JP2006328270A - Metal foil for coating and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain pigment that is more inexpensive pigment such as flaky aluminum powder, etc., and chemically more stable. <P>SOLUTION: The flaky metal powder for pigment is produced by a method comprising a process for forming a releasing agent layer on the surface of a substrate, a process for applying a catalyst to the surface of the releasing agent layer so as to activate the surface, a process for bringing the activated surface into contact with a desired electroless plating liquid to form an electroless plating coating film having 0.01-0.5μm thickness, a process for bringing the substrate with the electroless plating coating film into contact with a solvent, dissolving and removing the releasing agent and separating the electroless plating coating film from the substrate and a process for grinding the separated electroless plating coating film to give flaky metal powder for pigment having 1-300μm diameter. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a pigment used when decorating a metallic luster tone on a base material such as an automobile part or a home appliance part, and specifically relates to a flaky metal powder used as a pigment.

  As means for brightening the substrate, there are a method in which wet plating or vacuum deposition is directly performed on the substrate, and metallic coating. In particular, metallic coating has a simple method and is widely used. In this metallic coating, in order to brighten the substrate, first, a first coating layer (undercoat layer) is formed on the substrate, and a flaky aluminum powder, glass, mica, resin, or the like is formed thereon. Second coating layer (metallic glossy coating layer) using paint in which a metal layer such as aluminum is provided on the surface of the flaky powder (hereinafter referred to as “flaky aluminum powder”) as a pigment Is formed, and a clear coat layer (top coat layer) is provided thereon as a third layer to protect an aluminum portion such as flaky aluminum powder.

  In general, such flaky aluminum powder is formed by providing an aluminum layer or the like on the surface of an aluminum foil obtained by a dry film-forming method such as a vapor deposition method, a thin glass, a mica piece or a resin piece by electroless plating or a vacuum vapor deposition method. It is obtained by mechanically pulverizing using a method using a stamp mill, a dry ball mill, a wet ball mill or the like.

  By the way, when flaky aluminum powder or the like is used as a pigment, the surface reflectance of aluminum is as high as 80% or more in visible light, and there is a defect in appearance that the appearance becomes whitish and lacks a high-class feeling. In addition, aluminum reacts with oxygen to form an oxide film, resulting in a loss of glitter. Furthermore, with the growth of the oxide film, the adhesion between the base material and the coating film (coating film adhesion) decreases.

  In an environment containing moisture, a hydroxide film is formed instead of the oxide film. When a coating film obtained by using, as a pigment, flaky aluminum powder having a hydroxide film formed on its surface is dried and heated, the hydroxide film easily becomes an oxide film. The dry coating film thus obtained has water permeability. Therefore, moisture and aluminum that have passed through the coating film may react in the coating film, leading to corrosion and peeling of the coating film.

  For example, according to the description in paragraph 0007 of Patent Document 1, when an aluminum thin film having a film thickness of 0.05 to 1.0 μm is immersed in warm water of 40 to 60 ° C. without a top coat layer, it takes 24 to 100 hours by hydration reaction. Dissolve. Further, in the cast test (JIS H 8502), even if a top coat layer is provided, the test solution penetrates through the top coat layer and the aluminum thin film dissolves in 60 hours or more.

  Even if a pigment using aluminum with such properties is used, it can be said that if the thickness of the topcoat layer is increased and it is difficult to be damaged, no major problem will occur. It is difficult to make the top coat layer sufficiently thick. Also, when the base material is like a tire wheel, a tire using the tire wheel was mounted and the vehicle ran in a rough road area, a coastal area, a zone where salt was sprayed to prevent freezing, a hot and humid area, etc. In some cases, when the tire wheel surface is damaged and the top coat layer of the tire wheel is scratched, the aluminum of the pigment comes into contact with the external environment, and corrosion of the aluminum starts from the scratch. As this corrosion progresses, the aluminum portion such as the flaky aluminum powder that is the pigment dissolves and disappears, and the undercoat layer is exposed. Then, not only the original brilliant surface is damaged, but the adhesion between the undercoat and the topcoat is lost, and swelling occurs. Furthermore, there is a possibility of progressing to corrosion of the base material from that point.

