AU2518500A - Method for electromagnetic energy assisted curing of coating compositions - Google Patents

Description

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AUTSTRALIA

PATENT'S ACTr 1990 COMPLETE

SPECIFICATION

NAME OF APPLICANT(S): Robin and Haas Company ADDRESS FOR SERVICE: DAVIES COLUSON

CAVE

Patent Attorneys 1 Little Collins Street, Melbourne, 3000.

INVENTION TiTLE: Method for electromagnetic energy assisted curing of coating compositions The following statement is a full description of this invention, including the best method of performing it known to me/us:- The present invention relates to a method of electromagnetic energy assisted curing of coating compositions and the coating compositions thereof.

In one aspect, the present invention relates to a method for curing coating compositions with assistance of an electromagnetic energy having a suitable frequency and power. The method is suitable for coating or marking a surface of a substrate such as metal, wood, leather, road, pavement, runways, traffic areas, plastics or polymers, and combinations thereof. The method also may be used with one or more other conditions or parameters such as heat, hot or cold air (or other suitable gases), ultraviolet radiation and infrared radiation (IR).

The method of the present invention is especially useful for curing traffic paints.

The invention also relates to the coating compositions suitable for use with the method. Preferably, the coating compositions are water-borne compositions.

The advantages of the method and the coating compositions are shortened drying times and/or improved properties of the finished coatings. For traffic markings or coatings, improved properties may include, depending on the particular composition selected, water resistance, wear resistance, yellowing-resistance, dirt pickup resistance, etc.

Some methods involving use of radiations to cure coatings or paints are known. For example, WO 90/02613 discloses a method of applying a water-borne coating composition on a temperature sensitive substrate followed by irradiating the coated substrate with microwaves to cure the coating composition. The method is described to provide rapid curing of both zinc silicate paints and emulsion paint systems on temperature sensitive substrates that would otherwise be damaged by the stoving conditions normally required for curing, and to enable paint films to be cured very rapidly in on-line apparatus.

It would be advantageous if there is a method for an electromagnetic energy assisted curing of a coating composition wherein the curing is faster and/or the finished coating has improved properties. It is also desirable and commercially more advantageous that the composition of the coating is not limited to zinc-containing formulations and may interact with the electromagnetic energy in such a manner that the drying time is reduced and/or the property of the finished coating surface is improved. This is particularly important when the composition is used for marking the surfaces of roads, traffic areas, parking lots, or similar pavements where it is important to have as short a drying time as practicable to minimize interrupting traffic and/or closing of streets or other areas used by vehicles or pedestrians. A faster drying time also reduces the weather effects on the coating. A shorter (faster) or better controlled drying time is preferred when coating paper, metal, plastic, or wood surfaces, particularly when these surfaces are on parts on assembly lines. Certainly, the electromagnetic energy may be used as an energy source to vaporize volatile components in the composition under the curing conditions.

Accordingly, one object of the present invention is to provide a method of *see.: curing coating compositions on a surface, assisted by an electromagnetic energy having a suitable frequency and power. Another object is to provide such a method having a shortened drying/curing time and/or improved properties of the finished coating. A further object is to provide a waterborne coating composition 9 that may be used for exterior surfaces, such as roads, pavements, buildings, houses ships, etc.

The present invention provides a method for electromagnetic energy assisted curing of a waterborne coating composition comprising: applying the :....waterborne coating composition to a surface of a substrate; and exposing for a period in the range of from 0.001 seconds to 60 minutes the coating composition and the surface to an electromagnetic energy having a frequency in the range of 100 MHz to 50 GHz and a power in the range of from 1.0 Watts to 50,000 Watts; wherein the waterborne coating composition comprises an anionically stabilized emulsion polymer having a Tg greater than OOC; a polyfunctional amine having from 20% to 100% by weight of an amine or imine group containing monomer; and an amount of a volatile base sufficient to raise the pH of the waterborne coating composition to a point where essentially all of the polyfunctional amine is in a non-ionic state.

More preferably, the amine group containing monomer is selected from the group consisting of oxazolidinylethyl methacrylate, dimethylaminoethyl methacrylate, dimethylaminopropylmethacrylamide, and mixtures thereof. A preferred electromagnetic energy frequency is in the range of from 300 MHz to GHz. A preferred base is a volatile base selected from the group consisting of ammonia, ammonium hydroxide, ethanolamine and mixtures thereof.

Preferably, the exposure is carried out prior to, simultaneously with or after the application of the waterborne coating composition to the substrate. In another preferred embodiment of the present invention the waterborne coating composition further comprises in the range of from 0.01 wt% to 50wt% based on the total weight of the waterborne coating composition a chemical compound selected from the group consisting of silicon carbide, carbon black, a-silicon nitride, (-silicon nitride, boron nitride, tungsten nitride, aluminum nitride and mixtures thereof. Other preferred chemical compounds include a water soluble salt selected from the group consisting of sodium chloride, sodium bromide, sodium iodide, sodium acetate, potassium chloride, potassium bromide, potassium acetate, calcium acetate, magnesium acetate, calcium chloride, ammonium acetate, ammonium citrate, ammonium tartarate, and mixtures thereof.

