JP2014051692A - Method for producing aluminum film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing an aluminum film which can, at a low cost, form a favorable-quality aluminum film on a resin surface by means of an aluminum plating solution using a urea compound.SOLUTION: The method for producing an aluminum film has a step for electrodeposition of aluminum onto a resin subjected to conductivity processing in a plating solution containing a urea compound, aluminum chloride and xylene. In the plating solution, preferably, a molar ratio of the urea compound to the aluminum chloride is in the range of 1:1.10-1:1.50.

Description

  The present invention relates to a method for producing an aluminum film capable of electrodepositing aluminum on a resin surface.

By forming a metal film on the resin surface, it has been practiced to impart conductivity to various instruments, ornaments, etc., or to enhance aesthetic decoration.
For example, a porous metal body produced by applying metal plating to a resin porous body having a three-dimensional network structure is used in various fields such as various filters, catalyst carriers, and battery electrodes. As the metal porous body, cermet made of nickel (manufactured by Sumitomo Electric Industries, Ltd .: registered trademark) is used as an electrode material for batteries such as nickel metal hydride batteries.

  Celmet is a metal porous body having continuous air holes, and has a feature of high porosity (90% or more) compared to other porous bodies such as a metal nonwoven fabric. This can be obtained by forming a nickel layer on the surface of the porous resin skeleton having continuous air holes such as urethane foam, then heat-treating it to decompose the foamed resin molding, and further reducing the nickel. The formation of the nickel layer is performed by depositing nickel by electroplating after applying carbon powder or the like to the surface of the skeleton of the foamed resin molded body and conducting a conductive treatment.

  A porous body made of aluminum as the metal porous body as described above is promising as improving the capacity of the positive electrode of the lithium ion battery. Since aluminum has excellent characteristics such as conductivity, corrosion resistance, and light weight, currently, an aluminum foil whose surface is coated with an active material such as lithium cobaltate is used as a positive electrode of a lithium ion battery. By forming the positive electrode with a porous body made of aluminum, the surface area can be increased and the active material can be filled inside the aluminum. Thereby, even if the electrode is thickened, the utilization factor of the active material is not reduced, the utilization factor of the active material per unit area is improved, and the capacity of the positive electrode can be improved.

  As a method for producing a porous aluminum body, Japanese Patent No. 3413666 (Patent Document 1) discloses that a two-dimensional net-like plastic substrate having an internal communication space is subjected to an aluminum vapor deposition process by an arc ion plating method to be 2 to 20 μm. A method for forming a metallic aluminum layer is described. Japanese Patent Application Laid-Open No. 08-170126 (Patent Document 2) discloses a film made of a metal (such as copper) that forms a eutectic alloy below the melting point of aluminum on the skeleton of a foamed resin molding having a three-dimensional network structure. After forming, an aluminum paste is applied, and heat treatment is performed at a temperature of 550 ° C. or higher and 750 ° C. or lower in a non-oxidizing atmosphere to eliminate organic components (foamed resin) and to sinter the aluminum powder. Is described.

According to the method of Patent Document 1, it is said that an aluminum porous body having a thickness of 2 to 20 μm can be obtained. In some cases, it is difficult to form a uniform layer up to the inside. In addition, there are problems such as a slow formation rate of the aluminum layer and an increase in manufacturing cost due to expensive equipment. Furthermore, when a thick film is formed, there is a risk that the film may crack or aluminum may fall off.
Further, according to the method of Patent Document 2, a layer that forms a eutectic alloy with aluminum is formed, and a high-purity aluminum layer cannot be formed.

  As for the method of electroplating aluminum, aluminum has a high affinity for oxygen and its oxidation-reduction potential is lower than that of hydrogen. Therefore, it is difficult to perform electroplating in an aqueous plating bath. For this reason, as a method of electroplating aluminum, a method using a molten salt bath is performed. However, since the molten salt bath generally needs to be at a high temperature, there is a problem that the resin is dissolved when aluminum is electroplated on the surface of the resin molded body.

