Urethane-based waterproofing agent

Abstract

To provide a urethane-based waterproof agent that reduces a residual MDI monomer, forms a cured body of low viscosity the same as that of a conventional MDI-based urethane polymer and high intensity under the presence of water, and exhibits excellent waterproof property.SOLUTION: A urethane-based waterproof agent comprises: an urethane prepolymer having a terminal isocyanate group obtained by reacting a polyol and an organic polyisocyanate containing an MDI-based isocyanate so that an equivalent ratio of the isocyanate group derived from the MDI-based isocyanate and a hydroxy group is 1.5 or more and 2.0 or less, and a silicone-based antifoaming agent, wherein the polyol contains a polyether polyol A having a number average molecular weight of 300 or more and 7,000 or less obtained by addition polymerization of propylene oxide to a polyhydric alcohol or polyhydric phenol and a bifunctional low-molecular weight polyol having a number average molecular weight of less than 300, wherein the organic polyisocyanate contains polymethylene polyphenyl polyisocyanate.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a urethane-based waterproofing agent, and more specifically to a urethane-based waterproofing agent that has a low viscosity comparable to that of conventional MDI-based urethane prepolymers, forms a high-strength cured product in the presence of water, and exhibits excellent waterproofing properties. [Background technology]

[0002] Urethane water-stopping agents are widely used in tunnel construction for waterproofing, filling cavities, and waterproofing repairs for cracked concrete structures. Among them, water-stopping agents whose main component is lipophilic urethane prepolymer foam and harden with a small amount of solution, efficiently filling relatively large voids such as those behind tunnels, and exhibiting a high water-stopping effect.

[0003] In recent years, MDI-based isocyanates such as 4,4'-diphenylmethane diisocyanate have been widely used as the organic polyisocyanate that makes up urethane prepolymers. However, unreacted diphenylmethane diisocyanate (MDI) monomer remains in conventional urethane prepolymer-type waterproofing agents, which can potentially harm the working environment.

[0004] To reduce the amount of unreacted MDI monomer, a method has been proposed in which an excess amount of MDI is reacted with a relatively high molecular weight diol to produce a prepolymer, and the free MDI is then distilled off under reduced pressure (Patent Document 1), and a method has been proposed in which the prepolymer reaction product is distilled in the presence of at least one inert solvent having a boiling point slightly lower than that of the monomeric diisocyanate (Patent Document 2).However, these methods require costly purification steps such as thin-film distillation to remove the high-boiling MDI while avoiding thermal decomposition of the prepolymer.

[0005] On the other hand, if the stoichiometric reaction equivalent ratio (NCO / OH) of polyol and MDI is set to 2.0 or less, theoretically no MDI will remain in the prepolymer, but oligomers will be produced during the reaction, causing viscosity increase and impairing the long-term stability of the resulting prepolymer. As a method for producing a reactive polyurethane with a low content of monomeric diisocyanate that does not involve a post-treatment step or a purification step, a method has been proposed in which a monomeric diisocyanate containing 2,4'-MDI as the main component is reacted with a diol having a molecular weight of 60 to 2000 at an NCO / OH ratio of 1.05 / 1 to 2.0 / 1 (Patent Document 3). Furthermore, a method for producing a low-viscosity, low-monomer-content 2,4'-MDI prepolymer has been proposed in which 2,4'-MDI is reacted with a polyether polyol having an average functionality of 3 to 8 at an NCO / OH ratio of less than 2 (Patent Document 4). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 8-176252 [Patent Document 2] Special Publication No. 2003-515635 [Patent Document 3] Special Publication No. 2004-534132 [Patent Document 4] Japanese Patent Application Laid-Open No. 2006-37099 Summary of the Invention [Problem to be solved by the invention]

[0007] The NCO group at the 2-position of the 2,4'-MDI used in Patent Documents 3 and 4 is sterically in a position that makes it less reactive, and therefore less reactive than the NCO group at the 4'-position. Therefore, the NCO group at the 4'-position reacts preferentially to form a prepolymer, resulting in a low-viscosity urethane prepolymer without the need for an excess of MDI, and the amount of residual monomer can be reduced. However, when such a urethane prepolymer is used as a waterproofing agent, the low reactivity of the unreacted NCO group at the 2-position slows the curing rate, and insufficient waterproofing effect can be achieved. In addition, urethane prepolymers, which have a low amount of residual MDI monomer, have a low NCO content (the amount of NCO groups per unit mass), and therefore are difficult to cure in the presence of large amounts of water.

