement of the titanium dioxide pigment in the coating composition allows the modified extender to act as a spacer between the titanium dioxide pigment particles. By reducing the crowding of the titanium dioxide pigment particles and positioning itself between them, the modified extender enhances light scattering without compromising the coating composition’s opacity, brightness and whiteness. In another aspect of the present disclosure, there is provided a process for the preparation of a modified extender.

[0126] The process comprises the following steps:

[0127] i. mixing titanium dioxide pigment and a scalenohedral calcium carbonate in a predetermined mass ratio at a stirring speed in the range of 20 rpm to 60 rpm at a temperature in the range of 30 °C to 40 °C, in a ribbon blender to obtain a mixture; and

[0128] ii. maintaining the mixture for a time period in the range of 15 minutes to 30 minutes to obtain the modified extender.

[0129] In an embodiment of the present disclosure, the predetermined mass ratio of the scalenohedral calcium carbonate to the titanium dioxide pigment is in the range of 10:90 to 40:60. In an exemplary embodiment of the present disclosure, the mass ratio of the scalenohedral calcium carbonate to the titanium dioxide pigment is 30:70.

[0130] In an embodiment of the present disclosure, the titanium dioxide pigment is in a form selected from titanium dioxide rutile grade (such as sulphate grade, chloride grade) and titanium dioxide anatase grade. In an exemplary embodiment of the present disclosure, the titanium dioxide pigment is titanium dioxide rutile grade.

[0131] The scalenohedral calcium carbonate provides enhanced light scattering due to its multi-faceted shape, which increases light path length and enables partial TiCh replacement without sacrificing opacity. Its unique morphology ensures optimal TiCh spacing, preventing particle crowding and maximizing scattering efficiency. Further, it improves dispersion uniformity, enhances film properties such as whiteness, brightness, and smoothness, and supports better integration within the coating composition. Still further, the shape of scalenohedral calcium carbonate creates a synergistic scattering effect with TiCh, resulting in high-performance, cost-effective coating compositions.

[0132] In an embodiment of the present disclosure, the titanium dioxide pigment and the scalenohedral calcium carbonate are mixed in a ribbon blender. The ribbon blender is a horizontal U-shaped mixer that uses a rotating double helical ribbon agitator to mix materials.

[0133] In an exemplary embodiment of the present disclosure, the titanium dioxide pigment and the scalenohedral calcium carbonate are mixed at a temperature of 35 °C and at a stirring speed of 40 rpm in a ribbon blender to obtain the mixture.

[0134] In an exemplary embodiment of the present disclosure, the mixture is maintained for a time period of 20 minutes to obtain the modified extender. In still another aspect of the present disclosure, there is provided a coating composition. The coating composition comprises:

[0135] • a modified extender in an amount in the range of 2 mass% to 8 mass%;

[0136] • at least one dispersing agent in an amount in the range of 1 mass% to 2 mass%;

[0137] • at least one wetting agent in an amount in the range of 0.5 mass% to 1.5 mass%;

[0138] • at least one defoamer in an amount in the range of 0.2 mass% to 0.8 mass%;

[0139] • at least one biocide in an amount in the range of 0.2 mass% to 0.8 mass%;

[0140] • at least one pH neutralizer in an amount in the range of0.2 mass% to 0.8 mass%;

[0141] • at least one thickening agent in an amount in the range of 0.2 mass% to 0.8 mass%;

[0142] • at least one pigment in an amount in the range of 6 mass% to 10 mass%;

[0143] • at least one filler in an amount in the range of 40 mass% to 50 mass%;

[0144] • at least one binder in an amount in the range of 8 mass% to 12 mass%;

[0145] • at least one coalescing agent in an amount in the range of 1 mass% to 2 mass%;

[0146] • at least one co-solvent in an amount in the range of 0.5 mass% to 1 mass%; and

[0147] • water in an amount in the range of 20 mass% to 30 mass%,

[0148] wherein the mass% of each ingredient is with respect to the total mass of the coating composition.

[0149] In an embodiment of the present disclosure, the modified extender comprises a blend of scalenohedral calcium carbonate and a titanium dioxide pigment.

