FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFIC A TION
(See section 10, rule 13)
1. Title of the invention
A REVERSIBLE THERMOCHROMIC ADDITIVE
2. Applicant(s)
Name Nationality Address
TATA CHEMICALS LTD. INDIA BOMBAY HOUSE, 24 HOM1 MODI STREET,
MUMBAI-400001
3. Preamble to the description
COMPLETE SPECIFICA TION
The following specification particularly describes the invention and the manner in which it is
to be performed.

The disclosure relates to a reversible thermochrornic additive. The disclosure also relates to a process for production of the reversible thermochrornic additive.
BACKGROUND
Thermochrornic materials are substances that can bring variations in their colour, colour intensity, or transparency in response to temperature changes. These materials have a number of applications. For example thermochrornic materials are used as indicators to determine levels of propane in tanks; as temperature indicators in thermometers; as components in paints, as coating materials and for thermal printers. Thermochrornic materials are also used in baby bottles and kettles indicating through change in colour as to when the content inside the bottle is cool enough to drink.
The two widely-used thermochrornic materials are liquid crystals and leuco dyes. Liquid crystals exhibit properties between that of a pure liquid and a solid. Thermochrornic liquid crystals display varied colours at different temperatures owing to the selective reflection of certain wavelengths by their crystalline structure. Generally, such changes happen between the low-temperature crystalline phase through the anisotropic chiral or twisted nematic phase to the high temperature isotropic liquid phase. Since the nematic phase has thermochrornic properties, the effective temperature range of a particular liquid depends on this transition temperature. Liquid crystals are used in precision applications as their responses can be engineered to accurate temperatures. However, their colour range is limited by their principle of operation. Moreover, liquid crystals are difficult to work with and require specialized printing equipment.
The leuco dyes work on the principle of proton exchange at the melting points of the carrier substances involved, which lead to molecular re-structuring with concomitant change in colouration. Leuco dye thermochromes are generally based on three-component systems that comprise of an electron donating chromogen, an electron acceptor and a solvent that carries them. A marked impairment of thermochrornic behaviour seen in such compositions is when they are ad-mixed with resins due to the loss of one of the components. These thermochrornic materials are chemically less stable. When exposed to ultraviolet radiation, solvents and high temperatures their lifespan reduces.
Since thermochrornic materials can find vast usage like in paints, thermal printers, and charge indicators of batteries and inks, there is a need to develop such thermochrornic materials that are not only economical to produce but also are stable and maintain their

thermochromic effect when used as additives in paints, dyes, as coating materials and other applications.
SUMMARY
The disclosure relates to a reversible thermochromic additive. The reversible thermochromic additive includes a transition metal derivative of saturated anancardic acid or anancardic acid enes or both. The transition metal derivative is a 1:1 derivative having one transition metal ion bonded with one molecule of anancardic acid or anacardic acid enes or a 2: 1 derivative having two molecules of anacardic acid or anancardic acid enes bonded with one transition meta\ ion.
The disclosure further relates to a reversible thermochromic additive includes a transition metal derivative of saturated anancardic acid or anancardic acid enes or both, the transition metal derivative either a 1:1 derivative or a 2:1 derivative having one or two molecules of saturated anancardic acid or anacardic acid enes bonded with one transition metal ion and saturated anancardic acid or anacardic acid ene such that the ratio of anacardic acid or anacardic acid enes to metal is in the range of 2:1 to 10:1.
The disclosure also relates to a process for making a material with thermochromic properties. The process comprises adding to the material a reversible thermochromic additive comprising a transition metal derivative of saturated anancardic acid or anancardic acid enes or both, the transition metal derivative being a 1:1 derivative having one transition metal ion bonded with one molecule of anancardic acid or anacardic acid enes or a 2: 1 derivative having two molecules of anacardic acid or anancardic acid enes bonded with one transition metal ion.
The disclosure also relates to a process for the production of reversible thermochromic additive. The process includes reacting an anacardic acid feed including saturated anacardic acid or anacardic acid enes or both with a transition metal to obtain metal derivatives of saturated anacardic acid or anancardic acid enes or both, the transition metal derivative being a 1:1 derivative having one transition metal ion bonded with one molecule of saturated anancardic acid or anacardic acid enes or a 2: 1 derivative having two molecules of saturated anacardic acid or anancardic acid enes bonded with one transition metal ion. The derivative thus obtained has reversible thermochromic properties.
The disclosure further relates to a process for the production of a reversible thermochromic additive including reacting an anacardic acid feed including saturated

anacardic acid or anacardic acid enes or both with an alkali metal hydroxide to obtain an alkali metal derivative of anacardic acid or anacardic acid enes or both; and adding to the alkali metal derivatives of saturated anacardic acid or anacardic acid enes or both a transition metal to precipitate a transition metal derivative of saturated anacardic acid or anacardic acid enes or both; and separating the transition metal derivative of saturated anacardic acid or anacardic acid enes or both, the transition metal derivative being a 1:1 derivative having one transition metal ion bonded with one molecule of saturated anancardic acid or anacardic acid enes or a 2: 1 derivative having two molecules of anacardic acid or anancardic acid enes bonded with one transition metal ion, the derivative thus obtained having reversible thermochromic properties.
The disclosure also relates a process for the production of a reversible thermochromic additive including preparing a solution of anacardic acid feed including anacardic acid or anacardic acid enes or both in an organic solvent; preparing an aqueous solution of a metal salt of an organic acid; mixing the solution of anacardic acid feed including anacardic acid or anacardic acid enes or both with the aqueous solution of the metal salt of organic acid to obtain a reaction mixture containing an organic and an aqueous phase; holding the reaction mixture for a predetermined period of time to obtain metal derivatives of anacardic acid or anacardic acid enes or both in the organic phase; and separating the organic phase from the aqueous phase to obtain the metal derivative of anacardic acid or anacardic acid enes or both, the transition metal derivative being a 1:1 derivative having one transition metal ion bonded with one molecule of anancardic acid or anacardic acid enes or a 2: 1 derivative having two molecules of anacardic acid or anancardic acid enes bonded with one transition metal ion, the derivative thus obtained having reversible thermochromic properties.
The disclosure also relates to a reversible thermochromic composition. The composition includes a transition metal derivative of anancardic acid or anancardic acid enes or both, the transition metal derivative being a 1:1 derivative having one transition metal ion bonded with one molecule of anancardic acid or anacardic acid enes or a 2: 1 derivative having two molecules of anacardic acid or anancardic acid enes bonded with one transition metal ion; and atleast one binder medium, wherein the amount of transition metal derivative of saturated anacardic acid or anacardic acid enes or both is atleast 1 wt %.

