U.S. patent application number 12/921912 was filed with the patent office on 2011-01-27 for process for producing composite material comprising resin molded product.
Invention is credited to Hironori Ota, Satoshi Yamamoto, Atsushi Yusa.
Application Number | 20110020550 12/921912 |
Document ID | / |
Family ID | 41065268 |
Filed Date | 2011-01-27 |
United States Patent
Application |
20110020550 |
Kind Code |
A1 |
Ota; Hironori ; et
al. |
January 27, 2011 |
PROCESS FOR PRODUCING COMPOSITE MATERIAL COMPRISING RESIN MOLDED
PRODUCT
Abstract
The present invention provides a method for allowing a metal
complex to stably penetrate into a polymer and immobilizing the
metal complex in the polymer by a low temperature treatment, in a
batch processing for a plating pre-treatment wherein the metal
complex is allowed to penetrate into the polymer with the use of
high-pressure carbon dioxide. In particular, the present invention
provides a method for producing a composite material containing a
resin molded product, characterized in that a reducing agent is
brought into contact with the resin molded product so as to allow
the reducing agent to penetrate into the resin molded product, and
in that high-pressure carbon dioxide having an organic metal
complex dissolved therein is brought into contact with the resin
molded product into which said reducing agent has penetrated, so as
to immobilize the organic metal complex in the resin molded product
by the reducing agent.
Inventors: |
Ota; Hironori; ( Osaka,
JP) ; Yusa; Atsushi; ( Osaka, JP) ; Yamamoto;
Satoshi; ( Osaka, JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
41065268 |
Appl. No.: |
12/921912 |
Filed: |
March 12, 2009 |
PCT Filed: |
March 12, 2009 |
PCT NO: |
PCT/JP2009/054729 |
371 Date: |
September 10, 2010 |
Current U.S.
Class: |
427/306 ;
427/304 |
Current CPC
Class: |
C23C 18/1651 20130101;
C23C 18/30 20130101; C23C 18/2073 20130101; C23C 18/1682 20130101;
C23C 18/31 20130101; C23C 18/1653 20130101; C08J 7/06 20130101;
C23C 18/1685 20130101 |
Class at
Publication: |
427/306 ;
427/304 |
International
Class: |
C23C 18/28 20060101
C23C018/28; C23C 18/54 20060101 C23C018/54; C23C 18/31 20060101
C23C018/31 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 12, 2008 |
JP |
2008-062767 |
Claims
1. A method for producing a composite material containing a resin
molded product, said method being characterized by comprising the
steps of bringing a reducing agent into contact with said resin
molded product to allow said reducing agent to penetrate into said
resin molded product, and bringing high-pressure carbon dioxide
having an organic metal complex dissolved therein, into contact
with said resin molded product into which said reducing agent had
penetrated, so as to immobilize said organic metal complex in said
resin molded product by said reducing agent.
2. The method according to claim 1, wherein said reducing agent is
removed from the surface layer of said resin molded product into
which said reducing agent had penetrated, and then, said resin
molded product is brought into contact with said high-pressure
carbon dioxide having said organic metal complex dissolved
therein.
3. The method according to claim 1, wherein said high-pressure
carbon dioxide having said organic metal complex dissolved therein
is brought into contact with said resin molded product under an
atmosphere at a temperature lower than a thermal reduction
temperature of said organic metal complex.
4. The method according to claim 1, wherein a plating film is
further formed on said resin molded product having said organic
metal complex immobilized therein, by an electroless plating method
with the use of high-pressure carbon dioxide.
5. The method according to claim 3, wherein, after the
immobilization of said organic metal complex, said resin molded
product is further heated at a temperature higher than the thermal
reduction temperature of said organic metal complex.
6. The method according to claim 5, wherein said treatment for
heating said resin molded product at the temperature higher than
the thermal reduction temperature of said organic metal complex is
carried out after said organic metal complex has been recovered
from a reaction system.
7. The method according to claim 5, wherein, after said treatment
for heating said resin molded product at the temperature higher
than the thermal reduction temperature of said organic metal
complex, a plating film is further formed on said resin molded
product by an electroless plating method with the use of
high-pressure carbon dioxide.
8. The method according to claim 1, wherein said reducing agent is
dissolved in a solvent and is then brought into contact with said
resin molded product.
9. The method according to claim 8, wherein said solvent contains
high-pressure carbon dioxide.
10. The method according to claim 8, wherein said solvent contains
water or an alcohol.
11. The method according to claim 1, wherein said organic metal
complex contains a fluorine atom.
12. The method according to claim 1, wherein said organic metal
complex contains at least one metal element selected from Pd, Pt,
Ni, Cu and Ag.
13. The method according to claim 1, wherein said high-pressure
carbon dioxide in which said organic metal complex is dissolved is
in a supercritical state.
Description
TECHNICAL FIELD
[0001] The present patent application is filed claiming the
priority of the Japanese patent application No. 2008-62767 (filed
on Mar. 12, 2008) of which the entire content is incorporated in
the present patent application by reference thereto.
[0002] The present invention relates to a method for producing a
composite material containing a resin molded product.
BACKGROUND OF THE INVENTION
[0003] Electorless plating is a conventionally known method for
forming a metal film on a resin molded product such as a polymer
member (i.e., a polymer molded product) at lower cost. In the
electroless plating, to ensure adhesion of a plating film, an
oxidizing agent such as a hexavalent chromic acid, permanganic acid
or the like is used to etch the surface of the polymer member as a
pre-treatment for electroless plating, to thereby roughen the
surface of the polymer member. However, the use of the oxidizing
agent such as hexavalent chromic acid or permanganic acid gives a
large burden on the environment.
[0004] Selection of a polymer to be dipped in such an etching
solution, i.e., a polymer applicable to electroless plating, is
limited to a part of polymers such as ABS, etc. This is because the
ABS contains a butadiene rubber component into which an etching
solution selectively penetrates to roughen the surface of a polymer
member, while other polymer materials contain only bits of
components to be selectively oxidized by such an etching solution,
with the result that obtained polymer members are hard to be
roughened at their surfaces. Therefore, polycarbonates as the
polymers other than ABS are mixed with ABS or elastomers to enable
electroless plating. Such mixtures are commercially available as
plating grades. However, polymer materials of such plating grades
unavoidably tend to deteriorate in their physical properties such
as decrease in heat resistance, as compared with their main
components alone. Therefore, such polymer materials are hard to be
used for molded products which are required to have heat
resistance.
[0005] As an alternate method of such a chemical pre-treatment
method, there hitherto has been proposed a surface-modifying method
with the use of high-pressure carbon dioxide such as supercritical
carbon dioxide or the like (cf. Patent Publication 1). Patent
Publication 1 discloses a batch processing (i.e., a discontinuous
treatment within a high-pressure vessel) in which a metal complex
is dissolved in high-pressure carbon dioxide, and in which the
high-pressure carbon dioxide having the metal complex dissolved
therein is brought into contact with a polymer member, so as to
allow the metal complex to penetrate into the surface of the
polymer member.
[0006] Patent Publication 2 discloses the following method: that
is, a metal complex allowed to penetrate into a polymer is reduced
by heating, so that the metal complex is metalized and immobilized
in the polymer, and this metal is caused to function as a catalyst
nucleus for plating.
[0007] The present inventors already have disclosed the method for
forming an electroless plating film with high adhesion to a polymer
member, by using an electroless plating solution mixed with
high-pressure carbon dioxide, after allowing a metal catalyst to
penetrate into the polymer by the use of high-pressure carbon
dioxide (Patent Publication 3). That is, the mixture of the
electroless plating solution with the high-pressure carbon dioxide
is allowed to penetrate into the polymer at such a low temperature
as does not cause a plating reaction, and then, the temperature of
the polymer is raised to a temperature at which a plating reaction
can take place. According to the present inventors' studies, it is
considered that a plating film with adhesion equal to or higher
than a film obtained by the conventional etching method can be
obtained, because the catalyst nucleus formed by thermal reduction
of the metal complex is previously allowed to penetrate into the
polymer, so that the electroless plating reaction can grow from the
inner portion of the polymer by making use of this catalyst
nucleus.
[0008] Patent Publication 1: JP-A-2001-316832
[0009] Patent Publication 2: JP-A-2007-56287
[0010] Patent Publication 3: Japanese Patent No. 3926835
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0011] As described above, the conventional plating method for
resin molded products requires the pre-treatment which may burden
the environment, and there is a limitation in selection of the
kinds of the polymer materials.
[0012] When the method for surface-modifying the polymer member
with the use of high-pressure carbon dioxide such as a
supercritical fluid, according to Patent Publication 1, is employed
to allow fine metal particles as a plating catalyst to penetrate
into the polymer member by batch processing, the fine metal
particles as the plating catalyst tend to be present on the surface
portion of the polymer member after the thermal reduction of the
fine metal particles.
