JP4765902B2 - Surface-treated metal material with excellent adhesion and film adhesion - Google Patents

Description

  The present invention relates to a surface-treated metal material that is excellent in adhesion and film adhesion and suitable for structural adhesion to a wood material.

  In recent years, the use of composite materials of wood and steel has been increasing as a structural material for housing. The reasons include the fact that large-scale deforestation is being restricted and the stable mechanical properties of steel are being reviewed.

  Adhesion is mainly used for joining wood and steel. In general, it is said that chemical adhesion (intermolecular force: hydrogen bond, interaction between dipoles, interaction between quadrupoles, van der Waals force, etc.) is dominant in bonding metal materials. On the other hand, it is known that a mechanical adhesive force called anchoring effect acts rather than a chemical adhesive force in bonding wood materials. This is because wood is porous and the adhesive penetrates into the wood and hardens.

  By the way, when bonding is used for the structural material, not only the initial bonding strength but also the bonding strength does not decrease with time (hereinafter, this performance may be referred to as bonding durability) is required. The main factor that decreases the adhesive strength is the penetration of moisture into the adhesive interface. As moisture penetrates into the adhesive interface, the chemical adhesive strength (that is, hydrogen bonding, van der Waals force, etc.) among the adhesive strengths described above is greatly reduced, and the adhesive strength is reduced.

Conventional techniques for bonding wood and steel include the following.
In Patent Document 1, a steel material having a chromate film on a zinc-based plating film and an organic film including a urethane-based resin is bonded to wood with an aqueous emulsion adhesive. An adhesive composite is disclosed.

  Patent Document 2 discloses an adhesive composite in which a steel sheet in which a zinc-based plating film, a chromium-free Si-containing film, and an organic film are sequentially provided is bonded to wood with an adhesive.

  In patent document 1 and patent document 2, since there is almost no limitation regarding the resin film, it is considered that the bond with the adhesive is mainly hydrogen bond or van der Waals force, and between the surface organic film of the metal material and the adhesive. Therefore, good adhesiveness is not always obtained.

  In Patent Document 3, a metal material having a chemical conversion treatment layer containing at least one organic polymer compound having at least one functional group that undergoes a crosslinking reaction with a component of an adhesive on the outermost layer is provided via an adhesive. A composite metal material bonded to wood is disclosed. This technique seeks to obtain strong adhesiveness by causing a cross-linking reaction between an organic film of a metal material and an adhesive.

In the technique described in Patent Document 3, a chromate treatment layer, a silica-based treatment layer, and a phosphate layer are exemplified as the chemical conversion treatment layer. However, chromate treatment tends to be avoided because of environmental problems. On the other hand, silica-based treatment and phosphate-based treatment have a problem that the stability with time deteriorates due to the combination with a resin, especially for silica-based treatment. It has been considered that there are similar problems in acid treatment.
Japanese Patent No. 3022268 Japanese Patent Laid-Open No. 2003-181982 JP 2004-83977 A

  An object of the present invention is to provide a surface-treated metal material having excellent adhesion durability when adhesively bonded to a wood material.

  As a means for improving the adhesion of a metal material, as shown in Patent Document 3, a chemical conversion treatment layer is provided on the outermost layer of a metal material such as a steel plate, and the chemical conversion treatment layer and the components in the wood-based adhesive are subjected to a crosslinking reaction. It is very effective to contain the component which does. On the other hand, when a coating layer is provided on the surface of a metal material in this way, not only the interface between the adhesive and the coating layer but also the interface between the coating layer and the metal material is considered. Need to design. The present invention has been completed by studying various film components based on such an idea.

  The present invention is an application of an aqueous treatment liquid containing a water-soluble metal complex compound, a crosslinkable resin, and a silane coupling agent, which changes to hardly soluble by heating and drying, and does not contain hexavalent chromium, on at least one surface of the base metal material. And a surface-treated metal material comprising a surface-treated layer formed by heat drying as an outermost layer.

