Note: Descriptions are shown in the official language in which they were submitted.
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Filler-containing paper and a method for the production of filler-containing
paper
Description
The present invention relates to filler-containing paper and to a method for
the produc-
tion of filler-containing paper; more particularly, it relates to filler-
containing paper such
as base paper for construction materials, India paper or tip base paper for
cigarettes
which has excellent properties such as opacity and whiteness, etc, by
efficiently fixing
and uniformly dispersing, in the paper, an inorganic compound comprising
titanium
dioxide and/or calcium carbonate, and to a method for the efficient production
of this
filler-containing paper.
The properties demanded of paper include not only strength and degree of
sizing but
also optical properties such as the opacity and whiteness. In particular,
taking the case
of paper for construction materials typified by the base paper for decorative
laminated
sheet, since this is affixed to a base material, opacity is demanded so that
the base
material region is not visible therethrough. Furthermore, in the case of the
India paper
used for dictionaries and the like, it is important that text and images are
not visible
from the reverse side. In the case of the tip base paper used in the filter
region of ciga-
rettes, as well as it being necessary that a large amount of inorganic
material be incor-
porated into the paper so that it does not readily catch fire in the presence
of a flame,
opacity is required so that the part of the filter region containing active
carbon is not
visible through the white tip paper which is not usually printed over its
entire surface.
Moreover, recently, even in the case of paper for books, PPC (plain paper
copier) pa-
per and ordinary printing and writing paper, known as coated paper, the
problem has
arisen of a lowering of the level of opacity due to the trend for paper weight
to be re-
duced from the point of view of more economic use of pulp resources, so a
method for
improving the filler efficiency in the paper is required.
In order to enhance the optical characteristics of paper, namely the whiteness
and o-
pacity, there is known the method of performing papermaking with the addition
to the
pulp slurry of papermaking fillers typified by calcium carbonate and titanium
dioxide. In
particular, titanium dioxide has a high light scattering capacity and is
widely used for
the purposes of conferring a high level of opacity on paper. However, when
compared
to other papermaking fillers, the particle diameter of titanium dioxide is low
and the y-
ield at the time of papermaking in the papermaking machine is extremely low.
Since
the yield is low, build-up on and contamination of the papermaking machine and
other
ancillary equipment occurs. Hence, the frequency of cleaning of the
papermaking ma-
chine is increased and a lowering of the production efficiency is brought
about. Fur-
thermore, waste originating in this build-up and contamination by the filler
is incorpo-
rated into the paper, leading to the problem of a lowering of paper quality.
This is not
restricted to titanium dioxide and even when there are used fillers such as
light calcium
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2
carbonate, if it is desired to increase the proportion of filler in the paper
with the objec-
tive of enhancing the opacity it is necessary to increase the amount of filler
added to
the pulp slurry. However, in so doing, the amount of filler which is unfixed
and is dis-
charged into the white water system is also increased and the same kind of
problems
are brought about as in the case of the titanium dioxide above.
In order to raise the yield of filler, there have been used hitherto yield
enhancers such
as polyacrylamide resins, polyamideamine-epichlorohydrin resins or
polyethyleneimine
resins, etc. However, the filler yield is still inadequate and if the amount
of yield en-
hancer added is increased in order to improve the yield there is considerable
coagula-
tion of the filler, with the result that the distribution of the filler in the
paper becomes
non-uniform and, in spite of their being sufficient filler present in the
paper, the level of
opacity of the paper remains low.
While a method is already known for enhancing filler yield by means of a
polyvinyl-
amine polymer obtained by polymerization of N-vinylformamide followed by
hydrolysis
of the formyl groups, in the Specification relating thereto only clay is
specifically exem-
plified as a filler and there are no examples relating to titanium dioxide or
to calcium
carbonate (see JP-A-58-23809). Furthermore, in another known reference which
ex-
pressly describes the titanium dioxide yield enhancing effect of a
polyvinylamine poly-
mer obtained by polymerization of N-vinylformamide followed by hydrolysis of
the for-
myl groups, as well as the amount of added polymer being high it states that
it is nec-
essary to use an organic solvent in the polymer production process, which is
undesir-
able for operational and environmental reasons (see JP-A-2-6685).
Furthermore, recently there have been disclosures of a method using an
amphoteric
water-soluble copolymer and anionic colloidal silica and/or bentonite (see
Japanese
Patent No.3218557) and, in particular, as a method aimed at enhancing the
yield of
titanium dioxide, a method of papermaking in which there are added to the pulp
slurry a
wet paper strengthener, sodium aluminate and alum (see JP-A-8-246389) and a
method of papermaking in which carboxymethyl cellulose and aluminium sulphate
are
added to the pulp slurry (see JP-A-2003-89994) but, as yet, it has not been
possible to
achieve high opacity efficiently with just a small amount of filler.
The present invention has been made in view of this situation and has the
objective of
providing a filler-containing paper where, by efficiently fixing the filler to
the pulp fibre
without excessive coagulation thereof compared to hitherto, the ash content of
the pa-
per and the opacity of the paper are enhanced and it is possible to confer
outstanding
optical properties. Furthermore, the present invention also has the objective
of provid-
ing a method for the production of filler-containing paper which enables the
amount of
filler employed at the time of papermaking to be lowered, the contamination of
the pa-
permaking machine and ancillary equipment originating in unfixed filler to be
reduced,
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3
and a lowering of the environmental burden and an improvement in the economic
effi-
ciency to be realized.
The present inventors have carried out considerable investigation to resolve
the afore-
said problems, as a result of which they have discovered that by carrying out
paper-
making with a slurry which includes (A) the hydrolysate of polymer containing
at least
N-vinylformamide as a polymerization component and (B) titanium dioxide and/or
cal-
cium carbonate, it is possible to obtain paper which resolves the aforesaid
problems.
The present invention has been perfected based on this discovery.
Specifically, a first means for overcoming the aforesaid problems according to
the pre-
sent invention is
(1) filler-containing paper which is characterized in that it contains the
following compo-
nent (A) and the following component (B) and, furthermore, the ash content of
the pa-
per is 3-40 wt%.
(A) Polymer obtained by 20 to 100% hydrolysis of the total formyl groups in a
polymer
having at least N-vinylformamide as a polymerization component
(B) Titanium dioxide and/or calcium carbonate
A second means for overcoming the aforesaid problems according to the present
in-
vention is
(2)' filler-containing paper according to (1) above which is characterized in
that compo-
nent (A) is polymer obtained by polymerization in an aqueous medium.
A third means for overcoming the aforesaid problems according to the present
inven-
tion is
(3) filler-containing paper according to (1) or (2) which is characterized in
that it is base
paper for construction materials, India paper or tip base paper for
cigarettes.
A fourth means for overcoming the aforesaid problems according to the present
inven-
tion is
(4)" a method for the production of filler-containing paper which is
characterized in that
component (A) described in (1) or (2) above is added to the pulp slurry such
that the
percentage addition of said component (A) to the pulp slurry is least 0.0005%
but less
than 0.05% by solids concentration conversion in terms of the pulp.
