Water retention agent and method for retaining water in porous materials

Abstract

To solve the problem in which: when a composition that contains a polymer having a crosslinkable functional portion and a crosslinker is applied as a water-holding agent to a porous material such as porous pavement, it is difficult to adjust the time for its gelation, and if its density is adjusted for a required absorbency, the gelation takes too much time, so that the water-holding capacity cannot be sufficiently exhibited.SOLUTION: A water-holding capacity imparting agent contains: a compound comprising 5 mol or more of alkylene oxide added to 1 mol of a polyhydric alcohol having a valence of three or more, in which a terminal structure of polyalkylene oxide has hydrogen or a hydrocarbon group; and cyclodextrin.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a water retention agent and a water retention method. [Background technology]

[0002] Water-retentive materials (e.g., water-retentive sand, minerals, water-absorbent resins) are used in a wide range of applications (e.g., gardening, soil, land greening, air conditioning, paving). However, many issues remain to be addressed in order to properly fix water-retentive materials to objects (objects where water-retentive performance is required). As an example, we will explain the use of water-retentive materials for paving.

[0003] When using water-retentive materials for pavement, they are constructed by filling the pores of porous pavement on the road surface with the water-retentive material. Such water-retentive pavement retains moisture from rain and other sources, and as the retained moisture evaporates, the heat of vaporization is removed, thereby suppressing the rise in road surface temperature. This function is expected to mitigate the heat island effect. However, if the water-retentive material is not properly fixed in the pores, for example, during heavy rainfall, the water-retentive material may flow out of the pores, resulting in a decrease in water retention and making the road surface slippery. To address this issue, methods have been proposed for fixing the water-retentive material with cement. More specifically, methods have been proposed for spraying the water-retentive material onto uncured porous concrete (Patent Document 1), and methods have been proposed for applying, spraying, injecting, or filling a water-retentive agent containing a crosslinkable functional group that can be crosslinked with a crosslinking agent and a crosslinking agent onto the porous pavement, followed by gelation (Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-274743 [Patent Document 2] Japanese Patent Publication No. 2020-79502 Summary of the Invention [Problem to be solved by the invention]

[0005] When a composition containing a polymer with cross-linkable functional moieties and a cross-linking agent is used as a water retention agent in a porous material such as a porous pavement, it is difficult to adjust the time until gelation, and if the concentration is adjusted to the required water absorption, gelation takes too long, resulting in a problem in which the water retention performance is not fully demonstrated. The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a water retention agent that imparts good water retention performance to a porous material, and to provide a method for making a porous material retain water. [Means for solving the problem]

[0006] The present inventors have conducted extensive research to solve the above problems and have arrived at the present invention. Specifically, the water retention agent of the present invention relates to a water retention agent that contains a compound having a structure in which 5 moles or more of alkylene oxide are added to 1 mole of a trihydric or higher polyhydric alcohol, the polyalkylene oxide having a terminal structure containing hydrogen or a hydrocarbon group, and cyclodextrin. The present invention also relates to a water retention agent for use in an inorganic material molded product. The present invention also relates to a composition containing α-cyclodextrin and a compound selected from the group consisting of an alkylene oxide adduct of sorbitol, a polymer having structural units derived from an alkylene oxide adduct of methacrylic acid, a copolymer having structural units derived from an alkylene oxide adduct of 3-methyl-3-butenyl alcohol, a copolymer having structural units derived from an alkylene oxide adduct of methallyl alcohol, and an alkylene oxide adduct of an active hydrogen bonded to an amino group of polyethyleneimine. The present invention also relates to a method for retaining water in a porous material, which comprises a step of applying, spraying, injecting or filling a composition containing a compound (A) having a structure in which 5 moles or more of alkylene oxide are added to 1 mole of a trihydric or higher polyhydric alcohol, wherein the terminal structure of the polyalkylene oxide has hydrogen or a hydrocarbon group, and a cyclodextrin (B) to the porous material. The present invention also relates to a method for retaining moisture in an inorganic material molded body. [Effects of the Invention]

[0007] According to the present invention, a water retention agent is provided that has a sufficient pot life and does not require a long time for gelation. As a result, it is possible to impart good water retention to the target porous material. More specifically, by using such a water retention agent, the water retention agent does not gel during the time required for the application, spraying, injection, or filling of the water retention agent into the porous material (hereinafter, these may be collectively referred to as the "introduction operation"), and the gelation of the water retention agent can be completed without requiring an excessively long time. DETAILED DESCRIPTION OF THE INVENTION

[0008] Specific embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.

