RU2633536C1 - Composition for producing transparent bactericide oxide coating - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: composition contains high molecular weight polyvinylpyrrolidone, titanium alkoxide, salt (or salts) water-soluble and thermally decomposable upon heating to less than 550°C, polar organic solvents and water. The composition provides a two-component transparent oxide coating on the glass surface.

EFFECT: high bactericidal properties and the ability to efficiently generate active singlet oxygen are provided.

3 tbl, 2 ex

Description

The invention relates to inorganic bactericidal materials and methods for their preparation, which can be used in the manufacture of glass, ceramics, refractory materials, pigments and paints, various building materials, display screens, monitors and TVs, various devices.

A well-known example of solid inorganic bactericidal materials that have long been widely used in practice is silver. However, silver is an expensive material and therefore its practical use is limited.

To date, solid inorganic oxide materials cheaper than pure metallic silver have been developed, the bactericidal properties of which are due to the introduction of silver ions in their composition. So US patent No. 20060172877 (published on 08/03/2006 according to the IPC indices С03С 003/17, С03С 003/62) describes bactericidal phosphate glass having the following chemical composition in wt.%: P ₂ O ₅ - 66-80; Al ₂ O ₃ - 6.2-10; SiO ₂ 0-10; Na ₂ O - 9-20; Ag ₂ O - 0-5; MgO - 0-15; CaO - 0-25; SO ₃ - 0-40; BaO - 0-15. In US patent No. 20060166806 (published July 27, 2006 according to the IPC index C03C 003/16) a sulfophosphate glass having a similar chemical composition is described that contains in wt.%: P ₂ O ₅ - 15-60; SO ₃ - 5-40; MgO - 0-15; Ag ₂ O - 0.01-5.

It should be noted that, as is known, the bactericidal action of solid materials is manifested only when they are in direct contact with bacteria and viruses, i.e. it is due to the special properties of the surface layers of solid bactericidal materials. Therefore, the introduction of expensive silver in the volume of glass, as proposed in US patent No. 20060172877 and No. 20060166806, is impractical. In addition, phosphate and sulfophosphate glasses are quite expensive, and their production is environmentally unsafe.

The problem of rational placement of the antibacterial component in a metal material is more effectively solved in US patent No. 6509057 (published on 01/21/2003 by indices IPC A61K 006/00, A01N 025/00, B22F 003/00, B05D 001/16). In this patent, only the surface layer of the metal material contains antibacterial components (Ag, Cu). The surface antibacterial layer of the metal material is formed by thermally stimulated diffusion from an external source.

In RF patent No. 2404852 (published on 11/27/2010 by IPC indices B01J 21/06, B01J 23/89, C09D 5/14) a sol of photocatalytically active titanium oxide and a coating composition are described. The photocatalytically active titanium oxide sol contains titanium oxide, silver in an amount of 0.1-5 wt.%, Expressed as Ag2O / TiO2, copper, the proportion of which relative to the amount of silver, expressed as CuO / Ag ₂ O, is 1-30 by weight, and quaternary ammonium hydroxide. The coating composition is a titanium oxide sol dispersed in a binder. A method of manufacturing a part consists in applying said composition to a surface of a substrate.

US Patent No. 20030118733 (published June 26, 2003, IPC Index B05D 003/02) describes a low-temperature method for producing sol-gel antibacterial films applied to glass, ceramic, and plastic. These films include active bactericidal components, such as oxide compounds, compounds obtained by ion exchange of metals or zeolites and mainly contain silver. A method for producing such films involves heat treatment of films at temperatures of 300-800 ° C, but at temperatures below the melting or softening temperatures of the solid substrate. This patent also notes that melting or softening of the solid substrate leads to a dramatic decrease in the bactericidal properties of the coating. Note that the starting materials commonly used in the sol-gel method for producing films are relatively expensive (especially those containing silver) and the use of such bactericidal coatings may be limited for economic reasons.

Previously shown (Lei Huang, Dian-Qing Li, Yan-Jun Lin, Min Wei, David G. Evans, Xue Duan Controllable preparation of nano-MgO and investigation of its bactericidal properties. - Journal of Inorganic Biochemistry, v. 99, No. 5, 2005, p. 986-993.) That MgO nanocrystals have a strong bactericidal effect. Moreover, the bactericidal efficacy of these crystals increases with a decrease in their size.

