JPS6383176A - Primer composition - Google Patents

Abstract

PURPOSE:To improve the adhesion of resins to metal in coating the metal with the resins, by forming a primer compsn. from a high-silicon cast iron powder and a binder. CONSTITUTION:This primer compsn. is suitable for use in coating a metal with a resin and contains a high-silicon cast iron powder and a binder. As the binder, at least on org. binder selected from among crosslinking oligomers (e.g., a polyimide, a polyamide imide, an epoxy resin, etc.), linear high-molecular materials (e.g., a polyether sulfone, a polysulfone, a polyether imide, nylon, etc.) and fluororesins and/or at least one inorg. binder selected from among lithium polysilicate, amine silicate, an alkyl silicate and silicon dioxide colloid are/is used. It is preferred that the binder contains the same resin as that for use in coating metals. 15-900pts.wt. binder is used per 100pts.wt. high-silicon cast iron powder.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an undercoat composition that provides a resin coating layer with excellent adhesion to metal.

(Prior Art) When coating a metal with a resin, there is, for example, a method of subjecting the metal to a chemical conversion treatment in order to improve the adhesion of the resin to the metal.

Zinc phosphate or the like is used for chemical conversion treatment.

However, a treated layer formed by chemical conversion treatment lacks heat resistance. For this reason, after coating the metal surface with a chemical conversion treatment with a resin, the treatment layer deteriorates due to the heating during baking.
Adhesion between resin and metal is impaired.

In order to solve these drawbacks, a method has been proposed in which the metal is undercoated using an undercoat.

Japanese Patent Publication No. 59-44912 discloses an organic primer such as a polyamide-imide resin or a polyimide resin as an undercoat composition for coating a substrate with a fluororesin. However, since these organic primers are composed only of organic materials, there is a large difference in coefficient of linear expansion from that of metals. Therefore, if the resin is coated after undercoating with this organic primer, long-term adhesion between the resin and the metal cannot be obtained. As an undercoat composition, a mixture of finely divided particles of zinc and a heat-stable binder such as a polyalkyl silicate (disclosed in JP-A-49-128836), a granular aluminum powder, a 9-granular zinc powder, and an alkyl silicate condensate are used. A composition containing (JP-A-54-2934)
(disclosed in Publication No. 0) is also known. A low price composition in which metal powder, especially aluminum powder, is added to polyalkyl silicate or the like improves the adhesion between fluororesin or polyphenylene sulfide resin and metal. However, since aluminum and zinc lack corrosion resistance and water resistance, lasting adhesion between resin and metal cannot be obtained. Instead of metal,
Even if metal oxides such as iron oxide and titanium oxide are used, the corrosion resistance of the coating layer can be obtained, but the adhesion to the metal is insufficient.

(Problems to be Solved by the Invention) The present invention solves the above conventional problems, and its purpose is to provide an undercoat composition that provides a resin coating with excellent adhesion to metal. It's about doing.

(Means for Solving the Problems) The present invention uses high-silicon cast iron powder in place of the metals and metal oxides contained in conventional undercoating compositions.
Excellent adhesion to metal and corrosion resistance.

A subbing layer with water resistance is thereby obtained.

Adhesion between resin and metal is improved. It was completed based on the inventor's knowledge.

The undercoat composition of the present invention is an undercoat composition for coating metal with resin, and contains high silicon cast iron powder and a binder, thereby achieving the above object.

High-silicon cast iron is cast iron containing about 14 to 17% silicon, and has excellent heat resistance, Et corrosion resistance, and chemical resistance. High silicon-molybdenum cast iron containing about 3% molybdenum is also used. The composition of high-silicon cast iron is shown in the table below, for example.

(Margin below) The average particle size of the high-silicon cast iron powder is 0.1 to 100 μm.

Preferably it is in the range of 0.5 to 20 μm. 100μ
If it exceeds m, the dispersibility of the high-silicon cast iron powder in the undercoat composition decreases. High-silicon cast iron with such a grain size may be less than 0.1 μm.

Usually not available.

The binder may include 5, for example, organic binders such as polyimide, polyamideimide, epoxy resin, phenol resin,
Crosslinkable oligomers such as polyester; polyether sulfone, polysulfone.

Linear polymers such as polyparabanic acid, polyetherimide, polyetheretherketone, polyphenylene sulfide, and nylon; and fluorine resins. Inorganic binders include lithium polysilicate, amine silicate, and alkyl silicate.

