JPH01139896A - Production of cast coat paper - Google Patents

Abstract

PURPOSE: To efficiently produce cast-coated paper subjected to glazed finish and excellent in quality by coating base paper subjected to double dewatering with a layer including pigment and adhesive and then by pressing the paper onto a heated drum having a mirror finish surface. CONSTITUTION: The objective cast-coated paper is produced by making paper from (A) pulp such as chemical pulp, mechanical one or the like in a paper machine having a double dewatering mechanism equipped with e.g. two sets of movable nets to form base paper having high steam permeability, by coating the paper with a coating composition mainly comprising (B) pigment (e.g. clay, kaolin or the like) and (C) adhesive (e.g. starch, casein or the like) preferably in a quantity of 5-30 g/m<2> based on dry weight and then by pressing the coated paper onto a heated drum having a mirror finish surface.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a method for producing cast coated paper, and more particularly to a method for producing cast coated paper of high quality very efficiently.

``Prior Art'' Conventionally, methods for manufacturing cast coated paper include the wet casting method (for example, Japanese Patent Publication No. 3407/1986, 3B
-25160), a gel casting method in which the wet coating layer is made into a gel state and pressed onto the heating drum surface for a glossy finish (for example, Japanese Patent Publication No. 38-15751, 40-720).
No. 7, U.S. Patent No. 3,377,192, JP-A-51-404
No. 10), a rewet casting method in which the wet coating layer is once dried or semi-dried, then plasticized by rewetting and pressed against the heated drum surface (for example, U.S. Pat. No. 2,759,847).
No. 4B-38005, JP 51-102
1) No. 1) etc. are known.

In all of these methods for producing cast coated paper, a coating layer mainly composed of pigment and adhesive is provided on a base paper, and while the coating layer is in a wet state, the coating layer is pressed against a heated finished surface having a mirror surface. They have a common feature in that they produce coated paper that is smooth and highly glossy by copying a mirror surface onto the coated layer that is in a plastic state.

In such a manufacturing method for cast coated paper, the moisture in the wet coating layer cannot evaporate in the direction of the finished surface because the coating layer is in close contact with the heated finished surface, which is different from that in conventional coated paper production. Unlike the drying method, everything is evaporated and dried toward the back side through the base paper layer.

That is, the moisture in the wet coating layer is converted into water vapor by the heat of the heated finished surface, and if an undercoat layer is provided below the wet coating layer, it permeates through the undercoat layer, and then the base paper is heated. Drying is performed by passing through the layer and, if a back coating layer is provided, further passing through the back coating layer. For this reason, the production speed of cast-coated paper has traditionally been severely limited, and high-speed cast coating has been impossible.

``Problem to be solved by the invention'' For the above reasons, in the case of manufacturing cast coated paper, in order to increase the production speed even slightly, the coating amount of the wet coating layer is reduced as much as possible to reduce the burden of water evaporation. Measures are taken to reduce this. For this purpose, for example, a method is used in which an undercoat layer containing pigment and adhesive as the main components is first applied to the base paper surface, and after drying or semi-drying, a wet coating layer is applied as an overcoat layer.

According to this method, it is possible to maintain sufficient quality as a cast coated paper even if the coating amount of the wet coating layer is reduced, and in particular, it is possible to increase the coating amount of the undercoat layer, or to apply two or more layers. Providing multiple undercoating layers can significantly reduce the amount of wet coating. However, the vapor permeability of base paper with an undercoat layer is significantly reduced by the formation of the undercoat layer, and this tendency is particularly strong as the amount of undercoat layer is increased or the number of layers is increased. The current situation is that the production speed of cast coated paper has not been improved even though the amount of coating layer has been reduced and the amount of evaporated water has been reduced.

For many years, the inventors of the present invention have focused on improving the production speed of cast-coated paper, particularly focusing on the development of cast-coated base paper with excellent vapor permeability, and as a result of intensive research, we have found that It has been shown that the amount not only decreases in proportion to the amount of fine fibers and mineral pigments (called fillers) in the base paper, but also that it is greatly influenced by the distribution of fine fibers and fillers in the thickness direction in the base paper. I found it.

