Peelable aqueous coating composition for concrete, peelable coating, and temporary protective laminate

Abstract

To provide a peelable aqueous coating composition for concrete which permits thick coating and formation of a peelable coating that is easily peelable even when coating on concrete.SOLUTION: A peelable aqueous coating composition for concrete contains an aqueous urethane resin, an associative thickener, and water.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an aqueous strippable coating composition for concrete, a strippable coating film, and a temporary protection laminate.

Background Art

[0002] In recent years, in the civil engineering field such as tunnels and bridges, a precast method using precast concrete has been widely used. Usually, precast concrete is stored at a factory after production, but problems such as cracks occurring on the concrete surface during storage have arisen. In order to suppress the occurrence of such cracks, a curing sheet (blue sheet) or the like is used, but there are problems such as the labor of curing, the deterioration of the curing sheet over time, dirt and mold adhering to the gap between the concrete and the curing sheet, and the need for surface repair before shipping the precast concrete.

[0003] As a solution to these problems, it is conceivable to use a strippable coating composition (for example, Patent Document 1). By using these strippable coating compositions, curing can be easily performed, and the adhesion of dirt and mold to precast concrete can be suppressed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, it has been found that the peelable coating film formed from the conventional peelable coating composition has insufficient coating film strength. Since concrete has many irregularities such as cavities on its surface, when a coating film with insufficient coating film strength is formed on such concrete and the peelable coating film is peeled off, the peelable coating film will break, and it has been found that the workability during peeling will be significantly reduced. In recent years, it has also been desired to reduce the load on the human body and the environment during painting or the preparation of the coating composition even in the peelable coating composition.

[0006] Therefore, an object of the present invention is to provide an aqueous peelable coating composition for concrete that enables thick-film coating and can easily form a peelable coating film that can be peeled off even when applied to concrete.

Means for Solving the Problems

[0007] As a result of intensive studies by the present inventors, it has been found that according to the following exemplary embodiments, the above problems are solved, and the present invention has been completed. That is, the means for solving the above problems include the following exemplary embodiments.

[0008] [1] An aqueous peelable coating composition for concrete containing an aqueous urethane resin, an associative thickener, and water.

[0009] [2] Furthermore, the aqueous peelable coating composition for concrete according to [1], which further contains an acrylic resin.

[0010] [3] The aqueous peelable coating composition for concrete according to [1] or [2], which contains 20 to 40% by mass of the urethane resin based on 100% by mass of the total amount of the aqueous peelable coating composition for concrete.

[0011] [4] The concrete water-based peelable coating composition according to any one of [1] to [3], containing 0.5 to 5.0% by mass of the associative thickener with respect to 100% by mass of the non-volatile content.

[0012] [5] A peelable coating film formed from the concrete water-based peelable coating composition according to any one of [1] to [4].

[0013] [6] A temporary protection laminate including concrete and the peelable coating film according to [5]. [Advantages of the Invention]

[0014] According to one embodiment of the present invention, it is possible to provide a concrete water-based peelable coating composition capable of forming a peelable coating film that enables thick-film coating and can be easily peeled off even when applied to concrete. Further, according to the concrete water-based peelable coating composition according to one embodiment of the present invention, by forming a peelable coating film on the concrete, the concrete can be easily cured, cracks, stains, mold adhesion, etc. that may occur in the concrete over time can be suppressed, and furthermore, the moisture in the concrete can be retained, and the strength development of the concrete can also be promoted. In addition, since the concrete water-based peelable coating composition according to the present invention is an aqueous paint, the risk of fire is low, and the load on the human body and the environment can be reduced. [Embodiments for Carrying Out the Invention]

[0015] [[Concrete Water-Based Peelable Coating Composition]] The concrete water-based peelable coating composition according to the present invention (hereinafter also referred to as "this composition") contains an aqueous urethane resin, an associative thickener, and water.

[0016] The term "for concrete" means that at least a part of the peelable coating film obtained from this composition is used in contact with the concrete. In the present invention, "concrete" is not particularly limited and refers to concrete in a broad sense (a material obtained by hardening aggregates with a binder), which has been generally called concrete.

[0017] According to the present composition, it is possible to easily cure concrete, and it is possible to suppress the occurrence of cracks, adhesion of dirt, mold, etc. when storing concrete or the like. Further, by providing a peelable coating film obtained from the present composition on the concrete, it is possible to retain moisture in the concrete and promote the development of the strength of the concrete. Furthermore, since the present composition can easily form a peelable coating film having a high coating film strength, even when a peelable coating film is formed by coating concrete having many irregularities such as holes on the surface, the peelable coating film can be easily peeled from the concrete. From the above, the present composition is suitably used as an aqueous peelable coating composition for curing concrete used for curing concrete. Further, by applying the present composition to a dirty concrete surface to form a peelable coating film and peeling off the peelable coating film, it is also possible to remove the dirt adhering to the concrete.

[0018] The viscosity at 23°C measured using a B-type viscometer of the present composition is preferably 100 to 150,000 mPa·s, more preferably 20,000 to 100,000 mPa·s. The present composition having such a viscosity exhibits appropriate fluidity and excellent sag resistance, so that coating can be easily performed.

