Method of recovering valuable substances from printed circuit board

In a method of grinding a printed circuit board, a printed circuit board having various parts mounted thereon, or a residual ground product produced in the manufacturing process for the boards, and recovering valuable substances by separating the ground product into a portion containing a large amount of metal component such as copper and a portion consisting a resin, a filler material, and the like through a separation step, the separation step includes a specific gravity separation step of separating the ground product into a portion containing a large amount of substance having a high specific gravity and a portion containing a large amount of substance having a low specific gravity, and an electrostatic separation step of separating the ground product into a portion having a large amount of conductor and a portion containing large amount of insulator. The grinding step includes a coarse grinding step and a fine grinding step.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a method of grinding printed circuit 
boards and printed circuit boards having parts mounted thereon, which are 
used for electric devices, and residual molded portions such as frame 
members produced in the manufacturing processes for these boards, and 
separating and recovering the ground products into metals such as copper 
and other components such as resins and filler materials through a 
separation step including a specific gravity separation step and an 
electrostatic separation step. 
2. Description of the Prior Art 
As a conventional method of recycling printed circuit boards consisting of 
filler materials, resins, and metals as main components and printed 
circuit boards having electronic parts mounted thereon (to be referred to 
as parts-mounted boards hereinafter), a method of recovering thermal 
energy by incinerating these boards has been put into practice. As a 
method of recovering valuable substances from composite materials such as 
printed circuit boards, a method of separating and recovering valuable 
substances such as copper from these composite materials after heating and 
carbonizing resin components in the materials is available (Japanese 
Patent Laid-Open No. 2-88725). In addition, a reclamation method is 
disclosed in Japanese Patent Laid-Open No. 63-276509. In this method, a 
waste composite material consisting of a resin and a metal is ground after 
it is cooled to a temperature below the brittle temperature of the resin, 
and the metal and the resin are separated by using magnetic force. 
In the conventional recycling method and valuable substance recovery method 
of processing printed circuit boards and parts-mounted boards by 
incineration and carbonization, since various waste gases are produced, 
advanced waste gas processing facilities must be installed. Furthermore, 
valuable substances contained in printed circuit boards and parts-mounted 
boards tend to be oxidized. As a result, the additional values in recovery 
may decrease. As another recycling method, a method of etching copper and 
the like on parts-mounted boards may be employed. This method, however, is 
not practical because large-scale facilities are required for drainage and 
recovery of copper. In the reclamation method for a waste composite 
material consisting of a resin and a metal, disclosed in Japanese Patent 
Laid-Open No. 63-276509, the following problems are posed. First, large 
refrigeration facilities which consume great energy are required. Second, 
in this technique, since a metal and a resin are separated from each other 
by using magnetic force, a nonmagnetic metal such as copper or aluminum 
cannot be separated and recovered. 
As described above, establishment of a method of separating/recovering 
valuable substances such as metals from printed circuit boards and 
parts-mounted boards, and residual molded portions produced in the 
manufacturing processes for these boards has been an important subject. 
SUMMARY OF THE INVENTION 
The present invention has been made in consideration of the above 
situation, and has as its object to provide a method of recovering 
valuable substances from printed circuit boards and printed circuit boards 
having electronic parts mounted thereon. 
In order to achieve the above object, according to the first aspect of the 
present invention, there is provided a method of recovering valuable 
substances from a printed circuit board, wherein a printed circuit board, 
a parts-mounted board having various parts mounted thereon, or a residual 
molded portion produced in a manufacturing process for the boards is 
ground, and valuable substances are recovered by separating an obtained 
ground product into a portion containing a large amount of metal such as 
copper and a portion consisting of a resin, a filler material, and the 
like through a separation step, the separation step including the specific 
gravity separation step of separating the ground product into a portion 
containing a large amount of substance having a high specific gravity and 
a portion containing a large amount of substance having a low specific 
gravity, and the electrostatic separation step of separating the ground 
product into a portion containing a large amount of conductor and a 
portion containing a large amount of insulator. 
According to the second aspect of the present invention, there is provided 
a method of recovering valuable substances from a printed circuit board, 
wherein a printed circuit board, a parts-mounted board having various 
parts mounted thereon, or a residual molded portion produced in a 
manufacturing process for the boards is ground, and valuable substances 
are recovered by separating an obtained ground product into a portion 
containing a large amount of metal such as copper and a portion consisting 
of a resin, a filler material, and the like through a separation step, the 
separation step including the specific gravity separation step of 
separating the ground product into a portion containing a large amount of 
substance having a high specific gravity and a portion containing a large 
amount of substance having a low specific gravity, and the electrostatic 
separation step of separating the portion containing a large amount of 
substance having a high specific gravity which portion is separated by the 
specific gravity separation step into a portion containing a large amount 
of conductor and a portion containing a large amount of insulator. 
