Note: Descriptions are shown in the official language in which they were submitted.
J ~ ~ f~
COAT I NG COMP OS I T I ON FOR NEWS PR I NT
This invention relates to a coating composition
for paper for printing of newspaper thereinafter,
referred to as "a coating composition for newsprint")
suitable for mul~i-color offset printing. More speci-
fically, this invention relates to a coating compositionfor newsprint excellent in offset printabilities at the
time of cold set type high speed web offset printing such
as surface strength, print gloss and ink receptivity.
Recently, multi-color printing is conspicuous
in daily newspapers, particularly, sports papers, and
multi-color printing of the advertisement pages of daily
papers is also rapidly increasing. However, these
multi-color printing papers are poor-looking compared
with inserted leaflets whose material is often coated
paper, and thus short of ability appealing to readers.
On the other hand, due to the social mission of
newspapers, it is required to print them in large quan-
tities in a short time. Consequently, printing speed is
made faster and faster, and improvement of offset print-
abilities such as picking and an ink set is desired.
Heretofore, as a countermeasure for multi-color
printing and offset printing, a method has been adopted
whereby surface strength is enhanced using starch,
polyvinyl alcohol or the like. ~owever, by this method/
suficient offset printability such as print gloss could
not be obtained. Recently, in order to improve these
characteristics, pigment coating is proposed wherein the
amount of the oil to be absorbed in the coated layer is
enhanced by selection of pigment (Japanese Laid-Open
Patent Publication Nos. 174697/1989 and 169768/1990).
Further, a method for improvement is known wherein a
large amount of a pigment binder or an organic pigment is
used (Japanese haid-Open Patent Publication Nos.
;
,
. . :
. .
.. . .: .:
.
19595/1990 and 74698/1990). However, these methods
cannot satisfy all of the requirements for offset print-
abilities in a cold set web offset press using a cold set
type ink such as an ink set, surface strength, print
gloss, and water dissipation by use of fountain solution.
Moreover, these method could not provide newsprint having
brightness, opacity, etc.~ in addition to the above
offset printabilities.
The present inventors studied for solving the
disadvantages of the prior art, and considered, as one of
methods for solution, to use a usual coating composition
for slightly coated paper as it is, but merely with a
reduced coating amount thereof. However, in this method,
in the case of multi-color offset printing using a cold
set type ink, the coated paper has a poor oil absorption
property and a poor water absorp~ion property and thus is
poor in an ink set and ink receptivity, and consequently,
newsprint excellent in offset printabilities and thus
suitable for color printing could not be obtained.
Therefore, the present inventors further
continued to study intensively. As a result, they found
that, by using an amphoteric copolymer latex as a pigment
binder and setting the amount of the pigment binder in an
appropriate range, but without changing the pigment
composition having hitherto generally been used for
coated paper and slightly coated paper, there can be
obtained newsprint which has remarkably improved offset
printabilities such as an ink set, water dissipation,
surface strength (particularly wet pick resistance) and
print gloss, and is also good in brightness, opacity,
etc., and completed this invention based on this finding.
Thus according to this invention there is
provided a coating composition for newspaper-printing
paper which comprises 100 parts by weight of a pigment
and as a pigment binder 3 to 50 parts by weight in terms
of solid of an amphoteric copolymer latex.
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According to this invention is further provided a coating
composition for newsprint which comprises as a pigment
binder 15 parts by weight or less of a water soluble
polymer compound in addition to the amphoteric copolymer
latex, in such a range that the total amount of the
pigment binders becomes 3 to 50 parts by weight in terms
of solid per 100 parts by weight of the pigment.
The amphoteric copolymer latex to be used as a
pigment binder in this invention may be a copolymer latex
which gelates at a certain pH, and can be obtained by
introducing a specific monomer unit into a copolymer or
polymerizing monomers using an amphoteric surfactant, or
by another hitherto known method.
