CURING AGENT AND FLUOROCARBON POLYMER COATING COMPOSITION CONTAINING CURING AGENT

Abstract: A curing agent for fluorocarbon polymer coating compos­ itions selected from the following group: where R is R¹NH, R¹ is an aliphatic or cycloaliphatic hyd­ rocarbon radical, R² is C or an aliphatic hydrocarbon group, R³ is H or CH₃, where x is 3 when R² is a hydrocarbon group and x is 4 when R² is C; the curing agents form novel ambient curing fluorocarbon polymer coating compositions and these com­ positions are used to provide corrosion and abrasion resistant coatings for large structures in chemical plants, oil refineries, oil drilling platforms, and the interior of smoke stacks of large utility companies.

Description: TITLE Curing Agent and Fluorocarbon Polymer Coating Compositions Containing Curing Agent Background of the Invention This invention is real ted a curing agent and in particular to a curing agent for a fluorocarbon polymer coating composition and to fluorocarbon polymer coating composition containing the curing agent. Fluorocarbon polymers are inert to strong acids such as sulfuric acid, nitric acid, hydrochloric acid and strong bases such as sodium hydroxide and are resistant to weathering and salt water corrosion and are tough and abrasion resistant. Coatings of these polymers would be useful in chemical plants and oil refineries to coat pipes, vessels and other equipment, on off shore oil well platforms, on ships, and as protective coatings for the interior of smoke stacks of utility companies. Fluorocarbon polymer coatings would be particularly useful for metal smoke stack interiors which are subjected to abrasion from fly ash and corrosion 5 acids resulting from combustion products such as SOX and NOx and halogen ions. Bowever, conventional fluorocarbon polymer coatings require curing at elevated temperatures which could not be used on the aforementioned structures. An ambient curing fluorocarbon polymer coating composition is required. The curing agent of this invention is used in fluorocarbon polymer coating composition and provides novel compositions that cure at' ambient temperatures. Summary of the zit Invention A curing agent for fluorocarbon polymer coating compositions selected from the following group: EMI2.1 where R is R1NH2, R1 is an aliphatic or cycloaliphatic hydrocarbon radical, R2 is C or a hydrocarbon group, R3 is H or CH3; where x is 3 when R2 is a hydrocarbon group and x is 4 when R2 is C. Fluorocarbon polymer coating compositions containing the above curing agent also are part of the invention. Detailed Description of the Invention Curing agent (1) is prepared by reacting 1 mole of dialkyl :naleate with 3 moles of an aliphatic or cycloaliphatic polyamine at about 100-1500C for about 1-6 hours. Alkanol formed in the reaction is removed. Preferred reaction conditions are about 110-1300C for about 2-4 hours. Preferably, the above constituents are in an alkanol solvent such as methanol, propanol isopropanol and the lke. Typical dialkyl maleates that can be used to form the curing agent are dimethyl maleate, diethyl maleate, dipropyl maleate, diisopropyl maleate, methyl ethyl maleate, methyl propyl maleate, ethyl propyl maleate, dibutyl maleate and the like. Dimethyl maleate is preferred. Typical polyamines used to form the curing agent are isophorone diamine which is 3-aminomethyl-3,5,5-trimethylcyclohexylamine, hexamethylene diamine, ethylene diamine, 1,4cyclohexane bis(methylamine), I ,2-diarninopropane, propylene diamine, diethyl ether diamine, trimethylhexamthyl methylene diamine. One preferred curing agent is the reaction product of isophorone diamine and dimethyl maleate and has the following structural formula: EMI3.1 Curing agent (2) is prepared through a Michael's reaction in which a multifunctional acrylate or methacrylate is reacted with a polyamine. The polyamine is heated to about 1001500C and then the multifunctional acrylate or methacrylate is reacted with the polyamine for a 1-6 hour period to form an amine terminated curing agent. Typical multi functional acrylates or methacrylates that can be used to form curing agent (2) are trimethylol propane acrylate1 trimethylol propane methacrylate, pentaerythritol acrylate, pentaerythritol methacrylate and the like. Any of the aforementioned polyamines can be used to form the curing agent (2). The curing agents are used in fluorocarbon polymer coating compositions or primer compositions. Generally, about 0*5-254 by weight, based on the weight of the binder of the composition, of curing agent is used. One of the advantages of compositions that contain the curing agent is that these compositions