BRIEF DESCRIPTION OF ACCOMPANYING FIGURES
The accompanying drawing illustrates the preferred embodiments of the invention and together with the following detailed description serves to explain the principles of the invention.
Figure 1 illustrates the different fractions of natural cashew nut shell liquid and their abundance in the natural cashew nut shell liquid.
DETAILED DESCRIPTION
To promote an understanding of the principles of the invention, reference will be made to the embodiment and specific language will be used to describe the same. It will nevertheless be understood that no limitation of scope of the invention is thereby intended, such alterations and further modifications in the illustrated process and product and such further applications of the principles of the inventions as illustrated therein being contemplated as would normally occur to one skilled in art to which the invention relates.
A reversible thermochromic substance is disclosed. The reversible thermochromic substances may be beneficially used as a thermochromic additive for various applications. The reversible thermochromic additive is a transition metal derivative of saturated anacardic acid or anacardic acid enes or both. The transition metal derivative of saturated anacardic acid or anacardic acid enes may be a 1:1 derivative or 2:1 derivative or both.
In accordance with an aspect, the reversible thermochromic additive comprises of a transition metal derivative of saturated anacardic acid or anacardic acid enes or both and saturated anacardic acid or anacardic acid enes such that the ratio of saturated anacardic acid or anacardic acid enes or both to the transition metal in the additive is in the range of 2:1 to 10:1.
Saturated anacardic acid is a molecule having a salicylic acid unit linked to a saturated linear alkyl chain (R). The alkyl chain may have any number of carbon atoms, depending upon the source of the saturated anacardic acid. By way of an example, in the saturated anacardic acid obtained from cashew nut shell, the alkyl chain (R) is a saturated 15-carbon long alkyl chain represented as 1R below. The molecular structure of the saturated anacardic acid obtained from cashew nut shell liquid is illustrated below:


Anacardic acid enes are unsaturated anacardic acids having various degrees of unsati ration in the side chain. In accordance with aspect, the anacardic acid enes obtained from cashew nut shell liquid have 1 to 3 double bonds. The anacardic acid enes obtained from cashew nut shell liquid may be an 8'Z -monoene (2R); 8'Z, 11 'Z-diene(3R) and 8'Z, 11 'Z, 14'-triene (4R) anacardic acid enes having the following molecular structures:

The 1:1 transition metal derivative of saturated anacardic acid or anacardic acid enes has one transition metal ion (M) bonded with one molecule of the saturated anacardic acid or anacardic acid enes. The molecular structure of the 1:1 transition metal derivative of saturated anacardic acid or anacardic acid enes is illustrated below:

R may be a saturated or an unsaturated side chain. By why of an example the alkyl chain (R) is saturated 15-carbon chain represented by 1R above or unsaturated 15-carbon long chain having 1 to 3 double bonds represented as 2R, 3R and 4R above.
In the 2:1 transition metal derivative of saturated anacardic acid or anacardic acid enes, one transition metal ion (M) is bonded with two molecules of saturated anacardic acid


or anacardic acid enes. The molecular structure of the 2:1 derivative saturated of anacardic acid or anacardic acid enes is illustrated below:
R may be a saturated or an unsaturated side chain. By why of an example the alkyl chain (R) is saturated 15-carbon chain represented by 1R above or unsaturated 15-carbon long chain having 1 to 3 double bonds represented as 2R, 3R and 4R above.
The transition metal ion is a divalent transition metal ion including but not limited to iron, copper or cobalt.
In accordance with an aspect, the 1:1 transition metal derivative of saturated anacardic acic or anacardic acid enes is a transition metal derivative of any one of iron or cobalt. The 2:1 to 10:1 transition metal of saturated anacardic acic or anacardic acid enes is transition metal derivative of any one of iron cobalt or copper.
In accordance with an aspect, the reversible thermochromic additive further comprises of organic solvent including but not limited to aromatic hydrocarbon solvents, aliphatic hydrocarbon solvents, chlorinated solvents, carboxylic esters or hydroxylated solvents.
A process for production of a reversible thermochromic additive is also disclosed. The process includes reacting an anacardic acid feed including saturated anacardic acid or anacardic acid enes or both with a transition metal to obtain transition metal derivative of saturated anacardic acid or anacardic acid enes or both, the transition metal derivative thus obtained having reversible thermochromic properties. The transition metal derivative of saturated anacardic acid or anacardic acid enes obtained may be a 1:1 transition metal derivative of saturated anacardic acid or anacardic acid enes or both or a 2:1 transition metal derivative of saturated anacardic acid or anacardic acid enes or both.

In accordance with an aspect, the process for the production of reversible thermochromic additive comprises of reacting the anacardic acid feed including saturated anacardic acid or anacardic acid enes or both with an alkali metal hydroxide to obtain an alkali metal derivative of saturated anacardic acid or anacardic acid enes or both. A transition metal salt is added to the alkali metal derivative of saturated anacardic acid or anacardic acid enes or both to precipitate the transition metal derivative of saturated anacardic acid or anacardic acid enes or both, the transition metal derivative thus obtained having reversible thermochromic properties.
In accordance with an aspect, a pre-calculated amount of alkali metal hydroxide is reacted with the anacardic acid feed to obtain mono-alkali metal derivative or di-alkali metal derivative of saturated anacardic acid or anacardic acid enes or both.
In accordance with an aspect, one mole of alkali metal hydroxide is reacted with one mole of saturated anacardic acid or anacardic acid enes or both to obtain a mono-alkali metal derivative of saturated anacardic acid or anacardic acid enes or both. The transition metal salt is added to the mono-alkali metal derivative of saturated anacardic acid or anacardic acid enes or both thus obtained to precipitate the 2:1 transition metal derivative of saturated anacardic acid or anacardic acid enes or both.
In accordance with an aspect, two mole of alkali metal hydroxide is reacted with one mole of saturated anacardic acid or anacardic acid enes or both to obtain the di-alkali.metal derivative of saturated anacardic acid or anacardic acid enes or both. The transition metal salt is added to the di-alkali metal derivative of saturated anacardic acid or anacardic acid thus obtained to precipitate the 1:1 transition metal derivative of saturated anacardic acid or anacardic acid enes or both.
The precipitated transition metal derivative of saturated anacardic acid or anacardic acid enes or both are separated and dried. The precipitated transition metal derivative of saturated anacardic acid or anacardic acid enes or both may be separated by any means including but not limited to filtration, decantation or centrifugation.
In accordance with an embodiment, the process further comprises adding saturated anacardic acid or anacardic acid to the transition metal derivative of saturated anacardic acid or anacardic acid enes or both such that the ratio of saturated anacardic acid or anacardic acid enes to metal is in the range of 2:1 to 10:1.
Solid saturated anacardic acid or anacardic acid may be added to the precipitated transition metal derivative of saturated anacardic acid or anacardic acid enes or both to obtain

