JP7259001B1 - Coating film evaluation method, coated body and coating film - Google Patents

Abstract

Kind Code: A1 A coating film evaluation method capable of easily evaluating the weather resistance of a coating film is provided. A paint film evaluation method predicts deterioration of a paint film by measuring the amount of chemiluminescence of the paint film under conditions of continuous temperature rise in an oxygen or air atmosphere. [Selection drawing] Fig. 1

Description

Article 30, Paragraph 2 of the Patent Act applied Material Life Society "13th Chemiluminescence Study Group", held on the Web, Date: January 14, 2021 General Incorporated Association Color Material Association "2021 Color Material Research Presentation" ”, Web held, Date: September 17, 3rd year of Reiwa 13th Chemiluminescence Research Meeting Lecture Summary, pp. 55-56, Chemiluminescence Research Meeting, Distribution date: January 8, 2021 Color material research presentation collection of lecture abstracts, page 53, Color Material Association, publication date: September 3, 2021 (website publication date: September 8, 2021)

TECHNICAL FIELD The present invention relates to a coating film evaluation method, a coated body, and a coating film.

Coatings used outdoors are more susceptible to rainfall, ultraviolet rays, and temperature differences than indoors, so they tend to deteriorate. This is due to the fact that the polymer chains of the resin are cut by ultraviolet rays, and that low-molecular-weight components and film-forming components that are cut by rain fall out. Methods of selecting a resin with high energy, adding an ultraviolet shielding agent to block ultraviolet rays, and adding a light stabilizer or the like to suppress radicals generated by ultraviolet rays are being studied.

Japanese Patent Application Laid-Open No. 61-152771 (Patent Document 1) describes a fluorine-containing copolymer having a cross-linking site containing fluoroolefin and vinyl ether as essential constituents, and a polyfluoroalkyl group capable of co-crosslinking with the fluorine-containing copolymer. A coating resin composition containing a polymer and a polymer in a specific blending ratio is described, which can provide coating films with improved surface properties such as antifouling properties, water and oil repellency, and surface gloss, and excellent weather resistance. It is described that a solvent-soluble fluororesin coating composition can be provided.

JP-A-2002-256217 (Patent Document 2) contains a coating film-forming resin (A), a benzotriazole-based ultraviolet absorber (B), and a triazine-based ultraviolet absorber (C) as essential components, and A coating composition is described which comprises 0.1 to 30 parts of (B) and 0.1 to 20 parts of (C) with respect to 100 parts of (A). In Patent Document 2, this coating composition has the effect of forming a coating film having excellent ultraviolet shielding properties, and in particular, when used as a top layer, the coating composition can sufficiently exhibit lower layer protection properties. Furthermore, it is described that this effect can be maintained for a long period of time, and that the above effect can be maintained for a long period of time even in severe outdoor exposure tests at high temperatures and strong ultraviolet irradiation and accelerated weather resistance tests. In addition, in Patent Document 2, the wavelength range that the UV absorber mainly absorbs is determined according to its structure, and it is possible to select and use it as appropriate. is not sufficiently exhibited, and the protective function of the lower layer becomes insufficient, and if it is too large, the adhesion to the lower layer is impaired, and bleeding out from the coating film tends to occur.

Japanese Patent Application Laid-Open No. 53-67743 (Patent Document 3) discloses that when performing a clear finish on an automobile by a 2-coat 1-bake method, a coloring pigment and (or) an extender pigment and an ultraviolet-absorbing pigment are applied wet-on-wet after coating a metallic color. A method for the durability of a clear coating is described which comprises coating a clear containing a specific amount of agent relative to the resin solids content. Patent Document 3 describes that long-term weather resistance can be obtained by forming a coating film by a "two-coat, one-bake method" that combines wet-on-wet coating and bake-hardening.

Japanese Patent Application Laid-Open No. 2015-206603 (Patent Document 4) discloses an invention of a coating film weather resistance prediction method for predicting the weather resistance of a coating film made of an organic paint, which consists of a calibration curve creation process and a weather resistance prediction process. Are listed. In Patent Document 4, for the specimen of the organic coating film, from the data of the amount of chemiluminescence after the start of deterioration, the apparent activation energy of each specimen can be calculated, and this apparent activation energy and each organic system It is described that a calibration curve that can be used for general weather resistance prediction processing of coating films made of organic paints in general can be obtained from the correlation with the standard deterioration time until the coating film reaches the deterioration limit. , By using this calibration curve, it is possible to quantitatively predict the deterioration of the coating film in a short time, which could not actually be reached without a long-term test in the conventional test method. is described.

JP-A-61-152771 JP-A-2002-256217 JP-A-53-67743 JP 2015-206603 A

As shown in Patent Documents 1 to 3, for the purpose of preventing deterioration of the coating film and ensuring weather resistance, the type and amount of coating film-forming components such as resins, ultraviolet shielding agents, and light stabilizers, and further In this situation, various factors such as coating film formation conditions are being studied. For this reason, it cannot be said that there is a common index for obtaining a highly weather-resistant coating film for various paints, and it is often difficult to predict the weather resistance of a coating film from the formulation of the paint. Therefore, in order to check the weather resistance of the coating film, it is necessary to actually form the coating film and conduct a weather resistance test to determine the coating film performance. Therefore, there has been a demand for a method that can predict the weather resistance of a coating film in a short period of time and determine the coating film performance.

The present inventors have studied the deterioration of coating films, and in particular, the deterioration of coating films containing organic components is greatly affected by oxidation of the coating film. It was thought that the influence of the amount of impurities such as , and the degree of diffusion of oxygen in the coating film was large.

However, conventionally, the bond stability of the polymer of each raw material is estimated from the bond dissociation energy, but since the coating film obtained from the paint is formed by mixing various raw materials, It is difficult to predict deterioration. In addition, the state of the coating film, such as pigment distribution, resin cross-linking, and degree of fusion bonding, varies depending on the manufacturing and film-forming conditions, making it extremely difficult to estimate the bonding stability of the coating film. In addition, thermogravimetric differential thermal analysis is a conventional method for evaluating susceptibility to oxidation. It cannot be said that it is sufficient to be used as an evaluation of "sexiness".

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for evaluating a coating film that can easily evaluate the weather resistance of the coating film. Another object of the present invention is to provide a highly weather-resistant coated body and coating film by using such coating film evaluation method.

The inventors of the present invention focused on the "easiness of oxidation of the coating film" in examining the coating film deterioration prediction method, and considered a method of evaluating the weather resistance of the coating film by evaluating this. This "easiness to be oxidized" was evaluated by measuring the amount of chemiluminescence that can be evaluated by the coating film shape, which is also used in Patent Document 4. Patent Document 4 describes an invention that calculates the apparent activation energy of the sample to be evaluated from the amount of chemiluminescence measured at an arbitrary temperature and predicts the weather resistance of the coating film, but within the temperature range to be measured It was difficult to calculate the activation energy and predict the weather resistance of specimens that cause coating film changes such as component volatilization and decomposition.

As a result of investigation, the present inventors found that the weather resistance of a coating film can be predicted by measuring the amount of chemiluminescence from the coating film under conditions of continuous temperature rise. In particular, the luminescence start temperature obtained from the amount of chemiluminescence measured when the coating film is continuously heated and heated, and the difference in luminescence start temperature between the coating film degraded for a short period of time and the undegraded film It was found that there is a correlation with weather resistance. As a result, the degree of weather resistance of the coating film is derived from the measurement of the amount of chemiluminescence under continuous temperature rising conditions for the coating film before deterioration and the coating film that has been deteriorated for a short period of time, and the coating film with excellent weather resistance can be provided.

As a result of further studies by the present inventors, the difference between the initial temperature and the luminescence start temperature after short-term accelerated deterioration is small in a coating film with excellent weather resistance, and the difference is large in a coating film with poor weather resistance. I found out.

Therefore, the coating film evaluation method of the present invention predicts the deterioration of the coating film by measuring the amount of chemiluminescence of the coating film under conditions of continuous temperature rise in an oxygen or air atmosphere. It is a coating film evaluation method. .

In a preferred example of the coating film evaluation method of the present invention, the chemiluminescence amount of the coating film is measured under conditions of continuous temperature increase in an oxygen or air atmosphere, and the vertical axis is the chemiluminescence amount and the horizontal axis is the temperature. Plot it on a graph to draw a curve that shows the relationship between the amount of chemiluminescence and temperature, find the temperature at the intersection of the tangent line with the minimum differential coefficient and the tangent line with the maximum differential coefficient on this curve, and determine the deterioration of the coating film. to predict.

In another preferred example of the coating film evaluation method of the present invention,
(i) In an oxygen or air atmosphere, the chemiluminescence amount of the coating film is measured under conditions of continuous temperature rise, and plotted on a graph with the chemiluminescence amount on the vertical axis and the temperature on the horizontal axis. Draw a curve showing the relationship between temperatures, find the temperature (T1) at the intersection of the tangent line with the minimum differential coefficient and the tangent line with the maximum differential coefficient on this curve,
(ii) Under an oxygen or air atmosphere, the chemiluminescence amount of the coating film subjected to the accelerated deterioration test is measured under conditions of continuous temperature rise, and plotted in a graph with the vertical axis as the chemiluminescence amount and the horizontal axis as temperature. Draw a curve showing the relationship between the amount of chemiluminescence and temperature, and obtain the temperature (T2) at the intersection of the tangent line with the minimum differential coefficient and the tangent line with the maximum differential coefficient on this curve,
(iii) Deterioration of the coating film is predicted from temperature (T1) and temperature (T2).

