WO2013121845A1

WO2013121845A1 - Surface protection sheet

Info

Publication number: WO2013121845A1
Application number: PCT/JP2013/051368
Authority: WO
Inventors: 公平武田; 生島　伸祐; 二郎山戸
Original assignee: 日東電工株式会社
Priority date: 2012-02-15
Filing date: 2013-01-24
Publication date: 2013-08-22
Also published as: CN103254821A

Abstract

Provided is a surface protection sheet formed by the co-extrusion of a base layer containing a polyolefin resin, and an adhesive layer containing a styrene thermoplastic elastomer, said surface protection sheet having good adhesive strength with respect to various adherends, exceptional weather resistance, and good peelability when peeled from an adherend, with little increase in the adhesive strength even when used outdoors or stored at high temperatures. This surface protection sheet is formed by the co-extrusion of a base layer containing a polyolefin resin, and an adhesive layer containing a styrene thermoplastic elastomer. The base layer contains at least a whitish layer and a blackish layer, and the polyolefin resin is an ethylene polymer with a density of 0.88 to 0.93 g/cm³. The styrene thermoplastic elastomer is a styrene block polymer or a hydrogenated product thereof, wherein the temperature at which tan δ values for dynamic viscoelasticity measurements taken in a measured temperature range of -60 to 100°C reach a maximum is -40 to -25°C.

Description

Surface protection sheet

The present invention relates to a surface protection sheet. In detail, the present invention is, for example, when a member such as a metal plate, a painted metal plate, an aluminum sash, a resin plate, a decorative steel plate, a vinyl chloride laminated steel plate, or a glass plate is transported, processed, or cured. The present invention relates to a surface protective sheet that can be used for applications such as sticking to a surface for protection.

The characteristics required for the surface protective sheet include that the surface protective sheet does not float or peel off after being attached to the adherend, and that the adhesive layer does not remain on the adherend when it is peeled off. In particular, when the surface protection sheet attached to the adherend is subjected to harsh conditions such as high temperature or outdoor exposure before the surface protection sheet is peeled off, Even more advanced characteristics are required for the required characteristics.

Conventionally, a natural rubber pressure-sensitive adhesive in which an appropriate amount of a tackifier or the like is blended with natural rubber or modified natural rubber has been used for a pressure-sensitive adhesive layer of a surface protection sheet that is generally used. Such a surface protective sheet is not particularly problematic for indoor use. However, the natural rubber-based pressure-sensitive adhesive has an unsaturated double bond in its structure, and therefore, when exposed outdoors, it causes molecular cleavage by ultraviolet rays. For this reason, when peeling off the surface protection sheet in which the natural rubber-based pressure-sensitive adhesive is used, there arises a problem that the pressure-sensitive adhesive remains on the adherend. Therefore, a surface protective sheet with good weather resistance is desired.

In order to solve the above-mentioned problems, an acrylic pressure-sensitive adhesive having a cohesive force increased by three-dimensionally crosslinking the acrylic copolymer with an isocyanate compound or a methylol compound in order to form an adhesive layer, Synthetic rubber adhesives such as polyisobutylene have been proposed. However, since these pressure-sensitive adhesives are solvent-based, there are problems in terms of safety and hygiene of the surface protection sheet, in terms of pollution and economy.

In recent years, there has been a demand for a solvent-free adhesive to improve these problems. As an effective means, a method for producing a surface protection sheet by co-extrusion forming a pressure-sensitive adhesive layer made of a thermoplastic elastomer and a base material layer made of a polyolefin resin has been studied.

Generally, thermoplastic elastomers that can be co-extruded include styrene / ethylene-butylene copolymer / styrene block polymer (SEBS), styrene / ethylene-propylene copolymer / styrene block polymer (SEPS), etc. Are known. These styrenic block copolymers have sufficient adhesion to adherend surfaces such as stainless steel plates and resin plates having a relatively smooth adherend surface. On the other hand, these styrenic block copolymers have poor adhesiveness to adherend surfaces such as polished stainless steel plates (hairline plates) and rough resin plates. Therefore, a large amount of tackifier or softener is added to the styrenic block copolymer in the adhesive layer of the surface protective sheet applied to the adherend surface such as the rough surface resin plate. It is common to adjust the adhesive strength (see, for example, Patent Document 1 and Patent Document 2).

