Technical Field
[0001] The present invention relates to a W/O nanoemulsion and a method for producing the
W/O nanoemulsion, and a fuel comprising the W/O nanoemulsion.
Background Art
[0002] It is said that an emulsion fuel has effects to suppress generation of nitrogen oxides
and particulate matters and to reduce the environmental load caused by gas exhausted
from internal combustion engines. It is thought that, when the fuel is ignited in
the internal combustion engine, water droplets evaporate first because of low boiling
temperature and, at this time, the surrounding oil flies apart to make particles smaller
in size. Since the area per their volume of the oil particles in contact with oxygen
increases and the local imperfect combustion is suppressed, the efficiency of combustion
increases and the generation of particulate matters (PMs) decreases. At the same time,
since the temperature of the internal combustion engine decreases due to the influence
of water contained, the generation of nitrogen oxides due to the production reaction
of Zeldovich NO can also be suppressed. Increased combustion efficiency also leads
to decrease of CO and reduction of CO
2.
Prior Art Documents
Non-patent Documents
Summary of the Invention
Problems to be solved by the Invention
[0004] However, in many cases, the conventional emulsion fuel should be used immediately
after production since it causes oil/water separation over time. Even the high-quality
emulsion fuel which does not separate for a long time preserves its quality for about
three months at the longest.
[0005] In addition, there were problems that the conventional technique can only produce
and use microemulsion, but cannot produce nanoemulsion, even if possible, nanoemulsion
is not stable for a long time.
[0006] An object of the present invention is to solve the above problems.
[0007] Specifically, an object of the present invention is to provide a W/O type nanoemulsion
which remains stable even if stored for long periods, for example, six months.
[0008] Further, other than or in addition to the above-described object, an object of the
present invention is to provide a W/O type nanoemulsion having a combustion efficiency
better than kerosene, light oil or the like, or a fuel comprising the W/O type nanoemulsion.
[0009] More, other than or in addition to the above-described objects, an object of the
present invention is to provide a W/O type nanoemulsion which can suppress the amount
of NO
x and/or CO generated by combustion, or a fuel comprising the W/O type nanoemulsion.
Means to Solve the Problem
[0010] The present inventors have found the following inventions:
<1> A W/O type emulsion comprising:
- a) water: more than 0 wt% but no more than 30 wt%, preferably 5 to 20 wt%;
- b) oil: less than 100 wt% but no less than 70 wt%, preferably 95 to 80 wt%;
- c) at least one nonionic surfactant having an HLB value of 1 to 10, preferably 3 to
8: 1 to 30 parts by weight, preferably 10 to 20 parts by weight, which are normalized
in a case where an amount of the oil is considered as 100 parts by weight; and
- d) at least one selected from the group consisting of anionic surfactants, cationic
surfactants and amphoteric surfactants: 0.1 to 30 parts by weight, preferably 0.5
to 20 parts by weight, which are normalized in a case where an amount of the water
is considered as 100 parts by weight,
wherein 50% average particle size of the water particle in the W/O type emulsion is
100 nm or less.
<2> In the above item <1>, the 50% average particle size of the water particle in
the W/O type emulsion may be 5 to 100 nm, preferably 5 to 50 nm, more preferably 5
to 30 nm, most preferably 5 to 20 nm.
<3> In the above item <1> or <2>, the b) oil may be at least one selected from the
group consisting of kerosene, gasoline, light oil, heavy oil (including A-type heavy
oil, B-type heavy oil and C-type heavy oil), alcohol, biofuel and ethyl tert-butyl
ether, preferably at least one selected from the group consisting of kerosene, light
oil, A-type heavy oil and B-type heavy oil, more preferably kerosene or light oil.
<4> In any one of the above items <1> to <3>, the c) nonionic surfactant may be at
least one selected from the group consisting of polyoxyethylene glycol, fatty acid
sorbitan esters, alkyl polyglucosides, fatty acid diethanolamides, alkyl monoglyceryl
ethers, alkyl glycosides, polyethylene glycol, and polyvinyl alcohol, preferably at
least one selected from the group consisting of polyoxyethylene glycol, fatty acid
sorbitan esters, and alkyl polyglucosides, more preferably polyoxyethylene glycol.
<5> In any one of the above items <1> to <4>, the d) surfactant may comprise an anionic
surfactant.
<6> In any one of the above items <1> to <4>, the d) surfactant may consist of an
anionic surfactant(s).
<7> In any one of the above items <1> to <6>, the anionic surfactant may be at least
one selected from the group consisting of fatty acid salts, monoalkyl sulfates, alkyl
polyoxyethylene sulfates, alkylbenezene sulfonates, monoalkyl phosphates, and sulfosuccinate-type
surfactants (such as ethylhexyl sulfosuccinate and the like), preferably at least
one selected from the group consisting of fatty acid salts, monoalkyl sulfates, alkyl
polyoxyethylene sulfates, and alkylbenezene sulfonates, more preferably monoalkyl
sulfates.
<8> In any one of the above items <1> to <5> and <7>, the d) surfactant may comprise
a cationic surfactant.
<9> In any one of the above items <1> to <4>, the d) surfactant may consist of a cationic
surfactant(s).
<10> In any one of the above items <1> to <5> and <7> to <9>, the cationic surfactant
may be at least one selected from the group consisting of alkyltrimethyl ammonium
salts, dialkyldimethyl ammonium salts, and alkylbenzyldimethyl ammonium salts, preferably
alkyltrimethyl ammonium salts.
<11> In any one of the above items <1> to <5>, <7>, <8> and <10>, the d) surfactant
may comprise an amphoteric surfactant.
<12> In any one of the above items <1> to <4>, the d) surfactant may consist of an
amphoteric surfactant(s).
<13> In any one of the above items <1> to <5>, <7>, <8> and <10> to <12>, the amphoteric
surfactant may be at least one selected from the group consisting of alkyldimethylamine
oxides and alkylcarboxy betaines.
<14> A fuel comprising the W/O type emulsion described in the above items <1> to <13>.
<15> A fuel consisting of the W/O type emulsion described in the above items <1> to
<13>.
<16> A fuel consisting essentially of the W/O type emulsion described in the above
items <1> to <13>.