[0009] [Water retention agent] As described above, the water retention agent is a compound having a structure in which 5 or more moles of alkylene oxide are added to 1 mole of a trihydric or higher polyhydric alcohol. The compound (A) contains a compound in which the terminal structure of the polyalkylene oxide has a hydrogen or hydrocarbon group, and a cyclodextrin (B). In practical use, the water retention agent contains an aqueous dispersion medium (typically, water). Furthermore, the water retention agent has the ability to form a water-retaining gel at room temperature. As used herein, "water retention" refers to the ability to absorb and retain moisture. It may also include the ability to repeatedly absorb and release moisture. That is, the water-retaining gel formed from the water retention agent absorbs and retains moisture from rain, etc., and can release the retained moisture by evaporation, and can repeat this absorption, retention, and release process. In other words, the water-retaining gel can repeatedly swell and deswell. As described above, according to an embodiment of the present invention, water retention can be imparted to the gel itself formed on the surface and / or substantially the entire pores of a porous material without using a water-retaining agent (e.g., a water-absorbent polymer, a porous mineral). As a result, problems associated with technologies that use water-retentive materials (e.g., the water-retentive material being trapped in hardened concrete, preventing it from fully exhibiting its water-retentive properties, or the water-retentive material leaking out of the pores in the porous pavement) can be resolved. Furthermore, the water-retentive gel that is formed is insoluble and infusible, making it extremely stable. As a result, it is possible to achieve a water-retentive pavement whose water-retentive properties change very little due to changes in weather and / or the surrounding environment. Since one of the main features of the water-retentive method for porous materials of the present invention is the use of such a water-retentive agent, the present invention also encompasses such a water-retentive agent.

[0010] The water retention agent is typically a so-called one-component type, and is prepared in advance before being applied, sprayed, injected, or filled into the porous material (before the introduction of the water retention agent). Therefore, additional and complicated operations such as mixing two liquids can be omitted when introducing the water retention agent into the porous material. Furthermore, the water retention agent can maintain its liquid state during the introduction of the water retention agent into the porous material, resulting in excellent handleability and workability. Additionally, as described above, the water retention agent has the ability to form a water-retaining gel at room temperature (e.g., 20°C to 30°C), so the heating step can be omitted during the introduction of the water retention agent into the porous material. Thus, according to an embodiment of the present invention, water retention can be imparted to the porous material very simply. It goes without saying that, if necessary, the water retention agent may be prepared by mixing the compound (A) and cyclodextrin during the introduction process.

[0011] [Compound (A)] The compound (A) of the present invention is a polyalkylene oxide compound having a branched structure. Specifically, it is a compound having a structure in which 5 moles or more of alkylene oxide are added to 1 mole of a polyhydric alcohol having a valence of 3 or more, and the terminal structure of the polyalkylene oxide has hydrogen or a hydrocarbon group.

[0012] The alkylene oxide is preferably an alkylene oxide having 2 to 10 carbon atoms, more preferably an alkylene oxide having 2 to 8 carbon atoms, still more preferably an alkylene oxide having 2 to 6 carbon atoms, particularly preferably an alkylene oxide having 2 to 4 carbon atoms, and most preferably an alkylene oxide having 2 to 3 carbon atoms (i.e., ethylene oxide, propylene oxide), in terms of being able to more effectively exhibit the effects of the present invention. The alkylene oxide may be one type or two or more types.

[0013] The number of moles of alkylene oxide added per mole of polyhydric alcohol is preferably 10 moles or more, more preferably 20 moles or more, even more preferably 30 moles or more, even more preferably 40 moles or more, even more preferably 50 moles or more, even more preferably 100 moles or more, particularly preferably 500 moles or more, and most preferably 1000 moles or more, and the upper limit is preferably 100,000 moles or less, more preferably 50,000 moles or less, even more preferably 40,000 moles or less, even more preferably 30,000 moles or less, even more preferably 20,000 moles or less, even more preferably 10,000 moles or less, particularly preferably 7,000 moles or less, and most preferably 5,000 moles or less. By adjusting the number of moles of alkylene oxide added per mole of polyhydric alcohol within the above range, the viscosity of the solution before solidification can be kept low, and sufficient gel strength can be ensured.

