Claims:WE CLAIM
1. A coating composition comprising the following:
a. a binder component having hydroxyl value in the range of 30 mg KOH/g to 200 mg KOH/g, and acid value in the range of 2 mg KOH/g to 15 mg KOH/g, said binder component comprising:
i. an acrylic polyol component having hydroxyl value in the range of 50 mg KOH/g to 200 mg KOH/g; and
ii. a polyolefinic component having weight average molecular weight in the range of 1,000 to 30,000, and an acid value in the range of 30 mg KOH/g to 100 mg KOH/g;
b. a curing agent; and
c. an organosilane additive selected at least one from an epoxy silane compound, an isocyanate silane compound, and a mercaptosilane compound and an adduct between any two or more of the foregoing.
2. A coating composition comprising the following:
a. a binder component having hydroxyl value in the range of 80 mg KOH/g to 150 mg KOH/g, and acid value in the range of 2 mg KOH/g to 10 mg KOH/g, said binder component comprising:
i. an acrylic polyol component having hydroxyl value in the range of 90 mg KOH/g to 150 mg KOH/g; and
ii. a polyolefinic component having weight average molecular weight in the range of 5,000 to 20,000, and an acid value in the range of 30 mg KOH/g to 50 mg KOH/g;
b. a curing agent; and
c. an organosilane additive selected at least one from an epoxy silane compound, an isocyanate silane compound, and a mercaptosilane compound and an adduct between any two or more of the foregoing.
3. A coating composition comprising the following:
a. a binder component having hydroxyl value in the range of 100 mg KOH/g to 130 mg KOH/g, and acid value in the range of 2 mg KOH/g to 5 mg KOH/g, said binder component comprising:
i. an acrylic polyol component having hydroxyl value in the range of 110 mg KOH/g to 130 mg KOH/g; and
ii. a polyolefinic component having weight average molecular weight in the range of 10,000 to 15,000, and an acid value in the range of 30 mg KOH/g to 40 mg KOH/g;
b. a curing agent; and
c. an organosilane additive selected at least one from an epoxy silane compound, an isocyanate silane compound, and a mercaptosilane compound, and an adduct between any two or more of the foregoing.
4. The coating composition as claimed in claims 1 to 3, wherein said isocyanate silane compound is present in an amount in the range of 0.1 wt% to 10 wt%, and is at least one selected from the group consisting of 3-isocyanataopropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, tris-(trimethoxysilylpropyl) isocyanurate, and oligomeric isocyanate siloxane.
5. The coating composition as claimed in claims 1 to 3, wherein said mercapto silane compound is present in an amount in the range of 0.1 wt% to 10 wt%, and is at least one selected from the group consisting of mercaptopropyltrimethoxysilane, mercapto propyl methyl dimethoxysilane, mercaptopropyltriethoxysilane, and mercaptopropylmethyldiethoxysilane, and oligomeric mercapto silane.
6. The coating composition as claimed in claims 1 to 3, wherein said epoxy silane compound is present in an amount in the range of 0.1 wt% to 10 wt%, and is at least one selected from the group consisting of 3-glycidoxypropyltrialkoxysilane, 2-(3,4-epoxy cyclohexyl)ethyl trimethoxy silane, (3-glycidoxy propyl) bis(trimethyl siloxy)-methyl silane, 3-glycidoxy propyl diisopropyl ethoxy silane, 3-glycidoxy propyl dimethyl ethoxy silane, 3-glycidoxy propyl) methyl diethoxy silane, 3-glycidoxy propyl methyl diisopropenoxy silane, and 3-glycidoxy propyl trimethoxy silane.
7. The coating composition as claimed in claims 1 to 3, wherein said acrylic polyol component is a copolymer obtained by co-polymerizing at least one hydroxy acrylate monomer with at least one acrylate monomer.
8. The coating composition as claimed in claim 7, wherein said at least one hydroxy acrylate monomer is selected from the group consisting of hydroxyethyl acrylate, hydroxyl-ethoxyethyl acrylate, hydroxyl-poly(ethoxy)ethyl acrylate, and hydroxymethyl acrylate.
9. The coating composition as claimed in claim 7, wherein said at least one acrylate monomer is selected from the group consisting of butyl acrylate, n-butyl acrylate, methyl acrylate, methyl methacrylate, acrylic acid, and methacrylic acid.
10. The coating composition as claimed in claims 1 to 3, wherein said at least one polyolefinic component is selected from the group consisting of linear polyethylene, ethylene copolymer, polypropylene, and propylene copolymer.
11. The coating composition as claimed in claims 1 to 3, wherein said curing agent is selected from the group consisting of poly isocyanate, melamine-formaldehyde, urea formaldehyde, amines, amides, amido-amines, imido-amines, polyamines, polyamides, polyamido-amines, and polyimido-amines.
12. The coating composition as claimed in claims 1 to 3, comprises at least one fluid medium in an amount in the range of 3 wt% to 40 wt%, wherein said fluid medium is selected from hydrocarbons, esters, ethers, and glycols.
