MXPA97005361A - Painting with aqueous base for vine leaves - Google Patents

Abstract

The present invention relates to an aqueous-based paint composition containing sodium silicate, water, water-soluble base, metallic oxide pigment and zinc oxide as adhesion promoter. Preferably, it also contains glass frit and surfactants. In another aspect, it relates to the method of making the composition and the glass sheets having a zone of hardened paint therein and the method of making these sheets of glass.

Description

PAINT WITH AQUEOUS DASE FOR GLASS LEAVES FIELD OF THE INVENTION This invention is directed to water-based paint compositions particularly useful for providing an area of paint on glass sheets. The paint composition contains sodium silicate, water, water soluble base, finely divided metal oxide pigment and zinc oxide as adhesion promoter.

BACKGROUND OF THE INVENTION Various paint compositions are known to those skilled in the art to paint automotive and architectural glass. These paints are used, for example, to form opaque margins around peripheral marginal surfaces of glassware used as windshields, windows and medallions of motor vehicles. In general, these compositions are ceramic compositions that are formed from a mixture of metal oxides in an organic vehicle. The mixture of the metallic oxides is adjusted to achieve a specific color for the ceramic paint that is finally baked. For example, bands of marginal opaque peripheral paint baked on automotive glass are generally black and may include oxides such as chromium oxide, cobalt oxide and nickel oxide. The organic carriers that are generally included in these compositions, for example, pine oil, mineral oils, low molecular weight petroleum fractions and the like are used to allow the ceramic paint to be applied to the glass surface by the application with brush, spray or screen printing. Metal oxides are non-reactive with each other, as well as non-reactive with other materials such as glass frits that are usually contained in ceramic paint. These glass frits are materials that eventually melt together with the ceramic paint, and the glass sheet, to ensure that the ceramic paint remains fixed to the glass sheet after cooling to room temperature. When these materials are applied to a sheet of glass, they are heated to elevated temperatures, usually above the softening point of the glass, to harden the paint and make the painted glass sheets suitable for other handling during a forming process at a later elevated temperature. In view of environmental and commercial considerations, it would be desirable that water-based paints could be developed for use in place of these paints with organic carrier. It would also be desirable to develop an aqueous-based paint that could harden at relatively low temperatures instead of the high temperatures that are usually required to harden ceramic paint with organic vehicle. By subjecting the glass having the paint coating to high temperatures during the curing of the paint, undesirable optical deformations are imparted to the glass sheets. To be suitable as a substituent for traditionally used ceramic paints, water-based paint will need to provide a uniform coating that is durable and also adheres well to glass. One objective of the present composition is to provide an aqueous-based paint composition that exhibits excellent adhesion to glass. Another object of the present invention is to provide an aqueous based paint that hardens at relatively low temperatures and exhibits excellent durability. Advantageously, the aqueous-based paint compositions of the present invention achieve these objectives and thus overcome the disadvantages of ceramic paints with organic carrier of the prior art.

