A METHOD AND COMPOSITION FOR SUBSTRATE COATING

Abstract: A method and composition for coating a selected substrate including mixing a first liquid solution of first solvent and an epoxy resin, with a second solution including selected proportions of epoxy resin curing agent reactive with the epoxy resin of the first solution, second solvent, selected proportions of a selected wetting agent soluble in both water and in generally water insoluble liquid and a selected proportion of water, and applying the mixed first and second solutions to a selected substrate.

Description: A METHOD AND COMPOSITION FOR SUBSTRATE COATING DESCRIPTION TECHNICAL FIELD My invention relates to epoxy coating particularly useful in providing a coating for selected substrates where the coating provides improved adherence to the substrate by improved penetration of the coating into the substrate. In general, epoxy compounds are composed of monomers or prepolymers that further react with curing agents to yield high performance thermosetting plastics. Epoxy compounds have gained wide acceptance- as protecting coatings and in structural applications because of their exceptional combination of properties such as toughness, adhesion, chemical resistance, and superior electrical properties. Epoxy resins are Generally characterized by the presence of a three member cyclic ether group commonly referred to as an epoxy group, 1,2-epoxide, or oxirane. The most widely used epoxy resins are diglycidyl eithers of bisphenol A derived from bisphenol A and epichlorhydrin as typically shown in United States Patent No. 3,324,483 and U.S. Patent No. 2,456,408-Castan. 5 Epoxy resins are most frequently cured with anhydrides aliphatic amines or polyamides. BACKGROUND ART A variety of agents have been 10 described for converting liquid epoxy resins to a cured state, which is necessary for the development of the inherent properties of the resins. The curing agents or hardners are categorized generally as catalytic or 15 co-reactive. The functional groups of the resins are terminal epoxy groups together with pendant hydroxl per repeat unit of the polymer chain. Co-reactive curing agents are 20 generally employed in stoichiometric quantities with the epoxy resin. The -3- i portant classes include polya ines, polyaminoamides, polyphenols, polymeric thiols, polycarboxylic acid and anhydrides. Most systems utilized in current 5 practice are solvent based, that is the resin, or the curing agent, or both, are dissolved in selected solvents for ease in application. In general the solvents and the systems are generally water free. 10 Recently, water borne systems have been developed for replacement of solvent based systems. In general the water borne systems utilize either liquid or solid epoxy resins which have -been modified to allow use with 15 water. They are usually in the form of emulsions, suspensions, dispersions or water dilutable resins which can be heat or room temperature cured. DISCLOSURE OF INVENTION 20 The present invention provides a new and useful composition and method which provides unexpectedly improved penetration of the resin into pores of the substrate for better protection and greatly improved bonding between the substrate and the coating. Various substrates can be utilized where the composition of the coating can be varied to accomodate the character of the substrate. The substrates can be, for example, emulsified asphalt, cement, masonry materials or even metals. Further, many different types of fillers and extenders such as rock, sand, glass, carborundum, alumina, quartz, common slag, marble, grit, or granite can be incorporated to provide improved wear resistance. The resulting product is water proof, resistant to acid and alkali solutions and semi-flexible, yet very hard and strong and adheres tightly to the substrate, it is believed, because of the wetting agent which is a part of the invention and promotes resin penetration of the substrate. In application it has been found that the compositions provided by the present invention provide enhanced protection to bridge decks to prevent water and salt penetration and as a base for lead bearing coatings to provide radiation shielding for selected form of radiation. Further compositions within the scope of the present invention provide improved bonding with greatly reduced substrate surface preparation, for example by sandblasting or degreasing. Additionally, materials within the scope of the present ^ invention can be modified to provide fire and thermal resistance and the material can be provided on various substrates such as metals, cloth, paper, fiberglass, burlap and various plastics. Also the material is quick setting so that the substrate can be returned to use shortly after application of the material. More particularly the present invention provides an improved method and composition for coating a selected substrate including mixing a first liquid solution of first solvent and an epoxy resin, with a second solution included selected proportions of epoxy resin curing agent reactive