U.S. patent application number 15/037784 was filed with the patent office on 2016-10-13 for clay-like shaped body for forming sintered precious metal body.
This patent application is currently assigned to Mitsubishi Materials Corporation. The applicant listed for this patent is MITSUBISHI MATERIALS CORPORATION. Invention is credited to Yasuo Ido, Shinji Otani.
Application Number | 20160297004 15/037784 |
Document ID | / |
Family ID | 53199120 |
Filed Date | 2016-10-13 |
United States Patent
Application |
20160297004 |
Kind Code |
A1 |
Ido; Yasuo ; et al. |
October 13, 2016 |
CLAY-LIKE SHAPED BODY FOR FORMING SINTERED PRECIOUS METAL BODY
Abstract
A clay-like shaped body for forming a sintered precious metal
body, the clay-like shaped body obtained by shaping a clay-like
composition containing at least one powder selected from the group
consisting of precious metal powders and precious metal alloy
powders, an organic binder, an organic additive and water into
either a wire-like shape having a diameter of 0.5 mm to 3.0 mm or a
sheet-like shape having a thickness of 0.2 mm to 3.0 mm, wherein
cracking does not occur when the clay-like shaped body is wound
tightly once around the outer peripheral surface of a core rod
having a circular cross-sectional shape with a diameter of 13
mm.
Inventors: |
Ido; Yasuo; (Sanda-shi,
JP) ; Otani; Shinji; (Sanda-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MITSUBISHI MATERIALS CORPORATION |
Tokyo |
|
JP |
|
|
Assignee: |
Mitsubishi Materials
Corporation
Tokyo
JP
|
Family ID: |
53199120 |
Appl. No.: |
15/037784 |
Filed: |
November 27, 2014 |
PCT Filed: |
November 27, 2014 |
PCT NO: |
PCT/JP2014/081317 |
371 Date: |
May 19, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B22F 5/006 20130101;
A44C 27/00 20130101; B22F 3/02 20130101; B22F 2001/0066 20130101;
B22F 2302/45 20130101; B22F 1/0062 20130101; B22F 5/12 20130101;
B22F 2301/25 20130101; B22F 2301/255 20130101; C22C 1/0466
20130101 |
International
Class: |
B22F 1/00 20060101
B22F001/00; B22F 5/12 20060101 B22F005/12; B22F 5/00 20060101
B22F005/00; C22C 1/04 20060101 C22C001/04 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 28, 2013 |
JP |
2013-246152 |
Claims
1. A clay-like shaped body for forming a sintered precious metal
body, the clay-like shaped body obtained by shaping a clay-like
composition comprising at least one powder selected from the group
consisting of precious metal powders and precious metal alloy
powders, an organic binder, an organic additive and water into
either a wire-like shape having a diameter of 0.5 mm to 3.0 mm or a
sheet-like shape having a thickness of 0.2 mm to 3.0 mm, wherein
cracking does not occur when the clay-like shaped body is wound
tightly once around an outer peripheral surface of a core rod
having a circular cross-sectional shape with a diameter of 13
mm.
2. The clay-like shaped body for forming a sintered precious metal
body according to claim 1, wherein the clay-like shaped body has an
initial hardness measured using a type E durometer of E8 to E20,
and has a hardness after standing for one hour at room temperature
of E40 or less.
Description
TECHNICAL FIELD
[0001] The present invention relates to a clay-like shaped body for
forming a sintered precious metal body, obtained by shaping a
clay-like composition for forming a sintered precious metal body
into a wire-like or sheet-like shape.
[0002] Priority is claimed on Japanese Patent Application No.
2013-246152, filed Nov. 28, 2013, the content of which is
incorporated herein by reference.
BACKGROUND ART
[0003] Conventionally, jewelry and fine arts and crafts and the
like made of precious metals, typified by rings and the like, are
generally produced by the casting or forging of a material
containing a precious metal such as silver or gold.
[0004] However, in recent years, precious metal clays containing
precious metal powders such as silver or gold (clay-like
compositions for forming sintered bodies) have become commercially
available, and methods have been proposed for producing precious
metal jewelry and fine arts and crafts having any desired shape by
making these precious metal clays into the desired arbitrary shape
and then performing firing (for example, see Patent Documents 1 to
3).