[0008] As a result, the amount of residual MDI monomer is reduced, and there has not been a urethane-based waterproofing agent that has a low viscosity comparable to conventional MDI-based urethane prepolymers, cures in the presence of water, and forms a hardened product with sufficient water-stopping performance and strength. The present invention aims to provide a urethane-based waterproofing agent that has reduced residual MDI monomer, has a low viscosity comparable to that of conventional MDI-based urethane prepolymers, forms a high-strength cured product in the presence of water, and exhibits excellent water-stopping properties. [Means for solving the problem]

[0009] As a result of extensive research aimed at solving the above problems, the present inventors discovered that a urethane prepolymer obtained by reacting a specific combination of polyols with an MDI-based isocyanate containing polymethylene polyphenyl polyisocyanate forms a cured product with low viscosity in the presence of water and exhibits excellent waterproofing performance, which led to the completion of the present invention.

[0010] That is, the present invention relates to the following [1] to

[10] .

[0011] [1] A method for producing a polyol and an organic polyisocyanate containing at least one MDI-based isocyanate selected from the group consisting of diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, and modified products thereof, a urethane prepolymer having a terminal isocyanate group obtained by reacting the isocyanate group derived from the MDI-based isocyanate with a hydroxy group in an equivalent ratio (NCO / OH) of 1.5 or more and 2.0 or less; A urethane-based waterproofing agent containing a silicone-based antifoaming agent, The polyol is a polyether polyol A having a number average molecular weight of 300 or more and 7,000 or less, obtained by addition polymerization of propylene oxide alone or ethylene oxide and propylene oxide to a polyhydric alcohol or a polyhydric phenol in such a ratio that propylene oxide accounts for 80 mass% or more; and a bifunctional low-molecular-weight polyol having a number average molecular weight of less than 300, The organic polyisocyanate contains polymethylene polyphenyl polyisocyanate. Urethane-based waterproofing agent. [2] The urethane-based waterproofing agent according to [1], wherein the organic polyisocyanate contains polymethylene polyphenyl polyisocyanate in a proportion of 20% by mass or more and 70% by mass or less. [3] The urethane-based waterproofing agent according to [1] or [2], wherein the amount of remaining unreacted 4,4'-diphenylmethane diisocyanate is 5% by mass or less. [4] The urethane-based waterproofing agent according to any one of [1] to [3], wherein the polyol further contains polyether polyol B having a number average molecular weight of 800 or more and 5,000 or less, which is obtained by addition polymerization of ethylene oxide alone or ethylene oxide and an alkylene oxide having 3 or 4 carbon atoms to a polyhydric alcohol in such a proportion that ethylene oxide accounts for 20 mass% or more. [5] The urethane-based waterproofing agent according to any one of [1] to [4], wherein the polyether polyol A is obtained by addition polymerization of propylene oxide alone or ethylene oxide and propylene oxide to at least one polyhydric alcohol or polyhydric phenol selected from the group consisting of glycerin, diglycerin, pentaerythritol, trimethylolpropane, sorbitol, and bisphenol A, in a proportion of propylene oxide of 80 mass% or more. [6] The urethane-based waterproofing agent according to any one of [1] to [5], wherein the low-molecular-weight polyol is at least one selected from the group consisting of ethylene glycol, propylene glycol, diethylene glycol, 1,3-propanediol, and 1,4-butanediol. [7] The urethane waterproofing agent according to any one of [1] to [6], further comprising a diluent. [8] The urethane-based waterproofing agent according to [7], characterized in that the diluent is at least one selected from the group consisting of propylene carbonate, gamma-butyl lactone, vegetable oil-based fatty acid ester, 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 dimethyl adipate. [9] The urethane-based waterproofing agent according to any one of [1] to [8], further containing xylylene diisocyanate.

