Note: Descriptions are shown in the official language in which they were submitted.
~ ~4:J 2~5
The present inventlon relates toa process for grafting
a particular butadiene-styrene rubbery substrate ~hereinafter
: . . . ,~ ,
described) in two stages to provide a grafted butadiene-styrene
rubber substrate with a high nitrile content in the outer shell.
The resulting grafted rubber may be used per se or blended with
a high nitrile polymer matrix to form a polyblend~
In recent years rubber modified high nitrile polymers
have been taught in the art for packaging applications where
good impact resistance, good oxygen permeability and good water
vapor transmission properties are required. The same polymers
have been taught for use in external applications where, in
addition to the above propertiesr good weatherability properties
are required.
`~ The present invention fulfills a need in the art by
providing a process for preparing rubber modified high nitrile
polymers which may be used to pxepare polyblends which have good
optical properties as well as good impact, good oxygen permea-
bility, good water vapor barrier properties and good weather-
ability properties.
It is an object of the present invention to provide a
method for ~-k;ng a novel graft polymer component having a par-
ticular butadiene~styrene rubbery substrate and a composite
superstrate which is relatively rich in ethylenically unsatur-
ated nitrile monomer.
In a pref erred embodiment o the present invention
there is provided a process for preparing impact modified nitrile
polymer compositions which comprises:
A. a~;~;ng
(1) a rubbery polymer substrate having a butadiene
content of 68 to 72 percent by weight and a
styrene content of 28 to 32 pexcent by weight
~.
~ - 2 -
- ~,
2~5
based on the total weight of the butadiene-
styrene rubbery substrate which rubbery sub~trate
is further characterized as having a refractive
index in the range of from 1.5375 to 1.5425, a
particle size in the rang~ of from 0.06 to 0.2
micron, a gel content in the range of from 40 to
95 percent, a swelling index in the range of from
10 to 40, and a second order transition tempera-
.~ .
ture (Tg) less than -40C; and
10 ~ (2) a first polymerizable monomer composition com-
: prising: .
; ~ : (a) from 0.1 to 2 percent by weight of a non-
: :
~ conjugated diolefin monomer;
: : : : :
::~:: . (b) from O to 30 percent by weight of an ethyl-
enlcally unsaturzlted nitrile monomer
selected from the group consisting of acrylo-
:` nitrile, and mixtures o acxylonitrile and~
methacrylonltrile~
c) from 40 to 60 percent by weight of a vinyli-
dene aromatic hydrocarbon monomer and
d) from 20 to 50 percent by weight of an alkyl
ester of acrylic or methacrylic acid wherein
the alkyl group contains from I to 8 carbon
: atoms; wherein the percent by weight is based
: `
on the total weight of the monomer in the
~: first polymerizable monomer mixture;
:
B. subjecting the admixture to polymerization conditions to
effect pol~nerization of said monomer fonnulation and
grafting of the polymer beïng produced onto the rubbery
polymer substrate to form a graft copolymer, said graft
copolymer having a superstrate to substrate ratio of at
least 10:100;
C. admixing said graft copolymer with a second polymerizable
!
~ . , .", .
s
composition comprising from 65 to 85 percent by weight -
of an ethylenically unsaturated nitrile monomer selected
from the group consisting of acry~onitrile and mixture~
of acrylonitrile and methacrylonitrile which contains
up to 20 percent by weight of methacrylonitrile based on
the total weight of acrylonitrile and methacrylonitrile
and from 15 to 45 percent by weight of a monovinylidene
aromatic hydrocarbon monomer wherein the percent by weight
is based on the total weight of the monomers in the
second polymerizable ono~cr mixture; and
subjecting the second mentioned admixture to polymeriza-
tion conditions to effect polymeri.zation of the monomers
thereof and to produce grafting of the polymer being
produced onto said graft copolymer to form a compo~ite
graft copolymer, said grafted polymers of said first and
second admixtures providing a grafted superstrate which
contains a total of at least 40 percent by weight ethylen-
ically unsaturated nitrile monomer and wherein the ratio
of grafted superstrate to substrate is in the range of
: ,
: :~ 20 : from 15-200:100.
~: ~
In a further preferred embodiment of the present inven-
tion there is provlded a polymeric composition comprising:
A. A butadiene-styrene rubbery substrate having a butadiene
content of 68 to 72 percent~by weight and a ~tyrene content
of 28 to 32 percent by weight based on the total weight of
the butadiene-styrene rubbery substrate which rubbery sub-
strate is further characterized as having a refractive
: index in the range of from 1.5375 to 1.5425, a particle
size in the range of from 0.06 to 0.2 micron, a ~el con-
tent in the range of from 40 to 95 percent, a swelling
~ - 2b -
~",,~ .
2~5
index in the range of from 10 to 40, and a second order
transition temperature (Tg~ less--than -40C; and
B. a superstrate grafted onto the rubbery substrate which
superstrate comprises:
(1) the polymerization product of a first polymer-
izable monomer composition comprising:
(a) ~rom 0.1 to.2.percent by..weight of a
nonconjugated diolefin monomer;
: (b) from 0 to 30 percent by weight of an
ethylenically unsaturated nitrile monQ~?r
selected f~rom the group consisting of
.; acrylonitrile, and mixtures of acryloni-
.~ trile and methacrylonitrile which contain
, ~ up to 20 percent by weight of methacrylo-
nitrile;
(c) from 40 to 60 percent by weight of a vinyl-
i idene aromatic hydrocarbon on~ or; and
,
(d~ from 20 to 50 percent by weight of an alkyl-
ester of acrylic or methacrylic acid where-
20 ~ ~ ~ in the alkyl group contains from 1 to 8
carbon atoms, wherein the percent by weight
: is based on the total weight of the monomer
~ in the first polymerizable monomer mixture;
: .
and
(2) a second polymerizable monomer composition comprising
from 55 to 85 percent by weight of an ethylenically
unsaturated nitrile monomer selected from the group
consisting of acrylonitrile and mixtures of acrylo-
nitriie and methacrylonitrile which contain up to 20
percent by weight of methacrylonitrile based on the
total weight of acrylonitrile and methacrylonitrile
~ - 2c -
. ,! .
~\
lC~ 5
and from 15 to 45 percent by weight o~ a
monovinylidene aromatic hydrocarhon monomer
.wherein the percent by weight is based on
the total weight of the monomers in the
second polymerizàble monomer mixture;
wherein the grafted superstrate contains a total G at least 40
percant by weight ethylenically unsaturated nitrile on~ -r and
wherein the ratio of grafted superstrate to substrate is in the
:~ ~ ran~e of from 15-200:100.
