U.S. patent application number 15/077270 was filed with the patent office on 2016-10-06 for powder for three-dimensional shaping and three-dimensional shaped object.
This patent application is currently assigned to NORITAKE CO., LIMITED. The applicant listed for this patent is NORITAKE CO., LIMITED. Invention is credited to Akihiro OKASHIMO, Daishi YOSHIKAWA.
Application Number | 20160289415 15/077270 |
Document ID | / |
Family ID | 56937109 |
Filed Date | 2016-10-06 |
United States Patent
Application |
20160289415 |
Kind Code |
A1 |
OKASHIMO; Akihiro ; et
al. |
October 6, 2016 |
POWDER FOR THREE-DIMENSIONAL SHAPING AND THREE-DIMENSIONAL SHAPED
OBJECT
Abstract
An object of the present invention is to provide a powder for
three-dimensional shaping that allows shaping a three-dimensional
shaped object having excellent mechanical strength. The powder for
three-dimensional shaping provided by the invention includes
non-hydration reactive base particles and water-soluble bonding
particles. Upon preparation of a slurry through addition of 50
parts by mass of water to 100 parts by mass of the powder, the
viscosity of the slurry after 1 minute from addition of the water
ranges from 30 mPas to 8000 mPas.
Inventors: |
OKASHIMO; Akihiro;
(Nagakute-shi, JP) ; YOSHIKAWA; Daishi;
(Nissin-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NORITAKE CO., LIMITED |
Nagoya-shi |
|
JP |
|
|
Assignee: |
NORITAKE CO., LIMITED
Nagoya-shi
JP
|
Family ID: |
56937109 |
Appl. No.: |
15/077270 |
Filed: |
March 22, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08K 3/22 20130101; B33Y
80/00 20141201; C08K 2003/2227 20130101; B33Y 70/00 20141201 |
International
Class: |
C08K 3/22 20060101
C08K003/22 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 31, 2015 |
JP |
2015-073297 |
Claims
1. A powder for three-dimensional shaping, comprising non-hydration
reactive base particles and water-soluble bonding particles,
wherein upon preparation of a slurry through addition of 50 parts
by mass of water to 100 parts by mass of the powder, the viscosity
of the slurry after 1 minute from addition of the water ranges from
30 mPas to 8000 mPas.
2. The powder for three-dimensional shaping according to claim 1,
wherein the average particle size of the non-hydration reactive
base particles ranges from 1 .mu.m to 80 .mu.m.
3. The powder for three-dimensional shaping according to claim 1,
wherein the content of the water-soluble bonding particles ranges
from 1 part by mass to 20 parts by mass with respect to 100 parts
by mass as a total amount of the powder.
4. The powder for three-dimensional shaping according to claim 1,
wherein the water-soluble bonding particles are made up mainly of
at least one type selected from the group consisting of
thermoplastic resins, thermosetting resins and polysaccharides.
5. The powder for three-dimensional shaping according to claim 1,
wherein the non-hydration reactive base particles are made up
mainly of a metal containing at least one element selected from the
group consisting of Al, Zr, Ti, Zn, Ni and Fe, or an alloy of the
foregoing elements.
6. The powder for three-dimensional shaping according to claim 1,
wherein the non-hydration reactive base particles are made up
mainly of an oxide containing at least one element selected from
the group consisting of Al, Zr, Ti, Zn, Ni, Fe and Si.
7. A three-dimensional shaped object, which is formed by
solidifying a mixture of a water-containing shaping solution with
the powder for three-dimensional shaping according to claim 1.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a powder for
three-dimensional shaping and to a three-dimensional shaped
object.
[0003] The present international application claims priority based
on Japanese Patent Application No. 2015-073297, filed on Mar. 31,
2015, the entire contents of which are incorporated in the present
specification by reference.
[0004] 2. Description of the Related Art
[0005] Technologies are known that involve mixing a
water-containing shaping solution with at least part of a thin
layer of a powder for three-dimensional shaping, solidifying the
mixture, and repeatedly laying up solidified thin layers, to shape
as a result a three-dimensional shaped object (see for instance
Japanese Patent No. 3607300 and Japanese Patent No. 5589817).
Typical configurations of powders for three-dimensional shaping
that are used in such kind of additive manufacturing include, for
instance, configurations in which the powder includes a filler and
a water-soluble adhesive. For example, Japanese Patent No. 3607300
discloses a particulate mixture that includes a filler and a
water-soluble adhesive, wherein the particulate mixture includes
starch as the filler and sucrose as the water-soluble adhesive.
Further, Japanese Patent No. 3607300 discloses a feature wherein,
when an activating fluid having water as a solvent is injected into
a layer of the particulate mixture, a water-soluble adhesive
contained in the particulate mixture dissolves to wet the
particulate mixture and adhesively bond filler particles to each
other, whereby a cross-section portion of an article is formed.
SUMMARY OF THE INVENTION
[0006] Powders for three-dimensional shaping that are used in the
abovementioned additive manufacturing are required to exhibit
excellent mechanical strength so as to preclude breakage of the
obtained three-dimensional shaped object. Japanese Patent No.
3607300 discloses a technology that involves reinforcing the
strength of a final article by using a particulate mixture that
includes reinforcing fibers such as cellulose. Even when relying on
the above technology, however, sufficient strength may fail to be
obtained immediately after molding since the shaped body is formed
as a result of complex reactions, depending on the formulation.
Japanese Patent No. 5589817 discloses a technology of enhancing
planarity by imparting flowability such that a total energy amount
measured by powder rheometry lies within a specific range, to a
powder material that is used for three-dimensional shaping.
However, a high-strength three-dimensional shaped object as
described above cannot be achieved by focusing only on the
flowability of the powder material.
[0007] In view of the above, it is a main object of the present
invention to provide a suitable powder for three-dimensional
shaping that allows shaping a three-dimensional shaped object
having excellent mechanical strength. A related object of the
present invention is to provide a high-strength three-dimensional
shaped object that is shaped using such a powder for
three-dimensional shaping.
