Coating agent and spring

Abstract

A coating agent and a spring using the same, in which the cured product after curing has a tear strength of 20 kN / m or more at 25°C and 80°C, and a type A durometer hardness of 30 to 100 at 25°C.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a coating agent and a spring. BACKGROUND

[0002] Automobiles, railway vehicles, and the like use various springs. Most of these springs are made of steel, and the surface thereof is usually subjected to coating for imparting corrosion resistance.

[0003] For example, Patent Literature 1 discloses “a method for forming a coated portion of a coil spring, characterized by rolling at least an axial portion of a coil spring preheated to a prescribed surface temperature in a groove-shaped container having a thermoplastic resin powder having a melting point of 250°C or lower accommodated therein, and solidifying the resin powder adhering to a spring wire of the coil spring after being heated and melted”.

[0004] Further, Patent Literature 2 discloses “a high durability spring characterized by having a coating film having a thickness of 450 μm or less, the coating film containing an epoxy resin, a phenol resin, and zinc”. Patent Literature 2 also discloses “the coating film is a cured product of an epoxy resin-based powder coating material containing an epoxy resin, a phenol resin, and zinc”.

[0005] Further, Patent Literature 3 discloses “an anti-chipping powder overcoat on a steel substrate having a corrosion-resistant powder primer coating, the overcoat comprising a cured or fused product of a coating powder of: one or more resin components of a toughened epoxy resin, 0.1 to 5 parts per hundred resin (phr) of one or more waxes, and optionally up to 200 phr of one or more extenders”.

[0006] Further, Patent Literature 4 discloses “a suspension spring, which is a coil spring for a suspension of a vehicle, characterized in that a coating film is thicker at a portion where at least one of a stress at the time of use is higher than that at other portions and a probability of damage to the coating film due to a flying stone is higher than that at other portions than at the portion adjacent to the portion”.

[0007] PRIOR ART DOCUMENTS

[0008] PATENT LITERATURE

[0009] Patent Literature 1: Japanese Patent Application Laid-Open No. 57-136972

[0010] Patent Literature 2: International Publication No. WO 2017 / 163877

[0011] Patent Literature 3: Japanese Patent Application Laid-Open No. 2009-120812

[0012] Patent Literature 4: Japanese Patent Application Laid-Open No. 2007-308067 SUMMARY

[0013] PROBLEMS TO BE SOLVED BY THE INVENTION

[0014] As for the coating agent for springs, the cured product layer (coating layer) after coating on the spring is required to have durability against repeated extension and contraction of the spring, contact between the wires of the spring, and contact with other members. In addition, impact resistance against impact of a flying stone or the like is also required.

[0015] However, recently, while high level and durability at normal temperature are required, impact resistance at low temperature and at high temperature is particularly required, but the present situation is that sufficient studies have not been made.

[0016] The same characteristics are also required for coating agents other than the coating agent for springs.

[0017] Therefore, the problem of the present disclosure is to provide a coating agent capable of forming a cured product layer excellent in durability at normal temperature and at high temperature and in impact resistance at low temperature, and a spring using the same.

[0018] MEANS FOR SOLVING THE PROBLEM

[0019] The above problem is solved by the following means.

[0020] <1>

[0021] A coating agent, in which a cured product after curing has a tear strength at 25°C and at 80°C of 20 kN / m or more and a type A durometer hardness at 25°C of 30 to 100.

[0022] <2>

[0023] The coating agent according to <1>, in which the cured product after curing is a cured product having a urethane bond.

[0024] <3>

[0025] The coating agent according to <1> or <2>, in which the coating agent is composed of a composition containing (A) a high-molecular polyol, (B) an isocyanate, and (C) a chain extender, or a composition containing (D) a prepolymer obtained by reacting a polyol with an isocyanate.

[0026] <4>

[0027] The coating agent according to <3>, wherein the (A) high-molecular polyol contains at least one selected from the group consisting of (A1) polycarbonate-based polyol, (A2) polyether-based polyol having a bisphenol structure, (A3) lactone-based polyol, (A4) polyester-based polyol, and (A5) copolymer of polycarbonate-based polyol and lactone-based polyol.

[0028] <5>

[0029] The coating agent according to any one of <1> to <4> is used for a spring.

[0030] <6>

[0031] A spring having, at least a part of a surface, a cured product layer of the coating agent according to any one of <1> to <5>.

