JP5767670B2 - Primer composition and coated steel - Google Patents

Description

  The present invention relates to a primer composition and a coated steel material.

  Conventionally, a coated steel material is known in which a surface of a steel material is coated with an anticorrosive paint. Such a coated steel material can prevent corrosion caused by environmental conditions such as in water or under high humidity, for example, by having an anticorrosive layer as a coating film formed by the coating. As such an anticorrosion paint, for example, a paint containing a polyurethane resin composition is known.

  However, for example, if the anticorrosion layer formed on the surface of the steel material is immersed in water or high humidity for a long period of time, water or oxygen passes through the anticorrosion layer and reaches the adhesion surface between the anticorrosion layer and the steel material. When contact with water or oxygen reduces the adhesion of the anticorrosion layer to the steel and the anticorrosion layer peels off, or when contacted with water or oxygen causes the steel to corrode and the anticorrosion layer peels off There is.

  Moreover, for example, a structure is created using a corrosion-resistant steel material having a corrosion-resistant layer on a part of the surface of the steel material, and further, corrosion of a portion where the corrosion-resistant layer is not formed on the surface of the steel material (unpainted portion) is prevented. In some cases, the anti-corrosion is applied to the unpainted portion. In this case, the edge adjacent to the unpainted portion is affected by the hydroxide ions generated by applying the anti-corrosion current to the unpainted portion. The anticorrosion layer may peel off from the part side (cathode peelability).

  Therefore, in order to improve the adhesion of the anticorrosion layer to the surface of the steel material, a primer layer interposed between the surface of the steel material and the anticorrosion layer has been proposed. Such a primer layer is formed by coating and hardening a primer composition on the surface of a steel material.

  As this kind of primer composition, one having a polyol component and a polyisocyanate component has been proposed. Specifically, for example, the polyol component contains a mixture of aliphatic amine polyol, castor oil and alkylene glycol. (See Patent Document 1).

JP 11-323253 A

  However, when the primer composition as shown in Patent Document 1 is coated on the surface of a steel material in a high-temperature and high-humidity environment, foaming occurs when the primer composition is cured, and adhesion of the primer layer as a cured product May decrease.

  This invention makes it a subject to provide the primer composition which can form the primer layer which exhibits the outstanding adhesiveness in view of the said problem. It is another object of the present invention to provide a coated steel material that can exhibit excellent anticorrosion performance.

In order to solve the above problems, the primer composition according to the present invention is:
A primer composition having an active hydrogen group-containing component (A) and a polyisocyanate group-containing component (B),
The active hydrogen group-containing component (A) contains a hydroxyl group-terminated urethane prepolymer (a) produced using at least a polyether polyol (a1) obtained by adding an alkylene oxide to a bisphenol compound and a polyisocyanate (a2). ,
The polyisocyanate group-containing component (B) is an isocyanate group-terminated urethane produced by using at least a polyether polyol (b1) and a polyisocyanate (b2) obtained by adding butylene oxide to a polyol having three or more hydroxyl groups. It contains prepolymer (b).

According to such a configuration, since the active hydrogen group-containing component (A) and the polyisocyanate group-containing component (B) each contain a urethane prepolymer, than when the urethane prepolymer is not contained, The molecular weight of the urethane polymer in the cured product can be increased. As a result, even when coated in a high-temperature and high-humidity environment, it is possible to improve the adhesion of the primer layer that is a cured product. Can be demonstrated.
The active hydrogen group-containing component (A) contains a hydroxyl group-terminated urethane prepolymer obtained by adding an alkylene oxide to a bisphenol compound as the polyether polyol (a1). Adhesiveness can be improved.
Furthermore, since the polyether polyol (b1) obtained by adding butylene oxide to the polyol having three or more hydroxyl groups is relatively hydrophobic, the isocyanate group-terminated urethane prepolymer (b ) -Containing primer composition is also relatively hydrophobic. As a result, the primer layer formed by the primer composition has relatively high hydrophobicity and is excellent in heat and moisture resistance, and therefore has excellent adhesiveness even when used in a relatively high temperature and high humidity environment. Can be demonstrated.
Therefore, the primer layer formed exhibits excellent adhesion whether it is applied in a relatively high temperature and high humidity environment or is used in a relatively high temperature and high humidity environment. obtain.

