WO2000043324A1

WO2000043324A1 - Safety coating of frangible ware

Info

Publication number: WO2000043324A1
Application number: PCT/CA1999/000348
Authority: WO
Inventors: Henry Sawatsky
Original assignee: Henry Sawatsky
Priority date: 1999-01-25
Filing date: 1999-04-19
Publication date: 2000-07-27
Also published as: AU3694899A

Abstract

Frangible wares, comprising glassware, earthenware including china, and ceramics, the glassware including dishes and vessels such as drinking glasses, are coated with a protective plastic coating, including an initial adhesion-promoting silane, a shock absorbing layer of copolymer, and an outer coating of urethane, such as a high temperature urethane to give protection to the underlying layers in the environment of a commercial dishwasher. The plastic coating may serve as a safety coating, to diminish breakage during both handling and use, and to act as a safeguard and contain the glass particles against scatter in the event of breakage. The copolymer, as an intermediate, softer coating of polyethylene copolymer serves to cohesively retain the particles of frangible parent material, in the event of breakage of the drinking glass. The high temperature urethane outer coating is preferably a thermosetting urethane, capable of withstanding commercial dishwasher temperatures as high as 95 °C. With the capability of selectively varying the respective thicknesses of the ethylene copolymer and the urethane coatings, a range of desired characteristics for the vessel composite can be achieved. The urethane may be applied directly to the silane undercoat, and colour may be introduced by blending or by printing.

Description

SAFETY COATING OF FRANGIBLE WARE

BACKGROUND OF THE INVENTION

1. FIELD OF THE INVENTION

The present invention is directed to a method for applying a protective and safety coating to frangible wares, such as personal-use glassware, plateware of earthenware and china, and ceramics, and to the provision of safety-coated composites of glassware, plateware and ceramic produced by that method.

2. DESCRIPTION OF THE PRIOR ART

In the case of glass product composites the application of surface coatings to protect particular types of such articles is well known.

For beverage bottles, a so-called lubricious coating is applied to the exterior surface of the bottles and like articles which are subject to mechanical handling.

The coating is formed by mixing a dispersed polyethylene and a polyoxyethylene derivative of a fatty acid, which is applied to glass and heated to 160°F, to react and then to cure the components and form the lubricious coating. This coating diminishes the frictional contact of the bottles against each other, and against handling machinery, so as to diminish stress and breakage occurrences during processing, as taught in United States Patent No. 3,386,855 June 4 1968 and incorporated herein by reference.

United States Patent No. 3,415,673 Dec. 10 1968, Clock, also incorporated by reference, teaches the coating of glass containers such as bottles with a thin plastic coating. Surface pre-treatment with a polyethylene imine to promote adhesion is followed by an application of a copolymer coating in the range of 0.002- 0J50 inches, i.e. 2-150 mil. The copolymer comprises a major portion of ethylene, and an acidic comonomer of a specified wide group of acids, being applied to a considerable thickness as an electrostatic powder spray. A varnish finish is then applied by dip coating.

United States Patent No. 4,065,590 Dec. 27 1977, teaches the application of a modified protective plastic coating to glass soft drink bottles for carbonated beverages. Such bottles, more particularly the larger variety of 16-ounce capacity and greater, were known to fracture upon impact and explode in dangerous fashion, scattering glass fragments. The plastic of the protective coating was modified, so as to achieve reduced adhesive strength, in order to diminish the likelihood of fracture of the plastic while increasing its glass-retentive capability, so as to secure glass shards and fragments, in the event of fracturing of the bottle.

This usage has disappeared with the advent of plastic soft drink bottles, which have superseded glass in this area of use. In attempting to adopt the above- mentioned protective plastic coating for glass soft drink bottles to other uses it has been found to be susceptible to damage from hot water, such as that encountered in commercial dishwashers.

In tests of this prior art teaching it has been discovered, in the case of open topped glassware vessels, namely drinking glasses, having a coating of ethylene copolymer in accordance with the above identified U.S. Patent No. 4,065,590, and with a further thin outer protective coating of heat and wear resistant plastic such as urethane applied thereover, that the very first dishwashing resulted in the peeling off of the coatings. The further, polyurethane coating of heat resistant plastic, was applied in protective relation over the first coating, with the intention of protecting the first coating against degradation within a hot environment, to thereby enable use of the vessel in a commercial dishwasher, operating at a temperature of 82°C. or greater, but was unsuccessful.

