Note: Descriptions are shown in the official language in which they were submitted.
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IMPROVED PROCESS FOR rl-lE PREPARATION OF THIO-BIS-PHENOLS 81T72 ¦
~ackground cf the Invention
1. Field of the Invention
` This invention re1ates to an improved process for making thio-bis-
phenols and more partlcularly to a process for producing thio-bis-phenols by
reacting an alkylated hydroxyben~ene with sulfur dichloride in the presence of
a carboxamide.
2. ~ n of the Prior Art
Generally, th~o-b~s-phenols are made by the condensation o~ the
phenol with sulfur dichloride. For example, 4,4'-thio-bis-3-methyl-6-t- ¦
o butylphenol is made by the condensation of 3-methyl-6 t-butylphenol (i.e.,monobutyl-m-cresol) with sulfur dichloride, SC12, in an organic solvent. Past
experience has shown the preferred solvents for carrying out the reac-tion to
be aliphatic hydrocarbon solvents and the expected yields to be in the range
of 65 to 70% of the theory. 4,4'-thio-bis-3-methyl-6-t-butylphenol is a well
known, valuable antioxidant for rubber and plastics.
Summary of the Invention
It has now been found, surprisingly, that the addi-tion of a catalytic
amount of a N,N-dialkylcarboxamide to the reaction charge of-the hy(lroxybtn-
zene and sulfur dichloride improves the in-hand yield of the desired thio-bis-
phenol without affecting the quality of the product.
Detailed Description of the PreFerred Embodiment
In accordance ~ th this invention the hydroxybenzene is dissolve(l in
an organic solvent and then reacted with sulfur dichloride in the presellce of
.. . ' ~ .
a catalytic amount of a N,N-dialkylcarboxamideO The reaction may, usin~ as an i
example the starting material 3~methyl-6wtertiary-butylphenol, be generally
expressed as
CH3 CH3 CH3
2 HO ~ -~ SC12 ~ LY~lLl~A~ ~55~L~ IO- ~ S ~ )~ O~l ~ 2HCl
C(CH3) C(CH3)3 C(CH3~3
A wide range of hydroxybenzenes such dS cresol, resorcinol and
alkylated derivatives may be used as starting material. Typical products pro- ¦
duced include:
o (a~ when the starting material is a monoalkyphenol
, ~1 0
~5~
The R groups with respect to positions on the benzene ring and the
sulfur linkage between the phenolic groups being shown rando~ly located, She R
groups being the alkyl group associated with the alkylated hydroxybenzene and
the actual location being a function of the location of R in the starting
material.
(b) when the starting material is a dialkylphenol
R R
R '~J S
H OH
Typical bis-phenols that may be produced include:
4,4'-thio-bis(2,6-di-tert-bu-~ylphenol)
~,4'-thio-bis(2,6,-di-sec-butylpllenol)
4,4'-thio-bis(6-tert-butyl-m-cresol)
2,2'-thio-bis(6-tert-bu~yl 4-ethylphenolj
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(c) when the starting material is an alkylated resorcinol
~H O~
R~ ~R
The N,N-dialkylcarboxamides that are the additives in the present ~ ¦
~invention are known cornpounds which are commerci~lly available or readily made ¦
hy known methods and which can be represented by the following structure
,R2
o R1 -C -N
R3
whor~ln Rl represents a member of the group consisting of hydrogen, alkyl, i
cycloalkyl, aralkyl, lo~er alkoxy and lower dialkyl amlno radicals. R2 and R
represent members of the group consisting of alkyl and aralkyl radicals, and
wherein Rl, R2 and R3 may also represent, in pairs, common members oF a
heterocyclic ring which contains -the carboxamide nitrogen atom.
The pre~errecl catalysts are N,N-disubstitutecl carboxylic acid amides.
They may be derived from lower fatty acids such as forrnic acid and acetic
acid, as well as From higher fatty acids, such as lauric acid. Obviously,
amides of fatty acids wlth a medium number oF carbon atoms, as for exanll)le
with up to 7 carbon atolns, arè also suitable. ~non~ the fatty acicl amides
those derived from fatty acids havincJ up to 4 carbon atoms usually give the
best results. Besides fatty acid amides, there may also be used -the acicl
amides of araliphatic carboxylic acids, such as phenylacetic acid. Finally
there rnay also be used amides of cycloaliphatic carboxylic acids~ Sl.lCh as ,
hexahydrobenzoic acid.
