U.S. patent application number 14/659791 was filed with the patent office on 2015-07-02 for process of producing polylactic acid-based resin microparticles and polylactic acid-based resin microparticles.
The applicant listed for this patent is Toray Industries, Inc.. Invention is credited to Itaru Asano, Hiroshi Kobayashi, Makiko Saito, Hiroshi Takezaki.
Application Number | 20150183928 14/659791 |
Document ID | / |
Family ID | 46602370 |
Filed Date | 2015-07-02 |
United States Patent
Application |
20150183928 |
Kind Code |
A1 |
Takezaki; Hiroshi ; et
al. |
July 2, 2015 |
PROCESS OF PRODUCING POLYLACTIC ACID-BASED RESIN MICROPARTICLES AND
POLYLACTIC ACID-BASED RESIN MICROPARTICLES
Abstract
A process of producing polylactic acid-based resin
microparticles includes a dissolving step that forms a system,
which can cause phase separation into two phases of a solution
phase mainly composed of polylactic acid-based resin (A) having an
enthalpy of fusion of less than 5 J/g and a solution phase mainly
composed of polymer (B) different from polylactic acid-based resin,
by dissolving the polylactic acid-based resin (A) and the polymer
(B) different from polylactic acid-based resin in an ether-based
organic solvent (C); an emulsion-forming step that forms an
emulsion by applying a shear force to the system; and a
microparticle-forming step that precipitates polylactic acid-based
resin microparticles by contacting the emulsion with a poor solvent
which has lower solubility of the polylactic acid-based resin (A)
than the ether-based organic solvent (C).
Inventors: |
Takezaki; Hiroshi;
(Nagoya-shi, JP) ; Kobayashi; Hiroshi;
(Nagoya-shi, JP) ; Saito; Makiko; (Nagoya-shi,
JP) ; Asano; Itaru; (Nagoya-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Toray Industries, Inc. |
Tokyo |
|
JP |
|
|
Family ID: |
46602370 |
Appl. No.: |
14/659791 |
Filed: |
March 17, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13982804 |
Jul 31, 2013 |
9017812 |
|
|
PCT/JP2011/079776 |
Dec 22, 2011 |
|
|
|
14659791 |
|
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Current U.S.
Class: |
528/361 |
Current CPC
Class: |
G03G 9/0802 20130101;
A61K 8/85 20130101; G03G 9/0821 20130101; Y10T 428/2982 20150115;
A61Q 1/02 20130101; G03G 9/08775 20130101; C08J 3/14 20130101; C08G
63/81 20130101; G03G 9/08762 20130101; C08J 9/28 20130101; C08J
2367/04 20130101; A61K 8/0241 20130101; G03G 9/0804 20130101; A61Q
1/10 20130101; G03G 9/08722 20130101; C08G 63/08 20130101; A61K
2800/412 20130101; C08J 9/26 20130101; A61K 8/0279 20130101 |
International
Class: |
C08G 63/81 20060101
C08G063/81 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 31, 2011 |
JP |
2011-018041 |
Jun 30, 2011 |
JP |
2011-145913 |
Nov 24, 2011 |
JP |
2011-256061 |
Claims
1. A process of producing polylactic acid-based resin
microparticles comprising: a dissolving step that forms a system,
which can cause phase separation into two phases of a solution
phase mainly composed of polylactic acid-based resin (A) having an
enthalpy of fusion of less than 5 J/g and a solution phase mainly
composed of polymer (B) different from polylactic acid-based resin,
by dissolving said polylactic acid-based resin (A) and said polymer
(B) different from polylactic acid-based resin in an ether-based
organic solvent (C); an emulsion-forming step that forms an
emulsion by applying a shear force to said system; and a
microparticle-forming step that precipitates polylactic acid-based
resin microparticles by contacting said emulsion with a poor
solvent which has lower solubility of said polylactic acid-based
resin (A) than said ether-based organic solvent (C).
2. The process according to claim 1, wherein said ether-based
organic solvent (C) has a boiling point of 100.degree. C. or
higher.
3. The process according to claim 2, wherein said ether-based
organic solvent (C) is diethylene glycol dimethyl ether.
4. The process according to claim 1, wherein said polymer (B)
different from a polylactic acid-based resin is a polyvinyl
alcohol, a hydroxypropyl cellulose, a polyethylene oxide or a
polyethylene glycol.
5. The process according to claim 1, wherein said poor solvent is
water.
6. The process according to claim 2, wherein said polymer (B)
different from a polylactic acid-based resin is a polyvinyl
alcohol, a hydroxypropyl cellulose, a polyethylene oxide or a
polyethylene glycol.
7. The process according to claim 3, wherein said polymer (B)
different from a polylactic acid-based resin is a polyvinyl
alcohol, a hydroxypropyl cellulose, a polyethylene oxide or a
polyethylene glycol.
8. Polylactic acid-based resin microparticles having a sphericity
of 90 or greater, a particle diameter distribution index of 1 to
1.8 and a linseed oil absorption of less than 70 ml/100 g, except
for hollow microparticles, wherein said polylactic acid-based resin
has an enthalpy of fusion of less than 5 J/g.
9. The polylactic acid-based resin microparticles according to
claim 8, having a number average particle diameter of 1 to 100
.mu.m.
Description
RELATED APPLICATIONS
[0001] This is a divisional of U.S. Ser. No. 13/982,804, filed Jul.
31, 2013, which is a .sctn.371 of International Application No.
PCT/JP2011/079776, with an international filing date of Dec. 22,
2011 (WO 2012/105140 A1, published Aug. 9, 2012), which is based on
Japanese Patent Application Nos. 2011-018041, filed Jan. 31, 2011;
2011-145913, filed Jun. 30, 2011; and 2011-256061, filed Nov. 24,
2011.
TECHNICAL FIELD
[0002] This disclosure relates to a process of producing polylactic
acid-based resin microparticles and polylactic acid-based resin
microparticles.
BACKGROUND
[0003] Different from polymer molded products such as films,
fibers, injection molded products and extrusion molded products,
polymer microparticles are used for modification and improvement of
various materials by utilizing the large specific surface area and
the structure of microparticles. Their major uses include modifiers
for cosmetics, additives for toners, rheology modifiers for paints
and the like, agents for medical diagnosis and examination, and
additives for molded products such as automobile materials and
construction materials.
[0004] On the other hand, with interest growing in recent
environmental problems, there are increasing demands for using
materials of non-petroleum origin to reduce environmental loads,
even in the fields where polymer microparticles are used such as
cosmetics and paints. Polylactic acid is one of the representative
examples of such non-petroleum origin polymers.
[0005] As a conventional method of producing polylactic acid-based
resin microparticles or powders, there are several known methods:
for example, crushing methods (JP-A-2000-007789 and
JP-A-2001-288273) typified by freeze crushing method;
dissolution-deposition methods (JP-A-2005-002302 and
JP-A-2009-242728) in which deposition is performed by being cooled
after being dissolved in a solvent at a high temperature, or in
which deposition is performed by adding a poor solvent after being
dissolved in a solvent; and melt-kneading methods (JP-A-2004-269865
and JP-A-2005-200663) in which a resin compound containing both a
polylactic acid-based resin in dispersed phase and an incompatible
resin in continuous phase is formed by kneading the polylactic
acid-based resin together with the incompatible resin in a kneading
machine such as a two-axis extruder, and in which the incompatible
resin is removed subsequently to produce polylactic acid-based
resin microparticles.
[0006] However, the polylactic acid-based resin microparticles
produced by the above-described methods have several problems in
that the particles produced are not spherical in shape, particle
diameter does not become smaller, particle diameter distribution is
broad and, in some cases, it is impossible to keep the particles in
a round shape because of fiber-shaped ones or the like.
Particularly, in the fields such as cosmetics where great
importance is attached to feeling of touch and impression, or in
the fields such as paints where it is important to control
rheology, effects produced by adding such microparticles were not
sufficient hitherto.
[0007] On the other hand, as a method for production of polymer
microparticles, the method described in WO 2009-142231 is known as
a method utilizing emulsion. However, in WO '231, a concrete
example of polylactic acid-based resin is not disclosed and it is
not clear how to produce polylactic acid-based resin
microparticles.
[0008] It could therefore be helpful to provide a process of
producing polylactic acid-based resin microparticles, porous
polylactic acid-based resin microparticles which have small average
particle diameter and high oil absorption ability and are
appropriately usable for cosmetics and the like, and smooth surface
polylactic acid-based resin microparticles which have spherical
shape and narrow particle diameter distribution and are
appropriately usable for toners and the like.
SUMMARY
[0009] We thus provide: [0010] (1) A process for producing
polylactic acid-based resin microparticles comprising: [0011] a
dissolving process for forming a system, which can cause phase
separation into two phases of a solution phase mainly composed of
polylactic acid-based resin (A) and a solution phase mainly
composed of polymer (B) different from polylactic acid-based resin,
by dissolving the polylactic acid-based resin (A) and the polymer
(B) different from polylactic acid-based resin in ether-based
organic solvent (C); [0012] an emulsion-forming process for forming
an emulsion by applying a shear force to the system; and [0013] a
microparticle-forming process for precipitating polylactic
acid-based resin microparticles by bringing the emulsion into
contact with a poor solvent which has lower solubility of the
polylactic acid-based resin (A) than the ether-based organic
solvent (C). [0014] (2) The process for producing polylactic
acid-based resin microparticles according to (1), wherein the
ether-based organic solvent (C) has a boiling point of 100.degree.
C. or higher. [0015] (3) The process for producing polylactic
acid-based resin microparticles according to (2), wherein the
ether-based organic solvent (C) is diethylene glycol dimethyl
ether. [0016] (4) The process for producing polylactic acid-based
resin microparticles according to any of (1) to (3), wherein the
polymer different from a polylactic acid-based resin (B) is a
polyvinyl alcohol, a hydroxypropyl cellulose, a polyethylene oxide
or a polyethylene glycol. [0017] (5) The process for producing
polylactic acid-based resin microparticles according to any of (1)
to (4), wherein the poor solvent is water. [0018] (6) The process
for producing polylactic acid-based resin microparticles according
to any of (1) to (5), wherein the polylactic acid-based resin (A)
has an enthalpy of fusion of 5 J/g or greater. [0019] (7) The
process for producing polylactic acid-based resin microparticles
according to (6), wherein contact temperature of the poor solvent
is equal to or higher than crystallization temperature of the
polylactic acid-based resin (A). [0020] (8) The process for
producing polylactic acid-based resin microparticles according to
any of (1) to (5), wherein the polylactic acid-based resin (A) has
an enthalpy of fusion of less than 5 J/g. [0021] (9) Polylactic
acid-based resin microparticles characterized in that the
microparticles have a number average particle diameter of 1 to 90
.mu.m and a linseed oil absorption of 90 ml/100 g or greater.
[0022] (10) The polylactic acid-based resin microparticles
according to (9), wherein the microparticles comprise a polylactic
acid-based resin having an enthalpy of fusion of at least 5 J/g.
[0023] (11) The polylactic acid-based resin microparticles
according to (9) or (10), wherein the microparticles have a
particle diameter distribution index of 1 to 2. [0024] (12)
Polylactic acid-based resin microparticles characterized in that
the microparticles have a sphericity of at least 90 and a particle
diameter distribution index of 1 to 2. [0025] (13) The polylactic
acid-based resin microparticles according to (12), wherein the
microparticles comprise a polylactic acid-based resin having an
enthalpy of fusion of less than 5 J/g. [0026] (14) The polylactic
acid-based resin microparticles according to (12) or (13), wherein
the microparticles have a number average particle diameter of 1 to
100 .mu.m and a linseed oil absorption of less than 70 ml/100 g.
[0027] (15) Cosmetics which comprise the polylactic acid-based
resin microparticles according to any of 9 to 14.
[0028] According to the process of producing polylactic acid-based
resin microparticles, it becomes possible to produce polylactic
acid-based microparticles easily and, further, it becomes possible
to produce desired polylactic acid-based resin microparticles as
required, for example, porous polylactic acid-based resin
microparticles having excellent oil absorption ability and having
excellent hygroscopic property, or spherical polylactic acid-based
resin microparticles having smooth surface and having high
slidability. The polylactic acid-based resin microparticles are
suitable for various uses such as cosmetic foundation, lipsticks,
cosmetic material such as scrub agent for men's cosmetics,
flash-moldable material, rapid prototyping/rapid manufacturing
material, paste resin for plastic sol, powder blocking agent,
powder flowability improving agent, adhesive, lubricant, rubber
compounding ingredient, polishing agent, viscosity improver, filter
material/filter aid, gelatinizer, coagulation agent, additive for
paints, oil absorbing material, mold releasing agent, slippage
improving agent for plastic films/sheets, antiblocking agent, gloss
adjusting agent, frosted finish agent, light diffusion agent,
surface hardness improving agent, various other modifying agents
such as toughness improving material, spacer for liquid crystal
display equipment, filler/carrier for chromatography, base
material/additive for cosmetic foundation, assistant for
micro-capsules, medical materials for drug delivery
system/diagnostic reagents, support agent for perfume/pesticide,
catalyst/carrier for chemical reactions, gas adsorption agent,
sintered material for ceramic processing, standard particle
material for measurement/analysis, particle material for food
manufacture industry, material for powder coating, and toner for
electrophotographic development.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 is an observation diagram by a scanning electron
microscope, showing polylactic acid-based resin microparticles
produced in Practical Example 2.
[0030] FIG. 2 is an observation diagram by a scanning electron
microscope, showing polylactic acid-based resin microparticles
produced in Practical Example 4.
[0031] FIG. 3 is an observation diagram by a scanning electron
microscope, showing polylactic acid-based resin microparticles
produced in Practical Example 5.
[0032] FIG. 4 is an observation diagram by a scanning electron
microscope, showing polylactic acid-based resin microparticles
produced in Practical Example 7.
[0033] FIG. 5 is an observation diagram by a scanning electron
microscope, showing polylactic acid-based resin microparticles
produced in Practical Example 9.
[0034] FIG. 6 is an observation diagram by a scanning electron
microscope, showing polylactic acid-based resin microparticles
produced in Comparative Example 3.
[0035] FIG. 7 is an observation diagram by a scanning electron
microscope, showing polylactic acid-based resin microparticles
produced in Comparative Example 4.
[0036] FIG. 8 is an observation diagram by a scanning electron
microscope, showing polylactic acid-based resin microparticles
produced in Comparative Example 5.