U.S. Patent No. 4,256,788 Gras teaches the use of a urethane protective coating applied over a silane sub-coating. It appears that the coatings were applied in the form of a paste, leading to apparently uneven coat thickness, varying from 50-250 microns (2-15 mil) drinking glasses were coated in accordance with the teachings of Gras. The coating would be visibly perceptible and aesthetically unpleasing. The coated glass composites were impact tested. While the resistance of the coated glass composites against impact was impressively greater than for uncoated glasses, the eventual fracturing of the glass composites was characterized by fracturing of the glass, but with coinciding fractures of the protective plastic coating, so that scattering of the glass particles and shards was not effectively limited or prevented. Thus, in the case of frangible personal use items, such as cookware, drinking glasses and the like, a highly desired effect was missing; the desired cohesive retention of the shards and particles of the frangible substrate by way of the plastic coating, to limit or preclude its dissemination by scatter upon being fractured, was not achieved.

Other characteristics of the Gras process and its resultant products that may be significantly disadvantageous in potential fields of use are: the preferred thickness of coating (5-50mil), apparently necessary in order to achieve the desired impact protection; the associated high costs of the desired quantities of these plastics materials; and, the changed and non-standard appearance of the coated article, with diminished clearness and optical brightness.

In the food service industry most beverage glasses are still of glass, although plastic "glasses" have made some inroads into the market. However, in view of the relatively low initial cost of glass glasses, combined with their customary clarity and mass or "heft", and also their suitability for machine washing, as compared with the extreme lightness and higher cost of thin- walled plastic products, drinking "glasses" of glass have retained a significant share of the market.

However, this usage is typically associated with high annual replacement requirements; for instance, the some 60-million replacement glasses for example required by the relatively small. 30-million population of Canada. Much of this replacement quantity represents breakage loss that occurs in use, but also includes handling and transportation breakage losses. The hazards associated with the breakage of glass drink- ware are such that its use around swimming pools constitutes a very real safety hazard, due to the invisibility of glass in water. In the case of a pool with a vinyl liner, the incident of a broken glass in the pool generally requires the complete drainage of the pool, for visual detection and safe removal of the glass fragments, and to safeguard the vinyl liner. The act of drainage may, in turn, require the professional re-setting of the pool liner.

In addition to breakages of beverage glasses which occur in use there is also the hazard of chipping of the vessel lip, which can lead to liability claims by an injured user against the proprietor of a bar or restaurant.

It appears significant that of a number of prior patents that have been consulted, having teachings bordering on the present invention, none appears to be specifically directed to a major practical use or the capability of their respective process, in meeting the needs of the glass or ceramic drinking or serveware market. Also, no solution appears to have been offered to meet the problems imposed by the use of commercial or domestic dishwashers.

SUMMARY OF THE INVENTION

The present invention provides a method of coating a frangible, hollow vessel, with a visually imperceptible, aesthetically acceptable and commercially viable protective coat over at least a vulnerable surface portion, consisting of the steps of: applying to the vessel a first organo functional silicone coating, to promote adhesion thereto of a subsequent coating; applying a second coating of an ethylene copolymer as a fluent dispersion; and applying a third, outer protective plastic coating selected from the group consisting of thermosetting plastics and thermoplastics and having a minimum useful temperature of at least about 82°C, to provide a protectively coated vessel composite able to withstand extensive commercial dishwashing, and having enhanced fragment retention capability when fractured. The outer, heat-protective plastic preferably has a useful temperature of at least about 95 °C. The method includes using plastics coating materials in liquid form, to provide a composite having a smooth coating of predetermined thickness.

The steps of applying coatings to the vessel may be by way of flow coating, followed by a drying or a curing step, which serves also to remove the respective solvent or dispersant. The dispersant used may comprise a suitable liquid. Water is the preferred liquid.

The method may further include the step of curing the coated vessel composite under predetermined conditions of time and temperature.

The method may include the step of adding color to the vessel composite by way of the coating. The color may be added to one or more of the coatings.

The method may include the step of imprinting upon one of the coatings. The imprinting step may be applied to the outer coating, or to an underlying coating prior to the application of the outer coating. The ethylene copolymer may be applied as a plurality of coatings, to provide a desired agregate thickness. The agregate thickness may as much as 5 -mils or greater. The agregate thickness may be in a selected range such as 2 to 7 mils, with directional variation due in some measure to the occurrence of sag in the applied coatings. The third, outer layer may be a urethane, selected from thermosetting and thermoplastic urethanes. The preferred urethane is a thermosetting urethane.

Thirty commercial dishwasher cycles were judged as setting an acceptable commercial test standard, and was the standard adopted in the present invention.

The present invention provides a method of coating a frangible, hollow vessel, with a protective coat, consisting of the steps of: applying to the vessel a first organofunctional silicone coating, to promote adhesion thereto of a subsequent plastic coating; and applying at least one outer protective plastic coating selected from the group consisting of thermosetting plastics and thermoplastics to provide a protectively coated vessel composite.

