Industrial coating with color-change responsivity to acid and base contact

Abstract

A latex-based surface coating that can be applied to the surface of equipment to detect any leaks of acid or base onto the equipment. The latex-based surface coating changes color when a strong acid and/or a strong base makes contact with the surface coating, thereby providing a visual indication that a leak of a strong acid and/or a strong base has occurred. The surface coating is able to provide visual indications for acids with a pH between 0 and 3 in the liquid or gas phase. The surface coating is also able to provide visual indications for bases with a pH between 9 and 14 in the liquid or gas phase.

Description

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISC

Not applicable.

FIELD OF THE INVENTION

The subject invention relates generally to a surface coating composition with color change characteristics. More particularly, the subject invention relates to a surface coating composition with ingredients that change color when exposed to acidic or alkaline substances.

BACKGROUND OF THE INVENTION

A chemical plant is an industrial facility that manufactures (or otherwise processes) chemicals, usually on a large scale. In many instances, the chemicals manufactured or processed in a chemical plant are classified as strong acids or strong bases. Strong acids have a high pH and strong bases have a low pH. pH is a scale used to specify the acidity or basicity of an aqueous solution or other liquid solutions. pH translates the values of the concentration of the hydrogen ion in a solution—which ordinarily ranges between about 1 and 10⁻¹⁴ gram-equivalents per liter—into numbers between 0 and 14. In pure water, which is neutral (neither acidic nor basic), the concentration of the hydrogen ion is 10⁻⁷ gram-equivalents per liter, which corresponds to a pH of 7. A solution with a pH less than 7 is considered acidic; a solution with a pH greater than 7 is considered basic, or alkaline.

Strong acids have a very low pH, typically in the range of 0 to 4. The seven most common strong acids are hydrochloric acid, nitric acid, sulfuric acid, hydrobromic acid, hydroiodic acid, perchloric acid, and chloric acid. Strong bases have a very high pH, typically in the range of 10 to 14. Examples of strong bases include potassium hydroxide, sodium hydroxide, barium hydroxide, caesium hydroxide, sodium hydroxide, strontium hydroxide, calcium hydroxide, lithium hydroxide, and rubidium hydroxide. These types of acids and bases are highly corrosive and reactive. They can attack and destroy metal, stone, and living tissue. In addition, they can violently react with other chemicals and produce explosions, fires, and the rapid evolution of heat and toxic gases.

When strong acids and/or strong bases make contact with human skin, they can cause burns and irritation. Inhalation of strong acids and/or strong bases may cause irritation to the respiratory tract with burning pain in the nose and throat, coughing, wheezing, shortness of breath, and pulmonary edema. Eye contact with strong acids and/or strong bases can cause burns, irritation, and may cause blindness. Ingestion of strong acids and/or strong bases may cause permanent damage to the digestive tract.

Handling of strong acids and/or strong bases requires several precautions to protect personnel and property. If a leak of a strong acid and/or a strong base occurs within a process or from a storage vessel, then it is imperative to stop the leak as quickly as possible to prevent damage and harm to equipment and personnel. A reliable, fast, and visual leak detection system can facilitate the quick stoppage of a leak of a strong acid and/or a strong base.

In some cases, pH indicator patches are placed on pieces of equipment to give visual indication of an acid or base leak. The primary drawback of this solution is that the patch has a specific location, which may or may not be in the proper place to detect a leak. The present invention is a latex-based surface coating that can be applied to the entire surface area of a piece of equipment to detect any acid or base that leaks onto that piece of equipment. The latex-based surface coating changes color when a strong acid and/or a strong base comes into contact with the coating, thereby providing a visual indication that a leak has occurred.

DESCRIPTION OF THE INVENTION

While the present invention will be described with reference to preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the present invention not be limited to the particular embodiments disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments (and legal equivalents thereof).

The present invention is a latex-based surface coating that uses a pH indicator to change the color of the surface coating when a strong acid and/or a strong base makes contact with the surface coating. The neutral or initial color of the surface coating is bright yellow. The bright yellow color is comparable to the process safety yellow used in many industrial settings. The surface coating can be applied to pipes, valves, tanks, vents, fume hoods, hose connections, and any other equipment where acids or bases may be present. The surface coating can be applied to metal, masonry, wood, galvanized steel, painted surfaces, fiberglass, or plastic. The surface coating can be applied with a brush, roller, sprayer, or aerosol spray can then allowed to dry before use. The surface coating functions best on surface temperatures within the range of 35 to 220 degrees Fahrenheit. The surface coating is designed to detect strong acids and/or strong bases in the liquid or gas phase.