[0150] In an embodiment of the present disclosure, the dispersing agent is selected from ammonium polyacrylate and sodium polyacrylate. In an exemplary embodiment of the present disclosure the dispersing agent is ammonium polyacrylate.

[0151] In an embodiment of the present disclosure, the wetting agent is alkyl polyethylene glycol ether.

[0152] In an embodiment of the present disclosure, the defoamer is a mineral oil based defoamer (AM-1512).

[0153] In an embodiment of the present disclosure, the biocide is methylisothiazolinone (MIT). In an embodiment of the present disclosure, the pH neutralizer is a mixture of amines. In an exemplary embodiment of the present disclosure, the pH neutralizer is Nupol PHN 99.

[0154] In an embodiment of the present disclosure, the thickening agent is hydroxy ethyl cellulose. In an embodiment of the present disclosure, the pigment is selected from titanium dioxide rutile grade and titanium dioxide anatase grade. In an exemplary embodiment, the pigment is titanium dioxide rutile grade.

[0155] In an embodiment of the present disclosure, the fdler is selected from the group consisting of steatite, calcium carbonate, talc, dolomite and a combination thereof. In an embodiment of the present disclosure, the filler is CaCCh. In another embodiment of the present disclosure, the filler is talc. In an exemplary embodiment, the filler is a mixture of CaCCh and talc.

[0156] In an embodiment of the present disclosure, the binder is styrene acrylic emulsion.

[0157] In an embodiment of the present disclosure, the coalescing agent is 3 -hydroxy-2, 2,4-trimethylpentyl 2-methylpropanoate (Texanol).

[0158] In an embodiment of the present disclosure, the co-solvent is selected from monoethylene glycol and diethylene glycol. In an exemplary embodiment of the present disclosure, the cosolvent is diethylene glycol (DEG).

[0159] In an embodiment of the present disclosure, the coating composition comprises a sequestering agent. In an embodiment of the present disclosure, the sequestering agent is selected from sodium hexametaphosphate and tetra potassium pyrophosphate.

[0160] In an embodiment of the present disclosure, the coating composition is characterized by having at least one of the following:

[0161] • whiteness index is in the range of 80 % to 95 %;

[0162] • brightness index is in the range of 80 % to 95 %;

[0163] • contrast ratio is greater than 95; and

[0164] • reducing strength is greater than 100.

[0165] In an embodiment of the present disclosure, the contrast ratio is in the range of 95 to 98. In an embodiment of the present disclosure, the reducing strength is in the range of 100 to 107. The coating composition of the present disclosure provides a similar wet and dry hiding when compared to conventional coating composition containing only TiO pigment.

[0166] The coating composition of the present disclosure is used to develop different types of paints, master batches, powder coatings and other coating compositions.

[0167] The coating composition of the present disclosure contributes to cost reduction and sustainable solution for the all type of coatings.

[0168] In yet another aspect of the present disclosure, there is provided a process for the preparation of a coating composition. The process comprises the following steps:

[0169] i. mixing predetermined amounts of a first portion of water, a dispersing agent, a wetting agent, a defoamer and a biocide in a reactor at a temperature in the range of 30 °C to 40 °C under stirring at a speed in the range of 8 m / s to 15 m / s to obtain a first mixture;

[0170] ii. adding predetermined amounts of a pigment, a modified extender and a filler in the first mixture under stirring at a speed in the range of 8 m / s to 15 m / s for a time period in the range of 5 minutes to 20 minutes to obtain a second mixture;

[0171] iii . adding predetermined amounts of a pH neutralizer and a thickening agent in the second mixture under stirring at a speed in the range of 15 m / s to 30 m / s for a time period in the range of 20 minutes to 50 minutes to obtain a third mixture; and

[0172] iv. maintaining the third mixture under stirring at a speed in the range of 8 m / s to 15 m / s followed by adding predetermined amounts of a binder, a coalescing agent, a co-solvent and a second portion of water in the third mixture to obtain the coating composition.

[0173] The process is described in detail below.

[0174] In a first step, predetermined amounts of a first portion of water, a dispersing agent, a wetting agent, a defoamer and a biocide are mixed in a reactor at a temperature in the range of 30 °C to 40 °C under stirring at a speed in the range of 8 m / s to 15 m / s to obtain a first mixture.

