U.S. patent application number 13/203352 was filed with the patent office on 2011-12-22 for refrigerant composition containing hydrofluoropropene with low-global warming potential.
This patent application is currently assigned to DAIKIN INDUSTRIES, LTD.. Invention is credited to Hitomi Arimoto, Takashi Shibanuma, Tatsumi Tsuchiya, Yasufu Yamada.
Application Number | 20110312101 13/203352 |
Document ID | / |
Family ID | 42665655 |
Filed Date | 2011-12-22 |
United States Patent
Application |
20110312101 |
Kind Code |
A1 |
Tsuchiya; Tatsumi ; et
al. |
December 22, 2011 |
REFRIGERANT COMPOSITION CONTAINING HYDROFLUOROPROPENE WITH
LOW-GLOBAL WARMING POTENTIAL
Abstract
The present invention provides a stabilized refrigerant
composition containing a hydrofluoropropene with low global warming
potential (GWP) that can remain stable even in the presence of air
(oxygen) for a long period of time. More specifically, the present
invention provides a refrigerant composition containing a
hydrofluoropropene and a stabilizer. The stabilizer is at least one
member selected from the group consisting of alkylcatechols,
alkoxyphenols, benzoquinones, phenothiazines, and phthalates.
Inventors: |
Tsuchiya; Tatsumi; (Osaka,
JP) ; Shibanuma; Takashi; (Osaka, JP) ;
Yamada; Yasufu; (Osaka, JP) ; Arimoto; Hitomi;
(Osaka, JP) |
Assignee: |
DAIKIN INDUSTRIES, LTD.
Osaka-shi, Osaka
JP
|
Family ID: |
42665655 |
Appl. No.: |
13/203352 |
Filed: |
February 26, 2010 |
PCT Filed: |
February 26, 2010 |
PCT NO: |
PCT/JP2010/053108 |
371 Date: |
August 25, 2011 |
Current U.S.
Class: |
436/101 ; 252/68;
436/126 |
Current CPC
Class: |
C10N 2030/10 20130101;
C09K 5/045 20130101; C10M 171/008 20130101; Y10T 436/153333
20150115; C10M 2207/283 20130101; C09K 2205/126 20130101; Y10T
436/196666 20150115; C10M 2209/04 20130101; C10M 2209/103 20130101;
C10N 2020/101 20200501; G01N 33/2876 20130101 |
Class at
Publication: |
436/101 ; 252/68;
436/126 |
International
Class: |
C09K 5/04 20060101
C09K005/04; G01N 33/26 20060101 G01N033/26 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 26, 2009 |
JP |
2009-044929 |
Claims
1. A refrigerant composition comprising a hydrofluoropropene and a
stabilizer, the stabilizer being at least one member selected from
the group consisting of alkylcatechols, alkoxyphenols,
benzoquinones, phenothiazines, and phthalates.
2. The refrigerant composition according to claim 1 wherein the
hydrofluoropropene is at least one member selected from the group
consisting of 2,3,3,3-tetrafluoropropene (HFO-1234yf), (Z- or
E-)1,3,3,3-tetrafluoropropene (HFO-1234ze), (Z- or
E-)1,2,3,3,3-pentafluoropropene (HFO-1225ye), (Z- or
E-)1,1,3,3,3-pentafluoropropene (HFO-1225zc), and (Z- or
E-)3,3,3-trifluoropropene (HFO-1243zf).
3. The refrigerant composition according to claim 1 comprising the
stabilizer in an amount of 0.1 to 5.0 parts by weight per 100 parts
by weight of the hydrofluoropropene.
4. The refrigerant composition according to claim 1 further
comprising a lubricant.
5. The refrigerant composition according to claim 4 wherein the
lubricant comprises at least one member selected from the group
consisting of polyalkylene glycols, polyol esters, and polyvinyl
ethers, and has a kinematic viscosity at 40.degree. C. of 5 to 400
cSt.
6. The refrigerant composition according to claim 1 wherein the
refrigerant composition is used for at least one member selected
from the group consisting of refrigeration systems, refrigerators,
mobile air conditioners, coolers (chillers), container freezers,
domestic air conditioners, air conditioners for business use, and
vapor compression heat pumps such as hot-water supply systems.
7. A method for stabilizing a refrigerant composition containing a
hydrofluoropropene, the method comprising adding to the refrigerant
composition at least one member selected from the group consisting
of alkylcatechols, alkoxyphenols, benzoquinones, phenothiazines,
and phthalates.
8. A method for evaluating a refrigerant composition comprising a
hydrofluoropropene and a stabilizer, the method comprising
heat-treating the refrigerant composition in the presence or
absence of oxygen in an airtight container, and determining the
acid content of the refrigerant composition after the
treatment.
9. A method for evaluating a refrigerant composition comprising
hydrofluoropropene, a lubricant, and a stabilizer, the method
comprising heat-treating the refrigerant composition in the
presence or absence of oxygen in an airtight container, and then
determining the acid content of the refrigerant composition, and/or
the total acid value of the lubricant contained in the heat-treated
refrigerant composition.
Description
TECHNICAL FIELD
[0001] The present invention relates to a stabilized refrigerant
composition containing a hydrofluoropropene with a low global
warming potential, such as 2,3,3,3-tetrafluoropropene.
