JP2005053753A - Water retentivity imparting agent for porous material, method of use of the same and porous material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water retentivity imparting agent for a porous material which imparts stable water retentivity and water permeability to the porous material over a long period and a method of use of the same and the porous material. <P>SOLUTION: The water retentivity imparting agent for the porous material contains a water absorbent material having a water absorption masgnification 2-500 times of dead weight and a cross-linking agent capable of forming a chemical bond with the water absorbent material. The water absorbent material is preferably dispersed or dissolved in water. In the method of use of the water retentivity imparting agent for the porous material, the water retentivity is imparted to the porous material by scattering the water retentivity imparting agent for the porous material on the surface of the porous material to chemically bond the water retentivity imparting agent for the porous material with the cross-linking agent in many continuous void inside the porous material. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention has a large number of continuous voids inside represented by water-permeable asphalt (porous asphalt), water-permeable concrete (porous concrete), porous porcelain material, sludge incinerated ash fired body, lightweight aggregate, gravel, etc. The present invention relates to a water retention agent for a porous material used for permeable pavement and the like and a method for using the same.

Conventionally, in order to promote the penetration of rainwater into the ground, permeable pavement has been frequently used particularly in urban areas.
By the way, the water-permeable pavement generally has a large number of continuous voids in the interior, so that rainwater can quickly penetrate into the ground. In recent years, the water-permeable pavement has been developed for the purpose of eliminating the heat island phenomenon in urban areas. Attempts have been made to impart water retention to the pavement.

  As a method for imparting water retention to a water-permeable pavement, for example, a method is described in which a water-absorbing material is mixed with gravel on the surface of an outer wall concrete and solidified to create a concrete substrate with water retention (Patent Literature). 1). However, according to this method, most of the water-absorbing material is buried inside the concrete base material, and in order to impart high water retention to the base material, a large amount of water-absorbing material appears on the surface portion of the base material. It is necessary to increase the amount of water-absorbing material added, which causes higher construction costs and increases the proportion of the water-absorbing material in the base material, reducing the original physical strength of the base material. There was a problem.

  In addition, a method is also proposed in which cement milk mixed with a water-absorbing material is poured into an existing permeable pavement to solidify and impart water retention, but according to this method, the continuous inside of the permeable pavement is proposed. There was a problem that the air gap was blocked and the water permeability was hindered.

On the other hand, although a heat island mitigation measure by causing the water absorbent resin to exist in the continuous pores of the porous layer is also disclosed (see Patent Document 2), only the powdery water absorbent resin is illustrated. However, in the powder form, there is a problem that the construction for the construction must be stopped only by blowing the wind, and the water-absorbing resin gradually decreases after the construction, and the effect of relaxing the heat island is gradually reduced. Furthermore, only the part of the continuous pores where the powder has reached can absorb water and is dissatisfied with the effect. Also, it can only be used on newly constructed roads and buildings that cannot be used. There was also a problem that it was not possible.
JP-A-11-159106 (Claims) Japanese Patent Laid-Open No. 2001-146706 (Claims)

  In view of the problems of the conventional methods for imparting water retention, the present invention provides a water retention agent for porous materials that can impart stable water retention and water permeability to porous materials over a long period of time. And its usage.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors have finally completed the present invention. That is, this invention is the following water retention agent for porous materials, its usage, and a porous material.

(1) A water retention agent for a porous material, comprising a water absorbent material having a water absorption rate of 2 to 500 times its own weight and a crosslinking agent capable of forming a chemical bond with the absorbent material.

(2) The water retention agent for porous materials according to (1), wherein the water absorbing material is dispersed or dissolved in water.

(3) By dispersing the water retention agent for a porous material according to (1) or (2) from the surface of the porous material, the water-absorbing material and the cross-linking agent within the continuous voids inside the porous material. A method for using a water retention agent for a porous material, wherein the water is chemically bonded to impart water retention to the porous material.

(4) A porous material in which the water retention agent for a porous material according to (1) or (2) is supported in an internal continuous void.

