Note: Descriptions are shown in the official language in which they were submitted.
lOS6975
o. z . 30 ,59
MANUFACTURE OF IMPACT-RESISTANT THERMOPLASTIC MO~.DING MATERIALS
The present invention relates to a process for the manu-
facture of impact-resistant thermoplastic molding materials, -~-
preferably Or ABS polymers, by graft polymerization using an
agglomerated rubber latex.
Rubber latice~ obtained by conventional homopolymerization
or copolymerization of butadiene have particle diameters of the
order Or magnitude of about from 0.05 to O.1/u. The toughness of
ABS polymers manu~actured using such rubbers is relatively low.
However it is known that ABS polymers with more advantageous
properties may be obtained by employing rubber latices of larger
particle size for the graft polymerization.
~ erman Printed Appl~cations 1,247,665 and 1,269,360 respec-
tively recommend the use of butadiene polymer latices with particle
sizes of from 0.15 to o.6~u~ or latex particle diamters greater
than 0.3~u. These publications also state how such coarse latices
are obtained, eg. by polymerization in concentrated emulsion, by
using smaller amounts of emulsifier or by staggering the addition
of emulsirier. However, these direct polymerization processes for
: ~ ,
' the manufacture of coarse latices have the disadvantage of en- ~-
tailing relatively long polymerization timeæ. In general, several
days are required to reach practically complete conversion.
~ ..
' ,,. ~ ,~ .
~OS6975
O.Z. 30,591
- A different direct method of manufacture of coarse latices
is recommended in German Printed Application DAS 1,300,241.
According to this method, further monomer is added during the
polymerization, but here again long polymerization times are
needed.
An indirect method of manufacture of coarse latices is to
add electrolyte to a fine rubber latex and thereby increase the
size of the partlcles. An example of this method is described in
German Printed Application DAS 1,292,850. Using this process, the
10 agglomeration takes place during grafting. The process has two
disadvantages. Firstly, because Or the risk of coagulation large
amounts of emulsifier must be added, and this can interfere with
; the subsequent precipitation. Secondly, the ions added are par-
. . ~
tially retained in the product and can, during processing, cause
corrosion, and discoloration of the product.
A further lndirect method is free~e-agglomeration as des-
cribed in British ratent 1,063,439, in German Published Appli-
` ~ cation VOS 2,057,936 and in German Published Application
;~ DOS 2,223,186. However, this proce~s is very expensive and
20 consumes much energy; application of the process on an industrial
scale presents apparatus problems so that the process has not
found industrial acceptance in the manufact ure of ABS polymers.
The same is true of shear agglomeration described in German
Published Application DOS 2,101,650.
According to German Printed Application DOS 1,115,462, the
agglomeration is effected with polyvinyl ethers at from O to 15C.
This water-soluble agent remains in the agglomerated rubber latex
and interferes with the subsequent graft polymerization since it
also partially coagulates the graft polymer.
~30 A further process for coarsening rubber latices is described
in German Published Application DOS 2,218,444. In this proces~,
-- 2 --
~ 056975 o.z. 30,591
, acetic anhydride is added to the rubber latex. The acetic acid
formed by slow hydrolysis reacts with the emulsifier which
normally stabilizes the latex, and thereby annuls the emulsi-
~ fying action. This process is only applicable if soaps, or salts
; Or certain organic acids, are used as emulsifiers. With the highly
efficient emulsifiers based on organic sulfonic acids or sulfonates,
which are also used commonly, no agglomeration is caused by
acetic anhydride. The process has the further disadvantage that
acetic anhydride causes an increase in size of virtually all the
rubber particles so that a relatively narrow particle size dis-
tribution results, whilst it has been found that it is advantageous,
for the manufacture of ABS polymers, to have a broad rubber
particle size distribution, ie. to have small and lar~e particles
present alon6side one another.
~ Such a so-called bimodal particle size distribution of the
: ' .
rubber particles in ABS polymers is achieved, according to US
Patents 3,652,712 and 3,663,65~, by employing two different
rubbers, one with large particles and one with small particles.
However, these two rubbers must be manufactured separately, and
then mixed.
It is an object of the present invention to provide ABS
polymers which have an optimum combination of properties such
as toughness, flow and surface gloss. It i9 a further object to
;~ provide a process by which the particles of a rubber latex are
. ~
partially agglomerated, by a method which is simple and economical
to perform even on an industrial scale, so as to give an agglom-
~` erated latex with a broad or bimodal particle size distribution.
l~e have ~ound that these objects are achieved by usin~ an
acrylic ester polymer dispersion as the agglomeratin~ agent.