In the context of the present invention the term "scattering" means the scattering of the fractured pieces and shards of a fractured object; and the term "non- scattering" includes the fracturing of the object without substantial scattering of the pieces and shards. Initial work on the present invention, with a view to achieving the long term durability, essential for meeting the requirements of the food service industry included testing of drinking glasses that were coated in accordance with the teachings of Gras, which were then made the subject of impact tests, referred to above. In view of those results, further steps were necessitated to achieve the long term durability, essential for meeting the requirements of the food service industry.

The approach taught by U.S. Patent No. 4,065,590, involved the introduction of an adhesion-reduction agent into the protective plastic coating, with a view to retaining adherence of the plastic to the glass, upon the occurrence of glass fracture.

Instead, it was found necessary to seek enhanced adhesive characteristics for the coating. To that end, after trials of numerous adhesion enhancing materials it was found that excellent results were obtained with the use of a prime coat of organofunctional silicones. In particular it was found that Silane A- 1106 and Silane A- 1130 (trademarks), developed by the DOW-CORNING chemical company, and now supplied by ISO Specialties Inc.; a WITCO company, of Greenwich, Connecticut greatly enhanced the adhesion of a coating to the parent frangible substrate material, in this instance glass. The Silane was applied as a liquid, with water as the solvent, being applied by flow coating. Ethylene copolymer was selected to serve as a shock-absorbing layer for the glass composite.

In applying the ethylene copolymer it was found that, as distinct from blending one of the Silanes with the coating material, best results were obtained by applying a Silane coating to the parent glass material, and drying off the solvent water. Upon then applying an ethylene copolymer coating it was found that the wetting and adhesion of the coating to the parent material was significantly enhanced.

Unlike prior usage of ethylene copolymer, in which the resin has been applied by way of powder coating, by extrusion into sheet form or as a paste, in the present invention the ethylene copolymer is water based, being dispersed in water. It was applied by way of flow coating, each coating application being cured before applying a succeeding coating.

A protective, temperature-resistant coating was then applied over the cured ethylene copolymer. It was found that a catalysed cross-linked urethane protective outer coating yielded excellent dishwasher protection to the ethylene copolymer, enabling it to meet the adopted standard of thirty commercial dishwashings without visually evident deterioration.

At the same time, this cross-linked urethane coating possesses a degree of flexibility to complement the impact resistance of the underlying ethylene copolymer, while possessing a long-lasting clear and sparkling appearance.

A thermosetting polyurethane was preferred over a thermoplastic urethane, being applied as a solution, with ethyl acetate being the solvent.

The use of a water-based thermosetting urethane is contemplated, for environmental considerations.

It has been found that excellent coating results and improved material utilization are obtained using the flow coating process, as described in : Industrial Painting: Principles & Practice by Norman R. Roobal 1991 page 91, and incorporated herein by reference.

The plastic coatings are flow coated at about 20°C, applying the fluent plastics by nozzle under non-impact flow conditions, to flow a smooth layer over the object being coated. Water based plastics are particularly well suited, owing to the close control of flow conditions made possible, including control over the percentage of solids being deposited; the thickness of the wet state layer deposited; and the uniformity of layer thickness.

Also, during an operating work shift virtually all excess material from the process can be recovered as drainage, and recycled through the process, to achieve an extremely high degree of material utilization. Loss of material during coating and the clean-up at the end of a shift is expected to total no more than 15%, giving an overall high transfer efficiency of some 85%. This compares with a transfer efficiency of about 40 to 60 % in the case of many spray applications, and is especially the case for the ethylene copolymer layer, which has been found to be very difficult to spray. In the instance of drinking glasses and like open-topped personal use vessel composites, the glasses may be inverted on a conveyor system, being rotated to facilitate application of the plastic from the flow coating nozzles, with excess plastic falling into drip pans, for recycling in the process. Coating in an inverted position has the advantage that, with sag, the coating tends to be thicker at the lower, more vulnerable lip zone portion of the glass.

In the case of upright vessels, a mandrel may be inserted in the mouth of the vessel, to limit the penetration of the plastic coating to a desired extent into the mouth of the vessel. The usual extent of taper of the glass wall facilitates withdrawal of the mandrel. In the case of drinking glasses, penetration of the coating by about five mil past the lip affords a desired extent of lip protection. Modified mandrels that extend deeper into the glass may be used to facilitate its positioning

For inverted glasses, under flow coating, the coating plastic tends to spread across the lip surface, affording a degree of protection to the lip of the glass.

