Wetting reagent for measuring surface free energy, wetting reagent set for measuring surface free energy, method for measuring surface free energy of polyolefin member, and method for bonding polyolefin member

Abstract

To provide a wetting agent that can accurately measure surface free energy, a set thereof, a method for measuring the surface free energy of a polyolefin member using the wetting agent or the set thereof, and a method for bonding a polyolefin member using the method.SOLUTION: A wetting agent includes a plurality of mixed solutions. The mixed solutions each comprise two types of liquid compounds having different surface free energies, and the plurality of mixed solutions are different from each other only in the mixture ratio of the two types of liquid compounds. The two types of liquid compounds satisfy the following condition X. (Condition X): for respective liquids in which the mixture ratio (A / B) of a liquid compound A having a smaller surface free energy measured by the ring method and a liquid compound B having a larger one, of the two types of liquid compound, is 100 / 0, 80 / 20, 50 / 50, 20 / 80, and 0 / 100, when the surface free energies measured by the ring method are plotted for B / (A+B), the determination coefficient of a linear approximation of the plot is 0.92 or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a wetting reagent for measuring surface free energy, a wetting reagent set for measuring surface free energy, a method for measuring the surface free energy of a polyolefin member, and a method for bonding polyolefin members. [Background technology]

[0002] Conventionally, a method for measuring the surface free energy of a member such as a substrate (e.g., a polyolefin member) is known, for example, by measuring the contact angle and calculating it from the Fowkes equation. Also, a method using a wetting reagent is known as a simple method for measuring the surface free energy (e.g., Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 6-43088 Summary of the Invention [Problem to be solved by the invention]

[0004] Under these circumstances, the present inventors have investigated conventional wetting reagents and found that there is a large discrepancy between the surface free energy value obtained and the surface free energy value calculated from the contact angle, i.e., the obtained surface free energy value is sometimes inaccurate.

[0005] Therefore, in view of the above-mentioned circumstances, the present invention aims to provide a wetting reagent for measuring surface free energy that can measure surface free energy more accurately, a wetting reagent set for measuring surface free energy that includes a plurality of the wetting reagents, a method for measuring the surface free energy of polyolefin members using the wetting reagent or the wetting reagent set, and a method for adhering polyolefin members using the surface free energy measurement method. [Means for solving the problem]

[0006] As a result of extensive research into the above-mentioned problems, the inventors have discovered that the above-mentioned problems can be solved by using two liquid compounds whose coefficient of determination for linear approximation falls within a specific range when the surface free energy (ring method) is plotted against the mixing ratio, and have thus arrived at the present invention. That is, the present inventors have found that the above problems can be solved by the following configuration.

[0007] (1) A wetting reagent for measuring surface free energy, comprising a mixture of multiple liquids, the mixed liquid is composed of two liquid compounds having different surface free energies, The plurality of mixed liquids differ from one another only in the mixing ratio of the two liquid compounds. However, the above two types of liquid compounds satisfy the following condition X. (Condition X) For each liquid in which the mixing ratio (A / B) of liquid compound A, which is the liquid compound having the smaller surface free energy as determined by the ring method, and liquid compound B, which is the liquid compound having the larger surface free energy as determined by the ring method, is 100 / 0, 80 / 20, 50 / 50, 20 / 80, and 0 / 100, when the surface free energy as determined by the ring method is plotted against B / (A+B), the coefficient of determination of the linear approximation of the plot is 0.92 or more. (2) The wetting reagent for measuring surface free energy according to (1) above, wherein the two liquid compounds are isopropyl alcohol, ethanol, methanol, 2-ethoxyethanol, dimethylformamide, propylene glycol, dimethyl sulfoxide, diethylene glycol, ethylene glycol, formamide, or water. (3) The wetting reagent for measuring surface free energy according to (2) above, wherein the two liquid compounds are isopropyl alcohol, dimethylformamide, formamide, or water. (4) The wet reagent for measuring surface free energy according to (3) above, wherein the mixed solution is a mixed solution of the two liquid compounds into which a dye has been dissolved, and the difference in surface free energy measured by the Ring method compared to the mixed solution before dissolving the dye is less than 1.0 mN / m. (5) The wetting reagent for measuring surface free energy according to (4) above, wherein the dye comprises at least one selected from the group consisting of methylene blue trihydrate, FZ-SB (Blue) manufactured by Shin-Etsu Chemical Co., Ltd., FZ-5009 (White) manufactured by Shin-Etsu Chemical Co., Ltd., and FA-48 (Blue) manufactured by Shin-Etsu Chemical Co., Ltd. (6) A wet reagent set for measuring surface free energy, comprising a plurality of wet reagents for measuring surface free energy according to any one of (1) to (5), The plurality of wet reagents for measuring surface free energy are each a set of wet reagents for measuring surface free energy, wherein at least one of the two types of liquid compounds is a different liquid compound from the others. (7) A method for measuring the surface free energy of a polyolefin member, comprising applying a wet reagent for measuring surface free energy described in any one of (1) to (5) above or a wet reagent set for measuring surface free energy described in (6) above to the surface of the polyolefin member, and measuring the surface free energy of the polyolefin member. (8) a surface treatment step of performing a surface treatment on the surface of the polyolefin member; a surface free energy measurement step of measuring the surface free energy of the polyolefin member subjected to the surface treatment using the surface free energy measurement method described in (7) above; a wettability determination step of determining whether or not a desired surface treatment has been performed based on the surface free energy measured in the surface free energy measurement step; an adhesive application step of applying an adhesive to the surface of the polyolefin member determined to have been subjected to the desired surface treatment in the wettability determination step to form an adhesive layer; a lamination step of laminating another member onto the adhesive layer. [Effects of the Invention]