[0008] The present invention provides a powder for
three-dimensional shaping, to achieve the above objects. The powder
for three-dimensional shaping disclosed herein includes
non-hydration reactive base particles and water-soluble bonding
particles. Upon preparation of a slurry through addition of 50
parts by mass of water to 100 parts by mass of the powder, the
viscosity of the slurry after 1 minute from addition of the water
ranges from 30 mPas to 8000 mPas. The viscosity of the slurry
denotes herein viscosity that can be measured using a commercially
available vibrational viscometer. For instance, the viscosity of
the slurry after 1 minute from addition of water can be measured
easily by immersing in the slurry the probe tip of a standard
vibrational viscometer in the technical field in question (for
instance, a vibrational viscometer that conforms to JIS Z 8803:2011
"Methods for viscosity measurement of liquids").
[0009] The powder for three-dimensional shaping disclosed herein
has thus a viscosity characteristic as described above and, as a
result, the water-soluble bonding particles dissolve in water when
mixed with a water-containing shaping solution; the water-soluble
bonding particles spread uniformly thereby between the
non-hydration reactive base particles, and a strong adhesive
strength is elicited between the particles. By using a powder for
three-dimensional shaping having the above configuration,
therefore, it becomes possible to fabricate a high-quality
three-dimensional shaped object having superior mechanical strength
as compared with conventional ones.
[0010] In one preferred implementation of the powder for
three-dimensional shaping disclosed herein, the average particle
size of the non-hydration reactive base particles ranges from 1
.mu.m to 80 .mu.m. By prescribing the average particle size of the
non-hydration reaction base particles to lie within that range, it
becomes possible to secure effectively a suitable viscosity of the
slurry, and obtain a three-dimensional shaped object that delivers
yet better performance.
[0011] In one preferred implementation of the powder for
three-dimensional shaping disclosed herein, the content of the
water-soluble bonding particles ranges from 1 part by mass to 20
parts by mass with respect to 100 parts by mass as the total amount
of the powder. Enhancement of mechanical strength can be realized
at a yet higher level when the content of water-soluble bonding
particles lies within such a range.
[0012] In one preferred implementation of the powder for
three-dimensional shaping disclosed herein, the water-soluble
bonding particles are made up mainly of at least one type selected
from the group consisting of thermoplastic resins, thermosetting
resins and polysaccharides. A performance enhancing effect (for
instance, effect of enhancing mechanical strength) derived from
having the viscosity characteristic described above is readily
achieved herein through the use of any one from among thermoplastic
resins, thermosetting resins and polysaccharides.
[0013] In one preferred implementation of the powder for
three-dimensional shaping disclosed herein, the non-hydration
reactive base particles are made up mainly of a metal containing at
least one element selected from the group consisting of Al, Zr, Ti,
Zn, Ni and Fe, or an alloy of the foregoing elements. Metals and
alloys containing the foregoing elements boast high hardness and
high stability towards water, and accordingly can be advantageously
used as non-hydration reactive base particles that are suitable for
the purpose of the present invention.
[0014] In one preferred implementation of the powder for
three-dimensional shaping disclosed herein, the non-hydration
reactive base particles are made up mainly of an oxide containing
at least one element selected from the group consisting of Al, Zr,
Ti, Zn, Ni, Fe and Si. Oxides containing these metal elements or
metalloid elements boast high hardness and high stability towards
water, and accordingly can be advantageously used as non-hydration
reactive base particles that are suitable for the purpose of the
present invention.
[0015] The present invention provides also a three-dimensional
shaped object that is formed by solidifying a mixture of a
water-containing shaping solution with any one of the powders for
three-dimensional shaping disclosed herein. The three-dimensional
shaped object is shaped using the powder for three-dimensional
shaping described above, and accordingly can exhibit better
mechanical strength than conventional ones.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a graph illustrating the relationship between the
viscosity .alpha. of a slurry and strength; and
[0017] FIG. 2 is a graph illustrating a relationship between the
content of water-soluble bonding particles and strength.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0018] Preferred embodiments of the present invention will be
explained next. Any features other than the features specifically
set forth in the present description and which may be necessary for
carrying out the present invention can be regarded as instances of
design matter for a person skilled in the art on the basis of known
techniques in the technical field in question. The present
invention can be carried out thus on the basis of the features
disclosed in the present description and on the basis of common
technical knowledge in the relevant technical field.
[0019] <Powder for Three-Dimensional Shaping>
[0020] The powder for three-dimensional shaping according to one
preferred implementation of the present technology disclosed herein
is a powder for three-dimensional shaping that is used in order to
shape a three-dimensional shaped object. The powder for
three-dimensional shaping is made up of a mixed powder that
includes at least non-hydration reactive base particles and
water-soluble bonding particles. Upon preparation of a slurry
through addition of 50 parts by mass of water to 100 parts by mass
of the powder, the viscosity .alpha. of the slurry after 1 minute
from addition of the water ranges from 30 mPas to 8000 mPas. The
viscosity .alpha. of the slurry, the non-hydration reactive base
particles, the water-soluble bonding particles, a shaping solution,
a shaping method, and a method for fabricating the
three-dimensional shaped object will be explained next in
succession.
[0021] <Slurry Viscosity .alpha.>
[0022] In the present description the viscosity .alpha. of a slurry
is measured as described below. Specifically, a slurry is prepared
by adding 50 parts by mass of water to 100 parts by mass of a
powder for three-dimensional shaping, with kneading for 30 seconds.
The slurry is poured into a container, and the surface of the
slurry is flattened. The viscosity .alpha. (mPas) of the slurry can
be obtained by introducing the probe tip of a vibrational
viscometer (for instance, vibrational viscometer model "VM-100A",
by SEKONIC CORPORATION") into the slurry, and measuring then a
value at the point in time at which one minute has elapsed from
addition of water. As referred to in the present description, the
viscosity .alpha. of the slurry designates a value measured at a
liquid temperature ranging from 20.degree. C. to 22.degree. C.
[0023] The viscosity .alpha. of the slurry of the powder for
three-dimensional shaping disclosed herein, based on the above
viscosity measurement, is set to be equal to or smaller than 8000
mPas. As a result, it becomes possible to increase the mechanical
strength of a three-dimensional shaped object shaped using the
above powder, as compared with a conventional powder for
three-dimensional shaping having a viscosity .alpha. of the slurry
in excess of 8000 mPas.
