JP2005058918A - Application method for polyurethane type coating - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an application method for a polyurethane type coating film by which a coated underlayer excellent in the adhesion property to a top coating layer can be obtained and the curing property and mechanical strengths of which coating film are not deteriorated. <P>SOLUTION: The underlayer is formed by spraying a polyurethane-curable composition and then the top coating layer is formed on the surface of the underlayer, and as a curing agent of the polyurethane-curable composition, diethyltoluenediamine and a low activity amine compound having lower reactivity with isocynate group than that of the diethyltoluenediamine are used in combination. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for applying a polyurethane-based coating film, for example, to be sprayed and cured on an object such as a concrete frame or a steel plate, and more particularly to a multilayer method for forming a topcoat layer on the surface of a base layer.

  As a conventional spray coating method, an ultra-fast curing spray coating method is known, in which the main component and curing agent of a polyurethane curable composition are impact-mixed in a low-viscosity state and formed at high speed, and waterproofing of concrete roofs and metal roofs is known. As a coating method applied to a wide variety of applications, such as materials, open corridors, stairs, stadium stands, factory floors, parking lot floors, sewage treatment plants and pool inner surfaces, underground civil engineering waterproofing materials, etc. Applied.

  The raw material of the polyurethane curable composition used in such a spray coating method is similar to the composition used in the RIM method (Reaction Injection Molding method) that has been used in molding of bumpers and the like. There are many combinations of an isocyanate component composed of a terminal urethane prepolymer and an active hydrogen group-containing compound component composed of a diamine and a polyol.

  Specifically, a curing agent containing diethyltoluenediamine (hereinafter also referred to as DETDA) as an active hydrogen group-containing compound, a polyol, and lead 2-ethylhexanoate (lead octylate) as a curing catalyst, and an isocyanate group A spray coating method in which a main agent containing a terminal urethane prepolymer is mixed at a volume ratio of 1: 1 is the mainstream.

  In addition, there is a urea-based spray coating method that is applied to waterproofing materials for sewage treatment plants and has higher strength and higher chemical resistance, but this is based on the isocyanate group of the main agent compared to the polyurethane curable composition. The urea bond density is increased by increasing the content and increasing the DETDA content of the curing agent.

  As described above, in the spray coating method, DETDA having a relatively high reactivity has been conventionally used as a curing agent because a very fast curing rate is required.

  On the other hand, the polyurethane curable composition for hand-painted waterproofing material is not required to have such a very fast curing rate, but rather a slow curing rate, that is, a reasonably long pot life. For this reason, two or more kinds of curing agent components having different reactivity with respect to isocyanate are mixed as a curing agent.

  For example, a two-component room temperature curable coating waterproofing material comprising a main component mainly composed of an isocyanate group-terminated prepolymer obtained by reaction of tolylene diisocyanate and a polyol, and a curing agent mainly composed of an aromatic polyamine. In the production method, a technique using a mixture of DETDA and 4,4′-methylene-bis (2-chloroaniline) as an aromatic polyamine which is a main component of the curing agent has been proposed (see Patent Document 1).

  In addition, as a curing agent component, a technique has also been proposed in which a polyoxyalkylene glycol aminated at both ends of an average molecular weight of 300 to 5000 is blended with 5 to 70 mol% in DETDA and used as a curing agent (see Patent Document 2). ).

The reactivity of each aromatic diamine used as a curing agent component with respect to isocyanate can be expressed as a relative reaction rate. For example, the reaction rate of 4,4′-methylene-bis (2-chloroaniline) is 1. It is known as the relative reaction rate of each aromatic diamine (see Non-Patent Document 1).
JP-A-8-34829 Japanese Patent Laid-Open No. 10-17820 D. Nissen et al, Journal of Elastomers and Plastics, 15, p96-112 (1983)

  In the above spray coating method, when only DETDA is used as a curing agent as in the prior art, the curing speed is high, but there are the following problems.

  That is, in the construction of a polyurethane-based coating film, a polyurethane curable composition is sprayed and applied to form a base layer by reaction curing, and then a top coat layer may be further formed on the surface of the base layer. This can improve the weather resistance, abrasion resistance, aesthetics of the finished surface, and the like of the coating film. And as such a topcoat layer, the topcoat layer which consists of an acryl-urethane type resin and / or a fluorine-urethane type resin is used in many cases.

