Note: Descriptions are shown in the official language in which they were submitted.
Z
07800~
PROChSS FOR PREPA~ING AROMATIC
POLYPHOSPHITES
.
Description
The invention of this application r~lates to
aromatic polyphosphites and, in particular, to a process
for their preparation. More particularly, it relates
to a process for preparing phenol-free aromatic poly-
phosphites.
The aromatic polyphosphites which are prepared
by the process of this invention are useful as polymer
stabilizers. They are especially useful for such purpose
in olefin polymer compositions, which require a high degree
of thermal stability. One of the advantages of polypro-
pylene, for example, is the fact that it is readily
processed and fabricated in all of the conveutional
systems; these include solid foam molding, solid and
composite extrusion, spinning and orienting, rotocasting,
powder coating, thermoforming and pressure forming, stamping
and laminating. Moreover, post-fabrication operations
which are commonly applied include machining, weldi~g,
turning, sawing, drilling, butt and spin welding, and
hot stamping. ~any of these operations are carried out
at relatively high temperatures, however, and it is
necessary to protect the polypropylene from thermal
degradation at these temperatures.
Polypropylene is especially vulnerable to degradation
under conditions which favor oxidation, for example, because
of the recurring pres~nce in the molecular chain of tertiary
carbon atoms. These are notoriously susceptible to oxidative
attack.
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The problem of oxidative degration generally is
met by incorporation into the olefin polymer composition
of a small proportion of a high molecular ueight anti-
oxidant. Phenolic phosphite antioxidants are well known
and, in most instances are quite suitable for this purpose.
They frequently suffer one disadvantage, hcwever, because
of the invariable contamination of the antioxidant with
a small proportion of phenol. Such contamination tends
to render the polypropylene unsuitable for uses involving
probable contact with food, medicines and ~he like.
The contamination arises from the fact that the high
molecular weight phenolic phosphite compounds are prepared
by a transesteri~ication reaction involvin~ triphenyl
phosphite and a bis-phenol. The product which results
from such a reaction contains phenol as a by-product,
and it is not practical to remove all of this phenol from
the desired product.
U.S. 3,053,878 (~riedman et al.) shows the reaction
of diphenyl pentaerythritol diphosphite with bisphenol A
in the presence of a diphenyl phosphite catalyst to form a
polymeric phosphite.
~ .S. 3,305,608 (Baranauckas et al.) sho~s the reaction
of stoichiometric quantities of triphenyl phosphite, penta-
erythritol and 4,4-isopropylidenediphenol (bisphenol A)
in the presence of a sodium catalyst.
Japanese Patent Publication No. 1975-35097 shows
the reaction of triphenyl phosphite and pentaerythritol
to form an intermediate product whiGh then is reacted with
a mixture of more pentaerythrltol and bisphenol A.
Stoichiometric quantities are used. The resulting product
is said to be effective as a polymer sta~ilizer.
The process of the present invention does not utilize
triphenyl phosphite at any stage~ nor any other reactant
that can, upon hydrolysis, yield phenol. The resulting
product thus is not contaminated wlth phenol and, ln this
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07~0~ 3 -
respect, is entirely suitable for use in olefin polymer
compositions which are intended for uses which may bring
them in contact with food or medicines. The process
involves preparing a phenolic antioxidant composition
by reacting a pentaerythritol diphosphite compound having
the structure: OCH2 CH O
/\ / ~
X p / C j p y
2 CH20
where X and Y are the same or different groups selected
from the class consisting of halo, amino, di-(lower alkyl)
amino, anilino, morpholino and methylanilino, with a
stoichiometrically excessive amount, up to about 5 mols
per mol, of a bis-(hindered phenolic) compound having
the structure:
p. R'
R ~ A _ ~ OH
where the HO groups are on the 2- or 4- positions of the
benzene rings, R is the same or different alkyl group and
is ortho to the HO group, R' and R" are lo~Ner alkyl or
hydrogen, and A is alkylidene or sulfur. The term "lower
alkyl" denotes alkyl of 1-6 carbon atoms.