the reversible thermochromic additive. Alternatively, transition metal derivative of saturated anacardic acid or anacardic acid enes or both may be dissolved in an organic solvent and saturated anacardic acid or anacardic acid enes added to the solution such that the ratio of saturated anacardic acid or anacardic acid enes to metal is in the range of 2:1 to 10:1. In accordance with an aspect, solid saturated anacardic acid or anacardic acid enes is added to the solution of saturated anacardic acid or anacardic acid enes.
The alkali metal hydroxide used is a hydroxide of alkali metal including from the group comprising sodium, lithium, potassium, rubidium, caesium or francium. The transition metal salt is a divalent metal salt including but not limited to halides, nitrides, sulfates, phosphates or carboxylate salts of transition metals including but not limited to iron, copper or cobalt.
In accordance with an alternate embodiment, the process for the production of reversible thermochromic additive comprises of preparing a solution of anacardic acid feed including saturated anacardic acid or anacardic acid enes or both in an organic solvent and preparing an aqueous solution of an organic metal salt. The solution of saturated anacardic acid or anacardic acid enes or both and the aqueous solution of the organic metal salt are mixed to obtain a reaction mixture having an organic phase and an aqueous phase. The reaction mixture is held for a predetermined period of time till the transition metal derivative of saturated anacardic acid or anacardic acid ense or both are formed in the organic phase. The formation of transition metal derivative of saturated anacardic acid or anacardic acid enes or both in the organic phase is indicated by the appearance of colour in the organic phase.
The organic phase is then separated from the aqueous phase to obtain the transition metal derivative of saturated anacardic acid or anacardic acid enes or both, the transition metal derivative being thus obtained is a 1:1 derivative or a 2:1 derivative having reversible thermochromic properties.
In accordance with an aspect, the organic phase may be separated from the aqueous phase by any known method including but not limited to decantation.
In accordance with an embodiment, the process further comprises of recovering solid transition metal derivative of saturated anacardic acid anacardic acid enes or both from the separated organic phase by first evaporating the solvent from the separated organic layer and then drying the solid thus obtained.

In accordance with an embodiment, the process farther comprises adding saturated anacardic acid or anacardic acid enes to the organic phase containing the transition metal derivative of saturated anacardic acid or anacardic acid enes or both such that the ratio of saturated anacardic acid or anacardic acid enes or both to the transition metal is in the range of 2:1 to 10:1. In accordance with an aspect the saturated anacardic acid or anacardic acid enes added to the organic phase is in solid form.
In accordance with an aspect, the organic metal salt used is a metal carboxylate. The organic solvent used is selected from the group comprising aromatic hydrocarbon solvents, aliphatic hydrocarbon solvents, chlorinated solvents, carboxylic esters and hydroxylated solvents.
In accordance with an aspect, anacardic acid feed includes but is not limited to, cashew nut shell liquid (CNSL) containing a mixture of saturated anacardic acid and anacardic acid enes, anacardic acid enes or a mixture of anacardic acid enes obtained from cashew nut shell liquid, or saturated anacardic acid obtained by saturation of anacardic acid enes obtained from cashew nut shell liquid.
In accordance with an embodiment, the process further comprises obtaining the anacardic feed from cashew nut. By way of an example, fresh cashew nuts are broken and the kernels along the pericrap are removed. The shells are treated with organic solvent, which may be hexane, ether, ethyl acetate, chlorinated solvents or hydroxylated solvents, to extract the lipophilic phenols referred to as natural cashew nut shell liquid. The natural cashew nut shell liquid thus obtained is nearly 34% yield of the shell, in the form of a light brown coloured viscous liquid containing anacardic acid enes (as much as 75%) as the chief ingredient.
Natural cashew nut shell liquid may also be obtained from the cashew nut shell by cold pressing the shells.
The anacardic acid enes may be separated from the natural cashew nut shell liquid by any known method. By way of a specific example, the natural cashew nut shell liquid is subjected to column purification to separate the components of the natural cashew nut shell liquid as various fractions. The factions containing anacardic acid enes are pooled together to obtain a mixture of anacardic acid enes in the form of a pale yellow viscous liquid. The mixture of anacardic acid enes thus obtained may be used as the anacardic acid feed.

By way of another example the anacardic acid enes may also separated from the natural cashew nut shell liquid by treating the natural cashew nut shell liquid with calcium salts
Further, the anacardic acid enes may be converted to their saturated analog form to obtain saturated anacardic acid. Saturation of anacardic acid enes may be carried out by any known method including but not limited to catalytic hydrogenation using Pt/C catalyst. Saturated anacardic acid may also be used as the anacardic acid feed.
Similar methods of extraction, purification and saturation may also be used to obtain anacardic acid feed from other natural sources. Alternatively, saturated anacardic acid or anacardic acid enes may also be synthesized.
A process for making a material with thermochromic properties is also disclosed. The process comprises adding to the material a reversible thermochromic additive comprising a transition metal derivative of saturated anancardic acid or anancardic acid enes or both, the transition metal derivative being a 1:1 derivative having one transition metal ion bonded with one molecule of anancardic acid or anacardic acid enes or a 2: 1 derivative having two molecules of anacardic acid or anancardic acid enes bonded with one transition metal ion.
In accordance with an aspect the reversible thermochromic additive that is added to the material may further comprise of saturated anancardic acid or anacardic acid ene such that the ratio of anacardic acid or anacardic acid enes to metal in the additive is in the range of 2:1 to 10:1.
The material may include but is not limited to ink, epoxy resins or paint.
A reversible thermochromic composition is also disclosed. The composition comprises of a transition metal derivative of saturated anancardic acid or anancardic acid enes or both and at least one binder medium. The amount of transition metal derivative of saturated anacardic acid or anacardic acid enes or both in the composition is atleast 1 wt%. The transition metal derivative may be a 1:1 derivative having one transition metal ion bonded with one molecule of saturated anancardic acid or anacardic acid enes or a 2: 1 derivative having two molecules of saturated anacardic acid or anancardic acid enes bonded with one transition metal ion.
The binder medium may be any material into which the reversible thermochromic additive may be added. Such binder material may include but is not limited to polyurethanes, elastomers, polyacrylates, poly(ethylene terephthalate)s (PET), polysytrenes, polyolefins, polycarbonates, polyacrylics, polyacrylic acids, polyacrylamides, polymethacrylics, polyvinyl

