JP2002226813A - Adhesive and adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain both an adhesive which can form an adhesive layer having excellent adhesiveness capable of satisfying initial adhesiveness and peelability with time after outdoor exposure and high-temperature preservation and having excellent stress relaxation characteristics and an adhesive sheet obtained by forming the adhesive layer composed of the adhesive on at least one side of a substrate. SOLUTION: This adhesive is characterized in that the adhesive comprises a propylene-based copolymer composed of propylene, a 4-12C α-olefin and ethylene as copolymerization components and the propylene-based copolymer has no >=1 J/g endothermic peak by the measurement by a differential scanning calorimeter(DSC) in a temperature range of 9-200 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a pressure-sensitive adhesive and a pressure-sensitive adhesive sheet. The pressure-sensitive adhesive sheet of the present invention is particularly useful as a pressure-sensitive adhesive sheet having removability, such as a surface protection sheet or a temporary fixing pressure-sensitive adhesive sheet for electronic components. More specifically, surfaces that have applications such as pasting to protect the surface when transporting, processing and curing painted metal plates, aluminum sashes, resin plates, decorative steel plates, vinyl chloride laminated steel plates, glass plates, etc. Useful as a protective sheet.

[0002]

2. Description of the Related Art The characteristics required for a surface protection sheet include:
It is required that the protective sheet does not float or peel off after being attached to the adherend, and that the adhesive does not remain on the adherend during peeling and removal. In particular, when the substrate is subjected to severe conditions, such as high temperature or outdoor exposure, between the time when it is attached to the adherend and the time when it is peeled, even higher characteristics are required for the above characteristics.

[0003] For this reason, a pressure-sensitive adhesive for forming a pressure-sensitive adhesive layer of a surface protective sheet, which has been generally used in the past, is to crosslink an acrylic copolymer with an isocyanate compound or a methylol compound to such an extent that the tackiness is not lost. There are used ones that have been made three-dimensional to increase the cohesive strength, and those that have natural rubber or modified natural rubber mixed with an appropriate amount of a tackifier.

[0004] The surface protective sheet having such a pressure-sensitive adhesive layer has no particular problem when used indoors. However, when the pressure-sensitive adhesive is a composition containing a natural rubber or a modified natural rubber as a main component or a tackifier, the pressure-sensitive adhesive is constituted by a component having an unsaturated double bond. For this reason, when exposed outdoors, ultraviolet rays may cause molecular breakage of the component, and the adhesive may remain on the adherend when the surface protective film is peeled off. Therefore, a surface protection sheet having good weather resistance has been desired.

In order to solve the above problems, Japanese Patent Publication No.
No. 89312 and Japanese Patent Publication No. 5-74627, a hydrogenated styrene AB-
A surface protection sheet having excellent weather resistance, in which an adhesive layer is formed from an A-type block polymer, is disclosed. The surface protection sheet using the hydrogenated styrene type ABA type block polymer as an adhesive layer is attached to an adherend such as a metal plate or a resin plate having a rough (rough) surface. In this case, there is no problem, but when it is applied to a mirror-finished metal plate, highly polar acrylic resin plate, polycarbonate resin plate, acrylic or polyester coated steel plate, etc. Occurred in some cases. In particular, the above problem may occur in a coated steel sheet coated with a paint containing an aromatic as a main component such as polystyrene. In addition, there is a case where a polar component present in the paint is transferred to the pressure-sensitive adhesive layer and causes a problem such as deforming the surface of the coated steel sheet.

Further, Japanese Patent Application Laid-Open No. 6-1958 discloses a surface protective film having no adhesive property in which a polyethyleneimine and a phosphate ester surfactant are added to a styrenic ABA type block polymer. I have.
However, this surface protective film has a problem that a phosphate ester-based surfactant or the like as a release component contaminates the coated steel sheet. Further, the styrene ABA type block polymer has a poor stress relaxation property because of having a pseudo-crosslinked structure by a styrene domain. For this reason, when affixed to a coated steel plate or the like, there may be a problem that a step due to the sticking trace of the film is easily generated on the surface of the coated steel plate.