According to the third aspect of the present invention, there is provided a 
method of recovering valuable substances from a printed circuit board, 
comprising the coarse grinding step of coarsely grinding a printed circuit 
board, a printed circuit board having various parts mounted thereon, or a 
residual molded portion produced in a manufacturing process for the 
boards, the fine grinding step of finely grinding a coarse ground product 
obtained by the coarse grinding step, and the separation step of 
separating the fine ground product obtained by the fine grinding step into 
a portion containing a large amount of metal component such as copper and 
a portion consisting of a resin, a filler material, or the like, wherein 
the fine grinding step includes the fine grinding step of finely grinding 
the coarse ground product by applying external forces including 
compressing and shearing forces thereto, and the separation step includes 
the specific gravity separation step of separating the ground product into 
a portion containing a large amount of substance having a high specific 
gravity and a portion containing a large amount of substance having a low 
specific gravity, and the electrostatic separation step of separating the 
fine ground product into a portion containing a large amount of conductor 
and a portion containing a large amount of insulator. 
According to the fourth aspect of the present invention, there is provided 
a method of recovering valuable substances from a printed circuit board, 
comprising the coarse grinding step of coarsely grinding a printed circuit 
board, a printed circuit board having various parts mounted thereon, or a 
residual molded portion produced in a manufacturing process for the 
boards, the fine grinding step of finely grinding a coarse ground product 
obtained by the coarse grinding step, and the separation step of 
separating the fine ground product obtained by the fine grinding step into 
a portion containing a large amount of metal component such as copper and 
a portion consisting of a resin, a filler material, or the like, wherein 
the fine grinding step includes the fine grinding step of finely grinding 
the coarse ground product by applying external forces including 
compressing and shearing forces thereto, and the separation step includes 
the specific gravity separation step of separating the ground product into 
a portion containing a large amount of substance having a high specific 
gravity and a portion containing a large amount of substance having a low 
specific gravity, and the electrostatic separation step of separating the 
portion having a large amount of substance having a high specific gravity 
which portion is separated by the specific gravity separation step into a 
portion containing a large amount of conductor and a portion containing a 
large amount of insulator. 
The average particle sizes of a ground product and a fine ground product 
obtained in the grinding step and the fine grinding step according to the 
second and third aspects of the present are not less than 0.03 mm and less 
than 1.0 mm. 
The printed circuit board, the parts-mounted board, or the residual molded 
portion produced in the manufacturing process for the boards in the 
present invention is normally used for an electric device. The printed 
circuit board consists of a resin component, a filler material, and a 
metal component such as a circuit. Examples of the resin include epoxy 
resins, phenolic resins, polyimide resins, or the like. Examples of the 
filler material include glass fiber, paper, carbon fiber, or the like. 
Examples of the metal include copper, aluminum, iron, nickel, solder (tin 
and lead), or the like. The parts-mounted board is a board obtained by 
mounting electronic parts such as IC packages on the above printed circuit 
board. Note that the parts-mounted board includes a board obtained by 
removing some or all of the electronic parts from a printed circuit board. 
The residual molded portion includes a frame member produced in the 
process of manufacturing a printed circuit board, a defective copperclad 
prepreg, thermoset portions of these members, and the like. The residual 
molded portion consists of almost the same components as those of a 
printed circuit board as a product. 
The present invention is constituted by the grinding step of grinding a 
printed circuit board, a printed circuit board having parts mounted 
thereon, or a residual molded portion produced in the manufacturing 
process for the boards, and the separation step including the specific 
gravity separation step and the electrostatic separation step and serving 
to separate/recover the obtained ground product into a metal component and 
other components such as a resin and a filler material. Although the 
specific gravity separation step and the electrostatic separation step are 
indispensable to the separation step, other separation steps may be 
included before or after these steps. 
In the fine grinding step in the present invention, a grinder having a 
grinding mechanism for finely grinding a substance (to be ground) by 
applying external forces including compressing and shearing forces thereto 
is used. For example, a grinder having a mechanism for clamping a 
substance (to be ground) between a groove portion formed in a rotating 
grinding table in the circumferential direction and a hydraulically 
pressed grinding roller, and grinding the substance by applying external 
forces including compressing and shearing forces is preferably used. In 
addition, in order to obtain a ground product having an optimal particle 
size for separation through the fine grinding step, a grinder having a 
powder recovery mechanism capable of controlling the particle size during 
a fine grinding step is preferable. As this powder recovery mechanism, a 
powder recovery mechanism including the step of blowing a fine ground 
product upward with an air current and the step of recovering only a fine 
ground product having a predetermined particle size or less is 
exemplified. A powder recovery mechanism which has a mechanism for blowing 
upward a ground product above the grinding mechanism with an air current, 
and a mechanism, arranged above the grinding mechanism, for recovering 
only a ground product having a predetermined particle size or less by 
rotating a plurality of classification blades is preferably used. In the 
fine grinding step in the present invention, a grinder having the above 
grinding mechanism and powder recovery mechanism is preferably used. As 
this grinder, for example, a grinder (to be referred to as a roller mill 
with a rotating blade type classification unit hereinafter) available from 
Ishikawajima-Harima Heavy Industries Co., Ltd. is available, which has a 
classification unit arranged above a roller mill and including a mechanism 
for recovering only a ground product having a predetermined particle size 
or less by rotating a rotating shaft having a plurality of classification 
blades. 
