Coatings and springs

Abstract

DEPCT67 The coatings and springs used in this product exhibit tear resistance after hardening. At 25°C and 80°C, the hardness is greater than or equal to 20 kilonewtons per meter, and it is a durometer hardness. (Durometer hardness) Type A at 25 degrees Celsius equals 30-100;

Description

Coating agents and springs

[0001] The present disclosure relates to coatings and springs.

[0002] Various springs are used in automobiles, railway vehicles, etc. Most of these springs are made of steel, and their surfaces are usually coated with paint to provide corrosion resistance.

[0003] For example, Patent Document 1 discloses a "method for forming a coating portion of a coil spring, characterized in that at least a portion of the axial direction of a coil spring that has been preheated to a predetermined surface temperature is rolled in a trough-shaped container that contains thermoplastic resin powder having a melting point of 250°C or less, and the resin powder that has adhered to the spring wire of the coil spring is heated to melt and then solidified."

[0004] Furthermore, Patent Document 2 discloses "a highly durable spring having a single coating film with a thickness of 450 μm or less, the coating film containing an epoxy resin, a phenolic resin, and zinc." Patent Document 2 also discloses that "the coating film is a cured product of an epoxy resin-based powder coating containing an epoxy resin, a phenolic resin, and zinc."

[0005] Furthermore, Patent Document 3 discloses "a chip-resistant powder topcoat on a steel substrate having thereon a corrosion-resistant powder coating basecoat, the chip-resistant powder topcoat comprising the cured or fused product of a coating powder of one or more resin components of one or more toughened epoxy resins, 0.1 to 5 parts per hundred parts of resin (phr) of one or more waxes, and optionally up to 200 phr of one or more extenders."

[0006] Furthermore, Patent Document 4 discloses "a coil spring used in the suspension of a vehicle, characterized in that in a portion of the spring that satisfies at least one of the conditions that the stress during use is higher than in other portions and the probability of the paint being damaged by flying stones is higher than in other portions, the coating is made thicker in that portion than in portions adjacent to that portion."

[0007] Patent Document 1: JP 57-136972 A Patent Document 2: International Publication WO2017 / 163877 Patent Document 3: JP 2009-120812 A Patent Document 4: JP 2007-308067 A

[0008] In coating agents for springs, the cured layer (coating layer) formed after coating on the spring must be durable against repeated expansion and contraction of the spring, contact between the spring wires, and contact with other components. Impact resistance to withstand impacts from flying stones and the like is also required. However, the level of requirements has recently become higher, and impact resistance, particularly at low and high temperatures, is required in addition to durability at room temperature, but this has not yet been fully explored. Similar properties are also required for coating agents for applications other than spring coatings.

[0009] Therefore, an object of the present disclosure is to provide a coating agent capable of forming a cured layer that has excellent durability at room temperature and high temperatures and excellent impact resistance at low temperatures, and a spring using the same.

[0010] The above problems can be solved by the following means.

[0011] <1> A coating agent in which the cured product has a tear strength of 20 kN / m or more at 25°C and 80°C and a Type A durometer hardness at 25°C of 30 to 100. <2> The coating agent according to <1>, in which the cured product has a urethane bond. <3> The coating agent according to <1> or <2>, in which the cured product is a composition containing (A) a polymer polyol, (B) an isocyanate, and (C) a chain extender, or a composition containing (D) a prepolymer obtained by reacting a polyol with an isocyanate. <4> The coating agent according to <3>, in which the polymer polyol (A) is at least one selected from the group consisting of (A1) a polycarbonate polyol, (A2) a polyether polyol having a bisphenol structure, (A3) a lactone polyol, (A4) a polyester polyol, and (A5) a copolymer of a polycarbonate polyol and a lactone polyol. <5> The coating agent according to any one of <1> to <4>, which is used for a spring. <6> A spring having a cured product layer of the coating agent according to any one of <1> to <5> on at least a part of its surface.

[0012] According to the present disclosure, it is possible to provide a coating agent capable of forming a cured layer that has excellent durability at room temperature and high temperatures and excellent impact resistance at low temperatures, and a spring using the same.

