JPS6084365A - Paint composition for stainless steel - Google Patents

Abstract

PURPOSE:To provide a paint compsn. having excellent adhesion to stainless steel, containing a polyol resin and a blocked isocyanate compd. as main components and further an amino group-contg. silane coupling agent. CONSTITUTION:The titled compsn. contains a polyol resin (e.g. a resin having a hydroxyl value of 25-200 such as acrylic resin or polyester resin) and a blocked isocyanate (pref. an aliph. blocked isocyanate compd. from the viewpoint of weather resistance) as main components and further an amino group-contg. silane coupling agent (e.g., gamma-aminopropyltriethoxysilane). By blending said silane coupling agent, adhesion to stainless steel is greatly improved and the paint can be firmly bonded to stainless steel.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coating composition for stainless steel with excellent adhesion.

In recent years, stainless steel has been used for outdoor equipment such as solar systems,
As it has become widely used in structures, it has become increasingly common to apply paints to stainless steel for the purpose of adding aesthetic appeal or improving stain resistance, corrosion resistance, weather resistance, etc. It's starting to get worse.

However, as is well known, stainless steel has an inert surface and therefore has poor adhesion with paint, and therefore a paint suitable for stainless steel has not yet been developed.

By the way, epoxy resin paints are known as paints that have relatively good adhesion, but glaring paints have poor weather resistance, making them unsuitable as paints for stainless steel that are applied outside pressure relief. .

The present invention was made in view of the above-mentioned current situation, and it is an object of the present invention to provide a coating material 111 having excellent adhesion to stainless steel.

For this purpose, in a coating composition containing a polyol resin and a groffin cyanate compound as main components,
This is achieved by a stainless steel coating composition characterized by containing an amino group-containing silane coupling agent.

As the polyol resin and blocked isocyanate compound used in the present invention, those normally used in liquid area bake-curing type urethane resin paints can be used as they are.

Examples of the polyol resin include acrylic resin, polyester resin, silicone-modified acrylic resin, silicone-modified polyester resin, fluororesin, etc. with a hydroxyl value of 5 to 20.
Examples include resins of about 0.

In addition, if the hydroxyl value of the polyol resin is less than 2s, sufficient physical properties of the coating film will not be exhibited, and if it exceeds 206', performance such as flexibility and water resistance will deteriorate. do not have.

Blocked isocyanate compounds are obtained by masking the free incyanate groups of polyisocyanate with a blocking agent, and when heated, the blocked isocyanate compounds dissociate to generate free isocyanate groups, which react with the coexisting polyol resin to form a coating. A film is formed.

Examples of the polyisocyanate include hexamethylene diisocyanate, hydrogenated phenylene diisocyanate, isophorone diisocyanate, lysine diisocyanate methyl ester, tolylene diisocyanate, diphenylmethane diisocyanate, tetramethylene diisocyanate, methylcyclohexylene diisocyanate, and the like. Examples include derivatives such as known aliphatic, alicyclic, or aromatic polyinsyanates, polymers thereof, and addition reaction products of these with trimethylolpropane, trimethylolethane, and the like. Particularly in the present invention, aliphatic polyinsyanate is preferred from the viewpoint of weather resistance.

Examples of the blocking agent include oxime-based blocking agents such as porumaldoxime, acetaldoxime, acetoxime, methyl ethyl ketoxime, methyl isopropyl ketoxime, methyl butyl ketoxime, diethyl ketoxime, diacetyl monoxime, benzophenone oxime, and cyclohexanone oxime. Alcohol-based blocking agents such as methanol, ethanol, phthanol, flobyl alcohol, ethylene glycol monomethyl ether, diethylene glycol monoethyl ether; Phenol-based blocking agents such as phenol, cresol, xylenol, other mercaptan-based blocking agents, acids Examples include amide blocking agents and amine blocking agents.

In the present invention, the mixing ratio of the block isocyanate compound and the polyol resin is such that the ratio of the number of NCO groups in the block isocyanate compound to the number of JIWQOH groups in the polyol tree (number of NGO groups 10H groups) is θ6 to /3, preferably θ
An appropriate ratio is within the range of de~//.

The present invention is characterized in that an amino group-containing silane coupling agent is blended into a coating composition containing the polyol resin and the blocked isocyanate compound as main components. By blending the amino group-containing silane coupling agent in this way, the adhesion to stainless steel is significantly improved.

However, although the mechanism is not completely elucidated, it can be inferred as follows based on its amazing adhesion.

