Thermochromic coatings with resin vehicle.

(54) Title: THERMOCROMIC COATINGS WITH RESIN VEHICLE.

(54) Title: THERMOCHROMIC COATINGS WITH RESIN VEHICLE.

(57) Summary

Thermochromic coatings are enhanced by mixing thermochromic capsules with polymer resins in a manner that imparts self-stability to the liable precursors that can be cured to form relatively hard coatings that are capable of withstanding machine operations, such as the operations necessary to make lids of beverage cans, bottle caps, pull tabs and the like.

(57) Abstract

Thermochromic coatings are improved by mixing thermochromic capsules with polymer resins in a manner that imparts shelf stability to flowable precursors that may be cured to form relatively hard coatings that are capable of withstanding machine operations, such as the operations needed to make beverage can lids, bottle caps, pulí tabs and the like.

Mexican Property Institute

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Industrial □

PATENT TITLE NO. 346166

Owner (s): CHROMATIC TECHNOLOGIES, INC.

Address: 1096 Elkton Drive, Suite 600, Colorado Springs, Colorado, 80907, USA

Denomination: THERMOCROMIC COATINGS WITH RESIN VEHICLE.

Classification: lnt.CI.8: C09D5 / 00

Inventor (s): TIMOTHY J. OWEN; KRISTIN A. FLETCHER

REQUEST

Number: International filing date:

MX / a / 2013/009090 February 15, 2012

PRIORITY

Country: Date: Number:

US February 15, 2011 61 / 443,170

Validity: Twenty years

Expiration Date: February 15, 2032

The reference patent is granted based on articles 1, 2, section V, 6, section III, and 59 of the Industrial Property Law

In accordance with article 23 of the Industrial Property Law, this patent has a validity of twenty years, non-derogable, counted from the filing date of the international application and will be subject to the payment of a fee to keep the rights in force. .

Whoever signs this title does so based on the provisions of article * β “fractions tH and 7^or bis 2 of the Industrial Property Law (Official Owner of the Federation (DOF) 06/27/1991, amended on 08/02/1994, 10/25/1896, 12/26/1997, 05/17/1999, 01/26/2004, 06/16/2005, 01/25/2 «», 05/06/2009, 01/06/2010, 06/18/2010, 06/28/2010, 01/27/2012 and 04/09/2012), articles I^or, 3 »section V subsection a), 4 'and 12 ° sections I and III of the Regulations, of the Mexican Institute of Industrial Property (DO F. 12/14/1999, amended on 07/01/2002, 07/15/ 2004 »07/28/2 * 54 and 09/07/2007), article * V, 3^or, 4^or, 5^or fraction V subsection a), 18 sections I and III and 30 of the Organic Statute of the Mexican Institute of Industrial Property (DO F. 12/27/1988, MfcnMdaai 1O / 1W2O02,28 / 07/2004, 08/04/2004 and 13709/2007), 1^or, 3^orand 5th subsection a) of the Agreement that gives powers to the Directors &lt;ΜηΜΜ * ΑφΜ (08, Coordinator, Divisional Directors, Heads of Regional Offices, Divisional Deputy Director®, Departmental Coordinators and other subordinates of the Mexican Institute of Industrial Property. ( DOF 12/15/1999, amended on 02/04/2000, 07/29/2004, 08/04/2004 and 09/13/2007).

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MX / 2017/20774

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THERMOCROMIC COATINGS WITH GIRLS 'VEHICLE' 'BACKGROUND

Thermochromic encapsulated dyes undergo a color change over a specific temperature range. By way of example, a dye may change from a particular color at low temperature to colorless at high temperature, such as red at 29 ° C (85 ° F) and colorless above 32 ° C (90 ° F). The color change temperature is controllable, such that the color change can take place at different temperatures. In one example, the color change can occur at a temperature just below a person's external body temperature such that a color change occurs in response to human touch. For those skilled in the art of thermochromic microcapsule synthesis, precise control of the temperatures at which color changes occur is easily accomplished. For example, the ideal color change temperature for cold drinks can range from 0 ° C to 15 ° C, while the ideal temperature range for a heated or hot drink can be between 40 ° C and 65 ° C.

