MXPA97001716A - Aqueous compositions of coating, dryerap - Google Patents

Abstract

Aqueous coating compositions are disclosed which contain a latex having suspended amine functional groups, in which this latex has a glass transition temperature (Tg) greater than about 0 ° C, and is capable of film formation at temperatures of application, and a sufficient amount of base to raise the pH of the composition to a point where essentially all the amine functional groups are in a non-ionic state. Also described are methods for producing fast drying coatings on suitable substrates, by the application of such coatings, where these coatings develop an early resistance to the ag

Description

AQUEOUS COMPOSITIONS FOR COATING, QUICK DRYING BACKGROUND OF THE INVENTION The present invention relates to aqueous coating compositions having rapid drying characteristics and rapidly developing good water resistance. Such compositions are useful as coatings on metal, wood and other surfaces, where rapid drying characteristics are important. These compositions are particularly useful as coatings on substrates, where rapid water resistance of the coating is important, such as those surfaces that are routinely exposed to exteriors. The compositions of the present invention are especially useful as paints for traffic. Traffic paints have traditionally been formulated as solvent-borne systems, but with current environmental problems, traffic paints carrying water have received attention. The primary disadvantage so far with these paints for water-carrying traffic has been that the drying time is not fast enough, ie the "non-collection time" (the test rollers do not pick up paint) is not short enough . In addition, these traffic paints that carry water tend to be less resistant to wear than systems that carry solvents. US patent application, Serial No. 08 / 340,461, filed on November 14, 1994 (Landy et al.), Discloses aqueous coating compositions that dry quickly and soon develop a water resistance after application, where the composition contains an emulsion polymer, anionically stabilized, having a glass transition temperature (Tg) of about 00C, a functional amine polymer and a volatile base, to raise the pH of the composition, so that the groups of amine are essentially in a non-ionized state. It has now been discovered that latexes containing amine have similar properties of fast drying and early water resistance. EXPOSITION OF THE INVENTION One aspect of the present invention relates to a method for producing a fast drying coating, which has an early water resistance on a suitable substrate, this method comprises: applying a layer of an aqueous coating composition to the substrate , wherein this coating composition comprises a latex having functional pendant or suspended amine groups, wherein this latex has a Tg greater than about 0 ° C, a sufficient amount of base to raise the pH of the composition to a point where essentially all the amine functional groups are in a non-ionic state, and where the effective Tg is lower than the application temperature; and allowing the composition to harden, forming a water resistant coating on the substrate. Another aspect of the present invention relates to an aqueous traffic paint composition, comprising a latex having functional pendant amine groups, in which this latex has a Tg greater than about 02C, and a sufficient base amount to raise the pH of the composition to a point where essentially all of the amine functional groups are in a non-ionic state, where the effective Tg is less than the application temperature and such composition is of fast hardening. DETAILED DESCRIPTION OF THE INVENTION As used in this specification, the following terms have the following definitions, unless the context clearly dictates another way. "Amine-containing" or "functionalized amine" latex refers to a latex having pendant or suspended amine functional groups. Similarly, the terms "containing amine" or "carboxyl-containing", or the like, when used in combination with "latex" refers to latexes having pendant functional groups of the type indicated. "Latex" or "latex composition" refers to a dispersion of a water insoluble polymer, which can be prepared by conventional polymerization techniques, such as, for example, emulsion polymerization. "Polymer particle size" means the diameter of the polymer particles, measured with the use of a Brookhaven Model BI-90 Particle Sizer device (Brookhaven Instruments Corporation; Holtsville, New York), which employs a quasi-elastic light scattering technique to measure the size of polymer particles. (This technique is described by einer and collaborators in Chapter 3 of Uses and Abuses of Photon Correlation Spectroscopy in Particle Sizing (Uses and Abuse of Photon Correlation