AU645453B2 - Preparing and coating a glass substrate - Google Patents

Description

645 53

AUSTRALIA

Patents Act COMPLETE SPECIFICATION

(ORIGINAL)

Class Application Number: Lodged: Int. Class Complete Specification Lodged: Accepted: Published: Priority Related Art: c r Name of Applicant: Morton International, Inc.

Actual Inventor(s): Jack C. Allman John C Buchko Address for Service:

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Invention Title: *oo PHILLIPS ORMONDE FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne 3000 AUSTRALIA PREPARING AND COATING A GLASS SUBSTRATE Our Ref: 322271 POF Code: 1436/1436 The following statement is a full description of this invention, including the best method of performing it known to applicant(s): 1 -6006

PATENT

2090-30-24 PREPARING AND COATING A GLASS SUBSTRATE The present invention is directed to priming a glass substrate for coating and subsequently coating the glass substrate with a polyvinylidine fluoride/acrylic resin coating containing inorganic pigments.

BACKGROUND OF THE INVENTION The present invention is directed to an improved method of coating a glass substrate with pigmented coatings in which the resin system is a mixture of a fluorocarbon and a thermoplastic polyacrylic resin.

Fluorocarbon-based coating compositions have been recognized to have excellent weathering properties, including gloss retention, water resistance and color retention. The present invention is directed to coating glass with a fluorocarbon-based coating composition in a manner that provides excellent adherence of the coating to the glass. Glass so coated may have widespread application in curtain walls where they may provide economic advantages relative to aluminum skins that are currently used.

A long recognized problem of glass coated with a fluorocarbon-based coating is obtaining adequate adherence of the coating to the glass.

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PATENT

2090-30-24 U.S. Patent No. 4,879,345 to Connelly et al., the teachings of which are incorporated herein by reference, teaches a coating composition of a fluorocarbon, an organosilane, an acrylic resin having functional groups reactive with the organosilane and (optionally) pigments and fillers. This coating is applied directly to the glass surface, and it is theorized that the organosilane forms bonds between the glass and the functional acrylic resin.

U.S. Patent No. 4,510,282 to Goll, the teachings of which are incorporated herein by reference, teaches a composition which is an aqueous dispersion of polyvinylidine fluoride (PVDF), acrylic co-polymer and pigment. Examples are given in which the composition also contains an organosilane. This reference teaches that the work material may be pre-treated with gamma-methacryloxypropyltrimethoxysilane and then pre-impregnated with up to three coats of a PVDF latex prior to adding the coating composition. While the pre-treatment of the work material with organosilane may promote bonding to the PVDF later, the subsequent pre- :'2D impregnation with PVDF later would prevent bonding directly between the organosilane on the work material and components of the coating material. Although water-based systems are

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"desirable from an emissions and environmental point of view, organosilanes are unstable in the presence of water, converting to silanols and then to siloxanes. Thus a waterbased coating composition would lack long-term stability, changing in silane composition over time.

The present invention is directed to an improved method of coating glass with a fluorocarbon-based coating composition.

2 SUMMARY OF THE INVENTION According to the present invention, there is provided a method of providing a pigmented coating to a glass substrate including priming said glass substrate by coating it with a clear coat which includes a organosilane and organotitanate at a weight ratio of between 5:1 and and coating said primed glass substrate with a coating composition including a fluorocarbon, an organosilane and/or an organotitanate, a thermoplastic acrylic resin having no functionality reactive with said organosilanes of said organotitanates, and inorganic pigment, said components being carried in an organic solvent and applied at between 10 and 55% solids.

The present invention also provides a method of coating a single surface of a glass substrate to provide S..two distinct appearances when viewed from opposite sides, 20 the method including priming said glass substrate by coating it with a clear coat which includes a mixture of an organosilane and an organotitanate at a weight ratio of between 5:1 and and, 25 coating said primed glass substrate with a coating ***composition including a fluorocarbon resin, an organosilane and/or an organotitanate, a thermoplastic acrylic resin having no functionality reactive with said organosilanes or said organotitanate, and inorganic pigment, said components being carried in an organic solvent and applied at between 10 and 55% solids, and applying a second coating composition to said first coating including polyvinylidine fluoride, an organosilane, an acrylic binder having no functionality reactive with said organosilanes, and inorganic pigment, said first and second coatings being pigmented or colored to provide distinctly different appearances, each of said first and second coatings being applied to a thickness to make each completely opaque.

-3 The present invention further provides a product of a method defined in one of the two preceding paragraphs.