When an acid having a pH equal to or less than three contacts the surface coating of the present invention, the pH indicator in the surface coating composition changes the surface coating color from bright yellow to red. When a base having a pH equal to or greater than nine contacts the surface coating of the present invention, the pH indicator in the surface coating composition changes the surface coating color from bright yellow to blue. The pH of the acid or base making contact with the surface coating of the present invention effects the intensity of the color change. The lower the pH of the acid, the brighter the change in color to red. The higher the pH of the base, the brighter the change in color to blue.

After the surface coating is exposed to a strong acid or a strong base, the acid or base can be washed away with a neutral solution, after which the surface coating can be dried with a cloth or other means. If the acid or base remains in contact with the surface coating for a long period of time, then the acid or base may stain the surface coating. In those cases, additional layers of the surface coating composition can be applied to the stained surface for future service.

In general, the compositions of latex-based coatings vary. The various latex coating chemistries can affect the behavior of a pH indicator. The compositions of the latex-based surface coating of the present invention are provided in two embodiments. pH indicators may be added to the latex-based surface coating at 0.1 and 2.0 weight percent. Individual or combinations of pH indicators may be added, including but not limited to, azolitmin, cresolphhalein, naphtholphthalein, phenolphthalein, or thymolsulfonephthalein. In the preferred embodiments, only one pH indicator is used, namely, thymolsulfonephthalein, also known as Thymol blue. Thymolsulfonephthalein is a brownish-green or reddish-brown crystalline powder that is insoluble in water but soluble in alcohol and dilute alkali solutions.

Chemical Name	CAS Registry No.*	Ingredient Percent
Embodiment 1
2-ethylhexyl benzoate	5444-75-7	1-5 by weight
Kaolin	1332-58-7	1-5 by weight
Poly Butyl Acrylate/	25852-37-3	10-30 by weight
Poly Methyl Methacrylate
Thymol blue	76-61-9	0.25 by weight
Embodiment 2
Titanium Dioxide	13463-67-7	≥10-≤25 by weight
Talc	14807-96-6	≤10 by weight
Tetrachloroisothalonitrile	1897-45-6	<1 by weight
Heavy Paraffinic Oil	64742-65-0	≤1 by weight
Thymol blue	76-61-9	0.5 by weight
*A CAS Registry Number is a unique and unambiguous identifier for a specific chemical substance. CAS Registry Numbers are relied upon by scientists, manufacturers, regulators, and data scientists worldwide for accurate information on chemical substances.

It is understood that two embodiments of the present invention have been disclosed by way of example and that other modifications and alterations may occur to those skilled in the art without departing from the scope and spirit of the present invention.

Claims

1. A surface coating composition comprising: (a) from about 60 weight percent to about 88 weight percent of a base coating;(b) from about 1 weight percent to about 5 weight percent of 2-ethylhexyl benzoate;(c) from about 1 weight percent to about 5 weight percent of kaolin;(d) from about 10 weight percent to about 30 weight percent of Poly Butyl Acrylate/Poly Methyl Methacrylate; and(e) about 0.25 weight percent of a pH indicator.

2. The surface coating composition of claim 1, wherein the base coating is a latex-based paint.

3. The surface coating composition of claim 2, where said pH indicator is thymolsulfonephthalein.

4. The surface coating composition of claim 3, where said surface coating composition has a neutral color that is bright yellow.

5. The surface coating composition of claim 4, where said neutral color of said surface coating composition changes from bright yellow to red when an acid having a pH equal to or less than three contacts said surface coating composition.

6. The surface coating composition of claim 4, where said neutral color of said surface coating composition changes from bright yellow to blue when a base having a pH equal to or greater than nine contacts said surface coating composition.

7. A method of coating a surface with a surface coating composition, said method comprising the steps of: (a) applying a surface coating composition to a surface wherein the surface coating composition comprises: (i) from about 60 weight percent to about 88 weight percent of a base coating;(ii) from about 1 weight percent to about 5 weight percent of 2-ethylhexyl benzoate;(iii) from about 1 weight percent to about 5 weight percent of kaolin;(iv) from about 10 weight percent to about 30 weight percent of Poly Butyl Acrylate/Poly Methyl Methacrylate; and(v) about 0.25 weight percent of a pH indicator.

8. The method of claim 7, wherein the base coating is a latex-based paint.

9. The method of claim 8, wherein said pH indicator is thymolsulfonephthalein.

10. The method of claim 9, wherein said surface coating composition has a neutral color that is bright yellow.

11. The method of claim 10, further comprising the step of changing said neutral color of said surface coating composition from bright yellow to red when an acid having a pH equal to or less than three contacts said surface coating composition.

12. The method of claim 10, further comprising the step of changing said neutral color of said surface coating composition from bright yellow to blue when a base having a pH equal to or greater than nine contacts said surface coating composition.