[0032] Effects of the Invention

[0033] According to the present disclosure, it is possible to provide a coating agent capable of forming a cured product layer excellent in durability at normal temperature and at high temperature and in impact resistance at low temperature, and a spring using the same. DETAILED DESCRIPTION

[0034] Hereinafter, an embodiment as one example of the present disclosure will be described. These descriptions and examples exemplify the present disclosure, but do not limit the present disclosure.

[0035] In the present specification, a numerical range represented by "〜" indicates a range including the numerical values recited before and after "〜" as the minimum value and the maximum value, respectively.

[0036] In the numerical ranges recited in sections in the present specification, the upper limit value or the lower limit value recited in one numerical range can be replaced with the upper limit value or the lower limit value of the numerical range recited in another section. Further, in the numerical ranges recited in the present disclosure, the upper limit value or the lower limit value of the numerical range can also be replaced with the value shown in the examples.

[0037] In the present specification, each component can contain a plurality of respective substances. In the case where the amount of each component is mentioned in the present specification, in the case where a plurality of substances corresponding to each component exist, unless otherwise specified, it refers to the total amount of the plurality of substances.

[0038] The coating agent of the present embodiment is a coating agent whose cured product after curing has a tear strength of 20 kN / m or more at 25°C and 80°C, and a type A durometer hardness of 30 to 100 at 25°C.

[0039] Note that the cured product after curing refers to a cured product formed by drying a solvent, or a cured product formed by reaction of components.

[0040] The coating agent of the present disclosure, by the above constitution, can form a cured product layer that is excellent in durability at normal temperature and at high temperature and in impact resistance at low temperature.

[0041] Hereinafter, the details of the coating agent of the present embodiment will be described.

[0042] (Properties)

[0043] In the case of the coating agent of the present embodiment, the tear strength of the cured product after curing at 25°C is 20 kN / m or more, but from the viewpoint of improving the durability at normal temperature, it is preferably 60 kN / m or more, and more preferably 90 kN / m or more.

[0044] However, from the viewpoint of impact absorption, the upper limit of the tear strength at 25°C is, for example, 350 kN / m or less.

[0045] In the case of the coating agent of the present embodiment, the tear strength of the cured product after curing at 80°C is 20 kN / m or more, but from the viewpoint of improving the durability at high temperature, it is preferably 30 kN / m or more, and more preferably 40 kN / m or more.

[0046] However, from the viewpoint of impact absorption, the upper limit of the tear strength at 80°C is, for example, 150 kN / m or less.

[0047] Here, the tear strength is measured according to the tear test prescribed in JIS K 7311:1995.

[0048] In the case of the coating agent of the present embodiment, the type A durometer hardness of the cured product after curing at 25°C is 30 to 100, but from the viewpoint of improving the impact resistance at low temperature, it is preferably 50 to 100, and more preferably 70 to 100.

[0049] If the type A durometer hardness at 25°C is in the above range, the impact resistance at low temperature is improved. Furthermore, in the case where the coating agent of the present embodiment is applied to a steel spring use, since the hardness is softer than a steel spring, it is possible to seek to prevent abnormal noise.

[0050] The type A durometer hardness is measured according to the hardness test prescribed in JIS K 7311:1995.

[0051] (Composition)

[0052] The coating agent of the present embodiment can be any one of a composition of a thermoplastic resin, a composition for forming a thermosetting resin, as long as it can form a cured product satisfying the above properties.

[0053] As the thermoplastic resin, for example, an acrylic resin, a polystyrene resin, a polyethylene resin, a polypropylene resin, a polyamide resin, a nylon resin, a vinyl chloride resin, a polyacetal resin, a polycarbonate resin, a polyphenylene ether resin, a polybutylene terephthalate resin, a polyphenylsulfone resin, a polysulfone resin, a polyarylate resin, a polyetherimide resin, and the like can be given.

[0054] As the thermosetting resin, for example, a urethane resin, an epoxy resin, a cyanate ester resin, a melamine resin, a phenol resin, and the like can be given.

[0055] Further, for example, a natural rubber, a butadiene rubber, a chlorobutadiene rubber, a nitrile rubber, a styrene butadiene rubber, and the like can be given as the rubber material.