  The coated steel material according to the present invention includes a steel material, a primer layer obtained by coating and curing at least the primer composition on the surface of the steel material, and an anticorrosion layer.

  According to this configuration, since the surface of the steel material is provided with a primer layer at least coated with the primer composition and hardened, peeling of the anticorrosion layer formed on the surface side can be suppressed. Can exhibit excellent anticorrosion performance.

  As described above, the primer composition according to the present invention can form a primer layer exhibiting excellent adhesiveness. The coated steel material according to the present invention can exhibit excellent anticorrosion performance.

  Hereinafter, an embodiment of the primer composition according to the present invention will be described.

  The primer composition of this embodiment is a primer composition having an active hydrogen group-containing component (A) and a polyisocyanate group-containing component (B), wherein the active hydrogen group-containing component (A) is a bisphenol compound. Containing a hydroxyl group-terminated urethane prepolymer (a) produced by using at least a polyether polyol (a1) and an polyisocyanate (a2) obtained by adding an alkylene oxide to the polyisocyanate group-containing component (B) An isocyanate group-terminated urethane prepolymer (b) produced by using at least a polyether polyol (b1) obtained by adding butylene oxide to a polyol having three or more of the above and a polyisocyanate (b2).

  The primer composition has an active hydrogen group-containing component (A) and a polyisocyanate group-containing component (B), that is, a two-component polyurethane resin composition. These active hydrogen group-containing component (A) and polyisocyanate group-containing component (B) are applied to, for example, the surface of a steel material, and the active hydrogen group-containing component (A) and the polyisocyanate group-containing component (B) are reacted. Then, a primer layer, which is a polyurethane resin, is formed on the surface of the steel material.

  The primer composition preferably forms a primer layer which is a non-foaming polyurethane resin. Here, the non-foaming polyurethane resin means a polyurethane resin that does not have bubbles due to foaming when a hydroxyl group and an isocyanate group react. In addition, the polyurethane resin having air bubbles which are inevitably formed by entraining external air during the reaction between the hydroxyl group and the isocyanate group is included in the non-foaming polyurethane resin.

  The active hydrogen group-containing component (A) contains a hydroxyl group-terminated urethane prepolymer (a) produced using at least a polyether polyol (a1) obtained by adding an alkylene oxide to a bisphenol compound and a polyisocyanate (a2). ing.

Examples of the polyether polyol (a1) obtained by adding an alkylene oxide to the bisphenol compound include a polyether polyol obtained by adding an alkylene oxide to a bisphenol compound such as bisphenol A, bisphenol S, and bisphenol F. Among these, Bisphenol A is preferred.
Further, the alkylene oxide is preferably an alkylene oxide having 2 to 4 carbon atoms, more preferably an alkylene oxide having 3 to 4 carbon atoms, and further preferably propylene oxide.
From the above, the polyether polyol (a1) is preferably a polyether polyol obtained by adding propylene oxide to bisphenol A.
In the high-temperature and high-humidity environment, the active hydrogen group-containing component (A) contains a hydroxyl group-terminated urethane prepolymer obtained by adding an alkylene oxide to a bisphenol compound as the polyether polyol (a1). There is an advantage that the adhesion of the formed primer layer is excellent even when it is applied or when it is used in a high temperature and high humidity environment.

  The average hydroxyl value of the polyether polyol (a1) obtained by adding alkylene oxide to the bisphenol compound is preferably 50 to 500 mgKOH / g, and more preferably 100 to 400 mgKOH / g. Even if the average hydroxyl value is 50 to 500 mgKOH / g, the primer is formed even when it is applied in a high-temperature and high-humidity environment. There is an advantage that the adhesion of the layer is better.

