GB2139641A

GB2139641A - Dyestuff refining system

Info

Publication number: GB2139641A
Application number: GB08407973A
Authority: GB
Inventors: Masahiro Haruta; Kunitaka Ozawa; Takashi Hamamoto
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 1983-04-01
Filing date: 1984-03-28
Publication date: 1984-11-14
Also published as: GB2139641B; DE3411877C2; FR2543705B1; FR2543705A1; DE3411877A1; GB8407973D0; JPS59182861A

Abstract

A dyestuff refining system which is principally constructed with a device for producing dyestuff solution and a sensor for sensing concentration of inorganic salts in the dyestuff solution, and means responsive to the sensing means for maintaining salt concentration below a set maximum level.

Description

SPECIFICATION Dyestuff refining system This invention relates to a dyestuff refining system, and, more particularly, it is concerned with a dyestuff refining system capable of continuously supplying refined dyestuff which is suitable for preparing recording liquid (generally called "ink") adapted to use in ink jet recording, writing implements, and other uses.

Ink to be used for an ink jet recording system which implements recording of information by ejecting ink within a recording head through an ejection orifice by means of vibrations transmitted from a piezo-electric vibrator or other expedients, employs various dyestuffs and pigments which are dissolved or dispersed in a liquid medium such as water or other (e.g. organic) solvent. Similar ink is used in writing implements such as felt pens, fountain pens, etc.

Such ink may comprise the following three chief components: water soluble dyestuff, water as the solvent for the dyestuff, and glycols as a desication-preventive agent.

The water-soluble dyestuff can contain a large amount of inorganic salts such as sodium chloride and sodium sulfate either as byproducts of the dye-synthesis, or as added salting-out agents, diluents, or level-dyeing agents.

We have discovered that when recording ink is prepared with use of dyestuff containing such inorganic salts, problems can arise: the inorganic salts can lower the solution stability of the dyestuff in the ink to bring about agglomeration and sedimentation of the dyestuff. Further, in the ink jet recording heads and writing implements, if and when the ink is evaporated in the vicinity of the ejection orifice causing the liquid composition to change, deposition of the inorganic salts can be induced. These phenomena cause clogging to take place at the discharge orifice which is highly undesirable.

We have found-that by controlling the inorganic salt concentration within a predetermined maximum when producing the ink (in general, limited to 0.5 wt.% or less with respect to the total ink composition) these problems can be avoided. We have found such control to be indispensable when dyestuff available on the general market, which contains therein inorganic salts as impurities, is used for preparation of ink for the ink jet recording as well as for use in writing implements.

According to one aspect of the present invention, there is provided a dyestuff refining system, characterized by comprising: means for producing dyestuff solution; and means for controlling concentration of inorganic salts contained in said dyestuff solution.

According to another aspect of the present invention, there is provided a dyestuff refining system, characterized by comprising: means for producing dyestuff solution; means for detecting concentration of inorganic salts in said dyestuff solution; and means for controlling concentration of said inorganic salts on the basis of an output from said concentration detecting means.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic constructional diagram showing one embodiment of the dyestuff refining system according to the present invention; Figure 2 is composed of Figures 2A and 2B.

Figures 2A and 2B are block diagrams showing a control section of the system shown in Figure 1; and Figure 3 is composed of Figures 3A and 38.

Figures 3A and 3B are flow charts showing the sequential operations of the system shown in Figure 1.

DESCRIPTION OF THE PREFERRED EMBODI MENTS In the foliowing, the present invention will be described in detail in reference to the accompanying drawings.

Figure 1 shows one embodiments of the dyestuff refining system according to the present invention.

In the drawing, a reference numeral 21 designates a dyestuff feeding section storing therein dyestuff powder 22. The dyestuff powder 22 is fed from this dyestuff feeding section 21 into a preparation tank 24 through a dyestuff feeding valve 23. Also, into this preparation tank 24, pure water is supplied through a pure feeding pipe 26 having a pure water valve 25 interposed in one part thereof.