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A fifth means for overcoming the aforesaid problems is
(5) a method for the production of filler-containing paper according to (4)
which is char-
acterized in that component (A) and component (B) described in (1) or (2)
above are
added to the pulp slurry such that the mass ratio of said component (A) to
component
(B) described in (1) or (2) is of proportions [component (A)/component (B)] =
0.001 /100
to 0.5/100 by solids concentration conversion.
The invention as claimed in however more specifically directed to a method for
the
production of filler-containing paper by dewatering a pulp slurring in the
presence of
a cationic polymer containing vinylamine units and a filler to obtain an ash
content of
the paper of 3-40 wt%, which is characterized in that:
(A) at least 0.0005% but less than 0.05% wt%, by conversion to solids
concentration in terms of the pulp, of a polymer obtained by 20 to 100%
hydrolysis of the total formyl groups in a polymer having at least N-
vinylformamide as a poplymerization component is added to the pulp slurry
as a fixing agent for
(B) titanium dioxide and/or calcium carbonate.
In accordance with the present invention, it is possible to enhance the ash
content of
the paper and the level of paper opacity, and to confer outstanding optical
properties
on the paper, by efficiently fixing the filler to the pulp fibre without
excessive coagula-
tion thereof when compared to hitherto. Moreover, the amount of filler used at
the time
of production can be reduced, the contamination of the papermaking machine and
an-
cillary equipment due to unfixed filler can be lowered, and it is possible to
achieve a
reduction in the environmental burden and improved economic efficiency, so the
con-
tribution of the invention to developments in the industrial field of
papermaking is con-
siderable.
The present invention is now explained in detail.
The filler-containing paper of the present invention contains component (A),
which is a
specified polymer, and component (B), which is a specified inorganic compound.
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4a
Component (A) in the present invention is a polymer formed by 20 to 100%
hydrolysis
of the total formyl groups in a polymer having at least N-vinylformamide as a
polymeri-
zation component.
As examples of polymer in which at least N-vinylformamide is a polymerization
compo-
nent, there are the homopolymer obtained by the polymerization of N-
vinylformamide
and the copolymers obtained by the copolymerization of N-vinylformamide and
mono-
mers copolymerizable with N-vinylformamide (below said homopolymer and
copolyrner
are sometimes merely referred to together as'polymer'). In the present
invention, the-
re can also be used mixtures of homopolymer and copolymer.
Examples of the aforesaid monomers which are copolymerizable with N-
vinylformamide include the following vinyl compounds with a side chain group
which
contains a nitrogen atom, the vinyl or propenyl esters of saturated carboxylic
acids,
nonionic (meth)allyl monomers, (meth)allyl monomers having a side chain which
con-
tains a cationic nitrogen atom, olefins, ethylenically-unsaturated carboxylic
acids, es-
ters or amides of these ethylenically-unsaturated carboxylic acids, monomers
with a
nitrile group, monomers with a suiphonic acid group, monomers with a
phosphoric acid
group and styrene-type monomers.
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Specific examples of the aforesaid vinyl compounds with a side chain group
which con-
tains a nitrogen atom are N-vinyl carboxylic acid amides such as N-
vinylacetamide and
N-vinylpropionamide, N-substituted-N-vinyl carboxylic acid amides such as N-
methyl-
5 N-vinylacetamide and N-ethyl-N-vinylacetamide, N-vinyl lactams such as N-
vinyl-
pyrrolidone and N-vinylcaprolactam, N-vinyl-N-alkylamines in which an alkyl
group with
from 1 to 6 carbon atoms is bonded to the nitrogen atom such as N-vinyl-N-
methylamine and N-vinyl-N-ethylamine, and also vinyl-heterocyclic compounds
such as
N-vinylimidazole, 2-vinylimidazole, N-vinyl-2-methyl-imidazole, N-vinyl-4-
methyl-
imidazole, N-vinyl-5-methylimidazole, N-vinyl-2-ethylimidazole, N-
vinylimidazoline, N-
vinyl-2-methylimidazoline, N-vinyl-2-ethylimidazoline, N-vinyloxazole and N-
vinyloxazoline.
The N-vinylimidazole and N-vinylimidazoline can be employed in their free base
form,
or they can be employed in the form obtained by neutralization with acid or in
the qua-
ternized form. Examples of said acid are mineral acids such as hydrochloric
acid, car-
bonic acid, sulphuric acid and nitric acid, and organic acids such as
sulphonic or car-
boxylic acids like formic acid, acetic acid and propionic acid. The
quaternization can be
carried out for example using an alkyl halide such as methyl chloride or
methyl bro-
mide, an aralkyl halide such as benzyl chloride or benzyl bromide, a dialkyl
sulphate
such as dimethyl sulphate or diethyl sulphate, or an epihalohydrin such as
epichioro-
hydrin or epibromohydrin.
As examples of the aforesaid vinyl esters of saturated carboxylic acids, there
are vinyl
formate, vinyl acetate, vinyl propionate and vinyl butyrate, and as examples
of the pro-
penyl esters of saturated carboxylic acids, there are propenyl formate,
propenyl acetate
and propenyl propionate.
Examples of the aforesaid nonionic (meth)allyl monomers include (meth)allyl
alcohols
such as allyl alcohol and methallyl alcohol, (meth)allyl halides such as allyl
chloride,
allyl bromide, methallyl chloride and methallyl bromide, (meth)allyl ethers in
which an
alkyl group with from 1 to 18 carbons is ether-bonded such as allyl methyl
ether, allyl
ethyl ether, methallyl methyl ether and methallyl ethyl ether, and (meth)allyl
esters of
saturated carboxylic acids with from 1 to 18 carbons such as allyl formate,
allyl acetate,
allyl propionate, methallyl formate and methallyl acetate.
Examples of the aforesaid (meth)allyl monomers with a side chain group which
con-
tains a cationic nitrogen atom are (meth)allylamines like allylamine and
methallylamine,
N-alkyl (meth)allylamines which have an alkyl group with from 1 to 18 carbons
bonded
to the nitrogen atom such as N-methylallylamine, N-ethylallylamine, N-
stearylallylamine, N-methylmethallylamine and N-ethylmethallylamine, N,N-
dialkyl
(meth)allylamines which have alkyl groups with from 1 to 18 carbons bonded to
the
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nitrogen atom such as N,N-dimethylallylamine, N,N-diethylallylamine, N,N-
dimethylmethallylamine, N,N-diethylmethallylamine, N-methyl-N-
stearylmethallylamine
and N,N-distearylmethallylamine, N,N,N-trialkyl (meth)allylammonium halides
which
have alkyl groups with from 1 to 18 carbons bonded to the nitrogen atom such
as
N,N,N-trimethylallylammonium chloride, N,N,N-triethylammonium chloride, N,N,N-
trimethylmethallylammonium chloride, N,N,N-triethylmethallylammonium chloride,
N-
methyl-N,N-distearylmethallylammonium chloride and N,N-dimethyl-N-
stearylmethallylammonium chloride, di(meth)allylamines such as diallylamine
and di-
methallylamine, N-alkyl di(meth)allylamines which have an alkyl group with
from 1 to 18
carbons bonded to the nitrogen atom such as N-methyldiallylamine, N-
ethyldiallylamine, N-methyldimethallylamine, N-ethyidimethallylamine and N-
stearyldimethallylamine, and N,N-dialkyl di(meth)allylammonium halides which
have
alkyl groups with from 1 to 18 carbons bonded to the nitrogen atom such as N,N-
dimethyldiallylammonium chloride, N,N-diethyldiallylammonium chloride, N,N-
dimethyldimethallylammonium chloride, N,N-diethyldimethallylammonium chloride
and
N,N-distearyldimethallylammonium chloride.
