Note: Descriptions are shown in the official language in which they were submitted.
BASF Aktiengesellschaft 950119 O.Z. 0050/45803
Graft polymers comprising polymers, containing alkylene
oxide units, and ethylenically unsaturated compounds, their
preparation and their use
-
The present invention relates to graft polymers comprising
polymers, containing alkylene oxide units, and open-chain
N=vinylcarboxatnides, processes for their preparation and the
use of the graft polymers in the production of paper, board
and cardboard, as dispersants for pigments and as starch
cationizing agents.
US-A-4 880 497 and US-A-4 978 427 each disclose the
production of paper having high dry strength and wet
strength, a hydrolyzed copolymer which is obtainable by
copolymerization of N-vinylformamide and ethylenically
unsaturated monomers, for example vinyl acetate, vinyl
propionate or an alkyl vinyl ether, and hydrolysis of from
30 to 100 mol% of the formyl groups of the copolymer with
formation of amino groups being used as a strength agent
either on the surface of the paper or in the paper stock
prior to sheet formation. The hydrolyzed copolymers are used
in amounts of from 0.1 to 5% by weight, based on dry fibers.
EP-A-0 363 319 discloses graft polymers which are obtainable
by free radical polymerization of unsubstituted or
N-substituted acrylamide or methacrylamide and
N-vinyl-substituted amides or vinyl esters of a saturated
aliphatic monocarboxylic acid in the presence of adducts of
alkylene oxides with a trihydric or polyhydric aliphatic
alcohol of 3 to 10 carbon atoms. The graft polymers are used
as dyeing assistants for coloring cellulose fibers with
substantive dyes or reactive dyes.
US-A-5 334 287 discloses graft polymers which are obtainable
by free radical polymerization of N-vinylcarboxamides,
preferably 14--vinylformamide, and, if required, other
monomers in the presence of monosaccharides,
oligosaccharides, polysaccharides or derivatives of each of
these and, if required, hydrolysis of the polymerized
N-vinylcarboxamide group with formation of vinylamine units.
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The graft polymers are used as dry strenczth and wet str.ength
agents in the productiori of paper, board and cardboard.
In one aspect, the present invention seeks to provide novel
substances. In ar.zother aspe:~.t, che presF-:3nt invention seeks to,
provide process assistar,ts for the produ~::~t.ion of paper, board
and cardboard.
Thus, in one aspect, the present invention provides graft
polymers comprising polymers, containing alkylene oxide units,
and ethylenically unsaturated compounds, wherein the graft
polymers are o.bta.inab:le by free radical polymerization of
(A) monomers or monomer mixtures compris:Gng
(a) from 10 to 10096 by weight of- N--vinylcarboxarn.ides of
the formula
CH2 == CH - N ---- C _._._ RI
I {I (z),
R2 C~
where RI and R2 are each H or C1-C5-alkyl,
(b) from 0 to 90% by weight of other monoethylerzically
unsaturated monomers copolymerizable with the
monomers ( a ) and
(c) from 0 ta 5% by weight of monomers having at least
two ethylenically unsaturated, nonconjugated double
bonds in the molecule
in the presence of
(B) polymers which contain at l.east. 3 units of a
C2-C4-alkylene oxide, and/or polytetrahydrofurans,
in a weight ratio (A):(B) of (95 to 10):(5 to 80), and, if
required, subsequent eli.mination of the group
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3
- C - R1
I
0
from the polymerized monomers (a) of the graft polymer with
formation of units of the formula
CH2 - CH -
I
N
R2 H
The present invention furthermore relates to a process for
the preparation of graft polymers comprising polymers,
containing alkylene oxide units, and ethylenically
unsaturated compounds, wherein
(A) monomers or monomer mixtures comprising
(a) from 10 to 100% by weight of N-vinylcarboxamides of
the formula
CH2= CH - N - C- R1
i II (I),
R2 0
where R1 and R2 are each H or C1-C6-alkyl,
(b) from 0 to 90% by weight of other, carboxyl-free
monoethylenically unsaturated monomers
copolymerizable with the monomers (a) and
(c) from 0 to 5% by weight of monomers having at least
two ethylenically unsaturated, nonconjugated double
bonds in the molecule
are subjected to free radical polymerization in the presence
of
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(B) polymers which contain at least 3 units of a
C2-C4-alkylene oxide, and/or polytetrahydrofurans,
in a weight ratio (A) :(B) of (95 to 20) :(5 to 90), and some
oY all of the groups
- C- Rl
II
0
are then eliminated from the polymerized monomers (a) of the
graft polymer with formation of units of the formula
- CH2 - CH -
I
N
R2 H
In one aspect, the invention provides a graft polymer
comprising (1) at least one polymer containing alkylene oxide
units and (2) at least one polymerized ethylenically
unsaturated compound, wherein the graft polymer is obtained by
free radical polymerization of
(A) a monomer or monomer mixture comprising:
(a) from 10 to 100% by weight of a N-
vinylcarboxamide of the formula:
CH2 = CH - N - C- R1
(I),
I
Rz 0
where R' and R 2 are each H or C1-C6-alkyl,
(b) from 0 to 90% by weight of at least one other
monoethylenically unsaturated monomer which
is copolymerizable with (a), and
(c) from 0 to 5% by weight of at least one
monomer having at least two ethylenically
unsaturated nonconjugated double bonds in the
molecule,
in the presence of
(B) a material selected from the group consisting of a
polytetrahydrofuran and a polymer which contains at
least 3 units of a C2-C4 alkylene oxide
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4a
in a weight ratio (A):(B) ranging from (95 to 10):(5 to
90). Weight ratios ranges of (A):(B) may also be (95 to
10):(5 to 80), (95 to 10):(5 to 50), and (95 to 20):(5 to 90).
This is followed by eliminating some or all of the groups
- C - R1
11
0
from the polymerized monomers (a) in the graft polymer to form
units of the formula
- CH2 - CH -
I
N
R2 H
A preferably used monomer (A) is N-vinylformamide. In a
further process step, from 2 to 100%, preferably from 30 to
95% of the formyl groups of the polymerized N-vinylformamide
are eliminated from the graft polymers thus obtainable, with
formation of units of the formula
- CH2 - CH -
1
NE2
Preferably used monomer mixtures consist of from 10 to 99k by
weight of N-vinylformamide and from 90 to 1% by weight of
vinyl formate, vinyl acetate, vinyl propionate,
acrylonitrile, N-vinylpyrrolidone, N-vinylcaprolactam,
acrylic acid or mixtures of the stated monomers. From 1 to
100%, preferably from 30 to 95% of the formyl groups of the
polymerized N-vinylformamide are eliminated from the graft
polymers thus obtainable. Depending on the hydrolysis
conditions, the polymerized comonomers may also be
chemically modified, for example vinyl alcohol units are
formed from the polymerized vinyl esters. The hydrolyzed
BASF Aktiengesellschaft 950119 O.Z. 0050/45803
graft polymers thus obtainable are used as dry strength and
wet strength agents for paper, board and cardboard.
Suitable monomers for the preparation of the graft polymers
5 a-re N-vinylcarboxamides of the formula
CH2 = CH - N- C- Rl
1 11 (I)
R2 O
where R1 and R2 may be identical or different and are each
hydrogen or C1-C6-alkyl. Suitable monomers are, for example,
N-vinylformamide (R1=R2=H in the formula I),
N-vinyl-N-methylformamide, N-vinylacetamide,
N-vinyl-N-methylacetamide, N-vinyl-N-ethylacetamide,
N-vinyl-N-methylpropionamide and N-vinylpropionamide. For
the preparation of the graft polymers, the stated monomers
can be used either alone or as a mixture with one another.
From this group of monomers, N-vinylformamide is preferably
used.
The abovementioned N-vinylcarboxamides can, if required, be
used in the graft polymerization together with other
monoethylenically unsaturated monomers copolymerizable
therewith. Suitable monomers of group (b) are, for example,
vinyl esters of saturated carboxylic acids of 1 to 6 carbon
atoms, eg. vinyl formate, vinyl acetate, vinyl propionate
and vinyl butyrate. The esters, amides and nitriles of
monoethylenically unsaturated C3-C6-carboxylic acids are
also suitable. Examples of suitable amides are acrylamide,
methacrylamide and N-alkylmono- and N-alkyldiamides having
alkyl radicals of 1 to 6 carbon atoms, eg.