DESCRIPTION OF THE INVENTION This invention is an aqueous-based paint composition having excellent adhesion to glass. The composition comprises: (i) water-soluble sodium silicate forming from 20 to 40 by weight of the composition, (ii) water forming from 5 to 25% by weight of the composition; (iii) base soluble in water in an amount sufficient to provide the composition with a pH value of at least about 10.5; (iv) finely divided metal oxide powder selected from the group consisting of copper, iron, nickel, cobalt oxides and mixtures thereof forming from 25 to 40% by weight of the composition and with a particle size of less than 7. mieras; and (v) zinc oxide representing 2 to 10% by weight of the composition. The composition preferably also contains glass frit in small amounts. The invention is further directed to a process of making the water-based paint described which comprises the combination and the mixing of the components. According to another embodiment of the present invention, it comprises a glass sheet having at least one part coated with a hardened paint made from the composition described above. According to yet another embodiment of the invention, this comprises a method for providing a coating of the hardened paint on a glass sheet.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The composition of the invention is an aqueous-based paint useful as a coating on glass, such as for the "darkening" area around the periphery of a windshield. The composition comprises, as described above, water-soluble sodium silicate, water, water-soluble base, finely divided metal oxide powder which gives the paint its color from white to gray and zinc oxide as flattering. accession. Each of these components, as well as the optional components, will be described in detail below. Soluble water-soluble silicates form between about 20 and 40% by weight of the composition of this invention, more preferably between about 30 and 36% by weight of the composition, that is, when used in the present "% by weight of the composition" means a fraction of the total weight of the composition. These may consist of a single sodium silicate or a mixture of silicates. The water-soluble sodium silicates useful in this composition of the invention can be represented by the formula SiO?: Na? 0, wherein the molar ratio of the two oxides is from about 2: 1 to about 4: 1. In addition to the water-soluble sodium silicate, the water-soluble potassium silicates of the similar formula can also be included in the composition. When these are included, they are generally present in minor amounts, preferably less than 10% by weight, usually between about 5 and 10% by weight of the composition. Yet another required component of the composition is water that is included in an amount between about 5 and 25% by weight of the total weight of the composition, preferably in an amount between about 10 and 20% by weight. The composition also includes a water-soluble base which is employed to provide the paint composition with a pH of at least about 10.5, preferably above 12.5, most preferably around 13.5. The pH is required to be on the basic side as indicated by the required pH. This pH is necessary to impart a desirable storage life to the composition to the composition. The embodiments of the paints of the invention with a pH above about 13, for example, have been found to have a shelf life of at least 3 months. Examples of water-soluble bases that may be employed include but are not limited to sodium hydroxide and potassium hydroxide, with sodium hydroxide being preferred. The amount of base that is used depends on, for example, the particular base and the concentration that is used. For example, using a 1 N sodium hydroxide base, which is generally included in about 2 to 10% by weight of the composition, more preferably about 3 to 8% by weight and at an optimum concentration around 3 to 6% by weight. The optimum amounts and types of bases that can be employed will be apparent to those skilled in the art in view of the present disclosure. The composition further contains finely divided metal oxide pigment which is selected from copper oxide, iron oxide, nickel oxide, cobalt oxide and mixtures thereof, with the inclusion of copper oxide being preferred. This pigment gives the paint a black color and forms 25 to 40% by weight of the composition, preferably between about 25 to 35% by weight of the composition. The finely divided powder pigment has an average particle size (diameter) of less than about 7 microns, preferably between about 3 and 7 microns, more preferably about 5 microns. These compositions will vary in color from black to dark gray depending on the mixture and percentages of the metal oxides. Copper oxide, which is preferred, provides a black paint composition. It is undesirable to use chromium oxide in the composition since it interferes with the adhesion of the paint to the glass. Another essential component of the paint composition is a smaller amount of adhesion enhancer, that is, zinc oxide, in this painting of the invention. This adhesion promoter is