[0005] By using these types of methods, precious metal clays can be
used to freely shape forms in the same manner as typical clay work,
and by drying the shaped body obtained by shaping the precious
metal clay, and then firing the clay in a heating furnace, precious
metal jewelry and fine arts and crafts and the like can be produced
extremely easily.
CITATION LIST
Patent Documents
[0006] Patent Document 1: Japanese Patent No. 4,265,127
[0007] Patent Document 2: Japanese Unexamined Patent Application,
First Publication No. H04-26707
[0008] Patent Document 3: Japanese Unexamined Patent Application,
First Publication No. 2005-187858
DISCLOSURE OF INVENTION
Problems to be Solved by the Invention
[0009] When producing this type of sintered precious metal body,
the precious metal clay must first be shaped, but because this type
of shaping is mainly performed by hand, the clay can sometimes
start to dry during this shaping, making processes such as bending
more difficult. Ever increasing diversity in design and personal
preferences has resulted in more complex shapes for the sintered
precious metal bodies, meaning the time required for shaping these
bodies has tended to increase. This means conventional clay-like
compositions tend to dry out during the shaping process, and if an
attempt is made to bend this type of dried composition, then cracks
appear in the surface of the clay, and further bending can result
in breakage. As a result, when rings or the like are made, the
shaping must be completed within a limited time period, meaning
there is a limit to the design features that are possible.
[0010] The present invention has been developed in light of these
circumstances, and was completed as a result of intensive research
aimed at achieving the object described below.
[0011] The present invention has an object of providing a clay-like
shaped body for forming a sintered precious metal body, which
exhibits excellent flexibility and bendability during shaping of
the precious metal clay, enabling shaping operations such as
bending to be performed with ease, and is formed as a wire-like or
sheet-like shape that is convenient for shaping.
Means for Solving the Problems
[0012] The present invention provides a clay-like shaped body for
forming a sintered precious metal body, the clay-like shaped body
obtained by shaping a clay-like composition containing at least one
powder selected from the group consisting of precious metal powders
and precious metal alloy powders, an organic binder, an organic
additive and water into either a wire-like shape having a diameter
of 0.5 mm to 3.0 mm or a sheet-like shape having a thickness of 0.2
mm to 3.0 mm, wherein cracking does not occur when the clay-like
shaped body is wound tightly once around the outer peripheral
surface of a core rod having a circular cross-sectional shape with
a diameter of 13 mm.
[0013] The clay-like composition used for forming this type of
clay-like shaped body for forming a sintered precious metal body is
produced by mixing and kneading the one or more powders selected
from the group consisting of precious metal powders and precious
metal alloy powders, the organic binder, the organic additive and
water, and is typically stored and sold in a wrapped state with the
composition covered with a packaging material such as a film or the
like having excellent gas barrier properties in order to prevent
hardening of the composition as a result of drying. The composition
is usually in the form of a block, which is shaped into the desired
form after removal from the packaging material. At this time, prior
to completion of the target product such as a ring or the like, the
block of the clay-like composition is processed into a wire-like
shape or an elongated sheet-like shape by squeezing and stretching
and the like, and this wire-like shape or sheet-like shape is then
subjected to further processing such as bending into a round shape.
However, after removal from the packaging material, the clay-like
composition tends to start drying and hardening in a comparatively
short period of time, and because considerable time is required to
process the composition into a wire-like shape or sheet-like shape,
when that shape is subsequently bent into a round shape, there is a
possibility of cracking occurring. Accordingly, the clay-like
composition must be shaped within a relatively short time after
removal from the packaging material, meaning there is a limit to
the product shapes that can be produced.
[0014] The clay-like shaped body for forming a sintered precious
metal body according to the present invention is shaped into a
wire-like or sheet-like shape of prescribed dimensions, and suffers
no cracking when wound tightly once around the outer peripheral
surface of a core rod having a circular cross-sectional shape with
a diameter of 13 mm, and can therefore easily be shaped into a ring
or the like by bending the clay-like shaped body into a round shape
after removal from the packaging material. Because the clay-like
shaped body has already been formed into a wire-like or sheet-like
shape, the time required for processing the composition into this
type of shaped form can be saved, enabling a greater length of time
to be spent on shaping operations closer to the shape of the final
product, and therefore more intricate product shapes can be
produced, and a wider variety of demands can be met.
