WO2006091465A1 - Time/temperature indicators, their preparation and use - Google Patents

Time/temperature indicators, their preparation and use Download PDF

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Publication number
WO2006091465A1
WO2006091465A1 PCT/US2006/005445 US2006005445W WO2006091465A1 WO 2006091465 A1 WO2006091465 A1 WO 2006091465A1 US 2006005445 W US2006005445 W US 2006005445W WO 2006091465 A1 WO2006091465 A1 WO 2006091465A1
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Prior art keywords
time
temperature indicator
dye
indicator according
leuco
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PCT/US2006/005445
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French (fr)
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Farid Azizian
Michael William Leonard
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Sun Chemical Corporation
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Publication of WO2006091465A1 publication Critical patent/WO2006091465A1/en

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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N31/00Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods
    • G01N31/22Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods using chemical indicators
    • G01N31/229Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods using chemical indicators for investigating time/temperature history
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/75Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated
    • G01N21/77Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated by observing the effect on a chemical indicator
    • G01N21/78Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated by observing the effect on a chemical indicator producing a change of colour
    • G01N21/80Indicating pH value

Definitions

  • the present invention relates to a novel time/temperature indicator comprising an activated leuco dye or similar dye which undergoes a colour change in the presence of a base, for example can be bleached by a base, in association with a photolatent base.
  • time/temperature indicators There are referred to as "time/temperature indicators”.
  • 3M's MonitorMark (trade mark) uses the principle of diffusion along a wick to provide a time/temperature indicator.
  • VITSAB 's Time/Temperature Indicator is based on the colour change caused by the controlled enzymatic hydrolysis of a lipid substrate.
  • Lifelines Inc.'s FreshCheck (trade mark) is based on a polymerisation reaction leading to a coloured polymer, and is suggested for use, inter alia, with foodstuffs.
  • DOCSNY.182727.1 Although all of these are successful in their fields, they are all relatively expensive and add significantly to the cost of the products to which they are applied. They cannot, therefore, be used in practice with lost cost, low margin items, particularly everyday foodstuffs.
  • time/temperature indicator that makes use of relatively cheap components and which can be applied easily, for example by printing at the time that the packaging is printed.
  • the time/temperature indicator is applied to the packaging before the perishable product is packed in it, it is desirable that the indicator should be inactive until a time close to the time of packaging and then should be activated so that its response closely parallels that of the perishable product.
  • US Patent No. 4,917,503 discloses a time/temperature indicator which comprises a thermally inactive compound comprising a leuco base and a photosensitive compound that, on exposure to actinic radiation (e.g. ultraviolet), forms an acid that oxidises the colourless leuco base to a coloured leuco dye at a rate determined by the reaction temperature.
  • the photosensitive compounds suggested for use in this patent include o-nitrobenzaldehyde and derivatives thereof and trihaloalcohols.
  • the use of o-nitrobenzaldehyde is restricted in Europe and there are indications that it may be mutagenic.
  • certain of the trihaloalcohols are used as anaesthetics.
  • the compounds proposed also tend to be malodorous. Furthermore, the products of irradiation of these compounds are generally recognised to be harmful to health. For these reasons, it is difficult to use the time/temperature indicator of US Patent No. 4,917,503 in practice in association with foodstuffs or other perishable materials that may be ingested by humans.
  • the present invention consists in a time/temperature indicator, comprising a dye which undergoes a colour change in the presence of a base, in association with a photolatent base.
  • the dye is one which can be bleached by a base.
  • a dye which simply changes from one colour to another in the presence of a base is one preferred class of dyes which may be used in the present invention.
  • One preferred class of dyes which may be used in the present invention is the class of activated leuco dyes.
  • Leuco dyes are generally synthetic organic colourless powders which, upon oxidation/acidification (collectively referred to herein as "activation") become coloured. More details of such dyes maybe found in "Chemistry and Applications of Leuco Dyes", edited by R Muthyala, published in 1997 by Plenum Publishing Corporation, the disclosure of which is incorporated herein by reference.
  • leuco dyes which may be used in the present invention include the activated forms of known leuco dyes such as triphenylmethane compounds, fiuoran compounds, phenothiazine compounds, auramine compounds, spiropyran compounds, indolinophthalide and the like. These leuco dyes may be used alone or in combination. Specific examples of such leuco dyes include the activated forms of the following compounds:
  • the more preferred leuco dyes for use in the present invention include the activated forms of carbazolyl blue, indolyl red, leuco crystal violet, leuco malachite green, bis (p-dimethylaminophenyl)(9-ethylcarbazol-3-yl) methane, bisarylcarbazolylmethane, 3,3-bis(l-N-octyl-2-methyl-indol-3-yl) phthalide, 3-(N,N- diethylamino)-7- (N,N-dibenzylarnino) fluoran and crystal violet lactone.
  • a single such dye, or a mixture of any two or more such dyes, may be used.
  • Vat dyes are a class of water insoluble dyes, such as indigo and anthraquinone derivatives. These dyes in their reduced and water soluble form, reduced by a base, are colourless or different from their original colour, whilst when oxidised, which may be by an acid, they return to their original colour and their insoluble form. Examples are Vat Blue 3, Blue 5, Vat Green 1, Methylene Violet 3RAX, Light green SF Yellowish, Leuco xylene cyanole FF and Nile Blue A. Vat dyes are especially fast to light and produce brilliant colours with high lightfastness.