In Japanese Patent Application Laid-Open Nos. Hei 7-258617 and Hei 8-1577791, an ethylene / α-olefin copolymer is laminated on a base film as a surface protective film having excellent adhesion strength with time. The disclosed surface protection film is disclosed. However, these protective films must be adhered under heating and pressurizing conditions, and since the adhesiveness with time is stable, the initial adhesive strength at room temperature is 0.5 N / 25 mm or less. In some cases, such as those that are transported after being applied or those that are applied to the outside such as building exterior panels until the completion, they are peeled off by the generated wind or the like, which may cause a problem that the protective function is not satisfied. In particular, when these protective films are attached to a metal plate having a rough surface (rough surface), a coated steel plate subjected to emboss processing, a resin steel plate, or the like, a case where low adhesion strength is a problem. was there.

Further, Japanese Patent Application Laid-Open Nos. Hei 7-233354 and Hei 11-21519 disclose surface protective films exhibiting good adhesiveness using an α-olefin copolymer for the pressure-sensitive adhesive layer. However, among these surface protective films, those having good adhesive strength are those containing a styrene-based ABA type block polymer such as SEBS or SEPS in the pressure-sensitive adhesive layer. However, there is a problem of poor peeling and migration of substances under long-term storage due to the influence of the styrene block in the block polymer. Furthermore, since the pressure-sensitive adhesive layer formed by the mixed system of the α-olefin copolymer and the hydrogenated styrene-based ABA type block polymer is initially kneaded because the pressure-sensitive adhesive is mechanically kneaded. Although each polymer is finely dispersed, the finely dispersed state may be broken down with time, phase-separated, and adhesive residue may be generated when the polymer is left outdoors at a high temperature for a long time. Further, since the α-olefin copolymers used for these have a crystal part, they have a disadvantage that they are inferior in stress relaxation property, and a film sticking mark easily occurs on the surface of a coated steel plate or the like.

[0009]

SUMMARY OF THE INVENTION Accordingly, the present invention is intended to provide an initial adhesive property and a good adhesive property which can satisfy the peeling property even after aging after outdoor exposure or high-temperature storage, and has a good stress relaxation property. An object of the present invention is to provide a pressure-sensitive adhesive capable of forming a pressure-sensitive adhesive layer having the same. Still another object is to provide a pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive is formed on at least one surface of a substrate.

[0010]

Means for Solving the Problems The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, have found the following pressure-sensitive adhesive, and have completed the present invention.

That is, the present invention relates to a pressure-sensitive adhesive containing a propylene-based copolymer containing propylene, an α-olefin having 4 to 12 carbon atoms and ethylene as a copolymerization component, wherein the propylene-based copolymer is A pressure-sensitive adhesive having no endothermic peak of 1 J / g or more when measured in a temperature range of 0 to 200 ° C. with a differential scanning calorimeter (DSC).

[0012] The inventors of the present invention have found that styrene A
It was clarified that this was due to the influence of the styrene block portion of the -BA type block polymer, and an α-olefin copolymer containing no styrene block was examined as an adhesive. Furthermore, the present inventors have studied and found that the occurrence of the film sticking mark appearing on the surface of the coated steel sheet is due to wrinkles and bubbles generated when sticking the base film, and the stress of the base material generated at that time is reduced. It was found that it was transmitted to the surface of the coated steel sheet via the adhesive layer and appeared as a film sticking mark. Therefore, the pressure-sensitive adhesive layer capable of alleviating the transmission of stress of the substrate, that is, the pressure-sensitive adhesive excellent in stress relaxation properties was found to be able to reduce this film sticking trace, as the pressure-sensitive adhesive, the propylene-based copolymer It was found.