More particularly, the present invention provides a method for electromagnetic energy assisted curing of a waterborne traffic marking composition comprising: applying the waterborne coating composition to a surface of a substrate; and exposing for a period in the range of from 0.001 seconds to 60 minutes the coating composition and the surface to an electromagnetic energy having a frequency in the range of 100 MHz to 50 GHz and a power in the range of from 1.0 Watts to 50,000 Watts; wherein the waterborne coating composition comprises: an anionically stabilized emulsion polymer having a Tg greater than OOC;a polyfunctional amine having from to 100% by weight of an amine or imine group containing monomer; and an amount of a volatile base sufficient to raise the pH of the waterborne coating composition to a point where essentially all of the polyfunctional amine is in a non-ionic state.

The present invention also can be used for curing an organic solvent based or water dilutable organic solvent based coating compositions on a surface of a substrate. Proper selections and/or adjustments of reaction parameters frequency, power and exposure duration of electromagnetic energy, additional component in the compositions, temperature, humidity, and others are needed.

The substrate of the present invention is selected from the group consisting of road, pavement, runway, traffic area, paper, metal, leather, plastics or solid polymers, wood, interior or exterior surfaces of a building or house, exterior of a ship or boat, and combinations thereof. Some examples of metals are aluminum, copper, cast iron, carbon steel, stainless steel (such as grade 314, 316 and others), and alloys like monel(a trademark owned by Inco Alloys International, Inc.). The terms plastics and polymers are used herein interchangeably. Examples of plastics or polymers include, but are not necessarily limited to polyethylene, polypropylene, polybutene, polystyrene, oo polyesters, ethylene-propylene-diene monomer polymers (EPDM), polyurethane, 1 and combinations thereof. A road, pavement, runway, traffic area, and other similar substrates include, but are not necessarily limited to, cement, asphalt, bricks, cobble stones, or combinations thereof. Other possible cementitious "substrates are concrete roof tiles and fiber-cement composite materials.

The electromagnetic energy is provided by a suitable device or apparatus.

For road paintings, coatings, or markings, the device or apparatus should be open and mobile either self propelled or mounted on a moving vehicle. For S:painting, coating, or marking on paper, wood, leather, metal or plastic surfaces, the device or apparatus may be stationary or mobile, and closed or open. The choice of a suitable device/apparatus depends on both the coating composition, the substrate and the nature and property of the surface of the substrate.

A suitable frequency of an electromagnetic energy is in the range of from 100 MHz to 50 GHz, preferably, 300 MHz (Im wavelength) to 30 GHz (1cm wavelength). A more preferred frequency is in the microwave region, 2 GHz to 12 GHz (15 cm to 2.5cm wavelength). Two most preferred frequencies are at or within +20MHz of 2450 MHz in the range of from 2430MHz to 2470 MHz, or at or near 12.2 cm wavelength) and at or within ±20MHz of 915MHz(i.e. in the range of from 895 MHz to 935 MHz, or at or near 32.78 cm wavelength).

Exposure to an electromagnetic energy is for a period in the range of from 0.001 seconds to 60 minutes, preferably in the range of from 0.05 seconds to minutes, more preferably in the range of from 0.5 seconds to 5 minutes.

Another aspect of the present invention is that other conditions may be used or applied before, during or after the electromagnetic radiation, particularly after microwave range radiation. These conditions include, but are not necessarily limited to infrared radiation ultraviolet radiation hot gas, cold gas, ambient temperature gas, and combinations thereof. Suitable gases include, but not necessarily limited to air, nitrogen, helium, argon, oxygen, carbon dioxide, gaseous fluoro or fluorochloro hydrocarbons such as trifluorochloromethane, and mixtures thereof. A liquid compound or mixture at ambient conditions also may be used if it can be turned into a gaseous or vapor state under the curing and/or coating conditions.

:."The method also is useful when the surface of the substrate is already covered or treated by a coating composition for a variety of reasons or purposes.

For instance, the surface may be coated first with the same or a different coating composition which would facilitate or enhance curing with the electromagnetic energy. An example is a suitable primer. Another example is coating over a weathered coating, such as an existing old traffic marking without removal of 20 the old paint or marking.

o.oooi *A number of theories and/or hypotheses are discussed herein only for illustration purposes. They are not intended and should not be taken to limit either the scope or the spirit of the present invention.