[0024] Specifically, findings by the inventors have revealed that
in a powder for three-dimensional shaping that exhibits an
excessively high viscosity .alpha. of the slurry, the water-soluble
bonding particles dissolve in water upon mixing of the powder with
a water-containing shaping solution, and the slurry becomes
excessively thick; In consequence, water having the water-soluble
bonding particles dissolved therein does not spread uniformly
between the non-hydration reactive base particles. As a result,
sufficient adhesive strength fails to be brought out among
non-hydration reactive base particles, and the mechanical strength
of the three-dimensional shaped object that is shaped using the
powder tends to drop.
[0025] In the present configuration, by contrast, the viscosity
.alpha. of the slurry at the point in time at which 1 minute has
elapsed from addition of 50 parts by mass of water are added to 100
parts by mass of the powder for three-dimensional shaping, with
kneading, is kept not higher than 8000 mPas. Upon mixing with the
water-containing shaping solution, therefore, the slurry is
thickened suitably through dispersion of the water-soluble bonding
particles with water, and, as a result water having the
water-soluble bonding particles dissolved therein spreads uniformly
between the non-hydration reactive base particles. Accordingly,
strong adhesive strength is elicited between the non-hydration
reactive base particles, and the mechanical strength of the
three-dimensional shaped object that is shaped using the powder can
be enhanced as compared with conventional instances.
[0026] The viscosity .alpha. of the slurry based on the above
viscosity measurement of the powder for three-dimensional shaping
disclosed herein is ordinarily .alpha..ltoreq.8000 mPas, and is
preferably .alpha..ltoreq.6000 mPas, more preferably
.alpha..ltoreq.5000 mPas, yet more preferably .alpha..ltoreq.3000
mPas and particularly preferably .alpha..ltoreq.1000 mPas, in terms
for instance of increasing mechanical strength. On the other hand,
a powder for three-dimensional shaping in which the above viscosity
.alpha. of the slurry is lower than 30 mPas undergoes no
significant thickening when mixed with the water-containing shaping
solution, and, as a result water having the water-soluble bonding
particles dissolved therein does not remain properly between the
non-hydration reactive base particles. In consequence, the
mechanical strength of the three-dimensional shaped object that is
shaped using the powder may contrariwise decrease in some
instances. Further, water having the water-soluble bonding
particles dissolved therein may in some cases permeate up to a
portion of the powder for three-dimensional shaping that should not
solidify (typically, a thin layer filled with the powder in a
layered fashion), and the shape accuracy of the three-dimensional
shaped object constructed using the powder tends to drop. In terms
for instance of enhancing shape accuracy, the above viscosity
.alpha. of the slurry is about 30 mPas.ltoreq..alpha., preferably
50 mPas.ltoreq..alpha., more preferably 100 mPas.ltoreq..alpha.,
and particularly preferably 200 mPa.ltoreq..alpha.. For instance a
powder for three-dimensional shaping having a viscosity .alpha. of
the slurry in the range 30 mPas.ltoreq..alpha..ltoreq.8000 mPas
(further, in the range 200 mPas.ltoreq..alpha..ltoreq.5000 mPas,
and particularly in the range 400 mPas.ltoreq..alpha..ltoreq.900
mPas), is preferred from the viewpoint of combining mechanical
strength and shape accuracy at a high level.
[0027] The viscosity .alpha. of the slurry based on the above
viscosity measurement of a powder for three-dimensional shaping can
be adjusted for instance by modifying the material and/or
properties (for instance, average particle size and specific
surface area) of the non-hydration reactive base particles
contained in the powder for three-dimensional shaping. Generally,
the viscosity .alpha. of the slurry based on the above viscosity
measurement tends to increase as the average particle size of the
non-hydration reactive base particles becomes smaller (increasing
specific surface area). Therefore, the above viscosity .alpha. of
the slurry of the powder for three-dimensional shaping can be
adjusted to lie within the appropriate ranges disclosed herein by
properly selecting the average particle size and the specific
surface area of the non-hydration reactive base particles in the
powder for three-dimensional shaping. As a method for adjusting the
above viscosity .alpha. of the slurry of the powder for
three-dimensional shaping so as to lie within the appropriate range
disclosed herein, a method can be resorted to that involves, for
instance, modifying the content (proportion) of the non-hydration
reactive base particles in the powder, as well as the type content
(proportion), degree of polymerization and molecular weight of the
water-soluble bonding particles. Methods for controlling the above
viscosity .alpha. of the slurry may be resorted to singly or in
combination.
[0028] <Non-Hydration Reactive Base Particles>
[0029] The powder for three-dimensional shaping disclosed herein
contains non-hydration reactive base particles. As used herein, the
term "non-hydration reactive base particles" denotes a substance in
which no hydration reaction (typically, generation of a hydrate or
generation of a hydroxide) occurs when particles of the substance
come into contact with water, of even if such a hydration reaction
occurs, the reaction is limited to a microscopic area on the
surface of the particles, while the majority of the latter do not
substantially react with water. Therefore, the non-hydration
reactive base particles encompass herein conceptually also
instances where water molecules react locally at the surface of the
particles in small amounts (for instance, 0.1 moles or less,
preferably 0.01 moles or less and more preferably 0.001 moles or
less) with respect to 1 mole of the non-hydration reactive base
particles. Typical examples of substances that undergo hydration
reactions include, for instance, gypsum, cement and the like. The
non-hydration reactive base particles are a constituent component
of the base material of the three-dimensional shaped object that is
to be shaped.
[0030] The material and/or properties of the non-hydration reactive
base particles are not particularly limited, so long as the
viscosity .alpha. of the slurry based on the viscosity measurement
described above satisfies the above range. For instance, the
non-hydration reactive base particles may be inorganic particles,
organic particles or organic-inorganic composite particles. The
non-hydration reactive base particles are preferably inorganic
particles and, among the foregoing, preferably particles containing
metallic or metalloid compounds. For instance, non-hydration
reactive base particles made up mainly of an oxide, nitride or
carbide of any element belonging to group 4 through group 14 of the
periodic table can be suitably used herein. Preferred among the
foregoing are non-hydration reactive base particles made up mainly
of an oxide, nitride or carbide of a metal element or metalloid
element from among any of Al, Zr, Ti, Zn, Ni, Fe and Si.
