JPH0582425B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel method for treating metal powder pigments. When it is desired to impart a metallic feel to an object to be coated, the object is coated with a paint containing a metal powder pigment. For example, when the object to be coated is made of plastic material, the heat resistance, solvent resistance,
The paints that can be used are limited due to their adhesion to paint resins, and low-temperature drying paints such as acrylic lacquers and nitrocellulose lacquers are preferred because of the heat resistance of plastic materials. When metal powder pigments are added to low-temperature drying paints, the strength of the paint film decreases, and when a label, etc. pasted on the paint film is removed, a portion of the paint film may peel off due to cohesive failure. Various problems arose. One of the reasons for the decrease in paint film strength is poor adhesion between the metal powder pigment surface and the paint resin.
From the viewpoint of improving the adhesion, the paint is heated and aged: The amount of fatty acids adsorbed on the surface of the metal powder pigment is reduced: The surface of the metal powder pigment is modified with additives: The surface of the metal powder pigment is Treatment methods such as coating with resin have been proposed. however,
However, the methods described above do not have sufficient effects, and are impractical due to the high production cost of metal powder pigments.Currently, therefore, the current method is to blend metal powder pigments into low-temperature drying paints. No means have been found that can satisfactorily solve the problems that arise. On the other hand, when a paint containing metal powder pigments is used with an electrostatic coating method that has excellent coating efficiency, the insulating film on the surface of the metal powder pigments breaks down and the metal powder pigments connect with each other, causing the metal powder to A problem arose in that the current escaped through the pigment and the paint could not be charged. One way to solve this problem is to insulate the entire paint to prevent current from escaping and charge the entire paint: By adding a polar solvent to the paint and lowering the paint resistance, the current can flow through the metal powder pigment. The following treatment methods have been proposed: To prevent metal powder from escaping: To form an insulating film on the surface of the metal powder pigment by surface-treating the pigment; To prevent the metal powder from joining together by vigorously stirring the paint. ing. however,
Method (2) increases the risk during paint replacement work, method (2) does not sufficiently charge the paint, and method (2) requires special processes or equipment, making it impractical. At present, no means has been found that can sufficiently solve the problems that occur when using a paint containing a metal powder pigment in an electrostatic coating method. The present inventor aimed to solve all at once the problems that arise when a paint containing the metal powder pigments described above is applied to objects made of plastic materials, as well as the problems that occur when the paint is used in an electrostatic coating method. We focused on surface treatment methods for powder pigments. Conventional surface treatment methods for metal powder pigments include adding a treatment agent such as a silane coupling agent during the kneading process, which is an essential step in the production of metal powder pigments, and adding metal powder pigments in a treatment solution containing a treatment agent. There are methods such as stirring and mixing. However, the former method has the following drawbacks: (i) treatment agents react with each other to form aggregates, and (ii) sufficient treatment effects cannot be obtained; the latter method also requires (i) special equipment. (ii) requires a large amount of processing solution; (iii) requires post-treatment of the processing solution; and (iv) requires a large number of steps. It was hot. The method for treating metal powder pigments of the present invention is characterized in that an organic titanate and a basic substance are used in combination as a treating agent. The organic titanate used as one of the treatment agents in the present invention has the general formula Ti(OR) ₂ [OC ₂ H ₄ N(C ₂ H ₄ OH) ₂ ] ₂ (wherein, R is a carbon number of 1 ~8 alkyl group)
It is dialkoxy bis(triethanolaminato) titanium represented by As is clear from the fact that the organic titanate has the following structural formula:

