JP3088190B2 - Surface protective film and method of manufacturing the same - 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 temporarily attaching to a surface of an adherend such as a synthetic resin plate, a decorative plywood, a metal plate or the like to protect the surface from dust adhesion or scratching. And a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, a surface protection film of this type has been used which comprises a base film made of a thermoplastic resin and an adhesive layer formed on one side of the base film. In addition, as a base film, a polyolefin resin layer containing an additive and a polyolefin resin layer containing no additive are laminated to form a two-layer film. A three-layer surface protective film provided with an adhesive layer is also known (Japanese Patent Publication No. Sho 6-6677).

[0003] Such a surface protective film is obtained by co-extrusion of a resin as a base film and a resin as an adhesive layer by an inflation method, a T-die method or the like, or a polyolefin resin containing an additive and an additive. Is produced by co-extrusion molding with a polyolefin-based resin containing no, and then applying and drying the pressure-sensitive adhesive composition on the surface of the polyolefin-based resin layer containing no additive.

[0004]

As described above, the co-extrusion molding of the resin to be the base film and the resin to be the adhesive layer is performed by dissolving the adhesive raw material in a solvent and applying the resin film to the surface of the base film. The adhesive strength between the adhesive layer and the base film is higher than that of the surface protective film manufactured by applying and drying the film.However, the adhesive layer deteriorates when heated or left outdoors, causing the adhesive layer to deteriorate and adhere to the base film. Power may decrease.

In the adhesive film for surface protection described in JP-B-64-6677, the adhesive strength of two kinds of polyolefin resin layers is large, but the adhesive strength between the polyolefin resin layer and the pressure-sensitive adhesive layer is large. Is insufficient and may peel off during long-term use.

In the inflation method, which is a means of co-extrusion molding, the thickness of the formed tubular film varies in the circumferential direction. The thickness difference and the dimensional difference in the width direction at the portion accumulate, and a good rolled state cannot be obtained.
For this purpose, both ends of the film are cut off at a fixed width (this is called "ear trimming") and then rolled, so that both ends of the cut-off film (called "ears") are used.
Is discarded. Even in the case of the T-die method, fluctuations in thickness near both ends are inevitable, and "ear trimming" is performed in the same manner as in the inflation method.

The "ears" generated in this manner are a mixture of the base film and the resin constituting the adhesive layer, and there are various problems in mixing them as a recovered product with general-purpose raw materials, and they must be discarded. It is useless. The present invention aims to solve the above problems.

[0008]

According to a first aspect of the present invention, there is provided a surface protective film comprising a base film made of a thermoplastic resin and a base layer and an intermediate layer, and an adhesive layer on the intermediate layer surface. Wherein the intermediate layer is formed from a resin composition comprising a component constituting the base material layer and a component constituting the adhesive layer, and the thickness of the intermediate layer is 7 to 20 μm. It is characterized by the following.

A second aspect of the present invention is the surface protective film, wherein the thermoplastic resin as the intermediate layer is a recovered product of the surface protective film including the base layer and the adhesive layer.

In a third aspect of the present invention, there is provided a method for producing a surface protective film, comprising simultaneously extruding and laminating a thermoplastic resin as a base film and an adhesive layer by a co-extrusion molding method. The base film is a two-layer base material layer and an intermediate layer, a resin composition comprising a component constituting the base layer and a component forming the adhesive layer as the intermediate layer, the adhesive layer is laminated on the intermediate layer surface This is a method characterized by co-extrusion.

Hereinafter, the present invention will be described in detail. The base film is made of a thermoplastic resin having extrudability, and is composed of two layers, a base layer and an intermediate layer. An adhesive layer is laminated on the surface of the intermediate layer to form a surface protection film.

The base layer is the outermost layer when attached to an adherend (product) and has a protective effect on the adherend. The layers include low density polyethylene (LDPE), medium density polyethylene (MDPE), and high density polyethylene (HDP).
E), a thermoplastic resin such as linear low density polyethylene (LLDPE) or polypropylene (PP) is used. If necessary, additives such as antioxidants and ultraviolet absorbers may be added, and coloring agents such as pigments and dyes and inorganic substances may be added to the extent that transparency is not impaired. The thickness of the substrate layer is preferably in the range of about 20 to 80 μm.

The adhesive layer is easily peelable from the adherend,
Styrene diene blocks such as ethylene-vinyl acetate copolymer (EVA), ethylene-acrylic acid copolymer, ethylene-acrylate ester copolymer, or styrene-butadiene block copolymer and styrene-isoprene block copolymer A mixture of copolymers,
Further, if necessary, a tackifier, a stabilizer, and a coloring agent such as a pigment or a dye may be used. The thickness of the adhesive layer is preferably in the range of 5 to 30 μm.