This problem has been solved by the method described in Japanese Patent Application Laid-Open No. 2012-007233 (Patent Document 3), and at present, electroplating of aluminum on the surface of a resin porous body is possible. That is, in Patent Document 3, organic chloride salts such as 1-ethyl-3-methylimidazolium chloride (EMIC) and 1-butylpyridinium chloride (BPC) are mixed with aluminum chloride (AlCl ₃ ). In addition, it is described that a liquid aluminum bath is formed at room temperature, and electroplating of aluminum onto a porous resin body is possible. In particular, the EMIC-AlCl ₃ system has good liquid properties and is useful as an aluminum plating solution. Further, it is described that a smooth plating film can be obtained by adding xylene to an EMIC-AlCl ₃ -based plating solution.

  However, since there is no simple synthesis method for EMIC and BPC, synthesis takes time, and an aluminum plating solution using such an organic chloride salt is relatively expensive. For this reason, there is room for improvement in the selection of the plating bath from the viewpoint of performing electroplating of aluminum on the resin surface at a low cost.

By the way, it is known that an ionic liquid at room temperature can be formed by mixing acetamide or urea and aluminum chloride in a molar ratio of 1: 1 to 1: 1.5 (Hadi MA Abood, et al. Chem. Commun. 2011, 47, pp3523-3525 (Non-Patent Document 1)).
Non-Patent Document 1 discloses that among amide compounds, urea, acetamide, and dimethylurea can form an ionic liquid with aluminum chloride at room temperature, and electrochemical measurement of the ionic liquid formed using urea or acetamide ( When cyclic voltammetry is performed, it is described that peaks corresponding to electrodeposition and dissolution of aluminum were confirmed. It is described that when an electroplating was performed on a copper (Cu) rod using an ionic liquid of acetamide and aluminum chloride, an aluminum plating film was obtained.

  However, Non-Patent Document 1 only reports that the Cu rod was plated with aluminum using a relatively expensive ionic liquid using acetamide, and aluminum plating using a cheaper urea was performed. There is no track record. This is thought to be related to the fact that the urea bath has a lower ionic conductivity than the acetamide bath, and the result of electrochemical measurement of the ionic liquid formed using urea and that formed using acetamide. This can be seen by comparing the results of electrochemical measurements of ionic liquids.

Japanese Patent No. 3413662 JP 08-170126 A JP 2012-007233 A

Hadi M. A. Abood, et al., Chem. Commun. 2011, 47, pp3523-3525

  In view of the above problems, the present invention provides a method for producing an aluminum film capable of forming a smooth and glossy high-quality aluminum film on a resin surface at low cost by an aluminum plating bath using a urea compound. With the goal.

The present invention adopts the following configuration in order to solve the above problems.
(1) A method for producing an aluminum film in which aluminum is electrodeposited on a resin subjected to a conductive treatment in a plating bath containing a urea compound, aluminum chloride, and xylene.
According to the method for producing an aluminum film described in (1) above, a high-quality aluminum film having smoothness and gloss can be formed on the resin surface at high speed and at low cost.
(2) The method for producing an aluminum film according to (1), wherein in the plating bath, the molar ratio of the urea compound to the aluminum chloride is within a range of 1: 1.10 to 1: 1.50.
According to the invention described in (2) above, it is possible to increase the current density in the plating bath and efficiently obtain a smooth and glossy high-quality aluminum film at higher speed.
(3) The method for producing an aluminum film according to (1) or (2), wherein the urea compound is urea or dimethylurea.
According to the invention described in (3) above, a smooth and glossy high-quality aluminum film can be obtained at a lower cost.
(4) The method for producing an aluminum film according to any one of (1) to (3), wherein the xylene content in the plating bath is in the range of 5 mol% to 60 mol%.
According to the invention described in (4) above, an aluminum film having a sufficiently smooth and better mirror surface can be obtained.
(5) The method for producing an aluminum film according to any one of (1) to (4), wherein the resin is a porous body having a three-dimensional network structure.
According to the invention described in (5) above, it is possible to form a high-quality aluminum film that is smooth and glossy on the surface of a porous body having a three-dimensional network structure.
(6) The manufacturing method of the aluminum film as described in any one of (1)-(5) whose said resin is a polyurethane or a melamine resin.
According to the invention described in (6) above, it is possible to form a smooth and glossy high quality aluminum film on the surface of a porous body having a three-dimensional network structure with a high porosity and a uniform pore diameter.
(7) The manufacturing method of the aluminum film as described in any one of (1)-(6) which controls the temperature of the said plating bath to 15 to 60 degreeC.
According to the invention described in the above (7), the viscosity of the plating bath can be sufficiently lowered, and a smooth and glossy high-quality aluminum film can be efficiently obtained.
Hereinafter, a porous body having a three-dimensional network structure is also simply referred to as a “porous body”.