[0175] In an exemplary embodiment of the present disclosure, the mixing is carried out at 35 °C under stirring at a speed in the range of 10 m / s to 12 m / s. In an embodiment of the present disclosure, the first portion of water is in an amount in the range of 20 mass% to 25 mass% with respect to the total mass of the coating composition. In an exemplary embodiment of the present disclosure, the first portion of water is in an amount of 22 mass% with respect to the total mass of the coating composition.

[0176] In an embodiment of the present disclosure, the dispersing agent is selected from ammonium polyacrylate and sodium polyacrylate. In an exemplary embodiment of the present disclosure, the dispersing agent is ammonium polyacrylate.

[0177] In an embodiment of the present disclosure, the dispersing agent is present in an amount in the range of 1 mass% to 2 mass% with respect to the total mass of the coating composition. In an exemplary embodiment of the present disclosure, the dispersing agent is present in an amount of 1.2 mass% with respect to the total mass of the coating composition.

[0178] In an embodiment of the present disclosure, the wetting agent is alkyl polyethylene glycol ether.

[0179] In an embodiment of the present disclosure, the wetting agent is present in an amount in the range of 0.5 mass% to 1.5 mass% with respect to the total mass of the coating composition. In an exemplary embodiment of the present disclosure, the wetting agent is present in an amount of 1 mass% with respect to the total mass of the coating composition.

[0180] In an embodiment of the present disclosure, the defoamer is a mineral oil based defoamer (AM-1512).

[0181] In an embodiment of the present disclosure, the defoamer is present in an amount in the range of 0.2 mass% to 0.8 mass% with respect to the total mass of the coating composition. In an exemplary embodiment of the present disclosure, the defoamer is present in an amount in the range of 0.5 mass% with respect to the total mass of the coating composition.

[0182] In an embodiment of the present disclosure, the biocide is methylisothiazolinone derivative. In an embodiment of the present disclosure, the biocide is present in an amount in the range of 0.2 mass% to 0.8 mass% with respect to the total mass of the coating composition. In an embodiment of the present disclosure, the biocide is present in an amount of 0.5 mass% with respect to the total mass of the coating composition. In an embodiment of the present disclosure, a sequestering agent is used to prepare the first mixture. In an embodiment of the present disclosure, the sequestering agent is selected from sodium hexametaphosphate and tetra potassium pyrophosphate.

[0183] In a second step, predetermined amounts of a pigment, a modified extender and a filler are added in the first mixture under stirring for a time period in the range of 5 minutes to 20 minutes to obtain a second mixture.

[0184] In an exemplary embodiment of the present disclosure, the stirring is carried out at a speed of 10 m / s to 12 m / s for a time period of 10 minutes to 15 minutes.

[0185] In an embodiment of the present disclosure, the pigment is selected from titanium dioxide rutile grade and titanium dioxide anatase grade. In an exemplary embodiment of the present disclosure, the pigment is titanium dioxide rutile grade.

[0186] In an embodiment of the present disclosure, the pigment is present in an amount in the range of 6 mass% to 10 mass% with respect to the total mass of the coating composition. In an exemplary embodiment of the present disclosure, the pigment is present in an amount of 8 mass% with respect to the total mass of the coating composition.

[0187] In an embodiment of the present disclosure, the modified extender comprises a blend of a scalenohedral calcium carbonate and a titanium dioxide pigment.

[0188] In an embodiment of the present disclosure, the modified extender is present in an amount in the range of 2 mass% to 8 mass% with respect to the total mass of the coating composition. In an embodiment of the present disclosure, the modified extender is present in an amount of 6 mass% with respect to the total mass of the coating composition.

[0189] In an embodiment of the present disclosure, the filler is selected from the group consisting of steatite, calcium carbonate, talc, dolomite and a combination thereof. In an embodiment of the present disclosure, the filler is CaCCh. In another embodiment of the present disclosure, the filler is talc. In an exemplary embodiment, the filler is a mixture of CaCCh and talc.

[0190] In an embodiment of the present disclosure, the filler is present in an amount in the range of 40 mass% to 50 mass% with respect to the total mass of the coating composition. In an embodiment of the present disclosure, the filler is present in an amount of 45 mass% with respect to the total mass of the coating composition. In a third step, predetermined amounts of a pH neutralizer and a thickening agent are added in the second mixture under stirring at a speed in the range of 15 m / s to 30 m / s for a time period in the range of 20 minutes to 50 minutes to obtain a third mixture.

