JP2022022199A - Hydrophilic urethane cut-off agent - Google Patents

Abstract

To provide an urethane cut-off agent that achieves reduction in remaining MDI monomers, has low viscosity comparable to that of the conventional MDI urethane prepolymers, forms a gel body even in the presence of a large amount of water, and exhibits excellent curability.SOLUTION: A hydrophilic urethane cut-off agent contains an urethane prepolymer having a terminal isocyanate group formed by reacting a polyol and a diphenyl methane diisocyanate or a modified product thereof so that the equivalent ratio of isocyanate groups and hydroxy groups (NCO/OH) becomes 1.5-2.0. The polyol contains a polyfunctional polyol that is formed by the polymerization of ethylene oxide alone with a tri-octa-valent polyhydric alcohol or the addition polymerization of ethylene oxide and a C3-4 alkylene oxide therewith and has a number average molecular weight of 500 or more and 20,000 or less, and a low-molecular polyol having a number average molecular weight of less than 500.SELECTED DRAWING: None

Description

The present invention relates to a hydrophilic urethane-based waterproofing agent, and more specifically, the remaining MDI monomer is reduced, the viscosity is as low as that of a conventional MDI-based urethane prepolymer, and even in the presence of a large amount of water. The present invention relates to a hydrophilic urethane-based water blocking agent that forms a gel body and exhibits excellent curing performance.

Urethane-based waterproofing agents are widely used at tunnel construction sites and for waterproofing and repairing concrete structures where water leaks have occurred. Among them, the water-stopping agent containing hydrophilic urethane prepolymer as the main component contains a large amount of water with a small amount of chemical solution to form a gel body, so that it is highly water-stopping even for a large amount of spring water during tunnel excavation. It can be effective.

In recent years, MDI-based isocyanates such as 4,4'-diphenylmethane diisocyanate have been widely used as organic polyisocyanates constituting urethane prepolymers. However, unreacted diphenylmethane diisocyanate (MDI) monomer remains in the conventional urethane prepolymer type water blocking agent, which may impair the working environment of workers.

In order to reduce unreacted MDI monomers, a method of reacting an excessive amount of MDI with a relatively high molecular weight diol to produce a prepolymer and distilling off the free MDI under reduced pressure (Patent Document 1), or a prepolymer reaction. A method of distilling the product in the presence of at least one inert solvent having a boiling point slightly lower than the boiling point of the monomeric diisocyanate has been proposed (Patent Document 2). However, in these methods, high boiling point MDI is removed while avoiding thermal decomposition of the prepolymer, so that a high-cost purification step such as thin film distillation is required.

On the other hand, if the stoichiometric reaction equivalent ratio (NCO / OH) of the polyol and MDI is set to 2.0 or less, MDI does not theoretically remain in the prepolymer, but an oligomer is generated during the reaction to increase the viscosity. Or the long-term stability of the resulting prepolymer is compromised.
As a method for producing a reactive polyurethane having a low content of monomeric diisocyanate without a post-treatment step or a purification step, a monomeric diisocyanate containing 2,4'-MDI as a main component and a diol having a molecular weight of 60 to 2000 are used as NCOs. A method of reacting / OH at 1.05 / 1 to 2.0 / 1 (Patent Document 3) has been proposed.
Further, as a method for producing a 2,4'-MDI prepolymer having a low viscosity and a low monomer content, 2,4'-MDI and a polyether polyol having an average number of functional groups of 3 to 8 are reacted with an NCO / OH of less than 2. A method for causing the reaction (Patent Document 4) has been proposed.

Japanese Unexamined Patent Publication No. 8-176252 Special Table 2003-515635 Gazette Japanese Patent Publication No. 2004-534132 Japanese Unexamined Patent Publication No. 2006-37099

Since the 2-position NCO group of 2,4'-MDI used in Patent Document 3 and Patent Document 4 is in a position where it is difficult to react sterically, the reactivity is lower than that of the 4'-position NCO group. Therefore, the NCO group at the 4'position reacts preferentially to form a prepolymer, a urethane prepolymer having a low viscosity can be obtained without excessively blending MDI, and the amount of residual monomers can be reduced. However, when such a urethane prepolymer is used as a water blocking agent, the reactivity of the unreacted 2-position NCO group is low, so that the curing rate becomes slow and a sufficient water blocking effect cannot be obtained.
Further, since the urethane prepolymer having a small amount of residual MDI monomer has a low NCO content (amount of NCO groups per unit mass), it is difficult to cure in the presence of a large amount of water.

