Method for producing coating composition

Abstract

To provide a method for producing a coating composition by which the productivity of the coating composition can be improved.SOLUTION: The method includes a correction value acquisition step of acquiring a correction value which is a color difference between a color by liquid colorimetry of a coating composition and a color by colorimetry of a coating film with respect to a specific color, and a prediction step of predicting a blending composition of raw materials for color adjustment suitable for obtaining a target color by using the color by liquid colorimetry of the coating composition before adjustment and the correction value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing a coating composition. [Background technology]

[0002] Conventionally, when producing a paint composition, a pre-adjusted paint composition is first prepared and then repeatedly adjusted to approach the desired paint properties. When preparing the pre-adjusted paint composition, a large number of primary color paint compositions are prepared by dispersing pigments, resins, and solvents using an SG mill or the like. Then, in the preparation process, the primary color paint composition, resins, solvents, and additives are added to the prepared pre-adjusted paint composition, and the resulting mixture is dispersed and mixed to prepare a paint composition. Here, the amounts of the primary color paint composition, resins, solvents, and additives added are recorded using past data, such as a work management sheet, and by referring to this data, the desired paint properties can be approached to some extent.

[0003] For example, the process for adjusting a paint composition before adjusting its paint properties to the desired color and gloss is as follows (also referred to as the color matching process). That is, a prepared paint composition before adjusting its paint properties is applied to a substrate such as art paper or a steel plate to form a coating film, and the color and gloss are measured using a color difference meter or gloss meter. Based on the color difference and gloss difference from each target coated board and past data such as a work management sheet, a color matcher manually adds a base color paint composition for adjustment, a solvent, and a gloss adjuster. By repeating this process until the color difference and gloss difference from the target coated board are equal to or less than a certain value, a paint composition having the desired paint properties can be obtained.

[0004] Computer color matching (CCM) devices are used to mechanize this repetitive color-matching process. Computer color matching devices for typical automotive refinish and architectural coating compositions use theoretical formulas, such as Kubelka-Munk and Duncan, to obtain the color appearance pattern when mixing basic primary colors. Next, theoretical calculations based on actual measurements are performed using color measurements, such as the spectral reflectance spectrum of the paint composition when each individual primary color is used, and the color measurements when these colors are mixed in a predetermined ratio. This allows the calculation of unknown color mixture ratios or target color mixture ratios from limited actual measurement data (primary data). This calculation method calculates the corrective blend amounts to change (fill in the blending differences) the current color (known blend) to the target color (calculated blend).

[0005] Furthermore, in order to more accurately predict colors and calculate corrected blend amounts based on the predictions, it has been proposed to improve the efficiency of paint composition production by using a prediction method based on an artificial intelligence model using machine learning instead of calculations based on theoretical formulas (e.g., Patent Documents 1 and 2).

[0006] However, although these methods can reduce the number of repetitions of the color-matching process, there are limitations to improving the productivity of coating compositions. That is, when measuring the color of a coating composition (also called colorimetry), the coating composition must be applied to a substrate such as art paper or a steel plate, cured and dried at 100 to 140°C for 20 to 30 minutes to form a coating film, and then the color must be measured. Therefore, each time the color is repeatedly adjusted, it takes time to cure and dry the coating film.

[0007] In response to this, for example, Patent Document 3 proposes a method for estimating the color of a paint film, which uses a theoretical formula to convert the color of a paint composition (colored liquid) into the color of a dried paint film. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 4-235322 [Patent Document 2] Patent Publication No. 2021-107781 [Patent Document 3] Japanese Patent Application Publication No. 6-050816 Summary of the Invention [Problem to be solved by the invention]

[0009] However, the method of Patent Document 3 calculates parameters that enable estimation of the color of a coating film for any color of coating composition. Therefore, for a specific color, the accuracy of converting the color of a coating composition into the colorimetric color of a dried coating film is insufficient, and when applied to color matching, the number of repeated adjustments of the paint properties increases, which does not lead to a sufficient improvement in productivity, and further, if the control range (tolerance range) for the target value is small, color matching may not be completed.

[0010] Therefore, an object of the present invention is to provide a method for producing a coating composition that can improve the productivity of the coating composition. [Means for solving the problem]

[0011] The gist and configuration of the present invention are as follows. (1) A method for producing a paint composition, in which a raw material for adjusting color is added to a paint composition before adjustment to produce a paint composition having a target color, A correction value acquisition step for acquiring a correction value, which is a color difference between a color measured by colorimetry of a liquid of a coating composition and a color measured by colorimetry of a coating film, for a specific color; a prediction step of predicting a blending composition of raw materials for color adjustment suitable for obtaining the target color using the color of the liquid color before adjustment obtained by performing liquid color measurement of the coating composition before adjustment and the correction value, A method for producing a coating composition, characterized in that the prediction step is repeated until the difference between the color obtained by adding the predicted blending composition and the target color is equal to or less than a predetermined reference value.

[0012] (2) In the prediction step, the liquid color measurement of the coating composition before adjustment is carried out by placing the coating composition in a transparent cell for color measurement, stirring the coating composition before adjustment in the transparent cell, and immediately after a predetermined time has elapsed; The predetermined time is fixed to be the same when the prediction step is repeated, The method for producing a coating composition according to (1) above, wherein the predetermined time is fixed and selected from the range of 0.1 to 600 seconds.

[0013] (3) The method for producing a coating composition according to (1) or (2), wherein the correction value is fixed to the same value when the prediction step is repeated.

[0014] (4) further comprising a gap target value setting step of setting a color gap target value; In the gap target value setting step, the absolute value of the difference between the value obtained by converting the acquired liquid colorimetry of the coating composition before adjustment into the colorimetry of the coating film using the correction value and the gap target value is smaller than the absolute value of the difference between the value obtained by converting the acquired liquid colorimetry of the coating composition before adjustment into the colorimetry of the coating film using the correction value and the target color, The method for producing a coating composition according to any one of (1) to (3), wherein the prediction step is a gap target value corresponding blend composition prediction step for predicting a blend composition of the raw materials for color adjustment suitable for obtaining the color of the gap target value.

[0015] (5) A method for producing a coating composition according to (4), wherein in the gap target value setting step, the gap target value is set so that the smaller the absolute value of the difference between the value obtained by converting the liquid color measurement of the coating composition before adjustment into the color measurement of the coating film using the correction value and the gap target value, the closer the gap target value becomes to the target color, either continuously or stepwise.

[0016] (6) In the gap target value corresponding composition prediction step, the composition of the color-adjusting raw materials is predicted by theoretical calculation using a computer under conditions in which each amount in the composition of the color-adjusting raw materials is individually limited to a candidate solution generated from a finite numerical range, and the candidate solution includes a case in which the amount is 0. This is a method for producing a coating composition as described in (4).

[0017] (7) A method for producing a coating composition according to (6) above, comprising, in the gap target value corresponding composition prediction step, when a composition of the color-adjusting raw materials suitable for obtaining the color of the gap target value cannot be calculated by the theoretical calculation by the computer, a step of canceling some or all of the conditions and re-predicting the composition of the color-adjusting raw materials by the theoretical calculation by the computer.

