JP3325492B2 - Method for producing corona discharge treated foamed olefin resin sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a foamed olefin resin sheet which is suitable for an adhesive tape substrate and the like and has excellent surface wettability.

[0002]

2. Description of the Related Art Although an olefin resin foam sheet is widely used as an adhesive tape base material or the like, it has poor surface wettability as it is, so that a surface treatment is performed when applying an adhesive or an adhesive. Is normal. As a surface treatment for improving the surface wettability, for example, JP-A-2-255740 discloses that sodium or potassium remains on the surface by a treatment using a nitrate or a nitrite and subsequent washing. There is disclosed a technique for improving the surface wettability by using the method.

[0003] However, this technique merely improves the adhesiveness of the surface, and it is difficult to adjust the amount of residual sodium or potassium, so that sufficient surface wettability could not be obtained. Further, since a large amount of water is required for the cleaning treatment, environmental problems such as the generated wastewater treatment are inevitable.

The conventional corona discharge treatment has a disadvantage that its effect is lost with the passage of time after the treatment, and the effect is often insufficient, causing blisters and the like. Therefore, some measures have been taken to increase the discharge level. However, in the case of a long object, there is a possibility that blocking may occur or surface defects such as a large number of pinholes and avatars may occur.

[0005]

SUMMARY OF THE INVENTION In view of the above situation, an object of the present invention is to provide a method for producing a foamed olefin resin sheet capable of maintaining sufficient surface wettability for a long time.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a method for producing a foamed olefin resin sheet in which an olefin resin sheet containing a foaming agent is foamed, the surface of the sheet is textured, and then corona discharge treatment is performed. is there. Hereinafter, the present invention will be described in detail.

In the present invention, an olefin resin sheet containing a foaming agent is used. The olefin resin used for the olefin resin sheet containing the foaming agent is not particularly limited, for example, olefin homopolymer,
Copolymers of olefins and other monomers, and the like, may be mentioned. Specifically, for example, low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-octene copolymer, propylene- Butene copolymer, ethylene-propylene-butene copolymer, ethylene-vinyl acetate copolymer and the like. Among these, polyethylene, a copolymer containing ethylene as a main component, polypropylene, and a copolymer containing propylene as a main component are preferable. These may be used alone or in combination of two or more.

As the foaming agent used for the olefin resin sheet containing the foaming agent, a thermal decomposition type foaming agent which generates a decomposition gas by heating is preferable. Such foaming agents are not particularly limited, for example, azodicarbonamide, benzenesulfonyl hydrazide, dinitrosopentamethylenetetramine, toluenesulfonyl hydrazide,
4,4-oxybis (benzenesulfonyl hydrazide)
And the like. These may be used alone or in combination of two or more.

The amount of the foaming agent is preferably 0.1 to 30 parts by weight based on 100 parts by weight of the olefin resin. If the amount is less than 0.1 part by weight, the expansion ratio becomes low, and if it exceeds 30 parts by weight, the obtained olefin-based resin foam sheet tends to be broken. More preferably,
It is 0.5 to 20 parts by weight.

[0010] If necessary, other additives can be added to the olefin resin. The additives are not particularly limited, and include, for example, polyfunctional compounds such as divinylbenzene, diallyl phthalate, and trimethylolpropane trimethacrylate. The amount of the additive is preferably 2 to 5 parts by weight based on 100 parts by weight of the olefin resin.

The olefin resin sheet containing the foaming agent can be obtained by a usual method. For example, the foaming agent or the additive is added to the olefin resin, and a single screw extruder or a twin screw extruder is used. Melt-kneading at a temperature lower than the decomposition temperature of the foaming agent using a mixer, a Banbury mixer, or the like, and then forming into a sheet and crosslinking. The method of crosslinking is not particularly limited, for example, α-ray, β-ray,
A method of irradiating with ionizing radiation such as γ-ray, electron beam, neutron beam and the like; a method of adding a peroxide or the like to the above-mentioned olefin resin in advance to chemically crosslink.

In the present invention, the olefin-based resin sheet containing the above foaming agent is foamed. The foaming method is not particularly limited, and examples thereof include a method using hot air, an electric heater, a salt bath, and the like.