: 10 In the process, there is formed an admixture of a
particular butadiene-styrene rubbery substrate and a first
.
~ polymerizable monomer
. .
: :
: : :
,: :
:'
,
-
, .
- 2d -
lZ9~S
)-12-0261
composition comprising a difunctional monomer, an ethylenically unsaturated
nitrile, a monovinylidene aromatic hydrocarbon and an alkyl ester of acrylic
or methacrylic acid. This composition is subjected to polymeriza~ion condi-
tions to effect polymeri~ation of the monomer formulation and grafting of a
substantial portion of the polymer being produced onto the particular butadiene-
styrene rubbery substrate. The resultant graft copolymer has a superstrate to
substrate ratio of at least lO:100 and is thereafter admixed with a second poly-
merizable monomer composition consisting of at least 55 percent by weight of an
ethylenically unsaturated nitrile monomer. The second monomer co~position is
sub~ected to polymeri~ation conditions to effect polymerization of the monomers
thereof and to produce grafting of a substantial portion of the polymer being
produced onto the graft copolymer to form a composite graft copolymer. In the
composite graft copolymer, the grafted polymers of the first and second monomer
compositions provide a superstrate containing a total of at least 40 percent by
weight ethyl~n;r~lly unsaturated nitrile monomer.
Although the composite graft copolymer thus formed may be utili~ed
se for various applications as a rubber modlfied material such as those
where acrylonitrile-b~lt~pne-styrene (ABS) or styrene-acrylonitrile (SAN)
materials are employed, it has especial utility as an impact modifier for high
nitrile polymers. By proper selection of the chemical composition of the
butadiene-styrene polymer substrate and of monomers and the amounts thereof
grafted onto the rubber polymer substrate, the apparent refractive index of the
composite graft copolymer can be closely matched to the refrac~ive index of the
high nitrile matri~ polymer to provide a transparent composition having highly
desirable impact strength, good chemical resistance and a balance of other
properties Such impact modification has been especially useful in the manu-
facture of nitrile polymer blends for p~ck~g~ng and other applications.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
~ature of the Rubber Polymer Substrate
The particular butadiene-styrene rubbery polymer substrate onto which
.
~-08-12-0261 ~041 2~5
the monomers are grafted are copolymers of butadiene and styrene which contain
from 68 to 72 percent of butadiene and correspondingly from 28 to 32 percent
by weight of styrene based on the weight of the butadiene-styrene copolymer.
Optionally, up to 5 percent by weight of the butadiene may be replaced with a
nitrile monomer such as acrylonitrile or methacrylonitrile.
The butadiene-styrene rubbery substrate must have a refractive index
in the range of from 1.5375 to 1.5425, a particle size in the range of from
0.06 to 0.2 microns before grafting, a gel content in the range of from 40 to
95 percent, a swelling index in the range of from 10 to 40, and a second order
transition temperature (Tg) less than -20C. and preferably less than -40C. as
determined by ASTM Test D-746-52T. The above specified refractive index range
for the rubber substrate is required in order to have the refractive index of
the rubber substrate in the same range as the refractive indices for the grafted
superstrates and the high nitrile matrix in order to provide optimum optical
properties. The above specified rubber particle size, gel content, swelling
index and second order transition temperature is required in order to provide
optimum impact properties.
The Polymerizable Monomer Compositions of the Superstrate
The first polymerizable monomer composition comprises (1) from 0.1 to
2 percent by weight, preferably 0.1 to 1 percent by weight, of a nonconjugated
diolefin monomer, (2) from 0 to 30 percent by weight of an ethylenically un-
aturated nitrile selected from the group consisting of acrylonitrile, and
mixtures of acrylonitrile and methacrylonitrile which contain up to 20 percent
by weight ~ethacrylonitrile9 (3) from 40 to 60 percent by weight of a vinylidene
- 25 aromatic hydrocarbon monomer and (4) from 20 to 50 percent by weight of an alkyl
ester of acrylic or methacrylic acid wherein the alkyl group contains from 1 to
8 carbon atoms, wherein the percent by weight referred to above is based on the
total weight of the first polymerizable monomer mixture.
The nonconjugated diolefins employed in the practice of this invention
are monomers which have two nonconjugated ethylenically unsaturated double bonds
-4-
'
-08-12-0261 1~4~ 2~
per molecule, such that at least one double bond reacts readily causing the
diolefin to interpolymerize with the other monomers used in the first polymeri-
zable monomer formulation. Preferably, these diolefins have two ethylenically
unsaturated double bonds with a different degree of reactivity or having a
crossl;nk;ng efficiency of less than one. These diolefins may be aliphatic,
aromatic, aliphatic-aromatic, heterocyclic, cycloaliphatic, etc. Examples of
suitable diolefins would include divinyl ben~ene9 ethylene dimethacr~late7
ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene
glycol dimethacrylate, polyethylene glycol dimethacrylate, allyl methacrylate,
diallyl fumarate, diallyl maleate, vinyl crotonate, and nonconjugated alpha,
omega diolefins of at least 5 carbon atoms such as 1,4-pentadiene, 1,7- octa-
; diene, etc. Ethylene glycol dimethacrylate is the preferred difunctional
monomer.
Exemplary of the monovinylidena aromatic hydrocarbons which are
used in the superstrate are styrene, alpha-methylstyrene; ring-substituted
alkyl styrenes, e.g., vinyl toluene, o-ethylstyrene, p-ethylstyrene, 2,4-
dimethylstyrene9 etc.; ring-substituted halostyrenes, e.g., o-chlorostyrene,
p chlorostyrene, o-bromostyrene, 2,4-dichlorostyrene, etc.; ring-alkyl,
ring-halosubstituted styrenes, e.g., 2-chloro-4-methylstyrene, 2,6-dichloro-
4-methylstyrene, etc.; vinyl naphthalene; vinyl anthracene, etc. The alkyl
substituents generally have 1 to 4 carbon atoms and may include isopropyl and
isobutyl groups. Mixtures of the above monovinylidene aromatic monomers may
be employed. Styrene and alpha methyl styrene are preferred.