N-methylacrylamide, N,N-dimethylacrylamide,
N-methylmethacrylamide, N-ethylacrylamide,
N-propylacrylamide and tert-butylacrylamide and the basic
(meth)acrylamides thereof, such as
dimethylaminoethylacrylamide, dimethylaminoethylmeth-
acrylamide, diethylaminoethylacrylamide, diethylaminoethyl-
methacrylamide, dimethylaminopropylacrylamide, diethyl-
aminopropylacrylamide, dimethylaminopropylmethacrylamide and
diethylaminopropylmethacrylamide. The esters of the
monoethylenically unsaturated carboxylic acids with
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C1-C6-alcohols, eg. methyl acrylate, methyl methacrylate,
ethyl acrylate and ethyl methacrylate, or with glycols or
polyglycols, where in each case only one OH group of the
glycols and polyglycols is esterified with an ethylenically
unsaturated carboxylic acid, eg. hydroxyethyl acrylate,
hydroxyethyl methacrylate, hydroxypropyl acrylates,
hydroxybutyl acrylates, hydroxypropyl methacrylates,
hydroxybutyl methacrylates and the monoesters of acrylic
acid with polyalkylene glycols having a molecular weight of
from 1500 to 10,000, are also suitable. The esters of
ethylenically unsaturated carboxylic acids with amino
alcohols, eg. dimethylaminoethyl acrylate,
dimethylaminoethyl methacrylate, diethylaminoethyl acrylate,
diethylaminoethyl methacrylate, dimethylaminopropyl
acrylate, dimethylaminopropyl methacrylate,
diethylaminopropyl acrylate, diethylaminopropyl
methacrylate, dimethylaminobutyl acrylate, diethylaminobutyl
acrylate, dimethylaminopentyl acrylate,
dimethylaminoneopentyl methacrylate and dimethylaminohexyl
acrylate, are also useful. The basic acrylates and
acrylamides are used in the form of the free bases, of the
salts with mineral acids, eg. hydrochloric acid, sulfuric
acid and nitric acid, or in quaternized form. Suitable
quaternizing agents are, for example, dimethyl sulfate,
methyl chloride, ethyl chloride, benzyl chloride and diethyl
sulfate. Monoethylenically unsaturated mono- and
dicarboxylic acids or anhydrides of 3 to 6 carbon atoms,
such as acrylic acid, methacrylic acid, crotonic acid,
maleic acid, maleic anhydride, fumaric acid, itaconic acid,
itaconic anhydride, citraconic acid and citraconic
anhydride, are also suitable.
Other suitable monomers of group (b) are N-vinylpyrrolidone,
N-vinylcaprolactam, acrylonitrile, methacrylonitrile,
N-vinylimidazole and substituted N-vinylimidazoles, such as
N-vinyl-2-methylimidazole, N-vinyl-4-methylimidazole,
N-vinyl-5-methylimidazole, N-vinyl-2-ethylimidazole and
N-vinylimidazolines, eg. N-vinylimidazoline,
N-vinyl-2-methylimidazoline and N-vinyl-2-ethylimidazoline.
Apart from being used in the form of the free bases,
N-vinylimidazoles and N-vinylimidazolines are also used in a
form neutralized with mineral acids or in quaternized form,
quaternization preferably being effected with dimethyl
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sulfate, diethyl sulfate, benzyl chloride, methyl chloride
or ethyl chloride.
Sulfo-containing monomers, for example vinylsulfonic acid,
allylsulfonic acid, methallylsulfonic acid, styrenesulfonic
acid, 3-sulfopropyl acrylate, 3-sulfopropyl methacrylate and
2-acrylamido-2-methylpropanesulfonic acid, are also suitable
as monomers (b). The compounds having acid groups may be
used in the form of the free acids or of the ammonium,
alkali metal and alkaline earth metal salts in the graft
polymerization.
Among the monomers (b), vinyl formate, vinyl acetate, vinyl
propionate, acrylonitrile, N-vinylpyrrolidone,
N-vinylcaprolactam and acrylic acid are preferred.
In the preparation of the graft polymers, monomer mixtures
comprising from 10 to 100% by weight of at least one monomer
of group (a) and from 0 to 90% by weight of at least one
monomer of group (b) are used.
The graft copolymers can be modified by copolymerizing the
monomers (a) or monomer mixtures (a) and (b) with up to 5%
by weight of a monomer (c) having at least two ethylenically
unsaturated nonconjugated double bonds in the molecule, in
the presence of the compounds (B). The compounds (c) are
usually used as crosslinking agents in copolymerizations.
They may be added to the monomer mixtures comprising (a)
and, if required (b) which are used for the
copolymerization. Where they are employed, the preferably
used amount is from 0.05 to 2% by weight. The presence of
the monomers of group (c) during the copolymerization
results in an increase in the K values of the copolymers.
Suitable compounds of this type are, for example,
methylenebisacrylamide, esters of acrylic acid and
methacrylic acid with polyhydric alcohols, eg. glycol
diacrylate, glyceryl triacrylate, glycol dimethacrylate and
glyceryl trimethacrylate, and polyols, such as
pentaerythritol and glucose, which are diesterified or
polyesterified with acrylic acid or methacrylic acid. Other
suitable crosslinking agents are divinylbenzene, divinyl
dioxane, pentaerythrityl triallyl ether and
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pentaallylsucrose. Water-soluble monomers, such as glycol
diacrylate or glycol diacrylates of polyethylene glycols
having a molecular weight of up to 3000, are preferably used
from this group of compounds.
.
The polymerization of the monomers (a) and that of the
monomers (a) and (b) and, if required, in each case
additionally (c) is carried out, according to the invention,
in the presence of polymers containing alkylene oxide units.
Such products are polyalkylene oxides having at least 3
alkylene oxide units or polytetrahydrofurans consisting of
at least 3 units.
Polymers containing alkylene oxide units and
polytetrahydrofurans are known. Of particular interest are
the homo- and copolymers of C2-C4-alkylene oxides. They are
prepared, for example, by homo- or copolymerization of
ethylene oxide, propylene oxide, n-butylene oxide and/or
isobutylene oxide. The copolymers may be either random
copolymers, when mixtures of at least two alkylene oxides
are polymerized, or block copolymers, when first an alkylene
oxide, for example ethylene oxide, and then another alkylene
oxide, eg. propylene oxide, are polymerized. The block
copolymers may be assigned, for example, to the type AB, ABA
or BAB, where A is, for example, a polyethylene oxide block
and B is a block comprising polypropylene oxide. These
copolymers can, if required, also contain n-butylene oxide
and/or isobutylene oxide as polymerized units. The
polyethylene oxides contain at least 3 alkylene oxide units
in the molecule. The
polyalkylene oxides may contain, for
example, up to 50,000 alkylene oxide units in the molecule.
Preferred polyalkylene oxides are those which have from 3 to
1000 alkylene oxide units in the molecule. The
polytetrahydrofurans contain, for example, from 3 to 200,
preferably from 3 to 100, tetramethylene oxide units.
Preferably used compounds are homopolymers or block
copolymers of ethylene oxide and propylene oxide and random
copolymers of ethylene oxide and propylene oxide, which are
obtainable by copolymerization of a mixed gas comprising
ethyl'ene oxide and propylene oxide. For the purpose of the
present invention, polymers containing alkylene oxide units
are also to be understood as meaning adducts of
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C2-C4-alkylene oxides with alcohols, phenols, carboxylic
acids and amines.
Alcohols which are suitable for the reaction of the alkylene
oxides are of, for example, 1 to 30 carbon atoms, eg.
methanol, ethanol, n-propanol, isopropanol, n-butanol,
n-octanol, 2-ethylhexanol, decanol, dodecanol, palmityl
alcohol, cetyl alcohol and stearyl alcohol. Of particular
industrial interest are the alcohols obtainable by the oxo
process, for example clo-alcohols, c13 oxo alcohols or
natural alcohols, such as Clo/C18 tallow fatty alcohols.
In addition to the stated monohydric alcohols, it is of
course also possible to use dihydric and polyhydric
alcohols, eg. glycol, glycerol, erythritol, pentaerythritol
and sorbitol. The alcohols are reacted in a molar ratio of
from 1:3 to 1:200 with at least one C2-C4-alkylene oxide.
Further suitable polymers containing alkylene oxide units
are reaction products of fatty acids with alkylene oxides.
Particularly suitable fatty acids are those containing 8 to
10 carbon atoms in the molecule, for example lauric acid,
myristic acid, stearic acid, palmitic acid, coconut fatty
acid, tallow fatty acid and oleic acid.