Thermochromic systems consist of three main components: an electron donating chromophore, an electron accepting color developer, and a nonpolar solvent that facilitates color change over a specific temperature range. The properties of the systems

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. IMPI INSTITUTO MEXICANO ~ CE LA TOCHEDAD

INDUSTRIAL thermochromics have been exploited for more ”3é '' T5 ~~ years7 A technique used to produce thermochromic encapsulated dye is to combine water, dye, developer, oil, with urea-formaldehyde or melamine-formaldehyde resin and shake to create a very fine emulsification. The interfacial tensions are such that the oil, dye and developer end up inside a capsule of urea-formaldehyde or melamine-formaldehyde distributed mainly throughout the water phase. The urea-formaldehyde or melamine-formaldehyde substance, while very hard and resistant to high temperature decomposition, is permeable. Although there has been significant improvement in microencapsulation technology, thermochromic systems still have chemical instability inherent in polar solvent-based systems. For this reason, microencapsulated thermochromic pigments have found limited applicability in solvent-based systems. For example, United States Patent No. 6,139,779 describes how low molecular weight solvents (generally less than 100 g / mol) have been shown to permeate the relatively thin microcapsule wall and destroy the thermochromic system. A variety of thermochromic inks can be purchased commercially, for example from Chromatic Technologies, Inc. of Colorado Springs, Colorado.

United States Patents 4,421,560 and

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4,425,161 entitled Thermochromic Materials amb ^ cesstate that thermochromic inks can be made with conventional additives used to improve conventional printing inks. However, there are problems about which additives can be added to these inks.

Thermochromic dye is often sold in a pigment suspension formed from a water-based encapsulated dye. This results from the fact that the pH of this suspension is most frequently neutral in a range of 6.5 to 7.5. When the thermochromic dye is added to a formulation having a pH outside this range, the color change properties are often lost. This can be an irreversible effect and therefore it is important to adjust the pH before adding the thermochromic dye.

Various types of ingredients are traditionally added to ink formulations. The combination of all the ingredients in an ink, other than the pigment, is called the vehicle. The vehicle carries the pigment to the substrate and bonds the pigment to the substrate. The correct combination of vehicle ingredients will result in wetting of a pigment. This wetting means that the vehicle forms an absorbed film around the pigment particles. The main ingredient in an ink is the binder. This may be a

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resin, lacquer or varnish or some other. ...

Binder characteristics vary depending on the type of print you are doing and the final product desired. The second main ingredient is the colorant itself, for example, as described above. The remaining ingredients are added to increase the color and printing characteristics of the binder and colorant. These remaining ingredients may include reducers (solvents), waxes, surfactant, thickeners, driers and / or UV inhibitors.

Flat lids of the type used on beverage cans are stamped from a roll of aluminum, typically 5182-H48 alloy, and transferred to another press which converts the stamped materials into an easy-open end. The conversion press forms an integral rivet button in the lid and marks the opening, while concurrently forming the tabs in another mold from a separate strip of aluminum. The tab is pulled over the button, which is then flattened to form the rivet that attaches the tab to the lid. The top rim of the can is trimmed and pressed inward or neck shaped to form a conical taper where the can will then be filled and the lid (usually made of an aluminum magnesium alloy) attached. Lid components, especially tabs, can be coated before they are

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undergo such manufacturing processes-uumej ul ILÜllacliado of ends of cans, tabs, lids or lids.

Three-piece beverage cans are usually refilled before the top is folded into place. Fill and seal operations are fast and accurate. The filling head is centered over the can and discharges the beverage to flow down the sides of the can. The lid is placed on the can which is then folded in two operations. A sealing head engages the lid from above while a side sealing roller undulates the edge of the lid around the edge of the can body. The head and roller rotate the can in a full circle to seal the entire path around. A pressure roller then pushes the two edges together under pressure to make a gas-tight seal. Filled cans usually have pressurized gas inside, which hardens the filled cans for subsequent handling.