However, a surface protective sheet having a pressure-sensitive adhesive layer using a large amount of a tackifier or the like increases its adhesive strength in a relatively short time when stored at high temperatures, such as in a warehouse in a summer or in a container. End up. Such an increase in adhesive force has a problem such as causing a peeling failure. In addition, when such a surface protective sheet having increased adhesive strength is used for a smooth plate or the like, a peeling failure occurs due to the influence of a tackifier or the like.

JP 5-194923 A (page 2) JP-A-61-103975 (first page)

An object of the present invention is a surface protective sheet in which a base material layer containing a polyolefin-based resin and an adhesive layer containing a styrene-based thermoplastic elastomer are formed by coextrusion, and has an adhesive force to various adherends. Is excellent in weather resistance, even when used outdoors or stored under high temperature, there is little increase in adhesive strength, and good peelability when peeling from the adherend. The object is to provide a surface protection sheet.

The surface protective sheet of the present invention is
A surface protection sheet in which a base material layer containing a polyolefin-based resin and an adhesive layer containing a styrene-based thermoplastic elastomer are formed by coextrusion,
The base material layer includes at least two layers of a white layer and a black layer,
The polyolefin resin is an ethylene polymer having a density of 0.88 to 0.93 g / cm ³ ;
The styrenic thermoplastic elastomer is a styrenic block copolymer having a maximum tan δ value of dynamic viscoelasticity measurement in a measurement temperature range of −60 to 100 ° C. or hydrogenation thereof. It is a thing.

In a preferred embodiment, the adhesive layer has a shear storage modulus at 23 ° C. of 1.0 × 10 ⁵ to 8.0 × 10 ⁵ Pa.

In a preferred embodiment, the adhesive layer contains a softening agent, and the number average molecular weight of the softening agent is 5000 to 100,000.

According to the present invention, there is provided a surface protective sheet in which a base material layer containing a polyolefin resin and an adhesive layer containing a styrene thermoplastic elastomer are formed by coextrusion, and has an adhesive force to various adherends. Is excellent in weather resistance, even when used outdoors or stored under high temperature, there is little increase in adhesive strength, and good peelability when peeling from the adherend. A surface protective sheet can be provided.

In the surface protective sheet of the present invention, a base material layer containing a polyolefin resin and an adhesive layer containing a styrene thermoplastic elastomer are formed by coextrusion.

The styrenic thermoplastic elastomer forming the adhesive layer has a styrene block co-polymer with a maximum temperature of tan δ of dynamic viscoelasticity measurement in the measurement temperature range of −60 to 100 ° C. of −40 to −25 ° C. A coalescence or a hydrogenated product thereof is used.

In the present invention, a styrene block copolymer showing the maximum tan δ value of dynamic viscoelasticity measurement at a higher temperature than conventional is used as the styrene thermoplastic elastomer used for forming the adhesive layer. In the present invention, the adhesiveness of the adhesive layer increases as the temperature at which the maximum tan δ value is increased. Further, by adjusting the temperature showing the maximum tan δ value to −40 to −25 ° C., moderate wettability can be obtained. For this reason, the adhesive layer in this invention has sufficient wettability and adhesiveness, even if it does not add a tackifier etc. in large quantities. Therefore, the addition of a tackifier or the like can be suppressed to a small amount, and the occurrence of defective peeling or adhesive residue can be suppressed. The surface protective sheet of the present invention having such an adhesive layer adheres well to a rough surface by adjusting the physical properties of the adhesive layer, and does not cause poor peeling even when applied to a flat surface. In order to obtain better wettability and adhesiveness, the temperature at which the tan δ value of the dynamic viscoelasticity measurement is maximized is preferably −40 to −30 ° C. The dynamic viscoelasticity measurement will be described in detail in the examples.