DETAILED DESCRIPTION
[0037] The process of producing polylactic acid-based resin
microparticles is characterized by having: a dissolving process for
forming a system, which can cause phase separation into two phases
of a solution phase mainly composed of polylactic acid-based resin
(A) and a solution phase mainly composed of polymer (B) different
from polylactic acid-based resin, by dissolving the polylactic
acid-based resin (A) and the polymer (B) different from polylactic
acid-based resin in ether-based organic solvent (C); an
emulsion-forming process for forming an emulsion by applying a
shear force to the system; and a microparticle-forming process for
precipitating polylactic acid-based resin microparticles by
bringing the emulsion into contact with a poor solvent which has
lower solubility of the polylactic acid-based resin (A) than the
ether-based organic solvent (C).
[0038] The process of producing polylactic acid-based resin
microparticles is characterized in that the organic solvent used is
an ether-based organic solvent (C). By using an ether-based organic
solvent (C), it becomes possible to prevent polylactic acid-based
resin microparticles from fusing together when bringing a poor
solvent of polylactic acid-based resin (A) into contact. In the
case of using an organic solvent different from the ether-based
organic solvent (C), for example, an ester-based solvent such as
ethyl acetate and methyl acetate, an alkyl halide-based solvent
such as chloroform, bromoform, methylene chloride,
1,2-dichloroethane, 1,1,1-trichloroethane, chlorobenzene and
2,6-dichlorotoluene, a ketone-based solvent such as acetone, methyl
ethyl ketone, methyl isobutyl ketone and methyl butyl ketone, an
acetal-based solvent such as dimethyl acetal, diethyl acetal,
dipropyl acetal and dioxolane, aprotic solvent such as
N-methyl-2-pyrrolidone, dimethyl sulfoxide, N,N-dimethyl formamide,
N,N-dimethyl acetamide, propylene carbonate, trimethyl phosphate,
1,3-dimethyl-2-imidazolidinone and sulfolane, or a carboxylic
acid-based solvent such as formic acid, acetic acid, propionic
acid, butyric acid and lactic acid, owing to a good solubility of
polylactic acid-based resin, the performance of precipitation of
polylactic acid-based resin is not sufficient and it is difficult
to form particles. Furthermore, when bringing a poor solvent of
polylactic acid-based resin into contact, the solvent remains
inside the polylactic acid-based resin microparticles precipitated,
polylactic acid-based resin microparticles are liable to fuse with
each other, and it increases the possibility of a negative effect
on the shape of particles and the particle diameter
distribution.
[0039] Practically, representative ether-based organic solvents (C)
described above include linear aliphatic ethers such as diethyl
ether, dipropyl ether, diisopropyl ether, dibutyl ether, dipentyl
ether, dihexyl ether, dioctyl ether, diisoamyl ether, tert-amyl
methyl ether, tert-butyl ethyl ether, butyl methyl ether, butyl
ethyl ether, 1-methoxy ethane (monoglyme), 1-ethoxyethane,
diethylene glycol dimethyl ether (diglyme), ethylene glycol diethyl
ether, 2-methoxy ethyl ether, di(ethylene glycol)diethyl ether,
di(ethylene glycol)dibutyl ether and triethylene glycol dimethyl
ether, cyclic aliphatic ethers such as tetrahydrofuran, 2-methyl
tetrahydrofuran, 2,5-dimethyl tetrahydrofuran,
2,2,5,5-tetramethylhydrofuran, 2,3-dihydro-furan,
2,5-dihydro-furan, tetrahydropyran, 3-methyl tetrahydropyran and
1,4-dioxane, and aromatic ethers such as anisole, phenetole
(ethylphenol), diphenyl ether, 3-phenoxytoluene, p-tolyl ether,
1,3-diphenoxybenzene and 1,2-diphenoxyethane. Particularly, from
the viewpoint of industrial availability, dipropyl ether,
diisopropyl ether, dibutyl ether, 1-ethoxyethane, diethylene glycol
dimethyl ether (diglyme), ethylene glycol diethyl ether,
2-methoxyethyl ether, di(ethylene glycol)diethyl ether,
tetrahydrofuran, 2-methyl tetrahydrofuran, tetrahydropyran,
1,4-dioxane and anisole are preferred.
[0040] Further, from the viewpoint of simplifying the process in
which the ether-based organic solvent (C) is recycled by removing
the poor solvent of polylactic acid-based resin from the
ether-based organic solvent (C) and the polymer (B) different from
polylactic acid-based resin separated in an solid-liquid separating
process when producing the above-described microparticles of
polylactic acid-based resin, it is preferred that the
above-described ether-based organic solvent has a boiling point of
100 degrees Celsius or higher. For such an ether-based organic
solvent, for example, diethylene glycol dimethyl ether (diglyme)
and 1,4-dioxane can be used. Such an ether-based organic solvent
can be used either singly or in mixture, however, from the
viewpoint of simplifying the process for recycling the ether-based
organic solvent, it is preferred to be used singly.
[0041] Furthermore, other organic solvents can be added to the
ether-based organic solvent (C) as long as the desired effect is
not spoiled. If the amount of ether-based organic solvent is 100
parts by mass, the amount of other organic solvents added are
generally less than 100 parts by mass, preferably 75 parts by mass
or less, more preferably 50 parts by mass or less, still more
preferably 30 parts by mass or less, particularly preferably 20
parts by mass or less, and most preferably 10 parts by mass or
less. Typical examples of the other organic solvents include
ester-based solvents such as ethyl acetate and methyl acetate,
alkyl halide-based solvents such as chloroform, bromoform,
methylene chloride, 1,2-dichloroethane, 1,1,1-trichloroethane,
chlorobenzene and 2,6-dichlorotoluene, ketone-based solvents such
as acetone, methyl ethyl ketone, methyl isobutyl ketone and methyl
butyl ketone, acetal-based solvents such as dimethyl acetal,
diethyl acetal, dipropyl acetal and dioxolane, aprotic solvents
such as N-methyl-2-pyrrolidone, dimethyl sulfoxide, N,N-dimethyl
formamide, N,N-dimethyl acetamide, propylene carbonate, trimethyl
phosphate, 1,3-dimethyl-2-imidazolidinone and sulfolane, and
carboxylic acid-based solvents such as formic acid, acetic acid,
propionic acid, butyric acid and lactic acid. These other organic
solvents can be used either singly or in mixture.
[0042] The above-described polylactic acid-based resin (A) is a
polymer in which main components are L-lactic acid and D-lactic
acid. "A polymer in which main components are L-lactic acid and
D-lactic acid" means that, in the monomer units constituting
copolymers in the polylactic acid-based resin (A), the total of the
monomer units of L-lactic acid and D-lactic acid are 50 mole % or
more in the molar ratio. The molar ratio of the total of the
monomer units of L-lactic acid and D-lactic acid is preferably 50
mole % or more, more preferably 70 mole % or more, further more
preferably 80 mole % or more, particularly preferably 90 mole % or
more. The upper limit is generally 100 mole %.
[0043] "L" and "D" refer to kinds of optical isomers. The lactic
acid having a native type configuration is described as "L-lactic
acid" or "L-type lactic acid," and the lactic acid having a
non-native type configuration is described as "D-lactic acid" or
"D-type lactic acid."
[0044] In the above-described polylactic acid-based resin (A), the
arrangement of lactic acid monomer units is not particularly
limited and may be any of a block copolymer, an alternating
copolymer, a random copolymer and a graft copolymer. From the
viewpoint of lowering a fusing temperature, the random copolymer is
preferable.
[0045] Another characteristic is that wide variety of polylactic
acid-based resin (A) from crystalline ones to amorphous ones can be
used to produce polylactic acid-based resin microparticles, and
that it is possible to control the shape of polylactic acid-based
resin microparticles by selecting either crystalline or amorphous
polylactic acid-based resin (A).
[0046] When polylactic acid-based resin (A) has high
crystallization characteristics, it becomes possible to produce
porous polylactic acid-based resin microparticles. The
crystallization characteristics of the polylactic acid-based resin
(A) can be expressed in enthalpy of fusion. The higher enthalpy of
fusion indicates the higher crystal characteristics, and the lower
enthalpy of fusion indicates that the polylactic acid-based resin
is more amorphous.
[0047] When enthalpy of fusion of the polylactic acid-based resin
(A) is 5 J/g or more, the crystallization characteristics of the
polylactic acid-based resin (A) become high and polylactic
acid-based resin microparticles having a porous surface can be
obtained. When the crystallization characteristics of the
polylactic acid-based resin (A) become higher, polylactic
acid-based resin microparticles in more porous shape can be
obtained and properties taking advantage of porous structure such
as oil absorption property and hygroscopic property of the
polylactic acid-based resin microparticles improve. Therefore, when
producing polylactic acid-based resin microparticles having a
porous surface, the lower limit of enthalpy of fusion is preferably
10 J/g or more, more preferably 20 J/g or more, and most preferably
30 J/g or more. Further, the upper limit is preferably 100 J/g or
less, although it is not limited in particular.
[0048] On the other hand, in the case where the polylactic
acid-based resin (A) is amorphous, it is possible to produce
polylactic acid-based resin microparticles having a smooth surface.
Although the tangible reason is unclear, in the case where the
polylactic acid-based resin (A) precipitates in an amorphous state,
presumably because of inhibition of partial crystallization, the
particles precipitate in an homogeneous state and the surface of
those becomes smooth.
[0049] When producing polylactic acid-based resin microparticles
having a smooth surface, the less enthalpy of fusion the polylactic
acid-based resin (A) has, the more likely the precipitation occurs
in a homogeneous state. Therefore, the upper limit of enthalpy of
fusion is preferably less than 5 J/g, more preferably less than 3
J/g, further more preferably less than 2 J/g, and most preferably
less than 1 J/g. Further, the lower limit is 0 J/g, and it
indicates that the polylactic acid-based resin (A) is completely in
an amorphous state.
[0050] Enthalpy of fusion refers to a value calculated from a peak
area, which shows heat capacity of fusion at approximately 160
degrees Celsius, in a differential scanning calorimetry (DSC) where
a temperature is raised to 200 degrees Celsius with the temperature
rise of 20 degrees Celsius per minute.
[0051] As for a method of regulating enthalpy of fusion, it is
possible to use known methods such as a method of controlling
co-polymerization ratio (L/D) between L-lactic acid and D-lactic
acid which constitute the polylactic acid-based resin (A), a method
of adding an additive agent for promoting crystallization to the
polylactic acid-based resin (A), and a method of forming a stereo
block structure. Above all, due to its easiness of controlling
enthalpy of fusion of the polylactic acid-based resin (A), the
method of controlling co-polymerization ratio of L/D is preferred.
When L/D ratio is 95/5 or more, enthalpy of fusion becomes 5 J/g or
more and the polylactic acid-based resin becomes crystalline. It is
preferred that the co-polymerization ratio of L-lactic acid is high
because higher ratio facilitates crystallization. L/D is more
preferably 97/3 or more, and most preferably 98/2 or more. The
upper limit of L/D is less than 100/0. Further, when L/D is less
than 95/5, enthalpy of fusion becomes less than 5 J/g and the
polylactic acid-based resin becomes amorphous. It is preferred that
the co-polymerization ratio of L-lactic acid is low because lower
ratio facilitates being amorphous. The ratio is more preferably
less than 92/8 and most preferably less than 89/11. Further, the
lower limit of L/D is 50/50 or more. Because optical isomers such
as L and D are materials in which molecule structures are mirror
images of each other and physical properties are not different,
enthalpy of fusion remains unchanged when the above-described L/D
is substituted with D/L and consequently our process also includes
the extent where L/D is substituted with D/L.
[0052] Further, the polylactic acid-based resin (A) may contain
copolymerization ingredients other than lactic acid as long as the
desired effect is not spoiled. The other copolymerization
ingredient units can be, for example, a multivalent carboxylic
acid, a polyhydric alcohol, a hydroxycarboxylic acid or a lactone
and, specifically, can be multivalent carboxylic acids such as
oxalic acid, malonic acid, succinic acid, glutaric acid, adipic
acid, azelaic acid, sebacic acid, dodecanedioic acid, fumaric acid,
cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid,
phthalic acid, 2,6-naphthalenedicarboxylic acid, anthracene
dicarboxylic acid, 5-sodium sulfoisophthalic acid and 5-tetrabutyl
phosphonium sulfoisophthalic acid; polyhydric alcohols such as
ethylene glycol, propylene glycol, butanediol, heptanediol,
hexanediol, octanediol, nonanediol, decanediol,
1,4-cyclohexanedimethanol, neopentylglycol, glycerin,
pentaerythritol, bisphenol A, an aromatic polyhydric alcohol
produced by an addition reaction of ethylene oxide to a bisphenol,
diethylene glycol, triethylene glycol, polyethylene glycol,
polypropylene glycol and polytetramethylene glycol;
hydroxycarboxylic acids such as glycolic acid, 3-hydroxybutyric
acid, 4-hydroxybutyric acid, 4-hydroxyvaleric acid,
6-hydroxycaproic acid and hydroxybenzoic acid; or lactones such as
glycolide, .epsilon.-caprolactone glycolide,
.epsilon.-caprolactone, .beta.-propiolactone,
.delta.-butyrolactone, .beta.-butyrolactone, .gamma.-butyrolactone,
pivalolactone and .delta.-valerolactone. The volume content of the
other copolymerization units is preferably 30 mol % or less, more
preferably 20 mol % or less, further more preferably 10 mol % or
less, most preferably 5 mol % or less, relative to the total
monomer units of polylactic acid-based resin (A) as 100 mol %.
[0053] Although molecular mass and molecular mass distribution of
the polylactic acid-based resin (A) are not limited in particular
as far as it can be dissolved in the ether-based organic solvent
(C) substantially, from the viewpoint of ease of keeping particle
structure and of improvement of hydrolysis resistance, the lower
limit of weight average molecular mass of the polylactic acid-based
resin (A) is preferably 10,000 or more, more preferably 50,000 or
more, further more preferably 100,000 or more, most preferably
200,000 or more. Further, although not limited in particular, the
upper limit of weight average molecular mass is preferably
1,000,000 or less. The weight average molecular mass referred to
herein is weight average molecular mass in terms of polymethyl
methacrylate (PMMA), measured in gel permeation chromatography
(GPC) using hexafluoroisopropanol as a solvent.
[0054] For production of the polylactic acid-based resin (A), it is
not limited particularly and known methods can be used such as
direct polymerization from polylactic acid and ring-opening
polymerization via a lactide.
[0055] The above-described polymer (B) different from polylactic
acid-based resin may include a thermoplastic resin and a
thermosetting resin, however, in view of better solubility in the
ether-based organic solvent (C), thermoplastic resin is
preferred.
