Note: Descriptions are shown in the official language in which they were submitted.
0050/43722 ~ 14 ~ 2 8 ~
Use of hydrolyzed copolymers of N-vinylcarboxamides and monoethy-
lenically unsaturated carboxylic acids in papermaking
The present invention relates to the use of copolymers which are
obtainable by copolymerization of N-vinylcarboxamides with other
monoethylenically unsaturated compounds and partial or complete
elimination of formyl groups from the N-vinylcarboxamides poly-
merized in the copolymer, with formation of amino or ammonium
groups, as additives to paper stock for increasing the drainage
rate and retention in papermaking and the dry and wet strength of
the paper.
US-A-2 721 140 discloses the use of polyvinylamine hydrochloride
as an assistant in papermaking, in particular papers having high
wet strength being obtained. However, the paper treated in this
manner has a relatively high tendency to yellow.
US-4 421 602 discloses partially hydrolyzed, water-soluble homo-
polymers of N-vinylformamide which contain N vinylformamide units
and vinylamine units. These polymers are used as agents for
increasing the flocculation, retention and drainage rate in
papermaking.
EP-A-0 438 744 discloses copolymers which contain, as polymerized
units, from 99 to 50$ by weight of at least one monoethylenically
unsaturated carboxylic acid of 3 to 8 carbon atoms or salts
thereof and from 1 to 50~ by weight of N-vinylcarboxamides, pre-
ferably N vinylformamide, and which have been subjected to hydro-
lysis in which the formyl groups of the N vinylcarboxamides are
eliminated with formation of amino or ammonium groups. These
copolymers are used as water treatment agents for reducing lime-
scale and water hardness deposits in water-conveying systems and
in the concentration of sugar juice.
EP-A-0 216 387 discloses water-soluble copolymers which contain
vinylamine units and are obtainable by copolymerization of N vi-
nylformamide with monoethylenically unsaturated monomers selected
from the group consisting of vinyl acetate, vinyl propionate, C1-
to C~-alkyl vinyl ethers, the esters, nitriles and amides of
acrylic acid and methacrylic acid and N vinylpyrrolidone and
elimination of the formyl groups from the copolymers. These
copolymers and, preferably, copolymers of N-vinylformamide and
vinyl acetate, from 30 to 100 mold of whose monomer units are
hydrolyzed in each case, are used as agents for increasing the
dry and wet strength of paper.
AMENDED SHEET
' 0050/43722
2
EP-B-0 251-182 discloses copolymers which contain vinylamine
groups in salt form, vinylformamide groups and acrylonitrile
groups and, a-f requited, acrylamide and acrylic acid groups. The
amount of polymerized acrylic acid or methacrylic acid is not
5 more than 6.4 moI%. These copolymers are used in papermaking and
act as drainage and retention agents and as agents for increasing
the dry strength of paper.
It is an object of the present invention to provide a further
10 paper aid which, when added to the paper stock, leads to an
increase in the mechanical strengths of the papers thus produced
and at the same time increases the drainage rate and retention.
We have found that this object is achieved, according to the
15 invention, by the use of copolymers which are obtainable by
copolymerization of
a) from 5 to 99 mol% of N vinylcarboxamides of the formula
2 O R2
CH2- CH-N~
~C-Rl tI) r
O
where R1 and R~ are each H or C1--C6-alkyl,
b) from 95 to 1 mol% of monoethylenically unsaturated carboxylic
acids of 3 to 8 carbon atoms and/or the alkali metal and
ammonium salts thereof and, if required,
c) up to 30 mol% of vinyl acetate, N-vinylpyrrolidone or N-viny-
limidazole or mixtures thereof and, if required,
d) up to 2 mol% of compounds which have at least two ethyleni-
cally unsaturated nonconjugated double bonds in the molecule,
and subsequent partial or complete elimination of
-C-R1
O
AMENDED SHEET
0050/43722
3
from the monomers I polymerized in the copolymer, with formation
of amino or ammonium groups, as additives to paper stock for in-
creasing the drainage rate and the retention in papermaking and
the dry and wet strength of the paper.
The copolymers to be used according to the invention are prepared
by free radical copolymerization of N vinylcarboxamides and mono-
ethylenically unsaturated carboxylic acids, preferably acrylic
acid and/or methacrylic acid, and salts thereof and, if required,
other monoethylenically unsaturated monomers. The copolymeriza-
tion may be carried out, if required, additionally in the pres-
ence of crosslinking agents.