Thermochromic inks have been used successfully as indicators of a preferred usage temperature and as a brand differentiator. Specifically, thermochromic inks have been used as cold indicators in aluminum cans, via metal decoration inks, to communicate the optimum consumption temperature to the consumer. This interactivity through

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thermochromic color change up to ah'óTcr * ”ñ^Jor spreads to coating on can ends, tabs, lids and lids. To date, none of such coatings are commercially available. In part, this is due to the significant mechanical forces that are applied to the pre-coated fabric material to form can ends, tabs, lids, and other lids. Due to stress and bending during the tool machining process the coating must be flexible and resistant to cracking, peeling and other damage. In addition, the coating must be chemically resistant enough not to be affected by pasteurization or other processes. In order to meet the above requirements, the reversible thermochromic coating described herein must contain a thermochromic pigment, a formulated carrier system and / or a commercially available coating commonly used for coatings of cans and rolls. In order to design additional coating properties, for example chemical resistance or flexibility, the component such as a curing agent, an accelerator or catalyst to increase curing, or wax can be added to the component. In addition, thermochromic microcapsule wetting agents can be incorporated to aid dispersion of the pigment, and one or more solvents can be selected. United States Patent Application 2003/0127415 Al

IMPI

MEXICAN INSTITUTE OF INDUSTRIAL T non age

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describes the use of thermochromic inks paxa ___ apJdjcax ..- iiaÁgeft &amp; s ~ · printable on metal lids and lids. US Patent Application 2011/0226636 Al describes the use of thermochromic inks as they are applied in multiple ways to aluminum can ends, the offset tear panel and the non-detachable tab. While these descriptions describe the application of thermochromic inks, they do not teach practical means to achieve the described claims. Conventional thermochromic inks are generally unsuitable for the manufacturing efforts involved in making can ends and tabs which, practically speaking, are made from aluminum rolls commonly known as roll material that must be covered prior to machining operations. that form the ends of cans, tabs, lids and other lids. Due to the durability and chemical stability of epoxy coatings, they are commonly applied to aluminum and metal cans where direct or indirect food contact can occur. The prior art, however, does not provide detailed formulations for a reversible thermochromic epoxy-based system or other resin system, for use on can ends, tabs, lids or lids.

It is problematic that existing thermochromic coatings fail to withstand the stresses of

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these manufacturing operations which, for example, can excessively thin or scratch the coatings or crush the microcapsules that make up the thermochromic pigment.

SHORT DESCRIPTION

Currently described instrumentalities overcome the problems outlined above and advance the art by providing reversible thermochromic roll and can liners to fabricate Can ends, tabs, lids and / or lids using aluminum or steel alloys. Furthermore, the inventors have discovered processes in the manufacture of the thermochromic microcapsule as well as processing conditions when making the coating that increase the solvent stability of the thermochromic pigment.

The use of thermochromic systems as a substitute for conventional pigments in resin-based coatings creates an interactive effect that can provide an indicator or purely artistic effect. In addition to the visual appearance of thermochromic can ends, tabs, lids and lids, it also has a functional purpose that indicates the internal temperature of the beverage within the can, for example as the pigment changes from colorless to colored or from one color to a different color.

In one aspect, a thermochromic coating can

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include a pigment and a vehicle. The gmaotri-gsafcá prp ^ pnt-p in an amount ranging from 1% to 40% of the coating by weight, and the vehicle forms the remainder from 99% to 60% by weight. The pigment can be provided in a suspension form having various liquid contents, as for the consistency of the pigment weight it is estimated using the pigment which is completely dry. For example, the pigment provided in a water-based suspension would be estimated after removal of the water, although this is not strictly necessary to remove the water when all formulations are mixed.

The pigment includes thermochromic microcapsules. There are usually urea-formaldehyde or melamine-formaldehyde resins that encapsulate a core that contains a thermochromic system that includes a thermochromic dye (such as a leuco dye), a developer, and a solvent that controls the color activation temperature of the dye and the developer. Other thermochromic systems are known in the art. Methods for forming thermochromic capsules with predetermined activation temperatures are well known in the art. The pigment may also contain dyes or solids that impart color and are not thermochromic in nature.

The carrier contains a polymerizable resin that contains the pigment and can be, for example, epoxy, polyester, urethane, acrylic acid, and acrylate. These can

I My PI, „INfHWTO MEXICANO&gt; v DE LA PRORIOAD

INBltmiAL incorporate curing agents such as s-®r —- c-oaoGÍdos - ^ aawla technique, such as primary, secondary, tertiary and cyclic aliphatic amines, blocked amines (eg Hycat), amino resins with an alkylation range, amines 5 aromatics, polyamines, polyamides, amidoamines, ketimines, melamine resins, isocyanates or resins that can be cured using ultraviolet radiation. Surfactants or other dispersing agents can facilitate the dispersion of the pigment in the vehicle. Dispersing agents may suitably include, for example, nonionic, anionic, cationic or zwitterionic surfactants, polymers or copolymers, or reactive diluents such as aliphatic or cycloaliphatic glycidyl ethers. Non-polar or aromatic, polar alkane solvents, aprotic solvents, such as esters, ketones, amides, or protic, polar solvents such as alcohols or acids can be added for rheological control.