  The water-soluble metal complex compound that changes to hardly soluble by heat drying may be a compound in which two molecules of β-diketone and two molecules of water are coordinated to a trivalent transition metal ion, and the trivalent transition metal ion is an iron or chromium ion. The β-diketone can be acetylacetone.

The crosslinkable resin is preferably one that can react with at least a part of the components in the adhesive to form a crosslinked structure, and more preferably an oxazoline group-containing resin.
The mass ratio (A / B) based on the solid content of the water-soluble metal complex compound (A) to the crosslinkable resin (B) is preferably 0.1 or more and 3 or less, and is based on the silane coupling agent (C). The mass ratio [(A + B) / C] of the total amount of the water-soluble metal complex compound (A) and the crosslinkable resin (B) is preferably 4 or more and 50 or less.

The aqueous processing solution can further contain a zirconium compound and at least one compound selected from the group consisting of citric acid and salts thereof.
The adhesion amount of the surface treatment layer is preferably 5 mg / m ² or more and 500 mg / m ² or less, and the base steel plate is preferably a galvanized steel plate or a zinc alloy plated steel plate.

  The surface-treated metal material of the present invention is excellent in adhesiveness and film adhesion, and can maintain excellent adhesiveness even when water enters. This is because the surface treatment layer not only exhibits excellent adhesiveness by cross-linking reaction with the adhesive, but also has good film adhesion at the interface with the base steel plate. Therefore, the surface-treated metal material of the present invention is useful for structural adhesion with a wood material whose adhesion is liable to decrease due to intrusion of moisture, and has excellent adhesion durability when an adhesive composite with the wood material is created. Materials can be provided.

In the following description,% is mass% unless otherwise specified.
The base metal material of the surface-treated metal material of the present invention is not particularly limited, but is usually a steel plate, and is preferably a galvanized steel plate or a galvanized steel plate from the viewpoint of ensuring corrosion resistance. These may be any of an electroplated steel plate, a hot dip plated steel plate, and a vapor phase plated steel plate. Examples of galvanized steel sheets that can be used include hot dip galvanized steel sheets, electrogalvanized steel sheets, molten 5% Al—Zn alloy plated steel sheets, molten 55% Al—Zn alloy plated steel sheets, galvannealed steel sheets, and electrical Zn—Ni. Examples include alloy plated steel sheets. The plating adhesion amount is not particularly limited, and may be within a general range. If the coating amount is too small, the corrosion resistance is lowered, and if too much, the workability is deteriorated.

  The surface treatment layer is formed by applying the treatment liquid according to the present invention to the base steel plate and drying by heating. Prior to this surface treatment, as is well known to those skilled in the art, a surface cleaning treatment (alkali degreasing, pickling, etc.) of the base steel sheet may be appropriately performed. Moreover, the surface adjustment process using the acidic or alkaline aqueous solution containing an iron group metal ion performed for the purpose of the oxidation prevention of a plating surface can also be performed.

  The treatment liquid used in the present invention is a water-based treatment liquid that contains a water-soluble metal complex compound, a crosslinkable resin, and a silane coupling agent that are hardly soluble by heat drying and does not contain hexavalent chromium.

  As the water-soluble metal complex compound that changes to poorly soluble by heating and drying, it is possible to use any metal complex compound that is water-soluble before heating but changes its coordination form by heating and becomes insoluble in water. it can. One example of such a metal complex compound is a compound in which two molecules of β-diketone and two molecules of water are coordinated to a trivalent transition metal ion. More specifically, the trivalent transition metal ion may be iron, and the β-diketone may be acetylacetone. Although chromium can be used as the trivalent transition metal ion, it is often not preferred due to environmental problems.

