JP5563538B2 - Method for detecting film deterioration - Google Patents

Description

  The present invention relates to a coating film deterioration detection method for detecting deterioration of a coating film such as a heavy anticorrosion coating film.

  In recent years, in order to solve global environmental problems, strict environmental performance has been demanded for paints used for extending the life of structures and the like and for aesthetics. Against this background, heavy-duty anticorrosive paints that have been multilayered and formed thicker have been used for steel towers and bridge installations. These heavy anticorrosion paints, regardless of whether they are solvent-based, weak solvent-based, or water-based, have good adhesion to iron bases and are excellent in corrosion resistance and rust prevention.

  In such a heavy anticorrosion coating, it is sufficient that it can be used permanently, but in reality, there is a lifetime of each coating film. The life of the coating film is determined by the deterioration of the coating film. However, there was no way to know in advance when the coating film would deteriorate. A method for objectively and quantitatively evaluating and judging whether or not an appropriate repainting time has been reached has not been established.

  For this reason, in reality, deterioration of the heavy anticorrosive coating film is determined by visually detecting cracks, peeling, swelling, whitening, and the like. Also, “JIS.K5600-5-6: 1999. General test methods for paints—Part 5: Mechanical properties of coating film—Section 6: Adhesion (cross-cut method)” and “JISK5600-5-7 adhesion” The deterioration of the heavy anticorrosive coating film is determined by measuring the adhesive force and the like by the method prescribed in “Performance (pull-off method)” (see Non-Patent Document 1).

JIS standard JIS K 5600-5-7, 1999.

  However, the deterioration determination of the heavy anticorrosion coating film described above is a method of detecting a state in which the deterioration has already occurred, and the deterioration is determined for the first time in a state in which the deterioration has greatly progressed. Thus, in a state where the deterioration has progressed greatly, it leads to an increase in the cost of repair and repair, and there is a fundamental problem that damage is accumulated on the base and the structure itself and complete regeneration is difficult. It was.

  The present invention has been made to solve the above-described problems, and an object thereof is to detect deterioration of a coating film such as a heavy anticorrosion coating film at an earlier stage.

  The coating film deterioration detection method according to the present invention is a resin that measures the temperature change of the loss tangent at the initial stage of the coating film to be measured by dynamic viscoelasticity measurement, and constitutes the coating film in the measured temperature change of the loss tangent. The first step of detecting a peak due to β relaxation and setting the magnitude of this peak as an initial value, and the dynamic viscoelasticity measurement after performing dynamic viscoelasticity measurement for detecting β relaxation as the initial value Is used to measure the temperature change of the loss tangent of the coating film to be measured, detect the peak due to β relaxation of the resin constituting the coating film from the measured loss tangent temperature change, and determine the magnitude of this peak as the judgment value. And a third step for determining the deterioration state of the coating film by comparing the initial value and the determination value.

  In the coating film deterioration detection method, in the third step, a state in which the decrease value of the determination value with respect to the initial value exceeds the set reference value may be determined as coating film deterioration.

  As described above, according to the present invention, it is possible to obtain an excellent effect that the deterioration of a coating film such as a heavy anticorrosion coating film can be detected at an earlier stage.

FIG. 1 is a flowchart for explaining a coating film deterioration detection method according to an embodiment of the present invention. FIG. 2 is a characteristic diagram showing a peak of β relaxation that appears in the temperature dependence of the loss tangent. FIG. 3 is an explanatory diagram for explaining the mechanism of β relaxation. FIG. 4 is a characteristic diagram showing a state where the β relaxation peak appearing in the temperature dependence of the loss tangent changes corresponding to the deterioration.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a flowchart for explaining a coating film deterioration detection method according to an embodiment of the present invention. In this coating film deterioration detection method, first, in step S101, the temperature change of the loss tangent at the initial stage of the coating film to be measured is measured by dynamic viscoelasticity measurement. A peak due to β relaxation of the constituent resin is detected, and the magnitude of this peak is set as an initial value.

  Next, in step S102, the temperature change of the loss tangent of the coating film to be measured is measured by the dynamic viscoelasticity measurement after performing the dynamic viscoelasticity measurement for detecting β relaxation as the initial value. The peak due to β relaxation of the resin constituting the coating film is detected in the temperature change of the loss tangent, and the magnitude of this peak is used as a judgment value.

  In the dynamic viscoelasticity measurement described above, for example, a part of the target coating film is cut out, a cut out test piece is used, the frequency in the measurement is set to a predetermined value, and the temperature is about −60 ° C. to 200 ° C. The dynamic viscoelasticity may be measured with a well-known dynamic viscoelasticity measuring device. As the dynamic viscoelasticity measuring apparatus, for example, Toyo Seiki Rorograph S-1 can be used. In a heavy anticorrosion paint (coating film) generally used, a β relaxation peak appears in a temperature range (glass state) lower than 0 ° C. in a measured temperature change of loss tangent.