cure at ambient temperatures and baking is not required. Therefore, the compositions can be used on large structures such as chemical storage tanks, chemical reactors the interior of smoke stacks and the like which could not be subjected to baking temperatures using conventional techniques. Typical coating composition contains about 10-70% by weight binder and 30-90% by weight of an organic solnen,, in which the binder is a fluorocarbon polymer of vinylidene fluoride and hexafluoropropylene and has a weight average molecular weight of about 50,000,600,000 and a metallic oxide such as magnesium oxide which is an acid acceptor and the curing agent. Usually the composition contains a reinforcing pigment such as titanium dioxide or carbon black. The fluorocarbon polymer used in the coating composition contains about 50-70% by weight of vinylidene fluoride and 30-50% by weight of hexafluoropropylene. The polymer can contain up to 40% by weight of other maxrExs such as tetrafluoroethylene. One uve ful polymer contains out 20-30% by weight of tetrafluoroethylene; Preferably, fluorocarbon polymers are used that have a weight average molecular weight of about 75,000-450,000. Fluorocarbon polymers having a weight average molecular weight of 50,000300,000 are useful. Two particularly useful fluoro carbon polymers have weight average molecular weight of about 75,000-125,000 and 150,000-250,000. Polymers in the lower end cf the molecular weight range are preferred for forming a composition with higher binder content. Fluorocarbon polymers in the higher molecular weight range of 300,000-450,000 are also very useful for forming coating compositions. Molecular weight, as used herein, is determined by gel permeation chromatography using polymethyl methacrylate as a standard. A metallic oxide which is an acid acceptor is used in the composition t react with the hydrofluoric acid which is generated during the curing or crosslink.g reaction. Typical liit oxides are magnesium oxide, lead dioxide, calcium size, lead hydrogen phosphite and a mixture == calcim oxide ana magnesium oxide. Magnesium oxide is preferred. Highly purified magnesium oxide is particularly preferred for high quality finishes. Generally, the binder of a coating composition contains about 55-90% by weight, of the fluorocarbon polymer, 0.5-25% by weight of one of the above amine curing agents and 5-20% by weight of a metallic oxide which is an acid acceptor. The coating composition also can contain dispersed fluorocarbon polymers such as polytetrafluoroethylene, fluorinated ethylene/ propylene polymers, polyvinyl fluoride, polyvinylidene fluoride, copolymer of tetrafluoroethylene/perfluoro- alkoxy vinyl ether and the like. These dispersed fluorocarbon polymers are present in amounts of about 5-208 by weight, based on the weight of the binder of the composition and have a particle size of about 1-150 microns. A soluble low molecular weight fluorocarbon polymer of vinylidene fluoride and hexafluoropropylene having a weight average molecular weight of about 5,000-15,000 can be used in combination with a higher molecular weight fluorocarbon polymer of vinylidene fluoride and hexafluoropropylene. This low molecular weight polymer aids in dispersing pigments and the dispersed fluorocarbon polymer and forms films of 1000 microns and above without cracking of the coating on curing. - Coating compositions that contain the above low molecular weight fluorocarbon polymer have a binder containing about 50-84.5% by weight, of the solution fluorocarbon polymer, 5-20% by weight of a low molecular weight fluorocarbon polymer, 5-20% by weight of dispersed fluorocarbon polymer , 0.5-20% by weight of one of the above amine curing agents and 5-20% by weight of a metallic oxide which is an acid acceptor such as magnesium oxide. Typical organic solvents that are used in the coating composition are acetone, tetrahydrofuran, methyl ethyl ketone, ethyl acetate, propyl acetate, butyl acetate, isobutyl acetate, methyl isobutyl ketone, methyl amyl acetate, diisobutyl ketone, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether and mixtures of the above. These solvents are used to make the compositions and can be used to reduce the compositions to an application viscosity. Preferably, the coating composition contains a reinforcing agent such as titanium dioxide pigment usually in a pigment to binder weight ratio of about 20:100 to 200:100. Other inert pigments can be used such as barytes, barium sulfate, fibrous calcium silicate and the lwke. Carbon black, bone black or lamp black can also be used as a reinforcing pigment in a pigment to binder weight ratio of about 20:100 to 5:130. To decrease curing time and increase toughness of the resulting finnish of the coating composition about 0,01-3 by weight based on the weight of the binder, of z bicyclic amidine can be added. One preferred b oyclyic amidine is ,8-diaza-bicscloti,4,0)ur.