[0019] <aqueous urethane resin> Examples of the aqueous urethane resin include urethane resins having water or water as the main solvent or dispersion medium, or urethane resins that are miscible with water (dilutable with water). More specifically, examples include water-dispersed urethane resins, water-soluble urethane resins, and self-emulsifying urethane resins. Among these, from the viewpoints of handling workability and the like, water-dispersed urethane resins are preferred, and urethane resin emulsions or urethane resin dispersions are more preferred. Such aqueous urethane resins can be synthesized by conventionally known methods, for example, solution polymerization method, suspension polymerization method, emulsion polymerization method, seed polymerization method, miniemulsion polymerization method, microemulsion polymerization method, surfactant-free (soap-free) emulsion polymerization method. In addition to these, an aqueous urethane resin can also be obtained by emulsifying a urethane resin by a known method, for example, phase inversion emulsification, D-phase emulsification, forced emulsification, gel emulsification, inversion emulsification, high-pressure emulsification, etc. The aqueous urethane resin may be used alone or in combination of two or more.

[0020] As the aqueous urethane resin, known aqueous urethane resins can be used without limitation and are not particularly limited. For example, a urethane resin emulsion or a urethane resin dispersion obtained by dispersing a urethane prepolymer obtained by reacting a raw material containing a polyisocyanate and a polyol in water can be mentioned.

[0021] The polyisocyanate is a compound having at least two isocyanate groups in one molecule, and examples thereof include aliphatic polyisocyanates, alicyclic polyisocyanates, araliphatic polyisocyanates, aromatic polyisocyanates, and derivatives of the polyisocyanates. The polyisocyanate may be used alone or in combination of two or more.

[0022] Examples of the aliphatic polyisocyanate include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, 1,5-pentamethylene diisocyanate, 1,6-hexamethylene diisocyanate), 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, dimer acid diisocyanate, methyl 2,6-diisocyanatohexanoate and other aliphatic diisocyanate compounds; Aliphatic triisocyanate compounds such as 2-isocyanatoethyl 2,6-diisocyanatohexanoate, 1,6-diisocyanato-3-isocyanatomethylhexane, 1,4,8-triisocyanatooctane, 1,6,11-triisocyanatoundecane, 1,8-diisocyanato-4-isocyanatomethyloctane, 1,3,6-triisocyanatohexane, 2,5,7-trimethyl-1,8-diisocyanato-5-isocyanatomethyloctane; are mentioned.

[0023] Examples of the alicyclic polyisocyanate include alicyclic diisocyanate compounds such as 1,3-cyclopentane diisocyanate, 1,3-cyclopentene diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate), methylene bis(cyclohexyl isocyanate), methylcyclohexane diisocyanate, 4-methyl-1,3-cyclohexylene diisocyanate (hydrogenated TDI), 2-methyl-1,3-cyclohexylene diisocyanate, 1,3- or 1,4-bis(isocyanatomethyl)cyclohexane (hydrogenated xylylene diisocyanate), methylene bis(4,1-cyclohexanediyl) diisocyanate (hydrogenated MDI), norbornane diisocyanate; Aliphatic polyisocyanate compounds such as 1,3,5-triisocyanatocyclohexane, 1,3,5-trimethylisocyanatocyclohexane, 2-(3-isocyanatopropyl)-2,5-di(isocyanatomethyl)-bicyclo(2.2.1)heptane, 2-(3-isocyanatopropyl)-2,6-di(isocyanatomethyl)-bicyclo(2.2.1)heptane, 3-(3-isocyanatopropyl)-2,5-di(isocyanatomethyl)-bicyclo(2.2.1)heptane, 5-(2-isocyanatoethyl)-2-isocyanatomethyl-3-(3-isocyanatopropyl)-bicyclo(2.2.1)heptane, 6-(2-isocyanatoethyl)-2-isocyanatomethyl-3-(3-isocyanatopropyl)-bicyclo(2.2.1)heptane, 5-(2-isocyanatoethyl)-2-isocyanatomethyl-2-(3-isocyanatopropyl)-bicyclo(2.2.1)-heptane, 6-(2-isocyanatoethyl)-2-isocyanatomethyl-2-(3-isocyanatopropyl)-bicyclo(2.2.1)heptane; may be mentioned.

[0024] Examples of the araliphatic polyisocyanate include, for example, araliphatic diisocyanate compounds such as methylene bis(4,1-phenylene) diisocyanate (MDI), 1,3- or 1,4-xylylene diisocyanate, ω,ω'-diisocyanato-1,4-diethylbenzene, 1,3- or 1,4-bis(1-isocyanato-1-methylethyl)benzene (tetramethylxylylene diisocyanate); araliphatic triisocyanate compounds such as 1,3,5-triisocyanatomethylbenzene; may be mentioned.

[0025] Examples of the aromatic polyisocyanate include, for example, Aromatic diisocyanate compounds such as m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,4- or 1,5-naphthalene diisocyanate, 2,4-tolylene diisocyanate (2,4-TDI), 2,6-tolylene diisocyanate (common name: 2,6-TDI), 4,4'-toluidine diisocyanate, 4,4'-diphenyl ether diisocyanate, etc.; Aromatic triisocyanate compounds such as triphenylmethane-4,4',4''-triisocyanate, 1,3,5-triisocyanatobenzene, 2,4,6-triisocyanatotoluene, etc.; Aromatic tetraisocyanate compounds such as 4,4'-diphenylmethane-2,2',5,5'-tetraisocyanate, etc. can be mentioned.