Examples include silicon dioxide colloid. The binder includes
It is preferable that the resin contains the same type of resin as the resin coated on the metal. For example, if the coating resin is a fluororesin, the fluororesin is used as the binder.

For 100 parts by weight of high-silicon cast iron powder, the amount of binder is 15 to 9
00 parts by weight, preferably in the range of 25 to 400 parts by weight. If the amount is less than 15 parts by weight, the adhesion of the undercoat composition to metal will decrease. If it exceeds 900 parts by weight, lasting adhesion cannot be obtained.

The basecoat composition of the present invention is suitable for use on metals (e.g. iron).

Used as an undercoat to coat resin on materials (aluminum, stainless steel, various alloys). Examples of the resin include resins used in the above organic binders, such as fluororesins, engineering plastics, special engineering plastics, epoxy resins, and phenolic resins.

Using this undercoat composition, a metal is coated with a resin in one, for example, two steps, to form a coated metal body.

A metal surface is coated with an undercoat composition of the present invention.

The coated surface is then baked to form an undercoat layer. The baking temperature is preferably 100 to 250°C. The layer thickness of the undercoat layer is 5 to 100 μm, preferably 10 to 30 μm.
It is assumed to be in the μm range. If it is less than 5 μm, the undercoat layer will not be formed uniformly, and pinholes and cracks will likely occur. When it exceeds 100 μm.

Adhesion between the undercoat layer and metal decreases. In the undercoat layer,
Further resin is applied. The painted surface is baked,
A resin coating layer is formed. The thickness of the coating layer is 50 to 200
0 μm, preferably in the range of 250 to 750 μm. If it is less than 50 μm, the coating layer will not be formed uniformly and pinholes and cranks will likely occur. 2000μm
If it exceeds this value, it takes time for baking, etc., and foaming occurs, making it impossible to obtain a dense resin coating layer.

The coated metal body thus obtained is suitably used as a material requiring chemical resistance, such as pipes and containers for chemical plants.

(Example) The present invention will be described below with reference to examples.

20 parts by weight Tetrafluoroethylene-hexafluoropropylene copolymer (pulverized to an average particle size of 10 μm or less by freeze-pulverization) 5 parts by weight Amino bismaleimide resin 51 ! Amount N-Methyl-2-pyrrolidone 10 parts by weight The above formulation was blended and mixed uniformly to prepare an undercoat composition.

100 dragons x 100 tablets x 31 pieces of iron plate
After the last treatment, compressed air was blown to clean it.

The above-mentioned undercoat composition was applied to this iron plate with a brush.

Dry the coated surface at 200°C for 1 hour and at 380°C for 30 minutes.

Baked. The average layer thickness of the obtained undercoat layer was 20 μm. This undercoat layer is coated with the above tetrafluoroethylene.
Hexafluoropropylene was powder coated at an electrostatic voltage of 60 KV, defoamed at 340° C. for 1 hour, and then cooled with water to form a resin coating layer. The average thickness of the coating layer was 500 μm.

The adhesion between the resin coating layer of the obtained coated metal body and the metal was 1
Evaluation was made as follows.

(11 Peeling test Paint film peeling test (90° building strength test, JIS K-
6555), the fJ+separation strength of the coated metal body was measured at room temperature. As a result, the 90° peel strength was 1.6 kg/
It was cm.

(2) Hot water test After the coated metal body was immersed in hot water at 95°C for 100 hours, the state of the coating layer was observed, and no abnormality was observed.

Disaster dish l Ethyl silicate 40 (Condensation product of 5 molecules of ethyl silicate monomer, content calculated as SiO□ is 4
1 part by weight of IN salt and 40 parts by weight of ethyl alcohol were placed in a glass reactor, and while stirring, 11121 parts by weight of IN salt and 9 parts by weight of water were added.
It was dripped continuously over time. After the dropwise addition was completed, the mixture was stirred for an additional 3 hours and left to stand for 20 hours to obtain an ethylsilicate condensate solution. This ethylsilicate condensate solution contains
It contained 50% by weight of ethylsilicate condensate.

Ethyl silicate condensate solution 15 parts by weight High silicon cast iron powder 40 parts by weight Butyl cellosolve 5 parts The above formulations were blended and mixed to obtain an undercoat composition.

