JP4111531B2 - Anti-rust paint - Google Patents

Description

  The present invention relates to a thin film-type anticorrosive paint that does not contain harmful metals such as chromium, and more specifically, it has a high antirust function even if it is a thin film that can be applied to, for example, precision equipment and steel sheet for press forming of automobile The present invention relates to a paint capable of forming a coating film.

  In the field of coatings intended for rust prevention of steel, rust-proof coatings mainly composed of zinc powder and chromic acid have been frequently used. This paint can keep the zinc powder stable for a long time by the passivating action of hexavalent chromium, and is excellent in storage stability of the liquid. Moreover, the coating film which consists of a coating material containing this zinc powder is effective in the sacrificial anti-corrosion action by well-known zinc, and prevents the corrosion of the base steel, Therefore The outstanding rust prevention effect is acquired.

  However, in recent years, environmental pollution due to the toxicity of hexavalent chromium and health damage to the human body have become a concern, and the movement to legally restrict the use of harmful metals such as hexavalent chromium has been accelerated. In response to this trend, companies that manufacture consumer products such as precision equipment and automobiles are proceeding with examinations in a direction that does not use harmful metals such as hexavalent chromium. Therefore, in the field of rust preventive paints, paints that do not contain any harmful metals such as chromium are strongly desired.

  As an example of such a rust-free paint containing no chromium, there is a kind of paint in which zinc powder and a binder component are dispersed or dissolved in an organic solvent, that is, zinc rich paint. There are organic and inorganic types of zinc rich paint. From the viewpoint of durability, inorganic type with an organosilicon compound as a vehicle is superior. For example, it is used as a primer in heavy-duty anticorrosive coating on ships and bridges. It has been.

  However, inorganic zinc rich paints tend to generate voids in the film, and it is difficult to control the thickness of the coating film. In order to overcome such drawbacks, the following techniques are disclosed.

  Patent Document 1 discloses a technique of additionally containing whisker-like calcium carbonate having a major axis of 20 to 30 μm. In this technique, the added whisker has a function of preventing the occurrence of cracks in the coating.

  Patent Document 2 discloses a zinc rich paint in which an alkyl silicate resin having a weight average molecular weight / number average molecular weight ratio of 40 or less is used, and the morpholine gel time of the paint is 60 seconds or less. It is described that such a coating has a fast curing time, and therefore suppresses a phenomenon in which cracks develop and lead to voids.

  Although such a technique is certainly effective as a thick film zinc rich paint, it is possible to stably form a thin film of about 10 μm and to provide a paint having a high anticorrosive property. Not done.

  The main applications of such a thin film with high anticorrosion properties are office equipment, electrical equipment, automobiles, etc. Specifically, fastening parts such as bolts and nuts, fasteners such as clamps and clips, plates And press-molded products such as housings, hinges and panels. These members are often subjected to a strong shearing force at the time of processing or assembling, although the assembling accuracy is severe, and a high level is required for the strength and adhesion of the coating itself.

One effective means for meeting this requirement is baking of the coating film at a high temperature. However, when the zinc rich paint according to the prior art is baked at a high temperature of about 300 ° C., the organosilicon compound serving as the binder rapidly shrinks, and even if the technique according to the patent literature as described above is used, Crack growth cannot be stopped, and breakage may even occur in the steel material of the substrate.
JP 11-293200 A JP 2004-359800 A

  An object of the present invention is to provide a rust preventive paint that can form a thin film that does not generate cracks even when a baking process is performed at a high temperature without using any harmful metal compound such as chromium.

  According to this invention, the said subject can be solved by using the solution containing an organic silicon compound and an organic titanate compound as a non-aqueous binder containing a non-aqueous binder and metal powder.

Here, the present invention is a metal selected from 5 to 40% by mass of an organosilicon compound, 0.05 to 2% by mass of an organic titanate compound, zinc powder, zinc alloy powder and aluminum powder, based on the total paint. It is a rust preventive paint characterized by containing 20-60 mass% of powder and 10-60 mass% of organic solvents.

