A white colored coating without pigments

Abstract

The invention relates to an organic white colored coating without dyes or pigments, and to obtaining such a coating. In particular, the invention relates to a procedure and application which eliminates the use of white dye or white coloring titanium dioxide pigment in organic-based coatings curable with ultraviolet and / or visible wavelength light.

Description

[0001] A WHITE COLORED COATING WITHOUT PIGMENTS

[0002] Technical Area

[0003] The invention relates to an organic white colored coating without dyes or pigments, and to obtaining such a coating.

[0004] In particular, the invention relates to a procedure and application which eliminates the use of white dye or white coloring titanium dioxide pigment in organic-based coatings curable with ultraviolet and / or visible wavelength light.

[0005] Known State of the Art

[0006] Pigments are used to color paints, inks, plastics, fabrics, cosmetics, food and other materials. Most pigments used in manufacturing and the visual arts are dry colorants and are usually ground to a fine powder. White pigment, which is the most important of these pigments and constitutes about 80% of them, is white in color. The main ingredient of white pigment is titanium dioxide.

[0007] Titanium dioxide (TiO2) is a pigment widely used in various coatings, paints and other materials due to its excellent whitening and opacifying properties. However, there are several significant disadvantages associated with its use. Titanium dioxide production has a significant environmental footprint. The extraction and processing of titanium ore leads to air and water pollution as well as the generation of hazardous waste. There are also concerns about the potential environmental and health impacts of nanoparticle-sized titanium dioxide that can be released during production and application processes. Titanium dioxide is generally more expensive than other white pigments such as calcium carbonate or barium sulphate. This increases the overall cost of coatings and other products containing this pigment. On the other hand, titanium dioxide is a photocatalyst, i.e. it promotes the breakdown of organic compounds when exposed to UV radiation. This leads to degradation of the coating or the substrate to which it is applied, especially in outdoor environments with high UV exposure, and can be a disadvantage in some applications. While titanium dioxide is highly effective in providing opacity and whiteness, it can sometimes require a higher loading or thickness of the coating to achieve the desired level of coverage and hiding power compared to other pigments. Finally, there is ongoing debate and scientific studies on the potential health risks associated with exposure to titanium dioxide in nanoparticle form. This has led to increased scrutiny and regulation of its use in certain applications, such as personal care products. To summarize, it is important to note that the disadvantages of using titanium dioxide in coatings can vary depending on the formulation, application and overall performance requirements of the coating system. These factors need to be carefully considered when selecting the appropriate pigment for a particular application.

[0008] The documents identified in the patent and literature search for the state of the art are summarized below.

[0009] As stated in the titanium compounds section of the Kirk-Othmer Encyclopedia of Chemical Technologies, titanium dioxide has a high refractive index compared to other inorganic pigments. For this reason, long efforts are required to achieve true whiteness in organic coatings in which it is used. This situation negatively affects the production process.

[0010] As with all other inorganic metal oxides, the surface of titanium dioxide has a high polarity and therefore smaller and finer titanium dioxide particles tend to agglomerate together under environmental and processing conditions. These agglomerates affect the properties of the pigment such as gloss, opacity, shade difference and shelf life, as well as affecting a parameter such as powder fluidity, which is very important during the dispersion of the pigment. Difficulties encountered in the dispersion of the product undermine the production process and cause unexpected costs.

[0011] As stated in the brochures published by different pigment manufacturers, the white color given by titanium dioxide is the result of the scattering of the incident light by hitting the titanium dioxide particles. This scattering depends on the size of the titanium dioxide particles. For this reason, the titanium dioxide pigment to be used in coatings must be ground in the required amount and the particle size must be reduced to a certain extent. This situation poses a difficulty in terms of maintaining quality standards in the produced products.

[0012] Moreover, in the brochures published by the companies, it is reported that in the coatings made with titanium dioxide itself, the inorganic coating surface should be treated with organic chemicals after the process. The main classes of these chemicals are polyols and organic amines. The polyols used are swept from the surface by water and similar factors over time, causing the coating to lose its properties. The other chemical class, organic amines, are known for the carcinogenic effects of amine oxide compounds formed as a result of reaction with oxygen in the air. For these reasons, treatment with chemicals may cause human and environmental health. An example of the known state of the art in the literature research is document numbered CN114644850A. The said document relates to a white paint having high hiding power and a pigment used to increase the hiding power of this white paint. It is stated that the said paint contains pigments, amino resins, amine compounds, polyester resin, acrylic emulsion, acrylic resin other additives, color paste, 0 dodecyl phosphoric acid, solvent and the said pigment contains aluminum pigment and titanium dioxide pigment. However, there is no mention of a pigment-free white coating in the said document.