That is, one silanol group in the silane coupling agent is oriented and adhered to the stainless steel surface, and the other amine group in the silane coupling agent and the free isocyanate group (
In other words, the free isocyanate groups (generated by dissociation of the blocked isocyanate compound during baking) react with each other to form a strong bond. Since this amine group is basic, the reaction rate with free isocyanate groups is faster than the reaction between the hydroxyl groups of the polyol resin and free isocyanate groups.Therefore, almost all of the amino groups in the silane coupling agent react with free isocyanate groups. do. Therefore, it is thought that the stainless steel and the coating film are strongly bonded together using the amine group-containing silane coupling agent as a bridge, resulting in excellent adhesion. This can be clearly seen from the fact that when a normal silane coupling agent having no amine group is used, the adhesion does not improve much.

As the amino group-containing silane coupling agent, commercially available A-//θθ [(trade name manufactured by Nippon Unicar Co., Ltd.); r-aminopropyltriethoxysilane], A-//, 2θ[
(Product name manufactured by Nippon Unicar Co., Ltd.); N-β-(aminoethyl)-r-aminopropyltrimethoxysilane: ], A-
//Aθ [(Product name manufactured by Nippon Unicar Co., Ltd.) Sr-ureidopropyltriethoxysilane], Tone Silicone S
HEθkoθ [(trade name manufactured by Tone Silicone Co., Ltd.); n-
()rimethoxin rilprovir)-ethylenediamine]
etc. are cited as representative examples.

The above amino group-containing silane coupling agent is θ/~ in the paint.
It is appropriate to mix S Shigeura Chi.

If the blending amount is less than the above range, the above effects cannot be obtained, and conversely, if it is too large, no improvement in the above effects will be observed.

The coating composition of the present invention contains an organic solvent as other components, and further contains various rust-preventing pigments, coloring pigments, extender pigments, ultraviolet absorbers, catalysts, leveling agents, etc. as necessary. consists of things.

The coating composition of the present invention can be applied to a stainless steel surface generally by spray coating or by other means such as dipping or flow coating, with a dry film thickness of I about /θμ to about /θθ.
The film is baked at a temperature higher than the dissociation temperature of the block isocyanate compound, usually from /2θ to 250°C, for 10 to 3θ minutes.

As mentioned above, the coating composition of the present invention has extremely excellent adhesion to stainless steel, and its practical value is extremely high.

The coating composition of the present invention can also be applied to smooth and inert objects such as glass, tinplate, plated plates, etc.

Hereinafter, the present invention will be explained in detail with reference to Examples.

In the examples, [part J and r%J are expressed on a weight basis.

Example/ Acrylic resin solution [“Hytaloid 32θ3” (trade name, manufactured by Hitachi Chemical Co., Ltd.); hydroxyl value 39. '/- (in terms of solid content), solid content 5θg%] g 7 parts, aliphatic blocked isocyanate compound solution [[Coronate D C-27/7
J (Product name manufactured by Nippon Polyurethane Industries Co., Ltd.: NCO
%/3. ．． 3 (in terms of solid content), solid content ratio θ /, 2 parts, di-n-butyltin dilaurate (cured tS) 05
After uniformly mixing 0.5 parts of surface conditioner, add 1 part of amino group-containing silane coupling agent ('rA-//20J <trade name "I" manufactured by Nippon Unicar Co., Ltd.) i! Dilute with mixed solvent (/:/) to obtain a viscosity of 2.
．． A 2 second (Ford Cup #'I/2θ°C) paint was prepared.

This paint was applied to a stainless steel plate (5us430g, 2D) using air spray so that the dry film thickness was θμ.
/Otsu was baked and dried at 0°C for 1.20 minutes.

Example core acrylic resin solution [“Acrydec A-gθ/-P” (
Dainippon Ink & Chemicals Co., Ltd. product name); Hydroxyl value/θθ(
23 parts of titanium white was dispersed in 3/part of solid content (n), solid content 30%, and 0.3 part of curing catalyst was added to this.

05 parts of surface conditioning agent and aliphatic blocky anate compound solution [Duranate 77F3-60C, XJ (
Asahi Kasei Kogyo Co., Ltd. (trade name): 23 parts of N Col left 7 (in terms of solid content) and solid content 6θ Chi] were added and mixed uniformly. Next, λ part of an amino group-containing silane coupling agent [[Tone Silicone 5) 14θ20'' (trade name manufactured by Tone Silicone Co., Ltd.]) was added and diluted with a mixed solvent of butyl acetate and Kijirol (/:/) to obtain a viscosity of 27. The paint was prepared in seconds.

This paint was applied to a stainless steel plate using the dip coating method, and /S
It was baked and dried at 0°C for 30 minutes to obtain a coating film with a thickness of 2θμ.

