Note: Descriptions are shown in the official language in which they were submitted.
~IL3~67;~
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This invention relates to a process for the
production of substantially speck free carbo~ylated
rubber latices of acyclic conjugated dienes, aryl vinyl
monomers and/or (meth)acrylonitrile by emulsion poly-
merisation in the presence of a mercaptocarboxylic acidcorresponding to the general formula:
HS-(CH2)~-C2H
in which
x is an integer of from 1 to 5
and/or wa-ter~soluble salts thereof.
In conventional emulsion polymerisation processes,
the monomers are normally polymerised in the presence of
an initiator releasing free radicals and an emulsifier
which keeps the polymer particles formed in dispersion.
Ho~ever, the presence of emulsifiers leads to an often
undesirable reduction in surface tension. A reduction
in surface tension occurs in particular in carboxylated
rubber latices which, after production in acid medium,
are neutralised or alkalised by the addition of a base.
However, carbo~ylated rubber latices should have high
surface tension because it is only rubber latices such
as these which, by virtue of their minimal tendency
towards foaming, provide for satisfactory processing,
~or e~ample in high-speed machines.
~he use of a large quantity of anionic emulsi~iers,
for example of the sulphate or sulphonate type, is
generally necessary to prevent the formation of coagulate
and specks. However, this measure greatly reduces the
surface tension o~ the latices9 with the result that
processing difficulties arise, the polymer films generally
show considerably reduced wet strength and the adhesion
of the polymers used as binders to the substrates is
reduced. Although it i9 possible to suppress the effect
of anionic emulsifiers by using non-ionic emulsifiers,
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for axample polyglycol ethers of fatty alcohols or long-
chain alkyl-substituted phenols, relatively large
quantities of non-io~ic emulsifiers also result in a
reduction in the surface tension of the latices
obtained and in a decrease in the resistance to water
and adhesion of films produced from the latices.
Accordingly, attempts have always been made to
carry out polymerisation in the presence o~ only small
quantities of emulsifiers or in the complete absence o-f
emulsifiersO However9 this generally requires longer
reaction times and the dispersions thus produced have a
tendency towards instability which is reflected in
coagulate or speck formation. Whereas in most cases
the coagulate can be filtered off without difficulty,
the formation of specks is particularly undesirable
because specks having a particle diameter of from 10 to
100 ~ are e~tremely difficult to separate and lead to
processing di~ficulties and to inhomogeneous polymer
films. In order to obtain an acceptable volume/time
yield, polymerisation in the substantial or complete
absence o$ emulsifiers is in general only carried out at
high polymerisation temperatures (abo~e about 50C). At
temperatures as high as these, however, the molecular
weight regulators normally used, such as tert.-~odecyl
mercaptan ~or e~ample, retard the reaction to a
considerable extent with the result that the polymerisation
velocity, which in any case is already low, is even
further reduced and speck formation still occurs during
polymerisation. Although the reduction in polymerisation
velocity can be compensated by increasing the quantity of
polymerisation initiator, for e3ample a peroxodisulphate,
the degree of coagulate and speck formation is also increased
as a result.
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It is known ~rom German Auslegeschri~t No. 2,015,660
that speck-~ree polymer latices of high surface tension
can be produced by carrying out polymerisation in the
presence of a sufficient quantity o~ certain emulsifiers,
~or example salts of a-sulpho-fatty acids or their esters.
However, relatively finely divided latices are obtained
in this way9 so that mechanical stability is reduced and
viscosity is increased. In addition, the advantages o~
low-emulsifier and, above all, emulsi~ier-~ree latices,
such as in particular rapid drying9 hardening,
considerably improved resistance to water and ~ar greater
adhesion of the polymers to the particular substrates
used, cannot be achieved with latices such as these.
According to German Auslegesschrift No. 1,814,209,
spec~ formation can be suppressecl by using small
quantities (up to 0.1 ~0 by weigh1i, based on monomer) of
an emulsifier of the sulphonate type together with small
qu~ntities of water-soluble iron salts (10 5 to 10 1 0/O
by weight). However, the use o~ iron salts leads to
polymers which have an increased tendency towards dis-
coloration.
