JPH0150595B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an ethylene copolymer coated metal body. More specifically, the present invention relates to a method for manufacturing a coated metal body that has excellent low-temperature adhesion and heat-resistant adhesion.

Polyester-coated metal bodies, especially polyethylene-coated steel pipes, have excellent cold resistance, corrosion resistance, water resistance, weather resistance, and impact resistance, so they are used as steel pipes for transporting gases or liquids such as gas, oil, and water, or for cable protection. Widely used as steel pipes. on the other hand,
Since polyethylene has poor adhesion to metals, there are methods of chemical conversion treatment of the metal surface, methods of blasting, methods of applying adhesives, methods of oxidizing polyethylene, and methods of copolymerizing polyethylene with acrylic acid, maleic anhydride, etc. Alternatively, a method of grafting and denaturation has been proposed.

However, in the method using maleic anhydride-modified polyethylene, it is necessary to preheat the metal body to 120°C or higher in order to obtain sufficient adhesive strength. There is a strong need for the development of a method that can obtain adhesive strength.

The present inventors have discovered that preheating of the metal body is not possible under such circumstances.
In order to develop a method that can obtain sufficient adhesive strength at temperatures below 100°C, we conducted various studies and developed modified ethylene/α, which is a specific low-crystalline ethylene/α-olefin copolymer modified with an unsaturated carboxylic acid or its anhydride.
- It was found that by using an olefin copolymer, a laminate with sufficient adhesive strength not only at room temperature but also at high temperatures of around 50°C can be obtained, which led to the completion of the present invention. .

That is, the present invention provides a metal body preheated to 100° C. or lower, which is graft-modified with an unsaturated carboxylic acid or its anhydride, has an ethylene content of 88 to 95 mol%, an X-ray crystallinity of 10 to 25%, and a density.
A modified ethylene/α-olefin copolymer (A) of 0.880 to 0.900 g/cm ³ and a melting point of 65 to 90°C is bonded by heating at a temperature equal to or higher than the melting point of the copolymer (A), The present invention provides a method for producing an ethylene copolymer-coated metal body having excellent low-temperature adhesion and heat-resistant adhesion. The modified ethylene/α-olefin copolymer (A) (hereinafter sometimes referred to as modified ethylene copolymer) used in the method of the present invention is ethylene/α-olefin copolymer (A) (hereinafter sometimes referred to as modified ethylene copolymer).
- An olefin copolymer (B) grafted with an unsaturated carboxylic acid or its anhydride, or a blend of the grafted product and an unmodified ethylene/α-olefin copolymer (B), Ethylene content of 88 to 95 mol%, preferably 91
95 mol%, X-ray crystallinity 10 or more
25%, preferably 15 to 25%, density (ASTM
D1505) is 0.880 to 0.900 g/cm ³ , preferably
0.890 to 0.900g/ ^cm3 and melting point 65 to 90
℃, preferably in the range of 70 to 90℃, and preferably the amount of unsaturated carboxylic acid or its anhydride unit grafted to the modified ethylene copolymer (A)
0.01 to 1.0% by weight, preferably a melt flow rate (MFR: ASTM D1238, E) in the range of 0.1 to 30 g/10 min.

In the modified ethylene copolymer, the ethylene content, which has a correlation with the crystallinity by X-rays, the density, and the melting point, is less than 88 mol%,
X-ray crystallinity less than 10%, density 0.880
If the melting point is less than g/cm ³ and the melting point is less than 65°C, a laminate with sufficient adhesive strength can be obtained even if the preheating temperature of the metal body is 100°C or less, but the heat resistance is poor, such as
In an atmosphere of 50°C, only a small value of adhesive strength can be obtained, making it impractical. On the other hand, the ethylene content is 95 mol%, the X-ray crystallinity is 25%, and the density is 0.900.
If the g/cm ³ and melting point exceed 90°C, sufficient adhesive strength cannot be obtained if the preheating temperature of the metal body is 100°C or lower.

In addition, those with a grafting amount of unsaturated carboxylic acid or its anhydride units of less than 0.01% by weight tend to have low adhesive strength, while those with a grafting amount of more than 1.0% by weight have high water absorption and are higher than the melting point. Foaming may occur when coating a metal object at a temperature of .

