BPA FREE SPRAYABLE EPOXY RESIN

Abstract

A composition and method for a spray applied BPA free two-part, self-setting composition adapted for delivering the components of the composition at a temperature that promotes their spray application at a proper viscosity as well as inducing a self-setting reaction. Preferably, a self-setting BPA free epoxy coating compound is adapted for curing in place once applied. The self-curing compound includes a multi-part compound which, upon a mixing of the parts, chemically reacts and cures.

Claims

1. A food safe coating composition formed by the steps comprising: providing a resin component containing primarily 170 degrees Fahrenheit to 220 degrees Fahrenheit bisphenol F resin composition; providing a hardener component containing primarily 170 degrees Fahrenheit to 220 degrees Fahrenheit cycloaliphatic amine, said hardener component maintained separately from said resin component, and mixing said resin component and hardener component immediately prior to application.

2. The coating composition of claim 1, the resin component comprising: between 80% and 99% bisphenol F resin by weight; between 0.05% and 0.02% air release agent by weight; and between 2% and 6% thixotropic agent by weight.

3. The coating composition of claim 2, the resin component further comprising: between 1% and 4% pigment by weight.

4. The coating composition of claim 1, the resin component comprising: between 90% and 95% bisphenol F resin by weight; between 0.02% and 0.03% air release agent by weight, between 3% and 5% thixotropic agent by weight; and between 2% and 3% pigment by weight.

5. The coating composition of claim 1, the hardener component comprising: between 80% and 99% cycloaliphatic amine by weight; between 0.05% and 0.02% air release agent by weight; and between 2% and 6% thixotropic agent by weight.

6. The coating composition of claim 1, the hardener component comprising: between 94% and 96% cycloaliphatic amine by weight, between 0.04% and 0.02% air release agent by weight; and between 2% and 3% thixotropic agent by weight.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0015] Disclosed herein is a composition and method for a spray applied BPA free two-part, self-setting composition adapted for delivering the components of the composition at a temperature that promotes their spray application at a proper viscosity as well as inducing a self-setting reaction.

[0016] In one embodiment, a self-setting BPA free epoxy coating compound is adapted for curing in place once applied. The self-curing compound includes a multi-part compound which, upon a mixing of the parts, chemically reacts and cures.

[0017] Epoxy technology and methods of curing and reacting with amine-based hardeners have continued to evolve since the first epoxies were developed in the 1930s. The possible reactions combined with wide-ranging formulation additives have resulted in a myriad of products and a wide range of environmental factors that must be considered when choosing a protective coating system.

[0018] There are three types of epoxy resins that find application in the coating of water transport systems bisphenol A, bisphenol F, and novolac resins. These resins all result from reactions of epichlorohydrin with phenolic compounds. The type and number of phenolic groups determine both physical and performance properties of the cured resin.

[0019] Bisphenol A is a reaction product of phenol and acetone. Bisphenol A is reacted with epichlorohydrin to form diglycidylether bisphenol A resin or DGEBA. The resultant epoxy resin is a liquid with a honey-like consistency. DGEBA is most often used in solvent-free coatings and flooring systems. The molecular weight of the formulation is increased by adding more bisphenol A to liquid DGEBA to form semi-solid or solid resins. These resins are cut in solvent to allow their use as maintenance primers for steel or as corrosion-resistant films. Bisphenol A however is problematic in that it has been shown to leach significant byproducts into the transported material.

[0020] Bisphenol F is similar to bisphenol A except phenol is reacted with formaldehyde rather than acetone. The resultant phenolic chemical does not have the two methyl groups that are present between the ring structures in bisphenol A resins. Bisphenol F is reacted with epichlorohydrin to form diglycidylether bisphenol F (DGEBF) resins. Because of the missing methyl groups, the viscosity of bisphenol F resins are typically ⅓ lower than the bisphenol A resins. Further the crosslinking is higher and as a result bisphenol F does not exhibit significant leaching and is therefore considered safe for food contact. However the lower viscosity typically results in a low functionality for spray application and heat and chemical resistance.

[0021] The present invention provides a spray applied coating formed using a bisphenol F resin that is formulated and mixed in such a manner that it allows spray application in high build coating while also exhibiting low sag. The base resin is preferably a Diglycidyl Ether of Bisphenol F resin. More preferably the resin is a low viscosity, liquid epoxy resin manufactured from epichlorohydrin and Bisphenol-F. The blended resin will exhibit improved crystallization resistance properties when compared to the neat, liquid, Bisphenol-A.

[0022] In addition to the base bisphenol F resin an air release agent is preferably employed to prevent foaming during mixing and application of the epoxy coating. This enhances application and provides a coating that is free from blisters and pinholes. Preferably an air release agent in the nature of a polysiloxane polymer blend is employed.

[0023] Also blended into the base resin is preferably a thixotropic agent such as a fumed silica. More preferably a thixotropic agent is employed in the form of a treated fumed silica such as a fumed silica treated with a dimethyl silicone fluid that replaces the surface hydroxyl groups with a polydimethyl-siloxane polymer rendering the silica hydrophobic.

