WO2016196559A1

WO2016196559A1 - Pressure sensitive adhesive sheet for covering surface of a wet concrete material, and method of delaying the curing of a concrete structure by preventing the evaporation of the mixing water

Info

Publication number: WO2016196559A1
Application number: PCT/US2016/035168
Authority: WO
Inventors: Naohiro Takemoto; Yorinobu Takamatsu; Hitoshi Morimoto
Original assignee: 3M Innovative Properties Co
Current assignee: 3M Innovative Properties Co
Priority date: 2015-06-05
Filing date: 2016-06-01
Publication date: 2016-12-08
Anticipated expiration: 2017-12-05
Also published as: JP2017002132A; JP6787653B2

Abstract

A pressure sensitive adhesive sheet for covering a surface of cement material that is concrete, mortar, or cement, containing: a pressure sensitive adhesive layer containing a polymer derived from monomer components including an alkyl (meth) acrylate with 4 to 18 carbon atoms and a monomer with at least one functional group containing a nitrogen atom; wherein the pressure sensitive adhesive layer can adhere to the surface of the concrete material in a wet condition, and can be peeled from the surface of the cement material after hardening.

Description

PRESSURE SENSITIVE ADHESIVE SHEET FOR COVERING SURFACE OF A WET CONCRETE MATERIAL, AND METHOD

OF DELAYING THE CURING OF A CONCRETE STRUCTURE BY PREVENTING

THE EVAPORATION OF THE MIXING WATER

TECHNICAL FIELD

[0001] The present invention relates to a pressure sensitive adhesive sheet for covering a surface of a cement material, and to a method of manufacturing a cement structure.

BACKGROUND TECHNOLOGY

[0002] Cement materials such as concrete, mortar, and cement are widely used in various structures such as buildings, roads, bridges, dams, tunnels, port facilities, and the like. In many cases, cement structures which are made of hardened cement materials are required to have excellent strength and long-term retention (in other words durability). In order to provide sufficient quality to the cement structure, curing while maintaining a suitable temperature and moisture conditions and the like for a hardening reaction is important. Curing takes at least several days, depending on the structure and the climate conditions, and with a large-scale building, generally one month or longer, and preferably a period of 3 months or longer is required, and therefore there is demand to control the conditions such as temperature and humidity conditions, and the like of the submitted materials during this period. [0003] Methods for curing cement materials include a method of reducing the moisture that evaporates from the surface of the poured cement material, such as sealed curing and coated curing; a method that includes providing water on the surface of the poured cement material, such as water sprinkling curing and flood curing; a method that includes retaining moisture by providing a certain water absorbent sheet on the surface of the poured cement material, such as compress curing; and a method that includes holding a sheet against the surface of the poured cement material, and then supplying water between the sheet and the surface of the cement material, such as water supply curing, and the like. These methods are not necessarily clearly distinguished.

[0004] Patent document 1 describes a pressure sensitive adhesive tape that covers a surface of concrete and that is used when curing concrete, the tape including at least a base material layer and a pressure sensitive adhesive layer provided on one surface of the base material layer, and the maximum load F of the base material layer determined by multiplying the thickness t and the tear strength TR of the base material layer is between approximately 5 and 40 N.

[0005] Patent document 2 describes a curing sheet for concrete that includes a bubble layer and a pressure sensitive adhesive layer laminated on the bubble layer, wherein the adhesive force between the pressure sensitive adhesive layer and the bubble layer is 80% or less of the adhesive force produced between the surfaces of the pressure sensitive adhesive layer and the surface of the poured concrete, and the adhesive force that occurs between the pressure sensitive adhesive layer and the surface of the poured concrete is 0.15 N/cm² or higher.

PRIOR TECHNOLOGY DOCUMENTS

[0006] Patent document 1 : Japanese unexamined patent application 2002-255670 Patent document 2: Japanese unexamined patent application 2014-37693

SUMMARY OF THE INVENTION

[0007] The technology described in patent document 1 and 2 is thought to contribute to some degree to simplifying curing. However, when a cement material is poured using a frame, there is a tendency to require that the frame be removed at the earliest possible time due to restrictions in the fabrication process and restrictions of deadlines and the like. In particular, concrete that covers the inner walls of tunnels and is required to move the frame as digging of the tunnel hole proceeds, and early moving of the frame leads to a shortened construction. However, the cement material from which the frame is removed in an early stage will have a high moisture content because the hydration reaction is insufficient, and therefore achieving favorable adhesion to the cement material is difficult when using a conventional adhesive sheet. Furthermore, it is also difficult to obtain a pressure sensitive adhesive sheet that can adhere to cement material with a high water content and that can easily be peeled and removed after the cement material hardens. Therefore, there is demand for a pressure sensitive adhesive sheet for covering cement material that can shorten the construction period, And that can be removed without leaving a residual pressure sensitive adhesive layer on the cement structure that is obtained after use (after hardening of the cement material).

[0008] In light of the foregoing, an object of the present disclosure is to provide a pressure sensitive adhesive sheet for covering cement material that can shorten the construction period and that can provide a high-quality cement structure (for example, a concrete structure), and to provide a method of manufacturing a cement structure using this sheet.