[0018] (8) The method further includes a main colorant specifying step of specifying the colorant that is blended in the largest amount among the colorant blending compositions of the coating composition before the preparation, 7. The method for producing a coating composition according to claim 6, wherein in the gap target value corresponding blend composition prediction step, prediction is performed using conditions limited to solution candidates generated from the finite numerical range for at least the main colorant.

[0019] (9) A method for producing a coating composition according to any one of (4) to (8), wherein in the gap target value corresponding blend composition prediction step, a blend composition of the raw materials for color adjustment suitable for obtaining the color of the gap target value is calculated using one of a brute force search method, a mathematical optimization method, and a random search method. [Effects of the Invention]

[0020] According to the present invention, it is possible to provide a method for producing a coating composition that can improve the productivity of the coating composition. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a flowchart showing a method for producing a coating composition according to a first embodiment of the present invention. [Figure 2] 4 is a flowchart showing a method for producing a coating composition according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0022] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0023] First Embodiment The method for producing a coating composition according to a first embodiment of the present invention is a method for producing a coating composition having a target color by adding raw materials for adjusting color to a coating composition before preparation.

[0024] Here, the term "paint composition before adjustment" refers to a paint composition in which, of the materials constituting the target paint composition, materials having the same function as the color-adjusting materials are blended in a predetermined amount of 0 to 100%, and materials other than those having the same function as the color-adjusting materials are blended in a predetermined amount of 100%, and the color of the paint composition is approximately similar to the target color. The paint composition may or may not contain color-adjusting materials. The blending amounts of each material may be unknown. Here, the coating composition is, for example, prepared by dispersing a resin, a solvent, and one type of coloring pigment in an SG mill or the like, and preparing a plurality of coloring agents for various colors, and then adding a resin, a solvent, and an additive to one or more coloring agents to adjust to an arbitrary color, and mixing them. The coating composition is not particularly limited, and can be in the form of, for example, an aqueous coating composition, a solvent-based coating composition, a powder coating composition, a solventless coating composition, etc. The blending composition may include resin raw materials, pigments, design raw materials, solvents (including water), additives, etc. The resin raw materials may be modified resins of each other, such as acrylic resin, polyester resin, epoxy resin, alkyd resin, fluororesin, urethane resin, aminomelamine resin, isocyanate resin, blocked isocyanate resin, and urethane-modified polyester resin. The pigments may include inorganic pigments, organic pigments, coloring pigments, and extender pigments. The design raw materials may include lustrous materials such as metallics and pearls, aggregates, silica, resin beads, and wax. The additives may include viscosity modifiers, silicone-based additives, rust inhibitors, catalysts, and antifoaming agents. Examples of uses include coil coating compositions, general industrial coating compositions, automotive coating compositions, automotive repair coating compositions, architectural coating compositions, heavy-duty anticorrosion coating compositions, and marine coating compositions. Coating methods include spray coating, roller coating, brush coating, roll coating (including natural and reverse rotation), curtain flow coating, die coating, electrodeposition coating, powder coating, and electrostatic coating. Drying methods include bake drying, forced drying, natural drying, and ultraviolet curing.

[0025] Furthermore, "color-adjusting raw materials" refers collectively to materials used for adjusting color, such as colorants, gloss modifiers, viscosity modifiers, and design raw materials. The color-adjusting raw materials include at least one of multiple types of colorants, one or more types of gloss modifiers, and one or more types of viscosity modifiers. The color-adjusting raw materials preferably include at least multiple types of colorants. The colorants include color pigments, such as black pigments, white pigments, yellow pigments, green pigments, red pigments, blue pigments, titanium oxide, and red iron oxide. Examples of gloss modifiers include aggregates (sand, etc.), silica, reflective materials, and alumina. Examples of viscosity modifiers include synthetic resin-based viscosity modifiers, natural product-based viscosity modifiers, and inorganic viscosity modifiers. Examples of synthetic resin-based viscosity modifiers include polymer-based viscosity modifiers and associative viscosity modifiers. Solvents such as water and organic solvents can also be used as viscosity modifiers. The colorant, gloss adjuster, viscosity adjuster, and design raw material may be used as the raw material itself, or may be dispersed in a solvent such as water or an organic solvent using a dispersant or the like.

[0026] Also, "color" is, for example, L * a * b * L in color space * value, a * value, b * Value (JIS Z 8781-4 (2013)), XYZ color system, RGB color system, Yxy color system, Hunter Lab color system, L * C * h * The color can be measured using a known color measurement method, for example, by using a spectrophotometer CM-M6 (manufactured by Konica Minolta) to measure the L value by irradiating a light source at angles of 25°, 45°, and 75°, assuming that the light receiving part perpendicular to the coating film formed on the test plate is set to 0°. * value, a * value, b *The value can be measured. Alternatively, it can be measured using a spectrophotometer X-Rite MA68II (manufactured by X-Rite). The measurement angle can be adjusted appropriately depending on the purpose or the equipment used. Any other index can be used. Furthermore, any index can be used, such as reflection spectrum data, which is an index in which the reflection spectrum intensity at 5 nm intervals from 400 nm to 780 nm is used as a color index. The color may be evaluated directly from the obtained coating composition. As an example, the coating composition can be measured in a state where it is placed in a quartz glass cell or a plastic cell using a spectrophotometer SE7700 (manufactured by Nippon Denshoku Industries Co., Ltd.).

[0027] FIG. 1 is a flowchart of a method for producing a coating composition according to a first embodiment of the present invention. The example in FIG. 1 involves theoretical calculations using a computer. The target of adjustment is color. As shown in FIG. 1, in the first embodiment, primary data is first acquired (step S101). The primary data is actual measurement data of the spectral reflectance at wavelengths of 400 to 700 nm for each coating composition for calculation. By acquiring such data, the relationship between the formulation of the coating composition for calculation in an arbitrary coating formulation and color change can be determined, and this data can be used to predict, by theoretical calculation using a computer, the formulation of raw materials for color adjustment suitable for obtaining a target color. Note that in the present disclosure, prediction is not limited to theoretical calculations using a computer; if a computer is not used, it is preferable to omit step S101.

[0028] Next, in the first embodiment, the data necessary to convert the color measured by liquid colorimetry of the coating composition that will produce a coating film with the target color into the color measured by colorimetry of the coating film is prepared (steps S102, S103). That is, a paint composition that will give a paint film having a target color and a paint film obtained by applying the same are prepared, and the colors of each are measured (Step S102). The liquid color measurement method for a coating composition involves placing the unadjusted coating composition in a transparent cell for color measurement, stirring the unadjusted coating composition in the transparent cell, and then immediately after a predetermined time has elapsed. The predetermined time is fixed the same when the color measurement is repeated, and the fixed predetermined time is preferably selected from 0.1 to 600 seconds. Although not limited to a particular theory, performing color measurement after a predetermined time has elapsed after stirring allows the components of the coating composition to be uniformly dispersed in the transparent cell, while allowing for easy liquid color measurement without the need for large-scale equipment, as is the case when liquid color measurement is performed during stirring. Furthermore, fixing the same time when color measurement is repeated can prevent variation between repetitions. Furthermore, selecting a time of 0.01 seconds or more allows for easy liquid color measurement as described above, while selecting a time of 600 seconds or less allows for liquid color measurement before the components in the transparent cell become heterogeneous again. Incidentally, color measurement in the state of a coating composition is sometimes called "liquid color measurement." Furthermore, liquid colorimetry may not be performed in all steps of measuring color, and some of the steps may be replaced with colorimetry of the coating film. For example, only when it is expected to be the last adjustment, colorimetry of the coating film may be performed without liquid colorimetry.