Suitable monomers of group a) are N-vinylcarboxamides of the for-
mula
R2
CHy- CH-N~
~C-Rl CI).
O
where R1 and R2 are each H or C1-C6-alkyl. Examples of suitable
monomers are N vinylformamide, N-vinyl-N-methylformamide,
N-vinylacetamide, N vinyl-N~nethylacetamide, N vinyl-N-ethyl-
acetamide, N-vinyl-N~nethylpropionamide and N-vinylpropionamide.
For the preparation of the copolymers, the stated monomers may be
used either alone or as a mixture with one another. From this
group of monomers, N-vinylformamide is preferably used. The
copolymers contain the monomers of group a) in amounts of from 5
to 99, preferably from 30 to 95, mol% in polymerized form.
Suitabre monomers of group b) are monoethylenically unsaturated
carboxylic acids of 3 to 8 carbon atoms and the water-soluble
salts of these monomers. This group of monomers includes, for
example, acrylic acid, methacrylic acid, dimethylacrylic acid,
ethacrylic acid, malefic acid, citraconic acid, methylenemalonic
acid, allylacetic acid, vinylacetic acid, crotonic acid, fumaric
acid, mesaconic acid and itaconic acid. From this group of mono-
mers, acrylic acid, methacrylic acid, malefic acid or mixtures of
the stated carboxylic acids, in particular mixtures of acrylic
acid and malefic acid or mixtures of acrylic acid and methacrylic
acid, are preferably used. The monomers of group b) may be used
either in the form of the free carboxylic acids or in partially
or completely neutralized form in the copolymerization. The mono-
ethylenically unsaturated carboxylic acids are neutralized using,
for example, alkali metal or alkaline earth metal bases, ammonia
AMENDED SHEET
0050/43722
4
or amines,-for example sodium hydroxide solution, potassium
hydroxide solution, sodium carbonate, potassium carbonate, sodium
bicarbonate, magnesium oxide, calcium hydroxide, calcium oxide,
ammonium, triethylamine, ethanolamine, diethanolamine, tri-
ethanolamine, morpholine, diethylenetriamine or tetraethylene-
pentamine. The copolymers contain the monomers of group b) in an
amount of from 95 to 1, preferably from 70 to 5, mold in poly-
merized form.
The copolymers of the monomers a) and b) can, if required, be
modified by using in the copolymerization other monoethylenically
unsaturated compounds which are copolymerizable with the monomers
a) and b). Examples of suitable monomers of group c) are the
esters, amides and nitriles of the carboxylic acids stated under
a), for example methyl acrylate, ethyl acrylate, methyl methacry-
late, ethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl
acrylate, hydroxybutyl acrylate, hydroxyethyl methacrylate,
hydroxypropyl methacrylate, hydroxyisobutyl acrylate, hydroxyiso-
butyl methacrylate, monomethyl maleate, dimethyl maleate, mono-
ethyl maleate, diethyl maleate, 2-ethylhexyl acrylate, 2-ethyl-
hexyl methacrylate, acrylamide, methacrylamide, N~iimethylacryl-
amide, N-tert-butylacrylamide, acrylonitrile, methacrylonitrile,
dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate,
diethylaminoethyl acrylate or diethylaminoethyl methacrylate, and
the salts of the last-mentioned monomers with carboxylic acids or
mineral acids and the quaternized products. Other suitable mono-
mers of group c) are acrylamidoglycolic acid, vinylsulfonic acid,
allylsulfonic acid, methallylsulfonic acid, styrenesulfonic acid,
3-sulfopropyl acrylate, 3-sulfopropyl methacrylate and acrylami-
domethylpropanesulfonic acid and monomers containing phosphonic
acid groups, such as vinyl phosphate, allyl phosphate and acryl-
amidomethylpropanephosphonic acid. Further suitable compounds of
this group are N-vinylpyrrolidone, N-vinylcaprolactam, N vi-
nyl-2-methylimidazoline, diallylammonium chloride, vinyl acetate
and vinyl propionate. It is of course also possible to use mix-
tures of the stated monomers of group c), for example mixtures of
acrylates and vinyl acetate, mixtures of different acrylates,
mixtures of acrylates and acrylamides or mixtures of acrylamide
and hydroxyethyl acrylate. Among the monomers of group c),
acrylamide, acrylonitrile, vinyl acetate, N vinylpyrrolidone,
N-vinylimidazole or mixtures of these monomers, for example mix-
tures of acrylamide and vinyl acetate or mixtures of acrylamide
and acrylonitrile, are preferably used. If the monomers of group
c) are used for modifying the copolymers, they are present in the
copolymers in polymerized form in amounts of up to 30, preferably
from 1 to 20, mold.