For the purposes of the present invention, polymers
containing ethylene oxide units are furthermore adducts of
C2-C4-alkylene oxides with C1-C12-alkylphenols, such as
n-decylphenol, n-octylphenol, isobutylphenol and
methylphenol. Other suitable components (B) for the
preparation of the graft polymers are the adducts of
C2-C4-alkylene oxides with secondary C2-C30-amines, such as
di-n-butylamine, di n-octylamine, dimethylamine and
Distearylamine. The molar ratio of amine to at least one
alkylene oxide is from 1:3 to 1:200, preferably from 1:3 to
1:100. In the case of the adducts of alkylene oxides with
alcohols, phenols, acids or amines, the alkylene oxides in
the form of a mixed gas can be subjected to the addition
reaction with the abovementioned compounds, or the reaction
BECt-4A1gC{7f3REC11t7li is carried out first with ethylene oxide and then with
'~~~~~~FICATE propylene oxide. It is also possible to subject first
CMREC-f ON -ARTQE a propylene oxide and then ethylene oxide to the addition
9f{}ER CE#iTlRG4T
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reaction with the stated compounds. Apart from ethylene
oxide and propylene oxide, it is possible in each case also
to subject isobutylene oxide and/or n-butylene oxide to the
addition reaction. The successive addition of the alkylene
5 oxides results in the formation of block copolymers. In some
cases, it may also be advantageous to block the free OH
groups of the alkoxylation products with a terminal group.
Blocking with a terminal group may be effected, for example,
by means of an alkyl radical with formation of an ether
10 group. For example, the alkoxylation products can be reacted
with alkylating agents, such as dimethyl sulfate. The
terminal OH groups can, if required, also be esterified by
reaction with carboxylic acids, for example acetic acid or
stearic acid.
For the preparation of the graft polymers, the monomers (a),
mixtures of (a) and (b) and, if required, in each case
additionally (c) are subjected to free radical
polymerization in the presence of compounds of component
(B). In some cases, it may be advantageous for the action of
the resulting polymer to use two or more of the compounds
stated under (B). The graft polymerization can be carried
out in the presence or absence or inert solvents or inert
diluents. Since the polymerization in the absence of inert
solvents or diluents generally leads to nonuniform polymers,
the polymerization in an inert solvent or diluent is
preferred. Examples of suitable inert diluents are those in
which the compounds stated under (B) can be suspended and
those which dissolve the monomers (A). In these cases, the
polymers are present in suspended form after the
copolymerization and can readily be isolated in solid form
by filtration. Suitable inert diluents are, for example,
toluene, o-, m- and p-xylene and isomer mixtures,
ethylbenzene, aliphatic hydrocarbons, such as pentane,
hexane, heptane, octane, nonane, dodecane, cyclohexane,
cyclooctane, methylcyclohexane and mixtures of the stated
hydrocarbons, and gasoline fractions which contain no
polymerizable monomers. Chlorohydrocarbons, such as
chloroform, carbon tetrachloride, hexachloroethane,
dichloroethane and tetrachloroethane, are also suitable. In
the procedure described above, in which the compounds of
component (B) are suspended in an inert diluent, anhydrous
compounds of component (B) are preferably used.
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A preferred method for the preparation of the polymers is
solution polymerization, the compounds of component (B), the
monomers (A) and the resulting polymer being present in at
least dispersed, preferably dissolved, form. For example,
inert solvents, such as methanol, ethanol, isopropanol,
n-propanol, n-butanol, sec-butanol, tetrahydrofuran, dioxane
and water, and mixtures of the stated inert solvents are
suitable for the solution polymerization. The polymerization
can be carried out continuously or batchwise.
The graft polymers are generally prepared with the
concomitant use of free radical initiators.
Preferred free radical initiators are all those which have a
half-life of less than 3 hours at the particular
polymerization temperature chosen. If the polymerization is
first initiated at a lower temperature and completed at a
higher temperature, it is advantageous to use at least two
initiators which decompose at different temperatures, ie.
first to use an initiator which decomposes at the lower
temperature for initiating the polymerization and then to
complete the main polymerization with an initiator which
decomposes at the higher temperature. Water-soluble and
water-insoluble initiators or mixtures of water-soluble and
water-insoluble initiators may be used. The water-insoluble
initiators are then soluble in the organic phase. For
example, the initiators listed below can be used for the
temperature ranges stated below.
Temperature: from 40 to 60 C:
Acetylcyclohexanesulfonyl peroxide, diacetyl peroxy-
dicarbonate, dicyclohexyl peroxydicarbonate, di-2-ethylhexyl
peroxydicarbonate, tert-butyl perneodecanoate, 2,2'-azobis-
(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2-methyl-
N-phenylpropionamidine) dihydrochloride, 2,2'-azobis-
(2-methylpropionamidine) dihydrochloride.
Temperature: from 60 to 80 C:
tert-butyl perpivalate, dioctanoyl peroxide, dilauroyl
peroxide, 2,2'-azobis(2,4-dimethylvaleronitrile).
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Temperature: from 80 to 100 C:
dibenzoyl peroxide, tert-butyl per-2-ethylhexanoate,
tert-butyl permaleate, 2,2'-azobisisobutyronitrile, dimethyl
2,2'-azobisisobutyrate, sodium persulfate, potassium
persulfate, ammonium persulfate.
Temperature: from 100 to 120 C:
bis(tert-butylperoxy)cyclohexane, tert-butyl
peroxyisopropylcarbonate, tert-butyl peracetate, hydrogen
peroxide.
Temperature: from 120 to 140 C:
2,2-bis(tert-butylperoxy)butane, dicumyl peroxide,
di-tert-amyl peroxide, di-tert-butyl peroxide.
Temperature: >140 C
p-menthane hydroperoxide, pinane hydroperoxide, cumyl
hydroperoxide and tert-butyl hydroperoxide.
If, in addition to the stated initiators, salts or complexes
of heavy metals, for example copper, cobalt, manganese,
iron, vanadium, nickel and chromium salts, or organic
compounds, such as benzoin, dimethylaniline or ascorbic
acid, are also used, the half-lives of the stated free
radical initiators may be reduced. For example, tert-butyl
hydroperoxide can be activated with the addition of only
5 ppm of copper(II) acetylacetonate so that polymerization
can be carried out at as low as 100 C. The reducing
component of redox catalysts may also be, for example,
compounds such as sodium sulfite, sodium bisulfite, sodium
formaldehyde sulfoxylate and hydrazine. From 0.01 to 20,
preferably from 0.05 to 10, % by weight, based on the
monomers used in the polymerization, of a polymerization
initiator or of a mixture of a plurality of polymerization
initiators are used. From 0.01 to 15% of the reducing
compounds are used as redox components. Heavy metals are
used in an amount of from 0.1 to 100 ppm, preferably from
0.5 to 10 ppm. It is often advantageous to use a combination
of peroxide, reducing agent and heavy metal as the redox
catalyst.
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The polymerization of the essential monomers (a) and of (b),
which may be used, and of the monomers (c) which may be
present can also be carried out by the action of ultraviolet
radiation, in the presence or absence of UV initiators. The
conventional photoinitiators or sensitizers are used for the
polymerization under the action of UV radiation. These are,
for example, compounds such as benzoin, benzoin ethers,
a-methylbenzoin or a-phenylbenzoin. Triplet sensitizers,
such as benzil diketals, may also be used. For example, in
addition to high-energy UV lamps, such as carbon arc lamps,
mercury vapor lamps or xenon lamps, low-UV light sources,
such as fluorescent tubes having a high blue content, may be
used as UV radiation sources.
In order to prepare polymers having a low K value, the
polymerization is advantageously carried out in the presence
of regulators. Examples of suitable regulators are organic
compounds containing sulfur in bonded form. These include,
for example, mercapto compounds, such as mercaptoethanol,
mercaptopropanol, mercaptobutanol, mercaptoacetic acid,
mercaptopropionic acid, butyl mercaptan and dodecyl
mercaptan. Other suitable regulators are allyl compounds,
such as allyl alcohol, aldehydes, such as formaldehyde,
acetaldehyde, propionaldehyde, n-butyraldehyde and
isobutyraldehyde, formic acid, ammonium formate, propionic
acid, hydrazine sulfate and butenols. If the polymerization
is carried out in the presence of regulators, from 0.05 to
20% by weight, based on the monomers used in the
polymerization, of said regulators are required.
The graft polymerization of the components (A) and (B) is
usually carried out in an inert gas atmosphere in the
absence of atmospheric oxygen. During the polymerization,
thorough mixing of the reactants is generally ensured. In
the case of relatively small batches where reliable removal
of the heat of polymerization is ensured, the reactants,
which are preferably present in an inert diluent, can be
subjected to batchwise copolymerization by heating the
reaction mixture to the polymerization temperature and then
allowing the reaction to proceed. These temperatures are
from 40 to 1800C. In order to be able to control the course
of the polymerization reaction more readily, the monomers
(A) are added continuously or batchwise to the polymerizing
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mixture at the desired polymerization temperature at a rate
such that the polymerization is readily controllable in the
desired temperature range. A preferred method of addition of
the monomers of component (A) is that where the compounds of
cpmponent (B) or at least a part of the compounds of
component (B) are or is initially taken in the
polymerization reactor and heated therein to the desired
polymerization temperature while stirring. As soon as this
temperature is reached, the monomers (a) and, if required,
(b) and, if required, (c) and the initiator and, if
required, a regulator are added over a period of from about
1 to 10, preferably from 2 to 8, hours. Such a procedure is
used, for example, in the polymerization of components (A)
and (B) in an inert diluent in which the component (B) is
suspended, and also in the polymerization carried out in
solution.
