JP2012201872A - Method of manufacturing surface protective film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a surface protective film, by which the adherence of foreign matter such as dust on an adhesive layer is suppressed.SOLUTION: A tube-shaped laminated film having a base material layer-constituting resin arranged as an outer layer and an adhesive layer-constituting resin layer arranged as an inner layer is obtained by extruding at least a base material layer-constituting resin and an adhesive layer-constituting resin from a circular die by coextrusion inflation method, then, the tube-shaped laminated film is made flat to superpose the adhesive layers of two laminated films, and then, is punched into a prescribed shape, and thereby, the adhesive layers of two laminated films are made pealable.

Description

  The present invention relates to a method for producing a surface protective film.

  The surface protective film is mainly used by sticking to an adherend such as a resin product, a metal product, a glass product, etc. of an optical member, and plays a role to prevent scratches or foreign matter contamination during transportation, storage or processing. . These surface protective films generally comprise a non-adhesive base material layer and an adhesive layer for adhering to the adherend. As the adhesive coating method, any known method can be used, for example, a die coater method, a gravure roll coater method, a blade coater method, a spray coater method, an air knife coating method, a dip coating method and the like are preferable. Can be used alone or in combination (Patent Document 1).

  By the way, the adhesion layer for adhering to the adherend must avoid the adhesion of foreign substances such as dust, but it is difficult to completely avoid the adhesion of foreign substances even if the application process of the adhesive is sufficiently managed. is there.

JP 2002-275296 A

  This invention is made | formed in view of the said situation, Comprising: The solution subject is providing the manufacturing method of the surface protection film in which adhesion of foreign materials, such as refuse, to the adhesion layer was suppressed.

  That is, the gist of the present invention is that at least the base layer constituent resin and the adhesive layer constituent resin are extruded from the annular die by the coextrusion inflation method, the base layer constituent resin is arranged in the outer layer, and the adhesive layer constituent resin layer is arranged in the inner layer. The obtained tubular laminated film is obtained, and then the laminated tubular film is flattened, the adhesive layers of the two laminated films are overlapped, and then punched into a predetermined shape, whereby the adhesive layers of the two laminated films are obtained. It exists in the manufacturing method of the surface protection film characterized by making comrades peelable.

  In a preferred embodiment of the present invention, the base layer constituent resin, the foaming agent-containing intermediate layer constituent resin, and the adhesive layer constituent resin are extruded from an annular die during the co-extrusion, and the base layer constituent resin is formed in the outer layer. By placing the foamed resin layer on the intermediate layer and the foamed resin layer on the intermediate layer, the foamed resin layer is placed on the intermediate layer and a buffer function is added to the surface protective film. I can do it. Further, prior to the punching process, a half-cut process is performed to facilitate separation of the adhesive layers of the two laminated films.

  The above-described problems are solved by the present invention.

FIG. 1 is an explanatory diagram of an example of the manufacturing process in the first and second embodiments.

  Hereinafter, the present invention will be described in detail.

  First, in the present invention, a base layer constituent resin and an adhesive layer constituent resin are extruded from an annular die by a coextrusion inflation method to obtain a tubular laminated film in which an adhesive layer constituent resin layer is arranged on the inner layer. At this time, the base layer constituent resin, the foaming agent-containing intermediate layer constituent resin, and the adhesive layer constituent resin are extruded from the annular die, the base layer constituent resin is arranged in the outer layer, the foam resin is arranged in the intermediate layer, and the inner layer A tubular laminated film in which the adhesive layer-constituting resin layer is disposed can also be obtained.

  The substrate layer of the surface protective film is not particularly limited, but is generally composed of polyolefins such as low density polyethylene (LDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), and polypropylene (PP). The The thickness of a base material layer is 20-80 micrometers normally, Preferably it is 30-50 micrometers.

  The intermediate layer of the surface protective film is made of the same resin as the base material layer. As the foaming agent to be contained in the intermediate layer constituting resin, conventionally known organic foaming agents and inorganic foaming agents can be arbitrarily selected and used. In particular, an inorganic foaming agent is preferable because the generated gas is carbon dioxide, which is easy to handle, and an inorganic foaming agent having a decomposition temperature of 160 to 220 ° C. is preferable. Inorganic foaming agents such as sodium bicarbonate and sodium citrate are preferably used because they are all white and odorless and have high safety. The ratio of the foaming agent contained in the intermediate layer constituting resin is usually 0.5 to 10% by weight, preferably 2 to 6% by weight. The thickness of the intermediate layer is usually 10 to 120 μm, preferably 30 to 70 μm.