  However, the base layer using only DETDA as a curing agent cures very quickly, so that almost no free amino groups remain on the surface of the cured coating film. For this reason, since the chemical bond with the topcoat layer to be overcoated cannot be exhibited, there is a problem that the adhesion between the base layer and the topcoat layer is insufficient.

  The polyurethane curable compositions disclosed in the above-mentioned JP-A-8-34829 and JP-A-10-17820 all relate to hand-painted waterproofing materials, and extend the pot life. The polyurethane curable composition used in the spray coating method requiring a high curing speed is not disclosed because it aims to reduce the weight of the plasticizer. Moreover, it does not disclose improvement in adhesion to the top coat layer.

  Therefore, the object of the present invention is to obtain a ground layer excellent in adhesion with the top coat layer by spray coating without significantly changing the composition of the conventional polyurethane curable composition, and further, the curability of the coating film. Another object of the present invention is to provide a method for applying a polyurethane-based coating film that does not impair the mechanical strength.

In order to achieve the above object, a method for applying a polyurethane-based coating film according to the present invention includes a curing agent comprising diethyltoluenediamine, a low activity amine compound having a lower reactivity with an isocyanate group than the diethyltoluenediamine, and a polyisocyanate. A step of spray-coating a polyurethane curable composition formed by mixing a main component containing a compound, and reactively curing the polyurethane curable composition to form a base layer; and a top coat layer on the surface of the base layer. A method for constructing a polyurethane-based coating film comprising a forming step,
The ratio of active hydrogen-containing groups of the diethyltoluenediamine is 40 to 94 mol%, and the ratio of active hydrogen-containing groups of the low-activity amine compound is 1 to 20 mol with respect to all active hydrogen-containing groups in the curing agent. %, The diethyltoluenediamine and the low activity amine compound are contained.

  According to the construction method of the present invention, as the curing agent component, the low activity amine compound having a reactivity with the isocyanate group lower than that of DETDA is blended in the above proportion, so that the surface of the coating film is not yet formed even after the underlayer is cured. It is presumed that the free amino group of the reaction is present. Thereby, the adhesiveness of a base layer and a topcoat layer can be improved.

  Moreover, by making content of a low activity amine compound into said range, the hardening speed of a base layer, the surface appearance after hardening, and mechanical strength do not fall.

  In the present invention, a polyol is further contained in the curing agent, and the ratio of the active hydrogen-containing groups of the polyol is 5 to 50 mol% with respect to all active hydrogen-containing groups in the curing agent. It is preferable to contain a polyol. According to this aspect, since the volume ratio of the main agent and the curing agent can be adjusted by adding the polyol, the volume ratio of the main agent and the curing agent in spray coating can be easily adjusted to around 1: 1. Moreover, the elongation performance of the coating film of the underlayer can be greatly improved.

  In the present invention, the low activity amine compound is at least one selected from 4,4′-methylenebis (2-chloroaniline), dimethylthiotoluenediamine, and polytetramethylene oxide-di-p-aminobenzoate. The above is preferable. By using these compounds in combination with DETDA, it is possible to maintain almost the same curability and mechanical strength of the cured coating film as those of DETDA alone as the underlayer. Moreover, since the reactivity with an isocyanate group is sufficiently lower than DETDA, the said compound is excellent also in adhesiveness with a topcoat layer.

  Furthermore, in the present invention, the top coat layer is preferably a top coat layer made of an acrylic-urethane resin and / or a fluorine-urethane resin. According to this, since the isocyanate component of the urethane material in the topcoat layer is chemically bonded to a part of the free amino group of the undercoat layer, a polyurethane-based coating film that is particularly excellent in adhesiveness with the topcoat layer can be obtained. Further, the weather resistance, abrasion resistance and aesthetics of the finished surface can be improved by the top coat layer.

  In the present invention, the polyisocyanate compound is preferably an isocyanate group-terminated urethane prepolymer obtained by reacting a diphenylmethane diisocyanate compound and / or a polyol with a low molecular weight polyisocyanate compound. According to this, a polyurethane curable composition having sufficient curability can be provided.

  Furthermore, in this invention, it is preferable to perform the said spray coating using a collision mixing type spraying apparatus. According to this, the base layer can be formed at a high speed by colliding and mixing the polyurethane raw materials having two or more components at a high pressure in a low viscosity state.

  According to the construction method of the present invention, it exhibits excellent adhesion to the topcoat layer without significantly changing or improving the composition of the polyurethane curable composition of the underlayer, and it is also capable of rapid curing and machine. A polyurethane-based coating film that does not impair strength can be provided.