3 The basic rubber is defined by its glass transition tem-
- perature, which should be below -20 and preferably below -40~./ -
~ ~ 3 ~
. . .
~' .
., ,
- lOS6975
The present invention will be better understood
with reference to the accompanying drawing! wherein
figures 1 and 2 represent diagrams showing
respectively narrow and broad particle size distribution
.: (cumulative mass distribution) of the rubber latex obtained
by the process of the present invention.
.. . .
The rubber latex may be manufactured by conventional
. methods
.: ' /
.... . .
:'., /
.- /.
. . /
,
~ /
1 ~
'. / '
~/ .. ...
~ ~ - 3a - -
.
1056975 o.z. 30,591
an_ the rubber particles should have a mean particle size of
less than 0.15/u (d50 value of the cumulative mass distribution).
Butadiene is preferably used as the sole monomer. Since butadienet
acrylic ester rubbers have advantages for some purposes, monomer
mixtures of butadiene and acrylic esters, preferably containing
from 30 to 70~ by weight of acrylic e~ter, based on the mixture,
may also be employed. Acrylic esters derived from alcohols of
1 to 8 carbon atoms, such as ethyl acrylate, butyl acrylate or
ethylhexyl acrylate, are preferred. These acrylic esters can
likewise also be used alone, optionally together with up to 10%
by weight of crosslinking bifunctional monomers. Such compositions
give ASA polymers, which have better resistance to weathering.
Optionally up to 30Z by weight of ~her comonomers, eg. isoprene,
styrene, acrylonitrile or vinyl ethers, may be present during
polymerization.
The polymerization is carried out in the conventional way
~ at from 30 to 90C in the presence of emulsifiers, eg. alkali
i~ metal salts of alkylsulfonic acids or alkylarylsulfonic acids,
alkyl-sulfates, fatty alcohol-sulfonates or fatty acids of 10 to
30 carbon atoms; sodium salts of alkylsulfonic acids or of fatty
~'
acids of 12 to 18 carbon atoms are preferred. From 0.3 to 5,
especially from 1.0 to 2.0, per cent by weight of emulsifiers,
` based on the monomers, are used. The conventional buffer salts,
such as sodium bicarbonate and sodium pyrophosphate, are
~ employed.
! ' Likewise, the conventional initiators, such as persulfates
~ or organic peroxides together with reducing agents are employed;
"~ optionally, molecular weight~ regulators, such as mercaptans,
terpinols or dimeric ~C-methylstyrene are used, and these are
~ added at the start of, or duringJ the polymerization. The weight
`` ratio of water to monomer is preferably from 2:1 to 1:1. The
polymerization is continued until more than 90%, and preferably
more than 96%, of the monomers have polymerized. This conversion
1056975 o.z. 30,591
is in general achieved in from 4 to 20 hours. The rubber latex
thus obtained has a particle size of less than 0.15/u and prefer-
ably from 0.06 to 0.10/u. These figures relate to the d50 value
of the cumulative mass distribution (see Figure 1), which value
may be determined, eg., by means of an ultracentrifuge or from
counts on electron microphotographs. The particle size dis-
tribution of such rubber latices is relatively narrow so that
it may be described as an almost monodisperse system.
This rubber latex is now agglomerated. According to the
invention, this is done by adding a dispersion of an acrylic
acid alkyl ester polymer. Preferably, dispersions of copolymers
of acrylic esters of alcohols of 1 to 4 carbon atoms, preferably
of ethyl acrylate, with from 0.1 to 10 per cent by weight, of
monomers capable Or forming water-soluble polymers, eg. acrylic
acid, methacrylic acid, acrylamide or methacrylamide, N-methylol-
methacrylamide or N-vinylpyrrolidone, are employed. A copolymer
of 96% by weight of ethyl acrylate and 4% by weight of methacryl- -
amideis particularly preferred. The dispersion used to cause
agglomeration can optionally also contain several of the said
acrylic ester polymers.
~; The concentration of the acrylic acid alkyl ester polymer
`~ in the dispersion should in general be from 3 to 40 per cent
by weight. To produce agglomeration, from 0.2 to 20, preferably
from 1 to 5, parts by weight of the dispersion which causes
agglomeration are employed per 100 parts of the rubber latex,
the quantities in each case being based on solids. The agglom-
eration is effected by adding the dispersion which causes
i agglomeration to the rubber. The rate of addition is usually
not critical; in general, the addition takes about 1 to 30 minutes
at a temperature of between 20 and 90C, preferably 30 and 75C.
