DESCRIPTION
PARAFFIN-BASED LATENT HEAT STORING MATERIAL COMPOSITION
AND USE THEREOF
5
TECHNICAL FIELD
[0001] The present invention relates to a paraffin-based latent heat storage
material composition and use thereof, and in particular, to a paraffin-based
latent heat storage material composition having a melting point that is lower
10 than the melting point of n-hexadecane and close to the melting point of
n-pentadecane (near 10 °C) and having a large latent heat of fusion, and use
thereof.
BACKGROUND ART
15 [0002] There is an increasing demand for effective use of excess energy for
energy saving and more efficient energy utilization. As an effective solution
to meet this demand, methods have been used to achieve heat storage by
making use of latent heat caused as the result of a phase change of a substance.
Methods utilizing latent heat are more advantageous than methods using only
20 sensible heat without a phase change, in the sense that the volume of heat
storage material can be reduced because of the ability to store large amounts
of thermal energy with a high density in a narrow temperature range, and that
heat loss can be suppressed to a low level since the temperature variation is
not large for their large heat storage capacity.
25 [0003] Such heat storage materials are used in, for example, heat storage type
air conditioners, heat storage type building materials, a variety of heat
insulating tools or devices, and refrigerants, making use of the heat absorbed
or released at the time of a phase change between liquid and solid phases.
The purpose of the heat storage material used can be achieved by setting its
30 phase transition temperature (such as melting point and freezing point) to the
desired temperature, such as a temperature close to room temperature, a
temperature close to body temperature, and the like.
Heat storage materials containing paraffin are conventionally known as latent
heat storage material compositions that have latent heat of fusion caused as
- 2 -
the result of a phase change.
[0004] Paraffins have a melting point and a freezing point within a normal
temperature range for human life (5 °C to 30 °C). The melting point of a
paraffin is determined by the number of carbon atoms. Generally, the latent
5 heat of fusion of a paraffin with an odd number of carbon atoms that is
available in the normal temperature range for human life (which is, for
example, about 160 J/g for 15 carbon atoms) is smaller than that of a paraffin
with an even number of carbon atoms (which is, for example, about 240 J/g
for 16 carbon atoms). The reason is that a paraffin with an odd number of
10 carbon atoms and a paraffin with an even number of carbon atoms have a
different crystal system in solid state. In addition, supercooling occurs more
easily in a paraffin with an even number of carbon atoms alone.
[0005] As mentioned above, the melting points and available latent heat of
paraffins are different depending on the number of carbon atoms. For
15 example, it is known that n-tetradecane (C14) has a melting point of 6 °C and
a latent heat of about 230 J/g, n-pentadecane (C15) has a melting point of 10
°C and a latent heat of about 160 J/g, n-hexadecane (C16) has a melting point
of 18 °C and a latent heat of about 240 J/g. Paraffines with melting points
around 10 °C do not have a sufficiently large amount of latent heat.
20 [0006] On the other hand, paraffin mixtures are known to have melting points
and freezing points that are not chemically convertible (see, for example, PTL
1). This also applies to the amount of latent heat.
[0007] Conventional examples include: (i) a cold and heat storage material
that contains 10 wt% or more each of a normal paraffin component (A) having
25 a number Cn of carbon atoms and a normal paraffin component (B) having a
number Cn+2 of carbon atoms, and less than 10 wt% of a normal paraffin
component (C) having a number Cn+1 of carbon atoms, and that has a freezing
point higher than a melting point (see, for example, PTL 1); (ii) a technique
using a heat storage material dispersion obtained by microcapsulating a heat
30 storage material (see, for example, PTL 2); (iii) a heat storage material made
from a mixture of n-hexadecane (C16) and n-tetradecane (C14) (see, for
example, PTL 3); (iv) a paraffin-based latent heat storage material
composition that contains n-heptadecane (C17), n-octadecane (C18), and
n-nonadecane (C19), that has a melting point in the range of 20 °C to 25 °C at
- 3 -
the time of temperature rise, and that has an endothermic total latent heat of
200 J/g or more at the time of temperature rise in the range of 20 °C to 40 °C
(see, for example, PTL 4); and (v) a paraffin-based heat storage material
composition that is preferably used in air conditioners for cooling air, or the
5 like and that contains a latent heat storage material (A) made from a normal
paraffin (a) having a melting point in the range of - 1 5 °C to 10 °C and a
supercooling inhibitor (B) made from a normal paraffin (b) having a melting
point being higher by 35 °C or more than that of the normal paraffin (a) (see,
for example, PTL 5).
10 [0008] In recent years, demands are increasingly being made for a heat
storage material for use in air conditioners for cooling air, canisters of
automobiles, and the like that has a large latent heat (heat storage capacity) in
a temperature range near 10 °C.
However, the latent heat of n-pentadecane (C15), which has a melting point
15 near 10 °C (namely, 10 °C), is so small that prevents n-pentadecane (C15)
from providing desired heat storage material.
