Note: Descriptions are shown in the official language in which they were submitted.
111P6~S2
This invention relates to novel benzofuranylphenols.
This application is a division of Canadian Patent
Application S.N. 251,889, filed April 22, 1976.
Several benzofuranylphenols are described in the
prior art without discussion of utility. For example,
Coxsworth, 45 Can. J. Chem. 1777 (1967), teaches preparation
of 2-(5-methyl-3-benzofuranyl)-4-methylphenol and 2-(5-methyl-
7-t-butyl-3-benzofuranyl)-4-methyl-6-t-butylphenol. Coxworth,
44 Can. J. Chem. 1092 (1966), teaches preparation of chlori-
nated 2-(3-benzofuranyl)phenols. New stabilizers and new
stabilized organic compositions are desired.
Some benzofuranylphsnols are effective stabilizers
of a wide variety of organic materials against the deleter-
ious effects of oxygen, heat and visible or ultraviolet light.
The benzofuranylphenols are especially useful as nonstaining
stabilizers for dienic polymers and styrene-acrylonitrile
copolymers. Benzofuranylphenols suitable for use as such
stabilizers have the formula
Y ~Y
wherein each X and Y may be hydrogen, halogen, hydroxyl, or
an alkyl, alkoxyl or alkylthio group containing from 1 to 8
carbon atoms, but if any X is an alkyl, alkoxyl or alkylthio
group, then at least one Y must also be an alkyl, alkoxyl
or alkylthio group. Also suitable are the products of a
process comprising (1) reacting glyoxal with a dihydroxy-
lated compound in the prese~ of an acidic catalyst, the
dihydroxylated compound having the formula
-- 1 --
5~
~H OH
[~M
M
wherein each M is hydrogen, halogen or an alkyl group con-
taining 1 to 8 carbon atoms, and (2) thereafter hydrolyzing
the step (1) reaction product with an acidic or basic .
catalyst.
The present invention is particularly concerned
with novel benzofuranylphenols of the above.~formula and in
particular 2-(5-t-butyl~3-benzofuranyl)-4-t-butylphenol, 2-
(5,7-dimethyl-3-benzofuranyl)-4,6-dimethylphenol; 2-(5,6-
dimethyl-3-benzofuranyl)-4,5-dimethylphenol; 2-(4,6-di-
methyl-3-benzofuranyl)-3,5-dimethylphenol; 2-(5,7-di-t-
butyl-3-benzofuranyl)-4,6-di-t-butylphenol and 2-(5-methyl-
thio-6-methyl-3-benzofuranyl)-4-methylthio-5-methylphenol.
,
. ~ In another aspect of the invention there is
provided a stabilized composition comprising (a) 100 parts
by weigh* of an organic material subject to the deleterious
effects of oxygen, heat and light and (b) from about O.l parts
to about 10 parts by weight of at least one compound of the
! invention as set forth in the preceding paragraph.
~ .
.
.
~, .
: - 2 -
.,
. ~ , . ~ .
-
6852
Preferred benzofuranylphenols for use as
stabilizers include those of the above formula in which
each X and Y is hydrogen, bromo, chloro, hydroxyl or an
alkyl or alkylthio group containing from 1 to 8 carbon
atoms, but if any X is an alkyl or alkylthio group,
then at least one Y must also be an alkyl or alkylthio
group, . Even-more preferably each X and Y is hydrogen,
hydroxyl or an alkyl or alkylthio group containing from
1 to 4 carbon atoms,
~?6~352
but if any X is an alkyl or alkylthio group, then at least one
Y must also be an alkyl or alkylthio group. Examples of suit-
able benzofuranylphenols include 2-(6-methyl-3-benzofuranyl)-
5-methylphenol, 2-(5-methyl-3-benzofuranyl)-4-methylphenol,
2-(5-t-butyl-3-benzofuranyl)-4-t-butylphenol~ 2-(5-methyl-7-
t-butyl-3-benzofuranyl)-4-methyl-6-t-butylphenol, 2-(5-t-
butyl-7-methyl-3-benzofuranyl)-4~butyl-6-methylphenol,
2-(5,7-dimethyl-3-benzofuranyl)-4,6-dimethylphenol, 2-(4,7-
dimethyl-3-benzofuranyl)-3,6-dimethylphenol, 2-(5,6-dimethyl-3-
benzofuranyl)-4,5-dimethylphenol, 2-(4,6-dimethyl-3-benzo-
furanyl)-3,5-dimethylphenol, 2-(5,7-di-t-butyl-3-benzofuranyl)-
4,6-di-t-butylphenol, 2-(5-methylthio-6-methyl -3-benzofuranyl)-
4-methylthio-5-methylphenol and the like. The reaction products
of hydroquinone or 4-t-butyl catechol with glyoxal by the
process described herein, are also suitable. Excellent
results were obtained using 2-(5-methyl-3-benzofuranyl)-4-
methylphenol, 2 (5-t-butyl-3-benzofuranyl)-4-t-butylphenol,
2-(5,7-dimethy1-3-benzofuranyl)-4,6-dimethylphenol, 2-(5,6-
dimethyl-3-benzofuranyl)-4,5-dimethylphenol, 2-(4,6-dimethyl-
3-benz~furanyl)-3,5-dimethylphenol, 2-(5,7-di-t-butyl-3-
benzofuranyl)-4,6-di-t-butylphenol, 2-(5-methyl-7-t-butyl-3-
benzofuranyl)-4 methyl-6-t-butylphenol, and 2-(5-methylthio-
6-methyl-3-benzofuranyl)-4-methylthio-5-methylphenol.