[0015] For the clay-like shaped body for forming a sintered
precious metal body according to the present invention, it is
preferable that the initial hardness measured using a type E
durometer is from E8 to E20, and that the hardness after standing
for one hour at room temperature is E40 or less.
[0016] In the case of a conventional clay-like composition, the
composition is comparatively soft and easily shaped immediately
following removal from the packaging material, but the hardness
increases as time passes, making bending and the like of the
composition during shape formation difficult.
[0017] The clay-like shaped body for forming a sintered precious
metal body according to the present invention has an initial
hardness immediately following removal from the packaging material
of E8 to E20, and has a hardness after standing for one hour at
room temperature of E40 or less. Accordingly, the increase over
time in the hardness of the clay-like shaped body for forming a
sintered precious metal body is small, and therefore the ability to
further shape the shaped body during shaping operations is not
impaired as a result of large increases in the hardness of the
clay-like shaped body for forming a sintered precious metal body,
meaning the clay-like composition maintains excellent flexibility
and bendability, and rings and the like can be produced with
comparative ease.
[0018] In this description, the initial hardness refers to the
hardness value measured within the period of about one minute
required for removing the clay-like shaped body for forming a
sintered precious metal body from the enclosing packaging material
and then performing the measurement using a durometer. Further, the
hardness after standing refers to the hardness measured after
leaving the clay-like shaped body for forming a sintered precious
metal body to stand for one hour at room temperature after removal
from the enclosing packaging material.
[0019] When the type E hardness value satisfies the above range,
shaping of the clay-like shaped body is simple, and even if the
hardness increases somewhat during the shaping process, it does not
impede the shaping. Further, when the hardness after standing
satisfies the above range, satisfactory flexibility is maintained
even after one hour at room temperature, and shaping is possible
even after this one hour has passed. Consequently, it is possible
to shape the clay-like shaped body for about 30 minutes to prepare
a partially finished product, subsequently store the partially
finished product by sealing inside a packaging material, and then
once again remove the partially finished product from the packaging
material to complete the shaping process at a later time, meaning
the clay-like shaped body can be used in those cases where the
shaping operation is temporarily interrupted and then restarted at
a later time.
Effects of the Invention
[0020] Because the clay-like shaped body for forming a sintered
precious metal body according to the present invention is shaped
into a wire-like or sheet-like shape of prescribed dimensions,
subsequent shaping can be performed easily, and cracking does not
occur when the clay-like shaped body is wound tightly once around
the outer peripheral surface of a core rod having a circular
cross-sectional shape with a diameter of 13 mm, and therefore
shapes such as rings can be produced with comparative ease, and
more intricate product shapes can be produced.
Best Mode for Carrying Out the Invention
[0021] The clay-like shaped body for forming a sintered precious
metal body according to the present invention is obtained by
shaping a clay-like composition containing at least one powder
selected from the group consisting of precious metal powders such
as gold powder and silver powder and precious metal alloy powders,
an organic binder, an organic additive and water into either a
wire-like shape having a diameter of 0.5 mm to 3.0 mm or a
sheet-like shape having a thickness of 0.2 mm to 3.0 mm. Propylene
glycol can be used favorably as the organic additive, and glycerol
and polyethylene glycol may also be added.
[0022] This clay-like shaped body for forming a sintered precious
metal body is stored and sold in a wrapped state with the shaped
body sealed with a packaging material having gas barrier
properties, and following removal from the packaging material, the
clay-like shaped body has a property wherein cracking does not
occur when the clay-like shaped body is wound tightly once around
the outer peripheral surface of a core rod having a circular
cross-sectional shape with a diameter of 13 mm. Further, if the
hardness measured using a type E durometer immediately after
removal of the clay-like shaped body from the packaging material
(including the time of about one minute required for performing the
measurement) is deemed the initial hardness, and the hardness after
standing for one hour at room temperature after removal from the
packaging material is deemed the hardness after standing, then the
initial hardness is from E8 to E20, and the hardness after standing
is E40 or less.