[0191] In an exemplary embodiment of the present disclosure, the stirring is carried out at a speed of 20 m / s to 25 m / s for a time period in the range of 30 minutes to 50 minutes.

[0192] In an embodiment of the present disclosure, the pH neutralizer is a mixture of amines. In an exemplary embodiment of the present disclosure, the pH neutralizer is Nupol PHN 99.

[0193] In an embodiment of the present disclosure, the pH neutralizer is present in an amount in the range of 0.2 mass% to 0.8 mass% with respect to the total mass of the coating composition. In an exemplary embodiment of the present disclosure, the pH neutralizer is present in an amount of 0.5 mass% with respect to the total mass of the coating composition.

[0194] In an embodiment of the present disclosure, the thickening agent is hydroxy ethyl cellulose. In an embodiment of the present disclosure, the thickening agent is present in an amount in the range of 0.2 mass% to 0.8 mass% with respect to the total mass of the coating composition. In an exemplary embodiment of the present disclosure, the thickening agent is present in an amount of 0.5 mass% with respect to the total mass of the coating composition.

[0195] In a fourth step, the third mixture is maintained by lowering the stirring speed in the range of 8 m / s to 15 m / s followed by adding predetermined amounts of a binder, a coalescing agent, a co-solvent and a second portion of water in the third mixture to obtain the coating composition. In an exemplary embodiment of the present disclosure, the stirring speed is lowered in the range of 10 m / s to 12 m / s.

[0196] In an embodiment of the present disclosure, the binder is styrene acrylic emulsion.

[0197] In an embodiment of the present disclosure, the binder is present in an amount in the range of 8 mass% to 12 mass% with respect to the total mass of the coating composition. In an exemplary embodiment of the present disclosure, the binder is present in an amount of 10 mass% with respect to the total mass of the coating composition.

[0198] In an embodiment of the present disclosure, the coalescing agent is 3 -hydroxy-2, 2,4-trimethylpentyl)2-methylpropanoate (Texanol) . In an embodiment of the present disclosure, the coalescing agent is present in an amount in the range of 1 mass% to 2 mass% with respect to the total mass of the coating composition. In an embodiment of the present disclosure, the coalescing agent is present in an amount of 1.2 mass% with respect to the total mass of the coating composition.

[0199] In an embodiment of the present disclosure, the co-solvent is selected from monoethylene glycol and diethylene glycol. In an exemplary embodiment of the present disclosure, the cosolvent is diethylene glycol (DEG).

[0200] In an embodiment of the present disclosure, the co-sol vent is present in an amount in the range of 0.5 mass% to 1 mass% with respect to the total mass of the coating composition. In an exemplary embodiment of the present disclosure, the co-solvent is present in an amount of 0.8 mass% with respect to the total mass of the coating composition.

[0201] In an embodiment of the present disclosure, the second portion of water is in an amount in the range of 1 mass% to 5 mass% with respect to the total mass of the coating composition. In an exemplary embodiment of the present disclosure, the second portion of water is in an amount of 2 mass% with respect to the total mass of the coating composition.

[0202] The foregoing description of the embodiments has been provided for purposes of illustration and is not intended to limit the scope of the present disclosure. Individual components of a particular embodiment are generally not limited to that particular embodiment, but, are interchangeable. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure.

[0203] The present disclosure is further described in light of the following experiments which are set forth for illustration purpose only and not to be construed for limiting the scope of the disclosure. The following experiments are scalable to industrial / commercial process.

[0204] EXPERIMENTAL DETAILS

[0205] Experiment 1: Process for the preparation of a modified extender in accordance with the present disclosure

[0206] Titanium dioxide pigment (rutile grade) and scalenohedral calcium carbonate in form of precipitated calcium carbonate (PCC) in a ratio of 70:30 were mixed in a ribbon blender at a stirring speed of 40 rpm at 35 °C to obtain a mixture. The ribbon blender is a horizontal U-shaped mixer having a rotating double helical ribbon agitator to mix materials. The outer ribbon moves ingredients in one direction, while the inner ribbon moves them in the opposite direction, creating a well-balanced mixing action.

