JP2935772B2 - Corona discharge treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a corona discharge treatment method, and more particularly, to a corona discharge treatment for a resin molded product having various three-dimensional shapes in order to improve paintability, printability, adhesiveness and the like. The present invention relates to a method for performing surface treatment by electric discharge.

[0002]

2. Description of the Related Art It is well known that by applying a corona discharge treatment to the surface of a resin film made of polypropylene or the like, the printability and adhesiveness of the film surface can be improved, and it is used in the production of various products. Not only the resin film, but also the surface of the resin molded product having three-dimensional irregularities, that is, a three-dimensional shape, is subjected to corona discharge treatment under normal pressure to improve paintability and adhesion. I have.

In the conventional corona discharge treatment, a pair of electrodes, a discharge electrode and a counter electrode, is used. An object to be processed is placed between the pair of electrodes, and a high voltage is applied between the electrodes at normal pressure to apply the corona. By generating a discharge, a corona discharge treatment is performed on the surface of the object. At this time, as a high voltage applied between the electrodes, an AC high-frequency voltage was usually used. The AC high-frequency voltage is said to easily generate corona discharge and is excellent in surface treatment effect. In addition, JP
Japanese Patent Application Laid-Open No. 7-4890 states that the processing effect is improved by using a high-voltage pulse having a pulse width of about 100 to 200 μs in the corona discharge processing on the film.

In the case where the object to be processed is a resin molded product having a three-dimensional shape, it is required to perform a good corona discharge treatment on the uneven surface, and there are various restrictions as compared with a flat film or a plate material. Therefore, various improvement methods have been proposed. For example, in Japanese Patent Application Laid-Open No. 57-119931, the position of the tip of the discharge electrode is always kept at a certain distance from the surface of the object to be processed, with respect to the object held by the counter electrode. A corona discharge is generated by applying an AC high-frequency voltage between the counter electrode and the discharge electrode while relatively moving the counter electrode and the workpiece and the discharge electrode, and performing a corona discharge treatment on the surface of the workpiece. A method is disclosed. Japanese Patent Application Laid-Open No. 62-57431 discloses that an AC high-frequency output of 20 to 30 kHz is applied while relatively moving a discharge electrode having a curved discharge tip along the surface of a workpiece. A method for performing corona discharge treatment is disclosed.

However, in these corona discharge treatment methods for a resin molded product having a three-dimensional shape, spark discharge is apt to occur, and sufficient treatment is performed on an edge existing on the outer periphery of the resin molded product or the inner periphery of an opening. There was a problem that it was difficult to apply. This is because, in the conventional method, when the discharge electrode approaches the edge of the resin molded product, the distance between the discharge electrode and the counter electrode, the so-called interelectrode distance, becomes smaller, so that corona discharge that is effective for surface treatment is stabilized. Therefore, spark discharge occurs due to dielectric breakdown of the air layer. In order to prevent the spark discharge, the applied voltage may be reduced, but in this case, a sufficient corona discharge treatment effect is not improved.

As a method for solving such a problem, Japanese Patent Application Laid-Open No. Sho 62-57431 discloses a method in which a buffer plate made of a dielectric material such as epoxy resin is fitted into an opening of a resin molded product. A technique for preventing corona discharge from being disturbed in a hole is disclosed. However, in this method, it is necessary to prepare a buffer plate corresponding to the shape of the opening of the resin molded product, and to attach this buffer plate to a predetermined position of the resin molded product or the counter electrode, thereby increasing work efficiency and electrode production. The disadvantage is that the efficiency is very poor. Further, if there is a slight gap between the opening and the buffer plate, there is a problem that a dielectric breakdown occurs through this gap and spark discharge occurs.

[0007] In order to solve the above-mentioned problems of the prior art, the present inventors have studied the waveform of a high voltage applied to the discharge electrode.
Pulse width is 1μs or less, pulse frequency is 10 ~ 1000pp
It has been found that if a high-voltage pulse having a very narrow pulse width is used, spark discharge is unlikely to occur and a good corona discharge is generated, and a corona discharge treatment method using such a high-voltage pulse is disclosed in Japanese Patent Application No. Hei. A patent application has been filed under -98818.

[0008]

However, when the above-mentioned high voltage pulse having a very narrow pulse width is used, the energy efficiency is extremely deteriorated if a high applied voltage is applied in order to enhance the effect of the corona discharge treatment. Because
There is a disadvantage that the distance between the electrodes cannot be increased. In the conventional method, the distance between the electrodes which can be practically subjected to the corona discharge treatment is less than 3 to 5 cm, which is satisfactory when processing a three-dimensional article having various shapes thicker than the distance between the electrodes. No results were obtained.

[0009] This is because a high-voltage pulse having a pulse width of 1 µs or less as in the prior art can effectively prevent the generation of spark discharge. Increase the distance between electrodes, for example, 5 cm
In the case described above, it is difficult to form a corona streamer (accelerated electron flow) necessary for the corona discharge treatment, and even if the corona streamer is formed, the effective energy of the corona discharge is small, and the resin molded product is hardly formed. The effect of the surface treatment on the surface is small.

