JP2005194490A - Scaly zinc powder for water-based metal rust-proof paint, method for producing the same, and water-based nonchromic metal rust-proof paint in which the scaly zinc powder is dispersed - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a scaly zinc powder for water-based metal rust proof paints by adding a coating film preventing reaction with an aqueous binder solution and easily dispersing the scaly zinc powder in the aqueous binder solution in substantially a primary particle state on the surface of the scaly zinc powder used for water-based rust proof pigments expressing sacrificial corrosion protection effects, and provide a method for producing the same and a water-based nonchromic metal rust proof paint containing the scaly zinc powder. <P>SOLUTION: The scaly zinc powder for the water-based metal rust-proof paints is prepared by forming a thin film added with a silane compound having a hydrophobic group on the surface of particles of the scaly zinc powder and treating the surfaces of the zinc powder particles to be water repellent with the silane compound. A part of the scaly zinc powder may be substituted with a scaly aluminum powder. The silane compound having the hydrophobic group used for water repellent treatment has the hydrophobic group and an alkoxy group and the silane compound in which the alkoxy group is hydrolyzed to the hydroxy group is added to the surface of the scaly zinc powder. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a scaly zinc powder used as a rust preventive pigment exhibiting a sacrificial anticorrosive effect for an aqueous metal rust preventive paint mainly for anticorrosive coating on the surface of iron-based metal products such as steel and cast iron, and a method for producing the same, The present invention relates to a non-chromium aqueous metal rust preventive paint using the same.

  As a trend of rust preventive paints, non-chromium water-based metal rust preventive paints that do not contain a chromium component and have a low organic solvent content are desired so as not to pollute the environment. Water-based metal rust preventive paints that do not contain a chromium component using scaly zinc powder exhibiting a sacrificial anticorrosive effect as a rust preventive pigment are already on the market. However, water-based metal rust preventive paints using scaly zinc powder have problems such as inferior rust prevention performance compared to water-based metal rust preventive paints containing chromium components and short pot life due to changes over time. Even now, water-based metal anticorrosive paints containing chromium components are still used.

  The flaky zinc powder used as a rust preventive pigment exhibiting a sacrificial anticorrosive effect is produced by the following process. First, a granular zinc powder having an average particle diameter of 3 to 6 μm, an aluminum powder, a fatty acid, a higher alcohol, or the like is mixed in an organic medium such as mineral spirit and dispersed to obtain a slurry. Next, the zinc powder slurry is treated with a bead mill using zirconia beads having a diameter of about 0.5 mm, and the zinc particles are rolled and scaled by an impact force with which the zirconia beads collide with the zinc particles. Thereafter, organic media such as mineral spirits are removed by distillation under reduced pressure or the like, and dried and made of scale-like zinc particles covered with a lubricant / barrier layer such as stearic acid or higher alcohol whose surface is dissolved in mineral spirits. Use powder. The scale-like zinc powder particles usually have an average thickness of less than 0.5 μm, and an average length and width of about several μm to 10 μm.

  The scaly zinc powder particles whose surface is not coated with a lubricant / barrier agent, when the surface directly touches the binder aqueous solution of the anticorrosive paint, the zinc powder and aluminum powder are gradually oxidized to generate fine hydrogen bubbles. At the same time, the viscosity of the rust preventive paint gradually increases and paintability is impaired, and the rust preventive performance of the rust preventive paint gradually deteriorates.

  As a measure for preventing the oxidation of the flaky zinc powder, Patent Document 1 describes that a fatty acid such as stearic acid is added to the slurry when the flaky treatment is performed, and the fatty acid is coated on the surface of the flaky zinc powder to form a paint. A method is disclosed in which scaly zinc powder is mixed into an aqueous metal anticorrosive paint while preventing reaction with an aqueous medium.

  In this case, after the zinc powder is flaked with a bead mill, the mineral spirit is evaporated under reduced pressure so that the fatty acid remains on the surface of the flaky particles. The fatty acid remains as a film covering the surface of the scaly particles, and becomes a barrier when the scaly zinc powder comes into contact with water or moist air to prevent the oxidation reaction.

  When this scaly zinc powder is dispersed in an aqueous binder solution to form a rust-preventive paint, it is difficult to disperse because it repels water due to the barrier effect of the fatty acid coating. However, the scaly zinc powder is used in combination with a surfactant. Can be dispersed in the aqueous binder solution, and the reaction of generating hydrogen generated between the zinc powder particles and the aqueous binder solution can be suppressed.

In order to prevent oxidation of the scaly zinc powder, Patent Document 2 discloses the use of coated zinc-containing metal flakes in which an aqueous colloidal silica film is formed on the surface of the zinc powder to prevent reaction in water. However, the aqueous colloidal silica coating is hydrophilic and allows moisture to pass through, so it is imperfect as a moisture barrier.
JP 2003-3271 A JP-A-6-9897

  In this way, a scaly zinc powder coated with a fatty acid, a higher alcohol, or the like is dispersed in an aqueous binder solution to obtain an aqueous metal anticorrosive paint, but the stearic acid coating the scaly zinc powder particles And the like serve as an adhesive to bond the scaly zinc powder particles to each other, and there is a problem that the scaly zinc powder particles become secondary particles.