Example 3 Polyester resin solution [Tsuknok D-/3θ-7
5” (trade name manufactured by Dainippon Ink Chemical Industry Co., Ltd.); Hydroxyl value 7
．． 20 (in terms of solid content), solid content 7S] 35 parts, mixed solvent of butyl acetate and pheasant roll (/:/) 20 parts, iron oxide S part, titanium white S part, surface jtl! J conditioning agent θS part was uniformly dispersed, and 05 parts of curing catalyst and aliphatic blocked isocyanate compound solution [[)(-knock o-500J(
Dainippon Ink Chemical Industry Co., Ltd. (product name); NCo%/2
(solid content equivalent), solid content 43%) 3.2 parts, and part a of amino group-containing silane coupling agent [rA-//AOJ (trade name manufactured by Nippon Unicar Co., Ltd.)] were added and mixed uniformly to prepare a paint. did.

This paint was applied in the same manner as in Example/100°C.

It was baked and dried in three parts to obtain a coating film having a thickness of 0 μm.

Example 7 33 parts of polyester resin [Burnock D-/A/J (trade name manufactured by Inu Nippon Ink Chemical Industry Co., Ltd.); hydroxyl value/7θ], a mixed solvent of butyl acetate and kijirol (/:/), 2.
, 5 parts of phthalodianine blue, and 0.5 parts of a surface conditioner were uniformly dispersed, and 0.5 parts of a curing catalyst and an aliphatic blocked isocyanate compound solution [Burnock D-! ;0OJ
3 Otobe, amino group-containing silane coupling agent [Torre・
3 parts of silicone SHA O, 20J O, were added and mixed uniformly, and diluted with the above mixed solvent to prepare a paint having a viscosity of 7 gsec.

This paint was applied in the same manner as in Example/1 at 170°C.

It was baked and dried for 20 minutes to obtain a coating film with a thickness of 15 μm.

Example S Fluorine It Fat I liquid [[Lumiflon LF-λOθD]
Asahi Glass Co., Ltd. product name); hydroxyl value 2 (solid content equivalent), solid content 50%] 79 parts, aliphatic blocked isocyanate compound solution (rIPDl-B/37θ" (Chemis
che Werke H-sho 1s product name): NC01
/3.3chi (solid content equivalent), solid content 60chi] 79 parts, curing catalyst 05 parts, surface conditioner 05 parts, amino group-containing silane coupling agent ["A-1100" (trade name manufactured by Nippon Unicar Co., Ltd.) )]/parts were mixed uniformly and diluted with a mixed solvent of butyl acetate and Kijirol (/:/) to adjust the viscosity and 2 parts of the paint.

Apply this paint to a stainless steel plate (SUS#3θ4) with a mirror finish.
-BA) was coated with air spray to a dry film thickness of 30 μm, and baked and dried at 750° C. for 30 minutes.

Comparative Example/In Example/, the same paint as in Example/ was used except that the amino group-containing silane coupling agent was removed, and painting was carried out in the same manner.

Comparative Example In Example C, the same paint as in Example λ was used except that the amino group-containing silane coupling agent was removed, and painting was carried out in the same manner.

Comparative Example 3 In Example 1, a glycidyl group-containing silane coupling agent CrA- was used instead of the amino group-containing silane coupling agent.
1g7J (trade name, manufactured by Nippon Unicar Co., Ltd.); r-glycidoxypropyltrimethoxysilane] was used, but the same paint was used and the coating was carried out in the same manner.

Comparative Example 3 In Example 3, the same paint as in Example 3 was used except that the amino group-containing silane coupling agent was omitted, and painting was carried out in the same manner.

Comparative Example S The same paint as in Example S was used except that the amino group-containing silane coupling agent was omitted, and painting was carried out in the same manner.

For the coating films obtained in Examples/~S and Comparative Example/-5,
An adhesion test and a boiling water resistance test were conducted.

The results are shown in Table 7.

As is clear from Table 1, the coating composition of the present invention had excellent adhesion to stainless steel, but Comparative Examples/--Co did not contain a silane coupling agent.

Comparative Example 3 using a silane coupling agent containing no amino group and Nos. 11 and 5 had poor adhesion.

[Brief explanation of drawings]

The figure is an explanatory diagram showing an adhesion test method. In the figure, 1 is a coating film, 2 is an epoxy adhesive layer, 3.3' is a steel jig, and 4 is a stainless steel plate.

Claims (1)

[Claims] (1) In a coating composition containing Polymer 17J resin and blocked isocyanate compound I as the main component,
(a) Nito containing silane coupling agent
&Q “￥rxt. Ω) A paint composition for stainless steel, characterized in that the blocked isocyanate compound is an aliphatic blocked isocyanate compound.
f'r)i? Range No. (1) JJ'i iti simple material for stainless steel + i'lj liν, I proboscis.