EPOXY ESTER URETHANE GRAFT ACRYLIC WATER-BASED PRIMER SURFACES

Abstract: Dispersion of an epoxy ester urethane graft acrylic in water with a total of no more than 5 % of organic volatiles and amines. These dispersions can be used in primer compositions for metal substrates having a minimum of organic solvent emissions and which can crosslink at temperatures from 140-200 DEG C, giving a good balance of hardness, flexibility, humidity, corrosion resistance and anti-chipping properties.

Description: Epoxy Ester Urethane Graft Acrylic Water-Based Primer Surfaces CROSS REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part application of Serial No. 901.567, filed August 29, 1986. BACKGROUND This invention relates to epoxy ester urethane polymers having acrylic portions grafted thereto. More particularly, it relates to coating compositions containing such polymers. U.S. Patent 4.302.373 - Steinmetz (Nov. 24, 1981) describes water-borne coating compositions of epoxy resin, polymeric acid and tertiary amine, wherein the epoxy functionality is partially capped with a carboxylic acid polymer to form a hydrogel. Coating compositions made therefrom are taught for use in can coatings and for automotive and paper coatings. An acetic acid-neutralized aqueous polyaminoamido resin made using dimeric fatty acids is disclosed in European Patent Application Publication 60581 of September 22, 1982 - Guenter et al. (Akzo). Epoxy graft acrylic water-based primer surfacers are claimed in U.S. 4,564,648, of January 14, 1986 - Huybrechts and Vlerainckx, but they do not include urethane grafts. The present invention is an improvement over this one in giving better chip resistance over well cured electrocoats. for instance. This requires a careful balance of flexibility and hardness in different portions of the polymer. Other aqueous epoxy coating compositions also outside the present invention are disclosed in U.S. Patents 4,446.258 of May 1. 1984 - Chu et al. (Mobil Oil). 4.446.260 of May 1. 1984 - Woods et al. (International Paint), and b 4.444.806 of April 24. 1984 - Morgan et al. (W. R. Grace). SUMMARY OF THE INVENTION The present invention provides a dispersion in water, in percentages by weight based on the total 1Q dispersion, of-: - - - — (a) 10-60% of an epoxy ester urethane graft acrylic polymer formed by reacting 5-30% of an epoxy ester urethane polymer formed by reaction of n moles of a difunctional epoxy resin with terminal oxirane 15 groups and a number average molecular weight (Mil) of 300-5000. n-1 moles of a diacid-functional linear urethane ester, and 2 moles of a monofunctional acid to form a reaction product, onto which is grafted 5-30% of an acrylic monomer by using a peroxide or azo initiator, to produce said epoxy ester urethane -_l*J acrylic polymer with a Mn = 1000-50.000 and an acid number of 30-150, (b) tertiary amines being added to an extent equivalent to neutralizing 50-200% of the moles of 25 acid functionality. (c) organic solvents. such dispersion having not more than 10% volatile organic solvents plus amines, and (d) balance water. 0 The epoxy ester graft acrylic polymers of (a) above, and methods of making them, are different aspects of the invention. DETAILED DESCRIPTION The present invention is made possible by a 5 new method of synthesis of an epoxy ester urethane graft acrylic polymer. The process involves the synthesis of a linear epoxy ester formed by reaction at 80-190°C of an oxirane terminated bisphenol A epoxy resin with aliphatic diacid-functional linear urethane c esters and monoacids in approximately stoichiometric proportions so that all the oxirane groups and acid groups have reacted. The reaction is done in a minimum amount of an organic solvent, preferably aromatic for ease of stripping, preferably using a small percentage of a tertiary araine as catalyst. In - a second stage an acid functional acrylic is grafted onto the epoxy ester urethane using a peroxide or azo initiator. Grafting onto the epoxy ester urethane is believed to go via hydrogen abstraction of activated carbon-hydrogen bonds. In a third stage the acid functionality on the epoxy ester urethane is neutralized with a tertiary amine (50-200% neutralization), the polymer is dispersed in deionized water and the excess organic solvents are distilled off. These epoxy ester urethane