-ecene-7. To improve resistance to acids at ambient temperatures and elevated temperatures of finishes formed by the composition about 1-20% by weight, based on the weight of the binder, of a perfluoroalkylpropylene oxide can be added. The perfluoroalkylpropylene oxide has the formula EMI7.1 where R4 is a perfluoroalkyl group having 4-12 carbon atoms. Preferably, R4 is a perfluoroalkyl group of a mixture of 6-10 carbon atoms. Preferably, about 5-15% by weight based on the weight of the binder, of the perfluoroalkylpropylene oxide is added. Other advantages of the perfluoroalkylpropylene oxide are as follows: the surface tension of the coating is lowered and the resulting finish has improved release characteristics in comparison to finishes that do not contain the perfluoroalkylpropylene oxide; the wetting of pigments is improved and makes dispersion of pigments less difficult and fluorocarbon polymer solids of the composition can be increased. A combination of the aforementioned bicyclic amidine and the perfluoroalkyl propylene oxide allows the removal of the metallic oxide from the coating composition and still provides a composition that cures at ambient temperatures. Generally, about 1-10t by weight, based on the weight of binder, of the combination is used. The weight ratio of bicyclic amidine to perfluoroalkylpropylene oxide is about 1:1 to 1:5. To improve flow of the coating composition and enhance smoothness of the resulting finish about 1-20% by weight, based on the weight of binder, of a glycidyl ester can be added to the composition. Preferably, about 5-158 by weight of glycidyl ester is used. The ester has the formula EMI8.1 where R5 is a tertiary aliphatic hydrocarbon group having 8-10 carbon atoms. Generally, the coating composition is sold in two components. The solvents, fluorocarbon polymer, pigments such as titanium dioxide and metallic oxide acid acceptor are the first component and the amine curing agent is the second component. The second component is blended with the first component by the user to form a coating composition. The composition is then reduced with one of the aforementioned solvents ts an application viscosity and then applied to a substrate. The coating composition can be applied directly over a wide variety of substrates and provide a fluorocarbon polymer coating. Typical substrates are treated or primed steel, phosphatized steel, grit blasted steel, galvanized steel, aluminum, copper, brass, cement and cementitious surfaces such as fire brick, mortar used for fire brick and the like. The coating composition is sprayed applied to the substrate and the solvent is allowed to flash off between coatings then the resulting coating composition is cured at ambient temperatures. The coating can be cured in about 4 to 48 hours or longer or can be heated to 80"C to 1200C for 0.5 to 2.0 hours for rapid curing. Cured coatings are about 75-1500 microns thick. For some substrates such as untreated steel, a fluorocarbon primer is first applied and then while the primer is still wet the coating composition is applied and dried at ambient temperatures or at the above elevated temperatures. One useful primer contains the aforementioned fluorocarbon polymer of hexafluoropropylene and vinylidene fluoride, a metallic oxide acid acceptor such as magnesium oxide and an aminoalkyly-alkoxy silane such as amino-propyl trimethoxysilane or amino-propyl triethoxysilane. The ambient curing characteristics of the coating composition provided by the novel curing agent of this invention allows for the application of coatings on large vessels and reactors in chemical plants, and oil refineries, large structures and equipment and pipes, heat risers, i.e., pipes which are used to transport oil from the underground well to the structure, off shore oil well platforms, and on the interior of smoke stacks used by large utiiity companies. It is practical to use compositions that cure at ambient temperature for the above applications. The following examples illustrate the invention. All parts and percentages are on a weight basis unless otherwise indicated. Example 1 A curing agent was prepared by charging the following constituents into a reaction vessel equipped with a stirrer, a heating mantel and a condenser: Parts bv Portion 1 t Weight Isophorone diamine 535.5 Portion 2 methyl maleate l440 