The coated body of the present invention is a coated body provided with a highly weather-resistant coating film evaluated using the coating film evaluation method of the present invention.

In a preferred example of the coated body of the present invention, the temperature (T1) at the intersection of the tangent line with the minimum differential coefficient and the tangent line with the maximum differential coefficient on the curve showing the relationship between the amount of chemiluminescence and temperature is 190 to 330. It is a coated body with a coating film that is within the range of °C.
Here, the curve showing the relationship between the amount of chemiluminescence and temperature is obtained by continuously raising the temperature from 50 ° C. to 350 ° C. at a rate of 15 ° C./min in an oxygen or air atmosphere. It is a curve showing the relationship between the amount of chemiluminescence and temperature obtained by measuring the amount of chemiluminescence and plotting it on a graph with the amount of chemiluminescence on the vertical axis and the temperature on the horizontal axis.

In another preferred embodiment of the coated body of the present invention, the temperature (T1) is the temperature at the intersection of the tangent line with the minimum differential coefficient and the tangent line with the maximum differential coefficient on the curve showing the relationship between the amount of chemiluminescence and temperature. If the temperature (T2) is the temperature at the intersection of the tangent line with the minimum differential coefficient and the tangent line with the maximum differential coefficient on the curve showing the relationship between the amount of chemiluminescence and temperature after the accelerated deterioration test, the temperature ( T1) and temperature (T2) are
-3.0 ≤ (T1-T2)/T1 x 100 ≤ 7.0
It is a coated body provided with a coating film that satisfies the relational expression of
Here, the curve showing the relationship between the amount of chemiluminescence and the temperature for obtaining the temperature (T1) and temperature (T2) is continuously from 50 ° C. at a heating rate of 15 ° C./min in an oxygen or air atmosphere. A curve showing the relationship between the chemiluminescence amount obtained by measuring the chemiluminescence amount of the coating film under the condition of raising the temperature to 350 ° C. and plotting it on a graph in which the vertical axis is the chemiluminescence amount and the horizontal axis is the temperature. and the coating film for determining the temperature (T2) is a coating film that has undergone an accelerated deterioration test (xenon lamp irradiation time: 200 hours) in accordance with JIS K 5600-7-7:2008 Cycle A. .

The coating film of the present invention is a highly weather-resistant coating film evaluated using the coating film evaluation method of the present invention.

In a preferred example of the coating film of the present invention, the temperature (T1) at the intersection of the tangent line with the minimum differential coefficient and the tangent line with the maximum differential coefficient on the curve showing the relationship between the amount of chemiluminescence and temperature is 190 to 330. ℃ range.
Here, the curve showing the relationship between the amount of chemiluminescence and temperature is obtained by continuously raising the temperature from 50 ° C. to 350 ° C. at a rate of 15 ° C./min in an oxygen or air atmosphere. It is a curve showing the relationship between the amount of chemiluminescence and temperature obtained by measuring the amount of chemiluminescence and plotting it on a graph with the amount of chemiluminescence on the vertical axis and the temperature on the horizontal axis.

In another preferred embodiment of the coating film of the present invention, the temperature at the intersection of the tangent line with the minimum differential coefficient and the tangent line with the maximum differential coefficient on the curve showing the relationship between the amount of chemiluminescence and temperature is the temperature (T1) If the temperature (T2) is the temperature at the intersection of the tangent line with the minimum differential coefficient and the tangent line with the maximum differential coefficient on the curve showing the relationship between the amount of chemiluminescence and temperature after the accelerated deterioration test, the temperature ( T1) and temperature (T2) are
-3.0 ≤ (T1-T2)/T1 x 100 ≤ 7.0
It is a coating film that satisfies the relational expression of
Here, the curve showing the relationship between the amount of chemiluminescence and the temperature for obtaining the temperature (T1) and temperature (T2) is continuously from 50 ° C. at a heating rate of 15 ° C./min in an oxygen or air atmosphere. A curve showing the relationship between the chemiluminescence amount obtained by measuring the chemiluminescence amount of the coating film under the condition of raising the temperature to 350 ° C. and plotting it on a graph in which the vertical axis is the chemiluminescence amount and the horizontal axis is the temperature. and the coating film for determining the temperature (T2) is a coating film that has undergone an accelerated deterioration test (xenon lamp irradiation time: 200 hours) in accordance with JIS K 5600-7-7:2008 Cycle A. .

ADVANTAGE OF THE INVENTION According to this invention, the coating film evaluation method which can evaluate the weather resistance of a coating film simply can be provided. Moreover, by using such a coating film evaluation method, it is possible to provide a highly weather-resistant coated body and coating film.

A diagram showing the relationship between the amount of chemiluminescence and temperature plotted on a graph in which the amount of chemiluminescence of the coating film is measured under conditions of continuous temperature rise and the amount of chemiluminescence is plotted on the vertical axis and the temperature on the horizontal axis. is.

The present invention will be described in detail below. TECHNICAL FIELD The present invention relates to a coating film evaluation method, a coated body and a coating film.

One aspect of the present invention is a coating film evaluation method for predicting deterioration of a coating film by measuring the amount of chemiluminescence of the coating film under conditions of continuous temperature rise in an oxygen or air atmosphere. In this specification, this coating film evaluation method is also referred to as "the coating film evaluation method of the present invention".

Chemiluminescence is a phenomenon in which energy generated by a chemical reaction is emitted as light. Oxidation reaction is involved in most of chemiluminescence, and in the present invention, the luminescence phenomenon derived from oxidation reaction is also the object of measurement. Therefore, the chemiluminescence amount of the coating film is measured in an oxygen or air atmosphere.

The chemiluminescence of the coating at elevated temperature is described below. When heat energy is applied to the coating film when the temperature is raised, radicals are generated by decomposition of the substances constituting the coating film, and oxygen is added to the radicals (thermal oxidative decomposition) to generate peroxides. In the process of this thermal oxidative decomposition, it is presumed that light is emitted when the excited carbonyl produced by the bimolecular termination reaction of the peroxy radical becomes the ground state. Here, if there is an unstable bond in the coating film that is easily dissociated when energy is applied to the coating film, thermal oxidative decomposition proceeds and light is emitted from a low temperature. In addition, if oxygen easily diffuses in the coating film, oxidation progresses in many places.

The amount of chemiluminescence is the number of photons emitted per unit time (cps; counts per second) during chemiluminescence and can be measured by a weak luminescence detector. Examples of the faint luminescence detector include a chemiluminescence analyzer manufactured by Tohoku Denshi Sangyo Co., Ltd., and the like. In addition, the detection wavelength of the amount of chemiluminescence can be set to a range including a wavelength of 420 to 530 nm, since it is presumed that the chemiluminescence of the coating film is mainly derived from excited carbonyl. Since other excitants may also be present, it is preferable to measure chemiluminescence over a wide wavelength range, eg, 300-850 nm.

The amount of chemiluminescence measured by the coating film evaluation method of the present invention is an index of the deterioration of the coating film. It means that deterioration of the film is likely to occur, and it is possible to predict that the coating film has low weather resistance. In addition, if the amount of chemiluminescence is measured, it is not necessary to pulverize the coating film, and the coating film can be evaluated while maintaining the shape of the coating film.

In the coating film evaluation method of the present invention, the amount of chemiluminescence is measured under conditions of continuous temperature elevation. Here, the heating rate can be selected within the range of 0.1 to 25° C./min, preferably within the range of 5 to 20° C./min, most preferably 10 to 17° C./min. be. Moreover, the measurement temperature is preferably in the temperature range of 50 to 350.degree. Oxygen or air can be used as the measurement atmosphere, but the measurement is preferably performed in an oxygen atmosphere. The gas flow rate can be 50 mL/min. A metal plate having a thickness of 2 mm or less can be used as the object to be coated when measuring the coating film. Objects with low thermal conductivity, such as slate, may affect the measurement results. For example, when the amount of chemiluminescence is measured for a coating film on an object with low thermal conductivity, the luminescence initiation temperature tends to shift to the high temperature side. The measured thickness of the coating film is, for example, 0.01 to 100 μm, preferably 0.1 to 90 μm, more preferably 1 to 75 μm. Since the luminescence initiation temperature changes when the measurement area of the coating film differs, the surface area of the coating film was uniformed to 1 cm×1 cm in the examples of the present specification. The exposure time when measuring the amount of chemiluminescence can be measured in the range of 1 to 10 seconds. In the examples, the exposure time for measuring the amount of chemiluminescence was 1 second.

In a preferred embodiment of the coating film evaluation method of the present invention, the chemiluminescence amount of the coating film is measured under conditions of continuous temperature increase in an oxygen or air atmosphere, the vertical axis is the chemiluminescence amount, and the horizontal axis is the temperature. Draw a curve that shows the relationship between the amount of chemiluminescence and temperature by plotting it on a graph, and find the temperature at the intersection of the "tangent line with the minimum differential coefficient" and the "tangent line with the maximum differential coefficient" on this curve. , is a paint film evaluation method that predicts deterioration of the paint film.

Here, the “tangent line with the maximum differential coefficient” is the tangent line with the maximum increase in the amount of chemiluminescence when the temperature changes by 1° C. in the measurement temperature range (preferably 50 to 350° C.). The "tangential line with the minimum differential coefficient" is the maximum increase in the amount of chemiluminescence when the temperature changes by 1 ° C from the lowest temperature (preferably 50 ° C) in the measurement temperature range (preferably 50 to 350 ° C). In the region up to the temperature where , the increase value of the amount of chemiluminescence when the temperature changes by 1 ° C. is the tangent line with the smallest positive value.

