U.S. patent application number 11/630787 was filed with the patent office on 2008-01-31 for printability improving agents and papers coated with them.
Invention is credited to Satoshi Ishioka, Yasunori Nanri, Fuminari Nonomura, Tomohiro Yokohara.
Application Number | 20080023163 11/630787 |
Document ID | / |
Family ID | 35782643 |
Filed Date | 2008-01-31 |
United States Patent
Application |
20080023163 |
Kind Code |
A1 |
Ishioka; Satoshi ; et
al. |
January 31, 2008 |
Printability Improving Agents And Papers Coated With Them
Abstract
The present invention aims to provide printability improving
agents and surface-treating agents capable of improving offset
printability of papers, especially newsprint papers to be printed
with offset inks as well as papers, especially newsprint papers
that can be successfully printed with offset inks. According to a
first aspect of the present invention, a printability improving
agent comprising a cationic copolymer consisting of one or more
hydrophobic monomer unit(s) selected from a specific group and a
quaternary ammonium salt-containing monomer unit or a
surface-treating agent comprising the printability improving agent
and a water-soluble polymer material selected from a specific group
is applied on the surface of a base paper, especially a newsprint
base paper. According to a second aspect of the present invention,
a hydrophobic monomer unit selected from a specific group and a
quaternary ammonium salt-containing monomer unit is polymerized to
give a cationic copolymer, which is then further polymerized with a
hydrophobic monomer to give a copolymer. Alternatively, a
hydrophobic monomer unit selected from a specific group and a
quaternary ammonium salt-containing monomer unit is polymerized to
give a cationic copolymer, which is further polymerized with a
hydrophobic monomer in the presence of a surfactant to give a
copolymer. A printability improving agent comprising the copolymer
or a surface-treating agent comprising the printability improving
agent and a water-soluble polymer material selected from a specific
group is applied on the surface of a base paper, especially a
newsprint base paper.
Inventors: |
Ishioka; Satoshi; (Kita-ku,
JP) ; Yokohara; Tomohiro; (Kita-ku, JP) ;
Nonomura; Fuminari; (Kita-ku, JP) ; Nanri;
Yasunori; (Kita-ku, JP) |
Correspondence
Address: |
NIXON & VANDERHYE, PC
901 NORTH GLEBE ROAD, 11TH FLOOR
ARLINGTON
VA
22203
US
|
Family ID: |
35782643 |
Appl. No.: |
11/630787 |
Filed: |
June 23, 2005 |
PCT Filed: |
June 23, 2005 |
PCT NO: |
PCT/JP05/11520 |
371 Date: |
December 27, 2006 |
Current U.S.
Class: |
162/164.2 ;
162/168.3; 162/168.7 |
Current CPC
Class: |
D21H 19/20 20130101 |
Class at
Publication: |
162/164.2 ;
162/168.3; 162/168.7 |
International
Class: |
D21H 19/20 20060101
D21H019/20 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 30, 2004 |
JP |
2004-193314 |
Jun 30, 2004 |
JP |
2004-193284 |
Claims
1. A printability improving agent characterized in that it
comprises a cationic copolymer comprising one or more hydrophobic
monomer unit(s) selected from the group consisting of: (1) alkyl
acrylates and/or alkyl methacrylates (2) dialkyl diesters (3) vinyl
esters (4) N-alkyl acrylamides and/or N-alkyl methacrylamides (5)
methyl vinyl ethers and a quaternary ammonium salt-containing
monomer unit.
2. A surface-treating agent characterized in that it comprises the
printability improving agent of claim 1 and one or more
water-soluble polymer material(s) selected from the group
consisting of: (1) various modified starches (2) polyvinyl alcohols
(3) cellulose derivatives.
3. A paper characterized in that it is obtained by applying the
printability improving agent of claim 1 or the surface-treating
agent on the surface of a base paper.
4. The paper of claim 3 characterized in that the base paper is a
newsprint base paper prepared by a neutral papermaking process.
5. A printability improving agent comprising (I) a copolymer
obtained by polymerizing one or more hydrophobic monomer unit(s)
selected from the group consisting of: (1) styrenes (2) alkyl
acrylates and/or alkyl methacrylates (3) dialkyl diesters (4) vinyl
esters (5) N-alkyl acrylamides and/or N-alkyl methacrylamides (6)
methyl vinyl ethers and a quaternary ammonium salt-containing
monomer unit to give a cationic copolymer, which is further
polymerized with one or more hydrophobic monomer(s) selected from
the group shown above, or (II) a copolymer obtained by polymerizing
the cationic copolymer obtained by polymerization of the
hydrophobic monomer unit(s) and a quaternary ammonium
salt-containing monomer unit with one or more hydrophobic
monomer(s) selected from the group shown above in the presence of a
surfactant.
6. A surface-treating agent comprising the printability improving
agent of claim 5 and one or more water-soluble polymer material(s)
selected from the group consisting of: (1) various modified
starches (2) polyvinyl alcohols (3) cellulose derivatives.
7. A paper characterized in that it is obtained by applying the
printability improving agent of claim 5 or the surface-treating
agent on the surface of a base paper.
8. The paper of claim 7 characterized in that the base paper is a
newsprint base paper prepared by a neutral papermaking process.
Description
TECHNICAL FIELD
[0001] The present invention relates to printability improving
agents, surface-treating agents, and papers, especially newsprint
papers. More specifically, it relates to printability improving
agents and surface-treating agents capable of improving offset
printability of papers, especially newsprint papers to be printed
with offset inks, as well as papers, especially newsprint papers,
that can be successfully printed with offset inks.
BACKGROUND ART
[0002] Recent newsprint papers are required to have a lighter
weight and a higher proportion of deinked pulp as well as to
satisfy increasingly stricter requirements for printability in
response to the accelerating trend toward offset printing,
high-speed printing and color printing.
[0003] Conventional newsprint papers comprise newsprint base papers
coated on their surfaces with solution-type surface sizing agents
such as aqueous solutions of alkaline metal salts of styrene-maleic
copolymers, aqueous solutions of alkaline metal salts of
styrene-(meth)acrylic copolymers, and aqueous solutions of alkaline
metal salts of .alpha.-olefin-maleic copolymers. Papers coated with
these solution-type surface sizing agents show relatively good
sizing performance, but insufficient printability with offset
inks.
[0004] Thus, printability improving agents for offset inks
comprising an emulsion obtained by polymerizing a hydrophobic
monomer in the presence of a dispersant have been proposed (e.g.,
see patent document 1). These printability improving agents show
printability improving effect better than that of the solution-type
surface sizing agents but insufficient for papers having very low
contents of internal sizing agents.
[0005] Patent document 1: JPA No. 2003-306887.
[0006] With the recent trend toward using a small amount of
internal sizing agents, or none at all, in newsprint papers due to
operational issues, there are demands for printability improving
agents having high printability improving effect for such papers
with low sizing degrees.
[0007] On the other hand, conventional printing inks based on
petroleum solvents containing aromatic components have been rapidly
replaced by ecological inks in recent years for environmental
reasons, such as concern about influences of these components
evaporating during their preparation or use on the environment or
human bodies. However, newsprint papers coated with the
solution-type surface sizing agents were not sufficient in
printability when they were printed with ecological inks based on
non-petroleum solvents such as vegetable oils or hydrogenated
mineral oils.
[0008] Moreover, fountain solution wetting the coated surfaces of
newsprint papers coated with the solution-type surface sizing
agents during offset printing tend to invite redissolution of the
surface sizing agents or dissolution of modified starches included
therein, which may result in printing troubles such as fouling of
blankets or plates.
[0009] Currently, dominant newsprint papers among offset printing
papers are acidic, but will be neutral in future. However, the
solution-type surface sizing agents do not have sufficient sizing
effect on these neutral printing papers and must be increased to
prevent out-of-register colors in multicolor printing, which may
further deteriorate printability.
DISCLOSURE OF THE INVENTION
Problems to Be Solved By the Invention
[0010] The present invention aims to provide printability improving
agents and surface-treating agents capable of improving offset
printability of papers, especially newsprint papers to be printed
with offset inks as well as papers, especially newsprint papers
that can be successfully printed with offset inks.
Means to Solve the Problems
[0011] According to a first aspect of the invention, a printability
improving agent comprising a cationic copolymer comprising one or
more hydrophobic monomer unit(s) selected from the group consisting
of:
[0012] (1) alkyl acrylates and/or alkyl methacrylates
[0013] (2) dialkyl diesters
[0014] (3) vinyl esters
[0015] (4) N-alkyl acrylamides and/or N-alkyl methacrylamides
[0016] (5) methyl vinyl ethers
[0017] and a quaternary ammonium salt-containing monomer unit or a
surface-treating agent comprising the printability improving agent
and a water-soluble polymer material selected from a specific
group, is applied on the surface of a base paper, especially a
newsprint base paper.
[0018] According to a second aspect of the present invention, a
hydrophobic monomer unit selected from the group consisting of:
[0019] (1) styrenes
[0020] (2) alkyl acrylates and/or alkyl methacrylates
[0021] (3) dialkyl diesters
[0022] (4) vinyl esters
[0023] (5) N-alkyl acrylamides and/or N-alkyl methacrylamides
[0024] (6) methyl vinyl ethers
[0025] and a quaternary ammonium salt-containing monomer unit are
polymerized to give a cationic copolymer [A-1], which is then
further polymerized with a hydrophobic monomer [B] selected from
the group shown above to give a copolymer. Alternatively, a
hydrophobic monomer unit selected from the group shown above and a
quaternary ammonium salt-containing monomer unit are polymerized to
give a cationic copolymer, which is further polymerized with a
hydrophobic monomer [B] selected from the group shown above to give
a copolymer in the presence of a surfactant. A printability
improving agent comprising the copolymer or a surface-treating
agent comprising the printability improving agent and a
water-soluble polymer material selected from a specific group is
applied on the surface of a base paper, especially a newsprint base
paper.
ADVANTAGES OF THE INVENTION
[0026] Papers having improved adhesion to offset inks, especially
ecological inks and reduced starch dissolution, and consequently
high printability and fewer printing troubles such as plate fouling
can be provided by applying a printability improving agent of the
present invention or a surface-treating agent containing the
printability improving agent on the surface of a base paper.