Portion 3 Isopropanol 516.0 Total 1195.5 Portion 1 was charged into the reaction vessel and heated to about 1200C and then portion 2 was added at a uniform rate over a 4 hour period while the temperature was held at 1300C and methanol was removed from the vessel. After the 4 hour period heating was stopped and a sample was removed and tested in an infrared spectrophotometer which showed the reaction was complete. Then portion 3 was added to give a 55% solids solution. About 5 parts of the above curing agent was added to about 300 parts of each of the following coating compositions: Coating Composition A Fluorocarbon polymer solution containing 33% solids in ethyl acetate, of a copolymer of 40% hexafluoropropylene and 608 vinylidine fluoride having a weight average molecular weight of about 100,000 and about 5% by weight magnesium oxide. Coating Composition B Fluorocarbon polymer solution identical to composition A except the copolymer has a molecular weight of about 200,000. Coating ComDositzon C Fluorocarbon polymer solution identical to composition A except the composition contains additionally about 25% by weight of finely divided polyvinylidine fluoride. Each composition was diluted with methyl ethyl ketone to a spray viscosity and sprayed onto aluminum and steel panels to form a coating having a dry film thickness of about 1000 microns. After drying under ambient temperature conditions for 7 days, each of the coatings is resistant to sulfuric acid, sodium hydroxide, steam and methyl ethyl ketone which indicates that the coatings were fully cured and crosslinked. Example 2 The following amine curing agents were prepared: CURING AGENT Parts by Weight D E F G Isophorone diamine 510 - 562 exethylene diamine 321 - 388 Trimethyol propLe acrylate 296 296 - Pentaerythritol acrylate - - 298 298 Isopropanol 659 505 703 562 Total 1465 1122 1563 1248 In the preparation of each of the above curing agents D-G, the amine was charged into a reaction vessel and heated to 120-1400C and then the acrylate was slowly added at a uniform rate over a 4 hour period and then the reaction mixture was cooled and isopropanol added. Trimethylol propane acrylate and entaerythritol acrylate were prepared by conventional techniques well known to the skilled in the art in which an acrylate moiety was attached to trimethylol propane and with pentaerythritol. Separate coating compositions were prepared with each of the curing agents D-G using the seme constituents as in Example 1 for the coating composition A except the above curing agent was substituted for the curing agent of Example 1. In each case the resulting coating camposition was reduced to a spray viscosity with methyl ethyl ketone as in Example 1 and sprayed onto grit blasted steel panels allowing the coating to flash dry between each application to provide a 1000 micron thick dry coating. After 7 days, te coatings were fully cured but were softer and more elastic than the coating of Example 1. The coatings were resistant to sulfuric acid, sodium hydroxide and methyl ethyl ketone. FM?LE 3 A coating composition was prepared as follows: Portion 1 Parts by Weight Fluorocarbon polymer 1744.15 solution (33.3% solids in ethyl acetate of a copolymer of 60% vinylidene fluoride and 40% hexafluoropropylene having a weight average molecular weight of about 400,000) Barytes pigment 580.79 Carbon black pigment 0*60 Magnesium oxide 87.19 Perfluoroalkylpropylene oxide 29.06 of the forrrula EMI13.1 R is a mixture of perfluoroalkyl group of 1z 4, 48.5% C61 34.08 C81 12.0% C10, 2.5% C12 and 2% C14. Butyl acetate 1158.21 Portion 2 Amine curing agent solution 49.15 (prepared in Example 1) Total 3649.15 The constituents of portion 1 were charged into a mixing vessel and blended and charged into a ball mill and ground to thoroughly disperse the pigments. Portion 2 was added and blended. The resulting composition was reduced with methyl ethyl ketone solvent to a spray viscosity of about 25 seconds using a No. 2 Zahn cup and sprayed onto grit blasted steel panels and aluminum panels. In each case, thick films were applied by allowing flash drying between each application and the coatings were dried at ambient temperature in 24 curs to a tack free condition to provide a 1000 micron thick dry coating. In each case, the coating had excellent adhesion to the metal substrate. After 7 days, the coatings were fully cured and were resistant to sulfuric acid, sodium hydroxide and solvents such as methyl ethyl ketone and ethyl acetate. EXAMPLE 4 A pigment dispersion was prepared a. follows Parts by Weight Fluorocarbon polymer 1890.0 solution (described in Example 3) Titanium dioxide