Therefore, in order to sufficiently impart the effect of the corona discharge treatment to the surface of the resin molded article, it is necessary to take an extremely long treatment time or arrange the discharge electrode close to the surface of the resin molded article. . If the processing time is long, the productivity is reduced, so that it is not suitable for industrial implementation. In addition, if the discharge electrode must be arranged near the surface of the resin molded product, the structure of the discharge electrode becomes complicated when the shape of the resin molded product has a complicated three-dimensional shape. It is costly and costly. If the shape of the resin molded product is changed every time the shape of the resin molded product is changed even a little, it cannot be used for applications in which the shape of the resin molded product frequently changes. Further, when processing resin molded products having different shapes in one corona discharge processing line, the electrodes must be replaced each time the resin molded product changes, which requires a very troublesome operation.

Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, prevent generation of harmful spark discharge, and reliably perform processing up to the edge of the resin molded product. It is another object of the present invention to provide a corona discharge treatment method which has a high surface treatment effect on a resin molded product, is easy to produce an electrode, and can easily cope with a shape change of the resin molded product.

[0012]

According to the present invention, there is provided a corona discharge treatment method according to the present invention, in which a resin molded product having a three-dimensional shape is disposed between a discharge electrode and a counter electrode, and a high-level resin is provided between both electrodes. In a method of applying a voltage to generate corona discharge to perform corona discharge treatment on the surface of a resin molded product, the pulse width is 1 μs or more and 20 μs or less.
The corona discharge is generated by a high voltage pulse having an average electric field strength expressed as applied voltage (peak value) / distance between poles of 4 to 20 kv / cm and a pulse frequency of 10 pps or more.

As the material of the resin molded product, an arbitrary resin such as polypropylene, polyethylene or other polyolefin-based resin whose surface characteristics can be improved by corona discharge treatment is used. Since the polyolefin resin does not have a polar group, it has a problem of poor adhesiveness and printability. Corona discharge treatment is effective for improving these properties. Needless to say, in addition to the above-mentioned resin, various additives such as a rubber material, a pigment, a filler, an antioxidant, and an ultraviolet ray inhibitor are included in the material of the resin molded product as needed.

As the shape of the resin molded product, an arbitrary three-dimensional shape such as an uneven portion, a rib, or an opening portion is used in accordance with the purpose of use of the resin molded product. The present invention
Good processing effects can be exerted on a resin molded product in which an opening is formed in part. Specific examples of the resin molded product include an instrument panel pad for automobiles (so-called instrument panel pad), a bumper, a molding, and the like.

The structures of the discharge electrode and the counter electrode may be basically the same as those of a corona discharge treatment apparatus for an ordinary resin molded product, and a known electrode structure can be freely used. Specifically, for example, as the counter electrode, a plate-like or planar electrode composed of a curved surface or a plane substantially along the lower surface shape of the resin molded product is used. The counter electrode and the resin molded product do not need to be in close contact with each other, and there may be a gap between the counter electrode and the resin molded product, or a dielectric may be interposed between the counter electrode and the resin molded product. Therefore, even if the resin molded product has complex irregularities, the shape of the counter electrode may be a relatively simple curved surface or flat surface. As a material for the counter electrode, a conductive material used in a normal discharge device, such as copper, aluminum, stainless steel, or the like is used. The thickness of the counter electrode varies depending on its shape and dimensions, but is usually preferably about 1.0 mm or more. Alternatively, a thin foil or film made of a conductive material may be attached to the surface of a main body made of FRP or synthetic resin to form a counter electrode. Further, the counter electrode is not limited to a continuous plate or a plane, but may be a net or a cage having thin wires arranged vertically and horizontally, or a plate having a large number of holes or slits.

As the discharge electrode, a discharge electrode structure of a known shape generally used in corona discharge treatment is used. Specifically, for example, a thin plate or knife-edge electrode having an edge is arranged side by side at a position at a predetermined distance from the outer periphery of the resin molded product.
Further, a needle-shaped electrode may be arranged in a brush shape. The discharge electrode also does not need to exactly correspond to the outer shape of the resin molded product. The material of the discharge electrode is the same as that of the counter electrode. By swinging the discharge electrodes back and forth or left and right, or by alternately supplying high voltage pulses to the discharge electrodes arranged adjacently, it is effective to perform a uniform corona discharge treatment on the surface of the resin molded product. is there. The same effect can be achieved by swinging the resin molded product instead of swinging the discharge electrode.

The distance between the discharge electrode and the counter electrode, that is, the distance between the electrodes is set so as to satisfy the conditions described later.
If the discharge electrode and the counter electrode are arranged in parallel with each other, the distance between the electrodes is the same at all positions. However, the distance between the electrodes may be slightly different depending on the position of the electrode. If one or both of the discharge electrode and the counter electrode are movably provided, the distance between the electrodes can be changed as needed.

