WO2013121846A1

WO2013121846A1 - Surface protection sheet

Info

Publication number: WO2013121846A1
Application number: PCT/JP2013/051369
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: CN103254815A

Abstract

Provided is a surface protection sheet having an adhesive layer formed on one surface of a base layer, said surface protection sheet having good adhesive strength with respect to various adherends, excellent anti-tearing properties, 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 has an adhesive layer formed on one surface of a base layer. The base layer is a polyolefin resin layer with an initial modulus of elasticity of at least 5,000 kg/cm², as measured by JIS-K-7127. The base layer includes at least a whitish layer and a blackish layer. The adhesive layer is a styrene resin layer with an initial modulus of elasticity of 1-50 kg/cm², as measured by JIS-K-7127, and the Elmendorf tear strength of the surface protection sheet is at least 50 g.

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. Moreover, it is necessary to suppress tearing when peeling off the surface protective sheet attached to the adherend.

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. Moreover, there exists a problem that it is easy to tear when peeling the surface protection sheet affixed on the adherend.

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 protective 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 (for example, Patent Document 1, Patent). Reference 2).

However, these surface protective sheets also have a problem that they are still liable to tear when the surface protective sheet attached to the adherend is peeled off, and that the weather resistance is not sufficient.

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 an adhesive layer is formed on one side of a base material layer, which has good adhesion to various adherends, excellent anti-tear resistance, and extremely high weather resistance. An object of the present invention is to provide a surface protective sheet that is excellent and has little increase in adhesive force even when used outdoors or stored at high temperatures, and has good peelability when peeled from an adherend.

The surface protective sheet of the present invention is
A surface protective sheet in which an adhesive layer is formed on one side of the base material layer,
The base material layer is a polyolefin resin layer having an initial elastic modulus of 5000 kg / cm ² or more measured according to JIS-K-7127.
The base material layer includes at least two layers of a white layer and a black layer,
The adhesive layer is a styrene resin layer having an initial elastic modulus of 1 to 50 kg / cm ² measured according to JIS-K-7127.
The surface protective sheet has an Elmendorf tear strength of 50 g or more.

According to the present invention, it is a surface protective sheet in which an adhesive layer is formed on one side of a base material layer, has good adhesive strength to various adherends, excellent anti-tearability, and extremely weather resistance. Even when used outdoors or stored at high temperatures, it is possible to provide a surface protective sheet with little increase in adhesive strength and good releasability when peeled from an adherend.

In the surface protective sheet of the present invention, an adhesive layer is formed on one side of the base material layer.

The base material layer is a polyolefin resin layer having an initial elastic modulus of 5,000 kg / cm ² or more as measured according to JIS-K-7127. When the initial elastic modulus of the base material layer is less than 5000 kg / cm ² , there is a risk that the waist of the surface protection sheet will be lowered, and for example, there is a possibility that the manual pasting workability will be deteriorated. The initial elastic modulus of the base layer, preferably ^{6000kg / cm 2 ~ 20000kg / cm} 2, more preferably at ^{6500kg / cm 2 ~ 15000kg / cm} 2.

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.

As the polyolefin resin contained in the base material layer, any appropriate polyolefin resin can be adopted. From the viewpoint of film formation stability and incineration, propylene polymer such as polypropylene; low density polyethylene (LDPE) Ethylene-based polymers such as linear low density polyethylene (LLDPE) are preferred.

The density of the ethylene-based polymer that may be contained in the substrate layer is preferably, 0.88 ~ 0.93g / cm ^3, more preferably 0.895 ~ 0.920g / 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 at least one selected from a propylene polymer and an ethylene polymer, and more preferably a density of 0.88 to 0.93 g. / Cm ³ ethylene-based polymer. Specifically as a resin component which forms a white type | system | group layer, a polypropylene, a low density polyethylene (LDPE), and a linear low density polyethylene (LLDPE) are mentioned preferably. 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 at least one selected from a propylene polymer and an ethylene polymer, and more preferably a density of 0.88 to 0.93 g. / Cm ³ ethylene-based polymer. Specifically as a resin component which forms a black type layer, a polypropylene, low density polyethylene (LDPE), and linear low density polyethylene (LLDPE) are mentioned preferably. 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 adhesive layer is a styrene resin layer having an initial elastic modulus of 1 to 50 kg / cm ² measured according to JIS-K-7127. When the initial elastic modulus of the pressure-sensitive adhesive layer is less than 1 kg / cm ² , sufficient anti-tear property may not be exhibited. When the initial elastic modulus of the adhesive layer exceeds 50 kg / cm ² , the adhesive layer may become too hard. The initial elastic modulus of the adhesive layer is preferably 3 kg / cm ² to 40 kg / cm ² , more preferably 4 kg / cm ² to 30 kg / cm ² . In the present invention, the initial elastic modulus of the pressure-sensitive adhesive layer is measured by applying and drying a forming material (pressure-sensitive adhesive composition) for forming the pressure-sensitive adhesive layer on a separator to produce a test piece having only the pressure-sensitive adhesive layer.

