JP2010229328A - Surface protective film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface-protective film expected to exhibit excellent surface-protective characteristics by improving roll delivery better than conventional. <P>SOLUTION: The surface-protective film 1 constituted of a laminated structure of a surface layer 30, an intermediate layer 20 and a self-adhesive layer 10 is made. The surface layer 30 is constituted from a resin composition containing 55-95 wt.% of a polybutene-based resin and 5-45 wt.% of an ethylene-propylene copolymer. The intermediate layer 20 is constituted from a polypropylene resin. The self-adhesive layer 10 is constituted from a resin composition containing 20-30 wt.% os a thermoplastic olefin elastomer, 60-80 wt.% of a thermoplastic styrene elastomer, and 0-10 wt.% of a polypropylene resin. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a surface protective film (sheet) used for optical products, building materials, automobile parts, etc. for the purpose of protecting the surface, and more particularly to an improved technique for improving the feedability from a product roll. .

The surface protective film is affixed to adherends such as building materials, resin products such as acrylic resins for optical applications, metal products such as aluminum, and glass products. In order to prevent mixing, it is a film bonded for the purpose of protecting the surface.
A typical surface protective film is generally composed of a non-adhesive base material layer and an adhesive layer for adhering to the adherend. The base material layer is usually formed of a polyolefin resin such as polyethylene or polypropylene, or a polyester resin such as polyethylene terephthalate.

  These surface protective films are formed by laminating an adhesive layer on one side of the above-mentioned base material layer, such as lamination of an adhesive layer by coating, a method of laminating an adhesive layer by coextrusion using a T-die, and the like. is there. The surface protective film formed by these methods is wound once to become a roll product. A user purchases a product roll, pays out a film from a product roller at the time of use, and attaches an adhesive layer to the surface of an adherend to use the film. Therefore, the adhesive layer is required to have good adhesiveness in order to uniformly adhere the surface protective film to the surface of the adherend.

  On the other hand, when it becomes a roll-shaped product, the base material layer and the adhesive layer are in contact with each other inside the roll. Therefore, in the surface protective film having a high adhesive strength, the adhesive strength between the base material layer and the adhesive layer becomes strong. Because it is difficult to pay out from a roll-shaped product, it is made into a roll shape with a release film bonded to an adhesive layer, and the release film is peeled off when being attached to an adherend. . In such a configuration, since a large amount of waste is generated, there is a demand for a surface protective film that can be easily fed out from a roll without a release film. “Feeding property” refers to the magnitude of tension (also referred to as unwinding force or peeling resistance force, hereinafter referred to as peeling resistance force) required for unwinding a film from a product roll. It is evaluated as excellent.

JP 2004-2624 A JP 2008-214492 A

  When a surface protective film having a high adhesive strength is unwound from a product roll, the rewinding force may be heavy. In this case, it is necessary to unwind the film with a high tension. When the surface protective film drawn out with high tension is bonded to the adherend, wrinkles may be mixed in or residual stress may be generated. For this reason, after sticking the said film on a to-be-adhered body, there exists a possibility that the edge part of a film may float from an to-be-adhered body, and may peel. Further, when the rigidity of the adherend is small, the adherend may be curled.

Thus, the surface protection film still has problems to be solved.
This invention is made | formed in view of the above subject, Comprising: It aims at providing the surface protection film which can anticipate the outstanding handling property by improving the drawing | feeding-out property from a roll compared with the past.

  In order to solve the above-mentioned problems, the present invention provides a surface protective film obtained by laminating a pressure-sensitive adhesive layer on one surface of a substrate and a surface layer having good peelability on the other surface, And a resin composition containing 55 to 95% by weight of a polybutene resin and 5 to 45% by weight of an ethylene-propylene copolymer, an intermediate layer is made of a polypropylene resin, and an adhesive layer is an olefin thermoplastic. A film composed of a resin composition containing 20 to 30% by weight of elastomer, 60 to 78% by weight of styrene thermoplastic elastomer, and 2 to 10% by weight of polypropylene resin was obtained.

Here, it is preferable that the surface layer further contains 0 to 10% by weight of an ethylene or propylene component.
The intermediate layer preferably includes a nucleating agent.

  The surface protective film of the present invention having the above composition has a smaller peel resistance than conventional films. For this reason, a film can be let out from a product roll with low tension, and it is possible to effectively prevent wrinkles and peeling when the film is stuck.

It is typical sectional drawing which shows the structure of the surface protection film of embodiment.