In the corona discharge treatment, the characteristics of the generated corona discharge or the treatment effect on the resin molded product change depending on the waveform of the high voltage pulse applied between the discharge electrode and the counter electrode. In the present invention, among various elements of the high-voltage pulse waveform, first, the pulse width is set to 1 μs or more, preferably 2 to 20 μs. Under general processing conditions,
10 μs is preferred. When the pulse width is less than 1 μs, when the distance between the electrodes is increased, the surface treatment effect on the resin molded product is weak, and the energy efficiency becomes extremely low. If the pulse width is too large, harmful spark discharge (so-called spark) is likely to occur, which is not preferable.

Next, the average electric field strength expressed by applied voltage (peak value) / distance between poles is set to 4 to 20 kv / cm, preferably 6 to 20 kv / cm.
Set to 〜１０10 kv / cm. If the average electric field intensity is less than 4 kv / cm, effective corona discharge is unlikely to occur, and the surface treatment effect is poor. When the average electric field intensity exceeds 20 kv / cm 2, harmful spark discharge (spark) is liable to occur, which is not preferable.

The applied voltage is defined by the peak value of the voltage actually applied between the discharge electrode for performing corona discharge treatment on the resin molded product and the counter electrode. To specifically measure the applied voltage, the peak value of the high voltage pulse waveform flowing between the discharge electrode and the counter electrode may be measured. The preferred range of the applied voltage depends on the value of the distance between the electrodes, for example,
If the distance between the electrodes is 30 cm, the applied voltage should be 120 to 30
It is set in the range of 0 kv, more preferably in the range of 160 to 240 kv. When the applied voltage is relatively high and the average electric field strength is 6 kv / cm or more, it is desirable to interpose a dielectric, which will be described later, between the counter electrode and the resin molded product.

The distance between the electrodes is defined by the distance between the discharge electrode and the counter electrode. The actual distance between the electrodes may be determined in accordance with the maximum dimension of the resin molded product to be subjected to the corona discharge treatment.
In the present invention, the distance between the electrodes can be set to 5 cm or more, and practically, for example, when the resin molded product is a bumper, the distance between the electrodes is preferably set to a range of 25 to 35 cm. Next, the pulse frequency is set to 10 pps or more. Under normal processing conditions, it is set to 50 to 100 pps. When the pulse frequency is less than 10 pps, the effective energy of the corona discharge treatment per unit time is small, and the time required for the surface treatment is long, which is not preferable. When the pulse frequency exceeds 200 pps, it is technically difficult to generate a high-voltage pulse having such a high pulse frequency with the above-described pulse width and average electric field strength. 300pp pulse frequency
Attempting to set the value in a range exceeding s is not preferable because the high-voltage generator becomes very large, the equipment cost becomes excessive, and industrial profitability becomes impossible.

As the high voltage pulse generator for generating the high voltage pulse as described above, basically the same high voltage pulse generator as in the conventional corona discharge treatment method can be used. As long as the high-voltage pulse generator can generate the above-described high-voltage pulse from a commercial AC power supply or a DC power supply, the specific circuit structure can be set arbitrarily. Various circuit structures or devices conventionally used as an impulse high voltage generator can be used.

If a dielectric is interposed between the counter electrode and the resin molded product, a harmful spark discharge (spark) can be obtained even when the applied voltage (peak value) is high and the average electric field strength is high within the above-mentioned range of conditions. ) Can be reliably prevented. As the dielectric, a PVC resin, a Teflon resin, or another ordinary dielectric material is used. The thickness of the dielectric is 1 mm or more, preferably 5 to 20 mm. If the thickness of the dielectric is less than 1 mm, the desired effect of preventing spark discharge cannot be sufficiently achieved. Even if the thickness of the dielectric exceeds 20 mm, the effect of preventing spark discharge is not so different, and the disadvantages of increasing the bulk of the dielectric and increasing the cost are greater. The shape of the dielectric may be a curved surface or a planar shape substantially along the surface shape of the counter electrode, and need not be in close contact with the resin molded product. When a relatively thin dielectric layer is formed on the surface of the counter electrode, the counter electrode has a thickness of 1.0 mm or more,
If a plate material of 1.6 mm or more is desirably used, sufficient mechanical strength or durability can be provided. A thin foil or film of a conductive material such as copper or aluminum is formed on the back surface of the dielectric, and this conductive layer can be used as the above-described counter electrode. In this case, it is preferable that the thickness of the dielectric is made thicker in order to have mechanical strength, and generally about 5 mm or more.

When industrially performing a corona discharge treatment, a corona discharge can be generated between a discharge electrode and a counter electrode disposed above and below the transfer path of the resin molded product while transferring the resin molded product by a conveyor or the like. If this is the case, corona discharge treatment can be performed efficiently. The resin molded product can be transported while being placed on a counter electrode that moves together with the conveyor.

[0025]

[Function] When surface treatment of a resin molded product is performed by corona discharge using a high voltage pulse, it is known that the characteristics of the corona discharge change depending on the waveform of the high voltage pulse, and that the surface treatment effect on the resin molded product also differs. ing. Conventionally, it has been considered that the pulse width must be 1 μs or less in order to perform corona discharge processing without causing spark discharge. It has been considered that in order to perform a sufficient corona discharge treatment on the surface of the resin molded product with such a pulse width, it is necessary to bring the electrode and the surface of the resin molded product close to each other.

