U.S. patent application number 12/303392 was filed with the patent office on 2012-02-23 for cast-coated paper.
This patent application is currently assigned to NIPPON PAPER CRECIA CO., LTD.. Invention is credited to Nobumasa Hayashi, Noriyuki Ishibashi, Hidehiko Kai, Hiroshi Koyamoto, Koji Kutsuwa, Takashi Ochi, Masashi Okamoto, Koji Okomori.
Application Number | 20120043372 12/303392 |
Document ID | / |
Family ID | 38801548 |
Filed Date | 2012-02-23 |
United States Patent
Application |
20120043372 |
Kind Code |
A1 |
Koyamoto; Hiroshi ; et
al. |
February 23, 2012 |
Cast-coated paper
Abstract
The present invention aims to provide a cast-coated paper having
good coated paper quality and printability combined with the
property of decomposing hazardous substances upon exposure to
light. A cast-coated paper prepared by applying a cast-coating
layer based on a pigment and a binder on abase paper and finished
by pressing the cast-coating layer in the wet state against a
heated cast drum surface and drying it, wherein the cast-coating
layer contains 1-30 parts by weight of titanium dioxide having an
average secondary particle diameter of 300-2000 nm per 100 parts by
weight of the pigment and the titanium dioxide is premixed with a
silica sol or alumina sol at a ratio of the titanium dioxide to the
silica sol or alumina sol of 2:1-1:2.
Inventors: |
Koyamoto; Hiroshi; (Tokyo,
JP) ; Kutsuwa; Koji; (Tokyo, JP) ; Okamoto;
Masashi; (Tokyo, JP) ; Kai; Hidehiko; (Tokyo,
JP) ; Okomori; Koji; (Tokyo, JP) ; Ochi;
Takashi; (Tokyo, JP) ; Ishibashi; Noriyuki;
(Tokyo, JP) ; Hayashi; Nobumasa; (Tokyo,
JP) |
Assignee: |
NIPPON PAPER CRECIA CO.,
LTD.
Tokyo
JP
NIPPON PAPER INDUSTRIES CO., LTD.
Tokyo
JP
|
Family ID: |
38801548 |
Appl. No.: |
12/303392 |
Filed: |
June 7, 2007 |
PCT Filed: |
June 7, 2007 |
PCT NO: |
PCT/JP2007/061563 |
371 Date: |
October 22, 2010 |
Current U.S.
Class: |
229/5.81 ;
428/323 |
Current CPC
Class: |
D21H 19/66 20130101;
D21H 19/54 20130101; D21H 19/38 20130101; D21H 19/50 20130101; D21H
19/84 20130101; D21H 25/14 20130101; D21H 19/385 20130101; D21H
19/56 20130101; D21H 19/36 20130101; D21H 19/40 20130101; D21H
21/52 20130101; Y10T 428/25 20150115; D21H 19/80 20130101 |
Class at
Publication: |
229/5.81 ;
428/323 |
International
Class: |
D21H 19/38 20060101
D21H019/38; B65D 5/62 20060101 B65D005/62 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 7, 2006 |
JP |
2006-159104 |
Aug 3, 2006 |
JP |
2006-211559 |
Sep 8, 2006 |
JP |
2006-244869 |
Mar 27, 2007 |
JP |
2007-080402 |
Jun 5, 2007 |
JP |
2007-149476 |
Claims
1. A cast-coated paper prepared by applying a cast-coating layer
based on a pigment and a binder on a base paper and finished by
pressing the cast-coating layer in the wet state against a heated
cast drum surface and drying it, wherein the cast-coating layer
contains 1-30 parts by weight of titanium dioxide having an average
secondary particle diameter of 300-2000 nm per 100 parts by weight
of the pigment.
2. The cast-coated paper of claim 1, characterized in that the
cast-coating layer contains 5-40 parts by weight of an organic
binder per 100 parts by weight of the pigment and that the organic
binder includes 50% by weight or more of a copolymer latex.
3. The cast-coated paper of claim 1, characterized in that a
copolymer latex having a glass transition temperature of -20 to
40.degree. C. is used as a binder in the cast-coating layer.
4. A cast-coated paper of claim 1, wherein the titanium dioxide is
premixed with a silica sol or alumina sol.
5. The cast-coated paper of claim 4, characterized in that the
premixing is performed at a ratio of the titanium dioxide to the
silica sol or alumina sol of 2:1-1:2.
6. The cast-coated paper of claim 1, which has a sheet gloss of 80%
or more on the cast-coated surface as determined according to
JIS-P8142.
7. The cast-coated paper of claim 1, characterized in that the
titanium dioxide has a primary particle diameter of 5-100 nm.
8. The cast-coated paper of claim 1, characterized in that it is
cast-finished by the rewet cast coating method in which the coating
layer in the wet state is once dried and then rewetted with a
rewetting liquid.
9. A tissue carton or a tissue box prepared from the cast-coated
paper of claim 1.
10. The cast-coated paper of claim 4, which has a sheet gloss of
80% or more on the cast-coated surface as determined according to
JIS-P8142.
11. The cast-coated paper of claim 4, characterized in that the
titanium dioxide has a primary particle diameter of 5-100 nm.
12. The cast-coated paper of claim 4, characterized in that it is
cast-finished by the rewet cast coating method in which the coating
layer in the wet state is once dried and then rewetted with a
rewetting liquid.
13. A tissue carton or a tissue box prepared from the cast-coated
paper of claim 4.
Description
TECHNICAL FIELD
[0001] The present invention relates to cast-coated paper having
excellent coating runnability and good printability by keeping a
proper friction coefficient, and also having an excellent
air-cleaning effect.
BACKGROUND ART
[0002] Titanium dioxide is gaining the spotlight in line with a
growing desire to eliminate hazardous substances in everyday life
such as offensive odors as an interest in the living environment
rises. Titanium dioxide has been conventionally used as a pigment
having excellent opacity and brightness for papermaking, and fine
particles of titanium dioxide are known to use light energy to
induce redox reactions, thereby decomposing various hazardous
substances in the air, so that techniques for supporting them on
paper are under development in order to capitalize on this
phenomenon. For example, a photocatalytic paper as a filler a
water-soluble polymer and a photocatalytic material such as
titanium dioxide has been disclosed (see patent document 1), but it
cannot be said that the incorporation of a photocatalytic material
in paper layers is efficient and sufficiently effective because
such a material produces its catalytic effect by exposure to light.