That is, when producing base paper using a fourdrinier paper machine with a single-sided dewatering method, which is generally referred to as a Fourdrinier paper machine, some of the fine fibers and filler in the pulp slurry are wire (rope).
On the other hand, the upper surface (felt surface) not in contact with the wire has no dehydration effect, so fine fibers, etc. As a result, the distribution of fine fibers and filler in the base paper is different in the base paper produced on a long-length paper machine with a single-sided dewatering system compared to the base paper produced on a paper machine equipped with a double-sided dewatering mechanism. It was found that the amount of permeation was small.

Therefore, in the case of a base paper that has been dehydrated from both sides, the distribution amount of fine fibers and filler on both sides of the base paper is small, but the center of the base paper (in the Z direction) shows a relatively high distribution amount. When manufacturing cast coated paper using
The amount of water vapor permeated is significantly promoted, and the drying efficiency is greatly improved.

"Means for Solving the Problems" The present invention provides a coating layer mainly composed of pigment and adhesive on base paper, and presses the coating layer against a heated mirror drum while it is in a wet state. The method for producing cast-coated paper with a strong gloss finish is characterized in that the base paper is produced in a paper machine equipped with a double-sided dewatering mechanism.

"Function" The base paper manufactured by a paper machine equipped with a double-sided dewatering mechanism according to the present invention generally refers to base paper manufactured by a paper machine equipped with two sets of movable nets. That is, the pulp slurry can be simultaneously sandwiched between two sets of nets arranged above and below or parallel to each other in the wire part of the paper machine, or the slurry can be dehydrated from both sides of the pulp slurry at different times. This is a base paper manufactured using a paper machine equipped with a running net that can suck and dewater the slurry from both sides (usually referred to as the wire side and the felt side).

A portion of the fine fibers and filler in the pulp slurry separate from the pulp slurry together with the water that is dehydrated from both sides of the pulp slurry. The paper sheet formed while being dehydrated has a thinner distribution of fine fibers and filler and a lower paper density as it moves from the center to the surface on both sides. As a result, water vapor can easily permeate, and a base paper with a large amount of water vapor permeation can be obtained.

However, the glabella strength is relatively weak in the central part of the base paper where the fine fibers and filler are relatively distributed, and in the process of manufacturing cast coated paper (when pressed against the cast drum).
It is easy to cause the problem of peeling between the eyebrows called "blister".This tendency is particularly strong when producing cast coated paper that has a coating layer on the back side.

Considerable effects can be obtained by simply using base paper that has been dehydrated on both sides, but as the above-mentioned concerns remain, we have conducted various studies and decided to manufacture base paper by adding a specific paper strength enhancer to the pulp slurry. It is clear that if this is done, a cast-coated paper with improved interlaminar strength can be obtained without reducing the amount of water vapor permeation, and a cast-coated paper with better casting operability and quality can be obtained. became.

Note that base paper made using a paper machine equipped with a double-sided dewatering mechanism is coated with starch or other coatings using a size press or the like as necessary to strengthen its surface strength, but generally this treatment is performed using water vapor. It is desirable to keep it to a minimum since it causes a decrease in the amount of permeation.

Next, a specific paper strength enhancer used to further enhance the effects of the present invention will be explained. That is, the specific paper strength enhancer used in the present invention contains 1 to 20 mol% of anionic groups.
Acrylamide polymer containing 1 to 30 cationic groups
A small amount selected from an acrylamide-based paper strength agent consisting of an acrylamide-based polymer containing mol%, and a natural polymer paper strength agent consisting of a starch or cellulose derivative (both are a type of paper strength agent. Generally referred to as an internal paper strength agent, it is added to pulp slurry to improve papermaking and
Shows the effect of strengthening the glabellar paper strength of base paper by drying.

General internal paper strength agents tend to form a film and significantly inhibit the permeation of water vapor, but the above-mentioned specific acrylamide polymer and natural polymer paper strength agent used in the present invention are difficult to form into a film and are resistant to water vapor. There is little decrease in the amount of permeation.

Moreover, when used in combination with a paper machine equipped with the double-sided dewatering mechanism of the present invention, it effectively provides a base paper with almost no decrease in water vapor permeation and improved glabellar strength.

Specific examples of anionic groups constituting the above specific acrylamide polymers include sulfone groups, carboxyl groups, etc., and cationic groups include primary to tertiary amino groups, quaternary ammonium groups, etc. etc.