  As described above, when the determination value is detected at the stage of determining deterioration, the deterioration state of the coating film is determined by comparing the detected determination value with the initial value in step S103. The magnitude of the β relaxation peak decreases with the deterioration of the coating film. For this reason, it is possible to determine (determine) the deterioration of the coating film (resin) by reducing the size of the β relaxation peak. For example, the relationship between the progress of coating deterioration and the decrease in the magnitude of the β relaxation peak is known in advance through experiments, etc. The width should be specified. If the determination value decreases beyond the specified decrease range with respect to the initial value, it can be determined that the deterioration has occurred.

  Next, β relaxation will be described in more detail. As an example, β relaxation of a heavy anticorrosive coating film in which the undercoat and the intermediate coat are composed of a water-based epoxy resin and the topcoat is composed of a water-based urethane resin will be described. The undercoat film thickness is 50 μm, the intermediate coat film thickness is 50 μm, and the overcoat film thickness is 50 μm. From this heavy anticorrosion coating film, a 25 mm long and 5 mm wide portion is cut out to form a test piece.

  The test piece is mounted on a dynamic viscoelasticity measuring apparatus to perform dynamic viscoelasticity measurement. The measurement conditions are a frequency of 10 Hz, a static tension of 60 gf, and a strain of 8 μm, and the temperature is changed from −100 ° C. to 50 ° C. Thus, the temperature dependence is measured by dynamic viscoelasticity measurement, and the temperature change of the loss tangent tan δ is obtained. As a result of this measurement, as shown in FIG. 2, a peak of β relaxation, which is secondary relaxation, appears near a certain temperature.

  As shown in FIG. 3, this β relaxation causes the first coupling portion 301 and the sixth coupling portion 302 that exist at both ends of the six bonds of —O—C—C—C—O— in the epoxy resin. This is a relaxation phenomenon that occurs as a result of free rotation as a rotation axis. This rotation does not affect any other coupling part other than the coupling part. Therefore, even in the glass state, this relaxation occurs due to the thermal energy of the temperature. A large relaxation phenomenon (α relaxation) that changes from a glass state to a rubber state is well known as a glass transition.

  The β relaxation described above decreases with an increase in the age of the coating film. For example, if the peak area of the β relaxation peak in the initial state is expressed as 100, the peak area of the detected peak decreases to 70, 50, 30, 10 with the passage of time. Such a decrease in the peak of β relaxation represents a change in the environment surrounding the molecular chain.

  Here, the state of the molecular chains in the initial stage of the coating film (resin) having elasticity, viscosity, and the like is a pseudo equilibrium state, which tends to agglomerate and approach the true equilibrium state over time. When aggregation between molecular chains occurs in this way, the peak of β relaxation decreases. Along with this aggregation, the elasticity and viscosity of the coating film, which is a polymer, disappears and exhibits embrittlement. Various deterioration symptoms appear due to this embrittlement.

  One of deterioration phenomena due to embrittlement is cracking. Due to embrittlement, ductility is lost and cracks occur. Also, the internal stress becomes larger than the initial state. When the internal stress increases, an extra load is applied to the coating film, resulting in a decrease in adhesion with the substrate. Decrease in adhesion causes peeling. As described above, when cracking or peeling occurs, the steel material on which the coating film is formed is easily affected by external moisture, steam, temperature, suspended particles, and rust and corrosion are easily generated. become.

  As described above, since there is a correlation between the magnitude of β relaxation and the state of deterioration of the coating film, the timing of deterioration can be estimated in advance by grasping the decrease in β relaxation. For example, when it is detected that the β relaxation peak area obtained by measurement is less than 50% (reference value) of the peak area in the initial state, it is possible to take specific measures such as repainting. . On the other hand, if the β relaxation peak area obtained by measurement is less than 50% of the initial value, it can be determined that there is no need for repainting. In addition, if the relationship between the progress of coating deterioration and the decrease in the peak area of β relaxation is known in advance through experiments, etc., the time and period below 50% from the results of the measured peak area of β relaxation Can be predicted.

  This will be described in more detail below using examples.

[Example 1]
In the following, a heavy anticorrosive coating film in which the undercoat and the intermediate coat are composed of a water-based epoxy resin and the topcoat is composed of a water-based urethane resin is targeted. The undercoat film thickness is 50 μm, the intermediate coat film thickness is 50 μm, and the overcoat film thickness is 50 μm. A heat cycle is applied to this heavy anticorrosive coating film under an artificial accelerated deterioration environment. For example, using a constant temperature and humidity chamber, a heat cycle (1 cycle 12 hours) from -30 ° C. to 70 ° C. is repeated up to 100 cycles at a relative humidity of 90%.

  A test piece having a length of 25 mm and a width of 5 mm is cut out from the heavy anticorrosive coating film artificially deteriorated as described above. In addition, the 1st test piece cut out from the heavy-duty anticorrosion coating film of the initial state which is not artificially degrading, the 2nd test piece cut out from the heavy-duty anticorrosion coating film made into 25 cycles, and the heavy-duty corrosion prevention made into 50 cycles A third test piece cut out from the epoxy resin portion of the coating film, a fourth test piece cut out from the epoxy resin portion of the heavy duty anticorrosion coating film having 75 cycles, and an epoxy resin of the heavy anticorrosion coating film having 100 cycles The 5th test piece cut out from the part was produced.