It is knowu ~rom US Patent No. 29380,905 that the
polymerisation o~ 1,3-butadiene on its own or in
combination with suitable monom~rs can be carried out
in the presence of certain water-soluble sulphur-
containing compounds, such as for example mono- or di-
carboxylic acids containing mercapto groups, and optionally
water insoluble chain-trans~er agents in order to shorten
the polymerisation times and to improve the processing
properties o~ the isolated rubbers.
It is known ~rom US Pa-tent No. 2,635,090 that
mercaptocarboxylic acids, their esters and water-
soluble salts can be used as molecular weight regulators
in the production of polyacrylonitrile and copolymers
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~lL37G72
of acrylonitrile by suspension polymerisation in order
to obtain colourless polymers with improved physical
properties and good solubilities in solvents for
polyacryloni~ile fibres~
It is known from US Patent No. 3,388,109 that
hydrogen pero~ide can be used in combination with a
mercaptocarbo~ylic acid to initiate polymerisation
reactions carried out below 50C in order to obtain
colour-stable polymers in high yields and reasonable
polymerisation times.
According to US Patent No. 3,409,705, an initiator
combination of hydrogen peroxide and thioglycolic acid
may also be used for the production of two-phase plastics
materials by the graft polymerisation o-f suitable monomers
onto a rubber latex.
According to US Patent No. 3,501,432, thioglycolic
acid inter alia may be used in the emulsifiex-free
copolymerisation of (meth)acrylic acid esters, (meth)-
acrylic acid or (meth)acrylic acid hydroxyalkyl esters
in order to introduce stabilising dissociating terminal
groups into the polymers.
It has now been found that carboxylated rubber
latices of high surface tension can be produced by
polymeris~tion in the substa~tial or complete absence
2~ of emulsi~iers without significant quantities of coagulate
or specks being formed providing the polymerisation
reaction is carried out above 50C and in the presence
of a peroxodisulphate and a mercaptocaxboxylic acid
corresponding to the general ~ormula:
~IS- ( CH2)x-C2H
3o in which x is an integer of from 1 to 5,
and/or water-soluble salts thereof. Water-soluble salts
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are9 for e~ample, the alkali metal or ammonium salts of
monocarboxylic acids of the type in question.
It is surprising that the tendency towards speck
~ormation o~ warm-polymerised low-emulsi~ier or
emulsi~ier-~ree carboxylated latices o~ an acyclic
conjugated diene and an aryl vinyl monomer and/or
(meth)acrylonitrile is so drastically reduced, even
by small quantities oi the mercaptocarbo~ylic acid
~less than 0.1 /0 by weight, based on monomer). The
use o~ a mercaptocarboxylic acid has proved to be
particularly advantageous above all in cases where
polymerisation is carried out in the absence oY an
emulsi~ier with increased quantities o~ peroxodi-
sulphate, which normally leads to increased speck
formation.
In the process according to the invention, the
ratio of conjugated diene to aryl vinyl monomer and/or
(meth)acrylonitrile can be varied within very wi~e
limits. Accordingly, it is possible in accordance with
the invention to produce from the above~mentioned
monomers rubber latices which contain ~rom 10 to 90
parts by weight o~ one or more acyclic conjugated dienes
containing from ~ to 9 carbon atoms, from 0 to 90 parts
by weight of one or more aryl vinyl monomers containing
from 8 to 12 carbon atoms and/or irom 0 to 50 parts by
weight of (meth)acrylonitrile, the sum o~ the last two
components amounting to between 10 and 90 parts by
weight.
Accordingly, the present invention provides a
3o process for the production ofsubstantially speck-
~ree carboxylated rubber latices o~ high sur~ace tension
by polymerising a monomer mixture o~ 0.5 to 10 parts by
weight oi one or more a,~-monoethylenically unsaturated
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mono- or di-carboxylic acids and 90 to 99.5 parts by weight of a mixture of
10 to 90 parts by weight of one or more acyclic conjugated dienes containing
from 4 to 9 carbon atoms and 10 to 90 parts by weight of one or more aryl vinyl
monomers containing from 8 to 12 carbon atoms and/or (meth)acrylonitrile, the
quantity of (meth)acrylonitrile amounting to at most 50 parts by weight, basod
on the monomer total, wherein up to 25 parts by weight of the acyclic conjugated
dienes, aryl vinyl monomers and/or (meth)acrylonitrile may be replaced by acyclic
and/or methacrylic acid esters, diesters of ~,~-monoethylenically unsaturated
monocarboxylic acids, amides of ~,~-monoethylenically unsaturated mono- and di-
carboxylic acids, vinyl esters of carboxylic acids, vinyl chloride, vinylidenechloride, vinyl ethers, vinyl ketones or heterocyclic monovinyl compounds, the
polymerisation being carried ou~ in aqueous phase in the presence of from 0 to
0.5 parts by weight, based on the monomer total, of one or more water-soluble
emulsifiers of the sulphate and/or sulphonate type, characterised in that poly-
merisation is carried out at a temperature above 50C using a peroxodisulphate
as initiator and in the presence of a mercaptocarboxylic acid corresponding to
the formula:
~5 - ~CH2) X - C02H
in which
x is an integer of from 1 to 5, and /or water-soluble salts thereof.