  The adhesive layer of the surface protective film is composed of a low-adhesive resin that can achieve a peel strength of usually 2 to 15 gf / 25 mm, preferably 5 to 10 gf / 25 mm. Specific examples thereof include an ethylene-vinyl acetate copolymer. (EVA), linear low density polyethylene (L-LDPE), polyisobutylene, styrene-isoprene-styrene block copolymer, and the like. The thickness of the pressure-sensitive adhesive layer is usually 5 to 50 μm, preferably 10 to 30 μm.

  In addition, said peel strength is the value measured at 25 degreeC based on JISZ-0237, for example, a tensile tester (made by Intesco Co., Ltd .: Material test with thermostat) is used for the measurement of peel strength. A container 201X) is preferably used.

  As the inflation method, a known method (air cooling method) can be employed in which the film extruded from the die is guided above the die and cooled by blowing cooling air. Usually, an air ring that blows cooling air is arranged above the annular die, and an equipment in which an an inner plate and a winding roll are sequentially arranged above the air ring is used. The raw material resin is coextruded so that stretching does not occur substantially, and is passed between air rings and cooled, and then a tubular laminated film is obtained. In the case where the foaming agent-containing intermediate layer-constituting resin is coextruded and the foamed resin layer is disposed in the intermediate layer, the coextrusion temperature is set to the same level as the decomposition temperature of the blowing agent. The expansion ratio of the foamed resin layer is usually 1.5 to 5.0 times, preferably 1.2 to 2.0 times.

  Next, in the present invention, the tubular laminated film is flattened and the adhesive layers of the two laminated films are overlapped. As a result, therefore, the portion corresponding to the adhesive surface of the surface protective film is kept clean.

  In general, the tube-shaped laminated film obtained by the above-described inflation method is supplied as it is to the take-up roll through the an inner plate and is folded and wound up as a laminated film. However, when the tubular laminated film obtained by the above-described inflation method is directly subjected to the next punching process, a winding roll is unnecessary. In such a case, for example, the tubular laminated film can be flattened by passing through a linear gap before being subjected to punching.

  Thereafter, the two laminated films are punched into a predetermined shape so that the adhesive layers of the two laminated films can be peeled off. Each of the two laminated films may be adhered to the adherend and used as a surface protective film, one is used as a surface protective film, and the other is for protecting the adhesive layer of the surface protective film. It may be used as a release film and discarded after peeling.

  The punching process can be performed by general machining, for example, using a Thomson blade. The shape of the opening of the punching die is basically a shape that matches the shape of the adherend to which the surface protective film is applied.

  In the present invention, half-cutting may be performed prior to the above punching. Half-cut processing refers to cutting that leaves two laminated films without cutting them completely in the stacking direction, without cutting them one by one. That is, for example, only one surface protective film of the two laminated films stacked is cut. The half-cut line is generally shaped in accordance with the shape of the adherend, but such a half-cut line also has an advantage that the adhesive layers of the two laminated films can be easily separated. The half-cut line is a continuous shape such as a straight line or a curved line, and as a forming method thereof, a method of forming with a blade such as a die-cut roll and a method of forming by laser processing are generally used. The laser processing method has an advantage that uniform and stable cuts can be formed.

  EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to a following example, unless the summary is exceeded. In the following examples, the following materials were used.

(1) Low density polyethylene (LDPE):
"Novatec LF240" manufactured by Nippon Polyethylene (melting point: 112 ° C)

(2) Ethylene-vinyl acetate copolymer:
"Novatec LV430" manufactured by Nippon Polyethylene Co., Ltd. (melting point: 89 ° C)

(3) Linear low density polyethylene (L-LDPE):
“Kernel KF360T” manufactured by Nippon Polyethylene Co., Ltd. (melting point: 90 ° C.)