[0029] For example, the color of a coating film can be measured by applying the coating composition to a substrate, such as art paper or a metal plate, to prepare a sample plate, and measuring the color using a color difference meter or the like.

[0030] With respect to the target color, a correction value is obtained, which is the color difference between the color obtained by colorimetry of the liquid of the coating composition obtained in step 102 and the color obtained by colorimetry of the coating film (step S103: correction value obtaining step). As an example, it is also possible to use the formula "correction value = (color of the paint composition measured in liquid colorimetry) - (color of the paint film measured in colorimetry)". In this case, by subtracting the correction value from the color of the paint composition measured in liquid colorimetry, the color of the paint composition measured in liquid colorimetry can be converted into the color of the paint film measured in colorimetry. Another example is "correction value = (color of coating film measured by colorimetry) - (color of coating composition measured by liquid colorimetry)". In this case, by adding the correction value to the color of the coating composition measured by liquid colorimetry, the color of the coating composition measured by liquid colorimetry can be converted into the color of the coating film measured by colorimetry. In either case, the correction value can be positive, zero, or negative. As another example, the correction value may be defined as the absolute value of the color difference, and the color of the coating composition measured by liquid colorimetry or colorimetry of the coating film, whichever has the larger color measurement value, can be converted to the color of the coating film measured by colorimetry by subtracting the absolute value from the larger color measurement value, or by performing an equivalent calculation. In addition, various modifications and variations equivalent to the above examples are possible.

[0031] Next, in the first embodiment, the unadjusted coating composition is charged (step S104). At this time, the main colorant, which is the colorant with the largest blending amount, may be multiplied by a rate of 100%, so that the other colorants are mainly adjusted. In the first embodiment, the charging of the unadjusted coating composition is performed for a specific color, for example, an industrial coating composition, for which the target color is predetermined.

[0032] Next, the color of the unadjusted (initial) paint composition prepared in step S104 is measured (step S105: acquiring color data of the paint composition). The color of the unadjusted (initial) paint composition is measured by placing the unadjusted paint composition in a transparent cell for color measurement, stirring the unadjusted paint composition in the transparent cell, and immediately after a predetermined time has elapsed. This predetermined time is preferably selected from the range of 0.1 to 600 seconds. While not intended to be limited by a particular theory, performing color measurement after a predetermined time has elapsed after stirring allows the components of the paint composition to be uniformly dispersed in the transparent cell, while also allowing for easy liquid color measurement without the need for large-scale equipment, as is the case when liquid color measurement is performed during stirring. Furthermore, selecting a time of 0.01 seconds or more allows for easy liquid color measurement, as described above, while selecting a time of 600 seconds or less allows for liquid color measurement before the components in the transparent cell become non-uniform again.

[0033] Next, the color data of the liquid color measurement before adjustment obtained by performing liquid color measurement of the coating composition before adjustment and the correction value are used to convert the color data of the liquid color measurement before adjustment into color data of the coating film (step S106).

[0034] Furthermore, instead of measuring and converting the correction values ​​each time the paint is adjusted, it is also possible to register the values ​​for each paint color in advance in a computer and use them each time.

[0035] Next, the color data obtained by converting the coating composition before adjustment into a coating film is used to predict the blending composition of raw materials for color adjustment that is suitable for obtaining the target color (step S107: prediction step).

[0036] Since the target color is the color of the coating film, the prediction is made by converting the color measured using the liquid color into the color of the coating film. That is, by adding or subtracting the correction value obtained in the correction value acquisition process (step S106) to the color of the paint composition obtained by liquid colorimetry, the color of the paint composition obtained by liquid colorimetry can be converted into the color of the paint film obtained by colorimetry. In this embodiment, the prediction is performed by theoretical calculation using a computer (having a calculation unit). As described above, the theoretical calculation can be performed using the primary data acquired in step S101 and a known method such as the Kubelka-Munk equation or mathematical optimization. On the other hand, the prediction can also be performed using a method using an artificial intelligence model, or can be performed without using a computer.

[0037] From the predicted blend compositions, one blend composition is selected in which the difference between the target color difference and the calculated color difference is equal to or less than a predetermined reference value. If multiple candidates are predicted, the one with the smallest difference between the target color difference and the calculated color difference can be selected, although this is not particularly limited. In a calculation method in which only one blend composition can be selected, the one with the smallest difference between the target color difference and the calculated color difference is calculated and used as the blend composition of the raw materials for color adjustment. In the prediction process (step S107), when calculating the blend composition of raw materials for color adjustment suitable for obtaining the target color, it is preferable to use one of the following methods: brute force search method, mathematical optimization method, and random search method. The brute force search method is a technique in which a specified range and numerical interval of a parameter or an arbitrary numerical value is specified, and by calculating the color variation value using theoretical calculations for all patterns of the extracted variation amount (for example, 100,000 to 1 billion), various variation amounts are found when the difference from the target value is below a certain level. Here, it is synonymous with grid search. The mathematical optimization method is a technique for finding x1, x2, x3, and x4 as an optimization problem of a function of the amount of variation x1 in the addition ratio of colorant 1, the amount of variation x2 in the addition ratio of colorant 2, the amount of variation x3 in the addition ratio of gloss modifier, and the amount of variation x4 in the addition ratio of viscosity modifier. As the mathematical optimization method, it is preferable to use the simplex method, interior point method, gradient descent method, quadratic programming method, continuous linear programming method, sequential quadratic programming method, Lagrange's undetermined multiplier method, barrier function method, etc. Random search is a method of specifying the number of trials and calculating color variation values ​​using theoretical calculations for variation patterns randomly extracted from within the specified parameter value range, thereby determining various variation amounts when the difference from the target value is below a certain level.

[0038] Next, the predicted formulation is added to prepare a post-adjustment paint composition (Step S108). Next, the liquid color of the post-adjustment paint composition is measured (Step S109). Next, the color of the pre-adjustment paint composition is corrected (Step S110). Next, it is determined whether the difference between the color obtained by adding the predicted formulation and the target color is equal to or less than a predetermined reference value (Step S111). The color obtained by adding the predicted formulation is predicted in the prediction step of Step S107, and the color obtained by liquid color measurement of the paint composition adjusted by adding the formulation selected as described above can be obtained by converting the color into the color of the coating film using the correction value. The target color can be obtained by measuring the color of a standard plate (or using the measurement if it has already been measured). Then, it is determined whether the color difference between these is equal to or less than a predetermined reference value. If the color difference is greater than the predetermined reference value, the process returns to Step S107 and repeats the prediction step. In this case, the "paint composition before adjustment" in the nth (n≧2)th prediction step is the paint composition obtained by adding the blend composition predicted in the (n−1)th prediction step and is the paint composition before the nth adjustment is performed. When repeating the step of acquiring color data of the paint composition (step S109), the correction value acquired in step S103 may be used. On the other hand, if the color difference is equal to or less than the predetermined reference value, the color matching is completed (step S112). The effects of the method for producing a coating composition according to the first embodiment will be described below.

