JPH052589B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an antistatic plastic sheet molded container suitable for packaging electronic devices susceptible to electrostatic damage.

When plastic sheets such as polystyrene, polyvinyl chloride, and polypropylene are thermoformed to form containers and used to package items that are susceptible to static electricity, the surface resistance of these plastic sheets is determined by JIS K6911. compliant, hereinafter the same)
10 to ¹⁴ Ω or more, and the object itself is easily charged.
In addition, since other objects that come in contact with and rub against it are strongly charged, anti-static treatment is required. For the purpose of preventing static electricity, black sheets made of plastic sheets mixed with carbon black or sheets mixed with various antistatic agents are used, but the former is black, making it difficult to see the contents, and is aesthetically disadvantageous. The latter generally has a high surface resistance value, usually 10 ¹¹ Ω or more, and has the disadvantage that its antistatic performance is not necessarily sufficient. The present inventors conducted research on transparent plastic packaging materials with low surface resistance, and previously filed a patent application for an antistatic plastic film in Japanese Patent Application No. 57-225022.
The present invention relates to an antistatic plastic sheet molded container molded from a thermoformable sheet made using the above invention.

The present invention is based on one side of a plastic sheet (hereinafter referred to as A).
A conductive layer made of an ionic conductive resin or a mixture of an ionic conductive resin and an ionic or nonionic conductive agent is provided on the surface (referred to as a surface), and a layer of water-resistant plastic with a thickness of 10 μm or less is provided in close contact with the outside of the conductive layer. layer, and the opposite side (hereinafter referred to as B side) is not provided with the above layer, and this sheet is thermoformed so that side A is on the outside of the container and side B is on the inside of the container. It is a plastic sheet molded container.

The conductive resin that is the material for the conductive layer is a conductive resin with an ionic functional group that is known as a surface resistance lowering treatment agent for electrophotographic paper, electrostatic recording paper, etc., or as a surface resistance lowering treatment agent for other coatings. Resin is used.

Further, as the conductive agent mixed with the conductive resin, an ionic or nonionic organic conductive agent which is usually used for the purpose of preventing static electricity is used.
The conductive layer and the water-resistant plastic layer can be applied directly to the sheet, or they can be applied to a thin film and then laminated to a thicker film or sheet.

The important point of the present invention is that first, the above-mentioned conductive layer is provided only on one side (side A) of the plastic sheet, and the second point is that the conductive layer is provided on only one side (side B) of the plastic sheet.
The point is to mold the container so that it becomes the inner surface of the container.

The conductive layer has the effect of preventing the accumulation of static electricity, so it is common practice to place the A side with this layer on the inner surface of the container to prevent the contents from accumulating too much electricity. Contrary to common sense, placing side B on the inside has the effect of reducing the amount of charge on the contents compared to placing side A on the inside. Also, B
If the surface is treated in the same manner as the A side, the antistatic effect will be improved, but performing such treatment on both sides will increase the price, lack heat resistance, and cause stickiness.
There are drawbacks such as moldability which causes many problems in post-processing, and it is of great practical importance to manufacture products by processing only the A-side.

This will be explained below using examples.

Example 1 An ethyl alcohol solution of a mixture of 90 parts by weight of an acrylic conductive resin containing a cationic quaternary ammonium functional group and 10 parts by weight of mixed alkyltrimethylammonium chloride, which is a cationic conductive agent, was prepared to a thickness of 150 mm. One side of a micron biaxially oriented polystyrene sheet was treated with corona discharge to give a wetting tension of 41 dynes/cm, and a dry weight of 5 gr/cm was applied to the surface.
2 m ² was coated and dried, and then an isopropanol and toluene mixture solution of an acrylic lacquer resin was coated on top of it in a dry amount of 1 g/m ² and dried. In the state of a roll of this sheet, 4
After being left for a week, the surface resistance of the coated side (side A) was measured to be 4×10 ⁶ Ω. The surface resistance of the back surface (B surface) was 3×10 ¹¹ Ω. The reason why the surface resistance of the back surface is such a low value is because the mixed alkyltrimethylammonium chloride added as a cationic conductive agent diffuses into the sheet or moves to the back side and reaches the B side. It is assumed that In addition, surface resistance measurement is based on JIS
This was done in accordance with K6911.

This sheet was used to thermoform a shallow box-shaped container with a rectangular opening of 110 mm x 200 mm and a depth of 30 mm. The inside of the box is the B side, the outside is the A side,
The opening at the top was covered with the same sheet, with the inside side facing B.

