Note: Descriptions are shown in the official language in which they were submitted.
0791 2l~-M ~2~
ACETAL E STE RS
This invention relates to certain esters of monoacetals of
pentaerythritol. More particularly, it relates to such esters
as contain a phenolic group within their structure. It also
relates to a process by which such esters may be prepared.
The esters herein are useful as polymer additives. They
are especially useful in olefin polymer compositions, e.g.,
polypropylene compositions, where they act to impart thermal
stabllity to such compositions. They are useful also as
intermediates in the preparation of phenolic ethers which in
turn are useful as plasticizers in polyester resins. Generally,
olefin polymer compositions are vulnerable to deterioration of
physical and chemical properties during manufacture, storage,
processing and use. To overcome such deterioration, or at
least to inhibit it, there have been developed additive systems
which act to stabilize these polymers with respect to physical
and chemical degradation caused by exposure to ordinary environ-
mental conditions. All of these additive systems, howeYer,
while effective for their intended purpose, are characterized
by one or more shortcomings.
Olefin polymers are especially susceptible to oxidative
degradation. The relat;vely high temperatures required for
their customary processing procedures such as roll milling,
injection molding9 extrusion and the like, invariably promote
oxidation because these processes are carried out under
ordinary atmospheric conditions, i.e., they are exposed to
the oxygen of the aemosphere.
The significance of polymer oxidation lies in the adverse
effec~ i~ has on the rheology, morphology, color, clarity,
910s5 and other physical properties. Impact strength may be
lose; the surface may become cracked or cra~ed. Even a
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darkening of the color may provide a sufficient aesthetic dis-
advantage as to render the olefin polymer composition unsuitable
for its intended use.
U.S. 3,948,946 (Hofer et al.) shows acetals of hydroxy-
benzaldehydes. The acetals are the reaction products of 2,2-
dimethyl-1,3-propanediol, pentaerythritol, ethylene glycol,
1,2-ethanedithiol, toluene-3,4-dithiol, etc. That is, the
alcohol precursor is polyhydric. The reaction o~ pentaeryth-
ritol, however, is carried out ~o completion, i.e., all of the
aliphatic hydroxy groups are acetalized. The acetals are said
to be effective stabilizers for organ;c materials.
U.S. I~,013,619 (Schmidt) shows acetals of certain hydroxy-
phenylacetaldehydes and hydroxyphenylpropionaldehydes, in some
instances (see Columns 16 and 17), with pentaerythritol residues.
The acetals are either monoacetals or diacetals, but the mono-
acetals do not contain unreacted aliphatif hydroxy groups. The
acetals are said to be effective heat stabilizers in synthetic
resin compositions.
U.S. 4,151,211 (Hechenbleikner et al.) shows acetals of
4-hydroxyphenylpropionaldehydes and such hydroxy or mercapto
compounds as pentaerythritol, dodecyl mercaptan and various
other acetalizing reactants, as well as their use in stabili~ing
polypropylene. None of the acetals, however, contain unreacted
aliphatic hydroxy groups.
French Patent No. 2,301,558 shows certain diacetals of
pentaerythritol and 3,5-ditertiarybutyl-4-hydroxyphenyl
propionaldehyde and 3,5-ditertiarybutylbenzaldehyde.
The invention of this application i~ an ester of a
pentaerythritol monoacetal haviny the st.ucture
. ~ .
7~
079124-M
HO ~ CH2 ~ C~I ~ C(CH20)2(A-X)p
where R is alkyl, cycloalkyl or aralkyl having 3-10 carbon atoms,
Rl is alkyl of 1-6 carbon atoms, R2 is lower alkyl or hydrogen,
A is ll or P-0, X is an organic radical, n is 0-3, and p is
~-2. C
The invention also includes the process of preparing such
esters c~mprising reacting a monoacetal of pentaerythritol
having the structure
~ CH2 ~ CH ~ C(CH20H)2
where R is alkyl r cycloalkyl or aralkyl having 3-lO carbon atoms,
Rl is alkyl oF 1-6 carbon atoms and R2 is lower alkyl or hydro-
gen, with an ester-forming compou~d having the structure
Clm-A-X where m is 1 or 2, A is 1l or P-O, X is an organic
radtcal and n is 0-3. The term "lower alkyl" denotes an alkyl
group having 1-4 carbon atoms.