Moreover, the resulting color print quality such as ink adhesion,
print gloss or print clarity is not sufficient. Printing sheets
coated with a coating containing fine powder of titanium dioxide
complexed with an inorganic binder such as silica sol and further
bound by an organic adhesive have also been disclosed (see patent
documents 2 and 3). However, papers coated with a mixed coating of
titanium dioxide and silica sol suffered from poor coating
runnability because the particle diameters of titanium dioxide and
silica sol were so small that the viscosity of the coating color
extremely increased. They also had the disadvantage that they could
not achieve desired quality such as high sheet gloss and print
gloss, print uniformity and surface strength because of the
insufficient coverage by the coating. Moreover, even if a
photocatalytic effect was conferred on common printing papers such
as uncoated paper, lightweight coated paper and woodfree coated
paper used for printing texts in insert, magazines, catalogs, etc.,
it was difficult to sufficiently produce the photocatalytic effect
because they were not often used in environments where they were
exposed to light. On the other hand, it would be desirable to
confer a photocatalytic effect on cast-coated papers characterized
by high sheet gloss and print gloss because they are often used in
environments where they are exposed to a lot of light, such as in
the covers of magazines and posters, i.e., preferred environments
where photocatalytic papers should be used. However, it was
difficult to prepare a cast-coated paper having an excellent
air-cleaning effect by simply using photocatalytic titanium dioxide
in conventional formulations or processes because runnability or
productivity decreased with changes in the coatings properties or
it was difficult to achieve sufficient sheet gloss and good
printing quality.
[0003] Patent document 1: JPA HEI-10-226983.
[0004] Patent document 2: JPA 2000-129595.
[0005] Patent document 3: JPA HEI-11-117196.
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0006] In view of these circumstances, an object of the present
invention is to provide a cast-coated paper having good coated
paper quality and printability combined with the property of
decomposing hazardous substances upon exposure to light.
Means for Solving the Problems
[0007] As a result of careful studies to achieve the above object,
we found that a cast-coated paper having high print gloss and good
print uniformity combined with the property of decomposing
hazardous substances and odor components upon exposure to light can
be obtained by providing a cast-coated paper prepared by applying a
cast-coating layer based on a pigment and a binder on a base paper
and finished by pressing the cast-coating layer in the wet state
against a heated specular drum surface and drying it, wherein the
cast-coating layer contains 1-30 parts by weight of titanium
dioxide having an average secondary particle diameter of 300-2000
nm per 100 parts by weight of the pigment. Moreover, a good balance
between the printing quality such as good coating runnability,
excellent print gloss, print uniformity or surface strength and the
photocatalytic effect can be attained by including 5-40 parts by
weight of an organic binder per 100 parts by weight of the pigment
in the cast-coating layer, in which the organic binder includes 50%
by weight or more of a copolymer latex. The copolymer latex
preferably has a glass transition temperature of -20 to 40.degree.
C. In the present invention, a cast-coated paper in which the
deterioration of the paper due to decomposition reaction of the
photocatalyst and the deterioration of printing quality due to
decomposition of ink components or the like are further reduced and
which has good printability can be prepared by premixing titanium
dioxide with a silica sol or alumina sol at a ratio of titanium
dioxide to silica sol or alumina sol of 2:1-1:2.
Advantages of the Invention
[0008] According to the present invention, a cast-coated paper
having high sheet gloss typical of cast-coated paper, good printing
quality such as print gloss, print uniformity and surface strength,
and good printability by keeping a proper friction coefficient,
combined with the property of decomposing hazardous substances upon
exposure to light and good coating runnability can be obtained.
PREFERRED EMBODIMENTS OF THE INVENTION
[0009] In the present invention, it is important that the pigment
included in the cast-coating solution partially contains a specific
proportion of fine particles of titanium dioxide having a
photocatalytic effect and an average secondary particle diameter of
300-2000 nm, preferably 500-1500 nm, more preferably 700-1300 nm,
in order to confer an air-cleaning effect on the cast-coated paper.
Titanium dioxide per se has a photocatalytic effect irrespective of
the particle diameter. If the average secondary particle diameter
is less than 300 nm, the dispersibility of the titanium dioxide
slurry decreases and the viscosity of the coating extremely
increases to reduce the productivity, and moreover, titanium
dioxide falls off to impair the printing quality, printability and
photocatalytic function. If the average secondary particle diameter
exceeds 2000 nm, however, the smoothness of the coated paper
decreases and therefore, printing quality deteriorates. Titanium
dioxide preferably has a primary particle diameter of 5-100 nm,
more preferably 10-50 nm, still more preferably 10-35 nm. If the
primary particle diameter is less than 5 nm, the dispersibility of
the titanium dioxide slurry and the flowability of the coating tend
to decrease, thus impairing printing quality and printability. If
it exceeds 100 nm, the surface area decreases so that the
photocatalytic effect tends to be insufficient.
[0010] Fine particles of titanium dioxide can have the property of
decomposing hazardous substances in the air upon exposure to light.