The novel graft polymers are preferably prepared by
suspension or solution polymerization of the components (A)
and (B) in an aqueous medium, solution polymerization in
water being particularly preferred. In solution
polymerization in an aqueous medium, for example, at least a
part of the compounds of components (A) and (B) is initially
taken in an aqueous medium and the monomers (a and, if
required, b) and, if required, the monomers (c) are added
continuously or batchwise to the polymerizing reaction
mixture. In order to avoid hydrolysis of the monomeric
N-vinylcarboxamides during the polymerization in aqueous
solution, the polymerization is preferably carried out at a
pH of from 4 to 9, in particular from 5 to 8. In many cases,
it is advisable to carry out the reaction additionally in
the presence of buffers, for example to add primary or
secondary sodium phosphate to the aqueous phase. Where
monomers (b) containing acid groups are used, they are
employed in the form of the salts.
In the graft polymerization, the temperatures are usually
from 40 to 180 C, preferably from 50 to 1500C, in particular
from 60 to 110 C. As soon as the temperature in the graft
polymerization is above the boiling points of the inert
diluent or solvent or of the monomers, the polymerization is
carried out under superatmospheric pressure. The
concentration of components (A) and (B) in the graft
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polymerization in the presence of inert solvents or inert
diluents is from 10 to 80, preferably from 20 to 70% by
weight. The preparation of the graft polymers can be carried
out in the conventional polymerization apparatuses. For
5 example, stirred kettles which are equipped with anchor,
paddle or impeller stirrers or multistage impulse
countercurrent agitators are used for this purpose.
Particularly in the polymerization in the absence of
diluents, it may advantageous to carry out the
10 polymerization in a kneader. It may also be necessary to
carry out the polymerization in a kneader when high
concentrations are used.
Graft polymers which, where they are soluble in water, have
15 K values of from 8 to 250, preferably from 10 to 150
(measured in 1% strength aqueous solutions of the copolymers
at pH 7 and 25 C) are obtained. The graft polymers which can
be prepared by the abovementioned processes are colorless to
brownish products. In the case of polymerization in an
aqueous medium, they are present as emulsions or polymer
solutions. Depending on the particular composition of the
graft polymers, low-viscosity to pasty aqueous solutions or
aqueous emulsions are obtained.
The preparation of the graft polymers is followed by a
second process stage in which hydrolysis is carried out
under the action of acids, bases or enzymes. The polymers
contain at least 10% by weight of units of the formula
- CH2 - i H2.-
N
R2 c (II),
0 R1
where R1 and R2 are each H or C1-C6-alkyl. The units II are
converted by hydrolysis into units of the formula
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16
- CH - CH2
I (III),
N
R2 H
where R2 is H or C1-C6-alkyl. Here, units of the formula
- C - Rl
11 (IV),
0
where R1 has the meaning stated in the formula II, are
eliminated from the polymerized monomers (a) of the graft
polymer. Depending on the reaction conditions in the
hydrolysis, ie. on the amount of acid or base, based on the
polymer to be hydrolyzed, and on the reaction temperature in
the hydrolysis, either partial or complete hydrolysis of the
units of the formula (II) is obtained. The hydrolysis of the
graft polymers is continued until from 2 to 100%, preferably
from 30 to 95%, of the monomer units of the formula (II)
which are present in the graft polymers have been
hydrolyzed. For the hydrolysis, at least one acid or base is
added to the graft polymers prepared in the first process
stage. Suitable acids are, for example, mineral acids, such
as a hydrohalic acid (gaseous or in aqueous solution),
sulfuric acid, nitric acid or phosphoric acid
(ortho-phosphoric, meta-phosphoric or polyphosphoric acid),
and organic acids, for example C1-C5-carboxylic acids, such
as formic acid, acetic acid and propionic acid, or the
aliphatic or aromatic sulfonic acids, such as
methanesulfonic acid, benzenesulfonic acid or
toluenesulfonic acid. Hydrochloric acid or sulfuric acid is
preferably used for the hydrolysis. In the hydrolysis with
acids, the pH is from 0 to 5. For example, from 0.05 to 1.5,
preferably from 0.4 to 1.2, equivalents of acid are required
per equivalent of formyl groups in the polymer.
In the hydrolysis with bases, it is possible to use
hydroxides of metals of the first and second main groups of
the Periodic Table, for example lithium hydroxide, sodium
hydroxide, potassium hydroxide, calcium hydroxide, strontium
hydroxide and barium hydroxide being suitable. However,
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ammonia and alkyl derivatives of ammonia may also be used,
for example alkylamines or arylamines, eg. triethylamine,
monoethanolamine, diethanolamine, triethanolamine,
morpholine or aniline. In the hydrolysis with bases, the pH
i-s from 8 to 14. The bases may be used in the solid, liquid
or, if required, also gaseous state, diluted or undiluted.
Bases preferably used for the hydrolysis are ammonia, sodium
hydroxide solution and potassium hydroxide solution. The
hydrolysis at acidic or alkaline pH is carried out, for
example, at from 30 to 1700C, preferably from 50 to 120'C.
It is complete after from about 2 to 8, preferably from 3 to
5, hours. After these reaction times, the resulting degrees
of hydrolysis of the units of the formula (II) in the
polymer are from 1 to 100%. A procedure in which the
hydrolysis is carried out by adding the bases or acids in
aqueous solution has proven particularly useful. After the
hydrolysis, neutralization is generally effected so that the
pH of the hydrolyzed polymer solution is from 2 to 8,
preferably from 3 to 7. Neutralization is required when it
is intended to avoid or delay continuation of the hydrolysis
of artiall hydrolyzed
p y polymers. The hydrolysis may also be
carried out with the aid of enzymes.
Particularly preferred graft polymers are those which are
prepared using, as monomer (A), N-vinylformamide or a
monomer mixture comprising
(a) from 10 to 99% by weight of N-vinylformamide and
(b) from 90 to 1% by weight of vinyl formate and/or vinyl
acetate
and which are then subjected to hydrolysis in which from 1
to 100% of the formyl groups of the polymerized
N-vin lformamide are eliminated from the y graft polymer with
formation of units of the formula III where R2 is H. In the
acidic hydrolysis of graft polymers which, in addition to
N-vinylformamide, also contain acrylonitrile as polymerized
units, imide structures of the formula
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N \ 0 (V)
1
H
may also be formed from the last-mentioned monomer. The
amount of these structures in the hydrolyzed graft polymer
may be from 0 to 60 mol% of the units (V), depending on the
amount of polymerized acrylonitrile and on the reaction
conditions.
On the other hand, the hydrolysis with bases, in particular
metal hydroxides, leads to substantial formation of
carboxylate functions.
In order to prevent or substantially inhibit loss of
application efficiency of the hydrolyzed graft polymers
during storage and in order to obtain a polymer solution
having a substantially stable color, antioxidants, reducing
agents or aldehyde scavengers may be added during or after
the hydrolysis.
Antioxidants, which generally act as free radical scavengers
or UV stabilizers, are, for example, secondary aromatic
amines, phenol, alkylphenols, thioethers, phosphites or
mixtures of compounds of the stated classes of substances.
Suitable secondary aromatic amines are, for example,
4,4'-bis(tert-butyl)diphenylamine, 4,4'-bis(phenylmethyl)-
diphenylamine and mixtures thereof. Alkylphenols which are
suitable as antioxidants are, for example,
2,6-dimethyl-4-tert-butylphenol, 2,4,6-trimethylphenol,
2,4-di-tert-butyl-6-methylphenol and mixtures thereof.
Examples of suitable thioethers are dialkyl
3,3'-thiodipropionate, poly- 2, 3 -dimethylphenyl
1,4-disulfide, bis(2-methyl-4-hydroxy-5-tert-butyl) sulfide,
dibenzyl sulfide and dialkyl disulfides, eg. dioctadecyl
disulfide.
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Phosphites which are suitable as antioxidants are, for
example, trisnonylphenyl phosphite,
di(2,4-di-tert-butylphenyl) pentaerythrityl diphosphite and
diphenylene decyl phosphite.
-
Examples of suitable reducing agents are sodium borohydride,
sodium cyanoborohydride and dithionites, such as sodium,
potassium or zinc dithionite.