Hereafter, the construction method of the urethane type coating film of this invention is demonstrated in detail.
The construction method of the present invention is a step of spray-coating a two-component polyurethane curable composition formed by mixing a main agent and a curing agent, and reacting and curing the polyurethane curable composition to form a base layer. And a step of forming a topcoat layer on the surface of the underlayer.

  First, in the step of forming an underlayer, a curing agent containing diethyltoluenediamine, a low activity amine compound having a lower reactivity with isocyanate groups than diethyltoluenediamine, and a main agent containing a polyisocyanate compound are mixed. A polyurethane curable composition is used.

  The polyisocyanate compound contained in the main agent is not particularly limited, and examples thereof include diphenylmethane diisocyanate compounds and isocyanate group-terminated urethane prepolymers obtained by reacting polyols with low molecular weight polyisocyanate compounds.

  Examples of the diphenylmethane diisocyanate compound include 4,4′-diphenylmethane diisocyanate (hereinafter referred to as MDI), polyphenylpolymethylene polyisocyanate (hereinafter referred to as crude MDI), and carbodiimide-modified diphenylmethane diisocyanate (hereinafter referred to as carbodiimide-modified MDI). In the present invention, liquids such as crude MDI and carbodiimide-modified MDI are particularly preferable. These may be used alone or in combination of two or more. When crude MDI and carbodiimide-modified MDI are used in combination, the ratio is preferably 1: 1 to 1: 4 by mass ratio.

  As the isocyanate group-terminated urethane prepolymer, an isocyanate group-terminated urethane prepolymer obtained by reacting a polyol with a low molecular weight polyisocyanate compound such as tolylene diisocyanate or MDI is preferred, and an isocyanate group obtained by reacting a polyol with MDI. Terminal urethane prepolymers are more preferred.

  Examples of the polyol used as a raw material for the isocyanate group-terminated urethane prepolymer include polyether polyol (polyoxyalkylene polyol), polyester polyol, castor oil-based polyol, polybutadiene-based polyol, and the like. Examples of the polyether polyol include polyoxypropylene polyol, polyoxypropylene oxyethylene polyol, and polyoxytetramethylene glycol. Of the above, polyether polyol is preferable, and polyoxypropylene polyol is particularly preferable.

  The number of hydroxyl groups in the polyol is preferably 2-4. The hydroxyl value is preferably 25 to 280 mgKOH / g, particularly preferably 30 to 120 mgKOH / g. When the number of hydroxyl groups is less than 2 or the hydroxyl value is less than 25 mgKOH / g, the resulting cured coating film tends to have insufficient mechanical strength. Moreover, when the number of hydroxyl groups exceeds 4, or the hydroxyl value exceeds 280 mgKOH / g, the elasticity and elongation of the cured coating film tend to be inferior.

  In addition, in order to adjust the isocyanate group content rate in a main ingredient, a diphenylmethane diisocyanate type compound or an isocyanate group terminal urethane prepolymer may be used independently, and both may be mixed and used. By using the isocyanate group-terminated urethane prepolymer, the elasticity and elongation of the cured coating film can be controlled. The ratio of polyisocyanate to polyol in the isocyanate group-terminated urethane prepolymer is preferably 5 to 13 in terms of equivalent ratio (molar ratio) (NCO / OH) of isocyanate groups to hydroxyl groups. Moreover, 8-33 mass% is preferable and, as for the isocyanate group content rate in a main ingredient, 10-20 mass% is more preferable.

  A plasticizer may be used to adjust the isocyanate group content in the main agent. Examples of plasticizers include dioctyl phthalate, dibutyl phthalate, dinonyl phthalate, diisononyl phthalate, dioctyl adipate, methyl esters of lard, methyl esters of coconut oil, chlorinated paraffin, petroleum plasticizers, etc. It is done. Of these, dioctyl phthalate is particularly preferable. These plasticizers may be used but are preferably not used.

  The viscosity of the main agent is preferably 300 to 2500 mPa · s at 20 ° C., more preferably 300 to 1000 mPa · s.

  Next, the curing agent will be described. In the present invention, the curing agent includes DEATDA and a low activity amine compound having a lower reactivity with an isocyanate group than DEATDA.

  In addition, the reactivity with an isocyanate group in this invention means the relative reaction rate of each aromatic diamine, and is calculated | required by said nonpatent literature 1. As a low activity amine compound in this invention, it is preferable that a relative reaction rate is 50% or less compared with DEATDA, and it is preferable that it is 1 to 30%.