  For these reasons, various treatment methods for improving the corrosion resistance and chemical resistance of aluminum foils and thin films have been proposed (see Patent Documents 2 to 7). However, since the corrosion resistance and chemical resistance of aluminum itself is low, the actual situation is that a great effect is not obtained.

Despite these shortcomings, the reason why flaky aluminum powder or the like is frequently used as a pigment for metallic coating is that the material itself of aluminum is inexpensive.
JP 2003-292823 A JP 2000-354828 A JP-A-9-311561 Japanese Patent Laid-Open No. 9-122575 Japanese Patent Laid-Open No. 6-200932 JP-A-7-133440 JP-A-6-57171

  By the way, the recent demand for cost reduction is strongly desired for all types of industrial products. The above-mentioned pigments are no exception, and cheaper ones have been demanded. Looking at the flaky aluminum powder used as a pigment, the price of the aluminum metal itself used as a raw material is certainly cheap, but it cannot be said that the flaky aluminum powder itself is inexpensive.

  This is because the flaky aluminum powder or the like is obtained by the electroless plating or vacuum deposition method on the surface of the aluminum foil, thin glass, mica piece or resin piece obtained by the dry film forming method such as the vapor deposition method as described above. It is based on a method of manufacturing by providing an aluminum layer or the like by a dry film forming method, or by mechanically pulverizing using a stamp mill, a dry ball mill, a wet ball mill or the like.

  First, in the dry film forming method, a target and an object to be deposited are placed in a vacuum chamber and the inside of the vacuum chamber is depressurized to form a film, so that the apparatus becomes very large. Therefore, if mass production is attempted to reduce the manufacturing cost, a larger apparatus will be used. As a result, expensive capital investment is required, and it is difficult to reduce the manufacturing price of flaky aluminum powder or the like that is substantially a pigment.

  Further, this is particularly noticeable when a metal film having a high melting point is formed, but a metal to be formed, which is aluminum here, requires a high energy cost in accordance with the melting point. Furthermore, each time the target or film formation target is changed into the vacuum chamber, the vacuum state must be changed from normal pressure, which necessitates operations including complicated operations. As a result, it is difficult to reduce the running cost.

  Accordingly, there is a need to provide a pigment that is cheaper and chemically more stable than flaky aluminum powder or the like.

  The present invention has been made in view of the above situation, and an object of the present invention is to propose a novel pigment that is cheaper and more chemically stable than pigments such as flaky aluminum powder.

  As a result of many studies on the metal foil that can solve the above-mentioned problems, the inventors of the present invention can obtain a metal powder suitable for the pigment when pulverizing a thin film that becomes a poor electroless plating film. The inventors have found that the metal powder can be produced inexpensively and stably by selecting a specific electroless plating method, and have reached the present invention.

  That is, the present invention according to claim 1 is a flaky metal powder for pigment obtained by pulverizing a metal foil produced by an electroless plating method, having a thickness of 0.01 to 0.5 μm and a diameter of 1 to 300 μm. It is a flaky metal powder.

  The present invention according to claim 2 is the flaky metal powder for pigment according to claim 1, and the material thereof is at least one of Au, Ag, Pd, Ni, Cu, Co, or these metals as main metals. It is an alloy as a component.

  And this invention of Claim 3 is a manufacturing method of the flaky metal powder for pigments in any one of Claims 1-2, and makes the following processes the main processes.

(1) Step of providing a release agent layer on the substrate surface
(2) A step of applying and activating a catalyst on the surface of the release agent layer
(3) A process for producing an electroless plating film having a thickness of 0.01 to 0.5 μm by contacting with a desired electroless plating solution
(4) A process of separating the electroless plating film from the substrate by contacting the substrate with the electroless plating film with a solvent to dissolve and remove the release agent.
(5) A step of pulverizing the separated electroless plating film to obtain a flaky metal powder for a pigment having a diameter of 1 to 300 μm. The invention according to claim 4 is used in addition to the invention according to claim 3. The substrate is made of metal, resin film, or glass.

  In addition to the above, the present invention according to claim 5 is a urethane resin, a polyester resin, a polystyrene resin, an acrylic resin, a silicon resin, a paraffin resin, an epoxy resin, a melamine resin, a polyurethane resin, and a water-based acrylic resin as a release agent. At least one of alkyd resin, ultraviolet curable resin, and aqueous urethane resin is used.