[0039] The method for producing a coating composition according to the first embodiment includes a correction value acquisition step (step S103) for acquiring a correction value, which is the color difference between the color measured by liquid colorimetry of the coating composition and the color measured by colorimetry of the coating film for a specific color, and a prediction step (step S107) for predicting a blend of color-adjusting raw materials suitable for achieving the target color using the correction value and the color measured by liquid colorimetry of the coating composition before adjustment. The prediction step (step S107) is repeated until the difference between the color obtained by adding the predicted blend and the target color falls below a predetermined reference value. As described above, this eliminates the need to prepare a coating film from the coating composition each time, eliminating the need for curing and drying time when preparing a coating film and reducing the number of steps required. Furthermore, since the colorimetry is performed on a specific color to obtain a correction value specific to that specific color, highly accurate predictions (as shown in the examples described below) are possible, and the number of repetitions of the prediction process is reduced, which also makes it possible to reduce the number of steps. The reduction in steps as described above leads to improved productivity of the coating composition. As described above, the method for producing a coating composition according to the first embodiment can provide a method for producing a coating composition that can improve the productivity of coating compositions.

[0040] <Second embodiment> Next, a method for producing a paint composition according to a second embodiment of the present invention will be described. Figure 2 is a flowchart of the method for producing a paint composition according to the second embodiment of the present invention. The method for producing a paint composition according to the second embodiment of the present invention also involves adding raw materials for adjusting color to a paint composition before adjustment to produce a paint composition having a target color. Steps S201 (acquisition of primary data) to S206 (perform correction) are the same as steps S101 (acquisition of primary data) to S106 (perform correction) in the method for producing a paint composition according to the first embodiment shown in Figure 1, so repeated explanation will be omitted.

[0041] As shown in FIG. 2, in the second embodiment, after the correction is performed (step S206), a color gap target value is set (step S207: gap target value setting step) before the prediction step (step S208).

[0042] Here, the absolute value of the difference between the value obtained by converting the liquid color measurement of the unadjusted coating composition to the color measured by colorimetry of the coating film using the acquired correction value and the gap target value is smaller than the absolute value of the difference between the value obtained by converting the liquid color measurement of the unadjusted coating composition to the color measured by colorimetry of the coating film using the correction value and the target color. For example, if the liquid color measurement of the unadjusted coating composition is 23, and a correction value of 2 is added to it to obtain a coating color of 25, and the target color is 30, the absolute value of the difference between the coating color (converted value) and the target color is 5 (= 30 - (23 + 2)). Multiplying this by a rate of, for example, 0.5 to 0.9 (hereinafter also referred to as the approach rate) results in 3.5 (= 5 × 0.7) if the approach rate is 0.7. In this case, the gap target value can be 28.5 (= 23 + 2 + 3.5). In this case, the absolute value of the difference between the color of the coating film (converted value) and the target gap value is 3.5 (= 28.5 - 25), which is smaller than the absolute value of the difference between the color of the coating film (converted value) and the target color, which is 5 (= 30 - 25). When managing the same thing using color difference, if the difference (color difference) between the color of the coating film (converted value) and the target color is -5 and the approach rate is 0.7, the initial gap target value can be a color difference of -1.5. In this case, the absolute value of the color difference of the gap target value is "1.5," which is smaller than the absolute value of the color difference before multiplying by the approach rate, which was "5."

[0043] Next, using the color of the solution color measurement before adjustment and the correction value, a blending composition of raw materials for color adjustment suitable for obtaining the color of the target gap value is predicted (step S208). That is, the prediction step in the second embodiment is a gap target value corresponding blending composition prediction step that predicts a blending composition of raw materials for color adjustment suitable for obtaining the color of the target gap value. As described above, the theoretical calculation can be performed using known methods such as the Kubelka-Munk equation and mathematical optimization using the primary data acquired in step S201.

[0044] Next, one of the predicted blending compositions is selected such that the difference between the color difference of the gap target value and the calculated color difference is equal to or less than a predetermined reference value. If multiple candidates are predicted, the one with the smallest difference between the color difference of the gap target value and the calculated color difference can be selected, although this is not particularly limited. In a calculation method that can only select one blending composition, the one with the smallest difference between the color difference of the gap target value and the calculated color difference is calculated and used as the blending composition of the raw materials for color adjustment. In the gap target value corresponding blend composition prediction process (step S208), it is preferable to use one of the following methods to calculate the blend composition of raw materials for color adjustment suitable for obtaining the color of the gap target value: brute force search method, mathematical optimization method, or random search method.

[0045] Next, the predicted formulation is added to prepare a post-adjustment paint composition (step S209). Next, the liquid color of the post-adjustment paint composition is measured (step S210). Next, the color of the paint composition before adjustment is corrected (step S211). Next, it is determined whether the difference between the color obtained by adding the predicted formulation and the target color is equal to or less than a predetermined reference value (step S212). Here, the liquid color of the paint composition adjusted by adding the selected formulation is measured, and the corrected value is used to convert it into the color of the coating film, and it is determined whether the color difference is equal to or less than a predetermined reference value.

[0046] If the measured color difference exceeds the predetermined reference value, the process returns to step S207, and steps S207 to S212 are repeated. However, in each repetition, the target gap value set in step S207 is set based on the color obtained by adding the predicted formulation. For example, in the first step S207, if the color (converted value) of the coating film before adjustment is 25, the target color is 30, and the approach rate is 0.7, the initial target gap value will be 28.5 as described above. As a result, if the color (converted value) of the coating film formed from the paint composition adjusted by adding the selected formulation is 28.4, in the second step S207, based on the current value of 28.4, the absolute value of the difference between the current color (converted value) and the target color is 1.6 (= 30 - 28.4), and this can be multiplied by, for example, an approach rate of 0.9 to set the target gap value to 29.84 (= 28.4 + 1.6 × 0.9). In the case of a method of managing using color difference, for example, if the difference (color difference) between the color of the coating film (converted value) and the target color is -5 and the approach rate is 0.7, the initial gap target value will be a color difference of -1.5 as described above. As a result, if the similar color difference for a coating composition adjusted by adding the selected blending composition is -1.6, which is 0.1 lower than the gap target value (0.1 greater in absolute value) due to the influence of raw material lot differences, in the second step S206, this can be multiplied by, for example, an approach rate of 0.9 to set the gap target value to a color difference of -0.16 (= -1.6 + 1.6 × 0.9). On the other hand, if the difference between the color obtained by adding the predicted blend composition and the target color is equal to or less than a predetermined reference value, the color matching is completed (step S213). The effects of the method for producing a coating composition according to the second embodiment will be described below.