  • a further class of dyes which may be used comprises pH indicators which change colour on going from a neutral or acidic environment to a basic one.
  • pH indicators which change colour on going from a neutral or acidic environment to a basic one.
  • examples of such compounds include: methyl violet, crystal violet, ethyl violet, ethyl orange, malachite green, methyl green, cresol red, thymol blue, bromophenol blue, bromophenol red, Congo red, methyl orange, resorcin blue, alizarin red, methyl red, litmus, bromocresol purple, chlorophenol red, bromothymol blue, phenol red, neutral red, tumeric curcumin, phenolphthalein, thymophthalein, alizarin yellow R, alizarin yellow GG, clayton yellow, methyl yellow, tropaeolin O sodium salt, bromoxylenol blue, bromochlorophenol blue, brilliant green, metanil yellow, benzyl orange, Tashir
  • a single such dye, or a mixture of any two or more such dyes, may be used.
  • a photolatent base (sometimes called a "photobase generator”) is a compound which, in its normal state, is essentially neutral, but which, upon irradiation with ultraviolet light, generates a basic compound.
  • these include classes of compounds such as carbamates, O-acyloximes, O-carbamoyloximes, formamide, amineimide and onium salts.
  • Specific examples of such photolatent bases include: •
  • Quaternary ammonium salts such as l-phenacyl-(l-azonia-4-azabicyclo[2,2,2]- octane)bromide; l,4-dimethyl-l-phenacyl-(l-azonia-4-azabicyclohexane) bromide; and l-na ⁇ hthoylmethyl-l-phenacyl-(l-azonia-4-azabicyclo[2,2,2]octane)bromide;
  • Carbamates such as l-phenacyl-(l-azonia-4-azabicyclo[2,2,2]octane)-N,N- dimethylthiocarbamate; 1 -methyl- 1 -phenacyl-( 1 -azoniacyclohexane)-N,N- dimethyldithiocarbamate; 1 ,4-dimethyl- 1 -phenacyl-( 1 -azoniacyclohexane)-N,N- dimethyldithiocarbamate; and l-naphthoylmethyl-(l-azonia-4-azabicyclo[2,2,2]octane- N,N-dimethyldithiocarbamate;
  • Amineimides such as 1,1 -dimethyl- l-(2-hydroxy-3-phenoxypro ⁇ yl)amine-p- nitrobenzimide, 1 , 1 -dimethyl- 1 -(2-hydroxy-3 -phenoxypropyl)amine-p-cyanobenzimide; and l,l-dimethyl-l-(2-hydroxy-3-phenoxypropyl)amine benzimide.
  • N-substituted 4-(o-nitrophenyl)dihydropyridines optionally substituted with alkyl ether and/or alkyl ester groups, such as N-methyl nifedipine (Macromolecules 1998, 31, 4798), N-butyl nifedipine, N-butyl 2,6-dimethyl-4-(2-nitrophenyl) 1,4- dihydropyridine 3,5-dicarboxylic acid diethyl ester, and N-methyl 2,6-dimethyl 4-(4,5- dimethoxy-2-nitrophenyl)-l,4-dihydropyridine 3,5-dicarboxylic acid diethyl ester;
  • Quaternary organo-boron photoinitiators such as those disclosed in GB-A-2 307 473, the disclosure of which is incorporated herein by reference;
  • ⁇ -Aminoacetophenones such as 4-(methylthiobenzoyl)-l -methyl- 1- morpholinoethane (IrgacureR 907 ex Ciba Specialty Chemicals) and (4- morpholinobenzoyl)-l -benzyl- 1-dimethylaminopropane (IrgacureR 369 ex Ciba Specialty Chemicals); and
  • the amounts of dye and photolatent base in the time/temperature indicator composition of the present invention may vary depending on the required properties.
  • DOCSNY.182727.1 we prefer to employ from 0.01 to 10.0% by weight, more preferably from 1.0 to 3.0% by weight, of the leuco dye and from 0.01 to 10.0% by weight, more preferably from 0.05 to 2.0% by weight, of the photolatent base, based on the weight of the whole composition.
  • these amounts are not critical to the invention and amounts outside these ranges may be used, if desired. In particular, for a greater intensity of coloration, higher amounts may be used.
  • the dye and the photolatent base may be employed in a single composition and printed to form a single layer on a substrate, or they may each be used as a separate composition and printed to form two layers, one on top of the other, on the substrate.
  • the composition may contain other components to render the composition printable.
  • other components may include, for example, resins, solvents and binders [such as polyvinyl butyral (PVB), nitrocellulose, polyurethanes (PU), polyesters, cellulose acetate propionate (CAP), polyacrylates, polyamides and polyvinyl alcohol].
  • resins such as polyvinyl butyral (PVB), nitrocellulose, polyurethanes (PU), polyesters, cellulose acetate propionate (CAP), polyacrylates, polyamides and polyvinyl alcohol].
  • compositions may be printed using many conventional printing techniques, of which the flexographic and gravure printing techniques are preferred.
  • the compositions of the present invention will, of course, be formulated in accordance with the specific requirements of the printing technique used, as is well known in the art.