Embodiments of the present invention will be described below, but the present invention is naturally not limited to these embodiments, and can be appropriately modified and implemented without departing from the technical idea of the present invention. .
<Embodiment>
FIG. 1 is a cross-sectional view showing a laminated structure of a surface protective film 1 in the present embodiment.

The surface protective film 1 (hereinafter, simply referred to as “film 1”) is formed by laminating the adhesive layer 10 on one main surface of the intermediate layer 20 and laminating the surface layer 30 on the other main surface. The surface layer 30 / intermediate layer 20 / adhesive layer 10 are laminated in this order.
The total thickness of this film 1 can be set to 30-80 micrometers. Among these, it is preferable that the thickness ratio of each layer of the surface layer 30, the intermediate | middle layer 20, and the adhesion layer 10 is 3-10 micrometers, 20-50 micrometers, and 7-20 micrometers in the same order. As a specific example, when the total thickness of the surface protective film is 50 μm, the thickness of each layer can be set to 5 to 10 μm, 35 to 25 μm, and 10 to 15 μm in the same order as described above.

Hereinafter, each of these layers will be specifically described sequentially.
(About the surface layer 30)
The surface layer 30 is composed of a resin composition containing 55 to 95% by weight of a polybutene resin and 5 to 45% by weight of an ethylene-propylene copolymer.
Examples of the polybutene-based resin include a homopolymer of 1-butene or a copolymer of 1-butene and a small amount of ethylene or propylene. The addition amount of ethylene or propylene as a copolymerization component is 0 to 10% by weight (that is, 10% by weight or less). The melting point of the polybutene resin is 50 to 150 ° C., preferably 60 to 140 ° C., more preferably 70 to 130 ° C. It is preferable for the melting point to be in such a range because heat resistance can be maintained. The melt flow rate (MFR: JIS K7210, temperature: 230 ° C., load: 21.18 N) of the polybutene resin is preferably 0.5 to 5 (g / 10 minutes).

  On the other hand, the ethylene-propylene copolymer is a copolymer composed of an ethylene component and a propylene component, and may be a random copolymer or a block copolymer. The copolymerization ratio of ethylene and propylene is preferably 5 to 95% by weight of ethylene and 5 to 95% by weight of propylene. The melt flow rate of the ethylene-propylene copolymer (MFR: JIS K7210, temperature: 230 ° C., load: 21.18 N) is preferably 0.5 to 20 g / 10 minutes, more preferably 0.5 to 9 g / 10 minutes. preferable.

The surface layer 30 is preferably composed of a resin composition containing a polybutene resin and an ethylene-propylene copolymer in proportions of 55 to 95% by weight and 5 to 45% by weight, respectively. If the ethylene-propylene copolymer is less than 5% by weight, the peeling resistance is increased, which is not preferable. If it exceeds 45% by weight, the film forming property and heat resistance are deteriorated, which is not preferable.
In addition, the surface layer 30 is provided with a light stabilizer such as an antistatic agent, a release agent, an antioxidant, an ultraviolet absorber, a hindered amine light stabilizer, etc., as long as the characteristics as the surface protective film of the present invention are not impaired. It is also possible to add various additives such as anti-scratch agents and pigments as appropriate.

The thickness of the surface layer 30 is not particularly limited, but is preferably set to 3.0 μm or more as an example. When the thickness of the surface layer is less than 3.0 μm, it is not preferable because stable film formation cannot be performed during production.
(About the intermediate layer 20)
The intermediate layer 20 is made of a polypropylene resin, and is used for imparting rigidity (waist) to the surface protective film of the present invention. In particular, the use of a highly crystalline propylene homopolymer (hereinafter referred to as homo-PP) is preferable because the rigidity of the film can be increased and good handling properties can be imparted.

The homo PP is preferably an isotactic index (hereinafter referred to as II value) of 95% or more, more preferably 98% or more. Further, it is preferable to add a nucleating agent (crystallization nucleating agent) to the homo PP because higher rigidity can be obtained.
The MFR of homo PP (JIS K7210, temperature: 230 ° C., load: 21.18 N) is preferably 0.5 to 20 g / 10 minutes, and more preferably 1.0 to 15 g / 10 minutes. It is preferable that the MFR of homo PP is in the above range because it is suitable for extrusion molding.

  The crystallization nucleating agent is not particularly limited, and various inorganic compounds, various carboxylic acids or metal salts thereof, dibenzylidene sorbitol compounds, aryl phosphate compounds, cyclic polyvalent metal aryl phosphate compounds and aliphatic monocarboxylic acids. Examples thereof include mixtures of acid alkali metal salts or basic aluminum, lithium, hydroxy, carbonate, hydrate, α crystal nucleating agents such as various polymer compounds, and the like. These crystallization nucleating agents can be used alone or in combination of two or more materials.