0050/43722
The copolymers of the monomers a) and b) and, if required, c) may
furthermore be modified by carrying out the copolymerization in
the presence of monomers of group d), which are compounds which
have at least two ethylenically unsaturated nonconjugated double
5 bonds in the molecule. The presence of the monomers of group d)
in the copolymerization results in an increase in the K values of
the copolymers. Examples of suitable compounds of group d) are
methylenebisacrylamide, esters of acrylic acid and methacrylic
acid with polyhydric alcohols, such as glycol diacrylate, gly-
ceryl triacrylate, glycol dimethacrylate or glyceryl trimethacry-
late, and polyethylene glycols or polyols, such as pentaerythri-
tol and glucose, which are at least diesterified with acrylic
acid or methacrylic acid. Other suitable crosslinking agents are
divinylbenzene, divinyldioxane, pentaerythrityl triallyl ether
and 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. If the monomers of group d) are used for modifying the
copolymers, the amounts employed are up to 2 mol%. Where they are
used, they are preferably present in the copolymers in poly-
merized form in an amount of from 0.01 to 1 mol%.
It is preferable to use the compounds which are obtainable by
copolymerization of
a) from 30 to 95 mol% of N vinylformamide,
b) from 70 to 5 mol% of acrylic acid, methacrylic acid and/or
the alkali metal, alkaline earth metal, ammonium or amine
salts thereof and
c) from 0 to 30 mol% of acrylamide, acrylonitrile, vinyl ace-
tate, N-vinylpyrrolidone, N vinylimidazole or mixtures there-
of, and subsequent partial or complete hydrolysis of the
polymerized N-vinylformamide units, for example copolymers of
N-vinylformamide, acrylic acid and acrylamide, copolymers of
N vinylformamide, acrylic acid and acrylonitrile, copolymers
of N vinylformamide, acrylic acid and vinylacetate, copoly-
mers of N-vinylformamide, acrylic acid and N vinylpyrroli-
done, copolymers of N vinylformamide, acrylic acid, acrylo-
nitrile and vinyl acetate, and copolymers of N-vinylforma-
mide, acrylic acid, acrylamide and acrylonitrile. In the
copolymers last described, some or all of the acrylic acid
may be replaced by methacrylic acid. Acrylic acid or meth-
acrylic acid may be partially or completely neutralized with
0050/43722
214~2~88
6
sodium hydroxide solution, potassium hydroxide solution, cal-
cium hydroxide or ammonia.
The copolymers are prepared by known processes, for example solu-
tion, precipitation, suspension or emulsion polymerization, using
compounds which form free radicals under the polymerization
conditions. The polymerization temperatures are usually from 30
to 200~C, preferably from 40 to 110~C. Examples of suitable
initiators are azo and peroxy compounds and the conventional
redox initiator systems, such as combinations of hydrogen
peroxide and reducing compounds, eg. sodium sulfite, sodium
bisulfate, sodium formaldehyde sulfoxylate and hydrazine. These
systems can, if required, additionally contain small amounts of a
heavy metal salt.
The copolymers are preferably prepared by solution polymerization
in water, the monomers of group b) preferably being used in salt
form and the pH being kept at from 6 to 8 during the polymeriza-
tion. In order to keep the pH constant during the copolymeriza-
tion, it is advantageous to add small amounts, for example from
0.5 to 2% by weight, of a buffer, for example disodium hydrogen
phosphate. Preferably used polymerization initiators are water-
soluble azo compounds, such as 2,2'-azobis(2-methylpropion-
amidine) dihydrochloride, 2,2'-azobis(4-methoxy-2,4-dimethylval-
eronitrile) and 2,2'-azobis(2-methyl-N-phenylpropionamidine) di-
hydrochloride.