13. The coating composition as claimed in claims 1 to 3 has a viscosity in the range of 10 cps to 15000 cps at 5 % to 100 % solid concentration.
14. The coating composition as claimed in claims 1 to 3, wherein said coating composition comprises a pendant functional group having aceto-acetate functionality.
15. The coating composition as claimed in claims 1 to 3, wherein said coating composition comprises at least one vinylated aromatic component selected from the group consisting of styrene, vinyltoluene, and methylstyrene, wherein said vinylated aromatic component is present in the backbone of said acrylic polymer.
16. The coating composition as claimed in claims 1 to 3, wherein said coating composition comprises a catalyst in an amount in the range of 0.05 wt% to 0.3 wt% selected from the group consisting of butyl tin dilaurate, dibutyltin diacetate, titanium tetrabutoxide, 1,4-diazabicyclo[2,2,2]-octane, metal dionate complex, Co isooctate, Zn isooctate, Bi isooctate, Co-2-ethylhexoate, Zn-2-ethylhexoate, Bi-2-ethylhexoate, and Zn acetoacetate and Ti acetoacetate, in the range of 0.05 wt% to 0.3 wt%.
17. The coating composition as claimed in claims 1 to 3, wherein said coating composition comprises an additive selected from the group consisting of nanoparticles, wetting agents, dispersing agents, surfactants, plasticizers, flow agents, leveling agents, rheological agents, and de-foamers.
18. The coating composition as claimed in claim 17, wherein said nanoparticles are selected from the group consisting of silica, alumina, titania, carbon nanotubes, and graphene.
19. The coating composition as claimed in claims 1 to 3, wherein the proportion of said binder component is in the range of 40 wt% to 80 wt%, the proportion of said curing agent is in the range of 10 wt% and 40 wt% and the proportion of said organosilane additive is in the range of 0.1 wt% to 30 wt%.
20. A film obtained by applying said coating composition as claimed in claims 1 to 3 on a substrate selected from glass, metal, and wood, wherein the dried film has a thickness up to 100 µm.
21. The film as claimed in claim 20 is configured to provide a transparent coating having a light transmittance value in the range of 90 % to 99.99 %, with at least a 4B adhesion, when the substrate is glass.
22. A kit containing a two or three component system, wherein said kit comprises a coating composition comprising:
a. a binder component having hydroxyl value in the range of 30 mg KOH/g to 200 mg KOH/g, and acid value in the range of 2 mg KOH/g to 15 mg KOH/g, said binder component comprising:
i. an acrylic polyol component having hydroxyl value in the range of 50 mg KOH/g to 200 mg KOH/g; and
ii. a polyolefinic component having weight average molecular weight in the range of 1,000 to 30,000, and an acid value in the range of 30 mg KOH/g to 100 mg KOH/g;
b. a curing agent; and
c. an organosilane additive selected at least one from an epoxy silane compound, an isocyanate silane compound, and a mercaptosilane compound and an adduct between any two or more of the foregoing.
23. The kit as claimed in claim 22 comprises a fluid medium selected from hydrocarbons, esters, ethers, and glycols.
24. The kit as claimed in claim 22, wherein said organosilane additive is a mercaptosilane compound or an epoxy silane compound and said kit is a two-component system comprising the following:
a. component A comprising:
i. an acrylic polyol component having hydroxyl value in the range of 50 mg KOH/g to 200 mg KOH/g;
ii. a polyolefinic component having weight average molecular weight in the range of 1,000 to 30,000, and an acid value in the range of 30 mg KOH/g to 100 mg KOH/g;
iii. mercaptosilane compound or an epoxy silane compound as the organosilane additive; and
b. component B comprising a curing agent,
wherein the contents of component A and B are mixed prior to use.
25. The kit as claimed in claim 22, wherein said organosilane additive is an isocyanate silane compound and said kit is a two-component system comprising the following:
a. component A comprising:
i. an acrylic polyol component having hydroxyl value in the range of 50 mg KOH/g to 200 mg KOH/g; and
ii. a polyolefinic component having weight average molecular weight in the range of 1,000 to 30,000, and an acid value in the range of 30 mg KOH/g to 100 mg KOH/g;
b. component B comprising a mixture of a curing agent and an isocyanate silane compound as the organosilane additive,
wherein the contents of component A and B are mixed prior to use.
26. The kit as claimed in claim 22, wherein said organosilane compound is an isocyanate silane compound and said kit is a three-component system comprising the following:
a. component A comprising:
i. an acrylic polyol component having hydroxyl value in the range of 50 mg KOH/g to 200 mg KOH/g;
ii. a polyolefinic component having weight average molecular weight in the range of 1,000 to 30,000, and an acid value in the range of 30 mg KOH/g to 100 mg KOH/g; and
b. component B comprising a curing agent; and
c. component C comprising an isocyanate silane compound as the organosilane additive,
wherein the contents of component A, B, and C are mixed prior to use.
