DE2009566C2 - Process for the production of titanium dioxide or titanium dioxide aquate coatings - Google Patents

Description

For the application of titanium dioxide coatings on the subject of the invention is accordingly a various types of surfaces, several methods for the production of titanium dioxide or known, such as. B. hydrolysis of vapor-deposited titanium dioxide aquate coatings, which consists in that tetrachloride films by water vapor (Gmelins Hand- man to an aqueous suspension of zu überbuch der inorganic chemistry, 8th edition, vol. 41, 5 drawing materials at temperatures between titanium, p . 231), hydrolysis of Titansäureesterschichten about 50 and about 100 ⁰ C and a pH or solutions thereof in organic solvent of between 0.5 at the same time, an aqueous 0.001 to transmit (USA. patents 2,768,909 and 2,943,955 ) 5 molar solution of a titanium salt with a content or vapor deposition of metallic titanium and subsequently free acid corresponding to a normality of slow oxidation (German patent 855 767). ίο 0.002 to 3 and an aqueous, 0.025- to 10normal. Depending on the method used, the alkali or ammonium hydroxide solution or gas coatings are used to improve the optical characteristic ammonia adds, the supply of the adhesive of the coated objects, z. B. to the base is held in such a way that the acid that is mainly contained in the change in the reflectivity or for the generation of titanium salt solution and the acid that arises from the reaction of interference colors to achieve durable overion is able to neutralize and draws (German Auslegeschrift 1055 193 ) or in order to maintain a constant pH value, the formation of intermediate layers in order to create further coatings. The amount of titanium salt added per minute can be applied more firmly. The coated bodies in the range of about 0.01 to 20 · bodies are glass, metals or 10 ~ ^s mol of titanium salt per square meter of plastics to be coated. ao surface.

In part, these coatings are produced in such a way that it is essential that an excess of titanium salt is produced so that it is mechanically avoided from the coated surfaces. The process according to the present niche can be removed in order in this way thwarted an excess of titanium salt lamellar titanium dioxide pigments with iridescent and almost completely prevents free, hydrati properties to be obtained (USA. Patents as based titanium dioxide particles, which are not in the invention to over-3 071 482 and 2 941 895 as well as German Auslegeschrift laying surface, in the suspension 1 136 042). It has also already been suggested that they exist. Rather, the hydrated TiO ₂ forms pigment properties of finely divided mica sheet- homogeneous and amorphous deposits of the same size with those of titanium dioxide and a uniform layer thickness on the surface to be coated and possibly the pigment on the mica 30. This effect will be noticed (USA.-Patent 2 278 970). One achievement of driving only one amount of titanium dioxide-coated mica titanium salt for hydrolysis, such as that produced for pigments, is achieved in the USA patent specification that the hydrated 3,087,828 and in the Belgian patent 619 447 TiO _{1 is} required and as described per unit time of the. After this process, finely divided 35 available surface areas can be absorbed. Mica flakes in aqueous suspension by There are therefore no hydrated titanium dioxide hydrolysis of a dilute sulfuric acid titanium (IV) particles that are not deposited on the surface to be coated oxide sulfate solution at boiling point with titanium dioxide. If coated as oxide aquat to be coated. From the chemistry of the normal surface mica flakes are used, be-titanium dioxide pigments is known, what influence does the finished pigment rather exclusively from on the later pigment properties the type of small flakes, which with an even and equal hydrolysis of the sulfuric acid titanium used there moderate layer of hydrated titanium dioxide tan (IV) oxide sulfate solutions has been documented (G mel i η Ie, p. 97. This homogeneous layer contains none to 103). A large number of patents deal with these coarse particles of hydrated TiO ₁ , and there are circumstances, all of these methods also do not deposit such coarse particles on the surface of sulfuric acid titanium (IV) oxide sulfate solutions. Such non-homogeneous agglomerates go and lead to titanium dioxide products. of hydrated TiO ₁ would reduce the sheen of the