In order to prepare low molecular weight copolymers, the copoly-
merization is carried out in the presence of a regulator. Exam-
ples of suitable regulators are secondary alcohols, such as iso-
propanol and sec-butanol, hydroxylamine, formic acid and mercapto
compounds, such as mercaptoethanol, mercaptopropanol, mercaptobu-
tanol,-~hioglycolic acid, thiolactic acid, tert-butyl mercaptan,
octyl mercaptan and dodecyl mercaptan. The regulators are usually
used in amounts of from 0.01 to 5% by weight, based on the mono-
mers used. If secondary alcohols are used as regulators, the
polymerization may also be carried out in the presence of sub-
stantially larger amounts, for example up to 80% by weight, based
on the monomers. In these cases, the secondary alcohols are
simultaneously solvents for the monomers.
The copolymers thus obtainable have K values of from 30 to 300,
preferably from 50 to 250. The K values are determined according
to H. Fikentscher, in 5% strength aqueous sodium chloride solu-
tion at pH 7, 25'C and a polymer concentration of 0.1% by weight.
0050/43722
7
The hydrolyzed copolymers to be used according to the invention
are obtained, with formation of amino or ammonium groups, from
the copolymers described above, by partial or complete elimina-
tion of the formyl groups from the monomers I polymerized in the
copolymer:
- CH2 - CH- - CH2 - CH-
Hydrolysis
,\ ,\
R2 C- R1 R2 H
O
(II) (III)
In the formulae (II) and (III), R1 and Rz each have the meanings
stated in formula (I). Depending on the reaction conditions cho-
sen in the hydrolysis, either partial or complete hydrolysis of
the units II is obtained. The hydrolysis is continued so that
from 30 to 100, preferably from 60 to 95, % of the monomers a)
polymerized in the copolymer are hydrolyzed. In the case of the
hydrolysis of copolymers containing vinylformamide units, the
degree of hydrolysis can be determined, for example, by polyelec-
trolyte titration or by enzymatic analysis of the liberated for-
mic acid. If the copolymers contain polymerized monomers of group
c) in addition to the monomers a) and b), the polymerized mono-
mers c) may also be chemically changed, depending on the chosen
hydrolysis conditions; for example, vinyl alcohol units are
formed from vinyl acetate units, acrylic acid units from methyl
acrylate units, and acrylamide or acrylic acid units from acrylo-
nitrile units. The degree of hydrolysis of the abovementioned
units II is preferably from 60 to 95%.
Particularly suitable hydrolysis agents are mineral acids, such
as hydrogen halide, which can be used in gaseous form or in
aqueous solution. Hydrochloric acid, sulfuric acid, nitric acid
and phosphoric acid and organic acids, such as C1-C5-carboxylic
acids and aliphatic or aromatic sulfonic acids, are preferably
used. The pH in the acidic hydrolysis is from -1 to 5, preferably
from 0 to 2. From 0.05 to 2, preferably from 1 to 1.5, mole
equivalents of an acid are required per equivalent of formyl
groups which is to be eliminated from the polymerized units II.
0050/43722
8
The hydrolysis of the polymerized units of the structure II can
also be carried out with the aid of bases, for example metal
hydroxides, in particular alkali metal or alkaline earth metal
hydroxides. Sodium hydroxide or potassium hydroxide is preferably
used. The hydrolysis can, if required, also be carried out in the
presence of ammonia or amines.
The hydrolysis of the copolymers in aqueous solution or suspen-
sion at reaction temperatures of from 20 to 100°C has proven
particularly suitable. If the unhydrolyzed copolymers are poorly
soluble in water, they generally dissolve in the reaction medium
as the hydrolysis progresses. After an acidic hydrolysis, the
reaction mixture is, if required, neutralized with bases, prefer-
ably sodium hydroxide solution. If the hydrolysis has been car-
ried out using a base, the reaction mixture can, if required, be
neutralized by adding an acid, preferably hydrochloric acid.
After the hydrolysis, the pH of the reaction mixture may be from
1 to 10, preferably from 3 to 8. Depending on the composition,
the hydrolyzed copolymers may be poorly soluble in certain pH
ranges. The K value of the hydrolyzed copolymers is from 10 to
300, preferably from 15 to 200 (measured in 5% strength aqueous
sodium chloride solution at a polymer concentration of 0.1% by
weight, a pH of 1.5 and 25°C).