In the present invention, the shear storage modulus of the adhesive layer at 23 ° C. is preferably 1.0 × 10 ⁵ to 8.0 × 10 ⁵ Pa. From the viewpoint of adhesiveness to a rough surface, the shear storage elastic modulus of the adhesive layer at 23 ° C., which is a practical temperature range, is preferably 1.5 × 10 ⁵ to 7.5 × 10 ⁵ Pa, more preferably 2 0.0 × 10 ⁵ to 7.0 × 10 ⁵ Pa. The measurement of the shear storage elastic modulus is described in detail in the examples.

Examples of styrene block copolymers include styrene ABA block copolymers (triblock copolymers) such as styrene / butadiene / styrene copolymers (SBS) and styrene / isoprene / styrene copolymers (SIS). ); Styrenic ABAB type block copolymer (tetrablock copolymer) such as styrene / butadiene / styrene / butadiene copolymer (SBSB), styrene / isoprene / styrene / isoprene copolymer (SISI); styrene / butadiene・ Styrene-based ABABA block copolymer (pentablock copolymer) such as styrene / butadiene / styrene copolymer (SBSBS), styrene / isoprene / styrene / isoprene / styrene copolymer (SISIS); Styrene having repeating units Lock copolymers; and the like.

As the styrene block copolymer, it is preferable to use a hydrogenated product obtained by hydrogenating an ethylenic double bond. Examples of such a styrene block copolymer include styrene / ethylene-butylene copolymer / styrene copolymer (SEBS), styrene / ethylene-propylene copolymer / styrene copolymer (SEPS), styrene / ethylene copolymer, and the like. And ethylene-butylene copolymer / styrene / ethylene-butylene copolymer copolymer (SEBSEB).

Only one type of styrene block copolymer may be used, or two or more types may be used.

The styrene block content in the styrenic block copolymer can be appropriately set to any appropriate amount, but the temperature at which the maximum tan δ value of the dynamic viscoelasticity measurement is within the above range is used. Usually, when the styrene block content decreases, there is a possibility that adhesive residue due to insufficient cohesive force of the adhesive layer is likely to occur. On the other hand, when the styrene block content is increased, the pressure-sensitive adhesive layer formed with the styrenic block copolymer alone becomes hard, and it may not be possible to obtain good adhesion to a rough surface. From such a viewpoint, the styrene block content in the styrenic block copolymer is preferably 5 to 40% by weight, more preferably 7 to 30% by weight, and still more preferably 9 to 20% by weight.

Among styrenic block copolymers, water of styrenic block copolymers having a repeating structure (ABA type, ABAB type, ABABA type, etc.) more than triblock copolymers composed of styrene (A) and butadiene (B) Additives (SEBS, SEBSEB, SEBSEBS, etc.) are preferred. In order to obtain good wettability and tackiness, the proportion of the butylene structure in the ethylene-butylene copolymer block in the hydrogenated styrene block copolymer is preferably 60% by weight or more, more preferably It is 70 weight% or more, More preferably, it is 75 weight% or more. When the proportion of the butylene structure in the ethylene-butylene copolymer block in the hydrogenated styrene-based block copolymer is 60% by weight or more, the wettability is good, in particular, the adhesiveness is good. Adheres well to rough surfaces. The proportion of the butylene structure in the ethylene-butylene copolymer block in the hydrogenated styrene block copolymer is usually preferably 90% by weight or less.

The styrenic block copolymer can be mixed with other styrenic thermoplastic elastomers within the range that does not impair the object of the present invention for the purpose of adjusting the adhesiveness.

Other styrenic thermoplastic elastomers include styrene block copolymers other than those described above; styrene / butadiene copolymers (SB), styrene / isoprene copolymers (SI), styrene / ethylene-butylene copolymers. AB block polymer such as polymer (SEB) and styrene / ethylene-propylene copolymer (SEP); Styrene random copolymer such as styrene / butadiene rubber (SBR); Styrene / ethylene-butylene copolymer ABC type styrene / olefin crystal block polymers such as polymers / olefin crystal copolymers (SEBC); hydrogenated products thereof, and the like.