included in the composition in an amount of between about 2 to 10% by weight, preferably between about 3 and 6% by weight, most preferably between about 4 and 6% by weight with based on the weight of the composition. An optimum amount of about 6% by weight of zinc oxide is included in the composition. It is preferred that the zinc oxide be provided in the paint composition in a particle size of between about 2 and 3 microns on average, however, the size of the particle is not crucial. While not wishing to stick to the theory, the inventor believes that zinc oxide reduces the coefficient of expansion of the paint composition that makes it more closely match that of the glass composition. Therefore, during the heating and cooling of the glass, less stress develops in the paint because the glass and the paint coincide reasonably closely in the coefficients of thermal expansion. It is considered that the minor effort in the paint will result in good adhesion of the paint to the glass substrate. Neither the understanding nor the precision of this theory is, nevertheless, necessary for the practice of this invention. In addition to the components required in the foregoing, the paint co-option optionally, but preferably, comprises a small amount of low melting glass frit, ie, it generally contains less than about 10% by weight, more preferably between about 2 and 4% by weight of the composition of the blackish paint of the present invention. Preferably the low melting glass frit, when included, is present in the composition in an amount of about 3% by weight based on the total weight of the composition. By low-melting glass frit is meant a glass material that melts below about 705 ° C (1300 ° F). Examples of the preferred glass frit materials useful in the present invention, often known as enamel frit, are zinc borosilicate glass and bismuth borosilieate glass and mixtures thereof. Still other glass frits that can be employed in the present invention will be apparent to those skilled in the art in view of the present disclosure. I have found that the inclusion of this frit material in the glass composition also improves the adhesion of the paint to the glass. Yet another optional, but desirable component that is included in the black paint composition of this invention is a surfactant. Tensoaeti are well-known materials and are often added to paints to improve the wetting characteristics of liquid paint for the substrate to which they are applied. Examples of one of these materials is "FC-171" manufactured by 3M Company. Still other surfactants are known to those skilled in the art. It is desirable that it forms about 0.1 to 1.0% by weight of the paint composition, more preferably about 0.25 to 0.5% by weight. To make the composition, the components are usually added together and then crushed in a ball mill until a substantially uniform mixture of the components is obtained. This mixing is usually carried out at room temperature. Often the base is added after grinding. A commercially available water-based paint composition containing alkali silicates, water, base, and pigment such as copper oxide, eg, CERAM-VUE (CV1-112 Black, Industrial Control Development, Inc., Vancouver, WA), It is a water-based silicate paint, black of this type. If the zinc silicate powder is added to this composition at the levels indicated above, this composition then hardens becoming more adherent to the glass sheets onto which it is applied. After elaborating the composition object of the invention, can be applied to a substrate, particularly a glass substrate, by any technique. The glass sheet can be prepared from any type of glass generally known in the glassmaking art. The common glass sheets which are contemplated for use in accordance with the present invention are automotive and architectural soda-lime-silica glass which are usually produced by the well-known floating glass (on liquid metal) process. During operation, the paint is applied as a uniform layer to a surface of the glass sheet in a predetermined pattern by a conventional paint application method, for example by screen printing, where the paint is dispersed through the mesh with a rubber spatula to pass the paint through the pattern on the glass sheet. This is well known in the art of painting to apply a band of paint to the surface of an automotive glass by means of a silk mesh. In this situation, it is particularly desirable to maintain a humid environment around the paint during the screen printing process. The humid environment is maintained in an optimum form around 80 ± 5% RH for the preferred paint compositions of the present invention. The maintenance of this humid environment allows the prolonged use of the paint application system keeping the moisture content of the paint at a desirable viscosity for the application. This environment can be obtained in an optimal form, for example, as the invention described in the US Patent Application Serial No. 08/295, 574 filed on August 25, 1994 by Boaz and commonly assigned with this invention. This is entitled "Apparatus and method for applying