It was also found (Koper O.V., Klabunde JS, Marchin GL, Klabunde KJ, Stoimenov P., Bohra L. Nano-scale powders and formulations with biocidal activity toward spores and vegetative cells of Bacillus species, Viruses, and Toxins. - Current Microbiology, 2002, v. 44, p. 49-55.) That nanopowders of oxides such as MgO and CaO have a strong bactericidal effect both in air and in solutions. For example, it was shown that when these nanopowders come into contact with the vegetative forms of Escherichia coli, Bacillus cereus or Bacillus globigii, more than 90% of these forms die within a few minutes. According to (Sawai J., Kojima N., Igarashi N., Hashimoto A., Shoji S., Sawaki T., Hakoda A., Kawada E., Kokugan T., Shimizu M. Antibacterial characteristics of magnesium oxide powder. - World Journal of Microbiology and Biotechnology, 2000, v. 16, No. 2, p. 187-194.) The bactericidal effect of MgO is largely determined by the release of active oxygen from it.

The problems of creating oxide bactericidal layers are in many respects close to the development of photocatalytic coatings on various materials [6]. The developed photocatalytic coatings are capable of generating active singlet oxygen under the influence of UV radiation (for example, under the action of sunlight) and photochemically decompose organic compounds and impurities located on their surface. The most common and effective material for photocatalytic coatings is titanium dioxide (TiO ₂ ) [7].

In applications of the Russian Federation No. 2014125347 (published on December 27, 2015 according to the IPC index C05D 5/14) and No. 2014125349 (published on 12/27/2015 according to the IPC index C05D 5/14) a biocidal composition and a method for its preparation are described. A biocidal composition consisting of a solvent, a water-soluble polyelectrolyte and a salt, characterized in that it contains water as a solvent, as a polyelectrolyte it contains a charged polyelectrolyte, which is the product of the interaction of aqueous solutions of cationic polyelectrolyte and anionic polyelectrolyte, taken in a ratio in which the content of charged units of the anionic polyelectrolyte is from 3 to 30% of the content of charged units of the cationic polyelectrolyte, and as a salt it is holds at least one water-soluble salt selected from the group comprising an alkali metal or ammonium salt, or a mixture of such a salt with a calcium or magnesium salt, in the following ratio of components, wt.%: the product of the interaction of aqueous solutions of cationic polyelectrolyte and anionic polyelectrolyte 0,099-18 , 79; water soluble salt 0.20-17.40; water is the rest.

Transparent bactericidal coatings on glasses obtained by the polymer-salt method are described in RF patent No. 2395548 (published on July 27, 2010 according to IPC indices C09D 5/14; В82В 1/00). An important advantage of the polymer-salt method of producing oxide coatings is the possibility of a wide variation in the chemical composition of the coating and the introduction of the necessary modifiers. The introduction of the required amount of modifying component is achieved by adding soluble, thermally degradable compounds to the film-forming solution. After applying the solution to the surface of the substrate as the solvent evaporates, a composite coating is formed, consisting of polymer molecules and salt nanocrystals having a size of 10-15 nm and uniformly distributed in the polymer matrix (Jung K.T., Evstropiev SK, Lee KY, Lee KS Development of nano-sized protective layers for flat fluorescent lamps (FFLs). - Society of Information Displays International Symposium Digest of Technical Papers. - 2007, Long Beach, USA, SID-2007 (SID 07 Digest), May 22-25, 2007, p. 1844-1847. (SID 07 Digest, 2007, pp. 1844-1847).

However, the coating according to patent No. 2395548 has a significant drawback, determined by the fact that the bactericidal coatings described in this patent contain significant amounts of magnesium oxide, the surface of which can actively interact with carbon dioxide and the moisture of the surrounding atmosphere [8] (Minakova TS, Ekimova IA Fluorides and oxides of alkaline earth metals and magnesium. Surface properties. Tomsk: Publishing House of Tomsk State University, 2014, 148 pp.). This changes the acid-base properties of the surface of the coatings and can have a significant effect on their bactericidal properties.

According to the technical solution, the closest to the present invention is the method for producing bactericidal material described in RF patent No. 2470053 (published on December 20, 2012 according to IPC indices C09D 1/00; C09D 5/00; C09D 5/14; C09D 129/00; C03C 17 / 245). This patent describes porous anatase titanium dioxide coatings with improved photocatalytic activity, used as antibacterial and self-cleaning coatings. A method of manufacturing coatings includes: 1) manufacturing a sol-gel composition with at least one agent for forming a sol-gel composition and a porous structure; 2) applying the composition to a glass substrate; 3) heating the coated substrate to remove means for forming a sol-gel composition and porous structure. The means for forming the porous structure is selected from a high polymer substance.

