MXPA97000168A - Inorganic polymeric coatings united chemically and hardeners reticulating for mys - Google Patents

Abstract

The present invention relates to aqueous coating compositions for glass or ceramic substrates containing at least one water soluble alkali silicate and a crosslinking agent produced by reacting at least one alkali hydroxide with an aluminum phosphate. The coating compositions are applied to a glass or ceramic substrate and are cured or hardened with lime

Description

INORGANIC POLYMERIC COATINGS UNITED CHEMICALLY AND REINFORCING HARDENERS FOR THEMSELVES FIELD OF THE INVENTION The present invention relates to the field of coatings that can be cured or hardened with heat, inorganic, for glass and ceramic articles. More particularly, the invention provides water-based, curable or heat hardening coating compositions containing an alkali silicate and a crosslinking hardener. The compositions are particularly useful as coating compositions for glass and ceramic articles.

BACKGROUND OF THE INVENTION Aqueous ammonium or alkali metal silicate compositions containing inorganic curing agents are already known. See, for example, Neely, U.S. Pat. No. 4,288,252. In general, the prior art uses alkaline silicates which are crosslinked with aluminum trimetaphosphate of form B. The crosslinking of the alkali silicate is achieved by heating an article coated with the composition. Ref. 23831 water at an elevated temperature of 204.44 ° C (400 ° F) or higher. The aqueous composition is made by mixing alkali silicate with fillers and / or pigments and placing the mixture in a sealed container. The aluminum trimetaphosphate of form B is mixed in water with or without pigments and fillers, and stored in a second sealed container. Prior to its use, the separated materials are mixed together. Separate containers are necessary since the aluminum trimetaphosphate of form B and the alkali metal silicates undergo a non-crosslinking reaction even at room temperature to produce a solidified mass within about a day. Once the materials from the separate containers are mixed, the resulting inorganic paint composition should be used within the time period of approximately eight hours. Therefore, the paint system must be prepared as a two pack or package system to prevent this undesirable reaction.

BRIEF DESCRIPTION OF THE INVENTION The present invention avoids the use of aluminum trimetaphosphate hardener of Form B and other agents of inorganic curing or hardening which have been previously employed and which have an undesirable reaction at low temperature with the alkaline silicates. In the present invention, it is possible to formulate the composition as a package or packaging system since there is no significant low temperature reaction, for example, at room temperature, between the alkaline silicates and the crosslinking agent employed. This allows the formulation of the inorganic paints as a single recirculator system with a prolonged storage duration.

DETAILED DESCRIPTION OF THE INVENTION The present invention provides heat curable, inorganic, aqueous coating compositions comprising at least one water-soluble alkali silicate and an alkaline aluminum phosphate crosslinking agent. The invention also provides the method for producing and using such coating compositions. Alkaline aluminum phosphate crosslinking agents and the method for their production are also provided. Additionally, the invention provides substrates which are coated with a cured or heat hardened coating of the coating composition of the invention.