The pressure-sensitive adhesive containing the propylene-based copolymer containing propylene, an α-olefin having 4 to 12 carbon atoms and ethylene as a copolymerization component has a good initial adhesive property, It can suppress the increase in adhesion to the coated steel sheet and has good peelability after lapse of time. Further, since the propylene-based copolymer has substantially no crystalline portion, it is excellent in stress relaxation properties, relieves stress generated from the base material by the pressure-sensitive adhesive layer, and also applies to painted steel sheets and the like. Does not generate film sticking marks. In addition, the propylene-based copolymer has a good cohesive force, and can be satisfactorily peeled off even when left at high temperatures.

Among the above-mentioned pressure-sensitive adhesives, those in which the propylene copolymer does not have an endothermic peak of 1 J / g or more in a temperature range of 0 to 200 ° C. by a differential scanning calorimeter (DSC), It is preferable from the viewpoint of ease and adhesiveness. In particular, those not having the endothermic peak of 0.5 J / g or more are preferable.

It is to be noted that the propylene-based copolymer has no endothermic peak of 1 J / g or more in a differential scanning calorimeter (DSC) measurement in a temperature range of 0 ° C. to 200 ° C. When the DSC analysis of the propylene-based copolymer was performed by the method (conditions) shown in the examples, 0 ° C. to 20 ° C.
It means that in the temperature range of 0 ° C., no endothermic peak of 1 J / g or more, which is considered to be based on melting of the crystal, is observed.

In the pressure-sensitive adhesive, the propylene copolymer has a weight average molecular weight (Mw) of 4.0 × 10 ^{5 to} 12.0 × 10 ⁵ in terms of polystyrene by gel permeation chromatography (GPC). And the molecular weight distribution (Mw / Mn) is 1.5 to 3.5, and JI
The JISA hardness of SK6301 is preferably 20 to 50.

The weight average molecular weight of the propylene-based copolymer is not particularly limited, but the weight average molecular weight (Mw) in terms of polystyrene by the GPC method is 4.
0 × 10 ^{5 to} 12.0 × 10 ⁵ , more preferably 5.0
× 10 ^{5 to} 11.0 × 10 ⁵ , more preferably 6.0.
It is about × 10 ^{5 to} 10.0 × 10 ⁵ . Those having a weight-average molecular weight of 4.0 × 10 ⁵ or more have good cohesive force and can be peeled satisfactorily without adhesive residue. Further, those having 12.0 × 10 ⁵ or less have good moldability when extruding an adhesive containing a propylene-based copolymer, for example.

The molecular weight distribution (Mw / Mn) of the propylene copolymer is not particularly limited. 5-3. Five
And more preferably 1. 5-3. 0 is preferred. When the molecular weight distribution (Mw / Mn) is 3.5 or less, the generated low molecular weight component or the like causes peeling failure, or the high molecular weight component is present as a foreign substance in the pressure-sensitive adhesive layer and causes poor appearance. Can be suppressed.

Further, propylene-based copolymers of JIS-K
The JISA hardness at 6301 is not particularly limited, but is preferably 20 to 50, more preferably 22 to 40, and still more preferably 25 to 38. Those having a JISA hardness in the above range are soft and have good marks of film sticking.

Further, the present invention relates to a pressure-sensitive adhesive sheet wherein a pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive is formed on at least one surface of a substrate. Such a pressure-sensitive adhesive sheet is useful as a surface protection pressure-sensitive adhesive sheet used for surface protection applications.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The propylene copolymer used as the base polymer of the pressure-sensitive adhesive of the present invention is a copolymer containing propylene, an α-olefin having 4 to 12 carbon atoms and ethylene as copolymer components.

Specific examples of the α-olefin having 4 to 12 carbon atoms include butene-1, pentene-1, hexene-1,
Heptene-1, Octene-1, Nonene-1, Decene-1
, Dodecene-1, 4-methyl-pentene-1 and 4-methyl-hexene-1 and the like, but the α-olefin of the present invention is not limited to the above compounds. Of these, butene-1, hexene-1, and octene-1 are preferred. These α-olefins having 4 to 12 carbon atoms are 1
The species can be used alone or in combination of two or more.

