JPS6225756B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention uses a bath solution for a so-called etching process to roughen the surface of plastic materials as a pretreatment for electroplating plastic materials. This invention relates to improvement of a device for constant electrolytic regeneration.

<Prior art> In order to perform electroplating on plastic materials, prior to the plating process, the surface of the plastic material is roughened by immersing it in an etching bath consisting of a mixture of chromic acid and sulfuric acid, and then the surface of the plastic material is roughened. It is a common practice to improve the adhesion between the electroplated layer and the plastic material. This etching process partially oxidizes and dissolves the surface of the plastic material through the oxidizing action of chromic acid, so when the chromic acid performs its oxidizing action, the chromic acid itself is reduced, changing from the hexavalent chromium state. It changes to trivalent chromium state, weakening its oxidizing effect as an etching bath,
Eventually it becomes impossible to continue the etching action. Therefore, the etching bath solution is circulated to an electrolytic regeneration tank, and constant DC electrolysis is performed to reoxidize trivalent chromium to hexavalent chromium, keeping the concentration of hexavalent chromium in the etching bath constant and prolonging the etching action. Devices that maintain this over a period of time have been put into practical use.

Here, FIG. 1 shows an example of the electrolytic regeneration device for the etching bath solution, in which 1 indicates an etching bath containing an etching solution 2 whose main components are chromic acid and sulfuric acid. The plastic material 3 to be treated is immersed. Further, a pump 4 is connected to the etching tank 1 to send the etching solution 2 to the electrolytic regeneration tank 5, and a return pipe 6 is connected to return the etching solution 2 regenerated in the electrolytic regeneration tank 5 to the etching tank 1. It is connected.

The electrolytic regeneration tank 5 includes a tank 10 partitioned into an anode chamber 8 and a cathode chamber 9 by a bisque diaphragm 7, an anode 11 of lead or lead alloy immersed in the anode chamber 8, and an anode 11 of lead or lead alloy immersed in the cathode chamber 9. The etching liquid 2 sent from the liquid pump 4 is sent to the anode chamber 8.
and is returned to the etching bath 1 via the return pipe 6. Reference numeral 13 denotes a rectifier, the positive output terminal 14 of which is connected to the anode 11 and the negative output terminal 15 connected to the cathode 12.

In the electrolytic regeneration apparatus shown in FIG. 1, trivalent chromium ions contained in the etching solution 2 are anodized in the anode chamber 8 and converted back into hexavalent chromium ions. At the same time, during the etching process, the plastic material 3 to be treated is partially dissolved, and the dissolved products present in the etching solution 2 are also oxidized by the anode 11, becoming gaseous, and dissipated from the surface of the solution. Therefore, the etching liquid 2 is constantly regenerated, and the etching function is maintained for a long period of time.

Further, the catholyte chamber 9 accommodates a catholyte 16 in order to pass a direct current through the diaphragm 7, but the ions in the catholyte 16 pass through the diaphragm 7 to the anode chamber 8.
Chromic acid, sulfuric acid, or a mixture of the two, which are components of the etching solution 2, is used as the catholyte 16 because the composition of the etching solution 2 must not be changed and its etching function should not be inhibited. It will be done.

<Problems to be Solved by the Invention> By the way, during electrolytic regeneration operation, some of the trivalent chromium ions in the solution in the etching tank 1, which is the anode chamber solution, flow into the cathode chamber 9 through the diaphragm 7. Furthermore, anions, ie, chromate ions or sulfate ions, in the catholyte 16 move to the anode chamber 8 through the diaphragm 7, so as the operating time passes, the hydrogen ion concentration in the catholyte 16 decreases (the PH value increases). ) Eventually, trivalent chromium ions can no longer exist in an ionic state and precipitate as chromium hydroxide. Further, as the anions also move to the anode chamber 8 as described above, the number of ions in the catholyte 16 decreases, and its conductivity decreases, making it impossible to pass an electrolytic current. For this reason, the catholyte 16
needs to be updated.

When renewing the catholyte 16, conventionally, when the total etching amount of the plastic material 3 to be treated or the integrated value of the electrolysis time of the electrolytic regeneration device reaches a certain value, the catholyte 16 is discarded and replaced with a new solution. They were exchanging. However, even the catholyte 16 that is discarded may still be usable, which is uneconomical.

Therefore, as a means of knowing when to replace the catholyte, the present inventors devised a method of directly measuring the conductivity of the liquid using a conductivity meter or measuring the pH of the catholyte using a PH meter. However, in the former method, in order to avoid measurement errors caused by the electrolytic current, it is necessary to interrupt the electrolytic current when measuring conductivity, making current control troublesome. The latter method is PH
The range of change is narrow, making accurate detection difficult. Furthermore, in either case, it is necessary to immerse the measuring instrument in the catholyte, and chromium hydroxide or the like adheres to the periphery of the instrument, which tends to cause detection errors. Furthermore, there were other drawbacks such as the calculation and control being complicated.