In this preparation tank 24, aqueous solution of dyestuff is prepared by mixing and dissolving the dyestuff powder 22 and the pure water by means of an agitator 27 installed in the preparation tank 24. The liquid quantity of the aqueous solution of dyestuff staying in the preparation tank 24 is detected by a liquid quantity sensor 28 set in the preparation tank. The aqueous solution of dyestuff obtained in the preparation tank contains therein, as the residue, particles of the dyestuff powder which have not been dissolved in the pure water. This residual dyestuff powder is removed by a filter 29. For the filter 29, there may be used ordinary filter paper or "FLUOROPORE" (a trade name of a product of Sumitomo Denko K.K., Japan, which is made up of polytetrafluoroethylene as the principal constitutent), and so forth.

The aqueous solution of dyestuff, from which the residual particles, etc. have been removed through the filter 29, is forwarded to a feed ing tank 31.

The aqueous solution of the dyestuff sent into the feeding tank 31 stays therein so far as a feeding valve 32 is in a closed state. A liquid level controlling valve 33 is disposed in this feeding tank 31 to maintain the quantity of the aqueous solution of dyestuff to be stored in it to a certain definite level or below.

A reference numeral 41 designates a refining section where the inorganic salts are removed from the aqueous solution of dyestuff.

In this refining section 41, a reference numeral 42 designates a salt-stripping tank, a numeral 43 refers to a salt-stripping filter, and a numeral 44 represents a discharged salt storing tank. The aqueous solution of dyestuff is fed into the salt-stripping tank 42 through the feeding valve 32. The thus fed dyestuff solution is agitated by an agitator 45 set in the salt-stripping tank 42 to homogenize the aqueous solution, after which concentration of the inorganic salts therein is detected by a sensor 46 for the inorganic salts concentration. This detection of the inorganic salts concentration is carried out by, for example, the ion-chromatographic method. Further, concentration of the dyestuff in the aqueous solution is detected by use of a sensor 47 for the dyestuff concentration.This detection of the dyestuff concentration is carried out by, for example, the spectrophotometry. As will be described later, when the concentration of the inorganic salts is found to be above a predetermined value (e.g., 5 wt % with respect to the dyestuff), a circulation pump 48 is operated to circulate the aqueous solution of dyestuff in the salt-stripping tank 42 through the salt-stripping filter 43. For the salt-stripping filter, there may be used, for example, an urtra-filter, a reverse osmotic filter and so forth. By passage of the dyestuff solution through the salt-stripping filter 43, the inorganic salts such as sodium chloride, sodium sulfate, etc. contained in it are filtered out in the form of aqueous solution of these salts, and discharged into the salt-storing tank 44.As the result of this salt removal, a part of the water as the solvent for the dyestuff is also discharged into this salt-storing tank 44 along with the inorganic salts. In order, therefore, to replenish water for the portion as discharged and to maintain a desired concentration for the dyestuff solution in the saltstripping tank 42, pure water is supplied into this salt-stripping tank 42 through a valve 49.

In the above-described manner, there can be obtained the aqueous dyestuff solution in the saltstripping tank 42 with the concentration of both inorganic salts and dyestuff being in their predetermined range. By the way, the quantity of the aqueous solution of dyestuff in the salt-stripping tank 42 is detected by a sensor 50 for the liquid quantity in the saltstripping tank.

Thereafter, the aqueous solution of dyestuff which has been refined (stripped off its salts content) in the above-described manner is discharged into a refined dyestuff storing tank 52 through a storage valve 51, and stored in it.

Figure 2 is a block diagram for the control section of the refining system according to the present invention shown in Figure 1, in which a reference numeral 61 designates a controller to undertake the drive-control of every section in the system, a numeral 62 refers to a readonly memory (ROM) storing therein control programs such as the operational sequences, etc. as shown in Figure 3, and a numeral 63 refers to a random-access memory (RAM) temporarily storing therein various data.