Suitable mercaptocarboxylic acids are, for example, ~-mercaptoprop-
ionic acid and, preferably, thioglycolic acid. They are used in a quantity of
from 0.01 to 1.0 part by weight, based on the total quantity of monomers.
The peroxodisulphate employed as initiator in the process according
to the invention is used in a total quantity of from 0.5 to 3.0 parts by weight,
based on the total quantity of monomers. Suitable initiators are salts of per-
oxodisulphuric acid, such as sodium, potassium or, preferably, ammonium
~,,
~L~3~7'~
peroxodisulphate. The initiators may optionally be used in combination with
reducing agents such as, for example, sulphur dioxide7 alkali metal disulphites
and alkali metal and ammonium hydrogen sulphites.
Suitable acyclic conjugated dienes containing from 4 to 9 carbon
atoms are, for example, l,3-butadiene,
-7a-
~3~7;~
- 8 -
2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-
butadiene, piperylene, 2-neopentyl-1,3-butadiene and
other substituted dienes, such as ior example 2
chloro-1,3-butadiene (chloroprene), 2-cyano-1,3-buta-
S diene, and also substituted straight-chain conjugated
pentadienes and straight-chain or branched hexadienes.
Its ability to polymerise particularly effectively with
aryl vinyl monomers and (meth)acrylonitrile makes 1,3-
butadiene the pre~erred monomer.
Suitable aryl vinyl monomers are those in which
the vinyl group, which is optionally alkyl-substituted
in the a-position~ is directly attached to an aromatic
nucleus consisting o~ 6 to 10 carbon atoms. Examples of
aryl vinyl monomers such as these are styrene and
substituted styrenes~ such as 4-methyl styrene, 3-methyl
styrene, 2,4-dimethyl styrene, 2,4-diethyl styrene, 4-
isopropyl styrene, 4-chlorostyrene, 2,4-dichlorostyrene,
divinyl benzene, -methyl styrene and vinyl naphthalene.
By virtue of its accessibility and its ability to copoly-
; 20 merise effectively, particularly with 1,3-butadiene,
styrene reprasents the pre~erred monomer.
Suitable a~-monoethylenically unsaturated mono-
and di-carbo~ylic acids are, ~or example, acrylic acid,
methacrylic acid, itaconic acid, ~umaric acid and maleic
acid and also the monoesters of the above-mentioned
dicarboxylic acids such as, for example, mcnoalkyl ita-
conate, ~umarate and maleate.
Up to 25 parts by weight o~ the non-dissociating
monomers may be replaced by one or more monomers copoly-
0 merisable with the above mentioned monomers. Copolymerisablemonomers such as these are acrylic and/or methacrylic
acid esters o~ alcohols containing up to 8 carbon atoms
and also diesters o-~ alkane diols and ~ monoethylen-
ically unsatura-ted monocarboxylic acids, such as ethylene
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_ 9 _
glycol diacrylate and 1,4-butane diol diacrylate, amides
o~ a, ~-monoethylenically unsaturated mono- and di-
carbo~ylic acids, such as acrylamide and methacrylamide
and their N-methylol derivatives, and also N-alko~y-
methyl and N-a~yl- (meth)acrylamides containing ~rom 1
to 4 carbon atoms in the alkoxy group, for example N-
methylol(meth)acrylamide, N-methoxymethyl-(meth)-
acrylamide, N-n-butoxymethyl-(meth)acrylamide and N-
acetoxymethyl-(meth)acrylamide. Other suitable
comonomers are vinyl esters of carbo~ylic acids contain-
ing from 1 to 18 carbon atoms t particularly vinyl acetate
and vinyl propionate, vinyl chloride and vinylidene
chloride, ~inyl ethers, such as vinyl methyl ether, vinyl
ketones, such as vinyl ethyl ketone, and heterocyclic
monovinyl compounds, such as vinyl pyridine.