On the other hand, even when the pulse width is set to 1 μs or more as in the present invention, the average electric field intensity is 4 to 20 kv.
When the pulse frequency is 10 pps / cm 2 or more, spark discharge (spark) which is harmful to the surface treatment of the resin molded product is hardly generated, and good corona discharge treatment can be performed. Also, even if a slight spark discharge occurs, for example, by interposing a dielectric having a simple structure between the counter electrode and the resin molded product,
Spark discharge (spark) can be prevented without impairing the effect of the corona discharge treatment.

Generally, the discharge phenomenon caused by a high-voltage pulse tends to shift from corona discharge to spark discharge as the pulse width becomes wider. However, corona discharge and spark discharge are not theoretically strictly distinguishable,
It is conceivable that there is a stage in which either corona discharge or spark discharge can be said, or a state in which both exist. If the pulse width is less than 1 μs, it is possible to make a state in which spark discharge does not exist almost completely. However, even if the pulse width is 1 μs or more, the spark discharge does not adversely affect the surface treatment of the resin molded product. The occurrence can be suppressed.

On the other hand, as the pulse width increases, the effective discharge energy increases, so that the surface treatment effect on the resin molded product increases. Alternatively, the corona discharge extends far from the surface of the resin molded product. That is, the processing efficiency is improved, and the desired surface treatment effect can be achieved in a short time. In addition, even if the distance between the poles is increased, a corona discharge of sufficient strength can be generated, and a good surface treatment effect is achieved. Therefore, each electrode is arranged very close to the surface of the resin molded product. Eliminates the need. Therefore,
Using a counter electrode and a discharge electrode having simpler shapes, the discharge electrode can be arranged at a position away from the resin molded product. As a result, even in the case of a resin molded product having a complicated shape, a relatively simple electrode shape can be adopted, and it is not necessary to change the shape of each electrode for each resin molded product.

Next, the influence of the average electric field strength and the pulse frequency will be described. The discharge phenomenon is affected by the strength of the electric field applied to the space. That is, even when the applied voltage is the same, the magnitude of the voltage per unit distance, that is, the strength of the electric field is different between the case where the interelectrode distance is long and the case where the interelectrode distance is short, and the state of corona discharge or spark discharge changes.
Also, even if the magnitude of the effective discharge energy given in one pulse is the same, if the pulse frequency increases or decreases,
The total amount of discharge energy applied within a certain period of time also increases or decreases, and as a result, the surface treatment effect on the resin molded product also changes. Therefore, if the average electric field strength is set to 4 to 20 kv / cm 2 and the pulse frequency is set to 10 pps or more after setting the pulse width as described above, a good corona discharge treatment effect can be surely achieved, and at the same time, It is easy to suppress the generation of harmful spark discharge.

Next, when the average electric field strength is set in the range of 6 to 20 kv / cm in the above condition range, the effect of the corona discharge treatment is enhanced. However, in this case, spark discharge is more likely to occur than when the average electric field intensity is small. Therefore,
In such a case, if a dielectric having a thickness of 1 mm or more is interposed between the counter electrode and the resin molded product, the dielectric reliably prevents the generation of spark discharge.

[0031]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an external structure of an apparatus for performing a corona discharge treatment method according to the present invention. As the resin molded product 10, a substantially U-shaped bumper for automobile made of polypropylene resin is used, and a corona discharge treatment is performed as a pretreatment for coating the surface of the resin molded product 10. Resin molding 10
Is mounted on the counter electrode 20 having a bent plate shape having a U-shaped cross section along the lower surface shape. Although there are complicated irregularities on the back surface of the resin molded product 10, the surface of the counter electrode 20 may be flat, and a gap may be formed between the resin and the resin molded product 10. The counter electrode 20 is mounted on a support 30, and the support 30 is mounted on wheels 3 provided at four corners on the lower surface.
At 2, the vehicle runs on rails 34 installed on the floor. A drive conveyor 36 is connected to the center of the lower surface of the support 30. The drive conveyor 36 is linearly moved by a motor, a chain drive mechanism, or the like, so that the support 30 and the resin molded product 10 are moved in the arrow direction. It can be driven for traveling. Further, the current collector 31 attached to the support 30 and extending laterally is in contact with a bus bar 33 that is installed along the traveling path of the support 30 and is grounded. Since the support 30 runs while the current collector 31 slides on the bus bar 33, the counter electrode 20 and the support 30 are always grounded.

