WO2022064460A1

WO2022064460A1 - A polysiloxane copolymer and a coating composition prepared therefrom

Info

Publication number: WO2022064460A1
Application number: PCT/IB2021/058796
Authority: WO
Inventors: Rama Shanker MISHRA; Sundanthiramoorthy SUBRAMANIAN; Archana KAMBLE; Subarna Shyamroy; Shekhar TAMBE; Satchidanand GHURYE; Shrikant NAIK; Rajeev Kumar GOEL
Original assignee: Asian Paints Ltd
Current assignee: Asian Paints Ltd
Priority date: 2020-09-26
Filing date: 2021-09-27
Publication date: 2022-03-31
Anticipated expiration: 2023-03-26

Abstract

The present disclosure relates to a polysiloxane copolymer and a process for its preparation. The polysiloxane copolymer of the present disclosure can be cured at an ambient temperature and sustains at high temperatures without the loss of flexibility. Further, the present disclosure relates to a coating composition comprising the polysiloxane copolymer and a process for preparing the coating composition. The coating composition of the present disclosure can be used for high heat resistance coating and the corrosion under insulation (CUI) coating.

Description

A POLYSILOXANE COPOLYMER AND A COATING COMPOSITION PREPARED

THEREFROM

FIELD

The present disclosure relates to a polysiloxane copolymer and a coating composition prepared therefrom. Particularly, the present disclosure relates to a polysiloxane copolymer and a process for its preparation. Further, the present disclosure relates to a coating composition comprising the polysiloxane copolymer and a process for its preparation.

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.

Cyclic stress refers to the repetitive occurrence and redistribution of forces acting on a material. Periodic or regular cyclic stress conditions lead to increased wear and tear of the material, thus increasing the rate of material degradation and failure.

Thinning refers to a step in the preparation of a coating composition, wherein a suitable solvent is added to the coating composition for reducing thickness to obtain the coating composition with desirable consistency.

BACKGROUND

The background information herein below relates to the present disclosure but is not necessarily prior art.

Polysiloxane polymers are mainly used in the protective coatings, adhesives, sealants, stationary, craft and other various applications. Generally, polysiloxane polymers are known to impart flexibility, impact strength, weather and high heat resistance in end use applications. Polysiloxane polymers can also be combined with resins of other functionality to tune the properties of the final product such as when the polysiloxane polymer is combined with an epoxy resin, which is then cured with amine based curing agent to provide polysiloxane-epoxy resin based product with improved properties such as impact resistance, flexibility, and corrosion resistance. However, these polysiloxane-epoxy resin based products generally sustain maximum up to 300 °C temperature.

To make a product which can sustain at high temperature (greater than 300 °C), the use of the high molecular weight polysiloxane polymer is preferred, however the use of the high molecular weight polysiloxane polymer leads to the loss of flexibility of the final product after exposure to the high temperature environment and hence results in delamination from the substrate at higher temperatures. Further, if the lower molecular weight polysiloxane polymers are used to maintain the flexibility of the final product at a high temperature, longer curing time/ heat based curing/ crosslinking agent is required to cure the product to get the desired crosslinking density. The longer curing time and use of the heat or crosslinking agents are detrimental for flexibility of the final product at higher temperatures.

Corrosion under Insulation (CUI) is one of the major problems for oil and gas pipelines in refining, power and chemical processing industries, as well as marine environments. CUI is the corrosion that occurs at the substrate beneath an insulating material which can develop quickly depending on the availability of moisture, contaminates and temperature. Complete removal of insulation to thoroughly inspect the materials is a time consuming and expensive process. Such maintenance costs are spent mostly on external piping inspection, insulation removal and replacement, painting and pipe repairs. Systems with fluctuating temperatures are more susceptible to CUI, especially in the pipelines with repetitive cooling and warming of the insulated pipes. CUI can occur in temperatures ranging from 20 °C to 175 °C, and more severe conditions are seen at temperatures in the range of 50°C to 100°C. The conventional CUI coatings that are available in market suffer from limitations such as poor performance at higher temperatures (> 450°C) and cyclic stress. Moreover, most of the conventional CUI coatings are known for their heavy settling property due to which the applicator faces difficulties while applying the coating.

There is, therefore, felt a need to provide a polysiloxane copolymer and a coating composition comprising the polysiloxane copolymer that mitigates 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 polysiloxane copolymer.

Yet another object of the present disclosure is to provide a process for the preparation of a polysiloxane copolymer.

Still another object of the present disclosure is to provide a polysiloxane copolymer that is cured at an ambient temperature.

Yet another object of the present disclosure is to provide a coating composition comprising the polysiloxane copolymer that maintains flexibility at a temperature greater than 500 °C.

Still another object of the present disclosure is to provide a coating composition that can withstand cycling heat resistance, high stress level and weathering.