  Examples of the polyisocyanate (a2) include conventionally known general polyisocyanate compounds.

  Specifically, as the polyisocyanate (a2), for example, tetramethylene diisocyanate, dodecamethylene diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, Examples include aliphatic polyisocyanates such as lysine diisocyanate, 2-methylpentane-1,5-diisocyanate, and 3-methylpentane-1,5-diisocyanate.

  Examples of the polyisocyanate (a2) include isophorone diisocyanate, hydrogenated xylylene diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate, methylcyclohexylene diisocyanate, and 1,3-bis (isocyanate). Mention may also be made of alicyclic polyisocyanates such as methyl) cyclohexane.

  Examples of the polyisocyanate (a2) include tolylene diisocyanate, 2,2′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, 4,4′-diphenylmethane diisocyanate (MDI), and polymethylene polyphenyl polyisocyanate. (Polymeric MDI), 4,4′-dibenzyl diisocyanate, 1,5-naphthylene diisocyanate, xylylene diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, α , Α, α, α-tetramethylxylylene diisocyanate and the like, and aromatic polyisocyanates having an aromatic ring in the molecule. That.

  Furthermore, as said polyisocyanate (a2), polyisocyanate compound modified bodies, such as a carbodiimide body, an isocyanurate body, a burette body, an adduct body, etc. of each compound mentioned above can also be used.

  As said polyisocyanate (a2), the said aromatic polyisocyanate is preferable and the said 4,4'- diphenylmethane diisocyanate is more preferable at the point which is excellent by the reactivity with the said polyether polyol (a1).

  The hydroxyl group-terminated polyurethane prepolymer (a) is produced using at least the polyether polyol (a1) obtained by adding an alkylene oxide to the bisphenol compound and the polyisocyanate (a2). Specifically, it is obtained by reacting at least the polyether polyol (a1) and the polyisocyanate (a2) at a blending ratio such that the hydroxyl group becomes excessive. That is, it was obtained by the above reaction at a blending ratio such that the molar ratio (NCO / OH ratio) of the free isocyanate group of the polyisocyanate (a2) to the free hydroxyl group of the polyether polyol (a1) was less than 1. Is.

  Here, the closer the NCO / OH ratio is to 1 (the larger), the larger the molecular weight of the hydroxyl group-terminated urethane prepolymer, so that the adhesion of the formed primer layer becomes better, If the NCO / OH ratio is too close to 1, there is a risk that the adhesiveness will be lowered. Therefore, for example, considering this viewpoint, the NCO / OH ratio is preferably 0.1 to 0.9, and more preferably 0.2 to 0.8.

  In addition to the polyether polyol (a1) and the polyisocyanate (a2), the hydroxyl-terminated urethane prepolymer (a) is a polyol other than the polyether polyol (a1) obtained by adding an alkylene oxide to a bisphenol compound. For example, it may be produced by further using castor oil and its derivatives.

  When the hydroxyl group-terminated urethane prepolymer (a) is contained in the active hydrogen group-containing component (A), the molecular weight of the urethane polymer in the cured product is increased as compared with the case where the urethane prepolymer is not contained. can do. Thereby, even if it is a case where it paints in a high-temperature, high-humidity environment, the adhesiveness of the primer layer which is hardened | cured material can be improved.

  The hydroxyl group-terminated urethane prepolymer (a) can be produced in a solvent by a conventionally known general method. Examples of the solvent used for the production include toluene, xylene, methyl ethyl ketone, ethyl acetate, butyl acetate, ethylene glycol monoethyl ether acetate and the like.

  The active hydrogen group-containing component (A) may contain conventionally known additives such as antioxidants, toners, rust preventive pigments, and flake pigments in addition to the hydroxyl group-terminated urethane prepolymer (a). Good.