Above the running path of the resin molded product 10, the discharge electrodes 40 in the shape of a narrow band plate bent in a U-shape are arranged at regular intervals. The plate thickness of the discharge electrode 40 is 0.1-0.
It is preferable to use a plate having a thickness of about 2 mm and a width of about 10 to 50 mm. The shape of the lower edge of the discharge electrode 40 is the resin molded product 1
It roughly corresponds to the top edge shape of 0,
The lower edge of the discharge electrode 40 and the surface of the counter electrode 20 are arranged substantially in parallel, and are spaced apart by about several tens of cm. The upper portion of the discharge electrode 40 is supported by a rod-shaped connection fitting 42 and is electrically connected integrally. The discharge electrodes 40 are detachably attached to the connection fittings 42 with bolts or the like, and the attachment pitch of the discharge electrodes 40 can be changed as necessary. Both ends of the connection fitting 42 are attached to a frame 44 made of an insulating material such as vinyl chloride. A high-voltage cable 46 is connected to the connection fitting 42, and the high-voltage cable 46 is connected to a high-voltage pulse generator (not shown). Frame 4 made of insulating material
4 is installed on the floor via an insulator 48.

Therefore, the resin molded article 10 mounted on the counter electrode 20 runs under the discharge electrode 40 and applies a high voltage pulse between the discharge electrode 40 and the counter electrode 20 to generate a corona discharge. And corona discharge treatment can be applied to the surface of the resin molded article 10. FIG. 2 shows a specific example of the circuit structure of the corona discharge treatment device. The resin molded product 10 is mounted on the counter electrode 20, and a discharge electrode 40 is disposed above the resin molded product 10. The circuit connected to the discharge electrode 40 and the counter electrode 20 is provided with a waveform shaping circuit 52 and a negative high-voltage power supply 50. The negative high-voltage power supply 50 is capable of generating a desired high-voltage current, similarly to various normal high-voltage devices. The waveform shaping circuit 52, the fixed gap switch 53 for pulse generation, inductance L, charging and discharging capacitor C, the load resistor R ₁ is provided. Fixed gap switch 53
Is a so-called ball gap switch. By appropriately setting conditions such as circuit constants of the waveform shaping circuit 52, a high-voltage pulse having desired characteristics can be obtained.
It will be applied between the discharge electrode 40 and the counter electrode 20.

FIG. 3 shows the waveform of the high voltage pulse. This waveform is a waveform obtained when the waveform of the voltage applied between the discharge electrode 40 and the counter electrode 20 is measured by an oscillograph. The waveform P ₀ is a conventionally used high voltage pulse having a pulse width of 1 μs or less, having a pulse width t of 0.2 μs and a peak value Vp of about 50 kv.

On the other hand, a waveform P ₁ is a waveform showing an example of the high voltage pulse used in the present invention. This waveform
This shows a so-called damped oscillation waveform. In such a damped oscillation waveform, the pulse width t is defined by the pulse width of the first wave, and specifically, t = 4 μs. Peak value Vp
Is also specified in the first wave, and indicates 200 kv. Thus, in this embodiment, as compared with the conventional waveform P _0, wide much pulse width t, so that using a large waveform P ₁ peak value Vp. Then, as shown in FIG. 4, such a waveform P _1, thereby repeatedly generated at every predetermined time. In this embodiment, one pulse is generated about every 4/60 seconds, and the pulse frequency is 15 pps.

In the high-voltage pulse generator of FIG. 2, the decay time of the high-voltage pulse can be adjusted by the load resistance R ₁ in the circuit, and the decay time becomes longer as the load resistance R ₁ increases. The pulse width t is set by the value of the inductance L. The charge / discharge capacitor C varies depending on the total length of the discharge electrode, but is usually set to a value of about 10 times the capacitance of the processing discharge region.

Further, it is preferable to use a protection resistor R ₂ having an appropriate value in accordance with the value of the charge / discharge capacitor C.
The value other conditions of the protective resistance R _2, a pulse frequency is determined, as a result, it changes the length of processing time required to perform a predetermined corona discharge treatment on the resin molded product 10. Specifically, for example, as a constant capacitance C of the charge and discharge condenser, by increasing the protective resistance R _2, a pulse frequency is reduced, by reducing the protective resistance R _2, pulse frequency increases. Under normal processing conditions, the pulse frequency is 20 to 10
If it is 0 pps, the time required for processing is about 1 to 6 minutes. As the fixed gap switch 53, a spherical type switch is usually used, but a snow darma type switch having a small projection at the tip can exhibit good performance. If compressed air whose temperature and humidity are adjusted and controlled is supplied to the space around the fixed gap 53, better and more stable performance can be exhibited. In the pulse shaping circuit 52 of FIG. 2, a resonance phenomenon occurs, and a discharge voltage higher than the input voltage can be obtained, which is preferable in terms of both safety and economy.

Before performing the corona discharge treatment on the resin molded article 10, various pretreatments can be performed as in the conventional method. For example, in order to keep the surface of the resin molded product 10 clean, it is preferable to perform solvent cleaning, acid or alkali cleaning, and then wash and dry the resultant, and then perform corona discharge treatment. However, the washing step as described above is performed for the resin molded product 1
If it is not contaminated with oil or dust when molding 0 by injection molding or during storage after molding, it is possible to carry out corona discharge treatment without going through the washing process. it can.