In addition to the application of plastic coatings for purposes of safety, the present process also enables the economic introduction to the plastic coating, at one or other of its stages, of decorative enhancement such as colour; the provision of iridescence or pearlescence, and the application of additives to provide the characteristic of thermally-responsive colour change. A further characteristic that may be readily incorporated with the subject coating process is the introduction by blending of additives that glow when illuminated under "black light", i.e. infra-red light.

It will be understood that most, if not all of the advantages of the present process demonstrated to apply to glass composite ware also apply to a significant extent to many grades and types of frangible composites, including earthenware/chinaware and ceramic- wares. The virtual increase in strength of a coated composite and its reduced vulnerability to impact damage may permit the adoption of less bulky sections i.e. thinner walls and lighter structure, in which case significant cost savings may be achieved due to reduction in breakage during handling, shipping and ultimate use, with reduced shipping charges due to weight reduction, as well as savings in the costs of material for the products per se.

The coating of the product in an inverted position, as in a flow coating process, removes any need to mask-off the interior of the hollow vessel being coated, due to the inverted position. While spray application of the protective plastic coats is feasible, as in spray painting, the associated equipment costs are greater, and material utilization is reduced.

A prolonged period of experimentation and testing led to the following findings:

A water-based silane, flow coated on drinking glasses at the rate of approximately one quarter to one sixth of a gram per glass, produced an even, visually imperceptible wet-state coating of two to three microns thickness, the silane serving as an adhesion promoting agent for a subsequent plastic coating. The dried silane coating was found to significantly enhance the wetting and flow characteristics of the succeeding coating. Subsequent testing also showed significant enhancement in the adhesion of the succeeding coating to the glasses.

Ethylene copolymer, to serve as a shock absorber, was coated over the Silane coating. In one example the ethylene copolymer may consist of a blend of:

about 80 to 99 percent by weight, based on the total weight of the blend, of a random, normally solid ethylene copolymer selected from the group consisting of normally solid ethylene/acrylic acid copolymers, ethylene/methacrylic acid copolymers and copolymers having 10 to 90 percent weight of the carboxylic acid groups of the ethylene/acrylic or ethylene/methacrylic acid copolymers ionized by neutralization with metal ions having an ionized valence of one to three inclusive, wherein the random ethylene copolymers contain about 8 to about 25 percent by weight of acrylic or methacrylic acid copolymerized therein.

The copolymer was formed as a dispersion in a carrier liquid.

Application of the ethylene copolymer dispersion, in a series of sequential flow coatings, with intermediate curing phases to effect cross-linking of the ethylene copolymer also removes the liquid dispersant from the plastic, and enables the buildup of a smooth coating to a desired thickness, in accordance with the intended duty.

For some uses a 2-mil (0.002 inches) ethylene copolymer coating may provide adequate strength.

A further protective plastic coating can then be applied. In the instance of drinking glasses a high temperature resin coating, preferably a thermosetting resin, can be applied to serve as a protective coating, to withstand repeated washing cycles in a commercial dishwasher.

In one embodiment four coatings of ethylene copolymer were applied by flow coating, with intermediate curing, being built up to an agregate thickness of about 4 1/2 mil (0.0045 inches). Greater or lesser thicknesses may be readily achieved.

The preferred protective coating, selected from the group consisting of thermo-setting plastics, comprised polyurethane. Also, thermoplastics having a minimum useful temperature of at least about 82°C, which include polyurethane, may be suitable for withstanding commercial and household dishwashing. The vessel with its applied coating thereby provides a reinforced vessel composite having glass fragment retention capability, and the capability to withstand commercial or household dishwashing, as well as high abrasion resistance and chemical resistance.

In the case of a thermosetting plastic outer coating, the final, thermosetting coating is cured under predetermined conditions of time and temperature.

Alternative protective outer coatings may be selected from a catalysed acrylic or polyester.

Some thermoplastics, having a softening point at least close to the boiling point of water may also prove suitable for the outer coating.

The use of polycarbonate as the protective outer coating also is contemplated. The coatings are preferably liquid, in order to utilize the flow-coating process. For the reasons given above, water is the preferred liquid base.

With the flow-coating process, in instances where visible flow lines or

"crows feet" may occur, the applied coating can be "diluted" by reducing its concentration in the solvent or dispersant liquid, while increasing the number of coatings in order to achieve a smooth, unblemished coating of the desired thickness.