FIG. 1 is a partially sectional front view schematically showing an 
embodiment of the above roller mill with a rotating blade type 
classification unit. This roller mill comprises a charge pipe 6 which is 
arranged on a side wall portion of a body casing 2 and into which a 
substance 4 to be ground is charged, a grinding table 12 which is rotated 
by a motor 8 and has a groove portion 10 in the circumferential direction, 
a plurality of grinding rollers 14 hydraulically pressed against the 
groove portion 10, an air supply port 18 and a blowing nozzle 20 to which 
air 16 for producing an ascending air current in the casing 2 is supplied, 
a rotating shaft 24 having a plurality of classification blades 22 
arranged above the grinding rollers 14 (these members 18, 20, 22, and 24 
constitute the classification unit), and a discharge pipe 26 for 
discharging only a ground product having a predetermined particle size or 
less to the outside. Note that the discharge pipe 26 may serve as an air 
suction port to always draw air. 
In this roller mill with the rotating blade type classification unit, first 
of all, the grinding table 12 is rotated, and the grinding rollers 14 are 
hydraulically pressed against the grinding table 12. The substance 4 is 
ground between the groove portion 10 on the grinding roller 12 and the 
grinding rollers 14, and the ground product flows to the outer periphery 
of the grinding table 12. The ground product carried by an air current 
ascending from the outer periphery of the grinding table 12 is classified 
by the classification unit above the table and extracted together with the 
air current. A coarse ground product having a predetermined particle size 
or more is returned to the grinding table 12 and repeatedly ground 
together with the substance 4. 
In the fine grinding step described above, the roller mill incorporating 
the rotating blade type classification unit is used. However, this fine 
grinding step may use a grinding method of a closed circuit scheme, in 
which a rotating blade type classification unit is arranged outside a 
general roller mill. 
The separation step in the present invention uses a specific gravity 
separator for separating a ground product into a portion containing a 
large amount of substance having a high specific gravity, e.g., a metal, 
and a portion containing a large amount of substance having a low specific 
gravity, e.g., a resin or a filler material, and an electrostatic 
separator for separating a ground product into a portion containing a 
large amount of conductor and a portion containing a large amount of 
insulator such as a resin or a filler material. As the specific gravity 
separator, for example, a classification unit for performing 
classification by means of circulation of an air current (to be referred 
to as an air current centrifugal classification unit hereinafter) or a 
classification unit for performing classification by means of mechanical 
rotation of a classification rotor (to be referred to as a rotation 
centrifugal classification unit hereinafter) is preferably used. As the 
electrostatic separator, for example, an electrostatic classification unit 
using both static electricity and corona discharge (to be referred to as a 
composite type electrostatic classification unit hereinafter) is 
preferably used. 
In the separation step according to the second and fourth aspects of the 
present invention, first of all, a ground product of a printed circuit 
board or parts-mounted board is separated into a ground product containing 
a large amount of metal having a high specific gravity such as copper and 
a ground product consisting of a substance having a low specific gravity 
such as a resin or filler material through the specific gravity separation 
step. Subsequently, the ground product containing a large amount of 
substance having a high specific gravity, obtained through the specific 
gravity separation step, is separated into a ground product containing a 
large amount of metal as a conductor such as copper and a ground product 
containing a large amount of insulator such as a resin or filler material. 
Note that if the ground product consisting of a resin, a filler material, 
or the like, separated through the electrostatic separation step, is 
returned to the specific gravity separation step after it is ground to a 
predetermined particle size again, the metal separation efficiency can be 
improved. 
If a printed circuit board is finely ground by applying external forces 
including compressing and shearing forces to the board in the fine 
grinding step in the present invention, a metal such as copper is not 
easily ground finely, and a resin, a filler material, or the like is 
easily ground finely, as compared with the fine grinding step using a 
grinder having a grinding mechanism other than that described above. 
Therefore, according to the separation step in the present invention, a 
printed circuit board can be separated into a portion containing a metal 
such as copper at a very high content and a portion consisting of a resin, 
a filler material, or the like containing almost no metal. In addition, in 
the fine grinding step in the present invention, the wear resistance and 
the durability of the apparatus are much higher than those in the fine 
grinding step using a grinder having a grinding mechanism other than that 
described above. 