Therefore, the residual amount of MDI monomer is reduced, the resin is cured even at a low viscosity and a low concentration similar to that of the conventional MDI urethane prepolymer, and the urethane-based stopper can exert a water-stopping effect even in a large amount of spring water. There has never been a liquid agent.
In the present invention, the remaining MDI monomer is reduced, a gel body is formed in the presence of a large amount of water with a viscosity as low as that of the conventional MDI urethane prepolymer, and the urethane-based stop exhibiting excellent curing performance. The subject is to provide a liquid agent.

As a result of diligent studies to solve the above problems, the present inventors have a number average molecular weight of 500 or more and 20 by using ethylene oxide alone or by addition-polymerizing ethylene oxide and propylene oxide to a 3- to 8-valent polyhydric alcohol. A urethane prepolymer obtained by reacting a polyol containing a polyfunctional polyol of 000 or less and a low molecular weight polyol having a number average molecular weight of less than 500 with an MDI-based isocyanate is obtained in the presence of low viscosity and a large amount of water. However, it was found that a gel body was formed and an excellent water blocking effect was exhibited, and the present invention was completed.

That is, the present invention relates to the following [1] to [9].

[1] Urethane having a terminal isocyanate group obtained by reacting a polyol with diphenylmethane diisocyanate or a modified product thereof so that the equivalent ratio (NCO / OH) of an isocyanate group to a hydroxy group is 1.5 to 2.0. A hydrophilic urethane-based waterproofing agent containing a prepolymer,
The polyol is a polyfunctional polyol having a number average molecular weight of 500 or more and 20,000 or less, which is obtained by polymerizing ethylene oxide alone or addition-polymerizing ethylene oxide with an alkylene oxide having 3 or 4 carbon atoms to a 3- to 8-valent polyhydric alcohol. It is characterized by containing a low molecular weight polyol having a number average molecular weight of less than 500.
Hydrophilic urethane water blocking agent.
[2] The hydrophilic urethane-based water blocking agent according to [1], wherein the remaining unreacted 4,4'-diphenylmethane diisocyanate is 2% by mass or less.
[3] The trihydric polyhydric alcohol is at least one selected from the group consisting of glycerin, diglycerin, pentaerythritol, trimethylolpropane, and sorbitol, [1] or. The hydrophilic urethane-based water blocking agent according to [2].
[4] The low molecular weight polyol is at least one selected from the group consisting of ethylene glycol, propylene glycol, diethylene glycol, 1,3-propanediol, 1,4-butanediol and polyethylene glycol having a number average molecular weight of less than 500. The hydrophilic urethane-based waterproofing agent according to any one of [1] to [3], which is characterized by the above.
[5] The polyol is a polyether diol having a number average molecular weight of 3,000 or more and 20,000 or less, which is obtained by further polymerizing ethylene oxide alone with a dihydric alcohol or addition polymerization of ethylene oxide with an alkylene oxide having 3 or 4 carbon atoms. The hydrophilic urethane-based waterproofing agent according to any one of [1] to [4], which is characterized by containing.
[6] The diphenylmethane diisocyanate or a modified product thereof is at least one selected from the group consisting of 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, polyphenylpolymethylene diisocyanate and carbodiimide-modified diphenylmethane diisocyanate. The hydrophilic urethane-based water blocking agent according to any one of [1] to [5].
[7] The hydrophilic urethane-based water blocking agent according to any one of [1] to [6], which further contains a diluent.
[8] The diluent is gamma butyl lactone, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, triethylene glycol butyl methyl ether, 2-oxo-4-methyl-1,3-dioxolane, dimethyl glutarate, dimethyl succinate and adipine. The hydrophilic urethane-based waterproofing agent according to [7], which is at least one selected from the group consisting of dimethyl acid acid.
[9] The hydrophilic urethane-based water blocking agent according to any one of [1] to [8], which further contains a monoisocyanate.

The hydrophilic urethane-based waterproofing agent of the present invention is excellent because the residual MDI monomer is reduced, the viscosity is as low as that of the conventional MDI-based urethane prepolymer, and a gel body is formed even in the presence of a large amount of water. Demonstrates curing performance.

