Acrylic multistage graft copolymer products and processes

A resilient, acrylic graft polymer is produced by multi-stage, sequential polymerization in which the first stage is elastomeric, the second stage is nonelastomeric, the third stage is elastomeric and the fourth, and final stage is nonelastomeric. Upon blending with a nonresilient methacrylic matrix resin, followed by molding, an impact resistant molded product is obtained which has low stress-whitening, generally does not show substantial crack propagation on impact and does not readily break on subjection to fold endurance tests.

FIELD OF THE INVENTION 
This invention relates to resilient, acrylic graft polymers, and to blends 
of such polymers with hard nonresilient thermoplastic methacrylate matrix 
resins. 
BACKGROUND OF THE INVENTION 
Resilient, acrylic graft polymers are produced by a multi-stage, sequential 
polymerization technique which comprises alternately producing resilient 
and nonresilient layers around an acrylic core material. These resilient 
polymers are ordinarily admixed with a hard nonresilient thermoplastic 
methacrylic matrix resin in order to provide resiliency in articles molded 
from the resulting blend. Presence of the resilient acrylic graft polymer 
reduces susceptibility of the hard matrix resin in molded form to adverse 
effects resulting from impact with foreign objects. 
However, the resilient acrylic graft polymers tend to cause the resulting 
blend to haze or whiten when articles molded from the blend are subjected 
to stress. This phenomenon is called stress whitening. To reduce the 
degree of stress whitening, Owens U.S. Pat. No. 3,793,402 suggests that 
the resilient, acrylic graft polymer be one in which the resilient layer 
both (1) surrounds a hard, nonresilient core and (2) is surrounded by a 
hard, nonresilient shell layer. The Owens patent indicates that if the 
resilient portion of the acrylic graft polymer is in the core (i.e., the 
first stage), such arrangement contributes to an increased tendency to 
whiten under stress. 
Continued improvement is sought in the properties of articles molded from 
the blend of the acrylic graft polymer and the matrix resin. It has now 
been discovered that when the acrylic graft polymer of this invention is 
employed, articles from the blend have low stress whitening even though a 
resilient core is present in the acrylic graft polymer. Furthermore, at 
high loadings of selected acrylic graft polymer in the blend, the articles 
tend to have higher Gardner Impact values than those described in the 
Owens patent. In addition, some of the acrylic graft polymers of this 
invention when blended with the matrix resin tend to have higher fold 
endurance values than those described in the Owens patent. 
SUMMARY OF THE INVENTION 
This invention provides a resilient, acrylic, multi-stage, sequentially 
produced graft polymer comprising: 
(a) an elastomeric (resilient) first stage, i.e., core (defined by having 
glass transition temperature of between about -60.degree. C. and 
25.degree. C., and preferably -35.degree. to -20.degree. C.) comprising 
about 1-25% (preferably 3-20% and most preferably 10-20%) by weight of the 
polymer; 
(b) a nonelastomeric (nonresilient), relatively hard second stage (glass 
transition temperature greater than 25.degree. C.), comprising about 5-65% 
(preferably 15-30%) by weight. 
(c) an elastomeric (resilient) third stage defined as in part (a) 
comprising about 30-75% (preferably 40-60%) by weight; 
(d) a nonelastomeric (nonresilient), relatively hard fourth stage defined 
as in part (b) and which is usually the last stage comprising about 5-40% 
(preferably 10-20%) by weight. 
The first stage is polymerized from a monomer mixture of 50 to 100 weight 
percent of at least one alkyl acrylate wherein the alkyl group contains 1 
to 8 carbon atoms, 0 to 50 weight percent of another copolymerizable 
monoethylenically unsaturated monomer, 0 to 5 weight percent of a 
copolymerizable polyfunctional crosslinking monomer and 0 to 5 weight 
percent of a copolymerizable graftlinking monomer. 
The second stage is polymerized in the presence of the first stage product 
from a monomer mixture of 70 to 100 weight percent of at least one alkyl 
methacrylate wherein the alkyl group has 1 to 4 carbon atoms, 0 to 30 
weight percent of another copolymerizable monoethylenically unsaturated 
monomer, 0 to 5 weight percent of a copolymerizable polyfunctional 
crosslinking monomer and 0 to 5 weight percent of a copolymerizable 
graftlinking monomer. 
The third stage is polymerized in the presence of the first and second 
stage product from a monomer mixture of 50 to 100 weight percent of at 
least one alkyl acrylate wherein the alkyl group contains 1 to 8 carbon 
atoms, 0 to 50 weight percent of another copolymerizable monoethylenically 
unsaturated monomer, 0 to 5 weight percent of a copolymerizable 
polyfunctional crosslinking monomer and 0 to 5 weight percent of a 
copolymerizable graftlinking monomer. 
The fourth stage is polymerized in the presence of the product of the first 
three stages from a monomer mixture of 70 to 100 weight percent of at 
least one alkyl methacrylate wherein the alkyl group has 1 to 4 carbon 
atoms, 0 to 30 weight percent of another copolymerizable monoethylenically 
unsaturated monomer, 0 to 5 weight percent of a copolymerizable 
polyfunctional crosslinking monomer and 0 to 5 weight percent of a 
copolymerizable graftlinking monomer. 
The combined amounts of stages 1 and 3 comprise at least 40% by weight, 
based on weight of polymer. 
Preferably the final particle size will be between 0.15 and 0.35 micron. 
Blends of the resilient graft polymer with a hard, nonresilient 
thermoplastic methacrylate resin are also provided by this invention. 