Spectroscopy in Particle Measurement) (1987), pages 48-61, a series of American Chemical Society Symposium). "Dry" or "hardened" used with reference to a coating layer after its application to a substrate, refers to the development of the physical property of the coating, and is not necessarily an indication of the content of the water remaining in the coating. "Glass transition temperature" or "Tg" is the narrow temperature range at which the amorphous polymers change from a relatively hard and brittle state to a relatively soft and viscous (rubber-like) state. "Effective Tg" refers to the Tg of the composition of a coating and is a function of the Tg of the latex, as modified by the amount of the coalescer, if any, added to the composition. "non-collection time" means the time it takes for the layer of the traffic paint composition to dry to the point where no paint adheres to a free roller of the rubber test wheels, as described in ASTM D711. -89. The following abbreviations are used in the specification: g = gram (s); kg / 1 = kilograms per liter; nm = nanometers; cps = centipoises; and wt% = percent by weight. The specified intervals will be read as inclusive, unless specifically identified otherwise. The amine functionalized latexes of the present invention include any and all functionalized amine latices having a higher Tg of O, so that the aqueous coating compositions containing these latexes are capable of forming films at ambient or ambient temperatures. greater. These latexes have a number average molecular weight in the range of 1,000 to 1,000,000, preferably 10,000 to 800,000. The particle size of these latexes will generally vary between 20 and 1000 nm and preferably between 50 and 700 nm. No attempt is made to be limited to the morphology of the functionalized amine latices of the present invention in any way. Thus, these latexes can be in the form of single or multiple stage particles. The multi-stage particles will comprise at least two mutually incompatible copolymers, which have any number of morphological configurations - for example; core / cover; core / shell particles with cover stages incompletely encapsulating the core; core / shell particles with a multiplicity of nuclei, interpenetrating network particles; and the like, where the greater portion of the surface area of the particles will be occupied by at least one eternal stage, and the interior of the particle will be occupied by at least one internal stage. The amine functionalized latexes of the present invention can be prepared according to any of a number of methods, including, but not limited to, addition polymerization of ethylenically unsaturated monomers, containing amine functionality; the polymerization of monomers that easily generate amines by hydrolysis; reactions of aziridines with carboxyl-containing polymers; reactions of polymers containing an enolyl carbonyl group, for example acetoacetoxyethyl methacrylate ("AAEM"), and diamines; reactions of amines with epoxy-containing polymers and amine reactions with vinyl-benzyl chloride polymers. These polymerization reactions are known in the art and examples of preparation of these and other suitable functionalized amine latexes can be found in the following publications: US Patent 3,847,857 (Chou et al.), US 4,119,600 (Bakule et al.); Roark, D. N. and B. C. McKusick, "Aziridines" in Ullman's Encyclopedia of Industrial Chemistry, 5th Ed., VCH: 1985, page 239; US 5,364,891 (Pears et al.), US 5,494,961 (Lavoie et al.); and US 4,367,298. These publications are incorporated herein by reference in the extent to which they describe the preparation of functionalized amine latexes. The amount of amine present in the functionalized amine latices of the present invention will vary depending on the amine used and the method of preparation, but, in general, an amount of 2% by weight or more of the amine (based on the weight of the amine). monomer) will be used. It is preferred to use between 3-20% of the amine, more preferably between 5-10% of the amine. In aqueous coating compositions of the present invention, essentially all functionalized amine latex is maintained in a deprotonated state, raising the pH of the composition to a pH in the range of 7.5 to 11, preferably 9.5 to 10.5. This means that essentially all of the amine groups in the functionalized amine latex are in a deprotonated state. The pH can be raised by adding a base, such as ammonia; an alkali metal hydroxide, such as sodium hydroxide; or morpholine, or other lower alkyl amines, such as 2-methylaminoethanol, 2-dimethylaminoethanol, N-methylmorpholine and ethylenediamine. Volatile bases, such as ammonia or a mixture of volatile bases and non-volatile bases, such as sodium hydroxide, are preferred, and ammonia is