CA1154505A - Electrolytic capacitor for at least 200v service - Google Patents

Electrolytic capacitor for at least 200v service

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Publication number
CA1154505A
CA1154505A CA000410629A CA410629A CA1154505A CA 1154505 A CA1154505 A CA 1154505A CA 000410629 A CA000410629 A CA 000410629A CA 410629 A CA410629 A CA 410629A CA 1154505 A CA1154505 A CA 1154505A
Authority
CA
Canada
Prior art keywords
electrolyte
salt
hydrogen
dodecanedioate
capacitor according
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
CA000410629A
Other languages
French (fr)
Inventor
Manuel Finkelstein
Sidney D. Ross
Franz S. Dunkl
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sprague Electric Co
Original Assignee
Sprague Electric Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sprague Electric Co filed Critical Sprague Electric Co
Application granted granted Critical
Publication of CA1154505A publication Critical patent/CA1154505A/en
Expired legal-status Critical Current

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Classifications

    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01GCAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G9/00Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
    • H01G9/004Details
    • H01G9/022Electrolytes; Absorbents

Abstract

Abstract of the Disclosure An aluminum electrolytic capacitor capable of operation at 200 VDC or higher and 130°C contains as its electrolyte a tertiary amine or a dipropylamine mono salt of dodecanedioic acid dissolved in a sol-vent mixture of ethylene glycol and N-methyl-2-pyrro-lidinone and water.

Description

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This invention relates to an aluminum electro-lytic capacitor containing an electrolyte permitting capacitor operation at 130C and 200 VDC or above.
Electrolytes for aluminum electrolytic capaci-tors of the prior art capable of operating at voltages of200V or higher most commonly contain salts of boric acid or boric acid derivatives in ethylene glycol. The maxi-mum operating temperature for such an electrolyte system is less than 100C and normally 65-85C. The temperature limitation is due to the rapid reaction of glycol with boric acid and other borate species to form polymeric glycol-borates and water at about 100C. The minimum operating temperature in such a system is above -20C, since glycol freezes at -17.4C.
The effective operating range of electrolytic capacitors has been expanded in both directions in the prior art by replacing the glycol solvent with N,N-di-methylformamide (hereinafter DMF) which has a boiling point of 153C and a freezing point of -61C. However, DMF is a very aggressive solvent that attacks most mate-rials of construction. While the most resistant material for sealing gaskets and O-rings is Butyl rubber, DMF will be transmitted through a Butyl r~bber closure at a rate which increases with increasing L~mperature and which limits the life of the capacitor, since a capacitor will ~C
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not function adequately when the electrolyte loses half its solvent. This contlnuous slow loss oE DMF a].so intro-duces a new difficulty, particularly if the capacitor is operating in a confined space, because the flash point of DMF is only 67C.
In contrast glycol, which has a boiling point of 197.2C and a flash point of 116C, is a much safer material, is much easier to contain, and its rates of transmission through both Butyl rubber and EPR rubber are almost negligible.
In current power supply applications, it is desirable to have an electrolytic capacitor operating at 200 VDC, but capable of having superimposed on this DC
voltage sufficient AC ripple voltage to raise the internal temperature to 120-125C at an ambient temperature of 85C.
An electrolytic capacitor that could operate continuously at 200 VDC at an ambient temperature of 130C would meet the above high-temperature requirements.
The low-temperature requirements are much less stringent; it is likely that more than 90% would be met by a capacitor that retained 50V/o of its capacity at -40C, and 70V/o of its capacity at -20C. The requirements might, with some solutes, be met with an electrolyte in which glycol was the only solvent (other than water) and would certainly be met in an electrolyte in which glycol was mixed with an appropriate cosolvent.
Thus, it is desirable to develop an electroly-tic capacitor capable of operating continuously at a voltage of 200 VDC or higher at an ambient temperature of 130C and providing modest low temperature properties.
However, the solute cannot be a borate, since borates react with glycol. In fact, the solute must be one which does not react chemically with either glycol or any other cosolvent that is used.
In addition, the solute must have excellent stability at the operating temperature, 130C, and good stability at somewhat higher temperatures. Thus, 150C
was chosen for screening purposes, and resistivity in-creases must be less than 25V/o after lO00 hr at 150C.