[0026] Examples of the derivatives of the polyisocyanate include, for example, dimers, trimers, biurets, allophanates, uretdiones, uretoimines, isocyanurates, oxadiazinetriones, polyols (alcohol adducts), polymethylene polyphenyl polyisocyanates (crude MDI, polymeric MDI), and crude TDI of the polyisocyanate.

[0027] Examples of the polyol include diol compounds, polyether diol compounds, polyester diol compounds, polyether ester diol compounds, polycarbonate diol compounds, and aliphatic polyols having three or more hydroxyl groups. One type of the polyol may be used, or two or more types may be used.

[0028] Examples of the diol compound include, for example, Aliphatic diols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,2 - butanediol, 1,3 - butanediol, 2,3 - butanediol, 1,4 - butanediol, 2 - methyl - 1,3 - propanediol, 1,5 - pentanediol, neopentyl glycol, 3 - methyl - 1,5 - pentanediol, 2,4 - diethyl - 1,5 - pentanediol, 2,2,4 - trimethylpentane - 1,3 - diol, 1,6 - hexanediol, 2,5 - hexanediol, 1,5 - heptanediol, 1,7 - heptanediol, 1,8 - octamethylene diol, 2,2,4 - trimethyl - 1,3 - pentanediol, tricyclodecane dimethanol, 1,4 - cyclohexane dimethanol; Alicyclic diols such as hydrogenated bisphenol A, hydrogenated xylylene glycol, cyclohexanediol, cyclohexane dimethanol, hydrogenated dimer diol; Aromatic or araliphatic diols such as bisphenol A, bis - hydroxyethyl terephthalate, catechol, resorcinol, hydroquinone, 1,3 - or 1,4 - xylylene diol; are mentioned.

[0029] Examples of the polyether diol compound include alkylene oxide adducts of the diol compound, and ring - opening (co)polymers of alkylene oxides and cyclic ethers (e.g., tetrahydrofuran). Specific examples include polyethylene glycol, polypropylene glycol, (block or random) copolymers of ethylene glycol - propylene glycol, glycol, polytetramethylene glycol, polyhexamethylene glycol, polyoctamethylene glycol.

[0030] Examples of the polyester diol compound include compounds obtained by polycondensing a dicarboxylic acid such as adipic acid, succinic acid, sebacic acid, glutaric acid, maleic acid, fumaric acid, phthalic acid or its anhydride and the diol compound under conditions of an excess of hydroxyl groups. Specific examples include ethylene glycol-adipic acid condensate, 1,4-butanediol-adipic acid condensate, 1,6-hexanediol-adipic acid condensate, ethylene glycol-propylene glycol-adipic acid condensate, and polylactone diol obtained by ring-opening polymerization of lactone using glycol as an initiator.

[0031] Examples of the polyether ester diol compound include compounds obtained using a diol containing an ether group (e.g., the diol compound or the polyether diol compound), the dicarboxylic acid or its anhydride, and an alkylene oxide. Specific examples include polytetramethylene glycol-adipic acid condensate.

[0032] Examples of the polycarbonate diol compound include compounds represented by HO-R-(O-C(=O)-O-R)x-OH [where each R is independently a saturated fatty acid diol residue having 1 to 12 carbon atoms. x is the number of repeating units of the molecule and is usually an integer of 5 to 50.]. Such a polycarbonate diol compound can be obtained, for example, by a transesterification method in which a saturated aliphatic diol and a substituted carbonate (e.g., diethyl carbonate, diphenyl carbonate) are used and reacted under conditions of an excess of hydroxyl groups, or by a method in which the saturated aliphatic diol and phosgene are used and reacted.

[0033] Examples of the aliphatic polyol having three or more hydroxyl groups include glycerin, trimethylolpropane, pentaerythritol, and sorbitol.

[0034] When synthesizing the urethane prepolymer, conventionally known compounds that have been used in synthesizing urethane prepolymers, for example, compounds having two or more hydroxyl groups and one or more carboxyl groups in the molecule, or compounds having two or more hydroxyl groups and one or more sulfonic acid groups in the molecule, may be used. One kind or two or more kinds of the conventionally known compounds may be used.

[0035] The synthesis of the urethane prepolymer can be carried out based on conventionally known methods.

[0036] When the aqueous urethane resin used as a raw material of this composition is an aqueous urethane resin containing water (e.g., urethane resin emulsion, urethane resin dispersion), the solid content concentration of the aqueous urethane resin can be appropriately determined according to the purpose of use and the like, but is preferably 20 to 60% by mass. By using an aqueous urethane resin satisfying this concentration range, handling becomes easy and the concentration of the aqueous urethane resin in this composition can be easily adjusted.

[0037] As the aqueous urethane resin, a resin obtained based on a conventionally known method may be used, or a commercially available product may be used. Specific examples of the commercially available products include the "ADEKA BONTAITER" series manufactured by ADEKA CORPORATION.

[0038] The content of the solid content of the aqueous urethane resin relative to 100% by mass of the total amount of this composition is preferably 20 to 40% by mass, more preferably 25 to 35% by mass. Also, the content of the solid content of the aqueous urethane resin relative to 100% by mass of the non-volatile content of this composition is preferably 45 to 99.5% by mass, more preferably 50 to 99.0% by mass, and even more preferably 60 to 95% by mass. When the content of the aqueous urethane resin is within the above range, the peelable coating film formed from this composition can be easily peeled off even when applied to concrete.