Illus~rative species of R include methyl, ethyl, isopropyl,
tertiarybu~yl, tertiaryamyl, 2,2'-dimethylbutyl, cyclopentyl,
cyclohexyl, 2 methylcyclohexyl, ben~yl and phenylethyl9 illus-
trative species Of Rl include methyl, ethyl, isopropyl,
tertiarybutyl, tertiaryamyl and 2,2'-dimethylbutyl; illustra-
tiYe species of R2 include methyl, ethyl, n-propyl, isobutyl
and hydrogen. Preferably, at least one of R and Rl Is a
bulky group, e.g., tertiarybutyl or cyclohexyl.
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The organic radical X is an aromatic radical, i.e., it
contains a henzene ring. It may be a substituted aryl group,
i.e., an alkylphenyl group (where the alkyl has 1-6 carbons)
such as 4-tertiarybutylphenyl, 2,4-ditertiarybutylphenyl or
~,6-diisopropylphenyl; or a hydroxyphenyl group such as 4-
hydroxy-2-methyl-3-tertiarybutylphenyl, 4-hydroxy-2,3-
ditertiary~tylphenyl, 4-hydroxy-3,5-ditertiarybutylphenyl
or 4-hydroxy-2-tertiarybutyl-5-n-octylphenyl. The aromatic
radical may be one which is attached directly to the A group,
i.e., through a benzenoid carbon atom, or it may be attached
through an aliphatic carbon atoms, e.g., benzyl, 2-pheny1ethyl,
2-(4-hydroxyphenyl)ethyl and 2-(4-hydroxy-3,5-ditertiarybutyl-
phenyl)ethyl.
In general, X is phenyl, alkylphenyl, or (hydroxyphenyl)-
~5 alkyl, where the alkyl group(s) in each case have 1-6 carbon
atoms.
The process o~ the invention involves reactlng the above
pentaerythritol acetal with the acid chloride under such con-
ditions as to cause the evolution of hydrogen chloride. The
reaction is slightly exothermic and it is accordingly advisable
to employ external cooling to control the reaction. Stoichio-
metric quantities o~ the reactants should be employed for best
results, i.e., two mols of carboxylic acid chloride per mol of
pentaerythritol monoacetal, or one mol o~ the dichlorophosphite
per mol of pentaerythritol monoacetal.
A hydrogen chloride acceptor is employed, usually a
tertiary aliphatic amine such as triethylamine or tri-n-
butylamine, i.e., one having 3-12 carbon atoms, and the
reaction is best carried out in a solvent. Typical so1vents
3a include toluene, dioxane, benzene, and the like. Any inert
solvent is suitable. The temperature of the reaction
ordinarily is within the range of ~rom about 10C t~ about
100C.
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The reactants, solvent and hydrogenchloride acceptor are
mixed, stirred until reaction is complete and the desired solid
product separated. If a pure product is desired, crystalliza-
tion from a hot aliphatic hydrocarbon (such as hexane) usually
will serve that purpose.
The process is illustrated by the following examples.
EXAMPLE 1
A mixture of 13.0 9. (0.034 mol) of the monoacetal of
pentaerythritol and 3-(4-hydroxy-3,5-ditertiarybutylphenyl)-
propionaldehyde, 17.6 9. (o.066 mol) of 4-hydroxy-3,5-
ditertiarybutyl-benzoyl chloride and 115 ml. of toluene is
stirred in an ice bath until the temperature is about 3 C
whereupon ]1.5 ml. (8.38 g. - 0.083 mol) of triethylamine
is added. An exothermal reaction occurs and the temperature
rises to 30C. Stirring is continued for 45 minutes then
the mixture is heated to 80C and filtered. The filtrate is
s~ripped to a residue weighing 33.0 9.; it is crystallized
2Q from hot hexane to yield 11.75 9. (42.5~ of the theory) of
white crystals, M.P.~ 123-7C.