BACKGROUND ART
[0002] Chlorofluorohydrocarbons (CFCs) and hydrochlorofluorocarbons
(HCFCs) have been used as refrigerants in refrigerating systems and
as heating media in heat pumps. Chlorofluorocarbon (CFC) and
hydrochlorofluorocarbon (HCFC) alone, or as azeotropic compositions
or mixtures thereof, etc., are collectively called Freon or Freons.
In recent years, it has been indicated that Freons released into
the atmosphere deplete the ozone layer, thereby inflicting a
serious adverse influence on the ecosystem, including humans on
earth. Accordingly, the use and production of chlorofluorocarbons
that pose a high risk of ozone layer depletion have been restricted
under international agreements.
[0003] More specifically, dichlorodifluoromethane (CFC-12), mainly
used as a refrigerant for domestic refrigerators, car air
conditioners, turbo freezers, and container freezers, has been
replaced by 1,1,1,2-tetrafluoroethane (HFC-134a) in compliance with
the above-mentioned regulations.
[0004] However, more strict regulations have been implemented. For
example, in the EU, two regulations, the "Regulation on Certain
Fluorinated Greenhouse Gases," and the "Directive Relating to
Emissions of F-Gas from Air Conditioning Systems Fitted to Cars"
(F-gas regulations), were announced in June, 2006. According to
these regulations, car air conditioners installed in new model
vehicles sold on the market after 2011, and those in all vehicles
sold after 2017 must be configured to use a refrigerant having a
GWP of not more than 150. Because HFC-134a currently used in
vehicles has a GWP of 1,300, CO.sub.2, etc., have been proposed as
potential replacements for HFC-134a. However, such a replacement
entails various problems, such as required equipment modification
and insufficient refrigeration capacity at high temperatures due to
CO.sub.2 being a critical fluid. In addition, isobutane
(i-C.sub.4H.sub.10), etc., which have been used as refrigerants for
certain types of electric refrigerators, have not been used as
replacements in all technical fields due to their very high
combustibility.
[0005] In view of the above problem, there is a desire to develop a
refrigerant with low GWP, which achieves performance equivalent to
or better than HFC-134a in terms of energy efficiency, refrigerant
characteristics (e.g., refrigeration capacity, boiling point, and
pressure), etc., in LCCP (Life Cycle Climate Performance)
evaluation; and which requires no or only slight modification of
equipment.
[0006] In this regard, hydrofluoropropenes such as
1,2,3,3,3-pentafluoro-1-propene (HFO-1225ye) and
2,3,3,3-tetrafluoro-1-propene (HFO-1234yf) are known as low GWP
compounds having an unsaturated bond in the molecule. These
compounds, which have a GWP lower than saturated HFC compounds,
were expected to be less stable in the atmosphere than saturated
HFC compounds.
[0007] The present inventors evaluated the stability of such
hydrofluoropropenes, and found stability problems relating to
hydrofluoropropenes in the presence of air (oxygen). More
specifically, the evaluation results confirmed that progressive
oxidative degradation occurred even in the temperature range to
which refrigerant compositions may be exposed during actual use,
thus forming acids such as CF.sub.3COOH and HF. Therefore, problems
such as system corrosion, reduction of refrigeration capacity,
capillary blockage, etc., were expected to occur.
[0008] In general, in mobile air conditioners or like devices to
which a refrigerant is charged at the factory under construction
management, there is little possibility of an air (oxygen)
entrapment problem. However, stationary air conditioners or like
devices are required to be charged with a refrigerant on site. The
charging of the refrigerant relies on the contractor's management
ability. Thus, entrapped air (oxygen) has been considered to be a
primary cause of failures and problems, such as reduction of
refrigeration capacity.
[0009] In conventional HFC refrigerants, replacement of such
refrigerants can solve such a problem. However, in
hydrofluoropropene-containing refrigerants, oxidative degradation
of such refrigerants generates a large amount of acid, which may
corrode metal parts of the system, etc., and thus necessitate
equipment replacement. Accordingly, problems in installation,
maintenance, etc., may occur with the use of
hydrofluoropropene-containing refrigerants. Therefore, to use a
hydrofluoropropene as a component of refrigerant compositions, a
technique for enhancing the stability of the refrigerant
compositions in the presence of air (oxygen) is necessary.
[0010] For example, as a stabilization technique, Patent Literature
(PTL) 1 discloses that a stabilizer such as a phenolic compound,
thiophosphate, benzoquinone, or aryl alkyl ether is added to a
fluoroolefin.
CITATION LIST
Patent Literature
[0011] PTL 1: WO 2008/027511
SUMMARY OF INVENTION
Technical Problem
[0012] An object of the present invention is to provide a
stabilized refrigerant composition containing a hydrofluoropropene
with a low global warming potential (GWP), the refrigerant
composition being able to maintain a stable state for a long period
of time, even in the presence of air (oxygen).
Solution to Problem
[0013] To achieve the above objects, the present inventors carried
out extensive research. As a result, the inventors found that a
refrigerant composition comprising at least one hydrofluoropropene
and at least one stabilizer (an antioxidant) selected from the
group consisting of alkylcatechols, alkoxyphenols, benzoquinones,
phenothiazines, and phthalates can remain stable even in the
presence of air (oxygen) for a long period of time. Such a
refrigerant composition can maintain a stable state over a long
period of time, even when charged with entrapped air (oxygen) into
stationary air conditioners, such as domestic air conditioners.