[10] The urethane waterproofing agent according to any one of [1] to [9], further comprising a curing accelerator. [Effects of the Invention]

[0012] The urethane waterproofing agent of the present invention has reduced residual MDI monomer, has a low viscosity comparable to that of conventional MDI-based urethane prepolymers, and forms a high-strength cured product in the presence of water, thereby maintaining its waterproofing effect for a long period of time. DETAILED DESCRIPTION OF THE INVENTION

[0013] The urethane prepolymer having terminal isocyanate groups used as the main component of the urethane waterproofing agent of the present invention is obtained by reacting a specific combination of polyols with an organic polyisocyanate containing at least one MDI-based isocyanate selected from the group consisting of diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, and modified products thereof.

[0014] <Polyol> The polyol used in the present invention essentially contains polyether polyol A having a number average molecular weight of 300 or more and 7,000 or less, which is obtained by addition polymerization of propylene oxide alone or ethylene oxide and propylene oxide to a polyhydric alcohol or a polyhydric phenol in a proportion such that propylene oxide accounts for 80% by mass or more, and a bifunctional low-molecular-weight polyol having a number average molecular weight of less than 300.

[0015] <Polyether polyol A> Polyether polyol A is a polyol having a number average molecular weight of 300 or more and 7,000 or less, obtained by addition polymerization of propylene oxide alone or ethylene oxide and propylene oxide to a polyhydric alcohol or a polyhydric phenol in a proportion of propylene oxide of 80% by mass or more. Examples of polyhydric alcohols include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,3- and 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, glycerin, diglycerin, trimethylolpropane, sorbitol, pentaerythritol, and cyclohexanedimethanol. Examples of polyhydric phenols include monocyclic polyhydric phenols such as pyrogallol, hydroquinone, resorcinol, and phloroglucinol; and bisphenols such as bisphenol A and bisphenol sulfone. Among these, glycerin, diglycerin, pentaerythritol, trimethylolpropane, sorbitol, and bisphenol A are preferred from the viewpoint of increasing resin strength and stabilizing foamability. When ethylene oxide and propylene oxide are used in combination, the proportion of propylene oxide is preferably 80% by mass or more, and more preferably 90% by mass or more, based on the total mass of the alkylene oxides added. The number average molecular weight of the polyether polyol A is 300 or more and 7,000 or less, and more preferably 500 or more and 6,000 or less.

[0016] The content of polyether polyol A is preferably 5 to 90 mass%, more preferably 7 to 70 mass%, based on the total amount of polyol, from the viewpoints of increasing affinity with MDI-based isocyanates, exhibiting lipophilicity to improve water-stopping properties, and making the resulting urethane prepolymer less likely to thicken.

[0017] <Low molecular weight polyol> The curing properties of the urethane prepolymer can be improved by further using, as the polyol component, a bifunctional low-molecular-weight polyol having a number-average molecular weight of less than 300. Examples of low-molecular-weight polyols include ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, 1,3-propanediol, and 1,4-butanediol.

[0018] The content of the low molecular weight polyol is preferably 10 to 95 mass % of the total amount of polyol, and more preferably 30 to 93 mass %, from the viewpoint of the curability of the urethane prepolymer and the product stability.

[0019] <Other polyols> As the polyol component, polyether polyols other than the polyether polyol A can be used in combination within the scope of the present invention. Among these, from the viewpoint of increasing affinity with water and uniformly absorbing water throughout the resin to improve water-stopping properties, polyether polyol B having a number average molecular weight of 800 or more and 5,000 or less, which is obtained by addition polymerization of ethylene oxide alone or ethylene oxide and an alkylene oxide having 3 or 4 carbon atoms to a polyhydric alcohol in a proportion such that ethylene oxide accounts for 20% by mass or more, can be preferably used. As the polyhydric alcohol, those exemplified as the polyhydric alcohols that are the starting material for polyether polyol A can be mentioned. Among these, ethylene glycol, propylene glycol, diethylene glycol, and dipropylene glycol are preferred in order to prevent the viscosity from increasing during prepolymerization.

