Aqueous sealant composition and screwing member using same

Abstract

[Problem] Because a high temperature of 200°C or higher is applied when baking a polyamide powder onto a screwing member, it was difficult in the past to change additives in an aqueous sealant composition to prevent the color of a coating film from changing from the color of the composition before heating. [Solution] An aqueous sealant composition containing components (A)-(E): (A) a polyamide powder; (B) an epoxy resin; (C) water; (D) a rust inhibitor; and (E) a colorant, the aqueous sealant composition being such that component (D) contains at least one selected from the group consisting of inorganic acid salts, organic acid salts (excluding organic acid amine salts), and nitrogen-containing condensed ring compounds, and / or appears white after being heated for 20 minutes in a 200°C atmosphere.

Description

Aqueous sealant composition and screw fastening member using the same

[0001] This invention relates to an aqueous sealant composition and a screw-fastening member using the same.

[0002] Aqueous sealant compositions containing polyamide powder, such as that described in Patent Document 1, can form a coating film when applied to the threaded portion of a screw-fastened member, such as a bolt, and then dried. This coating film is known to have an anti-loosening effect. The "threaded portion" refers to, for example, the part of the shaft of a bolt or screw where a helical thread (male thread) is formed by machining, that is, the part that actually engages with a nut or the like to fasten it.

[0003] Japanese Patent Publication No. 2017-110100

[0004] There are a great many types of screw fastening components, and in the field, the color tone of the sealant coating is sometimes used as a clue to identify and manage the different types. However, the aqueous sealant composition described in Patent Document 1 does not contain a coloring agent. Therefore, we attempted to add a coloring agent to an aqueous sealant composition containing polyamide powder, as disclosed in Patent Document 1.

[0005] However, the inventors have discovered a problem in that when the screw-fastened member undergoes a baking process with polyamide powder (for example, at 200°C or above 200°C), the rust inhibitor undergoes thermal degradation, causing a change in the color tone of the coating. If the color tone differs before and after baking, the appearance will not match that of conventional products of the same type (even though they do not contain rust inhibitors), which could lead to mix-ups of parts and significantly reduce production efficiency.

[0006] Therefore, the object of the present invention is to provide an aqueous sealant composition that contains a rust inhibitor but does not discolor after baking.

[0007] As a result of diligent research to achieve the above objective, the inventors discovered a method to suppress changes in the color of the coating film, and thus completed the present invention.

[0008] The gist of the present invention is described below. The first embodiment of the present invention is an aqueous sealant composition comprising components (A) to (E).

[0009] (A) Ingredients: Polyamide powder (B) Ingredients: Water-dispersible epoxy resin (C) Ingredients: Water (D) Ingredients: Rust inhibitor that appears white after heating at 200°C for 20 minutes (E) Ingredients: Coloring agent.

[0010] A second embodiment of the present invention is an aqueous sealant composition according to the first embodiment, wherein component (D) is a solid at 25°C after heating in a 200°C atmosphere for 20 minutes, and is a rust inhibitor other than an organic acid amine salt.

[0011] A third embodiment of the present invention is an aqueous sealant composition according to the first embodiment, wherein component (D) is a rust inhibitor selected from the group consisting of inorganic salts, organic salts, sodium benzoate, and benzotriazole, and is solid at 25°C after heating in a 200°C atmosphere for 20 minutes.

[0012] A fourth embodiment of the present invention is an aqueous sealant composition according to the first embodiment, wherein component (B) is a water-dispersible epoxy resin containing a cresol novolac structure.

[0013] A fifth embodiment of the present invention is an aqueous sealant composition according to the first embodiment, wherein component (E) is an inorganic pigment.

[0014] A sixth embodiment of the present invention is the aqueous sealant composition according to the first embodiment, wherein the appearance of component (E) is green.

[0015] A seventh embodiment of the present invention is an aqueous sealant composition according to the first embodiment, further comprising an antifoaming agent as component (F).

[0016] The eighth embodiment of the present invention is the aqueous sealant composition described in the first embodiment, which does not include the curing agent of component (B).

[0017] The ninth embodiment of the present invention is a screw-fastened member obtained by applying the aqueous sealant composition described in the first embodiment to the screw portion and then heating and baking it.

[0018] The tenth embodiment of the present invention is a method for preventing loosening by screwing in a screw member as described in the ninth embodiment.

[0019] The present invention can suppress changes in the color of the coating film from the color of the composition before heating, even when high temperatures (e.g., 200°C or above 200°C) are applied when baking the aqueous sealant composition onto a screw member. In other words, it can provide an aqueous sealant composition that does not discolor after baking, even though it contains a rust inhibitor.

[0020] The present invention will now be described in detail. In this specification, "X to Y" is used to mean "X or more and Y or less," including the numerical values ​​(X and Y) described before and after it as the lower and upper limits, respectively. When multiple instances of "X to Y" or "X or more and Y or less" are described, for example, when "X1 to Y1, or X2 to Y2" is described, the disclosure of each numerical value as the upper limit, the disclosure of each numerical value as the lower limit, and all combinations of these upper and lower limits are disclosed (i.e., this provides a lawful basis for amendments). Specifically, amendments to X1 or more, amendments to Y2 or less, amendments to X1 or less, amendments to Y2 or more, amendments to X1 to X2, amendments to X1 to Y2, etc., must all be considered lawful. Unless otherwise specified, two or more components constituting a composition may be included in the composition, and the explanation of the amount used, the amount added, etc., may mean the total amount when two or more are combined. Furthermore, where this disclosure is described in terms of the Markush group, a person skilled in the art will recognize that this disclosure is described in terms of any individual component or subgroup of components of the Markush group. Also, unless otherwise specified, operations and measurements of physical properties, etc., are performed under room temperature (20-25°C) / relative humidity 40-55% RH conditions.

[0021] The aqueous sealant composition of the present invention will be described in detail below.

[0022] According to one embodiment of the present invention, an aqueous sealant composition is provided comprising the following components (A) to (E): (A) component: polyamide powder, (B) component: water-dispersible epoxy resin, (C) component: water, (D) component: rust inhibitor, (E) component: colorant, wherein component (D) comprises at least one selected from the group consisting of inorganic salts, organic salts excluding organic acid amine salts, and nitrogen-containing fused ring compounds, and / or having a white appearance after heating for 20 minutes in a 200°C atmosphere. The aqueous sealant composition of the present invention contains a rust inhibitor, yet discoloration after baking is suppressed. Hereinafter, the aqueous sealant composition may also be simply referred to as the composition. Component (A) that can be used in the present invention is polyamide powder. Component (A) melts upon heating to form a coating film. According to one embodiment of the present invention, component (A) can be an aliphatic polyamide obtained by condensation polymerization of an aliphatic diamine and an aliphatic dicarboxylic acid, an ω-aminocarboxylic acid, or lactams thereof, and a copolymerized polyamide obtained by copolymerizing an aromatic dicarboxylic acid or aromatic diamine with the aliphatic polyamide as the main chain component. According to one embodiment of the present invention, component (A) can be an aliphatic polyamide in which the number of carbon atoms between amide bonds (including carbonyl carbons) is 8 to 13, 9 to 12, 10 to 11, or 11. By using an aliphatic polyamide (particularly 11-nylon) in which the number of carbon atoms between amide bonds (including carbonyl carbons) is 11 in particular, the intended effects of the present invention can be efficiently achieved. Specific examples of component (A) include polyamides selected from polyamides such as 6-nylon, 6,6-nylon, 6,10-nylon, 7-nylon, 8-nylon, 9-nylon, 11-nylon, 12-nylon, hexamethylenediamine / adipic acid and caprolactam copolymer, and caprolactam / hexamethylenediamine and terephthalic acid copolymer, and copolymers thereof. In particular, 11-nylon, 12-nylon, or copolymers thereof are preferred for component (A). Furthermore, component (A) may be a mixture of multiple types of polyamide powders with different average particle sizes, and different types of polyamide powders, such as 11-nylon and 12-nylon, may be used in combination.