The previously known processes for the production of pigments and the formation of uniform titanium dioxide coatings are still relatively expensive, borrowed interference colors are just as disturbing as they are not, since according to these processes the production of very much whipped TiO ₁ . According to the process of the invention, uniform coatings only via the gas phase result in a coated pigment with an upper real light. surface that optimally corresponds to the flat,

It has now been found that the hydrolysis-warping surface, e.g. B. of mica flakes,

thin, aqueous acidic titanium salt solutions below

dance certain conditions to very even ss This effect is best achieved when one

Coatings of titanium dioxide aquates with a definable hydrolysis at as completely constant as possible

Layer thickness on a wide variety of substrates, temperature and with approximately constant pH values

leads. It also avoids performing the procedure after. The pH is adjusted by adding a

of the invention the use of a gas phase and base, preferably an alkali metal hydroxide, e.g. B.

the use of complex mechanical devices 60 NaOH, maintained,

services. According to the invention, neither organic become one of the most characteristic and important

Solvents still aggressive inorganic substances Features of the present invention is the addition

rather, the process is only used in (the rate of execution of the titanium salt in moles

aqueous, weakly acidic medium carried out, where- per minute per square meter of the to be coated

by using a special corrosion * · 4s area.

solid oil material on the one hand and safety precautions * According to the invention, the hydrolysis takes place in

Calculations due to flammable organic solvents aqueous solutions at temperatures between 50 and

on the other hand, 100 "C, preferably between 70 to 80" C, are unnecessary. At this

3 ^ 4

Hydrolysis must ensure that the amount of titanium salt introduced in the 0.01 to 20 · 10 " ^δ ΜοΙ titanium salt per square unit of time or the surface area to be covered from it. The amount of titanium dioxide aquat to be covered varies greatly over time depending on which surface is adequate, ie titanium salt solution is used from this surface and which material is completely absorbed and should not be covered with free suspension. Of course, the reaction liquid remains Roll, the hydrolysis is carried out in such a way that the covering can be achieved, for example, after only 1 to 4 hours of objects or substances in water (e.g. with barium sulfate), hung or suspended in it After the material suspension to be coated with others to the necessary temperature (about 50 io lien considerably long longer times - up to several to 100 ° C), a diluted day is required with stirring.

aqueous, 0.001 to 5 molar titanium salt solution, which naturally arise according to the process of a free acid content according to an invention titanium dioxide aquate coatings. These coatings Normality of 0.002 to 3 possesses, expediently under can by simply standing in the air or the liquid surface, fed. At the same time 15 by drying in the usual drying devices the dilute aqueous base is allowed to be completely or partially dehydrated in the suspension. The higher the flow in or feed in gaseous ammonia. The drying temperatures can be chosen. Base is used to neutralize those in the titanium salt solution, for example when looking at the coated materials contained and continuously deglowed from it by hydrolysis, the less water there is in the rising ones Acid necessary. ao brought layers and all the more are in the X-ray. Both the titanium salt solution and the base diagram show the anatase lines. Is at if it is advantageous to anneal at higher temperatures using suitable metering devices, this is indicated in the X-ray. In addition to the lines of the base body, the lines of the which recognize the usual dosing pumps and liquid rutile, rotameter in question. 25 The method according to the invention leads only under

If a Titai'OHJ salt solution is used, compliance with the specified conditions is the same additional oxidation is required. Preferred moderate coatings. This avoids being used as a secondary oxidizing agent Oxygen, especially in the form of products in the suspension liquids, is free Air. The oxygen required for oxidation was found in particles of titanium dioxide quatene will become 30 at the interface with vigorous stirring. Such freely moving particles in the Sus air recorded. In the case of unfavorably shaped vessels, pension can subsequently be applied to the it is necessary to get a weak flow of air through the surface and so the homogeneity of the To let the suspension liquid pearl. Interfering as titanium (III) coatings. The adhesive strength suffer as a result Salts come water-soluble titanium (III) -saize, preferred and the optical properties of the applied wise strong acids, especially titanium (III) chloride, 35 layers.