[0020] Examples of alkylene oxides having 3 or 4 carbon atoms include propylene oxide, 1,2-, 1,3-, 1,4-, or 2,3-butylene oxide. Ethylene oxide alone may be added without adding any of these alkylene oxides, or ethylene oxide and two or more of 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, the proportion of ethylene oxide is preferably 20% by mass or more, and more preferably 30% by mass or more, based on the total mass of the added alkylene oxides.

[0021] The number average molecular weight of the polyether polyol B is preferably 1,000 or more and 5,000 or less, and more preferably 1,500 or more and 4,500 or less.

[0022] From the above viewpoint, the content of polyether polyol B is preferably 1 to 20 mass % relative to the total amount of polyols, and more preferably 3 to 10 mass %.

[0023] Furthermore, polyols other than those mentioned above can be used as long as the object of the present invention is not impaired. Such polyols are not particularly limited, but examples thereof include polyester polyols, polycarbonate polyols, and polyacetal polyols. When using these polyols, they are preferably used in an amount of 0 to 30% by mass based on the total amount of polyols.

[0024] Examples of the polyester polyol include condensation products of polyols such as ethylene glycol, propylene glycol, butylene glycol, hexylene glycol, diethylene glycol, dipropylene glycol, neopentyl glycol, glycerin, or trimethylolpropane with saturated or unsaturated polyvalent carboxylic acids such as succinic acid, glutaric acid, adipic acid, maleic acid, fumaric acid, phthalic acid, or acid anhydrides thereof, and polycaprolactone polyols. These polyester polyols can be mixed and used in two or more kinds as necessary. 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.

[0025] Examples of the polycarbonate polyol include those obtained by reacting polyols such as ethylene glycol, propylene glycol, butylene glycol, hexylene glycol, diethylene glycol, or dipropylene glycol with diethylene carbonate, dimethyl carbonate, diethyl carbonate, or the like. These polycarbonate polyols can be mixed and used in two or more kinds as necessary.

[0026] <MDI-based isocyanate The organic polyisocyanate used in the present invention contains at least one selected from the group consisting of diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, and modified products thereof (hereinafter also referred to as MDI-based isocyanate), and is an organic polyisocyanate that essentially contains polymethylene polyphenyl polyisocyanate. The diphenylmethane diisocyanate may be any of 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, or any mixture thereof. The polymethylene polyphenyl polyisocyanate is a polynuclear condensate of diphenylmethane diisocyanate and is represented by the following general formula (1). TIFF0007744221000001.tif43169 (wherein n represents an integer of 1 or more, preferably an integer of 1 to 5.) Polymethylene polyphenyl polyisocyanate is also called polymeric diphenylmethane diisocyanate (polymeric MDI), and may be a mixture with diphenylmethane diisocyanate (monomeric MDI), which is called a binuclear compound and has two benzene rings and two isocyanate groups per molecule. Examples of modified diphenylmethane diisocyanate include those in which a portion of the isocyanate groups has been modified with biuret, allophanate, carbodiimide, oxazolidone, amide, imide, isocyanurate, uretdione, or the like. Among these, from the viewpoint of increasing lipophilicity and resin strength, those containing 20 mass or more of polymethylene polyphenyl polyisocyanate relative to the total mass of the organic polyisocyanate are preferred, those containing 30 mass or more are more preferred, and those containing 40 mass or more are even more preferred. From the viewpoint of the viscosity of the resulting urethane prepolymer, the content of polymethylene polyphenyl polyisocyanate is preferably 70% by mass or less, and more preferably 60% by mass or less, of the total mass of the organic polyisocyanate.

[0027] <Non-MDI isocyanate> As the organic polyisocyanate, a non-MDI isocyanate other than the MDI isocyanate can be used in combination within the scope of the present invention. Non-MDI isocyanates that can be added include m-xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and dicyclohexylmethane 4,4'-diisocyanate, but m-xylylene diisocyanate is preferred from the standpoint of legal regulations and safety. The non-MDI isocyanate is preferably used in an amount of 20% by mass or less based on the total amount of organic polyisocyanate.

