Hardener composition for waterproof top coat and coating composition for waterproof top coat

Abstract

To provide a curing agent composition for waterproof topcoat which is excellent in initial reactivity when used for a waterproof topcoat layer and can impart good water resistance, low temperature elongation and low temperature stress to the waterproof topcoat layer.SOLUTION: There is provided a curing agent composition for waterproof topcoat which comprises a polyisocyanate derived from at least one diisocyanate selected from the group consisting of an aliphatic diisocyanate and an alicyclic diisocyanate and at least one polyol selected from the group consisting of a polyether-based polyol having a number average molecular weight of 400 or more and 10000 or less and an oxypropylene group and a polyester-based polyol which is derived from a divalent or trivalent alcohol and ε-caprolactone and has a number average molecular weight of 250 or more and 4000 or less and contains an allophanate group, an isocyanurate group and an urethane group, wherein the molar ratio of the allophanate group to the isocyanurate group is 0 / 100 to 25 / 75.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a curing agent composition for a waterproof top coat and a coating composition for a waterproof top coat. [Background technology]

[0002] Polyisocyanate compositions are widely used as coating materials for construction, automobiles, plastics, information appliances, etc., because they can impart various functions to coating films, such as high appearance, high weather resistance, and high durability. In recent years, urethane-based waterproofing layers have been used to waterproof balconies and other structures in order to accommodate complex shapes. This method involves forming a coating on the surface of a substrate such as concrete in the following order: a primer layer, a urethane-based waterproofing layer, and a waterproof top coat layer. The waterproof top coat layer must be water-resistant and able to adapt to temperature changes, particularly low temperatures, to protect the urethane-based waterproofing layer and improve its appearance. Furthermore, the waterproof top coat layer must be easy to work with, as it is applied on-site, and must have high reactivity in the reaction between the base agent and curing agent.

[0003] Patent Document 1 discloses a top coat composition for waterproofing urethane coating films, which contains a polyisocyanate resin (A) obtained by reacting a polyisocyanate (A1) containing 30 mass% or more of a polyisocyanate (A1-a) containing one or more allophanate bonds and two or more isocyanate groups per molecule with a polyol (A2), wherein the polyisocyanate (A1-a) is at least one allophanate-modified product selected from aliphatic polyisocyanates and alicyclic polyisocyanates. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4919078 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the top coat composition for waterproofing urethane coating films described in Patent Document 1 has a high allophanate ratio and is poor in initial reactivity.

[0006] The present invention has been made in view of the above circumstances, and provides a curing agent composition for a waterproof top coat, which, when used in a waterproof top coat layer, has excellent initial reactivity and can impart good water resistance, low-temperature elongation, and low-temperature stress to the waterproof top coat layer. [Means for solving the problem]

[0007] That is, the present invention includes the following aspects. (1) at least one diisocyanate (A) selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates; at least one polyol (B) selected from the group consisting of polyether polyols having a number average molecular weight of 400 or more and 10,000 or less and having an oxypropylene group, and polyester polyols derived from a dihydric or more and trihydric or less alcohol and ε-caprolactone and having a number average molecular weight of 250 or more and 4,000 or less; and a polyisocyanate derived from Contains allophanate groups, isocyanurate groups, and urethane groups, A curing agent composition for waterproof top coats, having an allophanate group / isocyanurate group molar ratio of 0 / 100 or more and 25 / 75 or less. (2) The curing agent composition for waterproof top coats according to (1), wherein the polyol (B) is a polyether-based polyol having a number average molecular weight of 400 or more and 10,000 or less and having an oxypropylene group. (3) The curing agent composition for a waterproof top coat according to (1) or (2), wherein the polyisocyanate has an average number of isocyanate groups of 3.0 or more. (4) A coating composition for a waterproof top coat, comprising the curing agent composition for a waterproof top coat according to any one of (1) to (3) and a polyol. [Effects of the Invention]

[0008] According to the above-described embodiment of the curing agent composition for a waterproof top coat, it is possible to provide a curing agent composition for a waterproof top coat that, when used in a waterproof top coat layer, has excellent initial reactivity and can impart good water resistance, low-temperature elongation, and low-temperature stress to the waterproof top coat layer. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, a mode for carrying out the present invention (hereinafter referred to as "the present embodiment") will be described in detail. The following present embodiment is an example for explaining the present invention, and is not intended to limit the present invention to the following content. The present invention can be modified in various ways without departing from the gist of the present invention.

[0010] In this specification, the term "polyol" refers to a compound having two or more hydroxy groups (-OH) in one molecule. In addition, in this specification, the term "polyisocyanate" refers to a reaction product in which a plurality of monomer compounds having two or more isocyanate groups (-NCO) are bonded together. In addition, in this specification, unless otherwise specified, "(meth)acrylic" includes methacrylic and acrylic, and "(meth)acrylate" includes methacrylate and acrylate.

[0011] <Curing agent composition for waterproof top coat> The curing agent composition for a waterproof top coat of this embodiment contains a polyisocyanate derived from a diisocyanate (A) and a polyol (B). That is, the polyisocyanate is a reaction product of the diisocyanate (A) and the polyol (B).

[0012] The diisocyanate (A) is at least one diisocyanate selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates.

[0013] The polyol (B) is at least one polyol selected from the group consisting of polyether polyols (B1) and polyester polyols (B2). The polyether polyol (B1) is a polyether polyol having an oxypropylene group, and has a number average molecular weight of 400 or more and 10,000 or less. The polyester polyol (B2) is a polyol derived from a dihydric to trihydric alcohol and ε-caprolactone, i.e., a reaction product of a dihydric to trihydric alcohol and ε-caprolactone, and has a number average molecular weight of 250 or more and 4,000 or less. Among these, the polyol (B) is preferably a polyether-based polyol (B1) having a number average molecular weight of 400 or more and 10,000 or less and having an oxypropylene group. When the polyol (B) is the polyether-based polyol (B1), the curing agent composition for a waterproof top coat of this embodiment can impart better low-temperature elongation and low-temperature stress to the waterproof top coat layer.

[0014] The curing agent composition for a waterproof top coat of this embodiment contains an allophanate group, an isocyanurate group, and a urethane group. In the curing agent composition for a waterproof top coat of this embodiment, all of these functional groups may be contained in a single polyisocyanate, or the curing agent composition for a waterproof top coat of this embodiment may be a mixture of polyisocyanates containing at least one of these functional groups.

[0015] In the curing agent composition for a waterproof top coat of this embodiment, the ratio of the number of moles of allophanate groups to the number of moles of isocyanurate groups, i.e., the molar ratio of allophanate groups / isocyanurate groups, is from 0 / 100 to 25 / 75, preferably from 1 / 99 to 24 / 76, and more preferably from 3 / 97 to 23 / 77. When the molar ratio of allophanate groups / isocyanurate groups is within the above range, the maximum stress at low temperatures increases.

[0016] Furthermore, in the curing agent composition for a waterproof top coat of this embodiment, the ratio of the number of moles of urethane groups to the number of moles of isocyanurate groups, i.e., the molar ratio of urethane groups / isocyanurate groups, is preferably 0.06 to 5.50, more preferably 0.08 to 4.50, even more preferably 0.09 to 2.00, and particularly preferably 0.10 to 1.50. When the molar ratio of urethane groups / isocyanurate groups is equal to or greater than the above lower limit, the low-temperature elongation of the resulting coating film can be further improved.

[0017] The molar ratios of allophanate groups, isocyanurate groups, and urethane groups are as follows, as described in the Examples below: 13 It can be determined by C-NMR measurement.

[0018] Next, each of the components of the curing agent composition for a waterproof top coat of this embodiment will be described in detail below.

