WO2022210603A1 - Adhesive sheet for steel material rustproofing, steel structure, steel material rustproofing method, and steel material welding method - Google Patents

Abstract

An adhesive sheet 10 for steel material rustproofing, which is attached to a steel material and used for rustproofing, comprises a base material 11 and an adhesive layer 12 provided on one surface of the base material 11, the base material 11 having an elastic modulus of no greater than 900 MPa.

Description

Adhesive sheet for steel rust prevention, steel structure, steel rust prevention method, and steel welding method

The present invention provides a steel rust prevention pressure-sensitive adhesive sheet that is attached to steel materials to prevent rust, a steel structure having the steel rust prevention pressure-sensitive adhesive sheet, and a steel rust prevention pressure-sensitive adhesive sheet that uses the steel rust prevention pressure-sensitive adhesive sheet. It relates to a rust method and a steel welding method.

Conventionally, when welding steel materials such as steel plates, pipe materials, and steel frames, groove surfaces are formed at the ends of the steel materials. After the groove surface is formed, the steel material is often stored for about 1 to 6 months before welding. Coating is common. When the antirust paint is applied, polishing called scraping is required to peel off the antirust paint immediately before welding, which complicates the work.

Therefore, instead of applying rust-preventive paint, attempts have been made to apply adhesive tape to the groove surface to prevent rust. For example, in Patent Document 1, as a rust-preventive pressure-sensitive adhesive tape that is attached to a groove surface or the like, an intermediate layer made of a woven fabric and a surface layer and a back layer mainly made of low-density polyethylene provided on both sides are used. A pressure-sensitive adhesive tape is disclosed in which a pressure-sensitive adhesive is laminated on the entire back surface of a base material. As in Patent Document 1, if an adhesive tape is used, cleaning can be omitted, thereby improving workability.

JP-A-2001-64596

The anti-corrosion adhesive tape needs to be attached to the steel material with high adhesion in order to exhibit its anti-corrosion function by blocking it from the outside world during the storage period. However, the groove surface often has a complicated shape, such as a portion that is pointed or an angular shape that is connected to the peripheral portion. Similarly, the peripheral portion of the groove face may also have a complex shape. Therefore, when a general adhesive tape is applied over the groove surface or the groove surface and its peripheral portion, it may not follow the shape and wrinkles may occur, or peeling may occur during storage. If wrinkles or peeling occurs, an air space is generated between the anticorrosive adhesive tape and the steel material, and rust tends to occur in that portion.

Accordingly, an object of the present invention is to provide an adhesive tape for rust prevention of steel materials, which can be adhered to the surface of steel materials such as groove surfaces with high adhesion, and which can appropriately prevent rust on the adhered steel materials. .

As a result of intensive studies, the present inventors have found that, in a pressure-sensitive adhesive tape for rust prevention of steel materials comprising a substrate and an adhesive layer provided on one surface of the substrate, the elastic modulus of the substrate is set to 900 MPa or less. The inventors have found that the problem can be solved, and completed the present invention. That is, the present invention provides the following [1] to [20].
[1] A steel material-preventing pressure-sensitive adhesive sheet that is attached to steel materials and used for rust prevention,
A pressure-sensitive adhesive sheet for rust prevention of steel materials, comprising a base material and a pressure-sensitive adhesive layer provided on one surface of the base material, wherein the base material has an elastic modulus of 900 MPa or less.
[2] The pressure-sensitive adhesive sheet for rust prevention of steel materials according to [1] above, which has an ultraviolet transmittance of 1% or less in a wavelength region of 300 to 320 nm after accelerated deterioration under the following accelerated deterioration conditions.
(Accelerated deterioration condition)
In a weather resistance tester, the lamp light source is a xenon lamp, the wavelength is 365 nm, the illuminance is 60 W/m ² , the irradiation temperature is 63 ° C., and the shower is 18 minutes out of 120 minutes. The sheet is left for 1500 hours.
[3] The load at 10% elongation is 8.5 N / 10 mm or less, and the rate of change in the load at 10% elongation when accelerated deterioration is performed under the following accelerated deterioration conditions is 10% or less. ] or the pressure-sensitive adhesive sheet for rust prevention of steel materials according to [2].
(Accelerated deterioration condition)
In a weather resistance tester, the lamp light source is a xenon lamp, the wavelength is 365 nm, the illuminance is 60 W/m ² , the irradiation temperature is 63 ° C., and the shower is 18 minutes out of 120 minutes. The sheet is left for 1500 hours.
[4] The pressure-sensitive adhesive sheet for rust prevention of steel materials according to any one of [1] to [3] above, wherein at least one of the base material and the pressure-sensitive adhesive layer contains an ultraviolet absorber.
[5] The pressure-sensitive adhesive sheet for rust prevention of steel materials according to any one of the above [1] to [4], wherein the pressure-sensitive adhesive sheet for rust prevention of steel materials has a haze value of 40% or less.
[6] The pressure-sensitive adhesive sheet for rust prevention of steel materials according to any one of [1] to [5] above, wherein the pressure-sensitive adhesive layer has a reduced adhesive strength due to an external stimulus.
[7] The pressure-sensitive adhesive sheet for steel material rust prevention according to the above [6], wherein the external stimulus is heat.
[8] The pressure-sensitive adhesive sheet for rust prevention of steel materials according to any one of [1] to [7] above, wherein the substrate is a resin film.
[9] The pressure-sensitive adhesive sheet for rust prevention of steel materials according to [8] above, wherein the resin film is selected from the group consisting of a polyester resin film, a polyolefin resin film, an acrylic resin film, and a polyvinyl chloride resin film.
[10] The pressure-sensitive adhesive sheet for steel material rust prevention according to the above [9], wherein the resin film is a polyolefin resin film.
[11] The above [1], wherein the pressure-sensitive adhesive layer is formed from at least one pressure-sensitive adhesive selected from the group consisting of acrylic pressure-sensitive adhesives, rubber-based pressure-sensitive adhesives, urethane-based pressure-sensitive adhesives, and silicone-based pressure-sensitive adhesives. The pressure-sensitive adhesive sheet for rust prevention of steel materials according to any one of [10].
[12] The pressure-sensitive adhesive sheet for steel material rust prevention according to the above [11], wherein the pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive.

[13] A steel structure comprising the steel material rust-preventing pressure-sensitive adhesive sheet according to any one of the above [1] to [12] and a steel material, wherein the steel material rust-preventing pressure-sensitive adhesive sheet is attached to the steel material. .
[14] The steel material has a groove surface, and the pressure-sensitive adhesive sheet for steel material rust prevention is at least one of the groove surface and a peripheral portion where the distance along the steel material surface from the groove surface is within 100 mm. The steel structure according to [13] above, which is attached to a wall.
[15] The above-mentioned [13] or [14], wherein the pressure-sensitive adhesive sheet for rust prevention of steel materials is attached to the steel material by a valley fold folded at 45° or more or a mountain fold folded at 90° or more. steel structure.
[16] An adhesive sheet for rust prevention of steel material comprising a base material and an adhesive layer provided on one surface of the base material, wherein the elastic modulus of the base material is 900 MPa or less is attached to the steel material to prevent the steel material from rusting. A steel material rust prevention method.
[17] The steel material rust prevention method according to the above [16], wherein the steel material rust prevention pressure-sensitive adhesive sheet is attached at least to the groove surface of the steel material.
[18] The steel material rust prevention method according to the above [16] or [17], wherein the steel material rust prevention pressure-sensitive adhesive sheet attached to the steel material is peeled off.
[19] The pressure-sensitive adhesive layer is one whose adhesive strength is reduced by an external stimulus,
The steel material rust prevention method according to the above [18], wherein the pressure-sensitive adhesive layer of the steel material rust prevention pressure-sensitive adhesive sheet attached to the steel material is subjected to an external stimulus before the steel material rust prevention pressure-sensitive adhesive sheet is peeled off.
[20] Attaching a pressure-sensitive adhesive sheet for steel material rust prevention, comprising a base material and an adhesive layer provided on one side of the base material, wherein the base material has an elastic modulus of 900 MPa or less, at least on the groove surface of the steel material. death,
After a certain period of time has passed since the adhesive sheet for rust prevention of steel materials was attached, the adhesive sheet for rust prevention of steel materials is peeled off from the steel materials,
A steel material welding method for joining the groove surface to which the steel material has been affixed to another member by welding.

In another aspect, the present invention provides the following [21] to [29].
[21] A steel material-preventing pressure-sensitive adhesive sheet that is attached to steel materials and used for rust prevention,
A pressure-sensitive adhesive sheet for rust prevention of steel materials, comprising a base material and a pressure-sensitive adhesive layer provided on one surface of the base material, wherein the pressure-sensitive adhesive layer loses its adhesive force due to an external stimulus.
[22] The sheet according to [21] above, wherein the external stimulus is heat.
[23] A steel structure comprising the steel material rust-preventing pressure-sensitive adhesive sheet according to the above [21] or [22] and a steel material, wherein the steel material rust-preventing pressure-sensitive adhesive sheet is attached to the steel material.
[24] A pressure-sensitive adhesive sheet for rust prevention of steel materials, which comprises a base material and an adhesive layer provided on one surface of the base material, wherein the pressure-sensitive adhesive layer loses its adhesive force due to an external stimulus, is attached to a steel material. A rust-preventing method for steel materials.
[25] The steel material rust prevention method according to the above [24], wherein the steel material rust prevention pressure-sensitive adhesive sheet is attached at least to the groove surface of the steel material.
[26] The steel material rust prevention method according to the above [24] or [25], wherein the steel material rust prevention pressure-sensitive adhesive sheet attached to the steel material is peeled off.
[27] The steel material rust prevention method according to the above [26], wherein the pressure-sensitive adhesive layer of the steel material rust prevention pressure-sensitive adhesive sheet attached to the steel material is subjected to an external stimulus before the steel material rust prevention pressure-sensitive adhesive sheet is peeled off.
[28] Attaching at least a steel material rust-preventing pressure-sensitive adhesive sheet comprising a base material and an adhesive layer provided on one side of the base material, the adhesive strength of which is reduced by an external stimulus, to the groove surface of the steel material,
After a certain period of time has passed since the adhesive sheet for rust prevention of steel materials was attached, the adhesive sheet for rust prevention of steel materials is peeled off from the steel materials,
A steel material welding method for joining the groove surface to which the steel material has been affixed to another member by welding.
[29] The steel material rust preventive according to the above [28], in which an external stimulus is applied to the adhesive layer of the steel material rust preventive adhesive sheet attached to the steel material before the steel material rust preventive adhesive sheet is peeled off. Method.