When forming the adhesive layer, for the purpose of controlling adhesive properties, etc., for example, softener, olefin resin, silicone polymer, liquid acrylic copolymer, tackifier, anti-aging agent, hindered amine Additives such as system light stabilizers, UV absorbers, polyethyleneimine, fatty acid amides, phosphate esters, fillers and pigments (for example, calcium oxide, magnesium oxide, silica, zinc oxide, titanium oxide, etc.) are added as appropriate be able to.

For example, corona discharge treatment, ultraviolet irradiation treatment, flame treatment, plasma treatment, sputter etching treatment, and other surface treatments for the purpose of adhesion control and pasting workability are performed on the adhesive layer surface as necessary. You can also.

配合 Blending of tackifier is effective for improving adhesive strength. However, the blending amount of the tackifier is appropriately determined according to the adherend to which the surface protective sheet is applied in order to avoid the occurrence of the adhesive residue problem due to the decrease in cohesive force. The compounding amount of the tackifier is usually preferably 40% by weight or less, more preferably 30% by weight or less, and further preferably 10% by weight or less with respect to the styrene-based thermoplastic elastomer containing the styrene-based block copolymer. . In addition, when the adherend to which the surface protective sheet is applied is a metal plate, it is preferable not to add a tackifier when forming the adhesive layer.

Examples of the tackifier include petroleum-based resins such as aliphatic copolymers, aromatic copolymers, aliphatic / aromatic copolymer systems and alicyclic copolymers, and coumarone-indene resins. Terpene resins, terpene phenol resins, rosin resins such as polymerized rosin, (alkyl) phenol resins, xylene resins, hydrogenated products thereof, etc. Things can be used without any particular restrictions. Only one type of tackifier may be used, or two or more types may be used. Among these tackifiers, hydrogenated tackifiers are preferable from the viewpoint of peelability and weather resistance. In addition, what is marketed as a blend with an olefin resin can also be used for a tackifier.

Softener blending is effective in improving adhesive strength. Examples of the softening agent include low molecular weight diene polymers, polyisobutylene, hydrogenated polyisoprene, hydrogenated polybutadiene, and derivatives thereof. Examples of such derivatives include those having an OH group or a COOH group at one or both ends. Specifically, hydrogenated polybutadiene diol, hydrogenated polybutadiene monool, hydrogenated polyisoprene diol, water Examples thereof include polyisoprene monool. In particular, hydrogenated products of diene polymers such as hydrogenated polybutadiene and hydrogenated polyisoprene, olefinic softeners, and the like are preferable for the purpose of suppressing the improvement in adhesiveness to the adherend. As such a softening agent, specifically, trade name “Kuraprene LIR-200” manufactured by Kuraray Co., Ltd. is available. These softeners may be used alone or in combination of two or more.

The molecular weight of the softening agent can be appropriately set to any appropriate amount, but if the molecular weight is small, there is a risk of causing material transfer or heavy peeling from the adhesive layer to the adherend, while the molecular weight is large. Therefore, the softening agent has a number average molecular weight of preferably 5,000 to 100,000, more preferably 10,000 to 50,000.

When using a softener, the amount added can be set appropriately to any appropriate amount. However, as the added amount increases, the adhesive residue tends to increase at high temperatures and when exposed outdoors. The amount is preferably 40% by weight or less, more preferably 20% by weight or less, and still more preferably 10% by weight or less with respect to the pressure-sensitive adhesive composition containing a styrene-based thermoplastic elastomer containing a polymer and a softening agent. In addition, when the adherend to which the surface protective sheet is applied is a metal plate, it is preferable not to add a softener when forming the adhesive layer.

The thickness of the adhesive layer may be appropriately set to any appropriate thickness according to the required adhesive strength. The thickness of the adhesive layer is preferably 1 to 50 μm, more preferably 2 to 40 μm, and still more preferably 5 to 20 μm.

The base material layer contains a polyolefin resin. The content ratio of the polyolefin resin in the base material layer is preferably 60% by weight or more, more preferably 70% by weight or more, further preferably 80% by weight or more, particularly preferably 85% by weight or more, and most preferably 90% by weight. That's it. Such polyolefin resin may use only 1 type, and may use 2 or more types.