THE MOST PREFERRED EMBODIMENTS OF THE INVENTION
[0027] First, the printability improving agent used in the first
aspect of the present invention is explained. The printability
improving agent comprises a cationic copolymer comprising at least
a hydrophobic monomer unit and a quaternary ammonium
salt-containing monomer unit as described below, wherein the
"monomer unit" refers to a structural unit of a monomer when it is
copolymerized. The hydrophobic monomer unit constituting this
cationic copolymer is obtained by using a hydrophobic monomer
during copolymerization. The quaternary ammonium salt-containing
monomer unit is obtained by using a quaternary ammonium
salt-containing monomer during copolymerization, or by
copolymerizing an amino group-containing monomer and then
converting thus obtained copolymer into a quaternary ammonium salt
with a quaternizing agent. For example, a cationic copolymer can be
obtained by copolymerizing a hydrophobic monomer and a tertiary
amino group-containing monomer and then reacting thus obtained
copolymer with a quaternizing agent. In addition to the hydrophobic
monomer forming the hydrophobic monomer unit, the quaternary
ammonium salt-containing monomer forming the quaternary
ammonium-containing monomer unit and/or the amino group-containing
monomer capable of being quaternized after copolymerization, the
cationic copolymer can contain a nonionic monomer unit or an
anionic monomer unit partially replacing the hydrophobic monomer
unit, so long as the intended effect of the present invention is
obtained.
[0028] Hydrophobic monomers used to form the hydrophobic monomer
unit specifically include the following members, and these various
hydrophobic monomers can be used alone or in combinations of two or
more.
[0029] (1) alkyl(meth)acrylates: e.g., methyl(meth)acrylate,
ethyl(meth)acrylate, normal butyl(meth)acrylate,
isobutyl(meth)acrylate, tertiary butyl(meth)acrylate,
2-ethylhexyl(meth)acrylate, lauryl(meth)acrylate,
stearyl(meth)acrylate, cyclic alkyl(meth)acrylates, etc.;
[0030] (2) dialkyl diesters: e.g., dimethyl esters, diethyl esters
and the like of maleic acid, fumaric acid, etc.;
[0031] (3) vinyl esters: e.g., vinyl esters of tertiary carboxylic
acids containing 5-10 carbon atoms, vinyl propionate, etc.;
[0032] (4) N-alkyl(meth)acrylamides;
[0033] (5) methyl vinyl ethers.
[0034] Among them, alkyl(meth)acrylates are preferably used, in
terms of printability.
[0035] Nonionic monomers that can be used to form the nonionic
monomer unit capable of partially replacing the hydrophobic monomer
unit include polymerizable monomers having neither cationic nor
anionic group but having a hydrophilic group, e.g.,
(meth)acrylamides; acrylonitrile; hydroxyalkyl(meth)acrylates such
as 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate,
2,3-dihydroxypropyl(meth)acrylate, etc. These nonionic monomers can
be used alone or in combinations of two or more.
[0036] Monomers used to form the quaternary ammonium
salt-containing monomer unit include primary to tertiary amino
group-containing monomers and quaternary ammonium salt-containing
monomers, wherein the primary to tertiary amino group-containing
monomers form quaternary ammonium salts with a quaternizing agent
after copolymerization. Among them, preferred are quaternary
ammonium salt-containing monomer units obtained by copolymerizing
quaternary ammonium salt-containing monomers, and quaternary
ammonium salt-containing monomer units obtained by copolymerizing
tertiary amino group-containing monomers and then quaternizing the
tertiary amino group.
[0037] Primary amino group-containing monomers include e.g.,
allylamine and methallylamine, and secondary amino group-containing
monomers include e.g., diallylamine and dimethallylamine.
[0038] Tertiary amino group-containing monomers include tertiary
amino group-containing vinyl compounds, specifically the following
compounds, which can be used alone or in combinations of two or
more.
[0039] (1) (dialkyl)aminoalkyl(meth)acrylates: e.g., dimethyl
aminoethyl(meth)acrylate, diethyl aminoethyl(meth)acrylate,
dimethyl aminopropyl(meth)acrylate, diethyl
aminopropyl(meth)acrylate, etc.;
[0040] (2) (dialkyl)aminohydroxyalkyl(meth)acrylates: e.g.,
dimethyl aminohydroxyethyl(meth)acrylate, diethyl
aminohydroxyethyl(meth)acrylate, dimethyl
aminohydroxypropyl(meth)acrylate, diethyl
aminohydroxypropyl(meth)acrylate, etc.;
[0041] (3) (dialkyl)aminoalkyl(meth)acrylamides: e.g., dimethyl
aminopropyl(meth)acrylamide, diethyl aminopropyl(meth)acrylamide,
etc.;
[0042] (4) vinyl pyridines;
[0043] (5) vinyl imidazoles.
[0044] Among them, (dialkyl)aminoalkyl(meth)acrylates and
(dialkyl)aminoalkyl(meth)acrylamides are preferred, in terms of
printability performance.
[0045] Quaternary ammonium salt-containing monomers include the
tertiary amino group-containing monomers quaternized with a
quaternizing agent. Quaternizing agents used to obtain the
quaternary ammonium salt-containing monomers include epoxy
compounds and organic halides such as methyl chloride, ethyl
chloride, benzyl chloride, epichlorohydrin, alkylene oxides,
styrene oxide, glycidyl trimethylammonium chloride, and
3-chloro-2-hydroxyammonium chloride; dimethyl sulfate, and diethyl
sulfate. Among them, epichlorohydrin, alkylene oxides and styrene
oxide are preferred, in terms of performance. These quaternizing
agents can also be used after the tertiary amino group-containing
monomers have been polymerized.
[0046] The weight ratio of the hydrophobic monomer unit and the
quaternary ammonium salt-containing monomer unit forming the
cationic copolymer in the printability improving agent according to
the first aspect of the present invention is preferably
55-85:45-15, more preferably 60-80:40-20. If the cationic monomer
unit is less than 15% or exceeds 45%, printability may be
deteriorated.
[0047] The cationic copolymer used in the printability improving
agent according to the first aspect of the present invention can be
prepared by applying previously known polymerization methods, such
as e.g., solution polymerization using an organic solvent, bulk
polymerization using no solvent, emulsion polymerization in an
aqueous system using an oligomer or polymer emulsifier, etc.
[0048] The cationic copolymer can be obtained by e.g., polymerizing
a mixture of the hydrophobic monomer and the tertiary amino
group-containing monomer, or a mixture of the hydrophobic monomer
and the quaternary ammonium salt-containing monomer or a mixture of
such a mixture and one of other copolymerizable vinyl monomers in a
lower alcohol organic solvent such as methyl alcohol, ethyl alcohol
or isopropyl alcohol, or in an organic oily solvents such as
benzene, toluene or xylene, or in a mixed solution of such a lower
alcohol organic solvent and water, or in water, or in a
solvent-free system at 60-130.degree. C. for 1-10 hours using a
free-radical polymerization catalyst, and after completion of the
polymerization, distilling the organic solvent off if needed and
quaternizing the tertiary amino group by a known and common
method.
[0049] Free-radical polymerization catalysts include, but are not
limited to, e.g., oil-soluble azo catalysts such as
2,2'-azobisisobutyronitrile, dimethyl 2,2'-azobis(2-methyl
propionate); oil-soluble organic peroxides such as benzyl peroxide,
tertiary butyl peroxybenzoate, tertiary butyl peroxy-2-ethyl
hexanoate; persulfates such as ammonium persulfate, potassium
persulfate, sodium persulfate; water-soluble peroxides such as
hydrogen peroxide; redox polymerization catalysts formed by
combination of these persulfates and peroxides with reducing
agents; water-soluble azo catalysts such as
2,2'-azobis(2-amidinopropane)dihydrochloride; water-soluble organic
peroxides such as tertiary butyl hydroperoxide.
[0050] If desired, known chain transfer agents such as alkyl
mercaptans may also be used. It should be noted that the monomer
used to synthesize the cationic copolymer in the printability
improving agent according to the first aspect of the present
invention is substantially completely reacted to form a monomer
unit in the cationic copolymer.
[0051] Alkaline materials preferably used for coating with the
printability improving agent according to the first aspect of the
present invention include e.g., ammonia; alkyl amines;
aminoalcohols such as monoethanolamine, diethanolamine,
triethanolamine; inorganic alkalis such as sodium hydroxide,
potassium hydroxide; sulfites; carbonates; organic acid salts,
etc.
[0052] Next, the printability improving agent used in the second
aspect of the present invention is explained. The printability
improving agent comprises at least a copolymer obtained by
polymerizing a specific hydrophobic monomer unit and a quaternary
ammonium salt-containing monomer unit to give a cationic copolymer
[A-1], which is then further polymerized with a specific
hydrophobic monomer [B], or a copolymer obtained by polymerizing
the cationic copolymer [A-1] with a specific hydrophobic monomer
[B] in the presence of a surfactant [A-2]. Preferably, it comprises
a copolymer obtained by polymerizing the cationic copolymer [A-1]
with a specific hydrophobic monomer [B] in the presence of a
surfactant [A-2].
[0053] 1. Cationic Copolymer [A-1]
[0054] The "monomer unit" refers to a structural unit of a monomer
when it is copolymerized. The hydrophobic monomer unit forming the
cationic copolymer [A-1] is obtained by using a hydrophobic monomer
during copolymerization. The quaternary ammonium salt-containing
monomer unit is obtained by using a quaternary ammonium
salt-containing monomer during copolymerization, or by
copolymerizing an amino group-containing monomer and then
converting thus obtained copolymer into a quaternary ammonium salt
with a quaternizing agent. For example, a cationic copolymer can be
obtained by copolymerizing a hydrophobic monomer and a tertiary
amino group-containing monomer and then reacting thus obtained
copolymer with a quaternizing agent. In addition to the hydrophobic
monomer forming the hydrophobic monomer unit, the quaternary
ammonium salt-containing monomer forming the quaternary
ammonium-containing monomer unit and/or the amino group-containing
monomer capable of being quaternized after copolymerization, the
cationic copolymer can contain a nonionic monomer unit or an
anionic monomer unit partially replacing the hydrophobic monomer
unit, so long as the intended effect of the present invention is
obtained.