[0047] First, the method for producing a coating composition according to the second embodiment of the present invention can also provide a method for producing a coating composition that can improve the productivity of the coating composition, similar to the method for producing a coating composition according to the first embodiment of the present invention. Furthermore, the method for producing a coating composition according to a second embodiment of the present invention further includes a gap target value setting step (step S207) for setting a color gap target value. In the gap target value setting step (step S207), the absolute value of the difference between the value obtained by converting the acquired liquid color measurement of the coating composition before adjustment to the color measurement of the coating film before adjustment using a correction value and the gap target value is smaller than the absolute value of the difference between the acquired value obtained by converting the liquid color measurement of the coating composition before adjustment to the color measurement of the coating film before adjustment using a correction value and the target color. Then, in the gap target value-corresponding blend composition prediction step (step S208), a blend composition of raw materials for color adjustment suitable for obtaining the color of the gap target value is predicted. In this way, in the second embodiment, a gap target value that is lower than the original target value (smaller difference from the current color) is set, and the compound composition of the raw materials for color adjustment that corresponds to that gap target value is predicted. From the predicted compound compositions, one compound composition is selected such that the difference between the color difference of the gap target value and the calculated color difference is equal to or less than a predetermined reference value (in this example, the color difference is 0.1 or less), and the color is adjusted. Therefore, when adjusting the color of the paint composition, it is possible to prevent the compound amount for adjustment from becoming excessive. Then, the liquid color of the paint composition adjusted by adding the selected blending composition is measured, and the correction value is used to convert it into the color of the paint film, and it is determined whether the color difference is below a predetermined standard value (step S212).As a result, steps S207 to S212 are repeated as necessary to finally produce a paint composition having the target color. Here, the color is not linear in relation to the amount of blending and the amount of color change. * , a * , b * In contrast to this, in the second embodiment, the gap target value is set by multiplying the approach rate based on the color, and therefore, compared to, for example, a method of multiplying the predicted blend amount by the approach rate, it is possible to more accurately prevent the blend amount for adjustment from becoming excessive. For example, the amount of colorant added and the amount of color change are not in a linear relationship, and the more colorant added, the smaller the color change. In other words, if the predicted blending amount is multiplied by 90% of the approach rate, the color difference will be closer than if the color difference were multiplied by 90% of the approach rate. For example, if a white paint composition is used in combination with a black paint composition, the color difference will be closer than if the white paint composition is used with a black paint composition. * When the color difference approach rate is 90% and the color difference is adjusted to -0.5 to -0.05, a 90% dosage approach rate results in a color difference of -0.5 to -0.02, which is too close. If there are no colorant lot variations, the closer color difference may reduce the number of adjustments required. However, if there are colorant lot variations and the color strength is 20% stronger, a 90% color difference approach rate results in a color difference of -0.5 to 0.04 (= -0.5 + 0.5 x 0.9 x 1.2), which is only a slight overshoot, and the color adjustment is complete if the control range is ±0.05. However, if the dosage approach rate is 90%, the color difference will exceed the opposite range, from -0.5 to 0.076 (= -0.5 + (0.5 - 0.02) x 1.2), requiring the addition of more black paint composition to restore the color, which leads to the overproduction mentioned above. One possible way to anticipate this is to lower the approach rate of the amount of addition, but this requires checking the fluctuation curve of the amount of addition and the color, which is cumbersome and prone to errors. On the other hand, the color difference approach rate is efficient and easy to set because it is faithful to the intended approach to the target property.

[0048] When preparing industrial paints mass-produced in paint factories, if too much of the preparation compound is added, it is necessary to add more compound to restore the color of the paint film. For example, if the color is gray, a colorant of the opposite color (e.g., if too much black colorant is added, white colorant) is added to restore the color. In such cases, the amount of paint produced is significantly greater than planned, often resulting in waste in the form of material costs and disposal of the excess production. In particular, when industrial paints are mass-produced in paint factories, several hundred kilograms to several tons (tons) can be produced per batch, making this waste even more pronounced. Furthermore, there are drawbacks, such as increased labor costs due to the need to transfer the paint to a larger production container to prevent overflow. Therefore, preparation relies on the skill of an expert. However, preparations performed exclusively by experts have problems such as inconsistent quality due to differences in preparation accuracy depending on the level of expertise, and increased labor costs due to increased labor costs. Furthermore, in the preparation process, a specific colorant with the maximum blend amount is often blended close to the target value when the paint is prepared before preparation, and even a small amount of a colorant with the minimum blend amount can result in a large excess being added, resulting in a significant problem of overproduction, whereby an amount far exceeding the planned amount is produced in order to restore the original amount. For example, if the correct blend is 99 kg of white colorant and 1 kg of black colorant, even if each colorant is blended in the correct amount, if the lot has a black colorant with a 10% higher tinting strength, 9.9 kg of white colorant must be added to restore the original amount, resulting in an overproduction of at least 9.9 kg. The second embodiment, which uses a gap target value, has the advantage of being able to suppress such overproduction.

[0049] Here, in the second embodiment, in the gap target value setting process (step S207), it is preferable to set the gap target value so that the smaller the absolute value of the difference between the value obtained by converting the liquid color measurement of the paint composition before adjustment into the color measurement of the paint film using a correction value and the gap target value, the closer the gap target value becomes to the target color, either continuously or stepwise. As described above, the second embodiment involves repeating steps S207 to S212. However, as the color of the paint composition gradually approaches the target color, the amount of compounding composition added for adjustment gradually decreases, and therefore the excess amount in the event of adding too much of the compounding composition also decreases, gradually reducing the risk. Therefore, as steps S207 to S212 are repeated, the smaller the absolute value of the difference between the value obtained by converting the liquid color measurement of the paint composition before adjustment into the color measurement of the paint film using the correction value and the gap target value, the closer the gap target value becomes to the target color, either continuously or stepwise (for example, by adopting an approach rate closer to "1"), thereby reducing the number of repetitions required to produce paint as much as possible and improving production efficiency without compromising the effect of suppressing overproduction.

[0050] In the second embodiment, in the gap target value setting step (step S207), L * , a * , b * It is preferable to set an independent gap target value for each of the L. If a common gap target value is used, the problem of overproduction will occur if any of the colors exceeds the target value due to excessive filling. Also, if the common gap target value is set too low compared to the target color, productivity will decrease. * , a * , b * Setting gap targets independently for each of the above can further reduce overproduction while maintaining manufacturing efficiency.

[0051] For example, ΔL * If is greater than 1, the approach rate is set to 50% and ΔL * If ΔL is between 0.5 and 1.0, the approach rate is set to 70%. * If Δa is 0.5 or less, the approach rate can be set to 100%. * , Δb *can also be applied independently.

[0052] In the second embodiment, a prepared paint composition (hereinafter also referred to as the finished paint composition) and a paint film obtained by applying the same are prepared, and the color data for each is measured.The difference between the measured values ​​is then calculated as a correction value (Δdw), and the measured value of the paint film is estimated from the measured value of the paint composition.This method has the advantage that, when the target color changes each time, as in the case of automotive repair paint, it is difficult to prepare Δdw in advance, but when the target color is predetermined, the color of the paint film can be predicted with high accuracy. Here, paint colors for industrial products are usually prepared in advance in a laboratory, and the color is confirmed and agreed upon using a standard plate. When the product is produced in the factory based on the color of that standard plate, slight color variations resulting from pigment lots and production variations are adjusted in an adjustment process. Therefore, the target color is determined in advance, and the Δdw of the finished paint composition can be prepared in advance. Here, Δdw varies depending on the color, and even a slight change in color will cause a change in Δdw. Therefore, when high-precision color adjustment is required, the color of the coating film cannot be accurately predicted unless the Δdw of the color being adjusted is known. However, it is not realistic to measure Δdw in advance for all colors in the process of adjustment. To solve this problem, when adjusting colors, the target ΔL * , Δa * , Δb * Instead of setting a correction compounding composition that makes Δdw zero from the beginning, a gap target is set, and even if the Δdw after adjustment is used as the true Δdw for all colors in the process leading up to the adjustment, the true Δdw during the adjustment process gradually approaches the Δdw after adjustment, thereby enabling accurate adjustment. This method of converting liquid color measurements into the color of a coating film using a correction value is, of course, useful on its own, but by using it in combination with a method that uses a cap target value, the advantageous effects described above can be obtained. [Example]

[0053] The present invention will be explained in more detail with reference to the following examples, but the present invention is not limited to these examples.