<16> A method for producing a W/O type emulsion comprising:
- a) water: more than 0 wt% but no more than 30 wt%, preferably 5 to 20 wt%;
- b) oil: less than 100 wt% but no less than 70 wt%, preferably 95 to 80 wt%;
- c) at least one nonionic surfactant having an HLB value of 1 to 10, preferably 3 to
8: 1 to 30 parts by weight, preferably 10 to 20 parts by weight, which are normalized
in a case where an amount of the oil is considered as 100 parts by weight; and
- d) at least one selected from the group consisting of anionic surfactants, a cationic
surfactants and an amphoteric surfactants: 0.1 to 30 parts by weight, preferably 0.5
to 20 parts by weight, which are normalized in a case where an amount of the water
is considered as 100 parts by weight,
wherein 50% average particle size of the water particle in the W/O type emulsion is
100 nm or less, preferably 5 to 100 nm, preferably 5 to 50 nm, more preferably 5 to
30 nm, most preferably 5 to 20 nm,
the method comprising the steps of:
i) preparing the a) water;
ii) preparing the b) oil;
iii) preparing the c) nonionic surfactant;
iv) preparing the d) surfactant; and
v) mixing the a) to d);
to obtain the W/O type emulsion.
<17> In the above item <16>, the mixing step v) may comprises the steps of
v-1) mixing the oil of the step ii); and the nonionic surfactant of the step iii),
separately from the step v-1), v-2) mixing the water of the step i) and the surfactant
of the step iv) and
v-3) mixing the mixture obtained in the step v-1) and the mixture obtained in the
step v-2).
<18> In the above item <16> or <17>, the b) oil may be at least one selected from
the group consisting of kerosene, gasoline, light oil, heavy oil (including A-type
heavy oil, B-type heavy oil and C-type heavy oil), alcohol, biofuel and ethyl tert-butyl
ether, preferably at least one selected from the group consisting of kerosene, light
oil, A-type heavy oil and B-type heavy oil, more preferably kerosene or light oil.
<19> In any one of the above items <16> to <18>, the c) nonionic surfactant may be
at least one selected from the group consisting of polyoxyethylene glycol, fatty acid
sorbitan esters, alkyl polyglucosides, fatty acid diethanolamides, alkyl monoglyceryl
ethers, alkyl glycosides, polyethylene glycol, and polyvinyl alcohol, preferably at
least one selected from the group consisting of polyoxyethylene glycol, fatty acid
sorbitan esters and alkyl polyglucosides, more preferably polyoxyethylene glycol.
<20> In any one of the above items <16> to <19>, the d) surfactant may comprise an
anionic surfactant.
<21> In any one of the above items <16> to <19>, the d) surfactant may consist of
an anionic surfactant(s).
<22> In any one of the above items <16> to <21>, the anionic surfactant may be at
least one selected from the group consisting of fatty acid salts, monoalkyl sulfates,
alkyl polyoxyethylene sulfates, alkylbenezene sulfonates, monoalkyl phosphates, and
sulfosuccinate-type surfactants (such as ethylhexyl sulfosuccinate and the like),
preferably at least one selected from the group consisting of fatty acid salts, monoalkyl
sulfates, alkyl polyoxyethylene sulfates and alkylbenezene sulfonates, more preferably
monoalkyl sulfates.
<23> In any one of the above items <16> to <20> and <22>, the d) surfactant may comprise
a cationic surfactant.
<24> In any one of the above items <16> to <19>, the d) surfactant may consist of
a cationic surfactant(s).
<25> In any one of the above items <16> to <20> and <22> to <24>, the cationic surfactant
may be at least one selected from the group consisting of alkyltrimethyl ammonium
salts, dialkyldimethyl ammonium salts, and alkylbenzyldimethyl ammonium salts, preferably
alkyltrimethyl ammonium salts.
<26> In any one of the above items <16> to <20>, <22>, <23> and <25>, the d) surfactant
may comprise an amphoteric surfactant.
<27> In any one of the above items <16> to <19>, the d) surfactant may consist of
an amphoteric surfactant(s).
<28> In any one of the above items <16> to <20>, <22>, <23> and <25> to <27>, the
amphoteric surfactant may be at least one selected from the group consisting of alkyldimethylamine
oxides and alkylcarboxy betaines.
Effects of the Invention
[0011] The present invention can provide a W/O type nanoemulsion which remains stable even
if stored for long periods, for example, six months.
[0012] Further, other than or in addition to the above-described effect, the present invention
can provide a W/O type nanoemulsion having a combustion efficiency better than kerosene,
light oil or the like, or a fuel comprising the W/O type nanoemulsion.
[0013] More, other than or in addition to the above-described effects, the present invention
can provide a W/O type nanoemulsion which can suppress the amount of NO
x and/or CO generated by combustion, or a fuel comprising the W/O type nanoemulsion.
Brief Description of the Drawings
[0014]
Fig. 1 shows a schematic view of the W/O type emulsion according to the present application.
Fig. 2 shows the results of the ignition/combustion test for the W/O type emulsion
of Example 2.
Fig. 3 shows the results of the ignition/combustion test for Comparative Example 1
(kerosene alone).
Fig. 4 shows the results of the ignition/combustion test for Comparative Example 2
(a combination of nonionic surfactants).
Fig. 5 shows the average particle size dependent on the amount of the anionic surfactants
for the W/O type emulsions of Examples 1 and 7 to 9.
Embodiments Carrying Out the Invention
[0015] The present invention will be described in detail hereinafter.
[0016] The present invention provides a "W/O type emulsion", a fuel comprising the "W/O
type emulsion", a production method for the "W/O type emulsion", and the like. The
present invention will be described in order hereinafter.
<W/O type Emulsion>
[0017] The present application provides a W/O type emulsion in which the 50% average particle
size of the water particle is 100 nm or less.
[0018] The term "50 % average particle size" used herein means a median diameter at which
the accumulated distribution is 0.5.
[0019] In addition, the term "50% average particle size of the water particle in the W/O
type emulsion" used herein means the following. Namely, the W/O type emulsion according
to the present application has a structure as shown in Fig. 1. Fig. 1 shows, as an
example, the W/O type emulsion formed firstly by mixing water and a nonionic surfactant
to form a microemulsion, followed by further mixing an anionic surfactant to form
the nanoemulsion according to the present application. The nanoemulsion in Fig. 1
is configured having a water particle at its center with a hydrocarbon chain arranged
at its periphery. Therefore, "water particle in the W/O type emulsion" is a water
particle disposed at the center of the nanoemulsion in Fig. 1. Therefore, "50% average
particle size of the water particle in the W/O type emulsion" means a median diameter
at which the accumulated distribution is 0.5 for a water particle disposed at the
center of the nanoemulsion illustrated in Fig. 1.