The proportion of each component constituting the propylene copolymer is not particularly limited, and is appropriately adjusted according to the use. For example, when using an adhesive sheet for surface protection applications,
In order to obtain good adhesiveness and removability, the content of propylene in the propylene-based copolymer is preferably from 40 to 95% by weight, more preferably from 60 to 90% by weight, particularly preferably from 76 to 90% by weight of the monomer composition. Preferably it is ~ 85% by weight. In this case, the ratio of the α-olefin and ethylene, which are monomer components other than propylene, in the propylene copolymer is α-olefin: ethylene = 1: 1 to 40: 1, and more preferably 2% by weight of the monomer composition. : 1 to 3
A ratio of 0: 1 is preferable from the viewpoint of low-temperature adhesiveness.

When the pressure-sensitive adhesive sheet is used for a carrier of an electronic component, the content of propylene in the propylene-based copolymer is adjusted to the weight ratio of the monomer composition in order to obtain good wettability and light peelability. Is preferably 1 to 40% by weight, more preferably 2 to 30% by weight, and particularly preferably 3 to 20% by weight. In this case, the α- component which is a monomer component other than propylene in the propylene copolymer
The ratio of olefin to ethylene is preferably α-olefin: ethylene = 1: 1 to 1:20, more preferably 1: 2 to 1:10 in terms of the weight ratio of the monomer composition, from the viewpoint of light peelability.

The method for polymerizing the propylene copolymer is not particularly limited, and the propylene, α-olefin having 4 to 12 carbon atoms and ethylene can be obtained by solution polymerization, slurry polymerization, or gas phase polymerization. More specifically, for example, the polymerization can be carried out by using a catalyst described in JP-A-11-80233. The obtained propylene-based copolymer preferably has an endothermic peak in a differential scanning calorimeter (DSC) within the above range, and has a polymerization average molecular weight, a molecular weight distribution, and a JISA hardness in the above range. Further, the propylene-based copolymer preferably has an atactic structure in which the orientation of propylene and α-olefin is atactic.

The pressure-sensitive adhesive of the present invention contains the above-mentioned propylene-based copolymer as a main component, and usually contains the above-mentioned propylene-based copolymer in an amount of 80% by weight or more, more preferably 90% by weight or more. In addition to the propylene-based copolymer,
Hydrogenation such as styrene-ethylene-butylene copolymer-styrene (SEBS) or styrene-ethylene-propylene copolymer-styrene (SEPS), for the purpose of improving the adhesiveness, within a range not to impair the object of the present invention. Styrene ABA type block polymer, styrene-ethylene.
Hydrogenated styrene A such as butylene copolymer (SEB) and styrene-ethylene propylene copolymer (SEP)
-B type block polymer, styrene-ethylene / butylene copolymer-olefin crystal block polymer (SEB
Hydrogenated styrene ABC type block polymers such as C), hydrogenated random copolymers of styrene and diene hydrocarbons, and the like can be added. These can be used alone or in combination of two or more. The use ratio of the block polymer having a styrene component can be appropriately determined. However, when the use ratio is large, the adhesion increasing property, the substance transfer property, and the stress relaxation property are affected. 0
It is preferably from 40 to 40 parts by weight, more preferably from 0 to 20 parts by weight, further preferably from 0 to 10 parts by weight. If the amount exceeds 40 parts by weight, the stress relaxation property is impaired, and peeling failure due to the influence of the styrene component tends to occur.