  Specific examples of such low activity amine compounds having a lower reactivity with isocyanate groups than DEATDA include, for example, 4,4′-methylenebis (2-chloroaniline), dimethylthiotoluenediamine, 4,4′-methylenebis. (3-chloro-2,6-diethylaniline), N, N′-di-secondary-butyl-para-phenylenediamine, 4,4′-bis (secondary-butylamino) diphenylmethane, 4,4′-bis ( Methylamino) diphenylmethane, trimethylene-bis (4-aminobenzoate), polytetramethylene oxide-di-p-aminobenzoate, N-phenyl-N′-isopropyl-p-phenylenediamine, N-phenyl-N ′-(1 , 3-dimethylbutyl) -p-phenylenediamine and the like. In addition, said compound may be used independently and may use 2 or more types together.

  Among these, at least one selected from 4,4′-methylenebis (2-chloroaniline), dimethylthiotoluenediamine, and polytetramethylene oxide-di-p-aminobenzoate is more preferable. 4′-methylenebis (2-chloroaniline) is particularly preferred.

  The curing agent may contain a polyol in addition to the diethyltoluenediamine and the low activity amine compound.

  As the polyol, a polyol which is a raw material of the isocyanate group-terminated urethane prepolymer used in the above-mentioned main agent can be used, but a polyoxypropylene polyol having a hydroxyl number of 2 to 4 and a hydroxyl value of 10 to 112 mgKOH / g is preferable.

  If the number of hydroxyl groups is less than 2, it is difficult to increase the molecular weight of the cured product, resulting in poor curability and insufficient mechanical strength of the cured coating film. If the number of hydroxyl groups exceeds 4, the crosslink density becomes too high and the cured coating is cured. The elongation performance of the film deteriorates. Further, when the hydroxyl value is less than 10 mgKOH / g, the viscosity of the polyol becomes too high, and when it exceeds 112 mgKOH / g, the molecular weight is small, so the blending amount in the curing agent decreases, and as a substitute, the use amount of the plasticizer increases. Therefore, it is not preferable. By blending the polyol, the content of the active hydrogen-containing group of the curing agent can be adjusted according to the isocyanate group content of the main agent, and a cured film with high elongation and high elasticity can be obtained.

  Moreover, it is preferable that the viscosity of a hardening | curing agent is 300-2500 mPa * s at 20 degreeC, More preferably, it is 300-1000 mPa * s.

  The content of each of the above components in the curing agent is such that the ratio of the active hydrogen-containing groups of DETDA and the low activity amine compound to the total active hydrogen-containing groups in the curing agent is 40 to 94 mol% and 1 to 20 respectively. It is made to contain so that it may become mol%.

  If the content of DETDA is less than 40 mol%, the curability is lowered, and a high-strength cured coating film cannot be obtained. This is not preferable because free amino groups do not remain on the surface of the coating film, and the adhesiveness with the top coat to be overcoated becomes insufficient.

  In addition, if the content of the low-activity amine compound is less than 1 mol%, almost no free amino groups remain on the surface of the cured coating film, so that the adhesion with the top coat to be overcoated becomes insufficient. It is not preferable, and if it exceeds 20 mol%, the curability tends to be insufficient, and it becomes difficult to obtain a cured coating film having sufficient mechanical strength.

  Moreover, when using a polyol together in a hardening | curing agent, it is preferable to make it contain so that the ratio of the active hydrogen containing group of a polyol with respect to all the active hydrogen containing groups in a hardening | curing agent may be 5-50 mol%. If the polyol content is less than 5 mol%, the viscosity of the curing agent tends to increase and the workability tends to decrease, which is not preferred. If it exceeds 50 mol%, the curability tends to be insufficient, and sufficient machinery is required. Since it becomes difficult to obtain a strong cured coating film, it is not preferable.

  In addition, it is preferable that the curing agent contains a curing catalyst. As the curing catalyst, a known catalyst that accelerates the urea / urethanization reaction can be used, and examples thereof include organic acid lead, organic acid tin, and tertiary amine compounds. Of these, lead 2-ethylhexanoate is preferably used. The addition amount of the curing catalyst is preferably 0.05 to 1.0% by mass relative to the total amount (mass) of the main agent and the curing agent.