The present invention provides a solution to the catholyte 1 without causing the above-mentioned drawbacks.
The object of the present invention is to provide an electrolytic regeneration device that can detect when it is time to replace the liquid and can effectively use the liquid up to its usable limit.

<Means for solving the problems> The present invention provides an anode 11 and a cathode 12 of an electrolytic regeneration tank 5.
a voltage detector that detects a voltage between electrodes; an arithmetic device that calculates a ratio between a detected value of the voltage detector and a current value, and generates an output when the calculated value becomes a predetermined resistance value or more; The present invention is characterized by being provided with an alarm that issues an alarm based on the output of the arithmetic device.

<Function> When the conductivity of the catholyte 16 decreases, the electrical resistance between the anode 11 and the cathode 12 of the electrolytic regeneration tank 5 increases. Therefore, in order to measure the resistance, the anode 1
1 and the cathode 12 with a voltage detector, further calculate the resistance from the detected value and the current value, and compare the resistance value with a predetermined resistance value suitable for replacing the catholyte, An alarm is activated when the calculated value is greater than the predetermined resistance value. This results in
You can know the optimal time to replace the catholyte.

<Embodiment> FIG. 2 shows an embodiment of the present invention, in which parts common to the apparatus in FIG. 1 are given the same reference numerals.

Here, 17 indicates a DC current detector such as a shunt provided on the DC output side of the rectifier 13, and 18
1 shows a voltage detector that detects the voltage between the anode 11 and the cathode 12 of the electrolytic regeneration tank, that is, the voltage between the electrodes. An arithmetic unit 19 is connected to the output sides of the current detector 17 and voltage detector 18. The arithmetic device 19 calculates the ratio of the detected value of the voltage detector 18 and the detected value of the current detector 17, that is, the electrical resistance of the electrolytic regeneration tank, and compares the calculated value with a predetermined resistance value set in advance, It has a function of generating an output to the relay 20 when the resistance value exceeds the predetermined resistance value. The output causes the relay 20 to be driven, causing an alarm 21 such as a bell or buzzer connected to a power source (not shown) to ring through the contacts of the relay 20.

If the set value of the calculation device 19 is appropriately selected, the alarm 21 will not operate when the electrical resistance of the electrolytic regeneration tank 5 is below a predetermined resistance value, and will operate when the electrical resistance exceeds the predetermined resistance value. is easily possible. It goes without saying that the electrical resistance of the electrolytic regeneration tank depends on both the conductivity of the anolyte and the conductivity of the catholyte 16, but the anolyte is the bath solution itself in the etching tank 1, and originally has a constant composition. Since it is a highly concentrated electrolyte, the electrical conductivity is also sufficiently high and constant, so it can be considered that the electrical resistance depends only on the electrical conductivity of the catholyte 16. Therefore, by monitoring the electrical resistance of the catholyte 16, the usage limit of the catholyte 16 can be known.

In order to measure the electrical resistance of the electrolytic regeneration tank, it is not always necessary to use the current detector 17,
For example, a constant current adjustment type rectifier may be used as the rectifier 13 to keep the current constant. In this case, since voltage and resistance are in a proportional relationship, the electrical resistance of the electrolytic regeneration tank can be obtained simply by measuring the voltage between the anode 11 and the cathode 12.

<Effects of the Invention> As described above, the present invention automatically and constantly measures the resistance value of the catholyte, and when the resistance value exceeds a predetermined resistance value at which the catholyte should be replaced, an alarm is generated. Because of this, there is no need to immerse the measuring device in the catholyte, and stable detection is possible without chromium hydroxide or the like adhering to the measuring device and causing measurement errors. Furthermore, since the control can be performed by simple calculations, the control means can also be simplified. Therefore, with a simple configuration,
This has excellent effects such as knowing the optimal timing for replacing the catholyte and making it possible to replace the catholyte without waste.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a conventional electrolytic regeneration device, and FIG. 2 is a system diagram of an electrolytic regeneration device of the present invention. 1; Etching tank, 3; Plastic material,
4; Liquid pump, 5; Electrolytic regeneration tank, 6; Return pipe, 7; Diaphragm, 8; Anode chamber, 9; Cathode chamber, 11;
Anode, 12; cathode, 13; rectifier, 16; catholyte, 17; shunt, 18; voltage detector, 19; arithmetic device, 20; relay, 21; alarm.

Claims (1)

[Claims] 1. An anode chamber in which a plastic material etching bath solution consisting of a mixture of chromic acid and sulfuric acid is circulated, and a cathode chamber separated by a diaphragm and containing sulfuric acid, chromic acid, or a mixture of both. and a rectifier for supplying direct current to the anode immersed in the anode chamber and the cathode immersed in the cathode chamber, wherein: between the anode and the cathode of the electrolytic regeneration tank a voltage detector that detects voltage; an arithmetic device that calculates a ratio between a detected value of the voltage detector and a current value and generates an output when the calculated value becomes a predetermined resistance value or more; and an output of the arithmetic device. 1. An electrolytic regeneration device for an etching bath solution for plastic materials, characterized in that it is equipped with an alarm device that gives an alarm due to the above.