Photoreactive Titanium Dioxide Material

SWEDEN

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PUBLISHING WRITING No. 338 306 mt ci C 01 g 23/08 k .. 12 n 23/08

PATENTS AND REGISTRATION OFFICE

Patent Application. No. 8731/67

Validity Day on

Ans. widely available on

Income 20 VI 1967 20 VI 1967 1 VII 1968

Ans. published and the pamphlet published on 6 IX 1971

Priority requested from 22 VI 1966 (United States, 559,403)

TITAN CO. AS, FREDRIKSTAD, NORWAY

Inventor's HF Dantro

Ombuds N Larfeldt

Light-sensitive particulate titanium dioxide material with anatase structure and methods for its preparation

The present invention relates to the production of titanium dioxide materials having photosensitive properties and in particular to a titanium dioxide material which is sufficiently photosensitive for technical use in systems affected by light, e.g. photographic emulsions, copy paper and the like.

Several photosensitive materials are used in systems of this type.

Among such materials are carbon black and zinc oxide. Although carbon black has excellent photoconductive properties, it has few or none of the photosensitive properties necessary for use in copy paper, while zinc oxide has low opacity in copy paper, although it has been used with limited success.

It is therefore desirable that a photosensitive material be produced which has both a high reactivity in photosensitive system, especially in copy paper, and a high opacity.

The present invention therefore relates to the preparation of a titanium dioxide material having high opacity and light sensitivity.

Before describing the present invention, it is desirable to define what is meant by light sensitivity. A photosensitive material is a material that reacts in a photosensitive system, especially copy paper, so that an image is obtained when exposed to ultraviolet light. Although most types of titanium dioxide have a certain Dupl.kl. 12 nt25 / O4i 22 fi7 photosensitivity, cienna photosensitivity is insufficient for use in copy paper. The titanium dioxide material produced in accordance with the present invention is of non-pigment grade and has been specially developed for high light sensitivity and opacity and is therefore particularly useful in the copy paper manufacturing industry. Titanium dioxide materials prepared in accordance with the present invention were examined for photosensitivity and proved to satisfy the requirements considered technically desirable.

The experiments are described below.

The mandible acid test of the sensitivity of the titanium dioxide to the titanium dioxide is mixed with a sufficient amount of aqueous.

0.5 molar mandelic acid solution to give a soft paste. The paste is applied to a slide (127 x 127 x 1 mm), covered with a thick cover glass (127 x 127 mm double reinforced window glass) and compacted so that the paste is distributed over an area of ​​approximately 76 mm diameter. Slides (25 x 76 x 1 mm) were used between the glasses as spacers. The edges of the glass are bonded with a 25 mm tape to prevent evaporation. The reflection from the paste through the slides is measured using a Colormaster Differential colorimeter with green filter. The glass is then placed on a rotating table with the slide side facing upwards · 3 lamps for ultraviolet light (275 watts) arranged as an equilateral triangle, spaced 33 cm from center to center and about 33 cm above the rotating table. The ultraviolet radiation intensity of the lamps was measured for each experiment and for weak lamps were exchanged.

The reflection measurements were made at appropriate intervals, and the difference in the percentage reflection was determined with respect to time. This number is a measure of the light sensitivity of the titanium dioxide material. A change of reflection with at least 5 units within 10 minutes is the minimum required for technical usability.

The new titanium dioxide material and its process are described below:

The photosensitive titanium dioxide material of the present invention has anatase structure and consists of finely divided particles having an average size of the individual particles of 0.05-0.15 µm, of which at least 70% by weight of the particles have a size in the range of 0.03-0.13 µm. , a spectral characteristic of at least +4, a sulfur content, calculated as% S, in the range 0.03-0.15, an area of ​​14-35 m²/ g and a light sensitivity of at least 5 units change in reflectivity within 10 minutes when illuminated with ultraviolet light and measured under the conditions of the mandible acid test.

