JPS62197462A - Purification of dye - Google Patents

Abstract

PURPOSE:To obtain a dye which gives an ink which does not cause the clogging of nozzles, orifices, etc., through it contains dyes at a high concen, by previously dissociating associated molecules of a dye in a dye soln. and then purifying the dye. CONSTITUTION:In the purification of a dye, associated molecules of the dye in a dye soln. are dissociated before the due is purified. Water-soluble dyes in an aq. soln. do not exist in the form of a single molecule, but are dissolved in such a state that a plurality of molecules are mostly associated. Thus, when the dyes existing in the associated state are purified, it is difficult to remove impurities incorporated in the association molecules. High-purity dyes can be obtd., when purification is carried out after dissociation.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for purifying dyes, and more specifically,
The present invention relates to a dye purification method for providing highly pure water-soluble dyes useful as coloring components of recording liquids (hereinafter referred to as inks) for inkjet systems and writing instruments.

(Prior Art) Conventionally, water-soluble dyes such as direct dyes, acid dyes, and basic dyes 1-reactive dyes have been widely used for dyeing fibers, woven fabrics, etc. It has come to be widely used as a coloring component in so-called inkjet ink, which forms droplets and adheres them to a recording material such as paper according to an image signal. Also,
It is also widely used as a coloring component in the ink of writing instruments such as fountain pens, felt-tip pens, and ballpoint pens.

(Problems to be Solved by the Invention) The dyes that are the coloring components of the above-mentioned inks, particularly those used in inkjet systems, are generally dyes produced for dyeing textiles.

These dyes contain large amounts of additives or impurities, and it is known that various troubles occur frequently when these commercially available dyes are used as they are for inkjet inks.

The biggest problem is clogging of the ink ejection orifice, which is the core of the recording device, and in inkjet systems that utilize thermal energy, problems arise due to the deposition of foreign matter on the heat generating head.

To avoid such troubles, it has been proposed and implemented to purify the dyes used in ink, and improvements have been achieved to a certain extent, and by using highly purified dyes, ink There are fewer problems caused by

However, a phenomenon has been observed in which ink that does not have any problems at the time of manufacture is shipped from the manufacturer and after several injuries or years have passed, troubles that were unthinkable when the ink was first prepared occur again.

Such problems are particularly noticeable when using an inkjet method that uses thermal energy.

Therefore, the main object of the present invention (1) is to solve the above-mentioned drawbacks of the prior art, to prevent clogging of nozzles, orifices, etc. even during use and long-term storage despite high dye concentration, and to prevent An object of the present invention is to provide a dye that produces an ink with excellent stability that does not generate sediment in the heat-generating head of an inkjet device that uses energy.

As a result of intensive research to achieve the above object, the present inventor has found that commercially available dyes contain many impurities (e.g., various inorganic salt dispersants, dyes, etc., various organic and inorganic substances) in addition to dyes. Since these impurities mainly cause the above-mentioned problems, we researched various effects of these impurities and found that they can clog nozzles and orifices, form sediment during ink storage, and especially reduce the aging energy. The main cause of foreign matter depositing on the heating head in an inkjet method that uses ink is the presence of iron, silicon, phosphorus, and other polyvalent metal ions, as well as halogen ions, sulfate ions, phosphate ions, etc. contained in the ink. It is a colloidal substance consisting of ions and these compounds, and the present invention was completed by discovering that these harmful substances can be efficiently removed from dyes by a specific method.

(Disclosure of the Invention) That is, the present invention provides a method for purifying a dye, which is characterized in that the dye is purified through a process of disassociating associated molecules of a dye in a dye solution and a process of purifying the solution. be.

To explain the present invention in more detail, the main feature of the present invention is that in purifying the dye, the associated molecules of the dye present in the dye solution are first dissociated, and then the purification is carried out. .

In other words, in all conventionally known water-soluble dyes, in the state of an aqueous solution, the dye molecules do not exist as a single molecule, but are mostly dissolved in a state where multiple molecules are associated. Even if the dye is purified in this state, it is difficult to remove impurities contained in the associated molecules, so by performing purification after dissolving such an associated state,
It was discovered that a dye with a high purity that cannot be obtained by conventional general purification methods can be obtained.

The dyes targeted by the method of the present invention are water-soluble dyes such as direct dyes, female dyes, basic dyes, and reactive dyes, which have conventionally been mainly used for dyeing various types of fibers. Examples of inks that are suitable for use in ink and satisfy required properties such as clarity, water solubility, stability, and light resistance include C, 1, Direct Black 17.19.32.51.
71.108.146; c, r, direct blue 6.22.25.71.8
6.90.106.199; C, 1, Direct Red L, 4.17.28.83; C, 1, Direct Niro 12.24.26.98; C
,1, Direct Orange 34.39.44.46.6
0°C,! , Direct Violet 47.48; C, 1,
Direct Brown 109; C, 1, Direct Green 59; C, R, Acid Black 2.7.24.26.31.
52.63.112.118; C, 1, Ashy, Dobrou 9.22.40.59.93
, 102, 104.113.117.120.167.
229.234; C, 1, Ashy, Dread 1.6.32.35, 37.
51.52.80.85.87.92.94.115.
180.256.317.315; C, 1, Acid Yellow 11.17.23.25.29.42, 61.71
C,1, Acid Orange 7.19; C11, Acid Violet 49; C,1, Basic Black 2; C,1, Basic Blue 1.3.5.7.9.24.
25.26.28.29°C, 1, Basic Red l, 2.9.12.13°1
4.37; C, l Basic Violet 7.14.27; C1!
, Food Black 2, etc.