In the present invention, the surface of the sheet is subjected to graining after the foaming. The method of the graining is not particularly limited.For example, the surface of a foamed sheet obtained by foaming an olefin-based resin sheet containing the foaming agent may be heated on one side or near the melting point of the olefin-based resin. A method of changing the surface shape by applying pressure on both surfaces with one or more embossing rolls (embossing rolls) may be used.

The graining is preferably performed in-line immediately after the foaming and before the sheet surface is cooled. The method for performing the graining process in-line is not particularly limited. For example, a foamed sheet obtained by foaming an olefin-based resin sheet containing the foaming agent may be coated with two civolols before the surface thereof is cooled. To change the surface shape by passing through the gap, and then winding it through a cooling roll.

The grain shape of the grain roll is not particularly limited, and examples thereof include a pyramid shape (quadrangular pyramid), a cone, a fine pear ground pattern, and a silk grain shape. The size of the grain is such that the area of one protrusion is 0.2 to 1
0.0 mm ² is preferred. If less than 0.2 mm ² ,
Since the surface of the foam sheet itself is originally rough, it is difficult to obtain the effect of graining, and if it exceeds 10.0 mm ² , an anchor effect may not be expected in some cases.

The surface material of the civolol is not particularly limited as long as it has an adhesive property to the foam sheet and a good releasability. For example, hard chrome plating of mirror surface, Teflon plating, ceramics And the like.

The clearance between the two civolols is
The thickness is appropriately determined according to the thickness of the foamed sheet, but is preferably 60 to 90% of the thickness of the obtained olefin-based resin foamed sheet. If it is less than 60%, the bubbles of the foam sheet may be crushed, and if it is more than 90%, the effect of the graining may be lost.

In the graining process, the surface temperature of the foamed sheet is appropriately determined according to the type of the resin constituting the foamed sheet.
° C) to (melting point of resin + 50 ° C). (Melting point of resin-
If the temperature is less than 50 ° C), the crimped shape is difficult to form, and if the temperature exceeds (the melting point of the resin + 50 ° C), the foamed sheet is caught in a crimping roll, or the bubbles of the foamed sheet are reduced or broken. There is. More preferably,
(Melting point of resin−40 ° C.) to (melting point of resin + 20 ° C.). Here, the melting point of the resin refers to a differential scanning calorimeter (D
This is the temperature at the time of the crystal melting peak in SC).

In the present invention, the olefin resin sheet containing the foaming agent is subjected to a corona discharge treatment after the graining. The above-mentioned corona discharge treatment is 500 to 10
It is preferably performed with an applied energy of 000 J / m ² . If it is less than 500 J / m ² , a sufficient discharge effect may not be obtained. If it exceeds 10,000 J / m ² ,
The resulting olefin-based resin foam sheet may be deteriorated, which may cause a decrease in surface wettability. More preferably,
It is a 2000~8000J / m ^2.

The processing temperature at the time of the corona discharge processing is as follows:
It is preferably at least 0 ° C. and at most the melting point of the olefin resin. If it is too low, the discharging effect may be reduced.

The method of the corona discharge treatment is not particularly limited, and includes, for example, a method using a general corona discharge treatment machine for oxidizing the surface of an object with a high voltage to polarize the surface. The corona discharge treatment machine is not particularly limited, and includes, for example, a thyristor inverter type corona discharge treatment machine (HFS402, manufactured by Kasuga Electric Co., Ltd.).

The above corona discharge treatment is preferably performed in an inert atmosphere. By performing the reaction under an inert atmosphere, the obtained olefin resin foam sheet has better surface wettability. The inert gas used in the inert atmosphere is not particularly limited, for example,
Examples include nitrogen, helium, and carbon dioxide. These may be used alone or in combination of two or more.

According to the method for producing a foamed olefin resin sheet of the present invention, the ratio of the true surface area to the apparent surface area is increased by changing the fine shape of the sheet surface before corona discharge treatment. The purpose of the present invention is to increase the corona discharge treatment area and to exert an anchor effect due to unevenness. Accordingly, an olefin-based resin foam sheet having excellent surface wettability can be obtained.