[0023] The diameter and thickness and the like of the clay-like
shaped body for forming a sintered precious metal body can be
ascertained using calipers or the like.
[0024] Further, a type E durometer refers to a test instrument used
for measuring low hardness values prescribed in JIS K 6253-1
(hardness measurement range: <A20) (wherein JIS K 6253-1
conforms to ISO 18517, and in ISO 7619-1, a type E durometer is
referred to as a type AO durometer).
[0025] A more detailed description of the invention is provided
below.
(a) Precious Metal Powder, Precious Metal Alloy Powder
[0026] For the precious metal powder and/or precious metal alloy
powder used in the present invention, gold powder, silver powder,
copper powder, platinum powder, or powders of alloys of these
metals can be used. Further, a mixed powder of silver powder and
copper powder may also be used. In terms of silver alloy powders, a
silver-copper alloy can be used particularly favorably. At least
one powder selected from the group consisting of these precious
metal powders and precious metal alloy powders functions as the
main component of the clay-like composition that constitutes the
clay-like shaped body for forming a sintered precious metal body.
The amount of this powder is not a predominant condition, provided
the effects of the present invention are achieved, but in order to
obtain a more practical clay-like composition, the amount of the
powder is preferably at least 50 mass % but not more than 95 mass
%. In other words, if the amount is less than 50 mass %, then the
texture and luster of the precious metal may not appear, whereas if
the amount exceeds 95 mass %, then the extensibility and strength
of the clay-like composition tend to deteriorate undesirably. The
amount of the one or more powders selected from the group
consisting of precious metal powders and precious metal alloy
powders within the clay-like composition that constitutes the
clay-like shaped body for forming a sintered precious metal body is
more preferably at least 70 mass % but not more than 95 mass %.
(b) Organic Binder
[0027] The organic binder used in the present invention may be
formed from one material, or a combination of two or more
materials, selected from among cellulose-based binders,
polyvinyl-based binders, acrylic-based binders, wax-based binders,
resin-based binders, starch, gelatin and flour. Further, among the
above, the organic binder is preferably formed from a
cellulose-based binder, and is most preferably formed from a
water-soluble cellulose such as methyl cellulose.
[0028] The amount of this organic binder is not a predominant
condition, provided the effects of the present invention are
achieved, but in order to obtain a more practical clay-like
composition that constitutes the clay-like shaped body for forming
a sintered precious metal body, the amount of the organic binder in
the clay-like composition is preferably at least 2 mass % but not
more than 12 mass %, and is more preferably at least 2 mass % but
not more than 10 mass %.
(c) Organic Additive
[0029] Propylene glycol can be used as the organic additive used in
the present invention. In this case, if the amount of the organic
additive is too small, then the clay-like shaped body tends to dry
over time, increasing the likelihood of a reduction in the
flexibility, whereas if the amount of the organic additive is too
large, then the formability of the clay-like composition tends to
deteriorate, making shaping difficult, and therefore the amount of
the organic additive is preferably from 0.1 mass % to 3.0 mass %,
and more preferably from 0.5 mass % to 2 mass %.
[0030] Moreover, by also adding at least one other organic additive
selected from the group consisting of glycerol and polyethylene
glycol in addition to the propylene glycol, the flexibility of the
clay-like composition after drying can be further improved.
[0031] In those cases when glycerol and a polyethylene glycol are
added, the combined mass of the propylene glycol, the glycerol and
the polyethylene glycol is preferably adjusted so as to satisfy a
range from 0.1 mass % to 3.0 mass %, and is more preferably
adjusted so as to satisfy a range from 0.5 mass % to 1.8 mass %.
Glycerol and polyethylene glycol are liquid substances that have
both hydrophilic and lipophilic properties, and it is known that
including these substances in a clay-like composition imparts
viscosity to the composition, but by adding these substances to the
clay-like composition together with propylene glycol, the effect of
the invention in preventing drying of the clay-like composition and
deterioration in the flexibility of the clay-like composition even
when left to stand for a long period of time can be further
strengthened compared with the case where the propylene glycol is
added alone.