l~c~ 5 The major cause of resistivity increase, parti-cularly where the solute is an ammonium or substituted ammonium salt of a monobasic or dibasic carboxylic acid is amide formation which converts conducting salt to a non-conducting amide. Generally, this reaction manifests itself through an increase in the resistivity of the electrolyte. Amide formation is easiest with ammonium salts, and the reaction occurs more readily with salts of primary amines than with salts of secondary amines.
The reaction can even occur with salts of tertiary amines J
although it is more difficult, since amide formation now requires cleavage of a carbon-n;trogen bond.
Another possible degradative reaction is ketone formation. This reaction is likely for the formation of C5 to C7 ketones, i.e. with salts of adipic, pimelic and suberic acids, but is of little consequence for the higher dibasic acids.
Electrolytes in which the solutes are amine salts of dodecanedioic acid meet the requirements given above.
The diammonium salt of dodecanedioic acid has been dis-closed in Japanese Showa 52-85356, and a solution of this salt in glycol-water is satisfactory in capacitors at 85~C.
Dodecanedioic acid can form both mono- and di-salts with amines, but the monoamine salts are considered to be more suitable. The iso-electric point, i.e. the point of chemi-cal stability and minimum solubility for aluminum oxide is at pH 5.5. Therefore, a slightly acid solute (i.e. a mono salt) is less likely to attack the aluminum oxide dielec-tric than a slightly basic solute (i.e. a di-salt). This consideration is of dominant importance at temperatures as high as 150C.
In accordance with this invention an aluminum electrolytic capacitor has an electrolyte of a mono salt of dodecanedioic acid and a tertiary amine or a dipropyl-amine as solute, water and a mixture of ethylene glycoland N-methyl-2-pyrrolidinone as solvent.

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In drawings which illustrate embodiments of the invention, Figure 1 ~shows a wound capacitor section par-tially unrolled, Figure 2 is a cross-section of a completed capacitor containing a wound section, and Figure 3 compares resistivity of mono(N-ethyl-piperidinium) dodecanedioate in two different solvent mixtures .
In general, the aluminum electrolytic capacitor of this invention is capable of continuous operation at 130C and 2QQ VDC or above thraugh the use of an electro-lyte having a mono salt of dodecanedioic acid and a di-propylamine or tertiary amine as solute in a solvent of water and a mixture of ethylene glycol and N-methyl-2-pyrrolidinone. The preferred mono solts are di-n-propyl-ammonium, diisopropylammonium, trimethylammonium, tr;-ethylammonium, and N-ethyl-piperidinium.
Mono salts of dodecanedioic acid with primary amines were too unstable to be used at the temperatures required, as solutions of them rapidly increased in resis-tivity at above 100C. Most of the amine salts were also sufficie.ntly insoluble in glycol so that a cosolvent was required. Similarly, such salts with secondary amines, with the notable exceptions of the mono(di-n-propy]ammo-nium) salt and the mono(diisopropylammonium) salt, were either unsatisfactory or marginal with respect to stabi-lity or other electrolyte properties.
The choice of a cosolvent for glycol is criti-cal. The solvent chosen must have a boiling point andflash point such that the flammability of the mixture will not be significantly increased and such that vapor transmission of the mixture through capacitor closures will not be significantly greater than that observed with glycol alone. Glycol is a protic solvent which can func-tion as both a hydrogen donor and a hydrogen acceptor in hydrogen bonding, but its primary role in hydrogen bond-ing and in solvation and solubilization of a salt is in 5~S

its capacity as a hydrogen donor in hydrogen bonding. To enhance the solubility of the salts and maximize the con-duc~ity in the mixed solvent system, the cosolvent must be of a different type, i.e. an aprotic solvent which can function only as a hydrogen acceptor in hydrogen bond-ing and which is especially effective in solubilizing the cationic portion of the salt.
While DMF meets this latter requirement, it is not desirable for the reasons s~tated above. However, all of the requirements are met by adding N-methyl-2-pyrroli-dinone (NMP) to glycol. This aprotic solvent has a boil-ing point of 202C, a flash point of 95c and an auto-genous ignition temperature of 346~C. As will be shown subsequently, this solvent augments the properties of glycol and results in greater salt solubilities and more highly conducting solutions.
Figure 1 shows wound capacitor section 10 inclu-ding anode foil 11 of aluminum having on its surface an insulating oxide barrier layer. Cathode foil 13 is also aluminum. Electrolyte absorbent layers 12 and 14, pre-ferably paper, are positioned between the anode foil 11 and cathode foil 13 and interwound therewith. Tabs 15 and 16 are connected to electrodes 11 and 13, respectively, to provide for connection of the electrodes to leads.
25 When completely wound, section 10 is impregnated with elec-trolyte (not shown) of this invention.
Figure 2 shows a cross-section of a completed axial capacitor in which the cathode tab 16 of capacitor section 10 is welded to portion 17 o:E insert 18 positioned in bushing 19, and welded at 20 to anode lead 21. An elec-trolyte (not shown) of this invention impregnates section 10.
The electrolyte in the capacitors of Figures 1 and 2 is a solution of ethylene glycol, N-methyl-2-pyrroli-dinone, water, and a mono salt of dodecanedioic acid with a dipropylamine or with a tertiary amine. The following examples show the utility of these electrolytes.