To explain a specific example of the cleaning step, the following steps can be sequentially performed. First, 50-6
Perform alkali cleaning by shower spray at 0 ° C. for 0.5 to 1 minute. Next, hot water washing is performed by shower spray at 40 to 50 ° C. for 0.5 minute. Next, neutralization adjustment is performed at 40 to 50 ° C. for 0.5 minute. Again, at 40-50 ° C.
After washing with hot water for 5 minutes, drying is performed at 90 to 100 ° C. for 4 to 5 minutes, and the corona discharge treatment as described above is performed. The corona discharge treatment may be performed, for example, at 20 to 30 ° C. for about 3 to 6 minutes. After performing the corona discharge treatment, it is brought into a normal coating process.

Next, FIGS. 5 to 8 show different embodiments of the electrode structure. As shown in FIG. 5, with respect to the substantially L-shaped resin molded product 10, along the lower surface of the resin molded product 10,
The same L-shaped counter electrode 20 is used, and the discharge electrode 40 is also formed in the same L-shape. In this case, since the counter electrode 20 and the discharge electrode 40 are parallel, the distance W between the electrodes is the same at any position. The embodiment of FIG. 5 and the next FIG.
As shown in the embodiment shown in FIG.
When there is a bent portion or a curved portion at 0, it is preferable to set the radius of curvature of this portion to 50 mm or more. This is because if the radius of curvature is too small, the state of occurrence of corona discharge is different between a portion having a small radius of curvature and another portion, and the corona discharge treatment on the surface of the resin molded article 10 may be non-uniform. It is.

In FIG. 6, a plurality of needle-like electrodes are arranged as the discharge electrodes 40. Since corona discharge is easily generated from the tip of the needle-shaped electrode, a good corona discharge treatment effect can be achieved. The embodiment of FIG. 7 is substantially the same as the embodiment of FIG. 1 described above, in which a plate-shaped counter electrode 20 bent in a U-shape and a large number of discharge electrodes 40 in the form of a narrow U-shape are arranged at regular intervals. ing.

In the embodiment shown in FIG. 8, the counter electrode 20 is formed by combining thin wires in a cage shape, and the overall schematic shape is the same as that of the embodiment shown in FIG. Even if the opposing electrode 20 partially has a space as in this embodiment, a good corona discharge can be generated between the discharge electrode 40 and the discharge electrode 40 by appropriately setting the interval and density of the gap. Can be generated.

When the discharge electrode 40 or the counter electrode 20 has a divided structure, the shape of the resin molded product 10 can be adjusted.
The distance between the electrodes can be finely adjusted by changing the arrangement of the divided electrodes. Next, FIG. 9 shows a case where a dielectric 60 is interposed between the counter electrode 20 and the resin molded product 10. As shown in the figure, if a cut 62 is provided in the dielectric 60 disposed on the counter electrode 20 at an intermediate position between the adjacent discharge electrodes 40, 40, the discharge of each discharge electrode 40 becomes strong, and Also, no spark discharge occurs. As a result, a better corona discharge treatment can be performed than when the surface of the counter electrode 20 is completely covered with the dielectric 60.

Next, a more specific embodiment of the corona discharge treatment method of the present invention will be described. Example 1 A PP test piece M4800 (150 mm × 60 mm × 3 mm) manufactured by Mitsui Petrochemical Co., Ltd. was used as the resin molded product 10.

As shown in FIG. 10A, the counter electrode 2
0, the discharge electrode 40 and the resin molded product 10 were arranged, and a high voltage pulse was generated by a high voltage pulse generation circuit 500 having the same circuit structure as that shown in FIG. 2 to perform corona discharge treatment. . In some embodiments, the counter electrode 2
A 10 mm thick PVC sheet was placed as a dielectric 60 on the surface of the substrate 0 so as to cover the entire surface, and the resin molded product 10 was placed thereon. A high voltage pulse was applied with the distance W between the discharge electrode 40 and the counter electrode 20 set to 15 to 30 cm. The corona discharge treatment was applied to the resin molded article 10 by changing the waveform of the high voltage pulse in various ways. The characteristics of the high-voltage parf waveform
Measured with an oscilloscope. The processing time was set to 1 to 5 minutes. For comparison, the results obtained by using the same apparatus and performing processing even with a high voltage pulse in a conventional corona discharge processing method are shown as Comparative Examples 1.6 to 1.9. However,
In this comparative example, it was difficult to increase the applied voltage to 50 kv or more, and data with an applied voltage of 50 kv or more was not obtained.

Resin molded article 10 subjected to corona discharge treatment
Was painted. As a paint, R-271 manufactured by NBC
Using a (two-component curing type urethane paint), coating was performed by a conventional method and dried. Drying was performed at 90 ° C. for 30 minutes. 24
After leaving it for a time, perform a 180 ° peeling test,
The peel strength of the paint was measured, and the effect of the corona discharge treatment was confirmed. Tables 1 to 4 show test results.