The aforesaid (meth)allylamines, N-alkyl(meth)allylamines, N,N-
dialkyl(meth)allylamines and N-alkyldi(meth)allylamines can be employed in
their free
base form, or they can be employed in the form obtained by neutralization with
acid or
in the quaternized form. Examples of said acid are mineral acids such as
hydrochloric
acid, carbonic acid, sulphuric acid and nitric acid, and organic acids such as
sulphonic
or carboxylic acids like formic acid, acetic acid and propionic acid. The
quaternization
can be carried out for example using an alkyl halide such as methyl chloride
or methyl
bromide, an aralkyl halide such as benzyl chloride or benzyl bromide, a
dialkyl sulphate
such as dimethyl sulphate or diethyl sulphate, or an epihalohydrin such as
epichloro-
hydrin or epibromohydrin.
As examples of the aforesaid olefins, there are ethylene, propylene and
butadiene.
As examples of the aforesaid ethylenically-unsaturated carboxylic acids there
are acry-
lic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride,
fumaric acid,
itaconic acid, itaconic anhydride, citraconic acid, citraconic anhydride,
cinnamic acid,
vinyl ester acids, 2-(meth)acrylamidoglycolic acid, a,R-unsaturated-
tricarboxylic acids
and a,f3-unsaturated tetracarboxylic acids, together with the alkali metal
salts, alkaline
earth metal salts and ammonium salts thereof.
Examples of the aforesaid ethylenically unsaturated carboxylic acid esters are
(meth)acrylate esters in which an alkyl group with from 1 to 18 carbon atoms
is ester-
bonded, such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl
methacry-
late, isobutyl methacrylate, tert-butyl methacrylate, 2-ethylhexyl acrylate
and stearyl
acrylate, (meth)acrylate esters where only a single hydroxy group has been
esterified
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such as hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl
acrylate, hy-
droxybutyl acrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, 2-
methoxybutyl acrylate, 2-methoxybutyl methacrylate and the acrylic acid
monoesters of
polyalkylene glycols of molecular weight 500 to 10,000, and the esters of an
aminoal-
cohol and (meth)acrylic acid such as dimethylaminoethyl acrylate,
dimethylaminoethyl
methacrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate,
dimethyl-
aminopropyl acrylate, dimethylaminopropyl methacrylate, diethylaminopropyl
acrylate,
dimethylaminobutyl acrylate and diethylaminobutyl acrylate.
These carboxylic acid esters of aminoalcohols can be employed in their free
base form,
or they may be employed in the form obtained by neutralization with acid or in
the qua-
ternized form. Examples of said acid are mineral acids such as hydrochloric
acid, car-
bonic acid, sulphuric acid and nitric acid, and organic acids such as
sulphonic or car-
boxylic acids like formic acid, acetic acid and propionic acid. The
quaternization can be
carried out for example using an alkyl halide such as methyl chloride or
methyl bro-
mide, an aralkyl halide such as benzyl chloride or benzyl bromide, a dialkyl
sulphate
such as dimethyl sulphate or diethyl sulphate, or an epihalohydrin such as
epichloro-
hydrin or epibromohydrin.
The aforesaid amides of the ethylenically-unsaturated carboxylic acids include
the N-
alkyl monoamides and N-alkyldiamides of monoethylenically unsaturated
carboxylic
acids which have an alkyl group with from 1 to 6 carbons, examples of which
are acry-
lamide, methacrylamide, N-methylacrylamide, N,N-dimethylacrylamide, N-
methylmethacrylamide, N-ethylacrylamide, N-isopropylacrylamide and N-tert-
butylacrylamide, and N,N-dialkylaminoalkyl (meth)acrylamides such as
dimethylamino-
ethyl acrylamide, dimethylaminoethyl methacrylamide, diethylaminoethyl
acrylamide,
diethylaminoethyl methacrylamide, dimethylaminopropyl acrylamide,
diethylaminopro-
pyl acrylamide, dimethylaminopropyl methacrylamide and diethylaminopropyl
methac-
rylamide.
The aforesaid N,N-dialkylaminoalkyl (meth)acrylamides can be employed in their
free
base form, or they can be employed in the form obtained by neutralization with
acid or
in the quaternized form. Examples of said acid are mineral acids such as
hydrochloric
acid, carbonic acid, sulphuric acid and nitric acid, and organic acids such as
sulphonic
or carboxylic acids like formic acid, acetic acid and propionic acid. The
quaternization
can be carried out for example using an alkyl halide such as methyl chloride
or methyl
bromide, an aralkyl halide such as benzyl chloride or benzyl bromide, a
dialkyl sulphate
such as dimethyl sulphate or diethyl sulphate, or an epihalohydrin such as
epichloro-
hydrin or epibromohydrin.
Examples of the aforesaid monomers with a nitrile group are acrylonitrile,
methacryloni-
trile and 2-methylene-glutaronitrile.
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Examples of the aforesaid monomers with a sulphonic acid group are
vinylsulphonic
acid, allylsulphonic acid, methallylsuiphonic acid, isoprenesulphonic acid, 3-
allyloxy-2-
hydroxy-propanesuiphonic acid, styrene-sulphonic acid, 3-sulphopropyl
acrylate, 2-
acrylamido-2-methylpropanesulphonic acid, 2-methacrylamido-2-
methylp ropanesu I phonic acid, sulphoethyl acrylate, the sulphate ester of
hydroxyethyl
acrylate and the sulphate ester of polyoxyalkyleneoxide acrylate, together
with the al-
kali metal salts, alkaline earth metal salts and ammonium salts, etc, of these
acids.
As examples of the aforesaid monomers with a phosphoric acid group, there are
vinyl-
phosphonic acid and styrene-phosphonic acid, together with the alkali metal
salts, alka-
line earth metal salts and ammonium salts, etc, of these acids.