According to the pressure-sensitive adhesive tape for rust prevention of steel materials of the present invention, it is attached to the surface of steel materials such as groove surfaces with high adhesion, and the attached steel materials can be appropriately rust-proofed.

BRIEF DESCRIPTION OF THE DRAWINGS It is typical sectional drawing which shows one Embodiment of the adhesive tape for steel material rust prevention of this invention. FIG. 4 is a schematic cross-sectional view showing a specific example of a groove surface; It is a typical sectional view showing one embodiment of the steel structure of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS It is a typical perspective view which shows one Embodiment of the steel material of this invention. It is a typical sectional view showing one embodiment of the steel structure of the present invention.

Hereinafter, the present invention will be described in detail using embodiments.
The pressure-sensitive adhesive sheet for rust prevention of steel materials according to the present invention (hereinafter sometimes simply referred to as "adhesive sheet") 10 comprises a substrate 11 and an adhesive provided on one surface of the substrate 11, as shown in FIG. a layer 12; The pressure-sensitive adhesive sheet 10 is attached to the steel material via the pressure-sensitive adhesive layer 12, and is used to prevent the steel material from rusting.

[Base material]
The base material in the adhesive sheet has an elastic modulus of 900 MPa or less. When the modulus of elasticity is higher than 900 MPa, when the adhesive sheet is applied over the groove surface of the steel material, or over the groove surface and its surroundings, the adhesive sheet cannot follow the groove surface, etc., and wrinkles occur during application. , Peeling may occur after application.
On the other hand, when the elastic modulus is 900 MPa or less, wrinkles do not occur when the adhesive sheet is attached, and even if the steel material is stored outdoors, the adhesive sheet will not peel off due to wind and rain, and will be continuously isolated from the outside world. can properly prevent the occurrence of rust.

The elastic modulus of the substrate is preferably 820 MPa or less, more preferably 500 MPa or less, and even more preferably 450 MPa or less, in order to increase the adhesion to the adhered portion such as the groove surface and prevent the occurrence of wrinkles or peeling. 200 MPa or less is even more preferable.
The elastic modulus of the substrate is not particularly limited, but is preferably 25 MPa or more, more preferably 50 MPa or more, from the viewpoint of imparting a certain mechanical strength to the adhesive sheet and preventing breakage during peeling.

The elastic modulus of the substrate is a tensile elastic modulus that can be measured according to JISK7161. The elastic modulus of the substrate is obtained by measuring the MD and TD elastic moduli and adopting the lower elastic modulus. Moreover, when the direction of MD and TD is unknown, the elastic modulus of the direction with the lowest elastic modulus shall be adopted.
It should be noted that MD means machine direction, which is a direction that coincides with the extrusion direction, resin flow direction, etc., and TD means transverse direction, which is a direction orthogonal to MD.

Although the base material is not particularly limited, it is preferably a resin film. By using a resin film, it becomes easier to adjust the elastic modulus and the load at 10% elongation described later within a predetermined range. Specific resin films include polyester resin films such as polyethylene terephthalate (PET) resin films, polypropylene (PP) resin films, polyolefin resin films such as polyethylene (PE) resin films, acrylic resin films, polyvinyl chloride resin films, and the like. is mentioned. In addition to PP and PE, the polyolefin resin film may be an ethylene copolymer resin film such as ethylene-(meth)acrylic acid copolymer resin or its ionomer resin, ethylene vinyl acetate copolymer (EVA) resin. There may be. The resin film may be a multilayer film obtained by laminating a plurality of these resins, or may be a film obtained by mixing two or more of the resins described above, but it is also preferable to use a multilayer film.

Among these, polyester resin films and polyolefin resin films are preferred, polyolefin resin films are more preferred, and polyethylene (PE) resin films and EVA resin films are more preferred. Moreover, also in a multilayer film, the multilayer film which consists of several PE layers, and the multilayer film which consists of a PE layer and an EVA layer are preferable. By using these resin films, it becomes easy to improve the adhesion to the groove surface and its peripheral portion. Moreover, the transparency of the base film can be ensured, and the haze of the pressure-sensitive adhesive sheet can be easily reduced.
Further, the base film may be a non-stretched film or a stretched film such as a uniaxially stretched film or a biaxially stretched film.

The substrate preferably contains an ultraviolet absorber. By containing an ultraviolet absorber, deterioration of the base material and the adhesive layer can be prevented even if the adhesive sheet is left outdoors for a long period of time in a state where the adhesive sheet is attached to the steel material. In addition, the rate of change in load at 10% elongation, which will be described later, and the UV transmittance in the wavelength range of 300 to 320 nm after accelerated deterioration, which will be described later, can also be easily reduced.
As the ultraviolet absorber, those capable of absorbing light in the wavelength range of 300 to 320 nm can be used, and those having an absorption maximum in the wavelength range of 300 to 320 nm can be preferably used. The ultraviolet absorber is not particularly limited, but benzotriazole-based compounds, triazine-based compounds, benzophenone-based compounds, benzoate-based compounds, malonic acid ester-based compounds, oxalic acid anilide-based compounds, hindered amine-based compounds, and the like can be used.

The content of the ultraviolet absorber in the substrate is preferably 0.05 to 3% by mass based on the total amount of the substrate. By blending 0.05% by mass or more of the ultraviolet absorber, it is possible to appropriately prevent deterioration of the base material, adhesive layer, etc. due to ultraviolet rays. Moreover, by making it 3 mass % or less, it becomes easy to exhibit the effect commensurate with the content. The content of the ultraviolet absorber is more preferably 0.1 to 2% by mass, more preferably 0.3 to 1% by mass, from the viewpoint of effectively preventing deterioration due to ultraviolet rays even when used outdoors for a long period of time. is.

In addition, if the UV absorber contained in the base material is used outdoors for a long period of time, the UV absorber may seep out of the base material. A design that does not exude is preferable. For example, anti-fogging agents are often added to substrates used outdoors to prevent dew condensation. Preferably, the material does not contain anti-fogging agents. Surfactants are generally used as antifogging agents.

A surface layer such as a primer layer may be provided on the surface of the substrate by applying a primer agent. Moreover, the substrate may have optical transparency. Having light transmittance makes it easier to reduce the haze of the pressure-sensitive adhesive sheet. As will be described later, when the pressure-sensitive adhesive layer loses its adhesive strength due to light irradiation, the pressure-sensitive adhesive layer can be irradiated with light through the substrate.
Although the thickness of the base film is not particularly limited, it is, for example, 5 μm or more, preferably 10 μm or more, more preferably 25 μm or more, still more preferably 50 μm or more, and is, for example, 250 μm or less, preferably 200 μm or less, more preferably 150 μm. 100 μm or less, more preferably 100 μm or less.

[Adhesive layer]
The adhesive layer in the adhesive sheet is a layer composed of an adhesive. Examples of adhesives include, but are not particularly limited to, acrylic adhesives, rubber adhesives, urethane adhesives, and silicone adhesives. These may be used alone or in combination. Among these, the adhesive of the present invention is preferably an acrylic adhesive from the viewpoint of easily increasing adhesion to steel materials.
Therefore, the adhesive preferably contains a polymer component such as an acrylic polymer, a rubber component, polyurethane, or silicone as a base polymer that constitutes the adhesive main agent. is preferred.

The acrylic polymer includes a polymer obtained by polymerizing a polymerizable monomer (A) containing a (meth)acrylic acid alkyl ester monomer (A1). Specifically, the (meth)acrylic acid alkyl ester monomer (A1 ) and a polar group-containing monomer (A2), or a copolymer of the above monomers (A1) and (A2) and a monomer (A3) other than (A1) and (A2), etc. is mentioned.

(Meth)acrylic acid alkyl ester monomer (A1) is an ester of (meth)acrylic acid and an aliphatic alcohol, wherein the number of carbon atoms in the alkyl group of the aliphatic alcohol is, for example, 1 or more, preferably 2 or more, Alkyl esters derived from fatty alcohols, more preferably 4 or more and for example 18 or less, preferably 14 or less, more preferably 10 or less, are preferred. In this specification, "(meth)acrylic acid alkyl ester" means "acrylic acid alkyl ester or methacrylic acid alkyl ester". The same is true for other similar terms.

Specific (meth)acrylic acid alkyl ester-based monomers (A1) include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl ( meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate Acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate and the like.
Monomer (A1) may be used alone or in combination of two or more.
The amount of the (meth)acrylic acid alkyl ester monomer (A1) used is, for example, 50 to 100% by mass, preferably 70 to 99.9% by mass, more preferably 80 to 99.9% by mass, based on the total amount of the polymerizable monomer (A). 5% by mass.

In addition, the monomer (A1) is a (meth)acrylic having a small carbon number of the alkyl group of the aliphatic alcohol, from the viewpoint of improving the releasability (also referred to as re-peelability) when the pressure-sensitive adhesive sheet is peeled off after being attached. It preferably contains an acid alkyl ester monomer. Specifically, the monomer (A1) preferably contains a (meth)acrylic acid alkyl ester monomer in which the number of carbon atoms in the alkyl group of the aliphatic alcohol is preferably 6 or less, more preferably 4 or less.
That is, from the viewpoint of releasability and adhesiveness, the polymerizable monomer (A) particularly preferably contains a (meth)acrylic acid alkyl ester monomer in which the alkyl group of the aliphatic alcohol has 4 carbon atoms. The (meth)acrylic acid alkyl ester monomer having 4 carbon atoms in the alkyl group of the aliphatic alcohol is based on the total amount of the polymerizable monomer (A), for example 40 to 92% by mass, preferably 50 to 87% by mass, more preferably It is preferable to use 60 to 82% by mass.