a coating to glass". The predetermined pattern in which the paint can be applied to a glass sheet can consist, for example, of an opaque concealment band placed on a peripheral marginal surface of an automotive glass. These concealing bands are well known in the automotive glass technology as being useful for preventing the degradation, induced by solar radiation, of the adhesives that are used to install the glasses in a window opening of a vehicle and to hide to protect the connection of the hardware and structural components that are located below these edges of the glasses. The band usually extends to the margins of the glass, and is wide enough to hide the underlying adhesive and structural components, but is narrow enough to provide maximum visibility to the occupants of the vehicle. It is evident that other predetermined patterns can be used where the application of the various areas of paint to the glass surfaces depends on the final purpose of the hardened paint zone. In the case of coatings that are applied to automotive glasses as "concealment", the coating is preferably provided in a thickness of about 12-16 microns. The coating can be applied in any thickness, however, the optimum thickness is determined by the particular application desired. The curable compositions of the invention, after being applied to a substrate, are easily hardened by baking at an elevated temperature for a sufficient time to remove the water, whereby the coating hardens. This step can be carried out at any temperature, but a temperature below the softening point of the glass is desirable. Since this water vaporization and hardening can be carried out preferably at moderate temperatures, for example, below 400 ° C, even between around 100 ° C and 200 ° C, the painted glass is not subjected to a softening and therefore deformation is avoided at moderate temperatures. This is contrary to conventional paints with organic vehicle that require heating at temperatures above the softening point of the glass to harden these paints. The paint compositions applied to glass sheets usually harden first to make the painted glass first available for handling in a subsequent process, that is, by folding the painted glass sheet into a desired final shape. By heating the glass above the softening point of the glass to harden the paints with organic vehicle, the opportunity is given for the glass to be deformed. The subsequent beg of the painted glass, in a second firing, again at these elevated temperatures provides a second chance of deformations that are incorporated into the glass product. Therefore, since the paint of the present invention can be cured at relatively low temperatures, below the softening point of the glass, it desirably reduces the opportunity for deformation to be incorporated into the glass product. This drying and hardening of the water-based black paint composition can be carried out by any means. Two particularly preferred means comprise subjecting the paint applied to the glass to infrared (IR) radiation or microwave radiation as in a microwave oven. The latter is the particularly preferred method since it can be provided as a compact unit of relatively small size, consumes less energy and usually requires less maintenance. In the case of a 30.48 x 30.48 cm sample of the type of a windscreen with a paint composition, of one embodiment of the invention, applied to a part of its surface as a "concealment" band, it was found that the coating was it was able to harden in about 1 minute at 150 ° C in an IR oven or around 1 minute in a microwave oven (with 4 KW power). The particular embodiment of the paint composition that was employed and the coated area suggest the particular optimal parameters useful for hardening the paint of the invention. As is apparent, the moderate temperature curable compositions of the present invention have considerable advantage because they provide significant energy savings, as compared to compositions that require significant temperatures for curing. Furthermore, as described above, when the substrate is glass, optical deformations may be incorporated into the glass sheet when exposed to significantly elevated temperatures, such as those required to cure conventional organic glass vehicle coatings. The composition of the present invention overcomes this disadvantage of coatings of the prior art which require high temperatures to coat the paint. Although, as described above, the paint finds particular utility on glass, it can also be used to paint other substrates, which include, for example, metal or plastic. Generally, coated automotive glasses will subsequently undergo the formation which involves exposing the glass to high temperatures in the order of 550 ° C or more in an annealing furnace. This will allow greater hardening of the coating, although this is not necessary to provide a durable and adherent coating on a substrate. The following examples are presented by way of description of the invention and to establish the best mode contemplated by the inventor, but should not be construed as limiting.

