Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The inver.tion relates to an aqueous solution or dis-
persion of a styrene/maleic anhydride copolymer and a
process for the prep~ration thereof.
Preparation of copGlymers of maleic anhydride ~ith
vinyl compounds such as styrene is known for a long time
(see for example Ind.Eng.Chem. 41 (1949), p. 1509). These
copolymers are dissolved in water with addition of alkali,
because their action as pigment dispersing agent, protec-
tive colloid, thickener or sizing agent requires salt ~or-
mation.
Furthermore, there are described copolymers of s~yrene
and maleic anhydride having a molar ratio of styrene to
maleic anhydride of from 1:1 to 4:1. an average molecular
weight of from 400 to 100,000, and a melting point of from
80 to 300C (see for example U.S. Patent No. 3,444,151).
These copolymers are reacted with amines to yield nitrogen-
containing copolymers being nearly insoluble in water or
aqueous alkaline media; they are used as emulsifiers in the
emulsion po'ymerization of vinyl monomers.
It is also disclosed to use styrene/maleic anhydride
copolymers having a molar ratio of styrene to maleic anhy
dride of from 1:1 to 3:1 and a molecular weight of from
1,600 to 50,000 for the manufacture of adhesives on the ba-
sis of starch (see U.S. Patent ~lo. 3,939,108). These copo-
lymers are normally manufactured by solution polymerization
in an aromatic hydrocarbon, in the presence of a free radi-
cal-forming agent as catalyst, at a temperature of from 75
to 300C. After addition of ammonia or alkali metal hy-
droxide until a pH of 8 to 11 is adjusted, they can be
dissolved in water under heat.
It is the object of the invention to provide an aque-
ous solution or dispersion of a maleic anhydride copolymer
which solution or dispersîon does not have an alkaline
reaction and i3 suitable as emulsifier solution or emulsi-
fier dispersion for plastics dispersions.
lhe inveIItioil relates to an aqueous solution or dis-
persion of a hydrolyzed copolymer of styrene and maleic
5~
anhydride wherein the molar ratio of styrene to maleic anhydride is in the range
of from 1.5:1 to 6:1~ the molecular weight (number average) is from 500 to
80,000, 1 to 60 percent of the carboxyl groups of the copolymer are neutralized,
and the pH of the solution or dispersion is below 7.
The invention relates furthermore to a process for the preparation
of an aqueous solution or dispersion of a hydrolyzed copolymer of styrene and
maleic anhydride by hydrolysis of a styrene/maleic anhydride copolymer and
partial neutralization with an inorganic neutralizing agent, which comprises
heating a copolymer having a molar ratio of styrene to maleic anhydride of
from 1.5:1 to 6:1 and a molecular weight (number average) of from 500 to
80,000 to a temperature of from 75 to 250C in the presence of water and in the
presence of an amolmt of ammonia, an alkali metal hydroxide or alkaline earth
metal hydroxide, or zinc oxide that is sufficient to neutralize 1 to 60
percent of the carboxyl groups of the copolymer.
Moreover, the invention provides the use of the cited solution or
dispersion as stabilizer solution or dispersion for aqueous dispersions, and for
the dispersion polymerization of vinyl compounds.
The styrene/maleic anhydride copolymer used in accordance with the
invention has a molecular weight (number average) of from 500 to 80,000
preferably ~00 to 30,000. The molar ratio of styrene to maleic anhydride is
from 1.5:1 to 6:1, preferably 1.6:1 to 4:1.
In accordance with the invention, the styrene/maleic anhydride
copolymer is heated to a temperature of from 75 to 250 C, preferably 85 to 180 C,
in the presence of water and of an inorganic neutralizing agent, and
hydrolyzed. The free carboxyl groups of the copolymer so formed are thus
neutralized in a percentage of from 1 to 60, preferably 6 to 50, %.