, Description:FIELD
The present disclosure relates to coating compositions.
DEFINITIONS
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 indicates otherwise.
Hydroxyl value: The term “hydroxyl value” refers to the number of milligrams of potassium hydroxide required to neutralize the acetic acid taken up on acetylation of one gram of a chemical substance that contains free hydroxyl groups.
Acid value: The term “acid value” also known as “neutralization number" or "acid number" or "acidity”, refers to the mass of potassium hydroxide (KOH) in milligrams that is required to neutralize one gram of a chemical substance.
Coating: The term “coating” refers to a layer or a film formed by applying a binder composition or an anti-graffiti coating composition on a substrate.
Gloss value: The term “gloss value” refers to the perception by an observer of the shiny appearance of a surface. This perception changes whenever there is a change in the relative position or spectral distribution of the source, the sample, or the observer. Gloss is determined by projecting a beam of light at a fixed intensity and angle onto a surface and measuring the amount of reflected light at an equal but opposite angle.
Viscosity on Gardner Scale: The term “viscosity on Gardner Scale” refers to the measurement of kinetic viscosity of liquids in BYK-Gardner bubble viscosity tubes. The viscosity of the liquid being tested is directly proportionate to the amount of time that it takes the bubble in the tube to rise. A bubble that rises quickly shows a low range of viscosity.
Cross cut adhesion test: The term “cross cut adhesion test” refers to the testing of adhesion (ASTM D3359) of dry coats of paint on their substrate by means of a series of cuts through the coating. Two series of parallel cuts cross angled to each other to obtain a pattern of 25 or 100 similar squares. The ruled area is evaluated by using a table chart after a short treatment with a stiff brush, or adhesive tape for hard substrates and are classified from 0B to 5B, with 0B having least adhesion and 5B having the best adhesion.
Dirt-pickup resistance (DPUR): The term “dirt-pickup resistance” refers to the ability of a coating to resist dirt, which over the course of time, darkens the film and can result in an uneven appearance.
Weight average molecular weight: The “weight average molecular weight” is calculated from the weight fraction distribution of polymer molecules of different molecular weights.
Solid concentration: The term “solid concentration” volume of solid film forming ingredients in composition, i.e., the material that is left behind when the composition has dried.
BACKGROUND
A coating is usually applied on substrates for decorative and/or protective function. The coating can completely cover the substrate or it may only cover parts of the substrate. Coatings, such as paints and lacquers generally have the dual function of protecting the substrate and being decorative. Also, the presence of a coating on a substrate imparts resistance to dirt, and corrosion and can further ease the cleaning process. However, the coatings conventionally applied on a substrate can be easily removed/peeled off from the substrate due to poor adhesion to the substrate. Also, it is possible for substances, such as water to penetrate the coating and result in bulging, cracking, and peeling of the coating layer.
Therefore, there is felt a need to provide coating compositions for surface coating that mitigate the drawbacks mentioned hereinabove.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:
An object of the present disclosure is to ameliorate one or more problems of the prior art or to at least provide a useful alternative.
Another object of the present disclosure is to provide a coating composition.
Still another object of the present disclosure is to provide a coating composition having improved adhesion to a substrate.
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
The present disclosure provides a coating composition. The coating composition comprises i) a binder component having hydroxyl value in the range of 30 mg KOH/g to 200 mg KOH/g, and an acid value in the range of 2 mg KOH/g to 15 mg KOH/g ii) a curing agent, and iii) an organosilane additive. The binder component comprises an acrylic polyol component having hydroxyl value in the range of 50 mg KOH/g to 200 mg KOH/g, and a polyolefinic component having weight average molecular weight in the range of 1,000 to 30,000, and an acid value in the range of 30 mg KOH/g to 100 mg KOH/g. The organosilane additive is selected at least one from an epoxy silane compound, an isocyanate silane compound, and a mercaptosilane compound and an adduct between any two or more of the foregoing.
Typically, the proportion of the binder component can be in the range of 40 wt% to 80 wt%, the proportion of the curing agent can be in the range of 10 wt% and 40 wt% and the proportion of the organosilane additive can be in the range of 0.1 wt% to 30 wt%.
In one embodiment, the coating comprises at least one fluid medium selected from hydrocarbons, esters, ethers, and glycols in an amount in the range of 3 wt% to 40 wt%.
A film can be obtained by applying the coating composition of the present disclosure, having a dried film thickness of up to 100 µm. On a glass substrate, the film is configured to provide a transparent coating having a light transmittance value in the range of 90 % to 99.99 %, with at least a 4B adhesion.
The present disclosure further provides kits containing a two or three component system comprising the coating composition of the present disclosure. Typically, when mercapto silane compound or epoxy silane compound is the organosilane additive, it is present along with the acrylic polyol component and the polyolefinic component, i.e., the binder component, whereas the isocyanate silane compound as the organosilane additive can be present as a mixture with the curing agent or as a separate component.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
The present disclosure will now be described with the help of the accompanying drawing, in which:
Figure-1 illustrates the graphical representation of the transmission study of the coating composition of the present disclosure.