Excellent results were also obtained using the reaction
products of hydroquinone or 4-t-butyl catechol with glyoxal
described herein. In contrast, 2-(7-methyl-3-benzofuranyl)-
6-methylphenol is not covered by the above formula and was
found to be an ineffective antioxidant. Suitable benzofuranyl-
phenols may be used in an amount from about 0.1 to about 10
parts by weight, more preferably from about 0.5 part to
about 5 parts by weight, per 100 parts by weight of organic
material to be stabilized.
-4-
..
.
68S2
Benzofuranylphenols are produced by first reacting
glyoxal with a phenol in the presence of an acidic catalyst
at a temperature from about 0C to about 100C, more preferably
from about 0C to about 50C. An acetal is formed during
the first step of the reaction, with acetal yield decreasing
substantially if reaction temperature is above 50C during
the first step. After acetal formation is completed the
second reaction step is performed. Water may be added to
the reaction mixture, and the mixture is refluxed in order to
hydrolyze the acetal and form a benzofuranylphenol . Alterna-
tively, a solld acetal may be separated from the reaction
mixture by filtration in some cases and the acetal thereafter
hydrolyzed by refluxing in the presence of an acid or base
catalyst.
Phenols used in the above process pre~erably have
one unsubstituted position ortho to a hydroxyl group, but
certain groups such as t-butyl and the like may occupy an
ortho position and are displaced during acetal formation if the
other ortho position is occupied by another substituent.
Suitable phenols for use in the above process include m-
cresol, p-cresol, 4-ethylphenol, 4-n-propylphenol, 4-t-butyl-
phenol, 2-methyl-4-t-butylphenol, 2-t-butyl-p-cresol, 2,4-
dimethylphenol, 2,5-dimethylphenol, 3,4-dimethylphenol,
3,5-dimethylphenol, 2,4-di-t-butylphenol, 2,4-di-t-pentyl-
phenol, 2,6-di-t-butyl-4-methylphenol, 4-(methylthio)-m-
cresol, 4-chloro-3-methylphenol and the like. Excellent
results were obtained using p-cresol, 4-t-butylphenol,
2,4-dimethylphenol, 3,4-dimethylphenol, 3,5-dimethylphenol,
2-t-butyl-p-cresol, and 4-(methy~thio)-m-cresol. In contrast,
o-cresol was used to produce 2-(7-methyl-3-benzo~uranyl)-6-
methylphenol, which was an unsatisfactory stabilizer and
not within the scope of the formula given heretofore.
, . ' . .
~68S2
Furthermore, Bisphenol A was reacted with glyoxal by the
process of this invention to form a product which was an
unsatisfactory stabilizer and not within the scope of
the formula given heretofore.
Also suitable as phenolic starting materials for
the process described herein are dihydroxylated compounds
having the formula
- ~H
OH
+ M
~ M
wherein each M may be hydrogen, halogen or an alkyl group
containing 1 to 8 carbon atoms. More preferably each M
may be hydrogen or an alkyl group containing 1 to 4 carbon
atoms. The process comprises (1) reacting glyoxal with a
dihydroxylated compound in the presence of an acidic catalyst
and (2) thereafter hydrolyzing the step (1) reaction product
with an acidic or basic catalyst. Products of the process
just described may be the benzofuranylphenols described
heretofore. However, complex polymeric benzofuranylphenols
tend to form because of the presence of several reactive
hydroxyl groups in each dihydroxylated compound molecule.
Examples of suitable dihydroxylated compounds include hydro-
quinone, catechol, resorcinol, 4-t-butyl catechol and the like.
Excellent results were obtained using hydroquinone and 4-t-
butyl catechol.
The glyoxal may be used in the anhydrous form but
the commercial aqueous solutions of glyoxal are more prefer-
ably used. Derivatives of glyoxal which can generate glyoxal
in situ may also be used, such as glyoxal NaHS04. The
--6--
~68S2
glyoxal may be used in a molar ratio to the phenol from about
1/10 to about 10/1. More preferably, the ratio is about 1/2.