In addition, even the two-component system of n-tetradecane (C14) and
n-hexadecane (C16) is not chemically convertible in terms of melting point
and/or latent heat as mentioned above, and has not attained a desired heat
20 storage material.
[0009] As explained above, there have been strong demands in the
conventional art for development of a paraffin-based latent heat storage
material composition that has a melting point lower than the melting point of
n-hexadecane and close to the melting point of n-pentadecane (near 10 °C)
25 and that has a large latent heat of fusion, which has not yet been solved by the
conventional art.
30
CITATION LIST
Patent Literature
[0010] ! PTL 1:
! PTL 2:
! PTL 3:
! PTL 4:
! PTL 5:
JPH06234967A
JP2002241749A
JPH05214329A
JP2006321949A
JP2009173834A
- 4 -
SUMMARY OF INVENTION
(Technical Problem)
[0011] An object of the present invention is to provide a paraffin-based latent
5 heat storage material composition having a melting point lower than the
melting point of n-hexadecane and close to the melting point of n-pentadecane
(near 10 °C) and having a large latent heat of fusion, and use thereof.
(Solution to Problem)
[0012] In order to achieve the above object, the inventors of the present
10 invention made intense study, and as a result found that for a composition
containing predetermined amounts of n-hexadecane (C16), n-pentadecane
(C15), and, optionally, n-tetradecane (C14), it is possible to obtain a
paraffin-based latent heat storage material composition that has a melting
point lower than the melting point of n-hexadecane (18 °C) and close to the
15 melting point of n-pentadecane (near 10 °C) and that has a large latent heat of
fusion (200 J/g or more). The present invention was completed based on this
finding.
[0013] Specifically, a paraffin-based latent heat storage material composition
according to the present invention may comprise, as a main component, a
20 mixture of n-hexadecane, n-pentadecane, and, optionally, n-tetradecane,
wherein
1) the mixture contains 68 mass% or more of n-hexadecane, 1 mass% to 23
mass% of n-pentadecane, and 23 mass% or less of n-tetradecane, where the
total content of n-hexadecane, n-pentadecane, and n-tetradecane is 100
25 mass%,
2) the composition has a melting point lower than that of n-hexadecane, and
3) the composition has a latent heat of fusion of 200 J/g or more.
[0014] Preferred embodiments of the paraffin-based latent heat storage
material composition according to the present invention are as follows.
30 [0015] Preferably, in an embodiment of the present invention, a
paraffin-based latent heat storage material composition comprises, as a main
component, a mixture of n-hexadecane, n-pentadecane, and n-tetradecane,
wherein
1) the mixture contains more than 80 mass% of n-hexadecane, less than 5
- 5 -
mass% of n-pentadecane, and less than 20 mass% of n-tetradecane, where the
total content of n-hexadecane, n-pentadecane, and n-tetradecane is 100
mass%,
2) the composition has a melting point of 5 °C to 15 °C,
5 3) the composition has a latent heat of fusion of 200 J/g or more, and
4) the composition has a freezing point of 10 °C to 15 °C.
[0016] Preferably, in an embodiment of the present invention, a
paraffin-based latent heat storage material composition comprises, as a main
component, a mixture of n-hexadecane, n-pentadecane, and n-tetradecane,
10 wherein
1) the mixture contains 70 mass% or more of n-hexadecane and less than 30
mass% in total of n-pentadecane and n-tetradecane, where the total content of
n-hexadecane, n-pentadecane, and n-tetradecane is 100 mass%, and the
content by mass% of n-pentadecane and the content by mass% of
15 n-tetradecane satisfy the relation given by Expression (1):
0.3 [the content by mass% of n-pentadecane]/[the content by mass% of
n-tetradecane] 10 Expression (1)
20 2) the composition has a melting point of 5 °C or higher to 15 °C or lower,
3) the compositing has a latent heat of fusion of 210 J/g or more,
4) the composition has a freezing point of 10 °C or higher and 15 °C or lower,
and
5) the difference between the melting point and the freezing point is 5 °C or
25 less.
[0017] Preferably, in an embodiment of the present invention, a
paraffin-based latent heat storage material composition comprises, as a main
component, a mixture of n-hexadecane and n-pentadecane, wherein
1) the mixture contains more than 80 mass% of n-hexadecane and less than 20
30 mass% of n-pentadecane, where the total content of n-hexadecane and
n-pentadecane is 100 mass%,
2) the composition has a melting point of 10 °C to 16 °C,
3) the composition has a latent heat of fusion of 210 J/g or more, and
4) the difference between the melting point and the freezing point is 5 °C or
- 6 -
less.