  • plastics film There is no restriction on the nature of the substrate on which the composition of the present invention is printed. Examples include paper, cardboard, cellophane and various plastics films. Any plastic materials commonly used in the industry, especially for food wrapping, may be used as the plastics film. Examples of such materials include synthetic and semi-synthetic organic polymers, such as cellulose acetate, cellulose acetate butyrate (CAB), cellophane, polyvinyl chloride (PVC), polyvinyl fluoride, polyvinylidene chloride (PVDC), polyethylene, polypropylene (PP), polyamides, polyesters, polyphenylene oxide, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polymethyl methacrylate, poly(methyl pentene (TPX), polyvinyl acetal, polystyrene, acrylonitrile-butadiene-styrene (ABS), acrylonitrile-styrene-acrylate (ASA), polycarbon
  • DOCSNY.182727.1 polyether ketones, polyimides, and copolymers and/or mixtures thereof. If desired, films made from any of these polymers may be coated with coating materials well known in the art, and/or may be laminated to a film or films made of the same or different polymers. Further examples of such plastic materials may be found in standard reference texts, such as "Plastic Films", 3 rd Edition, by J. H. Briston, published by Longman Group in 1989.
  • the time/temperature indicator composition may be activated by exposure to UV radiation or similar energising radiation, including electron beam.
  • UV radiation or similar energising radiation, including electron beam.
  • the nature and amount of radiation used is similar to that used for the photoinitiation of UV-curable printing inks and is well known to those skilled in the art.
  • the dye and photolatent base are, of course, preferably inert with respect to each other until activation.
  • the invention is further illustrated by the following non-limiting Examples.
  • the ketonic resin used in the Examples was a neutral, unsaponifiable, hydrogenated ketonic resin supplied by HuIs as Synthetic Resin SK.
  • Solution (h) was coated on a LENETA (N2A) chart using a No. 1 K Bar and left to dry. This produced a clear and colourless print.
  • Print (k) was placed under different temperature conditions of O 0 C, 27° and 5O 0 C. After 2 days, only the print at 50°C started to fade further.
  • coating mixes were prepared by blending together a leuco dye and a photolatent base generating material.
  • the coating mixes were coated on LENETA (N2A) charts using a No. 1 K Bar, according to Example 1. All prints were irradiated using a UV rig running at 15m/minute. The examples and results are illustrated in Table 1.
  • coating mixes were prepared by blending together an oxidised leuco dye and the photolatent base generating material prepared as described in Example 10 or a sample of the photolatent base CGI277
  • DOCSNY.182727.1 supplied by CIBA The coating mixes were coated on LENETA (N2A) charts using a No. 1 K Bar, according to Example 1. AU prints were irradiated using a UV rig running at 15m/minute. The examples and results are illustrated in Table 2.
  • coating mixes were prepared by blending together the photolatent base CGI277 supplied by CIBA and a number of dyes.
  • the selected dyes (0.3g) were dissolved in a solvent mixture of propylene carbonate (PC) and isopropyl alcohol (IPA) (5g).
  • PC propylene carbonate
  • IPA isopropyl alcohol
  • the dye solutions were added to a solution of cellulose acetate propionate (CAP) resin in ethyl acetate at a ratio of 40:60 (20 g).
  • CAP cellulose acetate propionate
  • the dye/resin mixes were coated on LENETA (N2A) charts using a No. 2 K Bar, according to Example 1. All prints were irradiated using a UV rig running at 15m/minute. The examples and results are illustrated in Table 3.
  • the leuco dyes used in the above Examples were:
  • the photolatents used were:
  • Coating mixes were prepared by blending together an oxidised leuco dye and the photolatent base CGI277 supplied by Ciba, a photolatent base generating material.
  • the oxidised dye was prepared from Pergascript Black I-2R* (3-dibutylamino-6-methyl-7- anilinofluoran, a leuco dye, (0.5 g), which was dissolved in a solution of ketonic resin in ethyl acetate at ratio of 40:60 (5 g), by gentle heating and stirring over a magnetic stirrer. The resulting clear and colourless solution was left to cool down and to this, a solution of 5% citric acid in isopropyl alcohol was added slowly until the colour of the solution turned dark green-black.
  • the leuco dye solution was then blended with a 2% solution of the photolatent base CGI277 in propylene carbonate (PC) and isopropyl alcohol (IPA).
  • the coating mixes were coated on LENETA (N2A) charts using a No. 2 K Bar, according to Example 1. All prints were irradiated using a UV rig running at 15m/minute. The dark green colour on irradiation turned to greyish colour, which over period of time turned to lighter grey colour.

Abstract

A time/temperature indicator comprises a dye which undergoes a colour change, for example is bleached, in the presence of a base, in association with a photolatent base.

Description

TIME/TEMPERATURE INDICATORS, THEIR PREPARATION AND USE
The present invention relates to a novel time/temperature indicator comprising an activated leuco dye or similar dye which undergoes a colour change in the presence of a base, for example can be bleached by a base, in association with a photolatent base.
Many packaged goods, notably foodstuffs and medicines, have a limited shelf life, and such goods commonly have a "use by" date printed on packaging associated with the goods. However, this is, at best, only a crude indication, as the rate at which such goods deteriorate is a function of the temperature at which they are kept as well as the length of time for which they are kept. Moreover, the temperature may vary considerably during the life of the goods. For example, a product may be bought from a shop, where it is kept in a refrigerator, carried through a sunny car park, where its temperature rises, stored in a car, where its temperature rises further, and finally stored in a domestic refrigerator, where its temperature is lowered, but may still go up and down as the refrigerator door is opened and closed.