  In addition to the above, the present invention described in claim 6 employs a physical method as a method of pulverizing the electroless plating film.

  In the seventh aspect of the present invention, in the step (4), the substrate with the electroless plating film is immersed in a solvent to dissolve the release agent, and the substrate is removed from the solution. The electrolytic plating film is pulverized in a solvent using either ultrasonic waves or a homogenizer.

In order to obtain a conventional flaky metal powder for pigment, a thin film must first be obtained by a dry film forming method. As described above, in order to obtain a thin film by the dry film forming technique, for example, in the sputtering method, after the vacuum chamber is sufficiently evacuated to a pressure of about 10 ⁻³ Pa or less, an inert gas such as argon becomes 1 to 10 Pa. A metal thin film is formed on the substrate by applying a DC voltage of 1 to 2 kV between the metal cathode and the anode, and this is peeled and pulverized. Therefore, a large-sized apparatus is required, and a large investment is required. In addition, the running cost is high, and it is difficult to reduce the production cost of the flaky metal powder for pigment.

  On the other hand, since the flaky metal powder for a pigment of the present invention is produced using an inexpensive electroless plating method, the production cost can be reduced. This is because, in electroless plating, each operation can be performed under normal pressure. It can also be continuous. As a result, the amount of capital investment can be reduced. This is because it is possible to operate at a plating bath temperature of 90 ° C. or less at the highest, so that the running cost can be reduced.

  In addition, the method of the present invention is applicable to metals that can be electrolessly plated. Therefore, by selecting a metal as a material, a novel flake-like metal powder for pigments which has higher corrosion resistance than aluminum and can obtain a desired metallic luster can be obtained.

  In the present invention, the size of the flake metal powder for pigment is 0.01 to 0.5 μm and the diameter is 1 to 300 μm. When the thickness is less than 0.01 μm, the first coating layer can be seen through. The surface reflectance is too low. On the other hand, if it exceeds 0.5 μm, the stress of the flaky metal powder becomes high, and the possibility that the flake will curl is high. Further, even when the thickness exceeds 0.5 μm, the surface reflectance does not change, and when a film having a thickness exceeding 0.5 μm is formed, production time is required, and the cost increases. On the other hand, when the size of the flaky metal powder is less than 1 μm, the reflectivity is reduced and the glossiness is impaired. On the other hand, when the size of the flaky metal powder exceeds 300 μm, the gap between the flaky metal powder and the flaky metal powder becomes large and the first coating layer may be visible.

  In the present invention, the type of flaky metal powder for pigment is not particularly limited as long as it is a metal that can be electrolessly plated. From such a viewpoint, it is preferable to use at least one of Au, Ag, Pd, Ni, Cu, and Co or an alloy containing these metals as a main metal component.

  The outline of the method of the present invention is illustrated in FIG. 1, but the following steps are the main steps.

(1) Step of providing a release agent layer on the substrate surface
(2) A step of applying a catalyst to the surface of the release agent and activating it
(3) A process for producing an electroless plating film having a thickness of 0.01 to 0.5 μm by contacting with a desired electroless plating solution
(4) A step of contacting the substrate with the electroless plating film with a solvent to dissolve and remove the release agent to separate the electroless plating film from the substrate
(5) A step of pulverizing the collected electroless plating film to obtain a flaky metal powder for pigment having a diameter of 1 to 300 μm. The substrate used in step (1) of the present invention is dissolved in a plating solution or a release agent. Although it does not specifically limit if it is hard to be violated by the solvent used for (1), Glass substrates, such as metal substrates, such as a metal plate and a metal strip, a sheet-like or film-like resin substrate, or a glass plate, are preferable from such conditions. Among these, the use of a long film-like resin substrate is preferable because it can be manufactured by a reel-to-reel method and the manufacturing cost is reduced.

  In the present invention, an electroless plating film is prepared and peeled off. In order to facilitate this peeling, a release agent layer is provided on the substrate in step (1). The release agent that can be used for this purpose is preferably one that can be easily removed from the substrate surface in step (4) without being violated by the electroless plating solution. For example, urethane resin, polyester resin, polystyrene resin, acrylic resin, silicon resin, paraffin resin, epoxy resin, melamine resin, polyurethane resin, water-based acrylic resin, alkyd resin, ultraviolet curable resin, aqueous urethane resin and the like are preferable.