The adhesive layer contains a styrene resin. The content of the styrenic resin in the adhesive layer is preferably 50% by weight or more, more preferably 60% by weight or more, still more preferably 70% by weight or more, particularly preferably 80% by weight or more, and most preferably 90% by weight or more. It is. Only one kind of such styrenic resin may be used, or two or more kinds may be used.

Any appropriate styrene resin can be adopted as the styrene resin contained in the adhesive layer. In the present invention, the styrenic resin is preferably a hydrogenated product of A / B / A or a mixture of A / B / A and A '/ B'. Here, A and A 'are polymer blocks made of styrenic monomers, and B and B' are polymer blocks made of conjugated dienes.

The molecular weight of the polymer block composed of styrene monomer is preferably 1,000 to 1,000,000, more preferably 2,000 to 100,000. The glass transition temperature of the polymer block made of a styrene monomer is preferably 20 ° C. or higher.

The molecular weight of the polymer block composed of conjugated diene is preferably 1,000 to 1,000,000, more preferably 10,000 to 300,000. The glass transition temperature of the polymer block made of conjugated diene is preferably −20 ° C. or lower.

As the styrene monomer, any appropriate monomer having a styrene structure can be adopted. Examples of such styrenic monomers include vinyl styrene, vinyl xylene, ethyl styrene, isopropyl styrene, α-methyl styrene, and the like. Only one type of styrene monomer may be used, or two or more types may be used.

As the conjugated diene, any appropriate monomer having a conjugated diene structure can be adopted. Examples of such conjugated dienes include butadiene and isoprene. Only one conjugated diene may be used, or two or more conjugated dienes may be used.

The hydrogenation in the styrene-based resin is preferably in a state where the polymer block made of conjugated diene is selectively hydrogenated. The degree of hydrogenation of the polymer block composed of conjugated diene in the styrene-based resin is preferably 60% by weight or more, more preferably 80% by weight or more based on the entire conjugated diene component. When the degree of hydrogenation of the polymer block composed of conjugated diene in the styrene-based resin is less than 60% by weight based on the entire conjugated diene component, there is a possibility that sufficient anti-tearability cannot be expressed.

In the styrenic resin in the present invention, the ratio of A and B is preferably A: B = 5: 95 to 50:50, and the ratio of A ′ and B ′ is preferably A ′: B ′ = 5:95 to 50:50.

In the adhesive layer, other styrene resins can be mixed for the purpose of adjusting adhesiveness and the like within a range not impairing the object of the present invention.

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 60% by weight or less, more preferably 50% by weight or less, still more preferably 40% by weight or less, and particularly preferably 30% by weight or less based on the styrene resin.

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 appropriately set to any appropriate amount, but as the amount added increases, the adhesive residue tends to increase when exposed to high temperatures or outdoors. Thus, it is preferably 60% by weight or less, more preferably 50% by weight or less, still more preferably 40% by weight or less, and particularly preferably 30% by weight or less.

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 styrene resin before hydrogenation can be produced by any appropriate method. As such a production method, for example, living polymerization of a styrene monomer is carried out using sec-butyllithium or the like in an inert hydrocarbon solvent (for example, cyclohexane, etc.), and then a conjugated diene is added to produce styrene. A diblock structure of a polymer block composed of a monomer and a polymer block composed of a conjugated diene, and if necessary, a styrene monomer is further added to form a triblock structure. Moreover, it is good also as a triblock structure, a radial teleblock structure, etc. by using a coupling agent more than bifunctional.

Arbitrary appropriate methods can be employ | adopted as a method of hydrogenation to a styrene resin. As such a method, for example, a styrenic resin is dissolved in an inert hydrocarbon solvent (for example, cyclohexane, etc.), cobalt or nickel reduced with a catalyst such as alkylaluminum is added, and 25 to 50 is added. Examples thereof include a method of reacting under a pressure for about 10 to 60 minutes using about 5 to 40 kg / cm ³ of hydrogen at a temperature of about ° C.

The surface protective sheet of the present invention has an Elmendorf tear strength of 50 g or more.

Elemendorf tear strength is a value measured according to JIS-P-8116. When the surface protection sheet has an Elmendorf tear strength of 50 g or more, a surface protection sheet excellent in anti-tear property can be obtained.

