JP2013221081A - Normal temperature-drying type aqueous zinc-rich coating material, and method for coating the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a normal temperature-drying type zinc-rich coating material capable of effectively reducing flush rust and loose scale, and to provide a method for coating the normal temperature-drying type zinc-rich coating material by which the electric resistance of a coated film can be controlled properly.SOLUTION: The normal temperature-drying type aqueous zinc-rich coating material to be coated on the surface of a steel material is the one obtained by forming the coating material by mixing and stirring a second coating material obtained by kneading particulate silica with zinc powder, with a first coating material constituted of a rust-proofing agent of ≤0.5% by weight based on the whole coating material, an aqueous resin, an additive, water and a small amount of a volatile organic compound and the like at a coating site. The amount of the particulate silica to be mixed with the zinc powder in the second coating material is 100-5,000 ppm by the weight ratio to the weight of the zinc powder, and the normal temperature-drying type aqueous zinc-rich coating material obtained by mixing and stirring the second coating material with the first coating material at the site is coated.

Description

  The present invention relates to a room-temperature-drying water-based zinc rich paint that has a minimal volatile organic compound (VOC) component and does not deteriorate the environment, and a method for coating the same.

  The function of the paint is broadly classified to provide protection and beauty to the object to be coated. Among them, in order to impart a protective function to the coating film, it is roughly classified to have a blocking property against the environment of the coating film itself (rainwater, seawater, etc.) by selecting the resin that is the main constituent material of the coating film. There are two means of adding a water-soluble anticorrosive pigment to the coating film on the premise that water always enters the film.

  However, zinc rich paint was invented by a group of British scholars in the 1940s. This is because a large amount of metallic zinc powder is contained in the coating film to act as a metallic coating film, and the steel powder under the coating film is protected at the expense of zinc powder particles in the film.

  This paint uses an electrochemical reaction. The zinc dust particles and the zinc dust particles and the steel are in metal contact with each other. The steel is cathodic (cathode reaction: reduction reaction). The powder particles proceed in a pair with an anodic reaction (anodic reaction: oxidation reaction). This means that the electrical resistance value between the painted coating surface and the steel material under the coating is approximately zero Ω. That is, the coating film shows a sacrificial behavior like a metal film.

  For this reason, as long as the zinc dust particles exhibit metallic behavior, the steel material is protected, and even today, it is widely used on the surface of steel materials composed of large steel structures and the like as paints for protecting the steel materials.

  On the other hand, social concerns about large steel structures related to paints and coatings in recent years are environmental measures by switching from solvent-based paints to water-based paints and introduction of total costs.

  The concept of this total cost is a method in which the useful life is determined in advance at the design stage, initial construction costs, maintenance costs, dismantling / disposal costs are estimated, and these three costs are presented as total costs.

  Therefore, in the field of paints and paintings, it has become an important social background to respond to the presentation of the useful life of the coating film itself as well as being water-based.

Japanese Patent Application Laid-Open No. 07-133442 Japanese Patent Laid-Open No. 08-141498

  Due to recent environmental problems, there has been an increasing demand for conversion to organic solvent-free paints (so-called water-based paints). The same applies to conventional solvent-type zinc rich paints.

  Also, water-based zinc-rich paints have been proposed (Patent Documents 1 to 2), but do not teach a paint composition that can be applied and dried at room temperature. In addition, paint composition that can effectively reduce floating rust and flash last due to rust removal failure due to kelen on the surface of steel before painting, a method to suppress its growth, and the durability required for the steel to be coated It is not yet known how to properly apply the paint along.

In addition, a method for changing the electrical resistance value of a zinc rich coating film dried after coating to an appropriate electrical resistance value from zero Ω and a method for using the same, which should meet the surface condition of the steel material and the durability requirement of the steel material, are not yet known.

  The present invention has been made in view of the above problems, and can be painted and dried at room temperature to effectively reduce floating rust and flash rust, and further according to the service life of the steel material to be coated. It aims at providing the coating method which can implement | achieve the required performance of a coating film appropriately.