[0008] As described below, the present invention can provide a wetting reagent for measuring surface free energy that can measure surface free energy more accurately, a wetting reagent set for measuring surface free energy that includes a plurality of the above wetting reagents, a method for measuring the surface free energy of a polyolefin member using the above wetting reagent or the above wetting reagent set, and a method for adhering polyolefin members using the above surface free energy measurement method. DETAILED DESCRIPTION OF THE INVENTION

[0009] Below, we will explain the wetting reagent for measuring surface free energy of the present invention, the wetting reagent set for measuring surface free energy containing multiple wetting reagents, the method for measuring the surface free energy of polyolefin members using the wetting reagent or the wetting reagent set, and the method for adhering polyolefin members using the surface free energy measurement method.

[0010] [1] Wetting reagent for measuring surface free energy The wetting reagent for measuring surface free energy of the present invention (hereinafter also simply referred to as "the wetting reagent of the present invention") is A wetting reagent for measuring surface free energy containing a plurality of mixed liquids, the mixed liquid is composed of two liquid compounds having different surface free energies, The plurality of mixed liquids are wetting reagents for measuring surface free energy, which differ from one another only in the mixing ratio of the two liquid compounds. However, the above two types of liquid compounds satisfy the following condition X. (Condition X) For each liquid in which the mixing ratio (A / B) of liquid compound A, which is the liquid compound having the smaller surface free energy as determined by the ring method, and liquid compound B, which is the liquid compound having the larger surface free energy as determined by the ring method, is 100 / 0, 80 / 20, 50 / 50, 20 / 80, and 0 / 100, when the surface free energy as determined by the ring method is plotted against B / (A+B), the coefficient of determination of the linear approximation of the plot is 0.92 or more.

[0011] Hereinafter, the above-mentioned coefficient of determination for the wet reagent of the present invention will also be simply referred to as "coefficient of determination."

[0012] The wetting reagent of the present invention has a coefficient of determination of 0.92 or more, and is therefore believed to be capable of measuring surface free energy more accurately. Although the reason for this is unclear, the inventors' investigations have revealed two findings: (i) when the coefficient of determination of two liquid compounds is large, the ease of mixing does not change even when the mixing ratio is changed, and (ii) this tendency is particularly pronounced when the coefficient of determination is 0.92 or higher. In other words, the two liquid compounds constituting the wetting reagent of the present invention, which have a coefficient of determination of 0.92 or higher, are highly compatible. It is presumed that this enables the wetting reagent of the present invention to measure surface free energy more accurately.

[0013] The wet reagent of the present invention will be described in detail below.

[0014] [Multiple mixtures] The wetting reagent of the present invention contains a plurality of mixed liquids, and the mixed liquids are composed of two types of liquid compounds having different surface free energies. Of the two liquid compounds mentioned above, the liquid compound with the smaller surface free energy is referred to as "liquid compound A," and the liquid compound with the larger surface free energy is referred to as "liquid compound B." The surface free energy is measured by the ring method. Unless otherwise specified, the surface free energy is measured by the ring method. In this specification, the surface free energy measured by the ring method is measured in accordance with JIS K 2241.

[0015] [Mixed liquid] As described above, the mixed liquid is composed of two liquid compounds (liquid compound A and liquid compound B) with different surface free energies.

[0016] <Liquid compounds> The liquid compound (liquid) is not particularly limited as long as it satisfies the condition X described below. However, in order to obtain a more excellent effect of the present invention, it is preferably isopropyl alcohol, ethanol, methanol, 2-ethoxyethanol, dimethylformamide, propylene glycol, dimethyl sulfoxide, diethylene glycol, ethylene glycol, formamide, or water, and more preferably isopropyl alcohol, dimethylformamide, formamide, or water.

[0017] Furthermore, among the above liquid compounds, liquid compound A is preferably isopropyl alcohol, ethanol, methanol, 2-ethoxyethanol, dimethylformamide, or propylene glycol, and more preferably isopropyl alcohol, ethanol, methanol, 2-ethoxyethanol, or dimethylformamide, because this provides a better effect of the present invention.

[0018] Of the above liquid compounds, liquid compound B is preferably dimethylformamide, dimethyl sulfoxide, diethylene glycol, ethylene glycol, formamide, or water, because the effects of the present invention are more excellent.