The X and Y groups on the pentaerythritol diphosphite
reactant are, in the circumstances here, known as "leaving"
groups. That is, they "leave" the pentaerythritol di-
phosphite nucleus and are replaced in each case by the
phenolic group of a bis-(hindered phenolic) compound.
The reaction is illustrated below:
52
078004-~ - 4 -
C~ CH~ CH3 CH~
~CH2 \ / 2HO~/~3H7~0H
~ bc~ ` ' `_~ C ~oTH
where R is a tertiary alkyl group and n is at~least 1.
When X and Y are halo they may be either chloro or bromo.
As indicated, the bis-(hindered phenolic) compound
is characterized by the presence of at least one alkyl group
which is ortho to a phenolic group. This alkyl group may
contain 4-10 carbon atoms and preferably is tertiary butyl.
Other suitable groups include amyl, 1,1,2-trimethylpropyl,
l-methyl-2-ethylpropyl, l,l-diethylpropyl, l-methyl-l-
ethylpentyl, n-octyl and the like.
Moreover, when A in the bis-(hindered phenolic)
compound is alkylidene, the alkylidene may contain 1-10
carbon atoms. Methylene and butylidene are pre~erred
because o~ the ready availability of bis-(hindered phenolic)
compounds containing such alkylidene groups, but others
are suitable and include isopropylidene, ethylidene,
hexylidene, etc.
With respect to the pentaerythritol diphosphite
compound, the X and Y groups may, as indicated, be halo,
amino, di-(lower alkyl)amino, anilino, morpholino or
methylanilino. Lower alkyl groups include those containing
1-6 carbon atoms, such as methyl, ethyl, propyl, isopropyl,
butyl, etc.
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078004~ 5 -
The process may be carried out in a solvent although
a solvent is ordinarily unnecessary. Suitable solvents
include toluene, benzene, chloroform, carbon tetrachloride,
dioxane, etc. Ordinarily, it is necessary merely to mix
the reactants and heat the mixture with suitable agitation.
~ Vhen the leaving groups, i.e., X and Y in the
pentaerythritol diphosphite, are chloro the process can be
carried out as above, or a hydrogen chloride acceptor
may be used. In such case~ it is advisable to use a
solvent also. The hydrogen chloride acceptor may be any
basic amine, and low molecular weight tertiary amines
are preferred. These include trimethyl amine, triethyl
amine, tripropyl amine, i.e., those having up to 10
carbon atoms.
The product which results from the above process
has the structure:
._
R R R R
~ A - ~ OCH2 CH2O ~\ A ~ ¦
HO~ OP \, ~ , I I I r t
OCH2 CH2
R' R" R' R' R' R~ R~ R'
_ n
where the oxygen atoms linking phosphorus to the benzene
rings are in the 2- or 4- positions, R is the same or
different alkyl group and is ortho to the hydroxy or aryloxy
group, R' and R" are lower alkyl or hydrogen, n is at
least 1 and A is alkylidene or sulfur. Preferably n is
1-10, and still more preferably, n is 2-10.
The process of the invention is illustrated by the
following examples.
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Example 1
A mixture of 36.90 g. tO.l mol) of bis-(2-
hydroxy-3-tertiarybutyl-5-methylphenyl)methane and
8.75 g. (0.033 mol) of dichloro pentaerythritol di-
phosphite is heated with agitation at 170C under reducedpressure (water aspirator) for two hours. The cooled,
glassy residue weighs 43.5 g.~ has an acid number of 1.24,
melts at 75-160C and is soluble in benzene, hot cyclo-
hexane and (partially) in hot pentane.
Example 2
A mixture of 31.0 g. (0.083 mol) of bis-(2-hydroxy-
3-tertiarybutyl-5-methylphenyl)methane and 8.75 mg. (0.033
mol) of dichloro pentaerythritol diphosphite is heated with
agitation at 170C for two hours under reduced pressure
(water aspirator). The residual product has an acid number
of 0.62 and melts at 55-60C.