-bromide or -sulphate, in breakfast. Suitable titanium (IV) - According to the method of the invention, the

Salts are the chlorides and bromides as well as titanyl - the most varied of materials in the most varied

sulfates. The anions of these salts practically play forms with titanium dioxide or titanium dioxide aquat

does not matter for the course of the procedure. trains are provided. However, the prerequisite is that

The substances to be coated in the weakly acidic alkali in particular can be used as the aqueous alkali

hydroxide solutions, preferably sodium hydroxide solution or suspension medium at temperatures of about 50 to

Potash lye, or ammonium hydroxide, used around 100 ° C are sparingly soluble or no decomposition

will. It is advisable to use 0.025 to suffer. As soon as under the test conditions of

lOnormal solutions. However, the substances to be coated can also be gaseous or molecules

Ammonia can be used. The amount of the 45 discharged into the reaction medium to a greater extent

Unit of time supplied base can be given within narrow limits, is the occupancy still to be achieved

can be varied without undesirable side effects either imperfectly or practically

products are created. This variation changes feasible. For example, the following substances

the pH value, which is an important measurable variable: minerals, e.g. mica or

for the control of the whole procedure. There 50 graphite, glass, plastics, metals or others

it has been shown that pH values in the range from 0.5 to artificial or natural inorganic or organic

5.0, in particular between 1.5 and 2.5, for production see products such. B. barium sulfate, or

good coatings are particularly suitable. Phosphors such as calcium tungstate with manganese

In order to maintain this pH, desired activated zinc silicates, cadmium silicates or cad

If necessary, buffer substances can also be added. Bs as miumborate, or with manganese, antimony or

know all buffer systems used that contain cerium activated calcium halophosphates.

Usually for this pH range come into question, It is possible also larger coherent ones

z. 8. Phosphates, acetates, citrates or glycocollar surfaces with titanium dioxide in the specified manner

Buffer. occupy. It is advisable to use the relevant

According to the method of the invention, it is therefore possible to hang in a suspension of a finely divided material on the surfaces to be covered, if necessary with a different material unit to offer only so little titanium salt that it is also coated with titanium dioxide, so that the the total titanium hydroxide or titanium dioxide aquat is large enough on the total available surface area can separate the surfaces and none is free, in order to allow »prolonged expansion of free titanium dioxide * Movable by-products in the suspension * «a aquat germs in the suspension liquid to prevent liquid (liquid can arise. If, for example, larger glass plates

itit wants to occupy each minute used with titanium dioxide according to the invention, so

Titanium salt quantities are in the order of magnitude. It is advisable to put these glass plates in a suspension

to hang from mica flakes or glass beads, as it is possible to create a sufficiently large surface To provide that prevents freely moving titanium dioxide aquates from occurring in the reaction medium.

According to the process of the invention, products coated with titanium dioxide or titanium dioxide aquate are obtained obtained, which are characterized by a particularly uniform coating. The coated materials therefore all consist of such uniform titanium dioxide or titanium dioxide aquate coatings deriving advantages, such as good reflectivity, clarity, transparency, protection against corrosion and pure interference colors. So far, such coated materials could not have the same color quality and brilliance first made possible by the method of the present invention are.

Especially mica coated with titanium dioxide results in pearlescent pigments of any color. The interference colors obtained are only dependent on the thickness of the applied film. It is desirable to stabilize the photosensitive pigments obtained by the process of the invention by calcining at temperatures between 700 and 1000 ^° C., preferably between 900 and 1000 ^{° C.}

It is also possible to apply a metal oxide layer to or with the titanium dioxide layer mix. In this way special color effects can be achieved, especially with such Metal oxides that are colored themselves, such as iron, nickel, cobalt or chromium oxide. These extra oxides can tax their own color as well as interference colors and thus special color effects Evoke beauty.

