Claims:WE CLAIM:

1. A food-grade coating composition for coating internal surface of pipelines, comprising:
- a first component that includes:
- an epoxy resin in a range of 20-40 % by weight of the first
component;
- a diluent in a range of 10-22 % by weight of the first component;
- a deaerator in a range of 0.2-1 % by weight of the first component;
- a wetting agent in a range of 0.2-0.8 % by weight of the first
component;
- a reinforcing filler agent in a range of 0.2-1 % by weight of the first
component;
- three non-reinforcing fillers combinedly in a range of 34.2-52 % by
weight of the first component; and
- a thixotropic agent in a range of 0.2- 0.8 % by weight of the first
component; and
- a second component, such that the second component is mixed with the first component in a volumetric ratio of 3 parts of the first component and 1 part of the second component.

2. The composition according to claim 1, wherein the second component is a hardener.

3. The composition according to claim 2, wherein the hardener is phenalkamine.

4. The composition according to claim 3, wherein the phenalkamine is a Mannich adduct of cardanol, formaldehyde & polyamide, cycloaliphatic amines.

5. The composition according to claim 1, wherein the diluent is one from a group consisting of C8 to C10 alkyl glycidyl ether, C12 to C14 alkyl glycidyl ether, phenyl glycidyl ether, glycidyl ether of cashew nutshell liquid, cresyl glycidyl ether, diglycidyl ether of C2 to C6 alkane diol, neopentyl glycol diglycidyl ether, cyclohexane dimethanol diglycidyl ether, and C2 to C4 alkane trimethylol triglycidyl ether.

6. The composition according to claim 1, wherein the deaerator is one from a group consisting of organic polymers, modified polysiloxanes.

7. The composition according to claim 1, wherein the wetting agent is one from a group consisting of sodium salt of polyphosphates, sodium salt of polyacrylates, potassium salt of polyphosphates, potassium salt of polyacrylates, ammonium salt of polyphosphates, ammonium salt of polyacrylates, salts of unsaturated polyamine amides and salts of low-molecular acidic polyesters.

8. The composition according to claim 1, wherein the thixotropic agent is one from a group consisting of modified castor wax with polyamide, modified castor wax with epoxy resin and oxidized polyethylene wax.

9. The composition according to claim 1, further comprises a color pigment in a range of 5-12 % by weight of the first component.

10. The composition according to claim 9, wherein the colour pigment includes at least one pigment from a group consisting of Lead chromate, Lead Molybdate, Cadmium red, Red iron oxide or a combination thereof.

11. The composition according to claim 1, wherein the reinforcing filler includes a fumed silica.

12. The composition according to claim 1, wherein the three non-reinforcing filler includes:
- an organophilic clay in a range of 0.2- 1% by weight of the first component;
- a Barytes Off-white in a range of 18-26 % by weight of the first component; and
- a talc in a range of 16-25 % by weight of the first component.

13. The composition according to claim 1, wherein the first component includes:
- the epoxy resin as 30 by weight of the first component;
- the diluent as 13.3 % by weight of the first component;
- the deaerator as 0.7 % by weight of the first component;
- the wetting agent as 0.4 % by weight of the first component;
- the reinforcing filler as 0.6 % by weight of the first component;
- an organophilic clay as 0.6 % by weight of the first component;
- a Barytes Off-white as 23.4 % by weight of the first component;
- a talc as 22.6 % by weight of the first component; and
- a thixotropic agent as 0.3 % by weight of the first component.
, Description:FIELD OF THE INVENTION

[001] The present invention relates to the field of coating used for internal coating of pipelines and more particularly to a coating composition for coating of internal surface of pipelines carrying potable contents.

BACKGROUND OF THE INVENTION

[002] A water pipeline is designed to transport large quantities of water across long distances at adequate pressure and flow rates. Pipelines and storage vessels are predominantly used for transporting and storing water and food products consumed by human beings. The water pipeline can be made plastic, cement, and metals, however for transporting drinking water metals such as copper, aluminum, cast iron, carbon steel, stainless steel, and alloys thereof are preferably used. The metallic pipelines are prone to corrosion problems, due to different factors like the use of chemicals in the pipes and climatic conditions such as humidity at the site.