pigment 630.O Butyl acetate 1080.0 Total 3600.0 The above constituents were charged into a ball mill and ground to thoroughly disperse the pigment. A coating composition was prepared by thoroughly blending together the following constituents: Parts by Weight Pigment dispersion (prepared 971.4 above) Perfluoroalkylpropylene oxide 30.0 (described in Example 3) Aznine curing agent solution 6.0 (prepared in Example 1) Bicyclic amidine solution(10% 2.0 solids in butyl acetate of 1,8- diaza bicyclo(5,8,0)-undecene-7) Total 1009.4 The resulting composition was reduced with methyl ethyl ketone solvent to a spray viscosity of about 37 seconds using a No. 2 Zahn cup and sprayed onto grit blasted steel panels and aluminum panels. n each case, thick films were applied by allowing flash drying between each application and the coatings were dried at ambient temperature in 24 hours to a tack free condition to provide a 1000 micron thick dry coatings. In each case, the coating had excellent adhesion to the metal substrate. After 7 days, the coatings were fully cured and were resistant to sulfuric acid, sodium hydroxide and solvents such as methyl ethyl ketone and ethyl acetate. Example 5 A pigment dispersion was prepared as follows: Parts by Weight Fluorocarbon polymer 1890.0 solution (described in Example 3) Titanium dioxide pigment 630.0 Magnesium oxide 31.5 Bu-yl acetate 1138.5 Total 3690.0 The above constituents were charged into a ball mill and ground to thoroughly disperse the pigment. A coating composition was prepared by thoroughly blending together the following constituents: Parts by Weight Pigment dispersion 527.2 (prepared above) Perfluoroalkyloropylene oxide 10.0 (described in Example 3) Amine curing agent solution 3.0 (prepared in Example 1) Bicyclic amidine solution 1.0 (described in Example 4) ¯¯¯¯¯¯¯¯¯ Total 541.2 The resulting composition was reduced with methyl ethyl ketone solvent to a spray viscosity of about 37 seconds using a No. 2 Zahn cup and sprayed onto grit blasted steel panels and aluminum panels. In each case, thick films were applied by allowing flash drying between each application and the coatings were dried at ambient temperature in 24 hours to a tack free condition to provide a 1000 micron thick dry coating. In each case, the coating had excellent adhesion to the metal substrate. After 7 days, the coatings w.re fully cured and were resistant to sulfuric acid, sodium hydroxide and solvents such as methyl ethyl ketone and ethyl acetate. EXAMPLE 6 A coating composition was prepared by thoroughly blending together the following constituents: Parts by Weight Pigment dispersion 527.2 (prepared in Example 5) "Casduraw E Ester 10.0 (glycidyl ester of the formula EMI16.1 where R5 is a tertiary aliphatic hydrocarbon group of 8-10 carbon atoms) Amine curing agent solution 3.0 (prepared in Example 1) Bicyclic amidine solution 1.0 (described in Example 4) ¯¯¯¯¯¯¯¯ Total 541.2 The resulting composition was reduced with methyl ethyl ketone solvent to a spray viscosity of about 37 seconds using a No. 2 Zahn cup and sprayed onto grit blasted steel panels and aluminum panels. In each case, thick films were applied by allowing flash drying between each application and the coatings were dried at ambient temperature in 24 hours to a tack free condition to provide a 1000 micron thick dry coating. In each cas the coating was very smooth and had excellent adhesion to the metal substrate. After 7 days, the coatings were fully cured and were resistant to sulfuric acid, sodium hydroxide and solvents such as methyl ethyl ketone and ethyl acetate. E3VIMPLE 7 A coating composition was prepared by blending together the following constituents: Parts buy Weight Pigment Dispersion 527,2 (prepared in Example 5) "Cardura" E Ester 5.0 (described in Example 6) Perfluoroalkylpropylene oxide 5.0 (described in Example 3) Amine curing agent solution 3.0 (prepared in Example 1) Bicyclic amidine solution 1.0 (described in Example 4) ¯¯¯¯¯¯¯ Total 541.2 The resulting composition was reduced with methyl ethyl ketone solvent to a spray viscosity of about 37 seconds using a No. 2 Zahn cup and sprayed onto grit blasted steel panels and aluminum panels. In each case, thick films were applied by allowing flash drying between each application and the coatings were dried at ambient temperature in 24 hours to a tack free condition to provide a 1000 micron thick dry coating. In each case, the coating was very smooth and had excellent adhesion to the metal substrate. After 7 days, the coatings were fully cured and were resistant to sulfuric acid, sodium hydroxide and solvents such as methyl ethyl ketone and