The aqueous coating compositions of the invention are composed of, in addition to water as the only necessary solvent, at least one water-soluble alkali silicate and an alkaline aluminum phosphate crosslinking agent. The alkali silicates used herein are those which have been previously known for use in the formulation of silicate, inorganic coating compositions. See, for example, Neely, U.S. Pat. No. 4, 288,252. The sodium silicate and the potassium silicate and mixtures thereof are illustrative. The crosslinking agent employed herein is an alkaline aluminum phosphate agent which is free from aluminum trimetaphosphate and particularly from aluminum trimetaphosphate of form B. As previously stated, the presence of aluminum trimetaphosphate of form B in the crosslinking agent it is undesirable since even at low temperatures of about room temperature, this material undergoes a non-crosslinking reaction with the alkali silicate to produce a soli fi ed mass in the course of about a day. This avoids the formulation of a package or packaging system that uses these materials. However, this undesirable reaction at low temperature does not occur between the alkali silicate and the crosslinking agent of this invention, thus enabling the formulation of a system of a package or package which is stable in storage for extended periods of time. The alkaline aluminum phosphate crosslinking agent of this invention is the product produced by reacting at least one alkali hydroxide, for example, the sodium, potassium or lithium hydroxides or mixtures thereof, with an aluminum phosphate, for example , the aluminum diacid phosphate, at a high temperature in the range of about 400 ° C to 800 ° C for a period from several seconds to several hours. The preferred temperature range is from about 500 ° to 700 ° C. The reaction can be conducted in a single stage or in a two-step reaction. In a two-step reaction, there is a reaction at low temperature, for example, at room temperature, between the alkali hydroxide and the aluminum phosphate to obtain a precipitate. The precipitate is then subjected to a high temperature treatment in the range of about 400 ° to 800 ° C to form the crosslinking product. A one-step reaction in a liquid or solid state reaction, however, is not avoided. the amount of the alkaline hydroxide mixed with the aluminum phosphate can vary such that the pH of the mixture that has reacted varies from approx. 3 to 10, with the preferred range being from about 4 to 8. The high and low temperature reactions can be conducted in an open or ventilated vessel and the reaction at elevated temperature can be conducted using an ignition / drying technique. sprayed The reaction time at elevated temperature depends on the rate of heat transfer to the reaction mass and will vary with the heating mode and with the reaction vessel. In a reaction vessel, the reaction time can be from one to several hours to reach the reaction temperature in the center of the reaction mass, while in a spray-on / drying system the time can be an issue only seconds The product of the reaction at elevated temperature is typically a mixture of compounds and can be employed directly as the crosslinking agent of the invention without the isolation of the compounds of the individual components. Usually one or more of the compounds are present in larger amounts, with one or more of the compounds that are present in minor amounts. In general, 20% by weight or more could constitute a larger amount and less than 20% by weight could be considered as a smaller amount. However, the major constituents are generally in the range of 30-80% by weight and the minor constituents could be generally 10% or less. As an illustrative method, the crosslinking agent can be prepared by combining and mixing, at room temperature, an aqueous solution of the alkali hydroxide with an aqueous solution of an aluminum phosphate. An exothermic reaction is the result and a reaction product is formed as a precipitate during mixing. The precipitated reaction product is isolated and placed in a container and dried, for example, in the range of 100 to 150 ° C, for from about two hours to overnight. The dry reaction product is then heated to and maintained at an elevated temperature from about 400 to 800 ° C for several seconds to several hours to form the crosslinking product. The product can then be cooled and washed with water and then dried. In some cases, washing with water has been found desirable but not essential in all cases. The following is an illustrative list of the components which may be present in the mixture produced by the reaction of the potassium, sodium and lithium hydroxides respectively with an aluminum phosphate. These compounds do not need to be present in a single reaction product. Some of the components they may be present in larger amounts while others are present in smaller amounts.