MEANS FOR RESOLVING PROBLEMS

[0009] One aspect of the present disclosure provides:

A pressure sensitive adhesive sheet for covering a surface of cement material, containing: a pressure sensitive adhesive layer containing a polymer derived from monomer components including an alkyl (meth)acrylate with 4 to 18 carbon atoms and a monomer with at least one functional group containing a nitrogen atom; wherein the pressure sensitive adhesive layer can adhere to the surface of the concrete material in a wet condition, and can be peeled from the surface of the cement material after hardening.

[0010] Another aspect of the present disclosure provides a roll made by rolling the pressure sensitive adhesive sheet.

[0011] Another aspect of the present disclosure provides:

A method for manufacturing a cement structure, including: obtaining the cement material with an exposed surface; applying the pressure sensitive adhesive layer of the pressure sensitive adhesive sheet to the exposed surface while the exposed surface is in a wet condition;

obtaining a cement structure by hardening the cement material; and removing the pressure sensitive adhesive sheet from the cement structure.

EFFECT OF THE INVENTION

[0012] The pressure sensitive adhesive sheet of the present disclosure provides a pressure sensitive adhesive sheet for covering cement material that can shorten the construction period and that can provide a high-quality cement structure, and provides a method of manufacturing a cement structure using this sheet.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 is a diagram illustrating one aspect of the pressure sensitive adhesive sheet of the present disclosure.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] A detailed description while referring to the drawings as necessary is provided in order to present an example of a representative embodiment of the present invention, but the present invention is in no way restricted to these embodiments and drawings. It should be noted that these various property values in this disclosure are intended to be values that were measured by the method described in the section "Examples" of the present disclosure, or by a method that is understood by one skilled in the art to be a similar method, unless otherwise expressly noted.

[0015] The present disclosure provides a pressure sensitive adhesive sheet for covering a surface of cement material, containing: a pressure sensitive adhesive layer containing a polymer derived from monomer components including an alkyl (meth)acrylate with 4 to 18 carbon atoms and a monomer with at least one functional group containing a nitrogen atom; wherein the pressure sensitive adhesive layer can adhere to the surface of the concrete material in a wet condition, and can be peeled from the surface of the cement material after hardening. The present disclosure also provides a roll made by rolling the pressure sensitive adhesive sheet of the present disclosure.

[0016] The term "concrete" in the present disclosure is intended to include mixtures of sand, gravel, water, cement, and optional admixtures, and includes the hardened product obtained by hardening the mixture. Various types of concrete are conventionally known, and with the present disclosure, the type of concrete is appropriately selected based on the objective.

Examples of the concrete include general construction concrete, cold weather concrete, hot weather concrete, mass concrete, fluidized concrete, highly fluid concrete, high-strength concrete, low heat concrete, expansion concrete, prestressed concrete, low shrink concrete, fiber reinforced concrete, polymer concrete, watertight concrete, underwater concrete, water permeable and water impermeable concrete, resin containing concrete, shielding concrete, lightweight concrete, prepacked concrete, shotcrete, and the like.

[0017] The term "mortar" in the present disclosure is intended to include mixtures of sand, water, cement, and optional admixtures, and includes the hardened product obtained by hardening the mixture.

[0018] The term "cement" in the present disclosure is intended to include all powders that hardening by a hydration reaction or the like using water or a liquid agent or the like that can be used for producing concrete and mortar, and includes hardened objects obtained by hardening these materials, and includes organic materials, inorganic materials, and

combinations thereof. Cement includes standard cements such as Portland cement, mixed cement, and alumina cement and the like, as well as asphalt, glue, resin, plaster, lime, and the like. [0019] In the present disclosure, "cement material" refers to materials that are concrete, mortar, or cement according to the present disclosure.

[0020] The pressure sensitive adhesive sheet of the present disclosure is useful for concrete, mortar, and cement that include cement that hardened by hydration. Typical forms include tricalcium silicate (3CaO Si0₂), dicalcium silicate (2CaO Si0₂), tricalcium aluminate

(3CaO AI2O2), tetracalcium iron aluminate (4CaO AI2O2 Fe2Cb), gypsum (CaSC"4 2H2O), and the like, and cement may include one or more types of these.

[0021] In the present disclosure, curing of the cement material refers to a process of maintaining the temperature and humidity conditions required for hardening for a certain period of time after preparing the cement material (pouring (implanting) into a frame, spraying, and the like) in order to ensure the required quality of the cement material.