The urethane prepolymer having a terminal isocyanate group used as the main component of the hydrophilic urethane-based waterproofing agent of the present invention is a trihydric polyhydric alcohol containing ethylene oxide alone or an ethylene oxide and an alkylene having 3 or 4 carbon atoms. It is obtained by reacting a polyfunctional polyol having a number average molecular weight of 500 or more and 20,000 or less to which an oxide is added, a polyol containing a low molecular weight polyol having a number average molecular weight of less than 500 as an essential component, and a diphenylmethane diisocyanate or a modified product thereof. It is a thing.

<Polyol>
The polyol used in the present invention is a polyfunctional polyol having a number average molecular weight of 500 or more and 20,000 or less, which is obtained by adding ethylene oxide alone or ethylene oxide and an alkylene oxide having 3 or 4 carbon atoms to a 3- to 8-valent polyhydric alcohol. It is characterized by containing as essential a low molecular weight polyol having a number average molecular weight of less than 500.

<Polyfunctional polyol>
Examples of the trihydric polyhydric alcohol include glycerin, trimethylolpropane, erythritol, pentaerythritol, sorbitan, diglycerin, xylitol, triglycerin, sorbitol, dipentaerythritol, inositol and tetraglycerin.
Among these, glycerin, diglycerin, pentaerythritol, trimethylolpropane, and sorbitol are preferable.

Examples of the alkylene oxide having 3 or 4 carbon atoms include propylene oxide, 1,2-, 1,3-, 1,4-, and 2,3-butylene oxide. Only ethylene oxide may be added without adding these alkylene oxides, or two or more kinds of ethylene oxide and these alkylene oxides may be used in combination (block or random addition). Among these, it is preferable to use ethylene oxide and propylene oxide in combination, and it is more preferable to use them in the form of block addition. When ethylene oxide and an alkylene oxide having 3 or 4 carbon atoms are used in combination, it is preferable that the proportion of ethylene oxide is 50% by mass or more, and more preferably 70% by mass or more, based on the total mass of the added alkylene oxide. ..

The content of the polyfunctional polyol is preferably 0.5 to 95% by mass with respect to the total amount of the polyol, and more preferably 1 to 90% by mass, from the viewpoint of making it difficult for the obtained urethane prepolymer to thicken. preferable.

<Small molecule polyol>
Further, by using a low molecular weight polyol having a number average molecular weight of less than 500, the curability of the urethane prepolymer can be enhanced. Examples of the low molecular weight polyol include ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, 1,3-propanediol, 1,4-butanediol, and polyethylene glycol having a number average molecular weight of less than 500.

From the viewpoint of curability and product stability of the urethane prepolymer, the content of the low molecular weight polyol is preferably 0.1 to 20% by mass with respect to the total amount of the polyol, and more preferably 2 to 10% by mass. preferable.

<Other polyols>
A polyol other than the above can be used as long as the object of the present invention is not impaired. Such polyols are not particularly limited, and examples thereof include polyether polyols, polyester polyols, polycarbonate polyols, and polyacetal polyols. When these polyols are used, it is preferable to use them in an amount of 0 to 99% by mass with respect to the total amount of the polyols.

The polyether polyol has a structure in which an alkylene oxide having 2 to 4 carbon atoms is added to a compound having two or more active hydrogen atoms (for example, a polyhydric alcohol, a polyhydric phenol, an amine, etc.) (polyoxyalkylene chain). Includes) compounds and mixtures thereof.
Polyhydric alcohols include ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, neopentyl glycol, glycerin, trimethylolpropane, pentaerythritol, sorbitol, 1,3- and 1,4-butanediol, 1,2- and Examples thereof include 1,5-pentanediol, 1,6-hexanediol, and 1,4-cyclohexanedimethanol.
Here, it is preferable to use dihydric alcohols such as ethylene glycol, propylene glycol, diethylene glycol, and dipropylene glycol as the polyhydric alcohols in terms of improving the water blocking performance.
Examples of the alkylene oxide having 2 to 4 carbon atoms include ethylene oxide, propylene oxide, 1,2-, 1,3-, 1,4- or 2,3-butylene oxide.
Among these polyether polyols, those having a number average molecular weight of 500 to 50,000 are preferable, and polyether diols of 3,000 or more and 20,000 or less can be particularly preferably used.

Examples of the polyester polyol include polyols such as ethylene glycol, propylene glycol, butylene glycol, hexylene glycol, diethylene glycol, dipropylene glycol, neopentyl glycol, glycerin or trimethylolpropane, and succinic acid, glutaric acid, adipic acid, maleic acid and fumaric acid. Saturated or unsaturated polyvalent carboxylic acids such as acids and phthalic acids, condensation products with these acid anhydrides, polycaprolactone polyols and the like can be mentioned. If necessary, two or more of these polyester polyols may be mixed and used. Among these, those having a number average molecular weight of 100 to 50,000 are particularly preferable, and those having a number average molecular weight of 200 to 20,000 can be more preferably used.