most preferred. This deprotonation of the amine functional groups helps to preserve the colloidal stability of the composition. The aqueous coating compositions of the present invention may also optionally contain an acid-containing latex, or the amine-containing latex may optionally also contain acid functional groups; that is, the latex can optionally be a latex containing acid / amine. The addition of acid functional groups is believed, without being sure, improving the stability of the composition. Acid-containing latexes are well known to those skilled in the art and their preparation will not be discussed further here. The amount of the acid present in the acid-containing latex or the acid / amine-containing latex will vary, depending on the acid used and the method of preparation, but, in general, an amount of 10% by weight or less of the acid (based on in the weight of the monomer) will be used. It is preferred to use between 1 to 5% of the acid. The amount of the acid present in the acid-containing latex or the acid / amine-containing latex is also a function of the amount of amine. In general, the weight ratio of the amine to the acid should be greater than 3 to 1. It is preferred to have a weight ratio of 5 to 1 or greater, and it is more preferred to have a weight ratio of 27 to 1. The latexes containing acid / amine can be prepared according to known methods, including, but not limited to, those described in US Patent 3,404,114 (Snyder et al.) and US 4,760,110 (Das). These patents are incorporated herein by reference in the extent to which they describe the preparation of the acid / amine containing latexes. Surfactants are commonly used in emulsion or dispersion polymerization to provide stability, as well as to control particle size. Surfactants can also provide the dispersity for water-reducible resins. Conventional surfactants include anionic or non-ionic emulsifiers or their combinations. Typical anionic emulsifiers include, but are not limited to: alkyl, alkali or ammonium sulfates, alkyl sulfonates, fatty acid salts, sulfosuccinic acid salt esters, alkyl diphenylether disulfonates and salts of free acids of complex esters of organic phosphates. Typical nonionic emulsifiers include, but are not limited to: polyethers, for example condensates of ethylene oxide and propylene oxide, including alkyl and alkylaryl polyethylene glycols and polypropylene glycol ethers, and thioethers, straight or branched chain, alkyl phenoxy poly (ethyleneoxy) ethanols having alkyl groups with about 7 to 18 carbon atoms and with about 4 to 100 ethyleneoxy units, and polyoxyalkylene derivatives of hexitol, including sorbitans , sorbitans, manitans and manituros. The surfactants can be employed in the compositions of the present invention at levels of 0.1 to 3% by weight or more, based on the total weight of the final composition. The aqueous coating compositions of the present invention may optionally contain additional components including, but not limited to: thickeners, rheology modifiers, dyes; segregation agents, biocides,; dispersants, pigments such as titanium dioxide or carbon black; diluents, such as calcium carbonate, talc, clays, silicas and silicates; fillers such as glass or polymeric microspheres, quartz and sand; antifreeze agents, plasticizers, adhesion promoters; coalescents; soaking agents, waxes; surfactants; slip additives; interlacing agents; defoamers; colorants; condoms; freeze / melted protectors; corrosion inhibitors; and soluble alkali or water polymers. These components are preferably used in traffic paints. Other optional components of the compositions of the present invention include, but are not limited to: cosolvents, reactive pigments, UV radiation absorbers, antioxidants and stabilizers. These optional components (as desired) can be added in any order of addition that does not cause an incompatibility between the components. Components that do not dissolve in the aqueous carrier (such as pigments and fillers) can be dispersed in the latex or an aqueous or cosolvent carrier using a high shear mixer. The aqueous coating compositions of the present invention may be used to provide coatings on suitable substrates, such as wood and reconstituted wood products, concrete, asphalt, fiber cement, stone, marble, clay, plastics (e.g., polystyrene). , polyethylene, ABS, polyurethane, polyethylene terephthalate, polybutylene terephthalate, polypropylene, polyphenylene, polycarbonate, polyacrylate, PVC, Noryl® and polysulfone), paper, cardboard and metals (ferrous as well as non-ferrous). The fast-drying nature of these compositions makes them particularly useful as traffic paints and as maintenance coatings for substrates, where rapid development of water resistance is important. The aqueous