  According to the water retention agent for a porous material of the present invention and the method for using the same, the water retention agent is dispersed or dissolved in water and sprayed from the surface of the porous material. It can be supported in a number of continuous voids inside the porous material to provide water retention. And according to this water retention agent for porous materials and its method of use, the water retention agent stays physically and stably in the voids inside the porous material, due to the runoff of the water absorbing material due to rainfall or water sprinkling. A decrease in water retention performance can be suppressed. Furthermore, since the water retention agent does not block the voids inside the porous material, it is possible to construct an inorganic porous material excellent in water retention and water permeability, and it is possible to construct an inorganic porous material such as an existing water permeable pavement. It can be applied to materials without any restrictions.

  Further, according to the porous material of the present invention, a specific water retention agent is carried in a large number of continuous voids inside to impart water retention. And according to this porous material, since the water retention property is maintained by the water retention agent and does not block the voids inside the porous material, it becomes a porous material excellent in water retention and water permeability, It can also be applied to existing permeable pavements and the like.

Hereinafter, the present invention will be described in detail.
The water retention agent according to the present invention has a water absorbing material having a water absorption ratio of 2 to 500 times its own weight, and chemically reacts between the water absorbing materials by a crosslinking reaction in a large number of continuous voids inside the porous material. By forming a bond, it is immobilized on the inner walls of a large number of continuous voids inside the porous material to provide water retention.

Although there is no restriction | limiting in particular in the water absorbing material which has a water absorption capacity | capacitance of 2 to 500 times self-weight, For example, crosslinked (co) polymer which has carboxyl groups, such as an acrylic acid crosslinked polymer and a methacrylic acid crosslinked polymer, alkoxy polyalkylene Crosslinked (co) polymers having polyoxyalkylene groups such as glycol (meth) acrylate crosslinked polymers, alkoxypolyalkylene glycol (meth) acrylate / (meth) acrylic acid (salt) crosslinked copolymers; (meth) acrylamide / Crosslinked (co) polymer having an amide group such as (meth) acrylic acid (salt) crosslinked copolymer, N-vinylacetamide crosslinked polymer, N-vinylacetamide / (meth) acrylic acid (salt) crosslinked copolymer A crosslinked (co) polymer having an amino group such as a crosslinked polyallylamine or a crosslinked polyethyleneimine; Hydroxyl groups such as killed (meth) acrylate cross-linked polymer, hydroxyalkyl (meth) acrylate / (meth) acrylic acid (salt) cross-linked copolymer, vinyl alcohol / (meth) acrylic acid (salt) cross-linked (co) polymer Crosslinked (co) polymer having 2-acrylamide / 2-methylpropanesulfonic acid (salt) crosslinked polymer, 2-acrylamide / 2-methylpropanesulfonic acid (salt) / (meth) acrylic acid (salt) crosslinked copolymer Polymers, sulfoalkyl (meth) acrylate (salt) cross-linked copolymers, sulfoalkyl (meth) acrylate (salt) / (meth) acrylic acid (salt) cross-linked copolymers, sulfonated polystyrene cross-linked polymers ( Salt) cross-linked (co) polymer having groups; polyvinyl phosphonic acid cross-linked product, mono (2- (meth) acryloyloxyethyl) acid Crosslinked (co) polymers having phosphoric acid (salt) groups such as phosphate crosslinked (co) polymers; saponified products of crosslinked polyethylene oxide, crosslinked polyvinylpyrrolidone, crosslinked polyvinylpyridine, starch / poly (meth) acrylonitrile graft copolymer , Starch / poly (meth) acrylic acid (salt) graft copolymer crosslinked product, reaction product of polyvinyl alcohol and maleic anhydride (salt), isobutylene / maleic acid (salt) crosslinked copolymer, betaine monomer (co) A polymer, a cross-linked copolymer of an anionic monomer and a cationic monomer, and the like are exemplified, but not particularly limited. These water-absorbing resins may be used alone or in combination of two or more. Among these salt-resistant water-absorbing resins, a crosslinked (co) polymer having a sulfonic acid (salt) group is particularly preferable because of its excellent salt resistance and long-term stability.
Further, a water-retaining inorganic material obtained by finely pulverizing pearlite or vermiculite may be used. Moreover, as a water-soluble water-absorbing material, polyvinyl alcohol, polyacrylic acid soda, polysodium methacrylate, polyacrylamide, and copolymers thereof can be used. The same effect can be expected even if these water-soluble water-absorbing materials are used.