[0019] <Surface free energy> The surface free energy of liquid compound A is not particularly limited as long as it is smaller than the surface free energy of liquid compound B, but it is preferably 20 to 40 mN / m for the reason that the effects of the present invention are more excellent. The surface free energy of liquid compound B is not particularly limited as long as it is greater than the surface free energy of liquid compound A, but is preferably 30 to 75 mN / m for the reason that the effects of the present invention are more excellent. The difference between the surface free energy of the liquid compound A and the surface free energy of the liquid compound B is preferably 10 to 40 mN / m, because this provides a better effect of the present invention.

[0020] [Mixing ratio] As described above, the plurality of mixed liquids differ from one another only in the mixing ratio of the two liquid compounds. That is, in the above-mentioned multiple mixed solutions, all of the liquid compounds A are the same liquid compound, and all of the liquid compounds B are the same liquid compound, and the above-mentioned multiple mixed solutions differ from one another only in the mixing ratio (A / B) of liquid compound A to liquid compound B. In this specification, the mixing ratio (A / B) represents the ratio (volume ratio) when the total of liquid compound A and liquid compound B is 100. For example, if the volume ratio of liquid compound A is 80 and the volume ratio of liquid compound B is 20, it is expressed as 80 / 20.

[0021] [B ratio] In addition, the ratio (volume ratio) of liquid compound B to the total of liquid compound A and liquid compound B (100) in each mixed liquid (B / (A+B)) is also referred to as the B ratio. For example, when the volume ratio of liquid compound A is 80 and the volume ratio of liquid compound B is 20, the B ratio is 20.

[0022] When the multiple mixed solutions are arranged in order of the B ratio, the difference in the B ratio between adjacent mixed solutions is, for reasons of better effects of the present invention, preferably 10 or less, more preferably 7 or less, and even more preferably 5 or less. There is no particular lower limit to the difference in the B ratio, but it is preferably 1 or more, and more preferably 3 or more.

[0023] As described above, the two liquid compounds (liquid compound A and liquid compound B) constituting the above-mentioned mixed liquids have different surface free energies. Here, liquid compound B has a higher surface free energy than liquid compound A. Therefore, when the above-mentioned multiple mixed liquids are arranged in order of the B ratio, the smaller the B ratio, the smaller the surface free energy, and the larger the B ratio, the larger the surface free energy. In this case, the difference in surface free energy between adjacent mixed liquids is preferably 10 mN / m or less, more preferably 5 mN / m or less, because the effects of the present invention are more excellent. There is no particular lower limit to the difference in surface free energy, but it is preferably 1 mN / m or more.

[0024] [Condition X] The two liquid compounds constituting the above-mentioned mixed liquid satisfy the following condition X. (Condition X) For each liquid where the mixing ratio (A / B) of two liquid compounds, liquid compound A, which is the liquid compound with the smaller surface free energy measured by the ring method, and liquid compound B, which is the liquid compound with the larger surface free energy measured by the ring method, is 100 / 0, 80 / 20, 50 / 50, 20 / 80, and 0 / 100, the surface free energy measured by the ring method is plotted against B / (A+B). The coefficient of determination (R 2 ) is 0.92 or greater.

[0025] The definition of the mixture ratio (A / B) is the same as the mixture ratio described above. Also, the definition of B / (A+B) is the same as the B ratio described above.

[0026] In addition, the liquids having a mixing ratio (A / B) of 100 / 0, 80 / 20, 50 / 50, 20 / 80, and 0 / 100 described in condition X may or may not constitute the wetting reagent of the present invention. If there is any liquid that does not constitute a wetting reagent among the liquids with a mixing ratio (A / B) of 100 / 0, 80 / 20, 50 / 50, 20 / 80, and 0 / 100, prepare that liquid separately and determine whether or not it satisfies condition X.

[0027] <Linear approximation> The linear approximation of the plot above is a least squares linear approximation.

[0028] <Coefficient of determination> The coefficient of determination indicates the difference between the surface free energy calculated from the linear approximation curve and the actual surface free energy, and the closer it is to 1, the smaller the difference is. The coefficient of determination (R 2 ) is calculated by the following formula (1). R 2 =S R / S T (1) S R is the (Y-average y) of each liquid with a mixing ratio (A / B) of 100 / 0, 80 / 20, 50 / 50, 20 / 80, and 0 / 100. 2 where Y is the surface free energy calculated from the linear approximation curve, and the average y is the average of the measured surface free energy values. Also, S T is the (y-average y) of each liquid with a mixing ratio (A / B) of 100 / 0, 80 / 20, 50 / 50, 20 / 80, and 0 / 100. 2 where y is the measured value of surface free energy. The average y is as described above.

[0029] For reasons of superior effects of the present invention, the coefficient of determination is preferably 0.93 or more, more preferably 0.94 or more, even more preferably 0.95 or more, still more preferably 0.96 or more, even more preferably 0.97 or more, even more preferably 0.98 or more, and even more preferably 0.99 or more. The upper limit of the coefficient of determination is not particularly limited, and is 1.

