Note: Descriptions are shown in the official language in which they were submitted.
o
073~05-M - 1 -
STABILIZED OI.EFIN POLY~ERS
Description
This invention relates to phosphite esters ~vhich
are unusually stable to hydrolysis. ~ore particularly, it
relates to the use of such stable phosphite esters as heat-
stabilizing agents for olefin polymer compositions.
The normal processing operations to which olefin
polymers are subjected invariably lnvolves high temperatures
and these promote deterioration of the polymers. The for-
mulation of a thermoplastic polymer composition, i.e., onewhich contains the various stabilizing additives ordinarily
required, usually is accomplished on a heated two-roll mill,
or in a heated Banbury mi~er, or both, and the temperatures
at which such mixing steps are carried out are quite high,
well above the temperature at which the polymer becomes
fluid. At these temperatures the polymer will develop color,
become brittle, etc., and such evidence of deterioration
cannot be tolerated in the final product.
There are a number of heat-stabilizing additives
available which are effective to protect olefin polymers
from such deterioration. Among these are the organic
phosphites. While these are very effective heat-stabilizing
additives, their usefulness is limited by their susceptibilitp
to hydrolytic decomposition in a humid environment. Such
hydrolysis is accompanied by a corresponding loss of heat-
stabilizing effectiveness with respect to the olefin polymer
compositions in which they are used for that purpose.
.~oreoever, where the phosphite is a solid, such hydrolysis
also freq~lently is accompanied by a tendency to bloc~ing,
i.e., a tendency for the ordinarily granular phosphite
material to congeal into a single solid bloc~.
., ~
'
.
~a~18~14~
078205~ 2 -
~ any attempts have been made to solve this problem.
Additives such as triisopropanolamine have been found to
impart a significant hydrolytic stability to organic phosphite
esters. The solid phosphite can be stored in moisture-proof
containers such as polyethylene bags until just before use.
All of these have been very helpful, but they have not
eliminated the problem, nor the desirability of a solution
to the problem.
U.K. 1,490,938 (Ciba-Geigy) shows symmetrical
triarylphosphites having the formula:
I ' ~
wherein Rl represents tertiarybutyl, l,l-dimethylpropyl,
cyclohexyl or phenyl, and one of R2 and R3 is hydrogen and
the other is hydrogen, methyl, tertiarybutyl, l,l-dimethyl-
propyl, cyclohexyl or phenyl. The use of these compounds
in combination with phenolic antioxidants in polyolefins
is also shown.
U.S. 2,773,226 (Hunter) shows aryl phosphites
substitued with alkyl groups containing ei~ht or more carbon
atoms and their use as stabilizers for synthetic rubber.
The alkyl groups may be ortho, para or meta to the oxygen.
U.S. 3,578,620 (Prucnal) shows the stabilization
of non-rubbery, unsaturated interpolymers of cyclic polyenes
by means of a mixture o~ a tri-(alkylphenyl)phosphite in
which the alkyl ~roup has from 8 to 30 carbon atoms and an
epo.Yide. Tri-(o-octylphenyl)phosphite is shown.
U.S. 3,080,338 (~udenberg et al) shows the use
of "any conventional phosphite" in comblnation with a
phenolic antioxidant to stabilize synthetic rubbery polymers.
0
078205-l~ 3
Tri-(ortho-octyl-phenyl)phosphite is shown.
U.S.`2,7~2,319 (Lipke et al) shows the
stabilization of polyvinyl chloride compositions by means
of a combination of a glycol ester of an organic acid,
a triaryl phosphite (to stabilize the ester), and a metal
compound. The aryl phosphite can be tri-(orthoc~Jclohexyl-
phenyl)phosphite.
The invention here is a polymer composition com-
prising an olefin polymer and a minor amount, sufficient to
impart improved heat stability to said polymer, or a tris-
(alkylphenyl)phosphite mixture wherein (l) the alXyl group
contains 8-12 carbon atoms, (2) at least about 85% of one
of the ortho positions in each phenyl group are substituted
by said alkyl groups, and (3) at least about 85ao of the
para positions in each phenyl group are unsubstituted,
or substituted by methyl groups. The phosphite can be
represented by the structure:
~ Rl ~ o P
wherein at least about 85% of R2 is alkyl of 8-lO carbon
atoms, the remainder being hydrogen, and at least about 85%
of Rl is methyl or hydrogen.
The preparation of tris-(alkylphenyl)phosphites
requires, first) preparation of the alkylphenol and then,
reaction of this alkyl-phenol with phosphorous trichloride.
The first of these reactions can be accomplished by hy-
drogenating an acylphenol. This may be done collvenientlyby means of zinc plus hydrcchloric acid. An alternative
method affords somewhat be-tter yields; it involves alkylation
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of phenol (or p-cresol) with an appropriate olefin in
the presence o~ a catalyst. A preferred catalyst is
aluminum powder, or, more particularly, the aluminum
phenate which results from ~he reaction of aluminum and
the phenolic reactant. Such alkylation yields a high
proportion of ortho isomer and relatively little or no
para isomer.