[0055] Hydrophobic monomers used to form the hydrophobic monomer
unit of the cationic copolymer [A-1] specifically include the
following members, and these various hydrophobic monomers can be
used alone or in combinations of two or more.
[0056] (1) styrenes: e.g., styrene, .alpha.-methyl styrene, vinyl
toluene, divinyl benzene, etc.;
[0057] (2) alkyl(meth)acrylates: e.g., methyl(meth)acrylate,
ethyl(meth)acrylate, normal butyl(meth)acrylate,
isobutyl(meth)acrylate, tertiary butyl(meth)acrylate,
2-ethylhexyl(meth)acrylate, lauryl(meth)acrylate,
stearyl(meth)acrylate, cyclic alkyl(meth)acrylates, etc.;
[0058] (3) dialkyl diesters: e.g., dimethyl esters, diethyl esters
and the like of maleic acid, fumaric acid, etc.;
[0059] (4) vinyl esters: e.g., vinyl esters of tertiary carboxylic
acids containing 5-10 carbon atoms, vinyl propionate, etc.;
[0060] (5) N-alkyl(meth)acrylamides;
[0061] (6) methyl vinyl ethers.
[0062] Among them, the styrenes and alkyl(meth)acrylates are
preferably used alone or in combination, especially
alkyl(meth)acrylates alone in terms of stability of the
printability improving agent and printability.
[0063] Nonionic monomers that can be used to form the nonionic
monomer unit capable of partially replacing the hydrophobic monomer
unit include polymerizable monomers having neither cationic nor
anionic group but having a hydrophilic group, e.g.,
(meth)acrylamides; acrylonitrile; hydroxyalkyl(meth)acrylates such
as 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate,
2,3-dihydroxypropyl(meth)acrylate, etc. These nonionic monomers can
be used alone or in combinations of two or more.
[0064] Monomers used to form the quaternary ammonium
salt-containing monomer unit that can be used for the preparation
of the cationic copolymer [A-1] include primary to tertiary amino
group-containing monomers and quaternary ammonium salt-containing
monomers, wherein the primary to tertiary amino group-containing
monomers form quaternary ammonium salts with a quaternizing agent
after copolymerization. Among them, preferred are quaternary
ammonium salt-containing monomer units obtained by copolymerizing
quaternary ammonium salt-containing monomers and quaternary
ammonium salt-containing monomer units obtained by copolymerizing
tertiary amino group-containing monomers and then quaternizing the
tertiary amino group.
[0065] Primary amino group-containing monomers include e.g.,
allylamine and methallylamine, and secondary amino group-containing
monomers include e.g., diallylamine and dimethallylamine.
[0066] Tertiary amino group-containing monomers include tertiary
amino group-containing vinyl compounds, specifically the following
compounds, which can be used alone or in combinations of two or
more.
[0067] (1) (dialkyl)aminoalkyl(meth)acrylates: e.g., dimethyl
aminoethyl(meth)acrylate, diethyl aminoethyl(meth)acrylate,
dimethyl aminopropyl(meth)acrylate, diethyl
aminopropyl(meth)acrylate, etc.;
[0068] (2) (dialkyl)aminohydroxyalkyl(meth)acrylates: e.g.,
dimethyl aminohydroxyethyl(meth)acrylate, diethyl
aminohydroxyethyl(meth)acrylate, dimethyl
aminohydroxypropyl(meth)acrylate, diethyl
aminohydroxypropyl(meth)acrylate, etc.;
[0069] (3) (dialkyl)aminoalkyl(meth)acrylamides: e.g., dimethyl
aminopropyl(meth)acrylamide, diethyl aminopropyl(meth)acrylamide,
etc.;
[0070] (4) vinyl pyridines;
[0071] (5) vinyl imidazoles.
[0072] Among them, (dialkyl)aminoalkyl(meth)acrylates and
(dialkyl)aminoalkyl(meth)acrylamides are preferred in terms of
printability performance.
[0073] Quaternary ammonium salt-containing monomers include the
tertiary amino group-containing monomers quaternized with a
quaternizing agent. Quaternizing agents used to obtain the
quaternary ammonium salt-containing monomers include epoxy
compounds and organic halides such as methyl chloride, ethyl
chloride, benzyl chloride, epichlorohydrin, alkylene oxides,
styrene oxide, glycidyl trimethylammonium chloride, and
3-chloro-2-hydroxyammonium chloride; dimethyl sulfate, and diethyl
sulfate. Among them, epichlorohydrin, alkylene oxides and styrene
oxide are preferred in terms of performance. These quaternizing
agents can also be used after the tertiary amino group-containing
monomers have been polymerized.
[0074] Quaternizing agents used to quaternize the tertiary amino
group-containing monomer after copolymerization include organic
halides such as methyl chloride, ethyl chloride, benzyl chloride,
epichlorohydrin, glycidyl trimethyl ammonium chloride, and
3-chloro-2-hydroxyammonium chloride; dimethyl sulfate and diethyl
sulfate.
[0075] The cationic copolymer [A-1] can be obtained by e.g.,
polymerizing (1) a mixture of the hydrophobic monomer and the
tertiary amino group-containing monomer, or (2) a mixture of the
hydrophobic monomer and the quaternary ammonium salt-containing
monomer in a lower alcohol organic solvent such as methyl alcohol,
ethyl alcohol or isopropyl alcohol, or in an organic oily solvent
such as benzene, toluene or xylene, or in a mixed solution of such
a lower alcohol organic solvent and water, or in water at
60-130.degree. C. for 1-10 hours using a free-radical
polymerization catalyst, and after completion of the
polymerization, distilling the organic solvent off if needed and
quaternizing the tertiary amino group by a known and common
method.
[0076] Free-radical polymerization catalysts include, but are not
limited to, e.g., oil-soluble azo catalysts such as
2,2'-azobisisobutyronitrile, dimethyl 2,2'-azobis(2-methyl
propionate); oil-soluble organic peroxides such as benzyl peroxide,
tertiary butyl peroxybenzoate, tertiary butyl peroxy-2-ethyl
hexanoate; persulfates such as ammonium persulfate, potassium
persulfate, sodium persulfate; water-soluble peroxides such as
hydrogen peroxide; redox polymerization catalysts formed by
combination of these persulfates and peroxides with reducing
agents; water-soluble azo catalysts such as
2,2'-azobis(2-amidinopropane)dihydrochloride; water-soluble organic
peroxides such as tertiary butyl hydroperoxide.
[0077] If desired, known chain transfer agents such as alkyl
mercaptans may also be used. It should be noted that the monomer
used to synthesize the cationic copolymer [A-1] in the printability
improving agent according to the second aspect of the present
invention is substantially completely reacted to form a monomer
unit in the cationic copolymer [A-1].
[0078] The weight ratio of the hydrophobic monomer unit and the
quaternary ammonium salt-containing monomer unit in the cationic
copolymer [A-1] is preferably 40-85:60-15, more preferably
50-85:50-15. If the cationic monomer unit is less than 15% or
exceeds 60%, printability may be deteriorated.
[0079] 2. Surfactant [A-2]
[0080] The surfactant [A-2] optionally used in the printability
improving agent according to the second aspect of the present
invention can be a known emulsifier or dispersant that can be
normally applied for emulsion polymerization, such as e.g.,
cationic, nonionic, ampholytic and anionic surfactants, and
free-radically polymerizable surfactants, and at least one member
selected from these groups can be used.
[0081] Cationic surfactants that can be used include acetate salts
and epichlorohydrin-modified products of primary and secondary
amines, etc. Primary and secondary amines are represented by
general formulae R.sub.1NH.sub.2 and R.sub.2R.sub.3NH, wherein
R.sub.1, R.sub.2 and R.sub.3 each represent the same or different
linear or cyclic hydrocarbon group containing 1-30 carbon atoms.
R.sub.1, R.sub.2 and R.sub.3 include e.g., substituents such as
methyl, ethyl, propyl, isopropyl, allyl, butyl, isobutyl, S-butyl,
t-butyl, hexyl, cyclohexyl, octyl, 2-ethylhexyl, nonyl, decyl,
lauryl, myristyl, palmityl, stearyl, oleyl, phenyl, naphthyl,
dehydroabietyl, etc.
[0082] Other cationic surfactants include tetraalkylammonium
chlorides, trialkylbenzylammonium chlorides, acetate salts and
epichlorohydrin-modified products of rosin amines, monooxyethylene
alkylamines and polyoxyethylene alkylamines. These cationic
oligomer surfactants can be used alone or in combinations of two or
more.
[0083] Nonionic surfactants include e.g., polyoxyalkylene alkyl
phenyl ethers, polyoxyalkylene alkyl ethers, polyoxyalkylene fatty
acid esters, polyoxypropylene polyoxyethylene glycol glycerin fatty
acid esters, sorbitan fatty acid esters, polyethylene glycol fatty
acid esters, polyoxyethylene sorbitan fatty acid esters, sucrose
fatty acid esters, pentaerythritol fatty acid esters, propylene
glycol fatty acid esters, fatty acid diethanolamides, and
polyoxypropylene polyoxyethylene glycol. These nonionic surfactants
can be used alone or in combinations of two or more.
[0084] Anionic surfactants include e.g., phosphate ester salts,
sulfonate salts, succinate ester salts and sulfosuccinate ester
salts of polyoxyalkylene alkyl phenyl ethers, polyoxyalkylene
monostyryl phenyl ethers, polyoxyalkylene distyryl phenyl ethers,
polyoxyalkylene alkyl ethers and polyoxyalkylene fatty acid esters,
etc.; and alkylbenzene sulfonate, alkaline salts of naphthalene
sulfonate-formalin condensation products, alkenyl succinate salts,
alkaline metal salts of rosin and alkaline metal salts of fortified
rosin. These anionic surfactants can be used alone or in
combinations of two or more.