The alkyl esters of acrylic and methacrylic acids used in the first
polymeri~able monomer composition are those wherein the alkyl group contains
from 1 to 8 carbon atoms, e.g., methyl, ethyl, propyl, butyl, 2-ethylhexyl,
etc. Examples of such esters ;n~ de methyl acrylate, ethyl acrylate, butyl
acrylate, methyl methacrylate, butyl methacrylate, 2-ethyl hexylmethacrylate,
etc. The preferred ester is methyl methacrylate. A particularly preferred
first polymeri~able monomer composition contains (1) 0.1 to 2 percent by weight
:~
~ ~5-
-08-12-0261 ~'~41~4S
of ethylene glycol dimethacrylate; (2) 20 to 30 percent by weight of acrylo-
nitrile; (3) 40 to 60 percent by weight of styrene; and (4) 20 to 50 percent
by weight of methyl methacrylate; wherein the percent by weight referred to
above is based on the total weight of the first polymerizable monomer mixture.
The second polymer;zable monomer composition contains from 55 to 85
percent by weight of an ethylenically unsaturated nitrile monomer selected from
the group consisting of acrylonitrile and mixtures of acrylonitrile and meth-
acrylonitrile which contains up to 20 percent by weight of methacrylonitrile
based on the total weight of acrylonitrile and methacrylonitrile.
The second polymeriæable monomer composition contains from 1 to 45
percent by weight of a monovinylidene aromatic hydrocarbon monomer of the type
referred to above. Up to 10 percent of the monovinylidene aromatic hydrocarbon
monomer can be replaced with a vinylidene monomer selected from the group con-
sisting of alkyl vinyl ethers wherein the alkyl group contains from 1 to 4
carbon atoms, vinyl esters such as vinyl acetate and alkyl esters of acrylic
and methacrylic acids wherein the alkyl groups contain from 1 to 8 carbon atoms.
The preferred monovinylidene aromatic hydrocarbons are styrene and
alpha methylstyrene.
The preferred vinylidene monomers, which are used to replace up to
10 percent by weight of the monovinylidene aromatic hydrocarbon, include methyl
~; vinyl ether, ethyl vinyl ether, methyl acrylate, ethyl acrylate, butyl acrylate
and the corresponding metnacrylates, especially methyl methacrylates.
~; The percent by weight referred to above in regard to the second
monomer mixture is based on the total weight of the monomers in the second
monomer mi~ture.
The Graft Polymerization Process
Although the method of the present invention has previously been
described as being conducted with two distinct polymerization monomer formula~
tions in two separate polymeriæation steps, it should be apprec~ated that the
two steps can be blended into each other. Accordingly, the two formulations
--6~
z~s
C-08-12-0261
can be blended into each other in a process where monomers are added during
the course of polymerization. In such a technique, the first monomer formu- -
lation would be provided by the monomers present initially during the first
stage grafting reaction and thereafter the second stage monomer formulation
would be added during the course of the polymerization reaction to provide
the equivalent of the second or high nitrile monomer polymerizable formulation
as the grafting reaction progressed.
The amount of the first polymerizable monomer composition relative to
the amount of substrate may vary ~airly widely depending upon the efficiency
Qf the grafting reaction and the composition of the formulation. As previously
indicated, of the total graft superstrate provided by the two monomer composi-
tions, at least 40 percent by weight must be formed from ethylenically unsatu- ~ -
rated nitrile monomer. The weight ratio of the first monomer formulation to
substrate will normally be about 15-150:100 parts by weight, and preferably
15 about 25:120:100. It is essential that the superstrate to substrate ratio re-
sultlng from the polymerization of the first monomer formulat~on be at least
10:100 and preferably about 20-90:100. Since the barrier properties of the
composition will vary with the amount of non-nitrile polymer content, it is
generally desirable to m;nim;~e the amount of ungrafted polymer formed from
the first polymerizable monomer mixture.
:, ,
The ratio of the second polymerîzable composition to rubbery polymer
substrate also may vary fairly widely depending upon the amount of superstrate
produced by the first pol~merizable composition in view of the requirement that
; the nitrile monomer content comprise at least 40 percent by weight of the total
graft superstrate. Generally, the ratio of the second monomer composition to
rubber substrate will be about 20-250:100 and preferably about 40-150:100. For
econom~ of operation, the grafting reaction is ideally conducted under relatively
efficient conditions so as to m~n~m~ze the amount of ungrafted interpolymer which
is formed, although any ungrafted nitrile polymer would normally not adversely
affect the barrier properties of the blend.
C-08-12-0261 1~245
Various techniques are customarily employed for graft polymerizing
the monomers of the superstrate onto the rubbery polymer substrate including
mass9 suspension, solution and emulsion polymerization techniques, and com-
binations thereof. Emulsion and suspension polymerization techni~ues have
proven particularly useful.
In the emulsion graft polymerization process, the monomers and
rubbery substrate are emulsified in a relatively large volume of water by use
of suitable emulsifying agents such as fatty acid soaps, alkali metal or
ammonium soaps of high molecular weight alkyl or alkaryl sulfates and sul-
fonates, mineral acid salts of long chain aliphatic amines, etc. Emulsifyingagents which have proven particularly advantageous are sodium oleate, sodium
palmitate, sodium stearate, sodium lauryl sulfate and other sodium soaps.
Generally, the emulsifying agent is provided in amounts of about 1 to 10 parts
by weight per 100 parts by weight of the monomers. The amount of water in
which the monomers and rubbery polymer substrate are emulsified may vary de-
pending upon the emulsifying agent, the polymerization conditions and the
par~icular monomers. Generally, the ratio of water to monomer with alkali
metal soaps will fall within the range of about 80-300:100, and preferably
about 150-250-100. The aqueous latex formed in the emulsion polymerization
20 of the rubbery polymer substrate may provide the aqueous medium into whioh the
monomers are incorporated with or without additional emulsifying agents, etc.
.
However, the rubbery polymer may be dispersed in the monomers and the mixture
emulsified, or a latex thereof may be separately prepared.
Although actinic radiation and both water-soluble and monomer-soluble
peroxy-type and perazo-type catalysts with or without a reducing agent to form
a redox system may be employed for the graft polymerization reaction, it has
been found highly advantageous to use a redox system with a water-soluble
catalyst for emulsion polymerization reactions. Redox systems offer the
advantage of permitting the use of slower catalysts with equivalent conversion
periods.
-8-
C-08-12-0261 104~24S
Exemplary of the water-soluble peroxy catalysts are the alkali metal
peroxides; the alkali metal and ammonium persulfates, perborates, peracetates ~-
and percarbonates, and hydrogen peroxide. Exemplary of the monomer-soluble
peroxy and perazo compounds are di-tert-butyl peroxide, di-benæoyl peroxide,
di-lauroyl peroxide, di-oleyl peroxide, di-toluyl peroxide, di-tert-butyl
diperphthalate, di-tert-butyl peracetate9 di-tert-butyl perbenzoate, dicumyl
peroxide, di-tert-butyl peroxide, di-isopropyl peroxy dicarbonate, 2,5-dimethyl-2,
5 di~(tert-butylperoxy) hexane, 2,5-dimethyl-2,5-di(tert-butyl peroxy) hexyne-39
di-tert-butyl hydroperoxide, cumene hydroperoxide, p-menthane hydroperoxide,
cyclopentane hydroperoxide9 diisopropylbenzene hydroperoxide, p-tert-butyl-
cumene hydroperoxide, pinane hydroperoxide, 2,5-dimenthylhexane, 2,5-dihydro-
peroxide, etc.; azo-di-isobutyonitrile; and mixtures thereof.