The "intersection point of the tangent line with the minimum derivative and the tangent line with the maximum derivative" means the temperature at which the amount of chemiluminescence begins to increase, and is also referred to herein as the "luminescence initiation temperature". The present inventor believes that the temperature at the intersection of the tangent line with the minimum differential coefficient and the tangent line with the maximum differential coefficient is preferably 190 It was confirmed to be within the range of ~330°C, more preferably 200 to 330°C, still more preferably 210 to 330°C. Coatings with unstable bonds and coatings in which oxygen easily diffuses tend to deteriorate in a short period of time during exposure and accelerated deterioration tests. In such a coating film, oxidative decomposition progresses from a low temperature, and the light emission start temperature is low. In the coating film evaluation method of the present invention, the degree of unstable bonding in the coating film and the degree of easiness of diffusion of oxygen can be quantified. As a result of examining the relationship between weather resistance (gloss retention rate) and light emission start temperature, the present inventors found that a light emission start temperature within the above range can be evaluated as a coating film with high weather resistance. . In addition, if the paint film evaluation method uses "the temperature at the intersection of the tangent line with the minimum differential coefficient and the tangent line with the maximum differential coefficient", it can be used in a short time compared to conventional evaluation methods that require a long period of time. It is possible to predict the deterioration of the coating film over time.

FIG. 1 shows the amount of chemiluminescence of the coating film measured under conditions of continuous temperature rise, and plotted on a graph with the amount of chemiluminescence on the vertical axis and the temperature on the horizontal axis. FIG. 4 is a diagram showing relationships; In the curve of the example, the temperature (T1) at the intersection of the tangent line with the minimum differential coefficient and the tangent line with the maximum differential coefficient is in the range of 190 to 330 ° C., and such a coating film has excellent weather resistance. It is a coating film. In the curve of the comparative example, the temperature (T1) at the intersection of the tangent line with the minimum differential coefficient and the tangent line with the maximum differential coefficient is less than 190°C, and such a coating film has poor weather resistance. .

In a preferred embodiment of the coating film evaluation method of the present invention, the coating film deterioration is predicted by measuring the amount of chemiluminescence of the coating film before and after the accelerated deterioration test. Accelerated deterioration test can use various tests to evaluate weather resistance, preferably JIS K 5600-7-7: 2008 "Paint general test method-Part 7: Long-term durability of coating film-Section 7 : Accelerated Weatherability and Accelerated Lightfastness (Xenon Lamp Method)".

A preferred embodiment of the coating film evaluation method of the present invention is a coating film evaluation method including the following steps (i) to (iii).
(i) In an oxygen or air atmosphere, the chemiluminescence amount of the coating film is measured under conditions of continuous temperature rise, and plotted on a graph with the chemiluminescence amount on the vertical axis and the temperature on the horizontal axis. Draw a curve showing the relationship between temperatures, and obtain the temperature (T1) at the intersection of "a tangent line with a minimum differential coefficient" and "a tangent line with a maximum differential coefficient" on this curve,
(ii) Under an oxygen or air atmosphere, the chemiluminescence amount of the coating film subjected to the accelerated deterioration test is measured under conditions of continuous temperature rise, and plotted in a graph with the vertical axis as the chemiluminescence amount and the horizontal axis as temperature. Draw a curve showing the relationship between the amount of chemiluminescence and temperature, and obtain the temperature (T2) at the intersection of the "tangent line with the minimum differential coefficient" and the "tangent line with the maximum differential coefficient" on this curve,
(iii) Deterioration of the coating film is predicted from temperature (T1) and temperature (T2).

In the coating film evaluation method of the present invention, the measurements of the chemiluminescence amount of the coating film in steps (i) and (ii) are desirably performed under the same conditions. The coating of step (i) is the coating prior to being subjected to the accelerated aging test. The “coating film subjected to accelerated deterioration test” in step (ii) is preferably a coating film subjected to accelerated deterioration test according to Cycle A of JIS K 5600-7-7:2008. Further, the irradiation time of the xenon lamp is preferably 2 to 1000 hours, more preferably 100 to 300 hours, from the viewpoint of predicting coating film deterioration in a short period of time.

The present inventor found that a coating film with excellent weather resistance has a small difference between temperature (T1) and temperature (T2), and a coating film with poor weather resistance has a difference between temperature (T1) and temperature (T2). was found to increase. It is presumed that when new unstable bonds are formed due to the deterioration of the coating film in the accelerated deterioration test, or when the molecular chain is cut and the molecular weight is reduced, thermal oxidative decomposition proceeds at a lower temperature than the initial undegraded coating film, and light is emitted. be done. It is considered that the lower the weather resistance of the coating film, the more the above change progresses when the energy is applied, and the greater the change from the temperature (T1) to the temperature (T2).

In the coating film evaluation method of the present invention, when the accelerated deterioration test of the coating film is a test according to the provisions of Cycle A of JIS K 5600-7-7: 2008 (xenon lamp irradiation time: 200 hours), a highly weather-resistant coating As conditions required for the film, temperature (T1) and temperature (T2) are
-3.0 ≤ (T1-T2)/T1 x 100 ≤ 7.0
It is preferable to satisfy the relational expression (1) of
-2.0 ≤ (T1-T2)/T1 x 100 ≤ 6.0
It is more preferable to satisfy the relational expression (2) of
In the above relational expression, the value of "(T1-T2) / T1 × 100" is a negative value, which means that the coating film subjected to the accelerated deterioration test has a higher light emission start temperature than the coating film before the accelerated deterioration test. indicates that This was a tendency especially seen in water-based paints, but low-molecular-weight components that are easily oxidized, such as surfactants and water-based additives, which are necessary to maintain the state of the paint, leach out, and the paint film undergoes an accelerated deterioration test. It is considered that the temperature at which the light emission starts is higher. However, from the results of examining the relationship between weather resistance (gloss retention rate) and light emission start temperature, even if the value of "(T1-T2) / T1 x 100" is a negative value, if it is up to -3.0 , confirmed that it can be evaluated as a coating film with high weather resistance.

The coating film evaluation method of the present invention can be used for all coating films containing organic components. The main organic component that constitutes the coating film is an organic binder component, and examples include acrylic resin, urethane resin, fluorine resin, acrylic silicone resin, alkyd resin, epoxy resin, polyester resin, etc., but are limited to these. not to be Moreover, the organic binder component may be used singly or in combination of two or more. Coating films include various coating films formed from transparent paints, enamel paints, bright paints, and the like. As the paint, any kind of paint such as water-based paint, organic solvent-based paint, active energy ray-curable paint, powder-based paint, and non-solvent-based paint can be used.

In the coating film evaluation method of the present invention, the coating film to be evaluated may be a coating film formed on the coated body, in this case, the chemiluminescence amount of the coating film without peeling the coating film from the coated body can be measured. Moreover, in the coating film evaluation method of the present invention, the coating film may be a multilayer film, and in this case, the chemiluminescence amount of the multilayer film can be measured.

Another aspect of the present invention is a highly weather resistant coating evaluated using the coating evaluation method of the present invention. This coating is also referred to herein as the "coating of the present invention".

In one embodiment of the coating film of the present invention, the temperature (T1) at the intersection of the tangent line with the minimum differential coefficient and the tangent line with the maximum differential coefficient on the curve showing the relationship between the amount of chemiluminescence and temperature is 190 to 330. ℃ range.
Here, the curve showing the relationship between the amount of chemiluminescence and the temperature for determining the temperature (T1) is obtained by continuously raising the temperature from 50 ° C. to 350 ° C. at a heating rate of 15 ° C./min in an oxygen or air atmosphere. It is a curve showing the relationship between the chemiluminescence amount and the temperature obtained by measuring the chemiluminescence amount of the coating film under the conditions and plotting it on a graph with the chemiluminescence amount on the vertical axis and the temperature on the horizontal axis.

In the coating film of the present invention, when the temperature (T1) of the coating film is within the range of 190 to 330°C, the weather resistance is excellent. For example, by setting the temperature (T1) of the coating film to 190° C. or higher, the gloss retention time of the coating film can be lengthened. The temperature (T1) of the coating film is preferably within the range of 200 to 330°C, more preferably within the range of 210 to 330°C.

In one embodiment of the coating film of the present invention, the temperature at the intersection of the tangent line with the minimum differential coefficient and the tangent line with the maximum differential coefficient on the curve showing the relationship between the amount of chemiluminescence and temperature is the temperature (T1), When the temperature (T2) is the temperature at the intersection of the tangent line with the minimum differential coefficient and the tangent line with the maximum differential coefficient on the curve showing the relationship between the amount of chemiluminescence after the accelerated deterioration test and the temperature, the temperature (T1) and temperature (T2) are
-3.0 ≤ (T1-T2)/T1 x 100 ≤ 7.0
It is a coating film that satisfies the relational expression (1) of
Here, the curve showing the relationship between the amount of chemiluminescence and the temperature for determining the temperature (T2) is continuous at a heating rate of 15 ° C./min in an oxygen or air atmosphere, as in the temperature (T1) described above. Measure the amount of chemiluminescence of the coating film under the conditions of raising the temperature from 50 ° C. to 350 ° C., and plot the amount of chemiluminescence obtained by plotting the amount of chemiluminescence on the vertical axis and the temperature on the horizontal axis. Although it is a curve showing the relationship, the coating film for determining the temperature (T2) was subjected to an accelerated deterioration test (xenon lamp irradiation time: 200 hours) according to the provisions of cycle A of JIS K 5600-7-7:2008. It is a coating film.