[0013] In the meantime, as a result of the present inventors'
studies, it has been found that the use of a metal complex
containing a fluorine atom as a metal complex to be dissolved in
high-pressure carbon dioxide is effective for the pre-treatment
with the use of high-pressure carbon dioxide in a supercritical
state. The metal complex containing a fluorine atom has a higher
solubility in high-pressure carbon dioxide, so that it is possible
to increase the concentration of the metal complex in a
high-pressure vessel and to allow the metal complex to penetrate in
a high concentration, which leads to reduction of the
penetration-treating time. This will be described below in
detail.
[0014] For example, the solubility of an acetylacetonatopalladium
(II) complex, i.e., a metal complex containing no fluorine atom, in
a high-pressure liquid carbon dioxide (under an atmosphere at a
temperature of 40.degree. C. and a pressure of 15 MPa) is several
tens mg/L, which is a markedly low solubility. Therefore, 30
minutes to one hour or longer is required to allow this metal
complex to penetrate into the polymer in a high concentration.
Again, the thermal reduction of this metal complex requires a long
time because of the high thermal stability of the metal complex.
For the worse, the thermal reduction temperature is needed to be so
high as 200.degree. C. or higher.
[0015] In contrast, the solubility of a
hexafluoro-acetylacetonatopalladium (II) complex, i.e., a metal
complex containing a fluorine atom, in the same high-pressure
carbon dioxide is several tens g/L, which is 100 times hither than
the solubility of the former metal complex. Therefore, it is
possible to increase the concentration of the metal complex in a
high-pressure vessel in several minutes to several tens minutes, so
that the penetration time becomes shorter than that for the former
metal complex.
[0016] However, such a metal complex containing a fluorine atom is
low in affinity to a polymer member, despite its markedly high
solubility in high-pressure carbon dioxide. The metal complex
having penetrated into the polymer disadvantageously returns to the
high-pressure carbon dioxide side. Therefore, this metal complex
can not be immobilized as one expected, only by allowing the metal
complex to penetrate into the polymer, and thus, the concentration
of the metal complex in the polymer is hard to increase.
[0017] As a result of the present inventors' studies in order to
solve this problem, it becomes possible to increase the
concentration of the metal complex in the polymer by the following
method: the metal complex is allowed to penetrate into the polymer
and is immediately subjected to a thermal reduction treatment in
high-pressure carbon dioxide of a high temperature, to thereby
increase the concentration of the metal complex in the polymer. The
above-described metal complex containing a fluorine atom is low in
thermal stability and thus can be thermally decomposed and reduced
in perfect at a temperature of about 150.degree. C.
[0018] However, the metal complex is hard to be immobilized in the
polymer, if the thermal reduction is not carried out in the
high-pressure vessel for use in penetration of the metal complex.
The reasons therefor are described: firstly, the metal complex is
high in affinity to carbon dioxide, and when carbon dioxide is
discharged before the reduction treatment, the metal complex having
penetrated into the polymer is also discharged together with the
discharged carbon dioxide; and secondly, when the metal complex is
allowed to penetrate into the polymer with the use of high-pressure
carbon dioxide and the polymer is then taken out of the
high-pressure vessel and is subjected to a thermal or chemical
reduction treatment, the metal complex leaves the polymer before
this treatment.
[0019] The present inventors have intensively studied the
pre-treatment for plating by way of the batch processing with the
use of this high-pressure vessel. As a result, they have revealed
the following problems.
[0020] Firstly, when a plurality of polymer molded products are
treated at once in a single high-temperature vessel, a metal
complex tends to be thermally decomposed before it has penetrated
into the polymers, so that some of the molded products have
portions where the growth of plating films is poor and portions
where the adhesion strength of the plating films is poor. That is,
the molded products have variability in their qualilties.
[0021] Secondly, in case where the metal complex and carbon dioxide
are allowed to penetrate into the polymer at a low temperature and
then the temperature of the bath is raised to thermally decompose
and reduce the metal complex in the polymer, the above-described
variability in the qualities of the molded products can be
suppressed, while the metal complex in the high-pressure vessel is
not allowed to penetrate into the polymer molded products and is
entirely decomposed together with an excess of the metal complex
which does not penetrate into the polymer molded product but
retains in the vessel, with the result that the expensive metal
complex can not be recovered. In this regard, it is considered that
a reducing agent such as an alcohol may be introduced under high
pressure into the high-pressure vessel, instead of raising the
inner temperature of the bath. However, also in this case, an
excess of the metal complex which does not penetrate into the
molded products can not be recovered. In this way, only a part of
the metal complex fed into the high-pressure vessel is allowed to
penetrate into the polymer molded products. The conventional
reduction method is insufficient to recover the excess of the metal
complex, and the metal complex is thermally decomposed or reduced
in the vessel, which leads to a large loss, waste and significant
hindrance in commercial production.
[0022] Thirdly, in case where the above-described electroless
plating method with the use of high-pressure carbon dioxide is
employed for the above-described pre-treatment for plating with the
use of high-pressure carbon dioxide in a supercritical state, the
following problem is found to arise. That is, the metal complex is
allowed to penetrate into the molded products in the high-pressure
vessel, and then, this metal complex is thermally reduced,
metalized and immobilized in the molded products. In this case, the
metal complex is reduced and immobilized from the surface of the
resin molded product, so that the concentration of the fine metal
particles or the metal complex becomes higher toward the surface
layer of the resin molded product, as shown in FIG. 4(A). When a
plating solution mixed with high-pressure carbon dioxide is allowed
to penetrate into the polymer and a plating reaction is allowed to
take place from the inner portion of the polymer, the catalytic
activity of the surface layer of the polymer molded product becomes
higher, which makes it hard to grow a plating film from the
interior of the polymer. As schematically shown in FIG. 4(B), the
penetration depth of the plating film becomes shallow on some sites
of the molded product, and therefore, the adhesion strength of the
plating film, although it is high, is variable in its value.
[0023] The present invention is developed in order to solve the
foregoing problems. The first object of the present invention is to
provide a method for allowing a metal complex to reliably penetrate
into a polymer even by a low temperature treatment, and
immobilizing the metal complex therein, by a batch processing for a
pre-treatment for plating by which the metal complex is allowed to
penetrate into the polymer, using high-pressure carbon dioxide, and
to provide a method of pre-treatment for recovering an excess of
the metal complex from the high-pressure vessel.
[0024] The second object of the present invention is to provide a
method for improving and stabilizing an adhesion strength of a
plating film in an electroless plating method with the use of
high-pressure carbon dioxide, in which a plating reaction is caused
in the polymer.
Means for Solving the Problems
[0025] The present invention includes the following preferred
embodiments.
[0026] [1] A method for producing a composite material which
contains a resin molded product, and this method is characterized
by comprising the steps of
[0027] bringing a reducing agent into contact with the resin molded
product to allow the reducing agent to penetrate into the resin
molded product, and
[0028] bringing high-pressure carbon dioxide having an organic
metal complex dissolved therein, into contact with the resin molded
product into which the reducing agent has penetrated, to immobilize
the organic metal complex in the resin molded product by the
reducing agent.
[0029] [2] The method defined in the above item [1], wherein the
reducing agent is removed from the surface layer of the resin
molded product into which the reducing agent has penetrated, and
then, the resin molded product is brought into contact with the
high-pressure carbon dioxide having the organic metal complex
dissolved therein.
[0030] [3] method defined in the above item [1], wherein the
high-pressure carbon dioxide having the organic metal complex
dissolved therein is brought into contact with the resin molded
product under an atmosphere at a temperature lower than the thermal
reduction temperature of the organic metal complex.
[0031] [4] The method defined in the above item [1], wherein a
plating film is further formed on the resin molded product having
the organic metal complex immobilized therein, by an electroless
plating method with the use of high-pressure carbon dioxide.
[0032] [5] The method defined in the above item [3], wherein, after
the organic metal complex is immobilized, the resin molded product
is heated at a temperature higher than the thermal reduction
temperature of the organic metal complex.
[0033] [6] method defined in the above item [5], wherein the
treatment to heat the resin molded product at a temperature higher
than the thermal reduction temperature of the organic metal complex
is carried out after the organic metal complex is recovered from
the reaction system.
[0034] [7] The method defined in the above item [5], wherein a
plating film is further formed on the resin molded product by an
electroless plating method with the use of high-pressure carbon
dioxide, after the heat treatment at a temperature higher than the
thermal reduction temperature of the organic metal complex.
[0035] [8] The method defined in the above item [1], wherein the
reducing agent dissolved in a solvent is brought into contact with
the resin molded product.
[0036] [9] The method defined in the above item [8], wherein the
solvent contains high-pressure carbon dioxide.
[0037] [10] The method defined in the above item [8], wherein the
solvent contains water or an alcohol.
[0038] [11] The method defined in the above item [1], wherein the
organic metal complex contains a fluorine atom.
[0039] [12] The method defined in the above item [1], wherein the
organic metal complex contains at least one metal element selected
from Pd, Pt, Ni, Cu and Ag.
[0040] [13] The method defined in the above item [1], wherein the
high-pressure carbon dioxide having the organic metal complex
dissolved therein is in a supercritical state.