ethyl acetate. EXAMPLES A coating composition was prepared as follows: Portion 1 Parts by Weight Flourocarbon polymer 638.12 solution (33.3% solids in ethyl acetate of a copolymer of 60b vinylidene fluoride and 40% hexafluoropropylene having a weight average molecular weight of about 400,000) Perfluoroalkyl propylene oxide 12.50 of the formula EMI18.1 R4 is a mixture of perfluoroalkyl group of 1% C4, 48.5% C6, 34.0% C8, 12.0% C10, 2.5% C12 and 2% C14. wCardura E Ester 12.50 (glycidyl ester of the formula EMI18.2 where R5 is a tertiary aliphatic hydrocarbon group of 8-10 carbon atoms) Titanium dioxide pigment 125.00 Magnesium Oxide(99.6% pure) 12.50 Blanc Pixe Pigment (Barium sulfate) 112.50 Methyl ethyl ketone 18.44 Butyl acetate 18.44 Portion 2 Bicyclic amidine solution (10% 2.50 solids in isopropanol of 1,8- diazabicyclo (5,4,0) undecene -7) Curing agent P (prepared in 25.00 Example 2) Isopropanol 22.50 Total 1000.00 Portion 1 is charged into a pebble mill and ground to a 0.5 mil fineness and charged into a mixing vessel and then portion 2 is added and mixed with portion 1 for to form a coating composition. The resulting composition was reduced with methyl ethyl ketone solvent to a spray viscosity of about 37 seconds using a No. 2 Zahn cup and sprayed onto grit blasted steel panels and aluminum panels. In each case, thick films were applied by allowing flash drying between each application and the coatings were dried at ambient temperature in 24 hours to a tack free conditition to provide a 1000 micron thick dry coating. In each case, the coatings had excellent adhesion to the metal substrate. After 7 days, the coatings were fully cured and were resistant to sulfuric acid, sodium hydroxide and solvents such a methyl ethyl ketone and ethyl acetate. EXAMPLE 9 Coating compositions 1-10 were preared using the constituents shown in the attached Table. For each composition, the constituents of portion 1 were charged into a mixing vessel and thoroughly blended and portion 2 was added and blended. The resulting composition was reduced with methyl ethyl ketone solvent to a spray viscosity of about 25 seconds using a No. 2 Zahn cup and sprayed onto grit blasted steel panels and aluminum panels. In each case, thick films were applied by allowing flash drying between each application and the coatings were dried at ambient temperatures. The resulting dry coatings were a 1000 microns thick. In each case, the coatings from compositions 1-10 had excellent adhesion to the metal substrate. After 7 days, each of the coatings of compositions 1-10 were fully cured and were resistant to sulfuric acid, sodium hydroxide and solvents such as methyl ethyl ketone and ethyl acetate. TABLE EMI20.1 <SEP> 1 <SEP> ,111 <SEP> 8 <SEP> 10 <tb> II <SEP> Co.po.ition <SEP> I <SEP> I <SEP> By <SEP> I <tb> c <SEP> 1 <tb> <SEP> Ti <SEP> tent-n <SEP> dioxide <SEP> pii-t <SEP> 100 <tb> <SEP> h <SEP> oxide <SEP> 15 <tb> <SEP> Fluorocarbon <SEP> polymer <SEP> solution <SEP> 1M.5 <SEP> 151.5 <SEP> 151.5 <SEP> 151.5 <SEP> 151.5 <SEP> - <SEP> - <SEP> - <SEP> - <SEP> <tb> <SEP> Y <SEP> in <SEP> Example <SEP> I <SEP> polymr <tb> <SEP> s; <SEP> weigli <SEP> average <SEP> mo1eculr <tb> <SEP> " <SEP> of <SEP> 100,000) <tb> <SEP> ?luorocarbon <SEP> po1r <SEP> solutions <SEP> - <SEP> - <SEP> - <SEP> - <SEP> 151.5 <SEP> 151.5 <SEP> 151.5 <SEP> 151.5 <SEP> 151a5 <tb> <SEP> (S-c <SEP> as <SEP> F.xample <SEP> 1 <SEP> except <SEP> poly <tb> <SEP> mer <SEP> has <SEP> a <SEP> veiht <SEP> a"eraee <SEP> nolecular <tb> <SEP> C <SEP> of <SEP> 200,000) <tb> <SEP> Low <SEP> molecular <SEP> weight <SEP> fluorocarbon <SEP> 25 <tb> <SEP> guy <SEP> vinylidine <SEP> I <SEP> IN <tb> <SEP> rh <SEP> hexafluoropropytene <SEP> having <SEP> a <tb> <SEP> C <SEP> average <SEP> molecular <SEP> weight <tb> <SEP> of <SEP> 6400) <tb> <SEP> I <SEP> 25 <SEP> - <SEP> - <SEP> - <SEP> - <SEP> 25 <SEP> - <SEP> - <SEP> - <SEP> <tb> <SEP> vinyl <SEP> q'thtr <SEP> io,nlyr <SEP> (Q73 <SEP> ritir') <tb> <SEP> Polytetrsfluoroethviene <SEP> - <SEP> 25 <SEP> - <SEP> - <SEP> - <SEP> - <SEP> 25 <SEP> - <SEP> - <SEP> <tb> <SEP> Fluorinated <SEP> ethyleneipropylene <SEP> polymer <SEP> - <SEP> - <SEP> 25 <SEP> - <SEP> - <SEP> - <SEP> - <SEP> 25 <SEP> - <SEP> <tb> <SEP> Polyvinyl <SEP> fluoride <SEP> - <SEP> - <SEP> 25 <SEP> - <SEP> - <SEP> - <SEP> - <SEP> 25 <SEP> <tb> <SEP> ¯1 <SEP> rluoride <SEP> , <SEP> . <SEP> - <SEP> 25 <SEP> . <SEP> . <SEP> . <SEP> - <SEP> 25 <tb> <SEP> Fthyl <SEP> 50 <tb> Portion <SEP> 2 <tb> <SEP> t <SEP> - <SEP> <tb> <SEP> xap1e <SEP> I) <tb> <SEP> Slcvclic <SEP> itdine <SEP> (nesribed1n <SEP> P.xapleA) <SEP> Ï <SEP> b <tb> <SEP> C <SEP> -U <SEP> t <SEP> g <SEP> C <SEP> s <SEP> s <SEP> t <tb> <SEP> E <SEP> . <SEP> *, <SEP> o <SEP> e <SEP> - <SEP> c <SEP> e <SEP> g <SEP> g <SEP> g <SEP> > <SEP> > <SEP> o <SEP> e <SEP> fi <SEP> D <SEP> s <tb> <SEP> &verbar; <SEP> s <SEP> D <SEP> D <SEP> g <SEP> o <SEP> I <SEP> &verbar; <SEP> 0 <SEP> : <SEP> X <SEP> X <SEP> W <SEP> &commat; <SEP> E <tb> <SEP> i <SEP> o <SEP> c. <SEP> é <SEP> ,9 <SEP> e <SEP> <SEP> g <SEP> o <SEP> W <SEP> e <SEP> <SEP> tW <SEP> ol <SEP> e <SEP> [ <SEP> F <tb> EXAMPLE 10 Coating compositions 11-13 were prepared as follows: Coating Composition 11 12 13 (Parts ty Weight) Portion 1 Polytetrafluoroethylene 56.25 Powder Fluorinated ethylene/ - 56.25 propylene powder Polyvinylidene Fluoride - - 56.25 Powder Fluorocarbon polymer 430.74 430.74 430.74 solution (33.38 solids in ethyl acetate of a copolymer of 60% vinylidene fluoride and 40% hexafluoropropylene having a weight average molecular weight of about 400,000) Perfluoroalkylpropylene oxide 8.44 8.44 8.44 of the formula EMI21.1 R4 is a mixture of perfluoroalkyl group of 1% C4, 48.5% C6, 34.0% C8, 12.0% C10, 2.5% C12 and 2% C14. "Cardura" E Ester 8.44 8.44 8.44 (glycidyl ester of the formula EMI21.2 where R5 is a tertiary aliphatic hydrocrabon group of 8-10 carbon at=E) Titanium Dioxide Pigment 213.75 213.75 213.75 Magnesium Oxide (99.68 pure) 8.44 8.44 8.44 Butyl acetate 112.21 112.21 112.21 Methyl ethyl ketone 111.73 111.73 111.73 Coating Composition Portion 2 11 12 13 Bicyclic amidine Solution 16.87 16.87 16.87 (10% solids in isopro panol of bicyclic amidine described in Example 4) Amine Curring Agent 15.35 15.35 15.35 (prepared in Example 1) Isopropanol 17.78 17.78 17.78 Total 1000.00 1000.00 1000.00 For each coating composition Portion 1 was charged into a pebble mill and ground to a fineness of 0.5 mils. Portion 2 was then mixed with Portion 1 to forzn a coating composition. The resulting composition was reduced with methyl ethyl ketone to a spray viscosity of about 25 seconds using a No. 2 Zahn cup and sprayed onto grit blasted steel panels and aluminum panels. In each case, thick films were applied by allowing flash drying between each application and the coatings were dried at ambient temperatures. The resulting dry coatings were a 1000 microns thick. In each case, the coatings from compositions 11-13 had excellent adhesion to the metal substrate. After 7 days, each of the coatings of composition ll-13were fully cured and were resistant to sulfuric acid, sodium hydroxide and solvents such as methyl ethyl ketone and ethyl acetate.

Claims: CLAIMS 1. A curing agent for fluorocarbon polymers selected from the group consisting of EMI23.1 wherein R is R1NH21 R1is an aliphatic or cycloaliphatic hydrocarbon radical, R is C or a hydrocarbon group, R3 is H or CH3, where x is 3 when R2 is a hydrocarbon group and x is 4 when R2 is C. 2. The curing agent of claim 1 in which R1 is (-CH2-)6. 3. The curing agent of claim 1 having the formula: EMI24.1 4. The curing agent of claim 1 having the formula EMI24.2 where R is a cycloaliphatic radical and R2 is a hydrocarbon group. 5. The curing agent of claim 1 having the formula EMI24.3 where R is cycloaliphatic radical. 6. The curing agent of claim 4 or claim 5 in which R is EMI25.1 7. A coating composition containing a binder of a fluorocarbon polymer, a metallic oxide which is an acid acceptor and a curing agent as claimed in any preceding claims. 8. The composition of claim7 containing about 0.01-3 percent by weight, based on the weight of the binder, of a bicyclic amidine. 9. The composition of claim 8 in which the bicyclic amidine is 1,8-diaza-bicyclo- (5,4,0)undecene-7. 10. A composition as claimed in any one of claims 1 to 9 and comprising about 10-70% by weight binder and 30-90% by weight of an organic solvent; wherein the fluorocarbon polymer in the binder comprises vinylidene fluoride and hexafluoropropylene and has a weight average molecular weight of about 50,000 -600,000. 11. The composition of claim 10 containing in addition about 1-20% by weight, based on the weight of the binder, of a perfluoroalkypropylene oxide. 12. The composition of claim 11 in which the perfluoroalkylpropylene oxide has the formula EMI25.2 where R4 is a perfluoroalkyl group having 4-12 carbon atoms. 13. The composition of any one of claims 10 to 12, containing in addition about 1-20% by weight, based on the weight of the binder, of a glycidyl ester of the formula EMI26.1 where R5 is a tertiary aliphatic hydrocarbon group having 8-10 carbon atoms. 14. A composition as claimed in any one of claims 10 to 13 wherein the composition is a twocomponent composition where a first component consisting of the metallic oxide and a solution of the fluorocarbon polymer is mixed with the curing agent. 