Inside this container, place a 20g weight attached to a thin plate of foamed polystyrene (thin plate of styrene paper) cut into 100mm x 100mm.
The styrene paper and container were rubbed by vibrating from side to side. After giving 50 strokes,
Static electricity on the front side of styrene paper was measured. Measurement was performed using Rion Co., Ltd.'s electrostatic field measuring instrument EA03.
Using a mold, the strength of the electrostatic field was read as volt/cm when the measuring surface was placed 9 cm from the top of the measuring instrument. The electrostatic field was 110 volt/cm.

It was found that this container was able to fairly effectively suppress the charging of articles placed inside that were easily charged, such as Styrofoam.

Example 2 90 parts by weight of an acrylic conductive resin containing a cationic quaternary ammonium functional group, 4 parts by weight of a nonionic surfactant as a conductive agent, and 6 parts by weight of a cationic mixed alkyltrimethylammonium chloride. The mixture was made into a methyl alcohol solution and applied to a 200 micron sheet of polyvinyl chloride at a dry weight of 4g/m ² , dried, layered on top, and a toluene solution of polystyrene was applied at a dry weight of 2g.
r/m ² coated and dried. After this sheet was left in a wound roll for 4 weeks, the electrical resistance of the surface was measured to be 8 x 10 ⁶ Ω on the coated side (side A) and 8 x 10 ¹¹ Ω on the back side (side B). With this sheet,
As in Example 1, a box-shaped container was thermoformed with the inside of the box as side B and the outside as side A, and the static electricity of the styrene paper was measured. The electrostatic field was 120 volts.

Example 3 A dry amount of an aqueous emulsion of an acrylic polymer having a cationic quaternary ammonium functional group was applied to the corona-treated side of a 200μ polypropylene sheet which had been coated with an antistatic agent and had been treated with corona discharge on one side. On top of this, a polystyrene solution in toluene was applied in a dry amount ^{of 1 gr/m 2 and} dried. The surface resistance of the coated side (side A) was 9×10 ⁷ Ω, and the surface resistance of the back side (side B) was 4×10 ¹¹ Ω. Using this sheet, a shallow box-shaped container was made in the same manner as in Example 1.
The box was thermoformed with the inside as side B and the outside as side A, and the opening at the top was covered with side B of the same sheet as the inside.

In the same manner as in Example 1, styrene paper was
After 50 strokes, the static electricity was measured and the electrostatic field was 200 volts/cm.

Comparative Example 1 The same box as in Example 1 was molded using a normal biaxially oriented polystyrene sheet that had not been subjected to antistatic treatment, and the same measurements were performed. The value of the electrostatic field is
It was 2000volt/cm.

Comparative Example 2 Example 1 was repeated with the A side of the sheet used in Example 1 placed inside the box and the B side placed outside the box. The value of the electrostatic field was 1200 volt/cm. It can be seen that placing the B side on the inside of the box is particularly effective in preventing the contents from being electrostatically charged.

Comparative Example 3 The A side of the sheet used in Example 2 was placed inside the box, and the B side was placed outside the box, and the electrostatic field was measured in the same manner as in Example 1, and a value of 1000 volt/cm was obtained. B
It can be seen that it is particularly effective to place the surface inside the box to prevent the contents from becoming static.

Reference example: As an example of a container with very good antistatic ability, a container with the same shape as in Example 1 was made from a thin aluminum plate, and the electrostatic field was measured by performing the same operations as in Example 1. . It was 80volt/cm. When measuring items that are easily charged, such as styrofoam, under normal conditions, an electric field of several hundred volts/cm or more is applied from a position 9 cm away, similar to Example 1, so the value of 80 volts/cm is This operation removes static electricity. It can be seen that the molded container of the present invention has good antistatic performance as the reference example using a thin aluminum plate.

Claims (1)

[Claims] 1. A conductive layer made of an ionic conductive resin or a mixture of an ionic conductive resin and an ionic or nonionic conductive agent is provided on one side (hereinafter referred to as side A) of a plastic sheet, and the conductive layer is closely spaced on the outside of the conductive layer. , a layer of water-resistant plastic with a thickness of 10μ or less is provided, and the above layer is not provided on the opposite side (hereinafter referred to as the B side), and this sheet is thermoformed so that the A side is on the outer surface of the container and the B side is placed on the outer surface of the container. A molded container made of antistatic plastic sheet so that the inner surface of the container is made of antistatic plastic sheet.