Aldehyde scavengers are, for example, NH-containing
compounds, such as urea, ethyleneurea, propyleneurea,
melamine, guanidine, phenylbiguanidine and mixtures of the
stated compounds. Other aldehyde scavengers are, for
example, alkali metal bisulfites such as sodium or potassium
bisulfite.
Antioxidants, reducing agents and aldehyde scavengers are
each used in amounts of from 0.01 to 20, preferably from 0.1
to 16, % by weight, based on the polymers. These substances
may be added before, during or after the hydrolysis of the
amido groups contained in the graft polymers.
The graft polymers thus obtained and containing
N-vinylcarboxamides and/or vinylamine units are used in
papermaking for increasing the dry and wet strength of the
paper. The novel graft polymers are preferably used in
aqueous solution and are added to the paper stock in an
amount of from 0.1 to 10% by weight, based on dry fibers,
before sheet formation. The aqueous polymer solution can
also be applied to the surface of the paper, the amounts to
be used being from 0.1 to 10, preferably from 0.25 to 3, %
by weight, based on dry fibers. The aqueous solutions of the
polymers are effective in the case of all known paper, board
and cardboard qualities, for example in the production of
hygiene, writing, printing and packaging papers. The paper,
board and cardboard may be produced from a large number of
fiber materials, for example from sulfite or sulfate pulp
(bleached or unbleached), mechanical pulp, chemothermo-
mechanical pulp (CTMP), thermomechanical pulp (TMP) or waste
paper or mixtures of the stated fiber types. The pH of the
stock suspension is from 4 to 9, preferably from 6 to 8. The
copolymers described above are preferably added to the paper
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stock suspension in an amount of from 0.25 to 2% by weight,
based on dry fibers, prior to sheet formation, and lead to
an increase in the dry and wet strength of the paper.
5 -
The graft polymers are also suitable as fixing agents for
interfering substances and dyes in the production of paper,
board and cardboard. For this intended use, the graft
polymers are added directly to the paper stock or may be
added to the paper stock in the form of a mixture with the
10 rosin size. For example, from 1 to 100, preferably from 5 to
30, parts by weight, based on 100 parts by weight of rosin
size, of the graft polymers are used.
15 Graft polymers which have a high molecular weight, for
example K values of from about 150 to 250, are used as
retention aids and drainage aids in the production of paper,
board and cardboard. For this intended use, from 0.01 to 5,
preferably from 0.1 to 2, % by weight, based on the dry
20 fibers, of graft polymers are usually suitable. A further
application for the novel graft polymers is their use as
starch cationizing agents. Starch can be cationized, for
example, by heating an aqueous suspension of starch to
80-1800C in the presence of the graft polymers. At above the
boiling point of the aqueous reaction mixtures, the
procedure is carried out in closed pressure-resistant
apparatuses. For example, from 0.1 to 100, preferably from 1
to 10, % by weight, based on starch, of graft polymer is
used in starch cationization. All types of starch can be
cationized with the novel graft polymers, for example
natural starch, such as potato, rice, corn and wheat starch,
and degraded starches or starch types having amylopectin
contents of from at least 95 to 100%, for example
pregelatinized corn starches or pregelatinized potato
starches. Those graft polymers in which the degree of
hydrolysis of the polymerized N-vinylcarboxamides is at
least 60% are particularly suitable for this intended use.
The cationized starches thus prepared are used, for example,
in papermaking. They increase the dry and wet strength of
the paper and have particularly high retention compared with
unmodified starch.
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21
The novel graft polymers can also be used as dispersants for
pigments. The amounts usually used for this purpose are from
about 0.1 to 5, preferably from 0.5 to 2, % by weight, based
on the pigments. Examples of suitable pigments are chalk,
clay, talc and titanium dioxide. For use as a filler in
papermaking or for the preparation of paper-coating slips,
highly concentrated aqueous pigment suspensions are
prepared. Such pigment suspensions may contain up to 75% by
weight of a pigment.
The novel graft polymers are also suitable as promoters in
the diketene sizing of paper, board and cardboard. For this
purpose, the graft copolymers are emulsified together with
the diketene in the preparation of the diketene emulsions.
The diketene emulsions contain, for example, from 0.05 to 5%
by weight of a graft polymer. The novel graft polymers
ensure rapid development of the diketene size. The graft
polymers are also suitable as assistants in the production
of tissue papers. For this purpose, they are used in amounts
of from 0.05 to 0.5% by weight, based on dry fibers.
In the examples which follow, parts are by weight and
percentages are based on the weight of the stocks.
The K values of the polymers were determined according to
H. Fikentscher, Cellulose-Chemie, 13 (1932), 58-64 and
71-74, in 1% strength by weight aqueous solution at 250C.
The paper sheets were produced in a Rapid-Kothen*laboratory
sheet former. The dry tear length was determined according
to DIN 53112, page 1, and the wet tear length according to
DIN 53112, page 2.
Example 1
829.5 g of distilled water, 1.27 g of 75% strength
phosphoric acid and 0.87 g of 50% strength sodium hydroxide
solution and 33 g of polyethylene glycol having a molecular
weight of 1500, introduced into a heatable reactor provided
with a stirrer, reflux condenser, thermometer, feed
apparatuses, nitrogen inlet and outlet apparatuses, and the
* Trade-mark
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22
pH of the mixture is brought to 6.5 with phosphoric acid or
sodium hydroxide solution. The reactor content is then
heated to 70 C in a gentle stream of nitrogen (10 1/h), and
134.7 g of N-vinylformamide are metered in uniformly in the
course of 3 hours and a solution of 0.53 g of
2,2'-azobis(2-methylpropionamidine) dihydrochloride in 100 g
of distilled water is metered in uniformly in the course of
4 hours. Heating is then continued for a further 2 hours at
70 C. The clear, colorless viscous solution has a solids
content of 15.5% and a K value of 79.
Hydrolysis:
500 g of the graft polymer solution described above are
initially taken in a stirred apparatus having a reflux
condenser, a thermometer and a dropping funnel. 103 g of 38%
strength hydrochloric acid are added dropwise in the course
of 15 minutes with thorough stirring. The reaction mixture
is then heated at 70 C for 6 hours. The conversion is
determined by polyelectrolyte titration. The mixture is
cooled to room temperature, after which the pH is brought to
3.8 by slow dropwise addition of a total of 77.6 g of 50%
strength aqueous sodium hydroxide solution. 11 g of 30%
strength sodium bisulfite solution is added to the solution,
and stirring is continued for a further 10 minutes. Degree
of hydrolysis of the polymerized N-vinylformamide: 91%,
solids content: 21.8%, polymer content: 12.2%.
Example 2
831 g of distilled water, 0.96 g of aqueous 75% strength
phosphoric acid, 0.66 g of 50% strength aqueous sodium
hydroxide solution and 66 g of polyethylene glycol having a
molecular weight of 1500 are introduced into a reactor
according to Example 1 and brought to a pH of 6.5 as in
Example 1. The mixture is then heated to 70 C in a gentle
stream of nitrogen (10 1/h), and 101 g of N-vinylformamide
are metered in uniformly in the course of 3 hours and a
solution of 0.4 g of 2,2'-azobis(2-methylpropionamidine)
dihydrochloride in 100 g of distilled water is metered in
uniformly in the course of 4 hours at 70 C. Heating is then
continued for a further 2 hours at 70 C. The clear,
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colorless solution has a solids content of 15.1%. The K
value of the graft polymer is 62.3.
Hydrolysis:
500 g of the graft polymer solution described above are
initially taken in a stirred apparatus having a reflux
condenser, a thermometer and a dropping funnel. 74.8 g of
38% strength hydrochloric acid are added dropwise in the
course of 10 minutes with thorough stirring. The solution is
then heated at 700C for 6 hours. The conversion is
determined by polyelectrolyte titration. After the mixture
has cooled to room temperature, the pH is brought to 3.8 by
adding 56 g of 50% strength aqueous sodium hydroxide
solution a little at a time. 10.6 g of 30% strength sodium
bisulfite solution are added, and stirring is continued for
a further 10 minutes. 641.4 g of an aqueous solution of a
hydrolyzed graft polymer are obtained. The degree of
hydrolysis of the polymerized N-vinylformamide is 85%. The
solution has a solids content of 20% and a polymer content
of 12.5%.
Example 3
Example 1 is repeated with the single exception that,
instead of the polyethylene glycol having a molecular weight
of 1500 which is used there, a polyethylene glycol having a
molecular weight of 4000 is now used. A clear, colorless
solution having a solids content of 16.4% is obtained. The K
value of the polymer is 79.7.