Acids which may be used to catalyze the reaction of
glyoxal with phenols to form acetals include organic acids
containing l to 12 carbon atoms SUCil as acetic acid, propionic
acid, benzoic acid, monoesters and diesters of orthophosphoric
acid, alkaryl sulfonic acids such as p-toluenesulfonic acid,
and the like; inorganic acids capable of releasing protons
such as boric acid, hydrochloric acid, phosphoric acid, sulfur-
ic acid and the like; acid activated clays capable of releas-
ing protons such as Retrol (produced by Filtrol Corp.), benton-
ite and the like; acidic resins capable of releating protons
such as Dowex 50-X10 ~a cationic exchange resins which is a
sulfonated copolymer of styrene and divinylbenzene and is
produced by Dow Chemical Conpany) and the like; and Lewis
acids capable of accepting electrons such as aluminum chloride,
zinc chloride, boron trifluoride and the like. me amount
of acid catalyst used may be as little as about 0.01% based
on total reactant weight, or the catalyst may be used as the
solvent in which the reaction is run. Mixtures of acids may
also be used. Excellent results were obtained using mixtures
of acetic acid and sulfuric acid, zinc chloride and hydro-
chloric acid, and p-toluenesulfonic acid and acetic acid.
The acids described above may also be used at
higher temperature to catalyze hydrolysis of the acetal
in the second reaction step, thereby forming benzofuranyl-
phenols. Bases may be used in place of acids in the second
reaction step. Suitable bases include inorganic bases such
as sodium hydroxide, potassium hydroxide and the like.
Excellent results were obtained using potassium hydroxide.
Acetic acid is a preferred solvent for these
reactions because of its availability, boiling point, water
* trademark 7
1~1D685~: `
miscibility, ability to dissolve a wide variety of phenols,
and catalytic effect on the reaction. The reaction may also
be run in other solvents which include carboxylic acids
s~Lch as o-toluic acid, esters such as n-butyl acetate,
ethers such as bis[2-(2-methoxyethoxy)ethyl]ether, alcohols
such as l-pentanol, ketones such as benzophenone, and the
like. The réaction may also be run in a two-phase system
where one reactant is soluble in one phase and the other
reactant is soluble in a second phase, such as a hydrocarbon
and water system. An emulsifying agent may be u~ed to
facilitate the reaction in the two-phase system.
A preferred method for producing benzofuranylphenols
compr~ises mixing glyoxal and a phenol with a major amount of
acetic acid and a minor amount of sulfuric acid. The reaction
mixture is stirred and cooled below 30C for about one to
three hours. After that time, the temperature is raised to
about 50C, and the reaction is continued for about 0.5
to three more hours in order to complete acetal formation.
The second reaction step is performed by adding water to the
acetal reaction mixture and heating it to reflux temperature.
After about one to five hours the acetal is acid-hydrolyzed
substantially to a benzofuranylphenol.
Another preferred method for performing the second
reaction step (hydrolysis) comprises separating a solid
acetal from the reaction mixture by filtration, mixing the
acetal with water and an acid or base, and ac~d-hydrolyzing
or base-hydrolyzing the acetal to a benzofuranylphenol.
Refluxing is generally required for acidic hydrolysis, but
basic hydrolysis can be performed by simply warming the
mixture to be hydrolyzed at about 50 - 100C in a dimethyl
sulfoxide solution.
The benzofuranylphenol product may be separated
--8--
852
from the hydrolysis mixture ~y any of ceveral
methods. If the product is a solid it can be filtered
and optionally washed with a solvent such as hexane or
water. If the product is an oil it can be extracted with
an aromatic solvent such as benzene. If acidic hydrolysis
is used, the extract can be washed with a weak base or a
basic salt solution such as ~a2C03 in water. If basic
hydrolysis is used, the extract can be washed with a weak
acid or an acidic salt solution in water such as (NH4)2S04
in water. The extract can then be distilled to obtain a
substantially pure benzofuranylphenol.
Benzofuranylphenols within the scope of the
formula recited heretofore are effective stabilizers of a
wide variety of organic materials against the deleterious
effects of oxygen, heat and visible or ultraviolet light.
The benzofuranylphenols are nonstaining stabilizers of both
natural and synthetic polymers, such as uncured and vulcanized
dienic polymers. The dienic polymers are sulfur-vulcanizable
and m~y cont~in about 0.5% to a~)out 50~0 by weight of olefinic
(~C=C<) unsaturation based upon total polymer weight.
