Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
- 12332S~Ç;
079236-M -1-
STABILIZATION OF_POLY-(ALKADIENE-1,3)
The invention of this application relates
as indicated to the preparation of a stabilized polyp
5 (alkadiene-1,3). More particularly, it relates to
such stabilization in aqueous emulsion.
While certain aqueous polymer emulsions are
in many instances used as such, they often are used
as a starting material in the preparation of a graft
lo copolymer such as AS. It is important for many
applications that the ultimate graft copolymer product
be as colorless and as stable as possible. these are
difficult requirements for an ABS-type polymer because
of the presence of a large number of olefinic double
15 bonds in such a polymer. These double bonds are of
course readily susceptible to oxidation which gives rise
to color formation and other physical changes and which
is a prime cause of instability. It is necessary to
provide some means for preventing or inhibiting such
20 oxidation so as to provide the desired color and thermal
stability of the final copolymer product.
US. 4,213,892 (Scott) shows the stabilize-
lion of a polymer by reacting it with an antioxidant
in the presence of a free radical. The antioxidant is
25 one "which gives rise to a free radical in the mole-
cute", got. 1, line 50. The reaction may be carried
out in an aqueous emulsion, got. 6, line 29. In a
typical example a polypropylene film is stabilized by
irradiation in a solution of 3,5-ditertiarybutyl-4-
30 hydroxybenzyl acrylate and benzophenone in Bunsen pharaoh hours. The source of the irradiation is a US lamp
which radiates light of wave length above 250 mm.
~2~32~6
079236-M -2-
Although the preferred species of antioxidant is an
acrylate which contains a finlike group there is a
disclosure of a saturated they'll as an antioxidant, for
use with an unsaturated polymer. Nevertheless, there
5 is no suggestion that aliphatic esters containing a
they'll group might be effective to stabilize an alga-
Dunn polymer.
Quinine et at., in J. Apply Polymer Sat. 3,
No. 7, 11-19 (1960) show the reaction of natural
lo rubber, in latex form, with Marquette acid esters. The
reaction is catalyzed by a free-radical catalyst and
is carried out at 0C for at least 24 hours. The
reaction medium is quite acid (pi: 1-2). The result-
in product is hydrolyzed to the corresponding acid
15 which then is cross-linked, through the carboxyl
groups, by means of calcium hydroxide.
Chemical Abstracts I 6851 (1966),
shows the stabilization of a
polyolefin by dispersing it in an inert hydrocarbon
20 with dodecyl mercaptopropionate and heating the mixture
at 60-98 for 3-4 hours under US irradiation. It does
not show any such stabilization reaction in an aqueous
emulsion, nor does it show the stabilization of an
alkadiene-1,3 polymer.
US. 3,864,429 (Tanaka et at.) discloses
high impact-resistant vinyl chloride polymer compost-
lions which contain a modified MOBS resin. The MOBS
resin is treated as an aqueous emulsion with an alkyd
mercaptan.
The invention of the present application is
a process for stabilizing an alkadiene-1,3 polymer
comprising treating an aqueous emulsion of said alga-
Dunn polymer with from about 0.001 percent to
about 10.0 percent based on mows of alkadiene-1,3
35 units in the polymer, of an aliphatic ester of the
formula
aye I'
~,~
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079236-M -3-
HSCH2CH2COOR
where R is an alkyd group of 6-18 carbon atoms, in the
presence of a radical-generating compound.
Alkadiene polymers contemplated for use in
5 the process of this invention include chiefly polyp
butadiene, polyisoprene, and copolymers of butadiene
and isoprene such as butadiene/styrene and butadiene/
alphamethylstyrene copolymers. As indicated, the
polymers are used in the form of aqueous emulsions and
lo in the ordinary situation the aqueous emulsion in
which the alkadiene polymer or copolymer is prepared
is quite suitable for use in the process. The proper-
anion of these polymers and copolymers in aqueous
emulsion is well-known and is, in fact, the usual
method of their preparation.
The aliphatic ester which is in effect the
stabilizing agent is an alkyd mercaptopropionate
having the structure shown above. The alkyd group
contains 6-18 carbon atoms. Illustrative alkyd groups
include Huxley, hotly, octal, 2-ethylhexyl, isooctyl,
nonyl, decal, dodecyl, tetradecyl, hexadecyl and
octadecyl.