3xample 3
To a solution of 221.6 g. (0.58 mol) of 4,4'-
butylidene-bis-(6-tertiarybutyl-m-cresol) and 117.2 g.
(1.11 mol) of triethylamine in 800 g. of toluene is added,
over a period of one hour, a solution of 145.8 g. (0.55
mol) of dichloro pentaerythritol diphosphite in 500 g.
of toluene. The resulting solution is heated at reflux
temperature for 13 hours, then permitted to cool to room
temperature and filtered. The solid triethyl amine hydro-
chloride is removed by filtration and the filtrate is con-
centrated by heating to a final temperature of 165C/5mm.
The solid residual product (81% of the theroet~cal yield)
is shown to have an acid number of 1.7 and an average
molecular ~eight of 1670 (corresponding to three bis-
phenolic residues and two pentaerythritol residues).
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078004~ 7 ~
Example 4
A stirred mixture of 35.8 g. (0.094 mol) of
4,4'-butylidene-bis-(6-tertiarybutyl-m-cresol) a~d 8.75 g.
(0.033 mol) of dichloro pentaerythritol diphosphite is
heated at 170C (under reduced pressure) for two hours,
then cooled to room temperature. The solid residue
weights 42.1 g., has an acid number of 1.35 and melts
at 130-170C.
Example 5
A stirred mixture of 38.2 g. (0.10 mol) of 4,4'-
butylidene-bis-(6-tertiarybutyl-m-cr~soi) and 15.6 g.
(0.058 mol) of dichloro pentaerythritol diphosphite
is heated under reduced pressure at 170C for two
hours, then allowed to cool to room temperature. The
solid residue weights 47 g., melts at 130-155C and
has an acid number of 1.32. Its average molecular weight
is 920, indicating a molecule containing two bis-phenolic
residues and one pentaerythritol residue.
Example 6
A stirred mixture o~ 35.8 g. (0.10 mol) of bis-
(4-hydroxy-2-methyl-5-tertiarybutylphenyl) sulfide and
17.5 g. (0.066 mol) of dichloro pentaerythritol di-
phosphite is heated under reduced pressure at 170C
for two hours, then allowed to cool to room temperature.
2~ The residue weights 48 g. and has an acid number of 0.37.
The aromatic polyphosphites which are prepared
by the process of this invention are useful as polymer
additi~es. They provide thermal stability to polymer
compositions, especially to olefin polymer compositions.
For such use, preferred concentrations are from about
0.01 to about 1.0 percent, based on the ~eight of
polymer. Ordinarily, the aromatic polyphosphites are
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07800~-~l - 8 -
used in such concentrations in combination with
polyvalent metal salts of fatty a~ids or polyvalent
metal oxides in the stabilization of polypropylene;
the poly~ralent metal salt preferably is an alkaline
earth metal stearate and is used in concentrations o~
from about 0.02 to about 1.0 percent based on the weight
of polypropylene.
The efficacy of the phenolic antioxidants herein
as polymer stabilizers is shown by the data co~tained
in Table I, where there is shown the time required
for a polypropylene film to develop a crazed or embrittled
surface, in an oven at 150C. In each case the poly-
propylene film test sample contains 0.10 phr (parts per
hundred parts of resin) of calcium stearate, Q.25 phr
of distear~lthiodipropionate and 0.20 phr of a phenolic
antioxidant.
The test samples are prepared by dry blending the
polypropylene and additives, as above, in a Waring blender
for one minute. The mixture then is extruded into a two-
inch (wide) by 25-~il (thick) tape from which test
samples are cut. The samples are placed in a circulating
oven at 150C and chec~ed twice daily for signs of
crazing and/or embrittlement.