The action of the respective coatings is understood to be as follows: the initial Silane coating reacts chemically with moisture on the surface of the glass, to bond thereto; the ethylene copolymer reacts and links chemically with the Silane coating, which serves as a coupling agent. A second and subsequent coatings of ethylene copolymer react and link chemically with the underlying, coating of ethylene copolymer. The urethane coating, on the other hand adheres physically to the underlying, adjoining ethylene copolymer coating. The great adhesive quality of the urethane makes chemical linkage unnecessary. However, for other applications with different performance requirements, or for other reasons, a chemical linkage, provided by way of a reactive group to link with the underlying copolymer coating may prove desirable.

The provision of an article without the ethylene copolymer coating is contemplated; an outer protective resin coating may be flow-coated to adhere or to bond to a Silane undercoating. Colour may be introduced with the coating, by blending or by printing.

The vessel may be at ambient (room or workshop) temperature, for the application of each of the coatings, i.e. at about 20°C.

Provision is usually made for flash-drying off of the liquid carrier in ovens operating in the range 30 to 60°C, before setting-up and curing of the coatings, at 90 to 95°C.

It will be understood that for drinking glasses or commestible dishes the coatings need to be "Food and Drug" approved, and environmentally compatible.

The flow coating and associated drying procedures are sufficiently uncomplicated that coating of the vessels may take place on the glass manufacturer's line, at comparatively low temperatures.

In the case of catalysed outer coatings, these may cure at room temperature in some instances.

In addition to the tested use of the subject laminated coating for drinking glasses, its use may extend to include glassware such as mixing bowls, punch bowls, and the like, as well as the other above-mentioned groups of products where improved safety is a factor.

It will be understood that the present process enables the frangible composite to be "tailor-made" for its intended usage, in that the respective coating thickness of copolymer and of the outer protective coating can be selectively applied for optimum results. For example, in a first vessel composite having a 2-mil ethylene copolymer coating overlaid with a 1-mil urethane coating the first vessel composite would have less break resistance then a second vessel composite having 4.5 -mil ethylene copolymer and a 0.5-mil coating of urethane.

However, should breakage occur, the heavier urethane coating of the first vessel assisted by the ethylene copolymer provides a stronger skin to retain the shards and fragments together. Also, the heavier urethane coating provides more abrasion and chemical resistance. A further advantage of the present invention is in the use of color, or other appearance enhancements, referred to above.

In the case of normal, uncoated glass, other than the injection of coloured frit into the individual molds, the economics governing the addition of color directly to a batch or melt of the molten glass usually necessitate large scale action, when colour treatment of a furnace-full at a time is desirable. As a consequence the range of colors may be very limited. The subject plastic coating process may include the addition of color to the glassware, by way of the coating, in one or other of its stages, thereby enabling colouration in small batches, or even the individual coloration of articles.

The color may be a component of more than one of the coatings, so that the scale of a batch is no longer significant. Consequently, the range of colors can be extended without undue economic penalty.

In the case of articles for use with commestibles, these are subject to FDA (Food and Drug Administration) regulations, where a range of printing inks has been approved.

A further advantage of the subject process is that the plastic-coated outer surface of the composite is readily printed upon, using catalysed inks with conventional printing processes, which may include the use of ultra-violet or heat curing, to enhance dish washer and wear resistance. In the case of coated frangible composites intended for use with food or drink, the use of ultraviolet light to cure the urethane outer coating is not approved by the FDA, as undesirable components can be extracted during FDA's testing procedures.

A significant advantage of the present process is that the flowcoatings, whether single or laminated can be readily applied to a wide range of object configurations, enabling the products to compete with plastic products.

It is contemplated that composite vessels in accordance with this invention may be of lighter construction, having a thinner parent wall, which when protectively coated are capable of sustaining usage and handling stresses. This reduced mass in turn can afford very real savings in terms of hot water and drying energy requirements.

Testing evaluation of the both the subject glasses coated in accordance with the present invention and glasses coated in accordance with the Gras prior art process was carried out using a pendulum impact test. With a test specimen glass immovably mounted upon a test stand, a steel ball, positioned to impact the glass at its more vulnerable upper portion, is released to swing through a standard, predetermined arc, to impact the glass.

The conditions of ball weight, diameter, and impact velocity were selected to provide a standardized test such that in the case of unprotected glasses taken at random from a standard batch of glasses, two out often non-coated glasses survived the test unbroken.

In the instance of glasses of the same batch, but protectively coated in accordance with the present invention, the breakage survival rate was eight out often so tested.

The test stand incorporates a heavy base carrying a rigid mast. A cross bar adjustably secured to the mast has a pendulum cord secured thereto to which a steel ball of a given weight is secured. The cross bar is adjusted in accordance with the length of the cord selected for that type of glass, and in accordance with the height of the glasses being tested, such that impact of the ball will take place against the vulnerable upper portion of the glass, when supported upon the base.