  That is, even if the scaly zinc powder having fatty acid or the like attached to the surface is dispersed in the aqueous binder solution, the scaly zinc powder particles are bonded or laminated to form secondary particles.

  This type of water-based metal rust preventive paint is often used for rust preventive coating of fasteners such as steel bolts and nuts. As a method of painting fasteners, a dip and spin method is usually employed. That is, immerse the fasteners in a metal cage together with the cage in the paint tank, lift the metal cage from the paint tank, rotate it, and shake the excess paint adhering to the fastener surface by centrifugal force. Remove and bake after drying. Usually, this coating is repeated twice.

  When a rust preventive paint containing scaly zinc powder that is bonded or laminated to each other to form secondary particles is applied to the base material, a secondary particle structure in which the particles of scaly zinc powder are bonded or laminated in the coating film. Is recognized. The gap formed between the secondary particles is large, and the thickness of the coated film becomes non-uniform. In fasteners, it is necessary to cover the surface of the base material with a coating film that is relatively thin and has rust prevention power, but a rust prevention paint containing zinc powder that has become secondary particles cannot satisfy this condition.

  If the particles of flaky zinc powder are dispersed into primary particles in the rust preventive paint, the particles of the flaky zinc powder are displaced in parallel in the coating film when the rust preventive paint is applied to the substrate. Since they overlap each other and adhere to the surface of the base material, the surface of the base material can be covered with multiple layers with a thin rust-preventive coating, and it is expected that the anti-corrosion performance can be sufficiently exhibited.

  In order to break the secondary particles of the flaky zinc powder bonded or laminated together into primary particles, the flaky zinc powder coated with stearic acid or the like and dried was subjected to air classification using a jet mill and collected. However, when it is unrolled with a jet mill, some of the flaky zinc particles are torn off and some of the zinc powder is refined, and at the same time, the coating of stearic acid or the like covering the surface of the flaky zinc powder particles is damaged. A part of the metal surface of the zinc powder particles is exposed. When such flaky zinc powder is dispersed in a binder aqueous solution of an anticorrosive paint, a reaction between zinc particles and the aqueous binder solution occurs, and hydrogen bubbles are generated. Increases viscosity.

  On the other hand, since the aqueous colloidal silica film is hydrophilic, the effect of suppressing the reaction between water and zinc powder is not sufficient, and white rust of zinc oxide tends to occur.

  The present inventor does not need to treat the secondary particles of flaky zinc powder into primary particles with a jet mill or the like, covers the entire surface of the flaky zinc powder particles, inactivates them, and Various methods for making the zinc-like powder particles difficult to form secondary particles have been studied, and the present invention has been achieved.

  Therefore, the present invention forms a coating for preventing reaction with the aqueous binder solution on the flaky zinc powder used as a rust preventive pigment exhibiting sacrificial anticorrosive effect, and the flaky zinc powder An object of the present invention is to provide a flaky zinc powder for an aqueous metal anticorrosive paint that is difficult to be converted into secondary particles.

  The present invention also provides a method for producing a scaly zinc powder for an aqueous metal anticorrosive coating, which prevents the reaction between the scaly zinc powder and the aqueous binder solution and is provided with a coating in which the scaly zinc powder is difficult to form secondary particles. It is an object.

  Furthermore, another object of the present invention is to provide a non-chromium aqueous metal rust preventive coating material in which such flaky zinc powder for an aqueous metal rust preventive coating material is dispersed in a binder aqueous solution.

  A scaly zinc powder for an aqueous metal rust preventive paint according to the present invention comprises a scaly zinc powder and a silane compound having a hydrophobic group added to the particle surface, and the zinc powder particle surface is water-repellent by the silane compound. It is processed.

  It is preferable that the scale-like zinc powder for aqueous metal rust preventive paints of the present invention is a mixture containing 6 to 35% by weight of scale-like aluminum powder.

  In the flaky zinc powder for aqueous metal rust preventive paint of the present invention, the silane compound having a hydrophobic group has a hydroxy group formed by hydrolysis of the alkoxy group of the silane compound having a hydrophobic group and an alkoxy group. Is preferred.

  In the flaky zinc powder for aqueous metal rust preventive paint of the present invention, the flaky zinc powder added with a silane compound having a hydrophobic group on the surface has a property of floating on the water surface against water to which no surfactant is added. More preferably, it is shown.

  The method for producing scale-like zinc powder for an aqueous metal rust preventive paint according to the present invention comprises mixing zinc powder having an average particle size of 3 to 6 μm in an organic medium to form an organic medium slurry of zinc powder, and the zinc powder in the slurry The scaly treatment is made into scaly, and the slurry is allowed to stand to settle the scaly zinc powder in an organic medium to remove the supernatant organic medium, and the medium is replaced with alcohol to obtain an alcohol slurry of scaly zinc powder. Separately, an alcohol solution of a silane compound obtained by hydrolyzing an alkoxy group by adding a catalyst and water to an alcohol solution of a silane compound having a hydrophobic group and an alkoxy group is prepared. A silane compound having a hydrophobic group is added to the particle surface of the scaly zinc powder by mixing in the alcohol slurry, and the scaly zinc powder is By removing the alcohol from the combined alcohol slurry; and obtaining flaky zinc powder the silane compound was added to the particle surface with hydrophobic groups.