[0085] The free-radically polymerizable surfactants are generally
called reactive emulsifiers, which are compounds having a
hydrophobic group, a hydrophilic group and a carbon-carbon double
bond. The compounds having a carbon-carbon double bond include
e.g., compounds having a functional group such as (meth)allyl,
1-propenyl, 2-methyl-1-propenyl, isopropenyl, vinyl, and
(meth)acryloyl groups.
[0086] These free-radically polymerizable surfactants that can be
used are those normally applicable for emulsion polymerization, and
include, but are not limited to, e.g., polyoxyalkylene alkyl
ethers, polyoxyalkylene aralkyl ethers, polyoxyalkylene phenyl
ethers, polyoxyalkylene monostyryl phenyl ethers and
polyoxyalkylene distyryl phenyl ethers having one or more of the
functional groups in the molecule, and sulfonate salts, sulfate
ester salts, phosphate ester salts and sulfosuccinate ester salts
thereof; fatty acid carboxylate salts and aromatic carboxylate
salts of polyoxyalkylene alkyl ethers or polyoxyalkylene phenyl
ethers having one or more of the functional groups in the molecule;
acidic(meth)acrylate ester compounds; rosin-glycidyl(meth)acrylate
compounds; alkyl diphenyl ether disulfonate compounds, e.g., hexyl
diphenyl ether disulfonate, decyl diphenyl ether disulfonate,
dodecyl diphenyl ether disulfonate, hexadecyl diphenyl ether
disulfonate and alkaline metal salts such as sodium salts,
potassium salts or ammonium salts thereof. These surfactants having
polymerizable groups can be used alone or in combinations of two or
more.
[0087] In the printability improving agent according to the second
aspect of the present invention, at least one member selected from
the group consisting of the cationic surfactants, nonionic
surfactants and free-radically polymerizable nonionic surfactants
is preferably used in view of printability, stability during
emulsion polymerization and compatibility with other concomitant
chemicals.
[0088] The cationic surfactants, nonionic surfactants and
free-radically polymerizable nonionic surfactants preferably
contain a long-chain alkyl group and a polyalkylene oxide group in
terms of stability during preparation, more preferably an alkyl
group containing 6-22 carbon atoms and a polyethylene oxide group
having 5-40 EO moles in terms of the stability of the printability
improving agent, printability and compatibility with other
concomitant chemicals.
[0089] 3. Hydrophobic Monomer [B]
[0090] The printability improving agent according to the second
aspect of the present invention can be obtained by emulsion
polymerizing a hydrophobic monomer [B] in the presence of the
cationic copolymer [A-1] consisting of at least a hydrophobic
monomer unit and a quaternary ammonium salt-containing monomer unit
or the cationic copolymer [A-1] and the surfactant [A-2]. Suitable
hydrophobic monomers [B] are similar to those listed for the
cationic copolymer [A-1].
[0091] Specifically, examples include styrenes such as styrene,
.alpha.-methyl styrene, vinyl toluene, divinyl benzene;
alkyl(meth)acrylates having an alkyl group containing 1-18 carbon
atoms such as methyl(meth)acrylate, ethyl(meth)acrylate,
propyl(meth)acrylate, butyl(meth)acrylate, octyl(meth)acrylate,
2-ethylhexyl(meth)acrylate; cyclic alkyl(meth)acrylates such as
cyclohexyl(meth)acrylates, benzyl(meth)acrylate; dialkyl diesters
of maleic acid and fumaric acid; vinyl esters such as vinyl acetate
and vinyl propionate; N-alkyl(meth)acrylamides; and methyl vinyl
ethers; and one or more of them can be used.
[0092] Among the hydrophobic monomers [B], styrenes and
alkyl(meth)acrylates are preferred in terms of printability and
stability of the printability improving agent.
[0093] In addition to the hydrophobic monomers mentioned above,
other copolymerizable monomers such as nonionic monomers can be
used in a range of 20 mol % or less. Nonionic monomers include
polymerizable monomer having neither cationic nor anionic group and
having a hydrophilic group, e.g., (meth)acrylamides, acrylonitrile,
and hydroxyalkyl(meth)acrylates, e.g.,
2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate, and
2,3-dihydroxypropyl(meth)acrylate. These nonionic monomers can be
used alone or in combinations of two or more.
[0094] When the hydrophobic monomer [B] is polymerized in the
presence of the cationic copolymer [A-1] consisting of at least a
hydrophobic monomer unit and a quaternary ammonium salt-containing
monomer unit or the cationic copolymer [A-1] and the surfactant
[A-2], the weight ratio of the cationic copolymer [A-1] or the
cationic copolymer [A-1] plus surfactant [A-2] and the hydrophobic
monomer [B] is preferably chosen in such a manner that 30-100 parts
by weight of the cationic copolymer [A-1] is contained per 100
parts by weight of the hydrophobic monomer [B] in terms of the
stability of the resulting emulsion. Especially, 40-100 parts by
weight of the cationic copolymer [A-1] component is preferably
contained in terms of sizing performance.
[0095] The weight ratio of the hydrophobic monomer [B] and the
surfactant [A-2] is chosen in such a manner that normally 0-10
parts by weight, especially 1-5 parts by weight of the surfactant
[A-2] is contained per 100 parts by weight of the hydrophobic
monomer [B]. If more than 10 parts by weight of the surfactant
[A-2] is contained per 100 parts by weight of the hydrophobic
monomer [B], printability may not be sufficiently improved.
[0096] The hydrophobic monomer [B] component can be polymerized by
previously known emulsion polymerization methods, e.g., by emulsion
polymerizing the hydrophobic monomer [B] component in water in the
presence of a mixture of the cationic copolymer [A-1] and the
surfactant [A-2] using a free-radical polymerization catalyst. It
should be noted that the hydrophobic monomer [B] component is
substantially completely polymerized to form a copolymer.
[0097] Polymerization catalysts used for the polymerization
reaction include e.g., persulfates such as ammonium persulfate,
potassium persulfate, sodium persulfate; redox polymerization
catalysts formed by combination of these persulfates with reducing
agents; water-soluble azo catalysts such as
2,2'-azobis(2-amidinopropane)dihydrochloride; or organic peroxides
such as tertiary butyl hydroperoxide. In addition, oil-soluble azo
catalysts such as 2,2'-azobisisobutyronitrile, dimethyl
2,2'-azobis(2-methyl propionate); or oil-soluble organic peroxides
such as benzyl peroxide, tertiary butyl peroxybenzoate, tertiary
butyl peroxy-2-ethyl hexanoate can be used in combination with the
water-soluble free radical initiators mentioned above. If desired,
known chain transfer agents such as alkyl mercaptans may also be
used without inconvenience.
[0098] During the emulsion polymerization of the hydrophobic
monomer [B] component, known oligomer surfactants and polymer
dispersants can also be used without inconvenience, so long as the
performance of the printability improving agent according to the
second aspect of the present invention is not impaired.
[0099] Alkaline materials preferably used for coating with the
printability improving agent according to the second aspect of the
present invention include e.g., ammonia; alkyl amines;
aminoalcohols such as monoethanolamine, diethanolamine,
triethanolamine; inorganic alkalis such as sodium hydroxide,
potassium hydroxide; sulfites; carbonates; organic acid salts,
etc.
[0100] The ecological inks described below refer to printing inks
using only solvents having little environmental impact containing
1% or less of aromatic components such as aromatic hydrocarbons,
and include e.g., inks using animal or vegetable solvents such as
soybean oil inks, aromatic-free inks using aromatic-free solvents,
etc. Methods for printing newsprint papers with such ecological
inks include offset printing, etc.
[0101] The printability improving agent according to the first or
second aspect of the present invention is applied on various base
papers directly or after it has been mixed with a binder consisting
of a water-soluble polymer material to form a surface-treating
agent in the same manner as in normal paper-making processes. The
surface-treating agent refers to a mixed coating solution
containing the printability improving agent, water-soluble polymer
material, and other chemicals.
[0102] Water-soluble polymer materials include e.g., various
modified starches such as enzyme-modified starches,
thermochemically modified starches, oxidized starches, esterified
starches, etherified starches (e.g., hydroxyethylated starches,
etc.), cationized starches; polyvinyl alcohols such as polyvinyl
alcohols, completely saponified polyvinyl alcohols, partially
saponified polyvinyl alcohols, carboxyl-modified polyvinyl
alcohols, silanol-modified polyvinyl alcohols, cationically
modified polyvinyl alcohols, terminally alkylated polyvinyl
alcohols; and cellulose derivatives such as carboxymethyl
cellulose, hydroxyethyl cellulose, methyl cellulose. These are used
alone or in combinations of two or more.
[0103] The printability improving agent according to the first or
second aspect of the present invention may contain additives such
as anti-tack agents, preservatives, antifoaming agents, lubricants,
anti-slip agents, anti-rust agents, UV protective agents,
anti-fading agents, fluorescent whitening agents, viscosity
stabilizers, alkaline materials, etc. or other surface sizing
agents, so long as the effect of the printability improving agent
is not impaired. Among them, alkaline materials are preferably used
because printability with offset inks is improved.
[0104] Papers coated with the printability improving agent
according to the first or second aspect of the present invention or
a surface-treating agent containing the printability improving
agent, are explained. The printability improving agent or a
surface-treating agent containing the printability improving agent
is applied on the surface of a base paper prepared by an acidic or
neutral papermaking process. Various types of base papers can be
used, such as coated base paper, PPC paper, inkjet paper, business
form, woodfree paper, wood containing paper, coated board, liner
board, heat-sensitive transfer paper, etc.
[0105] The pulp material for the base paper is not specifically
limited. Bleached or unbleached mechanical pulps such as groundwood
pulp (GP), mechanical pulp (MP), thermomechanical pulp (TMP);
bleached or unbleached chemical pulps such as kraft pulp (KP),
sulfite pulp; or recycled pulps such as deinked pulp (DIP) can be
blended in appropriate proportions and used depending on the type
of the base paper to be prepared.