Alternatively, non-hydration reactive base particles may be used
that are made up mainly of a metal including any element belonging
to group 4 through group 13 of the periodic table, or alloys of the
those elements. Preferred among the foregoing are non-hydration
reactive base particles made up mainly of any metal elements from
among Al, Zr, Ti, Zn, Ni and Fe, or alloys of the foregoing
elements.
[0031] Specific examples include, for instance, non-hydration
reactive base particles made up mainly of oxide particles such as
aluminum oxide (for instance, alumina) particles, zirconium oxide
(for instance, zirconia) particles, titanium oxide (for instance
titania) particles, silicon oxide (for instance silica) particles,
zinc oxide particles, iron oxide particles, nickel oxide particles,
cerium oxide (for instance, ceria) particles, magnesium oxide (for
instance, magnesia) particles, chromium oxide particles, manganese
dioxide particles, barium titanate particles, calcium carbonate
particles, barium carbonate particles and the like; metallic
particles such as aluminum particles, nickel particles and iron
particles; nitride particles such as silicon nitride particles,
boron nitride particles and the like; and carbide particles such as
silicon carbide particles, boron carbide particles and the like.
The non-hydration reactive base particles may be used singly as one
type alone or in combinations of two or more types. Preferred among
the foregoing are alumina particles, zirconia particles, titania
particles, silica particles, zinc oxide particles, barium titanate
particles, aluminum particles, nickel particles or iron particles,
in terms of enabling formation of a high-strength three-dimensional
shaped object. Alumina particles, zirconia particles, titania
particles and silica particles are yet more preferred among the
foregoing, alumina particles being particularly preferred.
[0032] In the present description, the wording "made up mainly of
X" pertaining to composition of the non-hydration reactive base
particles denotes a feature wherein the proportion of X (purity of
X) in the non-hydration reactive base particles is 90% or higher
(preferably, 95% or higher, more preferably 97% or higher, yet more
preferably 98% or higher and for instance 99% or higher) on a mass
basis.
[0033] The shape (outline) of the non-hydration reactive base
particles is not particularly limited, and the particles may be
spherical or aspherical. Substantially spherical non-hydration
reactive base particles can be preferably used from the viewpoint
of mechanical strength, ease of fabrication and so forth. The
average particle size of the non-hydration reactive base particles
is not particularly limited, so long as the viscosity .alpha. of
the slurry based on a viscosity measurement described above
satisfies the above range, and is ordinarily 1 .mu.m or greater,
preferably 10 .mu.m or greater, more preferably 20 .mu.m or
greater, and particularly preferably 30 .mu.m or greater (for
instance, 40 .mu.m or greater). The viscosity .alpha. of the slurry
based on the above viscosity measurement can be effectively lowered
by virtue of the fact that non-hydration reactive base particles
have the above average particle size, and hence a high-strength
three-dimensional shaped object can be realized yet more
efficiently. The upper limit of the average particle size of the
non-hydration reactive base particles is appropriately of about 80
.mu.m or smaller from the viewpoint of moldability (for instance,
moldability when the powder for three-dimensional shaping is filled
in the form of a thin layer) or the like. The above average
particle size is preferably 70 .mu.m or smaller, and more
preferably 60 .mu.m or smaller (for instance, 50 .mu.m or smaller)
from the viewpoint of combining enhanced mechanical strength and
moldability at a yet higher level.
[0034] The "average particle size" in the present description is
not particularly limited, and refers to a 50% volume-average
particle size (D50 size), i.e. a particle size at a cumulative
value of 50% in a particle size distribution measured on the basis
of a particle size distribution measuring device that utilizes
laser scattering and diffraction. More specifically, the "average
particle size" refers to 50% volume-average particle size obtained
through dry measurement, without dispersion of particles by
compressed air, using a laser diffraction-scattering-type particle
size distribution measuring device.
[0035] The content of the non-hydration reactive base particles in
the powder for three-dimensional shaping is not particularly
limited, so long as the viscosity .alpha. of the slurry based on a
viscosity measurement described above satisfies the above range.
The content of the non-hydration reactive base particles is
ordinarily 80 parts by mass or higher with respect to 100 parts by
mass as the total amount of powder for three-dimensional shaping,
and preferably 85 parts by mass or higher, more preferably 90 parts
by mass or higher, in terms for instance of enhancing mechanical
strength. The upper limit of the content of non-hydration reactive
base particles is not particularly restricted, but is preferably 99
parts by mass or lower, more preferably 98 parts by mass or lower,
and particularly preferably 96 parts by mass or lower. The effect
of the present configuration can be elicited at a yet higher level
within such ranges of content of non-hydration reactive base
particles.
[0036] <Water-Soluble Bonding Particles>
[0037] The powder for three-dimensional shaping disclosed herein
contains water-soluble bonding particles. The "water-soluble
bonding particles" denote herein resin particles such that all or
some of the particles dissolve when 2 parts by mass of the bonding
particles are added to 100 parts by mass of water at a liquid
temperature of 90.degree. C., with stirring for 4 hours, so that,
as a result, an aqueous solution having the bonding particles
dissolved therein exhibits higher viscosity than that of water. In
one preferred implementation, the aqueous solution having the above
bonding particles dissolved therein exhibits viscosity at a level
that exceeds 1.2.times.A (preferably 1.5.times.A, more preferably
2.0.times.A), where A (mPas) denotes the viscosity of water. The
water-soluble bonding particles are a component which, upon mixing
with the water-containing shaping solution, dissolves in water and
binds thereby non-hydration reactive base particles to one
another.
[0038] The material and properties of the water-soluble bonding
particles are not particularly limited, so long as the viscosity
.alpha. of the slurry based on the viscosity measurement described
above satisfies the above range. For instance there are preferably
used water-soluble bonding particles made up mainly of any one of
thermoplastic resins, thermosetting resins and polysaccharides.