[0030] The method for obtaining a combination of two liquid compounds that satisfies condition X is not particularly limited, but examples thereof include a method in which the coefficient of determination is calculated as described above for various combinations of two liquid compounds that have different surface free energies, and a combination that satisfies condition X is selected. Examples of combinations of two liquid compounds that satisfy condition X include the combinations of Examples 1 to 7 described below, as well as combinations such as isopropyl alcohol / 2-ethoxyethanol, ethanol / 2-ethoxyethanol, ethanol / dimethylformamide, ethanol / dimethyl sulfoxide, methanol / 2-ethoxyethanol, methanol / dimethylformamide, methanol / propylene glycol, methanol / dimethyl sulfoxide, dimethylformamide / dimethyl sulfoxide, dimethylformamide / diethylene glycol, dimethylformamide / ethylene glycol, dimethylformamide / water, dimethyl sulfoxide / ethylene glycol, dimethyl sulfoxide / formamide, and dimethyl sulfoxide / water.

[0031] [Other liquids] The wetting reagent of the present invention may contain, as liquids other than the above-mentioned multiple mixed liquids, a liquid consisting only of liquid compound A that constitutes the multiple mixed liquids contained in the wetting reagent of the present invention (liquid with a B ratio of 0), and a liquid consisting only of liquid compound B that constitutes the multiple mixed liquids contained in the wetting reagent of the present invention (liquid with a B ratio of 100). In the following, the liquid consisting of only liquid compound A, the mixed liquid described above, and the liquid consisting of only liquid compound B will also be collectively referred to as "reagents."

[0032] [Liquid consisting of only liquid compound A] A suitable range of the difference between the B ratio of a liquid consisting only of liquid compound A (i.e., 0) and the B ratio of the mixed liquid having the smallest B ratio among the plurality of mixed liquids contained in the wetting reagent of the present invention is the same as the difference in the B ratio of adjacent mixed liquids among the plurality of mixed liquids described above. Furthermore, the preferred range of the difference between the surface free energy of a liquid consisting only of liquid compound A and the surface free energy of the mixed liquid having the smallest B ratio (smallest surface free energy) among the multiple mixed liquids contained in the wetting reagent of the present invention is the same as the difference in surface free energy between adjacent mixed liquids among the multiple mixed liquids described above.

[0033] [Liquid consisting of only liquid compound B] A suitable range of the difference between the B ratio of a liquid consisting only of liquid compound B (i.e., 100) and the B ratio of the mixed liquid having the largest B ratio among the plurality of mixed liquids contained in the wetting reagent of the present invention is the same as the difference in the B ratio of adjacent mixed liquids among the plurality of mixed liquids described above. Furthermore, the preferred range of the difference between the surface free energy of a liquid consisting only of liquid compound B and the surface free energy of the mixed liquid having the highest B ratio (highest surface free energy) among the multiple mixed liquids contained in the wetting reagent of the present invention is the same as the difference in surface free energy between adjacent mixed liquids among the multiple mixed liquids described above.

[0034] [Pigment] The reagents included in the wetting reagent of the present invention (a liquid consisting of only liquid compound A, a mixed liquid, and a liquid consisting of only liquid compound B) may have a dye dissolved therein. Dissolving a dye makes it easier to observe the state of the liquid film and to determine whether it is wet or not.

[0035] The concentration of the dye is not particularly limited, but is preferably 0.01 to 0.10 wt % (mass %), and more preferably 0.01 to 0.05 wt %, for reasons that result in better effects of the present invention.

[0036] [Preferred embodiment] For the reason that the effects of the present invention are more excellent, it is preferable that the surface free energy of the reagent, as measured by the ring method, does not change by 1.0 mN / m or more when the dye is dissolved therein. In other words, it is preferable that the difference in surface free energy, as measured by the ring method, between the reagent in which the dye has been dissolved and the mixed liquid before the dye has been dissolved (the difference between the surface free energy, as measured by the ring method, of the reagent in which the dye has been dissolved and the surface free energy, as measured by the ring method, of the reagent before the dye has been dissolved) is less than 1.0 mN / m.

[0037] The dye is preferably methylene blue trihydrate, FZ-SB (Blue) manufactured by Shin-Laihi Co., Ltd., FZ-5009 (White) manufactured by Shin-Laihi Co., Ltd., or FA-48 (Blue) manufactured by Shin-Laihi Co., Ltd., because this provides a better effect of the present invention, and is more preferably methylene blue trihydrate.

[0038] [Method for measuring surface free energy] When the surface free energy of a member is measured using the wetting reagent of the present invention, the measurement is carried out, for example, as follows. The reagents contained in the wetting reagent of the present invention (a liquid consisting of only liquid compound A, a mixed liquid, and a liquid consisting of only liquid compound B) are applied to the member in the order of the reagent with the smallest B ratio (smallest surface free energy). The state of the liquid film formed by the reagent is then observed, and if it is wet, it is marked with an O, and if it is not wet, it is marked with an X. If it is wet (O), the next wetting reagent is applied and observed in the same way. If it is not wet (X), the process ends. The surface free energy value of the wetting reagent is a value with the surface free energy (ring method) of the reagent that last became a ○ as the lower limit and the surface free energy (ring method) of the liquid that became an × as the upper limit. For example, in Example 1 (Substrate 1) described below, the surface free energy (ring method) of the reagent that finally received a ○ was 25.0 mN / m (lower limit), and the surface free energy (ring method) of the reagent that received an × was 27.8 mN / m (upper limit), so the surface free energy was 25.0 mN / m or more but less than 27.8 mN / m.