As examples of the aforesaid styrene-type monomers, there are styrene per se,
a-
methylstyrene, a-methylstyrene dimer and vinylbenzylamine. The
vinylbenzylamine
can be employed in its free base form, or it can be employed in the form
obtained by
neutralization with acid or in the quaternized form. Examples of said acid are
mineral
acids such as hydrochloric acid, carbonic acid, sulphuric acid and nitric
acid, and or-
ganic acids such as sulphonic or carboxylic acids like formic acid, acetic
acid and
propionic acid. The quaternization can be carried out using for example an
alkyl halide
such as methyl chloride or methyl bromide, an aralkyl halide such as benzyl
chloride or
benzyl bromide, a dialkyl sulphate such as dimethyl sulphate or diethyl
sulphate, or an
epihalohydrin such as epichlorohydrin or epibromohydrin.
Additionally it might be advantageous to modify the described copolymers by
adding
monomers, which contain at least 2 non-conjugated ethylenically double bonds.
Suit-
able monomers of this type for example are:
N,N'-methylenebisacrylamide, polyethylene glycol diacrylates and polyethylene
glycol
dimethacrylates, which are in each case derived from polyethylene glycols of a
molecu-
lar weight from 126 to 8500, preferably 400 to 2000, trimethylolpropane
triacrylate,
trimethylolpropane trimethacrylate, ethylene glycol diacrylate, propylene
glycol diacry-
late, butanediol diacrylate, hexanediol diacrylate, hexanediol dimethacrylate,
diacry-
lates and dimethacrylates of block copolymers of ethylene oxide and propylene
oxide,
polyhydric alcohols di- or triesterified with acrylic acid or methacrylic
acid, such as
glycerol or pentaerythritol, triallylamine, tetraallylethylenediamine,
divinylbenzene, dial-
lyl phthtlate, polyethylene glycol divinyl ethers of polyethylene glycols of a
molecular
weight from 126 to 4000, tri methylo I propane diallyl ether, butanediol
divinyl ether, pen-
taerythritol triallyl ether and/or divinylethyleneneurea.
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Preferred examples are triallylamine, allylethers of multifunctional polyols
and divi-
nylethyleneurea. Usually less than 5 % of theses monomers are applied.
Preferred are
quantities between 0,0001 % and 1 %.
In the production of the aforesaid N-vinylformamide polymer, there may be used
any
polymerization method such as an ionic polymerization method like anionic or
cationic
polymerization, or a radical polymerization method. It is preferred that there
be adop-
ted a radical polymerization method (see JP-A-11-322849) from the point of
view of
ready control of the molecular weight.
The production of the mentioned N-vinylformamide polymers can be carried out
by so-
lution polymerisation, emulsion polymerisation, suspension polymerisation or
precipita-
tion polymerisation. The polymerisation is generally run in an atmosphere free
of oxy-
gen. This can be achieved by feeding a current of inert gas through the
reaction mix-
ture during the polymerisation or by degassing the reaction mixture beforehand
and
running the polymerisation under pressure of an inert gas or under reduced
pressure.
Despite the fact that polymerisations in non-aqueous media are also known, for
exam-
ples in JP-A-2-6685 or in EP-374-646, methods in aqueous media are preferred
both
from the point of view of the operating environment and because no recovery
equip-
ment for the non-aqueous medium is required.
Therefore solution polymerisations are preferably run in water, where the
concentration
of the monomers ranges from 5 to 60 mass%. Furthermore, in the case of
emulsion
polymerisation, the polymerisation is preferably carried out in an oil-in
water emulsified
state normally using an aqueous suspension of monomer concentration 20 -
70 mass% and an emulsifier. Also preferred are aqueous dispersions of water
soluble
N-vinylformamide polymers as for example described in DE-A-1 9851024 or WO-A-
2003046024.
In producing an aforesaid copolymer of N-vinylformamide and monomer
copolymeriz-
able with said N-vinylformamide, there can be produced a graft polymer or a
block
polymer by graft polymerization or block copolymerization of the N-
vinylformamide and
monomer copolymerizable with said N-vinylformamide.
The aforesaid copolymer can be produced by the copolymerization of 90 to 1
mol% of
the N-vinylformamide and 10 to 99 mol% of the monomer copolymerizable
therewith,
preferably 95 to 50 mol% and 5 to 50 mol% respectively.
In the production of the aforesaid polymer, it is possible to use a normal
polymerization
initiator as the radical polymerization catalyst employed in the
polymerization reaction,
in particular in a radical polymerization reaction. As the polymerization
initiator, there
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can be used for example an azo type polymerization initiator, a persuiphate, a
perox-
ide, a bromate, a perborate, a percarbonate or a perphosphate. Specifically,
as the
azo type polymerization initiator, there can be used azobisisobutyronitrile,
2,2'-azobis-
(2,4'-dimethylvaleronitrile), 2,2'-azobis(4-methoxy-2,4-
dimethylvaleronitrile), 2,2'-
5 azobis(2-methylpropionitrile), 2,2'-azobis(2-methylbutyronitrile), 1, 1 -
azobis-
(cyclohexane-1 -carbonitrile), 2,2'-azobis-[2-methyl-N-(2-
hydroxyethyl)propionamide],
dimethyl 2,2'-azobis(2-methylpropionate), 2,2'-azobis-(2-amidinopropane), 2,2'-
azobis-
(2-amidinopropane), 2,2'-azobis-(N,N'-dimethyleneisobutylamine), 2,2'-azobis-
(N,N'-
dimethyleneisobutylamine), 2,2'-azobis(2-(2-imidazolin-2-yl)propane), 2,2'-
azobis(2-(2-
10 imidazolin-2-yl)propane) or 4,4'-azo-bis-(4-cyanovaleric acid) and the
salts thereof. As
examples of the persulphate, there are sodium persulphate, potassium
persulphate
and ammonium persuiphate. As examples of the peroxide, there are benzoyl
peroxide,
hydrogen peroxide, tert-butylhydroperoxide and di-tert-butylperoxide. As
examples of
the bromate, there are sodium bromate and potassium bromate. As examples of
the
perborate, there are sodium perborate and ammonium perborate. As examples of
the
percarbonate, there are sodium percarbonate, potassium percarbonate and
ammonium
percarbonate. As examples of the perphosphate, there are sodium perphosphate,
po-
tassium perphosphate and ammonium perphosphate.
These polymerization initiators can be used on their own or they can be used
in combi-
nations of two or more. Especially preferred initiators are 2,2'-azobis-4-
amidinopropane hydrochloride or acetate, the sodium salt of 4,4'-azobis-4-
cyanovaleric
acid, and azobis-N,N'-dimethyleneisobutylamidine hydrochloride or sulphate.
Furthermore, by jointly employing a reducing agent such as a sulphite like
sodium sul-
phite, a bisuiphite like sodium bisulphite, a metabisulphite like sodium
metabisulphite,
an organic amine like N,N,N',N'-tetramethylethylenediamine, or a reducing
sugar like
an aldose, the peroxide type polymerization initiators can also be used in the
form of
redox type polymerization initiators. These reducing agents can be used on
their own
or in combinations of two or more.
