DE2845945C2 - Use of an azo pigment - Google Patents

Description

For the coloring of such plastics in the fair, which will be processed at temperatures above 250 ⁰ C, are suitable for this high temperature stress just unverlackte azo pigments.

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Formula I.

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has the high heat stability of over 250 ^° C. required for such pigmentations.

The invention therefore relates to the use of the azo pigment of the formula I for pigmenting plastics whose processing requires ^{temperatures of more than 250 ° C.}

The pigment of the formula I and its use for coloring plastics are from DE-PS 1227585 known. The pigment is preferably produced by coupling the diazotized 3-amino-4-methylbenzanilide to 5-acetoacetylaminobenzimidazolone- (2). The diazotization can, for example, with Alkali nitrites or lower alkyl nitrites with sufficiently strong acids, especially a mineral acid, but can also be done with nitrosylsulfuric acid. As with the subsequent coupling of It may be useful to add surfactants such as nonionic, anionic or cationic dispersants.

Diazotization and coupling can also be carried out in the presence of suitable organic solvents, such as glacial acetic acid, lower alkanols, dioxane, formamide, dimethylformamide, dimethyl sulfoxide, pyridine or N-methylpyrrolidone. To achieve full color strength and a particularly favorable crystal structure, it is often advisable to heat the coupling mixture for some time, for example to boil it or ^{to keep it under pressure at temperatures above 100 °} C., optionally in the presence of organic solvents such as lower alkanols, for example ethanol, Halogen aromatic compounds,

z. B. chlorobenzene or dichlorobenzenes such as o-dichlorobenzene, Dimethylformamide or in the presence of resin soap. A particularly pure and strong color Pigment is obtained if, after coupling, the moist press cake or the dried powder is obtained a thermal aftertreatment with organic solvents such as alcohols, above all lower alcohols, Pyridine, glacial acetic acid, dimethylformamide, N-methylpyrrolidone, Dimethyl sulfoxide, halogenated aromatics, e.g. chlorobenzene or dichlorobenzenes such as o-dichlorobenzene, or subjecting it to nitrobenzene or grinding the pigment with the addition of grinding aids connects.

Plastics that require processing temperatures of over 250 ° C for pigmentation are for example Polyolefins, such as low pressure polyethylene, high pressure polyethylene and polypropylene, polystyrene, Polyamide or polymethacrylate.

One of the most important fastness properties of pigments in plastics is their resistance to the required processing temperatures for a corresponding period of time. For testing the temperature resistance, especially of polyolefins, after customary pigmentation, for. B. by metering the pigment, optionally in the form of a preparation, to the polyolefin in a mixer or kneader, in an injection molding machine, the colored measuring platelets are produced. With the help of a spectrophotometer, the standard color depth (according to DIN 53235) is then calculated (ST '/ 3 and ST' / 2S). Beginning at 200 ⁰ C in 10 ° C intervals, respectively after 1 minute and after 5 minutes residence time shims are manufactured; Final temperature is 280 ° to 320 ⁰ C.

The color measurement then takes place in the form of the CIE values (standard illuminant C). Compared to 200 ⁰ C-PrUfplättchen (starting temperature), the color difference calculations are carried out according to DIN 6174th

The total distance AEan is measured as a function of the injection temperature.
According to the test method described, very comparable values of temperature resistance ΔΕαν = / (7) are obtained.

The pigment can be easily processed in the media mentioned. The dyeings have very good lightfastness and in particular excellent heat stability and are against the influence of chemicals, especially Solvents, resistant.

It was surprising that from the large number of compounds described in DE-PS 12 27 585 the pigment of formula I has particularly good heat stability, so that it is used for coloring the special Plastics is suitable.

In the following example, percentages relate to weight.

example 1

23 g of 3-amino-4-methyl-benzoic anilide are concentrated in a mixture of 50 ml of glacial acetic acid and 40 ml. Hydrochloric acid stirred at room temperature for 1 hour. After adding 100 ml of water, diazotization is carried out at 0 to 5 ° C. by slowly adding dropwise 14 ml of 40% sodium nitrite solution. Thereafter, stirring is continued for 30 minutes at 10 ^° C., then small undissolved constituents are filtered off and the excess nitrite is destroyed with sulfamic acid.

25 g of 5-acetoacetylamino-benzimidazolone are placed in a second vessel Suspended in 300 ml of water by adding 22 ml of 33% sodium hydroxide solution dissolved and clarified using activated carbon.

The solutions of the diazonium salt and the coupling component thus obtained are allowed to run simultaneously over the course of one hour at 20 to 25 ° C. with vigorous stirring to a phosphate buffer solution (pH = 6 to 7) containing 20 ml of a 10% solution of the reaction product Stearyl alcohol and 25 moles of ethylene oxide are added. The orange pigment suspension obtained after coupling is heated to 90 to 95 ° C., filtered while hot and washed salt-free with water. The crude pigment is dried to 70 ⁰ C and milled at 60th For conversion to a product of good performance properties stirring the first hard grain pigment in glacial acetic acid, heated to about 60 ⁰ C, holding 45 minutes at that temperature, then filtered off, washed with methanol, dried and grinding the mixture.

The resulting reddish-yellow monoazo pigment of the formula I results when incorporated on 0.1% of the pig- ψί mentes in Low-pressure dyeing having very good ψ Lichiechiheiten, is characterized by high resistance $ Mitzej and therefore without changing the hue tion by injection can be processed. Low-pressure polyethylene pigmentations in ψι standard depth of color (ST '/ 3) show when used for 5 minutes ^; while at 280 ⁰ C a value of Ε _ΛΝ = 1.31

''% (Reference 200 ⁰ C).

The pigment is the same outstanding ■ i \ performance properties obtained when the obtained after the coupling of crude product as aqueous press cake to a thermal aftertreatment in dimethylformamide at temperatures between 50 and 70 ⁰ C, or with a mixture of isobutanol and water in a volume ratio of 1: 1 is subjected to ^{temperatures around 100 0} C in a closed vessel.

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Claims (3)

Patent claims: 1. Use of the azo pigment of the formula for the pigmentation of plastics, for the processing of which temperatures of more than 250 ^° C. are required. 2. Use of the azo pigment according to claim 1 for pigmenting polyolefins. 3. Use of the azo pigment according to claim 1 and 2 for pigmenting low-pressure polyethylene, High pressure polyethylene or polypropylene.