Yet another object of the present disclosure is to provide a coating composition that has a comparatively better adhesion on mild steel and stainless steel surfaces and has better abrasion resistance and high thermal shock resistance.

Still another object of the present disclosure is to provide a coating composition that controls the corrosion under insulation (CUI).

Yet another object of the present disclosure is to provide a process for the preparation of a coating composition comprising the polysiloxane copolymer.

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 relates to a polysiloxane copolymer being a product of part A comprising an alkyl and/or aryl substituted silanol-functional silicone prepolymer and part B comprising an alkyl and/or aryl substituted alkoxy- functional silicone prepolymer, wherein a ratio of the part A to the part B is in the range of 1:0.5 to 1:2.

The present disclosure further relates to a process for the preparation of the polysiloxane copolymer. The process comprises the step of mixing part A comprising an alkyl and/or aryl substituted silanol-functional silicone prepolymer and part B comprising an alkyl and/or aryl substituted alkoxy- functional silicone prepolymer in a fluid medium in the presence of an organometallic catalyst, optionally using a flexibilizer at a predetermined temperature for a predetermined time period to obtain the polysiloxane copolymer, wherein a ratio of the part A to the part B is in the range of 1:0.5 to 1:2.

Furthermore, the present disclosure relates to a coating composition comprising a polysiloxane copolymer; at least one pigment; at least one extender; at least one modifying agent; at least one additive; hollow glass microspheres; and at least one fluid medium.

Still further, the present disclosure relates to a process for preparing the coating composition. The process comprises a step of mixing predetermined amounts of a polysiloxane copolymer, at least one modifying agent and at least one additive in a first fluid medium under stirring at a first predetermined speed for a first predetermined time period at a first predetermined temperature to obtain a mill base. Predetermined amounts of at least one pigment and at least one extender are added to the mill base followed by grinding at a second predetermined speed for a second predetermined time period at a second predetermined temperature to obtain a slurry. A predetermined amount of glass microspheres is added to the slurry followed by thinning by using at least one second fluid medium at a third predetermined speed for a third predetermined time period at a third predetermined temperature to obtain a homogenized slurry. The homogenized slurry is cooled to a temperature in the range of 20 °C to 28 °C followed by filtration to obtain the coating composition.

DETAILED DESCRIPTION

Embodiments are provided so as 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, well-known apparatus structures, and well-known techniques are not described in detail.

The terminology used, in the present disclosure, is only for the purpose of explaining 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 particular 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.

Corrosion under Insulation (CUI) is one of the major problems for oil and gas pipelines in refining, power and chemical processing industries, as well as in the marine environments. The conventional CUI coatings that are available in the market suffer from limitations such as poor performance at higher temperatures (> 450°C) and cyclic stress. Moreover, most of the conventional CUI coatings are known for their heavy settling property due to which the applicator faces difficulties while applying the coating.

Polysiloxane polymeric material finds variety of applications in the coating, adhesive, sealant, stationary, craft industries because of the well-known properties of the product made therefrom. The polysiloxane polymer when combined with the other resins having functionality such as epoxy resins or acrylic resins, the so obtained product has the improved properties (when compared to the product made from either of the materials solely).

However, at points of applications which are subjected to high temperatures, the product prepared from the modified and unmodified polysiloxane based polymers possess the drawback of loss of flexibility after exposure of the same to high temperatures which results into delamination from the substrate.

The present disclosure provides a polysiloxane copolymer and a process for its preparation. Further, the present disclosure provides a coating composition comprising the polysiloxane copolymer and a process for its preparation.

In a first aspect, the present disclosure provides a polysiloxane copolymer being a reaction product of part A comprising an alkyl and/or aryl substituted silanol-functional silicone prepolymer and part B comprising an alkyl and/or aryl substituted alkoxy- functional silicone prepolymer, wherein a ratio of the part A to the part B is in the range of 1:0.5 to 1:2. In an embodiment of the present disclosure, the polysiloxane copolymer is represented by formula I:

Formula I wherein,

R 1 , R2 , R 3 and R 4 are independently selected from methyl, ethyl, propyl, butyl, pentyl, hexyl and aryl; and x and y are integers independently selected from 1 to 6.

In an embodiment of the present disclosure, the part A comprising an alkyl and/or aryl substituted silanol-functional silicone prepolymer is represented by formula la:

wherein,

R¹ and R⁴ are independently selected from methyl, ethyl, propyl, butyl, pentyl, hexyl and aryl; and n is an integers selected from 1 to 6.

In an embodiment of the present disclosure, the part B comprising an alkyl and/or aryl substituted alkoxy- functional silicone prepolymer is represented by formula lb:

Formula lb wherein,

R 2 and R 3 are independently selected from methyl, ethyl, propyl, butyl, pentyl, hexyl and aryl; and n is an integers selected from 1 to 6.