In the present embodiment, analog signals are output from the inorganic salts concentration sensor 46 and the dyestuff concentration sensor 47, and, after these signals are converted into the digital signals through the respective A/D converters 64 and 65, respectively, they are fed into the controller 61 through an input buffer circuit 66. On the other hand, digital signals are output from the preparation tank liquid quantity sensor 28 and the salt-stripping tank liquid quantity sensor 50, and are also fed into the controller 61 through the input buffer circuit 66.

Reference numerals 67 through 74 designate drive circuits to drive the afore-men tioned valves 23, 25, 49, 32 and 51, the agitators 27 and 45, and the circulation pump 48, respectively. These drive circuits are "onoff" controlled by drive signals supplied from the controller 61 through an output buffer circuit 75.

Numerals 81 and 82 refer to a range setting switch for the dyestuff concentration and a range setting switch for the inorganic salts concentration, respectively, from which sig- nals corresponding to the respective concentration ranges as set are supplied into the controller 61 through a console input-output buffer circuit 83. Numerals 84 and 85 respectively designate a display device for the dyestuff concentration and a display device for the inorganic salt concentration, on which are displayed a value of the dyestuff concentration and a value of the inorganic salts concentration in the aqueous solution of dyestuff during its refining operations. From these displayed values, the operator of the refining system is able to find out readily the quality of the aqueous solution of the dyestuff during its production.

The set values of the dyestuff concentration range and the inorganic salts concentration range by the respective switches 81 and 82 are temporarily stored in RAM 63. The concentration values of the inorganic salts and the dyestuff in the aqueous solution of dyestuff during the refining operations, as detected by the inorganic salts concentration sensor 46 and the dyestuff concentration sensor 47, are each compared with the set values in a comparison section of the controller 61, based on which result the driving operation of each load such as the circulation pump 48, etc. is controlled, as will be mentioned later.

Figure 3 is a flow chart for the operations of the dyestuff refining system shown in Figure 1. In the drawing, those steps STl to ST4 are for maintaining the dyestuff aqueous solution in the preparation tank 24 at a constant quantity. In more detail, at the step ST1, the detection is performed with an output from the sensor 28 for the liquid quantity in the preparation tank as to whether the liquid level of the aqueous solution of dyestuff in the preparation tank 24 is above a lower position defining a predetermined set range of the liquid level. If the liquid level is below the lower position, the operational sequence proceeds to the step ST2; otherwise, to the step ST3.At the step ST2, the dyestuff feeding valve 23 and the pure water feeding valve 24 are opened to fill the preparation tank 24 with predetermined quantities of the dyestuff powder and the pure water. In the preparation tank 24, since the agitator 27 is in constant operation, the dyestuff powder as charged is dissolved into the pure water to be the aquaous solution of dyestuff.. At the step ST3, detection is performed with an output from the liquid quantity sensor 28 as to whether the liquid surface level in the preparation tank 24 is above an upper position defining the predetermined set range, or not. If above the upper position, the operational sequence proceeds to the step ST4, and, if not, to the step ST5.At the step ST4, the dyestuff feeding valve 23 and the pure water feeding valve 25 in their open condition are closed to thereby stop feeding of the dyestuff powder and the pure water.

At a step ST5, a dyestuff concentration value of the dyestuff solution in the saltstripping tank 42 as detected by the dyestuff concentration sensor 47 is displayed on the diaplay device 84. In the same manner, at a step ST6, an inorganic salts concentration value as detected by the inorganic salts concentration sensor 46 is displayed on the display device 85.

At a step ST7, determination is made as to whether the dyestuff concentration as detected by the detector 47 is within the range of the dyestuff concentration set by the switch 81, or not. If it is within the set range, the operational sequence proceeds to a step ST8, and, if not, to a step ST9. At the step ST8, determination is made as to whether the inorganic salts concentration as detected by the sensor 46 is within the range of values set by the switch 82, or not. If it is within the set range, the operational sequence proceeds to a step ST10, and, if not, to the step ST9.