In the coating film of the present invention, when the temperature (T1) and the temperature (T2) satisfy the relational expression (1), the weather resistance is excellent. For example, when the temperature (T1) and the temperature (T2) of the coating film satisfy the relational expression (1), the gloss retention time of the coating film can be lengthened. Also, temperature (T1) and temperature (T2) are
-2.0 ≤ (T1-T2)/T1 x 100 ≤ 6.0
It is preferable to satisfy the relational expression (2).

Since the coating film of the present invention may be a matte coating film, the glossiness is not particularly limited. For example, in the case of a glossy coating film, it is preferable that the glossiness at 60° is 70 to 90. In addition, the glossiness of the coating film can be used as an index of weather resistance. can be determined to be gender. For example, the gloss value of the coating film after the accelerated deterioration test according to the provisions of JIS K 5600-7-7: 2008 cycle A is 50% lower than the gloss value (initial gloss value) of the coating film before the accelerated deterioration test. From the viewpoint of weather resistance, a coating film that can be irradiated with a xenon lamp for 2000 hours or more is preferable, and 3000 hours or more is more preferable.

In this specification, the glossiness at 60° is defined by JIS K5600-4-7 (ISO 2813: 1994) according to the specular glossiness (D60) at 60°, for example, gloss meter VG manufactured by Nippon Denshoku Co., Ltd. It can be measured using -2000.

The coating film of the present invention preferably has an oxygen permeability of 7.5 cc·μm/cm ² /day or less. In this specification, the oxygen permeability is measured by the isobaric method (Mocon method) using an oxygen permeability measuring device (for example, 8001 manufactured by Illinois). Specifically, the coating is fixed in a diffusion chamber within the apparatus, and the oxygen transfer rate (OTR) through the coating is detected. A standard film with a known transmittance is used to calibrate the detector. Moreover, the lower limit of the oxygen permeability is, for example, 0.005 cc·μm/cm ² /day.

The coating film of the present invention includes a binder component, coloring materials such as dyes and pigments, various pigments such as extender pigments, ultraviolet absorbers, radical scavengers, antioxidants, plasticizers, rust inhibitors, matting agents, and fillers. , charge control agent, light guide material, luster material, magnetic material, phosphor, wax, antibacterial agent, antiviral agent, antiseptic agent, surface control agent, antifoaming agent, dispersant, etc. can contain.

The coating film of the present invention is a coating film containing an organic component. The main organic component that constitutes the coating film is an organic binder component, and examples include acrylic resin, urethane resin, fluorine resin, acrylic silicone resin, alkyd resin, epoxy resin, polyester resin, etc., but are limited to these. not to be The organic binder components may be used singly or in combination of two or more. In the coating film of the present invention, the amount of binder component is, for example, 30 to 100% by weight.

In the coating film of the present invention, the binder component preferably has a crosslinked structure. By using a binder component having a crosslinked structure, the weather resistance of the coating film can be improved. For example, a crosslinked structure can be introduced into the binder component by synthesizing the binder component using a crosslinkable monomer or by combining the binder component with a crosslinker.

The crosslinkable monomer includes, for example, a compound having two or more polymerizable groups, a compound having a polymerizable group and a group having crosslinkability by chemical reaction, and the like. Examples of the polymerizable group include polymerizable unsaturated groups such as alkenyl groups (vinyl group, allyl group, etc.) and alkenylcarbonyl groups (eg, (meth)acryloyl group, crotonoyl group, etc.). Examples of the group having crosslinkability by chemical reaction include an epoxy group, a carbonyl group, an aziridinyl group, an isocyanato group, and a silane group. A crosslinkable monomer may be used individually by 1 type, and may be used in combination of 2 or more types.

Examples of cross-linking agents include melamine-based cross-linking agents, oxazoline-based cross-linking agents, acrylamide-based cross-linking agents, polyamide-based cross-linking agents, epoxy-based cross-linking agents, isocyanate-based cross-linking agents, aziridine-based cross-linking agents, titanate-based cross-linking agents, and urea-based cross-linking agents. cross-linking agents, alkyl alcoholic urea-based cross-linking agents, hydrazide-based cross-linking agents, carbodiimide-based cross-linking agents, silane coupling agents, zirconium compounds, zinc compounds, titanium compounds, and polyvalent metal compounds such as aluminum compounds. The cross-linking agents may be used singly or in combination of two or more.

The binder component preferably contains a structural unit derived from an ultraviolet absorber and/or a structural unit derived from a radical scavenger. For example, by using a polymerizable ultraviolet absorber or a polymerizable radical scavenger, structural units derived from the ultraviolet absorber or radical scavenger can be introduced into the binder component. By using a binder component containing a structural unit derived from an ultraviolet absorber and/or a structural unit derived from a radical scavenger, the weather resistance of the coating film can be improved.

Examples of the polymerizable ultraviolet absorber include ultraviolet absorbing monomers such as benzotriazole ultraviolet absorbing monomers and benzophenone ultraviolet absorbing monomers. Polymerizable radical scavengers include, for example, polymerizable photostable monomers such as hindered amine polymerizable photostable monomers. Examples of hindered amine-based polymerizable photostable monomers include polymerizable compounds (compounds having a piperazine skeleton and a polymerizable group) having a piperazine skeleton (especially a 2,2,6,6-tetramethylpiperidine skeleton), and the like. is mentioned.

The coating film of the present invention preferably contains an ultraviolet absorber. The ultraviolet absorber has the action of absorbing ultraviolet rays and preventing deterioration due to ultraviolet rays. By using an ultraviolet absorber, the weather resistance of the coating film can be improved. Examples of ultraviolet absorbers include benzophenone-based ultraviolet absorbers, benzoate-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, triazine-based ultraviolet absorbers (especially hydroxyphenyltriazine-based ultraviolet absorbers), benzylidene camphor-based ultraviolet absorbers, and the like. is mentioned. The UV absorbers may be used singly or in combination of two or more, but the UV absorbers preferably contain two or more UV absorbers having different absorption peaks. In the coating film of the present invention, the amount of UV absorber is, for example, 0.2 to 25 mass %. It is preferably 1 to 20% by mass.

The coating film of the present invention preferably contains a radical scavenger. A radical scavenger can scavenge free radicals and the like to improve photostability. In the present invention, radical scavengers also include substances that react with free radicals and have the function of preventing polymerization reactions (so-called polymerization inhibitors). By using a radical scavenger, the weather resistance of the coating film can be improved. Examples of radical scavengers include hindered amine-based compounds, hydroquinone-based compounds, phenol-based compounds, phenothiazine-based compounds, nitroso-based compounds, N-oxyl-based compounds, etc. Hindered amine-based light stabilizers (HALS) are particularly preferred. . A radical scavenger may be used individually by 1 type, and may be used in combination of 2 or more types. The amount of the radical scavenger in the coating film of the present invention is, for example, 0.1 to 20% by weight. It is preferably 1 to 18% by mass.

Hindered amine photostabilizers (HALS) include, for example, copolymerized HALS such as the hindered amine polymerizable photostable monomers described above, low molecular weight HALS, medium molecular weight HALS, high molecular weight HALS, It can be classified into resin-encapsulated HALS and the like. In this specification, HALS with a molecular weight of 500 or less are classified as low molecular weight type, HALS with molecular weight of more than 500 and less than 1000 are classified as medium molecular weight type, and HALS with molecular weight of 1000 or more are classified as high molecular weight type. The longer the HALS is retained in the coating film, the better the weatherability. Further, the higher the molecular weight of HALS, the easier it is retained in the coating film, and furthermore, it is retained for a longer period of time by copolymerization with the resin in the coating film, thereby improving the weather resistance. In addition, weather resistance is improved by arranging HALS in the surface layer portion where deterioration progresses most and radicals are likely to be generated. From the above, it is preferable to combine a low-molecular-weight HALS that easily migrates to the surface layer and a HALS that is easily retained for a long period of time. The resin-encapsulated HALS are HALS encapsulated in a resin and dispersed in water, and are easy to add stably to the paint and difficult to dissolve out of the paint film.

The coating film of the present invention can contain colorants such as dyes and pigments. As the coloring material, known materials can be used. aluminum/chromium, ultramarine blue), inorganic pigments/dyes such as titanium oxide, quinacridones, diketoprolopyls, benzimidazolones, isoindolinones, anthrapyrimidines, phthalocyanines, threnes, and dioxazines. organic pigments and dyes such as organic pigments and azo pigments. From the viewpoint of weather resistance, it is preferable to use an inorganic pigment. The coloring materials may be used singly or in combination of two or more. In the coating film of the present invention, the amount of coloring material is, for example, 0 to 60% by mass.

It is preferable that no polymerization initiator or curing catalyst remains in the coating film of the present invention. If a polymerization initiator or a curing catalyst is present in the coating film, the organic components in the coating film are likely to be oxidized, possibly deteriorating the weather resistance of the coating film.

The film thickness of the coating film of the present invention is, for example, 0.01 to 100 μm, preferably 0.1 to 90 μm, more preferably 1 to 75 μm. If the film thickness is too thin, the binder component cannot be sufficiently fused, and the coating tends to be permeable to oxygen, possibly deteriorating the weather resistance of the coating.

The coating film of the present invention may be a multilayer film.