The sui tabl e compounds may on the other hancl be derivecl Fran al i-
phatic, araliphatic amines and from polymethylene imilles. Of the alkyl-
substituted amines those with substituents wil:h up to about 4 carbon atoms anclespecially those containing ethyl or methyl groups are preferred. The ter
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"lower alky'l radicals," throughout this specification~ means those with up to
about ~ carbon atoms. Acid amides derived from cycloaliphatic imines wi~h 5
to about 7 ring members are also well suited as c:atalysts.
Lactams, such as pyrrolidone, caprolactaln and oenanthic lactam,
N-substituted by lower alkyl radicals, especially by ethyl or methyl radicals,
may also be used as catalysts. The alkyl-substituted compounds and especially
the ccmpounds substituted by lower cllkyl radicals are preferred.
In general the best results are achieved with catalysts which are
derived frcm formic acid on the one hand and from lower aliphatic secondary
amines or fr~n cycloaliphatic imines with 5 to 7 ring members on the other
hand, and also with lactams N-substituted by lower alkyl radicals.
Suitable ca-talyst are for example: N,N-clilrlethylforlnalnide, N,N-
cliethyl forrnamide, N,N-dibutyl Fonnamide, N-forrnylpiperidine, N,N-die-thyl~- I i
acetamide, N-acetylpyrrolidine, N,N-dimethylpropionamide, N,N-dimethylstearic j
acid amide, N-methylpyrrolidone, N-ethylcaprolactam, N,N-dimethylbenzamide,
N-formylpyrrolidine, N-formylhexamethylene imine, N,N'-diformylpiperazine,
N,N,-dicyclohexylformamide, butyric acid piperidide, butryic acid dipropyla
mide, isohutyric acid die~hylamide, hexahydrobenzoic acici dimethylanlide,
lauric acid dimethylamide, and N-cyclohexylpyrrolidone. I
The catalytic amount of N,N-dialkylcarhoxamide -to be used can vary
Fran 0.1% to 10% based on the weight of the hydroxybenzene. Less than 0~1~/o of ¦
-the carboxamide does not produce d noticeable efFect. More -than 10% Or t~le
carboxamide causes little if any further yield improvement. The pre~erreci
amount of carboxamide to be used is about 0.2% to 2.0% by weiyht basecl on the ¦weight of the cresol. I
The reaction is carried out in a liquid meclium. The organic so'lvents I
commonly used for dissolving the hydroxybenzene and the catalyst include, For
example, aliphatic hydrocarbons such as bu-tane, pentane, hexane, isohexane,
heptane, isoheptane, octane, isooctane, etc.; and alicyclic hydrocarbons such
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as cyclopentane, cyclohexanc, methylcyclohexane, etc. Solvent mixtures are
also suitable. Halogenated hydrocarbons, aromatic hydrocarbons, ethers, and
esters can also be used, as long as they are inert to sulfur dichloride and to ¦the carboxamide catalysts. The amount of solvent to be used generally ranges
from one-half to ten par1ts by volume and preferably from two to five parts by
volume per part by weight of the hydroxybenzene
Preferably, stoichiometric amounts of the reactants ar~ used: one
mole of sulfur dichloride is reacted with two moles of the hydroxybenzene, but
the amount may vary from 0.8 to 1.2 moles of sulfur dichloride per 2 moles of
o hydroxybenzene.
Sulfur d~chloride and the hydroxybenzenes react exothermically. The
temperature can be readlly controlled by agltation of the reactant, dilutlon
of the reactant, slow addition of the sulfur dichloride and external cooling.
The reaction may be carried out in a wide range of temperatures and pressures
for example, at 0-85C but preferably at 25C-45C, at atmospheric pressure.
Pressure has little effect, except possibly to hinder the removal of
the HC1. The lower the temperature, o~ course, the slower but the more
selective the reaction, higher temperatures can lead to undesirable side
reactions. It is preferred to carry out the reaction at a temperatllre of
20 15-25C at atmospheric pressure until the reaction is substantially completecl;
and, optionally, then heat the reaction to reflux and continue the reaction
under reflux conditions until the evolution of HCl ceases.