[0023] (A) Examples of commercially available products of component (A) include, but are not limited to, Arkema's Lilsan D-40 (11-nylon, average particle size 40 μm), Toray Industries' SP-500 (12-nylon, average particle size 5 μm) and SP-10 (12-nylon, average particle size 10 μm), and Evonik's VESTOSINT series (12-nylon) 2159 (average particle size 11 μm), 2161 (average particle size 28 μm), 2162 (average particle size 45 μm), and 2179 (average particle size 11 μm).

[0024] The average particle size of component (A) is preferably in the range of 0.5 to 500 μm, or 1 to 500 μm, and more preferably 5 to 300 μm. According to one embodiment of the present invention, the average particle size of component (A) is 10 to 100 μm, 15 to 80 μm, 20 to 60 μm, or 25 to 55 μm. If the average particle size is 1 μm or more, a uniform coating film can be formed without repulsion on the surface of the adherend during heat fusion. If the average particle size is 500 μm or less, it can follow the surface irregularities of the screw portion and form a uniform coating film. Any method can be selected for measuring the average particle size, but first, the approximate particle size is confirmed using an optical microscope, and if the median (approximate) is determined to be less than 1 μm, the average particle size is determined by image analysis using a scanning electron microscope (SEM). In SEM image analysis, the area equivalent circle diameter is measured for at least 10 particles (especially 100 particles) randomly selected from different fields of view, and the arithmetic mean is taken as the average particle size. If it is determined to be 1 μm or larger, it is measured using a laser diffraction particle size analyzer. Here, in laser diffraction particle size distribution measurement, the particle size at which the cumulative volume distribution is 50% (D50) is called the 50% average particle size.

[0025] According to one embodiment of the present invention, in component (A), the proportion of aliphatic polyamides in which the number of carbon atoms between amide bonds (including carbonyl carbons) is 8 to 13, 9 to 12, 10 to 11, or 11 is 85% by mass or more, 90% by mass or more, 95% by mass or more, 99% by mass or more, 99.5% by mass or more, 99.8% by mass or more, or 99.9% by mass or more (upper limit is 100% by mass).

[0026] The component (B) that can be used in the present invention is an epoxy resin. Here, component (B) refers to the epoxy resin itself, which is a solid component that does not contain a dispersion medium such as water, which is component (C) described later. However, this resin solid component may also be used in an emulsion or dispersion form by emulsifying or dispersing it in a dispersion medium (e.g., water). The water-dispersible epoxy resin used in one embodiment of the present invention is an epoxy resin that is substantially insoluble in water (preferably with a solubility in water at 25°C of 100 ppm by weight or less), and has the property of floating or suspending in water. Component (B) is preferably a solid at a 25°C atmosphere. By adding component (B) to the aqueous sealant composition, the adhesion to metal adherends in particular and its durability are improved, and good performance can be maintained even after repeated screwing and detaching.

[0027] Component (B) is not particularly restricted as long as it is a material having one or more epoxy groups in its molecule, and known materials can be used. Examples include bisphenol A type epoxy resin, bisphenol F type epoxy resin, halogenated bisphenol A type epoxy resin, phenol novolac type epoxy resin, cresol novolac type polyfunctional epoxy resin, polyalkylene oxide type epoxy resin, and telechelic alkylene type epoxy resin. In the present invention, cresol novolac type epoxy resin is particularly preferred because it has high adhesion to the adherend and is less likely to fall off during screw fastening. These epoxy resins may be used alone or in combination of two or more types. Component (B) used in the present invention is preferably an emulsion type or dispersion type epoxy resin, more preferably an emulsion type or dispersion type novolac type epoxy resin. Novolac type epoxy resins are typically obtained by condensing a phenol novolac resin or a cresol novolac resin with epichlorohydrin, with phenol novolac type and cresol novolac type being representative examples. According to one embodiment of the present invention, component (B) is a water-dispersible epoxy resin containing a cresol novolac structure. Component (B) is preferably an emulsion-type or dispersion-type cresol novolac epoxy resin. Such an aqueous dispersion of epoxy resin may be a commercially available product, or it may be prepared by dispersing and emulsifying a desired epoxy resin in water using a disperser or the like. The dispersion and emulsification method is not particularly limited, and known dispersion and emulsification methods such as high-pressure emulsification and phase inversion emulsification can be employed.

[0028] (B) Examples of commercially available products of component (B) include Mitsubishi Chemical Corporation's jER series, such as W2821R70 (bisphenol A type epoxy resin emulsion, solids content approximately 70%, epoxy equivalent approximately 230), W3435R67 (bisphenol A type epoxy resin emulsion, solids content approximately 67%, epoxy equivalent approximately 275), W8735R70 (bisphenol F type epoxy resin emulsion, solids content approximately 70%, epoxy equivalent approximately 200), and W1155R55 (bisphenol A type epoxy resin emulsion, solids content approximately 55%, epoxy equivalent approximately 560), as well as Yukareji from Yoshimura Oil Chemical Co., Ltd. Examples of the 'n' series include KE-002, KE-116, E-1022, and KE-301C. Other examples include Aqua Tote 5003 (novolac-type solid epoxy resin emulsion) from Nippon Steel Chemical & Material Co., Ltd., and EM-0517, EM-0526, EM-11-50B, EM-051R, and EM-101 from ADEKA Corporation's ADEKA Resin series. Examples of other examples include Denacol EM-160 (cresol novolac-type epoxy resin emulsion, solid content approximately 50%, epoxy equivalent approximately 450) from Nagase ChemteX Corporation, but these are not the only examples.

[0029] According to one embodiment of the present invention, the epoxy equivalent of component (B) is 350 to 550 g / eq, or 400 to 500 g / eq. The epoxy equivalent of the epoxy resin can be determined in accordance with JIS K7236:2009.

