Technical Field

The invention relates toa nanotechnologic, thermochromic coating to observe the overheating cases that may occur on the surfaces of ceramic insulators used at medium and high voltages.

The invention especially relates toananotechnologically developed coating material that combines cross-linking and sol-gel technology, supported with nano-sized particles, which changesits color irreversibly and preferably at a temperature of 50 °C and above. It can be applied permanently on ceramic surfaces by different methods such as dipping and spraying. It relates to a coating that can be cured by beam technology and whose physical properties are increased with the help of sol-gel technology.

The State of Art

If two different polymerization is used simultaneously to reinforce each other, the positive sides of the two different methods can be reflected in the final product in a way that supports each other. If the variables of polymerization such as temperature, concentration, curing technique andcross -linking degree are designed appropriately and complementary to each other, it is possible to design a final material where molecular level mixing, novel properties, functionality and performance enhancement will emerge. With these new properties, new materials different from traditional polymer or composite structures and more beneficial and efficient results are revealed. In general, organic polymers grow by condensation or addition polymerization, that is, by the monomer reaction and steady addition of monomers with each other. Condensation polymerization occurs by the removal of small molecules such as alcohol with small carbon number, water or ammonia from the long reacting chain during the progressionof monomer structures with each other. Apart from condenzation polymerization system, there are also inorganic polymerizationand the sol-gel reaction is one of the best example for inorganic step by step growth. It is known that inorganic polymerization produces silicate structures if silicon and oxygen are taken as precursor examples, or organic modified silicate structures when the starting molecules are organically modified. While these structures are forming, not only silicon but almost all transition elements in addition to boron, tin, gallium, indium, antimony and bismuth together with the controlled structures can contribute to this inorganic polymerization. As a result of these new monomers, new materials with different properties in terms of electronics, optics, elasticity or hardness are synthesized. Consequentlyit is also possible to add functionality (hydrophobic, oleophobic, hydrophilic oleophilic, antibacterial properties, increased dispersion feature, scratch and abrasion resistance, hardness and flexibility) to the final material obtained. Mixing these new structures with another copolymer at the molecular level requires special techniques. The dynamic polymerization in the sol-gel reactions generally occurs on the surface with another polymer precursor or particle structure. In these reactions, apart from hydrogen bonds, -OH condensation or alcohol condensation provides the growth of the skeleton, for example, structures such as -NH2, NH-, -OH, -Cl, COOH, NCO have the capacity to make covalent bonds with each other and are active structures for the progression of polymerization. Especially in acidic and basic catalysis of sol-gel reaction, it provides polymerization of different reagents at the same rate with each other. In general, basic catalysis provides the formation of particle-like structures in spherical geometry, since it has a rapid condensation. Acidic catalysis produces elongated polymer structures in sol-gel structures. This is because hydrolysis is faster than condensation and usually fiber or film type structures are obtained.

In addition to sol-gel polymerization, there are other techniques for the polymerization such as the double bonds contained in the monomers in radical-initiated environments can be extended. Such addition polymers join each other after the radical formation, attacking to the double bonds and expanding the monomers to the chain structure. Here, the amount of monomer and the properties of the polymer to be formed, the temperature, the energy of the UV light that will initiate the radical formation, and other groups of the structure determine the complex details of the final polymer. If radical or condensation polymerization is to be used together with inorganic polymerization, the whole formulation should be well designed and monomer structures should be mixed in a controlled manner. In order for these polymer structures to be mixed especially at the molecular level and become an effective nanocomposite, the mentioned monomeric structures are programmed and interacted with each other for the synthesis of materials with novel properties with other completing components. While condensation structures generally cured thermally, radical hardening plays also and important role. If the amount of radical initiator is too high, polymerization will start multiple oligomers simultaneously and rapidly at different reactionpoints in the pot and short-chain structures will form during curing process. Therefore, the amount of initiator of radical polymerization is very important and must be well oriented. For nanocomposite structures, the integration and hardening of a sol-gel-based starting material or a radically polymerizable trialkoxysilane compound with the system will result in an inorganic supported organic radical polymerization. Free radical polymerization is given below. initiator +

I - CHX - CH ₂ +

CHX=CH ₂ i - CHX - CH ₂ - CHX - CH ₂

The documents determined in the patent and literature research carried out for the state of the art are summarized below.

