JPH03199278A - Primer composition for polyamide and coated metal produced by using the same - Google Patents

Abstract

PURPOSE:To provide the subject composition composed of an epoxy resin oligomer, polyamide powder and a specific liquid elastomer, having excellent resistance to hot water and suitable for pipe, joint, etc., for water and hot-water supply system. CONSTITUTION:The objective composition is composed of (A) an epoxy resin oligomer of e.g. bisphenol-type, novolak-type or glycidyl ester-type, (B) polyamide power having particle diameter of <=300mum (especially <=100mum) and preferably composed of nylon 11, nylon 12 or nylon 12, 12 and (C) an elastomer having carboxyl group, amino group, mercapto group or epoxy group and exhibiting liquid state at normal temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a primer composition for polyamide and a coated metal body using the same.

(Prior Art) Metal products are coated with resin to prevent them from rusting and to make their surfaces beautiful. As the coating resin, it has been proposed to use fluororesin (Japanese Patent Publication No. 57-18557), polyphenylene sulfide, aromatic polyether sulfone resin (Japanese Patent Application Laid-Open No. 54-34335), and the like.

Although these resins have excellent heat resistance, water resistance, chemical resistance, and corrosion resistance, they have the drawbacks of being expensive and having poor adhesion to metals.

On the other hand, although polyamide does not have the same corrosion resistance as the above-mentioned resins, it has some corrosion resistance and is cheaper than the above-mentioned resins, so it has been used for coating metal products. . However, polyamide has poor adhesion to metal surfaces, and when a boria-adsorbed layer is provided directly on a metal surface, the polyamide layer immediately peels off from the metal surface. Therefore, in order to strongly adhere the polyamide to the metal surface, an undercoat layer was interposed between the metal surface and the polyamide. Brimer has been used as an undercoat in this way.

Various types of brimers for polyamide have been proposed so far, such as a mixture of epoxy resin and phenol resin (Japanese Patent Application Laid-open No. 35740/1983), a mixture of diene polymer and magnesium oxide ( Special Public Service 1977
-5045) have been proposed. However, these primers have the disadvantage that although they strongly adhere polyamide to metal surfaces immediately after application, they gradually lose their adhesive strength; that is, under conditions where the polyamide is repeatedly exposed to hot water. While using below,
This primer gradually lost its adhesion and caused the polyamide to peel from the metal surface. Therefore, there was a desire for a primer that would have even stronger adhesion and would maintain that adhesion for a long time.

(What the invention attempts to solve!!i!!) This invention was made in an attempt to provide a polyamide brimer free from the above-mentioned drawbacks.In other words, this invention provides a polyamide coating layer on a metal surface. When providing a metal surface, it is interposed between the metal surface and the polyamide to strongly adhere them. For example, even if the polyamide is repeatedly exposed to hot water, heated, and cooled, the polyamide This was done in an attempt to provide a brimer that would not peel off from the metal surface.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the inventor made a compound by blending various substances, adhered this composition to polyamide and metal, and bonded the composition to polyamide and metal. The force was measured. As a result, it has been found that a composition containing the three components of epoxy resin, polyamide, and elastomer satisfies the above requirements.

In addition, in this case, it is preferable to use an oligomer as the epoxy resin, a powder form as the polyamide, and an elastomer that has a functional group that reacts with the epoxy group in the epoxy resin and that can be used at room temperature. I found out that I should choose a liquid version to use. moreover,
The functional groups mentioned above include carboxyl group, amino group,
I learned that I should choose between a mercapto group and an epoxy group. This invention was completed based on such knowledge.

(Summary of the Invention) This invention comprises (a) an epoxy resin oligomer;
polyamide powder, (c) carboxyl group, amino group,
This invention relates to a primer base material for polyamide which is composed of an elastomer having a mercapto group or an epoxy group and which is liquid at room temperature.

The present invention also relates to a coated metal body in which the above-mentioned brimer composition is applied to the surface of the metal body and a polyamide layer is formed thereon.

Any epoxy resin oligomer that can be used in this invention can be used as long as it can be used to bond structural materials. Such oligomers include, for example, bisphenol-type epoxy resins and novolac-type epoxy resins.

These include glycidyl ester-based epoxy resins, glycidyl ester-based epoxy resins, glycidyl amine-based epoxy resins, and heterocyclic epoxy resins.