The catalyst is generally included within the range of 0.001 to l.0
percent by weight, and preferably on the order of 0.005 to 0.5 percent by weight
of the polymerizable material, depending upon the monomers and the desired
polymerization cycle.
Exemplary of the reducing agents which may be employed are alkali
metal and ammonium sulfites, hydrosulfites, metabisulfites, thiosulfates,
sulfinates, alkali metal formaldehyde sulfoxylates, ascorbic acid9 dioxyace-
. ~ ~~ 20 tone, dextrose, etc. Various other reducing agents-for redox systems may also
be employed. The amount of reducing agent will be about 0.001 to 1.0 percent
by weight, and preferably on the order of 0.005 to 0.5 percent by weight of the `~
.
polymerizable monomer formulation, depending on the catalyst and the amount
; thereof. Minute amounts of activators or promoters such as ferrous salts and
copper salts may be included in the redox systems.
Molecular weight regulators may be included in the formulation for
the graft polymeri~ation reaction so as to control the molecular weight and
achieve the desired properties. Exemplary of such molecular weight regulators
are alkyl mercaptans and terpenes, specifically N-dodecyl mercaptan, tert-
dodecyl mercaptan, n-butyl mercaptan, isopropyl mercaptan, terpinolene,
.9 ~
,
., ' ' ''
C-08-12-0261 1~245
d-limonene, etc., or their blends.
The particular polymerization conditions employed will vary with
the monomer formulation, the catalyst and the polymerization technique.
Generally, the reaction will increase with an increase in temperature although
a limiting factor is possible deterioration in product properties and also a
tendency to produce problems in maintaining latex stability. Generally,
temperatures of about 30 to 100 Centigrade and pressures of about 0-50 p.s.i.g.
have been found suitable for a fairly efficient emulsion graft polymerization
reaction. Preferably, an inert atm~sp~ere is employed over the poly-
merizing latex.
After the polymerization reaction has proceeded to the desired de-
gree of conversion of the monomers, which will normally be more than 90 percent,
any unreacted monomers should be stripped. After the graft polymerization,
the graft copolymerblend may be recovered from emulsion by various techniques
lS of coagulation in the form of a crumb, or by evaporation, and is washed for
subsequent processing Alternatively, the latex may be combined with a latex
of the matrix polymer and coagulated or spray dried therewith. The amount of
ungrafted interpolymers produced by the graft polymerization reaction will
vary with the type and efficiency of the graft reaction and the ratio of
20 ~ monomer formation to rubbery polymer substrate in the charge. By these factors,
~ the amount of ungrafted polymer in an emulsion reaction will normally vary
~ withln the range of about 10 to 150 parts of grafted rubbery polymer substrate
with the higher ratios being produced by high monomer/substrate charges.
The Matrix Interpolymer
., .
Generally, it is advantageous to conduct an bmulslon graft polymeri-
zation reaction under conditions which are reasonably efficient so that the
rubbery content of the emulsion product will range from about 25 to 65 percent
thereof. Normally, the rubbery substrate content desired for the polyblends
of the present invention will be in the range of 3 to 50 percent by weight and
preferably 5 to 20 percent. Thus, it is generally preferred to prepare matrix
--10--
^08-12-0261 1~4~ ~5
interpolymer by a separate reaction and this Matrix interpolymer is then
blended with the graft polymer component which may include (and will normally
include) some ungrafted interpolymer.
The matrix polymer contains from 55 to 85 percent, preferably 60
to ~5 percent by weight, based on the total weight of the polymer, of an
ethylenle~lly unsaturated nitrile monomer selected from the group consisting
o~ acrylonitrile and mixtures of acrylonitrile and methacrylonitrile which
contain up to 20 percent by weight of methacrylonitrile based on the total
weight of acrylonitrile and methacrylonitrile and from 15 to 45 percent of a
monovinylidene aromatic hydrocarbon monomer of the type referred to above.
Up to 10 percent of the monovinylidene aromatic hydrocarbon monomer can be re-
placed with a vinylidene monomer selec~ed from the group consisting of alkyl
; vinyl e~hers, wherein the alkyl group contains from 1 to ~ carbon atoms, vinyl
esters such as viny:L acetate;and alkyl esters of acrylic and methacrylic acids
lS wherein the alkyl groups contain from 1 to 8 carbon atoms. The preferred
monovinylidene aromatic hydrocarbons are styrene and methyl styrene~ The
preferred vinylidene monomers which can be used to replace up to 10 percent
of the monovinylidene aromatic hydrocarbon inc;Lude methyl vinyl ether, ethyl
vinyl ether, methyl acrylate, ethyl acrylate, b~ty~ acrylate and the corres-
ponding methacrylates, especially methyl methacrylate.
~ ~ Preferably, the composition of the matrix polymer is substantlally
;~ ~ the same as the composition o~ the second polymerizable monomer composition.
The method used to prepare the matrix interpolymer may be any which
is commonly practiced in the art; the polymerization may be effected en masse,
in solution or with the monomer in an aqueous dispersion as an emulsion or
suspension. From the standpoint of economics and process control, highly
suitable polymers can be prepared by a method in which the monomers are sus-
pended in watèr since emulsion polymerization tends to introduce coloring
impurities in the poly~er by reason of the salts used for coagulation, the
emulsifying agents, etc.
~-08-12-0261 ~4~24~
Since transparent blends are desirable for many applications, the
refractive index of the matrix interpolymer should closely approximate the
apparent refractive index of the graft copolymer component. Although the
refractive index may be measured in each instance, it is possible to present
graphically the refractive indices of the various resinous and rubber inter-
polymers and then calculate the refractive index for the graft copolymer com-
ponent.
Other Components
Various other optional materials may be added to the compositions
of the present invention depending upon the intended use and nature thereof
such as, for example, plasticizers, dyes, pigments, stabilizers, antioxidants,
lubricants, processing aids and fillers. The amount and nature thereof will
determine the possible effect upon the transparency of the blends. Generally,
it is necessary to incorporate stabilizers and antioxidants to prevent degrada-
tion of the graft polymer component. Although the stabilizers and antioxidantsmay be incorporated at the time of blending of the components into the final
polyblend, generally it is most advantageous to incorporate these materials into
; the individual components after they are formed so as to m;nim~7e the tendency
` ~ for degradation or oxidation during processing and storage.
