DESCRIPTION

Field of the invention

The present invention relates to emulsions comprising multi-microencapsulated thermochromic leuco colorants, for application thereof on the surface of the human body. The emulsion of the invention is applied on the human body in the form of a film. The microcapsules provide a different color as a function of the temperature of the corporal surface and are thus useful for carrying out a thermochromic study of the corporal surface. The microencapsulated thermochromic leuco colorants of the present invention are, for example spironolactones, fluorenes and spiropyrans. The present invention may be applied to the breast area where the thermochromic study is useful for carrying out a diagnostic assessment for breast cancer.

Background of the invention

In the prior art, various films have been described which contain thermochromic microcapsules. These films are applied to the human body in order to be able to carry out a thermographic study. The films are applied to the human body generally by means of the use of adhesives.

For example, said films can be applied to the breast area, where said thermographic study is useful for carrying out a diagnostic assessment for breast cancer. The films are applied to the breast area by means of the use of adhesives.

The films described hitherto exhibit poor adaptation on the corporal surface, in particular in the areas with a large number of bumps such as for example the breasts. Such poor adaptation results from the difficulty of placing the films on the area.

Furthermore, they are carried out with thicknesses greater than one millimeter, which causes a reduction in the output of thermal conductivity and thermal inertia in the adjacent areas.

Due to the lack of adaptability, the option to carry out a diagnostic assessment by symmetry is impossible since the diagnostic conditions are not the same at each side.

The problem posed by the technique consists of providing a film in order to carry out a thermographic study of the human body, with improved properties for adaptation to the human body and homogeneity of the emulsion with respect to the films and emulsions described in the prior art. The existing emulsions comprising leuco colorants allow for the use thereof in high precision applications in which more than 3 different leuco colorants are required. This is due to the difficulty of maintaining a single emulsion in a homogenous manner with more than 3 thermochromic leuco colorants due to their different physiochemical properties. This dehomogenization of the mixture of the different leuco colorants is made worse when the viscosity of the emulsion is reduced. Said viscosity is vital in the dispersion, provided by means of spraying, since it must be reduced in order for the dispersion thereof to be possible. DESCRIPTION OF THE INVENTION

The present invention, according to how it is defined below, provides a solution to the problems posed in the technique.

The present invention provides an emulsion comprising 5-30 % by weight of at least one microencapsulated thermochromic leuco colorant having a polymeric coating, between 30 and 50 % by weight of a polymer, between 1 and 10 % by weight of emulsifying and preserving agents, between 30 and 60 % by weight of solvent, hereinafter the emulsion of the invention.

In the emulsion of the invention, the sum of all the indicated percentages is equal to

100 %.

The emulsion of the invention is capable of creating a thermofilm in- situ at the time the product is applied to the surface to be controlled.

The emulsion of the invention remains in liquid state while it is in the receptacle which stores the emulsion, it being able to be applied by means of any type of propelling technology or dispersion (spray, pulverizing, brush...).

Thus, another embodiment is the emulsion of the invention, wherein its form of presentation is a spray.

The emulsion of the invention can be applied to the corporal surface, in particular to the breast area (breast cancer) or difficult corporal contours in order to be able to carry out a thermographic study. The emulsion of the invention contains a mixture of different leuco colorants, each leuco colorant having a determined base color and a determined action temperature and reflects the temperatures of the areas by means of chromatic matrices.

By means of the formation of the film being in direct contact with the surface of the body, the heat transfer properties are improved, while allowing uniformity and thus a diagnostic assessment by corporal symmetry.

When it is a film in a solid final state, it is released from the skin with ease, leaving practically no residues since the thermochromic leuco colorants are adhered to the polymer. The solvent present in the emulsion of the invention is the base of the emulsion of the invention, the rest of the ingredients are mixed in said solvent. The water and the isopropanol are adequately dissolved.

Thus, another embodiment is the emulsion of the invention, wherein said solvent is water and isopropanol.

The polymer present in the emulsion of the invention is maintained in the emulsion in contact with the solvent. It is responsible for forming a polymeric film in-situ in the application area. Said polymeric film fixes the thermochromic leuco colorants. The latex, the vinyl and the polyurethane provide good results like the polymers.

Thus, another embodiment is the emulsion of the invention, wherein said polymer is selected from the group composed of latex, vinyl and polyurethane.

In the emulsion of the invention, there can exist a mixture of various thermochromic leuco colorants. Each leuco colorant has a different activation temperature. As the temperature of the application area varies, the colors which show the leuco colorants vary. The leuco colorants can be spironolactones, fluorenes and spiropyrans, etc, without being limited to these.