[0056] Among them, as the coating agent of the present embodiment, the cured product after curing is preferably a cured product having a urethane bond, and specifically, a urethane resin is preferable.

[0057] In particular, the coating agent of the present embodiment is preferably a composition containing (A) a high-molecular polyol, (B) an isocyanate, and (C) a chain extender, or a composition containing (D) a prepolymer obtained by reacting a polyol with an isocyanate.

[0058] [Composition containing (A) a high-molecular polyol, (B) an isocyanate, and (C) a chain extender]

[0059] (A) High-molecular polyol

[0060] As the (A) high-molecular polyol, from the viewpoint of improving the durability at normal temperature and at high temperature and the impact resistance at low temperature, it is preferable to contain at least one selected from the group consisting of (A1) a polycarbonate-based polyol, (A2) a polyether-based polyol having a bisphenol structure, (A3) a lactone-based polyol, (A4) a polyester-based polyol, and (A5) a copolymer of a polycarbonate-based polyol and a lactone-based polyol.

[0061] As the (A1) polycarbonate-based polyol, for example, a polyol obtained by reacting a diol with an alkylene carbonate, a polyol obtained by reacting a diol with a diaryl carbonate, a polyol obtained by reacting a diol with a dialkyl carbonate, and the like can be given.

[0062] As the alkylene carbonate, for example, an ethylene carbonate, a 1,2-propylene carbonate, a 1,2-butylene carbonate, and the like can be given.

[0063] As the carbonic acid diaryl ester, for example, carbonic acid diphenyl ester, carbonic acid 4-methyl diphenyl ester, carbonic acid 4-ethyl diphenyl ester, carbonic acid 4-propyl diphenyl ester, carbonic acid 4, 4'-dimethyl diphenyl ester, carbonic acid 2-tolyl-4-tolyl ester, carbonic acid 4, 4'-diethyl diphenyl ester, carbonic acid 4, 4'-dipropyl diphenyl ester, carbonic acid phenyl toluoyl ester, carbonic acid bischlorophenyl ester, carbonic acid phenyl chlorophenyl ester, carbonic acid phenyl naphthyl ester, carbonic acid dinaphthyl ester, and the like can be exemplified.

[0064] As the carbonic acid dialkyl ester, for example, carbonic acid dimethyl ester, carbonic acid diethyl ester, carbonic acid di-n-propyl ester, carbonic acid diisopropyl ester, carbonic acid di-n-butyl ester, carbonic acid diisobutyl ester, carbonic acid di-t-butyl ester, carbonic acid di-n-pentyl ester, carbonic acid diisopentyl ester, and the like can be exemplified.

[0065] As the polyether-based polyol having a bisphenol structure (A2), for example, polyether polyols in which polyethylene oxide and / or polypropylene oxide is added to a cyclic diol (bisphenol A, hydrogenated bisphenol A, bisphenol S, bisphenol P, and the like), a propylene oxide adduct of bisphenol A, an ethylene oxide adduct of bisphenol A, an ethylene oxide adduct of hydrogenated bisphenol A, a propylene oxide adduct of hydrogenated bisphenol A, and the like can be exemplified.

[0066] Among these, as the polyether-based polyol, a propylene oxide adduct of bisphenol A is preferable.

[0067] As the lactone-based polyol (A3), for example, a ring-opening polymer of a lactone (ε-caprolactone, β-methyl-δ-valerolactone, and the like) and the like can be exemplified.

[0068] Among these, a ring-opening polymer of caprolactone (caprolactone-based polyol) is preferable.

[0069] As the polyester-based polyol (A4), for example, a condensation-based polyester-based polyol of a polybasic acid other than a lactone-based polyol and a polyol can be exemplified.

[0070] As the polybasic acid, for example, a polycarboxylic acid can be exemplified. Specifically, as the polybasic acid, for example, phthalic acid, isophthalic acid, tetrahydrophthalic acid, tetrahydroisophthalic acid, hexahydrophthalic acid, hexahydroterephthalic acid, trimellitic acid, adipic acid, sebacic acid, succinic acid, azelaic acid, fumaric acid, maleic acid, itaconic acid, pyromellitic acid, and anhydrides thereof can be exemplified.