  The polyurethane composition used in the present invention may contain additives such as pigments, plasticizers and stabilizers in addition to the above basic components.

  Examples of the pigment include inorganic pigments such as chromium oxide and titanium oxide, and organic pigments such as phthalocyanine pigments.

  Examples of the plasticizer include the same plasticizers as those used for the main agent. The plasticizer may be blended in either the main agent or the curing agent. However, in the two-component polyurethane curable composition for spray coating (super-fast curing spray type), the main agent has a particularly high viscosity. It is preferable to add a plasticizer. As described above, it is more preferable not to add a plasticizer.

  Examples of the stabilizer include an antioxidant, an ultraviolet absorber, and a dehydrating agent that are generally used for polyurethane resins.

In the polyurethane cured composition, the molar ratio (NCO / (NH ₂ + OH)) of the isocyanate group in the main agent to the active hydrogen-containing group in the curing agent is preferably 1.0 to 1.3, and 1.1 to 1. 2 is particularly preferred. If the molar ratio is less than 1.0, sufficient mechanical strength of the cured coating film may not be obtained, or tack may remain on the coating film surface. On the other hand, if the molar ratio exceeds 1.3, excess isocyanate groups are liable to foam under the influence of moisture, and the cured coating film tends to become brittle.

  The main agent and the curing agent preferably have substantially the same viscosity, and the difference in viscosity between the main agent and the curing agent at 20 ° C. is preferably 500 mPa · s. Moreover, it is preferable to heat and mix said main ingredient and hardening | curing agent at 30-90 degreeC. By heating, the viscosity of the main agent and the curing agent can be further reduced.

  The polyurethane curable composition is spray-coated to form an underlayer. The thickness of the underlayer is not particularly limited, but is preferably 1 to 3 mm.

  For spray coating, a conventionally known spray gun can be used, but it is more preferable to use a collision mixing type spray device. Here, the impingement mixing spraying device is a device used for ultrafast curing spray coating, which can be molded at high speed by colliding and mixing polyurethane raw materials having two or more components at a high pressure in a low viscosity state.

  Examples of such collision mixing and spraying devices include “H-2000”, “H-3500”, “FF-1600” (trade name) manufactured by Gasmer, and two-component high-pressure discharge mixing manufactured by Toho Machine Industry Co., Ltd. Examples of the machine include “MODEL HF-100” (trade name). Examples of spray guns include "GX-7 Gun" and "GX-7-400" (trade names) manufactured by Gasmer, and "Probler Gun" (trade names) manufactured by Glasscraft. It is done.

  Next, in the present invention, a topcoat layer is formed on the surface of the underlayer. This can improve the weather resistance, abrasion resistance, aesthetics of the finished surface, and the like of the coating film. In the present invention, since DETDA and a low activity amine compound are used in combination as a curing agent for the underlayer, there are unreacted free amino groups on the surface of the cured coating film of the underlayer. A polyurethane-based coating film having excellent adhesion to the top coat layer can be obtained.

  Although it does not specifically limit as a topcoat layer, It is preferable that it is a topcoat layer which consists of acrylic-urethane type resin and / or fluorine-urethane type resin. As a result, the isocyanate component of the urethane material in the topcoat layer to be overcoated chemically bonds with the free amino group of the underlayer, so that stronger adhesiveness can be obtained. In particular, when long-term weather resistance is required, a fluorine-urethane resin alone or a mixture of an acrylic-urethane resin and a fluorine-urethane resin is preferable. Further, the top coat layer may be a solvent system or an aqueous system.

  As the acrylic-urethane resin, a one-component type that is a mixture of a urethane resin and an acrylic resin, or a two-component type composed of a main agent mainly composed of an isocyanate group-terminated urethane prepolymer and a curing agent containing an acrylic polyol. Although it can be used, a two-component type is more preferable from the viewpoint of film forming properties and mechanical properties of a cured coating film.

  Examples of the isocyanate group-terminated urethane prepolymer in the acrylic-urethane resin include polyether polyols such as polyoxypropylene polyol and polyoxytetramethylene diol; polyols such as polyester polyols such as adipate and lactone; Those obtained by reaction with a polyisocyanate having no aromatic ring such as hexamethylene diisocyanate and isophorone diisocyanate are preferred. In this case, the main agent may be diluted with a viscosity reducing agent such as propylene glycol monomethyl ether acetate.