The polysiloxane copolymer of the present disclosure is formulated such that the rates of internal polymerization reaction can be controlled. The polymerization reaction can take place over a broad temperature range, including ambient and high temperatures.

In accordance with the embodiments of the present disclosure, the alkyl group in the part A and the part B is independently selected from methyl, ethyl, propyl, butyl, pentyl and hexyl.

In accordance with the embodiments of the present disclosure, the aryl group in the part A and the part B is independently selected from phenyl and benzyl.

In accordance with the embodiments of the present disclosure, the Part A and Part B independently comprises two or more reactive functionalities per repeat unit comprising two Si atom (-[-Si-O-Si]-O-). In one embodiment, the reactive functionality is silanol (-Si-OH). In another embodiment, the reactive functionality is alkoxy silane (-Si-O-C).

In an embodiment of the present disclosure, the part A and the Part B independently comprises at least one aryl substituent per repeating unit comprising two Si atom (-[-Si-O- Si]-O-).

In accordance with the embodiments of the present disclosure, the part A is optionally modified by incorporating polyurethane or polyurea based flexibilizer.

In accordance with the embodiments of the present disclosure, the part B is optionally modified with amine/epoxy/NCO/SH functional silane or their adducts with epoxy.

The backbone of the polysiloxane copolymer is kinetically optimized in such a way that a pre-determined molecular weight of the polysiloxane copolymer is obtained.

In accordance with the embodiments of the present disclosure, the pre-determined molecular weight of the polysiloxane copolymer is in range of 2000 g/mol to 15000 g/mol.

In accordance with the embodiments of the present disclosure, the polysiloxane copolymer is monomodal or bimodal depending on the specific application.

The polysiloxane copolymer of the present disclosure, is one component, ambient or low temperature moisture curable, and storage stable.

The polysiloxane copolymer of the present disclosure can be used in industries such as coating, adhesive, sealant, construction chemicals, admixture, stationary adhesives, and craft materials.

In accordance with the embodiments of the present disclosure, the polysiloxane copolymer is used for preparing a coating composition that maintains flexibility at a temperature in the range of 500 °C to 1000 °C.

In a second aspect, the present disclosure provides a process for preparation of the polysiloxane copolymer.

The process comprises the step of mixing part A comprising an alkyl and/or aryl substituted silanol-functional silicone prepolymer and part B comprising an alkyl and/or aryl substituted alkoxy-functional silicone prepolymer in a fluid medium in the presence of an organometallic catalyst optionally by using a flexibilizer at a predetermined temperature for a predetermined time period to obtain the polysiloxane copolymer, wherein a ratio of the part A to the part B is in the range of 1:0.5 to 1:2.

In accordance with the embodiments of the present disclosure, the organometallic catalyst is selected from tetra-isopropyl titanate (Tyzor TPT), tetra-n-butyl titanate (Tyzor TNBT), Tetrakis(2-ethylhexyl) orthotitanate (Tyzor TOT), titanium tetrapropanolate (Tyzor NPT), a mixture of tetra-isopropyl and tetra-n-butyl titanate (Tyzor TPT-20 B), titanium acetylacetonates (Tyzor AA, Tyzor AA-65, Tyzor AA-75, Tyzor AA-105, Tyzor GBA, Tyzor GBO), titanium ethylacetoacetate (Tyzor DC), triethanolamine titanium complex (Tyzor TE), organotin carboxylate (TIB KAT 218) and organotin carboxylate (DABCO T12). In an exemplary embodiment, the organometallic catalyst is tetra-n-butyl titanate (Tyzor TNBT).

In accordance with the embodiments of the present disclosure, the fluid medium is nonalcoholic or non-glycolic. In an embodiment, the fluid medium is at least one selected from the group consisting of ortho-xylene, mineral turpentine oil, solvent C-IX (a mixture of aromatic hydrocarbon solvents), n- butanol, Butyl acetate, methyl isobutyl ketone (MIBK) and methyl ethyl ketone (MEK). In an exemplary embodiment, the fluid medium is orthoxylene.

In accordance with the embodiments of the present disclosure, the flexibilizer is at least one selected from the group consisting of Lapox Bll (unmodified epoxy resin based on bisphenol-A), Lapox P101 (75% solution of solid epoxy resin (type-1) in xylene), DER-664U (epoxy resin of epichlorohydrin and bisphenol A), Dynasylan AMEO (3- aminopropyltriethoxy silane), adduct of Lapox Bl l and Dynasylan AMEO, adduct of Lapox P101 and Dynasylan AMEO, adduct of DER-664U and Dynasylan AMEO, Silquest A-link- 35 (isocyanate functional trimethoxy silane), Coatosil T-Cure (mercapto silane), adduct of Silquest A-link-35 and Coatosil T-Cure, adduct of Dynasylan AMEO and Coaosili T-Cure, adduct of Lapox Bl l and Coatosil T-Cure, adduct of Lapox P101 and Coatosil T-Cure, adduct of DER-664U and Coatosil T-Cure, KBE 803 ((3-mercaptopropyl)trimethoxysilane), adduct of KBE 803 and Lapox Bl l, KBE 9007 (3-isocyanatepropyltriethoxysilane) and adduct of KBE 9007 and Lapox Bl l. In accordance with the embodiments of the present disclosure, the predetermined temperature is in the range of 50 °C to 150 °C. In an exemplary embodiment, the pre-determined temperature is 120 °C.

