Titanium oxide colloidal sol and process for the preparation thereof

Technical field

0001The This invention relates to a titania sol and methods thereof for the manufacture. In particular, the present relates to Invention, a titanium dioxide colloid sol containing as a semiconductor photocatalyst is applicable, and a method of manufacturing the same. The Titanium dioxide colloid can be used as a raw material for various functional coating agent for the Purpose of the ultraviolet ray absorbent, pollution prevention, Hydrophilization, preventing fogging, preventing Fungus, deodorizing and be used for water treatment.

Background Art of the technique

0002As ceramic coating materials in the heat resistance and wear resistance excellent compared with organic coating materials are, are alkali metal silicate salts, phosphate salts, silica sol known and Metalloxidbeschichtungsmaterialien.

0003These ceramic coating materials have the characteristics of inorganic coating materials, such as excellent heat resistance and wear resistance. Currently, tests were carried out, to ceramic coatings, mainly metal oxide, to impart new functions.

0004Among various ceramics, titanium dioxide excellent show photocatalytic activity and when ultraviolet rays thereon are irradiated, the titanium dioxide exhibits a high oxidation effect. Consequently, it is known that if the titanium dioxide with an excellent photocatalytic activity on a surface to be coated a Material such as a metal, glass or ceramic arranged is, the titanium dioxide to increase pollution prevention, the decomposition of odor-causing Substances, the water treatment, the rust prevention, prevention fungal attack, preventing the growth of algae and the decomposition contributes of hard decomposable waste materials. A variety of titanium dioxide coating materials for the The purpose of forming Titantdioxidbeschichtungen with the above- mentioned Properties to substrate surfaces and process for the preparation of the coating materials was provided.

0005As a method for forming a Titantdioxidbeschichtung is the Method in which applied is a hydrolysis of a titanium alkoxide , ie, a sol-gel process, most popular. As a similar method to the sol-gel method disclosed Japanese Unexamined Patent Publication Number 4-83537 a method in which a mixture of a titanium alkoxide is applied with an amide or glycol, and Japanese Unexamined Patent Publication Number 7-100378 discloses a method in which a mixture of Alkoxide is applied with an alcohol amine.

0006As a process for producing a titania sol, which of the mentioned above The method is different, discloses the Japanese Unexamined Patent Publication Number 6-293519, a method in which fine through water heat treatment crystallized titanium dioxide particles in an acid solution with a pH of be 3 or less, and the dispersion obtained can be used for coating.

0007The mentioned above Sol-gel method or the method in which the titanium dioxide colloidal particles deagglomerated or dispersed, however, to the effect highly disadvantageous that since the colloidal solution is an acidic solution, if the colloidal solution is coated on a metal or paper surface, the coated corroded material or worsens. There is also the disadvantage that if the colloidal solution to a material having a high acid resistance is coated, for example, a resin, a ceramic or glass, the coating apparatus such as a coater or a spray gun, and a printing machine are corroded and the working atmosphere for the performers the coating is deteriorated.

0008As a means for solving mentioned the above Problems, Japanese Unexamined Patent Publication discloses Number 9-71418 a sol liquid, the hydrogen peroxide and titanium dioxide includes, and a method for the preparation of the sol liquid. The sol liquid is advantageous in that the sol liquid to be neutralized can. However, since an oxidizing agent is contained, the sol liquid disadvantageous that the effect of the sol liquid for preventing corrosion of the metal is low, the Solliquid colored yellow is and a colorless coating difficult from the sol liquid form is provided the coating is dried not warm.

Disclosure of the Invention

0009A Object of the present invention is the above mentioned Problems of the conventional photocatalytic titanium dioxide solution to solve and to provide a titanium dioxide colloid, the neutral in a is condition stable so that the coating process, with the carry Sol safe can and the formation of a colorless transparent coating allows is, even if dried at room temperature and a method for producing the same.

0010The above object can by the titania and the A process for producing the same according to the present invention dissolved will.

