JP3127731B2 - Method for producing substrate having water-repellent coating layer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a substrate having a water-repellent coating layer.

[0002]

2. Description of the Related Art Various surface treatment methods have been used to improve the durability of iron-based members, for example, steel plates. However, conventional methods, such as chromate treatment, have a temporary rust-preventive action and are not suitable for long-term rust-proofing. Further, the organic resin coating method has a rust-preventing action for a certain period of time. However, pinholes are present in the organic resin coating film, and moisture may enter through the pinholes to corrode the iron-based member. Further, the organic resin coating film has low heat resistance, and therefore cannot be used for iron-based members used in a high-temperature environment, for example, members of an internal combustion engine.

In order to solve such a problem, Japanese Patent Laid-Open No.
-68477, a fluoroalkylsilane and A
It has been proposed to increase the durability and heat resistance of a steel sheet by forming an inorganic oxide coating formed from alkoxides of 1, Zr, Ti, Si, W, Ce, Sn, and Y. This coating is a composite inorganic oxide coating formed by cross-linking by dehydration condensation of the above-mentioned metal, so that it has excellent durability and heat resistance, and also has water repellency derived from a fluoroalkyl group.

[0004]

The above-mentioned film forms a bond by de-alcoholization / dehydration with the OH group on the substrate surface and the alkoxyl group of the alkoxide or the OH group generated by hydrolysis. However, the ordinary fluoroalkyl present in the above-mentioned coating has poor reactivity with the substrate, and the fluoroalkyl concentration on the coating surface is low.

An object of the present invention is to solve the above-mentioned drawbacks of the coating, increase the concentration of the water-repellent functional portion on the surface, and provide a method for producing a substrate having a coating with high durability. I do.

[0006]

Means for Solving the Problems] According to the present invention To this end, the following formulas _{Rf m -Si (OR ') 4} -nm (OM (OR') x) n ( the above formula, Rf is A fluoroalkyl group, R ′ is alkyl having 1 to 5 carbons, M is titanium, zirconium, or aluminum, m is 1 to 3, n is 1 to 3, and x is a metal. A value determined by the valency of M, which is 1-3 for titanium and zirconium and 1 or 2 for aluminum), and this solution is applied to a substrate; There is provided a method for producing a substrate having a water-repellent coating layer, which is characterized by firing.

Further, according to the present invention,

Embedded image (Where R is alkyl having 1 to 4 carbon atoms), a solution of tetraalkylsilazane represented by the formula: is applied to a substrate, and then is calcined. A method for producing a substrate having a coating layer is provided.

[0008]

According to the first aspect of the present invention, by combining Ti, Zr or Al with fluoroalkylsilane,
The reactivity of the terminal alkoxyl group of the composite compound with the base material is improved, and the reaction with the OH group on the base material is promoted. Therefore, when this composite compound is applied to the surface of a substrate, the concentration of the alkyl group on the surface of the substrate is improved, and a substrate having a coating with higher water repellency can be obtained.

According to the second aspect of the present invention, the tetraalkylsilazane has good reactivity with OH groups on the surface of the substrate,
By reacting, the water-repellent alkyl group can be distributed on the surface of the substrate at a high density. As described above, due to the high density of the alkyl groups exhibiting water repellency,
Even if some alkyl groups are eliminated due to deterioration, many alkyl groups are still present, so that good durability is exhibited.

[0010]

Fluoroalkyl group-substituted alkoxide [Supplementary explanation of means for solving the problem] has the formula Rf _m -Si (OR) Structure of _4-m, but here the portion of the Si (OR) is hydrolyzed Speed and low reactivity. On the other hand, alkoxides of titanium, zirconium or aluminum have high reactivity. Therefore, a highly reactive alkoxide can be obtained by compounding Ti, Zr or Al with the above fluoroalkyl-substituted alkoxide. In this alkoxide, an alkoxide portion such as titanium reacts with a hydroxyl group on the substrate, and a water-repellent fluoroalkyl group is densely arranged on the surface.

The number of fluoroalkyl groups, ie, m is 1
３3, where m is higher, the water repellency is higher. Conversely, if the number of fluoroalkyl groups is large , the fluoroalkyl groups cannot be densely arranged on the surface due to steric hindrance. Therefore, the number m of the fluoroalkyl group is preferably 1. A fluoroalkyl group has the formula CF ₃ (CF
₂ ) _n (CH ₂ ) _2- , where n is 5 to
Preferably it is 10.

Such fluoroalkylsilanes have T
The alkoxide in which i, Zr or Al is compounded can be produced by a so-called sol-gel method. That is, it is obtained by mixing a fluoroalkylsilane trialkoxide in which a part of an alkoxyl group is substituted with a fluoroalkyl group with an alkoxide of titanium, zirconium or aluminum in the presence of an alcohol to form a solution. Alkyl in this alkoxide has 1 to 5 carbon atoms, that is, methyl, ethyl,
Propyl, butyl and pentyl.

The alkoxide thus produced is applied to a substrate to form a wet film. As this coating method, a known coating method such as dipping, spin coating, or spraying can be used. The thickness of the coating film is not particularly limited, and is usually about 10 nm. The substrate is not particularly limited, and various materials such as an iron-based material, an aluminum alloy, and glass can be used.