A coating composition suitable for use in the present invention comprises a binder, a polyamine or polyimine or a copolymer containing both amine and imine functionalities, and a diluent, most preferably, water. It may further comprise coalescent(s), rheology control additive(s), surface effect additive(s) (such as waxes or silicones), pigment(s) (either inorganic or organic or mixtures thereof), filler(s) (inorganic compounds such as glass beads, quartz sand, silica, organic materials such as polystyrene beads, or mixtures thereof), antifoam agent(s), wetting agent(s), and other additives known in the art as being useful in the formulation of a water-borne paint. In many cases, the desired paint is a transparent or semi-transparent varnish and in this case the coating composition is similar to the previous composition but the pigments and fillers are either absent or present only in small amounts. Additionally, the coating composition may contain soluble salts or other compounds capable of enhancing the amount of microwave energy absorbed by the paint.

In general, the anionically stabilized latex polymer is a polymer or copolymer prepared from a monomers which include, but are not necessarily limited to styrene, butadiene, ethylene, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, lauryl acrylate, stearyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, lauryl methacrylate, stearyl methacrylate, vinyl acetate, vinyl esters of "Versatic" acid (a tertiary monocarboxylic acid having C9, Clo and C 11 chain length, the vinyl ester is also known as vinyl versatate), vinyl chloride, vinylpyridine, vinylidene chloride, acrylonitrile, chloroprene, acrylic acid, methacrylic acid, itaconic acid, maleic acid, and fumaric acid. Polymers and copolymers of alpha-beta ethylenically unsaturated acid monomers and their esters, especially the acrylic and methacrylic esters are examples among the preferred emulsion polymers.

The dispersion polymer could also be materials like alkyd emulsions, polyurethane dispersions, epoxy emulsions, polyester emulsions, or other polymeric or oligomeric materials prepared in a dispersed or emulsified state.

The anionically stabilized emulsion polymer can be prepared by a number of known procedures. For example, US 5,804,627 describes some of such procedures. To the extent that the procedures are disclosed, it is incorporated herein by reference. Some of the preferred processes are described in "Emulsion Polymerization of Acrylic Monomers: May 1966" published by the Rohm and Haas Company, Philadelphia, Pennsylvania, "Polymer Syntheses," Vol. I, Chapter 10 by S. R. Sandler and W. Karo, 1974, published by Academic Press, New York, NY, both incorporated herein by reference, only to the extent that relevant processes are described.

Preferably, the polymers should have a glass transition temperature (Tg) higher than 0OC. Polymers having a Tg below about OOC, while usable, are generally not preferred since they tend to be too soft, resulting in a finished coating having undesirable scrub resistance and accelerated dirt pickup. The invention also may be practiced using polymers of more complex morphologies, such as the well-known core-shell particles. These complex polymer morphologies usually display multiple Tg's and may display a Tg value below 0°C, as one of the multiple Tg's. However, the average or effective Tg of the polymer should be above about OoC.

It is preferred that the coating composition of the present invention also comprises a base. The type and amount of a base should be sufficient to raise the pH value of the coating composition, waterborne coating composition in particular, to a level where essentially all of the polyfunctional amine is or essentially is in a non-ionic state, i.e. a deprotonated state. Without limiting the scope of the invention by any theories, it is believed that this non-ionic state is Spreferred because it tends to minimize interaction between the polyfunctional amine and the anionically stabilized emulsion polymer. A suitable pH value is in the range of from 7.5 to 12. Examples of such a base include, but are not necessarily limited to ammonia or ammonium hydroxide (ammonia in water), alkyl amines, substituted alkyl amines, 2-dimethylaminoethanol, di-, tri- or tetra-amines such as ethylene diamine, morpholine, substituted morpholine such as N-methylmorpholine, and mixtures thereof.

A volatile base is preferred. If a base has a vapor pressure of at least 3 kPa under ambient conditions (at about 250C and one atmosphere pressure or 9 9 S° about 101 kPa), it is considered as a volatile base for this invention. Examples of a volatile base include, but are not necessarily limited to, ammonia or ammonium hydroxide, lower alkyl (C 1 to C s or substituted alkyl amines such as methyl amine, dimethylamine, ethyl amine, ethanol amine, and diethylhydroxyl amine, and mixtures thereof. A most preferred volatile base comprises of or consists essentially of ammonia or ammonium hydroxide (ammonia in water) or ethanol amine. A volatile base usually will vaporize after application and the pH of the composition will decrease. It is believed that when the pH becomes low enough, protonation of the polyfunctional amine begins and the polyfunctional amine becomes cationic.

A waterborne coating composition is a preferred coating composition to be used for the method of the present invention. A preferred application of the present invention is for marking or painting road, parking lot, traffic area, runways, taxing area, or other pavements.

The coating composition, particularly a waterborne coating composition, of the present invention further comprises a polyfunctional amine, preferably a polymer containing in the range of from 20% to 100% by weight, more preferably from 50% to 100% by weight of amine or imine containing monomers as the monomeric units in the polymer. Both amine and imine functionalities may exist in the polymers simultaneously. Examples of such amine or imine containing monomers include, but are not necessarily limited to, the following classes and mixtures thereof.