The pressure-sensitive adhesive of the present invention may contain, for example, a silicone-based polymer, an acrylic-based copolymer, a surfactant, a softener, a tackifier, an antiaging agent, etc. for the purpose of controlling the pressure-sensitive properties. An appropriate additive such as a filler, a hindered amine light stabilizer, an ultraviolet absorber, and a filler or a pigment such as calcium oxide, magnesium oxide, silica, zinc oxide, and titanium oxide can be blended. Also,
In addition, the surface of the pressure-sensitive adhesive layer may be subjected to an appropriate surface modification treatment such as a corona treatment or an ultraviolet treatment for the purpose of controlling tackiness and preventing contamination.

The blending of a softener is generally effective for improving the adhesive strength. As the softening agent, for example, low molecular weight polyisobutylene, hydrogenated polyisoprene, hydrogenated polybutadiene and derivatives thereof can be used. Examples of the derivative include those having an OH group or a COOH group at one or both terminals, such as hydrogenated polybutadiene diol, hydrogenated polybutadiene monol, hydrogenated polyisoprene diol, and hydrogenated polyisoprene monool. In particular, a hydrogenated product of a diene-based polymer such as hydrogenated polybutadiene or hydrogenated isoprene, an olefin-based softening agent, or the like is preferable for the purpose of suppressing an improvement in the adhesiveness to an adherend. Specifically, Kuraray Co., Ltd. product name “Kuraprene LIR-200”
Etc. are available. One or more of these can be used arbitrarily, and the compounding amount can be appropriately set. However, the amount is preferably 0 to 40 parts by weight based on 100 parts by weight of the propylene copolymer. And more preferably 0 to 20 parts by weight, particularly preferably 0 to 10 parts by weight.
If the compounding amount exceeds 40 parts by weight, adhesive residue at high temperature or during outdoor exposure becomes remarkable. The molecular weight of the softening agent can be appropriately set, but the number average molecular weight is preferably about 5,000 to 100,000, and particularly preferably 10,000 to 50,000. Molecular weight 50
If it is less than 00, the substance may be transferred to the adherend or heavy peeling may occur.

On the other hand, the blending of a tackifier is also generally effective in improving the adhesive strength, and the amount of the tackifier is determined from the viewpoint of improving the adhesive strength by avoiding the problem of adhesive residue due to a decrease in cohesive strength.
It is preferably at most 50 parts by weight, more preferably at most 30 parts by weight, particularly preferably at most 5 to 20 parts by weight, based on 100 parts by weight of the propylene copolymer. Examples of the tackifier include petroleum resins such as aliphatic, aromatic, aliphatic / aromatic copolymers and alicyclic resins, coumarone indene resins, terpene resins, terpene phenol resins, and polymerization agents. A known adhesive such as a rosin-based resin, an (alkyl) phenol-based resin, a xylene-based resin, or a hydrogenated resin thereof may be appropriately selected, and one or more of them may be used. Hydrogenated tackifiers are preferred in terms of peelability and weather resistance. Also, a blend of a tackifier and an olefin resin is commercially available, and these may be used.

The substrate on which the pressure-sensitive adhesive layer is to be provided is not particularly limited. For example, polyester, polyamide,
Propylene polymers such as block copolymers (homopolypropylene) or block copolymers with ethylene components as copolymer components, random copolymers, and graft copolymers, low density, high density, and linear low density.
One or two types of olefin polymers such as ultra low density ethylene polymers and ethylene propylene copolymers
Various types of plastic films, papers, metal films, nonwoven fabrics and the like using more than one kind are used. When using a plastic film for the base material,
For example, light stabilizers and antistatic agents such as antioxidants and ultraviolet absorbers, hindered amine light stabilizers, and other fillers and pigments such as carbon black, calcium oxide, magnesium oxide, silica, zinc oxide and titanium oxide Appropriate additives can also be blended. Base material layer thickness is 5
About 300 μm, preferably 20 to 150 μm
However, the present invention is not limited to this.