[0014] A principal mechanism of decomposition of conventional HFC
refrigerants not containing unsaturated bonds is reduction of a
halogen atom. The durable stability of such refrigerants is
evaluated, for example, by tests that take into account
decomposition-promoting factors, such as temperature, metal
(catalyst), water content, and air. On the other hand, the
stability of hydrofluoropropenes is evaluated, for example, in
Patent Literature (PTL) 1, by a test method comprising heating a
mixture of a lubricant and a refrigerant (HFO-1225ye) in the
presence of air and a metal catalyst (Fe, Cu, or Al) at 175.degree.
C. for 2 weeks, and then evaluating the appearance of the mixture.
That is, the stability of hydrofluoropropenes is evaluated by the
same accelerated thermal stability test as for conventional
refrigerants (HFC refrigerants).
[0015] However, this method can only evaluate the appearance of
such a mixture in a liquid phase (coloring grade; rating). No
sufficient evaluation of refrigerants containing a
hydrofluoropropane has been made in terms of generation of acids
that cause corrosion in the system and low refrigeration
capacity.
[0016] The inventors of the present invention revealed that the
oxidation reaction between an unsaturated bond of a
hydrofluoropropene and oxygen is a primary mechanism of
decomposition of a hydrofluoropropene-containing refrigerant, and
the oxidation reaction generates acids such as CF.sub.3COOH and HF,
which are a principal cause of the above-mentioned problems. The
present inventors thus established a method for evaluating the
generation of acids. More specifically, the method comprises
heat-treating a hydrofluoropropene-containing refrigerant
composition at a predetermined temperature for a predetermined
time, and then evaluating the acid content of the heat-treated
refrigerant composition, or the total acid value of lubricant that
may be contained in the heat-treated refrigerant composition. This
method enables more practical evaluation of thermal stability of
hydrofluoropropene.
[0017] The present invention has been accomplished as a result of
further research based on the above finding.
[0018] More specifically, the present invention provides the
following refrigerant compositions containing a
hydrofluoropropene.
1. A refrigerant composition comprising a hydrofluoropropene and a
stabilizer, the stabilizer being at least one member selected from
the group consisting of alkylcatechols, alkoxyphenols,
benzoquinones, phenothiazines, and phthalates. 2. The refrigerant
composition according to item 1 wherein the hydrofluoropropene is
at least one member selected from the group consisting of
2,3,3,3-tetrafluoropropene (HFO-1234yf), (Z- or
E-)1,3,3,3-tetrafluoropropene (HFO-1234ze), (Z- or
E-)1,2,3,3,3-pentafluoropropene (HFO-1225ye), (Z- or
E-)1,1,3,3,3-pentafluoropropene (HFO-1225zc), and (Z- or
E-)3,3,3-trifluoropropene (HFO-1243zf). 3. The refrigerant
composition according to item 1 comprising the stabilizer in an
amount of 0.1 to 5.0 parts by weight per 100 parts by weight of the
hydrofluoropropene. 4. The refrigerant composition according to
item 1 further comprising a lubricant. 5. The refrigerant
composition according to item 4 wherein the lubricant comprises at
least one member selected from the group consisting of polyalkylene
glycols, polyol esters, and polyvinyl ethers, and has a kinematic
viscosity at 40.degree. C. of 5 to 400 cSt. 6. The refrigerant
composition according to any one of items 1 to 5 wherein the
refrigerant composition is used for at least one member selected
from the group consisting of refrigeration systems, refrigerators,
mobile air conditioners, coolers (chillers), container freezers,
domestic air conditioners, air conditioners for business use, and
vapor compression heat pumps such as hot-water supply systems. 7. A
method for stabilizing a refrigerant composition comprising a
hydrofluoropropene, the method comprising adding to the refrigerant
composition at least one stabilizer selected from the group
consisting of alkylcatechols, alkoxyphenols, benzoquinones,
phenothiazines, and phthalates. 8. A method for evaluating a
refrigerant composition containing a hydrofluoropropene and a
stabilizer, the method comprising heat-treating the refrigerant
composition in the presence or absence of oxygen in an airtight
container, and determining the acid content of the refrigerant
composition after the treatment. 9. A method for evaluating a
refrigerant composition containing hydrofluoropropene, a lubricant,
and a stabilizer, the method comprising heat-treating the
refrigerant composition in the presence or absence of oxygen in an
airtight container, and then determining the acid content of the
refrigerant composition, and/or the total acid value of the
lubricant contained in the heat-treated refrigerant
composition.
Advantageous Effects of Invention
[0019] The refrigerant composition of the present invention is
chlorine-free and bromine-free; therefore, the composition has no
risk of depleting the ozone layer when released into the
atmosphere. Further, the refrigerant composition of the invention
has a low global warming potential, and its stability in the
presence of air (oxygen) is equivalent to that of known HFC
refrigerants. Furthermore, the refrigerant composition of the
invention exhibits sufficient durability, even when used for
stationary refrigeration systems.
[0020] A feature of the refrigerant composition of the present
invention is that the composition comprises a hydrofluoropropene
and a stabilizer, and that the stabilizer is at least one member
selected from the group consisting of alkylcatechols,
alkoxyphenols, benzoquinones, phenothiazines, and phthalates.