_3_
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In this alkaline treatment of the copolymer, its concentra-
tion is from 5 to 50, preferably 10 to 30, ~ by weight (re-
lative to the total amount of water and copolymer). Depend-
ing on the concentration and composition of the copolymer
and the temperature chosen, this treatment takes from 5 mi
nu~es to 5 hours, preferably 10 to 200 minutes. Large sty-
rene amounts in the copolymer, high copolymer concentra-
tion and low treating temperature require generally a pro-
longed treatment time; that is, the treatment time can be
influenced by varying the above parameters. It is recom-
mended to operate under inert gas, for example nitrogen.
The styrene/maleic anhydride copolymer may contail1
additionally one or more further comonomers in an amGunt
of up to 20 mol % (relative to the total monomer amount),
incorporated by polymerization. Suitable are olefinically
unsaturated compounds such as vinyl es~ers, vinyl ethers,
acrylic esters, or unsaturated carboxylic acids such as
acrylic, methacrylic, itaconic, crotonic, vinylsulfonic or
N-rnethacryloyl-aminopropanesulfonic acid.
As inorganic neutralizing agent, there may be used
ammonium hydroY~ide or an alkali metal hydroxide such as
lithium hydroxide, sodium hydroxide or potassium hydroxide,
or an alkaline earth metal hydroxide such as magnesium hy-
droxide or calcium hydroxide, and furthermore zinc oxide.
Instead of one of these agents, a mixture of several of
them may be employed alternatively. The arnount has to be
chosen in such a manner that the intended neutralization
degree is attained; it is in the range of from 0.02 to
1.2, preferably 0.12 to 1, base equivalent (relative to 1
mol of maleic anhydride in the copolymer). Depending on
the kind and amount of neutralizing agent, a copolymer
solution or dispersion is obtained; for the preparation of
a solutioll, a larger amount of neutralizing agent is used
than for the preparation of a dispersion.
For preparing an acidic solution of a hydrolyzed sty-
rene/maleic anhydride copolymer it is recommended to carry
out the alkaline treatme!lt in the presence of an emulsi
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fier, preferably an aniorlic emulsifier. Suitable emulsi-
fiers are especially alkali metal salts or ammonium salts
of alkylsulfonic, arylsulfonic or alkylarylsulfonic acids
or the corresponding sulfuric, phosphoric or phosphonic
acids, the cited compounds possibly containing ethylene
oxide units between the hydrocarbon radical in question
(having preferably from 10 to 18 carbon atoms) and the an-
ionic group, the oxethylated compounds contain preferably
from 5 to 30 ethylene oxide units. Examples of suitable
emulsifiers are sodium laurylsulfate, sodium octylphenol-
glycol ether sulfate, sodium dodecylbenzene sulfonate,
sodium lauryldiglycol sulfate, and the ammonium salts of
oxethylated and sulfated tri-t.-butylphenol, t.-butylphenol
and nonylphenol.
The emulsifier is used in an amount of from 3 to 100,
preferably 5 to ~5, % by weight (relative to the styrene/
maleic anhydride copolymer).
The copolymer dispersion may be converted to a solu-
tion by heating it to a temperature within the abovemen-
tioned range of treatment temperature after having addedan emulsifier of the cited kind.
The aqueous solution or dispersion of a hydrolyzed co-
polymer of styrene and maleic anhydride according to the
invention has an acidic reaction. Its pH is below 7, pre-
ferably below 6; especially advantageous is a solution ordispersion having a pH of from 2.0 to 5.7. The copolymer
content of the solution or dispersion is in the range of
from 5 to 50, preferably 10 to 30, % by weight, and its
viscosity is from 20 to 20,000, preferably 50 to 3,000 mPa.s
(measured according to Epprecht).
The copolymer solution or dispersion of the invention
is applied as emulsifying, dispersing, sizing, gluing,
thickening, flocculating or hydrophobizing agent, and as
coating or binder in the fields of textile, paint and
varnish, adhesives and paper manufacture. The dissolved
or disperseà copolymer is fixed to materials such as
wood, paper, ceramics, metals or plasti.cs by applying the
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6 - HOE 79/F 253
solution or dispersion thereto and removing the water, o,
by electrochemical deposition.
The solution or dispersion is excellently suitable
for stabilizing aqueous dispersions of natural or synthe-
tie, i.norganie or organie substances, for example cellu-
lose, plasties, pigments or fi.llers. It is furthermore
a~pplied for the suspension or emulsion polymerization of
vinyl compounds, especially vinyl esters and aerylic esters.