The olefinic groups may be in the polymeric main chain (back-
bone) or in pendant (side-chain) groups, or both. Examples
of suitable dienic polymers include polymers such as
natural rubber, cis-polyisoprene, cis-polybutadiene (CB),
acrylonitrile-butadiene-styrene copolymers (ABS), butadiene-
acrylonitrile rubbers (NBR), isoprene-acrylonitrile rubbers,
polyisobutylene, polychloroprene, butadiene-styrene rubbers
(SBR), isoprene-styrene rubbers and the like. Also suitable
are polymers such as isoprene-isobutylene (butyl) rubbers,
copolymers of conjugated dienes with lower alkyl and alkoxy
acrylates such as ethyl acrylate, butyl acrylate, methoxyethyl
acrylate and the like, and ethylene-propylene-diene polymers
_9
'~ ,
~1~6852
(EPDM) containing from about 0.5 percent to about 20 percent
by weiF~ht of at least one dienic termonomer. ~ultable ~.PI)M
dienic termonomel~s include conjugated dienes such as
butadiene, 1,3-pentadiene, and the like; nonconjugated dienes
such as 1~4-pentadiene, 1,4-hexadiene, and the like; cyclic
dienes such as cyclopentadiene, dicyclopentadien~ and the
like; and alkenyl norbornenes such as 5-ethylidene-2-nor-
bornene and the 11ike.
The dienic polymers may be ~ulcanized by methods
known to the art. Suitable vulcanizing agents include
elemental sulfur and compounds capable of yielding elemental
,~ sulfur such as tetramethylthiuram disulfide, tetraethylthi-
uram disulfide, dipentamethylenethiuram hexasulfide, and the
like.
A broad ran~e of compounding ingredients can be
used in the dienic polymer vulcanizates, including sulfur-
containing and nitrogen-containing accelerators. Examples
of suitable accelerators include metal salts of dialkyl,
diaryl and alkaryl dithiocarbamates, such as bismuth, copper,
lead and zinc dimethyl dithiocarbamates, cadmium, selenium,
tellurium and zinc diethyl dithiocarbamates, sodium and
zinc dibutyl dithiocarbamates, zinc ethyl phenyl dithio-
carbamate, zinc dibenzyl dithiocarbamate, and the like;
other dithiocarbamates such as piperidinium pentamethylene
dithiocarbamate, N-cyclohexylethyl ammonium cyclohexylethyl
dithiocarbamate, N-pentamethylene-ammonium-N-pentamethylene
dithiocarbamate, and the likej benzothiazoles such as 2-
mercaptobenzothiazole and the zinc salt thereof, 2,2'-
benzothiazyl disulfide, 2-morpholinothiobenzothiazole,
3~ 2-(2,(-(limethyl-4-morpholinothio)benzotlliAzole and the Like;
I-enzothiazole-sulfenamides such as N-diethyl-2-benzottliazyl
sulfenamide, N-t-butyl-2-benzothiazole sulfenamide, N-cyclo-
--10--
g~ 68sZ
hexyl-2-benzothiazole sulfenamide, N-oxydiethylene-2-benzo-
thia.zole sulfenamide and the like; thiuram sulfides such as
tetramethyl thiuram disulfide, tetraethyl thirlram llisull`:ide,
dimethyl diphenyl thiuram disulfide, dipentalnet}lylenc thiuram
hexasulfide and the like; thioureas such as ethylene thiourea,
trimethyl thiourea, N,N'-diethyl thiourea, N,N'-dibutyl
thio'urea, N,N'-diphenyl thiourea, and the like; morpholines
such as 4,4'-dithiomorpholine and the like; polyamines such
as triethylene diamine, hexamethylene tetraamine, tricreto-
nylidene tetraamine, and the like; aldehyde-amine condensa-
tion products such as acetaldehyde-ammonia, heptaldehyde-
ammonia, butyraldehyde-aniline, and the like, imidazolines
such as 2-mercaptoimidazoline, and the like, and guanidines
such as diphenyl guanidine, di-o-tolyl guanidine, and the
].ike. Excellent results were obtained using 2-morpholino-
thiobenzothiazole.
Benzofuranylphenols within the scope of the formula
recited heretofore are also effective nonstaining antioxi-
dants in styrene-acrylonitrile copolymers. Suitable copolymers
for use in the compositions of this invention contain polymer-
ized therein (l) from about 50% to about 90% by weight based
upon total copolymer weight of styrene, or at least one
alkyl styrenc~ alkoxy :;tyrene or halostyrenc, r ~ lixt;~lle
thereof, wherein the alkyl or alkoxy group contains from 1
to 8 carbon atoms, (2) from about lO~ to about 50% by
weight based upon total copolymer weight of at least one
vinyl nitrile having the formula
,R
CH2=C-C_N
wherein R is hydrogen or an aIkyl radical containing from 1
to 3 carbon atoms, and (3) from 0~ to about 20% by weight
based upon total copolymer weight of at least one other
--11--
85;~
monoolefin. Preferred alkyl styrenes are those wherein an
aIkyl ~roup contains from 1 to 6 carbon atoms, more prefer-
ably from 1 to 4 ca~bon atoms. Preferred alkoxy styrenes
are those wherein an alkoxy group contains from 1 to 6 carbon
atoms, more preferably from 1 to 4 carbon atoms. Preferred
halostyrenes are those ~herein a halogen group is chloro or
bromo. Examples of suitable alkyl styrenes, alkoxy styrenes
and halostyrenes include methyl styrene, ethyl styrene,
methoxyethylstyrene, chlorostyrene, dichlorostyrene, and
the like. F~mples of suitable vinyl nitriles include
acrylonitrile, methacrylonitrile, ethacrylonitrile, and the
like. Excellent results were obtained using copolymers of
styrene and acrylonitrile.