Titanium dioxide according to the present invention is prepared by effecting titanium hydrate, which is filtered, bleached and washed to remove dissolved salts. The bleached hydrate is substantially free of iron and is alternatively treated with a phosphate compound in an amount of up to 0.3 t calculated as P₂0^ ^vThe phase of TiO2 ^oc^ ^{alt &amp; RRS}·· tive with 0.3% potassium salt, calculated as K 2 O by weight of TiO 2, after which the hydrate is calcined at a temperature of 76 ° -825 ° C to reduce the sulfur content, so that it is reduced to less than 0.15%. calculated as S, whereby a soft, calcined product is obtained which is ground until the milled product has obtained an average size of the individual particles of 0.05-0.15 µm, at least 70% by weight of the particles having the size of 0.03-0 , 13} im.

Although said process may appear to be similar to known processes for preparing pigment of Ti0₂, it should be noted that the present process is performed in an unusual manner so that the product cannot be compared with the technical TiO

A great difference lies in the fact that the afcititanate hydrate is directly calcined, ie. without the addition of treating agents or if used, only with very small amounts of salts commonly used in the preparation of pigmented TiO₂, i.e., etfc phosphate salt and / or potassium salt. In addition, the relatively low temperature of 770 ° -825 ° C is calcined by the calcined anhydrate until the calcined anatase phytite hydroxide contains less than 0.15 µm. sulfur, calculated as S on the weight of TiO₂. This special calcination gives a soft product.

This product can be referred to as subcalculated according to the standards used in the production of titanium dioxide pigmene and therefore has poor pigment properties such as color power, coverage, oil absorption, chalk resistance, etc., in relation to technical TiO₂-pigmenfc.

In addition to the subcalculation, the soft product is ground to a finely divided material. The spectral characteristics of the milled material have been found to be at least &lt;-4, determined by the method described below, and are much higher than the spectral characteristics of a technical TiOg pigment, which usually has a spectral characteristic in the range of +2-0.

Method for investigating the spectral characteristics of titanium dioxide

Titanium dioxide was mixed with a soybean binder containing carbon black and a paste made from the mixture.

3.3 g of TiO₂ and 0.1 g of carbon black was used in the paste. This was coated on a lacquered plate and the wet film was immediately examined in a Colormaster Colorimeter. The spectral characteristics of the titanium dioxide were measured by the afct reflection values ​​measured with red filter were subtracted

3.38306 from the reflection value measured with blue filter and the result was compared with the spectral characteristic of a previously investigated standard titanium dioxide.

This standard is a pigment extracted from a technical grade titanium dioxide pigment manufactured by the National Lead Company under the trade designation Titanox RA-4'5. Spectral characteristics of this particular standard pigment have been set at +2.1. This value was previously determined when a test of the technical quality of Titanox RA-45 was selected and examined, in combination with a special alkyd binder and a special type of carbon black. Since the alkyd binder and carbon black can vary from sample to sample, it is always necessary that a measurement of the standard pigment be performed simultaneously with the sample to be examined and with the same alkyd binder and the same carbon black and that the measured value be adjusted in accordance with the determined value for the standard sample. The difference between the measured spectral characteristic of the standard pigment and the previously determined value +2.1 is the correction value to be added and subtracted respectively from the measurement values ​​of the samples examined to obtain the correct spectral characteristics of the samples:

Determined Sample% blue% red blue - red sp. vats. Correct sp.kar.

_refl. refl, refl, value_tion_value

Standard 42.80 37.05 + 5.75 + 2.1 -3.65

Sample 43.84 36.00 +7.84 -3.65 + 4.19

Result: given spectral characteristic value +4.2.

Such a target, subcalcined material prepared according to the present process, has little or no use at all as a technical pigment, but it has been found to have a high sensitivity to light and is therefore well suited for use in photosensitive systems in which copy paper is used.

The following examples provide a more detailed description of the invention.

Example 1. A titanium hydrate was prepared by adding a titanium sulfate solution to warm water and boiling the mixture. The titanium sulfate solution had the following composition:

Ti0₂ 250 g / l

HgSO ^ 500 g / l

FeSOi, 169 g / l

HgSO4 / TiOg 2.0

Weight at 60 ° C 1.675

3000 ciB ^ titanium solution. heated to 96 ° C was added to 750 cm 2 96 ° C hot watch for 16 minutes. The whole mixture was heated to boiling and boiled for 3 hours for complete hydrolysis. 790 cm 2 of hot water was added to the mixture so that the concentration of TiOg was reduced to 165 g / l.

