JPH0315529Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an electrode for corona discharge treatment on the surface of a molded body made of a thermoplastic resin, and particularly to an improved lower electrode thereof.

(Prior Art) Recently, it has become popular to manufacture automobile parts using lightweight and strong polymer synthetic resin materials such as polypropylene, and it has become necessary to form and paint these automobile parts in large quantities. There is.

Generally, when a thermoplastic synthetic resin such as polypropylene is formed, the surface layer of the thermoplastic synthetic resin molded object is exposed to low molecular weight molecules due to the influence of heat during molding, so when the surface of the molded object is painted, low molecular weight molecules are removed. There is a problem in that the coating easily peels off along with the synthetic resin on the surface layer.

Therefore, in order to prevent the coating from peeling off easily, techniques are known in which a molded thermoplastic synthetic resin (molded body) is subjected to plasma treatment, primer treatment, etc. as a pretreatment for painting.

When discharged in a vacuum through the plasma treatment described above, the synthetic resin on the surface layer of the molded body, which has been reduced to a low molecular weight, is destroyed by the impact of the discharge and roughened into fine irregularities, and the rough synthetic resin surface is painted. This prevents the paint from peeling off easily.

However, in the case of the above-mentioned plasma treatment, a vacuum step is required, and this step takes a long time, which poses problems in terms of processing cost and processing time.

Further, the primer treatment is a process of applying an adhesive to the surface of the synthetic resin, and there is a problem in that it takes a long time to dry the adhesive.

Incidentally, there is a corona discharge treatment that can obtain the same effect as the above plasma treatment at normal pressure, and this treatment is also generally known.

For example, according to a corona discharge treatment apparatus for the surface of a molded article made of thermoplastic resin described in Japanese Patent Publication No. 60-46133, the upper electrode is composed of a chain or a cylindrical metal brush, and the corona discharge treatment is performed. A flexible discharge electrode that approximately conforms to the outer shape of the molded body is used, the lower electrode is made of a mold member made of a conductive material (for example, copper) that conforms to the inner shape of the molded body, and the molded body is placed on the lower electrode. The outer surface of the molded body is subjected to corona discharge treatment by placing the lower electrode and the molded body on a belt conveyor and moving the molded body along the upper electrode.

(Problem to be solved by the invention) In the corona discharge treatment apparatus for the surface of a molded article made of thermoplastic resin, the lower electrode is formed of a conductive material such as copper and formed into a mold member that conforms to the inner surface shape of the molded article. Therefore, there is a problem that not only is the production cost very high, but also that it is heavy and inconvenient to carry.

(Means for Solving the Problem) The electrode for corona discharge treatment on the surface of a molded body made of thermoplastic resin according to the present invention has a flexible upper part that follows and contacts the outer surface of the molded body made of thermoplastic resin. In an electrode for corona discharge treatment comprising an electrode and a shaped lower electrode along substantially the entire inner surface of the molded body, the lower electrode is formed of a laminate of a synthetic resin film and a conductive material film, and A shape-retaining material is attached to this laminate to maintain the shape of the laminate.

(Function) Since the electrode for corona discharge treatment on the surface of a molded body made of thermoplastic resin according to the present invention is configured as described above, the flexible upper electrode follows and contacts all the outer surfaces of the molded body. However, since the lower electrode contacts the inner surface of the molded body, applying a high voltage between the upper electrode and the lower electrode to perform corona discharge treatment will cause
The outer surface of the molded body is destroyed by the impact action of the electric discharge,
The surface becomes rough with minute irregularities.

The conductive material film of the lower electrode is protected and reinforced by the synthetic resin film, and the lower electrode is shape-retained by the shape-retaining material and held in a shape that fits the inner surface of the molded body.

(Effect of the invention) According to the electrode for corona discharge treatment on the surface of a molded body made of thermoplastic resin according to the invention, as explained above, the conductor of the lower electrode is made of a conductive material film,
Protecting and reinforcing the conductive material film with synthetic resin,
In addition, since the laminate formed of the synthetic resin film and the conductive material film is kept in shape with a shape-retaining material, the cost of the lower electrode can be reduced, and it can also be made lighter and more durable. .

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

This example relates to an electrode for corona discharge treatment, which is performed as a pretreatment for coating a molded body made of thermoplastic synthetic resin such as polypropylene (a polymeric material).In particular, the lower electrode is made of urethane. It is formed into a laminate of a resin film, copper foil, and glass cloth (glass fiber).