[0030] In one embodiment of the present invention, when the component (B) is an emulsion-type or dispersion-type epoxy resin, the solid content is 35% by mass or more, 40% by mass or more, or 45% by mass or more. In one embodiment of the present invention, when the component (B) is an emulsion-type or dispersion-type epoxy resin, the solid content is 75% by mass or less, 70% by mass or less, 65% by mass or less, 60% by mass or less, or 55% by mass or less. In one embodiment of the present invention, when the component (B) is an emulsion-type or dispersion-type epoxy resin, the solid content is 35% by mass or more and 75% by mass or less, 40% by mass or more and 65% by mass or less, or 45% by mass or more and 65% by mass or less. The solid content can be determined in accordance with JIS K5601-1-2:2008.

[0031] With respect to 100 parts by mass of the component (A), the content of the component (B) is in the range of 1 to 25 parts by mass, more preferably 2 to 20 parts by mass, and still more preferably 5 to 15 parts by mass. In one embodiment of the present invention, with respect to 100 parts by mass of the component (A), the content of the component (B) is 5.2 to 10 parts by mass, 5.4 to 9 parts by mass, 5.6 to 8 parts by mass, or 5.8 to 7.5 parts by mass. When the addition amount of the component (B) is 1 part by mass or more with respect to 100 parts by mass of the component (A), the film-forming ability becomes sufficient and a smooth coating film can be formed. When the addition amount of the component (B) is 25 parts by mass or less with respect to 100 parts by mass of the component (A), the volatility of the component (C) described below is maintained, and a smooth coating film can be formed following the unevenness of the substrate.

[0032] According to one embodiment of the present invention, in the component (B), the ratio of the water-dispersible epoxy resin containing a cresol novolac structure is 85% by mass or more, 90% by mass or more, 95% by mass or more, 99% by mass or more, 99.5% by mass or more, 99.8% by mass or more, or 99.9% by mass or more (the upper limit is 100% by mass).

[0033] In the aqueous sealant composition, it is preferable not to add a curing agent such as an amine compound, an acid anhydride, a thiol compound, or an isocyanate compound that has the ability to crosslink the component (B). Here, the curing agent refers to a compound or a combination thereof that has an action of chemically reacting with the epoxy group of the component (B) to form a crosslinked bond and chemically curing the composition, and both components that are not compatible with water and components that are compatible with water are known. Since the curing agent decomposes the component (A) during heating, there is a risk of deteriorating the coating film. On the other hand, since the amide bond of the component (A) is activated by heating and the component acts as a crosslinking component for the epoxy group of the component (B), it is preferable not to add a curing agent separately. According to one embodiment of the present invention, the aqueous sealant composition substantially does not contain at least one selected from the group consisting of an amine compound, an acid anhydride, a thiol compound, and an isocyanate compound that has the ability to crosslink the component (B). According to one embodiment of the present invention, the aqueous sealant composition substantially does not contain any of an amine compound, an acid anhydride, a thiol compound, and an isocyanate compound that has the ability to crosslink the component (B). Here, being substantially free means that the aqueous sealant composition contains none of these components (below the detection limit), or even if it contains them, it is 100 mass ppm or less in the composition.

[0034] The component (C) that can be used in the present invention is water. Water acts as a dispersion medium for keeping the component (A) and / or the component (B) in a dispersed state. The type of water is not particularly limited, and any water such as ion-exchanged water, tap water, alkaline electrolyzed water, etc. can be used.

[0035] It is preferable that component (C) is added in an amount of 50 to 250 parts by mass per 100 parts by mass of component (A), and more preferably 100 to 200 parts by mass. According to one embodiment of the present invention, the content of component (C) is 120 to 195 parts by mass, 130 to 190 parts by mass, 140 to 185 parts by mass, 150 to 180 parts by mass, 155 to 175 parts by mass, or 156 to 170 parts by mass per 100 parts by mass of component (A). If the content of component (C) is 50 parts by mass or more per 100 parts by mass of component (A), the workability of applying it to the screw fastener is good, and a smooth coating film can be formed. If the content of component (C) is 250 parts by mass or less per 100 parts by mass of component (A), the dispersion of component (A) and component (B) is stably maintained without aggregation or sedimentation. Here, the mass of component (C) is calculated including water that may be contained in component (B) and component (E) described later.

[0036] According to one embodiment of the present invention, component (D) comprises at least one selected from the group consisting of inorganic acid salts, organic acid salts excluding organic acid amine salts, and nitrogen-containing fused ring compounds. According to one embodiment of the present invention, component (D) is a rust inhibitor whose appearance is white after heating for 20 minutes in a 200°C atmosphere. Although high temperatures of 200°C or higher are applied in the process of baking polyamide powder onto the screw-fastened member, by employing component (D) of the present invention, it is possible to suppress changes in the color tone of the coating film from the composition before heating.

[0037] The determination of "white" may be done by visual inspection, but the L specified in JIS Z 8781-4:2013 may also be used. ＊ a ＊ b ＊ This can be done by determining whether the lightness (L value) of the color system is 80 or higher (preferably 90 or higher). In this specification, the L value can be calculated from the spectral reflectance obtained using a Konica Minolta CM-M6 spectrophotometer or a model with equivalent or better performance, at an illumination angle of 45° / receiving angle of 25° and a 10° field of view.

[0038] To measure the whiteness after heating, apply component (D) to the substrate so that it is dry to a thickness (e.g., approximately 30 μm or more) that is not affected by the substrate color, heat in a 200°C atmosphere for 20 minutes, and then measure under the above measurement conditions. ＊ Measure the value.

[0039] According to one embodiment of the present invention, the component (D) is preferably a rust inhibitor whose appearance property after heating at 200°C for 20 minutes in an atmosphere is solid at 25°C. In one embodiment of the present invention, the component (D) is preferably a rust inhibitor other than an organic acid amine salt. In one embodiment of the present invention, the component (D) has a property of being solid at 25°C after heating at 200°C for 20 minutes in an atmosphere, and the rust inhibitor is preferably a rust inhibitor other than an organic acid amine salt. In one embodiment of the present invention, the organic acid salts excluding the organic acid amine salts exclude sodium benzoate.

[0040] According to one embodiment of the present invention, the component (D) is preferably a compound selected from at least one of inorganic acid salts such as inorganic acid amine salts, organic acid salts excluding organic acid amine salts, sodium benzoate, and benzotriazole. According to one embodiment of the present invention, the component (D) has a property of being solid at 25°C after heating at 200°C for 20 minutes in an atmosphere, and is preferably a compound selected from at least one of inorganic acid salts such as inorganic acid amine salts, organic acid salts excluding organic acid amine salts, sodium benzoate, and benzotriazole.

[0041] In one embodiment of the present invention, the organic acid salts excluding the organic acid amine salts are fatty acid salts excluding the organic acid amine salts.

[0042] According to one embodiment of the present invention, as the organic acid of the organic acid salt excluding the organic acid amine salt, the general formula is R-Y － represented by, R represents an aliphatic hydrocarbon group, an aryl group or a heterocyclic group, -Y － represents -SO ２ S, -SO ３ ,, -SO ２ ,, -SSO ３ ,, -COS or -COO. When R is an aliphatic hydrocarbon group, the organic acid salt can be called a fatty acid salt.