0011The titanium dioxide colloid invention comprises 50 to 100 parts by weight of colloidal particles of titanium dioxide, the negative electricity are loaded, 5 to 50 parts by weight of a complexing agent and 1 to 50 parts by weight of an alkaline substance, wherein the Complexing at least one member selected from condensed phosphoric and condensed phosphate salts include,.

0012The titanium dioxide colloid invention preferably has a pH of 5 to 10

0013The A method for producing a Titandioxidkolloidsols characterized by mixing an alkaline substance into an acid titanium dioxide colloid sol, 50 to 100 parts by weight titanium dioxide colloid sol and 5 to 50 contains parts by weight of a complexing agent to adjust the pH-value of the sol to a height adjust 5-10 and whereby the titanium dioxide colloidal particles be induced to charge with negative electricity, wherein the complexing agent at least one member selected from condensed phosphoric acids and condensed phosphate salts include,.

Best Mode the invention

0014The Inventors a colloidal titanium dioxide solution by reacting an inorganic Titanium salt such as titanium chloride or titanium sulfate, or Alkoxide with water under acidic conditions forth to the titanium salt or hydrolyzing alkoxide and analyzed the electricity charging performance the acid colloid sol of the titanium dioxide. As a result of the analysis was confirmed, that the titanium dioxide colloidal particles stable with positive electricity acid in a Area to be charged and if the colloidal solution with an alkaline solution are neutralized in a pH range of 3 to 5, lose the titanium dioxide colloidal particles almost all of the electrical Charge and are clearly unstable and become such a amount determined each agglomerated that the agglomerated particles difficult separate from each other; and when the alkaline property the colloidal solution further increased is, the above-mentioned are agglomerated titanium dioxide colloidal particles charged with negative electricity.

0015then the inventors studied further measures to improve both a stable electric charge as well as a high dispersing power of titanium dioxide colloidal particles in the neutral range.

0016in the Result of further studies will be found a phenomenon that if a acidic titanium dioxide colloid with an aqueous solution of alkali metal hydroxide or ammonia are mixed to adjust the pH-value of the sol to an alkaline To move the field, the titanium dioxide colloidal particles strongly are agglomerated with each other to such an extent that the agglomerated particles can not be separated from each other and a slurry-like Suspension. It was also found that the above- mentioned phenomenon the titanium ions Ti⁴⁺ is due, in the sol liquid are present, which forms the colloidal titanium hydroxide and titanium dioxide parts be bound by the colloidal titanium hydroxide and another that, since the charge of the colloidal particles with negative electricity in the is neutral range low, the repulsive force between the particles is weak.

0017furthermore it was found that the titanium dioxide colloidal particles with negative electricity by mixing an acid Titandioxidkolloidsols with a complexing agent, selected from condensed phosphoric acids, For example, pyrophosphoric and condensed phosphate salt, a complex with Ti⁺⁴can form ions to the colloidal modifying titanium dioxide particles on the surfaces and then by Mixing of the complexing agent, mixed with colloid sol with an alkaline additive, for example, an aqueous solution of ammonia or morpholine, to increase the pH of the colloid sol to be charged to a desired level can and that a stable dispersed titanium dioxide colloid by loading the titanium dioxide colloidal particles with negative electricity in a neutral to alkaline pH range can be obtained and that a colorless, transparent coating of titanium dioxide having an excellent Adhesive property by coating the above-mentioned stable dispersed Titandioxidkolloidsols on a target particle and obtained by drying the coated sol at room temperature can.

0018It was also found that with respect the composition of a neutral titania sol containing a colloidal Titandioxidteilchenkomponente, charged with negative Electricity, a complexing agent and an alkaline component includes, good stability and a good dispersing shows and the above-mentioned Destination services provides.