The proportion of titanium dioxide is 1-30 parts by weight,
preferably 5-25 parts by weight, more preferably 5-20 parts by
weight per 100 parts by weight of the pigment. If the proportion of
titanium dioxide is less than 1 part by weight, the amount of the
photocatalyst is too small to achieve a sufficient air-cleaning
effect. In the present invention, it is important to use fine
particles of titanium dioxide having a high photocatalytic effect,
but fine particles of titanium dioxide have very high viscosity so
that they form a slurry with very low solids content when they are
used in a coating. Therefore, if the proportion exceeds 30 parts by
weight, an air-cleaning effect is obtained, but the solids content
of the coating extremely decreases so that it becomes difficult to
apply it at a certain coating weight or more and also difficult to
obtain high sheet gloss and the resulting paper has poor print
uniformity, surface strength and chalking resistance when compared
at a coating weight used in conventional cast-coated papers. The
chalking resistance refers to the resistance to dusting by
photodecomposition and deterioration of the coating layer surface
and the base paper layer after exposure to light. The titanium
dioxide particles in the present invention can be prepared from not
only titanium dioxide but also any titanium oxide or hydroxide
called hydrous titanium dioxide, hydrated titanium dioxide,
metatitanic acid, orthotitanic acid, and titanium hydroxide. In
addition to conventional UV-activatable photocatalysts, visible
light-activatable photocatalysts showing a photocatalytic effect in
response to visible light can also be used. The titanium dioxide
used in the present invention preferably has a specific surface
area of 10-350 m.sup.2/g. The titanium dioxide of the present
invention can also be mixed with a silica sol or alumina sol so
that the fine particles of titanium dioxide are covered with the
silica sol or alumina sol having an inorganic binder function,
thereby reducing the deterioration of the paper due to
decomposition reaction of the photocatalyst, and further reducing
the deterioration of printing quality due to decomposition of ink
components or the like. The ratio between titanium dioxide and an
inorganic binder consisting of a silica sol or alumina sol is in
the order of 5:1-1:5, preferably 2:1-1:2, more preferably 2:1-1:1.5
expressed in polymerization ratio. If the ratio of titanium dioxide
is much higher than 5:1, the paper tends to deteriorate due to
decomposition of organic binders or pulp fibers in the coating or
the printing quality tends to deteriorate due to decomposition of
ink components in printed matters or the like. If the ratio of
titanium dioxide is much lower than 1:5, the static friction
coefficient of the paper significantly increases to invite a paper
jam by multiple sheet feeding during printing, resulting in poor
printability. In terms of light transmission, a silica sol is
preferably used. In order to efficiently cover fine particles of
titanium dioxide during the preparation of the coating color, it is
preferable to mix titanium dioxide and a colloidal silica or
alumina solution at a predetermined ratio, and stir the mixture for
a predetermined period, and then add other pigments and
auxiliaries. In the present invention, a mixture of inorganic
binders of a silica sol and an alumina sol can also be mixed with
titanium dioxide.
[0011] The cast-coated paper can be used to prepare a quality
appearance tissue carton having high sheet gloss, but the surface
of the cast-coated paper may be damaged by friction during the
conversion into the carton. In this case, damages to the tissue
carton are improved by including preferably 5 parts by weight or
more, more preferably 5-50 parts by weight or more of the silica
sol per 100 parts by weight of the pigment. This is important for
improving the appearance of tissue boxes as final products. For use
in cartons, the ratio between titanium dioxide and an inorganic
binder consisting of a silica sol or alumina sol is also in the
order of 5:1-1:5, preferably 2:1-1:2, more preferably 2:1-1:1.5
expressed in polymerization ratio to prevent the deterioration of
paper or printing quality or to ensure high printability.
[0012] In the present invention, the cast-coating layer can also
contain one or more other pigments as appropriate selected from
those conventionally used for preparing coated papers, including
inorganic pigments such as kaolin, clay, delaminated clay, ground
calcium carbonate, precipitated calcium carbonate, talc, titanium
dioxide, barium sulfate, calcium sulfate, zinc oxide, silicic acid,
silicates, colloidal silica and satin white, as well as organic
pigments such as plastic pigments. In the present invention, it is
preferable to use kaolin preferably in an amount of 10 parts by
weight or more, more preferably 40 parts by weight or more per 100
parts by weight of the pigment, in order to improve the
photocatalytic effect, sheet uniformity and sheet gloss.
[0013] In the present invention, the cast-coating layer contains
5-40 parts by weight, preferably 8-40 parts by weight, more
preferably 8-30 parts by weight, especially 10-20 parts by weight
of an organic binder per 100 parts by weight of the pigment. If the
proportion of the organic binder is less than 5 parts by weight,
sufficient surface strength cannot be achieved and the suitability
for carton processing tends to decrease. However, more than 40
parts by weight are not preferred because the consistency of the
coating decreases to invite productivity problems such as
difficulty in controlling the coating weight, high drying load and
low coating speed or titanium dioxide is covered by the binders,
thereby reducing the air-cleaning effect. In terms of the
air-cleaning effect, the organic binders are preferably contained
at lower proportions. The binder used in the present invention can
be selected as appropriate from one or more of organic binders
conventionally used for coated papers, e.g., synthetic binders such
as various copolymer latexes including styrene-butadiene
copolymers, styrene-acrylic copolymers, ethylene-vinyl acetate
copolymers, butadiene-methyl methacrylate copolymers and vinyl
acetate-butyl acrylate copolymers, or polyvinyl alcohols, maleic
anhydride copolymers and acrylic-methyl methacrylate copolymers;
proteins such as casein, soybean protein and synthetic proteins;
starches such as oxidized starches, cationized starches, urea
phosphate-esterified starches and etherified starches such as
hydroxyethyl etherified starches; and cellulose derivative binders
such as carboxyethyl cellulose, hydroxyethyl cellulose and
hydroxymethyl cellulose, provided that a copolymer latex is
contained at preferably 50% by weight or more, more preferably
50-90% by weight, still more preferably 60-90% by weight or more of
the total organic binder composition. If the proportion of the
copolymer latex is less than 50% by weight, it becomes difficult to
achieve high sheet gloss typical of cast-coated paper and the
photocatalytic effect tends to decrease. If it exceeds 90% by
weight, the productivity tends to decrease due to sticking to the
casting drum. The copolymer latex used preferably has a glass
transition temperature of -20 to 40.degree. C., more preferably -20
to 30.degree. C., still more preferably -10 to 30.degree. C. If the
glass transition temperature exceeds 40.degree. C., sufficient
surface strength to usable printing cannot be attained. If the
glass transition temperature is less than -20.degree. C., the
photocatalytic effect tends to be insufficient or the runnability
tends to decrease due to sticking to rolls such as the casting
drum. In the case of copolymer latexes having different glass
transition temperatures in particles such as core-shell latexes,
the shell layer (surface layer) preferably has a glass transition
temperature in the range defined above and the core layer (inside
layer) preferably has a glass transition temperature lower than
that of the shell layer (surface layer). The copolymer latex
preferably has a particle diameter of 50-250 nm to ensure printing
quality and surface strength. Water-soluble polymer binders such as
starches are preferably present at 10 parts by weight or less.