[0014] The weight-average molecular weight (Mw) of compound (A) of the present invention is 3,000 to 500,000, as determined by gel permeation chromatography (GPC) using polyethylene glycol as the standard, as described in the Examples. The weight-average molecular weight (Mw) is preferably 4,000 to 200,000, more preferably 5,000 to 120,000, even more preferably 6,000 to 80,000, and particularly preferably 7,000 to 50,000. When the weight-average molecular weight (Mw) of compound (A) is within the above range, the gelling strength is excellent and the water retention time can be adjusted.

[0015] The polyhydric alcohol may be any compound having three or more hydroxyl groups, and may be a low molecular weight compound or a polymer. Any appropriate polyhydric alcohol may be used as long as it does not impair the effects of the present invention.

[0016] Specific structures of the compound (A) include, but are not limited to, compounds (A1) and (A2) having the following structures.

[0017] The compound (A1) is a compound having a structure represented by the following formula (1).

[0018] [ka] (In formula (1), R1 represents an atomic group containing carbon and / or nitrogen; R2, which may be the same or different, represents an alkylene group having 2 to 4 carbon atoms; R3, which may be the same or different, represents a hydrogen atom, a methyl group, or an ethyl group. R3 represents a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms; m is a number from 5 to 300; and n is a number of 3 or more.)

[0019] Examples of compounds having the above structure include glycerin, pentaerythritol, sorbitol, and alkylene oxide adducts to active hydrogens bonded to amino groups of polyethyleneimine. Here, "alkylene oxide adducts to active hydrogens bonded to amino groups of polyethyleneimine" refers to adducts in which alkylene oxides (such as ethylene oxide) are added to active hydrogens bonded to amino groups of polyethyleneimine in any appropriate number of moles.

[0020] The compound (A2) is a compound having the following structural unit (I) shown in the following formula (2).

[0021] [ka] (In formula (2), R4, R5, and R6 are the same or different and represent a hydrogen atom, a methyl group, or an ethyl group. R7 are the same or different and represent an alkylene group having 2 to 4 carbon atoms. R8 represents a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms. n2 is a number of 3 or more, p is a number of 0 to 2, q is a number of 0 or 1, and r is a number of 5 to 300.)

[0022] Examples of compounds having the above structure include copolymers having structural units derived from an alkylene oxide adduct of methacrylic acid, copolymers having structural units derived from an alkylene oxide adduct of hydroxyethyl vinyl ether, copolymers having structural units derived from an alkylene oxide adduct of hydroxypropyl vinyl ether, copolymers having structural units derived from an alkylene oxide adduct of hydroxybutyl vinyl ether, copolymers having structural units derived from an alkylene oxide adduct of allyl alcohol, copolymers having structural units derived from an alkylene oxide adduct of methallyl alcohol, copolymers having structural units derived from an alkylene oxide adduct of butenyl alcohol, copolymers having structural units derived from an alkylene oxide adduct of 3-methyl-3-butenyl alcohol, copolymers having structural units derived from an alkylene oxide adduct of 3-methyl-2-butenyl alcohol, and copolymers having structural units derived from an alkylene oxide adduct of 2-methyl-3-butenyl alcohol.

[0023] The compound (A2) exhibits the effects of the present invention as long as it contains the structural unit (I), but may further contain the following structural unit (II) shown in the following formula (3).

[0024] [ka] (In formula (3), R9 and R11 are the same or different and represent a hydrogen atom, a methyl group, or an ethyl group. R10 represents a hydrogen atom or -COOX2. X1 and X2 are the same or different and represent a hydrogen atom, a monovalent metal, a divalent metal, an ammonium group, or an organic amine group. -COOX1 and -COOX2 may form an anhydride.)