The examples of dyes mentioned above are particularly preferred in the present invention, but the invention is not limited to these dyes.

Water-soluble dyes such as those mentioned above are generally easily available on the market, but these commercially available products contain large amounts of various inorganic salts including monosalt and sodium sulfate, and also contain alkaline earth. It also contains inorganic substances such as metal salts and compounds of various metals, as well as various surfactants, dispersants, leveling agents, and many other organic substances.

The inventor of the present invention has developed the above-mentioned method. As a result of various studies on water-soluble dyes, it has been found that purification of dyes is not necessarily easy because both the dyes and the various additives mentioned above are water-soluble, but various conventional purification methods, such as filtration methods, have been found. ,
When dyes that have been sufficiently purified by salting out methods, ion exchange methods, etc. are used for inkjet inks, they exhibit the desired excellent performance when preparing the ink, but it takes several months or more to prepare the ink. Over time, various troubles such as those described above occur due to the ink. Such troubles after a period of time have elapsed after the preparation of the ink have been a serious problem that is difficult to recover from, since these inks are often already dispersed and distributed on the market.

As a result of intensive research to solve such a serious problem, the inventor of the present invention found that the above-mentioned troubles after a long period of time are caused by various factors in the associated molecules of the dye, even if the dye solution is purified. Impurities, such as colloidal substances and various anions such as halogen ions, sulfate ions, and phosphate ions, which are counter ions of various metals, are contained relatively stably, and these impurities are later absorbed by changes in the environment, such as temperature changes. , I learned that the main cause is loss of stability and precipitation due to concentration changes in the nozzle, thermal shock from the heating head, etc., and that the impurities contained in these associated molecules are Although it cannot be removed as it is by general methods, if the associated state of the dye is dissolved before purification, it can be easily removed by general methods afterwards, completely solving the various troubles mentioned above. I learned that the small side of the Kashiro IW that was going to be played was 11 degrees, and it was 1°.

"Disassociation" as used in the present invention means reducing or substantially eliminating the state of association of dye molecules in the dye solution, and making the dye solution into a true solution or a state close to it. As a method for carrying out such unification, any method that eliminates the association state of the dye may be used, but
Preferred methods include a method of ultrasonicating the dye solution (for example, treatment for about 1 minute to 30 minutes), a method of heating the dye solution (for example, heating to 50 to 100 ° C.), a method of increasing the pH of the dye solution ( For example, a method of raising the pH to 8 to 12) or a combination of these methods may be used.

The dye purification method of the present invention involves adding a desired dye to a concentration of 0.1 to 10% by weight, preferably 1 to 5% by weight in water alone or in a mixed solvent of water and a water-soluble organic solvent, preferably water. This is carried out by dissolving the resulting aqueous solution of the dye, subjecting it to the above-described dissociation treatment, and then subjecting it to a dye purification treatment. Such purification methods include salting out method, fractional precipitation method using a water-soluble organic solvent, extraction method, recrystallization method, ultrafiltration method, reverse osmosis method, ion exchange method, aeration method, lime softening method, and electrolysis method. Alternatively, any method such as a combination thereof may be used.

The purified aqueous dye solution obtained as described above can be made into an ink as it is or by adding necessary additives such as a water-soluble organic solvent, or it can be made into a powder by removing water. You can also do it. The amount of impurities such as inorganic substances present in such a purified dye aqueous solution or purified powder can be easily confirmed by ion chromatography, atomic absorption spectrometry, induced plasma emission spectrometry, etc. The concentration of impurities contained in the purified dye according to the present invention is as follows: in the form of powder dye, /% rogen ions are about 1% or less, sulfate ions are about 0.5% or less, iron, magnesium and phosphorus are each about 200 pp or less, Preferably, the silicon content is 250 ppm or less, the total amount of colloids containing these metal compounds is about 1.000 ppm or less, and the total amount of all inorganic substances is preferably about 2% by weight or less, and below these concentrations, the above-mentioned It is particularly useful for inkjet inks that use thermal energy, such as inkjet inkjet inks, and is particularly useful for inkjet inks that use thermal energy. Trouble never occurs.

Next, the present invention will be explained in more detail with reference to Examples and Usage Examples. Note that "%" or "%" in the text is based on weight.