DESCRIPTION OF THE INVENTION 
The resilient acrylic graft polymer of this invention can be produced by a 
multi-stage sequential emulsion polymerization in which each successive 
stage is polymerized in the presence of the previously formed stages. 
Thus, each successive stage is polymerized as a layer on top of the 
immediately preceding stage. Depending on the properties desired, the 
first stage may comprise a seed or may comprise a seed surrounded by more 
first stage. Thus, the first stage or a portion of the first stage is used 
as a seed or core around which either more of the first stage or the 
subsequent stages are polymerized in layers. The general polymerization 
procedure is well known in the art. The first stage or a portion thereof, 
which forms the seed provides a mechanism for determining final particle 
size; for, once the seed particles are formed, subsequent polymerization 
of the stage tends to result in polymerization on the existing particles, 
i.e., generally new particles do not form. Thus, the final particle size 
is controlled by the number of first stage seed particles. Generally, the 
final particle size should preferably be between about 0.15-0.35 microns 
and most preferably 0.2-0.3 microns. Within these particle sizes, the 
resulting blend has been found to have high ductility, i.e., upon impact, 
molded articles made from the blend do not tend to have cracks propagating 
from the area of impact. 
The polymerization of each stage is carried out in the presence of a 
catalyst and an emulsifier at ordinary and usual levels. Useful 
emulsifying agents include alkylbenzenesulfonates, 
alkylphenoxypolyethylene sulfonates, sodium lauryl sulfate, salts of long 
chain amines, salts of long chain carboxylic and sulfonic acids, and 
compounds containing long chain hydrocarbon groups coupled to alkali metal 
carboxylates, sulfonates, or sulfate esters. Useful catalysts include 
alkali metal persulfates. 
Polymerization temperatures can range from 0.degree.-125.degree. C. with 
about 60.degree.-90.degree. C. preferred. 
The alkyl acrylate used in elastomeric stages 1 and 3 can be methyl 
acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl 
acrylate or the like. Preferably, butyl acrylate is employed. 
The alkyl methacrylate used in nonelastomeric stages 2 and 4 can be methyl 
methacrylate, ethyl methacrylate, propyl methacrylate or butyl 
methacrylate. Methyl methacrylate is preferred. 
The copolymerizable monoethylenically unsaturated monomer which can be 
optionally employed in any of stages 1 through 4 can be any of the alkyl 
acrylates or alkyl methacrylates described previously herein or can be 
styrene, .alpha.-methyl styrene, monochlorostyrene, butyl styrene, 
acrylonitrile, methacrylonitrile, or the like. Preferably this 
copolymerizable monomer is present in each stage, and for elastomeric 
stages 1 and 3, it preferably is styrene, and for nonelastomeric stages 2 
and 4 it preferably is ethyl acrylate. 
The copolymerizable graftlinking monomer can be allyl acrylate, allyl 
methacrylate, diallyl maleate, diallyl fumarate, crotyl methacrylate, 
crotyl acrylate and the like. Preferably a graftlinking monomer is present 
in all stages except the last stage. Preferably also, the graftlinking 
monomer is allyl methacrylate. 
The polyfunctional crosslinking monomer can be ethylene glycol 
dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butylene glycol 
dimethacrylate, propylene glycol dimethacrylate, divinyl benzene, trivinyl 
benzene, ethylene glycol diacrylate, 1,3-butylene glycol diacrylate or the 
like. The degree of resiliency or nonresiliency is measured herein by the 
glass transition temperature. 
The resilient acrylic graft polymers of this invention are blended with a 
nonresilient methacrylate resin to add resiliency to articles molded from 
the blend. The amount of resilient graft polymer employed is dependent 
upon the modification of properties desired in the methacrylate resin. 
Generally, the graft polymer will be present in an amount of about 5-80 
percent by weight of blend and preferably 30-60 percent. At higher 
loadings of graft polymer, e.g., about 50% or more, it has been found that 
impact resistance (determined by the Gardner Impact test) is better than 
when a hard core graft polymer of the art is employed in place of the 
graft polymer used herein. The polymer and the resin can be blended by any 
known procedure; however, it is convenient to compound the two ingredients 
on a roll mill, at for example, 200.degree.-230.degree. C. for 10-20 
minutes. The nonresilient methacrylate resin can be the homopolymer of an 
alkyl methacrylate wherein the alkyl group has 1-4 carbon atoms, or can be 
a copolymer of two or more such alkyl methacrylate and another 
copolymerizable monoethylenically unsaturated monomer. Any of the alkyl 
methacrylates and copolymerizable monoethylenically unsaturated monomers 
previously described can be used. Preferably the methacrylate resin will 
contain 75-100% of the alkyl methacrylate and most preferably at least 90% 
by weight. 
The blended product is an impact resistant and fold resistant resin with 
low stress whitening in molded form and is employed to make film, sheets 
or shaped articles. If desired, light stabilizers, oxidation inhibitors, 
fillers, colorants, lubricants and the like may be added to the blend. 
EXAMPLES 
In the Examples which follow, the property test result values recited were 
obtained as follows: 
Gardner Impact (GI) values were determined using a model IG-1120 tester by 
placing a compression molded plaque made as described in the Examples 
below on a plate over a 0.64 inch diameter hole. A two pound weight was 
dropped on an impact head having 0.5 inch radius tip resting on the 
plaque. The impact (measured in in-lbs) required to break the plaque was 
found by using 2 inch-pound weight increments and is determined by either 
recording the maximum pass value (highest impact value at which the plaque 
does not fail) or by calculating the mean value using the Bruceton 
staircase method. 