In accordance with the embodiments of the present disclosure, the predetermined time period is in the range of 3 hours to 9 hours. In an exemplary embodiment, the pre-determined time period is 6 hours.

In a third aspect, the present disclosure provides a coating composition comprising a polysiloxane copolymer; at least one pigment; at least one extender; at least one modifying agent; at least one additive; hollow glass microspheres; and at least one fluid medium.

In an embodiment of the present disclosure, the coating composition comprises 10 to 20 wt% of the polysiloxane copolymer with respect to the total amount of the coating composition; 40 to 50 wt% of at least one pigment with respect to the total amount of the coating composition; 20 to 40 wt% of at least one extender with respect to the total amount of the coating composition; 1 to 5 wt% of at least one modifying agent with respect to the total amount of the coating composition; 0.5 to 2 wt% of at least one additive with respect to the total amount of the coating composition; 0.1 to 1 wt% of the hollow glass microspheres with respect to the total amount of the coating composition; and 5 to 15 wt% of at least one fluid medium with respect to the total amount of the coating composition.

In an embodiment of the present disclosure, the polysiloxane copolymer is represented by formula I:

Formula I wherein,

R , R , R and R are independently selected from methyl, ethyl, propyl, butyl, pentyl, hexyl and aryl; and x and y are integers independently selected from 1 to 6.

The polysiloxane copolymer used in the coating composition of the present disclosure, provides cycling heat resistant and stress resistant properties to the coating and helps to withstand weathering of the coating.

In accordance with the embodiments of the present disclosure, the pigment is at least one selected from carbon black pigment, zinc phosphate, zinc oxide and micaceous iron oxide.

In accordance with the embodiments of the present disclosure, a weight ratio of the pigment to the polysiloxane copolymer is in range of 1:0.15 to 1:0.4. This ratio is very crucial to achieve the desired flexibility and the heat resistance properties in the coating composition.

In an embodiment of the present disclosure, the micaceous iron oxide has a lamellar shape. The micaceous iron oxide with lamellar shape acts as an inert barrier to the vertical penetration of corrosive elements.

In accordance with the embodiments of the present disclosure, the extender is at least one selected from silica, mica and steatite. In an exemplary embodiment, the extender is a combination of silica and steatite. In another exemplary embodiment, the extender is a combination of mica and steatite. The extender provides reinforcement to the coatings when applied on the substrate and thus, improves the mechanical properties of the coatings on the substrate.

In accordance with the embodiments of the present disclosure, the modifying agent is at least one selected from an organic derivative of bentonite clay, modified hectorite (Bentone Jelly), molecular sieves, micronized amide wax, modified silica, trimethoxysilane, graphite, and silicon based defoaming agent.

The organic derivative of bentonite clay (commercially available as BENTONE SD-2) acts as an anti-settling agent and prevents the tendency of heavy settling in the coating composition even after 1 year of shelf life. The molecular sieves (Zeolith 141 4A powder) acts as moisture adsorbent with excellent kinetic gas adsorption present in the paint compaction. The micronized amide wax, commercially available as Crayvallac ultra is commonly used as rheology modifier that offers very good recoatability for ambient curing solvent-based coatings. Graphite powder provides functionality as thermal conductor and corrosion shield. Trimethoxysilane (Silane A- 187) acts as an adhesion promoter.

In an embodiment of the present disclosure, the silicon based defoaming agent is polymethylalkylsiloxane (commercially available as BYK 085). The silicon based defoaming agent is used to prevent foam and bubble formation during the processing and application of the coating composition.

Typically, the modified silica is a fumed silica aftertreated with DDS (Dimethyldichlorosilane), commercially available as Aerosil 972. The modified silica is generally used in coatings as anti-settling agent, for pigment stabilization and improvement of corrosion protection.

In accordance with the embodiments of the present disclosure, the additive is at least one selected from a high molecular weight block copolymer (commercially available as Disperbyk 163) and a structured acrylate copolymer (commercially available as Disperbyk 2000) as dispersing agents; and soyalecithin as an emulsifier.

In accordance with the embodiments of the present disclosure, the fluid medium is at least one selected from mixed xylene, n-butanol, isobutanol, solvent C-IX (a mixture of aromatic hydrocarbon solvents), and mineral turpentine oil. In an exemplary embodiment, the fluid medium is a combination of mixed xylene and isobutanol. In another exemplary embodiment, the fluid medium is a combination of mixed xylene, isobutanol and solvent C-IX (a mixture of aromatic hydrocarbon solvents).