As shown in FIG. 1, this metal complex compound takes the form of a mononuclear complex in which two molecules of acetylacetone (acac) and two molecules of water are coordinated to a metal ion (Fe ^{3+ in the} illustrated example) before heating. It is water soluble. However, when heated, these two metal complex compounds undergo a dehydration reaction, resulting in a binuclear complex that is poorly soluble in water, in which four molecules of acetylacetone and two molecules of water are coordinated to two molecules of iron ions, and precipitates. . That is, this metal complex compound is water-soluble in the surface treatment solution, but after being heated and dried as a “film”, it changes to a stable and poorly water-soluble compound.

  Therefore, by dissolving such a metal complex compound in the treatment liquid, the metal complex compound becomes poorly water-soluble during heating and drying after coating, preventing the surface treatment components from eluting even if water enters. Fulfills the function of Therefore, the cohesive strength of the surface treatment layer is maintained, and the durability of the coating is increased.

This water-soluble metal complex compound can be synthesized, for example, as follows. Powdered FeSO ₄ or FeCl ₂ is dissolved in water, and the resulting aqueous solution is heated to 80 ° C. Thereafter, 2 equivalents of acetylacetone diluted with a mixed solvent of water / ethanol is gradually added, and after the addition, when stirred at 80 ° C. for one day, [Fe (acac) ₂ (H ₂ O) ₂ ] ⁺ is synthesized. .

  The crosslinkable resin is preferably one that can react with at least a part of the adhesive components to form a crosslinked structure, more preferably an oxazoline group-containing resin. Oxazoline group-containing resins are commercially available from Nippon Shokubai Co., Ltd. under the trade name Epocross (R), water-soluble Epocross WS-500 and 700 (main chain is acrylic polymer), and emulsion type Epocross K-2000. Series (main chain is styrene / acrylic copolymer). Any of them can be used in the present invention.

  As shown in FIG. 2, the oxazoline group-containing resin undergoes a ring-opening reaction of the oxazoline group with the carboxyl group-containing component, thereby generating an amide ester type crosslinked structure without generating by-products. In the present invention, the oxazoline group of the oxazoline group-containing resin contained in the surface treatment layer reacts with the carboxyl group contained in the adhesive to form this cross-linked structure, thereby dramatically increasing the adhesive strength of the adhesive. . Examples of the adhesive having a carboxyl group include isocyanate adhesives, urethane adhesives, acrylic adhesives, and the like. In the case of adhesion to a wood material, a preferred adhesive is an isocyanate type, but other adhesives can also be used.

  Taking advantage of such properties of oxazoline groups, oxazoline group-containing resins have heretofore been mainly used in paints as cross-linking agents for base resins containing carboxyl groups. In this case, the oxazoline group-containing resin is used in a coexisting state with the base resin.

  On the other hand, in the present invention, the oxazoline group-containing resin is contained in the surface treatment layer alone or as a main resin component instead of the crosslinking agent. Other resin components can coexist in a small amount, but if the coexisting resin component contains a functional group reactive with an oxazoline group such as a carboxyl group, the oxazoline group and the resin component The oxazoline group that is consumed in the reaction of the above and usable for the crosslinking reaction with the components in the adhesive is insufficient, and the adhesiveness may be lowered. Therefore, even when other resin components are allowed to coexist, at least half of the oxazoline group is suppressed within a range where it remains unreacted. In general, when other resin components are allowed to coexist, the amount is preferably within 50%, particularly 30% or less, relative to the oxazoline group-containing resin.

Since the oxazoline group-containing resin is water-soluble or water-dispersible, the above-mentioned metal complex compound and the silane coupling agent described below are allowed to coexist in order to be fixed to the surface treatment layer.
The silane coupling agent is a trialkoxyalkyl or dialkoxydialkylsilane compound having a functional group, and the tertiary group having an organic group is subjected to hydrolysis and condensation reaction during heat drying after application of the surface treatment liquid. It is possible to form a film having an original cross-linked siloxane skeleton. The oxazoline group-containing resin is fixed in the surface treatment layer by this action of the silane coupling agent and the above-described metal complex compound hardly soluble. The silane coupling agent also acts to adsorb on the inorganic surface, that is, the steel plate surface in a hydrogen bond, and to exhibit adhesion.