The polar group in the polar group-containing monomer (A2) is a functional group that has an active hydrogen and is preferably reactive with a cross-linking agent described later, and specific examples thereof include a carboxy group, a hydroxyl group, an amino group, and the like. . Among these functional groups, at least one selected from the group consisting of a carboxy group and a hydroxyl group is preferable, and it is more preferable to contain at least a carboxy group. By using a carboxyl group, it becomes easier to increase adhesiveness and increase adhesion to steel materials. In addition, the carboxy group and hydroxyl group have high reactivity with a cross-linking agent described later, and can easily form a cross-linked structure.

Among the polar group-containing monomers (A2), monomers containing a carboxy group (hereinafter also referred to as "carboxy group-containing monomers") include acrylic acid, methacrylic acid, crotonic acid, and the like. Among these, at least one selected from the group consisting of acrylic acid and methacrylic acid is preferable, and acrylic acid is more preferable.
Among the polar group-containing monomers (A2), hydroxyl-containing monomers (hereinafter also referred to as "hydroxyl-containing monomers") include, for example, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 5-hydroxypentyl (meth) acrylate, 6-hydroxyhexyl (meth) having a hydroxyl group such as acrylate ( meth)acrylate, allyl alcohol, and the like. Among these, (meth)acrylates having a hydroxyl group are preferred.
The polar group-containing monomer (A2) may be used alone or in combination of two or more.
The amount of the polar group-containing monomer (A2) used is, for example, 0 to 20% by mass, preferably 0.1 to 8% by mass, more preferably 0.5 to 3% by mass, based on the total amount of the polymerizable monomer (A). be. When the amount of the polar group-containing monomer (A2) used is 0.1% by mass or more, the acrylic polymer can be crosslinked, and the adhesive performance can be easily improved. On the other hand, when the content is equal to or less than the above upper limit, it is possible to prevent the adhesive force from increasing more than necessary, and it becomes easy to improve the peelability of the adhesive sheet. In addition, 0% by mass means that the polymerizable monomer (A) does not contain the polar group-containing monomer (A2), and the same applies hereinafter.

The monomer (A3) other than the above (A1) and (A2) is not particularly limited as long as it is a monomer copolymerizable with the monomers (A1) and (A2). Examples include phenoxyethyl acrylate and phenoxypropyl acrylate. (meth)acrylates having a phenyl group represented by phenoxyalkyl (meth)acrylates such as styrene, α-methylstyrene, p-methylstyrene, p-chlorostyrene, styrene derivatives such as divinylbenzene, vinyl acetate, propionic acid Compounds having a vinyl ester group such as vinyl, N-vinylpyrrolidone, N-vinylmorpholine, (meth)acrylonitrile, N-cyclohexylmaleimide, N-phenylmaleimide, N-laurylmaleimide, N-benzylmaleimide, n-propyl vinyl ether , n-butyl vinyl ether, isobutyl vinyl ether, tert-butyl vinyl ether and the like.

Further, as the monomer (A3), hexanediol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, ethoxylated bisphenol A di(meth)acrylate, tris(2-hydroxyethyl) Isocyanurate tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, proxied trimethylolpropane tri(meth)acrylate, proxied glyceryl tri(meth)acrylate, neopentyl glycol adipate di(meth)acrylate, polyurethane Multifunctional monomers such as (meth)acrylates, epoxy (meth)acrylates, polyester (meth)acrylates, and liquid hydrogenated 1,2-polybutadiene di(meth)acrylates may also be used. By using a polyfunctional monomer, the acrylic polymer can be crosslinked without using a crosslinking agent, which will be described later. A polyfunctional monomer is preferably used when obtaining an acrylic polymer by photopolymerization.
Other monomers (A3) may be used alone or in combination of two or more.
The amount of the other monomer (A3) used is, for example, 0 to 20% by mass, preferably 0 to 15% by mass, more preferably 0 to 12% by mass, based on the total amount of the polymerizable monomer (A). When the monomer (A3) of is used, the amount used is, for example, 0.5% by mass or more, preferably 1% by mass or more.

Although the weight average molecular weight (Mw) of the acrylic polymer is not particularly limited, it is preferably 100,000 to 2,000,000, more preferably 300,000 to 1,500,000. By setting the weight-average molecular weight within the above range, the adhesive performance of the adhesive layer is enhanced, making it easier to enhance the adhesion to steel materials. In addition, a weight average molecular weight is a weight average molecular weight of standard polystyrene conversion measured by a gel permeation chromatography (GPC).

(crosslinking agent)
The base polymer constituting the pressure-sensitive adhesive of the present invention is preferably crosslinked. By cross-linking the base polymer, adhesive residue can be reduced when the pressure-sensitive adhesive sheet is peeled off from a steel material or the like, and the peelability can be improved. The adhesive of the present invention preferably contains a cross-linking agent and the base polymer is cross-linked by the cross-linking agent.
Examples of cross-linking agents include isocyanate-based cross-linking agents, epoxy-based cross-linking agents, aziridine-based cross-linking agents, and metal chelate-based cross-linking agents. Among these, at least one selected from the group consisting of isocyanate-based cross-linking agents and aziridine-based cross-linking agents is preferable, and aziridine-based cross-linking agents are more preferable.

The isocyanate-based cross-linking agent is not particularly limited as long as it is a compound having two or more isocyanate groups in one molecule. , isophorone diisocyanate, xylene diisocyanate, tolylene diisocyanate adduct of trimethylolpropane, and the like. Among these, tolylene diisocyanate and tolylene diisocyanate adduct of trimethylolpropane are preferable.
Examples of aziridine-based cross-linking agents include N,N'-hexamethylene-1,6-bis(1-aziridinecarboxamide), trimethylolpropane-tri-β-aziridinylpropionate, N,N'- diphenylmethane-4,4'-bis(1-aziridinecarboxamide), trimethylolpropane-tri-β-(2-methylaziridine)propionate, isophthaloylbis(2-methylaziridine) and the like.

A cross-linking agent is preferably used when the base polymer is an acrylic adhesive.
The amount of the cross-linking agent in the pressure-sensitive adhesive may be appropriately set according to the type of pressure-sensitive adhesive. 0.1 to 20 parts by mass, more preferably 0.5 to 15 parts by mass, still more preferably 1 to 8 parts by mass, and even more preferably 1 to 1.5 parts by mass. By setting the amount of the cross-linking agent to be within the above range, it is possible to impart appropriate adhesive performance to the pressure-sensitive adhesive layer while improving the releasability and preventing adhesive residue at the time of peeling.

(tackifying resin)
The adhesive preferably further contains a tackifying resin. Examples of tackifying resins include rosin-based resins, terpene-based resins, phenol-based resins, terpene-phenol-based resins, xylene-based resins, coumarone-based resins, ketone-based resins, and modified resins thereof.
Among these, terpene phenolic resins are preferred. In addition, a terpene phenol-based resin is a resin having a terpene structure and a phenol structure.
The tackifying resin may be used alone or in combination of two or more.
The content of the tackifying resin in the adhesive is preferably 1 to 50 parts by mass, more preferably 2 to 20 parts by mass, based on 100 parts by mass of the base polymer (for example, an acrylic polymer in the case of an acrylic adhesive). parts by mass, more preferably 3 to 10 parts by mass. By setting the content within the above range, appropriate adhesiveness can be imparted to the pressure-sensitive adhesive layer.

The pressure-sensitive adhesive layer of the present invention may lose its adhesive force due to an external stimulus. In the pressure-sensitive adhesive sheet of the present invention, if the pressure-sensitive adhesive layer uses a layer whose adhesive strength is reduced by an external stimulus, the pressure-sensitive adhesive strength can be reduced before peeling, so that easy peelability can be ensured during peeling. Therefore, even if the pressure-sensitive adhesive sheet of the present invention has high adhesion to steel materials, it can be easily peeled off without leaving adhesive residue or causing cuts in the base material. For example, if there is residue on the groove surface due to adhesive residue or cutting of the base material, the residue may cause blow holes during welding, which may lead to a decrease in weld strength. By preventing breakage, such a decrease in welding strength can be suppressed. In addition, it is possible to improve the workability when peeling off the pressure-sensitive adhesive sheet.
However, in the pressure-sensitive adhesive sheet of the present invention, from the viewpoint of workability, etc., it is preferable that the pressure-sensitive adhesive layer does not lose its adhesive force due to the external stimulus. The pressure-sensitive adhesive layer can have good releasability by appropriately adjusting the polymerizable monomer (A), the cross-linking agent, and the like as described above, without reducing the pressure-sensitive adhesive strength due to an external stimulus.

External stimuli include heat, light, moisture, contact with solvents such as alcohol, and the like. Among these, heat is preferred.
When the external stimulus is heat, the adhesive force can be easily reduced with a simple device. In addition, the steel material to which the pressure-sensitive adhesive sheet of the present invention is attached is often stored outdoors, but even if it is stored outdoors and left in an environment exposed to sunlight for a long period of time, the adhesive strength decreases. By making the temperature relatively high, it is possible to prevent the adhesion to the steel material from deteriorating during storage.

(adhesive strength reducing component)
The pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer of the present invention preferably contains a component (adhesion-reducing component) that reduces the adhesive strength of the pressure-sensitive adhesive layer due to an external stimulus. Specific examples include foaming agents, thermally expandable inorganic substances, heat-meltable powders, heat-dehydrating inorganic powders, and heat-meltable crystalline polymers. These may be used individually by 1 type, and may use 2 or more types together.