The surface protective sheet of the present invention can be obtained by forming a base material layer and an adhesive layer by coextrusion using a forming material for forming the base material layer and a forming material for forming the adhesive layer. . 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 can be 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]
A base material white layer forming material obtained by adding 20% by weight of a white pigment (Daiichi Seika Co., Ltd., HCM2035W) to polypropylene (Idemitsu Petrochemical Co., Ltd., F-744NP), and polypropylene (Idemitsu Petrochemical Co., Ltd., F-744NP) And base black layer forming material added with 2% by weight of carbon black (manufactured by Mitsubishi Chemical, carbon black “# 45”) by T-die coextrusion molding (extruder temperature: 200 ° C., die temperature: 200 ° C.) A black and white bilayer film A shown in Table 2 (white layer / black layer = 20 μm / 20 μm) was obtained.
The black layer side of film A is subjected to corona treatment, and on the treated surface, 36% by weight of rosin-based hydrogenated glycerin ester (softening point 85 ° C.) is added to polymer 1 shown in Table 1, 3% by weight of calcium carbonate, phenol-based An anti-aging agent 0.6% by weight was added and dissolved in toluene, and the resulting pressure-sensitive adhesive composition (solid content 60% by weight) was applied to prepare a surface protective sheet.
The obtained surface protective sheet had a base material layer thickness of 40 μm and an adhesive layer thickness of 15 μm.

[Example 2]
A base-molded polymer material prepared by mixing 60 parts by weight of polypropylene (Idemitsu Petrochemical Co., Ltd., F-744NP) and 40 parts by weight of high-density polyethylene (Tosoh Corp., Nipolon Hard 5700) was prepared. And white pigment (made by Dainichi Seika Co., Ltd., HCM2035W) added with 20% by weight of white base material, polypropylene (Idemitsu Petrochemical Co., F-744NP) and carbon black (Mitsubishi Chemical Co., Ltd., carbon black “# 45 ”) 2% by weight of the base material black layer forming material was formed into a film by T-die coextrusion molding (extruder temperature: 200 ° C., die temperature: 200 ° C.). B (white layer / black layer = 20 μm / 20 μm) was obtained.
The black layer side of film B is subjected to corona treatment, and on the treated surface, 20% by weight of an aliphatic petroleum resin (softening point 100 ° C.) is added to polymer 2 shown in Table 1, and an aliphatic petroleum resin (softening point 40 ° C.). 30% by weight and 0.5% by weight of a phenolic anti-aging agent were dissolved in toluene, and the resulting pressure-sensitive adhesive composition (solid content 60% by weight) was applied to prepare a surface protective sheet.
The obtained surface protective sheet had a base material layer thickness of 40 μm and an adhesive layer thickness of 10 μm.

Example 3
A base molding polymer material was prepared by mixing 80 parts by weight of high density polyethylene (Tosoh Corp., Nipolon Hard 5700) and 20 parts by weight of low density polyethylene (Tosoh Corp., Petrocene 225). Substrate white layer forming material to which 20% by weight of a pigment (manufactured by Dainichi Seika Co., Ltd., HCM2035W) is added, carbon black (manufactured by Mitsubishi Chemical, carbon black “# 45”) with polypropylene (Idemitsu Petrochemical Co., Ltd., F-744NP) ) The base black layer forming material to which 2% by weight was added and the adhesive layer forming material obtained by kneading the adhesive composition obtained in Example 2 (excluding toluene) with a kneader at 150 ° C. for 20 minutes, A film is formed by extrusion (extruder temperature: 200 ° C., die temperature: 200 ° C.), and a surface protection sheet (white layer / black layer / adhesive layer = 22 μm / 22 μm / 15 μm) is formed. It was.

Example 4
A base molding polymer material was prepared by mixing 80 parts by weight of high density polyethylene (Tosoh Corp., Nipolon Hard 5700) and 20 parts by weight of low density polyethylene (Tosoh Corp., Petrocene 225). Substrate white layer forming material to which 20% by weight of a pigment (manufactured by Dainichi Seika Co., Ltd., HCM2035W) is added, carbon black (manufactured by Mitsubishi Chemical, carbon black “# 45”) with polypropylene (Idemitsu Petrochemical Co., Ltd., F-744NP) And 2% by weight of the base material black layer forming material was formed into a film by T-die co-extrusion molding (extruder temperature: 200 ° C., die temperature: 200 ° C.). White layer / black layer = 20 μm / 20 μm).
The black layer side of film C was subjected to corona treatment, and on the treated surface, 33% by weight of an aliphatic petroleum resin (softening point 100 ° C.) was added to polymer 3 shown in Table 1 and dissolved in toluene. A pressure-sensitive adhesive composition (solid content 60% by weight) was applied to prepare a surface protective sheet.
The obtained surface protective sheet had a base material layer thickness of 40 μm and an adhesive layer thickness of 15 μm.