example 1

10 g of wet milled mica of the commercial type ORS with a surface area determined by the BET method (Journal American Chemical Society, Vol. 60 (1938), p. 309, and Journal American Chemical Society, Vol. 62 (1940), p. 1723) 2.3 m ² / g are suspended in 11 water. The suspension has a pH of 6.8. It is heated to 74 ° C. with stirring. During the occupancy, a gentle stream of air is passed through the suspension with a glass frit. A 0.0324 molar titanium (III) chloride solution, which is 0.118 N hydrochloric acid, is fed in at a rate of 225 ml / hour using a metering pump. fed under the liquid surface. After the pH of the suspension has fallen to 2.3 (5 minutes), a 0.22 normal aqueous sodium hydroxide solution is allowed to flow into the suspension using a second metering pump. The progressive coating of the mica surface with the titanium dioxide daquat can be recognized by the Newtonian interference colors that appear. The iridescence of the mica flakes in the suspension, which was weak at the beginning of the experiment, becomes increasingly stronger. Starting with a light gray-blue, the familiar color levels are passed through.

The procedure described is repeated several times, whereby the experiment is ended with the colors white, OeIb, red, blue and OrDn. The final pH value is between 1.9 and 1.7.15 ns. The ratio of the number of moles of tifnndioftide used / m '/ minute is 3.3. Hi * in the present case. After the desired low temperature has been reached, the suspension is filtered off, washed free of chloride with hot water and dried at 200.degree. Half of the substance obtained in this way is annealed at 500 ^° C., drying and annealing do not result in any change in the interference colors. The X-ray diagram of both products shows, in addition to the lines of mica, those of anatase uniform interference color to recognize a very even occupancy. The quantities of solutions required to achieve the respective color, as well as the duration of the coating and the titanium dioxide content of the end products can be found in the following table:

20th 3 hours 40 minutes Consumption 0.22no -
malet ⁰ L ΠΟ, 18.4 color 5 hours 25 minutes 0.0324- NaOH in the
End product 25.7 Duration 6 hours 15 minutes molar
TiCl ₃ - ml 28.4 8 hours lOMin. solution 34.9 * 5 9h 15min. ml 805 200 ° C | 500 ° C 38.2 White 1198 yellow 825 1385 17.8 Red 1218 1817 24.6 blue 1405 2060 27.7 green 1837 34.3 2080 36.8

Example 2

Fine glass beads, about 70 μ in diameter, such as those used for covering projection walls, are suspended in water (1 kg glass beads / 21 water). The pH of such a suspension is alkaline; it is acidified to about 2.5 by adding dilute aqueous hydrochloric acid. After heating to about 8O ⁰ C, the pH increases again. This addition of hydrochloric acid is continued until a set pH of 2.5 remains unchanged for several hours. The glass beads are then washed and dried. 550 g of the glass beads treated in this way are suspended in water. In this suspension is fed under stirring and heating to 74 ⁰ C 680 ml of a 0,0324molaren titanium (III) chloride solution, the hydrochloric 0.118 n-is, at a feed rate of 120 ml / hr. such as

670 ml of a 0.22 η sodium hydroxide solution and a feed rate of 120 ml / hour. over the course of 5 hours and 40 minutes. The ratio of TiO ₂ / m ^s / minute is 5.2 x 10 "*. After filtration, the beads can be seen with a microscope

So even layer covered by titanium dioxide. The reflectivity of the coated glass beads is greatly increased.

Example 3

Graphite as he used to eat heating baths is commercially available, is wet-ground in a ball mill with water and sieved through a sieve of 75 μ mesh size, filtered and dried. 10 g of the grapnite treated in this way are suspended in 11 water and heated to 74 ° C. with stirring. In this suspension is allowed to flow at a rate of 229 mt / h a dilute Titan (III) «chlorld solution flow according to example 1 and 2 through a dosing device. After 20 ml of this solution have been fed in, a second metering device is used to add 0.22 n-soda Lye added at the same rate of addition. There is a weak air flow during Jo's experiment

Initiated into suspension. The experiment is ended after consumption of 1818 ml of mineral oil solution and 1800 ml of sodium hydroxide solution, the pH value after the reaction is 2.1. The graphite is drained off, freed from chlorides with hot water and dried at 200 ° C , ir "Igt a Bronzefarhe; the Titendiö * id * oehalt beirlgt 29.6 · /» TIO ₁ the suspension fluid is clear;. in it no titanium is detected.