Stress whitening was determined by visual observation after subjecting 
plaques made in the Examples below to the Gardner Impact test. 
Ductility was determined by recording the number of ductile breaks (i.e., 
all breaks resulting from the G.I. test that are not straight radical 
cracks propagating beyond the 0.64 inch diameter impact circle) and 
recording the number of total breaks and inserting these recorded values 
into the equation: 
##EQU1## 
Particle size of the acrylic graft polymers was determined by evaluation of 
an integral involving the Rayleigh-Gans light scattering factor for 
spheres, as described by F. W. Billmeyer, J. Am. Chem. Soc. 76, 4636 
(1958). The results are expressed in the form of a graph which relates 
particle diameter to experimentally observed optical density values, based 
on the equation: 
EQU D/A.sub.o =1.5.times.10.sup.7 (d.sup.3 /F.sub.T) (1) 
where 
EQU D=optical density=log (100/% transmission) (2) 
EQU A.sub.o =R.sup.2 cT.rho. (3) 
R=refractive index gradient 
c=particle concentration (g./cc) 
T=optical cell thickness, cm. 
.rho.=particle density, g./cc 
d=particle diameter, microns, and 
F.sub.T =size parameter, function of d only at constant wavelength 
The refractive index gradient R is given with good accuracy by 
EQU R=(n.sub.p -n.sub.o)/.rho. (4) 
where n.sub.p =particle refractive index, and n.sub.o =substrate refractive 
index (The coefficient 1.5.times.10.sup.7 applied to measurements made 
with the Hg green line of .lambda.=0.546 microns only.) F.sub.T is a known 
function of d, so values of D/A.sub.o were calculated and tabulated as a 
function of d and used to construct the log-log plot. It may be useful to 
point out here that F.sub.T is practically unity for small particles, so 
that log d vs. log D/A.sub.o is essentially linear with a slope 1/3 for 
sizes up to about 0.08 microns. 
Experimentally, the emulsion is diluted so that the optical transmission is 
in the approximate range 20-80% in the cell selected (thickness, T=1, 2.5 
or 5 cm.). The transmission at .lambda.=0.546 microns is measured 
accurately and the optical density calculated (Eq. 2). A.sub.o is 
calculated from Eq. 3, using the known values of c, T, and .rho., and R 
from Eq. 4. The quotient D/A.sub.o referred to the graph will then give 
the particle diameter characteristic of the emulsion. For illustration 
assume that a liquid of index n.sub.p =1.5 and density .rho.=1.2 is 
emulsified in water (n.sub.o =1.333), the emulsion diluted to 0.1% 
(c=0.001), and the transmission (relative to water) or the dilution is 
found to be 50% in a 5 cm. cell. Then 
EQU D=log (100/50)=0.30 (from Eq. 2) 
EQU R=(1.5-1.333)/1.2=0.139 (from Eq. 4) 
EQU A.sub.o =(0.139).sup.2 (0.001)(5)(1.2)=1.159.times.10.sup.-4 
EQU D/A.sub.o =2.59.times.10.sup.3 
From the graph the diameter corresponding to D/A.sub.o =2.59.times.10.sup.3 
is 0.056 microns. 
Fold endurance values were obtained by preparing films of the blended resin 
of thickness described in the Examples below by compression molding at 
240.degree.-250.degree. C. and 40M lb force. They were cut into 1/2" wide 
strips (4-6" long) and subjected while under tension provided by a 1/2 lb. 
weight at 22.degree. C. to 180 degree bends on a MIT Folding Endurance 
tester (Tinius-Olsen Testing Machine, Co.) until the sample broke.

The following examples illustrate the invention in greater detail. 
EXAMPLE 1 
Polymerization 
Into a 3 liter resin kettle, equipped with a reflux condenser and a N.sub.2 
sweep, was placed 1000 g of oxygen free (N.sub.2 flushed overnight) 
demineralized water, 36.0 g of ethyl acrylate (EA), 0.2 of 
allylmethacrylate (ALMA) and 0.52 grams of a 75% solution of sodium 
dioctyl sulfosuccinate (SDOSS), an emulsifier. The mixture (Stage 1) was 
vigorously stirred for 15 minutes while the temperature was raised, using 
a surrounding water bath, to 80.degree.C. At 15 minutes, 5 ml of 1% 
K.sub.2 S.sub.2 O.sub.8 in demineralized water (KPS) was added to initiate 
reaction. At 25 minutes an additional 10 ml of KPS was added. At 
approximately 26 minutes a mixture (Stage 2) of 108 g of methyl 
methacrylate (MMA), 36 g of EA, 0.4 g of ALMA and 2.08 g of SDOSS was 
gradually added at a rate of about 3 ml/min. All of Stage 2 was in the 
kettle after 85 minutes. At 110 minutes 25 ml of KPS was added to the 
kettle and 5 minutes later (115 minutes) a mixture (Stage 3) of 190.6 g of 
butyl acrylate (BA), 44.7 g of styrene (S), 4.7 g of ALMA and 1.15 g of 
SDOSS was gradually added at a rate of about 10 ml/min. At 141 min. 20 ml 
of KPS was added to the kettle. At 144 min. all of Stage 3 was in the 
kettle. Stage 3 reached greater than 99% conversion (by gas 
chromatography) at 260 minutes. At 270 minutes 12 ml of KPS was added and 
5 minutes later (275 minutes) a mixture (Stage 4) of 169.2 g of MMA and 
10.8 g of EA was gradually added at a rate of about 4 ml/min. At 330 
minutes all of Stage 4 was in the kettle and at 360 minutes the reaction 
was complete and the polymer latex was cooled to room temperature. Stage 1 
comprised 6% by weight of the polymer; Stage 2, 24%; Stage 3, 40%; and 
Stage 4, 30%. 