  Various commercial products can be used for the silane coupling agent. Preferred silane coupling agents for use in the present invention are those containing any one of epoxy, amino, vinyl, chloro, methacryloxy, mercapto and cationic organic functional groups. Specific examples of such silane coupling agents include vinylethoxysilane, vinylmethoxysilane, N- (2-aminomethyl) 3-aminopropylmethyldimethoxysilane, N- (2-aminomethyl) 3-aminopropyltrimethyl. Methoxysilane, 3-aminopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-methacryloxy Examples include, but are not limited to, propyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, tetraethoxysilane, and tetramethoxysilane. Particularly preferred is a silane coupling agent having an epoxy group.

  The mixing ratio of the above components of the treatment liquid is such that the mass ratio (A / B) of the water-soluble metal complex compound (A) to the crosslinkable resin (B) such as an oxazoline group-containing resin is 0.1 or more, It is preferable to be 3 or less. The reason why the A / B mass ratio is set to 0.1 or more is that if the compounding of the metal complex compound is reduced and the compounding of the resin is increased, the required performance can be obtained at a low cost. The reason why this mass ratio was set to 3 or less is that when the A / B mass ratio becomes higher than this, the liquid stability decreases. The A / B mass ratio is more preferably 0.5 or more and 2 or less.

  The mass ratio [(A + B) / C] of the total amount of the water-soluble metal complex compound (A) and the crosslinkable resin (B) to the silane coupling agent (C) is preferably 4 or more and 50 or less. Even if this mass ratio is lower than 4 or higher than 50, the stability of the surface treatment liquid decreases. Moreover, if the mass ratio is too high, it is disadvantageous in terms of cost. The (A + B) / C mass ratio is more preferably 8 or more and 25 or less.

  In addition to the above components, the treatment liquid may further contain at least one compound selected from the group consisting of zirconium compounds and citric acid and salts thereof. Any of these additional components has an effect of improving corrosion resistance and adhesion. In addition, the stability of the treatment liquid is also improved.

  Examples of zirconium compounds that can be used include ammonium zirconium carbonate, basic zirconium carbonate, zirconium acetate, zirconium nitrate, zirconium hydroxide, potassium zirconium carbonate, zirconium zirconate fluoride, and zirconate hydrofluoric acid. As the citrate, ammonium salt and metal salt can be used.

  The aqueous treatment liquid can further contain additives other than those described above. Examples of such additives include acids and / or alkalis for pH adjustment, antifoaming agents, liquid stabilizers, and the like.

  In addition, although there exists silica effective for corrosion resistance improvement as a component conventionally used for a surface treatment liquid, in the case of this invention, a silica is not essential. It is because the adhesive improvement effect by containing a silica is not necessarily recognized.

  The solvent of the aqueous processing solution used in the present invention is water, but may contain a water-miscible organic solvent as long as it is less than water. For example, when Epocros WS-500 is used as it is as an oxazoline group-containing resin, it is commercially available as a 40% solution in a mixed solvent of water / 1-methoxy-2-propanol, so that an organic solvent is mixed therein. .

  Application of the aqueous treatment liquid and subsequent heat drying may be carried out in accordance with a conventional method. Application | coating can be implemented by immersion, spraying, roll application | coating, etc., for example. It is preferable that the heating temperature at the time of drying is such that the maximum plate temperature is in the range of 60 to 200 ° C. This heat drying can be performed by hot air drying or in-furnace drying. During this heating, as described above, the water-soluble mononuclear metal complex compound is changed to a hardly soluble polynuclear (binuclear) metal complex compound, and at the same time, the silane coupling agent is crosslinked through hydrolysis and condensation. As a result, the slightly soluble metal complex compound and the polysiloxane skeleton film derived from the silane coupling agent intermingle, and a surface treatment layer having a structure in which the crosslinkable resin is also fixed is generated.