[0054] The coating compositions were produced 20 times each by the methods according to Examples 1 and 2 and Comparative Examples 1 and 2, and the color matching accuracy (ΔL * , Δa * , Δb * ) and production rate were calculated and the arithmetic mean values ​​were compared.

[0055] First, the methods for preparing the colorants used in Examples 1 and 2 and Comparative Examples 1 and 2 will be described.

[0056] <White paint composition> A white coating composition was prepared by mixing 65.3 parts by mass of acrylic resin emulsion as the resin, 23.0 parts by mass of titanium oxide as the white pigment, and 12.0 parts by mass of tap water, and dispersing the mixture using a sand mill (dispersion medium: glass beads) until the maximum particle size of the pigment coarse particles was 20 μm or less. <Preparation examples of other color paint compositions> A black coating composition, a red coating composition, and a yellow coating composition were prepared in the same manner as in the preparation example of the white coating composition, except that the type and amount of each material was changed as shown in Table 1. The formulations of each color coating composition are shown in Table 1. Each coating composition was used to adjust the color of the coating composition described below (color-adjusting coating composition (white), (black), (red), (yellow)).

[0057] [Table 1]

[0058] Next, the methods for preparing the pre-adjusted coating compositions used in Examples 1 and 2 and Comparative Examples 1 and 2 will be described. <Preparation example of pre-adjusted coating composition 1> 98.2 parts by mass of the white paint composition, 0.4 parts by mass of the black paint composition, 0.2 parts by mass of the red paint composition, and 1.2 parts by mass of the yellow paint composition were mixed and stirred for about 10 minutes using a disper to prepare paint composition 1 before adjustment. <Preparation examples of other pre-adjusted paint compositions> Pre-prepared coating compositions 2 to 4 were obtained by the same method as in the preparation example of pre-prepared coating composition 1, except that the type and amount of each material was changed as shown in Table 2 below. The formulations of the pre-prepared coating compositions are shown in Table 2.

[0059] [Table 2]

[0060] Details of the materials used in preparing the coating compositions are as follows: Resin: Dianal BR112 (acrylic resin emulsion, manufactured by Mitsubishi Rayon Co., Ltd.), solid content: 40% by mass White pigment: TIPAQUE R-820 (titanium oxide, manufactured by Ishihara Sangyo Kaisha) Black pigment: Mitsubishi Carbon Black MA100 (carbon black, manufactured by Mitsubishi Chemical Corporation) Yellow pigment: TAROX synthetic iron oxide LL-XLO (yellow iron oxide, manufactured by Titan Kogyo Co., Ltd.) Red pigment: Bayferrox 180M (iron oxide, manufactured by LANXESS)

[0061] <How to prepare the dried coating> The coating composition was applied to the surface of a hiding power test paper (manufactured by Motofuji Co., Ltd.) using a 6 mil doctor blade and baked at 100°C for 15 minutes to obtain a dried coating film of the coating composition (film thickness: 40 µm).

[0062] The color data obtained in each of the examples and comparative examples was measured by the following method. <Measuring method for color data of coating film> (Color measurement of dry coating film) The coating film obtained by the coating composition and the method for preparing the dried coating film was measured for color (L) using a spectrophotometer CM-3600A (Konica Minolta). * , a * , b * value, or the L with the target standard plate * , a * , b * The difference between the values ​​was measured.

[0063] <Method for measuring color data of paint composition> (liquid color measurement) First, the coating composition was placed in a transparent cell. Then, the transparent cell was fixed with a support jig so that its side was in close contact with the window of the colorimeter. Then, the coating composition in the transparent cell was stirred with a stirring rod, and after 10 seconds, the color (L * , a * , b * value, or the L with the target standard plate * , a * , b * The colorimeter used was a spectrophotometer CM-3600A (manufactured by Konica Minolta).

[0064] A method for predicting the color of a dried coating film measured by colorimetry from the color of a liquid coating composition will be described below.

[0065] The method for obtaining the correction value (the color difference between the color of the coating composition measured in liquid form and the color of the dried coating film measured) will be described below.

[0066] <How to obtain correction values> First, the color data of the coating composition that can produce a coating film having the target color and the dried coating film obtained by applying the same are measured, and each measurement value (L * , a * , b * The differences (Δdw(L), Δdw(a), Δdw(b)) between the values ​​were calculated and used as the correction values.

[0067] <Method for predicting color data of dried coating film> The correction value was added to the color data of the liquid color measurement to obtain a predicted value of the dried coating film. L(d)=L(w)+Δdw(L) a(d)=a(w)+Δdw(a) b(d)=b(w)+Δdw(b) (However, L(d), a(d), b(d) are the L values ​​of the colorimetry of the coating film. * , a * , b *L(w), a(w), b(w) are the L values ​​of the liquid colorimeter. * , a * , b * value.)

[0068] The correction values ​​for each paint composition before adjustment are shown in Table 3.

[0069] [Table 3]

[0070] <Paint adjustment pass criteria> In each adjustment, the target value and the actual measured value L * value, a * value, b * The difference between the values ​​is called ΔL * , Δa * , Δb * When ΔE[=√(ΔL *2 +Δa *2 +Δb *2 )] is 0.2 or less, and ΔL * , Δa * , Δb * When each of the above values ​​was 0.2 or less, the paint was deemed to have passed the test, and the paint preparation was completed. The target values ​​refer to the color data of a dried coating film obtained by applying a coating composition that would give a coating film with the target color, and the measured values ​​refer to the color data obtained by liquid color measurement. <Adjustment time pass criteria> In 20 adjustments, an average adjustment time of less than 130 minutes was considered a pass, and an average adjustment time of 130 minutes or more was considered a fail. <Criteria for passing the number of adjustments> Of the 20 adjustments, a test piece was deemed to have passed if the average number of adjustments required to pass was less than 5, and failed if it was 5 or more. <Production volume rate acceptance criteria> In the 20 adjustments, if the average production rate up to passing was less than 105%, it was considered to be pass, and if it was 105% or more, it was considered to be fail. <Final pass criteria> The paint composition that has been adjusted by liquid color measurement is applied and dried to form a dried coating film. The target value of ΔE is 0.2 or less, and ΔL * , Δa * , Δb * When each of the above was 0.2 or less, it was considered to have passed.

[0071] <Example of creating primary data> <Example 1 of obtaining absorption coefficient and scattering coefficient> The white paint composition, the black paint composition, and a paint composition in which the white paint composition and the black paint composition were mixed in an 80:20 ratio were each applied and dried to obtain dried coating films. The spectral reflectance of each was measured, and the absorption coefficient K of the white paint composition and the absorption coefficient K and scattering coefficient S of the black paint composition were calculated.

[0072] <Example 2 of obtaining absorption coefficient and scattering coefficient> The absorption coefficient K and scattering coefficient S of the dried coating film of each of the red and yellow paint compositions were calculated in the same manner as in Example 1 for obtaining absorption coefficients and scattering coefficients, except that the black paint composition was changed to a red paint composition or a yellow paint composition.