acrylic dispersions then contain a minimum of organic solvents, so as to be able to formulate primer compositions, preferably with no more than 5% organic volatiles, including amines. When combined with water soluble or dispersible crosslinlcers, like hexamethoxymethylmelamine, pigments and extenders, primer surfacers can be formulated which show good corrosion resistance over bare steel, an excellent balance of hardness, flexibility, improved anti-chipping properties, good topcoat hold-out and appearance. These primer surfacers can be baked for 30 min at from 160°C to 200°C. still retaining their basic properties. The primers can be applied by conventional or electrostatic spraying. To further improve application and flow properties, rheology control agents and flow agents can be used. Silica or clay pastes are quite successful for rheology control to prevent pinholing and sagging, and water soluble or dispersible linear or branched polyethylene glycols or polypropyleneglycols are efficient for flow properties. The primer surfacers show excellent initial and wet—adhesion over bare steel and cathodic electrodeposited primers. Adhesion and hold-out of conventional topcoats (polyester, alkyd. acrylic) is very good over broad temperature ranges. Hold-out is the resistance to interpenetration at the interface between the layers of primer surfacer and topcoat applied in organic solvents. In the scope of the invention and the teachings of the examples, more or less equivalent substitutions for various ingredients can be made as follows. The lists ate illustrative and not complete. Alternatives for isocyanate: hexamethylene diisocyanate HDI isophorone diisocyanate IPDI hydrogenated bisphenyl methane HPMDI diisocyanate trimethyl hexane diisocyanate TMHDI toluene diisocyanate TDI bisphenyl methane diisocyanate PMDI m or p xylylenediisocyanate m or p XDI Alternatives for glycols: ethylene glycol EG propylene glycol DG 1,4 or 1.3 butane diol 1.4 or 1.3 BD neopentyl glycol NPG hexanediol HD trimethyl pentane diol TMPD polyethylene glycols(various MW) PEG polypropylene glycols(various MW) PPG cyclohexane dimethanol CHDM hydrogenated bisphenol A HBPA hydrogenated bishphenol F HBPF Alternatives for anhydrides: succinic anhydride SA maleic anhydride MA phthalic anhydride- PA tetrahydro phthalic anhydride THPA hexahydro phthalic anhydride HHPA methyl hexahydro phthalic MHHPA anhydride Alternative for graft monomers: reaction product of acrylic acid with equimolar Cardura E (glycidyl ester of versatic acid product of Shell.) methyl, ethyl, butyl, isobutyl. ethylhexyl and lauryl methacrylates and acrylates AA-^Cardura E MMA, EMA. BMA. IBMA. EHMA and MA. EA. BA. IBA. EHA. LA styrene S vinyl toluene VT hydroxy ethyl, hydroxy propyl, and hydroxy butyl methacrylates and acrylates HEMA. HPMA. HBMA. HEA. HPA and HBA Acrylic acid, methacrylic acid, B-carboxyethyl acrylate AA. MAA AND BCEA maleic acid MA fumaric acid FA 2-acylamido 2-methypropane sulfonic acid AMPS methacryloxyethyl phosphate MOP N-methylolacrylamide.N-butoxy methylolacrylamide and N-methoxy methylolacrylamide MAAM. BMAAM and MMAM acrylaraide and methacrylamide AM and MAM The following are examples describing manufacture of epoxy ester urethane graft acrylic dispersions. Parts, proportions and percentages are by weight except where indicated otherwise. EXAMPLE 1 Epoxy Ester Urethane Propolymer Into a 6L flask equipped with a thermometer. stirrer. condenser, nitrogen inlet and dropping funnel, are introduced in parts by weight: toluene(T) 150 NPG 832 Water is removed azeotropically by refluxing 60 min. with a water separator, then switch to direct reflux in a nitrogen atmosphere, and add: HDI 1176 T 52 over 30 min. refluxing until free isocyanate has disappeared, as determined by infrared (IR) techniques. Then add: SA 200 dimethylcyclohexylamine(DMCA) 4.4 T 17.8 Reflux until anhydride IR absorption has disappeared and the acid number (AN) is about 50. Then add: diethyleneglycolmonobutyl ether (DEBE) 385 Epon 1001 epoxy resin from Shell 1800 Diraethylolprouionic acid DMPA 268 DMCA 6 . 8 DEBE 355 Reflux until AN < 2 Then add: Isopropanol (IP) 210 to thin the product down to the desired level Example 2 Acrylic Graft on Epoxy Ester Urethane Thinned epoxyester urethane prepoly er, product of Ex. 1 1040 Heat at--slight reflux to..l20°C Then add Di-t-butylperoxide(DTBP) 2 IP 8 and start feeding over 3 hours at 120°C s 81 MMA 81 BA 445.5 HEA . 