The reaction of the o-alkylphenol and phosphorous
trichloride proceeds with good yields, at relatively
high temperatures. The product may be distilled to yield
a clear, colorless liquid product; alternatively, it
may be stripped in vacuo and the residual liquid taken
as the product.
This product, i.e., a tris-(o-alkylphenyl)phosphite
is as indicated characterized by unusual hydrolytic
stability and, correspondingly, long-lived effectiveness
as a stabilizer in polymer compositions, especially in
olefin polymer compositions. It is particularly effective
in such compositions which also contain a phenolic
antioxidant.
The olefin polymer most usually is polypropylene
although other olefin polymers are contemplated. These
include polyethylene, copolymers of ethylene and propyleneJ
polyisobutylene, and EPD~ polymersJ i.e. J terpolymers of
ethyleneJ propyleneJ propylene and a small proportion of
a non-conjugated diene.
The alkyl groups in the tris-(alkylphenyl)phosphite
containJ as indicated earlierJ 8-12 carbon atoms. Thus,
octyl J nonyl J decyl, undecyl and dodecyl groups are
specifically c~ntemplated. These groups may be attached
to the phenolic ring through a primary, secondary or
tertiary carbon atom.
The tris-(alkylphenyl)phosphite herein is deri~ed
from an alkylphenol of the structure:
18~
078205-M - 5 -
Rl <~ ~OEI
< ~
P~ '
where Rl is methyl or hydrogen and R2 is alkyl of 8-12
carbon atoms.
The amount of the tris-(o-alkylphenyl)phosphite
which is to be used ranges ~rom about 0.1 phr (parts
per 100 parts of resin) to about 5.0 phr.
The phenolic antioxidants are well known.
Specifically contemplated are the following: 2,6-di-
tert.-butyl-4-methylphenol, 2,6-di-tert.-butyl-4-methoxy-
methylphenol or 2,6-di-tert.-butyl-4-methoxyphenol;
2,2'-methylene-bis-(6-tert.-butyl-4-methylphenol),
2,2'-methylene-bis-(6-tert.-butyl-4-ethylphenol),
2,2'-methylene-bis-[4-methyl-6(~-methylcyclohexyl)-phenol~,
l,l-bis(5-tert.-butyl-4-hydroxy-2-methylphenyl)-butane,
2>2-bis-(5-tert.-butyl-g-hydroxy-2-methylphenyl)-butane,
2,2-bis-(3,5-di-tert. butyl-4-hydroxyphenyl)-propane,
l,1,3-tris-(5-tert.-butyl-4-hydroxy-2-methylphenyl)-
butane, 2,2-bis-(5-tert.-butyl-4-hydroxy-2-methylphellyl)-
4-n-dodecylmercapto-butane, l,1,5,5-tetra-(5-tert.-
butyl-4-hydroxy-2-methylphenyl)-pentane, ethylene glycol-
bis[3,3-bis-(3'-tert.-butyl-4'-hydroxyphenyl)-butyrate],
1,1-bis-(3,5-dimethyl-2-hydroxyphenyl)-3-(n-dodecylthio)-
butane, or 4,4'-thio-bis-(6-tert. butyl-3-methylphenol);
1,3,5-tri-(3,5-di-tert.-butyl-4-hydroxybenzyl)-2,4,6-
trimethylbenzene, 2,2-bis-(3,5-di-tert.-butyl-4-hydroxy-
benzyl)-malonic acid-dioctadecyl ester, 1,3,5-tris-
(3,5-di-tert.-butyl-4-hydroxybenzyl)-isocyanurate, or
3,5-di-tert.-butyl-4-hydroxybenzyl-phosphonic acid-
diethyl ester; amides of 3-(3,5-di-tert-butyl-4-hydroxy-
phenyl)-propionic acid, such as 1,3,5-tris-(3,5-di-tert.-
butyl-4-hydroxyphenyl-propionyl)-hexahydro-s-triazine,
N,N'-di-(3,5-di-tert.-butyl-4-hydroxyphenyl-propionyl)-
hexamethylenediamine; esters o~ 3-(3,5-di-tert-butyl-
L
~ I
4~
t_ ~
078205-M - 6 -
.
