JP4333420B2 - Urethane elastomer coated steel material excellent in low temperature impact resistance and resin composition used therefor - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a urethane elastomer-coated steel material excellent in low-temperature impact resistance and a resin composition used therefor, and in particular, a urethane elastomer-coated steel material that can prevent corrosion of steel structures such as oceans, harbors, and rivers over a long period of time and a resin composition using the same. Related to things.

  Since steel structures used in the ocean, harbors, rivers, etc. are exposed to severe corrosive environments, urethane elastomer coating is used as a heavy anticorrosion coating near the splash zone during tidal periods. However, when used in cold regions, the impact resistance is insufficient, and there is a problem that the anti-corrosion property is lost due to cracking during construction such as driving into the soil or the sea floor. It was.

  Conventionally, in order to improve the low-temperature impact resistance of urethane elastomer-coated steel materials, there are those in which an aromatic diol having a tertiary amino group and a saturated aliphatic diol component are added to the main component polyol. (See Patent Document 1).

JP-A-11-245331

  The urethane elastomer coating is performed for the purpose of preventing the arrival of corrosion factors such as water, oxygen and ions on the steel material surface, but the conventional urethane elastomer coating has insufficient impact resistance at low temperatures. The above-mentioned aromatic diol having a tertiary amino group and a saturated aliphatic diol component are added to achieve both low-temperature impact resistance and anti-corrosion properties, but have poor anti-corrosion properties and low-temperature resistance. The impact property was also insufficient.

  An object of the present invention is to provide a urethane elastomer-coated steel material that is excellent in low-temperature impact resistance in addition to anticorrosion properties and can prevent corrosion of steel structures such as oceans, harbors, and rivers over a long period of time.

  The inventors of the present invention have intensively studied to solve the above-mentioned problems, and have focused on the fact that the urethane elastomer undergoes a great change in elongation as the temperature changes. As a result of diligent investigation focusing on the strength balance of the resin skeleton, excellent low-temperature shock resistance was achieved by including a specific ratio of rigid specific bisphenol-based diol and flexible specific saturated aliphatic diol in the polyol component in a certain ratio. We have succeeded in obtaining a urethane elastomer-coated steel material with good properties.

That is, the present invention is a urethane elastomer-coated steel material in which at least one of a urethane resin or an epoxy resin as a main component is coated on the surface of a steel material, and a urethane elastomer is coated on the primer. The polyol and the isocyanate of the curing agent as main components, in the polyol,
(A) a bisphenol-based diol having a hydroxyl value of 250 to 400 mgKOH / g;
(B) A saturated aliphatic diol having a hydroxyl value of 800 to 1500 mgKOH / g is (b) / (a) = 0.08 to 0.35 (weight ratio), {(a) + (b)} / total polyol = A urethane elastomer-coated steel material excellent in low temperature impact resistance, characterized by containing 0.12 to 0.35 (weight ratio), a main component polyol and a curing agent isocyanate as main components, in the polyol,
(A) a bisphenol-based diol having a hydroxyl value of 250 to 400 mgKOH / g;
(B) A saturated aliphatic diol having a hydroxyl value of 800 to 1500 mgKOH / g is (b) / (a) = 0.08 to 0.35 (weight ratio), {(a) + (b)} / total polyol = It is related with the urethane elastomer resin composition for steel material coating | cover characterized by containing by 0.12-0.35 (weight ratio).

  Since the present invention improves the low-temperature impact resistance of the urethane elastomer-coated steel material, cracks are less likely to occur during construction such as driving into the soil in cold regions, and long-term corrosion resistance of the steel material can be established. Became.

  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 about 10 to 100 μm, preferably about 20 to 70 μm. If it is less than 10 μm, the adhesive strength is insufficient, and if it exceeds 100 μm, the primer tends to foam when it is cured.

  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 a bifunctional or trifunctional polyol such as polyether polyol, polyester polyol, polyester amide polyol, acrylic polyol, castor oil-modified polyol, epoxy-modified polyol, polyalkylene glycol, and terminal OH polybutadiene. It is characterized in that a part of bisphenol diol and saturated aliphatic diol are used in combination.

  The reason for using bisphenol-based diol is that it has a rigid skeleton derived from the benzene ring and has high hydrophobicity. When bisphenol-based diol is used as part of the polyol, the crosslink density increases as the amount of bisphenol-based diol increases. Therefore, by suppressing the permeation of water, oxygen, etc., the resistance to cathodic stripping is improved, the surface hardness, Abrasion and scratch resistance are improved, but low temperature impact resistance is reduced due to a decrease in elongation at low temperatures.

