JP6063810B2 - Method for estimating the degree of cure of epoxy resin-containing materials - Google Patents

Description

The present invention relates to a method for estimating the degree of cure of an epoxy resin-containing material typified by an epoxy resin paint.

Epoxy resin is a thermosetting resin that cures by cross-linking the remaining epoxy groups in the polymer, and is used in a wide range of applications such as adhesives, anticorrosion paints, laminate materials, impregnated materials, and molding materials. ing.

In recent years, there is a demand for extending the life of steel structures represented by bridges and the like, and the application of heavy anticorrosion coating is spreading. Heavy anti-corrosion coating has a long-lasting anti-corrosion function that protects steel materials from corrosion and an aesthetic function by color, and the coating system generally consists of an anti-corrosion base, undercoating paint, intermediate coating, and top coating. Has been. Epoxy resin-containing paints are used for the undercoat and intermediate coats. However, if the top coat is applied before being cured after coating, the adhesion with the top coat is reduced, resulting in poor coating and the function as a heavy anti-corrosion coating. Absent. Therefore, it is very important to accurately estimate the time required to reach the degree of cure at which the performance of the epoxy resin-containing material is exhibited. Furthermore, since most of the heavy-duty anticorrosion coatings for steel structures are painted outdoors, it is difficult to keep the temperature during curing constant. Since the epoxy resin-containing material has a different curing time depending on the ambient temperature at the time of curing, it is desirable to easily estimate the time required for achieving the degree of curing that exhibits the performance of the epoxy resin at any temperature.

Conventionally, as a method of evaluating the degree of curing of an epoxy resin-containing material, a method of evaluating from a calorific value measured using a DSC (differential scanning calorimeter), a method of evaluating from a peak of an epoxy group of IR (infrared spectroscopy) ( Patent Document 2), and a method for evaluating the degree of cure based on the Raman intensity ratio between the peak of the epoxy group and the peak of the aromatic ring in Raman analysis is known (see Patent Document 1 and Patent Document 3).
However, any of these measures the degree of cure of the epoxy resin-containing material, and the temperature and time required to reach the desired degree of cure cannot be predicted.

JP 2000-178522 A JP 2007-248431 A JP 2011-69653 A

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a method for easily estimating the degree of cure of an epoxy resin-containing material using DSC.

  The method for estimating the degree of cure of an epoxy resin-containing material according to the present invention is a method for estimating the temperature and time at which the epoxy resin-containing material is cured, and subjecting the epoxy resin-containing material whose degree of cure to be estimated to DSC measurement to a melting curve (FIG. 1), a logarithmic function is obtained for the relationship between -ΔH of the epoxy resin-containing material and the retention time expressed in logarithm from the above melting curve (FIG. 2), and the intercept at which −ΔH in the logarithmic function is 0 Is the curing time of the material, and similarly, for the temperature different from the predetermined temperature, the retention time of the material is obtained, and the index of the relationship between the reciprocal of the temperature and the retention time expressed logarithmically from the obtained data. A function is obtained (FIG. 3), and the exponential function is defined as the relationship between the temperature and holding time (curing time) of the material, and the hardness of the epoxy resin-containing material at various temperatures is determined based on the function curve. It is characterized by facilitating estimation of the degree of conversion.

According to the present invention, it is possible to estimate the time required to reach the degree of curing at which the quality of the epoxy resin-containing material is exhibited in any season (temperature), and it is possible to increase the efficiency of painting. Furthermore, in the material, it is possible to obtain the relationship between the degree of curing and the holding time for obtaining a desired degree of curing when the temperature changes during the curing. From this, it is possible to improve the coating efficiency without degrading the quality of the heavy-duty anticorrosion coating in which the material is applied. Furthermore, the relationship between the temperature and the holding time for obtaining a desired degree of curing can also be estimated. Further, since the estimation method is based on the calculation formula, it is not necessary to perform many preliminary measurements as standard data as in the conventional method, and the processing temperature and the curing time can be estimated simultaneously.

