DE956535C - Process for the production of alumina-containing pigments - Google Patents

Description

Process for making alumina-containing pigments The invention relates to the production of obtained by means of adsorptide of dyes through clay Pigments, in addition to being used for, for example, paints, varnishes, printing inks etc. are primarily intended to serve as a coloring additive to synthetic or natural resins: A relatively precisely defined water content is particularly important for the latter purpose of the additive precondition, which is not too high, but not too much either may be low.

A corresponding fineness of the alumina carrier is also of particular importance Advantage. It has been shown that a finely crystalline structure of alumina is too special useful adsorption pigments leads.

The use of aluminum oxide in the form of that which is dehydrated by heating Bauxite as an admixture to paints and varnishes has been suggested earlier, where the possibility was also mentioned, the alumina carrier plant or tar dyes . to be incorporated, which changes the color of the bauxite. However, since the natural Bauxite is almost always more or less colored by iron oxide and the like so it is difficult to achieve pure shades. In addition, the earlier ones are missing Proposals the knowledge that the content of the alumina carrier in water of hydration in must be kept quite narrow limits in order to arrive at a pigment that in particular is useful as an additive to synthetic and natural resins. It corresponds to the one at that time. State of the art (192q.), Not thinking of such a possibility and therefore to keep the regulation so far that the products that can be manufactured according to it are mostly too cannot be used for the purpose recently envisaged. The ones after the earlier ones Pigments obtained in the process are poorly distributed in the various plastic ones Masses, and their use usually results in "wandering" of the dye, i.e. H. to diffuse the dye from the pigment into the plastic mass.

It has now surprisingly been possible to obtain Pigmervte based on alumina manufacture which, apart from their pure hues, when used as an additive plastic materials or plastics never lead to incorrect results. A "wandering" does not take place, and the application of the pigments is particularly easy.

The knowledge on which the invention is based is that a pure clay must be used as a carrier for the dye, the content of which of hydration water is within very specific limits. This is the only way to guarantee that one arrives at pigments which are useful for the plastics industry; about that but also when used in paints and varnishes certain advantages (better Mixability, pure colors).

According to the invention, the adsorption of the dyes is incomplete dehydrated clay applied, the at least 0.51 / 9, preferably at least i 10 / a contains water of hydration.

The clay to be used for the production of the pigments can be obtained according to the invention by heating the alumina hydrate; Temperature and The duration of the heating is regulated so that the product obtained is preferably - if the starting material is a monohydrate of aluminum oxide (A12 03 "H2 O) - 1 to 12 percent by weight or - if you are from a more highly hydrated starting product assumes -i contains up to 18 percent by weight of water. According to the invention, it is special advantageous heating at temperatures below 575 °, preferably between 20o and 55o °.

Although the process is applicable to all hydrated clays, whatever structure and crystal size they may have, they are clays preferred, which are in the finely crystallized form possible.

Alumina trihydrate, which is in the form of submicroscopic crystals, the largest diameter of which is between 50 and 500 μm, and the monohydrate formed by dehydrating this trihydrate in an aqueous medium, is therefore best suited for the production of colored fillers for plastic masses. The monohydrate has the additional advantage that it leads to pigments which show a more intense coloring power with the same dye content.

If the alumina hydrate by the method according to the invention Heating is incompletely dehydrated, the obtained alumina with the or brought together the dyes that one wishes to fix on it. This process is carried out in a known manner in the liquid medium, the dye being either is dissolved or suspended in a solvent. The clay loaded with dye is then dried.

If the coloring of the clay is carried out in an aqueous solution, so is It is recommended to adjust the hydrogen ion concentration of the solution to the pH at which the fixation of the dye proceeds best.

Otherwise, depending on the nature of the dye, it may be desirable be able to carry out the coloring of the clay in the warm or in the cold.

The pigments to be produced according to the invention can with the help of under very different dyes or dyes belonging to different classes will. Some of them are given as examples only and not in any way limiting Character, listed below: Indigosol-Grün IB (sulfuric acid ester of the leuco compound von Bz-2-Bz-2'-Dirnethoxydibenzanthron), Indigosol-Goldengelb IRK (sulfuric acid ester the leuco compound of dibromo-3, 4, 8, 9-dibenzpyrenquinone-5, 1o), indigosol brown IRRD (sulfuric acid ester of the leuco compound of 6, 6'-dichloro-4, 4'-dimethylthioindigo), Chromocitronin R (Bradford Color Index No. 441, 1924 and 1928), Ecarlate Foulon DH (No. 443 of the British Color Index), Rhodamine B (No. 749 of the British Color index), Eosin DWC (# 768 of the British color index), various aluminum colors etc.

In the case of the colored ones obtainable by the process according to the invention The clay contained therein preferably has pigments at about 100 ° Drying carried out to constant weight has exactly the same water content as the clay used for their manufacture. In this respect, therefore, contains in the after preferably used procedure produced and up to constant weight dried pigments the clay more than i%, and less than 18% water. as well most of the other characteristic properties of the used can be found Clay in these pigments again.

