JPH04210275A - Formation of coating film - Google Patents

Abstract

PURPOSE:To obtain a coating film having strong binding power and stabilized adhesion by applying an undercoat contg. the resins (A), (B) and (C) of specified properties and a two-pack overcoat of polyurethane resins on a chromium-plated surface. CONSTITUTION:A resin (A) (e.g. based on PVC, polyolefin and polyester) having 20-35dyne/cm surface tension, -10 to 10 deg.C Tg and >=80% elongation of coating film and having a glycidyl group or a resin (B) (e.g. based on PVC and urethane elastomer) having 20-32dyne/cm surface tension, -10 to 10 deg.C Tg and >=80% elongation of coating film and a resin (C) (e.g. phenolic epoxy resin and aliphatic epoxy resin) having a glycidyl group are used on the chromium-plated surface as the undercoat. A two-pack polyurethane resin paint is then applied as the overcoat. A coating film having strong binding power and adhesion to the chromium-plated surface is obtained by this method even if there is a contaminant.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for forming a coating film with excellent adhesion and weather resistance on a chrome plated surface formed on various base materials such as metals and plastics.

[Conventional technology]

It is well known that chrome plating is performed on a variety of substrates. It is also known to paint such chrome-plated surfaces with paint.

However, when chrome plating is applied, dirt tends to remain on the surface, or the activity of the plating deteriorates over time, so when a paint film is formed on the chrome plating surface, it forms a paint film with excellent adhesion to the chrome plating surface. It is difficult to do so and tends to cause variations in adhesion.

Chrome-plated materials are often used in parts of automobiles and the like that are directly exposed to the outside, and their durability is further improved by coating them with a coating of paint.

Conventionally, when chrome plating is applied to a base material such as plastic, and the chrome plating surface is painted, a normal lacquer or two-component polyurethane resin paint is applied within a short period of time after chrome plating. The method is commonly used. The reason for this is that after chrome plating, if the coating is applied while the chrome plating surface has little change over time, a relatively stable coating film can be formed.

[Problems to be Solved by the Invention] Conventionally, a chrome-plated surface may have a large amount of dirt due to cleaning water, acid, or other contaminants depending on the formation conditions, or a plating surface with a different thickness of the plating layer or a plating formation On a plated surface that has been used for more than 5 days, the adhesion with the paint decreases, and the problem often arises that the coating film peels off at the interface between the plated surface and the coating film.

The surface tension of a chrome plated surface is originally low, and the condition of the plated surface is not fully understood, so that paint films tend to be difficult to adhere to. Among the conventional coating film forming methods using paints, two-component polyurethane resin paints improve the adhesion of the paint film at a relatively early stage after chrome plating by changing the structure of the polyol component, making it easier to peel off. is decreasing. However, if the chrome plating surface undergoes large changes over time, or under conditions where the polyurethane resin easily deteriorates, the paint film will peel, making it insufficient for use in harsh conditions such as outdoor applications. there were.

[Means for Solving the Problem] As a result of extensive research into the adhesion of paint films to chrome plating surfaces, the present inventors have determined that a specific surface tension, a specific elongation rate, and a specific composition as described below. It has been found that the above-mentioned conventional problems can be solved by using a paint containing a resin or a resin mixture as a lower ff1ffi material and painting a chrome-plated surface.

In the present invention, the chrome plated surface has (1) a surface tension of 20 to 3;
2 dyne/cm, a Tg of 110°C to 10°C, a coating elongation rate of 80% or more, and an undercoat containing a resin (A) having a glycidyl group, or (2) a surface tension of 20°C.
~32 dyne/cm, Tg -10℃~10℃
, a method of forming a coating film by applying an undercoat containing a resin (B) with a coating elongation rate of 80% or more and a resin (C) having a glycidyl group, and then applying a two-component polyurethane resin coating as a topcoat. be.

When painting a chrome-plated surface, the present invention focuses on the fact that the surface tension of the chrome-plated surface is small, and uses a resin that has a surface tension close to that surface tension, that is, a surface tension of 20 to 32 dyne/cm. In order to alleviate the curing stress strain, the elongation rate of the resin is made larger than the elongation rate of the undercoat paint film required for ordinary hard materials, that is, by using an undercoat paint containing a resin with an elongation rate of 80% or more. This was done so that the adhesion to the chrome plated surface, especially that surface, would not deteriorate even if the surface changed over time.