In addition, starch derivatives which are natural polymer paper strength enhancers include modified starches such as positive starch and oxidized starch, and cellulose derivatives include cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose.

When the above acrylamide polymer is used in the pulp slurry of the present invention, the amount of anionic acrylamide polymer added is 0.1 to 2.0 per valve.
Weight%, cationic acrylamide polymer: 0.03
It is preferable to add it in a range of about 0.7% by weight. If the ratio is less than the above-specified minimum ratio, the desired effect cannot be obtained, and if it exceeds the upper limit, it becomes difficult to redisintegrate the broken paper, which is also unfavorable from an economical point of view. In the case of a natural polymer paper strength enhancer, it is preferably used in a range of about 0.05 to 3.0% by weight based on the pulp. Of course, it is also possible to use a natural polymer paper strength enhancer and an acrylamide polymer in combination as appropriate.

As for the method of adding the acrylamide polymer to the pulp slurry, as long as it is avoided to add the anionic polymer and the cationic polymer at the same time, it does not matter which one is added first. However, in general, it is desirable to add the anionic type and the cationic type in this order, and add the latter after allowing time for the former to be sufficiently dispersed in the pulp. Of course, this does not apply to so-called amphoteric acrylamide polymers, which have amphoteric groups within the same compound.

In addition, when using a natural polymer paper strength agent in combination, taking into account its ionicity, there are particular restrictions on the place and time of its addition, provided that direct or short-term contact with ionic compounds of the opposite sign is avoided. It's not something you do.

The pulp used in making base paper with the double-sided dewatering paper machine referred to in the present invention is one that is used in ordinary paper machines, such as chemical pulp (KP, SP, A
P, etc.), mechanical pulp (SGP, SCP, RGP, CGP, etc.), mechanical pulp (SGP, SCP, RGP, CGP
, TMP, CTMP, etc.), waste paper pulp (DIP, etc.), etc. These pulps are blended appropriately according to the specifications of the final product, mechanically treated, and various necessary internal additives are added.
After pulp preparation, it is sent to a paper machine. Of course, the paper making method in this case may be any method such as acid paper making or neutral (alkali) paper making, and is not particularly limited. In addition, in these papermaking methods, pigments such as talc and kaolin are used in acidic papermaking, and carbonates such as heavy calcium carbonate and light calcium carbonate are used in neutral papermaking, as in the single-sided dehydration method. Calcium and further pigments such as talc and kaolin may be suitably incorporated into the pulp slurry. In addition, in the case of paper making using the double-sided dehydration method,
Depending on the type of pulp, blending, mechanical processing, and other papermaking conditions, base paper with relatively weak interlaminar strength can easily be produced, and in such cases, the use of specific acrylamide paper strength enhancers, etc. A desired effect can be preferably obtained by adding the following internal additives. In addition, cast coated paper pigments (
The base paper basis weight of the base paper is adjusted within a range of 30 to 400 g/n (approximately 30 to 400 g/n).

Thus, in the method of the present invention, cast coated paper is produced using the above-mentioned specific base paper, but the coating composition for cast finishing is not particularly limited, and generally contains pigments and adhesives as main components. A composition of ingredients is used. Examples of pigments include clay, kaolin, aluminum hydroxide, calcium carbonate, titanium oxide, barium sulfate, zinc oxide, satin white, plastic pigment, etc.
One or more of the commonly used pigments for coated paper may be used.

In addition, adhesives include natural adhesives such as starch, modified starch, casein, and protein, synthetic polymers such as styrene-butadiene copolymer latex, acrylic emulsion latex, butadiene-acrylonitrile copolymer latex, and polyvinyl alcohol. One or more of the various natural and synthetic adhesives used in conventional aqueous coating compositions, such as adhesives, may be used in appropriate combinations. Furthermore, various auxiliary agents such as a dispersant, a waterproofing agent, a preservative, a dye, and an antifoaming agent can be appropriately incorporated into the coating composition as required.

In addition, if necessary, a general pigment coating composition may be pre-coated on one or both sides of the specific base paper (base paper) in the present invention, in which case the coating amount is 5% by dry weight per side.
~30 g/rd is preferred.

