JPS6112516B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for adhering metal and polyolefin, and more specifically, the present invention relates to a method for adhering metal and polyolefin, and more specifically, by applying a specific composition to a metal surface that has been heated in advance to a temperature of 150 to 250°C, and immediately coating polyolefin thereon, it is possible to bond the metal and polyolefin. The present invention relates to a method for adhering metal and polyolefin that can provide adhesive strength and hot water resistance. pipes made of metal such as steel, zinc, aluminum,
It has already been industrially practiced to coat the surfaces of plate-like bodies, molded bodies, etc. with polyolefins such as polyethylene and polypropylene to improve the corrosion resistance of the above-mentioned metal products. However, polyolefin is generally a non-polar crystalline resin and is an extremely stable resin with good chemical and solvent resistance that does not dissolve in ordinary chemicals or solvents. That was extremely difficult. Conventionally, methods known for coating metal products with polyolefin include, for example, a method of treating the metal surface with phosphate, a method of heat-sealing an adhesive mainly composed of modified polyolefin to the metal surface, and the like. However, these methods have the disadvantage that polyolefin-coated metal products cannot be obtained that have sufficient adhesion or adhesive strength, and sufficient corrosion resistance and hot water resistance. In particular, in recent years, polyolefin-coated metal products, which are made by coating the inner and outer surfaces of steel pipes with polyolefin, have come into widespread use, and quality requirements have become stricter. The development of polyolefin-coated metal products is strongly desired both economically and practically. In view of the current situation, the present inventors have developed a method of bonding metal and polyolefin that eliminates the drawbacks of the conventional bonding method of metal and polyolefin and provides excellent adhesion, corrosion resistance, and hot water resistance. As a result of intensive research aimed at this purpose, the present invention has been completed. The method of bonding metal and polyolefin according to the present invention involves heating the surface of the metal in advance to a temperature of 150 to 250°C, and then adding (i) a bisphenol A-based epoxy resin with an epoxy equivalent of 170 to 280 and ( ii) Amine value
A solvent-free epoxy resin composition consisting of 200 to 500 heterocyclic modified amine curing agents is applied, and on top of that,
It consists of coating the object with polyolefin while the temperature of the object is 140°C or higher. According to the present invention, the surface of the metal is further prepared in advance.
After heating to a temperature of 150 to 250°C, (i) a bisphenol A epoxy resin with an epoxy equivalent of 170 to 280, (ii) a heterocyclic modified amine curing agent with an amine value of 200 to 500, and (iii) the above ( 0.5 to 5 parts by weight per 100 parts by weight of the total amount of components i) and (ii) of a solvent-free epoxy resin composition consisting of fine silica powder with an average primary particle diameter of 50 mμ or less is applied, and then Furthermore, there is provided a method for adhering metal and polyolefin, which comprises coating the object with polyolefin while the surface temperature of the object is 140° C. or higher. The solvent-free epoxy resin composition used in the method of the present invention includes (i) a bisphenol A liquid epoxy resin having an epoxy equivalent of 170 to 280, and (ii) an amine value of 200 that cures by reacting with the epoxy resin at room temperature. ~
500 heterocyclic modified amine liquid resin curing agent. Such a combination of epoxy resin and curing agent is
It is fast-curing and hardens within 30 seconds at a temperature of 150℃, and the next process can be carried out while the temperature of the coated object is 140℃ or higher after application.
That is, a polyolefin coating step can be started. In addition, since this epoxy resin composition is solvent-free, it can be applied to metal surfaces that have been preheated to a temperature of 150 to 250°C without causing coating defects such as wrinkles or sagging. With this combination, it is possible to form a coating on a metal surface that exhibits little shrinkage during curing and has excellent adhesive properties. In this way, solvent-free epoxy resin compositions have properties such as fast curing, good painting workability, solvent-free properties, and excellent adhesion and hot water resistance when formed into a laminate. is required. Epoxy resins that meet these requirements include:
It needs to be a bisphenol A-based epoxy resin in terms of hot water resistance, and it needs to be a solvent-free type because it needs to dry quickly. Furthermore, the resin needs to have a low viscosity so that it can be easily applied even though it is a solvent-free type. From this point of view, the epoxy equivalent is 170 to 280, preferably 180 to 200,
Select one with a viscosity of 5 to 160 poise. If the epoxy equivalent is less than 170, the desired performance as a bisphenol A type epoxy resin cannot be expected;
If it exceeds 280, the viscosity becomes too high, making painting itself difficult and making it impossible to form a uniform coating film.
On the other hand, as curing agents, aliphatic amines are unsuitable in terms of hot water resistance, polyamide resins are unsuitable in terms of quick curing, and aromatic amines are unsuitable in terms of adhesion. As a product, the epoxy resin has an amine value of 200, which reacts and cures at room temperature.