The coating film of the present invention includes various coating films formed from transparent paints, enamel paints, bright paints, and the like. Here, as the paint, any kind of paint such as water-based paint, organic solvent-based paint, active energy ray-curable paint, powder-based paint, and non-solvent-based paint can be used.

The paint can be prepared by mixing various components appropriately selected as necessary. Paint is a one-liquid type in which various components are pre-mixed and used as-is at the time of painting, and two or more components (for example, main agent and curing agent) that are stored separately are mixed at the time of painting. It may be in any form of a multi-liquid type (for example, a two-liquid type).

Although the minimum film-forming temperature (MFT) of the paint is not limited, it is preferably 0 to 70°C. If the minimum film-forming temperature is high, the binder component cannot be sufficiently fused, and the coating tends to be permeable to oxygen, possibly deteriorating the weather resistance of the coating.

As used herein, the minimum film-forming temperature is the minimum temperature at which a crack-free uniform coating film is formed when the paint is dried, and is measured in accordance with JIS K 6828-2: 2003. .

The paint has a viscosity of 0.001 to 1000 (Pa s, 23 ° C.) at a shear rate of 0.1 (1 / s), and a viscosity of 0.001 to 10 (Pa s) at a shear rate of 1000 (1 / s). · s, 23°C). As used herein, the viscosity is measured using a rheometer (for example, Rheometer ARES manufactured by TA Instruments) after adjusting the liquid temperature to 23°C.

The coating means of the paint is not particularly limited, and known coating means such as brush coating, roller coating, trowel coating, spatula coating, flow coater coating, spray coating (e.g. air spray coating, airless spray coating, etc.) are used. can.

The method of drying the paint is not particularly limited, and may be natural drying at ambient temperature, forced drying using a dryer or the like, or photocuring.

Another aspect of the present invention is a coated body provided with a highly weather-resistant coating film evaluated using the coating film evaluation method of the present invention. In this specification, this coated body is also referred to as "the coated body of the present invention".

In one embodiment of the coated body of the present invention, the temperature (T1) at the intersection of the tangent line with the minimum differential coefficient and the tangent line with the maximum differential coefficient on the curve showing the relationship between the amount of chemiluminescence and temperature is 190 to 330. It is a coated body with a coating film that is within the range of °C.
Here, the curve showing the relationship between the amount of chemiluminescence and the temperature for determining the temperature (T1) is obtained by continuously raising the temperature from 50 ° C. to 350 ° C. at a heating rate of 15 ° C./min in an oxygen or air atmosphere. It is a curve showing the relationship between the chemiluminescence amount and the temperature obtained by measuring the chemiluminescence amount of the coating film under the conditions and plotting it on a graph with the chemiluminescence amount on the vertical axis and the temperature on the horizontal axis.

A coated body provided with a coating film having a temperature (T1) within the range of 190 to 330° C. has excellent weather resistance. For example, by setting the temperature (T1) of the coating film to 190° C. or higher, the gloss retention time of the coating film can be lengthened. The temperature (T1) of the coating film is preferably within the range of 200 to 330°C, more preferably within the range of 210 to 330°C.

In one embodiment of the coated body of the present invention, the temperature at the intersection of the tangent line with the minimum differential coefficient and the tangent line with the maximum differential coefficient on the curve showing the relationship between the amount of chemiluminescence and temperature is the temperature (T1), When the temperature (T2) is the temperature at the intersection of the tangent line with the minimum differential coefficient and the tangent line with the maximum differential coefficient on the curve showing the relationship between the amount of chemiluminescence after the accelerated deterioration test and the temperature, the temperature (T1) and temperature (T2) are
-3.0 ≤ (T1-T2)/T1 x 100 ≤ 7.0
It is a coated body provided with a coating film that satisfies the relational expression (1).
Here, the curve showing the relationship between the amount of chemiluminescence and the temperature for determining the temperature (T2) is continuous at a heating rate of 15 ° C./min in an oxygen or air atmosphere, as in the temperature (T1) described above. Measure the amount of chemiluminescence of the coating film under the conditions of raising the temperature from 50 ° C. to 350 ° C., and plot the amount of chemiluminescence obtained by plotting the amount of chemiluminescence on the vertical axis and the temperature on the horizontal axis. Although it is a curve showing the relationship, the coating film for determining the temperature (T2) was subjected to an accelerated deterioration test (xenon lamp irradiation time: 200 hours) according to the provisions of cycle A of JIS K 5600-7-7:2008. It is a coating film.

A coated body having a coating film in which the temperature (T1) and the temperature (T2) satisfy the relational expression (1) has excellent weather resistance. For example, when the temperature (T1) and the temperature (T2) of the coating film satisfy the relational expression (1), the gloss retention time of the coating film can be lengthened. Also, temperature (T1) and temperature (T2) are
-2.0 ≤ (T1-T2)/T1 x 100 ≤ 6.0
It is preferable to satisfy the relational expression (2).

In the coated body of the present invention, the coating film may be a matte coating film, so the glossiness is not particularly limited. For example, in the case of a glossy coating film, the glossiness at 60° is preferably 70 to 90. In addition, the glossiness of the coating film can be used as an index of weather resistance. can be determined to be gender. For example, the gloss value of the coating film after the accelerated deterioration test according to the provisions of JIS K 5600-7-7: 2008 cycle A is 50% lower than the gloss value (initial gloss value) of the coating film before the accelerated deterioration test. From the viewpoint of weather resistance, a coating film that can be irradiated with a xenon lamp for 2000 hours or more is preferable, and 3000 hours or more is more preferable.

In the coated body of the present invention, the coating film preferably has an oxygen permeability of 7.5 cc·μm/cm ² /day or less. Moreover, the lower limit of the oxygen permeability is, for example, 0.005 cc·μm/cm ² /day.

In the coated body of the present invention, the description of the coating film of the present invention is similarly applied to the coating film. For example, in the coated body of the present invention, the coating film is a coating film containing an organic component, the main organic component constituting the coating film is an organic binder component, and the binder component preferably has a crosslinked structure, The binder component preferably contains a structural unit derived from an ultraviolet absorber and/or a structural unit derived from a radical scavenger, the coating film preferably contains an ultraviolet absorber, and the coating film contains a radical scavenger. Preferably, the coating film can contain a coloring material such as a dye or a pigment, and it is preferable to use an inorganic pigment as the coloring material, and it is preferable that no polymerization initiator or curing catalyst remains in the coating film. In the coated body of the present invention, the thickness of the coating film is, for example, 0.01 to 100 μm, preferably 0.1 to 90 μm, more preferably 1 to 75 μm, and the coating film is multi-layered. It may be a membrane.

In addition to the coating film (first coating film) described above, the coated body of the present invention can comprise one or more additional coating films (second coating film) different from the first coating film. In this case, the first coating film is preferably located on the surface layer of the coated body and is preferably used as a surface protective layer.

In the coated body of the present invention, the coating film is formed on the substrate.

Examples of base materials include plastic bases such as epoxy resins, ABS resins, polycarbonates, polyvinyl chlorides, polystyrenes, acrylic resins such as polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), polyolefins such as polypropylene (PP). Materials, steel, galvanized steel, tinned steel, stainless steel, magnesium alloy, aluminum, aluminum alloy, titanium, titanium alloy and other metal substrates, cement, mortar, concrete, slate, gypsum, calcium silicate, glass, ceramics , inorganic substrates other than metals such as calcium carbonate, marble, artificial marble, etc., woody substrates such as wood, and composite substrates in which two or more of these substrates are combined. Examples of composite base materials include composite base materials such as wood fiber reinforced cement boards, fiber reinforced cement boards, fiber reinforced cement/calcium silicate boards, metal base materials subjected to various surface treatments such as oxidation treatment, and the like. A plastic substrate whose surface is coated with an inorganic substance (for example, a plastic substrate coated with a vitreous substance) and the like can be mentioned.

The base material has various shapes, such as a plate-like base material. The surface of the substrate may be smooth or may have unevenness.

Specific examples of the substrate preferably include structures such as buildings and constructions, vehicles (automobiles, etc.), furniture, fittings, electronic devices (home appliances, etc.), and parts thereof. Here, the coated article of the present invention is suitable as a base material for the interior and exterior (for interior and/or exterior) of structures. In the present invention, a building means a structure built for the purpose of human residence or stay, for example, a house (especially a detached house or collective housing), a building, a factory, etc. Structures constructed for purposes other than human habitation or residence, such as bridges, tanks, plant piping, chimneys, and the like. Examples of structural members include roofs and walls (inner walls, outer walls, particularly curtain walls).

The coated body of the present invention is preferably a building material, particularly a building board. Specific examples of building base materials include wooden building materials such as veneers, plywoods, particle boards, and medium density fiberboards (MDF); ceramic siding boards, flexible boards, calcium silicate boards, gypsum slag barlite boards, and wood chips. Ceramic building materials such as cement board, asbestos cement board, pulp cement board, precast concrete board, lightweight aerated concrete (ALC) board or ALC panel, gypsum board; various building materials such as metal siding board, metal building materials such as aluminum, iron, stainless steel, etc. (especially building boards) are preferred. Specific examples of the substrate include plastic substrates such as vinyl chloride sheets, tarpaulins, plastic cardboard (plastic cardboard), acrylic plates, tiles, and glass plates.

The surface of the base material may be subjected to pretreatment such as degreasing treatment, chemical conversion treatment, polishing, sealer, primer coating, or the like. For example, if the base material is a base material (especially a porous base material) that may absorb excessive paint such as ceramic building materials, the surface of the base material is coated with a sealer to form a sealer layer on the base material. may have been. Moreover, when the base material is a metal building material or the like, the surface of the base material may be coated with a primer to form a primer layer on the base material.