  The polyisocyanate group-containing component (B) is an isocyanate group-terminated urethane produced by using at least a polyether polyol (b1) and a polyisocyanate (b2) obtained by adding butylene oxide to a polyol having three or more hydroxyl groups. Prepolymer (b) is contained.

  Polyols having three or more hydroxyl groups, that is, having three or more functionalities, such as triols such as glycerin and trimethylolpropane, tetraols such as pentaerythritol, sorbitan and mannitan, and polyols having six hydroxyl groups such as sorbitol, Examples thereof include polyols having 8 hydroxyl groups such as sucrose. Among these, as the polyol, a polyether polyol having 3 to 8 hydroxyl groups is preferable, and a polyol (triol) having 3 hydroxyl groups is considered considering that it is more excellent in reactivity with the polyisocyanate (b2). More preferably, among these triols, trimethylolpropane is more preferable.

  Since the polyether polyol (b1) obtained by adding butylene oxide to the polyol having three or more hydroxyl groups has a relatively hydrophobic ethyl group as a side chain, it is relatively hydrophobic. The primer composition containing the isocyanate group-terminated urethane prepolymer (b) produced by using this also has a relatively high hydrophobicity. As a result, the primer layer, which is a cured product of the primer composition, also has a relatively high hydrophobicity, and even when the primer layer is placed in a relatively high temperature and high humidity environment, water and oxygen are not contained inside. Since the intrusion can be suppressed, the moisture and heat resistance is excellent. Therefore, the primer layer has excellent adhesiveness. Moreover, since the said polyether polyol (b1) becomes comparatively high as mentioned above, when making it react with the said polyisocyanate (b2), reaction at the time of producing | generating the said polyisocyanate group terminal prepolymer It becomes possible to suppress foaming at the time. Moreover, even when the hydroxyl group in the active hydrogen group-containing component (A) is reacted with the isocyanate group of the polyisocyanate group-containing component (B), it is possible to suppress foaming during the reaction and The resulting decrease in adhesiveness can also be suppressed.

  As said polyisocyanate (b2), the thing similar to above-mentioned polyisocyanate (a2) is mentioned. Of these, the aromatic polyisocyanate is preferable, and the 4,4'-diphenylmethane diisocyanate is more preferable in that the adhesion of the primer layer is more excellent.

  The isocyanate group-terminated urethane prepolymer (b) is produced using at least the polyether polyol (b1) and the polyisocyanate (b2). Specifically, it is obtained by reacting at least the polyether polyol (b1) and the polyisocyanate (b2) at a blending ratio such that the isocyanate group becomes excessive. That is, it was obtained by the above reaction at a blending ratio such that the molar ratio (NCO / OH ratio) of the free isocyanate group of the polyisocyanate (b2) to the free hydroxyl group of the polyether polyol (b1) was larger than 1. Is.

  Here, the closer the NCO / OH ratio is to 1 (the smaller the molecular weight of the isocyanate group-terminated urethane prepolymer), the better the adhesion of the formed primer layer, If the NCO / OH ratio is too close to 1, there is a risk that the adhesiveness will be lowered. Therefore, for example, in consideration of such a viewpoint, the NCO / OH ratio is preferably 1.8 to 12, and more preferably 1.9 to 10.

  In addition to the polyether polyol (b1) and polyisocyanate (b2) obtained by adding butylene oxide to the polyol having three or more hydroxyl groups, the isocyanate group-terminated urethane prepolymer (b), for example, The reaction may be carried out using a polyether polyol obtained by adding an alkylene oxide other than the butylene oxide such as ethylene oxide or propylene oxide to the polyol having three or more hydroxyl groups.

  In addition to the above, the isocyanate group-terminated urethane prepolymer (b), in addition to the polyether polyol (b1) and the polyisocyanate (b2), further includes, for example, castor oil and derivatives thereof, polybutadiene polyol and the polyether. What was produced | generated using the compound etc. which were illustrated by the polyol (a1) may be used.

