JPH0622990B2 - Polyolefin coated steel - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polyolefin-coated steel material, and more particularly to a polyolefin-coated steel material having excellent low temperature impact resistance and scratch resistance.

(Prior Art) Polyolefin-coated steel materials such as polyolefin-coated steel pipes, polyolefin-coated steel sheets, and polyolefin-coated steel sheet piles are excellent in their anticorrosion performance.
It has come to be widely used as a marine heavy-duty anticorrosion steel pipe pile, a rustproof steel plate, and a heavy anticorrosion steel sheet pile.

However, the above-mentioned polyolefin-coated steel material has the following drawbacks because the impact resistance and flaw resistance of the polyolefin coating are insufficient. That is, (1) Defects are likely to occur during handling such as shipping at the time of shipping, land transportation, and local piping construction.

(2) In the case of the polyolefin-coated steel pipe pile and the polyolefin-coated steel sheet pile, since the casting is carried out, flaws are generated on the coating surface, particularly due to earth and sand and small stones.

As a countermeasure against this, since the scratched coating is successively repaired with a repair material such as an anticorrosion tape, the construction is troublesome.

Conventionally, in order to improve the flaw resistance of polyolefin-coated steel, a method has been proposed in which a fiber reinforcement is dispersed in the polyolefin coating to increase the surface hardness. For example, as shown in Japanese Patent Laid-Open No. 59-12846, as shown in FIG. 5, a maleic anhydride-modified polyolefin resin layer 2 is formed on the surface of a steel material 1, and a chopped strand of glass fiber or carbon fiber is added to the polyolefin resin. A polyolefin-coated steel material in which the mixed fiber-reinforced polyolefin resin layers 5 are sequentially laminated can be used.

(Problems to be solved by the invention) However, in the above-mentioned polyolefin-coated steel material, since the low temperature brittleness of the fiber-reinforced polyolefin resin layer is insufficient, when the fiber-reinforced polyolefin resin is impacted when it is installed in a low-temperature environment, the fiber-reinforced polyolefin resin There is a problem that cracking occurs in the layer and the low temperature impact resistance is significantly reduced.With the conventional technology, it is possible to obtain a polyolefin coated steel material having both excellent scratch resistance and low temperature impact resistance. It was difficult.

An object of the present invention is to provide a polyolefin-coated steel material which is excellent in both scratch resistance and low temperature impact resistance.

(Means for Solving the Problem) As a result of intensive studies to solve the above-mentioned problems, the present inventor has found that a modified polyolefin resin layer, a polyolefin resin layer, and a fiber reinforced resin layer are formed on the surface of a steel material that has been subjected to a base treatment. It has been found that a polyolefin-coated steel material excellent in both scratch resistance and low-temperature impact resistance can be obtained by sequentially laminating modified polyolefin resin layers, and the present invention has been completed.

That is, as shown in FIG. 1, the present invention is characterized in that a modified polyolefin resin layer 2, a polyolefin resin layer 3 and a fiber reinforced modified polyolefin resin layer 4 are sequentially laminated on the surface of a steel material 1 that has been subjected to a base treatment. The present invention relates to a polyolefin-coated steel material excellent in both scratch resistance and low-temperature impact resistance.

Hereinafter, the present invention will be described in detail.

The steel materials used in the present invention include cold rolled steel sheets, hot rolled steel sheets, steel sheets such as thick steel sheets, shaped steel such as H-section steel, I-section steel and L-section steel, steel sheet pile, bar steel, steel wire, cast iron pipe, Steel pipe and steel pipe sheet pile. or,
The surfaces of these steel plates, shaped steels, steel sheet piles, steel bars, steel wires, steel pipes and steel pipe sheet piles were plated with zinc, nickel, chromium, aluminum, zinc-aluminum, zinc-nickel, zinc-nickel-cobalt or the like. It may be steel.

Degreasing, pickling, sandblasting,
It is processed by grit blasting, shot blasting, etc. to remove oil and scale on the surface of steel materials. It is necessary to improve the adhesion between the steel material and the modified polyolefin resin layer by subjecting the surface of the steel material from which oil and scale have been removed to a base treatment such as a chromate treatment, an epoxy primer treatment and a silane coupling agent treatment. If the following base treatment is not performed, the adhesion between the steel material and the modified polyolefin resin layer is reduced, and peeling occurs at the interface between the steel material and the modified polyolefin resin layer due to low temperature impact, which is not preferable because corrosion resistance is reduced.