The coating layer thus formed on the base paper can be formed in a wet state as in the conventional method, or by turning the wet coating layer into a gel state, or by drying or semi-drying the wet coating layer. After that, the coating layer plasticized by rewetting is pressed against a heated drum surface having a mirror surface and dried to finish as cast coated paper.

"Example" The present invention will be described in more detail with reference to Examples below, but it is of course not limited to these.

Further, unless otherwise specified, parts and percentages in the columns indicate parts by weight and percentages by weight, respectively.

Example I A paper stock was prepared by adding 0.5 parts of rosin size, 2.8 parts of aluminum sulfate, and 7 parts of papermaking talc as a filler to a pulp composition consisting of 10 parts of NBKP and 90 parts of LBKP,
Paper machine with double-sided dewatering mechanism equipped with two sets of plastic double-woven wires (top wire and bottom wire) (twin wire machine/manufactured by Va1met)
Paper is made using 1.5g/rr of oxidized modified starch on both sides. Size press treatment is applied so that it adheres, and the weight is 64 g.
/rd base paper for cast coated paper was obtained. This base paper has the following composition: kaolin 70 parts heavy calcium carbonate 30 parts oxidized modified starch
A coating composition consisting of 10 parts styrene-butadiene copolymer latex and 15 parts with a solid content concentration of 57% was coated on both sides with a blade coater to give a dry weight of 20 g/rrr per side, and the water content was reduced. The cast-coated paper Kawahara paper was obtained by drying the cast coated paper to a concentration of 6%.

The following composition, kaolin, is applied to the top wire side of this base paper.
60 parts precipitated calcium carbonate 40 parts casein
Using a coating liquid with a solid content concentration of 48% consisting of 12 parts methyl methacrylate-butadiene copolymer latex and 1 part mold release agent, casting was performed using a wet casting method, and the product weight was 1) 8 g/ m
A cast coated paper was obtained.

At this time, there were no problems in casting operability (production speed, drum releasability, drum releasability) and quality, and the desired speed-increasing effect was obtained. The results obtained are shown in Table 1.

Comparative Example 1 All the same procedures as in Example 1 were carried out, except that instead of the paper machine with a double-sided dewatering mechanism, paper was made using a regular long-length paper machine (single-sided dewatering/manufactured by Be1oit) equipped with a plastic double-woven wire. A cast coated paper was obtained in the same manner as in the procedure. Table 1 shows the operability results during casting.

Examples 2 to 7 25 parts of NBKP and 75 parts of LBKP as in Example 1
0.15 parts of rosin size, 2.0 parts of aluminum sulfate, 7 parts of talc for papermaking as a filler, and an acrylamide polymer having 10 mol% of anionic groups as an internal paper strength enhancer and a cationic polymer. 0.6 parts and 0.6 parts of an acrylamide polymer having 15 mol% of groups, respectively.
A base paper for cast coated paper having a weight of 53 g/rrr was obtained in the same manner as in Example 1, except that 2 parts of the stock was used. This base paper was coated with the same coating liquid as in Example 1 on both sides using a blade coater so that the dry weight was 16 g/rrr per side to obtain a cast-coated Kawahara paper with a moisture content of 5%. A cast coated paper of 98 g/n (98 g/n) was obtained in the same manner as in Example 1. In Examples 3 to 7, the type and addition rate of the paper strength enhancer used in Example 2 were as described in Table 1. A cast coated paper was obtained in the same manner as in Example 2 except for the blending.Table 1 shows the results of cast operability.

Comparative Example 2 The paper was made in the same manner as in Example 2, except that instead of the paper machine with a double-sided dewatering mechanism, paper was made using a regular long-length paper machine (single-sided dewatering/manufactured by Be1oit) equipped with a plastic double-woven wire. A cast coated paper was obtained. Table 1 shows the operability results during casting.

Example 8 A pulp composition consisting of 40 parts of NBKP, 50 parts of LBKP and 10 parts of stone ground pulp (SGP) as mechanical pulp, 0605 parts of rosin size, 2.0 parts of sulfuric acid, 8 parts of papermaking talc as filler and internal filler. An acrylamide polymer having 10 mol% of anionic groups and 1 cationic group as a paper strength enhancer.
A double-sided dewatering mechanism was prepared by adding 0.45 parts and 0.15 parts of an acrylamide polymer containing 5 mol%, respectively, and equipped with two sets of plastic double-woven wires (top wire and bottom wire). A paper machine with
Paper was made using a twin wire machine (manufactured by Va1met), and size press treatment was performed so that 1.5 g/rrf of oxidized modified starch was deposited on both sides to obtain a base paper for cast coated paper with a weight of 53 g/nl. . Using this base paper, a 98 g/% cast coated paper was obtained in the same manner as in Example 1. The cast operability results at this time are shown in Table 1.