[0207] The mixture was stirred for 20 minutes to obtain the modified extender.

[0208] Figure 1 illustrates the schematic representation of the mechanism of partial replacement of titanium dioxide (TiCh) by using a modified extender (a blend of scalenohedral calcium carbonate (CaCCh) and titanium dioxide), in accordance with the present disclosure. It was seen from Figure 1 that the modified extender of the present disclosure provides proper spacing between the titanium dioxide particles which helps in improved light scattering and thereby enhances the whiteness and brightness of a coating composition comprising the modified extender of the present disclosure.

[0209] Characterization of the modified extender of the present disclosure

[0210] Figures 2 to 4 illustrate the scanning electron microscope images of the scalenohedral calcium carbonate, titanium dioxide and the modified extender, respectively.

[0211] The scalenohedral structure of C aCCh in the form of precipitated calcium carbonate was characterized by its elongated, pointed, and crystalline form, as shown in Figure 2.

[0212] Figure 3 shows that the titanium dioxide particles were nearly spherical, with smooth surfaces, and typically appear as clusters or aggregates composed of smaller particles.

[0213] It is seen from Figure 4 that the scalenohedral C aCCh appeared as elongated, pointed crystals, and TiCh as smaller, rounded particles. Further, it is seen that the scalenohedral CaC Os and the titanium dioxide particles were well -dispersed.

[0214] The particle size and refractive index of the modified extender obtained in Experiment 1 was analyzed. The particle size (D50) of the modified extender of the present disclosure was below 5 microns and the refractive index was 2.0.

[0215] Experiment 2: Process for the preparation of a coating composition in accordance with the present disclosure The modified extender obtained in Experiment 1 was used for the preparation of a coating composition in the form of a high pigment volume concentration (PVC) emulsion paint (PVC of 65 to 75).

[0216] The coating composition was prepared by initially mixing predetermined amounts of a first portion of water, ammonium polyacrylate (dispersing agent), alkyl polyethylene glycol ether (wetting agent), methylisothiazolinone (biocide), and AM-1512 (defoamer) in a Twin Shaft High Speed Disperser (TSHSD) at 35 °C under stirring speed at 10 m / s to 12 m / s to obtain a first mixture. Predetermined amounts of a TiCh rutile grade (pigment), modified extender (obtained in Experiment 1), and CaCCE and talc in a 1:1 ratio (filler) were then added to the first mixture under stirring at 10 m / s to 12 m / s for 10 minutes to 15 minutes to obtain a second mixture. Predetermined amounts of hydroxy ethyl cellulose (thickening agent) andNupol PHN 99 (pH neutralizer) was added to the second mixture under stirring at 20 m / s to 25 m / s for 30 minutes to 50 minutes to obtain a third mixture. The stirring speed was reduced to 10 m / s to 12 m / s and predetermined amounts of Texanol (coalescing agent), diethylene glycol (co-solvent), styrene acrylic emulsion (binder), and a second portion of water were added to obtain the coating composition. The ingredients used and their amounts are summarized in Table 1.

[0217]

[0218] Coating compositions based on rhombohedral calcium carbonate extender and irregular calcium carbonate extender were used for comparison. All the coating compositions were analyzed for whiteness, brightness, contrast ratio and reducing strength. The results obtained are summarized in Tables 2 to 4.

[0219]

[0220]

[0221]

[0222]

[0223]

[0224] It is seen from Tables 2 to 4 that the coating composition comprising the modified extender (blend of scalenohedral calcium carbonate and titanium dioxide) of the present disclosure provided improved whiteness, brightness, contrast ratio and reducing strength as compared to the coating compositions comprising standard TiO and coating compositions comprising extenders having rhombohedral calcium carbonate and irregular calcium carbonate.

[0225] The modified extender of the present disclosure comprising scalenohedral calcium carbonate showed enhanced light scattering and provided optimized titanium dioxide spacing and dispersion behavior. The surface characteristics of the scalenohedral calcium carbonate also improved the refractive index contrast of the modified extender. In contrast, the modified extenders with rhombohedral or irregular shapes performed poorly, emphasizing significant role of particle morphology and surface treatment extender performance. Further, in high-PVC coating systems, the use of the modified extender of the present disclosure, comprising a blend of scalenohedral calcium carbonate and titanium dioxide maintained the opacity and color properties of the coating composition. Still further, the partial titanium dioxide replacement made the coating composition more cost-effective without compromising appearance or performance of the coating composition.