[C] is a chelate compound containing a nitrogen atom in the molecule,
Due to the strong coordination force of the lone pair electron of the nitrogen atom with respect to the metal, it is strongly adsorbed to the metal powder, and hydrolysis proceeds gradually, so that aggregation of the metal powder pigment due to a rapid reaction does not occur. Therefore, metal powder pigments treated with organic titanates have excellent adhesion to various paint resins (e.g., acrylic resins, nitrocellulose resins, urethane resins, alkyd resins, epoxy resins, vinyl resins, etc.) and are also easy to store. It has excellent stability and does not require special equipment or processes for treatment, making it extremely practical. Furthermore, since the metal powder pigment of the present invention has an insulating coating formed on its surface, it is suitable for electrostatic coating. As the organic titanate, dimethoxy bis(triethanolaminate)
Titanium, diethoxy bis(triethanolaminate)
Examples include titanium, di-i-propoxy bis(triethanolamito)titanium, di-n-butoxybis(triethanolamito)titanium, di-2-ethylhexoxybis(triethanolamimato)titanium, etc. can be done. It is preferable to use the organic titanate in a proportion of 0.1 to 10 parts by weight based on 100 parts by weight of the metal content, and if the amount of the organic titanate is less than 0.1 part by weight, sufficient effects can be obtained from the organic titanate treatment. Furthermore, if more than 10 parts by weight of organic titanate is used, the storage stability of the metal powder pigment will deteriorate, leading to the problem of metal powder aggregation, and the paint may become thickened or gelled, which may affect the storage stability of the paint. In addition to having an adverse effect, it is not preferable because it also causes problems in coating performance due to repellency of the coating film and a decrease in the water resistance of the coating film. In the present invention, when a basic substance is used as a treatment agent in combination with an organic titanate, the dissociation constant of the hydrolysis reaction of the organic titanate can be increased and the metal An insulating film of organic titanate can be more reliably formed on the powder surface. Basic substances that can be used in the present invention include monoethanolamine, diethanolamine, triethanolamine, ethylmonoethanolamine, n-butylmonoethanolamine, dimethylethanolamine, diethylethanolamine,
Amino alcohols with 10 or less carbon atoms such as ethyldiethanolamine, n-butyldiethanolamine, 2-amino-2-methyl-1-propanol, triisopropanolamine, monoethylamine, (iso)propylamine, butylamine, amylamine, hexylamine, heptyl amine,
octylamine, nonylamine, decylamine,
2-ethylbutylamine, 2-ethylhexylamine, diethylamine, di(iso)propylamine, dibutylamine, diamylamine, ethylenediamine, propylene diamine, diethylenetriamine, tetraethylenepentamine, etc. with 10 carbon atoms
The following aliphatic amines may be exemplified. Number of carbons is 10
Even if a basic substance exceeding 100% is used, the desired basic substance treatment effect cannot be obtained, which is not preferable. The basic substance is 0.1 parts by weight per 100 parts by weight of metal powder.
It is preferable to use the basic substance in an amount of 5 parts by weight, and if the amount of the basic substance is outside the above range, sufficient effects cannot be obtained, which is not preferable. In the present invention, metal powder pigments that can be treated with organic titanates and basic substances are not particularly limited, but include dry ball milling, wet ball milling,
Metals such as aluminum, copper, zinc, iron, nickel, etc. that are crushed into flakes by grinding in the presence of grinding aids such as fatty acids, aliphatic amines, fatty acid amides, and aliphatic alcohols by the attritor method, stamp mill method, etc. Examples include metal powder pigments made of alloys thereof. The method of treating the organic titanate and the basic substance in the present invention is not particularly limited, but the method of adding the organic titanate and the basic substance in the kneading process, which is an essential process for producing metal powder pigments, is a special process. This is particularly preferred since no equipment is required. That is, in the kneading process, metal powder and various other additives are usually added to an organic solvent, and when kneaded in a mixer such as a ribbon mixer or a kneader mixer, the organic titanate and the basic substance are dissolved in the organic solvent. It is preferable to add. However, other processing methods may also be applied. Furthermore, the treatment of the metal powder pigment with the organic titanate and basic substance in the present invention is carried out in the presence of water. This is because water acts as a catalyst to promote the reaction between the organic titanate and metal powder shown in the following formula. Ti(OR) ₂ [OC ₂ H ₄ N(CH ₂ CH ₂ OH) ₂ ] ₂ +2H ₂ O→ Ti(OH) ₂ [OCH ₂ CH ₂ N(CH ₂ CH ₂ OH) ₂ ] ₂ +2ROH