In one embodiment, a thermochromic coating formulation includes:

<td>Ingredient</td><td>Weight percent of Coating</td>

<td>Pigment*</td><td>1% to 40%</td>

<td>Vehicle</td><td></td>

<td>Resin polymerizable</td><td>5% to 30%</td>

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'«NTVTO MtXíCANO nf Ia TRONBOaP indi irrwiAi

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<td>Dispersing agent</td><td>0% to 5% ...............</td>

<td>Solvent</td><td>0% to 50%</td>

<td>Curing agent</td><td>0% to 25%</td>

<td>Wax</td><td>0% to 5%</td>

Estimated by the solid content in the complete drying of pigment capsules, but it does not need to be dried and can be mixed as a suspension.

In one aspect, a reversible thermochromic coating for use in can and roll coatings contains a reversible thermochromic pigment in an amount of 1% to 40% by weight of the coating and a vehicle that forms the remainder of the coating. The carrier includes a resin selected from the group consisting of epoxy, polyester, urethane, acrylic acid, and acrylate resins, and combinations thereof. Commercially available thermochromic pigments are readily available in a variety of colors that demonstrate color transition temperatures of about 5 ° C and up to about 65 ° C. A range of color formulations can be made by mixing the pigment to include one or more of the following reversible thermochromic colors: yellow, magenta, cyano, and black. These can also be mixed to include other solid dyes or pigments that are not thermochromic in nature. The pigment can change from a colorless state to a colored state on cooling to

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INSTITUTO MNOCANU ¿elawwimwd INDUSTRIAL

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the reactive temperature, or a stage © - heating to the reactive temperature. It is preferred that the microcapsules are formed of urea-formaldehyde or melamine-formaldehyde which is acid catalyzed to increase inherent stability in low molecular weight, polar solvents having a molecular weight of about less than 100 g / mol.

When affirmed using a non-polar solvent, coatings can demonstrate self-stability exceeding 14 or 45 days when stored at approximately 20 ° C. Some coating formulations demonstrate self-stability for more than one year.

The curing agent is generally compatible with the resin for this purpose and can be, for example, a latent blocked amine to initiate a polymerization reaction on heating.

The coating is preferably roll coated onto the roll stock aluminum or steel and the roll stock aluminum is subsequently formed into one or more components of the beverage can. These components may be selected from the group consisting of beverage can end, beverage can tabs, bottle caps and / or beverage container lids. Aluminum is preferably an alloy that is commonly used in canning operations, such as aluminum alloy.

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aluminum 5182-H48. This' T'écuErnimiento process preferably occurs in one or more coatings to produce a dry film with a thickness ranging from 1 mg / pg² up to 5.5 mg / pg².

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 compares tipped beverage cans which are coated with a thermochromic coating in accordance with the present disclosure and cooled to different temperatures corresponding to Fig. 1A and Fig. IB.

Fig. 2 shows a beverage can lid having a pull tab with a thermochromic coating.

Fig. 3 shows a process for applying the coating to make thermochromically functional aluminum that can be used to make thermochromically functional beverage can components.

DESCRIPTION OF THE PREFERRED MODALITIES

Thermochromic ink coatings contain, in combination, a carrier and a pigment that includes thermochromic microcapsules. The thermochromic microcapsules are preferably present in an amount ranging from 1% to 50% of the coating by weight on a gradual scale. The vehicle contains a solvent which is preferably present in an amount ranging from 25% to 75% by weight of the coating. ·

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KTTTTVTO MEXICAN MUtKOmOAD INDUSTRIAL

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Pigment _ ..