In a preferred embodiment, the rust preventive paint of the present invention further has the following characteristics:
(1) The organosilicon compound is one or more compounds selected from the group consisting of tetraalkylsilicate compounds having an alkyl group having 3 or less carbon atoms and oligomers thereof;
(2) The organic titanate compound is one or more compounds selected from the group consisting of organic compounds represented by Ti (X) ₄ and oligomers thereof as a general formula, wherein X is methoxy, ethoxy, propoxy, iso From the group consisting of propoxy, butoxy, isobutoxy, and tert-butoxy having a carbon number of 4 or less, chelating substituents including lactate, triethanolamate, acetylcetonate, acetoacetate, and ethylacetoacetate, and hydroxyl groups One or more functional groups selected; and (3) the shape of the metal powder is scaly.

Since the rust preventive paint of the present invention does not contain a harmful metal compound such as chromium, there is no need to worry about environmental pollution and health damage to the human body.
Moreover, it is possible to form a thin film having a surface property of about 10 μm, and even if this thin film is baked at a high temperature, no cracks are generated in the film. Therefore, it is possible to form a rust preventive film having excellent corrosion resistance while being a thin film.

The rust preventive coating according to the present invention contains an organic silicon compound, an organic titanate compound, a predetermined metal powder, and an organic solvent as essential components, and a small amount of additives as necessary.
Hereinafter, these components will be described in detail. In the following description,% is mass% based on all paints unless otherwise specified.

(Organic silicon compound)
As a binder component in the rust preventive paint of the present invention, an organic silicon compound and an organic titanate compound are used so that cracks do not occur even when baking is performed at a high temperature.

Of these, the organosilicon compound is one or more selected from alkoxysilanes and hydrolysates thereof. The alkoxysilane is preferably a compound represented by the general formula (X ′) Si (X ″) ₃ .

  Here, X ′ is a hydroxy group, a lower alkoxy group such as methoxy, ethoxy or isopropoxy, a lower alkyl group such as methyl or ethyl, a lower alkenyl group such as a vinyl group, or γ-glycidoxypropyl. , Γ-methacryloxypropyl, γ-mercaptopropyl, and the like. X ″ is selected from a hydroxy group and an alkoxy group such as methoxy, ethoxy, isopropoxy, etc., and three X ″ may be the same or different.

  Specific examples of the alkoxysilane include tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and the like. But it is not limited to that. Various alkoxysilanes that are commercially available as silane coupling agents may be used.

  Among these alkoxysilanes, tetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane, and tetrapropoxysilane or oligomers thereof are preferable, and tetraalkoxysilanes having 3 or less carbon atoms or oligomers thereof are particularly preferable. When a condensation reaction is caused by the baking treatment, a film having a three-dimensional crosslinked structure can be formed, and the film strength is easily improved. Further, since the volume shrinkage during condensation is relatively small, cracks are difficult to grow.

  The amount of the organosilicon compound is desirably 5 to 40% of the total paint. If it is less than 5%, the coating strength tends to be low, and if the addition amount is further small, a clear void (void) is generated between the metal powders, so that the rust prevention function is also lowered. become. On the other hand, when it is added in excess of 40%, the dispersion concentration of the metal powder in the film is relatively lowered, so that the rust prevention function tends to be lowered. Moreover, since the overlapping area of the metal powders to be laminated is reduced, there is a possibility that the function of suppressing crack propagation is reduced. A particularly preferred range is 10 to 35%.

(Organic titanate compound)
In the present invention, an organic titanate compound is added to the medium in order to improve the film properties. The organic titanate compound means an organic compound represented by Ti (X) ₄ as a general formula and an oligomer thereof. Here, X is selected from a hydroxyl group, a lower alkoxy group, and a chelating substituent, and the four Xs may be the same or different.

  The lower alkoxy group means an alkoxy group having 6 or less carbon atoms, preferably 4 or less, such as methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, tert-butoxy and the like.