The plastics dispersions so stabiliæed have an inereased
stability to shearing forces and pigments. The moment of
adding the stabilizer solution or dispersion is irrelevant;
it may be added with similar results during or after the
preparation of the dispersion to be stabilized.
The eopolymer solution or dispersion of the invention
is applied above all in the polymerization of vinyl com-
poutlds in an aqueous medium under aeidie eondition3. Espe-
eially suitable monomers are olefinieally unsaturated com-
pounds of the formula
H2C = C - R1
R2
in whieh R1 is a hydrogen atom or a methyl radical, and
R2 is
a) an alkylcarboxyl radical having from 2 to 1~, preferably
2 to 12, carbon atoms,
b) an alkoxy radical having from 1 to 4 earbon atoms,
e) a nitrile group,
d) a halogen atom, preferably chlorine,
e) a carboxyl or sulfo group,
~) an alkoxyearbonyl radieal having from 2 to 12, prefer-
ably 2 to 9, carbon atoms,
g) an aminocarbonyl radical,
h) a hydrogen atom,
i~ a phenyl radical, or
k) a vinyl radleal.
B~.
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E~amples of such olefinically unsaturated compounds are
a) vinyl esters of aliphatic carboxylic acids having ~rom
2 to 18, preferably 2 to 12, carbon atoms, such as vinyl
acetate, vinyl propionate, vinyl butyrate, vinyl piva-
late, vinyl isononate, vinyl laurate or vinyl decanates,furthermore vinyl esters of a mixture of monocarboxylic
acids having from 9 to 11 carbon atoms;
b) vinyl ethers, such as vinylmethyl ether, vinylethyl
ether or vinyl-n-butyl ether;
c) acrylonitrile or methacrylonitrile;
d) vinyl halides, such as vinyl chloride or allyl chloride;
e) unsaturated monocarbGxylic acids such as acrylic, meth-
acrylic or vinylsulfonic acid;
f) acrylic esters or methacrylic esters of monohydric alka-
nols having from 1 to 11, prefrably 1 to 8, carbon atoms,
such as ~ethyl acrylate, ethyl acrylate, butyl acrylate,
2-ethylhexyl acrylate, methylmethacrylate, ethylmeth-
acrylate, butylmethacrylate, hexylmethacrylate, octyl-
methacrylate or 2-ethylhexylmethacrylate;
g) acrylic or methacrylic acid amides such as acrylic, N
methylolacrylic, methacrylic or N-methylolmethacrylic
acid amide;
h) ethyletle;
i) styrene or methylstyrene; or
k) butadiene or isoprene.
Especially suitable monomers are the vinyl esters a),
the vinyl ethers b), the vinyl halides d) and the acrylic
and methacrylic esters f). ~he monomers are used per se
or as mixtures with one another; monomer combinations are
for e~ample obtained from an acrylic ester and a methacry-
lic ester, an acrylic or methacrylic ester and a vinyl
ester, a mixture of different vinyl esters, especially
vinyl acetate and vinyl esters of a mixture of monocarboxy-
lic acids having from 9 to t1 carbon atoms, furthermore
from vinyl acetate and ethylene, or from vinyl acetate,
ethylene and vinyl chloride.
The polymerization is usually carried out in the pre.-
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sence of a free radical-forming initiator, prefer~bly a
peroxide compound or an aliphatic azo compoundO The ini~
tiator is oil-soluble or, preferably, water-soluble, and
used in an amount of from 0.05 to 2, prefer~bly 0.1 to
1, % by weight (relative to the total amount Or monomers).