Careful preparation of the reversible encapsulated thermochromic material increases coating stability in the presence of low molecular weight polar solvents that are known to adversely affect thermochromic behavior. One skilled in the art of microencapsulation can use well known processes to increase the stability of the microcapsule. For example, it is understood that increasing the cross-link density will reduce the permeability of the capsule wall, and also reduce the deleterious effects of low molecular weight polar solvents. It is also commonly understood that, under certain conditions, weak acids with a pK_to greater than about 2 can catalyze polymerization of the microcapsule wall and increase the resulting crosslink density. This is currently the case of the use of formic acid as a catalyst that increases the solvent stability of blue thermochromic microcapsules in the presence of low molecular weight ketones, diols and aldehydes at room temperature. Furthermore, it is well understood that increasing the diameter of the thermochromic microcapsule can result in increased solvent stability.

Selection of material for use as non-polar solvent for thermochromic dye and developer

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of color that is encapsulated within the pigment — thermoerrorrCTT determines the temperature at which the color change is observed. For example, changing from a single component solvent to a two component solvent system can shift the temperature at which full color is perceived by almost 7 ° C from just below 19 ° C to 12 ° C. This description shows how to apply this knowledge in preparing resin-based vehicle coatings for use in can and roll coatings with full color temperatures, i.e. the temperature at which the maximum color intensity is observed, as low as -5 ° C and as high as 65 ° C. No adverse effects were observed on the physical properties of the resulting coating as the entire color temperature was changed over the above temperature range using different straight chain alkyl esters, alcohols, ketones or amides.

Thermochromic materials that include encapsulated thermochromic systems with a variety of color properties are commercially available from such companies as Chromatic Technologies, Inc., of Colorado Springs, Colorado.

Control over the intensity of color observed is demonstrated in several ways, generally by presenting the provision of increased amounts of pigment. For a

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typical coating, the thickness of the 'material' 'VárTcT' '^ Γ mg / pg² at 6 mg / pg². Very intense color is observed for coatings with thicknesses greater than approximately 3 mg / pg². Increased thermochromic pigment solids can also result in a more intense observed color even as coating thickness is decreased. However, dry film properties such as flexibility and toughness can be compromised if too much thermochromic pigment is incorporated. The optimum range of thermochromic pigment solids is within 5 to 40% by weight of the coating.

Vehicle

The physical properties of the finished coating can be significantly affected by the selection of the resin that is used. When a reversible thermochromic coating is not used in the formulation, a matte finish is achieved that is capable of being formed on the ends of cans, tabs, lids and / or other lids. While this result may be desired, the inclusion of a relatively low molecular weight, low viscosity resin, monomer, oligomer, polymer, or combinations thereof, can increase gloss and affect other physical properties of the film such as hardness, flexibility and chemical resistance. The resin is designed to supplement the total solids deposited on the substrate, thereby impacting

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,₇ IMPI

MKiCANO INSTITUTE

B1 INDUSTRIAL FROmTY shapes the physical properties of the dry film. Any resin material, monomer, oligomer, polymer, or combination thereof, that can be polymerized in commercially available roll and can liner material is suitable for inclusion in the current reversible thermochromic roll and can liner formulation. . Acceptable classes of resins include, but are not limited to, epoxy, polyester, urethane, acrylic acid and acrylate, and suitably other types of high solids resin systems.

Topcoat properties such as chemical resistance, hardness, and flexibility can be manipulated through the selection of crosslinkers or curing agents. Materials that readily react with and are incorporated into the selected resin system are suitable for inclusion as a crosslinker or curing agent. Examples include, but are not limited to, primary, secondary, tertiary, and cyclic aliphatic amines, blocked amines, amino resins with an alkylation range, aromatic amines, polyamines, polyamides, amidoamines, ketimines, melamine resins, isocyanates, or resins that are they can cure using ultraviolet radiation. Care must be taken to balance reactivity needs with pot life / shelf life. For example, if the curing agent reacts very

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Quickly with resin, the reversible coating-R-fee-t-ei "macTúml'CT5 *" 'can cure before the coating can be applied to the aluminum or steel substrate.

In order to ensure that the reversible thermochromic coating is fully cured before the roll is rewound, accelerators and / or catalysts can be added to the coating formulation. Examples of suitable materials for use as cure accelerators or catalysts include, but are not limited to, imidazoles, linear phenolic amidoamines, blocked and unblocked acid catalysts, isocyanates, dihydrazides, or photoinitiators.

The properties of the coating can also be manipulated with the inclusion of natural or synthetic waxes. For example, carnauba, polytetrafluoroethylene (PTFE), or a combination thereof can be included to affect the physical properties of the film such as slip, coefficient of friction, and abrasion resistance.