For each test the ball is released from a predetermined measured height, with the cord just taut, for the ball to swing arcuately down and directly impact the glass being tested. The plane of swing is at right angles to the cross bar, such that the mast is not in the plane of swing, and consequently it does not contact or constrain the vessel under test.

In order to calibrate the test apparatus for a given batch of glasses, the length of the cord and the drop height are selected, with corresponding adjustment to the height of the cross-bar on the mast, in order to achieve a measurable high rate of breakage such as 80% of the virgin (untreated) glasses.

The treated glasses are then also tested under precisely the same conditions, enabling a statistical measurement of the improvement in durability to be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

Certain embodiments of the invention are described by way of illustration, without limitation of the invention thereto, other than as set forth in the claims hereof, reference being made to the accompanying drawings, wherein:

Figure 1 is a view of a drinking glass coated in accordance with the present invention, having portions of the protective outer plastic layer broken away;

Figure 2 is a view of a bowl coated with the subject coating, and shaded to show the application of colouring to one of the coatings;

Figure 3 is a schematic side view of a flow coating installation for the subject glasses;

Figure 4 is a tabular summary of the process; Figure 5 is a side elevational view of a test stand for the impact testing of glasses, and,

Figure 6 is a plan view of the Figure 5 arrangement.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 shows a drinking glass 10, the vulnerable outer surface of which is coated with a protective coat 14, in accordance with the present invention. An underlying copolymer shock-absorber coating 16 is crosshatched, to indicate the addition of colour therewith, which also shows through the clear protective coat 14 that is preferably of thermoset polyurethane.

Figure 2 shows a decorative bowl 12, the vulnerable surface of which has a protective coat 14 thereon. The coat 14 lends itself to the application therewith both of color and of printed patterns, etc.

Referring to the process embodiment illustrated in Figure 3, a moving belt 16 carries a batch of glasses 10 past eight workstations. The workstations comprise flowcoating stations 22, 24, 26 and 28, having drier station 30, and curing stations 32-40 in respective succeeding relation with the respective coating stations.

The first flow coating station 22 applies the ultra-thin adhesion- promoting Silane coating.

The second through fifth flowcoating stations 23, 24, 25 and 26 apply successive coatings of the shock-absorbing copolymer 16; which are cured by the respective succeeding curing stations 32, 34, 36, and 38. The last flowcoating station 28 applies the protective urethane coating 14 of Figures 1 and 2, illustrated as being cured by curing station 40.

Figure 4 shows the sequence of steps for the illustrated process of Figure 3. It will be understood that alternative sequences may be employed, for the purposes of the invention.

In the testing apparatus 40 of Figures 5 and 6 a baseplate 42 carries a mast 44, having a cantilever arm 46 adjustably secured at 48. A loop 50 has a cord 52 secured thereto, the cord 52 carrying a metal ball 54.

A resilient loop 58 locates a glass 10 in positioned, supported relation upon the baseplate 42. However, the loop 58 does not restrain the glass 10 against movement, when impacted. The length of the cord 52 is selected in accordance with an elected protocol of desired breakage of untreated glasses, in order to establish a basis for comparative testing of glasses treated in accordance with the present invention.

Having determined the desired cord length in order to meet the selected protocol, the height of the arm 46 upon the mast 44 is set so as to impact the ball 54 against the upper, most vulnerable portion of the glass 10 being tested.

TEST APPARATUS DURABILITY CALIBRATION

With the testing apparatus equipped with a 94-gram steel ball, it was found that a 32 5/8 inch effective length of cord, positioned such that the ball impacted the vulnerable upper portion of the test glass, as a durability test, produced a survival rate probability of two out often for untreated glasses, i.e. an 80 % breakage rate.

TEST 1.

Glasses were processed in accordance with the invention, being flow coated with a Silane (T.M.) organofunctional silicone, water-soluble SILQUEST (T.M.) A-l 106 Silane, being given a wet-state 2-3 micron coating, and dried.

The glass was then flow coated, to provide a 3-mil (0.003 inch) coating of water based ethylene copolymer, each successive coat being cured. A protective high temperature outer coating of urethane was then applied, by flow coating to a thickness in the range 0.5-1.0 mil, the solvent being ethyl acetate. This provided glass composites possessing clarity and sparkle substantially the same as that of glass, the presence of the plastic coating being unobvious to the point of being undetectable.

Three out often survived the durability test, i.e. a 70 % breakage rate was experienced.

These coated glasses however were undamaged after 30 machine dishwashings.