Under the conditions mentioned, only a part of the rubber
particles is agglomerated so that a bimodal or broad distribution
` ~ 5 -
`:-
1056975 o . z . 30,591
r~ llts. After arglomeration, in general more than 50%, andpreferably from 75 to 95%, Or the number of particles are present
in the non-agglomerated state. The average diameter of the rubber
particles (d50 value Or the cumulation mass distribution; see
~i~ure 2) is from 0.16 to 0.45/u, preferably from 0.20 to 0.35/u.
The agglomerated rubber latex obtained is relatively stable and
can, without requiring special measures, be stored and transported
without causing coagulation.
The next step is the graft polymerization. This is again
carried out in aqueous emulsion, under the conventional conditions
mentioned above. From 20 to 90 per cent by weight of styrene,
acrylonitrile, methylmethacrylate or mixtures of two or all three
of these monomers are polymerized in the presence of from 80 to
10 parts by weight of the rubber, the quantities being based on
solids. Preferably, from 25 to 45 per cent by weight of a mixture
-~
of styrene and acrylonitrile in the weight ratio of from 75:25
; to 65: 35 are grafted onto from 75 to 55 per cent by weight of
; rubber. At a very low monomer : rubber ratio, almost all monomers
; are chemically bonded, as side chains, to the base rubber; if the
ratio rises above about 50:50, a substantial portion Or the mono-
mers polymerizes separately. In the preferred embodiment, in
~` which only a small proportion of monomer is grafted on, a graft
'~ polymer which still retains rubbery properties is obtained. In
the text which follows, this graft polymer is referred to as the
soft component. It can be precipitated from the dispersion by
. .
conventional methods, eg. by adding electrolytes and can then be
separated off, dried and mixed with a rigid polymer (hard component).
. ~
However it is also possible to mix the hard component and soft
component as dispersions and to precipitate the mixture and work
up the product. A further possibility is to dehydrate the disper-
:
~ sion Or the soft component only partially and incorporate it,
- as a moist crumb, into a melt Or the hard component, as des-
cribed, for example, in German Printed Application DAS 2,037,784.
'
. .
105~975
O.Z. 30,591
The hard component may be a polymer of styrene, ~-methyl-
styrene, met~a methacrylate, acrylonitrile, methacrylonitrile
or vinyl chloride, or of mixtures of two or more of the~e
monomers. For ABS polymers, a copolymer of from 90 to 60 per
cent by weight of styrene and from 10 to 40 per cent by weight
of acrylonitrile is preferred. On mixing, the weight ratio of
hard component to soft components is from 80:20 to 50:50. The
content of base rubber in the finished ABS molding material is
preferably from 5 to 25 per cent by weight.
The molding materials according to the invention are
distinguished by an optimum combination Or impact strength, even
at low temperatures, surface gloss and flow, ie. thermoplastic
processability.
;
? Thqycan contain the conventional additives, such as fillers,
further plastics, stabilizers, antistatic agents, plasticizers,
.
flameproofing agents, lubricants, dyes and pigments, preferably
in amounts totaling about 30% of the weight of the molding
material. They may be converted to shaped articles by extrusion,
deep-drawing or injection molding.
The parts and percentages mentioned in the examples are
by weight. The particle size distribution of the nongrafted
rubber latex before and after agglomeration was determined,
using an analytical ultracentrifuge, by the method of W. Scholtan
and H. ~,ange, Kolloid-Z. and Z. Polymere 250 (1972), pages 782-
796. In every case, the correction of the measurements because
of the dilution effect and the Mie effect, described by these
authos, was made. At very low latex concentrations, of about
from 0.5 to 4 g/l, the correction of the concentration effect
: .
proved superfluous. The ultracentrifuge measurements give the
` 30 cumulative mass distribution of the latex particle diameter.
- From this it is possible to deduce what percentage by weight
of the latex particles have a diameter equal to or less than
lU5~;97S o.z. 30,591
a -rtain value. The d50 value of the cumulative mass dis-
tribution is defined as the particle diameter at which 50 per
cent by weight of the latex particles have a smaller diameter
than the diameter corresponding to the d50 value. Equally,
therefore, 50 per cent by weight Or the particles have a larger
diameter than the d50 value. In order to provide additional
characterization of the particle size distribution of the rubber
latices, the d1o and dgo values were determined in addition to
; the d50 value. They provide a measure of the breadth of dis-
10 tribution. The d1o and dgo value of the cumulative mass dis-
tribution is defined analogously to the d50 value except that
it relates to 10 and 90 per cent by weight of latex particles,
respectively.
