Aqueous alkyd resin emulsions containing non-fugitive, reactive emulsifying surfactants

Abstract

An aqueous alkyd resin coating composition, comprising (a) at least one alkyd resin as a dispersed phase; (b) an emulsifier based on styrenated phenols that have been converted into reactive surfactants by first reaction with one or more equivalents of an allyl glycidyl ether to provide pendant allyl groups and then oxyalkylated and (c) water. The invention also provides a method for preparing these aqueous alkyd resin coating compositions from solvent borne alkyd compositions.

Claims

1. A method for forming a coating comprising: providing a coating composition comprising: at least one alkyd resin as a dispersed phase; an emulsifier, comprising at least one polyoxyalkylene emulsifier of Formula I or II; ##STR00003## wherein: n is 1, 2, or 3; x is 1-10; y is 0-200; z is 4-200; Z.sup. is SO.sub.3 or PO.sub.3.sup.2; M+ is Na+, K+, NH.sub.4+ or an alkanolamine; and R is CH.sub.3, CH.sub.2CH.sub.3, C.sub.6H.sub.5 or C.sub.14H.sub.29; and a sufficient amount of water to maintain said alkyd resin in said dispersed phase; applying said coating composition to a surface; removing said water wherein upon said removing of said water said alkyd resin and said emulsifier cure wherein said cure comprises cross-linking of said alkyd resin and said emulsifier or autoxidation of said alkyd resin and said emulsifier.

2. The method for forming a coating of claim 1, wherein said emulsifier is a mixture of nonionic and anionic surfactants of Formulae I and II.

3. The method for forming a coating of claim 1, wherein said emulsifier of Formula I is a sulfate ester.

4. The method for forming a coating of claim 1, wherein said emulsifier of Formula I is a phosphate ester.

5. The method for forming a coating of claim 1, wherein said emulsifier of Formula II contains ethylene oxide and propylene oxide residues in a heteric, block, or block heteric arrangement.

6. A method for applying a protective coating to a substrate comprising the application of a coating composition to a substrate wherein said coating composition comprises: (a) at least one alkyd resin as a dispersed phase; (b) an emulsifier, comprising at least one polyoxyalkylene emulsifier of Formula I or II: ##STR00004## and (c) water; wherein: n is 1, 2, or 3; x is 1-10; y is 0-200; z is 4-200; Z.sup. is SO.sub.3 or PO.sub.3.sup.2; M+ is Na+, K+, NH.sub.4+or an alkanolamine; and R is CH.sub.3, CH.sub.2CH.sub.3, C.sub.6H.sub.5 or C.sub.14H.sub.29; and allowing the coating composition to dry in air and cure wherein said cure comprises cross-linking of said alkyd resin and said emulsifier or autoxidation of said alkyd resin and said emulsifier.

7. The method of claim 6, wherein the emulsifier is a mixture of nonionic and anionic surfactants of Formulae I and II.

8. The method of claim 6, wherein the emulsifier of Formula I is a sulfate ester.

9. The method of claim 6, wherein the emulsifier of Formula I is a phosphate ester.

10. The method of claim 6, wherein said emulsifier of Formula II contains ethylene oxide and propylene oxide residues in a heteric, block, or block heteric arrangement.

11. The method of claim 6 wherein said z is 5-60.

12. The method of claim 9 wherein said z is 5-40.

13. A method for forming a coating comprising: providing a coating composition comprising: at least one alkyd resin as a dispersed phase; an emulsifier, comprising at least one polyoxyalkylene emulsifier of Formula I or II; ##STR00005## wherein: n is 1, 2, or 3; x is 1-10; y is 0-200; z is 4-200; Z.sup. is SO.sub.3 or PO.sub.3.sup.2; M+ is Na+, K+, NH.sub.4+ or an alkanolamine; and R is CH.sub.3, CH.sub.2CH.sub.3, C.sub.6H.sub.5 or C.sub.14H.sub.29; and a sufficient amount of water to maintain said alkyd resin in said dispersed phase; applying said coating composition to a surface; removing said water wherein upon said removing of said water said alkyd resin and said emulsifier cure, wherein said cure comprises cross-linking of said alkyd resin and said emulsifier.

14. The method for forming a coating of claim 13, wherein said emulsifier is a mixture of nonionic and anionic surfactants of Formulae I and II.