[0014] In addition to the pigments and binders described above,
various additives can be used as appropriate in the cast coating
layer, including ammonium salts or metal salts of inorganic or
organic acids such as sodium chloride, ammonium chloride, zinc
chloride, magnesium chloride, sodium sulfate, potassium sulfate,
ammonium sulfate, zinc sulfate, magnesium sulfate, ammonium
nitrate, monobasic sodium phosphate, ammonium phosphate, calcium
phosphate, sodium polyphosphate, sodium hexametaphosphate, sodium
formate, ammonium formate, sodium acetate, potassium acetate,
sodium monochlorate, sodium malonate, sodium tartrate, potassium
tartrate, sodium citrate, potassium citrate, sodium lactate, sodium
gluconate, sodium adipate, and sodium dioctylsulfosuccinate; and
methyl amine, diethanolamine, diethylene triamine, diisopropyl
amine, etc. In addition, various auxiliaries included in typical
coating compositions for coated papers such as dispersants,
thickeners, water-retention agents, antifoamers, colorants, mold
release agents, fluidity modifiers, insolubilizers, preservatives
and printability improving agents are used as appropriate.
[0015] The base paper for the cast-coated paper of the present
invention contains conventional pulp, fillers, etc. In the present
invention, the type or the like of pulp contained in the base paper
is not specifically limited. For example, hardwood kraft pulp
(hereinafter referred to as LBKP), softwood kraft pulp (hereinafter
referred to as NBKP), thermomechanical pulp, groundwood pulp,
recycled pulp and the like are used. The pulp preferably contains
60% by weight or less of mechanical pulp in the total pulp
composition, most preferably wholly consists of chemical pulp in
terms of printing quality because papers excessively containing
mechanical pulp or deinking paper pulp derived from mechanical pulp
deteriorate and discolor upon exposure to light.
[0016] Fillers that can be used in the base paper include known
fillers such as ground calcium carbonate, precipitated calcium
carbonate, kaolin, clay, talc, hydrated silica, white carbon,
titanium deoxide, synthetic resin fillers, etc. The fillers are
used in an amount of about 1-30% by weight, preferably 3-20% by
weight based on the pulp weight. The base paper can be prepared
from the stock optionally containing chemicals conventionally used
in papermaking processes, such as paper strength enhancers, sizing
agents, antifoamers, colorants, softening agents, bulking agents
(density reducing agents) or the like in the range not inhibiting
the advantages of the present invention.
[0017] The process for preparing the base paper is not specifically
limited, and the base paper may be prepared by any process for
making acidic, neutral or alkaline papers using e.g., a Fourdrinier
paper machine including a top wire or the like or a cylinder paper
machine and may also be a wood containing base paper containing
mechanical pulp as a matter of course. The base paper may be coated
with a surface-treating agent based on a water-soluble polymer for
the purpose of improving surface strength or sizing performance.
Suitable water-soluble polymers include those commonly used as
surface-treating agents such as oxidized starches, hydroxyethyl
etherified starches, enzyme-modified starches, polyacrylamides and
polyvinyl alcohols, and they can be used alone or as mixtures
thereof. In addition to the water-soluble polymers, the
surface-treating agents can contain paper strength enhancers
intended for waterproofing and improving surface strength and
external sizing agents intended for conferring sizing effect. The
surface-treating agents can be applied by using coater such as film
transfer roll coater, e.g., two-roll size press coater, gate roll
coater, blade metering size press coater, rod metering size press
coater, and Sym-Sizer. In the present invention, base papers coated
with not only such a surface-treating agent but also a coating
color containing a pigment and a binder used for conventional
coated papers using any one of the coaters mentioned above or base
papers coated with the coating color using a blade coater, roll
coater, air knife coater or the like after the surface-treating
agent is applied and dried can also be used as base papers for cast
coating. In these cases, the coating weight is desirably about 5-30
g/m.sup.2 in dry weight per side. The base paper can be coated on
either one side or both sides depending on the purpose. The wet
coating layer is dried by using various types of dryers such as a
steam cylinder, hot air dryer, gas heater dryer, electric heater
dryer, infrared heater dryer or the like alone or in combination.
The coated paper is typically dried to a paper moisture in a range
of about 1-10%, desirably in a range of about 2-7%, depending on
the type of the base paper, the type of the composition to be
applied and other factors. The precoated base paper may be smoothed
in advance in a supercalender, soft calender or the like, if
desired.
[0018] Suitable base papers to be cast-coated are base papers
having a basis weight of about 25-600 g/m.sup.2 for use in
conventional coated papers and coated paperboards, preferably
50-200 g/m.sup.2 for coated papers, and 230-500 g/m.sup.2 for
coated paperboards.
[0019] A cast coating composition prepared can be applied on a base
paper by using known coaters such as film transfer roll coaters,
e.g., two-roll size press coaters, gate roll coaters, blade
metering size press coaters, rod metering size press coaters,
Sym-Sizers, JF sizers; flooded nip/blade coaters, jet
fountain/blade coaters, short dwell time applicator type coaters;
rod metering coaters using a grooved rod, plain rod or the like in
place of a blade; air knife coaters, curtain coaters or die
coaters; preferably at a coating weight of 5-30 g/m.sup.2, more
preferably 10-25 g/m.sup.2 per side of the base paper. After
applying a cast coating layer, it is cast-finished. Cast-finishing
methods include the direct method in which a coating layer is
cast-finished in the wet state; the gel casting method in which a
coating layer in the wet state is gelled and then cast-finished;
the rewet cast coating method in which a coating layer in the wet
state is once dried and then rewetted with a rewetting liquid and
cast-finished, etc., among which the rewet cast coating method is
preferred in terms of a photocatalytic effect. Either one side or
both sides can be cast-finished depending on the purpose. The
surface temperature of the heated specular drum is preferably
100.degree. C. or more during cast-finishing.