Formation of the Polymer Blends
The final polymer blends may be prepared by a~mi~ing the componen~s
thereof in any of the customary ways including mill rolling, extrusion blending,
etc. Where the matrix polymer is prepared by an emulsion poly_erization process,
` the latex thereof may be admixed with a latex of the graft copolymer blend and
the mixed latex coagulated, washed and dried.
Generally, the polymer blends may contain 3 to 50 percent by weight
of rubber provided by the rubbery substrate of the graft copolymer blend and
the préferred compositions will normally contain about 5 to 20 percent. Polymer
blends produced in accordance with the present invention are substantially
transparent, i.e., the transmittance through a molded specimen of 0.1 inch in
-12-
~ 12-0261 ;10~12~5
th~rknPsæ at 550 millimicrons wave length may have a value of at least 85
percent and generally considerably greater. In fact, suspension matrix
polymers having a definite yellow cast may be brought to a clear less yellow
blend when a~m;~d with a suitably formulated graft eopolymer component. For
5 a high degree of transparency, the refractive indices of the graft copolymer ~-
blend and matrix polymer must be closely matched, and the average particle
size of the graft copolymer component should be less than about 0 4 micron.
Yellowish coloration can be neutrali~ed by incorporation of the appropriate
blue dyes. However, blends which may be produced in accordance with the in-
vention afford significantly advantageous transparency enabling their appli-
cation to packaging, laminating and other uses where transparency is advanta-
geous and where the remaining balance of properties offers significant advantages.
Properties and Processing of the Polyblends
The polyblends of the present invention may be formed in conven-
tional processing equipment including injection molding apparatus, blow molding
apparatus and extrusion apparatus. In addition, the polyblends may be com-
pression molded if so desired. The processabil:Lty of the polyblends is satis-
factory for use in conventional equipment without the need for employing sol-
vents, lubricants or other flow modifiers.
p~rk~;ng sheet materials may be prepared from the po~yblend by
extrusion, r~l~n~er~ing~ casting and by other means well known to those skilled
in the art. Bottles and containers may be made by any of the conventional
methods such as blow extrusion, injection molding, vacuum forming~ etc. When
the sheet materials of the polyblends of this invention are subjected to ~mi~
or biaxial orientation, still further improvements in the ~~h~n~r~l properties
are notedO ~hen the films are so oriented, it is preferred that they be stretched
at least about 300 percent in one or both directions. It is further preferred
that the stretching be carried out at a rate of at least about 2000 percent per
minute. The preferred rate of stretching ranges 10,000-20,000 percent per
; 30 minute.
Biaxial stretching can be effected in a single or continuous opera-
tion. In piece operation, a lazy tongs-type cross-stretcher can be used to
-13-
~-08~12-0261 ~4~2~5
advantage, whereas in continuous-type operations either tenter-type cross-
stretching frames or blow-extrusion techniques can be used. When tenter-
frames are used, the differential in speed between the front and rear rollers
develops longitudinal stretching, while simultaneously the lateral spacing of
the frame develops transversel stretching so that the sheet material is bi-
axially stretched in both directions.
Although the polyblends of the present invention have been indicated
as being formed by a single g~aft polymerization component, it will be appre-
ciated that the polymeri~ation graft component need not be homogeneous. It may
be comprised of two or more polymerization graft components for benefits which
may be obtained thereby. Thus, although the graft polymer of the present
invention will have a total superstrate to substrate ratio of 15-200:100 and
preferably 20-150:100, one particle may have a ratio of 20-45:100 and another
may have a ratio of 55-150:100 with the amounts thereof being varied. Simi-
larly, the siæe of the particles may be multimodal or broadly distributed.
In addition, the polyblends of the present invention may bemechfln~cally blended with other polar polymers to form "alloys" offering certain
advantageous properties for given applications or to facilitate lamination.
Among such polar polymers are polycarbonate, polyvinyl chloride and poly-
sulfone resins; generally, such polar polymers may be included in amounts of
up to 30 percent by weight of the total ~h~n;cal blend.
The following examples are set forth in illustration of this invention
and are not ~o be construed as a limitation thereof. All parts and percentages
given are by weight unless otherwise indicated.
EXAMPLE 1
; This example illustrates the preparation of a butadiene-styrene
rubber of the type used in the present invention.
A bllt~d~n~-styrene rubber, which contains 70 percent by weight of
butadiene, and 30 percent by weight of styrene, is prepared using the following
charge:
-14-
~\
~-12-0261 ~ S
Deaerated distilled water 300 parts by weight
Rubber reserve soap (RRS) 6.0
Potassium chloride 1~0
Tert.-didecyl mercaptan (TDM)0.8 ~`
Ethylene glycol dimethacrylate (EGDM) 1.8
Potassium sulfate (K2S2O8) 0.6
Styrene 60.0
Butadiene (distilled) 140.0
The above ingredients are charged to a reaction vessel, heated at 55C. for
20 hours to a degree of conversion of 96%. The ethylene glycol dimethacrylate
, ~ - lS used~to crosslink the rubber. The resulting butadiene-styrene latices
characterized as follows:
Solids ~ ~ 40% by weight
pH 8.5-8.8
Surface tension 68-72 dynes/cm
` ~ Average particle size 0.09 to 0.1 micron
:;:
Gel content89% to 93%
Swelling index12 - 16
Refractive index nd25 1.5375 - 1.5395
Tg ~ -40C.
EXAMPLE 2 ~`
` ~ This example illustrates the use of a two-staga graf~ polymerization
reaction to prepare the grafted polymers of the present invention.