15. The method for forming a coating of claim 13, wherein said emulsifier of Formula I is a sulfate ester.

16. The method for forming a coating of claim 13, wherein said emulsifier of Formula I is a phosphate ester.

17. The method for forming a coating of claim 13, wherein said emulsifier of Formula II contains ethylene oxide and propylene oxide residues in a heteric, block, or block heteric arrangement.

18. A method for forming a coating comprising: providing a coating composition comprising: at least one alkyd resin as a dispersed phase; an emulsifier, comprising at least one polyoxyalkylene emulsifier of Formula I or II; ##STR00006## wherein: n is 1, 2, or 3; x is 1-10; y is 0-200; z is 4-200; Z.sup. is SO.sub.3 or PO.sub.3.sup.2; M+ is Na+, K+, NH.sub.4+ or an alkanolamine; and R is CH.sub.3, CH.sub.2CH.sub.3, C.sub.6H.sub.5 or C.sub.14H.sub.29; and a sufficient amount of water to maintain said alkyd resin in said dispersed phase; applying said coating composition to a surface; removing said water wherein upon said removing of said water said alkyd resin and said emulsifier cure, wherein said cure comprises autoxidation of said alkyd resin and said emulsifier.

19. The method for forming a coating of claim 18, wherein said emulsifier is a mixture of nonionic and anionic surfactants of Formulae I and II.

20. The method for forming a coating of claim 18, wherein said emulsifier of Formula I is a sulfate ester.

21. The method for forming a coating of claim 18, wherein said emulsifier of Formula I is a phosphate ester.

22. The method for forming a coating of claim 18, wherein said emulsifier of Formula II contains ethylene oxide and propylene oxide residues in a heteric, block, or block heteric arrangement.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 illustrates outlines of water drop on alkyd coating drawdown on a steel panel.

SUMMARY OF THE INVENTION

(2) It has now been surprisingly discovered that improved waterborne alkyd coatings can be produced from aqueous emulsions or dispersions of alkyd resins, where the surfactant is a nonionic or anionic surfactant reactive with the alkyd resin in conventional coating processes. The surfactants are polyoxyalkylene polyethers according to structures I or II below prepared by polyoxyalkylating a polystyrenated phenol that has previously been reacted with one or more allyl glycidyl ether groups, and that after polyoxyalkylation may be optionally be converted to an anionic surfactant such as a phosphate ester or a sulfate. The allyl groups pendant to the polyether chain on the surfactant provide reactive sites for participation in the alkyd autooxidative drying process.

(3) Formula (I) is an anionic surfactant of structure:

(4) ##STR00001##
where RCH.sub.3, CH.sub.2CH.sub.3, C.sub.6H.sub.5, or C.sub.14H.sub.29; n=1,2,3; x is 1-10, y is 0-200, z is 4-200, more preferably from about 5 to 60, and most preferably from about 5 to 40; Z can be either SO.sub.3.sup. or PO.sub.3.sup.2, and M.sup.+ is Na.sup.+, K.sup.+, NH.sub.4.sup.+, or an alkanolamine.

(5) The present invention is further directed towards the emulsion alkyd polymers in the presence of a nonionic surfactant of formula (II)

(6) ##STR00002##
where RCH.sub.3, CH.sub.2CH.sub.3, C.sub.6H.sub.5, or C.sub.14H.sub.29; n=1,2,3; x is 1-10, y is 0-200, z is 4-200, more preferably from about 5 to 60, and most preferably from about 5 to 40.

(7) The present invention is further directed toward a process for emulsifying solvent borne alkyd polymers comprising the addition of one or more of surfactants of formula I or II to a solventborne alkyd, adding water and emulsifying through an inversion process, followed by solvent removal from the aqueous emulsion.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

(8) The present invention thus involves synthesizing a special surfactant or emulsifier preferably using styrenated phenol as the hydrophobe. Styrenated phenol is commercially obtained as a mixture of mono-, di-, and tristyrenated phenols in various ratios. Styrenated phenol is a polyaromatic hydrophobe, so these surfactants have good affinity for the aromatic groups in the alkyd. They are also inherently lower foaming than most linear surfactants.