Further, the modified polyolefin resin, the polyolefin resin, and the fiber-reinforced modified polyolefin resin used in the present invention will be described.

The polyolefin referred to in the present invention means low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, polypropylene, ethylene-propylene block or random copolymer, ethylene-butene-1 block or random copolymer. Alternatively, it is one kind or a mixture of two or more kinds of thermoplastic resins such as ethylene-propylene-diene terpolymer.

The modified polyolefin resin used in the present invention includes a polyolefin modified with an unsaturated carboxylic acid such as maleic acid, acrylic acid, or methacrylic acid or an anhydride thereof, or a product obtained by appropriately diluting the modified polyolefin with a polyolefin, and a polyolefin. Is a silane-modified polyolefin obtained by modifying an unsaturated silane compound such as vinyltrimethoxysilane, vinyltriethoxysilane, vinylmethyldiethoxysilane, or vinylphenyldimethoxysilane, or a silane-modified polyolefin appropriately diluted with polyolefin.

Fiber-reinforced modified polyolefin resin used in the present invention,
One or a mixture of two or more kinds of chopped strands such as glass fiber, carbon fiber, slag fiber and stainless fiber is dispersed in a modified polyolefin resin.

The above fiber-reinforced modified polyolefin resin has a film strength of the fiber-reinforced modified polyolefin resin layer in which polar groups of unsaturated carboxylic acid and unsaturated silane compound added to the modified polyolefin molecule are firmly adhered to and integrated with the chopped strand surface. And the surface hardness is improved to significantly improve the scratch resistance, and the low-temperature brittleness of the film is improved because it is firmly adhered to and integrated with the lower polyolefin resin layer, and cracks particularly occur at low-temperature impact. It has an excellent effect of preventing

When a polyolefin resin is used instead of the modified polyolefin resin in the fiber-reinforced modified polyolefin resin, the surface hardness is improved but the film strength is hardly improved, and the adhesiveness with the lower polyolefin resin layer is improved. Since it is small and difficult to integrate, cracks occur in the coating due to low temperature impact.

In particular, when the above chopped strands are used as the chopped strands to be mixed / dispersed in the fiber-reinforced modified polyolefin resin, the modified polyolefin resin is obtained by modifying the polyolefin with an unsaturated silane compound, or the modified product is appropriately diluted with polyolefin. When a silane-modified polyolefin resin is used, the alkoxy group of the unsaturated silane compound added to the polyolefin molecule is dehydrated and condensed with the hydroxyl group on the surface of the chopped strand to form a silanol bond, and firmly adheres to integrate the film. The strength and surface hardness are dramatically improved, and it has a remarkable effect on scratch resistance and prevention of cracking of the film due to low temperature impact. Regarding the amount of chopped strands mixed, it is desirable that 5 to 50% by weight of chopped strands be mixed and dispersed in the modified polyolefin resin.

When the amount of chopped strands mixed with the modified polyolefin resin is 5% by weight or less, both the strength and surface hardness of the film are hardly improved and the scratch resistance is poor.
When the content is more than 5% by weight, the low temperature brittleness of the coating is deteriorated, so that the coating is cracked by low temperature impact. The diameter of chopped strands is 8-30μ, and the fiber length is 0.3-20mm
The degree is already good, but is not necessarily limited to this.

Further, when the fiber reinforced polyolefin resin is required to have weather resistance, the above fiber reinforced polyolefin resin may be kneaded with a weather resistant material such as an inorganic pigment such as carbon black or titanium oxide, or an organic pigment. .