[0028] <Urethane prepolymer> Prepolymerization is usually carried out by charging a polyol and an organic polyisocyanate into a synthesis reactor, stirring them, and reacting them at 60 to 160°C. In the present invention, the reaction equivalent ratio NCO / OH between the polyol and the MDI-based isocyanate is 1.5 or more and 2.0 or less. By setting the NCO / OH ratio to 2.0 or less, theoretically no MDI monomer remains. A catalyst may be used in the prepolymerization, if necessary. Examples of the catalyst include amine catalysts such as triethylamine, trimethylamine, dimethylmyristylamine, stearylamine, dimethyldecylamine, N-ethylmorpholine, triethylenetetramine, tolylenediamine, and xylylenediamine, and tin catalysts such as monobutyltin oxide, dibutyltin oxide, tetraoctyltin, dioctyltin oxide, dibutyltin dilaurate, and dioctyltin dilaurate. The NCO content of the urethane prepolymer is preferably 0.50 to 4.00 mass %, more preferably 1.50 to 3.50 mass %.

[0029] <Silicone-based antifoaming agent> Examples of silicone-based defoaming agents used in the present invention include oil-type silicone defoaming agents, oil compound-type silicone defoaming agents, self-emulsifying silicone defoaming agents, emulsion-type silicone defoaming agents, and modified silicone defoaming agents. Examples of modified silicone defoaming agents include amino-modified silicone defoaming agents, carbinol-modified silicone defoaming agents, methacrylic-modified silicone defoaming agents, polyether-modified silicone defoaming agents, alkyl-modified silicone defoaming agents, higher fatty acid ester-modified silicone defoaming agents, and alkylene oxide-modified silicone defoaming agents. Among these, oil compound-type silicone defoaming agents are preferred because of their excellent foam-breaking effect. The main component of the silicone-based defoaming agent can be selected from silicone resin and silicone oil, with dimethylpolysiloxane being particularly suitable. The oil compound type is a silicone oil blended with silica powder, and the emulsion type is an oil compound made into an O / W emulsion.

[0030] As the silicone-based antifoaming agent, commercially available products may be used, such as silicone antifoaming agents manufactured by Shin-Etsu Chemical Co., Ltd. (KM-72, KM-72F, KM-72S, KM-72FS) and silicone antifoaming agents manufactured by Dow-Toray Industries, Inc. (Silicon SAG-471, DK-Q1-049, ANTIFOAM A COMPOUND FOOD GRADE, SH 5500 COMPOUND, ANTIFOAM C EMULSION FOOD GRADE, SM5571 EMULSION). The silicone antifoaming agent is preferably used in an amount of 0.01 to 1% by mass relative to the total mass of all components of the one-component waterproofing agent of the present invention.

[0031] <Urethane-based waterproofing agent> The urethane prepolymer of the present invention has a low viscosity comparable to that of conventional MDI-based urethane prepolymers and forms a hardened product in a short time in the presence of water, making it particularly suitable for use as a water-stopping agent that is injected into areas where water springs from the ground or leaks in underground structures such as tunnels to stop water leakage.

[0032] <Diluent> The urethane waterproofing agent of the present invention can be blended with a diluent as needed to suppress thickening during and after the prepolymerization reaction. The diluent is preferably one that has a high boiling point, little odor, a high flash point, and no active hydrogen, and specific examples include propylene carbonate, gamma-butyrolactone, vegetable oil-based fatty acid ester, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, 2-oxo-4-methyl-1,3-dioxolane, methyl acetylricinoleate, butyl acetylricinoleate, dimethyl glutarate, dimethyl succinate, dimethyl adipate, and mixtures thereof. When a diluent is used, it is preferably used in an amount of 20 to 60% by mass based on the total mass of all the components of the urethane waterproofing agent of the present invention.

[0033] Furthermore, in order to lower the viscosity and increase the strength of the urethane prepolymer, a non-MDI isocyanate can be further blended into the urethane waterproofing agent of the present invention, if necessary. Non-MDI isocyanates that can be added include m-xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and dicyclohexylmethane 4,4'-diisocyanate, but m-xylylene diisocyanate is preferred from the standpoint of legal regulations and safety. Furthermore, the urethane waterproofing agent of the present invention can be blended with a monoisocyanate to improve storage stability. Examples of monoisocyanates include octadecyl isocyanate, 3-isocyanatepropyltriethoxysilane, 3-isocyanatepropyltrimethoxysilane, and p-toluenesulfonyl isocyanate (PTSI). Among these, p-toluenesulfonyl isocyanate is preferred.