[0021] Examples of hydrofluoropropenes usable as refrigerants
include 2,3,3,3-tetrafluoropropene (HFO-1234yf), (Z- or
E-)1,3,3,3-tetrafluoropropene (HFO-1234ze), (Z- or
E-)1,2,3,3,3-pentafluoropropene (HFO-1225ye), (Z- or
E-)1,1,3,3,3-pentafluoropropene (HFO-1225zc), (Z- or
E-)3,3,3-trifluoropropene (HFO-1243zf), and the like. Such
hydrofluoropropenes can be used singly, or in a mixture of two or
more.
[0022] The refrigerant composition of the present invention may
contain a known HFC refrigerant, in addition to a
hydrofluoropropene as mentioned above.
[0023] The HFC refrigerant content is 50 wt % or less, preferably
30 wt % or less, and more preferably 20 wt % or less, based on the
total weight of the refrigerant composition.
[0024] The refrigerant composition of the present invention may
contain, in addition to such a hydrofluoropropene, a lubricant
according to the purpose of use. The lubricant may be a known
lubricant. Examples thereof include poly(oxy)alkylene glycols,
polyvinyl ethers; polyphenylethers, poly(oxy)alkylene glycols,
copolymers of a poly(oxy)alkylene glycol monoether and a polyvinyl
ether; polyol esters, polycarbonates, silicone, polysiloxane,
perfluoroethers, mineral oils, olefin polymers,
alkyldiphenylalkanes, alkylnaphthalenes, alkylbenzenes, and the
like. Among such lubricants, at least one member selected from the
group consisting of poly(oxy)alkylene glycols, polyvinyl ethers,
and polyol esters is particularly preferable.
[0025] Such lubricants can be used singly, or in a mixture of two
or more. The lubricant has a kinematic viscosity at 40.degree. C.
of preferably 5 to 400 cSt, and more preferably 30 to 400 cSt. The
kinematic viscosity as used herein refers to a value determined by
a capillary viscometer among viscometers defined in JIS Z 8803 (a
liquid viscosity-measurement method).
[0026] When a lubricant is used, the amount of the
hydrofluoropropene-containing refrigerant is typically 16 to 50
parts by weight, per 10 parts by weight of the lubricant. However,
the amount of the hydrofluoropropene-containing refrigerant is not
particularly limited to this range, and may vary depending on the
specifications of the oil tank of the refrigeration system.
[0027] To impart stability against oxygen to a
hydrofluoropropene-containing refrigerant, the refrigerant
composition of the present invention contains at least one
stabilizer (antioxidant) selected from the group consisting of
alkylcatechols, alkoxyphenols, benzoquinones, phenothiazines, and
phthalates.
[0028] Examples of alkylcatechols include pyrocatechol compounds
represented by Formula (1):
##STR00001##
(wherein R.sup.1 is alkyl, and n is an integer of 1 to 4).
[0029] Examples of alkyl groups represented by R.sup.1 include
C.sub.1 to C.sub.10 linear, branched, or cyclic alkyl groups.
Specific examples thereof include methyl, ethyl, propyl, isopropyl,
n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, hexyl,
cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl. Tert-butyl is
preferable.
[0030] n is preferably 1 or 2, and is more preferably 1. When n is
an integer of 2 to 4, the groups represented by R.sup.1 may be the
same or different. Although R.sup.1 may be bonded to any position
on the benzene ring, R.sup.1 is preferably bonded to the 4- or
5-position.
[0031] A preferable example of alkylcatechol is
4-tert-butylpyrocatechol.
[0032] Examples of alkoxyphenols include phenolic compounds
represented by formula (2):
##STR00002##
(wherein R.sup.2 is an alkyl group, and m is an integer of 1 to
5).
[0033] Examples of the alkyl group represented by R.sup.2 include
C.sub.1 to C.sub.10 linear, branched, or cyclic alkyl groups.
Specific examples thereof include methyl, ethyl, propyl, isopropyl,
n-butyl, isobutyl, sec-butyl, and tert-butyl. Methyl, ethyl,
isopropyl, and tert-butyl are preferable. m is preferably 1 or 2,
and more preferably 1. When n is an integer of 2 to 4, the groups
represented by R.sup.2O may be the same or different. Although
R.sup.2O may be bonded to any position on the benzene ring,
R.sup.2O is preferably bonded to the p-position (4-position).
[0034] A preferable example of alkoxyphenol is 4-methoxyphenol.
[0035] Examples of benzoquinones include quinone compounds
represented by Formula (3):
##STR00003##
(wherein R.sup.3 is an alkyl group, and p is an integer of 1 to
4).
[0036] Examples of alkyl groups represented by R.sup.3 include
C.sub.1 to C.sub.10 linear, branched, or cyclic alkyl groups.
Specific examples thereof include methyl, ethyl, propyl, isopropyl,
n-butyl, isobutyl, sec-butyl, and tert-butyl. Methyl, ethyl,
isopropyl, and tert-butyl are preferable.
[0037] p is preferably 0, 1, or 2, and more preferably 0. When n is
an integer of 2 to 4, groups represented by R.sup.3 may be the same
or different. R.sup.3 may be bonded to any position on the
ring.
[0038] A preferable example of benzoquinone is
1,4-benzoquinone.
[0039] Examples of phenothiazines include phenothiazine compounds
represented by Formula (4):
##STR00004##
(wherein R.sup.4 is a hydrogen atom or an alkyl group, the groups
represented by R.sup.5 or the groups represented by R.sup.6 may be
the same or different, and each represents a hydrogen atom or an
alkyl group, q and r may be the same or different, and each
represents an integer of 1 to 4).
