JP4379167B2 - Urethane elastomer coated steel with excellent impact resistance - Google Patents

Description

  The present invention relates to a urethane elastomer-coated steel material having excellent impact resistance, and more particularly to a heavy anticorrosion-coated steel material designed to prevent corrosion of steel structures used in the ocean, harbors, rivers, etc. for a long period of time.

  Since steel structures used in the ocean, harbors, rivers, etc. are exposed to severe corrosive environments, urethane elastomer coatings are used as heavy-duty anti-corrosion coatings near the splash zone during tidal periods. Heavy anti-corrosion-coated steel materials are subjected to impacts such as collision of ships and driftwood during and after construction and after construction. This urethane elastomer-coated steel material has a problem that the coating is damaged by these impacts and the corrosion resistance is lost, and improvement is required.

  Conventionally, as means for solving this problem, a steel material in which a fiber cloth layer impregnated with a curable resin is coated on a urethane elastomer upper layer (see Patent Document 1), and a steel material in which a rubber lining layer is coated on an upper layer of the urethane elastomer ( Patent Document 2).

JP-A-10-272730 Japanese Patent Laid-Open No. 10-235791

  However, the steel material coated with a resin cloth layer impregnated with a curable resin is inferior in interlayer adhesion between the urethane elastomer layer and the fiber reinforced plastic layer that is the protective layer, and is easily dropped from the fiber reinforced plastic layer, Since the fiber-reinforced plastic layer is further formed after the urethane elastomer layer is formed, there is a problem that the manufacturing cost increases.

  Further, the steel material coated with the rubber lining layer also has a problem that the manufacturing cost becomes high because the rubber lining layer is further formed after the urethane elastomer layer is formed.

  An object of the present invention is to provide a urethane elastomer-coated steel material that can withstand various impacts and stably maintain the anticorrosion performance for a long period of time at low cost.

  As a result of intensive studies to solve the above problems, the present inventors have found that a steel material that can withstand various impacts and has excellent anticorrosion properties can be obtained by containing urethane elastomer with a specific content. The present invention has been completed based on this finding.

  That is, the present invention relates to a urethane elastomer-coated steel material having a primer layer mainly composed of at least one of a urethane resin or an epoxy resin on the surface of a steel material, and a urethane elastomer layer on the upper layer, and 2-9 vol in the urethane elastomer layer. % Urethane-containing steel material characterized by containing air bubbles.

  Since the present invention improves the impact resistance of urethane elastomer-coated steel materials, damage to the coating is less likely to occur during construction and collisions with driftwood, ships, etc., and establishes long-term corrosion resistance of steel materials Can now.

  Examples of the steel material used in the present invention include a steel pipe, a steel pipe sheet pile, a steel sheet pile, and a steel plate. Generally, in order to improve the adhesive strength between the steel material and the primer layer, it is important to keep the steel material surface clean. In the present invention, the specific means is not limited as long as the oxide layer and oil on the steel material surface can be removed, but steel blasting and steel grit are preferable.

  The primer layer is a layer composed of a main agent and a curing agent mainly composed of at least one of a urethane resin or an epoxy resin, and is preferably a room temperature curing type. The film thickness is 5 to 80 μm, preferably about 15 to 50 μm. If the thickness is less than 5 μm, the adhesive strength is insufficient, and if it exceeds 80 μm, the primer may foam when cured to reduce the corrosion resistance.

  The urethane elastomer layer is mainly composed of a polyol as a main agent and an isocyanate compound as a curing agent.

  Examples of the polyol include bifunctional or trifunctional polyols such as polyether polyol, polyester polyol, polyester amide polyol, acrylic polyol, castor oil-modified polyol, epoxy-modified polyol, polyalkylene glycol, and terminal OH polybutadiene.

  The type of the polyol used in the present invention is not particularly limited, but castor oil-modified polyol, polyester polyol, polybutadiene polyol and the like are preferable in terms of excellent corrosion resistance.