Isolation 
The polymer latex was passed through a coarse filter cloth to remove 
coagulum. A 500 ml portion of this latex was slowly added to a vigorously 
stirred hot (70.degree.80.degree. C.) solution of 1% Epsom salt (1000 ml). 
The resultant coagulated polymer was filtered, washed 3 times, and dried 
in a vacuum over at 60.degree. C. overnight to obtain a resilient acrylic 
graft polymer. First stage Tg was -21.degree. C.; second stage Tg was 
+64.degree. C.; third stage Tg was -35.degree. C.; and fourth stage Tg was 
+94.degree. C. The Tg values in this Example and all the other Examples 
were determined as described in "Rohm & Haas' Acrylic Glass Temperature 
Analyzer CM-24L/cb." 
Compounding and Testing 
The resilient acrylic graft polymer was compounded with a methyl 
methacrylate/ethylacrylate (MMA/EA) copolymer on a roll mill (at approx. 
220.degree. C.) for 15 minutes. The MMA/EA copolymer contained about 6% EA 
and 94% MMA and was compounded with 62.5 percent of the graft polymer. The 
blended resin was compression molded at 240.degree. C. and 40,000 lb force 
into a 60 ml thick plaque. Visual inspection showed the plaque had low 
haze. Upon carrying out the Gardner Impact test, the molded blend was 
determined to have a Gardner Impact (GI) value of 10 in-lb determined by 
the Bruceton method. The plaque was determined to have a Ductility value 
of 18%, and the particle size of the acrylic graft polymer was 0.155 
micron. The plaque exhibited low stress whitening. 
EXAMPLE 2 
Using the procedure of Example 1, a four (4) stage resilient acrylic graft 
polymer of the following composition was made with the sequence of steps 
indicated. 
______________________________________ 
Stage 1(4%) 
Stage 2(25%) 
Stage 3(56%) 
Stage 4(15%) 
______________________________________ 
19.1 g BA 
141.0 g MMA 266.8 g BA 84.6 g MMA 
4.5 g S 9.0 g EA 62.5 g S 5.4 g EA 
0.5 g ALMA 
0.6 g ALMA 6.7 g ALMA 
0.2 g SDOSS 
1.5 g SDOSS 2.3 g SDOSS 
Tg -35.degree. C. 
Tg +94.degree. C. 
Tg -35.degree. C. 
Tg +94.degree. C. 
Time (Minutes) Reaction Steps 
00 Added Stage 1 
20 Add 8 ml KPS 
50 Add 8 ml KPS 
55 Start addition of Stage 2 
80 All of Stage 2 is in 
98 Add 25 ml KPS 
100 Start addition of Stage 3 
136 Add 25 ml of KPS 
137 All of Stage 3 is in 
270 Add 8 ml KPS 
275 Start addition of Stage 4 
299 All of Stage 4 is in 
320 Cooled to room temperature 
______________________________________ 
The graft polymer was isolated and compounded as in Example 1 except that 
the graft polymer in the blend was 40%. The resultant plaque exhibited low 
visual haze, a Gardner Impact (GI) of 16 in-lb determined by recording the 
maximum pass value, and exhibited low stress whitening after subjection to 
the GI test. The plaque exhibited a ductility value of 100% and the 
acrylic graft polymer had a particle size of about 0.270 micron. 
EXAMPLE 3 
Using the procedure of Example 1, a four-stage resilient acrylic graft 
polymer of the following composition was made with the sequence of steps 
indicated. 
______________________________________ 
Stage 1(4%) 
Stage 2(25%) 
Stage 3(56%) 
Stage 4(15%) 
______________________________________ 
19.2 g BA 140.4 g MMA 268.7 g BA 84.6 MMA 
4.2 g S 9.0 g EA 59.1 g S 5.4 EA 
0.4 g ALMA 
0.6 g ALMA 6.7 g ALMA 0.5 EDMA 
0.1 g EDMA* 
0.6 g EDMA 1.7 g EDMA 
0.2 g SDOSS 
1.6 g SDOSS 2.6 g SDOSS 
Tg -35.degree. C. 
Tg +94.degree. C. 
Tg -35.degree. C. 
Tg +94.degree. C. 
Time (Minutes) Reaction Steps 
00 Add Stage 1 
15 Add 12 ml KPS 
75 Add 8 ml KPS 
80 Start addition of Stage 2 
116 All of Stage 2 is in 
126 Add 25 ml KPS 
131 Start addition of Stage 3 
183 Add 25 ml KPS 
188 All of Stage 3 is in 
295 Add 12 ml KPS 
300 Start addition of Stage 4 
327 All of stage 4 is in 
340 Cooled to room temperature 
______________________________________ 
*EDMA = ethylene glycol dimethacrylate crosslinking agent. 
The graft polymer was isolated and compounded as in Example 2. The 
resultant plaque had low haze, and upon subjection to the Gardner Impact 
test had a GI of 16 in-lb determined by the maximum pass method, had low 
stress whitening, and a ductility value of 95%. The acrylic graft polymer 
prepared in this Example has a particle size of 0.272 microns. 