In an embodiment of the present invention, a properly cleaned glass substrate is first primed with a clear, dilute solution of a mixture of an organosilane and an organotitanate. A coating composition is applied which comprises a fluorocarbon resin, an organosilane and/or an organotitanate, a thermoplastic polyacrylate resin having no groups reactive with the organosilane and/or an organotitanate, and an inorganic pigment, the components being carried in an organic solvent. Two successive coatings may be applied to a surface of a glass substrate, each having a pigment level and being applied to a sufficient thickness to be fully opaque and thereby give distinctly different appearances to the glass, which is coated on only one side, as viewed from opposite sides.

DETAILED DESCRIPTI' OF CERTAIN PREFERRED EMBODIMENTS 20 Fluorocarbons useful in forming the coating compositions of the present invention include polyvinyl fluorides, polyvinylidene fluorides (PVDF), vinyl fluoride copolymers and vinylidine fluoride copolymers. The S: preferred fluorocarbon is polyvinylidine fluoride. The S 25 copolymers preferably include at least about 75 wt.% and preferably at least about 90 wt.% vinyl fluoride or vinylidene fluoride monomers. Examples of monomers which

*SSS

may be copolymerized with vinyl fluoride or vinylidine fluoride are ethylene, propylene, isobutylene, styrene, difluorochlorothylene, tetrafluoroethylene, trifluoropropylene, hexafluoropropylene, vinyl formate, 3a

PATENT

2090-30-24 vinyl acetate, vinyl propionate, vinylbutyrate, acrylic acid and its salts, methyl methacrylate, allyl methacrylate, acrylonitrile, methacrylonitrile, N-butoxymethyl acrylamide, allyl acetate and ispropenyl acetate.

The fluorocarbon comprises between about 50 and about wt. percent of the resins of the coating, the thermoplastic polyacrylate resin comprises between about and about 50 wt. percent of the resins. Herein, unless otherwise stated, non-resin components will be expressed as parts per hundred (phr) resin based upon the total amount of resin, including the fluorocarbon and the polyacrylate.

A mixture of an organosilane and an organotitanate is used as a primer to treat the glass surface. An organosilane or organotitanate is also incorporated in the pigmented coating or coatings.

Organosilanes, such as those described in abovereferenced patent 4,879,345, are useful in the present invention both for application as a clear primer and as a component of the pigmented coating or coatings. Some *9 b preferred organosilanes for use in the method of the present invention are gamma-methacryloxy propyltrimethoxysilane, gamma-aminopropyltrie.thoxysilane, gammaglycidoxypropyltrimethoxysilane, gammamercaptopropyltrimethoxysilane, beta-3,4- 25 epoxycyclohexylethyltrimethoxysilane, gammaaminopropyltrimethoxysilane, aminoethylaminopropyltrimethoxysilane, gammamethacryloxypropyltrimethoxysilane, vinylbenzyl (trimethoxysilyl) propyl mono hydrochloride, 1,2-bis (trimethoxysilyl) ethane, phenylaminopropyltrimethoxysilane, 3CH-strylmethyl-2-amino ethylamino propyltrimethoxysilane hydrochloride, vinyltrimethoxysilane, N-C3-acryloxy-2hydroxypropyl)-3-amino-propyltriethoxysilane, 4

PATENT

2090-30-24 N-2(vinylbenzylamino)-ethyl-3-aminopropyltrimethoxysilane mono hydrogen chloride, 3-(N-styrylmethyl-2aminoethylamino)-propyltrimethoxysilane hydro chloride and triethoxysilyl modified polybutadiene.

Suitable organotitanates include, but are not limited to, tetraisopropyl titanate, tetrabutyl titanate, and tetrakis (2-ethylhexyl) titanate. Also, titanate chelates, such as titanium bis(ethyl-3-oxobutanolato-O 0 3) bis(2propenolato)-, ethanol, 2, 2',2"-nitrilotris-, titanium(4+)salt, and titanate (2-),dihydroxy bis [2hydroxypropanato are suitable.

In the primer, the organosilane and organotitinate are mixed together at a weight ratio of between about 5:1 and about 1:5, preferably between about 2:1 and about 1:2.

The organosilane/organotitanate primer is applied to a glass surface, generally as a dilute, 2-25 wt.%, solution in an organic solvent(s). The organosilane/organotitanate primer is preferably applied to between about 1.0 and about 5.0 gm. (organosilano plus 2 0 organotitinate) per m. In pigmented coating compositions in accordance with the present invention, organosilane and/or organotitanate is used at between about 2 and about 12 phr, preferably between about 3 and about C phr.