  As the acrylic polyol, an acrylic monomer having no hydroxyl group such as (meth) acrylic acid or (meth) acrylic acid alkyl ester, and an acrylic monomer having a hydroxyl group such as 2-hydroxyethyl (meth) acrylate, and Those obtained by optionally polymerizing other ethylenically unsaturated monomers are preferred. The curing agent may contain a pigment, a filler, a catalyst, various stabilizers, and the like.

  On the other hand, the fluorine-urethane resin is preferably composed of a main component mainly composed of the same isocyanate group-terminated prepolymer as described above and a curing agent containing a fluorine-containing polyol.

  As the fluorine-containing polyol, those obtained by polymerizing an ethylenically unsaturated monomer having a fluoroolefin and a hydroxyl group and optionally other ethylenically unsaturated monomers are preferable.

  Examples of the fluoroolefin include tetrafluoroethylene (TFE), chlorotrifluoroethylene (CTFE), hexafluoropropylene, perfluoropropyl vinyl ether, and the like. The said fluoro olefin may use only 1 type and may mix and use 2 or more types.

  Examples of the ethylenically unsaturated monomer having a hydroxyl group include hydroxyalkyl vinyl ethers such as hydroxybutyl vinyl ether (HBVE) and hydroxyethyl vinyl ether; hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate. And the like; hydroxyalkyl allyl ethers such as hydroxyethyl allyl ether; allyl alcohol; hydroxyalkyl isopropenyl ethers such as hydroxybutyl isopropenyl ether.

  On the other hand, other ethylenically unsaturated monomers are not particularly limited, and vinyl esters, vinyl ethers, isopropenyl ethers, allyl ethers, olefins, etc. can be used, but they are soluble in solvents. From the viewpoints of coating film hardness control and weather resistance, and from the viewpoints of alternating copolymerization and polymerization yield, vinyl ethers are preferred. Specific examples of vinyl ethers include alkyl vinyl ethers having an alkyl group / cycloalkyl group having about 2 to 8 carbon atoms such as ethyl vinyl ether (EVE), butyl vinyl ether (BVE), cyclohexyl vinyl ether (CHVE), and the like. And cycloalkyl vinyl ethers.

  The formation method of a topcoat layer is not specifically limited, The general methods, such as a roller, a brush, a trowel, a rake, etc. which are conventionally well-known coating methods are employ | adopted.

  The polyurethane coating film applied by the above method can form a topcoat layer with high adhesion to the undercoat layer, and can improve the weather resistance, abrasion resistance, aesthetics of the finished surface, etc. It is suitable for applications such as flooring and anticorrosion. The construction site is not particularly limited, but for example, waterproofing material for concrete roofs and metal roofs, open corridors, stairs, stadium stands, factory floors, parking lot floors, sewage treatment plants and pools, underground civil engineering It can be suitably used for waterproofing materials.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.
After adjusting the polyurethane type hardening composition of Examples 1-3 and Comparative Examples 1-3 by the following procedures, the coating film was formed by spray coating.

  The spray coating uses a high-pressure spray machine (trade name “H-2000”, manufactured by Gasmer) as a molding machine, and a probler gun (trade name, manufactured by Glass Craft) as a spray gun. Each was heated to 50 ° C., mixed at a volume ratio of 1: 1, and sprayed to a thickness of 2 mm.

Example 1
44.5 parts by mass of polyoxypropylene diol having a molecular weight of 3,000, 15 parts by mass of dioctyl phthalate, 37 parts by mass of MDI, and 3.5 parts by mass of carbodiimide-modified MDI (NCO / OH ratio = 10.8) And a prepolymer having an NCO group content of 12.2% by mass and a viscosity of 800 mPa · s was obtained as a main agent.

  14 parts by mass of DETDA (trade name: Etacure 100: manufactured by Albemarle Corporation), 83 parts by mass of polyoxypropylene diol having a molecular weight of 2000, and 3 parts by mass of 4,4′-methylenebis (2-chloroaniline) are melt mixed. Furthermore, 0.5 parts by mass of lead 2-ethylhexanoate (lead content: 24% by mass) was mixed as a curing catalyst to obtain a curing agent having a viscosity of 550 mPa · s (20 ° C.).

After forming the base layer by spraying the above-mentioned main agent and curing agent at a main agent / curing agent volume ratio = 1/1 (NCO / (NH ₂ + OH) equivalent ratio = 1.10), 1, 4 24 hours later, an aqueous two-component acrylic-urethane topcoat (trade name: Saraseine TW, manufactured by Asahi Glass Polyurethane Building Materials Co., Ltd.) was applied (coating amount 0.2 kg / m ² ) to form a topcoat layer. A polyurethane-based coating film of Example 1 was obtained.