[0039] The non-volatile content of the present composition means the coating film (heating residue) after sufficiently heating and drying the present composition. Specifically, the non-volatile content (mass %) of the present composition is measured by weighing 1 ± 0.2 g of the present composition into a flat-bottomed dish in accordance with JIS K 5601-1-2:2008, spreading it evenly using a wire of known mass, drying it at 23°C for 24 hours, and then measuring the heating residue and the mass of the wire when heated at a heating temperature of 105°C for 1 hour (under normal pressure). Note that this non-volatile content (mass %) is equivalent to the total amount of the solid content (components other than the dispersion medium and the solvent) of the raw material components used in the present composition.

[0040] <Associative thickener> The associative thickener is not particularly limited as long as it is a component other than the aqueous urethane resin, and a conventionally known associative thickener can be used. The associative thickener is usually a polymer having a hydrophilic group and a hydrophobic group in the molecule, and exhibits a thickening effect by the association of the hydrophilic groups or the hydrophobic groups with each other, such as between molecules. The present composition is not other thickeners other than the associative thickener among the conventionally known thickeners, but requires an associative thickener, and is included together with the aqueous urethane resin and water, so that it is possible to perform thick-film coating, and it is possible to easily obtain a composition that is difficult to sag, and the strength of the peelable coating film obtained from the composition can be increased. Therefore, the peelable coating film can be easily peeled off even when applied to concrete. The associative thickener may be used alone or in combination of two or more.

[0041] Examples of the hydrophilic group of the associative thickener include nonionic hydrophilic groups such as polyoxyalkylene groups, ionic hydrophilic groups (anionic hydrophilic groups such as carboxylate groups (-COO - ), sulfonate groups (-SO 3 - ), etc.), and cationic hydrophilic groups such as quaternary ammonium groups). Among these, as the hydrophilic group, a nonionic hydrophilic group is preferable.

[0042] Examples of the hydrophobic group include less polar functional groups such as an optionally substituted alkyl group and phenyl group. Among these, an alkyl group is preferred. The alkyl group may be linear, branched, or cyclic. The number of carbon atoms of the alkyl group is preferably 4 to 30. Among the alkyl groups, a branched alkyl group is particularly preferred in terms of dispersibility in water and the like.

[0043] The associative thickener is preferably a urethane-based associative thickener. That is, it is preferably an associative thickener having a polyurethane backbone. Examples of the compound serving as a raw material for the polyurethane of the backbone include the compounds exemplified in the column of the aqueous urethane resin. The urethane-based associative thickener can be classified into, for example, an ester-based, ether-based, carbonate-based, etc. depending on the type of polyol used as a raw material, and an ether-based associative thickener is more preferred. For example, in the case of an ether-based associative thickener in which the polyol used as a raw material is a polyether polyol, the polyether part of the polyether polyol becomes a hydrophilic group. When a polyisocyanate is used as a raw material for the urethane-based associative thickener, the polyisocyanate is preferably an aliphatic polyisocyanate.

[0044] As the associative thickener, a thickener obtained based on a conventionally known method may be used, or a commercially available product may be used. Examples of the commercially available products include SN thickener series such as SN thickener 612, 612NC, 619, 621N, 621TF, 623N, 624N, 625N, 627N, 629N, 660T, 665T manufactured by San Nopco Ltd.; Nopar series such as Nopar 700N, 710N, 3303 manufactured by San Nopco Ltd.; Adekanol UH140S, UH438, UH752, UH814 manufactured by ADEKA Corporation; Rheolate 288 manufactured by ELEMENTIS. Examples of the commercially available products also include Aquaflow XLS-530 commercially available from ASHLAND as a nonionic synthetic associative thickener.

[0045] The content of the associative thickener relative to 100% by mass of the non-volatile content of the composition is preferably 0.5 to 5.0% by mass, more preferably 0.5 to 2.5% by mass. When the content of the associative thickener is within the above range, coating with a thick film is enabled, and a composition that is not likely to sag can be easily obtained. The peelable coating film formed from the composition can be easily peeled even when applied to concrete.

[0046] <Water> When preparing the composition, raw materials such as aqueous urethane resin used may contain water. Therefore, the water contained in the composition may be only the water contained in the raw materials, but from the viewpoints of making it easier to prepare the composition and being able to easily obtain a composition with excellent coating workability, etc., when preparing the composition, it is preferable to blend water other than the water that can be contained in the raw materials such as aqueous urethane resin used when preparing the composition. The water other than the water that can be contained in the raw materials is not particularly limited, and examples include tap water, ion-exchanged water, deionized water, etc.

[0047] The content of water (including the water that can be contained in the raw materials used when preparing the composition) relative to 100% by mass of the total amount of the composition is preferably 20 to 75% by mass, more preferably 40 to 70% by mass, and even more preferably 50 to 65% by mass. When the water content is within the above range, a composition that enables thick-film coating and has excellent coating workability while being less likely to sag can be easily obtained.