[0018] An embodiment of the present invention provides use of a
paraffin-based latent heat storage material composition comprising, as a main
component, a mixture of n-hexadecane, n-pentadecane, and, optionally,
5 n-tetradecane, wherein
1) the mixture contains 68 mass% or more of n-hexadecane, 1 mass% to 23
mass% of n-pentadecane, and 23 mass% or less of n-tetradecane, where the
total content of n-hexadecane, n-pentadecane, and n-tetradecane is 100
mass%,
10 2) the composition has a melting point lower than that of n-hexadecane, and
3) the composition has a latent heat of fusion of 200 J/g or more.
(Advantageous Effect of Invention)
[0019] According to the present invention, a paraffin-based latent heat
storage material composition having a melting point lower than the melting
15 point of n-hexadecane and close to the melting point of n-pentadecane (near
10 °C) and having a large latent heat of fusion may be obtained.
BRIEF DESCRIPTION OF DRAWINGS
[0020] The present invention will be further described below with reference
20 to the accompanying drawings, wherein:
FIG. 1 schematically illustrates the composition range of the present
invention for a mixed system of n-hexadecane (C16), n-pentadecane (C15),
and n-tetradecane (C14);
FIG. 2 is an enlarged view schematically illustrating the main part of
25 the composition range of the present invention for the mixed system of
n-hexadecane (C16), n-pentadecane (C15), and n-tetradecane (C14);
FIG. 3 shows the model of a temperature-calorimetric curve
(thermogram) obtained by a differential scanning calorimeter (DSC);
FIG. 4 shows a temperature-calorimetric curve (thermogram) of a
30 paraffin-based latent heat storage material composition according to Example
1; and
FIG. 5 shows a model with two peaks observed in thermogram
obtained by DSC.
- 7 -
DESCRIPTION OF EMBODIMENTS
[0021] (Paraffin-based Latent Heat Storage Material Composition)
A paraffin-based latent heat storage material composition according to the
present invention comprises, as a main component, a mixture of n-hexadecane
5 (C16), n-pentadecane (C15), and, optionally, n-tetradecane (C14), as well as
other optional components.
[0022]
In the mixture as the main component of the paraffin-based latent heat storage
material composition, the content of n-hexadecane (C16) is not particularly
10 limited and may be selected as necessary as long as it is 68 mass% or more.
Preferably, the content thereof is in the range of 68 mass% to 99 mass%.
If the content of n-hexadecane is less than 68 mass%, a larger sub-peak forms
in the sub-zero range, where a sufficient latent heat of fusion is not available.
[0023]
15 In the mixture as the main component of the paraffin-based latent heat storage
material composition, the content of n-pentadecane (C15) is not particularly
limited and may be selected as necessary as long as it is in the range of 1
mass% to 23 mass%.
[0024]
20 In the mixture as the main component of the paraffin-based latent heat storage
material composition, n-tetradecane (C14) is optionally added. If this is the
case, the content thereof is to be set to 23 mass% or less (from 0 mass% to 23
mass%). The content of n-tetradecane (C14) is not particularly limited and
may be selected as necessary as long as it is 23 mass% or less.
25 If the content of n-tetradecane is more than 23 mass%, a larger sub-peak forms
in the sub-zero range, where a sufficient latent heat of fusion is not available.
[0025]
The mixture as the main component of the paraffin-based latent heat storage
material composition according to a first preferred embodiment contains more
30 than 80 mass% of n-hexadecane (C16), less than 5 mass% of n-pentadecane
(C15), and less than 20 mass% of n-tetradecane (C14), where the total content
of n-hexadecane (C16), n-pentadecane (C15), and n-tetradecane (C14) is 100
mass%.
[0026] <>
- 8 -
In the mixture as the main component of the paraffin-based latent heat storage
material composition according to the first preferred embodiment, the content
of n-hexadecane (C16) is not particularly limited and may be selected as
necessary as long as it is more than 80.0 mass%. However, the content
5 thereof is preferably more than 80.0 mass% and less than 98.0 mass%, and
more preferably more than 82.0 mass% and less than 96.0 mass%.
If the content of n-hexadecane is not more than 80.0 mass%, a larger sub-peak
forms in the sub-zero range, where a sufficient latent heat of fusion may not
be available.
10 If the content of n-hexadecane is not less than 98.0 mass%, the melting point
of the resulting material becomes too high to be suitable for a heat storage
material used at temperatures close to 10 °C. The material may also be prone
to a significant supercooling.
[0027] <>
15 In the mixture as the main component of the paraffin-based latent heat storage
material composition according to the first preferred embodiment, the content
of n-pentadecane (C15) is not particularly limited and may be selected as
necessary as long as it is less than 5.0 mass%. However, the content thereof
is preferably 1.0 mass% or more and less than 5.0 mass%, and more preferably
20 1.0 mass% or more and less than 4.0 mass%.
If the content of n-pentadecane is not less than 5.0 mass%, a sufficient latent
heat may not be available.
[0028] <>
In the mixture as the main component of the paraffin-based latent heat storage
25 material composition according to the first preferred embodiment, the content
of n-tetradecane (C14) is not particularly limited and may be selected as
necessary as long as it is less than 20.0 mass%. The content thereof is,
however, preferably 1.0 mass% or more and less than 20.0 mass%, and more
preferably 2.0 mass% or more and less than 15.0 mass%.