Proper dispersion of the thermochromic pigment throughout the resin is one aspect of achieving high quality coatings for commercial use. The inclusion of additional molecular or polymeric dispersing aids, such as nonionic, anionic, cationic or zwitterionic surfactants, polymers and copolymers, can ensure adequate dispersion. The active diluents Mexican insthVto '&gt; r LA »ROMtt&gt; A^r

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in addition to reacting with the resin sel e cci OR-adar-tambiérr they can function as a dispersant auxiliary. Additionally, active thinners can reduce the viscosity of the coating and affect the flexibility of the film and impact resistance. Suitable materials that are included as an active diluent include, but are not limited to, aliphatic or cycloaliphatic glycidyl ethers, monofunctional and polyfunctional glycidyl ethers.

Final adjustments to coating rheology can be made by adding select reducers, or solvents. A reversible thermochromic coating can be adjusted to meet established rheological criteria for use in a roll coating application. Many solvents are available for this purpose. Care must be taken to select solvents more compatible with thermochromic pigment systems. Non-polar solvents or low polarity solvents are preferred. However, the modifications to the thermochromic pigment preparation initiated by the inventors, as well as the different coating preparations available to the inventors increased the solvent options available to include low molecular weight polar solvents such as esters, for example butyl acetate. carbitol, low molecular weight alcohols such as

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ethanol or butanol, or zebones such as acetone. ____

The chemical stability and shelf life of the reversible thermochromic coating can be increased in several ways. In one aspect, this involves separating the thermochromic pigment from the organic solvents. A two-part coating system containing the thermochromic pigment and resin in Part A and the commercially coating material and other solvents in Part B is then mixed immediately prior to coating of the aluminum or steel alloys. The shelf life of the fully mixed coating material varies from several days to many months depending on the identity of the other selected components.

For those situations for which a two-part solution is not preferable, stability can be conveniently balanced by preparing a one-part reversible thermochromic coating. In this case, careful selection of formulation components is of great importance. The use of commercially available water-based can and roll coating material increases shelf life stability by minimizing the amount of organic solvents in contact with the thermochromic pigment system. In one example, coating degradation was observed within 14 days when red thermochromic coatings were prepared using '"butyl carbitol acetate and stored at emper a inira ambi at ± 6. ^. Increased stability was observed when formulation components were modified as well as stability when improved thermochromic pigment systems were used.

The non-limiting modalities that follow teach by way of example and should not be construed as unduly limiting the scope of this disclosure.

EXAMPLE 1 — Two-Part Coating

Part A (30% by weight of coating)

Thermochromic pigment (any color) *

Part B (70% by weight of coating)

Clear Coating (an epoxy coating available from Watson Standard of Pittsburgh, Pennsylvania) * This material is commercially available from Chromatic Technologies, Inc. of Colorado Springs, Colorado, and may include, for example S5BOXX3105W, a blue thermochromic suspension which goes from a colored to colorless state when the temperature exceeds 31 ° C.

EXAMPLE 2 — Two-Part Coating

Part A (60% by weight of the coating).

45% Thermochromic Pigment (any color) *

50% Epoxy Resin (for example Epon 863 available from

Lawter of LaVergne, Tennessee)

3.3% Dispersant Auxiliary (for example Disperbyk 2025 available from Byk of Wallingford, Connecticut)

1.7% Curing Agent (e.g. Ancamine 2458 available from Air Products of Allentown, Pennsylvania) Part B (40% by coating weight)

85% Clear Coating (an epoxy coating available from Watson Standard of Pittsburgh, Pennsylvania)

15% Solvent to reduce viscosity (for example, Butyl Carbitol Acetate available from Lawter of LaVergne, Tennessee) * This material is commercially available from Chromatic Technologies, Inc. of Colorado Springs, Colorado, and may include for example S5BOXX3105W, a blue thermochromic suspension that goes from a colored to colorless state when the temperature exceeds 31 ° C.