  In the measurement, these test pieces are mounted on a dynamic viscoelasticity measuring apparatus to perform dynamic viscoelasticity measurement. The measurement conditions are a frequency of 10 Hz, a static tension of 60 gf, and a strain of 8 μm, and the temperature is changed from −100 ° C. to 50 ° C. Thus, the temperature dependence is measured by dynamic viscoelasticity measurement, and the temperature change of the loss tangent tan δ is obtained.

  As a result of measurement of each test piece, as shown in FIG. 4, it can be seen that the β relaxation peak appearing in the vicinity of −50 ° C. becomes smaller as the number of cycles of the deterioration treatment increases. Assuming that the initial first test piece is 100, the peak area is about 75 for the second test piece (heat cycle 25), about 61 for the third test piece (heat cycle 50), and the fourth test piece (heat cycle 75). ) About 34, and the fifth test piece (heat cycle 100) is 11.

  Here, actual measurement data showing the relationship between the deterioration state of the coating film and the β relaxation peak area ratio is shown. Table 1 shows the heat cycle number and adhesion, loss tangent tan δ at room temperature, and β relaxation peak area ratio for coatings that are undercoat / intermediate epoxy coatings and topcoating urethane coatings.

  In the case of zero heat cycle, the adhesive force is sufficient at 4.1 MPa, and tan δ exceeds 0.1, and it is considered that the coating film has not deteriorated. As a matter of course, the β relaxation peak area is the standard 100. Next, in the case of the heat cycle 50, the adhesive force has increased to 5.3 MPa, but the value of tan δ has decreased to 0.07, which is less than 0.1, and the coating film has been deteriorated. It has been suggested. The β relaxation peak area ratio in this sample is reduced to 61. Next, in the case of the heat cycle 100, the adhesive force is less than 1 MPa, the value of tan δ is also reduced to 0.06, and it can be seen that the coating film is completely deteriorated. In this case, the β relaxation peak area ratio is also 11, which is smaller than the value of 50 cycles.

  From the above results, it can be seen that in the case of the heat cycle 100, the deterioration is already large. On the other hand, the condition of the heat cycle 50 has increased as the adhesive force, but since the β relaxation peak area ratio is close to 50, the molecular chain aggregates as the structure inside the coating film, and the initial It can be seen that elasticity and viscosity have disappeared and embrittlement has progressed.

  In this way, for example, by reducing the β relaxation peak area ratio, such as approaching 50 with an initial value of 100, the deterioration timing can be estimated in advance by grasping the decrease in β relaxation. In addition, a specific restoration operation such as repainting can be performed in a state where the reference value is reduced beyond the reference value set for the initial value. Moreover, the time and time when it becomes a state of decreasing beyond the reference value can be extrapolated.

  As described above, according to the present invention, a coating film made of heavy anticorrosive paint that has been treated for the purpose of anticorrosion and rust prevention of outdoor iron and galvanized steel pipe facilities such as steel towers and bridge installation facilities has been conventionally used. It is possible to detect the deterioration of the coating film at an early stage by detecting a change in the coating film molecular structure peculiar to the deterioration of the coating film for the coating film whose deterioration is difficult to judge and judge.

  In a heavy anticorrosion coating film, when the progress of deterioration is large, the cost of repair and repair becomes high, and damage to the ground or the structure itself may occur, making it difficult to completely regenerate. On the other hand, according to the present invention, as described above, it is possible to know the deterioration of the coating film at an early stage, and it is possible to prevent wasteful costs and the like, and to perform effective maintenance management adapted to the deterioration state of the equipment. Become.

  The present invention is not limited to the embodiment described above, and many modifications and combinations can be implemented by those having ordinary knowledge in the art within the technical idea of the present invention. It is obvious.

Claims (2)

Measure the temperature change of the loss tangent at the initial stage of the coating film to be measured by dynamic viscoelasticity measurement, and detect the peak due to β relaxation of the resin constituting the coating film in the measured temperature change of the loss tangent A first step in which the magnitude of this peak is an initial value;
The temperature of the loss tangent was measured by measuring the temperature change of the loss tangent of the coating film to be measured by dynamic viscoelasticity measurement after performing dynamic viscoelasticity measurement to detect β relaxation as the initial value. A second step of detecting a peak due to β relaxation of the resin constituting the coating film in the change and setting the magnitude of this peak as a determination value;
A coating film deterioration detection method comprising: a third step of determining a deterioration state of the coating film by comparing the initial value and the determination value. In the coating-film degradation detection method of Claim 1,
In the third step, the coating film deterioration detection method, wherein a state in which a decrease value of the determination value with respect to the initial value exceeds a set reference value is determined as deterioration of the coating film.

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