DSC melting curve and how to calculate -ΔH -ΔH and retention time -ΔH = 0 Relationship curve between temperature and holding time Estimated curve to obtain a certain degree of cure Method for estimating retention time at different temperatures Method for estimating holding time at different temperatures (Example)

Hereinafter, embodiments embodying the method of estimating the degree of cure according to the present invention will be described. In the present embodiment, when the degree of cure of the epoxy resin-containing material is estimated, the degree of cure measurement method according to the present invention is applied. However, preferably, the DSC curve of the epoxy resin-containing material does not include a peak derived from a solvent.

The epoxy resin-containing material is a thermosetting resin composition comprising an epoxy resin and an epoxy resin curing agent as essential components. The epoxy resin and the epoxy resin curing agent are mixed and immediately held at a predetermined temperature. Next, after holding for a predetermined time, the sample is subjected to DSC measurement.

  The obtained DSC results are shown in FIG. -ΔH is determined from the peak area that is convex upward. Further, the -ΔH is obtained at least once at a time different from the predetermined time at the predetermined temperature, and a relationship between -ΔH and a logarithmic holding time is obtained from the obtained plurality of data. FIG. 2 shows the result of obtaining the exponential relationship between -ΔH and holding time at the temperature.

This exponential function is expressed by the following equation (1).
−ΔH = B · ln t + C (1)
Here, B represents a slope specific to the epoxy resin-containing material, and C represents a specific section of the epoxy resin-containing material. The time t obtained when -ΔH = 0 is substituted into the above equation (1) is the time at which the curing reaction of the epoxy resin-containing material ends.

Further, the curing time of the material is similarly obtained for a temperature different from the predetermined temperature, and the relationship between the reciprocal temperature and the logarithmic retention time is represented by a straight line of the following equation (2) from the obtained plurality of data. It is.
ln t = ln A + E _a / RT (2)
The above equation (2) is a function based on the Arrhenius equation, A is a frequency factor, E _a is activation energy, and R is a gas constant.

FIG. 3 is a plot of the relationship between the retention time and the reciprocal of the processing temperature from the relational expression obtained from FIG. With respect to the relationship in which −ΔH becomes 0 mJ / mg, highly accurate linearity was obtained (1 in FIG. 3).
Therefore, the retention time t required until −ΔH = 0 can be estimated by obtaining the inherent A and E _a of the epoxy resin-containing material from the exponential function.

E _a obtained from the exponential function is a value unique to the epoxy resin-containing material. That is, even if the degree of curing is different, the slope is the same in the graph of the reciprocal of the arbitrary temperature and the logarithmically displayed time. The exponential function of 1 in FIG. 3 is the time and temperature required to reach a complete degree of cure, but in practice, practical performance can be obtained before curing to that extent. Therefore, in the material, the time required to reach a complete curing degree is 4.6 hours. However, as a result of measuring the holding time until a practically necessary curing degree is obtained, it is 2.2 at 40 ° C. It was time.

Next, in FIG. 3, an exponential function 1 in which 2.2 hours at 40 ° C. are plotted on the graph of the reciprocal of the temperature and the time indicated by the exponent, and the −ΔH is 0 mJ / mg passing through the plot. Draw an exponential function (estimation formula of 2) with the same slope (straight line 2 passing through 40 ° C in FIG. 4). Actual measured values (temperatures of 5 ° C., 10 ° C., 20 ° C., and 50 ° C. in FIG. 4) obtained by actually measuring the temperature and holding time for actually obtaining a predetermined degree of cure agree well with the straight line 2 of the estimation formula of FIG. .

From the above, when the processing temperature is determined, the curing time for obtaining the necessary degree of curing can be estimated. The method is as follows.

  FIG. 5 shows an estimation method when the epoxy resin-containing material is cured at different temperatures. When the epoxy resin-containing material is held at 20 ° C., the holding time required until −ΔH becomes 0 mj / mg is 19 hours. On the other hand, the degree of cure when held at 40 ° C. for 1 hour is equivalent to the degree of cure when cured at 20 ° C. for 4.2 hours from the slope of the exponential function. From this, it can be estimated that -ΔH becomes 0 mJ / mg by curing at 40 ° C for 1 hour and then curing at 20 ° C for 14.8 hours (= 19 hours-4.2 hours).