EFFECT OF THE INVENTION
[0041] Firstly, according to the present invention, in the batch
processing for the pre-treatment for plating in which the metal
complex is allowed to penetrate the polymer by the use of the
high-pressure carbon dioxide, the metal complex can be allowed to
reliably penetrate the polymer and can be immobilized therein by a
treatment even at a low temperature; and an excess of the metal
complex can be recovered from the high-pressure vessel. Secondly,
according to the present invention, the adhesion strength of the
resultant plating film can be improved and stabilized.
BRIEF DESCRIPTION OF THE DRAWINGS
[0042] FIG. 1 shows the steps of forming a plating film in
Examples.
[0043] FIG. 2 shows a schematic diagram of a high-pressure
apparatus used in Examples.
[0044] FIG. 3 shows the steps of forming a plating film in
Comparative Examples.
[0045] FIG. 4 shows the penetration state of fine metal particles
and the formation of a plating film in Comparative Examples.
[0046] FIG. 5 shows the penetration state of fine metal particles
and the formation of a plating film in Examples.
[0047] FIG. 6 schematically shows the distributions of the
concentrations of the fine metal particles in Examples and
Comparative Examples.
DESCRIPTION OF REFERENCE NUMERALS
[0048] 1: a resin material (or a resin molded product) [0049] 10: a
high-pressure apparatus [0050] 11: a carbon dioxide bomb [0051] 13:
a syringe pump [0052] 17: a second high-pressure vessel (or a
high-pressure vessel) [0053] 20: a first high-pressure vessel
[0054] 25: a separation recovering unit [0055] 26: a recovery tank
[0056] 51: fine metal particles [0057] 52: a plating film [0058]
61: a reducing agent
BEST MODES FOR CARRYING OUT THE INVENTION
[0059] A method for producing a composite material containing a
resin molded product, according to the present invention, is
characterized by comprising the steps of
[0060] bringing a reducing agent into contact with the resin molded
product so as to allow the reducing agent to penetrate into the
resin molded product; and
[0061] bringing the resin molded product into which the reducing
agent has penetrated, into contact with high-pressure carbon
dioxide having an organic metal complex dissolved therein, to
immobilize the organic metal complex in the resin molded product by
the reducing agent.
[0062] In the present invention, the organic metal complex which
has penetrated into the resin molded product is reduced with the
reducing agent which has previously penetrated into the resin
molded product, and is immobilized in the resin molded product.
Therefore, it is not needed to heat the organic metal complex up to
a temperature not lower than the thermal reduction temperature of
the organic metal complex, in order to immobilize the organic metal
complex in the resin molded product. That is, it is sufficient to
bring the above-described high-pressure carbon dioxide having the
organic metal complex dissolved therein, into contact with the
above-described resin molded product under an atmosphere at a
temperature lower than the thermal reduction temperature of the
organic metal complex. In contrast, when the organic metal complex
is immobilized by a thermal reduction reaction, it is needed to
heat the resin molded product up to a temperature at which the
thermal reduction reaction takes place, and to cool the resin
molded product to a normal temperature, with the result that the
throughput of the pre-treatment process is limited. For example, in
case of a resin molded product shaped by injection molding, the
resin molded product is caused to have a difference in residual
stress between its skin layer and its inner portion while being
shaped. Such a molded product, when heated and cooled, is likely to
foam or crack at its surface or inside. According to the present
invention, it becomes possible to solve these problems.
[0063] The resin molded product according to the present invention
is not limited, and it may be an optionally shaped resin material.
For example, the resin molded product is a resin material in the
form of a sheet, pipe or fibers shaped by extrusion molding,
injection molding or the like. The resin molded product in itself
may be a final molded product or an intermediate product in the
form of a sheet or the like to be fabricated later.
[0064] There is no particular limitation in selection of a resin
material for the above-described resin molded product, and any of
thermoplastic resins, thermosetting resins and photocurable resins
may be used. The kind of a thermoplastic resin, if used, may be
usually amorphous or crystalline, and it may be optionally
selected. Specific examples thereof include polyolefins such as
low-density polyethylene, high-density polyethylene, polypropylene
and poly-4-methylpentene-1; polyvinyls such as polyvinyl chloride,
polyvinyl alcohol and polyacrylonitrile; polyethers such as
polyoxymethylene and polyethylene oxide; and other polymeric
materials such as polyester, polyamide, polyimide, polymethyl
methacrylate, polysulfone, polycarbonate and polylactic acid.
Further examples thereof include aromatic polyesters such as
polyethylene terephthalate; aromatic amides such as
polyterephthalamide; and fluoropolymers such as
polytetrafluoroethylene. Examples of the thermosetting resin
include epoxy resins, phenol resins, polyimide, polyurethane,
silicone resins, etc. Examples of the photocurable resin include
photosensitive epoxy resins, photosensitive acrylic resins,
photosensitive polyimide, etc. There may be used any of these resin
materials which contains a filler such as glass fibers, carbon
fibers, an inorganic compound, a ceramic or the like.
[0065] [Reducing Agent Penetration Step]
[0066] The method of the present invention firstly comprises a step
of bringing a reducing agent into contact with the above-described
resin molded product to thereby allow the reducing agent to
penetrate into the resin molded product.
[0067] While the kind of the reducing agent to be used in the
present invention may be optionally selected, there may be used, as
the reducing agent, for example, dimethylamine borane, hydrazine,
formaldehyde, sodium boron hydride, hypophosphorous acid, sodium
hypophosphite or the like. Such a solid reducing agent, if used, is
dissolved in a solvent such as water or an alcohol to prepare a
solution thereof, and the resin molded product is immersed in this
solution to thereby allow the reducing agent to penetrate into the
resin. To improve the penetration of the reducing agent into the
resin molded product, a ultrasonic wave may be applied to the
solution, or the solution may be warmed, or the pH of the solution
may be controlled in accordance with the kind of the reducing
agent. For example, when sodium boron hydride is used as the
reducing agent, desirably, a solution thereof is adjusted in pH to
be alkaline. When sodium hypophosphite is used, desirably, a
solution thereof is adjusted in pH to be neutral or acidic. When
the reducing agent is used in the form of an aqueous solution
thereof, a solvent with a low surface tension, such as ethanol, may
be mixed with the aqueous solution, or an additive such as sodium
lauryl sulfate may be dissolved in the aqueous solution, so as to
decrease the surface tension of the aqueous solution and to
facilitate the penetration thereof. This step may be carried out
under stirring.
[0068] There is no limitation in selection of the solvent for use
in dissolving of the reducing agent. For example, there may be used
water; alcohols such as methanol, ethanol, isopropanol, butanol and
ethylene glycol; ethers such as diethyl ether and tetrahydrofuran
(THF); hexane; benzene; acetone; toluene; etc., among which water
and alcohols such as ethanol are preferable. The concentration of
the reducing agent to be dissolved in the solvent is not limited,
and an optimal concentration thereof may be variable in accordance
with the kinds of the reducing agent, the solvent and the resin
into which the reducing agent penetrates. In an embodiment of the
present invention, the concentration of the reducing agent is, for
example, from 0.5 to 15% by weight, preferably from 1 to 10% by
weight, when sodium hypophosphite is used as the reducing agent,
and water, as the solvent.
[0069] There also may be used, as the reducing agent, an alcohol,
polyalkylene glycol, phenol or the like, each having a hydroxyl
group which exhibits a reducing action. Particularly, the use of
ethanol is preferable, since ethanol is low in surface tension and
is easy to penetrate into the resin. Examples of the alcohol
include methanol, ethanol, isopropanol, butanol, ethylene glycol,
2-methoxyethanol, 2-ethoxyethanol, 1-methoxy-2-propanol,
1-ethoxy-2-propanol, 1,3-butanediol, etc. The use of a high
molecular-weight polyalkylene glycol such as polyethylene glycol or
the like is effective to inhibit the reducing agent from leaving
the inner portion of the resin and to inhibit elimination of the
effect of the reducing agent.
[0070] In the present invention, two or more selected from the
above materials may be used in combination.
[0071] When the resin molded product is immersed in the reducing
agent or the solvent containing the same to thereby allow the
reducing agent to penetrate into the resin molded product, treating
conditions such as a treating temperature (or a liquid
temperature), a treating pressure, application or non-application
of a ultrasonic wave, pH, etc. are not limited, and optimal
conditions may be variable in accordance with the kinds of the
reducing agent, the solvent and the resin material.
[0072] In an embodiment of the present invention, the treating
temperature (or the liquid temperature) is, for example, from 30 to
150.degree. C., preferably from 60 to 100.degree. C.; and the pH of
the reducing agent or the solvent containing the reducing agent is,
for example, from 3 to 11, preferably from 5 to 9.
[0073] Preferably, this step is carried out under an atmospheric of
a normal pressure, from the viewpoint of productivity, etc. The
normal pressure herein referred to means a non-pressurized
atmosphere.