  In order to achieve the above object, the inventor has conducted various experiments, and as a result, the production of a specific paint raw material, and the water-based paint to which a specific composition is added, is a steel material in which rust has occurred. Alternatively, the present invention has been completed by finding a method of coating in accordance with the service life required for the steel material to be coated.

  That is, the present invention is an aqueous paint to be coated on the surface of a steel material, containing an aqueous resin, 70% to 90% with respect to the entire paint, and 90% to 97% with respect to a solid component. It contains zinc powder at a weight ratio, 10% to 25% by weight of the entire paint is composed of volatile components, and volatile organic compounds are suppressed to less than 1% by weight of the entire paint. The volatile component of the present invention means a substance that does not remain in the coating film in a dry state, and is a concept including water as a dispersion medium. The numerical range of the present invention is defined as above and below, and includes both numerical ends.

  Although the water-based paint of the present invention uses water as a dispersion medium, it contains zinc powder in a weight ratio of 70% to 90% with respect to the whole paint and 90% to 97% with respect to the solid component. And since drying time is short, even if it apply | coats to the steel material which the metal surface exposed, the time for which the steel material surface is wet can be reduced, and generation | occurrence | production of floating rust can be suppressed effectively. Furthermore, by controlling the sacrificial anticorrosive action of the zinc dust particles, the spread of the rust portion on the steel material surface and the durability of the coating film can be controlled electrochemically.

  In addition, the greatest intention of the water-based paint of the present invention is that a coating material (hereinafter referred to as second coating material) in which the surface of zinc powder particles is appropriately inactivated by kneading zinc powder and an arbitrary amount of fine particle silica in advance. And a coating material (hereinafter referred to as the first coating material) mixed and dispersed with water, a resin, a dispersion medium, an additive, a small amount of a volatile organic compound, etc., and an essential rust inhibitor. Consists of.

When painting the paint of the present invention at the painting site, the coating film is formed by appropriately selecting the amount of fine particle silica in the second coating material according to the durability required for the steel material to be coated. The electrical resistance value can be a coating film having an appropriate electrical resistance value instead of a metal film of zero Ω which is the conventional basic concept.

  This concept of the present invention can also overcome the disadvantage that the anticorrosion property, which is the greatest feature of the conventional solvent-type zinc-rich coating film as well as the published aqueous-type zinc-rich coating film, cannot be controlled. That is, since it is a metallic coating film, the deterioration itself progresses depending on the electrochemical reaction in the natural environment. The fact that this deterioration rate can be controlled effectively is based on the fact that it depends on the electric resistance value of the coating film.

  However, although it is possible to apply this concept to conventional solvent-type zinc-rich paints, manufacturing costs, raw material costs, and coating costs have risen. Differentiation is difficult, and it was intentionally outside the scope of the present invention.

  In addition, since the content of the volatile organic compound is suppressed to less than 1% by weight of the entire paint, the water-based paint of the present invention has very little adverse effect on the working environment when the solvent is dried. The water-based paint of the present invention can be applied over the old paint film, but when rust is generated on the steel surface, it is preferable to precede the work of peeling off the old paint film. is there.

  In the present invention, the zinc dust content is 70% to 90% by weight with respect to the entire coating material, and more preferably 75% to 87% by weight. The zinc dust content should more preferably be 92.1% to 97% by weight relative to the solid component.

  The volatile component of the present invention is 10% to 25% by weight of the entire coating material, and more preferably 20% by weight or less. In such a case, typically, a second coating material in which zinc powder having a weight ratio of 75% or more is pre-treated with an appropriate amount of fine-particle silica and at least an appropriate type and amount of rust inhibitor having a weight ratio of 25% are used. It is preferable to separately prepare the first coating material containing, and mix and stir both at the painting work site to complete and paint the water-based paint of the present invention.

  According to such a composition, viscosity suitable for brushing and roller coating is realized, but in order to realize air spray painting and airless spray gun painting, additional dilution water is used as necessary. May be. The dilution water should be limited to no more than 2% by weight of the total paint.