A patent numbered US 7,465,693 B2, the polymer that can be used like asphalt or cement or together with a traffic sign defines a thermochromic structure that varies its color. It has been used in an application especially in terms of showing that the surface is at a temperature close to or below the freezing point of water.

In GB2401710A1, a thermochromic method of determining the temperature on its surface for the door system has been carried out. It can be considered as a warning method, especially in fire situations.

WO2015135949A1 describes an emulsion structure containing thermochromic leuco dye pigment obtained by microencapsulation. 5-30 % pigment, 30-50 % polymeric structure, 1-10 % emulsification molecule, 30-60 % solvent and leuco colorants are defined. Thermochromic systems with polymeric structures are revealed for the utilization. Brief Description of the Invention

The present invention relates to thermochromic coatings that change color with heat for ceramic type insulators used at medium and high voltages, which meet the above-mentioned requirements, eliminate all disadvantages and bring some additional advantages.

The invention is inspired by current situations and aims to solve the above-mentioned disadvantages.

The main purpose of the invention is to develop a coating material to be applied to the surfaces of ceramic insulators used at medium and high voltages in order to observe the situation that will occur due to heating.

Another purpose of the invention is to combine sol gel technology with radical polymerization and convert the obtained thermochromic formulation into an irreversible nanocomposite material quickly and reliably. In nanocomposite structures, one of several different phases is necessarily in nanometric dimensions and a special need or performance increase is observed. The nanometric phase creates a special interaction between the structure and nanostructure formed by one of the polymerization methods, and the nanocomposite material obtained due to its very large surface area causes very new and advanced mechanical and chemical properties. Therefore, with this invention, in order to combine sol gel technology with radical polymerization and transform the thermochromic formulation obtained into an irreversible nanocomposite material quickly and reliably, a completely (both chemically and physically) defined SiO2 nanoparticle, which can be added to the nanocomposite structure singly or in multiples, is used.

Another purpose of this invention is to synthesize a nanotechnologic coating which irreversibly changes its color at 50 °C or above. This nanotechnologic coating can be applied onto the ceramic insulator structures which changes its color irreversibly was obtained. By this way, problems arising from the insulator temperatures can be detected. This coating material is obtained by nanotechnological method by modifying proportions and different chemical features.

With this invention, an irreversible manifestation of the situation, which occurs as a result of heating in insulator systems due to an external reason or current jumps is described. A thermochromic material like nanotechnological coating which can be used for all kinds of substrates was developed.

The structural and characteristic features of the invention and all its advantages will be understood more clearly due to the detailed explanation given below, and therefore the evaluation should be made by taking this detailed explanation into consideration.

Detailed Description of the Invention

In this detailed description, the thermochromic coating and the properties of all components are described in a way that does not have any limiting effect.

The invention relates to a nanotechnological coating that changes color irreversibly with heat, to be applied to the surfaces of ceramic insulators in order to observe the situation that will occur due to heating. The nanotechnological comprises at least one encapsulated thermochromic pigment, SiO2 nanoparticles used to improve physical properties, at least one acrylic silane compound, at least one radical initiator to cure the mixture by UV activation, at least one acrylic resin, at least one amine -based silane compound, and at least solvent.The invention is based on combining two different polymerization system and an encapsulated low temperature thermochromic pigment together with nano-sized monodisperse SiO2 nanoparticles and a suitable radical polymerization with an acrylic resin together with a UV-activated radical initiator. This UV curable inorganic organic polymer structuredescribes a composition containing asol-gel reagent with another hardening silane reagent containing amines, as well as solvents (EtOH, IPA, Butyl Glycol, Acetone).

