Transparent anticorrosive coating material

Abstract

To provide a room-temperature curable transparent anticorrosive coating material which is substantially transparent and allows clear observation of the substrate, and which enables the formation of a highly durable anticorrosive coating film even as a single layer.SOLUTION: A room-temperature curable transparent anticorrosive coating material of the present invention has a viscosity of 0.1 to 50 Pa s at 23°C and contains a linear organopolysiloxane having silanol groups at both ends of the molecular chain and a reaction product of an aminobis-silane compound and a titanium alkoxide compound. Examples of the aminobis-silane compound can be bis[3-(trimethoxysilyl)propyl]amine, bis[3-(triethoxysilyl)propyl]amine, or the like, and examples of the titanium alkoxide compound can be tetranormalbutyl titanate, butyl titanate dimer, or tetraoctyl titanate.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a transparent rust preventive paint containing a transparent rust preventive agent, and particularly to a room temperature curable transparent rust preventive paint that is substantially transparent, has good visibility of the substrate, and can form a highly durable rust preventive coating film even with a single layer.

Background Art

[0002] Conventionally, as a rust preventive coating film, an epoxy-based paint containing a large amount of a rust preventive pigment is used as an undercoat paint, and a urethane-based enamel, a fluororesin-based paint, a silicone resin-based paint, etc. are used as a topcoat paint for imparting weather resistance, and a coating film having a multi-layer structure is formed by coating.

[0003]

[0004] For example, Patent Document 1 (Japanese Patent No. 6439022) discloses an invention of a rust preventive paint and a rust preventive coating film containing an alloy powder of at least one element selected from Si, In, and Bi and Al and Mg as a rust preventive component and further containing a coating film forming component (see Claims 1 and 5). Further, on the surface of this rust preventive coating film, an invention of a rust preventive laminated coating film having, in this order, an undercoat layer containing at least one resin selected from an epoxy resin, a urethane resin, and an acrylic resin and a topcoat layer containing at least one resin selected from a fluororesin, a urethane resin, and a silicone resin is disclosed (see Claim 6).

Prior Art Documents

[0005] ​​ [Patent Document 1] Japanese Patent No. 6439022 [Patent Document 2] Japanese Patent No. 6162912 [Non-Patent Document]

[0006] [Non-Patent Document 1] Hakki, A., Yang, L., Wang, F., Macphee, D.E. "The Effect of Interfacial Chemical Bonding in TiO2-SiO2 Composites on Their Photocatalytic NOx Abatement Performance." J. Vis. Exp. (125), e56070, doi:10.3791 / 56070 (2017). [Summary of the Invention] [Problems to be Solved by the Invention]

[0007] According to the invention disclosed in Patent Document 1, even if the rust preventive component does not contain zinc powder, a rust preventive coating film, a rust preventive laminated coating film having a long-term corrosion resistance equal to or higher than that of a conventional paint containing zinc powder, and a rust preventive paint capable of forming the same can be obtained. Further, according to the invention disclosed in Patent Document 2, a rust preventive paint composition or a multi-layer coating film excellent not only in the adhesion and finish of the coating film but also in quick drying property, storage stability and corrosion resistance can be obtained.

[0008] However, in the rust preventive paint disclosed in Patent Document 1, the rust preventive component is composed of alloy powder of at least one element selected from Si, In, and Bi and Al and Mg, and moreover, the rust preventive paint contains a large amount of the rust preventive component with a mass ratio of the rust preventive component to the coating film forming component of 20 / 80 to 90 / 10 (see

[0035] ). Therefore, the rust preventive coating film formed using this rust preventive paint becomes substantially opaque.

[0009] In addition, in the rust preventive paint disclosed in Patent Document 2, as the rust preventive pigment, zinc phosphate, a mixture of aluminum dihydrogen tripolyphosphate and zinc oxide, calcium phosphate, etc. are used, but all of these rust preventive pigments are white raw materials. Moreover, the content ratio of the rust preventive pigment in this rust preventive paint is such that, with respect to the entire rust preventive paint composition, the content of the epoxy resin is 5 to 20% by mass, the content of the amine curing agent is 1 to 10% by mass, the content of the rust preventive pigment is 0.5 to 15% by mass, and the content of the organic solvent is 5 to 20% by mass (see Claim 9). Since the organic solvent volatilizes in the rust preventive coating film, the content ratio of the rust preventive pigment in the rust preventive coating film becomes higher. Therefore, the rust preventive coating film formed using the rust preventive paint disclosed in Patent Document 2 is also substantially opaque.