81 AA 121.5 t-butyl peroxy 2-ethylhexanoate (BPEH) 12 mercaptoethanol (ME) 3 IP 25 Then add solvent, rinsing to clean the lines DEBE 20 Hold 15 min. at reflux. Then add over 30 min. BPEH 3 DEBE 27 Rinse the lines with DEBE 10 and hold at reflux. Then strip off volatiles under vacuum. 125 Then add DMEA 127.7 Then add neutralized deionized water(DW) 3473.3 over 20 min. and disperse to produce a product with 31.1% solids and pH of 8.04. Example 3 b c Epoxy Ester Urethane Propolymer Add as indicated to reaction flask as in Ex. 1 NPG 416 T 75 Reflux to remove water azeotropically, then " add with nitrogen atmosphere dibutyltin dilaurate (DBTDL) 1.15 Then add over 30 min and hold at reflux until the isocyanate IR indication has disappeared. HDI 588 T 26 Then add and hold at a slight reflux until AN is about 50. SA 100 DMCA 2.2 τ 8 - 9 Then add and hold at reflux until AN < 2 xylene(X) 192 Epon 1001 900 DMPA 120 DMCA 3.4 X 178 Example 4 Epoxy Ester Urethane Graft Acrylic Add as in Ex. 2: Epoxy ester urethane of Ex. 3 1110 Heat at reflux to 140 - 145°C Then feed over 2 hours at reflux S 180 MMA 180 BA 36 ° HEA 72 AA 108 t-butylperbenzoate(BPB) 18 X 25 ME 5 c Then add solvent, rinsing to clean the lines b X 5 and hold for 15 min. Then feed over 45 rain. BPB 3 X . ' 7 rinsing step X 5 and hold for 45 min. Cool to 110°C. then add and mix for 15 min. DMEA 133.5 Add over 20 min and disperse DW 3200 Strip off all X and T azeotropically to give a product of 39.3% solids and pH 8.34 Example 5 Epoxy Ester Urethane Prepolymer Thinned epoxy urethane prepolymer Ex.l 1157 Heat to 120-125°C Add and heat to 135-140°C Cardura E from Shell 522.5 Feed over 3 hrs. S 182.2 MMA 182.2 AA 328.1 BPB 24.3 DEBE 25.7 Rinse lines with DEBE 20 Hold 60 min at 135-140°C to strip Low-boiling volatiles. T and IP Add over 15 min DMEA 197.6. Add over 30 min while dispersing b DW 4965.4 ' to give a product of 24.8% solids and pH8. Example 6 Epoxy ester urethane of Ex. 1 142.7 Heat to 120°C and add over 3 hrs. 0 • s 160 MMA 160 BA 280 AA 120 HEA 80 B t-butyl peroxy 2 ethyl hexanoate (BPEH) 16 ME 5 IP 20 Rinse lines with (DEGMBE) 20 0 diethyleneglycol monobutylether Feed over 30 min BPEH 4 DEGMBE 26 5 Hold for 30 min. Then strip off low boiling volatiles under vacuum Add and mix 10 min. DMEA 141 Add over 20 min. and disperse DW 4140 to obtain a product of 29.8% solids and pH 7.7 Following are examples describing manufacture of paints (with no more than 5% organic volatiles), application and properties: EXAMPLE 7 Resin dispersion of Example 2 60.93 DW 6.08 DMEA 0.29 if- Surfynol 104 E anti-fo/m anti-cratering agent 1.84. Air Products Pluriol P 900 polypropylene oxide mol. weight 900 (reactive diluent) 2.26 BASF Cymel 303 hexamethoxyxmethyl- melamine 4.20 Cyanamid Aerosil 200 fumed silica 0.87 Degussa Blanc Fixe barium sulfate .0.13 Sachtleben 30 Aluminum silicate 2.56 Titanium dioxide pigment 6.73 Carbon black 0.034 Iron oxide 0.145 Deionized water 3.941 Pigment to binder ratio (P/B) = 74.3 / 100 Binder ratio: 76.5/15.3/8.2: Resin of Example 2/ Cymel 303/Pluriol P 900. The above mixture is ground to a fineness smaller than 15μm. Next there is added deionized water to obtain a package viscosity of 100 to 150 sec DIN cup 4 at 20°C. EXAMPLE 8 The procedure of Example 7 was repeated with the exception that the resin dispersion of Example 2 was replaced by resin dispersion of Example 4. EXAMPLE 9 The procedure of Example 7 was repeated with the exception that the resin dispersion of Example 2 was replaced by the resin dispersion of Example 6. PANEL PREPARATION The products of Examples 7-9 were reduced with deionized water to a spray viscosity of 20 seconds DIN cup 4 at 20°C. The coating composition obtained was sprayed over a cataphoretic electrocoated panel at a thickness of 35 μm dry film thickness and cured at a temperature of 170°C for 25 minutes. The obtained primer film was coated with different topcoats including alkyd/melamine//acrylic//melamine color coat - clear coat resulting in excellent adhesion gloss, flow and DOI. Test results on the coating properties are given in Table I in terms of: Buchholz hardness : DIN 53153 Erichson flexibility : DIN 53156 Salt spray : DIN 50021. The rust creepage from the scribeline is measured in mm. Chip resistance: According to test procedure described in Recommended Practice SAE-J-400 of the Society of Automotive Engineers. All Examples were submitted to the humidity cabinet according to DIN 50017 for 240 hours over bare steel .and 480 hours over electrocoated panels. In neither of the tests did any blistering occur. TABLE I Salt spray over electro- over Erichson coated bare Chip Example Buchholz Flexi- panel steel Resist- No. Hardness bility 500 hrs 144 hrs ance 7 83 6.1 mm 0 mm 5 mm 7 8 95 6.0 mm 0 mm 2 mm 6 9 117 4.8 mm 0 mm 4 mm 7-8