[0025] When the compound (A2) of the present invention contains the structural unit (II), the content ratio of the structural unit (I) and the structural unit (II) contained in the compound is 0.01 to 99.99 mass% for the structural unit (I) and 0.01 to 99.99 mass% for the structural unit (II), relative to 100 mass% in total of the structural unit (I) and the structural unit (II). Preferably, the structural unit (I) accounts for 0.1 to 95% by mass, and the structural unit (II) accounts for 5 to 99.9% by mass. More preferably, the structural unit (I) accounts for 1 to 90% by mass, and the structural unit (II) accounts for 10 to 99% by mass. Particularly preferably, the structural unit (I) accounts for 10 to 85% by mass, and the structural unit (II) accounts for 15 to 90% by mass. Most preferably, the structural unit (I) is 40 to 85% by mass, and the structural unit (II) is 15 to 60% by mass. When the content ratio of the structural unit (I) and the structural unit (II) is within the above range, the gelation time can be shortened.

[0026] (Method for producing compound (A2)) The method for producing compound (A2) is not particularly limited, but it can be produced, for example, by polymerizing a monomer component containing an unsaturated polyalkylene glycol monomer (a) in the presence of a polymerization initiator, and may contain an unsaturated carboxylic acid monomer (b) or other monomer (c) as necessary.

[0027] The structural unit (I) can be formed from an unsaturated polyalkylene glycol monomer (a) represented by the following formula (4).

[0028] [ka] (In formula (4), R4, R5, and R6 are the same or different and represent a hydrogen atom, a methyl group, or an ethyl group. R7 are the same or different and represent an alkylene group having 2 to 4 carbon atoms. R8 represents a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms. p represents a number from 0 to 2. q represents a number of 0 or 1, and r is a number from 5 to 300.)

[0029] Specific examples of the unsaturated polyalkylene glycol monomer (a) include polyethylene glycol monomethyl ether methacrylate, an ethylene oxide adduct of hydroxyethyl vinyl ether, an ethylene oxide adduct of hydroxypropyl vinyl ether, an ethylene oxide adduct of hydroxybutyl vinyl ether, an ethylene oxide adduct of allyl alcohol, an ethylene oxide adduct of methallyl alcohol, an ethylene oxide adduct of butenyl alcohol, an ethylene oxide adduct of 3-methyl-3-butenyl alcohol, an ethylene oxide adduct of 3-methyl-2-butenyl alcohol, and an ethylene oxide adduct of 2-methyl-3-butenyl alcohol, of which polyethylene glycol monomethyl ether methacrylate, an ethylene oxide adduct of methallyl alcohol, and an ethylene oxide adduct of 3-methyl-3-butenyl alcohol are particularly preferred.

[0030] The monomer (a) forming the structural unit (I) represented by the formula (2) can be obtained by adding an alkylene oxide to an unsaturated alcohol and / or an unsaturated carboxylic acid in an amount corresponding to a predetermined repeating number. Alternatively, the monomer (a) can be obtained by esterification of an alcohol obtained by adding an alkylene oxide to an alcohol or phenol having a hydrocarbon group having 1 to 30 carbon atoms in an amount corresponding to a predetermined repeating number with an unsaturated carboxylic acid and / or by transesterification with an unsaturated carboxylic acid ester.

[0031] In addition to the above-mentioned methods, the structural unit (I) can be formed by polymerizing an ethylenically unsaturated monomer (a1) containing a hydroxyl group or a carboxylic acid group, as shown in the following formula (5), and then adding a polyalkylene oxide to the polymer.

[0032] [ka] (In formula (5), R12, R13, and R14 are the same or different and represent a hydrogen atom, a methyl group, or an ethyl group. s represents a number of 0 to 2. t is a number of 0 or 1.)

[0033] Specific examples of the ethylenically unsaturated monomer (a1) containing a hydroxyl group or a carboxylic acid group include hydroxyethyl vinyl ether, hydroxypropyl vinyl ether, hydroxybutyl vinyl ether, allyl alcohol, methallyl alcohol, butenyl alcohol, 3-methyl-3-butenyl alcohol, 3-methyl-2-butenyl alcohol, 2-methyl-3-butenyl alcohol, (meth)acrylic acid, crotonic acid, tiglic acid, 3-methylcrotonic acid, 2-methyl-2-pentenoic acid, itaconic acid, maleic acid, itaconic acid, mesaconic acid, citraconic acid, and fumaric acid.

