MINIMIZING OIL EXUDATION FROM HYDROGENATED BLOCK COPOLYMER COMPOSITIONS

REDUCTION AU MINIMUM DE L'EXSUDATION D'HUILE A LA SURFACE DE COPOLYMERES SEQUENCES, HYDROGENES

English Abstract

A B S T R A C T
The bleeding of oil from a composition containing
a selectively hydrogenated block copolymer of a mono-
alkenyl or mono-alkenylidene aromatic hydrocarbon and
an aliphatic conjugated diene hydrocarbon, a polyolefin
and oil is minimized by the presence of a sterically
hindered phenol, a benzotriazole or a mixture of these
compounds.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS;
1. A composition which comprises:
(a) 100 parts by weight of a selectively hydrogenated block copolymer
having at least two polymer blocks A, having a number average
molecular weight between 7,500 and 50,000, of a mono-alkenyl or
mono-alkenylidene aromatic hydrocarbon, and at least one partially
or completely hydrogenated polymer block B, having a number average
molecular weight between 10,000 and 125,000, of an aliphatic con-
jugated diene hydrocarbon;
(b) 5-150 parts by weight of a polyolefin;
(c) 10-175 parts by weight of a rubber extending oil; and
(d) 0.2 5 parts by weight of a sterically hindered phenol, a benzotri-
azole or a mixture of these oil bleed-out reducing agents.
2. A composition as claimed in claim 1, wherein at least 98% of the
residual aliphatic double bonds of the diene polymer block B are hydrogenated.
3. A composition as claimed in claim 1, wherein the sterically hin-
dered phenol is a phenol or alkylene bisphenol of the formula:
<IMG>
wherein R represents a hydrogen atom or an alkyl group having from 1 to 20
carbon atoms, provided that at least one R ortho to the OH-group is an alkyl
or substituted alkylene group, and wherein, additionally one R may be a group
of the formula
or <IMG> or <IMG>
<IMG>
wherein R1 is an alkylene group having from 1 to 3 carbon atoms in the chain
and from 1 to 8 carbon atoms in the group and R is an atom or group as de-
12

fined above.
4. A composition as claimed in claim 3, wherein the sterically hin-
dered phenol is a methylene phenol having the general formula
<IMG>
wherein R1 and R2 are alkyl radicals having 2-5 carbon atoms each.
5. A composition as claimed in claim 1, wherein the benzotriazole is
one having the general formula
<IMG>
wherein R1 is an alkyl radical having from 1 to 6 carbon atoms and R2 is an
alkyl radical having from 1 to 6 carbon atoms or hydrogen.
6. A composition as claimed in claim 1, wherein the benzotriazole is
a chlorinated one having the general configuration
<IMG>
wherein R3 and R4 are alkyl radicals having from 2 to 5 carbon atoms each.
7. A composition as claimed in claim 1, 2 or 3, wherein the oil bleed-
out reducing agent is present in an amount of 0.75-2 parts by weight per 100
parts by weight of the block copolymer.
8. A composition as claimed in claim 1, 2 or 3, wherein the rubber
extending oil is a hydrocarbon oil.
9. A composition as claimed in claim 1, 2 or 3, wherein the rubber
extending oil is present in an amount of 50-125 parts by weight per 100 parts
13

by weight of the block copolymer.
10. A composition as claimed in claim 1, 2 or 3, wherein the poly-
olefin is present in an amount of 10-125 parts by weight per 100 parts by
weight of the block copolymer.
11. Moulded or extruded articles formed of a composition as claimed
in claim 1, 2 or 3.
14