40
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Hydrolysis:
500 g of the graft polymer solution described above are
hydrolyzed with 108 g of 38% strength hydrochloric acid, as
described in Example 1. After the mixture has been cooled,
73.4 g of 50% strength aqueous sodium hydroxide solution are
added, with the result that the pH is brought to 3.8. 11.3 g
of a 30% strength aqueous sodium bisulfite solution are also
added in order to stabilize the graft polymer. The degree of
hydrolysis of the polymerized N-vinylformamide is 90%. The
resulting reaction solution has a solids content of 22%. The
polymer content is 12.9.
Example 4
The procedure is as described in Example 1, except that a
methylpolyglycol having a molecular weight of 500 is used as
the grafting base. A clear, colorless solution having a
solids content of 10.4% is obtained. The graft polymer has a
K value of 77.6.
Hydrolysis:
500 g of the aqueous polymer solution described above are
hydrolyzed by adding 102 g of 38% strength hydrochloric
acid, as described in Example 1. After the reaction mixture
has cooled, 76.9 g of 50% strength aqueous sodium hydroxide
solution and 11 g of a 30% strength aqueous sodium bisulfite
solution are added to adjust the pH. The solution thus
obtained has a solids content of 21.7% and contains 12.1% of
polymer. The degree of hydrolysis of the polymerized
N-vinylformamide is 94%.
Example 5
Example 2 is repeated except that methylpolyglycol having a
molecular weight of 500 is used as the grafting base. A
clear, colorless polymer solution having a solids content of
15.8% is obtained. The graft polymer has a K value of 70.7.
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Hydrolysis:
500 g of the polymer solution stated above is treated with
5 781 g of 38% strength hydrochloric acid by the method stated
in Example 1. After the hydrolysis, 58.5 g of 50% strength
aqueous sodium hydroxide solution are added to adjust the pH
and 11 g of 30% strength sodium bisulfite solution are added
for stabilization. The solids content of the solution thus
obtained is 20.8% and the polymer content is 13%. 87% of the
polymerized N-vinylformamide is hydrolyzed.
Example 6
859 g of distilled water, 1.0 g of 75% phosphoric acid,
0.74 g of 50% strength sodium hydroxide solution, 22.3 g of
polyethylene glycol having a molecular weight of 1500 and
90.9 g of N-vinylformamide are initially taken in the
reactor described in Example 1 and brought to a pH of 6.5.
The stirred reaction mixture is heated to 50 C in a gentle
stream of nitrogen, and stirring is continued. A solution of
0.44 g of 2,2'-azobis(2-methylpropionamidine)
dihydrochloride in 150 g of water is added in eight portions
at regular intervals in the course of 8 hours and the
temperature of the reaction mixture is maintained at 50 C.
After the addition of the initiator, the reaction mixture is
stirred for a further 4 hours at 75 C. The clear, colorless
solution thus obtained has a solids content of 10.1%. The K
value of the graft polymer is 108.8 (measured in 0.5%
strength aqueous solution).
Hydrolysis:
500 g of the polymer solution described above are hydrolyzed
by the addition of 66.6 g of 38% strength hydrochloric acid,
according to the method described in Example 1. After the
hydrolysis, 50.2 g of 50% strength aqueous sodium hydroxide
solution and 10.1 g of 30% strength sodium bisulfite
solution are added. An aqueous solution having a solids
content of 15.8% is obtained. The polymer content of the
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solution is 8.8%. 95% of the polymerized N-vinylformamide is
hydrolyzed to vinylamine units.
Example 7
Example 6 is repeated with the single exception that a
polyethylene glycol having a molecular weight of 4000 is now
used as the grafting base. The clear, colorless solution
thus obtained has a solids content of 10.1%. The K value of
the graft polymer is 107.3.
Hydrolysis:
500 g of the aqueous polymer solution is hydrolyzed by the
addition of 66.7 g of 38% strength hydrochloric acid by the
method described in Example 1. After the reaction mixture
has been cooled, 45.8 g of a 50% strength aqueous sodium
hydroxide solution and 10.3 g of a 30% strength aqueous
sodium bisulfite solution are added. A polymer solution
having a solids content of 15.8% is obtained. The polymer
content of the solution is 8.8%. 90% of the N-vinylformamide
grafted onto polyethylene glycol is hydrolyzed.
Example 8
951 g of distilled water, 2.5 g of 75% strength phosphoric
acid, 1.95 g of 50% strength aqueous sodium hydroxide
solution and 39.2 g of polyethylene glycol having a
molecular weight of 1500 are initially taken in the reactor
described in Example 1 and the pH is brought to 6.8 as
described in Example 1. The solution is then heated to 70 C
in a gentle stream of nitrogen while stirring. As soon as
70 C is reached, 160 g of N-vinylformamide are added
uniformly in the course of 3 hours, an aqueous solution of
1.6 g of 2-mercaptoethanol in 50 g of distilled water is
added uniformly in the course of 2.75 hours and a solution
of 0.64 g of 2,2'-azobis(2-methylpropionamidine)
dihydrochloride in 160 g of distilled water is added
uniformly in the course of 4 hours, in separate feeds. After
the addition of the initiator, the reaction mixture is
stirred for a further 2 hours at 70 C. A clear, colorless
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polymer solution having a solids content of 14.9% is
obtained. The graft polymer has a K value of 50.8 (measured
in 1% strength aqueous solution).
-
Hydrolysis:
98.3 g of 38% strength hydrochloric acid are added to 500 g
of the aqueous polymer solution described above, by the
method described in Example 1. After the hydrolysis, 68.5 g
of a 50% strength aqueous sodium hydroxide solution and
11.2 g of 30% strength sodium bisulfite solution are added
to the reaction mixture. An aqueous solution having a solids
content of 21.7% and a polymer content of 11.9% is obtained.
86% of the N-vinylformamide grafted on is hydrolyzed.
Example 9
The procedure is as stated in Example 8, but polyethylene
glycol having a number average molecular weight of 4000 is
used as the grafting base. The solids content of the clear,
colorless polymer solution is 15.9%. The graft polymer has a
K value of 56.1, measured in 1% strength aqueous solution.
Hydrolysis:
102.2 g of 38% strength hydrochloric acid are added to 500 g
of the aqueous polymer solution described above, by the
method described in Example 1. After the reaction mixture
has cooled, 70.5 g of a 50% strength aqueous sodium
hydroxide solution and 11.1 g of a 30% strength sodium
bisulfite solution are added. An aqueous solution having a
solids content of 22.4% results. The polymer content of the
solution is 12.3%. 93% of the N-vinylformamide grafted onto
polyethylene glycol is hydrolyzed.
Example 10
951 g of distilled water, 2.5 g of 75% strength phosphoric
acid, 1.95 g of 50% strength aqueous sodium hydroxide
solution and 78.4 g of polyethylene glycol having a number
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28
average molecular weight of 1500 are initially taken in the
reactor described in Example 1 and brought to a pH of 6.5.
The solution is heated to 70 C in a gentle stream of
nitrogen. As soon as this temperature is reached, 120 g of
I~--vinylformamide are added uniformly in the course of 3
hours, a solution of 1.2 g of 2-mercaptoethanol in 50 g of
distilled water is added uniformly in the course of 2.75
hours and a solution of 0.48 g of 2,2'-azobis(2-methyl-
propionamidine) dihydrochloride in 100 g of distilled water
is added uniformly in the course of 4 hours, in separate
streams. After the end of the initiator addition, the
reaction mixture is stirred for a further 2 hours at 70 C.
The clear, colorless polymer solution thus obtained has a
solids content of 14%. The K value of the graft polymer is
44.4.
Hydrolysis:
500 g of the aqueous polymer solution described above are
hydrolyzed by the addition of 69.2 g of 38% strength
hydrochloric acid, according to the method stated in Example
1. After the hydrolysis, 47.7 g of a 50% strength aqueous
sodium hydroxide solution and 10.3 g of a 30% strength
sodium bisulfite solution are added. The aqueous solution
obtained has a solids content of 19.6% and a polymer content
of 11.8%. 83% of the N-vinylformamide grafted onto
polyethylene glycol is hydrolyzed.
Example 11
859 g of distilled water, 1.08 g of 75% strength phosphoric
acid, 0.74 g of 50% strength aqueous sodium hydroxide
solution, 44.6 g of polyethylene glycol having a molecular
weight of 1500 and 68.2 g of N-vinylformamide are initially
taken in the reactor described in Example 1 and brought to a
pH of 6.8. The reaction mixture is then heated to 50 C in a
gentle stream of nitrogen. As soon as the temperature has
been reached, a solution of 0.33 g of 2,2'-azobis(2-methyl-
propionamidine) dihydrochloride in 150 g of distilled water
is added in 8 portions at regular intervals in the course of
8 hours. A solution of 0.07 g of
2,2'-azobis(2-methylpropionamidine) dihydrochloride in 75 g
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of distilled water is then added all at once, and the
stirred reaction mixture is heated at 75 C for a further 4
hours. The clear, colorless solution thus obtained has a
solids content of 10.1%. The K value of the polymers is 91
(measured in 1% strength aqueous solution).