(4) Foaming agent:
Mixture of sodium bicarbonate and sodium citrate (1: 1 weight ratio)

Examples 1 and 2:
By extruding the base layer constituent resin and the adhesive layer constituent resin from the two-layer coextrusion annular die, obtaining a tubular laminated film in which the adhesive layer constituent resin layer is arranged on the inner layer, supplying it to the take-up roll and folding it The tubular laminated film was flattened to obtain an unstretched laminated film having a width of 100 mm in which the adhesive layers of two laminated films were overlapped. The layer structure is as shown in Table 1. The die temperature is 180 ° C., the air cooling temperature is 15 to 30 ° C., and the winding speed of the winding roll is 7.2 m / min. It was.

  Next, as shown in FIG. 1, half-cut processing of the shape indicated by the half-cut line (2) was performed on the unstretched laminated film (1). Half-cut processing was performed with a laser. In addition, the code | symbol (3) in FIG. 1 means the shape line punched by the next punching process.

  Subsequently, the unstretched laminated film was continuously supplied to a punching apparatus having a square shape of 45 mm × 40 mm and provided with a Thomson blade to produce a surface protective film. Each laminated film of the obtained surface protective film was easily peelable from the adhesive layer. As a result of sticking the adhesive layer of the surface protective film on the glass of the glass product, there was no problem with the adhesiveness, and no foreign matter such as dust adhered to the adhesive layer. In addition, the peeling strength of the adhesion layer was measured in the following way using the sample film cut out from the said unstretched laminated | multilayer film (1). The results are shown in Table 1.

(Measurement of peel strength)
A sample film (25 mm × 300 mm) is attached to an acrylic plate (width 50 mm, length 150 mm) using a 2 kg rubber roller, and is attached to a tensile tester (manufactured by Intesco Corporation: material tester 201 with thermostatic bath). The peel strength was measured (JIS Z-0237). The peeling force when peeled at 25 ° C. at a speed of 300 mm / min (180 degree peeling) was measured. The unit was “gf / 25 mm”.

Examples 3 and 4:
Extruding the base layer constituent resin, the foaming agent-containing intermediate layer constituent resin and the adhesive layer constituent resin from the three-layer co-extruded annular die, the base layer constituent resin is arranged in the outer layer, and the foam resin is arranged in the intermediate layer, Width obtained by obtaining a tubular laminated film in which an adhesive layer-constituting resin layer is arranged on the inner layer, flattening the tubular laminated film by supplying it to a take-up roll and folding it, and overlapping the adhesive layers of two laminated films A 100 mm unstretched laminated film was obtained. The intermediate layer constituting resin was used with 4% by weight of a foaming agent. The layer structure is as shown in Table 1. The die temperature is 180 ° C., the air cooling temperature is 15 to 30 ° C., and the winding speed of the winding roll is 7.2 m / min. It was. The expansion ratio of the intermediate layer was 1.5 times.

  Next, in the same manner as in Examples 1 and 2, half-cutting and punching were performed to produce a surface protective film having a buffer function. Each laminated film of the obtained surface protective film was easily peelable from the adhesive layer. As a result of sticking the adhesive layer of the surface protective film on the glass of the glass product, there was no problem with the adhesiveness, and no foreign matter such as dust adhered to the adhesive layer.

1: Unstretched laminated film 2: Half-cut wire 3: Shape line punched by punching

Claims (3)

  By extruding at least the base layer constituent resin and the adhesive layer constituent resin from the annular die by the coextrusion inflation method, a tubular laminated film in which the base layer constituent resin is arranged in the outer layer and the adhesive layer constituent resin layer is arranged in the inner layer is obtained. Then, after flattening the tubular laminated film and overlapping the adhesive layers of the two laminated films, the adhesive layers of the two laminated films can be peeled by punching into a predetermined shape. A method for producing a surface protective film.   The base layer constituent resin, the foaming agent-containing intermediate layer constituent resin and the adhesive layer constituent resin are extruded from an annular die, the base layer constituent resin is arranged on the outer layer, the foam resin is arranged on the intermediate layer, and the adhesive layer constitution is arranged on the inner layer. The manufacturing method of the surface protection film of Claim 1 which obtains the tubular laminated film by which the resin layer is arrange | positioned.   The manufacturing method of the surface protection film of Claim 1 or 2 which performs a half cut process prior to a punching process.

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