[0074] Again, in the present invention, the reducing agent or the
solution thereof in the solvent is mixed with (or dissolved in) a
high-pressure fluid to thereby improve the penetration of the
reducing agent. The use of high-pressure carbon dioxide or carbon
dioxide in a super-critical state (hereinafter optionally referred
to as "supercritical carbon dioxide") as the high-pressure fluid is
particularly effective to swell the surface of the resin and to
allow the reducing agent to deeply penetrate into the resin.
[0075] In the present invention, "high-pressure carbon dioxide"
means not only supercritical carbon dioxide but also a liquid
carbon dioxide and a carbon dioxide gas, obtained by highly
pressurizing carbon dioxide. For example, there is given a carbon
dioxide gas formed under a pressure of 5 MPa or higher, preferably
7.1 MPa or higher, at 20.degree. C. or higher, preferably
31.degree. C. or higher.
[0076] While there is no limitation in selection of the upper
limits of the temperature and pressure of the high-pressure carbon
dioxide, the upper limits thereof may be determined by the
capability of a reaction vessel to be used. For example, in case of
the high-pressure vessel used in Examples, the use of high-pressure
carbon dioxide with a temperature of 200.degree. C. or lower and a
pressure of 30 MPa or lower is desirable.
[0077] In this regard, carbon dioxide is put in a supercritical
state at 31.degree. C. or higher under a pressure of 7.1 MPa or
higher.
[0078] The treatment to allow the reducing agent to penetrate into
the resin molded product by the use of high-pressure carbon dioxide
is conducted as follows: for example, the resin molded product is
immersed in the reducing agent or the solution thereof in the
solvent in the high-pressure vessel; and then, the high-pressure
vessel is filled with high-pressure carbon dioxide. In this case,
it is considered that the high-pressure carbon dioxide swells the
resin molded product, which makes it possible for the solution
containing the reducing agent to penetrate into the resin molded
product.
[0079] A temperature for the treatment with the use of the
high-pressure carbon dioxide is, for example, from 20 to
200.degree. C., preferably from 31 to 100.degree. C.; and a
pressure therefor is, for example, from 5 to 30 MPa, preferably
from 7.1 to 20 MPa.
[0080] A treating time for the reducing agent penetration step is
not limited, and a time during which the reducing agent can
sufficiently penetrate into the resin molded product is enough for
this treating time. An optimal treating time may be variable
according to the kinds of the reducing agent, the solvent therefor
and the resin material, the treating temperature, the treating
pressure and application or non-application of a ultrasonic wave.
In an embodiment of the present invention, the treating time is,
for example, from 3 minutes to 3 hours, preferably from 15 minutes
to 1.5 hours.
[0081] This step may be carried out under stirring.
[0082] [Organic Metal Complex-Immobilization Step]
[0083] The method of the present invention includes a step of
bringing the above-described resin molded product into which the
reducing agent has penetrated, into contact with high-pressure
carbon dioxide having the above-described organic metal complex
dissolved therein, thereby immobilizing the organic metal complex
in the resin molded product by the above-described reducing
agent.
[0084] Preferable as the organic metal complex to be used in the
present invention is a material which contains at least one metal
element selected from Pd, Pt, Ni, Cu and Ag, any of which has a
certain solubility in high-pressure carbon dioxide and functions as
a plating catalyst. Examples of the organic metal complex include
bis(cyclopentadienyl)nickel, bis(acetylacetonato)palladium (II),
dimethyl(cyclooctadienyl)platinum (II),
hexafluoroacetylacetonatopalladium (II),
hexafluoroacetylacetonatohydrate copper (II),
hexafluoroacetylacetonatoplatinum (II),
hexafluoroacetylacetonato(trimethylphosphine)silver (I),
dimethyl(heptafluorooctanedionate)silver (AgFOD), etc.
[0085] Among the above-described organic metal complexes, an
organic metal complex containing a fluorine atom, that is, an
organic metal complex having a fluorine atom at its ligand, is
preferable in the present invention. The organic metal complex
containing a fluorine atom is well dissolved in carbon dioxide and
thus can be dissolved in high-pressure carbon dioxide at a high
concentration and is then brought into contact with the resin
molded product. The organic metal complex containing a fluorine
atom is hard to penetrate into the resin molded product. However, a
high concentration of the organic metal complex can be allowed to
penetrate into the resin molded product and can be efficiently
immobilized in the resin molded product, because the reducing agent
has previously penetrated into the resin molded product.
[0086] In this step, desirably, the high-pressure carbon dioxide
and the organic metal complex are formed into a homogeneous phase
by using a stirrer or the like.
[0087] Again, in this step, supercritical carbon dioxide may be
preferably used as the high-pressure carbon dioxide.
[0088] A treating temperature and a treating pressure in this step
are not limited, and an optimal treating temperature and an optimal
treating pressure may be variable according to the kinds of the
organic metal complex and the resin molded product, the treating
time, etc. In an embodiment of the present invention, the treating
temperature is, for example, from 20 to 200.degree. C., preferably
from 31 to 100.degree. C.; and the treating pressure is, for
example, from 5 to 30 MPa, preferably from 7.1 to 20 MPa.
[0089] Again, the treating temperature and the treating pressure in
this step desirably should satisfy the supercritical conditions for
carbon dioxide (31.degree. C. or higher and 7.1 MPa or higher), and
the treating temperature should not allow the organic metal complex
to be thermally reduced. Under such conditions, if in a
supercritical state, the organic metal complex decreases in its
surface tension and thus becomes easy to penetrate into the resin
molded product. Since the temperature does not allow the organic
metal complex to be thermally reduced, the organic metal complex
which does not penetrate into the resin molded product and remains
in the reaction system is not decomposed and thus can be recovered
and recycled. Further, it becomes possible to prevent the
concentration of the organic metal complex or the fine particles of
the reduced metal from increasing in the proximity of the surface
of the resin molded product, so that the metal complex or the fine
metal particles can more deeply penetrate into the resin molded
product. Consequently, it can be expected that the adhesion
strength of the resultant plating film will be improved, as will be
described later.
[0090] The upper limits of the treating temperature and the
treating pressure may be selected in accordance with the capability
of the reaction vessel to be used. For example, in case of the
high-pressure vessel used in Examples, desirably, the treating
temperature and the treating pressure should be 200.degree. C. or
lower and 30 MPa or lower, respectively, in order to ensure the
tight sealing of the reaction vessel.
[0091] The thermal reduction temperature of the organic metal
complex in the present invention indicates a temperature to which
the organic metal complex is heated to be thermally reduced. That
is, the thermal reduction temperature is the same as a temperature
at which the organic metal complex starts to thermally
decompose.
[0092] The organic metal complex decomposes when thermally reduced,
so that the metal atoms are liberated. The organic metal complex is
a polymer, and the metal atoms which are liberated in the polymer
are instable, with the result that several metal atoms collect to
form a cluster so as to be stabilized. On the other hand, the
ligand forming the organic metal complex is dissolved in
supercritical carbon dioxide and thus is not immobilized in the
resin molded product, leaving the resin molded product during a
degassing operation.
[0093] In this regard, the thermal reduction temperature (or the
thermal decomposition-starting temperature) of the organic metal
complex in the present invention is defined as a temperature at
which the mass of the organic metal complex starts to decrease,
when measured with a differential scanning calorimeter (DSC).
[0094] In the present invention, desirably, the treating
temperature in this step is controlled to a temperature 10.degree.
C. or more higher than the thermal decomposition-starting
temperature of the organic metal complex in an air or a nitrogen
atmosphere, wherein the thermal decomposition-starting temperature
of the organic metal complex is previously measured with a
differential scanning calorimeter (DSC). When the heat resistant
temperature of the organic metal complex is high, desirably, the
organic metal complex is subjected to a high-pressure treatment
under an atmosphere at such a temperature that the reducing agent
previously having penetrated into the resin molded product does not
deteriorate, sublime or boil. For example, when
hexafluoroacetylacetonatopalladium (II) is used as the organic
metal complex, the treating temperature may be set at 63.degree. C.
or lower, for example, 50.degree. C., since the thermal
decomposition-starting temperature of this metal complex is about
73.degree. C. or higher under a nitrogen atmosphere.
[0095] The treating time in this step is not limited, so long as
the organic metal complex can sufficiently penetrate into the resin
molded product. An optimal treating time may be variable according
to the kinds of the organic metal complex and the resin molded
product, the treating temperature, the treating pressure, etc. In
an embodiment of the present invention, the treating time is, for
example, from 5 minutes to 3 hours, preferably from 15 minutes to
1.5 hours.
[0096] In this step, the concentration of the organic metal complex
in the high-pressure carbon dioxide is not limited. An optimal
concentration of the organic metal complex may be variable
according to the kind of the organic metal complex, etc. In an
embodiment of the present invention, the concentration of the
organic metal complex is, for example, 100 mg/L or more, preferably
1,000 mg/L or more. Again, the upper limit of the concentration of
the organic metal complex is not limited, and the upper limit
thereof may be a saturated concentration of the organic metal
complex relative to the high-pressure carbon dioxide.