The coating material of the invention contains encapsulated thermochromic pigment. As the aforementioned pigment, a pigment that changes color at 50 ± 2 °C (at low temperature) and turns irreversibly from white to bright magenta is used. The pigment used in the invention is preferably LCR HALLCREST irreversible Magenta 60. In general, the pigment sizes are smaller than 10 microns and can be reacted with the resin during dispersion. In one embodiment of the invention, it is possible to add the thermochromic pigment in the solvent or directly to the dispersion medium. Especially at this stage, a good homogenization is required. This pigment, which changes color without recycling as encapsulation, has poor coverage and should be used in relatively high amounts. Coating material also includes S iO 2 particles were also synthesized by using the modified Stober method to improve the physical properties of the thermochromic coating. The addition of SiCE particles is of great importance for the reduction of molecular shrinkage caused by the nature of the final structure, especially playing an important role in the sol-gel reaction.

These nanoparticles can be obtained with different modifications on their surfaces. In the synthesis of nanoparticles, an ammonia-type base is added together with isopropyl alcohol and distilled water to bring the pH to around 10 -11. After a certain mixing time, silane initiators and TEOS can be added individually or in pairs to produce a modified particle which its size is controlled finely. The nanoparticles can be obtained in a spherical structure and in a fine tunedmonodisperse and size controlled manner, as evidenced by SEM (Scanning Electron Microscopy-Scanning Electron Microscopy) analyses.

In the invention, SiO2, AI2O3, ZrO2 nanoparticles, which can be used for the same purpose, are prepared from alkoxide compounds and cleaned by washing several times. It can be used especially because AI2O3 structures provide hardness. Since these nanoparticles are prepared separately for thermochromic coating, their size and surface can be controlled. With the increase of nanoparticles, the dispersion time of the nanocomposite coating mixture increases. In the use of nanoparticles, it is important that the dimensions are nano-sized and transparent polymers that will show transparent properties and that they will not prevent thermochromic color change. The nanoparticles used should have properties like SiCE nanoparticles.

Acrylic silane compound used in the invention generally defines a trialkoxy silane compound containing an acrylic side group. Other than different alkoxides, such as tetraalkoxysilane, methyl triethoxysilane or short side groups, compounds such as octyltrialkoxysilane, propyltrialkoxysilane can be used.

Binary mixtures of these compounds can be prepared by considering their hydrolysis condensation rates. Basically, the acrylic alkoxysilane compound forms the main structure and its hydrolysis and condensation must be initiated at least 12 hours before the coating reactions. The environment should be controlled since the amount of water required for the hydrolysis reaction, which is added directly, if not in large amounts, in equivalent amounts can be exothermic. Acrylic silane compound is prepared by adding the required amount of water for hydrolysis and condensation by mixing it with another silane compound at molecular level by desire. This silane system provides interaction with -OH functional groups on the surfaces of structures such as SiO2, AI2O3, ZrO2, which are especially in nanoscale and will be added to the system. Single or multiple silane system can be monitored with FT-IR.

In addition to the acrylic silane compound, different resins are added to the medium as a support component. These can be generally long-chain molecular structures with organic structures and acrylic side groups, but previously synthesized by the addition of acrylic groups. Said molecules can be called co-resins. The calculated amount of radical initiator is obtained by taking this resin into account.

Acrylic resin, which is included in the coating composition, can be added in a single or copolymerized form with another structure. The acrylic structure greatly increases the surface covering and cross-linking character of the system. After the acrylic structure is mixed with the initial acrylic silane, it should be mixed preferably at a speed of around 2000 - 4000 rpm. This will also increase inorganic nanoparticle dispersion. Mixing can be preferably 3-5 hours with the nanoparticle, the starting silane material and the additional acrylic component. Acrylic crosslinker provides better adhesion of the coating to the surface with thermochromic pigment.

Radical initiators are systems that produce radical electrons with UV light, and they are usually broken down by different energies and the molecular structure turns into a multiple state. Basically, ketone structures or peroxide structures can be used as radical initiators. In the invention, the radical initiator is added at the end to be activated by UV and cure the mixture. Although it is usually added in small amounts, the proportions may vary with the composition. After addition, the coating composition is dispersedfor a while at low speed (preferably 250-500 rpm) in a controlled manner. After the mixture with radical initiator is mixed for a certain period of time, it can be applied to all kinds of glass, metal, wood, ceramic surfaces.