The polyamide powder used in this invention is a linear polymer powder having acid amide bonds, which is produced by bonding an aliphatic carboxylic acid and an aliphatic amine. Polyamides include nylon 6, nylon 6.6, nylon 7, nylon 9, nylon 11, nylon 12, and nylon 12.1.
2, nylon 6.9, nylon 6.10, nylon 6.
There are various types such as 12, and any of these can be used. Among these, nylon 11, nylon 12, and nylon 12.12, which have a low water absorption rate and have little change in physical properties due to water absorption, are particularly preferred.The particle size of the powder is preferably 300 μm or less, especially 100 μm or less. This is preferable because if the particle size is 300 IIm or more, it becomes difficult to disperse the polyamide well in the brimer, and the adhesion between the brimer layer and the coating layer decreases.

The elastomer used in this invention is liquid at room temperature and has a functional group that reacts with an epoxy resin. The functional group that reacts with an epoxy resin refers to a group that can react with an epoxy group, and specifically refers to a carboxyl group, an amino group, a mercapto group, an epoxy group, and the like. Such elastomers include, for example, acrylonitrile-butadiene copolymer, 1,2-polybutadiene, 4-polybutadiene, polyester,
These include chloroprene rubber, silicone oil, etc., into which functional groups such as carboxyl, amino, mercapto, and epoxy groups that react with epoxy groups have been introduced, and sulfide rubber.

The functional group may be introduced in the middle of the trunk or at the end.

Next, the proportions of the three precepts (a), (b), and (c) in this invention will be described. Of the three precepts, (b) polyamide powder only exists in a mixture with other components,
Since the oligomer (al) and the elastomer (c) undergo a chemical reaction, the mutual amounts of (a) and (c) must be determined on the premise of a chemical reaction.

In this invention, the mutual blending ratio of the oligomer (a) and the elastomer (c) is determined by considering the value of the following formula 1.

However, when the functional group in Formula 1 is an amino group, the number of functional groups is calculated based on the number of active hydrogens.

The reason why formula 1 should be used is that if the value of 2 exceeds 1, the oligomer and unreacted elastomer will still exist in the composition after curing, which will reduce the adhesion between the brimer and the metal. Yes, and conversely, the value of formula 1 is 0.01
If it is lower than this, the elastomer cannot be uniformly dispersed in the composition, and therefore, uniform stress relaxation cannot be obtained and adhesion deteriorates.

When determining the blending ratio within the range of Formula 1, it is necessary to add an epoxy resin curing agent because unreacted oligomers will be present in the cured brimer. As the curing agent, those commonly used as curing agents for epoxy resins can be used. For example,
Amine-based curing agents, boria [noamide-based curing agents, acid anhydride-based curing agents, basic active hydrogen compounds, imidazoles, Lewis acids, breathed acids, polymercaptan-based curing agents, etc. can be used.

In this invention, the blending ratio of the oligomer (a) and the polyamide powder (b) is (oligomer) to (polyamide powder) by weight.The reason is that if the amount of oligomer is too large, the brimer layer This is because the adhesion with the coating layer decreases,
On the other hand, if the amount of polyamide powder is too large, the adhesion between the brimer layer and the metal will decrease.

The brimer composition according to the present invention may contain an inorganic filler if necessary. Inorganic fillers include metals, metal oxides, glass, carbon, ceramics,
Inorganic salts and the like can be used. As the metal, zinc, nickel alloy, stainless steel, cast iron, etc. can be used. As the metal oxide, alumina, iron oxide, titanium oxide, zirconium oxide, talc, chromium oxide, nickel oxide, etc. can be used. As the ceramic, silicon nitride, titanium nitride, boron carbide, silicon carbide, etc. can be used in addition to the metal oxides exemplified. As the inorganic salt, potassium titanate, barium sulfate, etc. can be used.

Further, a solvent can be added to the brimer Mi bottom according to the present invention, if necessary. The WI agent is (a)
It must be soluble in both the oligomer (1) and the elastomer (c), and not corrosive to the metal base material.