The types of bisphenol diol is not particularly limited, for example, bisphenol A oxide flop propylene adduct, bisphenol A ethylene oxide adduct and the like. The hydroxyl value of this bisphenol diol is 250 to 400 mgKOH / g.

  If it is less than 250 mgKOH / g, the molecular weight increases, so the crosslinking density decreases and the anticorrosion properties are poor. On the other hand, if it exceeds 400 mgKOH / g, the crosslinking density increases more than necessary, so that the flexibility at low temperature is lowered and the impact resistance is poor. Preferably it is about 280-380 mgKOH / g.

  In order to improve the low temperature impact resistance of the urethane elastomer-coated steel material, a saturated aliphatic diol is used in combination. The role of the saturated aliphatic diol is to maintain a high crosslinking density by a high hydroxyl value, to ensure hydrophobicity, and to provide flexibility at a low temperature to the urethane elastomer layer by a soft resin skeleton. .

  As for the position of the hydroxyl group, both terminals are preferred so as to react rapidly with isocyanate. The type of the saturated aliphatic diol is not particularly limited, and examples thereof include 1,4 butanediol, 1,5 pentanediol, 3 methyl-1,5 pentanediol, 4 methyl 1,8 octanediol and the like. The hydroxyl value of this saturated aliphatic diol is 800-1500 mgKOH / g.

  If it is less than 800 mgKOH / g, the molecular weight increases, so the crosslink density decreases and the anticorrosion properties are poor. On the other hand, if it exceeds 1500 mgKOH / g, the crosslinking density increases more than necessary, so that the flexibility at low temperature is lowered and the impact resistance is poor. Preferably it is about 900-1300 mgKOH / g.

  The blending amount of the (a) bisphenol diol and (b) saturated aliphatic diol in the polyol is (b) / (a) = 0.08 to 0.35 (weight ratio), preferably 0.1. About 0.3 (weight ratio). When (b) / (a) is less than 0.08, flexibility is low and impact resistance is poor. If it exceeds 0.35, the resin is soft and inferior in impact resistance, wear resistance and scratch resistance. Further, {(a) + (b)} / total polyol = 0.12 to 0.35 (weight ratio), preferably 0.10 to 0.30 (weight ratio). If {(a) + (b)} / total polyol is less than 0.12, the resin is soft and inferior in wear resistance and scratch resistance, and if it exceeds 0.35, flexibility is lowered and impact resistance is inferior.

  The components of the polyol other than (a) and (b) used in the present invention are not particularly limited in composition, but castor oil-based polyols, polyester polyols 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 curing agent of the urethane elastomer is preferably within about ± 10 wt% of the theoretical equivalent. If the curing agent is less than 10 wt% less than the theoretical equivalent, curing failure tends to occur, and if it exceeds 10 wt%, foaming tends to occur.

  The thickness of the urethane elastomer layer of the present invention is preferably 2 to 4 mm. If it is less than 2 mm, the suppression of water and oxygen permeation is insufficient, resulting in poor corrosion resistance, and if it exceeds 4 mm, the corrosion resistance is not improved and the cost is not met.

  In the present specification, the main component refers to a component that accounts for 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 or the urethane elastomer. For example, pigments such as carbon black and calcium carbonate may be blended in order to impart weather resistance and abrasion resistance. In addition, a solvent, a plasticizer, an auxiliary agent, a thickener, an antioxidant, a light stabilizer, and the like may be contained in order to impart characteristics.

  As shown in FIG. 1, in the present invention, a urethane elastomer-coated steel material 4 is manufactured by coating a primer layer 2 on one or both surfaces of a steel material 3 and coating a specific urethane elastomer layer 1. The urethane elastomer layer can be obtained by mixing the above-described polyol and isocyanate compound, and then applying and curing using a spray, a spatula or the like.

  Primers having different resin compositions were applied to a thickness of 20 to 40 μm using a bar coater on a 3.0 mm thick steel plate subjected to blasting with Rz = 50 μm. In the case of a urethane resin, the primer used the both terminal polyol as a main ingredient, and the both terminal isocyanate as a hardening | curing agent. In the case of an epoxy resin, bisphenol A was used as the main agent and polyamide was used as the curing agent. After the coated primer was cured at room temperature for 1 day, urethane elastomer paints having different main resin compositions were applied to a thickness of 3.0 to 3.2 mm by airless spray. The composition is shown in Table 1. 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 urethane elastomer was left at room temperature for 7 days to cure the urethane elastomer layer.