[0056] More specifically, the polymer (B) different from polylactic
acid-based resin may include one or more of the following: a
synthetic resin such as poly(vinyl alcohol) (may be either a
complete saponification type or a partial saponification type of
poly(vinyl alcohol)), poly(vinyl alcohol-ethylene) copolymer (may
be either a complete saponification type or a partial
saponification type of poly(vinyl alcohol-ethylene) copolymer),
polyvinylpyrrolidone, poly(ethylene glycol), poly(ethylene oxide),
sucrose fatty acid ester, poly(oxyethylene fatty acid ester),
poly(oxyethylene lauric fatty acid ester), poly(oxyethylene glycol
mono-fatty acid ester), poly(oxyethylene alkyl phenyl ether),
poly(oxyalkylether), polyacrylic acid, sodium polyacrylate,
poly(methacrylic acid), sodium polymethacrylate, polystyrene
sulfonic acid, polystyrene sodium sulfonate, poly(vinyl
pyrrolidinium chloride), poly(styrene-maleic acid) copolymer,
aminopoly(acrylic amide), poly-p-vinylphenol, polyarylamine,
polyvinyl ether, polyvinyl formal, poly(acrylic amide),
poly(methacrylamide), poly(oxyethyleneamine), poly(vinyl
pyrrolidone), poly(vinyl pyridine), polyaminosulfone and
polyethyleneimine, disaccharides such as maltose, cellobiose,
lactose and sucrose; cellulose derivatives such as cellulose,
chitosan, hydroxyethyl cellulose, hydroxypropyl cellulose,
methylcellulose, ethyl cellulose, ethyl hydroxy cellulose,
carboxymethylethylcellulose, carboxymethylcellulose, sodium
carboxymethylcellulose and cellulose ester; polysaccharides and
their derivatives such as amylose and its derivatives, starch and
its derivatives, dextrin, cyclodextrin, sodium alginate and its
derivatives; gelatin, casein, collagen, albumin, fibroin, keratin,
fibrin, carrageenan, chondroitin sulfate, arabian gum, agar and
protein; and from the viewpoint of narrowing the particle diameter
distribution, preferably includes one or more of the following:
poly(vinyl alcohol) (may be either a complete saponification type
or a partial saponification type of poly(vinyl alcohol)),
poly(vinyl alcohol-ethylene) (may be either a complete
saponification type or a partial saponification type of poly(vinyl
alcohol-ethylene)), poly(ethyleneglycol), poly(ethyleneoxide),
sucrose fatty acid ester, poly(oxyethylene alkyl phenyl ether),
poly(oxyethylene alkyl phenyl ether), polyacrylic acid,
poly(methacrylic acid), carboxymethylcellulose, hydroxyethyl
cellulose, hydroxypropyl cellulose, methyl cellulose, ethyl
cellulose, ethyl hydroxy cellulose, carboxymethylethylcellulose,
carboxymethylcellulose, sodium carboxymethylcellulose, cellulose
derivatives such as cellulose ester, and polyvinylpyrrolidone; more
preferably includes one or more of the following: poly(vinyl
alcohol) (may be either a complete saponification type or a partial
saponification type of poly (vinyl alcohol)), poly(vinyl
alcohol-ethylene) (may be either a complete saponification type or
a partial saponification type of poly(vinyl alcohol-ethylene)),
poly(ethylene glycol), poly(ethylene oxide),
carboxymethylcellulose, hydroxyethyl cellulose, hydroxypropyl
cellulose, methyl cellulose, ethyl cellulose, ethyl hydroxy
cellulose, carboxymethylethylcellulose, carboxymethylcellulose,
sodium carboxymethylcellulose, cellulose derivatives such as
cellulose ester, and polyvinylpyrrolidone; particularly preferably
includes one or more of the followings: poly(vinyl alcohol) (may be
either a complete saponification type or a partial saponification
type of poly(vinyl alcohol)), poly(ethylene glycol), poly(ethylene
oxide), and hydroxypropyl cellulose.
[0057] The molecular mass of the polymer (B) different from
polylactic acid-based resin is preferably in a range of
1,000-100,000,000, more preferably in a range of 1,000-10,000,000,
further more preferably in a range of 5,000-1,000,000, particularly
preferably in a range of 10,000-500,000, most preferably in a range
of 10,000-100,000, in terms of weight average molecular mass.
[0058] The weight average molecular mass referred to herein denotes
a weight average molecular mass measured in terms of polyethylene
glycol by gel permeation chromatography (GPC) using water as a
solvent. In the case where water cannot be used for the
measurement, dimethylformamide is used as a solvent and, if the
measurement cannot be performed, tetrahydrofuran will be used. In
case the measurement is still impossible, hexafluoroisopropanol
will be used.
[0059] The above-described "a system, which can cause phase
separation into two phases of a solution phase mainly composed of
polylactic acid-based resin (A) and a solution phase mainly
composed of polymer (B) different from polylactic acid-based resin,
by dissolving the polylactic acid-based resin (A) and the polymer
(B) different from polylactic acid-based resin in ether-based
organic solvent (C)" denotes a system comprising a solution in
which the polylactic acid-based resin (A) and the polymer (B)
different from polylactic acid-based resin are dissolved in the
ether-based organic solvent (C) and being capable of phase
separation into two phases of a solution phase mainly composed of
the polylactic acid-based resin (A) and a solution phase mainly
composed of the polymer (B) different from polylactic acid-based
resin.
[0060] By using such a system capable of phase separation, it is
possible to emulsify the system by mixing it under the condition of
phase separation and consequently to form an emulsion.
[0061] In the description above, whether the polymers can be
dissolved or not is determined by dissolving the polylactic
acid-based resin (A) and the polymer (B) different from polylactic
acid-based resin in the ether-based organic solvent (C) and
checking whether the polymers can be dissolved in the ether-based
organic solvent (C) by 1 mass % or more, at a temperature at which
the phase separation is caused.
[0062] In this emulsion, the solution phase of polylactic
acid-based resin (A) becomes a dispersed phase and the solution
phase of polymer B becomes a continuous phase. Further, by bringing
a poor solvent of polylactic acid-based resin (A) into contact with
the emulsion, polylactic acid-based resin microparticles are
precipitated out of the solution phase of polylactic acid-based
resin (A) in the emulsion and consequently polymer microparticles
consisting of polylactic acid-based resin (A) can be obtained.
[0063] The poor solvent of polylactic acid-based resin (A) refers
to a solvent having a lower solubility of polylactic acid-based
resin (A) than the above-described ether-based organic solvent (C)
and being hardly capable of dissolving polylactic acid-based resin
(A) and, more specifically, refers to a solvent in which the
solubility of polylactic acid-based resin (A) is 1 mass % or less.
The upper limit of the solubility of polylactic acid-based resin
(A) in the poor solvent is more preferably 0.5 mass % or less,
further more preferably 0.1 mass % or less.
[0064] In the above-described production process, the poor solvent
of polylactic acid-based resin (A) used is preferably a poor
solvent of polylactic acid-based resin (A) which can dissolve
polymer (B) different from polylactic acid-based resin. By using
this, it becomes possible to precipitate polylactic acid-based
resin microparticles consisting of polylactic acid-based resin (A)
efficiently. Further, the poor solvent of polylactic acid-based
resin (A) is preferably a solvent which can mix homogeneously with
a solvent capable of dissolving both polylactic acid-based resin
(A) and polymer (B) different from polylactic acid-based resin.
[0065] As regards the poor solvent described above, an optimally
suited one can be selected as appropriate in accordance with the
type of polylactic acid-based resin (A), preferably with the type
of polylactic acid-based resin (A) and the type of polymer (B)
different from polylactic acid-based resin. More specifically, it
may include one or more solvents selected from the group consisting
of the followings: an aliphatic hydrocarbon-based solvent such as
pentane, hexane, heptane, octane, nonane, n-decane, n-dodecane,
n-tridecane, cyclohexane and cyclopentane; an aromatic
hydrocarbon-based solvent such as benzene, toluene and xylene; an
alcohol-based solvent such as methanol, ethanol, 1-propanol and
2-propanol; and water. From the viewpoint of efficient
precipitation of polylactic acid-based resin (A), the poor solvent
of polylactic acid-based resin is preferably an aliphatic
hydrocarbon-based solvent, an aromatic hydrocarbon-based solvent,
an alcohol-based solvent or water, more preferably an alcohol-based
solvent or water, most preferably water.
[0066] By selecting the above-described polylactic acid-based resin
(A), polymer (B) different from polylactic acid-based resin,
ether-based organic solvent (C) capable of dissolving those and
utilizing those in combination, it becomes possible to precipitate
polylactic acid-based resin efficiently and consequently to obtain
polymer microparticles.
[0067] It is necessary that a liquid in which polylactic acid-based
resin (A), polymer (B) different from polylactic acid-based resin
and ether-based organic solvent (C) capable of dissolving those are
dissolved and mixed can cause phase separation into two phases of a
solution phase mainly composed of the polylactic acid-based resin
(A) and a solution phase mainly composed of the polymer (B)
different from polylactic acid-based resin. The two ether-based
organic solvent (C), one solvent is in the solution phase mainly
composed of polylactic acid-based resin (A) and the other solvent
is in the solution phase mainly composed of polymer (B) different
from polylactic acid-based resin, may be identical with or may be
different from each other. However, it is preferred that these
solvents are substantially identical.
[0068] The condition causing two phase separation varies according
to the types of polylactic acid-based resin (A) and polymer (B)
different from polylactic acid-based resin, the molecular masses of
polylactic acid-based resin (A) and polymer (B) different from
polylactic acid-based resin, the type of ether-based organic
solvent (C), the concentrations of polylactic acid-based resin (A)
and polymer (B) different from polylactic acid-based resin, and the
temperature and pressure to carry out our process.
[0069] To meet conditions under which the phase separation is
likely to occur, it is preferred that there is a significant
difference in solubility parameter (hereinafter, may also be
referred to as SP value) between the polylactic acid-based resin
(A) and the polymer (B) different from polylactic acid-based
resin.
[0070] Preferably, the lower limit of the difference between the SP
values is 1 (J/cm.sup.3).sup.1/2 or more, more preferably 2
(J/cm.sup.3).sup.1/2 or more, still more preferably 3
(J/cm.sup.3).sup.1/2 or more, particularly preferably 5
(J/cm.sup.3).sup.1/2 or more, and most preferably 8
(J/cm.sup.3).sup.1/2 or more. When the SP values are in this range,
the phase separation tends to occur easily, and the tendency to the
phase separation makes it possible to produce polylactic acid-based
resin microparticles containing more polylactic acid-based resin
ingredients. The upper limit of the difference of the SP values is
preferably 20 (J/cm.sup.3).sup.1/2 or less, more preferably 15
(J/cm.sup.3).sup.1/2 or less, further more preferably 10
(J/cm.sup.3).sup.1/2 or less. However, it is not particularly
limited thereto as long as both polylactic acid-based resin (A) and
polymer (B) different from polylactic acid-based resin can be
dissolved in ether-based organic solvent (C). The SP value referred
to herein is calculated in accordance with Fedor's estimation
method (hereinafter, may also be referred to as Computational
method) which is a calculation method based on coagulation energy
density and molar molecular mass (Hideki YAMAMOTO, "THE BASIS,
APPLICATION AND CALCULATION METHOD OF SP VALUE," Johokiko Co.,
Ltd., published at 31 Mar. 1999). Further, in the case where the
above-described calculation method cannot be used, the solubility
parameter which is determined by experiment on the basis of whether
it can be dissolved in a known solvent or not (hereinafter, may
also be referred to as Experimental method) is used as a substitute
for the SP value (J. Brand, "POLYMER HANDBOOK FOURTH EDITION,"
Wiley, published in 1998).
[0071] To determine appropriate conditions under which the phase
separation occurs, it is possible to utilize a three-component
phase diagram which can be prepared by a simple preliminary test of
observing state changes by varying the ratio among three
components, namely, polylactic acid-based resin (A), polymer (B)
different from polylactic acid-based resin and ether-based organic
solvent (C) in which those are dissolved.
[0072] The phase diagram is prepared by evaluating whether an
interface is formed among phases or not when polylactic acid-based
resin (A), polymer (B) different from polylactic acid-based resin
and ether-based organic solvent (C) are mixed at an arbitrary
ratio, dissolved together and left still for a certain period of
time. To prepare the diagram, the evaluations are performed under
at least three different conditions, preferably at least five
different conditions, more preferably at least ten different
conditions. By distinguishing between a region of two-phase
separation and a region of single phase according to the phase
diagram which can be prepared as described above, it becomes
possible to determine conditions under which the phase separation
occurs.
[0073] To determine whether the phase separation occurs or not,
after the volumes of polylactic acid-based resin (A), polymer (B)
different from polylactic acid-based resin and ether-based organic
solvent (C) are tuned to an arbitrary ratio, polylactic acid-based
resin (A) and polymer (B) different from polylactic acid-based
resin are dissolved in ether-based organic solvent (C) completely
and are stirred sufficiently, under certain temperature and
pressure conditions where the dissolving process will be performed.
Then, after keeping them still for three days, it is examined
macroscopically whether the phase separation occurs or not.
However, in the case where the emulsion becomes stable
considerably, the phase separation does not occur even after
keeping them still for three days. In such cases, the presence or
absence of the phase separation is determined on the basis of
whether the phase separation can be observed microscopically or not
by using an optical microscope, a phase-contrast microscope or the
like.
[0074] The phase separation occurs as a result of the separation of
polylactic acid solution phase mainly composed of polylactic
acid-based resin (A) and polymer B solution phase mainly composed
of polymer (B) different from polylactic acid-based resin in
ether-based organic solvent (C). The solution phase of polylactic
acid-based resin (A) is a phase in which polylactic acid-based
resin (A) is mainly distributed, and the polymer B solution phase
is a phase in which polymer (B) different from polylactic
acid-based resin is mainly distributed. In this case, it is
presumed that the solution phase of polylactic acid-based resin (A)
and the polymer B solution phase have a volume ratio varying with
types and amounts of polylactic acid-based resin (A) and polymer
(B) different from polylactic acid-based resin.
[0075] As an industrially feasible concentration where the phase
separation occurs, both concentrations of polylactic acid-based
resin (A) and polymer (B) different from polylactic acid-based
resin in ether-based organic solvent are not particularly limited
as long as the concentrations are within a range of being dissolved
in ether-based organic solvent. From the viewpoint of causing phase
separation and of industrially feasible concentration, the lower
limit of each of concentrations is preferably more than 1 mass %,
more preferably 2 mass %, further more preferably 3 mass %, further
more preferably 5 mass %, relative to the total amount of mass.