In the separation step in the present invention, if the average particle 
size of a fine ground product of a printed circuit board or a 
parts-mounted board is excessively large, a metal such as copper and a 
resin do not peel from each other at this interface sufficiently. As a 
result, the separation ratio between the metal and other components 
decreases. In contrast to this, if the average particle size is 
excessively small, a metal is ground to an excessively fine powder. As a 
result, the difference in physical property between a metal as a conductor 
having a high specific gravity and a resin or filler material as an 
insulator having a low specific gravity does not effectively work for 
separation, resulting in a decrease in separation ratio. For this reason, 
the average particle size of a fine ground product of a printed circuit 
board or partsmounted board is preferably set to be equal to or larger 
than 0.03 mm (30 .mu.m) and less than 1.0 mm (1,000 .mu.m). 
When a ground product of a printed circuit board or parts-mounted board is 
separated through the above separation step, a ground product containing a 
large amount of metal such as copper and a ground product containing a 
large amount of resin or filler material such as glass fiber can be 
separated/recovered. Especially, by grinding a printed circuit board or 
the like through the coarse grinding step and the fine grinding step, 
separation/recovery can be efficiently performed. 
A metal such as copper separated in this manner has not oxidized unlike a 
metal separated by incineration. Therefore, such a metal can be used as a 
metal resource having a high additional value. The remaining ground 
product of a resin or a filler material such as glass fiber contains 
almost no metal such as copper as an impurity. For this reason, such a 
ground product can be effectively used as a filler material for a 
building, structural material, or the like. 
The above and other advantages, features and additional objects of the 
present invention will become manifest to those versed in the art upon 
making reference to the following detailed description and accompanying 
drawings in which preferred embodiments incorporating the principle of the 
present invention are shown by way of illustrative example.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
The present invention will be described below with reference to several 
preferred embodiments. 
As samples, the following boards were used: a printed circuit board 
(composition: 30 wt % copper; 20 wt % glass fiber; 50 wt % epoxy) 
consisting of glass-fiber reinforced epoxy (to be abbreviated to glass 
epoxy hereinafter) and having a copper pattern; a board obtained by 
applying a solder on the copper pattern of the above printed circuit 
board; a printed circuit board (composition: 30 wt % copper; 20 wt % 
paper; 50 wt % phenolic resin) consisting of paper-phenolic resin (to be 
abbreviated to paper phenol hereinafter) and having a copper pattern; and 
a board obtained by mounting electronic parts such as IC packages and 
connectors on the above glass epoxy board having the copper pattern (to be 
abbreviated to a parts-mounted board; composition: 33 wt % copper, and 
other components such as epoxy, glass fiber, and silica). Each board was 
ground to a predetermined particle size by a shear and impact grinder, and 
the ground product having undergone the grinding step was used in a 
separation step in the present invention. The weight of each sample used 
was 10 kg. As the shear and impact grinder, a hammer mill for grinding a 
substance by using a rotating hammer, a bed knife in a chamber, and a 
screen at a discharge portion, or a disk mill for grinding a substance by 
using pins or grooves of opposing rotating disks is available. 
Tables 1 to 3 show Examples 1 to 9 associated with the first and second 
aspects of the present invention. Table 4 shows Comparative Examples 1 and 
2. Each table shows the conditions for grinding and separation, the copper 
content of a powder containing a large amount of copper (to be referred to 
as a copper-rich powder hereinafter) which is finally obtained through a 
grinding step and a separation step, and the copper recovery ratio. The 
copper recovery ratio is the ratio of the copper content in each 
copper-rich powder to the total amount of copper contained in the printed 
circuit board. 
In a separation step in each example, an air current centrifugal 
classification unit or rotation centrifugal classification unit was used 
in a specific gravity separation step, and a composite type electrostatic 
separator was used in an electrostatic separation step. Each example used 
a method of grinding a ground product which contained large amounts of 
filler material and resin as insulators, and was obtained through an 
electrostatic separation step, to a predetermined particle size again, and 
performing the initial separation step again. 
In a separation step in each comparative example, the above air current 
centrifugal classification unit and composite type electrostatic separator 
were independently used. 
The condition for specific gravity separation performed by the specific 
gravity separator was set such that the weight ratio of a ground product 
having a high specific gravity to a ground product having a low specific 
gravity was 50:50. The specific gravity separator was adjusted for each 
ground product in accordance with this weight ratio. As the air current 
centrifugal classification unit, a unit having a standard throughput of 5 
kg/h was used. The air suction amount was adjusted in the range from 1 
m.sup.3 /min to 5 m.sup.3 /min, and the wind velocity of secondary air was 
adjusted in the range from 10 m/s to 5 m/s, thereby setting the above 
specific gravity separation condition. As the composite type electrostatic 
separator, a unit having an average throughput of 120 kg/h was used. 