[0032] Moreover, if required, at least one additive selected from
among fatty substances, olive oil and surface active agents may
also be added to the clay-like composition of the present
invention.
[0033] The amount of this additive varies depending on its purpose,
but the amount within the clay-like composition is preferably at
least 0.1 mass % but not more than 1 mass %, and is more preferably
at least 0.1 mass % but not more than 0.5 mass %.
[0034] Examples of the fatty substance include organic acids (such
as oleic acid, stearic acid, phthalic acid, palmitic acid, sebacic
acid, acetylcitric acid, hydroxybenzoic acid, lauric acid, myristic
acid, caproic acid, enanthic acid, butyric acid and capric acid),
organic esters (such as organic acid esters having a methyl group,
ethyl group, propyl group, butyl group, octyl group, hexyl group,
dimethyl group, diethyl group, isopropyl group or isobutyl group),
higher alcohols (such as octanol, nonanol and decanol), polyhydric
alcohols (such as glycerol, arabitol and sorbitan), and ethers
(such as dioctyl ether and didecyl ether).
[0035] By adding and mixing a surface active agent into the
clay-like composition, the solid matter generated by the reaction
between the binder and the water can be converted to powder form,
and the mixability of the precious metal powder and the binder can
be improved. There are no particular limitations on the type of
surface active agent, and a typical surface active agent may be
used. The term "surface active agent" is a generic name for a
substance that has a water-compatible portion (hydrophilic group)
and an oil-compatible portion (lipophilic group, hydrophobic group)
within the same molecule, and if it satisfies this definition, then
the aforementioned polyethylene glycol used in the present
invention may also be considered a surface active agent. However,
when used in this instance, the term "surface active agent"
excludes the polyethylene glycol added with the anticipation of
achieving the characteristic effects of the present invention, but
rather refers to sodium lauryl sulfate or a polyoxyethylene alkyl
ether or the like that is added in a prescribed amount in order to
achieve a dispersion or aggregation effect, a foaming or defoaming
effect, a wettability improvement effect, a softening and smoothing
effect, or an antistatic effect or the like.
[0036] When producing a clay-like shaped body for forming a
sintered precious metal body with the type of composition described
above, first, the organic binder, the organic additive and the
water, and if required the fatty substance, olive oil and/or
surface active agent, are stirred and mixed inside a container
fitted with a stirrer. The resulting mixed solution is then
introduced into a kneading device together with the precious metal
powder.
[0037] There are no particular limitations on the amount of water
in the clay-like composition that constitutes the clay-like shaped
body for forming a sintered precious metal body, but the amount is
preferably from 3 mass % to 35 mass %, and is more preferably from
3 mass % to 20 mass %.
[0038] A stainless steel kneading device may be used as the
kneading device, and the internal walls of the kneading device are
preferably coated with CrN. This CrN coating has excellent wear
resistance as well as excellent lubricity, and can therefore
suppress Fe contamination.
[0039] By kneading the precious metal powder and the mixed solution
in the kneading device, a clay-like composition can be
produced.
[0040] In the method described above, the fatty substance or the
like was added during the stirring and mixing of the mixed
solution, but the organic binder, the organic additive and the
water may first be stirred and mixed, with the fatty substance or
the like then added when the precious metal powder is kneaded with
the mixed solution inside the kneading device.
[0041] Following removal from the kneading device, the clay-like
composition is divided into blocks of appropriate size, and then
shaped into either a wire-like shape having a diameter of 0.2 mm to
3.0 mm or a sheet-like shape having a thickness of 0.2 mm to 3.0 mm
to prepare the clay-like shaped body for forming a sintered
precious metal body. During this shaping, the block of the
clay-like composition is first stretched thinly into a sheet-like
form by flattening with a roller or the like. In order to form the
aforementioned sheet-like shaped body, the rolled sheet is cut into
strips of an appropriate size with a width of at least 1.0 mm. In
order to form the wire-like shaped body, the sheet is cut into
strips of an appropriate width, and these strips are then rolled
into a wire-like form.