[0019] <Diisocyanate (A)> The diisocyanate (A) is at least one diisocyanate selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates. Aliphatic diisocyanates are compounds having saturated aliphatic groups in their molecules. On the other hand, alicyclic diisocyanates are compounds having cyclic aliphatic groups in their molecules. Among them, aliphatic diisocyanates are preferably used. By using aliphatic diisocyanates, the resulting curing agent composition for waterproof top coats has a low viscosity.

[0020] Examples of aliphatic diisocyanates include 1,4-diisocyanatobutane, 1,5-diisocyanatopentane, 1,6-diisocyanatohexane (HDI), 1,6-diisocyanato-2,2,4-trimethylhexane, and methyl 2,6-diisocyanatohexanoate (lysine diisocyanate).

[0021] Examples of alicyclic diisocyanates include 5-isocyanato-1-isocyanatomethyl-1,3,3-trimethylcyclohexane (isophorone diisocyanate; hereinafter, sometimes abbreviated as "IPDI"), 1,3-bis(isocyanatomethyl)cyclohexane (hydrogenated xylylene diisocyanate), bis(4-isocyanatocyclohexyl)methane (hydrogenated diphenylmethane diisocyanate), and 1,4-diisocyanatocyclohexane.

[0022] These diisocyanates may be used alone or in combination of two or more.

[0023] Among these, HDI, IPDI, hydrogenated xylylene diisocyanate, or hydrogenated diphenylmethane diisocyanate is preferred as the diisocyanate (A) because it is easily available industrially. HDI is particularly preferred because it provides excellent weather resistance and coating film flexibility.

[0024] Hereinafter, aliphatic diisocyanates and alicyclic diisocyanates may be collectively referred to as diisocyanate monomers.

[0025] <Polyol (B)> The polyol (B) is at least one polyol selected from the group consisting of polyether polyols (B1) and polyester polyols (B2).

[0026] [Polyether polyol (B1)] The polyether polyol (B1) is a polyether polyol having a number average molecular weight of 400 to 10,000 and containing an oxypropylene group. The polyether polyol containing an oxypropylene group herein refers to a polyether polyol having an oxypropylene group in the molecular chain. In this case, the oxyalkylene repeating unit may contain other oxyalkylene groups, specifically, oxyethylene groups, oxytetramethylene groups, oxycyclohexyl groups, oxystyrene groups, etc. The content of oxypropylene groups having side chains relative to the total molar amount of oxyalkylene repeating units is preferably 60 mol % or more, more preferably 70 mol % or more, and even more preferably 80 mol % or more.

[0027] The upper limit of the number average molecular weight of the polyether polyol (B1) is 10,000, preferably 7,000, more preferably 5,000, and even more preferably 3,500. On the other hand, the lower limit of the number average molecular weight is 400, preferably 450, and more preferably 500. That is, the number average molecular weight of the polyether polyol (B1) is 400 or more and 10,000 or less, preferably 450 or more and 7,000 or less, more preferably 500 or more and 5,000 or less, and even more preferably 500 or more and 3,500 or less. When the number average molecular weight of the polyether polyol (B1) is within the above range, the flexibility of the coating film formed therefrom is more sufficient, and the curability of the coating film is also more sufficient. The number average molecular weight of the polyether polyol (B1) can be obtained by gel permeation chromatography (hereinafter sometimes abbreviated as "GPC") measurement.

[0028] Specific examples of polyether polyols include polypropylene glycol or triol, so-called Pluronic (registered trademark, hereinafter omitted) type polypropylene glycol or triol obtained by addition polymerization of ethylene oxide to the terminal of polypropylene glycol, polyoxypropylene polyoxyethylene copolymer diol or triol, polyoxypropylene polyoxyethylene block polymer diol or triol, polytetramethylene glycol or triol, polyoxydimethylpropylene polyoxybutylene copolymer diol or triol, polyoxydimethylpropylene polyoxybutylene block polymer diol or triol, and polyoxycyclohexane diol. Among these, polyether polyol (B1) is preferably polypropylene glycol or triol, or so-called Pluronic type polypropylene glycol or triol obtained by addition polymerization of ethylene oxide to the terminal of polypropylene glycol, due to its excellent solubility in low-polarity organic solvents. Furthermore, so-called Pluronic type polypropylene glycol or triol obtained by addition polymerization of ethylene oxide to the terminal of polypropylene glycol is more preferred as polyether polyol (B1) due to its excellent reactivity. These polyether polyols (B1) may be used alone or in combination of two or more.

[0029] Commercially available polyether polyols (B1) include, for example, Exenol 840 (trade name, manufactured by AGC Corporation, polypropylene triol, number average molecular weight 6500), Exenol 510 (trade name, manufactured by AGC Corporation, polypropylene glycol, number average molecular weight 4000), Exenol 230 (trade name, manufactured by AGC Corporation, polypropylene triol, number average molecular weight 3000), Exenol 2020 (trade name, manufactured by AGC Corporation, polypropylene glycol, number average molecular weight 2000), Exenol 1030 (trade name, manufactured by AGC Corporation, polypropylene triol, number average molecular weight 1000), Exenol 1020 (trade name, manufactured by AGC Corporation, polypropylene glycol, number average molecular weight 1000), Preminol 7012 (trade name, manufactured by AGC Corporation, polypropylene triol, number average molecular weight 10000), and PTG1000SN (trade name, manufactured by Hodogaya Chemical Co., Ltd., polytetramethylene glycol, number average molecular weight 1000).

[0030] Examples of methods for producing the polyether polyol (B1) include a method of adding propylene oxide (and, if necessary, other alkylene oxides, either alone or in mixture) to a polyhydric alcohol, a polyhydric phenol, a polyamine, an alkanolamine, or the like, alone or in mixture, using a catalyst, and a method of dehydrating and condensing a polyhydric alcohol. The polyhydric alcohol may be a dihydric alcohol or a trihydric alcohol. Examples of dihydric alcohols include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, neopentyl glycol, 1,4-butanediol, 1,6-hexanediol, and bisphenol A. Examples of trihydric alcohols include glycerin and trimethylolpropane. Examples of polyamines include diamines such as ethylenediamine. Examples of catalysts include hydroxides of lithium, sodium, potassium, etc.; strongly basic catalysts such as alcoholates and alkylamines; metal porphyrins; composite metal cyanide complexes; complexes of metals and chelating agents with tridentate or higher coordination; and composite metal complexes such as zinc hexacyanocobaltate complexes. Other examples of alkylene oxides include ethylene oxide, butylene oxide, cyclohexene oxide, and styrene oxide.

[0031] [Polyester polyol (B2)] The polyester polyol (B2) is derived from a dihydric to trihydric alcohol and ε-caprolactone, i.e., a reaction product of a dihydric to trihydric alcohol and ε-caprolactone. ε-Caprolactone is a type of cyclic ester and lactone, and is a seven-membered ring compound represented by the chemical formula (CH2)5CO2. Polycaprolactone, a polyester polymer, can be obtained by ring-opening polymerization of ε-caprolactone.

[0032] Examples of dihydric to trihydric alcohols include 1,2-propylene glycol, 1,3-butylene glycol, neopentyl glycol, neopentyl glycol hydroxypivalic acid ester, 2-methyl-1,3 propanediol, 2,3,5-trimethylpentanediol, ethylene glycol, diethylene glycol, 1,3-propanediol, 1,4-butylenediol, 1,5-pentanediol, 1,6-hexanediol, trimethylolpropane, glycerin, 1,1,7-trimethylolheptane, 1,2,7-trimethylolheptane, etc. These dihydric to trihydric alcohols may be used alone or in combination of two or more.

