POLYHYDROXY PHENOLS AND PROCESS FOR THEIR PREPARATION

PREPARATION DE POLYHYDROXYPHENOLS

English Abstract

ABSTRACT OF THE DISCLOSURE
Polyhydroxy phenol according to the formula:
<IMG>
where R is an alkyl radical containing from 1 to 10
carbon atoms, the methylene bridges being bonded to
the central phenol ring in the ortho- positions in
relation to the hydroxyl group and to the other phenol
rings in the ortho- or para- positions in relation to
the hydroxyl group.
This polyhydroxy phenol can be used as antioxi-
dants for plastics materials and stabilizers for unsaturated
polyester resins, and for preparing epoxy resins, novolaks
and resols.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A polyhydroxy phenol defined by the formula;
<IMG>
where R is an alkyl radical containing from 1 to 10 carbon
atoms, the methylene bridges being bonded to the central
phenol ring in the ortho- positions in relation to the
hydroxyl group, and to the other phenol rings in the ortho-
or para- position in relation to the hydroxyl group.
2. A process for preparing the polyhydroxy phenol
of claim 1, which comprises:
(a) reacting formaldehyde and a substituted phenol of the
formula:
<IMG>
where R is an alkyl radical containing from 1 to 10 carbon
atoms, in a formaldehyde/phenol molar ratio of at least 2:1
in the presence of an inorganic base and at a temperature
of at least 40°C, thereby to form a dimethylol derivative
of said phenol;
(b) adding an acid to the reaction products of (a) in an
amount at least equivalent to that of said inorganic base
and in the presence of water, and separating the aqueous
phase and the dimethylol derivative phase thus obtained;
(c) adding to said dimethylol derivative phase an organic
solvent capable of dissolving said derivative, normally
13

immiscible or slightly miscible with water and forming with
the latter an azeotropic mixture, contacting the resulting
solution with phenol in a molar ratio between said phenol
and said derivative of at least 2:1, in the presence of an
acid catalyst and at a temperature of at least 100°C, and
maintaining the resulting mixture at boiling point until
substantially complete reaction of said derivative with said
phenol, while distilling the forming water as an azeotrope
with said organic solvent; and
(d) recovering the polyhydroxy phenol from the reaction
products of (c).
3. The process of claim 2, wherein said substituted
phenol is selected from the group consisting of para-tert-
butylphenol, para-cresol, para-octylphenol, para-amylphenol
and para-nonylphenol.
4. The process of claim 2, wherein said formaldehyde
is fed into the reaction medium of (a) in the form of an
aqueous solution or a substance which frees formaldehyde
under the reaction conditions.
5. The process of claim 2, wherein said formaldehyde/
phenol molar ratio is from 2:1 to 3:1.
14

6. The process of claim 2, wherein said inorganic base
is an alkali metal hydroxide, the molar ratio between said
inorganic base and said substituted phenol being from
0.3:1 to 1:1.
7. The process of claim 2, wherein stage (a) is carried
out at a temperature of from 40 to 80°C.
8. The process of claim 2, wherein stage (a) is carried
out for a period of from 1 to 4 hours.
9. The process of claim 2, wherein the reaction mixture
of (a) does not contain more than 50% by weight of water.
10. The process of claim 2, wherein said acid of (b) is an
inorganic acid.
11. The process of claim 29 wherein said acid of (b) is
selected from the group consisting of hydrochloric, sulphuric
and phosphoric acids.
12. The process of claim 2, wherein said acid of (b) is added
in an amount such as to bring the pH to a value of from
2 to 6.5.
13. The process of claim 2, wherein said organic solvent
is an aromatic hydrocarbon having a boiling point not exceeding
160°C.

14. The process of claim 2, wherein said phenol of (c)
is used in an amount of from 2 to 3.5 moles for each mole
of substituted phenol used in (a).
15. The process of claim 2, wherein said mixture of (c)
is boiled a t a temperature of from 100 to 160°C.
16. The process of claim 2, wherein said acid catalyst is
an organic acid.
17. The process of claim 2, wherein said acid catalyst
is an acid having an acid dissociation constant, or else
(in the case of a polybasic acid) a first acid dissociation
constant above 1.10-5.
18. The process of claim 2, wherein said acid catalyst is
selected from the group consisting of oxalic, benzoic, para-
tert-butylbenzoic, salicylic and isophthalic acids.
19. The process of claim 2, wherein said acid catalyst is
used in an amount of from 0.1 to 5 parts by weight for each
100 parts of phenol.
20. The process of claim 2, wherein state (c) is carried out
for a period of from 2 to 4 hours.
' ' I
16

21. The process of claim 2, wherein said polyhydroxy
phenol is recovered by precipitating the acid catalyst
and removing the resulting precipitate, and distilling
off the organic solvent and the unreacted phenol present
in said reaction products of (c).
17

