JPH07119393B2 - Surface protection film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Field of the Invention The present invention is used for temporarily adhering to surfaces of synthetic resin plates, decorative plywood, metal plates, etc. to protect the surfaces from dust and scratches. More specifically, the present invention relates to a surface protective film which is free from deterioration of the initial adhesive strength with time and contamination of the surface of an adherend, and has good removability and rewindability when used as a wound body.

2. Description of the Related Art Surface protective films are widely used to prevent scratches and stains during processing and transportation of the surfaces of synthetic resin plates, decorative plywood, metal plates and the like.

The surface protection film has a structure in which a pressure-sensitive adhesive layer is formed on one side of a base material layer made of a thermoplastic resin, and has a suitable adhesiveness (temporary adhesion) It should be easy to peel off without contaminating the body surface with adhesive.

Conventionally, as a surface protection film of this type, for example, one side of a base film made of a thermoplastic resin such as a polyolefin resin, the general formula A-B-A (where A is a styrene polymer block, B is A block copolymer elastomer represented by a butadiene polymer block, an isoprene polymer block, or an ethylene-butylene polymer block) and a tackifier are mixed to form a surface protective film. It is known (Japanese Patent Publication No. 58-30911, Japanese Patent Publication No. 61-103975, etc.).

However, in the surface protective adhesive film,
Since the block copolymer elastomer has strong adhesiveness to the polyolefin resin, the upper adhesive layer and the lower substrate layer back surface are bonded with a relatively strong adhesive force when rolled up into a coiled body during manufacturing. It is difficult to peel off the film from the roll when using it, and if you try to peel it off forcibly, the film may partially stretch or deform, and in some cases it will not be usable. There was a problem.

Therefore, a means of applying a release agent such as a long-chain fatty acid modified product or silicone to the back surface of the base material to impart releasability to the back surface of the base material and the pressure-sensitive adhesive layer is also conceivable, but prior to the application of the release agent. It is necessary to perform corona discharge treatment on the back surface of the base material or to apply an undercoating agent to improve the anchoring effect of the release agent, which complicates the process and is difficult to industrially adopt.

On the other hand, in the surface protection film using polyethylene as a base material, not only the initial adhesive strength is deteriorated with time, but also the surface of the adherend that has been peeled after the surface protection film is once attached is transferred from the adhesive layer. There was a problem that it caused fogging due to things.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention An object of the present invention is to eliminate the drawbacks of the conventional techniques as described above, to manufacture by a simple process, and to have excellent rewindability, and
An object of the present invention is to provide a surface protective film in which the initial adhesive strength is less likely to decrease with time and the surface of the adherend material is not contaminated.

The present inventor first paid attention to the amount of solvent extract of polyethylene in the base material layer, and by reducing the amount of this extract, migration of low molecular weight substances such as oligomers contained in the base material layer to the pressure-sensitive adhesive layer. It was found that the reduction of the initial adhesive force and the contamination of the surface of the adherend due to the above are prevented. On the other hand, in order to improve the unwinding property of the wound body, it was found that a larger amount of the solvent extract in the base material layer is preferable.

Therefore, as a result of further study, it was found that the above object can be achieved by using, as the base material layer, a combination of two kinds of polyethylenes having different amounts of solvent extract.

The present invention has been completed based on these findings.

Means for Solving the Problems Thus, according to the present invention, the outermost layer consisting of polyethylene in which the amount of the extract by n-pentane extraction is 1% by weight or more, and the outermost layer consisting of polyethylene in which the amount of the extract is less than 1% by weight. There is provided a surface protective film having an intermediate layer and an adhesive layer laminated in this order.

Hereinafter, the present invention will be described in detail.

In the present invention, the amount of the extract by n-pentane extraction (hereinafter, simply referred to as the extraction amount) means polyethylene and n-pentane.
Pentane and a weight ratio of 1: 5 were placed in an eggplant-shaped flask and immersed in a boiling state of n-pentane for 6 hours.
The weight of the extract leached in pentane is measured, and the ratio to the total weight before extraction is calculated, and the value is shown in% by weight.