Although monomers to be used for synthesis of
the amphoteric copolymer latex to be used in this inven-
tion and their compositions are not particularly limited,
a monomer mixture is usually used comprising 20 to 50
weight % of an aliphatic conjugated diene monomer, 10 to
74 weight ~ of an aromatic vinyl monomer, 0.5 to 20
weight % of an ethylenic unsaturated acid monomer and 0
to 40 weight % of a monomer copolymerizable with these
monomers.
The aliphatic conjug~ted diene monomer imparts
flexibility to the polymer. When the amount is less than
20 weight %, the copolymer becomes too hard, and when it
is above 50 weight %, water resistance is lowered.
Specific examples of the aliphatic conjugated diene
monomer are 1,3-butadiene, 2-methyl-1,3-butadiene,
2-chloro-1,3-butadiene, etc., and 1,3-butadiene is
particularly preferred.
By use of the aromatic vinyl monom~r, effects
of imparting appropriate hardness and water resis~ance to
the copolymer are obtained. In an amount below 10 weight
% sufficient effects cannot be obtained, and in amount
above 74 weight ~ its film formation property is lowered
and its adhesive property is lowered. ~xamples of the
.
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- - : . . : -
~ . :
:- . . . :
-: . .. : . . .. .
:, . :
' ' ' ' ' . ' ~
aromatic vinyl monomer are styrene, ~-methylstyrene,
monochlorostyrene, vinyltoluene, etc., and styrene is
prèferred among them.
The ethylenic unsaturated acid monomer is
suitably used for enhancing the adhesive strength of the
copolymer and improving the colloidal stability of the
copolymer latex. When the amount is below 0.5 weight ~,
the above effects cannot be obtained, and when it is used
in an amount above 20 weight %, a problem takes place in
polymerization stability or the like. Further, when an
ethylenic unsaturated amine monomer is used, the
ethylenic unsaturated acid monomer is also effective for
adjus-tment of the gelation point. In this case, when the
amount of the ethylenic unsaturated acid monomer is too
large, the gelation point of the resulting copolymer
latex becomes out of the object of the invention.
Specific examples of the ethylenic unsaturated acid
monomer are unsaturated carboxylic acids such as acrylic
acid, methacrylic acid, crotonic acid, cinnamic acid,
itaconic acid, fumaric acid, maleic acid and butene-
tricarboxylic acid; unsaturated polycarboxylic acid alkyl
esters having at least one carboxyl group such as
itaconic acid monoethyl ester, fumaric acid monobutyl
ester and maleic acid monobutyl ester; unsaturated
sulfonic acids or their salts such as acrylic acid
sulfoethyl sodium salt, methacrylic acid sul~opropyl
sodium salt and acrylamidopropanesul~onic acid; etc.
In synthesis of an amphoteric copolymer latex
to be used in this invention, a monomer copolymerizable
with the above monomers can be copolymerized. Such a
monomer, if necessary, is used preferably in the range of
40 weight % or less. Specific examples of such monomers
are unsaturated carboxylic acid alkyl esters such as
methyl acrylate, methyl methacrylate, ethyl acrylate and
butyl acrylate; ethylenic unsaturated nitrile compounds
such as acrylonitrile and methacrylunitile; unsaturated
:
. ~ - , . . . .