Any appropriate polyolefin-based resin can be adopted as the polyolefin-based resin contained in the base material layer. From the viewpoints of film formation stability, incineration, etc., low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE) Etc.) are preferred. In order to impart bending workability to the base material layer, it is preferable to use linear low density polyethylene (LLDPE).

The polyolefin resin contained in the base material layer is preferably an ethylene polymer having a density of 0.88 to 0.93 g / cm ³ . Such a density is more preferably 0.895 to 0.920 g / cm ³ .

The base material layer includes at least two layers of a white layer and a black layer. Thereby, it can be set as the surface protection sheet excellent in the weather resistance.

The white layer is a layer showing a white color tone. For example, the whiteness specified by JIS-L-1015 is preferably 60% or more, more preferably 70% or more, still more preferably 80% or more, Particularly preferably, it is 85% or more. The white layer preferably contains a white pigment. Any appropriate white pigment can be adopted as the white pigment. An example of such a white pigment is titanium oxide. When the white layer contains a white pigment, the content is preferably 0.1 to 50% by weight, more preferably 1 to 30% by weight, based on the resin component forming the white layer. More preferably, it is 5 to 20% by weight.

The resin component forming the white layer is preferably a polyolefin resin, more preferably an ethylene polymer, and still more preferably an ethylene polymer having a density of 0.88 to 0.93 g / cm ³ . Specifically, preferred examples of the resin component forming the white layer include low density polyethylene (LDPE) and linear low density polyethylene (LLDPE). The content of the polyolefin resin in the white layer is preferably 60% by weight or more, more preferably 70% by weight or more, further preferably 80% by weight or more, particularly preferably 85% by weight or more, and most preferably 90% by weight. That's it. Such polyolefin resin may use only 1 type, and may use 2 or more types.

Any appropriate thickness can be adopted as the thickness of the white layer depending on the purpose. Such a thickness is preferably 1 to 50 μm, more preferably 3 to 40 μm, still more preferably 5 to 30 μm, and particularly preferably 10 to 30 μm.

The black layer is a layer showing a black color tone. The black layer preferably contains a black pigment. Any appropriate black pigment can be adopted as the black pigment. An example of such a black pigment is carbon black. When the black layer contains a black pigment, the content is preferably 0.01 to 10% by weight, more preferably 0.1 to 5% by weight, based on the resin component forming the black layer. More preferably, it is 0.5 to 3% by weight.

The resin component forming the black layer is preferably a polyolefin resin, more preferably an ethylene polymer, and still more preferably an ethylene polymer having a density of 0.88 to 0.93 g / cm ³ . Specifically, preferred examples of the resin component forming the black layer include low density polyethylene (LDPE) and linear low density polyethylene (LLDPE). The content of the polyolefin resin in the black layer is preferably 60% by weight or more, more preferably 70% by weight or more, still more preferably 80% by weight or more, particularly preferably 85% by weight or more, and most preferably 90% by weight. That's it. Such polyolefin resin may use only 1 type, and may use 2 or more types.

Any appropriate thickness can be adopted as the thickness of the black layer according to the purpose. Such a thickness is preferably 1 to 100 μm, more preferably 5 to 70 μm, still more preferably 10 to 60 μm, and particularly preferably 20 to 50 μm.

The base material layer may contain any appropriate additive for the purpose of preventing deterioration. Examples of such additives include antioxidants; UV absorbers; light stabilizers such as hindered amine light stabilizers; antistatic agents; fillers such as calcium oxide, magnesium oxide, silica, zinc oxide, and titanium oxide. Pigments, anti-scratch agents, lubricants, anti-blocking agents, foaming agents, and polyethyleneimine.

Any appropriate thickness can be adopted as the thickness of the base material layer depending on the purpose. Such a thickness is preferably 20 to 300 μm, more preferably 30 to 250 μm, and still more preferably 40 to 200 μm.

The back surface side of the base material layer may be subjected to uneven processing for the purpose of imparting slip resistance and handy cut property. Furthermore, you may form various functional layers, such as a printing layer, in the back side of a base material layer.