From the viewpoint of improving the weather resistance, an antioxidant, an ultraviolet absorber, a light stabilizer, a filler and the like can be added to the substrate layer. As the antioxidant, a known antioxidant such as a hindered phenol-based antioxidant, a phosphorus-based processing heat stabilizer, a lactone-based processing heat stabilizer, and a sulfur-based heat-resistant stabilizer can be used. To 100 parts by weight of the base resin of the base material layer (when the base material layer is a blend, the blend is the base resin).
Not more than 3 parts by weight, more preferably not more than 3 parts by weight,
More preferably, it is about 0.1 to 0.5 parts by weight.
In addition, as the UV absorber, a known UV absorber such as a benzotriazole-based UV absorber, a triazine-based UV absorber, or a benzophenone-based UV absorber can be used. 5 parts by weight or less, preferably 3 parts by weight or less, more preferably 0.1 to 1 part by weight, based on 100 parts by weight of the resin.
It is about parts by weight. As the light stabilizer, a known light stabilizer such as a hindered amine light stabilizer or a benzoate light stabilizer can be used. The light stabilizer is preferably 5 parts by weight or less based on 100 parts by weight of the base resin of the base material layer. , More preferably 3 parts by weight or less, still more preferably 0.1 to 1 part by weight.
It is about parts by weight. These additives can be used in combination.

Addition of an inorganic filler is also mentioned as one of the techniques for improving weather resistance, and carbon black, titanium oxide, zinc oxide and the like are preferably used. The mixing ratio is preferably 20 parts by weight or less, more preferably 1 to 2 parts by weight, based on 100 parts by weight of the base resin of the base material layer.
0 parts by weight, more preferably about 5 to 15 parts by weight. In addition, as for the ultraviolet transmittance of the substrate on which the pressure-sensitive adhesive layer is provided, the transmittance at a wavelength of 365 nm is preferably 5% or less, particularly preferably 1% or less.

The pressure-sensitive adhesive layer may be formed by, for example, applying a solution of a pressure-sensitive adhesive in a solvent or a hot melt to a base material, applying a pressure-sensitive adhesive layer formed in a separator form according to the method, A method for extruding and forming an adhesive layer-forming material on a supporting substrate, a method for extruding a substrate and an adhesive layer in two or multiple layers, a method for laminating a single-layer adhesive layer on a substrate, or with a laminate layer The method can be performed according to a known method for producing a pressure-sensitive adhesive sheet, such as a method of laminating a pressure-sensitive adhesive layer in two layers, a method of laminating a pressure-sensitive adhesive layer and a support base material such as a film or a laminate layer in two layers or a multilayer. it can. Among these production methods for pressure-sensitive adhesive sheets, a method of co-extrusion of a pressure-sensitive adhesive layer together with a base material layer made of a thermoplastic resin by a two-layer or multi-layer method using an inflation method or a T-die method is preferred in terms of productivity and cost. It can be preferably used.

The thickness of the pressure-sensitive adhesive layer to be formed is appropriately determined according to the adhesive strength and the like. Generally, it is preferably 3 to 50 μm, more preferably 5 to 40 μm, and particularly preferably 7 to 35 μm. If necessary, the pressure-sensitive adhesive layer can be protected by temporarily attaching a separator or the like until it is practically used.

On the surface of the supporting substrate on which the pressure-sensitive adhesive layer is not provided, for example, a fatty acid amide, polyethyleneimine, or the like is added to the substrate layer for the purpose of forming a roll that can be easily unwound. Release treatment, silicone-based,
A coat layer made of an appropriate release agent such as a long-chain alkyl type or a fluorine type may be provided.

The pressure-sensitive adhesive sheet of the present invention can be preferably used for applications requiring removability and temporary sticking property, and in particular, a metal plate, a painted metal plate, an aluminum sash, a resin plate, a decorative steel plate, a vinyl chloride laminate Transporting steel plates, glass plates, etc.
When processing and curing, the purpose was to simplify the production of surface protection sheets having applications such as pasting for surface protection, adhesive sheets for temporarily fixing parts of home appliances, electronic parts, etc. It can be suitably used as an adhesive sheet having removability such as an adhesive sheet.