,
- , :
,
fi~
carboxylic acid hydroxyalkyl es-ters such as ~-hydroxy-
ethyl acrylate, ~-hydroxypropyl acrylate and ~-hydroxy-
ethyl methacrylate; unsaturated carboxylic acid amides
and their derivatives such as acrylamide, methacrylamide,
N-methylolacrylamide and diacetoneacrylamide; unsaturated
carboxylic acid glycidyl esters such as glycidyl acryla~e
and glycidyl methacrylate; other vinyl compounds such as
acrolein and allyl alcohol, etc. The unsaturated car-
boxylic acid ester imparts moderate hardness to the
copolymer, and, at the same time, is effective to enhance
air permeability, and ~he amount is preferably 5 to 30
weight %. In an amount above 40 weight %, it has an
desirable influence on water resistance, etc. The
ethylenic unsaturated nitrile is effective to enhance the
print gloss of the coated paper, and its amount is pref-
erably S to 30 weight %. In an amount above ~0 weight %,
the ink receptivity and ink set of the coated paper is
10~7ered. The unsaturated carboxylic acid hydroxyalkyl
ester is effective for improvement of the mechanical
stability of the copolymer latex. By use of the
unsaturated carboxylic acid amide or its derivative, it
is possible to improve the chemical stability, mechanical
stability and water resistance of the copolymer latex.
When a comonomer is used to introduce a
gelation site into the copolymer as a method of obtaining
an amphoteric copolymer latex, its amount is 0.5 to 20
weight %, preferably 1 to 10 weight % based on all the
monomers. In an amount below 0.5 weight %, it is
difficult to make the latex amphoteric, whereas in an
amount above 20 weight ~, it becomes difficult to impart
a gelation point suitable for the composition of the
invention, and, besides, there arise problems~ for
example, that a large amount of coagula is formed at the
time of preparation of a copolymer latex.
As examples of a monomer to introduce a
gelation site into the copolymer, there can be mentioned
: ,: - -
.
-- 6
ethylenic unsaturated amines represented by the general
formula
Rl R3
CH2=C-A-R2-N
R4
, wherein Rl represents H or a methyl group, R2
represents an alkylene group having 2 to lO carbon atoms,
R3 and R~ each independently represents H or an alkyl
group having l to 12 carbon atoms, and A represents
-C(=O~-, -C(=O)NH- or -O-.
Specific examples of the ethylenic unsaturated
amine are ethylenic unsaturated carboxylic acid
aminoalkyl esters such as methylaminoethyl (meth)acryl-
ate, t-butylaminoethyl (meth)acrylate, N,N-dimethylamino-
ethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)-
acrylate, diethylaminoethyl (meth)acrylate and dibutyl- i
15 aminoethyl (meth)acrylate; ethylenic unsaturated ~:
carboxylic acid aminoalkylamide such as methylaminoethyl
(meth)acrylamide, N,N-dimethylaminoethyl (meth)acrylamide ;
and N,N-dimethylaminopropyl (meth)acrylamide; aminoalkyl
vinyl ethers such as aminoethyi vinyl ether, methylamino-
ethyl vinyl ether and N,N-dimethylaminoethyl vinyl ether;
vinylpyridines such as 2-vinylpyridine, 4-vinylpyridine,
2-methyl-5-vinylpyridine and 2,4-diethyl-5-vinylpyridine;
etc.
An amphoteric copolymer latex to be used in `
2~ this invention can also be obtained by using a suitable
kind of surfactant. Such surfactants include cationic
surfactants and amphoteric surfactants. In emulsion
polymerization of the above monomer mixture, such a
surfactant may either be used together with a nonionic
surfactant or the like or added after polymerization
using a nonionic surfactant or the like. The amount of
-- : ~ :
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. - : :
-: -: :- ': . .. .
,
a 2 ~
such a cationic or amphoteric surfactant is 0.1 to 5
weight %, preferably 0.2 to 2 weight ~ based on the
weight of a copolymer.
As cationic surfactants to be used for the
above purpose, those of quaternary ammonium salt type are
suitable. Specific examples thereof are, for example,
lauryltrimethylammonium chloride, cetyltrimethylammonium
chloride, lauryltrimethylammonium bromide, beef tallow
trimethylammonium chloride, N-(dodecylcolaminoformyl-
methyl)pyridinium chloride, cetylethylmorphonium etho-
sulfate, etc. As specific examples of the amphoteric
surfactant, alkylimidazoline type amphoteric surfactants,
etc. can be mentioned.
