Thermochromic container for hair removal compositions

Abstract

Thermochromic container for hair removal compositions The invention relates to a container for hair removal compositions, which is made of plastic, characterized in that said container comprises in the composition thereof at least one thermochromic material which contains two or more reversible thermochromic compositions, the first at a concentration of between 0.1 and 8% and the second at a concentration of between 0.05% and 8% by weight of the total weight of the thermochromic material, both being heat sensitive at a temperature above 40°C but different from each other, such that the first of them is heat sensitive in a lower temperature range than the second.Thanks to the thermochromic properties of the container object of the invention, said container has the capacity to change color depending on the temperature applied to it, after its heating, informing of the appropriate time of use and the prevention of non-use.

Description

Title of the invention: Thermochromic container for hair removal compositions Technical field

[0001] The invention falls within the field of cosmetics, specifically hair removal, and relates to a container with thermochromic properties for hair removal compositions.

[0002] Prior art Very different products are known in the field of hair removal for removing unwanted body hair, other than shaving. One type of composition, the most common, requires initial heating before being applied to the skin in a generally molten state, known as hot waxes. Once applied, it is allowed to solidify before being removed from the skin along with the unwanted hair. This is known in the technical field as depilation, since the hair is pulled from the skin at the root (patent ES2442918 T3). Also in common use in the prior art are warm waxes in which there is also prior heating but at a lower temperature and wax strips that are spread and applied to the area to be depilated, which use a support material to facilitate their removal (international application WO9730608 A1; ES2123430 B1).

[0003] Some of the most innovative compositions are in the form of an emulsion or cream, and can be applied to the skin at room temperature. The cream comprises a substance that degrades the keratin of the hair. Conventionally, said compositions are applied to the skin in the areas where unwanted hair is present, and left in this area for a predetermined time to allow the keratin of the hair to degrade. Finally, the composition along with the degraded hair is removed from the skin, generally with an instrument such as a sponge or spatula that drags it along. Such compositions are known in the art as depilatory creams (patent EP2355788 B1).

[0004] Hair removal wax compositions, which require preheating, can cause burn problems if the necessary precautions are not taken and if the instructions for use are not correctly followed, especially in the case of hot waxes.

[0005] Normally, the problem with these waxes generally results from the fact that the consumer has no reference of the temperature reached by the wax until it is used on the body, producing burns. Thus, the products that exist on the market either do not inform the consumer of the change in temperature of the product to be applied, or only inform when the temperature of use or non- use has been achieved. However, they do not indicate the temperature at which they should be used due to being at a suitable temperature and should not be used due to excessive heating in the same product. An example is found in patent ES2189990, in which a container for hair removal wax is described that has an applicator with a thermochromic compound to indicate the application temperature, which changes color between 40 °C and 60 °C. However, the invention described in ES2189990 has limitations: among the waxes that require heating, there are fat-soluble waxes and water-soluble waxes, and the applicator with a thermochromic compound does not work properly for the former, since it does not allow the pigment change to be correctly visualized during repeated uses due to the wax film that remains on the applicator during its use.

[0006] To solve the problems detected in the state of the art, and to avoid possible burns with these hair removal products, a container has been developed which informs the consumer by simple observation of when it is possible to make good use of the wax and when it is not recommended due to inadequate temperature conditions, either low or very high. The container proposed here has this information available to the user through a triple change of color and the intensity of said color: - At the origin of this, the product cannot be used and the color of the container is observed at room temperature; - At the first change in color due to a change in one of the pigments, the product is fit for use; and - When some areas of the container begin to appear in which the color changes again to another due to the color change of a second pigment, the product is too hot in these areas and there is a risk of burning, so it is not recommended to use it until it tempers. Statement of the invention

[0007] The present invention relates to a container for hair removal compositions (such as preferably warm waxes and hot waxes), which is made of a plastic material having thermochromic properties, characterized in that said plastic container comprises in the composition thereof at least one thermochromic material (dye type, for example masterbatch, known in French as master mixture) which contains two or more reversible thermochromic or thermosensitive compositions (pigments), the first at a concentration of 0.1 to 8% and the second at a concentration of 0.05% to 8% by weight of the total weight of the thermochromic material, both sensitive to heat at a temperature above 40°C (still cold for the application of the wax) but different from each other, so that the first of them is sensitive to heat in a lower temperature range than the second.