[0043] In one embodiment of the present invention, as the salt of the organic acid salt excluding the organic acid amine salt, metal ions (Na ＋ , K ＋ , Ca ２＋ ), and ammonium ions (NH ４ ＋) are some examples.

[0044] According to one embodiment of the present invention, the inorganic acid in the inorganic salt is SO ４ ２－ These are some examples.

[0045] According to one embodiment of the present invention, examples of salts in inorganic salts include amines and the like.

[0046] In one embodiment of the present invention, the nitrogen-containing fused ring compound comprises benzotriazole. In one embodiment of the present invention, component (D) comprises sodium benzoate and benzotriazole.

[0047] In one embodiment of the present invention, the amine of the amine salt can be a quaternary ammonium group, a guanidium group, a heterocyclic quaternary base, an ammonium group, a hydroxylammonium group, or the like, but is not limited to these. Furthermore, component (D) may be used as a raw material in the form of a mixture of components other than component (D).

[0048] (D) Specific examples of component include, but are not limited to, WZ, W-410, AFL, and W-16B from the Kileslight series manufactured by Kilesto Corporation, and AL4 and AL7 from the ASCOTRAN series manufactured by ASCOTEC Corporation.

[0049] In one embodiment of the present invention, a rust inhibitor containing an organic acid salt, rather than an organic acid amine salt, is used as component (D). This suppresses deterioration of the appearance of the coating after baking, limits the occurrence of rust to a very small amount, and further enhances the adhesive strength (tensile shear adhesive strength) of the coating.

[0050] In one embodiment of the present invention, component (D) is used in combination with a rust inhibitor containing an inorganic acid amine salt, a rust inhibitor containing an organic acid salt that is not an organic acid amine salt, and a rust inhibitor containing sodium benzoate and benzotriazole. This suppresses defects in the appearance of the coating film after baking, virtually eliminates rust, and further enhances the adhesive strength (tensile shear adhesive strength) of the coating film.

[0051] In one embodiment of the present invention, when component (D) is a combination of a rust inhibitor containing an inorganic acid amine salt, a rust inhibitor containing an organic acid salt that is not an organic acid amine salt, and a rust inhibitor containing sodium benzoate and benzotriazole, the content ratio of the rust inhibitor containing sodium benzoate and benzotriazole in component (D) is the lowest. This makes it possible to further increase the adhesive strength (tensile shear adhesive strength) of the coating film.

[0052] In one embodiment of the present invention, the ratio of the content of a rust inhibitor containing an inorganic acid amine salt to the content of a rust inhibitor containing sodium benzoate and benzotriazole is 1.1 or more, 1.2 or more, 1.3 or more, 1.4 or more, 1.5 or more, 1.6 or more, or 1.7 or more. In one embodiment of the present invention, the ratio of the content of a rust inhibitor containing an inorganic acid amine salt to the content of a rust inhibitor containing sodium benzoate and benzotriazole is 3 or less, 2.5 or less, or 2 or less. In one embodiment of the present invention, the ratio of the content of a rust inhibitor containing an inorganic acid amine salt to the content of a rust inhibitor containing sodium benzoate and benzotriazole is 1.1 or more and 3 or less, 1.4 or more and 2.5 or less, or 1.5 or more and 2 or less.

[0053] In one embodiment of the present invention, the ratio of the content of a rust inhibitor containing an organic acid salt that is not an organic acid amine salt to the content of a rust inhibitor containing sodium benzoate and benzotriazole is 1.3 or more, 1.5 or more, 1.7 or more, 1.9 or more, 2.1 or more, 2.3 or more, 2.5 or more, or 2.7 or more. In one embodiment of the present invention, the ratio of the content of a rust inhibitor containing an organic acid salt that is not an organic acid amine salt to the content of a rust inhibitor containing sodium benzoate and benzotriazole is 5 or less, 4.5 or less, 4 or less, 3.5 or less, or 3 or less. In one embodiment of the present invention, the ratio of the content of a rust inhibitor containing an organic acid salt that is not an organic acid amine salt to the content of a rust inhibitor containing sodium benzoate and benzotriazole is 1.5 or more and 5 or less, 1.9 or more and 4.5 or less, 2.1 or more and 4 or less, 2.3 or more and 3.5 or less, or 2.5 or more and 3 or less.

[0054] From the viewpoint of suppressing the occurrence of rust, it is preferable to add 1 to 30 parts by mass of component (D) per 100 parts by mass of component (A), and more preferably 2 to 20 parts by mass. According to one embodiment of the present invention, component (D) is blended in an amount of 5 to 19.5 parts by mass, 7 to 19 parts by mass, 9 to 18.5 parts by mass, 11 to 18 parts by mass, 13 to 18 parts by mass, 15 to 18 parts by mass, or 17 to 18 parts by mass per 100 parts by mass of component (A). According to one embodiment of the present invention, the content of component (D) per 100 parts by mass is 18 parts by mass or less, 15 parts by mass or less, 13 parts by mass or less, 10 parts by mass or less, 7 parts by mass or less, 4 parts by mass or less, or 3 parts by mass or less. According to one embodiment of the present invention, the content of component (D) per 100 parts by mass of component (A) is 1 part by mass or more, 2 parts by mass or more, or 2.5 parts by mass or more. According to one embodiment of the present invention, the content of component (D) per 100 parts by mass of component (A) is 1 part by mass or more and 7 parts by mass or less, 1.5 parts by mass or more and 4 parts by mass or less, or 2 parts by mass or more and 3 parts by mass or less. Reducing the amount of component (D) added tends to improve the adhesive strength (tensile shear adhesive strength) of the coating film. As described above, when two or more types of component (D) are used in combination, the calculation is based on the total amount added.

[0055] The component (E) that can be used in the present invention is a colorant. Here, component (E) refers to the colorant itself, which is a solid component that does not contain a dispersion medium such as water, which is component (C). However, this colorant may also be used in the form of a dispersion in which it is contained in a dispersion medium (e.g., water). Component (E) is preferably a solid at a 25°C atmosphere, and is particularly preferably an inorganic pigment. The appearance of component (E) is preferably green. In this specification, the determination of whether it is "green" can be made using the same conditions as for determining "white" (spectral reflectance obtained using a Konica Minolta CM-M6 spectrophotometer at an irradiation angle of 45° / receiving angle of 25°). The measurement can be performed by coating an aqueous dispersion containing component (E) onto a substrate, and the obtained L ＊ a ＊ b ＊ In terms of value, a ＊ The value is -25 or less and b ＊This refers to values ​​that fall within the range of -30 or greater. Component (E) may be added to the aqueous sealant composition in a dispersed state in a dispersion medium such as water.

[0056] Component (E) may include, but is not limited to, at least one selected from the group consisting of titanium dioxide (C.I.Name: PW-6), iron oxide yellow (C.I.Name: PY-42), iron oxide red (C.I.Name: PR-101), composite oxide green (C.I.Name: PG-50), composite oxide blue (C.I.Name: PB-28), carbon black (C.I.Name: PBk-7), and composite oxide black (C.I.Name: PBk-26).