The gelation point of the amphoteric copolymer
latex can be adjusted by changing the kind and amount of
monomers to be used in synthesis of the copolymer such as
an ethylenic unsaturated acid monomer, an ethylenic
unsaturated amine monomer and a hydrophilic monomer. The
gelation point can also be adjusted by changing the kind
or amount of an emulsifier or the kind or amount of an
initiator. It is preferred to adjust the gelation point
of the copolymer latex to be used in this invention in
the range of pH 3.5 to 8.5. The gelation point can be
measured by the method disclosed in Japanese Patent
Publication No. 49360/1984.
An amphoteric copolymer latex to be used in
this lnvention can be prepared by a known emulsion poly-
merization method. There is no particular limitation on
the polymerization temperature and the pressure, the way
of addition oE the monomers, etc., and subsidiary
mat~rials to be used for polymerization (a polymeriza~ion
initiator, a molecular weigbt modifier~ a pH adjusting-
agent and the like~.
Pigments to be used in this invention are not
particularly limited, and there can be mentioned as
specifîc examples mineral pigments such as clay, calcium
..
: :
~ ,
,
carbonate, aluminum hydroxide, titanium white, barium
sulfate, satin white and talc; organic pigments such as
polystyrenes and phenol resins. These pigments can be
used singly or in combination. In order to highly exert
the effects of this invention, it is preferred that 50
weight % or more of the pigments is clay, particularly
kaolinite clay.
The coating composition for newsprint of this
invention comprises a pigment and an amphoteric copolymer
latex as an indispensable pigment binder.
The amount of the amphoteric copolymer latex is
3 to 50 parts by weight in terms of solid per 100 parts
by weight of the pigment, but preferably 5 to 40 parts by
weight, more preferably 10 to 40 parts by weight. When
this amoun~ is below 3 parts by weight, it becomes
difficult to suppress binder migration in the drying
process at the time of preparation of coated newsprint,
and consequently, ink receptivity becomes unsatisfactory
and offset printabilities such as surface strength and
print gloss become poor. On the other hand, in an amount
above 40 parts by weight blocking resistance lowers due
to tackiness, etc. of the latex and runnability becomes
bad. Particularly, in an amount above 50 parts by
weight~ this tendency becomes impractically terrible, and
at the same time the brightness, opacity, water dissipa~
tion, ink set and the like of the resulting coated news-
print becomes bad.
In this invention, it is possible to use a
water soluble polymer binder together as a pigment
binder. Although use of the water soluble binder is not
indispensable, by using it together, i~ becomes easier to
adjust the viscosity of a coating color and there arise
effects in imparting opacity and adhesive strength to the
newsprint. Specific examples of the water soluble
polymer binder are starches such as phosphoric acid-
esterified starFh and enzyme-modified atarch; casein;
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polyvinyl alcohol; cellulose derivatives such as methyl-
cellulose and carboxylmethylcellulose; etc., but other
water soluble polymer binders which are usually used in
this technical fields may also be used.
The amount of the water soluble polymer binder
is ~5 parts by weight or less, preferably 10 parts by
weight or less in terms of solid per 100 parts by weight
of the pigment. When the amount of the water soluble
polymer binder is above 15 parts by weight, increase of
the viscosity of the coating color and decrease of
fluidity take place and thus coating runnability becomes
bad. The amount of the water soluble polymer binder must
be an amount in such a range that the total amount of it
and the amphoteric copolymer latex as an indispensable
pigment binder is 3 to 50 parts by weight per 100 parts
by weight of the pigment.
Further, so far as the effect of this invention
is not impaired, it is also possible to use together as a
pigment binder a conventional styrene-butadiene copolymer
latex, methyl methacrylate-butadiene copolymer latex or
the like in the coating composition of the invention.