After grafting and mixing, the notched impact strength,
the energy of fracture and the surface corrosion of the
impact-resistant polymers was tested. The notched impact
strength at 23C was determined in accordance with DIN 53,453.
The energy of fracture was determined by the dart drop test.
. i.
Round discs of 50 mm diameter and 1 mm thickness are injection-
20 molded at a material temperature of 260C. The damage work,
in cm.kp, caused by the dart in a biaxial piercing test on the
: ::
discs is measured. The surface corrosion was measured in an
accelerated test by treating the molded discs with 2 ppm of
ozone at room temperature for one or more days.
EXAMP~.E 1
. .
~ 150 parts of water, 1.2 parts of the sodium salt of a
:
paraffinsulfonic acid of 12 to 18 carbon atoms, 0.3 part of
potassium persulfate, 0.3 part of sodium bicarbonate and 0.15
part of sodium pyrophosphate were introduced into a V2A steel
kettle, designed to withstand 10 atmospheres gauge and fitted
i 30 with a blade stirrerO
~` The kettle was twice flushed with nitrogen to remove
the oxygen and the solution was then heated under nitrogen to
-- 8 --
1~5~975 .Z0 30 J 591
6 ~. 0~5 part of tertO-dodecylmercaptan and 1606 parts of
butadiene were then introducedO One hour arter polymerization
started, a rurther 8303 parts of butadiene were introduced in
the course of 5 hoursO 5 hours after the end of the addition
of butadiene, ieO after a total of 11 hours, a further 0.5 part
of tert.-dodecylmercaptan was added. After a total reaction time
Or 19 hours, the conversion was 96% and a polybutadiene emulsion
of 39.2~ solids content, based on emulsion, was obtainedO The
glass temperature of the polybutadiene latex was about -80C.
The particle size distribution (cumulative mass distribution)
determined by means of an ultracentrifuge is shown in Figure 1.
The particle diameter D is plotted on the abscissa and the
proportion of particles, expressed as per cent by weight, is
plotted on the ordinate. The distribution is characterized by
- the following values:
d1o value : o.o6/u
d50 value : o.o8/u
d50 value : 0.105/u
The following experiments were carried out with the poly-
2d butadiene emulsion obtained.
Reaction A:
255 parts of the polybutadiene emulsion were diluted with
74 parts of water at 6sc. To agglomerate the latex, 30 parts
of an aqueou8 dispersion Or an ethyl acrylate copolymer which
¢ontained 96 per cent by weight of ethyl acrylate units and
4 per cent by weight of methacrylamide units, were metered in.
`~. The solids content of this dispersion was 10 per cent by weight,
based on dispersion. After agglomeration, a polybutadiene latex
in which about 80% of the number of particles were in a non-agglom-
3 erated state, was obtained. Figure 2 shows the particle size
distribution (cumulative mass distribution) of the agglomerated
polybutadiene latex, as measured u~ing an ultracentri~uge. The
particle diameter D is plotted on the abscissa and the proportion
_ g _
' `' :
i ~S ~9 7 5 O.Z. 30,591
ol article~, in per cent by weight, on the ordinate. It may be
seen that a broad distribution of bimodal character ha~ resulted;
the distribution is characterized by the following values:
d1o value : 0.079/u
d50 value : 0.238/u
dgo value : 0.323/u
The polybutadiene emulsion thus obtained was heated to 70C
and at this temperature 0.13 part Or potassium persulfate (in the
-~ rorm of a 3 per cent strength aqueous solution), 0.02 part Or
tert.-dodecylmercaptan and 11 parts of a mixture of styrene and
acrylonitrile (in which the weight ratio of styrene to acrylo-
nitrile was 7 : 3) were added. 10 minutes arter the grafting
reaction had started, a mixture Or a further 39 parts of styrene,
17 parts of acrylonitrile and 0.1 part of tert.-dodecylmercaptan
was metered in over 2 3/4 hours. The reaction temperature assumed
a value of 75C. After the monomers had been added, the reaction
was continued for a further hour and the resulting graft polymer
'` was then precipitated by means of a calcium chloride solution
;~ at 95C, and filtered ofr. The moist crumb of grafted polybutadiene
was worked into a melt of a styrene~acrylonitrile copolymer
Al ( containing 65 per cent by weight of styrene units and 35 per cent
by weight of acrylonitrile units) in an extruder, the weight
ratio of grafted polybutadiene to styrene/acrylonitrile copolymer
~$ being 3 : 7-
Reaction B (for comparison):
~ In a second experiment, the non-agglomerated polybutadiene
`; emulsion produced in the primary step was subjected to the same
~` grafting reaction as that described for ~eaction A. However, in
this case no dispersion to cause agglomeration was added and
3 instead the non-agglomerated latex was grafted direct. In other -~
~ respects, the procedure followed was exactly the same as for
- reaction A. The amount of water was adjusted to give the same
final solids content.