[0024]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 Low density polyethylene resin (MI: 4.0, density: 0.9)
24 g / cm ³ , Tm (resin melting point): 110 ° C.) 100
6 parts by weight of azodicarbonamide as a foaming agent was added to the parts by weight, extruded into a sheet at a resin temperature of 140 ° C. (sheet thickness 0.4 mm), and irradiated with an electron beam (2.2 Mra).
Crosslinking according to d) was performed to obtain a raw sheet. The obtained raw sheet was placed in a heating furnace (230 ° C.) and foamed to obtain a foamed sheet (density: 0.1 g / cm ³ , thickness: 1.0 mm).

The foamed sheet is heated to a surface temperature of 100 ° C. (using a surface contact thermometer) using a far-infrared heater,
Graining was performed by passing between two grain rolls. The shape of the crimp roll was a pyramid of 1 × 1 mm, and the interval between the two crimp rolls was 0.7 mm.

Thereafter, a corona discharge treatment machine (thyristor inverter type, HFS40) is provided on the surface of the foam sheet.
2. Corona discharge treatment (applied energy: 6000 J / m ² , treatment speed: 20 m /
For 20 minutes at a temperature of 20 ° C.).

The wetting index of the surface of the obtained foamed sheet is expressed by J
It was measured in accordance with IS K 6768 (wetting test method for polyethylene and polypropylene films). In addition,
The storage condition of the sample was room temperature 30 ° C. and humidity 60%. After 3 weeks, the roll of the foamed sheet was developed, and the presence or absence of material breakage of the foamed sheet was evaluated for the presence or absence of blocking. The results are shown in Table 1.

Example 2 A foamed sheet was obtained in the same manner as in Example 1. Immediately after the foamed sheet was obtained, the foamed sheet was passed through two grain rolls to perform graining, and then wound by a winder. I took it. The shape of the crimp roll was a pyramid of 1 × 1 mm, and the interval between the two crimp rolls was 0.7 mm. The sheet temperature when passing between the rolls was 90 ° C. (measured with a surface contact thermometer).

Thereafter, the surface of the foamed sheet was subjected to a corona discharge treatment (in the condition of an applied energy of 6000 J / m ² , a treatment speed of 20 m / min and a temperature of 20 ° C.) in air using the above-mentioned corona discharge treatment machine. . The wetting index and the presence or absence of blocking on the surface of the obtained foamed sheet were measured in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 1 A foamed sheet was obtained in the same manner as in Example 1 except that graining was not performed, and the surface wetting index and the presence or absence of blocking were measured. The results are shown in Table 1.

COMPARATIVE EXAMPLE 2 A corona discharge treatment was applied without application of grain
A foamed sheet was obtained in the same manner as in Example 1 except that the treatment was performed at 700 J / m ² , a treatment time of 17 m / min, and a temperature of 20 ° C., and the surface wetting index and the presence or absence of blocking were measured. The results are shown in Table 1.

[0033]

[Table 1]

[0034]

As described above, the method for producing an olefin resin foam sheet subjected to corona discharge treatment of the present invention is as described above, so that the surface wettability of the obtained olefin resin foam sheet is maintained for a long time immediately after the corona discharge treatment. Is done. Therefore,
High degree of freedom in the production process and no defects such as adhesive drop-off. Further, the olefin-based resin foam sheet obtained by the present invention is excellent in surface wettability immediately after corona discharge treatment, surface wettability after lapse of time, and antiblocking property, so that it is suitable as a base material such as an adhesive tape. Things.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI B29L 7:00 B29L 7:00 C08L 23:02 C08L 23:02

Claims (2)

(57) [Claims] 1. A method for producing a foamed olefin resin sheet, comprising foaming an olefin resin sheet containing a foaming agent, subjecting the sheet surface to graining, and then subjecting the sheet surface to a corona discharge treatment. 2. An olefin characterized by foaming an olefin-based resin sheet containing a foaming agent, immediately after the sheet surface is cooled, the surface of the sheet is embossed before cooling, and then corona discharge treatment. A method for producing a resin foam sheet.