[0106] If desired, fillers may be added during the preparation of
the base paper depending on the properties required for the paper
including optical properties such as opacity, printing opacity and
brightness or paper quality such as smoothness. Fillers that can be
optionally used are those commonly used in acidic or neutral
papermaking processes and are not specifically limited. In neutral
papermaking processes, for example, inorganic fillers such as clay,
calcined kaolin, delaminated kaolin, ground calcium carbonate,
precipitated calcium carbonate, magnesium carbonate, barium
carbonate, titanium dioxide, zinc oxide, silicon oxide, amorphous
silica, aluminum hydroxide, calcium hydroxide, magnesium hydroxide,
and zinc hydroxide; or organic fillers such as urea-formalin
resins, polystyrene resins, phenol resins and hollow microparticles
can be used alone or as appropriate combinations of two or more of
them. In acidic papermaking processes, the fillers listed above for
use in neutral papermaking processes except for acid-soluble ones
can be used alone or in appropriate combinations of two or
more.
[0107] Internal sizing agents or internal paper additives may also
be contained, and such internal paper additives include aluminum
sulfate, aluminum chloride, sodium aluminate; basic aluminum
compounds such as basic aluminum chloride and basic aluminum
polyhydroxide; water-soluble aluminum compounds such as colloidal
alumina readily soluble in water; polyvalent metal compounds such
as ferrous sulfate and ferric sulfate; colloidal silica, etc.
[0108] Other paper additives that can be used include various
compounds, such as various starches, polyacrylamides, urea resins,
melamine resins, epoxy resins, polyamide resins, polyamides,
polyamine resins, polyamines, polyethyleneimine, vegetable gums,
polyvinyl alcohols, latexes, polyethylene oxide, hydrophilic
crosslinked polymer particle dispersions and derivatives or
modified products thereof.
[0109] In addition, internal paper additives such as dyes,
fluorescent whitening agents, pH adjusting materials, antifoaming
agents, pitch control agents, slime control agents or the like can
also be contained as appropriate depending on the purpose.
[0110] Base papers prepared by neutral papermaking processes are
more preferable than base papers prepared by acidic papermaking
processes because the effect of the printability improving agent of
the present invention becomes more visible.
[0111] The solids concentration of the printability improving agent
according to the first or second aspect in the surface-treating
agent (coating solution) is normally 0.05-2% by weight, preferably
0.1-1% by weight. If it is less than 0.05% by weight, the
printability improving effect may be insufficient, while
concentrations exceeding 2% by weight are economically
disadvantageous because the printability improving effect reaches
its peak around 2% by weight.
[0112] The coating amount of the printability improving agent on
the base paper is normally 0.005-0.3 g/m.sup.2, preferably 0.01-0.2
g/m.sup.2 on a solids basis. The printability is especially
improved within this range.
[0113] When a surface-treating agent comprising a mixture of the
printability improving agent and a water-soluble polymer material
is to be applied, the solids concentration of the printability
improving agent in the surface-treating agent and the coating
amount are as described above, while the solids concentration of
the water-soluble polymer material in the surface-treating agent
and the coating amount of the water-soluble polymer material on the
base paper are determined according to the target surface strength
of the paper, which depends on the type of the paper. Thus, the
ratio of the water-soluble polymer material and the surface coating
sizing agent is not specifically defined.
[0114] The apparatus for applying the printability improving agent
according to the first or second aspect of the present invention or
a surface-treating agent containing the printability improving
agent on the base paper is not specifically limited, and known
apparatus such as size presses, gate roll coaters, Sym-Sizer size
presses, blade coaters, bar coaters, air knife coaters, and knife
coaters can be chosen and used as appropriate.
[0115] Newsprint papers coated with the printability improving
agent according to the first or second aspect of the present
invention or a surface-treating agent containing the printability
improving agent are explained. Pulp materials may be those
conventionally used for newsprint papers, including mechanical
pulps (MP) such as groundwood pulp (GP), thermomechanical pulp
(TMP), chemithermomechanical pulp (CTMP) and semichemical pulp
(SCP); chemical pulps (CP) such as kraft pulp (KP) and sulfite pulp
(SP); deinked pulps (DIP) obtained by deinking waste paper
containing these pulps; and recycled pulps obtained by
disintegrating mill broke; and they are used alone or in admixture
at given proportions and converted into paper by known and common
machines. In view of demands for increasing the proportion of DIP
consistent with the recent growing interest in environmental
protection, the proportion of DIP is preferably in the range of
50-100% by weight.
[0116] Newsprint base papers can contain fillers such as white
carbon, clay, silica, talc, titanium oxide, calcium carbonate and
synthetic resin fillers (such as vinyl chloride resins, polystyrene
resins, urea-formalin resins, melamine resins, styrene-butadiene
copolymer resins, etc.), if desired. They may also contain internal
paper strength enhancers such as polyacrylamide polymers, polyvinyl
alcohol polymers, cationic starches, urea-formalin resins and
melamine-formalin resins; drainage and/or retention aids such as
salts of acrylamide-aminomethyl acrylamide copolymers, cationic
starches, polyethyleneimine, polyethylene oxide and
acrylamide-sodium acrylate copolymers; internal sizing agents such
as rosin sizing agents, AKD, ASA, petroleum sizing agents, and
neutral rosin sizing agents; and other additives such as UV
protective agents, anti-fading agents, etc.
[0117] The printability improving agent of the present invention is
applied on a newsprint base paper directly or after it has been
mixed with a binder consisting of a water-soluble polymer material
to form a surface-treating agent. Water-soluble polymer materials
include e.g., various modified starches such as enzyme-modified
starches, thermochemically modified starches, oxidized starches,
esterified starches, etherified starches (e.g., hydroxyethylated
starches, etc.), cationized starches; polyvinyl alcohols such as
polyvinyl alcohols, completely saponified polyvinyl alcohols,
partially saponified polyvinyl alcohols, carboxyl-modified
polyvinyl alcohols, silanol-modified polyvinyl alcohols,
cationically modified polyvinyl alcohols, terminally alkylated
polyvinyl alcohols; and cellulose derivatives such as carboxymethyl
cellulose, hydroxyethyl cellulose, methyl cellulose. These are used
alone or in combinations of two or more.
[0118] The printability improving agent or a surface-treating agent
containing the printability improving agent can be applied on a
newsprint base paper using a normal coater for papermaking. For
example, suitable coaters include two-roll size presses, blade
metering size presses, rod metering size presses, gate roll
coaters, bar coaters, air-knife coaters, spray coaters, etc. Among
them, film transfer coaters such as gate roll coaters are desirable
and gate roll coaters (GRC) are most preferably used for newsprint
papers.
[0119] The coating speed at which the printability improving agent
or a surface-treating agent containing the printability improving
agent is applied is not specifically limited, so long as it is
within the range of the machine speed at which normal newspapers
can be prepared, but normally 800-2500 m/min. By adopting a high
coating speed of 800 m/min or more, much of the surface-treating
agent remains near the surface to increase printability improving
effect because the surface-treating agent is dried before it
sufficiently penetrates paper layers.
[0120] The effect of the present invention is more remarkable when
the printability improving agent or a surface-treating agent
containing the printability improving agent is applied on newsprint
base papers prepared by neutral papermaking processes, than on
newsprint base papers prepared by acidic papermaking processes.
[0121] The solids concentration of the printability improving agent
in the surface-treating agent (coating solution) is normally
0.05-2% by weight, preferably 0.1-1% by weight. If it is less than
0.05% by weight, the printability improving effect may be
insufficient, while concentrations exceeding 2% by weight are
economically disadvantageous because the printability improving
effect reaches its peak around 2% by weight. The coating amount of
the printability improving agent on the base paper is normally
0.005-0.3 g/m.sup.2, preferably 0.01-0.2 g/m.sup.2 on a solids
basis. The printability is especially improved within this
range.
[0122] When a surface-treating agent comprising a mixture of the
printability improving agent and a water-soluble polymer material
is to be applied, the solids concentration of the printability
improving agent in the surface-treating agent and the coating
amount are as described above, while the coating amount (per both
sides) of the water-soluble polymer material is suitably in the
range of 0.05-2.0 g/m.sup.2. If the coating amount is less than
0.05 g/m.sup.2, the surface strength of the newsprint paper may be
insufficient. If the coating amount exceeds 2.0 g/m.sup.2, however,
there is a higher possibility of causing tack (i.e. so-called
"neppari"), a typical issue of newsprint papers for offset printing
(a trouble of stickiness caused by transfer and accumulation of a
coating material on a blanket during mass printing of
newspapers).
[0123] Newsprint papers of the present invention are preferably
calendered to ensure paper thickness and smoothness suitable for
offset printing after they have been coated with the printability
improving agent according to the first or second aspect or a
surface-treating agent containing the printability improving agent
and dried. Suitable calenders include normal hard nip calenders or
hot soft nip calenders (e.g., see "Paper and Pulp Technology
Times", Vol. 43, No. 1 (2000) p 23, etc.). Considering future
weight reduction of newsprint papers, soft nip calenders are more
preferably used for newsprint papers of the present invention. In
terms of color printability, the printability improving agent of
the present invention or a surface-treating agent containing the
printability improving agent should be combined with soft nip
calendering.
EXAMPLES
[0124] The following examples and comparative examples further
illustrate the present invention without, however, limiting the
invention thereto. Unless otherwise specified, "parts" and "%" used
herein mean parts by weight and % by weight, respectively. Examples
1-29 and Comparative examples 1-6 relate to printability improving
agents according to the first aspect of the present invention,
while Examples 30-67 and Comparative examples 7-12 relate to
printability improving agents according to the second aspect of the
present invention.
Example 1
[0125] A 1-liter four-neck flask equipped with a stirrer, a
thermometer, a reflux condenser and a nitrogen inlet tube was
charged with 70 parts of 2-ethylhexyl methacrylate, 30 parts of
dimethyl aminoethyl methacrylate, 2.5 parts of
2,2'-azobisisobutyronitrile and 44 parts of isopropyl alcohol, and
maintained at 80.degree. C. for 3 hours, and then 0.4 parts of
2,2'-azobisisobutyronitrile was added and the mixture was
maintained at the same temperature for further 2 hours. Then, 12.7
parts of acetic acid (100 mol % relative to dimethyl aminoethyl
methacrylate) and 251 parts of water were added, and isopropyl
alcohol was distilled off. Then, 34 parts of water, and 17.7 parts
of a quaternizing agent consisting of epichlorohydrin (100 mol %
relative to dimethyl aminoethyl methacrylate) were added, and the
mixture was maintained at 80.degree. C. for 2 hours. Then, the
mixture was diluted with water to give printability improving agent
1 having a solids content of 20.3%. It should be noted that
substantially no uncopolymerized monomer remained, and that little
unreacted epichlorohydrin used as a quaternizing agent
remained.