[0013] Hereinafter, exemplary embodiments of the present disclosure will be described. These descriptions and examples are intended to illustrate the present disclosure, but are not intended to limit the present disclosure.

[0014] In this specification, a numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In numerical ranges described in stages in this specification, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in numerical ranges described in this disclosure, the upper or lower limit value of that numerical range may be replaced with a value shown in an example.

[0015] In this specification, each component may contain multiple corresponding substances. When referring to the amount of each component in this specification, if there are multiple substances corresponding to each component, the total amount of the multiple substances is meant unless otherwise specified.

[0016] The coating agent according to this embodiment is a coating agent in which the cured product has a tear strength of 20 kN / m or more at 25°C and 80°C, and a Type A durometer hardness at 25°C of 30 to 100. Note that the cured product means a cured product formed by drying the solvent or a cured product formed by the reaction of the components.

[0017] The coating agent of the present disclosure, due to the above-described configuration, can form a cured layer that is excellent in durability at room temperature and at high temperatures and in impact resistance at low temperatures.

[0018] The coating agent according to this embodiment will be described in detail below.

[0019] (Characteristics) In the coating agent of the present embodiment, the tear strength of the cured product after curing is 20 kN / m or more at 25°C, but from the viewpoint of improving durability at room temperature, it is preferably 60 kN / m or more, and more preferably 90 kN / m or more. However, from the viewpoint of impact absorption, the upper limit of the 25°C tear strength is, for example, 350 kN / m or less.

[0020] In the coating agent of this 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 durability at high temperatures, it is preferably 30 kN / m or more, and more preferably 40 kN / m or more. 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.

[0021] Here, the tear strength is measured in accordance with the tear test specified in JIS K 7311:1995.

[0022] In the coating agent of this embodiment, the Type A durometer hardness of the cured product at 25°C after curing is 30 to 100, but from the viewpoint of improving impact resistance at low temperatures, it is preferably 50 to 100, and more preferably 70 to 100. If the Type A durometer hardness at 25°C is within the above range, impact resistance at low temperatures is improved. Furthermore, when the coating agent of this embodiment is applied to steel springs, the hardness is softer than that of steel springs, thereby preventing abnormal noise. The Type A durometer hardness is measured in accordance with the hardness test specified in JIS K 7311:1995.

[0023] (Composition) The coating agent of this embodiment may be either a thermoplastic resin composition or a composition for forming a thermosetting resin, as long as it can form a cured product that satisfies the above-mentioned properties. Examples of thermoplastic resins include acrylic resins, polystyrene resins, polyethylene resins, polypropylene resins, polyamide resins, nylon resins, vinyl chloride resins, polyacetal resins, polycarbonate resins, polyphenylene ether resins, polybutylene terephthalate resins, polyphenylene sulfone resins, polysulfone resins, polyarylate resins, and polyetherimide resins.

[0024] Examples of thermosetting resins include urethane resin, epoxy resin, cyanate resin, melamine resin, and phenol resin. Other examples include rubber materials such as natural rubber, butadiene rubber, chloroprene rubber, nitrile butadiene rubber, and styrene butadiene rubber.

[0025] Among these, in the coating agent of the present embodiment, the cured product after curing is preferably a cured product having a urethane bond, specifically a urethane resin. In particular, the coating agent of the present embodiment is preferably a composition containing (A) a high molecular weight 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] [Composition Comprising (A) High Polymer Polyol, (B) Isocyanate, and (C) Chain Extender] —(A) High Polymer Polyol— From the viewpoint of improving durability at room temperature and high temperature and impact resistance at low temperature, the (A) high polymer polyol preferably comprises at least one selected from the group consisting of (A1) polycarbonate polyols, (A2) polyether polyols having a bisphenol structure, (A3) lactone polyols, (A4) polyester polyols, and (A5) copolymers of polycarbonate polyols and lactone polyols.