  The chelating substituent means a group derived from an organic compound having chelating ability. Examples of such organic compounds include β-diketones such as acetylacetone, alkylcarbonylcarboxylic acids such as acetoacetic acid and esters thereof, hydroxy acids such as lactic acid, alkanolamines such as triethanolamine, and the like. Specific examples of chelating substituents include lactate, ammonium lactate, triethanolamate, acetylacetonate, acetoacetate, ethylacetoacetate, and the like.

  This organic titanate compound exhibits a high function with a small amount of addition as described later. That is, when subjected to baking treatment at a high temperature, the added organic titanate compound functions as a curing agent or a catalyst, and promotes a three-dimensional crosslinking reaction of the organosilicon compound. For this reason, the hardening rate of a binder component increases and the progress of a crack is suppressed.

  Further, the chemical bond between the organosilicon compound and the metal powder and the chemical bond between the organosilicon compound and the steel material as the base material are also promoted by the presence of the organotitanate compound, and the bond strength is increased. For this reason, the interfacial peeling between the metal powder and the binder and the interfacial peeling between the steel material and the binder are suppressed, and the progress of cracks is suppressed.

  The addition amount of the organic titanate compound is preferably 0.05 to 5.0%. If the amount of the organic titanate compound is too small, the effect cannot be obtained and cracks are likely to occur, and the rust prevention characteristics of the film may be lowered. On the other hand, when it becomes excessive, it tends to be hydrolyzed by absorbing humidity in the atmosphere, and the pot life tends to be shortened. A particularly preferred range is 0.1 to 2%.

(Metal powder)
As the metal powder, one or more selected from zinc powder, zinc alloy metal powder, and aluminum powder, which are conventionally used in zinc-rich rust-preventive paints, are used. Examples of the zinc alloy include Zn—Ni, Zn—Sn, Zn—Fe, Zn—Al, Zn—Al—Mg, and the like.

  The shape of the metal powder as the coating material is preferably a scale shape so as to have high corrosion resistance even when the thickness of the coating is reduced. By being scaly, it is realized that the metal powder is laminated in the thickness direction in the film. Even if a crack is generated in the film due to shrinkage caused by the polymerization of the binder component, this laminated structure suppresses the progress and prevents the generation of a large crack that exposes the substrate.

The average thickness of the scale-shaped metal powder is 1/200 to 1/2 of the average thickness of the film, and the average value of the major axis of the metal powder (the length of the longest part of the scale shape) is The average thickness is preferably 1/20 to 10 times . For example, when the film is about 10 μm, the average thickness of the scale-shaped metal powder is preferably 0.05 to 5 μm, and the average value of the major axis is preferably 0.5 to 100 μm.

  Even if the coating thickness varies depending on the coating conditions, the average major axis of the metal powder is 1.0 to 50 μm, particularly preferably 4.0 to 20 μm. In the case where the average thickness of the scale shape is in the range of 0.05 to 1.0 μm, particularly preferably in the range of 0.05 to 0.5 μm, cracks are hardly generated even by the baking treatment, and excellent antirust properties A coating film having the following is obtained.

  In addition, when the average value of a major axis is smaller than said range, it becomes difficult to obtain the structure where the scaly metal powder was laminated | stacked within the membrane | film | coat, and the suppression effect of a crack progress comes to become small. On the other hand, when it is larger than the above range, the distribution of the metal powder becomes sparse, which may adversely affect the rust prevention characteristics.

  In addition, when the average thickness of the scale shape is smaller than the above range, it becomes easy to be destroyed during the stirring and kneading operation of the paint, the scale shape is hardly formed, and the laminated structure is hardly obtained. On the other hand, when it is larger than the above range, it is difficult to obtain a structure in which a plurality of metal powders are laminated in the thickness direction of the film, and the effect of suppressing the progress of cracks may be reduced.

  The composition ratio of the metal powder in the paint is preferably mass% relative to the total paint, and is preferably in the range of 20 to 60%, more preferably 30 to 50%. When the amount is too large, it becomes difficult to apply the coating in a thin film state, and the strength of the film is lowered. On the other hand, if the amount is too small, cracks are likely to progress, and the rust preventive function of the film is reduced.