[0020] The W/O type emulsion according to the present invention comprises a) water, b) oil,
c) a nonionic surfactant having an HLB value of 1 to 10, preferably 3 to 8, and d)
at least one selected from the group consisting of anionic surfactants, cationic surfactants
and amphoteric surfactants, or consists essentially of a) to d), or consists of a)
to d).
[0021] A nonionic surfactant having an HLB value of 1 to 10, preferably 3 to 8, means that,
when only one nonionic surfactant is used, the HLB value of such nonionic surfactant
is within the above-mentioned range. Note that the HLB value is defined according
to the following equation (1):

[0022] In addition, when two or more nonionic surfactants are added, the total HLB
t value of the two or more nonionic surfactants used is calculated as the weight average
of the HLB values of the two or more nonionic surfactants (see following equation
(2), wherein W
i and HLB
i indicate the weight and the HLB value of the i-th nonionic surfactant, respectively.).
The HLB
t value is used as the HLB value in this application.

[0023] Furthermore, when two nonionic surfactants (nonionic surfactant A and nonionic surfactant
B) are used, the total HLB
t value is defined according to equation (3) which is derived from equation (2).

[0024] In addition, the mixing ratio of the above-mentioned a) to d) is preferably as follows.
- a) water: more than 0 wt% but no more than 30 wt%, preferably 5 to 20 wt%;
- b) oil: less than 100 wt% but no less than 70 wt%, preferably 95 to 80 wt%;
- c) at least one nonionic surfactant having an HLB value of 1 to 10, preferably 3 to
8: 1 to 30 parts by weight, preferably 10 to 20 parts by weight, which are normalized
in a case where an amount of the oil is considered as 100 parts by weight; and
- d) at least one selected from the group consisting of anionic surfactants, cationic
surfactants and amphoteric surfactants: 0.1 to 30 parts by weight, preferably 0.5
to 20 parts by weight, which are normalized in a case where an amount of the water
is considered as 100 parts by weight.
[0025] The oil b) may be at least one selected from the group consisting of kerosene, gasoline,
light oil, heavy oil (including A-type heavy oil, B-type heavy oil and C-type heavy
oil), alcohol, biofuel and ethyl tert-butyl ether, preferably at least one selected
from the group consisting of kerosene, light oil, A-type heavy oil and B-type heavy
oil, more preferably kerosene or light oil.
[0026] The nonionic surfactant c) may be at least one selected from the group consisting
of polyoxyethylene glycol, fatty acid sorbitan esters, alkyl polyglucosides, fatty
acid diethanolamides, alkyl monoglyceryl ethers, alkyl glycosides, polyethylene glycol,
and polyvinyl alcohol, preferably at least one selected from the group consisting
of polyoxyethylene glycol, fatty acid sorbitan esters, and alkyl polyglucosides, more
preferably polyoxyethylene glycol.
[0027] In one embodiment, the surfactant d) may comprise an anionic surfactant, or may consist
of an anionic surfactant(s). In this case, the anionic surfactant may be at least
one selected from the group consisting of fatty acid salts (for example, sodium linoleate,
sodium oleate), monoalkyl sulfates (for example, sodium dodecylsulfonate), alkyl polyoxyethylene
sulfates (for example, sodium polyoxyethylene lauryl ether sulfate), alkylbenezene
sulfonates (for example, sodium dodecylbenzene sulfonate), monoalkyl phosphates (for
example, sodium polyoxyethylene alkyl ether phosphate), and sulfosuccinate-type surfactants
(such as ethylhexyl sulfosuccinate and the like), preferably at least one selected
from the group consisting of fatty acid salts (for example, sodium linoleate, preferably
sodium oleate), monoalkyl sulfates, alkyl polyoxyethylene sulfates, and alkylbenezene
sulfonates, more preferably monoalkyl sulfates. Furthermore, examples of the salts
may include sodium salts, ammonium salts, potassium salts and the like. Preferably,
the salts may be sodium salts or ammonium salts, more preferably sodium salts.
[0028] In one embodiment, the surfactant d) may comprise a cationic surfactant, or may consist
of a cationic surfactant(s). In this case, the cationic surfactant may be at least
one selected from the group consisting of alkyltrimethyl ammonium salts (for example,
C
12H
25-N
+(CH
3)
3Cl
- and the like), dialkyldimethyl ammonium salts (for example, C
12H
25-N
+(C
8H
17)(CH
3)
2Cl
- and the like), and alkylbenzyldimethyl ammonium salts (for example, decylisononyldimethyl
ammonium salt), preferably alkyltrimethyl ammonium salts (for example, C
12H
25-N
+(CH
3)
3Cl
-).
[0029] In one embodiment, the surfactant d) may comprise an amphoteric surfactant, or may
consist of an amphoteric surfactant(s). In this case, the amphoteric surfactant may
be at least one selected from the group consisting of alkyldimethylamine oxides (for
example, C
12H
25- (CH
3)
2NO and the like) and alkylcarboxy betaines (for example, C
12H
25- (CH
3)
2N
+CH
2COO
- and the like).
<Fuel>
[0030] The present application provides i) a fuel comprising the above-mentioned W/O type
emulsion; ii) a fuel consisting of the above-mentioned W/O type emulsion; or iii)
a fuel essentially consisting of the above-mentioned W/O type emulsion.
[0031] In case of the i) fuel comprising the above-mentioned W/O type emulsion, the fuel
may contain alcohols (for example, methanol, ethanol and the like) other than the
W/O type emulsion according to the present application. Furthermore, the component
which may be contained other than the W/O type emulsion is not limited to them.
[0032] The W/O type emulsion according to the present application may be produced, for example,
according to the following method:
i) the step of preparing the a) water;
ii) the step of preparing the b) oil;
iii) the step of preparing the c) nonionic surfactant;
iv) the step of preparing the d) surfactant; and
v) the step of mixing the a) to d);
to obtain the above W/O type emulsion.
[0033] Furthermore, the a) water, the b) oil, the c) nonionic surfactant and the d) surfactant
used herein have the same definition as mentioned above.