Radical-generating compounds are those which
give rise to a fragment of a molecule having one or
more unpaired electrons. Redo systems are portico-
laxly convenient, including mixtures of a cumin
hydroperoxide plus iron, hydroperoxide plus a polyp
amine, a per sulfate plus a reducing agent, etc. Ago
compounds such as azoisobutyronitrile (AIBN) are
I
... . .. .
12332~6
079236-M -4-
useful; so are ditertiarybutyl peroxide, hydrogen
peroxide, p-menthane hydroperoxide, and potassium
per sulfate. In general, peroxides, hydroperoxides,
redo systems and ago compounds are suitable radical
generators for the process herein.
The pi of the process mixture is desirably
above 7.0 and preferably is within the range of from
about 7.0 to about 11Ø
The temperature of the process mixture
should be maintained within the range of from about
30C to about 100C. Obviously, the reaction will
proceed at a higher rate at a higher temperature, but
it ordinarily is unnecessary to heat the reaction
mixture above 70C to achieve a satisfactory reaction
rate. An especially suitable range is from about 40C
to about 70C. The optimum temperature will vary
depending, e.g., on the initiator used.
The amount of alkyd 3-mercaptopropionate
which should be used in the process of the invention
Wylie range from about 0.001 to about 10 percent, on a
molar basis, with respect to the alkadiene-1,3 content
of the polymer. Preferably, the concentration of
alkyd 3-mercaptopropionate will be within the range of
from about 0.01 to about 3.0 percent on a molar basis.
2sThe effectiveness of the 3-mercaptoprionate residue,
it will be seen, is not due (solely, at least) to the
disappearance of double bonds in the butadiene units.
The radical-generating compound should be
used in a concentration of from about 0.01 to about
301.0 percent of the polymer. Preferably the concentra-
tion-should be within the range of from about 0.1 to
about 0.5 percent.
The process of the invention and the improve
Ed properties of the product of that process are shown
in the following examples and table.
. , .
1233Z96
079236-M -5-
EXAMPLE 1
A mixture of 246 parts of polybutadiene
latex containing 40.66~ of polybutadiene having a
weight average particle of 700 A, 0.31 part of poles-
5 slum per sulfate (K2S2O8) and 5 parts (1.0 molar percent) of dodecyl 3-mercaptopropionate is placed in a
bottle, purged with argon and heated with agitation at
60C for 22 hours. The resulting product mixture is
coagulated with a 50-50 mixture of methanol and water
lo containing 10% of concentrated sulfuric acid. The
solid, crumb like product is reslurried with methanol (in
which the dodecyl 3-mercaptopropionate is
soluble), filtered and washed with more methanol. The
rubbery crumb is dried _ vacua for six days, yielding
15 a bright white product.
EXAMPLE 2
The procedure of Example 1 is repeated
except that the initial mixture contains no dodecyl
3-mercaptopropionate. The resulting product is a
20 light beige color.
To each of the products prepared as in
Examples 1 and 2 is added two phi (parts per hundred
parts of resin) of 2,2'-bis-(hydroxy-3-tertiarybutyl-
5-methylphenyl)methane TAO 425) dissolved in methanol.
25 The mixture is stirred for an hour and then flash
evaporated and the residue is vacuum dried for one
day.
The thermal stability of each of the dried
products is determined in an iso-DSC (Differential
- 30 Scanning Calorimeter) apparatus at 200C, i.e., the
~Z~3296
079236-M -6-
Scanning Calorimeter) apparatus at 200C, i.e., the
sample is heated at this temperature until the onset
of an exotherm, which indicates the beginning of
decomposition of the test sample, and the time no-
5 squired for this occurrence is noted. The sample is retained in the apparatus at this same temperature for
such additional time as required to develop a signify-
gently increased color, a further indication of decompo-
session. The data from these tests is shown in Table I.
TABLE I
Product of En. 1 Product of En. 2
Initial Lowry white light beige
unset of exotherm 96 min. 42 min.
Development of oilier light yellow dark brown after
after 110 min. 55 min.
It will be seen that the product of Example
1 is more stable at elevated temperatures than the
product of Example 2.