(9) The mixture of styrenated phenols are converted into reactive surfactants by first reaction with one or more equivalents of allyl glycidyl ether. This attaches pendant allyl groups for subsequent curing through fatty acid double bonds on the alkyd. These substituted styrenated phenols are oxyalkylated with ethylene oxide (EO), optionally together with propylene oxide (PO) or butylene oxide (BO). Other alkylene oxides may also be used, for example long chain ex-olefin oxides, but EO, and PO or BO are preferred, EO and PO being most preferred. The surfactants are designed by selecting the EO/PO or BO architecture to produce a product that emulsifies, disperses and stabilizes the alkyd resin or hybrid latex/alkyd resin, without conferring hydrophilic properties and to minimize its affinity for chelating metal ions used in the alkyd drying process. The nonionic emulsifier comprises ethylene oxide and propylene oxide residues in a heteric, block, or block heteric arrangement.

(10) A method for making ionic surfactants is to make them anionic by the addition of an anionic group such as a sulfate or a phosphate group onto the terminus of a polyoxyalkylated fatty acid or alcohol. The anionic character gives it the ability to charge stabilize alkyd emulsions.

(11) In general the surfactants may be envisioned as having at least two portions; a first portion which is hydrophobic and which will promote formation of a clear coating during coalescence of alkyd resin from aqueous dispersion, and a second portion which is hydrophilic. At least one of these two portions, generally the hydrophobic portion, must contain unsaturation, which is reactive with alkyd resins during cure. It is well known and accepted that nonionic surfactants are excellent products to emulsify and disperse a wide range of hydrophobic compounds including alkyd resins. Nonionic surfactants outperform anionic surfactants in making stabilizing emulsions as demonstrated by improved water sensitivity, better colloidal stability, and lower foam profile when compared to an emulsion made with an anionic surfactant. In some cases, those skilled in the art of making emulsions, a small amount of anionic surfactant is used in conjunction with the nonionic surfactant.

(12) Alkyd resins are synthesized with drying oils as a major part of the formulation. Drying oils are liquid vegetable or fish oils that react with oxygen to form solid films. Drying oils are raw materials for binders such as alkyd resins and epoxy esters. When these films are exposed to air, such as when the coating is curing, an autoxidative cross-linking reaction takes place. When a film is applied to a substrate, internal, naturally present hydroperoxides decompose to form free radicals. Hydrogen molecules on methylene groups between double bonds are particularly susceptible to abstraction, yielding a resonance-stabilized free radical that reacts with oxygen to give predominantly conjugated peroxy free radicals. The peroxy free radicals can abstract hydrogen molecules from other methylene groups between double bonds to form additional hydroperoxides and generate free radicals. Thus, a cross-linking chain reaction is established, resulting from autoxidation and the coating is cured.

EXAMPLES

(13) The following examples are intended to demonstrate the usefulness of the compositions of the present invention and should not be construed to limit the scope of the invention in anyway.

Example 1

(14) Distyrenated phenol (DSP) (694 g, 1 equivalent) was added to a stainless steel autoclave along with allyl glycidyl ether (AGE) (494 g, 2 equivalents) and potassium hydroxide KOH (2.3 g) and the autoclave sealed and heated to 105 C. When all of the AGE was consumed, the reaction mass was cooled, and the product discharged. This is AGE 2 DSP adduct. 1680 g of this AGE 2 DSP adduct (1 equivalent) was added to another autoclave and heated to 105 C. Ethylene oxide (2026 g, 15 equivalents) was then added over the course of several hours. After all of the EO was consumed, the reaction mass was cooled and the catalyst neutralized with the addition of a small amount of acid. This material is Example 1 (aka ERS 01617).

Example 2

(15) Example 1 ethoxylate was sulfated with sulfamic acid in a glass reactor equipped with a stirrer, thermometer, and reflux condenser by heating to 120 C until the % sulfate was >90%. The product, Example 2 (aka ERS 01618), was isolated as the ammonium salt.

Example 3

(16) Example 1 ethoxylate was phosphated with phosphoric anhydride (P2O5) following standard methods to produce Example 3 in its acid form as a viscous liquid.