The ethylene/α-olefin copolymer (B) that is the base material of the modified ethylene copolymer (A) used in the method of the present invention usually has an ethylene content of 88 to 95 mol%, preferably 91 to 95 mol%. 95 mol%, X-ray crystallinity 10 to 25%, preferably 15 to 25%
25%, a density of 0.880 to 0.900 g/cm ³ , preferably 0.890 to 0.900 g/cm ³ , and a melting point of 65 to 65%.
90℃, preferably in the range of 70 to 90℃,
The α-olefin usually has 3 or more carbon atoms, preferably 4 to 20 carbon atoms, and specifically includes, for example, propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, It is a copolymer of ethylene and one or more α-olefins such as 1-hexene, 1-octene, 1-decene, 1-tetradecene, and 1-octadecene.

In addition, the melting point (Tm) of the copolymer, etc. in the present invention
is a value measured according to ASTM D3417.

Specific examples of the unsaturated carboxylic acid or anhydride thereof to be grafted onto the ethylene/α-olefin copolymer (B) include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, citraconic anhydride, Examples include itaconic acid and itaconic anhydride. Among these, unsaturated dicarboxylic acids are preferred, and maleic anhydride is particularly preferred.

Various known methods can be used to graft the unsaturated carboxylic acid or its anhydride onto the ethylene/α-olefin copolymer (B). For example, a method can be adopted in which both are heated to a high temperature in the presence or absence of a solvent, with or without the addition of a radical initiator. Other vinyl monomers such as styrene may be present in the graft reaction. The modified ethylene copolymer (A) thus obtained is used as it is or after blending with the unmodified ethylene/α-olefin copolymer (B). In either case, it is preferable that the unsaturated carboxylic acid or its anhydride be present in the copolymer in an amount of about 0.1 to 1.0% by weight as a unit, as described above.

The metal bodies used in the method of the present invention are plate-shaped, cylindrical, tubular, rod-shaped, or other shaped bodies made of iron, copper, aluminum, nickel, cobalt, tin, zinc, or alloys containing these as main components. It is. The modified ethylene copolymer is added to the metal body.
When coating (A), it is sufficient if the surface of the metal body is clean, but it is more effective to perform blasting, pickling, chemical conversion treatment, etc. Further, the surface of the metal body may be coated with a primer such as an epoxy resin adhesive in advance, but when using such a primer, it is preferable to use a low temperature curing epoxy resin adhesive. . When a high temperature curing epoxy resin adhesive is used, the method of the present invention coats the modified ethylene copolymer (A) at a preheating temperature of 100°C or less, so the epoxy resin adhesive is sufficiently cured. In some cases, the process does not progress and a laminate with excellent adhesive strength cannot be obtained.

The method of the present invention is a method of heat-bonding the modified ethylene copolymer (A) to the metal body preheated to 100°C or lower at a temperature higher than the melting point of the copolymer, preferably 150 to 270°C. be.

The preheating temperature of the metal body is 100℃ or less, and even 40℃
A feature of the method of the present invention is that a laminate having sufficient adhesive strength can be obtained even at temperatures ranging from 80°C to 80°C.

After coating the metal body with the modified ethylene copolymer (A), sufficient adhesive strength can be obtained even if the laminate is immediately cooled.

Various known methods can be used to coat the metal body with the modified ethylene copolymer (A), such as electrostatic coating, fluidized dipping, and coating the metal body with the modified ethylene copolymer (A) in the form of a film or sheet. A method of fusion bonding, a method of extrusion coating, etc. can be used.

Modified ethylene copolymer (A) used in the method of the present invention
These include heat stabilizers, weather stabilizers, nucleating agents, lubricants, pigments, dyes, inorganic or organic fillers, flame retardants,
Compounding agents, such as anti-blocking agents and slip agents, which are usually added and mixed with polyolefins may be added to the extent that they do not impair the object of the present invention.

The modified ethylene copolymer (A) may further contain ethylene/α-olefin copolymers, low-density polyethylene, medium-density polyethylene, high-density polyethylene, etc. outside the range of the ethylene/α-olefin copolymer (B). They may be added within a range that does not impair the purpose of the present invention, but if the amount added exceeds 30% by weight, sufficient adhesive strength will not be obtained at a preheating temperature of 100° C. or lower.

When coating the metal body with the modified ethylene copolymer (A), it may be overlapped with the modified ethylene copolymer (A) layer and polyethylene may be coated on the outside thereof. In that case, the modified ethylene copolymer (A) and polyethylene may be simultaneously coated in multiple layers using a coextrusion die, or the modified ethylene copolymer (A) may be coated, and then polyethylene may be coated. It's okay.