- 10- ,
~, . ~ ., ''- ' ' . ': -
105~975 oOz. 30,591
The notched impact 3trength of the ABS molding materials
obtained by reaction A and reaction B is shown in Table lo The
molding material~ manuractured according to the invention, using
; agglomerated latex particles (reaction A) ~how substantially
better properties,
,i
TAB~E 1
InjectionNotched impact
temperat ure st rength
C kp.cm/cm2
Reaction A twith agglomerated 220 15
latex particles) 250 19
Reaction B (with non-agglomerated 220 3
latex particles) 250 4
EXAMPI,E 2
4.5 parts Or vinyl methyl ether, 9.5 parts Or acrylic acid
butyl ester and 6.5 parts Or butadiene in 150 partæ Or water, also
containing 1.2 parts Or the sodium salt Or a pararfin~ulfonic
acid of 12 to 18 carbon aotms, 0.3 part Or potassium persulfate,
~ 0.3 part of sodium bicarbonate and 0.15 part Or sodium pyrophos-
phate were heated to 65C, whilst stirring. After the polymerization
reaction had started, a mixt~re of a rurther 47.5 parts Or acrylic
acid butyl ester and 32 parts o~ butadiene was added in the course
5 hours. Arter the monomer had been added, the polymerization
reaction was continued for a further two hours at 65C and the
emulsion was then cooled. Its solid content was 38.4%. me rubber
latex obtained had a glass transition temperature Or about -55C
and a narrow particle size distribution characterized by the
~ollowing values:
~120 d1o value : 0.070/u
d50 value: 0.090/u
dgo value : 00115/u
The rubber emulsion thu~ obtained was divided and used for
the ~ollowing experimentsO
!
11 --
!
'
:
iO5~975 oO zo 30 ~591
R~ 'ion A:
2~9 parts of an aqueouY dispersion of an ethyl acrylate
copolymer which contained 96 per cent by weight Or ethyl acryl-
ate units and 4 per cent by weight of methacrylamide units,
were mixed into 25 parts of the rubber emulsion at 23C ~ whilst
stirringO The solids content of this dispersion used to cause
agglomeration was 10 per cent by weight; the agglomeration had
i ceased after one hour. The partially agglomerated rubber latex
had a broad particle size distribution of slightly bimodal
character, with the following characteristic values:
d1o value : 0.115/u
d50 value : 0O 310/U
dgo value : 0. 590~ u
; The emulsion thus obtained was mixed~ with 7.5 parts of
water and heated to 65~ 0~ 019 part of potassiumpersulfate
(as a 3 per cent strength aqueous solution), 0. oo6 part of
~' tert.-dodecylmpercaptan, 1.1 parts of styrene and 0~5 part of
acrylonitrile were then added under nitrogen. 15 minutes a~ter
the start of the graft polymerization, a mixture of a further
3.5 parts of 8tyrene, 1.4 parts of acrylonitrile and 0.019 part
o~ tert.-dodecylmercaptan was metered in over 1~5 hours. After
;~` the monomers had been added, the grafting reaction was continued
for a ~urther 1.~ hours and the resulting graft polymer was then
precipitated by means of a calcium chloride solution, filtered
-l off and dried under reduced pressure at 60C~ The graft polymer
thu~ obtained was mixed with a styrene/acrylonitrile (65 35)
copolymer in an extruder at 260Co Two mixtures, of the following
composition, were preparedc
Mixture 1:
Graft polymer 370 5 parts
Styrene/acrylonitrile copolymer 62~5 parts
- 12 -
'. ' , -
lOS~9~5 o.z. 30,591
Mi~_ure 2:
Gra~t polymer 37 o 5 parts
Styrene/acrylonitrile copolymer 62. 5 parts
Carbon black 2.0 parts
The notched impact strength and energy Or rracture, by the
dart drop test, were determined on the products from mixture 1.
ffl e product from mixture 2 was used for determination Or the
surrace corrosionO The values obtained are listed in Table 2.