  According to the present invention, it is possible to form a smooth and glossy high-quality aluminum film on a resin surface at high speed and at low cost.

It is a graph which shows a voltage value when current of 2.0 A / dm < ² > flows through the urea plating solution obtained in Example 1. It is a graph which shows a voltage value when the electric current of 2.0 A / dm < ² > current flows through the dimethylurea plating solution obtained in Example 2. FIG.

In the method for producing an aluminum film according to the present invention, aluminum is electrodeposited on a resin subjected to a conductive treatment in a plating bath containing a urea compound, aluminum chloride, and xylene.
The plating bath used in the present invention can be prepared by mixing a urea compound, aluminum chloride, and xylene. As long as the quality of the aluminum film formed on the resin surface is not impaired, the plating bath may contain components other than the urea compound, aluminum chloride, and xylene. Specifically, an organic compound such as benzene, toluene, 1,10-phenanthroline may be included.

但し、式（１）においてＲは、水素原子、炭素原子数が１個〜６個のアルキル基、又はフェニル基、であり、互いに同一であっても、異なっていてもよい。
前記尿素化合物は上記の中でも、尿素、ジメチル尿素を特に好ましく用いることができる。 The urea compound means urea and its derivatives, and may be any substance that forms a liquid when mixed with aluminum chloride. For example, a compound represented by the following formula (1) can be preferably used.

However, in Formula (1), R is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or a phenyl group, and may be the same or different.
Among the above urea compounds, urea and dimethylurea can be particularly preferably used.

  The mixing ratio of the urea compound and the aluminum chloride is preferably a molar ratio of urea compound: aluminum chloride = 1: 1.10 to 1: 1.50. If the mixing ratio of aluminum chloride is less than 1.10, the viscosity of the formed ionic liquid is increased, and a sufficient current density cannot be obtained, resulting in a lower plating efficiency. When the mixing ratio of aluminum chloride exceeds 1.50, impurities such as chloride are easily mixed with the aluminum film formed on the resin surface, and it is difficult to obtain a high-quality aluminum film. Further, considering the plating efficiency, it is preferable that the amount of aluminum chloride is large. However, since aluminum chloride is highly corrosive, it is not preferable to use too much.

The mixing ratio of the urea compound and aluminum chloride is more preferably a molar ratio of urea compound: aluminum chloride = 1: 1.10 to 1: 1.20, and 1: 1.13 to 1: 1. Most preferred is .17.
It has been found that when the mixing ratio of aluminum chloride is 1.13 to 1.17, particularly 1.15, the electrical resistance of the plating bath is significantly reduced. By making the mixing ratio of aluminum chloride within this range, the voltage required for electrodeposition of aluminum can be lowered, which can contribute to energy saving and cost reduction, which is preferable. Further, since the temperature rise of the plating solution during operation is reduced, it is advantageous when the solution temperature is kept constant.

  In the method for producing an aluminum film of the present invention, the plating solution having the above composition further contains xylene so that the smoothness of the aluminum film formed on the resin surface is improved, and the surface is glossy and mirror-finished. Can do. In addition, the inclusion of xylene can improve the ionic conductivity of the plating solution, eliminates the need to increase the operating temperature, and is advantageous in terms of energy.

  It is preferable to add xylene so that it may become 5-60 mol% with respect to the plating solution containing a urea compound and aluminum chloride as content of the said xylene. When the xylene content is 5 mol% or more, the smoothness of the formed aluminum film is sufficiently improved, and when it is 60 mol% or less, the layers are separated without hindering the stability of the plating bath. Aluminum plating can be carried out without this. The xylene content is more preferably 25 to 50 mol%, and most preferably 40 mol%.

  As xylene used in the present invention, any of xylene isomers can be preferably used, and a mixture thereof may be used. In general, since it is commercially available as a mixture of three isomers of o-xylene, m-xylene, and p-xylene, it can be operated at a low cost. In addition, when only m-xylene is used among the three types of isomers, the smoothness of the obtained aluminum film is most improved and an excellent mirror surface is obtained.