[0037]

EXAMPLES The present invention will be described in more detail with reference to examples of the present invention, but the present invention is not limited to these examples.

(Propylene copolymer) Table 1 shows the characteristic values of the propylene copolymer used.

[0039]

[Table 1] In Table 1, P: B: E indicates propylene: butene-1: ethylene. The weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) were measured by GPC method (column: Tosoh Corporation, TS
According to Kgel GMH-H (S) × 2, solvent: tetrahydrofuran, converted to polystyrene), JISA is JIS.
It is a value measured by -K6301.

FIG. 1 shows a DSC chart of the propylene-based copolymer (1).
2 are shown in FIG. Neither of the propylene-based copolymers (1) and (2) has an endothermic peak of 1 J / g or more at 0 ° C to 200 ° C. No melting point or heat of fusion was observed. The DSC chart was measured using a differential scanning calorimeter (device name: DSC; DSC2000, manufactured by Seiko Instruments Inc.) under the following measurement conditions: temperature: -40 to 200 ° C., atmosphere gas: nitrogen (20
0 ml / min), and the temperature was measured at a heating rate of 10 ° C./min. The temperature raising and lowering processes during the measurement were performed at 10 ° C./min.

Example 1 A propylene-based copolymer (1) was used as a material for forming an adhesive layer, and low-density polyethylene (Petrocene 172, manufactured by Tosoh Corporation) was used as a material for forming a base material layer. Coextrusion was carried out by a method to obtain a sheet for surface protection. The thickness of the pressure-sensitive adhesive layer was adjusted to 20 μm, and the thickness of the base material layer was adjusted to 60 μm.

Example 2 A toluene solution of a propylene copolymer (2) was applied as a pressure-sensitive adhesive to a polypropylene film having a thickness of 40 μm, and dried to form a pressure-sensitive adhesive layer. Thus, a sheet for surface protection was obtained. . The thickness of the pressure-sensitive adhesive layer was adjusted to be 15 μm.

Comparative Example 1 The procedure of Example 1 was repeated except that an ethylene / α-olefin binary copolymer (affinity PF-1140, manufactured by DuPont) was used as a material for forming the pressure-sensitive adhesive layer.
A sheet for surface protection was obtained in the same manner as described above. The ethylene / α-olefin binary copolymer used as a material for forming the pressure-sensitive adhesive layer had an endothermic peak of 95.7 under the above measurement conditions.
C (40.5 J / g). The DSC chart is shown in FIG.

Comparative Example 2 In the same manner as in Example 1, except that an ethylene / α-olefin binary copolymer (Esprene 201, manufactured by Sumitomo Chemical Co., Ltd.) was used as the material for forming the pressure-sensitive adhesive layer. Thus, a sheet for surface protection was obtained. The ethylene / α-olefin binary copolymer used as the material for forming the pressure-sensitive adhesive layer did not have an endothermic peak under the above measurement conditions.

Comparative Example 3 In Example 2, an ethylene / α-olefin binary copolymer (Affinity P, manufactured by DuPont) was used as a pressure-sensitive adhesive.
A sheet for surface protection was obtained in the same manner as in Example 2 except that the toluene solution of F-1140) was used.

Comparative Example 4 A surface protection sheet was obtained in the same manner as in Example 2, except that a toluene solution of SEPS (Septon 2043, manufactured by Kuraray Co., Ltd.) was used as the adhesive.

Comparative Example 5 In Example 2, a propylene / α-olefin binary copolymer (Tuffmer XR1 manufactured by Mitsui Chemicals, Inc.) was used as an adhesive.
07L) A sheet for surface protection was prepared in the same manner as in Example 2 except that a toluene solution of 40 parts by weight of a hydrogenated petroleum resin (Alcon P-100, manufactured by Arakawa Chemical Co.) was mixed with 100 parts by weight. I got The ethylene / α-olefin binary copolymer used as the material for forming the pressure-sensitive adhesive layer had an endothermic peak of 108.3 ° C. (24.
1 J / g). The DSC chart is shown in FIG.