[0071] As the diol, specifically, there can be mentioned ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, neopentyl glycol, hexanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2-butyl-2-ethyl-l,3-propanediol, methylpropanediol, cyclohexanedimethanol, 3,3-diethyl-l,5-pentanediol, and the like. As the polyol of three or more valencies, specifically, there can be mentioned glycerol, trimethylol ethane, trimethylol propane, pentaerythritol, dipentaerythritol, and the like.

[0072] As the (A5) polycarbonate-based polyol copolymer with the lactone-based polyol, there can be mentioned the copolymer of the above (Al) polycarbonate-based polyol with the above (A3) lactone-based polyol.

[0073] Note that the (A) high-molecular polyols can each be used singly or in combination of two or more.

[0074] The number average molecular weight of the (A) high-molecular polyol is preferably from 300 to 12,000, more preferably from 800 to 4,000.

[0075] Here, the number average molecular weight is the molecular weight in the case where it is calculated from the measured value of the hydroxyl value according to JIS K0070 and the number of functional groups. Note that the number average molecular weight of the other components is also measured in the same manner.

[0076] (B) isocyanate

[0077] As the (B) isocyanate, there can be mentioned 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, diphenylmethane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, xylene- 1,4-diisocyanate, 1,5-naphthalene diisocyanate, 1,4-naphthalene diisocyanate, 3,3'-dichloro-4,4'-diphenylmethane diisocyanate, and the like aromatic diisocyanates; hexamethylene diisocyanate, propylene- 1,2-diisocyanate, butylene- 1,2-diisocyanate, and the like aliphatic diisocyanates; isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, cyclohexylene diisocyanate, and the like alicyclic diisocyanates; and the like known polyisocyanates.

[0078] The (B) isocyanate can be used singly or in combination of two or more.

[0079] (C) chain extender

[0080] As the (C) chain extender, there can be mentioned difunctional to tetrafunctional polyols having a molecular weight of from 60 to 300.

[0081] As a di-functional polyol, the following can also be mentioned: aliphatic diols such as ethylene glycol, propylene glycol, butylene glycol, pentylene glycol, neopentyl glycol, methylpentylene glycol, hexylene glycol, heptylene glycol, octylene glycol, nonylene glycol, decylene glycol, dodecylene glycol; alicyclic diols such as cyclohexanediol, hydrogenated xylylene glycol; aromatic diols such as xylylene glycol; polyether polyols obtained by polyaddition of alkylene oxide (ethylene oxide, propylene oxide, etc.) to dihydric alcohol. Note that the polyaddition of multiple alkylene oxides can be random polyaddition or block polyaddition.

[0082] As a tri-functional polyol, as a trihydric alcohol, for example, the following can be mentioned: trihydric alcohols having 3 to 10 carbon atoms such as glycerol, trimethylolpropane. As a tri-functional polyol, the following can also be mentioned: polyether polyols obtained by polyaddition of alkylene oxide (ethylene oxide, propylene oxide, etc.) to trihydric alcohol. Note that the polyaddition of multiple alkylene oxides can be random polyaddition or block polyaddition.

[0083] As a tetra-functional polyol, for example, the following can be mentioned: polyether polyols obtained by polyaddition of alkylene oxide to ethylenediamine, pentaerythritol, etc.

[0084] Further, as a low-molecular polyol, the following can also be mentioned: ester-based polyols obtained by condensation of adipic acid and short-chain diols such as ethylene glycol, 1,4-butanediol, etc. with polyfunctional triols such as glycerol, etc.

[0085] (C) The chain extender can be used singly or in combination of two or more. It can also be used in advance by reacting with the polyisocyanate in the form of a prepolymer.

[0086] Among them, as the (C) chain extender, from the viewpoint of improving the durability at normal temperature and at high temperature and the impact resistance at low temperature, ethylene glycol, 1,4-butanediol, 1,6-hexanediol, trimethylolpropane, glycerol are preferred, and 1,4-butanediol and 1,6-hexanediol are more preferred.

[0087] [Composition containing a prepolymer obtained by reacting a polyol with isocyanate]

[0088] (D) Prepolymer

[0089] The prepolymer is a prepolymer obtained by reacting a polyol with isocyanate.

[0090] As the polyol, the following can be mentioned: the above-mentioned (A) high-molecular polyol, the low-molecular polyol exemplified in the above-mentioned (C) chain extender.

[0091] As the isocyanate, the above-mentioned (B) isocyanate can be mentioned.