30 If the content of n-tetradecane is not less than 20.0 mass%, a larger sub-peak
forms in the sub-zero range, where a sufficient latent heat of fusion may not
be available.
If the content of n-tetradecane is less than 1.0 mass%, the melting point of the
resulting material may be too high to be suitable for a heat storage material
- 9 -
used at temperatures close to 10 °C.
[0029] >
15 In the mixture as the main component of the paraffin-based latent heat storage
material composition according to the second preferred embodiment, the
content of n-hexadecane (C16) is not particularly limited and may be selected
as necessary as long as it is 70 mass% or more. The content thereof is,
however, preferably 75 mass% or more, and more preferably 80 mass% or
20 more. In addition, the content thereof is preferably 98 mass% or less, and
more preferably 96 mass% or less.
If the content of n-hexadecane is less than 70 mass%, a larger sub-peak forms
in a temperature range other than close to 10 °C, where a sufficient latent heat
of fusion may not be available.
25 If the content of n-hexadecane is more than 98 mass%, the melting point of
the resulting material may be too high to be suitable for a heat storage
material used at temperatures close to 10 °C. The material may also be prone
to a significant supercooling.
[0031] <>
30 In the mixture as the main component of the paraffin-based latent heat storage
material composition according to the second preferred embodiment, the
content (B) of n-pentadecane (C15) is not particularly limited and may be
selected as necessary as long as the total (A + B) of the content (A) of
n-tetradecane, as described later, and the content (B) of n-pentadecane is less
- 10 -
than 30 mass% and the ratio (B/A) of the content (B) of n-pentadecane to the
content (A) of n-tetradecane is 0.3 or more and 10 or less. Preferably, the
content (B) of n-pentadecane (C15) is 5 mass% or more.
If the content of the n-pentadecane (component B) is less than 5 mass%, the
5 melting point may deviate from the desired range and/or a sufficient latent
heat may not be available.
[0032] <>
In the mixture as the main component of the paraffin-based latent heat storage
material composition according to the second preferred embodiment, the
10 content (A) of n-tetradecane (C14) is not particularly limited and may be
selected as necessary as long as the total (A + B) of the content (A) of
n-tetradecane and the content (B) of n-pentadecane is less than 30 mass% and
the ratio (B/A) of the content (B) of n-pentadecane to the content (A) of
n-tetradecane is 0.3 or more and 10 or less.
15 [0033]
In the mixture as the main component of the paraffin-based latent heat storage
material composition according to the second preferred embodiment, the total
(A + B) of the content (A) of n-tetradecane (C14) and the content (B) of
20 n-pentadecane (C15) is not particularly limited and may be selected as
necessary as long as it is less than 30 mass%. However, the total content is
preferably 25 mass% or less, and more preferably 20 mass% or less.
If the total content is not less than 30 mass%, a sufficient latent heat of fusion
may not be available at temperatures close to 10 °C.
25 [0034]
In the mixture as the main component of the paraffin-based latent heat storage
material composition according to the second preferred embodiment, the ratio
(B/A) of the content (B) of n-pentadecane (C15) to the content (A) of
30 n-tetradecane (C14) is not particularly limited and may be selected as
necessary as long as it is 0.3 or more and 10 or less. However, the ratio is
preferably 0.5 or more, more preferably 0.8 or more, and even more preferably
1.0 or more. In addition, the ratio is preferably 8 or less, and more
preferably 6 or less.
- 11 -
If the aforementioned content ratio is less than 0.3, the latent heat of fusion
tends to be small and the difference between the melting point and the
freezing point tends to be large. If the content ratio is more than 10, a
sufficient latent heat of fusion may not be available. In contrast, the content
5 ratio within the preferable, more preferable, or even more preferable range as
identified above is advantageous in that the melting point is close to 10 °C, a
large latent heat of fusion is available, and the difference between the melting
point and the freezing point is small.
[0035]
10 The mixture as the main component of the paraffin-based latent heat storage
material composition according to a third preferred embodiment contains
more than 80 mass% of n-hexadecane and less than 20 mass% of
n-pentadecane, where the total content of n-hexadecane and n-pentadecane is
100 mass%.
15 [0036]
In the mixture as the main component of the paraffin-based latent heat storage
material composition according to the third preferred embodiment, the content
of n-hexadecane (C16) is not particularly limited and may be selected as
necessary as long as it is more than 80 mass%. However, the content thereof
20 is preferably 85 mass% or more, and more preferably 87 mass% or more.
If the content of n-hexadecane is not more than 80 mass%, a larger sub-peak,
whose melting point is out of the range of 10 °C to 16 °C, forms. In this case,
a sufficient latent heat of fusion may not be available in the desired
temperature range. In contrast, the content of n-hexadecane within the
25 preferable or more preferable range as identified above is advantageous in that
it reduces the difference between the melting point and the freezing point and
provides a large amount of heat available in a narrower operation temperature
range.