Potassium KAIPJOT KPOJ- KH2P04 A1P04 K3P04 A1J (P04) 2 (OH), 9HJO KJA12 (P04) J KsP3O, 0 »2H2O AlP04« xHjO K3HP2Cv3H20 KJP3O10 K4Pj07-2K2HP04 KlH2 [P04] 2 (P207) KAÍPO.JJÍPJO,) K, H, (P04) 2 KH2P04 Sodium Na ^ AlP ^ PO NajAl2 (P04) 3 Naj (? LPjOI0) -2HjO Naí (PO,) 4-6H20 Na4P20, NajHPjOr-HjO Na, P04 NaPO, A1P04-XH20 A1HJ (P04) J.HJO Ma2H2 (POj) 4 NajApy? HjO A1P04 N? AltP2Ou'10H2O NaAl (HP04) 2 Al | l (P04) 9 (aH) ß * xH20 3 NaPOj • 6HjO NaHjPOj • XH, 0 Lithium LI, P04 LltPjpj ijHPO, Al, (POJ (OH), A1P04 AlHPjO XHjO LYAL (P04), (OH) 2A1 (P04) '3H, 0 LiAlH * (PjO,),? LH, PjO, 0 LijP3O10-5H2O AIHPJQT -XHJ 4LiPO, »2HjO 4LiPO,« VBfi 4 LiPOj • 6H20 LijHPjO, • HjO A1H3 (P04) • 3H20 LijHPO, Following the reaction, the product is cooled and reduced to a fine powder. In the case of dry milling operations, the resulting powder is mixed with water to form a slurry or suspension. The slurry or slurry can then be further ground to improve the dispersion. Pigments can be added to the slurry or slurry to similarly improve the dispersion of the pigments in the final composition. The aqueous slurry or slurry containing the crosslinking agent as described above is then combined with the necessary alkali silicate such as sodium or potassium silicate or mixtures thereof. Prior to such combination, the fillers, pigments and other additives to modify the properties of the coating can be mixed with the alkali silicate or such materials can be added after the combination or mixing of the slurry containing the crosslinking agent with the alkali silicate. . The fillers can be minerals that are naturally present or man can make oxides or other inorganic materials. Examples of suitable fillers are silica, feldspar, mica, azuleite-nite, aluminum, zircon, graphite, silicon carbide, oxide glasses, silver, stainless steel and iron. The pigments which can be used are illustrated as follows: ferrous oxide / ferrite, ferric oxide, titanium dioxide, copper chromite, ferrite of manganese, chromium hematite, cobalt aluminate and zinc and mica coated with titania. The pigments used - either alone or as mixtures - will, of course, be those which are stable at the curing temperature employed when the composition is applied to the required substrate and is cured or thermally hardened. Water, surfactants, defoamers and other additives can be added to vary the solids content, the viscosity and other properties of the composition. Water is the only solvent needed. After all the ingredients are mixed to achieve the desired desired properties of the composition, such composition is sealed in a single container and stored until it is applied to a desired substrate by conventional methods and curing or heat hardening. The compositions may vary widely with respect to their content, the ratio or weight ratio of the alkali silicate solids to the aluminum phosphate crosslinking agent may be in the range of 1: 1 to 40: 1 with a preferred range from 2: 1 to 20: 1. The weight percent of the pigments and fillers in the composition can vary from 5 up to 70% with the preferred range of 15 to 60%. The percentages by weight of the pigments and fillers are interdependent with each other. When the percentage of one increases, the percentage of the other will decrease. In addition, the weight percentage of the pigment or filler is largely dependent on the particle size and particle size distribution of either. When the particle size distribution becomes smaller, the percentage of the pigment or filler must decrease to make or manufacture a coating with good properties. In general, the amounts of the surfactants, the defoaming agents and the additives that act as both a surfactant and a defoaming agent fall within the typical ranges suggested by the supplier of the additives for smaller applications. These intervals recommended by the providers are typically from 0.001% to 0.1%. The compositions curable with heat are particularly useful as functional or decorative coatings for glass and ceramic materials. The black coatings for the perimeter of the automotive glasses are considered as a primary application. The use of other pigment colors instead of black, will provide products for architectural glass and bottles The decorative coatings for the ceramic tile is visualized as an additional main use. The heat-curable coating composition, following the formulation, can be applied by conventional methods such as spraying, brush coating, screen printing, and the like, on the desired substrate such as, for example, the glass or the ceramics. The coated substrate is then heated to an elevated temperature of about 175 ° C (350 ° F) to 700 ° C (1300 ° F) to cure or harden the coating on the substrate. The surface of the substrate to which the composition is applied before curing should be clean, ie free of cutting oils, fingerprints or impressions of fingers and the like. In some cases, for example, in architectural glass, the substrate may be one that contains a metal / metal oxide film on the surface which has been formed by vapor deposition methods. "The following examples are provided for illustrate the invention Such examples are not intended to be construed as limiting the scope of the invention The following EXAMPLES 1-3 illustrate the preparation of the crosslinking product of the invention.

EXAMPLE 1 600 grams of a 50% by weight aqueous solution of potassium hydroxide is mixed with 1000 grams of a 50% by weight aqueous solution of aluminum diacid phosphate at room temperature. An exothermic reaction results and no precipitate or reaction product is formed during mixing. The reaction product is isolated and placed in a vessel and dried at 100 ° C for two hours. The dry reaction product is then heated to and maintained at 650 ° C for two hours to form a cross-linked product. After cooling to room temperature, the mixture is washed with water and dried. The product contains a mixture of compounds and the X-ray diffraction indicates the presence of K "A12 (P0,) ~, KA1P "20-7 ,, KP03 and AlP04.» XH20 as components of the mixture.

