JP2007247051A - High-adhesion coating method to metal-alloy molded object and metal-alloy molded object subjected to high-adhesion coating by the method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-adhesion coating method to an alloy molded object of a magnesium metal etc., and the metal-alloy molded object subjected to high adhesion coating by the method. <P>SOLUTION: The high-adhesion coating method to the alloy molded object of a magnesium metal etc., comprises entirely or partly spraying a flame including a modifier combination part such as silane atoms, to the surface of the alloy molded object of the magnesium metal etc., by using a known surface modification device to perform surface modification in such a manner that the surface of the metal-alloy molded object attains ≥73 dyn/cm in wetting index, then performing coating finish of a coating layer to serve as a direct design layer with one-coat finish without applying a primer. The metal-alloy molded object is subjected to the high-adhesion coating by the method described above. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention uses a metal alloy such as magnesium alloy, aluminum alloy, titanium alloy and the like, a novel high adhesion coating method on a metal alloy molded product molded by means such as injection molding, die casting molding, thixocasting molding, and the like, and The present invention relates to a molded metal alloy that has been coated with high adhesion by the same method.

  Currently, metal alloys such as magnesium alloy, aluminum alloy, titanium alloy, etc. are molded by means such as injection molding, die casting molding, thixocasting molding, etc., mini discs, video cameras, digital cameras, Widely used in various fields of electronics such as mobile phones. Among other metal alloys, magnesium alloys are light and have a strength that is more than an order of magnitude higher than that of ABS resin, etc., and have high thermal conductivity, excellent heat dissipation, and good electromagnetic shielding properties. Is attracting attention and its marketability is expanding year by year.

  By the way, metal alloy moldings molded by means such as injection molding typified by magnesium alloy, die casting molding, thixocasting molding, etc. have never been used as it is, and acrylic resin paints In general, the design is applied by a paint such as a paint system or a urethane resin paint system. On the other hand, the process leading up to the coating of metal alloy moldings is also difficult due to the casting surface being rough due to injection molding, die casting molding, thixocasting molding, etc. The present situation is that an extremely complicated process is required to ensure adhesion at the paint interface with the alloy molded product. In the case of painting magnesium alloy molded products, the following are examples: Workpiece loading → Hot water washing → Strong alkaline degreasing → Hot water washing → Pure water washing → Chemical conversion treatment (such as zinc phosphate film) → Pure water washing → Draining → Dust removal → Spray painting It is necessary to go through about 8 processes until the process and at least the painting process, and in addition, as a pre-process before entering the painting process, ensure the adhesion between the metal alloy molded product and various paints and achieve a good coating finish In order to ensure this, a large amount of process, time, labor, and cost were required, such as coating with an epoxy resin-based primer and adding a putty treatment process as necessary.

Therefore, the present inventor relates to ensuring adhesion at the paint interface of a metal alloy molded product represented by a magnesium alloy, which is disclosed in the following patent document that the present inventor has already developed and put into practical use. As a result, it was discovered and confirmed that the “interface modification technology” works extremely effectively for the interface modification of metal alloy molded products represented by magnesium alloys, and the present invention was completed.
JP 2003-238710 (Patent No. 3557194)

  The "Patent Document 1" discloses an outline of an interfacial reforming method and apparatus for a solid substance, which is an interfacial modifier compound containing a silane atom, a titanium atom, and an aluminum atom, each having a boiling point of 10 A storage tank for storing a fuel gas containing a surface modifier compound having a temperature of from 100 ° C. to 100 ° C., a transfer unit for transferring the fuel gas to the injection unit, and an injection unit for blowing a flame of the fuel gas An interfacial reforming technique that activates the processing section by preparing an interfacial reforming apparatus including a (burner), spraying silicic acid flame or the like entirely or partially on the surface of a solid material. It is disclosed.