[0033] The upper limit of the number average molecular weight of the polyester polyol (B2) is 4000, preferably 3000, and more preferably 2500. On the other hand, the lower limit of the number average molecular weight of the polyester polyol (B2) is 250. That is, the number average molecular weight (B2) of the polyester polyol is 250 or more and 4,000 or less, preferably 250 or more and 3,000 or less, and more preferably 250 or more and 2,500 or less. When the number average molecular weight of the polyester polyol (B2) is within the above range, the extensibility of the coating film formed therefrom becomes more sufficient, and an excessive increase in the viscosity of the resulting coating liquid can be more effectively suppressed. The number average molecular weight of the polyester polyol (B2) can be obtained by GPC measurement.

[0034] The polyester polyol (B2) may be used alone or in combination of two or more kinds.

[0035] Commercially available polyester polyols (B2) include, for example, Polylite OD-X-2722 (trade name, manufactured by DIC Corporation, number average molecular weight 2000) and Polylite OD-X-2542C (trade name, manufactured by DIC Corporation, number average molecular weight 850).

[0036] Examples of a method for producing the polyester polyol (B2) include a method of ring-opening polymerization of ε-caprolactone using a dihydric or greater and trihydric or less alcohol.

[0037] <Method of manufacturing a curing agent composition for a waterproof top coat> In the production of the curing agent composition for a waterproof top coat of this embodiment, it is preferable to use at least HDI as a raw material. In the method for producing a curing agent composition for a waterproof top coat of this embodiment, for example, the isocyanuration reaction, allophanation reaction, and urethanization reaction can be carried out sequentially or some of them can be carried out in parallel, and these reactions can be carried out in the presence of an excess of diisocyanate monomer and polyol (B) (polyether polyol (B1) and / or polyester polyol (B2)), and after completion of the reaction, the unreacted diisocyanate monomer can be removed to obtain the curing agent composition for a waterproof top coat. Alternatively, the above three reactions can be carried out separately and then mixed together to obtain the curing agent composition for a waterproof top coat.

[0038] Furthermore, in the method for producing a curing agent composition for a waterproof top coat of this embodiment, alcohols such as alkyl monoalcohols and alkyl diols can also be used in combination as auxiliary materials. When using alcohols, as described above, it is preferable to use them so that the molar ratios of allophanate groups / isocyanurate groups and urethane groups / isocyanurate groups in the curing agent composition for a waterproof top coat of this embodiment are within the above-mentioned ranges.

[0039] Alternatively, the curing agent composition for waterproof top coats of this embodiment can be obtained, for example, by subjecting a diisocyanate to an isocyanurate reaction and an allophanate reaction, followed by a urethanization reaction of the resulting reaction product with a polyol (B) (a polyether polyol (B1) and / or a polyester polyol (B2)). In this case, the molar ratio of isocyanate groups in the reaction product to hydroxyl groups in the polyester polyol is preferably 2 / 1 or more and 40 / 1 or less, more preferably 3 / 1 or more and 30 / 1 or less, and even more preferably 4 / 1 or more and 20 / 1 or less. Next, each of the isocyanuration reaction, allophanation reaction, and urethanation reaction will be described in detail below.

[0040] [Isocyanurate reaction] When an isocyanurate group-containing polyisocyanate is derived from a diisocyanate monomer, an isocyanuration reaction catalyst is usually used. The isocyanuration reaction catalyst is preferably one having basicity. Examples of such isocyanuration reaction catalysts include the following 1) to 7): 1) hydroxides or weak organic acid salts of tetraalkylammonium; 2) hydroxides or weak organic acid salts of hydroxyalkylammonium; 3) metal salts of alkylcarboxylic acids; 4) metal alcoholates such as sodium and potassium; 5) aminosilyl group-containing compounds such as hexamethyldisilazane; 6) Mannich bases; and 7) combinations of tertiary amines with epoxy compounds. Examples of tetraalkylammonium include tetramethylammonium and tetraethylammonium. Examples of organic weak acids include acetic acid and capric acid. Examples of hydroxyalkylammonium include trimethylhydroxypropylammonium, trimethylhydroxyethylammonium, triethylhydroxypropylammonium, and triethylhydroxyethylammonium. Examples of alkylcarboxylic acids include acetic acid, caproic acid, octylic acid, and myristic acid. Examples of metals constituting the metal salt include tin, zinc, lead, sodium, and potassium. Among these, from the viewpoint of catalytic efficiency, the isocyanuration reaction catalyst is preferably the above 1), 2), 3), 4) or 5), with the organic weak acid salt of 1) being more preferred.

[0041] The amount of the isocyanurate reaction catalyst added is preferably 10 ppm or more and 1000 ppm or less, more preferably 10 ppm or more and 500 ppm or less, and even more preferably 10 ppm or more and 100 ppm or less, based on the mass of the charged diisocyanate.

[0042] The lower limit of the isocyanurate reaction temperature is preferably 50° C., more preferably 54° C., even more preferably 57° C., and particularly preferably 60° C. On the other hand, the upper limit of the isocyanurate reaction temperature is preferably 120° C., more preferably 100° C., even more preferably 90° C., and particularly preferably 80° C. That is, the isocyanurate reaction temperature is preferably 50°C or higher and 120°C or lower, more preferably 54°C or higher and 100°C or lower, even more preferably 57°C or higher and 90°C or lower, and particularly preferably 60°C or higher and 80°C or lower. When the isocyanurate-forming reaction temperature is equal to or lower than the upper limit, changes in properties such as coloration can be more effectively prevented.

[0043] [Allophanation reaction] Allophanate group-containing polyisocyanates can be obtained by adding an alcohol to a diisocyanate and using an allophanate reaction catalyst. The alcohol used may contain an ether group, an ester group, or a carbonyl group in the molecule, but a monoalcohol consisting of a saturated hydrocarbon group and a hydroxyl group is preferred, and a branched monoalcohol is more preferred. Examples of such monoalcohols include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutanol, 1-pentanol, 2-pentanol, isoamyl alcohol, 1-hexanol, 2-hexanol, 1-heptanol, 1-octanol, 2-ethyl-1-hexanol, 3,3,5-trimethyl-1-hexanol, tridecanol, pentadecanol, palmityl alcohol, stearyl alcohol, cyclopentanol, cyclohexanol, methylcyclohexanol, and trimethylcyclohexanol. Among these, isobutanol, 1-butanol, isoamyl alcohol, 1-hexanol, 1-heptanol, 1-octanol, 2-ethyl-1-hexanol, tridecanol, pentadecanol, palmityl alcohol, stearyl alcohol, and 1,3,5-trimethylcyclohexanol are preferred as monoalcohols because they have particularly excellent solubility in low-polarity organic solvents.Furthermore, 1-propanol, isobutanol, 1-butanol, isoamyl alcohol, 1-pentanol, 2-pentanol, 1-hexanol, 2-hexanol, 1-heptanol, 1-octanol, 2-octanol, 2-ethyl-hexyl alcohol, and 3,3,5-trimethyl-1-hexanol are preferred because they have lower viscosity. Furthermore, since the solubility in low-polarity organic solvents is very good, isobutanol, 2-hexanol, 2-octanol, 2-ethyl-1-hexanol, or 3,3,5-trimethyl-1-hexanol is more preferred.

[0044] The amount of alcohol added is not limited to the following, but is preferably such that the molar ratio of isocyanate groups in the diisocyanate to hydroxyl groups in the alcohol is from 10 / 1 to 1000 / 1, and more preferably from 100 / 1 to 1000 / 1. When the molar ratio of isocyanate groups in the diisocyanate to hydroxyl groups in the alcohol is equal to or greater than the above lower limit, a more appropriate average number of isocyanate groups can be ensured in the resulting polyisocyanate.