[0047]

[Table 1] Distance between poles 30cm, pulse width 4μs 誘 電 Dielectric peak value Average electric field strength Pulse frequency Peeling strength kv kv / cm pps g / cm 処理 Treatment Time 1 minute 3 minutes 5 minutes ────────────────────────────────── Example 1.1 Yes 230 7.7 10 500 700 1000 Example 1.2 Yes 230 7.7 20 1000 1200 1500 Example 1.3 Yes 230 7.7 60 1500 1800 2000 Example 1.4 Yes 230 7.7 100 1500 2000 2000 Example 1.5 Yes 180 6.0 20 300 500 800 Example 1.6 With 180 6.0 100 1000 1200 1200 Example 1.7 Without 180 6.0 20 500 800 1200 Example 1.8 Without 180 6.0 100 1200 1500 1800 Example 1.9 A 120 4.0 20 100 150 250 Example 1.10 Yes 120 4.0 100 300 450 600 Example 1.11 None 120 4.0 20 200 350 500 Example 1.12 None 120 4.0 100 600 800 1000 Comparative Example 1.1 None 230 7.7 10 Spark generation Comparative example 1.2 Yes 100 3.3 20 to 100 000 Comparative example 1.3 No 100 3.3 100 0 50 ────────────────── ────────────────

[0048]

[Table 2] Distance between poles 15cm, pulse width 4μs ────────────────────────────────── Dielectric peak value Average electric field strength Pulse frequency Peeling strength kv kv / cm pps g / cm 処理 Treatment Time 1 minute 3 minutes 5 minutes ────────────────────────────────── Example 1.13 Yes 180 12.0 20 1800 2000 2000 Example 1.14 Yes 180 12.0 100 1900 2000 2000 Example 1.15 Yes 120 8.0 20 1200 1500 1800 Example 1.16 Yes 120 8.0 100 1800 2000 2000 Example 1.17 Yes 120 8.0 100 1800 2000 2000 Example 1.18 None 60 4.0 20 150 300 450 Example 1.19 None 60 4.0 100 550 700 900 Comparative Example 1.4 None 180 12.0 20 Spark departure Comparative Example 1.5 None 120 8.0 20 Spark generation Comparative Example 1.6 Yes 60 4.0 20 0 0 0 Comparative Example 1.7 Yes 60 4.0 100 0 0 60 ─────────────── ─────────────────── * In Example 1.14, a slight spark was observed, but there was no adverse effect on the treatment effect.

[0049]

[Table 3] Distance between poles 6cm, pulse width 0.2μs 誘 電 Dielectric Peak value Average electric field strength Pulse frequency Peeling strength kv kv / cm pps g / cm ─────────────────────────────────処理 Processing time 1 minute 3 minutes 5 minutes 比較 Comparative example 1.6 None 50 0 20 0 50 100 Comparative Example 1.7 None 50 8.0 100 100 300 500 ───────────────────────────────── ─

[0050]

[Table 4] Distance between poles 3cm, pulse width 0.2μs 誘 電 Dielectric Peak value Average electric field strength Pulse frequency Peeling strength kv kv / cm pps g / cm ─────────────────────────────────処理 Processing time 1 minute 3 minutes 5 minutes 比較 Comparative example 1.8 None 30 8 0 20 1000 1200 1500 Comparative Example 1.9 None 30 10.0 100 100 1500 1800 2000 ─────────────────────────────────結果 As a result of the above test, the conventional method using a high-voltage pulse with a very narrow pulse width shown in Tables 3 and 4 (Comparative Example 1.
6 to 1.9), a good corona discharge treatment effect can be obtained when the distance between the electrodes is small (3 cm). However, when the distance between the electrodes is slightly increased (6 cm), the treatment effect is extremely reduced. Further, in the high-voltage pulse generating circuit of FIG. 2 used for the test (without the inductance L), it is difficult to make the peak value 50 kv or more with a pulse width of 0.2 μs, In the case of 60 kv or more, a sufficient treatment effect was not obtained.

On the other hand, in the embodiment of the present invention, it was proved that even if the distance between the electrodes was 30 cm, the corona discharge treatment effect sufficient for practical use could be improved. Also, from the results in Table 1, the average electric field strength was less than 4 kv / cm (Comparative Examples 1.2 and 1.3).
) Indicates that there is no effect of the corona discharge treatment. From the results shown in Tables 1 and 2, when the average electric field strength is 7 kv / cm or more, sparks occur without a dielectric (Comparative Example 1.
1, 1.4, 1.5), it can be seen that good corona discharge treatment becomes possible by using a dielectric (Examples 1.1 to 1.4,
1.13 to 1.17). Also, when a dielectric is provided, the processing effect is insufficient at less than 6 kv / cm, but when it is 6 kv / cm or more, the processing effect can be enhanced by increasing the pulse frequency. Furthermore, when the average electric field strength is 4 kv / cm, a good processing effect can be obtained without a dielectric (Example 1.
18 and 1.19), there are cases where corona discharge treatment cannot be performed when a dielectric substance is present (Comparative Examples 1.6 and 1.7). Therefore, in the embodiment of the present invention, the average electric field intensity is relatively low (4 to 4).
At 6 kv / cm 2), it may be better not to interpose a dielectric.