  In the aluminum plating method of this invention, it is preferable to perform electrodeposition, controlling so that the temperature of the said plating bath may be 15 to 60 degreeC. By setting the temperature of the plating bath to 15 ° C. or higher, the viscosity of the plating bath can be sufficiently lowered, and the plating efficiency can be improved. Moreover, melt | dissolution of resin can be suppressed by making the temperature of a plating bath into 60 degrees C or less. The temperature of the plating bath is more preferably 30 ° C to 60 ° C, and further preferably 40 ° C to 50 ° C.

  The resin used in the method for producing an aluminum film of the present invention is not particularly limited, and any resin can be used as long as it has been subjected to a conductive treatment. Any resin can be used as long as the resin is used for plating aluminum. For example, polyurethane, melamine resin, polypropylene, polyethylene or the like subjected to a conductive treatment can be preferably used.

The resin may be of any shape as long as it is a resin that is used for plating aluminum. For example, when producing current collecting tab leads such as batteries and capacitors, aluminum may be electrodeposited by conducting a conductive treatment on a long and thin plate-like resin. As a result, a current collecting tab lead having sufficient strength can be obtained.
Further, according to the present invention, since the aluminum plating can be easily applied to the synthetic resin model and its assembly parts, the aesthetics of the model toy can be enhanced. In particular, the aluminum film formed on the surface of the resin by the plating method of the present invention is excellent in smoothness as it becomes mirror-like, and has excellent gloss and appearance.

  In addition, by using a porous body having a three-dimensional network structure as the resin, an aluminum porous body having a three-dimensional network structure that exhibits excellent properties for various filters, catalyst carriers, battery electrodes, etc. It can be produced and is preferable. Moreover, the metal porous body which has a porous structure is producible also by using resin which has a nonwoven fabric shape. The metal porous body having a nonwoven fabric shape thus produced can also be preferably used for various filters, catalyst carriers, battery electrodes, and the like.

  In addition, after electrodepositing aluminum to resin and producing a metal porous body, you may heat and remove by thermally decomposing resin, and you may use as a composite body of resin and aluminum as it is. When removing the resin, it is necessary to treat at a temperature not higher than the melting point of aluminum (660 ° C.) so as not to melt the aluminum. A preferable temperature range is 400 ° C. or more and 600 ° C. or less.

  Any resin can be selected as the material of the porous body. For example, a foamed resin molded article produced using polyurethane, melamine or the like can be exemplified as the material. Although described as a foamed resin molded article, a resin molded article having an arbitrary shape can be selected as long as it has continuous pores (continuous vent holes). For example, what has a shape like a nonwoven fabric entangled with a fibrous resin such as polypropylene and polyethylene can be used in place of the foamed resin molding.

  The porosity of the porous body is preferably 80% to 98%, and the pore diameter is preferably 50 μm to 500 μm. Foamed urethane and foamed melamine can be preferably used as a foamed resin molded article because they have high porosity, have pore connectivity and are excellent in thermal decomposability. Urethane foam is preferable in terms of pore uniformity and availability, and urethane foam is preferable in that a material having a small pore diameter can be obtained. In addition, since foamed resin moldings such as foamed urethane and foamed melamine often have residues such as foaming agents and unreacted monomers in the foaming process, it is preferable to perform a washing treatment.

The porosity of the porous body is defined by the following equation.
Porosity = (1− (weight of porous material [g] / (volume of porous material [cm ³ ] × material density))) × 100 [%]
The pore diameter is an average of the average pore diameter = 25.4 mm / cell count by enlarging the surface of the resin molded body with a micrograph and counting the number of pores per inch (25.4 mm) as the number of cells. Find the value.

In the present invention, the resin is subjected to a conductive treatment. The conductive treatment of the resin surface can be selected including known methods. A method of forming a metal layer such as nickel by electroless plating or a vapor phase method, or forming a metal or carbon layer by a conductive paint can be used.
By forming a metal layer on the resin surface by electroless plating or a vapor phase method, the conductivity of the resin surface can be increased. On the other hand, although it is somewhat inferior from the viewpoint of electrical conductivity, the conductive surface of the resin surface by carbon coating can be made without mixing any metal other than aluminum into the aluminum structure after plating. A structure can be manufactured. There is also an advantage that it can be made conductive at low cost.