Examples of the polycarbonate polyol include those obtained by reacting a polyol such as ethylene glycol, propylene glycol, butylene glycol, hexylene glycol, diethylene glycol or dipropylene glycol with diethylene carbonate, dimethyl carbonate, diethyl carbonate and the like. If necessary, two or more of these polycarbonate polyols can be mixed and used.

<MDI-based isocyanate>
The diphenylmethane diisocyanate (hereinafter, also referred to as MDI) used in the present invention is not particularly limited, and may be any of 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, and 4,4'-diphenylmethane diisocyanate. It may also be any mixture thereof, or may be a polypeptide diphenylmethane diisocyanate (polymeric MDI, polymethylene polyphenyl polyisocyanate). Examples of the modified product of diphenylmethane diisocyanate include those in which a part of the isocyanate group is modified with biuret, allophanate, carbodiimide, oxazolidone, amide, imide, isocyanurate, uretdione and the like.
Among these, from the viewpoint of curability of the obtained urethane prepolymer, those containing 4'-MDI in an amount of 5% by mass or more, more preferably 20% by mass or more, based on the total mass of MDI. , 30 mass or more is more preferable, and 40 mass or more is particularly preferable.
Further, from the viewpoint of the viscosity of the obtained urethane prepolymer, those containing 80% by mass or less of 4,4'-MDI are preferable, and those containing 70% by mass or less are more preferable, based on the total mass of MDI.

<Urethane prepolymer>
Prepolymerization is usually carried out by charging a polyol and an organic polyisocyanate into a synthetic reaction apparatus, stirring the mixture, and reacting the mixture at 60 to 160 ° C. In the present invention, the reaction equivalent ratio NCO / OH of the polyol and MDI is 1.5 to 2.0. By setting NCO / OH to 2.0 or less, no MDI monomer remains theoretically.
When prepolymerizing, a catalyst may be used if necessary. Examples of the catalyst include amine-based catalysts such as triethylamine, trimethylamine, dimethylmyristylamine, stearylamine, dimethyldecylamine, N-ethylmorpholin, triethylenetetramine, tolylenediamine, and xylylenediamine, monobutyltin oxide, dibutyltin oxide, and tetraoctyl. Tin-based catalysts such as tin, dioctyl tin oxide, dibutyl tin dilaurate, and dioctyl tin dilaurate may be used.
The NCO content of the urethane prepolymer is preferably 0.50 to 4.00% by mass, more preferably 0.70 to 2.50% by mass.

<Diluent>
Further, in order to suppress thickening during and after the reaction, a diluent can be added to the urethane prepolymer of the present invention, if necessary. The diluent preferably has a high boiling point, low odor, and no active hydrogen at a high ignition point. Specifically, gamma butyrolactone, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, etc. Examples thereof include 2-oxo-4-methyl-1,3-dioxolane, methylacetyllithinolate, butylacetyllithinolate, dimethyl glutarate, dimethyl succinate, dimethyl adipate, or a mixture thereof.
When a diluent is used, it is preferable to use it in an amount of 20 to 60% by mass with respect to the total mass of all the components of the hydrophilic urethane-based water blocking agent of the present invention.

<Monoisocyanate>
Further, the hydrophilic urethane-based waterproofing agent of the present invention may contain a monoisocyanate in order to improve storage stability. Examples of the monoisocyanate include octadecylisocyanate, 3-isocyanatepropyltriethoxysilane, 3-isocyanatepropyltrimethoxysilane, p-toluenesulfonylisocyanate (PTSI) and the like. Of these, p-toluenesulfonyl isocyanate is preferable.

Further, if necessary, additives such as a foam stabilizer, an antifoaming agent, a cross-linking agent, a colorant, a resin modifier, a flame retardant, an ultraviolet absorber, and a durability improver can be added within a range that does not impair the object of the present invention. Can be added with.

Further, depending on the construction situation, an epoxy resin, an acrylic resin (methyl methacrylate or the like), a styrene resin or the like may be used in combination in addition to the hydrophilic urethane water blocking agent of the present invention. When these resins are used in combination, 1 to 50% by mass can be blended with respect to the mass of the urethane prepolymer used for the water blocking agent of the present invention.