[0040] Examples of alkyl groups represented by R.sup.4 include
C.sub.1 to C.sub.10 linear, branched, or cyclic alkyl groups.
Specific examples thereof include methyl, ethyl, propyl, isopropyl,
n-butyl, isobutyl, sec-butyl, and tert-butyl. Methyl, ethyl,
isopropyl, and tert-butyl are preferable. R.sup.4 is preferably a
hydrogen atom.
[0041] Alkyl groups represented by R.sup.5 and R.sup.6 can be
suitably selected from those represented by R.sup.4. Preferably,
both R.sup.5 and R.sup.6 are hydrogen atoms.
[0042] q, and r are preferably 0, 1, or 2, and more preferably 0.
When q is an integer of 2 to 4, the groups represented by R.sup.5
may be the same or different. When r is an integer of 2 to 4, the
groups represented by R.sup.6 may be the same or different. R.sup.5
and R.sup.6 may be bonded to any position on the ring.
[0043] A preferable example of phenothiazine is a
phenothiazine.
[0044] Examples of phthalates include mono- or di-alkali metal
salts of phthalic acid. Mono-alkali metal salts of phthalic acid
are preferable. Specific examples thereof include potassium
hydrogen phthalate and sodium hydrogen phthalate. Potassium
hydrogen phthalate is preferable.
[0045] The amount of the stabilizer is typically 0.1 to 5.0 parts
by weight, and preferably 0.3 to 3.0 parts by weight, per 100 parts
by weight of hydrofluoropropene.
[0046] An excessively low stabilizer content relative to
hydrofluoropropene fails to provide its sufficient effects, whereas
an excessively high stabilizer content causes sludge formation, and
is undesirable in view of economy. Accordingly, use of the
stabilizer in an amount within the above-mentioned range is
preferable.
[0047] When the stabilizer is poorly soluble in the lubricant, a
suitable solvent may be added, insofar as it does not adversely
affect the stability of the hydrofluoropropene against oxygen.
Examples of usable solvents include glyme compounds. Diglyme is
preferable. The amount of the solvent used is 30 wt % or less,
preferably 15 to 25 wt %, and more preferably 15 to 20 wt %, based
on the total weight of the stabilizer.
[0048] The stabilizer used in the present invention exhibits an
extremely high stabilization (antioxidation) effect, compared to
the stabilizers exemplified in PTL 1 (see the Examples and
Comparative Examples).
[0049] This is because the stability evaluation method disclosed in
PTL 1 only evaluates the appearance (coloring grade; rating) of the
mixture in a liquid phase; and cannot evaluate the generation of
acids that is a principal cause of corrosion in the system, and
reduction of refrigeration capacity.
[0050] In contrast, the stability evaluation method according to
the present invention comprises heat-treating a refrigerant
composition in the presence or absence of oxygen in an airtight
container, and then analyzing the acid content of the heat-treated
refrigerant composition. When the refrigerant composition contains
a lubricant, the method of the present invention further comprises
analyzing the total acid value of the lubricant contained in the
heat-treated refrigerant composition.
[0051] The stabilizer's effect and the effect level can be reliably
evaluated by comparing the analysis results obtained in the absence
of oxygen (confirming no acid generation in the absence of oxygen)
with those obtained in the presence of oxygen.
[0052] Examples of airtight containers that can be used include
sealed tubes (for example, sealed Pyrex (registered trademark)
glass tubes). The evaluation method according to the present
invention corresponds to so-called accelerated tests. Accordingly,
the heating temperature can be selected, for example, from the
range of 90 to 200.degree. C. The heat-treatment time can be
selected from the range of 72 to 720 hours. The acid content
analysis of the heat-treated refrigerant composition, and the total
acid value analysis of the lubricant contained in the
oil-containing refrigerant composition can be made by the methods
described in the Examples below.
[0053] The evaluation method according to the present invention can
properly evaluate the generation of acids produced by the oxidation
reaction, such as CF.sub.3COOH and HF, which are a principal cause
of corrosion in the system and reduction of refrigeration capacity.
Accordingly, the evaluation method of the invention enables more
practical screening of stabilizers.
[0054] When high thermal stability is required, a thermal
stabilizer for lubricants, or HFC refrigerants used in conventional
HFC refrigerant systems, as disclosed, for example, in Japanese
Unexamined Patent Publications Nos. 2000-178543 and 2008-308610,
and Japanese Patent No. 2863159, may be used together.
[0055] Examples of such a thermal stabilizer include (i) aliphatic
nitro compounds such as nitromethane, nitroethane, and
nitropropane; aromatic nitro compounds such as nitrobenzene and
nitrostyrene; aromatic unsaturated fatty compounds such as
p-isopropenyltoluene and diisopropenylbenzene; (ii) phenols such as
2,6-di-t-butyl-p-cresol; epoxies such as 1,2-butylene oxide; and
amines such as phenyl-.alpha.-naphthylamine.
[0056] The thermal stabilizer may be one or more compounds selected
from the above compounds (i) and (ii). In this case, two or more
compounds may be selected from either of the compounds (i) or
(ii).
[0057] The amount of the thermal stabilizer may vary depending on
the type of thermal stabilizer used, insofar as it is selected
within a range in which the refrigerant performance is not
adversely affected. The refrigerant composition typically contains
the thermal stabilizer in an amount of about 0.1 to 5 wt %, and
more preferably about 0.3 to 0.3 wt %.