Using this undercoat composition, an undercoat layer was formed on an iron plate in the same manner as in Example 1. However, the baking time at 200°C was 30 minutes. This undercoat layer is powder coated with polyphenylene sulfide resin.

After baking at 380° C. for 40 minutes, it was cooled with water to form a resin corrugated layer. The layer thickness of the coating layer was 500 μm.

The adhesion between the resin coating layer of the obtained coated metal body and the metal was determined by
When evaluated using the same method as in Example 1, the peel strength was 3.5 kg/cm, and no abnormalities were observed in the hot water test.

A coated metal body was formed in the same manner as in Example 1, except that high-silicon cast iron powder was not used in the undercoating composition.

The adhesion between the resin coating layer of the obtained coated metal body and the metal was determined by
When evaluated by the same method as in Example 1, the peel strength was 1.3 kg/cn+, and some blisters occurred in the hot water test.

A coated metal body was formed in the same manner as in Example 1, except that 5 parts by weight of titanium oxide was added to the base coating composition in place of the high-silicon cast iron powder.

The adhesion between the resin coating layer of the obtained coated metal body and the metal was determined by
When evaluated by the same method as in Example 1, the peel strength was 1.2 kg/cm, and some blisters occurred in the hot water test.

Comparison ±1 A coated metal body was formed in the same manner as in Example 1, except that 10ififf 1 part of aluminum powder (average particle size 10 to 20 μm) was added to the undercoat composition in place of the high-silicon cast iron powder. .

The adhesion between the resin coating layer of the obtained coated metal body and the metal was determined by
When evaluated by the same method as in Example 1, the peel strength was 1.6 kg/an, and some blisters occurred in the hot water test.

Comparison ■↓ An IW metal body was formed in the same manner as in Example 2, except that the iron plate was treated with a phosphoric acid solution without using an undercoat composition.

The adhesion between the resin coating layer of the obtained coated metal body and the metal was determined by
When evaluated by the same method as in Example 1, the peel strength was 2.0 kg/am, and peeling of the coating layer occurred in some parts in the hot water test.

As is clear from the Examples and Comparative Examples, according to the undercoat composition of the present invention, a coated metal body with excellent adhesion between the resin coating layer and the metal can be obtained. This coated metal body does not peel off the coating layer or generate blisters even in peel tests and hot water tests. A coated metal body formed using an undercoat composition that does not contain high-silicon cast iron powder or an undercoat composition that contains metal powder or metal oxide instead of high-silicon cast iron powder lacks the peel strength of the resin coating layer. Blisters occur during hot water tests. Conventional coated metal bodies obtained by phosphate treatment also have low peel strength of the resin coating layer, and part of the coating layer peels off in a hot water test.

(Effects of the Invention) Since the undercoat composition of the present invention contains high-silicon cast iron powder as described above, it has good adhesion to metal. Therefore, by coating a metal surface with a resin using this undercoat composition as an undercoat, a coated metal body with excellent adhesion between the resin and the metal can be obtained.

This coated metal body is suitably used as a material that requires chemical resistance, such as pipes and containers for chemical plants.

Applicant: Akio Yasui, Chairman of the High Performance Resin New Manufacturing Technology Research Association

Claims (1)

[Scope of Claims] 1. An undercoat composition for coating metal with a resin, the undercoat composition containing high-silicon cast iron powder and a binder. 2. The binder is a crosslinkable oligomer such as polyimide, polyamideimide, epoxy resin, phenol resin, polyester; polyethersulfone, polysulfone, polyparabanic acid, polyetherimide, polyetheretherketone, polyphenylene sulfide, nylon, etc. A linear polymer; and at least one organic binder selected from fluororesin and/or at least one inorganic binder selected from lithium polysilicate, amine silicate, alkyl silicate, and silicon dioxide colloid. The undercoat composition according to item 1. 3. The undercoat composition according to claim 1, wherein the binder is contained in an amount of 15 to 900 parts by weight based on 100 parts by weight of the high-silicon cast iron powder. 4. The resin is at least one of linear polymers such as polyethersulfone, polysulfone, polyparabanic acid, polyetherimide, polyetheretherketone, polyphenylene sulfide, and nylon; and a fluororesin, and is a binder. The undercoat composition according to claim 1, which is the same resin as that contained in the undercoat composition.