Other compounding ingredients usable in the dienic
pol~mer compositions and styrene-acrylonitrile copolymers
include fillers such as carb`on blacks, calcium and magnesium
carbonates, caIcium and barium sulfates, aluminum silicates,
silicon dioxide, phenol-formaldehyde and polystyrene resins,
asbestos, and the like; plasticizers and extenders including
dialkyl and diaryl acid esters such as diisobutyl, diiso-
octyl, diisodecyl and dibenzyl oleates, stearates, sebacates,
azelates, phthalates, and the like~ and naphthenic and
paraffinic oils, castor oil, tall oil and the like; and
antioxidants, antiozonants and stabilizers such as di-~-
naphthyl-p-phenylenediamine, phenyl-~-naphthylamine,
N,N'-di-~2-octyl)-p-phenylenediamine, 2,2'-methylene-bis
(4-methyl-6-t-butylphenol), 2,6-di-t-butyl-p-cresol,
2,2'-thiobis(4-methyl-6-t-butylphenol), distearyl thiodipropion-
ate, dilauryl thiodipropionate, 2,4-bis(4-hydroxy-3,5-t-butyl-
phenoxy)-6-(n-octylthio)-1,3,5-triazine, tetrakis methylene
3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate methane,
4-isopropylamino diphenylamine, tri(nonylated phenyl)phosphite,
~ 68~2
and the like, Other compounding ingredients may also be used,
such as pigments, tackifiers, flame retardants, fungicides,
and the ]ike.
In addition to polymeric materials, the present benzo-
furanylphenols act to stabilize a wide variety of other organic
materials. Such materials include: waxes' synthetic and
petroleum-derived lubricating oils and greases, animal oils
such as fat, tallow, lard, cod-liver oil, sperm oil and the
like; vegetable oils such as castor, linseed, peanut, palm,
cotton seed and the like; fuel oil; diesel oil; gasoline, and -
the like.
The following examples illustrate the present
invention more fully.
EXAMPLE 1 - Preparation of 2-(7-methyl-3-benzo-
furanyl)-6-methylphenol
o-cresol (44 g. or 0.4 mole), 40% aqueous glyoxal
(30 g. or 0.2 mole), and acetic acid (200 ml.) were mixed
together. Concentrated sulfuric acid (80 ml. or 1.5 mole)
was added to the reaction mixture with stirring over a 60-
minute period. The mixture was stirred for a total of about3 hours with cooling as needed to keep reaction temperature
at about 30C. The mixture was heated thereafter to 50C and
stirred for about 1 hour. Water (100 ml.) was added and the
mixture refluxed for about 1.5 hours. The mixture then was
cooled and poured into 2 liters of water, and a solid was
separated therefrom. The solid was filtered and washed first
with water and then with 0.1 normal Na2CO3 solution in water.
The product weighed 44 g. The 2-(7-methyl-3-benzofuranyl)-6-
methylphenol was found to be an unsatisfactory stabilizer
in a vulcanized rubber composition.
_ 13 -
.
. :
6~S2
EXAMPLE 2 - Preparation of 2-(5-methyl-3-ben~o-
fu ranyl)-4-methylphenol
p-cresol (86.4 g. or o.8 mole), 40% aqueous glyoxal
(80 g. or 1.4 mole), and acetic acid (200 ml.) were mixed
together. Concentrated sulfuric acid (80 ml.) was added to
the reaction mixture with stirring over a 60-minute period.
The mixture was stirred for a total of about 3 hours with
cooling as necessary to keep reaction temperature at about
30C. The mixture was then allowed to stand overnight.
The acetal intermediate formed and was a solid. It was
collected by filtration, washed with 400 ml. of water, and
allowed to dry. It weighed 90 g. (95~ yield based on p-cresol)
and melted at 150-165C. This solid was dissolved in 200 ml.
of acetic acid, 10 ml. of water, and 2 ml. of concentrated
sulfuric acid. This solution was refluxed for 2 hours,
cooled and neutrali~ed with a solution of 4 g. of sodium
hydroxide in 10 ml. of water. The solvents were distilled
to give 77 g. of a black viscous oil. This oll was distilled
to give a light yellow oil(~.p. 120-145C/0.5 mm ).