(About adhesive layer 10)
The pressure-sensitive adhesive layer 10 is disposed for attaching the film 1 to the surface of an adherend such as various optical members or building materials. The thickness is about 10 to 15 μm, and is formed by blending a styrene thermoplastic elastomer, an ethylene-α-olefin copolymer, and polypropylene. The adhesive force can be controlled by changing the blending ratio of these compositions.

  Specifically, the adhesion layer 10 is composed of a resin composition containing 20 to 30% by weight of an olefinic thermoplastic elastomer, 60 to 78% by weight of a styrene thermoplastic elastomer, and 2 to 10% by weight of a polypropylene resin. Among these, the said olefin type thermoplastic elastomer is a C2-C20 alpha olefin polymer or copolymer, for example. Specific examples include an ethylene-propylene copolymer, an ethylene-1-butene copolymer, a propylene-1-butene copolymer, and a propylene-ethylene-1-butene copolymer.

The styrene thermoplastic elastomer has a polystyrene phase as a hard segment. Specifically, a styrene-butadiene copolymer, a styrene-isobutylene copolymer, or a hydrogenated product thereof.
The polypropylene resin may be the same as or different from the polypropylene resin used in the intermediate layer. Examples of the case where they are different include a propylene-ethylene copolymer having a small amount of ethylene as a copolymerization component, and may be a random copolymer or a block copolymer. The copolymerization ratio of ethylene is preferably 0.5 to 9% by weight.

It is desirable that the adhesive layer 10 be free from unwanted effects such as unnecessary floating and peeling after the film 1 is applied to the surface of the adherend. On the other hand, when the film 1 is peeled and removed, it is desired not to leave a sticking mark on the adherend surface. Moreover, when adhesiveness is too strong, there exists a possibility of giving an unnecessary residual stress to the film 1 at the time of unwinding from a product roll.
Therefore, the adhesive strength of the adhesive layer 10 should be adjusted in consideration of these points. If the surface of the adherend is rough (when AR treatment or AG treatment is applied to the surface), the surface protection film can be easily removed from the adherend after bonding unless the adhesive strength is set high. It will peel off. On the other hand, it is necessary to set the adhesive force to be lower with respect to the surface of the adherend having smoothness.

The adhesive layer 10 may contain additives such as known softeners, ultraviolet absorbers, light stabilizers, pigments, fillers, etc. as necessary, as long as the adhesiveness and contamination to the adherend are not impaired. It can also be added.
The film 1 having the above configuration has a smaller peel resistance than the conventional film, in particular by devising the composition of the surface layer 30. For this reason, it has the favorable drawability which can pay out a film from a product roll with low tension | tensile_strength. Therefore, if the film 1 is used, it is possible to effectively prevent wrinkles and peeling when the film 1 is attached.

(Method for producing surface protective film)
The surface protective film 1 having a laminated structure of surface layer 30 / intermediate layer 20 / adhesive layer 10 can be produced by multilayer coextrusion molding of the above resin composition constituting each layer.
That is, the above-mentioned surface layer resin composition, intermediate layer resin composition, and adhesive layer resin composition are dry-blended and supplied to each screw type extruder in this order. And it extrudes in a film form from a multilayer T die at a barrel temperature of 180 to 255 ° C., and is cooled while passing through a cooling roll of 20 to 40 ° C. and is taken out substantially unstretched. Alternatively, the resin for each layer may be once obtained as pellets and then extruded as described above.

This “substantially unstretched” includes unstretched or slight stretching that does not adversely affect the surface protective film. In general, the film may be pulled to such an extent that no sagging occurs when the film is taken up.
<Performance evaluation experiment>
In order to confirm the effects of the present invention, surface protective films of Examples and Comparative Examples were prepared and subjected to a predetermined peel test.

  As shown in Table 1, Examples and Comparative Examples were prepared in a total of 8 types, Examples 1 to 6 and Comparative Examples 1 and 2.

表１中に示す各層の材料は次の通りとした。
（表面層の材料）
「ポリブテン−１」として、エチレン０．５重量％を含有するのポリブテン共重合体（ＭＦＲ：０．９（ｇ／１０分）、Ｔｍ：１１４℃、密度：０．９０６）を用いた。

The material of each layer shown in Table 1 was as follows.
(Surface layer material)
As “polybutene-1”, a polybutene copolymer containing 0.5% by weight of ethylene (MFR: 0.9 (g / 10 min), Tm: 114 ° C., density: 0.906) was used.