The hydrate was filtered, washed clean from dissolved salts, bleached with 10 µl, δΟΟ and 0.1 µl of aluminum for 1 hour at 80 ° C and 20 µl of dry substance, filtered and washed with water until it was free of iron. The filter cake was then treated with 0.1% phosphoric acid and 0.22 µl of calcium hydroxide, calculated as P₂° 5 and K respectively₂0 on the weight of Ti0₂The treated titanium hydrate was calcined at 780 ° C for 1.5 hours to give a soft, calcined TiO

The soft, calcined TiO₂ was then ground in water vapor at the ratio of 5s1 between water vapor and pigment. The calcined and ground Ti0₂ had the following properties

1st An average particle size of 0.10 µm with 70 µl of the particles in the range 0.04-0.11 µm.

2nd A sulfur content of 0.09 f is calculated as S on the weight of Ti0₂.

3rd A spectral characteristic of +4.4,

4th A specific surface area of ​​14 m / g.

5th A light sensitivity expressed as a decrease in reflection with

12.3 after exposure for 10 minutes to ultraviolet light in a 0.5 molar mandelic acid solution.

Example 2. A TiO 2 material was prepared under substantially the same conditions as described in Example 1 except that the bleached hydrate was treated with 0.1 µl phosphoric acid and 0.1 µl potassium hydroxide, calculated as Ρ₂° 5 and K respectively₂0 on the weight of TiO₂· The hydrate was calcined at 800^islandC for 1 hour and milled in the same manner as peel tear in Example 1.

The TiOg material had the following properties.

1st An average particle size of 0.06 µm with 70 µl of the particles in the range 0.03-0.07 µm.

2nd A spectral characteristic of +6.6.

A sulfur content of 0.1 µm calculated as S.

2,

3.

4.

5.

A specific surface area of ​​29.1 m / g.

A light sensitivity expressed as a reduction of reflection by 20.4 after illumination for 10 minutes with ultraviolet light in a 0.5 molar mandelic acid solution.

Examples 3-4. The same procedure was used in these examples, except that no additive was added to the hydrate prior to calcination.

The calcination temperature was 77 ° C and 82 ° C respectively.

The results are presented together with the results of Example 1 and in the table below.

For comparison of the product of the present invention with a technical TiOg pigment, the following control pigments were prepared.

A titanium hydrate, similar to that used in the previous examples, was treated with 0.25 percent phosphoric acid and 0.39 percent potassium hydroxide, calculated as PgOO and KgO, respectively, by weight of TiOO. The treated hydrate was calcined at 985 ° C for two hours according to the procedure commonly used in the preparation of TiO 2 pigments. The calcined pigment was then ground. The results are given in the table below.

Compared to a technical TiOg pigment or known ZnO pigment qualities, TiOg materials according to the present invention showed superior light sensitivity and very good opacity and are therefore

<td>too suitable for</td><td>use</td><td colspan="2">in photosensitive</td><td>system.</td><td></td>

<td>Example No. ·</td><td>Chart 1</td><td> 2</td><td> 3</td><td> 4</td><td>Control</td>

<td>Treatment before calcination % KgO % P₂°₅calcination</td><td> 0,22 0,1 780</td><td> 0,1 0,1 800</td><td> 770</td><td> 820</td><td> 0,39 0,25 985</td>

<td>Time for hours</td><td> 1,5 .</td><td> 1,0</td><td> 2,0</td><td> 1,5.</td><td> 2,0</td>

<td>Calcined pigment % s</td><td> 0,09</td><td> 0,10</td><td> 0,14</td><td> 0,035</td><td> 0,006</td>

<td>Spec. Character.</td><td> +4,4</td><td> +6,6</td><td> +5,9</td><td> +4,0</td><td> +2,2</td>

<td>Mean Particle Size (µm)</td><td> 0,1</td><td> 0,06</td><td> 0,06</td><td> 0,07</td><td> 0,22</td>

<td>2 Specific surface area m / g</td><td> 14</td><td> 29</td><td> 31</td><td> 21</td><td> 11,5</td>

<td>Light sensitivity Ref erected reduction after 10 minutes</td><td> -12,3</td><td> -20,4</td><td> -20,1</td><td> -20,1</td><td> -3,0</td>