[0034] For the mixing step v), various techniques are utilized for production of the emulsion.
Examples of the techniques may include, but are not limited to, mechanical emulsification,
phase transition process, phase transfer emulsification, D-phase emulsification, gel
emulsification and the like. Furthermore, a homogenizer, a counter impact machine,
a screw type machine, an ultrasound type machine and the like based on the mechanical
emulsification may be used in order to produce the emulsion in a large amount.
[0035] As the mixing step v), components a) to d) prepared in the steps i) to iv) mentioned
above may be sequentially mixed or may be mixed all together. The emulsion of the
present application may be obtained by either method.
[0036] The preferred method is, however, sequential mixing including the steps of: v-1)
mixing the oil of the step ii) and the nonionic surfactant of the step iii);
v-2) separately from the step v-1), mixing the water of the step i) and the surfactant
of the step iv); and
v-3) mixing the mixture obtained in the step v-1) and the mixture obtained in the
step v-2).
[0037] Conventional mixing techniques may be used for the steps v-1), v-2) and v-3).
[0038] The present invention will be illustrated in more detail referring to the Examples,
to which the present invention is not limited.
Example 1:
[0039] To a liquid of 850g of kerosene (85 wt% of kerosene, based on 100 wt% of the total
of 150 g of water described later and 850 g of kerosene), 136 g of a nonionic surfactant
DSK NL-15 (polyoxyethylene lauryl ether, manufactured by Dai-ichi Kogyo Seiyaku Co.,
Ltd., HLB: 5.0, average molecular weight of polyoxyethylene moiety: 2,900) (16 parts
by weight, normalized in a case where an amount of kerosene is considered as 100 parts
by weight) and 34 g of a nonionic surfactant DSK NL-50 (polyoxyethylene lauryl ether,
manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., HLB: 10.6) (4 parts by weight, normalized
in a case where an amount of kerosene is considered as 100 parts by weight) were added,
and mixed by stirring to obtain a liquid A. The total HLB value of the nonionic surfactants
in the liquid A was 6.12, according to the above-mentioned equation (2).
[0040] Separately from the liquid A, to 150 g of water (15 wt% of water, based on 100 wt%
of the total of 150 g of water and 850 g of kerosene) was added 15 g of an anionic
surfactant, sodium dodecyl sulfate (manufactured by NACALAI) (10 parts by weight,
normalized in a case where an amount of water is considered as 100 parts by weight)
and mixed by stirring to obtain a liquid B.
[0041] The liquid A and the liquid B were mixed and stirred using a homogenizer (PH91 manufactured
by SMT Company) for 5 minutes, to obtain a colorless clear liquid, i.e., a W/O nanoemulsion.
[0042] The particle size distribution of the W/O nanoemulsion was determined by using the
laser light scattering method (LS-200F manufactured by Otsuka Electronics Co., Ltd.),
showing that the 50% average particle size of the water particle was about 10 nm.
[0043] Regarding the stability, separation was not observed after centrifugation (Type 4000
manufactured by Kubota Corporation) at 2200 G at ambient temperature for 60 minutes.
In addition, the W/O nanoemulsion was clear even after standing still at ambient temperature
for one year.
Example 2:
[0044] A W/O nanoemulsion was prepared using the liquids A and B in mixing ratio same as
Example 1, except that a counter impact machine (manufactured by Kankyou Kakushin
Kogyo Co., Ltd.) was used instead of the homogenizer (PH91 manufactured by SMT Company)
used in Example 1.
[0045] The resulting nanoemulsion was tested for ignition/combustion properties using a
fuel combustion analyzer FIA-100 manufactured by Fuel Tech Japan Ltd.
[0046] The results are shown in Table 1 and Fig. 2. The fuel ignition/combustion tests were
done ten times in the upper graph of Fig.2. In the upper graph of Fig.2, the horizontal
axis indicates time (ms) and the vertical axis indicates pressure (bar). The upper
graph of Fig.2 shows the pressure at the beginning of and after combustion, and the
average value of the pressure can be calculated from the graph. In the lower graph
of Fig. 2, the horizontal axis indicates time (ms) and the vertical axis indicates
pressure/time (bar/ms). The lower graph of Fig. 2 shows the temporal differentiation
of the upper graph of Fig. 2, for comparison of the combustion efficiency. Furthermore,
a W/O nanoemulsion was formed in a manner similar to Example 1, except that a blender
(HBB type, manufactured by Yamato Scientific Co., Ltd.) was used instead of the homogenizer
used in Example 1 (PH91 manufactured by SMT Company), to confirm that the results
similar to the present Example were obtained.
(Comparative Example 1)
[0047] A fuel consisting of kerosene was tested for ignition/combustion properties using
a fuel combustion analyzer FIA-100 manufactured by Fuel Tech Japan Ltd.
[0048] The results are shown in Table 2 and Fig. 3. The upper and lower graphs of Fig. 3
are similar to those in Fig.2, respectively.
(Comparative Example 2)
[0049] A mixture of the nonionic surfactants DSK NL-15 (same as described above) and DSK
NL-50 (same as described above) mixed in the weight ratio of 4:1 was tested for ignition/combustion
properties using a fuel combustion analyzer FIA-100 manufactured by Fuel Tech Japan
Ltd.
[0050] The results are shown in Table 3 and Fig. 4. The upper and lower graphs of Fig. 4
are similar to those in Figs. 2 and 3, respectively.