ethers, polyvinyl halides, poly(venyl nitrile)s, polyvinyl esters, polyesters, polysulfones, poly sulfonamides, polyamides, polyamines, polyimides and carbohydrates.
Specific embodiments are disclosed below:
A reversible thermochromic additive comprising a transition metal derivative of saturated anancardic acid or anancardic acid enes or both, the transition metal derivative being a 1:1 derivative having one transition metal ion bonded with one molecule of anancardic acid or anacardic acid enes or a 2: 1 derivative having two molecules of anacardic acid or anancardic acid enes bonded with one transition metal ion.
A reversible thermochromic additive comprising a transition metal derivative of saturated anancardic acid or anancardic acid enes or both, the transition metal derivative either a 1:1 derivative or a 2:1 derivative having one or two molecules of saturated anancardic acid or anacardic acid enes bonded with one transition metal ion; and saturated anancardic acid or anacardic acid ene such that the ratio of anacardic acid or anacardic acid enes to metal in the additive is in the range of 2:1 to 10:1.
Such reversible thermochromic additive(s), wherein the 1:1 transition metal derivative is a transition metal derivative of any one of iron or cobalt.
Such reversible thermochromic additive(s), wherein the 2:1 to 10:1 transition metal derivative is a transition metal derivative of any one of iron cobalt or copper.
Such reversible thermochromic additive(s), wherein the anacardic acid or anancardic acid enes is obtained from natural cashew nut shell liquid.
Such reversible thermochromic additive(s), further comprising an organic solvent in which the transition metal derivative of saturated anacardic acid or anacardic acid enes or both are dissolved, the organic solvent including aromatic hydrocarbon solvent, aliphatic hydrocarbon solvents, chlorinated solvents, carboxylic esters or hydroxylated solvent.
A process for making a material with thermochromic properties comprising adding to the material a reversible thermochromic additive comprising a transition metal derivative of saturated anancardic acid or anancardic acid enes or both, the transition metal derivative being a 1:1 derivative having one transition metal ion bonded with one molecule of anancardic acid or anacardic acid enes or a 2: 1 derivative having two molecules of anacardic acid or anancardic acid enes bonded with one transition metal ion.
Such process(s) for making a material with thermochromic properties, wherein the reversible thermochromic additive further comprises saturated anancardic acid or anacardic

acid ene such that the ratio of anacardic acid or anacardic acid enes to metal in the additive is in the range of 2:1 to 10:1.
Such process(s) for making a material with thermochromic properties, wherein the material is any one of ink, epoxy resins or paint.
A process for the production of a reversible thermochromic additive comprising reacting an anacardic acid feed including saturated anacardic acid or anacardic acid enes or both with a transition metal to obtain metal derivatives of saturated anacardic acid or anancardic acid enes or both, the transition metal derivative being a 1:1 derivative having one transition metal ion bonded with one molecule of saturated anancardic acid or anacardic acid enes or a 2: 1 derivative having two molecules of saturated anacardic acid or anancardic acid enes bonded with one transition metal ion, the derivative thus obtained having reversible thermochromic properties.
A process for the production of a reversible thermochromic additive comprising reacting an anacardic acid feed including saturated anacardic acid or anacardic acid enes or both with an alkali metal hydroxide to obtain an alkali metal derivative of anacardic acid or anacardic acid enes or both; adding to the alkali metal derivatives of saturated anacardic acid or anacardic acid enes or both, a transition metal salt to precipitate a transition metal derivative of saturated anacardic acid or anacardic acid enes or both; and separating the transition metal derivative of saturated anacardic acid or anacardic acid enes or both, the transition metal derivative being a 1:1 derivative having one transition metal ion bonded with one molecule of saturated anancardic acid or anacardic acid enes or a 2: 1 derivative having two molecules of anacardic acid or anancardic acid enes bonded with one transition metal ion, the derivative thus obtained having reversible thermochromic properties.
Such process(s) for the production of a reversible thermochromic additive, wherein the alkali metal hydroxide is a hydroxide of any one of sodium, lithium, potassium, rubidium, caesium, or francium.
Such process(s) for the production of a reversible thermochromic additive, wherein 1 mole of alkali metal hydroxide is added to 1 mole of anacardic acid or anacardic acid enes or both to obtain a mono-alkali metal derivative of anacardic acid or anacardic acid enes or both.
Such process(s) for the production of a reversible thermochromic additive,, wherein 2:1 metal derivative of anacardic acid or anacardic acid enes or both is obtained by reacting the mono-alkali derivative of anacardic acid or anacardic acid enes or both with the transition metal.

Such process(s) for the production of a reversible thermochromic additive, wherein 2 moles of alkali metal hydroxide is added to 1 mole of anacardic acid or anacardic acid enes to obtain a di-alkali metal derivative of anacardic acid.
Such process(s) for the production of a reversible thermochromic additive, wherein 1:1 metal derivative of anacardic acid or anacardic acid enes or both is obtained by reacting the di-alkali derivative of anacardic acid or anacardic acid enes or both with the transition metal.
Such process(s) for the production of a reversible thermochromic additive, wherein the transition metal is any one of halide, nitrate, sulfate, phosphate or carboxylate salts of iron, cobalt or copper.
A process for the production of a reversible thermochromic additive comprising preparing a solution of anacardic acid feed including anacardic acid or anacardic acid enes or both in an organic solvent; preparing an aqueous solution of a metal salt of an organic acid; mixing the solution of anacardic acid feed including anacardic acid or anacardic acid enes or both with the aqueous solution of the metal salt of organic acid to obtain a reaction mixture containing an organic and an aqueous phase; holding the reaction mixture for a predetermined period of time to obtain metal derivatives of anacardic acid or anacardic acid enes or both in the organic phase; and separating the organic phase from the aqueous phase to obtain the metal derivative of anacardic acid or anacardic acid enes or both, the transition metal derivative being a 1:1 derivative having one transition metal ion bonded with one molecule of anancardic acid or anacardic acid enes or a 2: 1 derivative having two molecules of anacardic acid or anancardic acid enes bonded with one transition metal ion, the derivative thus obtained having reversible thermochromic properties.
Such process(s) for the production of a reversible thermochromic additive, wherein the organic solvent is selected from the group comprising aromatic hydrocarbon solvent, aliphatic hydrocarbon solvents, chlorinated solvents, carboxylic esters or hydroxylated solvent.
Such process(s) for the production of a reversible thermochromic additive, wherein the organic acid metal salt is a metal carboxylate.
Such process(s) for the production of a reversible thermochromic additive, wherein the metal is iron, cobalt or copper.
Such process(s) for the production of a reversible thermochromic additive, further comprising of adding anacardic acid or anacardic acid enes to the transition metal derivative