Further, the polyolefin-coated steel sheet according to the present invention can be obtained, for example, by the manufacturing method shown in FIG. That is, the modified polyolefin resin pellets 6 are melted by a single-screw extruder 7 to extrude the modified polyolefin resin layer 2 in order from the lower layer of the three-layer T die 14, and the polyolefin resin pellets 8 are melted by a single-screw extruder 9. To extrude the polyolefin resin layer 3 and melt-knead the chopped strands 10 and the modified polyolefin resin pellets 11 with the twin-screw kneading machine 12 and supply them to the single-screw extruder 13 to extrude the fiber-reinforced modified polyolefin resin layer 4 to obtain the modified polyolefin. The resin layer 2, the polyolefin resin layer 3, and the fiber-reinforced modified polyolefin resin layer 4 are integrated into three layers to coat the surface of the steel sheet 1 which has been subjected to the base treatment, to manufacture a polyolefin-coated steel pipe.

Further, the polyolefin-coated steel pipe according to the present invention can be obtained, for example, by the manufacturing method shown in FIG. That is,
The modified polyolefin resin pellets 6 are melted by a single-screw extruder 7 to extrude the modified polyolefin resin layer 2 in order from the lower layer of the three-layer T die 14, and the polyolefin resin pellets 8 are melted by a single-screw extruder 9 to form a polyolefin. The resin layer 3 is extruded, the chopped strands 10 and the modified polyolefin resin pellets 11 are melt-kneaded by a twin-screw kneader 12 and supplied to a single-screw extruder 13 to extrude the fiber-reinforced modified polyolefin resin layer 4, and the modified polyolefin resin layer 2 and the polyolefin resin layer 3 are slightly overlapped in the width direction, and the polyolefin resin layer 3 and the fiber-reinforced modified polyolefin resin layer 4 are slightly overlapped in the width direction, so that a spiral is formed on the outer surface of the steel pipe 1 that has been subjected to the base treatment. It is wound into a shape, covered and manufactured.

Further, in FIG. 3, a method of extrusion coating the modified polyolefin resin layer 2, the polyolefin resin layer 3, and the fiber-reinforced modified polyolefin resin layer 4 with a three-layer T die is used, but as shown in FIG. The resin powder 2 is applied by a powder coating machine and melted to form a modified polyolefin resin layer, and then the polyolefin resin layer 3 and the fiber-reinforced modified polyolefin resin layer 4 are coated with a two-layer T die 17 to produce the layer. Method or method of extrusion coating the modified polyolefin resin layer 2, the polyolefin resin layer 3, and the fiber-reinforced modified polyolefin resin layer 4 by separate single-layer T die or round die, modified polyolefin resin layer 2, polyolefin resin by three-layer round die Layer 3
A conventionally known method such as a method of extrusion-coating the fiber-reinforced modified polyolefin resin layer 4 as an integral three layer can be adopted.

A partial cross section of the polyolefin-coated steel material according to the present invention obtained as described above is as shown in FIG. 1, and 1 in the figure is degreased, pickled, sand blasted, grit blasted, shot blasted, etc. A steel material from which oil and scale have been removed and which has been subjected to a surface treatment such as chromate treatment, epoxy primer treatment, silane coupling treatment, etc., 2 is a modified polyolefin resin layer, 3 is a polyolefin resin layer, 4 is a fiber-reinforced modified polyolefin The resin layer is shown.

In the figure, 2 is 0.05 to 0.5 mm thick, and 3 is 0.5 to 10 mm.
With a thickness of mm, 4 can obtain good results if it has a thickness of 0.2 to 8 mm.

(Example) Hereinafter, the present invention will be specifically described with reference to examples.

Example 1 A steel plate (75 × 150 × 6 mm) was degreased and grit blasted, and a chromate treatment agent was applied to the surface of the steel sheet and heated at 160 ° C. for baking, and then an epoxy primer was applied.
A steel sheet was prepared by heating to ℃ and hardening it. Heat the above-treated steel sheet to 190 ° C, electrostatically coat and melt maleic anhydride-modified polypropylene to a film thickness of 200μ, and melt it on the surface with a two-layer T-die using a low-density polyethylene resin. Polypropylene resin modified with vinyltrimethoxysilane and diameter 10μ, length 3
mm glass fiber chopped strands dispersed in 30% by weight of glass fiber reinforced silane-modified polypropylene resin in two layers, the polypropylene resin layer having a thickness of 2 mm,
Further, the glass fiber reinforced silane-modified polypropylene resin layer was extrusion-coated so that the film thickness was 1 mm to prepare a polypropylene-coated steel sheet (A) according to the present invention.