The intermediate layer is provided between the substrate layer and the adhesive layer, and functions to firmly bond the substrate layer and the adhesive layer. The intermediate layer is formed from a material containing at least one or two or more mixtures of the material (A) constituting the base material layer and one or two or more mixtures of the material (B) constituting the adhesive layer. Become.

The mixing ratio of the material (A) and the material (B) is preferably about 5: 1 to 1: 1 by weight, more preferably 3: 1 to 2: 1. If the mixture ratio of the material (A) and the material (B) is smaller than 1: 1, the compatibility between the intermediate layer and the base material layer is deteriorated, and the intermediate layer is easily peeled off. Although the adhesive strength between the layer and the base layer increases, the adhesive strength between the intermediate layer and the adhesive layer decreases, and the balance of the adhesive strength between the intermediate layer and the base layer and the adhesive layer cannot be maintained. As long as the material (A) and the material (B) are contained at such a mixing ratio, another component (C) may be contained.

For example, a coloring agent may be added if the base material layer does not contain a coloring agent, and a tackifier may be added if the tackifying agent is not contained in the adhesive layer. Components not used in the layer may be mixed. However, when the component (C) not used in the base material layer or the adhesive layer is mixed, it is preferable that the content of the component (C) is up to about 70% of the weight of the intermediate layer. If it exceeds 70%, the adhesive properties of the intermediate layer to the base material layer and the adhesive layer decrease, and the balance of the adhesive strength is biased,
This is because either of them is easily peeled.

As the intermediate layer, the "ears" of the conventional surface protective film consisting of only the two layers of the base material layer and the adhesive layer may be used as a recovered product, or the surface protective film having the intermediate layer of the present invention may be used as a recovered product. It is desirable to use the “ears” as a recovered product because the raw materials can be used effectively. However, if it satisfies the above conditions, it can be used even if it is not a collected product.

The thickness of the intermediate layer is in the range of 7 to 20 μm. If the thickness is less than 7 μm, the adhesive strength to the substrate layer and the adhesive layer is insufficient, and delamination tends to occur. Also, when using the "ears" by the "ear trimming" as the intermediate layer, because the heat history received when this resin was once co-extruded, the fish eye was re-heated during the co-extrusion. If the intermediate layer is too thick, fish eyes increase, and the layer is liable to be cohesively broken by the peeling force. Therefore, the thickness of the intermediate layer is set to 20 μm or less.

[0019]

The substrate layer protects the surface of the product. Since the intermediate layer contains both components of the base layer and the adhesive layer, the compatibility with these two layers is good, and when the resin melted by heat melting is co-extruded, the base layer and the adhesive layer are strongly bonded. To join. Therefore,
Even if this surface protective film is heated or left outdoors, peeling of the base material layer from the adhesive layer is prevented. In addition, since the "ears" of the surface protection film can be used as collected products, the raw materials can be used without waste.

[0020]

Embodiments will be described below. FIG. 1 is an enlarged sectional view showing an embodiment of a surface protective film 1 of the present invention, wherein 2 denotes a base film, 21 denotes a base layer, 22 denotes an intermediate layer, and 3 denotes an adhesive layer. FIG. 2 is an explanatory view showing one embodiment of the method for producing a surface protective film of the present invention, wherein 2a is a base layer resin, 2b is an intermediate layer resin, 3a is an adhesive layer resin, 4 is a T die,
5 is a cooling roll.

Example 1 Low density polyethylene (LDP)
E) (Mitsui Petrochemical Co., Ltd. product name "Mirason 16") 40
Ethylene-vinyl acetate copolymer (EVA) (trade name “V501H” manufactured by Mitsubishi Yuka Co., Ltd., 20% vinyl acetate content) with a thickness of 20 μm and a two-layer film with a T-die (not shown). Co-extrusion in the shape
The recovered raw material was cut off by cm.

The obtained recovered material was used as the intermediate layer resin 2b, and as shown in FIG.
Using the same EVA as the adhesive layer resin 3a, co-extrusion molding is performed with a T-die 4 to obtain a surface protective film 1 having a thickness of three layers of a base layer of 40 μm, an intermediate layer of 10 μm, and an adhesive layer of 20 μm. Was.

Example 2 A surface protective film was prepared in the same manner as in Example 1 except that LDPE was used as the base layer resin 2a and high-density polyethylene (HDPE) (trade name “5300F” manufactured by Mitsui Petrochemical Co., Ltd.) was used. Obtained.

(Example 3) The adhesive layer resin 3a was prepared by using a styrene butadiene block copolymer (trade name "Tafprene A" manufactured by Asahi Kasei Co., 80% by weight and EVA (Mitsubishi Yuka Corporation name "V501H" manufactured by 20% by weight) A surface protective film was obtained in the same manner as in Example 1 except that the mixture was used.