It would, therefore, be desirable to provide an indicator on packaging associated with the goods which will react to changing temperatures over time in the same way as do the goods themselves. These are referred to as "time/temperature indicators". A number of proposals have been made for such time/temperature indicators. For example, 3M's MonitorMark (trade mark) uses the principle of diffusion along a wick to provide a time/temperature indicator. VITSAB 's Time/Temperature Indicator is based on the colour change caused by the controlled enzymatic hydrolysis of a lipid substrate. Lifelines Inc.'s FreshCheck (trade mark) is based on a polymerisation reaction leading to a coloured polymer, and is suggested for use, inter alia, with foodstuffs.
DOCSNY.182727.1 Although all of these are successful in their fields, they are all relatively expensive and add significantly to the cost of the products to which they are applied. They cannot, therefore, be used in practice with lost cost, low margin items, particularly everyday foodstuffs.
To meet this requirement, it would be desirable to provide a time/temperature indicator that makes use of relatively cheap components and which can be applied easily, for example by printing at the time that the packaging is printed. Moreover, if the time/temperature indicator is applied to the packaging before the perishable product is packed in it, it is desirable that the indicator should be inactive until a time close to the time of packaging and then should be activated so that its response closely parallels that of the perishable product.
US Patent No. 4,917,503 discloses a time/temperature indicator which comprises a thermally inactive compound comprising a leuco base and a photosensitive compound that, on exposure to actinic radiation (e.g. ultraviolet), forms an acid that oxidises the colourless leuco base to a coloured leuco dye at a rate determined by the reaction temperature. The photosensitive compounds suggested for use in this patent include o-nitrobenzaldehyde and derivatives thereof and trihaloalcohols. However, the use of o-nitrobenzaldehyde is restricted in Europe and there are indications that it may be mutagenic. Moreover, certain of the trihaloalcohols are used as anaesthetics. The compounds proposed also tend to be malodorous. Furthermore, the products of irradiation of these compounds are generally recognised to be harmful to health. For these reasons, it is difficult to use the time/temperature indicator of US Patent No. 4,917,503 in practice in association with foodstuffs or other perishable materials that may be ingested by humans.
We have now discovered that the problems with the prior art may be overcome by the use of a dye which undergoes a colour change in the presence of a base, in association with a photolatent base.
DOCSNY.182727.1 Thus, the present invention consists in a time/temperature indicator, comprising a dye which undergoes a colour change in the presence of a base, in association with a photolatent base.
Preferably, the dye is one which can be bleached by a base. However, it is also possible to use a dye which simply changes from one colour to another in the presence of a base. One preferred class of dyes which may be used in the present invention is the class of activated leuco dyes. Leuco dyes are generally synthetic organic colourless powders which, upon oxidation/acidification (collectively referred to herein as "activation") become coloured. More details of such dyes maybe found in "Chemistry and Applications of Leuco Dyes", edited by R Muthyala, published in 1997 by Plenum Publishing Corporation, the disclosure of which is incorporated herein by reference.
Examples of leuco dyes which may be used in the present invention include the activated forms of known leuco dyes such as triphenylmethane compounds, fiuoran compounds, phenothiazine compounds, auramine compounds, spiropyran compounds, indolinophthalide and the like. These leuco dyes may be used alone or in combination. Specific examples of such leuco dyes include the activated forms of the following compounds:
3,3-bis(p-dimethylaminophenyl)phthalide, 3,3-bis(p-dimethylaminophenyl)-6- dimethylaminophthalide (i.e., crystal violet lactone), 3,3-bis(p-dimethylaminophenyl)- 6-diethylaminophthalide, 3,3-bis(p-dimethylaminophenyl)-6-chlorophthalide, 3,3-bis(p- dibutylaminophenyl)phthalide, 3-cyclohexylamino-6-chlorofluoran, 3-dimethylamino- 5,7-dimethylfluoran, 3-diethylamino-7-chlorofluoran, 3-diethylamino-7-methylfluoran, 3 -diethylamino-7, 8 -benzfluoran, 3 -diethylamino-6-methyl-7-chlorofluoran, 3 -(N-p- tolyl-N-ethylamino)-6-methyl-7-anilinofluoran, 3-pyrrolidino-6-methyl-7- anilinofluoran, 2-[N-(3-trifluoromethylphenyl)amino]-6-diethylaminofluoran, 2-[3,6- bis(diethylamino)-9-o-chloroanilino]xanthylbenzoic acid lactam, 3-diethylamino-6- methyl-7-(m-trichloromethylanilino)fluoran, 3-diethylamino-7-(o-chloroanilino)fluoran, 3-di-n-butylamino-7-(o-chloroanilino)fluoran, 3-N-methyl-N-n-amylamino-6-methyl-7- anilinofluoran, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluoran, 3-