[0039] Specific examples of thermoplastic resins include, for
instance, vinyl alcohol resins, isobutylene resins, polyamide
resins, polyester resins and the like. Vinyl alcohol resins are
typically resins (PVA) including vinyl alcohol units as the main
repeating units. In the above resin, the proportion of the number
of moles of the vinyl alcohol units in the number of moles of all
repeating units is ordinarily 50% or higher (for instance, in the
range 50% to 90%), preferably 65% or higher, more preferably 75% or
higher, for instance 85% or higher. All repeating units may be
substantially made up of vinyl alcohol units. The types of the
repeating units other than vinyl alcohol units in PVA are not
particularly limited, and may include for instance vinyl acetate
units or the like. For instance there can be used anionically
modified PVA or cationically modified PVA such as carboxyl
group-modified PVA, sulfonate group-modified PVA, phosphate
group-modified PVA or the like; or modified PVA obtained through
copolymerization with ethylene, a vinyl ether having a long-chain
alkyl group, a vinyl ester, (meth)acrylicamide, an olefin or the
like. The degree of polymerization of PVA is not particularly
limited, but can range for instance from 100 to 5000 (preferably,
from 500 to 3000). The isobutylene resin may be a homopolymer of
isobutylene or a copolymer (isobutylene copolymer) of isobutylene
with other monomers. The other monomers that copolymerize with
isobutylene in the isobutylene copolymer are not particularly
limited. Examples thereof include, for instance, monomers having
ethylenic double bonds. Examples of monomers having ethylenic
double bonds include, for instance, monomers with ethylenically
unsaturated carbons, such as maleic acid (anhydride), acrylic acid,
methacrylic acid, phthalic acid (anhydride), itaconic acid
(anhydride) and the like. Herein there may be used a chemically
modified isobutylene copolymer. The molecular weight of the
isobutylene copolymer is not particularly limited, but can range
for instance from 3.times.10.sup.3 to 2.times.10.sup.5 (preferably,
from 5.times.10.sup.3 to 1.7.times.10.sup.5). Examples of polyamide
resins include, for instance, water-soluble nylon resulting from
chemically modifying a nylon such as polycaproamide (nylon-6).
Examples of polyester resins include, for instance, water-soluble
polyesters in which a component having a hydrophilic group is
introduced, as a copolymerization component, into a polyester.
Among the foregoing thermoplastic resins, vinyl alcohol-based
resins and isobutylene resins are preferred in that these resins
afford strong adhesive forces, and allow adjusting easily the
viscosity .alpha. of the slurry to lie into the above range.
[0040] Preferred examples of thermosetting resins include, for
instance, melamine resins. The melamine resin may be herein a
melamine resin obtained through a polymerization reaction of
melamine and an aldehyde, or may be a copolymer resin of a monomer
(or initial polymer thereof) that is used to form a melamine resin)
and another monomer (or initial polymer thereof). The aldehyde that
polymerizes with melamine in the melamine resin is not particularly
limited. For instance, a melamine resin can be preferably used
herein that is obtained as a result of a polymerization reaction
between melamine and formaldehyde.
[0041] Preferred examples of polysaccharides include, for instance,
cellulose derivatives such as hydroxypropyl methyl cellulose,
hydroxyethyl methyl cellulose, hydroxyethyl cellulose,
hydroxypropyl cellulose, methyl cellulose, ethyl cellulose, ethyl
hydroxyethyl cellulose, carboxymethyl cellulose and the like, as
well as natural polymer compounds such as gum arabic, xanthan gum,
curdlan, starch, dextrin, glucomannan, agarose, carrageenan, guar
gum, locust bean gum, tragacanth gum, quince seed gum, pullulan,
agar, konjac mannan and the like. Among the foregoing,
hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose,
methyl cellulose, gum arabic and xanthan gum are preferably used in
terms for instance of adhesion and ease of viscosity
adjustment.
[0042] Other examples of the water-soluble bonding particles that
may be incorporated into the powder for three-dimensional shaping
disclosed herein include water-soluble bonding particles made up
mainly of, for instance, polyethylene glycol, partially neutralized
sodium polyacrylate, polyvinyl pyrrolidone, polyvinyl pyrrolidone
copolymers, sodium polyacrylate, copolymers of sodium polyacrylate,
sodium alginate, sucrose, dextrose, fructose, lactose, gelatin and
the like. The water-soluble bonding particles described above may
be used singly as one type or in combinations of two or more
types.
[0043] In the present description, the wording "made up mainly of
X" pertaining to the composition of the water-soluble bonding
particles denotes a feature wherein the proportion of X (purity of
X) in the water-soluble bonding particles is 90% or higher
(preferably, 95% or higher, more preferably 97% or higher, yet more
preferably 98% or higher and for instance 99% or higher) on a mass
basis.
[0044] Although not particularly limited thereto, the average
particle size of the water-soluble bonding particles is ordinarily
0.1 .mu.m or greater, preferably 1 .mu.m or greater. The upper
limit of the average particle size of the water-soluble bonding
particles is appropriately set to be about 250 .mu.m or smaller,
and is preferably 200 .mu.m or smaller.
[0045] The content of the water-soluble bonding particles in the
powder for three-dimensional shaping is not particularly limited,
so long as the viscosity .alpha. of the slurry based on a viscosity
measurement described above satisfies the above range. The content
of the water-soluble bonding particles is ordinarily 1 part by mass
or higher with respect to 100 parts by mass as the total amount of
powder for three-dimensional shaping, and preferably 2 parts by
mass or higher, more preferably 4 parts by mass or higher, in terms
for instance of enhancing mechanical strength. The upper limit of
the content of water-soluble bonding particles is not particularly
limited, but is preferably 20 parts by mass or lower, more
preferably 15 parts by mass or lower, and particularly preferably
10 parts by mass or lower. Within such a range of the content of
the water-soluble bonding particles, the viscosity .alpha. of the
slurry based on the above viscosity measurement decreases
effectively, and a high-strength three-dimensional shaped object
can be realized yet more efficiently.
[0046] In the technology disclosed herein, the water-soluble
bonding particles and the non-hydration reactive base particles may
be present not bonded to each other but as particles independent
from each other. The desired powder for three-dimensional shaping
can be easily achieved by virtue of the fact that the water-soluble
bonding particles and the non-hydration reactive base particles are
present as particles independent from each other. Alternatively,
the water-soluble bonding particles may be adhered to the surface
of the non-hydration reactive base particles. Specifically, part of
the entirety of the non-hydration reactive base particles may be
covered (coated) with the water-soluble bonding particles. As a
result, the water-soluble bonding particles can be present, in the
required amount, between non-hydration reactive base particles, and
hence water having the water-soluble bonding particles dissolved
therein can spread efficiently between the non-hydration reactive
base particles. Accordingly, the above-described enhancing effect
on the strength of the three-dimensional shaped object can be
elicited yet more effectively.