~500 heterocyclic modified amines are selected. If the amine value of the modified amine exceeds 500, the modified amine becomes crystalline, resulting in poor workability, while if the amine value is less than 200, the curing reaction slows down, which is not preferred. The epoxy resin used in the method of the present invention can be any bisphenol A-based epoxy resin having an epoxy equivalent of 170 to 280. Examples of such resins include Epototo YD128.
(manufactured by Toto Kasei Co., Ltd.) and Epicote 828 (manufactured by Yuka Ciel Epoxy Co., Ltd.). On the other hand, examples of the heterocyclic modified amine curing agent used in the present invention include Examples include modified products of. The ratio of the amounts of the epoxy resin to the curing agent used is not particularly limited, and can be determined as before according to the epoxy equivalent of the bisphenol A-based epoxy resin used. In a preferred embodiment of the method of the present invention, the epoxy resin composition comprises the aforementioned bisphenol A-based epoxy resin having an epoxy equivalent of 170 to 280 and an amine value of 200 to 280.
The composition further contains 0.5 to 5 parts by weight of fine silica powder having an average primary particle diameter of 50 mμ or less with respect to 100 parts by weight of the total amount of the heterocyclic modified amine. Surprisingly, the present inventors have found that by incorporating such fine silica powder, the hot water resistance of the epoxy resin composition coating is even more significantly improved. The mechanism by which hot water resistance is significantly improved by blending fine silica particles is not necessarily clear, but it is probably due to the strong surface activity of the fine silica powder, which has a very small average particle size, that the surface activity of the fine silica particles increases. It is assumed that the hydrophilic groups of are captured in the silica fine powder, and the hot water resistance of the epoxy resin composition coating and the laminate is significantly improved. In a preferred embodiment of the method of the present invention, if the average particle diameter of the fine silica powder blended into the epoxy resin composition exceeds 50 mμ, the effect of improving hot water resistance will not be significant, which is not preferred. If the amount of silica fine powder added is less than 0.5 parts by weight, no improvement effect on hot water resistance will be observed, and if it exceeds 5 parts by weight, the viscosity of the epoxy resin composition will increase and painting workability will be poor, which is not preferable. . For example, if 6 parts by weight of fine silica powder with an average particle diameter of 12 mμ is added, the viscosity of the epoxy resin composition will be 600 poise, which will impede painting workability. Note that any fine silica powder can be used as long as the average particle size is within the above range, such as Aerosil 200,
Aerosil OX50 (manufactured by Nippon Aerosil Co., Ltd.), Nip Seal LP (manufactured by Nippon Silica Co., Ltd.), etc. can be used. This fine silica powder is usually used by dispersing it in an epoxy resin or a hardening agent using a common dispersion means such as a roll mill or a disper. To explain the method of bonding metal and polyolefin in the method of the present invention, first, the oxide film on the metal surface is removed by a method such as pickling, sandblasting, shot blasting, etc., and then an appropriate heating means such as a heating furnace or a burner is used. Preheat the metal surface to a temperature range of 150 to 250°C, preferably 180 to 200°C. If the preheating temperature is too low, the adhesion of the epoxy resin composition will be reduced, whereas if it is too high, it will cause thermal deterioration and reduce the original objectives of adhesion and hot water resistance, which is not preferable. Metal materials that can be coated with polyolefin by the method of the present invention include, for example, plate-shaped, tubular, or other arbitrary shapes of aluminum, copper, zinc, iron, nickel, tin, stainless steel, brass, and tin. , commonly used metal materials such as galvanized iron. In the method of the present invention, as described above,
The epoxy resin composition is applied to a metal surface heated to a temperature of 150 to 250°C by, for example, airless spraying.
A coating of the epoxy resin composition is formed by coating by a common method such as roller coating, brush coating, or ironing, and a polyolefin coating is immediately formed thereon. Here, "immediately" means starting the next step before the metal surface temperature falls below 140°C. There is no limit to the coating thickness of the epoxy resin composition, but it is generally 20 to 100μ.