When conducting the conductive treatment by applying carbon, first, a carbon paint as a conductive paint is prepared. The suspension as the carbon paint preferably contains a binder, a dispersant and a dispersion medium in addition to the carbon particles.
When a porous body is used as the resin, it is necessary to maintain a uniform suspension state in order to uniformly apply the carbon particles in the porous body. For this purpose, the suspension is preferably maintained at 20 ° C to 40 ° C. By maintaining the temperature of the suspension at 20 ° C. or higher, a uniform suspension can be maintained, and only the binder is concentrated on the surface of the skeleton forming the porous network structure to form a layer. The carbon particles can be uniformly applied. Since the layer of carbon particles uniformly applied in this manner is difficult to peel off, it is possible to form a metal plating that is firmly adhered. On the other hand, when the temperature of the suspension is 40 ° C. or less, evaporation of the dispersant can be suppressed, and therefore, the suspension becomes difficult to concentrate as the coating processing time elapses.
The particle size of the carbon particles is 0.01 to 5 μm, preferably 0.01 to 0.5 μm. If the particle size is large, the pores of the porous resin molded body may be clogged or smooth plating may be hindered. If it is too small, it is difficult to ensure sufficient conductivity.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, these Examples are illustrations and the metal porous body of this invention is not limited to these. The scope of the present invention is defined by the scope of the claims, and includes meanings equivalent to the scope of the claims and all modifications within the scope.

[Example 1]
(Preparation of urea plating bath)
Urea, aluminum chloride (AlCl ₃ ) and xylene were mixed and liquefied so as to have the molar ratios shown in Table 1 below. Electrochemical measurement was performed on the obtained plating solutions having respective ratios. Specifically, the value of the voltage necessary for applying a current density of 2.0 A / dm ² was measured. The temperature of each plating solution was 60 ° C.
As shown in Table 1, it was found that a plating solution having a molar ratio of urea to aluminum chloride of 1: 1.15 showed the lowest voltage value and a high current density was obtained. And as the ratio of aluminum chloride increased from 1.15, the voltage value required to energize a current density of 2.0 A / dm ² gradually increased. That is, it was found that plating is most easily performed when the mixing ratio of urea and aluminum chloride is in the range of 1: 1.10 to 1: 1.50. A graph of the results of Table 1 is shown in FIG.

The plating solution having a urea / aluminum chloride ratio of 1: 1.00 does not have a current density of 2.0 A / dm ² even when a voltage of 16.00 V is applied, and a current of approximately 0.001 A flows. There was no state. That is, it was found that the plating reaction does not proceed with these plating solutions. Similarly, even when the ratio of aluminum chloride is 1.00 or less with respect to urea, it was confirmed that the liquid became liquid, but a sufficient current could not flow and the plating reaction could not proceed. It was.
When the molar ratio of aluminum chloride was larger than 1.50 with respect to urea, aluminum chloride was precipitated in the plating solution and mixed in the aluminum film, so that a good quality film could not be obtained.

(Aluminum plating on porous body)
As a resin-made porous body, urethane foam having a thickness of 1 mm, a porosity of 95%, and a pore number (cell number) per inch of about 50 was prepared and cut into 100 mm × 30 mm squares.
By immersing the urethane foam in a carbon suspension and drying, a conductive layer having carbon particles attached to the entire surface of the urethane foam was formed. The components of the carbon suspension include graphite + carbon black 25% and include a resin binder, a penetrating agent, and an antifoaming agent. The particle size of carbon black was 0.5 μm.

  Subsequently, as shown in Table 2 below, urea, aluminum chloride, and xylene were mixed to prepare two types of plating solutions. As the xylene, a mixture of o-xylene, m-xylene, and p-xylene was used (manufactured by Wako Pure Chemical Industries).

These plating solutions were heated to 60 ° C., and electroplating (electrodeposition) of aluminum was performed on the urethane foam subjected to the conductive treatment prepared above. The plating conditions were such that a current density of 6.0 A / dm ² would flow in each plating solution while stirring the plating solution. Stirring was performed with a stirrer using a Teflon (registered trademark) rotor.