[0020] The present invention is remarkably effective in cast-coated
papers having a sheet gloss of 80% or more, preferably 85-98% as
determined according to JIS-P8142. If the sheet gloss increases,
the structure of the coating layer becomes dense, which in turn
reduces the probability that the photocatalyst in the coating layer
comes into contact with hazardous components in the air, thereby
reducing the air-cleaning effect. However, the process of the
present invention allows even cast-coated papers having high sheet
gloss to show an excellent air-cleaning effect and good
printability.
[0021] In the present invention, the cast-coated papers or
cast-coated paperboards described above can also be used to prepare
tissue cartons and tissue boxes.
[0022] Next, processes for converting the coated papers as
described above into tissue cartons and tissue boxes are described
below.
[0023] Tissue as used herein refers to sanitary papers such as
facial tissue, toilet tissue, paper towels and table napkins as
well as paper or nonwoven wipers.
[0024] Tissue cartons are prepared by, but not specifically limited
to, the process described below, for example. Printing and
conversion of white board are reviewed in "White board and paper
containers", 1995, pp. 153-167 published by Shigyo Times Sha Co.,
Ltd.
[0025] An example of the preparation of a tissue box from a base
paper for tissue carton (coated paper) is explained. A picture for
enhancing the appearance during the use as a tissue box by
consumers, directions for use, the brand name, quality description,
the JAN code, an appeal of product characteristics and other
information are printed on a base paper for tissue carton having a
basis weight of 230 g/m.sup.2 to 640 g/m.sup.2 prepared by the
process described above. Printing methods that can be used mainly
include offset lithographic printing, intaglio gravure printing,
etc., as well as UV printing, silkscreen stencil printing,
flexographic relief printing, and hot stamping by which foil films
are transferred under heat and pressure. Hot stamping allows foil
films of gold, silver or the like to be applied as printed
layers.
[0026] The printed area of the tissue carton is preferably 1-80%,
more preferably 1-50% per area exposed to light, because the
air-cleaning effect and deodorizing effect of the photocatalytic
tissue carton tend to decrease by ink layers and printed film
layers. The tissue carton may be glazed or varnished during the
preparation, but this step may be omitted because it tends to make
the photocatalytic effect insufficient.
[0027] The tissue carton intermediate after printing is die cut.
The die cutting process comprises the steps of die cutting the
intermediate into the shape of the developed view of a box, forming
a perforating line for removal, and drawing ruled lines for folding
the box. The die cutting process may further comprise embossing for
decorative purpose.
[0028] A polyethylene film with a slit is then adhered to the
tissue carton intermediate with a vinyl acetate, EVA binder or the
like using a window patcher after the die cutting process. The
present invention may also include tissue boxes without a
polyethylene film similar to many such tissue boxes on the market
in view of the environmental issue of waste reduction.
[0029] Then, the tissue carton intermediate with or without a
polyethylene film is glued and folded by a sack-making machine to
prepare a tissue carton. Thus prepared tissue carton is fed to a
cartoning step. During the cartoning step, the tissue carton is fed
by a processing machine called cartoner and raised to fill tissue
paper such as facial tissue from the side face of the tissue
carton, then sealed with a binder and pressed to give a tissue box
containing tissue paper.
[0030] The contents of the tissue box in the present invention
include sanitary papers such as facial tissue, toilet tissue, paper
towels and table napkins as well as paper or nonwoven wipers for
domestic, business and industrial uses, which may be in the form of
V-, C- or Z-folded sheets or rolls. FIG. 1 shows an example of a
tissue box prepared in this manner, in which the area of A, B, C, D
and E sides of the tissue box shown in FIG. 1 (i.e., the sides
effectively exposed to sunlight, fluorescent light, incandescent
light, etc.) is preferably 400 cm.sup.2 to 2,000 cm.sup.2 from the
viewpoint of practical use, air-cleaning effect and deodorizing
effect.
[0031] The following examples further illustrate the present
invention without, however, limiting the invention thereto as a
matter of course. Unless otherwise specified, parts and % in the
examples mean parts by weight and % by weight, respectively.
Performance during the preparation of base papers for tissue
cartons consisting of cast-coated papers and during the conversion
from the tissue cartons into tissue boxes was tested by the
evaluation methods as shown below.
EXAMPLES
[0032] The following examples further illustrate the present
invention without, however, limiting the invention thereto as a
matter of course. Unless otherwise specified, parts and % in the
examples mean parts by weight and % by weight, respectively.
Coating solutions and the resulting cast-coated papers were tested
by the evaluation methods as shown below.
(Evaluation Methods)
[0033] (1) Particle size analysis of titanium dioxide: calculated
from scanning electron micrographs.
[0034] A thin layer of a slurry of fine particles of titanium
dioxide was applied on a sample mount for electron microscopy and
dried in a dryer set at 40.degree. C. Then, microphotographs of the
particles were taken at a magnification of 10000.times. using
FE-SEM (Field Emission Scanning Electron Microscope JSM-6700F
available from JEOL Ltd.) and observed and analyzed. The average of
the measured diameters of agglomerates of 100 particles was
reported as average secondary particle diameter. [0035] (2) Cast
coating runnability: determined from troubles such as sticking of
the cast-coated paper to the cast drum and staining on the cast
drum during cast coating. [0036] .circleincircle.: No trouble such
as sticking to the casting drum and staining on the casting drum
occurs. [0037] .smallcircle.: Little trouble such as sticking to
the casting drum and staining on the casting drum occurs. [0038]
.tangle-solidup.: Some trouble such as sticking to the casting drum
and staining on the casting drum occurs. [0039] .times.: Troubles
such as sticking to the casting drum and staining on the casting
drum occur so that cast-coated paper with good quality cannot be
produced. [0040] (3) Sheet gloss: determined at an angle of
75.degree. according to JIS P 8142: 1998. [0041] (4) Sheet
uniformity: visually evaluated from gloss ununiformity or the like
on the surface of the cast-coated paper. .circleincircle.: very
good, .smallcircle.: good, .tangle-solidup.: slightly poor,
.times.: poor. (5) Surface strength: visually evaluated according
to the 4-class scale by comparing the dry pick strength in an RI-II
print tester using SMX tack grade 20 (black) ink available from
Toyo Ink Mfg. Co., Ltd. .circleincircle.: very good, .smallcircle.:
good, .tangle-solidup.: slightly poor, .times.: poor. [0042] (6)
Printing runnability: evaluated according to the 4-class scale by
comparing the jamming frequency caused by multiple sheet feeding
during printing in a Roland sheetfed press at a printing speed of
8000 sheets/hr. .circleincircle.: no jamming with no multiple sheet
feeding, .smallcircle.: multiple sheet feeding slightly appears,
but no jamming occurs, .tangle-solidup.: multiple sheet feeding
appears and some jamming occurs, .times.: multiple sheet feeding
appears and jamming frequently occurs. [0043] (7) Photocatalytic
effect: evaluated according to the photocatalyst performance
evaluation test method II b "gas bag B-method" defined by the
Photocatalyst Product Technology Council. The degree of
acetaldehyde decomposition (%) was determined after UV irradiation
for 20 hours and evaluated according to the 4-class scale.