Hydrolysis:
500 g of the polymer solution described above are hydrolyzed
by the addition of 49.9 g of 38% strength hydrochloric acid
according to the method stated in Example 1. After the
hydrolysis, 37.1 g of a 50% strength aqueous sodium
hydroxide solution and 9.6 g of a 30% strength sodium
bisulfite solution are added. A solution having a solids
content of 15.7% results. The polymer content of the
solution is 9%. 91% of the N-vinylformamide grafted on is
hydrolyzed.
Example 12
Steam distillation apparatus is additionally attached to the
reactor described in Example 1. 550 g of methanol, 401 g of
distilled water, 2.5 g of 75% strength aqueous phosphoric
acid, 1.95 g of 50% strength aqueous sodium hydroxide
solution and 39.2 g of polypropylene glycol having a
molecular weight of 2000 are initially taken therein and the
pH of the aqueous solution is brought to 6.5. The stirred
mixture is heated to 70 C in a gentle stream of nitrogen. As
soon as this temperature is reached, 160 g of
N-vinylformamide are added uniformly in the course of 3
hours, a solution of 1.6 g of 2-mercaptoethanol in 50 g of
distilled water is added separately from this and uniformly
in the course of 2.7 hours and a solution of 0.64 g of
2,2'-azobis(2-methylpropionamidine) dihydrochloride is added
separately from this and uniformly in the course of 4 hours.
After the addition of the initiator, the reaction mixture is
stirred for a further 2 hours at 70 C. Steam is then passed
into the reaction mixture until the internal temperature is
100 C. The methanol is distilled off in this way. A white
dispersion having a solids content of 20.1% results.
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Hydrolysis:
500 g of the dispersion described above are mixed with
5 132.7 g of 38% strength hydrochloric acid and hydrolyzed by
the method stated in Example 1. 97.6 g of a 50% strength
aqueous sodium hydroxide solution and 11.9 g of a 30%
strength aqueous sodium bisulfite solution are then added.
An aqueous solution having a solids content of 25.9% is
obtained. The polymer content of the solution is 14.7%. 89%
10 of the N-vinylformamide grafted on is hydrolyzed.
Example 13
829 g of distilled water, 1.27 g of 75% strength phosphoric
acid, 0.87 g of 50% strength aqueous sodium hydroxide
solution and 49.5 g of the reaction product of 1 mol of a
C13 oxo alcohol with 20 mol of ethylene oxide are initially
taken in the reactor described in Example 1. The pH of the
aqueous solution is brought to 6.7. The stirred reactor
content is heated to 70 C in a gentle stream of nitrogen,
and 117.9 g of N-vinylformamide are metered in at this
temperature in the course of 3 hours and, separately from
this, a solution of 0.46 g of 2,2'-azobis(2-methyl-
propionamidine) dihydrochloride is metered in over 4 hours.
After the addition of the initiator, the reaction mixture is
stirred for a further 2 hours at 70 C. A very cloudy
solution having a solids content of 15% is formed.
Hydrolysis:
500 g of the solution described above are hydrolyzed by the
addition of 86.7 g of 38% strength hydrochloric acid
according to the method stated in Example 1. After cooling,
60.1 g of 50% strength aqueous sodium hydroxide solution and
8.1 g of a 30% strength sodium bisulfite solution are added.
An aqueous solution having a solids content of 19.9%
results. The polymer content of the solution is 12.2%. 80%
of the N-vinylformamide grafted on is hydrolyzed.
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Example 14
829 g of distilled water, 1.27 g of 75% strength aqueous
phosphoric acid, 0.87 g of 50% strength aqueous sodium
hydroxide solution, 0.25 g of polyvinylpyrrolidone having a
K value of 90 and 66 g of polyethylene glycol having a
molecular weight of 1500 are initially taken in the reactor
described in Example 1, brought to a pH of 6.7 and heated to
700C under a gentle stream of nitrogen while stirring. As
soon as the reactor content has reached this temperature, a
mixture of 50.5 g of N-vinylformamide and 49.5 g of
acrylonitrile is metered in uniformly in the course of
2 hours and, separately from this, a solution of 0.4 g of
2,2'-azobis(2-methylpropionamidine) dihydrochloride in 100 g
of distilled water is metered in uniformly in the course of
4 hours. A coarse 15% strength suspension of the graft
polymer is obtained.
Hydrolysis:
500 g of the polymer suspension described above are
initially taken in an apparatus equipped with a stirrer, and
37.4 g of 38% strength hydrochloric acid are added in the
course of 10 minutes. The suspension is stirred for 8 hours
at 700C. The reaction mixture is then allowed to cool and
the pH is brought to 3.0 by adding 83.0 g of 25% strength
aqueous sodium hydroxide solution. 9.3 g of a 30% strength
aqueous sodium bisulfite solution are then also added, and
the reaction mixture is stirred for a further 15 minutes. It
has a solids content of 16.9% and a polymer content of
12.4%. The degree of hydrolysis of the polymerized
N-vinylformamide is 90%.
Example 15
395 g of distilled water, 2.62 g of 75% strength aqueous
phosphoric acid, 1.8 g of 50% strength aqueous sodium.
hydroxide solution, 1.44 g of an aqueous solution of the
sodium salt of a molar copolymer of maleic acid and styrene,
having a molecular weight of 150,000, and 75.6 g of
polyethylene glycol having a molecular weight of 1500 are
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initially taken in the reactor described in Example 1 and
brought to a pH of 6.5. The stirred mixture is then heated
to 65 C in a gentle stream of nitrogen and, at this
temperature, 34 g of vinyl acetate are added uniformly in
the course of 2 hours, separately from this 81 g of
N-vinylformamide are added uniformly in the course of 3
hours and, likewise separately from this, a solution of
0.25 g of 2,2'-azobis(2-methylpropionamidine) dihydro-
chloride is added uniformly in the course of 4 hours. During
the polymerization, the reaction mixture becomes highly
viscous. It is therefore diluted with 300 g of distilled
water. After the addition of the initiator, the reaction
mixture is stirred for a further 2 hours at 65 C, after
which a solution of 0.05% of 2,2'-azobis(2-methyl-
propionamidine) dihydrochloride in 1 g of distilled water is
added all at once. The temperature of the reaction mixture
is then increased to 98 C in the course of 4 hours and the
reaction solution is then cooled. A clear, colorless
solution having a solids content of 18.9% is obtained. The
polymer has a K value of 67Ø
Hydrolysis:
500 g of the polymer solution described above are hydrolyzed
by the addition of 65.4 g of 38% strength hydrochloric acid
according to the method stated in Example 1. After the
hydrolysis, 45.2 g of a 50% strength aqueous sodium
hydroxide solution and 7.5 g of a 30% strength aqueous
sodium bisulfite solution are added. The reaction mixture
has a solids content of 22% and a polymer content of 15.5%.
The degree of hydrolysis of the polymerized N-vinylformamide
is 95% and that of the polymerized vinyl acetate is 35%.
Example 16
550 g of methanol, 401 g of distilled water, 2.5 g of 75%
strength phosphoric acid, 1.95 g of 50% strength aqueous
sodium hydroxide solution and 39.2 g of polytetrahydrofuran
having a molecular weight of 650 are initially taken in the
apparatus described in Example 12 and the pH of the solution
is brought to 6.5. The stirred solution is then heated to
70 C in a gentle stream of nitrogen. As soon as this
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temperature is reached, 160 g of N-vinylformamide is metered
in uniformly in the course of 3 hours and, separately from
this, a solution of 0.64 g of
2,2'-azobis(2-methylpropionamidine) dihydrochloride in 150 g
of distilled water is metered in uniformly in the course of
4 hours. The reaction mixture is then stirred for a further
2 hours at 70 C. Steam is then passed in until the internal
temperature is 100 C, in order to distill off the methanol.
The white dispersion thus obtained has a solids content of
19 . 2%.
Hydrolysis:
500 g of the dispersion described above are hydrolyzed by
the addition of 126.0 g of 38% strength hydrochloric acid
according to the method stated in Example 1. After the
hydrolysis, 85.6 g of 50% strength aqueous sodium hydroxide
solution and 11.8 g of 30% strength sodium bisulfite
solution are added. A dispersion having a solids content of
24.4% results. The polymer content is 14.4%. The
N-vinylformamide grafted on has a degree of hydrolysis of
88%.