[0045] The allophanatization reaction catalyst includes, but is not limited to, alkyl carboxylates of tin, lead, zinc, bismuth, zirconium, zirconyl, and the like. Examples of tin alkylcarboxylates (organotin compounds) include tin 2-ethylhexanoate and dibutyltin dilaurate. Examples of lead alkylcarboxylates (organic lead compounds) include lead 2-ethylhexanoate. Examples of zinc alkylcarboxylates (organic zinc compounds) include zinc 2-ethylhexanoate. Examples of bismuth alkylcarboxylates include bismuth 2-ethylhexanoate. Examples of zirconium alkylcarboxylates include zirconium 2-ethylhexanoate. Examples of zirconyl alkylcarboxylates include zirconyl 2-ethylhexanoate.

[0046] When the desired yield is achieved, the allophanation reaction can be stopped by adding a deactivator for the allophanation reaction catalyst, such as phosphoric acid or methyl paratoluenesulfonate.

[0047] The amount of the allophanate reaction catalyst used is preferably 10 ppm or more and 10,000 ppm or less, more preferably 10 ppm or more and 1,000 ppm or less, and even more preferably 10 ppm or more and 500 ppm or less, by mass ratio relative to the diisocyanate raw material.

[0048] The reaction temperature for allophanatization is preferably 60°C or higher and 160°C or lower, more preferably 70°C or higher and 155°C or lower, even more preferably 80°C or higher and 150°C or lower, and particularly preferably 90°C or higher and 145°C or lower.

[0049] By keeping the allophanate formation reaction temperature at or below the above upper limit, changes in properties such as coloration of the resulting polyisocyanate can be more effectively prevented. The reaction time for allophanatization is preferably from 0.2 to 8 hours, more preferably from 0.4 to 6 hours, even more preferably from 0.6 to 4 hours, particularly preferably from 0.8 to 3 hours, and most preferably from 1.0 to 2 hours. By setting the reaction time for allophanation to not less than the above lower limit, it is possible to achieve a lower viscosity, and by setting it to not more than the above upper limit, it is possible to further suppress coloration of the polyisocyanate itself.

[0050] The isocyanurate formation catalyst can also be used as an allophanate formation catalyst. When the allophanate formation reaction is carried out using the isocyanurate formation catalyst, an isocyanurate group-containing polyisocyanate is also produced at the same time. In particular, from the viewpoint of improving productivity from an economical standpoint, it is preferable to use the isocyanurate formation catalyst as the allophanate formation catalyst to carry out the allophanate formation reaction and the isocyanurate formation reaction.

[0051] [Urethanization reaction] In the method for producing a curing agent composition for a waterproof top coat according to the present embodiment, the urethanization reaction is preferably carried out after the isocyanuration reaction and the allophanation reaction. Specifically, it is preferable to carry out the isocyanuration reaction and the allophanation reaction sequentially or in parallel to obtain a polyisocyanate containing an isocyanurate group and an allophanate group, and then to carry out a urethanization reaction between the obtained polyisocyanate and the polyol (B) (a polyether-based polyol (B1) and / or a polyester-based polyol (B2)).

[0052] The lower limit of the urethanization reaction temperature is preferably 80°C, more preferably 100°C, while the upper limit of the reaction temperature is preferably 150°C, more preferably 130°C. That is, the urethane reaction temperature is preferably 80°C or higher and 150°C or lower, and more preferably 100°C or higher and 130°C or lower.

[0053] The polymerization reaction is terminated when the polymerization reaction of the above-mentioned isocyanurate-forming reaction, allophanate-forming reaction, and urethanization reaction reaches a desired degree of polymerization. The termination of the polymerization reaction can be achieved, for example, by adding an acidic compound to the reaction solution to neutralize the polymerization catalyst, or by inactivating it by thermal decomposition, chemical decomposition, or the like, but is not limited thereto. Examples of acidic compounds include phosphoric acid, acidic phosphate esters, sulfuric acid, hydrochloric acid, and sulfonic acid compounds. After the reaction is terminated, filtration is carried out if necessary.

[0054] The reaction liquid immediately after the reaction is stopped usually contains unreacted diisocyanate monomer, which is preferably removed by a thin film evaporator, extraction, etc. By carrying out such post-treatment, it is preferable to control the diisocyanate monomer concentration contained in the curing agent composition for waterproof top coats to 1 mass% or less. For example, when the diisocyanate monomer is HDI, the diisocyanate monomer concentration can be measured using the method described in the Examples below.

[0055] <Properties of the curing agent composition for waterproof top coat> [Average number of isocyanate (NCO) groups] The average number of isocyanate (NCO) groups in the polyisocyanate contained in the curing agent composition for a waterproof top coat of the present embodiment is preferably 3.0 or more, more preferably 3.0 or more and 10.0 or less, even more preferably 3.1 or more and 9.0 or less, still more preferably 3.1 or more and 8.5 or less, and particularly preferably 3.2 or more and 8.0 or less, when the curing agent composition for a waterproof top coat is not diluted with a solvent such as n-butyl acetate. By having the average number of isocyanate functional groups be equal to or greater than the above lower limit, the water resistance of the resulting coating film can be further improved, while by having the average number be equal to or less than the above upper limit, excessive viscosity increase can be more effectively prevented. The average number of isocyanate groups (hereinafter sometimes referred to as the "average number of NCO groups" or the "number-average functionality (fn)") can be calculated using the following formula, as described in the Examples below: In the formula, "NCO%" represents the isocyanate group content, and "Mn" represents the number-average molecular weight.

[0056] (Average NCO radix) = (Mn×NCO%×0.01) / 42

[0057] [viscosity] The viscosity at 25°C of the waterproof top coat curing agent composition of this embodiment when diluted with butyl acetate to a solids content of 75% by mass is not particularly limited, but in terms of the amount of organic solvent and the number of functional groups, it is preferably 100 mPa·s or more and 5000 mPa·s or less, more preferably 120 mPa·s or more and 4500 mPa·s or less, and even more preferably 130 mPa·s or more and 4000 mPa·s or less. If the viscosity is equal to or greater than the lower limit, the number of functional groups can be sufficiently increased, while if the viscosity is equal to or less than the upper limit, the amount of organic solvent can be reduced. As for the viscosity, a value measured at 25° C. using an E-type viscometer (manufactured by Tokimec Inc.) can be used, as described in the examples below.

[0058] [Isocyanate group content (NCO%)] The isocyanate group content (NCO%) of the waterproof top coat curing agent composition of this embodiment, when the waterproof top coat curing agent composition is diluted with butyl acetate and adjusted to a solids content of 75 mass%, is preferably 3.0 mass% or more and 20.0 mass% or less, more preferably 3.3 mass% or more and 19.0 mass% or less, and even more preferably 3.6 mass% or more and 18.0 mass% or less, from the viewpoint of performance when formed into a coating film. If the NCO% is equal to or more than the lower limit, the performance when formed into a coating film is better, while if it is equal to or less than the upper limit, the crosslink density does not become too high, forming a coating film that is less likely to crack. As described in the Examples below, NCO % can be determined by neutralizing the isocyanate groups with an excess of 2N amine and then back titrating with 1N hydrochloric acid.

[0059] <Usage> The waterproof top coat curing agent composition of this embodiment is suitably used as a curing agent component for a waterproof top coat paint composition for forming a waterproof top coat layer formed on a waterproof material layer consisting of a urethane coating film.

[0060] <Waterproof top coat coating composition> The waterproof top coat coating composition of this embodiment contains a polyol as a main component and the above-described waterproof top coat curing agent composition as a curing agent component.