~ he process according to the invention is carried
out at temperatures above 50C antl at pH-values o-~ from
2 to 7, because it is only at low pH-values that the
ethylenically unsaturated carboxylic acids are partially
dissolved in the water-insoluble monomers. At p~-
values such as these, suitable optional emulsifiers are
those derived ~rom highly dissociating acids, particularly
emulsi~iers o~ the sulphate and sulphonate type. ~ypical
representatives are higher fatty alcohol sulphates, higher
alkyl sulphonates and alkylaryl sulphonates and also their
condensation products with formaldehyde, higher hydroxy-
alkyl sulphonates, salts of sulphosuccinic acid esters
and sulphatea ethylene oxide adducts. In general, the
emulsi~iers are used in a quantity of no more than 0.5 /0
by weight, based on the monomer total.
The emulsion polymerisation reaction may optionally
be carried out in the presence of polymerisation aids,
such as bu~ers, chelating agents and accelerators.
Chain-trans~er agents such as, for example, tetrabromo-
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methane, bromoethyl benzene, alcohols, higher alkylmeroaptans and dialkyl di~anthogenates may also be
present during the pol~merisation reaction. The type
and quantity used is dependent inter alia upon the
effectiveness of the compounds and upon the quantity of
diene used and may readily be determined by the expert.
On completion of polymerisation, the late~ may be
~reed -from residual ~onomers in known manner, optionally
at a pH-value of from 6 to 8, and may be adjusted to a
pE-value of from about 8 to 10 in order to increase its
mechanical stability.
The dispersions obtained by the process according
to the invention have a surface tension of from 45 to 70
mN/m and preferably from 50 to 60 mN/m at pH-values
above 6Ø ~heir solids content may lie between 1 and
65 /0 by weight and preferably amounts to between 30 and
50 /0 by weigh$. The latices, which are substantially
or completely free from coagulate and specks, are
suitable inter alia for bonding non-woven fabrics, for
impregnating and coating textile materials and paper,
and for the production of aqueous paint binder formulatious.
The process according to the invention is illustrated
by the ~ollowing Examples.
E~PLE 1
133500 g o~ water and 1900 g of styrene are
introduced into a 40 litre stainless steel autoclave
equipped with a crossed arms paddle stirrer, a~ter which
the autoclave is evacuated and purged with nitrogen.
3000 g of 1,3-butadiene are then introduced under pressure
and the contents of the autocla~e are heated to 80C.
After this temperature has been reached, 111 g of 90 c/O
methacrylic acid ip 250 g of water and 120 g of ammonium
peroxodisulphate and 30 ml o~ a 25 % aqueous ammonia
solution in 500 g of water are introduced under pressure,
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11
and the miYture is polymerised at 80C until, after
about 3.5 hours, a solids concentration of 17 /0 by weight
is reached. A mixture of 3000 g of 1,3-butadiene, 1900 g
of styrene, 111 g of 90 % methacrylic acid and 20 g of
tert.-dodecyl mercaptan is then added, after which
another 50 g of ammonium peroxodisulphate and 40 ml of
25 % aqueous ammonia solution in 500 g o~ water are
; added to the emulsion. After 25 hours, a solids con-
centration of 40.1 /0 by weight is reached and polymerisation
is stopped by the addition o~ 280 g of a 7 /0 diethyl
hydroxylamine solution.
180 g of separated material (weighed moist) and
specks are formed during the polymerisation reaction.
The latex is substantially neutralised with dilute
aqueous ammonia 901ution, freed ~rom residual monomers
and adjusted to p~ 9.2 with dilute aqueous ammonia
solution. Thereafter, the solids content amounts to
37.7 % by weight and the surface tension to 45.2 mN~m.
E~A~PLE 2
13,500 g of water and 1900 ~ of styrene are
introduced into a 40 litre stainless steel autoclave
equipped with a crossed-arms paddle stirrer, after which
the autoclave is evacuated and purged with nitrogen.