0019The A method for producing the titanium dioxide sol with the above- mentioned Composition is further investigated. As a result, it has been found that titania having a low impurity content by Adding an alkaline substance to a sol comprising a colloidal Titandioxidteilchenkomponente and Komplexierungsmittelkomponente, can be obtained to neutral the pH of the sol in a adjust to alkaline range and subjecting the sol liquid a Desionisierungsbehandlung, such as dialysis or a Ionenaustauschharzbe action. The inventive method was mentioned by the above Results completed.

0020The titania invention comprises 50 to 100 parts by weight of titanium dioxide colloidal particles and the titanium dioxide colloidal particles are with negative electricity in a neutral sol solution Loading. When the titanium dioxide colloidal particles with positive electricity are loaded in the neutral range, the dispersion of colloidal is Particles unstable. The type of electricity, positive or negative of the Particles can easily by a zeta potential measurement apparatus and are determined on.

0021The For types of the present invention usable titanium include titanium dioxide anatase (including Metatitanic) Orthotitanium acid and other titanium dioxides, Titandioxidrutil, a. Under these be the Titandioxidanatas (including metatitanic) and Orthotitanium acid particularly preferably employed.

0022in of the present invention, there is no specific limitation on the particle size of the colloidal titanium dioxide particles. In general, the particle size is 1 nm to 500 nm, more preferably 3 to 120 nm.

0023in the present invention may the titanium dioxide colloidal particles by dissolving at least one member selected from inorganic titanium compounds such as titanium chloride, Titanium oxychloride, titanium sulfate and titanyl sulfate in water; possibly Addition of hydrochloric acid or nitric acid as a catalyst to the solution and hydrolyzing the titanium compound at room temperature or by Heating are produced. Also another process for producing of titanium dioxide colloidal particles, a hydrolytic process for the manufacture of organic titanium compounds, e.g. Titanium alkoxides and titanium acetylacetonate may be used. There in an acidic solution mentioned by the above Method produced kolloi dalen titanium dioxide particles with positive electricity are charged, it is necessary that when a sol having a pH of 6 or more by adding an alkaline component to the sol is prepared, the titanium dioxide particles with negative electricity by Adding a complexing agent to be loaded to the sol.

0024in the titanium dioxide sol according to the invention the complexing agent must be present in a proportion of 5 to 50 parts by weight be included. The solvent usable in the present invention include chelating complexing Compounds which condensed phosphoric acids such as pyrophosphoric acid and tripolyphosphoric, and salts of the aforementioned acids represent. More preferred complexing agents are the above mentioned condensed phosphoric acids, especially pyrophosphoric and tripolyphosphoric.

0025in the titanium dioxide colloid invention must be an alkaline substance in an amount of 1 to 50 parts by weight additionally be included to the complexing agent. The pH value of the sol liquid preferably adjusted within the range of 5 to 9 The carries alkaline substance to neutralize the acid ions, For example, chlorate and sulfate ions in the sol liquid remain in and gives a negative electric charge increased stability for the titanium dioxide colloidal particles.

0026The for the Titanium dioxide colloid usable alkaline substance preferably comprises at least one member selected from ammonium compounds, alkali metal compounds and amines, and therefore can for example, ammonium hydroxide (ammonia water), sodium hydroxide, Potassium hydroxide, lithium hydroxide, sodium silicate, and polyamines, for example, Ethylenediamine and triethylenetetramine, are applied. preferred alkaline substances, oxazine, for example, morpholine and piperidine and choline compounds. In cases where the titanium dioxide colloid sol the present inventions education as a coating material applied is, preferably the oxazine and piperidine, Ammonium hydroxide and amine compounds of low molecular weight, for example triethanolamine, slightly out of the coating layer be evaporated while the coating layer is sintered, applied.

0027For the complexing agent and the alkaline substance can certain compounds having both complexing activity as also alkaline property, such as ammonium pyrophosphate applied, will.