embedded image (In the formula, M represents a metal atom) As described above, when the hydrolysis reaction of organic titanate is carried out in the presence of a basic substance, the hydrolysis reaction is accelerated. Therefore, when the organic titanate and the basic substance are added to the organic solvent, it is preferable to add the organic titanate and the basic substance to the organic solvent in which water has been dissolved in advance or to the organic solvent together with water. It is preferable that water is added at a ratio of 0.05 to 1.5 parts by weight per 100 parts by weight of the metal content.If the amount of water added is less than 0.05 parts by weight, the effect of adding water cannot be obtained, and if the amount of water is added less than 0.05 parts by weight, Addition of water in excess of this amount is not preferable because problems such as agglomeration of the metal powder due to the reaction between the metal powder and water and swelling of the metal powder storage container due to generation of hydrogen gas occur. In addition, for the purpose of promoting the reaction, it is preferable to subject the metal powder pigment after addition of the organic titanate to heating aging at a temperature of 20 to 80° C. for about 1 to 1000 hours. Examples of the organic solvent to which the organic titanate and the basic substance are added include methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, i-butyl alcohol, n-butyl alcohol, t-butyl alcohol, isoamyl alcohol, and n-propyl alcohol. -amyl alcohol, n-hexyl alcohol, cyclohexanol, 2-ethylbutyl alcohol, benzyl alcohol, 1,
4-dioxane, acetone, methyl ethyl ketone, diacetone alcohol, ethylene glycol, methyl cellosolve, methyl cellosolve acetate, ethyl cellosolve, butyl cellosolve, methoxymethoxyethanol, diethylene glycol, methyl carbitol, ethyl carbitol,
It is desirable to use one or more hydrophilic organic solvents such as butyl carbitol. In addition, there is no limit to the amount of organic solvent used, but within the range where the liquid in which water, organic titanate, and basic substance are dissolved or dispersed is dissolved or dispersed in a hydrocarbon solvent such as mineral spirits contained in the metal powder pigment. The amount varies depending on the type of organic solvent. If the metal powder pigment does not contain a hydrocarbon solvent, it may deviate from this range. Hereinafter, the present invention will be explained in more detail with reference to Examples. Example 1 After mixing 3.3 g of di-n-butoxy bis(triethanolamineto) titanium, 1.7 g of triethylamine, and 0.33 g of deionized water with 85.0 g of butyl cellosolve, non-leafing type aluminum paste (manufactured by Toyo Aluminum Co., Ltd.) was mixed. 1200M, metal min 65
%) and kneaded for 3 hours using a 1-capacity kneader mixer to obtain an aluminum paste with a metal content of 55%. Examples 2 to 6 and Comparative Examples 1 to 3 Metal powder pigments were obtained in the same manner as in Example 1 under the kneading conditions shown in Table 1. However, the kneading time was 3 hours in all cases. Example 7 The following tests were conducted using the metal powder pigments obtained in each Example and Comparative Example. The test results are shown in Table 2. Test 1: Peeling resistance test A paint prepared with the following composition was spray-painted on an ABS board. The drying conditions for the coated plate were 50°C for 20 minutes, and the coating film thickness after drying was approximately 10μ. (Paint composition) Acrylic A-165 (Dainippon Ink Chemical Co., Ltd.)
acrylic lacquer) 35 parts by weight Metal powder pigment (metal equivalent) 5 parts by weight Solvent (ethyl acetate/ethyl cellosolve/cyclohexane = 40/30/30) 60 parts by weight Cellophane tape (Nichiban Co., Ltd.) was applied to the resulting coating film. ) made
CT-24) was applied and pressed down sufficiently to make it adhere, then the cellophane tape was quickly peeled off toward the user and the state of peeling of the paint film was observed. Peeling resistance was evaluated on the following five scales based on the ratio of the peeled area to the pasted area of the cellophane tape. 1 Approximately 90% or more peeling 2 Approximately 50 to 90% peeling 3 Approximately 10 to 50% peeling 4 Partial (10% or less) peeling 5 Almost no peeling. Test 2: Voltage Resistance Test The withstand voltage value of the paint prepared with the following composition was measured using the withstand voltage measuring device shown in the attached drawing. Acrylic 47-712 (Dainippon Ink & Chemicals Co., Ltd.)
80 parts by weight Super Betsukamine J-820 (melamine resin varnish manufactured by Dainippon Ink & Chemicals Co., Ltd.) 20 parts by weight n-butyl alcohol 25 parts by weight Metal powder pigment (in terms of metal content) 3.75 parts by weight Measurement was carried out according to the following steps. The paint to be measured is sealed in a glass tube with an inner diameter of 10 mm and a length of 120 mm. Apply a voltage of 5KV to the paint and hold for 1 minute while checking for current leakage using an ammeter. If there is no current leakage, further increase the voltage to 5KV
Raise it and perform the same operation. After that, increase the voltage in 5KV increments up to 60KV and perform the same operation as above, and the maximum voltage at which no current leakage occurs is the withstand voltage value of the paint. Test 3: Cohesiveness test The metal powder pigments obtained in each example and comparative example were tested immediately after trial production and after storage at 50°C for one month.
The 350 mesh screen residue was measured in accordance with JIS K5910-5.9 to evaluate the presence or absence of aggregation of metal powder pigment. As shown in Table 2, all of the metal powder pigments of the present invention have a peeling resistance of 4 or higher, a withstand voltage value of 55 KV or higher, and excellent storage stability without increasing screen residue. .

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【table】 [Brief explanation of the drawing]

The attached drawing is a schematic diagram of the withstand voltage measuring device. 1...Glass tube, 2...Rubber stopper, 3...Ammeter, 4...High voltage generator.

Claims (1)

[Claims] 1 General formula Ti(OR) ₂ [OC ₂ H ₄ N(C ₂ H ₄ OH) ₂ ] ₂ (wherein R is an alkyl group having 1 to 8 carbon atoms)
A metal powder pigment treated with an organic titanate represented by the formula and a basic substance in the presence of water in an amount sufficient to cause a hydrolysis reaction of the organic titanate. 2. The pigment according to claim 1, wherein the basic substance is an amino alcohol or an aliphatic amine having 10 or less carbon atoms. 3. The pigment according to claim 1 or 2, wherein the basic substance is used in an amount of 0.1 to 5 parts by weight per 100 parts by weight of the metal powder. 4. The pigment according to claim 1, wherein 0.1 to 10 parts by weight of organic titanate is used per 100 parts by weight of metal powder.