  However, the above-mentioned Patent Document 1 only describes a surface modification method common to various solid substances for interfacial modification of each solid substance, and is a specific problem to be solved by the present invention. There is no disclosure regarding a specific methodology for ensuring adhesion at a paint interface in a metal alloy molded product represented by a magnesium alloy.

  The present invention provides a specific methodology related to ensuring adhesion at the coating interface of a metal alloy molding represented by a magnesium alloy, and in addition, ensures adhesion at the coating interface of the metal alloy molding. Instead, the present invention relates to a high adhesion coating method for a metal alloy molding that can greatly simplify various processes in the painting process, which is a subsequent process, and a metal alloy molding that has been coated with a high adhesion by the coating method.

  More specifically, the molding technology of metal alloy moldings molded by means such as injection molding, die casting molding, thixocasting molding represented by conventional magnesium alloys, as represented by thixocasting molding, With the remarkable technological innovation in recent years, the casting surface has been improved to a much more beautiful condition than the situation where many cast holes have been scattered as before, but it is still a rough surface. As described above, the workpiece is charged → hot water → strong alkaline degreasing → hot water → pure water cleaning → chemical conversion treatment (as described above) until the process of applying the coating layer as the design layer to the metal alloy molded product. Zinc phosphate film, etc.) → Pure water cleaning → Draining drying → Dust removal → Spray painting process, it is necessary to go through at least about 8 processes to the painting process, and in addition, it is a post process As a pre-process of the painting process, it is indispensable to apply an epoxy resin-based primer in order to ensure close contact with various paints, and in addition, in many cases, putty treatment is performed to ensure smoothness of the casting surface. → It was necessary to go through each step of sanding → dust removal.

  As described in detail above, there are many processes leading to the coating of metal alloy moldings that are molded by means such as injection molding, die casting, and thixocasting, which are typified by magnesium alloys. In addition, the process is complicated and the processing cost is high, so that some process improvement is desired as an urgent issue.

  The present invention has been focused on the number and complexity of each process up to the coating of the metal alloy molded article described above. By interfacial modification, the number and complexity of each process up to the coating of the metal alloy molded product has been drastically improved.

First, a methodology for interfacial modification of a metal alloy molded product will be described. FIG. 1 is a flowchart showing an outline of an interface reforming apparatus according to the present invention, and description will be made based on the flowchart.
The interface reformer 100 is an interface modifier compound containing a silane atom, a titanium atom, and an aluminum atom, and includes an alkylsilane compound, an alkoxysilane compound, a siloxane compound, a silazane compound, an alkyltitanium compound, an alkoxytitanium compound, and an alkylaluminum. A storage tank unit 102 for storing the interfacial modifier compound 101 selected from the group consisting of a compound and an alkoxyaluminum compound, and a transfer for vaporizing by the heating means 103 and transferring to the injection unit (burner) 104 It comprises a passage 105, a fuel gas storage tank 106 such as propane gas and LPG gas, and a compressed air source 107 that supplies combustion air for the fuel gas and air for transporting the interfacial modifier compound. ing. A first sub-mixer 108 is also provided in the transfer path 105 for uniformly mixing the vaporized interface modifier compound and air mixed gas and the fuel gas delivered from the storage tank 106. The second main mixer 109 is configured.
Further, the delivery tanks 102 for storing the interfacial modifier compound 101, the compressed air source 107 for supplying air, and the delivery destination outlets of the fuel gas storage tank 106 have respective delivery flow rates. Flow control valves with flowmeters 110, 111, and 112 for control are provided, respectively, to constitute the interface reformer 100. Next, the detail of each said main structural member (part) is demonstrated.