Polymerization is initiated by the addition of the polymerization initiator to
the monomer
solution. Moreover, with the objective of reducing the amount of unreacted
monomer,
a supplementary addition of some polymerization initiator may be made during
the
course of the polymerization reaction, or continuous addition of the
polymerization ini-
tiator may be performed by a means such as the dropwise addition method. It is
also
possible to use the method of irradiating with ionizing radiation, an electron
beam or
ultraviolet light. These methods may be employed on their own or there can be
used a
combination of two or more types.
At the time of the polymerization, where required a chain transfer agent can
be suitably
employed. Examples of the chain transfer agent are compounds having one or
more
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11
hydroxy groups in the molecule, compounds having one or more mercapto groups
in
the molecule, compounds having one or more carbon-carbon unsaturated bonds in
the
molecule, peroxides such as dibutylperoxide, and hypophosphoric acid. The
chain
transfer agents may be used on their own or in combinations of two or more.
Furthermore, at the time of polymerization, a crosslinking agent may be
suitably added
where required. Examples of the crosslinking agent are bifunctional
polymerizable
vinyl monomers such as di(meth)acrylates, bis(meth)acrylamides and divinyl
esters
which possess two unsaturated bonds, monomers with a crosslinking action due
to
having functional groups which undergo chain transfer with vinyl groups,
monomers
which have a crosslinking action due to having groups which react with vinyl
groups,
trifunctional polymerizable vinyl monomers which have three unsaturated bonds,
tetra-
functional polymerizable vinyl monomers which have four unsaturated bonds,
water-
soluble aziridinyl compounds, water-soluble polyfunctional epoxy compounds and
sili-
con based compounds. These can be used on their own or in combinations of two
or
more.
Furthermore, insofar as the objectives of the present invention are not
impaired, the
polymerization of the N-vinylformamide or the copolymerization of the N-
vinylformamide and monomer copolymerizable therewith can be carried out in the
pre-
sence of a water-soluble polymer such as a starch like oxidized starch,
cationic starch,
amphoteric starch or enzyme-modified starch, a cellulose derivative such as
carboxy-
methylcellulose, polyvinyl alcohol, chitosan or a gum, etc.
The component (A) in the present invention is obtained by hydrolysis of the
formyl
groups in polymer in which at least N-vinylformamide is a polymerization
component.
The hydrolysis can be carried out using a known hydrolysis method such as for
exam-
ple an acidic hydrolysis method, a basic hydrolysis method, a method of acidic
hydroly-
sis in a hydrophilic solvent such as alcohol containing water, or an
alcoholysis method
under acidic conditions, either in the solution state or after dehydrating or
drying to pro-
duce a powder state. Amongst these methods of hydrolysis, the acidic and basic
hy-
drolysis methods are preferred.
The modifying agent used in acidic hydrolysis can be any compound which acts
as a
strong acid such as hydrochloric acid, hydrobromic acid, hydrofluoric acid,
sulphuric
acid, nitric acid, phosphoric acid, sulfamic acid or methanesulphonic acid,
but a mono-
basic acid is preferred in terms of facilitating the dissolution of the
hydrolysate in water.
The modifying agent used in basic hydrolysis may be any compound which acts as
a
strong base such as sodium hydroxide, potassium hydroxide, lithium hydroxide
or a
quaternary ammonium hydroxide.
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As examples of the alcohol used in the case of alcoholysis, there are alcohols
with from
1 to 4 carbons such as methanol, ethanol, isopropanol and butanol, but
methanol is
preferred.
The amount of modifying agent used for the hydrolysis will be suitably
selected in ac-
cordance with the desired percentage modification, normally from within the
range 0.2
to 5 times the molar quantity of the formyl groups in the aforesaid polymer,
so that the
percentage hydrolysis of the formyl groups in the polymer is 20-100 mol%. The
reac-
tion temperature at the time of the hydrolysis is normally in the range 30 to
110 C, and
the reaction time is normally from 0.1 to 24 hours.
The percentage hydrolysis of the formyl groups in the polymer in which at
least N-
vinylformamide is a polymerization component is from 20% to 100% and
preferably 50
to 100% of the total formyl groups in the polymer. If the percentage
hydrolysis is too
low, there is insufficient filler fixing effect and paper opacity enhancement
effect.
When carrying out the hydrolysis, for the purposes of preventing the gelling
brought
about by impurities, the modification may be conducted with the optional
addition of a
gelling inhibitor such as hydroxylamine hydrochloride or hydroxylamine
sulphate. Fur-
thermore, hydrolysis can also be carried out after performing treatment with
the gelling
inhibitor prior to modification. The hydrolysis can be conducted in a
homogeneous
solution using water or a mixture of water and a polar solvent such as
methanol, or in a
heterogeneous solution comprising a non-polar solvent such as hexane or
toluene and
a polar solvent containing at least water.
By means of the aforesaid polymerization process or process of derivative
preparation,
the solids concentration of the solution of polymer in which at least N-
vinylformamide is
a polymerization component and/or of derivative thereof obtained is normally
from 3 to
40 mass%. Furthermore, when the viscosity of this polymer solution and/or
derivative
solution is measured with a Brookfield rotary viscometer at 25 C, normally it
is no more
than 100,000 mPa.s and preferably no more than 20,000 mPas. In the present
inven-
tion, this solution of polymer and/or of derivative can be employed as it is
for use as the
fixing agent.
Component (B) in the present invention is titanium dioxide and/or calcium
carbonate.
Put another way, component (B) in the present invention is at least one type
of inor-
ganic compound selected from the group comprising titanium dioxide, light
calcium
carbonate and heavy calcium carbonate. The ash content of the filler-
containing paper
in the present invention lies in the range 3 to 40 wt% and, along with
aforesaid compo-
nent (B), it is possible to use the inorganic compounds normally used as
fillers for pa-
per such as kaolin, talc, clay, white carbon, aluminium hydroxide and the
like. Fur-
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13
thermore, there is no objection to incorporating filler derived from waste
paper, provid-
ing it is within the aforesaid range.
The titanium dioxide used in the present invention may either be of the
anatase or rutile
type. Furthermore, there can also be used material which has been coated with
alu-
mina or silica. Normally, in the case where titanium dioxide is added to a
papermaking
system, it is usually employed in a slurry state dispersed in water and, in
such circum-
stances, in order that the titanium dioxide be uniformly dispersed there may
be used a
dispersing agent such as sodium polyacrylate. However, there does not have to
be
used a dispersing agent and there may also be employed in the present
invention ma-
terial which does not use a dispersing agent.
The calcium carbonate used in the present invention may be light calcium
carbonate or
heavy calcium carbonate. As light calcium carbonate, there can be used the
material
obtained by a method such as reacting carbon dioxide with milk of lime, and as
heavy
calcium carbonate there can be used the material obtained by grinding
crystalline lime-
stone or marble. Normally, in the case where calcium carbonate is added to a
paper-
making system, it is usually used in a slurry state dispersed in water and, in
such cir-
cumstances, in order to uniformly disperse the particular type of calcium
carbonate
there may be used a dispersing agent such as sodium polyacrylate. However,
there
does not have to be used a dispersing agent and there may also be employed in
the
present invention material which does not use a dispersing agent.
