JPH08104986A - Production of substrate having water-repellent coating layer - Google Patents

Abstract

PURPOSE: To produce a substrate having a coating layer enhanced in water repellency by using a fluoroalkylsilane composite with titanium, zirconium or aluminum to form a coating film on the substrate. CONSTITUTION: A soln. of the alkoxide shown by Rfm -Si(OR')4-n-m (OM(OR')x )m (where Rf is fluoroalkyl, R' is a 1-5C alkyl, M is titanium, zirconium or aluminum, (m) is 1 to 3, (n) is 1 to 3, and (x) is the value determined by the valance of M) is prepared. The soln. is applied on a substrate to form a wet coating film and baked at 200-500 deg.C in the atmosphere or in an oxidizing atmosphere. Consequently, the concn. of alkyl is increased on the substrate surface, and a substrate having a highly water-repellent coating film is obtained.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION 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 such as steel plates. However, conventional methods such as chromate treatment have a temporary rust preventive action and are not suitable for long-term rust prevention. Further, although the organic resin coating method has a rust preventive action for a certain period of time, there are pinholes in the organic resin coating film, and water 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 high heat environments, for example, members of internal combustion engines.

In order to solve such a problem, Japanese Unexamined Patent Publication No.
-68477 publication, fluoroalkylsilane and A
It has been proposed to enhance the durability and heat resistance of a steel sheet by forming an inorganic oxide film formed from an alkoxide of 1, Zr, Ti, Si, W, Ce, Sn and Y. Since this coating is a composite inorganic oxide coating in which the above metal is dehydrated and condensed to crosslink, it has excellent durability and heat resistance, and also has water repellency derived from a fluoroalkyl group.

[0004]

The above-mentioned film is dealcoholized and dehydrated with the OH group on the surface of the substrate and the alkoxyl group of the alkoxide or the OH group generated by hydrolysis to form a bond. However, the usual fluoroalkyl present in the above coating has poor reactivity with the substrate, and the concentration of fluoroalkyl on the coating surface was low.

It is an object of the present invention to provide a method for solving the above-mentioned drawbacks of a coating film, increasing the concentration of water-repellent functional portions on the surface, and producing a substrate having a coating film with high durability. To 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 Is a fluoroalkyl group, R'is alkyl having 1 to 5 carbon atoms, 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 valence of M, which is 1 to 3 in the case of titanium and zirconium and 1 or 2 in the case of aluminum), and the solution is applied to a substrate, and then, A method for producing a substrate having a water-repellent coating layer is provided, which comprises firing.

Furthermore, according to the present invention,

Embedded image (Wherein R is alkyl having 1 to 4 carbon atoms), a solution of tetraalkylsilazane is formed, the solution is applied to a substrate, and then baked, A method of manufacturing a substrate having a coating layer is provided.

[0008]

In the invention described in claim 1, by combining the fluoroalkylsilane with Ti, Zr or Al,
The reactivity of the terminal alkoxyl group of the composite compound with the substrate is improved, and the reaction with the OH group on the substrate is promoted. Therefore, when this composite compound is applied to the surface of the base material, the concentration of the alkyl group on the surface of the base material is improved, and a base material having a coating film with higher water repellency is obtained.

In the invention of claim 2, the tetraalkylsilazane has good reactivity with the OH group on the surface of the substrate,
By reacting, the water-repellent alkyl group can be distributed at a high density on the surface of the substrate. In this way, due to the high density of the water-repellent alkyl group,
Even if some of the 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 Is slow and has low reactivity. On the other hand, titanium, zirconium or aluminum alkoxide is highly reactive. Therefore, a highly reactive alkoxide can be obtained by compounding Ti, Zr, or Al with the above fluoroalkyl-substituted alkoxide. In this alkoxide, the alkoxide portion such as titanium reacts with the hydroxyl group on the substrate, and the water-repellent fluoroalkyl group is densely arranged on the surface.

The larger the number of fluoroalkyl groups, that is, m, the higher the water repellency. On the contrary, when the number of fluoroalkyl groups is large, steric hindrance prevents the fluoroalkyl groups from being densely arranged on the surface. Therefore, the number m of fluoroalkyl groups is preferably 1. Fluoroalkyl group of the _{formula, CF 3 (CF 2) n} (CH 2) 2 - are those represented by, where n is preferably 5-10.

Such a fluoroalkylsilane has T
The alkoxide compounded with i, Zr or Al 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 the alkoxyl group is substituted with a fluoroalkyl group and an alkoxide of titanium, zirconium, or aluminum in the presence of alcohol to form a solution. The alkyl in this alkoxide is an alkyl having 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 base material is not particularly limited, and various materials such as iron-based materials, aluminum alloys, and glass can be used.

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

The tetraalkylsilazane has the following formula

Embedded image As represented by, the OH groups on the surface of the base material are bonded by a deammonification reaction to form small water-repellent groups on the surface of the base material densely. The alkyl group in the tetraalkylsilazane has 1 to 4 carbon atoms, and the tetraalkylsilazane having a larger alkali does not show a beneficial 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 materials, aluminum alloys, and glass can be used.

[0016]

【Example】Example 1 1 wt% CF in ethanol₃(CF₂)₇C₂H_FourSi (OCH₃)₂OTi
(OC₃H₇)₃Immerse SUS 440C substrate in the mixed solution for 5 minutes
After that, the substrate was taken out and dried in the atmosphere. Then
This substrate is baked at 150 ° C, and the fluorocarbon is applied to the substrate surface.
Sample 1 having a molecular film of an alkyl group was manufactured. It
In addition, CF₃(CF₂)₇C₂H_FourSi (OCH₃)₂OTi (OC₃H₇) ₃Instead of
CF₃(CF₂)₇C₂H_FourSi (OCH₃)₂OZr (OC₃H₇)₃And CF₃(CF₂)₇C₂H
_FourSi (OCH₃)₂OAl (OC₃H₇)₃Using the same way as sample 1.
Samples 2 and 3 were manufactured. Also CF₃(CF₂)₇C₂H
_FourSi (OCH₃)₂OTi (OC₃H₇)₃CF instead of₃(CF₂)₇C₂H_FourSi (OC
H₃)₃Comparative sample 1
Manufactured. The contact angle was measured on 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 absolute ethanol and mixed and stirred for 1 hour in a sealed container to obtain a uniform solution. . A quartz glass plate that had been degreased and washed 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 to stand at room temperature, dried, and then baked at 150 ° C. for 1 hour to prepare Sample 4. When the contact angle of this sample 4 was measured, it was 95
And showed water repellency.

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

The above Sample 4 and Comparative Sample 2 are 350
It was placed in a furnace at ℃ and heated isothermally to examine the change in contact angle. 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 decreased to about 40 °. On the other hand, the sample 4 obtained by the method of the present invention showed a contact angle of 80 ° or more even after 200 hours and had high durability.

[0020]

INDUSTRIAL APPLICABILITY In 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 drawings]

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

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Shoji Yokoishi 1 Toyota-cho, Toyota-shi, Aichi Toyota Motor Co., Ltd.

Claims (2)

[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 valence of the metal M). A method for producing a substrate having a water-repellent coating layer, which comprises forming a solution, applying the solution to the substrate, and then firing the solution. 2. The following formula: (Wherein R is alkyl having 1 to 4 carbon atoms), a solution of tetraalkylsilazane is formed, the solution is applied to a substrate, and then the solution is baked, A method for producing a substrate having a coating layer.