  In the method for producing a scaly zinc powder for an aqueous metal rust preventive paint according to the present invention, a zinc powder containing 6 to 35% by weight of a scaly aluminum powder obtained by mixing a scaly aluminum powder into the organic medium slurry of a zinc powder. It is preferable to add a silane compound having a hydrophobic group to the surface of the scaly zinc powder particles containing scaly aluminum powder as a slurry.

  In the method for producing scale-like zinc powder for aqueous metal rust preventive paint according to the present invention, the step of removing alcohol from the alcohol slurry mixed with scale-like zinc powder is obtained by removing most of the alcohol by a gradient method or siphon suction. Then, it is preferable to place the scaly zinc powder wetted with alcohol on the filter paper so that the liquid component is absorbed by the filter paper and then dried.

  The non-chromium aqueous metal rust preventive paint of the present invention is a binder in which a scaly zinc powder exhibiting water repellency by adding a silane compound having a hydrophobic group to the particle surface of the scaly zinc powder contains a surfactant. It is characterized by being dispersed substantially in the form of primary particles in an aqueous solution.

  In the non-chromium aqueous metal rust preventive paint using the scaly zinc powder according to the present invention, the scaly zinc powder particles are covered with a coating to which a silane compound having a hydrophobic group is added, and thus the binder is formed when the paint is formed. It is possible to form a coating film in which almost no hydrogen bubbles are generated by reaction with an aqueous solution, and no holes which are traces of hydrogen bubbles are observed.

  Since the reaction to generate hydrogen is suppressed, the viscosity of the paint is hard to increase, and the storability of the paint is improved.Since the particles of the scaly zinc powder are covered with a film having a low adhesiveness due to the addition of the silane compound, The scaly zinc powder particles can be prevented from being joined to each other to form secondary particles, or even if they are made into secondary particles, they can be easily broken into primary particles by a normal stirring operation. Thus, the scaly zinc powder particles are substantially dispersed in the form of primary particles in the aqueous metal rust preventive paint, so that the scaly zinc powder is coated in the paint film coated with the aqueous metal rust preventive paint on the surface of the object to be coated. A layered structure is formed in which the particles are displaced in parallel with each other, and a rust prevention performance of about 1000 hours can be secured in a salt spray test with only a thin coating film of about 10 μm.

  Furthermore, the surface treatment agent previously applied for in Japanese Patent Application No. 2004-52991 is applied onto this coating film, and a coating having a thickness of less than 2 μm is formed on the surface, so that 2000 hours can be obtained in the salt spray test. A coating film having an anticorrosive performance exceeding that can be formed. Therefore, it is possible to provide a non-chromium aqueous metal rust preventive coating material suitable for rust preventive coating of fasteners such as bolts and capable of obtaining a rust preventive performance exceeding 2000 hours in a salt spray test even when the coating film is thin.

  In general, when the thickness of the anticorrosive coating film is doubled, the antirust performance in the salt spray test is improved by about 4 times or more, and the aqueous solution using the scaly zinc powder according to the present invention is used. It can be said that the metal anticorrosion paint has remarkably improved antirust performance. In addition, by applying a surface treatment agent on the anticorrosive coating film, it is possible to form a non-chromium antirust coating film that can suppress the occurrence of white rust and black rust over a long period of time.

  In the present invention, the silane compound having a hydrophobic group exists as a very thin coating layer on the surface of the scaly zinc powder particles, and is less likely to adhere to each other as compared with a coating formed of a fatty acid or a higher alcohol. Is weak in secondary particles. Therefore, even if it is made into secondary particles, it can be broken down into primary particles by a simple operation, and at this time, it can be broken down into primary particles so that the scaly zinc powder particles are not torn or damaged.

  Since the surface of the scaly zinc powder particles is covered with the hydrophobic group of the silane compound, it has water repellency, and when the scaly zinc powder is put into pure water, it floats on the water, but you can add a surfactant to the water. Can be dispersed in water.

  Reaction of generating hydrogen that occurs when the surface of the flaky zinc powder particles comes into contact with water or moist air even though the coating of the silane compound having a hydrophobic group covering the surface of the flaky zinc powder particles is very thin Can be prevented. In addition, when the flaky zinc powder of the present invention is dispersed in a binder aqueous solution of an aqueous metal rust preventive paint to which a surfactant is added, the reaction of generating hydrogen can be effectively prevented.

  Particles of flaky zinc powder are prepared by dispersing the flaky zinc powder for aqueous metal anticorrosive paint surface-treated by the method of the present invention in a binder aqueous solution to which a surfactant is added to prepare an aqueous metal rust preventive paint. However, a non-chromium anticorrosive coating film having excellent antirust performance can be formed even when it is thin. Moreover, after forming into a coating material, it can prevent that a coating material changes in quality, when a binder aqueous solution and scale-like zinc powder react, and hydrogen bubbles generate | occur | produce.