(Organic solvent)
When the rust-preventive coating material of the present invention contains an organic solvent in the coating operation, it is possible to obtain a film having good adhesion to the member to be coated and high adhesion. In addition, regarding various additives added at the time of forming a coating material, a wide variety of additives can be used by including an organic solvent.

  Suitable organic solvents include alcohols such as methanol, ethanol, propanol, isopropanol, butanol, hexanol, methoxybutanol, methoxymethylbutanol, esters of these alcohols, esters such as propionate, ethylene glycol, diethylene glycol And glycols such as triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol and tripropylene glycol, and ethers of these glycols such as monomethyl ether, monoethyl ether and monobutyl ether. Moreover, you may use hydrocarbons, such as toluene, xylene, mineral spirit, and solvent naphtha. These may be used alone or as a mixture of several kinds.

  The amount of the organic solvent varies depending on the working environment, but is preferably 10 to 60% of the total coating material, more preferably 15 to 45%, and particularly preferably 20 to 30%. If this range is exceeded, it may be difficult to obtain a thin film, or it may be difficult for the metal powder to form a laminated structure in the film, and there may be a relationship with the content of other components, but it may be difficult to obtain the desired film. sell.

(Other additives)
The rust preventive paint of the present invention can contain various additives generally used in the paint as necessary. Examples of such additives include thickeners, rust preventive pigments, colloidal silica fine particles, and the like.

Examples of the thickener include fatty acid amides, polyamides, polyethylene oxide, hydroxypropyl cellulose, and silicate inorganic thickeners.
Examples of the rust preventive pigment include zinc phosphate, magnesium phosphate, zinc molybdate, and aluminum phosphomolybdate.

  The colloidal silica fine particles are sol-like silica particles having a particle diameter finer than 1 μm, and have the effect of improving the corrosion resistance and film strength of the film, similar to the silicon compound described above. Examples of colloidal silica fine particles include organosilica sol (for example, Snowtex manufactured by Nissan Chemical Industries, Ltd.), fumed silica (vapor phase silica), and the like in which colloidal silica is dispersed in an organic solvent.

In addition, conventional paint additives such as a wetting agent and an antifoaming agent can be contained in the paint of the present invention.
These other additives are preferably added in a total amount in the range of 0.1 to 10% of the total paint. If it is less than 0.1%, the effect of the additive may not be obtained. If it exceeds 10%, the composition ratio of the metal powder and binder component as the main agent is relatively lowered, and rust prevention is a basic characteristic. There is a risk that the characteristics will deteriorate.

As for each component which comprises the rust preventive coating material of this invention described above, all can use 1 type (s) or 2 or more types.
The anticorrosive paint of the present invention is prepared by sufficiently stirring and mixing the above-described components and uniformly dispersing the metal powder in the liquid.

  Steel members to which this rust preventive paint can be applied include all steel members from steel plates, rods, steel pipes, die steels to small articles such as molded products and bolts. The steel member may be subjected to a treatment widely used as a coating pretreatment for improving coating adhesion and corrosion resistance, such as shot blasting and phosphate coating.

  Application of the coating material to the steel member can be performed by, for example, conventional methods such as roll coating, spraying, brush coating, and dipping, and an appropriate coating method may be selected according to the form of the member. The coating is preferably performed so that the thickness of the film formed after the heat treatment is in the range of 2 to 30 μm.

  The heat treatment (baking) after coating is performed at 200 to 400 ° C. for 10 to 120 minutes. By the heat treatment, the organosilicon compound undergoes a condensation reaction using the organotitanate compound as a curing agent or catalyst, and a film containing a large amount of metal powder is formed on the surface of the steel member. Prior to the heat treatment, preheating may be performed for drying.

  Thus, the steel member to which the paint of the present invention has been applied exhibits a long-term rust prevention effect even if it is used as it is, but it can be further coated if desired.

  In accordance with the formulation (parts by mass) shown in Table 1, each component was sufficiently mixed by stirring for 3 hours using a high-speed stirrer for coating, and each coating of Examples 1 to 3 and Comparative Examples 1 and 2 Was made.