"Storage tank for interfacial modifier compound"
As shown in FIG. 1, a heating means 103 such as a heater for heating is provided below the interfacial modifier compound storage tank 102, and the interfacial modifier compound 101 is liquid at room temperature and normal pressure. It is configured to vaporize. The heating means 103 is controlled by a CPU (not shown). That is, the CPU is electrically connected to each sensor such as a liquid quantity sensor of the interfacial modifier compound, a liquid temperature sensor, etc., and the liquid quantity and the liquid temperature of the interfacial modifier compound are within a specified range. The heating means is controlled to fit.
In the present invention, an example in which a liquid interface modifying compound is used is given, but a gas or solid compound can also be used. When a gaseous interfacial modifier compound is used, the interfacial modifier compound storage tank section does not need to be provided with a heater, but instead may be provided with a flow regulating means such as a pressure regulating valve. . Further, when using a solid interfacial modifier compound, for example, the liquid transportation in which the solid compound is dissolved in a solvent or melted with heat and piped from the storage tank of this example to the vicinity of the flame of the burner. Interfacial reforming can be performed by passing through a pipe and feeding directly into a burner.

"Transportation part"
As shown in FIG. 1, the transfer unit 105 has a “pipe” structure, and as shown in FIG. 1, the vaporized interface modifier compound supplied from the compressed air source 107 and delivered from the storage tank 102. The first submixer 108 for mixing the fuel gas, the mixed gas mixed by the first submixer 108, and the second gas for uniformly mixing the fuel gas delivered from the fuel gas storage tank 106. The main mixer 109 is provided.

"Injection part (burner)"
As shown in FIG. 1, the injection unit (burner) 104 burns the combustion gas sent through the transfer unit 105 and sprays the obtained flame 113 onto the surface to be reformed (not shown). The reformed surface is subjected to interfacial reforming, and the state of the flame 113 includes the flow rate of the vaporized interfacial modifier compound 101, the amount of combustion air sent from the compressed air source 107, and the fuel gas. Each flow rate of the fuel gas delivered from the storage tank 106 is optimally adjusted to adjust the opening degree of the flow rate control valves 110, 111, 112 with flow meters provided in the respective gas flow paths. The The type of the burner is not particularly limited, and may be any of a premix burner, a diffusion burner, a partial premix burner, a spray burner, an evaporation burner, and the like. Further, the form of the burner is not particularly limited.

The interface modifier compound is not particularly limited as long as it is a compound containing a silane atom, a titanium atom or an aluminum atom and can burn in a flame of a general gas burner. In view of easy availability and handling, for example, a group consisting of an alkylsilane compound, an alkoxysilane compound, a siloxane compound, a silazane compound, an alkyl titanium compound, an alkoxy titanium compound, an alkyl aluminum compound, and an alkoxy aluminum compound. It is preferable that it is at least one compound selected from.
Preferred examples of the alkylsilane compound include methylsilane, dimethylsilane, trimethylsilane, tetramethylsilane, tetraethylsilane, dimethyldichlorosilane, dimethyldiphenylsilane, diethyldichlorosilane, diethyldiphenylsilane, methyltrichlorosilane, methyltriphenylsilane, and dimethyl. Substituents such as monosilane compounds which may have substituents such as diethylsilane, disilane compounds which may have substituents such as hexamethyldisilane, hexaethyldisilane and chloroheptamethyldisilane, and octamethyltrisilane A trisilane compound which may have
Preferred examples of the alkoxysilane compound include methoxysilane, dimethoxysilane, trimethoxysilane, tetramethoxysilane, ethoxysilane, diethoxysilane, triethoxysilane, tetraethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, and trimethylmethoxysilane. , Methyltriethoxysilane, dimethyldiethoxysilane, trimethylethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, dichlorodimethoxysilane, dichlorodiethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, trichloromethoxysilane, trichloroethoxysilane , Triphenylmethoxysilane, triphenylethoxysilane and the like alone or in combination of two or more .
Preferred examples of the siloxane compound include tetramethyldisiloxane, pentamethyldisiloxane, hexamethyldisiloxane, octamethyltrisiloxane, hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexa Examples thereof include siloxane.
Preferable examples of the silazane compound include hexamethyldisilazane. Moreover, as a suitable example of an alkyltitanium compound, tetramethyl titanium, tetraethyl titanium, tetrapolo pyr titanium, etc. are mentioned. Preferable examples of the alkoxytitanium compound include titanium methoxide and titanium ethoxide. Preferable examples of the alkyl aluminum compound include trimethyl aluminum, triethyl aluminum, tripropyl aluminum and the like. Preferable examples of the alkoxyaluminum compound include aluminum methoxide, aluminum ethoxide and the like. These compounds may be used alone or in combination.
Among the above preferable examples, silane compounds, alkoxysilane compounds, siloxane compounds, and silazane compounds are more preferable because they are easy to handle, easily vaporized, and easily available.