  (Comparative Example) In Comparative Example 1, (b) a saturated aliphatic diol was not blended in a urethane elastomer, and (a) a bisphenol-based diol was not blended, and an aniline propylene oxide adduct was used. In Comparative Example 3, (a) a bisphenol diol having a hydroxyl value of 450 mgKOH / g was used. In Comparative Example 4, (b) a saturated aliphatic diol having a hydroxyl value of 650 mgKOH / g was used. In Comparative Examples 5 and 6, (b) saturated aliphatic diol / (a) bisphenol diol in the urethane elastomer was less than 0.08, and more than 0.35. In Comparative Example 7, {(a) + (b)} / total polyol was more than 0.35. In Comparative Example 8, a primer mainly composed of an acrylic resin was used.

The low temperature impact resistance of the urethane elastomer-coated steel material was determined by a falling weight impact test at −20 ° C. using a falling 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 20 kV semi-through test, and the low temperature impact strength was determined from the limit height at which no destruction occurred.

  As can be seen from the results in Table 1, in Examples 1 to 8 of the urethane elastomer-coated steel materials of the present invention, good low temperature impact resistance (55 J or more) was obtained. In addition, the result using the primer which has the acrylic resin of the comparative example 8 as a main component did not show an effect, even if it used the urethane elastomer of this invention.

表１中の化合物の種類
（ａ）ビスフェノール系ジオール
Ａ：ビスフェノールＡ酸化プロピレン付加物
Ｂ：ビスフェノールＡ酸化エチレン付加物
（ｂ）飽和脂肪族系ジオール
Ｃ：１，４ブタンジオール
Ｄ：１，５ペンタンジオール
Ｅ：３メチル−１，５ペンタンジオール
その他のポリオール
Ｆ：ヒマシ油系ポリオール
Ｇ：ポリエステルポリオール
Ｈ：アニリン酸化プロピレン付加物
プライマーの主成分
Ｉ：ウレタン樹脂
Ｊ：エポキシ樹脂
Ｋ：アクリル樹脂

Types of compounds in Table 1 (a) Bisphenol diol A: Bisphenol A propylene oxide adduct B: Bisphenol A ethylene oxide adduct (b) Saturated aliphatic diol C: 1,4 butanediol D: 1,5 pentane Diol E: 3-methyl-1,5-pentanediol Other polyol F: Castor oil-based polyol G: Polyester polyol H: Main component of aniline propylene oxide adduct primer I: Urethane resin J: Epoxy resin K: Acrylic resin

  The urethane elastomer-coated steel material of the present invention has strong low temperature impact resistance in addition to corrosion resistance, and is particularly suitable for use in oceans, harbors, rivers, etc. in cold regions.

It is a fragmentary sectional view of the urethane elastomer covering steel material which shows an example of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Urethane elastomer layer 2 ... Primer layer 3 ... Steel material 4 ... Urethane elastomer covering steel material

Claims (2)

A urethane elastomer-coated steel material in which a steel material is coated with a primer mainly composed of at least one of a urethane resin or an epoxy resin, and a urethane elastomer is coated on the primer. As a main component of the isocyanate, in the polyol,
(A) a bisphenol-based diol having a hydroxyl value of 250 to 400 mgKOH / g;
(B) A saturated aliphatic diol having a hydroxyl value of 800 to 1500 mgKOH / g is (b) / (a) = 0.08 to 0.35 (weight ratio), {(a) + (b)} / total polyol = A urethane elastomer-coated steel material excellent in low-temperature impact resistance, characterized by containing 0.12 to 0.35 (weight ratio). Based on the main component polyol and the curing agent isocyanate, in the polyol,
(A) a bisphenol-based diol having a hydroxyl value of 250 to 400 mgKOH / g;
(B) A saturated aliphatic diol having a hydroxyl value of 800 to 1500 mgKOH / g is (b) / (a) = 0.08 to 0.35 (weight ratio), {(a) + (b)} / total polyol = A urethane elastomer resin composition for coating steel materials, characterized by containing 0.12 to 0.35 (weight ratio).

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