The adhesion amount of the surface treatment layer thus formed is preferably 5 mg / m ² or more and 500 mg / m ² or less. The lower limit value 5 mg / m ² of the adhesion amount is the minimum amount necessary for forming a treatment layer covering the entire surface of the base steel sheet. If the upper limit value of the adhesion amount exceeds 500 mg / m ² , the cost becomes too high. The adhesion amount of the surface treatment layer is preferably 10 mg / m ² or more and 200 mg / m ² or less.

  Examples of the adhesive suitable for adhering the wood material to the surface-treated metal material of the present invention include various wood adhesives conventionally used for metal-wood adhesion. Examples thereof are water-based polymer-isocyanate adhesives, resorcinol resin adhesives, phenol resin adhesives, melamine / urea copolymer resin adhesives, one-component urethane adhesives, and the like. In the curing reaction of the adhesive, an aqueous polymer-isocyanate-based adhesive is preferable in that no toxic formaldehyde is generated. In addition, a one-component urethane adhesive is good for on-site workability at a home construction site or the like. An adhesive that is reactive with the crosslinkable resin contained in the surface treatment layer is used. For example, as described above, when the crosslinkable resin is an oxazoline group-containing resin, it is preferable to use an adhesive containing a component containing a carboxyl group (eg, an aqueous polymer-isocyanate adhesive). .

(Creation of surface-treated metal material)
A hot-dip galvanized steel sheet (plate thickness: 0.8 mm, coating amount: 60 g / m ² per side, no alloying heat treatment) was used as the base steel sheet, and the surface of this plated steel sheet was washed with water and dried after alkaline degreasing. Thereafter, a treatment liquid having any of the compositions shown in Table 1 is applied to both surfaces of the plated steel sheet with a bar coater, and heated and dried in a hot air oven (maximum reached plate temperature of 80 ° C.) to form a surface treatment layer on the plated steel sheet surface. Formed. The adhesion amount of the surface treatment layer was adjusted by the treatment solution concentration and the bar coater count. This adhesion amount was calculated from the weight difference before and after the treatment. In addition, among the processing liquids shown in Table 1, the processing liquids of desired O to V were not used because of problems in liquid stability.

Details of each component used in the treatment liquid are as follows.
Metal complex compound: Fe (acac) ₂ (H ₂ O) ₂ (that is, the complex shown in FIG. 1 in which two molecules of acetylacetone and two molecules of water are coordinated to a trivalent iron ion, a synthetic product);
Crosslinkable resin: Oxazoline group-containing resin (Epocross WS-500 manufactured by Nippon Shokubai);
Silane coupling agent: 3-glycidoxypropyltrimethoxysilane (Chiasso Silaace S510);
Silica 1: Colloidal silica (Nissan Chemical Snowtex O);
Silica 2: Colloidal silica (Nissan Chemical Snowtex N).

(Creation of adhesive complex)
After applying an adhesive (water-based polymer-isocyanate-based adhesive, Oshika Shinko Piabond TP-111) to both surfaces of the obtained surface-treated metal material by brushing, a plate material of the same plane size of Yonematsu Adhesion was carried out by pressing (thickness 10 mm) at 0.2 MPa for about 12 hours, and the pressure was released to prepare a sandwich-like adhesive composite made of wood-steel plate-wood.

(Adhesive evaluation)
Test 1 (initial adhesive strength): The prepared adhesive composite was cut into a sample size (25 mm square) shown in FIG. 3 and subjected to a compression shear test (according to JIS-K6852). The applied compression shear rate was 2 mm / min.