  First, scaly zinc powder was prepared as follows. 100 parts by weight of metal zinc powder having an average particle size of 5 μm was dispersed in 200 parts by weight of mineral spirit, and a small amount of fatty acid was added to form a slurry having a dispersion concentration of metal zinc powder of about 30% by weight. This slurry is pulverized with a bead mill (Star Mill ZRS manufactured by Ashizawa Finetech Co., Ltd.), and the slurry after the treatment is evaporated to dryness under reduced pressure. A 0.3 μm-flaky zinc powder was obtained.

  Moreover, the scale-like aluminum powder uses Alpaste 0200M (average diameter 10 μm, average thickness 0.2 μm) manufactured by Toyo Aluminum Co., Ltd., and the granular zinc powder used as a comparative example is Zinc powder # 1 manufactured by Sakai Chemical Industry Co., Ltd. (Spherical shape with an average particle diameter of 5.0 μm).

  Next, each paint was applied to a mild steel plate previously degreased and washed with a bar coater. For Examples 1 to 3, after preliminary drying at 100 ° C. × 10 minutes, heat treatment at 300 ° C. × 30 minutes was performed, A rust preventive film having a thickness of 10 μm was formed. On the other hand, for Comparative Examples 1 and 2, since many cracks were generated in the film under the heating conditions as in Examples and the film did not function as a rust preventive film, a film obtained by curing at 80 ° C. for 120 minutes was used.

  The corrosion resistance of this rust-proof steel sheet was evaluated by visual inspection every 50 hours using a salt spray test specified in JIS-Z 2371. Whether or not red rust was generated was judged on a visual level, and when the red rust was observed in 1% or more of the co-tested steel sheets, it was judged as the upper limit of the corrosion resistance of the film.

  The pot life of the paint was obtained by adjusting the paint and storing it at 25 ° C. and 65% humidity, and measuring the time until the gelation of the paint progressed and a clear increase in viscosity was observed.

Detailed information about each raw material is as follows.
Ethyl polysilicate: Ethyl silicate 40 manufactured by Colcoat Co., Ltd.
Butyl titanate dimer: ORGATICS TA-22 manufactured by Matsumoto Pharmaceutical Co., Ltd.
Titanium ethyl acetoacetate: ORGATICS TC-750 manufactured by Matsumoto Pharmaceutical Co., Ltd.

  As can be seen from Table 1, the paints of Examples 1 to 3 containing an organic titanate compound according to the present invention exhibited extremely high rust prevention properties despite the film thickness being 10 μm. On the other hand, with the paints of Comparative Examples 1 and 2 using only the organic silane compound, it is difficult to perform the heat treatment at a high temperature as in the Examples, and therefore, with a thickness of 10 μm, only a corrosion resistance of about 400 hours is obtained at the maximum. I couldn't.

  In addition, the pot life of the paint according to this example was extremely longer than that of the comparative example (comparative example 1) using water as a medium.

Claims (4)

Based on the total paint, 5-40% by weight of organosilicon compound, 0.05-2% by weight of organic titanate compound, 20-60% by weight of metal powder selected from zinc powder, zinc alloy powder and aluminum powder, And an organic solvent 10 to 60% by mass.   2. The anticorrosive paint according to claim 1, wherein the organosilicon compound is at least one compound selected from the group consisting of tetraalkylsilicate compounds having an alkyl group having 3 or less carbon atoms and oligomers thereof. The organic titanate compound is an organic compound represented by the general formula Ti (X) ₄ and an oligomer thereof, wherein X is methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, and tert-butoxy having 4 or less carbon atoms. Or at least one functional group selected from the group consisting of a chelating substituent containing an alkoxy group, lactate, triethanolaminate, acetylcetonate, acetoacetate, and ethylacetoacetate, and a hydroxyl group 2. Anticorrosive paint according to 2.   The rust preventive paint according to any one of claims 1 to 3, wherein the metal powder is scaly.