TABLE I
_enolic Antioxidant Hours to Fail
1. Product of Example 1 1009
2. Product of Example 2 1000
3. Bis-~2-hydroxy-3-tertiarybutyl-
5-methylphenyl)methane 814
4. Bis-(4-hydroxy-2-methyl-5-
tertiarybutylphenyl)sulfide 828
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0780~4~ 9 -
The data in Table II also shows the stabilizing
properties of the antioxidants herein. Like the data
in Table I, it is based on oven stability tests. The
test samples each contain polypropylene, 0.25 phr of
distearylthiodipropionate and 0.20 phr of a phenolic
antioxidant.
The test samples are prepared by blending the dry
ingredients in a twin shell blender for 15 minutes,
then extruding the mixture. The extrudate is cut into
pellets whi~h are injection molded into 25-mil and
100-mil plaques. Three plaques of each size are mounted
on a biaxial rotator and placed in a circulating air
oven at 150C and the time required for development
of crazing and/or embrittlement is noted.
TABLE II
Hours to Fail
Phenolic Antioxidan~ 25-mil 100-mil
1. Product of Example 4621 1317
2. Product of Example 5677 1485
3. 4,4'-butylidene-bis-
(6-tertiarybutyl-m-cresol) 501 1045
It will be noted from the data above, both in
Tables I and II, that addition of the pentaerythritol
diphosphite residue to the bis-(hindered phenolic)
compound results in a polymer additive having improved
stabilizing properties.
Those aromatic polyphosphites herein having at
least two pentaerythritol residues and three bis-(hindered
phenolic) residues are especially effective polymer
additives, and for this reason, are preferred. Their
effectiveness is shown by the data in Table III wherein
the test samples are subjected to thermal gravimetric
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078004~ 10 -
analysis. In this test a carefully weighed sample is heated
at gradually increasing temperatures while the loss in
weight of the sample is noted. The temperature required
to produce a given percent weight loss, e.g., 10%, 20%
and 50%, is taken as a measure of the relative thermal
stability or volatility of the sample. Thus, if a sample
has suffered a 50% weight loss by the time the temperature
has reached 350C, it is regarded as more stable or less
volatile, for example, than a sample which has lost that
much weight at 300C.
In the tests here, the samples are heated under
ordinary atmospheric conditions.
TABLE III
Product of Product of
15 % Weight Loss DPD* Ex. 5 Ex. 3
onset 110-120C 130C 190C
10% 222C 250C 295C
20% 270C 285C 340C
50% 311C 360C 400C
*DPD: distearyl pentaerythritol diphosphite
The data above shows the clearly superior thermal
stability or lesser volatility of the higher molecular weight
aromatic polyphosphite, i.e., the product of Example 3, which
has at least two pentaerythritol residues and three bis-
(hindered phenolic) residues.
Another method o~ testing the stabilizing influenceof a test sample involves subjecting a polymer composition
to repeated extrusions and determining the melt index after
each such extrusion. A rapid increase in the meltindex
with repeated extrusions indicates a deterioration of the
polymer.
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The data of Table IV is taken after 1, 3 and 5
extrusions of four test samples. Each sample contains 100
parts of polypropylene, 0.05 phr of calcium stearate,
0.08 phr of Irganox 1010** and 0.07 phr, if any, of
stabilizer.
~ ~ao~ ~nark-
**f pentaerythritol tetrakis-3-(3,5-ditertiarybutyl-4-
hydroxyphenylpropionate)
TABLE IV
Melt Index After Extrusion No.
Stabilizer 1 3 5 AMI*
1. None 8.7 23.3 42.9 40
2. BHT (butylated
(hydroxytoluene) 4.5 7.1 13.4 10.5
3. Tris)nonylphenyl)
phosphite 3.5 5.0 8.9 6.0
4. Product of Example 3 3.3 4.8 5.9 3.0
*AMI: Melt Index a~ter 5th Extrusion minus 2.9 (MeltIndex before 1st Extrusion).
All parts and percentages herein are by weight unless
otherwise expressly stated.