The surface protective sheet of the present invention comprises a base material layer and an adhesive layer using a forming material for forming a base material layer containing the polyolefin resin and a forming material for forming an adhesive layer containing the styrenic thermoplastic elastomer. Can be obtained by co-extrusion. In the surface protective sheet of the present invention, since the base material layer includes at least two layers of a white layer and a black color layer, there are two or more forming materials for forming the base material layer. The base material layer and the pressure-sensitive adhesive layer are obtained by forming the base material layer and the pressure-sensitive adhesive layer in multiple layers by a co-extrusion method using two or more kinds of the material forming the base material layer and the forming material forming the pressure-sensitive adhesive layer.
The structure of the surface protective sheet of the present invention is not particularly limited, and any structure of “white layer / black layer / adhesive layer” and “black layer / white layer / adhesive layer” can be adopted. . Moreover, as a base material layer, it can also be set as the layer structure of 3 or more layers which formed layers other than a black-type layer and a white-type layer. Specifically, a configuration such as “transparent resin layer / white color layer / black color layer / adhesive layer” may be employed. Furthermore, the thickness of the white layer and the black layer may be the same, and the thickness may be different (a white layer is thinner than the black layer, and a white layer is thicker than the black layer). May be.

As the co-extrusion method, it can be carried out according to the inflation method, T-die method and the like generally used for film production. The substrate layer and the pressure-sensitive adhesive layer can be subjected to the surface treatment as necessary.

If necessary, the adhesive layer can be protected by temporarily attaching a separator or the like until it is put to practical use. For the surface of the base material layer where the adhesive layer is not provided, for example, a mold release treatment by adding fatty acid amide or polyethyleneimine to the base material layer for the purpose of forming a wound body that can be easily rewound. It is also possible to provide a coat layer made of an appropriate release agent such as silicone, long chain alkyl, or fluorine.

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples.

[Example 1]
20% by weight of white pigment (manufactured by Dainichi Seika Co., Ltd., HCM2035W) and 0.5% by weight of ethylene bisstearylamide (manufactured by Nippon Kasei Co., Ltd.) with respect to linear low density polyethylene (Mitsui Chemicals, Evolue SP2020) 1% by weight of carbon black (manufactured by Mitsubishi Chemical, carbon black “# 45”) with respect to low-density polyethylene (manufactured by Tosoh Corporation, Petrocene 180), and ethylenebisstearylamide (Nippon Kasei Co., Ltd.) Intermediate base material layer forming material added with 0.5% by weight, styrene / ethylene-butylene copolymer / styrene block polymer (Asahi Kasei Co., Ltd., Tuftec H1221, maximum tan δ temperature = −32 ° C. ) Is formed at a die temperature of 240 ° C. by an inflation method to obtain a surface protection sheet. . At this time, the thickness of the back substrate layer was 20 μm, the thickness of the intermediate substrate layer was 90 μm, and the thickness of the adhesive layer was 5 μm.
The density of linear low density polyethylene (Mitsui Chemicals, Evolue SP2020) is 0.916 g / cm ³ , and the density of low density polyethylene (Tosoh, Petrocene 180) is 0.922 g / cm ^3. Met.
Further, the styrene / ethylene-butylene copolymer / styrene block polymer (Taftec H1221 manufactured by Asahi Kasei Co., Ltd.) had a styrene content of 12% by weight, and the proportion of the butylene structure in the ethylene-butylene copolymer block was 76% by weight. It was.

[Example 2]
Back surface of 20% by weight of white pigment (manufactured by Dainichi Seika Co., Ltd., HCM2035W) and 0.5% by weight of ethylenebisstearylamide (manufactured by Nippon Kasei Co., Ltd.) to low density polyethylene (Tosoh Corp., Petrocene 173) 1% by weight of carbon black (Mitsubishi Chemical, carbon black “# 45”) and low-density polyethylene (Tosoh Corp., Petrocene 180) and ethylene bisstearylamide (Nippon Kasei Co., Ltd.) Manufactured) 0.5% by weight of the intermediate substrate layer forming material and the block polymer of styrene / ethylene-butylene copolymer / styrene (Asahi Kasei Corporation, Tuftec H1221, maximum tan δ temperature = −32 ° C.) An adhesive layer forming material to which 5% by weight of a petroleum resin (Arakawa Chemical Co., Ltd., Alcon P-100) is added is subjected to a die temperature of 2 by the T-die method. Was formed at 0 ℃, obtain a surface protective sheet. At this time, the thickness of the back substrate layer was 10 μm, the thickness of the intermediate substrate layer was 50 μm, and the thickness of the adhesive layer was 10 μm.
The density of the low density polyethylene (Tosoh Corp., Petrocene 173) was 0.924 g / cm ³ .