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

Preparation of acrylic resin emulsion <Resins A to F>
As resins A to F, the following water-dispersible resins were prepared. The particle size indicated the value of volume average particle size D50 measured by the dynamic light scattering method.
Resin A: Emulsion polymer of [monomer composition: MMA/CHMA/EHA/MAA/KBM503 (mass ratio 30/42/25/2/1)] using KH10 as an emulsifier, solid content 45% by mass, average particle diameter 90 nm
・Resin B: KH10 is used as an emulsifier and LA-82 is blended as a polymerizable radical scavenger [monomer composition: MMA/CHMA/EHA/MAA/KBM503/LA-82 (mass ratio 29/42/24/2 /1/2)], solid content 45% by mass, average particle size 90 nm
・Resin C: KH10 is used as an emulsifier and RUVA-93 is blended as a polymerizable ultraviolet absorber [monomer composition: MMA/CHMA/EHA/MAA/KBM503/RUVA-93 (mass ratio 29/42/24/2 /1/2)], solid content 45% by mass, average particle size 90 nm
Resin D: Emulsion polymer of [monomer composition: MMA/CHMA/EHA/MAA/KBM503 (mass ratio 30/42/25/2/1)] using Hitenol NF08 as an emulsifier, solid content 45% by mass, Average particle size 90nm
Resin E: Emulsion polymer of [monomer composition: MMA/CHMA/BA/BMA/MAA/KBM503 (mass ratio 27/30/20/20/2/1)] using KH10 as an emulsifier, solid content 45 mass %, average particle size 90 nm
Resin F: Emulsion polymer of [monomer composition: MMA/CHMA/BA/MAA (mass ratio 23/25/50/2)] using Hitenol NF08 as an emulsifier, solid content 45% by mass, average particle size 90 nm

Abbreviations have the following meanings.
・KH10: Reactive emulsifier, manufactured by Daiichi Kogyo Seiyaku Co., Ltd. ・Hitenol NF08: Non-reactive emulsifier, manufactured by Daiichi Kogyo Seiyaku Co., Ltd. ・MMA: Methyl methacrylate, homopolymer Tg 105 ° C., SP value 9.53
・CHMA: cyclohexyl methacrylate, homopolymer Tg 60°C, SP value 9.48
EHA: 2-ethylhexyl acrylate, Tg of homopolymer -50°C, SP value 9.2
・ BA: n-butyl acrylate, homopolymer Tg -55 ° C., SP value 9.67
· BMA: n-butyl methacrylate, homopolymer Tg 20 ° C., SP value 9.27
・MAA: methacrylic acid, homopolymer Tg 130°C, SP value 10.24
・KBM503: γ-methacryloyloxypropyltrimethoxysilane ・LA-82: 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate, radical scavenger, Adekastab LA-82, manufactured by ADEKA ・RUVA-93 : 2-[2′-hydroxy-5′-(β-methacryloyloxyethoxy)-3′-tert-butylphenyl]-4-tert-butyl-2H-benzotriazole, UV absorber, manufactured by Otsuka Chemical Co., Ltd.

Preparation of Alkyd Resin <Resin G>
12 parts by mass of phthalic anhydride, 2 parts by mass of adipic acid, 1.5 parts by mass of benzoic acid, 12 parts by mass of pentaerythritol, and soybean oil fatty acid were added to a reactor equipped with a heating device, stirrer, nitrogen gas injector and water separator. 22 parts by mass of linseed oil fatty acid, 9 parts by mass of linseed oil fatty acid, and 2 parts by mass of xylene are charged in a flask equipped with a reflux condenser, heated at 230° C. for about 8 hours while stirring in a nitrogen gas atmosphere, and dehydrated and condensed until the resin acid value reaches 15. reacted. After cooling to 130° C., 43 parts by mass of xylene was added to prepare an alkyd resin. The resulting alkyd resin solution had a solids content of 55% by weight, a viscosity of 20 stokes and a weight average molecular weight of 40,000.

Preparation of paint <Preparation of paints 1 to 7>
Paints 1 to 7 having a PWC (pigment weight concentration) of 45% were prepared using the resins shown in Table 1 (where the curing agent was also indicated when used) and titanium dioxide as follows.
In Paint 1, a solvent-based fluororesin was prepared using a solvent-based fluororesin (manufactured by Asahi Glass Co., Ltd., trade name LF200) and titanium dioxide 1 (manufactured by Ishihara Sangyo Co., Ltd., trade name TIPAQUE PFC105) as main ingredients. Isocyanate (manufactured by Asahi Kasei Corporation, trade name Duranate TPA-100, hexamethylene diisocyanate, nurate type) was used as a curing agent. A paint 1 having a PWC of 45% was prepared by mixing 80 parts by mass of a solvent-based fluororesin and 20 parts by mass of a curing agent.
As the paint 2, a fluororesin emulsion (manufactured by Asahi Glass Co., Ltd., product name Lumiflon FE4300) and titanium dioxide 1 were used.
As paint 3, an acrylic silicone resin emulsion (trade name Polydurex H7650, manufactured by Asahi Kasei Chemicals Corporation) and titanium dioxide 1 were used.
Paint 4 used an acrylic resin emulsion (prepared resin A) and titanium dioxide 1.
As paint 5, urethane dispersion (manufactured by Seiko Kasei Co., Ltd., product name: Rack Coat WN-3049) and titanium dioxide 1 were used.
Paint 6 used an alkyd resin (prepared resin G) and titanium dioxide 1.
For paint 7, an acrylic resin emulsion (prepared resin A) and titanium dioxide 2 (manufactured by Ishihara Sangyo Co., Ltd., trade name TIPAQUE CR-50) were used.
Furthermore, in paints 2 to 5 and paint 7, a solvent (diethylene glycol monobutyl ether) was added as a film-forming aid in an amount of 10% by mass based on the resin solid content.

Details of the titanium dioxide used are as follows.
Titanium dioxide 1: TIPAQUE PFC105
_TiO2 amount 87%, surface treatment Al, Si, Zr, organic matter, average particle size 0.28 μm
Titanium dioxide 2: TIPAQUE CR-50
_TiO2 amount 95%, surface treatment Al, average particle size 0.25 μm

<Preparation of paints 8 to 19>
Raw materials were mixed according to the formulation shown in Table 2 to obtain a paint.
For paint 8, prepared resin A was used.
In paint 9, prepared resin A was used, and HALS1 (manufactured by BASF Japan Ltd., trade name TINUVIN292, low molecular weight HALS, molecular weight 509, 370) was added.
In paint 10, prepared resin B (containing copolymerized HALS) was used.
In paint 11, prepared resin A was used, and HALS2 (manufactured by BASF Japan Ltd., trade name TINUVIN123DW, resin-encapsulated HALS) was added.
In paint 12, prepared resin A was used, and HALS3 (manufactured by BASF Japan Ltd., trade name TINUVIN123, middle molecular weight type HALS, molecular weight 737) was added.
In paint 13, prepared resin A was used, and UVA1 (manufactured by BASF Japan Ltd., trade name TINUVIN1130, non-reactive UVA) was added.
For paint 14, prepared resin C (containing copolymerized UVA) was used.
In paint 15, prepared resin A was used, and HALS1 and UVA1 were added.
In paint 16, prepared resin B (containing copolymer type HALS) was used, and 2% by mass of UVA1 was added to the coating film.
In paint 17, prepared resin B (containing copolymer type HALS) was used, and 2% by mass of HALS1 and 2% by mass of UVA1 were added to the coating film.
In paint 18, prepared resin B (containing copolymer type HALS) was used, and HALS1 was added in an amount of 7% by mass per coating film and UVA1 was added in an amount of 2% by mass per coating film.
In paint 19, prepared resin B (containing copolymer type HALS) was used, and 19% by mass of HALS1 and 10% by mass of UVA1 were added per coating film.
Furthermore, in paints 8 to 19, a solvent (diethylene glycol monobutyl ether) was added as a film forming aid in an amount of 10% by mass based on the resin solid content.

Details of the HALS and UVA used are as follows.
・ TN292: A mixture of bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and methyl-1,2,2,6,6-pentamethyl-4-piperidyl-sebacate, TINUVIN292, BASF Japan TN123: Bis (1-octoxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate, TINUVIN123, average molecular weight 737, manufactured by BASF Japan TN1130: Methyl-3-[3-tert-butyl -Condensation product of 5-(2H-benzotriazol-2-yl)-4-hydroxyphenyl]propionate and polyethylene glycol (molecular weight 300), TINUVIN1130, manufactured by BASF Japan

<Preparation of paints 20 to 29>
Raw materials were mixed according to the formulation shown in Table 3 to obtain a paint.
The coating material 20 was prepared by mixing fluororesin emulsion 1 (manufactured by Asahi Glass Co., Ltd., product name Lumiflon FE4300) and the prepared resin A in a solid mass ratio of 50:50.
Paint 21 was prepared by mixing fluororesin emulsion 1 and prepared resin E in a ratio of 50:50 in terms of solid content.
The paint 22 was prepared by mixing fluororesin emulsion 2 (manufactured by Arkema Co., Ltd., trade name: Kynor Aquatec ARC) and the prepared resin A in a solid mass ratio of 50:50.
Paint 23 was prepared by mixing fluororesin emulsion 1 and prepared resin D in a ratio of 50:50 in terms of solid content.
For paint 24, prepared resin A was used.
Paint 25 was prepared by mixing fluororesin emulsion 1 and prepared resin A in a ratio of 5 to 95 in terms of solid content.
Paint 26 was prepared by mixing fluororesin emulsion 1 and prepared resin A in a ratio of 10 to 90 in terms of solid content.
Paint 27 was prepared by mixing fluororesin emulsion 1 and prepared resin A in a ratio of 30:70 in terms of solid content.
Paint 28 was prepared by mixing fluororesin emulsion 1 and prepared resin A in a ratio of 70 to 30 in terms of solid content.
As the paint 29, the fluororesin emulsion 1 was used.