[0047] The powder for three-dimensional shaping disclosed herein
may further contain, as needed, known additives that are used in
powders for three-dimensional shaping, for instance dispersants,
thickeners, printing aids and the like, so long as the effect of
the present configuration is not impaired thereby. The content of
the above additives may be set in accordance with the purpose for
which additives are added, and will not be explained in detail here
since it is not a characterizing feature of the present
invention.
[0048] The method for preparing the powder for three-dimensional
shaping disclosed herein is not particularly limited. For instance,
the various components contained in the powder for
three-dimensional shaping may be mixed by relying on a known mixing
method, for instance using a Polymix. The way in which the
components are mixed is not particularly limited, and may involve
for instance mixing all components at one time, or mixing the
components according to an appropriately established sequence.
[0049] The powder for three-dimensional shaping disclosed herein is
used in additive manufacturing in which a three-dimensional shaped
object is shaped through repeated layering of solidified thin
layers that are obtained through mixing of a water-containing
shaping solution with at least part of the thin layer of the powder
for three-dimensional shaping having been filled in a layered
manner. The shape of the three-dimensional shaped object that is to
be shaped is not particularly limited. The powder for
three-dimensional shaping disclosed herein can be preferably used
for shaping of shaped objects having various three-dimensional
shapes.
[0050] <Shaping Solution>
[0051] The powder for three-dimensional shaping disclosed herein is
typically used for shaping a three-dimensional shaped object in an
implementation in which the powder for three-dimensional shaping is
mixed with a water-containing shaping solution. Herein it suffices
that the solvent used in the above shaping solution contains water.
Examples of the solvent that can be preferably used include pure
water, ultra-pure water, ion-exchanged water (deionized water),
distilled water and the like. The shaping solution disclosed herein
may further contain, as needed, an organic solvent (lower alcohol,
lower ketone or the like) that is homogeneously miscible with
water. Preferably, the 40 vol % or more of the solvent contained in
the shaping solution is water, more preferably 50 vol % or more
(typically, 50 to 100 vol %) of the solvent is water.
[0052] The shaping solution disclosed herein may further contain,
as needed, known additives that can be used in shaping solutions,
for instance dyes, organic pigments, inorganic pigments, wetting
agents and flow enhancers, so long as the effect of the present
configuration is not impaired thereby. The content of the above
additives may be set in accordance with the purpose for which
additives are added, and will not be explained in detail herein
since it is not a characterizing feature of the present
invention.
[0053] <Shaping Method>
[0054] The powder for three-dimensional shaping disclosed herein
can be used for instance in an implementation that includes the
operations below, to shape (fabricate) a three-dimensional shaped
object. An explanation follows next on one preferred embodiment of
a method for shaping a three-dimensional shaped object using the
powder for three-dimensional shaping disclosed herein. Shaping can
be carried out using a 3D printer for solid-shaping on the basis
for instance of three-dimensional data corresponding to the
three-dimensional shaped object that is to be shaped. Such a 3D
printer can have an inkjet for dripping the water-containing
shaping solution and a mounting table on which the powder for
three-dimensional shaping is disposed.
[0055] To shape the three-dimensional shaped object there is
prepared any one of the powders for three-dimensional shaping
disclosed herein. Preparation of the powder for three-dimensional
shaping involves, for instance, mixing the various components
contained in the powder for three-dimensional shaping according to
a known mixing method, for instance using a Polymix.
[0056] Operations 1 to 3 below are repeated next, to shape as a
result the three-dimensional shaped object through sequential
layering of a layer-like solid material. Operation 1: the above
powder for three-dimensional shaping is filled in a layer-like
manner on a mounting table, to a thickness (for instance in the
range 0.01 mm to 0.3 mm) corresponding to each layer of the
three-dimensional shaped object that is to be shaped. Operation 2:
the water-containing shaping solution is dripped, out of an inkjet
head, onto a portion to be solidified in the powder for
three-dimensional shaping having been filled in a layer-like manner
(i.e. portion corresponding to the part that is to be shaped in the
three-dimensional shaped object). The water-soluble bonding
particles contained in the drip portion dissolve and the
non-hydration reactive base particles become thereby bonded to each
other. A layer-like solid material becomes formed (solidified) as a
result. Operation 3: the mounting table is lowered vertically by
the extent of a thickness corresponding to each layer of the above
three-dimensional shaped object.
[0057] Thereafter, the powder for three-dimensional shaping that
has not solidified is removed lastly, to complete the shaping of
the three-dimensional shaped object. The three-dimensional shaped
object having been shaped using the powder for three-dimensional
shaping disclosed herein may be fired after shaping. The firing
temperature is not particularly limited, but is preferably set to
lie for instance in the range from 600.degree. C. to 1800.degree.
C. A three-dimensional shaped object of yet higher strength can be
formed as a result. The three-dimensional shaped object after
shaping may be then immersed in a firing aid and be subsequently
fired, as needed. A three-dimensional shaped object of yet higher
strength can be formed as a result.
[0058] <Method for Fabricating a Three-Dimensional Shaped
Object>
[0059] The technology disclosed herein there encompasses, for
instance, a method for fabricating a three-dimensional shaped
object. Specifically, the method according to the technology
disclosed herein includes a step of preparing a the powder for
three-dimensional shaping that includes the non-hydration reactive
base particles and the water-soluble bonding particles; and a step
of mixing the water-containing shaping solution with at least part
of a thin layer of the powder for three-dimensional shaping having
been filled in a layer-like manner, solidifying the mixture, and
repeatedly laying up solidified thin layers, to shape as a result a
three-dimensional shaped object. Upon preparation of a slurry
through addition of 50 parts by mass of water to 100 parts by mass
of the powder for three-dimensional shaping, with kneading in the
step of preparing the above powder for three-dimensional shaping in
this method for fabricating a three-dimensional shaped object, the
powder for three-dimensional shaping is prepared such that the
viscosity of the slurry after 1 minute from addition of the water
ranges from 30 mPas to 8000 mPas. The above fabrication method is
carried out by resorting preferably to the features of the powder
for three-dimensional shaping and the shaping method disclosed
herein. The above fabrication method provides a high-quality
three-dimensional shaped object having superior mechanical strength
as compared with conventional instances.