The present invention will be described below with reference to examples. However, the present invention is not limited to these Examples and Comparative Examples. In this example, the number average molecular weight was measured using GPC.
<GPC measurement conditions>
Equipment: Tosoh HLC-8120GPC
Solvent: Tetrahydrofuran Flow rate: 0.6 ml / min
Temperature: 40 ° C
Sample concentration: 0.1%
Sample injection amount: 20 μl
Detector: RI

Example 1
Ethylene oxide propylene oxide block adduct of glycerin as a polyfunctional polyol in a synthesizer with a content of 1 L equipped with a stirrer, thermometer, and temperature controller (ethylene oxide content 80% by mass based on the total mass of added total alkylene oxide, 9 g (number average molecular weight 900), 15.9 g of diethylene glycol as a low molecular weight polyol, ethylene oxide propylene oxide block adduct of diethylene glycol as a polyether diol (ethylene oxide content 90% by mass based on the total mass of added total alkylene oxide), 600 g (number average molecular weight 6,000) was added. Next, 132.5 g of a mixed MDI of 4,4'-MDI and 2,4'-MDI (Millionate NM manufactured by Tosoh Corporation) as an isocyanate component and 230 g of gamma butyl lactone as a diluent were added to the same apparatus, and the temperature was increased to 100 ° C. The temperature was raised and reacted for 5 hours to obtain a urethane prepolymer having an NCO content of 2.10%. Finally, 120 g of gamma-butyrolactone and 7 g of p-toluenesulfonyl isocyanate were added as diluents to obtain the hydrophilic urethane-based water blocking agent of the present invention.

Examples 2 to 13, Comparative Examples 1 to 6
Examples of Examples except that A to F shown in Table 1 were used as the polyfunctional polyol, and the types and blending amounts and reaction conditions of the low molecular weight polyol, the polyether diol, the isocyanate and the diluent were changed as shown in Table 3. In the same manner as in No. 1, a hydrophilic urethane-based water blocking agent was obtained.

<Small molecule polyol>
-DEG: Diethylene glycol-DPG: Dipropylene glycol-EG: Ethylene glycol-PEG200: (Polyethylene glycol manufactured by Toho Chemical Industry Co., Ltd., number average molecular weight 200)
PEG400: (Polyethylene glycol manufactured by Toho Chemical Industry Co., Ltd., number average molecular weight 400)

<MDI-based isocyanate>
・ 4,4'-MDI: 4,4'-diphenylmethane diisocyanate (trade name "Millionate MT" manufactured by Tosoh Corporation)
-Mixed MDI: A mixture of 4,4'-MDI and 2,4'-MDI (2,4'-diphenylmethane diisocyanate) (trade name "Millionate NM" manufactured by Tosoh Corporation)
-Modified MDI: Carbodiimide-modified 4,4'-diphenylmethane diisocyanate (trade name "Millionate MTL" manufactured by Tosoh Corporation)
-Polymeric MDI: Polymethylene polyphenylene polyisocyanate (trade name "Millionate MR-200" manufactured by Tosoh Corporation)
・ 2,4'-MDI: 2,4'-diphenylmethane diisocyanate (manufactured by Sigma-Aldrich Japan)
<Diluent>
・ GBL: Gamma Butyl Lactone ・ MTM: Triethylene Glycol Dimethyl Ether ・ BTM: Triethylene Glycol Butyl Methyl Ether ・ PC: Propylene Carbonate <Monoisocyanate>
-PTSI: p-toluenesulfonyl isocyanate

[Performance evaluation]
The urethane-based water blocking agents obtained in Examples 1 to 13 and Comparative Examples 1 to 6 were subjected to the performance evaluation tests of (1) to (7) below. The results are shown in Table 3.