0028The titanium dioxide colloid invention in addition mentioned to the above- Components chlorine ions, sulfate ions and / or alcohol, from the for the Preparation of the titanium material used sol are derivable contain. The addition mentioned to the above- made components present remaining components in the sol but essentially of water. When titanium dioxide colloid of the invention is applied as a coating material, a portion of the Water component, preferably by a water-soluble Solvent, comprising an alcohol, glycol or ketone, replaced.

0029in this case, by the property of the resultant coating Adding silica sol and / or a silane derivative, for example, a alkyltrimethoxysilane as a binder to the Titandioxidsoloidsol, be improved.

0030in the inventive method are if the ratio on the weight of the complexing agent to the titanium dioxide colloidal particles is too low, dispersed colloidal particles inadequate and a stable sol can not be obtained. Even if the content by weight the complexing agent is too high, shows the resultant coating undesirably reduced hardness. Even if the content of alkaline substance is too high, the Hardness of the resulting Coating was too low, or a metal such as aluminum or zinc, undesirably corroded. Further, when the content of the alkaline substance is too low is, the sol is undesirable angry.

0031in the method for producing the Titandioxidkolloidsols the present Invention is an acidic titanium dioxide colloid comprising 50 to 100 parts by weight of colloidal particles of titanium dioxide and 5 to 50 parts by weight the complexing agent is added to an alkaline substance, to adjust the pH-value of the sol liquid set to 5 to 10 and thereby the titanium dioxide colloidal particles to cause to be loaded with negative electricity.

0032The for the The method according to the invention usable acidic titania can inorganic by dissolving at least one Titanium compound selected, titanium chloride, titanium oxychloride, titanium sulfate and titanyl in water; optionally adding to the obtained solution of Catalyst selected from hydrochloric acid and / or nitric acid composed and hydrolyzing the titanium compound at room temperature are produced or by heating. Alternatively, the titanium dioxide colloidal particles by hydrolyzing an organic Titanium compound, such as a titanium alkoxide or titanium acetylacetonate, getting produced.

0033The in the inventive process suitable complexing agent is preferably selected from the chelating compounds, condensed phosphoric acids, for example, pyrophosphoric and tripolyphosphoric salts of the above-mentioned and Acids.

0034The in the inventive process for the manufacture of titanium dioxide sol usable alkaline substance is preferably selected from ammonium compounds, such as ammonium hydroxide, amines, for example ethanolamine, oxazine, for example, morpholine and piperidine and choline compounds. When the titanium dioxide colloid as a Be used coating material, are alkali metal hydroxides not actually preferred. The content of the alkaline substance in the sol corresponding to an amount of the alkaline substance, the causes the pH of the sol is within the range of from 5 to to be 10 set. By adding the alkaline substances are the titanium dioxide colloidal particles in the titanium dioxide colloid with negative electricity Loading.

0035at the manufacturing method according to the invention is when a silane derivative, such as epoxysilane or methylsilane, or a partial hydrolysis product of the silane derivative in the liquid mixture where the titanium dioxide colloidal particles with complexing is, before the alkaline substance to the mixed liquid is added and then added the alkaline substance to the mixture is the electric charge of the obtained titanium dioxide colloidal particles stabilized and when this sol as a coating material is used, the coating method with an improved can running coating efficiency will.

0036If Titanium dioxide colloid of the invention is applied to an article to be coated, the Amount contained in the resulting coating of titanium dioxide is preferably to 200 to 2000 mg / m² controlled. The coated Sol layer, by a heat-drying method be dried or at room temperature.

0037in the inventive electrically negatively charged titanium dioxide colloid are tetravalent titanium ions, as an unreacted component in the conventional acidic titania remain, by complexing, comprising a condensed phosphoric acid or a salt thereof, masked, whereby Gelation and precipitation the titanium dioxide colloidal particles is prevented in a neutral range and a negative electrical charge on the complexing agent absorbed in the titanium dioxide colloidal particles, neutralized a positive electrical charge on the titanium dioxide colloidal particles and causes further that the titanium dioxide colloidal particles with negative electricity load and thus a stable neutral titanium dioxide sol receive.