At the step ST9, determination is made as to whether the liquid surface level in the saltstripping tank 42 as detected by the sensor 50 is above the upper position defining the set range, or not. If it is below the upper position, the operational sequence proceeds to a step ST11, and, if not, to a step ST12. At the step ST11, the feeding valve 32 and the pure water feeding valve 49 are subjected to open-and-close controls, thereby feeding the aqueous solution of dyestuff and the pure water into the salt-stripping tank 42, thereby regulating the dyestuff concentration of the aqueous dyestuff solution in the salt-stripping tank 42 to be in the range set by the switch 81 as mentioned in the foregoing.After this, the operational sequence proceeds to a step ST13. On the other hand, closing operations of the feeding valve 32 and the pure water feeding valve 49 are carried out at the step ST12.

At the step ST13, the circulation pump 48 is operated to circulate the aqueous solution of dyestuff in the salt-stripping tank 42 through the salt-stripping filter 43 to thereby perform elimination of the inorganic salts from the aqueous solution of dyestuff.

As stated above, when the dyestuff concentration and the inorganic salts concentration are outside the set ranges, routine operations are repeated through the steps Sty 1 and ST13 or the steps ST12 and ST13 so as to bring the dyestuff concentration and the inorganic salts concentration within their set ranges. After these two concentration values have been put in the set ranges, the operational sequence proceeds to the step ST10.

At the step STl 0, determination is made as to whether the liquid surface level in the saltstripping tank 42 as detected by the sensor 50 is above the lower position defining the set range, or not. If it is above the lower position, the operational sequence proceeds to a step ST14, and, if not, to a step ST15. At the step ST14, the operation of the circulation pump 48 is stopped and the opening operation of the storing valve 51 is carried out. As the result of this, a predetermined quantity of the refined aqueous dyestuff solution obtained in the salt-stripping tank 42 is supplied into the storage tank 52.

At the step ST15, there are effected the closing operation of the storing valve 51 and the opening operations of the feeding valve 32 and the pure water feeding valve 49, thereby completing supply of the refined solution to the storage tank 52 and increasing the quantity of the aqueous dyestuff solution in the salt-stripping tank 42 so as to bring the liquid surface level within the set range.

Thereafter, the routine operations are again repeated through the steps ST11 and ST13 or through the steps ST12 and ST13 as mentioned in the foregoing, thereby obtaining in the salt-stripping tank 42 a predetermined quantity of aqueous solution of dyestuff with the dyestuff concentration and the inorganic salts concentration thereof being within the set ranges. After this, the operational sequence proceeds to the step ST14. Thus, according to the embodiment of the present invention, the aqueous solution of dyestuff can be refined for every certain definite quantity in the refining section 41.

As has so far been described, the dyestuff refining system according to the present invention is so constructed that, in its manufacture of the dyestuff solution, the concentration of inorganic salts contained in the dyestuff solution may be controlled Further, in its manufacture of the dyestuff solution, the concentration of inorganic salts contained in the dyestuff solution may be detected and controlled on basis of the detected value. Therefore, it is suitable for production of the refined dyestuff solution which meets the requirements for preparing the ink for the ink jet recording and for the writing implements, and others.

Claims

1. A dyestuff refining system comprising means for producing a dyestuff solution and means for controlling the concentration of inorganic salts contained in the dyestuff solution.

2. A system according to Claim 1 wherein the control means is provided with means for detecting the concentration of the inorganic salts.

3. A dyestuff refining system comprising: means for producing dyestuff solution; means for detecting the concentration of inorganic salts in the dyestuff solution; and means for controlling the concentration of the inorganic salts on the basis of an output from the concentration detecting means.

4. A system according to Claim 3 including means for displaying an output from the detecting means revealing the inorganic salt concentration.

5. A system according to Claims 3 or 4 wherein the control means includes a salt stripping filter, and means for circulating the dyestuff solution through the filter when the detecting means indicates a specified salt concentration.

6. A system according to Claim 5 including means for detecting the concentration of dyestuff in the solution and means for replenishing water or other solvent removed by the filter to maintain the dyestuff concentration within a determined range.

7. A dyestuff refining system substantially as described herein with reference to the accompanying drawings.