Additionally, in the mixture as the main component of the paraffin-based
30 latent heat storage material composition according to the third preferred
embodiment, the upper limit of the content of n-hexadecane is preferably 99
mass%, more preferably 98 mass%, and even more preferably 95 mass%,
although it is not particularly limited and may be selected as necessary.
If the content of n-hexadecane is more than 99 mass%, the melting point may
- 12 -
be too high to be suitable for a heat storage material used at temperatures in
the range of 10 °C to 16 °C, and significant supercooling (where ΔT (melting
point minus freezing point) is large) occurs easily, which may require a high
performance refrigerator. In contrast, if the content of n-hexadecane is
5 either 98 mass% or less or 95 mass% or less, supercooling is hardly or never
caused, which is advantageous.
[0037]
In the mixture as the main component of the paraffin-based latent heat storage
material composition according to the third preferred embodiment, the content
10 of n-pentadecane (C15) is not particularly limited and may be selected as
necessary as long as it is less than 20 mass%. However, the content thereof
is preferably 15 mass% or less, and more preferably 10 mass% or less.
If the content of n-hexadecane is not less than 20 mass%, a sub-peak, whose
melting point is out of the range of 10 °C to 16 °C, forms. In this case, a
15 sufficient latent heat of fusion may not be available in the desired temperature
range. In contrast, the content of n-pentadecane within the preferable or
more preferable range as identified above is advantageous in that it reduces
the difference between the melting point and the freezing point and makes a
large amount of heat available in a narrower operation temperature range.
20 Additionally, in the mixture as the main component of the paraffin-based
latent heat storage material composition according to the third preferred
embodiment, the lower limit of the content of n-pentadecane is preferably 1
mass%, more preferably 2 mass%, and even more preferably 5 mass%,
although it is not particularly limited and may be selected as necessary.
25 If the content of n-pentadecane is less than 1 mass%, the melting point may be
too high to be suitable for a heat storage material used at temperatures in the
range of 10 °C to 16 °C, and significant supercooling (where ΔT (melting
point minus freezing point) is large) may occur easily, which may require a
high performance refrigerator. In contrast, if the content of n-pentadecane is
30 either 2 mass% or more or 5 mass% or more, supercooling is hardly or never
caused, which is advantageous.
[0038] FIG. 1 is a triangular graph schematically illustrating the composition
range of the present invention, where the shaded area indicates a mixed
system of n-hexadecane (C16), n-pentadecane (C15), and n-tetradecane (C14).
- 13 -
FIG. 2 is an enlarged view of the main part thereof. In FIG. 2, numerals
pointing to black dots correspond to the numbers of examples described below,
and numerals to white dots correspond to the numbers of comparative
examples stated below. While the reason for excellent properties being
5 obtained in this area is unclear, the inventors of the present invention believe
that this phenomenon is caused by interaction, during the phase transition of
melting and freezing, of an n-paraffin with an even number of carbon atoms,
an n-paraffin with an odd number of carbon atoms, and an n-paraffin with an
even number of carbon atoms, where the even and odd numbers are close to
10 one another.
[0039]
Other components contained in the paraffin-based latent heat storage material
composition include, without compromising the object of the present
invention: (i) normal paraffins with a number other than 14 to 16 of carbon
15 atoms; (ii) hydrocarbons, such as isoparaffin, olefin, naphthene, and aromatic
compounds, having a structure other than those of the aforementioned
n-hexadecane (C16), n-pentadecane (C15), and n-tetradecane (C14); and (iii)
alcohols incorporated when preparing a normal paraffin.
In addition, the following materials can be added (externally added) to
20 produce products by using the paraffin-based latent heat storage material
composition according to the present invention: (i) substances including resin
monomers, polymerizing agents, and surfactants that are used to produce
applied products such as microcapsules; (ii) commonly-used additives,
including antioxidants and ultraviolet absorbers; (iii) additives, including
25 specific gravity control agents, colorants such as pigments and dyes,
aromatics, and gelling agents; and so on.
[0040]
The paraffin-based latent heat storage material composition according to the
present invention is such a paraffin-based latent heat storage material
30 composition that contains n-hexadecane (C16) having the longest chain length
and other n-paraffins substantially limited to n-pentadecane (C15) and
n-tetradecane (C14).
After the investigations, the inventors found that an interaction with a
long-chain paraffin of C17 or more during the phase transition of melting and
- 14 -
the like greatly reduces the latent heat of fusion available in the present
invention.
Here, examples of the long-chain paraffin of C17 or more include a part
having a long-chain paraffin structure, such as a crystalline part in a
5 polymerized portion of crystalline polyethylene. When the composition
according to the present invention is used as a latent heat storage material,
such interaction with a long-chain paraffin of C17 or more should be avoided
as much as possible.