EXAMPLE 3 — One Part Coating

20% (w / w) Thermochromic Pigment (any color) *

13% Polyester Resin (e.g. Decotherm 290 available from Lawter of LaVergne, Tennessee)

0.5% (w / w) Dispersing Aid (for example, Byk 370 available from Byk of Wallingford, Connecticut)

7% (w / w) Curing Agent 1 (e.g., Cymel 328 available from Cytec Industries of Woodland Park, New Jersey) 1.5% (w / w) Curing Agent 2 (e.g., imidazole available from Aldrich of St. Louis, Missouri) _______ ____

2% (w / w) Wax (e.g. Fluoron 735 available from

Lawter of LaVergne, Tennessee)

30% (w / w) Solvent (for example, ethyl-3-ethoxypropionate available from Univar of Redmond, Washington)

26% (w / w) Clear Coating (an epoxy coating available from Watson standard of Pittsburgh, Pennsylvania)

EXAMPLE 4 Coating a Part

15% (w / w) Thermochromic Pigment (any color) *

10% (w / w) Resin (for example, Epon 896 available from Lawter of LaVergne, Tennessee)

1.5% (w / w) Dispersant Aid (for example, Disperbyk 112 available from Byk of Wallingford, Connecticut)

0.5% (w / w) Curing Agent 1 (for example, Nacure 2500 available from King Industries of Norwalk, Connecticut)

4% (w / w) Curing Agent 2 (for example, Cymel 325 available from Cytec Industries of Woodland Park, New Jersey) 1.5% (w / w) Wax - 0.5% by weight (for example, Ultrapoly 211A available from Lawter of LaVergne, Tennessee)

5% (w / w) Solvent 1 (for example, Heloxy Modifier 62 available from Lawter of LaVergne, Tennessee)

21.5% (w / w) Solvent 2 (for example, 3-ethyl ethoxypropionate available from Univar of Redmond, Washington) 41% (w / w) Clear Coat (an epoxy coating available from Watson Standard of Pittsburgh, Pennsylvania)

- ·: - r.

Fig. 1 compares identical beverage can lids 100 (Fig. 1A) and 150 (Fig. IB). Cans 100, 150, differ in that can 100 is at room temperature and can 150 is cooled to room temperature. temperature preferred for human consumption of an inner beverage can 150. Lids 102, 152 are coated with thermochromic coatings at epoxy base 104, 154. The relative darkness of lid 152 compared to lid 102 indicates that a beverage (not shown) within can 150 is sufficiently cooled to a recommended temperature for improved palatability. As is known in the art, the lids 102, 152 contain tabs 106, 156 that can be pulled for open access to the space within the inner walls of the cans 100, 150, such that liquid or other matter can be emptied into. or out of the cans through the lids 108, 158 which are marked for rupture when the tabs 106, 156 are lifted.

As opposed to placing the thermochromic ink on the entire cap, it is possible to coat selected elements of the can cap, such as the tab only, the cap only, or both the cap and tab without covering the cap. This is shown for example in Fig. 2 where the can 200 has a tab 202 which is covered with a thermochromic coating as described above. The same coating or one that has a color

<img file="MX346166B_D0023.tif" />

Different and / or color transition temperature is selectively applied to any feature of lid 201, such as surface 204, lid 206, indented area 208, surrounding lid 206, and / or flange 210. '

Fig. 2 shows a beverage can 200 with a pull tab 202 that has been covered with the coating of any of Examples 1 through 4. The tab 202 is made of roll material that is pre-coated with any of the coatings described above before the tab is formed.

FIG. 3 is a process diagram showing the sequential processing steps 300 for applying the thermochromic coating to the aluminum roll material 302. As the sheet aluminum 303 is developed from the roll 302, a roll coater 304 receives an uncured thermochromic coating material 306, as described above. This places a 308 liquid film or coating on the aluminum. This film is cured, for example by applying ultraviolet heat radiation, at curing station 310, and sheet 309 including dry film 309 is rolled 311 onto roll 312. This roll 312 can then be used to make components of the beverage can as discussed in the context of Figs. 1 and 2. It will be appreciated that coating operations

<img file="MX346166B_D0024.tif" />

additional (not shown) can be rpal i zgr srjnro, _ww·309.

Those skilled in the art will appreciate that the various embodiments described herein are taught by way of example and not by limitation. These modalities can be subjected to insubstantial changes without departing from the true scope and spirit of the invention. Accordingly, the inventors hereby state their intention to rely on the Equivalents Doctrine for the protection of their rights in what is claimed.

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Mexican INSTITUTE? Α of industrial PROPERTY