15. A coating composition as claimed in any one of claims 10 to 14 wherein the binder comprises a fluorocarbon polymer in solution comprising vinylidene fluoride and hexafluoropropylene and having a weight average molecular weight of about 5,000-600,000, dispersed fluorocarbon polymer particles having a particle size of about 1-150 microns and selected from polytetrafluoroethylene, fluorinated ethylene/propylene polymer, polyvinyl fluoride, polyvinylidene fluoride and a copolymer of tetrafluoroethylene/perfluoroalkoxyvinylether; a metallic oxide which is an acid acceptor; and a curing agent of either of the formulae (1) and (2) set forth and defined in claim 1, and wherein the organic solvent is a non-aqueous organic liquid. 16. The coating compodition of claim 15 in which the binder comprises: (a) 50-84.5% by weight of a fluorocarbon polymer in solution consisting essentially of polymerized units of 50-70% by weight, based on the weight of the polymer, of vinylidene fluoride and 30-50% by weight, based on the weight of the polymer, of hexafluoropropylene and has a weight average molecular weight of about 75,000-450,000. (b) 5-20% by weight of a low molecular weight fluorocarbon polymer in solution consisting essentially of polymerized units of 50-70% by weight, based on the weight of the polymer, of vinylidene fluoride and 30-50 by weight, based on the weight of the polymer, of hexafluoropropylene and has a weight average molecular weight of about 5,000-15,000; (c) 5-20% by weight of dispersed fluorocarbon polymer selected from polytetrafluoroethylene fluorinated ethylene/propylene polymer, polyvinylfluoride, polyvinylidene fluoride and copolymer of tetrafluoroethylene/perfluoroalkoxyvinylether. (d) 5-20% by weight, based on the weight of the binder, of magnesium oxide; and (e) 0.5-20% by weight, based on the weight of the binder,of either (i) a curing agent of the formula: - EMI27.1 or (ii) a curing agent of the formula (2) set forth in claim 1, wherein R2 is C or C3H5, R3 is H and R is EMI27.2 17. The coating composition of claim 16 containing titanium dioxide pigment in a pigment to binder weight ratio of about 20:100-200:100. 18. The coating composition of any preceding claim containing about 0.1-3% by weight, based on the weight of a bicyclic amidine. 19. A coating composition comprising about 10-70% by weight binder and 30-90X by weight of a nonaqueous organic liquid; wherein the binder comprises; a fluorocarbon polymer in solution comprising vinylidene fluoride and hexafluoropropylene having a weight average molecular weight of about 5,000-600,000; dispersed fluorocarbon polymer particles having a particle size of about 1-150 microns and being selected from polytetrafluoroethylene, fluorinated ethylene/propylene polymer, polyvinyl fluoride, polyvinylidene fluoride, and copolymer of tetrafluoroethylene/perfluoroalkoxy vinyl ether; a curing agent of the formula: EMI28.1 where R is R1NH2 and R1 is aliphatic or cycloaliphatic hydrocarbon radical; perfluoroalkylpropylene oxide; and a bicyclic amidine. 20. A coating composition comprising about 10-70% by weight binder and 30-90% by weight of a nonaqueous organic liquid; wherein the binder comprises: a fluorocarbon polymer in solution comprising vinylidene fluoride and hexafluoropropylene having a weight garage molecular weight of about 5,000 - 600,000. dispersed fluorocarbon polymer particles having a particle size of about 1-150 microns and being selected from the group consisting of polytetrafluoroethylene, fluorinated ethylene/propylene polymer, polyvinyl fluoride, polyvinylidene fluoride, copolymer of tetrafluoroethylene/perfluoroalkoxyvinyl ether; a curing agent of the formula: EMI29.1 where R is a cycloaliphatic hydrocarbon radical, R is H or Ch3, X is 3 when Rê is a hydrocarbon group and X is 4 when Rê is C; perfluroalkylpropylene oxide; and a bicyclic amidine. 21. A composition as claimed in any preceding claim containing about 5-15% by weight, based on the weight of the binder, of perfluoroalkylpropylene oxide. 22. A compound comprising EMI29.2 wherein R is R1NH2, R1 is an aliphatic or cycloaliphatic hydrocarbon radical. 23. A compound comprising EMI29.3 wherein R is R1NH2, R1 is an aliphatic or cycloaliphatic hydrocarbon radical, R2 is C or hydrocarbon group, R3 is H or CH3, where X is 3 when R2 is a hydrocarbon group and X is 4 when R2 is C.

Inventors: VASTA, JOSEPH ANTHONY
Applicants: E.I. DU PONT DE NEMOURS AND COMPANY
Application year: 1984
Main classification: C07C103
IPC codes: C08K5, C08L79, C07C233, C09D127