[0027] Examples of the (A1) polycarbonate polyol include polyols obtained by reacting glycol with alkylene carbonate, polyols obtained by reacting glycol with diaryl carbonate, polyols obtained by reacting glycol with dialkyl carbonate, etc. Examples of the alkylene carbonate include ethylene carbonate, 1,2-propylene carbonate, 1,2-butylene carbonate, etc. Examples of diaryl carbonates include diphenyl carbonate, 4-methyldiphenyl carbonate, 4-ethyldiphenyl carbonate, 4-propyldiphenyl carbonate, 4,4'-dimethyldiphenyl carbonate, 2-tolyl-4-tolyl carbonate, 4,4'-diethyldiphenyl carbonate, 4,4'-dipropyldiphenyl carbonate, phenyltoluyl carbonate, bischlorophenyl carbonate, phenylchlorophenyl carbonate, phenylnaphthyl carbonate, dinaphthyl carbonate, etc. Examples of dialkyl carbonates include dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, di-n-butyl carbonate, diisobutyl carbonate, di-t-butyl carbonate, di-n-amyl carbonate, diisoamyl carbonate, etc.

[0028] (A2) Examples of polyether polyols having a bisphenol structure include polyether polyols obtained by adding polyethylene oxide and / or polypropylene oxide to a cyclic diol (such as bisphenol A, hydrogenated bisphenol A, bisphenol S, or bisphenol P), a propylene oxide adduct of bisphenol A, an ethylene oxide adduct of bisphenol A, an ethylene oxide adduct of hydrogenated bisphenol A, and a propylene oxide adduct of hydrogenated bisphenol A. Among these, the propylene oxide adduct of bisphenol A is preferred as the polyether polyol.

[0029] Examples of the lactone polyol (A3) include ring-opening polymers of lactones (ε-caprolactone, β-methyl-δ-valerolactone, etc.), and among these, ring-opening polymers of caprolactone (caprolactone polyols) are preferred.

[0030] (A4) The polyester polyol may be a condensation polyester polyol of a polybasic acid and a polyhydric alcohol other than a lactone polyol.The polybasic acid may be, for example, a polycarboxylic acid.Specific examples of the polybasic acid include 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.The polyhydric alcohol may be glycol or a polyhydric alcohol having a valence of 3 or more. Specific examples of glycols include ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, neopentyl glycol, hexylene glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2-butyl-2-ethyl-1,3-propanediol, methylpropanediol, cyclohexanedimethanol, 3,3-diethyl-1,5-pentanediol, etc. Specific examples of trihydric or higher polyhydric alcohols include glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, dipentaerythritol, etc.

[0031] Examples of (A5) the copolymer of a polycarbonate polyol and a lactone polyol include a copolymer of the above (A1) polycarbonate polyol and the above (A3) lactone polyol.

[0032] Each of the polymer polyols (A) may be used alone or in combination of two or more.

[0033] The number average molecular weight of the (A) polymer polyol is preferably 300 to 12,000, more preferably 800 to 4,000. Here, the number average molecular weight is the molecular weight calculated from the hydroxyl value measured according to JIS K0070 and the number of functional groups. The number average molecular weights of other components are also measured in the same manner.

[0034] —(B) Isocyanate— Examples of the (B) isocyanate include well-known polyisocyanates, such as aromatic diisocyanates such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, diphenylmethane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, xylene-1,4-diisocyanate, 1,5-naphthylene diisocyanate, 1,4-naphthylene diisocyanate, and 3,3′-dichloro-4,4′-diphenylmethane diisocyanate; aliphatic diisocyanates such as hexamethylene diisocyanate, propylene-1,2-diisocyanate, and butylene-1,2-diisocyanate; and alicyclic diisocyanates such as isophorone diisocyanate, 4,4′-dicyclohexylmethane diisocyanate and cyclohexylene diisocyanate. The isocyanate (B) may be used alone or in combination of two or more kinds.