[0022] Pressure sensitive adhesive sheet

The pressure sensitive adhesive sheet of the present disclosure is used for covering a surface of a cement material. In the pressure sensitive adhesive sheet of the present disclosure, the pressure sensitive adhesive layer can adhere to the surface of the cement material in a wet condition, and can be peeled from the surface of the cement material even after the cement material has hardened. In the present disclosure, the phrase "the surface of the cement material is in a wet condition" refers to the condition of the cement material when the frame is removed, for example, the following day after pouring the cement material. The phrase "the pressure sensitive adhesive layer can adhere to the surface of the cement material in a wet condition" means that the pressure sensitive adhesive sheet will not peel off from the weight of the sheet after being applied to the surface of the cement material in a wet condition on a ceiling surface, for example, and more preferably means that the sheet can adhere to the cement material with a stronger force than the unrolling force when the roll sheet is unrolled during application. Furthermore, the phrase "the pressure sensitive adhesive layer can be peeled from the surface of the cement material after hardening" means that the pressure sensitive adhesive layer can be peeled from the surface of the cement material without leaving residual pressure sensitive adhesive layer.

[0023] Generally, the water content of the cement material is reduced over time due to the consumption of water by the hydration reaction during the process of securing the cement material. For example, a cement material will have water content near the surface that is 4% or higher of the total water fraction of the concrete or mortar, directly after construction or after a relatively short period of time has passed after construction (for example, a material age of 8 hours to 15 hours), and in some cases, the water content may be measured at 12% or higher. The pressure sensitive adhesive sheet of the present disclosure is intended to adhere with sufficient adhesive strength even to the surface of the cement material in a wet condition in this manner, but the pressure sensitive adhesive layer can be removed from the surface of the cement layer without leaving residual pressure sensitive adhesive layer on the surface even after the cement material has hardened. With this type of pressure sensitive adhesive sheet, a cement structure can be produced without losing the desired surface state, and the time required for curing the cement material can be greatly shortened, so the construction period can be shortened.

[0024] Pressure Sensitive Adhesive Layer

The pressure sensitive adhesive layer contains a polymer derived from monomer components including an alkyl (meth)acrylate with 4 got 18 carbon atoms (in the present invention, this is also referred to as a C₄ to Cis alkyl (meth)acrylate. Note, in the present disclosure, the term "(meth)acrylate" is intended to include methacrylate and acrylate.), and a monomer with at least one functional group containing a nitrogen atom (in the present disclosure, this is also referred to as a nitrogen functional monomer).

[0025] Preferable examples of the C₄ to Cis alkyl (meth)acrylate include n-butyl acrylate, 2- ethyl hexyl acrylate, isooctyl acrylate, lauryl acrylate, n-octyl acrylate, isononyl acrylate, isodecyl acrylate, isostearyl acrylate, isomyristyl acrylate, and the like. Of these, 2-ethyl hexyl acrylate, isooctyl acrylate, and n-octyl acrylate are preferable, from the perspective of having even lower water permeability and a balance between the pressure sensitive adhesive properties and the peeling properties.

[0026] The nitrogen functional monomer is a monomer with at least one functional group containing a nitrogen atom. It is advantageous for the pressure sensitive adhesive layer to have a hydrophilic group in order for the pressure sensitive adhesive sheet to favorably adhere to the surface of the cement material in a wet condition. However, for a cement material that contains cement that forms calcium oxide by hydration, a hydrophilic group that is ion cross- linkable (in other words a carboxyl group or the like) may cause ionic cross-linking between to the calcium ions produced by the hydration reaction, and may provide a lower level of adhesion between the cement material and the pressure sensitive adhesive layer. Furthermore, the ionic cross-linking can affect the progress of hardening of the cement where calcium hydroxide is produced by hydration, and this may lead to delayed or insufficient hardening. The functional group with a nitrogen atom in the pressure sensitive adhesive layer of the present disclosure is a hydrophilic group that is relatively inert towards calcium ions because of this structure. Therefore, the nitrogen functional monomer can contribute to the favorable adhesive properties of the pressure sensitive adhesive layer to the cement material in a wet condition, and can contribute to the production of a high-quality cement structure with physical properties such as enhanced density, strength, high durability, and the like by not interfering the hardening of the cement material.

[0027] The functional group with a nitrogen atom is intended to include all functional groups that contain a nitrogen atom. Functional groups that contain a nitrogen atom are preferably groups that are neutral to weakly basic, from the perspective of minimizing the effect on the hardening reaction of the cement material. Examples of neutral to weakly basic groups include pyrrolidone, amide, substituted amide, morpholine, caprolactam, and the like.

[0028] Preferable examples of the nitrogen functional monomer include N-vinyl-2- pyrrolidone (NVP), Ν,Ν-dimethyl acrylamide (DMAA), Ν,Ν-diethyl acrylamide, N-isopropyl acrylamide, diacetone acrylamide (DAAM), acryloyol morpholine, N-final caprolactam, hydroxyethyl acrylamide, octyl acrylamide, and the like.