[0048] Also, from the viewpoints of being able to obtain a composition with excellent coating workability, etc., the content of the non-volatile content in the composition is preferably 25 to 80% by mass, more preferably 30 to 60% by mass, and it is preferable to use water or the like so that the content of such non-volatile content is obtained.

[0049] <Other components> The composition may further contain other components such as resins other than aqueous urethane resins such as acrylic resins, pigments (e.g., extender pigments, coloring pigments), pigment dispersants, thickeners other than associative thickeners, defoamers, film-forming aids, surface modifiers (leveling agents), curing agents, silane coupling agents, plasticizers, solvents, etc., as long as the object of the present invention is not impaired. These other components may each be used alone or in combination of two or more.

[0050] [Acrylic resin] As the resin other than the aqueous urethane resin, an acrylic resin is preferable, and the composition preferably contains an acrylic resin. By containing an acrylic resin, the peelable coating film formed from the composition exhibits better peelability. In addition, the "acrylic resin" in this specification is a general term for acrylic resins and methacrylic resins. Hereinafter, "(meth)acrylic" means methacrylic or acrylic, and similar expressions (e.g., (meth)acrylate) have the same meaning.

[0051] As the acrylic resin used as a raw material of the composition, an aqueous dispersion of an acrylic resin, particularly an emulsion, is preferable from the viewpoints that the composition which is an aqueous peelable coating composition can be easily prepared and a peelable coating film having desired physical properties can be easily formed.

[0052] Examples of the acrylic resin emulsion include conventionally known emulsions obtained by emulsion polymerization of a polymerizable unsaturated monomer component containing one or more (meth)acryloyl compounds as essential components and, if necessary, one or more other polymerizable unsaturated monomers in one or more stages in the presence of water and a dispersion stabilizer.

[0053] Examples of the (meth)acryloyl compound include linear or branched alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, and isostearyl (meth)acrylate; alicyclic alkyl (meth)acrylates such as cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and adamantyl (meth)acrylate; aralkyl (meth)acrylates such as benzyl (meth)acrylate; alkoxyalkyl (meth)acrylates such as 2-methoxyethyl (meth)acrylate and 2-ethoxyethyl (meth)acrylate; fluoroalkyl (meth)acrylates such as hexafluoro-i-propyl (meth)acrylate, perfluorooctylmethyl (meth)acrylate, and perfluorooctylethyl (meth)acrylate; phosphate group-containing (meth)acrylates such as (2-(meth)acryloyloxyethyl) acid phosphate and (2-(meth)acryloyloxypropyl) acid phosphate; N,N-dialkylaminoalkyl (meth)acrylates such as N,N-diethylaminoethyl (meth)acrylate; (meth)acrylamide; carboxyl group-containing (meth)acryloyl monomers such as (meth)acrylic acid and β-carboxyethyl (meth)acrylate; carbonyl group-containing (meth)acryloyl monomers such as acetoacetoxyethyl (meth)acrylate and diacetone (meth)acrylamide; epoxy group-containing (meth)acryloyl monomers such as glycidyl (meth)acrylate, β-methylglycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, 3,4-epoxycyclohexylethyl (meth)acrylate, and 3,4-epoxycyclohexylpropyl (meth)acrylate; isocyanato group-containing (meth)acryloyl monomers such as isocyanatoethyl (meth)acrylate;Alkoxysilyl group-containing (meth)acryloyl monomers such as γ-(meth)acryloyloxypropyltrimethoxysilane and γ-(meth)acryloyloxypropyltriethoxysilane; Oxidation-curable group-containing (meth)acryloyl monomers such as dicyclopentenyl oxyethyl (meth)acrylate, dicyclopentenyl oxypropyl (meth)acrylate, and dicyclopentenyl (meth)acrylate; Heterocyclic group-containing (meth)acryloyl monomers such as 1,2,2,6,6-pentamethylpiperidyl (meth)acrylate and 2,2,6,6-tetramethylpiperidinyl (meth)acrylate; Quaternary ammonium base-containing (meth)acrylates such as 2-((meth)acryloyloxy)ethyltrimethylammonium chloride, 2-((meth)acryloyloxy)ethyltrimethylammonium bromide, (meth)acryloylaminopropyltrimethylammonium chloride, (meth)acryloylaminopropyltrimethylammonium bromide, tetrabutylammonium (meth)acrylate, tetramethylammonium (meth)acrylate, trimethylbenzylammonium (meth)acrylate, and 2-((meth)acryloyloxy)ethyltrimethylammonium dimethyl phosphate; (Meth)acrylates having a polyoxyalkylene chain are included.;

[0054] Examples of the other polymerizable unsaturated monomers include cyano group-containing compounds such as acrylonitrile and methacrylonitrile; vinyl ester compounds such as vinyl acetate and vinyl propionate; vinyl aromatic compounds such as styrene and α-methylstyrene; carboxyl group-containing polymerizable unsaturated monomers such as maleic acid, itaconic acid, and crotonic acid; carbonyl group-containing polymerizable unsaturated monomers such as acrolein, methacrolein, formylstyrene, vinyl alkyl ketones having 4 to 7 carbon atoms (e.g., vinyl methyl ketone, vinyl ethyl ketone, vinyl butyl ketone), and acetoacetoxyallyl ester; epoxy group-containing polymerizable unsaturated monomers such as allyl glycidyl ether; isocyanato group-containing polymerizable unsaturated monomers such as m-i-propenyl-α,α-dimethylbenzyl isocyanate; alkoxysilyl group-containing polymerizable unsaturated monomers such as vinyltrimethoxysilane and vinyltriethoxysilane; oxidation-curable group-containing polymerizable unsaturated monomers such as reaction products of epoxy group-containing polymerizable unsaturated monomers or hydroxyl group-containing polymerizable unsaturated monomers with unsaturated fatty acids; and fluorovinyl ethers such as fluoroalkyl trifluorovinyl ether and perfluoroalkyl trifluorovinyl ether.