  The isocyanate compound used as a curing agent has two or more isocyanate groups, and is tolylene diisocyanate, difermethane isocyanate, triphenylmethane triisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, trimethylhexamethylene diisocyanate, isophorone diisocyanate. Lysine isocyanate methyl ester and modified derivatives thereof.

  The type of the isocyanate compound used in the present invention is not particularly limited, but for example, polymethylene-polyphenyl-polyisocyanate (MDI), tolylene diisocyanate (TDI) and the like are preferable.

  The blending ratio of the main component and the curing agent of the urethane elastomer layer is preferably about 10 to 20 wt% in excess when the blending ratio is adjusted as described later. In the case of foaming by other methods, the theoretical equivalent ratio may be about ± 10 wt%.

  The bubble content of the urethane elastomer layer is 2 to 9 vol%. When the bubble content of the urethane elastomer layer is less than 2%, the impact resistance is not improved, and when it exceeds 9%, the impact resistance of the urethane elastomer layer is lowered and the corrosion resistance is lost.

  A preferable bubble content is 2.5 to 7.0 vol%.

  The method of mixing bubbles in the urethane elastomer layer is not particularly limited, but a method of mixing a gas such as air, nitrogen, carbon dioxide, helium or the like in the main agent before coating, or a curing agent by adjusting the mixing amount ratio with the main agent There is a method in which 10 to 20 wt% is excessive and foamed after mixing.

  In addition, air that is trapped in the coating during spray coating and released before curing the coating increases the viscosity of the main agent, or increases the reaction rate of the main agent and the curing agent with a catalyst. There are ways to leave.

The bubble content rate calculation method is as follows. First, samples are cut out from arbitrary five locations of the urethane elastomer layer, and after cooling with liquid nitrogen, they are immediately broken to produce five samples having arbitrary cross sections. Two arbitrary fields of 1000 × 1000 μm in the cross section of these five arbitrary positions are observed and photographed with a scanning electron microscope. Next, the area ratio X of the bubble cross-section is measured by an image analysis apparatus with respect to 1000 μm × 1000 μm of 10 micrographs in total. The bubble content Y is obtained from the area ratio X by the following formula.
Y = X ^3/2
The average of the bubble content Y at 10 locations is taken as the bubble content of the urethane elastomer.

The bubble diameter is 150 μm or less, preferably 20 to 150 μm, and the maximum bubble diameter is 100 to 150 μm, preferably about 120 to 140 μm.
If the diameter of the bubbles exceeds 150 μm, the corrosion resistance is inferior and the impact resistance is not improved.
The method for measuring the diameter of the bubbles is as follows. In the same manner as the bubble content calculation method, a cross section of a total of 10 visual fields (arbitrary 5 locations × 2 visual fields) of 1000 μm × 1000 μm of the uratan elastomer layer is observed with a scanning electron microscope, and the area of each bubble in the observation visual field Is measured using an image analyzer. The diameter (circle equivalent diameter) of a circle having the same area as the bubble area is obtained, and this value is taken as the bubble diameter.

  The film thickness of the urethane elastomer layer is preferably about 1 to 7 mm. Furthermore, about 2-4 mm is more preferable. If the thickness is less than 1 mm, the permeation of water and oxygen cannot be suppressed, so that the corrosion resistance is inferior. If the thickness exceeds 7 mm, the corrosion resistance is not improved and the cost is not met.

  In the present specification, the main component means a component that occupies 50 wt% or more, preferably 60 wt% or more and 100 wt% or less, preferably 95 wt% or less of the entire coating composition.

  Various additives can be added to the primer layer or the urethane elastomer layer. For example, pigments such as carbon black and calcium carbonate may be blended in order to impart weather resistance and abrasion resistance. In order to impart other properties, a solvent, a plasticizer, an auxiliary agent, a thickener, an antioxidant, a light stabilizer and the like may be contained.

  As shown in FIG. 1, the urethane elastomer-coated steel material 4 of the present invention has a urethane elastomer layer 1 containing 2 to 9 vol% of air bubbles on one side or both sides of a steel material 3 via a primer layer 2.

  The urethane elastomer layer is obtained by mixing the polyol and the isocyanate compound described above, applying the mixture using a spray, a spatula, and the like, and then curing.