It should be noted that when using the liquid film-forming composition described in RF patent No. 2470053, after heat treatment of the glass coated thereon, the obtained oxide coating is one-component and consists only of TiO ₂ particles having a crystalline anatase structure. This is a significant drawback, since it significantly limits the possibility of optimizing or increasing the bactericidal and photocatalytic properties of coatings.

Another significant drawback of this composition and the one-component TiO ₂ coating obtained from it is that the refractive index of this coating is very high (the refractive index of TiO ₂ (anatase) at a wavelength of 550 nm is n = 2.55). This determines the high reflectivity of such coatings and, accordingly, the relatively low transparency of glasses with these coatings. So, glass with coatings, as described in RF patent No. 2470053, in the visible part of the spectrum have a transmittance> 75%. However, the relatively low transmittance, at the level of 75-80%, is too low and the coatings proposed in RF patent No. 2470053 cannot be used for many optical and other applications, such as displays for mobile phones, laptops, and stationary computers.

The technical task of the invention is to develop a composition for the formation of a transparent (transmittance T> 80%) bactericidal oxide coating that does not contain silver and is able to generate active singlet oxygen, which plays a significant role in the photocatalytic processes and bactericidal properties of the material.

To solve this technical problem, it is proposed to use a composition that provides the formation on the glass surface of a two-component transparent oxide coating that provides high bactericidal properties and has the ability to effectively generate active singlet oxygen. To obtain a two-component oxide coating, the composition contains high molecular weight polyvinyl pyrrolidone, titanium alkoxide, water-soluble and thermally decomposable zinc salts, salts, polar organic solvents and water when heated to a temperature of less than 550 ° C.

It is known that zinc oxide coatings may have bactericidal properties. RF patent 2162870 (published on 02/10/2001 by the IPC indices C09D 5/02 (2000.01) and C09D 5/14 (2000.01) describes an aqueous composition for applying a bactericidal coating containing zinc compounds selected from the group consisting of zinc oxides, hydroxides or salts and their combinations. Patent RF 2398804 (published on September 10, 2010 according to the IPC index C09D 5/14 (2006/01) describes an aqueous biocidal composition containing a product of the interaction of zinc oxide nanoparticles and a polymer. It should be noted that the use of zinc oxide which is poorly soluble in water can lead to film forming compositions aggregates of the oxide particles and, consequently, to the production of coatings of low transparency. Therefore, the use of water-soluble zinc salt is preferred for forming transparent bactericidal coatings.

The possibility of using soluble zinc salts to form transparent coatings consisting of zinc oxide nanoparticles was shown in [9] (using zinc acetate) (Dhanalakshmi A., Amutha C., Lawrence B., Kulathuraan K., Ramadas V., Natarajan B. , Structural and optical characterization of PVP / ZnO nanocomposites prepared by sol-gel dip-coating method. - International Journal of Current Research. 2013. V. 5. No. 11. P. 3408-3413.) And [10] (use of nitrate zinc) (Evstropyev S.K., Soshnikov I.V., Khrebtov A.A. Formation of ZnO coatings using solutions containing high molecular weight polyvinylpyrrolidone - Letters in ZhTF. 2016, v. 42, issue 9, pp. 49-55 )

When tetraethoxy titanium interacts with water present in the solution or atmospheric moisture, a quick hydrolysis of this compound occurs:

As a result of condensation of Ti (OH) ₄ molecules formed as a result of hydrolysis, colloidal particles of titanium dioxide are rapidly formed in the solution. The resulting colloidal solution (sol) at room temperature is able to rapidly increase viscosity, turning into a gel, which leads to the loss of the possibility of its use for coating. Therefore, to control the rate of chemical reaction (1) and slow down the gelation process, the water content in the film-forming solution is limited and does not exceed 5.00 wt.%. When the water content in the composition is less than 0.20%, when the components are mixed, an inhomogeneous colloidal solution is formed. The water content in the developed composition is 0.20-5.00 wt.%.