As a result, an aluminum film was formed on the entire surface of the urethane foam in a short time. The obtained aluminum film was glossy, mirror-like and very good in smoothness.
In addition, when the temperature of the urea plating bath was lower than 15 ° C., the current value that could be flowed was very small, and it took a very long time to cover the entire surface of the conductive foamed urethane with an aluminum film. .

[Example 2]
(Production of dimethylurea plating bath)
Dimethylurea, aluminum chloride (AlCl ₃ ), and xylene were mixed and liquefied in the molar ratios shown in Table 3 below. Electrochemical measurement was performed on the obtained plating solutions having respective ratios. Specifically, the value of the voltage necessary for applying a current density of 2.0 A / dm ² was measured. The temperature of each plating solution was 60 ° C.
As shown in Table 3, it was found that a plating solution having a mixing ratio of dimethylurea and aluminum chloride of 1: 1.15 in terms of molar ratio showed the lowest voltage value, and a high current density was obtained. Further, as the ratio of aluminum chloride increased from 1.15, the voltage value necessary to pass a current density of 2.0 A / dm ² gradually increased. That is, it was found that plating was most easily performed when the mixing ratio of dimethylurea and aluminum chloride was in the range of 1: 1.10 to 1: 1.50. A graph of the results in Table 3 is shown in FIG.

Note that the plating solution having a ratio of dimethylurea to aluminum chloride of 1: 1.00 does not have a current density of 2.0 A / dm ² even when a voltage of 16.00 V is applied, and a current of approximately 0.001 A flows. It was not in a state. That is, it was found that the plating reaction does not proceed with these plating solutions. Similarly, even when the ratio of aluminum chloride is 1.00 or less with respect to dimethylurea, it was confirmed that the liquid became liquid, but a sufficient current could not be passed, and the plating reaction could not proceed. There wasn't.
When the molar ratio of aluminum chloride was larger than 1.50 with respect to dimethylurea, aluminum chloride was precipitated in the plating solution and mixed in the aluminum film, and a good quality film could not be obtained.

(Aluminum plating on porous body)
The same urethane foam as in Example 1 was prepared, and subjected to a conductive treatment by carbon coating in the same manner as in Example 1.

  Subsequently, as shown in Table 4 below, dimethylurea, aluminum chloride, and xylene were mixed to prepare two types of plating solutions. As in Example 1, xylene was a mixture of three types of xylene isomers (manufactured by Wako Pure Chemical Industries).

These plating solutions were heated to 60 ° C., and electroplating (electrodeposition) of aluminum was performed on the urethane foam subjected to the conductive treatment prepared above. The plating conditions were such that a current density of 6.0 A / dm ² would flow in each plating solution while stirring the plating solution. Stirring was performed with a stirrer using a Teflon (registered trademark) rotor.

As a result, an aluminum film was formed on the entire surface of the urethane foam in a short time. The obtained aluminum film was glossy, mirror-like and excellent in smoothness.
When the temperature of the dimethylurea plating bath is lower than 15 ° C., the current value that can be flowed becomes very small, and it takes a very long time to cover the entire surface of the urethane foam subjected to the conductive treatment with the aluminum film. It was.

Claims (7)

  A method for producing an aluminum film, in which aluminum is electrodeposited on a resin subjected to a conductive treatment in a plating bath containing a urea compound, aluminum chloride, and xylene.   2. The method for producing an aluminum film according to claim 1, wherein in the plating bath, a molar ratio of the urea compound to the aluminum chloride is within a range of 1: 1.10 to 1: 1.50.   The method for producing an aluminum film according to claim 1, wherein the urea compound is urea or dimethylurea.   The method for producing an aluminum film according to any one of claims 1 to 3, wherein the xylene content in the plating bath is in the range of 5 mol% to 60 mol%.   The method for producing an aluminum film according to claim 1, wherein the resin is a porous body having a three-dimensional network structure.   The said resin is a polyurethane or a melamine resin, The manufacturing method of the aluminum film as described in any one of Claims 1-5.   The manufacturing method of the aluminum film as described in any one of Claims 1-6 which controls the temperature of the said plating bath to 15 to 60 degreeC.

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