[0013] As a result, due to the negativity described above and the inadequacy of the existing solutions on the subject, it has become necessary to make a development in the relevant technical field.

[0014] Brief Description of Invention

[0015] The present invention relates to an organic white coating obtained without the use of white colored pigments or dyes, which meets the above-mentioned requirements, eliminates all disadvantages and brings some additional advantages.

[0016] The invention is inspired by existing conditions and aims to solve the above-mentioned disadvantages.

[0017] The main object of the invention is to obtain a white-colored coating without the use of any whitecolored dye or pigment.

[0018] Another object of the invention is to make the coating production process simpler and faster by eliminating the preparation process of the pigments used in the coating.

[0019] Another object of the invention is to eliminate the necessity of using titanium dioxide to obtain white color in UV curable coatings. The main feature of the invention is the application of two different cross-linking mechanisms in the coating. The first of these is the ketal formation mechanism which operates independently of UV curing. The second mechanism is the UV curable acrylate crosslinking mechanism in the same environment. In an environment where these two mechanisms are present together, the white color is formed by trapping micro foam particles in a formulation mixed in emulsion form at high speed at a suitable viscosity, and when this formulation is applied as a coating as a film and then treated with UV rays and the three- dimensional thermoset structure is fixed, the white color structure with micro foam is preserved. In this way, there is no need to use titanium dioxide, which is a white pigment.

[0020] In order to fulfill the aforementioned objects, the invention is an organic white colored coating without dyes or pigments, comprising tetrathiol, ketone, acrylate emulsion, photoinitiator and anhydrous acid.

[0021] In order to fulfill the aforementioned objects, the invention is a method for obtaining a white colored organic coating without dye or pigments, comprising the following steps; i. Taking the acrylate emulsion into a light-proof container and mixing by adding a photoinitiator, ii. Adding tetrathiol to the mixture and stirring, ill. Adding ketone to the mixture prepared in the previous step and mixing, iv. Mixing by adding anhydrous acid, v. Application of the prepared formulation to the surface and drying of the formulation layer. vi. UV curing of the dried formulation applied to the surface.

[0022] The structural and characteristic features and all the advantages of the invention will be more clearly understood by the detailed description given below, and therefore the evaluation should be made in consideration of this detailed description.

[0023] Detailed Description of the Invention

[0024] In this detailed description, the method of the invention is described only for a better understanding of the subject matter and without any limiting effect.

[0025] The invention relates to obtaining white colored organic coatings without the use of any white dye or pigment (titanium dioxide). The inventive white organic coating without dyes or pigments comprises tetrathiol, ketone, acrylate emulsion, photoinitiator and anhydrous acid. In one embodiment of the invention, the white colored organic coating comprises a viscosity modifier in addition to tetrathiol, ketone, acrylate emulsion, photoinitiator and anhydrous acid. Preferred and usable amounts by weight of the inventive white colored organic coating formulation are given in Table 1 . Table 1 Recipe of the inventive white colored organic coating formulation

[0026] The coating according to the invention contains 10-30% tetrathiol, 5-15% ketone, 40-70% acrylate emulsion, 1 -5% photoinitiator, 0-10% viscosity modifier and 0,05-0,2% anhydrous acid.

[0027] The inventive white coating is in the form of an interpenetrating network structure. One of the systems forming the interpenetrating crosslink structure mentioned herein is ketal formation. The other system is a photopolymerizable acrylic system. In the invention, anhydrous acid is used to initiate interpenetrating network (IPN) formation.