[0034] If necessary, additives such as foam stabilizers, antifoaming agents, crosslinking agents, colorants, resin modifiers, flame retardants, ultraviolet absorbers, and durability improvers may be added within a range that does not impair the object of the present invention.

[0035] In the urethane-based waterproofing agent of the present invention, the urethane prepolymer reacts with water in the presence of water to form a cured product, and a tertiary amine such as triethylamine, dimethyltodecylamine, dimethyllaurylamine, or dimethylmyristylamine can be added as an additive to accelerate the curing reaction.

[0036] Furthermore, depending on the application conditions, epoxy resins, acrylic resins (methyl methacrylate, etc.), styrene resins, etc. may be used in combination with the urethane waterproofing agent of the present invention. When these resins are used in combination, they can be blended in an amount of 1 to 50% by mass relative to the mass of the urethane prepolymer used in the waterproofing agent of the present invention. [Example]

[0037] The present invention will be described below with reference to examples. However, the present invention is not limited in any way by these examples and comparative examples. In this example, the number average molecular weight was measured using GPC. <Measurement conditions of GPC> Apparatus: HLC-8120GPC manufactured by Tosoh Corporation Solvent: Tetrahydrofuran Flow rate: 0.6 ml / min Temperature: 40 °C Sample concentration: 0.1% Sample injection volume: 20 μl Detector: RI

[0038] Example 1 12.0 g of a propylene oxide adduct of bisphenol A (number average molecular weight 600), 6.0 g of an ethylene oxide propylene oxide adduct of diethylene glycol, and 82.8 g of dipropylene glycol as a low molecular polyol were added to a 1 L synthesis apparatus equipped with a stirrer, a thermometer, and a temperature controller. Next, 350 g of polymeric MDI (trade name "Lupranate M11S" manufactured by BASF INOAC Polyurethane Co., Ltd.) as an isocyanate component and 243 g of propylene carbonate as a diluent were added to the same apparatus, and the temperature was raised to 100 °C and reacted for 3 hours to obtain a urethane prepolymer having an NCO content of 12.0%. Finally, 139 g of castor oil fatty acid ester (trade name "Ricksaizer C-101" manufactured by Ito Seiyu Co., Ltd.) as a diluent, 139 g of xylylene diisocyanate (trade name "Takenate 500" manufactured by Mitsui Chemicals, Inc.), 0.2 g of a silicone foam stabilizer (trade name "Vorasurf L-5340" manufactured by Dow Corning Toray Co., Ltd.), and 0.1 g of a silicone defoamer (SAG-471; manufactured by Dow Corning Toray Co., Ltd.) were added to obtain a sample solution of the urethane-based waterstop agent 1 of the present invention.

[0039] Examples 2 to 16, Comparative Examples 1 to 7 A urethane-based waterstop agent sample solution was obtained in the same manner as in Example 1, except that the types and blending amounts of polyether polyol A, polyether polyol B, low molecular weight polyol, isocyanate, and diluent were changed as described in Tables 3 and 4. The abbreviations of each raw material in Tables 3 and 4 are as follows.

[0040]

Table 1

[0041]

