WATER REDUCIBLE WAX COATING

Abstract

A relatively low cost, water-based coating, intended to protect metal from corrosion, exhibiting excellent corrosion resistance, is formed by emulsification of oxidized soap wax containing a small amount of petroleum distillate, and other liquid additives. The resulting emulsion is modified to produce firm dry films, by addition of pigment followed by addition of highly polar acrylic resins. The pigmented composition is further modified with gelled metal sulphonates, to attain significant anti-corrosion properties.

Claims

1. A method for producing oxidized soap wax emulsion.

2. A method for producing a relatively inexpensive rust preventative that air-dries to form a firm film, and can protect metal substrate with or without pretreatment, and which is liquid at room temperature.

3. A method to prepare rust preventing coating that can be applied to transportation equipment or other substrate for corrosion protection.

4. A method for producing oxidized soap wax emulsion comprising the steps of: a. Adding a small concentration of aliphatic distillate, naphthenic or paraffinic oils, metal sulphonates to the emulsion particles to facilitate coalescence, before emulsification; b. Using amine and polyethylene phosphate to emulsify the oxidized soap wax; c. Using VOC-exempt co-solvent such as dimethyl carbonate as a co-solvent with water; d. Modifying the water with a flash rust inhibitor; e. Adding water and cosolvent to produce a stable emulsion; f. Use of a wetting agent to facilitate dispersion of pigment; g. Adding pigment or fumed silica to increase toughness of film; h. Adding highly polar and or acid-group-rich water based acrylic resin to encapsulate the added pigment; i. Adding gelled metal sulphonate to further increase the corrosion resistance of the coating; and j. Adding dispersion to provide color to the final coating.

5. An oxidized soap wax emulsion produced by the performing the steps of: a. Adding a small concentration of aliphatic distillate, naphthenic or paraffinic oils, metal sulphonates to the emulsion particles to facilitate coalescence, before emulsification; b. Using amine and polyethylene phosphate to emulsify the oxidized soap wax; c. Using VOC-exempt co-solvent such as dimethyl carbonate as a co-solvent with water; d. Modifying the water with a flash rust inhibitor; e. Adding water and cosolvent to produce a stable emulsion; f. Use of a wetting agent to facilitate dispersion of pigment; g. Adding pigment or fumed silica to increase toughness of film; h. Adding highly polar and or acid-group-rich water based acrylic resin to encapsulate the added pigment; i. Adding gelled metal sulphonate to further increase the corrosion resistance of the coating; and j. Adding dispersion to provide color to the final coating.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIG. 1 illustrates a flow chart detailing the method of forming a water-based emulsion of the present invention. In the pigment step, the order of addition is important: The copolymer is added slowly after the addition of pigment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0017] The various features and advantages of the invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment.

[0018] The first step in instant invention is to charge a process vessel with oxidized petrolatum (Chemical Abstract Service Registry Number 64743-01-7). This product is available from Lockhart Chemical under the tradename Counterrust 6000. The oxidized petrolatum, which melts at approximately 140° F., is raised to a temperature of approximately 250° F.

[0019] A lime slurry is prepared, consisting of 142 flash mineral spirits (Chemical Abstract Service Registry Number 64742-47-8); Mississippi Lime (Chemical Abstract Service Registry Number 01305-62-0); a catalyst such as Surfactant Calcium Acetate (Chemical Abstract Service Registry Number 62-54-4); a sodium sulphonate (Chemical Abstract Service Registry Number 68608-26-4, sold by Lockhart Chemical under the trade name EZ Mulz 2000); and 100 weight naphthenic oil (Chemical Abstract Service Registry Number 64742-52-5).

[0020] The lime slurry is then added to the heated oxidized petrolatum. The concentration of lime is stoichiometrically equivalent to the concentration of acid present in the oxidized wax. The mixture is held at 250° F., normal atmosphere, for two hours.

[0021] After two hours, Imidazoline T (Chemical Abstract Service Registry Number 61791-39-7) is added and the mixture is allowed to cool. The resulting mixture, the wax oxidate soap, is equivalent to Chemical Abstract Service Registry Number 68425-34-3, which is an oxidized petrolatum soap available from the Lubrizol Corporation as Alox 606, cut back with aliphatic petroleum distillates. Another substantial equivalent can be procured from Lockhart Chemical Co., sold under the brand Counterrust 6600. However, there is a significant difference between the mixture taught through the instant invention, which contains 6 to 8% mineral spirits, as Alox 606 and Counterrust 6600 each contain 45% mineral spirits.