Graft copolymers may be prepared from the
20 stabilized polymers of this invention by known methods
such as (1) preparing a polymer latex (substrate) by
polymerizing (in an aqueous emulsion) an alkadiene-1,3
or mixture thereof with styrenes and up to 10% (based
on monomer content of the latex) of acrylonitrilel (2)
:
.
.
1;~3325~6
079236-M -7-
adding to said latex a mixture of styrenes and up to
40% of acrylonitrile and/or methyl methacrylate (based
on monomer content of the added mixture,) and (3)
polymerizing the mixture of (2). Thus, the polymer
5 latex of (1), for example, may be polybutadiene,
polyisoprene, a copolymer of butadiene and styrenes or
a copolymer of butadiene, styrenes and acrylonitrile.
As little as 15% and up to 70% of styrenes based on
the overall monomer content, may be present in the
lo graft copolymer; and the mixture of (2) may be styrenes
and acrylonitrile, styrenes and methyl methacrylate, or
styrenes acrylonitrile and methyl methoacrylate. The
butadiene content of the graft copolymer will range
from about 10% to about 75%. Preferably the acrylo-
15 nitrite content in the graft copolymer will be in the range of from about 2 to about 10 percent.
When the substrate contains styrenes the
styrenes content thereof preferably is 2-30%. The
styrenes content of the superstrata ranges from about
20 15% to about 100%, while the preferred range is from
about 15% to about 80%. The acrylonitrile and methyl
methacrylate contents (in the superstrata) preferably
are each from about 10% to about 40%.
The substrate normally will comprise from
25 about 15% to about 60% of the graft copolymer and the
superstrata from about 85% to about 40% thereof.
Cross-linking agents can be used as desired
in the above process. They may be used both in the
step of preparing the latex and in step (3) involving
30 preparation of the superstrata. Illustrative cross-
~Z33Z~6
079236-M -8-
linking agents include divinylbenzene, and dimetha-
crylates such as Monday , in- and tetraethylene
glycol dimethacrylate and battalion glycol dimetha-
cruelty, triallyl phosphate, triallyl sonority,
5 tetraallyl Solon, Delilah itaconate, diethylene
glycol diacrylate, etc.
Methods of making the graft copolymers
herein are well known. US. 2,802,808 (Hayes), for
example, shows methods of preparing AS resins, as
10 does also US. 2,994,683 (Carver). The MOBS resins and
other graft copolymers herein are prepared similarly.
Preferred graft copolymers are those wherein
the superstrata, i.e., the grafted polymer, is
a copolymer of styrenes and acrylonitrile and the sub-
15 striate is polybutadiene. Another preferred species is
an MOBS resin, i.e., one where the superstrata is a
grafted copolymer of acrylonitrile, methyl methacryl-
ate and styrenes Still another preferred species
(MOBS) is prepared by copolymerizing styrenes and methyl
20 methacrylate in the presence of polybutadiene (as the
substrate).
A particularly preferred graft copolymer is
one wherein a copolymer of from about 70 parts to
about 90 parts of styrenes and from about 10 parts to
25 about 30 parts of methyl methacrylate is grafted onto
a polybutadiene substrate.
The product of the process herein, i.e., the
stabilized alkadiene polymer, is especially useful as
a substrate in the preparation of graft copolymers.
30 An AS copolymer prepared from such a substrate, for
example, is characterized by improved thermal stabile
fly. The data set out in Tables III show IV this.
, ;.
~l~332~6
079236-M -9-
EXAMPLE 3
Two batches of an AS graft copolymer were
prepared each according to the following recipe:
Grams
50.0 Polybutadiene
0.2 Potassium Thiosulfate
0.25 Tertiary-Dodecyl Mercaptan
1.0 Resinate 731
35.0 Styrenes
15.0 Acrylonitrile
233.0 Total Water
The first batch (No. 1) utilized an aqueous emulsion
of polybutadiene (prepared as in Example 1) which had
been treated with 5 parts of dodecyl 3-mercaptopro-
pinnate per 100 parts of polybutadiene; the second batch no. 2) utilized an aqueous emulsion of polybut-
adiene which was not so treated. Each batch was
heated with agitation at 60C for four hours, then
acid coagulated.