Example 3
20% by weight of white pigment (manufactured by Dainichi Seika Co., Ltd., HCM2035W) and 0.5% by weight of ethylene bisstearylamide (manufactured by Nippon Kasei Co., Ltd.) with respect to linear low density polyethylene (Mitsui Chemicals, Evolue SP2020) 1% by weight of carbon black (manufactured by Mitsubishi Chemical, carbon black “# 45”) with respect to low-density polyethylene (manufactured by Tosoh Corporation, Petrocene 180), and ethylenebisstearylamide (Nippon Kasei Co., Ltd.) Substrate layer forming material added with 0.5 parts by weight, styrene / ethylene-butylene copolymer / styrene block polymer (manufactured by JSR, Dynalon 8600P, maximum tan δ temperature = −39 ° C.) A pressure-sensitive adhesive layer-forming material was formed by a T-die method at a die temperature of 220 ° C. to obtain a surface protective sheet. At this time, the thickness of the back substrate layer was 20 μm, the thickness of the intermediate substrate layer was 90 μm, and the thickness of the adhesive layer was 10 μm.
Further, the styrene / ethylene-butylene copolymer / styrene block polymer (JSR, Dynalon 8600P) had a styrene content of 15% by weight and a proportion of the butylene structure in the ethylene-butylene copolymer block was 67% by weight. It was.

[Comparative Example 1]
In Example 1, instead of the styrene / ethylene / butylene copolymer / styrene block polymer (Asahi Kasei Co., Ltd., Tuftec H1221, maximum tan δ temperature = −32 ° C.) as the adhesive layer forming material, styrene / ethylene / butylene copolymer A surface protective sheet was prepared in the same manner as in Example 1 except that a polymer / styrene block polymer (manufactured by Shell Elastomer, Kraton G1657, maximum tan δ temperature = −50 ° C.) was used.
The styrene / ethylene-butylene copolymer / styrene block polymer (manufactured by Shell Elastomer, Kraton G1657) had a styrene content of 13% by weight.

[Comparative Example 2]
In Example 1, instead of the styrene / ethylene / butylene copolymer / styrene block polymer (Asahi Kasei Co., Ltd., Tuftec H1221, maximum tan δ temperature = −32 ° C.) as the adhesive layer forming material, styrene / ethylene / butylene copolymer Adhesive layer forming material in which 5% by weight of a petroleum resin (Arakawa Chemical Co., Alcon P-100) is added to a polymer / styrene block polymer (Shell Elastomer, Kraton G1657, maximum tan δ temperature = −50 ° C.) A surface protective sheet was prepared in the same manner as in Example 1 except that was used.

[Comparative Example 3]
In Example 2, instead of the styrene / ethylene-butylene copolymer / styrene block polymer (Taftec H1221, maximum tan δ temperature = −32 ° C.) as the adhesive layer forming material, a styrene / ethylene / propylene copolymer was used. Formation of an adhesive layer by adding 5% by weight of a petroleum resin (Arakawa Chemical Co., Ltd., Alcon P-100) to a polymer / styrene block polymer (Kuraray Co., Ltd., Septon 2063, maximum tan δ temperature = −51 ° C.) A surface protective sheet was prepared in the same manner as in Example 2 except that the material was used.
The styrene / ethylene-propylene copolymer / styrene block polymer (Kuraray Co., Ltd., Septon 2063) had a styrene content of 13% by weight.