  In addition, the water-based resin constituted in the water-based paint of the present invention is a water-based resin used for a general room temperature dry-type water-based paint, and is not a specially synthesized resin, but a water-based epoxy resin or a water-based urethane resin. The lacquer type can be used. Preferably, the content ratio should be 3% to 9% by weight with respect to the whole paint. According to a more preferred embodiment, the surface hardness based on JIS K5600-5-4 is B to 2H at a dry film thickness of 40 μm. More preferably, the surface hardness should be HB to 2H. In the water-based paint of the example, the surface hardness is HB or more.

  In the water-based paint of the present invention, the first coating material containing a rust inhibitor as an essential component preferably contains at least one of a water-based resin, water and a thickener, an antifoaming agent, and a dispersant. The viscosity is suitable for brushing and roller coating. The blending amount of the thickener is set corresponding to the necessary viscosity, but it is preferable that the weight concentration is about 1500 to 2200 ppm with respect to the entire coating material.

  And as a thickener, what contains a polyether polyol and an anionic active agent about 30 to 45 weight% with respect to the whole thickener is selected suitably. In addition, it is suitable that polyether polyol contains about 4.0-5.0 weight ratio with respect to a nonionic activator.

  The antifoaming agent and the dispersing agent are preferably added to each other at a weight ratio of about 0.7: 1 to 1: 0.7, more preferably about 0.9: 1 to 1: 0.9. It is preferable to do this.

In addition, the rust preventive agent is an oxide film forming agent, an inorganic film forming agent, an organic film forming agent, a sulfide film forming agent, a rust conversion agent (chelating agent), etc., on the zinc powder particle surface and the steel material surface. Combined in a timely manner, finally, the amount of fine particle silica in the second coating material is appropriately selected, and the electric resistance value of the coated film after coating is preferably 5 Ω / mm ^{2 to} 5000 kΩ / mm ² Complete the paint film. More preferably, it is suitable to select and combine so as to be 50 Ω / mm ^{2 to} 1000 KΩ / mm ² .

  For example, as a rust preventive agent, there is a combination of a nitrite or vanadate-based oxide film forming agent and a chelating agent, or a single additive. In the case of sodium nitrite, 0.5% by weight is the total weight ratio of the paint. Although preferred, the invention is not so limited.

  For the water-based paint of the present invention, zinc powder having an average particle size of about 4 to 5 μm is preferably used from the viewpoint of applicability and the like. More preferably, it is composed of zinc and zinc oxide, and is preferably kneaded and mixed with fine powder silica of 50 to 5000 ppm based on the weight of zinc powder. More preferably, 100 to 5000 ppm is suitable. A step of completing a second coating material having a function as an agglomeration inhibitor of zinc powder and a function of imparting electrical resistance between metals of the zinc powder, and an aqueous paint by kneading zinc powder and fine powder silica Due to the synergistic effect with the first coating material containing the anticorrosive agent added in (1), it is involved in the determination of the electrical resistance value of the coating film after painting from the conventional metallic coating film.

  As the fine powder silica, for example, fumed silica produced by burning silicon tetrachloride in a hydrogen flame is suitably used.

  In addition, the present invention applies a water-based paint on the surface of a steel material, and after drying the first coating process having a film thickness of 30 to 50 μm in a dry state and the water-based paint applied in the first coating process, And a second application step of forming a second coating film having a film thickness of 30 to 50 μm in a dry state. However, in this invention, depending on the steel material of the property used, only a 1st application | coating process may be apply | coated and it does not specifically limit.

  However, according to the present invention, it is sufficient to apply the same paint repeatedly, so that the workability is excellent. In addition, although it is not prohibited to overcoat three or more times, floating rust and flash last occurred immediately after the first coating step by providing a double coating film layer with a film thickness of 30 to 50 μm. Even in this case, the growth can be surely restrained. This point has been confirmed by many experiments.

  The first coating step of the present invention may be performed with the coating film left on the steel surface. However, when rust is floating on the coating film, the first coating step is performed to remove the coating film. It is preferable to execute it prior to.

  According to the above-described present invention, it is possible to realize a method of applying a water-based paint capable of effectively reducing flash last and floating rust and a water-based paint capable of arbitrarily setting the electric resistance value of the coated film after coating.