Table 1. Results of ignition/combustion test for W/O nanoemulsion of Example 2
Ignition (ID) dP=0.2bar |
7.75ms |
Start of main combustion (MRD) dP=1.0bar |
9.07ms |
Ignition to main combustion period (PCP) |
1.32ms |
End of combustion (EC) |
20.8ms |
Total combustion period (EMP) dP=1.0bar |
14.30ms |
Main combustion period (MCP) dP=1.0bar |
5.23ms |
MD standard deviation dP=1.0bar |
0.44 |
FIA Cetane number (FIA CN) dP=1.0bar |
48.5 |
ROHR index |
152.9 |
ROHR maximum time |
11.0ms |
After burning period (ABP) |
6.5ms |
Table 2. Results of ignition/combustion test for kerosene alone (Comparative Example
1)
Ignition (ID) dP=0.2bar |
10.95ms |
Start of main combustion (MRD) dP=1.0bar |
12.81ms |
Ignition to main combustion period (PCP) |
1.86ms |
End of combustion (EC) |
31.15ms |
Total combustion period (EMP) dP=1.0bar |
20.15ms |
Main combustion period (MCP) dP=1.0bar |
7.34ms |
MD standard deviation dP=1.0bar |
0.67 |
FIA Cetane number (FIA CN) dP=1.0bar |
41 |
ROHR index |
144.4 |
ROHR maximum time |
16.3ms |
After burning time (ABP) |
9.00ms |
Table 3. Results of ignition/combustion test for nonionic surfactant alone (Comparative
Example 2)
Ignition (ID) dP=0.2bar |
4.50ms |
Start of main combustion (MRD) dP=1.0bar |
5.22ms |
Ignition to main combustion period (PCP) |
0.72ms |
End of combustion (EC) |
15.20ms |
Total combustion period (EMP) dP=1.0bar |
11.00ms |
Main combustion period (MCP) dP=1.0bar |
5.78ms |
MD standard deviation dP=1.0bar |
0.41 |
FIA Cetane number (FIA CN) dP=1.0bar |
71.5 |
ROHR index |
174.7 |
ROHR maximum time |
6.1ms |
After burning time (ABP) |
4.20ms |
[0051] Tables 1 to 3 and Figs. 2 to 4 show that the W/O type nanoemulsion according to Example
2 ignites faster than kerosene alone (kerosene alone: 10.95 ms, W/O type nanoemulsion
according to Example 2: 7.75 ms).
[0052] It is also shown that the main combustion period (MCP) of the W/O type nanoemulsion
is shorter than kerosene alone and shorter than the nonionic surfactant alone (kerosene
alone: 7.34 ms, nonionic surfactant alone: 5.78 ms, W/O type nanoemulsion according
to Example 2: 5.23 ms).
[0053] It is also shown that the cetane number of the W/O type nanoemulsion according to
Example 2 is higher than kerosene (kerosene alone: 41, W/O type nanoemulsion according
to Example 2: 48.5).
[0054] These data show that the W/O type nanoemulsion according to Example 2 has the excellent
combustion properties.
Example 3:
[0055] To a liquid of 900g of kerosene (90 wt% of kerosene, based on 100 wt% of the total
of 100 g of water described later and 900 g of kerosene) were added 144 g of a nonionic
surfactant DSK NL-15 (same as described above) (16 parts by weight, normalized in
a case where an amount of kereosene is considered as 100 parts by weight) and 36 g
of a nonionic surfactant DSK NL-50 (same as described above) (4 parts by weight, normalized
in a case where an amount of kereosene is considered as 100 parts by weight), and
mixed by stirring to obtain a liquid A. The total HLB value of the nonionic surfactants
in the liquid A was 6.12, according to the above-mentioned equation (2).
[0056] Separately from the liquid A, to 100 g of water (10 wt% of water, based on 100 wt%
of the total of 100 g of water and 900 g of kerosene) was added 10 g of an anionic
surfactant, sodium dodecyl sulfate (manufactured by NACALAI) (10 parts by weight,
normalized in a case where an amount of water is considered as 100 parts by weight),
and mixed by stirring to obtain a liquid B.
[0057] The liquids A and B were mixed in a manner similar to Example 1, to obtain a colorless
clear liquid, i.e., a W/O nanoemulsion.
[0058] The particle size distribution of the W/O nanoemulsion was determined by using the
laser light scattering method similar to Example 1, showing that the 50% average particle
size of the water particle was about 10 nm.
[0059] Regarding the stability, observation was done in a manner similar to Example 1, and
separation was not observed. In addition, the W/O nanoemulsion was clear even after
standing still at ambient temperature for one year.
Example 4:
[0060] To a liquid of 800g of kerosene (80 wt% of kerosene, based on 100 wt% of the total
of 200 g of water described later and 800 g of kerosene) were added 128 g of a nonionic
surfactant DSK NL-15 (same as described above) (16 parts by weight, normalized in
a case where an amount of kereosene is considered as 100 parts by weight) and 32 g
of a nonionic surfactant DSK NL-50 (same as described above) (4 parts by weight, normalized
in a case where an amount of kereosene is considered as 100 parts by weight), and
mixed by stirring to obtain a liquid A. The total HLB value of the nonionic surfactants
in the liquid A was 6.12, according to the above-mentioned equation (2).
[0061] Separately from the liquid A, to 200 g of water (20 wt% of water, based on 100 wt%
of the total of 200 g of water and 800 g of kerosene) was added 20 g of an anionic
surfactant, sodium dodecyl sulfate (manufactured by NACALAI) (10 parts by weight,
normalized in a case where an amount of water is considered as 100 parts by weight),
and mixed by stirring to obtain a liquid B.
[0062] The liquids A and B were mixed in a manner similar to Example 1, to obtain a colorless
clear liquid, i.e., a W/O nanoemulsion.
[0063] The particle size distribution of the W/O nanoemulsion was determined by using the
laser light scattering method similar to Example 1, showing that the 50% average particle
size of the water particle was about 10 nm.
[0064] Regarding the stability, observation was done in a manner similar to Example 1, and
separation was not observed. In addition, the W/O nanoemulsion was clear even after
standing still at ambient temperature for one year.
<Steam boiler test> and <Color test of black particles onto white paper>
[0065] Steam boiler test was carried out for kerosene alone according to Comparative Example
1, a W/O type nanoemulsion according to Example 3 (water 10%), a W/O type nanoemulsion
according to Example 2 (water 15%) and a W/O type nanoemulsion according to Example
4 (water 20%).
[0066] As the test, kerosene alone according to Comparative Example 1, a W/O type nanoemulsion
according to Example 3 (water 10%), a W/O type nanoemulsion according to Example 2
(water 15%) and a W/O type nanoemulsion according to Example 4 (water 20%) were charged
in a steam boiler tester (SF350-3 manufactured by Ogata Ironworks, Inc.) in this order
and burned. The exhaust gas was analyzed qualitatively and quantitatively by gas chromatography
(GC manufactured by Shimadzu Corporation) on a timely basis.
[0067] The results are shown in Table 4.

[0068] From Table 4, it was confirmed that the increase in water mixing ratio in the W/O
type nanoemulsion causes reduction of NO
x as well as CO, due to lowering of combustion temperature (Although "exhaust temperature"
in Table 4 does not indicate the combustion temperature itself, low "exhaust temperature"
means low combustion temperature.).