[0057] Examples of component (E) include, but are not limited to, MF-5765 White, MF-5050 Yellow, MF-5160 Brown, MF-5363 Green, MF-5460 Blue, MF-5630 Black, and MF-5533 Black, all manufactured by Dainippon Seika Kogyo Co., Ltd.

[0058] From the viewpoint of achieving a more vivid color, it is preferable to add 0.5 to 10 parts by mass of component (E) to 100 parts by mass of component (A), and more preferably 0.5 to 5.0 parts by mass. According to one embodiment of the present invention, component (E) is blended in an amount of 1 to 8 parts by mass, 1.5 to 7 parts by mass, 2 to 6 parts by mass, 2.5 to 5 parts by mass, or 2.6 to 4 parts by mass to 100 parts by mass of component (A).

[0059] The component (F) that can be used in the present invention is an antifoaming agent. Component (F) can be appropriately selected from various compounds or compositions with antifoaming effects, such as surfactants.

[0060] (F) Component can be at least one selected from the group consisting of silicone defoamers (silicone-based surfactants), modified silicone-based defoamers, acetylene alcohol-based surfactants, silica-based defoamers, mineral oil-based defoamers, waxes, polyether-modified polydimethylsiloxanes, paraffin-based oils, and antifoaming aliphatic derivatives.

[0061] From the viewpoint of uniformly dispersing component (A), it is preferable to add 0.01 to 5.0 parts by mass of component (F) per 100 parts by mass of component (A), and more preferably 0.1 to 3.0 parts by mass. According to one embodiment of the present invention, it is desirable to blend component (F) in an amount of 0.2 to 2.0 parts by mass, 0.3 to 1.5 parts by mass, 0.4 to 1.0 parts by mass, or 0.5 to 0.8 parts by mass per 100 parts by mass of component (A).

[0062] According to one embodiment of the present invention, the proportion of silica-based defoaming agent in component (F) is 85% by mass or more, 90% by mass or more, 95% by mass or more, 99% by mass or more, 99.5% by mass or more, 99.8% by mass or more, or 99.9% by mass or more (upper limit is 100% by mass).

[0063] The composition of the present invention may contain appropriate amounts of additives (other components) such as solvents, inorganic fillers excluding component (E), organic fillers excluding components (A) and (B), rust inhibitors other than component (D), and pH adjusters, to the extent that they do not impair the properties. These additives can be used to adjust the appearance and adhesion of the coating film.

[0064] The solvent is preferably one that can disperse components (A) and (B) and does not impair the emulsified state of component (B) even when it is in emulsion form. Specific examples include, but are not limited to, at least one selected from the group consisting of ethanol, 1-propanol, 2-propanol, butanol, acetone, methyl ethyl ketone, diethyl ether, methyl ethyl ether, ethylcyclohexane, cyclohexane, hexane, isohexane, methanol, ethanol, ethylene glycol, and isopropyl alcohol. A solvent with good affinity for water is particularly preferred.

[0065] Examples of inorganic fillers excluding component (E) include, but are not limited to, at least one selected from the group consisting of silica powder, alumina powder, talc powder, diatomaceous earth powder, calcium carbonate powder, mica powder, kaolin powder, and glass powder. Among these, silica powder or diatomaceous earth powder with an average particle size of 1 to 50 μm is preferred because it is effective in preventing galling of the screw portion. According to one embodiment of the present invention, the average particle size of the inorganic filler excluding component (E) is 1.5 to 25 μm, 2 to 10 μm, or 2.5 to 5 μm. Here, the average particle size refers to the particle size at a cumulative volume ratio of 50% in the particle size distribution determined by laser diffraction scattering (D50).

[0066] Examples of organic fillers other than components (A) and (B) include, but are not limited to, at least one selected from the group consisting of fluororesin powder, polyethylene resin powder, and acrylic resin powder.

[0067] In order to fully exhibit the effects of component (D), it is preferable not to add any rust inhibitors other than component (D). However, they may be used in combination as long as they do not affect the appearance of the coating film. According to one embodiment of the present invention, the proportion of component (D) of the present invention among the rust inhibitors is preferably 85% by mass or more, 90% by mass or more, 95% by mass or more, 99% by mass or more, 99.5% by mass or more, 99.8% by mass or more, or 99.9% by mass or more (upper limit is 100% by mass).

[0068] Any alkaline compound soluble in water can be used as the pH adjusting agent. Specific examples of alkaline compounds, though not limited to those listed above, include ammonia, lithium hydroxide, potassium hydroxide, sodium hydroxide, and monomethylamine. The pH of the aqueous sealant composition in the examples was adjusted to 7-10. The pH measurement method conforms to JIS Z 8802 (2011).

[0069] According to one embodiment of the present invention, the proportions of each component in the aqueous sealant composition are as follows. The total of all components is adjusted to 100% by mass.

[0070] (A) The proportion of component (A) is 25-45% by mass, 30-40% by mass, or 35-37% by mass, relative to the whole composition.

[0071] The proportion of component (B) is 1 to 8% by mass, 2 to 5% by mass, or 2.65 to 3% by mass, relative to the total composition.

[0072] The proportion of component (C) is 40-70% by mass, 48-60% by mass, or 56-59% by mass, relative to the entire composition.

[0073] The proportion of component (D) is 0.5 to 12% by mass, 3 to 8% by mass, or 4 to 7% by mass, relative to the whole composition. Alternatively, the proportion of component (D) is 0.1 to 8% by mass, 0.3 to 3% by mass, or 0.4 to 2% by mass, relative to the whole composition.

[0074] The proportion of component (E) is 0.2 to 5% by mass, 0.5 to 2% by mass, or 0.7 to 1.3% by mass, relative to the whole composition.

[0075] The proportion of component (F) is 0.05 to 1% by mass, 0.10 to 0.50% by mass, or 0.10 to 0.40% by mass, relative to the entire composition.

[0076] The proportion of other components is 0.1 to 5% by mass, 0.2 to 3% by mass, or 0.3 to 1% by mass, relative to the total composition.

[0077] By blending each component within the above range, the aqueous sealant composition of the present invention can exhibit excellent rust prevention and adhesive properties while suppressing color changes of the coating film even after high-temperature baking.

[0078] The aqueous sealant composition of the present invention can be produced by stirring each component with a known stirrer. The order of adding components (A), (B), (C), (D), and (E), as well as component (F) and additives which may be added as needed, is arbitrary, but it is preferable to add component (A) to a mixed composition obtained by mixing the components excluding component (A). This makes it possible to obtain a homogeneous aqueous sealant composition and efficiently achieve the intended effects of the present invention. Examples of known stirrers include the Hyper (manufactured by Primix), and the mixing time is preferably, for example, about 10 to 90 minutes, or about 15 to 45 minutes.