EXAMPLE 2 An aqueous solution of sodium hydroxide is prepared by mixing 230 grams of sodium hydroxide with 585 grams of water. This solution is then mixed, at room temperature, or at room temperature, with 1000 grams or one kilogram of a 50% by weight aqueous phosphate solution or dispersion. to aluminum diacid. An exothermic reaction results and a precipitate or reaction product is formed during mixing. The reaction product is isolated and placed in a container and dried in an oven at 150 ° C overnight. The dry reaction product is then heated to and maintained at 500 ° C for three hours to form a crosslinked product. The product contains a mixture of compounds and X-ray diffraction indicates the presence of Na7 (AlP20?) 4, Na3Al2 (P04) 3, Na6 (P03) 6 • 6H20, Na ^ O. ,, A1P0, • xH 0, Na "P0, and NaP0" as the components of the mixture.

EXAMPLE 3 An aqueous solution of lithium hydroxide is prepared by mixing 270 grams of lithium hydroxide monohydrate with 2250 grams of water. This solution is then mixed, at room temperature, with 1000 grams of a 50% by weight aqueous solution of alu-minium diacid phosphate. An exothermic reaction results and a precipitate or reaction product is formed during mixing. The reaction product is isolated and placed in a container and dried in a microwave oven. The dry reaction product is then heated to and maintained at a temperature of 550 ° for three hours to form a cross-linked product. The product contains a mixture of compounds and X-ray diffraction confirms the presence of Li4P20-, Li3P04, A1P04, Li2HP03 and AlHP20? 'XH20 as components of the mixture.

The following EXAMPLES 4-7 illustrate the formulation of the coating compositions of the invention and the application of such compositions to a substrate followed by curing to form a durable adherent coating on the substrate.

EXAMPLE 4 120 grams of a potassium silicate solution with a silica / alkali oxide weight ratio of 2.5 / 1 is placed in a dispersion mill. A slurry or slurry containing 8 grams of water and 4 grams of a crosslinking product such as, for example, the material of "EXAMPLE 3 is prepared by mixing or processing in a dispersion mill.This mixture is then added to the silicate of potassium in the dispersion mill 20 grams of a copper chromite and 40 grams of manganese ferrite spinel pigments are added to the mill The mixture is ground for 30 minutes Other desired additives can be placed in the mill or aggregates the mixture after of the removal of the ground material. The black coating is then applied to a clean glass substrate by any convenient means. The coated substrate is then placed in an oven at 704.44 ° C (1300 ° F) for three minutes, removed, and cooled to room temperature by natural convection to form a durable, black, adherent coating on the glass.

EXAMPLE 5 120 grams of a potassium silicate solution with a silica / alkali oxide weight ratio of 2.5 / 1 is placed in a dispersion mill. A slurry or suspension containing 8 grams of water and 4 grams of a crosslinking product, such as, for example, that of EXAMPLE 1, is prepared by mixing or processing in a dispersion mill. This mixture is then added to the potassium silicate in the dispersion mill. 20 grams of the ferrite / ferrous oxide pigment are added to the mill. The mixture is ground for 60 minutes. Other additives can be placed in the mill or added to the mix after removal from the mill. The black coating is then applied to a clean glass substrate by any convenient means. The coated substrate is then placed in an oven at 232.22 ° C (450 ° F) for fifteen minutes, stir, and cooled to room temperature by natural convection to form a durable, black, adherent coating on the glass.

EXAMPLE 6 120 grams of a potassium silicate solution with a silica / alkali oxide weight ratio of 2.5 / 1 is placed in a dispersion mill. A slurry or suspension containing 8 grams of water and 4 grams of a crosslinking product such as, for example, that of EXAMPLE 2 is prepared by mixing or processing in a dispersion mill. This mixture is then added to the potassium silicate in the dispersion mill. 30 grams of copper chromium oxide pigment are added to the mill. The mixture is ground for 60 minutes. Other additives can be placed in the mill or added to the mix after removal from the mill. The black coating is then applied to a clean glass substrate by any convenient means. The coated substrate is then placed in an oven at 176.66 ° C (350 ° F) for 15 minutes, removed, and cooled to room temperature by natural convection to form a durable, black, adherent coating on the glass.