[0058] The refrigerant composition of the present invention can be
used in the same manner as conventional Freons for various
purposes, such as refrigerants, heat transfer media, working
fluids, and foaming agents. For example, the refrigerant
composition of the invention can be used for freezers,
refrigerators, mobile air conditioners, coolers (chillers),
container freezers, domestic air conditioners, air conditioners for
business use, hot-water supply systems, and like vapor compression
heat pumps, and various other low temperature machines. The
refrigerant composition of the invention is particularly useful for
stationary air conditioners, etc., that are required to be charged
with a refrigerant on site, thus resulting in high possibility of
entrapped oxygen.
EXAMPLES
[0059] The present invention is described below in more detail with
reference to Examples and Comparative Examples.
Examples 1 to 13 and Comparative Examples 1 to 22
Preparation of Refrigerant Compositions
[0060] The following compounds were prepared as refrigerants.
X: HFO-1234yf (CF.sub.3CF.dbd.CH.sub.2; produced by Daikin
Industries, Ltd.) Y (Comparative product): HFC-32 (CF.sub.2H.sub.2,
produced by Daikin Industries, Ltd.) Z: HFO-1225ye
(CF.sub.3CH.dbd.CF.sub.2, produced by Daikin Industries, Ltd.)
[0061] The following compounds were prepared as stabilizers.
A (Comparative product): Ethyl mercaptan B (Comparative product):
2-Hydroxy-4-methoxybenzophenone
C: 1,4-Benzoquinone
D: Phenothiazine
[0062] E: 4-t-Butylpyrocatechol
F: 4-Methoxyphenol
[0063] G: Potassium hydroxide phthalate H: (Comparative product,
solvent alone): Diglyme I: (Comparative product): A mixture of
2-hydroxy-4-methoxybenzophenone (2.5 parts by weight)+diglyme (0.5
parts by weight) J: A mixture of 1,4-benzoquinone (2.5 parts by
weight)+diglyme (0.5 part by weight) K: A mixture of phenothiazine
(2.5 parts by weight)+diglyme (0.5 part by weight) L: A mixture of
4-t-butylpyrocatechol (2.5 parts by weight)+diglyme (0.5 parts by
weight) M: A mixture of 4-methoxyphenol (2.5 parts by
weight)+diglyme (0.5 parts by weight)
[0064] A lubricant mainly consisting of a polyvinyl ether compound
having a constitutional unit represented by Formula (1) below and
having a kinematic viscosity at 40.degree. C. of about 70
mm.sup.2/s was prepared as the lubricant.
##STR00005##
[0065] Refrigerant compositions having the formulations shown below
in Tables 1 and 2 were prepared.
TABLE-US-00001 TABLE 1 Oxygen concentration relative to the
Refrigerant Stabilizer refrigerant mol % X Y Z A B C D E F G H I J
K L M Lubricant (post-adjustment) Com. 100 0 0 Ex. 1 Com. 100 0 0
Ex. 2 Com. 100 0 0 Ex. 3 Com. 100 0 0.185 Ex. 4 Com. 100 0 0.185
Ex. 5 Com. 100 0 0.185 Ex. 6 Com. 74 18 0 0.137 Ex. 7 Com. 100 3 0
0.185 Ex. 8 Com. 100 3 0 0.185 Ex. 9 Com. 100 3 0 0.185 Ex. 10 Com.
100 0 Ex. 11 Com. 100 0.185 Ex. 12 Com. 100 100 0 Ex. 13 Com. 100
100 0 Ex. 14 Com. 100 100 0 Ex. 15 Com. 100 100 0.185 Ex. 16 Com.
100 100 0.185 Ex. 17 Com. 100 100 0.185 Ex. 18 Com. 100 3 100 0.185
Ex. 19 Com. 100 3 100 0.185 Ex. 20 Com. 100 3 100 0.185 Ex. 21 Com.
100 3 100 0.185 Ex. 22 Com. 100 0.5 100 0.185 Ex. 23 Com. 74 18 92
0.137 Ex. 24 (In Table 1, the numerical values are parts by weight,
unless otherwise specified. In Comparative Example 12, the amount
of oxygen was the same as in Comparative Example 4.)
TABLE-US-00002 TABLE 2 Oxygen concentration relative to the
Refrigerant Stabilizer refrigerant mol % X Y Z A B C D E F G H I J
K L M Lubricant (post-adjustment) Ex. 1 100 3 100 0.185 Ex. 2 100 3
100 0.185 Ex. 3 100 3 100 0.185 Ex. 4 100 3 100 0.185 Ex. 5 100 3
100 0.185 Ex. 6 100 3 100 0.185 Ex. 7 100 3 100 0.185 Ex. 8 100 3
100 0.185 Ex. 9 100 3 100 0.185 Ex. 10 100 3 100 0.185 Ex. 11 74 18
2.8 92 0.185 Ex. 12 100 3 0 0.185 Ex. 13 100 3 0 0.185 (In Table 2,
the numerical values are parts by weight, unless otherwise
specified.)