[0097] In the method of the present invention, the resin molded
product into which the reducing agent has penetrated may be brought
into contact with the above-described high-pressure carbon dioxide
having the organic metal complex dissolved therein, after the
reducing agent has been removed from the surface layer of the resin
molded product. By this treatment, the reducing agent not only
simply penetrates into the resin molded product, but also, the
reducing agent penetrates into the resin molded product while the
reducing agent in the surface layer of the resin molded product is
removed. Therefore, the organic metal complex can be immobilized at
portions deeper inside from the surface layer of the resin molded
product. Consequently, the metal complex can be allowed to reliably
penetrate into the polymer and can be immobilized by the treatment
at a relatively low temperature.
[0098] In this regard, the surface layer herein referred to means,
for example, a surface portion with a depth of 50 mm or less from
the surface of the resin molded product. Within this range of
depth, a plating film is formed, when the resin molded product is
brought into contact with the organic metal complex without
removing the reducing agent and is further subjected to an
electroless plating. This plating film as a whole is poor in
adhesion to the resin molded product, having variability in its
adhesion degree to every site of the resin molded product.
[0099] The removal of the reducing agent from the surface layer of
the resin molded product may be confirmed based on a decrease in
the amount of the organic metal complex which has penetrated into,
at least, the surface layer of the resin molded product. Desirably,
the organic metal complex which has penetrated into the surface
layer of the resin molded product is decreased so that the amount
(or concentration) of the residual organic metal complex in the
surface layer can be smaller than that in a deeper site of the
resin molded product, or so that the amount (or concentration) of
the organic metal complex per a predetermined depth unit can be
maximal (or a peak) at a deeper site of the resin molded product
than the surface layer thereof.
[0100] This is described in detail. By positively removing the
reducing agent from the surface layer of the resin molded product,
the reduction reaction of the metal complex selectively takes place
only at the inner portion of the resin molded product, and the
metal complex is immobilized therein. Because of the low
concentration of the reducing agent in the surface layer of the
resin molded product, the metal complex is hard to be reduced in
the surface layer, while the metal complex is easily reduced in the
inner portion of the resin molded product where the concentration
of the reducing agent is higher. As a result, the concentration of
the dispersed metal complex in the inner portion of the resin
molded product becomes higher than that in the surface layer
thereof. For this reason, as will be described later, a plating
film is hard to grow at the surface layer of the resin molded
product, and the plating film is easy to reliably grow in the inner
portion thereof, when a plating reaction is allowed to take place
in the inner portion of the resin molded product by electroless
plating with the use of high-pressure carbon dioxide. Therefore,
the adhesion and stability of the resultant plating film is
improved.
[0101] The treatment for removing the reducing agent from the
surface layer of the resin molded product is made, for example, by
rinsing the resin molded product into which the reducing agent has
penetrated, with water within a predetermined time, or by blowing
an air onto the same resin molded product within a predetermined
time. By doing so, the reducing agent can be removed from the
surface layer of the resin molded product. That is, a part of the
reducing agent which has penetrated into the resin molded product
can be removed. Particularly when the reducing agent is an alcohol
or the like which is easy to volatilize, such a reducing agent can
be removed from the surface layer of the resin molded product, only
by exposing the resin molded product to an air within a
predetermined time.
[0102] [Thermal Reduction Step for Organic Metal Complex]
[0103] Again, in the method of the present invention, the
above-described resin molded product may be further heated at a
temperature higher than the thermal reduction temperature of the
organic metal complex, after the organic metal complex has been
immobilized, and before an electroless plating treatment as will be
described later. When the resin molded product is heated at a
temperature higher than the thermal reduction temperature of the
organic metal complex after the immobilization of the organic metal
complex in the deep site of the resin molded product inside the
surface layer thereof as described above, the organic metal complex
moves toward the side of the surface, so that the concentration of
the organic metal complex can be increased in the deep site inside
the surface layer of the resin molded product. Accordingly, the
amount of the catalyst nuclei in the deep site of the resin molded
product inside the surface layer thereof is increased, in
comparison with the amount of the catalyst nuclei in the just
previous step without the pre-treatment (or an anneal treatment) by
heating. As a result, the adhesion degree of the resultant plating
film to the resin molded product further can be improved. Since the
organic metal complex is present at a higher concentration in a
site with a predetermined depth in the resin molded product, the
plating film can stably grow from this predetermined depth, and
thus, stability in the adhesion degree of this plating film can be
further improved.
[0104] Why the adhesion of the plating film is improved by this
heat treatment is not clearly known. However, the following
mechanism is considered to work. In case where an electroless
plating film is grown from the inner portion of a resin molded
product of a thermoplastic resin or the like by the use of
high-pressure carbon dioxide, it is known that a depth of from 50
to 200 nm or less, more preferably from 50 to about 100 nm, is
appropriate for a plating solution to penetrate into the resin
molded product. It is considered that too large a plating solution
penetration depth increases the swelling of the uppermost surface
of the resin molded product and increases a stress thereto, which
leads to a decrease in the strength of the resin molded product.
Therefore, the penetration depth of the metal complex or the fine
metal particles is appropriately from 50 to 200 nm from the surface
of the resin molded product. However, in some of actual penetration
treatments, the metal complex or the fine metal particles tend to
penetrate into the resin molded product to a depth of 1 .mu.m or
more.
[0105] It is considered that, by the heat treatment under such a
situation, the fine metal particles which deeply penetrate into the
resin molded product and which are incompatible with the resin
molded product collect on a region with an appropriate depth in the
inner portion in the proximity of the surface of the resin molded
product, and that such collection of the fine metal particles may
contribute to improvement of a plating reactivity in the inner
portion of the resin molded product. It is also considered that
there may remain the metal complex which deeply penetrates into the
resin molded product, since this metal complex is not reacted with
the reducing agent and is not discharged from the surface of the
resin molded product, together with the discharge of the
high-pressure carbon dioxide under reduced pressure, thus remaining
in the deep site of the resin molded product. In either case, it is
considered that the metal complex tends to bleed out to the surface
of the molded product by the thermal reduction treatment, and
therefore that the fine metal particles tend to collect at a region
with an appropriate depth in the proximity of the surface of the
resin molded product.
[0106] A treating temperature for this heat treatment is not
limited, so long as this temperature is higher than the thermal
reduction temperature for the organic metal complex to be used. For
example, when hexafluoroacetylacetonato-palladium (II) of which the
thermal decomposition-starting temperature is 73.degree. C. is used
as the organic metal complex, the treating temperature is, for
example, 73.degree. C. or higher, preferably 100.degree. C. or
higher. The upper limit of the treating temperature may be variable
according to the kind of the resin, since the resin molded product
tends to deform when the treating temperature is far higher than
the glass transition temperature (Tg) of the resin.
[0107] A treating time for the heat treatment is not limited, as
long as the thermal reduction of the organic metal complex can be
sufficiently carried out. An optimal treating time may be variable
according to the kind of the organic metal complex to be used, the
treating temperature, etc. In an embodiment of the present
invention, the treating time is, for example, from 0.5 to 100
hours, preferably from 1 to 50 hours.
[0108] In the method of the present invention, the treatment for
heating the resin molded product having the organic metal complex
immobilized therein, up to a temperature higher than the thermal
reduction temperature of the organic metal complex is preferably
carried out after the organic metal complex has been recovered from
the reaction system. By doing so, the organic metal complex which
does not penetrate into the resin molded product can be recovered
as it is, in a non-reduced state. The recovered organic metal
complex may be recycled.
[0109] [Plating Film-Forming Step]
[0110] In the method of the present invention, an electroless
plating method with the use of high-pressure carbon dioxide may be
further employed to form a plating film on the resin molded product
having the organic metal complex immobilized therein, or on the
resin molded product after the heat treatment thereof at a
temperature higher than the thermal reduction temperature of the
organic metal complex.
[0111] In this regard, the electroless plating method herein
referred to means a method for depositing a metal film in the
proximity of the surface of a substrate having a catalytic
activity, by using a reducing agent, without using an external
electric supply.
[0112] When the electroless plating method with the use of
high-pressure carbon dioxide is employed, a plating film is grown
from the organic metal complex immobilized at a deep site inside
the surface layer of the resin molded product, so that the
resultant plating film is adhered to the resin molded product with
a high adhesion. In addition, no plating film is grown from the
surface layer of the resin molded product, since the organic metal
complex is absent or a little in amount if present, on the surface
layer of the resin molded product. Therefore, the adhesion of the
plating film is kept stable at a high value.
[0113] In contrast, for example, when a plating film is formed on a
resin molded product to which an organic metal complex is simply
added, by the electroless plating method with the use of
high-pressure carbon dioxide, the temperature of the resin molded
product is raised from the surface thereof toward the inside
thereof with a temperature gradient kept, and a plating film is
grown from the organic metal complex present at a high
concentration in the surface layer of the resin molded product,
since the organic metal complex is present at a higher
concentration on the surface of the resin molded product than the
inner portion thereof. Therefore, the adhesion of the plating film
to the resin molded product can not be improved. The surface layer
of the resin molded product includes a portion where the plating
film is grown from a site on the surface and a portion where the
plating film is grown from a site on the inner portion of the
surface, so that the plating film has portions with lower adhesion,
and this adhesion is instable.