[0029] In a preferred embodiment, the monomer component contains approximately 70 mass parts to approximately 92 mass parts of C₄ to Cis alkyl (meth)acrylate and approximately 8 mass parts to approximately 30 mass parts of the nitrogen functional monomer. In this embodiment, the amount of C₄ to Cis alkyl (meth)acrylate is preferably approximately 70 mass parts or more or approximately 72 mass parts or more, or approximately 74 mass parts or more, from the perspective of achieving favorable pressure sensitive adhesion, and the amount is preferably approximately 92 mass parts or lower, or approximately 91 mass parts or lower, or approximately 90 mass parts or lower, from the perspective of achieving the favorable advantages of adding the nitrogen functional monomer. Furthermore, in this embodiment, the amount of the nitrogen functional monomer is preferably approximately 8 mass parts or more, or approximately 9 mass parts or more, or approximately 10 mass parts or more, from the perspective of achieving favorable peeling and removing properties of the pressure sensitive adhesive layer after the cement material hardens and achieving favorable adhesion to the surface of the cement material with high water content, and preferably is 30 mass parts or lower, or approximately 28 mass parts or lower, or approximately 26 mass parts or lower, from the perspective of achieving favorable pressure sensitive adhesion.

[0030] In a typical embodiment, the monomer component may include additional monomers with a cross-linking site in addition to the aforementioned monomers. It is expected that cross- linking will increase cohesion and reduce the pressure sensitive adhesive residue that remains when peeling from the adhesion surface. For example, if a (meth)acrylate with a

benzophenone group is used as the additional monomer, cross-linking can be achieved by UV irradiation. As another example, if a (meth)acrylate with a hydroxyl group and a

polyfunctional isocyanate compound are used as the additional monomer, cross-linking by a ur ethane bond can be achieved.

[0031] The amount of additional monomer based on the total of the C₄ to Cis alkyl

(meth)acrylate and the nitrogen functional monomer being 100 mass parts can be

approximately 0.001 mass parts or higher, or approximately 0.01 mass parts or higher, or approximately 0.05 mass parts or higher, from the perspective of achieving favorable cross- linking, and for example can be approximately 10 mass parts or lower, or approximately 8 mass parts or lower, or approximately 5 mass parts or lower, from the perspective of achieving favorable pressure sensitive adhesion. If a (meth)acrylate containing a hydroxyl group and a polyfunctional isocyanate compound are used, the ratio between the number of equivalents of isocyanate of the polyfunctional isocyanate compound and the number of equivalents of hydroxyl groups of the (meth)acrylate having a hydroxyl group (NCO/OH) may be, for example, approximately 0.005 or higher and approximately 1.2 or lower, or approximately 0.01 or higher and approximately 0.5 or lower.

[0032] In a preferable embodiment, the monomer component does not include a carboxylic acid with an ethylenic unsaturated group (for example (meth)acrylic acid) or phosphoric acid with an ethylenic unsaturated group, or a sulfonic acid with an ethylenic unsaturated group, from the perspective of achieving favorable adhesion to the cement material in a wet condition and from the perspective of achieving favorable progress of the hardening reaction without negatively impacting the hardening reaction of the cement material. In another favorable embodiment, in addition to the two perspectives of adhesion and hardening reaction, and in order to achieve a balance from the perspective of the pressure sensitive adhesive sheet more easily peeling and separating from the cement material before hardening and after hardening, without leaving a residual pressure sensitive adhesive layer, the monomer component may contain approximately 0.001 mass parts or more, or approximately 0.01 mass parts or more, or approximately 0.05 mass parts or more, and approximately 6 mass parts or less, or

approximately 4 mass parts or less, or approximately 2 mass parts or less of a carboxylic acid with an ethylenic unsaturated group a phosphoric acid with an ethylenic unsaturated group, and/or a sulfonic acid with an ethylenic unsaturated group, in total, with regards to the total of 100 mass parts of the C₄ to Cis alkyl (meth)acrylate and the nitrogen functional monomer.

[0033] In a preferable embodiment, the glass transition temperature of the polymer derived from a monomer component containing the C₄ to Cis alkyl (meth)acrylate and the nitrogen functional monomer is approximately 25°C or lower, or approximately 10°C or lower, or approximately 0°C or lower, from the perspective of achieving favorable adhesion of the pressure sensitive adhesive sheet to the surface of the cement material, and is approximately - 100°C or higher, or approximately -90°C or higher, or approximately -80°C or higher, from the perspective of achieving a balance between favorable adhesion and cohesion.

[0034] In a typical embodiment, the pressure sensitive adhesive layer contains a polymer derived from a monomer component containing the C₄ to Cis alkyl (meth)acrylate and the nitrogen functional monomer, as described above, but additional polymers may also be included to the extent that the object of the present invention is not hindered. The amount of additional polymer may be approximately 25 mass % or less, or approximately 20 mass % or less, or approximately 15 mass % or less, based on the total mass of the pressure sensitive adhesive layer.

[0035] The pressure sensitive adhesive layer may also include additives such as antioxidants, pigments, dyes, fillers, light stabilizers (UV absorbers, light stabilizers, and the like), tackifiers, plasticizers, and the like.