1. Aminoalkyl vinyl ethers or sulfides, wherein the alkyl groups include, but are not necessarily limited to straight chain or branched chain having two to three carbon atoms and wherein the nitrogen atom of the amino group may be primary, secondary, or tertiary (see US Patent No. 2,879,178). For secondary or tertiary nitrogen atoms in the amino groups, one or both hydrogen on the nitrogen are substituted respectively by one or two substituents which are selected from the group consisting of linear or branched alkyl group, linear or branched hydroxyalkyl group, and linear or branched alkoxyalkyl groups wherein all the alkyl moieties have one to four carbon atoms, preferably one carbon atom.

Preferred examples include, but are not necessarily limited to: beta-aminoethyl vinyl ether, beta-aminoethyl vinyl sulfide, N-monomethyl-beta-aminoethyl vinyl ether, N-monomethyl-beta-aminoethyl vinyl sulfide, N-monoethyl-beta-aminoethyl vinyl ether, N-monoethyl-beta-aminoethyl vinyl sulfide, N-monobutyl-beta-aminoethyl vinyl ether, N-monobutyl-beta-aminoethyl vinyl sulfide, N-monomethyl-3-aminopropyl vinyl ether, N-monomethyl-3-aminopropyl vinyl sulfide; and mixtures thereof.

2. Acrylamides, methacr-ylamides, acrylic esters, or methacrylic esters, including, but not limited to, those of the following general formula:

H

2 -A-NR 'R 2 wherein R is H or CH 3 X is 0 or N-H; n isO0 or 1; When n is 0 (zero), A is 0(CH2),, or (-0-alkylene)y ,wherein z is 2 or 3, and (O-alkylene)y is a poly(oxyalkylene) group which has a molecular weight in the range of from 88 to 348, in which the individual alkylene radicals may be the same or different and may be either or -CH(0H 3

)-CH

2 or -CH 2

-CH(CH

3 or

-CH

2

-CH

2 and when n is 1 (one), A is an alkylene group having 2, 3, or 4 carbon atoms; R1 is H, OH 3 or C 2

H

5

R

2 is H, phenyl, benzyl, a-methylbenzyl, cyclohexyl, or C1 to C6 alkyl.

Preferred examples in this group include, but are not necessarily limited to: dimethylamninoethyl acrylate or methacrylate; 20 beta-aminoethyl acrylate or methacrylate; N-(mono-n-butyl-4-aminobutyl) acrylate or methacrylate; acrylamide; methacrylamnide; N-methylolacrylamide; N-methylolmethacrylamide; N-ethanolacrylamide; N-ethanolmethacrylamide; N-p-aminoethylacrylamide; N-f-aminoethylmethacrylamide; N-(monomethylaininoethyl)acrylamide; N-(monomethylaminoethyl)methacrylamide; methacryloxyethoxyethylamine; acryloxypropoxypropoxypropylamine, and mixtures thereof.

3. N-acryloxyalkyloxazolidines and N-acryloxyalkyltetrahydro-1,3oxazines and the corresponding derivatives in which the alkyl linkage is replaced by alkoxyalkyl or poly(alkoxyalkyl) moieties.

0 CH2 )m

H

2 C=C(R3)C-Al-N\ R R wherein, R3 is H or CH 3 A' is O(CH 2 )p or (O-alkylene)q in which(O-alkylene)q is a poly(oxyalkylene) 10 group which has a molecular weight in the range of from 88 to 348, in which the individual alkylene radicals may be the same or different and may be either

-CH(CH

3

)-CH

2 or -CH2-CH(CH 3 or -CH 2

-CH

2 m is 2 or 3;

R

4 and R 5 may be directly connected.

R

4 ,when not directly connected to R 5 ,is selected from the group consisting of H, phenyl, benzyl, and (C 1

C

1 2 alkyl groups;

R

5 ,when not directly connected to R 4 ,is selected from the group consisting of H and (C 1

C

4 alkyl groups; and

R

4 and R 5 ,when directly connected, form a five- or six-membered ring, including the connecting carbon in the formula, i.e. R 4 and R 5 are selected to have a total of four or five carbons in the ring.

Compounds of the formula may be hydrolyzed under various conditions to form secondary amines.

0 O II

H

2

C=C(R

3

)C-A-N(H)-(CH

2 )m-OH Many of these monomeric compounds, as disclosed in US 3,037,006 and 3,502,627, may be used as described herein and are incorporated by reference.