[0010] Thus, in the rust preventive paint using known rust preventive components, since metal powder or a rust preventive pigment is used as the rust preventive component, even when a rust preventive coating film is formed on the surface of the base, it has been difficult to visually recognize the surface state of the base because the rust preventive coating film itself is substantially lacking in transparency. Particularly when the base is a metal member or a mirror member having a design property, if the rust preventive coating film is substantially lacking in transparency, the benefits of imparting a design property or making it a mirror surface to the base cannot be enjoyed. In addition, in the rust preventive paints using the above-described known rust preventive pigments, in order to ensure weather resistance, a urethane-based coating film, an enamel-based coating film, a fluororesin-based coating film, a silicone resin-based coating film, etc. are further formed on the rust preventive coating film formed on the surface of the base, so there has been a problem that the number of processes increases and the construction period becomes long.

[0011] The inventors have conducted various studies to obtain a transparent rust-preventive coating composition that can overcome the drawbacks of rust-preventive coatings using known rust-preventive components as described above, such as being opaque and the need to form a coating film with a multilayer structure. As a result, by combining the reaction product of an aminobis-silane compound and a titanium alkoxide compound with a predetermined organopolysiloxane as a coating film-forming component, it has been found that a single-layer coating film can maintain a rust-preventive effect over a long period of time and a substantially transparent coating film can be obtained, thus completing the present invention. That is, an object of the present invention is to provide a substantially transparent room-temperature curable rust-preventive coating composition.

Means for Solving the Problems

[0012] According to the present invention, there is provided a room-temperature curable transparent rust-preventive coating composition containing a linear organopolysiloxane having a viscosity at 23°C of 0.1 to 50 Pa·s and having silanol groups at both ends of the molecular chain, and a reaction product of an aminobis-silane compound and a titanium alkoxide compound.

[0013] The general formula of the linear aminobis-silane compound having silanol groups at both ends of the molecular chain is shown below. However, in the following general formula, R represents an alkyl group. TIFF2025089061000002.tif26136

[0014] Further, the general formula of the titanium alkoxide compound is shown below. However, in the following general formula, R' represents an alkyl group. TIFF2025089061000003.tif7136 As this titanium alkoxide compound, it is preferable to use at least one selected from tetra-n-butyl titanate, butyl titanate dimer, and tetraoctyl titanate.

[0015] The reaction between the linear aminobis-silane compound having silanol groups at both ends of the molecular chain and the titanium alkoxide compound is presumed to be as shown in the following reaction formula. However, in the following general formula, R and R' represent alkyl groups. TIFF2025089061000004.tif102136

[0016] Although titanium alkoxide itself is known to react with moisture to form white titanium oxide, the reaction product of the aminobis-silane compound and the titanium alkoxide compound of the present invention is substantially transparent and far more stable than titanium alkoxide against moisture. By using it in combination with a linear organopolysiloxane having silanol groups at both ends of the molecular chain, a room-temperature curable transparent rust-preventive paint composition having a good rust-preventive effect over a long period can be obtained.

[0017] As this aminobis-silane compound, at least one selected from bis[2-(trimethoxysilyl)ethyl]amine, bis[3-(trimethoxysilyl)propyl]amine, bis[4-(trimethoxysilyl)butyl]amine, bis[2-(triethoxysilyl)ethyl]amine, bis[3-(triethoxysilyl)propyl]amine, and bis[4-(triethoxysilyl)butyl]amine can be used. More preferable aminobis-silane compounds are bis[3-(trimethoxysilyl)propyl]amine and bis[3-(triethoxysilyl)propyl]amine.