Example 4

12.8 g of polyamide powder with an average particle size of about 10 μ are suspended in 50 ml of water with vigorous stirring and heated to 74 ° C. In dit * suspension (pH 3.7) can men with a feed rate of 60 ml / hour. a dilute titanium <ni) - "chloride-Ld8uni - flow in according to Examples 1 to 3 through a metering device, which corresponds to a feed rate of about 5 · 10- · mol / min. / m *. After 10 minutes, the pH has set to 2.4. A 0.22 η sodium hydroxide solution is now added at the same feed rate via a second metering device. The experiment is ended after 42OmI titanium (III chloride solution and 410 ml sodium hydroxide solution) have been consumed (7 hours). The final pH is 2.4. The polyamide powder is filtered off, washed free of chloride with warm water and dried at M) C. It has a pale yellowish color and contains 7.9% titanium dioxide. No titanium can be detected as thrown into the clear suspension liquid. In contrast to the untreated material, no agglomerates can be seen under the microscope. The pourability has been increased significantly by the titanium dioxide coating.

Example p

10 g of wet-ground mica of the commercial type ORS with a surface area of about 3 m * / g are suspended in 1 liter of water. The suspension has a pH of 6.8. It is heated to 74 ° C. with stirring. During the occupancy, a gentle stream of air is passed through the suspension with a glass frit. Using a metering pump, add a 0.0167 molar titanium (HI> sulfate solution in 0.85 N sulfuric acid at a rate of 225 ml / hour) under the surface of the liquid. After the pH of the suspension has fallen to 2.2 to 2 is (5 minutes), a 0.96 η sodium hydroxide solution is allowed to flow into the suspension using a second metering pump. The progressive coating of the mica surface with the titanium dioxide aquat can be recognized by the Newtonian interference colors that occur. The weak iridescence of the mica flakes at the beginning of the experiment in the suspension becomes increasingly stronger.

The final pH is between 1.9 and 1.7. The ratio of the number of moles of titanium dioxide / m * / Mimite is 4 · 10- '. After reaching the desired hue, the suspension is filtered off, washed with hot water until chloride free and dried at 200 C ^c. Half of the substance obtained in this way is annealed at 500 ° C. Drying and annealing do not result in any changes in the interference colors. The X-ray diagram of both products shows, in addition to the lines of the mica, Hin of anatase.

5 hours, 00 min.

White

to

Example 6

Throw in a solution of 2.6 g of sodium chloride, 3.3 g of potassium chloride and 10.3 g of barium chloride dihydrate in 5.91 of water at room temperature

ι) tubes 1.21 of an I n-sulfuric acid slowly topgiben. During dtr the sulfuric acid is added I see barium sulphate as slightly iridescent Precipitation from. The precipitation is allowed to settle and it is decanted three times with 2 liters of ionized water each time. the

te yield is 10 g of barium sulfate. Under the microscope, the crystals show star-shaped adhesions, which disappear with irregular colors reveal thin leaflets. The Kristallausdehnup ^ in the platelet level is 50 to 70 μ;

«5 the crystal thickness is about 1 μ.

6 g of such a barium sulfate are suspended in 1 l of water and the suspension is heated ^{to 74 ° C.} A 0.324 molar titanium / D chloride solution is left under the surface of the liquid while stirring.

which is 0.118 n-hydrochloric acid. flow in. The feed rate is 22.5 ml per hour. After 15 minutes the suspension has reached a pH of 2.2 . A 0.22 η sodium hydroxide solution is now allowed to flow into the suspension at the same rate.

After a test duration of 1 hour, the feed rate of both solutions increases to 45 ml per hour elevated. After the course of a further hour throw the same to 90 ml per hour or 120 ml per hour increased for both solutions.

During the experiment, evaporated water is replaced from time to time, so that the suspension volume is kept at 11. After total The attempt is over after 4 hours. The final pH value is 1.8 to 2. There is none in the suspension liquid

4S dissolved TitarKlU) salt or colloidal titanium dioxide * aquate can be detected. The iridescence of the Bariurr nlfatkristaüe has intensified. The color is white. The crystals are filtered, washed free of chloride * with hot water and dried at 200 ° C. The titanium dioxide content is 10.7 ⁹ I ₉ .