Example 2
[0126] Printability improving agent 2 having a solids content of
20.5% was obtained by the same procedure as in Example 1 except
that the monomer composition was as shown in Table 1 for Example 2
without using a quaternizing agent and that no quaternization
reaction was performed.
Examples 3-9
[0127] Printability improving agents were obtained in the same
manner as printability improving agent 1 except that the type and
amount of the hydrophobic monomer, the type and amount of the
tertiary amino group-containing monomer, and the type and amount of
the quaternizing agent were varied as shown in Table 1. The solids
contents of the resulting printability improving agents 3-9 are
shown in Table 1.
[0128] [Table 1] TABLE-US-00001 TABLE 1 Quaternary ammonium
salt-containing Solids Hydrophobic monomer unit monomer unit
content Type Parts Type Parts Type Parts Type Parts % by weight %
Example 1 EHMA 70.0 -- -- DM 30.0 ECH 17.7 40.5 20.3 Example 2 EHMA
67.5 MMA 10.0 DMC 22.5 -- -- 22.5 20.5 Example 3 EHMA 85.0 -- -- DM
15.0 ECH 8.8 21.9 20.3 Example 4 EHMA 40.0 BA 40.0 DPA 20.0 ECH
11.8 28.5 20.0 Example 5 EHMA 40.0 EHA 40.0 DPA 20.0 ECH 11.8 28.5
20.5 Example 6 EHMA 40.0 IBMA 40.0 DPA 20.0 BTO 9.2 26.8 20.2
Example 7 EHMA 40.0 BA 40.0 DM 20.0 STO 15.3 30.8 20.3 Example 8
EHMA 60.0 -- -- DM 40.0 ECH 23.5 51.4 20.3 Example 9 EHMA 90.0 --
-- DM 10.0 ECH 5.9 15.0 20.0
[0129] In Table 1, abbreviations have the meanings below:
[0130] EHMA: 2-ethylhexyl methacrylate, MMA: methyl methacrylate,
BA: normal butyl acrylate, EHA: 2-ethylhexyl acrylate, IBMA:
isobutyl methacrylate, DM: dimethyl aminoethyl methacrylate, DMC:
dimethyl aminoethyl methacrylate quaternized with methyl chloride,
DPA: dimethyl aminopropyl acrylamide, ECH: epichlorohydrin, BTO:
butylene oxide, STO: styrene oxide.
Synthesis Example 1 for Comparative Examples
[0131] A 1-liter four-neck flask equipped with a stirrer, a
thermometer, a reflux condenser and a nitrogen inlet tube was
charged with 44 parts of toluene, 50 parts of diisobutylene, 50
parts of maleic anhydride and 3.3 parts of
2,2'-azobisisobutyronitrile, and the mixture was heated with
stirring to a temperature of 80.degree. C. Then, the mixture was
aged for 3 hours to complete the reaction. Then, 82 parts of a 48%
aqueous potassium hydroxide solution (50 mol % relative to maleic
anhydride), and 251 parts of water were added, and toluene was
distilled off. Then, a 48% aqueous potassium hydroxide solution was
added to a total of 100 mol % relative to maleic anhydride, and the
solution was diluted with water to a copolymer concentration of 20%
to give an aqueous potassium hydroxide solution of a water-soluble
diisobutylene-maleic anhydride copolymer (printability improving
agent 10 (for comparative examples)). The monomer composition ratio
in the polymer was diisobutylene:maleic anhydride=50:50 by
weight.
Synthesis Example 2 for Comparative Examples
[0132] A 1-liter four-neck flask equipped with a stirrer, a
thermometer, a reflux condenser and a nitrogen inlet tube was
charged with 35 parts of water, 65 parts of 95% isopropyl alcohol,
a mixed monomer solution of 60 parts of styrene and 40 parts of
maleic anhydride, and 3 parts of 2,2'-azobisisobutyronitrile, and
the contents of the flask were heated with stirring to a
temperature of 80.degree. C. Then, the mixture was aged for 4 hours
to complete the reaction. Then, isopropyl alcohol was distilled
off, and after cooling, 50 parts of a 28% aqueous ammonia solution
(100 mol % relative to maleic anhydride) was added, and the
solution was diluted with water to a copolymer concentration of 20%
to give an aqueous ammonia solution of a water-soluble
styrene-maleic copolymer (printability improving agent 11 (for
comparative examples)). The monomer composition ratio in the
polymer was styrene:maleic anhydride=60:40 by weight.
Synthesis Example 3 for Comparative Examples
[0133] A 1-liter four-neck flask equipped with a stirrer, a
thermometer, a reflux condenser and a nitrogen inlet tube was
charged with 35 parts of water, 65 parts of 95% isopropyl alcohol,
a mixed monomer solution of 70 parts of styrene and 30 parts of
acrylic acid, and 3 parts of 2,2'-azobisisobutyronitrile, and the
contents of the flask were heated with stirring to a temperature of
80.degree. C. Then, the mixture was aged for 4 hours to complete
the reaction. Then, isopropyl alcohol was distilled off, and after
cooling, 25.3 parts of a 28% aqueous ammonia solution (100 mol %
relative to maleic anhydride) was added, and the solution was
diluted with water to a copolymer concentration of 20% to give an
aqueous ammonia solution of a water-soluble styrene-acrylic
copolymer (printability improving agent 12 (for comparative
example)). The monomer composition ratio in the polymer was
styrene:acrylic acid=70:30 by weight.
[0134] Preparation of Newsprint Base Papers
[0135] (1) Preparation of an Acidic Newsprint Base Paper
[0136] To a deinked pulp slurry having a Canadian Standard Freeness
(CSF) of 160 and a concentration of 2.5% were successively added
15% (bone dry weight basis) relative to pulp of talc (ND talc
available from FUJI TALC INDUSTRIAL CO., LTD.), 1.5% (bone dry
weight basis) relative to pulp of aluminum sulfate, and 0.05% (bone
dry weight basis) relative to pulp of a rosin sizing agent for
acidic papers (AL120 available from Seiko PMC Corporation), and
then, this pulp slurry was diluted with dilution water at pH4.5 to
a concentration of 0.25%. Then, the pulp was converted into a paper
having a basis weight of 50 g/m.sup.2 in a test machine. The
running pH was 4.5. The wet paper was dried using a drum dryer at
100.degree. C. for 80 seconds.
[0137] (2) Preparation of a Neutral Newsprint Base Paper
[0138] To a deinked pulp slurry having a Canadian Standard Freeness
(CSF) of 160 and a concentration of 2.5% were successively added 2%
(bone dry weight basis) relative to pulp of calcium carbonate
(TP121S available from Okutama Kogyo Co., Ltd.) and 0.25% (bone dry
weight basis) relative to pulp of aluminum sulfate, and then this
pulp slurry was diluted with dilution water at pH7.5 to a
concentration of 0.25%. Then, the pulp was converted into a paper
having a basis weight of 50 g/m.sup.2 in a test machine. The
running pH was 7.5. The wet paper was dried using a drum dryer at
100.degree. C. for 80 seconds.
Example 10
[0139] An oxidized starch (MS3800 available from Nihon Shokuhin
Kako Co., Ltd.) was diluted with water to a concentration of 10%
and gelatinized at 95.degree. C., and then combined with
printability improving agent 1 described above to prepare a surface
treating solution having solids concentrations of 6% oxidized
starch and 0.3% printability improving agent 1 in the
surface-treating agent. Thus prepared surface-treating agent was
applied on the acidic newsprint base paper with No. 3 bar coater to
give an acidic newsprint paper. The coating amount of the
printability improving agent was 0.05 g/m.sup.2 on a solids basis.
Thus obtained acidic newsprint paper was used as a test piece and
conditioned in an environment at constant temperature and humidity
(23.degree. C., relative humidity 50%) for 24 hours and measured
for ink receptivity, drop test, contact angle and starch
dissolution by the methods shown below. The results are shown in
Table 2.
[0140] (Evaluation of Ink Receptivity)
[0141] Printing was performed using an RI printability tester (4
colors) available from Ishikawajima Industrial Machinery Co., Ltd.
with high-viscosity aromatic-free inks available from Dainippon Ink
and Chemicals, Incorporated as ecological offset printing inks
after a water film has been formed between the rubber roll for
printing the third color and the metal roll. Ink density was
measured with a Machbeth densitometer. Higher values represent
better ink receptivity.
[0142] (Evaluation of Drop Test)
[0143] A drop test was performed with a 1 .mu.l drop of water
according to the test method of J.TAPPI 33. Higher values represent
better sizing.
[0144] (Evaluation of Contact Angle)
[0145] Using an automatic contact angle meter available from Kyowa
Interface Science Co., Ltd., the contact angle was measured one
second after a drop of water has been applied. Higher values
represent better sizing.
[0146] (Evaluation of Starch Dissolution)
[0147] A paper sample cut into a rectangle of 2.5 cm.times.30 cm
was rotated 30 times in water on an Adams Wet Rub Tester to
dissolve starch. The amount of starch dissolved into water was
expressed as the percentage of the amount of starch in the paper.
Higher values represent less starch dissolution.
Examples 11-18, Comparative Examples 1-3
[0148] Coating and evaluations were performed in the same manner as
in Example 10, except that printability improving agents 2-9 or
printability improving agents 10-12 for comparative examples were
used in place of printability improving agent 1. The results are
shown in Table 2.
Example 19
[0149] Coating and evaluations were performed in the same manner as
in Example 10, except that the surface-treating agent of Example 10
was adjusted to pH 7 with aqueous ammonia. The results are shown in
Table 2.