(1) Viscosity measurement Based on the JISK1557-5: 2007 plastic-polyurethane raw material polyol test method, No. 1 was used with a B-type viscometer (manufactured by Brookfield). 2 and No. The rotor of No. 3 was rotated at 30 to 60 rpm, and the viscosity of each sample at 20 ° C. was measured.
(2) NCO content Measured based on the plastic-polyurethane raw material aromatic isocyanate test of JISK1603-1: 2007.
(3) Residual amount of 4,4'-MDI monomer Using a liquid chromatograph device HPLC-prominence (manufactured by Shimadzu Corporation) and a column Develosil C30-UG 5 μm (manufactured by Nomura Chemical Co., Ltd.), a calibration curve is used at THF: water = 4: 6. Was prepared, and the residual amount of 4,4'-MDI monomer contained in each sample was measured.
(4) Appearance of the sample It was visually confirmed that the sample liquid was in a transparent state with no turbidity or impurities, and if it was transparent, the appearance was good.
(5) Product stability The viscosity of each sample left at 70 ° C. for 7 days at 20 ° C. was measured based on the measurement method of (1).
(6) 20% concentration Curing time Add 10 g of the sample solution to the poly cup, add 40 g of tap water temperature-controlled to 20 ° C., and stir with a spatula for 10 seconds. The time when water was added and the mixed solution was cured and the yarn started to be pulled and the flow stopped was measured and defined as "curing time".
(7) Minimum gelation concentration Add a certain amount of sample solution to a polycup, add a certain amount of tap water to it, and stir with a spatula for 15 seconds to cure the gel body and draw a thread of resistant resin. The minimum concentration of the resin for this was measured.

As shown in the results of Table 3, the results were obtained that the hydrophilic urethane-based water blocking agent according to the present invention was excellent in any of the performances (1) to (7).
On the other hand, the urethane-based water blocking agent of Comparative Example 1 containing no small molecule polyol had a high viscosity and gelled after 7 days.
On the other hand, the urethane-based waterproofing agents of Comparative Examples 2 and 6 in which MDI was excessively blended had low viscosity and excellent curability, but a large amount of 4,4'-MDI monomer remained.
Further, the urethane-based waterproofing agents of Comparative Examples 3 to 5 in which a polyol containing at least one of a polyfunctional polyol and a low molecular weight polyol and 2,4'-MDI were reacted so as to have an NCO / OH of 2.0. Although the viscosity was low, it did not cure at a concentration of 20%.

Claims (9)

A urethane prepolymer having a terminal isocyanate group obtained by reacting a polyol with diphenylmethane diisocyanate or a modified product thereof so that the equivalent ratio (NCO / OH) of an isocyanate group to a hydroxy group is 1.5 to 2.0. It is a hydrophilic urethane-based water blocking agent that is contained.
The polyol is a polyfunctional polyol having a number average molecular weight of 500 or more and 20,000 or less, which is obtained by polymerizing ethylene oxide alone or addition-polymerizing ethylene oxide with an alkylene oxide having 3 or 4 carbon atoms to a 3- to 8-valent polyhydric alcohol. It is characterized by containing a low molecular weight polyol having a number average molecular weight of less than 500.
Hydrophilic urethane water blocking agent. The hydrophilic urethane-based water blocking agent according to claim 1, wherein the remaining unreacted 4,4'-diphenylmethane diisocyanate is 2% by mass or less. The invention according to claim 1 or 2, wherein the trihydric polyhydric alcohol is at least one selected from the group consisting of glycerin, diglycerin, pentaerythritol, trimethylolpropane, and sorbitol. Hydrophilic urethane-based waterproofing agent. The low molecular weight polyol is at least one selected from the group consisting of ethylene glycol, propylene glycol, diethylene glycol, 1,3-propanediol, 1,4-butanediol and polyethylene glycol having a number average molecular weight of less than 500. The hydrophilic urethane-based water blocking agent according to any one of claims 1 to 3, wherein the hydrophilic urethane-based water blocking agent is characterized. The polyol further contains a polyether diol having a number average molecular weight of 3,000 or more and 20,000 or less, which is obtained by further polymerizing ethylene oxide alone with a dihydric alcohol or addition polymerization of ethylene oxide with an alkylene oxide having 3 or 4 carbon atoms. The hydrophilic urethane-based water blocking agent according to any one of claims 1 to 4, wherein the hydrophilic urethane-based water blocking agent is characterized. The diphenylmethane diisocyanate or a modified product thereof is characterized by being at least one selected from the group consisting of 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, polyphenylpolymethylene diisocyanate and carbodiimide-modified diphenylmethane diisocyanate. The hydrophilic urethane-based water blocking agent according to any one of claims 1 to 5. The hydrophilic urethane-based water blocking agent according to any one of claims 1 to 6, further containing a diluent. The diluent is from gamma butyl lactone, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, triethylene glycol butylmethyl ether, 2-oxo-4-methyl-1,3-dioxolane, dimethyl glutarate, dimethyl succinate and dimethyl adipate. The hydrophilic urethane-based waterproofing agent according to claim 7, wherein the agent is at least one selected from the group. The hydrophilic urethane-based water blocking agent according to any one of claims 1 to 8, further containing a monoisocyanate.