The extract obtained by the n-pentane extraction is an oligomer such as low molecular weight polyethylene, and other low molecular weight substances.

The polyethylene used for the base material layer in the present invention is a combination of two kinds of polymers having different amounts of solvent extract.

In the intermediate layer adjacent to the pressure-sensitive adhesive layer, the extraction amount by n-pentane extraction is less than 1% by weight, preferably 0.7% by weight or less,
More preferably, 0.6% by weight or less of polyethylene is used.

When the extraction amount of polyethylene used for the intermediate layer is 1% by weight or more, a low molecular weight substance migrates to the surface of the pressure-sensitive adhesive layer with the lapse of time, which lowers the initial adhesive strength and causes surface contamination of the adherend.

The outermost layer contains 1% by weight of n-pentane extraction.
Or more, preferably 1.5% by weight or more, more preferably 2
Use polyethylene by weight or more.

If the extraction amount of polyethylene used for the outermost layer is less than 1% by weight, it becomes impossible to easily peel off and rewind when a wound body is formed due to a change with time.

The thickness of the base material layer can be appropriately determined depending on the application, but is generally about 10 to 80 μm in total, and the thickness ratio of the outermost layer and the intermediate layer (outermost layer: intermediate layer) is usually 5: 95 ~
70:30, preferably 8:92 to 50:50.

Polyethylene is usually melt-extruded by an inflation method or a T-die method using an extruder,
It is shaped like a film. In polyethylene with a solvent extraction amount of less than 1% by weight used for the intermediate layer, crystals are formed in the process of cooling the molten resin extruded in the form of a tube or a film, and due to the crystals, extremely minute particles are formed on the film surface. It is considered that unevenness is formed and the anchoring force with the adhesive layer is increased. On the other hand, in polyethylene having an extraction amount of 1% by weight or more used for the outermost layer, the low molecular weight substance bleeds to form a thin layer covering the outer surface of the base material even if crystals as described above are formed. There are no minute irregularities.

In the present invention, as the adhesive forming the adhesive layer,
ABA type styrene block copolymer elastomers such as styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS) and hydrogenated products thereof are available. Can be mentioned.

Further, since these elastomers do not easily exhibit tackiness by themselves, it is desirable to appropriately add a tackifying resin, and further blend a softening agent, a wax and the like.

The thickness of the pressure-sensitive adhesive layer is usually about 5 to 30 μm.

Any method may be adopted as the method for producing the surface protective film of the present invention, but it is preferable to co-extrude and laminate the resin forming the base material layer and the pressure-sensitive adhesive.

Action In the surface protective film of the present invention, the outermost layer of polyethylene whose extraction amount by n-pentane extraction is 1% by weight or more, the intermediate layer of polyethylene of less than 1% by weight, and the adhesive layer are laminated in this order. Thus, the low molecular weight substance in the base material layer migrates to the pressure-sensitive adhesive layer with the passage of time to impair the initial adhesive strength, or to contaminate the surface of the adherend material,
In addition, since the back surface of the base material layer has a good releasability, it can be easily peeled off without being partially stretched or deformed when the wound body is unwound.

EXAMPLES The present invention will be described more specifically below with reference to Examples and Comparative Examples, but the present invention is not limited to the Examples.

[Example 1] Low-density polyethylene (trade name "LK30" manufactured by Mitsubishi Petrochemical Co .; n-
2.1% by weight of hexane is the outermost layer, and linear low-density polyethylene (trade name "UF8400" manufactured by Mitsubishi Petrochemical Co., Ltd .; n
-Extracted amount of 0.4% by weight relative to hexane), intermediate layer, hydrogenated product of styrene-butadiene-styrene block copolymer (trade name "Clenton G1657" manufactured by Shell Chemical Co., Ltd.) 100
A surface protective film was obtained by a three-layer T-die coextrusion method using a pressure-sensitive adhesive consisting of 40 parts by weight of a tackifying resin (trade name "Alcon P100" manufactured by Arakawa Chemical Industry Co., Ltd.) as a pressure-sensitive adhesive layer. The thickness of each layer was 5 μm in the outermost layer, 50 μm in the intermediate layer, and 10 μm in the pressure-sensitive adhesive layer.