The following evaluations were performed on the surface protection sheets obtained in the examples and comparative examples. Table 2 shows the evaluation results.

(Initial Adhesive Strength) The obtained surface protecting sheet was applied to a metal plate coated with polyester melamine by 2 kg.
After sticking by two reciprocating pressure bonding of roller,
The adhesive strength (N / 25 mm) after standing for a time was measured. Measurement conditions: 23 ° C., 65% RH, peeling speed 300 mm /
Minute, 180 degree peel.

(Adhesion over time) The obtained surface protection sheet was applied to a metal plate coated with polyester melamine in an amount of 2 kg.
After sticking by two reciprocating pressure bonding of roller,
After standing for 0 days, the adhesive strength (N / 25 mm) was measured.
Measurement conditions: 23 ° C., 65% RH, peeling speed 300 mm /
Minute, 180 degree peel.

(Stress relaxation) The obtained sheet for surface protection was treated with bubbles (one circle having a diameter of 2 cm) and wrinkles (length 5 cm).
cm, height 5 mm), and attached to a metal plate coated with polyester melamine.
What was left for 0 days was visually observed for the presence or absence of adhesive residue (cohesion) on the metal plate and the presence or absence of a film sticking mark (marking property) when peeled off. Also, 60 ° C / 95% RH
After being left in the environment for 14 days, it was peeled off, and after standing for 24 hours at room temperature, the presence or absence of thinning of the coating film (observation of loss of thinning due to transfer of substances to the adhered portion) was visually observed.

[0052]

[Table 2] In Table 2, (-) shows no bubbles and wrinkles due to insufficient adhesive force, and no trace of film sticking. From Table 2, it can be seen from the examples that the examples have an initial adhesive strength, a small increase in the adhesive strength with time at high temperatures, a stable adhesive strength with time, good peelability, and a pressure-sensitive adhesive layer having a stress relaxation property. It can be seen that they have excellent properties such as cohesiveness at high temperature and substance transferability.

[Brief description of the drawings]

FIG. 1 is a DSC chart of a propylene-based copolymer (1).

FIG. 2 is a DSC chart of a propylene-based copolymer (2).

FIG. 3 is a DSC chart of an ethylene / α-olefin binary copolymer used in a comparative example.

FIG. 4 is a DSC chart of an ethylene / α-olefin binary copolymer used in a comparative example.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takaki Oyama 1-1-2 Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation (72) Inventor Shinichi Takada 1-2-1, Shimohozumi, Ibaraki-shi, Osaka No. Nitto Denko Corporation (72) Inventor Yuki Kobayashi 1-2-1, Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation F-term (reference) 4J004 AA07 AB01 FA04 4J040 DA031 DA111 DA131 JB09 LA01

Claims (4)

[Claims] 1. An adhesive comprising a propylene-based copolymer containing propylene, an α-olefin having 4 to 12 carbon atoms and ethylene as a copolymerization component, wherein the propylene-based copolymer is a differential scan. 0 on the calorimeter (DSC)
1 J / g in the measurement in the temperature range of ~ 200 ° C
An adhesive having no endothermic peak as described above. 2. The propylene copolymer has a weight average molecular weight (Mw) of 4.0 × 1 in terms of polystyrene by gel permeation chromatography (GPC).
0 ^{5 to} 12.0 × 10 ⁵ and molecular weight distribution (Mw / M
The pressure-sensitive adhesive according to claim 1, wherein n) is 1.5 to 3.5 and the JIS hardness according to JIS-K6301 is 20 to 50. 3. A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive according to claim 1 formed on at least one surface of a substrate. 4. The pressure-sensitive adhesive sheet according to claim 3, which is used for surface protection.