[0018] In the room-temperature curable transparent rust-preventive paint composition of such an embodiment, it is preferable that the reaction product of the aminobis-silane compound and the titanium alkoxide compound is one obtained by reacting the titanium alkoxide compound at a ratio of 0.1 to 0.3 mol with respect to 1 mol of the aminobis-silane compound. Thereby, the amount of the unreacted aminobis-silane compound or titanium alkoxide compound present in a free state is small, and a reaction product having a good rust-preventive effect can be obtained.

[0019] In addition, when the amount of the titanium alkoxide compound is less than 0.1 mol with respect to 1 mol of the aminobis-silane compound, the amount of the unreacted aminobis-silane compound with respect to the titanium alkoxide compound increases. As a result, the adhesion of the coating film to the base material of the coating composition becomes weak, and sufficient rust prevention and curing cannot be achieved. Similarly, when it exceeds 0.3 mol, the amount of the unreacted titanium alkoxide compound with respect to the aminobis-silane compound increases, so that the stability of the coating composition deteriorates.

[0020] Further, in the room temperature curable transparent rust preventive coating composition of the present invention, as the linear organopolysiloxysilane having silanol groups at both ends of the molecular chain, those having a viscosity at 23 ° C of 0.1 to 50 Pa·s are preferably used. According to such a transparent rust preventive coating composition, it has room temperature curability, and even with a single-layer coating film, it has good rust prevention properties, and a transparent and long-life coating film can be obtained. If the viscosity of the organopolysiloxysilane at 23 ° C is less than 0.1 Pa·s, the elongation of the obtained coating film cannot be sufficiently ensured. Similarly, if it exceeds 50 Pa·s, the workability during coating film formation deteriorates, which is not preferable.

[0021] In the transparent rust preventive coating composition of such an embodiment, the content ratio of the reaction product of the aminobis-silane compound and the titanium alkoxide compound is preferably 0.5 to 10% by mass in terms of solid ratio with respect to the organopolysiloxane. When the content ratio of the reaction product of the aminobis-silane compound and the titanium alkoxide compound with respect to the organopolysiloxane is less than 0.5% by mass, the adhesion of the transparent rust preventive coating film to the base material becomes weak and a sufficient rust prevention effect cannot be obtained. Similarly, when it exceeds 10% by mass, the obtained rust preventive coating composition thickens and becomes a gel state, which is not preferable.

Advantages of the Invention

[0022] As described above, according to the present invention, a room temperature curable transparent rust preventive coating composition can be obtained which is substantially transparent, has good visibility of the base, and can form a highly durable rust preventive coating film even with a single layer.

Brief Description of the Drawings

[0023]

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0024] Hereinafter, the room-temperature curable transparent rust-preventive paint according to the present invention will be described in detail using various examples and comparative examples. However, the various examples shown below are examples for embodying the technical idea of the present invention, and it is not intended to specify the present invention to those shown in these examples. The present invention can be equally applied to other embodiments included in the claims.

[0025] (Example 1) To a mixed solvent of 20 parts by mass of butyl acetate and 60 parts by mass of isopropyl alcohol, 16 parts by mass of bis[3-(trimethoxysilyl)propyl]amine (manufactured by Momentive Performance Materials Japan LLC) was added with stirring, and then 4 parts by mass of tetra-n-butyl titanate (manufactured by Matsumoto Fine Chemical Co., Ltd.) was added, and stirring was continued at 30 ° C for 60 minutes, and then sealed and allowed to stand at 25 ° C for 24 hours. The reaction solution gradually changed color from a colorless transparent liquid to a dark transparent yellow liquid. Next, 10 parts by mass of the reaction solution after standing for 24 hours was added to 100 parts by mass of a linear organopolysiloxysilane having silanol groups at both ends of the molecular chain with a viscosity of 6 Pa·s, to obtain the room-temperature curable transparent rust-preventive composition of Example 1.