[0034] Examples of the monomer that forms the structural unit (II) represented by the above formula (2) include the unsaturated carboxylic acid monomer (b) represented by the following formula (6).

[0035] [ka] (In formula (6), R9 and R11 are the same or different and represent a hydrogen atom, a methyl group, or an ethyl group. R10 represents a hydrogen atom or -COOX2. X1 and X2 are the same or different and represent a hydrogen atom, a monovalent metal, a divalent metal, an ammonium group, or an organic amine group. -COOX1 and -COOX2 may form an anhydride.)

[0036] The unsaturated carboxylic acid monomer is preferably an unsaturated monocarboxylic acid monomer or an unsaturated dicarboxylic acid monomer. The unsaturated monocarboxylic acid monomer may be any monomer having one unsaturated group and one group capable of forming a carbanion in the molecule. For example, (meth)acrylic acid, crotonic acid, tiglic acid, 3-methylcrotonic acid, 2-methyl-2-pentenoic acid, itaconic acid, etc.; and their monovalent metal salts, divalent metal salts, ammonium salts, and organic amine salts are preferred.

[0037] The unsaturated dicarboxylic acid monomer may be any monomer having one unsaturated group and two groups capable of forming a carbanion in the molecule, and preferred examples include maleic acid, itaconic acid, mesaconic acid, citraconic acid, fumaric acid, etc., and their monovalent metal salts, divalent metal salts, ammonium salts, and organic amine salts, anhydrides, or half esters.

[0038] Examples of the other monomer (c) include ethylenically unsaturated carboxylic acid esters and other ethylenically unsaturated monomers. Examples of the ethylenically unsaturated carboxylic acid esters include alkyl esters of maleic acid such as monomethyl maleate, dimethyl maleate, monoethyl maleate, and diethyl maleate; alkyl esters of fumaric acid such as monomethyl fumarate, dimethyl fumarate, monoethyl fumarate, and diethyl fumarate; alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, and stearyl (meth)acrylate; unsaturated carboxylic acid esters having a hydroxyl group such as hydroxyalkyl (meth)acrylates such as hydroxyethyl (meth)acrylate and hydroxypropyl (meth)acrylate; and polyalkylene glycol (meth)acrylates such as (methoxy)polyethylene glycol (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, naphthoxypolyethylene glycol (meth)acrylate, monophenoxypolyethylene glycol maleate, and carbazole polyethylene glycol (meth)acrylate.

[0039] [Cyclodextrin (B)] The cyclodextrin (B) of the present invention is a type of cyclic oligomer in which several molecules of D-glucose are bonded via α1,4-glycoxide bonds, and is a compound in which five or more glucose molecules are bonded. The number of glucose bonds is related to the size of the cyclic structure, and the interaction with the alkylene oxide chain of compound (A) is related to gelation, so it is preferably 8 or less. α-cyclodextrin, which has 6 bonds, β-cyclodextrin, which has 7 bonds, or γ-cyclodextrin, which has 8 bonds, is preferred, with α-cyclodextrin being particularly preferred in terms of gelation efficiency.

[0040] The cyclodextrin (B) of the present invention includes not only unmodified cyclodextrins but also modified cyclodextrins.

[0041] The content of compound (A) in the water retention agent is, for example, 0.1 to 50% by mass, preferably 0.5 to 30% by mass, and more preferably 1 to 10% by mass. When the content of compound (A) is within this range, a gel having a desired water absorption capacity can be formed.

[0042] The content of cyclodextrin (B) in the water retention agent is, for example, 0.1 to 30% by mass, preferably 0.5 to 20% by mass, and more preferably 1 to 10% by mass. If the content of the crosslinking agent is within this range, a gel with desired strength and stability can be formed.