[0039] [Materials] The member for measuring the surface free energy is not particularly limited, but specific examples include polyolefin members, butyl rubber members, composite materials such as CFRP (carbon fiber reinforced plastic), and metal members.

[0040] [2] Wetting Reagent Set for Surface Free Energy Measurement The wet reagent set for measuring surface free energy of the present invention (hereinafter also simply referred to as "the wet reagent set of the present invention") is A wetting reagent set for measuring surface free energy, comprising a plurality of the above-described wetting reagents of the present invention, The plurality of wetting reagents are a set of wetting reagents for measuring surface free energy, in which at least one of the two types of liquid compounds is a different liquid compound.

[0041] The wet reagent of the present invention included in the wet reagent set of the present invention is as described above.

[0042] [Preferred embodiment] In order to obtain a more effective effect of the present invention, it is preferable that when the multiple wet reagents of the present invention included in the wet reagent set of the present invention are arranged in order of decreasing surface free energy of the liquid compound A of each wet reagent, adjacent wet reagents have the liquid compound B of the wet reagent with the smaller surface free energy of liquid compound A and the liquid compound A of the wet reagent with the larger surface free energy of liquid compound B in common. For example, when considering a wetting reagent set including a wetting reagent (liquid compound A: ethanol, liquid compound B: 2-ethoxyethanol) and a wetting reagent (liquid compound A: 2-ethoxyethanol, liquid compound B: ethylene glycol), liquid compound B (2-ethoxyethanol) of the wetting reagent having a lower surface free energy of liquid compound A (the former wetting reagent) and liquid compound A (2-ethoxyethanol) of the wetting reagent having a higher surface free energy of liquid compound A (the latter wetting reagent) are common, and therefore this wetting reagent set falls under the above-mentioned preferred embodiment.

[0043] [Method for measuring surface free energy] A specific example of a method for measuring the surface free energy of a member using the wetting reagent set of the present invention is a method in which the reagents included in the wetting reagent set of the present invention are applied to a member in order of lowest surface free energy, and the surface free energy is determined using the wetting reagents in the same manner as the method for measuring surface free energy using the wetting reagent of the present invention described above.

[0044] [3] Method for measuring the surface free energy of polyolefin materials The method for measuring the surface free energy of a polyolefin member of the present invention (hereinafter also simply referred to as the "surface free energy measuring method of the present invention") is as follows: A method for measuring the surface free energy of a polyolefin member, comprising applying the above-described wetting reagent of the present invention or the above-described wetting reagent set of the present invention to the surface of the polyolefin member, and measuring the surface free energy of the polyolefin member.

[0045] Specific examples of the method for measuring the surface free energy of a polyolefin member using the wetting reagent of the present invention or the wetting reagent set of the present invention are as described above. Examples of polyolefin members include polypropylene substrates and polyethylene substrates.

[0046] [4] Polyolefin adhesion method The method for bonding polyolefins of the present invention (hereinafter also simply referred to as the "bonding method of the present invention") comprises: a surface treatment step of performing a surface treatment on the surface of the polyolefin member; a surface free energy measurement step of measuring the surface free energy of the polyolefin member that has been subjected to the surface treatment using the surface free energy measurement method of the present invention; a wettability determination step of determining whether or not a desired surface treatment has been performed based on the surface free energy measured in the surface free energy measurement step; an adhesive application step of applying an adhesive to the surface of the polyolefin member determined to have been subjected to the desired surface treatment in the wettability determination step to form an adhesive layer; and a lamination step of laminating another member onto the adhesive layer. [Example]

[0047] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0048] [Preparation of wet reagent] Each wet reagent (Comparative Examples 1 and 2, Examples 1 to 7) was prepared using two liquid compounds marked with a circle in Table 1 below. Tables 2 to 10 show the B ratio (B / (A+B)) of the liquid and the approximate surface free energy (Ring method) in each example. For example, Example 1 is a wetting reagent using methanol and diethylene glycol (DEG) as shown in Table 1. Here, the surface free energy (Ring method) of methanol is approximately 22 mN / m, and the surface free energy (Ring method) of diethylene glycol is approximately 45 mN / m. Therefore, methanol corresponds to the above-mentioned liquid compound A (the liquid compound with the lower surface free energy according to the Ring method) and diethylene glycol corresponds to the above-mentioned liquid compound B (the liquid compound with the higher surface free energy according to the Ring method) as shown in Table 4. Example 1 is a wetting reagent consisting of reagents with B ratios (DEG ratios) of 0.0, 5.0, 11.2, 20.0, 50.0, 69.4, 80.0, 93.7, 98.0, and 100.0 (a total of 10 reagents).

