JPH0460147B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing β-quinacridone, which is known as a purple pigment. More specifically, when producing a pigment by dissolving crude quinacridone having any crystalline phase in dimethyl sulfoxide in the presence of caustic alkali, and neutralizing and reprecipitating the resulting alkali salt solution of quinacridone with acid, The present invention provides a method for producing a purple β-quinacridone pigment by using maleic acid, succinic acid, or anhydrides thereof.

It has long been known that β-nacridone, a crystalline form of quinacridone, is useful as a high-grade purple pigment with excellent fastness, and various methods for its production have been studied and published to date. . Typical examples include () Solbend, which involves ball milling together with sodium chloride crystals in an organic medium such as xylene;
Salt milling method. (Japanese Patent Publication No. 36-13833) () A method of heat treating α-crystal phase quinacridone in 100% dimethylformamide. (U.S.
P.3534044) () A method in which a sulfuric acid solution of quinacridone is poured into an aqueous polar organic solvent solution (10 to 90%) such as methanol and reprecipitated. (Japanese Patent Publication No. 39-9271) () A method in which a quinacridone alkali salt is formed by soaking it in alkaline alcohol, and then water or a dilute mineral acid is added to this slurry to dissociate the salt into the β-form. (BP951451) () Conversion to β-form by immersion in AlCl ₃ -organic solvent (nitrobenzene etc.) system and heating.

() Dissolve in methyl sulfuric acid, pour into ice water and reprecipitate. (BP943957) () A treatment method in which a substance such as P-toluene sulfonic acid is added to a quinacridone sulfuric acid solution and the mixture is poured into hot water. (Japanese Patent Publication No. 45-33550) () A solvolysis method in which aqueous ethanol is added to a polyphosphoric acid solution of quinacridone to precipitate crystals, or the solution is diluted with orthophosphoric acid and then poured into methanol or acetone. (USP3265699) () α-type quinacridone with 1, 2, 4, 8,
A method in which a small amount of 9,11-hexachlor quinacridone is mixed and heat treated in a high dielectric constant organic solvent such as DMF. (Special Publication No. 47-7705) () Quinacridone sulfonic acid in dilute mineral acid
Beta-
How to make quinacridone pigments.

etc. are known. These methods require long processing times, are difficult to control the conditions for obtaining pigments of arbitrary sizes, are difficult to recover the solvent used, or are expensive to treat waste liquid. This is not a sufficient manufacturing method. Further, the obtained β-quinacridone pigment is not satisfactory because it often requires a separate pulverization step to further adjust the particle size.

The present inventors took these points into consideration and conducted various studies in order to develop a method for producing pigments that is simple and has excellent quality, and as a result, the present invention was achieved.

The present invention will be explained in detail below.

We found that quinacridone forms a salt and dissolves in dimethyl sulfoxide in the presence of caustic. Then, by neutralizing this solution with acid, it dissociates and precipitates out as quinacridone again. If dilute mineral acids such as sulfuric acid water are used at this time, quinacridone in the γ-type crystal phase can be obtained in a pigmented state. After confirming that
008547). This pigmentation method is extremely simple and can be treated by pure chemical means without the need for physical pulverization, so it can be said to be a useful method.
It has not yet been possible to arbitrarily obtain crystal forms other than the γ-type. In order to obtain the β-form using this method, there is a method of diluting the solution with a large amount of an organic solvent such as alcohol, but since it requires a large amount of diluent,
This method is disadvantageous in terms of productivity such as recovery of the solvent, and it is also difficult to control the pigment particles produced, so it cannot be said to be an appropriate method.

The present inventors have conducted extensive research to solve this problem, and have
The inventors have discovered that a β-type crystal phase can be easily obtained by replacing mineral acids such as sulfuric acid with maleic acid, succinic acid, or their anhydrides as the neutralizing agent used in the production of a type crystal phase. This is what led to this.

That is, the present invention dissolves crude quinacridone in dimethyl sulfoxide in the presence of caustic alkali,
Then, by neutralizing and reprecipitating with maleic acid, succinic acid, or anhydrides thereof, a clear purple color is obtained.
The present invention is characterized by obtaining a quinacridone pigment having a β-type crystal phase that has high tinting power and excellent heat resistance, weather resistance, chemical resistance, etc.

The crude quinacridone used in the present invention is
It refers to quinacridone produced by any method such as the ring-closing reaction of 2,5-dianilinoterephthalic acid or the oxidation of 6,13-dihydroquinacridone, and its crystal form is not specified, and it can be any of the currently known quinacridones. It may be any of these types or a mixture thereof.

The present invention begins by dissolving this crude quinacridone in a dimethyl sulfoxide solvent in the presence of caustic alkali. The usage ratio of the solvent is 5 to 20 times the amount (weight ratio) to the crude pigment, preferably 10
It is convenient to use around twice as much in terms of operability. In addition to this, the presence of an alkali is required for dissolution, and caustic soda, caustic potash, etc. are suitable for forming a salt with quinacridone in the solution.

This caustic alkali itself is difficult to dissolve by itself, and it takes a long time to complete the salt formation with quinacridone and achieve a completely dissolved state, so it is effective to add a small amount of water to assist in dissolution and salt formation. It is true.
When adding water, the problem is the amount; if it is more than necessary, the alkali salt of quinacridone that has been formed will dissociate and re-precipitate, making it impossible to achieve the goal of dissolution. It is necessary to press it to the extent that it does not cause dissociation. This amount of water needs to be 20% or less, preferably around 10% as the water content in the solvent.