of anacardic acid or anacardic acid enes or both such that the ratio of anacardic acid or anacardic acid enes to metal is in the range of 2:1 to 10:1.
Such process(s) for the production of a reversible thermochromic additive, wherein solid saturated anacardic acid or anacardic acid enes is added to the transition metal derivative of anacardic acid or anacardic acid enes or both.
Such process(s) for the production of a reversible thermochromic additive, wherein the anacardic acid feed is natural cashew nut shell liquid obtained from cashew nut shell by a process comprising treating the pericarp of cashew nuts with an organic solvent, the organic solvent including hexane, ether, ethyl acetate, chlorinated solvents or hydroxylated solvents.
Such process(s) for the production of a reversible thermochromic additive, wherein the saturated anacardic acid feed includes anacardic acid enes.
Such process(s) for the production of a reversible thermochromic additive, wherein the saturated anacardic acid enes are hydrogenated to obtain anacardic acid.
A reversible thermochromic composition comprising a transition metal derivative of anancardic acid or anancardic acid enes or both, the transition metal derivative being a 1:1 derivative having one transition metal ion bonded with one molecule of anancardic acid or anacardic acid enes or a 2: 1 derivative having two molecules of anacardic acid or anancardic acid enes bonded with one transition metal ion; and atleast one binder medium, wherein the amount of transition metal derivative of saturated anacardic acid or anacardic acid enes or both is atleast 1 % wt/wt.
Such reversible thermochromic composition(s), wherein the binder medium is selected from the group comprising polyurethanes, elastomers, polyacrylates, poly (ethylene terephthalate)s (PET), polysytrenes, polyolefins, polycarbonates, polyacrylics, polyacrylic acids, polyacrylamides, polymethacrylics, polyvinyl ethers, polyvinyl halides, poly(vinyl nitrile)s, polyvinyl esters, polyesters, polysulfones, polysulfonamides, polyamides, polyamines, polyimides and carbohydrates.
Examples:
The following examples are provided to explain and illustrate certain preferred embodiments of the process of the invention.
Example 1: Extraction of natural cashew nut shell liquid (CNSL):
Cashew nuts (anacardium occidentale) containing cashew nut shell liquid and the edible kernel were separated by de-shelling the nut and separating the kernel along with pericarp. The shell was treated with an organic solvent (e.g., ethyl acetate, acetone, ether,

hexane or a mixture thereof) to completely extract the cashew nut shell liquid. The natural cashew nut shell liquid thus obtained was used as a source of anacardic acids. Similarly, anacardic acids can be extracted from any source that contains these components. Anacardic acid containing cashew nut shell liquid can be sourced from vendors.
Example 2: Separation of anacardic acid ene mixtures from cashew nut shell liquid:
Natural cashew nut shell liquid was loaded on a silica cartridge (100-200 mesh size, prepared in hexane) and the column was irrigated with ethyl acetate: hexane (from 2 percent to 30 percent v/v of ethyl acetate) having varied polarity. Different fractions were individually collected. The fractions containing anacardic acid enes were pooled together and the solvent was evaporated under reduced pressures to obtain a mixture of anacardic acid enes. The mixture thus obtained was a pale yellow-coloured oil.
Alternately, cashew nut shell liquid was subjected to column purification to obtain a mixture of anacardic acid enes. Anacardic acid enes were also obtained by treating natural cashew nut shell liquid with calcium salts.
Example 3: Separation of anacardic acid ene mixture into individual components by reverse phase chromatography.
The anacardic acid ene mixture obtained by column purification was laid on a preparative reverse phase chromatographic plate (200 mg) using a solvent system of acetonitrile: water (66:33 v/v) containing 1 percent acetic acid. The triene, diene, monoene and the saturated fractions were individually collected by marking individual fractions, scraping the silica, and extracting individual fractions using ethyl acetate. Each individual fraction was refrigerated before use.
Of the individual fractions thus obtained, the triene, diene and monoene individual fractions and a mixture of anacardic acid enes obtained by pooling together triene, diene and monoene anacardic acid were catalytically hydrogenated using ethyl acetate as a solvent and 0.2 wt% of 5 wt% Pt/C as a catalyst, to obtain saturated anacardic acid.
The fractionated acnacardic acid ene mixture and the individual components therefrom (triene, diene, monoene and saturated) as well as the saturated analog prepared by catalytic hydrogenation reacted with metal salts to form coloured metal derivatives possessing thermochromic properties.