[0008] Thanks to the thermochromic properties of the container which is the subject of the invention, said container has the ability to change color depending on the temperature applied to it, after heating it. The container being specially designed to contain hair removal compositions, such as waxes which must be heated to be used, the change in color and the intensity thereof are intended to inform the consumer of the temperature that the container acquires when heated, so that by simple observation it is possible to check the temperature of the container to know if it is ideal for the use and / or application of the wax it contains.

[0009] The type of plastic material for the wax container is not particularly limited. However, the material from which the container is made can be many different types of plastics, preferably selected from the group consisting of: polypropylene (PP), polyethylene (PE), polystyrene (PS), polycarbonate and a combination thereof. Preferably, it is manufactured at a maximum temperature of 200 °C.

[0010] The hair removal composition is preferably a warm or hot hair removal wax. It should therefore be understood that any embodiment of the container, in which the pigments are added, is adapted to the product it contains, that is to say, according to the temperature suitable for its use or the overheating for each type of wax used, so that the composition of the thermochromic material is adjusted according to the temperature of use.

[0011] In this way, the thermochromic material is not particularly limited to a particular or specific type; the only condition, by the very nature of the invention, is that said thermochromic material must change color and intensity of said color within a suitable temperature range, which is determined by the wax contained in the container. Preferably, the first pigment is contained in the thermochromic material at a concentration of between 0.5 and 5% and the second pigment at a concentration of 0.1% to 5% by weight of the total weight of the thermochromic material. When the pigment or composition is indicated in this specification as being heat-sensitive at a certain temperature, this means that this pigment changes color from the original coloration thereof at room temperature to another coloration, even causing the coloration to disappear, upon stimulation at the indicated temperature.By using (at least) one colorant with two heat-sensitive compositions or pigments, the container can exhibit at least three colors depending on the temperature applied when the container is heated, namely: 1) the color formed by the basic color of the container itself plus that of the . colorant formed by the two thermochromic pigments at room temperature (room temperature being understood as that between 25°C and 30°C); 2) a characteristic color after the disappearance or change of color of one of the thermochromic pigments when a temperature suitable for the application of the wax is applied; and 3) a characteristic color after the disappearance or change of color of the second of the thermochromic pigments when a temperature too high for the application of the wax is applied.

[0012] Preferably, the upper temperature limit at which the first pigment completely changes color and reaches the maximum level of said change (the acquired color is homogeneous) coincides with the lower temperature limit at which the second pigment begins to change color.

[0013] The first pigment, which is the one that changes color at a temperature lower than the second, reacts at temperatures equal to or higher than 40 °C. The suitable temperature for applying the wax (preferably warm or hot) is understood to be between 42 °C and 64 °C depending on the type of wax. In the most preferred embodiment, the first pigment changes color at a temperature between 40 °C and 65 °C, while the second pigment changes color at a temperature between 45 °C and 70 °C.

[0014] It is obvious that the container acquires, when heated, a different (lower) temperature than that acquired by the wax it contains. Thus, for example, the container, depending on its thickness and the formulation of the wax it contains, generally acquires a temperature 1 °C to 11 °C lower than that of the wax it contains.

[0015] Obviously, the essence of the invention is the double color change of the container when the heating temperature varies, informing the appropriate time of use and preventing non-use; in this way, the type of color that informs of these moments is secondary, and depends on the type of thermo-chromic material selected. However, in a particular and preferred embodiment, the container with the coloring composition is violet in color at room temperature; the color of the first pigment disappears and the container becomes pink when the temperature is between 60 and 65 °C and the color of the second pigment disappears and the container becomes white (base color) when the temperature is equal to or higher than 65 °C, preferably higher than 70 °C.

[0016] Based on the above considerations, there are a wide variety of thermochromic compositions or pigments that can form the thermochromic material of the plastic container, such as those described in US Patent 4,028,118. The determining factor is that: a) said pigments change color at appropriate temperatures; b) they change color at different temperatures, between the two covering the temperature range of interest for the subject matter of the invention, and c) they change color over a wide temperature range, as specified above.

[0017] Description of the embodiments The experimental results of proofs carried out with containers prepared according to the present invention are described below. The objective of the proof is to verify whether the containers with thermochromic pigment dye or ink exhibit adequate behavior to change color at the desired times and conditions with warm or hot wax for hair removal, and to compare whether said behavior is the same with containers of different geometry, materials, capacity and colors.