Example 9 A pulp composition consisting of 50 parts of NrlKP and 50 parts of mechanical pulp (SGP), 0.1 part of rosin size, 2.5 parts of aluminum sulfate, 5 parts of talc for papermaking as a filler, and an example as an internal paper strength enhancer. 0.3 parts and 0.3 parts of the same anionic and cationic acrylamide polymers as in No. 8, respectively.
In the same manner as in Example 8, using a paper stock containing 1 part of
A base paper of g/rd was obtained followed by a cast coated paper of 64 g/d. The cast operability results at this time are shown in Table 1.

Example 1O 25 parts of NBKP, 65 parts of LBKP and mechanical valve (
Bleached CTMP) 0.15 parts of rosin size, and 0.6 parts and 0.2 parts of the same anionic and cationic acrylamide polymers as in Example 8 as internal paper strength enhancers were added to the pulp composition consisting of 10 parts (bleached CTMP). A cast coated paper of 98 g/rd was obtained in the same manner as in Example 8, except that the paper stock was used. The cast operability results at this time are shown in Table 1.

Example 1) 98 g / 98 g /
A cast coated paper of rrr was obtained. Table 1 shows the operational performance results of the cattle strike at this time.

Example 12 A valve composition consisting of 10 parts of NBKP and 90 parts of LBKP was mixed with 0.1 part of alkyl ketene dimer as an internal additive (rosin size and sulfate band were not added) and heavy calcium carbonate as a filler (average particle size 2μ). 98 g/r in the same manner as in Example 8, except that 10 parts of ) and 0.5 parts of cationic starch were added as an internal paper strength enhancer.
A cast coated paper of rr was obtained. The cast operability results at this time are shown in Table 1.

Example 13 A 98 g/+yr cast coated paper was obtained in the same manner as in Example 12, except that the pulp composition consisted of 10 parts of NBKP, 80 parts of LBKP, and 10 parts of mechanical valve (bleached CTMP). The cast operability results at this time are shown in Table 1.

Comparative Examples 3 to 5 Example 8, except that instead of the machine equipped with a double-sided dewatering mechanism, a normal Fourdrinier paper machine with a single-sided dewatering mechanism equipped with a plastic double-woven wire (CMA) was used as the paper machine. , 98 in accordance with 10.13.
A cast coated paper of g/rrr was obtained. That is, in Comparative Example 3, the addition of the internal paper strength enhancer in Example 8 was stopped, and
Comparative Example 4 was carried out under the same conditions as Example 10, and Comparative Example 5 was carried out under the same conditions as in Example 10, and in Comparative Example 5, the addition of the alkyl ketene dimer in Example 13 was reduced to 0.
A cast coated paper was obtained in the same manner as in each Example except that 0.05 parts of aluminum sulfate was added and 0.5 parts of sulfuric acid was added. The cast operability results at this time are shown in Table 1.

"Effects" As is clear from the results in Table 1, in all of the examples of the present invention, the production speed during casting processing is significantly increased compared to when base paper is made using a paper machine equipped with a single-sided dewatering mechanism. I was able to do that.

Claims (2)

[Claims] (1) Cast-coated paper in which a coating layer mainly composed of pigment and adhesive is provided on base paper, and while the coating layer is in a wet state, it is pressed against a heated mirror drum to give a strong gloss finish. A method for producing cast coated paper, characterized in that the base paper is produced in a paper machine equipped with a double-sided dewatering mechanism. (2) Acrylamide paper strength enhancer, starch derivative paper strength consisting of an acrylamide polymer containing 1 to 20 mol% of anionic groups and 1 to 30 mol% of cationic groups in the base paper The method for producing cast coated paper according to claim (1), which contains at least one selected from a reinforcing agent and a cellulose derivative paper strength enhancing agent.