  The test results were evaluated by the adhesive strength and the interfacial peel rate between the steel plate and the adhesive. The interface peeling rate between the steel sheet and the adhesive means the ratio of the area peeled at the interface by the compression shear test with respect to the total bonded area. For example, in measurement example 1 in FIG. 4, destruction of wood and interface peeling between the wood and adhesive have occurred, but no interface peeling between the steel sheet and adhesive has occurred, so that it is 0%. On the other hand, in Measurement Example 2 in FIG. 4, interface peeling between the steel sheet and the adhesive occurs in the peripheral portion of the evaluation surface. The area ratio is 40% when measured by applying to the 100 square gobang in the upper right of FIG.

Test 2 (Adhesive strength after immersion in boiling water): In order to simulate the decrease in adhesive strength due to water intrusion, the adhesive composite cut to the above size was immersed in boiling water for 4 hours, and immediately after taking out, the compression shear was applied. The test was conducted.
The results of Tests 1 and 2 are shown in Table 2.

  As can be seen from Table 2, the surface-treated metal materials (Examples 1 to 16) according to the present invention not only have high initial adhesive strength, but also the adhesive strength after immersion in boiling water is much lower than the initial adhesive strength. It wasn't. Moreover, since the peeling area rate in the wood-metal interface after a boiling water test is also small, it is estimated that the adhesive force in an interface has not dropped much. Among them, those containing citric acid (Examples 1 to 8) have a smaller interfacial peeling area ratio than those not containing, and the tendency is further strengthened by increasing the content of the crosslinkable resin ( Example, comparison of Examples 1-4 and Examples 5-8).

  On the other hand, all of the comparative examples do not contain a cross-linking material resin in the surface treatment layer. Among them, Comparative Examples 1 to 4 contained a silane coupling material, and thus the initial adhesive strength was high. However, after the boiling water test, the adhesive strength compared to the examples was small. Moreover, Comparative Examples 9-12 which do not contain a metal complex compound had lower initial adhesive strength than other comparative examples, and the interface peeling area rate was large.

It is explanatory drawing of the poor solubilization reaction of a metal complex compound. It is explanatory drawing regarding the mechanism of the crosslinking reaction of the oxazoline group of the oxazoline group containing resin contained in a surface treatment layer, and the carboxyl group in an adhesive agent. It is explanatory drawing which shows the sample size of the compression shear test employ | adopted in the Example. It is explanatory drawing which shows the measuring method of the interface peeling rate between a steel plate and an adhesive agent in the fracture surface by the said compression shear test.

Claims (7)

At least one side of the base metal material contains a compound in which two molecules of β-diketone and two molecules of water are coordinated to a trivalent transition metal ion, an oxazoline group-containing resin , and a silane coupling agent, and does not contain hexavalent chromium. A surface-treated metal material comprising a surface treatment layer formed by application of an aqueous treatment liquid and heat drying as an outermost layer. The surface-treated metal material according to claim 1 , wherein the trivalent transition metal ion is iron or chromium ion, and the β-diketone is acetylacetone. The surface-treated metal according to claim 1 or 2 , wherein a mass ratio (A / B) of the water-soluble metal complex compound (A) to the crosslinkable resin (B) based on the solid content is 0.1 or more and 3 or less. Material Water-soluble metal complex compound to silane coupling agent (C) (A) and the total amount of the mass ratio of the crosslinked resin (B) [(A + B ) / C] is 4 or more and 50 or less, according to claim 1 to 3 The surface-treated metal material according to any one of the above. The surface-treated metal material according to any one of claims 1 to 4 , wherein the aqueous treatment liquid further contains at least one compound selected from the group consisting of a zirconium compound and citric acid and a salt thereof. Adhesion amount of surface treated layer is 5 mg / m ² or more and 500 mg / m ² or less, a surface treated metal material according to any one of claims 1-5. The surface-treated metal material according to any one of claims 1 to 6 , wherein the base steel plate is a galvanized steel plate or a zinc alloy plated steel plate.

Images