[0028] The formulation that can give the inventive white colored coating consists of two different polymer systems that can polymerize in different ways. These two polymer systems form a structure called interpenetrating network (IPN) at the final stage. One of the two polymerization systems in the formation of this structure is the formation of a cross-linked ketal system and the other is a photo polymerizable acrylate system. The components required for both polymerization systems are brought together to form the coating. The chemicals required for ketal formation, which is one of these systems, are organic based. The classes of these chemicals consist of organic ketone, three or more functional thiols and an anhydrous organic acid. In this mechanism, when anhydrous acid is added, thiol groups react with the carbonyl group of ketones to form a crosslinked network structure. The use of aqueous acid destabilizes this structure by hydrolysis over time. Therefore, it is not possible to use aqueous acid. The ketones used in this mechanism are ketone molecules in liquid form with low molecular weight such as acetone, ethyl methyl ketone, cyclohexanone, etc. At the same time, the liquid form of these ketones provides support as a solvent in the application of the formulation viscosity until the last stage. The multifunctional thiol molecule, which is another component of this structure, contains thiol functional groups such as Pentaerythrityl tetrathiol, Pentaerythritol tetrakis(3-mercaptopropionate), Ethane-1 ,1 ,1 ,2,2- tetrathiol, Benzene-1 ,2,4,5-tetrathiol, Propane-1 ,2, 3-trithiol, trimethylolpropane tris(3- mercaptopropionate) etc. which can be easily found commercially, are organic molecules containing thiol functional groups. The anhydrous acids used are water-free organic acids such as para-toluene sulfonic acid, methane sulfonic acid, tosylic acid and dissolved in liquid ketone.

[0029] The other system that will form the IPN structure is acrylate systems that can be photopolymerized. These systems can be solvent-based or water-based. However, solvent-based systems are not preferred due to the recently developing environment and human health sensitivity. The invention covers water-based systems. Photopolymerized water-based acrylate systems are in emulsion form. This system consists of two main (necessary) and other auxiliary components as formulation. The first of the main components are photopolymerized acrylate systems. These are oligomeric structures such as polyester acrylate, polyurethane acrylate, epoxy acrylate, vinyl acrylate, etc., which can be of different molecular sizes, and whose end groups are acrylic acid esters. The other main component is photoinitiator systems that can absorb light at ultraviolet and visible wavelengths. These systems should be compatible with both the acrylate composition and the light source to be used for maximum efficiency. In other words, this photoinitiator should be able to absorb the light emitted by the light source to the maximum extent, produce active radicals that initiate polymerization efficiently and these radicals should be at standards that can efficiently polymerize acrylate groups. Auxiliary components are substances added to standard formulations such as viscosity regulating chemicals, antioxidants, etc. The acrylate emulsion used in the invention is a photopolymerizable acrylate emulsion and this acrylate emulsion can be in different forms. Acrylate emulsions include, but are not limited to, polyester acrylate, vinyl acrylate, epoxy acrylate, polyurethane acrylate, silicone acrylate or acrylates containing acrylate end groups. Since these acrylates are water-based, they are in emulsion form.

[0030] In addition, thiols used in the ketal system also have photopolymerization properties by playing an active role in the photoinitiator system.

[0031] The last step in the formulation formation is to add the other two formulations except anhydrous acid to each other and mix at high speed to form micro foam cells. At the same time, viscosity can be adjusted for convenience during application. Anhydrous acid is added just before application. Since the ketal system starts to form after the addition, the formulation must be applied. Tetrathiol used in the invention is also a molecule that can react with acrylate with photoinitiator and has polymerization property. It is insoluble in water and when added to a water-based emulsion, it directly forms organic phase droplets.

[0032] The ketone used in the invention is a chemical that reacts with tetriol to form thioacetal. However, like tetrathiol, ketone should be insoluble in the water phase of the emulsion.

[0033] Anhydrous acid provides the initiation of ketal formation, one of the two polymerization mechanisms.

[0034] The viscosity modifier is an optional component added to prevent the formulation from flowing and thickness change after application to the surface.

[0035] A method for obtaining a white colored organic coating without dyes or pigments according to the invention comprises the following steps. i. Taking the acrylate emulsion into a light-proof container and mixing by adding photoinitiator, ii. Adding tetrathiol to the mixture and stirring, ill. Adding ketone to the mixture prepared in the previous step and mixing, iv. Mixing by adding anhydrous acid, v. Application of the prepared formulation to the surface and drying of the formulation layer vi. UV curing of the dried formulation applied to the surface.

[0036] In the inventive method, the mixing operations are preferably carried out at 300 rpm with a magnetic or mechanical mixer at a temperature of 20-30CC.

[0037] In one embodiment of the inventive method, the viscosity of the mixture is adjusted by adding a viscosity modifier after process step iii).

[0038] Polyacrylate, carboxymethyl cellulose, xanthan gum, alginate and other synthetic thickeners are preferably used as viscosity modifiers, including but not limited to.

[0039] Viscosity measurement varies according to the formulation. Therefore, it is not possible to give a range for the required viscosity value. However, a viscosity that will maintain the application thickness when applied to the surface is required. In process step v) of the method of the invention, the formulation layer is dried with an infrared dryer or in an oven.