[Comparative Example 4]
In Example 1, a surface protective sheet was prepared in the same manner as in Example 1 except that the white pigment and carbon black were not added to the substrate.

〔Evaluation test〕
(Measurement of maximum tan δ temperature and storage modulus)
The maximum tan δ value of dynamic viscoelasticity measurement in the measurement temperature range of −60 to 100 ° C. of each styrene block copolymer used for the adhesive layer of the surface protective sheet, and shear storage of the adhesive layer at 23 ° C. The elastic modulus was measured by applying a temperature change of −60 to 150 ° C. (heating rate 5 ° C./min) while applying a shear strain having a frequency of 1 Hz using ARES manufactured by Rheometric Scientific. The measurement sample was measured by creating an adhesive layer having a thickness of about 5 mm. The pressure-sensitive adhesive layer was produced by a casting method using an organic solvent or a heat press method. In addition, the measurement of the shear storage elastic modulus of the adhesive layer can be measured by a method such as a method of obtaining by the difference between the shear storage elastic modulus of the surface protective sheet and the shear storage elastic modulus of the base material when these methods cannot be performed. . The results are shown in Table 1.

(Measurement of adhesive strength)
The adhesive strength of the surface protective sheets obtained in Examples and Comparative Examples was measured according to JIS-Z-0237. Specifically, SUS304BA board (smooth surface) and SUS304HL board (polishing surface) were used as adherends. After cleaning the surface of the SUS plate with toluene, it was pressure-bonded with a 2 kg roller, and after 30 minutes, with an Instron type tensile tester (manufactured by Shimadzu Corp., Autograph) at a pulling speed of 300 mm / min and 180 degree peel. It was measured. At this time, the measurement environment and the storage environment were 23 ° C./50%. As the adhesive strength after heat resistance, a SUS304BA plate affixed at 23 ° C./50% was left in a dryer set at 80 ° C. for 14 days, then left at 23 ° C./50% for 2 hours, and 23 ° C./50 % As above. The results are shown in Table 1.

(Measurement of weather resistance)
The surface protection sheets obtained in Examples and Comparative Examples were cut into strips having a width of 20 mm to prepare evaluation samples. This sample was pressed against a SUS430BA plate by reciprocating a 2 kg roller, and then put into a sunshine carbon weather meter (product of Suga Test Instruments Co., Ltd.) for 1000 hours, and then from one end of the sample to a length of 100 mm Was peeled in the 180 ° direction at a tensile speed of 0.3 m / min.
The above results were evaluated according to the following criteria. The results are shown in Table 1.
○: The sample was not broken and could be peeled off very well.
X: The sample was broken in the middle due to deterioration of the substrate, or the adhesive remained on the adherend and was contaminated.

From Table 1, the surface protective sheet of the present invention is very excellent in weather resistance, has a good adhesive force even with respect to an adherend that has been subjected to a polishing treatment, and has little increase in adhesive force even under heat resistance. It is recognized that the general peelability is good.

The surface protective sheet of the present invention is, for example, a member such as a metal plate, a painted metal plate, an aluminum sash, a resin plate, a decorative steel plate, a vinyl chloride laminated steel plate, a glass plate, etc. It can be used for purposes such as attaching to the surface to protect.

Claims

A surface protection sheet in which a base material layer containing a polyolefin-based resin and an adhesive layer containing a styrene-based thermoplastic elastomer are formed by coextrusion,
The base material layer includes at least two layers of a white layer and a black layer,
The polyolefin resin is an ethylene polymer having a density of 0.88 to 0.93 g / cm 3 ;
The styrenic thermoplastic elastomer is a styrenic block copolymer having a maximum tan δ value of dynamic viscoelasticity measurement in a measurement temperature range of −60 to 100 ° C. or hydrogenation thereof. Is a thing,
Surface protection sheet.
2. The surface protective sheet according to claim 1, wherein the adhesive layer has a shear storage elastic modulus at 23 ° C. of 1.0 × 10 5 to 8.0 × 10 5 Pa.
The surface protective sheet according to claim 1, wherein the adhesive layer contains a softening agent, and the number average molecular weight of the softening agent is 5000 to 100,000.