It is drawing which shows the coating composition of an Example and a comparative example. It is drawing which shows the performance of an Example and a comparative example. It is drawing which shows the kind of rust preventive agent of an Example and a comparative example. It is drawing which shows the combination of the antirust agent of an Example and a comparative example. It is drawing which shows the kneading | mixing composition of an Example and a comparative example. It is drawing which shows the method of measuring the electrical resistance value of a coating film. It is drawing which shows the effect of the electrical resistance value of the coating film of an Example and a comparative example.

  EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not specifically limited. FIG. 1 illustrates the coating compositions of Examples 1 to 6 and Comparative Examples 1 to 5 and the composition ratios of important components. In addition, the numerical value which shows a liquid composition means a weight part, and a composition ratio means the weight%. Regarding the antifoaming agent and the dispersing agent, it was difficult to clearly classify the solid and the liquid, and the ratio in the paint was extremely small. Therefore, they were treated as volatile organic compounds (VOC) in the calculation.

  As the water-based urethane resin A, the water-based acrylic emulsion resin B, the water-modified epoxy resin C, and the water-modified epoxy ester resin D, common resins available on the market are used, and the respective solid components are 38% and 35%. 33% and 37%. In addition, about resin A-D, although it experimented about several resin of the same kind, the substantially the same tendency was acquired. As the solvent-based paint, an in-house product was used.

  As zinc powder, a metal zinc content of 95.0% or more and a total zinc content of 98.0% or more are used. As fine powder silica, for example, fumes produced by burning silicon tetrachloride in a hydrogen flame. Dosilica was used, and both were kneaded to obtain a second coating material. In addition, the addition amount is shown by the weight concentration with respect to the zinc powder weight.

  And when zinc powder content in a dry coating film calculates about Example 1- Example 6, it is 94.59%, 92.16%, 94.84%, 94.77%, 94.41%, 96. Calculated as 14%. Further, Comparative Examples 1 to 4 are calculated as 85.57%, 96.11%, 96.02%, and 96.07%.

  FIG. 2 shows the results of the performance test of the water-based paint shown in FIG.

  Here, “resin single film physical properties” refers to film formation on the steel surface with a single resin, adhesion to the steel surface (cross-cut test), pencil hardness, solvent resistance (rubbing test), weather resistance (outdoors The visual appearance at the time of exposure) was verified, and the evaluation results of these five tests were combined to evaluate the physical properties of the resin single film.

  ○ is good, Δ is somewhat concerned, and × is a problem as a single resin film.

  Regarding the “kneading workability” here, the second coating material containing zinc powder previously kneaded with fine-particle silica and the coating liquid of the first coating material are kneaded (here, mixing and stirring operations are called kneading). ) And the presence / absence of aggregates were evaluated. ○ means good, Δ is slightly difficult to knead but can be easily dispersed, × means very difficult to knead and disperse. Δ- is an evaluation between Δ and ×.

  “Applicability (bake, roller)” mixes the first and second coating materials, paints after stirring with a brush and paints on a steel plate with a roller, and evaluates ease of coating and film formability did. ○ is good, Δ is difficult to apply, but a uniform film can be formed.

  As the “appearance of the coating film”, the dried film was visually evaluated after evaluating the coating performance. ○ means good, Δ means pinholes and spots slightly, but means an acceptable appearance as a whole, × means noticeable abnormalities such as pinholes and spots, and poor appearance.

  “Liquid precipitation resistance” was confirmed by mixing the first coating material and the second coating material and allowing them to stand for 3 hours after stirring, and then checking the condition of the bottom of the can. ○ indicates no precipitate, and Δ indicates a slightly hard precipitate, but it can be easily dispersed. X is an evaluation that a remarkably hard precipitate is generated and dispersion is very difficult.

  “Adhesiveness (cross cut test)” was evaluated by applying a cross-cut method (JIS K5600-5-6: 1999) (applying 1 mm). ○ means classification 0 to 1, Δ means classification 2-3, and x means classification 4-5.