Test Example 1
[0066] A total of 37 kinds (Examples 1 to 13, and Comparative
Examples 1 to 24) of refrigerant compositions (a refrigerant+a
stabilizer+a lubricant) shown in Table 1 were individually placed
into Pyrex (registered trademark) glass tubes (ID 8
mm.phi..times.OD 12 mm.phi..times.L 300 mm). Air was added to each
tube to achieve the oxygen concentrations shown in Table 1. After
the tubes were sealed, an accelerated test was performed by heating
the tubes at 150.degree. C. for 1 week (for 168 hours).
(Acid Content Analysis Method)
[0067] After the accelerated test, gas in each sealed tube was
completely solidified with liquid nitrogen. The sealed tube was
then opened. The gradually defrosted and evaporated gas was
collected in a Tedlar bag. Five grams of pure water was added to
the Tedlar bag and brought into close contact with the collected
gas; afterward, acids were extracted. The extract was subjected to
ion chromatography to determine the content (weight ppm) of
fluoride ion (F) and trifluoroacetic acid ion
(CF.sub.3COO.sup.-).
(Analysis of Total Acid Value of Lubricant)
[0068] The total acid value of the lubricant after collection of
gas was determined according to the total acid value analysis
method (for lubricant) of JIS K-2211. The lubricant subjected to
the accelerated test was weighed and dissolved in a mixed solvent
of toluene, isopropanol, and water. The solution was neutralized by
titration with 1/100N KOH ethanol solution using
.alpha.-naphtholbenzein as an indicator. The total acid value
(mgKOH/g) of the lubricant was determined from the titer.
[0069] Table 3 below shows the results of Comparative Examples.
Table 4 shows the results of Examples.
TABLE-US-00003 TABLE 3 Acid content of gas Total acid (mass ppm,
relative value of to the refrigerant) lubricant CF.sub.3COO.sup.-
F.sup.- (mg KOH/g) Comparative Example 1 <1 <1 Comparative
Example 2 <1 <1 Comparative Example 3 <1 <1 Comparative
Example 4 1850 310 Comparative Example 5 <1 <1 Comparative
Example 6 1815 300 Comparative Example 7 1505 245 Comparative
Example 8 1830 305 Comparative Example 9 1840 310 Comparative
Example 10 1800 295 Comparative Example 11 --* -- 0.070 Comparative
Example 12 -- -- 0.334 Comparative Example 13 <1 <1 0.072
Comparative Example 14 <1 <1 0.068 Comparative Example 15
<1 <1 0.074 Comparative Example 16 8 3 0.550 Comparative
Example 17 <1 <1 0.331 Comparative Example 18 10 3 0.579
Comparative Example 19 8 3 0.564 Comparative Example 20 7 2 0.560
Comparative Example 21 7 3 0.558 Comparative Example 22 9 2 0.510
Comparative Example 23 7 2 0.515 Comparative Example 24 6 2 0.508
*No refrigerant
TABLE-US-00004 TABLE 4 Acid content of gas Total acid (mass ppm,
relative value of to the refrigerant) lubricant CF.sub.3COO.sup.-
F.sup.- (mg KOH/g) Example 1 <1 <1 0.108 Example 2 <1
<1 0.104 Example 3 <1 <1 0.111 Example 4 <1 <1 0.113
Example 5 <1 <1 0.115 Example 6 <1 <1 0.112 Example 7
<1 <1 0.107 Example 8 <1 <1 0.101 Example 9 <1 <1
0.104 Example 10 <1 <1 0.106 Example 11 <1 <1 0.100
Example 12 <1 <1 Example 13 <1 <1
(Results)
[0070] In Comparative Examples 1 to 7, 11 to 18, and 24, no
stabilizers were used.
[0071] The compositions of Comparative Examples 1 to 3 respectively
consisted of HFO-1234yf, HFC-32, and HFO-1225ye, and their
stability in the absence of oxygen was evaluated. No noticeable
signs of decomposition were detected.
[0072] The compositions of Comparative Examples 4 to 6 were the
same as those of Comparative Examples 1 to 3, respectively, except
that oxygen was present therewith. In Comparative Examples 4 and 6
respectively using HFO-1234yf and HFO-1225ye as
hydrofluoropropanes, generation of largely increased amounts of
acids was observed. This result indicates that hydrofluoropropanes
are much less stable in the presence of oxygen, compared to a
conventional HFC refrigerant (HFC-32).
[0073] The amount of acids generated in Comparative Example 7 using
a mixture of HFO-1234yf and HFC-32 in the presence of oxygen was
approximately 80% that of Comparative Example 4 using HFO-1234yf
alone as a refrigerant, which is thus approximately proportional to
the composition ratio of HFO-1234yf in the mixture.
[0074] In Comparative Examples 8 and 9, ethyl mercaptan disclosed
in Patent Literature 1 (WO 2008/027511) was added as stabilizer A.
However, the amount of acids generated in Comparative Examples 8
and 9 was almost equivalent to that of Comparative Examples 4 and
6. This result indicates that stabilizer A did not exhibit
oxidation inhibitory effects. Stabilizer A (ethyl mercaptan) was
also added to lubricant-containing compositions in Comparative
Examples 19 and 20. The total acid value in Comparative Examples 19
and 20 was equivalent to that of Comparative Examples 16 and 18, in
which no stabilizers were used. This result indicates that ethyl
mercaptan does not have oxidation inhibitory effects on HFO-1234yf
or HFO-1225ye.