DOCSNY.182727.1 diethylamino-6-methyl-7-arnlinofluoran, 3-(N,N-diethylamino)-5-methyl-7-(N,N- dibenzylamino) fluoran, 24-benzoyl leuco methylene blue, 6'-chloro-8'-methoxy- benzoindolinospiropyran, 6'-bromo-3 '-methoxybenzoindolinospiropyran, 3 (2'-hydroxy- 4'-dimethylaminophenyl)-3-(2l-methoxy-5'-cliloroplienyl)phtlialide, 3-(2'-hydroxy-4'- dimethylaminophenyl)-3-(2'-methoxy-5'-nitrophenyl)phthalide, 3-(2'-hydroxy-4'- diethylammophenyl)-3-(2'- methoxy-5'-methylphenyl)phthalide, 3-(2'-methoxy-4'- dimethylaminophenyl) -3-(2'-hydroxy-C-cliloro-5'-methylplienyl)phtlialide, 3-(N-ethyl- N-tetrahydrofurfuryl)amino-6-methyl-7-anilinofluoran, 3-N-ethyl-N-(2- ethoxypropyl)amino-6-metliyl-7-anilinofluoran, 3-N-methyl-N-isobutyl-6-methyl-7- anilinofluoran, 3-morpholmo-7-(N-propyl-trifluoromethylanilino)fluoran, 3- pyrrolidino-7-m-trifluoromethylanilinofluoran, 3-diethylamino-5-chloro-7-(N-benzyl- trifluoromethylanilino)fluoran, 3-pyrrolidino-7-(di-p-chlorophenyl)methylaminofluoran, 3-diethylamino-5-chloro-7-α-ρhenylethylammo)fluoran, 3-(N-ethyl-p-toluidino)-7-α- phenylethylamino)fluoran, 3-diethylammo-7-(o-methoxycarbonylphenylamino)fluoran, 3-diethylamino-5-methyl-7-(α-phenylethylamino)fluoran, 3-diethylamino-7- piperidinofluoran, 2-chloro-3-(N-methyltoluidino)-7-(p-n-butylanilino)fluoran, 3-(N- methyl-N-isopropylamino)-6-methyl-7-anilinofluoran, 3-di-n-butylamino-6-methyl-7- anilinofluoran, 3 ,6-bis(dimethylamino)fluorenespiro(9,3 ')-6'-dimethylaminophthalide, 3-(N-benzyl-N-cyclohexylamino)-5,6-benzo-7-α-naphtliylaniino-4'-bromofluoran, 3- diethylamino-6-chloro-7-anilinofluoran, 3-diethylamino-6-methyl-7-mesidino-4',5'- benzofluoran, 3-N-methyl-N-isoproyl-6-methyl-7-anilinofluoran, 3-N-ethyl-N-isoamyl- 6-methyl-7-anilinofluoran, 3-diethylanimo-6-niethyl-7-(2',4'-dimethylanilino)fluoran, and the like.
The more preferred leuco dyes for use in the present invention include the activated forms of carbazolyl blue, indolyl red, leuco crystal violet, leuco malachite green, bis (p-dimethylaminophenyl)(9-ethylcarbazol-3-yl) methane, bisarylcarbazolylmethane, 3,3-bis(l-N-octyl-2-methyl-indol-3-yl) phthalide, 3-(N,N- diethylamino)-7- (N,N-dibenzylarnino) fluoran and crystal violet lactone. A single such dye, or a mixture of any two or more such dyes, may be used.
DOCSNY.182727.1 Another class of dyes which may be used are the vat dyes. Vat dyes are a class of water insoluble dyes, such as indigo and anthraquinone derivatives. These dyes in their reduced and water soluble form, reduced by a base, are colourless or different from their original colour, whilst when oxidised, which may be by an acid, they return to their original colour and their insoluble form. Examples are Vat Blue 3, Blue 5, Vat Green 1, Methylene Violet 3RAX, Light green SF Yellowish, Leuco xylene cyanole FF and Nile Blue A. Vat dyes are especially fast to light and produce brilliant colours with high lightfastness.
A further class of dyes which may be used comprises pH indicators which change colour on going from a neutral or acidic environment to a basic one. Examples of such compounds include: methyl violet, crystal violet, ethyl violet, ethyl orange, malachite green, methyl green, cresol red, thymol blue, bromophenol blue, bromophenol red, Congo red, methyl orange, resorcin blue, alizarin red, methyl red, litmus, bromocresol purple, chlorophenol red, bromothymol blue, phenol red, neutral red, tumeric curcumin, phenolphthalein, thymophthalein, alizarin yellow R, alizarin yellow GG, clayton yellow, methyl yellow, tropaeolin O sodium salt, bromoxylenol blue, bromochlorophenol blue, brilliant green, metanil yellow, benzyl orange, Tashiro's indicator solution, quinaldine red, tetrabromophenol blue, α-naphthyl red hydrochloride, brilliant yellow, phenol violet, thymol violet, tropaeolin, ethyl orange sodium salt, turmeric, j^-xylenol blue, bromocresol green sulphone, bromophenol blue sodium salt, m-cresol purple sodium salt, m-cresolsulphonephthalein sodium salt, quercetin dihydrate, o-cresolphthalein, α-naphtholphthalein, 2-nitrophenol, 4- nitrophenol, 3-nitrophenol,/?-rosolic acid, and thymolphthalein.
A single such dye, or a mixture of any two or more such dyes, may be used.