  “Corrosion resistance (salt spray test)” was evaluated by neutral salt spray resistance (JIS K 5600-7: 1999). Specifically, a crosscut reaching the substrate with a cutter knife was put into the coating film formed on the steel plate, and visually evaluated how long rusting from the crosscut portion was observed from the start of the test. Moreover, it observed also about the change of the coating film other than a crosscut part. ○ means no rusting for 1000 hours or more and no coating film abnormality. Δ means rusting in 500 to 1000 hours and no noticeable coating abnormality. X means that rusting or remarkable coating film abnormality (coating blister: blister etc.) occurred in 0 to 500 hours.

  As the “working environment (odor)”, the first coating material and the second coating material were mixed, and the odor of the paint after stirring was confirmed (presence or absence of solvent odor, discomfort was qualitatively evaluated). ○ means no discomfort and no problem, and Δ means a slightly unpleasant odor. X is evaluation that an unpleasant odor or a solvent odor may become a problem.

  “Heat resistance (170 ° C., 24 hours)” means that the coating film formed on the steel sheet is exposed to an environment of 170 ° C. (in a thermostatic chamber) for 24 hours, taken out and left in a state where the steel sheet is at room temperature. Sex evaluation was performed.

  As shown in FIG. 2, it contains a water-based urethane resin, and contains zinc powder at a weight ratio of 70% to 90% with respect to the whole paint and 90% to 97% with respect to the solid component, and the whole paint It was confirmed that 10% to 25% by weight of the volatile organic compound is composed of volatile components, and that the volatile organic compound exhibits an excellent effect when it is less than 1% by weight.

  FIG. 3 shows the results of visual observation of the state of occurrence of floating rust after coating in Examples 11 to 15 in which various rust inhibitors were added to the paint and Comparative Example 11 in which no rust inhibitor was added. Moreover, FIG. 4 shows mixing of the first coating material and the second coating material when various anticorrosive agents are similarly combined and added to the first coating material paint. Examples 21 to 26 and Comparative Example 21 in which the paint after stirring is applied are shown, and the comparative examples in FIGS. 3 and 4 are the same paint.

  In this case, the rating ○ indicates that there is no problem, Δ indicates that there is some concern, and × indicates that there is a problem.

  Symbol A in FIGS. 3 and 4 is an oxide film forming agent on the zinc powder surface and the steel sheet surface, symbol B is an inorganic film forming agent, symbol C is an organic film forming agent, symbol D is a sulfide film forming agent, Symbol E is a rust conversion agent (chelating agent).

  The amount of rust prevention added to the first coating material, whether alone or in combination, was 0.5% by weight or less based on the weight of the entire coating material. In addition, the addition amount of a rust preventive agent and the combination of a rust preventive agent do not limit this invention.

  Specific examples of the rust inhibitor A include vanadate, molybdate, manganate, tungstate, and nitrite.

  As a specific example of the rust inhibitor B, a phosphate system (phosphoric acid, calcium phosphate, magnesium phosphate, condensed phosphates) is preferable.

  As specific examples of the rust inhibitor C, tannic acid series, thiourea series, and benzotriazole series are preferable.

  As a specific example of the rust preventive agent D, a sulfur type (calcium sulfide, manganese sulfide, iron sulfide) is suitable.

  Appropriate selection methods for these rust preventives mentioned above include their own water solubility and reactivity to zinc and steel (electrochemical measurement: electric quantity in potential-current curve in cyclic voltammogram). ) As one of the measures.

  As shown in FIG. 3 and FIG. 4, the effect of adding the rust inhibitor appears remarkably. However, although the Example here does not show all the rust preventive agents and the combination, it has confirmed that it becomes the same result by selecting the quantity of each rust preventive agent.

  FIG. 5 shows an example and a comparative example of the second coating material having a silica amount at the time of kneading at a weight ratio of fine particle silica to the weight of zinc dust. The second coating material and the first coating material after kneading. Were mixed and stirred, and this was applied as a final paint and evaluated.

  The addition effect of the fine particle silica shown in FIG. 5 remarkably indicates that 100 to 5000 ppm is suitable from the result of the corrosion resistance in the neutral salt spray test.