Further, it is possible to add, if necessary,
to the coating composition of this invention, besides
water, the pigment and the pigment binder, a pigment-
dispersing agent, a viscosity-modifier, water-retention
agent, insolubilizerl a dye, a fluorescent dye, a
lubricant, a pH-adjusting agent, an antifoaming agent, a
surfactant, an antiseptic or the like. In this inven-
tion, it is necessary to maintain the pH of the coating
composition to a pH equal to or higher than the gelation
point of the amphoteric copolymer latex. When the pH is
below the gelation point, the improvement effect of ink
receptivity lowers. Although the pH-adjusting agent is
not particularly limited, ammonia water is pre~erably
USed.
Although the reason why the coating composition
. . .
-- 10 --
of this invention has excellent offset printabilities is
not certain, the following is considered as one possible
reason. Namely it is generally considered that poor ink
receptivity, etc. is caused by ununiformity of the
distribution of the binder at the drying process in
ooating paper with a coating compositio~, and that the
ununiformity is caused by so-called migration. On the
other hand, when the amphoteric copolymer latex is used
as a pigment binder, the p~ of the coating composLtion is
lowered at the drying process and the amphoteric
copolymer latex gelates at the gelation point, and thus
migration does not occur~ Thus, binder distribution
becomes uniform and excellent printabilities are
obtained.
This invention is more specifically illustrated
by the following examples. Unless otherwise indicated,
parts and ~ in the examples are based on weight.
Further, the weight of latexes is in terms of solid.
In examples, various characteristics of coating
compositions and coated papers were evaluated by the
following methods.
Coating color viscosity
A BL type viscometer is used. Color viscosity
is expressed by the value (unit: cp~ measured after 1
minute at 60 rpm using the No. 4 rotor.
Color fluidity
A Hercules type high shear viscometer is used.
Color fluidity is expressed by the apparent viscosity
~cp) at a revolution number of 4,000 rpm with G bob
(clearance 0.02 cm).
Ink set
By use of an RI tester (produced by Akira
Seisaku-sho Co., Ltd.), solid printing was carried out
with a newspaper ink and a coated paper is superposed
thereon. Then, the degree of transfer of the ink is
judged by visual observation.~ Ink set is evaluated by a
; . . ~ .: ...., : ~ : .
.
2 ~ 7~ i
five point method. 5 is best and 1 is worst.
Water dissipation
After application of fountain solution by a
rubber roller, a coated newsprint is subjected to solid
printing using an RI tester and a newspaper ink, and the
degree of transfer of the ink (the concentration of the
ink) is judged by visual observation~ Water dissipation
is evaluated by a five point method. 5 is best and 1 is
worst.
Dry pick resistance
The degree of picking when printing was carried
out using an RI tester and an ink for a picking test (its
tack value is 24) is judged by visual observation. Dry
pick resistance is evaluated by a five point method. 5
is best and 1 is worst.
Wet pick resistance
After application of water by a Molton roller,
a coated newsprint is subjected to solid printing using
an RI tester and an ink for a picking test (its tack
value is 16) and the degree of picking is judged by
visual observation. Wet pick resistance is evaluated by
a five point method, and 5 is best and 1 is worst.
Print gloss
After solid printing is carried out using an RI
tester and a newspaper ink, print gloss is measured by a
glossmeter (produced by Murakami Shikisai Co., ~td.
GM-26D).
Brightness is measured using a Hunter reflecto-
meter tproduced by Murakami Shikisai Co., Ltd. CM-8P) and
expressed by %. The larger the value is, the larger
brightness is.
Opacity
Opacity is measured using a Hunter reflecto-
meter (Produced by Murakami Shikisai Co., Ltd. CM~8P) and
expressed by %. The larger the value is, the larger --~
:
~ .
. .
2 i~J ~ t,J
opacity is.
slockin~ resistance
Blocking resistance is expressed by the degree
of adhesion of a coated newsprint to a metal-made
calender roll when the paper was twice passed through a
supercalender at 70C and 150 kg/cm.