(Example 4) A surface protection film was obtained in the same manner as in Example 1 except that polypropylene (trade name "F5101A" manufactured by Tosoh Corporation) was used as the base layer resin 2a.

(Embodiment 5) Embodiment 3 is used as the intermediate layer resin 2b.
A surface protective film was obtained in the same manner as in Example 1, except that the "ears" of the surface protective film obtained in [1] were used as a raw material for recovery.

(Embodiment 6) Embodiment 4 is used as the intermediate layer resin 2b.
A surface protective film was obtained in the same manner as in Example 1, except that the "ears" of the surface protective film obtained in [1] were used as a raw material for recovery.

Comparative Example 1 A surface protection film was obtained in the same manner as in Example 1 except that the thickness of the intermediate layer was changed to 1 μm.

Comparative Example 2 A surface protection film was obtained in the same manner as in Example 1 except that the thickness of the intermediate layer was changed to 40 μm.

(Comparative Example 3) LDPE as a base layer resin
(Milason 16 product name, manufactured by Mitsui Petrochemical Co., Ltd.), EVA (Mitsubishi Yuka Co., Ltd. product name "V501H") as an adhesive layer resin
Was used to obtain a surface protective film without an intermediate layer by coextrusion molding to a substrate layer thickness of 40 μm and an adhesive layer thickness of 20 μm.

With respect to the surface protective films of Examples 1 to 6 and Comparative Examples 1 to 3, the results of measuring the interlayer peel strength between the base material layer and the adhesive layer and the amount of fish eyes are shown in Table 1.

Method of Measuring Interlaminar Delamination Strength An adhesive was applied to a polyethylene terephthalate film having a width of 50 mm and a length of 200 mm, and a substrate layer surface of a surface protection film having a width of 25 mm and a length of 100 mm was adhered to the adhesive. Another sheet of the same material was prepared, and the surfaces of the adhesive layers of these surface protective films were put together and bonded with an adhesive (trade name “Cemedine C” manufactured by Cemedine Co., Ltd.). This was subjected to T-type peeling to confirm that the adhesive layers were peeled off, and the force required for the peeling was measured.

The observed number of more Fuisshu eye 0.2mm visually in Fuisshu eye of viewing surface protective film 1m per ^2.

[Table 1]

As is clear from Table 1, all of the surface protective films of Examples 1 to 6 having an intermediate layer having a thickness of 10 μm have a large delamination strength and a small number of fish eyes, In Comparative Example 1 having a thickness of 1 μm and Comparative Example 3 having no intermediate layer, delamination strength was low. In Comparative Example 2 having a thickness of 40 μm, delamination strength was large but many fish eyes were generated. It was extremely low.

[0035]

According to the surface protective film of the present invention, the base film is provided with an intermediate layer between the base layer and the adhesive layer, and the intermediate layer constitutes the intermediate layer and the components constituting the base layer. And the thickness of the intermediate layer is from 7 to
Since the thickness is in the range of 20 μm, the surface protection film is excellent in interlayer strength between the base material layer and the intermediate layer, and has a small fish eye and good quality. Further, according to the method for producing a surface protective film of the present invention, a high quality surface protective film having excellent interlayer strength between the base material layer and the intermediate layer can be easily produced by using the conventional coextrusion molding apparatus as it is. be able to. Furthermore, since a recovered product in which the raw materials of the base layer and the adhesive layer are combined can be used, the raw materials can be used without waste.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view showing an embodiment of the surface protective film of the present invention.

FIG. 2 is an explanatory view showing one embodiment of a method for producing a surface protective film of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Surface protective film 2 Base film 21 Base layer 22 Intermediate layer 2a Base layer resin 2b Intermediate layer resin 3 Adhesive layer 3a Adhesive layer resin 4 T die 5 Cooling roll

Claims (3)

(57) [Claims] 1. A surface protection film comprising a base film made of a thermoplastic resin and comprising a base layer and an intermediate layer and an adhesive layer provided on an intermediate layer surface, wherein the intermediate layer constitutes the base layer. Formed from a resin composition comprising a component and a component constituting the adhesive layer, and the thickness of the intermediate layer is 7 to 20.
Surface protective film having a thickness of μm. 2. The surface protective film according to claim 1, wherein the thermoplastic resin serving as the intermediate layer is a recovered product of the surface protective film including the base material layer and the adhesive layer. 3. A method for producing a surface protection film, comprising simultaneously extruding and laminating a thermoplastic resin as a base film and an adhesive layer by a co-extrusion molding method, wherein the base film is composed of two layers, a base layer and an intermediate layer. Surface protection characterized by using a resin composition comprising a component constituting a base material layer and a component constituting an adhesive layer as an intermediate layer, and co-extrusion molding so that an adhesive layer is laminated on the surface of the intermediate layer. Film manufacturing method.