  By containing the isocyanate group-terminated urethane prepolymer (b) in the isocyanate group-containing component (B), the molecular weight of the urethane polymer in the cured product is increased as compared with the case where the urethane prepolymer is not contained. can do. Thereby, even if it is a case where it paints in a high-temperature, high-humidity environment, the adhesiveness of the primer layer which is hardened | cured material can be improved.

  The isocyanate group-terminated urethane prepolymer (b) can be produced in a solvent by a conventionally known general method. Examples of the solvent used for the production include toluene, xylene, methyl ethyl ketone, ethyl acetate, butyl acetate, ethylene glycol monoethyl ether acetate and the like.

In addition to the isocyanate group-terminated urethane prepolymer (b), the isocyanate group-containing component (B) is not contained in the isocyanate group-terminated urethane prepolymer (b), and other polyisocyanates (c). May be contained. Examples of the polyisocyanate (c) include the same polyisocyanates (a2) described above.
By the said isocyanate group containing component (B) containing the said polyisocyanate (c), there exists an advantage that the adhesiveness of a primer layer is more excellent.
The polyisocyanate (c) is preferably the aromatic polyisocyanate or a carbodiimide thereof, more preferably polyphenylpolymethylene polyisocyanate or carbodiimide-modified 4,4′-diphenylmethane diisocyanate, in that the primer layer is more excellent in adhesion. .

  In addition to the above, the isocyanate group-containing component (B) may contain conventionally known additives such as an antioxidant, a toner, a rust preventive pigment, and a flake pigment.

  As a preferable embodiment of the combination of the active hydrogen group-containing component (A) and the polyisocyanate group-containing component (B), for example, the active hydrogen group-containing component (A) is an alkylene having 2 to 4 carbon atoms in a bisphenol compound. It contains a hydroxyl group-terminated urethane prepolymer (a) produced by using at least a polyether polyol (a1) and a polyisocyanate (a2) formed by adding an oxide, and the polyisocyanate group-containing component (B) is a hydroxyl group. An embodiment containing an isocyanate group-terminated urethane prepolymer (b) produced by using at least a polyether polyol (b1) and a polyisocyanate (b2) obtained by adding butylene oxide to a polyol having three Is mentioned.

The compounding ratio of the active hydrogen group-containing component (A) and the polyisocyanate group-containing component (B) is 1 mol of hydroxyl group contained in the active hydrogen group-containing component (A). The proportion of the isocyanate group contained in B) is preferably 1.2 to 2.5 mol, and more preferably 1.6 to 2.2 mol.
There exists an advantage that the adhesiveness of a primer layer is more excellent because the said compounding ratio is 1.2-2.5 mol.

  The primer composition can be obtained by mixing the active hydrogen group-containing component (A) and the polyisocyanate group-containing component (B) by a conventionally known general method.

The primer composition may contain a conventionally known metal catalyst in order to adjust the reactivity between the active hydrogen group-containing component (A) and the polyisocyanate group-containing component (B). Moreover, you may contain the polyamine. These are preferably contained in the active hydrogen group-containing component (A) when they are reacted.
Furthermore, in order to further improve the adhesiveness of the primer layer, a silane coupling agent may be contained. Examples of such silane coupling agents include epoxy group-containing silane coupling agents, amino group-containing silane coupling agents, and the like. Epoxy group-containing silane coupling agents are preferred because they are superior in adhesiveness. Of these, the amino group-containing silane coupling agent is preferably contained in the active hydrogen group-containing component (A) when reacted.