[0026] Separately, regarding the reaction solution, the measurement results by FTIR (Fourier transform infrared spectroscopy) method were obtained using a Cary 630 FTIR spectrophotometer (trade name, manufactured by Agilent Technologies, Inc.) immediately after production, 1 hour later, 6.5 hours later, and 3 months later. The results are summarized in Figure 1. The measurement results by the FTIR method of the room-temperature curable transparent rust-preventive composition of Example 1 shown in Figure 1 vary with the passage of time from the initial stage immediately after preparation, but it was confirmed that peaks occurred around 900 cm -1 -1. According to the description in Non-Patent Document 1, since this peak shows Ti-O-Si stretching vibration, it is considered that a reaction product of titanium and silica has been formed. The exact reason why the measurement results by the FTIR method change with time as shown in Figure 1 is not clear at present and needs to wait for future clarification. Probably, the reaction between the aminobis-silane compound and the titanium alkoxide compound is a hydrolysis reaction, so the reaction rate is slow, and it is presumed that some reaction occurs between the reaction product of the aminobis-silane compound and the titanium alkoxide compound and the linear organopolysiloxysilane having silanol groups at both ends of the molecular chain.

[0027] (Example 2) 16 parts by mass of bis[3-(triethoxysilyl)propyl]amine was added to a mixed solvent of 20 parts by mass of butyl acetate and 60 parts by mass of isopropyl alcohol while stirring, and then 3 parts by mass of tetra-n-butyl titanate was added, and stirring was continued at 30 °C for 60 minutes. Then, this was sealed and allowed to stand at 25 °C for 48 hours to obtain a transparent yellow reaction solution. 15 parts by mass of this reaction solution was added to 100 parts by mass of a linear organopolysiloxysilane having silanol groups at both ends of the molecular chain with a viscosity of 6 Pa·s to obtain a room-temperature curable transparent rust-preventive paint composition of Example 2.

[0028] (Example 3) To a mixed solvent of 20 parts by mass of butyl acetate and 60 parts by mass of isopropyl alcohol, 16 parts by mass of bis[3-(trimethoxysilyl)propyl]amine was added with stirring, and then 2.5 parts by mass of tetraisopropyl titanate was added. After stirring was continued at 30 °C for 60 minutes, this was sealed and allowed to stand at 25 °C for 24 hours to obtain a transparent yellow reaction solution. 6 parts by mass of this reaction solution was added to 100 parts by mass of a linear organopolysiloxane having silanol groups at both ends of the molecular chain with a viscosity of 25 Pa·s to obtain the room-temperature curable transparent rust-preventive paint composition of Example 3.

[0029] (Example 4) To a mixed solvent of 20 parts by mass of butyl acetate and 60 parts by mass of isopropyl alcohol, 16 parts by mass of bis[3-(triethoxysilyl)propyl]amine was added with stirring, and then 4 parts by mass of tetra(2-ethylhexyl) titanate was added. After stirring was continued at 30 °C for 60 minutes, this was sealed and allowed to stand at 25 °C for 48 hours to obtain a transparent yellow reaction solution. 20 parts by mass of this reaction solution was added to 100 parts by mass of an organopolysiloxane with a viscosity of 1 Pa·s to obtain the room-temperature curable transparent rust-preventive paint composition of Example 4.

[0030] (Comparative Example 1) To a mixed solvent of 20 parts by mass of butyl acetate and 60 parts by mass of isopropyl alcohol, 16 parts by mass of bis[3-(trimethoxysilyl)propyl]amine was added with stirring to obtain an aminobis-silane solution. 10 parts by mass of this solution was added to 100 parts by mass of an organopolysiloxane having silanol groups at both ends of the molecular chain with a viscosity of 6 Pa·s to obtain the room-temperature curable organopolysiloxane composition of Comparative Example 1. The mixed solvent of this Comparative Example 1 contains aminobis-silane but does not contain titanium alkoxide.

[0031] (Comparative Example 2) To a mixed solvent of 20 parts by mass of butyl acetate and 60 parts by mass of isopropyl alcohol, 4 parts by mass of tetra-n-butyl titanate was added with stirring to obtain a titanium alkoxide solution. 10 parts by mass of this solution was added to 100 parts by mass of an organopolysiloxane having silanol groups at both ends of the molecular chain with a viscosity of 6 Pa·s to obtain a room-temperature curable organopolysiloxane composition of Comparative Example 2. This mixed solvent of Comparative Example 2 contains a titanium alkoxide but does not contain an aminobis-silane.