Examples 1 to 6 A 10% aqueous solution of the commercially available dyes listed in Table 1 below was prepared,
Keep the pH at 9.0 and the temperature at 60°C, and use ultrasonic waves to
After treatment for a minute, the dye was purified by means such as fractional precipitation, ultrafiltration, reverse osmosis, and ion exchange to obtain a highly pure dye.

1 Direct Blue 189 Ultrafiltration 2 Direct Blue 86 Ultrafiltration 3 Acid Red 35 Ion Exchange 4 Direct Yellow 8B
Ion Exchange 5 Food Black 2 Ion Exchange 6 Acid Yellow 23 Solvent Purification Usage Example 1 Using the purified dyes obtained in Examples 1 to 6, inks for an inkjet system having the following compositions were prepared.

Dye 2 parts diethylene glycol 40 parts water
60 copies Using this ink, on-demand type multi-head (discharge orifice diameter 35 microns, heating resistor
Resistance value.

150 ohms, driving voltage 30 volts, frequency @ 2 KH
When the following Tl-T5 was investigated using a recording apparatus having 2), good results were obtained in all cases.

(T1) Long-term stability: Even after the ink was sealed in a plastic film bag and stored at -30℃ and 60℃ for 6 months, no precipitation of insoluble matter was observed, and there was no change in the physical properties or color tone of the liquid. A raft.

(T2) Ejection stability: Continuous ejection was performed for 24 hours in an atmosphere of room temperature, 5° C., and 40° C. Under all conditions, stable high-quality recording was possible from beginning to end.

(T3) Ejection responsiveness: Initial ejection for 2 seconds and ejection after standing for 2 months were investigated, and in both cases, there was no clogging at the orifice tip, and recording was stable and uniform.

(T4) Quality of recorded images: Images recorded on the recording materials listed in Table 1 below had high density and were clear. After six months of exposure to indoor light, the rate of decrease in concentration was less than 1%.

(T5) Fixability on various recording materials: After 15 seconds of printing on the recording materials listed in Table 1 below, rub the printed area with your finger to prevent image shift.
The presence or absence of bleeding was determined. All of them exhibited excellent fixing properties with no image shift or blurring.

Usage Example 2 The ink of each color prepared in Usage Example 1 was individually filled into felt-tip pens, the caps of each were removed and the pens were left for 10 days. When the ink was written on paper, the writing was smooth and there was no ink smearing. did it.

Usage example 3 Yellow ink and magenta ink in usage example 1.

Usage Example 1 was performed using a recording device that has an on-demand recording head (discharge orifice diameter: 50 microns, piezoelectric vibrator drive voltage: 60 volts, frequency: 4 KHz) that uses cyan ink and black ink to discharge ink using a piezoelectric vibrator. T1 to T5 were examined in the same manner. All of these showed excellent results.

Use Example 4 A full-color photograph was reproduced using the same inkjet recording apparatus as that used in Use Example 1 using the yellow ink, magenta ink, cyan ink, and black ink of Use Example 1, respectively. The resulting image had extremely clear colors and good color reproduction.

Example 7 A 10% aqueous solution of commercially available dye Direct Blue 199 was prepared, subjected to ultrasonication for 15 minutes in that state, and then purified by ultrafiltration to obtain a high purity dye of the present invention.

When this high-purity dye was used as in the above usage examples, excellent results were obtained in all cases as in the above usage examples.

Example 8 A 10% aqueous solution of commercially available dye Acid Yellow 35 was prepared, its pH was adjusted to 10, the solution was sufficiently stirred, and then purified by an ion exchange method to obtain a high purity dye of the present invention.

When this high-purity dye was used as in the above usage examples, excellent results were obtained in all cases as in the above usage examples.

Example 9 A 10% aqueous solution of the commercially available dye Food Black 2 was prepared and purified by fractional precipitation using ethanol and isopropyl alcohol kept at 65°C while maintaining its temperature at 70°C to obtain the high purity dye of the present invention. Obtained.

When this high-purity dye was used as in the above usage examples, excellent results were obtained in all cases as in the above usage examples.

Comparative Example Comparative inks were prepared in the same manner as in Use Example 1, except that the dyes of Examples 1 to 6 before purification were used.

When this ink was examined at T1 to T5 in the same manner as in Use Example 1, precipitation of insoluble matter was observed in the ink after one month of ink storage. In addition, at T2, ink often fails to be ejected, and the drive voltage is changed (voltage up).
When the surface of the 0-heat generating head was observed under a microscope, a brown precipitate was observed to be attached. In T3, it was observed that the orifice part was clogged and the ink ejection was unstable after being left for one month.

Claims (4)

[Claims] (1) A method for purifying a dye, which comprises purifying the dye through a process of disassociating associated molecules of the dye in a dye solution and a process of purifying the solution. (2) The purification method according to claim (1), wherein the dissociation treatment is ultrasonication. (3) The dissolution treatment is heat treatment (
The purification method described in section 1). (4) The purification method according to claim (1), wherein the dissociation treatment is pH adjustment of the solution.