Some suitable monomer in this category include, but are not necessarily limited to: oxazolidinylethyl acrylate; oxazolidinylethyl methacrylate; 3-(gamma-methacryloxypropyl)-tetrahydro-1 ,3-oxazine; 3-(beta-methacryloxyethyl)-2 ,2-pentamethylene oxazolidine; 3- [2-(2-inethacryloxyethoxy)ethyl-2,2-pentamethylene oxazolidine; 3- [2-(2-methacryloxyethoxy)ethyl-2,2-dimethyl oxazolicline; 3- [2-(2-methacryloxyethoxy) ethyl- 2-phenyl oxazolidine; 3-(beta-methacryloxyethyl)-2-methyl-2-propyl oxazolidine; N-2-(2-acryloxyethoxy)ethyl oxazolidine; N-24(2-methacryloxyethoxy) ethyl oxazolidine; oxzld.e n 2-(2 -macryloxyethoxy) ethyl- 5-methyl oxazolidine n 9. 4. Polymers prepared from monomers which readily generate amines or *amine derivatives by hydrolysis or alcoholysis are useful as the polyfunctional amine component or to generate the poly-ftnctional amine component of the aqueous coating composition, which is also referred to as the binder composition.

Examples of such monomers include, but are not necessarily limited to the Vv..'acryloxy ketimines and acryloxy aldimines of the general formulas shown below: 00.4 H 2 C=C(R6)-CO2=

H

2

C=C(R

6 0:ev wherein

R

6 is H or CH 3

A

2 is selected from Cl-Cl 2 alkylene groups; D, J, and K may be same or different, and are selected from oxyalkylene groups having the formula -OCH(R 7 ,wherein R 7 is H, CR 3 or C 2

H

5 Q is selected from the group consisting of C (HR")h

C(R

8

CH(R

10 and R8 and R9 may be the same or different and they are selected independently from the group consisting of (Cl-C 12 alkyl and cyclohexyl groups;

R

10 is selected from the group consisting of cyclohexyl, phenyl, halophenyl, (C1-C4) alkoxyphenyl, and (C 1

-C

12 alkyl groups; R" is H, or it may be CH 3 in only one of the CHR 11 units while the other

CHR

11 units are CH 2 d is an integer selected from 0 to 200; j is an integer selected from 0 to 200; k is an integer selected from 0 to 200; and d j k a value between 2 to 200; h is an integer selected from 4 to Examples of such monomers useful for the present invention include, but are not necessarily limited to: 2-[4-(2,6-dimethylheptylidene)-amino] -ethyl methacrylate; 2-[4-(2,6-dimethylheptylidene)-amino] -ethyl acrylate; 3-[2-(4-methylpentylidene)-amino]-ethyl methacrylate; 3-[2-(4-methylpentylidene)-amino]-propyl methacrylate; 12-(cyclopentylideneamino)-docecyl methacrylate; "beta-(benzylideneamino)-ethyl methacrylate; N-(1,3-dimethylbutylidene)-2-(2-methacryloxyethoxy)-ethylamine; N-(1,3-dimethylbutylidene)-2-(2-acryloxyethoxy)-ethylamine; N-(benzylidene)-methacryloxyethoxyethylamine; N-(benzylidene)-acryloxyethoxyethylamine; and mixtures thereof.

These compounds hydrolyze in acid, neutral, or basic (alkaline) aqueous media to produce the corresponding primary amines or salts thereof, in which the group -N=Q becomes -NH 2 and O=Q. The monomeric compounds disclosed in U.S. Patent No. 3,037,969 and 3,497,485 may be used in the making of the copolymers which may be used as the water-soluble polymer portion of the compositions of the present invention.

Polyfunctional amines, also referred to as amine-containing polymers herein, may have different various solubilities in water. The term water-soluble amine-containing polymer describes polymers that can become completely or partially soluble in free-base (in an essentially totally or completely deprotonated or non-ionic state), neutralized (protonated state) or salt form. The solubilities may also depend on the pH value. Some polymers may be soluble at all pH's, while others are soluble within a narrower range, for example in a range of pH from 5 to 10. Still other amine-containing polymers may be insoluble at high pH (above 9) and may become soluble or partially soluble under acidic conditions, particularly in a pH range from 5 to 7. "Partially soluble" means either only some of the polymers are soluble in the aqueous medium or all of the polymers are in the form of micelles or aggregates of individual molecules, generally highly water swollen aggregates. Such micelles or aggregates are often referred as colloidal solutions as well. For the present invention, it is preferred that the bulk by weight of total polyfunctional amine) of the polymers is soluble at the desired levels in an aqueous medium with an acidic pH value in the range of from 5 to 7.

In general, the polyfunctional amines, polyfunctional imines, or mixed amine/imine containing polymers may be obtained by solution polymerization in 15 an aqueous medium, which may be neutral, alkaline, or acidic, depending on the particular product desired. For example, US 4,119,600 teaches such an approach. The polymerization is usually carried out in an aqueous medium containing a small amount of an acid, either organic or inorganic, such as acetic acid or hydrochloric acid.

The amine-containing polymers include homopolymers or copolymers with up to 80% by weight (80wt%) of the homopolymer or copolymer one or more monoethylenically unsaturated monomer(s), such as methyl acrylate, acrylamide or its derivatives, and methacrylamide or its derivatives.