[0092] In the composition containing the (D) prepolymer, at least one selected from the group consisting of the (A) high-molecular polyol, the (B) isocyanate, and the (C) chain extender can be contained in addition to the (D) prepolymer.

[0093] - Other Components -

[0094] The coating agent of the present embodiment can also contain other components.

[0095] As the other components, known additives such as a catalyst, a thickening agent, an antioxidant, a coloring agent, an ultraviolet absorber, and an inorganic filler (calcium carbonate, etc.) can be exemplified.

[0096] Further, in order to improve the mechanical properties in a warm state, the structure of the resin itself can be made into a structure with high heat resistance, and in addition to this, a crosslinking agent, a reinforcing agent (CNT, etc.) can be added to improve the heat resistance.

[0097] - Ratio of Components -

[0098] From the viewpoint of improving the durability at normal temperature and at high temperature and the impact resistance at low temperature, the equivalent ratio of the (A) high-molecular polyol and the (C) chain extender to the (B) isocyanate and the (D) prepolymer obtained by the reaction of the polyol with isocyanate ((A+C) / (B+D)) is preferably 0.5 to 1.5 or 0.8 to 1.2.

[0099] From the viewpoint of improving the durability at normal temperature and at high temperature and the impact resistance at low temperature, the mass ratio of the (A) high-molecular polyol to the (C) chain extender (A / C) is preferably 1.0 to 35.0 or 1.5 to 10.0.

[0100] From the viewpoint of improving the durability at normal temperature and at high temperature and the impact resistance at low temperature, the mass ratio of the (D) prepolymer obtained by the reaction of the polyol with isocyanate to the (C) chain extender (D / C) is preferably 1.0 to 15.0 or 5.0 to 10.0.

[0101] (Use of the Coating Agent)

[0102] The coating agent of the present embodiment can be preferably used, for example, as a coating agent for forming a protective layer of a spring, a stabilizer, a bumper, a building material (wall tiles, etc.).

[0103] Among them, the coating agent of the present embodiment can be exemplified as a coating agent for a spring.

[0104] Specifically, the article of the present embodiment has, at least a part of a surface, a cured product layer of the coating agent for a spring of the present embodiment described above.

[0105] The spring of the present embodiment has a cured product layer of the coating agent for springs of the present embodiment on at least a part of the surface. The spring can be any of a coil spring or a leaf spring.

[0106] As a method of providing the cured product layer of the coating agent, for example, the following is described.

[0107] 1) The surface of the portion where the spring wires of the coil spring contact each other for the purpose of preventing abnormal noise caused by the contact of the spring wires with each other.

[0108] 2) The surface of the end coil portion of the coil spring or a part or the entire surface of the coil spring for the purpose of protecting the coating.

[0109] 3) A part or the entire surface of the leaf spring made of FRP for the purpose of moderating impact and preventing burrs.

[0110] (Coating method)

[0111] The coating method of the coating agent of the present embodiment is not particularly limited, and coating methods such as dip coating, spray coating, roll coating, brush coating, flow coating, and the like can be applied.

[0112] Here, in the case where the coating agent of the present embodiment is coated on the coil spring, the thickness of the cured product layer formed is preferably set to 1 mm or more (particularly 1 to 2 mm), and thus there is a concern about the sagging of the coating film.

[0113] Therefore, it is preferable to incorporate a thickening agent in the coating agent of the present embodiment to increase the viscosity.

[0114] Further, in order to be able to be cured by ultraviolet rays, it is also preferable to incorporate an acrylate-based resin and a photopolymerization initiator in the coating agent of the present embodiment, and to cure the surface layer portion of the coating film by irradiating ultraviolet rays immediately after the formation of the coating film.

[0115] [Examples]

[0116] Hereinafter, examples of the present disclosure will be described, but the present disclosure is not limited to these examples. Note that in the following description, "parts" and "%" with respect to the amount of incorporation (content, amount of addition) are all on a weight basis, unless otherwise specified.

[0117] <Examples 1 to 7, Comparative Examples 1 to 8>

[0118] The components (except isocyanate) shown in Table 1, which had been warmed to 50°C, were precisely weighed in plastic cups in the amounts (g) shown in Table 1, and stirred at 2000 rpm for 1 minute using a high-speed emulsifying / dispersing machine T.K. HOMOGENIZING DISPER Model 2.5 (DH-2.5 / 1001) manufactured by Primix (Co., Ltd.).