Description

1083283
-- 2 --
The invention relates to a composition comprising
a selectively hydrogenated block copolymer. It also relates
to shaped articles which are obtained by using such
compositions.
It is known that selectively hydrogenated block co-
polymers having at least two polymer blocks of a mono-
alkenyl or mono-alkenylidene aromatic hydrocarbon
and at least one partially or completely hydrogenated
polymer block of an aliphatic conjugated diene hydro-
carbon have certain advantages. However, their processability
; leaves something to be desired. It may be improved by
extending the block copolymers with certain olefinic
polymers. Furthermore, the blends may be extended with
rubber extending oils in order to both improve
,t, 15 processability and reduce the cost of the final compo-
sition. However, the resulting composltions show bleed-
out of oil following exposure to actinic radiation.
Oil bleed-out appears to occur with the compositions
comprising a selectively hydrogenated block copolymer,
3 20 a polyolefin and oil after injection moulding operation
which unavoidably results in surface stresses. No
adverse phenomena occur during the initial period~
Eventually, a thin film of oil, which is lar~ely identical ;~
with the extending oil, exudes to the surface and forms
, 25 a tacky surface film which gradually thickens under
continued ageing or exposure to light. Upon still further
-
:
. ' .
. ~,.. . . ~ . . . - . . . . .
. . ; ., , : . .

1083283
exposure, the oil appears to be absorbed into the shaped article. It
would be recognized by experts in the art, that even a temporary pre-
sence of an oily surface could result in a substantial technical dis-
advantage. The presence of the oil not only is unsightly, but causes
difficulty with adhesion to substrates or to paint films.
The object of the invention is to reduce or to eliminate oil
bleed-out from oil-extended compositions comprising a selectively hydro-
genated block copolymer and a polyolefin.
It has been found that oil bleed-out is minimized or prevented
by the presence of sterically hindered phenols and benzotriazoles.
Now, in accordance with the invention a composition is provided
comprising
(a) 100 parts by weight of a selectively hydrogenated block copoly-
, mer having at least two polymer blocks A, having a number average
3 molecular weight between 7,500 and 50,000, of a mono-alkenyl
or mono-alkenylidene aromatic hydrocarbon, and at least one
;,l partially or completely hydrogenated polymer block B, having a
I number average molecular weight between 10,000 and 125,000, of an
i aliphatic conjugated diene hydrocarbon;
~ 20 (b) 5-150 parts by weight of a polyolefin;
! (c) 10-175 parts by weight of a rubber extending oil; and
;'~
.. '~ ' ~ ' ~ . .
. .~ , . ,
,:, . . .

1083283
-- 4 --
(d) 0.2-5 parts by wei~ht of a sterically hindered
phenol, a benzotriazole or a mixturf~ of these
oil bleed-out reducing agents.
The selectively hydrogenated block copolymer present
in the composition according to the invention may have a
linear, branched or radial structure. It may be produced
by sequential block polymerization utilizing a lithium
initiator such as a lithium alkyl. Alternatively, a
coupling agent may be used in the production of the
block copolymer resulting in either a linear or a
branched or radial product. The resulting block copolymer
~ is then selectively hydrogenated.
t The polymer blocks A formed from a mono-alkenyl or
a mono-alkenylidene aromatic hydrocarbon ma~ have a number
average molecular weight between 7,500 and 50,000. The ; ~
polymer block B formed from an aliphatic conjugated diene ~ -
Z hydrocarbon may have a number average molecular weight
between 10,000 and 12,f,000. At least 90% of the residual
~i aliphatic double bonds of the diene polymer block B may
,~l 20 be hydrogenated. Preferably at least 98% of these double
bonds are hydrogenated.
~1 The polymer blocks A may be formed from styrene, alpha- ;~
,l methyl styrene or tert-butyl styrene. The polymer
block B may be formed from butadiene or isoprène. The
Z 25 block copolymer may have the linear structure polystyrene-
polybutadiene-polystyrene or polystyrene-polyisoprene-
polyetyrene.
.
.
:' .
.
- ,
, . . . .