Further, as a comparative material, the above polypropylene-coated steel sheet
Using the same method as in (A), 190
Preheat to ℃ and apply maleic anhydride-modified polypropylene resin electrostatically to a film thickness of 200μ and melt it, and then use a single-layer T-die on the surface of it to add low-density polyethylene with chopped strands of the above glass fiber Polypropylene-coated steel sheet (B) corresponding to JP-A-59-12846 coated with glass fiber reinforced polypropylene resin dispersed by weight% so as to have a film thickness of 3 mm, and glass fiber used for the polypropylene-coated steel sheet (B) A coated steel plate (C) having a reinforced polypropylene resin film thickness of 1 mm was prepared.

As for the above polypropylene coated steel sheets A to C, a needle penetration test (DIN30670, test temperature) was used as an index of scratch resistance.
100 ℃) and low temperature impact test (AS
TMG-14, test temperature -20 ° C) is shown in Table 1.

From the results shown in Table 1, a marked difference was observed in both the scratch resistance and the low temperature impact resistance, and particularly, the polypropylene-coated steel sheet according to the present invention using the polypropylene resin and the glass fiber reinforced silane-modified polypropylene resin ( A)
Uses a glass fiber reinforced polypropylene resin.
Polypropylene coated steel plate (B) equivalent to 59-12846
It was confirmed that a significantly superior result was obtained as compared with (C) and (C).

Example 2 By the same method as in Example 1, the types of modified polyolefin resin, polyolefin resin, and glass fiber reinforced modified polyolefin resin were changed as shown in Table 2 to prepare polyolefin-coated steel sheets D to G according to the present invention.

As comparative materials, the types of modified polyolefin resin and glass fiber reinforced polyolefin resin of polypropylene-coated steel sheet (B) corresponding to JP-A-59-12846 are changed as shown in Table 3 to obtain polyolefin-coated steel sheets H to K. It was created.

For the above polyolefin coated steel sheets, a needle penetration test (DIN 30670, test temperature 70 ° C) as an index of scratch resistance and an impact test (ASTM G-14, test temperature −45 ° C) as an index of low temperature impact resistance were performed. The results obtained are shown in Table 4.

From the results shown in Table 4, the polyolefin-coated steel sheets D, E, F, G according to the present invention using the polyolefin resin and the glass fiber reinforced silane-modified polyolefin resin in both the scratch resistance and the low temperature impact resistance are shown. I is a Japanese Patent Laid-Open No. 59-128 using glass fiber reinforced polyolefin resin.
Polyolefin-coated steel sheets H, I, corresponding to Japanese Patent No. 46
It was confirmed that a significantly superior result was obtained as compared with J and K.

Example 3 In the same manner as in Example 2, the above-mentioned linear low-density polyethylene-coated steel sheet (D) was prepared by changing the method of pretreating the steel sheet as follows.

1. A steel plate that is degreased and grit blasted, coated with a chromate treatment agent on its surface, heated at 160 ° C and baked, then coated with an epoxy primer and heated to 190 ° C to cure it.

2. A steel plate that has been degreased and pickled, the surface of which is coated with a chromate treatment agent, heated at 160 ° C, and baked.

3. Steel plate is degreased and grit blasted, chromate treatment agent is applied to its surface and heated at 160 ° C to bake, then silane coupling agent is applied and heated to 190 ° C to cure thing.

4. Steel plate degreased and grit blasted, coated with a phosphate treatment on its surface, heated at 160 ° C and baked, then coated with an epoxy primer and heated to 190 ° C to cure it. .

Also, as a comparative material, the above-mentioned base treatment is not performed, that is, 5. The steel plate is only degreased and grit blasted.

6. A steel plate that has been degreased and pickled.

It was created.

Regarding the above linear low-density polyethylene-coated steel sheet, a needle penetration test (DIN30670, test temperature 70 ° C) as an index for scratch resistance and an impact test (ASTM G
-14, test temperature -45 ° C) is shown in Table 5.

The results in Table 5 show good results in terms of scratch resistance regardless of the presence or absence of the base treatment, but regarding impact resistance, the performance decreases when the base treatment is not applied, but the base treatment is applied. In this case, good results were shown regardless of the type of base treatment, and it was confirmed that the steel material used in the present invention needs to be subjected to base treatment.