[003] Corrosion, particularly, deteriorates the material of the pipelines. Due to this, there is a need to replace the pipelines with a new pipeline. This results in increasing undesired maintenance costs, which in turn increases the capital expenditure (CAPEX) of the entire process. In order to avoid any undesired maintenance costs, the use of coatings is significantly increasing to protect the pipelines from corrosion problems.

[004] A pipeline coating is a cost-effective and viable solution to maintain pipelines' integrity. This coating provides a constant protective lining that helps save pipelines from the damaging effects of corrosion. Pipeline coating is one of the most reliable corrosion prevention methods used by industries today. It is well known in the art that epoxy-based coatings exhibit excellent properties including mechanical, thermal insulation and electrical insulation, resistance to chemical and heat and excellent adhesion. It is used for a wide range of applications such as coatings, paints, adhesives and composite materials. The use of epoxy resin has increased tremendously for coating purposes, particularly for coating the internal surface of the equipment predominantly used for transporting and storing products consumed by human beings. Particularly, for coating the internal surface of water pipelines, water storage vessels, and food products storage vessels.

[005] For such applications, i.e., for internal surface coating, the thickness of the coating is approximately in the range of 200 microns to 600 microns. The cost of epoxy resin has increased due to limited availability of the raw materials for preparing epoxy resin and increase in the use of epoxy resin. This in turn increases the entire cost (capital expenditure (CAPEX)) involved in coating the inner surface of the pipeline. There is, therefore, felt a need for an alternative to reduce the cost involved in coating the inner surface of the pipeline.

[006] This can be done by controlling the amount of epoxy resin to be used for coating the internal surface, which in turn facilitates in reducing the CAPEX. This is because, the CAPEX is dependent on the cost incurred due to the amount of epoxy resin used for coating the internal surface of the pipeline. The amount of epoxy resin to be used should be controlled in such a way that viscosity and flowability of epoxy resin remain unaffected.

[007] Conventionally, the amount of epoxy resin to be used for coating is controlled or reduced by mixing or diluting epoxy resin with hardeners which eventually reduces the price of the final composition. This enables in reducing the CAPEX for coating the surface of the pipeline. Few formulations are available in the market from different manufacturers who use their own proprietary hardeners and sell the composition as Food Grade, however most of the time the coating composition contains Triethylenetetramine (TETA) which is carcinogenic in nature. The TETA is harmful for people who are applying the coating to the pipelines because its fumes when inhaled can cause negative effects on the health of the person who is exposed to such coating material. There is also a possibility that TETA may leach out in the contents of the pipeline and in turn, deteriorates the quality of contents of the pipeline such as water passing through pipelines and food products stored in storage vessels and affects people’s health negatively. The contaminated water may deteriorate the health of humans if consumed for longer periods.

[008] In view of the limitations inherent in the available coating compositions, there exists a need for an improved coating composition for coating internal surface of pipelines which is TETA free and overcomes the disadvantages of the prior art and can be made in a simple, cost-effective, reliable, secure and environmentally friendly manner.

[009] The present invention fulfils this need and provides further advantages as described in the following summary.

SUMMARY OF THE INVENTION

[0010] In view of the foregoing disadvantages inherent in the prior arts, the general purpose of the present invention is to provide an improved combination of convenience and utility, to include the advantages of the prior art, and to overcome the drawbacks inherent therein.

[0011] A primary objective of the present invention is to provide a TETA free coating composition used for coating the inner surface of pipelines such as water or food pipelines in a simple and cost-effective way.

[0012] In one aspect, the present invention provides a food grade coating composition for coating internal surface of pipelines that comprises a first component and a second component, such that the second component is mixed with the first component in a volumetric ratio of 3 parts of the first component and 1 part of the second component. The first component includes an epoxy resin in a range of 20-40 % by weight of the first component, a diluent in a range of 10-22 % by weight of the first component, a deaerator in a range of 0.2-1 % by weight of the first component, a wetting agent in a range of 0.2-0.8 % by weight of the first component, a reinforcing filler agent in a range of 0.2-1 % by weight of the first component, three non-reinforcing fillers combinedly in a range of 34.2-52 % by weight of the first component and a thixotropic agent in a range of 0.2- 0.8 % by weight of the first component.

[0013] In another aspect of the present invention, the second component is a hardener such as phenalkamine.