[0061] The waterproof top coat coating composition of this embodiment may contain other main component(s) in addition to the polyol(s) as the main component(s). Furthermore, the waterproof top coat coating composition of the present embodiment may contain, as a curing agent component, other curing agent components in addition to the above-mentioned waterproof top coat curing agent composition, but it is preferable that the waterproof top coat coating composition of the present embodiment contains only the above-mentioned waterproof top coat curing agent composition as a curing agent component.

[0062] <Polyol> The lower limit of the hydroxyl value of the polyol as the main component is preferably 5 mgKOH / g, more preferably 10 mgKOH / g, even more preferably 15 mgKOH / g, and particularly preferably 20 mgKOH / g, while the upper limit of the hydroxyl value of the polyol is preferably 200 mgKOH / g, more preferably 160 mgKOH / g, even more preferably 120 mgKOH / g, and particularly preferably 80 mgKOH / g. That is, the hydroxyl value of the polyol is preferably 5 mgKOH / g or more and 200 mgKOH / g or less, more preferably 10 mgKOH / g or more and 160 mgKOH / g or less, even more preferably 15 mgKOH / g or more and 120 mgKOH / g or less, and particularly preferably 20 mgKOH / g or more and 80 mgKOH / g or less. When the hydroxyl value is within the above range, a more flexible and tough coating film can be obtained.

[0063] Examples of polyols include acrylic polyols, polyester polyols, polyether polyols, polyolefin polyols, silicon-containing polyols, fluorine-containing polyols, polycarbonate polyols, epoxy resins, and alkyd polyols. These polyols may be used alone or in combination of two or more. Furthermore, examples of polyols that can be used include urethane-modified acrylic polyols, urethane-modified polyester polyols, and urethane-modified polyether polyols, which are obtained by modifying acrylic polyols, polyester polyols, or polyether polyols with aliphatic diisocyanates, alicyclic diisocyanates, or polyisocyanates obtained therefrom. Polyols can be produced by known techniques, but the following describes the production methods of representative acrylic polyols, polyester polyols, and polyether polyols.

[0064] [Acrylic polyols] The acrylic polyols can be obtained, for example, by polymerizing only a polymerizable monomer having one or more active hydrogen atoms in one molecule, or by copolymerizing a polymerizable monomer having one or more active hydrogen atoms in one molecule with, as needed, another monomer copolymerizable with the polymerizable monomer.

[0065] Examples of the polymerizable monomer having one or more active hydrogens in one molecule include the following (i) to (vi). These may be used alone or in combination of two or more. (i) Acrylic acid esters having active hydrogens, such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and 2-hydroxybutyl acrylate. (ii) Methacrylic acid esters having active hydrogens, such as 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 3-hydroxypropyl methacrylate, and 4-hydroxybutyl methacrylate. (iii) (meth)acrylic acid esters having polyvalent active hydrogens, such as (meth)acrylic acid monoesters of triols.

[0066] Examples of the triol include glycerin, trimethylolpropane, etc. (iv) Monoethers of polyether polyols and the above-mentioned (meth)acrylic acid esters having active hydrogen.

[0067] Examples of the polyether polyols include polyethylene glycol, polypropylene glycol, polybutylene glycol, etc. (v) Adducts of glycidyl (meth)acrylate and monobasic acids. Examples of the monobasic acid include acetic acid, propionic acid, p-tert-butylbenzoic acid, etc. (vi) Adducts obtained by ring-opening polymerization of lactones with the active hydrogen of the above-mentioned (meth)acrylic acid esters having active hydrogen. Examples of the lactones include ε-caprolactone and γ-valerolactone.

[0068] Examples of other monomers copolymerizable with the polymerizable monomer include the following (i) to (v), which may be used alone or in combination of two or more. (i) (meth)acrylic acid esters such as methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, cyclohexyl methacrylate, lauryl methacrylate, and glycidyl methacrylate; (ii) unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, and itaconic acid; (iii) unsaturated amides such as acrylamide, N-methylolacrylamide, and diacetoneacrylamide; (iv) vinyl monomers having a hydrolyzable silyl group such as vinyltrimethoxysilane, vinylmethyldimethoxysilane, and γ-(meth)acrylopropyltrimethoxysilane; (v) other polymerizable monomers such as styrene, vinyltoluene, vinyl acetate, acrylonitrile, and dibutyl fumarate.

[0069] As a specific method for producing acrylic polyols, for example, the above-mentioned monomers are solution polymerized in the presence of a known radical polymerization initiator such as a peroxide or an azo compound, and the resulting solution is diluted with an organic solvent or the like as necessary, thereby obtaining acrylic polyols.

[0070] When the waterproof top coat coating composition of this embodiment contains a solvent with a high water content, it can be produced by a known method such as a method of solution polymerization of the above-mentioned monomers and converting them into an aqueous phase, or emulsion polymerization. In this case, water solubility or water dispersibility can be imparted to the acrylic polyols by neutralizing the acidic moieties of carboxylic acid-containing monomers such as acrylic acid and methacrylic acid, or sulfonic acid-containing monomers, with an amine or ammonia.

[0071] [Polyester polyols] The polyester polyols can be obtained, for example, by subjecting a dibasic acid, either alone or in a mixture of two or more kinds, to a condensation reaction with a polyhydric alcohol, either alone or in a mixture of two or more kinds.

[0072] Examples of the dibasic acid include succinic acid, adipic acid, dimer acid, maleic anhydride, phthalic anhydride, isophthalic acid, terephthalic acid, 1,4-cyclohexanedicarboxylic acid, and other carboxylic acids.

[0073] Examples of the polyhydric alcohol include ethylene glycol, propylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, trimethylpentanediol, cyclohexanediol, trimethylolpropane, glycerin, pentaerythritol, 2-methylolpropanediol, and ethoxylated trimethylolpropane.

[0074] As a specific method for producing polyester polyols, for example, the above components may be mixed and heated to about 160° C. or more and 220° C. or less to carry out a condensation reaction. Alternatively, for example, polycaprolactones obtained by ring-opening polymerization of lactones such as ε-caprolactone with polyhydric alcohols may also be used as polyester polyols.

[0075] [Polyether polyols] The polyether polyols can be obtained, for example, by using any one of the following methods (1) to (3). (1) A method of obtaining polyether polyols by random or block addition of an alkylene oxide or a mixture thereof to a polyhydroxy compound or a mixture thereof using a catalyst. Examples of the catalyst include hydroxides of lithium, sodium, potassium, etc., strong basic catalysts, composite metal cyanide complexes, etc. Examples of the strong basic catalysts include alcoholates and alkylamines, and examples of the composite metal cyanide complexes include metalloporphyrins and zinc hexacyanocobaltate complexes. Examples of the alkylene oxide include ethylene oxide, propylene oxide, butylene oxide, cyclohexene oxide, and styrene oxide. (2) A method of obtaining polyether polyols by reacting a polyamine compound with an alkylene oxide. Examples of the polyamine compounds include ethylenediamines. Examples of the alkylene oxide include those exemplified in (1). (3) A method of polymerizing acrylamide or the like using the polyether polyol obtained in (1) or (2) as a medium to obtain so-called polymer polyols. Examples of the polyhydric hydroxy compounds include the following (i) to (vi): (i) diglycerin, ditrimethylolpropane, pentaerythritol, dipentaerythritol, etc.; (ii) sugar alcohol compounds such as erythritol, D-threitol, L-arabinitol, ribitol, xylitol, sorbitol, mannitol, galactitol, and rhamnitol; (iii) monosaccharides such as arabinose, ribose, xylose, glucose, mannose, galactose, fructose, sorbose, rhamnose, fucose, and ribodesose; (iv) disaccharides such as trehalose, sucrose, maltose, cellobiose, gentiobiose, lactose, and melibiose; (v) trisaccharides such as raffinose, gentianose, and melezitose; and (vi) tetrasaccharides such as stachyose.