DETAILED DESCRIPTION
Conventionally known coating composition do not have good adhesion and are therefore easily removed from a substrate. Further, crosslinked polymers use expensive fluorinated or polysiloxane based raw materials.
Therefore, the present disclosure envisages a coating composition that is affordably priced and provides good adhesion to the substrate.
In one aspect of the present disclosure, there is provided a coating composition. The coating composition comprises the following:
a. a binder component having hydroxyl value in the range of 30 mg KOH/g to 200 mg KOH/g, and acid value in the range of 2 mg KOH/g to 15 mg KOH/g; the binder component comprises i) an acrylic polyol component having hydroxyl value in the range of 50 mg KOH/g to 200 mg KOH/g; and ii) a polyolefinic component having weight average molecular weight in the range of 1,000 to 30,000, and an acid value in the range of 30 mg KOH/g to 100 mg KOH/g;
b. a curing agent; and
c. an organosilane additive selected at least one from an epoxy silane compound, an isocyanate silane compound, and a mercaptosilane compound and an adduct between any two or more of the foregoing.
The binder component of the present disclosure having hydroxyl value in the range of 30 mg KOH/g to 200 mg KOH/g provides optimum crosslinking, such that the films formed using the coating composition having these binders demonstrate excellent physical properties including adhesion to a substrate. The viscosity of the polyolefinic component is controlled principally by its weight average molecular weight. The weight average molecular weight of the polyolefinic component of the present disclosure in the range of 1,000 to 30,000 imparts the required viscosity to the coating composition. The acid value of the binder component is critical for gloss of the coated surface.
Typically, the proportion of the binder component can be in the range of 40 wt% to 80 wt%, the proportion of the curing agent can be in the range of 10 wt% and 40 wt% and the proportion of the organosilane additive can be in the range of 0.1 wt% to 30 wt%.
The coating composition of the present disclosure can be applied to a substrate such as glass, metal, and wood to obtain a film, wherein the dried film has a thickness up to 100 µm. The coating composition of the present disclosure is configured to provide a transparent coating having a light transmittance value in the range of 90 % to 99.99 %, with at least a 4B adhesion, when a glass substrate is used.
The isocyanate silane compound is typically present in an amount in the range of 0.1 wt% to 10 wt%. The isocyanate silane compound can be selected from the group consisting of 3-isocyanatopropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, tris-(trimethoxysilylpropyl) isocyanurate, and oligomeric isocyanate siloxane.
The mercapto silane compound is typically present in an amount in the range of 0.1 wt% to 10 wt%. The mercapto silane compound can be selected from the group consisting of mercaptopropyltrimethoxysilane, mercapto propyl methyl dimethoxysilane, mercaptopropyltriethoxysilane, and mercaptopropylmethyldiethoxysilane, and oligomeric mercapto silane.
The epoxy silane compound is typically present in an amount in the range of 0.1 wt% to 10 wt%, and can be selected from the group consisting of 3-glycidoxypropyltrialkoxysilane, 2-(3,4-epoxy cyclohexyl)ethyl trimethoxy silane, (3-glycidoxy propyl) bis(trimethyl siloxy)-methyl silane, 3-glycidoxy propyl diisopropyl ethoxy silane, 3-glycidoxy propyl dimethyl ethoxy silane, 3-glycidoxy propyl) methyl diethoxy silane, 3-glycidoxy propyl methyl diisopropenoxy silane, and 3-glycidoxy propyl trimethoxy silane.
Typically, the acrylic polyol component is a co-polymer obtained by co-polymerizing at least one hydroxy acrylate monomer with at least one acrylate monomer. The at least one hydroxy acrylate monomer can be selected from the group consisting of hydroxyethyl acrylate, hydroxyl-ethoxyethyl acrylate, hydroxyl-poly(ethoxy)ethyl acrylate, and hydroxymethyl acrylate. The at least one acrylate monomer is selected from the group consisting of butyl acrylate, n-butyl acrylate, methyl acrylate, methyl methacrylate, acrylic acid, and methacrylic acid.
The at least one polyolefinic component can be selected from the group consisting of linear polyethylene, ethylene copolymer, polypropylene, and propylene copolymer. The acid value of the polyolefinic component is higher as compared to that of the coating composition and is a critical parameter in for selecting the appropriate polyolefinic component for the coating composition.
Typically, the weight proportion of the acrylic polyol component to the polyolefinic component is in the range of 99:1 to 90:10.
A curing agent is used to cure the coating composition prior to applying to the glass substrate, to obtain a glossy and transparent coat. Typically, the curing agent can be selected from the group consisting of poly isocyanate, melamine-formaldehyde, urea formaldehyde, amines, amides, amido-amines, imido-amines, polyamines, polyamides, polyamido-amines, and polyimido-amines. Typically, the proportion of the curing agent in the coating composition can be in the range of 10 wt% to 40 wt%. In one embodiment, the proportion of the curing agent is in the range of 15 wt% to 30 wt%.
