JPH0559197A - Surface treatment method for plastic molded products - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a surface treatment method for a plastic molded product by corona discharge, which has a good surface treatment effect and does not damage the product. [Composition] Immediately after corona discharge treatment on the surface of the molded plastic in the atmosphere, the corona is further treated in a gas atmosphere in which the mixing ratio of nitrogen and carbon dioxide is in the range of 100: 0 to 50:50. Discharge.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treatment method for a plastic molded article formed into a film.

[0002]

2. Description of the Related Art Generally, when a surface of a plastic molded product is subjected to secondary processing such as printing, vapor deposition, and adhesion, the secondary processing is often unsuccessful. For this reason, some kind of surface treatment must be performed in advance, and the surface treatment method includes a chemical method and a physical method. However, a physical method that is relatively widely used in practice is a physical method that is relatively easy to work, and examples thereof include a gas flame treatment method, a corona discharge treatment method, and a sputter etching method. In particular, a corona discharge treatment method is used as a surface treatment method for a plastic product molded into a film. As the corona discharge treatment method, a method of simply performing corona discharge on the surface of a plastic molded in the atmosphere, or a mixture ratio of nitrogen and carbon dioxide in volume ratio as proposed in Japanese Patent Publication No. 57-30854. Some have activated the plastic surface by corona discharge in a mixed gas atmosphere in the range of 99.5: 0.5 to 50:50.

[0003]

However, the corona discharge method in the general atmosphere and the corona discharge method in the mixed gas atmosphere of nitrogen and carbon dioxide generally require a power density in order to achieve sufficient treatment effect. It has often been a problem that the productivity is significantly lowered in the production of plastic products due to excessively high damage to the film and instability of the treatment effect due to uneven mixing of the mixed gas. The present invention provides a surface treatment method for a plastic molded product by corona discharge, which has a good surface treatment effect and does not damage the product.

[0004]

According to the present invention, immediately after the surface of a molded plastic is subjected to corona discharge treatment in the atmosphere, the mixing ratio of nitrogen and carbon dioxide is 100 by volume.
It is a surface treatment method for a plastic molded article that has been subjected to corona discharge treatment in a gas atmosphere in the range of 0 to 50:50.

The surface of the molded plastic of the present invention means a surface to be subjected to secondary processing after surface treatment.

The mixing ratio of nitrogen and carbon dioxide of the present invention of 100 to 0 means only nitrogen, and means corona discharge treatment in a nitrogen gas atmosphere.

[0007]

The surface treatment method for a plastic molded product by corona discharge according to the present invention comprises a two-stage corona discharge treatment of a corona discharge treatment in the atmosphere and a corona discharge treatment in a mixed gas atmosphere of nitrogen and carbon dioxide. As a result, the instability of the treatment effect caused by the variation in the mixture ratio of the mixed gas is reduced.

The surface treatment effect disappears with time, but since the corona discharge treatment is performed again in the mixed gas atmosphere immediately after the corona discharge treatment in the atmosphere, these two corona discharge treatment effects are obtained. Act synergistically.

Since the surface treatment method by corona discharge treatment of the present invention is performed in two steps, it is not necessary to apply a high power density at a time, and pinholes, slipperiness deterioration, and wrinkles generated on the film surface by corona discharge are caused. There is little film damage such as.

[0010]

EXAMPLE A method for treating a plastic molded article of the present invention by corona discharge is used in the case where secondary processing such as printing of characters or patterns, vapor deposition of metal such as aluminum or adhesion with another plastic film is applied to the surface of the plastic. It is used when activating the plastic surface. The plastic molded product to be treated is not particularly limited, but particularly remarkable effects can be obtained in the case of a film or sheet-like relatively thin product. The applicable plastic materials are mainly polyolefin, and include a wide range of materials such as polyethylene, polypropylene, polyethylene terephthalate, nylon, and polyvinylidene chloride.

The corona discharge treatment conditions are a power density of 30 to 150 W / m ² , a first stage in the atmosphere, and a second stage in which the mixing ratio of nitrogen and carbon dioxide is 100: 0 to 50 by volume ratio. Corona discharge treatment is preferably performed in a mixed gas atmosphere within a range of 50. The power density is 3
If it is less than 0 W / m ² , the treatment effect will be poor, and if it is greater than 150 W / m ² , film damage will occur.

[Specific Embodiment] FIG. 1 is an explanatory view of a corona discharge treatment apparatus used in an embodiment of the present invention. Further, FIG. 2 is a cross-sectional view of a laminated component for evaluating the effect of the example produced by the surface treatment method of the present invention.