[0042] The wire-like or sheet-like clay-like shaped body for
forming a sintered precious metal body shaped in this manner is
then wrapped in a packaging material for storage and sale.
[0043] Examples of materials that can be used as the packaging
material include films formed from resins having gas barrier
properties such as polyvinylidene chloride (PVDC), metal foils, and
laminated films comprising a metal layer and a resin layer. These
packaging materials cover the outer surface of the clay-like shaped
body for forming a sintered precious metal body in a tightly sealed
state, thereby preventing contact with the outside air. Further, a
bag-like packaging material formed from the types of films
described above may also be used. Moreover, instead of using a
film, a container capable of accommodating the clay-like shaped
body for forming a sintered precious metal body, such as a box or
can or the like formed from a material having gas barrier
properties, may also be used as the packaging material.
[0044] Immediately after removal from this packaging material, the
clay-like shaped body for forming a sintered precious metal body
suffers no cracking when wound tightly once around the outer
peripheral surface of a core rod having a circular cross-sectional
shape with a diameter of 13 mm. Further, the clay-like shaped body
has an initial hardness, measured using a type E durometer in
accordance with JIS K 6253, that is from E8 to E20, and from this
initial hardness, has a hardness after standing for one hour at
room temperature that is E40 or less. The initial hardness of the
clay-like shaped body for forming a sintered precious metal body is
more preferably from E8 to E18, and still more preferably from E8
to E15. Further, the hardness of the clay-like shaped body after
standing for one hour at room temperature is more preferably E36 or
less, and the lower limit for this value is preferably at least as
large as the initial hardness.
[0045] Room temperature refers to a temperature of 15 to 30.degree.
C., and preferably 23.degree. C.
[0046] In order to produce a sintered precious metal body from this
clay-like shaped body for forming a sintered precious metal body,
the clay-like shaped body for forming a sintered precious metal
body is first removed from the packaging material and used to form
the desired shaped product by operations such as rounding, and the
resulting shaped product is then dried by exposure to hot air or
the like. The shaped product hardens upon drying, and following
additional fine shaping using a file, cutter or chisel or the like
as required, the shaped product is fired to produce a sintered
precious metal body. Following firing, polishing of the surface
reveals the luster of the precious metal, enabling completion of
the ornament or the like.
[0047] Because this clay-like shaped body for forming a sintered
precious metal body has already been shaped into a wire-like or
sheet-like form, manual operations such as kneading and stretching
of the clay-like composition can be omitted, and in the case of
shaping a ring, the ring-like shape can be formed relatively simply
by bending the wire-like or sheet-like shaped body into a rounded
shape. Accordingly, greater time can be spent on fine shaping of
the ring and forming patterns on the ring surface and the like.
[0048] In the shaping operations described above, following removal
of the clay-like shaped body for forming a sintered precious metal
body from the packaging material, because the clay-like shaped body
suffers no cracking when wound tightly once around the outer
peripheral surface of a core rod having a circular cross-sectional
shape with a diameter of 13 mm, shaping of a ring or the like can
be performed easily. Further, because the initial hardness is from
E8 to E20, shaping of the clay-like shaped body by manual
operations following removal from the packaging material is very
easy. At this time, the clay-like shaped body exhibits excellent
flexibility, and exists in a state where only the surface has
dried, meaning it is unlikely to stick to the packaging material,
and can be removed easily from the packaging material.
[0049] Further, because the hardness of the clay-like shaped body
for forming a sintered precious metal body upon standing for one
hour at room temperature following removal from the packaging
material is E40 or less, the clay-like shaped body does not harden
so much that shaping becomes impossible during the shaping process.
The shaping of a ring or the like is usually substantially complete
within about one hour of removing the clay-like shaped body for
forming a sintered precious metal body from the packaging material,
and if the hardness after standing for this period is still E40 or
less, then an essentially stable shaping operation can be performed
from that start of shaping until the completion, thus enabling a
shaped product of the desired shape to be produced with comparative
ease. During the shaping process, if the clay-like shaped body is a
sheet-like shaped body, then this sheet-like shaped body may also
be stamped out using a mold or the like, and even in these types of
cases, the shaped body is unlikely to suffer cracking or the
like.