The hollow glass microspheres used in the coating composition of the present disclosure, enhance filler loading, lower the viscosity/improve the flow ability and reduce shrinkage of the coating composition. Further, the hollow glass microspheres enhance higher pigment loading and give high heat resistance along with extreme cryogenic resistance properties to the coating composition. In a fourth aspect, the present disclosure provides a process for preparing the coating composition.

The process comprises a step of mixing predetermined amounts of a polysiloxane copolymer, at least one modifying agent and at least one additive in a first fluid medium under stirring at a first predetermined speed for a first predetermined time period at a first predetermined temperature to obtain a mill base.

In accordance with the embodiments of the present disclosure, the first predetermined speed is in the range of 200 rpm to 300 rpm.

The first predetermined time period is in the range of 10 minutes to 15 minutes.

The first predetermined temperature is in the range of 30 °C to 35 °C.

Predetermined amounts of at least one pigment and at least one extender are added to the mill base followed by grinding at a second predetermined speed for a second predetermined time period at a second predetermined temperature to obtain a slurry.

The second predetermined speed is in the range of 1200 rpm to 1500 rpm.

The second predetermined time period is in the range of 30 minutes to 45 minutes.

The second predetermined temperature is in the range of 40 °C to 60 °C.

A predetermined amount of glass microspheres is added to the slurry followed by thinning by using at least one second fluid medium at a third predetermined speed for a third predetermined time period at a third predetermined temperature to obtain a homogenized slurry.

The third predetermined speed is in the range of 200 rpm to 300 rpm.

The third predetermined time period is in the range of 10 minutes to 15 minutes.

The third predetermined temperature is in the range of 35 °C to 40 °C.

The homogenized slurry is cooled to a temperature in the range of 20 °C to 28 °C followed by filtration to obtain the coating composition. The coating composition prepared by using the polysiloxane copolymer can maintain its flexibility at a temperature in the range of 500 °C to 1000 °C on suitable substrates, particularly upto 800 °C.

In accordance with the embodiments of the present disclosure, the coating composition prepared by using the polysiloxane copolymer is characterized by having the following properties:

• high stress level resistance;

• heat-cool cycle resistance;

• weathering resistance;

• excellent adhesion on various substrate;

• excellent thermal shock and high corrosion resistance;

• excellent impact and abrasion resistance;

• excellent boiling water resistance; and

• high heat/temperature resistance

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.

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 can be scaled up to industrial/commercial scale and the results obtained can be extrapolated to industrial scale.

EXPERIMENTAL DETAILS

Experiment 1: Preparation of a polysiloxane copolymer in accordance with the present disclosure

Example- 1: 48 g of an silanol-functional phenylpropyl polysiloxane prepolymer and 27g of an alkoxyfunctional phenyl polysiloxane prepolymer were mixed in 25ml of ortho-xylene (fluid medium) at 120 °C for 9 h to obtain the poly siloxane copolymer.

Example-2:

48 g of an silanol-functional phenylpropyl polysiloxane prepolymer and 27 g of an alkoxyfunctional phenyl polysiloxane prepolymer in 25 ml of ortho-xylene (fluid medium) in the presence of 0.03 g of tetra-n-butyl titanate (Tyzor TNBT) (organometallic catalyst) were mixed at 120 °C for 6 h to obtain the polysiloxane copolymer.

Example-3:

48 g of an silanol-functional phenylpropyl polysiloxane prepolymer and 27 g of an alkoxyfunctional phenyl polysiloxane prepolymer in 25 ml of ortho-xylene (fluid medium) in the presence of 0.03 g of orthotitanate (Tyzor TOT) (organometallic catalyst) were mixed at 120 °C for 6 h to obtain the polysiloxane copolymer.

Example-4:

42 g of an silanol-functional phenylpropyl polysiloxane prepolymer and 33 g of an alkoxyfunctional phenyl polysiloxane prepolymer in 25 ml of ortho-xylene (fluid medium) in the presence of 0.03 g of Tyzor TNBT (organometallic catalyst) were mixed at 120 °C for 6 h to obtain the polysiloxane copolymer.

Example-5:

47 g of an silanol-functional phenylpropyl polysiloxane prepolymer and 26 g of an alkoxyfunctional phenyl polysiloxane prepolymer in 25 ml of ortho-xylene (fluid medium) in the presence of 0.03 g of Tyzor TNBT (organometallic catalyst) and 2 g of adduct of Silquest A- link-35 and Coatosil T-Cure (flexibilizer) were mixed at 120 °C for 6 h to obtain the polysiloxane copolymer.