[0226] TECHNICAL ADVANCEMENTS

[0227] The present disclosure described hereinabove has several technical advantages including, but not limited to, the realization of:

[0228] >■ a modified extender that

[0229] • is used as a partial replacement of TiCh in the coating composition; and

[0230] • is cost effective,

[0231] >■ a coating composition having a modified extender that:

[0232] • has excellent opacity, brightness and whiteness; and

[0233] • is economic,

[0234] and

[0235] >■ a process for the preparation of a modified extender that;

[0236] • is simple and economical. The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

[0237] The foregoing description of the specific embodiments so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and / or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

[0238] The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results. While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Variations or modifications to the formulation of this invention, within the scope of the invention, may occur to those skilled in the art upon reviewing the disclosure herein. Such variations or modifications are well within the spirit of this invention.

[0239] Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.

[0240] The numerical values given for various physical parameters, dimensions, and quantities are only approximate values and it is envisaged that the values higher than the numerical value assigned to the physical parameters, dimensions, and quantities fall within the scope of the invention unless there is a statement in the specification to the contrary.

[0241] While considerable emphasis has been placed herein on the specific features of the preferred embodiment, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiment without departing from the principles of the disclosure. These and other changes in the preferred embodiment of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.

Claims

CLAIMS:

1. A modified extender comprising a blend of scalenohedral calcium carbonate and a titanium dioxide pigment.

2. The modified extender as claimed in claim 1, is characterized by having at least one of the following:• particle size (D50) below 5 microns; and• refractive index (RI) in the range of 1.6 to 2.2.

3. The modified extender as claimed in claim 1 , wherein a mass ratio of said scalenohedral calcium carbonate to said titanium dioxide pigment is in the range of 10:90 to 40:60.

4. The modified extender as claimed in claim 1, wherein said titanium dioxide pigment is in a form selected from titanium dioxide rutile grade and titanium dioxide anatase grade.

5. The modified extender as claimed in claim 1 is used in a coating composition.

6. A process for the preparation of a modified extender, said process comprising the following steps:i. mixing titanium dioxide pigment and a scalenohedral calcium carbonate in a predetermined mass ratio at a stirring speed in the range of 20 rpm to 60 rpm at a temperature in the range of 30 °C to 40 °C in a ribbon blender to obtain a mixture; andii. maintaining said mixture for a time period in the range of 15 minutes to 30 minutes to obtain said modified extender.

7. The process as claimed in claim 6, wherein said mass ratio of said scalenohedral calcium carbonate to said titanium dioxide pigment is in the range of 10:90 to 40:60.

8. The process as claimed in claim 6, wherein said titanium dioxide pigment is in a form selected from titanium dioxide rutile grade and titanium dioxide anatase grade.

9. A coating composition comprising:• a modified extender in an amount in the range in the range of 2 mass% to 8 mass%;• at least one dispersing agent in an amount in the range of 1 mass% to 2 mass%;• at least one wetting agent in an amount in the range of0.5 mass% to 1.5 mass%;• at least one defoamer in an amount in the range of 0.2 mass% to 0.8 mass%;• at least one biocide in an amount in the range of 0.2 mass% to 0.8 mass%; • at least one pH neutralizer in an amount in the range of 0.2 mass% to 0.8 mass%;• at least one thickening agent in an amount in the range of 0.2 mass% to 0.8 mass%;• at least one pigment in an amount in the range of 6 mass% to 10 mass%; • at least one filler in an amount in the range of 40 mass% to 50 mass%;• at least one binder in an amount in the range of 8 mass% to 12 mass%;• at least one coalescing agent in an amount in the range of 1 mass% to 2 mass%;• at least one co-solvent in an amount in the range of 0.5 mass% to 1 mass%; and • water in an amount in the range of 20 mass% to 30 mass%,wherein said mass% of each ingredient is with respect to the total mass of said coating composition.