  The release agent layer may be prepared by dissolving an appropriate amount of the above-described release agent in a solvent, applying the obtained solution to a substrate, and drying the substrate, immersing the substrate in the solution, and then drying the solution. Also good. Of course, there is no problem as long as a release agent layer such as a spray method that is commercially available is used as it is and a release agent layer is formed on the substrate surface and can be peeled off in the step (4).

  For example, when a urethane resin is used as a mold release agent, it is used as a 0.5 to 10% by weight solution and dried by natural drying, air blowing or hot air.

  In the method of the present invention, an electroless plating method is applied as a film forming method in steps (2) to (3).

  In step (3), the electroless plating solution and the substrate after step (2) are contacted to deposit an electroless plating film on the surface of the release agent layer. The thickness of the electroless plating film to be deposited varies depending on the immersion time, the temperature of the electroless plating solution, the concentration of the target metal component in the plating solution, and the like, and also varies depending on the contact method between the substrate and the electroless plating solution. for that reason. Each condition is selected so that the thickness of the obtained electroless plating film is 0.01 to 0.5 μm.

  In step (4), the release agent existing between the substrate surface and the electroless plating film is dissolved and removed with a solvent, and the electroless plating film and the substrate are separated to obtain an electroless plating film. In normal plating, the purpose is to produce a plating film with good adhesion to the substrate, but here the purpose is to peel off the plating film, so the use of cracks due to poor adhesion is utilized. In addition, by generating cracks or the like by bending the base material, the solvent easily penetrates to the release agent layer below the electroless plating film to dissolve the release agent. In principle, the solvent used may be a solvent in which the release agent is dissolved in step (1).

  In the step (5), the electroless plating film obtained in the step (4) is pulverized to obtain a flaky metal powder for pigment having a diameter of 1 to 300 μm. Since the electroless plating film obtained in the step (4) is a film thinner than the film thickness usually used for the plating film, it can be easily pulverized to a desired particle size by a physical method. The recovered flaky metal powder is recovered together with the solvent, and is finally used as a paint in a state of being dispersed in the solvent. Therefore, it is preferable to grind in the solvent using ultrasonic vibration, a homogenizer, or the like.

Hereinafter, the present invention will be further described with reference to study examples and examples.
(Examination example 1)
The film thickness of the Ni-P alloy coating was evaluated by changing the plating time. Each step of the electroless plating method was the same as the step according to Example 1 described later, and the test was performed while changing the plating treatment time.
FIG. 2 is a diagram showing the relationship between the plating time and the thickness of the plating film. As is apparent from FIG. 2, the plating thickness increased with the plating time. From this, the necessary film thickness can be controlled by controlling the plating time.

(Examination example 2)
After the release agent was peeled off, the recovered flaky metal powder was evaluated to be pulverized by ultrasonic treatment.
Each step of the electroless plating method is the same as the step according to Example 1 to be described later, but the test was performed by changing the pulverization time by ultrasonic waves. The ultrasonic test was performed under the conditions of a frequency of 50 kHz and an output of 70 W.
FIG. 3 is a graph showing the relationship between the pulverization time by ultrasonic waves and the average size of the flaky Ni—P alloy powder made by pulverization. As is clear from FIG. 3, it was found that the flaky Ni—P alloy can be pulverized by ultrasonic pulverization, and the size becomes finer with time. Therefore, in order to pulverize to a necessary size, it can be controlled by controlling the ultrasonic pulverization time.

(Examination example 3)
It was evaluated whether flaky Ni-P alloy powder could be recovered by changing the type of release agent.
Each process of the electroless plating method is the same as the process according to Example 1 described later, but the test was performed by changing the type of the release agent to a polyester resin. A polyester resin was dissolved in 2% by weight and 5% by weight of methyl ethyl ketone in a 10 cm square PET film having a thickness of 0.125 mm used as a base material, the base material was dipped, pulled up and naturally dried. Using the base material, electroless Ni plating was performed under the same conditions as in Example 1, and the release agent was dissolved with methyl ethyl ketone. As a result, flaky Ni—P alloy powder could be recovered in any case.