Twenty-five hundred parts of the latex prepared in Example 1 above,
Z5 after dilution to 20 percent rubber solids and addition of 1 percent, by weight
of rubber, of sodium lauryl sulfate, are charged to a reactor and heated under
nitrogen and with agitation to about 60C. An aqueous solution of 1.0 parts
of sodium formaldehyde sulfoxylate and a small qua~tlty of chelated iron is
added before graft monomer addition. To this latex is continuously added over
30 a one hour period a first monomer composition of 100 parts acrylonitrile, 200parts styrene, 100 parts methyl methacrylate and 4 parts ethylene glycol
3-12-0261 ~ O ~ ~ Z ~ S
dimethacrylate. During monomer addition, 1 part of potassium persulfate in
aqueous solution is charged to the reactor. Stirring is continued during the
addition of the first monomer composition and is continued for an additional
period of one hour thereafter. Then, 0.8 part of sodium formaldehyde sulfoxy-
late and 0.8 part of potassium persulfate in aqueous solution is added to thelatex and a second monomer composition of 130 parts acrylonitrile, 70 parts
styrene and 2 parts tert-dodecyl mercaptan is continuously added to the reactor
over a one-half hour period. Towards the end of the second monomer composi-
tion addition, a solution of 11 parts sodium lauryl sulfate is charged to the
reactor, and agitation and hea~ing are continued for about 30 minutes. The
latex is then cooled to 25C. and 5 parts of a conventional antioxidant is
added to the batch. The latex is then coagulated in a hot aqueous magnesium
sulfate solution, the coagulum is filtered, washed with water and dried. The
crumb is fused and sheeted on a two-roll mill at 160C. Thereafter test speci-
mens are compression molded at 175C. and 500U psi for five minutes.
Optical properties on the molded specimens are determined inaccordance with ASTM Test D-1033-52 and impact properties are determ;ned in
~;~ accordance with ASTM Test D-256-56. The properties of the test specimens are
listed in Table I below.
~`~ 20 EXAMPLE 3 ~CONTROL)
For comparison a graft copolymer is prepared by a one step grafting
procedure wherein the grafted superstrate is of substantially uniform composi-
tion throughout. In this test, the procedure of Example 2 is substantially
: .
repeated. However, to the 2500 parts of rubber latex, a mixture of 390 parts
:
; 25 acrylonitrile, 2IO parts styrene and 6 parts ~ert.-dodecyl mercapt~n is added
continuously over a ninety-minute period. The total amount of reducing agent
and of persulfate used is the same as in Example 2. The latex is stirred at
60C. for one hour after monomer addition and the graft copolymer is recovered,
processed and molded as in Example 2. The properties of the test specimens are
listed in Table I below.
.
-16
3-12~0261 ~4~ 2~5
TABLE I
Example 2 Example 3
Property Tested Two-stage Graft Single Stage Graft
Tensile stress (psi)
at yield (10% strain/
minute) 2640 2910 `
at failure (100% strain/
minute) 3630 3770 ~`
Percent elongation `
; at yield 4.1 4.6
at failure 197 121
Tensile modulus (psi X 105) 1.15 1.27
^ 10 Percent haze (60 mil at
550 nm`) 2.8 3.5
Yellowness index 5.2 26.2
Refractive index 1.5435 1.5428
The above test results show the improved optical properties which
are obtained with the graft copolymers of the present invention.
EXA~LE 4
This example illustrates polyblends made from an acrylonitrile/
~ styrene copolymer and the graft copolymers produced in Examples 2 and 3 above.
;;` The copolymer utilized for these blends is a copolymer of 63 percent by weight
acrylonitrile and 37 percent by weight styrene previously prepared by conven-
tional suspension polymerization. The copolymer has a specific viscosity
(0.1 g~100 ml DMF)~of 0.078 and a yellowness index of 35.5 and 1.5 percent
haze.
The blends are compounded by extrusion and test specimens are molded
on a reciprocating screw injection molding ~~^h~ne at 200C. barrel temperature.
Optical and impact properties are determined as outlined above.
Injection molded pla~ues, 0.1 inch thick, are used for determination of haze
at 550 nm wave length and yellowness is determined on the same specimen with
a IDL Color Eye. Izod impact strength is determined on 1/2 inch X l/2 inch
injection molded bars with 0.10 mil notch radius. The properties of the test
specimens are listed in Table II below.
17-
4~5
C-08-12-0261
TABLE II
- . . . . ... .
PROPERTIES OF POLYl~LENDS
Graft Copolymers
Example 2 Example 3(Control~
Two Stage Graft Single Stage Graft
Percent graft copolymer 0 26 33 26 33
in blend
Percent rubber in blend O 10 15 10 15
Izod impact strength
(ft.-lbs./in) 0.4 2.3 5.8 1.8 3.7
Percent haze 1.6 2.1 2.3 15.8 20.1
Yellowness index 35.526.823.2 42.1 45.6
As can be seen from the results in Table II, the blends prepared
using graft copolymers prepared according to the present invention provide
`~ significantly improved properties both in transparency, as shown by relatively
low ha&e, color and in impact resistance.
EXAMPLE 5
This example further illustrates the improved properties which are
obtained with the two-stage grafted rub~ers of the present invention.
.
~ PART A
.
P~PARATION OF TWO-STAGE GRAFTED RUBBER
A butadiene-styrene rubber latex with 71 percent butadiene and 29
percent styrene having a gel content of 91 percent, a swelling index of 15.2,
a refractive index of 1.5375, a particle size in the range of from .06 to 0.2
:: :
micron and a Tg of less than -40C. is used in this example.
To 2500 parts of this latex, diluted to ZO percent rubber content
and stabilized with 1 percent on rubber weight of sodium lauryl sulfate are
added under nitrogen and agitation at 60C., 0.8 part sodlum hydrosulfite and
trace qua~tities of ferrous sulfa~e and ethylene diamine tetraacetic acid
disodium salt. A first monomer composition of 150 parts styrene, 150 parts
methyl methacrylate, 3 parts ethylene glycol dimethacrylate and 0.75 parts
di~isopropyl benzene hydroperoxide ~100 percent active~ is continuously added
-18-
,,, " . ,, ,. ":, -
~ ,8 12-0261 ~4~245
to the reaction vessel over a period of 45 minutes while maintaining a
temperature differential of about 4C. between the cooling jacket temperature ~
and the temperature of the polymeri~ing latex. Agitation is continued for --
thirty minutes thereafter at 60C. then there is added 0.8 part sodium hydro-
~ 5 sulfite and continuously a second monomer composition of 240 parts acrylo- ~-
- nitrile, 6~ parts styrene, and 0.5 part n-butyl mercaptan. A solution of
0.8 part potassium persulfate is also added contlnusu~ly over a 45 minute
period. The latex is maintained with stirring at 60C. for one hour after
the termination of monomer addition. After cooling, 7.5 parts of a con-
yentional antioxidant mixture in the form of a dispersion are added to the
latex, which is then coagulated in an aqueous solutlon of magnesium sulfate
at 75C. to obtain a fine granular product which is washed and dried.