The content of tetraethoxy titanium in the film-forming composition is 0.10-1.00 wt.%. When the content of tetraethoxy titanium is more than 1.00 wt.% After mixing the starting components in the solution, colloidal particles of titanium dioxide are rapidly formed in the solution, the viscosity of the solution increases rapidly and the composition turns into a gel that cannot be used to obtain uniform coatings. When the content of tetraethoxy titanium in the composition is less than 0.10 wt.%, The obtained oxide coating does not have noticeable bactericidal properties.

Propanol-2 is a solvent of the main film-forming components. When the content of propanol-2 is less than 33.00 wt.%, The film-forming solution is characterized by high viscosity and low uniformity, and when oxide coatings based on these compositions are obtained, white spots are observed on the glass surface after heat treatment, which indicates a high heterogeneity of the obtained oxide coatings. When the content of propanol-2 in the composition is more than 89 wt.%, It is difficult to introduce metal salts into the composition because of their low solubility in this solvent. Therefore, the content of propanol-2 in the composition of the film-forming composition should be 33.00-89.00 wt.%.

To ensure a more complete solubility of zinc salts, propylene carbonate is included in the film-forming composition. When the composition contains less than 0.50 wt.% Propylene carbonate, the film-forming solution is heterogeneous. When the composition contains more than 50.00 wt.% Propylene carbonate, the film-forming solution is characterized by increased viscosity and the coating obtained during its use is not uniform. Therefore, the content of propylene carbonate in the composition is 0.50-50.00 wt.%.

To ensure greater uniformity of coatings, the composition of the film-forming composition includes 1-methyl-2-pyrrolidone. When the content of 1-methyl-2-pyrrolidone is less than 0.20 wt.%, The film-forming solution is characterized by low uniformity. When the content of 1-methyl-2-pyrrolidone is more than 18 wt.%, The film-forming solution is also heterogeneous. Therefore, the content of 1-methyl-2-pyrrolidone in the composition is 0.20-18.00 wt.%.

The content of zinc salts in the composition is 0.20-5.00 wt.%. When the salt content is less than 0.20 wt.%, The positive effect of their introduction into the composition of the composition is negligible. When the content of zinc salts of more than 5.00 wt.% There is a significant deterioration in the uniformity of the coatings.

The experiments carried out confirm the possibility of using various zinc salts with the indicated properties in the indicated amounts. To obtain a practical optimal research result, the Zn (NO ₃ ) ₂ salt was used.

The presence of high molecular weight polyvinylpyrrolidone in the film-forming solutions promotes the formation of homogeneous nanosized oxide particles in the forming coating and improves the adhesion of the solution to the glass surface. However, when the content of polyvinylpyrrolidone is more than 5.00 wt.%, The viscosity of the solution increases significantly, which complicates its use for coating and leads to a significant deterioration in their uniformity. When the content of polyvinylpyrrolidone is less than 0.20 wt.%, There is a significant deterioration in the adhesion of the liquid composition to the glass surface and a deterioration in the uniformity of the oxide coating. Therefore, the content of polyvinylpyrrolidone in the composition is 0.20-5.00 wt.%.

The composition of the proposed composition meets the criteria of patentability: novelty, inventive step, industrial applicability.

The effectiveness of the proposed film-forming compositions for bactericidal coatings is illustrated by examples No. 1 and No. 2.

Example No. 1. The following liquid mixture containing propanol-2,1-methyl-2-pyrrolidone, propylene carbonate and high molecular weight (molecular weight Ms = 1300000) polyvinylpyrrolidone was used as a solvent for the manufacture of film-forming solutions. Based on this liquid mixture, film-forming solutions were prepared by introducing zinc and tetraethoxy titanium salts, the chemical composition of which is shown in Table 1. Alkaline-silicate glass samples having dimensions of 20 × 20 × 0.2 were used as substrates.

The obtained film-forming solutions were used for coating the surface of glass substrates by immersion in solutions, followed by extraction and drying. The drying process of the coated samples was carried out at 80 ° C for 24 hours. After drying, the coated samples were heat treated in a laboratory electric furnace at 530 ° C for 2 hours. Table 1 shows the chemical compositions of the obtained oxide coatings.