Suitable are especially hydrogen peroxide, alkali metal or
ammonium salts of persulfuric, peroxydisulfuric or peroxy-
diphosphoria acid, for example sodium persulfate, potassium
peroxydisulfate or ammonium peroxydisulfate; furthermore
alkylhydroperoxides such as t.-butyl hydroperoxide; dialkyl
peroxides such as di-t.-butyl peroxide; diacyl peroxides
such as diacetyl peroxide, dilauroyl peroxide or dibenzoyl
peroxide; furthermore azo-di-isobutyric acid nitrile, azo-
dicarbonamide or azo-~ ~ bis(4~cyanovaleric acid). The
initiator i5 optionally used in combination with a reducing
agent, especially an ammonium salt, alkali metal salt or
alkaline earth metal salt of a sulfur-containing acid hav-
i.ng a reducing action; suitable are preferably sulfites,
~isulfites, pyrosulfites, dithionites, thiosulfates or
formaldehyde sulfoxylates. The amount of reducing agent
is from 0.05 to 20, preferably 0.5 to 10, % by weight
(relative to the styrene/maleic anhydride copolymer).
For increasing the polymerization speed, it is advan-
tageous to use a solution or dispersion of a hydrolyzed
styrene/maleic anhydride copolymer which has been prepared
in the presence of a sulfite. Suitable sulfites are neu-
tral or acidic salts of sulfurous or pyrosulfurous acid,
especially ammonium t alkali metal or alkaline earth metal
salts, and the amounts to be used are from 0.05 to 20, pre-
ferably 0.5 to 10, ~ by weight (relative to the styrene/ma-
leic anhydride copolymers).
In emulsion polymerization, the solution or dispersion
of the hydrolyzed styrene/maleic anhydride copolymer is
used in such an amount that the copolymer is present in a
~uantity`of from 0.1 to 10, preferably 0.5 to 5, ~ by weight
~relative to the total amount of monomers). In suspension
polymerization, from 0.01 to 2 and preferably 0.05 to 1, ~
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by weight ~relative to the total amoutlt of monomers) are
sufricie!lt. Polymerization is carried out at a tempera-
ture of from 25 to 90C, preferably 40 to 75C. Depending
on the kind and amount of the monomers in question the po-
lymerization time is in the range of from 2 to 8, p~efer-
ably 2.5 to 5, hours.
The resulting polymer dispersions are excellently
stable to shearing forces and have a very good pigment-
birding capacity. Therefore, they are applied above all as
binder dispersions in paints, especially dispersion paints,
and paper coating compositions. The paper so coated is
distinguished by high wet pick resistance and water re-
sistence of crating (determined be measuring the wet rub
in a so called Taber-Abraser).
The following examples illustrate the invention, the
percentages beillg by ~leight in all cases.
X _ M P L E 1:
In a vessel provided with agitator and reflux conden-
ser, 150 g of a copolymer of styrene and maleic anhydride(molar ratio 2:1) having an average molecular weight of
1,700 are heated for 2 hours at a temperature of 95 -
100C together with 790 g of water and 7.05 g of caustic
soda, and then cooled to room temperature. A clear solu-
tion having a pH of 4.7 and a polymer content of 16.5 p isobtained. lhe carboxyl groups of the hydrolyzed copolymer
are neutraliæed to an extent of 18 ~.
E X A M P L E` 2;
___
30 a) Example 1 is repeated; ho~ever, instea~ of 7.05 g
of caustic soda, 3.52 g only are used and the water
amount is 720 g instead of 790 g. Moreover, the reac-
tion mixture is filtered after cooling to room tempera-
ture, thus obtaining a residue of 30.9 g (after drying).
hs filtrate, a dispersion having a pH of 4.1 and a poly-
mer content of 14.9 % is obtained.
b) 8 g of the dispersion obtained according to a) are
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heated to 70C toge'her with 2 g of a 15 ~ aqueous solu-
tion of sodium laurylsulfate, thus causing the copolymer
to be dissolved.
c) 8 g of the dispersion obtained according to a) are
heated to 80C together with 2 g of a l5 ~ aqueous solu-
tion of the ammonium salt of a nony'phenol oxethylated
with 25 mol of ethylene oxide and then sulfated as emul-
sifier, thus dissolvlng the copolymer.