[0049] [Coefficient of determination] For each example, the surface free energy (ring method) was plotted against the B ratio for reagents with B ratios of 0.0, 20.0, 50.0, 80.0, and 100.0 (corresponding to reagents with A / B ratios of 100 / 0, 80 / 20, 50 / 50, 20 / 80, and 0 / 100, respectively). The coefficient of determination was then calculated using a linear approximation. The method for calculating the coefficient of determination is as described above. The results are shown in Table 1.

[0050] [Preparing the substrate] The following substrates 1 to 3 were prepared as objects for measuring the surface free energy. (1) Substrate 1 A polypropylene substrate that had not been subjected to plasma treatment was used as substrate 1. (2) Substrate 2 A polypropylene substrate that had been subjected to plasma treatment (irradiation distance: 20 mm, output: 21 kW, number of irradiations: 5, irradiation speed: 175 mm / sec) was used as substrate 2. (3) Substrate 3 A polypropylene substrate that had been subjected to plasma treatment (irradiation distance: 15 mm, output: 21 kW, number of irradiations: 1, irradiation speed: 175 mm / sec) was used as substrate 3.

[0051] The contact angle of each of the above substrates was measured as follows, and the surface free energy was calculated using the Fowkes equation. The results are shown below. (1) Substrate 1: 28.0 mN / m (2) Substrate 2: 36.8mN / m (3) Substrate 3: 39.5mN / m

[0052] <Contact angle measurement> 5 μL of water was dropped onto each substrate and the contact angle was measured. The dropping and measuring procedure was repeated five times, and the average value was taken as the contact angle for water. Similarly, 2 μL of methylene iodide was dropped onto each substrate and the contact angle was measured. In this case, the dropping and measuring procedure was also repeated five times, and the average value was taken as the contact angle for methylene iodide. All measurements were performed at room temperature.

[0053] [Measurement of surface free energy] The surface free energies of the above-mentioned substrates 1 to 3 were measured using the prepared wetting reagent. Specifically, the reagents were applied to the substrate in order starting with the reagent with the smallest B ratio (B ratio 0.0) (smallest surface free energy), and the state of the center of the liquid film was observed after 2 seconds had passed. If the liquid was wet, it was marked with an O, and if it was not wet, it was marked with an X. If the liquid was wet (O), the next reagent was applied and observed in the same way. If it was not wet (X), the process was terminated. The surface free energy value of the wetting reagent is a value with the surface free energy (ring method) of the reagent that finally became O as the lower limit and the surface free energy (ring method) of the reagent that finally became X as the upper limit. For example, in Example 1 (substrate 1), the surface free energy (ring method) of the reagent that finally became O is 25.0 mN / m (lower limit), and the surface free energy (ring method) of the reagent that finally became X is 27.8 mN / m (upper limit), so the surface free energy is 25.0 mN / m or more and less than 27.8 mN / m. Tables 2 to 10 show the surface free energy values ​​(lower and upper limits) determined by wetting reagents. In addition, if the reagent with the smallest B ratio (B ratio 0.0) was marked with an X, if the reagent with the largest B ratio (B ratio 100.0) was marked with an X, or if all reagents were marked with an O, it was indicated as "-" because the surface free energy could not be measured.

[0054] Table 1 also shows the surface free energy values ​​(lower and upper limits) for the wetting reagents.

[0055] Table 1 also shows the difference (ΔS) between the surface free energy (Fowkes equation) and the surface free energy (wetting reagent) divided into the lower limit and the upper limit. Here, the lower limit is the difference between the "surface free energy (Fowkes equation)" and the "lower limit of surface free energy (wetting reagent)", and the upper limit is the difference between the "surface free energy (Fowkes equation)" and the "upper limit of surface free energy (wetting reagent)". For example, for substrate 1 of Example 1, the lower limit is 25.0 mN / m and the upper limit is 27.8 mN / m, so the lower limit ΔS [mN / m] is 28.0-25.0=3.0 and the upper limit ΔS [mN / m] is 28.0-27.8=0.2. The smaller ΔS, the more accurately the surface free energy can be measured. In addition, when two ΔS are compared, if both the lower limit and the upper limit of one ΔS are smaller than both the lower limit and the upper limit of the other ΔS, it can be said that one ΔS is smaller than the other ΔS. For example, when ΔS of substrate 1 in Example 1 is compared with ΔS of substrate 1 in Comparative Example 1, the lower limit ΔS of Example 1 is 3.0 and the upper limit ΔS is 0.2, while the lower limit ΔS of Comparative Example 1 is 5.0 and the upper limit ΔS is 3.7. Since both the lower limit and the upper limit of ΔS of Example 1 are smaller than both the lower limit and the upper limit of ΔS of Comparative Example 1, it can be said that ΔS of Example 1 is smaller than ΔS of Comparative Example 1.