Five-stage electrostatic separation was performed while the applied 
voltage was set to 30 kV; and the rotational speed of the rotor, 80 r.p.m. 
In this five-stage electrostatic separation, five electrostatic separators 
were arranged in series, and a ground product which contained large 
amounts of insulators, and was separated by the electrostatic separator in 
each stage, was further separated by the electrostatic separator in the 
next stage. 
Each of Examples 1 to 9 of the present invention is associated with a 
method of grinding printed circuit boards and printed circuit board having 
parts mounted thereon, which are used for electric devices, and residual 
molded portions such as frame members produced in the manufacturing 
processes for these boards, and separating and recovering the ground 
products into metals such as copper and other components such as resins 
and filler materials through a separation step including a specific 
gravity separation step and an electrostatic separation step. Of these 
examples, Examples 1 to 8 are associated with the second aspect of the 
present invention, which relates to a valuable substance 
separation/recovery method of performing a separation step such that an 
electrostatic separation step is performed after a specific gravity 
separation step with respect to a ground product containing large amounts 
of substances having high specific gravities. 
In contrast to the examples of the present invention shown in Tables 1 to 
3, Comparative Examples 1 and 2 shown in Table 4 are associated with a 
method of separating/recovering valuable substances from a printed circuit 
board, in which a separation step after a grinding step includes either a 
specific gravity separation step or an electrostatic separation step. 
According to Examples 1 to 9 associated with the first and second aspects 
of the present invention, there is no need to install large-scale 
facilities such as advanced waste gas processing facilities required in a 
conventional valuable substance recovery method using incineration and 
carbonization. In addition, since valuable metal components contained in 
printed circuit boards and parts-mounted boards do not oxidize, they can 
be recovered as high-quality valuable substances. In these examples, since 
an electrostatic separation step is employed instead of a conventional 
separation step using magnetic force, nonmagnetic metals such as copper 
and aluminum, which are often used for the circuit portions of printed 
circuit boards, can also be separated/recovered. Furthermore, the copper 
content in the copper-rich powder in each example is higher than that in 
each comparative example shown in Table 4, in which the separation step 
includes either a specific gravity step or an electrostatic separation 
step. According to the present invention, the copper in the ground product 
of each printed circuit board is concentrated in the copper-rich powder, 
high-purity copper can be recovered. 
The differences in separation/recovery effect between the examples owing to 
the different particle sizes of the ground products are observed by 
comparing Examples 1 to 6 with Examples 7 and 8. It is apparent from the 
copper contents and the copper recovery ratios in Tables 1 to 3 that the 
separation ratio between a metal such as copper and other components such 
as a resin decreases if the average particle size of a ground product is 
excessively large as in Example 7, or is excessively small as in Example 
8. It is, therefore, apparent that Examples 1 to 6 of the present 
invention are excellent in terms of both copper content and copper 
recovery. That is, it is apparent that the average particle size of a 
ground product is preferably set to be equal to or larger than 0.03 mm (30 
.mu.m) and less than 1.0 mm (1,000 .mu.m) as in Examples 1 to 6. As 
described above, high-purity copper can be recovered at a high recovery 
ratio. That is, this effect can be obtained in addition to the effects of 
the first and second aspects of the present invention. 
TABLE 1 
__________________________________________________________________________ 
Example No. 1 2 3 
__________________________________________________________________________ 
Type of Printed Circuit 
glass epoxy 
glass epoxy 
*glass epoxy 
Board 
Separators in Separation 
air current 
rotation centrifugal 
air current centri- 
Steps centrifugal 
classification unit 
fugal classification 
classification unit 
.dwnarw. 
unit 
.dwnarw. 
composite type 
.dwnarw. 
composite type 
electrostatic sepa- 
composite type 
electrostatic sepa- 
rator electrostatic sepa- 
rator rator 
Average Particle Size 
0.056 0.098 0.21 
of Ground Product (mm) 
Copper- 
Copper 76 80 78 
Rich Content 
Powder 
(wt %) 
Copper 93 96 95 
Recovery 
Ratio (wt %) 
__________________________________________________________________________ 
(*copper pattern with solder) 
TABLE 2 
__________________________________________________________________________ 
Example No. 4 5 6 
__________________________________________________________________________ 
Type of Printed Circuit 
paper phenol 
parts-mounted 
parts-mounted 
Board board board 
Separators in Separation 
rotation centrifugal 
air current cen- 
rotation centrifugal 
Steps classification unit 
trifugal classifica- 
classification unit 
.dwnarw. 
tion unit .dwnarw. 
composite type 
.dwnarw. 