with the epoxy resin of the first solution, second solvent, selected proportions of a selected wetting agent soluble in both water and in generally water insoluble liquid and a selected proportion of water, and applying the mixed first and second solutions to a selected substrate. BEST MODE FOR CARRYING OUT THE INVENTION Examples within the scope of the present inveniton are discussed hereinafter and it will be understood that the examples are by way of illustration only and that various other compositions also within the scope of the present invention will occur to those skilled in the art upon reading the disclosure set- forth hereinafter. In accordance with the present invention it has been unexpectedly found that the use of a wetting agent in combination with an epoxy resin-curing agent system unexpectedly provides a base coat for application to a substrate which provides an unusually strong and effective substrate bond where the first coat can be then utilized as a base for application for subsequent coats of epoxy or other materials or where the material can, for example, be used as a grout or filler for example for concrete. Further, in accordance with the present invention it has been found that in the epoxy resin-curing agents systems the presence of solvents in the curing agent and epoxy resin facilitate the development of properties of the desired properties in the overall composition. Additionally, in some instances application of more than one coat of the base material utilizing the wetting agent as described hereinafter has been found useful where the composition of the material used in the first and second applications may be varied. In one example in accordance with the present invention a system was compounded including a solvent bond epoxy resin (Epi-rez™ 2036 product of the Celanese Plastics and Specialties Company) having a 75% by weight resin as solid in solution with metholisobutylketone solvent at approximately 16.6% by weight and xylene solvent at approximately 8.9% by weight. The curing agent used in stoictriometric amount included Epi-Cure * " CT-60-8534 by Celanese Plastics and Specialties Company as aliphatic amine in solution of solvents at concentrations of 8% by weight toluene, 8% by weight ethleyene glycol monoethylether and 24% by weight ethylene glycol monobutyl ether. An example wetting composition within the scope of the present invention was formulated in accordance with the following formulation by weight: Water 10% Methylethyl Ketone 10% Dimethyl Sulfoxide 64% Isopropyl Alcohol 16% The Methylethyl Ketone, Dimethyl Sulfoxide, and Isopropyl Alcohol act as a wetting agent to allow the water in the total mixture to be taken into the solution first with the curing agent and finally with the resin base. Other wetting agents can be utilized within the scope of the present invention and can include detergent compositions. An example formulation was then compounded wherein the wetting agent included at a concentration of 5% of the final composition, was mixed with the Epi-Cure * " CT-60-8534 which was then mixed with the resin solution so in the final mix -10- the curing agent was 47.5% by weight of the final composition the wetting agent was 5% and the balance (47.5% by weight) of the composition was the Epi-Res™ 2036. The material was then applied to a surface to be coated as compounded and allowed to harden. In some applications further dilution of the penetrating composition has been found advantageous. It has been found that active compositions can be prepared wherein the aforenoted composition including resin, curing agent and wetting agent is diluted in water at a ratio of three parts water to one part of the composition. While various compositions have been found to be satisfactory it has been found that so long as sufficient wetting agent is present to provide a complete solution of the water in the epoxy system, the system is effective. In this regard it is believed that the wetting agent need only be a material which is soluble in polar solvent composition including resin, curing agent and wetting agent is diluted in water at a ratio of three parts water to one part of the composition. While various compositions have been found to be satisfactory it has been found that so long as sufficient wetting agent is present to provide a complete solution of the water in the epoxy system, the system is effective. In this regard it is believed that the wetting agent need only be a material which is soluble in polar solvent such as water and non polar solvents such as the xylene, or other solvents normally found in resin-curing agent systems. In application, the composition previously described is diluted with water as previously described. A first coat can be applied at the rate of, for example, 300 square feet per gallon. The coating is allowed to dry and a second coat, which is somewhat less diluted (for example where the -12- resin, curing agent, wetting agent,is diluted with two parts water) is applied over the first coat and allowed to dry. As a third coat the solution