Further, the upper limit of each of the concentrations is
preferably 50 mass %, more preferably 30 mass %, further more
preferably 20 mass %.
[0076] It is presumed that, as regards the above-described two
phases of the solution phase of polylactic acid-based resin (A) and
the polymer B solution phase, the interface tension between two
phases becomes small because both phases are organic solvents and,
as a result, the emulsion generated is stabilized and the particle
diameter distribution becomes narrow.
[0077] The interfacial tension between the two phases described
above is too small to measure directly with the commonly-used
pendant-drop method in which a solution is added to another kind of
solution to take measurements. The interfacial tension, however,
can be estimated from the surface tension of each phase exposed to
air. Thus, assuming r1 and r2 represent the surface tension of each
phase exposed to air, the interfacial tension r12 is estimated to
be the absolute value of the difference between them as follows:
r12=|r1-r2| (the absolute value of r1-r2).
[0078] As regards the preferred range of r12, the upper limit is
preferably 10 mN/m, more preferably 5 mN/m, further more preferably
3 mN/m, and particularly preferably 2 mN/m. Further, the lower
limit is more than 0 mN/m.
[0079] The viscosity ratio between the two phases influences the
average particle diameter and the particle diameter distribution,
and the particle diameter distribution tends to decrease with a
decreasing viscosity ratio.
[0080] As regards the preferred range of the viscosity ratio
between the two phases described above, the lower limit is
preferably 0.1 or more, more preferably 0.2 or more, further more
preferably 0.3 or more, particularly preferably 0.5 or more,
remarkably preferably 0.8 or more. Further, the upper limit is
preferably 10 or less, more preferably 5 or less, further more
preferably 3 or less, particularly preferably 1.5 or less,
remarkably preferably 1.2 or less. The viscosity ratio between two
phases referred to herein is defined as "a viscosity of the
solution phase of polylactic acid-based resin (A)/a viscosity of
the solution phase of polymer (B) different from polylactic
acid-based resin" at a temperature at which the dissolution process
will be performed.
[0081] By using the system which can cause phase separation,
polymer microparticles are produced after a phase separated liquid
phase is mixed to be emulsified.
[0082] To form microparticles, the emulsion-forming process and the
microparticle-forming process can be carried out in a common
reaction vessel. As regards a temperature to carry out the
emulsion-forming process and the microparticle-forming process,
from the viewpoint of industrial feasibility, the lower limit is
generally 0 degrees Celsius or higher, preferably 10 degrees
Celsius or higher, more preferably 20 degrees Celsius or higher.
Further, the upper limit is preferably 300 degrees Celsius or
lower, more preferably 200 degrees Celsius or lower, further more
preferably 160 degrees Celsius or lower, particularly preferably
140 degrees Celsius or lower, remarkably preferably 100 degrees
Celsius or lower, although it is not particularly limited as long
as the temperature is in a range where polylactic acid-based resin
(A) and polymer (B) different from polylactic acid-based resin can
be dissolved to cause phase separation so that the desired
microparticles can be produced.
[0083] From the viewpoint of industrial feasibility, when carrying
out the emulsion-forming process, the pressure is in a range from
the standard pressure to 10 atm. The lower limit of the pressure is
preferably 1 atm. The upper limit of the pressure is preferably 5
atm, more preferably 3 atm, further more preferably 2 atm.
[0084] Further, it is preferred to use an inert gas in the reaction
vessel. The inert gas includes, more specifically, nitrogen,
helium, argon and carbon dioxide, and preferably includes nitrogen
and argon.
[0085] Emulsion is formed by mixing the phase separation system
described above under such conditions. In other words, emulsion is
formed by applying a shear force to a solution which is the phase
separation system obtained from the dissolution process described
above.
[0086] In a process of forming an emulsion, an emulsion is formed
such that the solution phase of polylactic acid-based resin (A)
forms into particle-like droplets. Generally, in a phase
separation, such an emulsion tends to be formed when the volume of
the solution phase of polymer (B) different from polylactic
acid-based resin is larger than the volume of the solution phase of
polylactic acid-based resin (A). In particular, the volume ratio of
the solution phase of polylactic acid-based resin (A) is preferably
less than 0.5, more preferably in a range of 0.4 to 0.1, relative
to the total volume of two phases as 1.
[0087] It is possible to define an appropriate range of the volume
ratio by measuring the volume ratio and concentration of each
component simultaneously when preparing the above-described phase
diagram.
[0088] The microparticles produced by the present production
process have a narrow particle diameter distribution because a
remarkably homogeneous emulsion is produced in a stage of forming
the emulsion. This tendency becomes apparent when using a single
solvent which can dissolve both polylactic acid-based resin (A) and
polymer (B) different from polylactic acid-based resin. Thus, to
obtain a sufficient shear force for forming the emulsion in the
present production process, it is possible to use generally known
methods such as liquid phase stirring method by stirring blades,
stirring method with a biaxial continuous mixer, mixing method with
a homogenizer, and ultrasonic irradiation method.
[0089] Particularly, in the case where stirring blades are used,
the stirring speed is preferably 50 rpm to 1,200 rpm, more
preferably 100 rpm to 1,000 rpm, further more preferably 200 rpm to
800 rpm, particularly preferably 300 rpm to 600 rpm, though the
speed is also affected by the shape of the stirring blades.
[0090] The stirring blades may have such shapes as propeller,
paddle, flat paddle, turbine, double cone, single cone, single
ribbon, double ribbon, screw, and helical ribbon, although they are
not particularly limited thereto as long as a sufficient shear
force can be applied to the system. Further, to perform stirring
efficiently, baffle boards and the like may be provided in the
reaction vessel.
[0091] Furthermore, to produce the emulsion, it is possible to use
not only a stirrer but also a generally known device such as an
emulsifier and an disperser.
[0092] Specific examples include batch type emulsifiers such as
Homogenizer (supplied by IKA), Polytron (supplied by Kinematica,
Inc.), TK Autohomomixer (supplied by Tokushu Kika Kogyo Co., Ltd.),
and others such as Ebara Milder (supplied by Ebara Corporation), T.
K. Filmics, T. K. Pipeline Homomixer (supplied by Tokushu Kika
Kogyo Co., Ltd.), Colloid Mill (supplied by Shinko-Pantec Co.,
Ltd.), and Slusher, Trigonal Wet Grinder (Mitsui Miike Kakoki Co.,
Ltd.), as well as ultrasonic homogenizers and static mixers.
[0093] The emulsion thus obtained is subsequently supplied to the
microparticle-forming process for precipitating microparticles.
[0094] To obtain microparticles of polylactic acid-based resin (A),
a poor solvent of polylactic acid-based resin (A) is brought into
contact with the emulsion produced by the above-described process
and microparticles having a diameter corresponding to the emulsion
diameter are produced as a result.
[0095] Although the method to bring the poor solvent into contact
with the emulsion can be either a method to put the emulsion in the
poor solvent or a method to put the poor solvent in the emulsion,
the method to put the poor solvent in the emulsion is preferable.
For the method of bringing the poor solvent into contact, although
both method of putting the emulsion in the poor solvent and method
of putting the poor solvent in the emulsion are available, the
method of putting the poor solvent in the emulsion is
preferable.
[0096] For the method of adding the poor solvent, it is not
particularly limited as long as desired polymer microparticles can
be produced, and any methods such as continuous dropping, split
dropping and batch addition can be used. However, to prevent the
emulsion from coagulation, fusion and coalescence which can cause
widening of particle diameter distribution or generation of bulky
grains larger than 1,000 .mu.m while adding the poor solvent,
continuous dropping and split dropping are preferable. Further,
from the viewpoint of industrially efficient operation, continuous
dropping is most preferably used.
[0097] For the temperature of bringing the poor solvent into
contact, it is not particularly limited as long as it is within a
range where polylactic acid-based microparticles can be
precipitated. The lower limit thereof is 0 degrees Celsius or
higher, and the upper limit is 300 degrees Celsius or lower. The
lower limit of the temperature is preferably 10 degrees Celsius or
higher, more preferably 20 degrees Celsius or higher, because the
poor solvent solidifies and consequently cannot be used if the
temperature is too low. Further, the upper limit of the temperature
is preferably 200 degrees Celsius or lower, more preferably 100
degrees Celsius or lower, further more preferably 90 degrees
Celsius or lower, because polylactic acid-based resin (A) and
polymer (B) different from polylactic acid-based resin are prone to
become deteriorated by heat if the temperature is too high.
[0098] When a crystalline polylactic acid-based resin (A) having
enthalpy of fusion of 5 J/g or more is used in the above-described
production process, polylactic acid-based resin microparticles
having porous forms are produced under normal conditions. However,
it is also possible to produce polylactic acid-based resin
microparticles having smooth surface by controlling the contact
temperature of the poor solvent to a higher temperature than the
crystallization temperature of the polylactic acid-based resin (A).
Although the tangible reason is unclear, it can be considered that
controlling the temperature of the crystalline polylactic
acid-based resin (A) to a higher temperature of the crystallization
temperature changes the resin into molten amorphous state and
consequently smoothes the surface thereof.
[0099] The crystallization temperature of polylactic acid-based
resin (A) refers to a recrystallization temperature in a process of
cooling a molten polylactic acid-based resin. As for the method of
measuring the crystallization temperature, a temperature of top
peak showing endothermic heat capacity is measured as lowering the
temperature at a rate of 1 degree Celsius per minute after raising
the temperature to 200 degrees Celsius at a rate of 20 degrees
Celsius per minute in a differential scanning calorimetry (DSC).
Further, in a case where the peak does not appear while lowering
the temperature, it is possible to measure it as a temperature of
top peak showing endothermic heat capacity as raising the
temperature up to 200 degrees Celsius at a rate of 0.5 degrees
Celsius per minute.
[0100] When using a crystalline polylactic acid-based resin (A)
having enthalpy of fusion of 5 J/g or more, the contact temperature
of the poor solvent of producing polylactic acid-based resin
microparticles having smooth surfaces is preferably more than the
crystallization temperature defined above. Because the polylactic
acid-based resin microparticles tend to transform into an amorphous
state and tend to have smooth surfaces when the temperature is
higher than the crystallization temperature, the lower limit of the
temperature is preferably 10 degrees higher than the
crystallization temperature, more preferably 20 degrees higher than
the crystallization temperature, further more preferably 30 degrees
higher than the crystallization temperature. Further, the upper
limit of the temperature is preferably 100 degrees higher than the
crystallization temperature, although it is not particularly
limited thereto.
[0101] Further, the time to add the poor solvent is preferably 10
minutes to 50 hours, more preferably 15 minutes to 10 hours,
further more preferably 30 minutes to 5 hours. If the time for
adding is shorter than those ranges, there is a fear that a
widening of the particle diameter distribution or a forming of
bulky grains may occur due to coagulation, fusion and coalescence
of the emulsion. Further, from the viewpoint of industrial
feasibility, it is impractical to spend time longer than those
ranges. By carrying out the adding within such a range, it becomes
possible to prevent particles from coagulation while transforming
the emulsion into polymer particles, and it becomes possible to
produce polymer particles having narrow particle diameter
distribution as a result.
[0102] The quantity of the poor solvent to add depends on a state
of the emulsion and is preferably 0.1 to 10 mass part, more
preferably 0.1 to 5 mass part, further more preferably 0.2 to 3
mass part, particularly preferably 0.2 to 2 mass part, most
preferably 0.2 to 1.0 mass part, relative to the total mass of the
emulsion as 1 mass part.
[0103] The contact time between the poor solvent and the emulsion
is not limited as long as it is sufficient to precipitate
microparticles. Although, to cause precipitation sufficiently and
achieve high productivity, the contact time is preferably from 5
minutes to 50 hours, more preferably from 5 minutes to 10 hours,
further more preferably from 10 minutes to 5 hours, particularly
preferably from 20 minutes to 4 hours, most preferably from 30
minutes to 3 hours, after adding the poor solvent.
[0104] By separating the thus produced polymer
microparticle-dispersed liquid into solids and liquids by a known
method such as filtration, vacuum filtration, pressure filtration,
centrifugation, centrifugal filtration and spray drying,
microparticle powders can be obtained. The polymer microparticles,
obtained by the separation into solids and liquids, are purified by
removing the adhered or contained impurities by washing with a
solvent or the like, as needed.
[0105] In the production process described above, the ether-based
organic solvent (C) and the polymer (B) different from polylactic
acid-based resin, which are separated through the solid-liquid
separation process in producing the microparticle powders, can be
recycled and utilized once again.
[0106] A solvent obtained through the solid-liquid separation is a
mixture of polymer (B) different from polylactic acid-based resin,
the ether-based organic solvent (C) and the poor solvent. This
solvent can be utilized as a solvent for forming an emulsion again
by removing the poor solvent therefrom. As a method of removing the
poor solvent, known methods can be used such as simple
distillation, reduced pressure distillation, precision
distillation, thin film distillation, extraction and membrane
separation, and simple distillation, reduced pressure distillation
or precision distillation is preferably used.
[0107] When operating distillation such as simple distillation and
reduced pressure distillation, as in the case of producing polymer
microparticles, there is a possibility that the system would be
heated and that thermal decomposition of polymer (B) different from
polylactic acid-based resin and the ether-based organic solvent (C)
is promoted as a result. Therefore, the operation is preferably
carried out in an oxygen-free atmosphere as much as possible, more
preferably in an inert atmosphere. Specifically, it is preferably
carried out in an atmosphere of nitrogen, helium, argon or carbon
dioxide. Further, antioxidants such as phenol-based compounds or
the like can be added thereto.
[0108] When carrying out the recycling described above, it is
preferred that the poor solvent is removed as much as possible.
Specifically, the remaining amount of the poor solvent is generally
10 mass % or less, preferably 5 mass % or less, more preferably 3
mass % or less, particularly preferably 1 mass % or less, relative
to the total amount of the recycled, namely, the ether-based
organic solvent (C) and the polymer (B) different from polylactic
acid-based resin. If the remaining amount of the poor solvent
exceeds such a range, there is a fear that the particle diameter
distribution of the microparticles widens and the particles
coagulate.
[0109] The volume of the poor solvent in a solvent used in
recycling can be measured by known methods such as gas
chromatography and the Karl Fischer method.
[0110] In the operation of removing the poor solvent, because there
may be a loss of the ether-based organic solvent (C) or polymer (B)
different from polylactic acid-based resin practically, it is
preferred that the composition ratio is adjusted to the initial
ratio as is appropriate.
[0111] Next, the polylactic acid-based resin microparticles will be
explained in detail.