EXAMPLE 3 - Preparation of 2-(5-t-butyl-3-benzo-
furanyl)-4-t-butylphenol
4-t-Butylphenol (60 g. or 0.4 mole ), 4S~ aqueous
glyoxal (30 g. or 0.2 mole), and 200 ml. of acetic acid were
mixed together. Concentrated sulfuric acid (80 ml.) was
slowly added (1 hour at 30C), and the mixture was stirred
for another ? hours at 30C and thereafter heated to 50C
for 0.5 hour. ~00 ml. of water was added and the mixture
was refluxed for 1.5 hours, cooled, poured into 1.5 liters
of water, and the product separated. The oily product was
washed with O.lN Na2C03 solution.
-14--
sz
EXAMPLE 4 - Preparation of 2-(5-t-butyl-7-methyl-
3-benzofuranyl)-4-t-butyl-6-methyl-
phenol
2-Methyl-4-t-butylphenol (~4 g. or 0.4 mole) and
acetic acid (200 ml.) were mixed together. Concentrated
sulfuric acid (80 ml.) was added to the reaction mixture
with stirring over a 60-minute period. The mixture was
stirred for a total of about 2 hours with cooling as needed
to keep reaction temperature at about 30C. The mixture was
- 10 heated thereafter to 50C and stirred for about 0.5 hour.
Water (lO0 ml) was added and the mixture refluxed for about
l.5 hours. The mixture then was cooled and pured into 1.5
! - liters of water, and a black oil was separated therefrom.
The oil was washed with a 0.1 normal Na2C03 solution in water~
and unreacted 2-methyl-4-t-butylphenol was removed by dis-
tillation. The product weighed 76 g. The product's IR
8pectrum was consistent with the assigned structure of
2-(5-t-butyl-7-methyl-3-benzofuranyl?-4-t-butyl-6-methyl-
phenol.
PLE 5 - Preparation of 2-(5,7-dimethyl-3-benzo-
- furanyl)-4,6-dimethylphenol
2,4-Dimethylphenol (49 g. or 0.4 mole), 40%
aqueous glyoxal (29 g. or 0.2 mole), and acetic acid
(250 ml.) were stirred together and 80 ml. of concentrated
sulfuric acid added in 1 hour. The reaction temperature was
maintained between 20 - 30C by cooling during the addition.
The temperature was raised to 50C for 1 hour. The mixture
was cooled, fiItered~ and washed with water to separate an
acetal intermediate, which was refluxed for 4 hours with
250 ml. of acetic acid and 5 ml. of concentrated hydrochloric
acid. The cool reaction mixture was poured into 1.5 liters
of water and the oil separated. It weighed 32 g., and its
IR spectrum was consistent with the assigned structure of
; 2-(5,7-dimethyl-3-benzofuranyl)-4,6-dimethylphenol.
-15-
"' ' '
~61352
EXAMPLE 6 - Preparation of 2-(5-methyl-7-t-
butyl-3-benzofuranyl)-4-methyl-6-
t-butylphenol
A mixture of zinc chloride (3 g.), 2-t-butyl-p-
cresol (65.7 g. or 0.5 mole), and 30~ aqueous glyoxal
(20 g. or 0.5 mole), and 30~ aqueous glyoxal (20 g. or 0.1
mole) was stirred and gaseous HCl bubbled into the mixture
for 0.5 hour. The temperature was kept below 35C by
cooling. The mixture stood overnight, after which HCl was
bubbled through the mixture for 3 hours more with the
temperature maintained between 10 - 20C by cooling.
A light gray solid formed. This solid was filtered and
washed first with water and then O.lN Na2C03 solution.
The white solid melted at 188 - 192C and was the acetal
described in U.S. Patent 2,515,909. The acetal, weighing
11 g., was slurried in 100 ml. of dimethylsulfoxide. A solu-
tion of potassium hydroxide (10 g.), ethanol (100 ml.), and
dimethylsulfoxide (100 ml.) was added directly to the acetal
slurry. This mixture was heated to reflux under nitrogen
for 4 hours. The mixture was poured into 1 liter of water
which contained 15 ml. of concentrated hydrochloric acid.
A solid formed and was collected by filtration and washed
with water. It weighed 9 g. and melted at 132 - 134C.
Its paramagnetic resonance and IR spectra were consistent
with the assigned structure of 2-(5-methyl-7-t-butyl-3-
benzofuranyl)-4-methyl-6-t-butylphenol.
EXAMPLE 7 - Preparation of 2-(5,6-dimethyl-3-benzo-
furanyl)-4,5-dimethylphenol
To a mixture of 3,4-dimethylphenol (62 g. or 0.5
mole), 40~ aqueous glyoxal (23 g. or 0.15 mole 3, and acetic
acid (200 ml.), was slowly added (0.5 hour) 30 ml. of con-
centrated sulfuric acid. The mixture was stirred at 50C
-16-
.
.