[0022] It is important that the oxidized soap wax contain a small amount of aliphatic petroleum distillates because the oxidized soap wax has a very high melting point (greater than 300° F.). The emulsion particles are unable to coalesce at room temperature when the emulsion coating is applied to a substrate. The inability to coalesce results in improper film formation and accelerated corrosion failure. Only a small amount of aliphatic petroleum distillate (“AP”) is required. For best results, 140 flash aliphatic petroleum distillate is preferred because it evaporates last from the drying film. While a range of amounts of aliphatic petroleum distillate will work, for the optimum performance, an amount of 6%, based on formula weight of wax, is best.

[0023] The 6% of aliphatic petroleum distillate in the final formula results in a negligible amount of VOC. In addition to the aliphatic petroleum distillate, in order to liquify the wax to form final film properties, an oil is also added to the wax before emulsification. We find that the best oil is 100 weight naphthenic oil, widely available from various chemical suppliers, although paraffinic oil also works. Additionally, an emulsifier is added to the wax before the wax is converted to a soap. We find the best emulsifier is sulphonate, such as sodium sulphonate available from Lockhart Chemical mentioned earlier.

[0024] The resulting mixture is liquid at room temperature. This is very important for room temperature film formation. The minimum film formation temperature can be increased by removal of the aliphatic petroleum distillate.

[0025] The mixture is now ready for emulsification in water. Emulsifier is added to the oxidized soap wax containing aliphatic petroleum distillate. Multiple emulsifiers allow for the transition of the oxidized soap wax to an emulsion; however, the best combination is AMP-95 (from Angus Chemical), in combination with PEG phosphate (Chemical Abstract Service Registry Number 39464-69-2, available from Colonial Chemical). AMP-95 is the only amine available which is not listed by the US Environmental Protection Agency, as a VOC (Volatile Organic Compound).

[0026] The amine and PEG phosphate are mixed with the oxidized soap wax mixture. Under agitation, ambient temperature water mixed with an organic cosolvent and anti-oxidant (to inhibit flash rust), is then slowly added to the wax mixture at room temperature. This mixture will become a brown emulsion. Many cosolvents are effective, but di methyl carbonate at 1.08% formula weight, is preferred, because it has a fast evaporation rate. This, which hastens film formation, is also preferred because it is not listed as a VOC by the US EPA. Many anti-oxidants are available, however, sodium nitrite, at 0.28% formula weight, performs best for this coating.

[0027] The emulsion formed exhibits excellent accelerated corrosion resistance but the film consistency is very soft. The dry film is easily deformed by abrasion. The emulsion formed at this stage of the procedure is an excellent corrosion protectant where abrasion of the film is not an issue.

[0028] The film can be made more abrasion resistant by addition of fumed silica. However, the addition of pigment is preferred over silica, which serves to impart film properties with more modulus of restoring force.

[0029] Adding pigment to the emulsion is required to render a tough film that can be utilized for corrosion protection. Adding pigment by most methods results in catastrophic film failure in accelerated corrosion testing. However, using a commercial water-based emulsion with a very high acid number to first encapsulate the pigment avoids this failure. The resin AVANCE 200, at 12.7% formula weight, from Dow Chemical Company, performs best. The technical information provided by DOW with regard to AVANCE 200 indicates that the resin encapsulates the pigment particles, and only is effective in encapsulating certain pigments, including titanium dioxide and calcium carbonate.

[0030] The best pigment is a calcium carbonate with a relatively large particle size. A good example of such a pigment is Omya Curb 6, at 54.2% formula weight, available from Omya.

[0031] Before adding the pigment to the emulsion, a dispersant is added to the emulsion to facilitate initial pigment wetting. Numerous dispersants work; however, Tamol 165A, at 0.5% formula weight, from Dow Chemical Company, works best.

[0032] The pigment is mixed into the emulsion. The concentration of pigment is added to produce a dry film with Pigment Volume Concentration of 38%. Hegman grind is used to determine that pigment dispersion is complete.

[0033] The AVANCE is added slowly to allow the encapsulation of the pigment. The final film is a dry firm film that exhibits an accelerated corrosion score of 500.

[0034] Accelerated corrosion testing of the composition at this stage of the procedure set forth herein exhibits some corrosion if the film is cut or damaged before exposure to accelerated corrosion. To mitigate this, gelled calcium sulphonate (Chemical Abstract Service Number 68783-96-0) is mixed into the composition, at 15% by weight of the oxidized wax. The resulting composition exhibits a corrosion protection score of 1000. This indicates that almost no corrosion occurs in accelerated corrosion testing, even at areas where the film has been removed.

[0035] Additional colorant dispersions can be added, where the effect upon accelerated corrosion protection must be determined.

[0036] The foregoing description is only exemplary of the principles of the invention. Many modifications and variations of the present invention are possible in light of the above teachings. The preferred embodiments of this invention have been disclosed, however, so that one of ordinary skill in the art would recognize that certain modifications would come within the scope of this invention. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. For that reason, the following claims should be studied to determine the true scope and content of this invention.