[0040] In process step v of the inventive method, the prepared formulation is applied to the surface in the 10-100 micron (micrometer) coating range and dried. Then, in step vi. the dried formulation applied to the surface is cured in a UV light emitting lamp at a wavelength suitable for the UV light absorption properties of the photoinitiator system.

[0041] A preferred embodiment of the method of the invention is as follows.

[0042] Step 1 : The water-based acrylate emulsion with the desired properties to be used is taken into a light-proof container. To this emulsion, an amount of photoinitiator capable of absorbing the wavelength of UV light sufficient to form a sufficiently active radical when exposed to UV light is added and stirred until dissolved. Stirring is carried out at a minimum of 300 rpm with a magnetic or mechanical stirrer at average room temperature (25CC).

[0043] Step 2: Add tetrathiol to this mixture and continue stirring at room temperature (25 *C) with a magnetic or mechanical stirrer at a minimum 300 rpm until homogenous.

[0044] Step 3: Add the other component, ketone, to the mixture prepared in the previous step and mix under the same conditions.

[0045] If the viscosity of the formulation is not sufficient, a viscosity modifier (e.g. enhancer, thickener) is added. Mixing is carried out at the same speed and temperature. When the desired viscosity is reached, the last chemical is added.

[0046] Step 4: The last chemical, anhydrous acid, is added and homogenous mixing is continued. After homogeneity is achieved, mixing is terminated.

[0047] Step 5: The prepared water-based formulation is applied to the desired surface with the applicator to give the desired thickness. Then, before the curing step, the aqueously applied formulation layer is dried in an infrared dryer connected to the equipment or in an oven heated below the decomposition temperature of the photoinitiator used.

[0048] Step 6: The dried formulation applied to the surface is cured to the maximum extent under a UV light emitting lamp of the appropriate wavelength. The application phase of the inventive coating consists of two stages. The first is the application of the prepared formulation to the surface. This process can be done with different apparatus. It can be applied to the surface in the desired thickness with the help of a plastering knife or applicator. Another point to be considered is to obtain the desired coating thickness after drying. After the final formulation with anhydrous acid is applied to the surface, it must be dried just before the second photopolymerization step. This drying process is carried out in infrared dryers attached in front of the photopolymerization belt or in ovens heated to temperatures that do not damage the normal photoinitiator. The dried coating is then exposed to ultraviolet and / or visible wavelength light for curing. During the curing process, the micro-foam cells trapped during mixing are fixed in the cross-linked tissue and when these micro-foams completely reflect the incoming visible light, the coating appears white in color.

Claims

CLAIMS1. An organic white colored coating that does not contain dyes or pigments characterized by comprising; tetrathiol, ketone, acrylate emulsion, photoinitiator and anhydrous acid.

2. The coating according to claim 1 , characterized by comprising; a viscosity modifier .

3. The coating according to claim 2, characterized by comprising; 10-30 wt.% tetrathiol, 5-15 wt.% ketone, 40-70 wt.% acrylate emulsion, 1 -5 wt.% photoinitiator, 0-10 wt.% viscosity modifier and 0.05-0.2 wt.% anhydrous acid.

4. The coating according to claim 1 , characterized by comprising; Type 1 and / or Type 2 type photoinitiator.

5. The coating according to claim 1 , characterized in that it is in the form of an interpenetrating network structure.

6. A method for obtaining a white colored organic coating without dye or pigments, characterized by comprising; i. Taking the acrylate emulsion into a light-proof container and mixing by adding a photoinitiator, ii. Adding tetrathiol to the mixture and stirring, ill. Adding ketone to the mixture prepared in the previous step and mixing, iv. Mixing by adding anhydrous acid, v. Application of the prepared formulation to the surface and drying of the formulation layer. vi. UV curing of the dried formulation applied to the surface .

7. The method according to claim 6, characterized in that; said mixing operations are carried out at 300 rpm with a magnetic or mechanical mixer at a temperature of 20-30CC.

8. The method according to claim 6, characterized in that; the viscosity of the mixture is adjusted by adding a viscosity modifier after process step iii).

9. The method according to claim 6, characterized in that; in process step v) the prepared formulation is applied to the surface in a coating range of 10-100 microns (micrometers).

10. The method according to claim 6, characterized in that; in process step v) the formulation layer is dried in an infrared dryer or in an oven.

11. The method according to claim 6 or claim 10, characterized in that; the drying process is carried out at a temperature range of 100-110 Ti fo r 5-10 s.