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-Example 1 It was unexpected and unanticipated to find that, contrary to previous experience with other dicar-boxylic acids, every tertiary amine that was~ tried with dodecanedioic acid gave results that met the objecti-ves of this invention.
A typical formulation involving the tertiary amine salt, trimethylammonium hydrogen dodecanedioate, is shown below.
Table la Formulation wt%
Dodecanedioic Acid 8.83 Trimethylamine 2.26 Glycol 42.52 NMP 39.60 Water 6.79 Ohm-cm, 25 707 Vmax 25 461 After 2063 hours at 125 the resistivity of the electro-lyte increased by 16% to 821 ohm-cm, and after 2063 hours at 150 the resistivity increased by 20.9% to 855 ohm-cm.
At both temperatures all of the change occurred in the first 70 hours.
With triethylammonium hydrogen dodecanedioate, also prepared in situ, as were all of the other tertiary amine salts, the formulations shown in Table lb were screened in the sealed tube test. After 1674 hours at 125C in a sealed tube, formulation A increased by 11% to 933 ohm-cm. After 1674 hours at 150C, the increase in resistivity was essentially the same, 930 ohm-cm. After 2417 hours in a sealed tube, the resistivity for Formula-tion C increased by 16.9% to 1493 ohm-cm. After 2282 hours at 150C, Formulation D increased by 9.2% to 1494 ohm-cm.
In addition, Formulation E had a 105C resis-tivity of 112 ohm-cm, a 105C Vmax of 440-450V, and a 125C Vmax of 435-445V.

~ ,4,-~5 Electrolytes in which the solute is N-ethylpiper-idinium hydrogen dodecanedioate are amongst the preferred embodiments, and some of the many formulations that were explored are shown in Table lc. Formulation ~ in this Table s~howed an increase in resistivity at 5. 9J/~ to 947 ohm-cm after 311 hrs at 150G, and after 650 hours there was only a slight additional resistivity increase to 958 ohm-cm. ~ormulation I did not show any resistivity change after 2282 hours at 150C, demonstrating the advan-tage of 24 hour refluxing as a pretreatment, but even with-out such pretreatment resistivity increases are less than 25% after 1000 hours at 150C.

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O ~ ~ ~ Z ~ ~ ~ ~3 0 ~ 45~5 _ g _ Electrolytes having N-ethylpiperidinium hydro-gen dodecanedioate as solute may be used to provide a systematic indication of the solvent effects due to variation of the ratio of NMP to glycol. These results are shown in Table 2a and Figure 3. It should be noted that the enhanced conductivities for all solvent mixtures compared to either pure solvent obtain, despite the fact that the two solvents have very similar properties, inclu-ding even the dielectric constants (37 for glycol and 32 for NMP). It should be emphasized that such symbiotic interactions do not result from using two solvents of the same hydrogen bonding type, e.g. N-methyl-2 pyrrolidinone (NMP) and butyrolactone (~LO). The effects due to using mixtures of these two solvents are shown in Table 2b and Figure 3.
In Figure 3, the solid line is a graph of the data presented in Table 2a and the dotted line is a graph of the data presented in Table 2b and show dramatically the difference between using solvents of different hydro-gen bonding types (solid line) and of the same hydrogen bonding type (dotted line).
Each solution in Tables 2a and 2b contain as solute N-ethylpiperidinium hydrogen dodecanedioate for-mulated from 0.67 g (0.0029 mole) dodecanedioic acid, 0.33 g (0.0029 mole) N-ethylpiperidene, and 0.5 ml water.

-Table 2a NMP (ml)Glycol (ml)Resistivity ohm-cm, 25C

6 4 125~
2 8 1482 Table 2b BL0 (ml)NMP (ml) ohm-cm, 25C
3 7 3694 Example 3 The behavior of these electrolyte formulations in capacitors is illustrated using capacitors in which the electrolyte is Formulation E in Table lb and in which the solute is triethylammonium hydrogen dodecanedioate.
The capacitors used were a special design, 50 ~F-200V
capacitors. They were built using 4-mil aluminum foil anode, aluminum foil cathode, and 3-mil Manila spacers.
The capacitors were aged for 2.5 hrs at 275V and 105C
on 50 KQ boards. Twenty-five capacitors were life-tested at 130C and 200 VDC. The results are shown in Table 3, where every value indicated is the average of twenty-five capacitors.