Example 4

Emulsion Preparation Procedure with Solvent Stripping

(17) TABLE-US-00001 CP-14 Emulsion Amount Material % By Weight Used short oil alkyd, 75% solids in methyl 49.4% 741 g propyl ketone solvent (available as Beckosol 6422-K3-75 from Reichhold) Example 2 4.0% .sup.60 g Ammonium hydroxide 0.74% 11.1 g Deionized water 45.86% 687.9 g 41% solids

(18) Charge short oil alkyd, Example 2, and ammonium hydroxide to a reactor flask equipped with nitrogen sparge, thermocouple, overhead mixing, and a condenser and start stirring. Once the mixture is homogenous, begin adding ambient temperature water to the mixture in a slow stream so that the water is incorporated evenly into the mixture. As the water is added the viscosity will rise until the inversion point is met, then the viscosity will begin to drop. When all of the water is charged, allow the emulsion to mix for several minutes and then check the particle size. This emulsion was 41% solids. The average particle size of this emulsion was 0.227 microns with a D50 of 0.209 microns.

(19) The temperature of the emulsion was then raised by heating to 70 C with a nitrogen sparge. The temperature was then gradually increased until vapors were detected in the condenser. The emulsion was then stirred until all of the solvent was removed. After cooling, the particle size, percentage solids, and viscosity were checked. This product emulsion was 48% solids and contained 0.4% residual solvent. The viscosity was not measured, but was quite low. The particle size of the solvent-stripped emulsion was 0.214 microns with a D50 of 0.198 microns.

(20) As the particle size data shows, the particle size of the alkyd emulsion remained very low, actually decreasing from the solvent-containing emulsion. The solids content was significantly higher. This result shows that the use of the anionic surfactants of this invention can overcome the viscosity increase problem inherent with the invert emulsion procedure by leaving the solvent in the mixture and then removing it after emulsion formation. The anionic sulfate has sufficient water solubility to perform as an effective emulsifier even at the elevated temperatures needed for practical solvent stripping. This procedure will allow coating manufacturers to convert existing low cost solventborne alkyds to waterborne products containing little or no VOC. This process also produces a product alkyd emulsion with higher solids (active ingredient) than the solvent-containing waterborne emulsion.

Example 5 and Comparative Example

Comparison of Coating Properties between Reactive and Non-Reactive Surfactant

(21) Two waterborne emulsions of a solventborne long oil alkyd (Beckosol 10-539 LOA from Reichhold) were prepared using the procedure of Example 4 with the amounts of each ingredient shown in Table 1 below. The only difference was the emulsifier. Both emulsifiers (Example 2 and POE 20 DSP) are styrenated phenol based, have nearly the same ethoxylate chain length, and both are sulfates. The only significant difference between them is that Example 2 is reactive, while POE 20 DSP contains no reactive allyl groups.

(22) After the emulsions were prepared, a cobalt-based drying catalyst package was added to the emulsion and four mil drawdowns were made on steel Q panels. After two weeks the adhesion, pencil hardness, gloss, and water contact angle were checked. Results are in Table 2.

(23) TABLE-US-00002 TABLE 1 Example 5 Amount Comparative Example 5 Amount Long oil alkyd 38.2 g Long oil alkyd 38.2 g (Beckosol 10-539) (Beckosol 10-539) Example 2 1.8 g POE 20 styrenated phenol 1.8 g Ammonium Hydroxide 0.6 g Ammonium Hydroxide 0.6 g Water 58.8 g Water 58.8 g Drier package 0.6 g Drier package 0.6 g

(24) TABLE-US-00003 TABLE 2 Property Example 5 Comparative Example 5 Cross-cut adhesion 0B (100% fail) 0B (100% fail) Pencil Hardness F 2B Gloss (60) 117 113 Water contact angle 84.5 79

(25) Review of the data in Table 2 shows that Example 5, the alkyd coating with the reactive surfactant, has a higher water contact angle than Comparative Example 5, the alkyd coating with the non-reactive surfactant. This indicates that the Example 5 coating is more water repellent, evidence that the reactive surfactant is cured into the alkyd and not available to dissolve into the water and reduce its surface tension.

(26) The Example 5 coating with the reactive surfactant is also significantly harder than the one with non-reactive surfactant. Presumably, this is due to the plasticization of the coating by the unbound surfactant.

(27) The gloss of the coating is also higher with the reactive surfactant. This suggests that the surface has fewer defects.