As for the dissolution conditions, stirring or shaking for 30 to 120 minutes at room temperature is sufficient, and heating is even more effective, but oxidation of the quinacridone itself may progress partially if the treatment is carried out at high temperatures for a long time. This is undesirable because it produces quinacridonequinone as a by-product and causes a change in color tone.

An alkali salt solution of quinacridone is obtained in this way and may be directly proceeded to the next step, but if insoluble impurities are likely to be mixed in, they may be separated and removed using a filter. The obtained solution exhibits a deep blue-purple color, has no viscosity, and has good fluidity. This solution is equipped with a high-torque stirrer and neutralized and reprecipitated with maleic acid, succinic acid, or their anhydrides to form a β-type crystal phase pigment.
Since the viscosity increases rapidly as neutralization progresses, the stirring speed should be adjusted appropriately to maintain a uniform state of the system. In this pigmentation operation, the temperature during neutralization and reprecipitation is one factor that controls the pigment particle size, and can be arbitrarily selected within the range of 0°C to 90°C depending on the purpose. The particle size is usually measured at around 20℃.
Pigment particles of around 0.1 to 0.2μ can be obtained, but if you want even smaller particles, perform reprecipitation at a lower temperature, and if you want a larger solid type, process at a higher temperature to obtain pigment particles of about 0.05 to 1.0μ. It can be arbitrarily adjusted within the range up to

As the neutralizing agent used in this neutralization reprecipitation, maleic acid, succinic acid, or anhydrides thereof are suitable, but other organic acids having a similar structure are not excluded. Maleic acid, succinic acid, or their anhydrides can be used directly in powder form or dissolved in an appropriate solvent, but from the viewpoint of operability such as controlling the neutralization temperature, It is preferable to use it in solution form. In this case, it may be advisable to use the same type of solvent as the solvent used to dissolve the quinacridone in order to avoid complicating the recovery of the solvent. However, other solvents that are normally inert to acids and can dissolve these organic acids, such as acetone, methyl ethyl ketone, and tetrahydrofuran, may also be used. Alcohol and water are unsuitable, and water in particular cannot be used for this purpose because it does not give the desired β-form but instead forms the γ-form.

The amount of neutralizing agent used should be limited to 75 to 95% of the amount calculated to completely neutralize the caustic alkali used to dissolve the crude quinacridone, so as to maintain the system in a slightly alkaline state. desirable. The purpose of this is to correct the morphology of the precipitated crystal grains through aging and turn the slightly mixed α-type into a complete β-type crystal phase. Since it can be adjusted by adding alkali, the conditions are not limited. Since the pigment is obtained in the form of a highly viscous slurry by neutralization and reprecipitation, it may be diluted with water before overtreatment to lower the viscosity and improve fluidity. After overtreatment, the organic solvents and organic acid salts are thoroughly washed and removed using conventional methods, and if necessary, surface modifier treatment is performed to create a purple pigment with excellent weather resistance, heat resistance, and coloring power. A certain β-type crystal phase quinacridone is obtained.

The present invention makes it possible to obtain β-type quinacridone pigments extremely easily compared to conventional methods, and the size of the pigment particles can be arbitrarily adjusted. It is effective in simplifying and shortening problems such as length and length, and the benefits of industrialization are large.

The present invention will be explained in more detail with reference to Examples below.

Example 1 15 parts of crude quinacridone and 150 parts of dimethyl sulfoxide containing 10% of water are weighed out, and 7.5 parts of caustic potassium is added while stirring at room temperature. When stirring is continued at room temperature, the system gradually turns blue-purple, changing from a slurry to a deep dark blue-purple solution. about
After stirring for 1.5 hours, if necessary, remove suction through a No. 4 glass filter to remove trace amounts of insoluble matter, and then cool to 10°C and add 20 parts of maleic anhydride. A solution of 30% of dimethyl sulfoxide was added dropwise from the dropping funnel, taking care to maintain the temperature at 10°C as much as possible. As neutralization progresses, the slurry rapidly thickens, so
Stirring is adjusted as the viscosity increases so that a homogeneous slurry is formed at all times. After completion of the dropwise addition, continue to stir and mature for 1 hour, then dilute with 150 parts of water to lower the slurry viscosity and filter through a No. 4 glass filter. After redispersing and washing with a dispersing mixer, pass it through again. Repeat this operation 3 times before and after 60
Drying was carried out at ℃/12 hours to obtain a purple pigment powder with an almost quantitative recovery rate.

To confirm that this substance has a β-type crystal phase,
- Linear diffraction detected strong peaks at 5.9° and 27.1° and moderate peaks at 11.8°, 15.9° and 22.0° at 2θ, which are completely consistent with the pattern data published as β-type quinacridone. This was done by matching the . Furthermore, observation of the particle state using electron micrographs (20,000x magnification) confirmed that the particles were fine particles with a particle size distribution of around 0.1μ.

Example 2 The formulation and treatment of Example 1 were followed except that the temperature during the neutralization and reprecipitation treatment was lowered to 40°C.
- type quinacridone pigment was produced. The β-type was confirmed by X-ray diffraction. Observation of the particle state using electron micrographs confirmed that the pigment particles had a particle size distribution of approximately 0.25μ and had extremely high hiding properties.

Claims (1)

[Claims] 1. When dissolving crude quinacridone in dimethyl sulfoxide in the presence of caustic alkali and converting it into a pigment by neutralization and reprecipitation, maleic acid, succinic acid, or anhydride thereof may be used as a neutralizing agent. A method for producing a quinacridone pigment having a characteristic β-crystalline phase. 2. The method for producing a β-quinacridone pigment according to claim 1, wherein the caustic alkali is caustic soda or caustic potash.