According to the invention, the hydrolyzed copolymers are used in
papermaking. They are added to the paper stock in amounts of from
0.01 to 5, preferably from 0.1 to 2, % by weight, based on dry
fibers. The hydrolyzed copolymers both increase the drainage rate
and the retention in papermaking and at the same time increase
the dry and wet strength of the paper.
The K values of the copolymers were determined according to
H. Fikehtscher, Cellulosechemie, ~ (1932), 48-64 and 71-74, in
5% strength aqueous sodium chloride solution at 25°C and at a
polymer concentration of 0.1% by weight, the K value of the unhy-
drolyzed copolymers being measured at pH 7 and that of the hydro-
lyzed copolymers at 1.5.
Examples
Preparation of the copolymers
Copolymer 1
991 g of distilled water, 1.54 g of 75% strength phosphoric acid
and 1.06 g of 50% strength aqueous sodium hydroxide solution are
heated to 70°C in a gentle stream of nitrogen in a polymerization
0050/43722 2 ~ 4,,5 2 8~~
9
apparatus equipped with a stirrer. As soon as this temperature
has been reached, in the course of 2 hours a solution of 50 g of
water, 39.2 g of acrylic acid and 43.6 g of 50% strength aqueous
sodium hydroxide solution, separately from this 160 g of N-vinyl-
formamide and likewise separately from this a solution of 25 g of
water and 0.05 g of 2,2'-azobis(2-methylpropionamidine) dihy-
drochloride, are added uniformly. After the end of the monomer
addition, a solution of 0.15 g of 2,2'-azobis(2-methylpropionami-
dine) dihydrochloride in 73 g of water is metered in over 1 hour,
and the reaction mixture is then stirred for a further 2 hours at
70°C and is then diluted with 800 g of water. The highly viscous
solution thus obtainable has a solids content of 10.9% and a pH
of 6.2. The K value of the copolymer is 177.
Hydrolysis of the polymerized N vinylformamide of copolymer 1
500 g of the aqueous solution, described above, of a copolymer of
75.4% by weight of vinylformamide and 24.6% by weight of sodium
acrylate, having a K value of 177, are initially taken in an
apparatus equipped with a stirrer and are diluted with 250 g of
water. The mixture is first stirred at room temperature, and
80.2 g of 38% strength hydrochloric acid are added in the course
of 20 minutes. Thereafter, the reaction mixture is heated at 70°C
for 7 hours and is cooled to room temperature, and 120 g of a 10%
strength aqueous sodium hydroxide solution are added. The pH of
the reaction mixture is then 1.5. In order to stabilize the reac-
tion mixture, 15 g of 0.5% strength aqueous sodium bisulfite
solution are added. The degree of hydrolysis of the polymerized
N-vinylformamide is 93%. The solution has a polymer content of
5.8% by weight (hydrolyzed copolymer 1). The K value of the
polymer is 135.
Copolymer 2
965.3 g of water, 1.34 g of a 75% strength aqueous phosphoric
acid and 0.92 g of a 50% strength aqueous sodium hydroxide solu-
tion are heated to 70°C in a stream of nitrogen in a polymeriza-
tion apparatus. As soon as this temperature has been reached, a
mixture of 100 g of water, 60 g of acrylic acid and 66.5 g of 50%
strength aqueous sodium hydroxide solution, separately from this
141.4 g of N vinylformamide and likewise separately from this a
solution of 0.05 g of 2,2'-azobis(2~nethylpropionamidine) dihy-
drochloride in 25 g of water are added uniformly, in each case in
the course of 2 hours. After the end of the addition of initiator
and monomers, a solution of 0.15 g of 2,2'-azobis(2~nethyl-
propionamidine) dihydrochloride, dissolved in 73 g of water, is
added in the course of 1 hour, the reaction mixture is kept at
0050/43722
~1~528~
i0
70'C during this time and for 2 hours after the addition of the
initiator. 800 ml of water are then added, and a highly viscous
solution which has a solids content of 11.0% and a pH of 6.6 is
obtained. The K value of the copolymer is 172.