<Blowing agent>
The foaming agent is a foaming agent that foams by an external stimulus such as heat or light. Specific examples include a heat-sensitive foaming agent that foams by heat and a photosensitive foaming agent that foams by light. , heat-sensitive blowing agents are preferred. A foaming agent may be used individually by 1 type, and may use 2 or more types together.
Moreover, expansive fine particles are preferable as the foaming agent. Expandable microparticles are microparticles having a shell-core structure, and the volume of a substance (core) contained within the outer shell (shell) increases due to an external stimulus such as light or heat, causing the outer shell to expand. particles.

The heat-sensitive foaming agent includes thermally decomposable foaming agents and thermally expandable fine particles, and among these, the thermally expandable fine particles are preferred. The thermally expandable fine particles are so-called thermally expandable microcapsules, and include a substance that volatilizes or expands when heated inside a shell resin.
In thermally expandable microcapsules, the outer shell resin is softened by heating, and the encapsulating substance volatilizes or expands, so that the pressure causes the outer shell to expand and the particle size to increase. The substance encapsulated inside the thermally expandable microcapsules may be gas, liquid, or solid, but preferably becomes gas or liquid at normal temperature (25° C.) when encapsulated inside the capsule.

The outer shell of the thermally expandable microcapsules is preferably made of a thermoplastic resin. Thermoplastic resins include, for example, vinyl polymers such as ethylene, styrene, vinyl acetate, vinyl chloride, vinylidene chloride, acrylonitrile, butadiene and chloroprene, copolymers thereof, polyamides such as nylon 6 and nylon 66, and polyethylene terephthalate. 1 type(s) or 2 or more types chosen from polyester can be used. Among these, copolymers of acrylonitrile are preferable because the included volatile substances, which will be described later, are difficult to permeate.
Examples of other monomer components that are copolymerized with acrylonitrile include acrylic acid, methacrylic acid, acrylic acid esters, methacrylic acid esters, styrene, vinyl acetate, and vinylidene chloride. The acrylonitrile copolymer preferably contains 50% by mass or more of structural units derived from acrylonitrile.

A volatile substance such as a low boiling point solvent is preferable as the inclusion substance. Volatile substances include hydrocarbons having 3 to 7 carbon atoms such as propane, propylene, butene, n-butane, isobutane, isopentane, neopentane, n-pentane, hexane and heptane, and methane such as petroleum ether, methyl chloride and methylene chloride. One or more low boiling point liquids selected from halides, chlorofluorocarbons such as CCl ₃ F and CCl ₂ F ₂ , tetraalkylsilanes such as tetramethylsilane and trimethylethylsilane, and the like are used.
Preferred examples of thermally expandable microcapsules include microcapsules in which a copolymer of acrylonitrile and vinylidene chloride is used as an outer shell resin and a hydrocarbon having 3 to 7 carbon atoms such as isobutane is encapsulated.

The average particle size of the heat-expandable microcapsules is preferably 5-100 μm, more preferably 10-80 μm.
In this specification, the average particle size is the average value of measured values when the primary particle size of 100 particles in the observed field of view is measured using a scanning electron microscope or the like. The average particle size means the average diameter of the particles when the particles are spherical, and the average major diameter of the particles when the particles are non-spherical.

The expansion starting temperature of the thermally expandable microcapsules is preferably 70 to 145°C, more preferably 80 to 140°C, still more preferably 90 to 135°C. By setting the expansion start temperature at or above these lower limits, when the steel material with the adhesive sheet attached is stored or left unattended, it will suddenly foam due to heating by sunlight or a rise in the outside temperature, causing the adhesive sheet to stick. It is possible to prevent the power from being lowered. Further, by setting the expansion initiation temperature to these upper limits or less, the adhesive strength of the adhesive layer can be reduced at a relatively low heating temperature, and workability is improved.
Also, the maximum expansion temperature of the thermally expandable microcapsules is preferably 110 to 190°C, more preferably 120 to 185°C, still more preferably 130 to 180°C. By setting the maximum expansion temperature within these ranges, the pressure-sensitive adhesive layer can be foamed by appropriate heating, and the pressure-sensitive adhesive strength can be reduced.

The expansion start temperature and maximum expansion temperature can be measured using a thermomechanical analyzer (TMA). Specifically, for example, 250 μg of a sample is placed in an aluminum container having a diameter of 7 mm and a depth of 1 mm, and a force of 0.1 N is applied from above, and the temperature is increased from 80° C. to 220° C. at a rate of 5° C./min. The temperature at which the displacement started to rise was defined as the expansion start temperature, the maximum displacement was defined as the maximum displacement, and the temperature at the maximum displacement was defined as the maximum expansion temperature. As a thermomechanical analyzer, "TMA2940" manufactured by TA Instruments can be used.

Commercially available thermally expandable microcapsules can be used. Specifically, "EXPANCEL" manufactured by Nippon Philite Co., Ltd., "Advancel" manufactured by Sekisui Chemical Co., Ltd., and "Matsumoto Micros" manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd. Fair", and "Kureha Microsphere" manufactured by Kureha Corporation.

Specific examples of thermally decomposable foaming agents include organic or inorganic chemical foaming agents having a decomposition temperature of about 160.degree. C. to 270.degree.
Organic foaming agents include azodicarbonamide, azodicarboxylic acid metal salts such as barium azodicarboxylate, azo compounds such as azobisisobutyronitrile, nitroso compounds such as N,N'-dinitrosopentamethylenetetramine, hydra Hydrazine derivatives such as zodicarbonamide, 4,4'-oxybis(benzenesulfonylhydrazide) and toluenesulfonylhydrazide, semicarbazide compounds such as toluenesulfonylsemicarbazide, and the like can be mentioned.
Examples of inorganic foaming agents include ammonium carbonate, sodium carbonate, ammonium hydrogencarbonate, sodium hydrogencarbonate, ammonium nitrite, sodium borohydride, and anhydrous monosoda citric acid. These thermal decomposition type blowing agents can be used alone or in combination of two or more.

Examples of photosensitive foaming agents include photodegradable compounds such as diazo compounds, tetrazole compounds, and azide compounds that decompose when irradiated with ionizing radiation such as ultraviolet rays to generate nitrogen gas. Moreover, the photosensitive foaming agent may be a photoexpandable microcapsule, for example, a microcapsule in which a photodegradable compound is encapsulated inside the outer shell.

The content of the foaming agent in the pressure-sensitive adhesive can reduce the adhesive strength to such an extent that it can be easily peeled off from the steel material without causing adhesive residue after foaming, while maintaining sufficient adhesive strength before foaming. quantity. Specifically, the content of the foaming agent in the pressure-sensitive adhesive is preferably 1 to 60 parts by mass, more preferably 5 to 50 parts by mass, and still more preferably 15 to 40 parts by mass with respect to 100 parts by mass of the base polymer.

<Thermal expandable inorganic material>
There are no particular restrictions on the thermally expansible inorganic material as long as it does not impair the effects of the present invention. Examples thereof include inorganic materials such as thermally expandable graphite, vermiculite (vermiculite), pearlite, mica, vermuludite, tammazite, and hydrosartite. These inorganic substances may be used alone or in combination of two or more. Among these, thermally expandable graphite is preferred.
The content of the thermally expandable inorganic material in the adhesive is, for example, 5 to 100 parts by weight, preferably 20 to 80 parts by weight, and more preferably 25 to 70 parts by weight with respect to 100 parts by weight of the base polymer.

<Heat meltable powder>
Examples of heat-meltable powders include powders that melt when heated to about 70 to 200°C, preferably about 80 to 150°C. Heat-meltable powders include non-adhesive resin powders. The non-adhesive resin powder is essentially non-adhesive to other members, and is heat-meltable resin powder that is solid at room temperature (25° C.) but melts when heated. . Usually, as the non-adhesive resin powder, one that is not compatible with the adhesive layer is used. The incompatible one is an adhesive layer to which the glass transition temperature (Tg) of the adhesive layer to which the non-adhesive resin powder is added is measured by a viscoelastic spectrometer or a differential thermal analyzer (DSC). refers to the one that hardly changes from the Tg of

Specific examples of the non-adhesive resin powder are not particularly limited, and fluororesins such as polyethylene, polypropylene, polyester, polyvinyl chloride, and polytetrafluoroethylene, perfluoro-based polymers, polycarbonates, polymers containing long-chain alkyl groups, and silicones. A powder of a polymer or oligomer, such as a base polymer, can be used. Examples of long-chain alkyl group-containing polymers include polystearyl acrylate, polystearyl acrylamide, polyvinyl stearate, polyvinyl stearyl ether, cellulose tristearate, polyvinyl stearyl carbamate, and polystearoylethyleneimine. Examples of silicone-based polymers include copolymers of phenylmethylsiloxane and dimethylsiloxane, condensation products of methylphenylsiloxane having a 2-(2-hydroxyethylthio)ethyl group and an acrylic polymer having a hydroxyl group, α,ω-dihydroxypoly Condensates of dimethylsiloxane/triacetoxyvinylsilane/TDI and the like can be mentioned. Examples of perfluoro-based polymers include poly(1,1-dihydroperfluorohexyl methacrylate), poly(N-ethyl-N-perfluorooctane sulfonamide ethyl methacrylate), methylol compounds of 11-methylperfluorooctane sulfonamide diaminotriazine, and the like. mentioned.