[0041]
10 The aforementioned latent heat of fusion (heat of fusion) means the amount of
latent heat involved in a phase transition from solid to liquid phase. As used
herein, the latent heat of fusion means the amount of heat at a melting
(endothermic) peak observed in a DSC thermogram, and for a DSC
thermogram showing multiple peaks, it refers to the amount of heat at a peak
15 (main peak) with a melting point of 0 °C or higher and a large amount of heat.
The latent heat of fusion of the aforementioned paraffin-based latent heat
storage material composition can be determined by, for example, the melting
peak on the DSC thermogram that is measured at a heating rate of 10 °C/min,
using a differential scanning calorimeter (DSC7020 manufactured by Seiko
20 Instruments Inc.).
The latent heat of fusion of the paraffin-based latent heat storage material
composition is not particularly limited and may be selected as necessary as
long as it is 200 J/g or more. However, the latent heat of fusion is preferably
210 J/g or more, more preferably 220 J/g or more, and most preferably 230 J/g
25 or more.
If the latent heat of fusion is less than 200 J/g, the amount of effective latent
heat (heat storage capacity) is so small that may prevent the composition from
having sufficient effect when used in air conditioners for cooling air,
refrigeration and cold storage containers, cold energy transportation media,
30 antifreezing agents, and the like.
[0042]
As used herein, the melting point refers to the temperature at a point where
the tangent of the maximum slope of the melting (endothermic) peak in a
thermogram, which is obtained using a differential scanning calorimeter (for
- 15 -
example, DSC7020 manufactured by Seiko Instruments Inc.) when heating is
performed at a heating rate of 10 °C/min, intersects the baseline. The
melting point of the paraffin-based latent heat storage material composition
(normal paraffin composition) can be normally represented by a single point
5 even when the composition contains many components. However, in the
case where two or more peaks are observed, the melting point refers to the
temperature at which the tangent of the maximum slope of one of the peaks
(main peak) that is observed at the temperatures side higher than 0 °C and that
has a large amount of heat intersects the baseline (see FIG. 5).
10 The melting point of the paraffin-based latent heat storage material
composition is preferably 5 °C to 16 °C, more preferably 5 °C to 15 °C, and
most preferably 7 °C to 13 °C, although it is not particularly limited and may
be selected as necessary as long as it is lower than the melting point (18 °C)
of n-hexadecane.
15 If the melting point is not lower than the melting point (18 °C) of
n-hexadecane, the melting point may be too high to be suitable for a heat
storage material for cooling. In addition, if the melting point is lower than 5
°C, the composition may melt at a temperature lower than the temperature
close to 10 °C at which it is to be used, while a melting point higher than 16
20 °C be too high to be suitable for a heat storage material for cooling. In
contrast, if the melting point is within the aforementioned particularly
preferable range, the composition can be used with a refrigerator of
reasonable performance and used in an optimum temperature range for a heat
storage material for cooling.
25 Note that a paraffin-based latent heat storage material composition (normal
paraffin composition) showing two or more distinct melting peaks when
measured by a differential scanning calorimeter is not preferably used as the
paraffin-based latent heat storage material composition according to the
present invention.
30 [0043]
As used herein, the freezing point refers to the temperature at a point where
the tangent of the maximum slope of the freezing (exothermic) peak in a
thermogram, which is obtained using a differential scanning calorimeter (for
example, DSC7020 manufactured by Seiko Instruments Inc.) when cooling is
- 16 -
performed at a cooling rate of 10 °C/min, intersects the baseline. The
freezing point of the paraffin-based latent heat storage material composition
(normal paraffin composition) can be normally represented by a single point
even when the composition contains many components. However, in the
5 case where two or more peaks are observed, the freezing point refers to the
temperature at which the tangent of the maximum slope of one of the peaks
(main peak) that is observed at the temperature side higher than 0 °C and that
has a large amount of heat intersects the baseline (see FIG. 5).
The freezing point of the paraffin-based latent heat storage material
10 composition is not particularly limited and may be selected as necessary.
However, the freezing point is preferably 10 °C to 16 °C, more preferably 10
°C to 15 °C, and most preferably 12 °C to 14 °C.
If the freezing point is lower than 10 °C, the heat storage material cannot
solidify without using a high performance refrigerator, placing a higher load
15 on the refrigerator, while if the freezing point is higher than 16 °C, the amount
of latent heat which is available at temperatures close to 10 °C may decrease.
[0044]
The heat of solidification means the amount of latent heat involved in a phase
transition from liquid to solid phase. As used herein, the heat of
20 solidification means the amount of heat at a freezing (exothermic) peak
observed in a DSC thermogram, and for a DSC thermogram showing multiple
peaks, it refers to the amount of heat at a peak (main peak) with a freezing
point of 0 °C or higher and a large amount of heat.