Example 4
A number of ammonium(-NR3+, -NH3+), alkali (Na+, K+, Li+), alkaline earth (Ca2+, Ba2+, Sr24), transition metal derivatives of anacardic acid feed were generated by both double decomposition and extraction methods and their thermochromic abilities were tested.
Most alkali derivatives of anacardic acid and alkaline earth metal derivatives of anacardic acid were white (colourless). The transition metal derivatives of anacardic acid exhibited varied colours depending on the transition metal and the relative ratio of the transition metal to anacardic acid. The colouration due to transition metal derivatives of anacardic acid was intense enough to mask the light brown colour of natural cashew nut shell liquid. Purified anacardic acid enes (pale yellow viscous liquid) or the saturated anacardic acid (white solid, m. pt. 76 °C) enabled better solutions.
Anacardic acid contained in the natural cashew nut shell liquid , the fractionated anacardic acid ene mixtures and the individual components therefrom (mono-, di- and triene), the saturated analog prepared by catalytic hydrogenation all form both 2:1 and 1:1 metal derivatives and a mixture thereof with any divalent metal ion.
Divalent early transition metal salts (in the form of halides, nitrates, sulphates, phosphates, carboxylates, amongst others) including but not restricted to Cr , Cu , Co , Ni , Mn +, Fe2+ and Zn2+ were used to generate colour-bearing anacardic acid-metal derivatives. Both the methods resulted in the formation of metal derivatives. By suitable manipulation, anacardic acid metal derivatives with anacardic acid to metal stoichiometric ratio as low as 0.75: 1 to as high as 10:1 were also generated. The care in preparation, use of appropriate amounts of the metal salt to the appropriate alkali metal derivative of anacardic acid combined with careful processing yielded desired anacardic acid metal derivatives. All these materials were used for testing their thermochromic properties. Though most of the transition metal derivatives of anacardic acid appear to provide very mild thermochromism, anacardic acid derivatives of Fe , Cu2+ and Co2+showed strong thermochromic properties.
Example 5: Preparation of a 2:1 and 1:1 copper derivative of anacardic acid by double decomposition:
In a 50 ml conical flask, 100 mg of saturated anacardic acid (m. wt. 348; 0.287 mmol) was treated with 11.5 mg of NaOH (0.287 mmol) dissolved in 20 ml of water. After stirring the solution at 60 °C for 5 min., a clear solution was formed. To this clear solution, 86 mg of copper acetate (mol wt. 199.65) dissolved in 10 ml of water was added to obtain a 2:1 copper derivative of anacardic acid in the form of a clear green precipitate. The clear green

precipitate was filtered, washed several times with water and dried. The precipitate was further dissolved in different organic solvents and its thermochromic properties were measured.
Similarly, 100 mg of saturated anacardic acid was treated with 23 mg of sodium hydroxide in aqueous solution. After stirring the solution at 60 °C for 5 min., a clear solution was formed. The clear solution thus obtained was treated with 100 mg of copper acetate dissolved in 10 ml of water to obtain a 1:1 copper derivative of anacardic acid in the form of a clear yellow precipitate. The precipitate solution was filtered, washed several times with water and dried. The clear yellow precipitate was also tested for thermochromic properties but no such properties were observed.
The clear yellow precipitate was suspended in an organic solvent. Anacardic acid in a quantity equivalent to the clear yellow precipitate was added to the solution, to obtain a soluble green derivative of copper anacardic acid. The soluble green derivative of anacardic acid thus obtained showed thermochromic properties. This appears to suggest that the 1:1 yellow copper derivative of anacardic acid and the 2:1 green copper derivative of anacardic acid are interchangeable.
2:1 copper derivative of anacardic acid was kept at temperatures below -10 °C for more than a week. After a week, it was observed that the solution contained a 1:1 metal derivative of anacardic acid and an equivalent amount of anacardic acid. This suggests that both 2:1 and 1:1 derivatives of anacardic acid are interchangeable.
Example 6: Thermochromic properties of anacardic acid metal derivatives:
20mg of green copper anacardic acid derivative (where anacardic acid to copper ration was greater than 1:1, >1: 1 copper derivative of anacardic acid) was dissolved in 5 ml of an organic solvent (e.g., xylene). The resulting green solution was kept in a thermostat maintained at 30 °C. The temperature of the thermostat was increased in stages with an increment of 5 °C and maintained at that temperature for 5 min. each time. The change in colouration was duly observed, and the temperatures at which changes in colour, if any occurred, were recorded. Apart from the visible changes observed, UV-visible spectral analysis was also performed to record colour changes.
The >1: 1 copper derivative of anacardic acid is green in colour at temperatures between zero to 60 °C. It changes to blue at sub-zero temperatures. The >1: 1 copper derivative of anacardic acid changes colour from green to greenish yellow at temperatures between 60 °C and 80 °C. The colour drastically changes to dark brown at temperatures between 80 and 85 °C.

The brown coloured copper derivative of anacardic acid reverts to greenish yellow colour between SO °C and 70 °C and to its original green colour at around 60 °C.
Similar experiments were performed on all the metal derivatives of anacardic acids and the results were recorded.
Example 7; Increasing the anacardic acid to metal ratio;
A 2:1 copper derivative of anacardic acid generated by double decomposition was dissolved in an organic solvent (e.g., o-xylene) to obtain a green coloured solution. To the green coloured solution, free anacardic acid was added externally in solid form till the ratio of anacardic acid to metal (copper) was as high as 10:1.
Gradual addition of free anacardic acid to the 1:1 anacardic acid copper derivative changed the colour to green instantaneously and further addition of anacardic acid to keep the anacardic acid to metal ratio of 10:1 kept the same colouration.
Thermo chromic properties were tested at different temperatures, and the results were recorded. The reversibility of the thermochromic properties of the solution at different temperatures was also recorded.
The 10: 1 to >1: 1 copper derivative of anacardic acid is green in colour at temperatures between zero to 60 °C. It changes to blue at sub-zero temperatures. The >1: 1 copper derivative of anacardic acid changes colour from green to greenish yellow at temperatures between 60 °C and 80 °C. The colour drastically changes to dark brown at temperatures between 80 and 85 °C. The brown coloured copper derivative of anacardic acid reverts to greenish yellow colour between 80 °C and 70 °C and to its original green colour at around 60 °C.
Example 8: Comparison of thermochromic properties in different organic solvents
The copper derivative of anacardic acid (2:1) was dissolved in different organic solvents that included but not limited to heptane, benzene, toluene, o-xylene, ethyl acetate, and chloroform. Thermochromic properties were tested at different temperatures, and the results were recorded. The reversibility of the thermochromic properties of the solutions at different temperatures was also recorded.
The green coloured derivative at room temperature showed thermochromic properties in all these solvents with slight variation in the temperature at which the colour transition took place. Benzene and chloroform solutions initiated the change in colouration at relatively lower temperatures of 60 °C. In other solvents, colour began to change at around 70 °C. The complete transition in all the solvents took around 80 °C.