  When a rust-proof paint in which scaly zinc powder consisting essentially of primary particles is dispersed in an aqueous binder solution is applied to the surface of fasteners such as bolts and nuts by the dip-and-spin method, the scaly zinc powder particles are parallel to each other. A thin film structure is formed that overlaps and overlaps, and even if it is thin, it becomes a film with a structure that covers the substrate with multi-layered scaly zinc powder particles, and forms a film that can fully exhibit rust prevention performance To do.

  Furthermore, the surface of the substrate is coated with an aqueous metal rust preventive paint containing the surface-treated flaky zinc powder, and rust-proof with a non-chromium surface treatment agent for galvanized products previously filed in Japanese Patent Application No. 2004-52991. By overcoating the coating film surface of the paint, it is possible to maintain the antirust performance against white rust and black rust as well as red rust for a long time, and it is possible to form a coating film exhibiting excellent rust prevention performance on the substrate surface even if it is thin.

  When the scaly zinc powder is a scaly zinc powder containing 6 to 35% by weight of scaly aluminum powder, the surface of the anticorrosive coating film applied to the object to be coated exhibits a metal color close to aluminum. This is presumably because the scaly aluminum powder tends to gather on the surface layer of the coating film because the specific gravity is lighter than that of the scaly zinc powder. In this case, the rust prevention performance of the rust prevention paint can be improved. If the amount of the flaky aluminum powder contained in the flaky zinc powder is less than 6% by weight, the effect of substitution is not recognized, and if it is more than 35% by weight, the effect of increasing is not recognized. A more preferable mixing ratio of the flaky aluminum powder is 7 to 30% by weight.

  The silane compound having a hydrophobic group to be added to the surface of the scaly zinc powder can be added using, for example, a silane compound having a hydrophobic group and an alkoxy group such as a silane coupling agent. When these silane compounds are dissolved in an alcohol solvent and a small amount of water is added using acetic acid as a catalyst, hydrolysis of the alkoxy group occurs, and a hydroxy group is generated at the position where the alkoxy group was present.

  When the alcohol solution of the hydrolyzed silane compound is mixed with the scaly zinc powder slurry dispersed in the alcohol solvent, the silane compound having a hydrophobic group is added to the particle surface of the scaly zinc powder, and the silane compound becomes scaly. The entire surface of the zinc-like zinc powder particles is coated to give a scaly zinc powder exhibiting water repellency.

  In order to add particulate zinc powder to scaly zinc powder and add a silane compound having a hydrophobic group to the surface of the scaly zinc powder, first, the zinc powder is scaly treated by a conventional method using a bead mill. In this case, the zinc powder is obtained by using a commercially available granular powder having an average particle size of 3 to 6 μm as a raw material, and scalping is performed by a bead mill. Specifically, zinc powder is mixed with an inexpensive and inert organic medium such as mineral spirit to form a slurry, and this slurry is passed through a bead mill to impact the zirconia beads having a diameter of about 0.5 mm. Strike and stretch particles to scale. In scaling, fatty acids and higher alcohols may be dissolved in mineral spirit and used as a lubricant.

  When a scaly aluminum powder paste is mixed in an organic medium slurry of zinc powder and then scaled by a bead mill, a scaly zinc powder in which the scaly aluminum powder is intimately mixed is obtained. The scaly aluminum paste may be mixed into the organic powder slurry of zinc powder after the scaly process using a bead mill.

  In the method for producing scaly zinc powder for an aqueous metal rust preventive paint according to the present invention, mineral spirit as a slurry medium is replaced with an alcohol solvent suitable for surface treatment to which a silane compound is added. As the alcohol solvent, ethyl alcohol, isopropyl alcohol, n-butyl alcohol, ethyl cellosolve, butyl cellosolve, 1-methoxy 2-propanol, methyl alcohol and the like can be used.

  The addition of the silane compound to the surface of the scaly zinc powder particles can be performed by a usual method of adding a silane coupling agent to the surface of the inorganic powder particles.

  After adding the silane compound to the surface of the scaly zinc powder particles, it is preferable to remove the alcohol solvent (which also dissolves the silane compound) used for the addition treatment as much as possible before drying. Excess silane compound is removed by removing alcohol solvent in which residual silane compound not added to the surface of scaly zinc powder is dissolved, so scaly zinc powder is not secondary particles or easily primary particles Can be recovered as flaky zinc powder. In order to remove the alcohol solvent in which the residual silane compound is dissolved, after removing the supernatant, the scaly zinc powder wet with alcohol may be transferred onto a sheet that absorbs liquid such as filter paper. If the alcohol solvent is absorbed by the filter paper, it is easy to dry the scaly zinc powder. Since the silane compound added to the surface of the scaly zinc powder particles cannot be removed by washing with alcohols, it can be dried after washing with alcohol having a low boiling point that is easy to dry.

  Alcohol solvent may be left in the room to evaporate, but in order to dry it more completely, place it in a heated drier and warm it to dry, or transfer it to a vacuum container while it is warming and reduce the pressure. The alcohol can also be evaporated and dried under.