TEST 2

Glasses treated with the 2-3 micron Silane (T.M.) coating and having a 3 -mil polyvinylbutyral coating showed reduced durability on the dishwasher test, with loss of adhesion of the protective coating and were considered to have failed the dishwasher test.

They also demonstrated inferior breakage resistance.

TEST 3

Glasses having been flowcoated with a 2-3 micron Silane coating, which was then dried, were then given four flowcoatings of ethylene copolymer, for a total 4-5 mil thickness, each coating being cured after application. This was followed by a high temperature coat of 0.5-mil thermoset urethane.

Eight out often of the glass composites, i.e. 80% survived the durability impact test. These eight surviving glass composites survived 30 machine dishwashings, undamaged.

In the two instances of glass composite breakage under the impact test, high fragment retention by the plastic coating secured virtually all the glass fragments. While greater thicknesses of ethylene copolymer can be applied, for potentially enhanced impact protection, possible undesirable appearance may result, with noticeable changes to the clarity and sparkle. Also, from the commercial standpoint, with thicker coatings the cost of the glass composites are correspondingly increased, with diminished marketability.

Claims

1. A frangible composite article consisting of an original frangible article being vulnerable to breakage; and a visually unobvious protective plastic coating adhering to said article, to resist breakage of the article.

2. The composite article as set forth in claim 1, said article being a vessel, said protective plastic coating including an adhesion enhancing undercoat.

3. The composite vessel as set forth in claim 2, said protective plastic coating including a shock-absorbing plastic coating adhered to said undercoat.

4. The composite vessel as set forth in claim 3, said protective plastic coating including a high temperature plastic outer coating.

5. The composite vessel as set forth in claim 2, wherein said undercoat is a water-soluble silane.

6. The composite vessel as set forth in claim 3. wherein said shock absorbing plastic coating is an ethylene copolymer.

7. The composite vessel as set forth in claim 4, wherein said high temperature outer coating is selected from the group consisting of a thermoplastic urethane and a thermosetting urethane, having a softening temperature at least above 82°C, to withstand washing in a commercial dishwasher machine.

8. The composite vessel as set forth in claim 1, wherein said original vessel is selected from the group consisting of glassware, earthenware including chinawear, and ceramics, that are vulnerable to impact fracture and shattering.

9. The frangible composite article of claim 1, said protective plastic coating including an adhesion enhancing undercoat of silane, having an outer protective resin coating, and incorporating colour enhancement therewith.

10. The composite vessel as set forth in claim 7, wherein said vessel composite is a protectively coated drinking glass.

11. The vessel as set forth in claim 1 , wherein said high temperature plastic being selected from the group consisting of thermosetting plastic and thermoplastics having a softening temperature at least above 82°C, to withstand washing in a commercial dishwasher machine.

12. The glassware vessel as set forth in claim 5, said laminated outer coating being a clear and transparent coating over at least said vulnerable area of said vessel and extending to the lip of the vessel in protective relation against chipping of said lip.

13. The vessel as set forth in claim 1, said plastic coating incorporating colour therein.

14. The method of coating an open-topped frangible vessel, including the steps of applying to the vessel a first organo functional silicone coating, to promote adhesion thereto of a subsequent plastic coating; applying at least one subsequent coating of an ethylene copolymer water in dispersion, curing each coating of ethylene copolymer as it is applied, and applying an outer overlaying plastic coating selected from the group consisting of thermosetting plastics, and thermoplastics having a minimum useful temperature of at least about 82°C, to withstand commercial dishwashing.

15. The method as set forth in claim 14, including the step of incorporating color with a said coating.

16. The method as set forth in claim 14, including the step of imprinting a said coating.

17. The method as set forth in claim 14, wherein said vessel is a drinking glass, said coating extending in protecting relation over a lip portion of said glass.

18. The method as set forth in claim 14, wherein said outer coating is a urethane, the respective thickness of said ethylene copolymer and of said urethane outer coating being selectively variable, to provide a vessel composite of selected characteristics.

19. The method as set forth in claim 18, wherein said urethane is thermosetting.

20. The method as set forth in claim 19, wherein said thermosetting urethane is waterbased.

AMENDED CLAIMS

[received by the International Bureau on 8 December 1999 (08.12.99); original claims 1-20 replaced by new claims 1-19 (3 pages )3

1. A frangible composite article having a protective plastic coating applied in adherent relation over a major surface portion thereof, characterized in that said coating consists of a first, adhesion enhancing undercoat adhering to said surface; a second, shock absorbing plastic coating in bonding relation with said undercoat, and a third, outer coating of high temperature plastic resistant to impact, in protective covering relation with said second coat.

2. The composite article as set forth in Claim 1 , wherein said first , said second and said third coating each have transparency and clarity such that the appearance of said article is substantially unchanged from its uncoated condition.