[0076] <nco oh> In the waterproof top coat coating composition of this embodiment, the mixing ratio of the curing agent to the base agent can be expressed as the molar ratio of isocyanate groups to hydroxyl groups (NCO / OH). The lower limit of NCO / OH is preferably 0.1, more preferably 0.3, even more preferably 0.4, and particularly preferably 0.5. Meanwhile, the upper limit of NCO / OH is preferably 5.0, more preferably 4.0, even more preferably 3.0, and particularly preferably 2.0. That is, NCO / OH is preferably 0.1 or more and 5.0 or less, more preferably 0.3 or more and 4.0 or less, even more preferably 0.4 or more and 3.0 or less, and particularly preferably 0.5 or more and 2.0 or less. By ensuring that the NCO / OH ratio is within the above range, a tougher waterproof top coat can be formed.

[0077] <Various additives> In addition to the polyol and the curing agent composition for a waterproof top coat of the present embodiment, the coating composition for a waterproof top coat of the present embodiment may contain, depending on the purpose and application, various additives used in the relevant technical field, such as coloring pigments, dyes, silane coupling agents for improving adhesion of the coating film, ultraviolet absorbers, curing accelerators, light stabilizers, matting agents, coating surface hydrophilizing agents, catalysts for curing acceleration, drying improvers, leveling agents, antioxidants, plasticizers, surfactants, etc., within a range that does not impair the effects of the present invention.

[0078] The color pigment may be an inorganic pigment or an organic pigment. Examples of inorganic pigments include carbon black and titanium oxide, which have good weather resistance. Examples of organic pigments include phthalocyanine blue, phthalocyanine green, quinacridone red, indanthrene orange, and isoindolinone yellow.

[0079] Examples of silane coupling agents include 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, ureidopropyltriethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, methyltriethoxysilane, and methyltrimethoxysilane.

[0080] Examples of the ultraviolet absorber include benzophenone-based, benzotriazole-based, triazine-based, and cyanoacrylate-based ultraviolet absorbers.

[0081] Examples of light stabilizers include hindered amine-based light stabilizers, and specific commercially available products include ADK STAB LA62 and ADK STAB LA67 (trade names, all manufactured by Adeka Argus Chemical Co., Ltd.), TINUVIN 292, TINUVIN 144, TINUVIN 123, and TINUVIN 440 (trade names, all manufactured by Chiba Specialty Chemicals Corporation), and SANOL LS765 (trade name, manufactured by Sankyo Lifetech Co., Ltd.).

[0082] The matting agents include, for example, ultrafine powder synthetic silica, which, when used, can produce a waterproof topcoat with an elegant semi-gloss, matte finish.

[0083] The catalyst for accelerating curing includes, but is not limited to, metal salts, tertiary amines, and the like. Examples of metal salts include dibutyltin dilaurate, tin 2-ethylhexanoate, zinc 2-ethylhexanoate, and cobalt salts. Examples of tertiary amines include triethylamine, pyridine, methylpyridine, benzyldimethylamine, N,N-dimethylcyclohexylamine, N-methylpiperidine, pentamethyldiethylenetriamine, N,N'-endoethylenepiperazine, and N,N'-dimethylpiperazine. Examples of drying improvers include CAB (cellulose acetate butyrate) and NC (nitrocellulose).

[0084] The leveling agent is not particularly limited, but examples thereof include silicone, aerosil, wax, stearates, polysiloxanes, and the like.

[0085] The plasticizer is not particularly limited, but examples thereof include phthalate esters, phosphate esters, fatty acid esters, pyromellitic acid esters, epoxy-based plasticizers, polyether-based plasticizers, liquid rubber, and non-aromatic paraffin oil. Examples of phthalate esters include dioctyl phthalate, dibutyl phthalate, diethyl phthalate, butyl benzyl phthalate, di-2-ethylhexyl phthalate, diisodecyl phthalate, diundecyl phthalate, and diisononyl phthalate. Examples of phosphoric acid esters include tricresyl phosphate, triethyl phosphate, tributyl phosphate, tri-2-ethylhexyl phosphate, trimethylhexyl phosphate, tris-chloroethyl phosphate, and tris-dichloropropyl phosphate. Examples of fatty acid esters include trimellitic acid esters, dipentaerythritol esters, dioctyl adipate, dimethyl adipate, di-2-ethylhexyl azelate, dioctyl azelate, dioctyl sebacate, di-2-ethylhexyl sebacate, methyl acetyl ricinoleate, etc. Examples of trimellitic acid esters include trimellitic acid octyl ester, trimellitic acid isodecyl ester, etc. Examples of pyromellitic acid esters include pyromellitic acid octyl ester. Examples of epoxy plasticizers include epoxidized soybean oil, epoxidized linseed oil, and epoxidized fatty acid alkyl esters. Examples of polyether plasticizers include adipic acid ether esters and polyethers. Examples of liquid rubber include liquid NBR, liquid acrylic rubber, and liquid polybutadiene.

[0086] Examples of surfactants include known anionic surfactants, cationic surfactants, and amphoteric surfactants.

[0087] <Method of manufacturing a coating composition for waterproof top coat> The waterproof top coat coating composition of this embodiment is useful as a solvent-based coating composition, and can be obtained by the production method described below. When the waterproof top coat coating composition of this embodiment is a solvent-based coating composition, for example, first, a polyol or its solvent dilution as the main agent is added, and various additives are added as necessary, and the above-mentioned waterproof top coat curing agent composition is added as a curing agent. Next, if necessary, a solvent is further added to adjust the viscosity. Next, by stirring by hand or using a stirring device such as a mixer, a solvent-based coating composition can be obtained.

[0088] Furthermore, the order of mixing the main component mainly composed of the polyol, the curing agent component mainly composed of the waterproof top coat curing agent composition, and the various additives is not particularly limited, and they can be mixed, for example, in the following order: 1) The main component, which is a mixture of various additives, is mixed with the hardener component at the painting site; 2) After mixing the main component and hardener component at the painting site, various additives are mixed; 3) The main component, which has been mixed with various additives in advance, is mixed with the hardener component, which has been mixed with various additives in advance, at the painting site.

[0089] <Usage> The waterproof top coat coating composition of this embodiment is suitably used to form a waterproof top coat layer that is formed on a waterproof material layer made of a urethane coating film.

[0090] <Waterproof top coat coating> The waterproof top coat coating film of this embodiment is obtained by curing the above-mentioned waterproof top coat coating composition, and exhibits high initial reactivity, and is excellent in water resistance, low-temperature elongation, and low-temperature stress.

[0091] <Method of manufacturing waterproof top coat film> The method for producing a waterproof top coat film of this embodiment is a method including a step of curing the above-mentioned waterproof top coat coating composition. The waterproof top coat coating film of this embodiment can be produced by applying the above-mentioned waterproof top coat coating composition to a substrate using a known coating method such as spray coating, air spray coating, brush coating, immersion coating, roll coating, curtain flow coating, bell coating, electrostatic coating, etc., and then curing the composition.

[0092] The substrate to be coated is not particularly limited, and examples thereof include molded articles made by molding materials such as metals (steel plates, surface-treated steel plates, etc.), plastics, wood, films, and inorganic materials. The shape of these molded articles is also not particularly limited, and may be thin articles such as films, sheets, and boards, or thick articles such as cylinders and three-dimensional structures. They may also be hollow articles such as tubes.