Furthermore, as mentioned above, there may be various contaminants on the chrome-plated surface, such as moisture, other foreign metal particles, and even acidic components used in forming the chrome-plated surface. This is a factor that reduces adhesion. In contrast, in the present invention, by using a resin (A) having a glycidyl group or a resin mixture [containing resin (C)] as the resin used for the lower mW material, even if the above contaminants are present, the bonding to the chrome plating surface is prevented. without reducing power,
This was done to ensure stable adhesion.

According to the present invention, after applying the above-mentioned specific undercoat paint, a two-component polyurethane resin paint is applied as a top coat, thereby imparting weather resistance to the formed paint film.

The chrome plating surface that is the object of the present invention can be formed not only on a regular metal base material but also on a resin base plate for plating products by a conventional method known to those skilled in the art, such as an electroless plating method. Any chrome plated surface.

The resin (A) used in the undercoat of the present invention can be any resin as long as it has the surface tension, elongation, and Tg described above and has a glycidyl group, such as polyvinyl, polyolefin, and polyester. Examples include resins having glycidyl groups.

Further, as the resin (B) used in the undercoat of the present invention, any resin can be used as long as it has the above-mentioned surface tension, elongation rate, and Tg, such as polyvinyl, polyester, polyether, polyolefin, and urethane elastomer. Resin can be used.

As the resin (C) having a glycidyl group used together with the resin (B), phenolic epoxy resins and aliphatic epoxy resins can be used.

The surface tension of the resins (A) and (B) is 20 to 32 d.
A range of yne/cm is preferred.

Also, the coating film elongation rate should be 80% or more, preferably 7 or 1.
00-160%, and Tg should be -10°C to 10°C.

According to the present invention, the resin (A) and the resin (C) used in combination with the resin (B) are those having a glycidyl group. In this case, the content of glycidyl groups in the resin (A) and the resin (C) relative to the total amount of the resin (B) and the resin (C)
The content of glycidyl groups contained in is preferably 5% (mol) or more and 15% (mol) or less. When the content of the glycidyl group is less than 5% (mol), when contaminants are present on the chrome plated surface, especially on the plated surface,
Or when there is a change over time, for example 5 days or more after plating,
Adhesiveness decreases, which is undesirable, and if it exceeds 15% (mol), drying properties decrease, which is undesirable.

The smaller the surface tension of resins (A) and (B) used in the primer coating of the present invention is below 20 dyne/cm, or the greater it exceeds 32 dyne/cm, the greater the difference in surface tension with the chrome-plated surface. This is not preferable because the affinity between the coated film surface and the chrome-plated surface decreases, resulting in deterioration of adhesion.

Moreover, if the elongation rate is less than 80%, internal stress during coating film formation becomes high, resulting in a decrease in adhesion, which is not preferable.

Further, the resins (A) and (B) have a glass transition temperature (Tg)
It is preferable to use one with a temperature of -10°C to 10°C. If the Tg of these resins is lower than -10°C, the hardness of the resulting paint film will be undesirable even if a two-component polyurethane paint is applied on top of these undercoat paint films, and this is not preferable. If it is higher, it will be difficult to obtain an elongation rate of 80% or more for the undercoat film, and it will also be easy to cause distortion in the curing of the paint film when forming the paint film on the glazed surface, resulting in a decrease in adhesion, which is not preferable for use in the present invention. The undercoat paint contains (1) the above-mentioned specific resin (
A) or (2) the specific resin (B) and resin (C)
In addition to this, it contains an organic solvent as a main component, and if desired, coloring pigments, extender pigments, and other commonly used additives can be added.

The undercoat paint can be applied by a commonly used coating method.

According to the present invention, after the undercoat is applied, a two-component polyurethane paint is applied on the formed undercoat film in a wet state or after drying for 20 to 60 minutes, usually at 40 to 100°C.

Suitable resins (A) used in the present invention are vinyl-based, polyolefin-based, and polyester-based glycidyl group-containing polymers, and resins CB) are vinyl-based, polyester-based, polyether-based, polyolefin-based, and urethane elastomer-based polymers. is preferred. Further, as the resin (C), phenolic epoxy resin, aliphatic epoxy resin, etc. are used. Also, the surface tension is 20 dyne/am
If it is smaller, the interlayer adhesion will be lowered when applying the top coat, and peeling will occur more easily.
If it is larger than cm, the wettability of the plating surface will decrease and the adhesion to the material will deteriorate.