Specific examples of amine group containing monomers include, but are not necessarily limited to, acrylic acid esters with C 1 to Cis alcohols, methacrylic acid esters with C 1 to Cis alcohols, particularly C 1 to C 4 alcohols, styrene, vinyltoluene, substituted styrenes, vinyl acetate, vinyl chloride, vinylidene chloride, ethylene, butadiene, substituted butadiene, nitriles and amides of acrylic or methacrylic acid.

Small amounts of relatively water-insoluble comonomers, in the range of from 0.01wt% to 20 wt% of the final polymer product, also may be incorporated into water-soluble copolymers, i.e. polyfunctional amines. If there are larger amounts of such comonomers present in the final polymer product, the polymer product may become water-insoluble with almost no measurable solubility.

A particular comonomer or comonomers used in making a desired polyfunctional amine or amine-containing polymers will depend on the identity and proportion of the amine-containing monomer(s) selected. An aminecontaining polymer is a polymer or copolymer of cationic and optionally, nonionic vinyl monomer(s). Examples of cationic monomers are amines or imines.

Styrenes, butadienes, ethylene are examples of nonionic monomers. Trace amount of acid groups may be present in the polyfunctional amines resulting 10 from impurities in the monomers used, or to the extent of hydrolysis of monomers during synthesis, storage, or use.

Many other components may be present in the coating composition.

Typical examples include fillers, thickeners, pigments, dispersants, and organic solvents. If a pigment is used in a coating composition suitable for traffic paint or markings, examples include, but are not necessarily limited to clays, calcium carbonate, talc, titanium dioxide, carbon black, various colored pigments, and mixtures thereof. If a pigment is used in a composition for traffic paint or markings, it is typically in the range of from fifty percent pigment volume content (PVC) to sixty percent PVC.

In addition, fillers such as glass beads, quartz sand and mixtures thereof may optionally be incorporated into the composition, particularly for coating composition for road, pavement or traffic area markings. The particle diameter of the glass beads or quartz sand may vary from 100l (micrometers or also called microns) to 1500p. The incorporation may be accomplished by either adding the fillers to the composition prior to, during, or immediately after applying the composition to the surface of the substrate.

Care must be exercised when selecting the type and amount of additives to avoid altering the pH value of the composition to an extent that would interfere with the essential properties of the composition, such as storage stability. The pH should not be buffered to an extent that after application the pH does not decrease sufficiently to initiate protonation of the polyfunctional amine.

A coating composition useful for traffic paint or markings typically has a solids content in the range of from thirty five percent to seventy percent by volume and a viscosity in the range of from 70 kreb units to 100 kreb units.

A number of other chemical compounds may be used in the coating composition of the present invention, in the range of from 0.001 wt% to 10 wt%, based on the total weight of the final coating composition, particularly when a microwave range electromagnetic energy is used to assist the curing. These chemical compounds may provide a number of beneficial effects to either the 10 curing stage, the application stage, or the properties of the finished coatings. A i first group of these chemical compounds includes, but is not necessarily limited to silicon carbide, carbon black, a-silicon nitride, 0-silicon nitride, boron nitride, tungsten nitride, aluminum nitride and mixtures thereof. Particle size of these chemical compounds may vary over a wide range, depending on the makeup and S 15 other properties of the coating composition, such as color, and electromagnetic energy used. A second group of such chemical compounds includes water soluble salts. A salt is considered as "water soluble" for the present invention if it has a solubility of at least 0.5 grams per 100 grams of water at 25C. Examples of such i *salts include, but are not necessarily limited to sodium chloride, sodium bromide, 20 sodium iodide, sodium acetate, potassium chloride, potassium bromide, potassium acetate, ammonium acetate, ammonium citrate, ammonium tartarate, lithium chloride, lithium bromide, calcium acetate, tetramethylammonium chloride, and mixtures thereof. The chemical compounds of the first group may be added to the coating compositions before, during, or after application of the coating, but they need to be added to or present in the coating compositions before the electromagnetic energy is turned off. Preferably, the chemical compounds are added to the composition before or during the electromagnetic energy is applied. The chemical compounds of the second group may be added to the coating compositions before, during, or after application of the coating, and they may be added to or present in the coating compositions before, during, or after exposure of the electromagnetic energy.

The invention is further illustrated by the following examples which are not intended and should not be construed to limit the scope of the present invention which is defined by the claims.

Example 1 Two paint formulations were used in this example. Their compositions are shown in Table I.

The drying test is performed as follows. With a drawdown blade having a gap of 500 microns waterborne Formulation I and II were applied to lacquer sealed paper charts (Leneta form 12H paint spreading rate test charts) to form 10 films. The films were tested for dry-to-no-pickup according to ASTM D711 method, using traffic paint drying time wheel, with or without microwave exposure. ASTM stands for American Society of Testing Materials (ASTM), Philadelphia, Pennsylvania.