[0035] -(C) Chain Extender- Examples of the (C) chain extender include bifunctional to tetrafunctional polyols having a molecular weight of 60 to 300. Examples of bifunctional polyols include aliphatic diols such as ethylene glycol, propylene glycol, butanediol, pentanediol, neopentyl glycol, methylpentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, and dodecanediol; alicyclic diols such as cyclohexanediol and hydrogenated xylylene glycol; aromatic diols such as xylylene glycol; and polyether polyols obtained by addition polymerization of alkylene oxides (ethylene oxide, propylene oxide, etc.) to dihydric alcohols. The addition polymerization of multiple alkylene oxides may be random addition polymerization or block addition polymerization. Examples of trifunctional polyols include trihydric alcohols having 3 to 10 carbon atoms, such as glycerin and trimethylolpropane. Examples of trifunctional polyols include polyether polyols obtained by addition polymerization of alkylene oxides (ethylene oxide, propylene oxide, etc.) with trihydric alcohols. The addition polymerization of multiple alkylene oxides may be random addition polymerization or block addition polymerization. Examples of tetrafunctional polyols include polyether polyols obtained by addition polymerization of alkylene oxides with ethylenediamine, pentaerythritol, etc. Other examples of low-molecular-weight polyols include ester-based polyols obtained by condensation of adipic acid and short-chain diols such as ethylene glycol and 1,4-butanediol with polyfunctional triols such as glycerin. The (C) chain extender may be used alone or in combination of two or more. It may also be reacted with polyisocyanate in advance to form a prepolymer.

[0036] Among these, as the chain extender (C), from the viewpoint of improving durability at room temperature and high temperatures and impact resistance at low temperatures, ethylene glycol, 1,4-butanediol, 1,6-hexanediol, trimethylolpropane, and glycerin are preferred, and 1,4-butanediol and 1,6-hexanediol are more preferred.

[0037] [(D) Composition containing a prepolymer obtained by reaction of a polyol and an isocyanate] -(D) Prepolymer- The prepolymer is a prepolymer obtained by reaction of a polyol and an isocyanate. Examples of the polyol include the above-mentioned (A) high molecular weight polyol and the above-mentioned low molecular weight polyol as examples of the above-mentioned (C) chain extender. Examples of the isocyanate include the above-mentioned (B) isocyanate.

[0038] The composition containing the (D) prepolymer may contain, in addition to the (D) prepolymer, at least one selected from the group consisting of (A) a high molecular weight polyol, (B) an isocyanate, and (C) a chain extender.

[0039] Other Components The coating agent of this embodiment may contain other components. Examples of other components include well-known additives such as catalysts, thickeners, antioxidants, colorants, UV absorbers, and inorganic fillers (calcium carbonate, etc.). In addition, in order to improve the mechanical properties at warm temperatures, the structure of the resin itself can be made highly heat-resistant, or a crosslinking agent or a reinforcing agent (CNT, etc.) can be added to increase heat resistance.

[0040] - Ratio of Components - The equivalent ratio ((A+C) / (B+D)) of the (A) high molecular weight polyol and (C) chain extender to the (B) isocyanate and (D) prepolymer obtained by reacting a polyol and an isocyanate is preferably 0.5 to 1.5, or 0.8 to 1.2, from the viewpoint of improving durability at room temperature and at high temperatures and impact resistance at low temperatures. The mass ratio (A / C) of the (A) high molecular weight polyol to the (C) chain extender is preferably 1.0 to 35.0, or 1.5 to 10.0, from the viewpoint of improving durability at room temperature and at high temperatures and impact resistance at low temperatures. The mass ratio (D / C) of the (D) prepolymer obtained by reacting a polyol and an isocyanate to the (C) chain extender is preferably 1.0 to 15.0, or 5.0 to 10.0, from the viewpoint of improving durability at room temperature and at high temperatures and impact resistance at low temperatures.

[0041] (Applications of Coating Agent) The coating agent of this embodiment can be suitably used as a coating agent for forming protective layers on, for example, springs, stabilizers, bumpers, and building materials (wall tiles, etc.). Among these, a coating agent for springs can be exemplified as a substitute for the coating agent of this embodiment. Specifically, the article of this embodiment has a cured layer of the coating agent for springs of this embodiment on at least a portion of its surface. The spring of this embodiment has a cured layer of the coating agent for springs of this embodiment on at least a portion of its surface. The spring may be either a coil spring or a leaf spring.