[0055] When the acrylic resin is a copolymer of a (meth)acryloyl compound and other polymerizable unsaturated monomers, the content of the structural unit derived from the (meth)acryloyl compound with respect to 100% by mass of all the structural units in the acrylic resin is preferably 20 to 99.9% by mass, more preferably 40 to 99.5% by mass.

[0056] The glass transition temperature (Tg) of the acrylic resin is not particularly limited, but from the viewpoint of further improving the peelability of the peelable coating film formed from the present composition, it is preferably 0 to 40°C. The glass transition temperature can be measured by a differential scanning calorimeter (DSC).

[0057] The content of the solid component in the emulsion is preferably 30% by mass or more, more preferably 35% by mass or more, preferably 70% by mass or less, and more preferably 60% by mass or less from the viewpoints of the stability of the emulsion and the like.

[0058] The aqueous dispersion or emulsion is a dispersion in which a resin is dispersed in a dispersion medium containing water (hereinafter also referred to as "aqueous medium"). The aqueous medium is not particularly limited as long as it contains water, but the water content in the aqueous medium is preferably 50 to 100% by mass, more preferably 60 to 100% by mass.

[0059] The aqueous medium may contain a medium other than water. Examples of such a medium include acetone, methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, diacetone alcohol, dioxane, ethylene glycol, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol monopropyl ether, and ethylene glycol monohexyl ether. These can be used alone or in combination of two or more.

[0060] The emulsion can be prepared, for example, by emulsifying a resin using a surfactant to form an emulsion. Also, an emulsion can be directly prepared by emulsion polymerization of the monomers forming the resin. The surfactant is not particularly limited and can be appropriately selected from anionic surfactants and nonionic surfactants, and may be one kind or two or more kinds.

[0061] As the acrylic resin, an acrylic resin obtained by a conventionally known method may be used, or a commercially available product may be used. Examples of the commercially available products include Mobinyl 6530 (manufactured by Nippon Coating Resin Co., Ltd.), Vinibran 2684 (manufactured by Nisshin Chemical Industry Co., Ltd.), Cybinol YC-455 (manufactured by Cyden Chemical Co., Ltd.), Cybinol EK-61 (manufactured by Cyden Chemical Co., Ltd.), and DXV-4051 (manufactured by VANORA).

[0062] When the composition contains an acrylic resin, the content of the solid component of the acrylic resin based on 100% by mass of the total amount of the composition is preferably 1 to 20% by mass, more preferably 2 to 18% by mass, and still more preferably 3 to 15% by mass. When the content of the acrylic resin is within the above range, the peelable coating film formed from the composition can be easily peeled off even when applied to concrete.

[0063] [Defoaming agent] The defoaming agent is preferably a material that can suppress the generation of bubbles during the production and coating of the composition, or a material that can break the bubbles generated in the composition. By using a defoaming agent, for example, the generation of bubble marks or pinholes in the obtained peelable coating film can be suppressed, and thus the coating film strength can be further improved. In addition, when curing concrete using a peelable coating film in which the generation of bubble marks or pinholes is suppressed, the concrete can be cured more easily, and cracks, dirt, and mold adhesion that may occur in the concrete over time can be more suppressed. Furthermore, the moisture in the concrete can be better retained, and the strength development of the concrete can also be promoted.

[0064] Examples of the defoaming agent include silicone-based defoaming agents, polymer-based (non-silicone-based) defoaming agents, and mineral oil-based defoaming agents.

[0065] When the composition contains an antifoaming agent, the solid content of the antifoaming agent is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, preferably 2% by mass or less, and more preferably 1.5% by mass or less based on 100% by mass of the non-volatile content of the composition.

[0066] [Film-forming aid] Examples of the film-forming aid include conventionally known alcohols, glycol ethers, esters, etc. For example, alcohols having 1 to 3 carbon atoms such as isopropyl alcohol, 2,2,4-trimethylpentanediol, 2,2,4-trimethylpentanediol, benzyl alcohol, etc.; glycol ethers such as ethylene glycol diethyl ether, diethylene glycol diethyl ether, propylene glycol diethyl ether, dipropylene glycol diethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, dipropylene glycol n-butyl ether, ethylene glycol monobenzyl ether, ethylene glycol monophenyl ether, etc.; esters such as 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, 2,2,4-trimethylpentanediol diisobutyrate, etc.

[0067] When the composition contains a film-forming aid, the content of the film-forming aid is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, preferably 15% by mass or less, and more preferably 5% by mass or less based on 100% by mass of the total amount of the composition from the viewpoints of excellent film-forming properties at low temperatures and easily forming a peelable coating film with excellent appearance.