[0112] The characteristics of the porous microparticles of
polylactic acid-based resin are that the number average particle
diameter is small, the surface is in a porous shape, it is possible
to improve lipophilic functionality and hydrophilic functionality
because a considerable amount of either oil or water can be held in
the pores, and because the particle diameter is small, it is
possible to impart smoothness which cannot be achieved by
traditional porous microparticles. Such porous microparticles of
polylactic acid-based resin are suitably used in the fields such as
cosmetics where achieving high performance is demanded in both oil
absorption and smoothness.
[0113] With reference to the number average particle diameter of
the porous microparticles of polylactic acid-based resin, it is
possible to determine an appropriate range of number average
particle diameter. For example, in the uses such as cosmetics,
because a smaller number average particle diameter improves
smoothness, the upper limit of the number average particle diameter
is generally 90 .mu.m or less, preferably 50 .mu.m or less, more
preferably 30 .mu.m or less. Further, in the uses such as
cosmetics, because coagulation of particles tends to occur when the
number average particle diameter is too small, the lower limit of
the number average particle diameter is generally 1 .mu.m or more,
preferably more than 1 .mu.m, more preferably 2 .mu.m or more, most
preferably 3 .mu.m or more.
[0114] With reference to the particle diameter distribution index
showing the particle diameter distribution of the polylactic
acid-based resin microparticles having porous shapes, it is
preferably 2 or less because it becomes possible in the uses such
as cosmetics to improve a flow of particles and impart a smoother
touch. The upper limit of the particle diameter distribution index
is preferably 1.5 or less, more preferably 1.3 or less, most
preferably 1.2 or less. Further, the lower limit is 1 in
theory.
[0115] The above-described number average particle diameter of
polylactic acid-based resin microparticles having porous shapes can
be calculated by measuring diameters of 100 random particles in a
scanning electron microscope image and computing the arithmetic
average thereof. If a shape of a particle in the SEM image is not a
perfect circle, for example, an ellipse, the maximum diameter of
the particle is used as its diameter. To measure the particle
diameter precisely, the measurement is carried out with a
magnification of at least 1000 times or more, preferably with a
magnification of 5000 times or more.
[0116] Further, the particle diameter distribution index is
calculated on the basis of the conversion equations described
below, using measurements of the particle diameters obtained by
measurement described above:
Dn = i = 1 n Ri / n Dv = i = 1 n Ri 4 / i = 1 n Ri 3 PDI = DV / Dn
Equation 1 ##EQU00001##
wherein Ri: particle diameter of single particle, n: the number of
measurements (=100), Dn: number average particle diameter, Dv:
volume average particle diameter, PDI: particle diameter
distribution index.
[0117] Although the actual amount of pores in a porous
microparticle of polylactic acid-based resin is difficult to
measure directly, it is possible to use linseed oil absorption
capacity as an indirect index, which is defined in pigment test
methods such as Japan Industrial Standards (Refined Linseed Oil
Method, JIS K 5101).
[0118] In particular, in the uses such as cosmetics and paints,
higher linseed oil capability is preferable, and the lower limit of
linseed oil capability is preferably 90 ml/100 g or more, more
preferably 100 ml/100 g or more, further more preferably 120 ml/100
g or more, particularly preferably 150 ml/100 g or more, remarkably
preferably 200 ml/100 g or more, most preferably 300 ml/100 g or
more. The upper limit of linseed oil absorption capability is
preferably 1000 ml/100 g or less.
[0119] Further, it is preferred that the above-described porous
microparticles of polylactic acid-based resin have enthalpy of
fusion of 5 J/g or more. Higher enthalpy of fusion brings higher
crystallization tendency and, as a result, heat resistance and
durability tend to become high. The lower limit of enthalpy of
fusion is preferably 10 J/g or more, more preferably 20 J/g or
more, further more preferably 30 J/g or more. Further, the upper
limit is preferably 100 J/g or less. Enthalpy of fusion can be
calculated from an area of peak showing thermal capacity of fusion
at approximately 160 degrees Celsius in Differential Scanning
calorimetry (DSC) in which a temperature is raised to 200 degrees
Celsius with a temperature rise of 20 degrees Celsius per
minute.
[0120] Sphericity of the above-described porous microparticles of
polylactic acid-based resin is preferably 80 or more, more
preferably 85 or more, further more preferably 90 or more,
particularly preferably 92 or more, most preferably 95 or more.
Further, in theory, the upper limit is 100. When sphericity is
within the above-described range, it becomes possible to achieve an
improvement in quality such as slidability. The sphericity is
calculated by observing particles by a scanning electron
microscope, measuring both the longest diameters and the shortest
diameters of 30 random particles and subsequently substituting the
measurements into the equation described below:
S = i = 1 n ( D S / D L ) n .times. 100 Equation 2 ##EQU00002##
wherein S: Sphericity, n: the number of measurements (=30),
D.sub.S: the shortest diameter of single particle, D.sub.L: the
longest diameter of single particle.
[0121] On the other hand, the characteristics of the polylactic
acid-based resin microparticles having smooth surfaces are that
surfaces are smooth, particles are highly spherical in shape and
particle diameter distribution is narrow. By using such
microparticles of polylactic acid-based resin as powders, it
becomes possible to improve fluidity, achieve improvements in
quality such as smoothness, and increase ease of viscosity control
in the case of being added to paints and the like. In addition,
because such polylactic acid-based resin microparticles having
smooth surfaces can move on a surface of a base member smoothly and
can be fused into place on the base member homogeneously due to
narrow particle diameter distribution, those particles are
particularly suitable for use in the fields such as toners where
excellent fluidity and low-temperature fusion characteristics are
demanded.
[0122] Preferably, sphericity of the polylactic acid-based resin
microparticles having smooth surfaces is 90 or more. From the
viewpoint of improving mobility in the use as toners, the lower
limit of sphericity is preferably 92 or more, most preferably 95 or
more. Further, the upper limit is 100 in theory. Sphericity is
calculated by observing particles by a scanning electron
microscope, measuring both the longest diameters and the shortest
diameters of 30 random particles and subsequently substituting the
measurements into the equation described below:
S = i = 1 n ( D S / D L ) n .times. 100 Equation 3 ##EQU00003##
wherein S means Sphericity, n means the number of measurements
(=30), D.sub.S means the shortest diameter of single particle, and
D.sub.L means the longest diameter of single particle.
[0123] With reference to number average particle diameter of the
polylactic acid-based resin microparticles having smooth surfaces,
a range of number average particle diameter can be determined
appropriately in accordance with the uses. The upper limit of
number average particle diameter is generally 100 .mu.m or less,
preferably 50 .mu.m or less, more preferably 30 .mu.m or less.
Further, in the uses such as toner, because coagulation of
particles tends to occur when number average particle diameter is
too small, the lower limit of number average particle diameter is
generally 1 .mu.m or more, preferably more than 1 .mu.m, more
preferably 2 .mu.m or more, most preferably 3 .mu.m or more.
[0124] Particle diameter distribution index showing particle
diameter distribution of the polylactic acid-based resin
microparticles having smooth surfaces is preferably 2 or less.
Because smaller particle diameter distribution index makes it
possible for toners to be fused onto a substrate more
homogeneously, the upper limit of particle diameter distribution
index is preferably 1.8 or less, more preferably 1.5 or less,
further more preferably 1.3 or less, most preferably 1.2 or less.
In addition, the lower limit is 1 in theory.
[0125] The above-described number average particle diameter of
polylactic acid-based resin microparticles having smooth surfaces
can be calculated by measuring diameters of 100 random particles in
a scanning electron microscope image and computing the arithmetic
average thereof. If a shape of a particle in the SEM image is not a
perfect circle, for example, an ellipse, the maximum diameter of
the particle is used as its diameter. To measure the particle
diameter precisely, the measurement is carried out with a
magnification of at least 1000 times or more, preferably with a
magnification of 5000 times or more.
[0126] Further, particle diameter distribution index is calculated
on the basis of the conversion equations described below, using
measurements of the particle diameters obtained by measurement
described above:
Dn = i = 1 n Ri / n Dv = i = 1 n Ri 4 / i = 1 n Ri 3 PDI = DV / Dn
Equation 4 ##EQU00004##
wherein Ri: particle diameter of single particle, n: the number of
measurements (=100), Dn: number average particle diameter, Dv:
volume average particle diameter, PDI: particle diameter
distribution index.
[0127] Although enthalpy of fusion of polylactic acid-based resin
microparticles having smooth surfaces is not particularly limited,
it is preferred that enthalpy of fusion is less than 5 J/g because
the melting point decreases and consequently it becomes possible to
use such microparticles suitably in the uses such as toners in
which low-temperature fusion characteristics are demanded. The
upper limit of enthalpy of fusion is preferably less than 3 J/g,
more preferably less than 2 J/g, most preferably less than 1 J/g.
In addition, the theoretical lower limit is 0, which indicates that
polylactic acid-based resin is completely amorphous. Enthalpy of
fusion can be calculated from the area of a peak showing thermal
capacity of fusion at approximately 160 degrees Celsius in
Differential Scanning calorimetry (DSC) in which a temperature is
raised to 200 degrees Celsius with a temperature rise of 20 degrees
Celsius per minute.
[0128] Furthermore, for the amount of pores in a porous
microparticle of polylactic acid-based resin, linseed oil
absorption capacity, which is defined in pigment test methods such
as Japan Industrial Standards (Refined Linseed Oil Method, JIS K
5101), is used as an indicator.
[0129] In particular, when the above-described polylactic
acid-based resin microparticles having smooth surfaces are used as
toners and the like, lower linseed oil absorption capability is
preferred because fusion onto a substrate takes place more
homogeneously. The upper limit of linseed oil absorption capability
is preferably less than 70 ml/100 g, more preferably less than 65
ml/100 g, further more preferably less than 60 ml/100 g. Further,
the lower limit is preferably 30 ml/100 g.
[0130] Thus, the porous polylactic acid-based resin microparticles,
which have small particle diameters and high linseed oil absorption
capability, and the smooth surface polylactic acid-based resin
microparticles, which have spherical shapes and narrow particle
diameter distribution, are quite useful and practical for various
uses in industry. Specifically, those can be used as, for example,
skin care agents such as face wash, sunscreens, cleansing agents,
cosmetic water, lotions, cosmetic liquid, creams, cold creams,
aftershave lotions, shaving soaps, oil absorbing sheets and
matifiants, cosmetics and modification agents thereof such as
foundations, foundation powder, face powder in liquid form,
mascara, face powder, Dohran, eyebrow pencil, mascara, eye line,
eye shadow, eye shadow base, nose shadow, lipsticks, gloss, cheek
brushes, tooth wax, manicure and topcoat, additives for hair care
products such as shampoo, dry shampoo, conditioner, rinse, shampoo
containing rinse ingredients, treatment, hair tonic, hair
conditioner, hair oil, pomade and hair color agent, additives for
amenity products such as perfume, cologne, deodorant, baby powder,
tooth powder, mouthwash, lip balm and soap, rheology improving
agents such as an additive for toner and paint, diagnostic test
agents for medical purpose, machine characteristics improving
agents for molded products such as car materials and building
materials, machine characteristics improving materials such as film
and fiber, raw materials for molding resin such as rapid
prototyping and rapid manufacturing, flash-moldable material, paste
resin for plastic sol, powder blocking agent, various modifying
agents such as powder flowability improving agent, lubricant,
rubber compounding ingredient, polishing agent, viscosity improver,
filter material/filter aid, gelatinizer, coagulation agent,
additive for paints, oil absorbing material, mold releasing agent,
slippage improving agent for plastic films/sheets, antiblocking
agent, gloss adjusting agent, frosted finish agent, light diffusion
agent, surface hardness improving agent and ductility improving
material, spacer for liquid crystal display equipment,
filler/carrier for chromatography, base material/additive for
cosmetic foundation, assistant for micro-capsules, medical
materials for drug delivery system/diagnostic reagents, support
agent for perfume/pesticide, catalyst/carrier for chemical
reactions, gas adsorption agent, sintered material for ceramic
processing, standard particle material for measurement/analysis,
particle material for food manufacture industry, material for
powder coating, and toner for electrophotographic development.
[0131] Furthermore, polylactic acid-based resin microparticles have
the potential to substitute traditionally used polymer
microparticles because they are materials of non-petroleum origin
and have characteristics as low environmental load materials.
Electricity, the electronic parts which are represented, for
example, for concrete uses such as the resin molding body mentioned
above, a film, the fiber by the housing of the electric apparatus,
the housing of the OA apparatus, various covers, various gears,
various cases, a sensor, an LED lamp, a connector, a socket, a
resistor, a relay case, a switch, various terminal boards, a plug,
a printed wiring board, a tuner, a speaker, a microphone,
headphones, a small size motor, a magnetic head base, a power
module, a housing, a semiconductor, liquid crystal, FDD carriage,
FDD chassis, a motor brush holder, a parabolic antenna, a computer
connection part. The applications of the above-described such as
resin moldings, films and fibers include, for example, electric or
electronic parts, typified by a housing of an electric apparatus, a
housing of an OA apparatus, various covers, various gears, various
cases, a sensor, an LED lamp, a connector, a socket, a resistor, a
relay case, a switch, various terminal boards, a plug, a printed
wiring board, a tuner, a speaker, a microphone, headphones, a small
size motor, a magnetic head base, a power module, a housing, a
semiconductor, liquid crystal, FDD carriage, FDD chassis, a motor
brush holder, a parabolic antenna and a computer connection part,
TV parts, irons, hair dryers, rice cooker parts, microwave oven
parts, audio equipment parts such as a sound part, an audio, a
laser disc (a registered trademark) and a compact disk, video
equipment-related parts such as a camera, a VCR, a picture-taking
lens (for projection TV and the like), a finder, a filter, a prism
and Fresnel lens, home and office electric appliance parts such as
an illumination part, a refrigerator part, an air-conditioner part,
a typewriter part and a word processor part, information
appliance-related parts such as an office computer-related part, a
telephone-related part, a facsimile-related part, a copier-related
part, films for protecting various disk boards, a Laser Disk player
pickup lens, optical fiber, a light switch and an optical
connecter, liquid crystal display, flat-panel display, light
guiding panel for plasma display, Fresnel lens, polarizing plate,
polarizing plate protection film, phase difference film, light
diffusion film, angle of field expansion film, reflection film,
reflection prevention film, anti-glare film, brightness improvement
film, prism sheet and light guiding film for touch panel,
machine-related parts, typified by a jig for washing, a motor part,
a writer and a typewriter, Optical equipments typified by a
microscope, binoculars and a clock, precision instrument-related
parts, various pipes for fuel, exhaustion and intake, an air intake
nozzle snorkel, intake manifold, a fuel pump, a connector for
fuses, Horne terminal, an electric equipment part insulation board,
a lamp socket, a lamp reflector, a lamp housing, an engine oil
filter and an ignition case, and are remarkably useful for such
various uses.