As an epoxy resin-containing material, NB coat NSW-1500 manufactured by Nikkiso Chemical Co., Ltd. was used. Next, the composition of the material will be shown.
Main agent: Epoxy resin, pigment, additive
Curing agent: Modified aliphatic polyamine, modified alicyclic polyamine, pigment, additive This material is coated on a steel plate of 150 mm x 70 mm x 0.8 mm to a thickness of 600 µm with a bar coater and kept at 20 ° C for 1 hour to cure. 10 mg of the coating is scraped off from the coated steel sheet, and this is used as a sample. This sample is analyzed by DSC at a heating rate of 20 ° C./min to determine −ΔH (FIG. 1). Next, the holding time is changed, and -ΔH at that time is further determined and plotted, and an intercept where -ΔH is 0 is determined. This operation was performed at 40 ° C. and 50 ° C., and the results shown in Table 1 were obtained.

Next, an exponential function (3) with which −ΔH was 0 mJ / mg was determined from the values obtained from Table 1 (FIG. 3).
t (hr) = 3.41 × 10 ^-9 × exp (6.58 × 10 ^-3 / (273 + T (° C)) (3)

Equation (3) represents the holding time required for complete curing. At 40 ° C., the time for −ΔH to be 0 mJ / mg is 4.2 hours, but suitable for reaching a predetermined degree of curing (Shore D hardness 60). The holding time at 40 ° C. was 2.2 hours. Therefore, Equation (4) having the same inclination as Equation (3) was derived through the value (plot).
t (hr) = 6.65 × 10 ^-10 × exp (6.58 × 10 ^-3 / (273 + T (° C)) (4)
Actually, the temperature and holding time in consideration of a predetermined degree of curing (Shore D hardness 60) are in good agreement with Equation (4). The results are shown in Table 2. As a result, it was proved that the estimation method was correct.

Based on the formula (4), the necessary curing time at 20 ° C. after the heating accelerated curing at 40 ° C. for 1 hour in the coating factory was calculated. Although the calculation result was 3.7 hours (FIG. 6), the result of actually curing at a coating factory and conducting a durometer hardness test was a Shore D hardness of 60, which was in good agreement.
As a result, the curing conditions including the promotion of heating can be set in advance in the coating factory, and it has become possible to achieve both quality and efficiency.

Claims (3)

A method of estimating the degree of cure of an epoxy resin-containing material, wherein the material is held at a predetermined temperature for a predetermined time, and then heated at a predetermined temperature increase rate using a DSC (differential scanning calorimeter), Obtaining enthalpy (-ΔH) during temperature rise, obtaining -ΔH at least once at a time different from the predetermined time at the predetermined temperature, and holding -ΔH and logarithm from the obtained plurality of data A logarithmic approximation formula is obtained for the relationship with time, an intercept where -ΔH in the logarithmic approximation formula is 0 is set as the curing time of the material, and the curing time of the material is similarly determined for a temperature different from the predetermined temperature. An epoch characterized by determining an exponential function for the relationship between the reciprocal temperature and the logarithmic retention time from a plurality of obtained data, and making the exponential function a relationship between the temperature and the curing time in the material. Curing degree estimation method of a resin-containing material. A method for obtaining a relationship between a temperature and a holding time for obtaining a desired degree of curing in the material, wherein an arbitrary temperature and a holding time at which the desired degree of curing is obtained are measured, and the arbitrary temperature and the time are measured. Is plotted on a graph of the reciprocal of the temperature and logarithmically expressed time, passing through the plot and obtaining an exponential function having the same slope as that of the exponential function according to claim 1, wherein the exponential function is obtained as desired in the material. A method for estimating the degree of cure of an epoxy resin-containing material, characterized by having a relationship between temperature and time for obtaining hardness. In the material, a method for obtaining a relationship between a temperature and a holding time for obtaining a desired degree of curing when the temperature is changed during the curing, wherein the time before the change and the time until the change are the reciprocal of the temperature An exponential function having the same slope as that of the exponential function according to claim 1 is obtained by plotting on a logarithmically displayed time graph, passing through the plot, and the holding time at the temperature position after the change on the exponential function It is regarded as the holding time until the degree of cure at the temperature change after the change is obtained, and the holding time until the desired degree of hardening at the temperature after the change is set as the remaining necessary time until the desired degree of hardening is reached. A method for estimating the degree of cure of an epoxy resin-containing material.

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