coating compositions of the present invention can be applied to the desired substrates using conventional application techniques, such as conventional airless spray, roller, brush, curtain, flood and immersion coating methods. Once applied to the substrate, the coating compositions of the present invention are typically cured at ambient temperatures or, in some cases, at elevated temperatures. For traffic paints, it is convenient to add glass spheres, disposed facially, to the paint, or before applying the paint to the road surface, or just after its application, but before drying the paint. If the spheres are applied separately, they can be sprayed, watered, dropped or otherwise applied to the wet paint layer, according to any of a number of known methods. These spheres work as reflectors of light, making it easier to mark the traffic to see at night and, under adverse environmental conditions (for example, fog or rain). The typical glass spheres, useful for this application, such as those described in the AASHTO Designation M 2247-81 (1993), developed by the American Association of State Highway and Transportation Officials (Washington, DC). These spheres will generally be applied at a rate of 0.72 to 2.9 kg / 1 or greater of the paint for visibility at night or under adverse environmental conditions. Similarly, for traffic paints, if desired, the non-collection time can be further improved by the contact of the applied layer with a coagulant. Suitable coagulants include, but are not limited to: weak acids, such as acetic acid or citric acid, and strong acids, such as hydrochloric or sulfuric acids, if diluted. Weak acids are typically used with a strength of 10 to 30% by weight, preferably 20% by weight; and the strong acids are typically diluted to a strength of 5 to 15% by weight, preferably 10% by weight. Citric acid is preferred. The coagulant can be applied by any of the conventional methods known in the art, for example, by spraying coagulant on the layer. It is believed, without being sure, that the coagulant when placed in contact with the layer coagulates the latex binder present in the layer, to improve the drying rate of this layer. The amount of the coagulant sprayed on the layer depends on the amount of latex binder present in the layer, like the type used of the latex binder, the amount of the coagulant sprayed on the applied layer of the traffic paint is dependent on the type of acid, its strength and the type of spray equipment used in carrying out the coagulation stage. The coagulant (for example 20% by weight citric acid) is typically applied at a rate of 0.6 to 2% by weight, preferably 1% by weight, based on the total weight of the coating composition applied as a layer . The following Examples 2-4 illustrate the preparation of amine-containing and acid-containing amine-containing latexes according to the present invention. Example 1 presented for comparison purposes, details the preparation of the typical latex (without amine) used in the aqueous coating compositions. Comparative Example 1; Preparation of a Standard Latex A (Without Amine) To a 2-liter reactor, containing 330 g of deionized water ("DI water"), under a nitrogen atmosphere, at a temperature of 922C, were added, with stirring, 3.8 g of ammonium bicarbonate dissolved in 25 g of DI water, 1.4 g of ammonium persulfate dissolved in 25 g of DI water and 34.3 g of a polymer dispersion having a total solids content of 42% by weight. The gradual addition of emulsion 1 of monomers (Table 1, below) and a solution of 0.7 g of ammonium persulfate dissolved in 50 g of DI water, was then carried out while the temperature was maintained at 852C. A catalyst / activator pair was added after completing the charges of the monomer emulsion and ammonium persulfate. The sample had a Brookfield viscosity of 15 cps with a solids content of 44.3% by weight and a particle size of 204 nm. TABLE 1; EMULSION OF MONOMERS 1 Example 2; Preparation of a Latex Containing Amine To a 2 liter reactor, containing 330 g of deionized water ("DI water") under a nitrogen atmosphere, at a temperature of 922 C, 3.8 g of sodium bicarbonate were added with stirring. ammonium, dissolved in 25 g of DI water, 1.4 g of ammonium persulfate dissolved in 25 g of DI water, and 34.3 g of the polymer dispersion having a total solids content of 42% by weight. The gradual addition of the monomer emulsion 2 (Table 2, below) and a solution of 0.7 g of ammonium persulfate dissolved in 50 g of DI water, was then carried out while the temperature was maintained at 85 ° C. catalyst / activator after completing the emulsion charges of monomers and ammonium persulfate. The sample had a Brookfield viscosity of 20 cps with a solids content of 42.9% by weight and a particle size of 226 nm.

