JPH0582426B2 - - 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. N-β (aminoethyl) γ-aminopropyltrimethoxysilane or N-β (aminoethyl)
Metal powder pigments for electrostatic coatings treated with silane coupling agents such as γ-aminopropylmethyldimethoxysilane are known. However, in order to obtain the desired effect, a large amount of silane coupling agent must be used, and if a large amount of silane coupling agent is used, the pigment tends to aggregate, resulting in a loss of storage stability. The method of surface treating powder pigments with a silane coupling agent has been unsatisfactory in solving the above-mentioned problems. The method for treating metal powder pigments of the present invention is characterized in that an organic titanate is used in combination with a coupling agent 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] It is a chelate compound that contains a nitrogen atom in its molecule, and it strongly adsorbs to metal powder due to the strong coordination force of the lone pair electron of the nitrogen atom to the metal, and because hydrolysis progresses gradually, it is not caused by a rapid reaction. Agglomeration of metal powder pigments does not occur. Therefore, metal powder pigments treated with organic titanates can be used in various coating resins (e.g., acrylic resins, nitrocellulose resins,
It has excellent adhesion with urethane resins, alkyd resins, epoxy resins, vinyl resins, etc.) and also has excellent storage stability, making it extremely practical as it does not require special equipment or processes for treatment. Further, since the organic titanate-treated 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 an amount of organic titanate exceeding 10 parts by weight is used, metal powder aggregation problems will occur, and the storage stability of the metal powder pigment will deteriorate, resulting in the paint becoming thickened or gelling, 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, in order to further improve the effects of the organic titanate treatment, a coupling agent having at least one amino group in the molecule is used in combination with the organic titanate. By combining the coupling agent treatment, the effect of improving the peeling resistance of the coating film on the coated object made of plastic material and the effect of improving the storage stability of the metal powder pigment, which can be achieved by the organic titanate treatment, can be achieved. In particular, it is possible to form an insulating film with further improved voltage resistance. In addition, the problem of storage stability, which was a drawback of conventional coupling agent-treated metal powder pigments, could be solved. The coupling agent includes a silane coupling agent such as N-β (aminoethyl) γ-aminopropyltrialkoxysilane, N-β (aminoethyl) γ-aminopropylalkyldialkoxysilane, and γ-aminopropyltrialkoxysilane. , isopropyl (N,N-dimethylethylamino) titanate, isopropyl (4-aminobenzoyl) isostearoyl titanate, isopropyl trianthranyl titanate, isopropyl 4-aminobenzenesulfonyl di(dodecylbenzenesulfonyl) titanate, isopropyl 4-aminobenzoyl isostearoyl Titanium coupling agents such as oxyacetate titanate may be exemplified. The silane coupling agent is preferably used in an amount of 0.1 to 1 part by weight per 100 parts by weight of metal powder, and the titanium coupling agent is preferably used in an amount of 0.1 to 5 parts by weight per 100 parts by weight of metal powder, and the lower limit value is If a smaller amount of coupling agent is used, the sufficient effect of coupling agent treatment will not be obtained, and if an amount of coupling agent exceeding the above upper limit is used, metal powder aggregation problems may occur, resulting in poor storage stability of metal powder pigments. This is not desirable as it will result in poor sex. The metal powder pigments that can be treated according to the present invention are not particularly limited, but may be treated with grinding aids such as fatty acids, aliphatic amines, fatty acid amides, and aliphatic alcohols by dry ball milling, wet ball milling, attritor processing, stamp milling, etc. Examples include metal powder pigments made of metals such as aluminum, copper, zinc, iron, nickel, etc., and alloys thereof, which have been crushed and flaked in the presence of the metal. The method of treating the organic titanate and coupling agent in the present invention is not particularly limited, but the method of adding the organic titanate and coupling agent in the kneading step, which is an essential step in the production of metal powder pigments, requires special steps and equipment. This is particularly preferred since it is not necessary.
That is, in the kneading process, metal powder and various other additives are usually added to an organic solvent and then mixed with a ribbon mixer.
When kneading in a mixer such as a kneader mixer, it is preferable to dissolve the organic titanate and the coupling agent in an organic solvent and add the mixture. However, other processing methods may also be applied. The treatment of metal powder pigments with organic titanates and coupling agents 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 N ₄ N(CH ₂ CH ₂ OH) ₂ ] ₂ +2H ₂ O→Ti(O
H) ₂ [OCH ₂ CH ₂ N (CH ₂ CH ₂ OH) ₂ ] 2+2ROH

[Chemical formula] (In the formula, M represents a metal atom) Therefore, when adding an organic titanate and a coupling agent to an organic solvent, the organic titanate and the coupling agent are added to the organic solvent in which water has been dissolved in advance or together with water. It is preferable to add it inside. 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. Furthermore, the treatment of the metal powder pigment in the present invention can be carried out in the coexistence of a basic substance such as an aliphatic amine having 10 or less carbon atoms or an amino alcohol having 10 or less carbon atoms. This is preferable because it can accelerate the reaction and more reliably form an insulating film on the surface of the metal powder. In addition, in order to further accelerate the reaction, the metal powder pigment after addition of the organic titanate was heated at a temperature of 20 to 80°C.
It is preferable to perform heating aging for about 1 to 1000 hours. Organic solvents to which organic titanates and coupling agents can be added include methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, i-butyl alcohol, n-
Butyl alcohol, t-butyl alcohol, isoamyl alcohol, n-amyl alcohol, n-
Hexyl alcohol, cyclohexanol, 2-
ethyl butyl 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. Although there is no limit to the amount of organic solvent used, it is important to note that there is no limit to the amount of organic solvent used, but within the range that the liquid in which water, organic titanate, and coupling agent are dissolved or dispersed is dissolved or dispersed in a hydrocarbon solvent such as mineral spirits contained in the metal powder pigment. The amount is preferred and 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 3.3 g of di-n-butoxy bis(triethanolamineto) titanium, N-β(aminoethyl)γ-
After mixing 1.7 g of aminopropyltrimethoxysilane and 0.33 g of deionized water with 85.0 g of isobutyl alcohol, add non-leafing type aluminum paste (1200M manufactured by Toyo Aluminum Co., Ltd., metal content).
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 2 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.)
acrylic resin varnish) 80 parts by weight Super Bethcomin J-820 (melamine resin varnish manufactured by Dainippon Ink and Chemicals Co., Ltd.) 20 parts by weight n-butyl alcohol 25 parts by weight Metal powder pigment (metal equivalent) 3.75 parts by weight Measurement was carried out according to the following steps. The material 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 do the same thing. 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 the metal powder pigments of the present invention have a peeling resistance of 5 and a withstand voltage value of
It has a voltage of 55KV or higher and has excellent storage stability with no increase in screen residue.

【table】

【table】 [Brief explanation of drawings]

The accompanying 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 obtained by treating an organic titanate represented by the formula above with a coupling agent having at least one amino group 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 coupling agent is a silane coupling agent or a titanium coupling agent. 3. The pigment according to claim 1 or 2, wherein 0.1 to 1 part by weight of the silane coupling agent is used per 100 parts by weight of the metal powder. 4. The pigment according to claim 1 or 2, wherein the titanium coupling agent is used in an amount of 0.1 to 5 parts by weight per 100 parts by weight of the metal powder. 5. The pigment according to any one of claims 1 to 4, characterized in that 0.1 to 10 parts by weight of organic titanate is used per 100 parts by weight of metal powder.