Example-6:

58.5 g of an silanol-functional phenylpropyl polysiloxane prepolymer and 16.5 g of an alkoxy-functional phenyl polysiloxane prepolymer in 25 ml of ortho-xylene (fluid medium) in the presence of 0.03 g of Tyzor TNBT (organometallic catalyst) were mixed at 120 °C for 6 h to obtain the polysiloxane copolymer. Comparative Example I:

36 g of an silanol-functional phenylpropyl poly siloxane prepolymer and 39 g of an alkoxyfunctional phenylmethyl polysiloxane prepolymer in 25 ml of ortho-xylene (fluid medium) in the presence of 0.03 g of Tyzor TNBT (organometallic catalyst) were mixed at 120 °C for 6 h

5 to obtain the polysiloxane copolymer.

Comparative Example II:

28 g of an silanol-functional phenylpropyl poly siloxane prepolymer and 47 g of an alkoxyfunctional phenylmethyl polysiloxane prepolymer in 25 ml of ortho-xylene (fluid medium) in the presence of 0.03 g of Tyzor TNBT (organometallic catalyst) were mixed at 120 °C for 6 h 10 to obtain the polysiloxane copolymer.

Comparative Example III:

37 g of an silanol-functional phenylpropyl polysiloxane prepolymer and 34 g of an alkoxyfunctional phenylmethyl polysiloxane prepolymer and 4 g alkoxy-functional phenyl polysiloxane prepolymer in 25 ml of ortho-xylene (fluid medium) in the presence of 0.03 g of

15 Tyzor TNBT (organometallic catalyst) were mixed at 120 °C for 6 h to obtain the polysiloxane copolymer.

Table 1: Performance comparison of polysiloxane copolymers between examples 1-6 of the present disclosure and comparative examples

From Table 1, it is observed that the polysiloxane copolymer of Examples 1-6, when studied for their performance at high temperature (at 500° C) on mild steel, maintained film integrity and there was no adhesion failure, whereas, brittle film and adhesion failure was observed for the polysiloxane copolymer of Comparative Examples I-III. Further, the flexibility (on 5 Conical Mandrel) of the polysiloxane copolymer of Examples 1-6 were found to be in the range of 74% to 82% at ambient temperature, which is much higher than the flexibility of the Comparative Examples I-II (which is 32% - when cured by heating) and Comparative Example III (which is 32%- at ambient temperature). Furthermore, the polysiloxane copolymer of Examples 1-6, when studied for the time required for drying the film on mild 10 steel at ambient temperature, was found to be in the range of 4 to 6 hours, whereas, for the polysiloxane copolymer of Comparative Examples I-II, it was found to be non-drying and for Comparative Example III, it was 12 hours.

Thus, the polysiloxane copolymer of Examples 1-6 were found to show better performance as compared to the Comparative Examples I-III.

15 Experiment 2: Preparation of a coating composition in accordance with the present disclosure General process:

Predetermined amounts of the polysiloxane copolymer prepared in Example 2 of Experiment 1, at least one modifying agent and at least one additive were mixed in a first fluid medium under stirring at a first predetermined speed for a first predetermined time period at a first 5 predetermined temperature to obtain a mill base. Predetermined amounts of at least one pigment and at least one extender were added to the mill base followed by grinding at a second predetermined speed for a second predetermined time period at a second predetermined temperature to obtain a slurry. A predetermined amount of glass microspheres was added to the slurry followed by thinning by using at least one second fluid medium at a 10 third predetermined speed for a third predetermined time period at a third predetermined temperature to obtain a homogenized slurry. The homogenized slurry was cooled to 25 °C followed by filtration to obtain the coating composition.

Examples 1- 16: Preparation of the coating composition

The coating composition of the examples 1-8 were prepared by following the process as 15 disclosed herein above, with variable ingredients with variable amounts.

The ingredients with variable amounts used and the test results obtained are summarized in Tables 2a and 2b herein below:

Table 2a: The ingredients with variable amounts used in the process for preparing the coating composition and the test results of the coating composition (Examples 1-8).

*MS: Mild Steel; SS: Stainless Steel; *UFC-Under film corrosion

Table 2b: The ingredients with variable amounts used in the process for preparing the coating composition and the test results of the coating composition (Examples 9-16).

The examples 1 to 16 were designed by varying the ingredient type and amount. The experiments are presented as a sequence to achieve desired physical- mechanical and heat resistance properties. The coating composition of example 16 shows the satisfactory performance as compared to the coating compositions of examples 1-15.

5 Experiment 3: Characterization of the coating composition of Example 16

The mechanical properties and long term performance properties of the optimized coating composition of Example 16 were studied and summarized in Table-3a and 3b. Table 3a: Mechanical properties of the coating composition of Example 16

Table 3b: Long term performance properties of the coating composition of Example 16

*UFC-Under film corrosion

Table 3a indicates the mechanical properties such as impact test, abrasion resistance and adhesion strength of optimized formulation. Table 3b shows the chemical resistance and corrosion resistance properties of coating in different corrosive environments.