As the heat-meltable powder, a solid surfactant that is incompatible with the adhesive is also suitably used. Specific examples include fatty acids, higher alcohols and esters thereof. Specific examples thereof include polyhydric alcohol esters such as sorbitan monopalmitate, sorbitan monostearate, and sorbitan distearate, polyethylene glycol monostearate, polyethylene glycol distearate, propylene glycol monostearate, stearic acid monoglyceride, and palmitin. Glycerin fatty acid esters such as acid monoglyceride, oleic acid monoglyceride, stearic acid monodiglyceride, propylene glycol fatty acid esters, fatty acid esters such as mystyryl mystylate, stearyl stearate, distearyl phthalate, higher alcohols such as stearyl alcohol and cetyl alcohol, stearin acids, fatty acids such as palmitic acid and myristic acid, alkyl sulfates such as sodium lauryl sulfate, and alkyltrimethylammonium chlorides such as stearyltrimethylammonium chloride.

The particle size of the heat-meltable powder is not particularly limited, but is, for example, about 5 to 100 μm. In general, the smaller the molecular weight of the heat-meltable powder, the faster the heating effect appears. Among them, those of about 500 to 50,000 are preferable.
As the heat-meltable powder, known ones can be used, for example, those described in JP-A-7-018231 can also be used.
In the adhesive, the content of the heat-meltable powder is, for example, 1 to 100 parts by mass, preferably about 5 to 50 parts by mass, per 100 parts by mass of the base polymer.

<Inorganic salt granules>
Examples of the heat-dehydrating inorganic salt granules include inorganic salt granules having a dehydration temperature of 50 to 150° C. and containing water of crystallization. _The inorganic salt _granules include _hydrates of various metal _salts such as _FeSO4.7H2O and _Na2S2O3.5H2O . As the inorganic salt granules, known ones can be used, for example, the inorganic salt granules described in Japanese Patent No. 3561324 can be used. The average particle size of the inorganic salt granules is, for example, 0.5 to 100 μm.
Since the pressure-sensitive adhesive layer contains heat-dehydrating inorganic salt granules and releases water of crystallization when heated, the adhesive force at the interface between the pressure-sensitive adhesive layer and the adherend (steel material) is weakened, resulting in increased adhesive strength. decreases.
The content of the inorganic salt particles in the adhesive is, for example, 1 to 100 parts by mass, preferably about 5 to 50 parts by mass, per 100 parts by mass of the base polymer.

<Crystalline polymer>
A heat-meltable crystalline polymer is a crystalline polymer that melts when heated. Crystalline polymers include polycaprolactone. Polycaprolactone can be easily melted when heated to a temperature higher than the melting point of polycaprolactone itself, thereby reducing adhesive strength. In addition, since polycaprolactone is a non-adhesive polymer, it can effectively improve the detachability and cleanability, leaving no adhesive residue on the adherend surface after detachment.
Also, the crystalline polymer is preferably a polymer compatible with the base polymer of the adhesive when melted. For example, polycaprolactone is compatible with the base polymer when the base polymer is an acrylic polymer.
When the crystalline polymer is compatible with the base polymer, the crystallization (recrystallization) of the crystalline polymer after heating can be delayed, and the low adhesive strength can be maintained for a long period of time after heating. .

When a crystalline polymer is used, in order to improve compatibility, the acrylic polymer constituting the base polymer contains (meth)acrylate having a hydroxyl group and (meth)acrylate having a phenyl group as the polymerizable monomer (A). ) acrylate or the like may be used. In addition, as the (meth)acrylic acid alkyl ester-based monomer (A1), an alkyl ester in which the alkyl group of an aliphatic alcohol has 4 to 10 carbon atoms may be used. Furthermore, as described below, a carboxy group-containing monomer may be used to react with a specific cross-linking agent.

As described above, the base polymer that constitutes the main adhesive agent is preferably crosslinked, but the polycaprolactone that constitutes the crystalline polymer does not need to be crosslinked. Since polycaprylactone usually has hydroxyl groups at both ends of the molecule, when cross-linking with the above-mentioned cross-linking agent, the base polymer preferably has a functional group other than a hydroxyl group (for example, a carboxy group) in the molecule. It is preferable to use agents that react with functional groups other than hydroxyl groups. Specifically, an aziridine-based cross-linking agent is preferred, and a bisamide-based one such as isophthaloylbis(2-methylaziridine) is more preferred.

Polycaprolactone may be any material as long as it is a substantially non-sticky solid at room temperature (25° C.) and has crystallinity capable of being melted by heating. Examples of polycaprolactone include polycaprolactone obtained by polymerizing a starting material containing caprolactone, and polycaprolactone containing polymerized units (units) obtained by ring-opening polymerization of caprolactone in the molecule.
The melting point of polycaprolactone varies depending on the molecular weight, but is usually 30 to 70°C, preferably 35 to 65°C, and particularly preferably 40 to 60°C.
The weight average molecular weight of polycaprolactone is usually in the range of 1,000 to 100,000, preferably 2,000 to 50,000, and more preferably 3,000 to 40,000.
As the crystalline polymer, a urethane-modified polymer obtained by reacting a diisocyanate compound and polycaprolactone to extend the chain may be used.
A known crystalline polymer can be used as such a crystalline polymer, and for example, the crystalline polymer described in Japanese Patent No. 4768106 can be used.

The content of the crystalline polymer in the adhesive is, for example, preferably 1 to 100 parts by mass, more preferably 5 to 75 parts by mass, and even more preferably 15 to 60 parts by mass with respect to 100 parts by mass of the base polymer.

Among the components described above, it is preferable to use a foaming agent, more preferably a heat-sensitive foaming agent, and particularly preferably a thermally expandable fine particle as the adhesive strength-lowering component. By using a heat-type foaming agent, particularly thermally expandable fine particles, it becomes easier to adjust the temperature at which the adhesive strength is reduced within a desired temperature range. In addition, the adhesive strength of the adhesive layer can be easily lowered by an external stimulus (that is, heating), and the releasability tends to be good.

The adhesive preferably contains an ultraviolet absorber. Specific examples of the ultraviolet absorber contained in the pressure-sensitive adhesive include those listed for the base material. The content of the ultraviolet absorber in the pressure-sensitive adhesive is preferably 0.05-4 parts by mass with respect to 100 parts by mass of the base polymer. By blending 0.05 parts by mass or more of the ultraviolet absorber, deterioration of the adhesive layer due to ultraviolet rays can be prevented. Moreover, by making it 4 mass parts or less, it becomes easy to exhibit the effect commensurate with content. The content of the ultraviolet absorber is more preferably 0.1 to 3 parts by mass, more preferably 0.3 to 2 parts by mass, from the viewpoint of preventing deterioration due to ultraviolet rays even when used outdoors for a long period of time. .
In addition, the ultraviolet absorber may be contained in one of the pressure-sensitive adhesive and the base material, or may be contained in both of them.

In addition to the above, the adhesive may contain fillers, antioxidants, ultraviolet inhibitors, plasticizers, viscosity modifiers, pigments, dyes, and other additives commonly used in adhesives (other additives). may be blended. Moreover, when the base polymer constituting the adhesive is photopolymerizable, a photopolymerization initiator or the like may be blended.

The thickness of the adhesive layer is not particularly limited, but may be, for example, about 10 to 1000 μm, preferably 20 to 700 μm, more preferably 30 to 200 μm.

A release sheet may be attached to the adhesive layer on the side opposite to the side on which the substrate is provided. When the release sheet is attached, the pressure-sensitive adhesive layer is protected by the release sheet before use.
The release sheet is usually peeled off and removed from the pressure-sensitive adhesive layer immediately before use. A known release sheet can be used, and for example, a release sheet substrate such as a resin film or a paper substrate having at least one surface treated with a release agent can be used.

The load of the pressure-sensitive adhesive sheet at 10% elongation is preferably 10 N/10 mm or less, for example, from the viewpoint of imparting constant adhesion. In addition, from the viewpoint of reducing performance changes even after long-term outdoor use, the pressure-sensitive adhesive sheet has a rate of change of 15% or less in the load at 10% elongation when accelerated deterioration is performed under the accelerated deterioration conditions described later. good.
In addition, the adhesive sheet has a load at 10% elongation of 8.5 N / 10 mm or less, and a rate of change in the load at 10% elongation when accelerated deterioration is performed under the accelerated deterioration conditions described later is 10% or less. is preferred. By keeping both the load at 10% elongation and the rate of change of the load at 10% elongation at or below these upper limits, the adhesive sheet can be attached to the steel material surface such as the groove surface with high adhesion, and the Even after being used outdoors for a period of time, the change in performance is reduced, and it becomes easy to maintain good peelability. From these viewpoints, the load at 10% elongation of the adhesive sheet is more preferably 7 N/10 mm or less, more preferably 5.6 N/10 mm or less, and the rate of change of the load at 10% elongation is 9.4%. The following is more preferable, 7% or less is even more preferable, and 3% or less is even more preferable.
The load at 10% elongation is not particularly limited, but from the viewpoint of imparting a certain mechanical strength to the base material, for example, it is preferably 1 N/10 mm or more, preferably 2 N/10 mm, more preferably 2.5 N/ 10 mm or more. In addition, the lower the change rate of the load at 10% elongation, the better, and it is sufficient if it is 0% or more.

(Accelerated deterioration condition)
In a weather resistance tester, the lamp light source is a xenon lamp, the wavelength is 365 nm, the illuminance is 60 W/m ² , the irradiation temperature is 63 ° C., and the shower is 120 minutes for 18 minutes. do.
The rate of change of the load at 10% elongation is calculated by |X2−X1|/X1×100, where X1 is the load at 10% elongation before accelerated deterioration and X2 is the load at 10% elongation after accelerated deterioration. be done.
In addition, the load at 10% elongation is preferably a value measured for MD.

The adhesive sheet of the present invention preferably has an ultraviolet transmittance of 1% or less in the wavelength range of 300 to 320 nm after accelerated deterioration under the following accelerated deterioration conditions. When the UV transmittance after the accelerated deterioration is 1% or less, deterioration of the base material and the adhesive layer is suppressed even when used outdoors for a long period of time, and adhesiveness, peelability, etc. are good over a long period of time. Become. Therefore, for example, even after long-term use, it is possible to prevent breakage of the base material and the occurrence of adhesive residue when peeling the adhesive sheet from the steel material.
The ultraviolet transmittance is more preferably 0.5% or less, still more preferably 0.3% or less, and even more preferably 0.2% or less. In addition, the lower the UV transmittance, the better.
(Accelerated deterioration condition)
In a weather resistance tester, the lamp light source is a xenon lamp, the wavelength is 365 nm, the illuminance is 60 W/m ² , the irradiation temperature is 63 ° C., and the shower is 120 minutes for 18 minutes. do.