When using the primer composition according to the present invention, it is necessary to use polyamide as a coating used thereon. The polyamide used as the coating is an aliphatic polyamide, which is a linear polymer having acid amide bonds. For example, nylon 6, nylon 6.
6, nylon 7, nylon 9, nylon 11. Nylon 12, Nylon 12.12, Nylon 6.9, Nylon 6.10. It is nylon 6.12. Among these, nylon 11, nylon 12, and nylon 12.12 are particularly suitable because they have a low water absorption rate and, therefore, change in physical properties due to water absorption is small.

When coating a metal body with the primer composition according to the present invention, the surface of the metal body is first subjected to pretreatment such as sandblasting, degreasing, and chemical conversion treatment. Thereafter, the composition of the present invention is applied and dried to form a primer layer. The thickness of the primer layer at this time is 55-10
0tI, but the preferred one is 10-3
It is 0 μm. The reason is that when the thickness is less than 5 μm,
This is because it becomes difficult to uniformly form the primer layer, and pinholes and cracks are therefore likely to occur.On the other hand, if the thickness exceeds 100 μm, the adhesion between the primer layer and the metal decreases.

A polyamide is coated on top of the primer layer.

Coating can be done in various ways, for example by dispersing the polyamide in a solvent and applying it as a suspension, or by applying it as a powder and then baking it by heating it above the melting point of the polyamide. The thickness of the coating layer is 50-200
0 μm1, preferably 250-2000 μm. The reason for this is that if the thickness is less than 50 μm, the coating layer will not be formed uniformly and pinholes and cracks will easily occur.On the other hand, if it exceeds 2000 pm, it will not only take longer to bake, but also cause foaming. This is because it becomes difficult to form a dense coating layer.

(Effects of the Invention) Since the primer composition according to the present invention uses an epoxy resin, it firmly adheres to metal, and since it uses polyamide, it firmly adheres to the polyamide coating layer. In addition, for this primer composition, an epoxy resin in the form of an oligomer is selected and used, and an elastomer is selected and used that has a carboxyl group, an amino group, a mercapto group, or an epoxy group and is liquid at room temperature. As a result, the oligomer and elastomer can be mixed uniformly, and the epoxy groups of the oligomer and the functional groups of the elastomer can then react with each other to form a uniform, elastic primer. can. Furthermore, since we decided to use polyamide in powder form, it is possible to uniformly disperse the polyamide while the oligomer and elastomer react to form the primer. A primer layer with adhesive elasticity can be formed.

According to the invention, a layer of polyamide can be formed on the primer layer thus formed to obtain a strong coated metal body. This coated metal body not only has a primer layer that firmly adheres to the metal and polyamide, but also contains an elastomer, so it has moderate elasticity, and therefore the polyamide and metal have a low expansion coefficient against heat. Even if it differs greatly, the primer layer relieves stress, making it difficult for the polyamide coating to peel off from the metal. Therefore, since the coated metal body of the present invention has excellent resistance to hot water, it exhibits particularly excellent performance when used for corrosion protection of metal surfaces that come into contact with hot water, such as pipes and joints for water supply. It is something to do.

(Example) Examples and comparative examples will be given below to specifically describe the advantages of this invention. In the following, parts are simply referred to as parts by weight.

Example 1 I created the following 11 powerful items.

Epoxy resin oligomer (manufactured by Yuka Shell Epoxy Co., Ltd., Epicoat 828, bisphenol type, epoxy weight 1190) 100 parts Elastomer (manufactured by Ube Industries, Ltd., Hiker CTBN, acrylonitrile-butadiene copolymer with carboxyl groups at both ends, carboxyl group equivalent weight 2000) ) 50 parts Epoxy resin curing agent (4,4'-diaminodiphenylsulfone, active hydrogen equivalent To') 35 parts Polyamide powder (manufactured by Nippon Rilsan Co., Ltd., FP840, nylon-11 powder, particle size 63 μm or less) 30 parts Solvent ( 200 parts of acetone) The above mixture was thoroughly mixed to prepare a brimer composition.

A 100 x 100 x 3 square iron plate was subjected to Grid Plast treatment and then cleaned by blowing compressed air. The above-mentioned brimer composition was applied with a brush to one side of this iron plate, and the coated surface was dried at 230°C for 30 minutes to perform baking.

The thickness of the obtained primer layer was 25 μm on average.