The pigments made by the process of the invention are for can be used for many different purposes, such as paints of all kinds, printing inks etc. and especially as an additive to plastic materials, such as plastics based on vinyl, acrylic acid and styrene and their copolymers, etc., in which they are well distributed and do not cause the dye to "migrate". the Pigments can also be used to advantage for rubber, provided that that the dye they contain is resistant to vulcanization.

Of course, the method of the invention is just as valuable for the production of mixed pigments that are used in addition to clay for fixing the dyes contain suitable substances.

The following examples supplement the above description without of course to somehow limit the scope of the invention.

Example i A very fine-grained alumina trihydrate was prepared on the following Method of preparation: Containing sodium aluminate liquor to be subjected to decomposition 150 g Nag 0 and 140 g Al, 03 in the liter. 2.15 g (calculated on A120 ,;) of a gel obtained by being put into a mechanically stirred container at the same time a dilute solution of sodium aluminate (10 g Na, O per liter) and sulfuric acid of 8 ° Be allowed to run in, with one during for the duration of this process a pH of 4.75 was maintained, and then that the precipitate obtained deposited on the filter press and washed.

The decomposition of the aluminate was carried out with the help of a trick carried out, which consists in introducing only part of the treatment to be treated Add lye (e.g. one tenth) to the reaction, and then, after stirring for a few hours, which lead to effective decomposition, on an ongoing, continuous basis add the rest of the lye.

The decomposition carried out at 25 ° lasted in this way on the whole 2 days. The hydrate obtained had an apparent density after drying at 100 ° of o, iio and a specific surface area of 14 m2 / g. The heating of the alumina trihydrate was performed at 43o ° for 2 hours.

The alumina thus obtained had a specific surface area of approximately 2.50 m 2 / g; it was colored with Indigosol-Green IB in the following way: 100 parts by weight of clay were introduced at 20 ° into 1000 parts of an aqueous solution containing 1 part of dye and 2 parts of 80% formic acid. After the mixture had been left to stand for 5 minutes, 2 parts of sodium nitrite were added and the mixture was stirred for 5 minutes, whereupon 10 parts of sulfuric acid at 66 ° Be were added and the reaction mixture was left to stand for a further 15 minutes. The dyebath was then diluted with excess cold water and filtered off. After washing and drying the colored clay contained approximately 10% dye. It was used as an additive to a polyvinyl chloride plastic. For this purpose, 1 part by weight was mixed with 60 parts of polyvinyl chloride, 20 parts of octyl phthalate, 10 parts of butyl phthalate, 10 parts of tricresyl phosphate and 1 part of titanium dioxide. The mass obtained in this way was completely uniformly colored and did not show any subsequent migration of the dye.

Example 2 The alumina trihydrate, the preparation of which in Example i is described, was heated in an aqueous medium in the autoclave at 2io ° for 1 hour and so converted into the monohydrate, which after washing and drying at 100 ° an apparent density of o, o65 and an oil uptake of 120 ccm on i oo g (measured according to the method of Gardner and Colmann).

The monohydrate was heated to 480-500 ° for 100 minutes, after which time the clay obtained in a bath of Ecarlat Foulon DH (No. 443 of British Bradford color index, 192.4, and 1928), the 10 g dye and 4 g H2 SO, per liter contained, colored. The proportion of dye was approximately 10%, based on that to be colored Clay.

The pigment obtained spread very easily in plastics, and the examination of the so colored plastic masses showed that it was, with the same Dye content of the clay, exhibited a more intense coloring power than that of others Pigments made from alumina hydrates.

Claims (5)

PAT EN'IANSPNÜCH? -: i. Process for the production of alumina-containing pigments by dehydrating heating of water-containing aluminum oxide and adsorptive coloring of the dehydrated product, characterized in that a pure alumina hydrate is subjected to incomplete dehydration by heating to zoo to 575 ° in such a way that it is still at least 0.5 0/0, however Contains a maximum of 180/0 water of hydration. 2. The method according to claim i, characterized in that the hydration water content according to after dehydration is 1 to 120 / a. 3. The method according to claim i or 2, characterized characterized in that an alumina hydrate containing more than one molecule H20 is heated to a molecule A1203 in such a way that it is then more than 100% water of hydration contains. 4, method according to claim i or 2; characterized in that the dem incomplete dehydration of all or part of the clay to be subjected Toncrdemonoi hydrate consists in the form of microcrystals, the largest diameter of which below 2, U is. 5. The method according to any one of claims i to 3, characterized characterized in that the clay to be subjected to incomplete dehydration, consists wholly or partly of alumina trihydrate in the form of microcrystals, whose largest diameter is below 50o my. Considered publications: German patent specification No. 484 969.