To determine the bactericidal properties of the coatings, we used a technique based on agar diffusion and described in the guidelines of the Federal Center for Sanitary Epidemiological Supervision (Determining the sensitivity of microorganisms to antibacterial drugs: Guidelines. - M .: Federal Center for Sanitary and Epidemiological Supervision of the Ministry of Health of Russia, 2004. - 91 p.). A representative of gram-positive bacteria Staphylococcus aureus ATCC 209P was used as test microorganisms. Antibacterial efficacy was assessed by determining the formation of inhibition zones in nutrient agar, which forms on the surface seeded with bacteria. This method is based on the fact that active radicals formed on glass samples with coatings diffuse into agar and inhibit the growth of the test microorganism. The more active radicals are formed, the larger the growth inhibition zone. The testing process included several stages:

1. Nutrient medium - meat peptone agar (MPA) was prepared from a dry environment of industrial production in accordance with the manufacturer's instructions. After autoclaving, the nutrient medium was checked for sterility and growth properties (only a new supply). On the day of the experiment, MPA was poured into sterile Petri dishes (diameter 90 mm) of 20 ml, previously melted in a water bath. The plates were left at room temperature to set.

2. For the preparation of the inoculum, a pure daily culture of microorganisms grown on a solid nutrient medium was used. Loops transferred a small amount of material into a test tube with sterile physiological saline, bringing the inoculum density to 1⋅10 ⁹ CFU / ml according to the bacterial turbidity standard. Inoculum was used for 15 minutes after preparation.

3. For inoculation of prepared Petri dishes, 0.1 ml of inoculum was introduced into the center of the plate and carefully distributed with a Drigalski trowel over the entire surface (inoculation with a “lawn”).

4. No later than 15 minutes after inoculation, glass samples were applied to the surface of the culture medium with sterile tweezers. Petri dishes were incubated at room temperature.

5. After the incubation, the plates were placed upside down on a dark matte surface so that the light incident on them at an angle of 45 ° (taking into account reflected light). The growth retardation zone was measured with an accuracy of 1 mm.

Table 2 shows the test results of the bactericidal properties of coatings obtained from solutions 1-3, as well as a control sample of glass without coating.

Based on the data in Table 2, we can conclude that the coating formed on the glass surface using solution 2 containing the organic titanium compound as the main film-forming component does not have bactericidal properties.

The experiments showed that the coating formed when using solution 3 containing the mixture of tetraethoxy titanium and zinc nitrate as the main film-forming component has the highest bactericidal activity.

Example No. 2. The chemical composition of the prepared film-forming solutions is shown in Table 3.

Solution 4, containing 0.19 wt.% PVP, is characterized by high uniformity and transparency. However, the low PVP content determines the low adhesion of this solution to the glass surface and when it is applied to the surface of the substrate, the coating breaks up into individual small droplets, which determines the low uniformity of the resulting coating.

Solution 5 containing 5.1 wt.% PVP is characterized by increased viscosity, which determines the heterogeneity of the resulting coating.

Solution 6, containing 0.1 wt.% Water, is a heterogeneous liquid mixture, which for this reason cannot be used to obtain a coating.

Solution 7 containing 5.1 wt.% Water is unstable, its viscosity rapidly increases immediately after mixing of the starting components and the colloidal solution quickly turns into a gel. It is impossible to use this colloidal solution to obtain uniform coatings.

Solution 8, containing less than 33 wt.% Propanol-2, is heterogeneous, the oxide coating obtained from this solution contains white inclusions.

Solution 9 containing more than 89 wt.% Propanol-2 is heterogeneous due to incomplete dissolution of the zinc salt and cannot be used to obtain a uniform oxide coating.

Solution 10, containing 1.10 wt.% Tetraethoxy titanium, is unstable and quickly forms a gel that cannot be used to obtain a uniform coating.

Solution 11, containing 0.05 wt.% Tetraethoxy titanium, is homogeneous and transparent, however, the oxide coating obtained with its use does not have noticeable bactericidal properties.

Solution 12, containing 0.10 wt.% Zinc salt, is transparent and homogeneous, however, the oxide coating obtained with its use does not have noticeable bactericidal properties.

Solution 13, containing more than 5.00 wt.% Zinc salt, is heterogeneous due to incomplete dissolution of the zinc salt and cannot be used to obtain a uniform oxide coating.

Solution 14 containing 0.4 wt.% Propylene carbonate is heterogeneous due to incomplete dissolution of the zinc salt and cannot be used to obtain a uniform oxide coating.

A solution of 15 containing 50.10 wt.% Propylene carbonate is viscous. The oxide coating obtained using this solution is characterized by low uniformity.