There are no particular restrictions on the pulp employed as the paper raw
material in
the present invention but it is preferred that it be a pulp used in the
production of paper
for construction materials, India paper or tip base paper for cigarettes. For
example,
there can be used kraft pulp, sulphite pulp and other such bleached and
unbleached
chemical pulps, groundwood pulp, mechanical pulp, thermomechanical pulp, che-
mithermomechanical pulp and other such bleached or unbleached high-yield
pulps,
and also pulps containing pulp from waste paper such as newspaper, magazine
paper,
cardboard and the like. As well as wood pulp, there may also be used non wood-
based pulps such as those based on straw or kenaf. Furthermore, there may be
used
a mixture of an aforesaid pulp and a synthetic fibre such as polyamide,
polyester, poly-
olefin or polyvinyl alcohol, etc.
Component (A) and component (B) can be added to the pulp slurry prior to the
dryer
part of the papermaking process, and the method of addition is not
particularly re-
stricted, but it is preferred that they be added to the pulp slurry prior to
the wet web
formation. There are no particular restrictions on the order of addition of
component
(A) and component (B) to the pulp slurry, and both may be added to the pulp
slurry at
the same location or they may be mixed together just before their addition to
the pulp
slurry. Furthermore, one may be added to the pulp slurry prior to the other.
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In the case where component (A) and component (B) are added to the pulp slurry
prior
to the wet web formation, they may be added at the same time as, or before or
after,
other chemical agents. There are no particular restrictions on these chemical
agents,
examples of which include coagulants, dry paper strengtheners, wet paper
strengthen-
ers, sizing agents, fillers other than component (B), yield enhancers and
drainage en-
hancers, and these are added where required so that there may be manifested
the
properties required in accordance with the paper type, or so that the
operational char-
acteristics are enhanced. One such chemical agent may be incorporated or there
may
be used two or more types in combination.
Examples of the aforesaid coagulants are poly(diallyldimethylammonium
chloride) and
the reaction product of amines and epihalohydrins. Examples of the dry paper
strengtheners are anionic polyacrylamide, cationic polyacrylamide, amphoteric
poly-
acrylamide, cationic starch and amphoteric starch. Examples of the wet paper
strengtheners are polyamide epichlorohydrin resins, polyamine epichlorohydrin
resins,
melamine formaldehyde resin and urea formaldehyde resin, etc.
Furthermore, examples of the sizing agents are fatty acid soaps, solution
rosin, acidic
rosin emulsion, neutral rosin emulsion, alkenylsuccinic anhydride emulsion or
its hydro-
lysate salts, 2-oxetanone emulsion, paraffin wax emulsion, cationic sizes
obtained by
the reaction of a carboxylic acid and a polyfunctional amine, emulsions of the
reaction
products of aliphatic oxyacids and aliphatic amines or aliphatic alcohols, and
cationic
styrene type sizes.
Examples of yield enhancers are anionic high molecular weight polyacrylamides,
cati-
onic high molecular weight polyacrylamides, amphoteric high molecular weight
poly-
acrylamides, silica sol and bentonite, etc.
Examples of drainage enhancers are polyethyleneimine, anionic polyacrylamide,
cati-
onic polyacrylamide and amphoteric polyacrylamide, while examples of other
types of
chemical agent include alum, polyaluminium chloride and other types of
aluminium
compounds, dyes, defoaming agents and pH regulators.
The levels of addition of component (A) and component (B) to the pulp slurry
should be
adjusted such that the ash content in the paper lies in the range 3 to 40 wt%.
The percentage addition of component (A) to the pulp slurry is normally at
least
0.0005% but less than 0.05%, preferably at least 0.001 % and no more than
0.04% in
terms of the dry mass of raw material pulp. If the amount of component (A)
added is
less than 0.0005%, then there may be an inadequate filler yield enhancement
effect
and an inadequate effect in raising the opacity. Conversely, if the amount of
compo-
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nent (A) added is 0.05% or more then, while the filler yield enhancement
effect is excel-
lent, there is considerable coagulation of the pulp fibre and filler, and
there may be a
reduction in the properties of the paper such as a deterioration in texture
and inade-
quate improvement in the opacity.
5
The level of addition of component (B) is not particularly restricted but
should be such
that the ash content of the paper is from 3 to 40 wt%. Normally, the amount
added to
the pulp slurry is from 3 to 100 wt%. With regard to the percentage addition
of compo-
nent (B), in actual papermaking part of all of the starting material may
comprise com-
10 ponent (B) from waste paper or damaged paper, and since it is necessary to
adjust the
ash content according to changes in the filler contained in such starting
material, the
amount of component (B) added may also vary.
The weight ratio of component (A) to component (B), by conversion to solids
concen-
15 tration, preferably lies in the range [component (A)/component (B)] =
0.001/100 to
0.5/100, and more preferably [component (A)/component (B)] = 0.01/100 to
0.3/100. If
the weight ratio of [component (A)/component (B)] is less than 0.001, there
may be an
insufficient filler yield enhancement effect and an inadequate effect in
raising the opac-
ity. Conversely, if the weight ratio of [component (A)/component (B)] is more
than 0.5
then, while the filler yield enhancement effect is excellent, there is
considerable coagu-
lation of the pulp fibre and filler, and there may be a reduction in the
properties of the
paper such as a deterioration in texture and inadequate improvement in the
opacity.
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Examples
Below, the present invention is explained in further detail by providing
examples and
comparative examples. As examples of paper production, the following three
sets of
conditions are exemplified but the present invention is not to be restricted
in any way
by these examples. Unless otherwise stated, reference to "%" means mass
percent.
Paper production example 1 paper containing titanium dioxide, under acidic
conditions
Paper production example 2 paper containing titanium dioxide, under neutral
condi-
tions
Paper production example 3 paper containing calcium carbonate, under neutral
condi-
tions
Component (A) Production Example 1
80 g (1125 mmol) of N-vinylformamide was dissolved in 385 g of water in a 2L
capacity
flask equipped with a stirrer, thermometer and means for operating under a
nitrogen
atmosphere. 0.65 g (2.4 mmol) of 2,2'-azobis-(2-amidinopropane) hydrochloride
was
mixed therewith and, by introducing nitrogen, oxygen was eliminated. The
reaction
mixture was then heated to 55 C within 1 hour. After maintaining for 5 hours
at this
temperature, in order to enhance the conversion the temperature was then
raised to
60 C for 30 minutes and the percentage conversion made 100%. Next, 114.5 g
(1129.4 mmol) of 36% aqueous hydrochloric acid solution was mixed with the
viscous
polymer solution thus obtained, and heating carried out for 2 hours at 90 C so
that hy-
drolysis was performed. In the aqueous polymer solution I of cationic resin
obtained,
the solids concentration of the polymer was 8.6%. The viscosity of the aqueous
poly-
mer solution was 1100 mPas (Brookfield viscosity, 25 C) and it was confirmed
by' H-
NMR that 95% of the formyl groups were hydrolysed.