EXAMPLE 4
Two additional batches of Ass graft Capella-
men were prepared according to the following recipe:
~233'~
079236-M -10-
Grams
20.0 Polybutadiene
0.15 Tertiary Dodecyl Mercaptan
1.25 Resinate 731
51.4 Styrenes
28.6 Acrylonitrile
180.0 Total Water
0.55 Dextrose
0.004 Phase OWE
lo 1 drop Sulfuric Acid
0.02 Tetrasodium Pyrophosphate
0.40 Cumin Hydroperoxide
The first batch (No. 3) utilized an aqueous emulsion
of polybutadiene (prepared as in Example 1) which had
been treated with 5 parts of dodecyl-3-mercaptopro-
pinnate per 100 parts of polybutadiene; the second
batch (No. 4) utilized an aqueous emulsion of polybut-
adiene which was not so treated. Each batch was
heated with agitation at 60C for 1.25 hours, then
acid coagulated.
Analyses of the AS graft copolymers obtain-
Ed from these four batches showed the following:
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079236-M -11-
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079236-M - 12 -
The above data show that the incorporation
of the dodecyl~3-mercaptopropionate in the polybuta-
dine molecule has no adverse effect on the subsequent
grafting reaction with styrenes and acrylonitrile.
5 That is, suitable AS copolymers can be prepared in
the normal manner from the stabilized alkadiene-1,3
polymers of this invention.
Moreover, the AS copolymers thus prepared
are characterized by increased thermal stability as
lo shown by relative iso-DSC values. These are set out
in Table III and are obtained by heating the sample at
a given temperature (190C and 200C in these instance
en) until the onset of an exotherm. Test samples Nos.
1-4 correspond to those shown in Table II. Test
samples nos. PA and PA differ from nos. 2 and 4 in
that they each contain an amount of dilaurylthiodipro-
pinnate, 5.0 and 2.0 parts, respectively, per 100
parts of AS resin which is equal to the number of mows
of dodecyl 3-mercaptopropionate in Nos. 1 and 3. Also,
20 test samples Nos. 1, 2 and PA each contain 0.1 pph of A
425 and test samples 3, 4 and PA each contain 0.4 pph of
A 4250
TABLE III
Sample Temperature Time (miss.)
25 No. 1 190C
No. 2 190C 21
No. PA 190 C 90
No. 3 200C 77
No. 4 200 C 25
30 No. PA 200 C 48
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079236-M - 13 -
The above data show the superior thermal
stability of an As prepared from the alkyd markup-
topropionate-treated polymers herein (Nos. 1 and 3)
with respect to AS prepared from untreated polymers
5 (Nos. 2 and 4) and from untreated polymers containing
an additive of similar structure (Nos. PA and PA).
EXAMPLE 5
A mixture of 246 parts of polybutadiene
latex containing 40~D of polybutadiene having a weight
10 average particle size of 3000 A , 1.0 phi (parts per
hundred parts of resin) of dodecyl 3-mercaptopropio-
Nate and 0.08 phi of 2,2'-azobis-(2,4-dimethyl-4-
methoxyvaleronitrile) is warmed at 100DF for ten days
in a tray drier.
The resulting polybutadiene latex is con-
vented to an AS resin according to the procedure of
Example 4 except that the styrenes contains 0.14 phi of
2,2'-bis-(hydroxy-3-tertiarybutyl-5-ethylphenyl)meelk-
aye and 0.45 phi of tri-(nonylphenyl)phosphite, and
20 the process is carried out in a continuous manner.
The enhanced thermal stability of the product
of Example 5 is shown by the data in Table IV. The data
is obtained in terms of iso-DSC and DISC valves, the
blank being an AS resin prepared as in Example 5 except
25 that the polybutadiene from which it is prepared is not
previously reacted with dodecyl 3-mercaptopropionate.
The iso-DSC valves (minutes) are obtained at 190DC and
the DISC valves are the temperatures at which the samples
decompose.
~Z;332~6
079236-M - 14 -
TABLE IV
Iso-DSC (min. at 190C DISC (C)
stank 0 203C
Product of En. 5 33.5 237C
All parts and percentages herein, unless
otherwise specifically stated, are by weight.