EXAMPLE 4 
Using the procedure of Example 1, a four-stage resilient acrylic graft 
polymer of the following composition was made with the sequence of steps 
indicated. 
______________________________________ 
Stage 1(5%) 
Stage 2(25%) 
Stage 3(55%) 
Stage 4(15%) 
______________________________________ 
24.1 g BA 140.4 g MMA 261.5 g BA 84.6 g MMA 
5.7 g S 9.1 g EA 61.3 g S 5.4 g EA 
0.6 g ALMA 
0.7 g ALMA 6.1 g ALMA 
0.23 g SDOSS 
1.52 g SDOSS 
2.52 g SDOSS 
Tg -35.degree. C. 
Tg +94 Tg -35.degree. C. 
Tg +94.degree. C. 
Time (Minutes) Reaction Steps 
00 Add Stage 1 
10 Add 12 ml KPS 
65 Add 8 ml KPS 
70 Start addition of Stage 2 
100 All of Stage 2 is in 
110 Add 25 ml KPS 
115 Start addition of Stage 3 
162 All of Stage 3 is in 
165 Add 25 ml KPS 
275 Add 25 ml KPS 
280 Start addition of Stage 4 
307 All of Stage 4 is in 
327 Cooled to room temperature 
______________________________________ 
The graft polymer was isolated and compounded as in Example 2. The 
resultant plaque had low haze, and upon subjection to the Gardner Impact 
test was found to have a GI of 20 in-lb determined by the maximum pass 
method and exhibited low stress whitening. The ductility value was found 
to be 100%. The acrylic graft polymer prepared in this Example had a 
particle size of 0.272 micron. 
EXAMPLE 5 
Using the procedure of Example 1, a four-stage resilient acrylic graft 
polymer of the following composition was made with the sequence of steps 
indicated. 
______________________________________ 
Stage 1(4%) 
Stage 2(20%) 
Stage 3(56%) 
Stage 4(20%) 
______________________________________ 
19.1 g BA 
112.3 g MMA 266.8 g BA 113.0 g MMA 
4.5 g S 7.2 g EA 62.5 g S 7.2 g EA 
0.2 g EDMA 
0.5 g ALMA 6.7 g ALMA 
0.2 g SDOSS 
1.2 g SDOSS 2.5 g SDOSS 
Tg -35.degree. C. 
Tg +94.degree. C. 
Tg -35.degree. C. 
Tg +94.degree. C. 
Time (Minutes) Reaction Steps 
00 Add Stage 1 
15 Add 10 ml KPS 
50 Start addition of Stage 2 
74 All of Stage 2 is in 
95 Add 25 ml KPS 
100 Start addition of Stage 3 
154 Add 25 ml KPS 
159 All of Stage 3 is in 
287 Add 12 ml KPS 
292 Start addition of Stage 4 
331 All of Stage 4 is in 
356 Cooled to room temperature 
______________________________________ 
The graft polymer was isolated and compounded as in Example 2. The 
resultant plaque had low haze, and upon subjection to the Gardner Impact 
test was found to have a GI value of 6 in-lb determined by the maximum 
pass method, and exhibited low stress whitening. The ductility value was 
found to be 100%. The acrylic graft polymer prepared in this Example had a 
particle size of 0.245 micron. 
EXAMPLE 6 
Using the procedure of Example 1, a four-stage resilient acrylic graft 
polymer of the following composition was made with the sequence of steps 
indicated. 
______________________________________ 
Stage 1(6%) 
Stage 2(24%) 
Stage 3(40%) 
Stage 4(30%) 
______________________________________ 
36.0 g EA 
144.0 g MMA 190.6 g BA 169.2 g MMA 
0.3 g SDOSS 
0.4 g ALMA 44.7 g S 10.8 g EA 
2.0 g SDOSS 4.7 g ALMA 0.40 g n-butyl- 
mercaptan (n-BM) 
1.0 g MAA 
1.15 g SDOSS 
Tg -21.degree. C. 
Tg +105.degree. C. 
Tg -35.degree. C. 
Tg +94.degree. C. 
Time (Minutes) Reaction Steps 
00 Add Stage 1 
15 Add 10 ml KPS 
72 Start addition of Stage 2 
94 All of Stage 2 is in 
114 Add 25 ml KPS 
119 Start addition of Stage 3 
144 Add 20 ml KPS 
147 All of Stage 3 is in 
212 Add 12 ml KPS 
217 Start addition of Stage 4 
271 All of Stage 4 is in 
291 Cooled to room temperature 
______________________________________ 
The graft polymer was isolated and compounded as in Example 1. The 
resultant plaque had low haze, and upon subjection to the Gardner Impact 
test was found to have a GI value of 20 in-lb determined by the Bruceton 
method, and exhibited low stress whitening. The ductility value was found 
to be 78%. The acrylic graft polymer prepared in this Example had a 
particle size of 0.174 micron. 
EXAMPLE 7 
Using the procedure of Example 1, a four-stage resilient acrylic graft 
polymer of the following composition was made with the sequence of steps 
indicated. 
______________________________________ 
Stage 1(6%) 
Stage 2(24%) 
Stage 3(40%) 
Stage 4(30%) 
______________________________________ 
7.2 g MMA 
144.0 g MMA 190.6 g BA 169.2 MMA 
28.8 g EA 
0.4 g ALMA 44.7 g S 10.8 g EA 
0.5 g SDOSS 
2.0 g SDOSS 4.7 g ALMA 0.45 g n-BM 
1.0 g MAA 
1.15 g SDOSS 
Tg -4.degree. C. 