The adhesive sheet of the present invention preferably has a haze of 40% or less. When the haze is 40% or less, the adhesive sheet has good visibility. Therefore, the groove surface and its peripheral portion can be visually observed with the adhesive sheet attached, and the state of the groove surface such as the presence or absence of rust can be confirmed without removing the adhesive sheet. The haze of the adhesive sheet is more preferably 30% or less, even more preferably 25% or less, and even more preferably 15% or less.
The haze can be adjusted within the above range by using highly transparent substrates and pressure-sensitive adhesive layers. Specifically, the substrate and the pressure-sensitive adhesive layer should not contain a coloring agent, or if they do contain a coloring agent, the amount should be small. Furthermore, the haze can be reduced by using a resin film made of a specific material as the base material.

(Manufacturing method of adhesive sheet)
The production method of the adhesive sheet is not particularly limited, but the adhesive sheet can be obtained, for example, by the following method.
First, a base polymer, a cross-linking agent that is appropriately blended as necessary, a tackifying resin, an adhesive force-lowering component, and other additives are mixed to obtain an adhesive, which is applied to a release sheet. The pressure-sensitive adhesive layer is preferably formed by heating and drying. The adhesive may be appropriately diluted with an organic solvent or the like, and the diluted adhesive may be applied to the release sheet. The pressure-sensitive adhesive layer formed on the release sheet can then be laminated to a substrate to obtain a pressure-sensitive adhesive sheet.
Alternatively, the pressure-sensitive adhesive sheet may be produced by directly applying the above-mentioned pressure-sensitive adhesive or a diluted product thereof to a substrate, and optionally drying by heating to form a pressure-sensitive adhesive layer on the substrate.

The heating conditions for forming the pressure-sensitive adhesive layer can be selected as appropriate. It is good to carry out at about 120 degreeC. Moreover, when using a foaming agent, the heating should be performed at a temperature at which the foaming agent does not foam. Therefore, for example, when the foaming agent is a thermally expandable microcapsule, the heating should be performed at a temperature lower than the expansion initiation temperature.
Similarly, when thermally expandable inorganic substances, heat-meltable powders, heat-dehydrated inorganic powders, etc. are used, they should be heated at a temperature at which they do not thermally expand, melt, or dehydrate.

In addition, when the base polymer can be obtained by photopolymerizing a polymerizable monomer, the polymerizable monomer, a cross-linking agent, a tackifying resin, an adhesive strength-lowering component, and a light The adhesive may be produced by photopolymerizing an adhesive precursor obtained by mixing a polymerization initiator and other additives. In this case, the base polymer is preferably an acrylic polymer, and the polymerizable monomer is preferably the polymerizable monomer (A).
The pressure-sensitive adhesive precursor may be applied to a release sheet and then polymerized by irradiation with light to form a pressure-sensitive adhesive layer. Alternatively, the pressure-sensitive adhesive precursor may be directly applied to a substrate and then irradiated with light to polymerize to form a pressure-sensitive adhesive layer to obtain a pressure-sensitive adhesive sheet.
Moreover, the method for producing the pressure-sensitive adhesive layer is not limited to the above.

[How to use the adhesive sheet]
The pressure-sensitive adhesive sheet of the present invention is used for rust-proofing the steel material by being attached to the steel material. In this specification, a structure including a steel material and an adhesive sheet attached to the steel material is also referred to as a steel structure. By attaching the adhesive sheet to the steel material, the adhered portion is shielded from the outside world, and the occurrence of rust is prevented.
In this specification, steel refers to a metal material containing at least one selected from the group consisting of iron and alloys containing iron. Specific examples of alloys containing iron include nickel-chromium steel, nickel-chromium-molybdenum steel, chromium steel, chromium-molybdenum steel, manganese steel, and other alloy steels, and various steel materials, such as carbon steel.
The shape of the steel material is not particularly limited, and may be steel plate, steel frame, pipe material, or the like. Also, the steel material may be used to construct bridges, steel towers, viaducts, tanks, plants, piers, pipelines, pillars of buildings, and the like.

The adhesive sheet may be attached to any portion of the steel material, but is preferably attached to a processed surface formed by polishing, grinding, cutting, cutting, or the like.
Further, the adhesive sheet is more preferably attached to the groove surface of the steel material. In the present invention, after groove processing for forming the groove surface of the steel material, by attaching an adhesive sheet to the groove surface and storing it, it is possible to prevent rust from occurring on the groove surface during the storage period. Therefore, when the steel materials are welded together or the steel material is welded to a member other than the steel material, problems such as a decrease in weld strength are less likely to occur.

A specific example of the cross-sectional shape of the groove surface is shown in FIG. The right side in FIG. 2 is the groove surface. The cross-sectional shape of the groove surface is not particularly limited, and as shown in FIG. As shown in FIG. 2(b), the groove surface may be an inclined surface. Moreover, as shown in FIG. 2(c), it may be composed of vertical planes perpendicular to the front and back surfaces of the steel material, or may be a combination of inclined planes and vertical planes (not shown). Moreover, the groove surface may include a curved surface as appropriate. Specifically, it may consist of one curved surface as shown in FIG. 2(d), or may consist of two curved surfaces as shown in FIG. 2(e).

When the adhesive sheet 10 is used by being attached to the groove surface 20 of the steel material 15, it may be used by being attached only to the groove surface. 20 and its peripheral portion 21. By attaching the adhesive sheet 10 to the peripheral portion 21 as well, the groove surface 20 can be more appropriately protected. The peripheral portion is, for example, a portion within 100 mm along the steel material surface from the groove surface 20 in the steel material 15 . Moreover, two or more adhesive sheets 10 may be attached to the groove surface 20 in some cases. Therefore, depending on the adhesive sheet 10 , it may be attached only to the peripheral portion 21 .
As shown in FIGS. 2 and 3, the groove surface 20 often has a complicated shape such as a part that is pointed or an angular shape that is connected to the peripheral portion 21. Since the adhesive sheet has a low elastic modulus of the base material, even when it is attached to such a groove surface, it can be appropriately stretched and can be attached so as to follow the adherend portion. Therefore, the pressure-sensitive adhesive sheet can be adhered to the groove surface of the steel material with high adhesion.

Similarly, as shown in FIGS. 4 and 5, the peripheral portion 21 of the groove surface 20 may also have a complicated shape. For example, H steel shown in FIGS. A connection portion between the plate portion 41 and the second plate portion 42 is provided with, for example, a notch 43 and may have a complicated shape. In order to properly protect the groove surface 20, the adhesive sheet 10 should also be applied to the peripheral portion having such a complicated shape. In the present invention, since the base material 11 has a low elastic modulus, the pressure-sensitive adhesive sheet 10 can be properly stretched and adhered even when attached to the peripheral portion 21 having such a complicated shape as shown in FIG. It can be attached by following the part. By attaching the adhesive sheet 10 to the peripheral portion 21 with high adhesion, the groove surface 20 can be more appropriately protected. In addition, by preventing the peripheral portion 21 from rusting in addition to the groove surface 20, the steel material can be welded more appropriately.

The adhesive sheet 10 is attached to the groove surface 20 and its peripheral portion 21 as described above. good. 3 and 5, the mountain fold M is folded with the substrate 11 side on the outside and the adhesive layer 12 on the inside. It is preferably folded at an angle RM greater than or equal to degrees.
In addition, the valley fold V is, as shown in FIG. 5, folded with the substrate 11 side inside and the adhesive layer 12 outside. It is preferably folded at angle RV. The angle RM of the mountain fold M is less than 180°, but usually about 150° or less. Similarly, the angle VM of the valley fold M is also less than 180°, but normally it may be about 150° or less, or about 120° or less.

When the pressure-sensitive adhesive sheet 10 is folded at 90° or more in a mountain fold or at 45° or more in a valley fold, it becomes easy to peel off from the adhered portion due to the elasticity of the base material 11 or the like. Since the rate and the load at 10% elongation can be reduced, even if the tape is folded at a large angle as described above, it can be prevented from being unexpectedly peeled off from the adhered portion. In addition, even if the adhesive sheet 10 is exposed to the outdoors for a long period of time, the pressure-sensitive adhesive sheet 10 can maintain a low load at 10% elongation, for example. Furthermore, since the adhesive tape 10 can be made to have excellent releasability even after being exposed outdoors for a long period of time, it is possible to suppress delamination defects such as adhesive residue and breakage of the base material during delamination.

In addition, the steel material (steel structure) to which the adhesive sheet is attached is preferably stored after a certain period of time has passed after the adhesive sheet is attached, and then the adhesive sheet is peeled off and the next processing is performed.
For example, as shown in FIGS. 3 and 5, the steel structure having the adhesive sheet 10 attached to the groove surface 20 or to the groove surface 20 and its peripheral portion 21 is attached to the adhesive sheet after a certain period of time has passed since the attachment. 10 is peeled off, and the exposed groove surface 20 may be welded to another member. Here, as the welding process, it is preferable to join the steel materials by preparing two steel materials, matching the groove surfaces of the respective steel materials, and welding the groove surfaces together.
The period of time from when the adhesive sheet is attached to when it is peeled off is not particularly limited, but is, for example, about 1 day to 1 year, but generally about 1 to 6 months.
The groove surface to which the pressure-sensitive adhesive sheet is attached may be roughened by surface treatment such as blasting.