Example 2
The same prepolymer as in Example 1 was used as the main agent.

  14 parts by mass of DETDA, 83 parts by mass of polyoxypropylene diol having a molecular weight of 2000, 3 parts by mass of dimethylthiotoluenediamine (trade name: Etacure 300: manufactured by Albemarle Corporation) are mixed, and lead 2-ethylhexanoate as a curing catalyst. (Lead content 24 mass%) 0.5 mass part was mixed and the viscosity of 500 mPa * s (20 degreeC) was obtained.

After forming the base layer by spraying the above-mentioned main agent and curing agent at a main agent / curing agent volume ratio = 1/1 (NCO / (NH ₂ + OH) equivalent ratio = about 1.08), Example 1 A topcoat layer was formed in the same manner as described above to obtain the polyurethane-based coating film of Example 2.

Example 3
The same prepolymer as in Example 1 was used as the main agent.

  14 parts by mass of DETDA, 83 parts by mass of polyoxypropylene diol having a molecular weight of 2000, and 3 parts by mass of polytetramethylene oxide-di-p-aminobenzoate (trade name: Elastomer 250P: manufactured by Ihara Chemical Co., Ltd.) are melt-mixed and 2 as a curing catalyst. -0.5 part by mass of lead ethylhexanoate (lead content 24 mass%) was mixed to obtain a curing agent having a viscosity of 500 mPa · s (20 ° C).

After forming the base layer by spraying the main agent and the curing agent at a volume ratio of main agent / curing agent = 1/1 (NCO / (NH ₂ + OH) equivalent ratio = 1.15), Example 1 A topcoat layer was formed in the same manner as in Example 3 to obtain a polyurethane-based coating film of Example 3.

Comparative Example 1
The same prepolymer as in Example 1 was used as the main agent.

  14 parts by mass of DETDA and 86 parts by mass of polyoxypropylene diol having a molecular weight of 2000 are mixed, 0.5 parts by mass of lead 2-ethylhexanoate (lead content: 24% by mass) is mixed as a curing catalyst, and the viscosity is 500 mPa · s (20 C.) curing agent was obtained.

After forming the base layer by spraying the above-mentioned main agent and curing agent at a main agent / curing agent volume ratio = 1/1 (NCO / (NH ₂ + OH) equivalent ratio = 1.19), Example 1 A top coat layer was formed in the same manner as above to obtain a polyurethane-based coating film of Comparative Example 1.

Comparative Example 2
The same prepolymer as in Example 1 was used as the main agent.

  20 parts by mass of DETDA and 80 parts by mass of polyoxypropylene diol having a molecular weight of 2000 are mixed, 0.5 parts by mass of lead 2-ethylhexanoate (lead content: 24% by mass) is mixed as a curing catalyst, and the viscosity is 500 mPa · s (20 C.) curing agent was obtained.

After forming the base layer by spraying the above-mentioned main agent and curing agent at a main agent / curing agent volume ratio = 1/1 (NCO / (NH ₂ + OH) equivalent ratio = about 0.95), Example 1 A topcoat layer was formed in the same manner as described above to obtain a polyurethane-based coating film of Comparative Example 2.

Comparative Example 3
The same prepolymer as in Example 1 was used as the main agent.

  11 parts by mass of DETDA, 80 parts by mass of polyoxypropylene diol having a molecular weight of 2000, and 9 parts by mass of 4,4′-methylenebis (2-chloroaniline) are melt-mixed and lead as a curing catalyst is 2-ethylhexanoate (lead content: 24 masses). %) 0.5 part by mass was mixed to obtain a curing agent having a viscosity of 700 mPa · s (20 ° C.).

After forming the base layer by spraying the main agent and the curing agent at a volume ratio of main agent / curing agent = 1/1 (NCO / (NH ₂ + OH) equivalent ratio = about 1.07), Example 1 A topcoat layer was formed in the same manner as described above to obtain a polyurethane-based coating film of Comparative Example 3.

The above Examples 1 to 3, the proportion of active hydrogen-containing group of the curing agent component when in Comparative Examples 1 to 3, and the total active hydrogen-containing group in the curing agent of the base layer is 100 (NH ₂ , OH molar ratio (%)) are shown in Table 1.