[0073] <Example of obtaining the theoretical formula for color variation> A theoretical calculation formula for color variation was obtained using these absorption coefficients and scattering coefficients, the refractive index of the pigment and the dried paint film, and the Kubelka-Munk theory, Duncan theory, and Sanderson correction formula.

[0074] Example 1 In Example 1, as shown in Figure 2, there were a correction value acquisition step of acquiring a correction value, which is the color difference between the color of the coating composition obtained by colorimetry of the liquid and the color of the coating film; a gap target value setting step of setting a color gap target value; a gap target value corresponding blend composition prediction step of using the correction value to predict a blend composition of the color-adjusting raw materials suitable for obtaining the color of the gap target value; and the prediction step was repeated until the difference between the color obtained by adding the predicted blend composition and the target color became equal to or less than a predetermined reference value.

[0075] <Getting correction values> First, the color data (color data 1) of the finished coating composition 1 and the coating film obtained by applying the finished coating composition 1 were measured. Correction values ​​were calculated from the measurement data. Each correction value is shown in Table 3. Next, the color data of the pre-adjusted coating composition 1 prepared above was measured. The correction value was added to the obtained color data to convert it into color data for the coating film obtained from Paint Composition 1 before adjustment. The difference between the converted color data and color data 1 is ΔL * Value = 3.44, Δa * Value = 0.45, Δb * The value was 0.35.

[0076] <Setting color gap targets using approach rates> The target gap value was set to an approach rate of 0.7. That is, the color difference was ΔL * Value = 1.03, Δa * Value = 0.14, Δb * The value was set to 0.11.

[0077] <Theoretical calculation and prediction of corrected blend composition for each color paint composition> Gap target value ΔL * value, Δa * value, Δb * The corrected combination of formulations (combination of white paint composition, black paint composition, red paint composition and yellow paint composition) for obtaining the value was calculated by mathematical optimization using a theoretical calculation formula. The corrected predicted blend values ​​for each color paint composition were 1.3 g for the black paint composition, 5.4 g for the red paint composition, and 18.8 g for the yellow paint composition, respectively.

[0078] <Acquisition of color data of the adjusted paint composition and acquisition of the difference from the target color> The predicted corrected formulation of each color paint composition was added to the unadjusted paint composition 1 to prepare the adjusted paint composition 1, and the color data of the paint composition was obtained. The color data of the dried coating film was predicted from the corrected values. The difference between the finished paint composition 1 and the dried coating film was ΔL *Value = 1.0, Δa * Value = 0.62, Δb * The value was 0.6.

[0079] <Re-adjustment of the prepared coating composition> The color of the prepared paint composition 1 did not meet the pass criteria for the target values ​​of the paint properties, and therefore it was judged to be unacceptable. The paint composition and its color data before readjustment at the time of readjustment were the paint composition after adjustment that had failed in the previous adjustment and its color data after adjustment. As in the previous case, the gap target value ΔL * value, Δa * value, Δb * The corrected combination of formulations (combination of white paint composition, black paint composition, red paint composition and yellow paint composition) for obtaining the value was calculated by mathematical optimization using a theoretical calculation formula. The corrected predicted blend values ​​for each color paint composition were 0.1 g for the black paint composition, 0.2 g for the red paint composition, and 0.8 g for the yellow paint composition. The predicted corrective blends of each color paint composition were added to the unadjusted paint in the same manner as for unadjusted paint composition 1, and the adjusted paint compositions were prepared to obtain color data. This readjustment procedure was repeated, and after confirming that the dried coating film properties of the adjusted paint compositions met the target pass criteria, the paint preparation was completed (number of adjustments: 3, color matching time: 93 minutes, production rate: 101%). The same procedure was carried out four times (a total of five times). The same procedure was also carried out for pre-adjusted paint compositions 2, 3, and 4. For each of the four types of paint, including pre-adjusted paint composition 1, the procedure was repeated five times for a total of 20 adjustments. The number of adjustments was 2.8, the adjustment time was 91 minutes, and the production rate was 101%, which was acceptable. The results are shown in Table 5.

[0080] <Example 2> In Example 2, the same procedure as in Example 1 was carried out except that the target gap value was not set using the approach rate in <Setting the target gap value for paint properties>.

[0081] Four types of paint (pre-adjusted paint compositions 1 to 4) were prepared 5 times each, for a total of 20 preparations. The number of preparations was 3.5, the preparation time was 121 minutes, and the production rate was 103%, passing the test. The results are shown in Table 5. In Example 2, the container of the pre-adjusted paint composition was replaced twice out of the 20 times, requiring 300 minutes each time, for a total of 600 minutes, and this time was added to the total preparation time.

[0082] <Comparative Example 1> It was assumed that within a given wavelength range, the reflectance of the coating composition at wavelength λi [Rw(λi)] and the reflectance of the dried coating film of the coating composition [Rd(λi)] approximately form a linear function, and αi and βi corresponding to the following equation within that range were determined. First, a coating composition capable of producing a coating film having the target color and the coating film obtained by applying the same were prepared, and the color of each was measured. The colorimetric method for the dried coating film and coating composition was performed using the same equipment as in Example 1. The reflectances Rw(λi) and Rd(λi) of the coating composition and the dried coating film obtained therefrom were measured every 10 nm in the wavelength range of 400 to 700 nm. This was repeated for 19 different coating colors. The αi and βi values ​​for each wavelength were calculated using the least squares method from the corresponding Rd(λi) and Rw(λi) values ​​for each wavelength obtained above. The αi and βi values ​​calculated for each wavelength are shown in Table 4. Rd(λi)=αiRw(λi)+βi Rd(λi): Reflectance of dry coating film at wavelength λi (%) Rw(λi): Reflectance (%) of the coating composition at wavelength λi αi, βi: Coefficients when coefficients α and β depend on wavelength λi

[0083] [Table 4]

[0084] <Method for predicting dry coating film color data of unadjusted coating composition> First, the reflectance Rw(λi) of the unprepared coating composition 1 was measured. Next, the reflectance of the coating composition at a wavelength of 400 nm, Rw(400) = 26.2%, with αi = 0.93 and βi = 1.67, was converted using the above formula to the reflectance of the dried coating film at a wavelength of 400 nm, Rd(400). Similarly, the reflectance Rw(λi) at every 10 nm from 410 to 700 nm was converted to the reflectance Rd(λi) of the dry coating film using the above formula. The obtained reflectance Rd(λi) of the dry coating film at each wavelength was converted to the XYZ color system hue value using the Sanderson correction formula, and then further * , a * , b * was calculated and used as a predicted value for the color data of the dried coating film. For Unprepared Paint Compositions 2 to 4, the color data of the dried coating film was predicted in the same manner.

[0085] <Theoretical calculation and prediction of corrected blend composition for each color paint composition> Target value ΔL * value, Δa * value, Δb * The corrected combination of formulations (combination of white paint composition, black paint composition, red paint composition and yellow paint composition) for obtaining the value was calculated by mathematical optimization using a theoretical calculation formula.