[0042] Examples of the manner in which a cured coating layer can be provided are as follows: 1) On the surface of a coil spring where spring wires come into contact with each other, for the purpose of preventing abnormal noise caused by contact between spring wires; 2) On the surface of the end turn of a coil spring, or on part or the entire surface of the coil spring, for the purpose of protecting the paint; 3) On part or the entire surface of an FRP leaf spring, for the purpose of absorbing impact and preventing splinters.

[0043] (Application Method) The application method for the coating agent of this embodiment is not particularly limited, and applicable methods include dip application, spray application, roller application, brush application, and flow coating. When applying the coating agent of this embodiment to a coil spring, the thickness of the cured layer formed is preferably 1 mm or more (particularly 1 to 2 mm), which raises concerns about sagging of the coating film. Therefore, it is also preferable to blend a thickener into the coating agent of this embodiment to increase the viscosity. It is also preferable to blend an acrylate resin and a photopolymerization initiator into the coating agent of this embodiment to enable ultraviolet curing, and then irradiate the coating agent with ultraviolet light immediately after formation to cure the surface layer of the coating film.

[0044] Examples of the present disclosure will be described below, but the present disclosure is not limited to these examples. In the following description, unless otherwise specified, "parts" and "%" regarding blend amounts (contents, added amounts) are all by weight.

[0045] Examples 1 to 7, Comparative Examples 1 to 8 The components (excluding isocyanate) in the amounts (g) shown in Table 1 were precisely weighed into a plastic cup and preheated to 50°C. The mixture was stirred at 2000 rpm for 1 minute using a T.K. Homo Disper 2.5 model (DH-2.5 / 1001) high-speed emulsifier / disperser manufactured by Primix Corp. Next, the isocyanate shown in Table 1, preheated to 50°C, was added to the resulting solution, and the mixture was stirred at 2000 rpm for 10 seconds using a T.K. Homo Disper 2.5 model (DH-2.5 / 1001) high-speed emulsifier / disperser manufactured by Primix Corp. to prepare a coating agent.

[0046] Next, the coating agent was applied to an aluminum plate coated with a release agent. The aluminum plate coated with the coating agent was placed in an oven and maintained at 160°C for 20 minutes, then removed from the oven and cooled at room temperature for 10 minutes. The cured coating agent was peeled off from the aluminum plate. In this way, a disc-shaped cured coating agent with a thickness of 1.5 mm and a diameter of 5 cm was obtained. However, in examples using a urethane prepolymer, the components shown in Table 1 were stirred for 10 seconds at 2000 rpm using a "High-Speed ​​Emulsifier / Disperser T.K. Homodisper 2.5 Model (DH-2.5 / 1001)" manufactured by Primix Corporation to prepare the coating agent.

[0047] <Evaluation> The cured products of the coating agents obtained in each example were subjected to the following evaluations.

[0048] (Tear Strength, Type A Durometer Hardness) According to the methods described above, the tear strength 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 of the cured product were measured.

[0049] (Durability at Room Temperature) The room temperature durability of the cured product of the coating agent obtained in each example was evaluated by conducting a 2-ton fatigue test at room temperature (25°C). Specifically, the test was carried out as follows. The coating material was applied to a coil spring and cured by heating to prepare a test specimen. A load of 2 ton was repeatedly applied to this test specimen, and a test was carried out to check whether the coating material had broken after each load application. Evaluation was then carried out according to the following evaluation criteria. ◎: No breakage was observed up to 30,000 times. ○: No breakage was observed up to 5,000 times. ×: Breakage was observed up to 5,000 times.

[0050] (Durability at High Temperatures) The durability at high temperatures of the cured products of the coating agents obtained in each example was evaluated by carrying out a 2-ton fatigue test at warm temperatures (80°C). Specifically, the test was carried out as follows. A coating material was applied to a coil spring, which was then cured by heating to prepare a test specimen. A load of 2 tons was repeatedly applied to this test specimen at high temperature, and a test was carried out to check whether the coating material had broken after each load application. Evaluation was then carried out according to the following evaluation criteria. ◎: No breakage was observed up to 30,000 times. ◯: No breakage was observed up to 5,000 times. ×: Breakage was observed up to 5,000 times.