[0075] In Comparative Examples 11 and 12, the total acid value of
lubricant alone in the presence and in the absence of oxygen was
compared. The total acid value was low (0.070 mgKOH/g) in the
absence of oxygen. The total acid value was high (0.334 mgKOH/g) in
the presence of oxygen. The total acid value in the absence of
oxygen (Comparative Example 11) was approximately that of
Comparative Examples 13 to 15. Thus, the results indicate that the
increase in total acid value is attributable to thermal degradation
of ether oil with no decomposition of the refrigerant.
[0076] The total acid value in the presence of oxygen (Comparative
Example 12) was approximately that of Comparative Example 17. This
result indicates that the increase in total acid value is
attributable to a reaction between ether oil and oxygen. Therefore,
the total acid value did not increase when HFC-32 existed in the
presence of oxygen. Accordingly, oxidation inhibitory effects of
stabilizers on hydrofluoropropenes (e.g., HFC-1234yf) were
determined using the results of Comparative Example 17 as a
reference.
[0077] In Comparative Examples 13 to 15, the compositions
containing the same components as in Comparative Examples 1 to 3
and additionally containing lubricant were evaluated. The
evaluation results of Comparative Examples 13 to 15 indicate that
the stability of HFO-1234yf in the absence of oxygen is equivalent
to that of HFC-32 regardless of the presence or absence of
lubricant.
[0078] In Comparative Example 16, the total acid value of the
lubricant increased, but detection level of acids was lower than
that of Comparative Example 4, in which lubricant was not used.
[0079] This is probably for the following reason. Since the
detected acids were HF (19.5.degree. C.) and CF.sub.3COOH (boiling
point: 72.4.degree. C.), most of the acids were dissolved in the
lubricant, which increased the total acid number of the
lubricant.
[0080] In Comparative Example 4, the acid content of the
lubricant-free composition in the presence of oxygen was 1850 mass
ppm of CF.sub.3COO.sup.- and 310 mass ppm of F Conversion of these
values to total acid value of lubricant would be 1.78 mgKOH/g,
which is about 9 times greater than 0.22 mgKOH/g, i.e., the
difference between the oil total acid value in Comparative Example
17 as a reference and that of Comparative Examples 16 and 18.
[0081] This is, for example, because in the presence of the
lubricant, contact of HFO-1234yf with oxygen is reduced due to
dissolution of the refrigerant in the oil, etc.
[0082] In Comparative Example 24, in which a mixture of
refrigerants, HFO-1234yf and HFC-32, existed in the presence of the
lubricant and oxygen, the oil total acid value (mgKOH/g) was 0.508.
When only HFO-1234yf was used as a refrigerant (Comparative Example
15), the oil total acid value was 0.550, and the oil total acid
value due to oxidation of lubricant (Comparative Examples 11 and
16) was 0.331. Thus, the oil total acid value in Comparative
Example 24 was approximately 80% of the difference, which is thus
approximately proportional to the composition ratio of HFO-1234yf
in the mixture, even in the presence of lubricant.
[0083] The oil total acid value in Examples 1 to 11 was lower than
that of Comparative Example 17. This is probably because the
stabilizer having inhibitory effects not only inhibits the
formation of acids by a reaction between HFO-1234yf and oxygen, but
also inhibits oxidation of ether oil with oxygen.
[0084] In Example 2 using HFO-1225ye as a refrigerant, the additive
added exhibited inhibitory effects as in Example 9 using HFO-1234ye
alone as a refrigerant. The result shows that even when a
hydrofluoropropene other than HFO-1234yf is used, the additive can
suppress the oil total acid number, thus exhibiting oxidation
inhibitory effects.
[0085] In Example 11 using a composition containing HFO-1234yf and
HFC-32 as a refrigerant, the oil total acid value was suppressed as
in Example 9 using HFO-1234yf alone as a refrigerant. This result
indicates that the stabilizer exhibits an oxidation inhibitory
effect even when the refrigerant is a composition containing
HFC.
[0086] In Examples 2 and 9, inhibitory effects of stabilizer L on
different types of hydrofluoropropenes were compared in the
presence of the lubricant. Regardless of the type of
hydrofluoropropene, both the acid content and the oil total acid
value were suppressed.
[0087] In Examples 12 and 13, inhibitory effects of the stabilizer
on different types of hydrofluoropropenes were compared in a system
not containing the lubricant. The amount of acids generated was
suppressed in Example 13 (using HFO-1225ye) as well as in Example
12 (using HFO-1234yf). Thus, the results indicate that the
stabilizer can exhibit inhibitory effects, regardless of the type
of hydrofluoropropene.
[0088] Thus, the results indicate that the stabilizer exhibits
inhibitory effects, regardless of the presence or absence of
lubricant and type of hydrofluoropropene.
[0089] The above results confirmed that when the stabilizer is
used, hydrofluoropropenes, such as 2,3,3,3-tetrafluoropropene, and
hydrofluoropropene-containing refrigerant compositions, even in the
presence of air (oxygen), can exhibit high stability against
oxygen, which is equivalent to that of HFC refrigerants. That is,
when the stabilizer of the present invention is added to a
hydrofluoropropene having an unsaturated bond, the stability of the
hydrofluoropropene in the presence of oxygen can be enhanced to a
level equivalent to that of HFC refrigerants. It was thus found
that the refrigerant composition of the present invention is useful
as a refrigerant composition for stationary air conditioners, which
is as stable as conventional HFC refrigerants and which exerts very
little effect on the global environment.
* * * * *