EXAMPLE 7 120 grams of a potassium silicate solution with a silica / alkali oxide weight ratio of 2.5 / 1 are placed in a dispersion mill. A slurry or slurry containing 10 grams of water and 4 grams of a crosslinking product such as, for example, that of EXAMPLE 1 is prepared by mixing or processing in a dispersion mill. This mixture is then added to the potassium silicate in the dispersion mill. 25 grams of the chromium hematite oxide pigment are added to the mill. The mixture is ground for 60 minutes. Other additives can be placed in the mill or added to the mix after removal from the mill. The green coating is then applied to an architectural glass substrate, which has a metal / metal oxide film coated under vacuum, by any convenient means. The coated glass is then placed in an oven at 176.66 ° C (350 ° F) for fifteen minutes, removed, and cooled to room temperature by natural convection to form a durable, green coating, adhered to and protecting the coating under vacuum on the glass.

It is noted that in relation to this date The best method known by the applicant to carry out the aforementioned invention is that which is clear from the present description of the invention.

Having described the invention as above, it is claimed as prooiedad the content in the following

Claims (17)

R E I V I N D I C A C I O N S

1. A heat curable, inorganic, aqueous cured coating composition characterized in that it comprises at least one water soluble alkali silicate and an effective crosslinking amount of a crosslinking agent which is a product produced by reacting at least one hydroxide alkaline with an aluminum phosphate at a temperature of about 400 ° to 800 ° C.

2. A composition according to claim 1, characterized in that it also contains an inorganic pigment.

3. A composition according to claim 2, characterized in that it also contains at least one element selected from the group consisting of a filler, a surfactant and a defoaming agent.

4. A composition according to claim 1, characterized in that the proportion of the solids of the alkali silicate with respect to the crosslinking agent is in the range of 1: 1 to 40: 1.

5. A composition according to claim 4, characterized in that the proportion of solids is in the range of 2: 1 to 20: 1.

6. A composition according to claim 3, characterized in that the percentage by weight of the pigments and the filler in the composition varies from 5 to 70 percent.

7. A composition according to claim 6, characterized in that the percentage by weight varies from 15 to 60 percent.

8. A composition according to claim 1, characterized in that the alkali hydroxide is at least one element selected from the group consisting of sodium hydroxide, potassium hydroxide and lithium hydroxide.

9. A composition according to claim 1, characterized in that the aluminum phosphate is the aluminum diacid phosphate.

10. A composition according to claim 1, characterized in that the crosslinking agent is produced by a process which comprises mixing, at room temperature, an aqueous solution of an alkali hydroxide with an aqueous solution of an aluminum phosphate, allowing the mixture to react to form a precipitate, isolating and drying the precipitate, and heating the precipitate dried at a temperature in the range of about 400 ° to 800 ° C for several seconds to several hours.

11. A crosslinking agent, characterized in that it is a product produced by reacting at least one alkali hydroxide with an aluminum phosphate at a temperature in the range from about 400 ° to 800 ° C.

12. A crosslinking agent according to claim 11, characterized in that the alkali metal hydroxide is at least one element selected from the group consisting of sodium hydroxide, potassium hydroxide and lithium hydroxide and aluminum phosphate is aluminum diacid phosphate.

13. A crosslinking agent according to claim 11, characterized in that the agent is produced by a process which comprises mixing, at room temperature, an aqueous solution of an alkaline hydroxide with an aqueous solution of an aluminum phosphate, allowing the mixture to react to form a precipitate, isolating and drying the precipitate, and heating the dry precipitate to a temperature in the range from about 400 ° to 800 ° C for several seconds to several hours.

14. A method for the production of a coated glass or ceramic substrate, characterized in that it comprises applying a composition according to claim 1 to a glass or ceramic substrate and subjecting said coated substrate to curing or heat setting at a temperature of approximately 176.66 ° C (350 ° F) to 704.44 ° C (1300 ° F).

15. A method for the production of a coated glass or ceramic substrate, characterized in that it comprises * applying a composition according to claim 2 to a glass or ceramic substrate and subjecting said coated substrate to curing or heat setting at a temperature from approximately 176.66 ° C (350 ° F) to 704.44 ° C (1300 ° F).

16. A glass or ceramic substrate recovered open, characterized in that it is produced in accordance with claim 14.

17. A coated glass or ceramic substrate, characterized in that it is produced in accordance with claim 15.