EXAMPLES
[0132] Hereinafter, our processes, microparticles and cosmetics
will be explained in detail based on examples, but this disclosure
is not limited to these examples.
(1) Measuring Methods for Enthalpy of Fusion and Crystallization
Temperature:
[0133] Enthalpy of fusion was calculated from area size of a peak,
which appears at approximately 160 degrees Celsius and shows
thermal capacity of fusion, in carrying out a measurement up to 200
degrees Celsius with a temperature rise of 20 degrees Celsius per
minute by using a differential scanning calorimeter (robot DSC
RDC220, supplied by SEIKO Instruments Inc.) under nitrogen
atmosphere.
[0134] Further, the crystallization temperature was determined as a
vertex temperature of a crystallization temperature peak, which
appears in a range approximately from 80 to 130 degrees Celsius
during cooling, in carrying out a measurement with a temperature
drop of 1 degree Celsius per minute after having raised the
temperature up to 200 degrees Celsius by using the above-described
instrument under the same conditions.
(2) Weight Average Molecular Mass:
(i) Determination of Molecular Weight of the Polylactic Acid-Based
Resin (A):
[0135] The weight average molecular mass was calculated by using
gel permeation chromatography with reference to the calibration
curve of polymethyl methacrylate (PMMA). [0136] Device: LC system
supplied by Waters Corporation [0137] Columns: two HFIP-806Ms
supplied by Showa Denko K.K. [0138] Mobile phase: sodium
trifluoroacetate 10 mmol/L hexafluoroisopropanol solution [0139]
Flow rate: 1.0 ml/min [0140] Detector: refractive index detector
[0141] Column temperature: 30 degrees Celsius (ii) Determination of
Molecular Weight of the Polymer (B) Different from Polylactic
Acid-Based Resin:
[0142] The weight average molecular mass was calculated by using
gel permeation chromatography with reference to the calibration
curve of polymethyl methacrylate (PMMA). [0143] Device: LC-10A
series supplied by Shimazu Corporation [0144] Columns: two GF-7MHQs
supplied by Showa Denko K.K. [0145] Mobile phase: 10 mmol/L lithium
bromide water solution [0146] Flow rate: 1.0 ml/min [0147]
Detector: refractive index detector [0148] Column temperature: 40
degrees Celsius
(3) Determination of Interfacial Tension
[0149] In reference to a solution phase of polylactic acid-based
resin (A) and a solution phase of polymer (B) different from
polylactic acid-based resin, liquid-air surface tensions, r1 and r2
respectively, of both phases were measured on a hot plate by using
an automatic contact angle meter DM-501 supplied by Kyowa Interface
Science Co., Ltd., and interfacial tension was calculated from the
absolute value of the differential (r1-r2).
(4) Measuring Methods for Average Particle Diameter and Particle
Diameter Distribution:
[0150] Each particle diameter of microparticles was measured by a
scanning electron microscope (JSM-6301NF, a scanning electron
microscope supplied by JEOL Ltd.) with a magnification of 1,000
times. When a particle was not spherical, the longest diameter was
measured as the particle diameter thereof.
[0151] Average particle diameter was calculated by measuring
particle diameters of 100 random particles in a scanning electron
microscope image and computing the arithmetic average thereof.
[0152] Particle diameter distribution index showing distribution of
particle diameters was calculated on the basis of the following
conversion equations, using measurement values of particle
diameters obtained by the above-described measurement:
Dn = i = 1 n Ri / n Dv = i = 1 n Ri 4 / i = 1 n Ri 3 PDI = DV / Dn
. Equation 5 ##EQU00005##
[0153] In the equations above, Ri means particle diameter of single
particle, n means the number of measurements (=100), Dn means
number average particle diameter, Dv means volume average particle
diameter, and PDI means particle diameter distribution index.
(5) Determination of Sphericity:
[0154] Sphericity was calculated by observing particles with a
scanning electron microscope, measuring both the longest and
shortest diameters of each of 30 random particles, and assigning
the measurement values to the following equation:
S = i = 1 n ( D S / D L ) n .times. 100. Equation 6
##EQU00006##
[0155] In the equations above, S means Sphericity, n means the
number of measurements (=30), D.sub.S means the shortest diameter
of a single particle, and D.sub.L means the longest diameter of a
single particle.
(6) Determination of Linseed Oil Absorption Capacity:
[0156] For an evaluation of the oil absorption capacity which is an
index of porosity of polylactic acid-based resin microparticles,
Japan Industrial Standards (JIS) K 5101 "Pigment Test Method:
Refined Linseed Oil Method" was used. Approximately 100 mg of
polylactic acid-based resin microparticles were weighed on a watch
glass with high precision. Then, refined linseed oil (supplied by
Kanto Chemical Co., Inc.) was added thereto drop by drop with a
burette and was kneaded by a palette knife The adding-kneading
process was repeated until the sample turns into a lump, and the
endpoint was determined as a point where the sample paste exhibited
smooth hardness. Oil absorption capacity (ml/100 g) was calculated
from the amount of refined linseed oil used in the process.
Production Example 1
Process 1 for Producing Polylactic Acid
[0157] 70.2 g of L-lactide (supplied by Sigma-Aldrich Co. LLC.:
more than 98% ee in optical purity), 30.1 g of D-lactide (supplied
by Sigma-Aldrich Co. LLC.: more than 98% ee in optical purity) and
1.1 g of octanol were put in a reaction tank having a mixing
machine and were dissolved homogeneously at a temperature of 150
degrees Celsius under nitrogen atmosphere. Then, 0.90 g of tin
octylate (supplied by Sigma-Aldrich Co. LLC.) was added thereto as
a toluene solution in which concentration ratio was adjusted to 10
mass % of dry toluene, and polymerization reaction was performed
for six hours. After the polymerization reaction had finished,
reactant was dissolved in chloroform and reprecipitated in methanol
with being stirred, and a solid matter was obtained by removing
monomers and catalysts therefrom. By performing filtration of the
solid matter obtained and performing vacuum heat-drying at 80
degrees Celsius, polylactic acid-based resin having an
copolymerization ratio L/D of 70/30, an enthalpy of fusion of 0 J/g
and Mw of 11200 (in terms of PMMA) was obtained. The SP value of
this polymer was 23.14 (J/cm.sup.3).sup.1/2 according to the
above-described computational method.
Production Example 2
Process 2 for Producing Polylactic Acid
[0158] A polylactic acid-based resin was produced in a manner
similar to Production Example 1 except that 49.9 g of L-lactide
(supplied by Sigma-Aldrich Co. LLC.: more than 98% ee in optical
purity), 49.8 g of D-lactide (supplied by Sigma-Aldrich Co. LLC.:
more than 98% ee in optical purity) and 0.95 g of tin octylate
(supplied by Sigma-Aldrich Co. LLC.) were used. The polylactic
acid-based resin obtained had a copolymerization ratio L/D of
50/50, an enthalpy of fusion of 0 J/g and Mw (in terms of PMMA) of
9,800. The SP value of this polymer was 23.14 (J/cm.sup.3).sup.1/2
according to the above-described computational method.
Production Example 3
Process 3 for Producing Polylactic Acid
[0159] A polylactic acid-based resin was produced in a manner
similar to Production Example 1 except that 70.1 g of L-lactide
(supplied by Sigma-Aldrich Co. LLC.: more than 98% ee in optical
purity), 29.8 g of D-lactide (supplied by Sigma-Aldrich Co. LLC.:
more than 98% ee in optical purity) and 0.90 g of tin octylate
(supplied by Sigma-Aldrich Co. LLC.) were used. The polylactic
acid-based resin obtained had a copolymerization ratio L/D of
70/30, an enthalpy of fusion of 0 J/g and Mw (in terms of PMMA) of
98,000. The SP value of this polymer was 23.14 (J/cm.sup.3).sup.1/2
according to the above-described computational method.
Example 1
[0160] 0.5 g of polylactic acid (L/D=98.8/1.2, Mw (in terms of
PMMA)=160,000, enthalpy of fusion=31.1 J/g, SP value=23.14
(J/cm.sup.3).sup.1/2), 0.5 g of hydroxypropyl cellulose (supplied
by Tokyo Chemical Industry Co., Ltd., weight average molecular
mass=118,000, SP value=29.0 (J/cm.sup.3).sup.1/2) as a polymer
different from polylactic acid and 9.0 g of tetrahydrofuran as an
ether-based organic solvent were put in a 100 ml four-neck flask,
heated to 50 degrees Celsius, and stirred until the polymers have
been dissolved completely. After bringing the temperature back to
room temperature, 5 g of ion exchanged water as a poor solvent was
added by dripping it with a pipette while stirring with a stirrer.
Stirring was continued for another 30 minutes after the whole
amount of water had been added, and the resulting suspension was
filtered and washed by 50 g of ion exchanged water. Then, by drying
the filtered matter in vacuum at 80 degrees Celsius for 10 hours,
0.4 g of white solid was obtained in powder form. According to an
observation with a scanning electron microscope, the powder
obtained was polylactic acid microparticles having a porous
microparticle shape, having an average particle diameter of 33.0
.mu.m and a particle diameter distribution index of 1.55.
Example 2
[0161] 1.5 g of polylactic acid (L/D=98.8/1.2, Mw (in terms of
PMMA)=160,000, enthalpy of fusion=31.1 J/g, SP value=23.14
(J/cm.sup.3).sup.1/2), 2.5 g of hydroxypropyl cellulose (supplied
by Tokyo Chemical Industry Co., Ltd., weight average molecular
mass=118,000, SP value=29.0 (J/cm.sup.3).sup.1/2) as a polymer
different from polylactic acid and 46.0 g of tetrahydrofuran as an
ether-based organic solvent were put in a 100 ml four-neck flask,
heated to 50 degrees Celsius, and stirred until the polymers have
been dissolved completely. After bringing the temperature back to
room temperature, 50 g of ion exchanged water as a poor solvent was
added by dripping it with a pump at a speed of 0.41 g per minute
while stirring with a stirrer. Stirring was continued for another
30 minutes after the whole amount of water had been added, and the
resulting suspension was filtered and washed by 50 g of ion
exchanged water. Then, by drying the filtered matter in vacuum at
80 degrees Celsius for 10 hours, 0.4 g of white solid was obtained
in powder form. According to an observation with a scanning
electron microscope, the powder obtained was polylactic acid
microparticles having a porous microparticle shape, having an
average particle diameter of 25.1 .mu.m, having a particle diameter
distribution index of 1.35, having a sphericity of 89 and linseed
oil absorption of 432 ml/100 g. Further, the enthalpy of fusion of
these polylactic acid microparticles was 57.8 J/g. An observation
diagram of these microparticles by a scanning electron microscope
is shown in FIG. 1.
Example 3
[0162] 2.5 g of polylactic acid (L/D=98.8/1.2, Mw (in terms of
PMMA)=160,000, enthalpy of fusion=31.1 J/g, SP value=23.14
(J/cm.sup.3).sup.1/2), 2.5 g of hydroxypropyl cellulose (supplied
by Tokyo Chemical Industry Co., Ltd., weight average molecular
mass=118,000, SP value=29.0 (J/cm.sup.3).sup.1/2) as a polymer
different from polylactic acid and 45.0 g of tetrahydrofuran as an
ether-based organic solvent were put in a 100 ml four-neck flask,
heated to 50 degrees Celsius, and stirred until the polymers were
completely dissolved. After bringing the temperature back to room
temperature, 50 g of ion exchanged water as a poor solvent was
added by dripping it with a pump at a speed of 0.41 g per minute
while stirring with a stirrer. Stirring was continued for another
30 minutes after the whole amount of water had been added, and the
resulting suspension was filtered and washed by 50 g of ion
exchanged water. Then, by drying the filtered matter in vacuum at
80 degrees Celsius for 10 hours, 2.2 g of white solid was obtained
in powder form. According to an observation with a scanning
electron microscope, the powder obtained was polylactic acid
microparticles having a porous microparticle shape, having an
average particle diameter of 59.5 .mu.m, having a particle diameter
distribution index of 11.5 and a linseed oil absorption of 661
ml/100 g.
Example 4
[0163] 2.5 g of polylactic acid (L/D=98.8/1.2, Mw (in terms of
PMMA)=160,000, enthalpy of fusion=31.1 J/g, SP value=23.14
(J/cm.sup.3).sup.1/2), 2.5 g of hydroxypropyl cellulose (supplied
by Tokyo Chemical Industry Co., Ltd., weight average molecular
mass=118,000, SP value=29.0 (J/cm.sup.3).sup.1/2) as a polymer
different from polylactic acid, 33.75 g of diethylene glycol
dimethyl ether (diglyme) as an ether-based organic solvent and
11.25 g of N-methyl-2-pyrrolidone as an other organic solvent were
put in a 100 ml four-neck flask, heated to 80 degrees Celsius, and
stirred until the polymers have been dissolved completely. With the
temperature maintained, 50 g of ion exchanged water as a poor
solvent was added by dripping it with a pump at a speed of 0.82 g
per minute while stirring with a stirrer. Stirring was continued
for another 30 minutes after the whole amount of water had been
added, and the resulting suspension was filtered and washed by 50 g
of ion exchanged water. Then, by drying the filtered matter in
vacuum at 80 degrees Celsius for 10 hours, 2.4 g of white solid was
obtained in powder form. According to an observation with a
scanning electron microscope, the powder obtained was polylactic
acid microparticles having a porous microparticle shape, having an
average particle diameter of 13.7 .mu.m, having a particle diameter
distribution index of 1.24, having a sphericity of 82 and a linseed
oil absorption of 524 ml/100 g. Further, the enthalpy of fusion of
these polylactic acid microparticles was 58.2 J/g. An observation
diagram of these microparticles by a scanning electron microscope
is shown in FIG. 2.