When the pressure-sensitive adhesive layer loses its adhesive strength due to an external stimulus, it is preferable to apply an external stimulus to the pressure-sensitive adhesive layer before peeling off the pressure-sensitive adhesive sheet attached to the steel material. The external stimulus may be appropriately selected according to the type of pressure-sensitive adhesive layer. For example, the adhesive layer may be heated, or the adhesive layer may be irradiated with light. Alternatively, the pressure-sensitive adhesive sheet may be exposed to a high-humidity environment, or the pressure-sensitive adhesive layer may be brought into contact with an organic solvent such as alcohol.
For example, the adhesive force-reducing component contained in the adhesive layer is a heat-sensitive foaming agent, a thermally expandable inorganic substance, a heat-melting powder, a heat-dehydrating inorganic powder, a heat-melting crystalline polymer, or the like. , the adhesive strength of the adhesive layer to the steel material may be reduced by heating.
When the external stimulus is heat, the heating temperature may be appropriately selected according to the type of the adhesive force-reducing component, and is, for example, 80 to 300°C, preferably 110 to 240°C, more preferably 120 to 200°C. By setting the heating temperature within the above range, the adhesive force can be reduced with a relatively simple heating device.

In addition, when the adhesive force-reducing component is a photosensitive foaming agent or the like, it is preferable to reduce the adhesive force of the adhesive layer to the steel material by irradiating the adhesive layer with light through the base material. The type of light may be appropriately selected according to the type of photosensitive foaming agent, and includes visible light, ultraviolet rays, electron beams, X-rays, neutron beams, etc. Among these, ultraviolet rays are preferred.

In another aspect, the present invention is used to prevent rust by being attached to a steel material, and comprises a base material and an adhesive layer provided on one surface of the base material, and the adhesive layer is used to prevent external stimulation. Also provided is a pressure-sensitive adhesive sheet for steel material protection, characterized in that the pressure-sensitive adhesive strength is reduced by
In the pressure-sensitive adhesive sheet for steel materials according to another aspect, the pressure-sensitive adhesive layer loses its adhesive force due to external stimulus, so that easy peelability can be ensured when peeling. Therefore, in another aspect, even if the adhesion of the pressure-sensitive adhesive sheet to the steel material is increased, the pressure-sensitive adhesive sheet can be easily peeled off without causing adhesive residue or cuts in the base material when peeled off. can. Therefore, as described above, a decrease in welding strength can be suppressed, and workability at the time of peeling off the pressure-sensitive adhesive sheet can be improved. Also in another aspect, the elastic modulus of the base material is preferably 900 MPa or less as described above.
The details of the base material, the details of the pressure-sensitive adhesive layer, the details of the method of using the pressure-sensitive adhesive sheet, and the like relating to other aspects are as described above, and thus the description thereof will be omitted.

Although the present invention will be described in more detail by way of examples, the present invention is not limited by these examples.

[Evaluation method]
The pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples were evaluated by the following methods. Each evaluation was performed under a room temperature environment (23° C., 50% RH) unless otherwise specified.
(1) Adhesion Test A tubular steel material having an outer diameter of 101.6 mm, a thickness of 40 mm, and a beveled end face having a triangular cross-section as shown in FIG. 3 was prepared. In addition, the groove surface was blasted to give a roughness of Ra=50 μm. As shown in FIG. 3, two adhesive sheets with a width of 150 mm and a length of 200 mm are pasted along the circumferential direction over the end surface where the groove surface is formed and the inner and outer surfaces of the tubular steel material, and the groove surface is The entire circumference was covered with the adhesive sheet. The adhesiveness of the adhesive sheet to the steel material at that time was evaluated according to the following evaluation criteria.
A: There are no wrinkles or peeling on the attached pressure-sensitive adhesive sheet.
B: The attached pressure-sensitive adhesive sheet has wrinkles, but is not peeled off. Alternatively, although the attached adhesive sheet does not have wrinkles, peeling or lifting occurs at the tape end.
C: The attached pressure-sensitive adhesive sheet has wrinkles and peeling.

(2) Peelability (1)
An adhesive sheet is attached to a steel plate (SS400), and the steel plate (SS400) to which the adhesive sheet is attached is measured by a sunshine weather meter (manufactured by Iwasaki Electric Co., Ltd., eye super xenon tester "XER-W83"), lamp light source: xenon. Under the conditions of a lamp, illuminance of 60 W/m ² (wavelength of 365 nm), irradiation temperature of 63° C., and shower for 18 minutes in 120 minutes, the film was left for 750 hours for accelerated deterioration. After that, it was taken out from the weather meter, the pressure-sensitive adhesive sheet was peeled off from the steel material, and the peelability at the time of peeling was evaluated according to the following evaluation criteria.
The adhesive sheet containing a foaming agent in the adhesive layer was heated at 130° C. for 1 minute immediately before peeling using a hot air processing machine “Plajet temperature variable type” manufactured by Ishizaki Electric Co., Ltd. to remove the foaming agent. foamed. When the adhesive sheet was attached to the steel plate (SS400), it was cut into a size of 50 mm×100 mm and attached only to one surface of the steel plate. The same was applied to the following evaluation of peelability (2) and measurement of ultraviolet transmittance after accelerated deterioration.
AA: Can be peeled off without adhesive residue, and has a strength of 10.0 N/25 mm or less in a 180° peel test.
A: It can be peeled off without adhesive residue, and the strength in the 180° peel test is higher than 10.0 N/25 mm and not higher than 18.0 N/25 mm.
B: Adhesive residue is clearly visible, but the substrate can be peeled off without breakage, and the strength is greater than 18.0 N/25 mm in the 180° peel test.
C: There is adhesive residue on the entire surface visually, or the base material is broken and cannot be peeled off, or the strength in the 180° peel test is greater than 18 N/25 mm.

(2) Peelability (2)
An adhesive sheet is attached to a steel plate (SS400), and the steel plate (SS400) to which the adhesive sheet is attached is measured by a sunshine weather meter (manufactured by Iwasaki Electric Co., Ltd., eye super xenon tester "XER-W83"), lamp light source: xenon. Under the conditions of a lamp, illuminance of 60 W/m ² (wavelength of 365 nm), irradiation temperature of 63° C., and shower for 18 minutes in 120 minutes, the film was left for 1500 hours for accelerated deterioration. Then, it was taken out from the weather meter, the pressure-sensitive adhesive sheet was peeled off from the steel material, and the peelability was evaluated according to the following evaluation criteria.
The adhesive sheet containing a foaming agent in the adhesive layer was heated at 130° C. for 1 minute immediately before peeling using a hot air processing machine “Plajet temperature variable type” manufactured by Ishizaki Electric Co., Ltd. to remove the foaming agent. foamed.
AA: Can be peeled off without adhesive residue, and has a strength of 10.0 N/25 mm or less in a 180° peel test.
A: It can be peeled off without adhesive residue, and the strength in the 180° peel test is higher than 10.0 N/25 mm and not higher than 18.0 N/25 mm.
B: Adhesive residue is clearly visible, but the substrate can be peeled off without breakage, and the strength in the 180° peel test is greater than 18.0 N/25 mm.
C: There is adhesive residue on the entire surface visually, or the base material is broken and cannot be peeled off, or the strength in the 180° peel test is greater than 18.0 N/25 mm.

(3) Ultraviolet transmittance after accelerated deterioration An adhesive sheet is attached to a steel plate (SS400), and the steel plate (SS400) to which the adhesive sheet is attached is subjected to a sunshine weather meter (manufactured by Iwasaki Electric Co., Ltd., eye super xenon tester "XER -W83") under the conditions of lamp light source: xenon lamp, illuminance 60 W/m ² (wavelength 365 nm), irradiation temperature 63° C., shower for 18 minutes in 120 minutes, and left for 1500 hours for accelerated deterioration. After that, it was taken out from the weather meter, the pressure-sensitive adhesive sheet was peeled off from the steel material, and the ultraviolet transmittance of the peeled pressure-sensitive adhesive sheet was measured under the following conditions.
(Method for measuring ultraviolet transmittance)
Cut out a sample to a size of about 20 mm × 30 mm, set it in a measuring instrument (manufactured by JASCO Corporation, "UV-visible light spectrophotometer V-750DS", perform measurement, and obtain a wavelength range of 300 to 320 nm. The average value of the transmittance was obtained from the integrated value of the absorptance.

(4) Haze A sample was set in a measuring device ("NDH8000" manufactured by Nippon Denshoku) to measure haze (cloudiness).

(5) Visibility Evaluation A pressure-sensitive adhesive sheet was attached to the blasted surface of a steel plate (SS400) whose surface was blasted to give a roughness of Ra=50 μm. The state of the blasting treatment on the surface of the pressure-sensitive adhesive sheet was visually observed and evaluated according to the following evaluation criteria.
A: The blasted surface condition can be confirmed (high visibility)
B: The color of the adherend can be confirmed (although it is transparent, visibility is low)
C: The color and surface condition of the steel plate cannot be confirmed at all

(6) Load at 10% elongation The load at 10% elongation is a pressure-sensitive adhesive sheet sample cut into strips of 10 mm x 150 mm. The load was measured when the sample was pulled at .The load when the sample was elongated by 10% with respect to the distance between the chucks was read, and the load at 10% elongation was taken.In this example and comparative example, when the MD was elongated by 10% load was adopted.

(7) Change rate of load at 10% elongation The adhesive sheet is attached only to one side of the steel plate (SS400), and the steel plate (SS400) with the adhesive sheet is attached to the sunshine weather meter (manufactured by Iwasaki Electric Co., Ltd., eye super xenon). Tester "XER-W83") under the conditions of lamp light source: xenon lamp, illuminance of 60 W/m ² (wavelength: 365 nm), irradiation temperature of 63° C., shower for 18 minutes in 120 minutes, and left for 1500 hours for accelerated deterioration. After that, it was taken out from the weather meter, the pressure-sensitive adhesive sheet was peeled off from the steel material, and the load at 10% elongation was measured by the same measuring method as described above, and the load at 10% elongation after accelerated deterioration was determined.
Let X1 be the load at 10% elongation before accelerated deterioration, and X2 be the load at 10% elongation after accelerated deterioration.
(8) Elastic modulus The elastic modulus of the substrate was measured according to the method described in the specification.