[0043] The solids mass ratio of the compound (A) content to the cyclodextrin (B) content in the water retention agent (compound (A) / cyclodextrin (B)) is preferably 50 / 1 to 1 / 50, more preferably 10 / 1 to 1 / 5. When this ratio is within this range, a gel with an excellent balance between water retention capacity and strength can be formed. As a molar ratio, the ratio of the number of moles of alkylene oxide in compound (A) to the number of moles of cyclodextrin (alkylene oxide in compound (A) / cyclodextrin (B)) is preferably 0.5 to 1700, more preferably 5 to 170, even more preferably 30 to 140, and most preferably 60 to 120. When this ratio is within this range, compound (A) easily enters the cyclic structure of cyclodextrin (B), and a gel with an excellent balance between water retention capacity and strength can be formed.

[0044] Compositions containing compound (A) and cyclodextrin (B) can be used as water retention agents in any combination, but a preferred combination of compound (A) is at least one selected from alkylene oxide adducts of sorbitol, polymers having structural units derived from alkylene oxide adducts of methacrylic acid such as polyethylene glycol monomethyl ether methacrylate, copolymers having structural units derived from alkylene oxide adducts of 3-methyl-3-butenyl alcohol, copolymers having structural units derived from alkylene oxide adducts of methallyl alcohol, and alkylene oxide adducts of active hydrogen bonded to the amino group of polyethyleneimine, and α-cyclodextrin as cyclodextrin (B). In the above combinations, compounds (A) that are particularly preferred are polymers having structural units derived from alkylene oxide adducts of methacrylic acid and alkylene oxide adducts of active hydrogens bonded to amino groups of polyethyleneimine.

[0045] The water retention agent may further contain any appropriate additive. Specific examples of the additive include dispersants, antifoaming agents, thickeners, rheology control agents, foaming agents, plasticizers, wetting agents, antiblocking agents, antioxidants, preservatives, antistatic agents, UV absorbers, UV stabilizers, leveling agents, plasticizers, dyes, pigments, and antioxidants. The types, combinations, amounts, etc. of the additives contained in the mixture can be appropriately set depending on the purpose.

[0046] The aqueous dispersion medium in the water retention agent is contained as the balance of the above components. The content of the aqueous dispersion medium can be, for example, 20% by mass to 99.98% by mass.

[0047] The gelation time of the water retention agent is preferably 30 minutes to 24 hours, more preferably 1 hour to 20 hours, and even more preferably 2 hours to 15 hours. If the gelation time is 30 minutes or more, the water retention agent can remain liquid during the installation process, ensuring an appropriate usable time. Therefore, good handleability can be achieved during the installation process, without having to worry about reduced workability due to gelation of the water retention agent. On the other hand, if the gelation time is 24 hours or less, gelation can be completed without requiring an excessively long time. As a result, a water-retaining gel can be formed in the porous pavement in a practically appropriate time, allowing the production of a water-retaining pavement. In this specification, "gelation time" refers to the time it takes for the water retention agent to lose its fluidity and become solidified in appearance.

[0048] The water-retaining gel formed from the water retention agent preferably has a 1-hour water absorption capacity in pure water of 0.5 g / g to 200 g / g, more preferably 1 g / g to 150 g / g, and even more preferably 2 g / g to 100 g / g. If the water absorption capacity is within this range, good water retention performance can be achieved.

[0049] The water retention agent of the present invention is introduced into an object to be fixed by coating, spraying, injecting or filling, and imparts a water retention function to the object to be fixed.

[0050] The object to be fixed may be any suitable object to which the compound (A) and the cyclodextrin (B) are fixed to exhibit water retention at the fixed position. Since the water-retaining gel formed from the water retention agent needs to be incorporated, the object to be fixed is preferably a porous material. The porous material may be organic, such as a polymer or resin, or inorganic. Specific examples include porous materials such as porous pavement, porous blocks, and buildings containing porous layers; inorganic material molded bodies such as mortar boards and concrete boards; resin molded bodies such as acrylic boards; and fibers. Because the material is used after being imparted with water retention, inorganic material molded bodies are preferred from the standpoints of weather resistance and durability. Inorganic material molded bodies can be used as porous pavement. Examples include drainage asphalt mixtures, water-permeable asphalt mixtures, drainage cement concrete, and water-permeable cement concrete.

[0051] The method for retaining water in a porous material of the present invention includes applying, spraying, injecting or filling a water retention agent into a porous material, and gelling the non-water retention agent to form a water-retaining gel.