After preparation, the coating composition of the invention can be applied by spray coating, dip coating or spin coating method for flat surfaces. Mentioned coating composition can be applied to insulator systems, glass surface, metal surfaces or wooden substrates. The applied coating generally transforms from white to bright magenta at around 50 + 2 degrees. This transformation occurs irreversibly with temperature activation. After the coating composition is applied to the surface, the coating is cured with a 600 W lamp for the required amount of time, usually 15 cm or the required distance. Before the coating is applied, the insulators should be cleaned with a surfactant cleaner and then dried.

In the invention, suitable solvents for the coating material can be used as single or multiple mixtures. Preferably, solvents such as EtOH, IPA, Butyl Glycol, Acetone are used. Long curing times can be observed if solvents such as butyl glycol or methoxypropylacetate are used. However, systems such as alcohol or acetone require a fast and controlled drying system.

In this coating mixture, Irgacure 184 or similar structures can be used for the polymerization of acrylic structures. At the end of the reaction, irreversible thermochromic coating material synthesis is realized together with the amino silane compound.After the hydrolysis of the silane compound is completed for total synthesis, nano-sized SiCL nanoparticles are added and homogenization is carried out with the addition of acrylic resin. A mixing speed between 2000 rpm and 3000 rpm can be used, and after the thermochromic pigment addition homogenization of the mixture is conductedin a more controlled manner and the homogenization is completed in 3-6 hours. Cooling may be required while this dispersion is carriedotherwise it was observed that the pigment becomes darker as the temperature increases. Afterwards ready formulation is applied to the desired surface by spray method, or if desired, with viscosity adjustment, serigraphic coating, dipping method and spin coating. Before coating, the surfaces of the insulators are prepared and cleaned with an alcohol (EtOH) or acetone solutions. After the spray application, curing is performed with the required amount time of with 600 W lamp.

In a typical example of the invention, the weight ratios for the synthesis process;

• Solventsin the range of 3-8%,

• Silane in the range of 40-60%,

• Acrylic resin in the range of 15-25%.

• SiO2 nanoparticle 1-6% range

• Radical initiator in the range of 2-8%

• Amine-based silane compound 2-10%

• Thermochromic pigmentin the range of 5-25% can be realized. The starting silane used in the invention is preferably MEMO (3 -methacryloxy propyl trimethoxy silane) compound. The amine-based silane compound is preferably AMEO (aminopropyl triethoxysilane) compound. AMEO is used to strengthen the hardening. Structures containing amino structures such as AMEO, DAMO, TRIAMO are prepared in alcohol or only hydrolyzed for the secondary reaction and used for the second curing in the reaction. In secondary curing, epoxy-containing structures or epoxysilane structures that are structurally suitable for amine groups can be used.

In this process, the compositions vary depending on the properties of the product to be obtained.

In the invention, nanoparticles are added generally in solid form, the resin structure and pigment solution are viscous liquids, silane compounds, radical initiators, amine-containing silane are in liquid form. After dispersion, the mixture is transformed into a standard industrial paint and the radical initiator is added last, and the system is ready to be cured by UV light. Solvent can be used for the whole mixing system for dilution aim and hydrolysis-condensation adjustment. Paint applications are carried out at room temperature.

In this text, the usage area and preferred application area of the invention are specified. However, it is clear that a person skilled in the art can also apply the whole, part, essential features and/or characterizing part of the invention to other purposeful fields. Therefore, it is obvious that such structuring will lack the criteria of innovation, and especially of overcoming the state of the art. Numerous specific details are set forth in the specification to provide a full understanding of the invention. However, it is possible to obtain the invention based on the technical features defined in the claim without using all of the mentioned details or alternatives. The component alternatives mentioned for the invention should not be considered as being limited to those listed.