[0032] (Comparative Examples 3 to 5) Furthermore, as Comparative Example 3, 40 parts by mass of a mixed solvent of xylene / methyl isobutyl ketone = 1 / 1 was added to 100 parts by mass of an acrylic resin WML-337 (non-volatile content 45%, trade name, manufactured by DIC Corporation) having good adhesion to metals, and 12 parts by mass of a transparent yellow liquid composed of the reaction product of the aminobis-silane compound and the titanium alkoxide compound obtained in Example 1 was added to obtain a paint composed of the transparent acrylic resin composition of Comparative Example 3. This transparent acrylic resin composition of Comparative Example 3 does not contain a linear organopolysiloxane. Further, as Comparative Example 4, a commercially available acrylic rust preventive paint (clear coat for iron parts, manufactured by Asahi Pen Co., Ltd.) was prepared, and as Comparative Example 5, a commercially available epoxy rust preventive paint (FOC rust preventive clear, manufactured by Fecto Co., Ltd.) was prepared. The composition of the main agent of this epoxy rust preventive paint consists of 42.5 parts by mass of an epoxy resin (epoxy equivalent: 450 - 500 g / eq), 16.7 parts by mass of propylene glycol monomethyl ether, 39.8 parts by mass of xylene, and 1 part by mass of an additive. Similarly, the composition of the curing agent consists of 40 parts by mass of a polyamide resin (amine value: 80 - 120 mg KOH / g, active hydrogen equivalent: 472 g / eq), 1.5 parts by mass of a curing accelerator, 52 parts by mass of xylene, and 6.5 parts by mass of n-butanol.

[0033] The compositions of the room-temperature curable transparent rust preventive compositions or transparent organopolysiloxane compositions of Examples 1 to 4, Comparative Examples 1 and 2 prepared as described above are shown in Table 1, and the compositions of various transparent paints of Comparative Examples 3 to 5 are shown in Table 2.

Table 1

[0034] [Table 2]

[0035] [Salt spray test] For the various paints of Examples 1 to 4 and Comparative Examples 1 to 5 prepared as described above, the rust prevention properties were investigated by a salt spray test according to JIS Z 2371:2015 as follows. The base metal plate used was a cold-rolled steel plate (150 × 50 × 0.6 mm), and each coating film was applied by a brush coating method so that the thickness after drying at 23°C for one day and one night was 80 to 100 μm. Also, the formation of scratches was formed by making incisions with a cutter knife so that the angle at the intersection was 30°. As the salt water, a mixed solution of 95% by mass of ion-exchanged water and 5% by mass of sodium chloride was used. As a specific method for measuring the scratches, the part with the widest rust width from the cut part was measured with a ruler.

[0036] As criteria for judging rust prevention properties, after the salt spray, when no rust generation was observed at the cut part for all samples after a predetermined time had elapsed, it was marked as "〇"; when rust generation was observed at the cut part in the same way, it was marked as "△"; when significant rust generation was observed beyond the cut part in the same way, it was marked as "×". When rust generation was observed only at the cut part for some samples, it was marked as "△~〇"; when significant rust generation was observed beyond the cut part only for some samples, it was marked as "△~×". For all samples with rust generation, the average dimension of the rust width was examined. Also, for those with rust generation, when swelling was observed in the coating film, it was judged according to the grade table shown in JIS K5600-8-2.

[0037] The results of the salt spray tests for each of Examples 1 to 4 and Comparative Examples 1 to 5 are shown in Table 3, and the appearances of each sample of Examples 1, 3, 4, and Comparative Examples 1, 2, 4, 5 after 2000 hours have elapsed are shown in Figure 2. [Table 3]

[0038] From the results shown in Table 3 and FIG. 2, the following can be understood. In the samples of Examples 1 to 4, no abnormalities were observed even after 1000 hours. Although rust generation was observed in some samples after 2000 hours, the line width of the rust was 1.0 mm or less and was substantially within the cut portion. On the other hand, in the samples of Comparative Examples 1 and 2, no rust generation was observed in all samples after 500 hours, but rust generation with a line width of about 1.5 mm was observed in all samples after 1000 hours, and at 2000 hours, not only rust generation but also swelling of the coating film occurred in all samples.