Tg +105.degree. C. 
Tg -35.degree. C. 
Tg +94.degree. C. 
Time (Minutes) Reaction Steps 
00 Add Stage 1 
15 Add 10 ml KPS 
60 Start Addition of Stage 2 
84 All of Stage 2 is in 
104 Add 25 ml KPS 
109 Start addition of Stage 3 
134 Add 20 ml KPS 
137 All of Stage 3 is in 
253 Add 12 ml KPS 
258 Start addition of Stage 4 
309 All of Stage 4 is in 
329 Cooled to room temperature 
______________________________________ 
The graft polymer was isolated and compounded as in Example 1. The 
resultant plaque had low haze, and upon subjection to the Gardner Impact 
test was found to have a GI value of 14 in-lb determined by the Bruceton 
method, and exhibited low stress whitening. The ductility value was found 
to be 100%. The acrylic graft polymer prepared in this Example had a 
particle size of 0.203 micron. 
EXAMPLE 8 
A. Into a 10 gallon stainless steel reactor was placed 20,000 g of 
demineralized water, 381 g BA, 87 g S, 9.0 g ALMA and 3.6 g SDOSS. The 
mixture (Stage 1) was vigorously agitated and the vessel was evacuated to 
about -25 inches of Hg for 30 seconds and then pressurized to 7 psi with 
nitrogen. The nitrogen was then vented to a final pressure of 2 psi. 
During this time the temperature was raised to 80.degree. C. Thirteen 
minutes after starting agitation, agitation was reduced by about half. At 
15 minutes 60 ml of KPS (2% K.sub.2 S.sub.2 O.sub.8 in demineralized 
water) was added. This was repeated at 48 minutes. At 109 minutes a 
mixture (Stage 2) of 2820 g MMA, 180 g EA, 12 g ALMA and 30 g of SDOSS was 
gradually pumped into the reactor. An additional 60 ml of KPS was added at 
110 minutes. At 126 minutes all of Stage 2 was in the reactor. At 150 
minutes an additional 250 ml KPS was added followed by gradually pumping 
in Stage 3 which consisted of 4863 g BA, 1110 g S, 110 g ALMA and 47 g 
SDOSS. At 186 minutes 250 ml of KPS was added and at 190 minutes all of 
Stage 3 was in the reactor. At 327 minutes 80 ml KPS was added and at 330 
minutes Stage 4, consisting of 2256 g MMA and 144 g EA, was gradually 
pumped into the reactor. 
All of Stage 4 was in at 354 minutes and the reaction was allowed to 
proceed for an additional 16 minutes after which time it was cooled to 
room temperature. 
Isolation 
The polymer latex was diluted 1 to 1 with demineralized (DM) water. It was 
then gradually pumped (0.5 gallon/minute) into a stirred 55 gallon drum 
containing a hot (50.degree.-60.degree. C.) solution of 17 gallons of DM 
water and 625 g Epsom salt. After coagulation was complete the mother 
liquor was drained off and the coagulated polymer was washed 3 times with 
hot (55.degree. C.) DM water. It was then dried in a vacuum oven overnight 
to obtain a resilient acrylic graft polymer (particle size was not 
measured). 
Compounding and Testing 
A blend of 20 lbs. of the graft polymer and 30 lbs. of Lucite.RTM. 47F 
(MMA/EA; 94/6) was prepared with a drum tumbler. This blend was then 
extruded in a twin screw extruder at about 150 pph and a melt temperature 
of about 270.degree. C. The resulting melt-compounded, pelletized product 
was then extruded in a single screw extruder equipped with a sheeting die. 
The resulting sheet was 68-75 mils thick, had very low haze, had a GI 
value of 27 in-lb (Bruceton method) and low stress whitening. This 
composition is at least 27 times tougher than sheet produced from 
Lucite.RTM. 47F alone. Ductility was observed to be about 100%. 
B. Into a 10-gallon stainless steel reactor was placed 20,000 g of 
demineralized water, 381 g BA, 87 g S, 9.0 g ALMA and 3.6 g SDOSS. The 
mixture (Stage 1) was vigorously agitated (250) rpm) and the vessel was 
evacuated to about -25 inches of Hg for 30 seconds and then pressurized to 
7 psi with nitrogen. The nitrogen was then vented to a final pressure of 2 
psi. During this time the temperature was raised to 78.degree. C. Twelve 
minutes after starting agitation, agitation was reduced by about half. At 
15 minutes, 120 ml of KPS (2% K.sub.2 S.sub.2 O.sub.8 in demineralized 
water) was added. Temperature was raised to 80.degree. C. at 16 minutes. 
At 40 minutes 80 ml more of KPS was added. At 45 minutes, a mixture (Stage 
2) of 2808 g MMA, 180 g EA, 12 g ALMA and 30 g of SDOSS was gradually 
pumped into the reactor. At 72 minutes, all of Stage 2 was in the reactor. 
An additional 250 ml of KPS was added at 95 minutes. At 100 minutes, Stage 
3 which consisted of 5342 g BA, 1243 g S, 134 g ALMA and 54 g SDOSS was 
gradually pumped into the reactor. At 139 minutes, 250 ml of KPS was added 
and at 144 minutes all of Stage 3 was in the reactor. At 275 minutes, 120 
ml KPS was added and at 280 minutes Stage 4, consisting of 1808 g MMA and 
117 g EA, was gradually pumped into the reactor. 
All of Stage 4 was in at 307 minutes and the reaction was allowed to 
proceed for an additional 23 minutes after which time it was cooled to 
room temperature. 