[0052] The water retention agent is applied, sprayed, injected, or filled into the porous material. Specifically, the applied water retention agent (liquid) penetrates into the pores of the porous material. The water retention agent of the present invention can properly penetrate into the pores of the porous pavement without any special operations. That is, according to the embodiment of the present invention, water retention can be achieved with significantly better workability and at significantly lower cost than techniques for forming a water retention layer in a porous material (for example, techniques for forming a water retention layer by spraying a water-absorbent resin on the surface of a porous material, and then applying a porous material to cover the water retention layer). Furthermore, by adjusting the amount of application, etc., the pores can be properly filled. The amount of application, etc. of the water retention agent is determined based on the amount of application, etc. per 1 m of porous pavement. 2 For example, the amount may be 0.2 to 7 liters per 1000g of water. If necessary, an operation to help the water retention agent penetrate into the pores may be carried out. Examples of such an operation include vibration and pressure.

[0053] Next, the water retention agent is gelled. As described above, the water retention agent has the ability to form a gel at room temperature for an appropriate gelling time, so if left for a predetermined period of time, a water-retaining gel will form in the porous pavement. In this way, according to an embodiment of the present invention, a water-retaining pavement can be produced by operations at room temperature. Heating may be performed to promote gelling of the water retention agent and / or as needed (for example, in winter). The heating temperature is preferably 50°C to 100°C, more preferably 70°C to 90°C. The heating time may vary depending on the heating temperature. The heating time may be, for example, 5 minutes to 2 hours. Note that, as the water-retaining gel is formed, the voids in the porous material are typically filled with the jelly-like water-retaining gel. Therefore, the formed water-retaining gel will not substantially flow out of the porous material, even in the event of heavy rainfall, for example.

[0054] In this manner, a porous material having water retention properties is produced, and this porous material can be suitably used for water retention. [Example]

[0055] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited thereto. Unless otherwise specified, parts mean parts by mass, and % means % by mass.

[0056] <Gelation time measurement> A stirrer tip (ASONE, strong magnetic stirrer, cylindrical, Φ4.5mm x 12mm), water (1.9941g), and α-cyclodextrin (0.8735g) were weighed into a glass container (Maruem, screw tube No. 5) and stirred at 500 rpm for 10 minutes using a magnetic stirrer (ASONE, REXIM RS-6AN) to pre-disperse the mixture. A predetermined amount of compound (A) (12.1324g as a 20% aqueous solution) was then added, and the mixture was stirred at 500 rpm using a magnetic stirrer (ASONE, REXIM RS-6AN). After 15 minutes, the stirrer tip was removed. The glass container was tilted every 15 minutes to check for gelation. The gelation time was measured when the contents no longer flowed even after inverting the glass container. The gelation time was the time (unit: minutes) required for gelation after adding compound (A). The glass container was kept covered except when adding the compound or removing the stirrer tip. The experiment was carried out in an atmosphere of 23°C.

[0057] <Method for measuring molecular weight> Columns used: TSKguard column α + TSKgel α-5000 + TSKgel α-4000 + TSKgel α-3000 manufactured by Tosoh Corporation were connected together and used. Eluent: A solution prepared by dissolving 62.4 g of sodium dihydrogen phosphate·2H2O and 143.3 g of disodium hydrogen phosphate·12H2O in 7794.3 g of ion-exchanged water and mixing this with 2000 g of acetonitrile was used. Detector: VIscotek triple detector "Model 302 Light Scattering Detector", 90° scattering angle for right-angle light scattering, 7° scattering angle for low-angle light scattering, 18 μL cell volume, 670 nm wavelength. Standard sample: Polyethylene glycol SE-8 (Mw=107000) manufactured by Tosoh Corporation was used, and the instrument constants were determined with its dn / dC set to 0.135 ml / g and the refractive index of the eluent set to 1.333. Amount of impact Standard sample: 100 μL of a solution prepared by dissolving the polymer in the eluent so that the polymer concentration was 0.2 vol % was injected. Sample: 100 μL of a solution prepared by dissolving the polymer in the eluent so that the polymer concentration was 1.0 vol % was injected. Flow rate: 0.8ml / mIn Column temperature: 40℃

[0058] In this specification, the names of compounds may be explained using the abbreviations in Table 1 below.