Example 4 In the same manner as in Example 2, the linear fiber low density polyethylene-coated steel sheet (D) was prepared by changing the modifier for the glass fiber reinforced modified linear low density polyethylene as follows.

1. Vinyltrimethoxysilane 2. Vinyltriethoxysilane 3. Vinylmethyldiethoxysilane 4. Vinylphenyldiethoxysilane 5. Maleic anhydride 6. Unmodified (no modification) The above linear low-density polyethylene coating For steel sheets, the needle penetration test (DIN30670, test temperature 70 ° C) is used as an index of scratch resistance and the impact test (ASTM G
-14, test temperature -45 ° C) is shown in Table 6.

From the results shown in Table 6, the glass fiber reinforced linear low density polyethylene in which chopped strands of glass fiber are dispersed in the unmodified linear low density polyethylene resin in both the scratch resistance and the low temperature impact resistance When using resin
Although the performance is reduced in (6), when a glass fiber reinforced modified linear low density polyethylene resin in which chopped strands of glass fiber are dispersed in a modified linear low density polyethylene resin modified with a modifier is used, Good results are shown regardless of the type of modifier, and it can be confirmed that the present invention requires the use of a fiber-reinforced modified polyolefin resin in which chopped strands are dispersed in a modified polyolefin resin.

Example 5 In the same manner as in Example 2, the type of fiber used for the fiber-reinforced silane-modified linear low-density polyethylene resin was changed as follows to prepare the above linear low-density polyethylene-coated steel sheet (D). did.

1. Glass fiber chopped strands (diameter 10μ, length 3mm) 2. Carbon fiber chopped strands (diameter 13μ,
Length 6mm) 3. Glass fiber chopped strands (diameter 10μ, length 6mm) and carbon fiber chopped strands (diameter)
13 μ, length 6 mm) mixed in a weight ratio of 3: 1 4. Slag fiber chopped strands (diameter 14 μ, length 2 mm), glass fiber chopped strands (diameter 10
μ, length 3 mm) and carbon fiber chopped strands (diameter 13 μ, length 3 mm) in a weight ratio of 2: 1: 1. 5. Stainless fiber chopped strands (diameter 18)
μ, length 3 mm), glass fiber chopped strands (diameter 10 μ, length 3 mm) and carbon fiber chopped strands (diameter 13 μ, length 3 mm) in a weight ratio of 1: 3: 1.
6. A mixture of aromatic polyamide fiber chopped strands (diameter 10μ, length 3mm), slag fiber chopped strands (diameter 16μ, length 3mm) and carbon fiber chopped strands (diameter 13μ, length 3mm) The weight ratio 1: 3:
Mixture mixed with 1.

7. Weight of chopped strands of Si-C ceramics fiber (diameter 19μ, length 3mm), glass fiber chopped strands (diameter 10μ, length 3mm) and carbon fiber chopped strands (diameter 13μ, length 3mm) Mixture of 1: 3: 1 ratio 8. Si-Ti-CO ceramic fiber chopped strand (diameter 10μ, length 6mm), glass fiber chopped strand (diameter 10μ, length 3mm) and carbon fiber A mixture of chopped strands (diameter 13 μ, length 6 mm) in a weight ratio of 1: 3: 1 9. Glass fiber chopped strands (diameter 10 μ, length 3 mm) and carbon fiber chopped strands (diameter)
10 μ, length 6 mm) and mica powder in a weight ratio of 2: 1: 1. Additive-free For the above linear low-density polyethylene-coated steel sheets, the needle penetration test (DIN30670, test temperature 70 ° C) as an index of scratch resistance and the impact test (ASTM G-
The test results are shown in Table 7.

From the results shown in Table 7, in both the scratch resistance and the low temperature impact resistance, the performance decreases when the fiber is not added to the silane-modified linear density polyethylene, but when the fiber is added, Shows good results regardless of the type of fiber, and it was confirmed that the present invention requires the use of a fiber-reinforced modified polyolefin resin in which chopped strands of fibers are dispersed in a modified polyolefin resin.