The heat of solidification of the aforementioned paraffin-based latent heat
25 storage material composition can be determined by, for example, the melting
peak on the DSC thermogram that is measured at a cooling rate of 10 °C/min,
using a differential scanning calorimeter (DSC7020 manufactured by Seiko
Instruments Inc.).
The heat of solidification of the aforementioned paraffin-based latent heat
30 storage material composition is not particularly limited and may be selected as
necessary. However, the heat of solidification is preferably 160 J/g or more,
more preferably 200 J/g or more, even more preferably 210 J/g or more, and
most preferably 220 J/g or more.
If the heat of solidification is less than 160 J/g, the effective heat storage
- 17 -
capacity is so small that may prevent the composition from having sufficient
effect when used in air conditioners for cooling air, refrigeration and cold
storage containers, cold energy transportation media, antifreezing agents, and
the like.
5 [0045]
The aforementioned difference between the melting point and the freezing
point refers to the result of the higher minus the lower of the melting point
and the freezing point ("the higher temperature of the melting point and the
freezing point" - "the lower temperature of the melting point and the freezing
10 point").
The aforementioned difference between the melting point and the freezing
point is not particularly limited and may be selected as necessary. However,
the difference is preferably 5 °C or less, more preferably 4 °C or less, even
more preferably 3 °C or less, and most preferably 1 °C or less.
15 If the difference between the melting point and the freezing point is greater
than 5 °C, the operation temperature range may be excessively broad, making
it difficult to achieve efficient absorption and release of latent heat in the
desired temperature range. In contrast, if the aforementioned difference
between the melting point and the freezing point is within the more preferable
20 or particularly preferably range as identified above, it is possible to make use
of repetitive absorption and release of a large amount of latent heat in a
narrow operation temperature range, which is advantageous.
[0046] The paraffin-based latent heat storage material composition according
to the present invention has a melting point close to the melting point of
25 n-pentadecane (near 10 °C) and has a large latent heat of fusion.
Additionally, the paraffin-based latent heat storage material composition is
stable even when subjected to repetitive fusion and solidification phase
changes, and is not corrosive.
30 EXAMPLES
[0047] The present invention will be described further in detail hereinafter
with reference to examples. However, the present invention is not limited to
the disclosed examples in any way.
[0048] Paraffin-based latent heat storage material compositions were
- 1 8 -
prepared by blending predetermined amounts of commercially available
n-hexadecane, n-pentadecane, and n-tetradecane. Each of the n-paraffins has
a purity of approximately 95 % to 98 %, and generally, the n-paraffins include
n-paraffins with a close number of carbon atoms.
5 Regarding the examples and comparative examples, gas chromatography
analysis was carried out for reference purpose to investigate the actual
compositions based on the peak areas, respectively.
The actual composition values determined from the peak areas by gas
chromatography analysis are shown in brackets ([ ]) in Tables 1 to 3. Tables
10 1 to 3 show some cases where the sum total of values in brackets does not
equal 100, indicating that peaks other than those of n-hexadecane (CI6),
n-pentadecane (CI5), and n-tetradecane (CI4) are detected (in this regard, the
inventors estimate that the residual parts are contained in the respective
reagents).
15 For each composition, measurements were made of its melting point, latent
heat of fusion, freezing point, heat of solidification, and the difference
between the melting point and the freezing point. The measurement results
are shown in FIGS. 1 and 2 and Tables 1 to 3.
[0049] [Table 1]
Table 1
- 1 9 -
[0052] It can be seen from the results shown in FIGS. 1 and 2 and Tables 1 to
3 that regarding the compositions according to the examples which satisfy the
10 composition conditions as specified in the present invention, the latent heat of
fusion is greater than 200 J/g, the melting point is lower than that of
n-hexadecane (18 °C), supercooling does not occur, the difference between the
melting point and the freezing point is as small as 6 °C or less, and the
- 20 -
operation temperature range is narrow, as compared to the compositions
according to the comparative examples not satisfying the composition
conditions of the present invention.
[0053] Note that the melting point, heat of fusion (latent heat of fusion),
5 freezing point, and heat of solidification shown in the tables were measured at
a heating rate of 10 °C/min and a cooling rate of 10 °C/min using a
differential scanning calorimeter, DSC7020 manufactured by Seiko
Instruments Inc. FIG. 3 shows the model of a temperature-calorimetric curve
(thermogram) obtained by the differential scanning calorimeter (DSC), and
10 FIG. 4 shows a thermogram of a paraffin-based latent heat storage material
composition according to Example 1.
[0054] In this case, (i) the melting point refers to the temperature at a point
where the tangent of the maximum slope of the melting (endothermic) peak in
the DSC thermogram obtained when heating was performed at a heating rate
15 of 10 °C/min intersects the baseline, (ii) the heat of fusion refers to the
amount of heat determined from the melting peak area on the DSC
thermogram when measurement was made at a heating rate of 10 °C/min, (iii)
the freezing point refers to the temperature at a point where the tangent of the
maximum slope of the freezing (exothermic) peak in the DSC thermogram
20 obtained when cooling was performed at a cooling rate of 10 °C/min intersects
the baseline, and (iv) the heat of solidification refers to the amount of heat
determined from the freezing peak area on the DSC thermogram when
measurement was made at a cooling rate of 10 °C/min.
