ES2702971B2 - SOLID SURFACE WITH THERMO-PHOTOCHROMIC PROPERTIES - Google Patents

Description

DESCRIPTION

SOLID SURFACE WITH THERMO-PHOTOCHROME PROPERTIES

FIELD OF THE INVENTION

The present invention belongs to the technical field of solid surfaces or "Solid Surfaoe", more specifically to a solid surface that presents a color change when applying a source of light or heat.

BACKGROUND OF THE INVENTION

Chromoactive materials respond with a color change to an external stimulus. The phenomenon of color change is classified and named based on the stimulus that causes the change. Thus, photochromism is a color change, usually from colorless to color, caused by UV light, electrochromism is a reversible color change through oxidation or reduction produced by an electric current or potential, and thermochromism is a change color caused by heat. These are the most common phenomena within chromoactive materials, however, there are many others that cater to different stimuli and that have evolved in recent years, although they are not yet at the same level of development.

Photochromic or photochromic materials are materials that, when sunlight or high UV light impinges on them, reversibly change their color (these materials are not seen in the dark).

On the other hand, thermochromic materials are materials that change color with temperature. They allow to select the color and the temperature range, allowing a very wide range of applications. In addition, they can be reversible or change color permanently with the increase in temperature depending on the pigment that is incorporated. They are normally materials of a semiconductor nature.

There are examples in the state of the art of materials with these color change properties that vary depending on light (photochromic) and temperature (thermochromic). An example is patent ES2645297B1, which describes a film of polymeric material with thermo-photochromic properties for color regulation of glazed surfaces and plastic materials. The invention relates to a film of polymeric material with thermo-photochromic properties comprising capsules of micrometric and / or nanometric size embedded and deposited in a homogeneously dispersed manner in its structure, said capsules being formed by a solid wall of a polymer other than polymer of the film containing within it a dispersion of at least one T-type photochromic compound that is selected from the group consisting of spiropyrans, spiroxacins, chromanes and any combination thereof, in a liquid phase-change type material non-volatile acid that interacts with photochromic depending on temperature.

This film can be used as a coating material for surfaces to which it is desired to confer photochromic color-changing properties, such as whiteboards, device screens, advertising surfaces, vehicles, and glass or plastic surfaces in general. However, this system has complex and expensive operation due to encapsulations with T-type chromophores. In addition, they have as limitations that it is not possible to obtain the entire range of desirable colorations and the change of color always implies a transparent beginning or end.

GB2431159A describes a composition comprising a microencapsulated thermochromic and / or photochromic material dispersed in a crosslinked polymer matrix. The polymeric matrix can comprise acrylic and / or polyvinyl polymers and the thermochromic material can comprise a liquid crystal. The composition contains 10-50% by volume of the polymer, 1-20% by volume of the microencapsulated material and 35-90% by volume of water based on the total composition. Unfortunately, this water base limits the use of many polymers and pigments and color change always implies a transparent start or finish

DESCRIPTION OF THE INVENTION

The present invention refers to a solid surface with thermophotochromic properties that has advantages in its composition and properties compared to the formulations described in the state of the art.

The present invention describes the use of a combination of coloring agents compatible with organic polymeric systems, overcoming the limitation of the aqueous phase, where the initial coloration can be selected to taste and expensive microencapsulations are not required.

When the solid surface of the present invention is subjected to the action of radiation (solar or different types of UV) or heat, the initial color changes to another color. When you stop applying this source of radiation or heat, the surface recovers the initial coloration. Therefore, the color change does not imply a transparent beginning or end, as occurs in the state of the art.

In a first aspect of the invention, the solid surface with thermophotochromic properties is composed of 30-35% by weight of a polymer, 60-65% by weight of mineral filler, 0.5-1% by weight of agent dye with respect to the total weight, and 0.4-0.6% by weight of polymerization initiating agent. All these weights are expressed with respect to the total weight.

In another aspect of the invention, the polymer is selected from the group comprising polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), ethyl cellulose, methyl methacrylate monomer (MMA), polymethylmethacrylate (PMMA), polystyrene, acrylic, styrenic, polyurethane , polyurea and polyamide. Preferably, the polymer is polymethylmethacrylate (PMMA).

In another aspect of the invention, the mineral filler is selected from the group comprising alumina trihydrate (ATH), quartz, oxalates, and carbonates, or mixtures thereof. Preferably, the mineral filler is alumina trihydrate (ATH).

In another aspect of the invention, the coloring agent is selected from the group comprising rutile TiO2, ZnS, SnO2, ZnO, SnO2, CdS, Fe2O3, Cu2O, WO3 and TiO2 anatase, or mixtures thereof. Preferably, the coloring agent is ZnS or TiO2 anatase.

These coloring agents are generally used as pigments, but for such use it is necessary that the transition metals (such as Zn, Ti, Cd, Sn, Cu, W, among others) be in stable crystalline structures or that they present coatings and / or stabilizers. However, the opposite is required in the present invention.