O : No adhesion
: A little adhesion
X : Considerable adhesion
[Preparation of amphoteric copolymer latexes]
Into an autoclave equipped with a stirrer were
charged 32 parts of water, 1.1 parts of tetrasodium
ethylenediaminetetraacetate, 1.1 parts of sodium lauryl
sulfate and 0.2 part of potassium persulfate, and then a
10 ~ portion of a monomer emulsion separately prepared in
a tank equipped with a stirrer and having a composition
shown in Table 1 was added. The reaction system was
heated to 80C to carry out reaction for 1 hour. Then,
0.8 part of potassium persulfate was added together with
20 parts of water, and then the remaining 90 % portion of
the monomer emulsion was continuously supplied into the
autoclave over a period of 4 hours. During the time, the
autoclave was maintained at 80C. Thereafter, the
reaction system was maintained at 80C for further one
hour, and then ammonia water was added to adjust the pH
of the latex to 9Ø Then, 4.0 parts of water, 2.0 parts
of N,N-dimethylaminoethyl methacrylate and 0.1 part of
ammonium persulfate were added and reaction was carried
out at 80C for 2 hours. Thus, amphoteric copolymer
latexes A, B and C were obtained. All the gelation
points of these latexes were 7.D.
t~ ~
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O ~ ~ O O O O O ~
O O O ~ O O U~ O ~ O
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O O O O ~ O O ~ O O
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- 14
[Preparation of usual styrene-butadiene copolymer latexes
having no gelation point]
Into an autoclave equipped with a stirrer were
charged 32 parts of water, 1.1 parts of tetrasodium
ethylenediaminetetraacetate, 1.1 parts of sodium lauryl
sulfate and 0.2 part of potassium persulfate, and a 10
portion of a monomer emulsion separately prepared in a
tank equipped with a stirrer and having a composition
shown in Table 2 was added. The reaction system was
heated to 80C to be allowed to react for 1 hour. 0.8
part of potassium persulfate was added together with 20
parts of water, and the remaining 90 % portions of the
monomer emulsion was continuously supplied into the
autoclave over a period of 4 hours. During the time~ the
autoclave was maintained at 80c. The reaction was
continued at 80C for further 2 hours. Consequently,
latexes D, E and F were obtained. None of these latexes
exhibited any gelation point.
.
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n Lno o oLn
O O O ~;LnLn~ O O
L~
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O ~i Lt~ O O O O r-l
O O Ç~ ~ O 011~ l O
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Et Ln ~ ~ ,~ ~
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[Coating compositions for newsprint]
Coating compositions for newsprint 1 to 6 each
having a solid concentration of 50 -~ and a pH of 9.5 were
prepared by a coating color formulation shown in Table 3
using the latexes A to F.
Table 3
. . ~ . . __.
Clay 60 parts
Ground calcium carbonate 40
Dispersant (1) 0.2
Sodium hydroxide 0.2
Phosphoric acid-esterified
starch (2) 6
Latex 20
(1) Sodium polyacrylate produced by Toagosei
Chemical Co., Ltd., Aron T-40
(2) produced by Nihon Shokuhinkako Co., Ltd.,
MS-4600
~Example 1]
Sheets of base paper for newsprint were coated
with each of the thus obtained coating compositions under
10 conditions shown in Table 4~ Resulting coated newsprint
was kept in an air-conditioned room of 20C and a
relative humidity of 65+5 % for a whole day and night,
and then subjected to various evaluativn tests. The
results are shown in Table 5.
- . .~. .
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- 17 -
Table 4
Method : Laboratory blade coater
Drying : Hot~air oven, 130C x 20 seconds
Calender : Laboratory supercalender
40C, 55 kg/cm, 2 nips
Base paper : Newsprint (46 g~m )
Coating weight: 5 g/m2/side
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a .. _ ..