[0036] In a preferable embodiment, the thickness of the pressure sensitive adhesive layer is approximately 5 μπι or more, or approximately 10 μπι or more, or approximately 15 μπι or more, from the perspective of achieving favorable adhesion of the pressure sensitive adhesive sheet to the surface of the cement material, and is approximately 300 μπι or less, or approximately 200 μπι or less, or approximately 150 μπι or less, from the perspective of reducing material cost. [0037] FIG. 1 is a diagram illustrating one aspect of the pressure sensitive adhesive sheet of the present disclosure. In reference to FIG. 1, in a preferred embodiment, the pressure sensitive adhesive sheet 1 as a base material 11 with a first main surface and a second main surface mutually facing opposite directions, and a pressure sensitive adhesive layer 12 provided on the first surface of the base material. This pressure sensitive adhesive sheet is transported, for example, as a roll, and the pressure sensitive adhesive layer can be successively applied to the surface of the cement material while unrolling the roll, and therefore this sheet is advantageous from the perspective of portability and productivity.

[0038] The base material 11 typically includes a film 11a. The film can be a plastic film such as polyolefin (polypropylene, polyethylene, and the like), polyethylene terephthalate, polyvinyl chloride, and the like, or can be paper, a woven material, a nonwoven material, or the like. The base material is preferably water impermeable, from the perspective of preventing evaporation of water from the surface of the cement material and maintaining the wet condition.

[0039] In a preferable embodiment, the thickness of the base material is approximately 5 μπι or more, or approximately 7 μπι or more, or approximately 10 μπι or more, from the perspective of achieving favorable strength, and is approximately 400 μπι or lower, or approximately 300 μπι or lower, or approximately 250 μπι or lower, from the perspective of operability and reducing material costs. The color of the base material may be white, milky, black, transparent, or the like, for example, but the color is preferably white are milky, from the perspective that temperature variation will occur on the surface of the cement material under the pressure sensitive adhesive tape due to the sunlight becoming biased and concentrated if the color is dark, and therefore curing uniformity will tend to be reduced, and if the base material is transparent, there will be a tendency for the pressure sensitive adhesive sheet to have low visibility.

[0040] The first main surface of the base material may be Corona treated, plasma treated, and/or primer treated, in order to increase the adhesion between the pressure sensitive adhesive layer and the base material. A primer treatment can form at least one type of primer layer selected from epoxy resins, vinyl copolymers with a carboxyl group, (meth)acrylate copolymers, polyester resins, polyether resins, polyurethanes, rubber materials, and the like.

[0041] The second main surface of the base material 11 may have a release agent layer l ib. In other words, the pressure sensitive adhesive layer of the sheet that is rolled into a roll may have a release agent layer on the surface (surface on the outer circumferential side of the sheet) that contacts with the pressure sensitive adhesive layer (surface on the inner circumferential side of the sheet) of the roll, in order to prevent adhering to the base material of the lower sheet, which may prevent removing and peeling. The release agent layer may be a coating layer made of a material with low adhesion, or may be a peeling agent made of a fluorine-based, olefin-based, silicone-based, urethane-based, or acrylic-based material, or the like.

[0042] Furthermore, the pressure sensitive adhesive sheet may also have a release liner on the opposite side as the base material side of the pressure sensitive adhesive layer. The release liner can be selected from various standard release films and peeling papers that are used on standard pressure sensitive adhesive sheets, as desired. However, a roll that does not have a release liner can apply the pressure sensitive adhesive sheet to the surface of the cement material while unrolling the roll, depending on the base material and the pressure sensitive adhesive layer (and if necessary, the release agent layer), and this is preferable for achieving such advantages as a simple operation and the fact that wastes material such as the release liner or the like is not generated at the construction site.

[0043] The pressure sensitive adhesive sheet can be produced by various methods. For example, the pressure sensitive adhesive sheet can be obtained by preparing a film for the base material, forming a primer layer as described above by coating or the like on one main surface thereof, applying the pressure sensitive adhesive agent for the pressure sensitive adhesive layer onto the primer layer, and then forming a release agent layer by coating or the like onto the other main surface of the aforementioned film.

[0044] The peel strength between the pressure sensitive adhesive sheet and the surface when the pressure sensitive adhesive sheet is applied to the surface of the cement material in a wet condition is preferably approximately 0.5 N/cm or higher, or approximately 1 N/cm or higher. This level of peel strength is advantageous for achieving favorable curing effects. The peel strength may be, for example, approximately 8 N/cm or lower, or approximately 6.5 N/cm or lower, from the perspective of the ease of peeling the pressure sensitive adhesive sheet after the cement material has hardened.

[0045] In a preferred embodiment, the peeling strength when the pressure sensitive adhesive sheet is peeled from the surface of the cement material 7 days after being applied is approximately 0.5 N/cm or higher, or approximately 1 N/cm or higher, or approximately 1.5 N/cm or higher, from the perspective of favorable progression of curing, and is approximately 8 N/cm or lower, or approximately 7 N/cm or lower, or approximately 6 N/cm or lower, from the perspective of the ease of peeling the pressure sensitive adhesive sheet after the cement material has hardened.