[0051] (Impact resistance at low temperatures) Automobile undercarriage parts are subject to collisions with flying stones, so the coating film is required to be flexible so that cracks do not occur even at low temperatures. Therefore, in order to evaluate the flexibility of the coating agent at low temperatures, a cast plate with a thickness of 1.5 mm, a width of 30 mm, and a length of 60 mm was left in a -36°C environment for 24 hours, then removed and immediately bent 180° to check for cracks. ◯: No cracks ×: Cracks

[0052] Details of the notation in Table 1 are as follows. -High polymer polyols- PH50: Polycarbonate polyol (manufactured by Ube Industries, Ltd., "ETERNACOLL PH50") BENEBIOL HS0830B: Polycarbonate polyol (manufactured by Mitsubishi Chemical Corporation, "BENEBIOL HS0830B") C-3090: Polycarbonate polyol (manufactured by Kuraray Co., Ltd., "Kuraray Polyol C-3090") BPX-33: Propylene oxide adduct of bisphenol A (manufactured by ADEKA Corporation, "ADEKA Polyether BPX-33") BPX-55: Propylene oxide adduct of bisphenol A (manufactured by ADEKA Corporation, "ADEKA Polyether BPX-55") T2305 : Caprolactone polyol ("PLACCEL T2305" manufactured by Daicel Corporation) L220LA: Caprolactone polyol ("PLACCEL L220LA" manufactured by Daicel Corporation) P-530: Polyester polyol ("Kuraray Polyol P-530" manufactured by Kuraray Co., Ltd.) F-3010: Polyester polyol ("Kuraray Polyol F-3010" manufactured by Kuraray Co., Ltd.) Capa7203: Copolymer of polycarbonate polyol and lactone polyol ("Capa 7203" manufactured by INGEVITY)

[0053] -Isocyanate- Coronate MX: 1,4-MDI (monomeric MDI) ("Coronate MX" manufactured by Tosoh Corporation)

[0054] - Urethane prepolymer - Adiprene E740: A urethane prepolymer that is a copolymer of polyether polyol and PPDI (Adiprene E740 manufactured by Lanxess KK) Hi-Ad 2867B: A urethane prepolymer that is a copolymer of polyester polyol and MDI (Hi-Ad 2867B manufactured by H&K Corporation)

[0055] -(C) Chain extender- 14BD: 1,4-butanediol

[0056] - Plasticizer - LIR-30: Polyisoprene ("Kuraray LIR-30" manufactured by Kuraray Co., Ltd.)

[0057] The results of measurements of physical properties and various tests for each example are listed in Table 1 below.

[0058]

[0059] From the above results, it is clear that the coating agent of this example is capable of forming a cured layer that is excellent in durability and impact resistance at low temperatures.

[0060] The disclosure of Japanese Patent Application No. 2021-098247 is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually indicated to be incorporated by reference.

Claims

DEPCT671. Coatings in which the tear resistance of the hardened product after curing at 25°C and 80°C is greater than or equal to 20 kN / m and the durometer hardness type A at 25°C is 30-100.

2. Coatings specified in claim 1 in which the hardened product after curing is a hardened product with urethane bonds.

3. Coatings specified in claim 1 or 2 which are derived from components including polymers, polyols (A), isocyanates (B) and chain extenders (C) or prepolymers (D) resulting from reactions.

4. Coatings specified in Reservation 3 in which the polyol polymer (A) includes at least one type selected from the group comprising polycarbonate-based polyols (A1), polyether-based polyols with a bisphenol structure (A2), lactone-based polyols (A3), polyester-based polyols (A4), and copolymers of polycarbonate-based polyols and lactone-based polyols (A5).

5. Any of the coatings specified in Reservations 1-4 which are used for springs. 6.A spring on which a layer of the hardened product of any of the coatings specified in claims 1-5 is located on at least part of the surface;