The microwave source had a frequency at 2450±20 MHz (in the range of 15 from 2430 MHz to 2470 MHz) a power of 1500 watts and reflectance from 20 to The conditions for the tests were: 24oC, 50% relative humidity and minimum air flow km/hr). Microwave exposure was achieved by taping the paper charts to a wood panel support and moving the support under the microwave cavity.

Microwave exposure time 0 seconds 3 seconds Total time to pass testa Formulation I 19 minutes 14 minutes Formulation H 2 minutes 30 seconds a: The test is dry-to-no-pickup No paint pickup and tracking; tested at second intervals.

The results show that Formulation II provided for a significantly shorter dry-to-no-pickup time than a Formulation I. The compositions of Formulations I and II are shown in Table I. When exposed to a suitable microwave range electromagnetic energy, reduction in dry-to-no-pickup time is proportionally much more significant for Formulation II than Formulation I 4X versus only 1.4X faster.

Example 2.

Formulation III was used in this example. The composition is shown in Table I.

The drying test was performed as follows: With a drawdown blade having a gap of 500 microns waterborne Formulation III was applied to lacquer sealed paper charts (Leneta form 12H paint spreading rate test charts) to form films. The paint films were tested for dry-to-no-pickup according to ASTM D711 method, using traffic paint drying time wheel. Test No. 1 was for a film tested for dry-to-no-pickup without electromagnetic energy exposure or blowing hot air on the film. Tests No. 2 and 10 3 were conducted by first having the films exposed to 3 seconds and 10 seconds, i respectively, of an electromagnetic energy at a frequency of 2450±20MHz in the range of 2430 MHz to 2470 MHz) and a power of 1500 watts, followed by testing for dry-to-no-pickup. The film in Test No. 4 was first exposed to hot air for 3 seconds using a forced hot air source about 10 cm above the film, followed 15 by testing for dry-to-no-pickup. The hot air source was set at 1600 watts power level, about 600C air temperature, and about 32 km/hour air flow. The film in Test No. 5 was exposed to 3 seconds of an electromagnetic energy at a frequency of 2450+20 MHz in the range of 2430 MHz to 2470 MHz) and a power of 1500 watts, followed by an exposure to 3 seconds of hot air as described for Test 20 No. 4, and then tested for dry-to-no-pickup. The dry-to-no-pickup conditions were at about 23.40C, atmospheric pressure, 50% relative humidity and minimal air flow km/hour).

The results are shown below.

Test No. 1 2 3 4 Microwave Exposure Time (sec) 0 3 10 0 3 Hot Air Exposure Time (sec) 0 0 0 3 3 Total Time to pass dry-to-no-pickup (min) a 5 4 2 3.5 2 a: ASTM D711 dry-to-no pickup test This example shows that a combination of microwave frequency range electromagnetic energy with heat, such as hot air, provides further improvement in shortening the dry-to-no pickup times.

Table I Compositions of Formulations I, II and III weight (grams) Ingredientsa,b,c I II III Add the following under moderate stirring Rhoplex AC-261 439.8 Rhoplex Fastrack 2706 445.15 Rhoplex Fastrack HD-21 468.4 water 20.2 14.85 Tamol 901 7.2 7.2 7.2 Surfynol CT-136 2.8 2.8 2.8 Drew L-493 2.0 2.0 Ti Pure R-900 100.0 100.0 100.2 Omyacarb 5 760.6 760.6 761.8 Mix the mixture above for 10 minutes, and then add with reduced stirring: Methanol 30.0 30.0 30.1 Texanol 23.0 23.0 23.0 Drew L-493 3.5 3.5 Natrosol 250HR aqueous 3.0 2.0 solution) Water 15.6 16.6 3.4 Total weight 1407.7 1407.7 1410.4 a: The ingredients above the double line are mixed with moderate stirring; after ingredients below the double line are added with a slower stirring.

10 minutes, the b: Trademark owners: Rhoplex and Rhoplex Fastrack are trademarks owned by Rohm and Haas Company; Tamol 901 Dispersant, an ammonium salt of an polyelectrolyte supplied by Rohm and Haas Company, Philadelphia, Pennsylvania 30 percent based on the solids; Surfynol CT-136 Surfactant, an acetylenic surfactant supplied by Air Products and Chemicals, Inc., Allentown, Pennsylvania; Drew L-493 defoamer supplied by Drew Chemical Company, Boonton, New Jersey; Ti Pure R-900 titanium dioxide supplied by E.I. duPont de Nemours Company, Wilmington, Delaware; Omyacarb 5, Ground natural calcium carbonate, evaluated under ASTM D 1199, Type GC, Grade II having a number average particle size of 5.5 microns with maximum oil absorption No. of 10, supplied by Omya, Inc., Proctor, Vermont; Texanol ester alcohol supplied by Eastman Chemicals, Kingsport, Tennessee.