Solution 16, containing 0.10 wt.% 1-methyl-2-pyrrolidone, is heterogeneous and cannot be used to obtain a uniform oxide coating.

Solution 17, containing 18.10 wt.% 1-methyl-2-pyrrolidone, is heterogeneous and cannot be used to obtain a uniform oxide coating.

Compositions 18-31 are manufactured within the stated limits of the constituent components.

Thus, the above examples illustrate the high bactericidal properties of transparent coatings obtained from film-forming solutions containing ethoxytitanium, polyvinylpyrrolidone and zinc nitrate. In addition, the developed solutions make it possible to form transparent coatings on the glass surface capable of efficiently generating chemically active singlet oxygen.

Literature

1. Lei Huang, Dian-Qing Li, Yan-Jun Lin, Min Wei, David G. Evans, Xue Duan Controllable preparation of nano-MgO and investigation of its bactericidal properties.-Journal of Inorganic Biochemistry, v. 99, No. 5,2005, p. 986-993.

2. Koper OB, Klabunde JS, Marchin GL, Klabunde KJ, Stoimenov P., Bohra L. Nano-scale powders and formulations with biocidal activity toward spores and vegetative cells of Bacillus species, Viruses, and Toxins.- Current Microbiology, 2002, v. 44, p. 49-55.

3. Sawai J., Kojima H., Igarashi H., Hashimoto A., Shqji S., Sawaki T., Hakoda A., Kawada E., Kokugan T., Shirnizu M. Antibacterial characteristics of magnesium oxide powder. - World Journal of Microbiology and Biotechnology, 2000, v. 16, No. 2, p. 187-194.

4. Jung K.T., Evstropiev S.K., Lee K.Y., Lee K.S. Development of nano-sized protective layers for flat fluorescent lamps (FFLs). - Society of Information Displays International Symposium Digest of Technical Papers. - 2007, Long Beach, USA, SID-2007 (SID 07 Digest), May 22-25, 2007, p. 1844-1847. (- „-, SID 07 Digest, 2007, pp. 1844-1847).

5. Kiselev B.M., Kislyakov I.M., Burchinov A.H. Generation of singlet oxygen on the surface of oxides. - Optics and spectroscopy, 2016, vol. 120, No. 4, p. 15-25.

6. Basnet P., Larsen GK, Jadeja RP, Hung Y.-C., Zhao Y. α-Fe ₂ O ₃ nanocolums and nanorods fabricated by electron beam evaporation for visible light photocatalytic and antimicrobial applications. - ACS Applied Materials and Interfaces, 2013, v. 5, No. 6, p. 2085-2095.

7. Zhang Jinhui, Li Si, Chen Long, Pan Yi, Yang Shuangchun, The progress of TiO ₂ photocatalyst coating. - IOSR Journal of Engineering, 2012, v. 2, No. 8, p. 50-53.

8. Minakova T.C., Ekimova I.A. Fluorides and oxides of alkaline earth metals and magnesium. Surface properties. - Tomsk: Publishing House of Tomsk State University, 2014, 148 p.

9. Dhanalakshmi A., Amutha C., Lawrence B., Kulathuraan K., Ramadas V., Natarajan B., Structural and optical characterization of PVP / ZnO nanocomposites prepared by sol-gel dip-coating method. - International Journal of Current Research. 2013. V. 5. No. 11. P. 3408-3413.

10. Evstropiev S.K., Soshnikov I.V., Khrebtov A.A. The formation of ZnO coatings using solutions containing high molecular weight polyvinylpyrrolidone - Letters in ZhTF. 2016, vol. 42, no. 9, p. 49-55.

Claims (2)

Composition for the manufacture of a transparent bactericidal oxide coating, including high molecular weight polyvinylpyrrolidone, tetraethoxy titanium and water, characterized in that it further contains propanol-2, 1-methyl-2-pyrrolidone, propylene carbonate and zinc salt Zn (NO ₃ ) ₂ in the following ratio, wt. .%: high molecular weight polyvinylpyrrolidone 0.20-5.00 tetraethoxy titanium 0.10-1.00 propanol-2 33.00-89.00 water 0.20-5.00 zinc salt Zn (NO ₃ ) ₂ 0.20-5.00 propylene carbonate 0.50-50.00 1-methyl-2-pyrrolidone 0.20-18.00