  Dipropylene glycol or the like contained in the aluminum paste replaces the mineral spirit with an alcohol solvent, and finally the alcohol solvent is removed and dried, so that a dry scaly zinc powder substantially free of dipropylene glycol or the like is obtained.

  Thus, it is avoided that the scaly zinc powder particles are bonded to each other and become strongly bonded secondary particles, and the water repellency of the scaly zinc powder is made up of primary particles or secondary particles that can be easily broken into primary particles. The dried scaly zinc powder is obtained. That is, it can be said that the dried scaly zinc powder mixed and stirred in the binder aqueous solution is substantially composed of primary particles.

  The scaly zinc powder of the present invention exhibits water repellency by adding a silane compound having a hydrophobic group, but is dispersed in an aqueous binder solution to which a surfactant is added to form an aqueous metal rust preventive paint. Can do.

  In the aqueous metal rust preventive paint according to the present invention, when the scale-like zinc powder is substantially dispersed in the state of primary particles in the aqueous metal rust preventive paint, The scaly zinc powder particles are overlapped in a state of being shifted in parallel with each other, covering the surface of the object to be coated several times to form a coating film having no voids or bubbles (bubble holes). Therefore, even if the coating film is applied as thin as about 10 μm on the surface of fasteners, the coating film exhibits excellent rust prevention performance. The water-based metal rust preventive paint can be made with various compositions described in Japanese Patent Application No. 2003-277284, for example.

  4 kg mineral spirit (wax made by Sanyo Chemical Co., Ltd.) and 1 kg aluminum powder (made by Showa Aluminum Powder Co., Ltd.) for 1 kg zinc powder with an average particle size of about 4 μm (F-3000 made by Honjo Chemical Co., Ltd.) 4111 GB, 100 g of mineral spirit 100 g containing 10% dipropylene glycol, and 20 g of lauryl alcohol (Kalco Co., Ltd. Calcoal 2098) were mixed to make a slurry, which was then circulated by flowing it from a service tank to a bead mill, Scaled.

  As the bead mill, an SC100 / 32A mill manufactured by Mitsui Mining Co., Ltd. was used. A zirconia ball having a diameter of 0.5 mm was introduced into an about 0.65 kg grinding chamber, and the rotor was rotated at 2650 rpm (corresponding to a peripheral speed of about 14 m / second). The zinc powder slurry charged into the service tank was passed through a bead mill and circulated between the service tank and scaled. The treatment time varies depending on the amount of slurry to be placed in the service tank, but it was set to 2 hours when 1 kg of zinc powder was scaled.

  When the mineral spirit slurry of zinc powder that has been flaked is transferred to a stainless steel container, 54 g of aluminum paste is added, mixed, and left for a while, then flaky zinc powder with a large specific gravity (9.7% by weight of flaky aluminum) (Including powder) settles to the bottom and forms a supernatant of mineral spirits. The supernatant was removed by a gradient method or siphon and replaced with butyl cellosolve to obtain a butyl cellosolve slurry of scaly zinc powder.

  Separately, 30 g of 2% aqueous acetic acid solution and 130 g of n-hexyltrimethoxysilane (Nihon Unicar Co., Ltd. AZ-6177) were added to 600 g of butyl cellosolve and kept at about 50 ° C. for 3 hours with stirring to hydrolyze the alkoxy group. A decomposed silane monomer solution was prepared.

  The silane monomer solution hydrolyzed while stirring the flaky zinc powder slurry substituted with butyl cellosolve and kept at about 55 ° C. was gradually mixed with the slurry over about 5 hours, and then left overnight with stirring.

  Stop stirring the slurry, let it stand, let the flaky zinc powder settle to the bottom, remove the supernatant again with a gradient method and siphon, spread the wet flaky zinc powder on the filter paper laid on an aluminum tray, and filter the butyl cellosolve Then, it was dried in a room for a whole day and night, and further placed in a dryer and dried at 120 ° C. for several hours.

  To unwind the scaled zinc powder after drying, put a ring of 1 kg of zirconia balls with a diameter of 5 mm and about 0.5 kg of dried zinc powder into a 2 liter polypropylene container, cover the ring, and rotate on a ball mill rotating base A polypropylene container was placed in a funnel can with a frame, the periphery was fixed with a cushioning material, and the polypropylene container was set to rotate in the vertical direction at 30 rpm. About 30 minutes later, the zirconia balls and the flaky zinc powder were taken out of the polypropylene container and sieved.

  The obtained scaly zinc powder had a good metallic luster. When a small amount was picked with a finger and dropped onto the water surface, it was water-repellent and all floated on the water surface even when the water was stirred.