As the water retention agent for the porous material, preferably, a water-absorbing material dispersed or dissolved in water can be used, and a microhydrogel aqueous dispersion can be used particularly preferably. The hydrogel here is a general term for substantially water-insoluble and water-swellable substances obtained by adding a crosslinked structure to a water-soluble or hydrophilic polymer. A microhydrogel has a fine particle diameter of 100 μm or less. The hydrogel which has is shown.
The microhydrogel aqueous dispersion is made of, for example, a polymer containing a cross-linked structure, and a salt-type carboxyl group represented by —COOX (X: alkali metal or ammonium ion) is introduced. A hydrogel containing a 1 mmol / g salt-type carboxyl group is stably dispersed in an aqueous medium.

Here, the measurement of the water absorption rate of the microhydrogel or water-soluble water-absorbing material is
1. About 8 g of the sample is precisely weighed in an aluminum petri dish, and the aluminum petri dish containing the dried sample after being dried for 5 hours or more in a 105 ° C. constant temperature dryer is put in a 500 ml beaker.
2. After adding 300 ml of pure water, the swollen gel is peeled off, the aluminum petri dish is taken out and the gel is allowed to settle.
3. Discard the supernatant and add 300 ml of pure water again.
4.3. Repeat three times.
5). Put in tea strainer and drain for 10 minutes.
6). About 1/4 of the tea strainer is placed in an aluminum petri dish and weighed precisely, dried for 5 hours or more in a constant temperature dryer at 105 ° C., and calculated according to the following formula.
Water absorption ratio (times) = (weight of sample (gel) before drying / sample weight after drying) −1

  More specifically, as the water-absorbing material, an aqueous dispersion of a water-absorbing resin represented by an aqueous microhydrogel dispersion in which hydrogel is stably dispersed in an aqueous medium, for example, containing an acidic group and a crosslinked structure A salt-type carboxyl group represented by —COOX (X: alkali metal or ammonium ion) by a hydrolysis reaction of the nitrile group, which comprises an acrylonitrile-based polymer (hereinafter, acrylonitrile may be abbreviated as “AN”). And at least a hydrogel containing a salt-type carboxyl group of 0.1 mmol / g is stably dispersed in an aqueous medium.

  The AN polymer containing a crosslinked structure used as a starting material for obtaining the microhydrogel or an aqueous dispersion thereof is obtained by copolymerizing AN with one or more other ethylenically unsaturated compounds. It is a general term for polymers containing a crosslinked structure. The AN content in such an AN polymer is 30% by weight or more, preferably 50% by weight or more, more preferably 70% by weight or more based on the total amount of monomers constituting the AN polymer. In the case where a polymer having an AN content less than the recommended range is used as a starting material, it is not sufficiently hydrophilized by the action of an alkaline substance, or even if it can be hydrophilized, it has a desired water absorption capacity. Hydrogels may be difficult to form. In addition, a method for introducing a crosslinked structure includes a method in which a polyfunctional compound having at least two functional groups capable of forming a covalent bond with a nitrile group after the synthesis of an AN polymer is reacted with a molecule in a copolymerization stage in advance. There is a method of copolymerizing a crosslinkable monomer having two or more vinyl groups therein.