[0069] Color test of black particles onto white paper was carried out simultaneously with
the steam boiler test. As the result, black particles were very hardly observed in
the test of the W/O type nanoemulsion (Examples 2 to 4). On the other hand, in the
case of kerosene alone (Comparative Example 1), slightly gray color and a small number
of black particles were observed.
Example 5:
[0070] A colorless clear liquid, W/O nanoemulsion, was prepared by mixing the liquids A
and B with the mixing ratio similar to Example 1 in a manner similar to Example 1,
except that sulfosuccinic acid dioctyl ester (Aerosol OT manufactured by Wako Pure
Industries, Ltd.) was used instead of the anionic surfactant, sodium dodecylsulfate
used in Example 1.
[0071] The particle size distribution of the resulting W/O nanoemulsion was determined by
using the laser light scattering method similar to Example 1, showing that the 50%
average particle size of the water particle was about 10 nm.
[0072] Regarding the stability, observation was done in a manner similar to Example 1, and
separation was not observed.
Example 6:
[0073] A colorless clear liquid, W/O nanoemulsion, was prepared in a manner similar to Example
1, except that 7.5 g of sodium dodecyl sulfate and 7.5 g of sulfosuccinic acid dioctyl
ester were used instead of 15 g of the anionic surfactant, sodium dodecyl sulfate
used in Example 1 and that a stirrer (MS3 manufactured by IKA Company) was used instead
of the homogenizer (PH91 manufactured by SMT Company) for mixing of the liquids A
and B.
[0074] The particle size distribution of the resulting W/O nanoemulsion was determined by
using the laser light scattering method similar to Example 1, showing that the 50%
average particle size of the water particle was about 10 nm.
[0075] Regarding the stability, observation was done in a manner similar to Example 1, and
separation was not observed.
Examples 7 to 9:
[0076] The liquid A was prepared in a manner similar to Example 1.
[0077] The liquid B was also prepared in a manner similar to Example 1, except that 0.75
g (0.5 parts by weight, normalized in a case where an amount of water is considered
as 100 parts by weight) (Example 7), 4.2 g (2.8 parts by weight, normalized in a case
where an amount of water is considered as 100 parts by weight) (Example 8), and 7.5
g (5 parts by weight, normalized in a case where an amount of water is considered
as 100 parts by weight) (Example 9) of sodium dodecyl sulfate were used instead of
15 g for the liquid B in Example 1. The liquids A and B were mixed in a manner similar
to Example 1, to obtain a colorless clear liquid, a W/O nanoemulsion.
[0078] The particle size distribution of the resulting W/O nanoemulsion was determined by
using the laser light scattering method similar to Example 1, and the results are
shown in Fig. 5 (The point of 10 wt% of the ionic surfactant was derived from Example
1). Fig. 5 shows a trend that the smaller amount of the anionic surfactant causes
larger average particle size of the emulsion and the larger amount of the anionic
surfactant causes smaller average particle size of the emulsion in the formulation
of Examples 1 and 7 to 9.
Example 10:
[0079] A colorless clear liquid, i.e., W/O nanoemulsion, was obtained in a manner similar
to Example 1, except that a nonionic surfactant, DSK NL-40 (polyoxyethylene lauryl
ether manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., HLB:9.5) was used instead
of the nonionic surfactant, DSK NL-50 in Example 1. The total HLB value of the nonionic
surfactants in the liquid A was 5.9 according to the above-mentioned equation (2).
[0080] The particle size distribution of the resulting W/O nanoemulsion was determined in
a manner similar to Example 1, showing that the 50% average particle size of the water
particle was about 10 nm.
[0081] Regarding the stability, observation was done in a manner similar to Example 1, and
separation was not observed.
Example 11:
[0082] A colorless clear liquid, i.e., W/O nanoemulsion, was obtained in a manner similar
to Example 10, except that an anionic surfactant, sodium oleate (manufactured by NACALAI)
was used instead of the anionic surfactant, sodium dodecyl sulfate in Example 10.
The total HLB value of the nonionic surfactants in the liquid A was 5.9, same as that
of Example 10.
[0083] The particle size distribution of the resulting W/O nanoemulsion was determined in
a manner similar to Example 1, showing that the 50% average particle size of the water
particle was about 50 nm.
[0084] Regarding the stability, observation was done in a manner similar to Example 1, and
separation was not observed.
Example 12:
[0085] A colorless clear liquid, i.e., W/O nanoemulsion, was obtained in a manner similar
to Example 3, except that the amount of sodium dodecyl sulfate was changed to 20 g
(20 parts by weight, normalized in a case where an amount of water is considered as
100 parts by weight) from 10 g in Example 3.
[0086] The particle size distribution of the resulting W/O nanoemulsion was determined in
a manner similar to Example 1, showing that the 50% average particle size of the water
particle was about 8 nm.
[0087] Regarding the stability, observation was done in a manner similar to Example 1, and
separation was not observed.
Example 13:
[0088] A colorless clear liquid, i.e., W/O nanoemulsion, was obtained in a manner similar
to Example 4, except that the amount of sodium dodecyl sulfate was changed to 40 g
(20 parts by weight, normalized in a case where an amount of water is considered as
100 parts by weight) from 20 g in Example 4.
[0089] The particle size distribution of the resulting W/O nanoemulsion was determined in
a manner similar to Example 1, showing that the 50% average particle size of the water
particle was about 20 nm.
[0090] Regarding the stability, observation was done in a manner similar to Example 1, and
separation was not observed.
Example 14:
[0091] To a liquid of 850g of gasoline (85 wt% of gasoline, based on 100 wt% of the total
of 150 g of water described later and 850 g of gasoline) were added 136 g of a nonionic
surfactant DSK NL-15 (polyoxyethylene lauryl ether, manufactured by Dai-ichi Kogyo
Seiyaku Co., Ltd., HLB: 5.0, average molecular weight of polyoxyethylene moiety: 2,900)
(16 parts by weight, normalized in a case where an amount of gasoline is considered
as 100 parts by weight) and 34 g of a nonionic surfactant DSK NL-50 (polyoxyethylene
lauryl ether, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., HLB: 10.6) (4 parts
by weight, normalized in a case where an amount of gasoline is considered as 100 parts
by weight), and mixed by stirring to obtain a liquid A. The total HLB value of the
nonionic surfactants in the liquid A was 6.12, according to the above-mentioned equation
(2).