[0024] Further, the coating material preferably includes a pigment such as a TiO2 to make application and verification of coating integrity easier.

[0025] Preferably the resin comprises between 80% and 99% bisphenol F resin, between 0.05% and 0.02% air release agent, between 2% and 6% thixotropic agent and between 1% and 4% pigment all by weight.

[0026] More preferably the resin comprises between 90% and 95% bisphenol F resin, between 0.02% and 0.03% air release agent, between 3% and 5% thixotropic agent and between 2% and 3% pigment all by weight.

[0027] The hardener component is preferably a cycloaliphatic amine. The hardener preferably does not contain phenol or benzyl alcohol. This facilitates a solvent free coating that is safe for food grade coatings.

[0028] In addition to the base hardener an air release agent is preferably employed to prevent foaming during mixing and application of the epoxy coating. This enhances application and provides a coating that is free from blisters and pinholes. Preferably an air release agent in the nature of a polysiloxane polymer blend is employed.

[0029] Also blended into the hardener is preferably a thixotropic agent such as a fumed silica. More preferably a thixotropic agent is employed in the form of a treated fumed silica such as a fumed silica treated with a dimethyl silicone fluid that replaces the surface hydroxyl groups with a polydimethyl-siloxane polymer rendering the silica hydrophobic.

[0030] Preferably the hardener comprises between 80% and 99% cycloaliphatic amine, between 0.05% and 0.02% air release agent and between 2% and 6% thixotropic agent all by weight.

[0031] More preferably the hardener comprises between 94% and 96% cycloaliphatic amine, between 0.04% and 0.02% air release agent and between 2% and 3% thixotropic agent all by weight.

[0032] In the present invention the base resin and hardener components are fully blended separate and apart from one another. The two components are then maintained separated until ready for direct application to the surface. In the prior art, the materials were mixed in small batches for application and then the mixed batches were brush or roller applied. In some cases the two components were mixed and then thinned or diluted with a solvent to a point where their viscosity allowed spray application. The difficulty in such cases is that the working time for the material is quite short once mixed requiring constant rebatching and, if spraying, cleaning of the spray equipment. Plus the addition of significant solvents makes spray application in closed environments dangerous to the worker making the application. Finally, the viscosity required for spray application results in a coating that is too thin to apply as a high build coating.

[0033] Generally, the base resin and hardener components are both very viscous and therefore difficult to pump. It has been found that the portions are easier to pump, and therefore easier to deliver to the spray device, if they are heated in a closed environment within the storage containers, and maintained in such a state all the way to the spray tip. This also facilitates more volumetrically-controlled delivery of each of the two portions of the compound to the spray device.

[0034] Accordingly, the teachings of this invention provide that both the base resin and hardener, in anticipation of application ne heated in a system generally includes means for heating the contents of the containers that hold the two components, for example by using temperature-controlled heaters. Recirculating pumps may be used in the containers to ensure mixing and uniform heating of the two portions. The heated hose may be heated by including an electrical resistance heating element for the hose and then using a temperature controlled power supply for the electrical resistance heating element to maintain an elevated compound temperature in the heated hose. The hoses may also be heated with steam. The hoses that carry the liquids from the containers to the mixing assembly should be insulated or possibly heated themselves as necessary to maintain the portions at an elevated temperature so they flow better, and for volume control at the spray gun.

[0035] The heated resin and hardener is mixed immediately prior to spray application in the sprayer itself. To reduce the viscosity of the components and enhance pumpability, the containers holding the resin and hardener components are maintained at an elevated temperature. Preferably, the components are maintained at about 170degrees Fahrenheit to 220 degrees Fahrenheit. More preferably the components are maintained at about 180 degrees Fahrenheit to 190 degrees Fahrenheit.

[0036] It should be recognized that the teachings herein are merely illustrative and are not limiting of the invention. Further, one skilled in the art will recognize that additional components, configurations, arrangements and the like may be realized while remaining within the scope of this invention. For example, configurations and applications of dopants, curing time, layers and the like may be varied from embodiments disclosed herein. Generally, design and/or application of compounds and techniques for making use of the compounds are limited only by the needs of a system designer, manufacturer, operator and/or user and demands presented in any particular situation.

[0037] Various other components may be included and called upon for providing for aspects of the teachings herein. For example, additional materials, combinations of materials and/or omission of materials may be used to provide for added embodiments that are within the scope of the teachings herein.

[0038] In the present application a variety of embodiments are described. It is to be understood that any combination of any of these variables can define an embodiment of the invention. For example, a combination of a particular dopant material, with a particular compound, applied in a certain manner might not be expressly stated, but is an embodiment of the invention. Other combinations of articles, components, conditions, and/or methods can also be specifically selected from among variables listed herein to define other embodiments, as would be apparent to those of ordinary skill in the art.

[0039] While there is shown and described herein certain specific structure embodying the invention, it will be manifest to those skilled in the art that various modifications and rearrangements of the parts may be made without departing from the spirit and scope of the underlying inventive concept and that the same is not limited to the particular forms herein shown and described except insofar as indicated by the scope of the appended claims.