Table 2

[0042] <Low molecular weight polyol> ·DPG: Dipropylene glycol ·EG: Ethylene glycol ·PG: Propylene glycol ·1,4’-BG: 1,4’-Butanediol <MDI-based isocyanate> ·M11S: Polymeric MDI: Polymethylene polyphenylene polyisocyanate (trade name "Lupranate M11S" manufactured by BASF INOAC Polyurethane Co., Ltd.) ·M5S: Polymeric MDI (same "Lupranate M5S") ·MR-200: Polymeric MDI (trade name "Millionate MR-200" manufactured by Tosoh Corporation) ·NM: Mixed MDI: Mixture of 4,4’-MDI and 2,4’-MDI (2,4’-Diphenylmethane diisocyanate) (trade name "Millionate NM" manufactured by Tosoh Corporation) ·MT: 4,4’-MDI (trade name "Millionate MT" manufactured by Tosoh Corporation) <Diluent> ·GBL: Gamma-butyrolactone ·PC: Propylene carbonate ·C-401: Castor oil fatty acid ester (trade name "Riciser C-401" manufactured by Ito Seiyu Co., Ltd.) <Non-MDI-based isocyanate> XDI: Xylylene diisocyanate (manufactured by Mitsui Chemicals, Inc., product name "Takenate 500") <Silicone foam stabilizer> L-5340: Silicone foam stabilizer (manufactured by Dow Toray Industries, Inc., product name "VORASURF L-5340") <Silicone-based antifoaming agent> SAG-471: Oil compound type silicone defoamer (manufactured by Dow Toray Industries, Inc.) DK-Q1-049: Oil compound type silicone defoamer (manufactured by Dow Toray Industries, Inc.)

[0043] [Performance evaluation] The sample solutions of the urethane waterproofing agents obtained in Examples 1 to 16 and Comparative Examples 1 to 7 were subjected to the following performance evaluation tests (1) to (11). The results are shown in Tables 3 and 4.

[0044] (1) Viscosity measurement Based on JIS K1557-5:2007 Plastics - Polyurethane Raw Material Polyol Test Method, the viscosity of each sample liquid at 20°C was measured using a B-type viscometer (manufactured by Brookfield) with rotors No. 2, No. 3, and No. 4 rotated at 30 to 60 rpm. (2)NCO content Measurement was based on JIS K1603-1:2007 Plastics - Polyurethane raw material aromatic isocyanate test. (3) Residual amount of 4,4'-MDI monomer Using a liquid chromatograph HPLC-prominence (Shimadzu Corporation) and a column Develosil C30-UG 5 μm (Nomura Chemical Co., Ltd.), a calibration curve was prepared using THF:water=4:6, and the amount of 4,4'-MDI monomer remaining in each sample was measured. (4) Sample appearance The sample liquid was visually checked to see if it was clear and free of turbidity or impurities, and if it was clear, the appearance was judged to be good. (5)Curing time 40g of sample liquid and 0.3g of dimethylmyristylamine were added to a 100mL plastic cup, and 2.0g of tap water adjusted to 20℃ was added and stirred with a spatula for 10 seconds. The time from the addition of water until the mixed liquid hardened and began to form strings was measured and used as the "hardening time." If the resin overflowed from the plastic cup, a 500mL plastic cup was used and the same test was repeated. (6) Appearance of cured resin The appearance of the cured resin obtained in the test (5) above was observed 30 minutes after curing. If there were no large bubbles or voids and the cured resin had low foaming, it was rated as good. (7) Hardness of cured resin The hardness of the cured resin obtained in the test (5) above was measured 30 minutes after curing using a SHORE D (manufactured by Ueshima Seisakusho Co., Ltd.). (8) Expansion Ratio The expansion ratio of the cured resin obtained in the test (5) above was measured 30 minutes after curing. The expansion ratio was determined by comparing it with the volume of the sample liquid. (9) Compressive strength Cylindrical test pieces (40 mmφ×20 mmH) were cut out from the cured resin obtained in the test (5) above, and the compressive strength after 24 hours of curing was measured using a Tensilon universal testing machine (UCT-2.5T, manufactured by Orientec Co., Ltd.) in accordance with JIS K7220-2006 "Rigid foam plastics - Determination of compression properties." (10) Shrinkage rate The shrinkage of the cured resin obtained in the test (5) above after 24 hours of curing was measured by comparing it with the volume after 30 minutes of curing. (11) Permeability coefficient The coefficient of permeability of the hardened resin obtained in the test (5) above was measured in accordance with JIS A-1218 "Testing method for soil permeability."