Description

~ 71
: `
This invention relal;es to new polyhydroxy phenols
defined by the following formula:
O~ ~ OH
I OH
(I) ~ C~2 - ~ C~I2
R
where R is an alkyl radical contalning from 1 to 10 carbor
atoms, the methylene bridge being bonded to the central
.
phenol rin~ in the ortho- positions in relati.on to the
.: hydroxyl eroup~ and to the other phenol rings in the ortho-
~, . .
or para po~ition in relation to the hydro~yl group.
The invention also concerns a method for preparing
the said polyhydroxy phenols, by reacting formaldehyde with
phenol substituted in the para position with an allcyl group
with from 1 to 10 carbon atoms, to give the dimethylol
derivative by substitution with two methylol groups in the
:
I ortho positlons in relation to the hydroxyl group o~ the said
-~ substituted phenol, and the said dimethylol derivative is
'
I reacted with phenol to give a polyhydroxy phenol (I).
`I .
-l~ In the followillg de~cription:
~ - by "para-substituted phenol" there is meant phenol sub~
i1 stituted ln the para position in relation to the phenolic
~¦ hydroxy group with an alkyl group having from 1 to 10 carbon
;1 atoms;
.1 .
¦ - by "dimethylol derlvative", or else by "dimethylol inter-
mediate" there is meant the para-substituted phenol sub~tituted
with two methylol groups in the ortho positions in relation
_ _
, ~