PART B (CONTROL)
PREPARATION OF SINGLE STAGE GRAFTED R~BBER
~; 15 The procedure of Part A is substantially repeated except that a
mixture of 240 parts acrylonitrile, 210 parts styrene, 150 parts methyl meth-
acrylate and 1 part n-butyl mercaptan, which contains no difunctional monomer,
is added continuously with a solution of 1.5 par~s potassium persulfate over
a period of one and one-half hours as opposed to the two-stage monomer mixtures
used in Part A.
ART C
BLENDING OF GRAFTED RUBBERS WITH MATRIX
The graft copolymers prepared in Parts A and B above are blended
with an acrylonitrile/styrene (63/37% by weight) poly~er previously prepared
by conventional polymerization so as to provide blends containing 15 percent
of the graft copolymer substrate in the blends. The blends are compounded and
tested as outllned in Example 4 above. The properties of the test specimens
are found to be as follows:
--19--
,-08-12-0261 ~4~z~5
Graft Copolymers
Part A Part B
Two Stage Graft Single Stage Graft
Izod impact strength
ft~lbs/in. notch 8.6 5.9
Percent haze 1.8 15.5
Yellowness index21.8 39.2
Melt viscosity, poises
at 200C.~
shear rate 100 sec~l 22500 28000
1000 sec~l 5100 5000
Again, it can be seen that the blends utilizing graft copolymers
prepared in accordance with the present invention evidence significantly
;;~ improved properties as compared to blends of similar compositions Ut; 1~ ~lng
a graft copolymer having a substrate of substantiaIly uniform composition
throughout.
EXAMPLE 6
This example illustrates a two-stage grafted rubber which is b]ended
vlth an acr~lonitrile/styrene polymer matrix which contains 68 percent by
weight of acrylonitrile and 32 percent styrene. A latex of a butadiene/styrene
rubbery copolymer (68/32) having a Tg of less than -40C., an average particle
siæe of 0.11 microns, a gel content of 87.5 percent, a swelling index of 13.6
`~ 20 snd a refractive index of 1.5396, is grafted in t~o stages. The first stage
graft is carried ou~ using a monomer composieion containing 15 percent acrylo-
nitrile, 45 percent styrene, 4 percent methyl methacrylate and 0.8 percent of
ethylene glycol dimethacrylate wherein the percent is by welght based on the
total monomer weight in the first monomer composition. The second stage graft
is carried out using a monomer composition containing 65 percent acrylonitrile,
2 percent methacrylonitrile and 33 percent styrene containing 0.5 percent by
weight tert-dodecyl mercaptan based on the total monomer weight in the second
monomer mixture. A combination of potassium persulfate and sodium thiosulfate
is used as a redox inltiator system for the grafting reaction. The ratio of
substrate/first stage graft superstrate/second stage graft superstrate is
1:0.8:0.4.
-.~
.
~
~8-12-0261 ~ Z ~
The average particle size after grafting is found to be 0.13 microns.
The graft copolymer is fused and sheeted by roll-milling and then the ~h~n;cal
and optical properties are determined on compression molded test specimens.
The physical and ~h~n;cal properties of the test specimens are found to be as
5 follows:
Tensile stress (psi)
at yield 2150
at failure 3360
Percent elongation
at yield 3.
at failure 223
Tensile modulus (psi X 105) 1.08
Percent haze (60 mil, 550 mm) 1.2
Yellowness index 12.5
Refractive index nd251.5404
The graft copolymer is then blended with a 68/32 acrylonitrile/
styrene copolymer, which was previously prepared by conventional suspension
polymerization, a various ratios to provide a rubber substrate level in the
blends of 7.5 percent, 10 percent, and lS percent. The blends are compounded -
` 20 by extrusion and test specimens are obtained by injection moldings as outlined
;~ above. The properties of the test specimens are found to be as follows:
::
Rubber Content
0 7.5% 10% 15%
Percent haze (100 mil, 550 mm) 1.2 1.1 1.3 1.5
Yellowness index 46.6 39.6 33.8 31.5
Refractive index nd25 1.5405 1.5410 1.5412 1~5411
Izod impact (ft.lbs/in.) 0.4 1.25 1.81 9.6
Density, grams/cc 1.128 1.112 1.105 1.090
FDI (falling dart impact)
Ft. lbs. (1) - 4.2 16.0 99.9
(1) FDI test conducted on 3 X 4 X 0.1 inch molded plaques
using a 1-1/2 steel tip dart using the Bruce Staircase
Method.
-21-
~L04~'~gS
~-08-12-0261
The above results further illustrate the superior properties which
are obtained with the graft copolymer$ of the present invention.
EXAMPLE 7
This example illustrates the blending of two latices to obtain
the rubber modified polymer blends of the present invention.
- A graft copolymer is prepared in a two-stage polymerization procedure
by grafting 100 parts of the butadiene/styrene rubber prepared in Example 1
with 60 parts of a styrene/acrylonitrile/methyl methacrylate/ethylene glycol
dimethacrylate mixture t50/25/25/0.8 % by weight) and 60 parts of an acrylo-
nitrile/styrene mixture (65/35% by weight~ in two consecutive steps using the
procedure outlined in Example 2. The resulting latex is blended with a latex
of acrylonitrile/styrene/methyl methacrylate (60/35/5% by weight) so as to
provide a polyblend having a solids content of 26 percent by weight providing
a rubber content of 10 percent in the polyblend. The polyblend is spray dried
and the resulting powder blend is compounded by extrusion into pellets which
are further extruded into a clear transparent sheet having a refractive index
of 1.5425. In a falling dart drop test (one inch tip) at a drop height of
2 feet, a ductile failure pattern and a strength of 0.15 foot pounds/ mil is
obtained, further illustrating the good physic~al properties of the polyblends
of the present invention.
~, .
EXAMPLE 8
This example illustrates the preparation of three different two-
stage graft copolymers. In Part A no difunctional monomer is used, in Part B
the difunctional monomer îs omitted from the first monomer mixture but included
in the second -r mixture, and in Part C the difunctional monomer is in-
cluded in the first monomer mixture in accordance with the ~e~;ng~ of the
present invention.
Each example uses a latex of a 70/30 butadiene/styrene rubbery co-
polymer having an average particle si7e of 0.151 microns, as determined by
turbidity measurement, a gel content of 48.0 percent, a refractive index
-22-
-
~4129~5
~-08-12-0261
of 1-538l~a swelling index of 37.7 and a Tg less than -40Co The two-stage
grafting procedure is carried out at $0C. using a persulfate/sulfoxylate/
iron redox initiator system.
PART A (CO~TROL)
In this example the graft polymerization procedure of Example 2 is
substantially repeated with the exception that the first monomer composition,
which contains 50 percent by weight styrene, 25 percent methyl methacrylate
and 25 percent acrylonitrile, does not contain a difunctional monomer.