As described above, in the primer composition of the present embodiment, the active hydrogen group-containing component (A) and the polyisocyanate group-containing component (B) each contain a urethane prepolymer. Even when it is painted, the curing can proceed sufficiently. Thereby, the said primer composition can form the primer layer which exhibits the outstanding adhesiveness by coating and hardening.
The active hydrogen group-containing component (A) contains a hydroxyl group-terminated urethane prepolymer obtained by adding an alkylene oxide to a bisphenol compound as the polyether polyol (a1). Adhesiveness can be improved.
Furthermore, since the polyether polyol (b1) obtained by adding butylene oxide to the polyol having three or more hydroxyl groups is relatively hydrophobic, the isocyanate group-terminated urethane prepolymer (b ) -Containing primer composition is also relatively hydrophobic. As a result, the primer composition can be applied and cured to form a primer layer having relatively high hydrophobicity and excellent heat-and-moisture resistance. Therefore, the primer composition is used in a high-temperature and high-humidity environment. However, a primer layer exhibiting excellent adhesiveness can be formed.
Therefore, even when it is applied in a high temperature and high humidity environment or when it is used in a high temperature and high humidity environment, a primer layer exhibiting excellent adhesiveness can be formed.

  In addition, the primer composition of the present embodiment is coated on the surface of a steel material from which surface scales and dirt have been removed by blasting or acid treatment in order to ensure adhesion, thereby forming a primer layer.

  One embodiment of the coated steel material according to the present invention includes a steel material, a primer layer obtained by coating and curing at least the primer composition of the above-described embodiment on the surface of the steel material, and an anticorrosion layer coated on the primer layer. It has.

  The steel material may be any kind of steel material such as ordinary steel, high-tensile steel or high alloy steel, for example, steel pipes used in buried corrosive environments, steel pipe piles used in offshore structures, steel pipe sheet piles, etc. It is applicable to steel sheet piles, H-section steel, wire rods, etc.

  Examples of the anticorrosion paint include conventionally known anticorrosion paints. For example, perm guard 137, perm guard 250, perm guard 601, perm guard 901, MACFLEX107, MACFLEX109 (all trade names manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and the like. An anticorrosive paint having a urethane resin composition of

  Since the coated steel material of the present embodiment includes a primer layer at least coated with the primer composition on the surface of the steel material and can be cured, it is possible to suppress peeling of the anticorrosion layer, and thus excellent anticorrosion performance. Can be demonstrated.

  Examples of a method for forming a primer layer on the surface of such steel material include conventionally known methods. For example, the active hydrogen group-containing component (A) and the polyisocyanate group-containing component (B) are mixed in a two-component spray. The active hydrogen group-containing component (A) and the polyisocyanate are accommodated in the respective accommodating portions of the coating machine, and are set from 20 ° C. to 30 ° C. in the respective accommodating portions from the nozzle of the two-component mixed spray coating machine. There is a method in which an isocyanate group-containing component (B) is mixed to form a primer composition, the primer composition is sprayed onto the surface of the steel material, and then cured. Moreover, a conventionally well-known method is mentioned as a method of forming an anticorrosion layer by applying an anticorrosion paint on the primer layer and curing it.

The primer composition and coated steel material of the above embodiment are as exemplified above, but the present invention is not limited to the above exemplified primer composition and coated steel material.
Moreover, the various aspects used in a general primer composition and a covering steel material can be employ | adopted in the range which does not impair the effect of this invention.

  EXAMPLES Next, an Example is given and this invention is demonstrated in more detail.

  Below, the detail of the raw material for manufacturing a primer composition is demonstrated.

<Raw materials>

(A1) Polyether polyol obtained by adding alkylene oxide to bisphenol compound (a1-1): Polyether polyol obtained by adding 5 mol of propylene oxide to bisphenol A (average hydroxyl value: 216 mgKOH / g)
(A1-2): Polyether polyol obtained by adding 2.3 mol of propylene oxide to bisphenol A (average hydroxyl value: 310 mgKOH / g)

(A1 ′) A polyether polyol (a1′-1) different from the polyether polyol (a1): a polyether polyol obtained by adding 7 mol of butylene oxide to trimethylolpropane (average hydroxyl value: 264 mgKOH / g)
Note that (a1′-1) is the same as (b1-2) described later.