Cross-linking agent: N,N'-hexamethylene-1,6-bis(1-aziridinylcarboxamide)
Tackifying resin: Terpene phenolic resin Blowing agent: Thermally expandable microcapsules, manufactured by Sekisui Chemical Co., Ltd., trade name "Advancel EMH204", average particle size 36-44 μm, expansion start temperature 110-130° C., maximum expansion temperature 160 ～180℃
UV absorber: benzotriazole type, manufactured by ADEKA "ADEKA STAB LA-32"

Resin film A: "Vegitalon NEXT-S" manufactured by Sumika Sekisui Film Co., Ltd., olefin resin film, thickness 75 μm
Resin film A-1: Sumika Sekisui Film Co., Ltd. "Vegitalon NEXT-S" (without anti-fogging agent), olefin resin film, thickness 100 μm
Resin film B: "Himilan 1707" manufactured by Mitsui Dow Co., Ltd., ethylene-based copolymer resin film, thickness 50 μm
Resin film C: "Tretec TR05HB" manufactured by Toray Industries, Inc., unstretched PP resin film, thickness 45 μm
Resin film D: "Acryprene MBS121E" manufactured by Mitsubishi Chemical Corporation, acrylic resin film, thickness 75 μm
Resin film E: "Hananoka UV Long" manufactured by Sumika Sekisui Film Co., Ltd., olefin resin film, thickness 150 μm
Resin film F: "Shinnoka" manufactured by Sumika Sekisui Film Co., Ltd., olefin resin film, thickness 100 μm
Resin film G: "Purelon" manufactured by Sumika Sekisui Film Co., Ltd., olefin resin film, thickness 65 μm

[Example 1]
99 parts by mass of 2-ethylhexyl acrylate (2-EHA), 1 part by mass of acrylic acid (Aac), and 0.2 parts by mass of AIBN (azobisisobutyronitrile) as a polymerization initiator were added and heated to 60°C in a flask. , to obtain a (meth)acrylic copolymer by solution polymerization for 6 hours.
To 100 parts by mass of the obtained acrylic copolymer, 5 parts by mass of a tackifier and 1.7 parts by mass of a cross-linking agent are added and mixed by stirring at room temperature using a spatula to prepare an adhesive. did. The pressure-sensitive adhesive was applied to one surface of the substrate using an applicator so that the thickness of the pressure-sensitive adhesive layer after drying was 50 μm. After coating, the adhesive tape was obtained by drying at 100°C for 3 minutes and aging at 40°C for 3 days. Each evaluation was implemented about the obtained adhesive tape. Table 2 shows the evaluation results.

[Examples 2 and 3]
It was carried out in the same manner as in Example 1, except that the base material was changed as shown in Table 1.

[Example 4]
The procedure was carried out in the same manner as in Example 3, except that the adhesive was changed to an adhesive obtained by further adding 20 parts by mass of a foaming agent.

[Example 5]
A (meth)acrylic copolymer was obtained by changing the formulation for synthesizing the acrylic polymer as shown in Table 1 and carrying out solution polymerization. To 100 parts by mass of the obtained (meth)acrylic copolymer, a cross-linking agent and a tackifying resin were added according to the formulation shown in Table 2 to prepare a pressure-sensitive adhesive. It was carried out in the same manner as in Example 1 except that it was changed to

[Examples 6 to 10, Comparative Example 2]
It was carried out in the same manner as in Example 5, except that the base material was changed as shown in Table 2.

[Example 11]
As shown in Table 2, the same procedure as in Example 1 was carried out, except that a pressure-sensitive adhesive obtained by further adding 0.8 parts by mass of an ultraviolet absorber was used, and the base material shown in Table 2 was used. did.

[Comparative Example 1]
It was carried out in the same manner as in Example 1, except that the base material was changed as shown in Table 2.

For each base material, the elastic modulus was measured. Table 1 shows the results. Table 1 also shows the content (% by mass) of the ultraviolet absorber in each substrate.

* indicates that the measurement could not be performed because the base material was broken.
2EHA = 2-ethylhexyl acrylate, BA = n-butyl acrylate, Aac = acrylic acid

As is clear from the results in Table 2 above, the pressure-sensitive adhesive sheet of this example can be attached with high adhesion to the end surface of the steel material on which the groove surface is formed by lowering the elastic modulus of the base material. was made. On the other hand, the pressure-sensitive adhesive sheets of the comparative examples could not be adhered to the end face of the steel material having the grooved surface with high adhesion because the elastic modulus of the base material was high.

In Example 4, in which the pressure-sensitive adhesive layer contained a foaming agent and the pressure-sensitive adhesive strength was reduced by heating, the heat was applied before the pressure-sensitive adhesive layer was peeled off from the steel material. Moreover, even if it did not apply an external stimulus, it had favorable peelability by using a specific adhesive layer other than Example 4.
Furthermore, the adhesive tapes of Examples 5 to 8 and Example 12, which have a relatively low 10% elongation load and a low rate of change in ultraviolet transmittance and 10% elongation load after accelerated deterioration, are after a long-term deterioration test. Peelability (Peelability (2)) was also good, and it was confirmed that even when exposed to the outdoors for a long period of time, there was little change in performance and the peelability was improved.

REFERENCE SIGNS LIST 10 steel material rust prevention adhesive sheet 11 base material 12 adhesive layer 15 steel material 20 groove surface 21 peripheral portion

Claims (15)

1. A pressure-sensitive adhesive sheet for rust prevention of steel materials that is attached to steel materials and used for rust prevention,
   A pressure-sensitive adhesive sheet for rust prevention of steel materials, comprising a base material and a pressure-sensitive adhesive layer provided on one surface of the base material, wherein the base material has an elastic modulus of 900 MPa or less.
2. 2. The pressure-sensitive adhesive sheet for rust prevention of steel materials according to claim 1, wherein the ultraviolet transmittance in the wavelength region of 300 to 320 nm after accelerated deterioration under the following accelerated deterioration conditions is 1% or less.
   (Accelerated deterioration condition)
   In a weather resistance tester, the lamp light source is a xenon lamp, the wavelength is 365 nm, the illuminance is 60 W/m ² , the irradiation temperature is 63 ° C., and the shower is 18 minutes out of 120 minutes. The sheet is left for 1500 hours.
3. Claim 1 or 2, wherein the load at 10% elongation is 8.5 N / 10 mm or less, and the change rate of the load at 10% elongation when accelerated deterioration is performed under the following accelerated deterioration conditions is 10% or less. Adhesive sheet for rust prevention of steel materials described.
   (Accelerated deterioration condition)
   In a weather resistance tester, the lamp light source is a xenon lamp, the wavelength is 365 nm, the illuminance is 60 W/m ² , the irradiation temperature is 63 ° C., and the shower is 18 minutes out of 120 minutes. The sheet is left for 1500 hours.
4. The pressure-sensitive adhesive sheet for rust prevention of steel materials according to any one of claims 1 to 3, wherein at least one of the base material and the pressure-sensitive adhesive layer contains an ultraviolet absorber.
5. The pressure-sensitive adhesive sheet for rust prevention of steel materials according to any one of claims 1 to 4, wherein the haze value of the pressure-sensitive adhesive sheet for steel rust prevention is 40% or less.
6. The pressure-sensitive adhesive sheet for rust prevention of steel materials according to any one of claims 1 to 5, wherein the pressure-sensitive adhesive layer has a reduced adhesive force due to an external stimulus.
7. The pressure-sensitive adhesive sheet for rust prevention of steel materials according to claim 6, wherein the external stimulus is heat.
8. A steel structure comprising the steel material rust-preventing pressure-sensitive adhesive sheet according to any one of claims 1 to 7 and a steel material, wherein the steel material rust-preventing pressure-sensitive adhesive sheet is attached to the steel material.
9. The steel material has a groove surface, and the steel material rust-preventing pressure-sensitive adhesive sheet is attached to at least one of the groove surface and a peripheral portion where the distance along the steel material surface from the groove surface is within 100 mm. 9. The steel structure of claim 8, wherein:
10. The steel structure according to claim 8 or 9, wherein the pressure-sensitive adhesive sheet for steel material rust prevention is attached to the steel material with a valley fold folded at 45° or more or a mountain fold folded at 90° or more.
11. An adhesive sheet for rust prevention of steel material, comprising a base material and an adhesive layer provided on one surface of the base material, wherein the base material has an elastic modulus of 900 MPa or less, is attached to the steel material to prevent the steel material from rusting. Steel rust prevention method.
12. The steel material rust prevention method according to claim 11, wherein the steel material rust prevention pressure-sensitive adhesive sheet is attached at least to the groove surface of the steel material.
13. The steel material rust prevention method according to claim 11 or 12, wherein the steel material rust prevention pressure-sensitive adhesive sheet attached to the steel material is peeled off.
14. The pressure-sensitive adhesive layer is one whose adhesive strength is reduced by an external stimulus,
    14. The steel material rust prevention method according to claim 13, wherein an external stimulus is applied to the adhesive layer of the steel material rust prevention adhesive sheet attached to the steel material before the steel material rust prevention adhesive sheet is peeled off.
15. A pressure-sensitive adhesive sheet for rust prevention of steel material comprising a base material and an adhesive layer provided on one surface of the base material, wherein the base material has an elastic modulus of 900 MPa or less, is attached at least to the groove surface of the steel material,
    After a certain period of time has passed since the adhesive sheet for rust prevention of steel materials was attached, the adhesive sheet for rust prevention of steel materials is peeled off from the steel materials,
    A steel material welding method for joining the groove surface to which the steel material has been affixed to another member by welding.

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