The reversibility of thermochromic properties was observed in all solvents, However the temperature at which reversibility was observed depended on the solvent. In most organic solvents, the reversal of colour was observed at about 60 °C. In chlorinated solvents (such as chloroform), the reversal of colour was observed at temperatures between 45 °C and 30 °C
Example 9
Iron derivatives of anacardic acid (both 2:1 and 1:1), which are brown in colour, deepened in colour at temperatures ranging between 60 °C and 70 °C in different organic solvents. The composition obtained by adding free anacardic acid to obtain a ratio of anacardic acid to metal as high as 10: 1 also exhibited thermochromic properties. The intensity of colour depends on the organic solvent in which the derivatives are dissolved, and on the amount of metal in the derivatives. The organic solvents included solvents such as aliphatic and aromatic hydrocarbons and their derivatives (for example, nitro-, halo-, and sulpho-), alkyl and aryl carboxylic esters, and halogenated solvents. Most derivatives were partially soluble or insoluble in most hydroxylic (e.g., alcohols) and aqueous solvents, and soluble in organic solvents. Reversibility in colour was seen in both the 2:1 and 1:1 derivatives at a range of 60 °C to 50 °C.
Example 10
Both 2:1 and 1:1 cobalt derivatives of anacardic acid were purple in colour, and completely soluble in organic solvents. Cobalt derivatives of anacardic acid showed drastic change in colour from purple to pink at temperatures 0 and 10 °C in aromatic hydrocarbon solvents (e.g., xylene).
Example 11
The use of technical cashew nut shell liquid and its components did not form metal derivatives and did not show thermochromic properties. The physical mixing of salicylic acid with technical cashew nut shell liquid components also did not form metal derivatives, and did not show thermochromism.
Example 12: Anacardic acid metal derivatives in ink composition.
A sample of commercial ink (white in colour) was blended with a 2:1 copper derivative of anacardic acid in 5% wt. The resulting homogeneous material was green in colour. The green coloured material turned brown upon being heated to temperatures above 65 °C. Reversibility in colour was also observed by cooling the material to below 55 °C. Similar experiments were carried out using cobalt and iron derivatives.

Example 13: Metal derivatives of anacardic acid as polymer composite composition:
2:1 copper derivative of anacardic acid was blended in 5 wt.% with commercially -available epoxy resins (commercial name DROPOXY obtained from D. R. Coats Ink and Resins Pvt. Ltd.). The resulting material was laid as a uniform layer on a glass sheet, and a uniform thin layer of green coloured transparent sheet was obtained.
The green coloured transparent sheet turned brown upon being heated to temperatures above 65 °C. Reversibility in colour was also observed by cooling the sheet to below 55 °C.
Example 14: Thermochromic anacardic acid metal derivative in paint compositions
Copper derivative of anacardic acid in 2 to 10 wt% was added to commercially-available white paint (premium gloss enamel BR White of Asian Paints Pvt. Ltd.). The resulting greenish-blue material was applied as paint on glass and metal surfaces. The surfaces were heated to temperatures above 90 °C. The colours of both the coated glass and metal surfaces changed to brown. When cooled, the colours of the surfaces returned to green indicating reversal of thermochromic properties.
INDUSTRIAL APPLICABILITY
The process as described above allows for the production of a reversible thermochromic additive in a simple manner. The process allows for the use of cashew nut shell liquid that is an obtained from shells of cashew nut a byproduct of the cashew nut industry for the production of the additive. The process therefore allows for the use of a renewable and biodegradable raw material from a vegetable source for the production of the additive. The additive produced is stable and has shown reversibility of thermochromic properties. It may therefore be used as an additive to various compositions including but not limited to ink compositions, paint compositions, additive compositions and a coating composition to impart thermochromic properties to these compositions. Moreover, the additive may also be mixed with a binder medium to produce reversible thermochromic compositions that find use in a number of applications.
Moreover, the reversible thermochromic additive disclosed shows thermocromic properties over different temperature ranges when dissolved in different organic solvents. ' This allows for the use of the same reversible thermochromic additive over different temperature ranges.

The embodiments of the invention described above are intended to be exemplary, and not limiting. Many variations are possible within the scope of the invention. These and other modifications are to be deemed within the spirit and scope of the following claims.

WE CLAIM:
1. A reversible thermochromic additive comprising:
a transition metal derivative of saturated anancardic acid or anancardic acid enes or both, the transition metal derivative being a 1:1 derivative having one transition metal ion bonded with one molecule of anancardic acid or anacardic acid enes or a 2: 1 derivative having two molecules of anacardic acid or anancardic acid enes bonded with one transition metal ion.
2. A reversible thermochromic additive comprising:
a transition metal derivative of saturated anancardic acid or anancardic acid enes or both, the transition metal derivative either a 1:1 derivative or a 2:1 derivative having one or two molecules of saturated anancardic acid or anacardic acid enes bonded with one transition metal ion; and
saturated anancardic acid or anacardic acid ene such that the ratio of anacardic acid or anacardic acid enes to metal in the additive is in the range of 2:1 to 10:1.
3. A reversible thermochromic additive as claimed in claim 1 or 2 wherein the 1:1 transition metal derivative is a transition metal derivative of any one of iron or cobalt.
4. A reversible thermochromic additive as claimed in claim 1 or 2 wherein the 2:1 to 10:1 transition metal derivative is a transition metal derivative of any one of iron cobalt or copper.
5. A reversible thermochromic additive as claimed in claim 1 or 2 wherein the anacardic acid or anancardic acid enes is obtained from natural cashew nut shell liquid.
6. A reversible thermochromic additive as claimed in claim 1 or 2, further comprising an organic solvent in which the transition metal derivative of saturated anacardic acid or anacardic acid enes or both is dissolved, the organic solvent including aromatic hydrocarbon solvent, aliphatic hydrocarbon solvents, chlorinated solvents, carboxylic esters or hydroxylated solvent.
7. A process for making a material with thermochromic properties comprising:

adding to the material a reversible thermochromic additive comprising a transition metal derivative of saturated anancardic acid or anancardic acid enes or both, the transition metal derivative being a 1:1 derivative having one transition metal ion bonded with one molecule of anancardic acid or anacardic acid enes or a 2: 1 derivative having two molecules of anacardic acid or anancardic acid enes bonded with one transition metal ion.
8. A process for making a material with thermochromic properties as claimed in claim 7 wherein the reversible thermochromic additive further comprises saturated anancardic acid or anacardic acid ene such that the ratio of anacardic acid or anacardic acid enes to metal in the additive is in the range of 2:1 to 10:1.
9. A process for making a material with thermochromic properties as claimed in claim 7 wherein the material is any one of ink, epoxy resins or paint.
10. A process for the production of a reversible thermochromic additive comprising:
reacting an anacardic acid feed including saturated anacardic acid or anacardic acid enes or both with a transition metal to obtain metal derivatives of saturated anacardic acid or anancardic acid enes or both, the transition metal derivative being a 1:1 derivative having one transition metal ion bonded with one molecule of saturated anancardic acid or anacardic acid enes or a 2: 1 derivative having two molecules of saturated anacardic acid or anancardic acid enes bonded with one transition metal ion, the derivative thus obtained having reversible thermochromic properties.
11. A process for the production of a reversible thermochromic additive comprising:
reacting an anacardic acid feed including saturated anacardic acid or anacardic acid enes or both with an alkali metal hydroxide to obtain an alkali metal derivative of anacardic acid or anacardic acid enes or both;
adding to the alkali metal derivatives of saturated anacardic acid or anacardic acid enes or both, a transition metal salt to precipitate a transition metal derivative of saturated anacardic acid or anacardic acid enes or both; and
separating the transition metal derivative of saturated anacardic acid or anacardic acid enes or both, the transition metal derivative being a 1:1 derivative