.circleincircle.: very good (decomposition degree: 70% or more),
.smallcircle.: slightly good (69-50%), .tangle-solidup.: slightly
poor (49%-10%), .times.: significantly poor (10% or less).
Example 1
[0044] In a Cellier mixer, 10 parts (solids) of slurry A of fine
particles of titanium dioxide (CSB-M from Sakai Chemical Industry,
Co., Ltd.; primary particle diameter 20-30 nm, average secondary
particle diameter 1000 nm) and 10 parts of colloidal silica
(Snowtex 40 from Nissan Chemical Industries, Ltd.) were stirred for
1 hr (titanium dioxide: colloidal silica=1:1). Into this mixture
was added a pigment slurry prepared from a pigment consisting of 60
parts of No. 1 grade kaolin (available from Engelhard under trade
name UW-90) and 30 parts of precipitated calcium carbonate (TP121
from Okutama Kogyo Co., Ltd.) dispersed with 0.2 parts of sodium
polyacrylate in a Cellier mixer to prepare a pigment slurry having
a solids content of 60%. To this were added 0.5 parts of a
defoaming agent (San Nopco 1407 from San Nopco Limited), 5 parts of
a releasing agent (Nopcote C104 from San Nopco Limited), 15 parts
of styrene-butadiene copolymer latex A (glass transition
temperature -10.degree. C., particle diameter 190 nm) and 7 parts
of casein as binders (latex proportion: 68%) and water to give a
coating color having a solids content of 50%. The coating solution
was applied on one side of a base paper having a basis weight of
100 g/m.sup.2 and containing 100 parts of chemical pulp and 12
parts of precipitated calcium carbonate as a filler at a coating
weight of 20 g/m.sup.2 using a blade coater and dried. Thus
obtained coated paper was rewetted on the surface of the coating
layer with a rewetting liquid (0.5% polyethylene emulsion) and then
passed through a press nip consisting of a forming roll and a
casting drum so that it was pressed against the casting drum at a
surface temperature of 115.degree. C. at a speed of 100 m/min and
dried, after which it was stripped off the casting drum using a
strip-off roll to give a cast-coated paper by rewet cast
coating.
Example 2
[0045] A cast-coated paper was obtained by the same procedure as in
Example 1 except that 10 parts (solids) of titanium dioxide slurry
A, 10 parts of colloidal silica, 60 parts of first grade kaolin
(available from Engelhard under trade name UW-90) and 30 parts of
precipitated calcium carbonate (TP121 from Okutama Kogyo Co., Ltd.)
in the coating solution in Example 1 were replaced by 20 parts
(solids) of the titanium dioxide slurry, 20 parts of colloidal
silica, 50 parts of kaolin (available from J. M. Huber under trade
name Japangloss) and 30 parts of precipitated calcium carbonate
(TP121 from Okutama Kogyo Co., Ltd.).
Example 3
[0046] A cast-coated paper was obtained by the same procedure as in
Example 1 except that 15 parts of styrene-butadiene copolymer latex
A (glass transition temperature -10.degree. C., particle diameter
190 nm) and 7 parts of casein (latex proportion: 70%) in the
coating solution in Example 1 were replaced by 19 parts of
styrene-butadiene copolymer latex A (latex proportion: 100%).
Example 4
[0047] A cast-coated paper was obtained by the same procedure as in
Example 1 except that styrene-butadiene copolymer latex A (glass
transition temperature -10.degree. C.) in Example 1 was replaced by
styrene-butadiene copolymer latex B (glass transition temperature
-23.degree. C.).
Example 5
[0048] A cast-coated paper was obtained by the same procedure as in
Example 1 except that 15 parts of styrene-butadiene copolymer latex
A (glass transition temperature -10.degree. C., particle diameter
190 nm) and 7 parts of casein (latex proportion: 70%) in the
coating solution in Example 1 were replaced by 6 parts of
styrene-butadiene copolymer latex A (glass transition temperature
-10.degree. C., particle diameter 190 nm), 12 parts of casein and
12 parts of polyvinyl alcohol (available from Kuraray under trade
name PVA117) (latex proportion: 20%).
Example 6
[0049] The cast coating in Example 1 was applied at a coating
weight of 20 g/m.sup.2 per side using a reverse roll coater
provided on a cast coater, and then the wet coating layer was
gelled by contact with a gelling solution consisting of an aqueous
calcium formate solution (10%), and the coated paper having thus
gelled coating layer was passed through a press nip consisting of a
forming roll and a casting drum so that it was pressed against the
casting drum at a surface temperature of 115.degree. C. at a speed
of 70 m/min and dried, after which it was stripped off the casting
drum using a strip-off roll to give a cast-coated paper by gel cast
coating.
Example 7
[0050] A cast-coated paper was obtained by the same procedure as in
Example 6 except that a cast coating was used in which 60 parts of
first grade kaolin (available from Engelhard under trade name
UW-90) and 30 parts of precipitated calcium carbonate (TP121 from
Okutama Kogyo Co., Ltd.) in the coating solution in Example 6 were
replaced by 70 parts of engineered kaolin (available from Engelhard
under trade name Eclipse 650) and 20 parts of precipitated calcium
carbonate (TP121 from Okutama Kogyo Co., Ltd.).