In one embodiment, the coating composition further comprises at least one fluid medium in an amount in the range of 3 wt% to 40 wt%. The fluid medium can be selected from hydrocarbons, esters, ethers, and glycols.
Typically, the coating composition has a viscosity in the range of 10 cps to 15000 cps at 5 % to 100 % solid concentration.
In one embodiment, the coating composition further comprises a pendant functional group having aceto-acetate functionality, in an amount in the range of 10 wt% to 30 wt%.
In an embodiment, the coating composition further comprises at least one vinylated aromatic component selected from the group consisting of styrene, vinyltoluene, and methylstyrene. The vinylated aromatic component is typically present in the backbone of the acrylic polymer.
In one embodiment, the coating composition further comprises at least one catalyst. The at least one catalyst can be selected from the group consisting of butyl tin dilaurate, dibutyltin diacetate, titanium tetrabutoxide, 1,4-diazabicyclo[2,2,2]-octane, metal dionate complex, Co isooctate, Zn isooctate, Bi isooctate, Co-2-ethylhexoate, Zn-2-ethylhexoate, Bi-2-ethylhexoate, Zn acetoacetate and Ti acetoacetate. Typically, the metal dionate complex can be formed by the interaction of Zn, Zr, Bi, Co, Mn, Al, and Ni, with 2,4-pentanedione. Typically, the proportion of the catalyst in the coating composition is in the range of 0.05 wt% to 0.3 wt%. In one embodiment, the proportion of the catalyst is in the range of 0.05 wt% to 0.2 wt%.
In one embodiment of the present disclosure, the coating composition comprises the following:

a. a binder component having hydroxyl value in the range of 80 mg KOH/g to 150 mg KOH/g, and acid value in the range of 2 mg KOH/g to 10 mg KOH/g; the binder component comprises i) an acrylic polyol component having hydroxyl value in the range of 90 mg KOH/g to 150 mg KOH/g, and ii) a polyolefinic component having weight average molecular weight in the range of 5,000 to 20,000, and an acid value in the range of 30 mg KOH/g to 50 mg KOH/g;
b. a curing agent; and
c. an organosilane additive selected at least one from an epoxy silane compound, an isocyanate silane compound, and a mercaptosilane compound and an adduct between any two or more of the foregoing.
In another embodiment of the present disclosure, the coating composition comprises the following:
a. a binder component having hydroxyl value in the range of 100 mg KOH/g to 130 mg KOH/g, and acid value in the range of 2 mg KOH/g to 5 mg KOH/g; the binder component comprises i) an acrylic polyol component having hydroxyl value in the range of 110 mg KOH/g to 130 mg KOH/g, and ii) a polyolefinic component having weight average molecular weight in the range of 10,000 to 15,000, and an acid value in the range of 30 mg KOH/g to 40 mg KOH/g;
b. a curing agent; and
c. an organosilane additive selected at least one from an epoxy silane compound, an isocyanate silane compound, and a mercaptosilane compound, and an adduct between any two or more of the foregoing.
The present disclosure in another aspect provides a kit containing a two or three component system. The kit comprises a coating composition comprising:
a. a binder component having hydroxyl value in the range of 30 mg KOH/g to 200 mg KOH/g; and acid value in the range of 2 mg KOH/g to 15 mg KOH/g, wherein the binder component comprises:
i) an acrylic polyol component having hydroxyl value in the range of 50 mg KOH/g to 200 mg KOH/g, and
ii) a polyolefinic component having weight average molecular weight in the range of 1,000 to 30,000, and an acid value in the range of 30 mg KOH/g to 100 mg KOH/g,
b. a curing agent; and
c. an organosilane additive selected at least one from an epoxy silane compound, an isocyanate silane compound, and a mercaptosilane compound and an adduct between any two or more of the foregoing.
In an embodiment, the kit further comprises a fluid medium selected from hydrocarbons, esters, ethers, and glycols.
In an embodiment of the present disclosure, the organosilane compound is a mercaptosilane compound or an epoxy silane compound and the kit is a two-component system comprising:
i) component A comprising:
- an acrylic polyol component having hydroxyl value in the range of 50 mg KOH/g to 200 mg KOH/g,
- a polyolefinic component having weight average molecular weight in the range of 1,000 to 30,000, and an acid value in the range of 30 mg KOH/g to 100 mg KOH/g, and
- mercaptosilane compound or an epoxy silane compound as the organosilane additive, and
ii) component B comprising a curing agent.
The contents of component A, and B are mixed prior to use.
In another embodiment of the present disclosure, the organosilane compound is an isocyanate silane compound and the kit is a two-component system comprising:
i) component A comprising:
- an acrylic polyol component having hydroxyl value in the range of 50 mg KOH/g to 200 mg KOH/g, and
- a polyolefinic component having weight average molecular weight in the range of 1,000 to 30,000, and an acid value in the range of 30 mg KOH/g to 100 mg KOH/g, and
ii) component B comprising a mixture of a curing agent and an isocyanate silane compound as the organosilane additive.