[0092] Separately from the liquid A, to 150 g of water (15 wt% of water, based on 100 wt%
of the total of 150 g of water and 850 g of gasoline) was added 15 g of an anionic
surfactant, sodium dodecyl sulfate (manufactured by NACALAI) (10 parts by weight,
normalized in a case where an amount of water is considered as 100 parts by weight),
and mixed by stirring to obtain a liquid B.
[0093] The liquids A and B were mixed and stirred using a homogenizer (PH91 manufactured
by SMT Company) for 5 minutes, to obtain a colorless clear liquid, i.e., a W/O nanoemulsion.
[0094] The particle size distribution of the resulting W/O nanoemulsion could not be determined
in a manner similar to Example 1, due to its higher transmittance. However, since
the resulting W/O emulsion was colorless and clear with no phase separation, it is
estimated that the 50% average particle size of the water particle was 100 nm or less.
[0095] Regarding the stability, observation was done in a manner similar to Example 1, and
separation was not observed. In addition, the W/O nanoemulsion was clear even after
standing still at ambient temperature for one month.
Example 15:
[0096] To a liquid of 850g of gasoline (85 wt% of gasoline, based on 100 wt% of the total
of 150 g of water described later and 850 g of gasoline) was added 170 g of a nonionic
surfactant DSK NL-15 (polyoxyethylene lauryl ether, manufactured by Dai-ichi Kogyo
Seiyaku Co., Ltd., HLB: 5.0, average molecular weight of polyoxyethylene moiety: 2,900)
(20 parts by weight, normalized in a case where an amount of gasoline is considered
as 100 parts by weight), and mixed by stirring to obtain a liquid A.
[0097] Separately from the liquid A, to 150 g of water (15 wt% of water, based on 100 wt%
of the total of 150 g of water and 850 g of gasoline) were added 10 g, 15 g and 30
g of an anionic surfactant, sodium dodecyl sulfate (manufactured by NACALAI) (7, 10
and 20 parts by weight, normalized in a case where an amount of water is considered
as 100 parts by weight, respectively), and mixed by stirring to obtain a liquid B.
[0098] The liquids A and B were mixed and stirred using a homogenizer (PH91 manufactured
by SMT Company) for 5 minutes, to obtain each of a colorless clear liquid, i.e., a
W/O nanoemulsion.
[0099] The particle size distribution of the resulting W/O nanoemulsion could not be determined
in a manner similar to Example 1, due to its higher transmittance. However, since
the resulting W/O emulsion was colorless and clear with no phase separation, it is
estimated that the 50% average particle size of the water particle was 100 nm or less.
[0100] Regarding the stability, observation was done in a manner similar to Example 1, and
separation was not observed. In addition, the W/O nanoemulsion was clear even after
standing still at ambient temperature for one month.
Example 16:
[0101] To a liquid of 850g of light oil (85 wt% of light oil, based on 100 wt% of the total
of 150 g of water described later and 850 g of light oil) were added 136 g of a nonionic
surfactant DSK NL-15 (polyoxyethylene lauryl ether, manufactured by Dai-ichi Kogyo
Seiyaku Co., Ltd., HLB: 5.0, average molecular weight of polyoxyethylene moiety: 2,900)
(16 parts by weight, normalized in a case where an amount of light oil is considered
as 100 parts by weight) and 34 g of a nonionic surfactant DSK NL-50 (polyoxyethylene
lauryl ether, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., HLB: 10.6) (4 parts
by weight, normalized in a case where an amount of light oil is considered as 100
parts by weight), and mixed by stirring to obtain a liquid A. The total HLB value
of the nonionic surfactants in the liquid A was 6.12, according to the above-mentioned
equation (2).
[0102] Separately from the liquid A, to 150 g of water (15 wt% of water, based on 100 wt%
of the total of 150 g of water and 850 g of light oil) was added 15 g of an anionic
surfactant, sodium dodecyl sulfate (manufactured by NACALAI) (10 parts by weight,
normalized in a case where an amount of water is considered as 100 parts by weight),
and mixed by stirring to obtain a liquid B.
[0103] The liquids A and B were mixed and stirred using a homogenizer (PH91 manufactured
by SMT Company) for 5 minutes, to obtain a colorless clear liquid, i.e., a W/O nanoemulsion.
[0104] The particle size distribution of the resulting W/O nanoemulsion was determined in
a manner similar to Example 1, showing that the 50% average particle size of the water
particle was about 10 nm.
[0105] Regarding the stability, observation was done in a manner similar to Example 1, and
separation was not observed. In addition, the W/O nanoemulsion was clear even after
standing still at ambient temperature for one month.
Example 17:
[0106] To a liquid of 850g of light oil (85 wt% of light oil, based on 100 wt% of the total
of 150 g of water described later and 850 g of light oil) was added 170 g of a nonionic
surfactant DSK NL-15 (polyoxyethylene lauryl ether, manufactured by Dai-ichi Kogyo
Seiyaku Co., Ltd., HLB: 5.0, average molecular weight of polyoxyethylene moiety: 2,900)
(20 parts by weight, normalized in a case where an amount of light oil is considered
as 100 parts by weight), and mixed by stirring to obtain a liquid A.
[0107] Separately from the liquid A, to 150 g of water (15 wt% of water, based on 100 wt%
of the total of 150 g of water and 850 g of light oil) were added 2.5 g and 7.5 g
of anionic surfactant, sodium dodecyl sulfate (manufactured by NACALAI) (1.7 and 5
parts by weight, normalized in a case where an amount of water is considered as 100
parts by weight, respectively), and mixed by stirring to obtain a liquid B.
[0108] The liquids A and B were mixed and stirred using a homogenizer (PH91 manufactured
by SMT Company) for 5 minutes, to obtain a colorless clear liquid, i.e., a W/O nanoemulsion.
[0109] The particle size distribution of each of the resulting W/O nanoemulsions was determined
in a manner similar to Example 1, showing that each 50% average particle size of the
water particle was about 10 nm, respectively.
[0110] Regarding the stability, observation was done in a manner similar to Example 1, and
separation was not observed. In addition, the W/O nanoemulsion was clear even after
standing still at ambient temperature for one month.