composite type 
electrostatic sepa- 
composite type 
electrostatic sepa- 
rator electrostatic sepa- 
rator 
rator 
Average Particle Size 
0.033 0.46 0.95 
of Ground Product (mm) 
Copper- 
Copper 75 77 75 
Rich Content 
Powder 
(wt %) 
Copper 95 92 89 
Recovery 
Ratio (wt %) 
__________________________________________________________________________ 
TABLE 3 
__________________________________________________________________________ 
Example No. 7 8 9 
__________________________________________________________________________ 
Type of Printed Circuit 
parts-mounted 
paper phenol 
*glass epoxy 
Board board 
Separators in Separation 
rotation centrifugal 
air current cen- 
composite type 
Steps classification unit 
trifugal classifica- 
electrostatic 
.dwnarw. 
tion unit separator 
composite type 
.dwnarw. 
.dwnarw. 
electrostate sepa- 
composite type 
air current centri- 
rator electrostatic sepa- 
fugal classification 
rator unit 
Average Particle Size 
1.3 0.022 0.46 
of Ground Product (mm) 
Copper- 
Copper 65 68 82 
Rich Content 
Powder 
(wt %) 
Copper 63 61 58 
Recovery 
Ratio (wt %) 
__________________________________________________________________________ 
(*copper pattern with solder) 
TABLE 4 
______________________________________ 
Comparative Example No. 
1 2 
______________________________________ 
Type of Printed Circuit 
glass epoxy parts-mounted board 
Board 
Separator in Separation 
air current centrifugal 
composite type 
Step classification unit 
electrostatic clas- 
sification unit 
Average Particle Size 
0.098 0.95 
of Ground Product (mm) 
Copper- 
Copper 57 38 
Rich Content 
Powder (wt %) 
Copper 95 32 
Recovery 
Ratio (wt %) 
______________________________________ 
Tables 5 to 7 show Examples 10 to 18 associated with the third and fourth 
aspects of the present invention. Table 8 shows Comparative Examples 3 and 
4. Each table shows the conditions for grinding and separation, the 
chromium concentration in a fine ground product obtained through a fine 
grinding step, the copper content of a powder containing a large amount of 
copper (to be referred to as a copper-rich powder hereinafter) which is 
finally obtained through a separation step, the copper recovery ratio, and 
the copper content in a powder containing filler materials such as a resin 
and glass fiber (to be referred to as a glass fiber/resin powder 
hereinafter) which is finally obtained through the separation step. In 
this case as well, the copper recovery ratio is the ratio of the copper 
content in each copper-rich powder to the total amount of copper contained 
in the printed circuit board. 
Samples identical to those used in Examples 1 to 9 were used. As a grinder 
used in a coarse grinding step, a hammer mill as a type of shear and 
impact type grinder was used in the examples and the comparative examples. 
This mill has a mechanism of grinding a substance by using a rotating 
manner, a bed knife in a chamber, and a screen at a discharge portion. In 
this case, the mesh size of the screen was set to be 3 mm. 
In each example, a fine grinding step was performed by using a method of 
grinding a substance by using a roller mill with a rotating blade type 
classification unit or a method of grinding a substance by a closed 
circuit scheme in which a rotating blade type classification unit is 
installed outside a roller mill, and a classified coarse powder from the 
classification unit is returned to the grinder (this method will be 
referred to as roller mill+rotating blade type classification unit (closed 
circuit scheme) hereinafter). The average particle size of each ground 
product was set by adjusting the rotational speed of each rotating blade 
type classification unit in the range from 50 r.p.m to 1,000 r.p.m; and 
the air suction amount in each roller mill, in the range from 5 m.sup.3 
/min to 20 m.sup.3 /min. 
As a grinder used in the fine grinding step in each comparative example, 
the above hammer mill or a disk mill as a type of shear and impact grinder 
having a mechanism of grinding a substance by using pins or grooves of 
opposing rotating disks was used. 
Each of the grinders used in the examples and the comparative examples has 
a standard ability of grinding a 10 kg plastic material per hour. As a 
material for the grinding portion of each grinder in a coarse grinding 
step, general steel containing no chromium was used in the examples and 
the comparative examples. As a material for the grinding portion of each 
grinder in a fine grinding step, high-chromium-concentration cast iron 
containing 25 wt % chromium was used in not only the examples but also the 
comparative examples. The wear resistances of the fine grinders were 
compared with reference to the chromium concentrations in the respective 
fine ground products. 
The classification units and separators used in the separation steps in 
Examples 10 to 18 and Comparative Examples 3 and 4 are the same as those 
in Examples 1 to 9 and Comparative Examples 1 and 2 described above. This 
applies to the conditions for specific gravity separation performed by the 
specific gravity separator. In addition, the composite type electrostatic 
separator used in these examples is the same as that in the above 
examples. 