c: Tamol 901 is a pigment dispersant; Surfynol CT-136 is a pigment wetting aid; Drew L-493 is a defoamer; TuPure R-900 is titanium dioxide, Omyacarb is calcium carbonate; Texanol is a coalescent; and Natrosol is a thickener.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

Claims (13)

1. A method for electromagnetic energy assisted curing of a waterborne coating composition, said method comprising: applying the waterborne coating composition to a surface of a substrate; and subjecting for a period in the range of from 0.001 seconds to 60 minutes the waterborne coating composition and the surface to an exposure of an electromagnetic energy having a frequency in the range of from 100 MHz to 50 GHz and a power in the range of from 1.0 Watts to 50,000 Watts; wherein the waterborne coating composition comprises: 0 an anionically stabilized emulsion polymer having a Tg greater than OOC; S" a polyfunctional amine having from 20% to 100% by weight based on the total weight of the polyfunctional amine of a monomer selected from the group consisting of an amine group containing monomer, an imine group containing monomer, and mixtures thereof; and o.0o an amount of a base sufficient to raise the pH of the waterborne coating composition to a point where essentially all of the polyfunctional amine is in a non-ionic state.

2. A method for electromagnetic energy assisted curing of a waterborne composition for traffic marking, said method comprising: applying the waterborne coating composition to a surface of a substrate; and subjecting for a period in the range of from 0.001 seconds to 60 minutes the waterborne coating composition and the surface to an exposure of an electromagnetic energy having a frequency in the range of from 100 MHz to 50 GHz and a power in the range of from 1.0 Watts to 50,000 Watts; wherein the waterborne coating composition comprises: an anionically stabilized emulsion polymer having a Tg greater than OOC; a polyfunctional amine having from 20% to 100% by weight of a monomer selected from the group consisting of an amine group containing monomer, an imine group containing monomer, and mixtures thereof; and an amount of a base sufficient to raise the pH of the waterborne coating composition to a point where essentially all of the polyfunctional amine is in a non-ionic state.

3. The method of claim 1 or 2, wherein the amine group containing monomer is selected from the group consisting of oxazolidinylethyl methacrylate, dimethylaminoethyl methacrylate, dimethylaminopropylmethacrylamide, and mixtures thereof.

4. The method of claim 1 or 2, wherein the frequency is in the range of from 2 GHz to 12 GHz and the base is a volatile base selected from the group consisting of ammonia, ammonium hydroxide, ethanolamine and mixtures thereof.

The method of claim 1 or 2, wherein the exposure is carried out prior to, simultaneously or after the applying the waterborne coating composition. 10

6. The method of claim 1 or 2, wherein the frequency is in the range of 2 GHz to 12 GHz and the waterborne coating composition further comprises in the range of from 0.01 wt% to 50wt% based on the total weight of the waterborne coating composition a chemical compound selected from the group consisting of silicon carbide, carbon black, a-silicon nitride, p-silicon nitride, boron nitride, tungsten nitride, aluminum nitride and mixtures thereof.

7. The method of claim 4, wherein the frequency is in the range of from 2430MHz to 2470 MHz.

8. The method of claim 1, wherein the substrate is selected from the group consisting of paper, road, pavement, runway, traffic area, metal, wood, plastic and combinations thereof.

9. The method of claim 1 or 2, wherein the waterborne coating composition further comprises a component selected from the group consisting of pigments, glass beads, quartz sand, and mixtures thereof.

The method of claim 1 or 2 further comprising adding in the range of from 0.01 wt% to 50wt% based on the total weight of the waterborne coating composition a chemical compound to the waterborne coating composition before or during the exposure of the electromagnetic energy, wherein the chemical compound is selected from the group consisting of silicon carbide, carbon black, a-silicon nitride, P-silicon nitride, boron nitride, tungsten nitride, aluminum nitride and mixtures thereof. 21

11. The method of claim 1 or 2 further comprising adding in the range of from 0.01 wt% to 50wt% based on the total weight of the waterborne coating composition a chemical compound to the waterborne coating composition before or during the exposure of the electromagnetic energy, wherein the chemical compound is a water soluble salt selected from the group consisting of sodium chloride, sodium bromide, sodium iodide, sodium acetate, potassium chloride, potassium bromide, potassium acetate, ammonium acetate, ammonium citrate, ammonium tartarate, and mixtures thereof. .0 S *ooo 22

12. A method for assisting curing of a waterborne coating composition substantially as hereinbefore described with reference to the Examples.

13. The steps, features, compositions and compounds disclosed herein or referred to or indicated in the specification and/or claims of this application, individually or collectively, and any and all combinations .of any two or more of said steps or features. DATED this THIRTY FIRST day of MARCH 2000 Rohm and Haas Company *4i by DAVIES COLLISON CAVE S* Patent Attorneys for the applicant(s)