  Primers having different resin compositions were applied to a thickness of 20 to 40 μm by a bar coater on a steel plate having a thickness of 3.0 mm subjected to blasting of Rz = 50 μm. The primer used the both terminal polyol as a main ingredient, and the both terminal isocyanate as a hardening | curing agent. After the coated primer is cured at room temperature for 1 day, air is blown into the main agent in advance, and the urethane elastomer paint whose bubble content is adjusted by adjusting the amount of the blow is 3.0 to 3.2 mm by airless spray. Painted to the thickness of The relationship between the bubble content of the urethane elastomer layer and the impact resistance is shown in Table 1 and FIG. Table 1 also shows the maximum bubble diameter. MDI was used as the curing agent, and mixed such that the isocyanate group concentration in the curing agent was 1: 1.05 with respect to the hydroxyl group concentration in the main agent. The steel sheet coated with the urethane elastomer layer was left at room temperature for 7 days to cure the urethane elastomer layer.

  Cross-sectional observation of the urethane elastomer was performed at an accelerating voltage of 15 kV using a scanning electron microscope (Hitachi, Ltd. S-800). The measurement of the bubble cross-sectional area in the micrograph was performed with an image analyzer (Nireco-Luzex III).

  The impact resistance of the urethane elastomer-coated steel material was determined by a drop weight impact test at 23 ° C. using a drop weight having a tip diameter of 15.9 mm and a weight of 5 kg in accordance with ASTM G14. The destruction of the coating of the urethane elastomer layer was confirmed by a continuity test of 20 kV, and the impact energy from the limit height at which no destruction occurred was obtained and used as an index of impact resistance.

  From the results shown in FIG. 2, the urethane elastomer-coated steel material of the present invention has a bubble content in the urethane elastomer of 2 to 9 vol%, but the impact resistance is improved by 35% or more compared to the case of containing no bubbles at all (55J Above). In addition, those having a bubble content of more than 9% had lower impact resistance than those having no bubbles.

  The urethane elastomer-coated steel material of the present invention is excellent in impact resistance in addition to corrosion resistance, and is suitable for use in the ocean, harbors, rivers and the like.

It is a fragmentary sectional view of the urethane elastomer covering steel material which shows an example of the present invention. It is a figure which shows the relationship between the bubble content rate and impact resistance of the urethane elastomer covering steel material of this invention. (A) is a scanning electron microscope (SEM) photograph of a cross section of a urethane elastomer layer containing no bubbles, (B) is a scanning electron micrograph (SEM) photograph of a cross section of a urethane elastomer containing 2.2 vol% of bubbles, ( C) is a scanning electron microscope (SEM) photograph of a cross section of an elastomer layer containing 7.2 vol% of bubbles, and (D) is a scanning electron microscope (SEM) photograph of a cross section of a urethane elastomer layer containing 11.0 vol% of bubbles. is there.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Urethane elastomer layer 2 ... Primer layer 3 ... Steel material 4 ... Urethane elastomer covering steel material 5 ... Urethane elastomer layer which does not contain air bubbles at all (Photo 1)
6 ... Urethane elastomer layer containing 2.2 vol% of bubbles (Photo 2)
7: Urethane elastomer layer containing 7.2 vol% of bubbles (Photo 3)
8 ... Urethane elastomer layer containing 11.0 vol% of bubbles (Photo 4)

Claims (3)

A urethane elastomer-coated steel material having a primer layer mainly composed of at least one of a urethane resin or an epoxy resin on the surface of a steel material and a urethane elastomer layer as an upper layer thereof, and the urethane elastomer layer contains 2 to 9 vol% of bubbles. A urethane elastomer-coated steel material. 2. The urethane elastomer-coated steel material according to claim 1, wherein the diameter of bubbles in the urethane elastomer layer is 150 μm or less. The urethane elastomer-coated steel material according to claim 1 or 2, wherein the primer layer has a thickness of 5 to 80 µm and the urethane elastomer layer has a thickness of 1 to 7 mm.

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