~ 4~5 Weight loss represents the weight of electro-lyte lost and is a measure of capacitor life. When a capacitor has lost 40-50% of its electrolyte, it can be predicted to start deteriorating and going off specifi-cation electrically. The capacitors below contained2000 mg of electrolyte originally.
Table 3 ~Iours 120 Hz 120 Hz 2 min. 5 min. wt.loss,mg Cap. ~F ESR ohms DCL ~A DC~ ~A
0 55.19 0.902.7 3.1 247 54.58 0.705.9 2.7 27.3 424 54.35 0.693.5 1.7 48.7 1000 54.28 0.752.5 1.2 120.2 1430 53.80 0.733.2 1.4 170.~
1572 54.12 0.762.3 1.1 190.2 2000 53.9 0.792.7 1.2 245.0 2500 53.7 0.852.6 1.2 308.4 3000 53.4 0.883.1 1.3 371.6 Example 4 Two electrolytes were evaluated in 10 ~F-450V
and 20 ~F-450V capacitors with and without a phosphate that had proved beneficial in other high voltage electro-lyte formulations. The capacitors were aged at 400V for 1 hr, 450V for 1 hr, and 475V for 2 hr, all at 85C on 50 KQ boards. Shorts represent the ratio of the number of units shorting to the total number of units tested.
Table 4a gives the electrolyte formulations, 25C resis-tivity in ohm-cm, and Vmax at 25C. Table 4b presents capacitor test results.

Table 4a Formulation A B C D
Dodecanedioic acid 57.5g 57.5g 40g ~og Diisopropylamine 25.3g 25.3g - -Triethylamine - - 17.5g 17.5g Water 50 ml 50 ml 48 ml 48 ml Glycol 500 ml 500 ml 420 ml 420 ml NMP 500 ml 500 ml 700 ml 700 ml Phosphate - 2.4g - 2.63g Ohm-cm 1528 1425 1737 1630 Vmax 510 520 530 530 Table 4b 10~F - 450V 20~F - 450V
Formulation Shorts DCL(avg)~A Shorts DCL(avg)~A
A1/10 94.3 1/12 43.1 B1/10 28.1 0/14 37.6 C0/10 113.6 3/15 64.8 D0/10 23.9 0/13 51.2 The phosphate is beneficial as far as leakage current is concerned but is not necessary for operation at high voltages as it is in the adipate electrolyte of a copending application filed concurrently herewith by Finkelstein, Dunkl and Ross.
Example 5 This example shows electrolyte properties for the dipropylamine salts of the present invention. Three electrolyte formulations, shown below, in which the solute was di-n~propylammonium hydrogen dodecanedioate, prepared in situ, had good electrical properties and adequate stability.

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Table 5a Formulation (wt%) A B C
Dodecanedioic acid 27.60 10.67 18.50 Di-n-propylamine 12.08 4.68 8.24 NMP 8.53 38.36 32.97 Glycol 49.54 41.19 35.42 Water 2.25 5.10 4.87 Ohm-cm, 25~ 1053 953 866 Vmax, 25~ 468 485 463 It is to be noted that the concentrations of the indivi-dual components above can be varied widely while still permitting useful electrolyte properties. In electrolyte A, the water content can be doubled without changing Vmax. The stability of these systems is suggested by the fact that 24 hours of reflux increases the resistivity for formulation C by less than 9%.
With diisopropylammon;um hydrogen dodecanedioate, prepared in situ, as solute, good stability was observed.
Some typical formulations are shown in Table 5b. After 24 hours of reflux, formulation A in Table 5b increased by less than 2% to 1022 ohm-cm and the resistivities of formulations D and E (Table 5b) were unchanged by 24 hours of reflux. After 2623 hours in a sealed tube at 150C, the resistivity of formulation A increased to 1126 ohm-cm, an increase of less than 11%.
A batch quantity of formulation E was made with and without 0.2% ammonium dihydrogen phosphate and put on life test in 840~F, 250V capacitors. The electrolyte without phosphate had a room temperature resistivity of 1044 ohm-cm and a Vmax of 485V at 25C; for the phosphate version, the resistivity was 1021 ohm-cm and Vmax, 468V.
Preliminary capacitor data is given in Table 5c.