10 E X A M P L E 3:
In a vessel provided with agitator and reflux conden-
ser, 300 g of a copolymer of styrene and maleic anhydride
(molar ratio 3:1) having an average mo1ecular weight of
1,900 are heated for 2 hours at a temperature of 96C to-
gether with 1,680 g of water and 29.3 g of caustic soda,and then cooled to room temperature. A solution having a
pH of 6.8 and a polymer content of 16.7 % is obtained. 50 %
of the carboxyl groups of the hydrolyzed copolymer are neu-
tralized.
E X A M P L E 4:
In a vessel provided with agitator and reflux conden-
ser, 150 g of a copolymer of styrene and maleic anhydride
(molar ratio 3:1) having an average molecular weight of
1,900 are heated for 2 hours at a temperature of 100C to-
gether with 790 g of water and 25 g of a 25 % aqueous ammo-
nia solution, and then cooled to room temperature. A solu-
tion having a pH of 6.8 and a polymer content of 16.1 ~ is
obtained. 50 ~ of the carboxyl groups of the hydrolyzed
copolymer are neutralized.
E X A M P L E 5:
a) In a vessel provided with agitator and reflux con-
denser, 150 ~ of a copolymer of styrene and maleic an~
hydride (molar ratio 3:1) havirg an average molecular
weight of 1,900 are heated f`or 3 hours at a temperature
of 97C toget'ner with 720 g of water and 7.3 g of caustic
~ HOE 79/F 253
soda, and then cooled to room temperature. A dispersion
having a pH of 5.6 and a polymer content of 17.6 ~ i9
obtained. 25 % of the carboxyl grcups of the hydrolyzed
copolymers are neutralized. The mean diameter of the
dispersed polymer particles is 0.038 /um.
b) 8 g of the dispersion obtained according to a) are
heated to 85C together with 2 g of a 15 % aqueous solu-
tion of sodium laurylsulfate, thus dissolving the copo-
lymer.
c) 8 g of the dispersion obtained according to a) are
heated to 90C together with 2 g of the 15 % aqueous so-
lution of the emulsifier of Example 2c), thus dissolving
the copolymer.
~5 E X A M P L_E S 6 to 8:
In a vessel provided with agitator and reflux conden-
ser, 150 g each of a copolymer of styrene and maleic anhy-
dride (molar ratio 3:1) having an average molecular weight
of 1,900 are heated for varying periods of time to a tem-
perature of 97C together with 720 g each of water anddifferent amounts of lithium hydroxide, and then cooled to
room temperature. Details and properties of the solution
or dispersion in question are listed in Table 1.
Table 1
Example 6 7 8
amount LiOH (g) 4.4 3.3 2.2
time of treatment (h) 2 2 3
result solution dispersion dispersion
pH 5.3 5.1 11.7
polyrner content (%) 17.6 17.3 16.9
neutralized 25 18.7 12.5
carboxyl groups (%)
__
~ 12 - 0 _79/~ 253
E X A ~5 P L E J-
In a vessel provided with agitator anà reflux conden~
ser, 150 g of a copolymer of styrene and maleic anhydride
(molar ratio 3:1) having an average molecular weight of
1,900 are heated under a nitrogen blanket for 2 hours at a
temperature of 96C iogether with 1,300 g of water~ 7.3 g
of caustic soda, ,25 g of a 30 ~ solution of the emulsifier
of Example 2c) and 12 g of sodium pyrosulfite, and then
oooled to room temperatur~. A solution having a pH of 5.3
and a polymer content of 13.3 % is obtained. 25 % of the
carboxyl groups of the hydrolyzed copolymer are neutralized.
The solution is adjusted with water to a concentration
of 7.8 ~, for application in the polymerization of viny1
acetate.
E X A M P L E 10:
In a vessel provided with agitator and reflux conden-
ser, 150 g of a copolymer of styrene and maleic anhydride
(molar ratio 2:1) having an average molecular weight of
1,700 are heated for 2 hours under a nitrogen blanket to a
temperature of 96C together with 1,300 g of water, 7.3 g
of caustic soda, 12~ g of a 30 ~ aqueous solution of the
emulsifier of Example 2c) and 12 ~ of sodium pyrosulfite,
and then cooled to room temperature. A solution having a
pH of 4.3 and a polymer content of 13 % is obtained. 18.6 ~
of the car~oxyl groups of the hydrolyzed copolymer are neu-
tralized.