Above-referenced U.S. Patent No. 4,879,345 teaches that an acrylate adjuvant resin having functional groups reactive with the organosilane is necessary to obtain adequate adhesion. Surprisingly and unexpectedly, it is found that in a coating composition containing an inorganic pigment or filler, it is preferred that the thermoplastic acrylate resin be non-reactive with the organosilane or the organotitanate of the primer or the organosilane or organotitinate of the coating composition. U.S. Patent No.

4,879,345 proposes that by using an organosilane-reactive 5

PATENT

2090-30-24 adjuvant resin, a bond is formed between the glass and the adjuvant resin. Although applicants are not bound by theory, evidence applicants have accumulated indicates that in an inorganic pigment-containing coating composition, a bond is formed through the organosilanes and organotitanate directly between the glass and the inorganic pigment particles, thereby achieving a stronger bond between the glass and the coating.

Preferred polyacrylates are polymers and copolymers formed from esterified acrylates having no additional functional groups, such as esters of acrylic acid and methacrylic acids with mono-functional alcohols. However, in accordance with the invention, the polyacrylates may have functional groups, providing they do not contain any significant amounts of functional groups reactive with the organosilane selected. On an equivalence basis, the polyacrylate resin should contain no more than about relative to co-reactive groups of the organosilane or organotitinate in the coating composition and preferably no co-reactive groups at all. This allows all bonding to take place between the organosilane and organotitanate, both in the primed glass surface and in the coating composition, and the inorganic pigment or filler.

The inorganic pigment or filler is used at a level of at least 2 phr, up to about 150 phr. Preferably, the selected pigment or filler is neither acid nor water sensitive. Examples of inorganic fillers useful in the present invention are silicates; such as mica, aluminum silicate and glass particulates, inorganic oxides, such as titanium dioxide; strontium chromate; and barium sulfate.

It is believed that the excellent glass-to-coating bonding achieved by the method of the present invention is a result of direct chemical bonding between the glass and some 6

PATENT

2090-30-24 of the inorganic pigment particles. It is believed that the absence of reactive functional groups on the acrylic resin, prevents the depletion of organosilane and organotitanate by reaction with the polyacrylate resin and the organosilane and organotitanate, which such reaction would result in bonds that are less strong than the bonds between the glass and the inorganic filler through the organosilane and organotitinate.

The coating composition may contain other components well known in the art, including UV-inhibitors, colorants, ceramic fiber, and organic pigments. Although organic pigments may be used in addition to inorganic pigments, organic pigments are found not to significantly promote bonding of the coating to the glass. Indeed, if organic S'pigments are used in the absence of inorganic pigments,

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there is insufficient bonding of the coating to the glass.

The types and amounts of pigments and colorants and the thickness to which the coating is applied determines the appearance of the final product. Typically the coating is applied directly over the primed glass to a thickness of .between about 5 and about 50 microns. The appearance of the coating may range from translucent, as is desirable for a lighting fixture, to fully opaque, as is generally desirable eo" in curtain wall panels.

In one aspect of the invention, a glass substrate will be primed, coated with a first coating, as described above, the first coating containing sufficient pigment and being applied to a thickness as to be fully opaque and then coated with a second coating, as described above, also containing sufficient pigment and being applied to a thickness as to be fully opaque. Through the use of different pigments and colorants, each side of the glass may have entirely different appearances. This may be particularly desirable 7

PATENT

2090-30-24 in curtain wall panels, particularly those used in the interior of a building, where a glass panel coated on one side only, but with two coats, can have entirely different appearances when viewed from opposite sides.

Best results are obtained when the glass is thoroughly cleaned. One very suitable protocol involves: 1. rinsing with water, 2. polishing with an abrasive, such as cerium oxide, 3. rinsing with water, 4. cleaning with a detergent solution, 5. rinsing with deionized water, and 6. drying.

The unpigmented organosilane/organotitanate primer is carried in an organic solvent as is the pigmented coating composition. Suitable organic solvents include, but are not limited to toluene, xylene and mixtures thereof.

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Preferably, the primer composition is water-free particularly if the primer contains organosilane, as water 4 tends to degrade organosilane. Generally, primer compositions in accordance with the invention are applied at between about 1 and about 45 percent solids; pigmented coatings are typically applied at between about 10 and about 55 percent solids. The method of applying the coating may determine the percent solids of application. The primer is typically applied by spray coating and then dried prior to application of the coating composition. The coating o" composition may be applied by a variety of methods, such as 25 spray coating, roller coating, silkscreen, curtain coating, and electrostatic spray coating, such as that involving too**: turbodisks and turbobells.