Example 5
[0164] 1.5 g of polylactic acid (L/D=96/4, Mw (in terms of
PMMA)=150,000, enthalpy of fusion=28.6 J/g, SP value=23.14
(J/cm.sup.3).sup.1/2), 2.5 g of hydroxypropyl cellulose (supplied
by Tokyo Chemical Industry Co., Ltd., weight average molecular
mass=118,000, SP value=29.0 (J/cm.sup.3).sup.1/2) as a polymer
different from polylactic acid and 46.0 g of tetrahydrofuran as an
ether-based organic solvent were put in a 100 ml four-neck flask,
heated to 60 degrees Celsius, and stirred until the polymers have
been dissolved completely. After bringing the temperature back to
room temperature, 50 g of ion exchanged water as a poor solvent was
added by dripping it with a pump at a speed of 0.41 g per minute
while stirring with a stirrer. Stirring was continued for another
30 minutes after the whole amount of water had been added, and the
resulting suspension was filtered and washed by 50 g of ion
exchanged water. Then, by drying the filtered matter in vacuum at
80 degrees Celsius for 10 hours, 1.3 g of white solid was obtained
in powder form. According to an observation with a scanning
electron microscope, the powder obtained was polylactic acid
microparticles having a porous microparticle shape, having an
average particle diameter of 10.0 .mu.m, having a particle diameter
distribution index of 1.10, having a sphericity of 85 and a linseed
oil absorption of 96 ml/100 g. Further, the enthalpy of fusion of
these polylactic acid microparticles was 34.3 J/g. An observation
diagram of these microparticles by a scanning electron microscope
is shown in FIG. 3.
Example 6
[0165] 2.5 g of polylactic acid (L/D=96/4, Mw (in terms of
PMMA)=150,000, enthalpy of fusion=28.6 J/g, SP value=23.14
(J/cm.sup.3).sup.1/2), 2.5 g of hydroxypropyl cellulose (supplied
by Tokyo Chemical Industry Co., Ltd., weight average molecular
mass=118,000, SP value=29.0 (J/cm.sup.3).sup.1/2) as a polymer
different from polylactic acid and 45.0 g of diethylene glycol
dimethyl ether as an ether-based organic solvent were put in a 100
ml four-neck flask, heated to 80 degrees Celsius, and stirred until
the polymers had been dissolved completely. With the temperature
maintained, 50 g of ion exchanged water as a poor solvent was added
by dripping it with a pump at a speed of 0.82 g per minute while
stirring with a stirrer. Stirring was continued for another 30
minutes after the whole amount of the water has been dropped, and
the resulting suspension was filtered and washed by 50 g of ion
exchanged water. Then, by drying the filtered matter in vacuum at
80 degrees Celsius for 10 hours, 2.3 g of white solid was obtained
in powder form. According to an observation with a scanning
electron microscope, the powder obtained was a polylactic acid
microparticle having a porous microparticle shape, having an
average particle diameter of 14.0 .mu.m, having a particle diameter
distribution index of 1.25, having a sphericity of 93 and a linseed
oil absorption of 149 ml/100 g. Further, the enthalpy of fusion of
these polylactic acid microparticles was 32.6 J/g.
Example 7
[0166] 1.5 g of polylactic acid (L/D=98.8/1.2, Mw (in terms of
PMMA)=160,000, enthalpy of fusion=31.1 J/g, SP value=23.14
(J/cm.sup.3).sup.1/2, crystallization temperature during
cooling=108 degrees Celsius), 2.5 g of hydroxypropyl cellulose
(supplied by Tokyo Chemical Industry Co., Ltd., weight average
molecular mass=118,000, SP value=29.0 (J/cm.sup.3).sup.1/2) as a
polymer different from polylactic acid and 46.0 g of diethylene
glycol dimethyl ether as an ether-based organic solvent were put in
a 100 ml autoclave, heated to 140 degrees Celsius, and stirred
until the polymers have been dissolved completely. With the
temperature maintained, 50 g of ion exchanged water as a poor
solvent was added by dripping it with a pump at a speed of 0.41 g
per minute while stirring with a stirrer. Stirring was continued
for another 30 minutes after the whole amount of water had been
added, and a suspension obtained was filtered and washed by 50 g of
ion exchanged water. Then, by drying the filtered matter in vacuum
at 80 degrees Celsius for 10 hours, 1.3 g of white solid was
obtained in powder form. According to an observation with a
scanning electron microscope, the powder obtained was polylactic
acid microparticles having a smooth surface microparticle shape,
having an average particle diameter of 1.6 .mu.m, having a particle
diameter distribution index of 1.40, having a sphericity of 95 and
a linseed oil absorption of 51 ml/100 g. Further, the enthalpy of
fusion of these polylactic acid microparticles was 40.8 J/g. An
observation diagram of these microparticles by a scanning electron
microscope is shown in FIG. 4.
Example 8
[0167] 1.5 g of polylactic acid (L/D=96/4, Mw (in terms of
PMMA)=150,000, enthalpy of fusion=28.6 J/g, SP value=23.14
(J/cm.sup.3).sup.1/2, crystallization temperature during
cooling=108 degrees Celsius), 2.5 g of hydroxypropyl cellulose
(supplied by Tokyo Chemical Industry Co., Ltd., weight average
molecular mass=118,000, SP value=29.0 (J/cm.sup.3).sup.1/2) as a
polymer different from polylactic acid and 46.0 g of diethylene
glycol dimethyl ether as an ether-based organic solvent were put in
a 100 ml autoclave, heated to 140 degrees Celsius, and stirred
until the polymers have been dissolved completely. While keeping
the system temperature, 50 g of ion exchanged water as a poor
solvent was added by dripping it with a pump at a speed of 0.41 g
per minute while stirring a stirrer. Stirring was continued for
another 30 minutes after the whole amount of water had been added,
and the resulting suspension was filtered and washed by 50 g of ion
exchanged water. Then, by drying the filtered matter in vacuum at
80 degrees Celsius for 10 hours, 1.3 g of white solid was obtained
in powder form. According to an observation with a scanning
electron microscope, the powder obtained was polylactic acid
microparticles having a smooth surface microparticle shape, having
an average particle diameter of 1.8 .mu.m, having a particle
diameter distribution index of 1.82, having a sphericity of 97 and
a linseed oil absorption of 58 ml/100 g. Further, an enthalpy of
fusion of these polylactic acid microparticles was 30.4 J/g.
Example 9
[0168] 1.5 g of polylactic acid (L/D=88/12, Mw (in terms of
PMMA)=150,000, enthalpy of fusion=0 J/g, SP value=23.14
(J/cm.sup.3).sup.1/2), 2.5 g of hydroxypropyl cellulose (supplied
by Tokyo Chemical Industry Co., Ltd., weight average molecular
mass=118,000, SP value=29.0 (J/cm.sup.3).sup.1/2) as a polymer
different from polylactic acid and 46.0 g of tetrahydrofuran as an
ether-based organic solvent were put in a 100 ml four-neck flask,
heated to 60 degrees Celsius, and stirred until the polymers have
been dissolved completely. After bringing the temperature back to
room temperature, 50 g of ion exchanged water as a poor solvent was
added by dripping it with a pump at a speed of 0.41 g per minute
while stirring a stirrer. Stirring was continued for another 30
minutes after the whole amount of water had been added, and the
resulting suspension was filtered and washed by 50 g of ion
exchanged water. Then, by drying the filtered matter in vacuum at
80 degrees Celsius for 10 hours, 1.3 g of white solid was obtained
in powder form. According to an observation with a scanning
electron microscope, the powder obtained was polylactic acid
microparticles having a smooth surface microparticle shape, having
an average particle diameter of 4.5 .mu.m, having a particle
diameter distribution index of 1.1, having a sphericity of 95 and a
linseed oil absorption of 58 ml/100 g. Further, an enthalpy of
fusion of these polylactic acid microparticles was 0 J/g. An
observation diagram of these microparticles by a scanning electron
microscope is shown in FIG. 5.
Example 10
[0169] By performing a procedure as in Practical Example 9 except
for using the polylactic acid of Production Example 1, 1.3 g of
white solid was obtained in powder form. According to an
observation with a scanning electron microscope, the powder
obtained was polylactic acid microparticles having a smooth surface
microparticle shape, having an average particle diameter of 7.8
.mu.m, having a particle diameter distribution index of 1.31 and a
sphericity of 91.
Example 11
[0170] By performing a procedure as in Practical Example 9 except
for using the polylactic acid of Production example 2, 1.3 g of
white solid was obtained in powder form. According to an
observation with a scanning electron microscope, the powder
obtained was polylactic acid microparticles having a smooth surface
microparticle shape, having an average particle diameter of 10.2
.mu.m, having a particle diameter distribution index of 1.20 and a
sphericity of 94.
Example 12
[0171] By performing a procedure as in Practical Example 9 except
for using the polylactic acid of Production example 3, 1.3 g of
white solid was obtained in powder form. According to an
observation with a scanning electron microscope, the powder
obtained was polylactic acid microparticles having a smooth surface
microparticle shape, having an average particle diameter of 12.1
.mu.m, having a particle diameter distribution index of 1.33 and a
sphericity of 90.
Example 13
[0172] 2.5 g of polylactic acid (L/D=88/12, Mw (in terms of
PMMA)=150,000, enthalpy of fusion=0 J/g, SP value=23.14
(J/cm.sup.3).sup.1/2), 2.5 g of hydroxypropyl cellulose (supplied
by Tokyo Chemical Industry Co., Ltd., weight average molecular
mass=118,000, SP value=29.0 (J/cm.sup.3).sup.1/2) as a polymer
different from polylactic acid and 45.0 g of diethylene glycol
dimethyl ether as an ether-based organic solvent were put in a 100
ml four-neck flask, heated to 80 degrees Celsius, and stirred until
the polymers have been dissolved completely. With the temperature
maintained, 50 g of ion exchanged water as a poor solvent was added
by dripping it with a pump for an hour while stirring with a
stirrer. Stirring was continued for another 30 minutes after the
whole amount of water had been added, and the resulting suspension
was filtered and washed by 50 g of ion exchanged water. Then, by
drying the filtered matter in vacuum at 80 degrees Celsius for 10
hours, 1.3 g of white solid was obtained in powder form. According
to an observation with a scanning electron microscope, the powder
obtained was polylactic acid microparticles having a smooth surface
microparticle shape, having an average particle diameter of 10.2
.mu.m, having a particle diameter distribution index of 1.32,
having a sphericity of 94 and a linseed oil absorption of 67 ml/100
g. Further, an enthalpy of fusion of these polylactic acid
microparticles was 0 J/g.
Comparative Example 1
[0173] 1.5 g of polylactic acid (L/D=98.8/1.2, Mw (in terms of
PMMA)=160,000, enthalpy of fusion=31.1 J/g, the SP value=23.14
(J/cm.sup.3).sup.1/2), 2.5 g of hydroxypropyl cellulose (supplied
by Tokyo Chemical Industry Co., Ltd., weight average molecular
mass=118,000, the SP value=29.0 (J/cm.sup.3).sup.1/2) as a polymer
different from polylactic acid and 46.0 g of N-methyl-2-pyrrolidone
as an alternative to an ether-based organic solvent were put in a
100 ml autoclave, heated to 50 degrees Celsius, and stirred until
the polymers have been dissolved completely. After bringing the
temperature back to room temperature, 50 g of ion exchanged water
as a poor solvent was added by dripping it with a pump at a speed
of 0.41 g per minute while stirring with a stirrer. Stirring was
continued for another 30 minutes after the whole amount of water
had been added. When filtering the resulting slurry liquid,
handling was not easy and it was difficult to extract it in powder
form. According to measurements of volume average particle diameter
and number average particle diameter in slurry state by using a
laser diffraction particle size analyzer (supplied by Shimadzu
Corporation, SALD-2100), the microparticles obtained had an average
particle diameter (volume average particle diameter) of 24.3 .mu.m
and a particle diameter distribution index of 9.1.
Comparative Example 2
[0174] 5 g of polylactic acid (D-isomer=1.2%, Mw (in terms of
PMMA)=160,000, melting point=168 degrees Celsius) and 50.0 g of
diethylene glycol dimethyl ether (diglyme) as an ether-based
organic solvent were put in a 100 ml four-neck flask, and were
dissolved in an oil bath under heat reflux conditions. After the
temperature was cooled down slowly to room temperature by switching
off the oil bath, a suspension of polylactic acid-based
microparticles was obtained. The suspension was filtered and washed
by 50 g of ion exchanged water, and by drying the filtered matter
in vacuum at 80 degrees Celsius for 10 hours, 4.88 g of white solid
was obtained in powder form. According to an observation with a
scanning electron microscope, the powder obtained was polylactic
acid microparticles having a porous microparticle shape, having an
average particle diameter of 64.0 .mu.m, having a particle diameter
distribution index of 3 or more and a sphericity of 50 or less.
Comparative Example 3
[0175] Polylactic acid-based resin microparticles were prepared
according to a procedure disclosed in JP-A-2009-242728. 1.0 g of
polylactic acid (L/D=98.8/1.2, Mw (in terms of PMMA)=160,000,
enthalpy of fusion=31.1 J/g, SP value=23.14 (J/cm.sup.3).sup.1/2)
and 9.0 g of orthodichlorobenzene were put in a 100 ml autoclave,
heated to 160 degrees Celsius and dissolved completely. The
autoclave was immersed in an oil bath of 30 degrees Celsius for 15
minutes, and the resulting powder was filtered and washed by 50 g
of ion exchanged water. By drying the filtered matter in vacuum at
80 degrees Celsius for 10 hours, 0.9 g of white solid was obtained
in powder form. According to an observation with a scanning
electron microscope, the powder obtained was polylactic acid
microparticles having a porous microparticle shape, having an
average particle diameter of 234.3 .mu.m, having a particle
diameter distribution index of 1.10, having a sphericity of 86 and
a linseed oil absorption of 86 ml/100 g. Further, the enthalpy of
fusion of these polylactic acid microparticles was 21.2 J/g. An
observation diagram of these microparticles by the scanning
electron microscope is shown in FIG. 6.
Comparative Example 4
[0176] Polylactic acid-based resin microparticles were prepared
according to a procedure disclosed in JP-A-2004-269865. 24.0 g of
polylactic acid (L/D=98.8/1.2, Mw (in terms of PMMA)=160,000,
enthalpy of fusion=31.1 J/g, SP value=23.14 (J/cm.sup.3).sup.1/2),
40.0 g of oligosaccharide (hydrogenated starch hydrolysate P0-10
supplied by Mitsubishi Shoji Foodtech Co., Ltd.) and 16.0 g of
pentaerythritol were put in a Labo-Plast Mill at a temperature of
200 degrees Celsius, and were kneaded for 5 minutes at a speed of
50 rotations per minute. After cooling, a resulting lump matter was
added to ion exchanged water, washed at a temperature of 60 degrees
Celsius and filtered. By drying the filtered matter in vacuum at 80
degrees Celsius for 10 hours, 21.0 g of white solid was obtained in
powder form. According to an observation with a scanning electron
microscope, the powder obtained was polylactic acid microparticles
having a smooth surface microparticle shape, having an average
particle diameter of 6.1 .mu.m, having a particle diameter
distribution index of 17.1, having a sphericity of 94 and a linseed
oil absorption of 56 ml/100 g. Further, the enthalpy of fusion of
these polylactic acid microparticles was 38.8 J/g. An observation
diagram of these microparticles by the scanning electron microscope
is shown in FIG. 7.