1083283
5 --
As used herein the term "a sterically hindered
phenol" is intended to include a phenol or alkylene
bisphenol of the formula:
OH
R ~ R
R ~ R
R
wherein R represents a hydrogen atom or an alkyl group
having from 1-20 carbon atoms, provided that at least
one R ortho to the OH-group is an alkyl or substituted
alkylene group, and wherein, additionally one R may be
a group of the formula
OH OH OH
R ~ Rl-- or R--~R or R --~ R
R ' R R1
wherein R1 is an alkylene group having from 1 to 3
carbon atoms in the chain and from 1 to 8 carbon atoms
in the group and R is a group as defined above.
:l Examples of these phenols are:
2-methylphenol
2,6-ditert.-butyl-4-methylphenol
2-methyl-6-isopropylphenol
2-tert.-butyl-4-methylphenol
2-amylphenol
~,
:
~, .
, , . ~ . . . .

1083283
2-nonylphenol
2-dodecylphenol
2-tetradecylphenol
methylenebis-2(2,6-ditert.-butyl)phenol
: 5 t2,2-bis(2-hydroxyphenyl)~propane
2-eicosylphenol
2,4,6-triicosylphenol
1,3-bis(2-hydroxyphenyl)-2-methyl-2-t-butylpropane ;
. and mixtures Or these phenols.
j 10~ Preferred hindered phenols include methylene
bisphenols having the general configuration
OH ,OH
~ CH ~ R
:, wherein R and R are alkyl radicals having 2-5 carbon .
atoms each. The preferred species is 2,2-methylene ;
bis(4-ethyl-6-tert.-but~phenol).
The benzotriazole which may be present in the
composition according to the invention can comprise -
any benzotriazole which has the general formula
' ~ / N ~ ;:
wherein R1 is an alkyl radical having from one-six
carbon atoms and R2 is an alkyl radical having from
20 one-six oarbon ~toms or hydrogen. Examples are:
'
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~,
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1083283
2(2-hydr~xy-3,5-di-n-hexylphenyl)benzotriazole
2(2-hydroxy-5-methylphenyl)benzotriazole
2(2-hydroxy-5-tert-buty~henyl)benzotriazole
2(2-hydroxy-3-methyl-5-isoamylphenyl)benzotriazole
2(2-hydroxy-3-hexyl-5-isopropylphenyl)benzotriazole
t 2(2-hydroxy-3,5-dimethylphenyl)benzotriazole.
In a specific embodiment 2~2-hydroxy-5-methylphenyl)
benzotriazole produced outstanding results.
Preferred benzotriazoles are chlorinated, having
the general configuration
C~ ~ \ N
~, I /
~ N R4
wherein R 3and R4 are alkyl radicals having from
j 2-5 carbon atoms each. The preferred species is 2-(3',5'-
ditert.-butyl-2'-hydroxyphenyl)-5-chlorobenzotriazole.
The sterically hindered phenols and benzotriazoles
are preferably present in an amount of 0.75-2 part by
weight per 100 parts by weight of the block copolymers.
;l~ The rubber extending oil which is present in the
composition according to the invention may be hydro-
carbon oils which may be paraffinic, naphthenic, or
.,
aromatic, relatively nonvolatile oils, at least under
the physical conditions to which the composition
;~ ~ would normally be exposed. It is preferably present
in an amount of 50-125 parts by weight per 100 parts
by weight of the block copolymer.
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~083283
The polyolefin which is present in the composition
according to the invention may be a homopolymer such as
polyethylene and polypropylene o~ a copolymer which may
be a tapered, random or block copolymer.
The polyolefin is preferably present in an amount
of 10-125 parts by weight per 100 parts by weight of
the block copolymer.
A preferred composition is as follows:
a) a block copolymer having the configuration
polystyrene-completely hydrogenated poly- -~
butadiene-polystyrene
b) Polypropylene ~
c) Mineral rubber extending oil -
d) 2,2'-methylene bis[4-ethyl-6-tert.-butylphenol]
e) 2-(3~,5'-ditert.-butyl-2'-hydroxyphenyl-5-
chlorobenzotriazole.
It is emphasized that the present invention relates ~ -
,
to compositions comprising at least the three essential -
components including the selectively hydrogenated block
,
copolymer. Since the diene blocks have been substantially
completely hydrogenated, the normal stability problems
encountered with non-hydrogenated diene polymers are
at a minimum. Thus, normal oxygen, ozone and light
sensitivity in the bulk properties ttensile strength,
viscosity and melt flow) are of little concern in the
hydrogenated block copolymers. On the other hand, the
:
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1083283
g
.
oil bleed-out problem has been f'ound to be of major
concern in the utility of the hydrogenated block copolymer
compounds, but it does not affect the utility, to any
appreciable extent, of compositions comprising the non-
hydrogenated block copolymers.
Other compounding ingredients may be present~
such as resins, fillers, pigment and stabilizers.
The ingredients may be mixed by dry blending procedures,
or in a typical Banbury mixing operation and the mixture
so formed is then subjected to shaping operation such
` as compression moulding or some form of extrusion
moulding or extrusion.
The following examples illustrate the reduction
in oil bleed-out effected by th~ use of the present
invention.
The basic composition was as follows:
Block copolymers 100 parts by weight ~ :
~ Polypropylene 40
; A Penrico EX26~ Oil 150
1 20 The block copolymer had the structure
polystyrene-completely hydrogenated polybutadiene-
polystyrene with block molecular weight of 25,000-100,000-
25,000. ~-
~; Plaques.measuring 10 cm x lO.cm x 0.16 cm were . `
, 25 injection moulded and exposed to GE Sunlamps in equipment
'I ~
~; resembling that required in the Fadeometer test, ~ .
~ ~ Tr~dQ~s
, ~
.,
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1~)83Z83
-- ~ o --
ASTM 0928 Method B until maximum oil bleed-out occurred.
For these tests, samples of the basic composition were
modified with one or more of th_ following additives,
wi~h the changes in maximum oil bleed-out noted below:
Table 1
Parts by Weight
Sample A B C D E
Additive;
Tetrakis ~methylene 3-(3',5'-
10 di-tert.butyl-4'hydroxyphenyl)
propionate~methane 1.0 1.0
Dilaurylthiodipropionate 1.72 1.0
2,2'-bis(4-methyl-6-tert. -
butylhydroxyphenyl)methane o ~ 58
2(3',5'-di-tert.butyl-2'-
hydroxyphenyl)-5-chloro- `~ ;~
~¦ benzotriazole 1.22
Max.~il Bleed-Out, mg/6.45 cm2 1.2 1.5 2.1 0.6 1.0
Note the low level of oil bleed-out especially in
?~ 20 Samples D and E, which are according to this invention.
The amount of oil bleed-out was determined by weighing
the plaque, blotting off the oil from the surface with
~-~ paper and re-weighing the sample to determine weight
loss due to oil removal.
A second series of samples were prepared wherein
Q : ~ ~ '
the basic composition noted above was modified with
. ;~
.
"
' ' " ' . ' '
.... . .