(28) Water drops were placed on each of these drawdown panels and allowed to stand covered so that they would not evaporate. The water drop on the Comparative Example 5 coating with the non-reactive surfactant had significantly wet the coating and had spread out to cover a much larger area than the drop on the reactive surfactant coating. After two days, rust on the panel was clearly visible on the panel with non-reactive surfactant (FIG. 1). The coating with the reactive surfactant resisted the ingress of water and protected the steel much better than did the non-reactive.

Example 6

(29) In another test of adhesion, 4 mil drawdowns were made of Example 4 aqueous short oil alkyd emulsion prepared with Example 2 difunctional reactive surfactant and of Synaqua 4804, a commercially available waterborne short oil alkyd (available from Arkema) assumed not to contain a reactive surfactant. Both alkyd emulsions were catalyzed prior to drawdown with the same drier package. After 24 hours of drying, the adhesion of the coatings was measured by ASTM Method D 3359-08 Measuring Adhesion by Tape Test. A crosscut pattern was scribed onto the alkyd surfaces. The attempt to scribe the crosscut pattern on the commercial alkyd coating failed, while it was successful on the alkyd emulsified with Example 2 reactive surfactant.

Examples 4, 7 and Comparative Example

(30) In another test of adhesion to metal, two short oil alkyd emulsions were prepared following the method of Example 4. One was a repeat of Example 4, while Example 7 used a mixture of Example 2 and Example 3 as emulsifiers. More water was required to prepare the emulsion of Example 7 to produce a suitable viscosity. After Example 4 and Example 7 emulsions were made they were heated to 80-90 C and the solvent was removed until the solvent content was less than 0.5%. A commercially available metal catalyst drier package was added to each emulsion prior to drawdown. The recipes for each example and their particles sizes after solvent removal are given in Table 3.

(31) TABLE-US-00004 TABLE 3 Comparative commercial Exam- Exam- waterborne short oil ple 4 ple 7 alkyd Short oil alkyd 49.4% 39.5% Synaqua 4804 (Arkema) (Beckosol 6422-K3-75) Example 2 4.0% 3.16% 0 Example 3 0 0.8% 0 Ammonium 0.74% 1.2% 0 Hydroxide DI H2O 45.86% 55.34% 0 Dura Chemicals 0.5% on 0.5% on 0.5% on DriCAT 507 Batch Batch Batch Weight Weight Weight pH 7.5 7.5 7.5 Particle Size D10 0.154 0.317 0.180 D50 0.198 2.418 0.226 D90 0.280 4.580 0.296

(32) Two aluminum and two steel panels were prepared prior to making drawdowns of each emulsion. One of each panel was wiped clean with acetone and one of each was scuffed with an abrasive plastic pad. A 4 mil drawdown was cast on each panel and allowed to air dry at room temperature. The 60 gloss on all panels for each emulsion was >100.

(33) After one week the adhesion of the coating to the metal panel was tested following the ASTM Method D 3359-08 Measuring Adhesion by Tape Test. All of the drawdowns of Examples 4 and 7 passed the adhesion test as did the comparative example on the scuffed steel panel. The comparative waterborne alkyd failed the adhesion test when applied to the acetone cleaned aluminum panel.

Example 8

(34) A short oil alkyd emulsion was prepared following the procedure and materials of Example 4 but without the solvent removal step. Another emulsion of the same alkyd was prepared in identical fashion except that another reactive surfactant, a commercially available alkoxylate of linseed fatty acid, was used instead of the Example 2 styrenated phenol surfactant. Equal amounts of the same metal drier catalyst package (DriCat 507) were added to each emulsion.

(35) The drying time of these two catalyzed emulsions were measured by drawing down films of each on a Leneta chart and allowing them to air dry at room temperature. The alkyd emulsion with the Example 2 reactive surfactant cured tack-free after 5.5 hours, while the linseed alkoxylate coating was not tack-free even after eight hours.

(36) All patents, patent applications and publications cited in this application including all cited references in those patents, applications and publications, are hereby incorporated by reference in their entirety for all purposes to the same extent as if each individual patent, patent application or publication were so individually denoted.

(37) While the many embodiments of the invention have been disclosed above and include presently preferred embodiments, many other embodiments and variations are possible within the scope of the present disclosure and in the appended claims that follow. Accordingly, the details of the preferred embodiments and examples provided are not to be construed as limiting. It is to be understood that the terms used herein are merely descriptive rather than limiting and that various changes, numerous equivalents may be made without departing from the spirit or scope of the claimed invention.