The contents of component A, and B are mixed prior to use.
In still another embodiment of the present disclosure, the organosilane additive is an isocyanate silane compound and the kit is a three-component system comprising:
i) component A comprising:
- an acrylic polyol component having hydroxyl value in the range of 50 mg KOH/g to 200 mg KOH/g, and
- a polyolefinic component having GPC average molecular weight in the range of 3,000 to 30,000, and an acid value in the range of 30 mg KOH/g to 100 mg KOH/g, and
ii) component B comprising a curing agent; and
iii) component C comprising an isocyanate silane compound as the organosilane additive.
The contents of component A, B, and C are mixed prior to use.
Conventional coatings on substrate have a poor adhesion. However, the present disclosure provides coating compositions comprising an organosilane additive (an isocyanate silane compound, a mercaptosilane compound, or an epoxy silane compound) along with the curing agents that provide a better adhesion.
In one embodiment, when the coating composition of the present disclosure is applied on a glass substrate, an adhesion of at least 4B is obtained. Further, the coating composition of the present disclosure imparts dirt resistance, anti-graffiti property and mechanical strength without hampering the gloss or the transparency of the coated surface.
The present disclosure is further described in light of the following laboratory scale experiments which are set forth for illustration purpose only and not to be construed for limiting the scope of the disclosure. These laboratory scale experiments can be scaled up to industrial/commercial scale and the results obtained can be extrapolated to industrial/commercial scale.
Experimental details
Experiment-1: General process for preparing the coating composition of the present disclosure
Ortho-xylene (fluid medium) was charged to a reactor and the temperature was raised to 140 °C. A mixture of monomer (BA, n-BMA, MMA, HEMA, as given in Table-1) and initiator (TBPB) was charged drop wise to the reactor over a period of 4 hours. After completion of addition of the mixture of monomer and initiator, digestion was carried out for 1 hour, followed by addition of the chaser catalyst (additional TBPB), and was further allowed to stir for 1 hour to obtain acrylic polyol component having hydroxyl value of 120 mg KOH/g. Polyethylene (polyolefinic component) having weight average molecular weight of 14000 and acid value 35 mg KOH/g (modified polyethylene) and o-xylene was added to the above mixture at 150 °C to obtain the binder component. After completion of the batch, the so obtained resin was cooled, filtered and discharged.
Experiment-2: Preparation of coating composition (two component system) of the present disclosure
The two component system with mercapto silane compound as the organosilane additive was prepared using the ingredients as specified in Table-1.
Table-1
S. No. Raw Material Quantity (g)
1 Butyl acrylate (BA) 5.43
2 n-Butyl methacrylate (n-BMA) 23.53
3 Methyl methacrylate (MMA) 10.86
4 Hydroxyethyl methacrylate (HEMA) 20.81
5 tert-Butyl peroxybenzoate (TBPB) 3.08
6 TBPB 0.09
7 O-Xylene 26.69
8 O-Xylene 7.66
9 Modified polyethylene (having acid value 35 mg KOH/g) 1.76
Total 100.00

The ingredients mentioned in Table-1 were used to prepare the binder component using the procedure mentioned in experiment-1. The binder component had Viscosity on Gardner scale – W-X-Y-Z (100 to 2300 centipoise), Solids – 60%, Hydroxyl value - 140 mg/g, Acid value – 3 mg KOH/g, Tg – 13 °C (measured in Differential scanning calorimetry [DSC]).
To this resin (100 g resin), 5 wt% of mercaptosilane compound (organosilane additive) was added to obtain component A. Component B comprises the curing agent poly isocyanate (Desmodur N3600 with isocyanate content of 23 %).
100 g of component A having solid: 60%; hydroxyl value: 140 mg KOH/g, viscosity of Y-Z on Gardner scale (1700 to 2300 centipoise), and acid value 2.5 mg KOH/g; and 30 g of component B having isocyanate content of 23% was mixed to obtain the coating composition.
Experiment-3: Preparation of coating composition (two component system) of the present disclosure
The two component system with isocyanate silane compound as the organosilane additive was prepared. The binder component as mentioned in Table-1 of experiment-2 was prepared to obtain component A. Component B was prepared by mixing the curing agent (21 g of polyisocyanate) and the 9 g of 3-isocyanatopropyltrimethoxysilane (organosilane additive).
100 g of component A was mixed with 30 g of component B to obtain the coating composition.
The transmission data of the coating composition prepared in accordance with the present disclosure was coated on a glass substrate was studied and the result obtained is represented in Figure-1. Line-A in Figure-1 represents glass substrate without coating, Line-B represents acrylic polyurethane coating cured with poly isocyanate N3600 (curing agent) on the glass slide, and Line-C represents acrylic polyurethane coating cured with isocyanate silane (organosilane additive) on glass slide. It is seen from Figure-1 that there is no interference of the coating to the transmission of light in visible range and has good transparency.