[0079] This invention describes the processing of the surface of screw-fastened members such as screws, bolts, and nuts using the aqueous sealant composition of the present invention. The aqueous sealant composition of the present invention is applied to the screw-fastened portion of screw-fastened members such as screws, bolts, and nuts, and then heated in a heating device such as a hot air drying oven or an IR furnace to volatilize component (C) and other components, and to melt and fuse component (A) to form a coating film. According to one embodiment of the present invention, the heating temperature when baking the aqueous sealant composition onto screw-fastened members such as screws, bolts, and nuts is 200 to 250°C, 210 to 240°C, or 215 to 230°C. According to one embodiment of the present invention, the heating time when baking the aqueous sealant composition onto screw-fastened members such as screws, bolts, and nuts is 15 to 90 minutes, 20 to 70 minutes, or 20 to 50 minutes. The coating film can be suitably used for preventing loosening of screw-fastened members. The principle of preventing loosening is that when fastening screw-fastened components to which the coating has been formed, the coating fills the gaps between the screw-fastened components, and the torque during fastening is maintained by the repulsive stress of the coating.

[0080] The present invention comprises the following embodiments and forms: 1. An aqueous sealant composition comprising the following components (A) to (E): (A) component: polyamide powder, (B) component: epoxy resin, (C) component: water, (D) component: rust inhibitor, (E) component: colorant, wherein component (D) comprises at least one selected from the group consisting of inorganic salts, organic salts excluding organic acid amine salts, and nitrogen-containing fused ring compounds, and / or has a white appearance after heating for 20 minutes in a 200°C atmosphere.

[0081] 2. The aqueous sealant composition according to 1, wherein the component (D) is white in appearance after heating in a 200°C atmosphere for 20 minutes.

[0082] 3. The aqueous sealant composition according to 1. or 2. wherein component (D) is solid at 25°C after heating for 20 minutes in a 200°C atmosphere, and / or is a rust inhibitor other than an organic acid amine salt.

[0083] 4. The aqueous sealant composition according to any one of 1 to 3, wherein component (D) is solid at 25°C after heating for 20 minutes in a 200°C atmosphere, and / or at least one selected from the group consisting of inorganic salts, organic salts excluding organic acid amine salts, sodium benzoate, and benzotriazole.

[0084] 5. The aqueous sealant composition according to any one of 1 to 4, wherein the component (B) is a water-dispersible epoxy resin containing a cresol novolac structure.

[0085] 6. The aqueous sealant composition according to any one of 1 to 5, wherein the (E) component is an inorganic pigment.

[0086] 7. An aqueous sealant composition according to any one of 1 to 6, wherein the appearance of component (E) is green.

[0087] 8. The aqueous sealant composition according to any one of 1 to 7, further comprising an antifoaming agent as component (F).

[0088] 9. An aqueous sealant composition according to any one of 1 to 8, which does not contain the curing agent of component (B) above.

[0089] 10. The aqueous sealant composition according to any one of 1 to 9, wherein the inorganic salt is an inorganic acid amine salt.

[0090] 11. The inorganic acid in the inorganic salt is SO ４ ２－ An aqueous sealant composition as described in any of 1. to 10.

[0091] 12. The organic acid in the aforementioned organic acid salt is R-Y － Represented as , where R represents an aliphatic hydrocarbon group, an aryl group, or a heterocyclic group, and -Y represents -SO２ S, -SO ３ , -SO ２ , -SSO ３ An aqueous sealant composition according to any one of 1. to 11., representing -COS or -COO.

[0092] 13. The aqueous sealant composition according to 10, wherein the amine of the amine salt in the inorganic acid amine salt is at least one selected from the group consisting of a quaternary ammonium group, a hydroxylammonium group, an ammonium group, a guanidium group, and a heterocyclic quaternary base.

[0093] 14. An aqueous sealant composition according to any one of 1 to 13, wherein the (D) component is a rust inhibitor containing an organic acid salt other than an organic acid amine salt.

[0094] 15. An aqueous sealant composition according to any one of 1 to 14, wherein the (D) component is a combination of a rust inhibitor containing an inorganic acid amine salt, a rust inhibitor containing an organic acid salt excluding an organic acid amine salt, and a rust inhibitor containing sodium benzoate and benzotriazole.

[0095] 16. The aqueous sealant composition according to 15, wherein the content ratio of the rust inhibitor containing sodium benzoate and benzotriazole in component (D) is the lowest.

[0096] 17. The aqueous sealant composition according to 16, wherein the ratio of the content of the rust inhibitor containing the inorganic acid amine salt to the content of the rust inhibitor containing the sodium benzoate and benzotriazole is 1.1 to 3, 1.4 to 2.5, or 1.5 to 2.

[0097] 18. The aqueous sealant composition according to 16. or 17., wherein the ratio of the content of a rust inhibitor containing an organic acid salt other than the organic acid amine salt to the content of the rust inhibitor containing sodium benzoate and benzotriazole is 1.5 or more and 5 or less, 1.9 or more and 4.5 or less, 2.1 or more and 4 or less, 2.3 or more and 3.5 or less, or 2.5 or more and 3 or less.

[0098] 19. An aqueous sealant composition according to any one of 1 to 18, wherein the content of component (D) is 1 to 30 parts by mass per 100 parts by mass of component (A).

[0099] 20. The aqueous sealant composition according to 19, wherein the content of component (D) is 18 parts by mass or less per 100 parts by mass of component (A).

[0100] 21. The aqueous sealant composition according to 20, wherein the content of component (D) is 4 parts by mass or less per 100 parts by mass of component (A).

[0101] 22. An aqueous sealant composition according to any one of 1 to 21, wherein the content of component (D) is 1.5 parts by mass or more, or 2% by mass or more, per 100 parts by mass of component (A).

[0102] 23. The aqueous sealant composition according to any one of 1 to 22, wherein component (A) is an aliphatic polyamide having 8 to 13, 9 to 12, 10 to 11, or 11 carbon atoms between amide bonds.

[0103] 24. An aqueous sealant composition according to any one of 1 to 23, wherein the average particle size of component (A) is 0.5 to 500 μm, 5 to 300 μm, 10 to 100 μm, 15 to 80 μm, 20 to 60 μm, or 25 to 55 μm.

[0104] 25. The aqueous sealant composition according to any one of 1 to 24, wherein the component (B) is an emulsion-type or dispersion-type epoxy resin, and the solid content is 35% by mass or more and 75% by mass or less, 40% by mass or more and 65% by mass or less, or 45% by mass or more and 65% by mass or less.

[0105] 26. An aqueous sealant composition according to any one of 1 to 25, wherein the content of component (B) is 5.2 to 10 parts by mass, 5.4 to 9 parts by mass, 5.6 to 8 parts by mass, or 5.8 to 7.5 parts by mass per 100 parts by mass of component (A).

[0106] 27. An aqueous sealant composition according to any one of 1 to 26, which substantially does not contain any amine compounds, acid anhydrides, thiol compounds, or isocyanate compounds, and which has the ability to crosslink component (B).