[0039] The sample of Comparative Example 1 is a paint composed of a mixture of a linear organopolysiloxane having silanol groups at both ends of the molecular chain and an aminobis-silane compound, and the paint of Comparative Example 2 is a paint composed of a mixture of a linear organopolysiloxane having silanol groups at both ends of the molecular chain and a titanium alkoxide. Therefore, both do not contain the reaction product of the aminobis-silane compound and the titanium alkoxide compound. Therefore, the difference in the results between Examples 1 to 4 and Comparative Examples 1 and 2 shown in Table 3 is considered to show a synergistic effect of both a linear organopolysiloxane having silanol groups at both ends of the molecular chain and the reaction product of the aminobis-silane compound and the titanium alkoxide compound. of

[0040] In addition, the sample of Comparative Example 3 is obtained by adding a reaction product of an aminobis-silane compound and a titanium alkoxide compound, which is used as a rust preventive component in the room temperature curable transparent rust preventive paint composition of Example 1, to a commercially available acrylic paint. The sample of Comparative Example 4 uses a commercially available acrylic rust preventive paint different from that of Comparative Example 3. However, due to the low water repellency of the acrylic rust preventive paint itself, slight rust generation was already observed in some samples after 500 hours, and rust generation was observed in all samples after 1000 hours. In some samples, rust with a width of about 1.5 to 2.0 mm was observed beyond the cut part. Furthermore, after 2000 hours, rust with a width of about 3.0 mm was observed beyond the cut part in all samples. However, no swelling was observed in the coating film.

[0041] That is, substantially no difference in rust preventive effect was observed between the samples of Comparative Example 3 and Comparative Example 4. Comparing the results of the samples of Comparative Examples 3 and 4 with the results of the samples of Examples 1 to 4, it can be seen that the reaction product of the aminobis-silane compound and the titanium alkoxide compound exhibits a selectively good rust preventive action when combined with a linear organopolysiloxane having silanol groups at both ends of the molecular chain.

[0042] Furthermore, in the sample of Comparative Example 5, since the epoxy paint inherently does not allow water to pass through and a coating film with a high rust preventive effect can be obtained, no rust generation was observed in any of the samples after 500 hours. However, rust with a width of about 1.5 mm was observed at the cut part of all samples after 1000 hours, and rust with a width of about 3.0 mm was observed in all samples after 2000 hours. However, no swelling was observed in the coating film.

[0043] As described above, it was confirmed that a coating film having a good rust preventive effect can be obtained by the room temperature curable transparent rust preventive paint composition of the present invention. However, in the results shown in Table 3 and FIG. 2, the transparency of the room temperature curable transparent rust preventive paint composition of the present invention has not been confirmed, so the transparency was separately examined.

[0044] [Haze Test] Since there is no established test method for the transparency of paints, the transparency of various samples was confirmed here by the haze test (cloudiness measurement test). The haze test is to obtain the ratio (%) of diffused light to the light transmitted through a substance as the haze value. Since a perfectly transparent body has no diffused light, the haze value = 0, and the haze value increases as the diffused light component increases. Therefore, various coating films were formed on one surface of a glass plate of a predetermined size as a reference, the haze values of the samples with various coating films were measured, and the glass plate portion was placed on a written surface regarded as a base to check how it could be visually recognized, and it was examined at what haze value it could be regarded as substantially transparent.

[0045] Here, the method for measuring the haze value adopted for confirming the transparency of the rust preventive paint of the present invention will be described with reference to FIG. 3. Note that FIG. 3 is a diagram showing the concept of the method for measuring the haze value, and specific measuring means are not shown.

[0046] First, a transparent glass plate 10 of 50×90×2.0 mm was prepared, and various coating films 11 were formed on one surface of this glass plate 10. For Samples 2 to 5, after flow coating, they were dried at room temperature for 3 days, and for Samples 6 and 7, after spray coating, they were forcibly dried at 80° C. for 30 minutes, and the thickness of each coating film was measured. Then, a haze meter HZ-V3 (trade name, manufactured by Suga Test Instruments Co., Ltd.) was used as the means for measuring the haze value, and the haze values of the samples on which various coating films 11 were formed were measured in accordance with JIS K 7136. The method for measuring the haze value by this measuring means is as follows: when the glass plate 10 on which various coating films 11 are formed is installed in the measuring means (not shown), the light from the light emitting part 12 of the measuring means incident from one surface (the side indicated as "right") of the glass plate 10 on which various coating films 11 are formed is measured by the light receiving part 13 arranged on the opposite surface (the side indicated as "left") of this glass plate 10, and the haze value (%) is obtained based on the case where the glass plate 10 on which various coating films 11 are formed does not exist.