4-hydroxyphenyl)-propionic acid wlth methanol, octadecanol,
1,6-hexar.ediol, ethylene glycol, thiodiethylene glycol,
neopentyl glycol, pentaerythritol, tris-hydroxyethyl-
isocyanurate; diphenolic spiro-diacetals or spiro-diketals,
such as 2,4,8,10-tetraoxaspiro-[5,5]- undecane substituted
in the 3- and 9-position with phenolic radicals, such as
3,9-bis-(3,5-di-tert.bu-tyl-4-hydroxyphenyl)-2,4,8,1Q-
tetraoxaspiro-[5,5]-undecane, 3,9-bis-[l,l-dimethyl-2-
(3,5-ditert.-butyl-4-hydroxyphenyl)-ethyl]-2,4,8,10-
tetraoxaspiro-[5,5]-undecane.
Particularly preferred are: 1,3,5~tri-(3,5-di-
tert.-butyl-4-hydroxybenzyl)-2,4,6-tri-methylbenzene,
pentaerythritol-tetra[3-(3,5-di-tert.-butyl-4-hydroxy-
phenyl)-propionate],~-(3,5-di-tert.-butyl-4-hydroxyphenyl)-
propionic acid-n-octadecyl ester, thiodiethylene glycol-
~-[4-hydroxy-3,5-di-tert.-butyl-phenyl~-propionate,
2,6-di-tert.-butyl-4-methyl-phenol, and 3,9-bis-[l,l-
dimethyl-2-(3,5-ditert.-butyl-4-hydroxyphenyl)-ethyl]-
2,4,8,10-tetraoxaspiro[5,5]-undecane, and 2,2'-methylene-
bis-(6-tertiarybutyl-4-ethylphenol).
The amount of phenolic antioxidant which is to
be used ranges from about 0.05 phr to about 1.0 phr.
Preparation of the phosphite esters herein is
illustrated by the following sp cific examples.
Example 1
To 200 g. of amalgamated zinc there is added a
solution of 200 ml. of concentrated hydrochloric acid in
300 ml. of water, then a 25% ethanolic solution of 72g.
(0.29 mol) of 4-methyl-2-nonanoyl-phenol. The mixture
is heated at reflux for nine hours with stirring, treated
with 200 ml. of toluene and then permitted to cool.
0'`
078205-M - 7 -
The organic layer is isolated, washed with water,
filtered and freed of solvents by stripping. The
residue is distilled to yield 57% (of the theory)
Of 4-methyl-2-n-nonylphenol.
Example 2
The procedure of Example 1 is repeated using
$0 g. (0.29 mol) of 4-methyl-2-dodecanoylphenol as a
reactant instead of 4-methyl-2-nonanoylphenol. The yleld
of 4-methyl-2-dodecylphenol is 56% of the theory.
Example 3
An 83-g. sample of phenol is dried by azeotropic
distillation until no more water distills, then heated
at 155C and treated portionwise, under argon, with 0.83 g.
of aluminum granules. After the evolution of hydrogen has
ceased, the temperature is allowed to drop to 145C and
50 g. of l-nonene is added slowly. The temperature is
maintained with stirring, at 145-150C for six hours.
The excess phenol and unreacted nonene are removed by
distillation at reduced pressure and the residue washed
with 5% aqueous hydrochloric acid solution, then with
water until the washings are neutral to litmus. Dis-
tillation of the residue yields 30 g (34% of the theory,
93% conversion) of a clear, colorless liquid boiling at
94C/10 mm. O~er 98% of it is the o-(l-methyloctyl)
phenol.
Example 4
The procedure of Example 3 is repeated using
l-octene instead of l-none. The product, a c]ear, water-
white liquid boiling at 100-107C/0.10-0.18 ~ contains
93% of the desired o-(l-methylheptyl)phenol; it was
obtained in a 76% (of the theory) yield.
1~ 140
078205-~ - 8 -
Example 5
The procedure of Example 3 is repeated using
propylene trimer instead of l-nonene. The product is
a clear, water-white liquid boiling at 105-110C/0.25 mm.
It is obtained in a 39% yield and contains 88% of the
desired o-nonylphenol.
Example 6
The procedure of Example 3 is repeated using
diisobutylene instead of l-nonene. A 45% yield of clear,
water-white liquid is obtained containing 89% of the
desired o-octylphenol.
The hydrolytically stable phosphites of the
invention may be prepared as follows:
To 1.0 mol of the o-alkylphenol, at 55C, there
is added, slowly, 0.30 mol of phosphorous trichloride.
The reaction initially is exothermic, but later, external
heating is required to maintain the temperature at 55C.
When all of the phosphorous trichloride has been added~
the temperature is raised, in an argon atmosphere, to
180-250C a~d kept there for 23-33 hours. The residue
is distilled yielding a clear, colorless liquid.
The following tris-(o-alkylphenyl)phosphites,
having the structural formula
R ~ --O ~ p
are prepared by this method:
t~o
078205-~ ~ 9 ~
R' R Yield
Example 7 methyl n-nonyl 99~0
Example 8 methyl n-dodecyl 99~0
Example 9 H l-methylheptyl 99%
Example 10 H l-methyloctyl 41%
The purity of the products obtained as above is
high, ranging from 93~0 to 99~0.