having one transition metal ion bonded with one molecule of saturated anancardic acid or anacardic acid enes or a 2: 1 derivative having two molecules of anacardic acid or anancardic acid enes bonded with one transition metal ion, the derivative thus obtained having reversible thermochromic properties.
12. A process for the production of a reversible thermochromic additive as claimed in 11, wherein the alkali metal hydroxide is a hydroxide of any one of sodium, lithium, potassium, rubidium, caesium, or francium.
13. A process for the production of a reversible thermochromic additive as claimed in 11, wherein 1 mole of alkali metal hydroxide is added to 1 mole of anacardic acid or anacardic acid enes or both to obtain a mono-alkali metal derivative of anacardic acid or anacardic acid enes or both.
14. A process for the production of a reversible thermochromic additive as claimed in claim 13, wherein 2:1 metal derivative of anacardic acid or anacardic acid enes or both is obtained by reacting the mono-alkali derivative of anacardic acid or anacardic acid enes or both with the transition metal.
15. A process for the production of a reversible thermochromic additive as claimed in 11, wherein 2 moles of alkali metal hydroxide is added to 1 mole of anacardic acid or anacardic acid enes to obtain a di-alkali metal derivative of anacardic acid.
16. A process for the production of a reversible thermochromic additive as claimed in claim 15, wherein 1:1 metal derivative of anacardic acid or anacardic acid enes or both is obtained by reacting the di-alkali derivative of anacardic acid or anacardic acid enes or both with the transition metal.
17. A process for the production of a reversible thermochromic additive as claimed in claim 10 or 11 wherein the transition metal is any one of halide, nitrate, sulfate, phosphate or carboxylate salts of iron, cobalt or copper.
18. A process for the production of a reversible thermochromic additive comprising:

preparing a solution of anacardic acid feed including anacardic acid or anacardic acid enes or both in an organic solvent;
preparing an aqueous solution of a metal salt of an organic acid;
mixing the solution of anacardic acid feed including anacardic acid or anacardic acid enes or both with the aqueous solution of the metal salt of organic acid to obtain a reaction mixture containing an organic and an aqueous phase;
holding the reaction mixture for a predetermined period of time to obtain metal derivatives of anacardic acid or anacardic acid enes or both in the organic phase; and
separating the organic phase from the aqueous phase to obtain the metal derivative of anacardic acid or anacardic acid enes or both, the transition metal derivative being a 1:1 derivative having one transition metal ion bonded with one molecule of anancardic acid or anacardic acid enes or a 2: 1 derivative having two molecules of anacardic acid or anancardic acid enes bonded with one transition metal ion, the derivative thus obtained having reversible thermochromic properties.
19. A process for the production of a reversible thermo chromic additive as claimed in claim 18 wherein the organic solvent is selected from the group comprising aromatic hydrocarbon solvent, aliphatic hydrocarbon solvents, chlorinated solvents, carboxylic esters or hydroxylated solvent.
20. A process for the production of a reversible tbermochrornic additive as claimed in claim 18 wherein the organic acid metal salt is a metal carboxylate.
21. A process for the production of a reversible thermochromic additive as claimed in 10, Jl or 18 wherein the metal is iron, cobalt or copper.
22. A process for the production of a reversible thermochromic additive as claimed in claim 10, 11 or 18 further comprising of adding anacardic acid or anacardic acid enes to the transition metal derivative of anacardic acid or anacardic acid enes or both such that the ratio of anacardic acid or anacardic acid enes to metal is in the range of 2:1 to 10:1.

23. A process for the production of a reversible thermochromic additive as claimed in claim 22 wherein solid saturated anacardic acid or anacardic acid enes is added to the transition metal derivative of anacardic acid or anacardic acid enes or both.
24. A process for the production of a reversible thermochromic additive as claimed in claim 10, 11 or 18 wherein the anacardic acid feed is natural cashew nut shell liquid obtained from cashew nut shell by a process comprising treating the pericarp of cashew nuts with an organic solvent, the organic solvent including hexane, ether, ethyl acetate, chlorinated solvents or hydroxylated solvents.
25. A process for the production of a reversible thermochromic additive as claimed in claim 24, wherein the saturated anacardic acid feed includes anacardic acid enes.
26. A process for the production of a reversible thermochromic additive as claimed in claim 25, wherein the saturated anacardic acid enes are hydrogenated to obtain anacardic acid.
27. A reversible thermochromic composition comprising:
a transition metal derivative of anancardic acid or anancardic acid enes or both, the transition metal derivative being a 1:1 derivative having one transition metal ion bonded with one molecule of anancardic acid or anacardic acid enes or a 2: 1 derivative having two molecules of anacardic acid or anancardic acid enes bonded with one transition metal ion; and
atleast one binder medium, wherein the amount of transition metal derivative of saturated anacardic acid or anacardic acid enes or both is atleast 1 % wt/wt.
28. A reversible thermochromic composition as claimed in 27 wherein the binder medium
is selected from the group comprising polyurethanes, elastomers, polyacrylates,
poly(ethylene terephthalate)s (PET), polysytrenes, polyolefins, polycarbonates,
polyacrylics, polyacrylic acids, polyacrylamides, polymethacrylics, polyvinyl ethers,
polyvinyl halides, poly(vinyl nitrile)s, polyvinyl esters, polyesters, polysulfones,
polysulfonamides, polyamides, polyamines, polyimides and carbohydrates.

29. A reversible thermochromic additive substantially as herein described with reference to and as illustrated by the accompanying figure.
30. A process for making a material with thermochromic properties substantially as herein described with reference to and as illustrated by the accompanying figure.
31. A process for the production of a reversible thermochromic additive substantially as herein described with reference to and as illustrated by the accompanying figure.
32. A reversible thermochromic composition substantially as herein described with reference to and as illustrated by the accompanying figure.