EXAMPLES The following three examples are embodiments of the paint compositions made in accordance with the present invention. All the amounts of the compos are in% by weight of the total composition of the paint.

Painting # 1 23 of 323925 sodium 4,513 silicate potassium Water 20 1916 8 6 sodium hydroxide (1N) Copper oxide 32 3234 Zin oxide 2 4.04.0 Frit (boron 1.8 2.01.7 zinc silicate) Surfactant (FC-0.2 0.20.3 171 3M Company) A paint composition (No. 4) was made, according to one embodiment of the present invention, by adding zinc oxide and surfactant (FC-171, 3M Company) to a commercially available silicate paint (CB-555- 195, AO Smith Company) in the following amounts in% by weight of the total composition: silicate paint 93.54, zinc oxide 6.0 and surfactant 0.51. The paint compositions indicated above were applied by means of a screen printing process to the glass sheets (soda-lime-silica) with a thickness of 12 microns and hardened in an IR oven for 3 minutes at 120 ° C. . The hardened black paint showed uniform coating and excellent adhesion to the glass as demonstrated by subjecting the painted glass to a hot water bath for 5 days at 60 ° C, whereby the paint did not show delamination. Similar paint compositions without the adhesion promoter, zinc oxide (hence not in accordance with the present invention) are subject to delamination under similar test conditions. The paints were also tested in their adhesion characteristic with urethane type adhesives, by the test described below, since these adhesive materials are often used in contact with glass for installation in the vehicle. Adhesive Adhesion Bond / Paint / Glass The surface of a glass panel is painted and the paint hardens completely by passing it through an oven that heats the glass above 550 ° C. A part (strip) of the painted surface is prepared for urethane adhesion by first applying a coating of the Essex-Prep glass primer. No. 43519. On this prepared surface another layer of Essex glass primer No. 43520A is applied. The primer is allowed to dry for about 10 minutes at room temperature and then a "bead" of Essex urethane polymeric adhesive is applied over the primer coatings. A second glass panel is prepared in an identical manner except that no urethane adhesive is applied. The two glass panels are then pressed in contact so that the urethane adhesive makes contact with the first and second panels leaving about 0.25 'between the painted surfaces of the panels. The pair is allowed to harden for 72 hours in the air. To pass the adhesion test, the urethane and the non-adhesive surface must be broken when the panels are rotated against each other. The adhesion reliability is tested after the adhered pair is immersed in water at 150 ° C for a selected time. The aforementioned paint compositions all showed excellent adhesion and satisfactorily passed the urethane adhesion test. The paint compositions of the following examples, both according to the embodiments of the present invention (No. 6 and No. 7) and the comparative example (No. 4 and 5) were tested on their adhesion property with polymer adhesive. of urethane as described above and also with polyvinyl butyral (which is used as an intermediate layer in the windscreen) as follows: "Vinyl / paint / glass adhesion knob" On a pair of laminated glass panels, a 7.62 cm edge is provided with a paint on a surface in contact with an intermediate layer of polyvinyl butyral. The laminate is cooled and stabilized at -10 ° C for 4 hours. At the end of the 4 hours, the laminate is quickly removed and the painted portion is placed on an anvil where the portion is subjected to a series of 5 minutes of blows with a heavy hammer. At this temperature, vinyl is hard and has bad adhesion to crushed glass particles. The adhesion of the glass particles with the vinyl is quantified by comparison with the defined standards of No. 1 to 10, 3, and where No. 1 indicates the complete loss of the vinyl / glass / glass adhesion and No. 10 indicates the complete vinyl / paint / glass adhesion. The following paints # 4, Ü, # 6 and # 7 contain relatively the same components of sodium silicate, potassium silicate, water and pigment. The additional components are listed for the particular examples (% by weight). Paint # 4: basic composition: sodium silicate potassium silicate, water and pigment (copper oxide). The comparative example is not according to one embodiment of the present invention since it does not contain zinc oxide. Paint # 5: basic composition with 2% zinc borosilicate frit. Comparative example, not according to one embodiment of the present invention since it does not contain zinc oxide. Paint # 6: basic composition with 2% zinc borosilicate frit and 5% ZnO according to one embodiment of the present invention. Paint # 7: Basic composition with 5% zinc oxide, according to one embodiment of the present invention.