A photolatent base (sometimes called a "photobase generator") is a compound which, in its normal state, is essentially neutral, but which, upon irradiation with ultraviolet light, generates a basic compound. In general, these include classes of compounds such as carbamates, O-acyloximes, O-carbamoyloximes, formamide, amineimide and onium salts. Specific examples of such photolatent bases include:
DOCSNY.182727.1 Quaternary ammonium salts, such as l-phenacyl-(l-azonia-4-azabicyclo[2,2,2]- octane)bromide; l,4-dimethyl-l-phenacyl-(l-azonia-4-azabicyclohexane) bromide; and l-naρhthoylmethyl-l-phenacyl-(l-azonia-4-azabicyclo[2,2,2]octane)bromide;
Carbamates, such as l-phenacyl-(l-azonia-4-azabicyclo[2,2,2]octane)-N,N- dimethylthiocarbamate; 1 -methyl- 1 -phenacyl-( 1 -azoniacyclohexane)-N,N- dimethyldithiocarbamate; 1 ,4-dimethyl- 1 -phenacyl-( 1 -azoniacyclohexane)-N,N- dimethyldithiocarbamate; and l-naphthoylmethyl-(l-azonia-4-azabicyclo[2,2,2]octane- N,N-dimethyldithiocarbamate;
Amineimides, such as 1,1 -dimethyl- l-(2-hydroxy-3-phenoxyproρyl)amine-p- nitrobenzimide, 1 , 1 -dimethyl- 1 -(2-hydroxy-3 -phenoxypropyl)amine-p-cyanobenzimide; and l,l-dimethyl-l-(2-hydroxy-3-phenoxypropyl)amine benzimide.
N-substituted 4-(o-nitrophenyl)dihydropyridines, optionally substituted with alkyl ether and/or alkyl ester groups, such as N-methyl nifedipine (Macromolecules 1998, 31, 4798), N-butyl nifedipine, N-butyl 2,6-dimethyl-4-(2-nitrophenyl) 1,4- dihydropyridine 3,5-dicarboxylic acid diethyl ester, and N-methyl 2,6-dimethyl 4-(4,5- dimethoxy-2-nitrophenyl)-l,4-dihydropyridine 3,5-dicarboxylic acid diethyl ester;
Quaternary organo-boron photoinitiators such as those disclosed in GB-A-2 307 473, the disclosure of which is incorporated herein by reference;
α-Aminoacetophenones, such as 4-(methylthiobenzoyl)-l -methyl- 1- morpholinoethane (IrgacureR 907 ex Ciba Specialty Chemicals) and (4- morpholinobenzoyl)-l -benzyl- 1-dimethylaminopropane (IrgacureR 369 ex Ciba Specialty Chemicals); and
The α-ammonium ketones, iminium ketones or amidinium ketones in the form of their tetraaryl- or triarylalkylborate salts as disclosed in US 6,551,761 Bl, the disclosure of which is incorporated herein by reference.
The amounts of dye and photolatent base in the time/temperature indicator composition of the present invention may vary depending on the required properties.
DOCSNY.182727.1 However, in general, we prefer to employ from 0.01 to 10.0% by weight, more preferably from 1.0 to 3.0% by weight, of the leuco dye and from 0.01 to 10.0% by weight, more preferably from 0.05 to 2.0% by weight, of the photolatent base, based on the weight of the whole composition. However, these amounts are not critical to the invention and amounts outside these ranges may be used, if desired. In particular, for a greater intensity of coloration, higher amounts may be used.
The dye and the photolatent base may be employed in a single composition and printed to form a single layer on a substrate, or they may each be used as a separate composition and printed to form two layers, one on top of the other, on the substrate.
In addition to the dye and the photolatent base, the composition may contain other components to render the composition printable. Such other components may include, for example, resins, solvents and binders [such as polyvinyl butyral (PVB), nitrocellulose, polyurethanes (PU), polyesters, cellulose acetate propionate (CAP), polyacrylates, polyamides and polyvinyl alcohol].
The compositions may be printed using many conventional printing techniques, of which the flexographic and gravure printing techniques are preferred. The compositions of the present invention will, of course, be formulated in accordance with the specific requirements of the printing technique used, as is well known in the art.
There is no restriction on the nature of the substrate on which the composition of the present invention is printed. Examples include paper, cardboard, cellophane and various plastics films. Any plastic materials commonly used in the industry, especially for food wrapping, may be used as the plastics film. Examples of such materials include synthetic and semi-synthetic organic polymers, such as cellulose acetate, cellulose acetate butyrate (CAB), cellophane, polyvinyl chloride (PVC), polyvinyl fluoride, polyvinylidene chloride (PVDC), polyethylene, polypropylene (PP), polyamides, polyesters, polyphenylene oxide, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polymethyl methacrylate, poly(methyl pentene (TPX), polyvinyl acetal, polystyrene, acrylonitrile-butadiene-styrene (ABS), acrylonitrile-styrene-acrylate (ASA), polycarbonate, polystyrene, polyether sulphone,
DOCSNY.182727.1 polyether ketones, polyimides, and copolymers and/or mixtures thereof. If desired, films made from any of these polymers may be coated with coating materials well known in the art, and/or may be laminated to a film or films made of the same or different polymers. Further examples of such plastic materials may be found in standard reference texts, such as "Plastic Films", 3rd Edition, by J. H. Briston, published by Longman Group in 1989.
The time/temperature indicator composition may be activated by exposure to UV radiation or similar energising radiation, including electron beam. The nature and amount of radiation used is similar to that used for the photoinitiation of UV-curable printing inks and is well known to those skilled in the art. The dye and photolatent base are, of course, preferably inert with respect to each other until activation.
The invention is further illustrated by the following non-limiting Examples. The ketonic resin used in the Examples was a neutral, unsaponifiable, hydrogenated ketonic resin supplied by HuIs as Synthetic Resin SK.