[0060] Various examples pertaining to the present invention will be
explained next, but the present invention is not meant to be
limited to or by the examples.
Preparation of a Powder for Three-Dimensional Shaping
Example 1
[0061] A powder for three-dimensional shaping was prepared through
stirring of non-hydration reactive base particles and water-soluble
bonding particles in a Polymix for 30 seconds.
[0062] Alumina particles having an average particle size of 40
.mu.m were used as the non-hydration reactive base particles.
Polyvinyl alcohol (PVA, Poval 205S by Kuraray Co., Ltd.) was used
as the water-soluble bonding particles.
[0063] The content of the non-hydration reactive base particles is
90 parts by mass and the content of the water-soluble bonding
particles is 10 parts by mass, with respect 100 parts by mass of
the powder for three-dimensional shaping.
[0064] <Measurement of Slurry Viscosity .alpha.>
[0065] Herein 4 g of water were added to 8 g of the above powder
for three-dimensional shaping, and the whole was kneaded for 30
seconds in a rubber bowl, to prepare a slurry. The slurry was
placed in a plastic container having diameter 36 mm.times.length 32
mm, while avoiding entrapment of bubbles, and the surface of the
slurry was flattened using a spatula. The viscosity .alpha. of the
slurry at a point in time where 1 minute had elapsed from addition
of water and kneading was measured using a vibrational viscometer
model "VM-100A" by Sekonic Corporation (liquid temperature 20 to
22.degree. C.). The result yielded a viscosity .alpha. of the above
slurry of 800 mPas.
Example 2
[0066] A powder for three-dimensional shaping and slurry according
to the present example were prepared in the same way as in Example
1, but herein a melamine resin (National melamine, by Kayo
Corporation) was used, instead of PVA, as the water-soluble bonding
particles. The viscosity .alpha. of the slurry was 80 mPas.
Example 3
[0067] A powder for three-dimensional shaping and slurry according
to the present example were prepared in the same way as in Example
1, but herein gum arabic was used, instead of PVA, as the
water-soluble bonding particles. The viscosity .alpha. of the
slurry was 110 mPas.
Example 4
[0068] A powder for three-dimensional shaping and slurry according
to the present example were prepared in the same way as in Example
1, but herein xanthan gum (KELZAN, by Sansho Co., Ltd.) was used,
instead of PVA, as the water-soluble bonding particles. The
viscosity .alpha. of the slurry was 7800 mPas.
Example 5
[0069] A powder for three-dimensional shaping and slurry according
to the present example were prepared in the same way as in Example
1, but herein xanthan gum (KELZAN, by Sansho Co., Ltd.) was used,
instead of PVA, as the water-soluble bonding particles; further,
the content of the non-hydration reactive base particles was set to
98 parts by mass and the content of the water-soluble bonding
particles was set to 2 parts by mass. The viscosity .alpha. of the
slurry was 1300 mPas.
Example 6
[0070] A powder for three-dimensional shaping and slurry according
to the present example were prepared in the same way as in Example
1, but herein an isobutylene resin A (ISOBAM 110, by Kuraray Co.,
Ltd.) was used, instead of PVA, as the water-soluble bonding
particles. The viscosity .alpha. of the slurry was 900 mPas.
Example 7
[0071] A powder for three-dimensional shaping and slurry according
to the present example were prepared in the same way as in Example
1, but herein an isobutylene resin A (ISOBAM 110, by Kuraray Co.,
Ltd.) was used, instead of PVA, as the water-soluble bonding
particles; further, the content of the non-hydration reactive base
particles was set to 99 parts by mass and the content of the
water-soluble bonding particles was set to 1 part by mass. The
viscosity .alpha. of the slurry was 60 mPas.
Example 8
[0072] A powder for three-dimensional shaping and slurry according
to the present example were prepared in the same way as in Example
1, but herein an isobutylene resin B (ISOBAM 104, by Kuraray Co.,
Ltd.) was used, instead of PVA, as the water-soluble bonding
particles. The viscosity .alpha. of the slurry was 400 mPas.
Example 9
[0073] A powder for three-dimensional shaping and slurry according
to the present example were prepared in the same way as in Example
1, but herein the content of the non-hydration reactive base
particles was set to 99 parts by mass and the content of the
water-soluble bonding particles was set to 1 part by mass. The
viscosity .alpha. of the slurry was 36 mPas.
Example 10
[0074] A powder for three-dimensional shaping and slurry according
to the present example were prepared in the same way as in Example
1, but herein the content of the non-hydration reactive base
particles was set to 85 parts by mass and the content of the
water-soluble bonding particles was set to 15 parts by mass. The
viscosity .alpha. of the slurry was 2500 mPas.
Example 11
[0075] A powder for three-dimensional shaping and slurry according
to the present example were prepared in the same way as in Example
1, but herein the content of the non-hydration reactive base
particles was set to 80 parts by mass and the content of the
water-soluble bonding particles was set to 20 parts by mass. The
viscosity .alpha. of the slurry was 4800 mPas.
Example 12
[0076] A powder for three-dimensional shaping and slurry according
to the present example were prepared in the same way as in Example
1 but herein the content of the non-hydration reactive base
particles was set to 50 parts by mass and the content of the
water-soluble bonding particles was set to 50 part by mass. The
viscosity .alpha. of the slurry was 22000 mPas.
Example 13
[0077] A powder for three-dimensional shaping and slurry according
to the present example were prepared in the same way as in Example
1, but herein silica particles having an average particle size of
80 .mu.m were used, instead of the alumina particles having an
average particle size of 40 .mu.m, as the non-hydration reactive
base particles. The viscosity .alpha. of the slurry was 1320
mPas.
Example 14
[0078] A powder for three-dimensional shaping and slurry according
to the present example were prepared in the same way as in Example
1, but herein silica particles having an average particle size of
15 .mu.m were used, instead of the alumina particles having an
average particle size of 40 .mu.m, as the non-hydration reactive
base particles. The viscosity .alpha. of the slurry was 1080
mPas.