0038Also the acidic property of the acid groups of the chelating Compound and the acidic property of contaminating acidic Anions such as Cl^- and so₄^2-. derived from the production of titanium dioxide material, by adding the alkaline substance such as ammonium compound, an amine, a Alkali metal compound or an oxazine or piperidine, in the sol for converting the Titandioxidkolloidsols a completely neutral Sol are neutralized.

0039The electrically negatively charged titanium dioxide colloid can be prepared by adding the above-mentioned alkaline Substance to the acidic Titandioxidsolbeschichtung the complexing agent be generated. Furthermore, by applying a Desionisierungsbehandlung through a dialysis process using a semipermeable said membrane to the above- obtain a titanium dioxide colloid sol having a further improved quality will.

Examples

0040The present invention is by the following examples explained, the limit the scope of the present invention in any way.

Examples 1 to 4 and Comparative Examples 1 to 4

0041in Examples 1 to 4 and Comparative Examples 1 to 4 were the following Materials applied.

(1) Titanium dioxide colloid

0042A of the following two types (A and B) of the colloids was applied.

0043(A) In Comparative Example 1, Comparative Example 2, Example 1, Examples 3 and 4 was a product manufactured by the following method Titanium dioxide applied.

0044A aqueous solution of titanium chloride (produced by SUMITOMO SITIX KK, Ti: 15 to 16 percent by weight) was diluted with water and then using an ion exchange membrane deionized, to provide a aqueous Titanium oxychloride. The solution was heated to a temperature of 70-85 ° C to the titanium oxychloride hydrolyze. The titanium dioxide colloid sol having a pH value of 1 to 2 was obtained. The resulting crystalline titania had a particle size of 0.002 to 0.01 microns, determined by an electron from Permeationstyp. The colloid sol contained the titanium dioxide colloidal particles in a dry weight content of 5.0%.

0045(B) , in Comparative Example 3, Comparative Example 4 and Example 2 Titandioxidpulverteilchen (agoprovided by Nibon AEROSIL KK, having a particle size of 0.02 microns and a dispersed type anatase-rutile mixture) in water and hydrochloric acid added to the dispersion to adjust the pH value of the dispersion to 1.5 adjust. The titanium dioxide colloid sol obtained was applied.

(2) complexing (chelating agent)

0046On Complexing agent selected, of glycolic acid, gluconic, Lactic acid, pyrophosphoric and tripolyphosphoric, as shown in Tables 1 and 2, was applied. These chemicals chemical reagents were first class manufactured by WAKO JUNYAKU KK

(3) An alkaline substance

0047A alkaline substance selected of ammonia water (ammonium hydroxide), sodium hydroxide, Lithium hydroxide, triethanolamine, triethylenetetramine, morpholine (tetrahydro-1,4-oxazine), Piperidine and choline, as shown in Tables 1 and 2, was applied. These chemicals were or corresponding chemical reagents first Class or the compositions used in Comparative Examples and Examples of the titanium dioxide colloidal sols are shown in Tables 1 and 2. FIG.

0048Regarding the sols were obtained the modes (positive and negative) from the loaded electricity on the titanium dioxide particles determined by a zeta potential measurement device.

0049Each Sol was used in an amount of 10 ml / m² on a surface a substrate selected Aluminium, acid paper sheet, Zinc plated (galvanized) steel strip or a stainless steel strip coated using a bar coater and was operated at 80 ° C dried. In terms of of the obtained coatings were formed on the substrate the appearance and photocatalytic effectiveness (with respect to fatty acid decomposition rate, Units: mg / m²· Dry) measured.

0050As a substrate, an aluminum alloy in Comparative Example 1 is applied, is an acidic paper sheet in Comparative Example 2 is applied, a zinc plated steel strip was in Comparative Example 3 applied, a steel strip was applied in Comparative Example 4 and a stainless steel strip (SUS 304) in Example 1 and Example 3 applied. Furthermore, in Examples 2 and 4 with a silicone resin primer coated polyester film used as a substrate.

