GB1575924A - Form of pigment yellow 61 - Google Patents

Abstract

The monoazo pigment of the formula I is prepared with an alkali metal content of less than 0.3%. For this, the alkali-metal-containing compound formed by translaking the corresponding alkali metal salt with a soluble calcium salt is freed of the alkali metal by washing. The low alkali metal content pigments obtained have significantly improved water fastness. <IMAGE>

Description

(54) IMPROVED FORM OF PIGMENT YELLOW 61 (71) We, BASF AKTIENGESELL SHAFT, a German Joint Stock Company of 6700 Ludwigshafen, Federal Republic of Germany, do hereby declare the invention for which we pray that a Patent. may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following Statement:- The present invention relates to an improved monoazo pigment, its manufacture and use. The pigment according to the invention has the formula I

The above compound, known as Pigment Yellow 61, has hitherto been known only in an impure form, containing as impurities one or more alkali metals in amounts exceeding 0.3 /" by weight (typically 0.4 /" to 1.2% by weight).In that form the compound exhibits a brilliant greenish yellow hue but has poor fastness to weathering and only moderate fastness to plasticizers.

It has now surprisingly been found that the compound of formula I shows a great improvement in fastness to weathering if the content of alkali metal impurities (especially sodium and potassium) is reduced to a level of 0.3 /" by weight or less, especially not more than 0.2V by weight. It has in particular been found that reduction of the sodium content of commercially available Pigment Yellow 61, prepared by conventional laking of the corresponding sodium compound, to a level of 0.3 /" by weight or less achieves a great increase in fastness to weather.

Accordingly, the invention provides the pigment of the above formula I in a form which contains not more than 0.3% by weight of alkali metal.

The product according to the invention will preferably contain less than 0.3 /,, by weight of alkali metal, and most preferably from 0 to 0.2 /" by weight of alkali metal.

The fact that the product according to the invention is distinguished by better fastness to weathering than prior art forms means that, in particular, it may be used in printing inks and in surface coating formulations such as paints or resin finishes, e.g.

melamine resin finishes or acrylate resin finishes, in plastics materials, e.g. PVC, polyolefins or polystyrene, or for coloring polymer dispersions, e.g. for paints used on wallpapers.

To manufacture the product of the invention, the corresponding alkali metal compound may be laked with a soluble calcium salt and the alkali metal salt removed, e.g. by careful washing out, until the alkali metal content is not more than 0.3% by weight. Alternatively, the diazotization and coupling may be carried out, from the start, in the absence of alkali metal salts, and the free sulfonic acid or ammonium salt thereby produced converted directly to the calcium salt. For this purpose, the method described in German Patent 2,049,620 may, for example, be used.

The process may be carried out as described in the Example which follows, in which the parts and percentages are by weight.

EXAMPLE 109 parts of 2-nitroaniline-4-sulfonic acid are dissolved in 650 parts of water at 800 C.

160 parts of 23 per cent strength sodium nitrite solution are then added to the above solution, after which the batch is run into a mixture of 600 parts of ice and 400 parts of concentrated hydrochloric acid. During the addition, the temperature is kept at from 0 to 30C while stirring and adding ice if necessary. Stirring is then continued for one hour at from 0 to 30C, and about 2 parts of amidosulfonic acid are added. 91 parts of acetoacetanilide and 1,000 parts of water are then added, finally followed by 240 parts of anhydrous sodium acetate, during which additions the temperature rises to 12--130C and the pH to 5. Stirring is continued for 2 hours.The batch is then heated to 900 C, 70 parts of anhydrous calcium chloride (dissolved in 150 parts of water) are added and stirring is continued for 3 hours at 90"C. A further 1,000 parts of water are then added, after which the precipitate is filtered off and thoroughly washed with hot water. 200 parts of the pigment of the formula I are thus obtained; this product contains 0.12 per cent of sodium and differs from the conventional products, which contain more than 0.3 per cent of sodium, in having better fastness to weathering when used in a finish.

WHAT WE CLAIM IS: 1. The monoazo pigment of the formula:

in a form which contains not more than 0.3 per cent by weight of alkali metal.

2. A product as claimed in claim 1 wherein the alkali metal content is from 0 to 0.2% by weight.

3. A process for preparing a product claimed in claim 1 or 2 which process comprises laking the corresponding alkali metal salt with a soluble calcium salt and removing the resulting alkali metal salt until the content of alkali metal in the calcium compound formed is not more than 0.3% by weight.

4. A process for preparing a product claimed in claim 1 or 2 which process comprises forming a corresponding ammonium compound or free sulfonic acid by diazotization and coupling in the absence of alkali metal and thereafter converting the ammonium compound or sulfonic acid to calcium salt form.

5. A process for preparing a product claimed in claim 1 carried out substantially as described in the foregoing specific Example.

6. A product as claimed in claim 1 whenever obtained by a process as claimed in any one of claims 3 to 5.

7. A printing ink containing as pigment a product as claimed in claim 1, 2 or 6.

8. A surface coating formulation containing as pigment a product as claimed in claim 1, 2 or 6.

9. A formulation as claimed in claim 8 which is in the form of a paint or resin finish.

10. A plastics material pigmented by the presence therein of a product as claimed In claim 1, 2 or 6.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (10)

**WARNING** start of CLMS field may overlap end of DESC **. of anhydrous sodium acetate, during which additions the temperature rises to 12--130C and the pH to 5. Stirring is continued for 2 hours. The batch is then heated to 900 C, 70 parts of anhydrous calcium chloride (dissolved in 150 parts of water) are added and stirring is continued for 3 hours at 90"C. A further 1,000 parts of water are then added, after which the precipitate is filtered off and thoroughly washed with hot water. 200 parts of the pigment of the formula I are thus obtained; this product contains 0.12 per cent of sodium and differs from the conventional products, which contain more than 0.3 per cent of sodium, in having better fastness to weathering when used in a finish. WHAT WE CLAIM IS:

1. The monoazo pigment of the formula:

in a form which contains not more than 0.3 per cent by weight of alkali metal.

2. A product as claimed in claim 1 wherein the alkali metal content is from 0 to 0.2% by weight.

3. A process for preparing a product claimed in claim 1 or 2 which process comprises laking the corresponding alkali metal salt with a soluble calcium salt and removing the resulting alkali metal salt until the content of alkali metal in the calcium compound formed is not more than 0.3% by weight.

4. A process for preparing a product claimed in claim 1 or 2 which process comprises forming a corresponding ammonium compound or free sulfonic acid by diazotization and coupling in the absence of alkali metal and thereafter converting the ammonium compound or sulfonic acid to calcium salt form.

5. A process for preparing a product claimed in claim 1 carried out substantially as described in the foregoing specific Example.

6. A product as claimed in claim 1 whenever obtained by a process as claimed in any one of claims 3 to 5.

7. A printing ink containing as pigment a product as claimed in claim 1, 2 or 6.

8. A surface coating formulation containing as pigment a product as claimed in claim 1, 2 or 6.

9. A formulation as claimed in claim 8 which is in the form of a paint or resin finish.

10. A plastics material pigmented by the presence therein of a product as claimed In claim 1, 2 or 6.