Example 17
829 g of distilled water, 1.27 g of 75% strength phosphoric
acid, 0.87 g of 50% strength aqueous sodium hydroxide
solution and 33 g of polypropylene glycol having a molecular
weight of 600 are initially taken in the reactor described
in Example 1 and brought to a pH of 6.7. The stirred
solution is heated to 70 C in a gentle stream of nitrogen.
At this temperature, 134.6 g of N-vinylformamide are added
uniformly in the course of 3 hours and, separately from
this, 0.53 g of 2,2'-azobis(2-methylpropionamidine)
dihydrochloride dissolved in 100 g of distilled water is
added uniformly in the course of 4 hours. After the addition
of the initiator, the reaction mixture is stirred for a
further 2 hours at 70 C. A virtually clear, colorless
solution having a solids content of 15.3% results.
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Hydrolysis:
500 g of the solution described above are hydrolyzed by the
addition of 109 g of 38% hydrochloric acid according to the
method stated in Example 1. After the hydrolysis, 68.7 g of
50% strength aqueous sodium hydroxide solution and 11.1 g of
30% strength sodium bisulfite solution are added. A solution
having a solids content of 20.9% and a polymer content of
12.2% results. The degree of hydrolysis of the
N-vinylformamide grafted on is 92%.
Example 18
829 g of distilled water, 1.27 g of 75% strength phosphoric
acid, 0.87 g of 50% strength aqueous sodium hydroxide
solution and 66.5 g of polypropylene glycol having a
molecular weight of 600 are initially taken in the reactor
described in Example 1 and brought to a pH of 6.7. The
stirred solution is heated to 70 C in a gentle stream of
nitrogen. As soon as this temperature is reached, 101 g of
N-vinylformamide are metered in uniformly in the course of 3
hours and, separately from this, a solution of 0.3 g of
2,2'-azobis(2-methylpropionamidine) dihydrochloride in 100 g
of distilled water is metered in uniformly in the course of
4 hours. A solution of 0.1 g of 2,2'-azobis(2-methylpropion-
amidine) dihydrochloride in 10 g of distilled water is then
added to the reaction mixture and heating is continued for a
further 2 hours at 70 C. A colorless, slightly cloudy
solution having a solids content of 14.8% is obtained.
Hydrolysis:
500 g of the solution described above are hydrolyzed by the
addition of 73.1 g of 33% strength hydrochloric acid
according to the method stated in Example 1. After the
hydrolysis, 51.0 g of 50% strength aqueous sodium hydroxide
solution and 10.5 g of 30% strength sodium bisulfite
solution are added. A solution having a solids content of
19.8% and a polymer content of 12.4% results. The degree of
hydrolysis of the N-vinylformamide grafted on is 89%.
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Comparative Examples
Polymer 1
5 -
74 g of 38% strength hydrochloric acid (120 mol%, based on
N-vinylformamide) are added dropwise to 300 g of a 15.3%
strength aqueous polyvinylformamide solution (K value of the
polymer is 85). The mixture is then heated for about 5 hours
10 at 70 C. The degree of hydrolysis (> 93%) is monitored by
polyelectrolyte titration. After cooling, the pH of the
solution is increased to 3.5 using 50% strength sodium
hydroxide solution (40.6 g). The polymer content of the
solution is 10.9% by weight.
Polymer 2
32 g of potato starch are mixed with 500 g of 15% strength
aqueous polyvinylformamide solution (K value 85). After the
starch has been completely mixed in, 121 g (120 mol%, based
on N-vinylformamide) of 38% strength hydrochloric acid are
added dropwise in the course of 10 minutes, stirring is then
continued for a further 15 minutes at room temperature and
the mixture is finally heated at 70 C for 6 hours. The end
point (degree of hydrolysis 95%) of the reaction is
determined by polyelectrolyte titration. A clear brownish
solution which contains 16.4% by weight of active ingredient
and, according to EP-A-0 301 372 is used as a dry and wet
strength agent for paper is obtained.
Polymer 3
A copolymer of 70% by weight N-vinylformamide and 30% by
weight of vinyl acetate, having a K value of 85, is prepared
according to US-A-4 978 427 and hydrolyzed by the addition
of 110 mol of a 38% strength hydrochloric acid per mole of
N-vinylformamide content of the polymer until at least 90%
of the polymerized N-vinylformamide and at least 80% of the
polymerized vinyl acetate have been hydrolyzed.
Use Examples
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Example 19
Sheets having a basis weight of 80 g/m2 were produced in a
Rapid-Kothen sheet former. The paper stock consisted of 50%
of bleached hardwood sulfite pulp and 50% of bleached
softwood sulfite pulp having a freeness of 320SR
(Schopper-Riegler) in 0.5% strength aqueous suspension. The
pH of the stock suspension was 7Ø The stock suspension was
divided into 22 equal parts. The substances stated under (b)
to (v) were added to 21 samples:
(a) The stock suspension contained no further additives.
(b) 1%, based on dry fibers, of an aqueous solution of a
commercial neutral wet strength resin based on a
reaction product of epichlorohydrin and a polyamidoamine
obtained from diethylenetriamine and adipic acid was
added to the stock suspension.
(c) 1%, based on dry fibers, of an aqueous solution of a
polyvinylamine hydrochloride having a K value of 85,
according to Comparative Example 1, was added to the
stock suspension.
(d) 1%, based on dry fibers, of an aqueous polymer solution
according to Comparative Example 2 was added to the
stock suspension.
(e) to (v)
1%, based on dry fibers, of the hydrolyzed graft
polymers according to Examples 1 to 18 was added to each
of the stock suspensions.
The pulps obtained were then drained on a Rapid-Kothen sheet
former to give sheets having a basis weight of 80 g/m2. The
dry and wet tear lengths stated in Table 1 were measured for
the abovementioned polymers.
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Table 1
Wet tear Wet tear Dry tear
Additive length [m] length [m] length
unaged aged* [m]
a) without 116 121 2376
polymer
b) comparison 68 837 2910
c) " 754 812 2932
d) 449 2456
e) according 753 804 3640
to the
invention
f) 652 675 3883
g) 685 724 3936
h) 765 845 3715
i) " 695 772 3687
j) 840 858 3944
k) 813 843 4068
1) " 662 697 3720
m) " 684 665 3886
n) 562 622 3753
o) " 687 742 3246
P) 682 693 3709
q) 801 799 3681
r) " 576 552 3446
s) 650 628 3717
t) 707 739 3816
u) 660 677 3808
v) 689 752 3864
* 5 min at 110'C
Example 20
Sheets having a basis weight of 80 g/m2 were produced in a
Rapid-Kothen sheet former. The paper stock consisted of 50%
of bleached hardwood sulfite pulp and 50% of bleached
softwood sulfite pulp having a freeness of 32 SR
(Schopper-Riegler) in 0.5% strength aqueous suspension. The
pH of the stock suspension was 4.5. The stock suspension was
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divided into 21 equal parts. The substances stated under (d)
to (v) were added to 20 samples:
5(a) The stock suspension contained no further additives.
(b) 1%, based on dry fibers, of an aqueous solution of a
commercial wet strength resin based on a reaction
product of urea/melamine with formaldehyde was added to
the stock suspension.
(c) 1%, based on dry fibers, of an aqueous solution of a
copolymer of vinylamine hydrochloride and vinyl alcohol,
according to Comparative Example 3, was added to the
stock suspension.
(d) to (u)
1%, based on dry fibers, of the hydrolyzed graft
polymers which were obtained according to Examples 1 to
18 was added to each of the stock suspensions, the
hydrolyzed graft polymer according to Example 1 being
used in the case of (d) and the hydrolyzed graft polymer
prepared according to Example 18 being used in the case
of (u).
The pulps obtained were then drained on a Rapid-Kothen sheet
former to give sheets having a basis weight of 80 g/m2. The
dry and wet tear lengths stated in Table 2 were measured for
the abovementioned polymers.
35
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Table 2
Wet tear Wet tear Dry tear
- Additive length [m] length [m] length
unaged aged* [m]
a) without 149 170 2376
addition
b) comparison 531 645 3710
c) " 599 607 4089
d) according 607 698 4562
to the
invention
e) 606 596 3913
f) " 649 655 3543
g) 558 620 3819
h) 441 601 3965
i) 533 657 4183
j) " 585 613 3924
k) 430 488 3736
1) 479 500 3189
m) 433 468 3655
n) 529 564 3652
o) " 507 547 4554
p) 614 597 4453
q) 675 835 4826
r) " 596 625 3600
s) " 559 558 3565
t) 585 566 3362
u) 615 571 3746
* 5 min at 110 C
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