[0014] In yet another aspect of the present invention, the phenalkamine is a Mannich adduct of cardanol, formaldehyde & polyamide, cycloaliphatic amines.

[0015] In a further aspect of the present invention, the diluent is one from a group consisting of C8 to C10 alkyl glycidyl ether, C12 to C14 alkyl glycidyl ether, phenyl glycidyl ether, glycidyl ether of cashew nut shell liquid, cresyl glycidyl ether, diglycidyl ether of C2 to C6 alkane diol, neopentyl glycol diglycidyl ether, cyclohexane dimethanol diglycidyl ether, and C2 to C4 alkane trimethylol triglycidyl ether.

[0016] In one aspect of the present invention, the deaerator is one from a group consisting of organic polymers, modified polysiloxanes.

[0017] In another aspect of the present invention, the wetting agent is one from a group consisting of sodium salt of polyphosphates, sodium salt of polyacrylates, potassium salt of polyphosphates, potassium salt of polyacrylates, ammonium salt of polyphosphates, ammonium salt of polyacrylates, salts of unsaturated polyamine amides and salts of low-molecular acidic polyesters.

[0018] In yet another aspect of the present invention, the thixotropic agent is one from a group consisting of modified castor wax with polyamide, modified castor wax with epoxy resin and oxidized polyethylene wax.

[0019] In a further aspect of the present invention, the coating composition further comprises a colour pigment in a range of 5-12 % by weight of the first component. The colour pigment includes at least one pigment from a group consisting of Lead chromate, Lead Molybdate, Cadmium red, Red iron oxide or a combination thereof.

[0020] In one aspect of the present invention, the reinforcing filler includes fumed silica.

[0021] In another aspect of the present invention, the three non-reinforcing filler includes an organophilic clay in a range of 0.2- 1% by weight of the first component, a Barytes Off-white in a range of 18-26 % by weight of the first component and talc in a range of 16-25 % by weight of the first component.

[0022] In yet another aspect of the present invention, the first component includes epoxy resin as 30 by weight of the first component, diluent as 13.3 % by weight of the first component, deaerator as 0.7 % by weight of the first component, wetting agent as 0.4 % by weight of the first component, reinforcing filler as 0.6 % by weight of the first component, an organophilic clay as 0.6 % by weight of the first component, Barytes Off-white as 23.4 % by weight of the first component, talc as 22.6 % by weight of the first component and a thixotropic agent as 0.3 % by weight of the first component.

[0023] These together with other aspects of the invention, along with the various features of novelty that characterize the invention, are pointed out with particularity in the description annexed hereto and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and the specific objects attained by its uses, reference should be made to the accompanying drawings and descriptive matter in which there are illustrated exemplary embodiments of the invention.

DETAILED DESCRIPTION

[0024] In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without these specific details.

[0025] As used herein, the terms ‘a’, ‘an’, and ‘at least’ do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.

[0026] Reference herein to “one embodiment” or “another embodiment” means that a feature, structure, or characteristic described in accordance with the embodiment can be included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments.

[0027] The composition of the present invention comprises a first component and a second component, such that the first component and the second component are mixed in a pre-determined volume ratio. In on preferred embodiment of the present invention, the components are mixed in a volumetric ratio of 3 parts of the first component and 1 part of the second component.

[0028] The first component includes an epoxy resin in a range of 20-40 % by weight of the first component, a diluent in a range of 10-22 % by weight of the first component, a deaerator in a range of 0.2-1 % by weight of the first component, a wetting agent in a range of 0.2-0.8 % by weight of the first component, a reinforcing filler agent in a range of 0.2-1 % by weight of the first component, three non-reinforcing fillers combinedly in a range of 34.2-52 % by weight of the first component and a thixotropic agent in a range of 0.2- 0.8 % by weight of the first component.

[0029] In accordance with one embodiment of the present disclosure, the epoxy resin is the base matrix and has epoxy equivalent weight 185-194 g/eq. and viscosity 11,000-14000 cps at 25 °C.

[0030] The diluent may be reactive or non-reactive, most preferably reactive. The reactive diluent may be aliphatic, aromatic or cycloaliphatic reactive diluent. The reactive diluent may be monofunctional e.g. C8-C10 alkyl glycidyl ether, C12-C14 alkyl glycidyl ether, phenyl glycidyl ether, glycidyl ether of cashew nutshell liquid, cresyl glycidyl ether or difunctional e.g. diglycidyl ether of C2-C6 alkane diol, Neopentyl glycol diglycidyl ether, Cyclohexane dimethanol diglycidyl ether; or trifunctional e.g. C2-C4 alkane trimethylol triglycidyl ether etc.