Example 1
An example of a flaky metal powder for Ni-P alloy pigment produced by electroless Ni plating will be described.
A 10 cm square PET film having a thickness of 0.125 mm was used as the substrate. A urethane resin was used as a release agent applied to the substrate. The urethane resin was dissolved in methyl ethyl ketone, the substrate was immersed in a 2% by weight urethane resin solution, pulled up and dried naturally.
The obtained substrate with a release agent was subjected to a general pretreatment, a treatment with a silane coupling solution and a catalyst treatment with a palladium chloride solution (see Non-Patent Document 1). And electroless Ni plating was performed. Electroless Ni plating conditions are nickel sulfate 30 g / liter, sodium hypophosphite 20 g / liter, sodium citrate 50 g / liter, pH 8.5 plating solution, and a Ni-P alloy coating with a thickness of about 0.05 μm. Made. The release agent was dissolved with methyl ethyl ketone, and the Ni-P alloy film was peeled off. The collected Ni—P alloy coating was pulverized by applying ultrasonic waves in methyl ethyl ketone to obtain a flaky Ni—P alloy powder having a size of about 50 μm.

(Example 2)
An example of a flaky metal powder for pigment produced by an electroless Cu plating method will be described.
The PET film used as the substrate and the kind and application method of the release agent were the same as in Example 1. Moreover, the pre-processing method similarly performed the silane coupling process and the catalyst process, and performed electroless Cu plating. Electroless Cu plating conditions are: copper sulfate 5g / liter, Rossell salt 25g / liter, formaldehyde (37%) 10ml / liter, sodium hydroxide 7g / liter, pH12 plating solution, thickness 0.07μm A Cu plating film was prepared. The release agent was dissolved using methyl ethyl ketone, and the recovered Cu coating was pulverized by applying ultrasonic waves in methyl ethyl ketone to obtain a flaky Cu powder having a size of about 80 μm.

(Example 3)
An example of a flaky Au powder for pigment produced by an electroless Au plating method will be described.
The PET film used as the substrate and the kind and application method of the release agent were the same as in Example 1. In the pretreatment method, silane coupling treatment and catalyst treatment were similarly performed, and electroless Au plating was performed. The electroless Au plating conditions were 2g / l potassium gold cyanide, 75g / l ammonium chloride, 50g / l sodium citrate, 10g / l sodium hypophosphite, pH 7.0, and a thickness of approx. A 0.03 μm Au plating film was prepared. The release agent was dissolved using methyl ethyl ketone, and the collected Au coating was pulverized by applying ultrasonic waves in methyl ethyl ketone, and a flaky Au powder having a size of about 40 μm was obtained.

Example 4
An example of a flaky metal powder for pigment produced by an electroless Ag plating method will be described.
The PET film used as the substrate and the kind and application method of the release agent were the same as in Example 1. In the pretreatment method, silane coupling treatment and catalyst treatment were similarly performed, and electroless Ag plating was performed. The electroless Ag plating conditions used silver nitrate 60g / l, ammonia (28%) 60ml / l, and formaldehyde (37%) 40ml / l, and produced an Ag plating film with a thickness of about 0.09μm. . The release agent was dissolved using methyl ethyl ketone, and the collected Ag coating was pulverized by applying ultrasonic waves in methyl ethyl ketone to obtain a flaky Ag powder having a size of about 100 μm.

(Example 5)
An example of a flaky metal powder for pigment produced by an electroless Co plating method will be described.
The PET film used as the substrate and the kind and application method of the release agent were the same as in Example 1. In the pretreatment method, silane coupling treatment and catalyst treatment were similarly performed, and electroless Co plating was performed. Electroless Co plating conditions use cobalt chloride 30g / liter, sodium citrate 35g / liter, ammonium chloride 50g / liter, sodium hypophosphite 20g / liter bath adjusted to pH 9.0 with ammonia water. Then, a Co plating film having a thickness of about 0.04 μm was produced. The release agent was dissolved using methyl ethyl ketone, and the recovered Co film was pulverized by applying ultrasonic waves in methyl ethyl ketone to obtain flaky Co powder having a size of about 100 μm.