[0059] [Table 1]

[0060] (Production Example 1) A glass reactor equipped with a thermometer, stirrer, dropping device, nitrogen inlet tube, and reflux condenser was charged with 141 parts of water and purged with nitrogen. After heating to 95°C under a nitrogen atmosphere, a monomer solution for dropping, consisting of 67 parts by weight of PGM25E, 26.3 parts by weight of MAA, 176 parts by weight of water, and 0.27 parts by weight of β-mercaptopropionic acid, and 8.4 parts by weight of a 4.2% aqueous ammonium persulfate solution, were added dropwise over one hour, followed by aging at 95°C for one hour. After aging, the pH was adjusted to 7 using a 30% aqueous sodium hydroxide solution, yielding an aqueous solution of copolymer (1) with a weight-average molecular weight of 32,000.

[0061] (Manufacturing Examples 2 to 6) Using the monomers shown in Table 1 and the composition ratios shown in Table 2, aqueous solutions of copolymers (2) to (6) were obtained by the same production method as in Production Example 1.

[0062] [Table 2]

[0063] <Examples 1 to 8 and Comparative Examples 1 to 3> The test was carried out based on the gelation time measurement described above. The results are shown in Table 3. The term "no gelation" indicates that no gelation occurred even after 24 hours had passed since the addition of compound (A). The ingredients in the table are as follows: ESP: Polyethyleneimine (weight average molecular weight = 600) to which 20 moles of ethylene oxide are added per mole of active hydrogen in the amino group. Weight average molecular weight = 23,000 SB300: 300 moles of ethylene oxide added to 1 mole of sorbitol, weight average molecular weight = 13,000 PEG 100,000: polyethylene glycol, manufactured by Aldrich, weight average molecular weight = 100,000 PEG20000: Polyethylene glycol, Fujifilm Wako Pure Chemical Industries, weight average molecular weight = 20000 PEG2000: Polyethylene glycol, Fujifilm Wako Pure Chemical Industries, weight average molecular weight = 2000

[0064] [Table 3]

[0065] As shown in Table 3, it was confirmed that the combinations of linear polyethylene glycol, which does not correspond to the compound (A) of the present invention, and cyclodextrin (B) (Comparative Examples 1 to 3) did not gel and could not impart water retention. On the other hand, the combinations of compound (A) of the present invention and cyclodextrin (B) (Examples 1 to 8) were able to impart water retention while having a sufficient pot life and not requiring a long wait for gelation. [Industrial Applicability]

[0066] The water retention agent of the present invention is excellent in workability and can impart good water retention properties, and water-retentive pavements and the like can be easily produced.

Claims

1. A water retention agent comprising a compound (A) having a structure in which 5 moles or more of alkylene oxide are added to 1 mole of a trihydric or higher polyhydric alcohol, wherein the terminal structure of the polyalkylene oxide has hydrogen or a hydrocarbon group, and a cyclodextrin (B).

2. 2. The water retention agent according to claim 1, wherein the compound (A) is a polycarboxylic acid polymer.

3. 3. The water retention agent according to claim 1, which is for use in an inorganic material molded product.

4. A composition containing α-cyclodextrin and a compound selected from the group consisting of an alkylene oxide adduct of sorbitol, a polymer having structural units derived from an alkylene oxide adduct of methacrylic acid, a copolymer having structural units derived from an alkylene oxide adduct of 3-methyl-3-butenyl alcohol, a copolymer having structural units derived from an alkylene oxide adduct of methallyl alcohol, and an alkylene oxide adduct of an active hydrogen bonded to an amino group of polyethyleneimine.

5. A method for retaining moisture in a porous material, comprising the step of applying, spraying, injecting or filling a composition containing a compound (A) having a structure in which 5 moles or more of alkylene oxide are added to 1 mole of a polyhydric alcohol having 3 or more valences, wherein the terminal structure of the polyalkylene oxide has hydrogen or a hydrocarbon group, and a cyclodextrin (B) to the porous material.

6. 6. The water retention method according to claim 5, wherein the porous material is an inorganic material molded body.

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