Some compositions show two melting and/or freezing peaks on the DSC
25 thermogram. FIG. 5 shows the model of a DSC thermogram having two such
peaks. In this case, for respective two peaks, a main peak and a sub-peak are
defined by dropping a perpendicular to the baseline from the valley point
between the two peaks, and a tangent is drawn to the main peak as shown in
FIG. 5 to determine the melting point and the freezing point. In this way, the
30 heat of fusion and the heat of solidification are determined from the areas of
the main peaks defined by the perpendiculars, respectively.
Many of the paraffin-based latent heat storage material compositions
according to the comparative examples showed such two peaks on the DSC
thermograms.
- 21 -
INDUSTRIAL APPLICABILITY
[0055] The paraffin-based latent heat storage material composition according
to the present invention will not change its properties, nor will separation
5 occur even when subjected to repetitive fusion and solidification, where the
composition conditions remain stable, and therefore, the composition has less
impact on the container and piping systems in contact therewith, and is
preferably used as a latent heat storage material (PCM) that requires, in
particular, highly precise melting-freezing temperature properties in a narrow
10 temperature range.
In addition, the paraffin-based latent heat storage material composition
according to the present invention is preferably used in, particularly, air
conditioners for cooling air, canisters of automobiles, and the like (5 °C to 15
°C), and otherwise, preferably used as a heat storage material for use in
15 refrigeration and cold storage containers, cold energy transportation media,
antifreezing agents, and the like.

WE CLAIM:-
1. A paraffin-based latent heat storage material composition
comprising, as a main component, a mixture of n-hexadecane, n-pentadecane,
5 and, optionally, n-tetradecane, wherein
1) the mixture contains 68 mass% or more of n-hexadecane, 1 mass%
to 23 mass% of n-pentadecane, and 23 mass% or less of n-tetradecane, where
the total content of n-hexadecane, n-pentadecane, and n-tetradecane is 100
mass%,
10 2) the composition has a melting point lower than that of
n-hexadecane, and
3) the composition has a latent heat of fusion of 200 J/g or more.
2. A paraffin-based latent heat storage material composition
15 comprising, as a main component, a mixture of n-hexadecane, n-pentadecane,
and n-tetradecane, wherein
1) the mixture contains more than 80 mass% of n-hexadecane, less
than 5 mass% of n-pentadecane, and less than 20 mass% of n-tetradecane,
where the total content of n-hexadecane, n-pentadecane, and n-tetradecane is
20 100mass%,
2) the composition has a melting point of 5 °C to 15 °C,
3) the composition has a latent heat of fusion of 200 J/g or more, and
4) the composition has a freezing point of 10 °C to 15 °C.
25 3. A paraffin-based latent heat storage material composition
comprising, as a main component, a mixture of n-hexadecane, n-pentadecane,
and n-tetradecane, wherein
1) the mixture contains 70 mass% or more of n-hexadecane and less
than 30 mass% in total of n-pentadecane and n-tetradecane, where the total
30 content of n-pentadecane, n-tetradecane, and n-hexadecane is 100 mass%, and
the content by mass% of n-pentadecane and the content by mass% of
n-tetradecane satisfy the relation given by Expression (1):
0.3 < [the content by mass% of n-pentadecane]/[the content by mass% of
2) the composition has a melting point of 5 °C or higher to 15 °C or
lower.
5 3) the composition has a latent heat of fusion of 210 J/g or more,
4) the composition has a freezing point of 10 3C or higher to 15 °C or
lower, and
5) the difference between the melting point and the freezing point is 5
°C or less.
10
4. A paraffin-based latent heat storage material composition
comprising, as a main component, a mixture of n-hexadecane and
n-pentadecane, wherein
1) the mixture contains more than 80 mass% of n-hexadecane and less
15 than 20 mass% of n-pentadecane. where the total content of n-hexadecane and
n-pentadecane is 100 mass%.
2) the composition has a melting point of 10 °C to 16 °C.
3) the composition has a latent heat of fusion of 210 J/g or more, and
4) the difference between the melting point and the freezing point is 5
20 °C or less.
5. Use of a paraffin-based latent heat storage material
composition comprising, as a main component, a mixture of n-hexadecane.
n-pentadecane, and, optionally, n-tetradecane. wherein
25 1) the mixture contains 68 mass% or more of n-hexadecane. 1 mass%
to 23 mass% of n-pentadecane. and 23 inass% or less of n-tetradecane. where
the total content of n-hexadecane. n-pentadecane. and n-tetradecane is 100
mass%.
2) the composition has a melting point lower than that of
30 n-hexadecane. and
3) the composition has a latent heat of fusion of 200 J/g or more.