Claims: CLAIMS 1. A dispersion in water of: (a) 10-60% of an epoxy ester urethane graft _> acrylic polymer formed by reacting 5-30% of an epoxy c b ester urethane polymer formed by reaction of n moles of a difunctional epoxy resin with terminal oxirane groups and a number average molecular weight (Mn) of 300-5,000, n-1 moles of a linear, acid terminated urethane ester prepolymer of 300-5.000 Mn. and 2 moles 10 of a monofunctional acid to form a reaction product, onto which is grafted 5-30% of an acrylic monomer by using a peroxide or azo initiator, to produce said epoxy ester acrylic polymer with a Mn = 1000-50,000 and an acid number of 30-150, , 5 (b) tertiary amines being added to an extent equivalent to neutralizing 50-200% of the moles of acid functionality, (c) organic solvents, such dispersion having not more than 10% 20 volatile organic solvents plus amines, and (d) balance water. 2. The dispersion of claim 1 with 5-20% epoxy ester urethane and 10-30% of an acrylic with acid number 60-140 in 50-80% deionized water, having 25 been azeotropically distilled to leave not more than 5% organic volatiles. 3. The dispersion of claim 1 with the epoxy ester urethane formed by reaction of n moles of a difunctional bisphenol A-based epoxy with Mϊi = 30 300-2000, and 2 moles of monofunctional acid having 2-25 carbon atoms, wherein the urethane ester prepolymer has a Mn of 1500-2000. 4. The dispersion of claim 1 with the acrylic graft formed by reaction of alkyl acrylate. 35 alkyl methacrylate. styrene. hydroxyfunctional FP-0166-A acrylates and/or methacrylates, acid functional acrylates and/or methacrylates. alkylmaleates and/or fumarates. using 0.01-10% by weight of initiator based on the acrylic content, at 60-180°C. with the acrylic ,b. having an acid number of 40-120. 5. The dispersion of claim 1 with the epoxy ester-graft acrylic having been neutralized with a tertiary amine which has a boiling point of 60-220°C. 6. The dispersion of claim 1 containing , 0-10% of a water soluble organic solvent. 7. The dispersion of claim 1 of which at least 5-15% is epoxy ester. 5-15% is acrylic graft, up to 5% is neutralizing amine plus organic solvent, and 60-80% is deionized water. 8. The dispersion of claim 1 with the epoxy ester and acrylic graft being formed in an aromatic solvent, neutralizing with the amine and the aromatic solvent distilling off. 9. The coating composition comprising Q (a) 10-40% of the epoxy ester graft acrylic polymer described in claim 1. including, up to 5% neutralizing amines plus organic solvents, and 30-80% of deionized water. B (b) 0-40% of pigments and extenders. (c) 0-20% of additives and/or reactive diluents, and (d) 0-30% of a water soluble or dispersible crosslinker. Q 10. The coating composition of claim 9 wherein the epoxy ester urethane graft acrylic polymer has at least 5-15% epoxy ester. 5-15% acrylic graft, up to 5% is neutralizing amine plus organic solvent, and 60-80% deionized water. 5 11. The coating composition of claim 9 wherein the additives are water soluble or dispersible linear or branched polyethylene oxides or polypropylene oxides with a Mn = 100-2500. 12. The coating composition of claim 9 wherein the water soluble or dispersible crosslinker is a methylated melaraine formaldehyde resin. 13. An epoxy ester urethane graft acrylic polymer made in accordance with paragraph (a) of claim 1. 14. A process of making an epoxy ester urethane graft acrylic polymer in accordance with paragraph (a) of claim 1.

Inventors: HUYBRECHTS JOZEF THERESIA, VLEMINCKX VICTOR ROGER, HUYBRECHTS, JOZEF, THERESIA, VLEMINCKX, VICTOR, ROGER
Applicants: DU PONT, E.I. DU PONT DE NEMOURS AND COMPANY
Application year: 1987
Main classification: C08F283
IPC codes: C08F4, C08F283, C08G59, C08K13, C08L51, C09D151, C09D175