Thus, another embodiment is the emulsion of the invention, wherein said thermochromic leuco colorant is selected from the group composed of spironolactones, fluorenes and spiropyrans.

The precision of the change of state (change of coloration) is realized with a margin of approximately +/-0.5 °C. The action temperatures are between approximately 28 °C and 36 °C. The thermochromic leuco colorants are dissolved in the emulsion, remaining fixed with the polymer once the rest of the components have evaporated. Depending on the clarity sought in the diagnostic assessment, more leuco colorants or less leuco colorants can be used. If greater clarity is sought, a mixture is carried out with little diversity of microencapsulated thermochromic leuco colorants.

The leuco colorants are microencapsulated; the microcapsules have a size of approximately 5 microns. In the microcapsules, the leuco colorants are coated with a water- based polymer having inert properties. The aminoplasts and the polyamides/polyureas are suitable for this coating. The percentage of leuco colorant/coating is approximately 85 %/15 % respectively.

Thus, another embodiment is the emulsion of the invention, wherein the proportion of leuco colorant/polymeric coating is 85 %/15 %.

And another embodiment is the emulsion of the invention, wherein said polymeric coating comprises aminoplasts or a mixture of polyamides and polyureas. The emulsifying and preserving agents present in the emulsion of the invention are responsible for keeping the components dissolved in a homogeneous manner and keeping the entire combination in good condition in order to avoid depositions, dryness and premature deterioration.

The present invention also provides a method for multi-microencapsulation of thermochromic leuco colorants which comprises:

(a) mixing microencapsulated thermochromic leuco colorants having a polymeric coating with an oil-based solution,

(b) mixing the resulting solution of step (a) with the suspension which comprises water-based gelatin and aminoplast or a mixture of polyamides and polyureas and

(c) adding a cross-linker,

hereinafter the method of the invention.

The process of multi-microencapsulation ensures the homogeneity of the mixture of leuco colorants during its useful life, allowing the mixing of various leuco colorants with different physical properties (density, weight, size) in one single emulsion independent of the viscosity of the final emulsion. Said viscosity can be adapted by means of the polymeric component without affecting the homogeneity of the mixture of the leuco colorants, with the aim of obtaining an optimal dispersion by means of spraying, in turn, fulfilling the functionality of the product.

The method of the invention allows greater homogeneity of the final mixture to be obtained. The method consists of carrying out a second microencapsulation, combining in its interior various microcapsules with leuco colorants having a different activation temperature. By means thereof, an attempt is made to ensure that the mixture is as homogenous as possible and thus avoid errors in the thermographic mapping due to poor distribution of the components in the application area.

The multi-microencapsulation is achieved by carrying out polymerization under stirring. While the leuco colorant microcapsules are mixed inside a receptacle with an oil- based solution, an aminoplast suspension or a polyamide and polyurea mixture is poured into water-based gelatin.

Lastly, small microspheres which contain the leuco colorant microcapsules are obtained by affinity. In order to finalize the process, the cross-linker is added, such as for example glutaraldehyde at 25 % in molar ratio, achieving the hardening of the exterior walls.

The cross-linker is added during the stirring process. It is added at this point in order to avoid microspheres, which have not yet hardened, binding due to the chemical affinity once the stirring has been completed, increasing the size of the spheres. Thus, it is an important component of the process, since the smallest possible size of the final capsules is sought.

Another embodiment is the method of the invention, wherein said cross-linker is glutaraldehyde.

Some advantages of the emulsion of the invention and the application of said emulsion of the invention to the human body are cited below:

-Approximate thickness of 0.5 mm

-Better thermal conductivity

-Absence of thermal inertias

-Perfect adaptability

-The polymeric base allows the retention of a large quantity of pigments

-The diagnostic assessment by thermal symmetry is enabled

-Easy visual interpretation of the results

-Easy application and extraction

PREFERRED MODES OF EMBODIMENTS

Example 1. Preparation of an emulsion according to the invention

The following emulsion was prepared:

Emulsion 1:

50 g deionized water,

37.5 g latex rubber

2 g ammonia and ammonia hydroxide,

0.3 g thiram,

0.2 g carboxin and

10 g microencapsulated spironolactones

A mixture of spironolactones was used, having a functional temperature of between 28 and 36 °C. The composition of said mixture is indicated in Table 1.

Table 1. Composition of the mixture of spironolactones; palette of colors

Optical color Activation temperature (°C) Proportion (%)

Light yellow 32, 35 25

Light turquoise-blue 34 17

Light pink 33 16

Intense red 32 12

Intense purple 31 10

Intense navy blue 30 10

Dark brown 29 5

Black 28 5