E~AMPLE_2
A mixture of 9.59 9. (0.025 mol) of the monoacetal of
pentaerythritol and 3-(4'-hydroxy-3',5'-ditertiarybutyl-
phenyl)propionaldehyde, 10.4 ml. (7.6 9. - 0.107 mol) of
triethylamine and 90 ml. of dioxane is prepared and stirred
until all is in solution; a solution of 15 9. (0.051 mol)
30 of 3-~4'-hydroxy-3',5'-ditertiarybutylphenyl)propionyl
chloride is added slowly with external cooiing and stirring
is continued for 90 minutes at room temperature after all
079124-M 1214174
-- 6 --
is added~ The temperature is raised to 80C and held there -for
90 minutes, then the mixture is filtered. The filtrate is
evaporated to dryness and the residue crystallized from hot
hexane to yield 16.15 9. (71~ of ~he theory) of the desired
diester, M.P., 95-100C.
EXAMPLE 3
To a stirred mixture of 9.5 g. (0.025 mol) of the mono-
acetal of pentaerythritol and 3-(4'-hydroxy-3',5'-ditertiary-
butylphenyl~propionaldehyde, 10 ml. (7.3 9. - 0.103 mol) of
triethylamine and 100 ml. of toluene there is added, with
stirring, 7.68 g. (0.025 mol) of dichloro 2,4-ditertiary-
butylphenyl phosphite. An exothermic reaction ensues and
the temperature of the reaction is kept below 40C by means
of an ice bath. When the reaction has subsided the product
mixture is filtered and the filtrate is evaporated to 15.0 9.
of a yellow, gummy residue. Crystallization from hot heptane
yields 12.5 9. (81~ of the theory) of a light yellow solid,
20 M.P., 138-140C.
EXAMPLE 4
The procedure of Example 2 is repeated except that ~hec~ ~_
monoacetal reactant is derived from 3-(2',3'-dimethyl
, ~ tertiarybutylphenyl)propionaldehyde.
., ~
EXAMPLE 5
The procedure of Example 3 is repeated except that the
phosphite reactant is d;chloro-2,6-diter~iarybutylphenyl
phosphtte.
079124-M ~2~7~
The acetal esters of the invention are, as indicated
earlier herein, useful in olefin polymer composit;ons. They
generally are present in such compositions in combination with
a dialkyl thiodipropionate where the alkyl group is one having
10-20 carbon atoms; distearyl dithiopropionate is preferred.
The acetal ester is used in concentrations ranging from about
0.01% to about 1.0%; the dialkyl thiodipropionate is used in
concentrations ranging from about 0.05~ to about 0.75%.
The efficacy of the acetal~esters herein as polymer
stabilizers is shown by the data set out in the Table below.
The data is derived from thermal stability tests carried out
at 150C. Each sample is heated at this temperature and
inspected at periodic intervals until it fails (as evidenced
by embrittlement, crazing and/or cracking). The samples each
consist of polypropylene containing O.tO pph (parts per
hundred parts of resin), calcium stearate and other additives
as shown. Color ratings ~Hunter L-b) are assigned to each
sample prior to (1nitial) and after ~Final) 600 hours at 150C.
The stabili~y rating is measured as the number of hours
required for failure, and is the average of these sa~ples.
Color
Acetal-Ester (pph) DSTDP (pph) Initial Final Stability
Product of
Example 1 0.03 0.25 75.874.o
0.05 0.20 ~ - 1264
0.05 0.30 ---- ---- 136~
0.075 0.25 75.673.9 1632
3Q 0.075 0.30 -~ 1800
~2~7~
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Color
Acetal-Ester (pph) DSTDP (pph) Initial Final Stability
Product of
Example 20.03 0.25 75.674.0 1304
0.05 0.20 ~ - 1464
0.05 0.30 ~ 1664
0.75 0.25 7~.872.1 1632
35 ~~~~~~~~ 1824
Product of
Example 30.05 0.25 74.3 ----
0.10 0.25 7~.567.9
Product of
Example 40.05 0.25 1416
Product of
Example 50.05 0.25 76.1 ---~
0.10 0.25 74.370.
None
---- 0.25 168
All parts and percentages herein, unless otherwise
expressly stated, are by weight.