[0114] In the electroless plating method with the use of
high-pressure carbon dioxide, according to the present invention,
there may be used any of the known electroless plating solutions
for use in the electroless plating methods: for example, an acidic
electroless plating solution such as a Ni--P plating solution
(e.g., Nicoron DK, etc. manufactured by OKUNO CHEMICAL INDUSTIRES
CO., LTD.) or the like may be used. The use of a plating solution
reactive with a neutral or alkaline substance is unsuitable, since
such a plating solution is oxidized with high-pressure carbon
dioxide.
[0115] The above-described electroless plating solution optionally
may be diluted with water or an alcohol for use. While the
electroless plating solution contains water as a main component, an
alcohol may be mixed therewith to make it easy to stably mix the
plating solution with high-pressure carbon dioxide. The surface
tension of the electroless plating solution admixed with an alcohol
becomes markedly lower because of the lower surface tension of the
alcohol than water, so that the plating solution is easier to
penetrate into the resin molded product. In general, to prepare an
electroless plating solution, a stock solution for the electroless
plating solution is diluted with water in a component ratio
recommended by a manufacturer. Further mixing of an alcohol with
water in an optional ratio makes it possible to prepare a stable
electroless plating solution which is uniformlay compatible with
high-pressure carbon dioxide. While a volume ratio of an alcohol to
water may be optionally selected, it is preferable to add 10 to 80%
of the alcohol relative to water, from the viewpoint of the
stability of the electroless plating solution.
[0116] The alcohol for use in the electroless plating solution may
be optionally selected. For example, there are given methanol,
ethernol, n-propanol, isopropanol, butanol, heptanol, ethylene
glycol, diethylene glycol, 2-methoxyethanol, 2-ethoxyethanol,
1-methoxy-2-propanol, 1-ethoxy-2-propanol, n,n-butanediol,
tert-butylalcohol, 2-(2-ethoxyethoxy)ethanol, 1-propoxy-2-propanol,
2(2-methoxypropoxy)propanol, 2(2-butoxyethoxy)ethanol,
3-methoxy-1-butanol, 2-methyl-2,4-pentanediol, etc., among which
ethanol, 2-methoxyethanol and 1,3-butanediol are preferable.
[0117] The electroless plating solution may contain publicly known
additives. For example, the electroless plating solution may
contain a complexing agent which forms a stable soluble complex
with a metal ion in the electroless plating solution, such as
citric acid, acetic acid, succinic acid, lactic acid or the like.
Again, the electroless plating solution may contain a stabilizer
such as a sulfur compound (e.g., a thiourea, etc.), lead ion, a
brightener or a wetting agent (or a surfactant).
[0118] In this step, as the high-pressure carbon dioxide,
supercritical carbon dioxide (with a temperature of 31.degree. C.
or higher and with a pressure of 7.1 MPa or higher) is preferably
used.
[0119] Preferably, a treating temperature and a treating pressure
for this step are so controlled as to satisfy critical conditions
for carbon dioxide and to cause formation of a plating film. In
particular, an optimal treating temperature may be variable
according to the kind of the plating solution to be used.
[0120] In an embodiment of the present invention, the treating
temperature is, for example, from 50 to 95.degree. C., preferably
from 70 to 90.degree. C., and the treating pressure is, for
example, from 5 to 30 MPa, preferably from 7.1 to 20 MPa.
[0121] There is no limitation in selection of the treating time in
this step, so long as a plating film can be sufficiently formed on
the resin molded product. An optimal treating time may be variable
according to the kind of the electroless plating solution, the
treating temperature, the treating pressure, etc. In an embodiment
of the present invention, the treating time is, for example, from 5
minutes to 3 hours, preferably from 15 minutes to 1.5 hours.
[0122] Again, this step may be carried out under stirring.
EXAMPLES
[0123] Hereinafter, Examples of the method for producing a
composite material containing the resin molded product of the
present invention will be described in detail, while the scope of
the present invention is not limited to the following Examples in
any way.
Example 1
[0124] In this Example, a predetermined high-pressure apparatus was
used in a pre-treatment for plating, so as to dissolve a reducing
agent and an organic metal complex in a high-pressure fluid and to
bring the resulting solution into contact with a resin material. In
this Example, carbon dioxide was used as the high-pressure fluid.
Firstly, the high-pressure apparatus used in this Example will be
described.
[0125] FIG. 2 shows a schematic diagram of the high-pressure
apparatus 10 for use in the pre-treatment for plating and
electroless plating according to the embodiment of the present
invention.
[0126] As shown in FIG. 2, the high-pressure apparatus 10 includes
a first high-pressure vessel 20 for holding a resin material (or a
resin molded product) 1; a liquid carbon dioxide bomb 11 for
storing carbon dioxide to be fed to the first high-pressure vessel
20; a syringe pump 13 for pressurizing carbon dioxide; a second
high-pressure vessel 17 for storing an organic metal complex; a
separation-recovering unit 25 for separating and recovering the
organic metal complex dissolved in high-pressure carbon dioxide;
and a recovery container 26 for receiving the recovered organic
metal complex. Again, as seen in FIG. 2, there are disposed, at
appropriate sites among the respective constitutive elements of the
high-pressure apparatus 10, valves 12, 16, 18, 19 and 27, pressure
gauges 14 and 22, a check valve 15 and a back pressure valve 24,
for use in control of a pressure and flowing of the high-pressure
carbon dioxide.
[0127] The first high-pressure vessel 20 can be cooled by a
cartridge heater (not shown) and a cooling circuit (not shown), and
the vessel 20 has a strength high enough to withstand a high
pressure from a supercritical carbon dioxide. The second
high-pressure vessel 17 also has a strength high enough to
withstand the high pressure from the supercritical carbon
dioxide.
[0128] Accordingly, it is possible to feed, to the first
high-pressure vessel 20, a solvent mixture of a reducing agent or a
solvent containing the reducing agent with high-pressure carbon
dioxide, and a solvent mixture of the organic metal complex with
high-pressure carbon dioxide. Again, the first high-pressure vessel
20 may be filled with an electroless plating solution.
[0129] In this Example, as the reducing agent, there was used a
solvent mixture of ethylene glycol with ethanol; as the resin
material 1, there was used a substrate of 70 mm in length, 15 mm in
width and 1 mm in thickness, which was formed of polyamide 6 (PA6)
mixed with 10% of glass fibers; and as the organic metal complex,
there was used hexafluoroacetylacetonatopalladium (II) containing a
plating catalyst Pd. A nickel-phosphorus film as a plating film was
formed by electroless plating with the use of high-pressure carbon
dioxide, and a nickel film was further formed on this film by
electrolytic plating.
[0130] In this Example, this plating film was formed on the surface
of the resin material 1, following the steps shown in FIG. 1.
[0131] Firstly, a liquid mixture of ethanol (100 mL) with ethylene
glycol (100 mL) was prepared and was charged together with the
resin material 1 into the first high-pressure vessel 20 with an
inner volume of 300 mL. The first high-pressure vessel 20 was
controlled in temperature at 80.degree. C. in a sealed state. Next,
a liquid carbon dioxide fed from the liquid carbon dioxide bomb 11
was pressurized with the syringe pump (260D manufactured by ISCO)
13 until the pressure gauge 14 indicated 15 MPa. Thus,
supercritical carbon dioxide was provided. Then, the manual needle
valve 19 was opened through the check valve 15 to raise the inner
pressure of the first high-pressure vessel 20 up to 15 MPa, to
thereby fill the first high-pressure vessel 20 with the
supercritical carbon dioxide. The manual needle valve 19 was closed
after the pressure had been raised. The inner pressure of the first
high-pressure vessel 20 was maintained for 60 minutes during which
the supercritical carbon dioxide was brought into contact with the
resin material 1 so as to allow ethanol and ethylene glycol to
penetrate into the resin material 1 (Step S21 on FIG. 1).
[0132] Next, the manual needle valve 23 was opened, and the back
pressure valve 24 was also opened, to open the first high-pressure
vessel 20 to an air. Next, the resin material 1 and the solvent
mixture of ethanol with ethylene glycol were removed from the first
high-pressure vessel 20; the resin material 1 was washed with water
and was then dried at a normal temperature in an air until ethanol
and ethylene glycol adhered to the surface of the resin material 1
was vaporized. Thus, out of the reducing agent which had penetrated
into the resin material 1, the reducing agent in the surface layer
(or a site on the uppermost surface) of the resin material 1 could
be removed from the resin material 1.