Test Example The performance as a waterproof coating material was evaluated by the following method for the foundation layer and the polyurethane-based coating film in Examples 1 to 3 and Comparative Examples 1 to 3. The results are shown in Table 2.

<Curing property of underlayer>
In a 23 ° C., 50% RH laboratory, each polyurethane-based cured composition was sprayed and applied at a coating amount of about 2 kg / m ² on a releasable polyethylene sheet plate to form a base layer, and after 2 hours (Confirmation of rubber formation by bending 180 degrees and Shore A hardness measurement) were compared.

<Physical properties of the underlying layer>
A base layer was formed by spraying on a releasable polyethylene sheet plate, and after 7 days of curing, mechanical properties of the base layer were measured according to JIS-A6021. In the table, Ts represents tensile strength (unit: N / mm ² ), and E represents elongation at break (unit:%).

<Topcoat adhesiveness>
After forming the polyurethane-based coating films of Examples 1 to 3 and Comparative Examples 1 to 3, the top coat adhesiveness after 24 hours at 23 ° C. and 50% RH was evaluated. 11 cuts are made vertically and horizontally with a razor on the surface of the top coat to make a grid of 100 squares of 1 mm square, and a cellophane tape is stuck on it, and then pulled vertically at a stretch. It was represented by the number of cells remaining without peeling off the top coat when peeled.

  From the results in Table 2, in the coating films of Examples 1 to 3, by using a small amount of a low activity amine that is less reactive with isocyanate than DETDA, compared to Comparative Examples 1 and 2 that do not use a low activity amine. It can be seen that the adhesion with the top coat is improved.

  In Comparative Example 2, an attempt was made to liberate amino groups by setting the isocyanate group equivalent ratio of the main agent to 0.95, but no improvement in adhesion with the top coat was observed. This is presumably because the equivalent ratio of amino groups of DETDA is less than the isocyanate group of the main agent because polyol is used in combination, and therefore there is no unreacted free amino group in the cured coating film. .

  In Comparative Example 3, since the blending amount of 4,4′-methylenebis (2-chloroaniline), which is a low activity amine, is not less than the specified range of the present invention, curability is remarkably lowered and sufficient mechanical strength is obtained. Was not expressed.

Since the polyurethane-based curable composition of the present invention is excellent in curability, mechanical strength, and adhesiveness with a top coat to be overcoated, it is suitable for waterproofing construction of a coating film that is sprayed and cured on an object such as a concrete frame or a steel plate. Used.

Claims (6)

Spray coating a polyurethane curable composition formed by mixing a curing agent containing diethyltoluenediamine, a low activity amine compound having a lower reactivity with isocyanate groups than the diethyltoluenediamine, and a main component containing a polyisocyanate compound. And a method of applying a polyurethane-based coating film comprising a step of reacting and curing the polyurethane curable composition to form an undercoat layer, and a step of forming a topcoat layer on the surface of the undercoat layer,
The ratio of active hydrogen-containing groups of the diethyltoluenediamine is 40 to 94 mol%, and the ratio of active hydrogen-containing groups of the low-activity amine compound is 1 to 20 mol with respect to all active hydrogen-containing groups in the curing agent. %. A method for applying a polyurethane-based coating film, which comprises adding the diethyltoluenediamine and the low-activity amine compound so that the ratio is%.   A polyol is further contained in the curing agent, and the polyol is contained so that a ratio of the active hydrogen-containing group of the polyol is 5 to 50 mol% with respect to all active hydrogen-containing groups in the curing agent. Item 2. A method for applying a polyurethane-based coating film according to Item 1.   The low-activity amine compound is at least one selected from 4,4'-methylenebis (2-chloroaniline), dimethylthiotoluenediamine, and polytetramethylene oxide-di-p-aminobenzoate. The construction method of the polyurethane-type coating film of 2.   The method for applying a polyurethane-based coating film according to any one of claims 1 to 3, wherein the topcoat layer is a topcoat layer made of an acrylic-urethane resin and / or a fluorine-urethane resin.   The polyurethane according to any one of claims 1 to 4, wherein the polyisocyanate compound is an isocyanate group-terminated urethane prepolymer obtained by reacting a diphenylmethane diisocyanate compound and / or a polyol with a low molecular weight polyisocyanate compound. How to apply a paint film. The construction method of the polyurethane-type coating film as described in any one of Claims 1-5 which performs the said spray coating using a collision mixing type spraying apparatus.