0051As a Ausgangstitandioxidsol was the aforementioned acidic Sol A) or B) applied. In Comparative Example 1, no complexing agent was to the sol liquid added and the alkaline substance was added to the sol liquid to adjust the pH of the sol liquid added at 7 to 8. FIG. Also in Comparative Example 2, Comparative Example 4 and Examples 1 and 2, the complexing agent is added to the acidic sol and Then, the alkaline substance is added thereto to adjust the pH-value of Sol to that as shown in Table 1, adjust.

0052furthermore in Comparative Example 3, the acid sol A) or B) is applied, the complexing agent was added to the sol and was then the alkaline substance is added to such an extent that the pH-value the added to the sol alkaline substance a level of 6 to 12 minutes, to disperse the titanium dioxide obtained. furthermore was in Examples 3 and 4, the obtained Titandioxidkolloidsolflüssigkeit by a semipermeable membrane (regenerated cellulose film) in deionized water for diffusionsdialysiert 24 hours. In addition, in Example 4 the sol liquid a Desionisierungsbehandlung instead of diffuse dialysis treatment subjected, wherein the sol liquid passed through a column filled with an anion and a cation resin column has been.

0053The Properties of the obtained coatings were by the test procedures and evaluation standards are shown below explains.

Appearance of coating

0054generation rust and discoloration one specimen was by the mere Eye observed, and namely good and bad, evaluated in two classes.

density attachment

0055The tight adhesion of a sample coating was measured according to JIS K 5400 Cross Cut Adhesion Test of Coating has been tested and in three Classes, namely well, slightly bad and poorly valued.

Hardness of the coating

0056A Coating a sample piece was a pencil hardness test according to JIS K 500 subjected to the coating by pencils for the pencil scratch test was scratched, the hardness the coating was shown by the pencil hardness. This test was on the specimens, the paper substrate specimens are different, applied.

Photocatalytic activity

0057On Specimen, to which a coating has been coated and dried, with a solution of stearic acid coated in ethanol, ultraviolet radiation from a black 20 watt lamp were irradiated to the coating for 24 hours and a fatty acid decomposition rate 24 Hours (units: mg / m²·dry) was on a difference in weight of the sample between, obtained before and after irradiation.

0058The Compositions of the titanium dioxide colloidal sols and properties of Coatings of Examples 1 to 4 and Comparative Examples 1 to 4 are shown in Tables 1 and 2. FIG.

table 1 <img img-content="tb" img-format="tif" he="47" wi="164" file="00160001.tif" />

note

0059<dl><dt>±₁ ... Aggl.</dt><dd>agglomerated</dd><dt>±₂ ... Disp.</dt><dd>dispersed</dd><dt>±₃ ... -</dt><dd>negative electricity</dd><dt>±₄ ... +</dt><dd>positive electricity</dd></dl>

table 2 <img img-content="tb" img-format="tif" he="47" wi="164" file="00170001.tif" />

0060tables 1 and 2 clearly show that the conventional titanium dioxide sols and in comparative examplePlay 1 to 4 according to conventional methods produced Titania sols satisfactory coating properties for the Material having a low resistance to corrosion and deterioration showed. The in Examples 1 to 4 according to the manufacturing method the present invention titanium dioxide colloid sols prepared show satisfactory coating properties.

Industrial applicability

0061how above explained in detail, is titanium dioxide colloid of the invention a neutral colloidal photocatalytic titania with high stability and high dispersing power and used as a coating material for objects, such as metal objects a low resistance opposite to Corrosion and organic objects with a low resistance to deterioration. When the titanium dioxide colloid for the purpose of decomposition of staining, Ultraviolet ray absorption, sterilization, gas decomposition and Water treatment is applied, the sol may be in a variety be applied by a variety of materials and the problems work atmosphere and security can dissolved will. Therefore, the titanium dioxide colloid and the method for producing the sol of the invention industrially valuable.