First, a non-stretched polypropylene film having a thickness of 25 μm, which is a substrate film for treatment [Nimura Chemical Co., Ltd.]
(1) is a second electrode facing the first electrode (12) in the atmospheric corona discharge treatment device (10) by the guide roll (3) from the unwinding part (2) as shown in FIG. The film surface was transferred to a certain treatment roll (11), and the film surface was subjected to corona discharge treatment in the atmosphere. This corona discharge is generated when a voltage controlled by a generator (manufactured by Sophtal, Inc.) (13) is applied to the first electrode and the second electrode.
The film (1) that has been subjected to corona discharge treatment in the atmosphere is treated with a guide roll in a mixed gas corona discharge treatment device (20).
Of the same film which has been transferred to the treatment roll (21) which is the second electrode facing the first electrode (22) inside and is surface-treated in the air, and the mixture ratio of nitrogen and carbon dioxide is a volume ratio. , As shown in Table 1, 100-0 (method 1-
A), 80:20 (method 1-B), 65:35 (method 1)
-C) and 50:50 (method 1-D) were separately subjected to corona discharge treatment in a mixed gas atmosphere of four types. This corona discharge is generated when a voltage controlled by the generator (23) is applied to the first electrode and the second electrode. The nitrogen and carbon dioxide supplied by the nitrogen supply pipe (24) and the carbon dioxide supply pipe (25) are
The mixed gas is supplied to the corona discharge treatment device (20) in the mixed gas from the mixed gas supply port (27) after being mixed in the gas mixing device (26) at a prescribed mixing ratio. The composition of the mixed gas supplied in the apparatus is monitored by a mixed gas concentration detection device installed near the mixed gas supply port (27) and the mixed gas discharge port (28). The surface-treated film was transferred to a winding section (4) by a guide roll and wound up. Further, the power density in the atmosphere and the mixed gas atmosphere were both corona discharge treated under the condition of 50 W / m ² (method 1a), and the power density in the atmosphere and the mixed gas were both 100 W / m ² . Two kinds of corona discharge treatment, one different from the one subjected to the corona discharge treatment under the condition (method 1b), are performed separately, and the treatment conditions are different depending on the surface treatment method of the present invention.
A variety of surface treated films were made.

At the same time, in order to compare and evaluate the surface-treated films obtained by the above-described eight kinds of surface-treatment methods of the present invention, corona discharge treatment was performed in the atmosphere at a power density of 50 W / m ² , and nitrogen was further added. A surface-treated film subjected to a corona discharge treatment under a condition (method 2) of a power density of 50 W / m ² in a mixed gas atmosphere of a volume ratio of 40:60 in which the mixing ratio of carbon dioxide is outside the scope of the present invention, and the atmosphere. In which the power density is 100 W / m ² and 200 W / m ² (method 3a
And two kinds of surface-treated films subjected to corona discharge treatment in b), and the mixing ratio of nitrogen and carbon dioxide is 80 by volume.
Power density of 100 W / m ² and 2 in a mixed gas of / 20
Two kinds of surface-treated films subjected to corona discharge treatment under the conditions of 00 W / m ² (methods 4a and b) were prepared, and five kinds of surface-treated films for comparative evaluation were prepared as a whole.

Next, the treatment effects of 13 kinds of surface-treated films produced by these various corona discharge treatments were compared and evaluated. As shown in Fig. 2, the evaluation method is as follows: Alumina (32) is vapor-deposited (400 Å) on the corona discharge treated surface of the surface-treated base film 25 μm unstretched polypropylene film (31), and this aluminum vapor-deposited surface 30 μm stretched polypropylene film (3
4) [Toyobo Co., Ltd.] with a fatty acid ester adhesive (3
3) Dry-laminate with a coating amount of 2.0 g / m ² to 5
After standing in an environment of 0 ° C and 90% RH for 60 days, the stretched polypropylene was peeled off (tensilon tensile tester, 15m
m width, descent rate of 200 mm / min), and the peeled state of the vapor-deposited aluminum at this time was observed and evaluated. The evaluation results are shown in Table 1.