Example 8
[0051] A cast-coated paper was obtained by the same procedure as in
Example 1 except that 10 parts of titanium dioxide slurry A, 10
parts of colloidal silica, 60 parts of No. 1 grade kaolin
(available from Engelhard under trade name UW-90) and 30 parts of
precipitated calcium carbonate (TP121 from Okutama Kogyo Co., Ltd.)
in the coating solution in Example 1 were replaced by 10 parts of
the titanium dioxide slurry, 16 parts of colloidal silica (titanium
dioxide colloidal silica=1:1.6), 60 parts of kaolin (available from
J. M. Huber under trade name Japangloss) and 30 parts of
precipitated calcium carbonate (TP121 from Okutama Kogyo Co.,
Ltd.).
Comparative Example 1
[0052] A cast-coated paper was obtained by the same procedure as in
Example 1 except that 10 parts of the titanium dioxide slurry, 10
parts of colloidal silica, 60 parts of kaolin (available from
Engelhard under trade name UW-90) and 30 parts of precipitated
calcium carbonate (TP121 from Okutama Kogyo Co., Ltd.) in the
coating solution in Example 1 were replaced by 70 parts of kaolin
(available from Engelhard under trade name UW-90) and 30 parts of
precipitated calcium carbonate (TP121 from Okutama Kogyo Co.,
Ltd.).
Comparative Example 2
[0053] A cast-coated paper was obtained by the same procedure as in
Example 1 except that 10 parts of the titanium dioxide slurry, 10
parts of colloidal silica, 60 parts of kaolin (available from
Engelhard under trade name UW-90) and 30 parts of precipitated
calcium carbonate (TP121 from Okutama Kogyo Co., Ltd.) in the
coating solution in Example 1 were replaced by 40 parts of the
titanium dioxide slurry, 40 parts of colloidal silica, 40 parts of
kaolin (available from Engelhard under trade name UW-90) and 20
parts of precipitated calcium carbonate (TP121 from Okutama Kogyo
Co., Ltd.).
Comparative Example 3
[0054] A cast-coated paper was obtained by the same procedure as in
Example 1 except that 10 parts of titanium dioxide slurry A in the
coating solution in Example 1 was replaced by 10 parts of slurry B
of fine particles of titanium dioxide (STR-60N from Sakai Chemical
Industry, Co., Ltd.; primary particle diameter 40-50 nm, average
secondary particle diameter 2500 nm).
[0055] The results are shown in Table 1.
TABLE-US-00001 TABLE 1 Pigments Organic binders Titanium Kaolin,
Precipitated calcium Casein, Latex, PVA, Latex Type dioxide, parts
parts carbonate, parts parts parts parts prop % of latex Example 1
A10 60 30 7 15 0 68 A Example 2 A20 50 30 7 15 0 68 A Example 3 A10
60 30 0 19 0 100 A Example 4 A10 60 30 7 15 0 68 B Example 5 A10 60
30 12 6 12 20 A Example 6 A10 60 30 7 15 0 68 A Example 7 A10
Engineered 70 20 7 15 0 68 A Example 8 A10 60 30 7 15 0 68 A
Comparative 0 70 30 7 15 0 68 A example 1 Comparative A40 40 20 7
15 0 68 A Example 2 Comparative B10 60 30 7 15 0 68 A example 3
Evaluation Sheet Sheet Surface Photocatalytic Coating Print gloss
uniformity strength effect runnability runnability Example 1 91
.circleincircle. .circleincircle. .circleincircle. .circleincircle.
.circleincircle. Example 2 88 .largecircle. .largecircle.
.circleincircle. .largecircle. .largecircle. Example 3 92
.circleincircle. .circleincircle. .circleincircle. .largecircle.
.circleincircle. Example 4 91 .largecircle. .circleincircle.
.largecircle. .largecircle. .circleincircle. Example 5 86
.largecircle. .circleincircle. .largecircle. .circleincircle.
.circleincircle. Example 6 93 .circleincircle. .largecircle.
.largecircle. .largecircle. .circleincircle. Example 7 93
.circleincircle. .largecircle. .circleincircle. .largecircle.
.largecircle. Example 8 91 .circleincircle. .circleincircle.
.circleincircle. .circleincircle. .largecircle. Comparative 93
.circleincircle. .largecircle. X .circleincircle. .circleincircle.
example 1 Comparative 81 X X .circleincircle. .tangle-solidup. X
Example 2 Comparative 84 .largecircle. .largecircle.
.tangle-solidup. .circleincircle. .circleincircle. example 3
[0056] Next, preparation examples of tissue cartons and tissue
boxes using cast-coated papers are shown.
Example 9
[0057] In a Cellier mixer, 10 parts (solids) of slurry A of fine
particles of titanium dioxide (CSB-M from Sakai Chemical Industry,
Co., Ltd.; primary particle diameter 20-30 nm, average secondary
particle diameter 1000 nm) and 16 parts of colloidal silica
(Snowtex 40 from Nissan Chemical Industries, Ltd.) were stirred for
1 hr. Into this mixture was added a pigment slurry prepared from a
pigment consisting of 60 parts of No. 1 grade kaolin (available
from Engelhard under trade name UW-90) and 30 parts of precipitated
calcium carbonate (TP121 from Okutama Kogyo Co., Ltd.) dispersed
with 0.2 parts of sodium polyacrylate in a Cellier mixer to prepare
a pigment slurry having a solids content of 60%.
[0058] To this were added 0.5 parts of a defoaming agent (San Nopco
1407 from San Nopco Limited), 5 parts of a releasing agent (Nopcote
C104 from San Nopco Limited), 15 parts of styrene-butadiene
copolymer latex A (glass transition temperature -10.degree. C.,
particle diameter 190 nm) and 7 parts of casein as binders (latex
proportion: 68%) and water to give a coating color having a solids
content of 50%. The coating color was applied on one side of a
patent coated board having a basis weight of 430 g/m.sup.2 at a
coating weight of 29 g/m.sup.2 using a blade coater and dried. Thus
obtained coated paper was rewetted on the surface of the coating
layer with a rewetting liquid (0.5% polyethylene emulsion) and then
passed through a press nip consisting of a forming roll and a
casting drum so that it was pressed against the casting drum at a
surface temperature of 115.degree. C. at a speed of 100 m/min and
dried, after which it was stripped off the casting drum using a
strip-off roll to give a cast-coated paper having a basis weight of
460 g/m.sup.2 by rewet cast coating. This cast-coated paper was
used as a base paper for tissue carton.