(A2) Polyisocyanate (a2-1): 4,4′-diphenylmethane diisocyanate
(Product name: Millionate MT, manufactured by Nippon Polyurethane Industry Co., Ltd.)

(B1) Polyether polyol (b1-1): Polyether polyol obtained by adding 5 mol of butylene oxide to trimethylolpropane (average hydroxyl value: 341 mgKOH / g)
(B1-2): Polyether polyol obtained by adding 7 moles of butylene oxide to trimethylolpropane (average hydroxyl value: 264 mgKOH / g)
(B1-3): Polyether polyol obtained by adding 9 mol of butylene oxide to trimethylolpropane (average hydroxyl value: 215 mgKOH / g)

(B1 ′) Polyether polyol (b1′-1): Polyether polyol obtained by adding 8.7 mol of propylene oxide to trimethylolpropane (average hydroxyl value: 264 mgKOH / g)

(B2) Polyisocyanate (b2-1): 4,4′-diphenylmethane diisocyanate
(Product name: Millionate MT, manufactured by Nippon Polyurethane Industry Co., Ltd.)

(C) Polyisocyanate different from polyisocyanate (b2) (c-1) Polyphenyl polymethylene polyisocyanate
(Product name: Millionate MR-100, manufactured by Nippon Polyurethane)
(C-2) Carbodiimide-modified 4,4′-diphenylmethane diisocyanate
(Product name: Lupranate MM-103, BASF INOAC Polyurethane)

(Reaction catalyst)
Dioctyltin dilaurate (trade name: Neostan U810 (manufactured by Nitto Kasei Co., Ltd.)

(Silane coupling agent)
(D-1): 3-Glycidoxypropyltriethoxysilane
(Product name: KBE-403, manufactured by Shin-Etsu Silicone)
(D-2): 3-aminopropyltriethoxysilane
(Product name: KBE-903, manufactured by Shin-Etsu Silicone)

<Preparation of active hydrogen group-containing component>
Active hydrogen group-containing components A1 to A7 and A9, which are hydrogen group-terminated urethane prepolymers, were produced by mixing in a nitrogen-substituted flask with the raw materials and blending ratios shown in Table 1 and reacting at 90 ° C. for 1 hour.
On the other hand, it mixed by the raw material and compounding ratio which are shown in Table 1, and obtained the active hydrogen group containing component A8 which does not contain a hydrogen group terminal urethane prepolymer.
Table 1 shows the average hydroxyl value of each of the active hydrogen group-containing components A1 to A9. The average hydrogen group value was measured as follows.
(Average hydroxyl value) Measured according to JIS K 1557.

<Preparation of polyisocyanate group-containing component>
Polyisocyanate group-containing components B1 to B8, which are isocyanate group-terminated urethane prepolymers, were obtained by mixing in a nitrogen-substituted flask with the raw materials and blending ratios shown in Table 2 and reacting at 90 ° C. for 1 hour.
On the other hand, it mixed by the raw material and compounding ratio which are shown in Table 2, and obtained polyisocyanate group containing component B9 which does not contain an isocyanate group terminal urethane prepolymer.
Table 2 shows the free isocyanate group content of each of the polyisocyanate group-containing components B1 to B9. In addition, free isocyanate group content was measured as follows.
(Free isocyanate group content)
It measured based on JISK1603-1.