EXAMPLE 1
(a) Pergascript Black I-2R* (3-dibutylamino-6-methyl-7-anilinofluoran, a leuco dye, supplied by CIBA Speciality Chemicals) (0.5 g) was dissolved in a solution of ketonic resin in ethyl acetate at ratio of 40:60 (5 g), by gentle heating and stirring over a magnetic stirrer. The resulting clear and colourless solution was left to cool down and to this, a solution of 5% citric acid in isopropyl alcohol was added slowly until the colour of the solution turned dark green-black.
(b) Benzyl carbamate (0.1 g), a photolatent base generating material Supplied by Aldrich, was dissolved in a solution of ketonic resin in ethyl acetate at ratio of 40:60 (10 g), by gentle heating and stirring over a magnetic stirrer to give a clear colourless solution.
(c) Solution (a) was coated on a LENETA (N2A) chart using a No. 1 K Bar and left to dry. This produced a dark green image.
DOCSNY.182727.1 (d) Solution (b) was coated over the print (c) using a No. 1 K Bar and left to dry. The colour of the print still remained dark green.
(e) Print (d) was irradiated using a UV rig running at 15m/minute. The dark green colour instantly faded to a greyish colour.
(f) Print (e) was placed under different temperature conditions of 00C, 27° and 5O0C. After 2 days, only the print at 500C started to fade further.
EXAMPLE 2
(g) Pergascript Black I-2R solution was prepared according to Example l(a).
(h) Benzyl carbamate was prepared according to Example l(b).
(i) Solution (h) was coated on a LENETA (N2A) chart using a No. 1 K Bar and left to dry. This produced a clear and colourless print.
Q) Solution (g) was coated over the print (i) using a No. 1 K Bar and left to dry. The colour of the print still remained dark green.
(k) The print (j) was irradiated using a UV rig running at 15m/minute. The dark green colour instantly faded to a greyish colour.
(1) Print (k) was placed under different temperature conditions of O0C, 27° and 5O0C. After 2 days, only the print at 50°C started to fade further.
EXAMPLES 3 TO 9
Using the procedure described in Example 1, coating mixes were prepared by blending together a leuco dye and a photolatent base generating material. The coating mixes were coated on LENETA (N2A) charts using a No. 1 K Bar, according to Example 1. All prints were irradiated using a UV rig running at 15m/minute. The examples and results are illustrated in Table 1.
DOCSNY.182727.1 Table 1
Figure imgf000011_0001
DOCSNY.182727.1
Figure imgf000012_0001
EXAMPLE 10
Preparation of 1-phenyl- (l-azonia-4-azabicycIo [2,2,21-octane) N,N-dimethyI- dithiocarbonate, photolatent base material
A sample of the title compound was synthesised according to the reference in "J.
Polymer Science; part A; Polymer Chemistry; Vol. 39, 1329-1441 (2001).
EXAMPLE 11
Using the procedure described in Example 1, coating mixes were prepared by blending together an oxidised leuco dye and the photolatent base generating material prepared as described in Example 10 or a sample of the photolatent base CGI277
DOCSNY.182727.1 supplied by CIBA. The coating mixes were coated on LENETA (N2A) charts using a No. 1 K Bar, according to Example 1. AU prints were irradiated using a UV rig running at 15m/minute. The examples and results are illustrated in Table 2.
Table 2
Figure imgf000013_0001
EXAMPLES 12-14
Using the procedure described in Example 1, coating mixes were prepared by blending together the photolatent base CGI277 supplied by CIBA and a number of dyes. The selected dyes (0.3g) were dissolved in a solvent mixture of propylene carbonate (PC) and isopropyl alcohol (IPA) (5g). To enhance the solubility of the dyes, a few drops of water were added to the solvent mix. The dye solutions were added to a solution of cellulose acetate propionate (CAP) resin in ethyl acetate at a ratio of 40:60 (20 g). The dye/resin mixes were coated on LENETA (N2A) charts using a No. 2 K Bar, according to Example 1. All prints were irradiated using a UV rig running at 15m/minute. The examples and results are illustrated in Table 3.