Component (A) Production Example 2
Reaction was carried out in the same way as in Example 1 except that instead
of the
114.5 g (1129.4 mmol) of 36% aqueous hydrochloric acid solution used in
Component
(A) Production Example 1, there was mixed 68.5 g (676 mmol) of 36% aqueous
hydro-
chloric acid solution. There was obtained aqueous polymer solution II of
cationic resin,
where the polymer solids concentration in the aqueous polymer solution was
12.0%,
the viscosity was 1400 mPas (Brookfield viscosity, 25 C) and 60% of the formyl
groups
were hydrolysed (confirmed by 'H-NMR).
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Component (A) Production Example 3
Reaction was carried out in the same way as in Component (A) Production
Example 1
except that instead of the 114.5 g (1129.4 mmol) of 36% aqueous hydrochloric
acid
solution used in Component (A) Production Example 1, there was mixed 34.25 g
(338 mmol) of 36% aqueous hydrochloric acid solution. There was obtained
aqueous
polymer solution III of cationic resin, where the polymer solids concentration
in the a-
queous polymer solution was 14.1 %, the viscosity was 2400 mPas (Brookfield
viscos-
ity, 25 C) and 30% of the formyl groups were hydrolysed (confirmed by 'H-NMR).
Example 1 (Paper Production Example 1)
Based on the solids concentration mass ratio in terms of the absolute dry mass
of pulp,
1.5% alum, 1.0% of a commercial cationic starch and 0.3% of a rosin emulsion
type
size (commercial name "AL1208", produced by the Seiko PMC Corporation) were ad-
ded in turn to a 2.4% pulp slurry (LBKP/NBKP = 9/1, Canadian Standard Freeness
400). After stirring, the pulp slurry was diluted with pure water to 0.5% and
then 20% of
anatase type titanium dioxide and 0.012% (by conversion to polymer solids
concentra-
tion) of the aqueous polymer solution I of cationic resin obtained in
Component (A)
Synthesis Example 1 were added to the pulp slurry, followed by 0.01 % of
cationic poly-
acrylamide type polymeric yield enhancer. Some of this pulp slurry was taken
and a
test of the fixing of component (B) carried out.
The fixing test was carried out using equipment identical to the Modified
Dynamic Drai-
nage Tester described on page 171 of TAPPI Papermakers Conference (1985) [of
construction whereby the pulp slurry is poured into a jar of diameter 7.5 cm,
stirred at a
rotation rate of 600 rpm and air conveyed from the bottom in such a way that
no mat is
formed and, at the same time as the stirring and air-conveyance are halted,
filtering is
performed]. 500 ml of pulp slurry was filtered with a 100 mesh strainer and
100 ml of
filtrate collected, then the light transmittance (%) at 620 nm measured. The
higher the
value of this light transmittance, the clearer the filtrate, indicating that
fine fibre and filler
were not discharged into the filtrate but were fixed to the fibre. In
particular, in the pre-
sent invention, where component (B) with a high light scattering capacity was
used, the
light transmission was taken as being an index of the amount of component (B)
con-
tained in the filtrate.
Then, using the remaining pulp slurry, wet paper of weight per unit area 40
g/m2 was
obtained by means of a Noble and Wood handsheet machine. The papermaking pH at
this time was 4.5. The wet paper obtained was pressed and then dried for 80
seconds
at 100 C with a drum dryer. The handsheet paper obtained was conditioned for
24
hours at 23 C and 50%RH, after which measurements were made of the weight per
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18
unit area (basis weight), the ash content of the paper and the opacity. The
results are
shown in Table 1.
The weight per unit area (basis weight) was measured in accordance with JIS
P8124
"Method of Measuring the Basis Weight of Paper and Board"; the ash content of
the
paper was measured in accordance with JIS P8251 "Method of Measuring the Ash
Content of Paper, Board and Pulp"; and the opacity was measured in accordance
with
JIS P8149 "Paper and Board - Opacity Test Method (paper backing) - Diffuse
Illumina-
tion Method). The measurements in the examples and comparative examples de-
scribed below were also carried out in the same way.
Examples 2 and 3
Papermaking was carried out in the same way as in Example 1, except that
aqueous
polymer solution I was changed to the cationic resin and amount thereof shown
in Ta-
ble 1. The results of the measurements performed on the paper obtained in each
case
are also shown in Table 1.
Example 4
Papermaking was carried out in the same way as in Example 2, except that the
posi-
tion of addition of the titanium dioxide was changed to prior to the alum. The
results of
the measurements performed on the paper obtained are also shown in Table 1.
Example 5
Papermaking was carried out in the same way as in Example 4, except that the
aque-
ous polymer solution I of cationic resin was changed to that shown in Table 1.
The
results of the measurements performed on the paper obtained are also shown in
Table
1.
Comparative Example 1
Papermaking was carried out in the same way as in Example 1, except that no
aque-
ous polymer solution I was added. The results of the measurements performed on
the
paper obtained are shown in Table 1.
Comparative Example 2
Papermaking was carried out in the same way as in Example 4, except that no
polymer
solution I was added. The results of the measurements performed on the paper
ob-
tained are shown in Table 1.
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Comparative Examples 3 and 4
Papermaking was carried out in the same way as in Example 1, except that
polyethyle-
neimine was added instead of aqueous polymer solution I in the amounts shown
in
Table 1. The results of the measurements performed on the paper obtained are
also
shown in Table 1.
Comparative Example 5
Papermaking was carried out in the same way as in Example 1, except that
instead of
adding aqueous polymer solution I the amount of added cationic polyacrylamide
type
polymeric yield enhancer was as shown in Table 1. The results of the
measurements
performed on the paper obtained are also shown in Table 1.
Comparative Example 6
Papermaking was carried out in the same way as in Example 4, except that
instead of
aqueous polymer solution I there was added the amount shown in Table 1 of
polyethyl-
eneimine. The results of the measurements performed on the paper obtained are
also
shown in Table 1.
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Table 1
Cationic Amount Ash Con- Opacity Light Transmis-
Added tent of Pa- o sion of Filtrate in
Resin (%) per (%) (~~) Test of Fixing (%)
aqueous poly-
Example 1 0.012 8.5 81.5 29.7
mer solution I
Example 2 aqueous poly- 0.024 8.7 81.6 33.8
mer solution I
aqueous poly-
Example 3 0.024 8.4 82.0 29.0
mer solution II
Example 4 aqueous poly- 0.024 9.0 82.2 29.8
mer solution I
aqueous po-
Example 5 lymer solution 0.024 8.8 82.0 29.5
I I
Comp.Ex.1 - - 7.5 80.9 18.4
Comp.Ex.2 - 7.6 79.6 14.9
Comp.Ex.3 PEI 0.0125 7.5 80.3 18.9
Comp.Ex.4 PEI 0.025 7.2 79.8 19.8
polymeric
Comp.Ex.5 0.01 8.2 81.2 19.1
yield enhancer
Comp.Ex.6 PEI 0.05 8.2 80.9 20.6
PEI = polyethyleneimine
5 polymeric yield enhancer = cationic polyacrylamide type polymeric yield
enhancer
It is clear from the results shown in Table 1 that, by means of the titanium
dioxide yield
enhancing effect of the present invention, there is obtained a more
outstanding titanium
dioxide fixing effect than in the case of the conventionally-employed
polyethyleneimine
10 (Comparative Examples 3, 4 and 6) or in the case where the added amount of
cationic
polyacrylamide type polymeric yield enhancer was increased (Comparative
Example
5). In other words, by means of the present invention the build-up of unfixed
titanium
dioxide within the papermaking system is reduced and contamination of the
papermak-
ing machine and ancillary equipment is suppressed.