[0119] Next, to the obtained solution, the isocyanate shown in Table 1 warmed to 50°C in advance was added, and a coating agent was prepared by stirring at 2000 rpm for 10 seconds using a "high-speed emulsifying / dispersing machine T.K. HOMOGENIZING DISPER Model 2.5 (DH-2.5 / 1001)" manufactured by Primix Co., Ltd.

[0120] Next, the coating agent was applied to an aluminum plate to which a release agent had been applied. The aluminum plate to which the coating agent had been applied was placed in an oven, and kept at a temperature of 160°C for 20 minutes, and then taken out of the oven and cooled at room temperature for 10 minutes.

[0121] The cured product of the coating agent was peeled off from the aluminum plate.

[0122] Thus, a cured product of the coating agent in the form of a disc having a thickness of 1.5 mm and a diameter of 5 cm was obtained.

[0123] In the case of using the urethane prepolymer, a coating agent was prepared by stirring the components shown in Table 1 at 2000 rpm for 10 seconds using a "high-speed emulsifying / dispersing machine T.K. HOMOGENIZING DISPER Model 2.5 (DH-2.5 / 1001)" manufactured by Primix Co., Ltd.

[0124] < Evaluation >

[0125] The cured product of the coating agent obtained in each example was subjected to the following evaluations.

[0126] (Tear strength, type A durometer hardness)

[0127] The tear strength of the cured product at 25°C and 80°C, the elongation at 25°C, the type A durometer hardness at 25°C, and the type D durometer hardness at 25°C were measured according to the above-described methods.

[0128] (Durability at normal temperature)

[0129] The durability at normal temperature of the cured product of the coating agent obtained in each example was evaluated by subjecting it to a fatigue test of 2 tons at normal temperature (at 25°C). Specifically, the following was done.

[0130] A test body was produced by applying the coating material to a coil spring and heat-curing it. The test body was repeatedly subjected to a load of 2 tons, and whether or not the coating material broke was tested by the number of times the load was applied. Then, the following evaluation criteria were used to evaluate it.

[0131] ◎: No breakage was confirmed up to 30,000 times.

[0132] O: No breakage was confirmed up to 5,000 times.

[0133] X: fracture was confirmed up to 5000 times.

[0134] (Durability at high temperature)

[0135] The durability at high temperature of the cured product of each of the coating agents obtained was evaluated by performing a fatigue test of 2 tons in a warm state (at 80°C). Specifically, the following was performed.

[0136] A test piece was produced by applying the coating material to a spiral spring and heat-curing it. The test piece was repeatedly subjected to a load of 2 tons at high temperature, and whether or not the coating material fractured was tested by the number of times of application of the load. Then, evaluation was performed based on the following evaluation criteria.

[0137] X: fracture was confirmed up to 30000 times.

[0138] O: fracture was not confirmed up to 5000 times.

[0139] X: fracture was confirmed up to 5000 times.

[0140] (Impact resistance at low temperature)

[0141] Since a flying stone can hit a running part of a car, the coating film is required to be soft so as not to generate a crack in the coating film even at low temperature. Therefore, in order to evaluate the softness of the coating agent at low temperature, a cast plate having a thickness of 1.5 mm, a width of 30 mm, and a length of 60 mm was left to stand in an environment of -36°C for 24 hours, then taken out and immediately bent by 180°, and whether or not a crack was generated was confirmed.

[0142] O: no cracking.

[0143] X: cracking.

[0144] Hereinafter, the details of the expressions in Table 1 are as follows.

[0145] -Polymer polyol-

[0146] • PH50: polycarbonate-based polyol ("ETERNACOLL PH50" manufactured by Ube Industries, Ltd.).

[0147] • BENEBIOL HS0830B: polycarbonate-based polyol ("BENEBIOL HS0830B" manufactured by Mitsubishi Chemical Corporation).

[0148] • C-3090: polycarbonate-based polyol ("Kuraray Polyol C-3090" manufactured by Kuraray Co., Ltd.).

[0149] ·BPX-33: A propylene oxide adduct of bisphenol A (manufactured by ADEKA Co., Ltd., "Adeka Polyether BPX-33").

[0150] ·BPX-55: A propylene oxide adduct of bisphenol A (manufactured by ADEKA Co., Ltd., "Adeka Polyether BPX-55").