Hydrolysis
500 g of the aqueous solution, described above, of the copolymer
of 64.1% by weight of N-vinylformamide and 35.9% by weight of
sodium acrylate are initially taken in a stirred apparatus and
are diluted by adding 250 g of water. 77.2 g of 38% strength
hydrochloric acid are then added in the course of 20 minutes at
room temperature. The reaction mixture is then heated to 70~C and
stirred for 8 hours at this temperature. Thereafter, it is cooled
to room temperature and 120 g of 10% strength aqueous sodium
hydroxide solution are added. The pH of the mixture is then 1.5.
In order to stabilize the reaction mixture, 15 g of 0.5% strength
aqueous sodium bisulfite solution are added. The degree of hydro-
lysis of the polymerized N-vinylformamide is 95%. The reaction
solution has a polymer content of 5.6%. The copolymer contains
vinylamine hydrochloride units, vinylformamide units and acrylic
acid units (hydrolyzed copolymer 2). The K value of the polymer
is 126.
Example 1
A 0.5% strength stock suspension in water was prepared from 50%
of spruce sulfite pulp and 50% of beech sulfite pulp. The pH of
the stock suspension was 7.0 and the Schopper-Riegler (SR) free-
ness was 30~. The stock suspension was then divided into 5 equal
parts, 4 of which were mixed with the additives stated under b)
to e). The 5 stock suspensions were then processed to give sheets
having-a basis weight of 80 g/ma in a Rapid-Kothen laboratory
sheet former:
Composition of the stock suspensions:
a) The stock suspension contained no further additives.
b) 1%, based on the fibers, of an aqueous solution of a commer-
cial neutral wet strength resin based on a reaction product
of epichlorohydrin aid a polyamidoamine obtained from diethy-
lenetriamine and adipic acid was added to the stock suspen-
sion.
0050/43722
11
c) 1%, ba-sed on fiber, of an aqueous solution of a polyvinyl-
amine hydrochloride according to US A 2 721 140 was added to
the stock suspension.
d) 1%, based on fiber, of the hydrolyzed copolymer 1 was added
to the stock suspension.
e) 1%, based on fiber, of the hydrolyzed copolymer 2 was added
to the stock suspension.
The sheets a) to e) were produced from the paper stock suspen-
sions described above. The whiteness, the dry breaking length and
the wet breaking length of the sheets obtained were measured. The
results are shown in Table 1.
Table 1
a) b) c) d) e)
Comparison (According
to the invention)
Whiteness (% 77.973.5 73.4 73.1 74.0
ref lectance )
Dry breaking length 23542903 2927 3102 2895
(m)
Wet breaking length
(m)
Unaged 104 908 978 1009 956
Edged 5 min at 110~C 106 1032 1005 1118 1040
Example 2
A 0.5% strength stock suspension in water was prepared from 50%
of spruce sulfite pulp and 50% of beech sulfite pulp. The pH of
the stock suspension was 4.5 and the freeness was 30~SR. The stock
suspension was then divided into 5 equal parts, of which the
samples b) tc~_e) were each mixed with 1%, based on dry fiber, of
the additives stated below. The following stock suspensions were
processed:
a) The stock suspension described above contained no further
additives.
b) An aqueous solution of a commercial wet strength resin based
on a reaction product of urea and formaldehyde was added to
the stock suspension.
c) ~ aqueous solution of a hydrolyzed copolymer of 70% of N vi-
nylformamide and 30% of vinyl acetate was added to the stock
suspension, the K value of the polymer being 100 and the
r . 0050/43722
12
degree of hydrolysis of N vinylformamide and vinyl acetate
being >90%.
d) The hydrolyzed copolymer 1 was added to the stock suspension.
e) The hydrolyzed copolymer 2 was added to the stock suspension.
The stock suspensions described above were processed on a Rapid-
Kothen apparatus to give the sheets a) to e). The whiteness, dry
breaking length and wet strength of the sheets obtained are shown
in Table 2.
Table 2
a) b) c) d) e)
Comparison (According
to the invention)
Whiteness (% 80.4 77.9 75.1 75.3 75.8
reflectance)
Dry breaking length 3278 3817 3950 4551 4159
(m)
Wet breaking length
(m)
Unaged 134 796 1024 1101 877
Aged 5 min at 130C 143 1031 1062 1196 998
Example 3
A 0.2% strength stock suspension in water was prepared from mixed
waste paper. The pH of the suspension was 7 and the freeness was
67°SR. The stock suspension was divided into 10 equal parts. One
sample of the stock suspension remained unchanged, while the
additives stated below were added to the other 9 samples. The
following samples were available:
a) The stock suspension described above contains no further
additives.
b) 0.1%, based on the solids, of a 0.1% strength aqueous solu-
tion 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 described above.
c) 0.2%, based on the solids, of the commercial neutral wet
strength resin described under b) was added to the stock sus-
pension described above.