Experiment-4: Preparation of coating composition (three component system) of the present disclosure
The three component system with isocyanate silane compound as the organosilane additive was prepared: component A=acrylic polyol and polyolefinic component (binder component), component B=isocyanate crosslinker (curing agent), component C=isocyanate silane (organosilane additive) and are summarized in Table-2.
Adhesion study for the coating composition of the present disclosure

The coating composition (two and three component system) of the present disclosure was prepared as per the process described in experiment-1, using the ingredients mentioned in Table-2.
Table-2
Sample No. Polyol (component A) Desmodur N3600 (Polyisocyanate) (Curing agent) Geniosil GF 40 (3-isocyanatepropyl trimethoxysilane) (isocyanate silane compound) CoatOSil T-Cure (mercaptosilane oligomer) Added to Polyol (mercaptosilane compound) Silquest A-187 (3-(glycidoxypropyl trimethoxysilane) (epoxysilane compound) O-xylene*
1
(Comparative example) 10 g 3.01 g - - - 3 g
2 10 g 2.1 g 0.9 g - - 3 g
3 10 g - 3.06 g - - 3 g
4
(Comparative example) 10 g 3.2 g - - - 3 g
5 10 g 3.01 g - 0.2 g - 3 g
6 10 g 3.01 g - 0.8 g - 3 g
7 10 g 3.01 g - - 0.2 g 3 g
*Added to lower the viscosity and assist in application of the coating composition.
The coating compositions (as mentioned in Table-2) were applied using 150 um applicator on glass plates and were used for the adhesion studies. The panels were allowed to cure for 7 days before testing under ambient conditions (25 °C, 50 % Relative Humidity [RH]).

Cross cut adhesion test (tape test: ASTM D3359) was performed on the samples to study the adhesion property. The reference rating chart for the cross cut tested samples are summarized in Table-3, and the result obtained for the coating compositions (Samples 1 to 7) are summarized in Table-4.
Table-3
Classification % of Area Removed Surface of Cross Cut Area from Which Flaking has Occurred for 6 parallel Cuts & Adhesion Range by %
5B 0 %
None
4B Less than 5 %
3B 5 – 15 %
2B 15 – 35 %
1B 35 % to 65 %
0B Greater than 65 %

Table-4
Sample No. Rating
1 (Comparative example) 0B
2 4B – 3B
3 5B
4 (Comparative example) 0B
5 5B
6 5B
7 5B

It is clearly seen from Table-4 that Sample-1 (Comparative example) and Sample-4 (Comparative example) cured with only the curing agent (Poly isocyanate) exhibited poor adhesion (0B). On incorporation of the organosilane additive, namely isocyanate silane (Sample-2 and Sample-3), there was a significant increase in the adhesion (5B). Similarly, incorporation of the mercaptosilane oligomer (Sample-5 and Sample-6), and epoxy silane compound (Sample-7) as the organosilane additive also resulted in an increase in adhesion to 5B.
Water resistance study for the coating composition of the present disclosure
Water dip test of the coated glass panels (Samples 1 to 7) was carried out. The observations (after 24 hours of dip test), i.e., blistering and delamination are provided in Table-5.
Table-5
Sample No. Blistering
1 (Comparative example) Yes
2 No
3 No
4 (Comparative example) Yes
5 No
6 No
7 No

It is seen from Table-5 that blistering was not observed, when the organosilane additive, namely, isocyanate silane, epoxy silane compound and mercaptosilane compounds were used to cure the polyolefin modified acrylic polyols along with organic poly isocyanate (curing agent).
The water dip test was continued for 7 days and the adhesion and the water resistance properties obtained is summarized in Table-6.
Table-6
Sample No. Blistering (Initial) Blistering (After one hour recovery) Adhesion (Cross cut)
1 (Comparative example) Yes Yes 0B-1B
2 Yes No 4B-5B
3 No No 5B
4 (Comparative example) Yes Yes 0B-1B
5 No No 4B-5B
6 Yes Yes 4B-5B
7 No No 4B-5B

It is seen from Table-6 that Sample-1 and Sample-4 cured with only the curing agent (poly isocyanate) exhibited poor wet adhesion (0B-1B). On incorporation of isocyanate silane (Sample-2 and Sample-3), mercaptosilane oligomer (Sample-5 and Sample-6), and epoxy silane compound (Sample-7), the adhesion increases to 5B.
Surface energy study for the coating composition of the present disclosure
The surface energy study of substrates coated with the coating composition of the present disclosure was carried out and the result obtained is summarized in Table-7.