The chrome-plated plate used in the present invention refers to a general chrome-plated plate that is applied on a plating plate, such as ABS, in a normal process.

The undercoating paint has a vehicle component and an organic solvent as its main components, and may further contain coloring pigments, extender pigments, other additives, etc. as necessary.

The vehicle component is suitable even if it is a thermoplastic resin or a two-component urethane system having a leaf group and using polyisocyanate as a curing agent, as long as it is within the above range. The polyisocyanates used at this time include toluene diisocyanate, diphenylmethane diisocyanate, methylene diisocyanate, xylene diisocyanate,
Hexamethylene diisocyanate, isophorone diisocyanate, triphenylmethane triisocyanate,
Suitable are phenylene diisocyanate, lysine diisocyanate, the above-mentioned methylol adducts or 3-5ji derivatives, and mixtures thereof.

Furthermore, the undercoat should be applied in a wet state after painting or
After drying for 20 to 60 minutes at 100°C to 100°C, a top coat may be applied.

On the other hand, the paint used as the top coat may be any general two-component polyurethane paint, and acrylic polyols and polyester polyols are particularly preferred, and 50-100'CX2
Drying conditions of 0 to 100 minutes are suitable.

[Example] The present invention will be explained below with reference to Examples.

Example ■, Sample preparation (1) Chrome plated plate (a) Chrome plated plate on ABS that has been used for more than 5 days (manufactured by Japan Test Panel Co., Ltd.) (b) Chrome plated plate on ABS at a concentration of 1 part Fully sprayed plate (2) Brimer (all parts by weight are shown) (a) Glycidyl-containing polyolefin resin (LPM 65 manufactured by Asahi Denka Co., Ltd.)
0-50X, Tg: 0℃, surface tension crab 26 dy
(b) Polyester resin (Toyobo Vylon 500, T
g: 4°C, surface tension 26 dyne/cm, elongation rate 1100%) 100 parts, 70 parts methyl ethyl ketone,
Epicoat 828 (
(C) Paint consisting of 10 parts of Shell Chemical's epoxy resin), 20 parts of titanium oxide, and 50 parts of Kijiroll (C) Paint with 0 parts of Epicoat 828 in (b) above (d) Polyester resin (Vylon 500) in (b) above
) instead of acrylic resin (I) (7g 15℃, surface tension 38 dyne/cm, elongation rate 30%) (e) In the above (b), polyester resin (Vylon 500
) Paint using acrylic resin (II) (7g8℃, surface tension 38 dyne/cm, elongation rate 85%) Polyurethane paint) (4) Acrylic resin (I)
Composition of (rI) (5) Manufacturing method of brimer paint The total amount of each resin, titanium oxide, and solvent was stirred uniformly for 20 minutes, then dispersed for 30 minutes with a paint conditioner, and it was confirmed that the particle size was 10μ or less. The glass peas are then filtered and used as paint.

H. Examples and Comparative Examples The samples prepared in the above process were coated using the combinations shown in Table 1 in the following steps: chrome plated board - brimer (10μ) - 5 minute intervals - topcoat (30μ) - drying at 80°C for 30 minutes. .

(2) Performance test results Table 2 shows the results of a performance test using the coated plates coated in the above Examples and Comparative Examples.

(Test method) ■Adhesiveness: 1m/m grid test ■Warm water resistance: 80°C x 120t (r Adhesion test after hot water immersion test Adhesion test after warm water immersion test (evaluation) 0 No abnormalities ×, plagiarism \

Claims (1)

[Claims] 1. The chrome plated surface has (1) a surface tension of 20 to 32 d.
yne/cm, Tg is -10°C to 10°C, a coating film elongation rate is 80% or more, and an undercoat containing a resin (A) having a glycidyl group, or (2) a surface tension of 20 to 32 dy.
ne/cm, Tg is -10°C to 10°C, coating elongation rate is 8
0% or more of resin (B) and resin having glycidyl group (
Apply a base coat containing C) and then apply 2 as a top coat.
A method for forming a coating film characterized by applying a liquid polyurethane resin paint