Thickness (thickness when dry). The polyolefins used in the method of the present invention include those commonly used in the past for coating metals or metal products, such as homopolymers such as polyethylene, polypropylene, or their combinations with vinyl acetate, acrylic acid, Copolymers with maleic anhydride, 1-butene, 1-hexene, etc. can be used, and these may be in any form such as sheet, pellet, or powder. Furthermore, these may contain pigments, various additives, extenders, etc., if necessary. When applying a polyolefin coating onto the epoxy resin coating, the polyolefin may be fused by a conventional method such as powder dispersion or extrusion coating. For example, when powdered polyolefin is used, electrostatic coating or fluidized dip coating is used. In electrostatic coating, polyolefin powder is electrostatically sprayed onto the heated surface of the object to be coated, so that the polyolefin powder adheres to the surface of the object to be coated and is fused to the epoxy resin composition coating at the temperature of the object to be coated. On the other hand, in fluidized dip coating, a heated object to be coated is introduced into a dipping tank in which negatively charged polyolefin powder is suspended in the air, and the polyolefin powder is adhered to the surface of the object by electrical attraction. The polyolefin powder fuses to the epoxy resin composition coating at the temperature of the object being coated. The polyolefin coating thus adheres onto the epoxy resin composition coating. When polyolefin pellets are used, the polyolefin coating can be adhered onto the epoxy resin composition coating using conventional extrusion coating methods; Pressure 0.1 at °C
It is sufficient to press it at ~5.0Kg/cm ² for 20 to 180 seconds.
The thickness of the polyolefin coating is not particularly limited, but is generally about 2 to 4 mm. In this way, according to the present invention, it is possible to obtain a polyolefin-metal coated body having sufficient adhesive strength, corrosion resistance, and hot water resistance. It has become possible to economically and practically produce a laminate of polyolefin and metal that retains water-warm properties. EXAMPLES The present invention will be specifically described below with reference to Examples, but it goes without saying that the scope of the present invention is not limited to these Examples. In addition, "part" and "%" in the examples mean a weight basis unless otherwise specified. Examples 1 to 5 and Comparative Examples 1 to 6 Epoxy resin compositions having the compositions shown in Table 1 were sandblasted on the surface in advance and placed on a preheated iron plate (dimensions 9 x 100 x 200 mm) to a thickness of 40 to 50 μm. Immediately apply modified polyolefin (manufactured by Mitsui Petrochemicals, trade name Admer NE050) to a thickness of 300 to 400μ.
A polyethylene film (film thickness 3mm) that was crimped at 170°C or preheated on top
(low density polyethylene with thickness, MI value 1.5, density 0.925)
were pressed together at a temperature of 170° C. under a pressure of 0.1 Kg/cm ² to obtain a two- or three-layer laminate of polyolefin and iron plate. The 180° peel strength (adhesive strength) of the resulting three-layer laminate and the 180° peel strength (hot water resistance) were measured in the same manner after immersing the laminate in 95°C hot water for 60 hours.
The results are summarized in the first section along with the characteristics of the epoxy resin composition.
Shown in the table. Note that the 180° peel strength is
After making a 10mm wide scratch that reaches the steel surface, part of it is peeled off and the steel surface and polyethylene coating are 180 mm thick.
゜Peel strength was measured at 20°C using a Tensilon type tensile tester (manufactured by Toyo Baldwin). The adhesive strength and hot water resistance of the resulting two-layer laminate were determined by making cross cuts with a knife at 2 mm intervals on the laminate surface.
100 goblets were made, then cellophane tape was pressed onto it and then peeled off, and the results were evaluated as "number of goblets that did not peel off/100". As is clear from the results in Table 1, the preheating temperature
It exhibits high peel strength when the temperature is in the range of 150 to 250°C, and the peel strength decreases when the temperature is higher or lower than this. Furthermore, the addition of fine silica powder improves hot water resistance. This result becomes less noticeable when the particle size of the fine silica powder is large, and when the amount is increased, workability decreases.

[Table] Example 6 and Comparative Examples 7 to 9 Polyolefin and iron plates were adhered in the same manner as Examples 1 to 5 and Comparative Examples 1 to 6 using epoxy resin compositions having the compositions shown in Table 2. A three-layer laminate was obtained. The results obtained were as shown in Table 2.

【table】

Claims (1)

[Claims] 1. After heating the surface of the metal to a temperature of 150 to 250°C in advance, (i) a bisphenol A-based epoxy resin with an epoxy equivalent of 170 to 280 and (ii) an amine value of 200
~500~A solvent-free epoxy resin composition consisting of a heterocyclic modified amine curing agent is applied, and a polyolefin is coated thereon while the temperature of the object to be coated is 140°C or higher. Adhesion method of polyolefin. 2. After preheating the surface of the metal to a temperature of 150 to 250°C, (i) a bisphenol A-based epoxy resin with an epoxy equivalent of 170 to 280, (ii) an amine value of 200 to 500
a heterocyclic modified amine curing agent; and (iii) 0.5 to 5 parts by weight per 100 parts by weight of the total amount of components (i) and (ii) above, consisting of fine silica powder whose primary particles have an average particle diameter of 50 mμ or less. 1. A method for adhering metal and polyolefin, which comprises applying a solvent-free epoxy resin composition and coating polyolefin thereon while the temperature of the object to be coated is 140°C or higher.