  Next, using the interface reformer according to the present invention illustrated in FIG. 1 described above, magnesium alloy: Mg—Al—Zn (AZ91D) is thixocast-molded, and the magnesium-based alloy molded product is used as a target. How the modified surface of the magnesium-based alloy molded product is modified will be described with reference to FIG.

  FIG. 2 schematically shows an enlarged cross-sectional view of a magnesium-based alloy molded product molded by a thixocasting molding method, and is for explaining the state of the cast skin surface. In FIG. 2, 201 is a Mg—Al—Zn-based (AZ91D) molded product, and when the surface of the molded product is observed microscopically, innumerable irregularities 202 and 203 on the order of several tens of μ to several hundreds of μ are seen. Even if it is a thixocasting molding method with a relatively smooth casting surface in the metal alloy molding method, when applying a coating layer as a design layer on the casting surface, as before, hot water washing → strong alkali Degreasing → Hot water → Pure water cleaning → Chemical conversion treatment (Zinc phosphate film, etc.) → Pure water cleaning → Draining drying → Dust removal The process must be followed. If this step is omitted, the Mg—Al—Zn system ( AZ91D) The adhesion between the molded product and the coating layer cannot be ensured, and has been recognized as an essential process for ensuring the adhesion.

  By the way, when the interface between the Mg—Al—Zn (AZ91D) molded product and the coating layer is modified using the interface reforming apparatus according to the present invention illustrated in FIG. 1, the same Mg—Al—Zn system is used. (AZ91D) The molded product is first degreased with a weak alkaline solution, then drained and dried, and then the interface reformer illustrated in FIG. 1 (interface modifier compound: silane compound-based interface modifier compound) When the surface of the Mg-Al-Zn-based (AZ91D) molded product is subjected to interfacial modification using the above-mentioned, a magnified cross section of the magnesium-based alloy molded product similar to that shown in FIG. For example, a silicate-based interface modified layer 301 having a thickness of several nm) to several tens of nm is formed.

  As described above in detail, according to the present invention, the interface modification performance of the interface modification layer 301 shown in FIG. 3 is 73 dyn / cm or more in terms of the wetting index (measured temperature: 25 ° C.) when measured with a wetting index reagent. Even when measured with a contact angle, a super hydrophilic effect of 10 ° (measurement temperature 25 ° C.) or less can be reliably obtained, and a coating process that becomes a design layer as a post-process in this interface modification state is a primer process. It was confirmed that there was no inferiority in the adhesion strength and the coating appearance of the interface between the Mg—Al—Zn-based (AZ91D) molded product and the coating layer. In addition, even with other aluminum-based or titanium-based alloy molded products, the interface modification device was used to modify the interface in the same manner as the magnesium alloy molded products, and the superhydrophilic effect could be achieved.

  The flow from the pretreatment process of the painting process to the formation of the design layer will be described using a magnesium alloy-based (Mg-Al-Zn-based: AZ91D) molded product molded by the thixocasting molding technique as an example. Weak alkaline degreasing process → Hot water washing or pure water washing process → Draining and drying process → Interfacial activation process → Dust removal process → Primerless / painting process, conventional process: Hot water washing → Strong alkaline degreasing → Hot water washing → Pure water Cleaning → Chemical conversion treatment (example: zinc phosphate coating) → Pure water cleaning → Draining dry → Dust removal → Compared with the primer application process, the number of conventional processes: 8 processes will be reduced to 5 processes. Therefore, it is possible to greatly reduce the manufacturing time and the manufacturing cost. In addition, even in the painting process for forming the design layer, the primer coating process is unnecessary, and one coat finish can be finished as it is, and there is a merit that can directly shift to the design layer formation, and the economic effect is enormous. is there.