[0046] In a preferred embodiment, the peel strength between the first main surface and the pressure sensitive adhesive layer is approximately 8 N/cm or higher, and the peel strength between the pressure sensitive adhesive layer and the second main surface can be

approximately 0.1% or more and approximately 95% or less than the peel strength between the pressure sensitive adhesive sheet and the main surface when the pressure sensitive adhesive sheet is applied to the surface of the cement material. By controlling the peel strength in this manner, the properties as a pressure sensitive adhesive sheet will be favorable, while at the same time, unrolling of the roll at the time of application can overcome the small peel strength even if the second main surface and the pressure sensitive adhesive layer are in contact in the roll. If the peel strength is too small, the exterior force applied to the pressure sensitive adhesive sheet in the area that has already been applied will be small when applying the pressure sensitive adhesive sheet to the surface of the cement material while unrolling the roll, and therefore peeling of the area that has already been applied is prevented, and workability is greatly improved.

[0047] In a preferred embodiment, the peel strength during unrolling when the pressure sensitive adhesive sheet is in a roll is preferably less than the peel strength between the pressure sensitive adhesive sheet and the surface when the pressure sensitive adhesive sheet is applied to the surface of the cement material in a wet condition, from the perspective of achieving favorable workability, and is approximately 0.001 N/cm or higher, or approximately 0.01 N/cm or higher, or approximately 0.1 N/cm or higher, from the perspective of the ease of producing the pressure sensitive adhesive sheet.

[0048] Method of manufacturing cement structure

The present disclosure also provides:

a method for manufacturing a cement structure, including: obtaining the cement material with an exposed surface; applying the pressure sensitive adhesive layer of the pressure sensitive adhesive sheet of the present disclosure to the exposed surface while the exposed surface is in a wet condition; obtaining a cement structure by hardening the cement material; and removing the pressure sensitive adhesive sheet from the cement structure.

[0049] The cement material with an exposed surface can be formed by pouring or spraying the cement material into a frame.

[0050] The timing for removing the frame depends on the design strength of the target structure, the environment such as the temperature and humidity and the like of the worksite, and the composition of the cement material, and the like, but in an exemplified embodiment, the timing is the day after the concrete is poured, aging of the cement material is performed for 8 to 15 hours, and the compressive strength of the cement material is approximately 2 N/mm² or higher. [0051] Next, the pressure sensitive adhesive layer of the pressure sensitive adhesive sheet of the present disclosure is applied while the exposed surface is in a wet condition. In other words, in an exemplified embodiment, the concrete material is poured into a frame, the frame is removed after the cement material loses fluidity to a degree that the shape can be maintained (for example, when hydration of the cement has proceeded so as to exceed a 50% conversion rate), and then the pressure sensitive adhesive sheet of the present disclosure is immediately applied to the surface of the cement material in a wet condition.

[0052] The peel strength between the pressure sensitive adhesive sheet and the surface when the pressure sensitive adhesive sheet is applied to the exposed surface is preferably approximately 0.5 N/cm or higher, or approximately 1 N/cm or higher. This level of peel strength is advantageous for achieving favorable curing effects. The peel strength may be, for example, approximately 8 N/cm or lower, or approximately 6 N/cm or lower, from the perspective of the ease of peeling the pressure sensitive adhesive sheet from the hardened cement material.

[0053] Next, the cement material is hardened. Hardening favorably proceeds without requiring any special action such as heating, cooling, spraying water, or the like, but the present disclosure does not exclude the use of one or more of these actions. In an exemplary embodiment, the timing from application of the pressure sensitive adhesive sheet until hardening is complete exceeds approximately one month, and may be approximately 3 months, for example.

[0054] When the cement material hardens, a cement structure is obtained as the hardened material. The pressure sensitive adhesive sheet can be peeled and removed from the cement structure by hand, or by other method. In an exemplary embodiment, the peel strength between the cement structure and the pressure sensitive adhesive sheet can be approximately 8 N /cm or lower, or approximately 6.5 N /cm or lower. The peel strength as described above is advantageous from the perspective that the pressure sensitive adhesive sheet can be peeled and removed without residual pressure sensitive adhesive layer remaining on the cement structure. The peel strength can be approximately 0.5 N/cm or higher, or approximately 1 N/cm or higher, for example, from the perspective of achieving favorable adhesion of the pressure sensitive adhesive sheet to the cement material before hardening.

[0055] The desired cement structure can be produced by the aforementioned procedures.

[0056] The cement structure of the present disclosure can be, for example, various types of structures such as a building, road, bridge, dam, tunnel, concrete structures of a port facility, or the like. The pressure sensitive adhesive sheet of the present disclosure is preferably used under conditions with high temperature and high humidity such as a tunnel or the like, because the adhesion to the surface of the cement material in a wet condition is favorable.

EXAMPLES

[0057] Specific embodiments of the present invention are described below in greater detail using examples, but the present invention is not restricted to these examples.

[0058] 1. Materials

Water impermeable base material film (polypropylene/polyethylene planned polyolefin film with a thickness of 80 μπι)

2EHA: 2-ethylhexyl acrylate, obtainable from Nihon Shokubai

BA: n-butyl acrylate, obtainable from Mitsubishi Chemical Corporation

AA: acrylic acid, obtainable from Toagosei Co., Ltd

HEA: 2-hydroxyethyl acrylate, obtainable from Osaka Organic Chemical Industry Ltd NVP: N-vinyl-2-pyrrolidone, obtainable from Wako Pure Chemical Industries, Ltd.