1~'78~7~ -
~o the hydroxyl ~roup.
- by "polyhydroxy phenol" there is meant a compound according :
to formula (I).
The methodfor preparing the polyhydroxy phenol of
this invention comprises the following stages:
(a) reacting formaldehyde and a substituted phenol of the ~.
formula:
HQ ~ R
where R is an alkyl radical containing from 1 to 10 carbon
atoms, in a formaldehyde/phenol molar ratio of at least 2:1,
in the presence of an inorganic base and at a temperature of
at least 40C, thereby to form a dimethylol derivative of
said phenol;
~ (b) adding an acid to the reaction products of (a) in an
; amount at least equivalent to that of said inorganic base and
. in the presence of water, and separating the aqueous phase
and the dimethylol derivative phase thus obtained;
(c) adding to said dimethylol derivative phase an organic
:~ solvent capable of dissolving said derivative, normally
immiscible or slightly miscible with water and forming with
the latter an azeotropic mixture, contacting the resulting
solution with phenol in a molar ratio between said phenol
and said derivative of at least 2:1, in the presence of
an acid catalyst and at a temperature of at least 100C, and
maintaining the resulting mixture at boiling point until
: substantially complete reaction of said derivative with said
~ phenol, while distilling the iorming wate~ as an a~eotrope
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~ithi ~iaid organic solvc~t; and
. (d) recovering the polyhydroxy phenol from tlle reaction
. products of ~c).
Stage a
. According to the process of this invention forMaldehyde
~ ~ is reacted with a para-substituted phen-ol, the~atter bein~
; preferably chosen from para-tert-butylphenol 9 para-cresol,
; para-octylphenol, para-amylphenol and para~llonylPhenol. The
~: formaldehyde can be fed into the reaction medlum as an
aqueous solution, especially in the form of those comme}cial
;; aqueous solutions which have a formaldehyde content of the
order of 37-38% by weight. Low polymers of formaldehyde,
: such as paraformaldehyde, or anyway, any substance which
- frees formaldehyde under the reaction condit:ions can also
be used for the purpose.
The reaction is catalyzed by an inorganic base and
pre~erably an alkali metal hydroxyde, such as sodium, potassium
or lithium hydroxide.
j.~ The molar ratio of the forn~aldehyde to the parasubGitituted.1 .
phenol is generally from 2:1 to 3:1 and that of the inorganic
base to the said p~ra-substituted phenol generally from 0.3i1
to 1~
Further~ the reaction is preferably carried out at a
; . .
! .I temperàture of from 40 to 8CiC and for a time such as to
:. ensure complete reaction of the para-substituted phenol or
. . ~ ~ - .
at least until the concentratlon of the latter is reduced to
-
~- va~ues below 0.5% by weig~lt in the reaction mediumO The
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reaction time is ~enerally rom 1 to 4 hours,
The way of contacting the reagents i~ not critical,
but it is preferable to yradually add an aqueous solution
of the inorganic base to the reaction medium containing
formaldehyde and the para-substituted phenol, and to
maintain the reaction mixture at the reaction temperature
for a certain length of time at the end of the addition of
the inorganic base.
The reaction is generally carried out in the presence
of water. Preferably, the reaction mixture should not contain
more than 50~ by weight of water.
In the preferred embodiment, the molar ratio of
alkali metal hydroxide to para-substituted phenol is
maintained at about 0.5:1 and that of formaldehyde to
para-substituted phenol at about 2.5:1. Further the reaction
: is carried out at a temperature of the order of 60C, aqueous
sodium hydroxide being fed gradually into the reaction medium.
Under these conditions, the para-substituted phenol reacts
almost completely with the formaldehyde in a period of about
2.5 hours.
Stage b
. .
An acid is added to the reaction products from
stage a) in an amount at least equivalent to that of the
inorganic base fed in stage a)~
Organic acids may be used for the purpose, but
mineral acids, such as, for example, hydrochloric, sulphuric
or phosphoric acids are preferable. Among the latter,
j phosphoric acid is preferred, for reasons of corrosion.
The amount of acid which is generally added is that
required o bring the p~ of the medium to a value of from
~ . .
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6.5 to 2,
Following the treatment with acid, the dimethylol
intermediate becomes insoluble in water and it becomes
possible to separate it from the aqueous phase containing
the unreacted formaldehyde and the neutralization products
of the inorganic base. Obviously, if stage (a) is carried
out in the absence of added water, water is added in stage
(b) of the process.
; In a preferred embodiment the reaction products
from the first stage are cooled down to about 50C and
phosphoric acid is added gradually up to an equivalent ratio
of sodium hydroxide to phosphoric acid of the order of 0.5:1
The mixture is then decanted at 40-50C with separation of
the aqueous layer (which is discharged) from the organic
layer consisting essentially of the dimethylol intermediateO
Stage c ~
To the dimethylol intermediate recovered in stage
b) there is added an organic solvent capable of dissolving
the said intermediate, normally immiscible or only slightly
miscible with water and forming an azeotropic mixture with
the latter.
Particularly useful for this purpose are aromatic
hydrocarbons such as toluene, xylene, cumene or other alkyl
benzenes, boiling at a temperature not exceeding 160C.
To the solution thus obtained phenol is generally
added in such amount as to ensure a molar ratio of the
para-substituted phenol (fed in in stage a) to the phenol,
of from 1:2 to 1:3.5.
The reaction is carried out at boiling point,
generally at a temperature of from 100 to 160C, the water
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which forms being dis~illed continuously in the form of an
azeotrope with the pr~selected organic solvent,
The reaction of the dimethylol intermediate with
phenol is carried out in the presence of an acid catalyst,
preferably an organic acid
The said acid should preferably have an acid
dissociation constan~, or else (in the case of a polybasic
acid) a first acid dissociation constant which is greater
than 1.10 '. Examples of organic acids suitable for the
purpose are: oxalic acid, benzoic acid, para-tert-
butylbenzoic acid, salicylic acid and isophthalic acid,
The amount of acid catalyst is generally from 0.1
to 5 parts by weight for every 100 parts by weight of phenol.
Reaction times are those necessary for practically
complete reaction of the dimethylol derivative and are
generally from 2 to 4 hours
In a preferred embodiment, the solution of the
dimethylol intermediate in the preselected solvent is added
to the phenol and the catalyst, the reaction mixture being
maintained at boiling point. The vapours which are e~olved
are condensed, with separation of an aqueous phase which is