As “polybutene-2”, a 1-butene homopolymer (MFR: 1.8 (g / 10 min), density 0.915) was used.
As the “ethylene-propylene copolymer”, a copolymer of 80 wt% ethylene and 20 wt% propylene (MFR: 8.1 (g / 10 min), Tm: 37 ° C., density: 0.87) was used. .
(Material for intermediate layer)
As “polypropylene-1”, a propylene homopolymer (II value: 99%, MFR: 2.1 (g / 10 min), Tm: 167 ° C.) was used.
(Adhesive layer material)
As the “olefin-based thermoplastic elastomer”, propylene-ethylene-1-butene copolymer (MFR: 7 (g / 10 minutes)) was used.

A styrene-isobutylene copolymer (MFR: 6 (g / 10 minutes)) was used as the styrene thermoplastic elastomer.
As “polypropylene-2”, homopolypropylene (MFR: 2.3 (g / 10 min), Tm: 160 ° C.) was used.
In the production of Example 1, first, 60% by weight of polybutene-1 and 40% by weight of ethylene-propylene copolymer were dry blended to obtain a resin composition for a surface layer. On the other hand, 100% by weight of polypropylene-1 was used to obtain a resin composition for an intermediate layer. Further, 20% by weight of the olefinic thermoplastic elastomer, 70% by weight of the styrenic thermoplastic elastomer, and 10% by weight of polypropylene-2 were dry blended to obtain an adhesive layer resin composition.

  Each of the adjusted surface layer resin, intermediate layer resin, and adhesive layer resin composition was supplied in the same order to each extruder adjusted to a barrel temperature of 180 to 260 ° C. Then, it was extruded from a T die heated to 230 ° C., cooled and solidified by a take-up roll having a set temperature of 20 ° C., and wound up in an unstretched state, and this was used as the surface protective film of Example 1. The thickness of the surface protective film (Example 1) obtained at this time was 5 μm for the surface layer, 35 μm for the intermediate layer, 10 μm for the adhesive layer, and 50 μm in total thickness.

For Examples 2 to 6 and Comparative Examples 1 and 2, surface protective films were obtained in substantially the same manner as in Example 1 except that the materials were adjusted at the blending ratios shown in Table 1, respectively.
The evaluation methods of Examples 1 to 6 and Comparative Examples 1 and 2 thus obtained were as follows.
[Sample Paste]
Two samples having a width of 50 mm and a length of 200 mm were cut out from the sample roll and bonded together in an atmosphere of 23 ° C. so that the surface layer and the adhesive layer overlapped. Then, pressure 3.0 MPa, 5.0 m / min. The sample for a measurement was obtained by pressure bonding at a speed of 2 mm.
[Peel resistance measurement]
The measurement sample was allowed to stand at room temperature (25 ° C.) for 24 hours. Then, using a peeling tester, the peeling speed: 1.0 m / min. The peel resistance between the surface layer and the adhesive layer was measured under the following setting conditions.

  At this time, those having a peel resistance of 4 N / 25 mm or less were evaluated as good. The evaluation results are shown in Table 2.

表２に示されるように、実施例１〜６は、いずれも比較例１、２に比べて良好な性能を呈することが分かった。これにより、従来技術に対する本発明の優位性が確認された。

As shown in Table 2, it was found that Examples 1 to 6 all exhibited better performance than Comparative Examples 1 and 2. This confirmed the superiority of the present invention over the prior art.

The surface protective film is affixed to adherends such as building materials, resin products such as acrylic resins for optical applications, metal products such as aluminum, and glass products. It is a film intended to protect the surface in order to prevent mixing.
Therefore, it has wide applicability.

DESCRIPTION OF SYMBOLS 1 Surface protective film 10 Adhesive layer 20 Intermediate layer 30 Surface layer

Claims (3)

A surface protective film formed by laminating an adhesive layer on one side of the intermediate layer and a surface layer on the other side,
The surface layer is composed of a resin composition containing 55 to 95% by weight of a polybutene resin and 5 to 45% by weight of an ethylene-propylene copolymer,
The intermediate layer is made of polypropylene resin,
The adhesive layer is composed of a resin composition containing 20 to 30% by weight of an olefinic thermoplastic elastomer, 60 to 78% by weight of a styrene thermoplastic elastomer, and 2 to 10% by weight of a polypropylene resin. Surface protection film. The surface protective film according to claim 1, wherein the surface layer further contains 0 to 10% by weight of an ethylene or propylene component. The surface protective film according to claim 1, wherein the intermediate layer contains a crystallization nucleating agent.

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