[0107] 28. An aqueous sealant composition according to any one of 1 to 27, wherein the content of component (C) is 120 to 195 parts by mass, 130 to 190 parts by mass, 140 to 185 parts by mass, 150 to 180 parts by mass, 155 to 175 parts by mass, or 156 to 170 parts by mass per 100 parts by mass of component (A).

[0108] 29. An aqueous sealant composition according to any one of 1 to 28, wherein the epoxy equivalent of component (B) is 350 to 550 g / eq, or 400 to 500 g / eq.

[0109] 30. The aqueous sealant composition according to any one of 1 to 29, wherein the proportion of component (A) is 25 to 45% by mass, 30 to 40% by mass, or 35 to 37% by mass, based on the entire composition.

[0110] 31. The aqueous sealant composition according to any one of 1 to 30, wherein the proportion of component (B) is 1 to 8% by mass, 2 to 5% by mass, or 2.65 to 3% by mass of the whole composition.

[0111] 32. The aqueous sealant composition according to any one of 1 to 31, wherein the proportion of component (C) is 40 to 70% by mass, 48 ​​to 60% by mass, or 56 to 59% by mass of the whole composition.

[0112] 33. The aqueous sealant composition according to any one of 1 to 32, wherein the proportion of component (D) is 0.5 to 12% by mass, 3 to 8% by mass, or 4 to 7% by mass, based on the whole composition, or the proportion of component (D) is 0.1 to 8% by mass, 0.3 to 3% by mass, or 0.4 to 2% by mass, based on the whole composition.

[0113] 34. The aqueous sealant composition according to any one of 1 to 33, wherein the proportion of component (E) is 0.2 to 5% by mass, 0.5 to 2% by mass, or 0.7 to 1.3% by mass, based on the entire composition.

[0114] 35. The aqueous sealant composition according to any one of 1 to 34, wherein the proportion of component (F) is 0.05 to 1% by mass, 0.10 to 0.50% by mass, or 0.10 to 0.30% by mass, based on the entire composition.

[0115] 36. The aqueous sealant composition according to any one of 1 to 35, wherein the proportion of the other components is 0.1 to 5% by mass, 0.3 to 3% by mass, or 0 to 1% by mass, relative to the whole composition.

[0116] 37. An aqueous sealant composition according to any one of 1 to 36, wherein the tensile shear adhesive strength of the cured product is 10 to 50 MPa, 16 to 48 MPa, 20 to 46 MPa, or 27 to 44 MPa.

[0117] 38. A method for producing an aqueous sealant composition, comprising mixing (A) component: polyamide powder, (B) component: epoxy resin, (C) component: water, (D) component: rust inhibitor, (E) component: colorant, and additives added as needed, wherein (D) component comprises at least one selected from the group consisting of inorganic salts, organic salts excluding organic acid amine salts, and nitrogen-containing fused ring compounds, and / or the appearance after heating in a 200°C atmosphere for 20 minutes is white, and further comprising adding component (A) to a mixed composition obtained by mixing the components excluding component (A).

[0118] 39. A screw-fastened member obtained by applying an aqueous sealant composition according to any one of items 1 to 37 above, or an aqueous sealant composition obtained by the manufacturing method described in item 38 above, to the screw portion and then heating and baking it.

[0119] 40. A method of fastening by screwing using the screw fastening member described in 39 above, and preventing loosening after fastening.

[0120] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0121] [Examples 1-7, Comparative Examples 1-7] The following components were prepared to prepare the compositions.

[0122] (A) Ingredients: Polyamide powder, 11-nylon powder with an average particle size of 40 μm, manufactured by Arkema, Lilsan D-40.

[0123] (B) Component: Epoxy resin / cresol novolac type epoxy resin dispersion (50% solids by mass) Denacol EM-160 manufactured by Nagase ChemteX Corporation (Note that Denacol EM-160 is in a form in which epoxy resin is dispersed in water).

[0124] (C) Ingredients: Water, deionized water.

[0125] (D) Components: Rust inhibitors that appear white after heating at 200°C for 20 minutes; rust inhibitors containing inorganic acid amine salts (colorless) - Kireslight WZ manufactured by Kiresto Co., Ltd.; rust inhibitors containing sodium benzoate and benzotriazole (pale yellow) - ASCOTRAN AL7 manufactured by ASCOTEC Co., Ltd.; rust inhibitors containing fatty acid salts that are not organic acid amine salts (pale yellow) - Kireslight W-410 manufactured by Kiresto Co., Ltd.; rust inhibitors containing inorganic acid salts (colorless) - Kireslight AFL manufactured by Kiresto Co., Ltd.; rust inhibitors containing organic acid salts that are not organic acid amine salts (colorless) - Kireslight W-16B manufactured by Kiresto Co., Ltd.; rust inhibitors containing sodium benzoate and benzotriazole (pale yellow) - ASCOTRAN AL4 manufactured by ASCOTEC Co., Ltd.

[0126] (D') Components: Rust inhibitors other than component (D) - Rust inhibitors containing fatty acid amine salts (pale yellow) - Kireslight WZ-5 manufactured by Kiresto Co., Ltd. - Rust inhibitors containing organic acid amine salts (colorless) - Rasmin AM-2 manufactured by Kyoeisha Chemical Co., Ltd. - Rust inhibitors containing organic acid amine salts (colorless) - Kireslight W-511 manufactured by Kiresto Co., Ltd. - Rust inhibitors containing organic acid amine salts (pale yellow) - Kireslight AL-2 manufactured by Kiresto Co., Ltd. - Rust inhibitors containing organic acid amine salts (pale yellow) - Kireslight WZ-2 manufactured by Kiresto Co., Ltd. - Rust inhibitors containing organic acid amine salts (pale yellow) - Kireslight W-530 manufactured by Kiresto Co., Ltd. - Triethanolamine (reagent) (colorless).

[0127] (E) Ingredients: Coloring agent / complex oxide green aqueous dispersion (solid content: 62% by mass) Manufactured by Dainippon Seika Kogyo Co., Ltd. MF-5363 Green (C.I. Name: PG-50).

[0128] (F) Ingredients: Antifoaming agent - hydrophobic silica-type mineral oil-based antifoaming agent, Nopco 8034-L, manufactured by Sunopco Corporation.

[0129] Other ingredients: Inorganic filler, diatomaceous earth powder with an average particle size of 3 μm, manufactured by Celite Co., Ltd. (Snow Floss).

[0130] Examples 1 to 7 and Comparative Examples 1 to 7 were prepared. Components (B), (C), (D) (or (D')) and other components were weighed into beakers and stirred for 30 minutes using a Hyper mixer (Primix). Then, component (A) was weighed and added, and stirred for another 30 minutes. Detailed preparation amounts are shown in Table 1, and all values ​​are expressed in parts by mass. Here, since components (B) and (E) are aqueous dispersions, the preparation amounts are shown on a solid content basis, and water is included in the calculation for component (C).