[0133] Next, the dried resin material 1 was charged in the first
high-pressure vessel 20, and the first high-pressure vessel 20 was
then sealed, while the organic metal complex (100 mg) was charged
in the second high-pressure vessel 17 with an inner volume of 100
mL, and the second high-pressure vessel 17 was then sealed and
controlled at 50.degree. C. Next, the liquid carbon dioxide fed
from the liquid carbon dioxide bomb 11 was pressurized with the
syringe pump 13 until the pressure gauge 14 indicated 15 MPa. Thus,
supercritical carbon dioxide was provided. Next, the manual needle
valve 16 was opened through the check valve 15, and the inner
pressure of the second high-pressure vessel 17 was raised to 15 MPa
to thereby dissolve the organic metal complex in the supercritical
carbon dioxide. Next, the manual needle valve 18 was opened, and
the supercritical carbon dioxide containing the organic metal
complex was brought into contact with the resin material 1 for 45
minutes to thereby allow the organic metal complex to penetrate
into the resin material 1 (Step S22 on FIG. 1)
[0134] In this Example, the solvent mixture in the first
high-pressure vessel 20 was always stirred with a stirrer 21.
[0135] The inner temperature of the first high-pressure vessel 20
which included the metal complex dissolved in the high-pressure
carbon dioxide so as to be brought into contact with the resin
material 1 was set at 50.degree. C. This temperature was 10.degree.
C. or more lower than a thermal decomposition-starting temperature
of about 73.degree. C. or higher of
hexafluoroacetyl-acetonatopalladium (II) used as the organic metal
complex under a nitrogen atmosphere.
[0136] After the organic metal complex had penetrated into the
resin material 1, the manual needle valve 23 was opened, and the
back pressure valve 24 was further opened to thereby open the first
high-pressure vessel 20 to an air through the separation-recovering
unit 25, and then, the resin material 1 was taken out. The organic
metal complex separated from the carbon dioxide was recovered in
the recovery container 26. The amount of the recovered metal
complex is shown in Table 1 below.
[0137] In this Example, after the organic metal complex had
penetrated into the resin material 1, the resin material 1 into
which the catalyst penetrated was subjected to a heat treatment at
150.degree. C. in an air for one hour. Thus, the resin material 1
used in this Example was pre-treated for plating as described
above.
[0138] Next, an electroless plating film was formed on the
pre-treated resin material 1 (Step S23 on FIG. 1). In this Example,
as a stock solution for an electroless plating solution, there was
used Nicoron DK manufactured by OKUNO CHEMICAL INDUSTRIES CO.,
LTD., which contained a metal salt of nickel sulfate, a reducing
agent and a complexing agent. In this Example, the electroless
plating solution was mixed with water and ethanol.
[0139] In the plating film-forming step, firstly, the resin
material 1 and the above-described Ni--P electroless plating
solution were charged and sealed in the first high-pressure vessel
20 shown in FIG. 2. The temperatures of the first high-pressure
vessel 20 and the Ni--P electroless plating solution were
controlled at 50.degree. C. which was lower than a plating reaction
temperature (from 70 to 85.degree. C.) Under these conditions, no
plating film was grown on the surface of the resin material 1,
since the resin material 1 was in contact with the electroless
plating solution of a temperature lower than the plating reaction
temperature (at which no plating reaction took place).
[0140] Next, high-pressure carbon dioxide was introduced into the
first high-pressure vessel 20 controlled at the low temperature
which permitted no plating reaction. In this Example, supercritical
carbon dioxide was used as the high-pressure carbon dioxide.
Concretely, the liquid carbon dioxide fed from the liquid carbon
dioxide bomb 11 was pressurized with the syringe pump 13 (260D
manufactured by ISCO) until the pressure gauge 14 indicated 15 MPa,
to provide the supercritical carbon dioxide. The manual needle
valve 19 was opened through the check valve 15 to raise the inner
pressure of the first high-pressure vessel 20 up to 15 MPa, to
thereby fill the first high-pressure vessel 20 with the
supercritical carbon dioxide, which was then brought into contact
with the resin material 1.
[0141] Next, the temperature of the first high-pressure vessel 20
was raised to 85.degree. C. to cause a plating reaction in the
first high-pressure vessel 20. As a result, an electroless plating
reaction took place on the surface of the resin material 1 to form
a plating film. According to this plating film-forming method, the
electroless plating solution had penetrated into the fine metal
particles present in the inner portion of the resin material 1 as
described above, and therefore, the plating film was grown by using
the fine metal particles as catalyst nuclei, which were present not
only in the surface of the resin material 1 but also in the inner
portion thereof. That is, in the plating film-forming method of
this Example, the plating film was grown in the inner portion with
a free volume of the resin material 1, so that the plating film
with high adhesion could be formed while being deeply rooted into
the inner portion of the resin material 1.
[0142] After completion of the plating, the manual needle valve 23
was opened, and the back pressure valve 24 was opened, to discharge
the carbon dioxide from the first high-pressure vessel 20. Then,
the first high-pressure vessel 20 was opened to take out the resin
material 1 therefrom. Next, the resin material 1 taken out of the
first high-pressure vessel 20 was dried for a while, so as to be
degassed to remove the carbon dioxide and the electroless plating
solution from the inner portion of the resin material 1.
[0143] Next, the resin material 1 was subjected to electroless
plating and electrolytic plating under a normal pressure (Step S24
on FIG. 1). Firstly, the oxidized surface of the plating film on
the resin material 1 was activated with hydrochloric acid. After
that, a conventional electroless nickel-phosphorus plating solution
was used in an air for electroless plating under a normal pressure,
to thereby deposit a plating film with a thickness of 1 .mu.m on
the resin material. Then, a conventional electrolytic plating
method was employed in an air to deposit a nickel film with a
thickness of 40 .mu.m by using as an electrode the plating film
formed by the electroless plating method. Thus, the entire surface
of the resin material 1 was coated with a metal film by the
above-described method.
Comparative Example 1
[0144] In this Comparative Example, a plating film was formed on
the surface of a resin material 1 by the steps shown in FIG. 3. In
this Comparative Example, a reducing agent was brought into contact
with the resin material 1, but the step of allowing the reducing
agent to penetrate into the resin material (Step S21 on FIG. 1) was
not carried out. The plating film was formed on the surface of the
resin material 1 in the same manners as in Example 1, except for
this point.
[0145] However, the plating film was hardly formed on the resin
material 1 in a step of carrying out electroless plating with the
use of high-pressure carbon dioxide (Step S32 on FIG. 3). This is
considered as follows: because of the low compatibility of the
metal complex to the resin material, the metal complex, although
once penetrated into the resin material, was discharged
simultaneously with the discharge of the high-pressure carbon
dioxide, and thus, most of the metal complex could not be retained
in the resin material 1.
Comparative Example 2
[0146] In this Comparative Example, supercritical carbon dioxide in
which an organic metal complex containing a plating catalyst was
dissolved was brought into contact with a resin material 1, and the
temperature of the high-pressure vessel 20 for use in penetration
was set at 150.degree. C. Except for these, a plating film was
formed on the surface of the resin material 1 by the same treatment
as in Comparative Example 1. Thus, the entire surface of the resin
material 1 was coated with a metal film.
Example 2
[0147] In this Example, a plating film was formed on a resin
material 1 by the same steps shown in FIG. 1, as well as Example 1.
However, the heat treatment carried out in Example 1 was omitted,
after the treatment (Step S22 on FIG. 1) wherein supercritical
carbon dioxide in which an organic metal complex containing a
plating catalyst was dissolved was brought into contact with the
resin material 1 to allow the supercritical carbon dioxide to
penetrate into the resin material; and instead, the resin material
1 was dried in an air at a normal temperature for one hour. After
that, plating films were formed (Steps S23 and S24 on FIG. 1).
Thus, the entire surface of the resin material 1 was coated with a
metal film.
Example 3
[0148] In this Example, a plating film was formed on a resin
material 1 by the steps shown in FIG. 1, as well as Example 1.
However, the step of bringing a reducing agent into contact with a
resin material to allow the reducing agent to penetrate into the
resin material (Step S21 on FIG. 1) was carried out in an air
without using the high-pressure apparatus shown in FIG. 2. In
concrete, the resin material 1 was charged in a sealed vessel (not
shown) containing a mixture of ethanol (100 mL) with ethylene
glycol (100 mL), which was then subjected to a ultrasonic wave at
80.degree. C. under a normal pressure for 60 minutes; and then, the
resin material 1 was taken out and was dried until ethanol and
ethylene glycol on the surface thereof were vaporized. Except for
these, plating films were formed on the resin material 1 in the
same manners as in Example 1 (Steps S22 to S24 on FIG. 1). Thus,
the entire surface of the resin material 1 was coated with a metal
film.
Example 4
[0149] In this Example, a plating film was formed on the surface of
a resin material by the same method as in Example 3. However,
instead of the mixture of ethanol (100 mL) with ethylene glycol
(100 mL), a solution of sodium hypophosphite (500 mg) in ethanol
(100 mL) and water (100 mL) was used. Thus, the entire surface of
the resin material 1 was coated with a metal film.
Example 5
[0150] In this Example, a plating film was formed on the surface of
a resin material 1 by the same steps shown in FIG. 1, as well as
Example 3. However, instead of the mixture of ethanol (100 mL) with
ethylene glycol (100 mL), a mixture of 2-methoxyethanol (90 mL),
water (90 mL) and hypophosphorous acid (20 mL) was used. Except for
these, the entire surface of the resin material 1 was coated with a
metal film in the same manner as in Example 3.