Example 6. Steel pipe (200A x 5500mm length x 5.8mm thickness) is grit blasted, and a chromate treatment agent is applied to the surface of the steel pipe at 160 ° C.
After baking with, apply epoxy primer and 190 ℃
Then, it was cured and treated as a base. On the surface of the steel pipe which has been subjected to the above-mentioned base treatment, by the method shown in FIG.
A maleic anhydride-modified ethylene / propylene block copolymer layer (200 μm thick), an ethylene / propylene block copolymer layer (1.5 mm thick) and a fiber-reinforced modified ethylene / propylene block copolymer layer (1 mm thick) are coated, and the ethylene A propylene block copolymer coated steel pipe was prepared. At that time, as the fiber-reinforced modified ethylene / propylene block copolymer, the ethylene / propylene block copolymer modified with trimethoxysilane was mixed with glass fiber chopped strands (diameter 10 μ, length 3 mm) and carbon fiber chopped strands (diameter 1
3 μ, length 3 mm) in a weight ratio of 2: 1 to obtain a mixture of 2% by weight, 5% by weight, 20% by weight, 30% by weight, 50% by weight and 55% by weight with respect to the modified ethylene / propylene block copolymer. Comparisons were made using those added and dispersed.

Regarding the above-mentioned ethylene / propylene block copolymer-coated steel pipe, the needle penetration test (DI
Table 8 shows the results of an impact test (ASTM G-14, test temperature −20 ° C.) as an index of low temperature impact resistance (N 30670, test temperature 100 ° C.).

From the results shown in Table 8, when the amount of the fiber added to the modified ethylene / propylene block copolymer is 2% by weight, both the scratch resistance and the low temperature impact resistance decrease, and at 55% by weight, the coating cracks due to the low temperature impact. It was confirmed that the low temperature impact resistance was significantly reduced, but in the range of 5 to 50% by weight, both the scratch resistance and the low temperature impact resistance showed good results.

(Effects of the invention) As is clear from the examples, the polyolefin-coated steel material according to the present invention is much more excellent in flaw resistance and low-temperature impact resistance than the conventional polyolefin-coated steel material, and therefore has an unprecedented durability. It has become possible to apply a polyolefin coated steel material that has properties.

[Brief description of drawings]

FIG. 1 is a partial cross-section of a polyolefin-coated steel material according to the present invention, FIGS. 2, 3 and 4 are schematic explanatory views showing an embodiment of the present invention, and FIG. 5 is a diagram showing a conventional polyolefin-coated steel material. FIG. 1 ... Steel material subjected to surface treatment 2 ... Modified polyolefin resin layer 3 ... Polyolefin resin layer 4 ... Fiber-reinforced modified polyolefin resin layer 5 ... Fiber-reinforced polyolefin resin layer 6 ... Modified polyolefin resin pellets 7 ... Single-screw extruder 8 …… Polyolefin resin pellets 9 …… Chopped strands 10 …… Twin-screw kneader 11 …… Three-layer T die 12 …… Crimping roll 13 …… Two-layer T die 14 …… Powder coating machine

Claims (6)

[Claims] 1. A polyolefin-coated steel material, characterized in that a modified polyolefin resin layer, a polyolefin resin layer, and a fiber-reinforced modified polyolefin resin layer are sequentially laminated on the surface of a steel material subjected to a base treatment. 2. A silane-modified polyolefin resin containing 5 to 50% by weight of one or a mixture of two or more chopped strands such as glass fiber, carbon fiber, slag fiber and stainless fiber.
The polyolefin-coated steel material according to claim 1, wherein a dispersed fiber-reinforced modified polyolefin resin is used. 3. The polyolefin-coated steel material according to claim 1, wherein the surface of the steel material is subjected to a chromate treatment as a surface treatment of the steel material. 4. The polyolefin-coated steel material according to claim 1, wherein the surface of the steel material is subjected to a chromate treatment and then an epoxy primer treatment as a base treatment of the steel material. 5. The polyolefin-coated steel material according to claim 1, wherein the surface of the steel material is subjected to a chromate treatment and then a silane coupling agent treatment as a base treatment of the steel material. 6. The polyolefin-coated steel material according to claim 1, wherein the surface of the steel material is subjected to a phosphate treatment and then an epoxy primer treatment as a base treatment of the steel material.