[0131]

[0132] [Visual Inspection of Rust Inhibitor] Only components (D) and (D') were weighed at 10 mg each into an aluminum pan. The pan was heated in a DG / DTA (Seiko Instruments TG / DTA7200 thermogravimetric differential analyzer) at a rate of 10°C / min from 25 to 200°C while purging with nitrogen, and heated for 20 minutes in a 200°C atmosphere. After cooling, the pan was visually inspected and labeled "Visual Inspection (25°C)". Immediately after cooling to 25°C, the aluminum pan was tilted at approximately 30° and held for 5 minutes to observe whether components (D) and (D') dripped. If dripping occurred, it was judged as "Liquid"; if not, it was judged as "Solid". The results are shown in Table 2.

[0133]

[0134] For Examples 1-7 and Comparative Examples 1-7, the appearance was checked after drying, the tensile shear adhesive strength was measured, and the appearance was checked after durability testing. The results are summarized in Table 3.

[0135] [Confirmation of appearance after drying] The composition was placed in a poly cup, and five JIS Class 2 M10 x 20 P1.5 zinc-plated chromate-treated hexagonal bolts were immersed in it, applying the composition to the entire circumference of the screw-fastening member. The bolts were fixed to a jig with the heads facing upwards, and any excess composition remaining at the bottom (tip of the screw-fastening member) was wiped off with a cloth. The bolts were left to stand at room temperature for 1 hour. Each bolt was photographed after standing, and this is shown in Figure 1. Then, a hot air drying oven was set to a 220°C atmosphere, and the jig was left in the oven for 20 minutes to dry the coating. The bolts were removed from the hot air drying oven and allowed to cool naturally at room temperature, and a photograph was taken, which is shown in Figure 2. Figures 1 and 2 were compared and visually confirmed based on the following evaluation criteria, and this was determined as the "appearance after drying".

[0136] Evaluation Criteria OK: The paint colors in Photo 1 and Photo 2 are the same (same color). NG: The paint colors in Photo 1 and Photo 2 are different (different colors).

[0137] [Measurement of Tensile Shear Bonding Strength] Two SPCC-SD steel plates, 150 mm long x 25 mm wide x 1.6 mm thick, as specified in JIS G3141:2017, were prepared and used as adherends. The composition was applied to the long end of one adherend in a 1 cm length to a thickness of approximately 0.1 mm, and the long end of the other adherend was placed on top of it so that the long end of the other adherend was 1 cm long. The two plates were left to stand horizontally at room temperature for 1 hour. After that, they were left in a 220°C oven for 20 minutes to form a dry coating. The test pieces were made after natural cooling at room temperature. The test was performed with n=3. The test pieces were set in a universal tensile testing machine and pulled in the tensile direction at 50 mm / min to measure the maximum strength. The tensile shear bonding strength was calculated from the bonding area and defined as "bonding force" (MPa). The average value of n=3 was used as the result. For more detailed test methods, refer to JIS K6850:1999. However, for compositions where the "appearance after drying" was "NG," no measurement was performed and it was marked as "-". According to one embodiment of the present invention, suitable adherends (screwed members) include metals such as steel and aluminum, as well as zinc chromate treated products, blackened products, and brass products.

[0138] [Visual Inspection After Durability Test] The dried bolts (Photo 2) obtained in the [Visual Inspection After Drying] above were left in a constant temperature and humidity furnace at 28°C and 95% RH for 72 hours. Each bolt was removed and photographed, which is Photo 3. Photo 2 and Photo 3 were compared based on the following evaluation criteria to check for rust formation and recorded as the "Visual Appearance After Durability Test".

[0139] Evaluation Criteria ◎: No rust was visible to the naked eye. ○: A very small amount of rust was visible to the naked eye. ×: Rust was visible to the naked eye on the entire bolt.

[0140]

[0141] From the comparison results of components (D) and (D') shown in Table 2 and the results of the appearance after drying shown in Table 3, it is considered that the deterioration of the rust inhibitor due to heating affects the color of the coating film. In particular, when components (D) / (D') remain in a solid state after heating, a tendency for discoloration to be suppressed is observed. As shown in Table 2, component (D') changes from brown to black, and as a result, it can be seen that it changes the color of the coating film derived from component (E) (Table 3). On the other hand, although component (D) is also susceptible to heat deterioration, the evaluation of adhesive strength (tensile shear adhesive strength) and appearance after durability (rust occurrence) shown in Table 3 indicates that the coating film performance is well maintained and that it exhibits sufficient effect as an aqueous sealant composition. According to one embodiment of the present invention, the tensile shear adhesive strength of the cured product is 10 to 50 MPa, 16 to 48 MPa, 20 to 46 MPa, or 27 to 44 MPa.

[0142] The aqueous sealant composition of the present invention suppresses appearance defects caused by high-temperature drying during processing and maintains a stable appearance, thereby improving productivity by enhancing the reliability of component identification. It maintains a stable appearance and forms an excellent coating film despite having a low environmental impact. The aqueous sealant composition of the present invention is particularly suitable for use in preventing loosening after fastening by being applied to the threaded portion of screw-fastened components.

[0143] This application is based on Japanese Patent Application No. 2024-227575, filed on 24 December 2024, the disclosures thereof being incorporated herein by reference in their entirety.

Claims

1. An aqueous sealant composition comprising the following components (A) to (E): (A) component: polyamide powder (B) component: epoxy resin (C) component: water (D) component: rust inhibitor (E) component: colorant, wherein component (D) comprises at least one selected from the group consisting of inorganic salts, organic salts excluding organic acid amine salts, and nitrogen-containing fused ring compounds, and / or has a white appearance after heating for 20 minutes in a 200°C atmosphere.

2. The aqueous sealant composition according to claim 1, wherein the component (D) is white in appearance after heating in a 200°C atmosphere for 20 minutes.

3. The aqueous sealant composition according to claim 2, wherein component (D) is a rust inhibitor other than an organic acid amine salt, and its properties at 25°C after heating for 20 minutes in a 200°C atmosphere are solid.

4. The aqueous sealant composition according to claim 3, wherein component (D) is solid at 25°C after heating for 20 minutes in a 200°C atmosphere, and is at least one selected from the group consisting of inorganic salts, organic acid salts excluding organic acid amine salts, sodium benzoate, and benzotriazole.

5. The aqueous sealant composition according to claim 1, wherein component (B) is a water-dispersible epoxy resin containing a cresol novolac structure.

6. The aqueous sealant composition according to claim 1, wherein the (E) component is an inorganic pigment.

7. The aqueous sealant composition according to claim 1, wherein the appearance of component (E) is green.

8. The aqueous sealant composition according to claim 1, further comprising an antifoaming agent as component (F).

9. The aqueous sealant composition according to claim 1, which does not contain the curing agent of component (B).

10. A screw-fastened member obtained by applying the aqueous sealant composition described in claim 1 to the screw portion and heating and baking it.

11. A method for fastening by screwing using the screw fastening member described in claim 10, and preventing loosening after fastening.

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