TECHNICAL ADVANCEMENTS

The present disclosure described herein above has several technical advantages including, but not limited to, the realization of a

- polysiloxane copolymer that

• can be cured at an ambient temperature;

• sustain at high temperatures without the loss of flexibility; and

- a coating composition prepared by using the polysiloxane copolymer that

• maintains flexibility at a temperature in the range of 500 °C to 1000 °C;

• has high stress level resistance, heat-cool cycle resistance, weathering resistance, excellent boiling water resistance, high heat/temperature resistance;

• has excellent adhesion on various substrates, particularly on mild steel and stainless steel;

• has excellent thermal shock and high corrosion resistance; and

• has excellent impact and abrasion resistance.

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.

Claims

CLAIMS:

1. A poly siloxane copolymer being a product of: i) part A comprising an alkyl and/or aryl substituted silanol-functional silicone prepolymer; and ii) part B comprising an alkyl and/or aryl substituted alkoxy-functional silicone prepolymer; wherein a ratio of said part A to said part B is in the range of 1 :0.5 to 1 :2.

2. The copolymer as claimed in claim 1, wherein said polysiloxane copolymer is represented by formula I:

wherein,

R 1 , R2 , R 3 and R 4 are independently selected from methyl, ethyl, propyl, butyl, pentyl, hexyl and aryl; and x and y are integers independently selected from 1 to 6. 3. The copolymer as claimed in claim 1, wherein said alkyl group in said part A and said part B is independently selected from methyl, ethyl, propyl, butyl, pentyl and hexyl.

4. The copolymer as claimed in claims 1 and 2, wherein said aryl group in said part A and said part B is independently selected from phenyl and benzyl.

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5. The copolymer as claimed in claim 1, wherein said part A is optionally modified with polyurethane/polyurea based flexibilizer.

6. The copolymer as claimed in claim 1, wherein said part B is optionally modified with amine/epoxy/NCO/SH functional silane or their adducts with epoxy.

7. The copolymer as claimed in claim 1, wherein a backbone of said polysiloxane copolymer is kinetically optimized to obtain a predetermined molecular weight.

8. The copolymer as claimed in claim 7, wherein said pre-determined molecular weight of the polysiloxane copolymer is in range of 2000 g/mol to 15000 g/mol.

9. Use of said poly siloxane copolymer as claimed in claims 1 and 2 for preparing a coating composition that maintains flexibility at a temperature in the range of 500 °C to 1000 °C.

10. A process for preparation of the polysiloxane copolymer as claimed in claim 1, said process comprises mixing part A comprising an alkyl and/or aryl substituted silanol- functional silicone prepolymer and part B comprising an alkyl and/or aryl substituted alkoxy-functional silicone prepolymer in a fluid medium in the presence of an organometallic catalyst optionally using a flexibilizer at a predetermined temperature for a predetermined time period to obtain said polysiloxane copolymer; wherein a ratio of said part A to said part B is in the range of 1 :0.5 to 1 :2.

11. The process as claimed in claim 10, wherein said organometallic catalyst is selected from tetra-isopropyl titanate, tetra-n-butyl titanate, Tetrakis(2-ethylhexyl) orthotitanate, titanium tetrapropanolate, a mixture of tetra-isopropyl and tetra-n-butyl titanate , titanium acetylacetonates, titanium ethylacetoacetate, triethanolamine titanium complex, organotin carboxylate and organotin carboxylate.