Stage 1 was 4% of total and had a Tg of -35; stage 2 was 25% with Tg of 
+96; stage 3 was 55 percent with Tg of -35; and stage 4 was 15% with Tg of 
+96. 
Isolations and Testing 
The rubber was isolated as in Example 8. The final latex particle size was 
0.275 microns. It was then compounded and compression molded as in Example 
1 except that graft polymer in the blend was 40% and the copolymer 
contained 16% EA and 94% MMA. 
The following physical properties were obtained: 
______________________________________ 
Gardner Tensile % 
Impact* Strength Elongation 
______________________________________ 
25 In.-Lb 5180 psi 32 
______________________________________ 
*Determined by Bruceton method. 
Stress whitening was low and ductility was observed to be about 100%. 
EXAMPLE 9 
Using the general procedure of Example 1, the following charges were 
consecutively placed in a 3-liter resin kettle and each reacted to obtain 
a four-stage resin of this invention and a three-stage resin not covered 
by this invention. 
______________________________________ 
Four-Stage Resin of this Invention 
Stage 2 
Stage 1 Charge (elastomeric) 
Charge (non-elastomeric) 
10.9 g styrene (S) 
113.5 g MMA 
48.0 g butylacrylate (BA) 
6.0 g ethylacrylate (EA) 
1.2 g allylmethacrylate (ALMA) 
0.5 g ALMA 
0.60 g Aerosol-OT (75% soln.) 
1.20 g A-OT 
(A-OT) 
Stage 4 
Stage 3 Charge (elastomeric) 
Charge (non-elastomeric) 
59.9 g S 85.5 g MMA 
263.6 g BA 4.5 g EA 
6.5 g ALMA 
3.30 g A-OT 
Time Reaction Temp., .degree.C. 
Remarks 
______________________________________ 
0 79 Added 26 ml of monomer 
charge Stage 1 
15 80 Added 12 ml of KPS 
35 80 Added 12 ml of KPS 
40 80 Started feeding rest of Stage 1 at 
approx. 4 ml/min. 
50 80 All of Stage 1 added 
110 81 Added 12 ml KPS 
115 80 Started feeding Stage 2 at 
approx. 5 ml/min 
140 80 All of Stage 2 added 
155 80 Added 25 ml of KPS 
160 80 Started feeding Stage 3 at 
approx. 8 ml/min 
200 80 Added 25 ml of KPS 
204 80 All of Stage 3 added 
305 81 Added 12 ml KPS 
310 80 Started feeding Stage 4 at 
approx. 3 ml/min 
339 81 All of Stage 4 added 
365 80 Cooled batch to room temp. 
Three-Stage Resin 
Stage 1 
Charge (non-elastomeric) 
Stage 2 Charge (elastomeric) 
170.3 g MMA 59.9 g S 
9.0 g EA 263.6 g BA 
0.7 g ALMA 6.5 g ALMA 
1.80 g A-OT 3.30 g A-OT 
Stage 3 
Charge (non-elastomeric) 
85.5 g MMA 
4.5 g EA 
Time Reaction Temp., .degree.C. 
Remarks 
______________________________________ 
0 79 Added 52 ml monomer charge 
Stage 1 
15 79 Added 15 ml KPS 
30 81 Started feeding rest of Stage 1 at 
approx. 5 ml/min 
60 80 All of Stage 1 added 
75 80 Added 25 ml KPS 
80 80 Started feeding Stage 2 at 
approx. 8 ml/min 
120 80 Added 25 ml of KPS 
127 80 All of Stage 2 added 
227 81 Added 12 ml KPS 
232 80 Started feeding Stage 3 at 
approx. 3 ml/min 
264 81 All of Stage 3 added 
289 80 Cooled batch to room temp. 
______________________________________ 
Each resin was isolated by evaporating the latex to dryness in vacuum at 
70.degree.-90.degree. C. and compounded as described in Example 1 with a 
MMA/EA (95/5) copolymer. They were compression molded at 240.degree. C. 
and 40,000 lb force into approximately 40 mil plaques for tensile testing 
and 12 mil films for fold endurance testing. 7 mil films were made by 
pressing at 250.degree. C. 
The Table following records the percent of each Stage, the Tg of each stage 
and the particle size of the resin. 
TABLE 1 
__________________________________________________________________________ 
Stages.sup.(1) Final 
Part. 
1 2 3 4 Size, 
% Tg % Tg % Tg % Tg Microns 
__________________________________________________________________________ 
Four-Stage 
Resin 10 -35 
20 +96 
55 
-35 
15 
+96 
0.280 
(4% seed) 
Three-Stage 
Resin 30 +96 
55 
-35 
15 
+96 
0.282 
(8% seed) 
__________________________________________________________________________ 
.sup.(1) Tg's were calculated. 
It is seen that the last two stages of each resin are identical in 
composition and amount present, and that the only difference is that the 
core portion of the three stage resin is non-elastomeric and comprises 30% 
of the total whereas in the four stage resin the core is 10% elastomeric 
with a 20% non-elastomeric second stage. 
Results of the Fold Endurance Test are as follows (in this Table loadings 
in MMA/EA blend are provided, along with film thickness and number of 
samples tested. 