Vinyl Knob / Paint / Glass Test Results Painting # 4: test knob # l- # 2 Painting # 6: test knob # 6- # 8 Painting #: test knob # 4- # 6 Painting # 7: test knob # 6- # 8 Results of urethane / paint / glass adhesion test, after 4 hours 24 hours 48 hours Painting # 4 failed Painting # 5 passes pasa pasa failed Painting # 6 passes raisin passes Painting # 7 passes raisin passes From the above test results it can be seen that the inclusion of zinc oxide significantly improves the adhesion of the paint, which is further improved by the inclusion of the zinc borosilicate frit.

Claims (1)

1. CLAIMS An aqueous-based paint composition having excellent adhesion to glass, consists of: (i) water-soluble sodium silicate forming from 20 to 40 by weight of the composition, (ii) water forming from 5 to 25% by weight water weight; (iii) base soluble in water in an amount sufficient to provide the composition with a pH value of at least about 10.5; (iv) finely divided metal oxide powder selected from the group consisting of copper, iron, nickel, cobalt oxides and mixtures thereof forming from 25 to 40% by weight of the composition and with a particle size of less than 7. mieras; Y (v) zinc oxide representing 2 to 10% by weight of the composition. An aqueous-based paint composition, according to claim 1, wherein the composition further contains less than about 10% by weight of glass frit based on the total weight of the composition: An aqueous-based paint composition according to claim 1, wherein the composition further contains potassium silicate. An aqueous-based paint composition according to claim 1, wherein the water-soluble base is sodium hydroxide. An aqueous-based paint composition, according to claim 1, wherein the composition further contains from 0.1 to 1.0% by weight of surfactant. An aqueous-based paint composition having excellent adhesion to glass, which contains: (i) water-soluble sodium silicate forming from 20 to 40 by weight of the composition, (ii) water forming from 5 to 25% by weight water weight; (iii) base soluble in water in an amount sufficient to provide the composition with a pH value of at least about 10.5; (iv) finely divided copper oxide powder forming from 25 to 35% by weight of the composition and with a particle size between 3 and 7 microns; and (v) zinc oxide forming from 4 to 6% by weight of the composition, (vi) surfactant forming from 0.1 to 1.0% by weight of this composition. A sheet of glass carrying at least a portion thereof a hardened coating of an aqueous-based paint composition, this composition consists of: (i) water-soluble sodium silicate forming from 20 to 40% by weight of the composition, O-i (ii) water that forms 5 to 20% by weight of water; (iii) base soluble in water in an amount sufficient to provide the composition with a pH value of at least about 10.5; (iv) finely divided copper oxide powder which is selected from the group consisting of copper, iron, nickel, cobalt oxide and mixtures thereof forming from 25 to 40% by weight of the composition and with a particle size between 3 and 7 microns; and (v) zinc oxide forming from 2 to 10% by weight of the composition. The glass sheet according to claim 7, wherein this composition also contains less than about 10% by weight of a glass frit based on the total weight of the composition. The glass sheet according to claim 7, wherein the composition further contains potassium silicate. The glass sheet according to claim 7, wherein the water-soluble base is sodium hydroxide. The glass sheet according to claim 7, wherein the composition further contains from 0.1 to 1.0% by weight of surfactant. The glass sheet according to claim 7, is a glass for automotive or architectural use. 13. A method for preparing an aqueous-based paint composition having excellent adhesion to glass, this method comprises the steps of: adding the components together comprising: (i) water-soluble sodium silicate forming from 20 to 40 by weight of the composition, (ii) water that forms from 5 to 20% by weight of the water; (iii) water-soluble base in a sufficient amount to provide the composition with a pH value of at least about 10.5; (iv) finely divided copper oxide powder which is selected from the group consisting of copper, iron, nickel, cobalt oxide and mixtures thereof forming from 25 to 40% by weight of the composition and with a smaller particle size of 7 microwaves; and (v) zinc oxide formed from 2 to 10% by weight of this composition; and milling these components in ball mill to form the paint composition. The method, according to claim 13, further comprising mixing with these components of less than about 10% by weight of glass frit based on the total weight of the composition. 15. A method for preparing a formed glass for architectural or atomotive use having a water-based paint zone hardened therein and adhering to the glass, this method comprising the steps of: providing a glass sheet having a surface; applying to at least a part of the surface, an aqueous-based paint composition containing: (i) water-soluble sodium silicate which forms from 20 to 40 by weight of the composition, (ii) water forming from at 25% by weight of water; (iii) base soluble in water in an amount sufficient to provide the composition with a pH value of at least about 10.5; (iv) finely divided copper oxide powder which is selected from the group consisting of copper, iron, nickel, cobalt oxide and mixtures thereof forming from 25 to 40% by weight of the composition and with a smaller particle size of 7 microns; and (v) zinc oxide formed from 2 to 10% by weight of this composition; and heating the glass sheet and water-based paint therein by means of microwaves or infrared radiation at a temperature below the softening point of the glass sheet which is sufficient to remove substantially all of the water present in the paint composition and toughen the paint composition and provide an adherent coating; cool the painted pot leaf, and heat the painted glass sheet to a temperature sufficient to form a sheet of glass in a desired shape. The method according to claim 15, wherein the step for providing the glass sheet comprises providing an automotive or architectural glass.