After application, the coating is dried, typically at elevated temperatures. After the coating(s) is applied and dried, it is typical to bake the coating to fuse the resinous material and promote bonding of the coating to the glass. Baking is typically at between about 200 and about 250 C. If more than one coating is applied, baking 3

PATENT

2090-30-24 generally follows application and drying of the two coatings.

Coatings produced in accordance with the present invention have proven to be extremely strongly bonded to glass substrates. It has proven difficult to scrape coating from a glass substrate without scraping away glass itself.

Coatings in accordance with the present invention are highly resistant to water, including boiling water and humid atmosphere.

The coatings may be applied to any glass substrate.

For curtain wall panels, particularly exterior curtain wall panels, tempered glass is preferred for safety reasons.

The invention will now be described in greater detail by way of specific examples.

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4. 4 Examples 1-7 (all parts by weight unless stated otherwise) Example 1 Tetra (2-methoxyethoxy) silane 2.5 parts Tetrabutyl titinate 2.5 parts Tetrapropyl orthosilicate 2.5 parts Naphtha (petroleum light aromatic) 42.5 parts Toluene 25.0 parts Example 2 (pigmented coating composition) parts Thermoplastic acrylic resin* 10.31 (60,000)MW(wt.ave) Toluene 12.93 Iron oxide 10.30 9

PATENT

2 090-3 0-24 Kynar 500 (PVDF) 24.21 Butyl cellosolve 8.77 Di-methyl phthalate 8.25 3-ethoxy propionate 9.34 (3-glycidoxypropyl) tr imethoxys ilane 2.00 *polymethylmethacrylate (ACRYLOYD B-44, Rohm Haas) Example 3 (pigmented coating composition) Thermoplastic acrylic resin 10.54 (60,000) MW (wt.ave) Mica (3-48 micron) 8.31 Kynar 500 24.42 3-ethoxypropionate 11.19 .Butyl cellosolve 9.44 :.Di-methyl phthalate 8.88 *Toluene 8.93 Lampblack, iron oxide 0.04 (3-glicidoxypropyl) tr imethoxys i lane 1.96 b 10

PATEN~T

2090-30-24 Example 4 (pigmented coating composition) Thermoplastic acrylic resin 11.63 (60,000) MW (wt.ave) Toluene 12.15 Lampblack 1.90 Kynar 500 27.32 Butyl cellosolve 9.70 Di-methyl phthalate 9.13 3-ethoxy propionate 10.49 N-2 (vinylbenzylamino) -ethyl-3aminopropyltrimethoxysiline mono(HC1) 1.96 (6,00 M (t ae Btemolalsi aryicrei 8.96 Titnumoxoideat 14.970 Di00 -methacylorphtltmteo~ n 8.29 4 11

PATENT

2090-30-24 Example 6 A surface of a sheet of tempered glass was thoroughly cleaned. To this surface was applied, by spraying, the primer of Example 1 in an amount sufficient to provide the organosilane and organotitanate at a level of about 3 gm per square meter and allowed to air dry.

Subsequently, the coating composition of example 4 above was applied by spraying to a thickness of about 125 microns and allowed to air dry. The coated glass was then baked at 245 0 C for 15 min. An opaque uniform film is formed.

A portion of the glass is submerged in boiling water for 2 hours. Another portion of the glass is submerged in water for 7 days at 600C. In both cases, there is no loss s5 of coating, indicating excellent adhesion.

*4 Example 7 Tempered glass was cleaned, primed with the composition of Example 1 in an amount to provide the 6: organosilane and organotitinate at a level of about 3 gm per square meter. Then the coating composition of Example 4 was applied as per Example 8. Subsequently, the pigmented coating of Example 7 was applied by spraying over the first coating composition to a thickness of 125 microns. After S. drying, the glass was again baked at 245 0 C for 15 min. When "viewed through the glass the first coating appears uniform with high gloss and excellent depth of image and with no change in appearance caused by the second coating. From the opposite side, 'he glass coated with two coating compositions appears uniform with no show-through of the first coating composition.

12

PATENT

2090-30-24 While the invention has been described in terms of certain preferred embodiments, modifications obvious to one with ordinary skill in the art may be made without departing from the scope of the present invention.

Various features of the invention are set forth in the following claims.