3S2
for 2 hours, cooled, and poured into 1.5 liters of water
to give 44 g. of a solid acetal. 40 g. of this acetal was
slurried in 250 ml. of dimethylsulfoxide, and a solution of
40 g. of potassium hydroxide in 250 ml. of methanol and
250 ml. of dimethylsulfoxide was added. This mixture was
refluxed for 2 hours, cooled, poured into 2 liters of water,
and extracted with benzene. The benzene was removed by
distillation to give 44 g. of a dark oil. Its IR spectrum
was consistent with the assigned structure of 2-(5,6-dimethyl-
3-benzofuranyl)-4,5-dimethylphenol.
EXAMPLE 8 - Preparation of 2-(4,6-dimethyl-3-benzo-
furanyl)-3,5-dimethylphenol
A stirred mixturé of 3,5-dimethylphenol (25 g. or
0.2 mole), 40% aqueous glyoxal (15 g. or 0.1 mole) and acetic
acid (150 ml. ? was maintained at 30C while 15 ml. of concen-
trated sulfuric acid was added in 0.5 hour. The mixture was
stirred 2 hours more at room temperature and then at 50C
for 0.5 hour. Water (35 ml.) was added and the mixture
refluxed for 1.5 hours. It was cooled and poured into 1
liter of water to give 18 g. of a black solid . The solid
was separated by filtration and had an IR spectrum consistent
with its structural assignment of 2-(4,6-dimethyl-3-benzo-
furanyl)-3,5-dimethylphenol.
EXAMPLE 9 - Preparation of 2-(5,7-di-t-butyl-3-
benzofuranyl)-4~6-di-t-butylphenol
A mixture of 2,4-di-t-butylphenol (82 g. or 0.4
mole), 40% aqueous glyoxal (30 g. or 0.2 mole), and acetic
acid (400 ml.) was treated with 80 ml. of concentrated
sulfuric acid while maintaining the temperature at 30C.
After 2 hours, the solid was collected by filtration.
Vapor phase chromatography showed that it was 30~ starting
phenol and 70~ acetal. The phenol was removed by washing
-17-
6~S2
with methanol. The substantially pure acetal remained, melted
at 236-238C, and weighed 51 g. This acetal (30 g.) was
dissolved in 100 ml. of benzene and 200 ml of dimethylsulfox-
ide. The acetal solution was treated with a solution of 20 g.
of potassium hydroxide in 200 ml. of methanol and 200 ml. of
dimethylsulfoxide. This mixture was refluxed for 2 hours,
cooled, poured into 1 liter of water, acidified with concen-
trated hydrochloric acid and extracted with ether. The ether
extract was washed with water and distilled to give 34 g. of
a yellow oil (b.p.220C/ 1 mm ). Its VPC and IR spectra
were consistent with the assigned structure of 2-(5,7-di-t-
I butyl-3-benzofuranyl)-4,6-di-t-butylphenol.
EXAMPLE 10 - Preparation of 2-(5-methylthio-6-methyl-
3-benzofuranyl)-4-methylthio-5-methyl-
phenol
A mixture of 4-(methylthio)-m-cresol (31 e or 0.2
mole), 40~ aqueous glyoxal (15 g. or 0.1 mole), and 150 ml.
of acetic acid was treated with 15 ml. of concentrated sulfuric
acid while maintaining the temperature below 30C for 2 hours.
Temperature was raised thereafter to 50C for 0.5 hour,
30 ml-of water was added to the mixture, and it was refluxed
for 1.5 hours, cooled, and poured into 1 liter of water.
An oil was separated and washed with a 0.lN Na2C03 solution
to yield 2-(5-methylthio-6-methyl-3-benæofuranyl)-4-methyl-
thio-5-methylphenol.
EXAMPLE 11 - Reaction of hydroquinone and glyoxal,
followed by hydrolysis
A mixture of hydroquinone (66 g. or 0.6 mole), 40
aqueous glyoxal (90 g. or o.6 mole), and 500 ml. of acetic
acid was treated with 60 ml. of concentrated sulfuric acid
while maintaining the temperature at 30C for 2 hours.
The mixture was then heated for 2 hours at 40 - 50C., poured
into 2 liters of water, ~iltered, washed with O.lN Na2C03,
-18-
52
and dried to yield 62 g. of a gray solid acetal. This acetal
(25 g.) was stirred with 100 ml. of dimethylsulfoxide. To
th~is mixture was added a solution of 25 g. of potassium
hydroxide, 200 ml. of methanol, and 200 ml. of dimethylsulf-
oxide. A dark brown ~ixture resulted and was stirred and
re~luxed for 4 hours. It was poured into 2 liters of water
and acidified with concentrated hydrochloric acid. A black
resin was collected by filtration and washed with O.lN
Na2C03. The resin's IR spectrum was consistent with a polymeric
benzofuranylphenol structure.