[0093] When the object to be coated is a laminate consisting of a substrate, a primer layer, and a waterproof material layer consisting of a urethane coating film laminated in this order, the method for manufacturing a waterproof top coat film of this embodiment can also be said to be a method for manufacturing a waterproof structure, and this method produces a waterproof structure that is excellent in water resistance, low-temperature elongation, and low-temperature stress. [Example]

[0094] Hereinafter, the present embodiment will be described in more detail by showing specific examples and comparative examples, but the present embodiment is not limited in any way by the following examples and comparative examples as long as they do not depart from the gist of the present embodiment. In the following, Examples 5 to 7 are considered as reference examples.

[0095] [Physical Properties 1] (molar ratio of isocyanurate groups to allophanate groups, molar ratio of urethane groups to isocyanurate groups) The waterproof top coat curing agent compositions obtained in the examples and comparative examples were tested using Biospin Avance 600 (trade name) manufactured by Bruker. 13 C-NMR measurements were carried out under the following specific measurement conditions:

[0096] (Measurement conditions) 13 C-NMR device: AVANCE600 (manufactured by Bruker) Cryoprobe (Bruker) CryoProbe® CPDUL 600S3-C / HD-05Z Resonance frequency: 150MHz Concentration: 60wt / vol% Shift standard: CDCl3 (77 ppm) Accumulation count: 10,000 times Pulse program: zgpg30 (proton fully decoupled, waiting time 2 seconds)

[0097] The integral values ​​of the following signals were divided by the number of carbon atoms being measured to determine the molar ratios of allophanate groups, isocyanurate groups, and urethane groups. Isocyanurate group: (integrated value around 148.6 ppm) ÷ 3 Urethane group: (integrated value around 156.5 ppm) ÷ 1 Allophanate group: (integrated value around 154 ppm) ÷ 1

[0098] [Physical Properties 2] (Average number of isocyanate groups (average number of NCO groups)) Using the curing agent composition for waterproof top coat before the addition of n-butyl acetate as a sample, the average number of isocyanate groups (average number of NCO groups) was calculated according to the following formula.

[0099] (Average NCO radix) = (Mn×NCO%×0.01) / 42

[0100] In the formula, "NCO%" represents the isocyanate group content, and the value obtained in "Physical Properties 4" described below is used. "Mn" represents the number average molecular weight, which was determined as the molecular weight based on polystyrene by GPC measurement under the measurement conditions shown below.

[0101] (Measurement conditions) Equipment: HLC-8320GPC (TOSOH) Column: TSKgel Super H2500 x 1 (TOSOH) TSKgel Super H4000 x 1 (TOSOH) TSKgel Super H5000 x 1 (TOSOH) TSKgel Super H6000 x 1 (TOSOH) Carrier: Tetrahydrofuran Flow rate: 0.6mL / min Sample concentration: 1.0% by mass Injection volume: 20μL Temperature: 40℃ Detection method: differential refractometer

[0102] [Physical Properties 3] (Viscosity at 25°C) The viscosity was measured at 25°C using an E-type viscometer (manufactured by Tokimec Co., Ltd.). A standard rotor (1°34' x R24) was used. The rotation speeds were as follows:

[0103] (Rotation speed) 100 rpm (less than 128 mPa·s) 50 rpm (128 mPa·s or more but less than 256 mPa·s) 20 rpm (256 mPa·s or more but less than 640 mPa·s) 10 rpm (640 mPa·s or more but less than 1280 mPa·s) 5 rpm (1280 mPa·s or more but less than 2560 mPa·s)

[0104] [Physical Properties 4] (Isocyanate group content (NCO%)) The NCO% was determined by back titration with 1N hydrochloric acid after neutralizing the isocyanate groups with an excess of 2N amine.

[0105] [Physical Properties 5] (HDI monomer concentration) The number average molecular weight was measured using polystyrene standards by GPC under the measurement conditions shown in "Physical Properties 2." The peak area % of the molecular weight (168) corresponding to the unreacted HDI monomer was then calculated as the HDI monomer concentration.

[0106] <Method for evaluating waterproof top coat coating compositions> Using each of the curing agent compositions for waterproof top coats, coating compositions for waterproof top coats were produced as follows, and evaluations were carried out.

[0107] [Manufacturing Example 1] (Production of waterproof top coat coating composition 1) First, an acrylic polyol (manufactured by Allnex, product name "Setalux1903", resin solids concentration 75% by mass, hydroxyl value 150 mg KOH / g resin) and each waterproof top coat curing agent composition were blended so that the molar equivalent ratio of hydroxyl groups to isocyanate groups was 1:1. Then, butyl acetate was used to adjust the paint viscosity to 20 seconds using a Ford Cup No. 4, and each waterproof top coat paint composition 1 was obtained.

[0108] [Rating 1] (water resistance) Each waterproof top coat coating composition 1 was applied to a glass plate so that the film thickness after drying was 30 μm, and the coating was left to cure at room temperature for 48 minutes to obtain each coating film. This coating film was kept at 60°C and 87% humidity for 72 hours, and then left at room temperature for 60 minutes. After the test, the coating film was visually observed. The water resistance (room temperature) of each coating film was evaluated according to the following evaluation criteria. (Water resistance: Evaluation criteria) ◎: No whitening or spots were observed 〇: Whitening or spots observed in 1 or 2 places △: Whitening or spots observed in 3 to 5 places ×: Whitening or spots were observed in 6 or more places

[0109] [Manufacturing Example 2] (Production of waterproof top coat coating composition 2) First, an acrylic polyol (manufactured by Allnex, product name "Setalux 1152", resin solids concentration 61% by mass, hydroxyl value 140 mg KOH / g resin) and each waterproof top coat curing agent composition were blended so that the molar equivalent ratio of hydroxyl groups to isocyanate groups was 1:1. Then, butyl acetate was used to adjust the paint viscosity to 20 seconds using a Ford Cup No. 4, yielding each waterproof top coat paint composition 2.

[0110] [Rating 2] (initial reactivity) Each waterproof top coat coating composition 2 was applied with an applicator to a film thickness of 50 μm after drying. After application, the coating was cured for one day at 23°C and 50% humidity to obtain each coating film. The resulting coating film was immersed in acetone at 20°C for 24 hours, and the gel fraction was calculated by calculating the ratio of the undissolved mass to the mass before immersion. The initial reactivity of each coating film was evaluated according to the following evaluation criteria.

[0111] (Initial reactivity: evaluation criteria) ◎: Gel fraction is 80% by mass or more Good: Gel fraction is 75% by mass or more and less than 80% by mass ×: Gel fraction is 0% by mass or more and less than 75% by mass

[0112] [Rating 3] (Low temperature elongation (coating film elongation) and low temperature stress (coating film stress)) Each waterproof top coat coating composition 2 was applied with an applicator to a film thickness of 50 μm after drying. After application, the coating was cured for 7 days at 23°C and 50% humidity to obtain each coating film. A tensile test was performed using the resulting coating film. The elongation of the coating film was measured at a temperature of -10°C using a tensile tester (Shimadzu Corporation, AGS 500G) at a pulling speed of 20 mm / min and a grip spacing of 20 mm. The low-temperature elongation and low-temperature stress of each coating film were evaluated according to the evaluation criteria shown below.