The starting materials should preferably be charged to the reactor in
the following order. The sul~ur dichloride is dissolved in an organic solvent
and added drop by drop at a controlled rate to the solution comprised of the
cresol and the catalys-t, carboxamide, dissolved in the organic solvent so thatlthe hydrogen chloride gas ~hich results from the reaction is evolvecl contin- ¦uously. I
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After the reaction is completed, the reaction mass is cooled to a
temperature of 0-25C. The precipitate, which is the-thio-bis-phenol, can
usually be separated by filtration, washed with t;he organic solvent, then
optionally with water and finally dried.
The invention is further illustrated by the following examples.
Exampl e 1
A 2-liter flask equipped with a stirrer, thermometer, reFlux condens-
er and 500 ml addition funnel .was charged with 212 9. (1.24 moles) of commer-
cial grade (96%) 3-methyl-6 t-buty1phenol d~ssolved in 633 g. of n-hexane and
o 1.1 g. N,N-dimethylfonnamide (0.5% based upon the we~ght of the alkylatecl
phenol) as a catalyst. I\ solution of 68 9. (0.63 moles) o~ 96% sulPur dichlo- ¦ride in 159 g. n-hexane was added dropwise to the stirred flask contents over ¦
1-2/3 hours, holding the reaction temperature at 20-25C. ilydrogen chloride
gas was evolved soon after the start of the sulfur dichloride addition. The
reaction mixture was stirred for two hours at 20-25C and sparged with
nitrogen to sweep out the hydrogen chloride. Then the m~xture was heated to
reFlux (63C) and held For 1-2/3 hours at reflux to complete the condensation
reaction. Next, the mixture was cooled to 20-25C ancl filtered. The 2~2 g.
of filter cake was washed with 1128 9. oF n-hexane and Filtered. lhe Filter
20 cake was washed again with 1000 g. oF n-hexane and then spread on Filter paper~
to air dry. Actual yield was 166 9. (75.1% of theoretical) of 4,4'-tilio-i)is-
3-methyl-6-t-butylphenol with a capillary melt point of lG0C ancl an o~f-white
col or.
. Exampl e 2
A 500 ml. Flask equipped with thermometer, s-tirrer, addition Funnel,
and reflux condenser was charged with 33.3 9. (0.2 nl) oF commercial grade 3-
methyl-6-t-butylphenol (97%), 150 ml. oF n-hexane and 3.0 g. (9 wt% based UpOII,the weight oF the alkylated phenol) of N~N-dilnethylFornlalnide. To the sl;irre(l
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~L2fL;~2~ 8
solution was added duriny 85 minO dt 19-25C dropwise a solution of 10.8 9.
(0.1 nI) oF commercial grade sulfur dichloride ~95%), with hydrogen chloricle
being evolved soon after start of the additionO The stirred mixture was held
at ambient temperature for another 68 nIin. and at 24-46C For another 167
min., then cooled to 25C and filtered. The solid product was washed with
50 ml, of n~hexane and 50 mlO of water, then dried to give 29.1 g. (81.3% of
the theory~ of 4,4'-thio-bis~3-methyl 6-t-butylphenol, capillary m.p. 158- ¦
9C, of off-white color.
~xample 3
o Example 2 was repeated except that the ca~alyst WdS changed. Substi-¦
tuted for the N,N,-dinIekhylForlnallIi(Ie was 0.7 9. (2 wt% based upon weight oFthe alkylated phenol) of N,N-dimethylacetamide. The crude product was washed
with n-hexane and dried to give 31.8 g. (88.8% oF the theory) of crude off-
white 4,4'-thio-bis-3-methyl-6-t-butylphenol.
Example 4
To a stirred slurry of 133.2 9 (0.6 m) ~-6-t-butylresorcinol in
500 ml of n-heptane was added 2.7 9 of N,N-dimethylfonman1ide (2 wt% on the
dibutylresorcinol). Then a solution of 3~.5 9 (0.3 m) oF 75U/o suIfur di-
chloride in 100 rnl of n-heptane was added over a period of 75 minutes while
the reaction was maintained at Z1-25C (temperature mdintained with a cold
water bath). The mixture was stirred at 24C -For another 2.0 hours, whert? the
evolution of hydrogen chloride began to 1essen. At this point a slow stean~ oF
nitrogen was passed through -the reactor to Facili-ta-te the removal oF I-ICl.
After another 1.5 hours at 25-26C, the slurry was Filtred, the cake was
washed with two 50 ml portions oF n-heptane ancl dried at ca. 10CC/50 Torr
(mm Hg). There was obtained 86 g (62% yield) oF 2,2'-thio-bis-~,6-cIi-t-
butylresorcinol, m.p. 217-8C.
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