Reaction B (for compari30n):
In another experiment, the non-agglomerated rubber latex,
prepared in the primary stage, was subjected to the same grafting
reaction as that described ror reaction A except that in the
present instance no dispersion to cause agglomeration was added
and instead the non-agglomerated latex was grarted direct. In
other respect, the procedure followed was exactly as for reaction
A. The amount o~ water wa~ adju~ted 80 as to give the same final
solids content as in reaction A. Equally, the mixtures Or the
resulting grart polymers were prepared analogously to the case
Or reaction A. The properties Or these molding materials are
shown in Table 2. It may be seen that the products manufactured
according to the invention (reaction A) give substantially better
Va1UeB Or all the propertieæ messured.
-- 13 --
-
1056975 o.z. 30,5
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EXAMPI.E 3
Reaction A:
16 part~ Or butyl acrylate and 0033 part of dicyclo-
pentadienyl acrylate in 150 part~ Or water, which al~o contained
1 part Or the sodium salt Or a pararfin~ulronic acid Or 12 to
18 carbon atoms, 003 part of sodium persulfate, 003 part Or
sodium bicarbonate and 0015 part of sodium pyrophosphate were
heated to 60C whilst stirring under nitrogenO 10 minutes after
the start of the polymerization reaction, a mixture of a further
82 parts of butyl acrylate and lo 67 parts Or dicyclopentadienyl
acrylate wa~ added over 3 hour~O One hour before the end Or the
addition of monomers, 7.7 parts of an aqueous di spersion of an
ethyl acrylate copolymer, which contained 96 per cent by weight
. of ethyl acrylate units and 4 per cent by weight of methacryl-
j amid~ were added simultaneously to the reaction mixture. The
:~ solids content of this dispersion which causes the agglomeration
;3
was 10 per cent by weight. After the nomer had been added, the
polymerization was continued ror a further two hours at 60C.
. ,~ A polybutyl acrylate emulsion Or 39.5% solids content was ob-
tainod. The already partially agglomerated latex had a glass
transition temPerature of about -40C and a bimodal particle
size distribution characterized by the rollowing values: -
` ` d1o value: 0.120~u
d50 value : 0.160/u
. dgo value : 0.365/u
100 parts of the emulsion thus obtained were mixed with
39 parts of water and the mixture was heated to 60C~ o.o8 part
of potassium persulfate (as a 3 per cent strength aqueous solution),
;.
0.01 part of lauroyl peroxide, 3 parts of styrene and 1.0 part
of acrylonitrile were then admixed, under nitrogenO 15 minutes
after the start of the graft polymerization, a mixture of a
further 16 parts of styrene, 5 5 parts of acrylonitrile and
-- 15 --
105~975 o. z o 30,591
00~ part Or lauroyl peroxide wa~ metered in, over 2 hoursO
After the monomer had been added, the grafting reaction was
continued for a further two hours and the graft polymer obtained
was then precipitated by means Or a calcium chloride solution
at 95C, and dried. 43 parts of the graft polymer thus obtained
were mixed with 5700 parts of a melt o~ a styrene/acrylonitrile
(65 : 35) copolymer in an extruder.
Reaction B (ror comparison):
Reaction A was repeated with the sole difference that no
dispersion to cause agglomeration was added to the reaction
mixture when preparing the basic rubberO The a unt Or water
wad adjusted to give the same final solids contentO The non-
agglomerated polybutyl acrylate latex thus obtained had a par-
ticle size distribution with the following characteristic values:
d1o value : 0.077/u
d50 value : 0.091/u ,
i dgo value : 0.109/u
1~ This latex was subjected to the same grafting reaction as
J in reaction A and mixtures Or the graft polymer were also pre-
20 pared analogously.
Table 3 ~hows the notched impa~t, strength of the products
obtained by reaction A and reaction B.
TABLE 3
InjectionNotched impact
temperaturestrength
` C kp.cm/cm2
., .
~ Reaction A (with 220 24
`i' agglomeration Or the 250 27
' latex particles) 280 27
. ~.
Reaction B (without 220 6
agglomeration Or the 250 9
latex particles) 280 8
- 16 -