PART B (CONTROL)
In this example the first monomer composition is the same as in
~ .
Part A above. ~lowever, the second monomer composition contains 65 percent by
weight of acrylonitrile, 35 percent styrene and 0.5 percent by weight of allyl
methacrylate difunctional monomer.
PART C
For comparison purposes a graft copolymer is prepared as in Parts A
and B but using a first monomer composition containing 0.5 percent by weight of
allyl methacrylate based on the total weight of monomers in the mixture.
Except for the presence or absence of a difunctional monomer, the
composition of the first and second stage ~ r mixtures and the graft
ZO ratios are the same for Parts A, B and C.
The graft copolymers are recovered by coagulation with calcium
chloride and optical and -~h~nlcal properties are determined on compression
molded specimens (125 mil th1 ~k~Pq5) . The properties of the test specimens
are fou~d to be as ~ollows:
.~ "
:,
i C~-08-12-026~
1041Z45 Copolymer
Part A Part B
(Control) (Control) Part C
Tensile stress (psi)
at yield no yield 1690 2580
at failure 920 2000 3440
Percent elongation
at yield - 3.1 4.1
at failure 65 125 233
Tensile modulus (psi X 105) 0.44 0.83 1.17
Percent haze (550 mm) 12.6 13.5 5.1
Yellowness index 11.8 13.1 12.0
Refractive index, nd25 1.5428 1.54301.5425
The tensile test results reported above indicate that the strength
of the graft copolymer prepared in the absence of a difunctional monomer in
the first graft monomer composition (Part A) is lower than that of the graft
copolymer prepared by the method of the present invention. using a difunctional
monomer in the first monomer COmpOsitiGn (Part C). The strength properties of
the graft rubber obtained by a two-stage procedure using a difunctional monomer
in the second monomer composition (Part B) are better than those of the graft
copolymer, which contains no difunctional monomer (Part A), but still lower
than those of~the graft copolymer prepared using a difunctional monomer pre-
sent in~the first :~age monomer composition (Part C~.
The graft copolymers prepared by procedures A, B and C are blended
,
with a 65/35 :crylonitrile/styrene copolymer previously prepared by conventional
~; ~ suspension polymerization to provide blends containing 15 percent of the graft
copolymer sub:trat: providing a rubber cont:nt of 15% in the polybl:nd. The
polyblends are compounded by extrusion and injection molded into test specimens.
~: :
~ The properties of the test specimens are found to be as follows: ~
'
-24-
I
C~8-12-0261 ~1 2~5
Graft Copolymer in Blend
Part A Part ~ Part C
Izod impact strength1
ft-lbs/in. of notch1.2 2.3 7.4
Percent haze (550 mm,
100 mils) 36.4 16.5 2.1
` 5 Yellowness index 25.3 28.2 21.3
The foregoing results further illustrate the improved properties
which are obtained when using a two-stage graft polymerization procedure
wherein the first stage contains a difunctional monomer in accordance with the
t~rh1nE~ of the present invention.
EXAMPLE 9
This example illustrates the use of a vinyl crotonate difunctional
monomer in the first monomer mi~ture of a two-stage grafting procedure. It
also illustrates various grafting levels and the preparation of polyblends in
accordance with the present invention.
Three different graft copolymers are prepared by the procedure des-
cribed in Example 2 above using a rubber latex containing 69.3 percent by
weight butadiene and 30.7 percent by weight styrene and having a Tg less than
-40C., a gel content of 87.5 percent, a swel:Ling index of 16.3, a particle
size of about 0.1 microns average and a refractive index of 1.5376.
~ The first graft monomer composition contains 1 percent by weight of
vinyl crotonate difunctional monomer, the second monomer composition contains
1 percent of a tertiary-dodecyl mercaptan chain transfer agent, both weight
percents based on the total monomer weight in the respective mixtures. The
graft ratios of substrate:first stage graft: second stage graft are
25 1:0.5:0.5, 1:0.6:0.6 and 1:0.8:0.4.
The graft copolymers prepared above are blended with an acrylonitrile/
styrene (63/37% by weight) previously prepared by conventional suspension poly-
merization, to provide polyblends having a rubber content of 15 percent by
` weight. The polyblends are injection molded into 1/2 X 1/2 X 5 inch bars,
3 X 4 X 0.1 inch plaques and 1/2 X 1/8 X 6-1/2 inch tensile bars which are
-25-
C~ 12-0261 ~124S
then tested for physical properties. The properties of the test specimens
are found to be as follows:
Graft Ratio1:0.5:0.51:0.6:0.61:0.8:0.4
Tensile stress (psi)
at yield 7560 8050 7350
at failure 6750 6780 6800
Percent elongation
at yield 4.2 4.5 4.1
at failure 48.9 42.7 47.7
Tensile modulus, psi X 1054.3 4.2 4.2
Refractive Index, nd251.5430 1.5445 1.5437
Izod impact 3.8 3.6 3.9
FDI, ft-lbs. 64 62 91
Percent haze (550 nm) 2.8 3.5 2.5
Yellowne~s index28.1 25.6 23.3
Density, grams/cc1.08751.0899 1.0855
The polyblends of this invention exhibit oxygen permeability of less
than 6.5 cc of oxygen for a film of 1 mil thickness and 100 square lnches over
a period of 24 hours at one atmosphere (760 mm.~ of oxygen and at 73F., and a
water vapor transmission rate (W~T) of less than 8.5 grams for such film of
equivalent dimensions over a 24 hour period maintained at 100F. and 95 percent
relative humidity (R.H.), as determined by-ASTM Method D-1434-63 and ASTM Method
E-96-63T, respectively.
The good barrier properties of these materials taken with the good
optical and mechanical properties make them especially useful for the prepara-
tion of p~a~rkagin~ materials such as films, and containers such as bottles, jars,
..
cans, etc.
.
`~
-26-
~lZ9~5
C-08-12-0261
Thus, it can be seen from the foregoing detailed specification
and examples that the present invention provides a process Eor preparing a
novel graft copolymer for blends with rigid matrices having highly desirable
optical and merh~n;c~l properties. The graft copolymers are particularly use-
ful as an impact modified for acrylonitrile-styrene copolymers high in acrylo-
nitrile content. The graft copolymers-and the matrix polymer are prepared so
as to have closely matching reEractive indices in order to provide optimum
me~hAn~ r~1 properties and optimum optical properties including a high degree
of transparency.
The present invention may be utilized to produce materials which are
, particul~rly advantageously employed in p~rk~g;ng and in outdoor applications.
.