[0056] [Table 1]

[0057] [Table 2]

[0058] [Table 3]

[0059] [Table 4]

[0060] [Table 5]

[0061] [Table 6]

[0062] [Table 7]

[0063] [Table 8]

[0064] [Table 9]

[0065] [Table 10]

[0066] As can be seen from Table 1, for all substrates 1 to 3, the wetting reagents of Examples 1 to 7, which had a coefficient of determination of 0.92 or more, had smaller ΔS and were able to measure surface free energy more accurately, compared to the wetting reagents of Comparative Examples 1 and 2, which had a coefficient of determination of less than 0.92. Comparing Example 1, Example 3, Example 5, and Example 7 (Substrate 2), it was found that Example 1, Example 3, and Example 7, in which liquid compound A was methanol, 2-ethoxyethanol, or dimethylformamide, were able to measure the surface free energy more accurately.

[0067] Furthermore, for each wet reagent (liquid consisting of only liquid compound A, mixed liquid, and liquid consisting of only liquid compound B) in Examples 1 to 7, a reagent in which Victoria Pure Blue was dissolved as a dye, a reagent in which methylene blue trihydrate was dissolved as a dye, a reagent in which FZ-SB (Blue) manufactured by Shin-Laihi Co., Ltd. was dissolved as a dye, a reagent in which FZ-5009 (White) manufactured by Shin-Laihi Co., Ltd. was dissolved as a dye, and a reagent in which FA-48 (Blue) manufactured by Shin-Laihi Co., Ltd. was dissolved as a dye were prepared. The dye concentration was 0.03 wt%. As a result, for the reagents in which Victoria Pure Blue was dissolved as a pigment, the difference in surface free energy measured by the ring method compared to the reagent before the pigment was dissolved (the difference between the surface free energy measured by the ring method of the reagent in which the pigment was dissolved and the surface free energy measured by the ring method of the reagent before the pigment was dissolved) was found to be 1 mN / m or more. On the other hand, the difference in surface free energy was less than 1 mN / m for the reagent containing methylene blue trihydrate dissolved as the dye, the reagent containing FZ-SB (Blue) manufactured by Shin-Etsu Chemical Co., Ltd. dissolved as the dye, the reagent containing FZ-5009 (White) manufactured by Shin-Etsu Chemical Co., Ltd. dissolved as the dye, and the reagent containing FA-48 (Blue) manufactured by Shin-Etsu Chemical Co., Ltd. dissolved as the dye.

Claims

1. A wetting reagent for measuring surface free energy containing a plurality of mixed liquids, the mixed liquid is a mixed liquid comprising two liquid compounds having different surface free energies and a dye dissolved therein, and the difference in surface free energy measured by a ring method with respect to the mixed liquid before dissolving the dye is less than 1.0 mN / m, and the dye contains at least one selected from the group consisting of methylene blue trihydrate, FZ-SB (Blue) manufactured by Shin-Louhi Co., Ltd., FZ-5009 (White) manufactured by Shin-Louhi Co., Ltd., and FA-48 (Blue) manufactured by Shin-Louhi Co., Ltd.; The plurality of mixed liquids differ from one another only in the mixing ratio of the two types of liquid compounds. However, the two liquid compounds satisfy the following condition X. (Condition X) When the surface free energy measured by the ring method is plotted against B / (A+B) for liquids in which the mixing ratio (A / B) of liquid compound A, which is the liquid compound having the smaller surface free energy measured by the ring method, to liquid compound B, which is the liquid compound having the larger surface free energy measured by the ring method, is 100 / 0, 80 / 20, 50 / 50, 20 / 80, and 0 / 100, the coefficient of determination of the linear approximation of the plot is 0.92 or more, provided that the surface free energy of liquid compound A is 20 to 40 mN / m, the surface free energy of liquid compound B is 30 to 75 mN / m, and the difference between the surface free energy of liquid compound A and the surface free energy of liquid compound B is 10 to 40 mN / m.

2. A wet reagent set for measuring surface free energy, comprising a plurality of wet reagents for measuring surface free energy, The wetting reagent for measuring surface free energy is A wetting reagent for measuring surface free energy containing a plurality of mixed liquids, the mixed liquid is composed of two liquid compounds having different surface free energies, the plurality of mixed liquids are wetting reagents for measuring surface free energy, each of which differs from the other only in the mixing ratio of the two types of liquid compounds; A wetting reagent set for measuring surface free energy, wherein at least one of the two types of liquid compounds in the plurality of wetting reagents for measuring surface free energy is a different liquid compound from each other. However, the two liquid compounds satisfy the following condition X. (Condition X) When the surface free energy measured by the ring method is plotted against B / (A+B) for liquids in which the mixing ratio (A / B) of liquid compound A, which is the liquid compound having the smaller surface free energy measured by the ring method, to liquid compound B, which is the liquid compound having the larger surface free energy measured by the ring method, is 100 / 0, 80 / 20, 50 / 50, 20 / 80, and 0 / 100, the coefficient of determination of the linear approximation of the plot is 0.92 or more, provided that the surface free energy of liquid compound A is 20 to 40 mN / m, the surface free energy of liquid compound B is 30 to 75 mN / m, and the difference between the surface free energy of liquid compound A and the surface free energy of liquid compound B is 10 to 40 mN / m.