Example 6
[0151] In this Example, a plating film was formed on the surface of
a resin material 1 by the same steps shown in FIG. 1, as well as
Example 1. However, ethanol was used as a reducing agent in the
step of bringing the reducing agent into contact with the resin
material 1 to thereby allow the reducing agent to penetrate into
the resin material (Step S21 on FIG. 1). The ethanol (10 mL) was
charged in the second high-pressure vessel 17 set at 80.degree. C.
to form a gaseous mixture of supercritical carbon dioxide with the
ethanol by opening the manual needle valve 16 while the manual
needle valve 19 being closed. After that, the manual needle valve
18 was opened to feed this gaseous mixture into the first
high-pressure vessel 20 including the resin material 1, so as to
bring the gaseous mixture into contact with the resin material 1.
Except for these, the plating films were formed on the resin
material 1 in the same manner as in Example 1 (Steps S22 to S24 on
FIG. 1). Thus, the entire surface of the resin material 1 was
coated with a metal film.
[0152] The qualities of the plating films of Examples 1 to 6 and
Comparative Examples 1 and 2 were evaluated. As the items for
quality evaluation, an environmental test and evaluation of
adhesion were conducted. As conditions for the environmental test,
the temperature and humidity were set at 80.degree. C. and 80%,
respectively; the time was set at 100 hours; and each 10 plated
resin materials were used. The evaluation of adhesion was conducted
as follows: the tensile strengths of each 10 plated resin materials
were measured with a tensile tester (AGS-J 100N manufactured by
SHIMADZU CORPORATION) (according to JIS H8630). The results thereof
are shown in Table 1, together with the evaluation of the external
appearances of the plating films and the amounts of the recovered
organic metal complexes. The tensile strengths are shown as the
minimum values, maximum values and average values of each 10 plated
resin materials. In this regard, the target value for a tensile
strength of a plating film with the use of an ABS resin by the
conventional etching method was 10 N/cm or higher.
TABLE-US-00001 TABLE 1 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 C. Ex. 1
C. Ex. 2 External .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. X .largecircle.
appearance Environmental .circleincircle. .circleincircle.
.circleincircle. .circleincircle. .circleincircle. .circleincircle.
-- .DELTA. test Tensile Minimum 18-25 10-15 14-21 17-23 19-27 12-19
-- 6-20 strength Maximum [N/cm] Average 21 12 17 20 23 15 -- 12
Amount of recovered 71 75 73 70 74 73 85 0 organic metal complex
[mg] (charged amount: 100 mg) External Appearance: .largecircle.
means that a plating film was formed without any problem and
without any defect in its external appearance. .DELTA. means that a
plating film was formed without any problem, however, peeling or
swelling was observed in a part of the plating film. X means that a
plating film was incomplete in some portions thereof, or no plating
film was formed. Environmental Test: .circleincircle. means that,
after the test, no peeling or swelling was observed in all of 10
plating films. .DELTA. means that, after the test, swelling was
observed in one or more plating films, however, no peeling was
observed in all of the plating films. X means that, after the test,
peeling and swelling were observed in one or more plating
films.
[0153] It was known from the results of Table 1 that the plating
films formed in Examples 1 to 6 had sufficient adhesion strengths
with quite no problem in practical use thereof. On the other hand,
the plating film of Comparative Example 1 was not successfully
formed, since the step of bringing the reducing agent into contact
with the resin material 1 so as to allow the reducing agent to
penetrate into the resin material 1 (Step S21 on FIG. 1) was not
carried out. It is known from this fact that, because of the
reducing agent allowed to penetrate into the resin material 1, the
organic metal complex was reduced to form fine metal particles
which functioned as the plating catalyst nuclei and were
immobilized in the resin material 1, in each of Examples 1 to
6.
[0154] As compared with the plating film formed by the conventional
method in Comparative Example 2, the variabilities in the tensile
strengths of the plating films formed in Examples 1 to 6 were found
to be smaller, and their average values were found to be larger.
Again in comparison with Comparative Example 2 wherein quite no
organic metal complex could be recovered, the organic metal
complexes could be recovered in Examples 1 to 6.
[0155] This is considered as follows. In Comparative Example 2, the
organic metal complex was allowed to penetrate into the resin
material 1 by the thermal reduction and was immobilized in the
resin material 1, in the first high-pressure vessel 20. Therefore,
as shown in FIG. 4(A), the concentration of the fine metal
particles or the metal complex 51 became higher toward the
uppermost surface of the resin material 1, with the result that, as
shown in FIG. 4(B), the catalytic activity was higher at the
uppermost surface thereof, and the plating film was hard to grow
from the inner portion of the resin material 1, when the plating
solution mixed with the high-pressure carbon dioxide was allowed to
penetrate into the resin material 1 and then the plating reaction
was caused from the inner portion of the resin material 1. In FIG.
4, numeral 51 refers to the fine metal particles or the metal
complex; and numeral 52, to the plating film.
[0156] On the other hand, in each of Examples 1 to 6, the organic
metal complex 51 was allowed to penetrate into the resin material 1
in the first high-pressure vessel 20, at a temperature at which the
organic metal complex 51 was not thermally reduced, and then, the
organic metal complex 51 was reduced with the reducing agent 61
which had previously penetrated into the resin material, and thus
was metalized and immobilized in the resin material, as shown in
FIG. 5(A). Therefore, as shown in FIG. 5(B), the concentration of
the fine metal particles or the metal complex 51 was higher in a
deep site away from the surface of the resin material, as compared
with the conventional method. Therefore, the plating film 52 was
grown from the inner portion of the resin material 1, as shown in
FIG. 5(C), in comparison with the conventional method, when the
plating solution mixed with the high-pressure carbon dioxide was
allowed to penetrate into the resin material 1 so as to cause the
plating reaction. Consequently, the adhesion strength of the
plating film was improved, and variability in the adhesion strength
was smaller.
[0157] The adhesion strength of the plating film of Example 1 which
had been subjected to the heat treatment as follows was known to be
higher than that of Example 2 from the results of Table 1: after
the supercritical carbon dioxide in which the organic metal complex
containing the plating catalyst had been dissolved was brought into
contact with the resin material 1 and was allowed to penetrate into
the resin material 1, the thermoplastic resin into which the
catalyst penetrated was subjected to the heat treatment at
150.degree. C. in an air for one hour in Example 1, while such a
thermoplastic resin was not subjected to any heat treatment but was
dried at a normal temperature in an air for one hour in Example 2.
It could be understood from this fact that the steps of bringing
the supercritical carbon dioxide in which the organic metal complex
containing the plating catalyst had been dissolved, into contact
with the resin material, so as to allow such supercritical carbon
dioxide to penetrate into the resin material 1, and then carrying
out the additional reduction treatment (or the thermal reduction in
Example 1) are effective to improve the adhesion strength of the
plating film.
[0158] FIG. 6, consisting of FIGS. 6(A), 6(B) and 6(C), shows the
graphs which quantitatively illustrate the distributions of the
concentrations of the fine metal particles in the resin materials
1, respectively. FIG. 6(A) shows the distribution of the
concentrations of the fine metal particles in Comparative Example
2, wherein the distributions of the concentration of the fine metal
particles was maximum at the surface layer of the resin material.
In this case, the plating solution was present at a high density on
the surface layer and was grown by the use of the activated fine
metal particles as the catalyst nuclei, so that the plating film as
shown in FIG. 4(B) was formed. In contrast, FIG. 6(B) shows the
distribution of the concentrations of the fine metal particles
found when the metal complex was allowed to penetrate after the
reducing agent had been removed from the surface layer of the resin
material, and it was found that the distributions of the
concentration of the fine metal particles was maximum at a deeper
site than the surface layer thereof. In this case, the plating
solution was allowed to more deeply penetrate into the resin
material from the surface layer thereof, and was grown from such
fine metal particles, so that the plating film as shown in FIG.
5(C) was formed.
[0159] FIG. 6(C) shows the distribution of the concentrations of
the fine metal particles found when the metal complex was allowed
to penetrate after the reducing agent was removed from the surface
layer of the resin material, and when such a resin material was
further subjected to the heat treatment. The concentration of the
fine metal particles was maximum at a deeper site than the surface
layer thereof, as well as that shown in FIG. 6(B). In addition, the
fine metal particles were decreased in number at the deep site, and
the fine metal particles were increased in number at a deep portion
where the concentration of the fine metal particles was maximum, as
compared with FIG. 6(B). Therefore, the plating film shown in FIG.
6(C) was grown from far more fine metal particles present at an
appropriate depth, as compared with the plating film shown in FIG.
6(B), so that the adhesion strength of this plating film was
improved.
INDUSTRIAL APPLICABILITY
[0160] According to the method for producing the composite material
containing the resin molded product of the present invention, a
plating film with a higher adhesion strength and with stability in
the high adhesion strength can be formed on the resin molded
product. When such a plating film is formed with the use of
high-pressure carbon dioxide by a batch processing, this method can
be preferably employed in order to improve the production stability
and the quality of plating films and to achieve lower running
cost.
* * * * *