[0018] Method The container is purple at room temperature, while it turns pink with the appropriate use temperature (due to the change or disappearance of the color of the first pigment) and white when it is too hot for its application (due to the change or disappearance of the color of the second pigment).

[0019] Three containers were used according to the invention, of different geometries and capacities (100 grams, 250 grams and 400 grams) and filled with two types of liposoluble wax, allowing them to cool before starting the tests. Subsequently, the wax was heated following the instructions for use and subsequently at successive intervals of 20 seconds of heating with 20 seconds of rest. A Daewoo 800W microwave was used to heat the container. The temperature of the wax was measured with a laboratory thermometer and the temperature of the walls of the container was measured with an infrared thermometer.

[0020] Results The results with the containers filled with 100 g, 250 g and 400 g of wax can be seen in the following table:

[0021] [Table 1] Behavior of the containers according to the present invention and of the waxes they contain as a function of temperature Wax Color Change 1 (PFC00272) 100 g 250 g 400 g Ta Pot wall T“ wax OK / NOT OK waxing T“ Pot wall T“ wax OK / NOT OK waxing T“ Pot wall T“ wax OK / NOT OK waxing Homogeneous color (pink) 55°C 61°C OK 55°C 65.3°C OK 55°C 61.3°C OK Starts at 63° 71° NOT OK 68° 68.3° NOT OK 60° 66°C NOT OK change from pink to white CCC cc Wax color change 2 (pfc00252) 100 g 250 g 400 g T“ Pot wall T“ wax OK / NOT OK waxing Ta Pot wall Ta wax OK / NOT OK waxing Ta Pot wall Ta wax OK / NOT OK waxing Even color (pink) 53 °C 53.8 °C OK 51 °C 56 °C OK 55 °C 59 °C OK Starting to change from pink to white 60 °C 66 °C NOT OK 65 °C 67 °C NOT OK 64 °C 69.6 °C NOT OK

[0022] Conclusion

[0023] After the results obtained, it was concluded that the containers exhibited optimal behavior for the intended purpose. Both the color change of the container, and the temperature of the wax in the 250 g and 400 g containers are a few degrees higher than those observed for the 100 g container. This difference in temperature of the container and the wax may be due to the homogenization of the product itself and to the geometry and thickness of the container.

[0024] Thus, the container works well with respect to the color change due to temperature if the color code is well explained in the instructions for use: - Wax suitable for hair removal when the container has a uniform pink color; -As soon as the white color begins to appear on the container, let the wax cool as it is too hot for application.

[0025] These results can be extrapolated to other container formats of different capacities and geometries such as 250 ml pots and 120 ml bottles and other types of wax such as liposoluble or hydrosoluble warm wax.

Claims

Claims

1. Container for hair removal compositions, which is made of plastic, characterized in that said container comprises in the composition thereof at least one thermochromic material which contains two or more reversible thermochromic compositions, the first at a concentration of between 0.1 and 8% and the second at a concentration of between 0.05% and 8% by weight of the total weight of the thermochromic material, both being heat sensitive at a temperature above 40°C but different from each other, such that the first of them is heat sensitive in a lower temperature range than the second.

2. A container according to claim 1, wherein the plastic material from which it is made is selected from the group consisting of polypropylene, polyethylene, polystyrene, polycarbonate and any combination thereof.

3. A container according to any one of claims 1 or 2, wherein the hair removal composition is warm or hot hair removal wax.

4. A container according to any preceding claim, wherein the first pigment is contained in the thermochromic material at a concentration of between 0.5 and 5% and the second pigment at a concentration of between 0.1% and 5% by weight of the total weight of the thermochromic material.

5. A container according to any preceding claim, wherein the upper temperature limit at which the first pigment completely changes color and reaches the maximum level of said change, producing a homogeneous color in the container, coincides with the lower temperature limit at which the second pigment begins to change color.

6. A container according to any preceding claim, wherein the first pigment changes color at a temperature between 40°C and 65°C, while the second pigment changes color at a temperature between 45°C and 70°C.

7. A container according to any preceding claim, which has a violet color at room temperature; a pink color when the color of the first pigment disappears; and a white color when the color of the second pigment begins to disappear.