[0150] [Table 2] TABLE-US-00002 TABLE 2 Printability Contact Starch
improving Ink Drop test, angle, dissolu- agent receptivity second
degree tion, % Example 10 1 1.00 45 101 18 Example 11 2 1.10 65 110
13 Example 12 3 1.08 60 108 13 Example 13 4 1.08 58 108 14 Example
14 5 1.11 63 110 14 Example 15 6 1.04 40 102 14 Example 16 7 1.06
38 100 15 Example 17 8 1.00 30 100 19 Example 18 9 0.99 28 97 19
Example 19 1 1.04 58 103 16 Comparative 10 0.91 17 105 22 example 1
Comparative 11 0.93 16 98 24 example 2 Comparative 12 0.96 26 102
23 example 3
Example 20
[0151] An oxidized starch (MS3800 available from Nihon Shokuhin
Kako Co., Ltd.) was diluted with water to a concentration of 10%
and gelatinized at 95.degree. C., and then combined with
printability improving agent 1 described above to prepare a surface
treating solution having solids concentrations of 4% oxidized
starch and 0.4% printability improving agent 1 in the
surface-treating agent. Thus prepared surface-treating agent was
applied on the neutral newsprint base paper with No. 3 bar coater
to give a neutral newsprint paper. The coating amount of the
printability improving agent was 0.08 g/m.sup.2 on a solids basis.
Thus obtained neutral newsprint paper was used as a test piece and
conditioned in an environment at constant temperature and humidity
(23.degree. C., relative humidity 50%) for 24 hours and measured
for ink receptivity, drop test, contact angle and starch
dissolution by the methods described in Example 10. The results are
shown in Table 3.
Examples 21-28, Comparative Examples 4-6
[0152] Coating and evaluations were performed in the same manner as
in Example 20 except that printability improving agents 2-9 or
printability improving agents 10-12 for comparative examples were
used in place of printability improving agent 1. The results are
shown in Table 3.
Example 29
[0153] Coating and evaluations were performed in the same manner as
in Example 20 except that the surface-treating agent of Example 20
was adjusted to pH 7 with aqueous ammonia. The results are shown in
Table 3.
[0154] [Table 3] TABLE-US-00003 TABLE 3 Printability Contact Starch
improving Ink Drop test, angle, dissolu- agent receptivity second
degree tion, % Example 20 1 0.99 39 102 19 Example 21 2 1.07 51 108
15 Example 22 3 1.05 46 107 16 Example 23 4 1.06 44 106 17 Example
24 5 1.08 50 108 18 Example 25 6 1.01 33 100 17 Example 26 7 1.04
30 99 17 Example 27 8 1.00 26 98 18 Example 28 9 0.97 20 97 19
Example 29 1 1.03 47 103 16 Comparative 10 0.85 7 91 28 example 4
Comparative 11 0.87 6 87 29 example 5 Comparative 12 0.89 10 89 26
example 6
[0155] The evaluation results of the acidic newsprint papers in
Table 2 show that the newsprint papers of Examples 10-19 have
better ink receptivity and less starch dissolution as compared with
the newsprint papers of Comparative examples 1-3. The newsprint
paper of Example 19 concomitantly using an alkaline material is
shown to have clearly better ink receptivity and sizing performance
as compared with Example 10.
[0156] The evaluation results of the neutral newsprint papers in
Table 3 show that the newsprint papers of Examples 20-29 have
better ink receptivity and clearly higher sizing effect as compared
with the newsprint papers of Comparative examples 4-6. The
newsprint paper of Example 29 concomitantly using an alkaline
material is shown to have clearly better ink receptivity and sizing
performance as compared with Example 20.
[0157] The following Examples 30-67 and Comparative examples 7-12
relate to printability improving agents according to the second
aspect of the present invention.
[0158] 1. Preparation of Printability Improving Agents
[0159] (1) Processes for Preparing Cationic Copolymers [A-1]
Synthesis Example 1
[0160] A 1-liter four-neck flask equipped with a stirrer, a
thermometer, a reflux condenser and a nitrogen inlet tube was
charged with 60 parts of styrene, 40 parts of dimethyl aminoethyl
methacrylate, 2.5 parts of azobisisobutyronitrile and 44 parts of
isopropyl alcohol, and maintained at 80.degree. C. for 3 hours, and
then 0.4 parts of azobisisobutyronitrile was added and the mixture
was maintained at the same temperature for further 2 hours. Then,
17.0 parts of 90% acetic acid (100 mol % relative to dimethyl
aminoethyl methacrylate) and 247 parts of water were added, and
isopropyl alcohol was distilled off. Then, 48 parts of water and
23.5 parts of a quaternizing agent consisting of epichlorohydrin
(100 mol % relative to dimethyl aminoethyl methacrylate) were
added, and the mixture was maintained at 80.degree. C. for 2 hours.
Then, the mixture was diluted with water to give cationic copolymer
(P-1) having a solids content of 20.7%. It should be noted that
substantially no uncopolymerized monomer remained, and that little
unreacted epichlorohydrin used as a quaternizing agent
remained.
Synthesis Example 2
[0161] Cationic copolymer (P-2) having a solids content of 20.2%
was obtained by the same procedure as in Synthesis example 1 except
that the monomer composition was as shown in Table 4 for cationic
copolymer (P-2) without using a quaternizing agent and that no
quaternization reaction was performed.
Synthesis Examples 3-6
[0162] Cationic copolymers were obtained in the same manner as in
Synthesis example 1 except that the type and amount of the
hydrophobic monomer, the type and amount of the tertiary amino
group-containing monomer, and the type and amount of the
quaternizing agent used were varied as shown in Table 4. The solids
contents of the resulting cationic copolymers (P-3) to (P-6) are
shown in Table 4.
[0163] [Table 4] TABLE-US-00004 TABLE 4 Quaternary ammonium
salt-containing Solids Cationic Hydrophobic monomer unit monomer
unit content copolymer Type Parts Type Parts Type Parts Type Parts
% by weight % P-1 St 60 -- -- DM 40 ECH 23.5 51.4 20.7 P-2 St 70
MMA 10 DMC 20 -- -- 20.0 20.2 P-3 St 60 EHA 20 DPA 20 ECH 11.8 28.5
20.1 P-4 IBMA 70 -- -- DPA 30 BTO 13.8 38.5 20.3 P-5 EHMA 40 -- --
DM 60 ECH 35.3 70.4 20.4 P-6 St 85 -- -- DM 15 ECH 8.8 21.9
19.3
[0164] In Table 4, symbols have the meanings below:
[0165] St: styrene, EHMA: 2-ethylhexyl methacrylate, MMA: methyl
methacrylate, EHA: 2-ethylhexyl acrylate, IBMA: isobutyl
methacrylate, DM: dimethyl aminoethyl methacrylate, DMC: dimethyl
aminoethyl methacrylate quaternized with methyl chloride, DPA:
dimethyl aminopropyl acrylamide, ECH: epichlorohydrin, BTO:
butylene oxide.
Example 30
[0166] A reactor similar to that of Synthesis example 1 was charged
with 192 parts of water, 121 parts of an aqueous solution of
cationic copolymer [A-1] consisting of cationic copolymer (P-1)
obtained in Synthesis example 1 (25 parts on a solids basis), 3
parts of surfactant [A-2] consisting of (N-1) shown in Table 2,
hydrophobic monomer [B] consisting of 50 parts of styrene and 50
parts of normal butyl acrylate, and 5 parts by weight of 10%
ammonium persulfate, and the mixture was heated to 80.degree. C.
with mixing/stirring under a nitrogen stream. The mixture was
maintained at 80.degree. C. for 2 hours to complete emulsion
polymerization to give printability improving agent 13 having a
solids concentration of 30.3%.
Examples 31-41
[0167] Printability improving agents 14-24 were obtained in the
same manner as in Example 30, except that the type and amount of
cationic copolymer [A-1], the type and amount of surfactant [A-2],
and the type and amount of hydrophobic monomer [B] used were varied
as shown in Table 5. The amounts of aggregates generated during
polymerization reaction and the solids concentrations of the
resulting printability improving agents are shown in Table 5.
[0168] [Table 5] TABLE-US-00005 TABLE 5 Cationic copolymer
Surfactant Hydrophobic monomer Solids A-1 A-2 B content Type
Content (%) Type Content (%) Type Content (%) % Example 30 P-1 25
N-1 3 St 50 30.3 BA 50 Example 31 P-1 100 -- -- St 50 29.5 BA 50
Example 32 P-1 50 N-1 5 St 50 30.4 BA 50 Example 33 P-1 100 N-1 3
St 50 30.2 BA 50 Example 34 P-1 50 N-1 10 St 50 30.2 BA 30 MMA 20
Example 35 P-1 50 N-2 3 St 50 30.9 BA 30 EHA 20 Example 36 P-1 50
N-3 3 St 60 30.0 MMA 20 EHA 20 Example 37 P-2 50 N-4 3 St 50 30.2
BA 50 Example 38 P-3 50 N-5 3 St 50 30.4 BA 50 Example 39 P-4 50
N-6 3 IBMA 50 30.2 BA 50 Example 40 P-5 50 N-7 3 St 50 30.4 BA 50
Example 41 P-6 50 N-1 5 St 50 30.0 BA 50
[0169] In Table 5, symbols have the meanings below:
[0170] P-1 to P-6: cationic copolymer (Synthesis examples 1-6)
[0171] N-1: C.sub.12H.sub.25--O-(EO).sub.20-H
[0172] N-2: C.sub.18H.sub.37--O-(EO).sub.20-H
[0173] N-3: C.sub.9H.sub.19--C.sub.6H.sub.4O-(EO).sub.20-H
[0174] N-4:
CH.sub.2.dbd.C(CH.sub.3)COO-(EO).sub.20-C.sub.12H.sub.25
[0175] N-5:
CH.sub.2.dbd.C(CH.sub.3)COO-(EO).sub.20-C.sub.18H.sub.37
[0176] N-6:
C.sub.12H.sub.25--N.sup.+--(CH.sub.3).sub.2(CH.sub.2C.sub.6H.sub.5)Cl.sup-
.-
[0177] N-7:
C.sub.6H.sub.5CH.sub.2--N.sup.+--(CH.sub.3).sub.3Cl.sup.-
[0178] St: styrene
[0179] BA: butyl acrylate
[0180] IBMA: isobutyl methacrylate
[0181] IBA: isobutyl acrylate
[0182] MMA: methyl methacrylate
[0183] EHA: 2-ethylhexyl acrylate
[0184] (Note) In N-1 to N-7, EO means ethylene oxide.