TABLE 2 
__________________________________________________________________________ 
FOLDING ENDURANCE TEST 
% Loading 
of Acrylic 
Graft 
Polymer in 
Film Thickness 
Composition 
MMA/EA Resin 
(Mils) No. of Samples 
Bends to Break.sup.(1) 
__________________________________________________________________________ 
Three-stage 
Resin 32 11.5 .+-. 0.4 
9 2.8 .+-. 1.1 
Four-stage 
Resin 32 11.1 .+-. 0.2 
10 3.1 .+-. 1.3 
Three-stage 
Resin 50 12.8 .+-. 0.3 
12 9.0 .+-. 3.1.sup.(2) 
Four-stage 
Resin 50 13.2 .+-. 0.4 
9 12.6 .+-. 4.1.sup.(2) 
Three-stage 
Resin 50 7.4 .+-. 0.4 
16 31.0 .+-. 8.4.sup.(3) 
Four-stage 
Resin 50 7.5 .+-. 0.5 
16 4.24 .+-. 12.4.sup.(3) 
__________________________________________________________________________ 
.sup.(1) No. of 180.degree. bends to break. 
.sup.(2) Based on statistical analysis carried out by the Variance 
Stabilizing Transformation method (See Advanced Theory of Statistics, M. 
G. Kendall and A. Stuart, Vol. 3, 2nd Edition, page 89) the improvement o 
40% (12.6 versus 9.0) is realizable with a greater than 95% degree of 
confidence. 
.sup.(3) Based on the same statistical analysis described in footnote 2, 
the improvement of 37% (42.4 versus 31.0) is realizable with a greater 
than 95% degree of confidence. 
It is evident from the % improvement values that four-stage resin of this 
invention exhibited better fold endurance at each loading level and 
particularly the higher levels for each film thickness tested. 
Results of tensile property, Gardner Impact, and ductility tests showed no 
significant difference between these three stage and four stage resins. 
EXAMPLE 10 
Using the general procedure of Example 1, a four stage resin with 20% 
elastomeric first stage was prepared and compared with a three stage 
resin. The following charges were prepared to produce stages in the 
amounts shown to obtain the two resins. 
______________________________________ 
Four Stage Resin of this Invention 
Stage 1 Stage 2 Stage 3 Stage 4 
(20%) (10%) (55%) (15%) 
______________________________________ 
96.0g BA 56.8g MMA 263.6g BA 85.5g MMA 
21.8g S 3.0g EA 59.9g S 4.5g EA 
2.4g ALMA 
0.25g ALMA 6.5g ALMA 
1.20g SDOSS 
0.60g SDOSS 3.30g SDOSS 
Time (minutes) Reaction Steps 
______________________________________ 
00 Add 20ml of Stage 1 
15 Add 12ml KPS 
35 Add 12ml KPS 
40 Start addition of remainder of 
Stage 1 
70 All of Stage 1 is in 
75 Add 12ml KPS 
158 Add 12ml KPS 
163 Start addition of Stage 2 
178 All of Stage 2 is in 
193 Add 25ml KPS 
198 Start addition of Stage 3 
240 Add 25ml KPS 
244 All of Stage 3 is in 
344 Add 12ml KPS 
349 Start addition of Stage 4 
379 All of Stage 4 is in 
399 Cooled to room temperature 
Particle size was 0.340 microns. 
Three Stage Resin 
Stage 1 (30%) 
Stage 2 (55%) Stage 3 (15%) 
______________________________________ 
170.3g MMA 263.6g BA 85.5g MMA 
9.0g EA 59.9g S 4.5g EA 
0.7g ALMA 6.5g ALMA 4.5g EA 
1.80g SDOSS 
3.30g SDOSS 
Time (minutes) Reaction Steps 
______________________________________ 
00 Add 38ml of Stage 1 
15 Add 15ml KPS 
30 Start addition of remainder of 
Stage 1 
62 All of Stage 1 is in 
82 Add 25ml KPS 
87 Start addition of Stage 2 
125 Add 25 ml KPS 
149 All of Stage 2 is in 
250 Add 12ml KPS 
255 Start addition of Stage 3 
286 All of Stage 3 is in 
311 Cooled to room temperature 
______________________________________ 
Particle size was 0.320 microns. 
Percent stages, resin particle size, and Tg of each stage are summarized as 
follows: 
______________________________________ 
Final 
Stages Part. 
1 2 3 4 Size, 
% Tg* % Tg % Tg % Tg Microns 
______________________________________ 
Three 
stage 30 +96 55 -35 15 +96 0.320 
resin (5% seed) 
Four 
stage 20 -35 10 +96 55 -35 15 +96 0.340 
resin (3% seed) 
______________________________________ 
*Calculated Tg's, .degree.C. 
The resins were isolated as in Example 9 and compounded as in Example 1 
with 95/5 MMA/EA at 32% loadings and 50% loading of the acrylic graft 
polymer. The compounded resins were tested for Gardner impact values with 
the following results: 
GARDNER IMT TOUGHNESS 
______________________________________ 
Three Stage Resin Blend 
Four Stage Resin Blend 
30/55/15 20/10/55/15 
______________________________________ 
50% Loading 50% Loading 
30.1 37.0 
31.5 45.3 
34.6 39.2 
32.1 .+-. 2.3 40.5 .+-. 4.3 
32% Loading 32% Loading 
14.7 13.1 
15.6 18.1 
15.6 15.8 
15.3 .+-. 0.5 14.8 
15.5 .+-. 2.1 
______________________________________ 
It is seen that at 32% loading acrylic graft polymer, there is no 
significant difference in Gardner Impact toughness, but at a 50% loading, 
the four stage polymer used in this Example gave a 26% improvement. No 
significant difference in stress whitening or ductility was observed. 
Tensile strengths were not measured.