utilizing the wetting agent with: Water 10% Methylethyl Ketone 10% Dimethyl Sulfoxide 64% Isopropyl Alcohol 16% is utilized and mixed with curing agent and epoxy resins so the wetting agent is 5% of the total mixture. Thus the curing agent is 47 1/2% of the final mixture and the epoxy resin is 47 1/2% of the final mixture. The third coat can be mixed with abrasive or wear resistant material when a protected surface is desirable or when surface roughness is needed. In this regard it has been further found that by utilization of one or two coats of the material including the wetting agent as a precoat on concrete, steel, or other material, and the subsequent addition of epoxy material either with or without the wetting composition, but mixed with up to 95% lead powder and applied to the precoated surface, an extremely efficient radiation shield is provided. A test was performed utilizing epoxy resin mixed with lead powder where the epoxy resin was approximately 2 to 3% of the mixture, the lead being the balance, as a radiation shield and the composition then tested with reference to equal thickness of steel and ' aluminum. The tests were performed utilizing samples of quarter inch thickness increments and varying the exposure time and the X-ray intensity in accordance with the data shown in Table I. In Table I the relative X-ray intensity is reflected by the combination of the voltage and current to the X-ray. The thickness of the materials exposed for the times indicated is also shown and the relative transmission of the various materials under each of the conditions is shown. * -14- TABLE I X-RAY TRANSMISSION DATA THICKNESS X-RAY EXPOSURE OF BARRIER KILOVOLT MILLIAMP TIME-MIN INCHES 0.25 140 20.0 3 0.5 200 15.0 3 0.75 220 12.0 4 1.0 280 10.0 3 1.25 300 10.0 5 1.5 300 10.0 10 1.75 300 10.0 15 BARRIER & RELATIVE TRANSMISSION-% Al Fe Epoxy Lead 62.5 25 0 100 50 0 100 50 0 100 87.5 6 100 87.5 6 100 100 12.5 100 100 2.0 -15- It will be seen that the epoxy-lead composition is highly effective in reducing X-ray transmission and that materials of this type which can be bonded to selected substrates using compositions within the scope of the present invention would be particulary effective as radiation shielding. It has further been found that fire retardant materials can be easily compounded with materials within the scope of the present invention to substantially provide fire retardant and in some cased fire protective shielding. It has further been found that compositions within the scope of the present invention can be admixed with substrate material, for example concrete to provide improved characteristics, particularly improved resistance to element penetration, reduction of reinforcing steel corrosion and reduction of spaling due to ice and salt. It will be recognized that the foregoing description of the present invention is not by way of limitation but that various other formulations, compositions, and applications also within the scope of the present invention will occur to those skilled in the art upon reading the disclosure set forth hereinbefore.

Claims: CLAIMS 1 A coating composition for coating a selected substrate including a mixture of: a) from 30 to 75% by weight of a liquid epoxy resin including active 5 epoxy groups; b) a stoicometric quantity of selected liquid curing agent for said liquid epoxy resin including at least 2.5% by weight of water and a selected proportion of a selected 10 wetting agent soluble in polar and nonpolar liquids in quantities sufficient to effect a solution of said water, wetting agent, curing agent and liquid epoxy resin. 15 2 The invention of Claim 1 wherein said liquid epoxy resin includes at least one nonpolar solvent. 3 The invention of Claim 1 wherein said curing agent is co-reactive with said 20 epoxy groups. 4 The invention of Claim 1 wherein said curing agent promotes catalytic polymerization of said epoxy groups. 5 The invention of Claim 1 wherein said curing agent includes nonpolar solvent. 6 The invention of Claim 1 wherein said 5 wetting agent includes alcohol. 7 The invention of Claim 6 wherein said alcohol includes propylalcohol. 8 The invention of Claim 1 wherein said wetting agent includes 10 dimethylsulfoxide. 9 The invention of Claim 1 wherein said wetting agent includes ketone groups. 10 The invention of Claim 9 wherein said ketone group is methylethylketone. 15 11 The invention of Claim 1 wherein said wetting agent is from 3 to 6% of the weight of said coating composition. 12 The invention of Claim 1 including a second composition provided by diluting 20 said cooling composition with water. 13 The invention of Claim 12 wherein said coating composition is diluted at least in equal parts with water. 14 The invention of Claim 1 wherein said composition is admixed with a calcium alumitate calcium silicate composition which hydrates in the presence of water 5 to form a hardened substance.

Inventors: SMITH CHARLES E, SMITH, CHARLES, E.
Applicants: SMITH CHARLES E, SMITH, CHARLES, E.
Application year: 1982
Main classification: C08L63
IPC codes: C08G59, C09D163