discharged, and of an organic phase, which is recycled into
the reaction medium.
- Stage d
The acid catalyst, the organic solvent, and any
excess phenol are removed from the reaction products derived
from stage (c).
In the case of the use of oxalic acid, the said
acid is insoluble in the reaction medium at temperatures of
the order of 30-40C. It can therefore be precipitated
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by cooling the xe~c~ion m~ss and can then be filt~red,
In other cases it may be necessary to neutralize
the acid catalyst and filtex the precipita~ed salt.
The organic solvent and the excess phenol may be
removed, the former by means of distillation at atmospheric
or near atmospheric pressure, the second at a pressure
lower than atmospheric, preferably by means of the thin film
method. Obviously the said organic solvent and phenol can
be re-used in the process for preparation of the polyhydroxy
phenol. This latter remains in every case as a distillation
residue~
By the process described the polyhydroxy phenol
is obtained in its isomeric forms, which can be used as
such for the purposes for which the polyhydroxy phenols are
normally employed. Obviously, if wished, the various isomers
can be separated by means of the usual methods, such as, for
` example, fractional crystallization.
The polyhydroxy phenols of this invention are
especially useful as antioxidants for elastomers and plastics
materials, as polymerization inhibitors for unsaturated
monomers such as styrene and the alkyl esters of acrylic or
methacrylic acid and as stabilizers for unsaturated polyester
resins tproducts of the polycondensation of unsaturated
polybasic acids and polyhydroxy alcohols, dissolved in
styrene or another unsaturated monomer).
The polyhydroxy phenols of the invention are also ~--
useful for preparing epoxy resins by reaction with epichloro-
hydrin in an alkaline medium and the said epoxy resins are
particularly ~uitable for paints with improved thermal and
dimensional resistance, and resistance to chemical reagents.
" .
Novolak phenolic resins with higher molecular weight
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than the conventional ones can be prepared by reacting the
polyhydroxy phcnols ~I) in an acid mediwn with formaldehyde,
possibly in the presence o phenol or phenolic compounds i
general.
Resol phenolic resins can also be prepared in basic
medium by reacting the same reagents in different ratios.
; The said Novolaks are particularly useful when -
employed in combination with hexamine, as binders for
mineral charges (for example sand for moulds or abrasives)
or vegetable fillings, such as wood flour, or else as
reinforcers or adhesives for ruhber.
The said resols are particularly useful for
impregnating paper and fabrics, for making laminates, or else,
suitably modified with vegetable oils, they can be used for
hard and chemically resistant glossy stove enamels.
In the following experimental example the parts
and percentages are by weight unless otherwise specified,
~ . ;
Into a reactor furnished with an agitator, a steam
heating system, a hypsometer, a reservoir for feeding in
the reagents, a condensor, a demixer, a reflux duct for the
condensate and collecting chamber for the distillate, there
are fed in 426:7 parts of para-tert-butylphenol and 604
parts of a 36% aqueous solution of formaldehyde. The molar
ratio of formaldehyde to para-tert-butylphenol is thus
equal to 2.5:1.
; The temperature is taken to 60C and 190 parts of
a 30~ aqueous solution of sodium hydroxide are added
gradually to the agitated mass.
At the end of the addition of the latter the molar
~ .
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ratio of para-tert-butylphenol to sodium hydroxide is equal
to 2:1. A~ter this acldition the temperature is maintained
at 60C until the amount o~ free formaldehyde in the
reaction medium is reduced to 4-4.5%.
119 parts of a 75~ aqueous solution of phosphoric
acid are then added. Agitation is maintained until
neutralization is complete, The agitator is then stopped
and an aqueous phase containing unreacted ~ormaldehyde and
sodium phosphates, and an organic phase containing the
dimethylol derivative of p-tert-butylphenol are separated.
The aqueous phase is discharged, and 360 parts of
toluene are added to the organic phase ~720 parts), thus
obtaining a toluene solution which has the following
characteristics:
dry matter: 52%
viscosity at 25C in cps: 25
free para-tert-butylphenol: absent
This last determination was carried out by means
of gas-chromatographic analysis.
A mixture of 737 parts of phenol and 32 parts of
oxalic acid, is heated to 100C and the toluene solution of
the dimethylol intermediate is added gradually to the heated
mixture over a period of three hours. During this period of
time the mass is kept boiling and the water is azeotropically
distilled and is continuously removed through a demixer.
The distilled toluene is recycled into the reaction
medium.
The temperature of the mass rises rapidly to
120-125C during the addition of the toluene solution and
remains at these values until the end of the said addition,
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~he molar ratio of the phenol to the para-t~l~t~bu~ylphenol
~fad in initially) in the reaction mediwn being then of
2,7:1.
After the addition of the toluene solution the
said temperature is maintained for 30 minutes and the mass
is then cooled to 30-40Co
At this temperature the oxalic acid, dispersed in
the solution, is removed by filtering.
- The resulting solution has the following
characteristics:
dry matter: 64%
viscosity at 40C in cps: 900
free phenol: 16%
Thls latter determination was carried out by means
of gas-chromatography.
The solution is subjected to distillation at
atmospheric pressure and 253 parts of toluene containing
' small amounts of phenol are distilled off.
The residue is distilled by the thin film method
at a pressure of 3 mm Hg to remove the residual toluene and
the unreacted phenol.
At the base of the evaporator about 1000 parts by
weight of a polyhydroxy phenol having the following
characteristics are recovered:
, - appearance : solid
- melting point (in capillary): 74C
~, - viscosity at 25C in 50% ethanol solution: 33 cps
, - pEI in 50~ ethanol solution: 4
- Gardner melting colour: 6
~ 30 - free phenol (gas-chromatography). < 0,5%
i/' - free para-tert-butylphenol (gas-chromatography): absent
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1~7~387~
The product iS solubl~ in mos~ of the organic
solvents.
~ nalysis o~ the NMR spectra gives the following
results:
- Mn(OM) = average numerical molecular weight: 364
- n -- average number of hydroxyl groups per molecule: 3,0
- RA = average number of aromatic protons per ring~ 3,0
~ RM~ = average number of methylene bridges per benzene ring:
0.6
- 10 - isomers : ortho~ortho' ~ 5%
ortho-para : 95%
- para-tert-butylphenol/phenol molar ratio: 1:2 :~
The product is therefore the polyhydroxy phenol of
formula (I) in its two isomeric forms.
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