By using the modified ethylene copolymer (A), the method of the present invention makes it possible to obtain a laminate with excellent cold resistance and heat resistance and adhesive strength without preheating the metal body to a high temperature. It can be applied to all coating fields, including difficult tank linings and steel pipe coatings under high speed conditions.

Next, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to these Examples unless the gist thereof is exceeded.

Example 1 Ethylene content 93 mol%, X-ray crystallinity 17%, density 0.893 g/
cm ³ , melting point 76℃, MFR 4.0g/10min and maleic anhydride graft amount 0.3% by weight modified ethylene 1
-Butene copolymer (hereinafter abbreviated as modified EBC-I)
0.3mm thick and upper layer MFR0.2g/10min, density
0.945g/ ^cm3 high density polyethylene (HDPE)
- abbreviated as I) with a thickness of 1.7 mm (temperature set at 220
A coated steel pipe was manufactured by extrusion coating using a temperature (°C) and cooling with water 1 second after coating. Next, the adhesive strength of the coated steel pipe was measured by the following method.

Adhesive strength (Kg/cm): After peeling off a portion of the coating material in a 10 mm width, using a tensile tester (Instron universal testing machine TMM type 100 kg type manufactured by Instron), test at -10℃, 23℃ and 23℃, respectively. The adhesive strength was measured by peeling off the coating material using a 90-degree peel method at a peel rate of 50 mm/min in an atmosphere of 50°C.

As a result, the adhesive strength was 15Kg/cm (-10℃), 15
It showed excellent values of Kg/cm (23℃) and 18Kg/cm (50℃).

Comparative Example 1 Instead of the modified EBC-I used in Example 1,
Ethylene content 81.5 mol%, X-ray crystallinity 3%, density 0.865g/cm ³ , melting point 48℃, MFR 3.1g/
10min and maleic anhydride grafting amount 0.3% by weight
The same procedure as in Example 1 was conducted except that the modified ethylene/propylene copolymer was used. As a result, the adhesive strength was 20Kg/cm (-10℃) and 16Kg/cm (23℃), which were excellent values below room temperature, but at 50℃ it was 2Kg/cm (23℃).
cm, and had poor heat resistance.

Comparative Example 2 Instead of the modified EBC-I used in Example 1,
Ethylene content 98 mol%, X-ray crystallinity 57
%, density 0.936g/cm ³ , melting point 124℃, MFR 1.8g/
10min and maleic anhydride grafting amount 0.3% by weight
The same procedure as in Example 1 was carried out except that the modified ethylene/1-butene copolymer was used. As a result, the coating material did not adhere to the steel pipe at all, and the adhesive strength could not be measured.

Comparative Example 3 Instead of the modified EBC-I used in Example 1,
Ethylene content 91.5 mol%, crystallinity by X-ray
16%, density 0.889g/cm ³ , melting point 72℃, MFR 4.0g/
^cm3 of ethylene/1-butene copolymer 50 parts by weight, ethylene content 97 mol%, X-ray crystallinity 51
%, density 0.922g/ ^cm3 , melting point 123℃, MFR2.3g/
Add maleic anhydride to a mixture with 50 parts by weight of ethylene/4-methyl-1-pentene copolymer for 10 min.
The same procedure as in Example 1 was carried out except that a modified ethylene copolymer composition grafted with 0.3% by weight was used. As a result, the adhesive strength showed a low value of 6 kg/cm (23°C).

Examples 2 and 3 The same procedure as in Example 1 was carried out except that the preheating temperature of the steel pipe in Example 1 was 60°C and 100°C. As a result, the adhesive strength was 13Kg/cm (23℃) and 15Kg/cm (23℃)
Both showed high values.

Claims (1)

[Claims] 1 A metal body preheated to 100°C or less, graft-modified with an unsaturated carboxylic acid or its anhydride, ethylene content 88 to 95 mol%, X-ray crystallinity 10 to 25%, density 0.880 to 0.900 g/
cm ³ , and modified ethylene α- with a melting point of 65 to 90°C.
1. A method for producing an ethylene copolymer-coated metal body, which comprises heat-bonding an olefin copolymer (A) at a temperature equal to or higher than the melting point of the copolymer (A).