<Examples 1-9, Comparative Examples 1-3>
In the combinations shown in Table 3, the active hydrogen group-containing components A1 to A9 and the polyisocyanate group-containing components B1 to B9 were accommodated in each accommodating portion of a two-component mixed spray coating machine. In the state where the interior of each container was set to 23 ° C., the mixture was sprayed from the two-component mixed spray coater at a mixing ratio of 2 moles of isocyanate groups with respect to 1 mole of active hydrogen groups. Under such conditions, the primer composition was applied to the surface of a spiral steel pipe of 600A adjusted to 50 ° C. so as to have a film thickness of 50 μm after being subjected to grid blasting by the two-component mixed spray coating machine, and 40 ° C. The primer layer was formed by curing at 80% RH for 1 hour. Subsequently, Permguard 137 (trade name, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was applied to the surface of the primer layer as an anti-corrosion paint as a top coat, and cured at 23 ° C. for 24 hours. Thus, an anticorrosion layer was formed. After performing the coating curing for one week, the coated steel pipe was cut into a size of 100 × 150 mm to obtain test pieces of Examples 1 to 9 and Comparative Examples 1 to 3.

<Evaluation>
Using the obtained test pieces of Examples 1 to 9 and Comparative Examples 1 to 3, an initial adhesion test, a cathode peeling test, and a cooling / heating cycle test were performed as various performances required for the heavy anticorrosion coating. The results are shown in Table 3. The test methods and evaluation methods for these tests are shown below.

<Initial adhesion test>
In the initial adhesion test, the adhesion of the anticorrosion layer and the primer layer of the steel material was confirmed by a pull-off adhesion strength test of 7.3.2 of JIS K 5600-5-7 (method for a test on one side only). The test was performed at 23 ° C. ± 3 ° C. and n = 3, and an average value (MPa) was obtained.

<Cathode peeling test>
In general, cathodic protection is performed for the purpose of anticorrosion in a corrugated part in a pipeline and in an anticorrosive part in the sea in a marine structure. On the other hand, however, there is a problem that cathodic protection promotes peeling of the coating, and in addition to corrosion peeling, resistance to cathode peeling is required. Since the cathode peeling occurs at the interface between the steel material and the primer layer, the performance of the primer layer is greatly affected. For this reason, the cathode peel resistance was evaluated in accordance with ASTM G8 (Standard Method for Cathodic Disbonding of Pipeline Coating), which is a method for evaluating the peel resistance from the buttock in the pipeline. A hole reaching the 6 mmφ steel surface was drilled in the coating layer (anticorrosion layer and primer layer), and then a cylindrical test cell having an inner diameter of 100 mm and a length of 150 mm was attached. Fill the test cell with 3% sodium chloride electrolyte, use a steel material as a cathode and a platinum wire as the counter electrode, and adjust the voltage so that it becomes -1.5 V with respect to the copper sulfate reference electrode. The cathode peeling test was carried out for 30 days in the environment of After the test, the coating layer was peeled off with a chisel and the peel diameter was measured in three directions to determine the average peel distance from the initial hole.

<Cooling cycle test>
Corrosion-proof steel is exposed to repeated cold heat stress outdoors, but the coefficient of thermal expansion differs greatly between resin and steel, so repeated shear stress is applied to the primer layer between the paint film (corrosion-proof layer) and the steel. From the above, the peel resistance of the coating film against thermal shock was evaluated by a cold cycle test. Thermal stress was applied to the coating layer by repeating the 100 × 150 mm test piece at −30 ° C. for 1 hour and at 60 ° C. for 1 hour 100 times. Thereafter, the coating layer was peeled off with a chisel, and the peel distance from the edge of the coating layer was measured.

Claims (2)

A primer composition having an active hydrogen group-containing component (A) and a polyisocyanate group-containing component (B),
The active hydrogen group-containing component (A) contains a hydroxyl group-terminated urethane prepolymer (a) produced using at least a polyether polyol (a1) obtained by adding an alkylene oxide to a bisphenol compound and a polyisocyanate (a2). ,
The polyisocyanate group-containing component (B) is an isocyanate group-terminated urethane produced by using at least a polyether polyol (b1) and a polyisocyanate (b2) obtained by adding butylene oxide to a polyol having three or more hydroxyl groups. A primer composition containing a prepolymer (b).   A coated steel material comprising a steel material, a layer obtained by coating and curing at least the primer composition according to claim 1 on the surface of the steel material, and a corrosion-proof layer.