Each of Examples 10 to 18 of the present invention shown in Tables 5 to 7 
is associated with a method of coarsely grinding printed circuit boards 
and printed circuit boards having parts mounted thereon, which are used 
for electric devices, and residual molded portions such as frame members 
produced in the manufacturing processes for these boards, by using a 
hammer mill, finely grinding the coarse ground products by applying 
external forces including a compressing force and a shearing force, and 
separating and recovering the fine ground products into metals such as 
copper and other components such as resins and filler materials through a 
separation step including a specific gravity separation step and an 
electrostatic separation step. Of these examples, Examples 10 to 17 are 
associated with the fourth aspect of the present invention, which relates 
to a valuable substance separation/recovery method of performing a 
separation step such that an electrostatic separation step is performed 
after a specific gravity separation step with respect to a ground product 
containing large amounts of substances having high specific gravities. 
In contrast to Examples 10 to 17, Comparative Examples 3 and 4 shown in 
Table 8 are associated with a method of separating/recovering valuable 
substances from a printed circuit board, in which a separation step after 
a grinding step includes either a specific gravity separation step or an 
electrostatic separation step. 
According to Examples 10 to 18 associated with the third and fourth aspects 
of the present invention, there is no need to install large-scale 
facilities such as advanced waste gas processing facilities required in a 
conventional valuable substance recovery method using incineration and 
carbonization. In addition, since valuable metal components contained in 
printed circuit boards and parts-mounted boards do not oxidize, they can 
be recovered as high-quality valuable substances. In these examples, since 
an electrostatic separation step is employed instead of a conventional 
separation step using magnetic force, nonmagnetic metals such as copper 
and aluminum, which are often used for the circuit portions of printed 
circuit boards, can also be separated/recovered. Furthermore, the copper 
content in the copper-rich powder in each example is as high as 75% or 
more, as compared with each comparative example shown in Table 8, in which 
the separation step includes either a specific gravity step or an 
electrostatic separation step. According to the present invention, since 
the copper in the ground product of each printed circuit board is 
concentrated in the copper-rich powder, high-purity copper can be 
recovered. On the other hand, the remaining glass fiber/resin powders 
contain almost no copper as an impurity. Therefore, the glass fiber/resin 
powders can be widely and effectively used as a structural material, a 
building material, and a filler material such as an insulating material. 
Furthermore, since the concentration of chromium, in a fine powder, which 
is produced because of friction on the grinder in each example of the 
present invention is extremely lower than that in each comparative 
example, the wear resistance in a fine grinding step can be improved by 
the present invention. 
The differences in separation/recovery effect between the examples owing to 
the different particle sizes of the ground products are observed by 
comparing Examples 10 to 15 with Examples 16 and 17. It is apparent from 
the copper contents and the copper recovery ratios in Tables 5 to 7 that 
the separation ratio between a metal such as copper and other components 
such as a resin decreases if the average particle size of a ground product 
is excessively large as in Example 16, or is excessively small as in 
Example 17. It is, therefore, apparent that Examples 10 to 15 of the 
present invention are excellent in terms of both copper content and copper 
recovery, which are about 90% or more. That is, it is apparent that the 
average particle size of a ground product is preferably set to be equal to 
and larger than 0.03 mm (30 .mu.m) and less than 1.0 mm (1,000 .mu.m) as 
in Examples 10 to 15. As described above, high-purity copper can be 
recovered at a high recovery ratio. That is, this effect can be obtained 
in addition to the effects of the third and fourth aspects of the present 
invention. 
TABLE 5 
__________________________________________________________________________ 
Example No. 10 11 12 
__________________________________________________________________________ 
Type of Printed Circuit 
glass epoxy 
glass epoxy 
*glass epoxy 
Board 
Grinder in Fine Grinding 
roller mill with 
roller mill with 
roller mill + rotating 
Step rotating blade type 
rotating blade type 
blade type classifi- 
classification unit 
classification unit 
cation unit (closed 
circuit scheme) 
Separator in Separation 
air current centrifu- 
rotation centrifugal 
air current centri- 
Steps gal classification 
classification unit 
fugal classification 
unit .dwnarw. 
unit 
.dwnarw. 
composite type elec- 
.dwnarw. 
composite type elec- 
trostatic separator 
composite type 
trostatic separator 
electrostatic 
separator 
Average Particle Size of 
0.054 0.12 0.23 
Fine Ground Product 
(mm) 
Chromium Concentration 
19 14 29 
in Fine Ground Product 
(ppm) 
Copper- 
Copper 92 94 96 
Rich Content 
Powder 
(wt %) 
Copper 96 97 98 
Recovery 
Ratio (wt %) 
Copper Content in Glass 
1.7 1.3 0.86 
Fiber/Resin Powder 
__________________________________________________________________________ 
(*copper pattern with solder) 
TABLE 6 
__________________________________________________________________________ 
Example No. 13 14 15 
__________________________________________________________________________ 
Type of Printed Circuit 
paper phenol 
parts-mounted board 
parts-mounted 
Board board 
Grinder in Fine Grinding 
roller mill with 
roller mill with 
roller mill + rotating 
Step rotating blade type 
rotating blade type 
blade type classifi- 
classification unit 
classification unit 
cation unit (closed 
circuit scheme) 
Separator in Separation 
rotation centrifugal 
air current clas- 
rotation centrifugal 
Steps classification unit 
sification unit 
classification unit 
.dwnarw. 