~083Z83
-- 11 --
180 parts of calcium carbonate and 2 parts by weight of
a polyepoxide. Injection moulded plaques of the above
dimensions were conta ning the same series of additives
listed in Table 1. The samples were exposed to a
fluorescent UV source and maximum oil bleed-out was determined
as described above. Table 2 lists the results obtalned.
Table 2
Parts by Weight
Sample F ~ ~ I
Tetrakis rmethylene 3-(3',5'-di-tert.
butyl-4'hydroxyphenyl)propionate~
methane 0.
Dilaurylthiodipropionate 0.5
2,2~-bis(4-methyl-6-tert.butyl-
hydroxyphenyl)methane 1.0 1.0
2(3',5'-di-tert.butyl--2'-hydroxy-
phenyl3-5-chloro-benzotriazole 1.0 1.0
Max.Oil Bleed-out, mg/6.45 cm2 1.8 0.2 0.1 0.0
Note that samples G, H, and I, all according to this
invention, showed exceptionally low oil bleed-out.
(QUV) Testing was carried out in a temperature
controlled circulating air accelerated weathering
environment chamber employing fluorescent light bulbs
the output of which closely matches that of unfiltered
sunlight at the short waveIength end of the spectrum,
producing virtually no radiation shorter than 295 nm.
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