The hydrolytic stability of these tris-)o-alkyl-
phenyl)phosphites may be shown by the results of a test
carried out in aqueous tetrahydrofuran. A 2% solution
of the phosphite sample in a mixture of 80 parts of
tetrahydrofuran and 20 parts of water is maintained at
44C and a pH of 4.5 for 48 hours. The disappearance
.
of phosphite is monitored by means of liquid chroma-
tographic analyses.
A commercial sample of tris-(nonylphenyl)phosphite
containing 92% of the para isomer, 6% of the ortho isomer
and 2% of the dinonyl compound, is found to be completely
hydrolyzed after 140 hours. 'A corresponding sample of
tris-(nonylphenyl)phosphite containing 88% of the ortho
isomer and 12~o of the para isomer is 10% hydrolyzed after
140 hours and only 50% hydrolyzed after 760 hours.
- Similarly, a sample of tris-(l-methylheptylphenyl)
phosphite (wherein 92% of the alkylphenyl groups are
2-alkylphenyl and 7% are 2,4-dialkylphenyl-) was only
50% hydrolyzed after 700 hours.
The hydrolytic stability of these tris-(o-alkyl-
phenyl)phosphites in acidic aqueous emulsions is shown by
the results of a test where 10 parts of a phosphite sample
is mixed with a solution of 2.1 parts of an anionic organic
phosphate in 34 parts of water. The resulting emulsion
is added to 400 parts of water, warmed to 55C and the
pH adjusted to 2.5 by the addition of concentrated hydro-
chloric acid. This diluted emulsion is allowed to cool
and stand for 10 hours. The pH is adjusted to 7 with
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dilute aqueous potassiwm hydroxide solution and the
emulsion poured into 600 parts of 5~0 aqueous calcium
chloride solution at 85C. The mixtllre is cooled,
extracted with benzene and the benzene extract dried
and evaporated to an oily residue. The extent of
hydrolysis is determined by liquid chromatographic
analysis.
Samples of the above commercially available
tris-(nonylphenyl)phosphite and tris-(ortho-l-methyl-
heptylphenyl)phosphite are subjected to the above test:the former is completely hydrolyzed; the latter is
hydrolyzed to the e~tent of 30%.
The effectiveness of the tris-(o-alkylphenyl)
phosphites herein as polymer stabilizers in a hydrolyzing
environment is shown as follows: A stabilizing emulsion
is prepared by adding a solution of 6.25 parts of the
phosphite and 1.15 parts of oleic acid to a hot solution
of 0.55 part of triethanol amine in 17 parts of de-
mineralized water and mixing with a high speed stirrer
for one minute. The resulting emulsion is added to 325
parts of polybutadiene latex and the mixture stirred for
12 hours. The mixture then is coagulated at 85C by
addition of 1.5% aqueous sulfuric acid and the polybuta-
diene crumb collected, washed and dried. The dried
crumb is aged in an oven at 100C and the time required
for the development of an overall brown color taken as
a measure of the stability of the polybutadiene.
Samples of the above commercially availabe tris-
(nonylphenyl)phosphite (A) and the tris-(ortho-l-methyl-
heptylphenyl)phosphite (B) of Example 9 are subjectedto this test, with the following results:
~, .
078205-M - 11 -
Table I
Phosphite Hours to Coloration
A 100
B 130
5 none 30
The superiority of the o-alkylphenyl-substituted
phosphite is apparent.
The efficacy of the tris-(o-alkylphenyl)phosphites
of the present invention as stabilizers in polypropylene
is shown by the results of heat stability tests carried
out as follows: The various ingredients (including a
phosphite stabilizer) of the polymer composition are
dry blended in a mechanical blender, then extruded into
a l-mil sheet which is cut into l~-inch discs. These
are aged in an oven, at 150C, until they begin to
develop color and surface crazing. The time required for
such failure is taken as a measure of the effectiveness
of the phosphite stabilizer. In each case the test
sample contained the following ingredients: 100 parts
of polypropylene, 0.10 phr (parts per 100 parts of
resin) of calcium stearate, and 0.10 phr of the
pentaerythritol ester of 3-(3,5-di-tert-butyl-4-hydroxy-
phenyl)-propionic acid.
Table II
25Test Sample Phosphi'te Hour's to Fail'ure
1. none448
2. 0.25 phr tris-(2-tert-
butyl-phenyl)phosphite 688
3, 0.25 phr tris-(nonylphenyl)
phosphite where 88/o of the
nonyl groups are ortho and
11% are para 70]
.'
. ~ll85.~'0
078205-M - 12 -
Other additives can also be added to the
olefin polymer compositions of this invention,
including ultraviolet stabilizers, anti-static agents,
~illers, pigments, lubricants and the like.