3000 g of 1,3-butadiene are then introduced under pressure.
The contents of the autoclave are heated to 80C, followed
by the introduetion under pressure of 111 g of 90 /0
methacrylic acid in 200 g of water, 120 g of ammonium
peroxodisulphate and 30 ml of a 25 ~0 aqueous ammonia
solution in 500 g of water. After a polymerisation
3o time of 5 hours, the solids concentration amounts to
19 /0 by weight~ A mixture of 3000 g of 1,3-butadiene,
1900 g of styrene and 20 g of tert.-dodecyl mercaptan
;~ is then added. A solution of 50 g of ammonium peroxo-
disulphate and 100 ml o~ a 25 /0 aqueous ammonia solution
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in 300 g of water and a solution o~ 111 g o~ 90 ~0 meth-
acrylic acid and 20 g of thioglycolic acid in 200 g of
wa-ter are than introduced under pressure into the
autoclave. A~ter 30 hours, the solids concentration
amounts to 39.2 ~0 by weight. Polymerisation is then
stopped by the addition of 280 g oi a 7 % diethyl
hydro~ylamine solution. The coagulate content amounts
to 123 g (weighed moist), although the dispersion is
completely speck free. A$ter it has been ~reed from
residual monomers, the latex is adjus-ted to pH 9.2 with
dilute aqueous ammonia solution. Its solid content
amounts to 37.6 Q~O by weight and its sur~ace tension to
49.3 mN/m.
EXAMPLE 3
The procedure i9 as described in Example 2, except
that no tert.-dodecyl mercaptan i9 added. In this
way, the polymeris~tion time (until a solids concentration
of 37.5 ~O by weight is reached) is shortened to 11 hours.
After polymerisation has been stopped and the mixture
worked up in the same way as in E~ample 2, a completely
speck-~ree latex is again obtained. Its coagulate content
amounts to 100 g (weighed moist). The pH is adjusted to
9.0 by the addition of an aqueous ammonia solution. The
latex has a solids content of 37.1 ~0 -by weight and a
sur~ace tension o~ 53.3 mN/m.
The results of E~amples 1 to 3 are summarised in
the following Table.
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Table
E~ample ExampleExample
1 2 3
tert.-dodecyl mercaptan
5 ~% by weight] 0.2 0.2
thioglycolic acid
[/0 by weight~ ~ 0.2 0.2
polymerisation time [h~
solids 28.5 35 11
10 concentration [/0 by
weight] 37.7 37.6 37.1
pH-value 9.Z 9.2 9.0
surPace tension [mN/m] 45.2 49.3 53.3
pecks yes no no
E~AMPLE 4
A mi~ture oP 12,500 g oP water, 1000 g of styrene
and 900 g of acrylonitrile is introduced into a 40 litre
stainless steel autoclave equipped with a crossed-arms
paddle stirrer. After evacuatio~ and purging with
nitroge~, 3000 g oP 1,3-butadiene are intro~uced under
pressure and the content~ of the autoclave are heated to
75C. A solution oP 111 g oP 90 /0 methacrylic acid in
250 g oP water and a solution oP 50 g oP ammonium peroxo-
disulphate and 30 ml oP a 25 /0 aqueous ammonia solution
in 300 g oP water are then introduced under pressure.
A~ter polymerisation Por 5 hours at 75C, $he solids
concentration amounts to 23 % by weight. A mixture oP
3000 g oP 1,3-butadiene, 1000 g o~ styrene, 900 g o~
acrylonitrile and 10 g of tert.-dodecyl mercaptan, a
solution o~ 100 g o~ methacrylamide in 400 g oi water
and a solution oP 100 g oP ammonium peroxodisulphate
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14 -
and 30 ml of a 25 % aqueous ammonia solution in 300 g
of water are then added. After polymerisation for another
9 hours (second polymerisation phase) 9 the solids content
amounts to 41.0 /0 by weight. The poly~erisation reaction
is then stopped by the addition of 280 g of 7 /0 diethyl
hydroxylamine solution. After it has been ~reed ~rom
residual monomers, the latex is adjusted to pH 7.6 with
dilute aqueous ammonia solution. For a solids concentration
of 40.3 /0 by weight, the dispersion has a coagulate
content o~ 320 g (weighed moist) and is full o~ specks.