[0068] <Preparation method of the composition> The preparation method of the composition is not particularly limited. An aqueous urethane resin, an associative thickener, water, and other components such as an acrylic resin, an antifoaming agent, and a film-forming aid, if necessary, can be added to a stirring container in any order, and the components can be mixed by known stirring and mixing means and dispersed or dissolved in water for preparation. As stirring and mixing means, for example, means using a paint shaker, a high-speed disperser, a sand grinder, a basket mill, a ball mill, a three-roll mill, a Ross mixer, a planetary mixer can be mentioned.

[0069] <Peelable coating film and temporary protection laminate> The peelable coating film according to the present invention is formed from this composition and is preferably formed on concrete. The temporary protection laminate according to the present invention includes concrete and the peelable coating film. The peelable coating film may be formed from this composition on a peelable support, and then peeled from the peelable support and provided on concrete. However, it is preferable to form the peelable coating film by applying this composition on concrete and drying it. This composition can be applied in a thick film, and even when applied in such a thick film, it is difficult to sag and has excellent coating workability. Therefore, a thick-film peelable coating film suitable for curing concrete can be easily formed. Further, since the peelable coating film has excellent coating film strength, it can be easily peeled even after being formed on concrete.

[0070] The coating method is not particularly limited, and a conventionally known coating method can be used. For example, it can be applied using a roller, a brush, a spray, etc. The drying temperature may be appropriately adjusted according to the solvent, etc. For example, when drying in a short time such as 10 seconds to 30 minutes is required, it can be set to 40 to 200 °C, and 60 to 160 °C is preferable. Further, when drying in a short time is not required, it may be dried at room temperature, for example.

[0071] The peelable coating film is preferably removed after being formed on concrete from the viewpoint that the effects of the present invention are more exerted, etc., but in some cases, it may not be removed.

[0072] The thickness of the peelable coating film (dry coating film) is preferably 100 to 1000 μm, more preferably 200 to 600 μm, from the viewpoints that sufficient curing of concrete and the like can be performed and it can be easily peeled from the concrete.

[0073] The concrete in the temporary protection laminate is not particularly limited, and specific examples include precast concrete and concrete structures such as bridges and tunnels.

Examples

[0074] Hereinafter, the present invention will be described in more detail based on examples. However, the present invention is not limited to these examples.

[0075] [Examples 1 to 6 and Comparative Example 1] (1) Preparation of water-based peelable coating composition for concrete Each component described in Table 1 was added to a container according to the amounts (numerical values) described in Table 1, stirred, and mixed to prepare a water-based peelable coating composition for concrete (hereinafter also simply referred to as "coating composition"). The explanations of each component described in Table 1 are shown in Table 3. The numerical values of each component in Table 1 indicate parts by mass.

[0076] (2) Evaluation test Each coating composition prepared in Examples 1 to 6 and Comparative Example 1 was evaluated by the following method. The results are shown in Table 1.

[0077] · Elongation test The elongation of the coating film obtained from each coating composition was evaluated in accordance with the 6) crack followability test method of the quality test method of the concrete coating material in the "Steel Road Bridge Anti-Corrosion Manual". Specifically, the prepared coating composition was applied to a polypropylene resin plate with a brush so that the dry film thickness of the coating film obtained was 200 μm, cured at 23°C for 120 hours, then heated at 80°C for 60 minutes and cooled to form a coating film. Next, the formed coating film was peeled off from the polypropylene resin plate to obtain a free coating film. Subsequently, it was confirmed that there were no deformations or pinholes in the free coating film, and test pieces were obtained using a punching machine. Using a material testing machine (manufactured by Shimadzu Corporation, Shimadzu small desktop testing machine, model "EZ-L") capable of maintaining a constant crosshead separation speed, the test piece was pulled at a crosshead separation speed of 5 mm / min, a gauge length of 40 mm, and a test temperature of 23°C. During the tensile test, a tensile load-displacement curve with the tensile load on the vertical axis and the displacement on the horizontal axis was recorded. From the tensile load-displacement curve obtained in this test, the elongation at the yield or the elongation at the moment of fracture (the length of displacement) of the test piece was divided by the gauge length (40 mm) and multiplied by 100 to calculate the elongation rate (%), and the elongation of the coating film obtained from each coating composition was evaluated. When the value of the elongation rate is in the range of 200 to 800%, it indicates that when the coating film is formed on concrete and then peeled off, the coating film will not tear during the peeling process and can be easily and neatly peeled off from the concrete.

[0078] ·Tensile Strength Test In the same manner as the above elongation test, during the tensile test, the tensile strength (N) at the time when the test piece broke was measured.