Example 5
The composition corresponding to the polymer 2 shown in Table 1 as an adhesive composition and having a ratio of A / B / A triblock to A / B diblock of 80:20 is mixed with an aliphatic petroleum resin (softening point). (100 ° C.) 42% by weight was added, and a surface protective sheet was prepared in the same manner as in Example 1 except that the pressure-sensitive adhesive composition (solid content 60% by weight) obtained by dissolving in toluene was used. .
The obtained surface protective sheet had a base material layer thickness of 40 μm and an adhesive layer thickness of 15 μm.

[Comparative Example 1]
A polymer was obtained by performing radical polymerization using a monomer component consisting of 100 parts by weight of butyl acrylate, 10 parts by weight of methyl methacrylate and 2 parts by weight of acrylic acid. The weight average molecular weight (Mw) of this polymer was 500,000 and Mw / Mn = 4. This polymer was dissolved in toluene to give a pressure-sensitive adhesive composition (solid content 30% by weight). The pressure-sensitive adhesive composition was the same as in Example 1 except that this pressure-sensitive adhesive was used. Produced.
The obtained surface protective sheet had a base material layer thickness of 40 μm and an adhesive layer thickness of 15 μm.

[Comparative Example 2]
A base-molded polymer material was prepared by mixing 40 parts by weight of high-density polyethylene (manufactured by Tosoh Corporation, Nipolon Hard 5700) and 60 parts by weight of ethylene-vinyl acetate copolymer (EVA) (manufactured by Tosoh Corporation, Ultrasen 515). A base material white layer forming material in which 20% by weight of a white pigment (manufactured by Dainichi Seika Co., Ltd., HCM2035W) is added to the base material molding polymer material, and carbon black (Mitsubishi Chemical Co., Ltd., made by Idemitsu Petrochemical Co., Ltd., F-744NP). The base black layer forming material added with 2% by weight of carbon black “# 45”) was formed into a film by T-die coextrusion molding (extruder temperature: 200 ° C., die temperature: 200 ° C.). The black and white bilayer film D shown in (white layer / black layer = 20 μm / 20 μm) was obtained.
The black layer side of the film D was subjected to corona treatment, and the pressure-sensitive adhesive composition obtained in Example 1 was applied to the treated surface to prepare a surface protective sheet.
The obtained surface protective sheet had a base material layer thickness of 40 μm and an adhesive layer thickness of 15 μm.

[Comparative Example 3]
When the film A in Example 1 was prepared, a white base material and carbon black were not added to the base material, but a single base material layer was prepared only from polypropylene (manufactured by Idemitsu Petrochemical Co., Ltd., F-744NP). A surface protective sheet was produced in the same manner as in Example 1.
The obtained surface protective sheet had a base material layer thickness of 40 μm and an adhesive layer thickness of 15 μm.

〔Evaluation test〕
(Extrusion conditions)
Extruder ・ Cylinder diameter: 50mmφ
・ L / D: 20
Dice ・ T-die use ・ Die lip: 1mm
Molding conditions ・ Taking speed: 20 mm / min ・ Extrusion temperature: 220 ° C.

(Initial elastic modulus of base material layer / adhesive layer)
According to JIS-K-7127. The results are shown in Table 3.

(Elmendorf tear strength)
According to JIS-P-8116. The results are shown in Table 3.

(Hand pasting workability)
Judgment was made from the ease of wrinkle generation and the ease of displacement when a surface protective sheet was bonded to a 10 cm × 10 cm stainless steel plate. The results are shown in Table 3.

(Peeling workability)
Judged from the tear resistance when the surface protective sheet of the bonded product was quickly peeled off from the corner. The results are shown in Table 3.

(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 3.
○: 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 3, the surface protective sheet of the present invention has good adhesion to various adherends, excellent anti-tearability, excellent weather resistance, and when used outdoors or stored at high temperatures. Even if it exists, the increase in the adhesive force is little and it turns out that the peelability at the time of peeling from an adherend is favorable.

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 protective sheet in which an adhesive layer is formed on one side of the base material layer,
The base material layer is a polyolefin resin layer having an initial elastic modulus of 5000 kg / cm 2 or more measured according to JIS-K-7127.
The base material layer includes at least two layers of a white layer and a black layer,
The adhesive layer is a styrene resin layer having an initial elastic modulus of 1 to 50 kg / cm 2 measured according to JIS-K-7127.
The Elmendorf tear strength of the surface protective sheet is 50 g or more,
Surface protection sheet.