<Preparation of paints 30 to 32>
Paints were obtained using the resins and matting agents shown in Table 4 as follows.
Paint 30 is prepared resin A, 2% by mass of HALS1 per coating film, 2% by mass of UVA1 per coating film, and matting agent 1 (Nihon Exlan Kogyo Co., Ltd., Tuftic 750SQ, acrylic fine particles). It was prepared by mixing 25 mass % per film and a film-forming aid.
Paint 31 was prepared by mixing prepared resin A, HALS 1, UVA 1, delustering agent 2 (SYLOID W500, silicon dioxide, manufactured by W. R. Grace Japan Co., Ltd.), and a film forming aid.
Paint 32 is the prepared resin D, 2% by mass of HALS1 per coating film, 2% by mass of UVA1 per coating film, and matting agent 1 (Nihon Exlan Kogyo Co., Ltd., Tuftic 750SQ, acrylic fine particles). It was prepared by mixing 25 mass % per film and a film-forming aid.
HALS1 and UVA1 used are as described in <Preparation of paints 8-19> above. In addition, the film-forming aid used was diethylene glycol monobutyl ether.

<Preparation of paints 33-34>
Paints 33-34 with 45% PWC were prepared using the resins shown in Table 4 and titanium dioxide as follows.
The paint 33 used prepared resin A, titanium dioxide 1, and HALS1.
As the paint 34, prepared resin F and titanium dioxide 1 were used.
Titanium dioxide 1 used is as described in <Preparation of paints 1-7> above, and HALS 1 is as described in <Preparation of paints 8-19> above.

Preparation of test plate <Test plates 1 to 7>
The test plate 1 was prepared by applying the coating material 1 on the base material by air spraying so that the coating amount was 100 g/m ² (equivalent to a dry film thickness of 30 μm), and then drying at 30° C. for 24 hours.
For test plates 2 to 5 and test plate 7, the base material was heated to 60° C., and the paints of the numbers shown in Table 1 were applied onto the base material by air spraying in an amount of 100 g/m ² (the dry film thickness was 30 μm equivalent), and then heated at 60° C. for 5 minutes.
The test plate 6 was prepared by applying the paint 6 onto the base material by air spraying so that the coating amount was 100 g/m ² (equivalent to a dry film thickness of 30 μm), and then drying at 30° C. for 7 days.

<Test plates 8 to 19>
For test plates 8 to 19, the base material was heated to 60° C., and the paints of the numbers shown in Table 2 were applied onto the base material by air spraying to a coating amount of 100 g/m ² (equivalent to a dry film thickness of 30 μm). After coating so that it becomes uniform, it was prepared by heating at 80° C. for 5 minutes.

<Test plates 20 to 29>
For test plates 20 to 29, the base material was heated to 60°C, and the paints of the numbers shown in Table 3 were air-sprayed onto the base material to a coating amount of 100 g/m ² (equivalent to a dry film thickness of 30 µm). After coating so that it becomes uniform, it was prepared by heating at 80° C. for 5 minutes.

<Test plates 30 to 38>
Preparation of multi-layer film Test plates 30 to 38 were composed of a base material having a multi-layer film. The base material was heated to 60°C, and the enamel paint with the number shown in Table 4 was applied in an amount of 130 g/m ^{2 .} (Dry film thickness: about 30 μm), and dried at 100° C. for 3 minutes to prepare an enamel plate. The surface temperature of the enamel plate was adjusted to 60°C, and the clear paint with the number shown in Table 4 was applied by air spray so that the coating amount was 100 g/m ² (equivalent to a dry film thickness of 30 µm). It was prepared by heating for minutes.

<Base material>
The following aluminum plates were used as substrates in the production of the test plates.
Aluminum plate (150 mm × 70 mm × 0.8 mm, manufactured by TP Giken Co., Ltd.)

Measurement of Chemiluminescence Amount The chemiluminescence amount of the prepared test plate was measured under conditions of continuous temperature rise.
Specifically, the test plate was cut into a size of 1 cm×1 cm without peeling off the coating film from the substrate to prepare a test piece for measurement (substrate with coating film). A test piece for measurement was placed in the sample chamber of a weak luminescence detector (CLA-FS4 manufactured by Tohoku Denshi Sangyo Co., Ltd.). Oxygen was flowed into the sample chamber at a rate of 50 mL/min to create an oxygen atmosphere, and the chemiluminescence amount was measured with an exposure time of 1 second while continuously raising the temperature at 15°C/min. The measurement temperature was 50 to 350° C., and the detection wavelength was 300 to 850 nm.
The measurement results were plotted on a graph with the chemiluminescence amount on the vertical axis and the temperature on the horizontal axis to obtain a curve showing the relationship between the chemiluminescence amount and the temperature. The temperature at the intersection of the tangent line with the minimum differential coefficient and the tangent line with the maximum differential coefficient on the curve showing the relationship between the amount of chemiluminescence and temperature in the temperature range of 50 to 350 ° C. is the luminescence start temperature of the initial film (T1 ). Tables 1-4 show the light emission start temperature (T1) of the initial film.

Measurement of the amount of chemiluminescence after accelerated deterioration For the prepared test plate, a xenon weather meter NX75 (manufactured by Suga Test Instruments Co., Ltd.) was used in accordance with the provisions of JIS K5600-7-7: 2008 cycle A. An accelerated deterioration test was performed by irradiating with a xenon lamp for 200 hours, and a test plate after accelerated deterioration was obtained.
Regarding the obtained test plate after accelerated deterioration, a test piece was prepared in the same manner as in the above "Measurement of chemiluminescence amount", and the chemiluminescence amount was measured under the same conditions as the temperature was continuously raised.
The measurement results were plotted on a graph with the chemiluminescence amount on the vertical axis and the temperature on the horizontal axis to obtain a curve showing the relationship between the chemiluminescence amount and the temperature. The temperature at the intersection of the tangent line with the minimum differential coefficient and the tangent line with the maximum differential coefficient on the curve showing the relationship between the amount of chemiluminescence and temperature in the temperature range of 50 to 350 ° C. is the luminescence start temperature after accelerated deterioration ( T2).
Furthermore, using the luminescence start temperature (T1) of the initial film obtained in the above "measurement of chemiluminescence amount" and the luminescence start temperature (T2) after accelerated deterioration, the value of the following relational expression was obtained. The values obtained are shown in Tables 1-4.
Relational expression: (T1-T2)/T1×100

(Evaluation of weather resistance) Evaluation of gloss retention rate due to accelerated deterioration Regarding the prepared test plate, a xenon weather meter NX75 was used to apply a xenon lamp to the test plate in accordance with JIS K5600-7-7:2008 cycle A. It was irradiated and an accelerated aging test was performed.
Here, the gloss value of the test panel before the accelerated deterioration test was measured as the initial gloss value, and the gloss value of the test panel was also measured during the accelerated deterioration test. The gloss value is specular gloss (D60) at 60° defined by JIS K5600-4-7 (ISO 2813:1994), and was measured using a gloss meter VG-2000 manufactured by Nippon Denshoku Co., Ltd.
The gloss retention rate (%) was obtained from the following formula from the initial gloss value and the gloss value during the accelerated deterioration test, and the irradiation time at which the gloss retention rate was 50% is shown in Tables 1 to 4.
Gloss retention rate = gloss value during accelerated deterioration test / initial gloss value x 100
As can be seen from Tables 1 to 4, when T1 is in the range of 190 to 330 ° C. and the value of (T1 - T2) / T1 x 100 is in the range of -3.0 to 7.0, It takes a long time for the gloss value to decrease by 50%, and it can be judged that the coating film has high weather resistance.

A coating similar to the oxygen permeability measurement test plates 20 to 29 was prepared on a PP plate, and an oxygen permeability measurement device (8001 manufactured by Illinois) was used to measure by the isobaric method, based on the following criteria. Oxygen permeability was evaluated using Table 3 shows the evaluation results.
○: 0.005 to 7.5 cc·μm/cm ² /day
×: a value larger than 7.5 cc·μm/cm ² /day

Evaluation of Degree of Fusion Adhesion The degree of fusion adhesion of the resin in the coating film was observed for the prepared test panels 20 to 29, and evaluated according to the following criteria. Table 3 shows the evaluation results.
Visual evaluation 〇: Good fusion, ×: Crack confirmed Evaluation by SEM 〇: Good fusion, ×: Crack confirmed

From Table 1, it was confirmed that a coating film with a long irradiation time (a coating film with good weather resistance) with a gloss retention rate of 50% has a high light emission start temperature (T1). In addition, the coating film with a long irradiation time when the gloss retention rate is 50% (a coating film with good weather resistance) has a smaller value of (T1-T2) / T1 × 100, from -3.0 to 7.0 was confirmed to be in the range of In test plate 6, since the coating film contained unsaturated bonds that are easily oxidized and the degree of oxidative polymerization was low, oxygen easily diffused in the coating film. presumably low.
The test plate 4 and the test plate 7 are coated with different types of titanium dioxide. Compared to test plate 4, test plate 7 had a shorter irradiation time at which the gloss retention rate reached 50% and had lower weather resistance, but T1 was 190° C. or higher. On the other hand, the value of (T1-T2)/T1×100 was large. It is considered that the titanium dioxide contained in the test plate 7 had a high photoactivity, so that the coating film was easily deteriorated.