Example 15
[0079] A powder for three-dimensional shaping and slurry according
to the present example were prepared in the same way as in Example
1, but herein titania particles having an average particle size of
0.2 .mu.m were used, instead of the alumina particles having an
average particle size of 40 .mu.m, as the non-hydration reactive
base particles. The viscosity .alpha. of the slurry was 40000
mPas.
Example 16
[0080] A powder for three-dimensional shaping and slurry according
to the present example were prepared in the same way as in Example
1, but herein titania particles having an average particle size of
2 .mu.m were used, instead of the alumina particles having an
average particle size of 40 .mu.m, as the non-hydration reactive
base particles. The viscosity .alpha. of the slurry was 5400
mPas.
Example 17
[0081] A powder for three-dimensional shaping and slurry according
to the present example were prepared in the same way as in Example
1, but herein zirconia particles having an average particle size of
30 .mu.m were used, instead of the alumina particles having an
average particle size of 40 .mu.m, as the non-hydration reactive
base particles. The viscosity .alpha. of the slurry was 280
mPas.
Example 18
[0082] A powder for three-dimensional shaping and slurry according
to the present example were prepared in the same way as in Example
1, except that herein no water-soluble bonding particles were used.
The viscosity .alpha. of the slurry was 17 mPas.
[0083] <Crushing Strength Measurement>
[0084] The slurry of each example was poured into a plate coated
with Teflon (registered trademark), and was dried for 24 hours. A
test piece 10 mm wide, 30 mm long and 2.4 mm thick was cut out of
each sample and was placed on a cylindrical stainless steel jig
having a diameter of 12 mm. A pressure attachment was lowered while
the attachment pressed against the test piece, and the load value
(crushing strength: kg) upon breakage of the test piece was
measured. The results are given in Table 1, FIG. 1 and FIG. 2. FIG.
1 is a graph illustrating the relationship between the viscosity
.alpha. of the slurry and crushing strength. FIG. 2 is a graph
illustrating a relationship between the content of water-soluble
bonding particles and crushing strength. Samples having a crushing
strength of 1 kg (=9.8 N) or higher were deemed to be good. Such a
crushing strength is necessary in order for the three-dimensional
shaped object after shaping to be removable from the shaping device
without breaking. It is found, on the basis of preliminary
experiments or the like, that a strong positive correlation exists
(correlation coefficient of 0.8 or higher) between the crushing
strength based on the above crushing test and the shaping strength
of the three-dimensional shaped object that is actually shaped
using a 3D printer.
TABLE-US-00001 TABLE 1 Non-hydration reactive base particles
Average Water-soluble bonding particles particle Content Content
Crushing size (parts by (parts by Viscosity .alpha. strength Type
(.mu.m) mass) Type mass) (mPa s) (kg) Example 1 Alumina 40 90 PVA
10 800 2.0 Example 2 Alumina 40 90 Melamine resin 10 80 1.1 Example
3 Alumina 40 90 Gum arabic 10 110 1.5 Example 4 Alumina 40 90
Xanthan gum 10 7800 2.7 Example 5 Alumina 40 98 Xanthan gum 2 1300
2.0 Example 6 Alumina 40 90 Isobutylene resin A 10 900 4.8 Example
7 Alumina 40 99 Isobutylene resin A 1 60 1.2 Example 8 Alumina 40
90 Isobutylene resin B 10 400 4.5 Example 9 Alumina 40 99 PVA 1 36
1.3 Example Alumina 40 85 PVA 15 2500 2.2 10 Example Alumina 40 80
PVA 20 4800 1.0 11 Example Alumina 40 50 PVA 50 22000 0.2 12
Example Silica 80 90 PVA 10 1320 2.0 13 Example Silica 15 90 PVA 10
1080 1.9 14 Example Titania 0.2 90 PVA 10 40000 0.2 15 Example
Titania 2 90 PVA 10 5400 1.0 16 Example Zirconia 30 90 PVA 10 280
2.1 17 Example Alumina 40 100 -- -- 17 0.0 18
[0085] As Table 1 and FIG. 1 reveal, a crushing strength of 1.0 kg
or greater could be realized in the powders for three-dimensional
shaping according to Examples 1 to 11, 13, 14, 16 and 17, in which
the viscosity .alpha. of the slurry lay in the range 30 mPas to
8000 mPas, and the strength of the three-dimensional shaped object
could be enhanced significantly as compared to that in Examples,
12, 15 and 18. In the case of the powder for three-dimensional
shaping provided herein, the crushing strength of the
three-dimensional shaped object tended to increase further
(Examples 6 and 8) through setting of the viscosity .alpha. of the
slurry to lie in the range 400 mPas to 900 mPas. It was found that,
as a result, the mechanical strength of the three-dimensional
shaped object can be enhanced by using a powder for
three-dimensional shaping in which the viscosity .alpha. of the
slurry ranges from 30 mPas to 8000 mPas (preferably, from 400 mPas
to 900 mPas).
[0086] As Table 1 and FIG. 2 reveal, it was found that in the case
of the powder for three-dimensional shaping disclosed herein the
crushing strength was enhanced (Examples 1 to 11, 13, 14, 16 and
17) by setting the content of water-soluble bonding particles to be
equal to or greater than 1 part by mass. By contrast, in Example 12
where the content of water-soluble bonding particles was set to 50
parts by mass, the effect of enhancing crushing strength tended to
be weaker than in Examples 1 to 11, 13, 14, 16 and 17, in which the
content of water-soluble bonding particles was set to range from 1
part by mass to 20 parts by mass. The above results indicate that
the content of the water-soluble bonding particles in the powder
for three-dimensional shaping is preferably set to range from about
1 part by mass to 20 parts by mass. The viscosity .alpha. of the
slurry in Example 15, where the average particle size of the
non-hydration reactive base particles was set to 0.2 .mu.m, was
excessively high, and accordingly the crushing strength was lower
than that in Examples 1 to 11, 13, 14, 16 and 17. This result
indicates that the average particle size of the non-hydration
reactive base particles is preferably greater than about 0.2 .mu.m
(preferably, 1 .mu.m or greater).
[0087] Embodiments of the present invention have been described in
detail above, but the embodiments are merely illustrative in
nature, and are not meant to limit the scope of the claims in any
way. The technical features set forth in the claims encompass
various alterations and modifications of the specific examples
illustrated above.
* * * * *