In the present invention, metals are used that have certain structural instability or crystalline defects, which with the effect of radiation or heat generate a color change. With this, oxygen vacancies are easily generated in the crystalline structure that provide a change in hue.

In another aspect of the invention, the polymerization initiating agent is tert-butyl peroxide maleate (TBPM), tert-butyl hydroperoxide, or benzoyl peroxide.

In a last aspect of the invention, the solid surface may additionally contain in its composition an organic or inorganic pigment.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1. Shows different solid surfaces with thermo-photochromic properties of the present invention. To the left of each solid surface the main coloration is observed and to the right the coloration obtained after applying radiation or heat.

DESCRIPTION OF MODES OF REALIZATION

Having described the present invention, it is further illustrated by the following examples.

Example 1. Preparation of different embodiments of the solid surface with thermo-photochromic properties of the present invention and results obtained 7 embodiments of the solid surface with thermophotochromic properties of the present invention were carried out. Generally, a coloring agent was added to a mixture of inorganic / organic pigment. This mixture was stirred and subsequently added to the inorganic filler and polymer, homogenizing. Subsequently, the polymerization agent was added and the solid surface was obtained. This procedure was carried out for solid surfaces C, D, E, F and G.

In the case of solid surfaces A and B, no inorganic / organic pigment was used, therefore, the coloring agent was added directly to the inorganic filler and the polymer, homogenizing. Subsequently, the polymerization agent was added and the solid surface was obtained.

Table 1 describes the compositions used in more detail.

Table 1. Realizations of the solid surface

These solid surfaces are subjected to the action of radiation (solar or different types of UV) or heat, changing their initial coloration to another final coloration. When you stop applying this source of radiation or heat, the surface recovers the initial coloration.

A color space has been used to assess the color variation of the solid surface. This color space is a standardized method that allows you to express the color of an object using an annotation type, such as numbers.

Specifically, the L * a * b * color space, also referred to as CIELAB, has been used, currently being one of the most popular and uniform color spaces used to evaluate the color of an object.

This color space is widely used because it correlates numerical color values consistently with human visual perception. Researchers and manufacturers use it to evaluate color attributes, identify inconsistencies, and precisely express their results to others in numerical terms.

The L * a * b * color space was modeled based on an opposing color theory that two colors cannot be red and green at the same time or yellow and blue at the same time. As shown below, L * indicates the luminosity and a * and b * are the color coordinates.

- L * = luminosity

- a * = red / green coordinates (+ a indicates red, -a indicates green)

- b * = yellow / blue coordinates (+ b indicates yellow, -b indicates blue)

The X-Rite Ci64 portable spectrophotometer was used to easily quantify these color attributes. This type of instrument allows determining the color of an object within the color space and shows the values for each coordinate L *, a *, and b *.

Table 2 collects the information obtained from the initial and final color space values for various embodiments of the solid surface of the present invention. The subscripts of L, a, and b represent the initial value as L ^o , a ^o , and b ^o and the final value as L ^f , a ^f , and b ^f . These color changes can also be seen in Figure 1.

Table 2. Initial and final color space values for various embodiments of the solid surface of the present invention.

In conclusion, a solid surface formulation has been obtained with thermo-photochromic properties compatible with the production system and low cost. This formulation allows to be applied on any basic color using pigment pastes and producing a very visible color change.

Claims (8)

1. A solid surface with thermo-photochromic properties characterized by comprising: - 30-35% by weight of a polymer with respect to the total weight, - 60-65% by weight of mineral load with respect to the total weight, - 0.5-1% by weight of coloring agent selected from the group comprising TiO ² rutile, ZnS, SnO ² , ZnO, CdS, Fe ² O ³ , Cu ² O, WO ³ and TiO ² anatase, or mixtures thereof , with respect to the total weight, and - 0.4-0.6% by weight of polymerization initiating agent with respect to the total weight. 2. The solid surface according to claim 1, wherein the polymer is selected from the group comprising polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), ethyl cellulose, methyl methacrylate (MMA), polymethylmethacrylate (PMMA), polystyrene, acrylic , styrenic, polyurethane, polyurea and polyamide. 3. The solid surface according to claim 2, wherein the polymer is polymethylmethacrylate (PMMA). 4. The solid surface according to claims 1 to 3, wherein the mineral filler is selected from the group comprising alumina trihydrate (ATH), quartz, oxalates and carbonates, or mixtures thereof. 5. The solid surface according to claim 4, where the mineral filler is alumina trihydrate (ATH). 6. The solid surface according to claim 1, where the coloring agent is ZnS or TiO ² anatase. 7. The solid surface according to claims 1 to 6, wherein the polymerization initiating agent is tert-butyl peroxide maleate, tert-butyl hydroperoxide or benzoyl peroxide. 8. The solid surface according to claims 1 to 7, characterized in that it further comprises an organic or inorganic pigment.