.dwnarw. 
.dwnarw. 
composite type elec- 
composite type elec- 
composite type 
trostatic separator 
trostatic separator 
electrostatic 
separator 
Average Particle Size of 
0.031 0.47 0.98 
Fine Ground Product 
(mm) 
Chromium Concentration 
9 42 32 
in Fine Ground Product 
(ppm) 
Copper- 
Copper 93 93 89 
Rich Content 
Powder 
(wt %) 
Copper 96 96 95 
Recovery 
Ratio (%) 
Copper Content in Glass 
1.7 2.0 2.5 
Fiber/Resin Powder 
__________________________________________________________________________ 
TABLE 7 
__________________________________________________________________________ 
Example No. 16 17 18 
__________________________________________________________________________ 
Type of Printed Circuit 
parts-mounted board 
paper phenol 
*glass epoxy 
Board 
Grinder in Fine Grinding 
roller mill with 
roller mill with 
roller mill + rotating 
Step rotating blade type 
rotating blade type 
blade type classifi- 
classification unit 
classification unit 
cation unit (closed 
circuit scheme) 
Separator in Separation 
air current centri- 
rotation classifica- 
composite type 
Steps fugal classification 
tion unit electrostatic 
unit .dwnarw. 
separator 
.dwnarw. 
composite type elec- 
.dwnarw. 
composite type elec- 
trostatic separator 
air current centri- 
trostatic separator 
fugal classification 
unit 
Average Particle Size of 
1.3 0.020 0.52 
Fine Ground Product 
(mm) 
Chromium Concentration 
21 11 30 
in Fine Ground Product 
(ppm) 
Copper- 
Copper 79 83 91 
Rich Content 
Powder 
(wt %) 
Copper 76 78 69 
Recovery 
Ratio (wt %) 
Copper Content in Glass 
11 9.2 12 
Fiber/Resin Powder 
__________________________________________________________________________ 
(*copper patten with solder) 
TABLE 8 
______________________________________ 
Comparative Example No. 
3 4 
______________________________________ 
Type of Printed Circuit 
glass epoxy parts-mounted board 
Board 
Grinder in Fine Grinding 
hammer mill disk mill 
Step 
Separator in Separation 
air current centrifugal 
composite type elec- 
Step classification unit 
trostatic classifica- 
tion unit 
Average Particle Size of 
0.098 0.95 
Fine Ground Product 
(mm) 
Chromium Concentration 
976 186 
in Fine Ground Product 
(ppm) 
Copper- 
Copper 57 38 
Rich Content 
Powder (wt %) 
Copper 95 32 
Recovery 
Ratio (wt %) 
Copper Content in Glass 
3.0 31 
Fiber/Resin Powder 
(wt %) 
______________________________________ 
As is apparent from the above description, according to the present 
invention, since incineration and carbonization as in a conventional 
recovery method are not used, there is no need to install large-scale 
facilities such as advanced waste gas processing facilities. In addition, 
since valuable metal components contained do not oxidize, they can be 
recovered as high-quality valuable substances having high additional 
values. Furthermore, according to the present invention, a metal component 
in the ground product of each printed circuit board is concentrated in a 
powder containing a large amount of metal component which is finally 
obtained through a separation step after a grinding step, a high-purity 
metal component containing only a small amount of other components such as 
a resin can be recovered. On the other hand, the remaining ground products 
containing a filler material such as glass fiber and a resin contain 
almost no metal component as an impurity. Therefore, these powders can be 
effectively used as a structural material, a building material, and a 
filler material such as an insulating material. Moreover, the wear 
resistance in a fine grinding step in the present invention is very high, 
and the durability of each apparatus is high. This makes it possible to 
realize a practical plant. 
In addition, a high-purity metal component can be recovered at a high 
recovery ratio from the ground product of a parts-mounted board. That is, 
this effect can be obtained in addition to the effects of the first to 
fourth aspects of the present invention. 
According to the present invention, therefore, efficient 
separation/recovery of metals and other components from ground products of 
printed circuit boards, parts-mounted boards, and residual molded portions 
produced in the manufacturing processes for these boards, which has been 
difficult to realize, can be realized, and the recovered metals and other 
components can be effectively used as resources.