As shown in FIGS. 1 and 2, the corona discharge device 1 includes a gate-shaped frame 2 when viewed from the front, a conductive electrode support plate 3, and a height adjustment mechanism by moving the electrode support plate 3 in the vertical direction. a height adjustment mechanism 4, a flexible upper electrode 5, a lower electrode 7 shaped like a mold that matches the internal shape of the molded body 6, a current-carrying plate 8 made of a conductor, and a molded body 6.
and a belt conveyor 9 for moving the lower electrode 7 and the lower electrode 7.
It basically consists of a high-frequency, high-voltage power supply device (not shown) that applies a high voltage between the upper electrode 5 and the lower electrode 7, and the like.

The frame 2 is erected from the floor so as to be perpendicular to the length direction of the belt conveyor 9.

The height adjustment mechanism 4 is composed of an air cylinder 10 and a pair of guide rods 11. On the upper surface of the top plate 2a of the frame 2, there is a vertical air cylinder 10 at approximately the center in the length direction. fixed,
A pair of guide rods 11 erected on the electrode support plate 3 are slidably inserted into the air cylinder 10 at positions separated from each other by an appropriate distance in the left and right directions.

The piston rod 12 of the air cylinder 10 is inserted through the top plate 2a, and the tip of the piston rod 12 is fixed to the electrode support plate 3 below the top plate 2a, and the air cylinder 10 is supplied from an air supply source (not shown). By driving the electrode support plate 3 with air, the position of the electrode support plate 3 can be adjusted up and down.

The flexible upper electrode 5 includes a plurality of thin conductive chains 13 made of thin copper, each of which is supported at one end by the electrode support plate 3 in a matrix of multiple rows and columns. , and a plurality of pointed copper needles 14 fixed to the tip (lower end) of each chain 13, and the length of each chain 13 corresponds to the outer shape of the molded body 6 to be subjected to corona discharge treatment. It can be adjusted within the electrode support plate 3 to suit.

Note that the chain 13 may be replaced with a thin wire or the like.

The belt conveyor 9 is perpendicular to the frame 2 and is disposed inside the frame 2, and is configured to reciprocate in the front and rear directions by a drive device (not shown).

A conductive current plate 8 is placed on the belt conveyor 9.
is placed, a lower electrode 7 is placed on the current-carrying plate 8, and a molded body 6 of thermoplastic synthetic resin such as polypropylene (polymer material) is placed on the lower electrode 7. .

The belt conveyor 9 is made swingable in the vertical direction when viewed from the front, and the tip (lower end) of the upper electrode 5 is
may follow and contact the entire outer shape of the molded body 6, including the side walls, curved portions, and corners.

Next, the structure of the lower electrode 7 and its manufacturing method will be explained.

FIG. 3 is a sectional view of a mold-shaped lower electrode 7 made of a laminate formed of a urethane resin film 15, a copper foil 16, and a glass cloth 17.

A urethane resin film 15 with a thickness of about 2 mm is provided on the top layer of the lower electrode 7, and a copper foil 16 with a thickness of about 200 to 500 μm is provided below as the lower electrode body by adhesion or adhesive. The foil 16 is protected by a urethane resin film 15.

On the underside of the copper foil 16, seven layers of urethane resin films 15 and glass cloths 17 are alternately laminated by adhesive as a shape-retaining material for the lower electrode 7. The shape-retaining material allows the lower electrode 7 to maintain its shape in close contact with the inner surface of the molded body 6.

Further, as shown in FIG. 4, the lower electrode 7 according to the modification includes a urethane resin film 15 and a glass cloth 1.
The copper foil 16 is laminated on the underside of the copper foil 16, and the shape-retaining material of the lower electrode 7 is formed on the underside of the copper foil 16. As, urethane resin film 15 and glass cloth 17
These are alternately laminated in five layers.

A method for manufacturing the lower electrode 7 will be briefly described (see FIG. 3).

Using a male mold made with the molded body 6, first apply urethane resin to the upper surface of the male mold by brush coating or spray gun coating, then layer glass cloth 17 on top of it along the urethane resin film 15, and then proceed in the same manner. Seven layers of urethane resin film 15 and glass cloth 17 are repeatedly laminated alternately, and then copper foil 16 is pasted on top of urethane resin film 15 using an adhesive-coated copper foil tape, and then a urethane resin film is placed on top of that. Apply 15,
The male mold is removed and dried to produce a lower electrode 7 having a shape that matches the internal shape of the molded body 6.

Next, the effect when the molded body 6 is subjected to corona discharge treatment by the discharge device 1 will be explained.