3. A wetting reagent for measuring surface free energy containing a plurality of mixed liquids, the mixed liquid is a liquid obtained by dissolving a dye in a mixed liquid consisting of two liquid compounds having different surface free energies, and the difference in surface free energy measured by a Ring method with respect to the mixed liquid before dissolving the dye is less than 1.0 mN / m; the dye contains at least one selected from the group consisting of methylene blue trihydrate, FZ-SB (Blue) manufactured by Shin-Louhi Co., Ltd., FZ-5009 (White) manufactured by Shin-Louhi Co., Ltd., and FA-48 (Blue) manufactured by Shin-Louhi Co., Ltd.; and each of the two liquid compounds is isopropyl alcohol, ethanol, methanol, 2-ethoxyethanol, dimethylformamide, propylene glycol, dimethyl sulfoxide, diethylene glycol, ethylene glycol, formamide, or water; The plurality of mixed liquids differ from one another only in the mixing ratio of the two types of liquid compounds. However, the two liquid compounds satisfy the following condition X. (Condition X) For each liquid in which the mixing ratio (A / B) of liquid compound A, which is the liquid compound having the smaller surface free energy by the ring method out of the two liquid compounds, and liquid compound B, which is the liquid compound having the larger surface free energy by the ring method out of the two liquid compounds, is 100 / 0, 80 / 20, 50 / 50, 20 / 80, and 0 / 100, when the surface free energy by the ring method is plotted against B / (A+B), the coefficient of determination of the linear approximation of the plot is 0.92 or more.

4. A wet reagent set for measuring surface free energy, comprising a plurality of wet reagents for measuring surface free energy, The wetting reagent for measuring surface free energy is A wetting reagent for measuring surface free energy containing a plurality of mixed liquids, the mixed liquid is composed of two kinds of liquid compounds having different surface free energies, and each of the two kinds of liquid compounds is isopropyl alcohol, ethanol, methanol, 2-ethoxyethanol, dimethylformamide, propylene glycol, dimethyl sulfoxide, diethylene glycol, ethylene glycol, formamide, or water; the plurality of mixed liquids are wetting reagents for measuring surface free energy, each of which differs from the other only in the mixing ratio of the two types of liquid compounds; A wetting reagent set for measuring surface free energy, wherein at least one of the two types of liquid compounds in the plurality of wetting reagents for measuring surface free energy is a different liquid compound from each other. However, the two liquid compounds satisfy the following condition X. (Condition X) For each liquid in which the mixing ratio (A / B) of liquid compound A, which is the liquid compound having the smaller surface free energy by the ring method out of the two liquid compounds, and liquid compound B, which is the liquid compound having the larger surface free energy by the ring method out of the two liquid compounds, is 100 / 0, 80 / 20, 50 / 50, 20 / 80, and 0 / 100, when the surface free energy by the ring method is plotted against B / (A+B), the coefficient of determination of the linear approximation of the plot is 0.92 or more.

5. The combination of the two liquid compounds that satisfies the condition X is methanol / diethylene glycol, isopropyl alcohol / dimethylformamide, dimethylformamide / formamide, ethanol / dimethyl sulfoxide, propylene glycol / water, methanol / ethylene glycol, 2-ethoxyethanol / ethylene glycol, isopropyl alcohol / 2-ethoxyethanol, ethanol / 2-ethoxyethanol, ethanol / dimethylformamide, ethanol / dimethyl sulfoxide, methanol / 2-ethoxyethanol, methanol / dimethylformamide, methanol / propylene glycol, methanol / dimethyl sulfoxide, dimethylformamide / dimethyl sulfoxide, dimethylformamide / diethylene glycol, dimethylformamide / ethylene glycol, dimethylformamide / water, dimethyl sulfoxide / ethylene glycol, dimethyl sulfoxide / formamide, or dimethyl sulfoxide / water. The surface free energy measurement wet reagent set according to claim 3 or claim 4.

6. The combination of the two liquid compounds that satisfies the condition X is methanol / diethylene glycol, isopropyl alcohol / dimethylformamide, dimethylformamide / formamide, ethanol / dimethyl sulfoxide, propylene glycol / water, methanol / ethylene glycol, or 2-ethoxyethanol / ethylene glycol. The wetting reagent or the wetting reagent set for measuring surface free energy according to claim 5, wherein

7. A method for measuring the surface free energy of a polyolefin member, comprising applying a wetting reagent for measuring surface free energy or a wetting reagent set for measuring surface free energy according to any one of claims 1 to 6 to the surface of the polyolefin member, and measuring the surface free energy of the polyolefin member.

8. a surface treatment step of performing a surface treatment on the surface of the polyolefin member; a surface free energy measurement step of measuring the surface free energy of the polyolefin member that has been subjected to the surface treatment using the surface free energy measurement method according to claim 7; a wettability determination step of determining whether or not a desired surface treatment has been performed based on the surface free energy measured in the surface free energy measurement step; an adhesive application step of applying an adhesive to the surface of the polyolefin member determined to have undergone the desired surface treatment in the wettability determination step to form an adhesive layer; and a lamination step of laminating another member onto the adhesive layer.

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