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Claims (8)

1. A method of providing a pigmented coating to a glass substrate including priming said glass substrate by coating it with a clear coat which includes a organosilane and organotitanate at a weight ratio of between 5:1 and and coating said primed glass substrate with a coating composition including a fluorocarbon, an organosilane and/or an organotitanate, a thermoplastic acrylic resin having no functionality reactive with said organosilanes of said organotitanates, and inorganic pigment, said components being carried in an organic solvent and applied at between 10 and 55% solids.

2. A method in accordance with claim 1 wherein said fluorocarbon is polyvinylidine fluoride. 20 3. A method in accordance with claim 1 wherein said fluorocarbon includes between 50 and 90 wt. percent of said coating composition, said thermoplastic acrylate resin including between 10 and 50 wt. percent of said Scoating composition, said organosilane being at levels of between 2 and 12 phr and said pigment being at levels from 2 to 150 phr.

4. A method in accordance with any one of claims 1 to 3 ""wherein said primer is applied to provide a total amount of both organosilane and organotitanate to said glass substrate at between 1.0 and 5.0 gm. per m 2 A method in accordance with any one of claims 1 to 4 wherein said applied coating composition is subsequently baked at between 200 and 250 C.

6. A method in accordance with any one of claims 1 to wherein said clear coat contains organosilane and organo- titanate at a weight ratio of between 2:1 and 1:2.

14- 7. A product of the method of claim 1. 8. A method of coating a single surface of a glass substrate to provide two distinct appearances when viewed from opposite sides, the method including priming said glass substrate by coating it with a clear coat which includes a mixture of an organosilane and an organotitanate at a weight ratio of between 5:1 and and, coating said primed glass substrate with a coating composition including a fluorocarbon resin, an organo- silane and/or an organotitanate, a thermoplastic acrylic resin having no functionality reactive with said organo- silanes or said organotitanate, and inorganic pigment, said components being carried in an organic solvent and applied at between 10 and 55% solids, and applying a second coating composition to said first coating including polyvinylidine fluoride, an organo- "silane, an acrylic binder having no functionality reactive 20 with said organosilanes, and inorganic pigment, said first and second coatings being pigmented or colored to provide distinctly different appearances, each of said first and second coatings being applied to a thickness to make each completely opaque. 9. A method in accordance with claim 8 wherein said fluorocarbon resin in each of said coating compositions includes between 50 and 90 wt. percent of said resin, said thermoplastic acrylate resin including between 10 and wt. percent of said resin, said organosilane being at levels of between 2 and 12 phr and said pigment being at levels from 10 to 150 phr. A method in accordance with claim 8 or claim 9 wherein said primer is applied to provide a total amount of both organosilane and organotitanate to said glass 2 substrate at between 1 and 5 gm. per m2 A/ 11. A method in accordance with any one of claims 8 to 15 wherein said applied coating compositions are sub- sequently baked at between 200 and 250 0 C. 12. A product of the method of claim 8. 13. A method of providing a pigmented coating to a glass substrate, substantially as herein described with reference to any one of the embodiments in the Examples. 14. A method of coating a single surface of a glass substrate to provide two distinct appearances when viewed from opposite sides, substantially as herein described with reference to any one of the embodiments in the Examples.

15. A product of a method of providing a pigmented coating to a glass substrate, substantially as herein described with reference to any one of the embodiments in the Examples.

16. A product of a method of coating a single surface of a glass substrate to provide two distinct appearances when viewed from opposite sides, substantially as herein described with reference to any one of the embodiments in 25 the Examples. S 9 .4 DATED: 1 November 1993 PHILLIPS ORMONDE FITZPATRICK Attorneys for: MORTON INTERNATIONAL, INC. 6727Z I A 16 PATENT

2090-30-24 PREPARING AND COATING A GLASS SUBSTRATE Abstract of the Disclosure *6S* e.g C. C C C S 0* *5 0 S SC. 5 CC CS S C. 56 C 0 0 0 CC.. SC C. 0 S. CO OS S *0g5 S seeS S. sees 0 S eOe**S S Glass is primed with a clear coat which is a mixture of an organosilane and an organatitanate. Subsequenv\1y the primed glass is coated with a coating composition comprising a fluorocarbon resin, an organosilane and/or an organotitinate, an inorganic pigm~ent and a thermoplastic polyacrylate resin that has no functional groups reactive with the organosilane or organotitinate, the coating composition being carried in an organic solvent. PA2 09000 .WEN 1171