Comparative Example 5
[0177] Polylactic acid-based resin microparticles were prepared
according to a procedure disclosed in JP-A-2004-269865. 24.0 g of
polylactic acid (L/D=88/12, Mw (in terms of PMMA)=150,000, enthalpy
of fusion=0 J/g, SP value=23.14 (J/cm.sup.3).sup.1/2), 40.0 g of
oligosaccharide (hydrogenated starch hydrolysate PO-10 supplied by
Mitsubishi Shoji Foodtech Co., Ltd.) and 16.0 g of pentaerythritol
were put in a Labo-Plast Mill at a temperature of 200 degrees
Celsius, and were kneaded for 5 minutes at a speed of 50 rotations
per minute. After cooling, a resulting lump matter was added to ion
exchanged water, washed at a temperature of 60 degrees Celsius and
filtered. By drying the filtered matter in vacuum at 80 degrees
Celsius for 10 hours, 21.5 g of white solid was obtained in powder
form. According to an observation with a scanning electron
microscope, the powder obtained was polylactic acid microparticles
including smooth surface microparticles and fiber-shaped ones,
having an average particle diameter of 4.7 .mu.m, having a particle
diameter distribution index of 6.2, having a sphericity of 79 and a
linseed oil absorption of 54 ml/100 g. Further, the enthalpy of
fusion of these polylactic acid microparticles was 0 J/g. An
observation diagram of these microparticles by the scanning
electron microscope is shown in FIG. 8.
Comparative Example 6
[0178] Polylactic acid-based resin microparticles were prepared
according to a procedure disclosed in JP-A-2005-002302. 1.4 g of
polylactic acid (L/D=98.8/1.2, Mw (in terms of PMMA) 160,000,
enthalpy of fusion=31.1 J/g, SP value 23.14 (J/cm.sup.3).sup.1/2)
was dissolved completely in 12.6 g of 1,3-dioxolane, and
subsequently 7.0 g of ethyl acetate was added thereto. 21.0 g of
water was dropped for 20 minutes while being stirred by a
homogenizer, however, it was not possible to obtain microparticles
because a lump matter was formed instead.
Comparative Example 7
[0179] Polylactic acid-based resin microparticles were prepared
according to a procedure disclosed in JP-A-2005-002302. 1.4 g of
polylactic acid (L/D=88/12, Mw (in terms of PMMA) 150,000, enthalpy
of fusion=0 J/g, SP value 23.14 (J/cm.sup.3).sup.1/2) was dissolved
completely in 12.6 g of 1,3-dioxolane, and subsequently 7.0 g of
ethyl acetate was added thereto. 21.0 g of water was dropped for 20
minutes while being stirred by a homogenizer, however, it was not
possible to obtain microparticles because a lump matter was formed
instead.
[0180] As for Examples 1-13 and Comparative Examples 1-7, the
conditions of production processes are shown in Table 1, and the
measurement results regarding the polylactic acid-based resin
microparticles obtained are shown in Table 2.
TABLE-US-00001 TABLE 1 CONDITIONS Polylactic Organic Solvent (C)
Acid-based Polymer (B) different Ether-based Poor Solvent Resin (A)
from polylactic acid- Boiling Mass Ratio Contact Enthalpy of based
resin Point Other Organic (Ether-based/ Temperature Fusion (J/g)
Type Type (.degree. C.) Solvent Others) (.degree. C.) Example 1
31.1 hydroxypropyl cellulose tetrahydofuran 60 -- -- 30 Example 2
31.1 hydroxypropyl cellulose tetrahydofuran 60 -- -- 30 Example 3
31.1 hydroxypropyl cellulose tetrahydofuran 60 -- -- 30 Example 4
31.1 hydroxypropyl cellulose diglyme 160 N-methyl-2- 75/25 80
pyrrolidone Example 5 28.6 hydroxypropyl cellulose tetrahydofuran
60 -- -- 30 Example 6 28.6 hydroxypropyl cellulose diglyme 160 --
-- 80 Example 7 31.1 hydroxypropyl cellulose diglyme 160 -- -- 140
Example 8 28.6 hydroxypropyl cellulose diglyme 160 -- -- 140
Example 9 0 hydroxypropyl cellulose tetrahydofuran 60 -- -- 30
Example 10 0 hydroxypropyl cellulose tetrahydofuran 60 -- -- 30
Example 11 0 hydroxypropyl cellulose tetrahydofuran 60 -- -- 30
Example 12 0 hydroxypropyl cellulose tetrahydofuran 60 -- -- 30
Example 13 0 hydroxypropyl cellulose diglyme 160 -- -- 80
Comparative 31.1 hydroxypropyl cellulose -- -- N-methyl-2- -- 30
Example 1 pyrrolidone Comparative Example 2 Comparative Example 3
Comparative Example 4 Comparative Example 5 Comparative Example 6
Comparative Example 7
TABLE-US-00002 TABLE 2 Polylactic Acid-based Resin Microparticles
Particle Diameter Linseed Oil Enthalpy Shape of Number Average
Particle Diameter Absorption of Fusion Observation Particle
Particle Diameter Distribution Index Sphericity (ml/100 g) (J/g)
Diagram Example 1 porous 33 1.55 Example 2 25.1 1.35 89 432 57.8
FIG. 1 Example 3 59.5 11.5 661 Example 4 13.7 1.24 82 524 58.2 FIG.
2 Example 5 10 1.1 85 96 34.3 FIG. 3 Example 6 14 1.25 93 149 32.6
Example 7 smooth 1.6 1.4 95 51 40.8 FIG. 4 Example 8 surface 1.8
1.82 97 58 30.4 Example 9 4.5 1.1 95 58 0 FIG. 5 Example 10 7.8
1.31 91 Example 11 10.2 1.20 94 Example 12 12.1 1.33 90 Example 13
10.2 1.32 94 67 0 Comparative X X X X X X X Example 1 Comparative
porous 64 3.ltoreq. 50.gtoreq. Example 2 Comparative 234.3 1.1 86
86 21.2 FIG. 6 Example 3 Comparative smooth 6.1 17.1 94 56 38.8
FIG. 7 Example 4 surface Comparative 4.7 6.2 79 54 0 FIG. 8 Example
5 Comparative X X X X X X X Example 6 Comparative X X X X X X X
Example 7
Example 14
Cosmetic Foundation
[0181] A composite was prepared in accordance with a prescription
containing 5 mass % of the polylactic acid-based resin
microparticles obtained in Example 2, 35 mass % of talc, 30 mass %
of mica, 10 mass % of synthetic fluorphlogopite, 5 mass % of
titanium oxide, 3 mass % of aluminium hydroxide, 4 mass % of
stearic acid, 3 mass % of iron oxide, 0.2 mass % of butyl paraben,
0.1 mass % of methyl paraben, 9 mass % of dimethicone, 1.7 mass %
of methicone, and 4 or more mass % of trimethylsiloxysilicate. This
composite had a good slidability and a soft feeling of touch.
Example 15
[0182] A composite was prepared as in Example 14 except that the
polylactic acid-based microparticles obtained in Example 3 were
used. This composite had a good slidability and a soft feeling of
touch.
Example 16
[0183] A composite was prepared as in Example 14 except that the
polylactic acid-based microparticles obtained in Example 4 were
used. This composite had a good slidability and a soft feeling of
touch.
Example 17
[0184] A composite was prepared as in Example 14 except that the
polylactic acid-based microparticles obtained in Example 5 were
used. This composite had a good slidability and a soft feeling of
touch.
Comparative Example 8
[0185] A composite was prepared as in Example 14 except that no
polylactic acid-based microparticles were used. This composite had
a low slidability and a coarse feeling of touch.
Example 18
Powder Eye Shadow
[0186] A composite was prepared in accordance with a prescription
containing 7 mass % of the polylactic acid-based resin in Example
9, 63.6 mass % of synthetic mica, 15 mass % of titanium dioxide
coating mica, 6 mass % of glycerin, 4 mass % of squalane, 1.8 mass
% of methicone, 0.2 mass % of silica, 2.0 mass % of ultramarine,
0.2 mass % of organic pigment, and 0.2 mass % or more of ethyl
paraben. This composite had a good slidability and was glossy in
appearance.
Example 19
Cosmetic Foundation
[0187] A composite was prepared in accordance with a prescription
containing 5 mass % of the polylactic acid-based resin
microparticles obtained in Example 9, 35 mass % of talc, 30 mass %
of mica, 10 mass % of synthetic fluorphlogopite, 5 mass % of
titanium oxide, 3 mass % of aluminium hydroxide, 4 mass % of
stearic acid, 3 mass % of iron oxide, 0.2 mass % of butyl paraben,
0.1 mass % of methyl paraben, 9 mass % of dimethicone, 1.7 mass %
of methicone, and 4 mass % or more of trimethylsiloxysilicate.
Because of its slidability, the composite could spread well, had a
non-viscous feeling of touch and was glossy in appearance.
Comparative Examples 9-10
[0188] Linseed oil absorptions of commercially available
microparticles were evaluated. The results thereof and the results
of Examples 2, 3, 4, 5 are shown in Table 3. [0189] Microparticles
which have been used [0190] Comparative Example 9: Nylon
microparticles SP-500 (supplied by Toray Industries, Inc.) [0191]
Comparative Example 10: Nylon microparticles TR-1 (supplied by
Toray Industries, Inc.)
TABLE-US-00003 [0191] TABLE 3 Comparative Comparative Example 9
Example 10 Example 2 Example 3 Example 4 Example 5 (SP-500) (TR-1)
Material Polylactic Acid Polylactic Acid Polylactic Acid Polylactic
Acid Nylon 12 Nylon 6 Microparticles Microparticles Microparticles
Microparticles Linseed Oil 432 661 524 96 72.8 135 Absorption
(ml/100 g)
Examples 20-23 and Comparative Examples 11-12
Evaluation as Toner Base Material
[0192] Whether the polylactic acid-based resin microparticles
prepared in Examples 9-12 can be used as toner base material having
low temperature fixation characteristics or not was evaluated from
the viewpoint of powder flowability and heat-fusion characteristics
at 80 degrees Celsius. The polylactic acid-based resin
microparticles prepared in Example 2 and Comparative Example 2 were
also evaluated. The evaluation results are shown in Table 4.
[0193] The polylactic acid-based resin microparticles of Example
9-12 had a good flowability and were formed into a film shape. In
Example 2, the polylactic acid-based resin microparticles did not
have sufficient flowability and remained to be in powder shape. In
Comparative Example 2, the microparticles had no flowability
because of broad particle distribution and low sphericity, and as
for heat-fusion characteristics, the microparticles melted and
formed into a membrane shape partially but not formed into a film
shape.
Powder Flowability
[0194] An angle (angle of repose) formed between a plane and a
ridge line of powders dropped from a powder funnel (made of
polypropylene) was measured, and an angle of 50 degrees or less was
evaluated as "acceptable." Further, the presence or absence of
residues in the funnel was inspected, and powders that no residue
remained were evaluated as "excellent."
Heat-Fusion Characteristics at 80 Degrees Celsius
[0195] Putting 100 mg of powders on a hot plate at 80 degrees
Celsius for 5 minutes, powders which did not maintain particle
shape and formed into a film shape were evaluated as "acceptable,"
and others were evaluated as "not acceptable."
TABLE-US-00004 TABLE 4 Polylactic acid Powder Flowability Fusion
Characteristics at 80.degree. C. microparticles Angle of Repose
Residues in funnel Evaluation Capability of forming film Evaluation
Example 20 Example 9 30.sup..degree. remained a bit acceptable
melted and formed into film shape acceptable Example 21 Example 10
31.degree. remained a bit acceptable melted and formed into film
shape acceptable Example 22 Example 11 27.degree. no residue
excellent melted and formed into film shape acceptable Example 23
Example 12 25.sup..degree. no residue excellent melted and formed
into film shape acceptable Comparative Example 2 70.degree.
remained not acceptable remained in powder form not acceptable
Example 11 Comparative Comparative no flowability remained not
acceptable partially melted and formed into not acceptable Example
12 Example 2 membrane shape, but not formed into film shape
INDUSTRIAL APPLICABILITY
[0196] Our porous polylactic acid-based resin micro-particles
having small particle diameters and high linseed oil absorption
capability and the smooth surface polylactic acid-based resin
microparticles having spherical shapes and narrow particle diameter
distribution are quite useful and practical for various uses in
industry. More specifically, these microparticles can be used for,
for example, face wash, sunscreen, cleansing agent, cosmetic water,
lotion, cosmetic liquid, cream, cold cream, aftershave lotion,
shaving soap, oil absorbing sheet, various skin care agents such as
matifiant, foundation, foundation powder, liquid foundation,
mascara, face powder, Dohran, eyebrow pencil, mascara, eye line,
eye shadow, eye shadow base, nose shadow, lipsticks, gloss, cheek
brushes, tooth wax, manicure, various cosmetics and various
modification agents thereof such as topcoat, shampoo, dry shampoo,
conditioner, rinse, shampoo containing rinse ingredients,
treatment, hair tonic, hair conditioner, hair oil, pomade,
additives for various hair care products such as hair color agent,
per-fume, cologne, deodorant, baby powder, tooth powder, mouthwash,
lip balm, additives for various amenity products such as soap,
additive for toner, various rheology-improving agents used for
paint and the like, diagnostic test agents for medical purpose,
agents for improving machine characteristics of molded products
such as car materials and building materials, film, materials for
improving machine characteristics of fiber and the like, raw
materials for resin molded products used in rapid prototyping,
rapid manufacturing and the like, flash-moldable material, paste
resin for plastic sol, powder blocking agent, powder flowability
improving agent, lubricant, rubber compounding ingredient,
polishing agent, viscosity improver, filter material/filter aid,
gelatinizer, coagulation agent, additive for paints, oil absorbing
material, mold releasing agent, slippage improving agent for
plastic films/sheets, antiblocking agent, gloss adjusting agent,
frosted finish agent, light diffusion agent, surface hardness
improving agent and ductility improving material, spacer for liquid
crystal display equipment, filler/carrier for chromatography, base
material/additive for cosmetic foundation, assistant for
micro-capsules, medical materials for drug delivery
system/diagnostic reagents, support agent for perfume/pesticide,
catalyst/carrier for chemical reactions, gas adsorption agent,
sintered material for ceramic processing, standard particle
material for measurement/analysis, particle material for food
manufacture industry, material for powder coating, and toner for
electrophotographic development.
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