  In addition, when the interface of the coating of various metal alloy molded products is modified by the interface reforming device as described above, the cast hole of the order of several tens to several hundreds of microns formed on the surface of the various metal alloy molded products, that is, the casting surface, etc. Since the uneven surface of the metal is in a super hydrophilic state, various paints formed later flow into the uneven surface and become familiar and adhere securely, and the coating process that is the subsequent process at the interface of various metal alloy molded products is a primer It was confirmed that sufficient adhesion could be secured in the state of less.

[Example 1]
A case of a mobile phone was obtained by a thixocasting molding method using a magnesium alloy (Mg—Al—Zn system: AZ91D). The casing was subjected to a pretreatment for forming a design layer through the following process.
(1) Pretreatment process Work input → Weak alkaline degreasing (1 minute) → Washing with water (1 minute) → Draining and drying (1 minute) → Interfacial activation treatment (2 seconds), modifier compound in interfacial activation treatment Used hexamethyldisiloxane and propane / GAS as the fuel GAS for flame treatment.
(2) Design layer formation process Next, the design layer was formed through the process shown below in the case of the cellular phone that completed the pretreatment process.
Workpiece input → Dust removal (2 seconds) → Primerless spray coating: Average film thickness (25μ) • (10 seconds): Thermosetting paint (2-component urethane resin: ISIMAT Japan: IMS-100) → Setting ( Room temperature: 10 minutes) → curing and drying (70 ° C. × 30 minutes) → cooling (5 minutes) → work removal.
(3) Appearance of the coating film The appearance of the coating film was a primer-less, one-coat finish with an extremely smooth finish, and no problems with appearance were observed.
(4) Physical properties of coating film

It is a figure which shows the outline | summary of an interface reforming apparatus. The expanded sectional view of a magnesium system alloy molding. The expanded sectional view of a magnesium system alloy molding.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100: Interface modifier 101: Interface modifier compound 102: Storage tank part 103: Heating means 104: Injection part (burner)
105: Transfer path 106: Fuel gas storage tank 107: Compressed air source 108: Submixer 109: Main mixer 110: Flow rate adjustment valve 111 with flow meter 111: Flow rate adjustment valve 112 with flow meter
112: Flow control valve with flow meter 113: Flame 201: Mg—Al—Zn (AZ91D) molding 202: Concavity and convexity 203: Concavity and convexity 301: Interface modification layer

Claims (4)

A high adhesion coating method on a metal alloy molded product that requires at least the following steps.
1. Alkali degreasing process of metal alloy molding.
2. A cleaning step of the metal alloy molded product described in the previous item 1 with pure water, water, or warm water.
3. A draining and drying process of the metal alloy molded product described in the previous item 2.
4. After the previous No. 3 step, a flame of a fuel gas containing a modifying compound containing a silane atom, a titanium atom or an aluminum atom and having a boiling point of 10 ° C. to 105 ° C. is formed into a metal alloy. A step of spraying the entire surface or a part of the surface of the object to perform surface activation treatment so that the surface of the metal alloy molded product has a wetness index (measurement temperature of 25 ° C.) of 73 dyn / cm or more.
5, The coating process which applies the coating layer used as a design layer through the surface activation treatment process as described in No. 4 above.   The high adhesion coating method in which the metal alloy molded product according to claim 1 is a magnesia alloy, an aluminum alloy, or a titanium alloy.   A metal alloy molded product coated with high adhesion according to claim 1.   A metal alloy molded product coated with high adhesion according to claim 2.

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