Example 18:
[0111] A colorless clear liquid, i.e., a W/O nanoemulsion was obtained in a manner similar
to Example 17, except that "A-type heavy oil" was used instead of "light oil" in Example
17.
[0112] The particle size distribution of the resulting W/O nanoemulsion was determined in
a manner similar to Example 1, showing that the 50% average particle size of the water
particle was about 10 nm, respectively.
[0113] Regarding the stability, observation was done in a manner similar to Example 1, and
separation was not observed. In addition, the W/O nanoemulsion was clear even after
standing still at ambient temperature for one month.
Example 19:
[0114] To a liquid of 850g of C-type heavy oil (85 wt% of C-type heavy oil, based on 100
wt% of the total of 150 g of water described later and 850 g of C-type heavy oil)
were added 136 g of a nonionic surfactant DSK NL-15 (polyoxyethylene lauryl ether,
manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., HLB: 5.0, average molecular weight
of polyoxyethylene moiety: 2,900) (16 parts by weight, normalized in a case where
an amount of C-type heavy oil is considered as 100 parts by weight) and 34 g of a
nonionic surfactant DSK NL-50 (polyoxyethylene lauryl ether, manufactured by Dai-ichi
Kogyo Seiyaku Co., Ltd., HLB: 10.6) (4 parts by weight, normalized in a case where
an amount of C-type heavy oil is considered as 100 parts by weight), and mixed by
stirring to obtain a liquid A. The total HLB value of the nonionic surfactants in
the liquid A was 6.12, according to the above-mentioned equation (2).
[0115] Separately from the liquid A, to 150 g of water (15 wt% of water, based on 100 wt%
of the total of 150 g of water and 850 g of C-type heavy oil) was added 15 g of an
anionic surfactant, sodium dodecyl sulfate (manufactured by NACALAI) (10 parts by
weight, normalized in a case where an amount of water is considered as 100 parts by
weight), and mixed by stirring to obtain a liquid B.
[0116] The liquids A and B were mixed and stirred using a homogenizer (PH91 manufactured
by SMT Company) for 5 minutes, to obtain a colorless clear liquid, i.e., a W/O nanoemulsion.
[0117] The particle size distribution of the resulting W/O nanoemulsion could not be determined
in a manner similar to Example 1, due to its lower transmittance. However, since the
resulting W/O emulsion was colorless and clear with no phase separation upon observation
similar to Example 1 regarding the stability, it is estimated that the 50% average
particle size of the water particle was 100 nm or less.
[0118] In addition, the W/O nanoemulsion was clear even after standing still at ambient
temperature for one month.
Example 20:
[0119] To a liquid of 850g of C-type heavy oil (85 wt% of C-type heavy oil, based on 100
wt% of the total of 150 g of water described later and 850 g of C-type heavy oil)
was added 170 g of a nonionic surfactant DSK NL-15 (polyoxyethylene lauryl ether,
manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., HLB: 5.0, average molecular weight
of polyoxyethylene moiety: 2,900) (20 parts by weight, normalized in a case where
an amount of C-type heavy oil is considered as 100 parts by weight), and mixed by
stirring to obtain a liquid A.
[0120] Separately from the liquid A, to 150 g of water (15 wt% of water, based on 100 wt%
of the total of 150 g of water and 850 g of C-type heavy oil) were added 2.5 g, 10
g and 15 g of anionic surfactant, sodium dodecyl sulfate (manufactured by NACALAI)
(1.7, 6.7 and 10 parts by weight, normalized in a case where an amount of water is
considered as 100 parts by weight, respectively), and mixed by stirring to obtain
a liquid B.
[0121] The liquids A and B were mixed and stirred using a homogenizer (PH91 manufactured
by SMT Company) for 5 minutes, to obtain a colorless clear liquid, i.e., a W/O nanoemulsion.
[0122] The particle size distribution of the resulting W/O nanoemulsion could not be determined
in a manner similar to Example 1, due to its lower transmittance. However, since the
resulting W/O emulsion was colorless and clear with no phase separation upon observation
similar to Example 1 regarding the stability, it is estimated that the 50% average
particle size of the water particle was 100 nm or less.
[0123] In addition, the W/O nanoemulsion was clear even after standing still at ambient
temperature for one month.
Example 21:
[0124] To a liquid of 850g of kerosene (85 wt% of kerosene, based on 100 wt% of the total
of 150 g of water described later and 850 g of kerosene) were added 136 g of a nonionic
surfactant DSK NL-15 (polyoxyethylene lauryl ether, manufactured by Dai-ichi Kogyo
Seiyaku Co., Ltd., HLB: 5.0, average molecular weight of polyoxyethylene moiety: 2,900)
(16 parts by weight, normalized in a case where an amount of kerosene is considered
as 100 parts by weight) and 34 g of a nonionic surfactant DSK NL-50 (polyoxyethylene
lauryl ether, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., HLB: 10.6) (4 parts
by weight, normalized in a case where an amount of kerosene is considered as 100 parts
by weight), and mixed by stirring to obtain a liquid A. The total HLB value of the
nonionic surfactants in the liquid A was 6.12, according to the above-mentioned equation
(2).
[0125] Separately from the liquid A, to 150 g of water (15 wt% of water, based on 100 wt%
of the total of 150 g of water and 850 g of kerosene) was added 15 g of an anionic
surfactant, sodium oleate (manufactured by NACALAI) (10 parts by weight, normalized
in a case where an amount of water is considered as 100 parts by weight), and mixed
by stirring. Then, the aqueous solution of sodium oleate was placed in a direct current
field across the cation exchange membrane, to obtain the aqueous alkaline solution
containing oleate ion at the anode as a liquid B. The resulting liquid B contained
no sulfur (S) and smaller amount of sodium ion compared to aqueous solution of sodium
dodecyl sulfate.
[0126] The liquids A and B were mixed and stirred using a homogenizer (PH91 manufactured
by SMT Company) for 5 minutes, to obtain a colorless clear liquid, i.e., a W/O nanoemulsion.
[0127] The particle size distribution of the resulting W/O nanoemulsion was determined by
using the laser light scattering method similar to Example 1, showing that the 50%
average particle size of the water particle was about 10 nm.
[0128] Regarding the stability, observation was done in a manner similar to Example 1, and
separation was not observed. In addition, the W/O nanoemulsion was clear even after
standing still at ambient temperature for one month.