  Examples of other ethylenically unsaturated compounds copolymerized with AN include known unsaturated compounds that can be copolymerized with AN, for example, vinyl halides and vinylidene halides such as vinyl chloride and vinylidene chloride; allyl alcohol , Unsaturated alcohols such as methallyl alcohol and ethers thereof; unsaturated carboxylic acids such as acrylic acid and methacrylic acid and salts thereof; acrylic acid esters such as methyl acrylate and ethyl acrylate; methyl methacrylate and methacrylic acid Methacrylic acid esters such as ethyl acid; Unsaturated ketones of methyl vinyl ketone; Vinyl esters such as vinyl formate and vinyl acetate; Acrylamide and alkyl-substituted products thereof; N-methylol acrylamide; Unsaturation such as p-styrene sulfonic acid Hydrocarbon sulfonic acids and their salts; Sulfoalkyl esters of acrylic acid or methacrylic acid such as sulfobutyl sulfonate and sulfoethyl methacrylate and salts thereof; styrene such as styrene, α-methylstyrene, and chlorosterene, and alkyl or halogen substituted products thereof; basic vinyl compounds such as vinylpyridine Vinyl nitrile compounds such as methacrylonitrile and hydroxyethyl acrylonitrile; vinyl aldehyde compounds such as acrolein and methacrolein; glycidyl esters of unsaturated carboxylic acids such as glycidyl acrylate and glycidyl methacrylate; glycidyl allyl sulfonate and the like Examples thereof include glycidyl esters of unsaturated sulfonic acids; unsaturated glycidyl ethers such as vinyl glycidyl ether and allyl glycidyl ether. Moreover, when using a crosslinkable monomer, divinyl monomers, such as ethylene glycol di (meth) acrylate, methylenebisacrylamide, and divinylbenzene, can be used.

In the production of an aqueous dispersion of a water-absorbing material, first, the water-absorbing material is prepared to a predetermined amount of water. In the case of a dry powder, the amount of water can be adjusted by dropping or dispersing in water under stirring, or by adjusting the humidity.
On the other hand, since the polymer supplied from the polymerization reaction step is usually in the form of a hydrous gel, depending on the water content of the gel, a water addition operation is performed or direct dehydration is performed by a known drying method.
Next, the water-absorbing material adjusted to a predetermined moisture content is added and dispersed with stirring. The water-absorbing material at this time may be as it is or in the form of a slurry. In order to obtain a desired particle size and a narrow particle size distribution of the aqueous dispersion of the water-absorbing material, it is preferable to uniformly disperse. Examples of the apparatus to be used include a vibration type mixer and a high-speed rotary paddle machine. Surfactants, dispersants, flocculants, inorganic substance additives, and the like can also be used.

  In order to obtain an aqueous dispersion of a water-absorbing material having high fluidity used in the present invention, it is preferable to balance the average particle diameter and the water-absorbing magnification. Further, when dispersed in water, the water-absorbing material and water It is preferable to consider the ratio. In order to permeate into the continuous voids inside the porous material, the ratio of the water-absorbing material in the aqueous dispersion is usually 1 to 50% by weight, preferably about 2 to 20% by weight. At this time, even when using a water-absorbing material that balances the average particle diameter and the water-absorbing ratio, if the proportion of water-absorbing material added to water is too large when dispersed in water, the fluidity during construction is impaired. End up. In addition, the larger the average particle size of the water-absorbing material, the more difficult it is for the water dispersion of the water-absorbing material to penetrate into the continuous voids inside the porous material. It is practical that the average particle size is relatively low when the average particle size is large.

  And even when the balance between the average particle diameter of the water-absorbing material and the water absorption ratio is not in the optimum range, by stirring for a long time when water-absorbing and dispersing in water, the fluidity of the uniformly dispersed water-absorbing material It is possible to obtain an aqueous dispersion. In addition, it is possible to obtain a water dispersion of a water-absorbing material by leaving still after performing a certain amount of stirring and taking out only the uniformly dispersed portion by a decantation method, but there is a problem that many steps are required. is there.

  As an example of a material most suitable as an aqueous dispersion of such a water-absorbing material, “Espec L” manufactured by Toyobo Co., Ltd. can be mentioned. The water dispersion of this water-absorbing material is a microhydrogel and can be used in a state of being uniformly dispersed in water. In addition, for example, it is preferable that the average particle size of the water-dispersed particles of the water-absorbing material swollen with water is about 0.1 to 10 μm. Further, it is also preferable to use the solid content (weight conversion ratio of the water-absorbing material to water) as 5 to 20% by weight.