Example 6 (Paper Production Example 2)
Based on the solids concentration mass ratio in terms of the absolute dry mass
of pulp,
2% of polyamidepolyamine-epichlorohydrin resin (commercial name "WS4020", pro-
duced by the Seiko PMC Corporation), 0.024% (by conversion to polymer solids
con-
centration) of the aqueous polymer solution I of cationic resin obtained in
Component
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(A) Synthesis Example 1, 100% rutile type titanium dioxide, 1 % alum and 0.9%
sodium
aluminate were added in turn to a 2.4% pulp slurry (LBKP/NBKP = 9/1, Canadian
Standard Freeness 440). After stirring, the pulp slurry was diluted with pure
water to
0.5%. Papermaking was carried out using this pulp slurry by means of a Noble
and
Wood handsheet machine, and wet paper of weight per unit area 80 g/m2
obtained.
The papermaking pH at this time was 7.2. The wet paper was pressed and then
dried
for 80 seconds at 100 C with a drum dryer. The handsheet paper obtained was
condi-
tioned for 24 hours at 23 C and 50%RH, after which measurements were made of
the
weight per unit area, the ash content of the paper and the opacity. The
results are
shown in Table 2.
Example 7
Table 2 shows the results of measurements in the case of handsheet paper
obtained in
the same way as in Example 6 except that the added amount of aqueous polymer
solu-
tion I was as shown in Table 2.
Example 8
The same procedure was followed as in Example 6, except that the position of
addition
of the aqueous polymer solution I was changed to after the dilution of the
pulp slurry
with pure water to 0.5%.
Examples 9 and 10
Table 2 shows the results of measurements in the case of handsheet paper
obtained in
the same way as in Example 8 except that aqueous polymer solution I was
changed to
the cationic resin and amount thereof shown in Table 2.
Comparative Example 7
Table 2 shows the results of measurements in the case of handsheet paper
obtained in
the same way as in Example 6 except that there was no addition of aqueous
polymer
solution I.
Comparative Example 8
Table 2 shows the results of measurements in the case of handsheet paper
obtained in
the same way as in Example 7 except that instead of aqueous polymer solution I
there
was added polyamidepolyamine-epichlorohydrin resin.
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Table 2
Cationic Amount Ash Content
Opacity (%)
Resin Added (%) of Paper (%)
Example 6 aqueous
polymer solu- 0.024 29.7 96.5
tion I
Example 7 aqueous
polymer solu- 0.036 30.6 96.7
tion I
Example 8 aqueous
polymer solu- 0.024 31.8 96.6
tion I
Example 9 aqueous
polymer solu- 0.036 32.7 96.7
tion I
Example 10 aqueous
polymer solu- 0.024 32.1 96.7
tion II
Comp.Ex.7 - - 27.4 95.7
Comp.Ex.8 PAE 0.036 27.6 95.8
PAE = polyamidepolyamine-epichlorohydrin resin
From the results in Table 2, it is clear that by means of the titanium dioxide
yield en-
hancing effect of the present invention there can be obtained paper with a
higher ash
content and opacity than in the case of using the conventionally-employed
polyamide-
polyamine-epichlorohydrin resin (Comparative Example 8), and this is suitable
for the
decorative laminate base paper which falls into the category of construction
material
base paper.
Example 11 (Paper Production Example 3)
Based on the solids concentration mass ratio in terms of the absolute dry mass
of pulp,
0.5% of commercial cationic starch, 0.3% of AKD size (commercial name "AD1
602",
produced by the Seiko PMC Corporation) and 35% light calcium carbonate were
added
in turn to a 2.4% pulp slurry (LBKP/NBKP = 9/1, Canadian Standard Freeness
250).
After stirring, the pulp slurry was diluted with pure water to 0.5% and
0.0006% (by con-
version to polymer solids concentration) of aqueous polymer solution I of
cationic resin
obtained in Component (A) Synthesis Example 1 added to the pulp slurry.
Papermak-
ing was carried out using this pulp slurry by means of a Noble and Wood
handsheet
machine, and wet paper of weight per unit area 35 g/m2 obtained. The
papermaking
pH at this time was 8Ø The wet paper was pressed and then dried for 80
seconds at
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23
100 C with a drum dryer. The handsheet paper obtained was conditioned for 24
hours
at 23 C and 50%RH, after which measurements were made of the weight per unit
area,
the ash content of the paper and the opacity. The results are shown in Table
3.
Examples 12-17
Table 3 shows the results of measurements in the case of handsheet paper
obtained in
the same way as in Example 11 except that the aqueous polymer solution I was
chan-
ged to the cationic resin and the amount thereof shown in Table 3.
Comparative Example 9
Table 3 shows the results of measurements in the case of handsheet paper
obtained in
the same way as in Example 11 except that there was no addition of aqueous
polymer
solution I.
Comparative Examples 10 and 11
Table 3 shows the results of measurements in the case of handsheet paper
obtained in
the same way as in Example 11 except that instead of aqueous polymer solution
I the-
re was added the amount shown in Table 3 of polyethyleneimine (PEI).
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Table 3
Cationic Amount Ash Content
Resin Added (%) of Paper (%) Opacity (%)
Example 11 aqueous poly- 0.0006 15.6 87.6
mer solution I
Example 12 aqueous poly- 0.0012 16.1 86.1
mer solution I
Example 13 aqueous poly- 0.0024 17.3 87.8
mer solution I
Example 14 aqueous poly-
0.0012 15.6 88.8
mer solution II
Example 15 aqueous poly- 0.0024 16.9 89.6
mer solution II
Example 16 aqueous po-
lymer solution 0.0012 15.8 88.4
III
Example 17 aqueous po-
lymer solution 0.0024 16.6 87.7
III
Comp.Ex.9 - - 14.7 84.2
Comp.Ex.10 PEI 0.0013 14.5 85.5
Comp.Ex.11 PEI 0.0025 15.1 85.5
PEI = polyethyleneimine
From the results in Table 3 it is clear that by means of the calcium carbonate
yield en-
hancing effect of the present invention it is possible to obtain a higher ash
content and
opacity that in the case of increasing the added amount of conventionally-used
poly-
ethyleneimine (Comparative Examples 10 and 11) and, as well as cigarette tip
base
paper and India paper, this can be applied to ordinary paper for books, PPC,
coated
base paper and the like.