TABLE 2: EMULSION OF MONOMERS 2 Example 3: Preparation of Latex Containing Acid / Amine To a 2 liter reactor, containing 330 g of deionized water ("DI water"), under a nitrogen atmosphere, at a temperature of 922 C, 3.8 g of ammonium bicarbonate, dissolved in 25 g, was added with stirring. of DI water, 1.4 g of ammonium persulfate dissolved in 25 g of DI water, and 34.3 g of the polymer dispersion having a total solids content of 42% by weight. The gradual addition of the monomer emulsion 3 (Table 3, below) and a solution of 0.7 g of ammonium persulfate dissolved in 50 g of DI water, was then carried out while the temperature was maintained at 85 ° C. A catalyst / activator pair was added after completing the charges of the monomer emulsion and ammonium persulfate. The sample had a Brookfield viscosity of 20 cps with a solids content of 42.6% by weight and a particle size of 224 nm.

TABLE 3; EMULSION OF MONOMEROS 3 Example 4; Preparation of Latex Containing Acid / Amine To a reactor containing 665 g of deionized water ("DI water") under a nitrogen atmosphere, at a temperature of 922C, 7.6 g of ammonium bicarbonate, dissolved, was added with stirring in 56 g of DI water, 2.8 g of ammonium persulfate dissolved in 28 g of DI water, and 68.6 g of the polymer dispersion having a total solids content of 42% by weight. The gradual addition of the monomer emulsion 5 (Table 4, below) and a solution of 1.4 g of ammonium persulfate dissolved in 84 g of DI water, was then carried out while the temperature was maintained at 852C. A catalyst / activator pair was added after completing the charges of the monomer emulsion and ammonium persulfate. The sample had a solids content of 46.8% by weight and a particle size of 199 nm.

TABLE 4: EMULSION OF MONOMERS 4 Example 5; Coating Compositions The following coating compositions (Formations A-D) were prepared using the latexes of Examples 1 to 3. Formulation A, a standard coating composition, was used here for comparison purposes. Formulations B, C and D are typical coating compositions of the present invention, and are particularly useful as paints for traffic. 1 Dispersant, Tamol® 901, an ammonium salt of a polyelectrolyte (Rohm and Haas Co .; Philadelphia, Pennsylvania) at 30 wt% solids 2 Surfactant Surfynol® CT-136, an acetylenic surfactant (Air Products and Chemicals, Inc .; Allentown, Pennsylvania) 3 Drew® L-493 Defoamer (Drew Chemical Co., Boonton, New Jersey) 4 QR-708® Rheology Modifier (Rohm and Haas Co., Philadelphia, Pennsylvania) at 10% by weight solids. 5 Texanol® alcohol ester (Eastman Chemicals; Kingsport, Tennessee).

To an appropriate amount of latex, the following components were added in order, with stirring: ammonium hydroxide, dispersant, surfactant, defoamer, pigment, diluent and rheology modifier. These components were mixed for about 10 minutes to achieve a smooth dispersion of the pigment and diluent. Then the following components were added, in order: methanol, coalescing agent, defoamer, deionized water and additional rheology modifier. The following table shows the percentages of the amine and acid functional groups, based on the total monomer charge, in the coating compositions of this Example 5.

A B C D% of Amine 0 6. 8 6. 8 6. 8% Acid 1. 3 0 0 25 0. 25 In the following Examples 6 and 7, the coating compositions of Example 5 were tested on drying speed and prompt resistance to washout. The test methods used are described below. Touch Hardness Time - This test is similar to ASTM D1640, which is a test for the drying of organic coatings at room temperature. The paint compositions were applied to a non-porous substrate (glass plate or metal panel) by means suitable for the specified film thickness. The test panels were then placed promptly in a test chamber (Victor Associates, Inc., Hatboro, Pennsylvania) equipped with a certified hygrometer and temperature indicator, and maintained at the specified relative humidity for the duration of the test period . The specified humidity was achieved before placing the test panels by filling the container at the bottom of the test chamber with 2 cm. of water, and carefully opening the doors on the sides of the chamber to mix the ambient air with the saturated air from the chamber. The measurements were taken in 5 minute intervals, opening the door of the test chamber briefly to touch the wet paint films lightly with the tip of a clean finger. The ASTM method was modified in that the time of "hardness to the touch" in these examples is defined by the time it takes for the wet paint to be free of stickiness, in addition to not having adhered paint to the tip of the finger after a slight I touched. Drying Time of Non-Collection - The paint compositions were applied to a glass substrate by suitable means, at the specified film thickness. The test panels were then placed promptly into a test chamber and treated as in the Touch Hardness Time test, described above. When the film is dry at a light touch, the panel is removed from the test chamber and the Non-Harvest Drying Time is determined, according to ASTM D711, by rolling a traffic paint drier wheel on the wet film. The end point for the Non-Harvest Drying Time is defined as the point in time where no paint adheres to the rubber rings of the test wheel.