  The electrical resistance value of the painted dry coating film was measured by the method shown in FIG. A copper or gold-plated terminal with a diameter of about 2 mmφ is in contact with the surface of the painted film, and a similar terminal is brought into contact with the bare part of the coated steel sheet (the mirror surface with the material exposed), and the electrical resistance value between the two terminals Is measured with an ordinary resistance meter. In addition, a coating film of about 50 μm is formed on a steel sheet (S40) having a thickness of 1 cm, and a contact probe (cylindrical copper bar) having a diameter of 2 mm is brought into contact with the dried coating film and the mirror surface of the steel sheet. Measured.

  When measuring the electrical resistance value of the coating film, the contact pressure of the terminal, the fine uneven shape of the coating surface, the dispersion state of the zinc particles in the coating film, and the like cannot be said to be uniform from the whole coated surface. Further, the coating film resistance value varies greatly depending on the amount of fine particle silica.

For this purpose, in the coating area of about 100 cm ² , the electrical resistance values of 10 coatings were measured, and the average value of 8 locations excluding the maximum and minimum values was taken as a large approximate value, and the electrical resistance of the coatings Value.

In addition, although the area of the terminal which contact | connects the coating-film surface is about 3 mm < ² >, the measured value was converted into 1 mm < ² > and it was set as the rough value of the electrical resistance value of a coating film.

  FIG. 7 is the same composition as FIG. 5, and includes a first coating material in which a certain amount of sodium nitrite and a chelating agent as a rust preventive agent is added in an amount of 0.5% by weight, zinc dust and fine particle silica. The amount was changed and the kneaded second coating material was mixed and stirred to apply a paint.

  The amount of fine-particle silica in FIG. 7 shows the weight ratio with respect to the weight of zinc dust added during kneading, as in FIG. Here, it is an Example and comparative example of 50-5000 ppm as the quantity of fine particle silica.

  From FIG. 7, the electrical resistance value of the coating film varies depending on the amount of fine particle silica due to the combined action with the rust inhibitor. In a conventional solvent-type zinc-rich coating film or a publicly-known aqueous-type zinc-rich coating film, the coating film itself is metallic, and the electrical resistance value of the coating film is approximately zero Ω.

  As shown in FIG. 7, the result that the coated coating film has electrical resistance is extremely unusual as a zinc rich coating film, and the electrical resistance value is limited, but the result of FIG. The results show that the higher the electric resistance value, the longer the anticorrosion property is maintained.

  From FIG.5 and FIG.7, the corrosion resistance with respect to rust generation | occurrence | production from a crosscut part is so favorable that the electrical resistance value of a coating film is high. In Comparative Example 31 similar to the conventional solvent type, the electric resistance value is substantially zero Ω, and the ability to suppress rust generation from the crosscut portion is not recognized.

  Thus, depending on the electrical resistance value of the coating film, in the case of a metallic film, the film in the vicinity of the scratched part is sacrificed, and if the electrical resistance value of the coating film becomes high, the distance to the scratched part is increased. This means that the sacrificial action works, the sacrificial action reaction of the coating film itself is moderately suppressed, and the conventional anticorrosive property is not achieved.

  Thus, although the conventional zinc rich paint exhibits a certain anticorrosion property, it does not have a function of controlling its performance. However, the room temperature dry aqueous zinc rich paint of the present invention realizes a very wide range of anticorrosion properties by a coating method for controlling the electric resistance value of the coated film.

Claims (3)

  A first coating material containing an aqueous resin, water as a dispersion medium, additives, a small amount of a volatile organic compound, and an essential rust preventive agent, and a second coating material in which fine-particle silica and zinc dust are kneaded. Room temperature dry-type water-based zinc rich paint   A room-temperature drying type aqueous zinc rich characterized in that the second coating material of claim 1 kneaded with an arbitrary amount of fine particle silica and the first coating material of claim 1 are mixed and stirred at the coating site and then coated. How to paint A coating method of room temperature dry type water-based zinc rich paint, characterized in that the electric resistance value of the coating film coated with the addition amount of fine particle silica of claim 2 is 10 Ω / mm ² or more.

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