Example 2 As shown in FIGS. 10A and 10B, the position and orientation of the resin molded product 10 are changed in the space between the discharge electrode 40 and the counter electrode 20. Corona discharge treatment was performed under the same treatment conditions as in Example 1.2. The processing time was set to 3 minutes.
The evaluation of the peeling test was performed on the upper surface (in the case of the horizontal posture) and the vertical side surface (in the case of the vertical posture) indicated by arrows in the drawing, of the surface of the resin molded product 10. In the drawing, Hb, Hc, He, and Hf indicate the height of the resin molded product 10 from the surface of the dielectric 60. Table 5 shows the results of the test.

[0053]

[Table 5] 姿勢 Posture Height Peel strength H cm g / cm ──────── 2.1 Example 2.1 FIG. 10 (a) A horizontal 0 1100 Example 2.2 FIG. 10 (a) B Horizontal 10 1140 Example 2.3 FIG. a) C horizontal 201 260 Example 2.4 FIG. 10 (b) D vertical 0 1100 Example 2.5 FIG. 10 (b) E vertical 10 1250 Example 2.6 FIG. 10 (b) F vertical 20 1060 °結果 As a result of the above test, even if the posture or position of the resin molded product 10 between the electrodes is changed, there is no significant difference in the effect of the corona discharge treatment. In each case, practically sufficient processing effects are achieved. Further, it was confirmed that good corona discharge treatment was possible even when the resin molded product 10 was not in close contact with the counter electrode 20.

[0054]

According to the corona discharge treatment method according to the present invention described above, a high-voltage pulse waveform for generating corona discharge has a specific range of pulse width, average electric field intensity and pulse frequency. By using, even if the resin molded product to be treated and the electrode do not have to be close to each other,
The effect of corona discharge treatment can be exhibited well,
Does not cause harmful spark discharge.

As a result, there is no need to manufacture a discharge electrode or a counter electrode in strict accordance with the shape of the resin molded product. Further, even if the shape of the resin molded product is changed, it is not necessary to re-produce the electrodes. Therefore, the labor and time for manufacturing the electrode can be greatly reduced, the working efficiency of the entire corona discharge treatment can be increased, and the working cost can be reduced. further,
A single corona discharge processing line enables continuous processing of resin molded products with different shapes without having to replace the electrodes one by one. If applied to a production site of a product, it can greatly contribute to improving the workability of the corona discharge treatment or reducing the work cost.

[Brief description of the drawings]

FIG. 1 is an overall perspective view of a corona discharge treatment apparatus showing an embodiment of the present invention.

FIG. 2 is a circuit diagram illustrating a circuit configuration of a high-voltage pulse generator.

FIG. 3 is a diagram showing a waveform of one pulse of a high-voltage pulse.

FIG. 4 is a diagram showing a state of occurrence of a high-voltage pulse over time.

FIG. 5 is a front view showing a specific example of an electrode arrangement.

FIG. 6 is a front view showing another specific example of the electrode arrangement.

FIG. 7 is a perspective view showing another specific example of the electrode arrangement.

FIG. 8 is a perspective view showing another specific example of the electrode arrangement.

FIG. 9 is a perspective view illustrating a specific example of an electrode arrangement when a dielectric is used.

FIG. 10 is a schematic explanatory view showing an electrode arrangement when a performance confirmation test is performed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Resin molded product 20 Counter electrode 40 Discharge electrode 60 Dielectric

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Koichi Kuwano 19-17 Ikedanakamachi, Neyagawa City, Osaka Japan Paint Co., Ltd. (72) Inventor Kensuke Akutsu 19-17 Ikedanakamachi, Neyagawa City, Osaka Japan Paint Stock In-house (72) Inventor Koji Ueki 19-17 Ikedanakamachi, Neyagawa-shi, Osaka Japan Paint Co., Ltd. (72) Inventor Ikuo Tochizawa 19-17 Ikedananakacho, Neyagawa-shi, Osaka Japan Paint Co., Ltd. (56) Reference Document JP-A-2-107371 (JP, A) JP-A-47-4890 (JP, A) JP-A-62-57431 (JP, A) Shin-ichi Masuda, "Journal of the Electrostatics Society of Japan", Vol. 6, p473-479 (1990) (58) Fields investigated (Int. Cl. ⁶ , DB name) C08J 7/00

Claims (2)

(57) [Claims] 1. A resin molded product having a three-dimensional shape is disposed between a discharge electrode and a counter electrode, and a corona discharge is generated by applying a high voltage between the two electrodes. In the method of performing discharge treatment, the pulse width is 1
μs or more and 20 μs or less, and the applied voltage (peak value) /
A corona discharge treatment method characterized in that a corona discharge is generated by a high voltage pulse having an average electric field strength represented by a distance between the electrodes of 4 to 20 kv / cm and a pulse frequency of 10 pps or more. 2. The method according to claim 1, wherein an average electric field intensity of the high-voltage pulse is 6 kv / cm or more, and a dielectric having a thickness of 1 mm or more is interposed between the resin molded article and the counter electrode. Corona discharge treatment method.