[0059] The base paper for tissue carton was printed in a printing
step (offset printing) to include characters or pictures on sides
A, B, C, D and E of a finished tissue box shown in FIG. 1. The
printed area was 20% of the total area of sides A+B+C+D+E. Then,
the base paper was die cut into the shape of the developed view of
the box by a die cutter and processed to form a perforating line
for removal and ruled lines for folding in E on the face of FIG. 1,
thereby giving a tissue carton.
[0060] A film was adhered to side E on the reverse side of FIG. 1
showing a top view by a window patcher, after which the carton was
die cut by a sack-making machine and then folded and pressed with a
vinyl acetate binder applied on overlaps in the developed view of
the finished box.
[0061] Then, the carton was filled with 200 sheets of facial tissue
in a tissue cartoning step (cartoner) to give a tissue-containing
box.
Example 10
[0062] A tissue-containing box was obtained by the same procedure
as in Example 9 except that the cast coating in Example 9 was
applied at a coating weight of 30 g/m.sup.2 per side using a
reverse roll coater provided on a cast coater, and then the wet
coating layer was gelled by contact with a gelling solution
consisting of an aqueous calcium formate solution (10%), and the
coated paper having thus gelled coating layer was passed through a
press nip consisting of a forming roll and a cast drum so that it
was pressed against the casting drum at a surface temperature of
115.degree. C. at a speed of 70 m/min and dried, after which it was
stripped off the cast drum using a strip-off roll to give a
cast-coated paper for use as a base paper for tissue carton by gel
cast coating.
Example 11
[0063] A cast-coated paper for use as a base paper for tissue
carton having a basis weight of 360 g/m.sup.2 was obtained by using
a patent coated board having a basis weight of 330 g/m.sup.2 in
place of the patent coated board having a basis weight of 430
g/m.sup.2 in Example 9.
[0064] Then, the base paper was printed by offset printing so that
the printed area (on sides A, B, C, D and E) represented 40%. Then,
the base paper was processed through the steps similar to those
subsequent to the printing step in the preparation process of a
tissue carton described in Example 9, and filled with toilet tissue
in a tissue cartoning step to give a box containing toilet
tissue.
Example 12
[0065] A tissue-containing box was obtained by the same procedure
as in Example 9 except that 10 parts (solids) of slurry A of fine
particles of titanium dioxide (CSB-M from Sakai Chemical Industry,
Co., Ltd.; primary particle diameter 20-30 nm, average secondary
particle diameter 1000 nm) and 16 parts of colloidal silica
(Snowtex 40 from Nissan Chemical Industries, Ltd.) in Example 9
were replaced by 10 parts (solids) of slurry A of fine particles of
titanium dioxide (CSB-M from Sakai Chemical Industry, Co., Ltd.;
primary particle diameter 20-30 nm, average secondary particle
diameter 1000 nm) and 10 parts of colloidal silica (Snowtex 40 from
Nissan Chemical Industries, Ltd.).
Comparative Example 4
[0066] A cast-coated paper was obtained by the same procedure as in
Example 9 except that 10 parts of the titanium dioxide slurry, 16
parts of colloidal silica, 60 parts of kaolin (available from
Engelhard under trade name UW-90) and 30 parts of precipitated
calcium carbonate (TP121 from Okutama Kogyo Co., Ltd.) in the
coating solution in Example 9 were replaced by 70 parts of kaolin
(available from Engelhard under trade name UW-90) and 30 parts of
precipitated calcium carbonate (TP121 from Okutama Kogyo Co.,
Ltd.). This cast-coated paper was used as a base paper for tissue
carton to give a tissue-containing box in the same manner as in
Example 9.
[0067] The results are shown in Table 2.
(Evaluation Methods)
[0068] (8) Fade test: evaluated from the loss of ISO brightness
determined before and 24 hours after UV irradiation (samples were
irradiated with a UV black light at an intensity of 2.5
mW/cm.sup.2).
[0068] Loss of brightness (%)=(brightness before UV
irradiation-brightness after UV irradiation)/brightness before UV
irradiation .times.100. [0069] (9) Resistance to carton damage:
visually evaluated for the resistance to damages to the surface of
the coating layer during the conversion from a base paper for
carton into a box according to the 4-class scale below:
.circleincircle.: very good, .smallcircle.: slightly good,
.tangle-solidup.: slightly poor, .times.: significantly poor. (10)
Transportability of carton: evaluated by comparison for the
transportability during the preparation of a tissue carton and
during the conversion into a tissue box according to the 4-class
scale below: .circleincircle.: very good, .smallcircle.: slightly
good, .tangle-solidup.: slightly poor, .times.: poor.
TABLE-US-00002 [0069] TABLE 2 Trans- Photo- Fade test: Resistance
porta- Sheet Surface catalytic brightness to carton bility of gloss
strength effect loss (%) damage carton Example 9 93
.circleincircle. .circleincircle. 2.7 .circleincircle.
.largecircle. Example 10 95 .circleincircle. .largecircle. 2.8
.largecircle. .largecircle. Example 11 93 .circleincircle.
.circleincircle. 2.7 .circleincircle. .largecircle. Example 12 94
.circleincircle. .circleincircle. 2.9 .circleincircle.
.circleincircle. Comparative 96 .largecircle. X 6.1
.tangle-solidup. .circleincircle. examples 4
[0070] As shown in Table 2, Examples 9-12 exhibit high sheet gloss,
photocatalytic effect and fade resistance as well as excellent
suitability for carton processing such as resistance to carton
damage and transportability of carton. In contrast, Comparative
example 4 is poor in photocatalytic effect, fade resistance and
resistance to carton damage.
* * * * *