JPS6220912B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a metal-resin laminate, and more particularly to a metal-resin laminate formed by sequentially laminating a metal layer such as a steel pipe, an anticorrosive resin layer, and a protective resin layer for the resin layer. The present invention relates to a metal-resin laminate in which a specific resin layer is used as a protective resin layer to improve the releasability of the protective resin layer and improve workability. Resin-coated steel pipes are used for the purpose of transporting various fluids and protecting cables, etc., and the resin layer at this time is generally a polyethylene resin layer for corrosion protection. Furthermore, a protective layer is formed on the surface of the resin layer for transportation, handling, etc. of the resin-coated steel pipe. When welding such resin-coated steel pipes, it is necessary to peel off the protective layer. Therefore, in order to prevent fusion between the two layers, there is a method of applying an anti-fusion agent such as low molecular weight polyolefin or polybutene.
-2083), a method of spraying inorganic powder such as calcium carbonate or talc as an anti-fusing agent (Japanese Patent Laid-Open No. 50
-139422) has been adopted. However, these conventional methods have the drawback of complicating the manufacturing process and reducing productivity. In addition, a method using a composition consisting of polyethylene and polypropylene as a protective layer (Japanese Patent Application Laid-Open No. 1986-
No. 42449) is also known, but it did not have sufficient scratch resistance. The present inventors solved the above-mentioned drawbacks,
We have conducted extensive research to develop resin-coated steel pipes and metal-resin laminates that can be used in a wide range of applications. As a result, they discovered that by using polypropylene having a predetermined melt index and low molecular weight component content as a protective layer, resin layers can be easily peeled off, and moldability and productivity can be significantly improved. The present invention was arrived at based on this knowledge. That is, the present invention provides a metal-resin laminate formed by sequentially laminating metal, polyethylene, and polypropylene, in which the polypropylene has a melt index (hereinafter abbreviated as MI) of 0.1 to 2.0.
g/10 minutes or less and the content of low molecular weight components having a weight average molecular weight of 5000 or less is 0.1 to 1.0% by weight. In the present invention, polypropylene is used as a protective layer, and has an MI of 0.1 to 2.0 g/10 minutes and a content of low molecular weight components with a weight average molecular weight of 5000 or less of 0.1 to 1.0% by weight. It is necessary. Note that the weight average molecular weight refers to a value measured by gel permeation chromatography (GPC). Here, if the MI of polypropylene exceeds the upper limit value, it is not preferable because the coating moldability deteriorates. In addition, the content of low molecular weight components is 0.1% by weight.
If the amount is less than 1.0% by weight, the moldability will deteriorate, and if it exceeds 1.0% by weight, the peeling strength between the polyethylene layer and the polyethylene layer described later will increase, making peeling work difficult and impractical. Any polypropylene can be used as long as it satisfies the above conditions, but ethylene-propylene block copolymers with an ethylene content of 10 to 40% by weight and propylene homopolymers containing 10 to 40% by weight of polyethylene are particularly suitable. suitable. The polypropylene used in the present invention can be produced by known methods. In order to adjust the content of low molecular weight components, for example, polypropylene is washed by contacting it with an organic solvent such as hexane, heptane, or cyclohexane at 60 to 100°C for 0.5 to 6 hours under heating to remove some of the low molecular weight components. This can be done by removing . In addition, it can also be produced directly by employing an appropriate catalyst and polymerization method. Next, polyethylene is used as a corrosion protection layer for metals, and any conventionally used polyethylene can be used arbitrarily. Usually MI0.5
g/10 minutes or less, high-density polyethylene, linear low-density polyethylene, copolymers of ethylene and other α-olefins (α-olefin content of 20% by weight or less), etc. are used.
In particular, the MI is 0.5 g/10 minutes or less, and the content of low molecular weight components with a weight average molecular weight of 1000 to 3000 is 0.05 to 3000.
When 0.5% by weight of polyethylene is used, peeling from the polypropylene becomes easy and workability is improved. This polyethylene can be obtained in the same manner as in the case of polypropylene. Metal layers include steel, tin, galvanized iron, copper, lead,
There are tubes, plates, etc. made of materials such as aluminum. The metal-resin laminate of the present invention can be produced by various methods, such as a method of extruding and coating the above-mentioned resin material on a metal layer in a tube shape,
This can be carried out by a method such as a method of spirally winding a resin sheet for coating. During manufacturing, primer treatment, heat treatment, etc. are performed as necessary. Furthermore, various additives such as antioxidants, ultraviolet absorbers, lubricants, and flame retardants can be added to polyethylene and polypropylene. Furthermore, an adhesive can be applied to the surface of the metal layer in order to improve the adhesive strength and resistance to warm salt water between the metal layer and the polyethylene layer. In that case, known adhesives such as thermosetting epoxy resin adhesives and thermoplastic epoxy resin adhesives can be used as the adhesive. The thickness of each layer in the metal-resin laminate of the present invention is 0.5 to 3 mm for the metal layer and 0.2 mm for the polyethylene layer.
-2 mm, preferably 0.5-1.5 mm, and the polypropylene layer 0.2-2 mm, preferably 0.5-1.5 mm. Since the metal-resin laminate of the present invention uses a specific polypropylene as the polypropylene layer serving as the protective layer, it is easy to separate the polyethylene layer from the anti-corrosion layer, resulting in excellent workability. Furthermore, since the temperature dependence of peel strength is small, the peel strength does not increase even if a polyethylene layer and a polypropylene layer are laminated at high temperatures. Furthermore, since a specific polypropylene is used as the protective layer, it has excellent scratch resistance and durability. Next, the present invention will be explained in detail with reference to examples. Examples 1 to 8 and Comparative Examples 1 to 3 Sandblasted steel pipe (thickness 2 mm, SPCC-SD)
After applying a thermosetting bisphenol A type epoxy resin adhesive on top and allowing it to cure at 160°C for 10 minutes, a specified polyethylene sheet (thickness 1 mm, surface temperature 80°C) was layered, and a specified polyethylene sheet (thickness 1 mm, surface temperature 80°C) was placed on top. Ethylene-propylene block copolymer sheets (ethylene content: 25% by weight, thickness: 1 mm, resin temperature: 190°C) were stacked and heat-pressed at 40 kg/cm ² for 5 minutes. Results first
Shown in the table. 【table】

Claims (1)

[Claims] 1 In a metal-resin laminate formed by sequentially laminating metal, polyethylene and polypropylene, the polypropylene has a melt index of 0.1.
~2.0g/10min or less, weight average molecular weight 5000
A metal-resin laminate characterized in that the content of the following low molecular weight components is 0.1 to 1.0% by weight.