DMAA: Ν,Ν-dimethyl acrylamide, obtainable from Kohjin Film and Chemicals, Co., Ltd. DAAM: diacetone acrylamide, obtainable from Nippon Kasei Chemical Co., Ltd.

ABP: acryloyoloxy benzophenone

AEBP: acryloyoloxy ethyl benzophenone Coronate L-45: ethyl acetate solution of a polyfunctional isocyanate compound with a solid fraction of 45 mass %, obtainable from Soken Chemical and Engineering Co., Ltd.

Bisamide cross-linking agent: 3 mass % toluene solution of Ι, Γ-isophthaloyl bis(2-methyl aziridine)

V-65:Azobis (2,4-dimethylvaleronitrile), obtainable from Wako Pure Chemical Industries, Ltd.

[0059] 2. Preparation of PSA solution

(l) PSA solution (PSA-1)

90 mass parts of 2 EHA, 10 mass parts of NVP, 0.1 mass parts of ABP, 233.33 mass parts of ethyl acetate (as solvent), and 0.20 mass parts of V-65 (as initiator) were blended. Nitrogen gas purge was performed, and a reaction was performed for 24 hours at 50°C to obtain and ethyl acetate solution with 30 mass % of PSA polymer (PSA-1).

(2) PSA solution (PSA-2 to PSA-11)

PSA-2 to PSA-11 were prepared similar to PSA-1, except for using the component monomers shown in Table 1.

[0060] 3. Fabrication of pressure sensitive adhesive sheet

The PSA-1 prepared as described above was coated onto a water impermeable base material film, and then dried in an oven at 100°C for 5 minutes to form a PSA layer with a dry thickness of 30 μπι. The PSA layer was cross-linked by UV irradiation (UV-C intensity: 75 mJ/cm²) using a FUSION UV system to obtain the PSA tape according to example 1 as a pressure sensitive adhesive sheet.

[0061 ] <Examples 2 to 7>

PSA tape was obtained in a manner similar to example 1, except that the PSA solutions shown in Table 1 were used.

[0062] <Example 8>

A coating solution was obtained by adding 0.67 mass parts of Coronate L-45 to 100 mass parts of PSA-8 (prepared as described above). PSA tape according to example 8 was obtained by coating this coating solution onto a water impermeable base film, drying in an oven at 100°C for 5 minutes to obtain a coating layer with a dry thickness of 30 μπι, and then allowing to sit for 7 days at 25°C.

[0063] <Example 9>

PSA tape was obtained in a manner similar to example 8, except that the PSA solution shown in Table 1 was used.

[0064] <Example 10>

1.2 mass parts of bisamide cross-linking agent was added to 100 mass parts of PSA- 10 (prepared as described above) to obtain a coating solution. PSA tape according to example 10 was obtained by coating this coating solution onto a water impermeable base film, drying in an oven at 100°C for 5 minutes to obtain a coating layer with a dry thickness of 30 μπι.

[0065] <Comparative example>

A PSA tape according to a comparative example was obtained in a manner similar to example 1, except that PSA-11 was used as the PSA solution.

[0066] 4. Evaluation

(1) Glass transition temperature (Tg) of PSA

The dynamic viscosity properties of each PSA polymer were evaluated using a ARES (product of Rheometric Scientific Co., Ltd.) using shear mode, a frequency of 1.0 Hz, a measurement temperature range of -40°C to 120°C, and a temperature rise rate of 5.0° C/minute. The tan5 (loss elasticity G'Vstorage elasticity G') of the peak temperature was used as Tg. The results are shown in Table 1.

[0067] (2) Peel strength to mortar surface

A test piece with a size of 10 mm x 100 mm was cut from the PSA tape. A mortar plate with a size of 10 mm x 70 mm x 120 mm (produced by Nihon Tact Co., Ltd.) was used as the base material. The mortar plate that was used had a water content value of less than 4% when measured by a water content meter (produced by Kett Electric Laboratory ). The PSA tape was laminated onto the mortar plate using a 2.0 kg collar at a temperature of 25°C such that the PSA side of the PSA tape test piece was facing the mortar plate. After 20 minutes, the peel strength of the PSA tape from the mortar plate surface was evaluated by 90° peeling at a peel rate of 300 mm/minute (using a Tensilon Universal material tester RTC-1325A produced by Orientec Co., Ltd.).

[0068] On the other hand, a similar mortar plate was immersed in water for 24 hours, and then removed. The water on the surface of the mortar plate was removed using a paper towel. The mortar plate that was used had a water content value of 4% or higher when measured by a water content meter (produced by Kett Electric Laboratory). The PSA tape was laminated onto the mortar plate using a 2.0 kg collar at a temperature of 25°C such that the PSA side of the PSA tape test piece was facing the mortar plate. After 20 minutes, the peel strength of the PSA tape from the mortar plate surface was evaluated by 90° peeling at a peel rate of 300 mm/minute (using a Tensilon Universal material tester RTC-1325A produced by Orientec Co., Ltd.).