10. The coating composition as claimed in claim 9, wherein• said modified extender comprises a blend of scalenohedral calcium carbonate and a titanium dioxide pigment;• said dispersing agent is selected from ammonium polyacrylate and sodium polyacrylate;• said wetting agent is alkyl polyethylene glycol ether;• said defoamer is a mineral oil based defoamer;• said biocide is methylisothiazolinone;• said pH neutralizer is a mixture of amines;• said thickening agent is hydroxyethyl cellulose;• said pigment is selected from titanium dioxide rutile grade and titanium dioxide anatase grade;• said filler is selected from the group consisting of steatite, calcium carbonate, talc, dolomite and a combination thereof;• said binder is styrene acrylic emulsion;• said coalescing agent is 3-hydroxy-2,2,4-trimethylpentyl 2-methylpropanoate;and• said co-solvent is selected from monoethylene glycol and diethylene glycol.

11. The coating composition as claimed in claim 9 is characterized by having at least one of the following:• whiteness index is in the range of 80 % to 95 %;• brightness index is in the range of 80 % to 95 %;• contrast ratio is greater than 95; and• reducing strength is greater than 100.

12. A process for the preparation of a coating composition, said process comprising the following steps:i. mixing predetermined amounts of a first portion of water, a dispersing agent, a wetting agent, a biocide and a defoamer in a reactor at a temperature in the range of 30 °C to 40 °C under stirring at a speed in the range of 8 m / s to 15 m / s to obtain a first mixture;ii. adding predetermined amounts of a pigment, a modified extender and a filler in said first mixture under stirring for a time period in the range of 5 minutes to 20 minutes to obtain a second mixture;iii. adding predetermined amounts of a thickening agent and a pH neutralizer in said second mixture under stirring at a speed in the range of 15 m / s to 30 m / s for a time period in the range of 20 minutes to 50 minutes to obtain a third mixture; andiv. maintaining said third mixture under stirring at a speed in the range of 8 m / s to 15 m / s followed by adding predetermined amounts of a coalescing agent, a cosolvent, a binder and a second portion of water in said third mixture to obtain said coating composition.

13. The process as claimed in claim 12, wherein• said first portion of water is in an amount in the range of 20 mass% to 25 mass%;• said dispersing agent is present in an amount in the range of 1 mass% to 2 mass%;• said wetting agent is present in an amount in the range of 0.5 mass% to 1.5 mass%;• said biocide is present in an amount in the range of 0.2 mass% to 0.8 mass%;• said defoamer is present in an amount in the range of 0.2 mass% to 0.8 mass%;• said pigment is present in an amount in the range of 6 mass% to 10 mass%; • said modified extender is present in an amount in the range in the range of 2 mass% to 8 mass%;• said filler is present in an amount in the range of 40 mass% to 50 mass%; • said thickening agent is present in an amount in the range of 0.2 mass% to 0.8 mass%;• said pH neutralizer is present in an amount in the range of 0.2 mass% to 0.8 mass%;• said coalescing agent is present in an amount in the range of 1 mass% to 2 mass%;• said co-solvent is present in an amount in the range of 0.5 mass% to 1 mass%;• said binder is present in an amount in the range of 8 mass% to 12 mass%; and • said second portion of water is in an amount in the range of 1 mass% to 5 mass% wherein said mass% of each ingredient is with respect to the total mass of said coating composition.

14. The process as claimed in claim 12, wherein• said dispersing agent is selected from ammonium polyacrylate and sodium polyacrylate;• said wetting agent is alkyl polyethylene glycol ether;• said biocide is methylisothiazolinone;• said defoamer is a mineral oil based defoamer;• said pigment is selected from titanium dioxide rutile grade and titanium dioxide anatase grade;• said modified extender comprises a blend of scalenohedral calcium carbonate and a titanium dioxide pigment;• said filler is selected from the group consisting of steatite, calcium carbonate, talc, dolomite and a combination thereof;• said thickening agent is hydroxyethyl cellulose;• said pH neutralizer is a mixture of amines;• said coalescing agent is 3 -hydroxy-2, 2, 4-trimethylpentyl 2-methylpropanoate;• said co-solvent is selected from monoethylene glycol and diethylene glycol; andsaid binder is styrene acrylic emulsion.

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