  100 parts by weight of the scaled zinc powder (containing 9.7% by weight of aluminum powder) and 2.7 parts by weight of an aqueous block isocyanate resin emulsion (containing a prominate manufactured by Ganz Kasei Co., Ltd. and a resin component of 45% by weight) , Β (3,4-epoxycyclohexyl) ethyltriethoxysilane (Coat Sil 1770, 11.5 parts by weight manufactured by Nippon Unicar Co., Ltd., 58.4 parts by weight of polyethylene glycol having an average molecular weight of 1000, nonionic natural alcohol ethoxylate ( Asahi Denka Co., Ltd. (surfactant) 2.8 parts by weight, sodium molybdate 1.4 parts by weight, water 106.2 parts by weight mixed in an aqueous binder solution, and slowly stirred with a stirrer. Zinc powder can be easily dispersed in a binder aqueous solution to which a surfactant is added, hydrogen bubbles are not generated, Less performance change with time of the degree (increase) to obtain a stable flaky zinc powder containing aqueous metal anticorrosive paint.

  Applying this water-based metal anticorrosive paint after about 24 hours has been applied to a M8 bolt with a length of about 30 mm by the dip and spin method (rotation radius of spear about 200 mm, rotation speed of 340 rpm) and baking at 250 ° C. for 15 minutes Was repeated twice to obtain 20 bolts coated with a rust preventive paint.

  Next, a surface treatment agent was applied to 10 coating films of M8 bolts coated with this aqueous metal anticorrosive paint by a dip-and-spin method (rotating radius of cocoon of about 150 mm, rotating speed of 350 rpm) at 15O 0 C at 15 ° C. Baked for a minute. This surface treatment agent is 16.7% by weight of titanium oxide ultrafine powder (Showa Denko K.K.) with respect to 80 parts by weight of an alcohol solution of an ethoxysilane oligomer (weight average molecular weight 2240) containing about 20% by weight of a silica component. 8 parts by weight of a titanium oxide slurry containing ethyl cellosolve containing Super Titania F-6 (average particle size of primary particles: 15 nm) (dispersed for 24 hours by a ball mill).

  This bolt, which was coated with a rust-preventive paint and coated with a surface treatment agent, was embedded in the resin and cut, and when the cross section of the coating film was examined by taking a 2000-fold photomicrograph, it was substantially dispersed in primary particles. Scale-like zinc powder was observed in the coating. That is, in the coating film having a thickness of about 10 μm, the scaly zinc powder dispersed in the primary particles is arranged in a state shifted from each other in a direction parallel to the substrate surface, and the scaly zinc powder covers the substrate surface in multiple layers. A membrane structure was formed. Moreover, the coating thickness of the surface treatment agent baked on the surface of the anticorrosive coating film was a little less than 2 μm.

  The cross section of the coating film structure according to the present invention observed in FIG. 1 is schematically shown. In FIG. 1, reference numeral 2 denotes a coating film having a thickness of about 10 μm formed on the surface of a base material (bolt) 1, and there is a thin solidified layer of an aqueous binder between primary particles 4 of scaly zinc powder. The primary particles 4 of the zinc-like powder are bonded to each other. 3 is a coating of a surface treatment agent formed on the coating film.

  In the same manner as in Example 1, a hydrophobic silane compound was added to the surface of the flaky zinc powder particles, and the treatment of breaking the flaky zinc powder in Example 1 in a ball mill was omitted. The added flaky zinc powder was dried, mixed as it was in an aqueous binder solution to which a surfactant was added, and stirred. As a result, the flaky zinc powder could be easily dispersed substantially in the form of primary particles. The obtained water-based metal anticorrosive paint did not generate hydrogen bubbles and was stable with little change (increase) in the viscosity of the paint over time.

  This aqueous metal anticorrosive paint was applied to 20 M8 bolts of about 30 mm in length by the dip and spin method in the same manner as in Example 1, and the operation of baking at 250 ° C. for 15 minutes was repeated twice. Next, a surface treatment agent was applied to 10 of the coating bolts by the dip and spin method (rotation radius of cauldron of about 150 mm, rotation speed of 350 rpm) in the same manner as in Example 1, and baked at 180 ° C. for 15 minutes.

  The bolt was embedded in the resin and cut, and the cross-section of the coating film was examined with a 2000-fold photomicrograph. It was. The coating film structure was almost the same as that shown in FIG. 1, the coating film thickness was about 11 μm, and the coating formed by the surface treatment agent was less than 2 μm.

  Instead of the n-hexyltrimethoxysilane monomer used in Example 1, 125 g of n-octyltriethoxysilane (Nihon Unicar Co., Ltd. silane monomer A-137) was added to 600 g of butyl cellosolve, and water was added using acetic acid as a catalyst. A decomposed silane monomer solution was prepared.

  Other than that, an aqueous metal anticorrosive paint was prepared in the same manner as in Example 2 and applied to M8 bolts by the dip-and-spin method to obtain 20 painted bolts of Example 3. Next, a surface treatment agent was applied onto 10 bolts coated with a water-based metal anticorrosive paint in the same manner as in Example 1 by the dip-and-spin method (rotating radius of cocoon approximately 150 mm, rotating speed 350 rpm) at 180 ° C. Baked for 15 minutes. When the coating film attached to the surface of the bolt was examined by taking a micrograph of 2000 times of the cut surface, the coating film thickness was about 11 μm, and the thickness of the coating formed by the surface treatment agent on the coating film was It was a little less than 2 μm. In the micrograph of the cross section of the coating film, a coating film composed of a coating structure in which particles of scaly zinc powder were displaced in parallel with each other and overlapped was observed on the substrate (bolt) surface. This coating film structure was almost the same as that shown in FIG. Further, the obtained water-based anticorrosive paint did not generate hydrogen bubbles and was stable with little change (increase) in the viscosity of the paint over time.