Synthesis Example 1 for Comparative Examples
[0185] A 1-liter four-neck flask equipped with a stirrer, a
thermometer, a reflux condenser and a nitrogen inlet tube was
charged with 44 parts of toluene, 50 parts of diisobutylene, 50
parts of maleic anhydride and 3.3 parts of
2,2'-azobisisobutyronitrile, and the mixture was heated with
stirring to a temperature of 80.degree. C. Then, the mixture was
aged for 3 hours to complete the reaction. Then, a 48% aqueous
potassium hydroxide solution (50 mol % relative to maleic
anhydride), and 251 parts of water were added, and toluene was
distilled off. Then, a 48% aqueous potassium hydroxide solution was
added to a total of 100 mol % relative to maleic anhydride, and the
solution was diluted with water to a copolymer concentration of 20%
to give an aqueous potassium hydroxide solution of a water-soluble
diisobutylene-maleic anhydride copolymer (printability improving
agent 25 (for comparative examples)). The monomer composition ratio
in the polymer was diisobutylene:maleic anhydride=50:50 by
weight.
Synthesis Example 2 for Comparative Examples
[0186] A 1-liter four-neck flask equipped with a stirrer, a
thermometer, a reflux condenser and a nitrogen inlet tube was
charged with 35 parts of water, 65 parts of 95% isopropyl alcohol,
a mixed monomer solution of 60 parts of styrene and 40 parts of
maleic anhydride, and 3 parts of 2,2'-azobisisobutyronitrile, and
the contents of the flask were heated with stirring to a
temperature of 80.degree. C. Then, the mixture was aged for 4 hours
to complete the reaction. Then, isopropyl alcohol was distilled
off, and after cooling, 50 parts of a 28% aqueous ammonia solution
(100 mol % relative to maleic anhydride) was added, and the
solution was diluted with water to a copolymer concentration of 20%
to give an aqueous ammonia solution of a water-soluble
styrene-maleic copolymer (printability improving agent 26 (for
comparative examples)). The monomer composition ratio in the
polymer was styrene:maleic anhydride=60:40 by weight.
Synthesis Example 3 for Comparative Examples
[0187] A 1-liter four-neck flask equipped with a stirrer, a
thermometer, a reflux condenser and a nitrogen inlet tube was
charged with 35 parts of water, 65 parts of 95% isopropyl alcohol,
a mixed monomer solution of 70 parts of styrene and 30 parts of
acrylic acid, and 3 parts of 2,2'-azobisisobutyronitrile, and the
contents of the flask were heated with stirring to a temperature of
80.degree. C. Then, the mixture was aged for 4 hours to complete
the reaction. Then, isopropyl alcohol was distilled off, and after
cooling, 25.3 parts of a 28% aqueous ammonia solution (100 mol %
relative to maleic anhydride) was added, and the solution was
diluted with water to a copolymer concentration of 20% to give an
aqueous ammonia solution of a water-soluble styrene-acrylic
copolymer (printability improving agent 27 (for comparative
example)). The monomer composition ratio in the polymer was
styrene:acrylic acid=70:30 (by weight).
[0188] Preparation of Newsprint Base Papers
[0189] (1) Preparation of an Acidic Newsprint Base Paper
[0190] To a deinked pulp slurry having a Canadian Standard Freeness
(CSF) of 160 and a concentration of 2.5% were successively added
15% (bone dry weight basis) relative to pulp of talc (ND talc
available from FUJI TALC INDUSTRIAL CO., LTD.), 1.5% (bone dry
weight basis) relative to pulp of aluminum sulfate, and 0.05% (bone
dry weight basis) relative to pulp of a rosin sizing agent for
acidic papers (AL120 available from Seiko PMC Corporation), and
then this pulp slurry was diluted with dilution water at pH4.5 to a
concentration of 0.25%. Then, the pulp was converted into a paper
having a basis weight of 50 g/m.sup.2 in a test machine. The
running pH was 4.5. The wet paper was dried using a drum dryer at
100.degree. C. for 80 seconds.
[0191] (2) Preparation of a Neutral Newsprint Base Paper
[0192] To a deinked pulp slurry having a Canadian Standard Freeness
(CSF) of 160 and a concentration of 2.5% were successively added 2%
(bone dry weight basis) relative to pulp of calcium carbonate
(TP121S available from Okutama Kogyo Co., Ltd.) and 0.25% (bone dry
weight basis) relative to pulp of aluminum sulfate, and then this
pulp slurry was diluted with dilution water at pH7.5 to a
concentration of 0.25%. Then, the pulp was converted into a paper
having a basis weight of 50 g/m.sup.2 in a test machine. The
running pH was 7.5. The wet paper was dried using a drum dryer at
100.degree. C. for 80 seconds.
Example 42
[0193] An oxidized starch (MS3800 available from Nihon Shokuhin
Kako Co., Ltd.) was diluted with water to a concentration of 10%
and gelatinized at 95.degree. C., and then combined with
printability improving agent 13 described above to prepare a
surface treating solution having solids concentrations of 7%
oxidized starch and 0.2% printability improving agent 13 in the
surface-treating agent. Thus prepared surface-treating agent was
applied on the acidic newsprint base paper with No. 3 bar coater to
give an acidic newsprint paper. The coating amount of the
printability improving agent was 0.04 g/m.sup.2 on a solids basis.
Thus obtained acidic newsprint paper was used as a test piece and
conditioned in an environment at constant temperature and humidity
(23.degree. C., relative-humidity 50%) for 24 hours and measured
for ink receptivity, drop test, contact angle and starch
dissolution by the methods described above. The results are shown
in Table 5.
Examples 43-53, Comparative Examples 7-9
[0194] Coating and evaluations were performed in the same manner as
in Example 42 except that printability improving agents 14-24 or
printability improving agents 25-27 for comparative examples were
used in place of printability improving agent 13. The results are
shown in Table 5.
Example 54
[0195] Coating and evaluations were performed in the same manner as
in Example 42 except that the surface-treating agent of Example 42
was adjusted to pH 7 with aqueous ammonia. The results are shown in
Table 6.
[0196] [Table 6] TABLE-US-00006 TABLE 6 Printability Contact Starch
improving Ink Drop test, angle, dissolu- agent receptivity second
degree tion, % Example 42 13 1.00 35 99 17 Example 43 14 1.01 40
102 16 Example 44 15 1.07 50 108 13 Example 45 16 1.05 51 108 14
Example 46 17 1.06 48 106 14 Example 47 18 1.10 60 110 12 Example
48 19 1.10 58 108 13 Example 49 20 1.04 45 105 14 Example 50 21
1.11 62 111 12 Example 51 22 1.09 56 110 13 Example 52 23 1.03 41
105 14 Example 53 24 1.00 32 98 18 Example 54 13 1.06 44 104 15
Comparative 25 0.92 20 103 21 example 7 Comparative 26 0.93 19 98
23 example 8 Comparative 27 0.95 27 100 24 example 9
Example 55
[0197] An oxidized starch (MS3800 available from Nihon Shokuhin
Kako Co., Ltd.) was diluted with water to a concentration of 10%
and gelatinized at 95.degree. C., and then combined with
printability improving agent 13 described above to prepare a
surface treating solution having solids concentrations of 5%
oxidized starch and 0.3% printability improving agent 13 in the
surface-treating agent. Thus prepared surface-treating agent was
applied on the acidic newsprint base paper with No. 3 bar coater to
give a neutral newsprint paper. The coating amount of the
printability improving agent was 0.07 g/m.sup.2 on a solids basis.
Thus obtained neutral newsprint paper was used as a test piece and
conditioned in an environment at constant temperature and humidity
(23.degree. C., relative humidity 50%) for 24 hours and measured
for ink receptivity, drop test, contact angle and starch
dissolution by the methods described above. The results are shown
in Table 7.
Examples 56-66, Comparative Examples 10-12
[0198] Coating and evaluations were performed in the same manner as
in Example 55, except that printability improving agents 14-24 or
printability improving agents 25-27 for comparative examples
described above were used in place of printability improving agent
13 described above. The results are shown in Table 7.
Example 67
[0199] Coating and evaluations were performed in the same manner as
in Example 55, except that the surface-treating agent of Example 55
was adjusted to pH 7 with aqueous ammonia. The results are shown in
Table 7. TABLE-US-00007 TABLE 7 Printability Contact Starch
improving Ink Drop test, angle, dissolu- agent receptivity second
degree tion, % Example 55 13 0.96 25 97 18 Example 56 14 0.97 31
100 16 Example 57 15 1.02 39 107 14 Example 58 16 1.00 42 107 15
Example 59 17 1.02 37 104 14 Example 60 18 1.04 51 110 13 Example
61 19 1.04 47 107 13 Example 62 20 0.99 33 105 14 Example 63 21
1.06 53 110 13 Example 64 22 1.04 43 108 13 Example 65 23 1.01 34
105 15 Example 66 24 0.97 23 96 19 Example 67 13 1.02 35 104 16
Comparative 25 0.84 6 90 28 example 10 Comparative 26 0.85 5 87 29
example 11 Comparative 27 0.88 10 89 26 example 12
[0200] The evaluation results of the acidic newsprint papers in
Table 6 show that the newsprint papers of Examples 42-53 have
better ink receptivity and less starch dissolution as compared with
the newsprint papers of Comparative examples 7-9. The newsprint
paper of Example 54 concomitantly using an alkaline material is
shown to have clearly better ink receptivity and sizing performance
as compared with Example 42.
[0201] The evaluation results of the neutral newsprint papers in
Table 7 show that the newsprint papers of Examples 55-66 have
better ink receptivity and clearly higher sizing effect as compared
with the newsprint papers of Comparative examples 10-12. The
newsprint paper of Example 67 concomitantly using an alkaline
material is shown to have clearly better ink receptivity and sizing
performance as compared with Example 55.
* * * * *