JPS6039704B2 - Process for producing gamma quinacridone from polyphosphoric acid and alcohol - Google Patents

Description

[Detailed description of the invention] This invention relates to quinacridone pigments.

More specifically, the present invention relates to gamma crystal phase quinacridone (
The present invention relates to a method for producing gamma quinacridone (hereinafter referred to as gamma quinacridone). Linear quinacridones are presented in a foundational format and exist as a number of crystalline phases, including alpha, beta, and gamma phases, as disclosed in US Pat. No. 2,844,581.

Gamma quinacridone has recently found a ready market in the automotive and building industries due to the fact that it produces deep red metallic finishes in the quinacridone color range. Previously, gamma quinacridone pigments were commercially produced by grinding quinacridone made by oxidation of di/hydroquinacridone. U.S. Patent No. 284458
See No. 1. Other patents in this same general field include U.S. Pat.
No. 69, No. 3342823, No. 3362957, and No. 3547925. The grinding of quinacridone to make gamma quinacridone pigments is, of course, an additional step in pigment production and requires additional energy input, time, counterfeiting, etc. However, until now, the only known methods for producing gamma quinacridone pigments have involved grinding quinacridone crystals. One of the objects of the present invention is to produce gamma quinacridone.

Another object of the present invention is to produce gamma quinacridone directly from the cyclization of dianilinoterephthalic acid. These and other objects will become apparent from the description below. According to the present invention, dianilinoterephthalic acid in the presence of polyphosphoric acid is heated to a temperature above about 70°C, the mixture is then cooled to below 290°C, and an alcohol, such as methanol, is heated to a temperature above 25°C. A method of making a gamma quinacridone pigment is provided which comprises diluting the mixture by addition at a rate that does not exceed . When operating according to the method of the invention, i.e. when cyclization of dianilinoterephthalic acid is followed by diluting the reaction mixture with alcohol under controlled temperature conditions, the product produced is essentially a pure gamma quinacridone pigment. That is, it exhibits an X-ray diffraction pattern that is consistent with the X-ray diffraction pattern generally accepted to identify the gamma crystal form of quinacridone.

The process of the present invention thus provides a direct method for the production of gamma quinacridone pigments and eliminates the need for special grinding steps previously required for the production of the crystalline phase of these quinacridone pigments.
The gamma quinacridone pigments produced by the method of the present invention have excellent outdoor durability and can be used in automotive finishes, inks, etc.
Useful for coloring house paint.

It is particularly useful in the production of red architectural finishes and clear automotive metal finishes. The process of the present invention provides a simple, economical route to this crystalline phase of quinacridone that eliminates the need for certain manipulations previously thought to be necessary for the production of gamma quinacridone.

Furthermore, that the process of the present invention yields gamma quinacridone is completely unexpected since current quinacridone technology would normally predict that soaking a polyphosphoric acid solution of quinacridone in alcohol would yield a bright-colored beta-phase quinacridone. It is. This is not the case, and it has been found that the quinacridone obtained by operating within the scope of the invention exhibits a pure gamma-type X-ray pattern. In the practice of this invention, dianilinoterephthalic acid is dissolved in polyphosphoric acid.

The use of polyphosphoric acid as a ring-closing agent is disclosed in U.S. Pat.
No. 57405 and No. 3342823 are well known in the quinacridone art. As shown in this prior art, the polyphosphoric acid should have an acid content (P04) of at least 100%. Preferably the concentration of this polyphosphoric acid is 114-120%. The mixture is heated to a temperature higher than 7000 q or more, preferably 80 to 120 q
It is heated while being worshiped in the room. Ring opening usually takes 4 to 1 hour and after this is completed the mixture is heated between 0°C and 25°C.
added to the alcohol, which is maintained at a temperature between. The addition rate is such that it does not exceed 25 qo. The amount of alcohol required will of course depend on the volume of the mixture. Enough alcohol must be used to dissolve all the polyphosphoric acid. Preferably there is an excess of alcohol to facilitate thickening of the mixture. After heating the mixture below 260°C for a sufficient time to dissolve the acid mixture, the entire mixture is heated to reflux temperature, poured into water, filtered, washed to remove the acid, and boiled with caustic soda to remove the acid. After removing traces, filtering, washing to remove alkali and drying, an essentially pure red solid gamma phase quinacridone pigment is obtained. Alcohols useful in the process of this invention are alcohols having from 1 to 5 carbon atoms, namely methanol, ethanol, propanol, butanol and pentanol.

Methanol is preferred because the greater the number of carbon atoms in the alcohol, the greater the tendency for some of the quinacridone to precipitate as a bright red beta phase. As shown above, the temperature of the alcohol during the steeping stage is oo~25qC,
Preferably it should be between 00 and 15°C.

If the temperature is not controlled, the higher temperature of the polyphosphoric acid mixture will result in temperatures above 25°C and result in beta phase quinacridone. The lower limit of 000 is chosen for this convenience as it is most economical to keep the temperature of the alcohol low using an ice bath. The following examples are given by way of example only.

All parts are by weight unless otherwise indicated. 118%
To 130 parts of polyphosphoric acid (118% 3P04) was added 18 parts of dianiline terephthalic acid, and the mixture was stirred for 16 hours.
Heat at 0~106℃.

Claims (1)

[Claims] 1 (1) 2,5-dianilinoterephthalic acid is heated in polyphosphoric acid at a temperature higher than 70°C, (2) carbon number 1
The reaction mixture is added to a sufficient amount of the water-miscible alcohol to dissolve the polyphosphoric acid, maintaining the temperature of the ~3 water-miscible alcohols at about 0°C to 25°C during the addition. and (3) then separating gamma quinacridone from the resulting reaction mixture.