[0151] • T2305: Caprolactone-based polyol ("PLACCEL T2305" manufactured by Daicel Co., Ltd.).

[0152] • L220LA: Caprolactone-based polyol (manufactured by Daicel Co., Ltd., "PLACCEL L220LA").

[0153] • P-530: Polyester-based polyol (Kuraray Polyol P-530 manufactured by Kuraray Co., Ltd.).

[0154] F-3010: Polyester polyol (Kuraray Polyol F-3010 manufactured by Kuraray Co., Ltd.).

[0155] •Capa7203: A copolymer of polycarbonate polyol and lactone polyol (manufactured by INGEVITY, "Capa7203").

[0156] -Isocyanate-

[0157] ・CORONATE MX: 1,4-MDI (Monomeric MDI) ("CORONATE MX" manufactured by Tosoh Co., Ltd.)

[0158] - Carbamate prepolymer -

[0159] • ADIPRENE E740: A urethane prepolymer of a copolymer of polyether polyol and PPDI (manufactured by LANXESS Co., Ltd., "ADIPRENE E740").

[0160] HEI-AD 2867B: A urethane prepolymer of a copolymer of polyester polyol and MDI (manufactured by H&K Co., Ltd., "HEI-AD 2867B").

[0161] - (C) Chain extender -

[0162] ·14BD: 1,4-Butanediol.

[0163] - Plasticizer -

[0164] • LIR-30: polyisoprene (Kuraray Co., Ltd. "KURAPRENE LIR-30").

[0165] Hereinafter, the results of measurement of the physical properties of each example, and the results of various tests are shown in Table 1.

[0166] [Table 1]

[0167]

[0168] From the above results, it was found that the coating agent of the present embodiment is capable of forming a cured product layer that is excellent in durability and impact resistance at low temperatures.

[0169] Note that the disclosure of Japanese Patent Application No. 2021-098247 is incorporated herein by reference in its entirety.

[0170] All of the literature, patent applications and technical standards cited in the present specification are hereby incorporated by reference to the same extent as if each individual literature, patent application and technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. A coating agent, a cured product of which after curing has a tear strength at 25°C and at 80°C of 20 kN / m or more as measured by a tear test according to JIS K 7311:1995, and a type A durometer hardness at 25°C of 30 to 100 as measured by a hardness test according to JIS K 7311:1995, the coating agent being composed of a composition containing (A) a high-molecular polyol, (B) an isocyanate containing an aromatic isocyanate, and (C) a chain extender, or a composition containing (D) a prepolymer obtained by reacting a polyol with an isocyanate containing an aromatic isocyanate, and the (C) chain extender, a mass ratio A / C of the (A) high-molecular polyol to the (C) chain extender being 1.5 to 10.0, and a mass ratio D / C of the (D) prepolymer obtained by reacting a polyol with an isocyanate to the (C) chain extender being 1.0 to 15.

0.

2. The coating agent according to claim 1, wherein the cured product after curing has a tear strength at 25°C of 45 kN / m or more.

3. The coating agent according to claim 1, wherein the cured product after curing has a tear strength at 25°C of 90 kN / m or more, a tear strength at 80°C of 40 kN / m or more, and a type A durometer hardness at 25°C of 70 to 100.

4. The coating agent according to claim 1, wherein the cured product after curing is a cured product having a urethane bond.

5. The coating agent according to claim 1, wherein the (A) high-molecular polyol contains at least one selected from the group consisting of (Al) a polycarbonate-based polyol, (A2) a polyether-based polyol having a bisphenol structure, (A3) a lactone-based polyol, (A4) a condensed polyester-based polyol of a polybasic acid and a polyol, and (A5) a copolymer of a polycarbonate-based polyol and a lactone-based polyol.

6. The coating agent according to claim 1, wherein the (B) isocyanate containing an aromatic isocyanate is an isocyanate consisting of an aromatic isocyanate, and the (D) prepolymer obtained by reacting a polyol with an isocyanate containing an aromatic isocyanate is a prepolymer obtained by reacting a polyol with an isocyanate consisting of an aromatic isocyanate.

7. The coating agent according to claim 1, which is used for a spring.

8. A spring having a cured product layer of the coating agent according to any one of claims 1 to 7 on at least a part of a surface. ​ ​ ​ ​ ​ ​

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