From test plates 8 and 9, it was confirmed that the addition of HALS to the coating film increased the irradiation time at which the gloss retention rate reached 50%, and also increased the light emission start temperature (T1). Presumably, the presence of HALS scavenged radicals generated during thermal oxidative decomposition, resulting in an increase in T1.
From test plates 9 to 12, it can be seen that the irradiation time at which the gloss retention is 50% and the luminescence start temperature (T1), (T1-T2)/T1×100 values change depending on the type of HALS added to the coating film. confirmed. Compared to the low-molecular-weight HALS of test plate 9, the HALS copolymerized coating film of test plate 10 is less likely to elute HALS from the coating film, the value of (T1-T2)/T1×100 is smaller, and the gloss is maintained. It is considered that the irradiation time at which the rate reaches 50% was increased. In addition, HALS was less likely to volatilize from the coating film during measurement, and T1 was considered to be high.
Similarly, for test plates 11 and 12, resin-encapsulated HALS and medium-molecular-weight HALS are less likely to elute from the coating film than low-molecular-weight HALS, so the value of (T1−T2)/T1×100 becomes smaller. It is considered that the irradiation time at which the gloss retention becomes 50% was increased. In addition, HALS was less likely to volatilize from the coating film during measurement, and T1 was considered to be high.
From test plates 8, 13, and 14, the behavior when UVA was added to the coating film was confirmed. The addition of UVA does not greatly affect T1, but the addition increases the irradiation time at which the gloss retention rate reaches 50%, and decreases the value of (T1-T2)/T1×100. Furthermore, by using the copolymer type UVA, the irradiation time at which the gloss retention rate becomes 50% became longer, and the value of (T1−T2)/T1×100 became smaller. This is probably because the UVA copolymerized with the resin is less likely to elute from the coating film than the non-polymerized UVA.
Test plates 15 and 16 are coating films to which both HALS and UVA have been added. The x100 value was confirmed to be smaller.
Test plate 17, test plate 18, and test plate 19 are coating films in which copolymer type HALS and low-molecular-weight HALS are used in combination, and non-polymerization-type UVA is added, and the addition amount of low-molecular-weight HALS is varied. . Compared to test plate 10, test plates 17 and 18 had higher T1. This is probably because the amount of radicals that can be captured increased as the amount of HALS added to the coating film increased. Further, test plates 17 and 18 had a longer irradiation time for a gloss retention of 50% than test plate 10, and the value of (T1-T2)/T1×100 was smaller. Presumably, the presence of copolymerized HALS in the coating film facilitates retention of low-molecular-weight HALS with a similar structure to the coating film, thereby reducing the degree of HALS elution during acceleration.
On the other hand, in Test Plate 19, although the largest amount of low-molecular-weight HALS was added, the irradiation time at which the gloss retention reached 50% was increased, and the value of (T1-T2)/T1×100 increased. This is probably because the excessive addition of low-molecular-weight HALS plasticized the resin in the coating film and reduced the density, making it easier for the HALS to elute and failing to maintain the initial state of the coating film.

In Table 3, the evaluation was performed by changing the mixing ratio of various fluororesin emulsions and various acrylic resin emulsions.
From the test plate 20, the test plate 21, the test plate 22, and the test plate 23, depending on the type of fluorine resin emulsion and acrylic resin emulsion, the irradiation time at which the gloss retention rate becomes 50%, the light emission start temperature (T1), A difference was found in the value of (T1-T2)/T1×100. In the test plates 22 and 23, T1 decreased and (T1-T2)/T1×100 increased. In the test plate 22, cracks due to poor fusion bonding were visually confirmed, and it is considered that the test plate 22 was easily deteriorated because oxygen also easily permeated therethrough. In the test plate 23, no cracks were visually observed, and no cracks were observed by SEM observation. On the other hand, since oxygen easily permeated the film, it is considered that the fusion was slightly defective and the film easily deteriorated.
From the test plate 20 and test plates 24 to 29, even if the same fluororesin emulsion and the same acrylic resin emulsion are used, if the mixing ratio is changed, the irradiation time and the light emission start temperature (T1) at which the gloss retention rate becomes 50%. , (T1−T2)/T1×100. Compared to the other test plates, test plate 27 had a shorter irradiation time at which the gloss retention rate reached 50%, a lower emission start temperature (T1), and a larger value of (T1−T2)/T1×100. . Although no cracks were visually observed in the test plate 27, slight fine cracks were confirmed by SEM observation, and it is considered that the emulsion was poorly fused and oxygen easily permeated, resulting in easy deterioration.
From this, it was confirmed that deterioration in weather resistance due to defects in the coating film such as poor adhesion, which cannot be visually detected, can also be evaluated using this method.

Table 4 evaluates multilayer films.
Compared to test plate 30, test plate 31 had a longer irradiation time at which the gloss retention rate reached 50%, and a higher light emission start temperature (T1). Since the test plate 31 contained low-molecular-weight HALS in the clear, it is considered that it was difficult to deteriorate. Furthermore, with the test plate 32, the irradiation time was longer at which the gloss retention was 50%, and the light emission start temperature (T1) was higher. Also, the value of (T1-T2)/T1×100 became smaller. The test plate 32 used a combination of a HALS-copolymerized resin and a low-molecular-weight HALS. Presumably, the presence of HALS facilitates the retention of low-molecular-weight HALS with a similar structure to the coating film, thereby reducing the degree of HALS elution during acceleration.
From test plate 30 and test plate 33, it was confirmed that when titanium dioxide 2 is used for the enamel coating film, the irradiation time at which the gloss retention rate becomes 50% is shortened, and the value of (T1−T2)/T1×100 is increased. rice field. This is probably because the titanium dioxide 2 has a high photoactivation ability, and the deterioration progressed between the clear and enamel coating layers due to light rays slightly transmitted through the clear coating during acceleration.
From Test Plates 30 and 34, when Resin F was used for the enamel coating, the irradiation time at which the gloss retention rate reached 50% was shorter, and the value of (T1-T2)/T1×100 was larger. It is considered that the Tg of resin F is different from that of resin A used for the clear coating film, so partial separation occurs between the clear and enamel coating layers during acceleration, making it easier for oxygen to permeate.
Compared to test plate 30, test plate 35 was confirmed to have a shorter irradiation time at which the gloss retention rate reached 50%, a lower T1, and a larger value of (T1−T2)/T1×100. It is considered that the test plate 35 had insufficient fusion adhesion due to insufficient amount of film-forming aid for the clear film.
Test plates 36 to 38 contain a matting agent in the clear film. Compared to test plates 36 and 37, test plate 38 had a shorter irradiation time at which the gloss retention rate reached 50%, a lower T1, and a larger value of (T1−T2)/T1×100. It is considered that the PMMA beads (PMMA is an abbreviation of polymethyl methacrylate) existed unevenly on the test plate 38, and the clear film was not a continuous film.
If the coating film contains a large amount of matting agents such as PMMA beads and silica, it may be difficult to evaluate deterioration by other methods such as infrared absorption spectrum and hardness. It was confirmed that the weather resistance can be evaluated even in a coating film containing a large amount of.

According to the coating film evaluation method of the present invention, it is possible to evaluate the weather resistance of a coating film or a coated body whose weather resistance is difficult to predict by a simple method without conducting a long-term weather resistance test. of coating can be provided.

Claims (3)

A coating film evaluation method that predicts deterioration of a coating film by measuring the amount of chemiluminescence of the coating film under conditions of continuous temperature rise in an oxygen or air atmosphere. Measure the amount of chemiluminescence of the coating film under conditions of continuous temperature rise in an oxygen or air atmosphere, and plot it on a graph with the amount of chemiluminescence on the vertical axis and the temperature on the horizontal axis to see the relationship between the amount of chemiluminescence and temperature. 2. The coating film evaluation according to claim 1, wherein a curve is drawn and the temperature at the intersection of the tangent line with the minimum differential coefficient and the tangent line with the maximum differential coefficient on this curve is obtained to predict deterioration of the coating film. Method. (i) In an oxygen or air atmosphere, the chemiluminescence amount of the coating film is measured under conditions of continuous temperature rise, and plotted on a graph with the chemiluminescence amount on the vertical axis and the temperature on the horizontal axis. Draw a curve showing the relationship between temperatures, find the temperature (T1) at the intersection of the tangent line with the minimum differential coefficient and the tangent line with the maximum differential coefficient on this curve,
(ii) Under an oxygen or air atmosphere, the chemiluminescence amount of the coating film subjected to the accelerated deterioration test is measured under conditions of continuous temperature rise, and plotted in a graph with the vertical axis as the chemiluminescence amount and the horizontal axis as temperature. Draw a curve showing the relationship between the amount of chemiluminescence and temperature, and obtain the temperature (T2) at the intersection of the tangent line with the minimum differential coefficient and the tangent line with the maximum differential coefficient on this curve,
(iii) The coating film evaluation method according to claim 1, wherein deterioration of the coating film is predicted from the temperature (T1) and the temperature (T2).

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