Its sur$ace tension amounts to 51.9 mN/m~
EXAMPLE 5
The procedure is as described in E~ample 4, e~cept
that, before the second polymerisation phase, lO g o~
thioglycolic acid and lO ml of a 25 % aqueous ammonia
solution are additionally introduced. Polymerisation is
stopped in the same way as in E~ample 4, and, a~ter it
has been freed from residual monomers, the late~ is
adjusted to a pH-value of 7.5 with dilute aqueous
ammonia solution. Its coagulate content amounts to 200 g
(weighed moist), although it contains considerably ~ewer
specks than the late~ of Example 4. The surface tension
amounts to 52.9 mN/mO
EXAMPLE 6
129 500 g o~ water, lO00 g of acrylonitrile and lO g
of tert.-dodecyl mercaptan are introduced into a 40
litre s~ainless-steel autoclave equipped with a crossed-
arms paddle stirrer. Aiter evacuation and purging with
nitrogen3 2200 g o~ 1,3-butadiene are introduced under
pressure and the contents o~ the autoclave are heated to
75C. A solution of 222 g o~ 90 /0 m0thacrylic acid in
500 g of water, 50 g o~ ammoni~um peroYodisulphate and
30 ml oi a 25 /0 aqueous ammonia solution in 500 g o~
water are then added in rapid succession. After poly-
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~3~67~
merisation for 5 hours, the solids content amounts to15 % by weight. A mixture of 200 g of l,3-butadiene3
1100 g of acrylonitrile, 25 g of tert.-dodecyl mercaptan
and 2.5 g of thioglycolic acid i9 then introduced under
pressure, followed by the addition of a solution of 50 g
of ammonium pero~odisulphate and 15 ml of a 25 % aqueous
ammonia solution in 250 g of water. After another 3
hours, the solids concentration amounts to 30 % by
weight. A mixture of 2200 g of 1,3-butadiene, 1000 g
of acrylonitrile, 100 g of N-methogymethyl methacrylamide7
25 g of tert.-dodecyl mercaptan and 2.5 g of thioglycolic
acid is then introduced under pressure, followed by the
addition of another solution of 50 g of ammonium peroxo~
disulphate and 15 ml of 25 % aqueous ammonia solution in
250 g of water. After 5.5 hours, a final solids concen-
tration of 40.5 /0 by weight is reached by reacti~ation
with a solution of 20 g of ammOnium pero~odisulphate in
100 g of water at a solids oontent of around 38 /0 by
weight. ~his procedure gives a latex which is free both
from coagulate and from specks. ~fter polymerisation
has been stopped in the same way as in Example 4, the
dispersion is freed from residual monomers and the pH
is adjusted to 9.0 by the addition of dilute aqueous
ammonia ~olution. The dispersion has a solids content
of 40.7 /0 by weight and a surface tension of 55.3 mN/m.
15 g of sodium paraffin sulphonate, with an average
of 15 carbon atoms in the alkyl residue, in 8250 g of
water are introduced into a 40 litre stainless steel
autoclave equipped with a crossed-arm paddle stirrer.
After evacuation and purging with nitrogen, 10 parts by
weight of a mi~ture (1) of 9000 g of styrene, 5550 g of
1,3-butadiene, 500 g of 90 /0 methacrylic acid, 60 g of
thioglycolic acid and 15 g of tert.-dodecyl mercaptan
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are introduced under pressure, the contents of the
autoclave are heated to 80C and the polymerisation
reaction is started by the addition of a solution of
15 g of ammonium pero~odisulphate and 30 ml of a 25 %
aqueous a~monia solution in 450 g of water. The rest
of mixture (1) and a mixture (2) of 225 g of ammonium
peroxoaîsulphate, 45 g of sodium paraffin sulphonate
and 165 ml of a 25 % aqueous ammonia solution in 6000 g
of water are then uniformly run in at the same time over
a period of 8 hours. On completion oY the addition, the
mixture is stirred for 4 to 5 hours at 80C, after which
the polymerisation reaction is stopped at a solids content
of 45.8 /0 by weight by the addition of 320 g of 7 /0 diethyl
hydroxylamine solution. After residual monomers have
been removed, a substantially speck-free latex i~ obtained
which can easily be freed from the minimal coagulate
; formed. ~his latex has a pH-value of 6.o and a surface
tension of 49.1 mN/m.
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