  The water-absorbing material used in the present invention has a water absorption ratio of 2 to 500 times its own weight, but preferably 3 to 400 times, more preferably 10 to 350 times considering the balance of water dispersibility and other characteristics. Next, it is preferably 80 to 120 times.

  In the water retention agent of the present invention, a crosslinking agent capable of forming a chemical bond with the absorbent material is used in addition to the water absorbent material.

  The cross-linking agent used in the present invention is a polyfunctional compound having two or more functional groups in the molecule capable of forming a chemical bond with a functional group in the main chain and / or side chain of the polymer constituting the water-absorbing material. It is a sex compound. The chemical bond referred to here is a covalent bond, an ionic bond, or a hydrogen bond, and it is preferable that the chemical bond to be formed is a covalent bond in consideration of an actual application.

  Examples of such cross-linking agents include polyfunctional compounds having two or more functional groups of any one functional group such as hydroxyl group, epoxy group, amino group, and methylol group, specifically, ethylene glycol, propylene glycol, and glycerin. , Diglycidyl ether, glycerin triglycidyl ether, ethylene glycol diglycidyl ether, ethylene diamine, propylene diamine, polyethylene glycol, polyvinyl alcohol, trimethylol melamine, trimethylol propane, polyethylene imine, urea, polylysine and the like. A crosslinking agent such as ammonium zirconium carbonate or potassium zirconium carbonate can also be used. The amount of these crosslinking agents used is from 0.1 to 20.0% by weight, more preferably from 0.5 to 10.0% by weight, most preferably from 1 to 6.0% by weight, based on 100% by weight of the water-absorbing material. It is suitable to use. When the amount of the crosslinking agent is too small, the number of chemical bonds formed between the water-absorbing materials is small, the physical strength of the water-absorbing material film is lowered, and the effect of adding the crosslinking agent may not be sufficiently exhibited. On the other hand, when the concentration of the crosslinking agent is high, the physical strength of the water-absorbing material film formed is increased, but the water retention performance itself may be greatly reduced. As a method for adding these crosslinking agents, a method of dissolving or emulsifying the crosslinking agent in an aqueous dispersion of a water-absorbing material can be used.

The porous material used in the present invention is permeable asphalt (porous asphalt), permeable concrete (porous concrete), porous ceramics, regardless of whether the porous material has a large number of continuous voids in the interior. The present invention can be widely applied to porous materials having a large number of continuous voids in the interior, represented by materials, sludge incinerated ash fired bodies, lightweight aggregates, gravel and the like. This porous material with water retention capability can reduce the temperature of the porous material by evaporative cooling of water, increase the amount of waste heat due to cooling and heating, which has been a problem in recent years, and concrete or asphalt of buildings and roads This is particularly useful for increasing the absorption of solar heat due to heat treatment and preventing urban heat islands from being released into the atmosphere.
The porous material to which the water retention material of the present invention is applied is most preferably a water-permeable pavement used in roads, plazas, parking lots, various sites, etc. It can also be used for those used as panels, ceiling materials, roofing materials, and the like.

  The porous material in the present invention has a large number of continuous voids inside, and the degree of the voids can be expressed by the porosity. The porosity of the porous material can be obtained from the amount of water absorbed by cutting the porous material into a predetermined volume. The larger the porosity, the more water retaining material dispersed or dissolved in water can be adhered, and more water retaining property can be imparted to the porous material. However, although the increase in porosity depends on the specific application because it lowers the physical strength of the porous material itself, for example, about 3 to 60% is preferable.