  Instead of the n-hexyltrimethoxysilane monomer used in Example 1, 125 g of phenyltriethoxysilane (GE Toshiba Silicone Co., Ltd. alkoxysilane TSL-8178) was dissolved in 600 g of butylcellosolve, and an alkoxy group was prepared using acetic acid as a catalyst. A silane monomer solution hydrolyzed was prepared.

Otherwise, an aqueous metal rust preventive paint was prepared in the same manner as in Example 2 to obtain a rust preventive paint in which the particles of scaly zinc powder were dispersed substantially in the form of primary particles in the paint. This rust preventive paint was applied to M8 bolts by the dip and spin method in the same manner as in Example 1 to obtain 20 coated bolts of Example 4. A surface treatment agent was applied to 10 bolts coated with this anticorrosive paint by the dip and spin method (rotation radius of cauldron of about 150 mm, rotation speed of 350 rpm) in the same manner as in Example 1, and baked at 180 ° C. for 15 minutes. . The bolt was buried in a resin and cut, and the cross section of the coating film was examined by taking a 2000 × microscopic photograph. The coating thickness of the bolt surface was about 10 μm, and the particles of scaly zinc powder were displaced in parallel with each other. Overlapping film structures were observed on the substrate (bolt) surface. The coating film structure was almost the same as that shown in FIG. 1, and the thickness of the coating formed by the surface treatment agent was less than 2 μm.
(Comparative Example 1)
1 kg zinc powder with an average particle size of about 4 μm (F-3000 manufactured by Honjo Chemical Co., Ltd.) is mixed with 4 kg mineral spirit, 154 g aluminum paste, and 20 g lauryl alcohol to form a slurry, which is then transferred from the service tank to a bead mill. It was made to flow and circulate, and the scaly process was carried out similarly to Example 1.

  The scaled zinc powder slurry was placed in a mixer equipped with a vacuum vessel equipped with a stirrer (FM20BX Henschel mixer manufactured by Mitsui Mining Co., Ltd.) and dried under reduced pressure to obtain dry scale-like zinc powder. The surface of the dried flaky zinc powder was coated with a higher alcohol lauryl alcohol, but was formed into secondary particles due to the presence of adhesive lauryl alcohol and could not be easily broken into primary particles. As a countermeasure, the secondary particles were broken down into primary particles with a jet mill (N-CONDUX CGS type 16 from Mitsui Mining Co., Ltd.), and the scaly zinc powder was recovered by wind classification.

  When a small amount of the obtained scaly zinc powder was picked with a finger and dropped onto the water surface, it was water repellent and floated on the water surface even when the water was stirred.

  This scaly zinc powder was mixed with the same aqueous binder solution used in Example 1 to form a paint. However, after standing for a while, hydrogen bubbles were generated little by little, and an increase in the viscosity of the paint was observed after several days. This phenomenon is caused by the scaly zinc powder particles being torn or the coated particle surface being damaged, so that part of the zinc of the scaly zinc powder particles is exposed and the surface of the zinc reacts with the aqueous binder solution to generate hydrogen bubbles. It was estimated that this was caused by the occurrence of

  About 24 hours after coating, the water-based metal anticorrosive paint was applied to 20 M8 bolts with a length of about 30 mm by the dip and spin method (rotating radius of cauldron of about 150 mm, rotating speed of 340 rpm), and at 250 ° C. for 15 minutes. The coating operation of Comparative Example 1 was obtained by repeating the baking operation twice. Furthermore, a surface treatment agent was applied to 10 of the bolts coated with this water-based metal anticorrosive paint in the same manner as in Example 1 by the dip-and-spin method (rotation radius of the ridge approximately 150 mm, rotation speed 350 rpm). Baked at 180 ° C. for 15 minutes. When the cross section of the coating film was examined with a micrograph of 2000 times the cross section obtained by embedding the bolt in the resin, the average thickness of the coating film formed on the surface of the M8 bolt was about 17 μm and formed by the surface treatment agent. The resulting coating thickness was less than 2 μm. The thickness of this coating film was uneven and had a thick part and a thin part, and a trace of bubbles was observed in the coating film. Moreover, many secondary particles in which particles of scaly zinc powder were laminated were observed on the cross section of the coating film, and voids were also observed between the secondary particles.