0050/43722
13
d) 0.4%, based on the solids, of the commercial neutral wet
strength resin described under b) was added to the stock sus-
pension described above.
e) 0.1%, based on the solids, of a 0.1% strength aqueous solu-
tion of the hydrolyzed copolymer 2 was added to the stock
suspension described above.
f) 0.2%, based on the solids, of a 0.1% strength aqueous solu-
tion of the hydrolyzed copolymer 2 was added to the stock
suspension described above.
g) 0.4%, based on the solids, of a 0.1% strength aqueous solu-
tion of the hydrolyzed copolymer 2 was added to the stock
suspension described above.
h) 0.1%, based on the solids, of a 0.1% strength aqueous solu-
tion of the hydrolyzed copolymer 1 was added to the stock
suspension described above.
i) 0.2%, based on the solids, of a 0.1% strength aqueous solu-
tion of the hydrolyzed copolymer 1 was added to the stock
suspension described above.
j) 0.4%, based on the solids, of a 0.1% strength aqueous solu-
tion of the hydrolyzed copolymer 1 was added to the stock
suspension.
After the additive had been allowed to act for 5 minutes, the
samples b) to j) were each drained in a laboratory sheet former
with formation of sheets having a basis weight of 68 g/m2. In
order to determine the ash content and hence obtain a measure of
the retention, the sheets were incinerated in a muffle furnace at
from 900 to 1-OOO~C and the residue on ignition was determined
gravimetrically. The results obtained are shown in Table 3.
Table 3
Example % Ash in paper Addition in
%
a) Comparative Example 5.1 0
b) Comparative Example 8.6 0.1
c) Comparative Example 9.0 0.2
d) Comparative Example 10.1 0.4
e) (According to the invention)10.2 0.1
f) (According to the invention)11.2 0.2
g) (According to the invention)11.6 0.4
. 0050/43722
14
h) (Accordi-ngto invention) 10.4 0.1
the
i) (Accordingto invention) 11.1 0.2
the
j) (Accordingto invention) 11.4 0.4
the
Example 4
A 0.2% strength stock suspension in water was prepared from mixed
waste paper. The pH of the stock suspension was 7 and the free-
ness was 67°SR. The stock suspension was divided into 10 equal
parts, 9 of which were mixed with the additives stated below:
a) This sample contained no additives.
b) 0.1%, based on the solids, of a 0.1% strength aqueous solu-
tion 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) 0.25% of the commercial neutral wet strength resin described
under b) was added to the suspension described above.
d) 0.4%, based on the solids, of the neutral wet strength resin
described under b) was added to the stock suspension
described above.
e) 0.1%, based on the solids, of a 0.1% strength aqueous solu-
tion of the hydrolyzed copolymer 2 was added to the stock
suspension.
f) 0.25% of the hydrolyzed copolymer 2 was added to the suspen-
sion.
g) 0.4%, based on the solids, of the hydrolyzed copolymer 2 was
added to the suspension.
h) 0.1%, based on the solids, of a 0.1% strength aqueous solu-
tion of the hydrolyzed copolymer 1 was added to the stock
suspension described above.
i) 0.25%, based on the solids, of the hydrolyzed copolymer 1 was
added to the stock suspension.
~) 0~4%, based on the solids, of the hydrolyzed copolymer 1 was
added to the suspension.
0050/43722 ~ 14 ~ 2 8 ~
After an action time of 5 minutes, the samples described above
were drained on a Schopper-Riegler apparatus at room temperature.
The drainage time is shown in Table 4.
5 Table 4
Example Drainage time (s/700 Addition
ml) in
a) Comparative Example 89 0
10
b) Comparative Example 68 0.1
c) Comparative Example 60 0.25
d) Comparative Example 50 0.4
e) (According to the invention)57 0.1
15f) (According to the invention)21 0.25
g) (According to the invention)10 0.4
h) (According to the invention)46 0.1
i) (According to the invention)31 0.25
j) (According to the invention)21 0.4
30
40