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Claims (8)

  1. The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
    l. An aluminum electrolytic capacitor comprising two contiguously wound aluminum foil electrodes with interleaved spacers, one of said foils bearing a barrier layer dielectric oxide on its surface, and an electrolyte in contact therewith, said electrolyte comprising as solute a tertiary amine or a dipropylamine monosalt of dodecanedioic acid dissolved in a solvent mixture of ethylene glycol, N-methyl-2-pyrrolidinone, and water, said electrolyte exhibiting lower 25°C resistivity than an electrolyte absent ethylene glycol or N-methyl-2-pyrrolidinone and providing a capacitor that operates at 130°C and at least 200V.
  2. 2. A capacitor according to claim 1 wherein said tertiary amine of said salt is chosen from the group con-sisting of trimethylamine, triethylamine, and ethyl-piperidine.
  3. 3. A capacitor according to claim 2 wherein said salt is trimethylammonium hydrogen dodecanedioate.
  4. 4. A capacitor according to claim 2 wherein said salt is triethylammonium hydrogen dodecanedioate.
  5. 5. A capacitor according to claim 2 wherein said salt is N-ethylpiperidinium hydrogen dodecanedioate.
  6. 6. A capacitor according to claim 1 wherein said salt is di-n-propylammonium hydrogen dodecanedioate.
  7. 7. A capacitor according to claim 1 wherein said salt is diisopropylammonium hydrogen dodecanedioate.
  8. 8. A capacitor according to claim 1 wherein said electrolyte additionally contains a phosphate.
CA000410629A 1981-09-30 1982-09-01 Electrolytic capacitor for at least 200v service Expired CA1154505A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US306,992 1981-09-30
US06/306,992 US4373176A (en) 1981-09-30 1981-09-30 Electrolytic capacitor for at least 200 V service

Publications (1)

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CA1154505A true CA1154505A (en) 1983-09-27

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Country Status (5)

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US (1) US4373176A (en)
JP (1) JPS5868921A (en)
CA (1) CA1154505A (en)
DE (1) DE3236095A1 (en)
GB (1) GB2107120B (en)

Families Citing this family (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4454567A (en) * 1979-03-21 1984-06-12 Sprague Electric Company Electrolytic capacitor containing a mixed solvent system
US4509094A (en) * 1984-02-21 1985-04-02 Sprague Electric Company Electrolytic capacitor for at least 150 V service
JPS6124219A (en) * 1984-07-12 1986-02-01 エルナ−株式会社 Electrolyte for driving electrolytic condenser
JPS61226913A (en) * 1985-04-01 1986-10-08 エルナ−株式会社 Electrolytic liquid for driving of electrolytic capacitor
US5202042A (en) * 1987-03-09 1993-04-13 Nippon Chemi-Con Corporation Heterocyclic electrolyte salts for electrolytic capacitors
US4823236A (en) * 1988-05-23 1989-04-18 Sprague Electric Company High temperature aluminum electrolytic capacitor
US4835660A (en) * 1988-08-15 1989-05-30 North American Philips Corporation Use of choline as the cation in capacitor for electrolytes
US4860169A (en) * 1988-12-14 1989-08-22 North American Philips Corporation Long chain carboxylic acids for very high voltage aluminum electrolytic capacitors
EP0504293A4 (en) * 1989-12-06 1992-12-30 Robert T. Bush Method and apparatus for energy production using cold nuclear fusion with a lithium deuteroxide electrolyte
US5160653A (en) * 1990-02-28 1992-11-03 Aerovox M, Inc. Electrolytic capacitor and electrolyte therefor

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3293506A (en) * 1966-12-20 Electrolytic capacitors and electrolyte therefor
US3351823A (en) * 1967-11-07 Non-aqueous capacitor electrolyte having a salt dissolved in a co- solvent
DE1263932B (en) * 1963-11-21 1968-03-21 Canadian Patents Dev Electrolyte for electrolytic capacitors with at least one aluminum electrode
US3588625A (en) * 1968-02-05 1971-06-28 Tokyo Shibaura Electric Co Electrolytic condenser and paste composition therefor
US3609468A (en) * 1968-02-05 1971-09-28 Tokyo Shibaura Electric Co Paste composition for an electrolytic condenser and electrolytic condenser containing same
US3547423A (en) * 1968-04-12 1970-12-15 Gen Electric Electrolytic capacitor and electrolyte material therefor
DE2209095C3 (en) * 1971-02-25 1978-03-09 Sanyo Electric Co., Ltd., Moriguchi, Osaka (Japan) Electrolyte for electrolytic capacitors
GB2005918B (en) * 1977-10-11 1982-03-10 Sangamo Weston Electrolyte system for electrolytic capacitors

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Publication number Publication date
DE3236095A1 (en) 1983-04-07
JPH0324766B2 (en) 1991-04-04
US4373176A (en) 1983-02-08
JPS5868921A (en) 1983-04-25
GB2107120B (en) 1985-04-17
GB2107120A (en) 1983-04-20

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