~ U~ o ~ U~ ~ ~ ~
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o o ~
~ C~ ~ ~ ~ ~ C~ ~ ~
_ ._ _ _
o'~ U~ o U~ o
~ ~ m ~ u~
U~ ~.~
X ~ u~ r- o
,1 E~
Q r I ¢
E~ . er ~D
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O ~ ~
'~ U~ 0
'0 '0
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0
~r~ Ul O U~
O ~ ~ X .~ ~ ~
81 (U ~ 1 ~ ~
~3 0 ~ ~ ~ lJ S ~r l
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O
1a) h S-l 0
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~ o 3~ ~ ~
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2 ~
From the results of Table 5, it is seen that in
the case where the coating compositions l to 3 of this
invention co~prising an amphoteric latex were used,
coated newsprint excellent in an ink set, water dissipa-
tion, surface strength, print gloss, brightness andopacity could be obtained, whereas in the case of the
coating compos.itions 4 to 6 wherein usual latexes were
used, only coated papers poor in these characteristics
could be obtained.
[EXample 2]
Coated newsprint were prepared in the same
manner as in Example l except that coating compositions 7
to 12 were used obtained by coating color formulations
shown in Table 6 using the latex A or D, and subjected to
the same various evaluation tests as in Example 1. The
results are shown in Table 7.
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-- 20 --
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C~ ~ o o C~ ~ o o
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o o ~ o o
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0-~ X OD O O ~ ~ O O
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. o o o o ~ ~ CO
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l ~ ~ ~ ~ .
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~ ~ ~ .
~
~ ~ td
Id _1 ,1
~ u~ rn
. ~ Q)
o m o~Q
Z .,., ,y ,y ~ ~ ~ .
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O ~Q h1:~ Q. ~ S ~-1
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O ~ h ~ ~
C) ~ o ~ `
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E~
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;
- ~
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:~
- 22 -
From the results of Tabl~ 7, it is seen that in
the case where the coating compositions 7 to 9 of the
invention were used, as the amount of the pigment binder
was increased, surface strength and print gloss were
enhanced and at the same time coated newsprint excellent
in an ink set, water dissipation, brightness and opacity
were obtained, whereas in the case of coating composi-
tions 10 to 12 wherein usual latexes were used, although
print gloss and surface strength were enhanced in
accordance with increase of the amount of the pigment
binder, an ink set and water dissipation were strikingly
lowered and only coated newspaper could be obtained which
did not withstand practical use as newsprint.
[Example 3]
Coated newsprint were prepared in the same
manner as in Example 1 except that coating compositions
13 to 20 obtained by coating color formulations shown in
Table 8 using the latex A were used, and subjected to the
same various evaluation test as in Example 1.
The results are shown in Table 9.
' ,' ~, , , , ~ : . .
` :' ~ :
'
-- 23 --
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o
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OD ~
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O o o o o c~ In
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- - - - - - --
a~
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z O ~
t) ~ ~ h U~ V~
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_ _ ~F:~s~ ele~ p~nleAa
~ .
~ !
- 25 -
It is seen from the results of Table 9 that in
the case where the coating compositions of the invention
were used, coated newsprint were obtained excellent in an
ink set~ water dissipation, surface strength, print
gloss, brightness and opacity, whereas in the case where
the amount of the pigment binder was too large (composi-
tion 18), a coated newsprint strikingly poor in an ink
set and water dissipation was obtained, in the case where
the amount of tbe amphoteric copolymer latex was too
small (composition 19), a coated newsprint having
strikingly low surface strength was obtained, and in the
case where the amount of the water soluble polymer binder
was too large (compositions 19 and 20), coating color
viscosity became too high and coated papers poor in
various characteristics were obtained.
Thus according to this invention, it is
possible to obtain a coated newsprint more excellent in
an ink set, water dissipation, surface strength (parti-
cularly, wet picking resistance and print gloss as cold
set type of~set printabilities and comparable brightness
and opacity, compared with the prior art.
,
- :