[0050] Furthermore, because the hardness after standing is still
comparatively low, the clay-like shaped body for forming a sintered
precious metal body still retains satisfactory flexibility even one
hour after removal from the packaging material, and can therefore
still be shaped even after this one-hour period has elapsed.
Accordingly, it is possible to shape the clay-like shaped body for
forming a sintered precious metal body for about 30 minutes to
prepare a partially finished product, subsequently store the
partially finished product for a period of time by sealing inside a
packaging material, and then once again remove the partially
finished product from the packaging material to complete the
shaping process.
[0051] Because the clay-like shaped body for forming a sintered
precious metal body can be used in these types of cases where the
shaping operation is temporarily interrupted and then restarted at
a later time, it is possible to perform shaping across a plurality
of steps, with the shaping operation interrupted between steps and
then restarted at a later time, and therefore shaping can be
performed using all manner of methods in shaping classrooms and the
like.
EXAMPLES
[0052] First, methyl cellulose as the organic binder, propylene
glycol as organic additives, glycerol, polyethylene glycol, a
surface active agent and olive oil, and water were stirred and
mixed inside a container fitted with a stirrer, and the resulting
mixed solution was then introduced, together with a silver powder,
into a kneading device.
[0053] By kneading the silver powder, the binder mixed solution and
the water inside the kneading device, clay-like compositions having
the formulations shown in Table 1 were produced, and after
stretching into a sheet-like form by flattening with a roller, each
composition was used to prepare two different shaped materials,
namely a strip-like sheet material having a width of 5 mm, a
thickness of 2 mm and a length of 70 mm, and a wire-like material
having a diameter of 1.5 mm. These shaped materials were each
wrapped in a film-like packaging material formed from
polyvinylidene chloride.
[0054] One week after production, each clay-like shaped body for
forming a sintered precious metal body was removed from the
packaging material and wound tightly once around the outer
peripheral surface of a stainless steel circular rod (core rod)
having a diameter of 13 mm, and the outer peripheral surface of the
clay-like shaped body was checked for cracking. If one or more
cracks of 1 mm or more (visually detectable cracks) had formed, an
evaluation of "B" was recorded, whereas if no cracks of 1 mm or
more were detected, an evaluation of "A" was recorded.
[0055] Further, the hardness immediately following removal from the
packaging material was measured using a type E durometer in
accordance with JIS K 6253. Removing the clay-like shaped body for
forming a sintered precious metal body from the packaging material,
installing it in the durometer and then starting the measurement
required about one minute. The hardness at this point was recorded
as the initial hardness.
[0056] Further, the hardness after the clay-like shaped body for
forming a sintered precious metal body was left to stand for 30
minutes in a constant-temperature constant-humidity chamber at room
temperature and a humidity of 40% following removal from the
packaging material was also measured in the same manner using the
type E durometer.
[0057] The evaluation results are shown in Table 1.
TABLE-US-00001 TABLE 1 Composition formulation (mass %) Hardness
(type E) Silver Methyl Surface active Propylene Polyethylene Water
and Initial Hardness Cracking upon powder cellulose agent glycol
Glycerol glycol others hardness after standing winding Example 1 90
1 0.2 0.8 0.2 0.2 balance 10 30 A Example 2 90 1.2 0.2 0.6 0.2 0.2
balance 15 35 A Example 3 90 1.7 0.2 0.3 0.1 0.1 balance 20 40 A
Comparative 90 1.2 0.2 0 0 0.1 balance 22 60 B Example 1
[0058] From the results in Table 1 it is evident that each of the
clay-like shaped bodies for forming a sintered precious metal body
in the Examples suffered no cracking even when wound tightly once
around the outer peripheral surface of the stainless steel circular
rod with a diameter of 13 mm. Further, not only was the initial
hardness low, but the increase in the hardness over time was
minimal, with the hardness after standing being E40 or less,
meaning shaping was still possible even after about one hour had
elapsed from the initial state.
[0059] The present invention is not to be considered as being
limited by the above examples, and various modifications can be
made without departing from the spirit or scope of the present
invention.
* * * * *