Nylon-11 powder (manufactured by Ube Industries, Ltd., FP840, particle size of 63 μm or less) was electrostatically coated on this brimer layer in two parts. Each coat was flowed out at 230''C for 5 minutes, and then allowed to cool at room temperature to form a coated metal body.

The average thickness of the coating layer was 650 μm.

The coated metal body thus obtained was tested for normal adhesion and hot water resistance. Normal adhesion was determined by making incisions in the resin coating layer of the coated metal body with a knife at two square intervals that reached the metal surface, and then observing the condition of the resin coating layer. In addition, hot water resistance is measured by using the coated metal body as a partition and immersing the coated layer side in hot water at 95°C and the metal side in hot water at 65°C for 200 hours. We observed whether this was occurring.

The test results showed that the adhesion under normal conditions was good, and there was no change at all in hot water resistance.

Note that Y in this example is 0.047
5, and Z (polyamide powder) was 62.5/37.5. Hereinafter, these ratios will be expressed as Y and Z.

Example 2 In Example 1, 100 parts of polysulfide rubber (manufactured by Toshi Thiokol Co., Ltd., Thiokol LP-3, mercapto equivalent 500) was used instead of the acrylonitrile-butadiene copolymer having carboxyl groups at both ends as the elastomer, and an epoxy resin was used. As a curing agent, 10 parts of 2.4.6-tris(dimethylaminomethyl)phenol was used instead of 4.4'-diaminodiphenylsulfone, and an additional 50 parts of talc (manufactured by Nippon Talc Co., Ltd., 5WE) was used. A coated metal body was obtained by processing in exactly the same manner as in Example 1 except for the addition of the following ingredients, and this was further tested.

Normal adhesion was good, and there was no change in hot water resistance.

In this example, Y was 0.380 and Z was 62.5/37.5.

Example 3 Same as Example 2 except that 50 parts of polybutadiene having an epoxy group in the molecule (manufactured by Nippon Soda Co., Ltd., BFlooo, epoxy equivalent weight 213) was used instead of polysulfide rubber as the elastomer. It was carried out in exactly the same way.

Normal adhesion was good, and there was no change in hot water resistance.

In this example, Y was 0.446 and Z was 62.5/37.5.

Example 4 In Example 1, nylon-1 was used as the polyamide powder.
Instead of 1, use nylon-12 (manufactured by Ube Industries, Ltd., 301
4 U, particle size of 100 μm or less) was used in the same amount,
Also, instead of nylon-11 as the N-resin, 25
Example 1 was carried out in exactly the same manner as in Example 1, except that the same amount of nylon-12 containing talc at % by weight was used.

The above-mentioned nylon-12 containing 25% by weight of talc is
Talc (SWE) manufactured by Nippon Talc Co., Ltd. was added to the above 3014 U manufactured by Ube Industries, and the talc content was 25% by weight.
A &Il bottom product was prepared, which was melt-kneaded and then freeze-pulverized to a particle size of 200 μm or less.

Normal adhesion was good, and there was no change in hot water resistance.

In this example, Y was 0.475 and Z was 62-5/37.5.

Comparative Example 1 The same procedure as in Example 1 was carried out except that no brimer was applied.

Normal adhesion was poor, hot water resistance was poor, and blisters occurred at 30% and 0%.

Comparative Example 2 The same procedure as in Example 1 was carried out except that polyamide powder was not used in the primer composition.

Regular B adhesion was good, but hot water resistance was poor and blisters occurred at 10%.

In addition, Y in this comparative example was 0.475, and Z was 10010.

Comparative Example 3 In Example 1, no elastomer was used,
Further, the same procedure as in Example 1 was carried out except that the amount of 4,4'-dimethyldiphenylsulfone used as the epoxy resin faeces agent was increased to 36.8 parts.

Although the normal adhesion was good, the hot water resistance was poor and 6% of blisters occurred.

In addition, Y in this comparative example is 0, and 2 is 62.5/
It was 37.5.

Claims (1)

[Claims] 1. For polyamides consisting of (a) epoxy resin oligomers, (b) polyamide powder, and (c) elastomers that are liquid at room temperature and have carboxyl groups, amino groups, mercapto groups, or epoxy groups. Primer composition. 2. A coated metal body obtained by applying the primer composition according to claim 1 to the surface of the metal body and forming a polyamide layer thereon.