[0031] In the present invention, the reactive diluent used can be a mono-functional aromatic reactive diluent based on cashew nut shell liquid. The purpose is to decrease the viscosity of the system and also increasing the liquid content in the system. Moreover, since it is a reactive diluent, it has epoxy functional groups, those can take part in the final curing reaction. This means, this additive also controls the functionality (in terms of epoxy equivalent weight) of the resin. The presence of a long fifteen carbon atom chain imparts flexibility to the coating.

[0032] In one embodiment of the present invention, the reactive diluent can be selected from the group consisting of C8 to C10 alkyl glycidyl ether, C12 to C14 alkyl glycidyl ether, phenyl glycidyl ether, glycidyl ether of cashew nutshell liquid, cresyl glycidyl ether, diglycidyl ether of C2 to C6 alkane diol, neopentyl glycol diglycidyl ether, cyclohexane dimethanol diglycidyl ether, and C2 to C4 alkane trimethylol triglycidyl ether.

[0033] In accordance with one embodiment of the present disclosure, the viscosity of the reactive diluent at 25 °C is 3 centipoise (cP) to 250 centipoise (cP). In accordance with another embodiment of the present disclosure, the viscosity of the reactive diluent is 10 cP to 120 cP. In accordance with still another embodiment of the present disclosure, the viscosity of the reactive diluent is 35 cP to 75 cP.

[0034] In accordance with one embodiment of the present disclosure, an epoxy equivalent weight of diluent is in the range of 145 to 600 g/eq. In accordance with another embodiment of the present disclosure, an epoxy equivalent weight of diluent is in the range of 250 to 580 g/eq. In accordance with still another embodiment of the present disclosure, an epoxy equivalent weight of diluent is in the range of 425 to 550 g/eq.

[0035] The diluent in the present invention is used for different purposes such as it facilitates in controlling the viscosity of the entire composition for ease of application, it can be used in the final curing reaction since the diluent includes epoxy functional groups, it facilitates in enhancing the flexibility of the coating, and the like.

[0036] The deaerator can be organic polymers or modified polysiloxanes comprising silicone. The modified polysiloxanes can be poly alkyl siloxanes or polyether alkyl siloxanes.

[0037] The absence of the deaerator in the composition results in foam formation. Due to the formation of foam, it can be difficult to identify whether the internal surface of the pipelines is coated appropriately and hence, foam formation is not desired. Therefore, the deaerator or defoaming agent is essentially used in the present composition and it plays a crucial role to avoid foam formation. Particularly, the low surface tension property of the deaerator enables inhibition of foam and bubble formation at the time of producing coating and/or its application. More particularly, the deaerator facilitates in removing bubbles/micro-air inclusions from the coating. This results in the destabilization of the foam, which is desired.

[0038] The wetting agent helps in homogenous distribution of solid additives in the liquid resin. In one embodiment of the present invention, the wetting agent can be selected from the group consisting of sodium salt of polyphosphates, sodium salt of polyacrylates, potassium salt of polyphosphates, potassium salt of polyacrylates, ammonium salt of polyphosphates, ammonium salt of polyacrylates, salts of unsaturated polyamine amides, and salts of low-molecular acidic polyesters.

[0039] The filler facilitates in improving the mechanical strength of the coating and controlling the density and rheology of the composition. In one embodiment of the present invention, the reinforcing filler includes a fumed silica. The fumed silica may be hydrophilic or hydrophobic with a surface area of 200 (±25) m2/g.

[0040] In one embodiment of the present invention, the three non-reinforcing filler includes an organophilic clay in a range of 0.2- 1% by weight of the first component, a Barytes Off-white in a range of 18-26 % by weight of the first component and talc in a range of 16-25 % by weight of the first component.

[0041] Bentonite and Hectorite (plate-like clays) and Attapulgite and Sepiolite (rod-shaped clays) are the examples of organophilic clays. These organophilic clay is used for controlling viscosity, thixotropic and sag properties, flow and labelling maintains properties of the resin.