The solution is adiusted with water to a concentration
o~ 7.8 % for use in the polymerization of vinyl acetate.
3o
EXAMPLE OF APPLICATION 1:
510 g ¢f water, 1.77 g of a 6 % aqueous sodiu~ alkyl-
sulfonate solution (mean chain leng~h of the alkyl group:
12 to 14 carbon atoms), and 2 g of a 30 % aqueous solution
of the ammonium salt of nonylphenol oxethylated with 25 mols
of ethylene oxide and then sulfatQd are intr-oduced into a
vessel provlded with agitator t and then flushed with nitro~-
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gen. After having added a solution of 2.25 g of ammoniurn
persulfate in 20 g of water, the mixture is heated to a
tem~erature of 50C. While rnaintaining this temperature,
750 g of vinyl acetate and a solution of 0.39 g of sodium
formaldehyde-sulfoxylate in 50 g of water are added sepa-
rately and uniformly within 3 hours to the mixture. With-
in the 1st hourj the same amount of the emulsifier combi-
nation is added again to t,he batch; withln the following 2
hours, 100 g of the copolymer solution obtained according
to Example 9 and 1.87 g of the above alkylsulfonate solu-
tion and 21.2 g of the above 30 % ammonium sa;t solution
are added in corresponding doses. Subsequently 9 a solution
of 0.75 g of ammonium persulfate in 30 g of water is added
to the mixture, and the batch is heated for 30 minutes to
75C and then cooled to room temperature.
A coagulate-free polyvinyl acetate dispersion is ob-
tailled whicn is adjusted to pH 6 with 3.2 g of 12.5 %
ammonia solution. The solids content of the dispersion is
50.8 ~, and the polymer particles have a mean diameter of
0.22 /um. The dispersion is stable to shearing;after a 2
minutes' agitation by means of a high-speed agitator (5000
rpm) no coagulate formation can be observed, and the mean
particle size of the polymer has not changed.
EXAMPLE OF APPLICATION 2:
Example of application 1 is repeated; however, the co-
pol.ymer solution of Example 10 is used instead of that of
Example 9. The polyvinyl acetate dispersion obtained is
coagulate-free. The solids content of the dispersion is
50.~ ~, and the polymer particles have a mean diameter of
0.18 /um. The dispersion is stable to shearing (test ac-
cording to Example of application 1).
0MPARATIVE EXAMPI,E 1:
1,620 g oF the styrene/maleic anhydride copolymer used
in Example 3 are a~itated for 6 hours 3/4 at a temperature
of ~0C in 8,024 g of water with addition of 316 g of
14 - _OE ~9/F 253
caustic soda. Tne suspension obtained after coolinx to
room temperature is filtered, thus obtaining a solid resi-
due of 47 g. The filtrate has a pH of 10.0 and a polymer
content of 18.7 %. 100 ~ of the carboxyl groups of the
hydrolyzed copolymer are neutralized.
COMPARATIVE EXAMPLE 2:
Example 4 is repeated; however, the temperature of
heating is 70C only. 50 ~ only of the styrene/maleic
anhydride copolymer are dissolved; the solution has a pH
of 5.2.
COMPARATIVE EXAMPLE 3:
Example 4 is repeated, the temperature of heating be-
ing only 70C, and the double amount of ammonia solutionis used. The solution obtained has a pH of 9.3.
COMPA~ATIVE EXAMPLE 4:
Example of application 1 is repeated while replacing
the copolymer solution obtained in Example g by water.
The polyvinyl acetate dispersion obtained coagulates in
the test for stability to shearing,
COMPARATIVE EXAMPLE 5~
_
Example of application 1 is repeated while replacing
the copolymer solution obtained in Example 9 by a corres-
pondingly prepared solution of a styrene~maleic anhydride
copolymer (molar ratio 1:1) having an average molecular
weight of 1,600, the carboxyl groups of which being neu-
tralized to an extent of 12.3 % after hydrolysis. The
polyvinyl acetate dispersion obtained coagulates in the
test for stability to shearing.