The obtained surface protection film was wound around a paper core having an inner diameter of 3 inches to obtain a roll.

[Example 2] The outermost layer was made of low-density polyethylene (trade name "Petrosene 18
6 "manufactured by Tosoh Co., Ltd .; extraction amount 2.4% by weight with respect to n-hexane), the middle layer of low density polyethylene (trade name" Mirason
12P ”manufactured by Mitsui Petrochemical Co., Ltd .; extraction amount with respect to n-hexane of 0.6
(% By weight), except that the surface protection film was obtained in the same manner as in Example 1 to obtain a wound body.

[Comparative Example 1] Low-density polyethylene (trade name "LK30" manufactured by Mitsubishi Yuka; n-
Extraction amount of 2.1% by weight with respect to hexane) as a base layer, 100 parts by weight of hydrogenated styrene-butadiene-styrene block copolymer (trade name "Clenton G1657" manufactured by Shell Chemical Co.) and tackifying resin (trade name " Alcon P100 "(manufactured by Arakawa Chemical Industry Co., Ltd.) A surface protective film was obtained by a two-layer T-die co-extrusion method using 40 parts by weight of an adhesive as an adhesive layer. The thickness of each layer was 55 μm for the base material layer and 10 μm for the adhesive layer.

The obtained surface protection film was wound around a paper core having an inner diameter of 3 inches to obtain a roll.

[Comparative Example 2] A linear low-density polyethylene (trade name "UF8400") was used as the base material layer.
Mitsubishi Yuka Co., Ltd .; extraction amount 0.4% by weight with respect to n-hexane)
A surface protective film was obtained in the same manner as in Comparative Example 1 except that.

Table 1 shows the measurement results of the physical properties of the surface protective films obtained in the above Examples and Comparative Examples.

The measuring conditions and measuring methods for physical properties are as follows.

<Curing after winding>: After the surface protection film was made into a roll, it was left under the conditions of three combinations shown in Table 1 for temperature and time, and the spreading force and the initial adhesive force were measured.

<Expansion force>: The expansion force from the roll is the force required when the surface protective film is unwound from the roll at a speed of 10 m / min.
It is shown in 50mm width conversion value.

<Initial adhesive strength>: The surface protection film unwound from the roll was attached to the stainless steel plate specified by JIS Z0237 with a laminator, left at 23 ° C for 30 minutes, and then at 23 ° C at a speed of 300 mm / min.
The force required for peeling at an angle of 180 ° is shown in g / 50 mm width conversion value.

As is clear from Table 1, a surface protective film using two layers of polyethylene with different extraction amounts as a base material layer (Examples 1 to 1)
In 2), there are few changes in the developing force and the initial adhesive force over time, and good physical properties are shown. On the other hand, the surface protection film having a base material layer of a polyethylene single layer with a large extraction amount (Comparative Example 2) has a remarkable decrease in initial adhesive strength over time, and a polyethylene single layer with a small extraction amount is used as a base material. The surface protective film as a layer shows a marked increase in both the spreading force and the initial adhesive force over time, and is difficult to use.

EFFECTS OF THE INVENTION According to the present invention, there is provided a surface protective film which is free from deterioration of the initial adhesive strength with time and contamination of the surface of an adherend, and has good removability and rewindability when used as a wound body. .

Claims (1)

[Claims] 1. An outermost layer made of polyethylene having an amount of extract by n-pentane extraction of 1% by weight or more, an intermediate layer made of polyethylene having an amount of extract of less than 1% by weight, and an adhesive layer in this order. A surface protection film that is laminated.