Example 7

Throw 30 g of mica in a 5-1 beaker a specific surface area of 3.37 m * / g (determined according to BET) with stirring in 11 deionized water suspended and heated to 75 ° C. With the help of a dosing device, first drop by drop an O, 132 molar titanium CIVychloride solution containing 0.948 n-hydrochloric acid, with a feed rate of 120 ml per hour introduced. As soon as the pH of the suspension has dropped to around 2, a second metering device and the same feed rate a 1,475 N sodium hydroxide solution initiated; this corresponds to a precipitation amount of 2.61 -10- · Mol TiOj / m * / minute. The known Color levels are run through. After the desired shade is achieved. the pigment is removed

Claims (9)

filtered, washed neutral with deionized water, dried at 120 ° C. and calcined at 95O0C. Example 8 15 kg of mica of the muscovite type, particle size S approx * Gef & D is suspended so that a 5% to 10% solution is formed, which is brought to a pH of 2.2 by adding a 25% hydrochloric acid (0.93 N) solution of titanium tetra · chloride. The solution is stirred and heated to a temperature of 70 to 73 ° C. and kept at this temperature during the entire treatment process The pH is kept constant by adding 35% aqueous NaOH. Coating is complete when 1.00 kg of titanium tetrachloride per kilogram of mica has been consumed. The pigment obtained is washed with deionized water, dried and glued for 30 minutes at 950 ° C üht. The pigment is silver in the transmitted light. Example 9 aJ The procedure is analogous to Example 8, with the exception that, in order to obtain other color pigments, the following amounts of TiCl are used per kilogram of mica: 30 33 patent claims: 1. A process for the production of uniform titanium dioxide or titamlioxtdaquatfiberzügen, d a- 4 »characterized in that an aqueous suspension of materials to be coated at temperatures between about 50 and about 100 ⁹ C and a pH between 0.5 and 5.0 at the same time an aqueous, 0.001 to 5 molar solution of a titanium salt with a content of free acid corresponding to a normality of color kg TiO ₁ Ag mica gold
Red
blue
GrQn 1.85
2.07
2.52
3.30 0.002 to 3 and an aqueous, 0.025 'to 10normad alkali or ammonium hydroxide solution or the corresponding amount of gaseous ammonia is supplied, the supply of the base being controlled so that that contained in the titanium salt * solution and that formed during the reaction "acid is neutralized while maintaining a nearly constant · ρ Η value, and that the pr minute amount of titanium salt added is in the sizes' order of about 0.01 to 20 · 10 · mol per square meter of tu slip resistant finish. 2. The method according to claim 1, characterized in that the reaction is carried out at a temperature between 70 and 80 "C, a pH of 1.3 to 5.0 and a feed rate of the titanium salt of less than 5 10 · mol per minute and square meter of surface to be covered, preferably between 0.1 and 1 · 10- · Mol. 3. The method according to claim 1 or 2, dadurc characterized in that one is to be coated Material used mica flakes. 4. Process according to Claims 1 to 3, characterized in that the titanium salt is titanium tetrachloride is used. 5. Process according to claims 1 to 3, characterized in that the titanium salt is a Ti tan (I U) -SaIz is used and the process is carried out under the influence of atmospheric oxygen. 6. The method according to claims 1 to 5 as characterized in that the pH before dei Hydrolysis is adjusted to a value between 0.5 and 5j by adding an acidic titanium salt solution. 7. Process for the production of pigments based on glim coated with titanium dioxide mica flakes, characterized in that the titanium dioxide is applied to the mica flakes Hydrolysis of a titanium salt according to claims to 6 is noticeable. 8. The method according to claims 1 to 7, characterized in that it is for production Perlglan / pigments is used. 9. The method according to claims 1 to 8, since ' characterized in that it is used for the production of arbiger pearlescent pigments.