Table 3
Figure imgf000013_0002
DOCSNY.182727.1
Figure imgf000014_0001
The leuco dyes used in the above Examples were:
1 Black Nl 02 (2-Anilino-6-diethylammo-3-methylfluoran, supplied by
Yamamoto)
2 ODB-2 (2-Anilino-6-dibutylammo-3-methylfluoran, supplied by Yamamoto)
3 ODB-7 [6-Diethylamino-3-methyl-2-(3-toluidino) fluoride, supplied by Yamamoto]
4 Pergascript Black- 2IR (Diaminofluoran), supplied by Ciba Speciality Chemicals
5 Pergascript Red I-6B* (Bisindolyl phthalide compound), supplied by Ciba Speciality
6 Pergascript Blue SRB (Bisarylcarbazolylmethane compound), supplied by Ciba Speciality Chemicals
7 Eriochrom Black T
8 Brilliant Green
9 Nile Blue A
The photolatents used were:
A 4-Methoxybenzyloxycarbonyl azide (supplied by Aldrich)
B 1-Benzylimidazole (supplied by Aldrich)
DOCSNY.182727.1 C Benzyl-4-oxo- 1 -piperidinecarboxylate (supplied by Aldrich)
D 1 - Fluorenylmethoxycarbonyl-4-piperidone (supplied by Aldrich)
E Benzyloxycarbonyl-Glycinamide (supplied by Aldrich)
F N-(Benzyloxycarbonyl)- 1 -H-pyrazole- 1 -carboxamidine (supplied by Aldrich)
G N-(Benzyloxycarbonyl)-2-aminoacetonitrile (supplied by Aldrich)
H Benzyl carbamate (supplied by Aldrich)
I CGI277 supplied by ClBA
EXAMPLE 15
Coating mixes were prepared by blending together an oxidised leuco dye and the photolatent base CGI277 supplied by Ciba, a photolatent base generating material. The oxidised dye was prepared from Pergascript Black I-2R* (3-dibutylamino-6-methyl-7- anilinofluoran, a leuco dye, (0.5 g), which was dissolved in a solution of ketonic resin in ethyl acetate at ratio of 40:60 (5 g), by gentle heating and stirring over a magnetic stirrer. The resulting clear and colourless solution was left to cool down and to this, a solution of 5% citric acid in isopropyl alcohol was added slowly until the colour of the solution turned dark green-black. The leuco dye solution was then blended with a 2% solution of the photolatent base CGI277 in propylene carbonate (PC) and isopropyl alcohol (IPA). The coating mixes were coated on LENETA (N2A) charts using a No. 2 K Bar, according to Example 1. All prints were irradiated using a UV rig running at 15m/minute. The dark green colour on irradiation turned to greyish colour, which over period of time turned to lighter grey colour.
DOCSNY.182727.1

Claims

CLAIMS:
1. A time/temperature indicator, comprising a dye which undergoes a colour change in the presence of a base, in association with a photolatent base.
2. A time/temperature indicator according to Claim 1, in which said dye is an activated leuco dye.
3. A time/temperature indicator according to Claim 2, in which the activated leuco dye is the activated form of carbazolyl blue, indolyl red, leuco crystal violet, leuco malachite green, bis (p-dimethylaminophenyl)(9-ethylcarbazol-3-yl)methane, bisarylcarbazorylmethane, 3,3-bis(l-N-octyl-2-methyl-mdol-3-yl)phthalide, 3-(N5N- diethylamino)-7-(N,N-dibenzylamino)fluoran or crystal violet lactone.
4. A time/temperature indicator according to Claim 1, in which said dye is a vat dye.
5. A time/temperature indicator according to Claim 4, in which said vat dye is Vat Blue 3, Blue 5, Vat Green 1, Methylene Violet 3RAX, Light green SF Yellowish, Leuco xylene cyanole FF or Nile Blue A.
6. A time/temperature indicator according to any one of the preceding Claims, in which the photolatent base is a quaternary ammonium salt, a carbamate, an O-acyloxime, an O-carbamoyloxime, a formamide, an amineimide or an onium salt.
7. A time/temperature indicator according to any one of the preceding Claims, in which the photolatent base is 4-methoxybenzyloxycarbonyl azide, 1-benzylimidazole, benzyl- 4-oxo- 1 -piperidinecarboxylate, fluorenylmethoxycarbonyl-4-piperidone, N- (benzyloxycarbonyl)glycinamide, N-(benzyloxycarbonyl)- 1 -H-pyrazole- 1 - carboxamidine, or N-(benzyloxycarbonyl)-2-aminoacetonitrile.
8. A time/temperature indicator according to any one of the preceding Claims, in which the dye and the photolatent base are employed as a mixture.
9. A time/temperature indicator according to Claim 8, in which the mixture also comprises a resin.
DOCSNY.182727.1
10. A time/temperature indicator according to Claim 9, in which the dye and the photolatent base are suspended in the resin.
11. A time/temperature indicator according to any one of the preceding Claims, in which the dye and the photolatent base are printed on a substrate.
12. A packaged perishable product where the packaging bears a time/temperature indicator according to any one of the preceding Claims.
13. A product according to Claim 12, in which the perishable product is a food.
14. A product according to Claim 12, in which the perishable product is a drug.
15. A method of activating a time/temperature indicator in which a product according to any one of Claims 12 to 14 is exposed to ultraviolet radiation sufficient to convert said photolatent base to a base form.
DOCSNY.182727.1
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EP2511379A1 (en) 2011-04-11 2012-10-17 Universidad Pública De Navarra Time and temperature monitoring device
US9310311B2 (en) 2013-06-13 2016-04-12 Performance Indicator, Llc Time validation indicator

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KR101794790B1 (en) 2007-01-11 2017-11-07 프레시포인트 퀄리티 어슈어런스 리미티드 Time temperature indicator
CN110208441A (en) * 2019-01-17 2019-09-06 广西科技大学 The rapidly extracting and detection method of concealed malachite green in fresh-water fishes

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EP1985670A1 (en) * 2006-01-18 2008-10-29 Arkray, Inc. Liquid reagent of color former and method of stabilizing the same
EP1985670A4 (en) * 2006-01-18 2011-06-22 Arkray Inc Liquid reagent of color former and method of stabilizing the same
EP2511379A1 (en) 2011-04-11 2012-10-17 Universidad Pública De Navarra Time and temperature monitoring device
US9310311B2 (en) 2013-06-13 2016-04-12 Performance Indicator, Llc Time validation indicator
US9645552B2 (en) 2013-06-13 2017-05-09 Performace Indicator, Llc Time validation indicator

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