Next, the coating film is fired. This calcination may be carried out by a general method, and is carried out at 200 to 500 ° C. in the air or in a non-oxidizing atmosphere. When baking is performed in the air, it is preferable to perform baking at 350 ° C. or lower to prevent decomposition of the fluoroalkyl group. By this baking, a substrate having a water-repellent coating is obtained.

The tetraalkylsilazane is represented by the following formula

Embedded image As shown in the formula, the OH groups on the surface of the substrate are bonded by a deammonification reaction, and small water-repellent groups are densely formed on the surface of the substrate. The alkyl group in the tetraalkylsilazane has 1 to 4 carbon atoms, and a tetraalkylsilazane having a larger alkali has no advantageous effect. Therefore, as the tetraalkylsilazane, specifically, tetramethylsilazane, tetraethylsilazane, tetrapropylsilazane, and tetrabutylsilazane can be used. Furthermore, instead of tetraalkylsilazane, polyalkylsilazane (HR ₂ Si (NHR ₂ Si) _m NHSiR ₂
H) can also be used. By using this tetraalkylsilazane, a water-repellent film having durability can be formed on the substrate, and the substrate is not particularly limited,
Various materials such as iron-based, aluminum alloy, and glass can be used.

[0016]

【Example】Example 1 1% by weight of CF in ethanol_Three(CF_Two)₇C_TwoH_FourSi (OCH_Three)_TwoOTi
(OC_ThreeH₇)_ThreeSUS 440C substrate for 5 minutes
Then, the substrate was taken out and dried in the air. Then
The substrate is fired at 150 ° C, and the fluorocarbon
Sample 1 having an alkyl group molecular film was produced. Sa
And CF_Three(CF_Two)₇C_TwoH_FourSi (OCH_Three)_TwoOTi (OC_ThreeH₇) _ThreeInstead of
CF_Three(CF_Two)₇C_TwoH_FourSi (OCH_Three)_TwoOZr (OC_ThreeH₇)_ThreeAnd CF_Three(CF_Two)₇C_TwoH
_FourSi (OCH_Three)_TwoOAl (OC_ThreeH₇)_ThreeUsing the same method as sample 1
Thus, Samples 2 and 3 were manufactured. Also, CF_Three(CF_Two)₇C_TwoH
_FourSi (OCH_Three)_TwoOTi (OC_ThreeH₇)_ThreeInstead of CF_Three(CF_Two)₇C_TwoH_FourSi (OC
H_Three)_ThreeTo obtain a comparative sample 1 in the same manner as the sample 1.
Manufactured. Measure the contact angle for these samples
Was. The results are shown below.

Example 2 1 mol of tetramethylsilazane (H (CH ₃ ) ₂ SiNHSi (CH ₃ ) ₂ H) was added to 31 mol of anhydrous ethanol, and mixed and stirred for 1 hour in a sealed vessel to obtain a uniform solution. . A degreased and washed quartz glass plate was immersed in this solution and pulled up at a speed of 60 mm / min to form a wet coating film. This coating film was left standing at room temperature, dried, and baked at 150 ° C. for 1 hour to produce Sample 4. When the contact angle of this sample 4 was measured, 95
° and water repellency was observed.

29 moles of ethanol, 0.9 mole of tetraethoxysilane, 0.1 mole of fluoroalkylsilane (CF ₃
(CF ₂ ) ₇ C ₂ H ₄ Si (OCH ₃ ) ₃ ), 9 mol of water and 0.01 mol of hydrochloric acid were mixed to obtain a comparative solution. In this solution, degreased quartz glass was immersed in the same manner as above, to form a wet coating film, and then baked to produce Comparative Sample 2. When the contact angle of this comparative sample 2 was measured, it was about 110
° and the water repellency was high.

The above sample 4 and comparative sample 2 were compared with 350
The sample was placed in a furnace at a temperature of ° C., heated at an isothermal temperature, and the change in the contact angle was examined. The result is shown in FIG. Comparative sample 2 had an initial contact angle of 110 °, which was higher than that of sample 4, but after heating for 100 hours, the contact angle was reduced to about 40 °. On the other hand, Sample 4 obtained by the method of the present invention showed a contact angle of 80 ° or more even after 200 hours, and was high in durability.

[0020]

According to the present invention, by forming a coating film on a substrate using a fluoroalkylsilane in which titanium, zirconium, or aluminum is compounded,
The concentration of the water-repellent fluoroalkyl group on the coating film can be increased, and the water repellency is improved. Further, by forming a coating film on a substrate using tetraalkylsilazane, a coating film having high water repellency and high durability can be obtained.

[Brief description of the drawings]

FIG. 1 is a graph showing the heat resistance of coating films of a sample of the present invention and a comparative sample in Example 2.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shoji Yokoishi 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (58) Field surveyed (Int. Cl. ⁷ , DB name) C23C 18/00- 18/54

Claims (2)

(57) [Claims] During 1. A following formula _{Rf m -Si (OR ') 4} -nm (OM (OR') x) n ( the above formula, Rf is a fluoroalkyl an alkyl group, R 'is an alkyl of 1 to 5 carbon atoms And M is titanium, zirconium, or aluminum, m is 1 to 3, n is 1 to 3, and x is a value determined by the valency of the metal M. A method for producing a substrate having a water-repellent coating layer, comprising forming a solution, applying the solution to a substrate, and then firing. 2. The following formula: (Where R is alkyl having 1 to 4 carbon atoms), a solution of tetraalkylsilazane represented by the formula: is applied to a substrate, and then is calcined. A method for producing a substrate having a coating layer.