3. The composite article as set forth in Claim 1 , wherein said first undercoat is silane, an organo-functional silicone, being reactively bonded to said surface of said article, and being in reactive, bonded relation with said second plastic coating.

4. The composite article as set forth in Claim 3, wherein said second coating is a copolymer selected from the group consisting of normally solid ethylene/acrylic acid copolymers, ethylene/methacrylic acid copolymers and copolymers having 10 to 90 percent weight of carboxylic acid groups of said ethylene/acrylic or ethylene/methacrylic acid copolymers ionized by neutralization with metal ions having an ionized valence of one to three inclusive, and wherein said random ethylene copolymers contain about 8 to about 25 percent by weight of acrylic or methacrylic acid copolymerized therein.

5. The composite article as set forth in Claim 1, wherein said second coating is in smooth, substantial conformity with the underlying surface on which the second coating is applied.

6. The composite article as set forth in Claim 1, wherein said third coating is a catalysed, cross-linked, non-melting, thermosetting polyurethane, able to withstand commercial dishwashing.

7. The composite article as set forth in Claim 6, wherein said catalysed, cross-linked, non-melting, thermosetting polyurethane consists of a catalyst and a polymer selected to enable the adoption of a predetermined pot life.

8. The composite article as set forth in Claim 6, wherein the respective thicknesses of said second and third coatings is selected to provide predetermined impact and particle retention characteristics.

9. The composite article as set forth in Claim 1, wherein said frangible article is a hollow vessel having a base portion and a lip portion, said lip portion having greater susceptibility to damage by impact, at least one of said second and third coatings having greater thickness adjoining said lip portion, to enhance the shock protection thereof, and in the event of fracture, to better retain the fragments of said vessel.

10. The composite article as set forth in Claim 1, wherein said article includes decorative enhancement material, introduced by way of at least one of said plastic coatings, said enhancement material being selected from the group characterized by colour, thermally responsive colour change, infra-red responsive, irridescence and pearlescence.

11. The composite article as set forth in Claim 1 , wherein said frangible article is a hollow glass vessel.

12. The composite article as set forth in Claim 9, wherein said frangible article is a hollow glass vessel.

13. The composite article as set forth in Claim 10 or Claim 12, wherein said frangible article is a drinking glass.

14. The method of coating an open-topped frangible vessel with a protective plastic coating, characterized in that said coating consists of a first adhesion enhancing undercoat, said method including the steps of applying said first plastic as a water dispersed undercoat in adhering relation with selected portions of said surface; applying a second, shock absorbing plastic coating as a water dispersion in bonding relation with said undercoat, and applying a third, outer coating of high temperature plastic resistant to impact, in protective covering relation with said second coat.

15. The method of coating an open-topped frangible vessel with multiple layers of plastic in protective relation therewith, characterized in that said vessel is positioned in an inverted condition; a first organo-functional silicone coating is applied thereto; said first coating is dried; at least one second plastic coating consisting of an ethylene copolymer in water dispersion is applied thereto, and dried; and a third coating of plastic is applied, being selected from thermosetting and thermoplastic having a minimum useful temperature of about 82 Celsius, and enabling said coated vessel to withstand commercial dishwashing.

16. The method as set forth in Claim 15, including the step of incorporating a decorative substance with a said plastic coating prior to application of said coating to said vessel.

17. The method as set forth in Claim 15, including the step of applying an imprinting upon a selected coating of said plastic coatings.

18. The method as set forth in Claim 15, wherein said vessel has said coating applied within a rim portion thereof.

19. The method as set forth in Claim 15, wherein said third coating consists of a waterbased thermosetting urethane. WO 00/43324 _.._ PCT/CA99/00348

STATEMENT UNDER ARTICLE 19(1)

The original claims are hereby cancelled, in favour of the 19 claims presented herewith.

The amended claims, in European form now more clearly distinguish over the references cited by the Examiner.

Referring to the amended claims:

Claim 1 now recites a frangible article having three protective plastic components; 1) An adhesion enhancing undercoat; 2) A shock absorbing coating, and 3) A durable, high temperature protective outer coat that is "dishwasher resistant".

While the use of protective plastic coating elements on the surface of frangible articles is not new, this particular combination of three protective elements is novel, and particularly useful, from both an economic and a safety standpoint.

None of the references cited by the Examiner, taken singly or in combination, teach this new and improved result and product.

Claim 2 recites the transparency of the coating.

The first, silane, organo-functional silicone undercoat recited in Claim 3 serves to promote adherence of the second, shock-absorbing coating, while also promoting the tenacity of the