JPS6256761B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for recovering pigments from waste ink with high purity. Inks used for various types of printing, such as convex, concave, offset, and gravure, generally contain pigments, resins,
It consists of additives such as a solvent and a plasticizer, and as schematically shown in FIG. 1, it is thought that pigment particles 1 are uniformly dispersed in a solvent 3 with a resin 2 interposed therebetween. These pigment particles are broadly classified into extender pigments, inorganic pigments, and organic pigments, each of which has physical properties as shown in Table 1.

【table】

[Table] It goes without saying that appropriate additives such as solvents, resins, and plasticizers are used depending on the type of pigment mentioned above. The hues of new inks are broadly classified into red, blue, yellow, white, and black, and depending on the purpose, they are used alone or in combination of two or more colors. Incidentally, ink that has darkened and become unusable, as well as waste liquid after washing printing machines, etc., are discharged in large quantities from ink manufacturing processes and printing factories as waste ink, and both waste inks are used as inks of various hues. The dull colored waste ink contains black ink made of carbon black,
Contains blue ink consisting of phthalocyanine blue. It is difficult to recover valuable materials such as pigments and solvents from the above waste ink, and conventionally, most of it has been incinerated or dumped, and in rare cases, hot air, steam, etc. have been injected into the waste ink to dissipate the solvent. , recovery using a condenser or the like was possible, but sufficient recovery could not be achieved. The present inventors recovered pigments from waste ink, and in order to increase the reuse of the recovered pigments, they removed carbon black and blue pigments (phthalocyanine blue) that cause dullness of colors, and produced red, yellow, brown, etc. As a result of repeated research into methods for recovering pigments with vivid hues, the following findings were obtained. First, the pigment particles used in the inks shown in Table 1 show different dispersibility depending on the type of solvent, as shown in Table 2.