  In the present invention, the water retention agent is infiltrated into the continuous voids of the porous material, and the water absorbing material and the crosslinking agent in the water retention agent form a chemical bond in the continuous voids and are supported in the voids. Provides water retention. When the imparting agent of the present invention is water-dispersible or water-soluble, it is allowed to permeate a wide range of continuous voids by simply spraying the imparting agent on the porous material, and then the moisture is naturally dried by solar heat. It is possible to promote chemical bonding between the water-absorbing material and the cross-linking agent alone, and this water-holding agent can be supported inside the voids. It is immobilized inside the porous body without returning to the water retention agent having fluidity again. Immobilization has the effect of improving adhesion to the inside of the gap and preventing runaway from the two sides of the water retention agent being swollen in the gap and becoming larger than the gap opening due to volume increase. is expected. Therefore, the construction method is extremely easy and construction in a short period of time is possible. In addition, it is possible to construct a road that has already been laid, and there is no need to construct a new road. It is also very easy to apply to already built materials.

  Although the water retention agent for inorganic porous materials of this invention and its usage method are shown concretely using an Example and a comparative example below, this invention is not limited to these. All percentages and parts described in the examples are based on weight unless otherwise specified.

Measuring method of water absorption ratio (times) of water-absorbing material About 8 g of the sample is precisely weighed in an aluminum petri dish, and the aluminum petri dish containing the dried sample after being dried for 5 hours or more in a 105 ° C. constant temperature dryer is put in a 500 ml beaker.
2. After adding 300 ml of pure water, the swelling gel is peeled off, the aluminum petri dish is taken out, and the gel is allowed to settle.
3. Discard the supernatant and add 300 ml of pure water again.
4.3. Repeat three times.
5). Put in tea strainer and drain for 10 minutes.
6). About 1/4 of the tea strainer is placed in an aluminum petri dish and weighed precisely, and dried in a constant temperature dryer at 105 ° C. for 5 hours or longer. Calculate with the following formula.
Water absorption ratio (times) = (weight of sample (gel) before drying / sample weight after drying) −1

  ESPEC L manufactured by Toyobo Co., Ltd. was used as an aqueous dispersion of the water-absorbing material. The concentration of the water-absorbing material is 9% by weight, and the viscosity measured with a B-type viscometer is 450 mPa · s. The average particle size of the water-absorbing material at the time of swelling is 8 μm, and the water-absorbing magnification of the water-absorbing material is 100 times. Hereinafter, this is referred to as an aqueous dispersion A of a water-absorbing material.

  A 60% by weight hydrazine aqueous solution was added to water dispersion A of water absorbent material so as to be 5% by weight, and after keeping the temperature at 100 ° C. for 2 hours, the water absorbent material concentration was adjusted to 9% by weight. An aqueous dispersion B of the functional material. The viscosity of the water dispersion B of the water-absorbing material was 220 mPa · s with a B-type viscometer, the average particle diameter when the water-absorbing material was swollen was 2 μm, and the water absorption ratio was 2.3 times.

  Two types of crosslinking agents were used: polyglycidyl ether (hereinafter abbreviated as EGDGE) of ethylene glycol / epichlorohydrin 0-2 mol adduct mixture and ammonium zirconium carbonate. As EGDGE, Epiol E-100 (manufactured by Nippon Oil & Fats Co., Ltd.) and Baycoat 20 (manufactured by Nippon Light Metal Co., Ltd.) were used as ammonium zirconium carbonate.

  Porous asphalt was used as the inorganic porous material. The porous asphalt used was a 15% porosity and was cut into a size of 10 cm × 10 cm × 5 cm.

Example 1
A water retention agent was prepared by dissolving 5% by weight of Epiol E-100 in 100% by weight of the water absorbent material (resin solid content) in the aqueous dispersion A of the water absorbent material. After the porous asphalt is completely buried for 5 minutes in this water retention agent, the porous asphalt is pulled up and kept at 30 ° C. for 12 hours, the weight is measured, and the weight of the porous asphalt alone is subtracted from the water retention agent. The filling amount was used. Subsequently, the porous asphalt filled with the water retention agent was completely immersed in pure water for 30 minutes, then pulled up, drained on a wire mesh for 10 minutes, weighed, and the weight of the porous asphalt alone was subtracted from this weight. Was calculated. The test specimen after the weight measurement was dried at 30 ° C. for 12 hours, immersed again in pure water and drained, and the second water retention amount was measured. The results of repeating this operation a total of 5 times are summarized in Table 2. The determination was made according to the following criteria.