[0016]

[Table 1]

Method 1 in Table 1 corresponds to the surface treatment method of the present invention, and is used in the atmosphere and in a mixed gas atmosphere within the scope of the claims of the present invention (N ₂ / CO ₂ : 1-A 100/0). , 1-B
80/20, 1-C 65/35, 1-D 50/50)
And the two-stage corona discharge treatment
During mixed gas atmosphere outside the claims of the atmosphere and the invention _{(N 2 / CO 2: 40/60} ) is obtained by a two-stage corona discharge treatment with. The method 3 is one in which corona discharge treatment is performed only in the atmosphere, and the method 4 is in a mixed gas atmosphere of nitrogen and carbon dioxide (N ₂ / CO ₂ : 20/8).
Corona discharge treatment only with 0). The evaluation rank 5 in the evaluation judgment of the treatment effect is that the vapor-deposited aluminum completely remained on the base film, and the evaluation rank 3 was that 20% of the vapor-deposited aluminum remained on the base film. The evaluation rank 1 is that the vapor-deposited aluminum was completely taken from the base film. The evaluation rank 4 is between the evaluation ranks 5 and 3, and the evaluation rank 2 is between the evaluation ranks 3 and 1. The surface wetting tension was measured by the wetting test method (JIS K 6768) for polyethylene and polypropylene films of Japanese Industrial Standards. In addition, the film damage was evaluated by pinholes generated by corona discharge treatment,
Judgment was made based on deterioration of lubricity and wrinkles.

The results of evaluation of the surface treatment effect by various corona discharge treatments (Table 1) show that the film treated by the surface treatment method of the present invention has a power density of 50 W / m ² in the atmosphere and in a mixed gas atmosphere. Four kinds of films (method 1-Aa, 1-Ba, 1-Ca, 1-Da) that have been subjected to electrical discharge treatment
Four kinds of films (method 1-Ab, which were subjected to corona discharge treatment in the atmosphere and a mixed gas atmosphere at a power density of 100 W / m ²⁾
1-Bb, 1-Cb, 1-Db) also showed a sufficient treatment effect as judged from the surface wetting tension and aluminum vapor deposition strength. Also, film damage is pinhole,
Judging from the deterioration of lubricity and wrinkles, there were no problems in practical use. On the other hand, the film (method 2), which was subjected to the corona discharge treatment in the air at a power density of 50 W / m ² of the comparative product and in a mixed gas atmosphere having a mixing ratio outside the scope of the claims of the present invention, is It was judged that the treatment effect was not sufficient, but there was no film damage. In addition, the film whose power density was 100 W / m ² (Method 3a) was treated by corona discharge treatment only in the atmosphere.
In the case of the power density of 200 W / m ² (method 3b), the treatment effect was insufficient as judged from the surface wetting tension and the aluminum vapor deposition strength, and film damage due to corona discharge treatment was observed. Furthermore, the film treated by corona discharge only in a mixed gas atmosphere has a power density of 10
The power density of 200 W is also 0 W / m ² (method 4a).
In the case of / m ² (method 4b), a large variation was observed in the treatment effect as judged from the surface wetting tension and the aluminum vapor deposition strength, and film damage due to corona discharge treatment was observed.

[0019]

EFFECTS OF THE INVENTION When the surface treatment method for a plastic molded article by corona discharge treatment of the present invention is used, the surface treatment is performed in two stages, that is, in the atmosphere and in a mixed gas atmosphere, so that the treatment effect is good and the treatment There is little variation in the effect.

When the surface treatment method of the present invention is used, the corona discharge treatment is carried out in two stages, so that it is not necessary to apply a high power density at a time, and there is little film damage such as pin poles, slippage deterioration, and wrinkles.

From the above two points, when the surface treatment method for a plastic molded product of the present invention is used, the productivity in manufacturing a plastic product can be improved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a corona discharge treatment device used in an example of the present invention.

FIG. 2 is a side partial cross-sectional view of a laminated component for evaluating the treatment effect of an example produced by the surface treatment method of the present invention.

[Explanation of symbols]

 1 …… Plastic film to be treated 2 …… Unwinding part 3 …… Guide roll 4 …… Winding part 10 …… Corona discharge treatment device in the atmosphere 11,21 …… Treatment roll (second electrode) 12,22 …… First electrode 13,23 …… Generator 20 …… Corona discharge treatment device in mixed gas 24 …… Nitrogen supply pipe 25 …… Carbon dioxide supply pipe 26 …… Gas mixing device 27 …… Mixed gas supply port 28 …… Mixed gas Discharge port 30 …… Laminated component for evaluating the treatment effect of the example 31 …… Unstretched polypropylene film 32 …… Evaporated aluminum 33 …… Aliphatic ester adhesive 34 …… Stretched polypropylene film

Claims (1)

[Claims] 1. Immediately after the surface of the molded plastic is subjected to corona discharge treatment in the atmosphere, a gas atmosphere in which the mixing ratio of nitrogen and carbon dioxide is in the range of 100: 0 to 50:50 by volume. A surface treatment method for a plastic molded article, which is characterized by being subjected to corona discharge treatment in.