EXAMPL~ 12 - Reaction of 4-t-butyl catechol and
glyoxal, followed by hydrolysis
A mixture of 4-t-butyl catechol ~32.3 g. or 0.2
mole) 40/' aqueous glyoxal (15 g. or 0.1 mole) and acetic
acid (150 ml.) was treated with 15 g. of concentrated sulfuric
acid while maintaining the temperature at 30C for 2 hours.
The mixture was then heated for 0.5 hour at 50C, poured into
35 ml. water and stirred and refluxed for 1.5 hours.
The mixture was cooled and poured into 1 liter of water .
- 20 A black oil formed and was extracted with benzene and washed
with a O.lN Na2C03 solution. The extract was distilled to
give 21 g. of product.
EXAMPLES 13 - 31
.
Examples 13 - 31 demonstrate stabilizing properties
of benzofuranylphenols in cured rubber vulcanizates. A master-
batch was prepared by mixing the following materials in a
banbury mixer:
TABLE I
MaterialsParts by Wei~ht
Ribbed Smoked Sheet100.0
Natural Rubber
HAF Carbon Black 50.0
Zinc Oxide 5.0
Stearic Acid 3.0
Sulfur 2.5
160.5
-lg~
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.
6~i2
In each example, 176 g. of the masterbatch described in
Table I was compounded and cured with 1.1 gram of
2-morpholinothiobenzothiazole accelerator and 1.1 gram of
a given stabilizer. The compounding and curing procedure
was as follows. A 4-inch, 2-roll mill was heated to 160F
and each ingredient was charged to the mill in the order
listed, with thorough milling between each addition.
Each milled rubber composition was sheeted off the mill and
cut into approximate 6 in. x 6 in. x 0.090 in. sections.
The sections were wrapped separately in aluminum foil and
cured for 35 minutes at 302F.
Physical testing of the vulcanizates was performed,
and the results are set forth in Tables II, III and IV.
300~ modulus, tensile strength and ultimate elongation were
determined according to ASTM D412-68 using Die C dumbbells.
Test tube aging was performed according to ASTM Do65-62 for
24 hours at 100C. Crack Growth Test results in Table II
were measured using the B.F.Goodrich Rotating Ring Crack
Growth Test described in 38 Rubber Chemistry & Technology
714 (1965). Standard conditions used for the latter test
were 70C., 3 lbs. load and 300 cycles/minute.
The data in Tables II, III and I~ indicates that
thc benzofuranylphenols tested have stabilizing properties
as good as or better than control stabilizers when tested
in cured rubber vulcanizates.
-20-
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-23-
~1~6Z~52
EXAMPLES 32 - 34
Examples 32 - 34 demonstrate stabilizing properties
of benzofuranylphenols in uncured SN rubber. In each example,
o.68 g. of a given stabilizer was mixed with 68 g. of repre-
cipitated SN rubber in a Brabender Plasticorder for 2 minutes
at 80C. Each sample was prepared and tested for Mooney
viscosity before and after aging according to ASTM D-1646-72
uslng a large rotor and a l-minute warm-up time. Mooney
buttons were aged at 70C for 10 days in an oven according
to ASTM D-573-67. Test results are summarized in Table V.
The Mooney viscosity data indicates that the benzofuranyl-
phenols maintain Mooney viscosity as well as or better than
the control stabilizer.
-24-
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--25--
.
352
EXAMPLES 35 - 42
Examples 35 - 42 demonstrate stabilizing properties
of benzofuranylphenols in a styrene-acrylonitrile (SAN)
copolymer composition. The SAN copolymer contained about
30~ by weight acrylonitrile based upon total copolymer weight
and had a weight-average molecular weight of about 118~000
and a number-average molecular weight of about 51,000.
In each example, about 75 g. of SAN copolymer was mixed in
a Brabender Plasticorder fitted with a cam head. Mixing was
performed at 175C and 30 rpm until fluxing occurred (typi-
cally about 1.5 minutes after mixing began). At that time,
! 75 g. more of SAN copolymer and 0.75 gram of a given stabil-
izer were charged to the Brabender, and mixing was continued
for about another 2.5 minutes. The mix was dumped, cold-
pressed into sheets about 0.25 inch thick, cut into 0.25
inch cubes, pressed into 6 in. x 6 in. x 0.02 in. sheets
at 175C for about 4.5 minutes, cooled, and cut into
1 in. x 1 in. x 0.02 in. squares which were aged at 100C
in a circulating oven for varying times shown in Table VI.
A Brinkman Fiber Optics Probe Colorimeter Model PC-100 was
used to measure percent light transmission at 450 nm of
heat-aged samples in comparison to unaged samples. Reduced
light transmission indicates increased color development
and is a measure of increased copolymer oxidation. Test
results are summarized in Table VI. The data indicates
the benzofuranylphenols have stabilizing properties as
good as or better than the control stabilizers.
-26-
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--27 -