Example 2
Table 2 shows the results when the same operation as in Example 1 was performed except that the crosslinking agent was changed to Baycoat 20 in Example 1.

Example 3
Table 2 shows the results when the same operation as in Example 1 was performed except that the water-absorbing material concentration in Example 1 was changed to 1% by weight.

Example 4
Table 2 shows the results when the same operation as in Example 1 was performed except that the concentration of the crosslinking agent in Example 1 was changed to 9% by weight.

Example 5
Table 2 shows the results when the same operation as in Example 1 was performed except that the water dispersion of the water-absorbing material was changed to B and the concentration of the crosslinking agent was changed to 1% by weight.

Example 6
Table 2 shows the results when the same operation as in Example 1 was performed except that the concentration of the crosslinking agent in Example 1 was changed to 0.1% by weight.

Comparative Example 1
Table 2 shows the results when the same operation as in Example 1 was performed except that the water-absorbing material and the curing agent were not used in Example 1.

Comparative Example 2
Table 2 shows the results when the same operation as in Example 1 was performed except that no crosslinking agent was added in Example 1.

  Examples 1 and 2 show that by using a microhydrogel water-absorbing material, the inside of the porous asphalt is sufficiently filled with the microhydrogel, and the water retention amount is not greatly reduced by repeated water retention amount measurement. Example 3 shows that the water-absorbing material concentration is low, the viscosity is low, the filling amount is reduced, and the water-retaining material is small because the absolute amount of the water-absorbing material is small, but it has an excellent water-retaining amount. Example 4 shows that the concentration of the crosslinking agent is high and the water retention amount itself is slightly low, but the decrease in the water retention amount due to repetition is small. In Example 5, the water retention amount of the water-absorbing material is low, so that the water retention amount is slightly insufficient. In Example 6, the concentration of the crosslinking agent is low, and the water retention amount itself is very high, but the durability by repetition is slightly low.

Since the comparative example 1 does not use the water absorbing material, it shows that the amount of water retention is insufficient.
Comparative Example 2 does not contain a crosslinking agent, and the formed film is weak, indicating that the durability against repeated measurement is insufficient.

  The water retention agent according to the present invention imparts water retention by being supported in the voids of the porous material. As long as it has a large number of continuous voids, regardless of whether it is newly installed or existing, water permeable asphalt (Porous asphalt), water permeable concrete (porous concrete), porous ceramic materials, sludge incinerated ash fired bodies, lightweight aggregates, porous materials having many continuous voids inside such as gravel be able to.

  In addition, the porous material provided with water retention by the water retention agent of the present invention enables the temperature of the porous material to be reduced by evaporative cooling of water, and an increase in the amount of waste heat due to cooling and heating, which has been a problem in recent years, It is particularly useful for increasing the absorption of solar heat due to concrete and asphalt of buildings, roads, etc., and preventing urban heat islands due to heat dissipation from the stored heat to the atmosphere.

  Furthermore, the porous material to which the water retention agent of the present invention is applied is most preferably a water-permeable pavement used for roads, plazas, parking lots, various sites, etc. It can also be used for interior and exterior panels, ceiling materials, roofing materials, and the like.

Claims (4)

  A water retention agent for porous materials, comprising a water absorbent material having a water absorption ratio of 2 to 500 times its own weight and a crosslinking agent capable of forming a chemical bond with the absorbent material.   The water retention agent for porous materials according to claim 1, wherein the water absorbing material is dispersed or dissolved in water.   By spraying the water retention agent for a porous material according to claim 1 or 2 from the surface of the porous material, the water absorbing material and the crosslinking agent are chemically bonded within the continuous voids inside the porous material, A method for using a water retention agent for a porous material that imparts water retention to a porous material.   A porous material in which the water retention agent for a porous material according to claim 1 or 2 is supported in an internal continuous void.