[0069] (3) Peel strength to concrete surface

A test piece with a size of 10 mm x 120 mm was cut from the PSA tape. Raw concrete (a blend of 88 mass parts of instant concrete produced by Cainz Co., Ltd. with 12 mass parts of water) was placed in a frame with a size of 10 mm x 70 mm x 120 mm, and allowed to sit for 24 hours at 25°C. The frame was removed (at this time material with a water content of 7% as measured by a water content meter (produced by Kett Electric Laboratory) was used), and then the PSA tape was laminated onto the surface of the concrete using a 2.0 kg collar at 25°C in a condition where the PSA side of the test piece was facing the surface of the concrete. Favorable application was possible even on the unhardened concrete. The laminated concrete was heated for 1 week in an oven at 60°C to complete hardening of the concrete. The peel strength of the PSA tape that had been applied before hardening and then peeled from the surface of the concrete after hardening was evaluated by peeling at 90° at a peel rate of 300 mm/minute and a temperature of 25°C, similar to (2).

[0070] Table 1

[0071] The PSA tape of each example was compared with the PSA tape of the comparative example, and favorable peeling strength was demonstrated toward the surface of the cement material in a wet condition. Furthermore, the PSA tape could easily be peeled from the surface of the concrete even after passing through severe environments of 60°C for 1 week. Note that residual PSA was not observed on the surface of the hardened concrete after peeling the PSA tape, with both the examples and the comparative example.

[0072] Fabrication of pressure sensitive adhesive sheet roll

Polyment (registered trademark) NK350 (adjusted to 10% solid fraction, obtainable from Nippon Shokubai Co., Ltd.) was applied by a gravure coater on to the first main surface of a polyolefin film with a thickness of 80 μπι (PP/PE/master batch = 57/38/5 (mass ratio)), and then the solvent was evaporated off in a drying oven. Next, KS-3703 (obtainable from Shinetsu Chemical Co., Ltd) /ethyl acetate/ CATPL-50 T (obtainable from Shinetsu Chemical Co., Ltd. ) = 10/90/0.3 (mass ratio), an addition type silicone release agent, was applied by a gravure coater on to the second main surface, and then the solvent was evaporated off using a drying oven. Next, a coating solution obtained by adding 0.67 mass parts of Coronate L-45 to PSA-8 (prepared as described above) was applied at a rate of 30 g/m² using a knife coater on to the first main surface, and then the coating solution that was coated on the surface was dried using forced air in a drying oven. The sheet was rolled up using a rollup roller. The roll was allowed to sit for 7 days at 25°C to obtain a PSA sheet roll according to example 11.

[0073] Peel strength when unrolling from pressure sensitive adhesive sheet roll

The pressure sensitive adhesive sheet roll of example 11 was slit to a width of 5 cm, and then the peel strength when unrolling the pressure sensitive adhesive sheet roll was evaluated at each peel speed using a high-speed peel tester (produced by Tester Sangyo Co., Ltd.). [0074] Table 2

[0075] As shown in Table 2, the peel strength when unrolling the PSA tape roll according to example 11 was smaller than the peel strength from the surface of the cement material in a wet condition shown in Table 1. In other words, this shows that the sheet can be unrolled by pulling the roll while applying to the cement material in a wet condition. In actuality, the PSA tape roll according to example 11 could be unrolled by the adhesive force toward the surface of the concrete of the PSA side of the test piece that was unrolled beforehand, even on the surface of concrete in a wet condition.

POSSIBILITY OF INDUSTRIAL APPLICATION

[0076] The pressure sensitive adhesive sheet of the present disclosure can be favorably used for producing various types of cement structures such as buildings, roads, bridges, dams, tunnels, and port facilities and the like.

DESCRIPTION OF CODES

[0077] 1 pressure sensitive adhesive sheet

11 base material

11a film

1 lb release agent layer

12 adhesive layer

Claims

What Is Claimed Is:

1. A pressure sensitive adhesive sheet for covering a surface of cement material that is concrete, mortar, or cement, comprising:

a pressure sensitive adhesive layer containing a polymer derived from monomer components including an alkyl (meth)acrylate with 4 to 18 carbon atoms and a monomer with at least one functional group containing a nitrogen atom;

wherein the pressure sensitive adhesive layer can adhere to the surface of the concrete material in a wet condition, and can be peeled from the surface of the cement material after hardening.

2. The pressure sensitive adhesive sheet according to claim 1, wherein the monomer component contains 70 to 90 mass parts of the alkyl (meth)acrylate with 4 to 18 carbon atoms, and 10 to 30 mass parts of the monomer with at least one functional group containing a nitrogen atom.

3. A roll, made by rolling the pressure sensitive adhesive sheet according to claim 1 or 2.

4. A method for manufacturing a cement structure which is concrete, mortar, or cement, comprising:

obtaining the cement material with an exposed surface;

applying the pressure sensitive adhesive layer of the pressure sensitive adhesive sheet described in any one of claims 1 through 3 to the exposed surface while the exposed surface is in a wet condition;

obtaining a cement structure by hardening the cement material; and

removing the pressure sensitive adhesive sheet from the cement structure.