(Example 6)
An example of a flaky metal powder for pigment produced by an electroless Pd plating method will be described.
The PET film used as the substrate and the kind and application method of the release agent were the same as in Example 1. In the pretreatment method, silane coupling treatment and catalyst treatment were similarly performed, and electroless Pd plating was performed. As electroless Pd plating conditions, a plating solution of tetramine palladium chloride 5.4 g / liter, EDTA 3 g / liter, ammonia 350 g / liter, hydrazine 0.3 g / liter was used, and a Pd plating film having a thickness of about 0.1 μm was prepared. The release agent was dissolved using methyl ethyl ketone, and the recovered Pd film was pulverized by applying ultrasonic waves in methyl ethyl ketone to obtain a flaky Pd powder having a size of about 120 μm.

(Example 7)
The flaky Ni—P alloy powder obtained in Example 1 was applied by the following method. The base material to apply | coat was produced as follows. Was formed in 80 to 150 g / m ² of chromium amount conversion coating with chromate treatment to the aluminum alloy casting AC4C (Al-Si-Mg based) plate material. Next, in order to smooth the surface, 100 μm of acrylic powder paint was applied and dried at 150 ° C. for 1 hour. A 30 μm thick polyester / melanin resin was formed thereon with an air gun as an undercoat, and dried at 140 ° C. for 30 minutes.
The flaky Ni-P alloy powder obtained in Example 1 was prepared in a solvent (MEK) and applied by air spray on the substrate prepared by the above method. A 25 μm thick acrylic / melanin resin topcoat was formed on it with an air spray gun and dried at 140 ° C. for 3 hours.
The substrate produced by the above method has no cracks or cracks, and has a metallic coating appearance with high radiance, and the surface reflectance measured with a spectrophotometer (manufactured by Hitachi, Ltd.) with light at a wavelength of 550 nm is 60%. A coated surface having good glossiness can be produced.

As described above, according to the present invention, the flaky metal powder for pigment can be produced using an inexpensive electroless plating method, and the reel-to-reel method can be adopted, which is more cost effective than using the dry film forming method. It is clear that a significant reduction in the above becomes possible. For this reason, it is possible to manufacture a cheaper pigment as a pigment even if a metal having higher corrosion resistance than aluminum is used as a raw material.

It is the figure which showed the process example of the flaky metal powder preparation method. It is the figure which showed the relationship between the plating time by the examination example 1, and the film thickness of a plating film. It is the figure which showed the relationship between the grinding | pulverization time by the ultrasonic wave by examination example 2, and the average magnitude | size of the flaky Ni-P alloy powder made by grinding | pulverization.

Claims (7)

A flaky metal powder for pigment obtained by pulverizing a metal foil produced by an electroless plating method, having a thickness of 0.01 to 0.5 μm and a diameter of 1 to 300 μm. Metal powder. 2. The flaky metal powder for pigment according to claim 1, wherein the material is at least one of Au, Ag, Pd, Ni, Cu and Co or an alloy containing these metals as a main metal component. The manufacturing method of the said flake-like metal powder for pigments which makes the following processes the main processes.
(1) Step of providing a release agent layer on the substrate surface
(2) A step of applying and activating a catalyst on the surface of the release agent layer
(3) A step of producing an electroless plating film having a thickness of 0.01 to 0.5 μm by contacting with a desired electroless plating solution
(4) A step of contacting the substrate with the electroless plating film with a solvent to dissolve and remove the release agent to separate the electroless plating film from the substrate
(5) A step of pulverizing the separated electroless plating film to obtain a flaky metal powder for pigment having a diameter of 1 to 300 μm 4. The method according to claim 3, wherein the substrate to be used is any one of a metal, a resin film, and a glass. As a release agent, at least of urethane resin, polyester resin, polystyrene resin, acrylic resin, silicon resin, paraffin resin, epoxy resin, melamine resin, polyurethane resin, water-based acrylic resin, alkyd resin, ultraviolet curable resin, and aqueous urethane resin The manufacturing method according to claim 4, wherein one kind is used. 6. The production method according to claim 5, wherein the method of pulverizing the electroless plating film is a physical method. In the step (4), the substrate with the electroless plating film is immersed in a solvent to dissolve the release agent, the substrate is removed from the solution, and the electroless plating film is ultrasonicated or dissolved in the solvent. 6. The method according to claim 5, wherein the homogenizer is pulverized by using any one of the in-use.

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