Table-7
Sample No. Contact angle (°) Surface free energy (mN/m)
Water Di-iodomethane Total energy Polar component Disperse (non-polar) component
7 94.7 54.9 32.5 1.0 31.5
8 92.5 55.9 32.5 1.5 30.9
9 91.0 58.0 31.8 2.1 29.7
10 90.9 55.7 32.9 1.9 31.1
11 92.9 59.9 30.4 1.8 28.6

Sample-7=Acrylic polyol + Polyisocyanate [1:1 PHR]
Sample-8= Acrylic polyol + Polyisocyanate + (3-isocyanatepropyl trimethoxysilane) [70:30 proportion of hardener]
Sample-9= Acrylic polyol + (3-isocyanatepropyl trimethoxysilane) [1:1 PHR]
Sample-10=Acrylic polyol + Polyisocyanate [1:1 PHR] + 2% mercaptosilane oligomer in formulation
Sample-11= Acrylic polyol + Polyisocyanate [1:1 PHR] + 8% mercapto silane oligomer in formulation
It is seen from the Table-7, there is no significant change in the surface energy on incorporation of the organosilane additive, namely, isocyanate silane, the mercapto silane.
Anti-graffiti study for the coating composition of the present disclosure
The anti-graffiti property was studied using different stains such as permanent marker, sketch pens, white board marker and water based paint. The cleaning was carried out by wiping with a dry cloth and the result obtained is summarized in Table-8. The stains applied were allowed to dry for 4 hours and then cleaned.
Table-8
Sample No. Rating (white board/permanent marker/sketch pen/crayon)
1 10/8/10/10
2 10/5/10/10
3 10/9/10/10
4 10/8/10/10
5 10/9/10/10
6 10/7/10/10
7 10/9/10/10
Rating - 10 best and 1 poor. In all cases dry cloth wiping done.
White board marker, sketch pen and crayon stains were cleaned by dry cloth wiping with a rating of 10. For the permanent marker stains, the rating varied from a 5 to 9 depending on the curing agents used with 9 being obtained for Sample-3 cured with isocyanate silane (organosilane additive) and Sample-5 cured with poly isocyanate (curing agent) and mercaptosilane oligomer (organosilane additive).
Dirt-pickup resistance (DPUR) study for the coating composition of the present disclosure
The dirt-pickup resistance study was carried out to test the ability of the coating to resist dirt, and the result obtained is summarized in Table-9. DPUR was conducted as per the following procedure:
1] The coating was cast on white Leneta paper followed by curing for 7 days;
2] White rectangular strips of appropriate size were cut which were able fit in a rectangular DPUR box;
3] 1 g of charcoal/Terrace dust was added to the DPUR box containing the above rectangular strips;
4] The box was shaken in to and fro motion for 40 cycles;
5] The strips were removed from the box and the loose dust was removed by gently tapping behind the strip;
6] A comparative visual rating was given as summarized in Table-9.
Table-9
Sample No. Charcoal Natural Dirt
1 2 3
3 2 2
5 3 4
6 3 4
Where 5 is the best and 0 is poor.
It is seen that the Sample-5 (cured with the curing agent and the organosilane additive) and Sample-6 (cured with organosilane additive) had comparatively better resistance to dirt as compared to when only the curing agent was used.
Study of mechanical properties of the coating composition of the present disclosure
The mechanical properties were determined after 7 days of ambient curing. All the properties were checked DTM on sanded MS panel, and the result obtained is summarized in Table-10. The coatings were applied directly to metal (DTM) by spray application on a MS panel which was sanded by 320 mesh sand paper.
Table-10
Sample No. Scratch Hardness Pencil Hardness DFT
(micron) Gloss
(@60)
1 2100g H pass 40-50 96 GU
3 1900g H Pass 40-50 90 GU
5 2000g H pass 40-50 98 GU
6 2000g H pass 40-50 98 GU

Study of the Effect of different silanes and silicones on adhesion promotion
Non-functional silanes (silanes not becoming part of the resin backbone) were blended into the coating formulation at 2 wt% loading as illustrated in Table-11. For comparison, mercapto silane, epoxy silane and isocyanate silane (organosilane additive) were used. The adhesion properties were studied and the results obtained are summarized in Table-11.
Table-11
S. No. Ingredient Dosage Adhesion
1 Mercaptosilane 2% 4B-5B
2 Isocyanate silane 2% 4B-5B
3 Epoxy silane 2% 4B-5B
4 Vinyl Trimethoxy silane 2% 0B (Film delaminates)
5 Silres IC 232 (Phenyl methyl Methoxy silicone) 2% 2B
6 Fluorosilane 2% 0B (Film delaminates)
7 Blank Coating 0% 0B (Film delaminates)

It is seen from Table-11 that when non-functional silanes (Sample 4, 5, and 6) are used (silanes/silicones that did not react or interact with the binder component or the curing agent) significant improvement in adhesion is not achieved. Whereas, when functional silanes (silanes that react or interact with the binder component) were used, a significant improvement in the adhesion was achieved.
TECHNICAL ADVANCES
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of a coating composition having improved adhesion, particularly an adhesion of at least 4B to glass surface. Further, coating composition provides dirt resistance, anti-graffiti property and mechanical strength without hampering the gloss or the transparency of the coated surface.
Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
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.
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.
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.