FIG. 2 is a schematic view showing a cross section of the coating film structure of Comparative Example 1. In FIG. 2, there are secondary particles 5 in which scaly zinc powder is laminated in the coating film 2 on the surface of the base material (bolt) 1, and voids 7 are observed between the secondary particles. A trace 6 with bubbles was observed. The trace 6 with bubbles is considered to be due to hydrogen bubbles generated by the reaction.
(Comparative Example 2)
14 g of stearic acid was added to the zinc powder slurry in place of lauryl alcohol, and the others were made in the same manner as in Comparative Example 1, and a rust-proof coating was produced in the same manner. I got a book. Furthermore, the sample which coat | covered the surface treating agent on the coating film similarly to the comparative example 1, and coat | covered the surface treating agent was obtained. When the cross section of the coating film was examined with a 2000 × photomicrograph, the average thickness of the coating film formed on the surface of the bolt was about 17 μm, and the thickness of the coating formed by the surface treatment agent was less than 2 μm. . Moreover, the thick part and the thin part existed similarly to the comparative example 1 in the coating film. As in Comparative Example 1, a mark with bubbles was observed on the surface of the coating film. This coating film structure was almost the same as that shown in FIG.

  Samples obtained by coating the rust preventive paints produced in Examples 1 to 4 and Comparative Examples 1 and 2 on M8 bolts by the dip-and-spin method, and samples obtained by applying both the rust preventive paint and the surface treatment agent to M8 bolts. Was put in a salt spray tester based on JIS-Z-2371 to evaluate the rust prevention performance. That is, five samples were put in a salt spray tester, and the evaluation results were summarized in Table 1 with the time when red rust was observed in three of the five samples as the time representing rust prevention performance. . From Table 1, in Examples 1 to 4, a thin coating film of about 10 μm shows the same level of anticorrosion performance as the coating film having a thickness of about 17 μm in Comparative Examples 1 and 2, and is further less than 2 μm. By coating the surface treatment agent with a thickness (12 μm and 19 μm, respectively, by adding the coating thickness of the surface treatment agent to the coating thickness of the anticorrosive paint, respectively), antirust performance exceeding 2000 hours was exhibited. Further, it was found that the generation of white rust and black rust was suppressed for a long time in the sample coated with the surface treatment agent.

It is a schematic diagram which shows the cross section of the coating-film structure | tissue which apply | coated the water-based metal rust preventive coating material by Example 1 of this invention. It is a schematic diagram which shows the cross section of the coating-film structure | tissue which apply | coated the aqueous metal rust preventive coating material by the comparative example 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base material 2 Coating film 3 (Surface treatment agent) Coating 4 Primary particle (of scaly zinc powder) Secondary particle (of scaly zinc powder) 6 Foam trace 7 Void

Claims (8)

A scale for aqueous metal rust preventive paint, characterized by comprising a scale-like zinc powder and a silane compound having a hydrophobic group added to the particle surface, wherein the surface of the scale-like zinc powder particle has been subjected to water repellency treatment. Zinc powder. 2. The scaly zinc powder for an aqueous metal anticorrosive paint according to claim 1, wherein the scaly zinc powder is a mixture containing 6 to 35% by weight of a scaly aluminum powder. The aqueous metal rust preventive according to claim 1 or 2, wherein the silane compound having a hydrophobic group has a hydroxy group formed by hydrolysis of an alkoxy group of the silane compound having a hydrophobic group and an alkoxy group. Scale-like zinc powder for paint. The scaly zinc powder added with a silane compound having a hydrophobic group on the surface exhibits a property of floating on the water surface with respect to water to which no surfactant is added. The scale-like zinc powder for aqueous metal rust preventive coatings described. Zinc powder having an average particle diameter of 3 to 6 μm is mixed in an organic medium to form an organic medium slurry of zinc powder, and the zinc powder in the slurry is scaled to a scaly shape. The sedimentary zinc powder is precipitated in an organic medium to remove the supernatant organic medium, and the medium is replaced with alcohol to form a scaly zinc powder alcohol slurry, which is separately catalyzed by an alcohol solution of a silane compound having a hydrophobic group and an alkoxy group. And water are added to make an alcohol solution of the silane compound that hydrolyzes the alkoxy group, and the alcohol solution of the silane compound is mixed with the alcohol slurry of the flaky zinc powder to make the silane compound having a hydrophobic group scaly. Hydrophobic by adding alcohol to the surface of zinc powder particles and removing alcohol from the alcohol slurry mixed with scaly zinc powder Method for producing a water-based metal anticorrosive paint flaky zinc powder, characterized in that the silane compound to obtain a flaky zinc powder was added to the particle surface with. A scaly zinc powder containing 6 to 35% by weight of scaly aluminum powder is mixed with the organic medium slurry of zinc powder, and a silane compound having a hydrophobic group is contained in the scaly zinc powder containing scaly aluminum powder. 6. The method for producing scaly zinc powder for an aqueous metal anticorrosive paint according to claim 5, wherein the powder particle surface is added. The step of removing alcohol from the alcohol slurry of scaly zinc powder is to remove most of the alcohol by the gradient method or siphon suction, and then place the scaly zinc powder wet with alcohol on the filter paper to absorb the liquid component on the filter paper The method for producing a scaly zinc powder for an aqueous metal rust preventive paint according to claim 5 or 6, wherein the powder is then dried. The scaly zinc powder exhibiting water repellency due to the addition of a silane compound having a hydrophobic group on the particle surface is substantially dispersed in a primary particle state in an aqueous binder solution containing a surfactant. Non-chromium aqueous metal rust-proof paint.

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