[0042] Barytes Off-white is used as non-reinforcing as well as an extender pigment. This is basically used as a density controller of the coating composition. It improves paint’s gloss, fluidity, filling, and compatibility with different kinds of pigment.

[0043] Talc is a perfect filler for the paint industry owing to its lamellar, hydrophobic and chemical inert structural characteristic. This is used as an extender as well as non-reinforcing agent. This material is specifically used to improve the resistance and prevents cracking and peel off properties of paint and coating. It has several advantages like water repellence characteristics, viscosity, and dispersion controller, enhance adhesion properties, etc.

[0044] In one embodiment of the present invention, the thixotropic agent can be selected from the group consisting of modified castor wax with polyamide, modified castor wax with epoxy resin and oxidized polyethylene wax. The thixotropic agent plays a vital role in providing sag resisting property to the coating. This thixotropic agent results in a coating that will not flow under its own weight when applied to vertical surfaces. This is called sag resistance.

[0045] The second component of the composition includes a hardener. The hardener is used for curing of the epoxy resin and also imparts different properties, such as improved flexibility, resistance to salt and water, pot life and surface tolerance, to the coating composition. In one embodiment of the present invention, the hardener is phenalkamine which is a Mannich adduct of cardanol, formaldehyde & polyamide, cycloaliphatic amines. In accordance with one embodiment of the present invention, the viscosity of the hardener at 25 °C is in the range of 2000 cP to 50000 cP. In accordance with another embodiment of the present invention, the viscosity of the hardener at 25 °C is in the range of 10000 cP to 30000 cP. In accordance with still another embodiment of the present invention, the viscosity of the hardener at 25 °C is in the range of 12000 cP to 50000 cP.

[0046] In accordance with one embodiment, the coating composition of the present disclosure further comprises a colour pigment in a range of 5-12 % by weight of the first component. The colour pigment is added to the coating composition to achieve desired colour along with a rust preventive property. In one embodiment the coating composition is desired of red colour and the colour pigment can be inorganic compounds which may be selected from Lead chromate, Lead Molybdate, Cadmium red, Red iron oxide or a combination one or more of these compounds.

[0047] A spraying nozzle has been used to spray the liquid epoxy inside the pipe as per the required thickness. Before applying the epoxy paint, the internal surface of the pipe is cleaned. Heating the epoxy resin is intended to reduce the viscosity thereof so that the epoxy resin, with ease, can be sprayed from a sprayer. Particularly, heating reduces the possibility of the epoxy resin getting stuck in the sprayer.

[0048] The coating composition of the present invention enables coating of a desired thickness on the internal surface of the pipelines can be applied without sagging. The hardener facilitates in enhancing the curing rate. Further, the enhanced curing rate enables achieving a high level of crosslinking at a faster rate, which is desired to produce a stable coating. Furthermore, enhanced curing rate facilitates in protecting the coating from coating failures, i.e., it improves the application productivity. The coating can be applied to the internal surface of the pipelines by a brush/brushes or sprayers.

[0049] In one preferred embodiment of the coating composition of the present invention, the first component includes epoxy resin as 30 by weight of the first component, diluent as 13.3 % by weight of the first component, deaerator as 0.7 % by weight of the first component, wetting agent as 0.4 % by weight of the first component, reinforcing filler as 0.6 % by weight of the first component, organophilic clay as 0.6 % by weight of the first component, Barytes Off-white as 23.4 % by weight of the first component, talc as 22.6 % by weight of the first component and a thixotropic agent as 0.3 % by weight of the first component. The coating composition further includes a colour pigment as 8 % by weight of the first component. In the present invention, the color pigment is used to provide red color to the coating composition.

[0050] This coating composition of the present invention eliminates the TETA component and yet fulfills all the required technical properties required as well as completely food-grade categories to serve for protection of water pipelines.

[0051] Although a particular exemplary embodiment of the invention has been disclosed in detail for illustrative purposes, it will be recognized to those skilled in the art that variations or modifications of the disclosed invention, including the rearrangement in the configurations of the parts, changes in steps and their sequences may be possible. Accordingly, the invention is intended to embrace all such alternatives, modifications, and variations as may fall within the spirit and scope of the present invention.

[0052] The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching.

[0053] The foregoing description of the specific embodiments will 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 appended claims.