1 and 2, a terminal 18 provided on the electrode support plate 3 and a terminal 19 provided on the current-carrying plate 8 connected to the copper foil 16 are connected to a voltage (approx. 30,000 volts) is applied and the belt conveyor 9 moves forward at a predetermined speed by the drive device, the molded body 6 placed on the belt conveyor 9, the lower electrode 7, and the current-carrying plate 8 move simultaneously, and the upper electrode The tip (lower end) of 5 is the molded body 6
while following and contacting the outer surface of the upper electrode 5.
Corona discharge is started between the lower electrode 7 and the outer surface of the molded body 6 is subjected to a corona discharge treatment.

Then, the low-molecular surface layer of the molded body 6 is finely broken and gouged out by the impact force caused by the corona discharge, resulting in a rough surface with many fine irregularities.

When the outer surface of the molded body 6 that has been subjected to the corona discharge treatment is painted, the paint fills even the minute recesses on the surface, increasing the contact area between the paint and the synthetic resin that has not been reduced to a low molecular weight. Since the total contact area with the resin increases significantly, the adhesion between the paint and the synthetic resin is strengthened and the paint does not peel off.

The upper electrode 5 may be made of a horizontal circular metal brush instead of the chain 13, and the metal brush may be rotated to follow and contact the outer surface of the molded body 6, or a spring or other suitable material may be used for the upper electrode 5. It may be made of a flexible conductive material.

When the corona discharge is started and the molded body 6 is being subjected to the corona discharge treatment, the lower electrode 7 uses a shape retaining material made of a laminate of the urethane resin film 15 and the glass cloth 17 to absorb the heat generated due to the corona discharge. On the other hand, deformation of the lower electrode 7 is prevented and its shape is maintained.

The lower electrode 7 can also be configured as follows.

The lower electrode 7 can also be made by press working with a male mold and a female mold.

It can be made of only the copper foil 16 and a thick synthetic resin layer as a shape-retaining material, or in short, it is sufficient to consist of the copper foil 16 and a shape-retaining material that retains the copper foil 16. The material can be made of a metal frame or a solid foam.

Note that carbon fiber cloth may be used instead of the glass cloth 17, and copper mesh or other thin metal film may be used instead of the copper foil 16.

Hereinafter, modified examples of the upper electrode 5 will be described with reference to FIGS. 5 to 7 for reference.

When the molded body 6 is subjected to corona discharge treatment by corona discharge, it is desirable that the distance between the upper electrode 5 and the lower electrode 7 be as uniform as possible at any position.

Therefore, as shown in FIGS. 5 and 6, a conductive synthetic resin or a conductive synthetic resin mixed with metal powder is molded into a shape that fits the outer surface of the molded body 6, and the molded Countless small needles 2 with metal tips of appropriate length are placed all over the inner surface of the synthetic resin.
0 is implanted to constitute the upper electrode 5A.

Then, by applying a high frequency high voltage to the terminal of the upper electrode 5A and the terminal of the lower electrode 7, a corona discharge is caused between the tip of the needle 20 that contacts the molded body 6 and the lower electrode 7, and the outer surface of the molded body 6 is is corona discharge treated.

In addition, as shown in FIG. 7, a thin metal plate 21 is attached to the entire inner surface (the surface facing the molded body 6) of a conductive synthetic resin or a synthetic resin mixed with metal powder.
The adhesive is formed into a shape that fits the molded body 6, and the inner surface of the metal plate 21 is subjected to electrical discharge treatment, so that the surface of the metal plate 21 becomes rough and has a finely pointed shape.

When this is used as the upper electrode 5B and a corona discharge is caused, countless minute tips of the metal plate 21 and the lower electrode 7
Corona discharge will occur between the two.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a perspective view of a corona discharge device, and FIG. 2 is a perspective view of a corona discharge device.
3 is a partial vertical sectional view of the lower electrode, FIG. 4 is a view corresponding to FIG. 3 of the lower electrode of the modified example, and FIG. 5 is a state in which discharge treatment is performed using the upper electrode of the modified example. 6 is a partially enlarged sectional view of the upper electrode of FIG. 5, and FIG. 7 is a view corresponding to FIG. 6 showing another modification of the upper electrode. 1... Corona discharge device, 5... Upper electrode, 6...
... Molded object, 7 ... Lower electrode, 13 ... Chain, 15 ...
...Urethane resin, 16...Copper foil, 17...Glass cloth.

Claims (1)

[Claims for Utility Model Registration] A flexible upper electrode that follows and contacts the outer surface of a molded body made of thermoplastic resin, and a shaped lower electrode that runs along substantially the entire inner surface of the molded body. In the electrode for corona discharge treatment, the lower electrode is formed of a laminate of a synthetic resin film and a conductive material film, and a shape-retaining material is attached to the laminate to maintain the shape of the laminate. An electrode for corona discharge treatment on the surface of a molded body made of characteristic thermoplastic resin.