Early Flushing Time - The paint compositions were applied to a suitable substrate by means appropriate to the specified film thickness. The test panels were then placed promptly in a test chamber and treated as in the Touch Hardness Time test, described above. After a predetermined period of time, specified in the examples, the panels were removed and placed under a stream of water for 3 minutes, so that the water would come into contact with the surface of the paint film at a perpendicular angle . If at the end of 3 minutes, the paint film has not been dissolved or has been interrupted, the film is considered to pass the test. If the films dissolve or break under running water, they are classified as failing the test. Example 6: Coating Applied to a Glass Substrate. The paint compositions of Example 5 were applied to glass panels at a film thickness of about 320 microns and evaluated at a relative humidity of 60% and at 22ac, for hardness at touch, drying until no harvest and resistance to washout, after 1 hour of drying.

A B C D Hardness at Touch (minutes) 45 20 25 25 Drying up Do not Pick up Paint 45 25 30 30 Fadeout Resistance Failure Passage Passes Early Results: The paint compositions of the present invention (formulations B-D) all dried significantly faster than the control (Formulation A) and each Formulation B-D exhibited an early washout resistance, while Formulation A did not exhibit it. . Example 7; Coatings Applied to a Metal Substrate The paint compositions of Example 5 were applied to steel panels treated with phosphate at a film thickness of approximately 150 microns, and were evaluated at a relative humidity of 75% and 22 ac for the hardness touch and resistance to washout after 1 hour of drying.

A B C D Touch Hardness (minutes) 35 25 25 25 Dewet Resistance Fail Paste Passes Early Results: The paint compositions of the present invention (BD Formulations) all dried significantly faster than the control (Formulation A), and each of the BD Formulations exhibited an early washout resistance, in both Formulation A did not exhibit it.

Claims (9)

1. CLAIMS 1. A method for producing a fast-drying coating on a suitable substrate, in which the coating develops an early resistance to water when applied to the substrate, this method comprises: applying a layer of an aqueous coating composition to the substrate, where this coating composition comprises a latex having suspended amine functional groups, in which this latex has a glass transition temperature greater than 02C, a sufficient amount of base to raise the pH of the composition to a point where essentially all the groups amine functional groups are in a non-ionic state, and where the effective glass transition temperature is lower than the application temperature; and allowing the composition to harden, forming a water resistant coating on the substrate.
2. 2. The method according to claim 1, wherein the composition is a traffic paint, which is applied to the surface of a taxiway.
3. 3. The method according to claim 2, wherein the composition further comprises facially disposing glass spheres.
4. 4. The method according to claim 1, wherein the composition, when applied, dries to the touch and is resistant to washout within 1 hour after application to the substrate.
5. The method according to claim 1, wherein the composition is applied to a substrate, selected from the group consisting of: wood and reconstituted products of wood, concrete, asphalt, fiber cement, stone, marble, clay, plastics, paper, cardboard and metal.
6. The method according to claim 1, wherein the composition further comprises a latex having suspended acid functional groups, and wherein the weight ratio of the amine to the acid is greater than 3 to 1.
7. 7. The method, according to Claim 1, wherein the latex, having suspended amine functional groups, also has suspended acid functional groups, and wherein the weight ratio of the amine to the acid is greater than 3 to 1.
8. 8. An aqueous paint composition of traffic, which comprises: a latex having suspended amine functional groups, in which this latex has a glass transition temperature of greater than about zero and a sufficient amount of base to raise the pH of the composition to a point where essentially all the amine functional groups are in a non-ionic state; wherein the effective glass transition temperature is lower than the application temperature, and this composition is fast drying and develops an early resistance to water when applied to a suitable substrate.
9. 9. The composition according to claim 8, wherein this composition develops resistance to water within 1 hour, after application to a substrate.