[Table] Next, as mentioned above, when pigment particles are used in ink, a resin (2 in Figure 1) is used, but depending on the type of resin, the dispersibility in Table 2 is as follows. to come in different ways. (1) Aromatic hydrocarbons such as toluene and xylene are
As shown in Table 2, none of the pigments is dispersed and tends to settle, and this tendency does not change regardless of the type of intervening resin. (2) With ethers such as methyl cellosolve and ketones such as cyclohexanone, all pigments are well dispersed as shown in Table 2, and this tendency does not change regardless of the type of intervening resin. (3) As shown in Table 2, esters such as ethyl acetate, alcohols such as methyl alcohol, ethyl alcohol, and isopropyl alcohol exhibit selectivity in dispersibility depending on the type of pigment, and also depending on the type of intervening resin. However, for example, methyl alcohol, ethyl alcohol: If the intervening resin is an alkyd resin, the dispersibility is poor regardless of the type of pigment.If the intervening resin is nitrocellulose, these alcohols dissolve the nitrocellulose. Isopropyl alcohol: Regardless of whether the intervening resin is alkyd resin or nitrocellulose, isopropyl alcohol does not have the effect of dissolving these resins, regardless of the type of pigment. Ethyl acetate: Regardless of whether the intervening resin is an alkyd resin or nitrocellulose, ethyl acetate has the effect of dissolving these resins, so it shows the same dispersibility as shown in Table 2. Shows selectivity in sex. (4) Blue pigments (phthalocyanine blue) and carbon black tend to be somewhat easily dispersed in any solvent. The above findings indicate that if a solvent with poor pigment dispersibility is added to the waste ink, the pigment particles will coagulate and settle, allowing them to be separated and recovered. However, as mentioned above, in addition to pigment particles, waste ink contains additives such as intervening resins and plasticizers. resins and the like are mixed in as impurities. For example, when recovering pigments using aromatic hydrocarbons as a solvent with poor pigment dispersibility, aromatic hydrocarbons dissolve alkyd resins but do not dissolve nitrocellulose, so a large amount of nitrocellulose is mixed into the recovered pigments. Resulting in. Figure 2 shows pigment recovered by adding aromatic hydrocarbons (solvent with poor dispersibility) to waste ink [Figure 2 A]
2 shows the infrared absorption spectra of a new pigment [Fig. 2 B] and nitrocellulose [Fig. 2 C]. As is clear from the figure, the recovered pigment contains
Characteristic absorptions of nitrate esters in the nitrocellulose infrared absorption spectrum are observed at wavelengths of 1630, 1270, and 820 cm ^-1 , and impurity absorptions at 1210 and 1060 cm that are not observed in the infrared absorption spectrum of new pigments are observed.
^-1st class is accepted. When an ink is prepared using the recovered pigment as described above, the ink has disadvantages in terms of printability. Therefore, in order to improve the purity of the recovered pigment,
It is necessary to wash the recovered pigment to remove impurities such as resins. The conditions that the solvent used for this cleaning must meet are: It must be used as an ink solvent (purification can be omitted) It must dissolve the intervening resin, especially nitrocellulose It must have poor dispersibility for pigments. As a result of conducting a cleaning test in consideration of these factors, it was found that methyl alcohol and ethyl alcohol are suitable. However, when cleaning with methyl alcohol, as is clear from Table 2, some pigments such as iron oxide yellow and clay may be redispersed. The present invention has been made in view of the above points, and involves adding a solvent with poor pigment dispersibility to waste ink, stirring it, separating the precipitated pigment from the liquid phase, and washing this with alcohol. The present invention relates to a method for recovering pigments from waste ink, which is characterized by recovering high-purity pigments. As is clear from the above findings, aromatic hydrocarbons such as toluene and xylene are examples of solvents with poor pigment dispersibility used in the method of the present invention. It is preferable to use the above solvent in an amount of 3 to 10 times the volume of the waste ink. If it is less than 3 times, the pigment separation effect is not sufficient, and as the ratio increases, the amount of processing increases, resulting in larger equipment and increased costs, which is disadvantageous, so the upper limit of the ratio is Appropriately, it is about 10 times larger. Toluene was selected as a solvent with poor pigment dispersibility,
FIG. 3 shows the results of testing the influence of the toluene/waste ink ratio on pigment recovery by varying the amount of toluene from 50 to 91 ml and the amount of waste ink from 50 to 9 ml. In the figure, the numbers attached to the graph are toluene/waste ink (capacity). When the above solvent is added to the waste ink in the above ratio, the pigment particles in the waste ink lose their dispersibility, coagulate, and settle. At this time, carbon black and blue pigments, which cause dullness of color, do not lose much of their dispersibility in the solvent as described above, so they remain on the solvent side, and pigments with bright hues can be separated and recovered. Since the pigment thus separated and recovered contains impurities such as intervening resin, it is then washed with alcohol to obtain a highly pure pigment. Examples of the alcohol include methyl alcohol and ethyl alcohol, as is clear from the above-mentioned cleaning test. For the same reason as in the case of the solvent having poor pigment dispersibility, the ratio of the alcohol to the recovered pigment is approximately 2 to 10 times the volume ratio. FIG. 4 shows the same test results as in the case of using methanol as the alcohol and using the solvent with poor pigment dispersibility. In addition to recovering pigments from waste ink, the method of the present invention
It can also be applied to the separation and recovery of dyes with similar properties to pigments. The method of the present invention provides the following functions and effects. When a solvent with poor pigment dispersibility (aromatic hydrocarbons such as toluene xylene) is added to waste ink, the pigments or dyes dispersed in the waste ink lose their dispersibility, settle, and separate from the liquid phase. The pigments and dyes separated from the liquid phase contain impurities such as some resins. When this is washed with alcohol (methyl alcohol, ethyl alcohol), the mixed resins are dissolved and removed from the pigment or dye. Therefore, highly pure pigments or dyes can be recovered from waste ink. FIG. 5 shows a flowchart for recovering and purifying the pigment (or dye) in the present invention. A solvent 12 having poor pigment dispersibility is added to the waste ink 11, mixed 13, stirred 14, and then the pigment component is separated 15 from the liquid phase. Separated solid phase (including pigment)
16 is taken out and washed 19 is repeated using a washing solvent, ie, alcohol 18, to remove impurities and obtain a highly pure pigment 20. The solvent 21 is regenerated by distillation and purification, and recycled as the cleaning solvent 18. Furthermore, the liquid phase 17 from which the solid phase 16 has been separated is similarly purified by distillation and recycled as a solvent 12 with poor pigment dispersibility. Example 10 parts of waste ink and 90 parts of toluene in a 200ml beaker
After stirring vigorously, the pigment suspension layer is allowed to settle. After removing the supernatant liquid from this liquid by decantation, 50 parts of methanol was added, shaken vigorously, and left to stand. Remove the supernatant liquid by decantation again and add methanol. After repeating this washing 3 to 4 times, the solid content was collected by filtration and dried. 10g of pigment was recovered from 50g of waste ink.

[Brief explanation of the drawing]

Figure 1 is a diagram schematically showing the dispersion state of pigment particles in ink, Figures 2A to C are diagrams showing each infrared absorption spectrum of recovered pigment, new pigment, and nitrocellulose, and Figures 3 and 4 The figures are graphs showing test results on the effects of the ratios of diluting solvent and waste ink, and of cleaning solvent and separated pigment, on the separation of recovered materials, and Figure 5 is a diagram showing the basic flow of the method of the present invention. be.

Claims (1)

[Claims] 1. From waste ink, which is characterized by adding a solvent with poor pigment dispersibility to waste ink, stirring it, separating the precipitated pigment from the liquid phase, and washing this with alcohol to recover high-purity pigment. Pigment recovery method.