[0045] [Table 3]

[0046] [Table 4]

[0047] As shown in Tables 3 and 4, the urethane waterproofing agent of the present invention reduces residual MDI monomer and forms a cured resin that has a low viscosity comparable to that of conventional MDI-based urethane prepolymers, high strength in the presence of water, and a sufficiently low hydraulic conductivity. Furthermore, if the cured resin has high compressive strength and a low hydraulic conductivity, it can be expected to maintain its waterproofing effect for a long period of time. In contrast, in Comparative Example 1, the resin had weak lipophilicity and poor defoaming properties, so the expansion ratio did not decrease and the strength of the cured resin was low. In Comparative Example 2, the isocyanate raw material was used in large excess, so a large amount of MDI monomer remained. In Comparative Example 3, the resin was made of a low-molecular-weight polyol, so a homogeneous cured resin could not be obtained and the water permeability coefficient was high. In Comparative Example 4, the prepolymer was made only of a lipophilic polyol, so the viscosity was high and the defoaming properties and compatibility with water were poor, resulting in a high water permeability coefficient. In Comparative Example 5, the ratio of isocyanate groups to OH groups was low, so the entire resin gelled during the reaction. In Comparative Example 6, the content of polymeric MDI was low and the strength of the cured resin was low. In Comparative Example 7, the lack of an antifoaming agent prevented the expansion ratio from decreasing and the strength of the cured resin was low.

Claims

1. A polyol and an organic polyisocyanate containing at least one MDI-based isocyanate selected from the group consisting of diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, and modified products thereof, a urethane prepolymer having a terminal isocyanate group obtained by reacting the isocyanate group derived from the MDI-based isocyanate with a hydroxy group in an equivalent ratio (NCO / OH) of 1.5 or more and 2.0 or less; A urethane-based waterproofing agent containing a silicone-based antifoaming agent, The polyol is a polyether polyol A having a number average molecular weight of 300 or more and 7,000 or less, obtained by addition polymerization of propylene oxide alone or ethylene oxide and propylene oxide to a polyhydric alcohol or a polyhydric phenol in such a ratio that propylene oxide accounts for 80 mass% or more; and a bifunctional low-molecular-weight polyol having a number average molecular weight of less than 300, The organic polyisocyanate contains polymethylene polyphenyl polyisocyanate. Urethane-based waterproofing agent.

2. 2. The urethane-based waterproofing agent according to claim 1, wherein the organic polyisocyanate contains polymethylene polyphenyl polyisocyanate in a proportion of 20% by mass or more and 70% by mass or less.

3. 3. The urethane-based waterproofing agent according to claim 1, wherein the amount of remaining unreacted 4,4'-diphenylmethane diisocyanate is 5% by mass or less.

4. The urethane-based waterproofing agent according to any one of claims 1 to 3, wherein the polyol further contains a polyether polyol B having a number average molecular weight of 800 or more and 5,000 or less, which is obtained by addition polymerization of ethylene oxide alone or ethylene oxide and an alkylene oxide having 3 or 4 carbon atoms to a polyhydric alcohol in such a proportion that ethylene oxide accounts for 20 mass% or more.

5. The urethane-based waterproofing agent according to any one of claims 1 to 4, wherein the polyether polyol A is obtained by addition polymerization of propylene oxide alone or ethylene oxide and propylene oxide to at least one polyhydric alcohol or polyhydric phenol selected from the group consisting of glycerin, diglycerin, pentaerythritol, trimethylolpropane, sorbitol, and bisphenol A, in a proportion of propylene oxide of 80 mass% or more.

6. The urethane-based waterproofing agent according to any one of claims 1 to 5, characterized in that the low-molecular-weight polyol is at least one selected from the group consisting of ethylene glycol, propylene glycol, diethylene glycol, 1,3-propanediol, and 1,4-butanediol.

7. The urethane-based waterproofing agent according to any one of claims 1 to 6, further comprising a diluent.

8. The urethane-based waterproofing agent according to claim 7, characterized in that the diluent is at least one selected from the group consisting of propylene carbonate, gamma-butyl lactone, vegetable oil-based fatty acid ester, 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 dimethyl adipate.

9. The urethane-based waterproofing agent according to any one of claims 1 to 8, further comprising xylylene diisocyanate.

10. The urethane-based waterproofing agent according to any one of claims 1 to 9, further comprising a curing accelerator.

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