[0086] <Acquisition of color data of the adjusted paint composition and acquisition of the difference from the target color> The predicted corrected formulation of each color paint composition was added to the unadjusted paint composition 1 to prepare the adjusted paint composition 1, and the color data of the paint composition was obtained. The color data of the dried coating film was calculated using the conversion formula.

[0087] <Re-adjustment of the prepared coating composition> The color of the prepared paint composition 1 did not meet the pass criteria for the target values ​​of the paint properties, and therefore it was judged to be unacceptable. The paint composition and its color data before readjustment at the time of readjustment were the paint composition after adjustment that had failed in the previous adjustment and its color data after adjustment. As in the previous case, the gap target value ΔL * value, Δa * value, Δb *The corrected combination of formulations (combination of white paint composition, black paint composition, red paint composition and yellow paint composition) for obtaining the value was calculated by mathematical optimization using a theoretical calculation formula. In the same manner as in the case of the unadjusted paint composition 1, the predicted corrective blend of each color paint composition was added to the unadjusted paint, and the adjusted paint composition was adjusted to obtain color data. Repeat the same procedure, and after completing the color adjustment, create a dry coating film and measure ΔL * , Δa * and Δb * When we checked, ΔE=6.0 and ΔL * =5.6, Δa * =-0.1 and Δb * = 2.6, and the pass criteria for paint adjustment (ΔE and ΔL * , Δa * and Δb * The test was rejected because it did not reach the standard of 0.2 or less. In addition, the same operation was carried out for unadjusted paint compositions 2, 3, and 4, and for the four types of paint, including unadjusted paint composition 1, it was repeated five times for each. In all cases, the pass criteria for paint adjustment (ΔE and ΔL * , Δa * and Δb * The test was rejected because it did not reach the standard of 0.2 or less.

[0088] <Comparative Example 2> Comparative Example 2 was carried out in the same manner as Example 1, except that the color data of the coating composition (liquid colorimetry) was not measured, the color data of the dried coating film was measured, and no target gap value was set. That is, a pre-adjustment color information acquisition process was performed to acquire color data before adjustment, and a blending composition prediction process was performed to predict the blending composition of raw materials for color adjustment suitable for obtaining the target color. The prediction process was repeated until the difference between the color obtained by adding the predicted blending composition and the target color became equal to or less than a predetermined reference value. The primary data was obtained by calculating the absorption coefficient K and scattering coefficient S of each dried coating film obtained by applying and drying each of the color paint compositions and mixed paint compositions used in the liquid colorimetry. Four types of paint (paint compositions 1 to 4 before preparation) were prepared 5 times each, for a total of 20 preparations. The number of preparations was 3.5, the preparation time was 174 minutes, and the production rate was 104%, which was unacceptable.

[0089] In this disclosure, the terms used have the following meanings. "Number of adjustments" refers to the arithmetic mean number of times the color had to be adjusted until it passed the test, when a total of 20 paint compositions (five for each of the four paint colors) were prepared and adjusted. A smaller number of adjustments indicates higher prediction accuracy. "Adjustment time" refers to the arithmetic mean value of the adjustment time required to pass a test when a total of 20 paint compositions, five for each of the four paint colors, were prepared and adjusted. A shorter adjustment time means a shorter manufacturing process and higher manufacturing efficiency. Specifically, in step S211 of Figure 2, if the paint composition did not fall below the predetermined standard value, and if the next predicted blending composition was added, there was a risk that the paint composition would overflow from the container (approximately when the production rate exceeded 105%), and the container was replaced. "Production volume rate" refers to the proportion of the adjusted production volume when the planned production volume of the target paint composition is set to 1. Here, the fact that the production volume rate does not greatly exceed 100% means that the accuracy of the color prediction and the calculation method for the corrected blend composition are high, and that it is an efficient method that does not produce more paint composition than necessary, while allowing for raw materials and errors. The evaluation results are shown in Table 5 below.

[0090] [Table 5]

Claims

1. A method for producing a coating composition, comprising adding a raw material for adjusting color to a coating composition before adjustment to produce a coating composition having a target color, A correction value acquisition step for acquiring a correction value, which is a color difference between a color measured by colorimetry of a liquid of a coating composition and a color measured by colorimetry of a coating film, for a specific color; a prediction step of predicting a blending composition of raw materials for color adjustment suitable for obtaining the target color using the color of the liquid color before adjustment obtained by performing liquid color measurement of the coating composition before adjustment and the correction value, A method for producing a coating composition, characterized in that the prediction step is repeated until the difference between the color obtained by adding the predicted blending composition and the target color is equal to or less than a predetermined reference value.

2. In the prediction step, the liquid color measurement of the coating composition before adjustment is carried out by placing the coating composition in a transparent cell for color measurement, stirring the coating composition before adjustment in the transparent cell, and immediately after a predetermined time has elapsed; The predetermined time is fixed to be the same when the prediction step is repeated, The method for producing a coating composition according to claim 1, wherein the predetermined time is selected from the range of 0.1 to 600 seconds.

3. The method for producing a coating composition according to claim 1 or 2, wherein the correction value is fixed to the same value when the prediction step is repeated.

4. The method further includes a gap target value setting step of setting a color gap target value, In the gap target value setting step, the absolute value of the difference between the value obtained by converting the acquired liquid colorimetry of the coating composition before adjustment into the colorimetry of the coating film using the correction value and the gap target value is smaller than the absolute value of the difference between the value obtained by converting the acquired liquid colorimetry of the coating composition before adjustment into the colorimetry of the coating film using the correction value and the target color, 3. The method for producing a coating composition according to claim 1, wherein the prediction step is a gap target value corresponding blend composition prediction step that predicts a blend composition of the raw materials for color adjustment that is suitable for obtaining the color of the gap target value.

5. 5. A method for producing a coating composition according to claim 4, wherein in the step of setting the target gap value, the target gap value is set so that the smaller the absolute value of the difference between the value obtained by converting the liquid colorimetry of the coating composition before adjustment into the colorimetry of the coating film using the correction value and the target gap value, the closer the target gap value becomes to the target color, either continuously or stepwise.

6. 5. The method for producing a coating composition according to claim 4, wherein in the gap target value corresponding composition prediction step, the composition of the color adjusting raw materials is predicted by theoretical calculation by a computer under conditions in which each blending amount in the composition of the color adjusting raw materials is individually limited to solution candidates generated from a finite numerical range, and the solution candidates include cases in which the blending amount is 0.

7. 7. The method for producing a coating composition according to claim 6, further comprising, in the gap target value corresponding composition prediction step, when a composition of the color-adjusting raw materials suitable for obtaining the color of the gap target value cannot be calculated by the theoretical calculation by the computer, canceling some or all of the conditions and re-predicting the composition of the color-adjusting raw materials by the theoretical calculation by the computer.

8. The method further includes a main colorant specifying step of specifying a colorant that is blended in the largest amount among the colorant blending compositions of the coating composition before the preparation, 7. The method for producing a coating composition according to claim 6, wherein in the gap target value corresponding blend composition prediction step, prediction is performed using conditions limited to solution candidates generated from the finite numerical range for at least the main colorant.

9. 5. The method for producing a coating composition according to claim 4, wherein in the gap target value corresponding blend composition prediction step, when calculating a blend composition of the raw materials for color adjustment suitable for obtaining the color of the gap target value, any one of a brute force search method, a mathematical optimization method, and a random search method is used.

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