[0113] (Low temperature elongation: evaluation standard) ◎: Coating elongation is 40% or more 〇: Coating elongation is 35% or more but less than 40% ×: Coating elongation is 0% or more and less than 35%

[0114] (Low temperature stress: evaluation criteria) ◎: Coating stress is 100 MPa or more 〇: Coating stress is 50MPa or more but less than 100MPa ×: Coating stress is 0 MPa or more and less than 50 MPa

[0115] <Synthesis of Polyisocyanate> [Synthesis Example 1] (Synthesis of Polyisocyanate A-1) A four-neck flask equipped with a stirrer, thermometer, reflux condenser, nitrogen inlet, and dropping funnel was purged with nitrogen and charged with 1000 g of HDI and 100 g of 2-ethylhexanol. The urethane reaction was carried out at 90°C for 1 hour with stirring. 1 g of a solution of tetramethylammonium caprate diluted to 5% by mass with isobutanol was added as an allophanation and isocyanuration catalyst, and the isocyanuration reaction was carried out. When the refractive index of the reaction solution increased to 0.015, phosphoric acid was added to terminate the reaction. After filtering the reaction solution, it was purified twice using a thin-film evaporator at 160°C and 0.2 Torr to obtain Polyisocyanate A-1. The resulting Polyisocyanate A-1 had a viscosity of 400 mPa·s (25°C), an NCO content of 17.7% by mass, and an HDI monomer concentration of 0.11% by mass.

[0116] [Synthesis Example 2] (Synthesis of Polyisocyanate A-2) 1000 g of HDI was charged into an apparatus similar to that used in Synthesis Example 1, and the temperature inside the reactor was maintained at 80°C for 2 hours while stirring. Subsequently, 1 g of a solution prepared by diluting tetramethylammonium caprate with isobutanol to a concentration of 5% by mass was added as an isocyanuration catalyst, and an isocyanuration reaction was carried out. When the refractive index of the reaction solution increased to 0.012, phosphoric acid was added to terminate the reaction. The reaction solution was filtered, and unreacted HDI was removed in the same manner as in Synthesis Example 1 to obtain Polyisocyanate A-2. The resulting Polyisocyanate A-2 had a viscosity of 1300 mPa·s (25°C), an NCO content of 23.1% by mass, and an HDI monomer concentration of 0.11% by mass.

[0117] [Synthesis Example 3] (Synthesis of Polyisocyanate A-3) In a similar apparatus to that used in Synthesis Example 1, 1000 g of HDI and 30 g of 2-ethylhexanol were charged and subjected to a urethane-forming reaction at 90°C for 1 hour with stirring. 1 g of a solution of tetramethylammonium caprate diluted to 5% by mass with isobutanol was added as an allophanation and isocyanuration catalyst, and the isocyanuration reaction was carried out. When the refractive index of the reaction solution increased to 0.012, phosphoric acid was added to terminate the reaction. After filtering the reaction solution, unreacted HDI was removed in the same manner as in Synthesis Example 1, yielding Polyisocyanate A-3. The resulting Polyisocyanate A-3 had a viscosity of 500 mPa·s (25°C), an NCO content of 20.6% by mass, and an HDI monomer concentration of 0.11% by mass.

[0118] [Synthesis Example 4] (Synthesis of Polyisocyanate A-4) 1000 g of HDI and 44 g of 1,4-butanediol were charged into the same apparatus as in Synthesis Example 1 and maintained at a reactor temperature of 160°C for 1 hour with stirring. The reaction solution was then filtered, and unreacted HDI was removed in the same manner as in Synthesis Example 1 to obtain Polyisocyanate A-4. The obtained Polyisocyanate A-4 had a viscosity of 600 mPa s (25°C), an NCO content of 19.2% by mass, and an HDI monomer concentration of 0.2% by mass.

[0119] <Production of Curing Agent Composition for Waterproof Top Coat> [Example 1] (Production of waterproof top coat curing agent composition P-a1) To an apparatus similar to that used in Synthesis Example 1, 31 g of the polyisocyanate A-2 obtained in Synthesis Example 2, 31 g of the polyisocyanate A-3 obtained in Synthesis Example 3, 7 g of polyether-based polyol B-3 (manufactured by AGC Corporation, "EXCENOL 1030" (trade name), number average molecular weight 1000), 31 g of polyether-based polyol B-4 (manufactured by AGC Corporation, "EXCENOL 1020" (trade name), number average molecular weight 1000), and 0.01 g of 2-ethylhexyl phosphoric acid ester (manufactured by Johoku Chemical Industry Co., Ltd., trade name "JP-508") were added. Next, the mixed solution was subjected to a urethane reaction at 120°C for 4 hours while stirring, and then 0.1 g of a hindered amine light stabilizer (manufactured by BASF Japan Ltd., trade name "Tinuvin 765") and 33 g of n-butyl acetate as a dilution solvent were added to obtain a waterproof top coat curing agent composition P-a1. The obtained waterproof top coat curing agent composition P-a1 was a transparent liquid with a viscosity of 400 mPa·s (25°C) and an NCO content of 7.7 mass%.

[0120] [Examples 2 to 7 and Comparative Examples 1 and 2] (Production of waterproof top coat curing agent compositions P-a2 to P-a7 and P-b1 to P-b2) Each waterproof top coat curing agent composition was obtained in the same manner as in Example 1, except that the formulations shown in Tables 1 and 2 were used.

[0121] In Tables 1 and 2, the polyols (B) are as follows: (Polyether-based polyol (B1)) B1-1: AGC Corporation, "Exenol 840" (trade name), number average molecular weight 6500, trifunctional polypropylene glycol B1-2: AGC Corporation, "Exenol 230" (trade name), number average molecular weight 3000 B1-3: AGC Corporation, "Exenol 1030" (trade name), number average molecular weight 1000 B1-4: AGC Corporation, "Exenol 1020" (trade name), number average molecular weight 1000 (Polyester polyol (B2)) B2-1: Manufactured by DIC Corporation, "Polylite OD-X-2722" (product name), number average molecular weight 2000 B2-2: Manufactured by DIC Corporation, "Polylite OD-X-2542C" (product name), number average molecular weight 850

[0122] Furthermore, the water resistance, initial reactivity, low-temperature elongation, and low-temperature stress of each of the obtained waterproof top coat curing agent compositions were evaluated according to the methods described above. The results are shown in Tables 1 and 2.

[0123] [Table 1]

[0124] [Table 2]

[0125] As can be seen from Table 1, the coating films obtained by curing the waterproof top coat paint compositions using the waterproof top coat curing agent compositions P-a1 to P-a7 (Examples 1 to 7) were excellent in all of water resistance, initial reactivity, low-temperature elongation, and low-temperature stress.

[0126] On the other hand, as can be seen from Table 2, none of the coating films obtained by curing the waterproof top coat paint compositions using the waterproof top coat curing agent compositions P-b1 to P-b2 (Comparative Examples 1 and 2) were excellent in all of water resistance, initial reactivity, low-temperature elongation, and low-temperature stress. [Industrial Applicability]

[0127] According to the curing agent composition for a waterproof top coat of the present embodiment, it is possible to provide a curing agent composition for a waterproof top coat that, when used in a waterproof top coat layer, has excellent initial reactivity and can impart good water resistance, low-temperature elongation, and low-temperature stress to the waterproof top coat layer.< / nco>

Claims

1. at least one diisocyanate (A) selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates; a polyol (B) which is a trifunctional polyether polyol having a number average molecular weight of 400 or more and 5,000 or less and having an oxypropylene group; and a polyisocyanate derived from Contains allophanate groups, isocyanurate groups, and urethane groups, the molar ratio of allophanate groups to isocyanurate groups is 1 / 99 or more and 25 / 75 or less; The curing agent composition for waterproof top coats, wherein the polyisocyanate has an average number of isocyanate groups of 3.0 or more.

2. A coating composition for a waterproof top coat, comprising the curing agent composition for a waterproof top coat according to claim 1 and a polyol.

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