[0079] ·Adhesion Test On a 300 mm × 300 mm × 60 mm (thick) concrete paving slab (base material) specified in JIS A 5371:2016, each of the paint compositions prepared above was applied with a brush so that the dry film thickness of the paint film obtained was 200 μm, and left standing for 24 hours under the conditions of a temperature of 23°C and a relative humidity of 50% to form a paint film. Next, on the formed paint film, the same paint composition as the paint composition on which the paint film was formed was further applied so that the dry film thickness of the obtained paint film was 200 μm, and then dried for 7 days under the conditions of a temperature of 23°C and a relative humidity of 50% to form a 400-μm-thick paint film. Thereafter, the peelability (initial) when the formed 400-μm-thick paint film was peeled from the base material under the conditions of a temperature of 23°C and a relative humidity of 50% was evaluated according to the following criteria. Instead of drying for 7 days, a 400-μm-thick paint film was formed in the same manner as above except that it was dried for 1 year under the conditions of a temperature of 23°C and a relative humidity of 50%. Thereafter, the peelability (after 1 year) when the formed 400-μm-thick paint film was peeled from the base material under the conditions of a temperature of 23°C and a relative humidity of 50% was evaluated according to the following criteria. ◎ The paint film can be easily peeled from the base material (the paint film does not stretch and tear). ○ It is difficult to peel the paint film from the base material, but peeling is possible (the paint film does not stretch and tear). △ It is difficult to peel the paint film from the base material, but peeling is possible (peeling is possible, but a part of the paint film stretches and tears). × The paint film cannot be peeled from the base material (it stretches and tears).

[0080] [Table 1]

[0081] [Examples 7 to 9 and Comparative Examples 2 to 8] (1) Preparation of water-based strippable paint composition for concrete Each component described in Table 2 was added to a container according to the amounts (numerical values) described in Table 2, stirred, and mixed to prepare a water-based strippable paint composition for concrete (hereinafter also simply referred to as "paint composition"). The explanations of the respective components described in Table 2 are shown in Table 3. The numerical values of the respective components in Table 2 each indicate parts by mass.

[0082] (2) Evaluation Test Each of the coating compositions prepared in Examples 7 to 9 and Comparative Examples 2 to 8 was evaluated by the following method. The results are shown in Table 2.

[0083] · Sag resistance test Each of the coating compositions prepared in Examples 7 to 9 and Comparative Examples 2 to 8 was applied to a glass plate of 200 mm × 200 mm × thickness 0.3 mm under the conditions of 23°C and relative humidity 50% on a horizontal table using a box-type sag tester (gap 500 μm) shown in 6.4 of JIS K 5400:1990. Immediately after that, the glass plate was vertically stood so that the track line of the sag tester became horizontal, and the sag resistance of the coating film was examined. When the coating composition that flowed out into the gap (3 mm) between the coating layers formed by the sag tester did not reach 1 / 2 of the gap distance (when the length hanging down from the coating layer formed by the sag tester did not reach 1.5 mm), it was judged that sag did not occur (○), and when it reached 1 / 2 of the gap distance, it was judged that sag occurred (×).

[0084] · Adhesion test An adhesion test was conducted in the same manner as in Examples 1 to 6 and Comparative Example 1 except that the coating compositions prepared in Examples 7 to 9 and Comparative Examples 2 to 8 were used, and the adhesion (initial) was evaluated according to the same criteria.

[0085] · Viscosity measurement 300 g of each of the coating compositions prepared in Examples 7 to 9 and Comparative Examples 2 to 8 was put into a paper cup, and the viscosity was measured under the conditions of a temperature of 23°C and a relative humidity of 50% using a B-type viscometer (manufactured by THRMO, HAAKE Viscotester 6 plus).

[0086] · Coating workability The workability of each paint composition prepared in Examples 7 to 9 and Comparative Examples 2 to 8 was evaluated according to the following criteria when applied to a concrete paving slab (substrate) of 300 mm × 300 mm × 60 mm (thickness) specified in JIS A 5371:2016 using a brush. ○ Appropriate viscosity, and can be easily applied × High viscosity and difficult to apply

[0087] · Moisture release test Mortar with a water / cement / sand = 1 / 3 / 1 (mass ratio) was molded using a cylindrical mold with a diameter of 5 cm and a height of 10 cm, and cured for 3 days under the conditions of 23°C and a relative humidity of 50%. Then, the test specimen was obtained by demolding from the mold. Immediately after demolding, the mass of the test specimen was measured. After the mass measurement, each paint composition prepared in Examples 7 to 9 and Comparative Examples 2 to 8 was applied to the entire surface of the cylindrical test specimen except for the bottom surface so that the dry film thickness was 200 μm. After 2 hours of application, the test specimen was touched with a finger to confirm that the applied paint composition was dry, and then the mass of the test specimen was measured. Next, after curing for 7 days under the conditions of 23°C and a relative humidity of 50%, the mass of the test specimen was measured, and the moisture release property was evaluated from the mass change of the test specimen 2 hours after application and 7 days after application. ○ Mass change is less than 1% × Mass change is 1% or more

[0088] This composition with the result of ○ in the moisture release test is presumed to be able to promote the strength development of concrete because it is easy to retain the moisture in the concrete.

[0089]

Table 2

[0090]

Table 3

Claims

1. A water-based strippable coating composition for concrete, comprising a water-based urethane resin, an associative thickener, and water.

2. The water-based strippable coating composition for concrete according to Claim 1, further comprising an acrylic resin.

3. The water-based strippable coating composition for concrete according to Claim 1, containing 20 to 40% by mass of the urethane resin based on 100% by mass of the total amount of the water-based strippable coating composition for concrete.

4. The water-based strippable coating composition for concrete according to Claim 1, containing 0.5 to 5.0% by mass of the associative thickener based on 100% by mass of the non-volatile content of the water-based strippable coating composition for concrete.

5. A strippable coating film formed from the water-based strippable coating composition for concrete according to any one of Claims 1 to 4.

6. A temporary protection laminate, comprising concrete and the strippable coating film according to Claim 5.

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