12. The process as claimed in claim 10, wherein said fluid medium is at least one selected from the group consisting of mixed xylene, mineral turpentine oil, solvent C-IX (a mixture of aromatic hydrocarbon solvents), n-butanol, Butyl acetate, methyl isobutyl ketone (MIBK) and methyl ethyl ketone (MEK). The process as claimed in claim 10, wherein said flexibilizer is at least one selected from the group consisting of Lapox Bl l, (unmodified epoxy resin based on bisphenol-A), Lapox P101 (75% solution of solid epoxy resin (type-1) in xylene), DER-664U (epoxy resin of epichlorohydrin and bisphenol A), Dynasylan AMEO (3- aminopropyltriethoxy silane), adduct of Lapox Bll and Dynasylan AMEO, adduct of Lapox P101 and Dynasylan AMEO, adduct of DER-664U and Dynasylan AMEO, Silquest A-link-35 (isocyanate functional trimethoxysilane), Coatosil T-Cure (mercapto silane), adduct of Silquest A-link-35 and Coatosil T-Cure, adduct of Dynasylan AMEO and Coaosili T-Cure, adduct of Lapox Bl l and Coatosil T-Cure, adduct of Lapox P101 and Coatosil T-Cure, adduct of DER-664U and Coatosil T- Cure, KBE 803 ((3-mercaptopropyl)trimethoxysilane), adduct of KBE 803 and Lapox Bl l, KBE 9007 (3-isocyanatepropyltriethoxysilane) and adduct of KBE 9007 and Lapox Bl l. The process as claimed in 10, wherein said predetermined temperature is in the range of 50 °C to 150 °C. The process as claimed in claim 10, wherein said predetermined time period is in the range of 3 hours to 9 hours. A coating composition comprising: i. a polysiloxane copolymer; ii. at least one pigment; iii. at least one extender; iv. at least one modifying agent; v. at least one additive; vi. hollow glass microspheres; and vii. at least one fluid medium. The coating composition as claimed in claim 16 comprises: i. 10 to 20 wt% of said polysiloxane copolymer with respect to the total amount of the coating composition; ii. 40 to 50 wt% of said at least one pigment with respect to the total amount of the coating composition; iii. 20 to 40 wt% of said at least one extender with respect to the total amount of the coating composition; iv. 1 to 5 wt% of said at least one modifying agent with respect to the total amount of the coating composition; v. 0.5 to 2 wt% of said at least one additive with respect to the total amount of the coating composition; vi. 0.1 to 1 wt% of said hollow glass microspheres with respect to the total amount of the coating composition; and vii. 5 to 15 wt% of said at least one fluid medium with respect to the total amount of the coating composition. The coating composition as claimed in claims 16 and 17, wherein said polysiloxane copolymer is represented by Formula I,

wherein,

R 1 , R2 , R 3 and R 4 are independently selected from methyl, ethyl, propyl, butyl, pentyl, hexyl and aryl; and x and y are integers independently selected from 1 to 6. The coating composition as claimed in claims 16 and 17, wherein said pigment is at least one selected from carbon black pigment, zinc phosphate, zinc oxide and micaceous iron oxide.

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20. The coating composition as claimed in claims 16 and 17, wherein a weight ratio of said pigment to said polysiloxane copolymer is in range of 1: 0.15 to 1: 0.4.

21. The coating composition as claimed in claims 16 and 17, wherein said extender is at least one selected from silica, mica and steatite.

22. The coating composition as claimed in claims 16 and 17, wherein said modifying agent is at least one selected from an organic derivative of bentonite clay, modified hectorite, molecular sieves, micronized amide wax, modified silica, trimethoxysilane, graphite, and silicon based defoaming agent.

23. The coating composition as claimed in claims 16 and 17, wherein said additive is at least one selected from a high molecular weight block copolymer and a structured acrylate copolymer as dispersing agents; and soyalecithin as an emulsifier.

24. The coating composition as claimed in claims 16 and 17, wherein said fluid medium is at least one selected from mixed xylene, n-butanol, isobutanol, solvent C-IX (a mixture of aromatic hydrocarbon solvents), and mineral turpentine oil.

25. A process for preparing the coating composition as claimed in claim 16; said process comprising the following steps: a) mixing predetermined amounts of a polysiloxane copolymer, at least one modifying agent and at least one additive in a first fluid medium under stirring at a first predetermined speed for a first predetermined time period at a first predetermined temperature to obtain a mill base; b) adding predetermined amounts of at least one pigment and at least one extender to said mill base followed by grinding at a second predetermined speed for a second predetermined time period at a second predetermined temperature to obtain a slurry; c) adding a predetermined amount of glass microspheres to said slurry followed by thinning by using at least one second fluid medium at a third predetermined speed for a third predetermined time period at a third predetermined temperature to obtain a homogenized slurry; and

30 d) cooling said homogenized slurry to a temperature in the range of 20 °C to 28 °C followed by filtration to obtain the coating composition. The process as claimed in claim 25, wherein said first predetermined speed is in the range of 200 rpm to 300 rpm, said second predetermined speed is in the range of 1200 rpm to 1500 rpm and said third predetermined speed is in the range of 200 rpm to 300 rpm. The process as claimed in claim 25, wherein said first predetermined time period is in the range of 10 minutes to 15 minutes, said second predetermined time period is in the range of 30 minutes to 45 minutes and said third predetermined time period is in the range of 10 minutes to 15 minutes. The process as claimed in claim 25, wherein said first predetermined temperature is in the range of 30 °C to 35 °C, said second predetermined temperature is in the range of 40 °C to 60 °C and said third predetermined temperature is in the range of 35 °C to 40 °C. The process as claimed in claim 25, wherein said predetermined amounts of said polysiloxane copolymer is in the range of 10 to 20 wt%, said at least one modifying agent is in the range of 1 to 5 wt%, said at least one additive is in the range of 0.5 to 2 wt%, said at least one pigment is in the range of 40 to 50 wt%, said at least one extender is in the range of 20 to 40 wt% and said glass microspheres is in the range of 0.1 to 1 wt%, wherein said amount of each ingredient is with respect to the total amount of the coating composition.

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