[0047] Here, the case of only the glass plate was taken as Sample 1, a sample with a rust-preventive coating film thickness of 1000 μm using the transparent rust-preventive paint composition of Example 1 was taken as Sample 2, a sample with a thickness of 450 μm was taken as Sample 3, and a sample with a thickness of 150 μm was taken as Sample 4. Furthermore, a sample with a thickness of 400 μm using a silicone rubber paint from another company was taken as Sample 5, a sample with a thickness of 10 μm using an acrylic matte paint was taken as Sample 6, and a sample with a thickness of 20 μm using a paint mixed at a ratio of acrylic semi-gloss paint / clear paint = 1 / 1 was taken as Sample 7. The haze value was measured for each of them. These measured values were summarized and shown on the side indicated as "right" in the coating film position in Table 3. Since the haze value also changes depending on the light incident direction, the results when the incident direction to the samples was reversed for Samples 1 to 7 described above were summarized and shown on the side indicated as "left" in the coating film position in Table 3, and furthermore, the average of the two was summarized and shown in the column of "average value".

[0048]

Table 4

[0049] Next, for each of Samples 1 to 7, it was confirmed how they could be visually recognized when placed on a newspaper with the glass surface as the base. The results were arranged in order of haze value and summarized in FIG. 4. Note that FIG. 4 is a diagram showing the states when the glass surfaces of Samples 1 to 7, on which coating films were formed on the glass surface using each paint, were placed on a newspaper, arranged in order of haze value.

[0050] From the results shown in Fig. 4, the underlying characters can be read to some extent when the haze value is up to 61.2% (Sample 2). However, when the haze value is 67.5% (Sample 5), the characters are difficult to read. Therefore, it is recognized that the underlying characters can be read to some extent if the haze value is 65% or less. Accordingly, for a rust-preventive coating film with a haze value of 65% or less, it is considered that the surface of the substrate can be visually recognized well. Thus, "substantially transparent" in the present invention can be defined as having a haze value of 65% or less. Samples 2 to 4 formed using the rust-preventive paint corresponding to Example 1 of the present invention all have a haze value of 65% or less, and thus satisfy the condition of "substantially transparent" in the present invention.

Explanation of Signs

[0051] 10…Glass plate 11…Coated film 12…Light-emitting part 13…Light-receiving part

Claims

1. A linear organopolysiloxane having a viscosity at 23°C of 0.1 to 50 Pa·s and having silanol groups at both ends of the molecular chain, a reaction product of an aminobis-silane compound and a titanium alkoxide compound, A room-temperature curable transparent rust-preventive paint composition characterized by containing the above.

2. The aminobis-silane compound is at least one selected from bis[2-(trimethoxysilyl)ethyl]amine, bis[3-(trimethoxysilyl)propyl]amine, bis[4-(trimethoxysilyl)butyl]amine, bis[2-(triethoxysilyl)ethyl]amine, bis[3-(triethoxysilyl)propyl]amine, bis[4-(triethoxysilyl)butyl]amine, The titanium alkoxide compound is at least one selected from tetranormal butyl titanate, butyl titanate dimer, and tetraoctyl titanate. The room-temperature curable transparent rust-preventive paint composition according to Claim 1.

3. The reaction product of the aminobis-silane compound and the titanium alkoxide compound is obtained by reacting the titanium alkoxide compound at a ratio of 0.1 to 0.3 mol per 1 mol of the aminobis-silane compound. The room-temperature curable transparent rust-preventive paint composition according to Claim 1.

4. The content ratio of the reaction product of the aminobis-silane compound and the titanium alkoxide compound is 0.5 to 10% by mass in terms of solid ratio with respect to the organopolysiloxane. The room-temperature curable transparent rust-preventive paint composition according to any one of Claims 1 to 3.

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